CRUDE VACUUM & NAPTHA STABILIZER UNITS
SECTION 7.3.2 Delayed Coker Unit
7.3.2.1 FEASIBILITY STUDY REPORT
CB&I Lummus carried out revamp feasibility report for 134% increase in unit throughput considering vacuum residue feedstock quality same as FEED case 2 ( VR of 65% AL & 35% AH crude) of design package and feed CCR as 23.99wt% & API as 4.18.
For specified feed and considering no modifications in existing coke drums, the confidential coking yield correlations were fine-tuned and simulation model was updated to bench mark unit operation based on the results of the test run data that has been performed in August 2012 in order to closely match plant performance.
Lummus envisaged following operating parameters for 34% expanded capacity due to system hydraulics and other design considerations.
Coke Drum Pressure = 1.52-2.5 kg/cm2g
Main Fractionator inlet pressure = 1.17-2.15 kg/cm2g Wet Gas Compressor Discharge pressure = 14.3 kg/cm2g
Wet Gas Compressor first stage inlet pressure = 0.16-1.5 kg/cm2g Recycle ratio = 5%
Coke Drum Cycle = 18 hours C3+C4 recovery = 90%
The remaining operating parameters are close to the original design case.
Revamp feasibility study submitted by Lummus comprises process evaluation including key revamp operating parameters, yield structure and required
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DFR for Debottlenecking of Bharat Oman Refineries Limited
A439-RP-02-41-0001 Rev B Ch 7.3.2 Page 3 of 7
modifications along with preliminary engineering for two options i.e. i) coke drum overhead pressure of 1.52kg/cm2g and ii) coke drum overhead pressure of 2.5 kg/cm2g.
In order to minimize fuel gas yield and coke make, option 1 of coke drum overhead pressure of 1.52kg/cm2g is pursued for revamp of 34% increase in unit capacity.
The key features and modification as reported in Lummus Revamp feasibility report which are considered under this project are summarized below:
Post revamp yield pattern for coker overhead pressure of 1.52kg/cm2g are tabulated below in Table 7.3.2.1.
Table7.3.2.1: Theoretical Yield (Wt% of Fresh Feed)
Coker Gas 6.57
LPG 4.05
Coker Naphtha (C5-140°C) 8.74
LCGO (140°C-370°C) 31.58
HCGO (370°C Plus) 19.18
Coke 29.88
Coker Heaters: Lummus has carried out preliminary adequacy check of heater and identified potential changes to the furnace and its auxiliary systems. Since the furnace rating was not included in the Lummus scope of revamp feasibility report, detailed rating of the heater and interaction with the auxiliary equipment suppliers will be performed during design stage. The modifications as reported in revamp feasibility study are listed below:
Radiant Section: To meet the revamp duty of 41.98MMKcal/hr and to achieve both EOR TMT and allowable pressure drop, replacement of all existing tubes with higher metallurgy i.e. SS347H of sch 40. Additional 6 tubes per pass of MOC SS347H of sch 40. Total no of passes are two per heater.
Subsequently it is found that SS347H MOC is not suitable for high content of chloride ( around 20ppm as per BORL data) as exist presently in vacuum residue feed, Lummus proposed to consider Inconel800 tubes in place of SS347H.
Convection Coil: Use of two future rows is required. The use of future rows will help reduce the radiant flux by shifting some duty to convection section and also help in maintaining the heater efficiency.
Tube supports: Tubes supports will be adequate with reduced load of 40 schedule tubes. However tube supports need to be checked for revamp conditions and thermal movements which might be controlling in tube support design during design stage.
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Process Description DFR for Debottlenecking of Bharat Oman Refineries Limited
Document No.
A439-RP-02-41-0001 Rev B Ch 7.3.2 Page 4 of 7
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL – All rights reserved
Convection intermediate Tube Supports: Flue gas temperature profile has changed to 70°C from 50°C throughout convection. Design margin has reduced from 110°C to 65°C. Mechanical check is required during design stage to verify the design of supports for revamp conditions.
