China Nonferrous Metallurgy

Abstract:The paper briefly introduced the market development status of the lithium industry, summarized the future production plans of major mining companies on the resource side, and forecast the supply and demand of lithium resources in combination with the development expectations of the downstream market. In addition, the historical price trend of lithium products and the reasons for their changes were expounded, the production costs of domestic and foreign lithium mines were analyzed, the price trend of lithium in the future was predicted, and the uncertain factors that may affect the development of the lithium industry were proposed. Based on the research, it's believed that with the active development of resources, the current tight supply situation will be alleviated and oversupply will occur in 2023 while the demand for lithium resources will continue to improve in the future, and it's expected that both supply and demand will remain strong in the next few years. According to prediction, the price of lithium carbonate will remain fluctuated at a high level in 2022, begin to decline gradually in 2023 and remain low for a period of time before starting to rebound in 2027.

Abstract:Currently, arsenic is the only impurity known to inhibit copper anode passivation. In copper electrorefining, copper anodes must contain a certain amount of arsenic to obtain high quality cathode copper. Anode passivation is prone to occur in low-arsenic anode electrolysis, which can cause such problems as increased power consumption, worsen cathode copper quality and reduced production capacity. Based on this, the paper analyzes the formation mechanism of low-arsenic anode passivation with respect to the impact the arsenic on the microstructure of copper anode, discusses the impact of copper and acid concentration, temperature and additive in the electrolyte on the electrolytic process and proposes key technology of inhibiting anode passivation. Under the process conditions that the electrolyte temperature is 65℃, copper and acid concentration is lowered to 40g/L and 165g/L respectively, glycerine is added based on the original additive, the current density rises to 280A/m² and there is no anode passivation of low-arsenic anode, which significantly improves the production efficiency of copper electrolysis.

Abstract:In view of large amount of nickel-containing solid waste stockpiling and high energy consumption and cost of the existing technology, the paper makes use of strong viscosity of iron-containing red mud, carries out pelletizing it with nickel containing sludge, and solid medium high temperature direct reduction-grinding magnetic separation process to extract ferronickel , and conducts the test according to the orthogonal method L9 (34) with four factors and three levels, and draws the following conclusions. It is feasible to extract ferronickel from iron-containing red mud and nickel-containing sludge by synergistic reduction after pelletizing. The optimum process parameters are as follows: coal blending ratio 4%, roasting temperature 1150℃, roasting time 45min, and grinding time 30 min; under the above conditions, the nickel grade of ferronickel powder is above 75.00%, ferronickel grade is above 93.00%, and ferronickel recovery is above 80.00%. According to 95% grade correction, the material cost is below 475RMB/t, energy consumption below 712kgce/t and CO₂ emission below 0.99t/t. In the test, it was found that the factors affecting the cost of ferronickel extraction process materials, energy consumption and CO₂ emissions were changed in the weakening order: coal blending ratio, roasting temperature, grinding time and roasting time. Compared with the existing nickel-containing solid waste treatment process, this process not only realizes the extraction and utilization of ferronickel from nickel-containing sludge and iron-containing red mud under the conditions of low energy consumption and low emission, but also reduces the stacking of solid waste. The ferronickel alloy produced can be used for steel enterprises to produce high value-added stainless steel. The main components of the remaining oxides after reduction are SiO₂, Al₂O₃ CaO and MgO, which can be used to produce cement raw materials.

Abstract:A large amount of SO2-bearing off-gas dust is generated during copper smelting process, which turns into acid mud after being sprayed. The acid mud mainly contains lead compounds, and a certain amounts of valuable metals, such as selenium and copper, and some scattered precious metals. An experimental study was carried out with the acid mud produced by a copper smelter as raw material by adopting the process of pressure oxidative leaching-LIX984 extraction for Cu removal-iron powder reduction for Se precipitation-purification of crude selenium, to extract Se, Cu and other valuable elements from the acid mud. The results show that under proper POX leaching conditions, the leaching rate of Se is more than 91% and that of Cu is more than 95%; in the section of LIX984 extraction for Cu removal, the Cu extraction rate is more than 92% and the Cu stripping rate is more than 95%; selenium powder product with 99.26% Se grade can be obtained after the crude selenium resulting from the iron powder reduction is subject to further purification. The process is environment-friendly due to low reagent consumption and zero discharge of wastewater. The research has realized comprehensive utilization of Cu and Se from the acid mud.

