1. www.ieagreen.org.uk Overview of CO 2 Capture Processes John Davison IEA Greenhouse Gas R&D Programme Workshop on CCS, KEPRI, 19 th October 2007

2. www.ieagreen.org.uk Overview of this Presentation Descriptions of leading CO 2 capture technologies for power generation Main advantages and disadvantages Comparison of power plant efficiencies

3. www.ieagreen.org.uk CO 2 Capture Technologies Capture of CO 2 from flue gases Post-combustion capture Burning fuel in pure oxygen instead of air Oxy-combustion Conversion of fuel to H 2 and CO 2 before combustion Pre-combustion capture

4. www.ieagreen.org.uk Post-Combustion Capture Fuel Boiler or gas turbine Solvent scrubbing (FGD) Air Power CO 2 to storage N 2, O 2, H 2 O to atmosphere Steam turbine Steam CO 2 compression Capture Power generation

5. www.ieagreen.org.uk Liquid Solvent Scrubbing CO 2 CO 2 -rich solvent Steam CO 2 -lean solvent Condenser Flue gas Reduced-CO 2 flue gas Absorber (40-60°C) Stripper (100-120°C) Reboiler

6. www.ieagreen.org.uk Post-Combustion Solvent Scrubbing Most common solvent is MEA (mono-ethanolamine) Widely used for reducing gases, e.g. natural gas Less widely used for oxidising flue gases MEA is used in small post-combustion capture plants CO 2 is used mainly for chemicals and food and drink

7. www.ieagreen.org.uk Post-Combustion CO 2 Capture Warrior Run power plant, USA 180 MW e coal fired circulating fluidised bed combustor 150 t/d of CO 2 is captured from a slipstream About 5% of the total MEA solvent is used

8. www.ieagreen.org.uk Post-Combustion Solvent Scrubbing Up to 95%+ of CO 2 can be captured in coal-fired plants CO 2 purity is high (99%+) MEA solvent is degraded by oxygen and impurities Low SO X (<10 ppm) and NO 2 (<20 ppm) is recommended Trade-off between costs of gas clean-up and solvent loss Corrosion inhibitors are needed

9. www.ieagreen.org.uk New solvents are being developed and used Amine blends, e.g. MEA - MDEA Hindered amines, e,g MHI’s KS-1 solvent Ammonia Lower energy consumption, solvent losses and corrosion Some solvents are more expensive Overall cost may be lower if the rate of loss is lower Post-Combustion Solvent Scrubbing

10. www.ieagreen.org.uk Post-Combustion CO 2 Capture Petronas urea plant Kedah, Malaysia 200 t/d of CO 2 captured from gas fired furnace flue gas KS-1 solvent is used Courtesy of MHI

11. www.ieagreen.org.uk Post-Combustion CO 2 Capture 3,000 t/d plant (MHI) ‘Ready for delivery’ Equivalent to 150 MW e coal fired plant Larger designs being developed Aim is to have one scrubber per boiler The same as FGD Courtesy of MHI

12. www.ieagreen.org.uk Ammonia Scrubbing Chilled ammonia scrubbing proposed by Alstom Ammonium carbonate reacts with CO 2 to form bicarbonate 5 MWe plant built in Wisconsin, USA 80,000 t/y plant to be built in Norway, more plants elsewhere Advantages Much lower solvent regeneration energy High pressure regeneration - less CO 2 compression power Cheaper solvent Waste production and disposal is less of a problem Disadvantages Power consumption for flue gas refrigeration and fans Capital cost may be higher

13. www.ieagreen.org.uk Post-Combustion Capture - Summary Advantages Existing combustion technology can be used Retrofit to existing plants is possible Demonstrated at some small power plants High CO 2 purity Disadvantages High energy consumption Penalty is being reduced by process developments Solvent is degraded by oxygen and impurities Scale-up is needed

14. www.ieagreen.org.uk Oxy-Combustion - Solid Fuel Fuel BoilerPurification/ compression Cooling (+FGD) Air separation Air Power Oxygen CO 2 Vent Recycled flue gas Steam turbine Steam

15. www.ieagreen.org.uk Oxy-Combustion – Solid Fuel Oxy-combustion boilers can be similar to conventional boilers Air leakage into the boiler needs to be minimised Heat transfer, ash deposition and corrosion are issues to be considered in the detailed design Possibility of making more compact boilers High percentage capture of CO 2 Impurities need to be removed from the CO 2 Cryogenic flash or distillation can be used High cost of oxygen Oxy-combustion is at a relatively small scale

16. www.ieagreen.org.uk Vattenfall 30MW Oxy-Combustion Plant Courtesy of Vattenfall Schwarze Pumpe, Germany

