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GAS PROCESSING PRESENTATION.pdf

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GAS PROCESSING PRESENTATION.pdf

  1. 1. PDD 9.01.08 Slide Number1 - 1 of 67 PROCESS DESIGN AND DEVELOPMENT PRESENTATION ON GAS PROCESSING TECHNOLOGY DEPARTMENTAL ORIENTATION PROGRAMME Jan 2008
  2. 2. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 2 of 67 OBJECTIVE OF THE PRESENTATION ◼ TO OBTAIN AN OVERVIEW OF TECHNOLOGY OPTIONS IN GAS PROCESSING ◼ SALIENT FEATURES OF EACH PROCESS ◼ PROCESS SELECTION AND APPLICATION
  3. 3. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 3 of 67 NEED FOR PROCESSING ◼ Tapped from geological formation, well fluid hydrocarbons are a mixture of oil with dissolved gases, water and other impurities ◼ Thus these must be separated into oil and gas in a process called stabilization ◼ Further processing is dependent on the impurities present, quality and downstream use
  4. 4. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 4 of 67 OIL & GAS PLATEFORM WELL FLUID FROM OFFSHORE OIL & GAS FROM ONSHORE OIL TO TANKER GAS PROCESSING COMPLEX LEAN GAS SOUR GAS C2/C3 LPG OVER ALL BLOCK FLOW DIAGRAM ONSHORE PROCESSING FACILITIES OIL/GAS OIL TO TRUNK LINE
  5. 5. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 5 of 67 OIL AND GAS PROCESSING ◼ OFFSHORE PROCESSING ◼ ONSHORE PROCESSING ◼ This presentation focuses on the technologies in the onshore gas processing areas.
  6. 6. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 6 of 67 NEED FOR PROCESSING cont ◼ To remove undesirable components like moisture which results in plant blockages due to ice hydrate formation, also causes pipeline corrosion ◼ Heavy hydrocarbons which causes wax deposition ◼ Metals like mercury attack aluminum and vanadium attack turbine blades ◼ Presence of oxygen and methanol/glycol which cause which effect mol sieve dryers
  7. 7. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 7 of 67 BASIC FEEDSTOCK FOR CRYOGENIC PLANTS ◼ Offshore Oil & Gas Fields ◼ Offshore Gas Fields ◼ Onshore Oil & Gas Fields ◼ Onshore Gas Fields
  8. 8. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 8 of 67 ON-SHORE FACILITIES ◼ Oil / Gas Separation ◼ Crude condensate processing ◼ Gas Processing ◆ Gas gathering stations ◆ Slug catcher ◆ Gas sweetening ◆ Gas dehydration ◆ Dew point depression ◆ LPG / Ethane/Propane Recovery ◆ NGL recovery ◆ Sulfur recovery
  9. 9. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 9 of 67 PRODUCTION CONCEPTS ◼ Two approaches ◼ Decentralized ➢ Widely adopted in onshore installations ➢ Dehydration and desalting of crude in the heater treater ➢ HP and LP gas is sent to nearby users ➢ Oil stored and pumped ➢ Local effluent disposal in evaporation pits or pumped to effluent centres ◼ Centralized ➢ For larger fields ➢ In use at most offshore installations ➢ Lower operating costs, better automation ➢ Better recovery ➢ Good environmental control
  10. 10. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 10 of 67 DECENTRALIZED APPROACH GGS GGS CTF STABILIZED CRUDE WELL HEAD WELL HEAD EFFLUENTS FOR DISPOSAL EFFLUENTS FOR DISPOSAL TRUNK LINE TRANSPORT HP GAS LP GAS LP GAS HP GAS
