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The effect of nickel oxide additive on the smelting behaviors of chromium-bearing vanadium titanomagnetite pellets (CVTP) was investigated while analyzing the transfer behavior of nickel in iron and slag. The results show that when NiO added to CVTP increases from 0 to 6 wt.%, softening start temperature increases from 1148 to 1212 °C, and the softening end temperature increases from 1280 to 1334 °C; the melting start temperature increases from 1318 to 1377 °C, and the dripping temperature decreases from 1558 to 1521 °C. The pig iron comprises a compound of Fe–Ni–C. The slag structure depolymerizes with increasing nickel addition. The softening-melting behaviors of CVTP, the reduction of nickel into pig iron, and the depolymerization of slag structure indicate the feasibility of producing nickel–iron alloy through the blast furnace process.

At present, reducing carbon emissions and energy consumption have become the most crucial ironmaking development objectives. Hot metallurgical off-gas (MOG) is one of the most valuable by-product resources containing great underutilized heat and recyclable gas. A sustainable strategy of reinjecting hot MOG as one of the raw materials into the Cr-bearing vanadiferous titanomagnetite ore (CVTO) blast furnace (BF) to achieve its recovery and reuse was proposed and investigated in this study. It is considered feasible according to the obtained results of heat-carbon balance calculations and softening–melting–dripping experiments. First, hot MOG reinjection was beneficial to ameliorate the industrial smelting index and reduce carbon emission and consumption. With the CO2 in the hot MOG increased from 0 to 30 vol%, the softening zone increased from 11 to 135 °C, the dripping temperature increased from 1486 to 1534 °C, and the melting–dripping zone increased from 150 to 198 °C, and it could reduce a considerable carbon rate of 17.2 kg-C/t-Fe. Besides, it could suppress the generation of titanium carbonitride in Ti compounds with a remarkable decrease from 14.4 to 11.9 wt%. Besides, it also improved the high-temperature properties of the titania slag. The melting temperature of the titania slag decreased from 1348.2 to 1331.2 °C, and its surface tension increased from 0.302 to 0.551 N/m. Moreover, the corrected viscosity of TiN-bearing slag was calculated, and it showed a profitable decrease from 0.433 to 0.414 Pa·s at 1500 °C. In addition, the high-basicity pellet was used to replace the conventional sinter in the above experiments, which was conducive to achieve energy saving and emission reduction in practical applications.

To reduce the consumption of aluminum in the traditional production process of ferrotitanium, the use of economic electrical energy is considered to replace the chemical energy provided by the reaction of aluminum and heating agent. Analysis of slag by x-ray diffraction (XRD) and FactSage 7.2 revealed that heating-assisted aluminothermic reduction of ilmenite was a thermal explosion process. Increasing the Al ratio could promote the reduction of ilmenite and increase the recovery rate of Ti according to inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis and calculation. The optimal molar ratio of CaO to Al2O3 was 1:4 for the preparation of FeTi50, achieving good separation of alloy and slag and better Fe and Ti recovery rates than without CaO addition.

In this paper, detailed investigations on the reduction characteristics and kinetics mechanism of Russian high-chromium vanadium–titanium magnetite pellets under gas atmospheres of CO–CO2–N2 and CO...

A new comprehensive utilization of vanadium slag (VS) method focusing on inhibiting leaching of iron (Fe) during the leaching of vanadium (V) using sulfuric acid (SA) was proposed. In this process, Cr2O3 was added to VS to conjugate with Fe in the VS to form (Fex,Cr1-x)2O3 which is insoluble in SA, resulting in the decrease of leaching ratio (LR) of Fe to avoid the subsequent separation difficulty of V in leachate. The phase evolutions of VS during the roasting and SA leaching process, and the influences of roasting temperature, roasting time, and addition of Cr2O3 on the LR of V, Fe and chromium (Cr) from VS were studied. When the addition of Cr2O3 is 12 wt.%, the mass concentration of V in the leachate is 1 order magnitude higher than Fe and the mass ratio of V to Fe reaches 18.34. The LR of V, Fe and Cr are 91% 1.39% and 0.28%, respectively. The leaching residue can be reused as ironmaking raw material. More importantly, the (Fex,Cr1-x)2O3 and Fe2TiO5 can be separated from the leaching residue and recycled as raw materials for black ceramic pigments and titanium dioxide production by mineral processing technology, respectively.

