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Membranes for Gas Conditioning Hope Baumgarner Chelsea Ryden.

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Presentation on theme: "Membranes for Gas Conditioning Hope Baumgarner Chelsea Ryden."— Presentation transcript:

1 Membranes for Gas Conditioning Hope Baumgarner Chelsea Ryden

2 How is natural gas currently processed?

3 Current Natural Gas Processing Well & Condensate Removal Amine Unit Sulfur Recovery Dehydration Nitrogen Rejection Natural Gas Liquid Recovery Natural Gas Liquid Fractionation Sale Gas

4 Amine Unit: CO 2 and H 2 S Removal Sour Gas Treated Gas Wash Water CO 2 Lean Amine Inlet Separator Cooler Filter Water Wash Drum Lean Amine Pump Cross Exchanger Stripper Amine Solution Tank Reboiler Pressurized Hot Water Water Condenser CO 2 & H 2 S Removed Rich Amine PumpAmine Pump Water Wash Pump To Atmosphere Rich Amine Flash Drum Contactor

5 Current Natural Gas Processing Well & Condensate Removal Amine Unit Sulfur Recovery Dehydration Nitrogen Rejection Natural Gas Liquid Recovery Natural Gas Liquid Fractionation Sale Gas

6 Claus Unit: Sulfur Recovery Furnace Catalytic Section Liquid Sulfur Tail Gas °C Overall Reaction: 2H 2 S+O 2 S 2 + 2H 2 O Thermal Reaction: 2H 2 S +3O 2 2SO 2 + 2H 2 O Catalytic Reaction: Al 2 O 3 2H 2 S+SO 2 3S + 2H 2 O

7 Current Natural Gas Processing Well & Condensate Removal Amine Unit Sulfur Recovery Dehydration Nitrogen Rejection Natural Gas Liquid Recovery Natural Gas Liquid Fractionation Sale Gas

8 Glycol Dehydration Unit Rich Glycol Wet Gas Lean Glycol Wet Gas Glycol Contactor Filter Reboiler Flash Gas Water Vapor

9 Current Natural Gas Processing Well & Condensate Removal Amine Unit Sulfur Recovery Dehydration Nitrogen Rejection Natural Gas Liquid Recovery Natural Gas Liquid Fractionation Sale Gas

10 Nitrogen Rejection Nitrogen Vent Feed Gas Condenser Low Pressure Column High Pressure Column Reboiler

11 Current Natural Gas Processing Well & Condensate Removal Amine Unit Sulfur Recovery Dehydration Nitrogen Rejection Natural Gas Liquid Recovery Natural Gas Liquid Fractionation Sale Gas

12 Natural Gas Liquid Recovery Natural Gas Feed Refrigerant Turbo Expander Sale Gas Demethanizer Cold Reflux Compressor Cold Separator NGL

13 Current Natural Gas Processing Well & Condensate Removal Amine Unit Sulfur Recovery Dehydration Nitrogen Rejection Natural Gas Liquid Recovery Natural Gas Liquid Fractionation Sale Gas

14 Natural Gas Liquid Fractionation Deethanizer Depropanizer Debutanizer Recycle Vapor Propane ProductButane Product Reboiler Condenser Reflux Drum

15 Overview of Problem 9 % CO 2 89 % CH % H 2 S 0.98 % C 2 H % C 3 H % C 4 H % N % CO 2 97 % CH % H 2 S 0.68 % C 2 H % C 3 H % C 4 H % N 2 94% CO % CH % H 2 S 2.14% C 2 H % C 3 H % C 4 H % N 2

16 Overview of Problem

17 Current Technology: Amine Absorption Sour Gas Treated Gas Wash Water CO 2 Lean Amine Inlet Separator Cooler Filter Water Wash Drum Lean Amine Pump Cross Exchanger Stripper Amine Solution Tank Reboiler Pressurized Hot Water Water Condenser CO 2 & H 2 S Removed Rich Amine PumpAmine Pump Water Wash Pump To Atmosphere Rich Amine Flash Drum Contactor

18 Overview of Problem

19 How do membranes work?

20 Membrane Theory Ideal membrane o High permeance = o High separation factor (selectivity) = A, B = components y i = mole fraction in permeate x i = mole fraction in retentate

