China Nonferrous Metallurgy

Abstract:Chinese carbon emission ranks first in the world, with an amount of 11.5 billion tons in 2020. In China’s primary energy consumption, fossil energy especially coal still remains dominant, which accounts for 57.7%. In recent years, although China’s carbon emission per unit GDP has decreased significantly, it is still higher than the world average. The development of polysilicon and crystalline silicon photovoltaic industry is expected to become an important support for clean energy and primary measure to achieve the goal of “carbon neutrality”. In 2019, China’s total photovoltaic power generation was 224.3 billion kW·h, accounting for 3.1% of the country’s total power generation. It is planned to reach 39% in 2050 when the power generation will be 6 trillion kW·h and the CO2 emission will be reduced by 7.1 billion tons approximately, which is the absolute main force of carbon neutrality. In recent years, the energy consumption and cost of polysilicon production have been greatly reduced. The development of monocrystalline silicon technology and diamond wire cutting technology has greatly reduced the material consumption. It is expected that the cost of crystalline silicon solar power generation will be the lowest among all power generation modes in the future, reaching 0.13RMB/kW·h, which provides a guarantee for the realization of the goal of photovoltaic power generation planning.

Abstract:In order to tackle the global climate change and promote the carbon neutrality to be a global consensus, the development of new energy vehicle (NEV) industry has become an important technical path and strategy choice. As a major power battery producer in the world, enterprises related to the industrial chain in China have restructured their layouts in the raw materials field to ensure the supply of raw materials for power battery. In which, nickel, as the main raw materials of power battery, has attracted so much attention in the technical and industry development trend diverting from the resource development to smelting and processing, as well as raw material production. Combined with the development policy of power battery in the process of realizing the goal of “carbon neutrality”, this paper calculates and analyzes the carbon emission intensity of battery nickel products produced by treating laterite nickel ore with different processes, further analyzes the development trend of battery nickel industry in the future, and puts forward countermeasures for the industry development, especially the cutting-edge layout of enterprises, so as to provide reference for relevant enterprises and decision-makers to better understand the development trend of the industrial chain from the overall situation.

Abstract:In recent years, the amount of industrial hazardous waste produced in China grows year by year, but the existing hazardous waste treatment equipment is backward, creating a huge gap between throughput and production. The side-blowing submerged combustion bath smelting technology (SSC for short) independently developed by ENFI has been successfully applied to production on an industrial scale, and currently the application of this technology is expanding to such fields as treatment of anode slime, copper dross and electronic waste. Due to major changes in components of hazardous waste, the originally designed SSC furnace is difficult to adapt to this working condition. Hence, ENFI has improved it and named the new version “comprehensive recovery and treatment furnace”. This paper carries out an analysis of advantages and disadvantages of SSC technology, elaborates on features of comprehensive recovery and treatment furnace, and introduces the application of this furnace. Practices show that comprehensive recovery and treatment furnace can not only treat hazardous waste, but also leverage heat in industrial hazardous waste and recover valuable metals such as copper, which accords with the philosophy of green metallurgy and enjoys a bright market prospect.

Abstract:It has been a hot spot and challenge in the research on copper electrorefining process to maintain Cu²⁺ concentration within the range required by production. The evaporative crystallization of copper electrolyte is a key factor in ensuring proper Cu²⁺ concentration. Effects on crystal mass by strong magnetic field circulating system in the process of electrolyte evaporative crystallization and cooling are tested to analyze the internal mechanism of resonance associated with magnetization time, flow rate and copper electrolyte under strong magnetic field. Based on the results, when strong magnetic field acts synergically on copper electrolyte, resonance will occur to maximum between the constant magnetic field intensity and the rotational energy state of molecules in the copper electrolyte, promoting evaporative crystallization and cooling of the electrolyte. The lower the flow rate and the longer the magnetization time, the better the evaporative crystallization and cooling of electrolyte will be. At the optimal parameters for evaporative crystallization, i.e. magnetic field intensity 3T, flow rate 0.3m/s and magnetization time 1.5h, the evaporation rate of electrolyte increases by 14%. For the cooling process, the optimal parameters of magnetic field intensity 3T, flow rate 0.3m/s and magnetization time 1.5h contribute to an evaporation rate increase of 5% and a crystal mass increase of 19.73%. To optimize the evaporative crystallization process of copper electrolyte by magnetic field can significantly improve electrolyte purification efficiency. It is positive to mitigate the concentration polarization of copper electrolysis process and stimulates the copper acid ratio of electrolyte to stay in dynamic equilibrium. The quality of copper cathode is thus improved at lower energy consumption during the copper electrolysis process.

