Direct reduction of pellets through hydrogen: Experimental and model behaviour

This paper presents the hydrogen reduction behaviour of industrial pellets designed for the efficient hydrogen based direct reduction. The pellets were provided with very low non ferrous oxides percentage (0.52 of basicity index) and with the absence on TiO2 oxides. The pellets measured diameters in the range 1.14-1.72 cm and were characterized in terms of porosity, pores size, tortuosity and compression strength. The pellets were reduced in hydrogen atmosphere in a laboratory shaft furnace in the temperature ranges of 600-1200 degrees C at the pressures of 1 and 5 bar. The pellets' reduction behaviour was analysed in terms of time to reduction, rate of reduction and kinetics constant. All the obtained results were analysed through the employment of a commercial multiobjective optimization tool (modeFrontier) in order to precisely define the effect of each single parameter on the pellets' reduction. It was also defined the effect of the ongoing reduction rate of the final metallization of the starting iron oxides.