Experimental Investigation of the Desalination Process for Direct Contact Membrane Distillation Using Plate and Frame Membrane Module

Abstract

Through experiments, the effect of membrane material selection and operating conditions on permeate fluxes in direct contact membrane distillation (DCMD) desalination was investigated. The experiment used a plate and frame membrane module, and with nine different hydrophobic porous membranes, a comparative analysis of the desalination performance of 3 wt% NaCl solution was performed. The results of this experiment were compared to find out the effect of different materials, pore sizes and membrane thicknesses on the permeate flux under same operating conditions. Further, a three-factor, three-level orthogonal experiment was designed. The effects of hot-side temperature, hot-side inlet flow and cold-side inlet flow on the permeate flux of PTFE membranes with a pore size of 0.22 μm were investigated when the temperature on the cold side was set at 20 °C. The results showed that in the DCMD experiments, both PTFE and PVDF membranes performed well, and that hot-side inlet temperatures and cold-side inlet flow rates had significant effects on the permeate flux.

Experimental Investigation of a Plate–Frame Water Gap Membrane Distillation System for Seawater Desalination

“…In addition, the PTFE membrane has a lower surface energy compared to the PVDF membrane [ 58 ], which also contributes to more vapor attraction, thereby improving the membrane flux and pore-wetting resistance of the PTFE membrane. The GOR for the PTFE membrane was also higher than the PVDF membrane due to the higher vapor flux, although both had a similar thermal conductivity with values of 0.18–0.22 W/m-K and 0.235–0.2651 W/m-K for PVDF membrane and PTFE membrane, respectively [ 59 , 60 ]. The slightly lower thermal conductivity and thicker active layer thickness of the PVDF membrane supported the lower mean gap temperature reported in Table 3 .…”

“…Other conditions under which each test was conducted are presented below each figure for convenience. The coolant and feed stream temperatures were measured For the WGMD bench-scale tests, the coolant stream was chilled to 15 • C in the recirculating cold bath and supplied to the MD coolant chamber at 2000 mL/min, while the feed saline water was heated to the necessary temperatures (40,50,60, and 70 • C) in the recirculating hot water bath and fed to the MD feed chamber at 600, 800, 1000, and 1200 mL/min. Other conditions under which each test was conducted are presented below each figure for convenience.…”