Sustainable Mining and Metallurgy

Abstract:

Abstract:In the mining of double-system extra-thick coal seams in Datong Coal Mine, the use of aggregate-containing slurry grouting filling technology to seal rock fractures can reduce the disturbance of mining to fractures and reduce the water conductivity of broken rock masses. It is a key measure to prevent goaf water and harmful gas leakage and prevent collapse of mining areas. Using mine solid waste fly ash as green filling material can realize the reuse of solid waste resources. Based on the Euler two-way coupling model, the CFD-DEM coupling model was constructed by using the coupling function of Fluent and Edem software. The migration and deposition behavior of aggregate particles in cracks with slurry and its influence on slurry flow velocity were analyzed. It is found that the aggregate particles with smaller particle size and lower density have a longer migration distance, and the particle size is a more important factor affecting the aggregate deposition rate compared with the density. During the migration process, the aggregate-solid ratio of each particle size and density shows a trend of increasing firstly and then decreasing. The sedimentation rate gradually increases with the increase of the migration distance, and at the same position, the aggregate with higher density shows a higher sedimentation rate. The research results provide a theoretical basis for the rational utilization of mine solid waste filling materials and the improvement of grouting plugging technology.

Abstract:Mixing shear significantly enhances the homogeneity of full tailings, cement and admixtures, and also affects the physicochemical properties of prepared paste slurries. However, the underlying mechanisms remain poorly understood. In order to deeply understand the effect of mixing shear on the properties of paste slurry, the meso-structure of paste slurry was tested by the Focused Feam Reflectometry (FBRM) technique to analyze the effect of shear rate on the meso-structure of full tailings paste. The results indicate that the mixing shear has a significant effect on the pastemeso-structure. As the shear rate increases,the aggregated particles in the paste are dispersed, the average chord length decreases, and the number of real-time particles increases; However, beyond a certain threshold the average chord length of the particles in the paste increases, and the measured number of real-time particles decreases, which suggests that the high-speed shear may alter the physicochemical characteristics of particle surfaces, thereby enhancing inter-particle interaction forces, and these changes further influence the rheological behavior and post-curing mechanical properties of the paste.

Abstract:Grouting is one of the main technical means to prevent water inrush disaster of aquifer in coal seam floor. By grouting reconstruction of floor limestone aquifer, it can be changed into water barrier or weak aquifer, which can effectively cure floor water damage and realize safe and efficient mining. In this paper, based on Bingham grout, a one-dimensional seepage grouting theoretical model with time-varying slurry viscosity under constant grouting rate was established. The quantitative relationship between the diffusion distance and grouting pressure of fissure grout was analyzed. The diffusion law of horizontal fissure grout was studied, and the diffusion mechanism of horizontal fissure grout was revealed. In this model, the grouting pressure required for a predetermined grout diffusion radius can be obtained by using known aquifer hydrostatic pressure and grouting flow. Finally, combined with the field grouting reconstruction project of L1-2 limestone aquifer in Zhaojiazhai 22 mining area, the research results were verified. The results of grouting reinforcement and reconstruction show that the gronting quality meets the design requirements, and the L1-2 limestone aquifer is effectively reconstructed.

Abstract:The raffinate in the production of copper sulfate in a non-ferrous metal smelting enterprise is a kind of oily high-salt wastewater. The concentration of petroleum is 92.5mg/L, the concentration of TOC is 89.5mg/L, and the main salt is sodium sulfate. In this paper, the air flotation oil removal method was selected as the pretreatment process, and the fixed bed activated carbon adsorption method was used to remove the oil from the wastewater. The results show that the oil removal effect of air flotation method is limited, the removal rate of petroleum pollutants is 30.9%, the removal rate of TOC is 33.1%, and there are still most of the oil residues. In the fixed bed activated carbon adsorption method, the up-flow water inlet method has a higher oil removal rate, which can reach about 80%. When the water flow rate is set to 500~1000mL/h, the better treatment effect and higher treatment efficiency can be obtained, and the effluent effect is stable from 2h after the adsorption to the end of the adsorption. Anhydrous sodium sulfate (sodium sulfate) can be obtained by separating and extracting the wastewater after oil removal, and its quality is close to the first-class product of national standard I by analysis.

Abstract:In order to recover the valuable metals Ni, Co and Cd in the waste water of cobalt refining raffinate and make the concentration of heavy metal ions reach the discharge standard, an H-type IDA chelating resin D854 resin was used to remove the heavy metals in the raffinate after precipitation, and the heavy metal adsorption and regeneration performance were compared with the Na-type D851 resin commonly used in the existing industry. The results showed that compared with D851 resin, H-type D854 resin had larger adsorption capacity of heavy metals, and the adsorption priority was Ni²⁺＞ Co²⁺＞ Cd²⁺. The adsorption capacity of H-type D854 resin is not easily affected by the pH change of the original solution, and the adsorption effect was stable in the range of pH 4 ~ 8. The resin could be effectively eluted by 5BV H2SO4 with mass fraction of 10%, and the elution order of heavy metals was Cd²⁺, Co²⁺ and Ni²⁺. The adsorption capacity of the regenerated H-type D854 resin can still reach more than 90% of the first time after three times of reuse, and the removal effect of heavy metals was stable. The H-type D854 resin has a wide pH range, long service life, easy desorption, no alkali transformation, and short regeneration time, which greatly improves the treatment efficiency of raffinate wastewater.

