Exergoenvironmental analysis and thermoeconomic optimization of an industrial post-combustion CO2 capture and utilization installation

Abstract

CO2 utilization is one of several tools available to us to mitigate climate change. This paper aims to study and optimize the urea production in the largest CO2 utilization plant in Iran. The location, magnitude, and source of thermodynamic inefficiencies of the plant are evaluated using exergy, exergoeconomic and exergoenvironmental analyses. The optimization process uses as decision variables the temperature of the lean monoethanolamine solution and loading, along with the height of the absorber and the stripper of the plant. The decision variables and objective functions are trained with a hybrid combination of an artificial neural network with a genetic algorithm. The multi-objective genetic algorithm results in a pareto front of solutions. The exergy efficiency of the overall system is found to be 30.89% and 3.57, 2.86, 2.21% of the exergy of the fuel provided to the plant is destroyed in the soda ash wash direct contact, the stripper, and the absorber columns (424.07, 339.71 and 258.61 kW), respectively. The exergoeconomic analysis shows that the heat exchangers E-7 and E-8 result in relatively low exergoeconomic factor; therefore, an enhancement in the thermodynamic performance of the heat exchangers should be considered. The absorber column is found to have the largest environmental impact, equal to approximately 0.1205 mPt/s. The highest environmental impact of exergy destruction, equal to 33,256.3 mPts/hr is found in the stripper.