Mathematical programming formulation for scheduling of batch operations based on nonuniform time discretization

A flexible formulation for handling a wide range of short-term scheduling problems arising in multi-product/multipurpose batch chemical plants is presented. Time is directly used to model events arising in the schedule and thus use of binary variables over periods during which no changes in system state occur is avoided. Batch processes involving a variety of operational complexities can be readily represented. The scheduling problem is formulated as a mixed integer nonlinear program (MINLP). The resulting model can be simplified via exact linearization to yield a mixed integer bilinear program (MIBLP) in which the only nonlinearity arises in the objective function as a product of continuous variables. A preliminary computational comparison is made against a uniform time discretization formulation. (C) 1997 Elsevier Science Ltd.