| Membrane-based separation process is a novel technology which combines membrane separation with conventional separation. These new processes include membrane distillation (MD), membrane absorption (MA) and membrane extraction (ME), which have demonstrated a number of prevailing advantages including a larger interfacial area and independent control of flow rate of two phases as compared to conventional packed columns, for an example. Hydrophobic porous membranes are often used in these processes. They are not selective and are used to create a fixed interfacial area between two phases.With the scope of the application of membrane-based separation processes getting broader and broader, it is required that the principle of mass transfer about them is studied further and the accurate mathematical model used for the design of the practical module and the prediction of mass transfer performance in new module is established. The mass transference in porous membrane and modules has been researched experimentally and theoretically in three aspects.(1) The permeabilities of five kinds of gas, He, N2, O2, CO2 and water vapor, across six polytetrafluoroethylene(PTFE) flat membranes were tested experimentally. Results indicated that the greater the mean pore size and porosity of membrane and the smaller the thickness and tortuosity of membrane, the greater the gas permeability. A gas permeation model, including the effects of membrane structure parameter and gas properties, was established. The predicted permeation coefficients were in good agreement with experimental data. A simple method for characterizing porous membrane structure, the regression of gas permeation data with model, was provided.A comprehensive characteristic parameter (including porosity, thickness and tortuosity) was found more effective to express the influence of membrane structure in gas permeation process.(2) In order to determine the effect of the structure of porous membrane on the mass transfer of fluid phase, the mass transfer performances of CO2 absorbed into water or into NaOH aqueous for microporous PTFE flat membrane with different porosity were tested. The experiments were done in two states of the unsteady penetration and steady flow. The results showed that there was no difference among the different porosity membranes for the mass transfer in the system of CO2 — water. It means that there was no effect of the porosity of membrane on the mass transfer in this system. But there was a significant effect of the porosity of membrane on the mass transfer in the system of CO2 — NaOH aqueous. The mass transfer coefficient was higher for the big porosity membrane than for the small porosity one at same experiment condition.Based on the two-film theory, a model, describing the influence of membrane porosity on the mass transfer of liquid phase in membrane-based absorption process, was established. The predicted mass transfer coefficients by model were in good agreement with experimental data.An influence factor of membrane porosity was proposed. The bigger the influence factor, the smaller the effect of the membrane porosity on the mass transfer. (3) The mass transfer performances of CO2 absorbed into water or into NaOH aqueous were tested in two microporous polypropylene hollow fiber membrane modules. The results showed that the mass transfer in liquid phase was the controlling step for the absorption CO2 into water, and the overall mass transfer coefficient increased as the flow rate of liquid phase increased. The experimental data were close to the values calculated by Wu's empirical correlation. For the absorbent of NaOH aqueous, with increased the flow rate of gas and liquid phase, respectively, the overall mass transfer coefficients increased. It can be obtained that the overall mass transfer coefficients were associated with the mass transfer in both gas and liquid phase. Based on the membrane-based absorption experiment, shell-side flow distribution and mass transfer in a randomly packed hol...
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