Sustainable Mining and Metallurgy

Abstract:Isothermal pyrolysis of waste PCB (printed circuit board) was studied by using tubular pyrolysis furnace under nitrogen protective atmosphere to explore the law of effect of pyrolysis temperature and holding time on pyrolysis rate and pyrolysis products of waste PCB, and analysis was made for the pattern of distribution of bromine in pyrolysis products. The results of the experiment show that the waste PCB can be fully pyrolyzed at the temperature of 700℃ with a pyrolysis time of 40min. The waste PCB can be fully pyrolyzed with a pyrolysis rate of 97.74%, and the solid, liquid and gas product yields are 72.67%, 15.51% and 11.82% respectively, and the distribution proportion of bromine in the solid, liquid and gas products are 15.02%, 5.72% and 79.26%, respectively.

Abstract:In the process of recovering indium from the post-reduction leaching solution during hydrometallurgical refining of zinc, part of tin enters the stripping solution, which affects the quality of subsequent refined indium. Due to the impurities such as indium and tin in the tin removal residue, tin will be gradually enriched in the system, as to affect the service life of extractant and reduce the production efficiency. In this paper, the removal of tin in the solution after stripping was studied by using the pre-adjustment of pH value-H₂O₂ oxidation method. Condition tests were made on endpoint pH value, amount of hydrogen peroxide added, reaction duration, etc. to investigate the tin removal effects under different conditions, and exploration was made on tin removal from tin removal residue by means of acid leaching and alkali leaching. The results show that the separation of indium and tin can be achieved by controlling the temperature of indium stripping solution at 50℃, endpoint pH at about 2.0, reaction time at 1h, amount of hydrogen peroxide added at 5g/L and the hydrogen peroxide being added in a low speed. Using concentrated sulfuric acid or concentrated hydrochloric acid to leach tin removal residue can not meet the requirements of indium leaching, and part of tin is leached into the solution during the process, which cannot realize the complete separation of indium and tin. If alkaline leaching approach is adopted, when the reaction temperature is controlled at 90℃, the liquid to solid ratio at 3∶1, the reaction duration at 2h and amount of sodium hydroxide added at 100g/L or more, 80% of tin can be separated from tin removal residue and enters the solution, and indium is basically not react with sodium hydroxide and remains in slag, thus realizing the complete separation of indium and tin.

Abstract:Taking the dry arsenic collection technology of oxygen-enriched side-blown smelting flue gas of As-bearing gold-copper concentrate as the research object, the effects of sulfur trioxide content in flue gas, spray gun layout of quench tower, effective height of quench tower and inlet temperature of bag collector on dry arsenic recovery were analyzed, and the related technical control difficulties were studied. Sulfur trioxide content in flue gas can be controlled by controlling oxygen content ; cancelling the top spray gun of the quench tower, and increasing two spray guns in the tower body can effectively cool the flue gas ; by increasing the height of the quench tower, the residence time of the absorbent in the quench tower can be prolonged to make it completely vaporized. By controlling the spraying amount of the absorbent of the spray gun in the quench tower, the inlet temperature of the bag filter can be maintained at 150-170℃. The above measures have been successfully applied to production practice. At present, this system under stable operation treats 1900t/d ore feed with As grade of 1.5% and collects 23t/d As. The As content in purified dilute acid from acid-making section drops from 18000mg/L to 4000mg/L. Resistance of primary high-efficiency scrubber used in purification procedure decreases by around 2000Pa and the filter press residue of dilute acid dramatically declines.

Abstract:Manually horizontal casted silver anode plates and traditional ship-type silver electrolytic cells are adopted by a certain smelter to recover silver from lead anode slime by electrolysis, presenting multiple issues such as large footprint, large amounts of capital tied up, high production costs and poor operating environment, so it’s urgent to introduce new high efficiency silver electrolysis equipments. The principles, advantages and application of anode plates produced by manually vertical mould casting and automatically horizontal continuous casting, vertical high-efficiency electrolytic cells and no residuals anode electrolytic cells were introduced in this paper. The silver recovery process of automatically horizontal continuous casted anode plates together with vertical high-efficiency electrolytic cells and no residuals anode electrolytic cells, results in an anode scrap ratio of 5%~10%, down by 15% compared with traditional electrolysis equipment, an increase in current density by about 70A/m2 and a rise in current efficiency by around 35%, saving production costs. The produced silver powder is up to the national standards and the gold content in it drops from 16.5g/t to 0.5g/t, leading to remarkable economic benefits.

