Sustainable Mining and Metallurgy

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Abstract:At present, sodium hydroxide alkali leaching method is usually used to extract tungsten from spent SCR denitration catalyst，and tungsten-containing alkaline leaching solution is obtained. In addition to tungsten, the alkaline leaching solution also contains impurity elements such as vanadium, silicon, and sulfur. Due to the high alkali concentration of the solution, traditional extraction and adsorption methods are difficult to implement. The traditional hydrochloric acid neutralization-calcium chloride precipitation method would take Cl^- into the system, resulting in equipment corrosion. In this paper, a new magnesium sulfate desilication-calcium oxide precipitation process was proposed to remove silicon and precipitate tungsten to prepare scheelite concentrate. In the process of magnesium sulfate desilication, by using sulfuric acid to adjust the pH value of the system to 11, under the condition of magnesium-to-silicon molar ratio of 0.9, the silicon removal rate can reach 97.6%. The desilication solution was precipitated by calcium oxide to produce scheelite concentrate. Under the optimum process conditions of calcium-to-tungsten molar ratio of 1.1 and boiling temperature of 108℃, the WO₃ content in the obtained scheelite concentrate product reached 74.69%, the sulfur content was 0.90%, and the silicon content was 1.00%, which met the requirements of YS/T 231—2015 Grade Ⅰ scheelite concentrate. The process realizes the efficient recovery of tungsten from the alkaline leaching solution of spent SCR denitration catalyst, and avoids the potential equipment corrosion issues associated with the traditional hydrochloric acid neutralization-calcium chloride precipitation method.

Abstract:In order to promote the large-scale consumption of electrolytic manganese residue (EMR) in cement and other building materials industry, which is conducive to the harmless, reduction and resource disposal of EMR, the parameters of deamination, desulphurization and iron extraction of EMR were explored, and a series of EMR based active gelling materials were prepared. The results show that the ammonia content and sulfur content of EMR decrease with the increase of roasting temperature. When the temperature is 400℃, the residual ammonia content in the slag is 0.09%, and the deamination rate is greater than 90%. When the roasting is held at 600℃ for 10min, the deamination rate is greater than 98%. When taking higher temperature deamination, better deamination effect can be achieved in a shorter holding time. When held at 1300℃ for different holding time, the sulfur content of electrolytic manganese slag can be reduced to less than 1%, and the desulfurization rate is greater than 96%. The content of Fe in the desulphurized EMR with added auxiliary materials can be reduced to about 1% after holding at 1500℃ for 5min, which can be regarded as an ideal effect of iron extraction. The gelling activity of undisturbed EMR powder is low and it can't reach the standard of S75 slag powder by physical or chemical excitation method. The desulphurized EMR powder can meet the requirements of S75 slag powder after increasing the specific surface area or mixing with activator. The EMR powder after extracting iron has good gelling activity and can be directly used in building materials such as cement mixture after grinding, and the incorporation amount is as high as 50%，which is conducive to bulk consumption of EMR.

Abstract:Carbon slag is a kind of dangerous solid waste produced in the process of electrolytic aluminum production, which contains high content of electrolyte. A company treated carbon residue by high temperature roasting and recovered the electrolyte. In this paper, the process conditions of industrial high temperature roasting treatment of electrolytic aluminum carbon slag were studied, and the phase composition of the main products in the process of high temperature roasting treatment of electrolytic aluminum carbon slag was studied by X-ray diffraction analysis. The results show that when the overall temperature in the furnace reaches more than 1200℃, the electrolyte in the carbon slag is completely melted and has good fluidity and no curing state, the electrolyte and carbonaceous components in the carbon slag were effectively separated. After high temperature roasting, a new phase will be formed. The electrolyte is mainly composed of Na₃AlF₆, CaF₂, Al₂O₃, K₂NaAlF₆, LiNa₂AlF₆, Li₃N, LiF, Mg₃Al₂ (SiO₄)₃ and NaAl₁₁O₁₇. Tailings are mainly composed of Na₃AlF₆, CaF₂, Al₂O₃, K₂NaAlF₆, LiNa₂AlF₆, Li₃N and C; the dust is mainly composed of Na₅Al₃F₁₄, Na₃AlF₆, LiNa₂AlF₆, AlF₃, NaAlF₄ and KAl₁₁O₁₇. The calcium salts in the carbon residue in aluminum electrolysis always exit in the form of dissociative CaF₂, part of which is included in the recovered electrolyte, and the other part exits in the tail residue.

Abstract:The content of scandium in laterite nickel ore is 50~600g/t. The simultaneous extraction of scandium metal from the separation and enrichment process of nickel and cobalt is a very promising way to develop and utilize scandium resources in the future. In this paper, the current research status of separation and extraction of scandium from laterite nickel ore was analyzed, and the main process flow of scandium extraction was introduced. Then, the possible forms of scandium in different concentrations of mineral acid medium, as well as the extraction mechanism, extraction characteristics and extraction conditions of scandium under high acidity were reviewed, providing theoretical guidance for the full utilization of scandium resources in laterite nickel ore.

