China Nonferrous Metallurgy

Abstract:In view of the current situation of wide particle size distribution and lack of high-end production capacity of titanium dioxide by sulfuric acid method in China， in this study， low-concentration industrial titanyl sulfate solution was used as raw material， and authigenic seed hydrolysis process was used to systematically explore the internal regulation mechanism of bottom water volume， titanium liquid TiO2 concentration and curing time on the particle size distribution of metatitanic acid. The structure-activity relationship between the final particle size and structure morphology was analyzed by the characterization results， and the following main conclusions were obtained. The optimal hydrolysis process parameters were as follows： bottom water 16%， titanium solution concentration 205 g/L， and curing time 25 min. Under these conditions， the diameter-to-distance ratio of the prepared metatitanic acid product was as low as 1. 01， which belonged to a narrow particle size distribution and had excellent process stability. The metatitanic acid prepared by hydrolysis is a spherical polycrystalline aggregate formed by the accumulation of （30-60） nm grains through grain boundaries. Due to the adsorption of anions （SO4 2- ， OH- ） on the surface of the crystal nucleus at the initial stage of hydrolysis， the steric hindrance effect and electrostatic repulsion generated hinder the evolution of the crystal nucleus to single crystal， which promotes the formation of a mesoporous hydrated colloidal. The particle size control is based on the multi-stage competitive coupling of 'nucleation-growth-agglomeration'. The bottom water volume reduces the nucleation barrier by adjusting the initial supersaturation and establishes the nucleation advantage. The concentration of TiO2 increases the mass transfer resistance by adjusting the viscosity of the system， and inhibits grain coarsening and hard agglomeration. The ripening time effectively inhibits the particle size broadening caused by the Ostwald ripening effect by regulating the hydrolysis rate. The results can provide production parameters and process reference for industrial preparation of high-performance titanium dioxide.

Abstract:Conventional hydrolysis via the sulfate process produces metatitanic acid exhibiting broad particle size distribution， low specific surface area， and inadequate purity， which severely limits its applicability in high-end fields such as battery materials and catalysis. This study innovatively developed a dispersant-regulated one-step hydrolysis process for preparing metatitanic acid from industrial titanyl sulfate solution. Using a single-factor variable method， we systematically investigated the effects of parameters such as dispersant polyacrylamide（PAM） dosage， stirring speed， and hydrolysis time on metatitanic acid properties. The co-evolution mechanism of particle size distribution and specific surface area of metatitanic acid was explained by experimental results and characterization results， and the following main conclusions were obtained. The optimum hydrolysis process conditions were as follows： PAM dosage 0. 9%， stirring rate 420 r/min， hydrolysis time 2. 65 h. Under these conditions， the average specific surface area of metatitanic acid was 262 m² /g， the average purity of calcined TiO₂ was 99. 58%， and the average particle size range was 2. 65-2. 95 μm， which was better than the food grade standard （GB 1886. 341—2021） and nano grade standard （GB/T 19591—2023）. The prepared metatitanic acid has an anatase TiO₂ structure and has colloidal properties. The metatitanic acid contains a large amount of water molecules， hydroxyl groups and sulfate radicals. It is easy to form coarse metatitanic acid aggregates by Ostwald ripening and agglomeration. The porous structure between the aggregates increases the specific surface area of metatitanic acid. The hydrolysis mechanism reveals that the dispersant reduces surface tension through a longchain adsorption layer， inhibits dense particle packing， accelerates nucleation rates， and promotes the formation of fine， porous metatitanic acid. This process is simple， green， and efficient， providing a new pathway for the industrial preparation of battery-grade high-specific-surface-area metatitanic acid and advancing the high-quality development of high-performance titanium dioxide.

