TRAINING MODULE SULPHUR RECOVERY UNIT (SRU)
DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
TRAINING MODULE
SULPHUR RECOVERY UNIT (SRU) UNIT: 22
0 21/03/08 A 29/11/07 REV DATE TRAINING DURATION
Benoit Rabaud Paul Walsh Benoit Rabaud Paul Walsh PREPARED BY CHECKED BY VENUE
JB Guillemin JB Guillemin APPROVED BY
ATTENDANCE ATTENDEES REQUIREMENTS MODULE OBJECTIVES
INSTRUCTORS NAME/POSITION SUMMARY/AGENDA
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IMPORTANT
THIS TRAINING MODULE HAS BEEN PREPARED BY ARAMIS FOR THE DUNG QUAT REFINERY. THIS MODULE MUST BE RECOGNIZED AS A TOOL AND GUIDE ONLY. IT WOULD BE IMPOSSIBLE TO ANTICIPATE AND PRESENT ALL POTENTIAL VARIABLES AND PROCESS CONDITIONS THAT OPERATIONAL PERSONNEL MIGHT BE EXPOSED TO. IT IS IMPERATIVE THAT THE READER ALWAYS AS CERTAIN THAT REFERENCE MATERIALS UTILIZED, WHILE PERFORMING OPERATIONAL DUTIES, CONFORM AT A MINIMUM TO THE LATEST ISSUE OF STANDARD OPERATING PROCEDURES, SAFETY CODES, ENGINEERING STANDARDS, AND GOVERNMENT REGULATIONS. SOME DESIGN FIGURES MIGHT NOT BE IN LINE DURING THE START-UP OF THE REFINERY.
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TABLE OF CONTENT SECTION 1 : GENERAL description ......................................................................................... 10 1.1.
Purpose of the Unit ............................................................................................... 13
1.2.
Basis of Design .................................................................................................... 15 1.2.1. Duty of Plant .............................................................................................. 15 1.2.2. Feed Characteristics ................................................................................. 15 1.2.2.1. Feed Composition & Capacity for production of degassed liquid sulphur 15 1.2.2.2. Feed Composition and Capacity to Incinerator ............................ 16 1.2.2.3. Designed Feed Composition and Capacity for Production of Degassed Liquid Sulphur........................................................................... 17 1.2.3. Product Specifications ............................................................................... 19 1.2.3.1. Degassed Liquid Sulphur Specifications ...................................... 19 1.2.3.2. Emissions from Incinerator ........................................................... 19 1.2.4. Utility/Power/Chemicals/Catalyst consumption.......................................... 19 1.2.4.1. Utility Consumption ...................................................................... 19 1.2.4.2. Catalysts & Chemicals ................................................................. 22
1.3.
Glossary of terms and Acronyms ......................................................................... 24 1.3.1. Acronyms .................................................................................................. 24 1.3.2. Glossary .................................................................................................... 27
SECTION 2 : Process Flow Description .................................................................................... 29 2.1.
Claus Section ....................................................................................................... 31 2.1.1. ARU Off Gas from Unit 19 & H2S Rich Off Gas from Unit 18 .................... 31 2.1.2. Combustion air feeding to Claus section ................................................... 31 2.1.3. Thermal Reactor and Burner ..................................................................... 32 2.1.4. Claus Waste Heat Boiler and 1st Sulphur Condenser ................................ 33 2.1.5. 1st Process Gas Reheater & 1st Catalytic Reactor ..................................... 33 2.1.6. 2nd Condenser, 2nd Process Gas Reheater & 2nd Catalytic Reactor .......... 34 2.1.7. 3rd Condenser, 3rd Process Gas Reheater & 3rd Catalytic Reactor ............ 34 2.1.8. Final Sulphur Condenser and Tail Gas Coalescer .................................... 36
2.2.
Liquid Sulphur Storage Pit .................................................................................... 36
2.3.
Sulphur Degassing Section .................................................................................. 37
2.4.
Incinerator Section ............................................................................................... 39
2.5.
DCS Printouts – SRU Process Overview ............................................................. 39
SECTION 3 : Process control .................................................................................................... 44 Page 4 of 161
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Control narrative & operating parameters ............................................................ 44 3.1.1. ARU Off Gas KO Drum A-2201-D-01 Pressure Control ............................ 44 3.1.2. H2S Rich SWS Off Gas KO Drum A-2201-D-02 Pressure Control............ 46 3.1.3. A-2201-D-01/02/03 Level Control .............................................................. 50 3.1.4. Thermal Reactor Combustion Air Control .................................................. 52 3.1.4.1. Main Combustion Air Flowrate to Thermal Reactor...................... 52 3.1.5. Trim Air Flow to Thermal Reactor Control by Tail Gas Analysis ................ 55 3.1.6. Quench Steam Flowrate Control ............................................................... 56 3.1.7. Combustion Air to Incinerator Flowrate Control (A-2201-H-01) ................. 58 3.1.7.1. Incinerator Residence Zone Temperature Control (A-2201-H-01) 60 3.1.8. Inter-Unit Controls & Interfaces ................................................................. 62 3.1.9. Operating Parameters ............................................................................... 62
3.2.
Instrument List ...................................................................................................... 62
3.3.
Main Equipment ................................................................................................... 63 3.3.1. Thermal Reactor........................................................................................ 63 3.3.2. Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 ........................ 66 3.3.3. Catalytic Reactors A-2201-R-02/03/04 ...................................................... 73 3.3.4. Liquid Sulphur Storage Pit A-2201-TK-01 & Degassing Tank A-2201-TK-02 75 3.3.5. Incinerator A-2201-H-01 ............................................................................ 78 3.3.6. Blowers ..................................................................................................... 81
SECTION 4 : Safeguarding devices .......................................................................................... 85 4.1.
Alarms and Trips .................................................................................................. 85
4.2.
Safeguarding Description ..................................................................................... 85 4.2.1. Interlock UX-501 – General ESD............................................................... 85 4.2.2. Interlock UX-502 – Incinerator ESD .......................................................... 87 4.2.3. Interlock UX-503 – Thermal Reactor ESD ................................................. 92 4.2.4. Interlock UX-504 – A-2201-B-01 A/B Protection ....................................... 97 4.2.5. Interlock UX-505 – A-2201-P-01 A/B Protection ....................................... 97 4.2.6. Interlock UX-506 – A-2201-P-02 A/B Protection ....................................... 98 4.2.7. Interlock UX-507 – A-2201-P-03 A/B Protection ....................................... 98 4.2.8. Interlock UX-508 – Sulphur Degassing ESD ............................................. 99 4.2.9. Interlock UX-509 – A-2201-P-05 A/B Protection ..................................... 100
4.3.
Safeguarding Equipment .................................................................................... 102 4.3.1. Pressure Safety Devices ......................................................................... 102
SECTION 5 : Fire & Gas Systems ........................................................................................... 105 Page 5 of 161
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5.1.
Fire & Gas detection ........................................................................................... 105
5.2.
Fire Protection .................................................................................................... 108 5.2.1. Precautionary measures to avoid fuel gas explosions in Claus area....... 111 5.2.2. Precautionary measures to avoid sulphur burning .................................. 112 5.2.3. Extinguishing Sulphur Pit fires ................................................................. 112 5.2.4. Sulphur Fires ........................................................................................... 112
SECTION 6 : Quality control .................................................................................................... 116 6.1.
Sampling Analysis .............................................................................................. 116 6.1.1. Sampling Connections ............................................................................ 117 6.1.2. Sampling Frequency ............................................................................... 117 6.1.3. Safe handling of samples ........................................................................ 118 6.1.3.1. Handling of gas samples containing H2S ................................... 118 6.1.3.2. Handling of liquid sulphur ........................................................... 118
6.2.
On-line analysers ............................................................................................... 118
SECTION 7 : Causes and effect .............................................................................................. 121 7.1.
Cause & Effect Matrix: ........................................................................................ 121 7.1.1. Example from Cause and Effect Chart .................................................... 121 7.1.1.1. UX-502: Incinerator ESD ............................................................ 121
SECTION 8 : Operating practices ............................................................................................ 126 8.1.
Normal Operation ............................................................................................... 126 8.1.1. Operating conditions ............................................................................... 126 8.1.2. Combustion air / acid gas ratio and Thermal Reactor temperature ......... 135 8.1.3. Claus Reactors Temperatures in normal operating conditions ................ 136 8.1.4. Claus Reactors Temperatures during sulphur sweeping operations ....... 136 8.1.5. Incinerator temperature ........................................................................... 137 8.1.6. Process Variable Effect on Product Quality............................................. 137 8.1.7. Process Variable Effect on Sulfur Yield ................................................... 137 8.1.8. Sulphur Degassing Section ..................................................................... 138
8.2.
Start-up Procedure ............................................................................................. 138 8.2.1. Preparation for Initial Start-Up ................................................................. 139 8.2.2. Initial Start-up .......................................................................................... 140 8.2.3. Plant Re-start-up following a shutdown ................................................... 142 8.2.3.1. Quick restart of warm plant ........................................................ 142 8.2.3.2. Restart of cold plant ................................................................... 142
8.3.
Shutdown Procedures ........................................................................................ 143
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8.3.1. Planned Shutdown .................................................................................. 143 8.4.
Emergency Shutdown ........................................................................................ 145 8.4.1. Emergency Shut-down System Activation ............................................... 145 8.4.2. Power Failure .......................................................................................... 145 8.4.3. Lack of Feedstock ................................................................................... 145 8.4.4. Failure of Liquid Sulphur Export Line ...................................................... 146 8.4.5. Instrument Air Failure .............................................................................. 146 8.4.6. Steam Failure .......................................................................................... 146 8.4.7. Boiler Feed Water Failure ....................................................................... 146 8.4.8. Fuel Gas Failure ...................................................................................... 147 8.4.9. Combustion Air Blowers (A-2201-B-01A/B) Failure ................................. 147 8.4.10. Incinerator Combustion Air Blowers (A-2201-B-02AIB) Failure ............. 147 8.4.11. Dilution Air Blowers (B-2203A/B) Failure ............................................... 147 8.4.12. Off Gas K.O. Drum Pumps (A-2201-P-01A/B, 02A/B, 03A/B) Failure ... 148 8.4.13. Sulphur Circulation and Sulphur Pumps (A-2201-P-04A/B, 05A/B) Failure 148
SECTION 9 : HSE ................................................................................................................... 150 9.1.
Hazardous Areas................................................................................................ 150 9.1.1. Prevention of H2S and SO2 leaks ........................................................... 152
9.2.
Safety Equipment ............................................................................................... 152
9.3.
Specific PPE....................................................................................................... 152 9.3.1. H2S ......................................................................................................... 152 9.3.2. Sulphur Dioxide ....................................................................................... 153 9.3.3. Sulphur .................................................................................................... 153
9.4.
Chemical Hazards .............................................................................................. 154 9.4.1. Hydrogen Sulfide Toxicity ........................................................................ 154 9.4.1.1. Acute Hydrogen Sulfide Poisoning ............................................. 154 9.4.1.2. Subacute Hydrogen sulfide Poisoning ....................................... 155 9.4.2. Sulphur Dioxide Toxicity .......................................................................... 156 9.4.3. Sulphur .................................................................................................... 157 9.4.4. Process gas and tail gas ......................................................................... 157
SECTION 10 : Reference documents index ............................................................................ 159 10.1. Operating Manual/ Licensor Documentation ...................................................... 159 10.2. Arrangement Drawings, Layouts and Plot Plans ................................................ 159 10.3. Process Flow Diagrams ..................................................................................... 159 10.4. Piping and Instrumentation Diagrams ................................................................ 159 Page 7 of 161
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10.5. Equipment list ..................................................................................................... 160 10.6. Main Equipment Data Sheet............................................................................... 160 10.7. Instrument List .................................................................................................... 160 10.8. Cause & Effect Matrix ......................................................................................... 160 10.9. Safety Logic diagram .......................................................................................... 160 10.10.
Fire & Gas Cause & Effect Chart ............................................................. 160
10.11.
Fire & Gas Detectors Layout ................................................................... 160
10.12.
Fire Protection Layout.............................................................................. 161
10.13.
Hazardous Area Classification................................................................. 161
10.14.
MSDS ...................................................................................................... 161
10.15.
Vendors Documentation .......................................................................... 161
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DATE: 21/03/08
TRAINING MODULE
SULPHUR RECOVERY UNIT (SRU) UNIT: 22
Course Content: Section 1 - General Description
X
Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 1 : GENERAL DESCRIPTION The Sulphur recovery Unit (SRU) has been designed for the Bach Ho crude operation to convert all suphur compounds present in the acid gas feed from the ARU and the SWS into liquid elemental sulphur. First a part of H2S is burned and converted into SO2 while the remaining reacts with SO2 to give elemental sulphur before being condensed. The produced liquid sulphur is then degassed and cleared from dissolved H2S. Treated gas is finally incinerated to convert the remaining pollutants into SO2. The SRU is located at the south west of the area 4, next to the LCO HDT, ARU and SWS units.
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Figure 1: 2D Refinery Plot Plan Page 11 of 161
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Figure 2: 3D Refinery Plot Plan Page 12 of 161
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1.1. Purpose of the Unit The scope of the Sulphur Recovery Unit (SRU) is to convert all sulphur compounds present in the acid gas feeds into liquid elemental sulphur, This unit consists of the following sections: Section
Purpose
Sulphur Recovery (Claus) Section
Section based on the Claus Process where the major scope is to convert H2S into elemental liquid sulphur. Section composed of a thermal stage (Thermal Reactor) followed by 3 catalytic steps: The purpose of the thermal reactor is to burn approx. 1/3 of the H2S contained in the total acid gases feed with air to convert it into SO2. (Reaction H2S + 3/2 O2 = SO2 + H2O) The purpose of the catalytic converters is to make the remaining 2/3 of the H2S react with the produced SO2 to give elemental sulphur (Reaction: 2 H2S + SO2 = 3/x SX + H2O) In the Claus section, produced sulphur is also condensed. The overall recovery of the Claus section is approx 96.5% at design conditions.
Liquid Sulphur Storage and Degassing Section
The scope of the Degassing Section is to ensure the liquid sulphur degassing and to remove the dissolved H2S from the produced sulphur, in order to avoid H2S local pollution (H2S desorbed from liquid sulphur) and toxic/explosion hazards during sulphur handling. With this section, H2S content in the liquid sulphur is decreased to less than 20 wt. ppm (much below the explosivity of H2S with air)
Incinerator Section
The purpose of the incinerator section is to convert residual H2S contained in the treated gas leaving the Claus section and the degassing section into SO2 and to finally discharge the flue gas to the atmosphere through the stack. NH3 rich SWS off gas and CNU off gas are also incinerated here.
Sulphur Apron
The sulphur apron is where is collected the solid sulphur from the degassing pit.
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SRU
Figure 3: Unit 22 - 3D Drawing Page 14 of 161
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SULPHUR RECOVERY UNIT (SRU)
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1.2. Basis of Design 1.2.1. Duty of Plant The SRU ahs been designed to recover sulphur from the following acid gas streams: •
ARU off gas (from unit 019)
•
H2S rich off gas (from unit 018)
The Incinerator Unit has been designed to directly treat the following acid gases: •
NH3 rich off gas from SWS (unit 018)
•
CNU off gas (unit 020)
The Sulphur Degassing Section has been designed to treat the total sulphur produced by the Claus Unit at design capacity. The SRU is designed for a production capacity of 5 ton/day of produced degassed liquid sulphur with a Sulphur Recovery Efficiency (SRE) of 95% minimum of the sulphur entering the SRU. The SRU can operate in steady conditions in the range of 50% to 100% of the design conditions.
1.2.2. Feed Characteristics The SRU has been designed to treat 2 feed cases of the BACH HO CRUDE: •
Max Distillate Case
•
Max Gasoline Case
1.2.2.1. Feed Composition & Capacity for production of degassed liquid sulphur 1.2.2.1.1. ARU Off Gas FeedStock Specifications Max. Distillate Case
Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
H2S
102.6
3.01
18.97
119.6
3.51
20.66
NH3
0.0
0.00
0.00
0.0
0.00
0.00
H2O
16.5
0.92
5.77
19.0
1.05
6.21
Cyanide
0.0
0.00
0.00
0.0
0.00
0.00
CO2
511.4
11.62
73.24
531.4
12.08
71.11
N2
1.0
0.04
0.23
1.0
0.04
0.21 Page 15 of 161
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Max. Distillate Case
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Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
CO
0.1
0.004
0.02
0.1
0.00
0.02
H2
0.3
0.15
0.94
0.3
0.15
0.87
C1
1.4
0.09
0.55
1.6
0.10
0.59
C2
1.1
0.04
0.23
1.1
0.04
0.22
C3
0.4
0.01
0.06
0.8
0.02
0.11
Total
634.8
15.87
100.00
674.9
16.98
100.00
1.2.2.1.2. SWS H2S Rich Off Gas Feedstock Specifications Max. Distillate Case
Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
H2S
82.0
2.41
88.94
50.3
1.48
88.09
NH3
0.0
0.00
0.00
0.0
0.00
0.00
H2O
4.8
0.27
9.96
3.1
0.17
10.12
Cyanide
0.7
0.03
1.10
0.7
0.03
1.79
CO2
0.0
0.00
0.00
0.0
0.00
0.00
N2
0.0
0.00
0.00
0.0
0.00
0.00
CO
0.0
0.00
0.00
0.0
0.00
0.00
H2
0.0
0.00
0.00
0.0
0.00
0.00
C1
0.0
0.00
0.00
0.0
0.00
0.00
C2
0.0
0.00
0.00
0.0
0.00
0.00
C3
0.0
0.00
0.00
0.0
0.00
0.00
Total
87.5
2.71
100.00
54.1
1.68
100.00
1.2.2.2. Feed Composition and Capacity to Incinerator 1.2.2.2.1. SWS NH3 Rich Off Gas FeedStock Specifications Max. Distillate Case
Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
H2S
14.7
0.43
3.24
8.9
0.26
2.76
NH3
157.6
9.27
69.75
112.3
6.61
70.25
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Max. Distillate Case
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Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
H2O
64.7
3.59
27.01
45.7
2.54
26.99
Cyanide
0.0
0.00
0.00
0.0
0.00
0.00
CO2
0.0
0.00
0.00
0.0
0.00
0.00
N2
0.0
0.00
0.00
0.0
0.00
0.00
CO
0.0
0.00
0.00
0.0
0.00
0.00
H2
0.0
0.00
0.00
0.0
0.00
0.00
C1
0.0
0.00
0.00
0.0
0.00
0.00
C2
0.0
0.00
0.00
0.0
0.00
0.00
C3
0.0
0.00
0.00
0.0
0.00
0.00
Total
237.0
13.29
100.00
166.9
9.41
100.00
1.2.2.2.2. CNU Off Gas Feedstock Specifications Naphtenic / Sulfidic Sour (Mixed Crude)
Naphtenic / Sulfidic Sweet (Bach Ho Crude)
Phenolic Sour (Mixed Crude)
Phenolic Sweet (Bach Ho Crude)
Std Vol. Flowrate 22.5 m3/hr
29.3
Min
Min
H2O wt%
7
7
7
7
H2S wt%
53
28
-
-
RSH wt%
-
5
-
-
Fuel Gas wt%
40
60
93
93
In normal condition, NH3 rich off gas (from SWS, unit 18) and CNU Off gas (from unit 20) are used as support fuel to achieve 750°C inside the incinerator combustion chamber.
1.2.2.3. Designed Feed Composition and Capacity for Production of Degassed Liquid Sulphur The design feed rate of ARU off gas and H2S rich off gas is proportionally increased from the given feed stock (Refer to section 1.2.2.1) to get 5 ton/day produced degassed liquid sulphur.
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1.2.2.3.1. ARU Off Gas FeedStock Specifications Max. Distillate Case
Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
H2S
129.6
3.802
18.97
164.2
4.818
20.66
NH3
0.0
0.00
0.00
0.0
0.00
0.00
H2O
20.8
1.157
5.77
26.1
1.448
6.21
Cyanide
0.0
0.00
0.00
0.0
0.00
0.00
CO2
645.9
14.676
73.24
729.6
16.578
71.11
N2
1.3
0,045
0.23
1.4
0.049
0.21
CO
0.1
0.005
0.02
0.1
0.005
0.02
H2
0.4
0.188
0.94
0.4
0.202
0.87
C1
1.8
0.110
0.55
2.2
0.137
0.59
C2
1.1
0.04
0.23
1.1
0.04
0.22
C3
1.4
0.046
0.23
1.5
0.050
0.22
Total
801
20.040
100.00
926.6
23.312
100.00
1.2.2.3.2. SWS H2S Rich Off Gas Feedstock Specifications Max. Distillate Case
Max. Gasoline Case
Composition kg/hr
kg-mol/hr
Mol%
kg/hr
kg-mol/hr
Mol%
H2S
103.6
3.039
88.94
69.0
2.026
88.09
NH3
0.0
0.00
0.00
0.0
0.00
0.00
H2O
6.1
0.340
9.96
4.2
0.235
10.21
Cyanide
1.0
0.038
1.10
1.1
0.039
1.70
CO2
0.0
0.00
0.00
0.0
0.00
0.00
N2
0.0
0.00
0.00
0.0
0.00
0.00
CO
0.0
0.00
0.00
0.0
0.00
0.00
H2
0.0
0.00
0.00
0.0
0.00
0.00
C1
0.0
0.00
0.00
0.0
0.00
0.00
C2
0.0
0.00
0.00
0.0
0.00
0.00
C3
0.0
0.00
0.00
0.0
0.00
0.00
Total
110.7
3.416
100.00
74.3
2.300
100.00
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SULPHUR RECOVERY UNIT (SRU)
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DATE: 21/03/08
1.2.3. Product Specifications 1.2.3.1. Degassed Liquid Sulphur Specifications Component
Specification
Purity (as S) (wt %)
≥ 99.9 (dry basis)
Organics (wt %)
≤ 0.02 (dry basis)
Ashes (wt %)
≤ 0.04 (dry basis)
Water (wt %)
≤ 0.10
H2S content (wt.ppm)
≤ 10
Colour
Bright Yellow
1.2.3.2. Emissions from Incinerator The emissions to the atmosphere from the incinerator must not exceed the following limits as per the requirements of the Vietnamese Air Quality Standard TCVN 5939 – 1995: Component
Limit
3
500 max (dry basis)
3
2 max (dry basis)
SO2 (mg/m ) H2S (mg/m ) 3
NOX (mg/m )
1000 max (dry basis)
CO (mg/m3)
500 max (dry basis)
Particulate in Smoke (mg/m3) 3
Dust containing silica (mg/m ) 3
Ammonia (mg/m )
400 (dry basis) 50 (dry basis) 100 (dry basis)
The above specifications are only applicable in normal operation and not in bypass condition).