Abstract:To solve the technical problems of conventional copper hydrometallurgy such as high acidity of pressure leaching solution, large amount of residue and big loss of copper in downstream neutralization operations, a deacidification technology of copper sulfide concentrate pressure leaching, which is clean, environmental friendly, and easy to operate in industry, is proposed herein based on the acid production mechanism in the process. Findings from associated tests are as follows: a circulation section of pressure leaching solution returning to the previous process can be added in the original production system to reduce the circulation amount of spent electrolyte, decreasing acid from source, subsequent limestone dosage and the loss of copper into the neutralization residue; an efficient leaching of copper from copper sulfide concentrate can be realized under medium temperature and pressure conditions, which also retard the oxidation of elemental sulfur. With appropriate dosage of surfactant, calcium lignosulphonate, the phenomenon of sulfur wrapping copper minerals can be mitigated, improving the leaching efficiency of copper; under appropriately controlled leaching conditions, when the return rate of pressure leaching solution ranges between 40%-50%, copper leaching rate can reach more than 98.5%, the final acid of leaching solution can be reduced to 30g/L and Cu in neutralization residue can drop to less than 1.5%.

Abstract:In the process of electric furnace copper smelting, a proper thickness of the furnace accretion can form a protective layer on the furnace body, while a much larger one would lead to a great reduction of the effective volume ratio of the furnace and increase of copper content in the slag. The determination of thickness of the furnace accretion and high copper content in the slag are two major technical issues in electric furnace copper smelting production, and also the final way to increase the capacity of electric furnaces. By analyzing the composition and properties of the furnace accretion in this paper, it is concluded that the content of Fe₃O₄ in slag is the key to the thickness of furnace accretion. The high content of Fe₃O₄ not only increases the mechanical entraining of copper in slag, but also increases the loss of chemical dissolution of copper in slag. By analyzing the thermodynamic and kinetic conditions of the reduction and decomposition of Fe₃O₄ effective measures to reduce the content of Fe₃O₄ in the slag are given in this paper: diesel oil, white sand and N2 are sprayed into the bottom of the furnace by a small oil gun; When the volume ratio of oil to gas ranges from 1∶17 to 1∶20, the optimal insertion depth of oil gun is 0.2~0.3m when the Fe₃O₄ in reducing slag is reduced, the oil gun is inserted into 1/2~3/5 of the slag layer thickness when the copper content in slag is reduced, and the oil gun is inserted into the bottom of furnace and then lifted 50~100mm when the furnace accretion is treated. Besides a proper control on the ratio of raw materials, Na₂CO₃ flux with slag content of 1.6‰ should be added in proportion. When this scheme was carried out, it is found that the thickness of the furnace accretion is reduced to an average of 452mm, and the copper content of the slag is reduced to a monthly average of 0.498%, indicating a good economic benefit.

Abstract:The increasing use of copper sulfide ore with high fluorine content as raw material for smelting has caused higher F concentration in the smelting off-gas, forming high-F sulfuric acid, which leads to process index fluctuation and equipment failure. To tackle the problem of F removal from acid-making system, a smelter carried out analysis on the F distribution in F removal process and F removal principles, and finally determined rationale solutions, which include controlling the F content in the feed concentrate below 0.05% whenever possible, strengthening the daily maintenance of the primary high-efficiency scrubber to guarantee purification efficiency, adding appropriate amount of diluted sodium silicate at an even speed, etc. By adopting the above-mentioned measures, the off-gas from the primary scrubber enters ESP for further purification, the purified off-gas can completely meet the standard with F≤0.3mg/Nm³, As≤0.05mg/ Nm³, acid mist concentration ≤5mg/Nm³ and dust content ≤2mg/Nm³. It has no effect on the equipment and operation index of the subsequent process. In later monthly repairs and cold repairs of the system, no large-area corrosion, collapse and damage of equipment are found, which proves the F in the acid-making system of the copper smelter has been controlled effectively.

