Roles of SiO 2 Additive on Preparation of Ferrotitanium from Ilmenite Concentrate by Electrochemical Reduction in CaCl 2
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https://doi.org/10.1007/s11837-020-04366-3 Ó 2020 The Minerals, Metals & Materials Society
ELECTROMETALLURGICAL PROCESSING
Roles of SiO2 Additive on Preparation of Ferrotitanium from Ilmenite Concentrate by Electrochemical Reduction in CaCl2 Molten Salt GANGHUA AI,1 YIXIN HUA,1,2 CUNYING XU,1 JIAN LI,1 YAN LI,1 and JUANJIAN RU1,3,4 1.—Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China. 2.—e-mail: [email protected]. 3.—e-mail: rujuanjian@ foxmail.com. 4.—e-mail: [email protected]
The effect of the content of an SiO2 additive on the electrochemical reduction of ilmenite concentrate to prepare ferrotitanium is investigated in CaCl2 molten salt. A thermodynamic analysis of the Ti-Fe system and possible reactions has been carried out, and it demonstrated that SiO2 and FeTiO3 can be readily reduced to Si and intermediates (Fe and CaTiO3), respectively. The experimental results demonstrated that the optimal molar ratio of Ti:Fe:Si in the cathode mixtures is 1.2:1:0.2. The porous ferrotitanium with uniform particle sizes were successfully obtained by electrolysis at 1173 K with a cell voltage of 3.2 V for 2 h. The SiO2 additive plays an important role during the formation process of ferrotitanium, which is first reduced to Si and then serves as a reductant to catalyze CaTiO3 and Fe to form FeTi alloys.
INTRODUCTION Ferrotitanium, one of the best ferroalloys, has been widely employed as hydrogen storage material or has served as a deoxidizer in the steel-making industry. Generally, ferrotitanium is produced either by aluminothermic reduction of ilmenite concentrate as well as from titanium slag, or by re-melting iron and titanium scraps together at high temperatures.1,2 However, these two methods have obvious disadvantages, such as high residual oxygen content, high impurities in products, and high energy consumption.3,4 In recent decades, many efforts have been made to modify the refinement process for the production of ferrotitanium. The direct electrolysis of a solid oxide in molten salt, known as the Fray–Farthing–Chen Cambridge (FFC) process with the merits of short-flow course and lower energy consumption, has been applied widely since 1998.5,6 Numerous metals (e.g., Cr,7 Ti,8 Nb,9 Ta,10 Zr11), and alloys (e.g., LaNi,12 TiC/ SiC,13 FeTi,14 and TiSi15) have been prepared from corresponding oxides via the FFC method. Panigrahi et al. reported the preparation of (Received November 30, 2019; accepted August 28, 2020)
ferrotitanium alloys from the direct electrolysis of TiO2 and Fe2O3 mixtures in CaCl2 molten salt.16 However, a relative slower deoxidization rate and higher energy consumption were observed on account of the difficult reduction of TiO2 and the multi-intermediates formed, such as CaTiO3 and TiO. It has become imperative to develop an effective way to promote the reduction process. A great number of endeavors, including lowering the cathode mold pressure, and improving the cathode sintering temperature and cathode porosity, have been p
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