Blast Furnace Ironmaking Process with Super-High TiO 2 in the Slag: Viscosity and Melting Properties of the Slag
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UCTION
THERE are about 10 billion tons of vanadium titano-magnetite (VTM) in Panzhihua, China, which contains many useful elements such as vanadium and titanium.[1,2] Currently, most of the vanadium titano-magnetite concentrates are used as the main materials for the blast furnace (BF) process in China. Figure 1 shows the BF ironmaking process in Panzhihua, China, using VTM.[3,4] Vanadium can be reduced into hot metal, which is subsequently used to extract vanadium. Titanium exists in the slag phase in the form of oxides, which are difficult to recover economically, and therefore there is still solid waste. At present,[5–7] the
ZHENGDE PANG, XUEWEI LV, YUYANG JIANG, and JIAWEI LING are with the Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials, Chongqing University, China and also with the College of Materials Science and Engineering, Chongqing University, No. 174 Shazheng Street, Shapingba District, Chongqing, 400044, P.R. China. Contact e-mail: [email protected] ZHIMING YAN is with the WMG, University of Warwick, Coventry, CV4 7AL, UK Manuscript submitted 26 August, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
ratio of VTM in the BF is about 65 pct; as a result, the TiO2 in the slag is about 22 to 23 mass pct, which is called BF slag with high TiO2. Further increasing the utilization fraction of V-Ti magnetite ore in the BF burden improves the extraction efficiency of V and Ti in the subsequent process after blast furnace ironmaking. The content of TiO2 in slag increases from 22 to 29 mass pct as the ratio of VTM is increased from 70 to 100 pct. However, it is extremely difficult to increase the TiO2 content in the slag beyond 23 mass pct in long-term practice. The main reason is the formation of Ti(C, N) during the reduction in the BF hearth, resulting in the problem slag foaming and difficult operation conditions.[8–12] Consequently, the core technology when using a smoothing operation BF with a higher TiO2 content involves retarding the reduction of TiO2. In the present study, the BF slag with super-high TiO2 means the TiO2 content varies between 25 and 30 mass pct. The extensive literature shows that the step-by-step reduction of TiO2 to form TiC can be easily performed in the BF, and the key factor is the temperature. This means that a slag zone with a lower liquidus temperature should satisfy the smelting requirement of a higher TiO2 (> 23 mass pct) content BF slag in the hearth. Figure 2 gives the liquid region (1773 K, 1723 K and 1673 K) calculated using the FactSage6.2 thermodynamic
Fig. 1—Process of the blast furnace performed on vanadium titano-magnetite.
Fig. 3—Effect of the MgO/CaO ratio on the liquidus temperature of the CaO-SiO2-14 mass pct Al2O3-MgO-30 mass pct TiO2 slag.
Fig. 2—Liquid region calculated from FactSage6.2 (1773 K, 1723 K and 1673 K) and predicted suitable flow region of the CaO-SiO2-Al2O3-MgO-TiO2 slags.
software (Module: Phase Diagram, Database: FToxide) and predicts suitable flow regions of the CaO-SiO2-Al2O3-MgO-TiO2 slags. The black dot represents the cur
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