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The lack of thermodynamic data on vanadium slag, the main raw material for vanadium extraction, limits the efficient extraction of vanadium from vanadium slag. According to the composition and smelting process of industrial vanadium slag, this study firstly investigated the phase equilibria of the “FeO”–SiO 2 –CaO–16 wt pctV 2 O 3 system at 1673 K and 1473 K under oxygen partial pressure of 10 −10 atm via XRD, SEM and EPMA, based on which the phase diagrams of that at 1673 K and 1473 K were constructed. The results showed that the vanadium-enriched phases mainly consisted of V 2 O 3 , Fe 2 VO 4 , and Ca 3 [Fe,V] 2 (SiO 4 ) 3 , where Ca 3 [Fe,V] 2 (SiO 4 ) 3 was generated due to the replacement of a large amount of Fe 3+ by V 3+ in Ca 3 Fe 2 (SiO 4 ) 3 . On this basis, the phase relations of the “FeO”–SiO 2 –CaO–16 wt pctV 2 O 3 system were further discussed. It was found that the decrease in temperature promoted the crystallization of Fe 2 VO 4 and Ca 3 [Fe,V] 2 (SiO 4 ) 3 , but had an inhibitory effect on the crystallization of V 2 O 3 . And Fe 2 VO 4 was transformed to V 2 O 3 or Ca 3 [Fe,V] 2 (SiO 4 ) 3 by decreasing Fe/Si (Mass fraction of “FeO” and SiO 2 ). This study supplements the thermodynamic data for vanadium slag and provides a theoretical basis for the recovery of vanadium from vanadium slag.

The hydrogen-based reduction and electric smelting technology is a green and low-carbon process for treating low-grade ore and complex symbiotic iron ore. In this study, the hydrogen-based reduction of boron-bearing iron concentrate and the low-temperature separation compared with the high-temperature melting separation of slag and iron from a boron-bearing iron concentrate were studied. The metallization rate of the boron-bearing iron concentrate reached 99.63% after hydrogen-based reduction at 1 050 °C and the metallic iron was interwoven with olivine (Mg2SiO4) in the reduced ore. In addition, the high-temperature melting separation of iron and slag could be accomplished at 1 550 °C for 60 min, where boron was mainly distributed in the form of a glass phase in the slag with a mass fraction of B2O3 of 22.69% and 0.35% of boron (mass fraction) was melted into liquid iron. By contrast, iron and slag were efficiently separated at a lower temperature (1 300 °C) for 10 min and enhanced by super-gravity. Almost all the boron content was enriched into a suanite phase in the slag with a considerably high mass fraction of B2O3 (35.61%) and a high recovery ratio (99.37%), and the mass fraction of boron decreased to 0.15% in iron. Compared with high-temperature melting separation, low-temperature separation combined with hydrogen-based reduction greatly improved the enrichment of boron in slag and prevented the melting of boron into iron.

A new approach to enriching britholite phase from the rare-earth-rich slag by super gravity was investigated. The Bayan Obo iron ore, which was used as raw material, was reduced and melting separated to produce iron nugget and rare-earth-rich slag. Subsequently, the slag was heat-treated and enriched in the super gravity filed. The volume fraction and equivalent diameter of britholite phase were measured by scanning electron microscope (SEM) and image analyzer, whereas the mineral composition and chemical component were characterized by X-ray diffraction and X-ray fluorescence. The results indicated that the samples obtained by the gravity coefficient G ≥ 500, t ≥ 15 minutes, and T ≥1423 K (1150 °C) show significant layers and britholite phase present gradient size distribution in the sample along the super gravity. The layered sample was central cut and characterized by SEM, and it is difficult to find any britholite particles in the upper area of the sample. The britholite phase gathers at the middle and bottom areas of the sample. The mechanism of moving speed of britholite particles in super gravity field was discussed, and the conclusion indicates that the moving speed of britholite particles is proportional to the square of the britholite particle size. As a result, large britholite particles move farther than the small ones and gather at the bottom of the sample, whereas small britholite particles accumulate in the middle of the sample. Under the hypothesis that rare earth (RE) exists in the slag in terms of RE 2 O 3, with the gravity coefficient G = 500, t = 15 minutes, and T = 1423 K (1150 °C), the mass fraction of RE 2 O 3 in the concentrate is up to 23.29 pct whereas that of the tailing is just 5.57 pct. Considering that the mass fraction of RE 2 O 3 is 12.01 pct in the parallel sample, the recovery ratio of RE in the concentrate is up to 71.19 pct by centrifugal enrichment.

Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize, which makes it difficult to separate the mineral phases through conventional beneficiation. This study proposed a new treatment called flash reduction-melting separation (FRMS) for boron-bearing iron concentrates. In this method, the concentrates were first flash-reduced at the temperature under which the particles melt, and the slag and the reduced iron phases disengaged at the particle scale. Good reduction and melting effects were achieved above 1550°C. The B 2 O 3 content in the separated slag was over 18wt%, and the B content in the iron was less than 0.03wt%. The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and temperature on the reduction and melting steps with and without pre-reducing the raw concentrate. The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.

