Moisture swing adsorption for direct air capture: Establishment of thermodynamic cycle

Abstract

As a rising branch of DAC technology, moisture swing adsorption (MSA) could be regenerated through humidity regulation that can avoid such high energy consumption. However, for capture energy consumption, advantages of MSA have yet to be fully explored. Thus, a 6-step MSA thermal cycle is initially proposed in this work. Three working conditions are considered: temperature swing, moisture swing, as well as temperature and moisture co-swing. It is found that the synergic control of temperature and moisture can improve energy consumption and efficiency limits of MSA cycle due to the increase in saturated vapor pressure. Under the adsorption condition of 25 ℃ and 30% RH, it reveals that the introduction of temperature swing process effectively reduces specific energy consumption of MSA cycle by 28%, increases thermodynamic efficiency by 119%, and increases adsorbent efficiency by 30%. The findings of this cycle analysis help to guide the optimization of MSA process and promote the development of DAC.