A real-time optimisation system for reheating furnace fuel gas distribution

The South African iron and steel industry is under immense pressure to remain competitive and reduce the cost of operation. Energy consumption contributes about 20% to the operational costs of an integrated steelmaking facility. 20% of the energy is consumed by the finishing rolling operations. Hot rolling operations are equipped with reheating furnaces that operate on process by-product gases and purchased gases such as natural gas. When a gas supply shortage occurs, which is frequent in the older plants of South Africa, the gas can be supplemented with natural gas. A human operator is responsible for controlling the by-product gases distributed in a complex network throughout the works. Quick reactions are required in this process where changes to the system occur frequently. The operator cannot always distribute the gases optimally based on the energy efficiency of the reheating furnaces. Losses occur that increase the costs of production. In this paper, a methodology has been developed that optimises the energy consumption of reheating furnaces in a network. The model simulates the energy consumption of each furnace under different workloads and the effect of changing fuel supply. These furnace models are configured in a network and used to develop a real-time optimisation system that can optimise the by-product gas distribution to the reheating furnaces for improved cost performance on purchased gases. Implementing the optimisation model on historical data indicated a possible 9% reduction in natural gas. Implementing the real-time optimisation system for a period showed natural gas consumption improvements of up to 13% per day.