Effect of Na₂SO₄ on the Embedding Direct Reduction of Beach Titanomagnetite and the Separation of Titanium and Iron by Magnetic Separation

摘要

A novel process for separating iron and titanium from Indonesian beach titanomagnetite (TTM) concentrates is proposed. This process involves several steps, including mixing the TTM concentrate and additive, pressing the mixture into pellets, embedding direct reduction of the pellets, and magnetic separation. Given that coal and additives are the main factors influencing the coal-based direct reduction of beach TTM, this study employed embedding reduction, where pellets are embedded under the coal to be reduced, and Na_(2)SO_(4) was used as an additive. The best result was obtained when the Na_(2)SO_(4) dosage was 4%, and the direct reduction iron powder (DRI powder) with an iron grade of 94.45%, iron recovery of 85.18%, and TiO_(2) content of 0.44% were obtained. Titanium concentrate assay yielded 40.43% TiO_(2) containing main titanium minerals of ilmenite and ferrous pseudobrookite. The results showed that a suitable Na_(2)SO_(4) addition (4–6%), DRI powder and titanium concentrate presented better iron recovery and TiO_(2) grade as compared without addition, while this advantage disappeared as Na_(2)SO_(4) addition increased (>6%). The characteristics of roasted pellets were analyzed through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Results showed that FeS and nepheline are formed by addition of Na_(2)SO_(4), thereby benefiting the migration and growth of metallic iron particles in the redox system and separation of titanium and iron. While a suitable dosage of Na_(2)SO_(4) could promote porosity and induce a reducing atmosphere, but more liquid phase formed by an excessive Na_(2)SO_(4) was unfavorable and caused expansion of the pellets.