Gasoline Merox

INDEX S. NO. 1.0

2.0

DESCRIPTION

PAGE NO.

General Introduction 1.1 Glosssary 1.2 Plant Description Design Basis 2.1 2.2Process Description 2.3Equipment Description 2.4 Process Principles 2.5 Simplified Flow Diagram 2.6 Material Balance 2.7 Unit Layout Plan 2.8 Feed and Product Specification 2.9 Utility Description 2.10 Utility condition and requirement

3.0 4.0 5.0

Interconnectivity Precommissioning Activities Normal Start-Up Process Variable

6.0 7.0

Normal Shutdown. Emergency Shutdown Procedure

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8.0

Unit Protection System

9.0

Laboratory Requirements and Schedule

10.0 11.0 12.0

Equipments and Instruments Summary Special Procedure Reactor Hot Bed Washing. Catalyst Reimpregnation 12.1 List of Special Equipments. 12.2 Trouble Shooting

13.0 14.0

Chemical Consumption During Initial and Normal Operation. Fire & Safety

15.0

16.0


CHAPTER1

GENERAL 1.1 INTRODUCTION Petroleum distillates normally contain small amount of mercaptans (organic sulfur compounds) which impart obnoxious odour to the product. The LPG feed from FCC and Delayed Coker may contain some mercaptans, but most of them are formed during cracking reactions. Mercaptans are also formed when sulfur compounds decompose or H 2S and olefins react. Mercaptans may be alkyl or aryl in nature. UOP Merox process is an efficient and economical catalytic process for the treatment of light hydrocarbon products . This process is used for the conversion of mercaptan sulfur to another less objectionable form of sulfur compound or remove the mercaptan sulfur from the distillates. The UOP Minalk Unit (Minimum Alkali) is employing a sweetening process to oxidize mercaptans to disulfides using air as the source of oxygen. This reaction proceeds at nominal temperature in presence of a catalyst in alkaline environment. Merox treatment has the following objectives 1. To improve lead susceptibility of light gasolines 1. To improve the susceptibility of gasoline to oxidation inhibitors 1. To improve the odour of the products 2. To meet product specification /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 3 / 66

1.2

GLOSSARY azeotrope

a mixture of substances that behaves as a single substance in that the vapor produced by partial evaporation has the same composition as the

antioxidant barrel BPD caustic C/H disulfide

liquid. chemical additive to inhibit oxidation reaction. 42 U.S. gallons measured at 60°F barrels per day (also BPSD) sodium hydroxide solution caustic/hydrocarbon volume ratio class of sulfur compounds characterized by a sulfur-to-sulfur bond and relatively low volatility

EP extraction GC or GLC gph gpm gum hydroperoxide

represented by the general formula RSSR. endpoint (ASTM distillation). removal of mercaptan sulfur from hydrocarbon. gas chromatography U.S. gallons per hour U.S. gallons per minute polymerized hydrocarbon compound responsible for propagation of gum

IBP inhibitor

forming chain reaction (-OOH) initial boiling point (ASTM distillation) compounds responsible for delaying

LHSV mercaptan

terminating a chemical reaction liquid hourly space velocity common name given to class of compounds

or

having thiol functional groups represented by the naphthenic acid Nm3 std. m3 organo-metallic

general formula RSH organic (carboxylic) acid normal cubic meter ( 1 atm. 0°C) standard cubic meter ( I atm. 15°C) complex compound characterized

PW

carbon to metal bonds prewash

re-entry sulfur

entrained disulfide sulfur in regenerated caustic that

enters

and

dissolves

into

by

the

weak

exiting


RX SCFH sweetening

hydrocarbon product from an extractor reactor standard cubic feet per hour ( 1 atm. 60°F) conversion of mercaptan to disulfide without

stability

desulfurization quality of a fuel to remain unchanged for long

thiol thiophenol

periods of time in storage sulfur-to-hydrogen bond common name given to aryl mercaptans: also the compound C6H5SH


CHAPTER2

2.1

PLANT DESCRIPTION

DESIGN BASIS

This unit is designed to process 30,000 BPSD of Gasoline which will be coming from Main column section and unsaturate gas concentration section of FCC unit ( 413 , 414 ). Gasoline containing 90 ppm RSH ( Max. ) and 1 ppm H2S ( Max. ) can be processed in this unit. This unit can process Light Mogas and Heavy Mogas. .

URG COMPONENTS (Light Mogas) ::

1.

Naphtha Splitter Overhead stream (C5-105 deg C)

2.

Depentaniser bottom stream (C6-105 deg C)

3.

Deisohexaniser overhead stream (iC6)

RFG COMPONENTS: (Heavy Mogas) :

1.

Naphtha Splitter sidecut stream (105 – 180 deg C)

2.

Heavy cracked Naphtha stream (180-215 deg C)


2.9 UTILITIES DESCRIPTION LP STEAM SYSTEM

Refer P & ID :G 42 – RF 416 – 101 A 6” header provided with battery limit isolation valve, blind, local PG – 100, TG – 050, DCS flow indication ( FI060 ), totaliser indication ( FQI 060). Main header divided into several branch headers, which supply LPsteam to the following equipment.



A 6” header supplies LP steam to Desuper heater

The unit is also provided with 10 Nos. of LP steam utilities stations.

COOLING WATER SYSTEM

Refer P & ID :G 42 – RF 416 – 121 A 12” cooling water supply header provided with battery limit isolation valve, blind, local PG – 103, TG – 051, DCS flow indication ( FI 061 ), totaliser indication ( FQI 061). A 12” cooling water return header with battery limit isolation valve, blind, local TG – 052 and corrosion coupon CC001. Cooling water distribution :




A 8 “ Cooling water supply header is provided to Gasoline Cooler No.1 (S51), S52, S53. Same size of return header is provided.



A 6 “ Cooling water supply header is provided to spent wash water cooler(S54). Same size of return header is provided.

POTABLE WATER DISTRIBUTION SYSTEM

Refer P & ID :G 42 – RF 416 – 122 A 3” potable water header provided with battery limit isolation valve, local PG – 105, TG – 053. The main header serves potable water to the following points. 

fountain through 3/4“ line.



Safety Drinking water Shower & Eye wash ( PYWRF001) through 1 ½ “ line.

COLD CONDENSATE SYSTEM

Refer P & ID :G 42 – RF 416 – 122


A 6” cold condensate header provided with battery limit isolation valve, local PG – 107, TG – 055, DCS flow indication ( FI 063 ), Flow recorder ( FR 063 ).

The main header serves cold condensate to the following points. 

A 4” line to water heater ( Y 52 )



A 4 “ line to Caustic storage tank ( MT RF416- 01 )

UTILITY WATER SUPPLY SYSTEM

Refer P & ID :G 42 – RF 416 – 122 A 2” potable water header provided with battery limit isolation valve, local PG – 106. The main header serves Utility water to the following points. 

To pump seal P 01 A. ( ¾ “ line).



To pump seal P 01 B. ( ¾ “ line).


The unit is also provided with 10 Nos. of utility water stations.

FUEL GAS SYSTEM

Refer P & ID :G 42 – RF 416 – 131 A 3” header provided with battery limit isolation valve, local PG – 114, TG – 071, DCS flow indication ( FI 062 ), flow recorder ( FR 062). Main header divided into several branch headers, which supply fuel gas to the following equipment.



A 3” header supplies fuel gas to URG header for startup purposes.



A 2” header supplies fuel gas to LP flare header.



A 2” header supplies fuel gas to LP flare sub header.

PLANT AIR SYSTEM

Refer P & ID :G 42 – RF 416 – 141 A 3” plant air header header with battery limit isolation valve, local PG – 109.


A 1 ½ “ header is supplying air to Caustic storage tank(MT-RF416 -01) The unit is provided with 10 Nos. of plant air utility stations.

NITROGEN SYSTEM

Refer P & ID :G 42 – RF 416 – 141 A 2” plant air header provided with battery limit isolation valve, local PG – 108. Main header divided into several branch headers, which supply Nitrogen to the following equipment. 

