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C O 2

C O 2. Reading: Chap 22. Magnitude of the CO 2 problem Formation Prevention Conservation, Alternative Fuels, Efficiency Improvements, Supercritical PC Power Plants, Integrated Gasification Combined Cycle (IGCC) Plants, Oxy-Fuel Combustion Flue Gas Treatment

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C O 2

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  1. CO2 Reading: Chap 22 • Magnitude of the CO2 problem • Formation Prevention • Conservation, Alternative Fuels, Efficiency Improvements, Supercritical PC Power Plants, Integrated Gasification Combined Cycle (IGCC) Plants, Oxy-Fuel Combustion • Flue Gas Treatment • Wet Scrubbing, Biogenic Capture, Dry Sorption, Conversion • Transportation and Sequestration Aerosol & Particulate Research Laboratory

  2. Magnitude of the CO2 Problem 2009 US CO2 Emission by Fossil Fuel Combustion, by Fuel Type and End-Use Sector http://epa.gov/climatechange/emissions/downloads11/GHG-Fast-Facts-2009.pdf Two largest sectors: Electricity generation (from coal) and Transportation (from petroleum) In 2008, there were 494 coal-fired power plants + 105 industrial/commercial boilers for internal consumption Aerosol & Particulate Research Lab

  3. Coal Rank Which rank is better? http://theenergylibrary.com/node/12174 http://pubs.usgs.gov/of/1996/of96-092/index.htm Aerosol & Particulate Research Lab

  4. World Energy Overview World energy consumption World’s largest CO2 emitters In 2007, China was building one new 1000 MW plant per week. Aerosol & Particulate Research Lab

  5. CO2 Prevention • Conservation • Efficiency improvement • Alternative fuels: • Wind • Solar • Biomass • Geothermal Can wind farm be in a city? Geothermal Pump Micro Wind Turbines Wind Farm http://metaefficient.com http://signatureforum.com http://fiddlersgreen.net What factors are limiting the growth of alternative fuels?

  6. CO2 Prevention – Supercritical PP • Operating above the critical point of water (374 oC and 3206 psi) – liquid and vapor indistinguishable • Advantages: • No need to separate water from steam • Higher efficiency • Less fuel for the same power output • Less NOx and SO2 and their control • Disadvantages: • Stronger/thicker materials (cost) How is CO2 reduction achieved? Aerosol & Particulate Research Lab

  7. CO2 Prevention – IGCC Plant • Combined gas turbine and steam turbine: higher eff ~ 43% • Gasifier to produce syngas (H2+ CO) as fuel (treated to remove PM and sulfur compounds) • Can also employ a water-gas shift reactor to convert CO to CO2; the high conc. CO2 can be absorbed; plant eff down to 35% http://en.wikipedia.org/wiki/Integrated_gasification_combined_cycle

  8. CO2 Prevention – Oxy-fuel Combustion • Burn with O2 rather than with air (i.e. min dilution by N2) • Advantages: • More efficient ~ 52-55% (excl. air separation unit) • Volume of flue gas greatly reduced • CO2 concentration greatly increased • Disadvantages: • Air Separation Unit (ASU) required (cost) Aerosol & Particulate Research Lab

  9. CO2 Capture – Wet Scrubbing • Amine (e.g. Monoethanolamine (MEA); Diethanolamine (DEA); Methyldiethanolamine (MDEa)) – weak bases that neutralizes weak acids to form water soluble salts; amine needs to be regenerated • Chilled ammonia – forming ammonium carbonate/bicarbonate solids; also needs to regenerate Can we use CaO? Why isn’t scrubbing widely adopted yet? Desulfurization is needed before the flue gas enters CO2 scrubber. Why? Aerosol & Particulate Research Lab

  10. Schematic flow diagram of a two-tower amine scrubbing and regeneration system for CO2 control Aerosol & Particulate Research Lab

  11. CO2Transformation – Microalgae • Single cell microscopic algae, a few to a few hundred µm; produce half of atmospheric O2 using CO2 • More effective than land-based plants – up to 250 kg/hectare-day or as little as 1 acre/MW • 50% C (dry basis); up to 40% as lipids (dry weight) • Fed by CO2 captured from power plant flue gas • Open ponds vs. close circulating systems What are the pros and cons of each system? http://japantechniche.com http://davidstrahan.com http://popsci.com Aerosol & Particulate Research Lab

  12. CO2Transport • Not economical to transport in gas phase because of low density – Liquid or Supercritical fluid • Ship: high-pressure (> 5.2 atm) low-temperature (< -52 oC) tanker • Pipeline: for transport across land; require special insulation or refrigeration stations along the way What’s the major risk in CO2 transport? CO2 Sequestration • In Geological Formations: abandoned coal mines, oil/gas reservoirs, deep saline aquifers • Ocean Sequestration: ocean fertilization, direct injection to create an underwater “CO2” lake Aerosol & Particulate Research Lab

  13. Quick Reflection Aerosol & Particulate Research Lab

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