聚四氟乙烯膜气体吸收数学模型和孔隙率的影响

Mathematical Model of Gas Absorption for PTFE Membrane and the Effect of Porosity

膜吸收是将膜分离与传统的吸收技术相结合的一种新型分离技术。在这些过程中经常使用多孔膜,多孔膜对过程的传质性能有一定的影响。对不同孔隙率的微孔聚四氟乙烯(PTFE)疏水性平板膜的膜气体吸收过程中液相传质性能进行了实验研究。当采用去离子水-CO2吸收体系时,多孔膜的孔隙率对液相传质性能没有影响;当采用NaOH水溶液-CO2吸收体系时,多孔膜的孔隙率对液相传质性能有明显的影响。在相同流速下,孔隙率大的膜液相传质系数高于孔隙率小的膜。以双膜理论为指导,建立了多孔膜气体吸收过程中液相传质模型。用该模型描述多孔膜孔隙率对液相传质系数的影响,其结果与实验数据具有良好的一致性。

The porous membranes are often used in the membrane absorption processes, which are a kind of novel technology combining membrane separation with conventional absorption process. The structure of the porous membrane used has some effect on the mass transfer of the process. The mass transfer performances of CO2 absorbed by water or NaOH aqueous through microporous polytetrafluoroethylene (PTFE) flat membrane were studied. It is found that the membrane porosity has no effect on the mass transfer performance of liquid phase for the CO2-water system. But it has significant effect on the mass transfer performance of liquid phase for the CO2-NaOH aqueous system, and the mass transfer coefficient of liquid phase is higher for the membrane with bigger porosity than that with the smaller one. Based on the two-film theory, a model considering the influence of membrane porosity on the mass transfer of liquid phase for membrane-based absorption process was established. The predicted mass transfer coefficients calculated by the model are in good agreement with the experimental data.