1.2.4. Utility/Power/Chemicals/Catalyst consumption 1.2.4.1. Utility Consumption The following describes the utility consumption of the SRU based on the Estimated Utility Consumption Document: 8474L-022-CN-0003-001
Design Case – Bach Ho
Note: In the following subsections EXCEPT ELECTRICAL POWER: Page 19 of 161
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( ): Intermittent Producer/Consumer +: Indicates Quantity Produced -: Indicates Quantity Consumed
Service
Duty
Usage Factor
1.2.4.1.1. Electrical Power
BM-2203A
Motor for Dilution Air Blower
200.0
148.00
155.60
N
C
1
BM-2203B
Motor for Dilution Air Blower
200.0
148.00
155.60
N
S
0
A-2201-BM01A
Motor for combustion air blower
22.00
17.00
18.10
N
C
1
A-2201-BM01AA
Motor for canopy fan
0.75
0.60
0.60
N
C
1
A-2201-BM01B
Motor for combustion air blower
22.00
17.00
18.10
N
S
0
A-2201-BM01BA
Motor for canopy fan
0.75
0.60
0.60
N
S
0
A-2201-BM02A
Motor for incineration combustion air blower
30.00
18.20
19.40
N
C
1
A-2201-BM02B
Motor for incineration combustion air blower
30.00
18.20
19.40
N
C
0
A-2201-BM02A
Motor for incinerator combustion air blower
45.00
32.00
34.00
N
C
1
A-2201-BM02B
Motor for incinerator combustion air blower
45.00
32.00
34.00
N
S
0
A-2201-PM01A
Motor for ARU off gas KO drum pump
1.50
1.40
1.50
N
C
1
A-2201-PM01B
Motor for ARU off gas KO drum pump
1.50
1.40
1.50
N
S
0
A-2201-PM02A
Motor for H2S rich SWS off gas KO drum pump
1.50
1.40
1.50
N
I
0.1
A-2201-PM02B
Motor for H2S rich SWS off gas KO drum pump
1.50
1.40
1.50
N
S
0
A-2201-PM03A
Motor for NH3 rich SWS off gas KO drum pump
1.50
1.40
1.50
N
I
0.1
Electrical Power (kW) Item No.
Description
Rated Power
Mech. Consumed Absorbed Normal Normal Active Power Power
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Item No.
Description
Usage Factor
DATE: 21/03/08
Duty
REV: 0
Service
SULPHUR RECOVERY UNIT (SRU)
A-2201-PM03B
Motor for NH3 rich SWS off gas KO drum pump
1.50
1.40
1.50
N
S
0
A-2201-PM04A
Motor for sulphur circulation pump
3.00
3.00
3.20
N
I
0.1
A-2201-PM04B
Motor for sulphur circulation pump
3.00
3.00
3.20
N
S
0
A-2201-PM05A
Motor for Sulphur Pump
5.50
5.50
5.90
N
I
0.1
A-2201-PM05B
Motor for Sulphur Pump
5.50
5.50
5.90
N
S
0
WS-2201
Welding Socket 1 (unit 22)
63.00
63.00
37.10
N
S
0
Electrical Power (kW) Rated Power
Mech. Consumed Absorbed Normal Normal Active Power Power
1.2.4.1.2. Steam, Condensate & Boiler Feed Water
Description
A-2201
HP STM
MP STM
LP STM
HP cond
MP cond
LP cond
BFW (T/h) Losses (T/h) LP BFW
-0.3
-0.1
0.4
0.3
0.1
0.25
-0.8
(-0.4)
(-0.1)
(-0.4)
(0.4)
(0.1)
(0.25)
Steam (T/h)
Item No.
SRU Package
Condensate (T/h)
0.15
st
A-2201
1 start-up & prior to shutdown
(0.15)
1.2.4.1.3. Cooling Water & Fresh Water Item No.
Description
Cooling Water (m3/h)
Fresh Water (T/h)
A-2201
SRU Package
-3.2
-0.2
A-2201
Start-up & shutdown
(-3.7)
-(2.0)
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1.2.4.1.4. Instrument & Plant Air
Item No.
Description
Instrument Air (Nm3/h)
A-2201
SRU Package
-103.4
A-2201
Start-up & shutdown [1]
(-161.6)
Plant Air (Nm3/h) Continuous Intermittent -400.0
Note: [1]: Instrument air consumption is in the extreme case where all control valves and on/off valves act together.
1.2.4.1.5. Nitrogen
Item No.
Description
A-2201
SRU Package
A-2201
Start-up & shutdown
Nitrogen Nm3/h Continuous
Intermittent
-26.0 -138.0
1.2.4.1.6. Furnace & Boilers
Item No.
Description
A-2201
SRU Package
A-2201
Start-up & shutdown Pilot Gas
Furnace & Boilers Fuel Fired (MW) -0.1 (-1.4) -0.1
1.2.4.2. Catalysts & Chemicals The catalyst used in the Claus Catalytic Reactors is Alumina-Titanium for 1st Reactor and only Alumina for 2nd and 3rd Reactors. The Claus catalyst is easily available on the market, from Euro Support or Axens for instance. Claus reactors catalyst is supported on a layer of catalyst support with a remarkable activity towards the Claus reaction. The temperature of structural change of the catalyst is above 550 °C (far from the operating conditions of normal run and during plant heat-up). Catalyst is very resistant to plant upset (the only exception is the plugging by soot), but the following phenomena may decrease the activity: Page 22 of 161
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•
Thermal and Hydrothermal Ageing
•
Sulphate Poisoning
DATE: 21/03/08
In present case Euro Support has been chosen as preferred supplier. The trade names are S-2001 for Alumina-based Catalyst, S-7001 for Titanium Oxide Catalyst and 1/2" Ceramic Balls as active catalyst support. Catalyst Item
Description
A-2201-R-02
1st reactor nd
Catalyst
Volume to be loaded (m3)
Alumina-based catalyst
0.94
Titanium oxide catalyst
0.94
A-2201-R-03
2
reactor
Alumina-based catalyst
1.32
A-2201-R-04
3rd reactor
Alumina-based catalyst
1.88
Catalyst Bed Support Item
Description
Volume to be loaded (m3)
A-2201-R-02
1st reactor
0.28
A-2201-R-03
2nd reactor
0.20
A-2201-R-04
3rd reactor
0.28
When the SRU is processing a feed with the design feed quality, the Claus catalyst life shall be minimum 2 years.
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1.3. Glossary of terms and Acronyms 1.3.1. Acronyms COMPANIES/ORGANISATIONS DQR DQIZMB EVN FW MOC MOSTE MPI SRV TPC
Dung Quat Refinery Dung Quat Industrial Zone Management Board Electricity Authority of Vietnam Foster Wheeler Energy Limited Ministry of Construction Ministry of Science, Technology and Environment Ministry of Planning and Investment Socialist Republic of Vietnam Technip Consortium
OTHERS ACE
ADP AER
Application Control Environment Analyser Data Acquisition System Alarm Display Panel Application Engineers Room
AI
Analyser Indicator
AIT
Auto Ignition Temperature
MCC MCR MCS MOV Control System MDF
AMS
Asset Management System
MIS
ANSI
American National Standards institute
MMS
APC
Advanced Process Control
MMT
API ARU ASC
American Petroleum Institute Amine Regeneration Unit Analyser Speciality Contractor American Society of Mechanical Engineers
MOC MOM MOV
Minimum Maintained Temperature Madrid Operating Center Minutes of Meeting Motor Operated Valve
MP
Medium Pressure
MPT
Minimum Pressurization Temperature
MR
Material Requisition
MRR MSD MSDS MTBF MTTR
Marshalling Rack Room Material Selection Diagram Material Safety Data Sheet Mean Time Between Failures Mean Time To Repair
ADAS
ASME ASP ASTM ATM BCS BEDD BFD BFW
Analyser Systems Package American Society of Testing and Materials Asynchronous Transfer Mode Blending Control System Basic Engineering Design Data Block Flow Diagram Boiler Feed Water
MC
Marshalling Cabinet
MCB
Main Control Building Motor Control Center Main Control Room MOV Control System Main Distribution Frame Management Information System Machine Monitoring System
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BL BOM
Battery Unit Bill of Materials
MTO MTPA
BPC
Blending Properties Control
MVIP
BPCD
Barrels per Calendar Day
NACE
BPSD BRC
Barrels per Stream Day Blending Ratio Control
NCR NDE
CAD
Computer Aid Design
NFPA
CALM CBT
NHT NIR NPSH
Net Positive Suction Head
CCC CCR CCTV CD
Catenary Anchor Leg Mooring Commercial Bid Tabulation Control Complex Auxiliary Room Central Control Complex Continuous Catalytic Reformer Closed Circuit Television Chart Datum
Material Take-Off Metric Tonnes per Annum Multi Vendor Interface Program (Honeywell) National Association of Corrosion Engineers Non Conformance Report Non Destructive Examination National Fire Protection Association Naphtha Hydrotreater (Unit) Near Infrared Spectroscopy
NPV NTU OAS OJT
CDU
Crude Distillation Unit
OM&S
OSBL
Net Present Value Naphtha Treater Unit Oil Accounting System On Job Training Oil Movement and Storage Control System Oil Movement and Storage automation Operation Override Switch Operations Planning and Scheduling System Outside Battery Limit
OTS
Operator Training Simulator
CCAR
CENELEC CFC CFR C&I CMMS CNU
European Committee for Electrotechnical Standardization Chlorofluorocarbons Cooperative Fuel Research (Engine) Control and Instrumentation Computerized Maintenance Management System (Spent) Caustic Neutralization Unit
OMSA OOS OPSS
PABX
CPI
Corrugated Plate Interceptor
PAGA
CSI DAF DAU DCS
Control Systems Integrator Dissolved Air Flotation Data Acquisition Unit Distributed Control System
PCB PFD PFM PDB
DEA
Diethanolamine
PGC
Private Automatic Branch Exchange Public Address / General Alarm Printed Circuit Board Process Flow Diagram Path Find Module Project Documents Base Process Gas Chromatograph (Analysers)
PHD
Plant History Database
DMDS DMS
Detailed Environmental Impact Assessment Dimethyldisulfide Document Management System
PI PIB
DNV
Det Nork Veritas
PID
Plant Air Process Interface Building Piping and Instrument Diagram Project Implementation Manual Process Knowledge System (Honeywell DCS) Pipeline End Manifold Planning Project Management
DEIA
DPTD DQMIS DQRP DVM DWT
Design, Pressure, Temperature Diagram Dung Quat Management Information System Dung Quat Refinery Project Digital Video Manager Dead Weight Tonnes
PIM PKS PLEM PLG PMC
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EL EOR
ERP ES ESD ETP ETS EWS FDC FAP
Equipment List End of Run Electronic Document Management System Electromagnetic Compatibility Engineering Procurement, Construction and Commissioning Enterprise Resource Planning Ethernet Switch Emergency Shut Down Effluent Treatment Plant Effluent Treatment System Engineering Work Station Feed Development Contract Fire Alarm Panel
FAT
Factory Acceptance Test
FEL
Front End Loading
F&G FIU FIC
Fire and Gas System Field Interface Unit Flow Indicating Controller
FM
Factory Mutual (Approval body)
FOTC
Fibre Optic Termination Cabinet
EDMS EMC EPC
FTE GC GFT
Fail Safe Controller (Honeywell ESD) Fault Tolerant Ethernet Gas Chromatograph Ground Fault
HAZAN
Hazard Analysis Study
HAZOP
Hazard and Operability Study
HDT
Hydrotreater
HEI
Heat Exchange Institution
HHP HGO HIC HP HSE
High High Pressure (Steam) Heavy Gas Oil Hydrogen Induced Cracking High Pressure Health, Safety and Environment Heating Ventilation Air Conditioning Instrument Air International Civil Aviation Organisation Instrument Clean Earth
FSC
HVAC IA ICAO ICE
REV: 0
DATE: 21/03/08
PMI PMT
Consultant Positive Material Identification Project Management Team
PO
Purchase Order
POC
Paris Operating Center
PP
Project Procedure
PPB PPM PRU PWHT QA QC RA R&D
Parts per Billion Parts per Million Propylene Recovery Unit Post Weld Heat Treatment Quality Assurance Quality Control Risk Analysis Research and Development Real Time Database RDBMS Management System Residue Fluid Catalytic RFCC Cracking RFSU Ready for Start-Up RLU Remote Line Unit ROW Right of Way Refinery Performance RPMS Management System Resistance Temperature RTD Detector Real Time Data Base RTDB (System) RTU Remote Terminal Unit SAT Site Acceptance Test SBT Segregated Ballast Tanks Software Bypass Management SBMS System Supervisory Control and Data SCADA Acquisition SCC Satellite Control Complex Simulation Control SCE Environment SCR Satellite Control Room SDH Synchronous Digital Hierarchy SE Safety Earth S&E Safety & Environmental SGS Safeguarding System SOE
Sequence of Events
SOR
Start of Run
SOW
Scope of Work
SP
Specification Page 26 of 161
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ICS
Integrated Control System
SPIR
IIP I/O IP
SPM SR SRU STC
Construction Standard
IRP IRR
Initial Interface Plan Input/Output Institute of Petroleum Instrumented Protective System Interposing Relay Panel Internal Rate of Return
Spare Parts and interchangeability Record Single Point Mooring Scope of Supply Sulphur Recovery Unit
STD STEL
IS
Intrinsically Safe
SVAC
ISA ISE ISBL ISOM
Instrument Society of America Intrinsically Safe Earth Inside Battery Limit Isomerisation Unit
SWS TAS TBT
ITB
Invitation to Bid
TCF
ITP
Inspection and Test Plan
TCM
JB
Junction Box
TEMA
JCC
Jetty Control Complex
TGIF
JCR JSD JSS
Jetty Control Room Job Specification for Design Job Specification for Supply
TLCR TLCS TN
JVD
Joint Venture Directorate
TPS
KLOC KTU LAN LCO LCOHDT
Kuala Lumpur Operating Center Kerosene Treatment Unit Local Area Network Light Cycle Oil LCO Hydrotreater
TQM TS TWA UFD U/G
LDE
Lead Discipline Engineer
UL
Design Standard Short Term Exposure Limit Shelter Ventilation and Air Conditioning System (Analyser houses) Sour Water Stripping (Unit) Terminal Automation System Technical Bid Tabulation Temporary Construction Facilities Task Control Module Tubular Exchanger Manufacturers' Association Temperature Gauge Indication Facilities (Tankage) Truck Loading Control Room Truck Loading Control System Transmittal Note Total Plant Solution (Honeywell) Total Quality Management Terminal Server Time Weighted Average Utility Flow diagram Underground Underwriter Laboratories (Approval body)
IPS
LEL LGO LIMS
Lower Exposition Limit (F&G, Analysers) Light Gas Oil Laboratory Information Management System
UPS
Uninterruptible Power Supply
VDU
Visual Display Unit
VPU
Vendor Package Unit
LIS
Laboratory Information System
WABT
LLU LP LPG LTU LPG
Local Line Unit Low Pressure Liquefied Petroleum Gas Treater Unit
WBS WHB YOC
Weight Average Bed Temperature Wash Breakdown Structure Waste Heat Boiler Yokohama Operating Center
1.3.2. Glossary Refer to separate glossary.
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Course Content: Section 1 - General Description Section 2 - Process Flow Description
X
Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 2 : PROCESS FLOW DESCRIPTION
Figure 4: SRU Block Flow Diagram
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Figure 5: SRU Simplified Process Flow Diagram Page 30 of 161
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2.1. Claus Section 2.1.1. ARU Off Gas from Unit 19 & H2S Rich Off Gas from Unit 18 The ARU Off Gas (from Unit 19) and the H2S Rich Off gas (from Unit 18) are fed to 2 dedicated KO drums (A-2201-D-01 & A-2201-D-02), provided with mist eliminators, in order to separate acid condensate and all liquid carry-over coming from upstream units. Indeed liquid carry-over is very dangerous to the life of downstream equipment and to the correctness of operation. 2 dedicated pumps, A-2201-P-01 A/B & A-2201-P-02 A/B, send acid condensate collected in A-2201-D-01 & A-2201-D-02 respectively to closed drain drum in unit 19 and unit 18 respectively. The pumps operate on level control of their respective KO drum. ARU Off gas from KO drum A-2201-D-01 is heated against HP superheated steam in the ARU off gas preheater A-2201-E-01. The steam is fed to A-2201-E-01 on temperature control of the ARU off gas at the discharge of the preheater. ARU off gas is then fed to the burner of the thermal reactor A-2201-R-01 on flow control reset by PIC-529 at the off gas outlet of A-2201-D-01. Part of the ARU off gas is not fed to the thermal reactor burner but flows straight to the 2nd zone of the reactor. After being mixed with the off gas from A-2201-D-01 downstream of the ARU off gas preheater A-2201-E-01, H2S rich SWS off gas from KO drum A-2201-D-02 is fed to the burner of the thermal reactor A-2201-R-01 on flow control reset by PIC530 at the off gas outlet of A-2201-D-02.. Condensation in the separator downstream line is prevented by low pressure steam tracing. In case of the Claus section is temporarily out of operation, the ARU Off Gas and the H2S Rich Off Gas are bypassed to the Incinerator (A-2201-H-01) via dedicated lines from each K.O. drum.
2.1.2. Combustion air feeding to Claus section Air required for acid gases combustion is compressed in the Combustion Air Blower A-2201-B-01 A/B. The compressed air pressure at the blowers discharge is controlled by PIC-545 which vent excess air to atmosphere. A small fraction of the compressed air is used to strip H2S from produced sulphur, inside the Liquid Sulphur Degassing Pit (A-2201 -TK-01). Once compressed, combustion air is preheated in the Combustion Air Preheater A-2201-E-02 against HP superheated steam in order to increase as much as possible the adiabatic flame temperature in Thermal Reactor (A-2201-R-01). The flow of steam to the preheater is temperature controlled by TIC-523 measuring the temperature of the heated air at A-2201-E-02 discharge. Then combustion air is fed to the burner of the thermal reactor A-2201-R-01.
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2.1.3. Thermal Reactor and Burner Thermal Reactor (A-2201-R-01) and relevant burner are the most important items in the Claus section and correct operation in that area is mandatory to assure smooth run. Combustion of acid gases is done under highly controlled condition, in order to assure proper air feeding and, as a result, proper run conditions. All acid stream flow rates are corrected for pressure and temperature and are controlled keeping the header pressure at the constant value. Combustion air is managed in order to assure proper flow rate. The air fed to the main burner is exactly sufficient to accomplish the complete oxidation of hydrocarbons and all the impurities (such as HCN) present in the total feed gases and to burn approximately one-third of the total H2S to SO2 maximizing the overall sulphur recovery efficiency. Burner is provided with a fuel gas gun and ancillaries to burn refinery fuel gas in heating up conditions, when the unit is too cold to accept acid gas in safe conditions. Fuel gas line is equipped with flow control system and shut down valves. Air flow rate required for proper combustion is fed via ratio control, using same criteria as for acid gas feeding. The Thermal Reactor (A-2201-R-01) is a 2 zones reaction furnace, each zone operating at different temperature: •
In the 1st zone all combustion air, all H2S Rich Off gas and a fraction of ARU Off Gas are burnt. Combustion air flow rate present in flame area is relatively higher than the required for Claus reactions, due to the by-pass of the part of ARU Off Gas flow rate to the second zone. The resulting flame temperature is higher than expected (regarding standard Claus reactions only) and in this way is guaranteed flame stability and complete hydrocarbon and impurities combustion.
•
In the 2nd zone the hot flue gas from the first zone and the remaining ARU Off Gas are mixed. As the remaining ARU Off Gas is injected, temperature is lowered and modifications in flue gas composition take place in order to satisfy the overall heat and material balances.
Optimum temperature is achieved by-passing about 50% of ARU Off Gas to the second zone at design flowrate. The flue gas leaving then leaves the reactor and enters into the Claus Waste Heat Boiler and Sulphur Condensers A-2201-SG-01. The temperature inside the first zone is approx. 1240°C and the temperature of flue gas leaving the reactor is approx. 900°C. The expected overall conversion of H2S to sulphur in the Thermal Reactor (A2201-R-01) is approx. 16.4% at design conditions (Max. Gasoline Case).
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2.1.4. Claus Waste Heat Boiler and 1st Sulphur Condenser The Claus Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 is a 5 passes boiler producing saturated low pressure steam at 4.1 kg/cm2G: •
pass I = 1st pass of WHB
•
pass II = 2nd pass of WHB
•
pass III = 1st sulphur condenser
•
pass IV = 2nd sulphur condenser
•
pass V = 3rd sulphur condenser
LP steam is generated shell side and delivered to the LP steam header. Produced steam is controlled at 4.1 kg/cm2G by pressure controller PIC-555. Boiler feed water is fed to the A-2201-SG-01 under level control of A-2201-SG-01 by LIC-514. A-2201-SG-01 is equipped with the Claus Blow Down Cooler (A-2201-D-06), on which service water is used in open circuit to cool the water blown down from A2201-SG-01. The water blown down is then discharged into oily surface water sewer at a maximum temperature of 50°C. The combustion products leaving the Thermal Reactor A-2201-R-01 are sent into the tubes and are cooled down to about 240°C in pas ses I & II of the Claus Waste Heat Boiler. The process gas leaving the Claus Waste Heat Boiler is further cooled down to about 162°C in the 1 st Sulphur Condenser (A-2201-SG-01 pass III). The sulphur produced in the A-2201-R-01 is condensed in the tube side of A-2201-SG-01 pass III and discharged by gravity to the sulphur pit (A-2201-TK-02) through its dedicated sulphur seal leg (A-2201-D-05 A).
