Abstract
Steady state simulation of multistage flash desalination plants involved the solution of several hundreds of non-linear equations. Such equations were interdependent but sparse in nature with iterative methods used to solve the non-linear problem. An efficient and reliable solution method was developed in which, following delinearization, the equations were decomposed into subsets grouped by type rather than by stage. The enthalpy balance equations were formulated into a tridiagonal matrix form solved by the Thomas algorithm. This approach combined stability, rapid convergence and modest requirements for computer time and storage compared to the traditional stage-to-stage method. Both brine recycle and once-through type plants were simulated for different operating conditions, thus extending the application of the algorithm. The development of linearized equations was discussed with full documentation of all physical property correlations. A numerical example was given using data from the Al Khobar plant in Saudi Arabia.