Conductive heating vacuum membrane distillation for brine desalination: Study on operational conditions, temperature polarization and energy consumption

Membrane distillation (MD) has gained significant attention for treating hypersaline brine. However, conven-tional MD is still constrained by technical issues such as temperature polarization (TP) caused by the feed being continuous heated. Herein, through the use of a thermal conducting layer, this study introduced a conductive heating vacuum membrane distillation (CH-VMD) system capable of transmitting external heat directly to the membrane-water interface without preheating the feed. The influence of operational conditions on distillate flux and salt rejection was investigated. In both CH-VMD and conventional VMD systems, the temperature profile at the membrane-water interface were examined and compared. In addition, we analyzed the TP differences be-tween the two systems under different operational conditions. In CH-VMD system, with a 35 g/L NaCl feed solution, thermal conducting layer temperature of 60 degrees C, a flow velocity of 3.1 cm/s, and 90 kPa vacuum level, the distillate flux reached 9.8 L/m2.h and the salt rejection achieved 99.9%. The temperature polarization co-efficient was greater than unity, resulting in a thermal efficiency as high as 83.2%. Heat conduction increased the temperature of the membrane-water interface, which is critical for optimizing MD performance in terms of overcoming TP, enhancing distillate flux and salt rejection, and lowering energy consumption