Simulation and exergy analysis of processes for CO2 capture and utilisation for methanol production

Carbon dioxide (CO2) capture and methanol production processes were simulated using Aspen RefSYS. Exergy analysis was done with EXCEL spreadsheet. Parametric study was done on the CO2 process to investigate the effects of absorber and reboiler pressure, absorber stages and amine circulation rate on CO2 absorption, CO2 recovery and process exergy efficiency. The result shows that stripper recovered almost 90% by mass of CO2 in the flue gas. The highest irreversibility in the CO2 capture plant occurred in the rich/lean heat exchanger (820516.24 MW); this is followed by the lean cooler (481343.23 MW) and the stripper (404273.57 MW). CO2 emissions reduction was 171,838.1 tonnes CO2/yr. For the methanol plant, the highest irreversibility occurred in the distillation column (25088.4 MW). The study concluded that onsite utilisation of CO2 from thermal plant would minimise CO2 leakage during transportation or storage.