Production Scheduling For Steelmaking Continuous Casting Via Unit-specific Event Based Continuous Time Representation

Steelmaking and continuous casting (SCC) production scheduling plays animportant role in iron and steel company because it transfers the molten iron into slabswith the predefined chemical components. Optimal SCC scheduling can improvemachine utilization, reduce material and energy consumption, ensure orders’ due dateand cut down production costs. Therefore, it is necessary and significant to develop anoptimal formulation and improve the efficiency and effe ctiveness of SCC productionscheduling.In this paper, a novel unit-specific event-based continuous-time mixed-integerlinear optimization model based on ladles other than casts is proposed to solve SCCproduction scheduling problem.Discrete and continuous time representation methods are described in detail.Deduce the unit-specific event-based continuous-time representation applied in SCCscheduling problem.The production process and characteristics of SCC production scheduling problemand existing problems are analyzed respectively.Then rolling horizon method integrated heuristic is proposed to decompose thelarge scale problem into several smaller horizons in medium-term scheduling stage.Each small horizon is treated as a short-term scheduling.A novel mathematical model based on ladles other than casts is proposed inshort-term scheduling stage. This model uses unit-specific event-based continuous-timemixed-integer linear optimization technology and consists of two parts,(1) to allocateladles to continuous casters with the objective of balancing the workload among themand (2) to allocate and sequence ladles under the constraint of caster allocation.Industrial cases are employed to demonstrate the efficiency and effectiveness of theproposed model and the rolling horizon method. Comparative studies with Li et al.(2012) are performed and it is shown that the proposed optimization model results inimprovements.