  11. 11. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 11 of 67 CENTRALIZED APPROACH MANIFOLD STATION -1 MANIFOLD STATION -2 MANIFOLD STATION -3 CENTRAL STATION MANIFOLD OIL GAS SEPARATION UNIT BOOSTER GAS COMPRESSOR UNIT GAS DEHYDRATION UNIT OIL BLOCK STATION GAS FOR PROCESSING/ COMRESSOR STATION HIGH PRESSURE GAS MEDIUM PRESSURE GAS CRUDE OIL TO REFINERIES
  12. 12. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 12 of 67 CRUDE OIL STABILIZATION ◼ Multistage separation ◼ Multistage separation with vapor recompression ◼ Multi stage separation with NGL recovery ◼ Multi stage with Hot stripping ◼ Multi stage hot stripping with gas compression ◼ Two stage fractionation requires dehydration desalting upstream
  13. 13. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 13 of 67 GAS PROCESSING COMPLEX SLUG CATCHER GAS SWEETENING GAS DEHYDRATION GAS TO PIPELINE CONDENSATE FRACT’N LPG DEW POINT DEPRESSION LPG RECOVERY NGL KEROSENE RECOVERY NAPHTHA KEROSENE GAS HEAVY FR’N SULPHUR RECOVERY SULPHUR
  14. 14. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 14 of 67 SLUG CATCHER ◼ Receive and hold condensate that is pushed out from the line during pigging ◼ Transportation of gas from long offshore pipeline results in condensation thus also receives condensate slugs during normal operation ◼ Trap and hold liquid particles carried over with the gas ◼ Inlet sequentially to very long pipes with large diameter (called fingers) ◼ These pipes have large slope(5%) in the front end necessary for separation ◼ The slope reduces further to 0.5% in the storage section ◼ Liquid is removed from each finger and via a header is routed for fractionation ◼ Gas is collected from risers and also sent for sweetening, dehydration, LPG and C2/C3 recovery
  15. 15. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 15 of 67 SLUG CATCHER
  16. 16. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 16 of 67 GAS SWEETENING ◼ Removal of acid gases (H2S, CO2) is termed as gas sweetening ◼ Acid gases cause corrosion especially in presence of moisture. ◼ H2S is to be removed to contain corrosion in pipeline transportation ◼ CO2 freezes in cryogenic gas plants and interrupts operation also to contain corrosion ◼ In LPG recovery CO2 removal generally not required ◼ However, in C2/C3 recovery units CO2 must be removed ◼ Typically sweet gas would have 4ppm H2S and 50ppm CO2
  17. 17. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 17 of 67 GAS SWEETENING ◼ A very large number of sweetening processes are available ◼ Key factors which select the process are operating pressure, feed composition, treated gas specification, (for eg gas at has CO2 as 5.74mol%, H2S as 0.13mol% , while LACQ gas in France has an H2S content of as high as 15mol%) ◼ Requirements: bulk removal, selective removal. ◼ Mainly divided in four categories ➢ Chemical solvent ➢ Physical solvent ➢ Direct conversion ➢ Dry bed
  18. 18. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 18 of 67 GAS SWEETENING PROCESSES ◼ Gas sweetening by absorption using chemical solvents (alkanolamines in aqueous solution) ◆ Primary amine – MEA ◆ Secondary amine – DEA, DIPA ◆ Tertiary amine – MDEA ◆ Activated MDEA ◼ Physical solvents suited for bulk removal, and work on the principles of partial pressure concept some- hybrid process like Sulfinol-D ◼ Direct conversion: H2S is directly converted to elemental sulfur , like LOCAT ◼ Dry bed processes employ molecular sieves normally used for gases with very low acid content.