21 Membrane Theory Fick’s Law describes mass transport N i = molar flux species i D i = diffusivity component i l m = membrane thickness

22 Membrane Theory Assume thermodynamic equilibrium at interface Fick’s Law can be related to partial pressure by Henry’s Law Assume H i independent of total pressure and same temperature at both interfaces

23 Membrane Theory Combining equations Neglecting external mass transfer resistances Substituting

24 Membrane Theory Where permeability depends on the solubility and the diffusivity High flux with thin membrane and high pressure on the feed side permeance

25 Membrane Designs

26 Common Membrane Modules Spiral wound <20% of membranes formed High permeances and flux More resistant to plasticization High production cost: $10-100/m 2 Allow wide range of membrane materials

27 Common Membrane Modules Most common More membrane area per volume Low production cost: $2-5/m 2 Low reliability due to fouling Careful and expensive treatment Hollow Fiber

28 Common Membrane Modules Spiral-WoundHollow-Fiber Packing Density, m 2 /m ,000 Resistance to foulingModeratePoor Ease of cleaningFairPoor Relative costLow Main applicationsD, RO, GP, UF, MFD, RO, GP, UF D=Dialysis, RO=Reverse Osmosis, GP=Gas Permeation, PV=Pervaporation, UF=Ultrafiltration, MF=Microfiltration

29 Membrane Material Permeated Component Preferred Polymer Material Polymer usedSelectivities over CH 4 (%) CO 2 GlassyCellulose Acetate Polyimide Perfluoropolymer H2SH2SRubberyAmide block co- polymer N2N2 Glassy Rubbery Perfluoropolymer Silicone rubber H2OH2ORubbery/Glassyseveral>200 C3+C3+RubberySilicone rubber5-20 Table 1. Typical selectivities for high pressure natural gas (Baker & Lokhandwala)

30 Membrane Material Glassy Polymer Temperature below glass transition point Polymer chains fixed, rigid & tough Separate gases based on size

31 Membrane Material Rubbery Polymer Temperature above glass transition point Motion of polymer chain material becomes elastic & rubbery Separate gases based on sorption

32 Membrane Material Cellulose AcetateHigh CO 2 / CH 4 selectivity Lower H 2 S / CH 4 selectivity Non-reactive to most organic solvents Polyimide Rigid, bulky, non-planar structure Inhibited local motion of polymer chains High Permeability to water vapor

33 Membrane Advantages and Disadvantages

34 Membrane Advantages Lower capital cost o Skid mounted  Cost and time are minimal  Lower installation cost Treat high concentration gas o Membrane plant treating 5 mil scfd w/ 20% CO 2 would be less than half the size of plant treating 20 mil scfd w/ 5% CO 2

35 Membrane Advantages Operational simplicity o Unattended for long periods (Single Stage) o Start up, operation, and shutdown can be automated from a control room with minimal staffing (Multistage) Space efficiency o Skid construction o Offshore environments

36 Membrane Advantages Design efficiency o Integrate operations  Dehydration, CO 2 & H 2 S removal, etc. Power generation o Reduce electric power/fuel consumption Ecofriendly o Permeate gases used as fuel or reinjected into well

37 Membrane Disadvantages Plasticization o Membrane materials absorb cm 3 of CO 2 /cm 3 polymer  Absorbed CO 2 swells and dilates the polymer Increases mobility of polymer chains Decreases selectivity Physical aging o Glassy polymers are in nonequilibrium state  Over time, polymer chains relax, resulting in lower permeability

38 Membrane Disadvantages High compressor cost o Membranes only 10-25% of total cost o Significant reductions in membrane cost might not markedly change total plant cost o Compressor cost is 2-3 times the skid cost

39 Membrane Network

40 2 Membrane Network 3 Membrane Network How do we find the membrane network? Superstructure Membranes, compressors, mixers, splitters, streams

