Emerging Technologies for the Production of Ultraclean IGCC Syngas R. Gupta, B.S. Turk, T.C. Merkel and A. Lopez-Ortiz Research Triangle Institute RTP, NC 2001 Gasification Technologies Conference October 7-10, 2001
Driving Force Vision 21 Energyplex Coal Other Fuels POWER F u e l C e l l H ig h E f f ic ie n c y T u r b in e FU ELS Oxygen Membrane Gasification Gas Stream Cleanup Hydrogen Separation L iq u i d s C o n v e r s io n Process Heat/ Steam CO2 Sequestration Gas stream cleanup Near-zero (ppb) emission limits Modular design Power/electricity + Fuel cells + Turbines Fuels/chemicals Fuels/Chemicals Ele ctricity
Contaminant Tolerance Limits Contaminants Tolerance Limits (by Volume) Fuel Cells Chemical Production MCFC PAFC SOFC Total Sulfurs 60 ppb <0.5 ppm <50 ppm <0.1 ppm Total Halides 10 ppb <0.5 ppm NS <1 ppm Ammonia NS <1 vol% 0.2 vol% <5,000 ppm NS - Not Specified
Technology Development Approach
Technology Development Approach (Bulk Desulfurization)
Permeability of Syngas Components in a Solubility Selective Membrane 10 5 PDMS 23 C Permeability, Barrers 10 4 10 3 H 2 CO CH 4 CO 2 COS H 2 S SO 2 N 2 10 2 0 100 200 300 400 500 600 700 T c, K NH 3 H 2 O
Acid-Gas Separation in a Polymer Membrane Module
Schematic of Gas Permeation Apparatus at RTI Pressure gauge Feed high-pressure cylinder Pressure regulator MFC Pressure Regulator Residue Temperature control Membrane cell Permeate He Sweep MFC GC Vent to atmosphere
Gas Permeation System at RTI
Summary of Acid Gas Permeation Results at Room Temperature Polymer CO Mixed Gas Selectivity 2 Permeability (Barriers) CO 2 /H 2 H 2 S/H 2 PDMS 3400 3.6 5.4 Medal 001 19 3.3 8.3 Medal 002 7.5 3.5 12 Medal 003 300 3.6 4.9 Medal 004 200 3.5 4.9 Medal 005 120 3.0 4.5 Medal 006 74 4.2 16 Medal 007 47 4.3 17 Medal 016 115 4.6 33 Medal 017 92 4.7 26 Medal 018 115 6.4 36 Medal 019 38 3.0 - Medal 020 42 4.5 22 Medal 021 95 6.5 27 Medal 022 34 6.2 22 Pebax 4011 58 6.4 31
Mixed-gas H 2 S/H 2 Selectivity as a Function of Temperature Mixed-gas Selectivity, CO 2 /H 2 35 30 25 20 15 10 5 PDMS Medal 001 Medal 002 Medal 003 Medal 004 Medal 005 Medal 006 Medal 007 Medal 016 Medal 017 Medal 018 0 0 50 100 150 200 Temperature, C
Membrane Simulation Countercurrent, Shell-Side Feed Feed: T = 25 C, P = 600 psia Residue A = 377 m 2 Permeate: P = 20 psia 500,000 fibers, ID = 150 µm OD = 300 µm, L = 1 m Component Feed mole fraction Permeance (GPU)* H 2 0.35 10 CO 0.47 4 N 2 0.026 3 CO 2 0.14 80 H 2 S 0.009 250 H 2 O 0.002 350 * Permeance values based on H 2 flux of 10 gpu [10-5 cm 3 (STP)/(cm 2 s cm Hg)] and the current best case room temperature selectivities. Membrane simulator reference: Coker, D.T., Freeman, B.D., and Fleming, G.K., AIChE Journal, Vol. 44, No. 6, June (1998)]
Simulation Results 45 45 6000 40 decreasing feed flow rate increasing stage cut 40 5000 % of Inlet H 2 in Permeate 35 30 25 20 15 10 35 30 25 20 15 10 4000 3000 2000 1000 ppm H 2 S in Residue 5 20 30 40 50 60 70 80 90 100 % of Inlet CO 2 Removed in Permeate 5 0 40 50 60 70 80 90 100 % of Inlet H 2 S Removed in Permeate
Membrane Simulation H 2 S Removal 50 Percent H 2 in Permeate 45 40 35 30 25 20 15 10 5 S = 50 S = 40 S = 30 0 50 60 70 80 90 100 Percent H 2 S Removed in Permeate
Summary of Bulk Desulfurization Testing (polymer membranes) Process Membranes can separate H 2 S, COS, CS 2 in addition to CO 2, H 2 O, HCl and NH 3 Selectivity is strongly dependent on temperature Simulations indicate that 80 to 90% H 2 S removal without appreciable loss of H 2 Materials Films with selectivities of H 2 S/H 2 >30 were synthesized These polymer compositions are readily adaptable to hollow fiber production for membrane modules
Technology Development Approach (Polishing Desulfurization)
Comparison of Various Sulfur Polishing Steps Desulfurization Sub-ppm Kinetics Removal Capacity Regenerability Cost ZnO Guard Bed + + + Activated Carbon + + Monoliths + + ++ + + Regenerable + + + + + Sorbents (RVS)
Bench-Scale Facility for Monolith Testing at RTI