Abstract:A certain amount of ferroferric oxide will be produced in the process of smelting concentrate by oxygen-enriched air oxidation in side-blowing furnace. When the ferroferric oxide content in slag is too high, the viscosity of melt will increase and accretion will form in the bath to make the furnace bottom rise so as to reduce the bath volume. In more serious situation, the foamed slag will be produced, resulting in slag-spillage accident. In this article, by combining the production practice of side-blowing smelting furnace, the ferroferric oxide generation in smelting process in side-blowing furnace and controlling measures were discussed, and the elimination measures of ferroferric oxide in various parts were introduced. The results show that the main cause of ferroferric oxide is its inclusion in raw material and slag peroxidation. In production, the ferroferric oxide content can be controlled by means of controlling the content of ferroferric oxide and high-melting-point impurities in raw material, adjusting coal feed amount, adding appropriate amount of quartz and other measures.

Abstract:The content of copper, arsenic and bismuth in the lead anode slime of a company is high. Lead oxide is used as the ingredient in the lead-fire gold test method, and the ability to remove impurities is limited. To address this problem，potassium nitrate was added as the oxidant to prepare the test material, and the process of melting and slagging was controlled, so that impurities were volatilized and oxidized, creating favorable conditions for the next ash blowing. In the ash blowing process, the operating furnace temperature was controlled and the auxiliary conditions were adopted to make base metals such as copper, arsenic and bismuth not affect the ash blowing process and be absorbed by the ash pan, so as to obtain accurate gold and silver analysis results.

Abstract:In view of the problems of insufficient emergency support capacity, large oxygen emission, excessive steam consumption by liquid oxygen vaporization, and lack of nitrogen emergency and peak shaving reserve in the oxygen supply system of a certain group, with the development of variable multi-cycle cold energy utilization technology as the core, a new technology of high-efficiency oxygen variable load + nitrogen energy-saving recovery was introduced by expanding the liquid oxygen storage tank and vaporization system, constructing the liquid nitrogen storage tank and vaporization system, and constructing the oxygen and nitrogen cold energy utilization device to realize the liquefaction of oxygen using the cold energy of liquid nitrogen and vaporization of nitrogen using latent heat of oxygen. The new process finally realizes the variable recycling process of cold energy, greatly improves the utilization rate of oxygen and nitrogen resources, reduces steam consumption, and improves the stability of oxygen supply system and liquid nitrogen storage guarantee ability, which can produce good economic benefits.

Abstract:The acidic solution of high-aluminum zinc sulfate produced in the process of zinc hydrometallurgy was chosen as the research object, and ammonium sulfate as the aluminum remover. The experimental results shows that under the conditions of reaction temperature of 80℃, reaction time of 120min, mole ratio of NH₄⁺/Al³⁺ of 1.0, cooling terminal temperature of 25℃, and cooling time of 30min, the aluminum removal rate is more than 80%, zinc loss rate is less than 0.6%, and sulfuric acid loss rate ranges from 60% to 65%. The optimized conditions were applied to production practice, and the practice show that the method had the characteristics of simple operation and high stability in aluminum removal, but there are also issues such as high concentration of NH₄⁺ in liquid after aluminum removal, high loss rate of sulfuric acid, difficult utilization of aluminum removal residue and high residue rate, which should be adjusted appropriately in practical applications.

Abstract:Using FLUENT to simulate the flue gas flow field and temperature field of electrolytic cell, and combined with the design experience, the multi-stage equal air suction and gas collection flue structure and double flues technology suitable for SY series electrolytic cell were successfully developed. The structure of multi-stage air suction and gas collection flue adopts the form of upper flue gas collection. While strengthening the gas collection effect and balancing the wind pressure distribution in the tank chamber, it can greatly reduce the smoke exhaust volume of the electrolytic tank and reduce the flue resistance by 17%~27%. The double flues technology is improved on the schemes of HYDRO and SOLIOS. The main and auxiliary flues are provided with negative pressure power by the purification fan. During the slotting operation, the main and auxiliary smoke flues collect gas at the same time, and the amount of flue gas can be instantaneously increased by 2~3 times, so as to effectively control the unorganized emission of pollutants in the electrolysis workshop and achieve the purpose of energy conservation and emission reduction.

