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R31 filter aid containing macromolecular long-chain organic compounds with carboxyl, sulfonic, amide groups was used to improve the filtration of fine hematite concentrate in this study. The carboxyl, sulfonic and amide groups adsorbed on the surface of hematite concentrate particles. The macromolecular long-chain organic compounds flocculated fine hematite concentrate particles to increase the apparent particles size. The H+ ions ionized by carboxylic acid and sulfonic groups compressed hydration film of hematite concentrate particles. The hydrophobic groups in the organic matter decreased the surface wettability of fine hematite concentrate particles. Thinner hydration film and less wettability decreased the water adhesion on surface of hematite concentrate particles. The dehydration rate of filter cake increased from 1.82 × 10−3 ml∙cm2∙s−1 to 3.20 × 10−3 ml∙cm2∙s−1 with a 75.82% increase, when the mass concentration of R31 filter aid increased from 0 to 1800 g/t, and the filter cake moisture content decreased from 19.88% to 17.72%.

The effects of corrosion temperature, oxygen flow rate and corrosion time on the transformation of metallic iron were systematically studied, and the effects of mineral phases of Fe-bearing products on Ti–Fe separation were investigated. The reaction mechanism of metallic iron in corrosion process was proposed. The results showed that corrosion temperature played a key role in determining the transformation of metallic iron in reduced ilmenite during corrosion process. Under suitable corrosion conditions, Fe-bearing mineral in reduced ilmenite could be converted to amorphous ferric hydroxide, lepidocrocite, hematite and magnetite, respectively, and lepidocrocite was the most easily separated Fe-bearing mineral from corrosion products owing to the significant density difference between lepidocrocite and Ti-rich materials. The Ti-rich material with 77.81 wt.% TiO2 and Fe-bearing product with 52.69 wt.% total Fe were obtained by gravity separation. The Ti recovery ratio and Fe recovery ratio were 91.16% and 86.27%, respectively.

The method of carbon powder mixed injection with a shrouding supersonic oxygen jet was proposed to increase the utilization efficiency of carbon powder and improve the foaming slag operation during the electric arc furnace (EAF) steelmaking process by delivering the carbon powder more deeply into the molten bath. In this study, the fluid flow characteristics of the carbon powder mixed injection with a shrouding supersonic oxygen jet were studied and analyzed using numerical simulations, which were first validated by a cold test experiment. Compared with the conventional carbon powder injection without a shrouding jet, the shrouding supersonic oxygen jet can protect the central gas-powder jet against the entrainment of the surrounding atmosphere, increase the velocity of carbon powder and make the carbon powder cluster together in a longer distance. Furthermore, the industrial application research was carried out in a 50-ton commercial Consteel EAF, and the relative metallurgical effects were also studied. Compared with EAF steelmaking using conventional carbon powder injection without a shrouding jet, the powder consumption, tap-to-tap time, FeO content in the final molten slag and phosphorus content of the final molten steel were reduced by 19.3 kWh/ton, 4 min/heat, 2.6 pct and 1.2 × 10−3 pct, respectively, after using the method of carbon powder mixed injection with a shrouding supersonic oxygen jet.

The effects of CaO content, MgO content and smelting temperature on the vanadium behavior during the smelting of vanadium titanomagnetite metallized pellets were investigated. The thermodynamics of reduction and distribution of vanadium was analyzed and the high-temperature smelting experiments were carried out. The thermodynamic calculations show that the distribution ratio of vanadium between the slag and the hot metal decreases with the increments of CaO and MgO content in the slag as well as the increase of the smelting temperature. The smelting experiments demonstrate that the vanadium content in iron and the recovery rate of vanadium in pig iron increase as the CaO content, MgO content and smelting temperature increase, whereas the vanadium distribution ratio between the slag and iron tends to decrease. Moreover, the recovery rate of vanadium in pig iron has a rising trend with increasing the optical basicity of the slag. The addition of MgO in the slag to increase the slag optical basicity can not only improve the vanadium reduction but also promote the formation of magnesium-containing anosovite, which is beneficial to following titanium extraction.

