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Development of SO2 Phase Change Absorption: Viscosity Change and Component Distribution Rules

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journal contribution
posted on 2019-09-20, 21:30 authored by Shengchao Xu, Wenbo Zhao, Muyuan Chai, Tian Si, Yuan Chen, Qingming Jia
As phase change absorption of CO2 could drastically reduce energy consumption, a liquid–liquid phase change absorption process of SO2 was developed in the present work using N,N-dimethylethanolamine (DMEA) as absorbent and hexadecane as solvent. The homogeneous solution was split into two immiscible phases when the absorption capacity reached 0.02 mol/mol. The phase change mechanism was attributed to the formation of a zwitterionic compound, through the reaction of SO2 with DMEA and its separation from the solution. The viscosity of the absorption product was related to the absorption capacity and temperature, which is described by an Arrhenius-type equation. The gravimetric absorption capacity was found to be 1.56 g SO2/g DMEA at 1.0 atm, which is the highest value reported in the literature. At 0.02 atm, its capacity still reached 0.59 g/g, which is also much higher than those of other absorbents at similar conditions. The distribution of DMEA, hexadecane, and SO2 in the two phases is described by two differential equations and material balance. Ternary phase diagram representation was used to provide an intuitive visual of the phase separation behavior. High temperature was found to play a role in weakening phase separation. Ultimately, DMEA was chemically regenerated by the reaction of the absorption product and cyclohexene oxide.

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