Sustainable Mining and Metallurgy

Abstract:With the implementation of China’s carbon peak and carbon neutrality strategies, the non-ferrous metal industry has become an important part of China’s low-carbon transformation and a key driver in achieving carbon peak and carbon neutrality goals. It is of great significance to explore the green and low-carbon development path of the non-ferrous metal industry. This article analyzed the energy consumption structure and carbon emissions of the non-ferrous metal industry and a specific non-ferrous enterprise, and proposed the strategic goals and seven main paths for achieving green and low-carbon development of this non-ferrous enterprise: promoting green and low-carbon transformation of energy, implementing energy-saving and carbon-reducing measures, accelerating industrial transformation and upgrading, advancing process technology progress, enhancing electrification levels, improving resource recycling rates, and promoting green and low-carbon technological innovation. Based on this, the article put forward major policy recommendations to ensure the green and low-carbon development of the non-ferrous industry: adhering to a systematic approach to fully understand the carbon emission structure of enterprises, scientifically quantify carbon peak and carbon neutrality goals, guiding non-ferrous enterprises to develop new energy through policy guidance and financial support, promoting the application of information and intelligent energy management systems. By exploring the green and low-carbon development path of the specific non-ferrous enterprise, it can provide reference for China’s non-ferrous industry to promote green and low-carbon development.

Abstract:The ecological restoration of coal mining subsidence area has great significance to promote the green transformation and high-quality development of coal resource-based cities. This paper analyzed the current situation of coal mining subsidence areas in Anhui Province, sort out the relevant laws, regulations and policy plans issued by the state and Anhui Province in recent years, and provided reference for correctly understanding and accurately grasping policy requirements, scientifically formulating work plans and ecological restoration measures. In addition, this paper analyzed the problems existing in the ecological management of coal mining subsidence areas in Anhui Province, mainly including heavy repair tasks, large capital investment gap, imperfect supervision and management mechanism, and ecological management technology to be improved, and put forward countermeasures from the aspects of government, mining enterprises, scientific research and funds.

Abstract:The copper slag matte produced by ISA matte smelting is settled and separated in the settling electric furnace. The effect of copper slag separation directly affects the direct yield of copper, and has a great influence on the production and economic benefit of copper products. In this paper, through the comprehensive microscopic examination of ISA slag, matte and electric slag in the process of settling matte separation of copper slag, the composition, production form, structure distribution, particle size and particle size distribution of the main copper minerals and gangue minerals of the three were identified and analyzed in detail. The microstructural changes and element distribution of copper slag matte in the process of sedimentation separation were shown in detail, which provided reference and guidance for further research and refinement of sedimentation separation measures.

Abstract:The main process of recovering indium by wet zinc smelting hematite method is to use sulfur dioxide to reduce and leach indium from low acid leaching residue. The acidity of the solution after reduction leaching is about 30g/L, which needs to be neutralized in advance to reduce the acidity to 10g/L, and then calcium carbonate is added to neutralize the precipitation of indium and enrich indium. The precipitation of indium residue is recovered by leaching, purification and extraction. The gypsum slag produced in the pre-neutralization process will entrain part of indium, resulting in the loss of indium. In this paper, the effects of Fe³⁺ concentration, end-point acidity and reaction time on the indium content, settlement and filtration performance of gypsum slag were studied by single factor test. The results show that, due to the similar properties of In³⁺ and Fe³⁺, In³⁺ can partially replace Fe³⁺ to form intergranular compounds and stably enter the slag during the formation of sodium jarosite. Therefore, the higher the content of Fe³⁺, the higher the indium content of pre-neutralized gypsum slag. When the end-point acidity is less than 10g/L, Al and Si in the solution are easy to form gel, which react with Ca to form gehlenite precipitation, affecting the sedimentation performance and filtration performance of the slurry. The lower the end-point acidity is, the higher the indium content of gypsum slag is, and the worse the filtration performance is. With the extension of reaction time, the more Fe²⁺ is oxidized to Fe³⁺ in the solution, the more indium is contained in the gypsum slag.

Abstract:The emission of pollutants in coking industry is large, and the national requirements for flue gas emission are becoming more and more strict. This paper analyzed the characteristics of coke oven gas, compared the main desulfurization and denitrification technologies in China and their advantages and disadvantages, and analyzed the characteristics and application of five kinds of desulfurization and denitrification combined processes commonly used in coking industry. When selecting the flue gas purification process route, coking enterprises should fully consider the factors such as the temperature of coke oven flue gas, the concentration of pollutants, coke oven process, resource situation and by-product treatment requirements, and select reliable, advanced and mature desulfurization and denitrification technology. Under the premise of meeting the export indicators, the flue gas temperature gradient should be maximized to reduce energy consumption.