Abstract:The stability of hydrolytic seeds is crucial for the hydrolysis process in the sulfate process for titanium dioxide production. Using industrial titanyl sulfate solution as raw material， hydrolysis seeds were prepared by alkali neutralization method. The effects of alkali-to-TiO2 ratio， aging temperature， and aging time on seed stability were systematically investigated， and the intrinsic relationship between process-structure-performance was explored by using multiple analytical methods， and the following main conclusions were obtained. The alkali-titanium ratio， curing temperature and curing time all affect the stability of the hydrolyzed seed crystal by affecting the reaction process and system properties. Appropriate increase of these process parameters can promote the nucleation rate and growth rate of the crystal nucleus； The optimum process parameters for the hydrolysis of industrial titanium liquid are as follows： alkali-titanium ratio 14%， curing temperature 95℃， curing time 18-21 min， stirring speed 300 r/min. Under these conditions， the stability of seed crystal is stable in the qualified range of 100-130 mL， the hydrolysis rate is 10. 16%， and the repeatability of the verification experiment is good. The particle size of the hydrolyzed seed is in the range of 21±6. 5 nm， and the particle size distribution is narrow， which ensures the high stability and activity of the seed. After optimization， the Ti—O bond of the hydrolysis seed is strengthened， the cluster structure is densified， and the Ti—S—O coordination structure is improved， significantly enhancing surface stability. This study provides a novel strategy for preparing highly stable seeds for titanium dioxide production by the sulfate process.

Abstract:China generates approximately 8 million tons of magnesium slag annually. Constrained by treatment costs and technological limitations， most magnesium slag is currently stored haphazardly or landfilled. Numerous scholars have explored the recent resource utilization of magnesium slag. In this paper， the physical and chemical properties， environmental hazards and resource utilization of magnesium slag are systematically reviewed. The key points and improvement strategies of its application in cementitious materials， cement clinker and carbon sequestration materials are discussed， which provides theoretical support and technical reference for the comprehensive utilization of magnesium slag. Primarily composed of CaO and SiO?， with a mineral composition dominated by β -C ? S and γ -C ? S， magnesium slag has been explored of applications in cementitious materials， ceramics， and carbon sequestration materials. Extensive research exists on magnesium slag as a cementitious material and cement clinker admixture. When used in cementitious materials， it requires synergistic application with other industrial solid wastes to enhance reactivity and improve mechanical properties. Its latent cementitious activity can also be released through physical or chemical activation. As a cement clinker admixture， its dosage impact must be carefully considered. Magnesium slag exhibits promising application potential in high-value-added innovation fields： magnesium slag-based carbon sequestration materials offer advantages such as low cost， high strength， and relative stability， with future applications in road subgrades and mine backfilling； magnesium slag thermal storage ceramics， with their high specific heat capacity and excellent thermal stability， are suitable as heat storage media for solar thermal power generation systems； magnesium slag adsorbents can achieve contaminant removal； magnesium slag can replace traditional precious metals as catalysts， reducing production costs. At present， the actual utilization rate of magnesium slag is still very low. The main problems in the field of cementitious materials are low activity， unstable volume and high cost of excitation technology， which still need to be explored continuously. In the future， the comprehensive utilization of magnesium slag can be studied in high value-added fields and mine filling fields to broaden its available range.

Abstract:The molybdenum ore of an enterprise is a typical low-grade and semi-oxidized ore. Its ore composition and structure are complex. It is embedded in the form of molybdenite， molybdenum calcium ore and molybdenum oxide ore. Molybdenite is associated with other minerals. Some molybdenum calcium ore and other minerals are isomorphic to form new minerals. The ore particle size is fine and evenly distributed. The molybdenum content is 0. 45%， which belongs to low-grade refractory molybdenum ore. In this study， the synergistic oxidation leaching of sodium percarbonate and sodium hydroxide was used to recover molybdenum， and the effects of different factors on the leaching rate of molybdenum were investigated. The results show that the leaching rate of molybdenum is 88. 32% under the optimum conditions of ore particle size of 80%-45 μm， liquid-solid ratio of 3 mL/g， sodium percarbonate dosage of 20 kg/t， sodium hydroxide dosage of 15 kg/t， leaching temperature of 85℃， leaching time of 4 h and stirring rate of 500 r/min. The results of kinetic study show that the leaching process of molybdenum ore is controlled by chemical reaction and diffusion， and the activation energy of reaction is 19. 98 kJ/mol. Before and after leaching， the composition of gangue minerals is basically unchanged， and a small amount of molybdenum calcium ore remains in the slag. Molybdenite has been completely leached. In the future， the structure of molybdenum calcium ore can be destroyed by strengthening ore pretreatment or the reaction conditions can be optimized to obtain higher leaching rate. The oxidant used in this process is mild， stable and environmentally friendly， and the leaching impurities are less. The whole leaching process has no high temperature， no flue gas and short process， which realizes the efficient recovery of metal molybdenum resources and provides a reference for the utilization of this kind of low-grade complex molybdenum ore resources.

