The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V_(2)O_(5),which is the predominant binary mixture involved in the vanadium recovery process.Thermal an...The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V_(2)O_(5),which is the predominant binary mixture involved in the vanadium recovery process.Thermal analysis,X-ray diffraction spectroscopy,scanning electron microscopy,and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples.The extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray patterns.The results indicate that the solid reaction of the CaO−V_(2)O_(5)mixture is strongly influenced by the reaction temperature and CaO/V_(2)O_(5)mole ratio.The transformation of calcium vanadate in-volves a step-by-step reaction of CaO−V_(2)O_(5),CaO−CaV_(2)O_(6),and CaO−Ca_(2)V_(2)O7 depending on the CaO/V_(2)O_(5)mole ratio.The kinetic data of the solid reaction of the CaO−V_(2)O_(5)(1:1)mixture followed a second-order reaction model.The activation energy(Ea)and preexponential factor(A)were determined to be 145.38 kJ/mol,and 3.67×10^(8)min^(−1),respectively.展开更多
Preparation of high acidity coefficient slag wool fiber with molten slag and modifying agents is considered to be a positive approach for value-added utilization of blast furnace slag. In order to achieve the multi-pu...Preparation of high acidity coefficient slag wool fiber with molten slag and modifying agents is considered to be a positive approach for value-added utilization of blast furnace slag. In order to achieve the multi-purposes of fiber-forming, energy saving, and waste heat recovery, the modifying agents that can improve the acidity coefficient of slag effectively, economically, and environmentally were investigated. Three agents with different acidity coefficients were adopted to modify slag and manufacture wool fibers. The effect of agent and slag proportion on the melting temperature and viscosity of molten slag was studied at a fixed acidity coefficient of 1.8 and 2.0. The results indicate that the sample modified with high acidity coefficient agent and high slag proportion has lower melting temperature and viscosity. The effect of agent and slag temperature on the fiber diameter was also investigated when the acidity coefficient of slag is 2.0. At a fixed slag proportion of 50 wt.%, the mean diameter decreases with increasing temperature and decreasing viscosity coefficient. Besides, the temperature drops caused by the addition of agents and energy consumption of samples for heating the slag were also analyzed.展开更多
High-quality upgraded titanium slag obtained through semi-molten reduction with the addition of Na_(2)CO_(3)is important for the fluidizing chlorination process to produce TiO_(2)pigments.The key is the effect of Na_(...High-quality upgraded titanium slag obtained through semi-molten reduction with the addition of Na_(2)CO_(3)is important for the fluidizing chlorination process to produce TiO_(2)pigments.The key is the effect of Na_(2)CO_(3)on the reduction behavior of iron.Therefore,the effects of Na_(2)CO_(3)on reduction mechanism and kinetics of iron during deep reduction of ilmenite concentrate were studied.The results indicated that the metallization ratio of the reduced sample increased with increasing temperature,time,and dose of Na_(2)CO_(3).The addition of Na_(2)CO_(3)significantly accelerated the reduction of iron in the ilmenite concentrate and promoted the growth of iron particles.However,the addition of Na_(2)CO_(3)produced sodium iron titanates;thus,the metallization ratio of the sample decreased with an increase in the temperature and time when the temperature was above 1200℃and the time was more than 30 min.When the doses of Na_(2)CO_(3)were 0,3,and 6 wt.%,the reduction of iron was controlled by the interfacial chemical reaction,both the interfacial chemical reaction and diffusion,and diffusion,respectively,and the apparent activation energies were 134.91,64.89,and 120.82 kJ/mol,respectively.展开更多
To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The...To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) molar ratios on the roasting and leaching behaviours of vanadium slag was investigated, and the optimum process conditions were obtained. The results show that in the roasting experiment, under the conditions of roasting temperature of 850 ℃ and roasting time of 2 h, the main kinds of vanadate transformed from Ca_(2)V_(2)O_(7) to Ca_(5)Mg_(4)V_(6)O_(2)4 and then to Mg_(2)V_(2)O_(7) with the increase in the MgO/(CaO + MgO) molar ratio. In the leaching experiment, under the conditions of particle size less than 75 μm, leaching temperature of 50 ℃, pH of 2.5, liquid–solid ratio of 20:1, and MgO/(CaO + MgO) molar ratio of 1:3, the leaching efficiency of vanadium is increased by about 5%, but the substitution of MgO for most or all of CaO will significantly reduce the leaching efficiency of vanadium. Furthermore, the leaching efficiency of impurities (P and Cr) can also be decreased by a composite addictive (CaO + MgO) roasting process. The X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and X-ray photoelectron spectroscopy of the original vanadium slag and solid products of both roasting and leaching processes were also evaluated.展开更多
