Optimal design of batch-storage network under sporadic operating time loss

The purpose of this study is to find the analytic solution of determining the optimal capacity(lot-size) of batch-storage network to meet the finished product demand under periodic or sporadic operating time losses. Batch processes are bound to random but infrequent operating time losses. Two common remedies for these failures are duplicating another process or increasing process and storage capacity, which are very costly. An optimization model minimizing total cost composed of setup and inventory holding costs as well as the capital costs of constructing processes and storage units is pursued with the framework of batch-storage network of which flows are susceptible to periodic or sporadic operating time losses. The superstructure of the plant consists of a network of serially and/or parallel interlinked batch processes and storage units. The processes transform a set of feedstock materials into another set of products with constant conversion factors. A novel production and inventory analysis method, PSW(Periodic Square Wave) model, is applied. The advantage of PSW model comes from the fact that the model provides a set of simple analytic solution in spite of realistic description of the material flow between processes and storage units. The resulting simple analytic solution can greatly enhance the proper and quick investment decision at the early plant design stage confronted with diverse economic situations.