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Oxy Coal Combustion at the US EPA
Citation:
Linak, Bill. Oxy Coal Combustion at the US EPA. Joint US EPA-NCSU Poster Session, Raleigh, NC, May 15, 2012.
Impact/Purpose:
The state of the science behind oxy-coal combustion technology is far from mature, although a number of academic, governmental, and industrial research organizations are investigating various aspects of the technology. These ongoing efforts, however, are focusing primarily on resolving technical and operational issues such as ignition and flame stability, fouling, slag behavior, corrosion, heat transfer, and efficiency. There is a significant lack of understanding regarding the environmental issues which must also be addressed before oxy-coal combustion can be adopted commercially. These include effects on pollutant formation, and how changes in pollutant behavior, concentrations, and the flue gas environment affect existing pollution control devices, and the characteristics of the various process and waste streams. Key questions include what purity of CO2 is required to ensure safe long term GS, whether trace levels of sulfuric and nitric acids and other impurities can be compressed and sequestered with the CO2, and what are the characteristics of the ash and especially the fly ash and volatile metals such as mercury and selenium (Hg, Se) that would normally penetrate the particle control devices as an air emission, but now may be compressed and sequestered with the CO2. Other questions include the effect of a CO2 environment on particle charging and electrostatic precipitator (ESP) operation, as well as similar concerns related to the operation of selective catalytic reduction (SCR) units and acid gas scrubbers.
Description:
Oxygen enriched coal (oxy-coal) combustion is a developing, and potentially a strategically key technology intended to accommodate direct CO2 recovery and sequestration. Oxy-coal combustion is also intended for retrofit application to existing power plants. During oxy-coal combustion, combustion air is separated into its oxygen (O2) and nitrogen (N2) components and the coal is burned in a mixture of O2 and recycled flue gas. By eliminating the N2, ~80% of the volumetric flow through the utility plant is eliminated. The resulting effluent composed primarily of CO2, H2O, and small amounts of residual O2 and pollutant species (SOX, NOX, fly ash, metals, Hg, HCl, organics, etc.) must be further processed before the CO2 can be compressed, transported, and sequestered.