Process-performance of solid sorbents for Direct Air Capture (DAC) of CO2 in optimized temperature-vacuum swing adsorption (TVSA) cycles

The process performance of five solid sorbents was evaluated for direct air capture (DAC) of CO2 in temperature-vacuum swing adsorption (TVSA) and steam-assisted temperature vacuum swing adsorption (s-TVSA) cycles via detailed process modelling. The unary CO2, H2O and binary CO2-H2O isotherm data, wherever available, were fit to suitable isotherm models and then integrated with the detailed process model. The trade-off between specific energy and CO2 productivity has been studied through rigorous process optimizations. The study shows that thermal energy demand is substantial in comparison to the electrical energy. The role of steam was primarily found to improve the productivity. The range of minimum specific energy values is between 6.25-30.4 MJth/kg CO2, although, for some of the sorbents, the lack of H2O adsorption data impedes reliable calculations. The range of maximum CO2 productivities observed is between 0.01-0.15 TPD of CO2/m3 of sorbent