A 1” header supplies Nitrogen to Reactirs (R01,R21) and for R31 & R41 (future).



A 2” header supplies Nitrogen to LP flare header.



A 2” header supplies Nitrogen to LP flare sub header.

BREATHING AIR SUPPLY SYSTEM

Refer P & ID :G 42 – RF 416 – 142 A 2” breathing air header provided with battery limit isolation valve, local PG – 111 and DCS pressure indication ( PI 135 ) with low pressure and high pressure alarm.


The unit is provided with 1 Nos. of breathing air utility stations.

INSTRUMENT AIR SUPPLY SYSTEM

Refer P & ID :G 42 – RF 416 – 142 A 2” instrument air header provided with battery limit isolation valve, local PG – 110. Various instrument air tapping are taken from this header.

LP FLARE AND RELIEF SYSTEM

Refer P & ID :G 42 – RF 416 – 111 A 18” flare header provided in the unit enters LP flare knockout drum ( 415 V 17 ). The header is provided with battery limit blind, isolation valve(Valve up side down), local PG – 101.


The PSVs & vent etc. ..discharge to LP flare header.



PSVs on Reactor (R 01) 101 A/B.



PSVs on Reactor (R 21) 121 A/B.



PSVs on Reactor (R 31) 131 A/B. (future)



PSVs on Reactor (R 41) 141 A/B.(fututre) PSVs on Gasoline feed cooler No.1 (S51) PSVs on Gasoline feed cooler No.2 (S52) PSVs on Gasoline feed cooler No.3(S53)

The header is provided with battery limit blind, isolation valve(Valve up side down), local PG – 044 and sampling point.



Fuel gas purge to main header through PCV 090.



Nitrogen PCV 091 for purge connection.

CLOSED DRAIN (CRACKED SLOP) SYSTEM

Refer P & ID :G 42 – RF 416 – 152 Underground main header of 6” size provided in the unit with several branch header connected to it for collecting drain from various points. All lines are connected to headers or branch header are provided with


an isolation valve and spectacle blind. Following drains are connected to main header. 

Drains from S51



Drains from S52



Drains from S53



Drain from HV015, HV017, PSV 153, PSV 154



Drain from R01,



Drain from sample points PA002, PA004, PA007, PA009.



Drain from R21.



Drain from PA005, PV001, PA010 and PV002.

This header is discharging into V 09 ( CRACKED SLOPS DRAIN TANK). This tank is provided with 2” nitrogen supply line through PCV 072, local press indicator PG 053 and Flow Orifice FO 050. V09 is provided with pump P 06A & local PG 053 which is discharging to Cracked slops. P 06A motor is on auto start from DCS MHS 020, run hours ML 020, based on LI 030 low low level stop and high high level start facility is also provided. V 09 is vented to LP flare through 8” line, which is provided isolation valve (Valve up side down) and blind.

CLOSED DRAIN (CAUSTIC) SYSTEM

Refer P & ID : G 42 – RF 416 – 151 Underground main header of 6” size provided in the unit with several branch header connected to it for collecting drain from various points. /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 14 / 66

All lines are connected to headers or branch header are provided with an isolation valve and spectacle blind. Following drains are connected to main header. 

From V 04 (2” line).



From MP RF 416 P51A (3/4” line).



On spent caustic line to ETP (2” line)



From LG022 and LT001 drain( both these combined and come in 2”line)



From LG023, LT002



From LV002 drain (1” line)



From LV 001 (1” line).

Drain (2” line) from Caustic Storage tank , LG020 drain(3/4” line) and LG020 drain(3/4” line) joins in a sub header (6” line) and this subheader joins the main header. This header is discharging into V 08 ( CAUSTIC DRAIN TANK). This tank is provided with 2” nitrogen supply line through PCV 073, local press indicator PG 061 and Flow Orifice FO 051. V08 is provided with pump P 05A & local PG 060 which is discharging to caustic system. P 05A motor is on auto start from DCS MHS 021, run hours ML 021, based on LI 031 low low level stop and high high level start facility is also provided. V 08 is vented to LP flare through 8” line, which is provided isolation valve (Valve up side down) and blind.


2.4 PROCESS PRINCIPLES The word `Merox' has been derived from the prefixes of 2 words MER - Captan and OXidation. The Merox process is a chemical treatment of Hydrocarbons to remove mercaptans or to convert mercaptans into disulfides. The principle is based on the ability of catalyst to promote the oxidation of mercaptans to disulfides at ambient temperature using air as the source of oxygen. Mercaptans are represented by general formula RSH, where ` R ' stands for hydrocarbon alkyl group and `SH' for mercaptan group consisting of sulphur and hydrogen atoms. Mercaptan concentration is represented in terms of the sulphur in the mercaptan molecule. Mercaptans are undesirable in finished petroleum products, due to odour, stability and total sulfur content. In Gasoline Merox treatment a fixed bed sweetening is used. The Merox 8 catalyst (It is an activated carbon which have been impregnated with Merox F B reagent ) which is water insoluble is deposited on a support bed of a selected granular activated charcoal. Merox 8 is loaded directly into the fixed bed reactor and requires no additional impregnation or activation prior to use. The activated charcoal bed adsorbs Phenols , Naphthenic Acids and Basic Nitrogen compounds, which affect the conversion reaction. The Hydrocarbon (Gasolinee), air, and caustic are simultaneously contacted over a solid support (charcoal bed) in the reactors, impregnated with Merox catalyst. The sweetening reaction proceeds at normal refinery product rundown temperature, in the presence of alkali and Merox Catalyst according to the following formulae. 4RSH + O2 ------------->

2SSR + 2H2O

RSH + NaOH ---------> NaSR + H2O

--- (1)

---- (2)


Merox 2NaSR + 1/2 O2 + H2O -----> -------- + 2NaOH + RSSR ----(3) catalyst Mercaptans, react with sodium hydroxide to form sodium mercaptide and water, which is reversible. The sodium mercaptide is then oxidized over Merox catalyst, to form disulfide, thus regenerating sodium hydroxide. The total reaction is as follows; 4 RSH + O2 ------------>

2 RSSR + 2 H2O

------- (4)

The disulphide is insoluble in caustic and remains in the Gasoline.

CHAPTER 6

PROCESS VARIABLES 6.1

FEED

STOCK PROPERTIES:-

Hydrogen sulfide :The presence of sulfide suppresses the oxidation of mercaptan, as sulfides get oxidised at a slower rate than mercaptan. Hydrogen Sulfide if present in the feed stock results in formation of Sodium Sulfide which gets oxidised to Sodium Thiosulphate. This is a neutral salt which causes no hindrance except that it consumes more caustic. Boiling range : As the end point of feed stock is increased the presence of catalyst poison in the feed increases and it becomes more and more difficult to convert the mercaptan present in the feed. /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 17 / 66

Mercaptan : As the concentration of mercaptan (RSH 90 WtPPM max) increases the ease of treating decreases. Also the molecular structure of mercaptan determines its ease of sweetening. Generally branched secondary or tertiary alkyl mercaptans, do not get sweetened as easily, as primary mercaptan. Sweetening is defined as conversion of Mercaptan to dilsulfide or some other form of innocuous sulfur compound, without actually removing it.

6.2

REACTION TEMPERATURE

:

The higher the temperature the easier the oxidation of mercaptan processes. But in normal operation the reaction temperature of Gasoline will be kept at 38 50°C. 6.3

REACTOR PRESSURE :Sufficient pressure ( 5.7 kg/cm2) should be held on reactor to keep air in dissolved form. The pressure should be sufficient to consume all the air used while sweetening. Channeling will take place through the reactor if a separate air phase is present. Pressure drop across reactor should be less than 0.7 Kg/cm2

6.4

AIR

INJECTION RATE

:-

Air injection is controlled to provide 120 to 200 % of the stoichiometric oxygen requirement. The stoichiometric oxygen requirement is 0.89 NM3/Kg/RSH-S present in the feed. Air is injected by means of air compressor ( C 01 A / B ) through FIC 003. The air injection rate is governed by the Gasoline feed rate, and mercaptan sulfur loading. Air must be completely dissolved in the Gasolineo by sufficient system pressure. Undissolved air will cause channeling in packed beds of charcoal and it must be vented off the system and /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 18 / 66

appropriate actions must be taken to avoid the situation. Hence air to be injected slowly to required level.