Abstract:A lead smelter adopts the process of “oxygen-enriched bottom blown oxidation-oxygen side blowing reduction” for crude lead smelting. The high lead slag produced by the bottom blown furnace has a high sulfur content of 1.3%~1.6%, which has a certain impact on the subsequent tail gas desulfurization system and increases the cost of environmental protection treatment. In order to solve this problem, this paper analyzed the main reasons for the high sulfur content of high lead slag in lead smelting bottom blown furnace based on theory and production practice. It can be seen that the sulfur in high lead slag mainly exists in the form of sulfate. Some of these sulfates come from the sulfate lead materials in the furnace materials, and the other part is generated by the oxidation reaction of lead sulfide concentrate in the smelting process. The main way to reduce the sulfur content of high lead slag is to increase the temperature of molten pool smelting and reduce the partial pressure of SO₂ in the system.Combined with the production practice, the ways and methods to reduce the sulfur content of high lead slag in bottom blown furnace were discussed from the aspects of slag type, oxygen-to-material ratio, sulfur content in granular ore and SO₂ partial pressure of the system. Under the condition such as lead-containing slag material ratio of about 30%, slag temperature 1050~1100℃, slag type FeO/SiO₂ 1.4~1.8, CaO/SiO₂ 0.4~0.6, oxygen-to-feed ratio of 100~110Nm³/t, effective sulfur content in pellet ore12.5%~13.5% and appropriate negative pressure, the residual sulfur content of high lead slag can be kept below 1.2%.

Abstract:In view of the problems of less theoretical experiments and insufficient research on process diversification in the treatment of zinc leaching residue by SO₂ reduction leaching process, the experimental study on the treatment of high-iron acid leaching residue by pre-acidification and SO₂ reduction leaching process was carried out to explore the effect of pre-acidification on the zinc leaching rate of SO₂ reduction leaching, the reaction time of SO₂ reduction leaching section and the sedimentation of pulp after reduction. The results show that the leaching rate of zinc can reach 96% and the reaction time of SO₂ reduction section can be shortened to 1.5h under the conditions of concentrated sulfuric acid concentration of 100g/L, reaction temperature of 90℃ and reaction time of 1.5h. When the concentration of pre-acidified sulfuric acid is 90~110g/L, the slurry sedimentation after reduction is better.

Abstract:Aiming at the problem that the amount of gypsum residue produced by the treatment of contaminated acid by lime neutralization method in zinc hydrometallurgy is large, this paper proposed a process of using zinc calcine-calcium carbonate two-stage neutralizations method to treat the liquid after vulcanization. The process neutralizes part of the acid by zinc calcine and then neutralizes it by calcium carbonate, which removes fluorine and reduces the production of waste acid gypsum residue. When zinc calcine is used for neutralization, the pH value is controlled to be 2.0~2.5, and the neutralization is carried out at 35℃ for 1h. After sedimentation and filtration, calcium carbonate is used for the second stage neutralization. The end point pH is controlled to be 5.0~5.5, and the reaction time is 1h. Under these conditions, the fluorine content of the solution after fluorine precipitation is less than 20mg/L, and the fluorine precipitation rate is more than 98%. The output gypsum slag is only 24.94% of the gypsum slag produced by the traditional lime neutralization method. The solution can be returned to the wet system after subsequent dechlorination.

Abstract:The shelling hammer works in a strong magnetic field and high temperature environment. Due to the corrosion of molten salt electrolyte and the impact wear of the hard shell surface of the discharge port, the shelling hammer is gradually consumed. The impurities such as iron and cadmium enter the original aluminum liquid and affect the original aluminum grade of the electrolytic cell. In this paper, the experimental research and development of special aluminum-based shell hammer were carried out. The wear resistance, heat resistance and corrosion resistance of aluminum-based shell hammer samples are studied, and the performance combination suitable for shelling operation was found out. The test data show that the high temperature strength, hardness, wear resistance and corrosion resistance of aluminum alloy hammer can meet the requirements of field use. The practical application results show that the iron content in the original aluminum liquid of the electrolytic cell is reduced by 0.0178% after using the aluminum-based hammer. The aluminum-based hammer fundamentally solves the problem of primary aluminum pollution caused by the consumption and wear of the iron shelling hammer. If it is promoted on the 250000t/a series of electrolytic cells, the annual cost savings and the benefits brought by the improvement of aluminum quality can reach 1.32 million yuan, and the economic benefits are good.

