Optimized process configurations of post-combustion CO2 capture for natural-gas-fired power plant-Exergy analysis

Several chemical absorption CO2 capture process configurations were analyzed and compared according to their associated exergy losses. The total work demand was decreased from 1.39 MJ/kg CO2 for the Base case chemical absorption process configuration to 1.23 MJ/kg CO2 for the modified chemical absorption process configuration of lean vapor recompression with absorber inter-cooling (best case). Considering the minimum work requirement of separation processes, the exergy efficiency of capture and compression plants was increased from 31.6% for the Base case chemical absorption process to 35.6% for the best case. Respectively, irreversibilities were reduced from the 1.60 MJ/kg CO2 for the Base case to 1.29 MJ/kg CO2 for the case with absorber inter-cooling and lean vapor recompression. The rational efficiency for the natural-gas-fired combined cycle power plant with CO2 capture and compression shows an increase from 48.5% for the Base case chemical absorption process configuration to 49.5% for the best case. (C) 2011 Elsevier Ltd. All rights reserved.