Optimization of the design and operating parameters of a large-scale vacuum membrane distillation system to improve process performance

This study investigates the performance and optimal operating of a proposed large-scale vacuum membrane distillation (VMD) system with an external condenser for enhanced productivity and energy consumption. The VMD configuration reduces the resistance of vapor mass transfer across the membrane to increase its permeation rate. A comprehensive parametric analysis to evaluate the effects of various operational and design parameters of the MD module and the condenser unit has been performed. The optimized results were compared to the conventional direct-contact membrane distillation (DCMD) configuration. Results revealed that the feed temperature and flowrate have the most significant impacts on system productivity and energy consumption. Increasing the vacuum improves productivity, while increasing the membrane thickness decreases system productivity. Increasing the membrane pore diameter slightly enhances system productivity. Using smaller coil diameters for condenser and cooling the system using water at room temperature can minimize the energy consumption of the system. The proposed model outperforms the traditional DCMD unit of the same module design. The system can produce 388 L/h of freshwater, with a minimum SEC of 645 kWh/m3 at the optimum conditions. These findings demonstrate the potential of the vacuum membrane distillation process as a promising technology for water desalination treatment applications.