Abstract:In view of the high cost of iron powder in rare earth metallurgy and the low utilization rate of iron in NdFeB waste recovery process， this paper proposes a co-processing of rare earth concentrate with NdFeB waste sulfuric acid roasting-magnesium sulfate wastewater leaching. The purpose is to use the iron in NdFeB waste instead of iron powder in rare earth metallurgy process. The parameters of sulfuric acid roasting-magnesium sulfate wastewater leaching process were optimized by single factor test. Thermogravimetric analysis was carried out to further verify the reaction mechanism， and the following main conclusions were obtained. The optimal parameters of the co-processing are the acid-to-ore ratio of 1. 7∶1， the acidification time of 0. 5 h， and the 2 # roasting temperature curve. Under this condition， the decomposition rate of the roasted ore reaches more than 94. 0%， and the REO content in the discharged slag is less than 4. 0%. Thermogravimetric analysis shows that the roasting process is an endothermic reaction， and the heat absorbed by the reactants in the ideal state is about 589 kJ. When the temperature reaches 350℃， the decomposition activation energy of rare earth concentrate and NdFeB is greater than other side reactions， and the chemical reaction rate reaches a maximum of 1. 7 g/min. The verification test shows that the key indicators of the process， the content of REO in the discharge slag and the yield of REO， meet the requirements of the company's internal control， and the iron element in the waste is reused， which effectively reduces the discharge of solid waste and reduces the production cost. The results of this paper can provide reference for rare earth smelting enterprises and the treatment of NdFeB waste.

Abstract:To address the problems of low leaching efficiency and poor adaptability of existing processes for lowgrade complex copper sulfide tailings， this study adopts ethylene thiourea （ETU） synergistically with microorganisms for leaching flotation tailings from an overseas enterprise in a ferric sulfate system. The effects of ETU concentration， leaching time， and pulp density on copper leaching efficiency were systematically investigated， along with the decomposition law of ETU and treatment methods for its residues， aiming to eliminate interference with subsequent solvent extraction-electrowinning （SX-EW） processes. The results show that the copper leaching efficiency increases with the rise of ETU concentration and extension of leaching time， while decreasing with the increase of pulp density. Under the optimal conditions （ETU concentration of 200 mg/L， pulp density of 20%， pH=1. 5， and leaching at room temperature for 72 h）， the copper leaching efficiency reaches 87. 32%. Fe3?， Cu2?， and aeration can accelerate ETU decomposition， whereas an acidic environment and sodium hexametaphosphate can stabilize ETU. Residual ETU in the leachate reduces the copper extraction rate from 95% to 38% and causes nodulation on electrodeposited cathode copper. Complete removal of ETU and elimination of its impact on subsequent processes can be achieved through aeration treatment. This study provides key process parameters and technical support for the efficient treatment of similar complex copper sulfide tailings.

