Experimental study on the effect of THF/DTAC and adsorption coupling on the separation and carbon capture process of CH4/CO2 gas mixture by hydrate-based method

The mixed gas separation technology of the gas hydrate-based method can realize the efficient capture and separation of CO2 from biogas, thus realizing the efficient purification of biogas. This study systematically examined the formation of CH4/CO2 mixed gas hydrate and the capture and separation properties of CO2 gas using THF/DTAC and adsorption coupling. The effects of different initial pressures, initial temperatures, and initial component ratios (40/60, 55/45, and 67/33) on the gas consumption, CO2 separation factor, CO2 hydration rate, CH4 recovery rate, and pressure drop rate of the CH4/CO2 mixed gas separation process were deeply analyzed. The findings demonstrated that, in the presence of 1 mol% THF and 0.5 wt% DTAC solution, the ideal temperature condition was 283.65 K at three distinct initial CH4 concentrations of 40%, 55%, and 67%. The corresponding optimal separation pressures were 3 MPa, 4 MPa, and 4 MPa, respectively. Meanwhile, the CH4/ CO2 gas mixture's CO2 molecules were more selectively picked up by the reaction system. At an initial pressure of 5 MPa, the rapid formation of hydrates reduces the subsequent sustained trapping of CO2 molecules, which in turn reduces the total gas consumption. Using activated carbon (16.67 wt%) as a basis, the quantitative impact of adsorption-hydration on the CH4/CO2 gas mixtures' separation process was further examined. With activated carbon present, the reaction system was able to increase CO2 intake while decreasing CH4 molecule uptake. Finally, a new model for CH4/CO2 mixed gas separation by multistage hydration method was proposed.