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Impurities in the CO2 stream should be removed to prevent eventual phase changes in CO2 transportation because a two-phase flow caused by the phase change in the pipeline necessitates additional overpressure and can induce equipment damage. In this study, CO2 compression and liquefaction (CCL) processes with a distillation column were used to remove non-condensable impurities and were compared with those with a flash. Three different feeds with a flow rate of 50.1 t/h (400,500 t/y) were supplied to the CCL processes and compressed to 65 bar to gauge pressure (barg) and 20 °C. Although the CO2 mixtures obtained through dehydration and flashing met the purity requirements for transportation and storage recommended in literature, the flash-separated CO2 product at 65 barg demonstrated the coexistence of gas and liquid phases, which restricted the temperature window for liquid CO2 transportation. When the distillation column was used instead of the flash, the operating temperature window at 65 barg widened by 3–6 °C owing to the high purity of CO2. However, the levelized cost of CO2 liquefaction (LCCL) increased by 2–4 $/t-CO2 varying with the feed purity because the distillation column consumed more cooling and heating duties than the flash. This study highlighted that a two-phase flow existed under certain operating conditions despite a high purity of CO2 (over 97 mol%), and the distillation column enhanced the operability of liquid CO2 transportation. [ABSTRACT FROM AUTHOR]

Summary: 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°C, dry FGR (dFGR) at 68°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. [ABSTRACT FROM AUTHOR]