Sustainable Mining and Metallurgy

Abstract:Under the background of the transformation from energy consumption dual control to carbon emission dual control, non-ferrous metals, as a key industry with high energy consumption, are facing severe pressure of carbon emission reduction. How to establish a scientific and efficient carbon emission management system has become the key to the green and low-carbon development of enterprises. This paper took the construction of carbon budget system of non-ferrous metal enterprises as the starting point, and designed a carbon budget system including carbon emission sub-budget, carbon emission reduction and cost sub-budget, carbon emission trading sub-budget, and carbon emission reduction net profit and loss sub-budget. The carbon emission reduction target, energy-saving diagnosis mechanism and enterprise carbon budget were closely integrated. This paper provides a reference for non-ferrous metal enterprises to reshape the development logic, accelerate the process of low-carbon transformation and enhance the resilience of sustainable development under the strategic goal of “ dual carbon”.

Abstract:The supporting electrolyte in the molten salt electrolysis process needs to have good conductivity, low viscosity, and take into account the physical and chemical properties such as surface tension, density, and melting temperature. In this paper, based on the previous research of molten salt electrolysis process, the effects of different temperatures (750℃, 800℃, 850℃, 900℃, 950℃, 1000℃) and different molar ratios (LiF/NaF=1.5,1.2,1.0,0.8,0.6,0.4) on the density, viscosity, surface tension and conductivity of LiF-NaF molten salt mixture of fluoride binary system were studied by means of high temperature melt physical property test system. The results show that the density of the LiF-NaF molten salt system decreases with the increase of temperature and increases with the decrease of the molar ratio of LiF to NaF. The viscosity of LiF-NaF molten salt system decreases with the increase of temperature, and tends to be stable after 950℃. It decreases with the decrease of the molar ratio of LiF to NaF. The surface tension of the LiF-NaF molten salt system decreases with the increase of temperature and the decrease of the molar ratio of LiF to NaF. The electrical conductivity of LiF-NaF molten salt system increases with the increase of temperature and decreases with the decrease of LiF/NaF molar ratio. When using LiF-NaF molten salt system, the most suitable molar ratio and temperature should be selected for specific electrolysis target products.

Abstract:Red mud is a strong alkaline industrial solid waste produced in the process of alumina production. Its long-term storage not only occupies a large amount of land, but also causes soil damage, water quality reduction, air pollution and other environmental safety hazards. Large-scale consumption of red mud has become an urgent problem to be solved. This paper introduced the physical and chemical properties of red mud, and summarized and analyzed the resource utilization of red mud in valuable metal extraction, building materials, environmental management materials, and soil in-situ remediation. The key contents included: the recovery technology of iron, aluminum and rare metals in red mud; the application of red mud in the construction field of cement, brick products, glass-ceramics, ceramics, new functional materials, roadbed materials and mine filling materials; the potential of red mud in environmental treatment such as wastewater treatment, waste gas purification, contaminated soil remediation, fertilizer carrier and the technical path of soil improvement in red mud yard. Finally, the future development trend of red mud resource utilization was prospected.

Abstract:The arsenic-fixing process of waste acid in a foreign copper pyrometallurgical plant was adjusted from neutralization arsenic-fixing process to crystalline iron arsenate arsenic-fixing process. After adjustment, the arsenic-fixing liquid reached the discharge standard, and the leaching toxicity of arsenic-fixing slag met the TCLP requirements. In order to solve the problem of a large amount of neutralization slag hazardous waste left over from the previous treatment of waste acid by neutralization precipitation method, combined with the process of solid arsenic treatment of waste acid by crystalline iron arsenate after on-site production adjustment, the test of synergistic waste acid treatment of neutral slag hazardous waste was carried out. The alkaline substances such as CaO in the stored gypsum slag hazardous waste were used as neutralizers in the pre-neutralization process of arsenic fixation of waste acid. The test results show that with the increase of the amount of gypsum slag added in the field storage, the available alkaline substances increase, and the amount of limestone powder decreases accordingly. The unstable arsenate precipitation and alkaline heavy metal precipitation in the neutralized slag were dissolved by the waste acid. Therefore, the concentrations of As, Cu, Ni, Pb, Zn, F, Fe, Cd and Sb in the pre-neutralized solution were significantly increased, and the purity of the pre-neutralized gypsum slag was improved, and the toxicity leaching of the pre-neutralized gypsum slag met the TCLP requirements. The process converts gypsum slag hazardous waste into gypsum slag products that meet the external sales standards, realizes “treating waste with waste” and “turning waste into treasure”, and has good economic and social benefits.

