Mechanism Of Separating Iron And Titanium From Beach Titanomagnetite By Direct Reduction-magnetic Separation

The beach titanomagnetite is characterized by high abundance and low cost on mining and mineral processing. However, the concentrates with low Fe grade and high TiO2 content are obtained by current methods. These concentrates are difficult for smelting, resulting in a reduced quality of iron ore and waste of titanium resources.Previous studies show that coal-based direct reduction followed by magnetic separation is the most effective method to achieve titanium and iron separation from beach titanomagnetite. But there are still such problems as poor effect on the separation of titanium and iron and ambiguous mechainism of separation. To solve these problems, a more detailed study about coal-based direct reduction followed by magnetic separation of beach titanomagnetite is investigated in this thesis.The titanomagnetite ore used in the thesis was obtained from the Indonesian coasta. The ore had Fe and TiO2 contents of 51.85mass% and 11.33mass%, respectively. Coal-based direct reduction followed by magnetic separation was used to separate iron and titanium. The dosages and types of coal and additives, reduction time, and reduction temperature were investigated.The reduced ore with best result was obtained when the reductant dosage of Ningxia bitumite A was 20 mass%, the additive dosage of calcium fluoride was 10 mass%, reduction temperature was 1250℃, reduction time was 60min, and the reduced ore was treated by two stage of grinding-magnetic separation. And then the DRI with an iron grade of 91.80 mass%, iron recovery of 88.52 mass%, and TiO2 content of 0.46 mass% was obtained. Titanium product with TiO2 grade of 24.05 mass%and TiO2 recovery of 97.97 mass% was obtained.The mechanisms of coal types and additives in titanium and iron separation from beach titanomagnetite by magnetic separation have been ascertained by XRD analysis and SEM-EDS analysis. The results showed that there are two reasons for the poor effect on the separation of titanium and iron when coal added individually. One reason was that armalcolite in the roasted ore was hard to reduced, and the other reason was that the size of metallic iron particles was small, and it was hard to achieve the liberationof iron. Therefore, the additives were the key to achieve the separation of titanium and iron. According the studies of additives, the results showed that sodium carbonate, sodium sulfate and calcium fluoride could promote the separation of titanium and iron, but the effect of calcium fluoride was best. All of the additives were conducive to the reduction of armalcolite and the growth of metallic iron particles, and then promoted the separation of iron and titanium. Sodium carbonate and sodium sulfate were beneficial to forming the low-melting point silicate minerals in reducing atmosphere. Meanwhile, adding sodium sulfate could form low-melting point of Fe-FeS solid solution in the redox system, which could be enriched in the surface of metallic iron particle and decrease the surface tension of metallic particles. The mechanism of calcium fluoride was that calcium fluoride could decrease the melting point of the redox system, which was beneficial to generate more liquid phase.