427249 Compact MILP Formulation for Scheduling of Multipurpose Batch Plants: Rigorous Sequencing of Tasks

Monday, November 9, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Esmael Reshid Seid and Thokozani Majozi, School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg, South Africa

In recent years, batch processes have been getting more attention due to their suitability for the production of small volume, high value added products. The flexibility of batch plants allows the production of different products within the same facility which mandates sharing of different types of resources (raw materials, equipment, utilities and manpower). Despite the advantage of batch plants being flexible, they also pose a challenging task to production scheduling. The profitability of these batch plants is highly dependent on the way the production schedule is optimized. Considerable scheduling models have been proposed from the academic research in the last two decades. The research direction has been to improve the existing scheduling models in terms of model size, computational time and optimal objective value in order to effectively apply and solve industrial scale problem. However, there is still a gap for improvement and new efficient model.

This study also has the same objective of developing a better scheduling model that is compact and computationally efficient. The model is rigorous in handling the different intermediate storage policies and unit wait time. Almost the binary variables, continuous variables, constraints and computational time required are reduced by 41%, 15%, 43% and 42% respectively, when compared to the recent rigorous unit-specific event based model for short-term scheduling of batch plants.

Keywords: Scheduling; Multipurpose batch plant; Optimization; MILP

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