Optimization of Midrex direct reduced iron use in ore-based steelmaking

Iron and steel industry contributes by more than 5% to the global anthropogenic CO2 emissions, so new ways to reduce the emissions in this industrial sector must be found. In order to facilitate a transition to more sustainable production concepts, economic factors must be considered. The potential of using direct reduced iron from the Midrex process, based on shaft furnace technology, as a partial substitute of pellets in a blast furnace was studied in the paper. Mathematical models of the different operations in a steel plant, including the shaft furnace, form the basis of the model of the system, which was optimized by non-linear programming with respect to costs. The main objective was to analyze the prerequisites for an economically feasible operation of a steel plant integrated with a direct reduction plant under different raw material prices and varying costs of CO2 emission allowances. The results illustrate the conditions under which it would be beneficiary in a steel plant to integrate the shaft furnace in the operations. The implications of the integration on the overall CO2 emissions of the plant are also discussed.