Low Temperature Multi Effects Desalination-Mechanical Vapor Compression Powered by Supercritical Organic Rankine Cycle

Abstract

Utilizing low grade heat sources such as geothermal, solar or waste heat has received a high attention in recent years. A lot of research has discussed using Organic Rankine Cycle (ORC) as subcritical or supercritical in power generation. However, very few studies extend their research in utilizing ORC in other applications such as desalination. For reverse osmosis (RO) desalination, which is considered a membrane technology, the use of supercritical-ORC in low grade heat sources is more favorable than subcritical-ORC. Thus, studies of utilizing either subcritical-ORC or supercritical-ORC for thermal desalination that use power and heat from Rankine cycle are rare or have not been done yet. Thermal desalination technologies are dominant for desalination in the Gulf Corporation Countries (GCC) and are getting more focus to treat high concentration feed and provide drinking water due to shortage of clean water in the world. This study proposes a novel system that combines a supercritical-ORC with multi-effect desalination and mechanical vapor compressor (MED-MVC) for desalination using low grade heat sources at temperatures less than 150°C. A numerical model was developed, which was used to conduct performance, exergy and economic analyses under various parameters such as: salinity of the feed, temperature of motive steam and pressure of ORC. The proposed system was compared with different MED combinations with respect to specific energy consumption and unit cost of water produced