Modelling and simulation of flux prediction and salinity variation in direct contact membrane distillation for seawater desalination and brine treatment

Abstract

As one of the state-of-art desalination technologies, membrane distillation (MD) has been widely studied in recent years. In order to better control the performance of the MD, a new model that can predict the membrane surface temperatures, permeate flux as well as salinity variation with the operating time has been proposed in this study. Using the model, impacts of operating parameters such as bulk temperature, flow rate, different membrane materials and feed salinity on the permeate flux as well as the efficiency of driving force were simulated. The results of the simulations indicate that feed temperature, feed flow rate and membrane pore size have the most significant influence on the permeate flux. However, the feed and permeate flow rates have the highest impacts on the temperature polarization coefficient (TPC) which has the highest value of 0.68 under certain conditions. Besides, the simulations predicted that the water recovery from the MD for the seawater and the desalination brine at the saturation point of NaCl to be 86.8 % and 72.1 %, respectively. Finally, the salinity variations with operating time were also simulated and the new model would be vital for the salinity control in desalination processes such as membrane distillation crystallization.