Abstract:This paper put forward the idea of making full use of the advantages of high iron content of hematite slag produced by zinc hydrometallurgy, mixing hematite slag with pyrite, and using fluidized roasting furnace to produce iron slag. The mechanism of fluidized roasting of hematite slag and pyrite was analyzed, and the roasting furnace body, dust removal and slag discharge equipment were partially reformed, so as to meet the working condition requirements of the zinc concentrate roasting furnace to burn the mixture of pyrite and hematite slag, and realize the internal coordination of zinc system resources. The iron slag with sulfur content less than 0.5% and iron content more than 55% can be produced by using roasting furnace to treat the mixture of hematite slag and pyrite, which can reduce the treatment capacity of rotary kiln per ton of zinc leaching slag, save production cost and have good economic benefits.

Abstract:A large amount of purified waste dust and waste tar are produced in the production process of aluminum electrolysis anode block and cathode carbon block. The fixed carbon content of dust is more than 85%, which has high secondary resource utilization value. Containing a variety of inorganic and organic compounds, waste tar is a flammable product that can be used as a fuel, and binder for carbon products and other synthetic fiber raw materials. In this paper, a process for preparing formed coke by synergistic utilization of dust collection dust and waste tar was studied. With dust collection dust as raw material, waste tar and asphalt as binder, through stirring, kneading, briquetting, roasting in high temperature resistance furnace, and finally forming formed coke. The test process shows that the formed coke produced by this process can achieve the expected technical indicators. The fixed carbon content of the formed coke product is ＞ 96%, the ash content is ＜ 4%, and the sulfur content is ＜0.5%. It can be used as a high-quality recarburizer for steel mills, other metal smelting reductants or high-calorie fuels. This method can achieve high-value utilization of electrolytic aluminum solid ( hazardous ) waste, which is of great significance for energy conservation and emission reduction in the electrolytic aluminum industry.

Abstract:Perfluorocarbons (PFCs) are currently considered to be greenhouse gases with a very strong warming potential. The perfluorocarbons produced during the production of aluminum electrolysis include CF₄ and C₂F₆. China’s electrolytic aluminum production has ranked first in the world for more than ten years. Reducing PFCs emissions during aluminum electrolysis production is one of the ways to reduce greenhouse gas emissions in the aluminum industry. In this paper, the generation mechanism and emission of PFCs in aluminum electrolysis were analyzed. Taking a 300kA series electrolytic cell of an enterprise as an example, the CO₂ equivalent corresponding to PFCs emission was measured and calculated, and compared with the PFCs emission data calculated according to the default value of the guide. The comparison results show that the CO₂ equivalent intensity of PFCs emissions is 0.2523 t CO₂e/t-Al, which is far less than the measured value of 0.8839 t CO₂e/t-Al, which cannot reflect the real PFCs emissions of enterprises. The direct way to reduce PFCs emissions from aluminum electrolysis production is to reduce the number of anode effects and shorten the effect time. Therefore, in order to reduce PFCs emissions, suggestions are made from the aspects of electrolytic cell optimization design, cell control system upgrade, process technology optimization, bulk raw material control, equipment operation and maintenance, etc.

Abstract:Due to the proposal and implementation of the national carbon peak and carbon neutrality strategic goal, the technical upgrading direction of the electrolytic aluminum industry has gradually shifted to energy-saving transformation. The 330kA electrolytic cell in an aluminum plant has the problems of high energy consumption and low current efficiency. After review, it is found that the magnetic field distribution of the cell bus is uneven and the value is too large, and the lower flue gas collection form of the superstructure has poor effect. At the same time, the traditional gas-controlled shelling and blanking system is not conducive to reducing the impact of aluminum oxide blanking on the superheat and heat balance of the electrolytic cell. In view of these problems, this paper adopted the green low-carbon deep energy-saving aluminum electrolysis technology system, applied network self-balancing bus technology, “long healthy life” lining structure and heat balance technology and energy-saving superstructure to optimize the energy saving of the electrolysis series. After optimization, the current intensity was increased to 350kA, the DC power consumption per ton of aluminum liquid was reduced by 634kW·h/t-Al, and the current efficiency was increased by 1.89%, and the effect of energy saving and production increase was significant.

Abstract:Aiming at the lime digestion residue of alumina enterprises, this paper proposed a new process of recycling the digestion residue instead of lime to return to the alumina production process. The digestion residue was mixed with lime milk for causticization of sodium carbonate after crushing and grinding. The results of causticization test showed that the causticization efficiency increased gradually with the increase of lime digestion residue, indicating that the effective component CaO in lime digestion residue could carry out causticization reaction, and it was feasible to replace lime with digestion residue. Therefore, the traditional treatment process was reformed and the residue treatment process was added, so that the residue was changed from completely open storage and transportation treatment to continuous closed retreatment. The process was applied to an alumina enterprise, and good economic benefits were obtained. The process avoids the anti-causticization of the residue returning to the front end of the production system, reduces the sodium carbonate entering the system, reduces the salt discharge consumption, realizes the online continuous closed treatment of the residue, solves the shortcomings of the traditional complete open treatment of the residue, and achieves better economic and social benefits. It has certain application value.

