Embed Size (px)
Citation preview
www.ieagreen.org.uk
Overview of COOverview of CO22 Capture Capture
ProcessesProcesses
John Davison
IEA Greenhouse Gas R&D Programme
Workshop on CCS, KEPRI, 19th October 2007
www.ieagreen.org.uk
Overview of this PresentationOverview of this Presentation
• Descriptions of leading CO2 capture technologies
for power generation
• Main advantages and disadvantages
• Comparison of power plant efficiencies
www.ieagreen.org.uk
COCO22 Capture Technologies Capture Technologies
• Capture of CO2 from flue gases
• Post-combustion capture
• Burning fuel in pure oxygen instead of air• Oxy-combustion
• Conversion of fuel to H2 and CO2 before
combustion• Pre-combustion capture
www.ieagreen.org.uk
Post-Combustion CapturePost-Combustion Capture
Fuel Boiler or gas turbine
Boiler or gas turbine
Solvent scrubbingSolvent
scrubbing(FGD) (FGD)
Air
PowerCO2 to storage
N2, O2, H2O to atmosphere
Steam turbineSteam turbine
Steam
CO2 compression
CO2 compression
CapturePower generation
www.ieagreen.org.uk
Liquid Solvent ScrubbingLiquid Solvent ScrubbingCO2
CO2-rich solvent
Steam
CO2-lean solvent
Condenser
Flue gas
Reduced-CO2 flue gas
Absorber (40-60°C) Stripper
(100-120°C)
Reboiler
www.ieagreen.org.uk
Post-Combustion Solvent Scrubbing 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
• CO2 is used mainly for chemicals and food and drink
www.ieagreen.org.uk
Post-Combustion COPost-Combustion CO22 Capture Capture
• Warrior Run power plant, USA
• 180 MWe coal fired circulating
fluidised bed combustor
• 150 t/d of CO2 is captured
from a slipstream
• About 5% of the total
• MEA solvent is used
www.ieagreen.org.uk
Post-Combustion Solvent Scrubbing Post-Combustion Solvent Scrubbing
• Up to 95%+ of CO2 can be captured in coal-fired plants
• CO2 purity is high (99%+)
• MEA solvent is degraded by oxygen and impurities
• Low SOX (<10 ppm) and NO2 (<20 ppm) is recommended
• Trade-off between costs of gas clean-up and solvent loss
• Corrosion inhibitors are needed
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 Post-Combustion Solvent Scrubbing
www.ieagreen.org.uk
Post-Combustion COPost-Combustion CO22 Capture Capture
• Petronas urea plant
• Kedah, Malaysia
• 200 t/d of CO2 captured
from gas fired furnace flue gas
• KS-1 solvent is used
Courtesy of MHI
www.ieagreen.org.uk
Post-Combustion COPost-Combustion CO22 Capture Capture
• 3,000 t/d plant (MHI)
• ‘Ready for delivery’
• Equivalent to 150 MWe coal fired plant
• Larger designs being developed
• Aim is to have one scrubber per boiler• The same as FGD
Courtesy of MHI
www.ieagreen.org.uk
Ammonia ScrubbingAmmonia Scrubbing
• Chilled ammonia scrubbing proposed by Alstom• Ammonium carbonate reacts with CO2 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 CO2 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
www.ieagreen.org.uk
Post-Combustion Capture - SummaryPost-Combustion Capture - Summary• Advantages
• Existing combustion technology can be used• Retrofit to existing plants is possible• Demonstrated at some small power plants
• High CO2 purity
• Disadvantages • High energy consumption
• Penalty is being reduced by process developments
• Solvent is degraded by oxygen and impurities
• Scale-up is needed
www.ieagreen.org.uk
Oxy-Combustion - Solid FuelOxy-Combustion - Solid Fuel
Fuel Boiler Boiler Purification/ compressionPurification/ compression
Cooling (+FGD)Cooling (+FGD)
Air separation
Air separation
Air
Power
Oxygen
CO2
VentRecycled flue gas
Steam turbineSteam turbine
Steam
www.ieagreen.org.uk
Oxy-Combustion – Solid Fuel 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 CO2
• Impurities need to be removed from the CO2
• Cryogenic flash or distillation can be used
• High cost of oxygen
• Oxy-combustion is at a relatively small scale
www.ieagreen.org.uk
Vattenfall 30MW Oxy-Combustion PlantVattenfall 30MW Oxy-Combustion Plant
Courtesy of VattenfallSchwarze Pumpe, Germany
www.ieagreen.org.uk
Oxy-Combustion – Gaseous FuelsOxy-Combustion – Gaseous Fuels
Fuel Gas turbine
Gas turbine
