Non-isothermal Reduction Kinetics of Iron During Vacuum Carbothermal Reduction of Ilmenite Concentrate
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THE most important primary minerals of titanium are rutile and ilmenite. Only rutile and ilmenite are suitable for titanium production and titanium white industry at present.[1] The utilization of low-grade minerals, such as ilmenite, has attracted increasing attention considering the worldwide decrease in sources of high-grade titanium mineral. Over 90 pct of titanium resources of China are located in Panxi, which account for 35 pct of the world reserves. However, they are mainly complex symbiotic ores.[2] Panzhihua ilmenite concentrate is re-beneficiated from tailing after the first beneficiation. The content of TiO2 is in the range 45.5 to 48.5 pct, that of iron is 30.0 to 33.5 pct, and that of non-ferrous impurities is 11.0 to 12.0 pct.[3] The production process of Ti-rich materials is mainly divided into hydrometallurgy and pyrometallurgy. Hydrometallurgy mainly includes direct acid leaching[4,5] and reduction rust,[6] and the pyrometallurgy mainly includes electric smelting[7] and selective chlorination.[8] In the experiments of Lv et al.,[9] an economical and clean method for semi-molten reduction followed by magnetic separation to produce titanium slag from HUANG RUN, LV XIAODONG, WU QINGHUI, WU QINZHI, and ZHANG JINZHU are with the School of Materials and Metallurgy, GuiZhou University, Guiyang 550000, China. Contact e-mail: [email protected] Manuscript submitted July 5, 2018.
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Panzhihua ilmenite concentrate was presented. In study of Zhang et al.,[10] a new process named vacuum separation was found to produce high-grade TiO2 materials. The smelting of titanium slag by electric furnace has become the main technical means for preparing titanium-rich materials from ilmenite because of the research situation and the properties of raw materials. Nevertheless, the removal of non-ferrous impurities (Mg, Ca) cannot be achieved, which can influence the production of sponge titanium or titanium white by chlorination. The effective separation of slag and iron in the process of smelting titanium slag in electric furnace is the key, and the selective reduction of ilmenite is the basis. Many studies have been conducted on the mechanism and kinetics of the reduction of different ilmenites in recent years. Dewan et al.[11] studied the process of carbothermal reduction of ilmenite and considered that the reduction process could be divided into two main stages: FeTiO3 was reduced to Fe and TiO2 and TiO2 to TiCxOy. Li et al.[12] investigated the reduction process of Panzhihua ilmenite and found that the reduction and decomposition of ilmenite mainly occurred below 1273 K (1000 °C). Fe3O4 continued to transform to metal iron, and TiO2 was reduced to Ti3O5 with increasing temperature. Welham et al.[13] observed that ilmenite was rapidly reduced to Fe and TiO2, and then TiO2 was reduced to a series of low-valence oxide TinO2n1. Ti3O5 was finally formed. The existence of Fe was considered to be beneficial to the reduction of Ti3O5. Gou et al.[14] conducted an experiment on the carbotherma
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