Sulfur Removal by Monolith Sorbents H2S Effleunt Concentration (ppmv) 5000 5 4500 4.5 4000 4 3500 3.5 3000 3 2500 2.5 2000 2 1500 1.5 1000 1 500 0.5 Sulfidation Conditions Pressure: 280 psig Temperature: 1,000 F Space Velocity: 2,000 h -1 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Proposed Limit 0 0 50 100 150 200 250 300 Time (min)
Desulfurization Performance between 200 and 1,000 F for Monolithic Sorbents 50 14 H2S Leak (ppmv) 45 40 35 30 25 20 15 Sulfidation Conditions Pressure: 280 psig Space Velocity: 2,000 h -1 H 2 S Feed Concentration: 5,000 ppmv H2S leak, ppm Sulfur Load, g 12 10 8 6 4 Sulfur Load (wt%) 10 5 2 0 0 1000 900 800 700 600 500 400 300 200 Temperature ( F)
H 2 S Removal Using RVS-1 Sorbent H2S (ppm), Wet Basis 20,000 18,000 16,000 14,000 12,000 10,000 8,000 8 6,000 6 4,000 4 2,000 2 Sulfidation Conditions: Pressure: 450 psig Temperature: 550-480 F Feed Gas composition (vol, %) CO 18.9 CO 2 3.9 H 2 13.2 H 2 S 1.0 (10,000 ppmv) H 2 O 63.0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 7 0 0 50 100 150 200 250 Time (min)
Summary of Polishing Desulfurization Work Two sets of materials tested for H 2 S removal to <1 ppmv These materials are regenerable for multiple cycles They can operate at temperatures as low as 200 F Work is continuing to reduce the sulfur levels down to <100 ppbv
Preliminary Process Flowsheet 6 Residue HP Air Intercooling 2-Stage Compressor 3 DSRP Reactor Q = -156278.7 Btu/hr Q = 302330.7 Btu/hr 11 14 2 Raw Syngas 1 HTHP Barrier Filter (if needed) 5 B3 7 Q = -48445.3 Btu/hr Monolith 1 Sulfidation Q = 0 Btu/hr 9 H2O HCL NH3 B5 10 Monolith 3 Regeneration Q = -13022.6 Btu/hr Permeate SEP2 Polymer Membrane Module Monolith 3 Heating 13 Q = 433429.7 Btu/hr Q = -61232.9 Btu/hr W = 27 HP 4 POX Reactor Q = -279539.4 Btu/hr Regeneration Gas 22 16 27 Q = -406090.6 Btu/hr B13 21 26 CO2 Rich Tail Gas Sulfur HP Air 23 24 8 29 30 Vent 17 Clean Syngas N2 25 Booster Inert Heating Gas Q = 38345.6 Btu/hr 20 Make up N2 2% O2/N2 19 12 18
Summary of Material/Energy Balance Description Raw Syngas Clean Syngas Tail Gas Condensate Stream # 1 17 21 10 Temperature ( F) 700 673.5 100 80 Pressure (psia) 600 595 200 600 Total Flow (lbmol/hr) 100.3 69.9 26.7 15.1 Mole Fraction H 2 0.299 0.381 850 PPM 2 PPB CO 0.399 0.545 0.01 CO 2 0.12 0.043 0.398 N 2 0.022 0.03 0.588 H 2 S 8000 PPM 392 PPB 76 PPM 245 PPM NH 3 0.002 11 PPB 0.012 H 2 O 0.15 0.001 0.003 0.986 HCl 299 PPM 3 PPB 0.002 LHV (Btu/scf) 206 274 3.4 0 Generated using laboratory and bench-scale test data collected and the ASPEN simulation software at RTI and the membrane simulator at NCSU
Nexant Evaluation Evaluated the design information supplied by RTI Sized equipments and estimated their cost for a 500-MWe IGCC based on Texaco gasifier Used the Rectisol process as a benchmark for cost comparison
Results of Nexant Evaluation Total Sulfur Installed Removal Cost Process Target 2001 $ MDEA 70 ppm $18M 1 Rectisol <1 ppm $75M RTI <1ppm $42M 2 1 Does not include the cost of COS hydrolysis reactor. 2 Future improvements in membrane and sorbent materials are expected to lower this number significantly.
Potential Impact of this Technology Significant cost advantage for sulfur removal RTI vs. Rectisol Enrichment of Btu content of syngas without pressure loss Significant concentration of CO 2 in the tail gas stream Highly modular Highly integrated overall contaminant control Individual process components for specialized treatment
Conclusions/Future Steps Feasibility of RTI s syngas desulfurization process confirmed at laboratory scale Preliminary economic evaluation indicates 75% lower installed cost than a Rectisol system In Phase II work, membrane modules of 1 ft 2 will be tested at bench-scale, and plans are being made to test a 150 ft 2 module with real syngas Both monolith and sorbent materials are being advanced to reduce the sulfur levels to <100 ppbv
Acknowledgments DOE/NETL funded this research through contract No. DE-AC26-99FT40675 MEDAL North Carolina State University Süd-Chemie Prototech Inc. SRI International Nexant, Inc. Texaco Power and Gasification