China Nonferrous Metallurgy

Abstract:Solid oxide electrolysis cell (SOEC) can efficiently and cleanly couple with renewable energy and convert it into chemical energy. It is an efficient and environmentally friendly energy conversion device, but there is a problem of long-term operational performance degradation, which is also the key to achieving large-scale commercialization of hydrogen production through solid oxide electrolysis of water. This article briefly introduces the development history, categories, composition, and operating principles of SOEC. Elaborating on the advantages, disadvantages and operating costs of this technology. The main factors causing performance degradation of SOEC are analyzed, including its composition, operating mode, connecting plate material, and operating conditions. Finally, the research status and future development trends of SOEC are analyzed through the number of papers and patents. It is believed that although the development of solid oxide fuel cells (SOFCs) is relatively mature, but due to current environmental needs, in order to fully utilize clean energy and reduce carbon emissions, the large-scale commercialization of SOEC hydrogen production technology is bound to be the direction of future industry development. At present, the performance stability and low-cost preparation of SOEC are the main problems，facing the development of this technology.

Abstract:The bubbles generated during the water electrolysis process can affect the stable operation of the electrolytic cell. Understanding the nucleation, growth, and detachment of bubbles is a prerequisite for effectively managing them. Bubble growth is a mass transfer process through the phase interface. Simulating the evolution of bubbles at the single bubble scale can help us to deepen our understanding of the gas-liquid mass transfer process on the electrode surface, as well as the relationship between bubble generation and its impact on the local flow field and concentration field. This can help achieve the stable operation of the electrolytic cell, reduce energy consumption, and improve current efficiency. Visualizing the growth behavior of single bubbles is essential, and the preparation of microelectrodes is indispensable for this purpose, as microelectrodes can stably and periodically produce individual bubbles. Currently, the main methods for preparing microelectrodes include platinum wire embedded in epoxy resin, photolithography and electrochemical codeposition, nanodisk electrode method, and printed circuit board method. This paper elaborates and analyzes the research status of these microelectrode preparation methods. Experimental conclusions on the preparation of microelectrodes by different scholars differ and require experimental verification. Currently, microelectrode preparation technology still cannot visualize the nucleation stage of bubbles. In the future, the visualization of the nucleation process of bubbles under electrochemical control and the use of faster electrochemical instruments to study the nucleation kinetics of bubbles will be the focus.

Abstract:The stockpile of red mud in China has exceeded 1 billion tons, and the main type of red mud is Bayer method red mud, which contains iron up to 30% or more, and is an iron resource with high economic value. The current method of recovering iron resources in red mud is mainly high-temperature reduction roasting-magnetic separation, with solid carbon-based reductant and gas-based reductant as the main reductant, which requires a large amount of energy consumption and cost. China is a large agricultural country, the annual output of the main crop residues is 700 million t. These biomasses have the advantages of carbon neutrality, high reactivity, low ash content, high storage capacity, renewable, etc., and the pyrolysis temperature is much lower than the solid carbonaceous reductant, and the temperature of its reduction of trivalent iron is only 300~800℃, which belongs to the low-temperature pyrolysis, so that the use of biomass reduction roasting of red mud can greatly reduce the energy consumption and cost. This paper focuses on the comparison of the parameters of trivalent iron reduction by solid carbonaceous reductant, gas-based reductant and biomass reductant, and elaborates in detail the pyrolysis process of biomass and the mechanism of reducing Fe₂O₃ in red mud, and concludes that the biomass reduction roasting-magnetic separation technology can realize the reduction and high-value utilization of solid wastes, such as red mud and agricultural straw, and has very high economic value and environmental benefits. Finally, the following suggestions are made for the future study of iron resource recovery in red mud: to strengthen the exploration of technology coupling to achieve the industrialized disposal of red mud; to recycle the gas and heat produced by the pyrolysis of biomass; to explore the ways to comprehensively utilize the tailing slag; and to enhance the research on the separation of iron and aluminum minerals in order to achieve the continuous and dynamic production of iron ore concentrates.