  19. 19. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 19 of 67 Gas sweetening- major equipments ◆ Inlet KOD ◆ Contactor − Packed or tray column (22 – 24 valve trays or equivalent packing) − Feed gas enters at the bottom − Lean amine enters at the top tray − Operates at 50 C to 60 C ◆ Amine circulation pumps ◆ Flash tank - flashed dissolved hydrocarbons from amine - operated at 5-6kg/cm2g - located between contactor and feed bottom exchanger ◆ Rich lean amine exchanger (Shell and tube/ plate frame) design minimizes acid gas flashing reduces reboiler duty by 50%)
  20. 20. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 20 of 67 Gas sweetening major equipments ◆ Stripper column - Trayed – valve trays or packing − Steam in reboiler for stripping − 90 – 95% acid gas stripped in column − Condensed stripping steam returned to column as reflux for water balance & to reduce amine carryover ◆ Reboiler − Generates steam for stripping by boiling amine − Heat by steam or fuel gas etc − Type may be vertical/horizontal kettle or thermosyphon − Max. reboiler temperature : 123 – 125 C to avoid amine degradation ◆ Acid Gas condenser - Condenses steam vapor in acid gas (either Cooling water or air condenser) ◆ Lean Amine Cooler − Cools lean amine good for absorption
  21. 21. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 21 of 67 Gas sweetening major equipments ◆ Filtration – cartridge filters − Removes particles that can promote foaming in contactor, corrosion and off spec product − Cartridge or pre coat type − 1 – 100 micron range − Usually slip stream of amine from amine circulation pump − Provided before and after carbon filterAbsorbs entrained hydrocarbon, amine degradation products − Carbon usually lignite or charcoal − On slip stream of amine ( 10 % of total amine in circulation) ◆ Amine storage tanks − Nitrogen blanketted for make-up amine ◆ Water Wash − To remove entrained amine in sweet gas
  22. 22. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 22 of 67 Gas sweetening ◼ Material of Construction ◆ Vessels in amine service – CS+ 6 mm CA ◆ Vessels in H2S/CO2 & moisture – SS 316 L ◆ Piping in amine/+CO2 service – SS 316 L / CS ◆ Column internals – SS 316 L ◆ Exchangers (amine) – Shell CS, Tubes SS316L ◆ Pumps – SS 316 L ◆ All CS in amine service – stress relieved ◆ H2S service – NACE standards
  23. 23. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 23 of 67 Gas sweetening ◼ Aux. Equipments ◆ Anti foam injection facility ◆ Amine blowdown system ◆ Desuperheater
  24. 24. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 24 of 67 Gas sweetening ◼ Major operating problems in sweetening plant ◆ Corrosion − Oxygen in water / condensate used for making amine solution − Presence of CO2 & H2S and water ◆ Amine degradation − Excessive temperature in reboiler ◆ Foaming in contactor − Degraded products − Liquid hydrocarbon in gas
  25. 25. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 25 of 67 Gas sweetening ◼ Overcome operating problem by ◆ Proper selection of MOC ◆ Proper plant operation ◆ Ensure Good filtration ◆ Controlling reboiler operating temperature ◆ Avoiding hydrocarbon condensation in contactor ◆ Using antifoam as and when required
  26. 26. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 26 of 67 GAS DEHYDRATION ◼ Normally gas is saturated with water at plant inlet ( as it is available from a sweetening unit) ◼ Gas dehydration is required ➢ Prevent formation of hydrates and condensation of free water in processing and transportation facilities ➢ To meet water content specifications for pipeline transportation ➢ And to prevent corrosion
  27. 27. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 27 of 67 Gas Dehydration ◼ Glycols are commonly used to dehydrate gas for pipeline transportation ◼ Required water content for pipeline transport is 5- 7lb/MMSCFD, or equal to 85kg/MMNM3D ◼ For cryogenic use the water dew point is (-) 70 deg C for LPG plants and (-) 100 Deg C for C2/C3 recovery plants which is obtained only by mol sieve dryers. ◼ .
