Thermoeconomic analysis and optimization of post‐combustion CO2 recovery unit utilizing absorption refrigeration system for a natural‐gas‐fired power plant

Abstract

Exergy and exergoeconomic analyses have been used to set out weaknesses of the postcombustion CO2 capture unit of Besat power plant that uses an ammonia absorption refrigeration system for CO2 liquefaction. The energy required for the absorption system is provided by the flue gas. The liquefied CO2 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 CO2 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 CO2 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