Decoupling control and dynamic characteristics analysis of strongly coupled Multi-Effect Desalination with Thermal Vapor Compressor system

Abstract

The Multi-Effect Desalination with Thermal Vapor Compression (MED-TVC) represents a highly promising desalination process for integration with variable heat sources, offering a sustainable solution for freshwater production. The effective control of MED-TVC system, however, presents significant challenges attributable to wide operating conditions, strongly coupled parameters, and complex nonlinearities. This paper begins by outlining the working principle of MED-TVC and identifying a model based on open-loop step-response data. Subsequently, a novel control strategy, Feedforward decoupling Active Disturbance Rejection Control (FADRC), is proposed. This approach innovatively combines static feedforward decoupling with dynamic decoupling within an ADRC framework to eliminate interactions between the brine temperature and brine level control loops. A practical tuning procedure for the FADRC is detailed. The proposed strategy is evaluated through a simulation case study, where it demonstrates superiority over two alternative controllers in achieving independent loop control, enhanced dynamic performance, and robust stability. Furthermore, its practical efficacy is confirmed via a field application in a MED-TVC plant with a total freshwater production of 2.5 t/h, highlighting improvements in operational stability, response rapidity, and control accuracy. The successful application underscores the potential of FADRC for improving the stability and efficiency of MED-TVC system and other similarly coupled industrial processes.