Investigation of water co-adsorption on the energy balance of solid sorbent based direct air capture processes

Abstract

The energy penalty induced by the desorption of water can significantly increase the carbon dioxide specific energy demand of direct air capture (DAC) processes with solid sorbents. An analysis of the water to carbon dioxide desorption ratio on an isotherm and unit operation level shows that a well-designed desorption step of the DAC unit may significantly reduce the co-desorption of water, even if still high H2O:CO2 ratios are to be expected on a unit operation level. Aiming for an even lower energy penalty to allow for the design of an autothermal operated DAC - power-to-gas (PtG) process, the possibility of compensating a part of the water's heat of desorption by recovering the energy stored in the water vapor desorbed through vapor recompression is investigated.