In order to better develop and utilize the low-grade vanadiferous titanomagnetite concentrate with high titanium (LVCHT) and provide reference for the treatment of similar minerals. Oxidation process and kinetics of the LVCHT were investigated in this study. The results show that LVCHT presents weight loss at temperatures less than 600 °C, which is attributed to the removal of moisture and volatile components. Above 600 °C, the weight gain of LVCHT is due to the persistence of oxidative behavior, and the oxidation process is most likely controlled by external diffusion, and the associated activation energies (Ea) and the value of k 0 are 29.89 kJ/mol and 0.64, respectively.

Blast furnace smelting process has advantages in producing ferronickel products because of its low comprehensive energy consumption and high production efficiency. However, laterite nickel ore has poor performance of pellets and lump ore due to its own characteristics. At present, the main lumping method is low basicity sinter, which is difficult to optimize the charge structure. This paper mainly studies the preparation process of laterite nickel carbon composite hot briquette (LN-CCHB) and the influence of process parameters on the basic compressive strength properties, so as to explore a new charge for smelting laterite nickel in blast furnace process. Results showed that the influence of pressure and temperature of hot briquette on the compressive strength of NL-CCHB is obvious. The compressive strength of NL-CCHB increases with the increase of briquetting pressure increases first and then decreases with the increase of hot briquetting temperature. The FC/O ratio (the ratio of the fixed carbon mol (C) in coal to the reducible oxygen mol (O) in iron oxides) has little effect on the compressive strength of NL-CCHB. In the experimental range, the mixture of laterite nickel ore and pulverized coal can obtain NL-CCHB with compressive strength of more than 1300N after hot briquetting. After heat treatment, NL-CCHB with compressive strength of more than 1800N can be obtained. The optimum hot briquetting process parameters are: FC/O ratio 1.25, hot briquetting temperature 450°C, hot briquetting pressure 80MPa. The optimum heat treatment process parameters are: FC/O ratio 1.50, heat treatment temperature 550°C.

Recovery of rare earth elements (REEs) from tailings is the solution to the waste of valuable resource and hazard of tailing dam. In order to lower the cost and increase the rate of REEs recovery, we investigated leaching kinetics and dissolution mechanisms of REE slag in hydrochloric acid (HCl) solution, and present a method for selectively recovering REEs directly from the leachate. Experiments were performed to elucidate the effects of the initial concentration of HCl, liquid–solid ratio, and reaction temperature on the leaching efficiency of REEs. The maximum leaching efficiency of REEs in this work exceeded 99%. The leaching kinetics and dissolution mechanism have also been analyzed by model fitting and microstructural observation. The leaching reaction was controlled by both of the interfacial transfer and diffusion across the product layer. The pitting corrosion and the colloidal silicic acid generated at the interface of REE-rich phase showed positive and negative effects on the leaching reaction rate, respectively. Finally, the selective recovery of REEs from the leachate was developed, and both the recovery of REEs and purity of the REE precipitate exceeded 99%. This study is expected to provide a feasible method for the recovery of REEs from the silicates containing slag.

