MASS TRANSFER IN A LIQUID-LIQUID CONTINUOUS FLOW STIRRED TANK REACTOR.

摘要

This thesis comprises a theoretical and experimental performance evaluation of a liquid-liquid continuous flow stirred tank reactor (CFSTR) as an extractor. The dynamics of the dispersed phase droplet interactions and microscopic interphase mass transfer in a turbulent dispersion is modelled and digitally simulated to attain a better understanding of the fundamental drop processes in liquid-liquid contactors. The validity of the simulation results is tested against the experimental results.; The interval of quiescence method used for time management in the Monte Carlo simulation algorithm allows the dispersion system evolution in a natural continuous manner without artificial discretization of time. The algorithm employs the drop rate functions based on the hydrodynamic considerations and represents the most realistic simulation reported so far. The steady state drop size distribution and mass transfer efficiency are experimentally obtained for a cyclohexane/carbontetrachloride-iodine-water system dispersed in a 1 liter CFSTR. The drop size distribution is obtained by in situ photomicrography. The mass transfer efficiency is estimated by the spectrophotometric measurement of solute concentration of the two phases separated by in situ filtration.; The comparisons of the theoretical and experimental results agree well. The simulated sauter mean diameters are within (+OR-)10% of the experimental values with an average deviation of 5%. The average difference in the present predicted and experimental extraction efficiencies is 3.4%. This agreement substantiates the validity of the homogeneous dispersion models used in the present simulation algorithm.; The dispersion is found to be dominated by breakage and therefore extraction appears to take place in the segregation mode. The drop micromixing enhances the mass transfer as evidenced by the increasing efficiencies with increasing dispersed phase fraction. The higher simulated extraction efficiencies for completely mixed dispersions as compared to completely segregated dispersions also confirm the enhancement effect of micromixing. The experiments indicate that the mass transfer direction from the dispersed phase to the continuous phase facilitates coalescence.