Sustainable Mining and Metallurgy

Abstract:By analyzing the carbon emission and intensity of global primary aluminum production, as well as the change trend of carbon emission intensity of each process, the article reveals that primary aluminum production, AC power consumption by aluminum electrolysis and power structure are the three most important factors affecting carbon emission. Of the three factors, the structure of the energy used for producing electrolytic aluminum is the most important factor affecting carbon emission intensity, and the resultant increase in carbon emission intensity completely offsets the contribution of non-power carbon emission sources. Therefore, controlling the carbon emission of electric power is the most important measure to reduce the carbon emission of electrolytic aluminum. In the future, China will further reduce the AC power consumption by electrolytic aluminum, adjust the energy structure, and significantly increase the proportion of green electricity, so as to make greater contributions to achieving the goal of carbon neutrality and coping with climate change.

Abstract:High-salinity effluent produced from Chinese non-ferrous metals metallurgical plants are difficult to degrade as it has a high ion concentration and hardness. Its conventional treatment methods, such as multi-effect evaporation, has typical issues including scaling and high energy consumption. The article first summarized sources of exhaust steam and high-salinity effluent from non-ferrous metal metallurgical plants in China, then described two commercial applications of the ENFI-LTE process, and calculated their operation costs and carbon-emission reduction contribution. By treating effluent with waste heat in a short process, with low energy consumption, no softener added, and giving a high concentration factor and water quality, the ENFI-LTE technology is highly efficient, and conducive to energy saving and carbon-emission mitigation.

Abstract:With the proposal of “carbon peaking and carbon neutrality” goals, the secondary industry, which is the main carbon emitter in China, is also experiencing accelerated transformation. This article first described the progress being made towards the “carbon peaking and carbon neutrality” goals around the globe, then analyzed the status quo of carbon emission reduction in a number of major industries in China: electricity, steel, architecture, and transportation. The article then commented on speeding up the transformation towards a green and low-carbon economy, discussed the opportunities and challenges faced by the nonferrous metallurgical industry, and made suggestions on the pathway and measures to be taken by the Chinese nonferrous industry towards the “carbon peaking and carbon neutrality” goals.

Abstract:The article first provided an overview of the current cobalt refining process of the plant, and then discussed various technical problems that exist in different unit operations: high-efficiency leaching of complex raw material, solvent silicon removal, calcium sulphate crystallization, extraction purification, Ni & Co high-efficiency separation, intensified Ca & Mg removal, high-quality cobalt chloride preparation, conversion production of cobalt nitrate (as precursor to synthetic cobaltosic oxide) solution, intensified chloride removal for the anodic solution of cobalt electrodeposition, and intensified purification of cobalt chloride solution, and finally proposed solutions accordingly.

Abstract:The study aims at better controlling the purity of metallic zinc by improving from its upstream: modificiation of zinc electrolytic anode plate from impurity removal and alloy optimization, and compared the improved anode with the conventional Pb-Ag anode in terms of their physical and chemical performance. During the experiment, after analyzing the reduction potential of various elements in electro-chemical reactions, proper amounts of additives were dosed during the casting process of zinc anode, to form stable intermetallic compounds together with Fe and Cd in order to lower the reduction potential of Fe and Cd, prevent them from oxidation on the anode sheet. After analyzing the effect of various elements on Pb base and metallurgical performance, Ag, Ca, Sr, RE, etc. were chosen as the additives to improve the performance of the anode alloy. The improved anode sheets have shown notable increase in tensile strength, mild increase in hardness, and limited decrease in plasticity. Compared with the product zinc produced with conventional Pb-Ag anodes, the levels of various impurities of product zinc produced with the new node are lower, and the purity of the product zinc has increased markedly.

