SEQUENCING INTERMEDIATE PRODUCTS - A PRACTICAL SOLUTION FOR MULTIPURPOSE PRODUCTION SCHEDULING

In the present work, the production scheduling problem in multipurpose batch chemical plants operating under mixed intermediate storage poli cies is submitted to a new practical review leading to simplified and realistic solutions. Customer satisfaction is set as the main problem objective instead of minimization of well-known performance criteria s uch as makespan or flowtime and deviation of resulting production prof ile from desired deliveries is minimised using penalty functions inclu ding costs for stock and delay. The need to synchronise requirements a nd availability of the precise amounts of intermediates and products t o a timetable is achieved by identifying multipurpose schedules as seq uences of integers related to production runs of stable intermediates. Such a dramatic simplification of the problem allows the satisfactory use of stochastic optimization techniques (SA) for the matching of de liveries and due dates.