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FLARE RADIATION REPORT
25/01/12
Issued For Information
DATE
DESCRIPTION
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BY
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APPD
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PT. SUMBER PETRINDO PERKASA
PT. CITRA PANJI MANUNGGAL
GAS SUPPLY TO TAMBAK LOROK POWER PLANT
TABLE OF CONTENT
1.OBJECTIVES................................................................................................................................3 2.SYSTEM DESCRIPTION..............................................................................................................3 3.FLARE LOAD AND CAPACITY.....................................................................................................3 3.1. Flare Load........................................................................................................................3 4.FLARE STACK DESIGN CRITERIA..............................................................................................5 4.1. Thermal Radiation Limit...................................................................................................5 4.2. Design Criteria.................................................................................................................5 5.FLARE RADIATION ANALYSIS....................................................................................................5 5.1. Flare Stack Height............................................................................................................6 5.2. Flare Load........................................................................................................................6 5.3. Environmental Condition..................................................................................................6 5.4. Receptor Point.................................................................................................................6 5.5. Calculation Method..........................................................................................................6 5.6. Fluid Properties Design Data...........................................................................................7 5.7. Flare Radiation Analysis Result.......................................................................................8 6.REFFERENCES...........................................................................................................................9
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1. OBJECTIVES This document covers the flare radiation analysis in Randu Blatung Gas Transfer and Booster Station (RBGTBS). 2. SYSTEM DESCRIPTION The flare system in the RBGTBS is designed to relieve emergency process upsets that require release of large volumes of gas and also be used to control vent streams from various process operations. The relief hydrocarbon gas are piped to a remote, elevated by using flare stack, and burned in an open flame in the open air using specially designed burner tip. Relief and blowdown from the systems will be routed to the flare headers, depending on the system pressure. The hydrocarbon will be burned in flare tips. High pressure system flare load comes from high pressure relieving device and blowdown gas. The pressure relieving device is provided for overpressure protection. Blowdown system is provided to depressurize the system during emergency or maintenance. In this facility, two automatic blowdown valves are provided at downstream of Slug Catcher and Discharge Scrubber. It will contribute to the addition of thermal radiation received by the receptor, as will as the thermal addition from solar radiation. 3. FLARE LOAD AND CAPACITY 3.1.
Flare Load To determine the flare load and capacity, the scenarios are considered as given below. 3.1.1 Depressurization Case (Blowdown) In emergency shutdown for confirmed fire, there is a need to dispose the hydrocarbon pressurized inventory. The pressurized isolated equipments and plant sections are depressurized by opening the blowdown valve. Depressurized gas is routed to the flare system. Blowdown from the isolated sections will occur one and followed the other section automatically. The blowdown flare load are from Slug Catcher V-101 and Discharge Scrubber V-104. Initial blowdown pressure is the vessel operating pressure of 675 psig for case of confirmed fire from fire and gas. Blowdown is started at its initial pressure and down to 100 psig in 15 minutes as per API standard 521, resulting peak blowdown load 8.2 MMscfd gas flared from Slug Catcher and 4.9 MMscfd gas flared at Discharge Scrubber.
3.1.2 Emergency Case (PSV Relief) Page 3 of 9
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An emergency case due to PSV relief will not coincide with a depressurizing scenario. The amount to be relief depend on the requirement to prevent the inventory from overpressure the relevant sections. and the maximum flare load will be the maximum from PSV Compessor. The maximum relief load is 25 MMscfd gas flared.. The selected flare stack height will be verified at this maximum relief load.
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4. FLARE STACK DESIGN CRITERIA 4.1.
Thermal Radiation Limit
The flare stack height shall be calculated so the exposed radiation heat in the vicinity of the flare shall comply with the radiation exposure limit as per API Standard 521 given below. Table 4.1. Recommended Design Thermal Radiation for Personnel Permissible Level Btu/hr-ft2
Radiation kW/m
3000
9.46
Maximum radiant heat intensity at any location where urgent emergency action by personnel is required. When personnel enter or work in an area with the potential for radiant heat intensity greater than 6.31 kW/m2 (2000 Btu/hr-ft2), then radiation shielding and/or special protective apparel (e.g. a fire approach suit) should be considered.
2000
6.31
Maximum radiant heat intensity in areas where emergency actions lasting up to 30 second can be required by personnel without shielding but with appropriate clothing.
1500
4.73
Maximum radiant heat intensity in areas where emergency actions lasting 2 minutes to 3 minutes can be required by personnel without shielding but with appropriate clothing.
500
1.58
Maximum radiant heat intensity at any location where personnel with appropriate clothing may be continuously exposed.
Conditions 2
The permissible radiation levels on table 4.1 is considered at grade level as stated per API std 521 section 3.60. Solar radiation of 300 Btu/hr ft2 is included in the radiation calculation. 4.2.
