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Publisher: Earthscan, UK Homepage: earthscan.co.uk/?tabid=101808

Energy and the New Reality, Volume 2: C-Free Energy Supply Chapter 9: Carbon capture and storage L. D. Danny Harvey harvey@geog.utoronto.ca. Publisher: Earthscan, UK Homepage: www.earthscan.co.uk/?tabid=101808.

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Publisher: Earthscan, UK Homepage: earthscan.co.uk/?tabid=101808

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  1. Energy and the New Reality, Volume 2:C-Free Energy SupplyChapter 9: Carbon capture and storage L. D. Danny Harveyharvey@geog.utoronto.ca Publisher: Earthscan, UKHomepage: www.earthscan.co.uk/?tabid=101808 This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see www.earthscan.co.uk for contact details.

  2. Definitions: • Carbon Capture and Storage (CCS) refers to the capture and disposal of CO2 released from industrial processes • This has also been referred to as Carbon Sequestration, but this term has also been applied to the removal of CO2 from the atmosphere through the buildup of biomass (above-ground vegetation) and/or soil carbon • CCS involving burial of captured CO2 in geological strata (either on land or under the sea bed), shall be referred to here as geological carbon sequestration, while buildup of soil or plant C shall be referred to as biological carbon sequestration

  3. CCS is viable only where there is a concentrated stream of CO2 that would otherwise be released to the atmosphere • Electric power plants • Oil refineries • Petrochemical plants • Blast furnaces (an old-fashioned technology) • Cement kilns • N fertilizer plants

  4. Figure 9.1 A chemical solvent-based plant that captures a mere 200 tCO2/day Source: Thambimuthu et al (2005, IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press, Cambridge, UK)

  5. CO2 is easiest to capture when both the concentration and absolute partial pressure are large

  6. Table 9.1 Properties of gas streams Source: Gale et al (2005, ‘Sources of CO2’, in IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press, Cambridge, UK)

  7. All of the stationary CO2 sources worldwide of 0.1 MtCO2/yr or more account for about 54% of total world CO2 emissions (see Table 9.2)

  8. Options for capture of CO2 from fossil fuel powerplants: • From the flue gases after normal combustion of fuel in air • From the flue gases after combustion of fuel in pure oxygen • Prior to combustion, during the gasification of coal • During the operation of fuel cells using fossil fuels

  9. Processes for separating CO2 from other gases (applicable to capture after combustion in air or during gasification) • Absorption - chemical (if low CO2 concentration) (MEA is a common solvent) - physical (if high CO2 concentration) (Selexol is a common solvent) • Adsorption • Membrane • Liquefaction

  10. Energy is required • Chemical solvents require heat to drive off the CO2 (in concentrated form) and regenerate the solvent • Physical solvents require heat or a pressure drop for regeneration • Adsorbants require heat or a pressure drop for regeneration • Membrane systems require electrical energy to maintain a high P on one side of the membrane • Liquefaction requires cooling the exhaust gas to as low as ~ 220 K

  11. Figure 9.2 CO2 phase diagram, showing the T-P combinations needed to liquefy CO2 Source: Holloway (2001, Annual Review of Energy and the Environment 26, 145–166)

  12. Combustion in oxygen • The only gases produced are CO2 and water vapour • Pure CO2 is produced by cooling the gas enough to condense out the water vapour (giving 96% CO2) followed by distillation if desired • Energy is required to separate O2 from air in liquid form (usually by cooling the air to 89 K, at which point O2 condenses as a liquid)

  13. IGCC • Involves converting the coal to CO2, CO, and H2 by heating it in 95% oxygen • The CO can be reacted with steam to produce more CO2 and H2 • The resulting stream is almost completely CO2 and H2, and the CO2 is easily removed prior to combustion of the H2 • Conversely, CO and H2 can be fed to the turbine, burned in air, and the CO2 removed after combustion using a chemical solvent • Finally, CO and H2 can be fed to the turbine, burned in O2, and the CO2 separated by condensing the water vapour that is produced from combustion of the H2