Alkali-activated cement(AAC)is either clinker-less or free,and it is also environmentally friendly due to its low carbon footprint and wide range sources.Industrial wastes,like steel slag and blastfurnace slag,usually...Alkali-activated cement(AAC)is either clinker-less or free,and it is also environmentally friendly due to its low carbon footprint and wide range sources.Industrial wastes,like steel slag and blastfurnace slag,usually have latent hydraulic reactivity,and can be used as precursors of AAC.Both clinkerless and clinker-free AAC were prepared from the mixture of steel slag and blastfurnace slag by using water glass as an activator,and four different recipes which satisfied the strength requirement of 42.5R Portland cement were obtained.Each recipe of AAC exhibited better resistance to sulfate attack and frost attack than Portland cement.AAC showed huge drying shrinkage,but it was equivalent to that of Portland cement as steel slag content increased to 40%.The AAC also had quite low risk of alkali-aggregate reaction.Microstructure analysis showed that the major products were calcium silicate hydrate(C–S–H),calcium aluminosilicate hydrate(C–A–S–H)and zeolite-like phases.Ettringite was also detected in the binder when gypsum was contained in the precursors.展开更多
As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is pres...As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is presented herein.Using an auxiliary molten salt,V_(2)O_(3)was successfully transformed into V by Mg reduction.The by-product,MgO,was transformed into MgCl_(2)by adding ZrCl_(4),which prevented the generation of MgV_(2)O_(4)and allowed the reaction to proceed smoothly.The rod-like alloy phases,Zr_(0.03)V_(1.97),which formed in the presence of excess Mg,may hinder the diffusion of oxygen from the product.The recovery rate of vanadium after separation and purification was approximately 45%–50%,where the main loss occurred during ball milling.Under the optimal conditions(Mg content of 48.3%,reduction time of 1.5 h,and temperature of 850℃),the purity of vanadium exceeded 99 wt.%,and the O content decreased to 0.34 wt.%.展开更多
The preparation of high-strength pellets from Panzhihua ilmenite concentrate is important for the hydrogen-rich smelting of titania slag and was investigated.The effects of the magnetite concentrate and heating proced...The preparation of high-strength pellets from Panzhihua ilmenite concentrate is important for the hydrogen-rich smelting of titania slag and was investigated.The effects of the magnetite concentrate and heating procedure including the pre-heating temperature and period as well as roasting temperature and period on the compressive strength of the roasted pellets were investigated.High-strength ilmenite concentrate pellets(>2000 N)were prepared by optimizing the roasting process.The addition of magnetite concentrate is beneficial for increasing the compressive strength of the Panzhihua ilmenite concentrate pellet by oxidizing hematite which filled the pseudobrookite particles,functioned as a bridge bond,and improved the interconnection between the grains.The compressive strength can reach up to 2900 N when the ilmenite concentrate pellet with 15%magnetite concentrate is pre-heated above 800℃ for 20 min and then roasted at 1250℃ for 20 min.In addition,there is an overall upward trend in the compressive strength with an increase in the pre-heating temperature and period as well as the roasting temperature and period.The micromorphology and strengthening consolidation mechanism of Panzhihua ilmenite concentrate pellets were also discussed.展开更多
Driven by the double carbon policy,the iron and steel industry urgently needs to implement a new development concept to strengthen the use of solid waste resources from ironmaking and steelmaking and effectively enhan...Driven by the double carbon policy,the iron and steel industry urgently needs to implement a new development concept to strengthen the use of solid waste resources from ironmaking and steelmaking and effectively enhance the economic benefits of recycling resources in order to reduce the accumulation of solid waste resources in the iron and steel industry.The iron and steel production process produces more than 600 million tons of solid waste annually,including metallurgical dust sludge,blast furnace slag and steel slag,etc.From the perspective of environmental friendliness,the efficient utilization of ironmaking and steelmaking solid waste resources through innovative cross-industry technologies is of great significance to the low-carbon,green and high-quality development goals of the iron and steel industry.展开更多