6.5

ALKALI INJECTION RATE : Injection of dilute caustic (3°Be) is done on ppm basis. First enough caustic is injected to supply the alkalinity required to maintain the mercaptan sweetening reaction. Additional caustic will be consumed by H2S. The amount of spent caustic will vary according to moisture in feed, temperature of feed stock, H2S content and air injection rate.

6.6

CATALYST UOP Merox 8 ( 44 m3 /reactor) is the catalyst used. It is in solid form ready to use. The Merox catalyst is not dispersible in caustic and this property prevents the caustic from removing the catalyst from the charcoal surface.

6.7

UOP MEROX PLUS (CATALYST PROMOTER) 7.4 Ltrs/hr (Max)( Typical inj.rate is 1.5lL/hr) of UOP Merox Plus is continuously added to the reactor charge. This is because, over a period of time gradual catalyst deactivation occurs as evident by a gradual increase in the RSH content of the product. Merox plus is a reagent, a liquid activity promoter, that boosts the catalytic activity of the system and extends the treatment period. This is an alternative to avoid unscheduled hot water washing to remove foreign materials absorbed by charcoal and effecting reactivity of the catalyst. In short Merox Plus allows long term stable operations for all fixed bed Merox applications and can extend run length, increase unit flexibility and reduced air and caustic consumption.


2.2

PROCESS DESCRIPTION Gasoline (Light Mogas and Heavy Mogas) from Main column section and Unsaturate Gas concentration


sections of the FCC ( 413 & 414 ). Light Mogas is received at Gasoline Merox B/L by a 10" line, provided with block valve and bleeder valve at 9.0 Kg/cm2g pressure and 112°C temperature and Heavy Mogas at 6.5 Kg/cm2g pressure and 91oC. Gasoline(Light Mogas at 91 deg C and 6.5 Kg/cm2g and Heavy Mogas at 112 deg C and 9 kg/cm2g are coole din the Gasoline Feed coolers (S52 and S53) .The Gasoline is flow is measured by the flow transmitters FT 015A/B. To this Gasoline stream 3 o Be caustic from 3

o

Be caustic storage

tank ((MT RF 416 01) pumped by caustic injection pumps P01 A and P21 and Merox Plus (activity promotor) pumped by Merox Plus injection pumps P02 A and P22 are joined. The caustic injected Gasoline is mixed with the air in a special mixer and this air plus Gasoline mixture is sent to Reactor R01 and R21 where the catalytic oxidation takes place. The air is supplied from air compressors in Kerosene Merox unit. The normal flow is 53kg/hr at 12.9 kg.cm2g and 55 deg C. The air flow is controlled by FV 016 for Reactor No. 1 and FV 018 for Reactor No.2. Air line is provided with ESD valves XV 001 and XV002 . When the Gasoline flow is low as sensed by FT 015A/ FT 015B the ESD valve XV 001 on the air line to Reactor No. 1 will automatically get closed. Similarly for the Reactor No.2 FALL 017 will trip XV 002. To the treated Gasoline UOP No. 5 inhibitor is added to increase the oxidation stability. The pressure in the reactor is controlled by the backpressure controllerPIC 001 for reactor No.1 and by PIC 002 for reactor No.2 MEROX REACTOR ( R 01 )


Merox reactors, is a vertical vessel packed with UOP Merox 8 (It is an activated carbon which have been impregnated with Merox F B reagent ) catalyst. The function of the activated carbon is to provide a vast surface where Mercaptan, catalyst, caustic and oxygen may come into contact for completion of the sweetening reaction. To provide the alkaline medium the charcoal is kept saturated with caustic solution with intermittant flow of caustic ( 3o Be ) by circulation pump P 01 A / B. Reactor consists of an upper inlet distributor, lower side outlet collector and bottom drain screen. The function of the inlet distributor is to provide a uniform lateral flow distribution over the reactor cross section. The distributor holes are oriented upward. The outlet collector and vessel drain pipes are specially constructed stainless steel and provided with UOP Johnson screen Reactor bottom header is filled with concrete and epoxy resin coated. Merox promoter (UOP Merox Plus) is continuously added to the reactor charge at the reactor upstream at a rate of 1.5 Ltrs/hr. Air under FIC 016 is sent to a mixer where it is mixed with hydrocarbon charge and then sent to the reactor. This stream then proceeds downward over the Merox catalyst bed. The Mercaptans present in Gasoline are converted to disulfides which goes along with the sweetened Gasoline.

2.8 FEED AND PRODUCT SPECIFICATIONS

RSH - S wppm H2S wppm

Operating Conditions Inlet pressure Kg/cm2 g Inlet temperature °C

: :

90 ( Max.) 1 ( Max.)

: :

7.7 38


Product Quality Mercaptan

:

5 ppm

2.3 EQUIPMENT DESCRIPTION : MEROX REACTOR (R 01 )

Merox reactors, is a vertical vessel packed with UOP Merox 8 catalyst (It is an activated carbon which have been impregnated with Merox FB reagent, which is not soluble in water ). Merox reactor consists of an upper inlet distributor, lower side outlet collector and bottom drain screen. The function of inlet distributor is designed to provide a uniform lateral flow distribution over the reactor cross section. The distributor holes are oriented upward. The outlet collector and vessel drain pipes are specially constructed stainless steel and provided with UOP Johnson screen. Reactor bottom head is filled with concrete and epoxy resin coated. The flow of the hydrocarbon, caustic and air is charged downward through the bed. The sweetening reaction takes place during, the course of movement through the charcoal bed. Particulates in the feed will be absorbed on and filtered out by the charcoal bed. Hence a hot water washing /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 23 / 66

procedure for removing foreign materials absorbed by the charcoal is done whenever required.

It is provided with following connections : vent 1 No. 6” Inlet for Gasoline feed 1 No. 12”outlet for Gasoline 1 No. 2” Air vent 1 No. 4” Drain. 1 No. There are two safety valves located on the top of the reactor PSV 101 A / B, which are set at 17.5 kg/cm2 g pressure to safeguard the vessel from emergency. Discharge of these PSV’S are routed to LP Flare. The purpose of reactor is to allow the catalytic oxidation of mercaptans to disulfides. The vessels dimensions are 3100 mm I.D and a total tangential length of 6400 mm. The vessel has got a inlet distributor (6”) for the feed. The vessel is provided with MEROX No. 8 catalyst . The height of the packing is 5500 mm. Merox No.8 is charcoal impregnated with Merox FB reagent. The vessel has got collector of 12” size. The vessel is designed for an internal pressure of 18.7 kg/cm2g at 70 deg C. The Vessel’s material of construction is carbon steel. The outlet os the reactor pipe is provided with a drain screen.

Drain Pot No.1 (V02, V22) : The vessel dimenstions are 450 mm I.D and a total tangential length of 900 mm. The vessel’s material of construction is carbon steel. The vessel is designed for an internal pressure of 18.7 kg/cm2g at 70 deg C. Inhibitor Injection Tank (V51) : The purpose is to store the UOP No. 5 inhibitor. The vessel dimensions are 600 mm I.D and a total tangential length of /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 24 / 66

750 mm I. D . The vessel’s material of construction is carbon steel. The vessel is designed for an internal pressure of 3.5 kg/cm2g at 70 deg C.

CHAPTER 4

PRECOMMISSIONING ACTIVITIES Before initial start up; Each vessel is to be inspected for proper fitting of internals, valves, pressure gauges, dial thermometer /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 25 / 66

All lines are to be checked to see that they conform to the detailed piping drawing Attention should be given to location of vents, drains, and Gauge Glasses. Each vessel is to be flushed with water thoroughly to ensure complete removal of construction debris, muck, rust etc., For initial commissioning adequate safety equipment, fire extinguishers, fire hose connections, emergency eye wash and showers are required to be provided at various locations in the plant. Personnel protective clothing like rubber gloves, helmets, apron, gum boots, hand gloves, eye goggles, ear muffs are to be supplied to the operating personnel Reactor Charcoal Loading, initial Merox catalyst impregnation and reactor bed alkalination are to be done prior to the start up.