  14. Fuel cells • Require a hydrogen-rich input fuel, which can be produced from natural gas or coal • Solid oxide and molten carbonate fuel cells can both use CO and H2 as fuel, which is fed to the anode • Unreacted CO and H2 in the anode exhaust can be combusted in pure oxygen to produce additional electricity with a gas turbine • The final exhaust consists of H2O and CO2, which can be separated by condensing the water vapour

  15. All methods of CO2 capture involve an energy penalty • Capture after combustion in air requires either a physical or chemical solvent that absorbs the CO2 but which needs to be regenerated using heat, or uses membranes but requires ~ 15% of the powerplant output to create high pressures • Capture after combustion in oxygen is easy (only H2O and CO2 are produced), but energy is required to separate oxygen from air (cryogenically) • Capture during gasification of coal or during operation of fuel cells entails a very small penalty (a few % at most)

  16. Table 9.3: Energy penalties associated with CO2 capture only. PC=pulverized coal, IGCC=integrated gasification combined cycle, NGCC=natural gas combined cycle, MCM=mixed conducting membrane. a Rhodes and Keith (2005) b Möllersten et al (2004)

  17. Figure 9.3 Efficiency penalty associated with the capture of CO2 Souce: Davison (2007, Energy 32, 1163–1176, http://www.sciencedirect.com/science/journal/03605442)

  18. Because of the efficiency penalty, more fuel is needed to produce the same amount of electricity, and the effective CO2 capture fraction is reducedFor example, if 80% of the CO2 in the exhaust is captured but the efficiency of the powerplant drops from 40% to 35%, then 40/35=1.143 times as much fuel is required. The CO2 emission is this 0.2 x 1.143 = 0.229, so the effective capture fraction is only 77.1% (1.0-0.229)

  19. Table 9.4: Effective fraction of CO2 captured. PC=pulverized coal, IGCC=integrated gasification combined cycle, NGCC=natural gas combined cycle, MCM=mixed conducting membrane. a Rhodes and Keith (2005) b Möllersten et al (2004)

  20. Table 9.5: Capital cost ($/kW) of powerplants equipped with technologies for capture of CO2. PC=pulverized coal, IGCC=integrated gasification combined cycle, NGCC=natural gas combined cycle, MCM=mixed conducting membrane. Costs are projected costs after some period of learning. a Rhodes and Keith (2005)

  21. Figure 9.4 Contribution of different costs to the cost of electricity with and without capture, transport and sequestration of CO2 Source: Tzimas and Peteves (2005, Energy 30, no 14, 2672-2689, http://www.sciencedirect.com/science/journal/03605442)

  22. Reality Check: A proposed 450-MW IGCC powerplant with carbon capture in Saskatchewan was abandoned after estimated costs ballooned from Cdn$3778/kW to Cdn$8444/kW.The US DOE FutureGen project (a 275-MW IGCC plant that would co-produce electricity and hydrogen) was cancelled after projected costs rose from $3250/kW to $6500/kW.State-of-the-art NGCC (60% efficiency) costs $400-900/kW in mature marketsWind turbines cost $1000-1500/kW

  23. Progress RatiosMany new technologies initially increase in price after being introduced, due to the discovery of defects in the original design, the correction of which entails greater costs. Later, costs begin to decline following a progress ratio formulation, wherebyC(t) = Co PR(lnR(t)/ln2)where Co is the initial cost after corrections of defects and R(t) is the ratio of cumulative production at time t to the cumulative production pertaining to Co. The cost is multiplied by a factor PR for every doubling in the cumulative production.

