Sustainable Mining and Metallurgy

Abstract:Inspired by the goal of “double carbon”, new energy has ushered in new development opportunities, which urgently needs to be incorporated into the power market as soon as possible. This paper analyzed the current situation and existing problems of green power trading market and green certificates trading market, and put forward suggestions for the construction of green power market. At present, the pilot launch of China’s green power market has promoted the gradual increase of green power trading volume; With the decoupling of green certificates from subsidies, the price of green certificates has changed to “parity”, promoting the growth of trading volume. However, in the green power transaction, there is no distinction between the electricity price and the environmental premium in the green power price, and there are differences in the green power transaction prices in different regions. In addition, there is a serious imbalance between the supply and demand of green power in China. In provinces rich in renewable energy, there is a contradiction between the export and internal consumption of new energy, and the peak of electricity consumption in the morning and evening on both sides of the supply and demand gradually converge. In order to break through barriers and improve the market mechanism of green electricity, a market mechanism should be established to promote consumption, promote green electricity trading through the “dual control” assessment of energy consumption, and promote the integration of green electricity market and carbon market as soon as possible.

Abstract:Electronic-grade dichlorosilane (DCS) is mainly used for strained silicon epitaxial growth and thin film deposition production process of silicon oxide, silicon nitride and metal silicides in advanced integrated circuit chip processing. The fast deposition speed, even deposition film and low temperature associated with the usage of DCS has resulted in its widespread use in IC manufacturing, but its import dependence remains an issue. This paper introduced the principles and applications of DCS preparation methods such as distillation purification, adsorption complexation and disproportionation reactions. It compared the above three methods, summarized future research directions, and provided an outlook on the application of advanced silicon-based precursors using electronic-grade DCS as raw material.

Abstract:A smelter adopts Ausmelt oxygen enriched top blowing bath smelting technology. In order to build a green plant, the production of three converters was reduced to two, and the processing capacity of Ausmelt furnace was reduced from 210t/h to 180t/h, leading to a decline in production capacity. In order to improve the production capacity of crude copper, the plant increased the oxygen concentration from 55% to 62%~65%, and the copper matte grade from 67% to 72%~75%. This paper studied the impact of increasing the oxygen concentration and copper matte grade on copper smelting, carried out feasibility demonstration, and analyzed the problems encountered in the Ausmelt furnace process, boiler dust collection process, settling electric furnace process, and converter process through experimental research, and put foward corresponding solutions. Through the operation of high oxygen concentration and high copper matte grade, the first is to reduce the amount of smelting flue gas and improve the processing capacity of Ausmelt furnace; Second, improve smelting heat efficiency and reduce energy consumption of Ausmelt furnace system; Third, the copper matte quantity is greatly reduced, the converter converting time is shortened, and the converter processing capacity is improved; Fourth, the total flue gas volume of smelting and converting is greatly reduced to reduce the load of the acid making system.

Abstract:A copper smelter adopts the oxygen-enriched bottom-blowing furnace bath smelting process for the production of copper matte. In production, low melting point substances such as Pb, Zn, As and Bi in copper concentrate volatilize into the vertical offgas duct and form large coke, seriously hindering the long-term stable operation of the oxygen-enriched bottom-blowing furnace. This paper studied the mechanism of coking in the vertical offgas duct of the oxygen-enriched bottom-blowing furnace, analyzed the factors affecting coking, and proposed counter measures to solve the coking problem. The formation of coking in vertical flue is related to copper concentrate composition, oxygen lance pressure, copper matte grade, flue gas temperature and melt depth.Through reasonable dosing, standardized control of bottom-blowing furnace smelting technical indicators, strict control of the upper-section temperature in the vertical offgas duct, and the addition of coking inhibitors, coking was reduced and the coke pieces became smaller and looser. Cleaning time was cut down significantly, and heat exchange efficiency of water wall and the bottom-blowing furnace operation rate steadily improved.

Abstract:This paper analyzed the causes for the high iron content in lean cadmium solutions and the fact that such solutions cannot be directly reused in the purification system in zinc hydrometallurgy. Experiment shows the iron in the lean cadmium solution mainly comes from the skim of the supernate.By comparing the iron removal effect of potassium permanganate, manganese ore powder, hydrogen peroxide and other oxidants, potassium permanganate has the best iron removing abilities under the following process parameters: using 1.6 times the theoretical amount of potassium permanganate, with a pH value of around 5 and a reaction time of 1h. The paper also proposed that the integrated utilization process of “lean cadmium solution supernate filtration-oxidation and iron removal-return to purification system”. This process can relieve the pressure caused by the high turnover of leaching liquid, and can achieve the purposes of reducing the zinc content in the slag, improving the zinc recovery rate, and reducing the consumption of zinc powder.

