JOB SCHEDULING IN PETROCHEMICAL PRODUCTION - 2-STAGE PROCESSING WITH FINITE INTERMEDIATE STORAGE

Abstract

In the following paper a new heuristic for product scheduling in a semicontinuous production environment is presented. A two-stage processing structure with a finite number of processors at each stage is assumed wherein intermediate tank storage of limited capacity exists between stages. Product output consists of both simple final products and blends. The objective in scheduling is to achieve as small a makespan as possible-that is, to produce a schedule with near-optimum throughput. Scheduling techniques for related applications tend to position jobs as early as possible in the schedule horizon with the result of producing high resource utilization near the beginning of the schedule and a significant drop in resorce utilization towards the schedule's end. The heuristic method herein starts with an initial schedule which is to be modified through a balancing of the use of available resources, this being accomplished by the identification and repositioning of sets of critical jobs. Evaluation of results from a battery of test problems suggests that notable reductions in schedule makespans can be achieved through use of the strategy described.