Technoeconomic analysis of different multistage membrane distillation configurations with heat recovery

Development of efficient and economically viable desalination processes and technologies is a global challenge. This study presents a comparative technoeconomic analysis of three multistage membrane distillation (MD) configurations, namely direct contact (DCMD), water gap (WGMD), and water gap MD with gap circulation (C-WGMD) to identify the most promising configuration for applying heat recovery (HR) for cost-effective water desalination. Co-current and Counter-current flow arrangement between feed and intake streams were tested for heat recovery potential. A comparative evaluation of the heat recovery performance for three configurations was conducted, followed by an in-depth parametric study of the best-performing design. The evaluation focuses on key performance indicators such as freshwater productivity, specific energy consumption (SEC), and water production cost. The results indicate that counter-current feed-intake flow arrangement surpasses co-current one by sustaining a stage-wise stable thermal gradient, thereby enhancing heat recovery and thermal performance. Under counter-current operation, both DCMD and C-WGMD outperform WGMD. With heat recovery, the SEC decreased by 31.8% and 58% while the production cost was reduced by 30.8% and 62.6%, respectively, for DCMD and C-WGMD, respectively. Although DCMD and C-WGMD achieved nearly the same productivity, the C-WGMD demonstrated superior performance in energy and cost metrics, with SEC and production cost reduced by 41.23% and 39.15%, respectively compared to DCMD. The study shows that the C-WGMD system with counter-current flow arrangement and heat recovery delivers the highest performance with a SEC of 365 kWh/m 3 and an estimated cost of 18 $/m 3 , highlighting its strong potential for energy-efficient desalination of low-to moderate-salinity feedwaters and as a promising configuration for seawater desalination when combined with further system’s optimization.