Sustainable Mining and Metallurgy

Abstract:Using traditional electric heating for preparation of α-hemihydrate gypsum (α-HH) from phosphogypsum (PG) takes a long time, and the addition of modifier will further prolong the reaction time and reduce the production efficiency. This study proposed the rapid synthesis of α-HH by microwave radiation heating, and the mechanism of microwave radiation enhanced synthesis of α-HH was clarified. The results show that when the concentration of CaCl₂ is 2.70mol/L, the microwave heating can convert PG into α-HH within 60min, while the electric heating requires 180min. Maleic acid can effectively regulate the crystal morphology of α-HH and obtain short columnar α-HH in 2.47mol/L CaCl₂ solution, but adding too much maleic acid will inhibit the conversion of PG into α-HH and prolong the reaction time. Compared with other heating methods, microwave radiation heating has significant advantages in shortening reaction time, and can also reduce the concentration of the reaction medium to a certain extent. The reason is that both CaCl₂ solution and PG have a high dielectric constant, exhibiting a good absorption performance for microwaves. In addition, the higher the CaCl₂ concentration, the greater the dielectric constant, dielectric loss, and conductivity of the solution, and the better the microwave absorption property, which can quickly heat the reaction slurry to promote the conversion of PG into α-HH. Therefore, microwave radiation is an efficient and energy-saving heating method for synthesizing α-HH.

Abstract:Steel slag contains a large number of valuable elements, among which phosphorus is considered to be one of the most valuable elements. It is very important to recover phosphorus in steel slag efficiently. In this paper, the steel slag was modified by biological ash, and hydrochloric acid was used as leaching agent to study the leaching law of modified steel slag. The results show that the activities of Ca₃P₂O₈ and K₄CaP₂O₈ in the molten steel slag increase, and the activities of Ca₃SiO₅ and Ca₂SiO₄ decrease after biomass ash modification, which promote the formation of phosphorus-containing solid solution. The crystal form of the phosphorus-containing solid solution phase in the modified steel slag changes, which increases the dissolution rate of the solid solution. The modification treatment has little effect on the Mg-Fe phase; when the addition amount of biomass ash is 20%, the phosphorus leaching rate of steel slag can be increased from 39.91% to 61.12% in 0.07mol/L hydrochloric acid solution, and the iron leaching rate is only 23.86%.

Abstract:Aim of this study was to establish an electrochemical method for sensitive detection of Cd²⁺ ions in environmental water samples. Utilizing the advantages of Nafion films with three dimensional networks, Nafion-coated bismuth film electrodes on glassy carbon electrode (GCE) were obtained via electrodeposition. The electrodeposition conditions like the Bi(NO₃)₃ concentration, electrodeposition time and the coated Nafion volume were systematically optimized. The electrochemical detection of Cd²⁺ ions was carried out by differential pulse anodic stripping voltammetry (DPASV), and the enrichment potential and time of Cd²⁺ ions, electrolyte type and other conditions were optimized.The experimental results show that the optimum conditions for electrodeposition of Bi are as follows: Bi(NO₃)₃ concentration of 200mg/L, deposition time of 100s, Nafion solution dosage of 3μL; the optimum conditions for the detection of Cd²⁺ by DPV are as follows: the enrichment time is 300s, the enrichment potential is -1.2V, and the ABS electrolyte solution with pH of 4.5 is used.Under the above optimal conditions, the linear range of DPV detection of Cd²⁺ is 2~40μg/L, and the detection limit is 0.5μg/L. The electrochemical sensor was successfully used to analyze the concentration of Cd²⁺ in environmental water samples， holding the recoveries from 98.5% to 112.6% and the relative standard deviation less than 10%. Further detection results from standard addition method confirmed the reliability, which were agreed with the detection data by using ICP-AES method. This study provides a novel approach for exploring electrochemical sensors for Cd²⁺ ions with low cost, high sensitivity and selectivity.