The titanium industry can hardly bypass the titania-containing slags,and the slag physicochemical properties are essential in the metallurgical reactor design and process control.The TiO_(2)–FeO-based slags and TiO_...The titanium industry can hardly bypass the titania-containing slags,and the slag physicochemical properties are essential in the metallurgical reactor design and process control.The TiO_(2)–FeO-based slags and TiO_(2)–SiO_(2)–CaO-based slags are the main metallurgical slag systems in the titanium resource utilization processes.To elaborate the role of TiO_(2) in the physicochemical properties of titania-containing metallurgical slags,the physicochemical properties including titanium redox ratio,liquidus temperature,viscosity,electrical conductivity,density,surface tension,thermal conductivity,and sulfide capacity were critically reviewed.Moreover,the property prediction models were briefly introduced with regards to the limitations of the existing models.The property prediction models are still required to evolve since not all properties of titania-containing slags can be well modeled.As the slag structure has an intimate relationship with slag properties,the structural details of the titania-containing slag were investigated by using a combination of spectroscopic technologies,but the knowledge of the slag structure was not fully ascertained.The potential research fields related to the physicochemical properties and structure of the titania-containing slags were also suggested.展开更多
The effect of the Al2O3 content and basicity (the molar ratio of MgO to SiO2) on the viscosity of a SiO2-MgO-FeOAl2O3-CaO slag was studied to fully understand the smelting process of the ferronickel alloy. Experimenta...The effect of the Al2O3 content and basicity (the molar ratio of MgO to SiO2) on the viscosity of a SiO2-MgO-FeOAl2O3-CaO slag was studied to fully understand the smelting process of the ferronickel alloy. Experimental results show that the slag is a mixture of liquid and solid phases at the experimental temperature. The viscosity decreased as the basicity increased and increased as the Al2O3 content increased. To determine the effect of the Al2O3 content and basicity on the structure of the molten slag, Raman spectroscopy was performed on the slag sample, which was quenched from the high temperature with water. The Raman spectra showed that the fractions of the polymerization structural units decreased significantly as the basicity of the slag increased, resulting in a decrease in the apparent viscosity. However, Al2O3 acts as a network former in the slag system, thereby making the slag structure further polymerized and increasing the viscosity.展开更多
The formation behavior of CaTiO3 during electro-deoxidization of ilmenite concentrate to prepare Fe–Ti alloy was investigated by experiments and simulation.The results indicate that the formation and decomposition of...The formation behavior of CaTiO3 during electro-deoxidization of ilmenite concentrate to prepare Fe–Ti alloy was investigated by experiments and simulation.The results indicate that the formation and decomposition of intermediate products,CaTiO3,are inevitable steps during electro-deoxidization of ilmenite concentrate.CaTiO3 can be generated through the hydrolyzation of molten salt and electrochemistry reaction during electrochemical process.The main reason for the generation of CaTiO3 is the electrochemistry reaction between Ca^2+ from molten salt and TiO2 in the cathode.With the proceeding of the electro-deoxidization,CaTiO3 is further electrolyzed to form titanium sub-oxide.The current efficiency can be improved when CaTiO3 forms in the cathode by adding CaCO3 during sintering process.展开更多
The effect of magnesia on calcium ferrite(CaO.Fe2O3)reduction by CO was examined by isothermal thermogravimetry.Samples of calcium ferrite added with 0,2,4,and 8 wt.%magnesia(abbreviated as CF,CF2M,CF4M,and CF8M)were ...The effect of magnesia on calcium ferrite(CaO.Fe2O3)reduction by CO was examined by isothermal thermogravimetry.Samples of calcium ferrite added with 0,2,4,and 8 wt.%magnesia(abbreviated as CF,CF2M,CF4M,and CF8M)were prepared.Phase composition was analyzed by X-ray diffraction,and the results indicated that CF2M and CF4M are reduced to lower reduction degree and with lower apparent activation energy than CF;and CF8M with more MgO.Fe2O3 is reduced to a lower degree and with more difficulty compared with CF.Reduction rate analysis revealed that CF,CF2M,CF4M,and CF8M reductions are all typical two-step reactions with the order of CF→CWF(CaO.FeO.Fe2O3)→Fe.The apparent reduction activation energies of CF,CF2M,CF4M,and CF8M are 46.89,37.30,17.30,and 29.20 kJ/mol,respectively.Sharp analysis depicted that CF2M,CF4M,and CF8M reductions are all described by 2D Avrami–Erofeev(A–E)equation(A2)in the whole process,while CF reduction is first expressed by A2 and then by 3D A–E equation(A3).Different from shrinking core model,a new kinetic model for powdery samples reduction was proposed to illustrate the relationship among reduction rates,reduction routes,and model functions.展开更多
