Characteristics of dual purpose MSF desalination plants

Abstract

All of the Saudi large MSF plants operate within the context of dual-purpose facilities for the simultaneous production of power and water. Such co-generation arrangement uses either backpressure or extraction condensing turbine. Co-generation cycles which were used till 1982 were employing extraction condensing turbines with a power to water ratio ranging between 10.2 to 17.5 MW/migd. From 1983 onwards backpressure turbines were used in all new co-generation plants. Backpressure turbines give lower power to water ratio (high water demand) and they are also characterized by high thermal efficiencies. They make the best use of low-grade heat that would otherwise be rejected by the power generating plant cycle. This paper aims to study the characteristics of the dual-purpose MSF desalination plants with special reference to the Saudi experience in this field. The challenge that faces these plants is to provide an operation that satisfy the diverse operational requirements imposed by power and water production and yet retain the inherent economic advantages of the dual-purpose concept.