Abstract

Carbon dioxide (CO2) absorption process using amine has been considered as one of the most practical technologies for reducing carbon emissions from industrial waste gases. A critical issue for this process is its significant energy requirement for solvent regeneration. The main goal of this work is to explore the feasibility of integrating heat-pump or refrigeration cycles into the CO2 absorption unit that would result in significant energy saving. The feasibility study was carried out by conducting simulation of the heat pump-assisted carbon capture process model that combines both CO2 absorption process and heat pump cycles into the same computational framework. The typical absorption process using Monoethanolamine (MEA) was used as the benchmark technology for capturing CO2. Three heat pump configurations were evaluated for their energy-saving performance. These configurations are i) single-stage vapour compression, ii) cascade vapour compression, and iii) gas refrigeration cycle. The heat pump cycles were configured as a waste-heat recovery unit within the absorption process. The simulation was performed at the reboiler temperature ranging from 105 to 115oC, lean-cooler temperature ranging from 20 and 40oC, and CO2 loading of lean amine ranging from 0.15 to 0.35 mol/mol. The results were generated in terms of specific reboiler heat duty (SRD) in the unit of kJ/kg CO2 captured. It was found that the integration of heat pump cycles results in a significant reduction in total energy supply from the external source without compromising operation quality of absorption process. The level of energy saving was found to have a direct relationship with the performance of individual heat pump cycles. With proper integration strategies, the overall energy consumption of carbon capture process could be reduced by 47% when using the gas refrigeration cycle, by 66% when using the single-stage vapour compression cycle, and by 70% when using the cascade vapour compression cycle.