Abstract:More than 3 million tons of titanium-bearing blast furnace slag are discharged every year in China， and the TiO₂ content of the slag is 10%-25%. At present， the comprehensive utilization of the slag is mainly to prepare building materials. An industrial demonstration production line for the preparation of titanium-rich materials， titanium carbide or titanium carbonitride from titanium-containing blast furnace slag has been built in Panxi area， but there are some limitations. At present， most of the titanium-containing blast furnace slag is disposed by stacking. Some scholars have proposed selective precipitation technology， that is， titanium-containing blast furnace slag is modified by additives to make titanium exist in the form of perovskite， and then perovskite is separated by gravity separation and used as raw material for titanium extraction. The titanium recovery rate of this method is less than 48%. In view of this problem， this study proposes a perovskite crystal transformation technology on this basis， that is， by adding CaO， high titanium slag， and CaTiO₃ to transform the perovskite crystal to improve the recovery rate of gravity separation. The effects of various additives on the recovery rate of titanium were investigated by experiments， and the mechanism of crystal transformation was analyzed according to the characterization results. The following main conclusions were obtained. When the addition amount of CaO， high titanium slag and CaTiO₃ is 20%，25% and 17% respectively， the perovskite is precipitated as equiaxed crystal， and the recovery rate of titanium is 68. 41%. In the subsequent cycle production， the gravity concentrate is used instead of perovskite. The optimum concentrate addition is 50%， and the gravity recovery of titanium is 68. 42%. The main difference between perovskite crystal transformation technology and selective precipitation technology is the crystal form of perovskite. The product of crystal transformation technology is equiaxed crystal， and the product of selective precipitation technology is dendrite. The degree of dissociation of equiaxed perovskite monomer is higher， thus increasing the recovery rate of titanium. The results of this study can provide a reference for the resource recovery and utilization of titanium-containing blast furnace slag.

Abstract:Vanadium-titanium magnetite in South Africa has the characteristics of ‘low titanium and high vanadium’. Titanium element is mainly dissolved in the lattice of magnetite. The content of TiO₂ in titanium slag produced by rotary kiln-electric furnace smelting process is similar to that of titanium concentrate， which can be applied to the production of titanium dioxide by sulfuric acid method. However， its phase composition is complex， which is very different from the acidolysis behavior of conventional titanium concentrate and acid-soluble titanium slag. At present， there are few studies on the titanium slag. In this study， the phase composition of titanium slag and the effects of various parameters in the process of ‘hydrochloric acid leaching-sulfuric acid hydrolysis-water leaching’ on its acid hydrolysis performance were investigated， and the control factors affecting its acid hydrolysis performance were analyzed. The following main conclusions were obtained. The higher the proportion of active phases such as anosovite in the slag sample， the lower the content of SiO₂ and Al₂O₃， the better the acidolysis rate. The silica gel and calcium sulfate crystallites formed by the decomposition of diopside are easy to form a passivation layer， which becomes the main limiting factor of the mass transfer process. The appropriate acid residue ratio （3. 8∶1） and sulfuric acid concentration （93%） can enhance the reaction kinetics， but excessive acid amount or curing process will inhibit mass transfer due to the increase of system viscosity. Appropriate refinement of particle size （?45 μm） can destroy the surface structure of insoluble phase， but too fine particles are easy to cause local agglomeration. When the main phase of the titanium slag is anosovite and the content of SiO₂ and Al₂O₃ is low， the acid hydrolysis rate of the titanium slag can reach 89. 96 % without curing under the conditions of particle size of ?45 μm， acid-slag ratio of 3. 8∶1 and sulfuric acid concentration of 93%. The results of this study can provide a basis and reference for the application of the titanium slag in the sulfuric acid titanium dioxide process.

Abstract:The total iron （TFe） content of carbide slag is 2. 0%-3. 5%， when used in the low-temperature chlorination process to produce titanium dioxide， the iron in the slag reacts with chlorine gas to form ferric chloride， which blocks the low-temperature chlorination rinsing system and affects the stability and smooth operation of the system. Therefore， this paper conducted process mineralogy and iron removal experiments on carbide slag to provide a reference for the control of iron content in slag. Through the study of process mineralogy， it was found that carbide slag is mainly composed of silicate glass （85. 71%）， titanium carbide （11. 53%）， metallic iron （0. 87%）， and iron oxide （0. 53%）. Metallic iron is embedded in silicate glass in a spherical or ellipsoidal shape. Its particle size distribution is uneven， more than half distributed between 0. 08 mm and 0. 32 mm； TiC is mainly distributed in the silicate glass phase and coexists with metal iron and other substances. Its particle size is primarily below 0. 01 mm； The particle size of iron oxide is primarily below 0. 04 mm. Wet magnetic separation experiments were conducted to remove iron from carbide slag. The results showed that increasing the magnetic field intensity and grinding time was beneficial for the removal of TFe from the slag， but also resulted in a decrease in the recovery of TiC. When the magnetic field intensity reaches 3 000 Gs and the grinding time is more than 15 min， the TFe content in the tailings is reduced to less than 1. 50%， which meets the requirements for low temperature chlorination raw materials. In the actual production， different magnetic field intensities and grinding times can be selected according to the production needs to control the TFe content in the slag while minimizing the TiC loss.

