CO₂ Absorption Into Aqueous Solution Enhanced By Organic Phase In A High Shear Reactor

Industrial processe expends a huge quantity of fossil fuel and leads to a large amount of CO2 emission in the combustion process.The increase of CO2 concentration in atmosphere results in greenhouse effect which poses a serious threat to ecological environment.Therefore,the capture,utilization and storage of CO2 is crucial to improving ecological environment and relieving greenhouse effect.Chemical absorption is a common method in CO2 capture.Intensifying the chemical absorption process of CO2 can improve the absorption efficiency and reduce the energy consumption,which is the core content of CO2 capture research.Gas-liquid-liquid(G-L-L)systems have important applications in organic synthesis and biochemical engineering.The special mass transfer characteristics in these systems have attracted wide research interest.High gravity technology is an efficienct intensification method for chemical processes.Therefore,this thesis combined the high gravity technology and G-L-L systems to intensify CO2 absorption.A novel high gravity device named high shear reactor(HSR)was used in this thesis.The effect of organic phase on CO2 absorption in water,K2CO3/KHCO3 buffer solution,K2CO3 solution and DEA promoted K2CO3 solution was investigated.The effective gas-liquid specific interfacial area(ae)was also determined.The major conclusions are as follows:(1)The absorption of CO2 in cyclohexane-water system in HSR was studied.Results indicated that the addition of cyclohexane enhanced C02 absorption in water.CO2 absorption percentage increased wirh the increase of rotating speed of HSR,liquid flow rate and liquid temperature.The increase of gas flow rate decreased CO2 absorption percentage.(2)Absorption of CO2 in organic-K2CO3/KHCO3 system in HSR was investigated.Results showed that cyclohexane and n-heptane enhanced CO2 absorption into K2CO3/KHCO3 buffer solution and the optimum volume fraction of organic phase was about 5%-7.5%.However,toluene and n-octanol had little effect on CO2 absorption.CO2 absorption percentage rose with the increase of rotating speed of HSR but decreased with the increase of gas/liquid ratio and temperature.The emulsifier of Tween 80 made insignificant influence on CO2 absorption,but NaClO as a promoter enhanced CO2 absorption.(3)Absorption of CO2 in cyclohexane-K2CO3 system in HSR was investigated.With the increase of cyclohexane volume fraction,CO2 absorption percentage and enhancement factor rose first and then remained stable.The optimum volume fraction of cyclohexane was determined as 4.8%.The increase of rotating speed of HSR,liquid flow rate,liquid temperature and the decrease of gas flow rate led to the increase of CO2 absorption.(4)The absorption in cyclohexane-DEA/K2CO3 system in HSR was studied.With the increase of cyclohexane volume fraction,CO2 absorption percentage and enhancement factor rose first and then remained stable.The optimum volume fraction of cyclohexane was determined as 2.5%-7.5%.The increase of rotating speed of HSR,liquid flow rate,liquid temperature and the decrease of gas flow rate enhanced CO2 absorption.(5)The ae in HSR was investigated by Danckwerts-plots method.The ae obviously increased in the presence of cyclohexane compared to that in the absence of cyclohexane.On the contrary,the addition of toluene caused a slight decrease in ae.Higher rotating speed of HSR gave rise to a larger value of ae.This thesis explored the absorption of CO2 in the G-L-L systems in HSR for the first time and has provided a new pathway for the intensification of CO2 absorption.