Abstract:In the disassembly of spent lithium-ion batteries, the remaining aluminum slag after the stripping of the cathode sheet powder contains valuable metals such as Al, Li, and Fe. In this paper, based on the basic principles of molten salt method and vacuum metallurgy, the comparative experiments of conventional aluminum slag recovery process (molten salt method) and vacuum distillation were carried out. The effects of smelting atmosphere, temperature, time and additive dosage on the grade and direct yield of recycled aluminum were studied, and the recovery way of metal Li was discussed. The results show that in the atmospheric pressure recovery method, under the conditions of melting temperature 850℃, melting time 60min and CaF₂ addition amount 3%, the Al grade of regenerated aluminum reaches 98.54% and the direct recovery rate is 68.43%. The metal Li reacts with the flux and enters the brine after washing. In the vacuum distillation method, under the condition of melting temperature of 1050℃ and melting time of 3h, the grade of recycled aluminum Al is 99.55%, and the direct recovery rate is 85.50%. Most of the metal Li volatilizes into the flue gas under vacuum. The advantages of atmospheric pressure recovery process are low energy consumption, low cost and simple equipment，and the disadvantage is that the process is long, the flux needs to be added, the grade of recycled aluminum and the direct recovery rate are low. The advantages of vacuum recovery process are short process, no other flux, high aluminum grade and direct recovery rate，and the disadvantages are high energy consumption, high cost and high equipment requirements.

Abstract:In view of the disadvantages of the traditional wet gold refining process, such as the excessive silver content of gold products, the pressure on the environment caused by the environmental protection recovery of acid-containing wastewater, nitrogen oxides, silver chloride and other by-products, the vacuum distillation technology was used for gold refining, and the experimental research and industrial practice were carried out. The technical advantages of gold vacuum refining and the problems found in production practice were briefly described, and the prospect of gold vacuum refining technology was prospected. The experimental results show that under the conditions of distillation temperature of 1300℃, distillation time of 60min and gold and silver alloy amount of 6kg, the gold refining effect is the best, the purity of the product is high, up to 92.89%, and the direct yield of the product is the highest, reaching 99.57%. The feasibility of gold refining by vacuum distillation technology was verified by experiments. Industrial practice shows that the recovery rate of gold and silver is more than 99%.

Abstract:This paper introduced the pyrometallurgical process used in the comprehensive recovery of copper metal in crude lead, analyzed the advantages and disadvantages of different production processes, and put forward the prospect of the recovery process of copper metal in crude lead. It is pointed out that the copper scum oxygen-enriched bath smelting process, copper scum low-temperature oxidation smelting process and crude lead continuous refining copper removal process have good application prospects. After solving the problems of high arsenic content in crude lead, high lead content in lead matte, long furnace junction in raw material room and circulating boiler, the preliminary pyrometallurgical continuous refining copper removal process of crude lead will become the mainstream process of comprehensive recovery of copper metal in crude lead.

Abstract:Due to the rapid development of the battery industry, manganese sulfate, as the main raw material for the cathode material of lithium ion batteries, the requirements of its product quality and performance are getting higher and higher. A new method with low cost and large-scale separation of calcium from manganese sulfate solution is urgently needed. In this paper, the extractant P204 with low toxicity and low price to human body was used to extract calcium preferentially, and then the manganese saponification mechanism was used to inhibit the extraction of manganese ions. The calcium ions in manganese sulfate solution were removed without losing manganese ions, and a solution that meets the requirements of battery-grade high-purity manganese sulfate extraction was obtained. The effects of aqueous phase equilibrium pH, extraction temperature, O/A ratio, saponification rate and extraction stage on the separation efficiency of manganese and calcium were investigated. The experimental results show that the optimum conditions for calcium extraction by P204 are as follows: sodium saponification rate of 15%, pH value of 2, extraction temperature of 35℃, O/A ratio of 1∶1.5. After 30-stage manganese soap cross-flow extraction, the calcium concentration in the manganese sulfate solution after extraction was 0.02g/L, the calcium extraction rate was 94.47%, and the manganese loss rate was only 0.02%.

