Implications of Direct Use of Slag from Ironmaking Processes as Molten Oxide Electrolyte

Abstract

The thermochemical and electrical behaviour of ironmaking slag produced from titanomagnetite concentrates was assessed in the vicinity of its tapping temperature. A combination of electrochemical measurements in a modified thermal imaging furnace and computational thermodynamic calculations was employed to elucidate its potential use as a molten oxide electrolyte for the extraction of high-purity metal. The results show that the presence of entrained iron species in the ironmaking slag decreases the faradaic efficiency of the electrolysis. Thermodynamic predictions reveal a small electrochemical window of operation between the decomposition of silica and titania, which might result in the co-reduction of titanium and silicon ions from the melt. Practical considerations for the electrochemical production of metal directly from the ironmaking process are discussed, and further experimental investigation of the electrochemical behaviour of this material is justified.

Electrochemical Study on the Reduction of Si and Ti from molten TiO2–SiO2–Al2O3–MgO–CaO Slag

“…32 : a current efficiency of (29 ± 6)% for electrolysis of a slag with 21 wt% TiO 2 at 1903 K was achieved considering just reduction of Ti 4+ , 11 and the fraction of total current borne by electronic carriers was determined to be 0.24 at 1823 K in a slag with 33 wt% TiO 2 . 12 The results indicate that the extraction of pure metallic Ti from TiO 2 -SiO 2 -Al 2 O 3 -MgO-CaO slag is unlikely without the prior removal of SiO 2 . Even though it was out of the scope of the current study, the small potential window between the reduction of silicon and titanium ions from the melt motivates the further study of the effect of chemical modifications to the oxide system, such as changes in the concentration of the electronegative species, 33 on the deposition series of the electrolyte.…”

“…Upon the application of a potential, any iron oxide will be reduced first as it requires the minimum thermodynamic cell voltage. 12 Silica is the component of the slag that will be next to reduce, closely followed by titania. Thermodynamics seem to indicate that an electrolytic route for the production of more reactive 3d metals, such as titanium, might need silica-free electrolytes.…”

Ultra‐High Temperature Molten Oxide Electrochemistry

“…Although the concept of UTE was proposed for ironmaking as early as 1906, UTE has not received widespread attention in the past 100 years (Figure 1d) [26–40] . Recently, traditional metal extraction technologies, such as ironmaking by blast furnace and Ti extraction by the Kroll process, have been confronted with serious environmental and energy bottlenecks limitations.…”

“…c) Periodic table of elements for UTE. d) Timeline for the development of UTE in molten oxides [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. e) Decomposition voltages of iron oxides in aqueous solutions, molten salts, and molten oxides.…”

Ultra‐High Temperature Molten Oxide Electrochemistry

“…Although the concept of UTE was proposed for ironmaking as early as 1906, UTE has not received widespread attention in the past 100 years (Figure 1d). [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] Recently, traditional metal extraction technologies, such as ironmaking by blast furnace and Ti extraction by the Kroll process, have been confronted with serious environmental and energy bottlenecks limitations. A low-carbon extraction technology for Fe or Ti is urgently needed in view of the global goal of carbon neutrality.…”