Abstract:In this paper, the electric melting furnace was used to smelt low-grade DRI, and the expansion test of 100kg was carried out to explore the smelting characteristics of low-grade DRI electric melting furnace, including slag-iron separation effect, molten iron carburizing effect, iron yield, etc., and the design software was used to calculate the power consumption and coal consumption per ton of iron. The experimental results show that the DRI ball always floats above the molten pool during the smelting process due to its loose and porous structure. Under the secondary voltage of 120V, the electrode is always immersed operation, and the brush arc or open arc operation cannot be realized. By adding a mixture of anthracite and DRI from the top, good iron reduction and carburizing of molten iron can be achieved, and the average carbon content of molten iron is 3.09%. Under the low basicity slag type and high slag rate, the average FeO content of the obtained slag is 1.47%, and the average iron yield is as high as 98.84%. The theoretical power consumption per ton of iron required for the production of liquid hot metals by low-grade DRI hot charging is 511kW·h/t, while the theoretical power consumption per ton of iron for cold charging is 770kW·h/t. The direct charging of hot DRI can save energy by about 50%.

Abstract:In this paper, the electrolytic experiment of a complex crude copper with high precious metal content and low copper content was carried out to realize the efficient recovery of copper and precious metals and other valuable elements. The results show that under the conditions of copper ion concentration of 45g/L, current density of 200~250A/m2, temperature of 45℃ and cycle speed of 20~40mL/min, the morphology of cathode copper is dense and smooth, and the current efficiency is more than 97%. When Ag+＜0.03g/L and Cl-＜0.01g/L in the electrolyte are controlled, the silver inclusion and surface roughness of cathode copper can be effectively avoided. Adding 0.01g/L bone glue to the electrolyte can increase the purity of cathode copper to 99.95%. The purity of cathode copper was 99.95%, and the contents of Au and Ag were 0.0002% and 0.0012%, respectively. The precious metals in the crude copper are efficiently enriched in the anode slime. The Au grade is increased to 8.43%, which is 8.3 times higher than that of the raw material, and the Ag grade is increased to 0.35%, which is 11.6 times higher than that of the raw material.

Abstract:With the development of new energy, the process of preparing battery-grade nickel sulfate from low-copper and high-nickel matte has gradually become one of the current mainstream processes. The exploration of low-copper and high-nickel matte atmospheric pressure leaching process has important guiding significance for subsequent engineering applications. In this paper, the two-stage atmospheric pressure leaching process of low copper nickel matte was carried out. The effects of acid-to-ore ratio and oxygen-enriched air flow rate on the leaching effect in the first-stage atmospheric pressure leaching were investigated. The effects of total acid-to-ore ratio, leaching temperature and oxygen concentration on the total leaching effect in the second-stage atmospheric pressure leaching were investigated. The test results show that in the first stage of atmospheric pressure leaching, the acid-to-ore ratio is recommended to be controlled at 250~300kg/t, and increasing the oxygen-enriched air flow rate has little effect on the leaching rate. It is recommended to carry out leaching at low oxygen-enriched air flow rate, which is more economical. In the two-stage atmospheric pressure leaching, the increase of the total acid-to-ore ratio will reduce the end-point pH value. When the end-point pH value is within 2, the leaching rate of metal phase nickel and cobalt can reach 98%. When the leaching temperature is above 75℃, the temperature rise has little effect on the leaching of nickel matte. The increase of oxygen concentration promotes the leaching. However, considering that the leaching rate of metal phase nickel and cobalt is above 98% under the condition of 40% oxygen-enriched concentration, it is not recommended to increase the oxygen concentration to pursue better leaching effect.

Abstract:The pretreatment of the high carbon bauxite was performed by Using sodium hydroxide solution，the carbonate in the high carbon bauxite was leached into the solution phase and the purpose of decarbonization was achieved. The effects of sodium hydroxide concentration, reaction temperature, reaction time and mineral slurry fixation content on the decarbonization effect of the high carbon bauxite were studied respectively. According to the test results, the carbon in high-carbon bauxite is mainly inorganic siderite carbonate，and its optimal reaction conditions for decarbonization are as follows: sodium hydroxide concentration 10%, reaction temperature 60℃, reaction time 80min, and slurry solid content control 800g/L. Under the optimal treatment conditions, the total carbon content of high-carbon ore can be reduced from 1.34% to below 0.35%, and the inorganic carbon removal rate can reach more than 90%. After pretreatment, the sodium carbonate solution was recovered by caustic reaction of lime milk, and the base solution was returned to circulation. The sodium carbonate solution obtained by this method does not contain sodium aluminate, which will not cause alumina loss in the caustic reaction process of lime milk, and effectively solves the problem of traditional sodium aluminate solution system cannot avoid alumina loss. After pretreatment, the carbon content of the ore can reach less than 0.35%, which meets the carbon control requirements of the Bayer alumina production system. The Bayer alumina production process no longer needs salt discharge, saves the consumption of salt discharge steam, and eliminates the impact of sodium carbonate on the Bayer alumina production process.