Abstract:The 350kA electrolysis series in a Chinese plant adopted high Li-K alumina for production. As the enrichment of Li and K in the electrolyte, an electrolyte system of Na₃AlF₆-Al₂O₃-AlF₃-CaF₂-MgF₂-LiF-KF was formed, meanwhile, the production became unstable and indicators were deteriorated. Against this background, laboratory and field tests were carried out to measure the properties of the electrolyte, and industrial tests were conducted using the trial-and-error method to analyze the impact of electrolyte compositions on current efficiency, liquidus temperature, conductivity and alumina solubility, and finally proper electrolyte compositions were determined, that is, molecular ratio of 2.50±0.05, CaF₂≤4.77%, MgF₂≤0.68%, LiF≤5% and KF≤3%. The test results were further put into industrial application, and good effects have been obtained by combining process and operation management, which were reflected by reduced noise level, anode effect within control, improved hearth condition, current efficiency improved by 2.91% and DC power consumption reduced by 326kWh/t.

Abstract:Most mining enterprises, with large electricity loads, are located in areas without electricity which are difficult to be covered by power supply network or economically underdeveloped, hence they adopt the isolated grid self-supply mode of diesel generator unit, bringing problems such as low power generation efficiency, high power generation cost, large operation and maintenance workload and environmental pollution. By making full use of the characteristics of the energy storage system and with a view to the needs of overseas mining enterprises, a new energy storage diesel generator power supply network was built, and its network architecture, system composition and working principle were introduced. In this paper, several project cases were given to illustrate that the power generation efficiency is significantly improved, the fuel consumption per unit of power generation is reduced, the air and noise pollution to the environment is reduced, which means that it can achieve energy saving with reduced emission, increased efficiency with reduced cost as well as more environment-friendly benefits.

Abstract:The heating system in the unit works of a mine project does not fully consider the influence of external temperature changes on the water temperature required for the buildings to be heated.The office is continuously heated for 24 hours under constant temperature and constant pressure. The heat source adopts artificial heating strategy, which cannot be adjusted automatically according to the change of system load in real time, resulting in energy waste and low intelligence. In this research, the latest 5G technology and climate compensation technology were used for intelligentized renovation of the heating system, and an intelligent control system comprising computer operation management center and energy conservation supervision service platform were established, moreover, the focuses of the intelligentized renovation were introduced, realizing the purposes of heating on time and demand, energy conservation, consumption reduction and efficiency improvement.

Abstract:This article introduced the process control of the gas roasting start-up technology, and compared the coke roasting technology and the gas roasting technology from the aspects of roasting effect and cost-effectiveness. The comparison results show that the overall uplift of the coke roasting electrolytic cell is smaller than that of the gas roasting electrolytic cell; the initial heat-up rate of coke roasting electrolytic cell is somewhat faster with a bit poorer controlability relatively while the heat-up rate of gas roasting electrolytic cell is slightly slower with a constant temperature rise, allowing for easy control; there is no obvious differentce in cathode steel bar temperature, furnace bottom plate temperature and melt zone shell temperature between the two roasting methods; in terms of cost-effectiveness and environmental protection, gas roasting of a single electrolytic cell saves about 13,000 yuan compared with coke roasting, with which the energy utilization rate is higher, being conducive to carbon reduction and emission abatement, and there is no need to salvage the carbon residue after startup.

Abstract:At present, small and medium scale kitchen waste treatment plants adopt the traditional process of kitchen food treatment process, which has the problems of complex process, high investment, high operation cost and difficult profit. Developing a simple, high degree of resource utilization, intelligent and efficient kitchen waste treatment process is a hot issue at present. Collaborative disposal of kitchen waste and domestic waste incineration is the mainstream trend of food waste treatment in the future.This paper introduced the conventional process flow and advantages of collaborative disposal of kitchen waste, and took several actual projects as examples to introduce the applicable scale, advantages and disadvantages of different collaborative disposal treatments of kitchen waste, in order to provide reference for the construction of kitchen waste treatment projects in China.

