Experimental Study on Simultaneous Absorption and Desorption of CO₂, SO₂, and NO_x Using Aqueous N -Methyldiethanolamine and Dimethyl Sulfoxide Solutions

MDEA+DMSO aqueous solutions, made up of N-methyldiethanolamine (MDEA) and dimethyl sulfoxide (DMSO), were explored for the simultaneous absorption of CO₂, SO₂, and NO_x. Experiments in a semibatch absorption-desorption system were carried out to measure the absorption and desorption performance of aqueous MDEA+DMSO solutions. The influences of concentration proportion, MDEA/DMSO concentration, absorption temperature, desorption temperature, and cycle index on the simultaneous absorption and desorption were investigated. The experimental results indicated that under all experimental conditions the desulfurization efficiency was constant of 100% and the NO₂ absorption efficiency was above 98%, whereas the absorption of CO₂ and NO was significantly affected by the solution concentration and absorption temperature. The 5 mol/L MDEA + 2.5 mol/L DMSO solution exhibited optimal absorption performance with the CO₂, SO₂, NO, and NO₂ absorption efficiency of 91.04%, 100%, 97.14%, and 100%, respectively. A semiempirical formula of CO₂ absorption rate was obtained, and the optimal operating conditions were established; the reusability and stability of MDEA+DMSO solution were also verified in absorption-desorption circulation experiments. Meanwhile, the reaction mechanisms of the absorption and desorption were discussed based on the characterization of removal product by Fourier transform infrared spectroscopy and ion chromatography. Consequently, the aqueous MDEA+DMSO solution would be expected to be a renewable absorbent for simultaneous removal of CO₂/SO₂/NO_x.