Direct Reduction Roasting Process Limonite New Steel Pit

The iron ore resources are rich in our country, but the free-milling iron ore resources aredecreasing, so the refractory iron ore of poor,varieties, and mixed has been to be the centre ofattention.Because of the low-grade and grinding is easy to slime and so on characteristics of thelimonite, it is geared to the refractory iron ore,so it is difficult to increase the iron concentrategrade by using the method of conventional preparation.Now, the limonite ’s relative maturity ofthe main mineral processing technology is reselection,magnetic separation, flotation, magneticseparation-reverse flotation, flocculation-magnetic separation, magnetizing roasting-lowintensity magnetic separation, These process of separating index is about50%-70%iron oreconcentrate grade and50-80%recovery, the effect of separation is not very ideal. Therefore,taking the Tiekeng limonite ore as the research object, the experimengtal method of directPelletization-dirct reduction roasting-magnetic separation was used to reach the aim ofiron-increasing and silicon-reduction in this paper.Total iron grade of Tiekeng limonite ore is low, only38.25%, quartz is the main ganguemineral and it has the less harmful impurities. First, the effect of cruslring strength of pellets wasinvestigated in the experiments of pelletization, then the effect of roasting temperature, roastingtime, coal dosage, outer coal dosage, flux type and dosage, heating way, cooling way, grindingfineness and magnetic field intensity on the indicators of iron concentrate were investigated inthe experiments of direct reduction roasting-magnetic separation. The proposedoptimumconditions were as follows: roasting time of50min, roasting temperature of1150℃, coal dosageof20%, outer coal dosage of0%, rapid heating, natural cooling, etc.And the best effect is CaCO3dosage of5%at adding flux condition. The method of two grinding-two magnetic separationwas adopted. The first grinding fineness of the roasted product was <0.043mm with a proportionof more than80.66%and secondary grinding fineness of the roasted product was <0.02mm witha proportion of more than80.23%, under the above-mentioned the total iron content of90.56%,recovery rate of92.74%could be obtained; the silicon content below2%.The result of the study of the roasting product at different condition by XRD andmicroscope showed that: With the extension of reduction time, particles of iron began to form,merge and grow up, but when the reduction time was too long, it would reduce the index ofmetallic iron,because the particles of iron would be oxidation again and reacted a solid phasewith quartz. Raised the temperature, the particles of iron became bigger and bigger with clearboundary between ferrous mineral particles and impuritise particles, which was help to grindingand mineral processing’s follow-up homework.The addition of CaCO3promoted the reduction of F₂SiO₄, increased the recovery of metallic iron. The pressure ball was helpful to improve directreduction efficiency, reduce fuel consumption, etc.