41 Superstructure Superstructure allows for all possible network configurations

42 For example: Superstructure

43 Resulting membrane network:

44 How do we build this superstructure?

45 Mathematical Model Mathematical programming model Assumptions: Countercurrent flow in hollow fiber module Uniform properties in each segment Steady-state No pressure drop across permeate or retentate side Constant permeabilities independent of concentration No diffusion in axial direction Deformation not considered

46 Hollow Fiber Mathematical Model Flux through membrane Shell side component balance Tube side component balance

47 Hollow Fiber Mathematical Model Mixer/Splitter Balances Feed balance

48 Hollow Fiber Mathematical Model Mixer/Splitter Balances Splitter balance 1 2

49 Hollow Fiber Mathematical Model Mixer/Splitter Balances CO 2 composition rcomp=0.02

50 Hollow Fiber Mathematical Model Mixer/Splitter Balances Mixer Balance 1 2

51 Hollow Fiber Mathematical Model Permeate power 1 2

52 Non-linear equations in model Non-linear equations discretized to give linear program Hollow Fiber Mathematical Model

53 Objective Function Annual Process Cost: minimized Fcc: Capital Charge Fmr: Membrane Replacement Fmt: Membrane Maintenance Fut: Utility Cost Fpl: Cost of Product loss

54 Objective Function Fixed Capital Investment: fmh: Membrane Housing ($200/m 2 ) fcp: Capital Cost of Gas Powered Compressor ($1000/kW) Wcp: Compressor Power (kW) ηcp: Compressor efficiency (70%)

55 Objective Function fcc: Capital Charge (27%/yr) fwk: Working Capital (10% Ffc) Capital Charge:

56 Objective Function Membrane Replacement: fmr: Membrane Replacement ($90/m 2 ) tm: Membrane Life (3 yr)

57 Objective Function Membrane Maintenance: fmt: Membrane Maintenance (5% Ffc)

58 Objective Function Utility Cost: fsg: Utility and Sale Gas Price ($35/Km 3 ) fhv: Sales Gas Gross Heating Value (43 MJ/ m 3 ) twk: Working Time (350 days/yr)

59 Objective Function Product Loss: m p : total flow rate of methane in permeate

60 How is this implemented?

61 Program Set and Parameter Declaration Variable Declaration

62 Program Equations

63 Program

64 Results

65 Results

66 2 Membrane Network at 79 lb-mol/hr Objective function: $163,000 % CH 4 lost: kW

67 3 Membrane Network at 79 lb-mol/hr Objective function: $130,000 %CH 4 lost: 7.77

68 4 Membrane Network at 79 lb-mol/hr Objective function: $130,000 %CH 4 lost: 7.77

69 Results: Comparison Objective Function ($) Area (m 2 )W cp (KW)% CH 4 Lost 2-Membrane Network 163, Membrane Network 130, Membrane Network 130, Comparison between membrane models at 79 lb-mol/hr

70 3 Membrane Network at 127 lb-mol/hr Objective function: $230,000 %CH 4 lost: 9.44

71 3 Membrane Network at 238 lb-mol/hr Objective function: $539,000 %CH 4 lost: 10.90

72 Membrane Network Verification

73 CompressorModel Work (kW)Pro-II Work (kW) C C C C C Work comparison for 238 lb-mol/hr

74 Results Total Annualized Cost vs. flow rate for an amine unit and 3 membrane network at 19% CO 2 in the feed

75 Results: Cost Analysis Flow rate (MMscfd)FCI ($) Operating Cost ($/yr) TAC ($/yr) 15 yr. Membrane M13 M15 M M26 M30 M M39 M45 M M52 M60 M M65 M75 M M77 M90 M Amine 90 3 M21 M M30 M M37 M38 M M43 M44 M M49 M50 M M54 M55 M Comparison between 3 membrane network and amine unit at 19 %CO 2

76 Results Adjusted existing cost for membrane network

77 Results

78 Results Total Annualized Cost vs. flow rate for an amine unit and 3 membrane network at 9% CO 2 in the feed

79 Results: Cost Analysis Comparison between 3 membrane network and amine unit at 9 %CO 2 Flow rate (MMscfd) FCI ($) Operating Cost ($/yr) TAC ($/yr) 15 yr. Membrane9018M9M10M 18036M18M20M 27055M27M31M 36073M36M41M 45591M45M51M M54M61M Amine905M12M 1806M17M18M 2707M22M 3608M26M 45510M29M30M 55011M33M