Abstract:Based on the experiment analysis of manganese supplementation in the oxidation leaching of zinc sulfide concentrate, the optimum reaction conditions were obtained, including reaction time of 8h, reaction temperature of 80-90℃ and initial acid concentration of 160-180g/L. Applying these optimum reaction conditions in industrial production, the leaching rate of zinc and manganese can reach more than 92%, and the content of manganese ions in the hydrometallurgical system can be increased to more than 4g/L, which meets the standard requirements of manganese content control in a zinc hydrometallurgical plant. At the same time, the zinc content of the leaching residue before and after the manganese supplement process was adopted was analyzed and compared. The results showed that there was no significant difference in the zinc content in the leaching residue.

Abstract:There is a long-term problem of large heat balance difference in 350kA electrolyzers in a company. The main reasons are that the smoke exhaust volume of each electrolyzer cannot be uniform by the smoke pip valve, and the gas gathering performance of the flue is low. Through on-line modification of branch gas pipes and gas ducts, the exhaust gas and heat dissipation conditions at the upper part of the cell were adjusted to improve the sealing efficiency of the electrolytic cell and optimize the uniformity of heat balance. The results shows that the measured ventilation deviation of branch pipes for exhaust gas between cells of is optimized from -23%~30% to within ±10%, and the gas gathering uniformity deviation in a single cell chamber is optimized from -52%~30% to -7%~5%, which completely solves the problem of dust accumulation and significantly improves the sealing efficiency of electrolytic cells and the working environment; the measured cell temperature deviation between aluminum outlet and flue end is lowered from 6℃ to 3℃, the precipitation at the gas duct end is significantly reduced, and the heat balance uniformity of the electrolytic cell is improved.

Abstract:This article compared two temporary short-circuiting busbar schemes: busbar along the passage and across each cell section. Along the passage temporary short-circuiting busbars are suitable for new plants, and enables section-by-section start-up/shut-down; across-section busbars are suitable for operating plants, particularly adaptable to cases where the cells to be shutdown are located in the middle of a section; both schemes can be installed alone, and together as well. Both schemes also show good economic performance, with a short payback period. In particular, the along-the-passage scheme provides considerable benefits. Both schemes are also quite safe and highly operable, and reliable in their technology. Apart from sound economic performance, the across-sections scheme helps save electricity and mitigate the plant’s power press, and has limited impact on the existing production system.

Abstract:The principle, advantages and disadvantages and operation cost of three desulfurization processes, limestone-gypsum method, hydrogen peroxide method and regenerated amine absorption-desorption method, were analyzed and compared according to the actual production of a copper smelter in China. The comparison results show that the hydrogen peroxide desulfurization process has several advantages: short process, low investment, recyclable SO2, low water consumption, less land occupation, no wastewater nor waste residue discharge, and the balanced operating cost-slightly is higher than that of the limestone-gypsum method and is lower than that of the regenerated amine absorption-desorption method. After comprehensive comparison, the hydrogen peroxide method was recommended for the retrofit of the fugitive off-gas desulfurization system in this plant. And a scheme of the retrofit following the hydrogen peroxide method was put forward.

Abstract:Taking the outlet fluid of two flue gas fans in a smelter as the resear ch object, a 3D offgas flow model was built and finite element simulation was used to determine the offgas hydraulics under various working conditions of the fans. The reliability of the 3D model was then verified against actual fan operation, and optimal fan control strategies and methods for two process routes were developed. According to the simulation results, when the two fans operate in series, the inducing effect of the fans at full workload differ widely. When the fans operate in parallel, remarkable inducing effect can be achieved when one operates at full load while the other flow is controlled at 222000m³/h. Further increasing the load however will reduce the total induction performance.

Abstract:The frequency conversion cabinet emits a large amount of heat during operation, which needs to be dissipated in time to avoid affecting the normal operation of the cabinet. Taking frequency conversion cabinet rooms in three lead smelters with similar configurations as examples, this article introduced different ventilation and air conditioning design schemes that suit different outdoor ambient temperatures. These three smelters are located in severe cold zone C, cold zone B and hot summer and warm winter zone respectively. By summarizing the ventilation and air conditioning measures that suit different outdoor environments, the article provided a reference for the ventilation and air conditioning design of frequency conversion cabinet rooms to be more reasonable and energy-efficient.