Abstract:As an industrial desulfurizer, aluminum industrial red mud has the advantages of abundant source, low price and high overall sulfur capacity. It achieves the purpose of “waste to waste” while desulfurizing at low cost. In this paper, the application of aluminum industrial red mud in flue gas desulfurization was summarized, and the research progress of dry and wet red mud removal SO₂ and H₂S in flue gas was comprehensively reviewed. The advantages and disadvantages of several research directions were compared and analyzed from several dimensions, such as utilization efficiency of active components, energy consumption, complexity of process and subsequent environmental problems. The possible problems and further research directions of market application in the future are also prospected. It is pointed out that in the SO₂ removal from flue gas by wet grout process, it is still necessary to overcome the technical problems such as pipeline blockage, low efficiency, high energy consumption, and the resulting large amount of dilute salt treatment. At the same time, the reaction mechanism and activation means of the transition metals contained in it should be studied. In terms of dry removal of H₂S, further research should be carried out from the aspects of low-cost activated iron oxide, applicability in extreme environment, recycling of waste desulfurizer, and collaborative treatment with other industrial solid wastes.

Abstract:The iron oxide content of high-iron red mud is more than 30%, which is an important source of iron resources.In order to realize the large-scale, resourcefulness, and harmless utilization of high-iron red mud, a pilot-scale experiment on vortex smelting reduction of high-iron red mud was conducted in this paper on the basis of laboratory research. The pilot study achieved good resultswith the use of industrial reagents instead of analytically pure laboratory reagents. The iron recovery was 97.12% under the experimental conditions of the experimental temperature of 1500℃, the carbon ratio of 1.3, the holding time of 30 minutes, the stirring speed of 125r/min, the alkalinity of 1.0, and the amount of calcium fluoride was 10% of the amount of calcium oxide. The content of P and S in the pig iron was low, which can meet the requirements of the national standard L03 for steelmaking. The main phases in the reduction slag are gehlenite, calcium titanate, and nepheline, which are effective components for cement clinker production. The pilot-scale experiment on vortex smelting reduction of high-iron red mud can provide relevant data for large-scale industrial applications and has great guiding significance. Currently the production is in intermittent mode. In the future, continuous charging, continuous slagging and iron production can be realized by designing a continuous reaction unit.

Abstract:Gallium and germanium are important rare metals, and the comprehensive recovery of gallium and germanium from the zinc metallurgy process has become an important source for the metals. At present, acid leaching process is mainly used to recover gallium and germanium, with low recovery rate and resource utilization rate. In this paper, based on the properties of gallium and germanium amphoteric substances, the experimental study on the recovery of gallium and germanium from zinc refinery residues was carried out by alkali leaching-reduction volatilization process,andthe following main conclusions are obtained.The single factor optimum process conditions of alkali leaching test are as follows, NaOH concentration 4mol/L, reaction temperature 90℃, liquid-solid ratio 8mL/g, stirring speed 400r/min. Under these conditions, the leaching rates of gallium and germanium of zinc refinery residues reach 91.25% and 78.95%, respectively.Enhanced ball milling leaching does not improve the leaching rate of gallium and germanium.The single factor optimum process conditions of reduction volatilization test were as follows, temperature 1200℃, pulverized coal dosage 30%, volatilization time 4h. Under these conditions, the volatilization rate of germanium in alkaline leaching residue reached 91.02%.The volatile residue and calcium arsenate residue produced by the process are returned to the pyrometallurgical lead smelting system to comprehensively recover valuable metals such as copper and arsenic, and the harmless treatment of the residue is realized.The volatile residue and calcium arsenate residue produced by the process are returned to the pyrometallurgical lead smelting system to comprehensively recover valuable metals such as copper and arsenic.The method of recovering gallium and germanium in this paper can provide reference for similar enterprises to recover gallium and germanium from zinc metallurgy process.

