Roasting-Magnetic Separation And Direct Reduction Of A Refractory Oolitic-Hematite Ore

In this paper,roasting-magnetic separation and direct reduction methods were used to treat an oolitic-hematite ore in the laboratory conditions to produce magnetite concentrate and sponge iron respectively.And this research will be of significance in the rational and effective utilization of the refractory oolitic-hematite ore.The influences of reduction time,temperature and reductant amount were investigated and designed fractional factorial experiment L9(3⁴),the result showed that the descending order of the influences to the roasting-magnetic separation was temperature,time and reductant amount.The single factor experiments showed the optimum experimental conditions depend on the following things.The temperature of roasting is at 850℃for 45 minutes, mixture ratio of ore and reducing agent is 50:2.5,and the grinding size is 93% -200 mesh before magnetite separation.Under these conditions,a magnetite concentrate grading 61%Fe with recovery 96%can be obtained.The Fe-O equilibrium chart and XRD analysis showed that some of magnetite oxidized toγ-Fe₂O₃ under the cooling process. Using the oolitic-hematite ore to produce the sponge iron,the optimum experimental conditions rely to many things.The reduction temperature is at 1050℃for 5.0 hours,the concentric ring should be used,the anthracite should be used as reducing agent,and CaCO₃ as aerification accelerant and desulfurizer, then the mixture ratio of ore,reducing agent and additive is 50:60:8,and the grinding size is 70%-400 mesh.Under the optimum experimental conditions, sponge iron containing 89%Fe with metallization 90%and recovery 85%can be produced.The experiments were characterized by thermodynamic analysis, elemental analysis and energy spectrum analysis,the results show that reduction process is Fe₂O₃→Fe₃O₄→FeO→Fe.