Study On Absorption Of CO₂ In Aqueous [Bmim][BF₄]/MEA Blended System

CO₂ capture and storage?CCS?technologies have become research hotspots as they are recognized as options to reduce the emissions of CO₂ which is widely regarded as a major greenhouse gas that leads to global climate change.Chemical absorption is the most viable near-term approach to post-combustion capture.However,it has several disadvantages including the loss of solvent,large stripping energy consumption,unfavorable degradation,and corrosion problems.Therefore,the development of new solvents and better processes are the current emphasis.In this work,[Bmim][BF₄]-MEA-H₂O,an ionic liquid amine mixed aqueous solution system,was studied.In this system,the introduction of ionic liquid can improve the performance of the absorbent,which is a liquid-liquid biphasic absorbent under a certain concentration condition with the potential of reducing energy consumption.The absorption rate,rich loading,lean loading and the cyclic capacity of the absorbent were measured.The analysis of quantitative ¹³C-NMR showed that the increase of the concentration of carbamate is the direct cause of the liquid-liquid stratification,and the mechanism of the stratification was revealed.The enrichment of the CO₂ reaction products after stratification was pointed out,and the distribution of substances after stratification was also analyzed.The density,viscosity and physical solubility data of[Bmim][BF₄]-MEA-H₂O mixture were measured and regression analysis was performed using semi-empirical formulas.It was pointed out that the introduction of[Bmim][BF₄]does not significantly increase the viscosity of the absorbent in a certain concentration range,and[Bmim][BF₄]can improve the physical solubility of CO₂ of the absorbent.The self-diffusion coefficient of[Bmim][BF₄]-MEA mixture and[Bmim][BF₄]-MEA-H₂O mixture were measured by pulsed field gradient NMR technique.The influence of temperature,concentration were analyzed.The relationship between self-diffusion coefficient and temperature was described by the Arrhenius law,and the variation of the diffusion activation energy with the concentration was obtained.From the perspective of diffusion,the importance of H₂O in the system is demonstrated.the existence of H₂O can obviously improve the diffusion properties of the solution.The vapor-liquid equilibrium data of[Bmim][BF₄]-MEA-H₂O mixture?or rich phase of the mixture?and CO₂ were measured.By using eNRTL model,vapor-liquid equilibrium data in a wider rang were obtained.The estimation of desorption energy consumption showed that when the mass fraction of[Bmim][BF₄]was more than 40%,the sensible heat of desorption energy consumption could be reduced by about 40%.An experimental platform has been designed and built,which can continuously measure the reaction flux in stable atmosphere.The gas and liquid mass transfer coefficients were calculated using the two-film theory.The results showed that the increase of CO₂ loading lead to the decrease of the mass transfer coefficient,and the phenomenon of liquid-liquid stratification would lead to abrupt change of liquid mass transfer performance.Based on the systematic study of the absorbent,a comprehensive analysis of the concentration of the liquid-liquid two phase absorbents was made.