Study On The Influence Of Microporous Membrane's Parameters On The Mass Transfer Performance In Membrane Distillation

Membrane distillation (MD), which is being developed for desalination, concentration of thermally labile substances and waste water treatment, is a relatively new separation technique. For predicting mass flux in MD process by means of mass transfer model, it is necessary to correctly determine the parameters of the porous hydrophobic membrane employed in this process. On analyzing direct connect membrane distillation (DCMD) and vacuum membrane distillation (VMD), this research work mainly focused on the influence of membrane compaction and pore size distribution on mass transfer across membrane in MD.Based on the mass transfer mechanism of gas in porous medium, the mass transfer equation for single gas in membrane pores was obtained. The gas permeation experiments, in which three kinds of PTFE membrane were employed, were conducted, and the results show the relation of membrane parameters with the pressure difference between the two sides of the membrane. The membrane pore size decreases with the pressure difference, and the ratio of porosity to its effective thickness increase with pressure difference. This is an indication of the compaction of employed membranes.For investigating the influence of pore size distribution on mass transfer across the membrane in MD, three kinds of mass transfer equation were established for DCMD and VMD process respectively: CD mass transfer rate predicted with mean pore size;...