Robust QFT-based TBT control of MSF desalination plants

Scarcity of water resources along with population increase, industrialization, and agricultural expansion in many regions of the world mandates the use of modern technology to supply the increasing demands for potable water. Due to the complexity and large-scale nature of MSF plants, improving their reliability of operation under continuous and heavy loads while maintaining their efficiency compared to other well known processes has not been studied thoroughly. However, there have been some simple preliminary efforts based on limited static simulation and classical dynamic performance cases. Recently, some rigorous control and automation applications of MSF plants have been treated in the literature which showed some promising results in the cultivation of modern control techniques to the problem. In this work the recently developed robust quantitative feedback theory (QFT) control technique is introduced and applied to the design of robust controllers for the top brine heater temperature (TBT) loop of large MSF plants. This paper focuses on the design of robust linear controllers for the regulation of TBT of large MSF desalination plants using the QFT approach. The particular Ii-stage linearized model at the Abu-Dhabi Um-Annar plant was used as a test system. The robust controller obtained has considerable advantages over conventional PID controllers in that it can handle plant parametric uncertainties due to disturbances or modeling errors.