Evolution of Viscosity and Structure Property of Vanadium Slag during Iron‐Extracting Reduction Process

Abstract

Photovoltaic cutting waste (PCW) is a promising prereductant to enrich vanadium and to extract iron present in vanadium slag. To understand the kinetic conditions during the reduction and separation of Fe from vanadium slag when using PCW as a reductant, the evolution of the viscosity with decreasing FeO contents is measured. The composition and structure of the melt are analyzed using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The results show that the slag comprises a solid–liquid mixture system during the entire prereduction at 1873 K. At this temperature, as the FeO/SiO2 mass ratio decreases from 2.18 to 0.30, the solid–liquid ratio of the slag decreases from 21.5% to 1.9%, and the viscosity of the slag increases from 0.12 to 0.47 Pa s, indicating that the silicate structure of the melt significantly affects the slag viscosity, while the effect of the spinel phase is limited. The transition of the dominant silicate structure from FeO to SiO2 results in a significant decrease in the amount of the simple unit Q0 as well as the occurrence of the more complex structural unit Q3, suggesting a significant enhancement of the degree of polymerization in the vanadium slag.

Evolution of Viscosity and Structure Property during Aluminothermic Reduction of Vanadium‐Enriched Slag

“…To analyze the slag structural units accurately and quantitatively, the Raman spectra were corrected according to the equation described in a previous study. [ 36 ] The deconvoluted results of the Raman spectra are shown in Figure 6 ; these results were obtained through the Gaussian deconvolution method by assuming contributions from the silicate structural units of Q 0 , Q 1 , Q 2 , and Q 3 with a minimum correlation coefficient r 2 ≥ 0.998. [ 51 ] The different Raman bands are related to various structural units, as detailed in Table 3 .…”

“…As a continuation of previous work concerning the prereduction of vanadium slag, [23,36] the viscosity of the FeO-Cr 2 O 3 -MnO-V 2 O 3 -SiO 2 -TiO 2 -CaO-Al 2 O 3 system in the final reduction process was experimentally measured in this study. The composition of the slag during the final reduction process was analyzed using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).…”

“…This duration was found in previous studies to be sufficient to ensure that the cation valence reached equilibrium. [36,37] Subsequently, an iron rod was dipped into the experimental slag and rapidly quenched in liquid nitrogen, and the quenched slag samples adhered to the iron rod were separated and used for further analysis. The Mo crucible was removed from the furnace and quenched rapidly in liquid nitrogen under a high-flow protective atmosphere, and the pre-melted slag was prepared.…”

Element Migration Behaviors During the Reduction of Vanadium Slag for Iron‐Removal and Vanadium‐Enrichment

“…The degree of polymerization of slag was significantly enhanced, resulting in poor fluidity of the slag and reduction conditions. [47,48] Furthermore, agglomerations of metal droplets also became difficult. Therefore, to achieve better slag-metal separation, maximum removal of Fe and Cr, and without loss of vanadium in the residual slag, the proper S/V should be kept at 0.15.…”

Direct Vanadium Alloying of Liquid Steel with Self‐Reduction Vanadium Slag Briquette

“…It is commonly believed that vanadium oxides mainly exist in the form of V 2 O 3 under high temperature. [4,29] When the temperature was lower than 1475 C, only FeO could be reduced by solid carbon, whereas V 2 O 3 and MnO are hardly reduced. As the temperature is more than 1500 C, the reduction reactions of FeO, MnO, Cr 2 O 3 , and V 2 O 3 could take place.…”