Design Criteria
Flare stack height is sized based on following design criteria:
•
For depressurization and emergency cases, maximum radiation limit is 1500 Btu/hr-ft2 (including 300 Btu/hr-ft2 solar radiation).
•
Flare tip is pipe flare type, vertical orientation
•
As worst case scenario, flare stack height is calculated with design load Compressor PSV. The total load will be 25 MMScfd.
•
No assist fluid is used for the flare tips.
•
As worst case, wind direction toward to the plant.
5. FLARE RADIATION ANALYSIS Page 5 of 9
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5.1. Flare Stack Height Based on Flare Stack Height design criteria, it is resulting stack height of 30 m. For detailed calculation is attached in Attachment. 5.2. Flare Load The flare radiation is analyzed at two flare loads as follows :
•
Case 1 Emergency Case (PSV relief from Compressor)
•
Case 2 Depressurized Case (Blowdown from Slug Catcher and Discharge Scrubber)
5.3. Environmental Condition The Flare radiations are analyzed based on following environmental condition :
•
Design wind speed toward the receptor of 6.9 m/s (23 ft/s)
•
Solar radiation : 300 Btu/ hr ft2
•
Relative humidity : 80%
•
Background noise : 60 dB (based on Flaresim simulation)
•
Ambient temperature : 89°F
5.4. Receptor Point Radiation will be analyzed at grade level (same as the stack base) and receptor point of 58 m (process equipment) horizontal from stack base. The radiation will be observed to estimate receptor point at radiation level of 500 Btu/hr ft2 and maximum radiation. The solar radiation of 300 Btu/hr-ft2 is included in the calculation of radiation analysis. 5.5. Calculation Method •
Radiation contours around the flare at the various flare loads are determined by utilizing Flaresim Simulation Software Version 2.0.
•
Calculation method used in the Flaresim Simulation Software is M. Point Brz.
•
Emmisivity / Fraction heat radiated is 0.7.
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5.6. Fluid Properties Design Data Flare radiation is calculated based on following fluid properties: Table 5.6. Fluid Properties for Flare Radiation Analysis Component (mole fraction)
NORMAL
C1
0.8774
C2
0.0274
C3
0.0099
i-C4
0.0021
n-C4
0.0024
i-C5
0.0010
n-C5
0.0008
n-C6
0.0032
n-C7
0.0012
N2
0.0058
CO2
0.0685
H2S
0.0001
H2O
0.0002
TOTAL
1.0000
Molecular Weight
19.25
Cp/Cv
1.273
Mass Flow (lb/hr) Molar Flow (MMscfd) LHV (Btu/lb)
52853 25 17730
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5.7. Flare Radiation Analysis Result The result of flare radiation analysis at flare stack lenght 100 ft (30 m) is shown in following table. Table 5.7.1 Radiation Analysis for Emergency Relief Case
Stack Base KO Drum Rail way (note 3)
Gas Engine
Design Wind Speed : 23 ft/s (note 2) Flare stack length : 100 ft Relief Receptor Elevation Load Point Horizontal Distance lb/hr / from stack ft / (m) (MMscfd) base ft / (m) 0 / (0) 0 / (0) 52852 / 190 / (58) 1 / (0.3) (25) 141 / (43) 0 / (0) (note 1)
148/ (45)
1 / (0.3)
Radiation
Radiation criteria
Btu/hr ft2
Btu/hr ft2
401 220
1500 500
Meet requirement Meet requirement
275
500
Meet requirement
267
500
Meet requirement
Description
Note : 1. Since, deperessuirized flow rate is very low compare to PSV case flaring, hence calculation only perform for PSV case. 2. Wind direction is assumed toward the receptor poin (northing), hence no calculation in regards to wind speed below this wind direction speed. 3.
Since the Mushola is the closest building with the same function to the railway from safety perpective where people should continuosly emited to flare radiation, hence this receptor can be joined with the mushola as closer distance.
As per above table, the maximum radiation level is 401 Btu/hr ft 2 for stack base. These radiation are lower than maximum permissible radiation level of 1500 Btu/hr ft2. And also for KO Drum, Mushola, and Gas Engine, the radiation are lower than maximum permissible radiation level of 500 Btu/hr ft2. Hence the selected 100 ft (30 m) flare stack height and with flare radius assumption of 40 m is considered safe with exposure time limitation based on API Standard 521 - Guide for Pressure Relieving and Depressuring Systems.
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6. REFFERENCES 1.
API STD 521 “Guide for Pressure Relieving and Depressuring Systems”, 5th edition, Jan 2007.
2.
SPP-10-60-PP-007 General Plot Plan Randu Blatung Gas Transfer Station_Rev 3
3.
SPP-10-50-DS-014 Data Sheet Flare System_Rev.0
4.
SPP-00-40-SP-002 Project Design Basis_Rev.1
5.
SPP-00-40-SP-005 Process Design Criteria_Rev.0
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ATTACHMENT Flare Radiation Simulation Result
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