Based on computational fluid dynamics, chemical reaction kinetics, principles of transfer in metallurgy, and other principles, a multi-fluid model for a traditional blast furnace was established. The furnace conditions were simulated with this multi-fluid mathematical model, and the model was verified with the comparison of calculation and measurement. Then a multi-fluid model for an oxygen blast furnace in the gasifier-full oxygen blast furnace process was established based on this traditional blast furnace model. With the established multi-fluid model for an oxygen blast furnace, the basic characteristics of iron ore reduction process in the oxygen blast furnace were summarized, including the changing process of the iron ore reduction degree and the compositions of the burden, etc . The study found that compared to the traditional blast furnace, the magnetite reserve zone in the furnace shaft under oxygen blast furnace condition was significantly reduced, which is conducive to the efficient operation of blast furnace. In order to optimize the oxygen blast furnace design and operating parameters, the iron ore reduction process in the oxygen blast furnace was researched under different shaft tuyere positions, different recycling gas temperatures, and different allocation ratios of recycling gas between the hearth tuyere and the shaft tuyere. The results indicate that these three factors all have a substantial impact on the ore reduction process in the oxygen blast furnace. Moderate shaft tuyere position, high recycling gas temperature, and high recycling gas allocation ratio between hearth and shaft could significantly promote the reduction of iron ore, reduce the scope of the magnetite reserve zone, and improve the performance of oxygen blast furnace. Based on the above findings, the recommendations for improvement of the oxygen blast furnace design and operation were proposed.

Vanadium extraction tailings, as a highly alkaline and hazardous solid waste, pose not only serious environmental risks but also severely hinder the large-scale recycling of secondary iron resources. This study proposes an innovative process of “mild alkali leaching for vanadium extraction coupled with deep calcification and dealkali removal”. The vanadium extraction slag from a steel plant in China was used as a raw material to carry out the experimental and pilot study of alkali leaching of vanadium and calcification dealkalization. Experimental results show that under the conditions of 120 °C, 1% NaOH solution, liquid-solid ratio of 4:1 to 6:1, and reaction time of 1 h, vanadium leaching rate can reach 50%, which can be effectively used as a high-value-added economic hedge. Subsequently, under the conditions of 200 °C, calcium oxide concentration of 19.29%, stirring speed of 800 rpm, liquid-solid ratio of 4:1, and reaction time of 1 h, the Na2O content in the tailings was successfully reduced to below 1%. A large number of tailings can be converted into high-quality secondary iron ore resources, which are suitable for subsequent iron-bearing briquette preparation and blast furnace ironmaking. Furthermore, pilot-scale testing in a 200 L reactor verified the engineering scalability of this combined process, maintaining a vanadium extraction rate of over 50% and an alkali removal rate of over 80%. This study provides a robust, scalable, and highly profitable pathway for the comprehensive utilization of high-alkali metallurgical solid waste.

In this study, the effects of different Cr 2 O 3 contents and optical basicity (denoted by Λ) on the viscosity and structure of the Cr 2 O 3 -bearing CaO-SiO 2 -MgO-Al 2 O 3 slag were investigated. The viscosities of Cr 2 O 3 -bearing CaO-SiO 2 -MgO-Al 2 O 3 slags in the liquid phase below 1823 K (1550 °C) were measured by rotating-cylinder method, and the structures of the slags were examined via Raman spectroscopy. Three different parameters were used to characterize the structures of the slags. The results showed that the viscosity of the slags increased as the Cr 2 O 3 content increased, but decreased as Λ increased. The Cr 3+ ions acted as network formers and increased the degree of polymerization (DOP), and thus, the addition of Cr 2 O 3 to the slag increased the number of bridging oxygen atoms in the silicate structural units. Generally, the viscosity increased by increasing DOP. In addition, there was a linear inverse relationship between the viscous activation energy ( E μ ) and Λ. Furthermore, as the Cr 2 O 3 content increased, the gradients of the plots of E μ vs Λ decreased. This indicates that for a slag with a high Cr 2 O 3 content, trying to improve the fluidity of the slag by increasing Λ has a limited effect.

Selective precipitation and concentrating of perovskite crystals from titanium-bearing slag melt in the supergravity field was investigated in this study. Since perovskite was the first precipitated phase from the slag melt during the cooling process, and a greater precipitation quantity and larger crystal sizes of perovskite were obtained at 1593 K to 1563 K (1320 °C to 1290 °C), concentrating of perovskite crystals from the slag melt was carried out at this temperature range in the supergravity field, at which the perovskite transforms into solid particles while the other minerals remain in the liquid melt. The layered structures appeared significantly in the sample obtained by supergravity treatment, and all the perovskite crystals moved along the supergravity direction and concentrated as the perovskite-rich phase in the bottom area, whereas the molten slag concentrated in the upper area along the opposite direction, in which it was impossible to find any perovskite crystals. With the gravity coefficient of G = 750, the mass fraction of TiO 2 in the perovskite-rich phase was up to 34.65 wt pct, whereas that of the slag phase was decreased to 12.23 wt pct, and the recovery ratio of Ti in the perovskite-rich phase was up to 75.28 pct. On this basis, an amplification experimental centrifugal apparatus was exploited and the continuous experiment with larger scale was further carried out, the results confirming that selective precipitation and concentrating of perovskite crystals from the titanium-bearing slag melt by supergravity was a feasible method.

A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution of the copper slag with increasing temperature were studied using in situ high-temperature confocal laser scanning microscopy and ex situ scanning electron microscopy and X-ray diffraction methods. Fe3O4 particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO2 at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at G = 1000 and 1473 K (1200 °C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.

TiCx/Al composites were successfully prepared in this study by dissolving graphite particles in Al-Ti melt based on the principle of a solid–liquid in situ reaction. It was observed that the microstructure of the TiCx/Al composites changed with changes in the reaction temperature and graphite particle size. With an increase in reaction temperature, the TiCx particles in the TiCx/Al composites transitioned from a spider-like distribution to being evenly dispersed in the Al matrix. Additionally, the morphology of the TiCx particles changed from polygons of various sizes to quasi-spherical shapes with a uniform particle size, while the presence of Al4C3 and Al3Ti in the matrix diminished. The size variation of the graphite particles had minimal impact on the particle size and stoichiometric ratio of TiCx generated in the sample. Furthermore, an appropriate graphite particle size was found to mitigate the agglomeration and residue of graphite particles during the in situ reaction.