The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of appare...The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy(Ea)were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction(G(α)=1-(1-α)~2,whereαis the conversion degree)plays an important role in the whole oxidation process.At the first stage(α=0.05-0.30),the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage(α=0.30-0.50),the oxidation process is completely controlled by the secondary chemical reaction(G(α)=1-(1-α)~2).At the third stage(α=0.50-0.95),the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G(α)=(1-α)^(-1)(β=10K·min^(-1),whereβis heating rate),G(α)=(1-α)^(-1/2)(β=15-20K·min^(-1)),and G(α)=(1-α)^(-2)(β=25K·min^(-1)),respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol^(-1).展开更多
The effect of pre-oxidation degree of Panzhihua ilmenite concentrate on the gaseous reduction by carbon monoxide was investigated.The raw ilmenite concentrates were pre-oxidized at 600,700,800,900,and 1000°C for ...The effect of pre-oxidation degree of Panzhihua ilmenite concentrate on the gaseous reduction by carbon monoxide was investigated.The raw ilmenite concentrates were pre-oxidized at 600,700,800,900,and 1000°C for 2 h,respectively.The phase change,FeO content,and morphology after the oxidation at various temperatures were characterized.The oxidation degree was calculated according to the change of FeO content.Thermogravimetry was performed on the oxidized ilmenite concentrate samples(oxidized at 600,800,and 1000°C)at 850,900,and 950°C,respectively.The results show that the pre-oxidation of ilmenite concentrate can accelerate the reduction process:the higher pre-oxidation degree,the faster reduction rate.The high pre-oxidation degree of ilmenite concentrate is beneficial to accelerate the subsequent reduction process in two ways.Three stages of the reduction process were divided via the first derivatives of reduction degree,and the reduction mechanism and apparent activation energy were discussed subsequently.展开更多
A novel granulation process that involved the use of a rotary multi-nozzles cup atomizer and water cooling was proposed for ferroalloy manufacturing.The effects of rotating speed and nozzle diameter on the properties ...A novel granulation process that involved the use of a rotary multi-nozzles cup atomizer and water cooling was proposed for ferroalloy manufacturing.The effects of rotating speed and nozzle diameter on the properties of FeSi75 alloy(containing 75 wt.%Si)granules were investigated.Results indicated that median granule diameter decreased as rotating speed in creased,and initially increased and then decreased as nozzle diameter in creased.The optimal conditi ons for the gra nulation of FeSi75 alloy were a rotating speed of 150 r/min and nozzle diameter of 10 or 12 mm.The phase composition,micromorphology,and elemental distribution of the FeSi75 alloy granules were also studied by X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectrometry.In order to provide guidance for the layout and water depth of the tank,the solidification behavior of ferrosilicon alloy droplet was numerically studied.A simplified model was established to elucidate the traveling trajectory and heat transfer of alloy droplet in air and cooling water during the atomization process.The solidification time of droplet with different thicknesses of solidification layer increased with the in crease in alloy droplet diameter.展开更多
The chromium-bearing titanomagnetite ore will turn to be the important raw material for blast furnace process in Panxi area,China.The reduction behavior of Cr2O3 between CaO-SiO2-Al2O3-TiO2-Cr2O3 and Fe-C systems was ...The chromium-bearing titanomagnetite ore will turn to be the important raw material for blast furnace process in Panxi area,China.The reduction behavior of Cr2O3 between CaO-SiO2-Al2O3-TiO2-Cr2O3 and Fe-C systems was investigated.The effect of TiO2 content in the slag system on the reduction of Cr2O3,TiO2,and SiO2 and the con sumption of C in hot metal was investigated by both theoretical calculation and physical experiment.The theoretical calculation results reveal that higher reduction temperature promotes the reduction of Cr and Ti,while high basicity and TiO2 content have little influence on the reduction of chromium but significantly influence the reduction of Ti.The smelting reduction experiment results show that the content of Cr in hot metal significantly in creases with extendi ng the reduction time and decreases with the increase in TiO2 content.However,the content of Ti in hot metal significantly increases as the TiO2 increases,reaching 0.073,0.085,0.107,and 0.121 wt.%for 5,10,15,and 20 wt.%of TiO2 input,respectively.Kinetic studies proved that the reduction of Cr2O3 was a first-order reaction.The addition of TiO2 inhibited the reduction of Cr2O3 and resulted in the decrease in reaction rate constant.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.52004044)the Natural Science Foundation of Chongqing,China(No.cstc2019jcyj-bshX0068)Chongqing Postdoctoral Innovation Program(No.CQBX201904),and the Open Project Founded by the State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization.