4.1

REACTOR CHARCOAL LOADING

Before to loading the charcoal into the unit, all reactor internals should be installed and inspected. The reactor ( R 01) is a vertical vessel designed to contain the charcoal bed upon which Merox catalyst is impregnated . The inlet distributor spray pattern should be checked to ensure an adequate distribution with cold condensate.

4.1.1

LOADING PROCEDURE

The Merox Reactor, must be isolated from the system depressurised and blinded. The top side manways opened. The holes in the inlet distributor should be protected from plugging during charcoal loading by wrapping the distributor with canvas or plastic covering. A catalyst hopper with telescopic or segmented loading sock, that extends approx. to the level of the outlet collector pipe, is mounted on the top manway for Merox 8 catalyst loading. The sack position and length are /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 26 / 66

adjusted as the Merox 8 catalyst loading progresses to prevent any coning effect which could later cause maldistribution of Hydrocarbon flow through bed by channeling. After the loading of Merox 8 catalyst has commenced and the bed level is just slightly over the top of the UOP Johnson screen collector pipe and assembly, Merox 8 catalyst loading should be stopped. Once the dust has settled, someone wearing a fresh air pack or self contained breathing apparatus should enter the reactor via the bottom side manway to verify that the collector pipe assembly has been completely submerged with Merox 8 catalyst and to make certain that there are no unfilled spaces present underneath any of the laterals. The reactor bottom side manway flange faces should be checked and a new gasket should be installed. After the manway is closed Merox 8 catalyst loading can then be resumed, shortening the sock as loading progresses. When the top of the Merox 8 catalyst bed has risen uniformly to within 750mm of the inlet distributor the loading is stopped. Towards the end of the Merox 8 catalyst loading, the bed depth can be satisfactorily gauged by dropping a probe through the reactor manway. After the dust has settled and the bed is visible. Personnel entering the reactor should wear scot air pack. If necessary additional charcoal may be loaded to provide a level surface of 450 MM below the inlet inlet distributor centre line . A load in diagram is attached showing the appropriate outages and a record should be kept of the weight, volume of Merox 8 catalyst loaded. When Merox 8 catalyst loading is completed the hopper and loading sack is removed. Also the Merox 8 catalyst bed is checked for cleanliness and extraneous matter. The distributor pipe is uncovered and the top manway positioned and secured on four sides.


4.1.2 DISPERSION

OF

MEROX CATALYST

IN

AMMONIA WATER

The following formula used is to calculate the quantity of ammonia required for carrying out the reimpregnation. A = 0.002 W (T - 0.2 L + D/6) (3.14 D2/4) where A = Kg of NH3 required D = Internal diameter of reactor in meter L = Length of charcoal bed loaded in meters T = Tangent length of reactor in meters W = Kg/m3 of water It should be noted that some charcoals are washed with acid during manufacture and may ultimately required as much as 50% additional Ammonia. Unhydrous Ammonia is used for impregnation /reimpregnation before handling NH3, refer t Industry Safety bulletins regarding the proper handling of this toxic chemical. Install the cylinders as shown in figure . The NH3 cylinder outlet connection should face up. This will allow liquid NH3 to be drawn from the cylinder through the internal dip leg. Adjust the NH3 rate into the circulating water using the globe valve at the point of addition to regulate the flow. PG 005 will indicate pressure in cylinder. The rate of addition (observed by cylinder weight loss), should be adjusted to add, the required amount over a two hour period. When the NH3 concentration is stabilised , verify that it is a min of 0.2 Wt % by case analysis. A minimum NH3 concentration of 0.2 WT% required for good dispersion of the Merox reagent. High concentration will not have adverse effects but may present an odour problem. Obtain the desired quantity of Merox FB reagent prepare for impregnation as follows :

and

Into a clean 0.2 M3 drum add about 0.1 M3 of circulating NH3 water. A small air flow should be provided through the air sparger to keep the catalyst in suspension. Do not agitate too much as excessive foam will develop due to too much air. /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 28 / 66

Shake the Merox FB container to disperse any reagent that may have settled and pour the contents directly into the drum upto 15 Kg, 6 bottles of 2.5 Kg each of Merox reagent may be added to the drum at one time. If more than 15 Kg of reagent is required the reagent should be added in equal batches of 15 Kg each. The recommended quantity of Merox FB reagent, is approx 1.4 Kg/cubic meter of effective reactor charcoal inventory which is the charcoal bed volume above the outlet collector assembly. Once the reagent has been transferred to the drum, begin adding it to the circulating Ammonia water via the Eductor ( Y 51 ). The total reagent required should be added at a uniform rate over a four to eight hour period. Note : The Ammonia water effluent from the reactor outlet should remain colurless throughout the initial Merox catalyst impregnation procedure and this should be verified by periodically inspecting a sample of reactor outlet Ammonia water for colour. Should the Ammonia water from the reactor become intensely blue in colour, there is reason to suspect channeling of the charcoal bed in which case the catalyst Impregnation should be stopped and steps undertaken to remove the bed channeling. The channeling may be due to several reasons one being improper distribution by the distributor pipe due to breakarage etc., During subsequent catalyst reimpregnations, a blue colour will appear in the Ammonia water coming from the reactor outlet. This is not unusual, since the old aged charcoal may no longer be able to absorb all of the Merox reagent. Particularly some of the more soluble isomers. As little as 1 PPM of Merox reagent is sufficient to give a faint blue colour to the Ammonia water. The following procedure must be used to remove channels  block in the reactor inlet , outlet lines.  Inject a full amount of air for no longer than thirty seconds to bubble or fluff the charcoal bed. ,  if convenient, somebody should observe at the bubble patterns from the top manway. Large coagulated bubbles would be an indication of


channeling. A uniform bubble distribution would be an indication that channeling no longer exists. When the drum is nearly empty of Merox reagent, flush it several times with carrier solution and educt this into the reactor in order to get all the residual recycle/catalyst into the reactor. Continue circulation of NH3 water through the reactor for a min of 1 hour if time permits the circulation should be continued over night, which will aid in attaining a more even distribution of catalyst on the charcoal. At the conclusion of the catalyst impregnation procedure, the NH3 water is stopped. The reactor may now be drained using air or Nitrogen to the sewer. Open the reactor top manway and obtain an outage measurement from the top of the bed. Also collect 8 10 spot samples of the impregnated. Charcoal from predetermined representative positions at the top surface of the reactor bed, so as to enable future determination of the lateral catalyst distribution profile, if necessary. These samples should be held for analysis in case trouble indicating maldistribution of catalyst, should develop, when the unit is put into operation. Close the reactor manway and bring the reactor upto a slight positive pressure with Nitrogen added through vent line. The valves which were opened should be closed and NH3 cylinder disconnected. Now the bed is ready for alkalinization.

4.1.3

REACTOR BED ALKALINIZATION : The reactor charcoal must be alkalinized with 3o Be aqueous sodium hydroxide solution. Before this. we have to remove the excess water that is remaining in balance in the charcoal bed .


Suffficient caustic is to be injected to maintain a pH in the range of 9 to 12 at the reactor drain pot outlet. The caustic injection pump P01, P21 to be checked frequently to assure that sufficient caustic is being pumped to the reactors. . The conventional fixed bed Merox reactor is now prepared to receive some HC feed. During continuous operation of a conventional fixed bed or Merox 10 Unit, the HC feed will gradually wash caustic out of the charcoal bed. This caustic will collect in reactor water drain or interface pot. When the caustic on the charcoal become depleted, mercaptan conversion via the Merox reaction will cease to take place. However, depletion is gradual, not sudden. A regular lab analysis program to determine mercaptan sulfur in the product will show a gradual increase in mercaptan concentration with time. This is largely caused by loss of alkalinity and it becomes necessary to realkalinize the bed periodically. The amount of surface active material present:Both naturally occurring sulfonates and naphthenates and synthetic corrosion inhibitor additives. i.e. if prewashing to remove Naphthenates is inefficient realkalinizing of the bed must be done more frequently.

