Investigation of microwave-based CO2 regeneration in a packed bed reactor for Direct Air Capture

This study investigates a microwave-assisted Direct Air Capture (DAC) application using Zeolite 13X to capture CO₂ from the atmospheric air in Tuscaloosa, Alabama. For the regeneration process, a mono-mode solid state microwave generator with E orientation cavity was applied to desorb CO₂ from the sorbent. The main purpose of this study is to explore microwave-based DAC system since there is no detailed parametric study which evaluates all desorption characteristics including temperature and microwave initial power effects on CO₂ productivity, regeneration efficiency, desorption kinetics, energy consumption, temperature homogeneity, adsorption, and desorption capacities. In order to investigate all these desorption characteristics, sixteen non-cycling and ten cycling experiments were performed. In non-cycling experiments, regeneration temperature and microwave initial power changed from 45 ℃ to 100 ℃ and from 5 W to 60 W, respectively. The results illustrate that energy consumption to desorb a kg of CO₂ can be as low as 60.37 MJ and 23.97 MJ for 100 % and 70 % regeneration, respectively. In cycling experiments, adsorption capacity of each experiment and the effects of 70 % desorption on the adsorption capacity of following experiments were analyzed at the lowest temperature and power conditions (45 ℃ and 5 W). It was found that 70 % desorption does not have significant effects on the adsorption capacity for the following cycles. This study also proves that complete CO₂ regeneration can be achieved even at low temperature and initial power values in 3100 seconds.