Abstract:In actual production operation, issues such as particle segregation, non-uniform distribution and raw material settlement often occur within copper flash furnace. In order to study the influence of non-uniform particle inlet distribution on gas-particle distribution, heat transfer and reaction characteristics in the reaction shaft of flash furnace, the particle non-uniform distribution at the outlet of the concentrate nozzle was set as the reaction shaft inlet boundary conditions. A CFD-DEM coupled model was employed for simulation analysis on an industrial-scale copper flash smelting furnace. The simulation results show that the uniformity of particle at the inlet directly affects the gas-particle distribution characteristics in the reaction shaft. Under non-uniform particle inlet conditions, the distribution of both gas and particles in the reaction shaft undergoes deformations, which may lead the high temperature closer to the wall, and consequently reduce the service life of the flash furnace. The non-uniform inlet distribution leads to localized particle accumulation. The heating rate and reaction rates increase within the 2m zone below the shaft top, and the average residence time in the reaction shaft slightly increases. By considering the non-uniform particle inlet distribution, the accuracy of multi-physics coupled simulation for copper flash melting furnace has been further improved, making the simulation results more consistent with actual production conditions, thereby providing more reliable guidance for process optimization.

Abstract:A gold mine in Guizhou contains arsenic, sulfur and carbon. Its a fine-grained disseminated gold deposit and a typical Carlin-type refractory gold deposit. A series of flotation parameters such as grinding fineness, pH regulator, copper sulfate dosage and collector type were tested, and no good flotation effect was obtained. The concentrate rate was low, the gold grade enrichment degree was low, the gold recovery rate was less than 60%, and the gold loss of tailings was high. In view of the above problems, this paper broke through the limitations of traditional flotation process, and innovatively proposed a treatment technology of pressurized oxidation-cyanidation of refractory gold ore and easy flotation gold concentrate. This method comprehensively considers the acid-base balance, thermodynamic balance and efficient utilization of resources in ore treatment. The ore blending of refractory gold ore and easy-to-float gold concentrate can not only comprehensively utilize the excess acid generated by the oxidation of refractory gold ore, but also achieve a gold leaching rate of 98%, which greatly improves the economic value and development and utilization efficiency of refractory mineral resources.

Abstract:With the rapid development of the new energy industry, lithium hydroxide, as a key raw material for lithium-ion batteries, has seen a continuous growth in market demand. Therefore, optimizing the production process of lithium hydroxide has become a current research hotspot. The process of preparing lithium hydroxide via the lithium carbonate-lime causticization features simplicity and high efficiency, and it can convert low-grade lithium carbonate into high-value-added lithium products. However, during the causticization reaction, calcium carbonate slag with 0.5%~1.2% lithium is generated, leading to the loss of lithium resources. To improve the lithium recovery rate, it is necessary to wash the calcium carbonate slag with water to reduce its lithium content. Based on the lithium carbonate-lime causticization process, this study explored the purification effect of multi-stage water washing on calcium carbonate slag through experiments. The results show that after two-stage washing, the main component content of the obtained calcium carbonate slag reaches 98.21%, and the residual lithium content is reduced to 0.09%, which significantly improves the lithium recovery efficiency.

Abstract:Based on the principle of bulk solid waste utilization, the exploration test of mechanical-thermal-chemical composite activity stimulation of coal gangue was carried out. It is found that the original coal gangue has low activity after direct mechanical grinding due to the large amount of volatiles such as carbon, and cannot replace cement for concrete materials. The 28d compressive strength of the mortar sample prepared by thermal activation of coal gangue at 950℃ can reach 39.77MPa, and the activity index reaches 84.3%. Under the condition of adding 10% quicklime and roasting temperature of 950℃, the 28 d compressive strength of the mortar sample prepared by coal gangue reaches 43.07MPa, and the activity index reaches 87.8%. Under the condition of adding 7.5% industrial gypsum and roasting temperature of 950℃, the 28d compressive strength of the mortar sample prepared by coal gangue reaches 45.68MPa, and the activity index reaches 85.7%. When the roasting temperature is 950℃ and the additive ratio is 3.75% industrial gypsum and 3.75% quicklime, the 28d compressive strength value of the mortar sample prepared from coal gangue is relatively stable, and the activity index exceeds 100%, which can replace part of cement. From the perspective of energy saving and emission reduction, the suitable conditions for the stimulation of coal gangue are as follows: additive ratio 3.75% industrial gypsum +3.75% quicklime, roasting temperature 950℃, roasting time 30min.

