China Nonferrous Metallurgy

Abstract:The recycling of spent/discarded lead-acid batteries was highly regarded by the state for a long time, and the recycling technology and equipment have been also improved and upgraded constantly. The paper briefly introduced the technical status of the recycled lead industry, including crushing and separation of waste lead-acid batteries and recovery of waste lead paste resources, described the evolution process of mechanical, automatic and intelligent crushing and sorting of waste lead-acid batteries, and focused on the progress of high temperature smelting, pre-desulfurization and low temperature smelting, smelting-free conversion and other technologies in the recovery of waste lead paste resources. The systematic layout and modular implementation of waste lead-acid battery resource recovery technology and equipment is the fundamental guarantee for the progress of industrial technology and equipment, and intelligent and green conversion is the future development trend, and the technology of intelligent crushing and separation of spent lead-acid batteries and short-flow preparation of lead-based power supply materials from waste lead paste without melting is expected to lead the development of the industry and promote the realization of the carbon peaking and carbon neutrality goals.

Abstract:There are a lot of physical impurities (plastic, lead grid/powder and fiber) in the lead paste of spent lead battery, which have strong adhesion to the lead paste particles and are difficult to separate, which has an important impact on smelting-free recovery process of lead paste. In this paper, alkyl phenol polyoxyethylene polyoxypropylene ether (APEP) is used as dispersant to disperse the waste lead paste particles, and a double-cyclone forced dispersion device and a hybrid power fine screening device are designed to carry out fine separation of physical impurities. The effects of APEP addition, pH value and device parameters on the separation effect were investigated, and the results showed when the APEP dosage was 0.1mg/L and pH was 5.0, the emulsification and dispersion effect was better; the Zeta potential of the waste lead paste reached 22.5mV, and the average particle size was only 3.2μm; the equipment parameters were further optimized under these conditions, and when the mixture inlet flow rate and gas content rate were 8m/s and 15%, and the gyration frequency and compressed air volume were 50 times/min and 2.5m3/h, the removal rates of plastic, lead grid/powder and fiber could reach 99.75%, 82.54% and 99.65%, respectively, the entrainment rates to lead paste were also only 0.17%, 0.06% and 0.36%. The paper provides a stable, reliable and efficient method for producing pure lead paste for the regenerated lead industry, and provides favorable conditions for the application of lead-paste smelting free recovery technology.

Abstract:Pre-desulfurization of lead paste is the key process of clean production technology in recycled lead industry. Due to high price of raw material sodium carbonate and low price of the product sodium sulfate, the economic benefit of the existing sodium carbonate desulfurization of lead paste is poor, hindering the development of the clean process. For the problems of mass transfer hindrance and volume expansion of the reaction system, a new ammonium bicarbonate desulfurization device with liquid-gas separation and surface shell breaking has been designed and investigated based on the “storage and reaction separation”. The flow field of the slurry storage tank and the structure of forced desulfurization components were optimized, and the influence of reaction conditions on desulfurization efficiency was investigated. The results showed that the slurry volume expansion rate of the new device with flexible particle and “storage and reaction separation” was significantly reduced, and the mass transfer rate was greatly increased by comparing with the traditional device；the sulfur content of lead paste was kept to be lower than 0.5% after the reaction for 60 min under the high concentration of lead paste slurry (40%~60%), which could well meet the demand of industrial application of ammonium desulfurization of lead paste. Ammonium bicarbonate (NH4HCO3) is expected as a new desulfurizer to greatly improve the economic benefit of lead paste desulfurization.

Abstract:Lead oxide from waste lead paste can be directly used as active material for lead battery electrode, but its overall electrical performance is often not very well compared with ball-malled lead powder. In the paper, a new nanosized lead sulfate/acetylene black (PbSO4@Pb/AB) composite was prepared by microwave method as a negative electrode active additive for recovery of lead oxide from spent lead-acid batteries, and the physical and chemical properties and the performance of the lead-acid battery were systematically studied. The results showed compared with AB and AAB black, PPA composite used as additive could greatly improve the performance of batteries made from the recovery of lead powder, effectively maintain the HRPSoC cycle performance of the lead-acid battery made of recycled lead powder, and greatly improve its battery discharge capacity; the HRPSoC cycle life (11551 times) of 3.0wt% lead sulfate and acetylene black composite cell was 3.9 times longer than that (2960 times) of blank battery, in particular, 0.2C discharge capacity was about 942.5mAh, 9.9 times that(94.8mAh) of blank battery.

