Numerical study of a hybrid multi-stage vacuum membrane distillation and pressure-retarded osmosis system

Abstract

In this study, we introduce a hybrid system that integrates a multi-stage vacuum membrane distillation (MVMD) with pressure-retarded osmosis (PRO). The MVMD system employs a recycling flow scheme (MVDM-R) for the continuous production of both distillate water and highly concentrated brine. The concentrated brine that is produced from the MVMD-R system is then used as a draw solution for power generation in the PRO system. We theoretically assessed the distillate and power production of the MVMD-R-PRO system with respect to inlet feed flow rate and recycling flow ratio in the MVMD-R system. When the inlet feed flow rate is constant, the production of distilled water increases slightly, with a decrease in the recycling flow. The maximum possible brine concentration from the MVMD-R system is 1.9M NaCl at an inlet feed flow rate of 3kg/min and a 90% recycling flow. A maximum power density of 9.7W/m2 is achieved when river water is used as a feed solution in the PRO system at feed and draw solution flow rates of 0.5kg/min and a constant hydraulic pressure difference.