FD Fans: Two FD fans running at 50% capacity will be adequate for revamp volumetric flow and static pressure required. For fuel oil firing single FD fan will not be adequate. Some reduction of load or combination of fuel oil with fuel gas or reduction in excess air is required.
ID Fans: ID fans are adequate for fuel gas firing. But for fuel oil firing it is marginally short. Adequacy of ID fans to be verified by vendor during detail engineering.
Burner: Burner tips may need modification. To be confirmed by vendor during detail engineering.
Stack: Stack is adequacy to be checked during detail engineering for ID fan trip and APH bypass. Load need to be reduced during natural draft operation.
Wet Gas Compressor: The adequacy for the WGC was checked by compressor vendor for the process conditions provided by licensor. Vendor reported maximum Possible flows with given operating conditions as given below in table :
Stage 1 31910 Kg/hr 20128 m3/hr Compressor is adequate subject to 1stage discharge pressure is st considered as 4.04 kg/cm2g instead of 3.5 kg/cm2g
Stage 2 24322 Kg/hr 4521 m3/hr
Compressor is not found adequate for the required revamp flow rate of 40912*1.1 kg/hr for stage 1 and 31182*1.1 kg/hr for stage 2.
Therefore a new compressor of balance capacity in parallel to existing compressor is considered to handle the revamp load. The new compressor is envisaged of fixed rating of 1.3MW motor driven machine.
The adequacy and modifications suggested for other equipments as well as requirement of new equipments as proposed in Lummus revamp feasibility study report are summarized below in Table 7.4.2 and overall equipment list is tabulated in Annexure 2.
Table 7.3.2.2: List Of New/Modified Equipments
S.NO TAG NO DESCRIPTION MODIFICATION
FURNACE 1
14-FF-00-101A/B Coker Heater
Radiant section: Replacement of Existing Tubes change with Inconel 800 material.
Convection Section: Use of
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DFR for Debottlenecking of Bharat Oman Refineries Limited
A439-RP-02-41-0001 Rev B Ch 7.3.2 Page 5 of 7
additional two future rows.
COLUMNS 1
14-CC-00-101 Coker Fractionator
Top trays (26-15): modification of tray panel with VG-10, modify Downcomer width.
HCGO Frac (14-7) Trays: number of valves to be increased.
HCGO PA trays (6-1): modification of panels with Pro-Valve and Downcomer width modification.
2 14-CC-00-102 LCGO Stripper Trays (2-6): Increase number of valves.
3 14-CC-00-104 Absorber Trays (1-30): Modification in Downcomer width and clearance.
4 14-CC-00-105 Stripper
Tray (1-30): Modifiy Downcomer width and clearance along with increase in number of valves.
5 14-CC-00-107 Debutanizer
Top Section: Increase in number of valves and Downcomer clearance.
Bottom Section: Modification of downcomer width and clearance along with increase in number of valves.
EXCHANGERS
1 14-EE-00-101A Feed/HP Stream
Exchanger New (Area: 597 m2, No. of Shells: 1) 2
14-EE-00-107E/F Compressor
Interstage Cooler New in parallel with exchanger 14-EE-00-107A/B/C/D. (Area: 147 m2, No. of shells: 2)
3
14-EE-00-109E/F Compressor
Discharge Cooler New in parallel with exchanger 14-EE-00-109A/B/C/D. (Area: 278 m2,
New in parallel with exchanger 14-EE-00-115A/B/C/D. (Area: 204 m2, No. of Shells: 2)
5 14-EE-00-118B Absorber Intercooler New in parallel with exchanger 14-EE-00-118B. (Area: 37 m2, No. of Shells: 1)
6 14-EE-00-119 Debutanizer Steam
Reboiler Replaced with new 14-EE-00-121.