Abstract:A smelting enterprise adopts the technical route of zinc acid leaching slag zinc concentrate synergistic leaching-gas phase sulfidation-high temperature mineralization to treat zinc acid leaching slag. After gas phase sulfidation， valuable metals such as indium and copper in the acid leaching slag are precipitated and enrich in the slag. The solution only contains Zn2 + （ about 90 g/L ） and Fe2 +（ about 25 g/L ）， and zinc and iron need to be separated. In this paper， the solution of co-leaching solution of zinc acid leaching residue and zinc concentrate after gas phase sulfidation （ hereinafter referred to as sulfidation solution ） was taken as the research object. Based on the analysis of the potential-pH diagram of Zn-Fe-S-H2O system， the effects of reaction temperature， time， initial pH of solution and SO4 2- concentration on iron precipitation behavior were investigated， and the quality， phase and microstructure of mineralized iron slag were analyzed. The results show that Fe2O3 has high stability under high acid conditions. When the reaction temperature is higher than 150℃， the complexation and hydration of Fe3+ can be effectively destroyed， and the iron is precipitated in the form of Fe2O3. The solubility of Fe2O3 can be further reduced by increasing the sulfate concentration. Under the conditions of reaction time 4 h， reaction temperature 190℃， initial pH=4 and SO4 2- concentration ＜280 g/L， the removal rate of iron was 89. 19%， and the loss rate of zinc was less than 0. 2%. The effective separation of zinc from the leaching solution of zinc acid leaching residue was realized. The mineralized iron slag contains more than 60% iron with less impurities， and has a dense and fine granular shape， which can be used as a raw material for recovering iron.

Abstract:This article innovatively proposes the design concept of a cyclone reactor based on the structural characteristics of the cyclone separator in the suspension preheating equipment of cement plants and the characteristics of the high sulfur bauxite roasting reaction， and applies it for the first time in the experimental study of desulfurization in high sulfur bauxite roasting. The calcination desulfurization reaction in this reactor belongs to "suspension calcination"， with particles in a good fluidized motion state， high gas-solid mass and heat transfer efficiency， and high desulfurization efficiency. This study analyzed the velocity and pressure field distribution inside the reactor through numerical simulation. Fluent software was used to simulate the unipolar cyclone reactor， focusing on the distribution laws of tangential， axial， and radial velocities， as well as the changes in static pressure， dynamic pressure， and total pressure. The results indicate that the tangential velocity reaches its peak in the contraction section of the snail shell region， while the axial velocity exhibits a bimodal distribution in the snail shell region， effectively prolonging the residence time of particles； The static pressure distribution shows the characteristics of low center and high sides， and the dynamic pressure distribution is similar to the tangential velocity. The total pressure distribution is generally consistent with the static pressure； As the gas velocity increases， the pressure drop loss gradually increases， and the greater the velocity， the more significant the change in pressure drop； While ensuring reaction efficiency， priority should be given to using lower gas flow rates to reduce energy consumption. This study provides a theoretical basis for optimizing the design of cyclone reactors， which helps to improve the desulfurization efficiency of high sulfur bauxite and reduce production costs.