Abstract:A large amount of contaminated acid and acidic wastewater are produced in the operation of each process of a copper smelting enterprise. The contaminated acid has the characteristics of high acidity and high arsenic concentration, which is easy to cause harm to the environment and human body. In this paper, the combined process of “two-stage sulfidation + two-stage neutralization” was used to treat the contaminated acid and acidic wastewater. The two-stage sulfidation used sodium hydrosulfide precipitation to remove heavy metal elements such as arsenic and copper in the contaminated acid. The two-stage neutralization used limestone to neutralize the acid in the contaminated acid, and then used calcium carbide slag and iron salt to neutralize the heavy metal ions. After treatment, the arsenic content was reduced from 8~14g/L to less than 0.5mg/L, and the H₂SO₄ content was reduced from 125g/L to 0.5mg/L, which met the requirements of national standard and could meet the water requirements of other processes in the plant area, and achieve the goal of “zero discharge” for the recycling of contaminated acid and acid wastewater.

Abstract:There are cyanide, thiocyanate, metal-cyanide complexes, heavy metals and other composite pollutants in the gold mine heap leaching tailings, which seriously endanger the health of the surrounding environment. The microbial treatment of gold mine heap leaching tailings has the characteristics of low cost, high efficiency and low secondary pollution. It is a green and efficient treatment method, but the cyanide-reducing strain has a single function and has limitations. Therefore, this paper used a composite flora to treat the heap leaching tailings. A functional bacterium TCD-1 with heavy metal tolerance and cyanide degradation ability was screened, and its degradation performance of cyanide and metal-cyanide complex was studied. It was mixed with thiocyanate degrading bacteria TDB-1 and surfactant producing bacteria Z-90 to make a composite microbial eluent. The leaching process of compound bacteria in gold mine heap leaching site was established, and the optimum tailings particle size, optimum pH value and optimum bacteria liquid ratio were determined. Under the condition that the particle size of heap leaching tailings is 20 mesh, the pH value is 8, and the ratio of bacteria to liquid is TDB-1∶TCD-1∶Z-90=2∶1∶1, the treatment effect of thiocyanate and heavy metals in tailings is the best. The small-scale amplification test showed that the content of pollutants in the heap leaching tailings and leachate after leaching met the requirements of relevant standards.Finally, the eluent produced in the leaching process was deeply purified, and the residual metal-cyanide complex in the eluent was broken by the oxidation ability of hydrogen peroxide. At the same time, the flocculant was used to flocculate and precipitate the heavy metals, so as to achieve the effect of simultaneous removal of complex and heavy metals in the eluent.

Abstract:Lead-based solid waste mainly comes from zinc, lead and copper smelting process and waste lead-acid battery recycling system. It contains a large number of valuable metals and pollutes the environment. Therefore, it is particularly important to find out the source structure, output and regional distribution of lead-based solid waste. Based on the field investigation of enterprises, this paper analyzed the main smelting technologies of zinc, lead and copper and their production of lead-based solid waste. According to the output solid waste ratio of single ton refined metal and the output of refined metal, the output of lead-based solid waste was calculated. Based on the distribution of zinc, lead and copper smelting output, the regional distribution of lead-based solid waste was described. According to the content of lead-based solid waste pollution elements and the output of lead-based solid waste, the output of valuable elements was calculated, in order to provide basic support for the development research and industrial layout of lead-based solid waste disposal technology.

Abstract:Energy conservation and consumption reduction is a key concern for non-ferrous metallurgical enterprises. Strengthening the level of enterprise energy management and control is an important way to achieve energy conservation and consumption reduction. However, due to the long production process, multiple processes, and complex process of non-ferrous metallurgical enterprises, energy management and control are more difficult. Utilizing artificial intelligence technology to achieve reasonable energy management and control for enterprises is the future development direction. On this basis, this article analyzed the application scenarios and key technologies of artificial intelligence technology in energy management of non-ferrous metal smelting based on the current energy consumption status and energy management characteristics of non-ferrous metallurgical enterprises, providing a foundation for the combination of artificial intelligence technology and the non-ferrous metallurgical industry.

Abstract:In this paper, the hazand sources of fire and explosion in the electrolysis workshop of an aluminum plant were identified, and the possible causes of fire and explosion accidents in the electrolysis workshop was found out by building a complete accident tree. Taking the fire accident as the top event, by analyzing the minimum cut set, the minimum path set, and the structural importance ranking of each basic event,It was found that the basic events such as furnace gang destruction, voltage supervision not in place, accidental shorting at the busbar short intersection, and so on have a greater impact on the top event. For the reasons that may lead to accidents, improvement measures were proposed from the aspects of process technology and safety management, respectively. In terms of process technology, it was recommended to strengthen the maintenance and inspection of the furnace gang, strengthen the monitoring of cathode soft connection, and strengthen the setting and maintenance of voltage monitoring system, etc. In terms of safety management, it was recommended to strengthen the staff's safety training and education, establish a perfect safety management system and operating procedures, and strengthen the regular inspection and maintenance of equipment, etc., in order to effectively prevent the occurrence of fire and explosion accidents in aluminum electrolysis plants.