Stochastic evaluation and optimization of flexibility in multiproduct batch plants

This paper deals with the problem of evaluating and optimizing a stochastic measure that integrates flexibility and reliability in multiproduct batch plants. It is assumed that uncertainties in the product demands are given in terms of statistical distributions, and that expected failure rates of the equipment are given in terms of discrete probabilities. Based on recent work by the authors (Straub and Grossmann, 1989), an efficient computational method is proposed to evaluate the expected stochastic flexibility in multiproduct batch plants. It is also shown that this method can be incorporated in the optimization for determining the sizes and parallel equipment that maximize the expected stochastic flexibility under a capital investment constraint. By varying the specification of the latter, trade-offs can be established between investment cost and flexibility.