A reactive optimization strategy for the simultaneous planning, scheduling and control of short-period continuous reactors

The efficient and economic operation of processing systems is normally addressed within a planning, scheduling and control framework. Due to its complexity, these activities are commonly approached in a decoupled rather than in a simultaneous manner. Although the decoupled approach leads to a computationally tractable problem, the solution of such a problem can result in a suboptimal solution because interaction among planning, scheduling and control activities are neglected. Even when the optimal simultaneous solution of this problem can result in large scale optimization problems, such a solution can represent economical advantages making feasible its computation using optimization decomposition and/or few operating scenarios. After reducing the complexity of the optimal simultaneous deterministic solution, it becomes feasible to take into account the effect of model and process uncertainties on the quality of the solution. In this work we will consider that changes in plant product demands hit the process once the process is already under continuous operation. Therefore, a reactive strategy is proposed to meet the new product demands. Based on an optimization formulation for handling the simultaneous planning, scheduling, and control problem of continuous reactors, we propose a heuristic strategy for dealing with unexpected events that may appear during operation of a plant. Such strategy consists of the rescheduling of the products that remain to be manufactured after the given disturbance hits the process. Such reactive strategy for dealing with planning, scheduling and control problems under unforeseen events is tested using two continuous chemical reaction systems.