2.1.5. 1st Process Gas Reheater & 1st Catalytic Reactor The process gas leaving the 1st Sulphur Condenser (A-2201-SG-01) pass III is heated up to 240°C in the 1 st Process Gas Reheater (A-2201-E-03), by means of superheated HP steam fed under temperature control by TIC-541 of the process gas leaving the reheater, prior to being sent to the 1st Catalytic Reactor (A-2201R-02). The process gas enters the A-2201-R-02 where the Claus reaction between H2S and SO2 continues until equilibrium is reached at that condition, producing elemental Sulphur. Equilibrium temperature is approximately the temperature of process gas leaving the reactor (A-2201-R-02), i.e. 321°C at design con ditions (Max. Gasoline Case).
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2.1.6. 2nd Condenser, 2nd Process Gas Reheater & 2nd Catalytic Reactor The process gas leaving the 1st Catalytic Reactor (A-2201-R-02) is fed to the 2nd Sulphur Condenser (A-2201-SG-01 pass IV). The sulphur produced in the A-2201R-02 is condensed in the tube side of A-2201-SG-01 pass IV and discharged by gravity to the Sulphur Pit (A-2201-TK-02) through its dedicated sulphur seal leg (A-2201-D-05B). A mist eliminator device is provided on the outlet channel of the A-2201-SG-01 pass IV to remove the sulphur entrained as mist in the process gas. The process gas leaving 2nd Sulphur Condenser (A-2201-SG-01 pass IV) at 170°C is fed to the 2nd Process Gas Reheater (A-2201-E-04) to be heated up to 205°C by means of superheated HP steam fed under temperature control by TIC-539 of the process gas leaving the reheater. The process gas then enters the 2nd Catalytic Reactor (A-2201-R-03) where the Claus reaction between H2S and SO2 continues until equilibrium is reached at these conditions, producing elemental Sulphur. Equilibrium temperature is approximately 223°C at d esign conditions (Max. Gasoline Case).
2.1.7. 3rd Condenser, 3rd Process Gas Reheater & 3rd Catalytic Reactor The process gas leaving the 2nd Catalytic Reactor (A-2201-R-03) is fed to the 3rd Sulphur Condenser (A-2201-SG-01 pass V). The sulphur produced in the A-2201R-03 is condensed in the tube side of A-2201-SG-01 pass V and discharged by gravity to the Sulphur Pit (A-2201-TK-02) through its dedicated sulphur seal leg (A-2201-D-05C). A mist eliminator device is provided on the outlet channel of the A-2201-SG-01 pass V to remove the sulphur entrained as mist in the process gas. The process gas leaving the 3rd Sulphur Condenser (A-2201-SG-01 pass V) at 162°C is fed to the 3 rd Process Gas Reheater (A-2201-E-05) to be heated up to 190°C by means of superheated HP steam fed under te mperature control by TIC540 of the process gas leaving the reheater. Heated process gas then enters the 3rd Catalytic Reactor (A-2201-R-04) where the Claus reaction between H2S and SO2 continues until equilibrium is reached under these conditions, producing Sulphur. Equilibrium temperature is approximately 193°C at d esign conditions (Max. Gasoline Case).
The .following DCS printout shows the catalytic reactors:
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2.1.8. Final Sulphur Condenser and Tail Gas Coalescer The process gas leaving the 3rd Catalytic Reactor (A-2201-R-04) at 193°C is fed to the tube side of the Final Sulphur Condenser (A-2201-E-06) for the final cooling against boiler feed water (shell side), to recover sulphur produced in the A-2201R-04. Cooling down has been maximized to decrease to the minimum the sulphur present as elemental sulphur in the tail gas. The sulphur produced is condensed in the tube side of A-2201-E-06 and discharged by gravity to the Sulphur Pit (A-2201-TK-02) through its dedicated sulphur seal leg (A-2201-D-05D). The sensible heat of the process gas entering the Final Sulphur Condenser (A2201-E-06) vaporizes the BFW coming from the Steam Condenser (A-2201-E-07). Produced steam is pressure controlled at 1 kg/cm2G (120°C) by PIC-562 on the A-2201-E-06 outlet line to the steam condenser, in order to ensure that in all operating conditions, the tube temperature of A-2201-E-06 is always higher than freezing point of sulphur, avoiding operating problems, but still as low as possible. Steam fed to A-2201-E-07 is condensed against cooling water before being returned to the final sulphur condenser. For warm-up or turndown operations, to avoid sulphur solidification, LP Steam is send to the shell of the Final Sulphur Condenser (A-2201-E-06) via a dedicated sparger. The process gas coming from the A-2201-E-06 is fed to the Tail Gas Coalescer (A-2201-D-04) to remove any sulphur mist from the process gas. Condensed liquid elemental sulphur is then sent by gravity to the Sulphur Pit (A-2201-TK-02) via sulphur seal leg (A-2201-D-05D). The tail gas leaving the Sulphur Coalescer (A-2201-D-04), at approx. 130°C, is fed directly to the Incinerator (A-2201-H-01).
2.2. Liquid Sulphur Storage Pit The elemental liquid sulphur condensed in the 4 condensation steps is discharged by gravity to the Liquid Sulphur Storage Pit (A-2201-TK-02) through the sulphur seal legs (A-2201-D-05A/B/C/D). Each sulphur seal leg has been provided with dedicated filter (perforated plate type) to avoid plugging by catalyst and refractory dust. Sulphur seal legs are fully steam jacketed and sized to avoid blow up of process gas in all operating conditions, also in case of heavy upset. Note that each sulphur seal leg has a dedicated manual, steam jacketed valve, to isolate the items in case of scheduled maintenance and during the dry out operations. In no other conditions the valve should be closed. Sulphur pit is divided in two different sections, a non-degassed sulphur pit and a degassed sulphur storage pit: •
The non-degassed sulphur storage section, sized for about one day of production of Claus section, is equipped with 2 fully steam jacketed sulphur pumps (A-2201P-04 A/B). Page 36 of 161
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A-2201-P-04 A/B transfer continuously the produced sulphur to the Liquid Sulphur Degassing Pit (A-2201-TK-01). •
The degassed sulphur storage section is sized for about one day of production of Claus section and is equipped with two fully steam jacketed sulphur pumps (A2201-P-05 A/B) that transfer the degassed sulphur to the Sulphur Apron.
Sulphur pit operates under approx. -50 mmH2O (G). Air intake is sucked from A-2201TK-01 by the Pit ejector (A-2201-J-01 A/B) which is fully steam jacketed. Air is then discharged to the Incinerator (A-2201-H-01).
2.3. Sulphur Degassing Section Liquid sulphur leaving the Claus section may cause environmental and safety problems due to the presence of H2S, which is partly physically dissolved and partly present in the form of polysulphides (H2Sx). On the average, liquid sulphur contains 250-300 wt.ppm H2S. During the transport and storage the H2S will be released from the sulphur resulting in the creation of an explosive mixture if the lower explosion limit of H2S in air exceeded. This limit ranges between 3.7 vol% H2S at 130°C and 4.3 vol% H2S at ambient tempe rature. The sulphur degassing process is used to strip liquid sulphur down to 10 wt.ppm H2S/H2SX, which is the safe level top avoid exceeding of the lower explosion limit. For this, process air from A-2201-B-01A/B is bubbled through the sulphur to decompose the polysulphides and to release the physically dissolved H2S, without chemicals addition. The degassing is carried out in the Liquid Sulphur Degassing Pit (A-2201-TK01) provided with suitable perforated plates to allow contact between not degassed sulphur and stripping air. The air bubbling through the sulphur decreases the partial pressure of H2S and induces a vigorous agitation. Consequently a good contact between liquid sulphur and oxygen is obtained, which accelerates the decomposition of polysulphides into H2S and S, strips the dissolved H2S from the sulphur and oxidises a part of H2S to sulphur. An additional amount of air (sweep air) is drawn into the Liquid Sulphur Storage Pit (A2201-TK-02) to ventilate the vapour space above the sulphur level and to keep the H2Sconcentration below its lower explosion limit. The stripped H2S is removed by the steam ejector (A-2201-J-01A/B) and sent to the Incinerator (A-2201-H-01). Degassed elemental sulphur then flows to the degassed sulphur storage section before being pumped by A-2201-P-05 A/B to the sulphur apron.
The following DCS printout shows the sulphur storage pit and degassing section:
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2.4. Incinerator Section The tail gas leaving the Claus section, as well as vent air from ejectors, are fed to the Incinerator (A-2201-H-01) to burn the residual H2S. In order to meet the requirements on the flue gas delivered to the atmosphere, dilution air from Dilution Air Blower (B-2203 A/B) is fed to the Stack. In normal condition NH3 Rich Off gas (from Unit 18) and CNU Off gas (from Unit 20) are used as support fuel to achieve 750°C inside the co mbustion chamber. A refinery fuel gas is used to guarantee the maintenance of the required temperature in case of NH3 Rich Off gas and/or CNU Off gas flowrate fluctuations. NH3 rich SWS off gas is fed to the NH3 Rich Off Gas KO Drum A-2201-D-03, provided with mist eliminator in order to separate NH3 condensate and all liquid carry-over coming from NH3. The NH3 Rich Off Gas KO Drum Pumps A-2201-P-03 send any condensate collected in A-2201-D-03 back to the closed drain drum in SWS unit. The pumps operate on level control of A-2201-D-03. The separated off gas from A-2201-D-03 is then sent to the combustion chamber of the incinerator A-2201-H-01. NH3 Rich Off gas and/or CNU Off gas or support fuel gas are burnt with combustion air from the Incinerator Combustion Air Blower (A-2201-B-02A/B), operating at relatively high air excess in order to achieve optimum flame temperature. The Claus tail gas and the vent gas from pit ejectors (A-2201-J-01 A/B) are mixed with hot flue gas, at controlled temperature, and all sulphur bearing compounds are oxidised to SO2. Expected residual H2S content is lower than 10 vol.ppm. The combustion air is supplied by the Incinerator Combustion Air Blower (A-2201-B-02 A/B) and controlled as a ratio to the NH3 Rich Off gas, CNU Off gas and refinery fuel gas flow. If the Claus section is not in operation, all the ARU Off Gas and H2S Rich Off gas are sent to the Incinerator Burner.
2.5. DCS Printouts – SRU Process Overview The following DCS printouts show the overview of the SRU process:
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Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control
X
Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 3 : PROCESS CONTROL The following is a description of the main control loops of the SRU. For a detailed description of the control loops and the controllers, refer to the control narrative, vendor document No. 8474L022-A3505-4110-300-003. 3.1. Control narrative & operating parameters 3.1.1. ARU Off Gas KO Drum A-2201-D-01 Pressure Control This control system acts in order to maintain a stable pressure in the ARU off gas KO drum feeding the thermal reactor when the SRU is in normal operation mode (or the incinerator when the SRU is in bypass mode). The pressure in A-2201-D-01 is controlled by 022-PIC-529 acting in split range control on 2 control valves: •
022-PV-529 controlling the ARU gas flow to the incinerator A-2201-H-01
•
022-FV-530 controlling the ARU gas flow to the thermal reactor A-2201-R01. In that case, PIC-529 is in cascade with FIC-530
In case of a pressure increase measured by PT-529 at the outlet of A-2201-D-01, PIC-529 will 1st open the FV-530 by resetting the setpoint of FIC-530 via PY-529A, while PV-529 will remain close. This is the low range case (0-50%). If the pressure continue to increase (high range: 50-100%), then PIC-529 will open PV-529 via PY-529B, while FV-530 remains open.
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Figure 6: A-2201-D-01 Pressure Control Since in normal operation, the ARU off gas line to the incinerator is closed by a cut-off valve 022-XV-516, the action of PV-529 valve opening has no effect in mitigating the pressure increase. Therefore, the ARU off gas will be flared to the sour flare by the control valve on the upstream unit (i.e.: Amine Regeneration). In the same manner, during SRU bypass operation, the ARU off gas line to the Thermal Reactor is closed by a cut-off valve 022-XV-505, therefore the action of 022-FV-530 valve opening has no effect in mitigating the pressure increase and the ARU off gas will be flared to the sour flare header by the control valve on the upstream (i.e.: Amine Regeneration). There is only one operating mode during which both cut off valves are opened: This is when the plant is in bypass mode with the incinerator receiving acid gases and the SRU is to be re-started with acid gases. In this case, FV-530 is operated Page 45 of 161
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in manual mode (gradual opening) by acting directly on the controller FIC-530. This cause a pressure decrease and PIC-529 controller output acts by closing gradually PV-529 up to complete closure. This way, gradual acid gas cut-in to the thermal reactor and acid gas cut-off the incinerator are ensured. 3.1.2. H2S Rich SWS Off Gas KO Drum A-2201-D-02 Pressure Control The pressure control of A-2201-D-02 is strictly the same than the pressure control of A-2201-D-01: This control system acts in order to maintain a stable pressure in the H2S rich off gas KO drum feeding the thermal reactor when the SRU is in normal operation mode (or the incinerator when the SRU is in bypass mode). The pressure in A-2201-D-02 is controlled by 022-PIC-530 acting in split range control on 2 control valves: •
022-PV-530 controlling the H2S rich off gas flow to the incinerator A-2201H-01
•
022-FV-515 controlling the H2S rich off gas flow to the thermal reactor A2201-R-01. In that case, PIC-530 is in cascade with FIC-515
In case of a pressure increase the controller will first open FV-515 while PV-530 will remain close. Then PIC-530 will open PV-530, while FV-530 remains open.
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Figure 7: A-2201-D-02 Pressure Control Since in normal operation, the H2S rich SWS off gas line to the incinerator is closed by a cut-off valve 022-XV-516, the action of PV-530 valve opening has no effect in mitigating the pressure increase. Therefore, H2S rich SWS off gas will be flared to the sour flare by the control valve on the upstream unit (i.e.: SWS). In the same manner, during SRU bypass operation, the H2S rich SWS off gas line to the Thermal Reactor is closed by a cut-off valve 022-XV-501, therefore the action of FV-515 valve opening has no effect in mitigating the pressure increase and the H2S rich SWS off gas will be flared to the sour flare header by the control valve on the SWS. There is only one operating mode during which both cut off valves are opened: This is when the plant is in bypass mode with the incinerator receiving acid gases and the SRU is to be re-started with acid gases. In this case, FV-515 is operated in manual mode (gradual opening) by acting directly on the controller FIC-515.
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This cause a pressure decrease and PIC-530 controller output acts by closing gradually PV-530 up to complete closure. This way, gradual acid gas cut-in to the thermal reactor and acid gas cut-off the incinerator are ensured.
The following DCS printout shows the ARU off gas KO drum and the H2S rich SWS off gas KO drum:
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3.1.3. A-2201-D-01/02/03 Level Control The level in the KO drums A-2201-D-01/02/03 is controlled by LIC-503/504/505 on/off controllers with the starting/stopping of the KO drum pump A-2201-P01/02/03 A/B, respectively. The control scheme is the same for these 3 KO drums: For each of them, the level controller of the KO drum will start the duty pump when the level increases to the upper setpoint and will stop the pump when the level in the KO drum falls to the lower setpoint. For this to be effective, the duty has to be selected in remote (at local selector) and auto operation (on the DCS). In addition, if pump doesn’t start at upper setpoint or doesn’t stop at lower setpoint, High and Low level alarms will be respectively displayed at DCS. The pumps will also be tripped in case of low low level (refer to section 4 of the present document).
The following DCS printout shows the NH3 rich SWS off gas KO drum:
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3.1.4. Thermal Reactor Combustion Air Control The task of the Burner Control System is to control the amount of combustion air to the main burner and to provide smooth operation. According to the overall operation when optimisation of sulphur recovery is the required goal (Claus Mode operation) the control system ensures that the proper amount of the feed H2S will be burnt in order to obtain the downstream Claus reaction as complete as possible. So, during Claus Mode operation, a too high or too low air flowrate will decrease the sulphur recovery rate, and once a gas having an incorrect air/gas ratio has entered the main burner, the resulting conversion loss cannot be compensated. The correct amount of air is determined by two process variables: the feed gas flowrate and the specific air demand of the feed gas, which depends upon the H2S content and the content of other combustible components. The combustion air control system must adjust the air flow according to these two variables. The feed gas flowrate can vary quite fast; consequently the ratio control part of the system must be very fast and accurate. The variations of the specific air demand are normally much slower. Changes of this demand are detected downstream the Claus reactors, by measuring the H2S content in the tail gas. If this content shows a deviation from the desired value, the Operator will adjust the desired air/gas ratio.
3.1.4.1. Main Combustion Air Flowrate to Thermal Reactor The purpose of this control is to maintain correct combustion conditions within the Thermal Reactor A-2201-R-01 by ensuring the correct ratio of combustion air to acid gases or by ensuring the correct ratio of combustion air to Fuel Gas during the fuel gas combustion. The control scheme is a feed-forward air control system based on predetermined feed gases compositions. Variations in acid gases compositions are handled by the feed-back control signal from the tail gas analyzer to the trim air control loop (see next paragraph). Main combustion air flowrate is controlled by FIC-527 receiving its setpoint from the combustion control system. FIC-527 setpoint is determined by the flowrates of combustible gases in the following manner: •
Fuel Gas flowrate is measured by FIC-526 and the value is multiplied by a proper Air/Fuel Gas Ratio in the block FY-554. Air/Fuel Gas Ratio is assigned by a manual setting station HIC511. The output of the ratio function (or manipulated variable) stands for the air quantity required to burn with a predetermined ratio the Fuel Gas.
•
H2S Rich Off Gas flowrate to the thermal reactor 1st zone is measured by FIC-515 and the signal enters the compensation block FY-548. Then the compensated H2S Rich Off Gas flowrate value from FY-548 is multiplied by a proper Air/ H2S Rich Off Gas ratio in the FY-549 block. Air/ H2S Rich Off Gas ratio is assigned by a manual setting station HIC-509. The output of the ratio block Page 52 of 161
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represents the air quantity required in order to burn with a predetermined ratio the H2S Rich Gas. •
ARU Off Gas flowrate to the thermal reactor 1st zone is measured by FIC-530 and the signal enters the compensation flow block FY551. ARU Off Gas flowrate to thermal reactor 2nd zone is measured by FIC-524 and the signal enters the compensation block FY-522. The 2 compensated ARU Off Gas flowrates values are summed up in FY-558 block, generating as output the total ARU off gas flowrate. This value is then multiplied by a proper Air/ARU off gas ratio in the FY-550 block. Air/ARU gas ratio is assigned by a manual setting station 022-HIC-510. The ratio function output represents the air quantity needed in order to burn with a predetermined ratio the ARU Off Gas.
•
The 3 air flowrate contributions calculated above are summed up in the FY-553 block and the resulting manipulated variable represents the total air quantity needed to maintain correct combustion conditions.
The output from FY-553 block is assumed as setpoint for FIC-527 which regulates the main combustion air flowrate to the thermal reactor with FV527 accordingly. In addition, FIC-527 receives a signal from FY-556 compensation block in order to compensate the flowrate according to the actual conditions.
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Figure 8: Main Combustion Air Flowrate Page 54 of 161
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3.1.5. Trim Air Flow to Thermal Reactor Control by Tail Gas Analysis The purpose of the controller is to control the efficient acid gas conversion within the thermal reactor by monitoring the residual levels of H2S and SO2 in the tail gas from the Claus Section. The trim air flowrate permits to achieve he optimum H2S/SO2 ratio of 2:1 in tail gas leaving the Tail Gas Coalescer A-2201-D-04. The controller acts in feed-back control mode on the trim air control valve FV-022 and takes into account small deviations of acid gases composition with respect to the predetermined one.
Figure 9: Trim Air Flowrate to Thermal Reactor
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Air demand signal is measured by 022-AT-501 and provides set point for combustion trim air controller FIC-522. The later adjust the trim air flowrate with FV-522 on the trim air line to the thermal reactor. When the output value of the controller AIC-501 is less than zero, the setpoint of FIC-522 is increased thereby opening the control valve. When the output value of the controller AIC-501 is greater than zero, the setpoint of FIC-522 is decreased, thereby closing the control valve. 022-AY-501 calculates the air demand of the Claus section expressed in terms of the stoichiometric air required by the process, that is 2 x [SO2] – [H2S]. When the optimum H2S/SO2 content ratio of 2:1 in tail gas is achieved, then the air demand calculated is zero and no control action is required. When the calculated air demand is greater than zero (SO2 content ≥ 0.5 H2S content in the tail gas) it means that there is an excess of air and the controller shall close the control valve. Conversely, when the air demand is less than zero, there is deficient air and the controller shall open the control valve. The output of trim air controller 022-AIC-501, representing the desired air/gas ratio, is a very important signal. Normally it varies between very narrow limits, following the specific air demand of the feed gases. In order to avoid heavy upsets, e.g. as a consequence of H2S analyser malfunctioning, this signal should be limited slightly outside the normal operating range. Outside the expected range, the controller 022-AIC-501 is switched automatically to manual mode and the air/gas ratio control is operated in automatic mode, using the manual output signal as the ratio set points. If required, these set points should be changed very slowly and carefully.
3.1.6. Quench Steam Flowrate Control This control is design to gradually increase and maintain correct combustion temperature within the thermal reactor by feeding steam as a tempering medium in a suitable ratio to fuel gas. Quench steam flowrate is controlled by FIC-025 receiving its setpoint from the combustion control system. FIC-525 set point is determined by the fuel gas flowrates in the following manner: Fuel gas flowrate is measured by FIC-526 and the process value is multiplied by a proper Steam/Fuel Gas ratio in the FY-555 block. Steam/Fuel Gas ratio is assigned by a manual input setting station HIC-512. The output of the ratio block represents the steam quantity needed in order to temper the combustion temperature in the thermal reactor. The output from 022-FY-555 block is assumed as setpoint for FIC-525 which regulates the flow of steam to the thermal reactor with FV-525. The following DCS printouts show the thermal reactor, waste heat boiler and sulphur condenser section: Page 56 of 161
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3.1.7. Combustion Air to Incinerator Flowrate Control (A-2201-H-01) The control system is designed to maintain stable and adequate combustion conditions within the incinerator. Combustion air flowrate controller FIC-539 setpoint is determined by the flowrates of combustible gases in the following manner: •
Fuel Gas flowrate is measured by FI-535 and the value is multiplied by a proper Air/Fuel ratio in the FFY-535 block. Air/Fuel ratio is assigned by a manual setting station HIC-504. The manipulated variable represents the air quantity needed in order to burn with a predetermined excess air the fuel gas.