4.1.5 INITIAL COMMISSIONING Preliminary Inspection : Inspection is the most important step in start up preparation. All equipments must be carefully inspected to see that it conforms in all respects to the detailed drawing and specifications. All respective lines should be traced to see that they conform to the detailed piping drawing and specifications. Attention should be given to locations of vents/drains/gauge glasses pressure gauges, sample points, pressure gauge, temperature indicator, relief valves to ensure that they are installed in accessible locations. Great attention must be given to installation of trays packing supports and internal distributors. Detailed inspection criteria will be covered later along with specific loading instructions. /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 31 / 66

Pressure Testing : After ascertaining by careful check that all internal equipment is properly installed and all vessels are clean and free of construction debris, vessel manholes should be closed and the vessels and piping should be pressure tested Hydraulically, using water in accordance with the rating set forth in the pressure certificate for the particular vessels. Blinds must be installd in suitable locations to isolate vessels and equipment which have a lower pressure rating than the particular vessel or equipment being tested. Usually the Hydraulic pressure test is carried out at 1.5 times the design pressure, but the proper test pressures must be ascertained for each vessel in question.

Very Important : All new pumps should be run for sufficient time to properly wear in the packing , so that bearings will not overheat when the pumps are finally placed in service. In practice it is run for 24 hours, suction strainers should be in place during this time and for the first several days after commencing actual operation. This is for the protection of the pump from any dirt or construction debris. Instruments : These must be carefully checked for correct installation and calibration by a qualified instrument personnel. All tests that can be performed to simulate actual operating conditions should be carried out to ensure that the instrument will operate properly. All orifice plates should be checked to see that they conform to the specifications.


CHAPTER 5

NORMAL START-UP Before the feed is taken into the unit, it is necessary to expel air from all equipments and pipelines, as it is a potential fire hazard. Air elimination can be done by Nitrogen purging. Entire system is lined up and air elimination done by Nitrogen purging. Merox Reactor ( R 01 ) Reactor should be N2 purged to an Oxygen content of less than 5% by lining up N2 through Reactor vent line. Reactor inlet , outlet valves to be closed and drain pot exit valve (i/v u/s of LV001) to be closed.. Ensure all the drains and vents are closed. Nitrogen Purging should be carried out by Pressurising the reactor with N2 to approx 15-20 Psig. Depressurising to atmospheric pressure. Again pressurising the reactor to 15 - 20 Psig.with N2 and again depressurising it to atmospheric pressure. This method of pressurization and depressurisation should be repeated until the oxygen content is less than 5 vol%. Reactor to be pressurised with FG by opening the feed inlet valve of the reactor. Now the system is ready for receiving Gasoline. Steps undertaken operation are ; Check with blending people ( RTF) whether the designated tank is ready to receive the product. Then open the B/L valves. Inform FCC of starting the treatment of Gasoline. When Gasoline product from FCCU is confirmed to specified properties, route Gasoline to Merox Unit. Caustic injection pumps P01A and P21 to be started and caustic injection to be started at the maximum rate.. Gasoline flow through the unit is lined up as follows: Gasoline feed ---- Gasoline feed cooler S52 --- HV 015 ---Reactor (R 01) ---Designated Tank or slop tank. Gasoline feed ---- Gasoline feed cooler S53--- HV 017 ----Reactor(R 21) ---- Designated Tank or slop tank. /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 33 / 66

The Merox reactors are filled with Gasoline completely and this is ascertained by overflow in vent line. Wnem the reactor is full of hydrocarbon, reactor pressure to be increased to operating pressure with the backpressure controller. Inform Kerosene Merox for want of air, open the air flow indicating controller ( FIC 016 ) to R01 and FIC 018 to R21 to a desired amount and switch over to automatic operation. When aqueous effuluent apperas at the reactor water drain or interface pot, the interface level controller (LIC 001) to be commissioned and the caustic injection rate in increments to obtain 9-12 pH drain effulent. Start the Merox plus injection pump ( P 02 A and P22) to inject Merox plus activator into the untreated Gasoline line. The system pressure controlled at 3.5 Kg/cm 2g by PIC 001 for R01 and by PIC 002 for R21.. Sample product for doctor test. If negative, treated product can be sent to storage tank .


CHAPTER 7

NORMAL SHUT DOWN Usually normal shutdown takes place to carryout scheduled turn around for maintenance jobs. Just before shut down, inform RTF to switch over Gasoline rundown as there will be no more sweetening and confirm, that Gasoline rundown switched over to some other tank. Cut off air injection to R01 reactor by closing FV 016 and to R21 by closing FV018. Inform Kerosene Merox about the shutdown. Divert Gasoline flow to slop tank. Block off Gasoline Merox battery limit Valve. Depressure Merox Unit through back pressure control. Then pump out through P 51 A to slop tank. Stop caustic injection pump (P 01 A and P21) to cut off in caustic injection. Stop Merox plus injection pump P 02A and P22 to cut off the injection of catalyst activated. Complete isolation must be attained between feed stock line and injection lines of air and caustic soda by closing each isolation valves located upstream of injection points. 7.1

TRANSFERRING INVENTORY LIQUID Use the globe valve for caustic disposal and monitoring the gauge glass and take care to ensure that the Hydrocarbon does not go to spent caustic in tank. Pump out the Gasoline in the following vessels to the HC slop oil tank by using caustic circulation pump (P 51 A), Each vessel must be under a slight pressure to avoid pulling a vacuum. This can be done by a small flow stream of Nitrogen through the following vessels.

R 01 R21

-

Merox reactor Merox Reactor


N.B : Permanent steam connection is provided for the following vessels : 7.2

PREPARATION FOR MAINTENANCE Steam out unit thoroughly N.B. : (1) Reactor must be steamed out from top to bottom inorder not to disturb the charcoal bed. Install isolation blind when required (as per master blind list). Open vessels certify and condition vessels for safe entry. 8.2 8.3


CHAPTER 8

EMERGENCY SHUT DOWN PROCEDURES An emergency shut down warranted if on or more combinations of the following occurs. FCCU upset/feed failure. Power Failure Instrument Air Failure Steam Failure. For all the above, the unit can be temporarily isolated, until the failed service is brought back to normal condition, can then be restarted simply by opening the isolation valve. It should borne in mind to protect the product tanks, as contamination should be avoided. (1) FCCU Failure Bypass Gasoline Merox and route the Gasoline to slop immediately, to avoid off spec. Gasoline from coming in contact and contaminating the Merox reactor beds. Return the unit to service once upset is corrected and Gasoline results are ok. For the above close B / L isolation valve on the Gasoline feed line and PIC 001 on treated Gasoline line. Cut off air injection by closing the XV 001 & FIC 016. Similarly cut off air injection by closing the XV 002 and FIC 018. Isolate Gasoline feed and Close PIC 002 on treated Gasoline line. Stop the following pumps and close the discharge valves P 01 A and P21 caustic circulation pump P 02 A and P22 Merox Plus injection pump (2) Power Failure Gasoline feed pump, caustic injection and Merox plus injection cease functioning. By pass the unit as above and


bottle up. As power is recovered restart pumps and return to normal operation. (3) Instrument Air Failure In case of instruments air failure happens, all control valves go to fail safe position. This results in all control valves in the unit to shut down and isolate the unit. List of instruments on FC/FO are given at the end of the manual. Bypass unit until air is restored. Also close caustic injection, Merox plus injection pumps. (4)

Steam Failure

Even though no steam is used in Gasoline Merox in normal operation, steam failure will affect the FCCU. There is a danger that off spec. Gasoline may come to Merox Unit. By pass Merox unit and bottle up until Gasoline comes on spec. Keep RTF informed of the situation and confirm that Gasoline is switched over. Once Gasoline comes on spec inform to RTF to switch to product tanks.