Abstract:When the electrowinning displacement method is used to recover cadmium from Copper-cadmium-bearing Slag, the electrowinning process will produce floating sponge cadmium, which leads to low cadmium recovery efficiency and is not conducive to the subsequent briquetting and smelting.Based on the analysis of the principle of cadmium electrowinning, the experiment of ultrasound-assisted cadmium electrowinning was carried out by using the cavitation of ultrasonic.The effects of current density、temperature、ultrasonic power、area ratio of cathode to anode and electrowinning time on the recovery rate of cadmium were investigated, and the following main conclusions were obtained.The results of cyclic voltammetry test show that cadmium in the electrolyte can be replaced by electrodepositionin the sulfate system, andthe precipitation of cadmium is better than thezinc, and zinc in the outer layer of cadmium will be partially dissolvedin the progress of electrowinning;The comparison test of cadmium electrodeposition with and without ultrasonic assistance showed that,the recovery rate of cadmium was 16.25% without ultrasonic assistance, and the electrodeposited cadmium was fluffy, porous and easy to float. The recovery rate of cadmium was 25.11% with 180W ultrasonic assistance, and the electrodeposited cadmium was dense and easy to fall off;The results of single factor experiment show that: the recovery rate of cadmium in leaching solution can reach 100% under the conditions of current density of 150A/m², temperature of 35℃, ultrasonic power of 240W, area ratio of anode to cathode plate of 1∶3, and electrowinning time of 2.5h; The electrochemical experiments at different temperatures show that the increase of temperature is beneficial to the precipitation of cadmium, and the precipitated zinc is more easily oxidized and dissolved, cadmium is more difficult to oxidize and dissolve, thus improving the recovery rate and purity of cadmium.

Abstract:Electrolytic copper foil has been widely used in the field of new energy because of its advantages of high strength and good ductility. At present, there are few studies on the factors affecting the performance of 5μm electrolytic copper foil. In this paper, the effects of PEG, HVP, HP and other additives on Cu electrodeposition were investigated by single variable method. The effects of PEG, HVP and HP compound additives on the performance of 5μm electrolytic copper foil were investigated by orthogonal test, and the effects of different additives on the appearance of 5μm electrolytic copper foil were compared. The following conclusions were reached: PEG and HVP can enhance the polarization, and the polarization increases with the increase of the concentration. HP can depolarization, and the depolarization increases with the increase of the concentration. The optimal concentration of the compound additive was PEG 0.36g/L, HVP 0.12g/L and HP 0.05g/L, and the best properties were tensile strength 485.17MPa, elongation 3.72% and roughness 1.31. Compared with a single additive, the surface of the composite coating under the optimal ratio of composite additive is more uniform and smooth, and the particles are fine.

Abstract:It is difficult to achieve industrial production of low rubidium lepidolite because of the large differences in the occurrence forms of Rb. In this paper, the extraction of Li and Rb from rubidium-rich lepidolite ore in Australia was studied by using NaCl-CaCl₂ roasting-water leaching method. The effects of roasting temperature, ingredient ratio, time and leaching liquid-solid mass ratio, leaching time and temperature on the extraction of Li and Rb were investigated. The results show that under the conditions of rubidium-rich lepidolite ore∶NaCl∶CaCl₂ mass ratio of 1∶0.6∶0.4, roasting temperature of 800℃, roasting time of 1.5h, water leaching temperature of 25℃, liquid-to-solid ratio of 4∶1 and leaching time of 15min, the leaching effect of Li and Rb is the best. The leaching rates of Li and Rb were 87.8% and 94.9%, respectively. X-ray diffraction (XRD) analysis of calcinate and leaching residue showed that Li and Rb mineral phases in lepidolite transformed into soluble LiCl and RbCl phases after chlorination roasting, meanwhile KCl and insoluble substances CaAl₂Si₂O₈, NaAlSi₃O₈, CaF₂ were generated. The ΔG^Θ_T-T and ΔH^Θ_T-T diagrams showed that the reaction order of NaCl-CaCl₂ with alkali metal oxides was Rb＞K＞Li. The participation of SiO₂ and Al-O phase in ores promoted the chlorination reaction for alkali metals.

