The Development Of Phase Change Absorbents For CO₂ Capture Based On Cosolvent Effect

Global warming caused by greenhouse gases is becoming more and more serious,and CO₂ emissions reduction is getting to be global trend.Chemical absorption method is the most mature of CO₂ capture method,but the energy consumption of this method is too high,which restricts its widely use.Phase change absorbent causes concern for it can reduce the desorption energy consumption by reducing the amount of liquid entering the desorption unit.However,there are several problems in the study of phase change absorbers:?1?the phase separation mechanism of phase change absorbers is not clear;?2?At present,there are few kinds of amine species reported,and the selected amine is not common with a high price,such as BDA,DEEA and MAPA,which are more restrictive for future industrial applications of phase change absorbers.The preliminary study of this group suggests that the addition of physical solvent can improve the absorption and desorption properties of alcohol amine absorber and reduce the desorption energy consumption.However,some physical solvents are incompatible with water.Based on this,the amine solvent is regarded as a cosolvent,and the solubility of the physical solvent in water is increased by the solubilizing effect of the alcoholamine.Then,a method is proposed.We can screen a proper alcohol amines for phase-change absorbers by determining the liquid-liquid equilibration of alcoholamine + hydrophobic physical solvent + water system.And verify if the chosen alcoholamine+ hydrophobic physical solvent + water system changes into two phases after absorbing CO₂.The results show that it is feasible to determine whether the system has the potential as a CO₂ phase change absorbent by measuring the liquid-liquid equilibrium data of the cosolvent + hydrophobic physical solvent +water system.The structure and amount of alkanolamine have some effect on the solubility of n-butanol in water.For the alcohol amine with a similar structure,when the hydrophobic physical solvent is determined,the longer the carbon chain,the better cosolvent effect will be on the solubility of the hydrophobic physical solvent into water;when the amount of alcohol amine is less than 0.2mol,the cosolvent effect is similar between isomer.DEA is screened to make a phase change absorbent as a cosolvent.The phase change absorbent of DEA+ n-butanol +water is divided into two layers after absorbing CO₂.The n-butanol is mainly present in the upper liquid and the concentration is up to 12.25 mol · Kg-1,CO₂ mainly concentrated in the lower liquid,the concentration of up to 2.715 mol · Kg-1.The CO₂ capacity of the phase change absorber of DEA + n-butanol + water system used in this paper is not less than the literature value while the liquid amount sent to the desorption section is reduced nearly 73%,which greatly reduces the desorption energy consumption.