Effects of flue gas recirculation on energy, exergy, environment, and economics in oxy-coal circulating fluidized-bed power plants with CO2 capture

CO2 capture and storage(CCS) are required for coal-fired power plants, which are major sources of anthropogenic CO2 emission. In this study, energy, exergy, environment, and economic (4E) analyses were performed for a 500-MWe oxy-coal ultra-supercritical circulating fluidized-bed (CFB) power plant with CO2 capture. The effect of the location of flue-gas recirculation (FGR) on the 4E values was investigated for wet FGR (wFGR) at 170 degrees C, dry FGR (dFGR) at 68 degrees C, and 80% wet and 20% dry FGR (wdFGR). The net electricity efficiencies of the wFGR and dFGR power plants were 37% and 36%, respectively. The exergy loss was the largest in the combustor and boiler area, where process improvement was possible. The levelized cost of electricity was approximately 60 $/MWh. The return on investment was 6.7% and 6.1%/y for the wFGR and dFGR plants, respectively. The CO2 emission rate decreased by 90% (from 690 to 76 kg-CO2/MWh) in the oxy-coal power plants with CO2 capture. Relative to the wFGR, the dFGR was advantageous for preventing material corrosion because of the lower sulfur content in the FGR stream. For the wdFGR power plant, the process performance was intermediate, that is, between that of the wFGR plant and that of the dFGR plant. The study provided an effective tool for identifying the technological and economic effects of the FGR location for the oxy-coal power plant with CCS via 4E analyses.

Automated summary

This study conducted 4E analyses on a 500-MWe oxy-coal ultra-supercritical circulating fluidized-bed (CFB) power plant with CO2 capture, exploring the effect of flue-gas recirculation (FGR) location on energy, exergy, environment, and economic values. Results showed that dry FGR was more advantageous than wet FGR, while the wdFGR plant demonstrated intermediate performance between the two.