Multi-dimensional process optimization of temperature-vacuum swing adsorption for CO2 capture from humid air

Direct air carbon capture (DAC) is a promising technology for achieving net-zero carbon emissions. However, current DAC technology still faces challenges such as low CO2 productivity and high energy consumption, which have become one of the main bottlenecks restricting its commercial-scale deployment. In this work, a temperature vacuum swing adsorption (TVSA) cycle based on a two-dimensional packed bed was designed for a DAC system, with the co-adsorption of CO2 and H2O taken into consideration. Through multi-dimensional parameter analysis, results determined that within the relative humidity (RH) of 0.4–0.6, the CO2 productivity and energy consumption performance are optimal, and this advantage is almost unaffected by variations in other parameters. Adsorption parameters analysis indicates that an optimal gas velocity of 1 m/s and achieving a 95 % breakthrough time (t95) for DAC can maximize CO2 productivity. Desorption parameters studies highlight a trade-off between productivity and energy consumption at different vacuum pressures. At 0.4 RH, the lowest energy consumption of 2.13 MJ/kgCO2 and a CO2 productivity of 5.52 mol/kg/day are achieved at a vacuum pressure of 150 mbar. Regarding the desorption temperature, increasing the temperature while ensuring the thermal stability of the material helps both the CO2 productivity and energy consumption approach optimal values simultaneously. Finally, our findings demonstrate that lowering the vacuum pressure effectively prevents any re-adsorption of CO2 and H2O in the packed bed during the desorption step. This study presents groundbreaking insights into operational strategies for adsorption-based DAC systems, delivering essential guidance for their real-world deployment and performance enhancement.