Abstract:After leaching and copper extraction of copper-cobalt ore in a certain area, the content of iron and manganese in the raffinate is high. Direct precipitation of cobalt will affect the purity of cobalt hydroxide products, so neutralization precipitation method is used to remove iron. For the iron slag produced in the neutralization process, the cobalt content in the slag was reduced by slurry washing. The single factor and orthogonal experiments of iron slag slurry washing process conditions were carried out to analyze the effects of different washing water, pH value of reaction end point, time and liquid-solid ratio on cobalt washing efficiency and iron leaching rate in iron removal slag. The results show that the cobalt content of the obtained iron slag is less than 0.1%, the cobalt washing efficiency reaches 85%, and the iron leaching rate is less than 10% when the cobalt precipitation lean solution is used for washing, the reaction end point pH value is 3, the liquid-solid ratio is 5∶1, and the washing time is 30min.

Abstract:As the basic material of photovoltaic industry and semiconductor industry, polycrystalline silicon has developed rapidly in recent years. As the key link of polysilicon production, the equipment and technology level, the advanced process flow and the rationality of system heat energy utilization are the important factors related to the stable production of polysilicon. This paper introduced the development process of polysilicon reduction equipment, analyzed the selection of liquid phase feeding mode and gas phase feeding mode of reduction system, and focused on the waste heat recovery and utilization technology of reduction furnace bell water, reduction tail gas and chassis water in the reduction production process, so as to provide reference for the construction and operation of polysilicon production, in order to achieve the goal of high efficiency, energy saving and green environmental protection of polysilicon reduction production.

Abstract:According to the results of multi-element analysis and phase analysis of the acid sludge produced by the acid system of copper smelting flue gas, the copper, selenium, mercury and gold, silver, lead and other metals of the acid sludge were separated by atmospheric pressure oxidation leaching process, so that copper, selenium and mercury entered the leaching solution, while gold, silver and lead remained in the slag to form precious lead slag, so as to realize the separation and recovery of valuable elements in the acid sludge. The factors affecting the leaching effect of copper, selenium and mercury were investigated, and the optimum process conditions for the oxidative leaching of acid mud were determined: liquid-solid ratio 2∶1, reaction temperature 75℃, reaction time 3h, and sodium chlorate dosage 2.0 times of the theoretical amount. Under these conditions, the leaching rates of copper, selenium and mercury reached more than 95%, 96% and 99%, respectively, which achieved the purpose of separating valuable elements from acid mud.

Abstract:In order to study the impact of underground mining process on surface artifacts of a mine, combined with the engineering geological conditions of the mine, three mining schemes were proposed considering different mining ranges, mining sequences and pillar retention, and a three-dimensional numerical model of the mine back-mining process has been established by using Flac3D numerical simulation software, which analyzed the surface tilt, curvature and horizontal deformation of the mine under the different mining schemes, revealed the spatial and temporal evolution characteristics of surface deformation of the mine under the different mining schemes, and determines the optimal mining scheme for the mine. The study shows that: compared with mining scheme 1 and 2, mining scheme 3 can effectively reduce the surface deformation caused by underground mining; mining scheme 3, after all the ore bodies are mined, the deformation value of the surface is less than the permissible value of “Code for Design of Nonferrous Metal Mining”, when the protection level of the buildings and structures is class I. The results of this study can be used for the safety of mines and for the development of the mining industry. The results of this study can provide technical guidance and decision-making basis for the safe and efficient production of mines, and are of great significance for the protection of surface cultural relics.

Abstract:In recent years, great achievements have been made in the construction of green mines, but there are also problems such as the difficulty of multi-sectoral collaborative supervision and the high proportion of qualitative indicators. Benchmarking the new evaluation indicators of green mine construction, using high-resolution remote sensing images to carry out green mine assessment, review and supervision, is conducive to improving the level of green mine assessment and strengthening green mine supervision. Based on the new stage, new situation and new requirements of green mine, aiming at the characteristics of mine mining, ecological restoration, environmental protection and other scenes, this paper expounds and analyzes the working mechanism of remote sensing monitoring of green mine on the basis of combing the working process of remote sensing monitoring. This paper analyzed the monitoring objects and contents of remote sensing monitoring in the ecological environment, resource development mode, comprehensive utilization of resources, green low carbon and so on. According to the stage characteristics of green mine construction, this paper discusses the key points of remote sensing monitoring in the early, middle and late stages of green mine construction, so as to realize the purpose of rapid filtering and screening of problem mines.

