Performance test of a sea water multi-stage flash distillation plant: Case study

Abstract

Multi-Stage-Flash (MSF) Distillation is a large scale sea water desalination plants that are widely used in Gulf area. Most installations of MSF plants are operated in cogeneration with a power plant. Also, MSF plants can be combined with other desalination technologies such as Nano filtration and Reverse osmosis (RO) in new installation. However, the new MSF plants are recommended, where large amounts of cheap or waste energy are available (e.g. conventional power plants). Also, the plant location is playing an important role for economic operation due to cold or hot weather conditions.The present study is applied on the seawater multi-stage flash (MSF) desalination plant that is currently under operation in Al-Khafji operations plant located in Saudi Arabia (KSA). The plant contains 20 evaporator stages at capacity of 600,000 gallon per day (GPD). The presented operating data has been collected during a visit of the plant. Theobjectiveis to presentfieldresults of this MSF plant operation in order to measure and evaluate the performance at 70% and 100% capacity during summer (case-1) and winter (case-2) operation. Then, the plant overall performance indicators are presented to compare between the studied two cases in terms of specific cooling water flowrates and performance ratio. Finally, the seasonal performance variation of the plant is included. The results showed that, for the same plant output, the main cooling water flow rates is decreased from 47.1% to 20.1% for case-1 and case-2 respectively, which in turns directly reduces the pumping power by the same ratio. Consequently, running the large scale thermal desalination MSF plant in cold regions is more economic than hot regions for pumping power energy saving considerations. This is to be considered in future large scale desalination plants.