Sustainable Mining and Metallurgy

Abstract:Organic hazardous wastes have a wide variety of types and sources, which almost cover most industries of the national economy, and it is difficult to accurately count all the properties and characteristics of them. According to the order of National Catalogue of Hazardous Wastes (2021 Edition), this paper described the representative 11 kinds of organic waste, summarized the industry category and the production and discharge characteristics of organic wastes and analyzed the typical pollutants systematically, which provide the basis for hazardous waste management, safe disposal and pollution control.

Abstract:At present, the utilization rate of nonferrous metallurgical slag in China is far from the ideal level. Long-term open-air accumulation of waste slag not only wastes land resources and pollutes the environment, but also causes the waste of valuable resources. Therefore, it is urgent to make high-value and harmless use of nonferrous slag. This paper introduced the classification and physicochemical properties of the four kinds of typical nonferrous slag: red mud, ferronickel slag, copper slag and lead-zinc slag systematically, and then introduced the resource utilization of nonferrous metallurgical slag from two aspects of valuable metals extraction and building materials preparation, analyzing the the characteristics of various valuable metal extraction technologies such as mineral processing, hydrometallurgy, pyrometallurgy and the combined technology of hydrometallurgy and pyrometallurgy, as well as the application of nonferrous metallurgical slag in the filed of building materials such as the preparation of cement, concrete, brick, roadbed, glass ceramics and mine filling and the field of environmental protection such as waste water, waste gas treatment and soil remediation, and finally put forward some suggestions to improve the comprehensive utilization rate of nonferrous slag.

Abstract:High concentration sodium metaaluminate solution will be produced when invalid catalyst is recovered by alkali method. The leaching solution has significant recovery value because of its high aluminum content and less impurities. In this paper, sodium metaaluminate was converted into aluminum hydroxide precipitation by carbon separation to recover aluminum. Response surface methodology was used to study the significance of CO₂ ventilation rate, aeration time and dilution ratio on the conversion rate of Al(OH)₃ precipitation, and to explore the best process parameters of aluminum hydroxide precipitation. The results show that the average precipitation conversion rate of Al(OH)₃ is 98.59% with the CO₂ aeration rate of 0.360L/min, the aeration time of 116min, and the dilution ratio of 4 times. The precipitation process is controlled by many factors, among which the aeration time and dilution ratio have significant effects on the precipitation conversion of Al(OH)₃.

Abstract:There are many ways to recycle waste circuit boards, among which pyrolysis is the most promising method, and the pyrolyzing furnace for industrial application and the optimized type are steel belt furnace. This paper introduced the composition and key technologies of the continous anaerobic pyrolysis system of waste circuit boards of a company, and described the two times of modification and optimization for solving the issues such as the material cannot be cooled, the processing capacity was insufficient, there was no self-heating reuse system, and there was no oil-gas separation system. After the completion of upgrading and modification, the processing capacity of this device can reach the level of ten thousand tons, and after the efficient oil-gas targeted separation, the pyrolysis oil and gas can be recycled efficiently and with high quality, realizing the purpose of energy conservation and emission reduction. The overall technology of the device has reached the international advanced level.

Abstract:Aluminum ash is a by-product produced in the process of electrolytic aluminum production, which contains high content of alumina. Chinas electrolytic aluminum industry produces a large amount of aluminum ash every year. The traditional landfill method not only has a bad impact on the environment, but also causes a waste of resources.Waste acid is a kind of hazardous waste, the traditional neutralization process has the problems of large slag production and high cost of subsequent treatment. This paper reviewed the recycling process of aluminum ash and waste acid, and introduced the detailed process flow of preparing polyaluminum chloride by using waste HCl and waste H2SO4 with aluminum ash. The indexes of the water purifying agent prepared by this process can meet those of the national standard.This method realizes the recycling of waste, and has good economic and environmental benefits.

Abstract:This paper explored the production of reusing the antimony smelting alkali slag as an auxiliary material instead of part of sodium carbonate to the lead smelting system. The slag melting point is lower than the temperature of the lead smelting system, so it can be melted before the copper removal slag and promote the latter to melt, and increase the fluidity of the surface slag layer to provide good conditions for the formation of the molten pond. In addition, the antimony smelting alkali slag has a high Na₂O content, so it can be used to replace part of the sodium carbonate for smelting, thus forming a new process. When the reuse ratio of the slag increased to 4%, the slag yield of lead smelting system decreased from the highest 19.17% to 13.52%. The Pb, Cu and Ag contents decreased in varying degrees, among which the content of Pb decreased from 5.76% to 2.00%, Cu from 3.92% to 1.97%, and Ag from 82.73g/t to 47.82g/t.

