Flash recovery system analysis and flashing tank optimization in desalination plants

Abstract

This study established and calculated the flash system model of 7-effects low-temperature multi-effect distillation (LT-MED) system with an installed capacity of 4500 m3/d. The calculation results showed that the brine and distillate flashing accounts for 6.0% of the total water production, which indicate the significant effect of such flashing heat recovery system. Furthermore, a three-dimensional simulation of water–vapor flow in the flashing tank of a LT-MED plant was conducted by using a FLUENT CFD code coupled with a user-defined function. The factors related to the flash efficiency, including flashing tank diameter, length, and internal platform height, were simulated and analyzed. Finally, an improved scheme for setting a platform inside the flashing tank was proposed. The simulation results revealed that the improved scheme ensures the sufficient flash of water inside the tank. These finds of the present study can serve as a reliable reference for the design of flashing tank in LT-MED plant.