Abstract:Lithium mica is one of the important lithium resources, and its lithium extraction process involves multiple processes. Among them, the grinding process has a significant impact on the subsequent lithium leaching rate and the overall production cost. This paper analyzed and compared the technical characteristics of milling process equipment such as dry ball milling, wet ball milling, vertical mill and generalized disc grinding, including key parameters such as processing capacity, particle size control, and electricity cost. The results show that the power consumption of the generalized disc mill is the lowest, but the particle size of the mill powder is the coarsest, which has an adverse effect on the subsequent lithium leaching rate. It is suitable for the process of extracting lithium from lepidolite with low requirement for leaching filter particle size. The wet ball mill is more prominent in energy saving and high efficiency, while the dry ball mill has a large processing capacity, but the energy consumption is relatively high. The vertical mill has the highest power consumption, but the particle size of the mill powder is the smallest, and the particle size distribution of the discharged material is uniform, which has a certain effect on the improvement of the subsequent lithium leaching rate. It is suitable for the process of extracting lithium from lepidolite with high requirements for leaching filter particle size. The research in this paper can provide reference for the reasonable selection of grinding process equipment in the actual production of lithium mica lithium extraction.

Abstract:The corrosion control of the heating surface of biomass boiler of power plant is the key technology for the effective utilization of biomass energy. It is of great significance to study the influencing factors of high temperature corrosion of the heating surface of biomass boiler for guiding the safe operation of biomass boiler. In this paper, the common biomass-maize straw in China was taken as the research object. Based on the tube furnace experimental system, the experimental platform of metal heating surface deposition corrosion was built. The effects of ash, washing and additives on the high temperature corrosion of boiler heating surface in biomass power plant were deeply studied, which provides theoretical support for the corrosion prevention and control of biomass boiler. The results show that the presence of biomass ash will accelerate the corrosion of the heating surface of the biomass boiler. The corrosion rate of the boiler with ash deposition is 21.15% higher than that without ash deposition. Washing and adding mineral additives will inhibit the corrosion of biomass ash on the heating surface of boilers. Under the condition of simulated boiler temperature of 650℃, the corrosion rate of biomass ash after washing decreased by 8.93%, while the corrosion rate of biomass ash after adding 5% kaolinite decreased by 9.62%.

Abstract:To explore the effect of particulate organic matter (POM) on the characteristics of aerobic granular sludge（AGS）, two sequencing batch reactors（Rs and Rp）with soluble organic matter and POM influent were established. AGS variations in its treatment performance, physicochemical characteristics, and microbial community were investigated. The results showed that the effluent concentrations of COD and NO-3-N in the Rp reactor were higher than those in Rs reactor. which were 35.5 and 32.9mg/L, respectively. Typical AGS did not form in Rp, and its sludge exhibited inferior settling ability and mechanical strength, with a sludge volume index (SVI) of 36.5mL/g and an integrity coefficient of 95.4%. In contrast, well-structured AGS was successfully developed in Rs. The presence of POM stimulated the secretion of extracellular polymeric substances (EPS). The contents of polysaccharide (PS) and protein (PN) in EPS were 3.2 times and 2.1 times higher in Rp than those in Rs, respectively. Moreover, the PN/PS ratio decreased from 2.1 in Rs to 1.4 in Rp, which adversely affected AGS formation. Microbial community analysis revealed that the dominant genera in Rp were Pseudofulvimonas, Rhodobacter, and Nannocystis, whereas Micropruina and Flavobacterium were predominant in Rs.. The specific bacterial genera in Rp failed to aggregate effectively into granular structures. These findings offer theoretical insights for the cultivation and stable maintenance of AGS.

Abstract:In view of the complexity of the current source of hazardous waste in a hazardous waste disposal center, this paper quantitatively analyzed the moisture, ash, calorific value and heavy metal content of 38 typical organic hazardous wastes. The results show that the water content of the hazardous waste treated in this paper is 30.62%, the ash content is 27.40%, and the low calorific value is 2497kcal/kg. It is a typical organic hazardous waste with low calorific value, high water content and rich in heavy metal elements such as Zn, Cu, Cr and Ni. At the same time, this paper introduced the principle of countercurrent incineration technology, compared and analyzed the technical characteristics of countercurrent and downstream, summarized the advantages and technical difficulties of countercurrent incineration technology, and introduced the incineration operation, flue gas purification process and economic indicators of countercurrent incineration technology through the incineration production practice of organic hazardous waste with low calorific value and high water content. Countercurrent incineration technology can achieve lower slag ignition loss rate, dioxin and incineration flue gas emissions. It is an advanced incineration technology, which broadens the scope of feeding, realizes the efficient disposal of organic hazardous waste with low calorific value and high water content, and helps to reduce the cost of enterprises.