Overview of CO

2

Processes Capture

John Davison IEA Greenhouse Gas R&D Programme Workshop on CCS, KEPRI, 19 th October 2007 www.ieagreen.org.uk

Overview of this Presentation • • • Descriptions of leading CO 2 for power generation capture technologies Main advantages and disadvantages Comparison of power plant efficiencies

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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 combustion • 2 Pre-combustion capture and CO 2 before

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Air Post-Combustion Capture Power generation Capture N 2 , O 2 , H 2 O to atmosphere Fuel Boiler or gas turbine Steam Steam turbine Power (FGD)

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Solvent scrubbing CO 2 compression CO 2 to storage

Liquid Solvent Scrubbing Reduced-CO 2 flue gas CO 2 CO 2 -lean solvent Condenser Absorber (40-60 °C) Stripper (100-120 °C) Flue gas CO 2 -rich solvent

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Steam Reboiler

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

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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

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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

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Post-Combustion Solvent Scrubbing • • • • 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

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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

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Post-Combustion CO 2 Capture Courtesy of MHI • • • • • 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

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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 Cheaper solvent compression power Waste production and disposal is less of a problem Disadvantages • Power consumption for flue gas refrigeration and fans • Capital cost may be higher

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• • 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

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Air Oxy-Combustion - Solid Fuel Air separation Recycled flue gas Oxygen Vent Fuel Boiler Cooling (+FGD) Purification/ compression CO 2 Steam Steam turbine Power

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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

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Vattenfall 30MW Oxy-Combustion Plant Schwarze Pumpe, Germany

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Courtesy of Vattenfall

Air Oxy-Combustion – Gaseous Fuels Air separation Recycled flue gas Oxygen Vent Fuel Gas turbine HRSG Purification/ compression CO 2 Power Steam Steam turbine

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Oxy-Combustion – Gas Turbines • • • • • New types of gas turbine are needed • • CO 2 has different expansion properties to N 2 /O 2 Higher pressures are needed etc 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 higher than for coal • For CH 4 , half the O 2 is used to burn hydrogen is Water can be used instead of recycle CO 2

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Oxygen Water Cycle Fuel Fuel Combustor 80 bar Water CO 2 Compressor

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0.1 bar Condenser

CES Water Cycle Plant 5 MW e plant at Kimberlina, California

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

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• • 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

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Pre-Combustion Capture IGCC without CO 2 capture Coal Gasification CO, H 2 O H 2 , CO 2 etc Oxygen Sulphur recovery H 2 S Acid gas removal Sulphur Fuel gas Air Air separation Nitrogen Air Combined cycle Power Air

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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

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IGCC without CO 2 Capture Shell gasifier IGCC plant, Buggenum, Netherlands

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

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• 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.

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• 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

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

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• 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

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Power Generation Efficiency

Efficiency, % LHV 60 50 40 30 20 10 0 Post comb IGCC slurry IGCC dry Oxyfuel Coal Without capture With capture www.ieagreen.org.uk

Post comb Oxyfuel Natural gas

Source: IEA GHG studies

Efficiency Decrease due to for Capture

Percentage points 12 10 8 6 4 2 CO2 compression and purification O2 production and power cycle impacts Shift conversion and related impacts Power for CO2 separation Steam for CO2 separation 0 Post comb IGCC slurry Coal IGCC dry Oxyfuel Post comb Oxyfuel Natural gas 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

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