Abstract
This work focuses on the integration of multiple effect evaporation (MEE) and membrane distillation (MD) processes. The MEE brine is treated by the MD allowing at the same time a preheating of the MEE feed water. Different structures of integration are assessed theoretically. Simulation models based on the heat and mass transfer balances are developed for the parallel feed (PF), parallel cross (PCF), forward feed (FF)-MEE, and direct contact MD (DCMD) configurations. The main performance parameters such as the performance ratio, recovery ratio, and specific energy consumption are investigated via simulation of various MEE-MD configurations and operating parameters. The results show that hybrid MEE and MD structures outperform the standalone MEE systems. The performance ratio increased by more than 25% when hybrid structure is used as compared to standalone MEE. The results revealed also that the hybrid parallel PF-MEE-MD configuration yields the best performance compared to other hybrid configurations. It also outperforms the standalone PCF-MEE which is widely adopted and used in practice. Besides, the performance of the hybrid configurations is especially sensitive to the feed temperature's variation in both MEE and MD units. Increasing MD feed temperatures has a positive impact on the recovery ratios of the combined systems.
•Integration of multiple effect evaporation and membrane distillation processes.•Different structures of integration are assessed and compared theoretically.•Key performance indices of hybrid MEE-MD system outperform that of standalone MEE.•Sensitivity of the hybrid system to several input parameters is investigated.