  28. 28. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 28 of 67 Dew Point Depression ◼ Normally done to obtain a hydrocarbon dew point as desired to eliminate hydrocarbon condensation in the pipeline. ◼ Expander or refrigeration scheme is used
  29. 29. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 29 of 67 Condensate Fractionation Unit ◼ Gas condensate from the slug catcher or the gas separators will be rich in LPG components ◼ This condensate is fractionated in a two column configuration to recover LPG and heavier liquids known as Natural Gas Liquids (NGL) ◼ The balance gas which is light and devoid of LPG components after compression joins back the main gas stream
  30. 30. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 30 of 67 Cryogenic recovery of hydrocarbons ◼ Cryogenic recovery of Hydrocarbons ◆ Front end feed gas treatment. ◆ Alternate Process schemes for production of C2/C3, LPG considering natural gas as feed stock. ◆ Typical block flow diagram for cryogenic recovery of light hydrocarbons. ◆ Major Equipment in the unit. ◆ Material of constructions ◆ Supporting systems ◆ Operating problems ◆ Major LPG and C2/C3 plants
  31. 31. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 31 of 67 Cryogenic Recovery of Hydrocarbons ◼ Front end feed gas treatment ◆ Gas Sweetening – Removes H2S,CO2 ◆ Gas Drying – Removes moisture ◆ Here gas drying is via molecular sieves
  32. 32. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 32 of 67 Cryogenic Recovery of Hydrocarbons ◼ Alternate process schemes ◆ Turbo-expander process ◆ Cascade refrigeration process ◆ Refrigerated absorption process
  33. 33. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 33 of 67 Cryogenic Recovery of Hydrocarbons ◼ Various sections of C2/C3 & LPG plant. ◆ Feed gas compression ◆ Feed gas drying ◆ Feed gas chilling/ liquefaction using expansion of the gases/cooling using refrigerant ◆ Separation of lean gas & liquid hydrocarbon ◆ Fractionation
  34. 34. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 34 of 67 B7544001 LEAN GAS COMPR. GSU COMPRESSOR RESIDUE COOLING COMPR. DRYING CHILLING SEPARATION EXPANDER LPG COLUMN PROPANE COLUMN C C COLUMN 2 3 DEMETHANIZERCOLUMN NGL C + 5 LPG (C +C ) 3 4 C (PROPANE) 3 C /C TO CRACKER 2 3 COMPRESSOR REFRIGERATION DEMETH. BOTTOM LIQUID FOR C2/C3 & LPG RECOVERY SEPARATED LIQUID GAS PIPELINE LEAN GAS C0 ,H S 2 2 GAS PIPELINE H O 2 FIGURE : 2.1 - FLOW SCHEME FOR C2/C3 AND LPG RECOVERY PLANT EIL NEW DELHI ENGINEERS INDIA LIMITED REV. APPD CH BY REVISION DATE NO. REF. DRAWING DWG. NO. JOB NO 7544 LIQUEFACTION SECTION FRACTIONATION SECTION
  35. 35. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 35 of 67 Cryogenic Recovery of Hydrocarbons ◼ Feed gas compression ◆ Compression to moderate pressures (if required) to ensure liquefaction of gas when chilled ◆ Thus pressure selection is determined by parameters like feed quality, pressure, composition and lean gas pressure requirement ◆ Centrifugal compressors ◆ Motor driven or turbine driven
  36. 36. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 36 of 67 Cryogenic Recovery of Hydrocarbons ◼ Gas drying ◆ To avoid hydrate formation (water + HC = solid hydrate] in cryogenic temperature region. ◆ Generally part of any cryogenic plant ◆ Moisture in gas reduced to < 1 ppm ( dew point =(-)100Deg C) ◆ Drying by molecular sieves ◆ Generally two beds – on under drying and one under regeneration ◆ Regeneration by hot lean gas ◆ Normally a guard bed is used below the main bed in both dryer vessels.
  37. 37. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 37 of 67 Cryogenic Recovery of Hydrocarbons Feed gas chilling ◆ Feed gas chilling to a 2 phase (vapour +liquid) region ◆ Achieved by expansion in turbo-expander use of Joule Thompson effect ◆ Cold stream after expansion in an expander is used to cool the feed gas ◆ Level of LPG and C2/C3 recoveries achieved depending on feed gas pressure temperatures, composition ◆ In case the gas is very lean and has lower pressures cold available from expansion may not be sufficient for condensing the desired LPG components, in which case external refrigerant may be called for. ◆ C2/C3 recovery normally required external refrigerant to achieve above 90% recovery.
  38. 38. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 38 of 67 Typical flow scheme –cryogenic recovery of HCs
  39. 39. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 39 of 67 Cryogenic Recovery of Hydrocarbons ◼ Expansion using turbo-expanders ◆ Chilling to liquefy the feed gas ◆ Using the work extracted from expanding gas stream to compress feed gas / lean gas ◆ Reduces external compression ◆ Normal pressure ratio : 3 – 4 in gas plants ◆ > 80 % expander efficiency ◆ Inlet stream must be free of liquids/solids ◆ (-) 45 C to (-) 60 C after expansion for LPG recovery ◆ (-) 75 C after expansion for C3 recovery ◆ (-) 115 C in case of C2/C3 recovery
  40. 40. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 40 of 67 Reversible expansion Constant entropy path from a to b However actual Expansion would Follow a non ideal Path a to c Del H ideal and del H actual
  41. 41. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 41 of 67 Cryogenic Recovery of Hydrocarbons ◼ Chilling of feed gas using cold streams generated after expansion ◆ Feed gas is cooled before expansion to achieve lower cryogenic temperatures ◆ Achieved in Cold Box which can handle multiple hot and cold stream ◆ MOC – brazed Aluminium
  42. 42. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 42 of 67 Cryogenic Recovery of Hydrocarbons Fractionation ◆ Demethaniser ◆ LEF column ◆ LPG column ◆ Propane column (if reqd.)
