Process optimization of high purity CO2 compression and purification system from oxygen-rich combustion flue gas

Abstract

The CO₂ compression and purification units (CO2CPU) is an effective process to capture CO₂ from oxygen-rich combustion flue gas. However, the quality of CO₂ products needs to be improved for high-value-added utilization. In this study, the CO2CPU with high concentration of impurities (SO_X, NO_X, H₂O) was optimized by Aspen Plus and Matlab with genetic algorithm. The model is validated with similar experiment from reference. The results showed that under the compressor pressure of 30 bar and condensation temperature of −36 °C, the liquid CO₂ product with a high purity of 99.9991 % with the total cost of 26.98 $/tCO₂ could be obtained. Sensitivity analysis was utilized to investigate the influences of key parameters on the system performance, including the number of plates of towers, pressure, reflux ratio, and gasification fraction. The required cooling capacity and performance of compressor are closely related to the ambient temperature. One impurities removal tower with sideline extraction was used to further improve the process performance. Energy consumption and total cost are reduced by 140.55 kW and 0.23 $/t CO₂, respectively. Methanol is introduced as the hydrate inhibitor for icing protection. Despite the additional three towers, the total cost is reduced by 1.86 % with heat coupling.