In this paper, orthogonal experiments are designed to study the sintering and smelting characteristics of the ludwigite ore. The predominant influencing factors of the optimal ratio, basicity and carbon content on different single sintering indexes, including the vertical sintering speed, yield rate, drum strength and low-temperature reduction pulverization index, are firstly explored by the range analysis method, and the main influencing factors on comprehensive indexes are obtained by a weighted scoring method based on different single index investigation. Considering the sintering characteristics, the primary and secondary influencing factors are: ordinary ore ratio, carbon content and basicity, and the optimal ore blending scheme is: basicity 1.7, ordinary ore blending ratio 60% and carbon content 5%. In terms of the smelting characteristics, the research obtains the order of the influencing factors on the softening start temperature, softening end temperature, softening zone, smelting start temperature, dripping temperature, smelting-dripping zone, maximum pressure difference and gas permeability index of the ludwigite sinters by simply considering various single smelting indexes. On this basis, considering the comprehensive softening-melting-dripping characteristics, the primary and secondary influencing factors are: carbon content, ordinary ore ratio and basicity, and the optimal ore blending scheme is: basicity 1.9, ordinary ore blending ratio 60% and a carbon content of 5.5%. Comprehensively, considering the sintering and smelting property of the ludwigite ore, the primary and secondary influencing factors are: carbon content, ordinary ore ratio and basicity, and the optimal ore blending scheme is: basicity 1.9, ordinary ore blending ratio 60% and a carbon content of 5.5%.

The catalytic activities of pyrite in the heterogeneous Photo-Fenton processes for oxidation of methylene blue (MB) were systematically investigated. Experimental results revealed that nearly 100% MB (50 mg/L)could be completely degraded after 20 min under the optimum conditions. The excellent oxidation ability could be attributed to the photocatalytic activity of pyrite under visible light illumination, and the Fenton catalytic reaction occurring at the surface of FeS2 together with dissolved iron ions in the aqueous phase. Most importantly, the FeS2 nanoparticles assembled on graphene sheets were synthesized via a one-step solvothermal method with higher photocurrent response, reduced charge transferring resistance, and superior cycling stability. The obtained materials were also characterized by XRD, SEM, TEM, XPS, TG, and ESR for structural, morphological, chemical, and reaction mechanism studies.

In this work, carbothermal reduction followed by sulfuric acid (H2SO4) leaching of Bayan Obo tailings has been studied for the selective concentration of Fe and rare earth (RE) minerals. The effect of basicity on the metallization rate of Fe, transfer behaviors of metallic Fe and RE elements, phase composition, and element migration was investigated using XRD, SEM-EDS, EDS mapping, and FT-IR spectroscopy. At a roasting temperature of 1100–1200 °C and a basicity of 1.87, more than 99% of Fe was metallized and 97.91% of Fe and 94.94% of RE were separated magnetically. After roasting, the RE elements mainly existed in Ca2RE8(SiO4)6O2 and Ca8RE2(PO4)6O2, 88% of which were leached out by H2SO4 at 25 °C with an initial concentration of 2 mol/L and a stirring speed of 900 r/min. The precipitation of RE2(SO4)3 was responsible for the incomplete recovery of RE elements during leaching.

Through thermodynamic smelting experiments, nonisothermal and isothermal kinetics experiments, the effects of CO2–containing gas injection on the smelting of chromia–bearing vanadiferous titanomagnetite ore were investigated. The experiments at 900 °C, 1000 °C, 1100 °C, 1200 °C, and 1300 °C, and CO2 concentration of 0, 10 vol.%, 20 vol.%, and 30 vol.% were studied. The samples after the kinetics experiments were analyzed through thermodynamic calculations and characterized by XRD, XRF, XPS, and SEM. The results of thermodynamic experiments show that the injection of CO2–containing gas significantly improves the softening–melting–dripping behavior during the smelting process. As the concentration of injected CO2 increased from 0 vol.% to 30 vol.%, the range of softening temperature [T40–T4] decreased from 109 °C to 97 °C, and the range of droplet temperature [Td–Ts] decreased rapidly from 196 °C to 162 °C. Moreover, when CO2 concentration was 20 vol.%, the minimum apparent activation energy of nonisothermal kinetics reached 75.58 kJ·mol−1. Combining the lowest permeability index and the fastest nonisothermal reduction rate, the optimal CO2 concentration in the fuel gas was considered to be 20 vol.%. The isothermal parameters were fitted according to 1 − (1 − α)1/3 − t (CG3 model), and the apparent activation energy was 121.93 kJ·mol−1 (less than 150 kJ·mol−1), which means that the restrictive step of the polymetallic reaction is mainly determined by diffusion. Finally, thermodynamic calculations and characterizations show that CO2–containing gas injection helps titanium stabilize in a higher valence state, which is conducive to improve the high–temperature characteristics of titanium–containing slag.

