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.