Thermal analysis and kinetic investigation of using a hybrid adsorption-hydration method to promote CO2 capture

In this work, a hybrid adsorption-hydration method was utilized to promote CO₂ capture. The CO₂ capture performance in the fixed bed of coal particles was assessed at various water saturations (0 %, 20 %, 40 %, 70 %, and 100 %), 277.15 K, and 3.2 MPa. It was found that gas consumption at 100 % water saturation increased by 45 % compared to that at 0 % water saturation (dry coal particles). Moreover, as the water saturation increased, CO₂ capture became dominated by hydrate formation rather than gas adsorption. The thermal analysis for CO₂ capture at 0 % and 100 % water saturation detected the exothermic peaks associated with CO₂ adsorption and CO₂ hydrate formation, as well as the endothermic peaks corresponding to CO₂ desorption and CO₂ hydrate dissociation. This confirms that CO₂ capture in the fixed bed of water-saturated coal particles consists of CO₂ adsorption followed by hydrate formation. The morphologies of CO₂ hydrate formation in the fixed bed of 100 % water-saturated coal particles were observed, and the mechanism of CO₂ capture using the hybrid adsorption-hydration method was illustrated based on the thermal analysis and kinetic investigations. It was also found that after the adsorption-hydration process, the average cumulative pore volume of the coal particles decreased by 14.47 % compared to the original coal particles, and the micropores and mesopores were predominantly affected. Therefore, utilizing the hybrid adsorption-hydration process in a fixed bed of coal particles provides a promising method to enhance CO₂ capture.