Hybrid desalting systems

Abstract

Currently, most large scale seawater desalting complexes are dual-purpose Multi-Stage Flash (MSF) plants producing both power and desalinated water. These plants produce high purity distilled water and also provide excess electrical power for sale at a typical ratio of 10 MWe power per 1 million gallon per day (MGD) of water. In the hybrid MSF/RO desalination power process, a seawater Reverse Osmosis (RO) plant is combined with either a new or existing dual purpose MSF/power plant with the following advantages: 1. The capital cost of the combined RO-MSF plant can be reduced. 2. A common, considerably smaller seawater intake can be used, in view of the smaller feedwater requirements for RO plants. 3. Product waters from the RO and MSF plants are blended to obtain suitable product water quality. Taking advantage of the fact that the MSF product typically exceeds potable water specifications, the product water specification in the RO system can thereby be reduced. 4. A single stage RO process can be used and the RO membrane life can be extended because of the reduced product water specification. 5. Electric power production from the MSF plant can be efficiently utilized in the RO plant, thereby reducing net export power production. 6. By blending with RO product water, the temperature of the MSF product water is reduced.