Abstract:In this paper, the three-stage jarosite leaching process was proposed based on the economy and environmental protection of the harmless treatment of zinc leaching residue in rotary kiln equipped with zinc hydrometallurgy leaching process. The quality of the supernatant produced by the process and the change of Fe²⁺, Fe³⁺, H⁺ and other contents in the process control were investigated. The characteristics of the economic and technical indicators of the process, such as zinc leaching rate, slag rate, zinc content in slag, were studied. The advantages of supporting rotary kilns in harmless treatment of zinc leaching slag were analyzed. According to the production practice, the quality of the medium and supernatant produced by the three-stage potassium jarosite process is similar to that produced by the conventional method and potassium jarosite, which can meet the requirements of the purification process of zinc hydrometallurgy. The zinc leaching rate of the three-stage potassium jarosite process is 94.67%, the residue rate is 37.27%, the zinc content and sulfur content of the residue are about 8% and 10% respectively, and the liquid-solid separation effect is good. The three-stage potassium jarosite leaching process has the advantages of short process, low energy consumption, low residue rate, moderate zinc content and low sulfur content in the leached residue, which is suitable for the harmless treatment of rotary kiln.

Abstract:This paper analyzed and compared the mainstream processes and equipment applications of evaporation, crystallization, centrifugation and drying involved in battery-grade cobalt sulfate evaporative crystallization, taking into account actual project conditions.By comparing the multi effect evaporation and MVR evaporation, since the project has sufficient supply of raw steam, the three effect countercurrent evaporation process was selected; Due to the disadvantages of discontinuous crystallization process, such as low productivity and automation, the continuous crystallization process was selected, and DTB type crystallizer with small volume, large monomer capacity and low energy consumption was used; By comparing the dehydration effect and the degree of crushing to crystal morphology of horizontal screw discharge filter centrifuge, bipolar piston push filter centrifuge and single-stage piston push filter centrifuge, the horizontal screw discharge filter centrifuge with the best dehydration effect was selected; In the drying part, the fixed fluidized bed with large single capacity was selected.

Abstract:This paper studied the new process of solid-phase reduction of lead sulfate in a low-chloride system using white offgas dust acid leaching residue as raw material and iron powder as reducing agent. It examined the effects on lead recovery posed by single-factor conditions such as liquid-solid ratio, calcium chloride concentration, iron powder dosage, and reduction temperature and time. The study obtained the following optimum reduction conditions: liquid-solid ratio of 2∶1, calcium chloride concentration of 40g/L, iron powder dosage of 1.2 times the theoretical amount of lead, reduction temperature of 70℃ and reduction time of 3h. Under these conditions, the lead recovery rate was more than 92%.

Abstract:Through statistical analysis of aluminum levels at the furnace gate of 140 sets of 350kA electrolysis cells, the variation regularity of aluminum level with the position of the anode replacement was studied. A correction model was developed to eliminate the effect from anode replacement and verified by actual electrolytic cells. The research methods are as follows: first, count the median aluminum level corresponding to each rotating pole single cell, then count the difference between the aluminum level when replacing anodes at different positions and the median aluminum level of this rotating pole, and the median aluminum level deviation of different electrolytic cells when replacing anodes at the same position.Analysis results indicate that the aluminum level changes periodically with the change of pole changing position: when changing anodes at different positions in each round, the aluminum level deviation first increases, then decreases, and then maintains the same level; The aluminum horizontal deviation at the incoming and outgoing terminals shows obvious antisymmetry with the pole changing position. The aluminum level deviation interquartile spacing (10mm) can be used as the corresponding maximum deviation reference value to correct the aluminum level. It is proved that the fluctuation of aluminum level becomes smaller after correction, which is more conducive to guiding production.

Abstract:The synergistic disposal of burning sludge along with domestic refuse is an effective method to achieve the “reduction, stabilization, reutilization and harmlessness” of sludge . This paper introduced the physical and chemical properties of sludge with different water contents and the main blended incineration method of sludge with 80% and 40% water contents, analyzed the advantages and disadvantages of various blended incineration methods, and provided some solutions to the problems of blended incineration in light of actual cases.The mixing and burning methods of sludge with a moisture content of 80% mainly include sending the sludge to the incinerator for mixing and burning in the hopper and sending the sludge to the incinerator for direct injection mixing and burning. The problem of the former in practice is that the sludge sent into the feed hopper is cylindrical and cannot be burned through, so it is necessary to improve and optimize the sludge nozzle; The latter has problems and risks that affect the stable operation of incinerator, but the process is simple and the investment is small, which is the future research direction. There are many ways to mix and burn the sludge with a moisture content of 40%, such as sending the sludge to the garbage pit and mixing and burning the garbage, sending the sludge to the garbage feed hopper for mixing and burning, sending the sludge to the pusher platform for mixing and burning, and sending the sludge to the furnace side wall for mixing and burning, each of which has its advantages and disadvantages. In practical application, a variety of mixing and burning methods are usually used cooperatively, which can give full play to the reliability and flexibility of these common mixing and burning methods and ensure reliable operation.