7 14-EE-00-120 Stripper Reboiler New (Area: 113 m2, No. of Shells: 1) 8 14-EE-00-121 Debutanizer Steam
Reboiler New (Area: 88 m2, No. of Shells: 1) 9 14-EE-00-123 Debutanizer Bottom
Water Cooler New (Area: 126 m2, No. of Shells: 1) AIR COOLERS
1
14-EA-00-102A-L Coker Fractionator
Overhead Condenser One additional Bay of 5.0m X10.0m to existing 6 bays. (Surface Area:
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Process Description DFR for Debottlenecking of Bharat Oman Refineries Limited
Document No.
1 14-VV-00-103 Compressor
Interstage Drum In situ increase the length of vessel (Note: 1).
2 14-VV-00-104 Recontact Drum In situ increase the length of vessel (Note: 1).
3 14-VV-00-107 Debutanizer
Overhead Receiver Replaced with new vessel. (Dia:
2,500 mm and Length: 7,500 mm) 4 14-VV-00-122 Feed/HP Steam
Exchanger Condensate Pot
New (Diameter: 910 mm and length 1,700 mm)
5 14-VV-00-123 Stripper Reboiler
Condensate Pot New (Diameter: 910 mm and length 1,700 mm)
PUMPS
1
14-PA-CF-101A/B Coker Unit Feed Pump
Impeller change with larger diameter and motor replacement (75 KW)
2
14-PA-CF-105A/B Debutanizer Bottom Pumps
Replaced with new pump of motor rating 95 KW. (Flow: 256.74 m3/hr,
Impeller change with larger diameter and motor replacement (150 KW)
Impeller Change with larger diameter
5
14-PA-CF-113A/B Stripper Feed Pumps
Replaced with new pump of motor rating 75 KW.(Flow: 256.25 m3/hr, Head: 99.73 m)
6
14-PA-CF-121A/B Absorber Bottom Pumps
Replaced with new pump of motor rating 30 KW. (Flow: 195.9 m3/hr, Head:59.8 m)
7
14-PA-CF-122A/B Absorber Intercooler Pumps
Replaced with new pump of Rating 30 KW.(Flow: 220.88 m3/hr,
Head:48.61 m) COMPRESSOR
1 14-KA-CF-101B Wet Gas Compressor New in parallel to existing 14-KA-CF-101. HT Motor Driven (1.3 MW).
2 14-KA-CF-102 Blowdown Ring
Compressor New. Motor Driven (45 KW).
NOTES
1. Replacement of vessel is not feasible from implementation/constructability point of view. Licensor shall confirm the adequacy of this vessel in view of retaining the same diameter and increasing the length in situ.
Lummus recommended that it is feasible to increase the capacity of existing coker up to 1.822MMTPA at 5vol% recycle rate with above mentioned additions and alternations.
DFR for Debottlenecking of Bharat Oman Refineries Limited
A439-RP-02-41-0001 Rev B Ch 7.3.2 Page 7 of 7
7.3.2.2 CONSTRUCTABILITY
For the feasibility of implementation and constructability of all new/ modified equipment were evaluated at site and following are the findings:
Wet Gas Compressor: There is space to locate shed of 8m width for new WGC at the north side of existing shed & to accommodate it, existing staircase on northern side of existing compressor shed will be needed to be relocated.
Blowdown Ring Compressor: The location of new blowdown ring compressor is identified in west side of northern battery limits of pipe rack.
Vessels: Replacement of Recontact drum due to its size cannot be taken out and replaced with new one. Therefore diameter of existing recontact drum shall be retained ( To be confirmed by licenser during design stage) and length of Recontact drum can be increased in situ.
It is more economical to increase the length of Compressor Inter-stage vessel as required post revamp, at site instead of replacement with other vessel.
Debutanizer Overhead Receiver can be replaced with new vessel.
Other Equipments: Implementation/ constructability of all other equipments (modified or new) were checked and found feasible.
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Process Description DFR for Debottlenecking of Bharat Oman Refineries Limited
Document No.
A439-RP-02-41-0001 Rev B Ch 7.3.3 Page 1 of 19
Template No. 5-0000-0001-T2 Rev. 1 Copyright EIL – All rights reserved