Executive Summary : | The energy demand in the steel sector is dominated by coal and accounts for 42% of carbon emissions in the industrial sector. Shifting from predominantly a coal-based reduction to the gas-based reductions of iron ores, with increasing proportion of H2, is the way forward for India to achieve the goal of decreased carbon emissions. MIDREX, the gas-based reduction unit to produce Direct Reduced Iron (DRI), is finding increasing interest in Indian Steel Sector. To efficiently increase the H2 proportion in input gas, a theoretical model is required for MIDREX which, to the best of the investigator’s knowledge, is hardly available at present for Indian steel industry. The MIDREX is a counter current reactor where iron ore pellets are charged at the top, hot reducing gas is passed through the mid-section and cooling gases are passed at the bottom zone. In this work, countercurrent solid and gas flow, temperature distribution and reaction kinetics in two and three-dimensions will be modeled using openFoam opensource platform. At present, there is no existing solver present in the openFoam software to handle this complex problem. This solver can be later used as the main modeling tool for future development of the whole plant simulations with proper tuning of the relevant parameters. The effect of discrete inlets of preheated reducing gas along the azimuthal directions in three-dimensional model will be explored on the temperature distribution. Iron ore reaction kinetics will be modeled with unreacted shrinking core model or grain models with the multiple reaction front modelling. In cooling zone, the carburization reaction kinetics will be modeled. The reduction reaction of iron ore slows down excessively in the wustite to Iron transformation stage resulting into incomplete metallization, especially with H2. Any unreduced oxide consumes considerable amount of extra energy during the later process in electric arc furnace (EAF). However, there are limited insights available about this stage of iron ore reduction. To explore this phenomenon experimentally, thermo-gravimetric analysis (TGA) will be performed with powdered sample isothermally at the temperature range of 700-1000 ℃ with H2, H2+ CO, CO, with or without carrier gases. The experiments will involve the processing of whole powder particles to wustite by controlling the input gas composition so that solely wusite/Iron transformation kinetics can be studied. Effect of annealing in this preparation step of wustite, existence of any critical iron layer thickness, above which the cracking of the iron layer becomes less probable, the partial pressure of gases at the wustite/iron interface, the initial pore structure on the microstructure of product iron will be explored. The microstructural evolution of product iron will be carried out through SEM or TEM studies. |