Abstract:Panzhihua iron and Steel Group‘s Xichang strip roaster production line is the first production line of vanadium-titanium ore strip roaster pellets in China, the average compressive strength of the finished pellets was lower than that of the original pellets, per pellet only ≥1950N. This paper analyzes the reasons from the aspects of raw material structure, pelletizing process, technological operation of belt roaster, etc., the optimization measures adopted include: controlling the mass fraction of TiO₂≤12%, V₂O₅≤1%, Al₂O₃＜2.0%, MgO＜1.8%, and the concentrate particle size of 200 mesh 75%~80%, the alkalinity should be controlled about 0.6 times, the proportion of bentonite should be reduced to 1.2%~1.4%, the proportion of green ball particle size 10~12.5mm≥60%, the proportion of gravity dust ＞1.5%, or the proportion of Sintering Machine Head dust ＞1.5%, The operating regulations of the roaster is as follows: the temperature of the drum drying section is 300~330℃, the temperature of the drying section is 370~390℃, the preheating temperature gradient is 500→1200℃, the temperature of the roaster section is 1230~1240℃, and the oxygen content in the hood is 17.3%~18.0%. After optimization, the average compressive strength of single pellet was about 2348N, and the smoke dust content was 2.54mg/Nm₃, SO₂ content was 3.13mg/Nm³, NO_x content was 41.42mg/Nm³, and the reference oxygen content was 17.54%, all meet national emission standards.

Abstract:Gold nickel chromium iron silicon boron alloys is a kind of excellent brazing material, which is widely used in aerospace field. It is of great significance to establish an accurate, simple and rapid detection method for guaranteeing the properties of gold-nickel-chromite ferrosilicon-boron alloy powders.The existing GB/T 39138.20—2020 has strict requirements on dissolution conditions and is difficult to master. In this paper, a sample of 0.2g alloy powder was measured and dissolved by HNO3-HCl-HF with sealed-digestion at 140℃±10℃ and dilute solution 60min and boric acid complex excess HF. The contents of chromium, iron and silicon were determined simultaneously by inductively coupled plasma optical emission spectrometry (ICP-OES). It is selection wavelength Cr284.325,Fe238.204,Si288.158 to result computation. The results were same with GB/T 39138.20—2020，the results adding standard recovery was 97.2%~101.1%, the results ofrelative standard deviationwas 0.97%~1.41%.The experimental data show that the method is reliable. This method overcomes the defects of the current national standard method with strict dissolution conditions,makes the dissolution more complete, avoids the loss of silicon content, and reduces the difficulty of sample pretreatment.It is an easy to master,high accuracy and environmentally friendly analysis method.

Abstract:In order to solve the problem of sample dissolution in the determination of impurity elements in ferric phosphorus samples by inductively coupled plasma emission spectrometry (ICP-OES), this paper uses sodium hydroxide + sodium carbonate to melt the tested ferric phosphorus samples, and then uses inductively coupled plasma emission spectrometer to determine silicon, manganese, titanium, vanadium and chromium in the samples. The results showed that the detection limit of each element was 0.0016%~0.0080% and the lower limit was 0.0064%~0.032%. The relative error RE of each element content between the results and the standard sample was less than 5%, the recovery rate was 95.1%~102.4%, and the relative standard deviation was less than 5%. RSD of the three actual samples is less than 5%, which indicates that the method has good precision and accuracy, and can meet the detection requirements. The method overcomes the insoluble characteristics of the phosphorus and iron samples, and obtains the ideal detection results in a short time, and the determination results have high stability, precision and accuracy. The test method has the advantages of repeatability, short process and low cost, and is suitable for rapid analysis of large quantities of samples. It can be used as a simple, rapid and economic important means to detect iron phosphorus products.

Abstract:The spent cathode carbon is a large amount of solid waste produced in the industrial production process of aluminum electrolysis. At present, the main treatment method is stockpiling. The spent cathode carbon is mainly composed of carbon (60%~70%), and also contains some Na₃AlF₆, NaF, CaF₂ and NaCN. The cyanide and fluoride in the spent cathode carbon will cause serious harm to the environment and are hazardous wastes. At present, there are studies on the use of spent cathode carbon instead of carbonaceous reducing agent for ironmaking, and the related research on the reduction of laterite nickel ore has not been found. In this paper, Yunnan Yuanjiang laterite nickel ore was used as raw material, spent cathode carbon was used as reducing agent, and CaCO₃ was used as additive to study the reduction effect and fluorine fixation effect of spent cathode carbon reduction laterite nickel ore. The results show that under the optimum conditions of spent cathode carbon addition of 14%, reduction temperature of 1250℃, reduction time of 75min and CaCO₃ addition of 8%, the nickel and iron grades of the reduction roasting product are 5.82% and 66.23%, respectively, and the nickel recovery rate is 94.04%. The fluorine fixation rate was 94.9%, and the concentration of Fin the toxic leaching solution was 30mg·L-1, which was far less than the emission requirement of 100mg·L-1. Under the condition of reduction roasting, CN- in waste cathode carbon generates CO₂ and N₂, F- remains in the form of CaF₂ in the roasted ore, and can be used as a flux to reduce the melting point of ferronickel alloy, which is beneficial to the treatment of roasted ore in the later stage. This study provides a new idea for the harmless treatment of spent cathode carbon.

