Reduction of Emissions from Combined Cycle Plants by CO 2 Capture and Storage John Davison Project Manager IEA Greenhouse Gas R&D Programme (IEAGHG) The Future Combined Cycle Plant Berlin, 28 th -30 th March 2012
Overview CO 2 capture and storage (CCS) technologies Impacts of CCS on efficiencies and costs Combined cycle plants with CCS in systems with high amounts of renewables
IEA Greenhouse Gas R&D Programme (IEAGHG) An collaborative research Implementing Agreement established in 1991 by the International Energy Agency Based at Cheltenham, UK Aim: Provide members with definitive information on the role that technology can play in reducing greenhouse gas emissions. Scope: All greenhouse gases, all fossil fuels and comparative assessments of technology options Focus: On CCS in recent years About 20 country members and 20 industrial sponsors
Membership
CO 2 Emission Projections <100g/kWh by 2030 More difficult to achieve without CCS Chart from UK Committee on Climate Change, 2009
CO 2 Storage Snøhvit capturing and injecting 0.7 Mt/y CO 2 since 2006 Sleipner capturing and injecting 1 Mt/y CO 2 since 1996 Weyburn capturing and injecting 2.5 Mt/y CO 2 since 2000 In-Salah capturing and injecting 1.2 Mt/y CO 2 since 2004
CO 2 Capture Post combustion capture Separation of CO 2 from flue gas Pre-combustion capture Reaction of fuel to produce H 2 and CO 2 Separation of CO 2 Combustion of H 2 in a gas turbine Oxy-combustion Combustion of fuel using purified O 2 rather than air
Post Combustion Capture Liquid solvent scrubbing Reduced-CO 2 flue gas CO 2 Water Direct contact cooler Water wash Absorber (40-60 C) CO 2 -lean solvent Stripper (90-120 C) Condenser Flue gas Cooling water Low pressure steam Excess water CO 2 -rich solvent Reboiler
Post-Combustion Capture Courtesy of Fluor CCGT, Bellingham, USA Operated 1991-2005 330 t/d of CO 2 captured MEA solvent Food grade CO 2 product Urea plant, Kakinada, India 450 t/d of CO 2 captured from natural gas steam reformer flue gas KS-1 solvent Courtesy of MHI
Plant Layout CO 2 capture plant CCGT (2x450MW) CO 2 compressor Stripper Absorber Direct contact cooler HRSG Gas turbine
Flue Gas Recycle Natural gas CO 2 Air Gas turbine HRSG CO 2 capture Reduced-CO 2 flue gas Recycled flue gas Direct contact cooler and fan CO 2 concentration in absorber feed is increased Smaller absorber tower Extra cost for recycle gas cooling and duct Overall cost is lower and efficiency is marginally higher Impacts on combustor operation and emissions
Thermal Efficiency Source: Study for IEAGHG by Parsons Brinckerhoff, 2012
Efficiency Reduction
Capital Cost 2011 EPC costs, excluding owner s costs and interest during construction Source: Report for IEAGHG by Parsons Brinckerhoff, 2012
Cost of Electricity Low CO 2 emission cost 2011 costs 8% discount rate 25 year plant life Base load operation 6/GJ (LHV) gas price 5/t CO 2 stored 10/t CO 2 emission cost
Cost of Electricity Breakeven CO 2 emission cost 65/t CO 2 emission cost required for no capture to match the proprietary solvent CCS cost of electricity
Pre-Combustion Capture Gas, coal or biomass Reforming or gasification CO+H 2 O = H 2 +CO 2 Shift conversion CO 2 capture CO 2 Compression, transport and storage Air or O 2 and steam Steam Hydrogenrich gas Combined cycle power plant Flue gas Power
Pre-Combustion Capture Natural gas fuel Pre-combustion capture is less attractive in general than post combustion capture o Lower efficiency o Higher capital cost Scope for technological improvement Coal and biomass gasification Economics depend on relative prices of natural gas and solid fuels Issues to be considered Combustion of hydrogen-rich gas in gas turbines is being addressed by turbine manufacturers
The Role of CCS Plants in Electricity Systems How will CCS plants have to operate? Variability of electricity demand Impacts of high amounts of other low-co 2 generation technologies Operating flexibility of CCS plants Impacts of load factor on economics
Electricity Demand 60 Electricity generation, GW 50 40 30 20 10 Winter maximum Summer minimum 0 0 4 8 12 16 20 24 Hours UK data, 2011
Electricity Demand Electricity demand, GW 60 50 40 30 20 10 0 Intermediate/ peak load (40% of total generation) Base load (60% of total generation) Need to decarbonise this electricity to achieve low emissions targets 0 2000 4000 6000 8000 10000 Hours UK data, 2011