Abstract:In the process of gold refining, high concentration of chlorine-containing wastewater will be produced by solution chlorination. Usually, the concentration of chloride ion can reach about 100g/L, which needs to be dechlorinated. In this paper, the copper salt precipitation method was used to reduce the chlorine content in wastewater, and the optimum process conditions for the treatment of chlorine-containing wastewater by copper salt method were investigated. The experimental results show that the optimal control parameters of wastewater dechlorination production are as follows: initial sulfuric acid acidity 42g/L, reaction temperature 20℃, reaction time 1h, copper powder dosage 1.5 times of the theoretical value, and copper salt dosage 1.2 times of the theoretical value. Under these conditions, the chloride ion precipitation rate is more than 90%. In the multiple dechlorination cycle test, the dechlorination rate remained above 90%, indicating that the copper slag was used to remove chlorine from multiple circulating wastewater, which had strong stability and high efficiency. This technology can provide reference for the industrial treatment of high concentration chlorine-containing wastewater.

Abstract:A large domestic smelting enterprise adopts bottom-blown furnace reduction process to treat copper scum, which has problems such as low arsenic removal rate, low tin recovery rate, high yield of arsenic matte, high arsenic content of black copper produced by smelting, and large amount of intermediate return material treatment. In this paper, the low temperature oxidation process of bottom-blown furnace was proposed. The copper scum was directly added to the bottom-blown furnace for smelting. No longer adding any auxiliary materials to make slag, that is, no longer artificially manufacturing high melting point FeO-SiO₂-CaO slag type, but choosing PbO slag type with relatively low melting point, and the furnace temperature was reduced to 750℃. Using low temperature oxidation process , the smelting atmosphere in the bottom-blown furnace was changed from the traditional reducing atmosphere to the weak oxidizing atmosphere, and the production of arsenic matte was finally eliminated. At the same time, the recovery rate of tin was increased from 18.13% to 93.23%, the smelting slag type was changed from the original high melting point FeO-SiO₂-CaO slag type to the low melting point PbO slag type, the smelting temperature was reduced from 1100℃ to about 750℃, the smelting energy consumption was greatly reduced, the processing cost of copper scum smelting was reduced by more than 60%, the labor intensity was greatly reduced, and the production process was more smooth.

Abstract:Aiming at the problem that the refractory material loss of a precious metal smelting electric furnace is too fast, which greatly affects the production efficiency, a three-dimensional multi-physical field coupling simulation model was constructed to simulate and analyze the electromagnetic field and temperature field in the electric arc furnace, so as to clarify the heat transfer mechanism in the smelting electric arc furnace and optimize its water cooling design. By comparing the calculation results of Maxwell and Comsol electromagnetic field simulation software, the accuracy of the calculation was ensured. The results show that the magnetic induction intensity on both sides of the electrode is the largest in the upper part of the molten pool electrode, and gradually decreases from the inside to the outside. In the lower part of the molten pool electrode, the magnetic induction intensity gradually increases from the inside to the outside. The heating power density is mainly concentrated in the electrode area, and the heating power in the molten pool accounts for about 98% of the total heating power. The furnace wall temperature gradually decreases with the increase of the distance between the furnace wall and the molten pool. Aiming at the problem of high temperature on the upper outer wall of the copper water jacket, a solution to optimize the design of the copper water jacket was proposed. By increasing the distance between the two copper water jackets, the temperature of the local high point of the furnace wall is reduced from 452℃ to 277℃, and the temperature difference between the inlet and outlet of the water jacket cooling water is increased by 9.45%, which reduces the consumption of refractory materials and enhances the production efficiency.

Abstract:The indium of crude indium casting slag mainly exists in the form of indium trioxide, indium oxychloride and indium hydroxide. In this paper, acid leaching-replacement-electrolysis process was used to recover and treat crude indium casting slag, and the leaching behavior of indium in hydrochloric acid leaching process was studied.The E-pH diagram analysis of Cl-In-H2O system shows that controlling the reaction pH＜2 and increasing the potential are beneficial to the decomposition of indium compounds in the casting slag.The leaching test results show that the optimum reaction conditions are as follows: liquid-solid ratio of 2.0, hydrochloric acid concentration of 7mol/L, reaction time of 4h, stirring speed of 300r/min and reaction temperature of 25℃.Under these conditions, the leaching rate of indium was 52.25%, and the concentration of indium in the leaching solution could reach 165g/L. The sponge indium with purity of 99.95% was obtained by replacement with aluminum plate, which met the quality requirements of electrolytic anode plate.