Abstract:In the process of mixing and dispersion in gas-liquid stirring， the size and distribution of bubbles not only determine the rising velocity of bubbles and the residence time of gas in the liquid phase but also directly affect the gas holdup and the gas-liquid contact area. Many scholars have employed computational fluid dynamics （CFD） to study bubble size distribution， gas content， and liquid velocity， yet none have considered the effects of bubble coalescence and breakup. The population balance model （PBM） reconstructs the bubble size distribution and establishes kernel functions for bubble breakup and coalescence. When combined with CFD， PBM can yield considerably accurate bubble sizes in process equipment such as stirred tanks. This paper employs a CFD-PBM coupled model to investigate the fluid dynamics of the gas-liquid dispersion process in a stirred tank， exploring the effects of rotational speed and gas flow rate on bubble size distribution， flow field， number concentration， and gas holdup. The following key conclusions are drawn. The model demonstrates higher accuracy than Basavarajappa's predictions， with a maximum error of no more than 10% in simulation results， enabling effective prediction of bubble size distribution. The stirring speed significantly influences gas-liquid mixing efficiency， with higher speeds （400 r/min） resulting in smaller and more uniformly distributed bubbles， along with notably enhanced gasliquid mass transfer performance. At low gas flow rates （0. 5 vvm）， bubble generation is limited and unevenly distributed； appropriately increasing the gas flow rate （0. 7 vvm） helps prolong bubble residence time， whereas excessively high flow rates （0. 9 vvm） may lead to bubble coalescence and a decline in mass transfer efficiency. At high rotational speeds （400 r/min）， a noticeable cavitation phenomenon occurs in the back liquid surface area of the stirring blade. This is caused by the aggregation of gases due to local negative pressure， forming stable gas cavities， which adversely affect the stirring efficiency and gas-liquid dispersion effect. By reasonably adjusting the rotational speed and impeller design， the adverse impacts caused by cavitation can be mitigated， thereby further enhancing the stirring efficiency and gas dispersion effect. In actual production， optimizing the stirring speed and gas flow rate can improve bubble distribution and gas-liquid mixing effectiveness.

Abstract:In the process of copper electrorefining， the flow behavior and mass transfer characteristics of the electrolyte have a significant impact on electrolytic efficiency， product quality， and energy consumption. In industrial electrolytic cells， the electrode size is much larger than the spacing between electrodes， forming a special narrow space between the anode and cathode plates， making the electrolyte flow and mass transfer characteristics more complex and variable. This study establishes a two-dimensional finite element numerical model of a industrial-scale electrolytic cell and conducts an in-depth analysis of the electrolyte flow velocity distribution， copper ion concentration distribution， and transport characteristics within the narrow space between the anode and cathode plates， leading to the following main conclusions. The electrolyte flow velocity between the plates is uneven， slower in the upper region and faster in the lower region， with multiple vortex areas formed； near the surfaces of the anode and cathode， the horizontal velocity is almost 0， the vertical velocity fluctuates in the range of 0. 3-15 mm/s， the horizontal velocity along the centerline fluctuates in the range of 0-22 mm/s， and the vertical velocity fluctuates in the range of 0-9 mm/s. The vortices between the plates have a significant effect on the copper ion concentration distribution. Near the cathode surface， copper ion concentration fluctuates in the range of 440-620 mol/m3； near the anode surface， it fluctuates in the range of 530-740 mol/m3； along the centerline， it fluctuates in the range of 500-630 mol/m3， with the concentration fluctuations corresponding to the vortex areas. Copper ion transport is primarily driven by convection， and the lateral flow between vortices achieves direct transport of copper ions from the anode to the cathode. While transferring copper ions from the anode to the cathode， the vortices also carry suspended impurities formed near the anode to the cathode surface， resulting in higher impurity content on the lower region of the cathode surface compared to the upper region.