Abstract:To oxidize Fe²⁺in Ga and Ge leaching solution to Fe³⁺, industrial oxidants such as sodium persulfate, manganese ore powder and hydrogen peroxide were used for oxidation. The effects of oxidant addition, reaction temperature and reaction time on the oxidation rate of Fe²⁺in Ga and Ge leaching solution were investigated respectively. The results show that the mass concentration of Fe²⁺in Ga and Ge leaching solution oxidized by industrial oxidants sodium persulfate, manganese ore powder and hydrogen peroxide is ≤0.03g/L, which can meet the production control standard of less than 0.05g/L, and the oxidation rate of Fe²⁺is more than 99.75%. When manganese ore powder is used as oxidant, the oxidized solution cannot be separated during re extraction. The cost of using industrial grade hydrogen peroxide as oxidant is the lowest. According to the actual situation of industrial production and the comprehensive consideration of production cost, it is more appropriate to select industrial hydrogen peroxide as the oxidant. The optimal oxidation process conditions are: rotational speed of 500r/min, hydrogen peroxide addition amount of theoretical chemical reaction molar ratio of 4.0, reaction temperature of 45℃, and reaction time of 20min. Under these conditions, the oxidation rate of Fe²⁺in Ga and Ge leaching solution reached 99.82%. In industrial applications, the corresponding safety storage devices required on site and the safe use specifications shall be implemented, so as to ensure production safety.

Abstract:The NaOH-NaNO₃ molten salt method was used to separate Pb, Sn, Sb and Bi in the silver separating residue, and the optimal process conditions are as follows: the ratio of NaOH∶NaNO₃∶silver concentrate is 45∶20∶10, smelting temperature is 700℃, smelting time is 2.5h, leaching temperature is 80℃, leaching time is 40min and the liquid-solid ratio is 6∶1. Under the optimal conditions, Pb and Sn in the silver concentrate entered into the leachate, and the recovery rates reached 83.77% and 86.92%, respectively. More than 98% Sb and Bi entered into the leaching residue.

Abstract:This paper introduced the process flow and the main techno-economic indicators of the production practice of Pb-Cu mixed materials treatment by oxygen enriched side blowing furnace-dilution furnace coprocessing of a company, and analyzed the characteristics and advantages of the process. The practice shows that compared with the process before modification, reverberatory furnace + blast furnace, this process has the advantages of comprehensive improvement of the processing capacity of unit furnace hearth, continuous feeding, good Pb-Cu separation effect, high Pb-Cu recovery, good slag indicators, low energy consumption, high production efficiency, good environmental protection effect, stable operation and broad prospect, which provides a new technical process for the treatment of Pb-Cu materials.

Abstract:The electrothermal blowing dry box was used to reduce arsenic sulfide slag, and the process parameters of the drying process were studied. From the perspective of energy saving and process difficulty, the drying temperature of 125℃ and the drying time of 60min were selected to dry arsenic sulfide slag, and the weight loss rate was 29.1%, reaching the goal of reducing arsenic sulfide slag (the slag reduced by more than 20%). The rotary kiln drying experiment of arsenic sulfide slag was carried out, and the weight loss rate reached 36.8%. The annual smelter treatment of arsenic sulfide slag can save 1.638 million yuan, with significant economic and environmental benefits, providing theoretical support and direction for other smelting enterprises.

Abstract:This paper focused on the process of zinc dross treatment with offgas washing supporting rotary kiln, analyzed the chlorine content of calcine produced by small kiln under different temperatures and kiln speeds, and obtained the optimal reaction conditions of kiln tail temperature of 400℃±10℃, kiln speed of 13Hz, reaction time of 3h, and kiln head charge level temperature of about 850℃, so that the chlorine content of calcine in small kiln is less than 0.08%, and the dechlorination efficiency of zinc dross reaches 97%. The pressure drop, temperature difference, chlorine distribution and balance were analyzed, and key points of process control were proposed.

