Numerical Simulation And Experimental Study On Liquid-liquid Multicomponent Mass Transfer In Microchannel

Great effort has been devoted to the liquid-liquid capillary microreactor in recentyears due to its efficient performance in enhancing heat and mass transfer forextraction and biphasic reactions. In this paper, first of all, one appropriate salt-MgCl2was been selected according to its outstanding dehydration and dealcoholizationperformance to the ternary ethyl acetate-ethanol-water system for the LLE research.Then, the mass transfer behavior of slug flow was investigated in PTFEmicrochannels with diameters of0.6mm and0.8mm respectively. Finally, wemanipulated the CFD simulation method using our inner-developed UDF toinvestigate the behaviors of hydrodynamics and multicomponent mass transferprocess in order to establish design guidelines for mass-transfer operation based onliquid-liquid slug flow.The slug length has been measured by means of the CCD high speed cameravisualization technique and then analyzed the interfacial area. In addition, theinfluences of slug velocity, diameter of the channel, salt concentration of aqueoussolution, capillary length on the multicomponent mass transfer process wereinvestigated. The results showed that the range of interfacial area was3500~5000m2/m3, the extraction efficiency of30%~95%was obtained, and thevolumetric mass transfer coefficients were in the ranges of0.2~1s-1. It was found thatthe interfacial area increased with decreasing the capillary diameter, and so do themass transfer coefficients of different species; when increased the aqueous saltconcentration, the water mass transfer coefficient remain unchanged basically, but theethyl acetate and ethanol mass transfer coefficients decreased obviously.A fixed interface slug unit approach and Lagrange algorithm were applied tosimulate the hydrodynamics and mass transfer process. First, the effect of differentfactors on mass transfer coefficients was eliminated, such as mesh density, iterationtime step and iteration numbers per time step; Then the steady flow field wasestablished by solving the continuous equation and flow equation; Finally, themulticomponent mass transfer process was simulated by loading the custom UDFbased on the steady flow field, discussed the influences of slug velocity, capillarydiameter, diffusion coefficients of different species in both organic phase and aqueous phase, salt concentration on mass transfer process and supplied the elucidationmechanisms.The experimental results and simulated results were compared, and it was foundthat the deviation was about70%at the entrance stage and about+30%~-10%at thefully developed stage, which agrees well with each other. This can be explained thatbecause of the slug formation process and entrance effect makes the experimentalresults on the higher side to the simulated results. On the whole, the simulated resultsare in accordance with the experimental results, and the developed model can simulatethe multicomponent mass transfer process very well.