Abstract:The form of sulfur in high-sulfur bauxite is complex， mainly sulfide. If it is not effectively desulfurized， it will not only cause corrosion and loss to the production equipment， but also reduce the quality of alumina products. At present， the desulfurization method has the problems of high cost， high energy consumption， limited desulfurization efficiency and environmental pollution. In this study， a method of base hydrogen reduction roasting desulfurization was proposed. During the roasting process， calcium oxide in the alkaline medium reacted with sulfide FeS2 to form calcium sulfide （CaS）， which played a role in desulfurization and sulfur fixation. At the same time， under the reduction of hydrogen， Fe2+ is further promoted to generate elemental iron （Fe）， which can be recovered. The influence of process parameters on the desulfurization effect was investigated， and the microstructure and crystal structure of the ore were analyzed by various characterization techniques to verify the roasting desulfurization mechanism. The results show that the optimal process parameters are reduction temperature of 700℃， reduction time of 80 min， alkalinity of 1 and hydrogen flow rate of 1. 4 m3 /h. Under these conditions， the reduction rate of high-sulfur bauxite reaches 95. 83%， and the desulfurization rate reaches 99. 72%. SEM and EDS characterization results show that the surface of the roasted ore is densified， and the removal effect of sulfur is significant， which verifies the desulfurization mechanism of the method. Compared with the traditional pretreatment process of high-sulfur bauxite， the base hydrogen reduction method increases the recovery of iron resources while effectively desulfurization and sulfur fixation， which provides an economic and feasible technical way for the clean and efficient utilization of high-sulfur bauxite.

Abstract:At present， the main production method of metal europium is vacuum reduction-distillation method， and the recovery rate can reach 95%. However， there are still some problems， such as long reduction period， high energy consumption， unstable preparation process and inability to produce continuously. In recent years， Professor Zhang Ting'an team proposed the 'relative vacuum' smelting technology， and achieved good results in the field of magnesium smelting. In this paper， the relative vacuum smelting technology is applied to the production of metal europium by lanthanum thermal reduction. The relative vacuum reduction experiment is carried out on the prefabricated pellets made of lanthanum powder and europium oxide by a medium frequency induction furnace， in order to explore the optimal experimental conditions. The results demonstrate that the relative vacuum technology can be applied to the preparation of europium metal by lanthanum thermal reduction. The reduction rate of europium oxide can be improved by appropriately increasing the carrier gas flow rate， the pressure of the sample and the excess coefficient of the reducing agent. The optimum experimental conditions are as follows： argon flow rate v=0. 2 m3 /h， reduction temperature T=1 100℃， reduction time t=1. 5 h， pelleting pressure P=20 MPa， and excess ratio of reducing agent M=1. 1. This technology breaks the limitation of vacuum conditions to achieve continuous production， and the inert gas can be recycled， but there are still problems of low reduction rate and poor product purity. Under the optimal conditions， the reduction rate of europium oxide is only 87. 29%， and the purity of metal europium product is only 97. 88%. Subsequent research will continue to optimize the process and provide a more solid technology basis for the industrial continuous production of metal europium. .

Abstract:Based on the characteristics of biochar containing more hydrogen， less carbon， more oxygen， and lower sulfur compared with traditional coal energy， this study investigates the thermal reduction mechanism of three types of biomass char-high iron red mud composite pellets， and compares the effects of three biomass chars on metallization rate， phase structure， micromorphology， and pore size. The following conclusions were drawn. Wheat bran char exhibits superior performance in enhancing the metallization rate and optimizing the phase structure of the composite pellets compared to the other two biomass chars. After thermal reduction at 1 100℃ for 2 h， the metallization rate reaches 86. 5%， which is 5. 2% higher than that of metallurgical coke and much higher than those of pine wood char composite pellets and corn char composite pellets under the same conditions. The main phase compositions of wheat bran char-high iron red mud composite pellets are metallic iron （44. 3%）， carbon （10. 6%）， gehlenite （Ca ?Al ? SiO?）， and nepheline （NaAlSiO?）， making them suitable for the vortex melting reduction ironmaking process. The wheat bran char-high iron red mud composite pellets possess a more uniform pore structure with a pore size of approximately 2-4 nm， a larger specific surface area， a better overall structure， a higher degree of surface metallization， and fewer residual impurities. The research results provide important reference for the efficient utilization of biomass resources.