Slag basicity (mass ratio of CaO to SiO2) is an important index to ensure smooth operation and efficient separation between the metal and slag within the metallurgical industry. Effects of basicity of the high titanium slag on the recovery of iron and vanadium, the separation behaviors between iron and slag, as well as the slag foaming behavior during the smelting process with the operating temperature of 1550 °C have been experimentally investigated. The results show that the recovery ratios of iron and vanadium increase with higher slag basicity. The amount of dispersed metallic iron droplets in the slag decreases sharply when the basicity increases from 0.5 to 0.8, then decreases slowly when the basicity is from 0.8 to 1.1. Furthermore, the perovskite (CaTiO3) phase appears when the basicity is above 0.8. The foaming height is at a high level when the basicity is from 0.5 to 0.6, then it decreases when the basicity is increased from 0.6 to 0.7, whereas it slowly increases with higher slag basicity. Finally, the optimum basicity range of titanium slag for efficient smelting of vanadium titanomagnetite is proposed to be 0.8 to 1.1 by considering the combined effects on the recovery, foaming, and minimization on the retention of the metal droplets within the slag.

A novel method for recovering zinc from zinc ferrite by reduction roasting-ammonia leaching was studied in this paper. The reduction thermodynamic of zinc ferrite by CO was analyzed. The effects of roasting parameters on the phase transformation and conversion rate of zinc ferrite, and the leaching behavior of zinc from the reductive roasted samples by ammonia leaching, were experimentally investigated. The mineralogical phase compositions and chemical compositions of the samples were characterized by X-ray diffraction and chemical titration methods, respectively. The results showed that most of the zinc ferrite was transformed to zinc oxide and magnetite after weak reduction roasting. 86.43% of the zinc ferrite was transformed to zinc oxide under the optimum conditions: CO partial pressure of 25%, roasting temperature of 750°C, and roasting duration of 45 min. Finally, under the optimal leaching conditions, 78.12% of zinc was leached into the solution from the roasted zinc ferrite while all iron-bearing materials were kept in the leaching residue. The leaching conditions are listed as follows: leaching duration of 90 min, ammonia solution with 6 mol/L concentration, leaching temperature of 50°C, solid-to-liquid ratio of 40 g/L, and stirring speed of 200 r/min.

In order to improve the control on sulphur content at the endpoint of Kanbara Reactor (KR) desulphurization process, the case-based reasoning (CBR) method based on mechanistic model correction is u...

The suitable titanium slag composition with high titanium content for electric furnace smelting of vanadium titanomagnetite was investigated through thermodynamics and related phase diagram analysis. According to the thermodynamic results, low-melting-point regions and MgTi2O5 primary phase area in the phase diagrams, the suggested titanium slag composition for the present vanadium titanomagnetite metallized pellets should consist of 50% TiO2, 8%–12% MgO and 13% Al2O3 (mass fraction) with a binary basicity of 0.8–1.2. Finally, the verified smelting experiments were conducted and successful separation of the molten iron from the titanium slag is obtained. The obtained vanadium-containing molten iron contains 0.681% V and 0.267% Ti, and the obtained titanium slag contains 52.21% TiO2 (mass fraction), in which MgTi2O5 is the primary phase. The titanium resource in the final titanium slag production could be used to produce TiO2 pigment by acid leaching methods.

Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH4Cl–NH3·H2O solution. The thermodynamics and phase conversion of Zn2SiO4 to zinc oxide (ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn2SiO4 mole ratio (n(CaO)/n(Zn2SiO4)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn2SiO4 was first converted to Ca2ZnSi2O7 and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn2SiO4 to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.

Generally in the nickel converter slag, metals are mainly in the form of sulfides, which are difficult to separate from slag. Although metal oxides in the slag, such as NiO, CoO, and Cu2O, are easily reduced into metal using carbon, the presence of sulfur inhibits the reduction reaction. In this study, the addition of Fe2O3 to nickel converter slag produced desulfurized slag, which enhanced the carbothermal reduction process. Increasing the desulfurization rate promoted the conversion of sulfides into oxides in slag, which significantly increased the activity of NiO, Cu2O, and Fe2O3. However, the residual sulfur content had no significant effect on the activity of FeO and CoO, due to the high initial FeO content and cobalt existing mainly in the form of oxides. The optimum addition of Fe2O3 was 15.0 g per 100 g nickel slag, while the desulfurization ratio was 36.84% and the rates of nikel, cobalt and copper recovery were 95.33%, 77.73%, and 73.83%, respectively.