•
CNU Off Gas flowrate is measured by FI-538 and the value is multiplied by a proper Air/CNU Off Gas ratio in the FFY-538 block. Air/CNU Off Gas ratio is assigned by a manual setting station HIC-506. The manipulated variable represents the air quantity needed in order to burn with a predetermined excess air the CNU Off Gas.
•
NH3 Rich SWS Off Gas flowrate is measured by FI-518 and the value is multiplied by a proper Air/ NH3 Rich SWS Off Gas ratio in the FFY-518 block. Air/ NH3 Rich SWS Off Gas ratio is assigned by a manual setting station HIC-505. The manipulated variable represents the air quantity needed in order to burn with a predetermined excess air the NH3 Rich SWS Off Gas.
•
The 3 contributions calculated above are summed up in the FFY-539B block and the resulting manipulated variable represents the total air quantity needed to burn the combustible gases in order to result the desired degree of oxygen excess in the tail gas.
The output from FFY-539B block is then compare to the thermal reactor temperature (with the output from TY-560B) in the high signal selector FFY-539A, which selects the greatest signal to reset the setpoint of FIC-539. FIC-539 controls the air flowrate from the combustion air preheater to the thermal reactor with FV539. FIC-539 is reverse acting: The valve FV-539 opening will be decreased when the process variable of FIC-539 increases.
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Figure 10: Control of Combustion Air Flowrate to Incinerator
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3.1.7.1. Incinerator Residence Zone Temperature Control (A-2201-H-01) The control system is deigned to maintain stable and adequate temperature conditions within the incinerator. Incinerator residence zone temperature is controlled by TIC-560 acting in split range control on 2 control valves: •
TV-560 controlling the fuel gas flow to the incinerator (In the low range (0-50%) signal output from TIC-560)
•
FV-539 controlling the air flow to the incinerator (In the high range (50-110%) signal output from TIC-560). In this case, TIC-560 is in cascade with FIC-539.
When the temperature increases, the controller output first closes TV-560 by means of TY-560A while TY-560B output remains zero. In this condition the controller action is ignored on FIC-539 set point and FV-539 valve remains in its position determined only by the setpoint based on combustible gases air requirement, as described previously. If the temperature rise continues until TV-560 is fully closed, then TY560B output is increased and the controller action enters the FFY-539A, thus contributing to the setpoint of FIC-539.
The following DCS printout shows the incinerator section:
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3.1.8. Inter-Unit Controls & Interfaces There are no inter-unit controls in the SRU.
3.1.9. Operating Parameters For operating conditions of the SRU refer to the following Process Flow Diagrams: 8474L-022-A0102-4110-300-001 Claus Section – Max Distillate 8474L-022-A0102-4110-300-002 Incineration Section – Max Distillate 8474L-022-A0102-4110-300-003 Claus Section – Max Gasoline 8474L-022-A0102-4110-300-004 Incineration Section – Max Gasoline 8474L-022-A0102-4110-300-005 Heat & Material Balance – Max Distillate 8474L-022-A0102-4110-300-006 Heat & Material Balance – Max Distillate 8474L-022-A0102-4110-300-007 Heat & Material Balance – Max Gasoline 8474L-022-A0102-4110-300-008 Heat & Material Balance – Max Gasoline
3.2. Instrument List Refer to attached extracted instrument list: Unit 022 extracted instrument list.xls
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3.3. Main Equipment 3.3.1. Thermal Reactor The purpose of the thermal reactor is to accomplish the complete oxidation of hydrocarbons and all the impurities (such as HCN) present in the total feed gases and to burn approximately one-third of the total H2S to SO2. The Thermal Reactor (A-2201-R-01) is a 2 zones reaction furnace, each zone operating at different temperature: •
In the 1st zone all combustion air, all H2S Rich Off gas and a fraction of ARU Off Gas are burnt.
•
In the 2nd zone the hot flue gas from the first zone and the remaining ARU Off Gas (about 50% of the total ARU off gas) are mixed.
The temperature inside the first zone is approx. 1240°C and the temperature of flue gas leaving the reactor is approx. 900°C. The Thermal Reactor Burner is combined burner type with two lances, one for Fuel Gas combustion during plant heating up, turndown case, or during refractory dry-out and the other one for acid gas combustion during normal operation. The Reactor Burner has a lot of ancillaries to assure smooth and safe operation, such as 2 flame scanners, ignitor, etc. A permanent low pressure steam line (Quench) has been foreseen to moderate the flame temperature in the fuel gas run. The steam requirement shall be approximately 6 kg/kg of fuel gas. The quench steam flowrate shall be set by the operator to limit the adiabatic flame temperature to 1400°C max. Reaction chamber is internally refractory lined to protect the vessel from high temperature and it is equipped with one optical pyrometer and special thermocouples to detect continuously the temperature in both reaction zones. The expected overall conversion of H2S to sulphur in the Thermal Reactor (A2201-R-01) is approx. 16.4% at design conditions (Max. Gasoline Case).
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Thermal Reactor A-2201-R-01 Burner Nozzle Data for Burner Design Pressure (kg/cm2g)
5.2
Operating Pressure (kg/cm2g)
0.49
Design temperature (°C)
343
Operating temperature (°C)
250
Material: Acid Gas Lance / Tip
Stainless Steel / AISI 310
Fuel Gas Lance / Tip
Stainless Steel / AISI 310
Burner Front Plate
Killed Carbon Steel
Burner Construction Installation
Horizontal, flanged to the thermal reactor
Gas Tight Construction
Yes
Fuel Gas connection
Flexible pipe to allow gun withdrawal during acid gas operation
Flame control
2 flame amplifier
Max noise level
85 dB at 1 m distance
detectors,
each
complete
with
Thermal Reactor A-2201-R-01 Length (TL to TL) (mm)
2700
Internal Diameter (mm)
1290
Position
Horizontal
Design Temperature (Fuel Gas Firing only)(°C)
1450
MIN/MAX Operating temperature (°C)
Zone I: 1250/900
Zone II: 1250/850
Refractory Bricks Group
Grade 28
Classification Temperature
1540°C
Thermal Conductivity at 600°C
0.34W/m°C
CaO content
1% typ.
Fe2O3 content
1.5% max.
Alkalies content
2% max.
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Figure 11: Thermal Reactor Burner
Figure 12: Thermal Reactor
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3.3.2. Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 The Claus Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 is a 5 passes boiler producing saturated low pressure steam at 4.1 kg/cm2G in the shell side by condensing sulphur in the tube side: •
pass I = 1st pass of WHB
•
pass II = 2nd pass of WHB
•
pass III = 1st sulphur condenser
•
pass IV = 2nd sulphur condenser
•
pass V = 3rd sulphur condenser
For all the 5 passes, there is one pass per shell or per unit. They are all oriented horizontally. The tubes of each pass are plain tubes, made of killed carbon steel. A-2201-SG-01 is provided with 2 mist eliminators at Pass IV and V outlets to minimize the entrainment of condensed elemental sulphur with the process gas at the outlet of the pass.
Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS I Surface (m2)
7.5 Operating Conditions at Design Flowrate
Service
Shell Side
Tube Side
BFW / LP steam
Process Gas
Inlet
Outlet
Vapour (kg/hr)
Inlet
Outlet
1533.8
1533.8
455
Liquid (kg/hr) Steam (kg/hr)
790.5
Water (kg/hr)
814.6
24.1
Temp.(°C)
112
152
897
4.1
0.44
Press. (kg/cm2g) Duty (kW)
245 2
Service heat transfer coefficient (W/m °C):
66.1
Clean: 68.1
Construction of the shell No. Passes per Shell
Shell Side: 1
No. of tubes:
6
Tube Side: 1
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Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS I Tubes Diameter (mm)
7.62
Length (mm)
4500
Pitch
125 (SQUARE)
Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS II 2
Surface/unit (m )
11.9 Operating Conditions at Design Flowrate
Service
Shell Side
Tube Side
BFW / LP steam
Process Gas
Inlet
Outlet
Vapour (kg/hr)
Inlet
Outlet
1533.8
1533.8
240
Liquid (kg/hr) Steam (kg/hr)
790.5
Water (kg/hr)
814.6
24.1
Temp.(°C)
112
152
455
4.1
0.420
Press. (kg/cm2g) Duty (kW)
107 2
Service heat transfer coefficient (W/m °C):
51.6
Clean: 53.0
Construction of the shell No. Passes per Shell
Shell Side: 1
Tube Side: 1
No. of tubes:
14
Tubes Diameter (mm)
5.54
Length (mm)
4500
Pitch
85 mm (TRIANGULAR)
Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS III Surface/unit (m2)
15.7 Operating Conditions at Design Flowrate Shell Side
Tube Side Page 67 of 161
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Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS III Service
BFW / LP steam
Process Gas
Inlet
Outlet
Vapour (kg/hr)
Inlet
Outlet
1533.8
1504.4
Liquid (kg/hr)
29.4
Steam (kg/hr)
790.5
Water (kg/hr)
814.6
24.1
Temp.(°C)
112
152
240
4.1
0.40
Press. (kg/cm2g) Duty (kW)
37
Service heat transfer coefficient (W/m2 °C):
65.7
162
Clean: 67.9
Construction of 1 shell No. Passes per Shell
Shell Side: 1
Tube Side: 1
No. of tubes:
35
Tubes Diameter (mm)
2.77
Length (mm)
4500
Pitch
46 mm (TRIANGULAR)
Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS IV 2
Surface/unit (m )
16.2 Operating Conditions at Design Flowrate
Service
Shell Side
Tube Side
BFW / LP steam
Process Gas
Inlet
Outlet
Vapour (kg/hr)
Inlet
Outlet
1504.4
1356.6
Liquid (kg/hr)
147.8
Steam (kg/hr)
790.5
Water (kg/hr)
814.6
24.1
Temp.(°C)
112
152
321
4.1
0.28
Press. (kg/cm2g) Duty (kW)
171
84 2
Service heat transfer coefficient (W/m °C):
75.8
Clean: 78.9 Page 68 of 161
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Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS IV Construction of 1 shell No. Passes per Shell
Shell Side: 1
Tube Side: 1
No. of tubes:
36
Tubes Diameter (mm)
2.77
Length (mm)
4500
Pitch
46 mm (TRIANGULAR)
Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 PASS V 2
Surface/unit (m )
14.4 Operating Conditions at Design Flowrate
Service
Shell Side
Tube Side
BFW / LP steam
Process Gas
Inlet
Outlet
Vapour (kg/hr)
Inlet
Outlet
1356.6
1329.5
Liquid (kg/hr)
27.1
Steam (kg/hr)
790.5
Water (kg/hr)
814.6
24.1
Temp.(°C)
112
152
223
4.1
0.173
Press. (kg/cm2g) Duty (kW)
28
Service heat transfer coefficient (W/m2 °C):
62.7
162
Clean: 64.8
Construction of 1 shell No. Passes per Shell
Shell Side: 1
Tube Side: 1
No. of tubes:
32
Tubes Diameter (mm)
2.77
Length (mm)
4500
Pitch
46 mm (TRIANGULAR)
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Figure 13: A-2201-SG-01
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3.3.3. Catalytic Reactors A-2201-R-02/03/04 The purpose of the catalytic reactors R-02/03/04 is to convert H2S into gaseous elemental sulphur by reaction between H2S and the SO2 formed in the thermal reactor R-01 on the catalyst beds. The reaction between H2S and SO2 produces elemental sulphur in each reactor for as long as the equilibrium is not reached for the pressure and temperature conditions within each reactor. The reactors R-02, 03 and 04 are physically located in a unique vessel divided into 3 compartments. The reactors vessel is equipped with an external MP steam coil operating at 250°C and 14.1 kg/cm 2g. A-2201-R-02
A-2201-R-03
A-2201-R-04
Service
1st catalytic reactor
2nd catalytic reactor
3rd catalytic reactors
Catalyst Volume (m3)
Alumina-based: 0.94
Alumina-based: 1.32
Alumina-based: 1.88
Titanium oxide: 0.94 I.D. (mm)
1900
1900
1900
Length (mm)
1375
1300
1375
Material: Shell
Killed Carbon Steel
Heads
Killed Carbon Steel
Flanges
Killed Carbon Steel
Coils
Killed Carbon Steel
Beam
Killed Carbon Steel Design Case Operating Conditions (Max. Gasoline)
Liquid Flow (kg/hr)
0
0
0
Vapour Flow (kg/hr)
1504.4
1356.6
1321.5
IN Press. (kg/cm2g)
0.33
0.21
0.09
OUT Press. (kg/cm2g) 0.28
0.173
0.05
IN Temp. (°C)
240
205
190
OUT Temp. (°C)
321
223
193
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Figure 14: Catalytic Reactors R-02/03/04
3.3.4. Liquid Sulphur Storage Pit A-2201-TK-01 & Degassing Tank A-2201-TK-02 The purpose of A-2201-TK-01 is to collect the liquid elemental sulphur at the outlet of the 1st, 2nd, 3rd and final sulphur condensers via sulphur seal legs (A-2201-D05A/B/C/D). Each sulphur seal leg has been provided with dedicated filter (perforated plate type) to avoid plugging by catalyst and refractory dust. Sulphur seal legs are fully steam jacketed and sized to avoid blow up of process gas in all operating conditions, also in case of heavy upset. Note that each sulphur seal leg has a dedicated manual, steam jacketed valve, to isolate the items in case of scheduled maintenance and during the dry out operations. In no other conditions the valve should be closed. Sulphur pit is divided in two different sections, a non-degassed sulphur pit and a degassed sulphur storage pit, each sized for one day of production and equipped with 2 steam jacketed transfer pumps. Sulphur pit operates under approx. -50 mmH2O (G). The purpose of the sulphur degassing tank A-2201-TK-02 is to reduce the H2S entrained with liquid elemental sulphur to a safe level. Both pits are made of concrete.
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Figure 14: Sulphur storage pit
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Figure 15: Sulphur degassing pit
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3.3.5. Incinerator A-2201-H-01 The duty of the incinerator and associated burner is to oxidize all sulphur bearing compounds in waste gases (tail gas from sulphur recovery unit and vent air from sulphur degassing pit) to sulphur dioxide prior to release to atmosphere. The incinerator operates at 750°C. In normal operation, this condition is obtained by burning NH3 rich SWS off gas (coming from unit 18) and CNU off gas (coming from unit 20) in the incineration burner. The Incinerator Burner is equipped with dedicated lances for: •
Fuel Gas
•
CNU Off Gas
•
NH3 Rich Off Gas
•
ARU Off Gas + H2S Rich Off Gas (Bypass Gas)
The Claus Section Tail Gas and the Vent Gas from Degassing Section are injected just downstream of the flame via dedicated nozzles. The fuel gas is fed into the center of the burner with a single tip. If SRU is shut-down, the Incinerator is capable to receive the ARU OFF GAS and the H2S RICH SWS OFF GAS. In this case these acid gases will be received into the Incinerator Summer to ensure efficient mixing into the flame zone and combustion of sulphur and its compound to sulphur dioxide. During start-up operation firing will be supported by Fuel Gas. Sufficient excess air must be used to limit effluent gas temperature. The turndown capacity of the incinerator is 50% of Design capacity (2.5 T/D) for tail gas from Claus Section and 50% of given capacity for NH3 rich SWS off gas and for CNU off gas. The incinerator is cylindrical and horizontally installed. The internal diameter of the incinerator chamber is 1450 mm. The incinerator is connected to the stack A2201-SK-01 via a refractory lined duct The incinerator burner is of the forced draft type. It is horizontally installed and flanged to the incinerator. The air box is incorporated in the burner. Incinerator Burner is equipped with several ancillaries in order to achieve smooth and fully controlled run. It has a flame detection system with 2 flame detectors having the pilot flame in view, able to originate plant shut down in case of flame failure, pilot burner, cut off valves activated by emergency shut down system etc. Burner management has been designed in order to accept only local light off operation. A forced draft pilot burner is provided for the main burner light off. The pilot is continuously operated and releases approx. 70 kW of heat.
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SRU tail gas 1322 (kg/h)
1217
661
609
SRU tail gas 130 (°C)
130
130
130
Vent Gas (kg/h)
321
321
160
160
321
321
Vent Gas (°C)
145
145
145
145
145
145
ARU off gas (kg/h)
926.6
801.7
ARU off gas (°C)
50
50
H2S rich off gas (kg/h)
74.3
110.7
H2S rich off gas (°C)
90
90
Fuel Gas (kg/h)
8
8
Fuel Gas (°C) [1]
45
43
Fuel Gas M.W.
15.39
NH3 rich off gas (kg/h)
23
8
14
8
8
15.39
15.39
15.39
15.39
15.39
15.39
167
237
84
118.5
167
237
NH3 rich off gas (°C)
90
90
90
90
90
90
CNU off gas (kg/h)
19
19
9
9
19
19
CNU off gas (°C)
65
65
65
65
65
65
Combustion air (kg/h)
2141
3229
2120
1820
7006
8082
90
750
Max. Distillate
SRU Bypass
Max. Gasoline
SRU Bypass
Start-Up / Hot Standby Operation
Max Distillate
Turndown Operation
Max Gasoline
Turndown Operation
Design operation – Max. Distillate
Design operation – Max. Gasoline
The following table displays the operating conditions of the incinerator according to the operating case:
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Combustion air (kg/h) [2]
2500
3594
Combustion air (°C)
36
36
36
36
Flue Gas (kg/h)
3977
5032
3057
Flue Gas M.W.
27.78
27.44
Flue Gas (°C)
750
750
7377
8420
36
36
36
2727
764
8521
9582
27.83
27.48
27.92
28.78
28.47
750
750
750
750
750
Max. Distillate
SRU Bypass
Max. Gasoline
DATE: 21/03/08
SRU Bypass
REV: 0
Start-Up / Hot Standby Operation
Turndown Operation
Max Gasoline
Turndown Operation
Design operation – Max. Distillate
Design operation – Max. Gasoline
SULPHUR RECOVERY UNIT (SRU)
Max Distillate
TRAINING MODULE
Notes: [1]: If CNU and NH3 rich SWS off gas not available [2]: If vent air from sulphur pit is not fed to the incinerator Incinerator Operating Data Firing Zone
Residence Zone
Design Pressure (kg/cm g)
0.1
0.1
Operating Pressure (kg/cm2g)
ATM
ATM
Operating Temp. MIN / NORM. / MAX (°C)
750 / 1100 / 1500
650 / 750 / 850
Design Temp (casing) (°C)
343
343
2
The expected pressure in the incinerator is slightly positive at maximum load
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Figure 16: Incinerator A-2201-H-01
3.3.6. Blowers There are 6 blowers in the SRU: •
The Combustion Air Blowers A-2201-B-01 A/B provides the combustion air necessary for the combustion reactions in the thermal reactor R-01
•
The Incinerator Combustion Air Blowers A-2201-B-02 A/B supply the incinerator with the necessary air for burner operation
•
The Dilution Air Blowers A-2201-B-03 A/B ensure the emission limits are satisfied at the stack outlet by diluting the flue gas at the incinerator outlet with air. Combustion Air Blowers A-2201-B-01 A/B
Number Required
2 (1 operating + 1 standby)
Manufacturer & Model
Robuschi & ES65/2P RVP 80 ATEX3
Blower Type
Rotary Compressor
Driver Type & Manufacturer
Electric Motor & ABB
Driver Rated Power (kW)
22
Driver Speed (RPM)
2930
Drive System
Direct Coupled
Accessories:
Inlet air filter Page 81 of 161
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Combustion Air Blowers A-2201-B-01 A/B Inlet, Discharge & Blow-off Silencers PSV Discharge Blow-off valve Operating Conditions
MIN.
MAX.
RATED
Delivered Flow (Nm3/h)
79
549
604
Inlet Pressure (kg/cm2g)
ATM
ATM
ATM
Outlet Pressure (kg/cm2g)
0.6
0.6
0.6
Inlet Temperature (°C)
36
36
36
Outlet Temperature
115
115
115
Speed (RPM)
2784
Estimated Absorbed Power (kW) 9.8
15.7
16.9
Incinerator Air Blowers A-2201-B-02 A/B Number Required
2 (1 operating + 1 standby)
Manufacturer & Model
Not available
Blower Type
Centrifugal Fan
Driver Type & Manufacturer
Electric Motor, fixed speed
Driver Rated Power (kW)
Not available
Driver Speed (RPM)
Not available
Drive System
Direct Coupled
Accessories:
Inlet air filter Silencer Blowoff silencer Outlet expansion joint
Operating Conditions
NORMAL
MAX.
RATED
Delivered Flow (Nm /h)
2429
6077
6332
Inlet Pressure (kg/cm2g)
ATM
ATM
ATM
Outlet Pressure (kg/cm2g)
0.11
0.11
0.11
Inlet Temperature (°C)
36
36 (MIN.:14)
36
36.1
37.5
3
Estimated Absorbed Power (kW) 15
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Dilution Air Blowers A-2203 A/B Number Required
2 (1 operating + 1 standby)
Manufacturer & Model
Not Available
Blower Type
Centrifugal Fan
Driver Type
Electric Motor
Operating Conditions
DESIGN
NORMAL
Total Dry Flow (kg/h)
176000
160000
Inlet Pressure (mmH2O)
ATM
ATM
Outlet Pressure (mmH2O)
300
250
Inlet Temperature (°C)
36
36
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Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices
X
Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 4 : SAFEGUARDING DEVICES 4.1. Alarms and Trips Refer to attached list: Unit 022 Alarms & Trips List.xls
4.2. Safeguarding Description The Emergency Shutdown System (ESD) provides trips and interlocks for preventing or controlling emergency situations which could give rise to hazardous situations leading to injuries to personnel, significant economic loss and/or undue environmental pollution. Uncontrolled loss of containment is prevented by the provision of pressure safety relief valves and by the ESD system which automatically bring the relevant part of the Unit to a safe condition. Trip/interlock is composed of one or more initiators and one or more actions for preventing hazards. Each trip/interlock shall be provided with a reset and an operational override for start-up, where necessary. In general, if interlock is invoked, the interlock action shall be held on until all initiators have returned to the safe state and the interlock reset has been pressed.
