Simulation of CO2 capture for an existing pulverized coal power plant

Coal-fired power plants have been identified as major emitters Of CO2, the leading greenhouse gas responsible for global warming. With growing initiatives aimed at the reduction of greenhouse gases, there is a need to develop economically viable technologies to capture CO2 from existing coal-fired power plants. One option is to separate CO2 from the flue gas in a conventional power plant, but this technique may not necessarily represent the most economical or technically viable approach. A more elegant technique, commonly known as O-2/CO2 recycle combustion, involves modification of an existing plant by combusting coal with recycled flue gas and pure oxygen from an air separation unit (ASU). This configuration yields a flue gas with a high CO2 concentration but with residual nitrogen from air leakage to the boiler in conventional plant retrofits. When very high purity Of CO2 is required, as in enhanced oil recovery, a separation,process would be added, but with incremental albeit lower energy requirements compared to the ASU. In this study, O-2/CO2 recycle combustion combined with low temperature flash (LTF) to achieve 98% CO2 purity has been investigated. The sensitivity of the CO2 capture by an LTF to air infiltration has been investigated. The ASU and the LTF demand significant amounts of energy, mostly for compression. In order to keep the coal power plant at its rated capacity, gas turbines have been added to drive the compressors in both the ASU and LTF. The gas turbines produce CO2, which needs to be captured. Because the concentration Of CO2 from the flue gas of the gas turbine is low, the CO2 is captured by an amine scrubber. Preliminary results obtained using a process simulator software (HYSYS) to combine and integrate the power plant with the gas turbines are presented in this paper.