Resource-Task Network Approach to Simultaneous Scheduling and Water Minimization of Batch Plants

This paper presents a mathematical model for simultaneous scheduling and water minimization in multipurpose batch plants. The scheduling framework is based on the Resource-Task Network, with the objective function that represents the profit taking into account the net income from production and water-related costs. Because of the bilinear terms appearing in the mass balance equations, the overall formulation is a mixed-integer nonlinear program, which is generally more difficult to solve than a mixed-integer linear program or a nonlinear program. A solution strategy that involves relaxation linearization is therefore developed to facilitate the computation. Two literature examples are used to illustrate the proposed approach.