The melting behavior of titanium-bearing electric furnace slag is a key factor for effective smelting of vanadium titanomagnetite in electric furnaces. The melting behavior of synthetically produced CaO-SiO2-MgO-Al2O3-TiO2 slags with different TiO2 contents (48 wt.% to 54 wt.%), CaO/SiO2 mass ratios (0.8 to 1.4), and MgO contents (8 wt.% to 14 wt.%) was experimentally investigated in this study. The results demonstrate that the softening and melting temperatures decreased as the CaO/SiO2 ratio was increased but increased with increasing contents of TiO2 and MgO. The predicted slag phase composition showed that increasing the CaO/SiO2 mass ratio promoted CaTiO3 formation, whereas the proportion of MgTi2O5 phase increased with increasing MgO content. Appropriate slag compositions with binary basicity of 0.8 to 1.0, 10 wt.% to 12 wt.% MgO, and more than 48 wt.% TiO2 are suggested to obtain titanium-bearing electric furnace slag with low melting temperature and appropriate phase composition for titanium extraction.

The compressive strength of the roasted fluoride-containing iron ore pellets reached to 2463 N/P at roasting temperature 1080 °C for 10 min with appropriate preheating conditions. However, its compression strength drastically dropped no matter increasing or decreasing the roasting temperature and time. Unfortunately, the narrow suitable roasting temperature range seriously affects the normal pellets productions, while the low compressive strength of pellets limits their application in the blast furnace. In the present study, The SEM-EDS, TG-DSC techniques, and thermodynamic software were adopted to systematically investigate the roasting behaviors of fluoride-bearing iron concentrate pellet and the formation mechanism of liquid phases in the pellets during the roasting process. Furthermore, according to the EDS results and the phase diagram analysis, the low-melting-point phase Ca4Si2F2O7 was generated with the existence of fluorine and Na(K)AlSi3O8 was formed with the existence of alkali metal. These low-melting-point phases can react with the CaAl2Si2O8, CaSiO3, SiO2, and CaF2 to form the complex eutectics which had lower melting points. Briefly, the excessive amount of liquid phases in pellet generated from the fluorine and alkali metals primarily caused the poor roasting properties of the fluoride-containing pellet.

The suppression of titanium oxide reduction enables both successful separation of iron from slag and smooth production operations for the smelting of vanadium titanomagnetite. This study investigates the distribution behavior of titanium between the hot metal and enriched titanium slag during the electric furnace smelting of vanadium titanomagnetite metallized pellets. Activity calculations indicate that the TiO2 activity decreases with increasing amounts of CaO and MgO, whereas the TiO2 activity increases with smelting temperature. Additionally, high temperature experiments demonstrate that the titanium distribution ratio between the molten iron and titanium slag decreases with increasing CaO content in the slag. With the presence of high CaO content, increasing MgO content does not have a significant influence on the titanium distribution ratio. The titanium distribution ratio decreases with an increase in slag optical basicity but increases with an increment of the smelting temperature.

The behavior of silicon during smelting of vanadium titanomagnetite metallized pellets in an electric furnace has been investigated thermodynamically and experimentally. Thermodynamic calculations indicated that the activities of free oxygen ion and silicate increase with increasing CaO and MgO content in the titanium slag, whereas silica activity decreases as CaO and MgO increase. High-temperature experiments demonstrated that the Si content in the molten iron and distribution ratio of silicon between metal and slag decreased with suitable additions of CaO and MgO, but increased with smelting temperature. The Si content in the iron positively correlated with the Ti content in the iron but showed no obvious relationship with the V content in the iron. The Si and Ti contents increased with increasing smelting temperature. The Si content should be controlled below about 0.2 wt.% for effective and comprehensive smelting of vanadium titanomagnetite.

With the increase of hot metal ratio in electric arc furnace (EAF) steelmaking process, physical sensible heat and chemical latent heat of gas increased significantly. As EAF raw material condition is similar to basic oxygen furnace (BOF), and the condition of BOF gas waste heat utilization technology is mature, waste heat utilization technology in EAF steelmaking will be getting more and more attention. Scrap preheating and steam production as mature technology is the main way of EAF gas waste heat utilization. Power generation converted high temperature steam to electricity will further improve the EAF gas utilization value. The previous ways are to recycle physical sensible heat of EAF gas. To use chemical latent heat of gas, the secondary combustion technology is usually adopted to make CO fully burn into CO2. Coal gas production can fully recycle the chemical latent heat of gas theoretically, which is higher efficiency than other ways. Coal gas production needs a stable steelmaking process to stabilize high temperature gas. And the way need to develop EAF sealing technology, oxygen removal technology and gas purification technology, to make gas content meet the requirements of coal gas production in EAF steelmaking process.