Abstract:As a by-product from vacuum distillation of crude selenium, distilled selenium slag is enriched in copper, lead, selenium, tellurium, gold, silver, platinum, palladium and other valuable metals and is an important resource for precious metals recovery. The high content of selenium and tellurium, as well as their presence in multiple phase structures, and the formation of intercalation and inclusions with copper, gold and silver have limited the selective removal of copper, lead, selenium, tellurium, etc. from the slag. To achieve subsequent enrichment of precious metals, the process flow of “two-stage oxidation roasting-atmospheric alkaline leaching and nitric acid leaching” was proposed to treat the slag, in which, the primary oxidation roasting-atmospheric leaching can completely leach tellurium out, the secondary oxidation roasting-atmospheric leaching can realize selenium removal, the nitric acid leaching can remove copper and lead. After the three simple steps, the removal rate of selenium, tellurium, copper and lead can reach 92.72%, 95.84%, 95.43%, 99.57%, resp. The process has provided a feasible way for separating precious metals from base metals in distilled selenium slag.

Abstract:In a high-arsenic and high-sulfur heavy mineral sand, partial gold minerals are associated with arsenic-bearing sulfide minerals, and the gold is often distributed in arsenopyrite in the form of wrapped micro-fine partciles or intergrowns with the arsenopyrite. Hence, it is quite difficult to obtain a high gold recovery index by conventional smelting method. According to the occurrence characteristics of gold in the heavy mineral sand, a combined process of mineral processing and metallurgy was investigated. The results show that a high-grade gold concentrate containing 35% of gold can be obtained by grinding and shaking bed gravity separation, which can be directly smelted and pre-recovered; after regrinding of tailings from shaking bed, biological oxidation pretreatment process is adopted; under the conditions of 10% feed concentration, 3.5mg/L dissolved oxygen and 9 days of biological oxidation, the arsenic oxidation rate is up to 98.52% and the sulfur oxidation rate is 94.29%. The total gold recovery in the combined process of shaking bed gravity separation + biological oxidation + cyanidation carbon in leach (CIL) process is up to 99.42%. Efficient recovery of refractory gold is realized in this study, providing technical reference for the recovery of gold from a high-arsenic and high-sulfur heavy mineral sand.

Abstract:With the implementation of the “coal to gas” project in the zinc pyrometallurgical process of a smelter in Shaoguan, problems of mismatch between high calorific value fuels and the existing combustion system occurred in the key equipment such as zinc refining column. These problems include uneven temperature distribution in the hearth, incomplete combustion of natural gas, low thermal efficiency of the system, etc. In this paper, based on heat balance calculation, thermal tests, followed by diagnostic analysis and simulation, were conducted to the zinc refining column using a variety of measuring instruments. The results show that the thermal efficiency of tower B# is 52.79%. Through the thermal diagnosis and simulating calculation, it can be seen that the temperature of the combustion chamber, the pressure of the branch pipe of the natural gas burner and the flow rate of the gas outlets are unevenly distributed, the phenomenon of blow-by exists between the off-gas and preheated air in the heat exchange chamber. In addition, the energy saving and consumption reduction of the zinc refining furnace can be achieved by optimizing the nozzle structure and arrangement of natural gas system, applying air distribution combustion method with active air supply, optimally adjusting the process parameters such as reflux ratio, evaporation ratio, the feeding temperature of tower B^# and strengthening the waste heat gradient recovery and utilization.

Abstract:The current research and application of Spectrophotometric IPB method is mainly focused on the detection with an ammonia concentration of appr. 1g/mL, while in actual production activities, the ammonia nitrogen concentration in the places involving ammonia nitrogen production and solid waste treatment is relatively high, and errors may occur while using this method for detection. In this paper, the Spectrophotometric IPB method was used to detect the absorbance of ammonia nitrogen in the solutions with different ammonia concentrations, it was found that the absorbance increased first and then decreased in the concentration range of 0-100.00g/mL; when the ammonia concentration was 0-1.00g/mL, there was a linear positive correlation between the ammonia content and the absorbance; when the ammonia concentration was 0-3.00g/mL, the ammonia content had a linear positive relationship with the absorbance, but the slope of the curve decreased; when the ammonia concentration was 3.00-7.00g/mL, the ammonia content and the absorbance were positively correlated, but the slope further reduced; when the ammonia concentration was 7.00-100.00g/mL, the ammonia content was negatively correlated with the absorbance, and with the increase of the concentration, the ammonia reacting dose lessened; furthermore, the reacting dose of ammonia at high ammonia concentration of 100.00g/mL was even lower than that of 0.50g/mL. Through analysis and experimental research, the reasons for such abnormal phenomenon were speculated that when the ammonia concentration was too high, the sodium nitroprusside would bring the reaction conversion rate down, and excess chloramines might react with the cyano group of the sodium nitroprusside, resulting in catalyst deactivation and weakening the activity of catalytic reaction.

