A comparative study on CO2 capture performance of vacuum-pressure swing adsorption and pressure-temperature swing adsorption based on carbon pump cycle

Currently, the significant energy penalty and performance limitation of energy consumption are the main technical barriers to the large-scale applications of CO2 capture. Carbon pump, which realizes an enrichment of CO2 from carbon source to carbon sink, is applied in a modeling for energy-efficiency analysis of CO2 capture technologies. In this study, two adsorption technologies, including vacuum-pressure swing adsorption (VPSA) and pressure-temperature swing adsorption (PTSA), are compared in terms of the minimum separation work and the second-law efficiency. Based on carbon pump, two adsorption cycles can be presented through the process expression in the adsorption isotherm diagram, which is an easy pathway to show CO2 adsorbed amounts for each step. The influence of process parameters for VPSA and PTSA were studied as well. Results show that the maximum values of the second-law efficiency are 24.30% and 19.09%, respectively for VPSA and PTSA with the change of CO2 concentration from 5% to 25%. However, the second-law efficiency for VPSA and PTSA decreases with the increase of the other three factors, including desorption temperature, pressure of the feed and percent of unused bed. Parameters of component in cycle should also receive more attention for energy-efficiency analysis.