80 Recommendations Membrane networks have an overall lower total annualized cost and utility cost compared to an amine unit at flow rates less than 200 MMscfd Cost evaluation for membranes to replace other gas conditioning units CO 2 concentrations other than 20% need to be investigated in more detail

81 Questions?

82 References Baker, Richard. “Future Directions of Membrane Gas Separation Technology.” Industrial & Engineering Chemistry Research Sarkey’s Senior Lab. 7 Feb Baker, Richard and Kaaeid Lokhandwala. “Natural Gas Processing with Membranes: An Overview.” Industrial & Engineering Chemistry Research Sarkey’s Senior Lab. 4 Feb Kookos, I.K. “A targeting approach to the synthesis of membrane network for gas separations” Membrane Science, 208, , Mohammadi, T., Moghadam, Tavakol, and et al. “Acid Gas Permeation Behavior Through Poly(Ester Urethane Urea) Membrane.”Industrial & Engineering Chemistry Research Sarkey’s Senior Lab. 4 Feb Natural Gas Supply Association Sarkey’s Senior Lab. 7 Feb Perry, R.H.; Green, D.W. (1997). Perry’s Chemical Engineers’ Handbook (7 th Edition). McGraw-Hill. Seader, J. D., and Henley, E. J. "Separation Process Principles.” New York: John Wiley & Sons, Inc., 1998.

83 APPENDIX

84 Membrane Simulation Results CO 2 flow rate: 0.2 CH 4 flow rate: 0.8 Figure 1. Molar compositions with varying membrane area.

85 2 Membrane Network at 79 19%CO kW

86 3 Membrane Network at 79 19%CO 2

87 Programming Output

88

89

90

91 3 Membrane Network at %CO 2

92 3 Membrane Network at %CO 2

93 3 Membrane Network at 79 9% CO 2

94 Hollow Fiber Mathematical Model Discrete Equations Lower bound component flow rate tube side : discrete variable : binary variable : total flow rate segments binary variables

95 Hollow Fiber Mathematical Model Discrete Equations Upper bound component flow rate tube side : discrete variable : binary variable : total flow rate segments binary variables

96 Amine Unit Simulation

97 Equipment & Utility Cost at 79 lb-mol/hr ColumnsTypeNo. of trays Operating pressure Cost 1AbsorberValve trays6 250 psia $15,334 2StripperValve trays12 16 psia $32,736 ExchangersMOCDuty (MMBtu/hr)Area (ft2) 1Rich amine / Lean amineStainless Steel $4,772 2Lean amine / waterStainless Steel $2,651 3Lean amine / waterStainless Steel $2,439 PumpMOCPower (HP) Pump lean amine solutionStainless Steel130 $1,803 ValveMOCDiameter (m) Type Rich amine expansion valveStainless Steel0.2 Flanged $8,484 MDEA initial amt cost $552 Total $68,771 Cooling water Flow(1000 kg/hr)Price ($ /m3)Cost ($ / yr) $42,726 Natural gas as heating utility for reboiler Reboiler (MMBtu/hr)Price ( $ / MMBTU) 2.735$114,516 Electricity Duty (kW)Price ($ / kWh) $2, MDEA Recycle Flow (lb/hr)Price ($/lb) $1, Total$161,086

98 Equipment & Utility Cost at 127 lb-mol/hr ColumnsTypeNo. of trays Operating pressure Cost 1AbsorberValve trays6 250 psia $15,424 2StripperValve trays12 16 psia $37,434 ExchangersMOC Duty (MMBtu/hr)Area (ft2) 1Rich amine / Lean amineStainless Steel $9,544 2Lean amine / waterStainless Steel $3,075 3Lean amine / waterStainless Steel $4,242 PumpMOCPower (HP) Pump lean amine solutionStainless Steel130 $1,909 ValveMOCDiameter (m) Type Rich amine expansion valveStainless Steel0.2 Flanged $8,484 MDEA initial amt cost $701 Total $80,813 Cooling water Flow(1000 kg/hr)Price ($ /m3)Cost ($ / yr) $109,150 Natural gas as heating utility for reboiler Reboiler (MMBtu/hr)Price ( $ / MMBTU) 6.965$292,374 Electricity Duty (kW)Price ($ / kWh) $5, MDEA Recycle Flow (lb/hr)Price ($/lb) $1, Total$408,930

