Effective technique for scheduling in multipurpose batch plants

Several scheduling techniques exist in literature based on either even or uneven discretizations of the time horizon. The latter are commonly referred to as continuous time representation due to their exactness in handling time. Over the years, most work in the area of batch process scheduling has adopted the continuous time representation over even discretization of time. This choice is attributable to the fact that methods based on continuous time representation tend to result in much fewer binary variables compared to even discretization of time. Continuous time formulations are also divided into unit specific and global time point representations. The models based on unit-specific time points have shown better solution efficiency by reducing the number of time points and problem size. In this chapter, novel scheduling techniques based on unit-specific time point continuous time representation are presented. The proposed models allow nonsimultaneous material transfer into a unit. Nonsimultaneous transfer is encountered when a task requires more than one intermediate state. In this situation, it is possible for one state to be transferred and stored in a unit that is dedicated to processing it and wait for a while for the other intermediates to come together to commence the task. This approach gives a better schedule as compared to most published formulations.