Abstract:There are many kinds of copper-containing hazardous waste with complex composition. The application of oxygen-enriched top-blown molten pool reduction smelting technology in the comprehensive recovery of copper-containing hazardous waste is increasing. The process flow, process principle and main process parameters of oxygen-enriched top-blown molten pool reduction smelting technology are introduced. The process application improvements including top-blown furnace optimization design, high calorific value waste collaborative treatment and flue gas treatment process optimization are proposed. The advantages and characteristics of this technology in the treatment of copper-containing multi-metal hazardous waste are analyzed. The reduction smelting technology of oxygen-enriched top-blown molten pool has the characteristics of strong adaptability of raw materials, rapid smelting reaction, energy saving and environmental protection, easy control of reaction atmosphere, and adjustable depth of stirring molten pool. It realizes the technological innovation of copper-containing hazardous waste treating and high calorific value hazardous waste materials co-processing, and has certain promotion value.

Abstract:The production of polycrystalline silicon is a continuous production, and the electricity load is relatively stable. Under the peak-valley-flat electricity price mode, the electricity cost is higher. Taking a polysilicon production enterprise in Henan Province as an example, this paper combined the time-of-use electricity price policy of Henan Province in three periods of the year, analyzed the characteristics of the reduction furnace of the key power consumption process of polysilicon production, and established the power consumption optimization model of polysilicon reduction furnace to explore the power consumption mode of peak shaving and valley filling. According to the electricity optimization model, through the optimization of production organization, the operation time of the reduction furnace is adjusted. If the the reduction furnace runs at 19:00 every day, the electricity cost of each operation cycle can be reduced by about 12000 yuan, which can reduce the electricity cost of the reduction furnace by about 4%, and the cost reduction effect is obvious.

Abstract:At present, there is a huge amount of coal gangue, which can be made into ceramsite instead of sand aggregate to achieve mass consumption. Using coal gangue as the main raw material, the experimentals study on the preparation of ceramite with desulfurized gypsum, limestone and dolomite were carried out. The results showed that when the raw ball made of 90% coal gangue and 10% desulphurized gypsum was calcined at 1150℃ for 60min, the packing density of the prepared ceramsite was 729.80kg/m3, the water absorption rate was 2.49%, and the barrel compression strength was 8.15MPa; When the raw ball made of 90% coal gangue combined with 10% limestone was calcilled at 1150℃ for 60min, the packing density of the prepared ceramsite was 686.00kg/m3, the water absorption rate was 1.43%, and the barrel compression strength was 8.30MPa; When the raw ball made of 90% coal gangue and 10% dolomite was calcined at 1150℃ for 60min, the packing density of the prepared ceramsite was 721.44kg/m3, the water absorption rate was 5.40%, and the barrel compression strength was 9.39MPa. The properties of these three kinds of ceramsite can meet the requirements of national standards for high strength ceramsite.

Abstract:In order to reduce the potential threat of fly ash to the environment and human health, it is necessary to carry out harmless treatment of waste incineration fly ash. In this paper, the principles, advantages and disadvantages of solidificationabilization treatment, heat treatment technology, cement kiln co-processing and safe landfill technology were reviewed. The technical economy, technical points and development trend of each technology were introduced. The comprehensive utilization strategy of waste fly ash was put forward, and the measures for the improvement of fly ash harmless treatment technology are proposed from the aspects of policy support and technological innovation. Low-temperature pyrolysis + washing + building materials application, cement kiln co-processing and other treatment technologies have low energy consumption and low cost, but they still need to be further explored in terms of technical maturity and market application.

Abstract:Urban solid waste has a wide range of sources and complex physical composition and morphology. The calorific value and combustion thermal efficiency of waste are the key factors of heat recovery during incineration. In this paper, typical industrial solid waste was selected as raw material, and the preparation process and product quality of solid recovered fuel were introduced. By comparing the incineration indexes of solid recovered fuel and general mixed solid waste, and comparing the incineration indexes of solid recovered fuel under the different main steam parameters, the incineration and waste heat utilization thermal efficiency of solid recovered fuel were analyzed, and the heat balance calculation and finite element simulation were carried out to study the energy flow distribution and heat recovery effect of incineration process.

Abstract:At present, the domestic kitchen waste treatment adopts the process route based on anaerobic fermentation. This paper introduced the development process of anaerobic fermentation treatment process of kitchen waste, analyzed the influencing factors of anaerobic fermentation treatment process, such as solid content, temperature, tank form, material transportation, material stirring, tank top scum crust and tank bottom sand, etc., discussed the adaptability of dry anaerobic fermentation and wet anaerobic fermentation, and pointed out that many factors need to be considered when choosing dry anaerobic fermentation or wet anaerobic fermentation process, such as local garbage classification, kitchen waste composition,pretreatment process, etc.