Thermoeconomic analysis and optimization of post‐combustion CO 2 recovery unit utilizing absorption refrigeration system for a natural‐gas‐fired power plant

Exergy and exergoeconomic analyses have been used to set out weaknesses of the postcombustion CO 2 capture unit of Besat power plant that uses an ammonia absorption refrigeration system for CO 2 liquefaction. The energy required for the absorption system is provided by the flue gas. The liquefied CO 2 is used for beverage and food industries. The exergoeconomic costs of all utility streams and processes are calculated through a systematic method of assigning exergetic cost relations to the streams. The results point out that the exergy destruction of the CO 2 stripper and absorber columns are the highest, and according to the cost‐based information, potential locations for the process improvement are proposed. A comprehensive method based on thermodynamic and mathematical methods has been proposed to acquire efficient design parameters and consumed power in compressors. It is based on a combination of Aspen HYSYS ® and MATLAB ® to do calculations and then an optimization procedure based on genetic algorithms. Results show that the production cost of each ton CO 2 is equal to 6.05 (USD/ton) and return on investment can also be obtained by 2.5 years considering USD 1,600,000 of annual revenue. © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1075–1084, 2018