Abstract:Anode carbon slag is a hazardous waste generated during the aluminum electrolysis process, mainly composed of cryolite, subglotite, and carbon. Currently, it is mainly stored in a temporary manner through stacking, which not only pollutes the environment but also causes resource waste. This article uses anode carbon slag provided by an electrolytic aluminum plant in Gansu as raw material, and conducts characterization analysis on it. Based on thermodynamic analysis and TG-DSC analysis within the calcination temperature range, a single factor calcination test is conducted, and the following main conclusions are obtained. In areas with low electrolyte content in anode carbon slag, electrolytes adhere to the surface and gaps of particles, while higher areas wrap around carbonaceous materials; The Gibbs free energy analysis of chemical reactions indicates that the roasting method is feasible for recovering electrolytes from anode carbon slag; The optimal roasting process obtained from the single factor experiment is a temperature of 800℃, a heating rate of 5℃/min, and a holding time of 1.5 hours. Under these conditions, the weight loss rate of anode carbon slag is 23.73%, the removal rate of electrolyte carbon is 96.17%, and the recovery rate is 91.32%; K₂NaAlF₆ and LiF new phases appeared in the recovered electrolyte, with a uniform distribution and increased content of Na, Al, F, Mg, Ca, and K elements. The initial crystallization temperature of the electrolyte was 921.5℃, which can meet the industrial application requirements of aluminum electrolysis.

Abstract:In order to comprehensively recover valuable metals from zinc smelting fuel dust and electrolytic waste liquid, a synergistic treatment experiment of zinc smelting electrolytic waste liquid and oxygen pressure leaching zinc smelting fuel dust was researched, zinc and magnesium precipitation products were obtained through a process of leaching, neutralization of zinc precipitation with sodium carbonate, and neutralization of magnesium precipitation with sodium hydroxide, indium-rich slag and by-product lead silver slag were obtained through two-stage leaching, extraction-stripping and indium neutralization-precipitation，and the experimental conditions were optimized. The results show that the liquid-solid ratio is 4∶1, the leaching temperature is 80℃, and the leaching time is 75minutes. under these conditions, the zinc leaching rate can reach 78.69%, while the indium leaching rate is only 8.4%; the optimal endpoint pH range for zinc magnesium separation is 6.86 to 7.80; the endpoint pH value is 1.08, the liquid-solid ratio is 3∶1, the leaching temperature is 75℃, and the leaching time is 10h, which is the optimal process conditions for two-stage leaching,under these conditions, the leaching rate of indium can reach 86.84%, which can provide new ideas for open circuit impurity removal and comprehensive recovery of valuable metals in zinc smelting plants.

Abstract:The milling residues from PCB (Printed Circuit Board) cutting typically contain copper and aluminum metals along with a high plastic content. The electrochemical dissolution and electrodeposition process offer an effective method for stripping copper and obtaining high-purity cathode copper from these residues. This process is characterized by its short duration, high current efficiency, and the production of high-purity copper, making it highly promising for various applications. However, the electrochemical mechanism underlying this process remains unclear.In this study, PCB-generated copper-containing solid waste was utilized as the anode, with titanium plates serving as the cathode. A series of experiments was carried out using a diaphragm electrolysis process in an NH₃-(NH₄)₂SO₄ system. These experiments included investigations into different ammonium salt systems, various electrodes in the ammonia/ammonium sulfate system, electrochemical behavior curves of different electrolyte compositions in the ammonia/ammonium sulfate system, and control steps and nucleation mechanisms of copper electroplating in the NH₃-(NH₄)₂SO₄ system. The results indicate that the starting reduction potential of copper electroplating in the ammonia/ammonium sulfate system is the lowest, resulting in low energy consumption during electroplating. Additionally, the hydrogen deposition potential in this system is negative, which helps avoid side reactions such as hydrogen evolution and enhances the cathodic current efficiency. The electroplating reaction of Cu²⁺ on the titanium electrode surface in the NH₃-(NH₄)₂SO₄ system is found to be an irreversible process and a two-electron one-step transfer process, with diffusion control as the controlling step. The nucleation mechanism of Cu²⁺ on the titanium electrode is close to instantaneous nucleation. These findings provide valuable theoretical insights for the NH₃-(NH₄)₂SO₄ system diaphragm electrolysis copper process.

