Disturbance rejection control for multiple-effect falling-film evaporator based on disturbance observer

The multiple-effect falling-film evaporator (MEFFE), as a widely used process in industry, is usually affected by strong disturbances, which make it very difficult to control. Several control strategies have been applied to MEFFE; however, most of them did not focus on the disturbance rejection, which may lead to poor control performance when disturbances occur. Although model predictive control (MPC) shows the ability to decouple multivariable and control complex processes, it rejects disturbances merely through feedback regulation and does not deal with disturbances directly. To improve disturbance rejection in MEFFE, a control scheme based on MPC and disturbance observer is proposed in this paper. The scheme combines a feedforward compensation part-based on disturbance observer and a feedback regulation part using MPC. The performance of disturbance rejection is analysed in both a nominal case and a model mismatch case. The results of simulation illustrate that the proposed method obtained remarkable superiority in disturbance rejection compared with the MPC method in MEFFE control.