Abstract:The purification slag produced in the purification process of silver electrolyte has a high copper content. There are the features of long copper removal period, low gold and silver direct yield in the traditional pyrotechnic process and the generated soot containing gold and silver needs secondary treatment, which increases the treatment cost for the treatment of purification slag. In this paper, sulfuric acid method was used to treat the purification residue produced in the purification process of silver electrolyte. The results showed that the leaching rate of copper could reach more than 99% and the silver content in the solution could be reduced to 0.5mg/L by sulfuric acid wet process with sulfuric acid concentration of 6%, reaction temperature of 75℃, reaction time of 2h, liquid-solid ratio of 5∶1, and salt dosage of 11g. The separation of silver and copper was realized and the silver content in the leaching residue could be stabilized at more than 70% and the copper content was less than 0.4% by the production process application. Compared with the traditional treatment process, this process has the advantages of simple operation and good economic and environmental benefits.

Abstract:The intermediate material arsenic alkali slag produced during the treatment of a non-ferrous metal smelting enterprise in Shandong Province produced lead anode slime for recovery of gold and silver, has a tellurium content up to 14%, but the existing process has low recovery rate of tellurium. In this paper, the experimental study was carried out on wet leaching of high-tellurium arsenic-alkali residue produced in the process of smelting lead anode slime to produce antimony trioxide. Tellurium in arsenic alkali residue was leached by Na₂S-H₂O system. The effects of liquid-solid ratio, NaOH concentration, Na₂S concentration, leaching time and leaching temperature on tellurium leaching rate were studied. The results showed that under the conditions of liquid-solid ratio of 6∶1, NaOH concentration of 15g/L, Na₂S concentration of 40g/L, leaching time of 1h and leaching temperature of 45℃, the leaching rate of tellurium could reach 82%. Compared with the traditional water leaching process, the leaching rate of tellurium could be increased by 20%, which provides theoretical basis and data support for the clean, efficient and short flow path separation and extraction of tellurium containing materials.

Abstract:Firstly, thermodynamic calculation was used to obtain the relationship between the Gibbs free energy and time of the main reaction when smelting Kaldor slag. It showed that under the condition of temperature 750~1500℃, with coke as reducing agent and limestone as flux, all main reactions could occur, and finally copper-nickel alloy and calcium silicate slag could be obtained. On this basis, combined with difference in reducibility of different elements in Kaldor slag, granular coal was used as a reducing agent, and Kaldor slag was selectively reduced and smelted in a DC electric arc furnace to obtain qualified copper-nickel alloy and discarded slag. The test results showed that under the conditions of smelting temperature of 1420℃, reducing agent rate of 10%, flux rate of 15%, and settling time of 60 minutes, high-grade copper-nickel alloys were obtained, and the alloy grades were all greater than 90.00%; the recovery rates of copper and nickel were both greater than 98.50%, and the content of nickel and copper in the slag were reduced to 0.15% and 0.32% respectively, achieving one-step extraction of valuable metals from the slag. The research is conducive to improving the secondary resource recovery rate of non-ferrous metals, and lays a theoretical and practical foundation for smelting of Kaldor slag in the DC electric arc furnace.

Abstract:The electricity consumption of electrolytic copper foil production process accounts for about 60% of energy consumption for the whole copper foil production, and there is a lot of energy saving space. The energy consumption of copper electrolytic process is directly related to the tank voltage and current efficiency of electrolytic process. However, complex influencing factors and serious coupling of process parameters in copper electrolytic process make it difficult to model energy consumption in copper electrolytic process, and the control of energy consumption in copper electrolytic production process is in a “blind” state, which is difficult to operate in the optimal energy consumption condition. Therefore, a high-precision fitting method based on Random Forest regression model was proposed in the paper to establish an energy consumption model of copper electrolytic process, and a Random Forest regression model was established to characterize the internal relationship between current density, sulfuric acid concentration, copper ion concentration and electrolytic temperature as input variables and electrolytic energy consumption. The problem of energy consumption modeling in copper electrolysis process is solved. According to the established objective function (Random Forest regression model of energy consumption) and the constraint conditions of electrolytic process, the improved competitive group optimization algorithm was used to solve the optimal process parameters of electrolytic process, which reduced the energy consumption of copper foil production from 5400kW·h/t before optimization to 4850kW·h/t. It greatly reduces the production cost of enterprises and effectively improves the production efficiency of enterprises.