The effect of diboron trioxide (B2O3) on the crushing strength and smelting mechanism of high-chromium vanadium–titanium magnetite pellets was investigated in this work. The main characterization methods were X-ray fluorescence, inductively coupled plasma–atomic emission spectroscopy, mercury injection porosimetry, X-ray diffraction, metallographic microscopy, and scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results showed that the crushing strength increased greatly with increasing B2O3 content and that the increase in crushing strength was strongly correlated with a decrease in porosity, the formation of liquid phases, and the growth and recrystallization consolidation of hematite crystalline grains. The smelting properties were measured under simulated blast furnace conditions; the results showed that the smelting properties within a certain B2O3 content range were improved and optimized except in the softening stage. The valuable element B was easily transformed to the slag, and this phenomenon became increasingly evident with increasing B2O3 content. The formation of Ti(C,N) was mostly avoided, and the slag and melted iron were separated well during smelting with the addition of B2O3. The size increase of the melted iron was consistent with the gradual optimization of the dripping characteristics with increasing B2O3 content.

Due to the advantage in deactivating fluorine and enhancing the decomposition of rare earth (RE) minerals, MgO was applied to the magnetizing roasting of Bayan Obo tailings in this work. The effects of MgO dosages, roasting temperature, and holding time on the decomposition rate of RE minerals were experimentally studied. With a MgO dosage of 10 wt.%, the decomposition rate of RE minerals reached 98.09% at 750 °C. The phase composition of roasted samples was characterized by XRD and SEM-EDS. The incomplete decomposition rate was investigated with the observation of leaching residual by SEM-EDS. The decomposition kinetics of the RE minerals with the addition of MgO was analyzed with the Ginstling-Brundshtein model, where the reaction rate was controlled by chemical reaction.

Ilmenite is a vital raw material for the production of metal titanium and titanium-containing materials. In this paper, microstructure and chemical transformation of natural ilmenite in air atmosphere were investigated by the analysis of XRF, X-ray diffractometer, and SEM-EDS. Results showed that the untreated ilmenite had three layers after oxidation at 800 °C for 60 min, which were Fe2O3, TiO2 and the inside mixture layer of Fe2O3 and TiO2 in turn. Subsequently, it was roasted at 900 °C, and Fe2Ti3O9 was firstly developed between Fe2O3 and TiO2 layers. With the increase in the roasting time, the Fe2Ti3O9 layer was decomposed into Fe2TiO5 and TiO2, and Fe2Ti3O9 continued to be formed along the diameter direction toward the center of the particle until Fe2TiO5 and TiO2 were formed as the final products in the center of particles. Pseudorutile in natural ilmenite was directly decomposed into TiO2 and Fe2O3 in the roasting process.

The effects of CO2 injection on the high-temperature metallurgical performance of Cr-bearing vanadia-titania magnetite (CVTM) in blast furnace (BF) smelting were investigated. The dry air or O2-enriched air is not necessarily suitable for any blast furnace production, and CO2-containing high-temperature energy-carried gas (CHEG) also can be an alternative injection gas with lower cost and pollution. This kind of CHEG can be blast furnace gas, basic oxygen furnace gas, coke oven gas, sintering gas and rotary kiln gas and so on, which contained high sensible heat and CO2, H2 and CO. Injecting CHEG into the blast furnace can replace air injection to achieve the heat balance in the cohesive zone and raceway. The calculated boundary injection ratio of CO2 is approximately 15.3%, and the experimental optimal CO2 injection ratio is about 10∼20%. CO2 injection benefits the blast furnace operation, the permeability of cohesive zone, recovery ratio of Cr and V. With increasing injected content of CO2, the temperature range of softening zone [T40-T4] and melting-dripping zone [Td-Ts] decrease almost 20℃, and the dripping ratio increases from 62.36% to 69.76%, the recovery of V increases from 32.75% to 47.96%, and the recovery of Cr increases from 42.35% to 64.41%. The CO2 injection affects the melting temperature of the high-titanium slags to be higher and the maximum temperature difference can reach 45℃, which is beneficial to the slag stability and separation of slag-iron and restrain the over-deduction of titania to TiN upon the slag-coke interface with lower N2.