Abstract:Roaster is the core piece of equipment for zinc smelting and was initially introduced into China from abroad. Based on absorption of the associated technology, China ENFI made multiple optimizations and developed the first 152m² large fluidized roaster of independent intellectual property rights in China. Thereafter, a number of roasting systems have been up and run in China, realizing the promotion and penetration of technology for Chinese-made large roaster. Design features of the 152m² large fluidized roaster include optimized design of roaster roof in accordance with temperature field model and stress field model, grate hood of special design, roof of integral tamping patented technology and new ramming materials to replace brickwork for the lower part of roaster. Production practices prove that roaster of optimized design is advantageous in low residual sulfur, good product quality, low capital cost, small footprint, stable production operations and convenient for centralized intelligent control and information management. Large roaster is the future trend of zinc smelting equipment.

Abstract:Application of oxygen enriched air roasting technology in zinc concentrate roaster has stayed in the experimental stage in China over the years. Chihong Zn & Ge is the first to have realized large-scale production of zinc concentrate by oxygen enriched air roasting. The company adds oxygen-enriched air distribution device on the original blast system piping, provided with fittings such as high concentration oxygen regulating valve group and instrumentations for flow and pressure monitoring, along with equipment optimization to fluidizing cooler, high-temperature ID fan and blower. Production practice shows that under proper process parameters, the production capacity of oxygen-enriched air roasting technology can be fully released, and the specific capacity of fluidized-bed roaster can be increased to 8.03t/m2·d; the quality of roasted ore can be improved effectively and the sulfur content of roasting dust can be lowered to 3.5%; the energy consumption per ton of zinc is greatly reduced the unit consumption of compressed air, electricity and high concentration oxygen are 194.0Nm3/t , 135.80kWh/t and 81Nm3/t respectively. In conclusion, the application of oxygen-enriched air roasting technology with 109m2 roaster can obtain better economic benefits. It also improves the utilization rate of facilities of roasting system and sulfuric acid system, reduces the volume of blast, and effectively prevents fugitive dust, improving the production environment on site.

Abstract:In order to reduce the unit consumption of zinc powder in the purification process and improve the quality of electrowinning feed, Yunxi Wenshan Zinc Indium Smelting Co. Ltd. conducted a test on Co removal from the primary purified solution by using antimony trioxide method, and analyzed the test results. In the test, better process parameters obtained are: agitation speed of 400r/min, temperature of 85~90℃, Sb-Co ratio of 0.2~0.25, zinc powder of 2.5~3.0g/L, pH value of 4.5 and reaction lasting 2~2.5h. Under such conditions, the Co content in the solution can be reduced to below 0.4mg/L and the quality of electrowinning feed is improved, creating a good condition for the downstream process. Meanwhile, the good process control in the secondary purification has guaranteed a lower unit consumption of zinc powder and played a positive guiding role in stabilizing production, reducing cost and increasing efficiency.

Abstract:Yunxi Wenshan Zinc Indium Smelting Co., Ltd adopted hematite Fe removal combined with SO2 reduction leaching for Zinc hydrometallurgy. Cu recovery had been relatively low in early production. To address the problem, the Company analyzed the behaviors and balance status of Cu in the production system, and found that low Cu leaching rate in SO₂ reduction leaching section was the major cause for the low Cu recovery in the system. By increasing the reaction temperature by 10-15℃, leaching time by 30-45min and initial acidity to 20-30g/L in SO₂ reduction leaching section, Cu leaching rate can be increased by about 11%; in addition, by controlling the volume of SO₂ input at an appropriate level, generally 1.2 times the content of Fe³⁺ in the solution, Cu precipitation caused by excessive SO₂ input can be avoided, and the loss of Cu into the leaching slag can be reduced. With the above measures, the final Cu recovery rate of the system is improved by about 10% up to 93%.

Abstract:Lead-silver slag is produced during smelting of sphalerite with high Fe and In contents in a smelter in Yunnan. This slag contains a high content of metals that are worthy of recovery. At present, the treatment process of such a type of lead-silver slag is dominated by pyrometallurgical volatilization which has shortcomings such as low recovery rate of valuable metals, high energy consumption and environmental pollution. This smelter conducts hydrometallurgical tests about silver and valuable metal recovery, and explores the influence on recovery rates of silver and valuable metals by acidity of nitric acid system and sulfuric acid system and consumption of leaching agents, including ammonia water and sodium sulfite. The final process flow for lead-silver slag treatment is determined as pretreatment—oxidizing roasting—two-stage acid leaching—complexation by ammonia water—silver reduction and extraction by hydrazine hydrate—sponge silver casting. With preferable process parameters, production indicators can be: silver leaching rate＞96%; comprehensive silver recovery rate＞98%; copper leaching rate＞99%; indium leaching rate＞80%. After silver extraction, the Pb content in final residue is up to 45% and can serve as desirable raw material for lead smelting in the next step. This process flow is characterized by low equipment costs, simple process control, high silver recovery rate and a great number of recoverable valuable metals, providing reference for pyrometallurgical zinc smelting companies that conduct comprehensive silver recovery from lead-silver slag.

