Effect of CO2 Purity on Energy Requirement of CO2 Capture Processes

The purity of CO2 influences on energy performance in CO2 capture process. The effects of that were evaluated for post-combustion capture and pre-combustion capture using a process simulation method. In post-combustion capture using a chemical solvent, high purity CO2 with the concentration of more than 99% was easily obtained, but a large reboiler heat duty was required. In pre-combustion capture from IGCC syngas using a physical solvent, CO2 purity changed by operating conditions such as the pressure of a flash tank. Since energy requirement gradually increased with increasing the CO2 purity and steeply increased when the CO2 purity reached 99%, CO2 purity of below 99% will be reasonable for the physical absorption. Membrane also should be operated under not so high CO2 purity condition to attain an energetic merit. Around 95% should be a reasonable CO2 purity.