The high-temperature metallurgical property of high-titania slag is one of the most significant indicators to measure the production status of Cr-bearing vanadia-titania magnetite blast furnace (CVTM-BF). Due to the continuous high temperature in the furnace, titania is over-reduced to titanium carbonitride with a high melting point (over 3000°C), which causes the viscosity of the slag to be too high to separate the molten iron and molten slag well. However, a high proportion of N2 in the air blasted into the furnace participates in the generation of TiN, and the large required air volume causes a high coke ratio and excessively high furnace temperature, which is not conducive to suppressing the over-reduction of titania. Here we show that TiN was significantly reduced and the metallurgical properties of high-titania slag were improved by injecting abandoned basic oxygen furnace gas (ABOFG), which is a kind of by-product gas containing CO, CO2, lower N2 and high physical heat. The experimental results demonstrated that the ABOFG was likely to function in suppressing TiN from 2.46% to 1.06%, dropping the melting temperature down from 1478.8°C to 1290.3°C, pushing the slag-iron interface tension from 0.641 N/m to 0.882 N/m as well as bring the viscosity down from 0.353 Pa⋅s to 0.341 Pa⋅s. Overall, ABOFG as a kind of endothermic atmosphere compared to O2-enriched air is beneficial to restrain the over-deduction of titania to TiN upon the slag-coke interface with lower N2. It also helps CVTM-BF to be recovered from the continued deterioration as soon as possible.

High chromium vanadium–titanium magnetite has not been exploited and made full use of on a large scale so far due to the immature utilisation technology and the reality that the utilisation efficiency of valuable metals still urgently needs to be improved. In the present paper, the isothermal reduction kinetics and mechanism of high chromium vanadium–titanium pellets were studied at 800–1100°C. The microstructures were examined by a SEM equipped with EDX capabilities to reveal the elemental distributions. The effect of reduction temperature on the volumetric swelling degree and cold crushing strength was also studied. It was found that reduction temperature has a large effect on the reduction rate of pellets, and the increase in reduction rate is more obvious in the range 1000–1100°C than 800–1000°C. The volumetric swelling degree of pellets increased with increasing reduction temperature, while the cold crushing strength decreased. The apparent activation energy of the reduction reaction was calculated t...

As a very effective metallurgical method for processing complex metal minerals, Chlorination metallurgy has been widely used in the metallurgical industry. In this paper, the chlorination agents used in the process of chlorination metallurgy were summarized as gaseous chlorination agents and solid chlorination agents. the advantages and disadvantages of each of them were compared and analyzed, and the main mechanisms involved in the process of chlorination roasting and chloride separation were discussed and analyzed, respectively; The research results of related scholars on chlorination metallurgy were summarized, and the application progress on sulfide ores, oxidized ores, wolframite concentrates and rare earth ores was introduced in detail, and from the perspective of thermodynamics, the feasibility of treating complex metal ores with chlorination metallurgy was analyzed, in order to provide some help and reference for the subsequent research and application of chlorination metallurgy.