文摘The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V_(2)O_(5),which is the predominant binary mixture involved in the vanadium recovery process.Thermal analysis,X-ray diffraction spectroscopy,scanning electron microscopy,and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples.The extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray patterns.The results indicate that the solid reaction of the CaO−V_(2)O_(5)mixture is strongly influenced by the reaction temperature and CaO/V_(2)O_(5)mole ratio.The transformation of calcium vanadate in-volves a step-by-step reaction of CaO−V_(2)O_(5),CaO−CaV_(2)O_(6),and CaO−Ca_(2)V_(2)O7 depending on the CaO/V_(2)O_(5)mole ratio.The kinetic data of the solid reaction of the CaO−V_(2)O_(5)(1:1)mixture followed a second-order reaction model.The activation energy(Ea)and preexponential factor(A)were determined to be 145.38 kJ/mol,and 3.67×10^(8)min^(−1),respectively.
基金the National Natural Science Foundation of China(Grant No.51974054)Scientific and Technological Research Program of Chongqing Municipal Education Commission(No.KJQN202201537)+2 种基金Research Foundation of Chongqing University of Science and Technology(No.ckrc2020017)Natural Science Foundation Project of Chongqing(No.cstc2021jcyj-msxmX0911)Chongqing Science and Technology Commission(No.sl202100000144).
文摘Preparation of high acidity coefficient slag wool fiber with molten slag and modifying agents is considered to be a positive approach for value-added utilization of blast furnace slag. In order to achieve the multi-purposes of fiber-forming, energy saving, and waste heat recovery, the modifying agents that can improve the acidity coefficient of slag effectively, economically, and environmentally were investigated. Three agents with different acidity coefficients were adopted to modify slag and manufacture wool fibers. The effect of agent and slag proportion on the melting temperature and viscosity of molten slag was studied at a fixed acidity coefficient of 1.8 and 2.0. The results indicate that the sample modified with high acidity coefficient agent and high slag proportion has lower melting temperature and viscosity. The effect of agent and slag temperature on the fiber diameter was also investigated when the acidity coefficient of slag is 2.0. At a fixed slag proportion of 50 wt.%, the mean diameter decreases with increasing temperature and decreasing viscosity coefficient. Besides, the temperature drops caused by the addition of agents and energy consumption of samples for heating the slag were also analyzed.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U1902217 and 52104325).
文摘High-quality upgraded titanium slag obtained through semi-molten reduction with the addition of Na_(2)CO_(3)is important for the fluidizing chlorination process to produce TiO_(2)pigments.The key is the effect of Na_(2)CO_(3)on the reduction behavior of iron.Therefore,the effects of Na_(2)CO_(3)on reduction mechanism and kinetics of iron during deep reduction of ilmenite concentrate were studied.The results indicated that the metallization ratio of the reduced sample increased with increasing temperature,time,and dose of Na_(2)CO_(3).The addition of Na_(2)CO_(3)significantly accelerated the reduction of iron in the ilmenite concentrate and promoted the growth of iron particles.However,the addition of Na_(2)CO_(3)produced sodium iron titanates;thus,the metallization ratio of the sample decreased with an increase in the temperature and time when the temperature was above 1200℃and the time was more than 30 min.When the doses of Na_(2)CO_(3)were 0,3,and 6 wt.%,the reduction of iron was controlled by the interfacial chemical reaction,both the interfacial chemical reaction and diffusion,and diffusion,respectively,and the apparent activation energies were 134.91,64.89,and 120.82 kJ/mol,respectively.
基金supported by the National Natural Science Foundation of China(No.52004044)the Natural Science Foundation of Chongqing(Nos.cstb2022nscq-msx0801 and cstc2019jcyjqX0024)+3 种基金the Foundation of Chongqing University of Science and Technology(No.ckrc2022030)the Graduate Research Innovation Project of Chongqing University of Science and Technology(No.YKJCX2220216)the Science and Technology Innovation Training Program of Chongqing University of Science and Technology(No.2022046)the College Students'innovation and entrepreneurship training program of Chongqing University of Science and Technology(No.2022007).
文摘To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) molar ratios on the roasting and leaching behaviours of vanadium slag was investigated, and the optimum process conditions were obtained. The results show that in the roasting experiment, under the conditions of roasting temperature of 850 ℃ and roasting time of 2 h, the main kinds of vanadate transformed from Ca_(2)V_(2)O_(7) to Ca_(5)Mg_(4)V_(6)O_(2)4 and then to Mg_(2)V_(2)O_(7) with the increase in the MgO/(CaO + MgO) molar ratio. In the leaching experiment, under the conditions of particle size less than 75 μm, leaching temperature of 50 ℃, pH of 2.5, liquid–solid ratio of 20:1, and MgO/(CaO + MgO) molar ratio of 1:3, the leaching efficiency of vanadium is increased by about 5%, but the substitution of MgO for most or all of CaO will significantly reduce the leaching efficiency of vanadium. Furthermore, the leaching efficiency of impurities (P and Cr) can also be decreased by a composite addictive (CaO + MgO) roasting process. The X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and X-ray photoelectron spectroscopy of the original vanadium slag and solid products of both roasting and leaching processes were also evaluated.
