Fuzzy TBT control of multi-stage flash desalination plants

The paper describes the application of fuzzy algorithms to the control of top brine temperature (TBT) of multi-stage flash (MSF) seawater desalination plants. A linearized model of a six inputs and six outputs 18-stage MSF plant is considered in this study. The transfer function matrix of this model is subjected to interaction between the loops. The design of fuzzy logic controller (FLC) for one of the important loops, namely the TBT loop is considered in detail. A set of fuzzy rules that make the controller look like a proportional-plus-derivative controller (PD-like FLC) is obtained and applied to a first order plus dead time approximation of the plant model. In order to improve the performance, an integration effect is added to the output of the PD-like FLC to produce PID-like FLC. A tuned version of the latter controller has been applied to the full plant model in its nonparametric form. The fuzzy controller was found to give good results compared to those obtained from the existing conventional controllers