Abstract:At present, rare earth molten salt electrolysis is one of the main industrial production methods for producing rare earth metals, and the insulating layer of the electrolytic cell is one of the important conditions that affect the electrolytic temperature. An enterprise 8 kA in Ganzhou rare earth electrolytic cell as the research object, using COMSOL software to carry on the simulation, the temperature field and electric field under different thermal insulation layer thicknesses was studied to obtain the distribution of temperature field and thermal field of aluminum reduction cells. The results showed that the temperature difference between the insulation layer and the graphite crucible wall during the electrolytic process of the electrolytic cell was much greater than that of the graphite crucible wall, indicating that the insulation layer played a major role in the thermal insulation during the electrolytic process of the electrolytic cell; with the increase of the insulation layer thickness, the temperature in the electrolytic region increased gradually, the temperature gradient decreased gradually, and the temperature field distribution was more uniform; the current density on the cathode surface of the electrolytic cell increased firstly and then decreased; when the thickness of the insulation layer was 78mm, the current density on the cathode surface reached the maximum value, i.e., 3.568×104^A/m²; the higher the current density on the cathode surface, the higher the electrolytic efficiency of the electrolytic cell. Combined with the distribution of electric field and temperature field, the electrolysis efficiency of electrolytic cell was the highest when the thickness of insulation layer was 78mm.

Abstract:China’s bauxite is highly dependent on foreign countries. Due to fly ash as an aluminum-rich product, how to recycle aluminum from fly ash is one of the hotspots in the aluminum and coal chemical industry. The development of aluminum extraction technology from fly ash is of great significance for improving the environment and realizing the optimal allocation of resources. The physical and chemical properties of fly ash from different places (Inner Mongolia, Shanxi, Anhui and Beijing) were analyzed, the technical progress of extracting alumina from fly ash was introduced, and the technological processes, principles and shortcomings of alkali method (alkali sintering method and alkali dissolution method), acid method (sulfuric acid leaching method, hydrochloric acid leaching method and ammonium bisulfate method), acid-alkali combination method and other methods (carbothermal reduction method, microwave assisted dissolution method and biological leaching method) were systematically summarized. The industrial production progress of aluminum oxide extraction from fly ash by some enterprises in China was investigated, and suggestions were put forward to develop more economical and efficient processes and further realize resource utilization of aluminum tailings and extraction of other valuable metals.

Abstract:Lead-silver slag is a kind of hazardous waste produced in the hot acid leaching process of zinc hydrometallurgy. The clean and efficient enrichment and recovery of valuable metals is of great significance to promote the green recycling development of zinc hydrometallurgy industry. Valuable metals were recovered from lead-silver slag after desulfurization by fuming method. The fuming volatilization method is used to recover valuable metals from lead silver slag after desulfurization. The feasibility of fuming volatilization of Zn, Pb, In and Cd was studied with FactSage 8.1 thermodynamic software. The main factors affecting the metal volatilization rate in the fuming volatilization process were experimentally studied. The results showed that in the process of fuming and volatilizing, Zn, In and Cd were firstly reduced and then oxidized, and finally enriched in smoke and dust as oxides; under the optimum conditions of fuming and volatilization temperature 1250℃, fuming and volatilization time 60 min and carbon ratio 25%, the volatilization rates of Zn, Pb, In and Cd were 99.69%, 82.26%, 99.09% and 99.90% respectively, which realized the efficient enrichment and recovery of metals. SEM images showed that the fuming slag contained metal Fe, calcium aluminosilicate, etc., iron resources could be recovered through magnetic separation with re-utilization value. The study provides theoretical and data support for industrial application of pyrometallurgical treatment of lead-silver slag.

Abstract:The research topic is proposed on the basis of modern dry scrubbing technology for the treatment of fluoride-containing gas fume generated during aluminum electrolysis process. Two alumina samples are chosen as the absorbents for hydrogen fluoride gas in the laboratory adsorption experiments, respectively, one is a certain kind of domestic Bayer alumina while the other is a kind of alumina produced from coal fly ash. Firstly, a new setup of apparatus is designed and assembled to meet up the requirements for the static adsorption method for the investigation of hydrogen fluoride capacity on alumina. The influences of temperature and contact time on the adsorption process are carried out under 4 different temperatures of 25℃, 80℃, 95℃, 110℃ and 5 time intervals of 12min, 20min, 30min, 45min, 60min. The fluoride ion selective electrode method is employed for the determination of fluorine content in the reacted alumina, which is then used to calculate the average accumulated adsorption efficiency. Through the investigation of these two alumina samples, it is found that the adsorption capacity of hydrogen fluoride on the two kinds of alumina behaves slightly different. For the tested Bayer alumina, the adsorption rate under 110℃ is the fastest among all the tested temperatures in the early state of the adsorption process, the saturated adsorption capacity at 110℃ is 3.06g HF/100g Al₂O₃ While for the alumina manufactured from the coal fly ash, the fastest early stage adsorption rate appears at 95℃, and the saturated adsorption capacity at 95℃ reaches up to 2.94g HF/100g Al₂O₃.