Abstract:Generation of acid mist mainly occurs during electrowinning of the hydrometallurgical zinc refining process. Acid mist irritates respiratory tract and skin, corrodes teeth and contaminates ambient air and soil. Fugitive acid mist in zinc electrowinning operations has been a major concern in Danxia Refinery. Control measures are taken including strict control of the quality of purified solution, optimized ventilation system of electrolysis cells, improved liquid distribution system and spray trap of air-cooled tower and provision of foam trap. As a result, acid mist discharge to atmosphere decreases by more than 99.5%. Ambient acid mist concentration drops to lower than 0.025mg/m³ and acid mist discharge from air-cooled tower declines to 0.025mg/m³. It is not only in compliance with state discharge limits but also far ahead in the industry. Meanwhile, the increased height and optimized spray system of the air-cooled tower improves the cooling range to 5-6℃, which meets the requirements of normal and stable operations of zinc electrowinning.

Abstract:Thanks to the excellent corrosion resistance, high notch self-healing and formability of Zn-Al-Mg alloy coating, the preparation of high-purity Zn-Al-Mg alloy has become a research focus of large steel enterprises at home and abroad. Two Zn-2%Al-2%Mg and Zn-5%Al-5%Mg alloys for hot galvanizing were prepared by power frequency induction furnace in Henan Yuguang Zinc Industry Co., Ltd., and by analyzing the microstructure and composition segregation of the alloys, it is found that the microstructure of the alloys is uniformly dispersed, and there is no inclusion and oxide. The solidification microstructure of Zn-2%Al-2%Mg is mainly composed of primary Zn phase, Zn/MgZn₂ binary eutectic structure and Zn/MgZn₂/Al ternary eutectic structure. There are lots of coarse Al/MgZn₂ binary eutectic and coarse Mg₂Zn₁₁ phase in the solidification microstructure of Zn-5%Al-5%Mg. The remelting experiment of Zn-2%Al-2%Mg shows that no oxide slag exists after remelting. Through the analysis of alloy ingot from transverse and longitudinal sampling, it is found that the transverse segregation of aluminum and magnesium is small, and the longitudinal segregation is about 0.1%. This paper provides a description on the detailed process and technological parameters of Zn-Al-Mg alloy preparation experiment, with an expectation to serve as a reference for researchers in this field.

Abstract:In order to explore the process of recovering tellurium from copper anode slime, which features short process flow, simple operation, low Te loss and high Te recovery, direct or indirect alkaline leaching tests are carried out for four kinds of Te bearing materials produced in the processing of copper anode slime, and impurity removal test is carried out for the product from the leaching process with higher Te recovery. The following conclusions are drawn: Te leaching rate reports 1.26% at most in the alkaline leaching test for selenium-removed residue, which contains a small amount of Te4+; that is 1.2% in the alkaline leaching test for the neutralization residue of the solution resulting from Au precipitation, in the solution Te exists mainly in the form of Te6+; that is no more than 20% in the alkaline leaching test for Pt-Pd concentrate, which contains elemental tellurium and Te6+ mostly and small amount of Te4+; while the leaching rate of Te can reach 98.69% in the alkaline leaching test for the neutralization residue of the solution from primary reduction, in the residue Te exists in the form of Te4+, and Na2S is used to remove the heavy metals in the leachate, showing good effect.

Abstract:Since Cr furnace differs greatly from traditional pyrometallurgical furnaces in process, few research literature can be found about the corrosion mechanism of magnesia-chromite bricks. This paper studies residual refractory bricks of Cr furnace used in the scale-up test, and adopts such methods as chemical analysis, physical property test and electron microprobe to analyze the corrosion process and probe into the corrosion mechanism of magnesia-chromite refractory bricks by slag. The following conclusions are drawn. Furnace wall bricks suffer more damage than furnace bottom bricks. Damage to furnace wall bricks is mainly caused by corrosion and penetration of slag. MgO first dissolves in slag and slag reacts to generate silicate, hortonolite, magnesium ferrite and magnesium silicate in refractory materials. Copper matte does not react with refractory materials. By contrast, damage to furnace bottom bricks is mainly caused by penetration of copper matte and metal elements such as Cu, Fe and Pb.

