Feedforward-feedback control of an industrial multicomponent distillation column

The problem of regulating the distillate impurity content in a two-feed (paraffin-olefin) industrial multicomponent distillation column (iso-normal butane splitter) by manipulating the heat duty according to olefin-to-total feedflow load disturbance and tray temperature measurements is addressed. First, the detailed model-based nonlinear state-feedback robust control problem is addressed, identifying the solvability conditions and attainable closed-loop behavior. Then, the behavior of this controller is recovered with an output feedback PI temperature controller with dynamic feedforward setpoint compensation and antiwindup protection. The proposed approach is illustrated and tested through numerical simulations with a detailed model calibrated with industrial data, establishing the feasibility of improving the existing control scheme with PI temperature control plus manual setpoint compensation.