A novel process to prepare titanium dioxide from Ti-bearing electric furnace slag by NH4HF2-HF leaching and hydrolyzing process has been developed. In this present study, the effects of [NH4+]/[F] mXolar ratio, leaching temperature, [F] concentration, liquid/solid mass ratio, leaching time on the Ti extraction, and the phase transformations have been investigated to reveal the leaching mechanism of Ti-bearing electric furnace slag in NH4HF2-HF solution. In the NH4HF2-HF leaching process, the MgTi2O5 and Al2TiO5 are converted to TiF62− and Mg-Al-bearing precipitate. Ti extraction rate reached 98.84% under the optimal conditions. In addition, 98.25% iron ions can be removed in the presence of NaCl prior to hydrolysis process. The effects of pH and temperature on the selective hydrolysis of TiF62− during hydrolysis process were also studied. In the hydrolysis process, the TiF62− is converted to (NH4)2TiOF4. By calcination, high grade TiO2 powder with its purity of 99.88% was obtained, using which the products, well crystallized anatase and rutile, were obtained through roasting at 800 °C and 1000 °C, respectively.

In modern EAF steelmaking process, control of the nitrogen content of molten steel has become more and more important and bottom-blowing technique has been widely applied to promote the molten bath...

Fluorine-bearing iron ore is unique and complex. Serious preheating and roasting problems of fluorine-bearing iron concentrate pellets appear during the industrial production by the grate-kiln process. Besides, specularite has low hydrophilicity, undesirable particle size and shape, dense and smooth particle surface and poor assimilation performance. Thus, it has not yet been widely applied in production. This study applied the specularite to improve the preheating and roasting characteristics of the fluorine-bearing iron concentrate pellets. The experiment results indicated that the roasting properties of fluorine-bearing iron concentrate pellets were improved and the compression strength of roasted pellets increased with the addition of 10% specularite. The suitable roasting temperature range was expanded to more than 140 °C. Compared to other addition, the total iron of pellets was also increased. In addition, the improvement mechanism of adding specularite on the properties of fluorine-bearing iron concentrate pellets was discussed.

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

Supersonic oxygen-supplying technologies, including the coherent supersonic jet and the conventional supersonic jet, are now widely applied in electric arc furnace steelmaking processes to increase the bath stirring, reaction rates, and energy efficiency. However, there has been limited research on the impact characteristics of the two supersonic jets. In the present study, by integrating theoretical modeling and numerical simulations, a hybrid model was developed and modified to calculate the penetration depth and impact zone volume of the coherent and conventional supersonic jets. The computational fluid dynamics results were validated against water model experiments. The results show that the lance height has significant influence on the jet penetration depth and jet impact zone volume. The penetration depth decreases with increasing lance height, whereas the jet impact zone volume initially increases and then decreases with increasing lance height. In addition, the penetration depth and impact zone volume of the coherent supersonic jet are larger than those of the conventional supersonic jet at the same lance height, which illustrates the advantages of the coherent supersonic jet in delivering great amounts of oxygen to liquid melt with a better stirring effect compared to the conventional supersonic jet. A newly defined parameter, the k value, reflects the velocity attenuation and the potential core length of the main supersonic jet. Finally, a hybrid model and its modifications can well predict the penetration depth and impact zone volume of the coherent and conventional supersonic jets.

The vanadium-titanium magnetite concentrate from Panxi region of China was pretreated by high pressure roller grinding (HPRG) and then used in pelletization. Size distribution change of the vanadium-titanium magnetite concentrate after HPRG and the improvement of its green pellet strength were investigated. The results indicated that, besides the increase of fine particles, the vanadium-titanium magnetite concentrate after HPRG had a smaller size ratio of fine particle to coarse particle of 0.126, meaning a lower porosity, compared with the size ratio of raw material of 0.157. The concentrate particles were more closely packed when there was a smaller size ratio of fine particle to coarse particle. The particle packing in the green pellets was closer after HPRG, which strengthened the green pellets with an average drop number of 5.1 (drop height of 0.5 m) and average compressive strength of 13.1 N per pellet of 11 mm in diameter.

A SiC/ZrSiO4–SiO2 (SZS) coating was successfully fabricated on the carbon/carbon (C/C) composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock resistance. The anti-oxidation properties under different oxygen partial pressures (OPP) and thermal shock resistance of the SZS coating were investigated. The results show that the SZS coated sample under low OPP, corresponding to the ambient air, during isothermal oxidation was 0.54% in mass gain after 111 h oxidation at 1500 °C and less than 0.03% in mass loss after 50 h oxidation in high OPP, corresponding to the air flow rate of 36 L/h. Additionally, the residual compressive strengths (RCS) of the SZS coated samples after oxidation for 50 h in high OPP and 80 h in low OPP remain about 70% and 72.5% of those of original C/C samples, respectively. Moreover, the mass loss of SZS coated samples subjected to the thermal cycle from 1500 °C in high OPP to boiling water for 30 times was merely 1.61%.