Abstract:Due to the unreasonable design of electromagnetic field and heat balance, the mismatch of process operation parameters, the 500kA aluminum electrolytic cell in an electrolytic aluminum plant has serious early damage problem, it brings great risk to the long life and high efficiency operation of electrolytic cell. In this paper, through the anatomy of the electrolytic cell, the damage mechanism of the cathode carbon block of the electrolytic cell was deeply analyzed. It can be seen that the early damage of the electrolytic cell is mainly divided into several categories, such as the deformation of the tank shell, the damage of the cathode carbon block, and the damage of the side. In order to solve the problem of cathode damage, the lining and process technical parameters of the electrolytic cell were optimized in depth without changing the structure of the cathode busbar. Finally, the risk of early damage of the electrolytic cell was effectively solved, and the purpose of prolonging the service life of the electrolytic cell was realized.

Abstract:Ethyl orthosilicate, which has the properties of inorganic materials and organic materials, is widely used in many fields such as chemical industry, electronics and electrical industry. The application field of electronic grade ethyl orthosilicate was mainly introduced. The product composition, particle size and impurity content of industrial grade ethyl orthosilicate and electronic grade ethyl orthosilicate were compared. In view of the quality gap between industrial grade ethyl orthosilicate and electronic grade ethyl orthosilicate, the research progress of the preparation process of electronic grade ethyl orthosilicate at home and abroad was reviewed, including complexation separation, adsorption and ion exchange, combined refining and other technologies. These technologies use industrial grade ethyl orthosilicate as raw material to obtain electronic grade ethyl orthosilicate products by effectively removing water, chloride ions, metal ions and other impurities in ethyl orthosilicate. By comparing various purification methods, the development direction of electronic grade ethyl orthosilicate purification technology was prospected.

Abstract:Silicon-based materials are one of the key materials in integrated circuit processes, which are widely used in epitaxy, chemical vapor deposition, ion implantation, doping, etching, cleaning, and mask generation and other processes. The purity of silicon-based materials directly affects the performance, integration and yield of integrated circuits. In this paper, the principle and application progress of separation and purification technologies which are widely used in silicon-based materials for integrated circuits were described, including adsorption distillation, complexation distillation, sub-boiling distillation, vacuum distillation, photochlorination, cyclic filtration, etc. The advantages and disadvantages of various separation and purification technologies were compared, and the prospect of purification of silicon-based materials was analyzed and prospected.

Abstract:In order to find out the technical development status and future technical development trend of hazardous waste in China, this paper combed and compared the characteristics and application scope of various hazardous waste pretreatment and harmless treatment technologies at home and abroad, and analyzed the methods and technical status of various hazardous waste resource utilization. According to the classification of metallurgical hazardous waste, petrochemical and chemical hazardous waste, medical hazardous waste, recycling of renewable resources, and collaborative treatment of various hazardous wastes, the current mainstream technologies, advanced technologies and future technologies were summarized. The analysis results show that incineration is the main treatment methods of hazardous waste in China, and rotary kiln incineration technology is widely used. There is still a certain gap between China and developed countries in the technical level of hazardous waste resource utilization. In the future, harmless, resource-based, collaborative and intelligent treatment technologies will be the main direction of technological innovation or optimization of hazardous waste treatment.

Abstract:This paper analyzed and summarized the research and application of ozonation-biological aerated filter ( BAF ) combined process in the advanced treatment of landfill leachate in recent years. The characteristics of biochemical effluent quality of landfill leachate, the principle of ozone-BAF combined process for treating organic pollutants, the form and influencing factors of ozone-BAF, and the production cost were mainly introduced. The ozonation-BAF process can use the strong oxidation of ozone to oxidize refractory macromolecular organic matter into small molecular organic matter, improve the biodegradability of wastewater, reduce biological toxicity, and then further adsorb, oxidize and decompose the small molecular organic matter through the biofilm in the biological aerated filter, so that the effluent is further purified to achieve COD standard discharge. It is a promising non-membrane advanced treatment method.

Abstract:The combined process of “coagulation-electrochemical oxidation” was used to carry out advanced treatment of the MBR effluent of leachate in a landfill, The effects of coagulation process, electrode types and operating parameters in the electrochemical oxidation process on the removal of COD in MBR effluent were explored, and the importance of coagulation pretreatment in the electrochemical oxidation of MBR effluent was discussed. The experimental results show that the combined process of “coagulation-electrochemical oxidation” has a significant effect on the degradation of COD in the MBR effluent of landfill leachate. Coagulation pretreatment can remove more than 68% of the COD content in the MBR effluent, at the same time it can alleviate the organic load of electrochemical oxidation, shorten the electrolysis time, save energy consumption, strengthen the degradation efficiency of COD in the water sample by electrochemical oxidation, and avoid additional The deep degradation process and cost input, and have better economic and environmental benefits. In the electrochemical oxidation process, the processing capacity of the three electrodes on the MBR effluent of the landfill leachate is PbO₂＞ Ru-based electrode＞Pt electrode; When the MBR water sample after electrolysis and coagulation with Ti/PbO₂ electrode is used, it only needs to be carried out at room temperature, and when the current density is 50~70A/m², the removal rate of COD in the water sample can reach more than 96%, and the COD content of the effluent can be reduced to about 10mg/L, and the treatment effect is better.