Steelmaking-Continuous Casting Scheduling Using a Hybrid Meta-heuristic (Case Study: Khoozestan Steel Complex)

In this paper, Steel-making Continuous Casting (SCC) scheduling problem is investigated. The scheduling of SCC processes is of major importance in steel industries. Since it is often a bottleneck in steel production, optimal scheduling of it can minimize production cost and increase profit notably. This problem is a specific case of hybrid flow shop scheduling problem accompanied by technological constraints of steel-making and hence classic optimization methods fail to obtain an optimal solution for a real life problem over a suitable time. In this paper, a meta-heuristic algorithm based on an Ant colony algorithm (ACO) which is accompanied with a heuristic timing algorithm is developed. In the proposed algorithm the resource assignment and sequencing is determined with ACO and the timing of jobs is determined using a heuristic forward-backward algorithm. Considering the real constraints in the problem definition, designing a heuristic timing algorithm, embedding the proposed timing algorithm in ACO framework and a novel design of ACO algorithm in pheromone matrix and heuristic information are the main features of this paper. The proposed algorithm is implemented in Khuzestan steel complex and the efficiency of it is compared with a heuristic algorithm of commercial scheduling software which is used in Mobarakeh Steel Company. Numerical results show that the average percent of improvement is about 65% in a limited scheduling time.