基金supported by the Natural Science Foundation Project of Chongqing(cstc2020jcyj-msxmX0954)the Chongqing Outstanding Youth Project(cstc2019JCYJQX0024)the National Natural Science Foundation of China(52204415.U1902217)。
文摘Alkali-activated cement(AAC)is either clinker-less or free,and it is also environmentally friendly due to its low carbon footprint and wide range sources.Industrial wastes,like steel slag and blastfurnace slag,usually have latent hydraulic reactivity,and can be used as precursors of AAC.Both clinkerless and clinker-free AAC were prepared from the mixture of steel slag and blastfurnace slag by using water glass as an activator,and four different recipes which satisfied the strength requirement of 42.5R Portland cement were obtained.Each recipe of AAC exhibited better resistance to sulfate attack and frost attack than Portland cement.AAC showed huge drying shrinkage,but it was equivalent to that of Portland cement as steel slag content increased to 40%.The AAC also had quite low risk of alkali-aggregate reaction.Microstructure analysis showed that the major products were calcium silicate hydrate(C–S–H),calcium aluminosilicate hydrate(C–A–S–H)and zeolite-like phases.Ettringite was also detected in the binder when gypsum was contained in the precursors.
基金the National Key Research and Development Program of China(2018YFC1900500)Technology of Preparing High Purity Metal Vanadium Powder by Magnesium Reduction(2018CDPZH-16)the open project founded by State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization for financial support of this research.
文摘As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is presented herein.Using an auxiliary molten salt,V_(2)O_(3)was successfully transformed into V by Mg reduction.The by-product,MgO,was transformed into MgCl_(2)by adding ZrCl_(4),which prevented the generation of MgV_(2)O_(4)and allowed the reaction to proceed smoothly.The rod-like alloy phases,Zr_(0.03)V_(1.97),which formed in the presence of excess Mg,may hinder the diffusion of oxygen from the product.The recovery rate of vanadium after separation and purification was approximately 45%–50%,where the main loss occurred during ball milling.Under the optimal conditions(Mg content of 48.3%,reduction time of 1.5 h,and temperature of 850℃),the purity of vanadium exceeded 99 wt.%,and the O content decreased to 0.34 wt.%.
基金supported by the National Natural Science Foundation of China(Grant Nos.52104325 and U1902217)Chongqing Outstanding Youth Project(Grant No.cstc2019jcyjjqX0024)Key Research and Development Program of Hebei Province(Grant No.21314001D).
文摘The preparation of high-strength pellets from Panzhihua ilmenite concentrate is important for the hydrogen-rich smelting of titania slag and was investigated.The effects of the magnetite concentrate and heating procedure including the pre-heating temperature and period as well as roasting temperature and period on the compressive strength of the roasted pellets were investigated.High-strength ilmenite concentrate pellets(>2000 N)were prepared by optimizing the roasting process.The addition of magnetite concentrate is beneficial for increasing the compressive strength of the Panzhihua ilmenite concentrate pellet by oxidizing hematite which filled the pseudobrookite particles,functioned as a bridge bond,and improved the interconnection between the grains.The compressive strength can reach up to 2900 N when the ilmenite concentrate pellet with 15%magnetite concentrate is pre-heated above 800℃ for 20 min and then roasted at 1250℃ for 20 min.In addition,there is an overall upward trend in the compressive strength with an increase in the pre-heating temperature and period as well as the roasting temperature and period.The micromorphology and strengthening consolidation mechanism of Panzhihua ilmenite concentrate pellets were also discussed.
文摘Driven by the double carbon policy,the iron and steel industry urgently needs to implement a new development concept to strengthen the use of solid waste resources from ironmaking and steelmaking and effectively enhance the economic benefits of recycling resources in order to reduce the accumulation of solid waste resources in the iron and steel industry.The iron and steel production process produces more than 600 million tons of solid waste annually,including metallurgical dust sludge,blast furnace slag and steel slag,etc.From the perspective of environmental friendliness,the efficient utilization of ironmaking and steelmaking solid waste resources through innovative cross-industry technologies is of great significance to the low-carbon,green and high-quality development goals of the iron and steel industry.