4.2.1. Interlock UX-501 – General ESD Initiators: No.
Initiator Tag No.
P&ID
Description
1
UXHS-501-A
002
Control room general ESD pushbutton
2
UXHS-501-B
002
Control room general ESD pushbutton (bypass)
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-101
1, 2
101
Dilution Air Blower B-2203A shutdown
2
MXS-102
1, 2
101
Dilution Air Blower B-2203B shutdown
3
UXA-501-A
1, 2
002
DCS trip alarm activated
4
UXA-501-B
1, 2
002
Control room trip alarm activated
Note: ESD pushbutton UXHS-501 on Aux. Console in CCC has 2 contacts: UXHS-501-A (CCC man contact) & UXHS-501-B (CCC ESD Bypass contact) The following ESD printout shows the logic UX-501:
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DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
Page 86 of 161
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DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
REV: 0
DATE: 21/03/08
4.2.2. Interlock UX-502 – Incinerator ESD Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
UXHS-502-A
008
Control room ESD pushbutton
3
UXHS-502-B
008
Local panel ESD pushbutton
4
FXALL-534
008
Low low flow of combustion air
5
TXAHH-561
008
High high temperature of incinerator
6
BXALL-503-A/B
008
Flame failure (2 out of 2 voting system). If at least one of the flame detectors confirms the presence of the main flame, the only response of the logic system is to close the LPG pilot gas cut-off valve 022-XV-515.
7
MGL-101/102
101
Dilution air blower B-2203-A/B stop (both machines stop: 2 out of 2 voting system)
8
BXALL-504
008
Pilot Flame Failure Note: Pilot flame failure causes only the closure of XV-515 in case at least one of the main flame detectors confirms the presence of the flame. Otherwise, total incinerator shutdown will be initiated.
9
LXAHH-509
003
High high level in NH3 rich SWS off gas KO drum A-2201D-03
10
LXAHH-501
002
High high level in ARU Off Gas KO drum A-2201-D-01
11
LXAHH-504
002
High high level in H2S rich SWS Off Gas KO drum A-2201D-02
12
FXAL-534
008
Low flow of combustion air purge. This cause is only active during the air purge period.
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
UX-503
2, 3, 4, 5, 6, 004 7, 8
Activation of Thermal Reactor ESD after a delay of 20 min.
2
UX-508
2, 3, 4, 5, 6, 011 7, 8
Activation of Sulphur Degassing ESD
3
XSY-512
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of CNU off gas cut-off valve XV-512 XV-512 can be open/closed from local control panel via XHSO/C-512 Page 87 of 161
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DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
No.
Action Tag No.
Initiated by initiator No:
P&ID
4
XSY-513
1, 2, 3, 4, 5, 008 6, 7, 8, 9
REV: 0
DATE: 21/03/08
Description Closing of NH3 rich SWS off gas cut-off valve XV-513 XV-513 can be open/closed from local control panel via XHSO/C-513
5
XSY-514
1, 2, 3, 4, 5, 008 6, 7, 8
Activation of the Fuel Gas block & Bleed Valve shutdown sequence: Closing of Fuel Gas cut-off valve XV-514 [1]
6
XSY-557
1, 2, 3, 4, 5, 008 6, 7, 8
Activation of the Fuel Gas block & Bleed Valve shutdown sequence: Closing of Fuel Gas cut-off valve XV-557 [1]
7
XSY-558
1, 2, 3, 4, 5, 008 6, 7, 8
Activation of the Fuel Gas block & Bleed Valve shutdown sequence: Opening of fuel gas bleed valve XV-558 [1]
8
XSY-515
1, 2, 3, 4, 5, 008 6, 7, 8
Activation of the LPG block & Bleed Valve shutdown sequence: Closing of LPG cut-off valve XV-515 [1]
9
XSY-559
1, 2, 3, 4, 5, 008 6, 7, 8
Activation of the LPG block & Bleed Valve shutdown sequence: Closing of Fuel Gas cut-off valve XV-559 [1]
10
XSY-560
1, 2, 3, 4, 5, 008 6, 7, 8
Activation of the LPG block & Bleed Valve shutdown sequence: Opening of fuel gas bleed valve XV-560 [1]
11
XSY-516
1, 2, 3, 4, 5, 008 6, 7, 8, 10, 11
Closing of BYPASS cut-off valve XV-516 XV-516 can be open/closed from local control panel via XHSO/C-516
12
MXS-513
1
008
Trip the incinerator combustion air blower M-2201-B-02A
13
MXS-514
1
008
Trip the incinerator combustion air blower M-2201-B-02B
14
FIC-539
2, 3, 4, 5, 6, 008 7, 8
Override the combustion air control valve FV-539. For this, FIC-539 is forced to manual mode with output 50% to close FV539. The air purge procedure is activated [2].
15
PIC-539
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of the NH3 rich SWS off gas control valve PV-539 by forcing the controller PIC539 to manual mode and output 0%.
16
TIC-560
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of the fuel gas control valve TV560: Page 88 of 161
TRAINING MODULE
DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
No.
Action Tag No.
Initiated by initiator No:
P&ID
REV: 0
DATE: 21/03/08
Description Controller TIC-560 is forced to manual mode at 50% to put TY-560-A in manual mode at 0% in order to close TV-560.
17
-
12
Purge timer is reset
18
UXA-502-A
1, 2, 3, 4, 5, 008 6, 7, 8
DCS trip alarm activated
19
UXA-502-B
1, 2, 3, 4, 5, 008 6, 7, 8
Control room trip alarm activated
20
UXA-502-C
1, 2, 3, 4, 5, 008 6, 7, 8
Local Panel Trip Alarm activated
Note: [1]: The logic will open the main fuel gas and LPG pilot gas vent valves only if both the cut-off valves are confirmed fully closed by their limit switches. [2]: Air purge procedure: A purge by means of air from Incinerator Combustion Air Blower (A-2201-B02A/B) is automatically started either when the shutdown chain is activated by the initiators or when the SYSTEM RESET push button (022-UHSR-502) has been pressed and the purge validity time mentioned here below is fully expired (preignition purge). In both cases the logic system shall automatically: open the combustion air valve 022-FV-539 to the "air purge set point" acting on its controller 022-FIC-539. As soon as the air flow rate exceeds the set point of 022-FT-534, the Logic shall Illuminate the PURGE ON lamp at Local Panel 022-XL-530-B and start to compute a 5 minutes purge time. When the 5 minutes purge time is expired, the logic system shall: •
De-illuminate the PURGE ON lamp at Local Panel 022-XL-530-B
•
Light the PURGE COMPLETED lamp at Local Panel 022-XL-53 1-B
•
Start to compute a 15 minutes purge validity time
In the event the next light-off attempt is not completed within the 15 minutes purge validity time, the logic system shall illuminate the LIGHT-OFF TIME OUT lamp (Local Panel) 022-XL-532-B. Remarks: i) The minimum air flow rate shall be continuously satisfied during the purge. In case the air flow falls below the set-point of 022-FXAL-534 before the 5 minutes purge time is expired, the Logic shall reset the purge time counter and light the PURGE LOW FLOW lamp at Local Panel 022-XL-534-B. The time shall be automatically re-started by the Logic only when the minimum air flow rate has been re-established.
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DATE: 21/03/08
ii) If the validity time following a shutdown air purge is expired and the Incinerator is still in shutdown condition (the SYSTEM RESET pushbutton 022-UHSR-502 has not been pressed), the logic system remains in shutdown condition waiting for SYSTEM RESET. Otherwise, if the SYSTEM RESET pushbutton has been pressed, but the ignition is not initiated within the 15 minutes of validity time, at the end of the validity time the logic system activate the shutdown sequence. Reset: The incinerator ESD is reset via UHSR-502.
The following ESD printout shows the logic UX-502:
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DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
Page 91 of 161
TRAINING MODULE
DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
REV: 0
DATE: 21/03/08
4.2.3. Interlock UX-503 – Thermal Reactor ESD Initiators No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
UXHS-503-A
004
Control room ESD pushbutton [1]
3
UXHS-503-B
004
Control room ESD pushbutton (Bypass) [1]
4
UXHS-503-C
008
Local panel ESD pushbutton
5
MGL-101/102
101
Dilution air blower B-2203-A/B stop (both machines stop: 2 out of 2 voting system)
6
UX-502
002
Incinerator ESD
7
LXAHH-501
002
High high level in ARU Off Gas KO drum A-2201-D-01 (active only during acid gas operation, XV-505 opened)
8
FXALL-521
004
Low low flow of combustion air to the thermal reactor
9
FXALL-517
005
Low low level in waste heat boiler A-2201-SG-01
10
BXALL-501-A/B
004
Flame failure (2 out of 2 voting system)
11
PXAHH-551
004
High high pressure in the Thermal Reactor
12
LXAHH-504
002
High high level in H2S rich SWS Off Gas KO drum A-2201D-02
13
FXALL-523
004
Low low flow of ARU off gas to the thermal reactor
14
FXALL-528
004
Low low flow of N2 purge
Notes: [1]: ESD pushbutton UXHS-503-A on Aux. Console in CCC has 2 contacts: UXHS503-A (CCC man contact) & UXHS-503-B (CCC ESD Bypass contact) Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
XSY-501
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 12, 13
Closing of the H2S rich SWS off gas cut-off valve XV-501. XV-501 can be opened / closed from local panel via XHSO/C-501
2
XSY-504
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Closing of combustion air cut-off valve XV504.
3
XSY-505
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10,
Closing of the ARU off gas cut-off valve XV505. Page 92 of 161
TRAINING MODULE
DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
No.
4
Action Tag No.
XSY-507
Initiated by initiator No: 11, 13
P&ID
REV: 0
DATE: 21/03/08
Description XV-505 can be opened / closed from local panel via XHSO/C-505
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Closing of the quench steam cut-off valve XV-507 XV-507 can be opened / closed from local panel via XHSO/C-507
5
XSY-508
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Closing of the fuel gas cut-off valve XV-508 [2]
6
XSY-555
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Closing of fuel gas cut-off valve XV-555 [2]
7
XSY-556
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
XV-555 can be opened / closed from local panel via XHSO/C-508 Opening of fuel gas bleed valve XV-556 [2] XV-556 can be opened / closed from local panel via XHSO/C-508
8
XSY-509
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Nitrogen cut-off valve XV-509 opened to purge the thermal reactor [3].
9
XSY-510
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Purge air cut-ff valve closed
10
XSY-516
2, 3, 4, 7, 8, 008 9, 10, 11, 13
Bypass cut-off valve XV-516 opened. XV-516 will be opened only in case the incinerator is in operation (XL-540 ON) XV-516 can be opened / closed from local panel via XHSO/C-516
11
-
14
-
Reset purge timer
12
FIC-515
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Controller is set to manual mode and output 0% to close H2S rich SWS off gas control valve FV-515
13
FIC-527
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Controller is set to manual mode and output 0% to close combustion air main control valve FV-527
14
FIC-522
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Controller is set to manual mode and output 0% to close air trim control valve FV-522
15
FIC-530
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Controller is set to manual mode and output 0% to close ARU Off Gas control valve FV530
16
FIC-525
1, 2, 3, 4, 5, 004
Controller is set to manual mode and output Page 93 of 161
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DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
No.
Action Tag No.
Initiated by P&ID initiator No: 6, 7, 8, 9, 10, 11, 13
REV: 0
DATE: 21/03/08
Description 0% to close Steam Control Valve FV-525
17
FIC-526
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Controller is set to manual mode and output 0% to close fuel gas control valve FV-526
18
FIC-524
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Controller is set to manual mode and output 0% to close ARU off gas control valve FV524
19
UXA-503-A
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
DCS trip alarm activated
20
UXA-503-B
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Control room trip alarm activated
21
UXA-503-C
1, 2, 3, 4, 5, 004 6, 7, 8, 9, 10, 11, 13
Local panel trip alarm activated
Notes: [2]: The logic will open the main fuel gas vent valve only if both the cut-off valves are confirmed fully closed by their limit switches. [3]: Nitrogen Purge Sequence: A purge by means of nitrogen shall automatically start either when the shutdown chain is activated by the initiators or when the SYSTEM RESET pushbutton (022UHSR-503) has been pressed and the purge validity time mentioned here below is fully expired (pre-ignition purge). In both cases, the logic system shall automatically open the nitrogen cut-off valve. As soon as the nitrogen flow rate exceeds the set point 022-FXALL-528, the logic system shall illuminate the PURGE ON lamp (Local Panel) 022-XL-521-B and start to compute a 5 minutes purge time. Once the 5 minutes purge time is expired, the logic system shall: •
Close the Nitrogen cut-off valve 022-XV-509
•
De-illuminate the PURGE ON lamp (Local Panel) 022-XL-52 1 -B
•
Illuminate the PURGE COMPLETED lamp (Local Panel) 022-XL-522-B
•
Start to compute a 10 minutes purge validity time
In case the burner ignition trial is not completed within the 10 minutes purge validity time, the logic system shall illuminate the LIGHT-OFF TIME OUT lamp Page 94 of 161
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DATE: 21/03/08
(Local Panel) 022-XL-523-B. In this case another nitrogen purge is requested before the burner ignition. Remarks : i) If the validity time following a shutdown purge is expired and the Claus section is still in shutdown condition (the SYSTEM RESET pushbutton has not been pressed), the logic system remains in shutdown condition waiting for SYSTEM RESET. Otherwise, if the SYSTEM RESET (022-UHSR-503) pushbutton has been pressed but BURNER ON status is not reached within the 10 minutes of validity time, at the end of the validity time the logic system activate the all shutdown sequence. ii) The opening of 022-XV-509 is inhibited in case 022-PXAHH-551 is active (Thermal Reactor high high pressure). iii) The minimum nitrogen flow rate shall be continuously verified during the purge. In case the nitrogen flow rate falls below 022-FXALL-528 set point before the purge time is fully expired, the logic system shall automatically: •
Reset the purge time counter
•
Illuminate PURGE LOW FLOW lamp (Local Panel) 022-FXALL-528-B
•
De-illuminate the PURGE ON lamp (Local Panel) 022-XL-522-B
The purge time counting shall be automatically re-initiated by the logic system only when a minimum nitrogen flow rate (higher than 022-FT-528 set point) has been reestablished.
Reset: UX-503 can be reset by local reset pushbutton UHSR-503 when all initiators become healthy except initiators 7 & 13.
The following ESD printout shows the logic UX-503:
Page 95 of 161
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DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
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DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
REV: 0
DATE: 21/03/08
4.2.4. Interlock UX-504 – A-2201-B-01 A/B Protection Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
TXAHH-525
003
High high temperature of combustion air blower B-01-A
TXAHH-587
003
High high temperature of combustion air blower B-01-B
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-509
ALL
003
Combustion air blower A-2201-B-01-A tripped
2
MXS-510
ALL
003
Combustion air blower A-2201-B-01-B tripped
3
UXA-504
ALL
003
DCS Trip Alarm activated
Reset: Once all the initiators are healthy, UX-504 can be reset via DCS software reset pushbutton UHSR-504.
4.2.5. Interlock UX-505 – A-2201-P-01 A/B Protection Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
LXALL-501
002
Low low level in ARU gas KO drum A-2201-D-01
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-501
ALL
002
ARU off gas KO drum pump A-2201-P-01A is tripped
2
MXS-502
ALL
002
ARU off gas KO drum pump A-2201-P-01B is tripped
3
UXA-505
ALL
002
DCS trip alarm activated
Reset:
Page 97 of 161
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DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
REV: 0
DATE: 21/03/08
Once all the initiators are healthy, UX-505 can be reset via DCS software reset pushbutton UHSR-505.
4.2.6. Interlock UX-506 – A-2201-P-02 A/B Protection Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
LXALL-504
002
Low low level in H2S rich SWS off gas KO drum A-2201-D02
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-503
ALL
002
H2S rich SWS off gas KO drum pump A2201-P-02A is tripped
2
MXS-504
ALL
002
H2S rich SWS off gas KO drum pump A2201-P-02B is tripped
3
UXA-506
ALL
002
DCS trip alarm activated
Reset: Once all the initiators are healthy, UX-506 can be reset via DCS software reset pushbutton UHSR-506.
4.2.7. Interlock UX-507 – A-2201-P-03 A/B Protection Initiators: No.
Initiator Tag No.
P&ID Description
1
UX-501
002
General ESD
2
LXALL-507
002
Low low level in NH3 rich SWS off gas KO drum A-2201-D-03
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-507
ALL
002
NH3 rich SWS off gas KO drum pump A2201-P-03A is tripped
2
MXS-508
ALL
002
NH3 rich SWS off gas KO drum pump A2201-P-03B is tripped
3
UXA-507
ALL
002
DCS trip alarm activated Page 98 of 161
TRAINING MODULE
DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
REV: 0
DATE: 21/03/08
Reset: Once all the initiators are healthy, UX-507 can be reset via DCS software reset pushbutton UHSR-507.
4.2.8. Interlock UX-508 – Sulphur Degassing ESD Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
MGL-101/102
101
Dilution air blowers B-2203 A & B stopped (2 out of 2 voting system)
3
UX-502
-
Incinerator ESD (Time delay = 20 minutes)
4
LXALL-525
010
Low low level in liquid storage pit A-2201-TK-02
5
MGL-509/510
003
Combustion air blowers A-2201-B-01-A & B stopped
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-517
1, 2, 3, 4
010
Sulphur circulation pump A-2201-P-04A tripped
2
MXS-518
1, 2, 3, 4
010
Sulphur circulation pump A-2201-P-04B tripped
3
UHSC-521
1, 2, 3
011
Steam to ejector cut-off valve closed UV521 by forcing UHSC-521 to close position
4
UHSC-522
ALL
011
Degassing air cut-off valve UV-522 closed by forcing UHSC-522 to close position
5
UHSC-523
ALL
011
Steam to degassing pit cut-off valve UV-523 closed by forcing UHSC-523 to close position
6
UHSC-524
ALL
011
Sulphur to degassing pit cut off valve UV524 closed by forcing UHSC-524 to close position
7
UXA-508
ALL
011
DCS trip alarm activated
Reset: Once all the initiators are healthy, UX-508 can be reset via DCS software reset pushbutton UHSR-508.
Page 99 of 161
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DOC NO: 8474L-022-A5016-0000-001-012
SULPHUR RECOVERY UNIT (SRU)
REV: 0
DATE: 21/03/08
4.2.9. Interlock UX-509 – A-2201-P-05 A/B Protection Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
LXALL-526
010
Low low level in liquid storage pit A-2201-TK-02
Actions: No.
Action Tag No.
Initiated by initiator No:
P&ID
Description
1
MXS-519
ALL
010
Sulphur pump A-2201-P-05A tripped
2
MXS-520
ALL
010
Sulphur pump A-2201-P-05B tripped
3
UXA-509
ALL
010
DCS trip alarm activated
Reset: Once all the initiators are healthy, UX-509 can be reset via DCS software reset pushbutton UHSR-509.
The following ESD printout shows the logics UX-504, UX-505, UX-506, UX-507, UX-508 and UX-509:
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DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
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DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
4.3. Safeguarding Equipment 4.3.1. Pressure Safety Devices Over pressuring of the equipment occurs in many ways. The basic cause of power pressure is imbalance in heat and material flow in the equipment or piping. Pressure safety devices have been installed to protect and/or section against over pressure. Here is the list of the pressure safety valves found in the SRU: TAG No.
Description
022-PSV -525-A 022-PSV -525-B 022-PSV -527-A 022-PSV -527-B 022-PSV -532 022-PSV -533 022-PSV -535 022-PSV -536 022-PSV -523-A 022-PSV -523-B 022-PSV -540-A 022-PSV -540-B 022-PSV -543 022-PSV -544 022-PSV -556-A 022-PSV -556-B 022-PSV -556-C 022-PSV -563-A 022-PSV -563-B 022-PSV
Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve (Spring) Relief Valve
Type RV RV RV RV RV RV RV RV RV RV RV RV
Location PG FROM A-2201-D-01 TO FLARE PG FROM A-2201-D-01 TO FLARE PG FROM A-2201-D-02 TO FLARE PG FROM A-2201-D-02 TO FLARE CONDENSATE FROM A2201-P-01A TO B.L. CONDENSATE FROM A2201-P-01B TO B.L. CONDENSATE FROM A2201-P-02A TO B.L. CONDENSATE FROM A2201-P-02B TO B.L. PG FROM A-2201-E-02 TO A-2201-R-01 PG FROM A-2201-E-02 TO A-2201-R-01 PG FROM A-2201-D-03 TO FLARE PG FROM A-2201-D-03 TO FLARE
PID:
Setting (kg/cm2g)
002
5.9
002
5.9
002
7.7
002
7.7
002
6.0
002
6.0
002
7.7
002
7.7
003
1.0
003
1.0
003
3.5
003
3.5
RV
A-2201-P-03A PROT
003
6
RV
A-2201-P-03B PROT
003
6
RV
A-2201-SG-01 PROT
005
6.3
RV
A-2201-SG-01 PROT
005
6.3
RV
A-2201-SG-01 PROT
005
6.3
RV
SL FROM A-2201-E-06
007
6.3
RV
SL FROM A-2201-E-06
007
6.3
RV
SL FROM A-2201-E-06
007
6.3 Page 102 of 161
TRAINING MODULE SULPHUR RECOVERY UNIT (SRU)
TAG No.
Description
-563-C 022-TSV -556 022-PSV -559 022-PSV -602
(Spring) Relief Valve (Thermal) Relief Valve (Thermal) Relief Valve (Thermal)
DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
DATE: 21/03/08
Type
Location
PID:
Setting (kg/cm2g)
RV
A-2201-E-07 PROT
007
9.2
RV
A-2201-B-01-A VENT
003
0.65
RV
A-2201-B-01-B VENT
003
0.65
For further details, refer to the Flare Discharge Summary of the SRU: Doc. No. 8474L022-NM-0006-001.
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TRAINING MODULE
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Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems
X
Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 5 : FIRE & GAS SYSTEMS 5.1. Fire & Gas detection Refer to the following documents: 8474L-018-DW-1950-001
Fire & Gas Detector Layout SWS/ARU/CNU/SRU units
8474L-018-DW-1960-002
Escape Route Layout SWS/ARU/CNU/SRU units
8474L-018-DW-1514-201
Fire and gas Cause and Effect Chart Area 4
The following figures are extracted from the above document and focus on the SRU and its close surroundings only.