  24. Observed progress ratios after an initial price increase: • Flue gas desulphurization, 0.89 • Selective catalytic reduction, 0.88 • Gas turbine combined cycle, 0.90 • Production of liquefied natural gas, 0.86 Progress ratios without an initial price increase • Pulverized coal boilers, 0.95 • Production of oxygen, 0.90 • Steam methane reforming to produce H2, 0.73

  25. Capturing CO2 from biomass powerplants The most efficient method of producing electricity from biomass is through biomass integrated gasification combined cycle (BIGCC), a technology that is still under developmentGasification of biomass would occur in pure O2, producing syngas (a mixture of CH4, CO2, CO and H2) and a char residue that is combusted to provide heat for the gasification process.

  26. The syngas would be used in a gas turbine to generate electricity, with waste heat from the gas turbine used to produce steam for use in a steam turbine to generate further electricity (as in natural gas combined-cycle power plants, NGCC)NGCC state-of-the art powerplants have an efficiency of 55-60%BIGCC efficiency would be after 34% without capture of CO2 and only 25% with capture of CO2The result is an effective CO2 capture fraction of only 39% and an increase in the required biomass by 33%

  27. Figure 9.5 Capture of CO2 from BIGCC electricity generation

  28. Table 9.6Characteristics of capture of CO2 from BIGCC powerplants (with or without the water shift reaction) that could be available after 10 years of intensive R & D Source: Rhodes and Keith (2005, Biomass and Bioenergy 29, 440–450

  29. Various schemes for capturing CO2 that would be produced from gasification of black liquor (a processing waste) in integrated pulp and paper appear to be much more favourable, but would also require many years of intensive research and development

  30. Capturing CO2 during the production of H2 from fossil fuels • Steam reforming of methane • Gasification of coal

  31. Figure 9.6 Mass and energy flows for production of H2 from natural gas with capture of CO2

  32. Figure 9.7 Projected breakdown of costs in producing H2 from natural gas with capture of CO2 Source: Tzimas and Peteves (2005, Energy 30, no 14, 2672-2689, http://www.sciencedirect.com/science/journal/03605442)

  33. Capture of CO2 during the production of N fertilizer • Production of ammonium nitrate from natural gas or coal releases CO2 chemically, in addition to the CO2 released through the combustion of fuels in order to provide heat for the chemical reaction 3CH4 + 4N2 + 2H2O + 8O2→ 4NH4NO3 + 3CO2 ↑ • Production of ammonium bicarbonate consumes CO2 chemically, offsetting (at least in part) the CO2 produced from combustion of fuels to supply heat for the reaction 3CH4 + 4N2 + 14H2O + 5CO2→ 8NH4HCO3 ↓

  34. Conversely, flue gases from combustion of fossil fuels or biomass could be used as a source of C for the production of ammonium bicarbonate through the net reaction2CO2 + N2 +3H2 + 2H2O → 2NH4HCO3↓with the H2 produced electrolytically from water using renewable energy to generate the required electricity. 90% of CO2 in flue gases would be taken up by the above net reaction.

  35. Capture of CO2 from ambient airOne direct capture scheme involved the following steps: • Absorption of CO2 by NaOH solution, producing dissolved Na2CO3 • Reaction with Na2CO3 with Ca(OH)2 to produce CaCO3 and NaOH • Decomposition of CaCO3 to CaO (lime) and CO2 • Reaction of CaO with H2O to regenerate Ca(OH)2

  36. C balance of the preceding scheme: • If heat and electricity are provided by cogeneration using coal, the C capture per GJ of coal energy is 32kg, while the C released from combustion of the coal is 25kgC – giving only a small net gain • If 1 GJ of solar energy is used to cogenerate heat and electricity at 30% electrical efficiency, 29 kgC are captured, whereas using solar generated electricity to displace coal-generated electricity would avoid an emission (from coal) of 17 or 21 kgC (for coal powerplant efficiencies of 45% or 35%, respectively)

  37. Thus, using solar energy to capture CO2 instead of displacing coal would be worthwhile from a CO2 emission point of view (although landscape and other impacts related to the use of coal would remain)

