4E evaluation and multi-objective optimization of low concentration flue gas CO₂ capture and multi-product conversion process

In order to address the current global warming, this work proposes CO₂ capture from flue gas and CO₂ hydrogenation to produce methane, methanol, and CO₂ to produce ammonium bicarbonate. Aspen Plus process simulation model is developed for the three processes. Based on the thermodynamic model, sensitivity analysis of main operating parameters is conducted on the energy, economic, environment, and exergy (4E) indicator. Non-dominated sorting genetic algorithm is used to achieve multi-objective optimization. The optimum operating parameters of the three processes are obtained under the 4E indicators. It is concluded that the CO₂ to ammonium bicarbonate is the optimal process route for CO₂ conversion. The corresponding total annual cost is 4.071 M$/year, the CO₂ equivalent emission per unit product is −0.0667 tCO₂/t pro, the annual total utility consumption is 7062.75 kW/year, and the exergy efficiency of system is 53.42 %. This work shows significance for achieving resource utilization with capture CO₂.