99 Equipment & Utility Cost at 238 lb-mol/hr ColumnsTypeNo. of trays Operating pressure Cost 1AbsorberValve trays6 250 psia $27,932 2StripperValve trays12 16 psia $53,235 ExchangersMOCDuty (MMBtu/hr)Area (ft2) 1 Rich amine / Lean amineStainless Steel $15,907 2 Lean amine / waterStainless Steel $4,242 3 Lean amine / waterStainless Steel $3,712 PumpMOCPower (HP) Pump lean amine solutionStainless Steel130 $2,651 ValveMOCDiameter (m) Type Rich amine expansion valveStainless Steel0.2 Flanged $8,484 MDEA initial amt cost $871 Total $117,033 Cooling water Flow(1000 kg/hr)Price ($ /m3)Cost ($ / yr) $130,281 Natural gas as heating utility for reboiler Reboiler (MMBtu/hr)Price ( $ / MMBTU) $349,088 Electricity Duty (kW)Price ($ / kWh) $7, MDEA Recycle Flow (lb/hr)Price ($/lb) $3, Total$489,545

100 Membrane Theory For binary gas mixture If P F >>P P

101 Membrane Theory Rearranging to get the Ideal Separation Factor Achieve large separation with large diffusivity or solubility ratio

102 Independent Verification

103 Comparison of GAMS and Excel Membrane Concentration Profile Figure 4. Excel simulation tube side 0.9 CH 4 & 0.1 CO 2 Figure 5. simulation tube side 0.9 CH 4 & 0.1 CO 2

104 Comparison of GAMS and Excel Membrane Concentration Profile Figure 6. Excel simulation shell side 0.9 CH 4 & 0.1 CO 2 Figure 7. GAMS simulation shell side 0.9 CH 4 & 0.1 CO 2

105 Comparison of GAMS and Excel Membrane Concentration Profile Figure 8. Excel simulation tube side 0.8 CH 4 & 0.2 CO 2 Figure 9. GAMS simulation tube side 0.8 CH 4 & 0.2 CO 2

106 Comparison of GAMS and Excel Membrane Concentration Profile Figure 10. Excel simulation shell side 0.8 CH 4 & 0.2 CO 2 Figure 11. GAMS simulation shell side 0.8 CH 4 & 0.2 CO 2

107 Comparison of GAMS and Excel Membrane Concentration Profile Figure 12. Excel simulation tube side 0.7 CH 4 & 0.3 CO 2 Figure 13. GAMS simulation tube side 0.7 CH 4 & 0.3 CO 2

108 Comparison of GAMS and Excel Membrane Concentration Profile Figure 14. Excel simulation shell side 0.7 CH 4 & 0.3 CO 2 Figure 15. GAMS simulation shell side 0.7 CH 4 & 0.3 CO 2

109 Comparison of GAMS and Excel Membrane Concentration Profile Figure 16. Excel simulation tube side 0.6 CH 4 & 0.4 CO 2 Figure 17. GAMS simulation tube side 0.6 CH 4 & 0.4 CO 2

110 Comparison of GAMS and Excel Membrane Concentration Profile Figure 18. Excel simulation shell side 0.6 CH 4 & 0.4 CO 2 Figure 19. GAMS simulation shell side 0.6 CH 4 & 0.4 CO 2

111 Comparison of GAMS and Excel Membrane Concentration Profile Figure 20. Excel simulation tube side 0.5 CH 4 & 0.5 CO 2 Figure 21. GAMS simulation tube side 0.5 CH 4 & 0.5 CO 2

112 Comparison of GAMS and Excel Membrane Concentration Profile Figure 22. Excel simulation shell side 0.5 CH 4 & 0.5 CO 2 Figure 23. GAMS simulation shell side 0.5 CH 4 & 0.5 CO 2


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