Abstract:Currently the ultra-low emission of incineration off-gas mainly adopts the following two schemes: Scheme 1, SNCR furnace denitration + mechanical rotary spray semi-dry deacidification + auxiliary dry deacidification + activated carbon adsorption + bag filter + wet deacidification +SCR denitration; Scheme 2, SNCR furnace denitrification + mechanical rotary spray semi-dry deacidification + auxiliary dry deacidification + activated carbon adsorption + bag filter +SCR denitration + wet deacidification. The main difference between the two processes is the different positions of wet deacidification and SCR denitration. Through the detailed analysis of the flue gas experience of the two process schemes and the comparison of their system equipment settings, the system process reliability and operation cost, it is found that Scheme 1 and Scheme 2 all can meet the ultra-low emission requirements of off-gas pollutants. Although Scheme 1 has a high investment in initial stage, the catalyst consumption is less, and there is no need to set a catalyst regeneration device, so the system is more stable and reliable; In addition, according to the 30-year operation life of the waste incineration plant, Scheme 1 can save about 18 million yuan of operation cost. From the perspective of long-term stable operation and cost, it is recommended to adopt Scheme 1 in engineering practice, that is, the SCR denitration system is set after the wet deacidification.

Abstract:This paper introduced the crystallization of equipment and pipeline in the acid-making cleaning system of Yantai Guorun Copper Co., Ltd., analyzed the composition and causes of the crystallization one by one, and finally had the conclusion that the chlorine element in copper concentrete and coals enter the smelting flue gas, and then enter the waste acid in the purification process, and react with calcium hydroxide to form calcium chloride, which leading to the high content of calcium in the reclaimed water returned to the cleaning process, and the formation of calcium sulfate causes the crystallization of equipment and pipeline in the cleaning process. The bench-scale test of removing chloride ion by ultra-high lime aluminum method was carried out, and the results could not achieve the effect in theory. Finally, through the control of raw and auxiliary materials, the chlorine element brought into the cleaning process by off-gas and the content of chloride ion in waste acid and reclaimed water was decreased, which generated less calcium content in reclaimed water and reduced the crystallization of cleaning equipment and pipeline, thus the acid making system can be operated normally and stably.

Abstract:For the traditional production process adopting acid salt washing method to pretreat the ammonium molybdate, strong acid is mostly used to pretreat industrial molybdenum oxide. The wastewater generated from such process contains unreacted strong acid, nitrogen oxides and heavy metals, which are usually treated by chemical precipitation method and such method is easy to cause secondary pollution. Through evaporative thickening and chemical precipitation of the wastewater generated from the ammonium molybdate production line which adopts acid salt pretreatment process, the acid and metal ions are effectively removed, while the generated evaporation condensate and the filtrate resulting from impurity removal can be returned to the acid washing process for recycle, thereby reducing the risk in terms of environmental protection of the acid salt pretreatment process and promoting the advantages of this process in ammonium molybdate production process.

Abstract:The circulating water system of the furnace body supplies cooling water to the industrial furnaces and kilns as well as air blowers in the smelter. As the key auxiliary process of the smelter, this system’s safety and reliability is closely related to the safe and stable operation of the furnaces and kilns. At present, the water pump room of the smelter is often only equipped with conventional detection devices such as liguid level, flow and metor current detection devices, which maily depends on manual inspection, so that there is a large demand for manpower and a lot of maintenace work. Therefore, the circulating water system of the furnace body demands upgrading and transformation for intelligentization and unattended operation. This paper introduced the frome of unattended circulating water system, and discusses the integrated design of unattended circulating water system from the aspects of intelligent upgrading of power supply and distribution, upgrading of detection and automation, as well as green & energy conservation. The unmanned furnace circulating water system should set up a complete sensing detection component and control system. The equipment body, signal detection and perception, power supply and distribution, and process control should be organically integrated to realize the effective integration of intelligent perception, production control, equipment health status assessment and pre-maintenance.