Hybrid reverse multi-stage flash and multi-effect evaporator systems powered by low grade energy for water desalination

Abstract

Integration of a reversal multistage flash (RVMSF) and multi-effect evaporators (MEE) desalination technologies driven by waste heat source is studied. The warm RVMSF reject brine is used as a sensible heat source for the MEE process. Three different configurations are compared and proved to outperform the standalone MSFRV system. Based on the best hybrid structure, 69 %, 67 %, and 287 % enhancement in the recovery ratio, the specific energy consumption (SEC), and the gain output ratio (GOR), respectively over the standard RVMSF process were observed. However, this was achieved at the expense of a 46 % increase in the specific heat transfer area. The recovery ratio, specific area, SEC, and GOR were found to improve with primary feed temperature, and temperature drop of the sensible heat powering the MEE. However, for a fixed number of effects, the full leverage of the supplied energy is limited causing variable or slow progress of the key performance indicators. Increasing the number of MEE effects had a positive effect on the performance causing proportional growth of the recovery ratio and GOR. A maximum value of 20.2 % for the recovery ratio and 5.7 for the GOR was observed when ten effects were used in the MEE system.