Advance control scheme for Desalination Plant

The multistage flash desalination (msf) process is used to separate brine from sea water and provide distilled water. The factors that determine the performance of the plant (distillate produced) depends on the output temperature of the brine heater which is known as top brine temperature.Single loop controllers are usually used to control top brine temperature. Control of top brine temperature of MSF plants is a multivariable control problem, due to interaction between other variables like, brine inlet flow to the brine heater, brine heater level, brine concentration etc., the use of simple PID controllers cannot cope with the compound interactions with other variables which affects the top brine temperature. Hence it is necessary to have dependable model of the plant behavior to account for the interaction between the controlled and manipulated variables. For this purpose, a non-linear dynamic model was developed for the MSF plant with multi variable interaction approach. Simulation studies were carried out to maintain top brine temperature by varying brine flow and brine heater level. A feed forward controller was developed and the performance was compared with the conventional PID controller. The merits of the proposed scheme were highlighted. [19],[20],[21]