Optimal design of batch plants with uncertain demands considering switch over of operating modes of parallel units

This paper addresses the problem of the optimal design of batch plants with uncertain demands of products' quantities. A conceptual two-stage stochastic programming problem is formulated with an objective function containing investment costs and expected revenues from products. With the proposed formulation, the mode of operation of parallel units could be optimized so that, for different products, the operation of parallel units may take a different mode (i.e., in-phase or out-of-phase). The original formulation is transformed into different forms either for multiproduct and multipurpose batch plants. A hybrid algorithm for solving the problems is developed. Compared with previous work where the operating mode of parallel units was considered to be fixed during operation, more economic optimality is obtained.