CHAPTER 12

SPECIAL PROCEDURES

REACTOR BED HOT WATER WASHING When adjustment of the operating variables is no longer sufficient to maintain catalyst bed activity, the charcoal bed can be hot water washed to remove sundry organic compounds and caustic neutralization soaps which have deposited in the charcoal pores or otherwise physically blocked off the active catalyst surface. Since many of these compounds are water soluble, catalyst bed activity will be restored when they are flushed from the charcoal. Hot water washing is also necessary to remove sodium soaps and alkalinity from the charcoal prior to catalyst reimpregnation. The phenomenon of charcoal pore plugging or coating is gradual and, hence, allows the bed washing to be scheduled with minimum inconvenience to general refining operations /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 38 / 66

and scheduling. Hot water washing may also be effective in reducing or eliminating reactor bed pressure drop which should never be allowed to exceed 0.7 Kg. The water used for reactor washing should be either clean steam condensate or deionized water that is free of dirt, suspended matter, hardness, excessive salts, and active chlorine as in hypochlorite. The washing procedure is as follows Stop the air injection and hydrocarbon flow to the reactor. Provision should be made to pump - or pressure - out all hydrocarbon from the Merox reactor under steam or nitrogen pressure. 1. Fill the reactor with warm, 50°C warm water. This should be done by passing Cold Condensate through Y 52 and opening LP steam after filling half of the vessel stop water. Pump this wash water to spent caustic facilities. Repeat this procedure. This step will greatly reduce the alkalinity of the wash water discharged to the sewer system and will also protect the vessel from caustic attack. 2. After the hydrocarbon has been pumped from the reactor and the major portion of the residual caustic has been removed, begin steam injection downflow through the bed via the water heater in the reactor. It will take approximately one or two hours for this step to remove most of the remaining hydrocarbon from high aromatic feedstocks. The reactor drain effluent is usually cooled for safety using direct cold water quench of an effluent heat exchanger. 3. Commission the water heater and introduce hot, 200 210°F, (95 - 99°) water via the reactor inlet distributor at a rate of approximately 0.65 M3/hr/cubic Meter of activated carbon. Initially the reactor drain valve is closed. When the reactor is liquid full, open the reactor drain valve and begin draining the hot water from the reactor drain line to the sewer ( or an alternative disposal point) at a rate approximately equal to the rate at which hot, freshwater is flowing into the reactor. 4. During the initial stages of hot water washing, the reactor effluent from the drain line will be highly discoloured,, e.g black or dark brown, and foamy. As the washing proceeds, the water will lighten in shade and pass through a series of colour hues. (colour changes). Eventually the water will become clear and essentially colourless.


If the bed is being washed solely to reactivate the catalyst by cleaning the charcoal pores, the washing is completed when the wash water is clean and essentially colourless. If the bed is being water washed prior to a catalyst reimpregnation, hot water washing is continued until the effluent water pH is reduced to between 8 and 9. This will minimize acetic acid consumption in a later step. 6. Gradually stop the steam flow, but continue to introduce cool condensate through the water heater into the reactor to cool the heater into the reactor to cool the charcoal bed down to a temperature of about 140°F (60°C). Nitrogen can be used to maintain the reactor under slight positive pressure. 7. After the bed is cooled, the water is displaced with nitrogen pressure and all of the water in the reactor is drained. 8. For a conventional fixed bed Merox Unit, the catalyst bed must be alkalinized with fresh caustic (20° to 30° Be') as discussed in _REACTOR BED ALKALINIZATION -- CONVENTIONAL FIXED BED UNITS section. 5.

CATALYST REIMPREGNATION Requirements : Catalyst reimpregnation is necessary only when hot water washing is no longer effective in reactivating the catalyst to provide long period of satisfactory mercaptan oxidation. The internal between catalyst reimpregnation is a /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 40 / 66

function of proper operation HC and mercaptan types, crude source, feed impurities etc and may vary from 3 months to a year or even longer, when required the catalyst reimpregnation is to be done. Procedure 1.

2.

3. 4.

5.

:

The washing procedure has to be followed from steps 1 to 7. When effluent water pH is reduced to 8 to 9 or to a pH which no longer seems to be dropping, stop washing, while washing the reactor bed also flush out the circulation pump suction and discharge lines to remove any residual alkalinity with slight positive pressure on the reactor. Please note that the water drained after acidification is colored. This indicates the acid addition was effective in releasing additional contamination from the catalyst bed. Stop circulation when the level is below distributor pipe. Approximately 20 M3 of water to be drained. Close the reactor drain valve and fill the reactor with warm 50-60°C Cold Condensate. Vent Nitrogen as required to maintain a slight positive reactor pressure. Stop the water and block in the water heater when the reactor is full and catalyst bed is submerged. Open the valves in the reactor drain and the side outlet lines going to the circulation (caustic) pump (P 51 A ) suction. Line up the valves in the pump discharge back to the reactor inlet line and into the reactor and start the pumps and establish circulation. The water is circulated in a closed loop system at a maximum rate. Valves in the suction lines to the circulation pump from both the reactor bottom drain and the reactor side outlet are open. Inject steam occasionally, into the circulating water to maintain temp of 50-60°C, the water temperature can be satisfactorily estimated by feeling the circulating pump casing/discharge piping.

Acidification of Charcoal Bed Acidification of charcoal is important to assure liberation of sodium salt of organic acid which were not removed during hot water washing procedure. Hence after warm water circulation is established, the last traces of alkalinity can be removed from the charcoal by educting acid into the circulation wash system. 2. Glacial Acetic acid is recommended as it is readily available and is much less corrosive than mineral acid. 1.


3.

Place about 28 lt of Acetic acid in to the acetic acid addition pot provided. The acetic acid can be placed in the drum used for catalyst impregnation or a rubber hose can be put directly into the Acetic Acid container. Educt the acid into the circulating water by regulating the globe valve in the line from pump discharge into the suction of the eductor. The glacial Acetic Acid should be added to the system over a period of 5-10 minutes.

Note : 28 lts per reactor of commercial grade glacial acetic acid required Acetic Acid is not required for the initial impregnation of reactor. It is needed only for subsequent Reimpregnation. After circulating the acidified water for one hour, check the water pH at the sample point in the circulation pump suction line. If the circulating water pH exceeds 6.5, educt another about 20 lt of Acetic Acid, as described above. After another hour, again check pH of water from the reactor outlet. continue this procedure until the water pH is 6.5 or less. This provides on the bed slight acidic medium. 5. Drain the acidified water from the reactor drain using nitrogen to maintain a slight positive pressure on the reactor. Note that the water drained after acidification is coloured; this is an indication that acid addition was effective in releasing additional contaminants from the catalyst bed. 6. Once the bed is drained the reimpregnation is done as disscussed in the impregnaiton procedure. 4.


CHAPTER 14

TROUBLE SHOOTING The failure in mercaptan sweetening in the Merox inlet can be attributed to one or more or combination of the following; a) Lack of caustic b) Insufficient Air c) Reactor channeling d) Mechanical interference with the catalyst e) Loss of catalytic activity f) Emulsification and caustic entrainment.

(a) Lack of Caustic : The presence of caustic is essential in the Merox Reactor. When the Sodium Hydroxide is either consumed out or weakened out, Mercaptan oxidation will no longer proceed. This is evident by the increase in mercaptan sulfur content in the treated Gasoline. Hence resaturation of the catalyst bed must be carried out to restore the sweetening process. Use of 20 °Be fresh caustic is advised. Only by operating experience frequency of saturation can be determined. However a mere frequent caustic wash will ensure sufficient alkalinity. Sulfides may seriously impede caustic regeneration due to oxidation of sulfide ion in preference to mercaptide ion. H2S + 2NaOH ---- Na2S + 2H2O.

