Effect of Alumina on the Behavior of V-Rich Spinel Phase in CaO-SiO 2 -FeO t -MgO-Al 2 O 3 -V 2 O 3 -P 2 O 5 Slags at 15
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TRODUCTION
VANADIUM titano-magnetite is an important V-bearing resource. In the current production process, vanadium titano-magnetite is reduced in the ironmaking process, and the reduced vanadium dissolves in the hot metal. For hot metals containing more than 0.2 mass pct vanadium, oxygen is blown to oxidize vanadium to form high-grade vanadium slag. This vanadium slag is used as feedstock to extract vanadium using the salt roasting–water leaching technique. Although most of the vanadium dissolved in the hot metal is oxidized and transferred to the vanadium slag, a small amount of vanadium inevitably remains in the hot metal. When this hot metal is used to make steel, the remaining vanadium is further oxidized, and consequently a type of steelmaking slag bearing vanadium is produced, which may
LIUSHUN WU, CUNJUN QI, JUE WANG, and YUANCHI DONG are with the School of Metallurgical Engineering, Anhui University of Technology, Maanshan 243032, Anhui, P.R. China. BAIJUN YAN is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: [email protected] Manuscript submitted January 20, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
contain approximately 1.0 to 5.0 mass pct V2O5. If this type of V-bearing steelmaking slag is exposed for a long time in a natural environment, the vanadium in the slag will leach out[1,2] and greatly harm the ecosystem.[3–5] Therefore, from an environmental and economic perspective, the vanadium contained in the steelmaking slag must be recovered. However, traditional wet methods, such as the direct leaching[6–8] and roasting–leaching[7,9,10] methods, are limited to a great degree because of the low vanadium grade of the slag. In the pyrometallurgical process, the phosphorus in the V-bearing hot metal is enriched.[11] However, the high phosphorus content makes it difficult to recycle vanadium. Considering that the selective-precipitation method has achieved some progress in the enrichment of valuable elements from complex slag systems, such as titanium[12,13] and phosphorus,[14,15] it was introduced to process the V-bearing steelmaking slag[16–19] for obtaining a V-rich phase without phosphorus. In this process, the occurrence states of vanadium were changed by adjusting the composition and temperature of the slag to form new V-rich mineral phases. The V-rich mineral phases were then separated from other phases to obtain a high-grade vanadium concentrate. To facilitate the separation of V-rich minerals, the magnetic (Fe, Mg)OÆ(Al, Fe, V)2O3 spinel phase[20,21] was proposed as the target mineral. In a
previous study,[22] we investigated the formation of V-rich spinel phase in CaO-SiO2-MgO-FeOt-Al2O3V2O3-P2O5 slags with 2.9 mass pct Al2O3. To form the (Fe, Mg)OÆ(Al, Fe, V)2O3 spinel phase, we found that the basicity of the slag, i.e., the mass ratio of CaO to SiO2, needs to be maintained below 2. Therefore, to form a V-rich spinel mineral in the V-bearing steelmaking slag, a large amount of SiO2
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