Zero liquid discharge of desalination brine via innovative membrane distillation system coupled with a crystallizer

This study theoretical examines the integration of a crystallizer with multi-stage Vacuum Membrane Distillation (M-SVMD) for zero liquid discharge (ZLD) applications, focusing on the effects of feed temperature, flow rate, and vacuum pressure on system performance, both with and without energy recovery. The existing research on VMD-crystallizer often overlooks key aspects such as economic and energy analysis, energy recovery, detailed mathematical modeling, and evaluation of different integrated system layouts. This study addresses these gaps by offering a comprehensive theoretical analysis of various multi-stage VMD configurations integrated with a crystallizer. The current research explores the energy and economic implications of these integrated systems, highlighting its novel contribution to the field. The key findings from the study include a 39 % reduction in specific thermal energy consumption and improved gained output ratio (GOR) through energy recovery, enhancing system sustainability and efficiency. The integration also leads to a 22 % decrease in specific area requirements and lower specific water production costs, underscoring the economic advantages of incorporating heat recovery. Higher feed temperatures were found to optimize system efficiency by increasing GOR and reducing energy and space demands. Adjustments in feed flow rate and vacuum pressure significantly influence water productivity and system economics. Economic assessments demonstrate that scenarios incorporating energy recovery exhibit lower specific production costs, with additional savings realized through the sale of produced salt. Notably, the study identifies configurations combining energy recovery and salt sales as achieving a freshwater production price as low as $0.3099/m³. Furthermore, the sensitivity analysis indicates that the feed temperature and vacuum pressure are the most significant factor influencing the system's performance.