Reduction of fine iron ore with circulating fluidized bed

By means of pre-reduction of iron ore fines, productivity of a blast furnace can be increased and iron ore unsuitable for sintering process can be easily used in the blast furnace. As a pre-reduction process a circulating fluidized bed (CFB) has been developed with a pilot plant. The riser of CFB is 550 mm in inside diameter and 10 m in height. The CFB pilot plant processed iron ore of wide size distribution in the feed rate range of 0.5-1.0 t/h. Test result shows that the reduction degree ranges from 60 to 90% at the reduction temperature of 850-900°C with no sticking problem. The degree of gas utilization (the increase of oxidation degree of gas) was 10% at the superficial gas velocity until 10 m/s. The pressure drop in the riser was 30 kPa at the same condition. From the analysis of reduction rate the retention time for reducing iron ore to the reduction degree of 60 and 90% are 20 and 120 rain at 880°C respectively. The productivity at the reduction degree of 60% is expected to be about 6 times higher than that of the reduction degree of 90%.