Hence the source of hydrogen sulfide must be eliminated. When all of the sulfide is oxidized, the catalyst will again begin to oxidize mercaptan. Raising the catalyst concentration, caustic temperature and air rate may be used to speed /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 43 / 66

up elimination of sulfide interference. Hence two batch type caustic prewasgh is employed in series. This will allow greater utilisation of caustic without risking H2S leakage into Merox Unit. Up to a certain point the presence of acid oils improves extraction. When their presence interferes with caustic flow in the extractor caustic entrainment may take place. Accumulation of regenerated acidic materials may consume casutic, by CO2 picked up from the regeneration air. Only experience can determine the extent to whcih spending the caustic with weak acid can be tolerated before extracting efficiently drop off. (b)

Insufficient Air

This often happens when there is an increase in mercaptan sulfur, or the total Gasoline treated through this unit. Air injection rate must be adjusted. Accordingly to accomodate these changes in air concentration is generally kept at 150 - 200% of stoichiometric requirement, higher conentration is possible as long as all the air is dissolved. Oxidation reactions other than that of mercaptans will be promoted at higher concentration and this must be considered when using a higher injection rate. If insufficient air is suspected check the reactors pressure to make sure all air is dissolved. Check the air flow meter to see if air is going in at the right rate. Submit Gasoline samples to analyse the mercaptans load and see if there is any change. Adjust air rate accordingly.

(c)

Reactor Channelling

When the catalyst is new or known to have lost activity and when it has been determined that adequate air is present, channeling should be suspected. A separate air phase will almost always induce channelling. Adjust system pressure to dissolve the injected air. Channelling can then be corrected by fuffing the bed with air or nitrogen for 30-40 second. The air or Nitrogen hose should be connected to the Gasoline outlet at the reactor bottom. (D)

Mechanical Interference of Catalyst


The activated charcoal bed absorbs Naphthenic acids, trace compounds such as high molecular weight Hydrocarbon, particulates and Nitrogen compounds. Accumulation of these materials will plug catalyst pores and plug up active sites thus reducing the activity of the catalyst. This is evident by observing the increasing pressure drop across the reactor. The catalyst activity can be partially recovered by hot water washing the reactor bed. If water washing is ineffective, the charcoal bed must be impregnated. (e)

Loss of Catalytic Activity

It is normal for the Merox catalyst to gradually lose its effectiveness, as the unit ages. The treated Gasoline becomes more concentrated in mercaptan sulfur and does not produce specification product. It is necessary to caustic wash the reactor more frequently and more concentrated caustic solution is to be used. Other means to help the Merox reaction are to increase reactor temperature and the oxygen content eventually mercaptan requirement can no longer be made despite continuous saturation, reimpregnation will be required. (f)

Emulsification and Caustic Entrainment

Merox catalyst in caustic solution does not increase the tendency of caustic solution to emulsify with Hydrocarbons. It does however, increase the detergent properties of caustic. Scale and dirt will be almost dislodged/absorbed by Merox catalyst.

completely

Finely diluted suspended material can stabilise emulsions. It may be necessary to discard the first batch of caustic if it picks up a big load of scale and dirt from used equipment. Part of this scale and dirt may be iron sulfide. It appears that preferential oxidation of such sulfide may prevent the catalyst from promoting oxidation of mercaptan.



CHAPTER 13

LIST OF SPECIAL EQUIPMENT 1. 2. 3. 4. 5.

Special check valve Eductor Air Mixer Spray Nozzles Desuperheater

Y Y Y Y

Y 21 51 22 03,23 53

(1) Special Check Valve

(Y 03 )

The purpose of this piece of equipment is to prevent a back flow of either caustic (Extraction Unit) or H.C. (Sweetening Unit) to the source of air, whether it be a dedicated compressor or the plant air system. It is installed directly on the air line just upstream of the injection point into either the rich caustic or the sour H.C. stream. The features of this cracking requirement (0.14 spring loaded closing action. 100% fail safe, these valves reliable over the years.

check valve include its low - 0.28 Kg/cm2) and positive Although no check valves are have proven themselves quite

The valve must be installed in a vertical position, and it is recommended to use stainless steel tubing on its inlet side inorder to prevent extended pipe threads either hindering the operation or damaging the valve internals. Note : In the event of air failure H.C./caustic mixture may be in contact with the check valve Internals: (2) Eductor ( Y 01 ) This is used for catalyst and acetic acid injection. Size Motive force ammoniated water Inlet Pressure

: :

1" Water/0.2

:

5.27 Kg/cm2g

wt

%


Inlet Temperature Liquid handled

:

: 38°C Glacial Acetic Acid and

:

Mixing of Air and

water (3)

Air Mixer ( Y 04 ) Service

Hydrocarbon Air Pipe Size

:

1”

Tee Size

:

6”

MOC

:

Carbon Steel, except SS filter

element

( 4 ) Spray Nozzles ( Y 03, Y23 ) Service : For Caustic injection to the hydrocarbon Type : Removable injection nozzle assembly MOC : 303 SS Nozzle No. : ¼ LNN – SS14 Connection : ¼ “(NPT) Operating Conditions Temperature : 38°C Pressure Drop : 21.1 Kg/cm2g Operating outlet pressure : 7.5 Kg/cm2g Capacity : 19.8 Lts/Hr. ( 5 ) Desuperheater ( Y 53) Service : Type : Inlet steam Flow rate : Turndown : Max. Temp. : Normal Temp. Outlet Steam Press. :

Reactor steam - out Attemperator 2.527 T / h 5 to 1 232 oC : 177 oC 1.5 kg/cm2g


Temp. : 177 oC Allowalbe temp. : 11 oC Variation Desuperheater Water Temp. : 60 oC Flow Rate : 0.11 m3/h

CHAPTER 10

LABORATORY REQUIREMENT SCHEDULE The ultimate objective of petroleum refining is to produce product hydrocarbon streams which meet all specifications required for their ultimate end use. To accomplish this objective, it becomes necessary to characterize the important physical and chemical properties of the various refinery streams utilizing specific laboratory analytical testing procedures. Thus, satisfactory refinery operation depends largely upon proper analytical procedures for quality control. The sample point should be well purged to eliminate aged material, water, dirt, etc., and assure withdrawal of sample representative of the material in the pipe at that point in time. The sample container must be adequate for the analysis to be obtained. Once a proper sample has been obtained, it must be preserved intact until analyzed. This require the preservation of it’s physical and chemical changes in the sample.


10.1 SCHEDULES AND TEST METHODS

Suggested analytical schedule for the Gasoline Merox unit is given below. These represent a minimum recommendation for an adquate quality control program.

S.N. STREAM NAME & TEST

TEST METHOD

FREQUENCY

Once in a day

NAME 1 Gasoline Feed 

Distillation

ASTM D 86



Hydrogen sulfide

UOP 163

“



Mercaptan Sulfur

UOP 163

“



Particulates

ASTM D 2276

Weekly



Gravity

ASTM D 1298

Daily




2 Fixed bed reactor inlet 

3 

Diagnostic Drain Pot effluent



PH

UOP 314 or ASTM D1293

Daily



Total Alkalinity

UOP 210

Daily



Gravity

ASTM D 1429

Daily



Acid oils

UOP 743

4 

As required

Reactor No.1 outlet Diagnostic

 

“



“ “



Inhibited Product



Doctor Test

UOP 41

“



H2S

UOP 163

“



Mercaptan sulfur

UOP 163

“



Sodium

UOP 549

“



copper Strip corrosion

ASTM D 1266 or ASTM D

“



Distillation

1552 ASTM D 86 

Oxidn stability induction ASTM D 525



Lead content



Phosphorus



Benzene

ASTM D 3237 ASTM D 3231

“ “ “ “ “

ASTMD 3606 /var/www/apps/conversion/tmp/scratch_5/312514705.rtf 51 / 66



Octane Number

ASTM D 2699 and 2700



Oxygen Content



VOC

EPA formula



Toxics Reduction

EPA formula



Nox reduction

EPA formula



Existent Gum

ASTM D 381

“ “ “


Note:

The sampling and analysis same for Reactor No.2.

CHAPTER 16

SAFETY All the rules of safety in the refinery operation apply to the operation of the Merox Process. All employees and persons responsible for operation of the Merox process should be familiar with applicable safety practices. All necessary precautions should be taken to avoid accidents.

16.1 INTERNAL FIRE


The presence of air and hydrocarbons in Merox Process equipment, particularly the excess air vent line, is not considered to be any more hazardous than other situations in refineries in which air and hydrocarbons vapors exist.