Abstract:Aiming at the problem of low activity of copper slag due to high iron content in copper slag, a method of removing magnetic ore powder in copper slag by magnetic separation pretreatment is proposed to improve activity of copper slag. SEM, XRD and other methods were used to study the change of the phase structure of copper slag by magnetic separation, and the copper slag powder without magnetic separation and one with magnetic separation were used as the main material to prepare copper slag powder cementitious materials.The effects of magnetic separation on compressive strength of cementitious materials were investigated.The results showed that the magnetic separation pretreatment of the copper slag could reduce the content of magnetic oxides in some areas of the copper slag, which would change the mineral structure; the magnetic separation rate could increase with the decrease of the particle size of the copper slag, and when the particle size of the copper slag was less than 74, the magnetic separation rate reached 9.8%; the compressive strength of the cementitious material prepared by using the magnetic separation copper slag increased by 25%, 32.5%, and 61.6% respectively after 3d, 7d, and 28d of curing, the 28d strength reached 20.18MPa; and magnetic separation could change mineral structure of copper slag and improve compressive strength of cementitious materials. Magnetic separation pretreatment provides new ideas for further improving the activity of copper slag powder, and has certain reference value for practical engineering.

Abstract:Metallurgical and cement industries were the main industries of CO₂ emission in the world, and has been faced a huge challenge of “carbon emission reduction”. Steel slag, a solid waste produced by metallurgical industry, has high carbonation reactivity into a CO₂ rich environment. In this paper, the CO₂ capturing capacity of steel slag under room temperature and atmospheric pressure was explored. Carbonated steel slag admixture for cement industry was prepared. And its influences on the fluidity, mechanical properties and microstructures of cement-based materials were investigated. The results showed that the carbonation weight gain of steel slag could reach 9.11%, indicating that about 90kg CO₂ could be captured by per ton of steel slag. Due to the porous microstructures of carbonated steel slag, the water absorption rate was increased, which had a certain impact on the fluidity of cement mortar. The mechanical strength of cement mortars mixed with carbonated steel slag was better than that of mixed with non-carbonated steel slag, and the higher the carbonation weight gain, the higher the 28d compressive strength of cement mortar.

Abstract:Steel slag is a by-product produced in the steelmaking process, which contains a variety of useful components. However, at present, steel slag is mainly used for steel slag brick, subgrade material and waste water treatment in China, and the effective components in steel slag are not re-used. The calcium base in steel slag, where its content is 40%-60%, plays a positive role in the preparation of industrial grade calcium carbonate products. Therefore, the study on calcium component extraction technology of steel slag is of great significance to the comprehensive utilization and carbon reduction of steel slag. The paper focused on the calcium component leaching treatment technology of steel slag at home and abroad, mainly including deionized water leaching method, acid leaching method and ammonium salt leaching method. The paper briefly described the research progress of calcium component extraction technology from steel slag in China in recent years, compared the advantages and disadvantages of several mainstream leaching methods, makes simple suggestions on the limitations of its current technology and prospects the future development direction.

Abstract:In order to promote the resource utilization of red mud and phosphogypsum industrial solid wastes, the paper uses red mud, phosphogypsum and cementing materials (including cement, steel slag and ore slag) as raw materials to prepare composite mortar. The effect of the amount of phosphogypsum added on the phenochemical properties of the composite material was investigated. The tests showed that when the red mud dosage was 70wt%, phosphogypsum dosage was 10wt%, the 7d and 28d compression strength of the composite were 14.97MPa and 15.2MPa, respectively. By the characterization and analysis of the mineral structure and micromorphology of the composite materials by XRD, SEM-EDS, TG and FTIR, it showed that the addition of an appropriate amount of phosphogypsum could effectively fill the internal structure of the composite material and improve the mechanical properties; the addition of excessive phosphogypsum could cause formation of a large amount of ettringite, thus increasing the internal aperture of the composite, at the same time, the large enrichment of components(P and F) in phosphogypsum will reduce the mechanical properties of composite materials; the composite material could fix sodium element in the red mud through properly proportioning. The leaching test of composite materials by ICP-OES showed that the concentration of heavy metal elements in the composite leaching liquid met the III groundwater discharge standard and could be used for engineering applications.