Abstract:The dense population, developed heavy and chemical industries and large output of solid waste in Beijing-Tianjin-Hebei region has posed a serious challenge on resources and environmental protection. In addition, there are some problems in the treatment and disposal of solid waste in the region, such as discrepancy of statistical data from different sources, low utilization rate of solid waste resources, insufficient coordinated utilization among various types of solid waste, which greatly hinder the progress of Beijing-Tianjin-Hebei coordinated and integrated construction. In this paper, based on the principles and targets of solid waste harmlessness, quantity reduction and recycling, the feasibility is analyzed on the coordinated utilization of solid waste from various sectors involved in industry, agriculture and urban areas in Beijing-Tianjin-Hebei Region. The overall idea and solution is proposed for the cross-industry and cross-region coordinated utilization of solid waste. The analysis suggests that, based on the solid waste database establishment, high proportion of coordinated utilization, high added-value products development, industrial materials application and new technologies & equipment for ultra-low off-gas emission shall constitute the support for the solution. The objective is to form an integrated demonstration base for solid waste coordinated treatment, optimize its economic operation indicators, explore new business operation modes, and accelerate industrial progress. In addition, all sectors of society shall, from the macro perspective of the integration of Beijing-Tianjin-Hebei region, actively formulate and implement new standards and regulations, and form a coordinated management system, to realize the cross-industry and cross-region coordinated utilization of solid waste in the Beijing-Tianjin-Hebei industrial, agricultural and urban areas, and solve the problem of solid waste treatment by industries and by regions.

Abstract:Exploring efficient treatment methods and low-cost treatment material for copper-polluted water resources has been forefront research topics of the academia. The desulfurization slag of molten iron pretreatment (KR desulfurization slag) has been widely used as the adsorbent for wastewater treatment in recent years because of its small grain size, small aperture size and large specific surface area. In this paper, the desulfurization slag of molten iron pretreatment in an iron and steel enterprise in Jiangsu was used as the adsorbent to study the adsorption performance of Cu²⁺ ions, and investigate the effects of the desulfurization slag amount, adsorption time, initial concentration of Cu²⁺ ions and reaction temperature on the adsorption performance. The dynamic and isothermal adsorption models were analyzed according to the test results. The research results show that the desulfurization slag has good adsorption performance on Cu²⁺ ions. The comparatively good treatment conditions for wastewater containing Cu²⁺ are: 4g/L desulfurization slag, the temperature about 30℃, the concentration of Cu²⁺ in wastewater 20mg/L, and the treatment duration 2h. Under such conditions, the adsorption rate reaches 94.14%. The results of adsorption dynamics and adsorption isotherm model show that the adsorption curve of Cu²⁺ ions by desulfurization slag conforms to pseudo-first reaction kinetics model and Freundlich isotherm adsorption model, that is, the adsorption rate of Cu²⁺ ions by desulfurization slag is greatly affected by diffusion and belongs to the adsorption process of complex adsorption surface.

Abstract:China is a major lead consumer, but its degree of security for lead resources is not high. The scientific calculation of the in-use stock of secondary lead as a supply for future lead demand can provide significant data support for lead resource supply. In this paper, a dynamic analysis model of lead material flow is built, with two methods used to verify in-use lead stock: one is the top-down method to analyze the lead inflow, outflow and stock in China’s socio-economic system from 1949 to 2018 to calculate the in-use lead stock; the other is the bottom-up approach to analyze the changes of the most important types of carriers and battery capacity of lead-acid batteries, and calculate the in-use lead stock of lead-acid batteries in 2018, from which the in-use lead stock of the year can be calculated. Results show that the in-use lead stock of 2018 is calculated as 23200000t by the top-down method, and 18920000t by the bottom-up method. The difference rate between the two methods is 14%, which is reliable in general. The in-use lead stock mainly lies in lead-acid batteries, and the cumulative consumption accounts for approximately 71%. Relevant policies and regulations should be formulated in China to improve the recovery system of secondary lead, optimize the layout of secondary lead enterprises and battery producers, and gradually increase the utilization rate of secondary lead.