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Figure 17: SRU Fire & Gas Detectors Layout
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Figure 18: Fire & Gas Detectors Layout Legend for AREA 4
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Figure 19: SRU Escape Route Layout
5.2. Fire Protection Refer to the following documents: 8474L-018-DW-1933-001 Safety Equipment Layout SWS/ARU/CNU/SRU units 8474L-018-DW-1933-002 Fire Protection Layout SWS/ARU/CNU/SRU units The following figures are extracted from the above document and focus on the SRU and its close surroundings only: Page 108 of 161
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Figure 20: SRU Safety Equipment Layout Page 109 of 161
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Figure 21: Fire Protection Equipment Layout Page 110 of 161
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Figure 19: Fire Protection Equipment Layout Legend for AREA 4
5.2.1. Precautionary measures to avoid fuel gas explosions in Claus area Before starting burners lighting trials it is recommended that the area around the plant is tested with a flammable gas detector. During an extended shut-down all fuel gas and acid gas lines should be spaded at the SRU plant battery limit. Before attempting to light or relight the fuel gas burners (Reaction furnace or Incinerator) they must be purged. The times settled in the lighting procedures (cycles, sparkling, waiting time and so on) have been calculated to assure safe operation; no modifications are allowed without the approval of the Start-up Leader. Page 111 of 161
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5.2.2. Precautionary measures to avoid sulphur burning Sulphur burns exothermically with oxygen. In case of uncontrollable sulphur fire it is possible to destroy the catalyst in Claus Section and to damage vessels, refractory materials and paperwork either for the resulting high temperatures or for the corrosive atmosphere due to the formation of SO3 during the sulphur combustion. Therefore whenever sulphur is present in the unit care must be taken to limit its contact with oxygen. During the plant heat-up steps in case of presence of liquid sulphur and when operating with fuel gas, the fuel gas must be burnt stoechiometrically. During plant heat-up the flue gas has to be analyzed to control that CO and O2 are contained in the following safe limits. •
O2 : 0.4vol.%max.
•
CO : 0.4 vol.% max.
The process equipment and pipes must not be opened to the atmosphere until the sulphur is completely removed and the catalyst in the reactors is cooled below 150°C; at temperature higher than 150°C the liquid sulphur can auto ignite in presence of oxygen. 5.2.3. Extinguishing Sulphur Pit fires Snuffing steam shall be used in case of fire in the sulphur pit. This operation shall be done at a safe distance from the pit by opening a LP steam valve. The steam shall break the rupture disc and shall enter the sulphur pit. When the fire is extinguished the steam valve shall be closed and a new rupture disc shall be installed. 5.2.4. Sulphur Fires All operating personnel must be aware of the possible areas susceptible to fire and of the fire fighting procedures. In the event of a fire, Operators must comply with the Refinery Emergency Procedures. The spontaneous ignition temperature of sulphur in air is about 170°C. When the sulphur is ignited, it is difficult to extinguish it and it can re-ignite spontaneously. In order to minimize the risk of sulphur fires all sulphur spillage must be removed as soon as they occur. When sulphur fires are extinguished with water a white toxic choking acidic fume is released. This sulphuric acid vapor is extremely hazardous and inhalation or contact with the skin should be avoided. While fighting a fire the fireman should wear suitable breathing apparatus and stand on the windward side of the fire. Care must be taken with the water used to extinguish a sulphur fire as this may also be acidic. After any sulphur fire a water hose must be trained into the fire area for a reasonable time to prevent re ignition and to wash and remove any acidic water. Sulphur fires can also be extinguished by smothering with some more sulphur, or sand or earth. Carbon dioxide fire extinguishers or steam smothering may also be used.
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The following Fire & Gas System printout displays the F&G layout of the area 4 (units 18, 19, 20 & 22) and shows the alarms, detectors and F&G protection system located in this area:
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Page 114 of 161
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DOC NO: 8474L-022-A5016-0000-001-012 REV: 0
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TRAINING MODULE
SULPHUR RECOVERY UNIT (SRU) UNIT: 22
Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control
X
Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 6 : QUALITY CONTROL
6.1. Sampling Analysis The control analysis procedures for the SRU include determination of the H2S and NH3 content of the plant feed gas, determination of the ratio of H2S to SO2 in the plant tail gas and determination of sulphur purity. The performance test procedures include determination of H2S and non acid gas contents in the plant feed gas, determination of non acid gas, acid gas, H2S and SO2 in the plant tail gas and on stack gas, calculation of sulphur vapors in plant tail gas and determination of sulphur purity. During H2S combustion the only parameters to be periodically checked are concentrations of H2S and SO2 in the tail gas, to optimize the relevant ratios. During plant start-up and shut-down, when fuel gas is fired in the plant, Orsat analysis or Firyte test will be conduced to detect the O2 and CO content in the tail gas. Flue gas analysis is normally required any time the rate of combustion is changed. During heating of the unit by burning fuel gas, it is necessary to control the following: •
Oxygen content
•
Carbon monoxide content
•
Soot presence
•
Sulphur presence
The first two parameters are important for safe unit operation; the third can be reduced to a minimum when the first two give values advisable limits. Carbon monoxide can be readily detected with calorimetric glass tubes. Soot presence in the combustor flue gas can be detected by placing a piece of wet filter paper in contact with the gas. It will turn black in the presence of soot. Sulphur contained as a vapor can be detected by bubbling flue gases in a glass pot containing water. In presence of sulphur a colloidal deposit is formed (light yellow color). Such a test is particularly interesting towards the end of a sweeping sulphur operation, so as to ascertain, if it has been fully removed. Control of operating parameters is essential for efficient unit operation and to minimize maintenance. It is not necessary to conduct daily analysis, but quick checks can be made by Operators, if are necessary, particularly during start-up and shut-down of the unit. For all the sampling procedures, refer to the chapter 12 of the licensor operating manual doc. No. 8474L-022-ML-001.
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6.1.1. Sampling Connections Connection Tag
Service
PID
SC-501
A-2201-SG-01 process gas to 3rd process gas reheater A2201-E-05
005
SC-502
A-2201-SG-01 process gas to 2nd process gas reheater A2201-E-04
005
SC-503
A-2201-SG-01 process gas to 1st process gas reheater A2201-E-03
005
SC-512
Blow down water from Claus blow down drum A-2201-D-06 to OWS
005
SC-506
Gas effluent from 1st reactor to A-2201-SG-01 pass IV
006
SC-507
Gas effluent from 2nd reactor to A-2201-SG-01 pass V
006
rd
SC-508
Gas effluent from 3 reactor to final condenser A-2201-E-06
006
SC-511
Tail gas from tail gas coalescer A-2201-D-04 to incinerator A2201-H-01
007
6.1.2. Sampling Frequency The following frequencies are valid for normal, stable operation but can be changed according to plant requirement. A typical schedule is: •
H2S and hydrocarbons in ARU Off gas : once a week
•
H2S, NH3 and HC in SWS Off gas : once a week
•
Purity of product sulphur : once every two weeks
•
Chromatographic analysis of fuel gas : every day
•
H2S in liquid sulphur : every week
Analysis of H2S/S02 in the tail gas may be required every 2 hours during plant start-up. Analysis of H2S/SO2 in the tail gas is continuously performed by the analyzer. Chemical analysis will be used periodically to check the results of the continuous analyzer. Sulphur purity analysis may be required more frequently while the plant is being stabilized and some hours after plant start-up. In heat-up/shut-down operations, the following analyses are required: •
O2 content in combustor flue gas: Every hour (for at least for a period of four hours). Analysis may be done with standard gas chromatographic, by Orsat or calorimetric detectors.
•
CO content in combustor flue gas: Every hour (for at least eight hours - at each start-uplshut-down). Analysis can be done with colorimetric detectors.
•
H2S in treated gas: Every six hours for two days.
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6.1.3. Safe handling of samples All samples taken on SRU plant are considered to be hazardous and the sampler must be experienced of sample taking and be aware of the hazards involved. The sampler must wear suitable breathing apparatus and acid resistant gloves. The equipment used must be gas tight and able to withstand temperatures up to 180°C. 6.1.3.1. Handling of gas samples containing H2S The acid gases are analyzed for H2S, H2, hydrocarbon and ammonia concentration. The tail gas is analyzed to check the H2S (and SO2) and to check the tail gas analyzer and the O2 analyzer. In order to purge the acid gas sample line, the gas may be passed into a freshly prepared strong caustic solution or sent to flare. The sample must be taken in an airtight container that shall be stored in a fun cupboard when taken to the laboratory for analysis. The sampler must wear breathing apparatus and protective gloves and have an assistant at hand in case of emergency. 6.1.3.2. Handling of liquid sulphur Sulphur collected from the sulphur pit or sulphur seals outlet will be hot, about 140°C and care must be taken to avoid burns a nd contact with the skin. When taking a sample from the sulphur pit a rod with a cup on the end is used. When standing on top of the pit taking a sample through the inspection hole, the sampler must wear an anti-gas mask with suitable filter for H2S protection.
6.2. On-line analysers The plant is equipped with continuous analyzer for Claus tail gas (H2S and SO2) and a NOx/SOx analyzer at the Incinerator Stack Gas - emission monitor.
Analyzer tag
Service
Physical property analyzed
SO2 content 022AE/AT-501
Tail gas from tail gas coalescer A-2201-D-04 to incinerator A-2201-H-01 H2S content
022AE/AT-504
Flue gas from incinerator A2201 at stack outlet
SOx (normal operation)
Normal value of analyzed component
PID:
Max. Distillate: 0.2861 mole% Max. Gasoline: 0.2802 mole% Max. Distillate: 0.1431 mole%
8474L022A01034110300-007
Max. Distillate: 0.1400 mole% Max. Distillate: 476.31 mg/Nm3 Max. Gasoline: 401.09 mg/Nm3
8474L022A01034110-
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NOx (Bypass operation)
NOx (normal operation)
DATE: 21/03/08
Max. Distillate: 2698.51 mg/Nm3
300-008
Max. Gasoline: 2966.44 mg/Nm3 Max. Distillate: 1158.0 mg/Nm3 MAX Max. Gasoline: 1141.7 mg/Nm3 MAX
For more details on each analyzer, refer to the following data sheets: •
For H2S/SO2 Tail Gas Analyser, refer to vendor doc. No. 8474L-022-A3101-4110300-017
•
For NOx/SOx analyser, refer to vendor doc. No. 8474L-022-A3101-4110-300-025
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TRAINING MODULE
SULPHUR RECOVERY UNIT (SRU) UNIT: 22
Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects
X
Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 7 : CAUSES AND EFFECT
7.1. Cause & Effect Matrix: Refer to the following documents: Cause and Effect Chart, Doc. No. 8474L-022-A3505-4110-300-002 Fire and gas Cause and Effect Chart for Area 4, Doc. No. 8474L-018-DW-1514-201-2 Note: The cause & effect matrix Doc. No. 8474L-022-A3505-4110-300-002 details the safety trips and protections evoked in the safeguards narrative in section 4 of this document. The fire & gas cause and effect chart deals with all the fire & gas detection system in the area 4 (units 018, 019, 020 and 022). 7.1.1. Example from Cause and Effect Chart To better understand how the Cause & Effect Matrix can be interpreted, an example is given, which details the information that can be extracted from a sheet of the Cause & Effect Diagram. It shall be read in conjunction with the corresponding sheet of the Cause & Effect Diagram.
7.1.1.1. UX-502: Incinerator ESD Initiators: No.
Initiator Tag No.
P&ID
Description
1
UX-501
002
General ESD
2
UXHS-502-A
008
Control room ESD pushbutton
3
UXHS-502-B
008
Local panel ESD pushbutton
4
FXALL-534
008
Low low flow of combustion air
5
TXAHH-561
008
High high temperature of incinerator
6
BXALL-503-AB
008
Flame failure (2 out of 2 voting system)
8/9
MGL-101/102
101
Dilution air blower B-2203-A/B stop (both machines stop: 2 out of 2 voting system)
10
BXALL-504
008
Pilot Flame Failure Note: Pilot flame failure causes only the closure of XV-515 in case at least one of the main flame detectors confirms the presence of the flame. Otherwise, total incinerator shutdown will be initiated.
11
LXAHH-509
003
High high level in NH3 rich SWS off gas KO drum A-2201Page 121 of 161
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No.
Initiator Tag No.
P&ID
Description D-03
12
LXAHH-501
002
High high level in ARU Off Gas KO drum A-2201-D-01
13
LXAHH-504
002
High high level in H2S rich SWS Off Gas KO drum A-2201D-02
14
FXAL-534
008
Low flow of combustion air purge. This cause is only active during the air purge period.
Actions: No.
Action Tag No.
Initiated by initiator No:
1
UX-503
2, 3, 4, 5, 6, 004 7, 8
Activation of Thermal Reactor ESD after a delay of 20 min.
2
UX-508
2, 3, 4, 5, 6, 011 7, 8
Activation of Sulphur Degassing ESD
3
XSY-512
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of CNU off gas cut-off valve XV-512
4
XSY-513
P&ID
1, 2, 3, 4, 5, 008 6, 7, 8, 9
Description
XV-512 can be open/closed from local control panel via XHSO/C-512 Closing of NH3 rich SWS off gas cut-off valve XV-513 XV-513 can be open/closed from local control panel via XHSO/C-513
5
XSY-514
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of Fuel Gas cut-off valve XV-514 [1]
6
XSY-557
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of Fuel Gas cut-off valve XV-557 [1]
7
XSY-558
1, 2, 3, 4, 5, 008 6, 7, 8
Opening of fuel gas bleed valve XV-558 [1]
8
XSY-515
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of LPG cut-off valve [1]
9
XSY-559
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of Fuel Gas cut-off valve XV-559 [1]
10
XSY-560
1, 2, 3, 4, 5, 008 6, 7, 8
Opening of fuel gas bleed valve XV-560 [1]
11
XSY-516
1, 2, 3, 4, 5, 008 6, 7, 8, 10, 11
Closing of BYPASS cut-off valve XV-516 XV-516 can be open/closed from local control panel via XHSO/C-516
12
MXS-513
1
008
Trip the incinerator combustion air blower M-2201-B-02A
13
MXS-514
1
008
Trip the incinerator combustion air blower Page 122 of 161
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No.
Action Tag No.
Initiated by initiator No:
P&ID
REV: 0
DATE: 21/03/08
Description M-2201-B-02B
14
FIC-539
2, 3, 4, 5, 6, 008 7, 8
Override the combustion air control valve FV-539. For this, FIC-539 is forced to manual mode with output 50%. The air purge procedure is activated.
15
PIC-539
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of the NH3 rich SWS off gas control valve PV-539 by forcing the controller PIC539 to manual mode and output 0%.
16
TIC-560
1, 2, 3, 4, 5, 008 6, 7, 8
Closing of the fuel gas control valve TV560: Controller TIC-560 is forced to manual mode at 50% to put TY-560-A in manual mode at 0% in order to close TV-560.
17
-
13
Purge timer is reset
18
UXA-502-A
1, 2, 3, 4, 5, 008 6, 7, 8
DCS trip alarm activated
19
UXA-502-B
1, 2, 3, 4, 5, 008 6, 7, 8
Control room trip alarm activated
20
UXA-502-C
1, 2, 3, 4, 5, 008 6, 7, 8
Local Panel Trip Alarm activated
Note: [1]: The logic will open the main fuel gas and LPG pilot gas vent valves only if both the cut-off valves are confirmed fully closed by their limit switches. Reset: Local reset pushbutton UHSR-502 resets all above actions except actions 1, 2 and 17. The C&E chart also indicates the Maintenance Override Switches (MOS) and Operation Override Switches (OOS) associated with the instrument triggering the logic. These switches allow the operator to bypass the conditions tripping the system, whenever this is required (testing, maintenance). In normal operation, these switches shall never be activated. Instrument
OOS
MOS
UXHS-502-A
N/A
N/A
UXHS-502-B
N/A
N/A Page 123 of 161
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Instrument
OOS
MOS
FXALL-534
FHS-534-B
FHS-534-A
TXAHH-561
N/A
THS-561-A
BXALL-503-A
N/A
N/A
MGL-101
N/A
MHS-101-A
MGL-102
N/A
MHS-102-A
BXALL-504
N/A
N/A
LXAHH-509
N/A
LHS-509-A
LXAHH-501
N/A
LHS-501-A
LXAHH-504
N/A
LHS-504-A
FXAL-534
N/A
FHS-534-A
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TRAINING MODULE
SULPHUR RECOVERY UNIT (SRU) UNIT: 22
Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures
X
Section 9 - HSE Section 10 - Reference Document Index
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SECTION 8 : OPERATING PRACTICES 8.1. Normal Operation 8.1.1. Operating conditions The following is a narrative of the main process conditions of the SRU in steady state and FOR THE BACH HO MAX GASOLINE CASE ONLY. For a complete description of the Heat and material Balance & Operating Conditions of the unit 022, refer to the following process flow diagrams: 8474L-022-A0102-4110-300-001 Claus Section – Max Distillate 8474L-022-A0102-4110-300-002 Incineration Section – Max Distillate 8474L-022-A0102-4110-300-003 Claus Section – Max Gasoline 8474L-022-A0102-4110-300-004 Incineration Section – Max Gasoline 8474L-022-A0102-4110-300-005 Heat & Material Balance – Max Distillate 8474L-022-A0102-4110-300-006 Heat & Material Balance – Max Distillate 8474L-022-A0102-4110-300-007 Heat & Material Balance – Max Gasoline 8474L-022-A0102-4110-300-008 Heat & Material Balance – Max Gasoline Normal operation Narrative
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Figure 20: Simplified PFD of the SRU (BACH HO – MAX GASOLINE CASE) Page 127 of 161
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Figure 21: Simplified PFD legend and Utilities conditions Page 128 of 161
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ARU Off Gas from Unit 19 & H2S Rich Off Gas from Unit 18 Refer to P&ID’s: 8474L-022-A0103-4110-300-002/003/004 927 kg/hr of ARU Off Gas is fed from the unit 19 to the ARU off gas KO drum A2201-D-01 at 50°C and 0.6 kg/cm2g. The acid condens ate recovered in A-2201D-01 is pumped back to the battery limits by the duty ARU off gas KO drum pump A-2201-P-01-A at 4.9 kg/cm2g via PG-531. This line is normally no flow (NNF) as the condensate is pumped intermittently, on level control of the KO drum, back to the unit 19. 74 kg/hr of H2S rich SWS off gas is fed from the unit 18 to the H2S rich off gas KO drum A-2201-D-02 at 90°C and 0.6 kg/cm2g. The acid condensate recovered by the mist eliminator of the KO drum is pumped by the H2S rich SWS Off Gas KO drum pump on duty, A-2201-P-01-A, back to the SWS at 4.8 kg/cm2g via PG-534. This line is normally no flow (NNF) as the condensate is pumped intermittently, on level control of the KO drum, back to the unit 18. ARU off gas exits the KO drum A-2201-D-01 and flows to the ARU off gas preheater A-2201-E-01 via PIC-529. In A-2201-E-01, ARU off gas is heated to 250°C against 88 kg/hr of superheated HP steam. The duty of the ARU preheater is 52 kW. Superheated HP steam is fed from the header to A-2201-E-01 via TV522. The heated ARU off gas then flows to the thermal reactor A-2201-R-01 via TIC522, TI-526 and XV-505 before being split into 2 streams: 464 kg/hr of heated ARU off gas are fed to the 1st zone of the thermal reactor A2201-R-01 (reactor burner) via FV-530 and PG-552. 463 kg/hr of heated ARU off gas are fed to the 2nd zone of the thermal reactor via FIC-524 and FV-524. H2S rich SWS off gas exits A-2201-D-02 to be mixed with the heated ARU off gas downstream of A-2201-E-01, via PIC-530, TI-521, FIC-515, FV-515 and XV-501. Combustion air feeding to Claus section Refer to P&ID’s: 8474L-022-A0103-4110-300-003/004 Air required for acid gases combustion is compressed to 8.6 kg/cm2g in the Combustion Air Blower on duty A-2201-B-01 A and flows to the combustion air preheater A-2201-E-02 via PG-550, PIC-545 and TI-524. Excess air pressure is vented to atmosphere at the blower discharge via PV-545 and a silencer. Air pressure is monitored upstream the duty compressor by PG-696 and downstream of it by PG-597. A small fraction of the compressed air, 152 kg/hr, is sent to the Liquid Sulphur Degassing Pit (A-2201 -TK-01), to strip H2S from the liquid elemental sulphur.
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A tiny fraction of the compressed air is also sent to the flame detectors and the sight glass nozzles of the thermal reactor burner section via XV-510, PG-595 and restriction orifices. Once compressed, 533 kg/hr of combustion air is preheated to 253°C in the Combustion Air Preheater A-2201-E-02 against 44 kg/hr of HP superheated steam. The duty of the preheater is 26 kW. The preheated combustion air flows towards the thermal reactor A-2201-R-01 via XV-504 before being split into 2 streams to accurately adjust the flow of combustion air to the thermal reactor according to the acid off gas flow (main combustion air) and to the H2S/SO2 ratio in the Claus section tail gas (trim air): •
The main combustion air flows through FIC-527 and FV-527
•
The trim air flows through FIC-522 and FV-522.
These 2 combustion air streams are then recombined and 533 kg/hr of combustion air flows to the section 1 of the thermal reactor at 250°C and 0.49 kg/cm2g, via PG-547 and PXA-551.
Thermal Reactor and Burner Refer to P&ID: 8474L-022-A0103-4110-300-004 The Thermal Reactor (A-2201-R-01) is a 2 zones reaction furnace, each zone operating at different temperature: •
In the 1st zone all combustion air, all H2S Rich Off gas and a fraction of ARU Off Gas are burnt. The temperature of this zone is approx. 1240°C.
•
In the 2nd zone the hot flue gas from the first zone and the remaining ARU Off Gas are mixed. As the remaining ARU Off Gas is injected, temperature is lowered and modifications in flue gas composition take place in order to satisfy the overall heat and material balances.