基金The authors are pleased to acknowledge the support from the National Key R&D Program of China(No.2018YFC1900500)EPSRC(UK)under the grant number EP/N011368/1(EPSRC Fellowship).
文摘The titanium industry can hardly bypass the titania-containing slags,and the slag physicochemical properties are essential in the metallurgical reactor design and process control.The TiO_(2)–FeO-based slags and TiO_(2)–SiO_(2)–CaO-based slags are the main metallurgical slag systems in the titanium resource utilization processes.To elaborate the role of TiO_(2) in the physicochemical properties of titania-containing metallurgical slags,the physicochemical properties including titanium redox ratio,liquidus temperature,viscosity,electrical conductivity,density,surface tension,thermal conductivity,and sulfide capacity were critically reviewed.Moreover,the property prediction models were briefly introduced with regards to the limitations of the existing models.The property prediction models are still required to evolve since not all properties of titania-containing slags can be well modeled.As the slag structure has an intimate relationship with slag properties,the structural details of the titania-containing slag were investigated by using a combination of spectroscopic technologies,but the knowledge of the slag structure was not fully ascertained.The potential research fields related to the physicochemical properties and structure of the titania-containing slags were also suggested.
基金the National Natural Science Foundation of China(Grant No.51234010)the Fundamental Research Funds for the Central Universities(Project Nos.2018CDXYCL0018 and 2018CDPTCG0001/11)for the financial support of this research.
文摘The effect of the Al2O3 content and basicity (the molar ratio of MgO to SiO2) on the viscosity of a SiO2-MgO-FeOAl2O3-CaO slag was studied to fully understand the smelting process of the ferronickel alloy. Experimental results show that the slag is a mixture of liquid and solid phases at the experimental temperature. The viscosity decreased as the basicity increased and increased as the Al2O3 content increased. To determine the effect of the Al2O3 content and basicity on the structure of the molten slag, Raman spectroscopy was performed on the slag sample, which was quenched from the high temperature with water. The Raman spectra showed that the fractions of the polymerization structural units decreased significantly as the basicity of the slag increased, resulting in a decrease in the apparent viscosity. However, Al2O3 acts as a network former in the slag system, thereby making the slag structure further polymerized and increasing the viscosity.
基金financially supported by the Fundamental Research Funds for the Central Universities of China (No.CDJZR12130049)Chongqing University Postgraduates’ Science and Innovation Fund (No.CDJXS12131105)
文摘The formation behavior of CaTiO3 during electro-deoxidization of ilmenite concentrate to prepare Fe–Ti alloy was investigated by experiments and simulation.The results indicate that the formation and decomposition of intermediate products,CaTiO3,are inevitable steps during electro-deoxidization of ilmenite concentrate.CaTiO3 can be generated through the hydrolyzation of molten salt and electrochemistry reaction during electrochemical process.The main reason for the generation of CaTiO3 is the electrochemistry reaction between Ca^2+ from molten salt and TiO2 in the cathode.With the proceeding of the electro-deoxidization,CaTiO3 is further electrolyzed to form titanium sub-oxide.The current efficiency can be improved when CaTiO3 forms in the cathode by adding CaCO3 during sintering process.
基金the financial support of the National Natural Science Foundation of China(51234010 and 51522403)the Program for New Century Excellent Talents in University and the Program for the Youth Top-Notch Talents of Chongqing(20151001)Ultrasonic Assisted Iron Ore Sintering Technology Research(cstc2014kjrc-qnrc90001),and China Scholarship Council.
文摘The effect of magnesia on calcium ferrite(CaO.Fe2O3)reduction by CO was examined by isothermal thermogravimetry.Samples of calcium ferrite added with 0,2,4,and 8 wt.%magnesia(abbreviated as CF,CF2M,CF4M,and CF8M)were prepared.Phase composition was analyzed by X-ray diffraction,and the results indicated that CF2M and CF4M are reduced to lower reduction degree and with lower apparent activation energy than CF;and CF8M with more MgO.Fe2O3 is reduced to a lower degree and with more difficulty compared with CF.Reduction rate analysis revealed that CF,CF2M,CF4M,and CF8M reductions are all typical two-step reactions with the order of CF→CWF(CaO.FeO.Fe2O3)→Fe.The apparent reduction activation energies of CF,CF2M,CF4M,and CF8M are 46.89,37.30,17.30,and 29.20 kJ/mol,respectively.Sharp analysis depicted that CF2M,CF4M,and CF8M reductions are all described by 2D Avrami–Erofeev(A–E)equation(A2)in the whole process,while CF reduction is first expressed by A2 and then by 3D A–E equation(A3).Different from shrinking core model,a new kinetic model for powdery samples reduction was proposed to illustrate the relationship among reduction rates,reduction routes,and model functions.
