Separation of ethanol-water mixtures using sweeping gas membrane distillation: Experimental approach

In the present study, the feasibility of using sweeping gas membrane distillation process as a possible method for direct separation of ethanol-water using a flat sheet PTFE membrane located in a plate and frame module with 169cm2 active area and air stream as sweeping gas was investigated. Feed concentration, temperature and flow rate, as well as the flow rate of the sweeping air were taken into consideration as operating parameters and their effects on thepermeate flux and ethanol selectivity were studied. The highest feed concentration applied was 7wt.% ethanol, as higher values than 7% would increase the risk of membrane wetting. Increases in feed temperature led to an increased permeate flux and selectivity, and within thefeed temperature range of 35 to 55oC and at lower feed concentrations (3wt%), ethanol selectivity of 18.5 to 25 was achieved,however, by increasing the feed concentration more than 5wt%, selectivity decreased. The increased permeate flux and ethanol selectivity at higher feed flow rates was mainly due to the reduced effects of temperature and especially concentration polarizations. Results obtained showed that the present process could be used as a stand-alone dehydration technique for ethanol aqueous mixtures

Keywords:

sweeping gas membrane distillation , ethanol-water mixture , PTFE membrane , operating parameters