Abstract:Based on microwave digestion pretreatment-ion chromatography (IC), an analytical method was established for the determination of chloride ion content in electroplating sludge, and the consumption of digestion solution, digestion time and digestion temperature were optimized by experimental conditions. The results show that the best addition standard recovery can be obtained by such method when the amount of digestion solution is 8mL, the digestion time is 4h and the digestion temperature is 60℃. Under the optimal pre-treatment conditions, the standard curve equation of chloride ion was y=0.1529x+0.0321 (R²=0.9998), the detection limit of the method was 0.005mg/L the relative standard deviation (RSD) was 0.77% and the addition standard recovery ranged from 96.17% to 104.09% within the scope of standard curve. In the actual electroplating sludge sample detection, it could be seen that the content of chloride ions in electroplating sludge ranged from 43321mg/kg to 62113mg/kg, and the RSD values of the detection results were less than 3%. This indicates that the linear relationship, sensitivity, precision and addition standard recovery of this method can meet the detection requirements and has certain value of popularization and application due to batch detection, simple and easy operation.

Abstract:The current standard method YS/T 1329.3—2019 can accurately determine the content of gold and silver in copper telluride, but it is difficult to meet the requirements of copper smelting enterprises for rapid determination of gold and silver in copper telluride due to its complicated operation and long cycle. In this experiment, acid pretreatment to remove impurities such as copper and tellurium was abandoned, and the optimal detection conditions were explored through a series of experiments. The direct fire assay gravimetric method was established to accurately and quickly determine the content of gold and silver in copper telluride samples. The main characteristic of the method lies in the direct analysis and detection of gold by fire assay gravimetric method, which is not only accurate and efficient, but also suitable for low content (Au＜10g/t) samples. The relative standard deviations (RSDs) of the results of five copper telluride samples determined based on the test method were 0.34%-2.76%, n=7. The addition standard recoveries of gold and silver were 98.7%-101.2% and 97.5%-99.0%, respectively. Gold and silver in copper telluride were determined according to the test method and compared with the results determined by YS/T 1329.3—2019 method, the results were consistent. The test method is suitable for the determination of gold and silver in copper telluride samples during copper smelting, and can be used for daily detection and analysis.

Abstract:With the rapid development of Chinas economy and the improvement of urbanization level, waste incineration has gradually become a main way for harmless treatment of urban domestic waste, but the produced fly ash, due to its high leaching toxicity and high heavy metal concentration, is classified as a hazardous waste. The harmless disposal and recycling of incineration fly ash have become a social focus. In this paper, the source, harm and current situation of production and discharge of fly ash were discussed; the focus was given on the harmless disposal technologies and recycling methods of fly ash, involving solidification/stabilization technology, separation and extraction technology, heat treatment technology and collaborative disposal technology, etc. The advantages and disadvantages of these technologies were comprehensively analyzed. Moreover, based on the existing pain points of fly ash disposal, a new idea of multi-technology combination was put forward, including two processes: one-step solution of main problems, supported by multiple methods, and sequential multi-step solution of problems. At last, suggestions and prospects for harmless disposal and recycling of fly ash were provided.

Abstract:Zinc is a significant nonferrous metal, but the global zinc resource cant support the future demand for zinc. Hence, the recovery of zinc from industrial solid wastes becomes an important method to resolve the shortage of zinc. The steelmaking dust has a high content of Fe and Zn. If zinc can be effectively separated from the steelmaking dust, the recovered zinc can be a zinc resource and the remained Fe can be recycled in the metallurgical process. Most of the zinc in the steelmaking dust exists in the form of ZnO and ZnFe₂O₄ Since ZnFe₂O₄ is stable, it is difficult to separate and recover zinc from the steelmaking dust. Based on the difference in physicochemical properties of various phases and compounds, many methods of zinc recovery from the steelmaking dust have been proposed by Chinese and foreign scholars, including pyrometallurgical process, hydrometallurgical process, and a hydrometallurgical-pyrometallugical combined process. In this paper, the principles and characteristics of each method were summarized, the new techniques and research development of the combined process were highlighted and the advantages and disadvantages of these methods were discussed. Finally, the future development of resource recycling of the steelmaking dust was analyzed.