Model-based control of multi-unit systems under partial shutdown conditions

A systematic control strategy is proposed for the optimal operation of multi-unit systems undergoing a partial shutdown. The strategy entails manipulating the degrees-of-freedom available during and after a shutdown such that production is restored in a cost-optimal fashion while meeting all safety and operational constraints. In this work, we investigate the coordination of buffer tanks, production rates and recycle streams during a partial shutdown. The problem is cast as a nonlinear dynamic optimization problem. Disturbances are handled using a nonlinear predictive controller that is explicitly aware of shutdown events.