Locations of Safety shower 1. North of MT-RF416-01 (Caustic Storage tank) 2. South of MT-RF416-02

Material Safety Data Sheet for Caustic : Properties and characteristics: Physical state

:

Turbid solution

Colour

:

Water white to slightly coloured

Water solubility

:

Complete

Molecular weight :

40.01

Flash point

Non flammable

:

Mode of entrance into body Reactivity

:

Inhalation, ingestion and contact

:


The solution is stable in nature and hazardous. It is slowly corrosive to iron and copper. Reacts violently with many organic chemicals such as acrolein, acrylonitrile, alcohols, chloroform, malei anhydride etc Health Hazards : Injury may result before one realizes that chemical is in contact. It is toxic and damages tissures.

Inhalation

:

Injury to entire respiratory tract.

Prolonged exposure may lead to inflammation of lungs. Skin

:

Destruction of tissues, burns and

:

Severe damage and may lead to

ulcerations. Eyes

conjunctivitis, corneal burn etc. Ingestion

:

Severe burns of the mucous

membranes of the mouth, throat, esophagus and stomach. Perforation of tissue may follow. Fire and Explosion Hazards : Instances of violent decomposition of organic materials have been recorded following usuage of caustic soda solution for cleaning production equipment. Contact with water or moisture may generate sufficient heat to ignite combustible material. Handling and Storage

:

For protection of


1. Respiration - Filters respirators 2. Hands

- Vinyl or neoprene

gloves 3. Eyes

-

Goggles. Face shield

4. Body

-

safety shoes, gum

boots & vinyl or rubber clothing. Keep away from acids, metals, explosives, organic peroxides and easily ignitable materials. Emergency shower etc., should be nearby where the chemical is handled. Spillage disposal

: Dilute the solution with large quantities of water taking care not to splash the material.

Neutralising Chemical

: HCl or other mineral acid solutions

Disposal

: Neutralize with dilute HCl acid. Discharge into sewer with sufficient water.

Fire Extinguishment

: Caustic soda is not flammable, however fire extinguishing equipment and adequate water for fire fighting should be available in all process or storage areas.

First Aid

: In case of

Inhalation

: Leave the area, report for medical evaluation.


Skin contact

: Emergency shower bath, followed by removal of clothing while still under the shower. See the physician.

Eye contact

: Irrigate for at least 15 minutes. Keep eye lids apart and move eyes in all directions and have irrigation continued.

Ingestion

: Drink lot of water/milk. Don’t induce vomiting unless advised by physician. 1% acetic acid solution can be given.


CHAPTER 15

CHEMICAL CONSUMPTION

15.1 CHEMICAL CONSUMPTION 1. 2.

3.

4. 5. 6.

UOP Merox 8 catalyst – 44 m3/reactore UOP Merox plus injection : Normal 1.5.Ltrs / hr & Maximum 7.4 Ltrs/h. continuously to the reactor charge. Acetic Acid - 28 Litres/reactor Commercial grade glacial acetic acid is used. Not required for initial impregnation but required for further reimpregnation. Ammonia - 124 Kg/reactor Liquid anhydrous ammonia in cylinders is used. Caustic 10°Be - 68 M3/3 days Caustic 3°Be - 0.02 m3/h



CHAPTER 11

EQUIPMENT DETAILS

S.NO

TAG NO

EQPT.

DESIGN

OPERATING

ID MM COLUMN

TITLE

1 2

MV RF416 REACTOR V01 MV RF

NO. 1 REACTOR

416 V02

NO.2

MOC TEMP

PRESS

TEMP

PRESS

DEG C 70

KG/CM2G 18.7

DEG C 38

KG/CM2G

70

18.7

38

3100

CARBON

3100

STEEL CARBON STEEL


VESSEL DETAILS

S.NO.

TAG NO

EQPT TITLE

DESIGN

OPERATING

ID MM

TEMP 1

MV RF416-

DRAIN POT

2

V02 MV-RF416

INHIBITOR

V51

INJECTION

3*

MT-RF416-01 3

O

PRESS

TEMP

DEG C KG/CM2G DEG C 70 18.7 38

TANK Be Caustic

70

3.5

70

254mmHg

PRESS KG/CM2G -450

38

600

Type = Cone Roof

Storage tank * - Caustic Storage tank has got a partitioned section sized to hold 15% of Nominal tank capacity.


6800

L

PRESSURE RELIEF VALVES

S.

TAG SERVICE

NO

NO

SET PR

PRESS KG/CM2G

TEMP DEG C

KG/CM2G

BASIS OF SELECT

1

101A Reactor 1

17.5

NORMAL 5.6

MAX 18.7

NORM 38

MAX 70

FIRE

2

vent 101B Reactor 1

17.5

5.6

18.7

38

70

FIRE

36

30

36

38

70

BLOCKEDO

3

vent 102 CSTC Pump

18.2

6

18.7

38

70

UTLET FIRE

18.2

6

18.7

38

70

FIRE

18.2

6

18.7

38

70

FIRE

18.2

6

18.7

38

70

FIRE

8

outlet 121A Reactor 2

17.5

5.6

18.7

38

70

FIRE

9

vent 121B Reactor 2

17.5

5.6

18.7

38

70

FIRE

36

30

36

38

70

BLOCKED

4

discharge 110A Gasoline Cooler 2

5

outlet 110B Gasoline Cooler 2 outlet

6

111A Gasoline Cooler 3

7

outlet 111B Gasoline Cooler 3

10

vent 122 Caustic inj pump 2 dis

OUTLET


S.

TAG SERVICE

NO

NO

11

SET PR

PRESS KG/CM2G

TEMP DEG C

BASIS OF

KG/CM2G

NORMAL MAX

NORMAL MAX

SELECT

151A Kero 1

24.6

14

24.6

38

70

BLOCKED

Caustic inj. 12

OUTLET

Pump A 151B Kero 1

24.6

14

24.6

38

70

BLOCKED

Caustic inj. 13

OUTLET

Pump B 152 Kero 2

24.6

14

24.6

38

70

BLOCKED

Caustic inj.

OUTLET

14

Pump 153 Air mixer out

15

to Reactor 1 154 Air mixer out

17.9

5.7

17.9

38

5.7

38

70

BLOCKED

70

OUTLET BLOCKED

to Reactor 2

OUTLET HEAT EXCHANGERS

S.NO TAG NO

SIDE

SER

SURFACE

HEAT

MO

VICE

AREA

DUTY

C

TEMP DEG C

PRESS

KG/CM

M2/SHELL MMK 1

S51

2

S53

3

S54

SHELL Gasoline TUBE CW SHELL Gasoline TUBE CW SHELL Hot Water

CAL/HR 2.43 CS CS 5.04 CS CS 0.82 CS

I/L

O/L DES NORM

112 32 102 32 93

38 49 38 49 54


IGN 140 120 130 120 120

8.16 3.5 9.0 3.5 4.7

wash TUBE

effuluent CW

CS

32

49

120

3.5

CENTRIFUGAL PUMPS S.NO

TAG

SERVICE

SUC. PR

NO MAX 1

RATED

KG/CM2G P51A/B Ammoniate 1.05

1.05

PRESS

CAPACITY

KG/CM2G

M3/HR

DIS SHUTO NORM 5.27

FF 6.3

30

PO

RATED

HYD

30

3.5

d water

PROPORTIONATING PUMPS :

S.N TAG NO

SERVICE

O

SUCTION PR

CAPACITY L/HR

TYPE

KG/CM2G

3 oBe

1

P01,P21,

2

P31,P41 Caustic P02,P22, Merox Plus

KG/CM2G

MAX RATED MAX MIN 0.75 0.07 99 9.9 --

0.07

DIS PR

7.37

0.74

Norm MAX 19.8 DIAPHR

RATE 28.62

AGM DIAPHR

28.62

1.5


3

P32,P42 P52,P53

o

3 Be

0.75

0.07

1356

136

678

Caustic 4

P03,P23,

UOP No.5

AGM DIAPHR

13.3

AGM 0.07

6400

640

1600

6.75

P33,P43



Gasoline Merox

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