Experimental and theoretical investigation of a high performance PTFE membrane for vacuum-membrane distillation

Abstract

Vacuum-membrane distillation (VMD) is a membrane-based separation process that utilizes hydrophobic membrane and vacuum pressure to distillate hot saline feed stream into high purity fresh water. Despite the recent interests in the VMD, comprehensive membrane characterization and theoretical performance analysis relevant to system-level scales are limited. In this work, we present experimental and theoretical investigation of a commercial high performance PTFE membrane for the VMD application. With a careful examination of the membrane properties with a module that captures both hydrodynamic and thermal behaviors with coupled heat and mass transfer analysis, we evaluated the membrane distillation performances. Because laboratory observation does not elucidate larger scale performances, experimentally validated theoretical model is used to evaluate the performances of a PTFE membrane-based single-stage VMD system with a module length of up to 10 m at salinities of 30 and 60 g/kg. Influence of various operating conditions, such as feed temperatures, mass flow rates, and vacuum pressures, as well as temperature and concentration polarizations on the desalination performances are examined. We show that the PTFE membrane investigated in this study can generate high permeate fluxes at the system-scale, a promising candidate membrane for the VMD application.