Optimum temperature is achieved by-passing about 50% of ARU Off Gas to the second zone at design flowrate. 1533 kg/hr of flue gas then leaves the reactor at 0.44 kg/cm2g and 897°C and enters into the Claus Waste Heat Boiler and Sulphur Condensers A-2201-SG-01. The expected overall conversion of H2S to sulphur in the Thermal Reactor (A2201-R-01) is approx. 16.4% at design conditions (Max. Gasoline Case). Claus Waste Heat Boiler and 1st Sulphur Condenser Refer to P&ID’s: 8474L-022-A0103-4110-300-005/009 815 kg/hr of boiler feed water is sent from the header to the Claus Waste Heat Boiler and 1st sulphur Condenser A-2201-SG-01 via LV-514. 791 kg/hr of LP steam is generated shell side and delivered to the LP steam header at 4.1 kg/cm2g and 152°C, thru PIC-555, FI-531 and PV-555. Page 130 of 161
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24 kg/hr of blow down from A-2201-SG-01 is sent to the Claus Blowdown drum A2201-D-06, where is cooled against a 130 kg/hr of service water circulated to the blowdown drum in open circuit. Both water streams are then discharged to the oily water sewer at 50°C max via TG-537. The combustion products leaving the Thermal Reactor A-2201-R-01 are sent into the tubes and are cooled down to about 240°C in pas ses I & II of the Claus Waste Heat Boiler. The process gas leaving the Claus Waste Heat Boiler is further cooled down to about 162°C in the 1 st Sulphur Condenser (A-2201-SG-01 pass III). 29 kg/hr of sulphur produced in the A-2201-R-01 is condensed in the tube side of A-2201-SG-01 pass III and discharged by gravity to the sulphur pit (A-2201-TK-02) through its dedicated sulphur seal leg (A-2201-D-05 A). The entire line of condensed sulphur from the 1st sulphur condenser to the sulphur seal leg A-201-D-05-A and the seal leg are steam jacketed with LP steam from the header Level in A-2201-SG-01 is controlled by LIC-514 and is monitored locally by LG515/516. 1st Process Gas Reheater & 1st Catalytic Reactor Refer to P&ID’s: 8474L-022-A0103-4110-300-005/006 1504 kg/hr of process gas leaving the 1st Sulphur Condenser (A-2201-SG-01 pass III) at 162°C flow to the 1 st Process Gas Reheater A-2201-E-03, via TI-536 and SC-503. In A-2201-E-03, the process gas is heated up to 240°C against a flow of 35 kg/hr of HP steam. The process gas line from the 1st sulphur condenser is steam traced until the 1st process gas reheater. The duty of A-2201-E-03 is 60 kW. HP steam is fed from the header to A-2201-E03 via TV-541. HP condensate exits the reheater at 253°C towards the HP condensate header. Downstream of A-2201-E-03, 1504 kg/hr of reheated process gas flow to the 1st catalytic reactor A-2201-R-01 at 240°C and 0.33 kg/ cm2g, thru TI-583, TG-582 and TIC-541. The process gas enters the A-2201-R-02 where the Claus reaction between H2S and SO2 continues until equilibrium is reached at that condition, producing elemental Sulphur. Equilibrium temperature is approximately the temperature of process gas leaving the reactor (A-2201-R-02), i.e. 321°C. The temperature inside A-2201-R-03 is monitored via TI-542/543/544. 2nd Condenser, 2nd Process Gas Reheater & 2nd Catalytic Reactor Refer to P&ID’s: 8474L-022-A0103-4110-300-005/006/009 Page 131 of 161
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The process gas leaving the 1st Catalytic Reactor (A-2201-R-02) is fed to the 2nd Sulphur Condenser (A-2201-SG-01 pass IV) at 321°C v ia TI-553 and SC-506. 148 kg/hr of sulphur produced in the A-2201-R-02 is condensed in the tube side of A-2201-SG-01 pass IV and discharged by gravity to the Sulphur Pit (A-2201-TK02) through its dedicated sulphur seal leg (A-2201-D-05B). The entire line of condensed sulphur from the 2nd sulphur condenser to the sulphur seal leg A-201-D-05-B and the seal leg are steam jacketed with LP steam from the header. 1356 kg/hr of process gas leaving 2nd Sulphur Condenser (A-2201-SG-01 pass IV) at 170°C is fed to the 2 nd Process Gas Reheater (A-2201-E-04), via a mist eleiminator at the sulphur condenser channel outlet, TI-535 and SC-502. In A-2201-E-04 the process gas is heated up to 205°C against 25 kg/hr of HP steam. The process gas line from the 2nd sulphur condenser is steam traced until the 2nd process gas reheater. The duty of the reheater is 15 kW. HP steam is fed form the header to A-2201-E04 via TV-539 and HP condensate exits the reheater at 253°C towards the HP condensate header. 1356 kg/hr of process gas then flows to the 2nd Catalytic Reactor (A-2201-R-03) at 0.21 kg/cm2g and 205°C thru TI-584, TG-554 and TIC- 539. In the 2nd catalytic reactor the Claus reaction between H2S and SO2 continues until equilibrium is reached at these conditions, producing elemental Sulphur. Equilibrium temperature is approximately 223°C. The temperature inside A-2201-R-03 is monitored via TI-545/546/547. 3rd Condenser, 3rd Process Gas Reheater & 3rd Catalytic Reactor Refer to P&ID’s: 8474L-022-A0103-4110-300-005/006/009 The process gas leaving the 2nd Catalytic Reactor (A-2201-R-03) is fed to the 3rd Sulphur Condenser (A-2201-SG-01 pass V) at 223°C vi a TI-552 and SC-507. 27 kg/hr of sulphur produced in the A-2201-R-03 is condensed in the tube side of A-2201-SG-01 pass V and discharged by gravity to the Sulphur Pit (A-2201-TK02) through its dedicated sulphur seal leg (A-2201-D-05C). The entire line of condensed sulphur from the 3rd sulphur condenser to the sulphur seal leg A-201-D-05-C, as well as the seal leg, is steam jacketed with LP steam from the header. 1330 kg/hr of process gas leaving the 3rd Sulphur Condenser (A-2201-SG-01 pass V) at 162°C is fed to the 3 rd Process Gas Reheater (A-2201-E-05). In A-2201-E05, the process gas is heated up to 190°C by means of 20 kg/hr HP steam. HP steam is fed from the header to A-2201-E-05 via TV-540 and HP condensate exits the reheater at 253°C to the HP condensate header.
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1330 kg/hr of heated process gas then flows to the 3rd Catalytic Reactor (A-2201R-04) at 190°C and 0.09 kg/cm2g via TI-585, TG-555 and TIC-540. IN the 3rd catalytic reactor, the Claus reaction between H2S and SO2 continues until equilibrium is reached under these conditions, producing Sulphur. Equilibrium temperature is approximately 193°C. The temperature inside A-2201-R-04 is monitored via TI-548/549/550. Final Sulphur Condenser and Tail Gas Coalescer Refer to P&ID’s: 8474L-022-A0103-4110-300-006/007/008/009 The process gas leaving the 3rd Catalytic Reactor (A-2201-R-04) at 193°C is fed to the tube side of the Final Sulphur Condenser (A-2201-E-06), via SC-508 and TI551, for the final cooling against boiler feed water (shell side). 8 kg/hr of sulphur produced is condensed in the tube side of A-2201-E-06 and discharged by gravity to the Sulphur Pit (A-2201-TK-02) through its dedicated sulphur seal leg (A-2201-D-05D). The entire line of condensed sulphur from the final sulphur condenser to the sulphur seal leg A-201-D-05-D, as well as the seal leg, is steam jacketed with LP steam from the header. 44 kg/hr of vaporized BFW exits the final sulphur condenser at 121°C and flows to the steam condenser A-2201-E-07, via PIC-562 and PV-562, where it is cooled down against 3227 kg/hr of cooling water. Spent cooling water exits the A-2201-E07 at 39.2°C to the cooling water return header. Th e duty of A-2201-E-07 is 27 kW. Cooled BFW is then returned to the final sulphur condenser A-2201-E-06 via TG558. The level in A-2201-E-06 is monitored remotely via LI-522 and locally via LG520 and LG-521. 1322 kg/hr of process gas coming from the A-2201-E-06 is fed to the Tail Gas Coalescer (A-2201-D-04), via TI-559, to remove any sulphur mist from the process gas. Condensed liquid elemental sulphur is then sent by gravity to the Sulphur Pit (A-2201-TK-02) via steam jacketed sulphur seal leg (A-2201-D-05D). 1322 kg/hr of tail gas leaves the Sulphur Coalescer (A-2201-D-04) at approx. 130°C and 0.02 kg/cm2g and flows directly to the I ncinerator (A-2201-H-01), via AE-501 and SC-511. Liquid Sulphur Storage & Degassing Pits Refer to P&ID’s: 8474L-022-A0103-4110-009/010/011 212 kg/hr of liquid sulphur collected in the 4 seal legs are sent by gravity at 145°C to the non-degassed sulphur storage section.
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18 kg/hr of sweep air is drawn into the Liquid Sulphur Storage Pit A-2201-TK-02 (non-degassed sulphur section) via FI-541 and through a steam jacketed line. Nitrogen for bubbling is introduced inside the non-degassed liquid sulphur storage section via 2 steam jacketed nozzles. Temperature in this section is monitored via TI-570 and TI-571. Sulphur pit operates under approx. -50 mmH2O (G). Air intake is sucked from A2201-TK-01 and A-2201-TK-02 through a steam jacketed line by the Pit ejector A2201-J-01 A (fully steam jacketed). The pit ejector is fed with 150 kg/hr of LP steam from the header via UV-521, FG-544 and PG-588. 321 kg/hr of air is then discharged to the Incinerator (A-2201-H-01), via a steam jacketed line, at 145°C and 0.01 kg/cm2g. Liquid sulphur is pumped by the sulphur circulation pump on duty A-2201-P-04 A to the sulphur degassing pit A-2201-TK-01, via PG-581 and UV-524, by means of a steam jacketed line. In the sulphur degassing pit, 152 kg/hr of process air from A-2201-B-01A/B is bubbled through the sulphur by means of perforated plates. Process air is introduced into the degassing pit, via UV-522 and FG-545, by means of 2 steam jacketed lines. The temperature in the degassing pit is monitored remotely via TI-576, TI-577 & TI-578. Degassed elemental sulphur then flows by gravity to the degassed sulphur storage section through a steam jacketed line with 3 inlets. From the degassed sulphur storage section, 212 kg/hr of sulphur is pumped by the sulphur pump on duty A-2201-P-05 A at 145°C and 2.0 kg/cm2g to the sulphur apron via PG-589 and through a steam jacketed line. Incinerator Section Refer to P&ID’s: 8474L-022-A0103-4110-003/008 & 8474L-022-PID-0021-101 132 kg/hr of tail gas leaving the Claus section at 130°C and 0.02 kg/cm2g, as well as 321 kg/hr of vent air from the pit ejectors at 145°C and 0.01 kg/cm2g, are fed to the Incinerator (A-2201-H-01). The tail gas is fed to the incinerator via a steam traced line, while the vent air is fed through a steam jacketed line. In order to meet the requirements on the flue gas delivered to the atmosphere, 160000 kg/hr of dilution air from Dilution Air Blower on duty B-2203 A is fed to the Stack via PG-101. In normal operating conditions, NH3 Rich Off gas (from Unit 18) and CNU Off gas (from Unit 20) are used as support fuel to achieve 750°C inside the combustion chamber: •
19 kg/hr of CNU off gas from the unit 020 are fed to the incinerator burner at 65°C and 0.5 kg/cm2g, via XV-512.
•
927 kg/hr of NH3 rich SWS off gas is fed to the NH3 Rich Off Gas KO Drum A-2201-D-03. The condensate recovered by the mist eliminator of the KO drum is pumped by the NH3 rich SWS Off Gas KO drum pump on duty, APage 134 of 161
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2201-P-03-A, back to the SWS at 4.9 kg/cm2g via PG-542. This line is normally no flow (NNF) as the condensate is pumped intermittently, on level control of the KO drum, back to the unit 18. The separated off gas from A-2201-D-03 is then sent to the combustion chamber of the incinerator A-2201-H-01 via PIC-539, FI-518, PV-539, XV513 and PG-569. 8 kg/hr of fuel gas is also fed from the fuel gas header to the combustion chamber, via FT-535A, TV-560, XV-514 and XV-557, to guarantee the maintenance of the required temperature in the incinerator. 2141 kg/hr of Combustion air is compressed by the incinerator combustion air blower on duty A-2201-B-02-A and is fed to the combustion chamber of the incinerator A-2201-H-01 at 36°C and 3.3 kg/cm2g via PG-573, TI-562, FIC-539, FV-539 and HV-562. Any air excess pressure is vent to atmosphere at the blower discharge via FV-536 and thru a silencer. The Claus tail gas and the vent gas from pit ejectors (A-2201-J-01 A/B) are mixed with hot flue gas, at controlled temperature, and all sulphur bearing compounds are oxidised to SO2. Expected residual H2S content is lower than 10 vol.ppm. The operating conditions of the stack are as per the following: Flue gas flowrate: 163978 kg/hr Temperature: 57°C 8.1.2. Combustion air / acid gas ratio and Thermal Reactor temperature During the acid gas operation the flame temperature will become considerably higher than normal if the hydrocarbon content of acid gas increases and/or if more air than necessary is sent to the Reaction Chamber. A quick check of H2S/S02 ratio may be achieved by observing the temperature of the process gas in first condenser separation. Higher temperatures mean that more H2S than expected is burned to SO2. H2S/S02 ratio must be in any case higher than 1; that is to say tail gas must contain unburned residual hydrogen sulphide. •
In case of H2S excess (ratio H2S/S02 higher than 2), the only problem is a small decrease in plant efficiency.
•
In case of prolonged operations with rate lower than 1, catalyst life is considerably reduced due to the superficial sulphanation of the catalyst.
•
If H2S is absent, SO3 formation may occur. The higher is the free oxygen content, the higher is SO3 content. When water is present (in process gas it is always present) sulphur trioxide easily reacts giving sulphuric acid which is highly corrosive for carbon steel parts.
It is to be noted that more far is the H2S/S02 ratio from 2 and less will be the reaction heat developed in the reactor. For plant run at design conditions, such an increase is as high as 49°C for the first reactor a nd 12°C for the second reactor. Operator shall always control temperature trends in the reactors, together with values indicated by laboratory analyses or analyser results. In case of Page 135 of 161
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considerable discrepancy, it is recommended to check. In principle, the thermocouple values are the more reliable. Because it is possible to have the same flame temperature with different air/gas ratios (refer to the section 3.3.3.1 of the licensor operating manual), the only operational parameter to be used to operate the SRU plant is the Claus tail gas analysis. During the normal acid gas operation no quench steam has to be used for moderating the flame temperature, unless in case of upset conditions (i.e. acid gas with very high hydrocarbons content).
8.1.3. Claus Reactors Temperatures in normal operating conditions Since sulphur is a reaction product, the best would be to reduce its content in feed gas to reactors as much as possible to emphasise H2S conversion. Sulphur quantity in the feed gas to the reactors is conditioned by the working pressure in condenser (steam side) and therefore allowable cooling temperature and achieved sulphur condensation. However, steam produced pressure is conditioned by user needs, and therefore, cannot fall under a predetermined limit. At plant design conditions LP steam pressure is 3.6 kg/cm2g. In principle, if the Claus reactor inlet temperature is kept higher than stated values, the sulphur dew point approach increases, while the sulphur yield decreases. On the contrary, with lower Claus reactor inlet temperatures, the sulphur dew point approach becomes lower, while sulphur yield increases. The limit sulphur dew point approach considered for unit design is 15 °C min. The optimum inlet temperature of reactors (with the scope to reach the best H2S/S02 conversion to sulphur) is the one that achieves the maximum temperature difference between reactors inlet and outlet.
8.1.4. Claus Reactors Temperatures during sulphur sweeping operations Even if the reactors are operated according to the given instructions, it is possible that some sulphur condenses on the catalysts. In order to overcome sulphur condensation, the Claus reactors inlet temperatures shall be increased as much as possible (the best approach should be of additional 10 – 20°C) for about 24 hou rs every month. In this way, the liquid sulphur present on the catalyst shall evaporate and the initial conditions of run shall be restored (Sulphur sweeping operation). This special run can be performed every time when the catalyst activity decreases or the pressure drop increases.
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During this run the efficiency in the sulphur recovery of the plant shall be a little lower than during the normal run.
8.1.5. Incinerator temperature The normal Incinerator combustion chamber temperature is 750°C and the oxygen content in outlet flue gas is minimum 2 mol% in order to achieve good oxidizing conditions to burn NH3. Claus catalyst de-activation can have the consequence of producing a tail gas rich of unreacted H2S; the hydrogen sulphide contained in the tail gas shall therefore burn in the Incinerator combustion chamber and there will be an abnormally high flame temperature. It is important to note that in case of Incinerator shut down for high temperature the tail gas shall continue to be sent to the incinerator for some minutes.
8.1.6. Process Variable Effect on Product Quality The quality of sulphur produced in a Claus plant is normally very good, as the content of non-sulphur material is very low. The only impurity that can be present in noticeable quantity is carbon. Carbon can be originated from bad combustion of fuel gas during plant heating up period, or during normal plant operation with acid gas (containing abnormally high quantity of hydrocarbons), or in case of operation with strong process air deficiency. The sulphur produced in the Claus plant is saturated with H2S and contains sulphur polysulphides. In case of bad operation of the degassing system, the H2S and polysulphides contained in the product sulphur could be remarkably higher than normal with peaks of 200 - 250 wt.ppm in case of prolonged degassing upsets of the degassing system and with Claus section in normal operation.
8.1.7. Process Variable Effect on Sulfur Yield The following conditions will decrease the sulphur yield (refer to section 3.3.1 of the licensor operating manual for more information): •
Lower H2S concentration in the acid gas
•
Higher hydrocarbons content in the acid gas
•
Higher ammonia content in the acid gas
•
Higher steam content in the acid gas
•
Higher CO2 content in the acid gas
•
Incorrect air/acid gas ratio
•
H2S content in tail gas outside recommended limits (H2S/S02 ratio 2:1)
•
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•
Higher Claus reactors inlet temperature
•
Higher produced steam pressure in A-2201-SG-01
•
Catalysts fouled or poisoned or deactivated
8.1.8. Sulphur Degassing Section Here are some important considerations about this section: •
H2S is an extremely poisonous gas. Utmost care must be taken to avoid exposure to it. In special circumstances protective masks should be worn. During normal conditions in the degasification process only traces of SO2 are present. Sulphur fires in the pit can form large quantities of SO2, which is very poisonous. It is important to keep the over pressure (if possible) in the degasification pot.
•
Above 160°C, degassed sulphur undergoes a change i n molecular structure, which is characterised by a viscosity increase in a small temperature range. This will stop the stripping process and may damage the sulphur pumps. The temperature in the degassing and pumping compartment should therefore always be kept below 150°C.
•
If the stripping air is interrupted for too long the off-spec sulphur will be pumped to storage.
For more information on the process variables and the operating conditions of the SRU during normal operation, refer to the chapter 3.3 of the licenser operating manual doc. No. 8474L-022-ML-001.
8.2. Start-up Procedure The following will present the main steps of the start-up procedure without detailing the procedure to perform each action. For a detailed description of the start-up procedures, refer to specific procedures into the SRU Operating Manual doc. No. 8474L-016-ML-001.
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8.2.1. Preparation for Initial Start-Up
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8.2.2. Initial Start-up The difference between first and the other start-ups is the presence of sulphur in the plant. When sulphur is present, the plant heating-up has to be performed by burning fuel gas in stoechiometric conditions in the main burner; this is not necessary when no sulphur is present, as it happens for the first start-up. The start-up consists in heating-up the plant by fuel gas combustion; when the temperature of certain parts of the unit reaches desired values, the plant can be switched to acid gas.
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8.2.3. Plant Re-start-up following a shutdown After the sulphur (Claus) unit has been on stream and then shut-down, the method used for start-up will depend on the circumstances under which the Claus unit was shut down, the length of time it was shut down, and its existing conditions. Unless all sulphur in the plant was completely removed during the shutdown, the plant (in particular the Claus reactors) may contain trapped sulphur in some locations that will burn if contacted with the air at a high enough temperature. Permanent damage to plant equipment by overheating could result. Whenever the plant is being re-started, all temperature should be monitored particularly those in the reactors. If a temperature begins to rise rapidly, the unit should be shut down and cooled off with nitrogen purge. 8.2.3.1. Quick restart of warm plant If the plant has been shut down for a short time and no air has been admitted, it can be quickly restarted, maintaining the catalytic section on stream. In this case, the restart-up will be carried over using fuel gas in stoichiometric combustion and the switch to ARU Off gas will be done only when the minimum acceptable temperature is reached (refer to section 6.3.1 of the licensor operating manual doc. No. 8474L-022-ML001). If the plant was shutdown by the Emergency Shutdown System, it is necessary to be sure the problem has been corrected. •
Make a complete check of the unit including proper water level in the Waste Heat Boiler/Sulphur Condensers.
•
Make sure all air and feed gas valves are shut.
Proceed with the start-up according to the initial start-up sequence.
8.2.3.2. Restart of cold plant If the plant has been shut down long enough for the refractory and catalysts to cool and sulphur was not removed from the Claus catalyst beds, the start-up procedure must be modified to prevent the combustion of sulphur as well as reactors temperatures are increased. The sulphur present on the Claus catalyst must be evaporated and swept from the catalyst without allowing actual combustion to take place, which would result in damage to unit equipment. Maximum O2 = 0.4 vol% can be tolerated in the hot gas flowing in the Claus section. In fact every time when some sulphur is present in the plant, the combustion of fuel gas has to be performed in stoichiometric conditions, in order to avoid damages of the catalyst contained in the Claus reactors (containing sulphur). Stoichiometric combustion conditions are defined as to burn H2 and hydrocarbon contained in the fuel gas to CO2 and H2O, with no excess oxygen in the flue gas. During the stoichiometric combustion of fuel gas it is necessary to moderate the flame temperature by using steam as quench agent. Page 142 of 161
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Note that an incorrect (not stoichiometric) operation during fuel gas combustion, in plant heating up stages could be dangerous due to the possibility of carbon formation (oxygen deficiency) and to the presence of excess oxygen in the flue gas. In the first case, oxygen deficiency, the carbon black formed during the fuel gas combustion can plug and/or deactivate the reactors catalyst; in the second case, excess of oxygen, the sulphur present in the equipment unit can burn with localized increase of temperature. To avoid any of the above mentioned risks it is suggested to start-up the plant according to the procedure for hot condition.
