Steelmaking process has significant amount of dependencies around the movement and storage of hot metal and steel across various units like the Blast Furnace (BF), the Basic Oxygen Furnace (BOF), the Ladle Refining Furnace (LRF), the Vacuum Degassing (VD) unit and the Continuous Caster. For maximum productivity and synchronization of production across units, the logistics, routing and scheduling of equipments like cranes, ladle cars, hot metal ladles, steel ladles etc. has to be appropriately designed such that congestions,interferences coupled with process and cycle time variations, do not limit the end-to-end production and also delays/stoppages are minimized to prevent blockages or idle times at the production units. Additionally, equipment redesign and addition of processing facilities may be required to optimize the end-to-end operation. This paper presents how steelmaking throughput improvement study using simulation helped to identify the bottlenecks causing capacity loss and experiment with options to redesign the system by suggesting mechanisms for improvement and additional facilities and logistical resources.
From a unit optimization perspective, it is essential that the BOF does not have any wait time other than the preparation time. Liquid steel is moved to the casters from the BOF via LRF and for some grades VD, such that the heat sequences for different grades are maintained while maximizing the utilization of the casters. The simulation model of the steel-melting-shop unit included all these elements and constraints to reflect the behaviour of the unit in operation.
Based on the objective of maintaining the sequence continuity in the casters while maximizing its utilization, our simulation model helped discover the bottleneck due to BOF delays and the number of existing LRFs. Redesigning and simulating again yielded the changes in BOF, optimal number of LRF units, the optimal number of hot metal ladles and steel ladles in active circulation and also ensured maximum possible capacity utilization and throughput in the melt shop.