Sliding mode control of vertical double wall dividing-wall columns

Since a multi-component distillation system has more complex process nonlinearities and time delays than a traditional three-column system, sliding mode control (SMC) is often adopted for multi-component systems. In this paper, a new type of dividing-wall column, called the vertical double-wall dividing-wall column (VDWDWC), is proposed for the separation of quaternary systems. This column has the potential for both higher separation efficiencies and lower equipment costs than the traditional three-column sequence. Therefore, SMC was adopted for the multivariable VDWDWC system and the Smith hysteresis compensation is added to reduce the impact of chattering. The results revealed that the settling time, the oscillations, and steady-state errors of the SMC controller were less than those of the PID controller. Finally, optimal parameters of the SMC controller were obtained by response surface methodology. These parameters reduced the overshoot of the controller, further indicating that SMC could control the VDWDWC system better.