Abstract:In view of the problems such as large storage of vanadium extracted tailings, low utilization of valuable components and great harm to the environment, the process of calcification alkaline leaching under normal pressure was adopted to remove the alkali and extract the valuable metal vanadium. The reaction mechanism was studied and the effects of leaching temperature, alkali concentration, calcium oxide addition and liquid-solid ratio on the leaching rate of sodium and vanadium were investigated through single factor experiments. The results showed that the leaching rate of vanadium and sodium reached 82.25% and 85.36% respectively after 60min leaching under the optimum conditions of 160℃ leaching temperature, 100g·L-1 alkali concentration, 15% CaO addition and 8∶1 liquid-solid ratio. At the same time, the vanadium precipitation method with ammonium metavanadate was also used to obtain V₂O₅ products with purity greater than 97%. The analysis of final slag shows that the content of Na₂O is less than 0.5%, and combined with the alkali metal balance data of chengsteel blast furnace, it can be used in blast furnace ironmaking and ore blending.

Abstract:With the quickly increasing of demanding in the lithium ion battery diaphragm, boehmite were valuable accordingly. The hydrothermal preparation of boehmite with aluminium hydroxide as precursor is a technical proposal which is easily to be applied in the plant. The influence of reaction conditions, such as slurry solid content, reaction temperature, reaction time and particle size of precursoron conversion rate of boehmite were researched in the article. The results showed that the reaction temperature was the most important influence factor in all tests. The conversion was scarcely occurred when the reaction temperature was less than 180, the conversion were finished more than 45 minutes when the temperature was 200. when the temperature was 220, the conversion was finished in 15 minutes.The original particle of boehmite from hydrothermal preparation was presented in a quadrangular rhombic shape in a submicron scale, the final product was agglomeration of submicrom particles. The research results showed some basic reaction behaviors in hydrothermal preparation boehmite, which can be used to produce boehmite in lithium ion battery diaphragm.

Abstract:In the process of crude lead smelting, arsenic, cadmium and thallium in lead concentrate and other lead-containing materials are distributed in each process, which is not conducive to the recovery of valuable metal resources, but also increases the difficulty of smelting waste treatment, and has a negative impact on human health and the environment. The distribution and trend of arsenic, cadmium and thallium in the smelting process of crude lead have not been reported in the existing literature. Based on the actual production situation of a smelting enterprise, this paper statistics two sets of material balance data for 14 days in 2021 and 2022 respectively, and analyzes the distribution of arsenic, cadmium and thallium in each smelting process. The distribution of arsenic is as follows. In the bottom blowing process, about 85% arsenic enters into high lead slag, about 9% arsenic enters into dust, and about 6% arsenic enters into sulfuric acid purification system; In the process of the reduction furnace, about 70% of the arsenic forms lead copper matte into the crude lead, about 20% of the arsenic enters the reduction furnace dust, and less than 10% enters the fuming furnace through the reduction slag. The cadmium and thallium is highly enriched in the bottom blown furnace and side blown furnace soot, of which the enrichment ratio of the bottom blown furnace dust is 85% to 95%, only 5% to 15% enter the process of transferring the high lead slag to the reduction furnace, and very little enters the sulfuric acid system. Enterprises adopt transferring bottom-blown furnace dust to reduce the content of arsenic, cadmium and thallium in the crude lead smelting system. The transfer standard is when the dust contains more than 20% cadmium, and stop transfer when the dust contains less than 15% cadmium. The dust taken out can be directly sold as raw materials for cadmium recovery. The analysis results and the solution in this paper can provide reference for similar enterprises to control the distribution of arsenic, cadmium and thallium in smelting system.