Abstract:In the study, advanced vitrification technology is adopted to achieve harmless treatment of hazardous side-blown smelting ferrous smelting slag. Various proportions of silica were added to control the basicity of the raw materials, and different melting temperatures as well smelting atmospheres were set to prepare glassy products. The results showed that: with the decrease of alkalinity, the vitrification degree of the slag system increased, the hemispheric temperature decreased significantly, the Fe³⁺/Fe²⁺ ratio decreased slightly, and the viscosity increased; meanwhile, when the oxygen partial pressure of the smelting atmosphere decreased, the vitrification degree, the hemispheric temperature and the Fe³⁺/Fe²⁺ ratio of the slag system all showed a decreasing trend; in the range of 1380~1420℃, smelting temperature had little effect on the above comprehensive properties; the vitrification degree, hemispherical temperature and viscosity decreased slightly with the increase of temperature; under the optimal experimental conditions (temperature 1400℃, COCO₂=1∶1, holding time 3h and basicity 0.7), the toxic substances and acid dissolution rate in the glassy products prepared from side-blown ferrous smelting slag were much lower than that of the limited value, and could realize the harmless disposal.

Abstract:Microwave arsenic removal has the technical advantages of fast temperature rise, no heat source gas and no turnover of materials during temperature rise, which is conducive to sintering agglomeration of materials in the furnace. The chemical arsenic phase analysis, thermodynamic calculation, and microwave arsenic-removal agglomeration test were carried out on the secondary zinc oxide dust from zinc smelting. The results showed that the main material phase of arsenic in zinc smelting secondary zinc oxide dust was arsenic(Ⅲ) oxide, and also contained a small amount of high valence arsenic(Ⅴ) oxide, arsenic sulfide and arsenate; and the increase of arsenic removal temperature and the prolongation of arsenic removal time were beneficial to the removal of arsenic from secondary zinc oxide. The thermodynamic analysis of arsenic removal by microwave showed that the arsenic removal reaction mainly occurred at low temperature. The suitable reaction conditions for low temperature microwave arsenic removal test were as follows: microwave arsenic removal temperature 580℃, arsenic removal time 60min and agglomeration temperature 750℃. Under these conditions, the average arsenic content in the final dust agglomeration was 0.87%, the arsenic removal ratio was 89.29%, and the agglomeration ratio was 72.41%. The study is of great significance to improve the technical level of arsenic containing solid waste recycling.

Abstract:As one of the main leaching methods in China at present, heap leaching of uranium ore has the advantages of low cost and no secondary pollution to the environment, but it also has the disadvantages of long leaching cycle and easy to cause blockage. In order to improve the previous problem of long uranium leaching cycles, this paper studied the uranium ore column leaching process using 5 g/L sulfuric acid and 5 g/L Fe³⁺ as leaching agent, including acidification and iron-added leaching two phases, and investigated the effects of different particle sizes and different seepage velocities on pH value, Eh value, iron concentration and uranium leaching period. The experimental results showed the percolation velocity had a significant impact on the uranium leaching cycle, that was, the faster the percolation velocity, the shorter the acidification time, and the shorter the uranium leaching cycle; at the same time, too high percolation velocity would make the leaching solution and the ore unable to fully react, resulting in a low leaching rate; the leaching period of the system (particle size of -8mm) with percolation velocity of 382.16L·h^-1·m^-2 , 178.34L·h^-1·m^-2 and 127.38L·h^-1·m^-2 (particle size of -8mm) was gradually extended, which was 38 h, 50 h and 72 h respectively, and the final uranium leaching rate was 81.14%, 84.48% and 85.02% respectively; under the condition of high speed seepage, the smaller the particle size, the longer the reaction period and the higher the leaching rate; uranium leaching rates of -5mm and -8 mm particle size systems (5g/L sulfuric acid, 5g/L Fe³⁺, 178.34L·h^-1·m^-2 percolation velocity) were 88.61% and 84.48% respectively, and the leaching cycle was 60 h and 54 h respectively. The paper aims to provide reference for green and efficient uranium leaching.