MILP scheduling model for multipurpose batch processes considering variousintermediate storage policies

MILP (Mixed Integer Linear Programming) scheduling models for non-sequentia l multipurpose batch processes are presented. Operation sequences of produc ts have to be made in each unit differently by considering production route of each product under a given intermediate storage policy to reduce idle t ime of units and to raise the efficiency of the process. We represent the s tarting and finishing time of a task in each unit with two coordinates for a given storage policy. One is based on products, and the other is based on operation sequences. Then, using binary variables and logical constraints, we match the variables used in the two coordinates into one. We suggest MI LP models considering sequence dependent setup times to guarantee the optim ality of the solutions. Two examples are presented to show the effectivenes s of the suggested models.