Sustainable development of primary steelmaking under novel blast furnace operation and injection of different reducing agents

This paper presents a numerical study of economics and environmental impact of an integrated steelmaking plant, using surrogate, empirical and shortcut models based on mass and energy balance equations for the unit operations. In addition to the steelmaking processes, chemical processes such as pressure/temperature swing adsorption, membrane, chemical absorption technologies are included for gas treatment. A methanol plant integrated with a combined heat and power plant forms a polygeneration system that utilizes energy and gases of the site. The overall model has been applied using mathematical programming to find an optimal design and operation of the integrated plant for an economic objective under several development stages of the technology. New concepts studied are blast furnace operation with different degrees of top gas recycling and oxygen enrichment of the blast to hill oxygen blast furnace. Coke in the process may be partially replaced with other carbon carriers. The system is optimized by maximizing the net present value, which includes (i)nvestment costs for the new unit processes as well as costs of feed materials, CO2 emission and sequestration, operation costs and credit for products produced. The effect of using different fuels such as oil, natural gas, pulverized coal coke oven gas, charcoal and biomass is studied, particularly focusing on biomass torrefaction and the effect of integration on arising reductant in steelmaking to reduce emissions from the system. The effects of steel plant capacity on the optimal choice of carbon carriers are also studied. It is demonstrated that it is possible to decrease the specific CO2 emissions of primary steelmaking from fossil fuels from 1.6 t of CO2 to a level of 0.75-1.0 t and further by more than 50% through the integration of biofuels in considered scenarios.