Purification/ compressionPurification/ compression
HRSGHRSG
Air separation
Air separation
Air
Oxygen
CO2
VentRecycled flue gas
Steam turbineSteam turbine
Steam
Power
www.ieagreen.org.uk
Oxy-Combustion – Gas TurbinesOxy-Combustion – Gas Turbines
• New types of gas turbine are needed• CO2 has different expansion properties to N2/O2 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 CO2 is higher than for coal• For CH4, half the O2 is used to burn hydrogen
• Water can be used instead of recycle CO2
www.ieagreen.org.uk
Water CycleWater Cycle
Condenser
CO2
Combustor
Compressor
Oxygen
Fuel
Water
0.1 bar80 bar
Fuel
www.ieagreen.org.uk
CES Water Cycle PlantCES Water Cycle Plant
5 MWe plant at Kimberlina, California
www.ieagreen.org.uk
Chemical Looping Combustion 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
CO2
Air
Metal oxide
Reduced metal oxide
Oxygen depleted air
www.ieagreen.org.uk
Oxy-combustion - SummaryOxy-combustion - Summary• Advantages
• Existing boiler technology can be used
• Possibility of avoiding FGD and SCR
• Near-zero CO2 emissions are possible
• Disadvantages • Least mature of the 3 leading capture technologies
• High cost of oxygen production
• CO2 purification is needed
• New gas turbine designs are needed
www.ieagreen.org.uk
Pre-Combustion CapturePre-Combustion Capture
Coal Gasification
Gasification
Acid gas removalAcid gas removal
Air separation
Air separation
Combined cycle
Combined cycle
Air
Fuel gas
Nitrogen Power
Oxygen
Sulphur recoverySulphur recovery
Sulphur
Air
CO, H2O H2, CO2 etc
H2S
Air
IGCC without CO2 capture
www.ieagreen.org.uk
IGCC Without COIGCC Without CO22 Capture 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
www.ieagreen.org.uk
IGCC without COIGCC without CO22 Capture Capture
Shell gasifier IGCC plant, Buggenum, Netherlands
www.ieagreen.org.uk
Pre-Combustion CapturePre-Combustion Capture
Coal Gasification
Gasification
Acid gas removalAcid gas removal
Shift conversion
Shift conversion
Air separation
Air separation
Combined cycle
Combined cycle
Air
Fuel gas (mainly H2)
Nitrogen Power
Oxygen
CO2CO2 compression
CO2 compression
Sulphur
Air
H2S
Air
CO+H2O→H2+CO2
IGCC with CO2 capture
Sulphur recoverySulphur recovery
www.ieagreen.org.uk
COCO22 Capture in IGCC Capture in IGCC
• Advantages of IGCC for CO2 capture
• High CO2 concentration and high overall pressure
• Lower energy consumption for CO2 separation
• Compact equipment
• Proven CO2 separation technology can be used
• Possibility of co-production of hydrogen
• CO2 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.
www.ieagreen.org.uk
COCO22 Capture in IGCC Capture in IGCC
• Disadvantages• IGCC is unfamiliar technology for power generators• Existing coal fired plants have had relatively low
availability
• IGCC without CO2 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
www.ieagreen.org.uk
Pre-Combustion Capture – Gaseous FuelsPre-Combustion Capture – Gaseous Fuels
FuelPartial
Oxidation Partial
Oxidation Acid gas removalAcid gas removal
Shift conversion
Shift conversion
Gas turbineGas turbineAir
Fuel gas (mainly H2)
Flue gas
CO2CO2 compression
CO2 compression
CO+H2O→H2+CO2
Air separation
Air separation
Power
www.ieagreen.org.uk
COCO22 Capture in Natural Gas Power Plants 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 CO2 capture
• Gas turbine issues are the same as for IGCC
www.ieagreen.org.uk
Power Generation Efficiency Power Generation Efficiency Efficiency, % LHV
Source: IEA GHG studies
0
10
20
30
40
50
60
Post-comb
IGCCslurry
IGCC dry Oxyfuel Post-comb
Oxyfuel
Without capture With capture
Coal Natural gas
www.ieagreen.org.uk
Efficiency Decrease due to for CaptureEfficiency Decrease due to for Capture
0
2
4
6
8
10
12
Post-comb
IGCCslurry
IGCCdry
Oxyfuel Post-comb
Oxyfuel
CO2 compressionand purification
O2 production andpower cycle impacts
Shift conversionand related impacts
Power for CO2separation
Steam for CO2separation
Percentage points
Coal Natural gas
www.ieagreen.org.uk
Summary Summary
• CO2 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