  43. 43. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 43 of 67 Cryogenic Recovery of Hydrocarbons- C2/C3 recovery ◼ Demethaniser ◆ Separation of methane from other components ◆ Top temp = - 115 C ◆ Valve trays / packing ◆ 45 – 55 trays (typical) ◆ Side reboiler & main reboiler - Reboiling using hot feed gas or lean gas ◆ Overhead condenser – chilling using external refrigerant or cold process streams
  44. 44. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 44 of 67 Cryogenic Recovery of Hydrocarbons ◼ LEF (Light end fractionation ) column ◆ Separation of methane+ethane from other components ◆ Top temp = - 45 C ◆ Valve trays ◆ 40 trays (typical) ◆ Reboiler - Reboiling using LP steam or hot oil ◆ Overhead condenser – chilling using external refrigerant or cold process streams
  45. 45. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 45 of 67 Cryogenic Recovery of Hydrocarbons ◼ LPG Column ◆ Separation of propane + butane (LPG) from C5 + components ◆ Valve trays ◆ 30 trays (typical) ◆ Reboiler - Reboiling using LP steam or Hot oil ◆ Overhead condenser – cooling using cooling water
  46. 46. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 46 of 67 Cryogenic Recovery of Hydrocarbons ◼ Propane Column ◆ Separation of propane from C4 + components ◆ Valve trays ◆ 20 trays (typical) ◆ Reboiler - Reboiling using LP steam or Hot oil ◆ Overhead condenser – cooling using cooling water
  47. 47. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 47 of 67 Cryogenic Recovery of Hydrocarbons ◼ Lean gas compression ◆ Compression of lean gas (mainly methane) to required pipeline pressure ◆ Centrifugal compressors ◆ Motor driven or turbine driven
  48. 48. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 48 of 67 Cryogenic Recovery of Hydrocarbons ◼ Material of Construction ◆ Carbon steel upto –27C ◆ LTCS (low temp. CS) upto –45 C ◆ Alloy steel upto –75 C ◆ 3.5wt% Ni upto –100 Deg C (depending upon availability) ◆ Stainless steel < -100C
  49. 49. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 49 of 67 Cryogenic Recovery of Hydrocarbons ◼ Other systems ◆ Dryer regeneration system – Fired heater, regeneration gas compressor, cooler ◆ Methanol injection – To prevent hydrate formation ◆ Hot oil system – Hot oil heater, surge vessel, pump ◆ Steam system ◆ Flare system
  50. 50. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 50 of 67 Cryogenic Recovery of Hydrocarbons ◼ Other systems ◆ Instrument air / plant air system ◆ Cooling water system ◆ Inert gas system ◆ Closed blowdown system ◆ Refrigeration system (propane or propylene)
  51. 51. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 51 of 67 Cryogenic Recovery of Hydrocarbons ◼ Operating problems ◆ Poor moisture removal in dryer – Hydrate formation in cryogenic region − Methanol injection during start-up ◆ Amine & hydrocarbon liquid carryover from upstream facilities – Damage of molecular sieves, coke formation − KOD upstream of dryer, proper operation of upstream
  52. 52. Engineers India Ltd – Delivering excellence through people PDD 9.01.08 Slide Number– 52 of 67 C2-C3 RECOVERY PLANTS GAS SWEETENING Feed Gas GAS DRYING (MOLECULAR SIEVES) GAS CHILLING & LIQUEFACTION FRACTIONATION C2 / C3 LPG NGL CO2
  53. 53. PDD 9.01.08 Slide Number53 - 1 of 67 Thank you visit us at: www.engineersindia.com

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