The Role of CCGTs with CCS in Electricity Systems Marginal operating cost merit order Wind / solar / marine energy Nuclear Coal with CCS Natural gas with CCS Fossil fuels without CCS Lower marginal cost - operate whenever available Higher marginal cost - operate at lower load factor Combined cycle plants with CCS will have to be able operate flexibly and at intermediate load CCS flexibility requirements depend on how much renewables and nuclear are used
Impact of Renewables/Nuclear on Fossil Fuel Plant Operation 60 Total demand Electricity generation, GW 50 40 30 20 10 0 0 2000 4000 6000 8000 10000 Residual demand with 35% wind Residual demand with 35% wind, 25% nuclear Hours IEAGHG modelling of UK electricity system, Based on half-hourly power demand and wind data, 2011 Wind generation scaled to 35% of total demand
Plant Load Factors 100 Plant load factor % 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 % of annual residual generation (fossil fuels etc) UK system assuming 35% wind, 25% nuclear
Flexibility of CCS Plants CO 2 capture imposes some additional constraints on operating flexibility Constraints can in general be overcome by design Possibility of better flexibility than non-ccs plants Interaction between the electricity system requirements and plant capabilities
Flexibility of CCS Plants CO 2 compressors Turndown limited to c70% Can be overcome by use of multiple compressors or CO 2 recycle Post combustion capture Ability to vent flue gas o A low-cost technique for peak generation but high CO 2 emissions Ability to operate the absorber and stripper independently by including buffer storage solvent o Enables faster start-up and possibility of higher peak generation Pre-combustion capture Integrated plants have relatively poor flexibility o Long start up and shut down times o Gasification/ reforming, shift conversion and pre-combustion capture is a chemical plant Non-integrated plants can overcome these constraints
Pre-combustion Capture - Non-integrated Plant Fuel Methane reforming or coal gasification Shift conversion CO 2 capture CO 2 Compression, transport and storage Fuel conversion and CO 2 capture - full load operation Hydrogenrich gas Underground hydrogen storage (salt cavern) Power plant - flexible operation Power plant (combined or simple cycle) Flue gas Power Only the power plant has to operate flexibly CCS can operate continuously, no need for flexibility High utilisation of CCS equipment Capture cost is almost independent of power plant load factor Can build-up H 2 infrastructure for later use by renewables
Hydrogen Storage Salt caverns are widely used for natural gas storage Solution mined caverns Commercial experience of hydrogen storage in salt caverns UK o Chemical complex at Teesside o 3 caverns, 200-300 tonnes H 2 each o Operated for many years, no discernible leakage USA o E.g. Air Liquide, Texas o Cavern 75m diameter, 450m long o Enough hydrogen for 1000MWe plant for a week o No scale-up needed for CCS plants
Costs of Electricity Effects of CCS, load factor and fuel 2011 costs 8% discount rate 25 year plant life Natural gas 6/GJ (LHV) Coal 2/GJ (LHV) 5/tonne CO 2 stored No CO 2 emission cost Lower load factors do not necessarily mean lower profitability
Costs of Electricity with CCS Post combustion capture 2011 costs 8% discount rate 25 year plant life 5/tonne CO 2 stored No CO 2 emission cost
Costs of Electricity with CCS Pre and post combustion capture 2011 costs 8% discount rate 25 year plant life Natural gas 6/GJ Coal 2/GJ 5/tonne CO 2 stored No CO 2 emission cost
Costs of Electricity with CCS Pre and post combustion capture 2011 costs 8% discount rate 25 year plant life Natural gas 8/GJ Coal 2/GJ 5/tonne CO 2 stored No CO 2 emission cost
Barriers to CCS Technical issues Scale-up to large plant sizes Demonstration of operation of CCS in power plants More demonstration of long term CO 2 storage in various geologies Economics Obtaining funding for demonstration plants has been difficult Uncertainty about economic incentive for large scale CO 2 abatement in the longer term Regulatory and public acceptance Many regulatory hurdles have been overcome but some remain Level of public awareness of CCS is low
Summary Increasing interest in CCS for combined cycle plants Gas turbine power plants with CCS can complement other low- CO 2 generation technologies Flexible Relatively low fixed costs Able to achieve very low overall electricity system emissions The optimum CCS technology depends on various factors: Fuel prices Emission requirements Other generation technologies on the grid CCS has been demonstrated at industrial plants and small power plants but full-size power plant demonstrations are needed
Thank you john.davison@ieaghg.org