Experimental study of hollow fiber AGMD modules with energy recovery for high saline water desalination

Hollow fiber AGMD modules with energy recovery for high saline water desalination were successfully developed by using parallel hollow fiber membranes and heat-exchange hollow fibers. Latent heat of distillate water vapor was recovered by heat-exchange hollow fibers directly to heat the cold feed within the AGMD module. Water permeate flux (JD) and gained-output ratio (GOR) parameters were used to characterize the operation performance of the AGMD process. GOR obtained in the AGMD process was higher than that obtained in traditional membrane distillation processes. The maximum value of JD and GOR could reach 6.98 kg/m2h and 6.44 respectively. The effects of various operation parameters including feed temperatures and feed flow rate on the performance of the AGMD process had been investigated. The effects of various membrane module parameters such as membrane porosity (ε), membrane pore size (dr), the rate of hollow fibers and membranes (Nd/Nm), the thermal conductivity coefficient of heat-exchange hollow fibers (kd), the thickness of hollow fibers (dd) and the air gap width (da) were experimentally studied. The high saline water of 70 g/L was concentrated to about 308 g/L in the deep-concentration experiment. In the long-term stability test lasting for 45 days, the maximum value of the electrical conductivity of the distillate was always less than 200 μS/cm.