Purification of Oxyfuel Derived CO 2 for Sequestration or EOR

Transcription

1 2nd Workshop International Oxy-Combustion Research Network Hilton Garden Inn Windsor, CT, USA 25th and 26th January 2007 Hosted by: Alstom Power Inc. PRESENTATION - 10 Purification of Oxyfuel Derived for Sequestration or EOR by: Vince White Air Products PLC, UK

2 Purification of Oxyfuel-Derived for Sequestration or EOR Vince White Air Products PLC, UK 25 th January 2007 Purification of Oxyfuel-Derived for Sequestration or EOR produced from oxyfuel requires purification Cooling to remove water Inerts removal Compression Current design has limitations SOx/NOx removal Oxygen removal Recovery limited by phase separation New concepts for purification have been developed (since the IEA GHG Oxyfuel report) 2 2nd Int'l Oxy-Combustion Workshop Page 1

3 Flue Gas Vent 1.1 bar 20 C 25% 75% inerts Compression and Purification System Inerts removal and compression to 110 bar Flue Gas Expander Flue Gas Heater Aluminium plate/fin exchanger -55 C Driers 3 30 bar Raw 76% 24% Inerts product 110 bar 96% 4% Inerts -60 C dp Purity Depends On Feed Pressure Composition Feed Pressure, bar At -55 C 4 2nd Int'l Oxy-Combustion Workshop Page 2

4 Recovery Depends On Feed Composition Recovery Feed Composition At -55 C, 30 bar 5 Recovery Depends On Feed Composition Vent Composition Feed Composition At -55 C, 30 bar 6 2nd Int'l Oxy-Combustion Workshop Page 3

5 Purity and Recovery -55 C is as cold as we can make the phase separation purity depends on pressure At 30 bar and -55 C, purity is 95% Higher pressure gives lower purity recovery depends on pressure Lower pressure gives lower recovery At 15 bar and -55 C, recovery is 75% At 30 bar and -55 C, recovery is 90% recovery depends on feed composition Increases from zero at 25mol% to 90% at 75mol% Reducing air ingress increases capture rate 7 Raw and Product Compositions Raw Flue Gas Product 35 C, C, C, 1.1 bar mol% mol% mol% Prior Art Prior Art N 2 O Ar SO NO 400 ppm 13 ppm 1180 ppm NO 2 10 ppm 0 0 H 2 O nd Int'l Oxy-Combustion Workshop Page 4

6 Purity Issues H 2 O SO 2 NO O 2 Ar + N 2 + O 2 Basic Design Case < 500 ppm > 90% mol From H&MB From H&MB < 4% mol < 4% mol EOR Case < 50 ppm > 90% mol < 50 ppm From H&MB 100 ppm < 4% mol Regulations regarding onshore and off-shore disposal are being drafted world-wide Co-disposal of other wastes (NOx, SOx, Hg) is a sensitive issue Important that the can be purified for disposal or EOR 9 NOx SO 2 Reactions in the Compression System We realised that SO 2, NOx and Hg can be removed in the compression process, in the presence of water and oxygen. SO 2 is converted to Sulphuric Acid, NO 2 converted to Nitric Acid: NO + ½ O 2 = NO 2 (1) Slow 2 NO 2 = N 2 O 4 (2) Fast 2 NO 2 + H 2 O = HNO 2 + HNO 3 (3) Slow 3 HNO 2 = HNO NO + H 2 O (4) Fast NO 2 + SO 2 = NO + SO 3 (5) Fast SO 3 + H 2 O = H 2 SO 4 (6) Fast Rate increases with Pressure to the 3 rd power only feasible at elevated pressure No Nitric Acid is formed until all the SO 2 is converted Pressure, reactor design and residence times, are important. 10 2nd Int'l Oxy-Combustion Workshop Page 5

7 Compression and Purification System Removal of SO 2, NOx and Hg 1.02 bar 30 C 67% 8% H 2 O 25% Inerts SOx NOx SO 2 removal: 100% NOx removal: 90-99% BFW Condensate 15 bar 30 bar cw Water 30 bar to Driers 76% 24% Inerts cw cw Dilute HNO 3 11 Dilute H 2 SO 4 HNO 3 Hg SOx/NOx Removal Key Features Adiabatic compression to 15 bar: No interstage water removal All Water and SOx removed at one place NO acts as a catalyst NO is oxidised to NO 2 and then NO 2 oxidises SO 2 to SO 3 : The Lead Chamber Process Hg will also be removed, reacting with the nitric acid that is formed 12 2nd Int'l Oxy-Combustion Workshop Page 6

8 Corrected Purity Raw Flue Gas Product Vent Product 35 C, C, C, C, C, 1.1 bar mol% mol% mol% mol% mol% Prior Art Prior Art Corrected Corrected N 2 O Ar SO NO 400 ppm 13 ppm 1180 ppm < 10 ppm < 100 ppm NO 2 10 ppm 0 0 < 10 ppm 0 H 2 O And Oxygen removal from the? Where does the distillation column go? Driers bar Raw 76% 24% Inerts 2nd Int'l Oxy-Combustion Workshop Page 7

9 Oxygen removal Option 1 Driers Remove this Feed to distillation column bar Raw 76% 24% Inerts Oxygen removal Option 1 Recycle to Feed Impure 17 bar column Pure To exchanger for refrigeration duty Reboiler heated with feed stream 16 2nd Int'l Oxy-Combustion Workshop Page 8

10 Oxygen removal Option 2 Driers Feed to distillation column bar Raw 76% 24% Inerts Oxygen removal Option 2 Recycle to Feed Impure 30 bar column Pure Pump to pipeline pressure or flash to tanker pressure Reboiler heated with feed stream 18 2nd Int'l Oxy-Combustion Workshop Page 9

11 Can we improve on 89% Capture? Vent stream is at pressure and is (and O 2 ) rich Driers bar Raw 76% 24% Inerts Put membrane in vent stream Recycle and O 2 rich stream to boiler To Boiler Membrane Driers bar Raw 76% 24% Inerts 2nd Int'l Oxy-Combustion Workshop Page 10

12 Purity, Recovery and Power Power includes ASU and system power Description Purity Oxygen Content Pressure Recovery Relative Specific Power Standard Cycle mol% 0.91 mol% 110 bar 89.0% 1.00 High Purity Option mol% ppm 110 bar 87.4% 1.03 High Purity Option mol% ppm 110 bar 87.7% bar liquid mol% ppm 30 bar 87.7% bar liquid mol% 5.01 ppm 7 bar 87.7% 1.02 Standard with membrane High purity Option 1 with membrane mol% 0.73 mol% 110 bar 97.7% mol% ppm 110 bar 97.9% Conclusions FGD and DeNOx systems are not required to meet tight purity specifications Co-disposal of SO 2 with is not possible Compressing with NO + SO 2 + O 2 + Water will result in H 2 SO 4 production Low NOx burners are not required for oxyfuel combustion Oxygen can be removed for EOR-grade No penalty if liquid is required Capture of increased to 98% with membrane Also reduces ASU size (~5% reduction) 22 2nd Int'l Oxy-Combustion Workshop Page 11

13 Thank you tell me more 2nd Int'l Oxy-Combustion Workshop Page 12