Abstract:The super-magnetic separation technology has the advantages of good water discharge effect, fast treatment speed, simple process flow, etc. In recent years, it has been rapidly promoted in the field of water treatment and its application scope has gradually increased. The core of the technology includes the selection of super-magnetic particles, super-magnetic separation and magnetic seed recovery equipment. This paper summarized the application fields and effects of the super-magnetic separation technology, reviewed the development of magnetic seeds, point out that the development of high performance magnetic particles is one of the future research directions, and also introduces the research results on the preparation of magnetic ferroferric oxide particles by co-precipitation method.

Abstract:In view of the problems such as instantaneous excessive chlorine gas at the outlet of the chlorine-containing tail gas spray tower, high content of valuable metal elements in the absorption liquid and frequent damage to the circulating pump in anode slime metallurgy of a company, FeCl2 process was adopted to treat the chlorine-containing tail gas. The results show that after five stages of absorption, the chlorine absorption efficiency of the FeCl2 solution prepared by reaction of FeCl3 and iron powder is higher than 99%, and the chlorine content at the outlet of the absorption tower is less than 60mg/m³. The chlorine emission can reach the standard. The process reduces the damage rate of circulating pump by more than 70%, and chlorine gas emission by more than 50%, and also reduces the loss of Cu, Se, Te, etc., caused by being brought into the absorption system. It provides a reference for reducing the emission of chlorine-containing tail gas in metallurgy and green production.

Abstract:This paper briefly described the principle, process and characteristics of organic amine desulfurization, and analysed its application in the lead smelting offgas treatment. The results show that the organic amine desulfurization has the advantages of high desulfurization efficiency, low operation cost, high reliability, simple operation, recycled SO2, no waste water and slag, etc. It can provide a circular economy way for efficient and clean production of offgas desulfurization in lead smelting industry.

Abstract:After hydrometallugical desulfurization, the offgas is basically saturated. As the offgas contains a large amount of steam, once discharged into the atmosphere and cooled by the surrounding cold air, a large amount of white smoke will be produced. Taking a copper containing solid waste treatment project as an example, this paper introduced the composition of process offgas and secondary offgas after ionic liquid desulfurization, and the condensation reheating method was selected through comparison of white smoke eliminating technology， and analyzed the design parameters of the equipment and the characteristics of the technology. The production shows that this technology not only realizes the combined recovery of water and harmful substances, but also has good elimination effect. There is basically no white smoke and tailing throughout the year, and no additional heat source is required. It saves energy consumption and has low operating cost.

Abstract:Taking the waste rock before and 2 years after the ecological restoration of a copper mine stockyard as the object, the acid production potential was evaluated by static method, and the acid waste water generation and metal ion release were studied in combination with the dynamic humidity box simulation weathering test. The static test results show that the waste rocks before and after ecological restoration have potential acid production capacity, and the stacking process has certain acidification risk to the environment. The results of dynamic humidity box test showed that the waste rocks before remediation continuously discharged acidic wastewater and heavy metals, and the concentration of Cu, Zn exceeded the standard; the time of acid wastewater discharge and the release of Fe, Cu, Zn and other metal ions from the restored waste rocks were delayed by 40 weeks compared with the waste rocks before remediation, which indicated that the ecological remediation using neutralization residues had a certain inhibition effect on the acid wastewater generation and the release of metal pollution factors.

Abstract:According to the characteristics of low ambient temperature in cold regions, domestic waste is easy to freeze into clusters, and calorific value is low, this paper discussed the measures of heating waste with hot waste water and hot leachate, increasing the ambient temperature above the waste pond, expanding the pond capacity, and adding waste crushing pretreatment system and wet hydrolysis pretreatment system. The implementation of these measures can promote the fermentation of domestic waste, reduce the moisture content, improve the calorific value, and help the combustion of waste furnace and the emission of offgas in winter.

Abstract:At present, the domestic sewage treatment rate in rural areas is still at a quite low level, which affects the rural comprehensive development and ecological civilization construction. This paper discussed the engineering design and process selection of a rural domestic sewage treatment project in Hebei Province. It is pointed out that the rural sewage treatment should be treated by different strategies according to local conditions on the basis of ensuring the technical feasibility and economic rationality, to ensure that the effluent quality meets the discharge standard. It also briefly analyzed and summarized the common problems existing in the current rural domestic sewage treatment, including the lack of sewage treatment facilities, the collecting difficulty of sewage system, and the large fluctuation of water quality and quantity.