The tin-bearing middling obtained by flotation in Huanggang, Inner Mongolia, is with SnO2 content of 3–5 wt%, which was stacked and cannot be utilized, leading to the tin resource wasting and environmental pollution. In order to recover this tin resource, the tin volatilization behaviour in the tin-bearing middling during carbothermic reduction in rotary kiln process was studied in this paper. The results show that the volatilization rate can reach 87.4% and the SnO2 content in the residue decreased to 0.57 wt% under the conditions of Kiln tail: Kiln middle: Kiln head (coal addition ratio) with 1:2:7, the proportion of ball and coal was 20 kg: 20 kg and the pellets size was 5–10 mm at 1000 °C for 2 h. The research could provide a technical reference for the utilization of the tin-bearing middling.

Lateritic iron ore has not been used effectively due to excess content of multiple metals. In this work, separation of aluminium from a high-aluminium lateritic iron ore was achieved by the process of ‘direct reduction with sodium sulfate-magnetic separation’, with a powdered direct reduced iron (DRI) produced. It is found that the presence of 12% sodium sulphate during reductive roasting significantly improves separation of iron and aluminium in magnetic separation: the total iron grade (TFe) of powdered DRI increases from 80.6 to 92.0% and the Al2O3 content decreases from 9.8 to 1.3% correspondingly. The presence of sodium sulphate results in formation of sodium aluminosilicates instead of FeAlO2. Moreover, sodium sulphate significantly promotes growth of metallic iron grains which is beneficial to sufficient liberation and separation of metallic iron grains from gangue minerals in grinding and magnetic separation.

Considering the complicated and harsh conditions in the electric arc furnace (EAF) steelmaking process, the precise endpoint control technology is a crux that influences the product quality and production costs of the molten steel because precise endpoint control can control the endpoint carbon content and the endpoint oxidation. In this paper, a new hybrid prediction model was established to predict the endpoint carbon content in EAF steelmaking, which included the mechanism model based on the mass transfer process and the Extreme Learning Machine (ELM) optimized by the Evolving Membrane Algorithm (EMA). The mechanism model was calibrated with corrected parameters obtained from the ELM-EMA algorithm. As a result, the shortages that the mechanism model can’t work precisely and that the single mathematical algorithm model lacks the analysis of the metallurgy process were overcome by the hybrid prediction model. Meanwhile, modifying ELM algorithm by EMA algorithm can improve the generalization performance of single-hidden-layer feed-forward neural networks. The experiments on a 50t EAF demonstrated that the proposed model had a good generalization performance and good prediction accuracy.

The application of the bottom-blowing in the steelmaking process of EAF can effectively shorten the mixing time of the molten bath, accelerate the removal of carbon, phosphorus and sulfur, and improve the production efficiency and product quality. Information about the effects of changing molten steel velocity during the smelting process would help to accurately model molten bath dynamics. In this study, numerical simulation software was employed to simulate the EAF steelmaking process under variable eccentric bottom-blowing gas flow situations. Velocity field data were obtained for the different bottom-blowing schemes. When other nozzles’ bottom-blowing gas flow rates were maintained at 133 L/min, the average velocity of molten steel in EBT (Eccentric Bottom Tapping Area) was increased from 2.8 × 10−3 to 3.4 × 10−3 m/s with the eccentric gas flow rate of bottom-blowing from 100 to 267 L/min, the average velocity of molten steel in the bath increased from 4.3 × 10−3 to 4.6 × 10−3 m/s with the eccentric gas flow rate of bottom-blowing from 100 to 267 L/min.

Zinc ferrite (ZnFe2O4), one of the major forms of zinc in Electric Arc Furnace (EAF) dust and zinc leaching residue, is very difficult to chemically dissolve in either acidic or alkaline solutions. In spite of the zinc resources in the Electric Arc Furnace (EAF) dust and zinc leaching residue are abundant, there is no mature utilization technology. This situation not only causes the waste of resources, but also produces the harm to the environment. In the paper, the basic principle of this process has been established by revealing the phase equilibria in the CaO–Fe2O3–ZnO system, where Ca2Fe2O5 can be in equilibrium with ZnO rather than ZnFe2O4 at higher CaO region. It has also been demonstrated that the formed ZnO can be solved by ammonia-leaching and Ca2Fe2O5 keep in solid residue, which can be used as a flux for steel refining.