A novel process to prepare high-titanium slag by carbothermic reduction of pre-oxidized ilmenite concentrate with the addition of Na2SO4

In this paper, a novel process was studied for the recovery of iron and titanium from ilmenite concentrate. The ilmenite powders first underwent an oxidation pretreatment and were reduced isothermally at 1350–1450 °C by graphite with the addition of Na₂SO₄. The influence of temperature, C/O molar ratio and the dosage of the added Na₂SO₄ on the metallization ratio, phase transformation and titanium grade were studied. The results demonstrated that Na₂SO₄ not only significantly promotes the aggregation and growth of metallic iron-grain particles but also enhances the reduction ability. Under the promotion of added Na₂SO₄, the highest metallization ratio reached 94%, and the theoretical calculation of the highest grade of titanium dioxide is approximately 75%. The Na₂SO₄ additive decreases the melting point of the slag and metal, resulting in the effect of semi-melting reduction. The carbothermic reduction order of phase transitions of pre-oxidized ilmenite concentrate was also discussed.