Economic assessment of options for biomass pretreatment and use in the blast furnace

The steel industry still strongly relies on fossil sources of reductants and energy and a considerable part of the global carbon dioxide emissions therefore derives from this industrial sector. Plausible remedies to reduce the emissions are to minimize raw material use and to shift to using renewable energy sources. This paper investigates computationally the options of using biomass as an auxiliary reductant in the blast furnace, and the required pre-processing steps, focusing on energy use and process economics. In order to evaluate the economic feasibility, the problem is tackled as a process optimization task, minimizing the operation costs under different biomass preheating strategies. The paper provides a comparison between two preheating concepts, namely utilization of heat from hot stove flue gases or from combustion of blast furnace top gas. The use of hot stove flue gases reduces the annual operating costs of the preheating by about 0.5 M€ for a plant with a yearly steel production of 1.4 Mt.