A novel configuration for low-grade heat-driven desalination based on cascade MED

Abstract

A novel MED-based desalination system for low-grade heat sources with a temperature between 65 ° C and 90 ° C has been proposed. Low-grade heat-driven desalination systems are of the most important methods for increasing energy efficiency and assisting the environment along with alleviating the water scarcity problem. The new proposed system is known as cascade multi-effect distillation (CMED). It is designed based on multi-step heat extraction from the heat source fluid (HSF). Multi-step heat absorption helps to form two arrays of MED effects and to utilize two boosters to achieve better performance. The advantage of this system is less complexity (for example, lower vapor injection), and improved performance along with reduced electricity consumption in comparison with the most recent MED-based configurations, including flash boosted MED (FB-MED) and distributed boosted MED (DBMED). The results show that the CMED’s production rate is increased on average by 15.5% compared to FB-MED, and up to 7.3% relative to DBMED. The normalized pumping power consumption (NPPC) is dropped by 14.5% and 11.5% on average compared to FB-MED and DBMED, respectively. Also, the specific capital cost is reduced by about 1.15% and 0.80% on average.