The reduction performance and mechanism of low-grade vanadia–titania magnetite (LGVTM) were investigated using stoichiometric Al powder as a reductant. Subsequently, experiments were conducted to study the effect of Al ratio on the composition and microstructure evolution of ferroalloys and recoveries of Fe, V, Ti, and Cr. It was found that the oxides of valuable elements were reduced to metals simultaneously in a thermal explosion at 940 °C, forming a multicomponent ferroalloy. Ti, V, and Cr contents had common regularities in the ferroalloy, which first increased and then decreased, while Fe decreased with an increase in Al ratio. The main oxide inclusion transformed from Fe2SiO4 to Al2O3 in the ferroalloy with an increasing Al ratio. The recovery of Fe increased at first and then basically was constant. The recoveries of V, Ti, and Cr first increased and then decreased with Al ratio. The optimum Al ratios are different for each element, being 1.1, 1.15, 1.0, and 0.9 for Fe, Ti, V, and Cr, respectively. The combination of Al2O3 and TiO and the formation of (Al0.948Cr0.052)2O3 negatively affected the recovery of Ti and Cr, respectively.

In the iron and steel industry, improving the usage amount of New Zealand sea sand ore as a raw material for ironmaking can reduce the production costs of iron and steel enterprises to a certain extent. In this paper, the New Zealand sea sand ore without any grinding pretreatment was used as raw material, oxidized pellets were prepared by using a disc pelletizer, and the experimental conditions for preparing oxidized pellets were investigated and optimized. The effects of binder dosages, roasting temperature and roasting time on the properties of pellets were mainly investigated, and the effects of roasting temperature and roasting time on the microstructure of oxidized pellets was discussed by researching XRD patterns and SEM-EDS. With the increase of binder dosages, the drop strength of green pellets and the compressive strength of oxidized pellets were gradually increased. With the increase of roasting temperature and roasting time, the compressive strength of oxidized pellets increased gradually. When the amount of New Zealand sea sand ore was increased to 40–50%, the optimal process conditions for the preparation of oxidized pellets were as follows: the dosage of binder was 1.5%, the roasting temperature was 1200 °C, and the roasting time was 20 min.

The present work studied the softening and melting properties of different burden structures including pellet, sinter and mixed burden (pellet mixed with sinter) with a pellet ratio of 33.65%. The content of high chromic vanadium titano-magnetite in sinter and pellet was different. The experimental results indicated that the compositions of the burden have an important effect on the softening and melting properties. The softening and melting properties of pellet burden structure were improved when the high basicity sinter was added into the acid pellet forming mixed burden. The softening and melting properties of mixed burden with a pellet ratio of 33.65% were better than other burden structures. The initial softening temperature, the temperature interval of softening, the starting melting temperature, the temperature interval of melting, and maximum differential pressure were 1100 °C, 130 °C, 1250 °C, 130 °C and 15.7 kPa, respectively. By comparing the contents of Ti, V and Cr of iron that had dripped through the different burden structures, the content of valuable components (Ti 0.349%, V 0.244% and Cr 0.094%) was highest of the pig iron collected from the mixed burden.

In the present study, the reduction process of pellet containing high chromic vanadium–titanium magnetite in cohesive zone has been investigated. To elucidate the reduction process including the softening and melting properties, structure changes and migration processes of valuable components (Fe, V, Ti, and Cr) in pellet containing high chromic vanadium–titanium magnetite in cohesive zone, the experiment was carried out at different temperatures and the pellet samples were analyzed by the methods of XRD, SEM, and chemical analysis. The results of reduction process show that the temperature range of cohesive zone of pellet is from 1087.9 to 1338.3 °C and the maximum differential pressure of the burden is 15 859 Pa at the temperature of 1291 °C. The reduction process of pellet was gradually conducted from outside to inside, which could form a layer of iron shell on the outer surface of the pellet. A lot of wustite could be generated in the core of pellet when the reduction temperature exceeded 1100 °C. The migration process of iron is Fe2O3 → Fe3O4 → FeO → Fe, while the generated FeO could react with SiO2 forming 2FeO · SiO2. The reduction process of titanium is Fe2O3 · 3TiO2 → Fe5TiO8 → Fe2TiO4 → FeTiO3 → Ti(O0.19C0.53N0.32) → Ti(C,N) → [Ti] and MgO · TiO2 → Ti(C,N) → [Ti]. The migration process of vanadium is V2O3 → VN, VC → [V] and the chromium oxide was reduced as follows: (Fe0.6Cr0.4)2O3 → FeCr2O4 → [Cr].