  38. Compression of CO2 • Compression would be required prior to transport by pipeline, with an energy requirement of 300-400 kWh/tC if compressed from 1.3 to 110 atm • If applied to all of the CO2 produced by a coal powerplant with 40% efficiency, this corresponds to an energy cost of 7-10% of the electricity produced

  39. Liquefaction of CO2 • Liquefaction would be required prior to transport by ship, with an energy requirement of about 400-440 kWh/tC. • The latter would amount to an efficiency penalty of 10-12% if applied to the CO2 produced from a coal powerplant, but less than 2% if applied to the 71% of the CO2 that can be easily captured while producing H2 from natural gas

  40. Figure 9.8 Cost of CO2 transport by offshore and onshore pipeline Source: Doctor et al (2005, IPCC Special Report on Carbon Dioxide Capture and Storage, World Meteorological Organization, Geneva)

  41. Figure 9.9 Cost of CO2 transport by offshore and onshore pipeline and by ship Source: Doctor et al (2005, IPCC Special Report on Carbon Dioxide Capture and Storage, World Meteorological Organization, Geneva)

  42. Table 9.10Compounded energy penalty for capture and subsequent sequestration of carbon produced during the generation of electricity using different fuels and technologies, or from the production of hydrogen using different feedstock. PC=pulverized coal power plant, NGCC=natural gas combined cycle power plant, IGCC=integrated gasification combined cycle power plant (using coal).

  43. Disposal sites: • Deep saline aquifers on land and beneath the ocean bed • Depleted oil and gas fields • Active oil fields, as part of enhanced oil recovery • Coal beds (displacing coal-bed methane) • Injection below the 3000 m depth in the ocean (liquid CO2 is denser than seawater at this and greater depths)

  44. Storage of CO2 in deep saline aquifers • Some remains as a gas, under pressure • Some dissolves very slowly into pore water • In aquifers rich in calcium and magnesium silicates, the CO2 will react with the rock and carbonate will precipitate, reducing the permeability of the rock and creating a permanent trap where none existed before – flood basalts are particularly good

  45. Existing and planned aquifer storage projects: • Sleipner West gas field, underneath the North Sea (off of Norway) • Deep aquifers in Japan and US, planned for Australia, Germany, and Norway

  46. Storage of CO2 in depleted oil and gas fields and for enhanced oil and gas recovery • CO2 is currently injected into the base of oil and gas fields in order to increase the oil or gas pressure, thereby increasing the amount of oil or gas that can be extracted • Only the net CO2 storage should count as credits against emissions • Storage in already-depleted oil and gas fields is another possibility, but would provide no economic credits and, like enhanced oil or gas recovery, would require long-distance transport of CO2 from the major emission regions to the major oil and gas fields

  47. Storage of CO2 in coal beds • Coal usually contains methane that is adsorbed onto the surfaces of micro-pores • This methane is call coal-bed methane, and there can be up to 0.76 GJ methane/tonne of coal (compared to a heating value of coal itself of 32 GJ/t) • CO2 has a greater affinity for coal, so injection of CO2 into coal beds will displace methane while being stored in the coal • Up to CO2 molecules are adsorbed for every CH4 molecule displaced • The methane would be collected and used as an energy source

  48. Estimated Cost of Storage Step Alone: • Onshore saline aquifers: $1-23/tC • Offshore saline aquifers: $2-110/tC • Onshore depleted oil fields: $2-15/tC • Onshore depleted gas fields: $2-45/tC

  49. Estimated Worldwide Storage Potential on Land • Oil and gas reservoirs: 230 GtC • Deep saline aquifers: 55-15,000 GtC, likely minimum: 270 GtC • Coal beds, 16-54 GtC theoretical potential, 2 GtC practical potential • TOTAL MINIMUM: about 500 GtC, equal to about 125 years if storing the one half of current fossil fuel emissions that would be amenable to capture

  50. Environmental and Safety Issues Associated with Capture, Transmission and Storage of CO2

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