Effects of salinity and feed temperature on permeate flux of an air gap membrane distillation unit for sea water desalination

This paper reports on an experimental study of the effect of feed water temperature and sea salt concentration on the permeate flux of an air-gap membrane distillation (AGMD) unit developed by Scarab Development AB. In addition, the specific energy consumption is computed for two sea salt concentrations and different feed solution temperatures. The performance of the unit is evaluated by assessing the distillate flux and the thermal energy input. Our strategy involves capturing waste heat to raise the temperature of a saltwater solution (feed water) via a heat exchanger. This feed water of known sea salt concentration is pumped into the hot inlet of the membrane distillation module, while the cold side of the module is maintained at a lower temperature (~20°C) using an air-to-water heat exchanger. We report the system-level energy consumption per unit volume of purified water at different feed water temperatures and the permeate flux production for sea salt concentrations of 0 g/L, 35 g/L and 55g/L for feed water temperatures in the range 20°C to 90°C.