Abstract:The copper content of copper smelting slag in an oxygen-enriched bottom blowing copper smelting slag in Shanxi is 4.19%. In order to better recover the copper metal in the smelting slag, an roughing test was carried out to determine the optimal grinding fineness and reagent system. Under the conditions, a comparative test study of the conventional process and the optimized process was carried out. The experimental results show that the final grinding fineness is -0.045mm accounting for 85%, and the rapid flotation reagent system is Z-200 and butyl xanthate each 200g/t, pine oil 50g/t. The conventional process before optimization is to carry out two-stage flotation after the rapid flotation tailings enter the two-stage grinding, including one roughing, three scavengings, and the scavenging concentrate is returned to the previous operation in sequence. The optimized process flow is that the fast flotation tailings enter the second-stage grinding and then carry out the second-stage flotation, including one roughing, two cleanings and two scavengings, the first tailings and the first scavenging tailings are combined into the middle ore and returned to the middle ore for regrinding, the second cleaning and the second scavenging order are returned to the last operation. Under the condition that the first-stage grinding fineness is -0.074mm accounting for 60% and the second-stage grinding fineness is -0.045mm accounting for 85%, the optimized process can obtain the index of copper concentrate grade of 33.02% and the recovery rate of 94.32%.

Abstract:In response to the application challenges of intelligent control for the grate furnace system of domestic waste incineration facilities in China, this paper proposed a smart control technology solution for waste incineration based on “big data + machine learning + process mechanism model”. By integrating industrial big data, process mechanism models and machine learning algorithms, an intelligent combustion control technology and system was developed for the incinerator, the core facility of waste incineration, achieving precise and efficient intelligent control. The function and control loop of the intelligent combustion control system are introduced, and the intelligent combustion control system was applied to a 400t/d waste grate furnace in a waste incineration plant. The production practice showed that after the system is put into operation, the operation rate without manual intervention can reach 96.53%, the oxygen content decreased from 6.8% to 5.6%, the furnace temperature increased from 911.9℃ to 977.4℃, and the main steam flow increased from 28.1t/h to 32.8t/h. Compared with manual control, the standard deviation of the operation data of the main control indexes after the system was put into use can be reduced by more than 10%, which significantly improved the operation stability of the grate furnace. The intelligent combustion control system can not only make the operation index meet the requirements of environmental protection and safe production, but also realize the stable control of the main parameters. This technical solution can provide strong technical support and guarantee for the sustainable development of the waste disposal industry.

Abstract:Weifang is one of the key water-deficient cities in China, water resource is one of the factors limiting the economic development. In order to explore the distribution of local groundwater and water quality, 6 water supply sources were selected as research objects, 55 representative water samples were collected and analyzed the main ion concentration as well as TDS. Piper three-line diagram method and ion ratio coefficient method were used to systematically study the hydro-chemical characteristics and evolution of groundwater. The results show that: ①The cations of groundwater on the east side of Weifang are mainly Ca2+ and Na+, without obvious dominant anions, and the hydrochemistry type was transformed from HCO₃·SO₄·Cl-Ca type to HCO₃·SO₄·Cl-Ca·Na type from south to north. ②Water-rock interaction and evaporation are the main factors controlling the chemical composition of groundwater, and silicate rock and carbonate karst filtration are the main types of water-rock interaction. ③ Ca²⁺ and HCO₃^- in the groundwater of Chijian and Dahuan in Qingzhou mainly come from calcite dissolution, and the dissolution sources of groundwater in this two places are consistent, which may come from the same limestone.

Abstract:With the rapid development of Chinas economy, the problem of ecological environment has become increasingly prominent, and the supervision of ecological environment has become an important task. As a new management mode, grid supervision has been widely used in the field of ecological environment supervision. Based on the analysis of the current situation of grid supervision of ecological environment, this paper reveals that there are many problems in grid supervision of ecological environment, such as unscientific grid division, unclear responsibilities, low level of informatization, insufficient supervision ability, low level of social participation, difficulties in data sharing, insufficient laws and policies, and puts forward corresponding countermeasures and suggestions, in order to provide useful reference for grid supervision of ecological environment in China.