Application of Heuristics to Solve Scheduling Problems of Intermediate Transfer Policies in Multiproduct Chemical Batch Processes

Batch processes are considered to be very efficient in producing fine as well as specialty chemicals. The efficiency of batch processes is attributed to the scheduling of various tasks involved in the production of a desired product. A very common purpose of scheduling is to reduce the total completion time of the process and is referred to as makespan. One of the ways to reduce makespan is the selection of a proper production sequence i.e. a sequence in which the raw materials are processed to produce specific products. The determination of such production sequence becomes a time consuming task with increase in the number of products. The complexity further increases when dealing with various transfer policies used for the transfer of product intermediates during the production cycle. Although numerous techniques are available but most of them are based on complex mathematical equations and thus take longer CPU time to solve even for a small batch scheduling problem. Further, the search of the optimal solution is not an easy task when the number of optimal solutions increases with increase in problem size. The motivation behind current work is to reduce the mathematical complexity as well as suggesting some rule based guidelines that could speed up the solution procedure for any batch scheduling problem. A new heuristic approach is developed and applied to various problem sizes in conjunction with mathematical formulations developed in our previous work for various transfer policies. The results so obtained are very promising and shows significant contribution towards the solution of batch scheduling problems with less computational effort.