Modeling multistage flash desalination plants

Multistage flash (MSF) desalination plants are among the major sources of potable water in the world, in particular in the Arab Gulf area [1]. These are very large, complex and expensive plants, in which large amounts of seawater and energy are consumed. Accordingly, big quantities of concentrated brine are disposed of after the desalination treatment. These characteristics of MSF plants make issues such as optimization of the operation and minimization of the corresponding environmental impact of the greatest importance. To the aim of addressing all these aspects, mathematical models provide a very useful tool. This work describes a steady-state mathematical model developed to analyze the MSF desalination process. It is based on a detailed physico-chemical representation of the process, including all the fundamental elementary phenomena. In particular, the model accounts for the geometry of the stages, the variation of the physical properties of water with temperature and salinity, the different non-idealities involved in the process, the mechanism of heat transfer and the role of fouling. The developed model allows to analyze the role of operating and design variables in determining the process performances in terms of steady-state behavior. These information are used not only for design purposes, but also to support the development of a dynamical model through which the time-dependent behavior of the plant can be studied.