Studies on simulation and experiments of ethanol-water mixture separation by VMD using a PTFE flat membrane module

Model parameters modification and numerical simulation based on the Knudsen-viscous transition model to predict the vacuum membrane distillation (VMD) performance of ethanol-water mixture and experiments were studied in a polytetrafluoroethylene flat-sheet membrane module. A novel approach to determine the model parameters K and B (modified Knudsen diffusion and viscous flow membrane characteristics, respectively) consisted of membrane morphological parameters was especially developed by fitting the water VMD experimental results. Furthermore, linear relations between the modified model parameter K or B and feed temperature were first established, and then successfully employed to predict by simulation the separation performances of 5 wt% ethanol-water mixture. The experiments of ethanol-water VMD demonstrated that the fluxes of ethanol and water both increased with temperature or vacuum degree, but the separation factor decreased. The simulation values agree quite well with experimental ones, finding the minimum and maximum discrepancies are 0.5% and 9.6% for flux and separation factor, respectively.