Intensified integrated direct air capture-power-to-gas process based on H2O and CO2 from ambient air

Solid sorbent based air capture facilities (DAC) of carbon dioxide can come along with high water co-adsorption. Integrating the latter in power-to-gas (PtG) concepts might reverse this disadvantage by using water separated from air as a feedstock for electrolysis based hydrogen production. Investigation of the overall integrated system by detailed simulation reveals the possibility of realizing high degrees of synergies within the strongly coupled DAC-PtG process. Efficient water recovery can reduce the process water demand by a factor of 4. Focusing on the overall energy demand, detailed pinch analysis of the integrated DAC-PtG concept is performed. High tem- perature water condensation allows for heat recovery in the order of 1.5 times the heat of reaction released in methanation process. Electrolysis operation point was found to be of high importance. Operation at 1.5 equilibrium cell voltage results in excess heat production of 475 kJ per mole CO2 captured, whereas at equilibrium cell voltage process heat demand of 16 kJ mol(-1) is observed. Overall, the possibility of designing an auto- thermally operated process for the production of methane based on carbon dioxide and water from ambient air is confirmed, where the synergies between the process sections revealed are of interest for general power-to-X (PtX) applications.