17. www.ieagreen.org.uk Oxy-Combustion – Gaseous Fuels Fuel Gas turbinePurification/ compression HRSG Air separation Air Oxygen CO 2 Vent Recycled flue gas Steam turbine Steam Power

18. www.ieagreen.org.uk Oxy-Combustion – Gas Turbines New types of gas turbine are needed CO 2 has different expansion properties to N 2 /O 2 etc Higher pressures are needed Development of new turbines is very expensive Will only happen if there is a large market Retrofit to existing turbines is not possible Quantity of oxygen required per tonne of CO 2 is higher than for coal For CH 4, half the O 2 is used to burn hydrogen Water can be used instead of recycle CO 2

19. www.ieagreen.org.uk Water Cycle Condenser CO 2 Combustor Compressor Oxygen Fuel Water 0.1 bar 80 bar Fuel

20. www.ieagreen.org.uk CES Water Cycle Plant 5 MW e plant at Kimberlina, California

21. www.ieagreen.org.uk Chemical Looping Combustion Iron, nickel, copper and manganese are considered Early state of development Durability of solids is a concern Potential for low energy consumption Fuel CO 2 Air Metal oxide Reduced metal oxide Oxygen depleted air

22. www.ieagreen.org.uk Oxy-combustion - Summary Advantages Existing boiler technology can be used Possibility of avoiding FGD and SCR Near-zero CO 2 emissions are possible Disadvantages Least mature of the 3 leading capture technologies High cost of oxygen production CO 2 purification is needed New gas turbine designs are needed

23. www.ieagreen.org.uk Pre-Combustion Capture Coal GasificationAcid gas removal Air separation Combined cycle Air Fuel gas Nitrogen Power Oxygen Sulphur recovery Sulphur Air CO, H 2 O H 2, CO 2 etc H2SH2S Air IGCC without CO 2 capture

24. www.ieagreen.org.uk IGCC Without CO 2 Capture 4 coal-based IGCC demonstration plant in the USA, Netherlands and Spain Availability has been poor but is improving IGCC is not at present the preferred technology for new coal-fired power plants Main commercial interest in IGCC is currently for use of petroleum residues Several plants built and planned at refineries

25. www.ieagreen.org.uk IGCC without CO 2 Capture Shell gasifier IGCC plant, Buggenum, Netherlands

26. www.ieagreen.org.uk Pre-Combustion Capture Coal Gasification Acid gas removal Shift conversion Air separation Combined cycle Air Fuel gas (mainly H 2 ) Nitrogen Power Oxygen CO 2 CO 2 compression Sulphur Air H2SH2S CO+H 2 O→H 2 +CO 2 IGCC with CO 2 capture Sulphur recovery

27. www.ieagreen.org.uk CO 2 Capture in IGCC Advantages of IGCC for CO 2 capture High CO 2 concentration and high overall pressure Lower energy consumption for CO 2 separation Compact equipment Proven CO 2 separation technology can be used Possibility of co-production of hydrogen CO 2 capture is generally seen to improve the competitiveness of IGCC versus pulverised coal IGCC is generally seen as more attractive for bituminous coals than for low rank coals.

28. www.ieagreen.org.uk CO 2 Capture in IGCC Disadvantages IGCC is unfamiliar technology for power generators Existing coal fired plants have had relatively low availability IGCC without CO 2 capture has generally higher costs than pulverised coal combustion Different gas turbine combustors are needed Hydrogen combustion is not available for the most advanced gas turbines

29. www.ieagreen.org.uk Pre-Combustion Capture – Gaseous Fuels Fuel Partial Oxidation Acid gas removal Shift conversion Gas turbine Air Fuel gas (mainly H 2 ) Flue gas CO 2 CO 2 compression CO+H 2 O→H 2 +CO 2 Air separation Power

30. www.ieagreen.org.uk CO 2 Capture in Natural Gas Power Plants Technology for production of hydrogen from natural gas is well proven A large amount of extra equipment is needed for CO 2 capture Gas turbine issues are the same as for IGCC

31. www.ieagreen.org.uk Power Generation Efficiency Efficiency, % LHV Source: IEA GHG studies Coal Natural gas

32. www.ieagreen.org.uk Efficiency Decrease due to for Capture Percentage points Coal Natural gas

33. www.ieagreen.org.uk Summary CO 2 can be captured using existing technology Capture technology needs to be demonstrated at larger scales The optimum technology is uncertain Depends on fuel type, other local conditions and future technology developments etc. Utilities are seeking to gain experience of a broad range of technologies