Direct air capture by direct steam heating - experiments and comparison with indirect heating

The energy consumption of the Direct Air Capture (DAC) process is heavily dominated by the thermal energy required during desorption. To accelerate regeneration and improve efficiency, this work proposes to leverage the latent heat of condensation of saturated steam released when contacted with a cold sorbent. To this end, amine-functionalized monoliths were regenerated via direct heating using condensing saturated steam in a custom-built setup and compared to indirect (conventional) heating using a heating jacket under DAC-relevant conditions. The results show that direct heating substantially accelerates desorption, releasing the equivalent CO 2 in one-sixth of the time required by indirect heating, while operating under a milder vacuum and lower temperature. A key operational challenge of direct heating is the management of condensate accumulation in the column. A simple thermodynamic model shows that a small H 2 O sorbent capacity could be sufficient to prevent steam condensation and its associated complications, provided heat losses are appropriately managed. These findings confirm that direct steam heating has the potential to be a fundamentally faster and more efficient approach for sorbent regeneration, offering a pathway to significantly enhance DAC productivity and energy efficiency.