Abstract:This paper introduced the equipment and operation status of air compressor station system of large copper smelter, and summarized the energy-saving measures taken in the long-term operation, so as to provide some reference for the equipment selection, energy saving and consumption reduction of air compressor station in smelting enterprises.

Abstract:The basic chemical composition and physical properties of hazardous waste incineration fly ash and bottom slag in some parts of China were investigated. The study shows that the chemical composition and mineral composition of ash and slag are obviously different and the components of slag system are also different due to the different types, chemical compositions, occurrence forms, raw materials compatibility and incineration treatment processes of hazardous wastes. According to the leaching toxicity test of ash residue, the contents of Pb, Zn, Cu, Ni and other heavy metals in the leaching solution are different. In some areas, there are many heavy metal elements exceeding the standard seriously. This study can provide support for harmless treatment and resource utilization of hazardous waste incineration fly ash and bottom slag .

Abstract:Based on the analysis of noise sources in a WTE plant, noise reduction measures such as sound absorption, silencing and sound insulation were taken accordingly for the turbine room, air compressor station, cooling tower and Roots blower in the plant. After these noise reduction measures were taken, the field test results showed that the noise from all noise sources and at the plant boundary met the design emission standards. These measures effectively reduce the environmental impact of the noise on the neighboring region and ensure the occupational health of workers, which can provide a reference for the noise control of similar projects.

Abstract:With the cyanidation heap leaching residue in a gold mine in the arid zone in Western China as the object of study, acidic & water leaching toxicity tests were conducted to study the pollution characteristics. The test results indicates that while the legacy residue is hazardous, the leaching toxicity (acidity) does not reach the leaching toxicity standard for hazardous waste. The reason is that after years of natural degradation, the cyanide content has decreased. The water leaching test results show that the residue is typical of China’s Class II general industrial solid waste.

Abstract:To improve the product water quality, oxidation ponds and surface flow constructed wetlands are used to treat the effluent from sewage treatment plants and replenish the river. At the initial stage of project construction, ecological restoration materials were used to repair the bottom soil of oxidation ponds and wetlands in situ. By setting up ecological base and solar aeration devices in the oxidation pond, using diatomite and volcanic rock as wetland fillers, and planting a variety of aquatic plants in the wetland, the effluent of the project can stably meet the class V standard of the Environmental Quality Standard of Surface Water(GB 3838—2002), which not only ensures the water quality of the river, but also beautifies the landscape.

Abstract:During the upgrading process, to prevent production disruption and ensure stable product water quality, a sewage treatment plant has made full use of the existing and new process units through reasonable construction planning, and established a temporary process line of “super magnetic pretreatment+membrane grille+MBR membrane cisterns” to carry out in-plant diffluent treatment, effectively solving the sewage discharge problem that may be caused by upgrading-induced production reduction of the original system. By adopting the emergency quality guarantee process, the product water quality during the upgrading was kept stable and met the discharge requirements (CODcr≤50mg/L, ammonia nitrogen≤5(8)mg/L, total nitrogen≤15mg/L, total phosphorus≤0.5mg/L). The emergency process thus prevented the possible environmental pollution of sewage discharge due to production reduction, and the investment was low.

Abstract:To address issues that plague the overhead crane for aluminum hydroxide bins during the alumina production process, including difficulty in monitoring material levels and equipment status and properties, the inhospitable working environment of the loading site, extended and intense working hours of the crane operator, low operation efficiency and great electricity consumption, this article first analyzed the patterns of the operation process, then proposed an IOT-based unattended system, which integrated laser scanner for bin level sensing and overhead crane movement control techniques, to upgrade the system and realize unattended crane operation.

Abstract:Electronic special gases (ESG) have dangerous characteristics such as high pressure, corrosiveness, toxicity, flammability, explosion, suffocation, etc. Because of these, accidents have occurred frequently in the filling process, endangering personnel safety. This article briefly introduced the general process of special gas filling and analyzed precautions for prefilling inspection, filling process and post filling cylinder management, as well as emergency measures during filling to improve the filling capability and safety management of electronic gas manufacturing enterprises.