8.3. Shutdown Procedures 8.3.1. Planned Shutdown The planned shut-down is normally carried out when an acid gas leak is detected, or an inspection is needed on some equipment, or maintenance works are required, or much simpler if the acid gas feed is no longer available at SRU plant battery limits. Whichever is the case of planned shut-down the first action to carry out is to remove sulphur in Claus section. Sulphur is condensed and absorbed in the pores of the Claus catalyst during normal operation, leading to a temporary deactivation of the catalyst activity as discussed. In addition, sulphur fires may rise on if the catalyst is exposed to air at temperatures higher than 180°C. Finally, sulphur wi ll solidify during the plant cooldown preceding the main burner shut-down. Due to the above consideration, sulphur shall be removed from the plant prior to proceeding with the cool-down.
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8.4. Emergency Shutdown Emergencies must be recognized and acted upon immediately. The operators and supervisory personnel should carefully study in advance, and become thoroughly familiar with, the proper steps to be taken in such situations. Some of the emergency conditions described here will not only result in a unit shutdown, but if the situation is not handled properly, can lead to serious damage to the unit. It is strongly recommended that the emergency procedures and the automatic shutdown systems be understood by all persons involved in the operation. In general, the objective of the emergency procedures is to avoid damage to unit. 8.4.1. Emergency Shut-down System Activation The Thermal Reactor Burner shut-down shall be initiated by pressing any of the following push buttons: •
Control Room ESD push button 022-UXHS-503-A/B
•
Local Panel ESD push button 022-UXHS-503-C
The Thermal Reactor Burner shut-down shall be also initiated by General ESD push button (022-UXHS-501) from Control Room. The emergency shut-down activation should be decided by the Operators shift supervisor only. The SRU plant shall be re-started if the initiator generating the shut-down is no longer active; the normal shutdown procedures shall be followed if the acid gas operation cannot be restarted immediately.
8.4.2. Power Failure Effects
All machineries will shut in case of electric power failure
Consequences
The plant shall trip for combustion air low flow rate and/or for flame failure
Actions
The cause of the electrical fault shall be found out as soon as possible to allow a restart-up when the plant is warm
8.4.3. Lack of Feedstock Effects
The pressure in the system will decrease
Consequences
Sulphur production will stop and care should be taken that all sulphur is removed from the Claus section to avoid sulphur fires
Actions
In case of a short interruption of the acid gas feed to the unit, the unit should be maintained on hot stand-by. If the lack of feed is for a planned period, the shut-down of the SRU plant should be performed Page 145 of 161
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8.4.4. Failure of Liquid Sulphur Export Line
Effects
Sulphur will no longer be exported and the level in the degassed sulphur pit (A-2201-TK-01) will rise
Consequences
Sulphur production might have to be stopped by a planned shutdown of the sulphur plant
Actions
If sulphur export can not be restored in a short period or if the levels in the Liquid Sulphur Storage Pit (A-2201-TK-02) and the Degassed Sulphur Pit (A-2201-TK-01) are high, the SRU plant should be shut-down. Note that the total combined sulphur storage capacity of the two sulphur pits is approximately 2 days of sulphur production.
8.4.5. Instrument Air Failure Effects
All control valves shall move to their safe position
Consequences
The plant shall trip for air and/or acid gas low flow rates or for flame failure
Actions
The cause of the instrument air failure shall be found out as soon as possible to allow a restart-up when the plant is warm
8.4.6. Steam Failure Effects
Heating system shall be no longer in operation
Consequences
Sulphur solidification will occur thus leading to plugging problems
Actions
The most common cause of the steam failure is the low pressure; LP steam pressure control loop shall be checked
8.4.7. Boiler Feed Water Failure Effects
The liquid level in the boilers shall drop
Consequences
Plant shutdown shall occur due to low liquid level in the waste heat boiler
Actions
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and reduce the firing rate to the burners to have a little more time to correct the problem.
8.4.8. Fuel Gas Failure Effects
The fuel gas header pressure shall drop
Claus section shut-down shall occur due to flame failure during Consequences fuel gas operation; anyway due to the shut-down of Incinerator (after a delay time) Actions
The plant restarts after Fuel Gas pressure adjustment
8.4.9. Combustion Air Blowers (A-2201-B-01A/B) Failure Effects
The Blower in operation trip
Consequences
Claus shut-down for combustion air low low flowrate (FXALL521)
Actions
Claus can be restarted using the spare blower. The failed blower can be putted in maintenance during plant operation, intercepting discharge line.
8.4.10. Incinerator Combustion Air Blowers (A-2201-B-02AIB) Failure Effects
The Blower in operation trip
Consequences
Incinerator shut-down for combustion air low low flowrate (FXALL-534)
Actions
Incinerator can be restarted using the spare blower. The failed blower can be putted in maintenance during plant operation, intercepting discharge line
8.4.11. Dilution Air Blowers (B-2203A/B) Failure Effects
Both operating blowers trip Thermal reactor shut-down for dilution air blower both machines stop (022-MGL-101/102, 2oo2)
Consequences Incinerator shut-down for dilution air blower both machines stop (022-MGL- 101/102, 2oo2). Sulphur degassing section shut-down for dilution air blower both Page 147 of 161
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machines stop (022-MGL-101/102, 2oo2). Sulphur production will stop and care should be taken that all sulphur is removed from the Claus section to avoid sulphur fires Actions
In case of a short interruption for maintenance, the unit will be maintained on hot stand-by. If the long period is required, the shutdown of the SRU plant should be performed
8.4.12. Off Gas K.O. Drum Pumps (A-2201-P-01A/B, 02A/B, 03A/B) Failure Effects
The Pump in operation trip
Consequences
Spare pump will be started to continue Off Gas K.O. drum condensate unloading operation
Actions
The failed pump can be putted in maintenance during plant operation, intercepting discharge line
8.4.13. Sulphur Circulation and Sulphur Pumps (A-2201-P-04A/B, 05A/B) Failure Effects
The Pump in operation trip
Consequences
Spare pump will be started to continue liquid sulphur transfer operation
Actions
The failed pump can be putted in maintenance during plant operation, intercepting discharge line
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Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE
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Section 10 - Reference Document Index
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SECTION 9 : HSE 9.1. Hazardous Areas Refer to the following documents: •
8474L-018-DW-0051-001 Plot Plan – SWS/ARU/CNU/SRU units
•
8474L-018-DW-1920-001 Hazardous Area Classification Plan – SWS/ARU/CNU/SRU units
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Figure 22: Abstract of the Hazardous Area Classification Diagram for AREA 4 Page 151 of 161
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9.1.1. Prevention of H2S and SO2 leaks It is strictly forbidden, without an authorization issued by the appropriate Refinery Safety Authority to flange, unflange or conduct any kind of maintenance to equipment in physical contact with H2S and SO2. Very strict controls on the toxicity of the working area must be carried out, particularly during the first start-up, and from time to time, during normal operation. During the first start-up the gaskets of all connections on lines containing H2S must be tested using filter paper soaked with lead acetate, which turns black in the presence of H2S gas. All leaks must be immediately eliminated. The alarm level for the H2S automatic analyzer in the plant area must be set at 10 ppm. It is advisable to carry on spot checks on the toxicity of working area by means of Drager tubes. The operating personnel must be well trained in the use of the safety devices available for the unit. All safety equipment must be readily available and periodically checked to ensure their reliability. All valves and flange connections in contact with H2S and SO2 must be regularly checked for tightness.
9.2. Safety Equipment Refer to: 8474L-018-DW-1933-001 Safety Equipment Layout for SWS/ARU/CNU/SRU units, in section 5 of the present manual. 9.3. Specific PPE All personnel involved in chemical handling related work in the SRU must wear the specific PPE required. Moreover, all personnel shall be read and understand the MSDS of the chemicals they will handle before proceeding to work. 9.3.1. H2S The best method for prevention of H2S poisoning is to stay out of areas known or suspected to contain it. The sense of smell is not an infallible guide as to the presence of H2S, for although the compound has a distinct and unpleasant odor (rotten eggs), it will frequently paralyze the olfactory nerves to the extent that the victim does not realize that he is breathing it. This is particularly true of higher concentrations of the gas. Fresh air masks or gas masks suitable for use with hydrogen sulfide must be used in all work where exposure is likely to occur. Such masks must be checked frequently to make sure that they are not exhausted. People who must work on or in equipment containing appreciable concentrations of H2S, must wear fresh air masks and should work in pairs so that one may effect a rescue or call for help should the other be overcome. As mentioned above, the atmosphere in which people work should be checked from time to time for appreciable concentrations of H2S.
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REMEMBER - JUST BECAUSE YOUR NOSE SAYS IT'S NOT THERE, DOESN'T MEAN THAT IT IS NOT. PPE recommendation for protection against H2S: Ventilation Respiratory Protection
Use adequate ventilation to control exposure below recommended levels For concentrations exceeding the recommended exposure level, use NIOSH/MSHA approved air purifying respirator. If conditions immediately dangerous to life or health (IDLH) exist, use NIOSH/MSHA approved self-contained breathing apparatus (SCBA) equipment.
Eye Protection
For splash protection use chemical goggles and face shield
Skin Protection
Gloves and coveralls of rubber or neoprene construction if liquid contact could occur. Avoid unnecessary skin contamination with material
9.3.2. Sulphur Dioxide PPE recommendation for protection against SO2: Respiratory Protection
A NIOSH/MSHA approved air-purifying respirator equipped with acid gas/fume, dust, mist cartridges for concentrations up to 20 ppm. A powered air-purifying respirator with acid gas cartridges up to 50 ppm. A full-facepiece air-supplied respirator for concentrations ≥ 100 ppm
Skin Protection
Heavyweight coveralls, safety boots and insulated impervious (i.e., neoprene, PVC) gloves
Eye Protection
Tight-fitting chemical goggles and face shield
Other PPE
Impervious gas-tight overall body protection depending on exposure. Safety showers and eyewash fountains should be installed in an area not likely to be affected by a release of SO2 and near storage and handling areas. Insulated gloves should be worn if liquid contact is anticipated
9.3.3. Sulphur PPE recommendation for protection against Elemental Sulphur: Respiratory Protection
Dust-type respirators shall be provided for dusty conditions. Breathing apparatus must be available for emergency use in case of fire.
Skin Protection
Workers whose skin may be sensitive to sulphur dust should button collars, roll sleeves down, and gather trousers at the ankle. Gloves may be helpful
Eye Protection
Dust-tight goggles with plastic or rubber frames may be helpful in dusty conditions
Other
Hard hat and safety shoes. Fire-retardant fabric is recommended. Sulphur impregnated clothing should not be worn. Page 153 of 161
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For More information, refer to the MSDS attached in the section 9.6 of the licensor operating manual doc. No. 8474L-022-ML-001.
9.4. Chemical Hazards It is of the utmost importance that all employees involved in this unit read and understand the MSDS of the chemical they will handle before proceeding to work. No work or operation should be allowed to commence before all employees involved in chemical handling related work have demonstrated knowledge of the health hazards they my face.
9.4.1. Hydrogen Sulfide Toxicity Classification:
Hydrogen sulfide is both an irritant and an extremely poisonous gas. Breathing even low concentrations of hydrogen sulfide (H2S) gas can cause poisoning. Hydrogen sulphide at concentrations greater than 500 ppm is highly toxic and can cause immediate death. Since the most parts of process streams have H2S content greater than 10,000 ppm, the unit must be completely gas tight and leaks repaired immediately when occur. It can be lethal to under-estimate an H2S leak. H2S acts by deadening nerve endings including those associated with smell. At concentration greater than 20 ppm it is no longer possible to smell the gas, thus greatly increasing its hazard. No work should be undertaken on the unit where there is danger of breathing H2S, and one should never enter or remain in an area containing it without wearing a suitable fresh air mask. 9.4.1.1. Acute Hydrogen Sulfide Poisoning Breathing air or gas containing more than 500 mol-ppm H2S can cause acute poisoning and possibly be fatal. Symptoms of Acute Poisoning
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The symptoms of acute H2S poisoning are muscular spasms, irregular breathing, lowered pulse, odor to the breath and nausea. Loss of consciousness and suspension of respiration quickly follow. Even after the victim recovers, there is still the risk of edema (excess accumulation of fluid) of the lungs which may cause severe illness or death in 8 to 48 hours. First Aid Treatment of Acute Poisoning Move the victim at once to fresh air. If breathing has not stopped, keep the victim in fresh air and keep him quiet. If possible, put him to bed. Secure a physician and keep the patient quiet and under close observation for about 48 hours for possible edema of the lungs. In cases where the victim has become unconscious and breathing has stopped, artificial respiration must be started at once. If a Pulmotor or other mechanical equipment is available, it may be used by a trained person; if not, artificial respiration by mouth-to-mouth resuscitation must be started as soon as possible. Speed in beginning the artificial respiration is essential. Do not give up. Men have been revived after more than four hours of artificial respiration. If other persons are present send one of them for a physician. Others should rub the patient's arms and legs and apply hot water bottles, blankets or other sources of warmth to keep him warm. After the patient is revived, he should be kept quiet and warm, and remain under observation for 48 hours for the appearance of edema of the lungs. 9.4.1.2. Subacute Hydrogen sulfide Poisoning Breathing air or gas containing H2S anywhere between 10 to 500 molppm for an hour or more may cause subacute or chronic hydrogen sulfide poisoning. Symptoms of Subacute Poisoning The symptoms of subacute H2S poisoning are headache, inflammation of the eyes and throat, dizziness, indigestion, excessive saliva, and weakness. These can be the result of continued exposure to H2S in low concentrations. Edema of the lungs may also occur. First Aid Treatment of Subacute Poisoning Keep the patient in the dark to reduce eyestrain and have a physician treat the inflamed eyes and throat. Watch for possible edema. Where subacute poisoning has been suspected, the atmosphere should be checked repeatedly for the presence of H2S by such methods as testing by odor, with moist lead acetate paper, and by Tutweiler H2S determination to make sure that the condition does not continue.
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9.4.2. Sulphur Dioxide Toxicity Classification:
Sulphur dioxide is a colorless, non-flammable gas. In the presence of mist or water this gas forms sulphurous acid. The gas has a sour taste. It irritates the respiratory tracts because it forms with the water present sulphurous acid and further sulphuric acid. At low concentrations it irritates the mucous membranes. The toxic effects vary to some extent with individual susceptibility. A certain immunization to SO2 is possible, to a maximum of 30 to 50 ppm. Human beings can withstand a maximum of 20 ppm, without adverse effects. Higher concentrations can give the victim a pale appearance, cause an unpleasant taste in the mouth, and can even make the gustatory nerves insensitive. Additional effects are loss of appetite and constipation. SO2 Health Hazards Summary: Vapors are extremely irritating to throat, mucous membranes and upper respiratory tract. Short exposures to concentrations as low a 1 ppm may produce a reversible decrease in lung function. Inhalation of higher concentrations causes hoarseness, pain and a feeling of pressure on the chest and bronchitis. It is sometimes impossible to speak or to swallow. Inhalation
Concentrations as low as 5 ppm have produced constriction of the bronchiole tubes. Very high concentrations cause acute bronchitis, tightness of the chest, and a quick start of perturbance of consciousness. Suffocation can cause death quickly. SO2 also causes an increase of hemoglobin in the blood. Severe overexposure may result in pulmonary edema, permanent lung injury or death. The effects of pulmonary edema which include coughing and shortness of breath may be delayed for hours or days after exposure.
Ingestion
Not applicable. Since material is a gas at room temperature, ingestion is unlikely to occur Page 156 of 161
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Liquid sulfur dioxide can cause frostbite and skin burns. Skin
Sulfur Dioxide converts to sulfurous acid in moist environments, which may cause skin irritation. This acid etches the human tissue. Mildly irritating at low concentrations of 5.4 ppm.
Eyes
Moderate to severe irritation above 8 ppm. Liquid sulfur dioxide can burn the eye and permanently affect vision.
Long Term Exposure
Dental caries, loss of fillings, gum disorders and the rapid and painless destruction of teeth may result from over-exposure.
9.4.3. Sulphur Sulphur Health Hazards Summary: Inhalation
Sulphur dust may irritate the mucous membranes of the respiratory passages
Ingestion
Solid sulphur is virtually non-toxic. It can be taken internally in fairly large doses without injury
Skin
In some individuals, sulphur dust has an irritant action, which may be aggravated by perspiration or moisture
Eyes
Sulphur dust in the atmosphere has a highly irritating effect upon the human eye. Therefore the need of wearing safety goggles when working in an atmosphere where dust contaminates the air cannot be overemphasized. Note: Sulphur dust clouds will ignite at a temperature of approximately 190°C.
9.4.4. Process gas and tail gas Process gas and tail gas have a variable composition. However it is always composed of strong acid and toxic gases. H2S contents may easily exceed 1% in Claus Section, if everything is proceeding in the best possible way.
For More information, refer to the MSDS attached in the section 9.6 of the licensor operating manual doc. No. 8474L-022-ML-001.
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Course Content: Section 1 - General Description Section 2 - Process Flow Description Section 3 - Process Control Section 4 - Safeguarding Devices Section 5 - Fire & Gas Systems Section 6 - Quality Control Section 7 - Cause & Effects Section 8 - Operating Procedures Section 9 - HSE Section 10 - Reference Document Index
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SECTION 10 : REFERENCE DOCUMENTS INDEX 10.1. Operating Manual/ Licensor Documentation 8474L-022-ML-001
SRU Operating Manual
10.2. Arrangement Drawings, Layouts and Plot Plans 8474L-018-DW-0051-001
Plot Plan – SWS/ARU/CNU/SRU units
8474L-018-DW-1960-001
Escape Route Layout SWS/ARU/CNU/SRU units
10.3. Process Flow Diagrams 8474L-022-A0102-4110-300-001 Claus Section – Max Distillate 8474L-022-A0102-4110-300-002 Incineration Section – Max Distillate 8474L-022-A0102-4110-300-003 Claus Section – Max Gasoline 8474L-022-A0102-4110-300-004 Incineration Section – Max Gasoline 8474L-022-A0102-4110-300-005 Heat & Material Balance – Max Distillate 8474L-022-A0102-4110-300-006 Heat & Material Balance – Max Distillate 8474L-022-A0102-4110-300-007 Heat & Material Balance – Max Gasoline 8474L-022-A0102-4110-300-008 Heat & Material Balance – Max Gasoline 10.4. Piping and Instrumentation Diagrams 8474L-022-A0103-4110-300-001 Interconnecting and distribution piping 8474L-022-A0103-4110-300-002 ARU and H2S rich SWS off gas KO drums 8474L-022-A0103-4110-300-003 NH3 rich SWS off gas KO drum 8474L-022-A0103-4110-300-004 Thermal reactor 8474L-022-A0103-4110-300-005 Waste Heat Boiler and Sulphur Condensers 8474L-022-A0103-4110-300-006 Catalytic Reactors 8474L-022-A0103-4110-300-007 Final Condenser 8474L-022-A0103-4110-300-008 Incinerator 8474L-022-A0103-4110-300-009 Sulphur Seal Legs 8474L-022-A0103-4110-300-010 Sulphur Pit 8474L-022-A0103-4110-300-011 Sulphur Degassing Box 8474L-022-A0103-4110-300-012 Combustion control 8474L-022-A0103-4110-300-013 Utilities distribution 8474L-022-A0103-4110-300-014 Utilities distribution 8474L-022-A0103-4110-300-015 Utilities distribution 8474L-022-A0103-4110-300-016 Utilities distribution Page 159 of 161
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8474L-022-A0103-4110-300-019 Utilities distribution 8474L-022-A0103-4110-300-020 Utilities distribution 8474L-022-A0103-4110-300-021 Distribution Manifolds 8474L-022-A0103-4110-300-022 Recovery Manifolds 8474L-022-PID-0021-101
Dilution Air Blowers
10.5. Equipment list Refer to the attached equipment list of unit 022: Unit 022 Extracted Equipment List.xls 10.6. Main Equipment Data Sheet 8474L-022-A1001-4110-300-007 Thermal Reactor Process Data Sheet 8474L-022-A1001-4110-300-008 Incinerator Process Data Sheet 8474L-022-A1001-4110-300-009 Catalytic Reactors Process Data Sheet 8474L-022-A1001-4110-300-011 WHB and Sulphur Condensers Process Data Sheet 8474L-022-A1001-4110-300-025 Incinerators Air Blowers Process Data Sheet 8474L-022-A1001-4110-300-028 Liquid Sulphur Storage Pit Data Sheet 8474L-022-A1001-4110-300-029 Liquid Sulphur Degassing Pit Data Sheet 8474L-022-A1001-4110-300-034 Combustion Air Blowers Process Data Sheet 8474L-022-SP-1040-200
Dilution Air Blowers Data Sheet
10.7. Instrument List Refer to attached extracted instrument list of unit 022: Unit 022 Extracted Instrument List.xls 10.8. Cause & Effect Matrix 8474L-022-A3505-4110-300-002-1
10.9. Safety Logic diagram 8474L-XX-XXXX-XXX
10.10. Fire & Gas Cause & Effect Chart 8474L-018-DW-1514-201 10.11. Fire & Gas Detectors Layout 8474L-018-DW-1950-001 Fire & Gas Detector Layout SWS/ARU/CNU/SRU units Page 160 of 161
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10.12. Fire Protection Layout 8474L-018-DW-1933-002 Fire Protection Layout SWS/ARU/CNU/SRU units 10.13. Hazardous Area Classification 8474L-018-DW-1920-001 Hazardous Area Classification SWS/ARU/CNU/SRU units 10.14. MSDS Refer to the following MSDS in the chapter 9.6 of the licensor operating manual, doc. No. 8474L-022-ML-001: •
A-2201-R-02/03/04 Catalyst
10.15. Vendors Documentation N/A
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