基金supported by the National Natural Science Foundation of China(Grant No.51234010)Special Fund for Basic Scientific Research in Colleges and Universities of the Central Business (No.0903005203413)
文摘The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy(Ea)were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction(G(α)=1-(1-α)~2,whereαis the conversion degree)plays an important role in the whole oxidation process.At the first stage(α=0.05-0.30),the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage(α=0.30-0.50),the oxidation process is completely controlled by the secondary chemical reaction(G(α)=1-(1-α)~2).At the third stage(α=0.50-0.95),the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G(α)=(1-α)^(-1)(β=10K·min^(-1),whereβis heating rate),G(α)=(1-α)^(-1/2)(β=15-20K·min^(-1)),and G(α)=(1-α)^(-2)(β=25K·min^(-1)),respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol^(-1).
基金This work was supported by the National Natural Science Foundation of China(Grant No.U1902217).
文摘The effect of pre-oxidation degree of Panzhihua ilmenite concentrate on the gaseous reduction by carbon monoxide was investigated.The raw ilmenite concentrates were pre-oxidized at 600,700,800,900,and 1000°C for 2 h,respectively.The phase change,FeO content,and morphology after the oxidation at various temperatures were characterized.The oxidation degree was calculated according to the change of FeO content.Thermogravimetry was performed on the oxidized ilmenite concentrate samples(oxidized at 600,800,and 1000°C)at 850,900,and 950°C,respectively.The results show that the pre-oxidation of ilmenite concentrate can accelerate the reduction process:the higher pre-oxidation degree,the faster reduction rate.The high pre-oxidation degree of ilmenite concentrate is beneficial to accelerate the subsequent reduction process in two ways.Three stages of the reduction process were divided via the first derivatives of reduction degree,and the reduction mechanism and apparent activation energy were discussed subsequently.
基金the National Natural Science Foundation of China(Grant No.2018YFC1900501)Graduate Scientific Research and Innovation Foundation of Chongqing(CYB19003).
文摘A novel granulation process that involved the use of a rotary multi-nozzles cup atomizer and water cooling was proposed for ferroalloy manufacturing.The effects of rotating speed and nozzle diameter on the properties of FeSi75 alloy(containing 75 wt.%Si)granules were investigated.Results indicated that median granule diameter decreased as rotating speed in creased,and initially increased and then decreased as nozzle diameter in creased.The optimal conditi ons for the gra nulation of FeSi75 alloy were a rotating speed of 150 r/min and nozzle diameter of 10 or 12 mm.The phase composition,micromorphology,and elemental distribution of the FeSi75 alloy granules were also studied by X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectrometry.In order to provide guidance for the layout and water depth of the tank,the solidification behavior of ferrosilicon alloy droplet was numerically studied.A simplified model was established to elucidate the traveling trajectory and heat transfer of alloy droplet in air and cooling water during the atomization process.The solidification time of droplet with different thicknesses of solidification layer increased with the in crease in alloy droplet diameter.
基金supported by the project funded by China Postdoctoral Science Foundation(Grant No.2018M640898)the National Key Research and Development Program of China(2018YFC1900500)+1 种基金the National Natural Science Foundation of China(No.51674055)the open project funded by State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization.
文摘The chromium-bearing titanomagnetite ore will turn to be the important raw material for blast furnace process in Panxi area,China.The reduction behavior of Cr2O3 between CaO-SiO2-Al2O3-TiO2-Cr2O3 and Fe-C systems was investigated.The effect of TiO2 content in the slag system on the reduction of Cr2O3,TiO2,and SiO2 and the con sumption of C in hot metal was investigated by both theoretical calculation and physical experiment.The theoretical calculation results reveal that higher reduction temperature promotes the reduction of Cr and Ti,while high basicity and TiO2 content have little influence on the reduction of chromium but significantly influence the reduction of Ti.The smelting reduction experiment results show that the content of Cr in hot metal significantly in creases with extendi ng the reduction time and decreases with the increase in TiO2 content.However,the content of Ti in hot metal significantly increases as the TiO2 increases,reaching 0.073,0.085,0.107,and 0.121 wt.%for 5,10,15,and 20 wt.%of TiO2 input,respectively.Kinetic studies proved that the reduction of Cr2O3 was a first-order reaction.The addition of TiO2 inhibited the reduction of Cr2O3 and resulted in the decrease in reaction rate constant.