Abstract:Soil contamination hazards were identified in a certain copper smelter as per applicable standards in order to protect the soil. Focusing on areas of liquid storage and transportation, cargo storage and transportation, production, etc., sites were identified where leakage, loss and dispersion of hazardous and noxious substances is possibly/likely to occur and inspections were conducted on associated installation and operation as well as the development and implementation of soil pollution management system. Results show that soil and groundwater contamination hazards exist in some areas of the plant, such as the acid making area and the waste acid treatment area. Corrective actions were proposed as per applicable regulations.

Abstract:The offgas produced in copper smelting process contains SO₂ and detrimental dust, which leads to poor working conditions in the smelting plant, posing occupational health hazards to workers there. The fugitive offgas collection system is critical in improving work conditions and reducing occupational disease hazards. Taking as an example the fugitive offgas collection system in a certain copper smelting plant, this paper introduced the design scheme of fugitive offgas collection system, the calculation method of the ventilation volume of the offgas hood and the air distribution scheme in the plant building. It also analyzed the problems in the operation of the fugitive offgas collection system through test data of the vent of the side-blowing furnace. Finally, it pointed out that to ensure working conditions requires both sound system design and standard field operation.

Abstract:In order to explore the ecological restoration pattern of abandoned aggregate quarries, this paper analyzed the geological conditions and ecological problems of abandoned aggregate quarries by taking a certain aggregate quarry as an example, based on which ecological restoration solution was proposed. There were several waste heaps, waste slopes and mining pits in the study area that was suffering from seriously ecological damage. Due to a lack of growing conditions, vegetation was no longer able to hold soil, resulting in serious soil erosion and water loss in the wet season; extensive stripping of overburden and waste heaping was also likely to generate fugitive dust. By terrain restoration engineering, waste heaps, mining pits and waste slopes were turned into land for greening, where rehabilitation was applied. Results show that ecological restoration for abandoned quarries can restore the topography and geomorphologic landscape, recover the damaged land and reconstruct the ecosystem.

Abstract:Rural ponds serve for ecological protection, drought relief, flood storage and farmland irrigation, but they have been vulnerable to pollution in recent years. Based on the investigation and analysis of the current situation of pond pollution in a certain area of northern China, according to the source of pollutants, ponds were classified into four types: initial rainwater ponds, domestic sewage ponds, industrial pollution ponds and livestock and poultry breeding pollution ponds. The pH, COD, nitrates/ammonia, total phosphorus of water bodies and heavy metal concentration in bottom sediment of various ponds were measured, in order to understand pond environmental features. Finally, Finally, the main problems and causes of pond pollution were summarized, and the treatment suggestions of “rubbish cleanup-interception at source-bottom sediment restoration-water purification-ecosystem building” were put forward.

Abstract:The scattered geographic locations of rural villages, disparate local sewage discharge conditions, and a common lack in sewage network construction result in the low rate of sewage collection and treatment and the subsequent threat to pollute local water bodies in rural areas. This paper took a wastewater treatment project in a North China waterfront village as example, to introduce the characteristics of rural wastewater discharge in North China, such as wastewater quantity, water quality, discharge requirements, wastewater collection methods, etc., and to analyze with emphasis the principles and advantages of different biochemical and ecological treatment technologies. Rural wastewater treatment should be based on local sewage discharge characteristics, while taking into account financial investment, maintenance and other factors, and adopt classified treatment measures tailored to local conditions.

Abstract:A flow field model was developed for the crust breaking and feeding device of aluminum electrolysis cell to simulate the flow regime of the new alumina into and out of the constant feeder. The structure of the device was designed based on simulation results and verified under cold-state and hot-state tests. Results show that at a feeding time of 6s, the feeder’s action is stable, smooth and consistent with a constant discharge accuracy higher than 98.36%. It also integrates the relatively independent crust breaking system and feeding system into one single simplified system of crust breaking and feeding, saving costs on equipment maintenance. This offers a solution to the challenges of new alumina fines, which is likely to generate fugitive dust.

Abstract:Digital plant is the direction for future plant construction. A digital control system can transcend spatial, systematic and organizational divides in a plant, realize the integration and collaboration of human and financial resources, materials, production, and supply, and provide data support for production and optimization decisions. A hydrometallurgical plant adopted the “1+1+N” intelligent plant architecture, and combined cloud computing, big data, the Internet of Things, artificial intelligence and other emerging technologies to conduct digital upgrading of production management and control. This paper introduced the hardware and network architecture involved in the digital upgrading, as well as the core functions of the software, and analyzed the application effect and value of the digital engineering to the factory.The digital upgrade provides users with mobile and real-time access to situations of the production line, cuts down on the manual transferring of information, and improves significantly the efficiency of the plant’s production process control.