| With the micro-dispersion technology gradually applied to the reaction and separation process,how to use this technology to achieve the process intensification become a hot topic.Compared with the two-phase system of microscale gas/liquid,liquid/liquid and so on,the research on the flow,mass transfer and application of gas/liquid/liquid three-phase system is not perfect.The research results show the microscale three-phase fluid has some advantages in mass transfer,residence time and fluid mixing control.Therefore,a gas–liquid–liquid microdispersion system was specially designed to realize a microbubble-agitated extraction process and improve the efficiency of the extraction process extreme with phase ratio.In this paper,the complex extraction process of sodium nitrate-formic acid/trioctylamine/n-octanol system was taken as a typical case,and the basic research is carried out.Firstly,the thermodynamic equilibrium data of the system was determined.The effects of the mass transfer time,phase ratio,the extractant concentration in the oil phase and temperature on the extraction process were investigated.The following system was selected as the model system of dynamic research:the experimental temperature was 25 oC,the water/oil phase ratio was 75:1,the TOA volume fraction in the extractant was 30%.Secondly,a millimeter T-channel and microfiltration membranes as the dispersion medium were respectively developed to generate the liquid/liquid dispersion system.The mass transfer performance of the system with different dispersion sizes was investigated,the results of which show the mass transfer efficiency of the millimeter-level droplet system is low and when the mass transfer time is over 28 s,the Murphree efficiency is only 45%.The mass transfer performance of the liquid/liquid micro-dispersion system was improved obviously compared with millimeter-level droplet system,the Murphree efficiency can reach more than 90%under certain experimental conditions.However it is still need a longer mass transfer time to achieve high Murphree efficiency.Thirdly,the microbubbles was introduced into the liquid/liquid microdispersed system to realize the complexation extraction process.The effects of gas/liquid/liquid microdisperse structure,flow rate of gas phase and residence time on the Murphree efficiency were investigated in order to understand the mechanism of process intensification of the complexation exation with the microbubbles.The most efficient mode was suggested with lower addition of gas,by which the Murphree efficiency could reach higher than 90%and the overall volume mass transfer coefficient could range in 0.5-17 s-1,which is 2-30 times greater than the extraction process without introducing microbubbles.Mathematical models are used to developed to predict the complexation extraction process with/without gas addition. |
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