Effect Of Physical Solvent On Liquid-Liquid Equilibrium And Absorption Performance Of Phase Changing Absorbents In Mdea System

The issue of carbon emission reduction has attracted global attention.The capture of CO2 by chemical absorption is one of the most mature and effective technologies for carbon emission reduction,but the biggest problem is the high energy consumption.The phase changing absorbent has great development potential in reducing the energy consumption of capture,because it can reduce the amount of desorption liquid.Amine-physical solvent-water phase changing absorbent has good absorption and desorption performance and low cost.Thus,it has great research value.At present,the research of Amine-physical solvent-water phase changing absorbents mainly focus on the investigation of the absorption and desorption performance,and there are few studies on the liquid-liquid equilibrium of the upper and lower liquid phases after the phase change of the phase changing absorbents.In addition,the effect of physical solvents on the absorption rate of MDEA system absorbents has not been systematically studied.In this paper,based on commonly used MDEA-water system absorbents,five physical solvents are selected to form phase change absorbents(dioxane,n-butanol,acetonitrile,sulfolane,propylene carbonate),and the effect of the added physical solvents on the physical properties,upper and lower liquid phase composition,absorption and desorption performance of MDEA system absorbent are investigated.The results show that CO2 loading in the absorbent CO2 rich liquid phase is related to the dielectric constant of physical solvent and its solubility in water.When the amount of physical solvent was reduced,the mass fraction of physical solvent and MDEA/MDEAH+ in the CO2 rich liquid phase of absorbent decreased,while the mass fraction of salt and water increased.The reasons were related to the solvation effect,salting-out and cosolubility of each substance in the solution.Compared with the traditional MDEA absorbent,the absorption rate and cyclic loading of MDEA-physical solvent-water absorbent increased,and the higher the content of physical solvent,the faster the absorption rate.By comparing the absorption and desorption performance of the five MDEA-physical solvents-water absorbents studied,the MDEA-n-butanol-water system phase changing absorbents have better absorption and desorption performance.