Sustainable Steelmaking Using Biomass and Waste Oxides (TRP9902)

Abstract

A new process for ironmaking was proposed to employ renewable energy in the form of wood charcoal to produce hot metal. The process was aimed at the market niche of units ranging from 400,000 to 1 million tons of hot metal a year. In the new process, a Rotary Hearth Furnace (RHF) would be combined with a smelter to produce hot metal. This combination was proposed to overcome the technical hurdles of energy generation in smelters and the low productivity of RHFs, and also allow the use of wood charcoal as energy source and reductant. In order to assess the feasibility of the new process, it was necessary to estimate the productivity of the two units involved, the RHF and the smelter. This work concentrated on the development of a productivity model for the RHF able to predict changes in productivity according to the type of carbon and iron oxides used as feed materials. This model was constructed starting with the most fundamental aspect of reduction in composites measuring intrinsic rates of oxidation of different carbons in CO{sub 2}-CO atmospheres and reduction of different oxides in the same atmospheres. After that, a model was constructed considering the interplay of intrinsic kinetics and the transfer of heat to and within pellets such as used in the RHF. Finally, a productivity model for the RHF was developed based on the model developed for a pellet and the differences in heat transfer conditions between the laboratory furnace and the actual RHF. The final model produced for the RHF predicts production rates within 30% of actual plant data reported with coal and indicates that productivity gains as high as 50% could be achieved replacing coal with wood charcoal in the green balls owing to the faster reaction rates achieved with the second carbon. This model also indicates that an increase of less than 5% in total carbon consumption should take place in operations using wood charcoal instead of coal.