The influence of NaOH-Ca(OH)2 on magnetizing roasting of iron minerals and on the decomposition reactions of rare earth minerals during coal-based magnetizing roasting is explored in the present work. The effect of alkaline additives was determined by means of SEM-EDS and X-ray diffraction methods in NaOH-Ca(OH)2-coal-tailings mixtures under optimal magnetizing roasting conditions (mass ratio of NaOH, Ca(OH)2, coal and tailings equal to 2.5: 4.5: 2.5: 100, roasting at 650 °C for 2.5 h). Although NaOH results in an adverse impact on magnetizing roasting of hematite, iron in silicate minerals could be released by NaOH-Ca(OH)2 additive as a form of hematite, which is further reduced to ferromagnetic magnetite. Moreover, the reduction ability of gas is improved in presence of coal and water from decomposition reaction of Ca(OH)2. Regarding the decomposition of bastanasite, no evident effect of NaOH-Ca(OH)2 is observed. The roasted products of pristine bastnasite particles are mainly composed of rare earth oxides (REO) with little fluorine, independent on the use of alkaline additives. No high purity REO were determined in the monazite particle by SEM-EDS, which is mainly decomposed into REO and REFeO3.

The sintering pot test was used to investigate the effect of TiO2 on the sintering behavior of chromium-bearing vanadium&ndash, titanium magnetite (CVTM) sinter. The main characterization methods of X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy-energy disperse spectroscopy (SEM-EDS), and metallographic microscopy were employed. In this study, yield, tumbler index (TI), vertical sintering speed, productivity, reduction degradation index (RDI), and reduction index (RI) were tested and calculated. The yield first increases from 82.87% to 84.37% and then decreases to 83.65%, vertical sintering speed first increases from 17.00 mm&middot, min&minus, 1 to 23.45 mm&middot, 1 and then decreases to 20.61 mm&middot, 1, and productivity first increases from 2.33 t&middot, m&minus, 2&middot, h&minus, 1 to 3.14 t&middot, 1 and then decreases to 2.69 t&middot, 1 with increasing TiO2 content. The TI increases from 45.81% to 52.09%, and RDI increases from 74.99% to 96.74%, while RI decreases from 67.92% to 47.15% with increasing TiO2 content.

Coal-based reduction and magnetic separation behavior of low-grade vanadium-titanium magnetite pellets were studied in this paper. It is found that the metallization degree increased obviously with an increase in the temperature from 1100 °C to 1400 °C. The phase composition transformation was specifically analyzed with X-ray diffraction (XRD). The microscopic examination was carried out with scanning electron microscopy (SEM), and the element composition and distribution were detected with energy dispersive spectroscopy (EDS). It is observed that the amounts of metallic iron particles obviously increased and the accumulation and growing tendency were gradually facilitated with the increase in the temperature from 1100 °C to 1400 °C. It is also found that the titanium oxides were gradually reduced and separated from ferrum-titanium oxides during reduction. In addition, with increasing the temperature from 1200 °C to 1350 °C, silicate phases, especially calcium silicate phases that were transformed from calcium ferrite at 1100 °C, were observed and gradually aggregated. However, at 1400 °C some silicate phases infiltrated into metallic iron, as it appears that the carbides, especially TiC, could probably contribute to the sintering phenomenon becoming serious. The transformation behavior of valuable elements was as follows: Fe2VO4 → VO → V → VC; FeTiO3 (→ FeTi2O5) → TiO2 → TiC; FeCr2O4 → Cr → CrC; FeTiO3 (→ FeTi2O5) → Fe0.5Mg0.5Ti2O5; (Fe3O4/FeTiO3→) FeO → Mg0.77Fe0.23O. Through the magnetic separation of coal-based reduced products, it is demonstrated that the separation of Cr, V, Ti, and non-magnetic phases can be preliminarily realized.