Sustainable Mining and Metallurgy

Abstract:Active Ti (IV) salt was used in tests to separate and recover As and Bi from the white dust leaching solution, test conditions of As adsorption and desorption were optimized, and the impact of recycling adsorbent on As adsorption was investigated. The test results demonstrate that active Ti (IV) salt can adsorb As in the white dust leaching solution and the optimal test conditions are the liquid-solid ratio of 14∶1, reaction temperature at 60℃, agitation speed at 100r/min and reaction duration of 1.5h. Under such conditions, the As concentration of leaching solution can drop from 8.33g/L to 0.69g/L, achieving an As removal rate of 91.7% and Bi loss rate of less than 2%. The optimal test conditions for desorption of As-loaded adsorbent are the liquid-solid ratio of 3∶1, sodium hydroxide concentration of 80g/L, reaction temperature at 40℃, and reaction duration of 0.5h. Under such conditions, the As desorption rate reaches 99.1%. The regenerated adsorbent of titanium salt can still remain quiet active even after 5 cycles of adsorption and desorption. When the amount of iron powder reductant added to the solution after As removal is 1.2 times the theoretical one, sponge Bi with purity higher than 92% can be obtained and the total recovery rate of Bi can surpass 95%. These tests have accomplished separation of Bi and As from the hydrochloric acid system, shortened the process flow of Bi recovery, and provided a new method for treatment of As-containing solution from nonferrous metallurgy.

Abstract:Arsenic sulfide residue produced from sulfidization of As-containing acidic wastewater contains a high As content, categorized as typical hazardous waste. In this paper, the hydrogen peroxide oxidation process was adopted to treat arsenic sulfide residue and produce sulfur residue and As-rich solution that is reduced by sulfur dioxide to generate the arsenic trioxide product. Optimal reaction conditions were obtained through tests on oxidation leaching process. The dosages of sulfuric acid, industrial grade hydrogen peroxide and catalyst should be 10%, 30% and 0.1% of the amount of arsenic sulfide residue respectively. The liquid-solid ratio should be 1∶1, temperature should be at 85℃ and reaction duration should be 2h. Under such conditions, the As removal rate can exceed 93%, and the arsenic trioxide product obtained from reduction of As-rich solution is up to the As₂O₃-1 requirements stipulated in GB 26721—2011.

Abstract:The purification process of zinc hydrometallurgy in a smelter has the problems of high content of zinc and codmium and low grade of lead. The main reasons are that the particle size of alloy zinc powder used for purification is coarse, the efficiency of cadmium removal in the first stage purification is low, cobalt is enriched in the system, and the leaching rate of cobalt and nickel slag is low. In view of the above problems, the purification process was optimized : the screening process of alloy zinc powder was increased, the original one-stage purification process of copper and cadmium was changed to the two-stage copper and cadmium removal processes, the high cobalt slag and electrolytic zinc anode slime were combined for multiple high temperature and high acid oxidation leaching, and the lead slag washing process was increased. After the process optimization, the amount of lead slag produced by the comprehensive recovery of cobalt-nickel slag decreased by more than 60%, the lead grade reached more than 35%, the zinc content decreased to about 10%, and the zinc recovery rate reached more than 91%. This technology comprehensively recovers valuable metals with remarkable benefits, and achieves the goal of energy conservation, emission reduction and environmental friendliness.

Abstract:A large amount of gypsum produced during the waste acid treatment of a copper smelter is disposed as for sale, producing minimal benefit. In this paper, the production process of gypsum during acid making process was introduced; based on the property of gypsum that CaSO4 as its main composition is decomposed into CaO, SO2 and O2, and combining the high temperature conditions of flash converting furnace, the comprehensive utilization of gypsum was conducted; moreover, the influence of gypsum blending on flash furnace process, problems in gypsum recycling and corresponding optimization measures were set forth. The calcium oxide produced in the pyrolytic reaction of the blending of gypsum and pulverized coal in the flash furnace can be used to replace the quick lime required for production; the sulfur dioxide produced in the reaction is converted to sulfuric acid during the follow-up off-gas acid making process, increasing the output of sulfuric acid as a byproduct; the oxygen produced in the reaction can reduce the oxygen consumption in copper smelting. The comprehensive utilization of gypsum not only solves the environmental protection related issues of enterprises but also brings considerable economic benefits.

Abstract:In this paper, the causes of secondary pollution resulting from hazardous wastes incineration in rotary kiln were analyzed, and a cooperative hazardous wastes treatment scheme by “rotary kiln incineration + side blowing furnace smelting” was proposed to eliminate the secondary pollution resulting from rotary kiln incineration; finally, a study was made on the scheme from the aspects of environmental protection, investment and return on investment. The study shows that the secondary pollution is mainly caused from the complex compositions of hazardous wastes, the incineration temperature of rotary kiln is relatively low and cant reach the value needed for vitrification of those materials with high melting points. While in the process of “rotary kiln incineration + side blowing furnace smelting”, the smelting slag has been vitrified, the hazardous elements therein have been solidified in the vitreous slag, without permeation into the natural environment, and the smelting slag becomes general solid waste. The process has efficiently solved the secondary pollution caused by rotary kiln incineration. By adding cost of about 10% on the basis of the rotary kiln incineration system, good environmental and economic benefits can be obtained.

Abstract:Ultrafiltration technology is widely used in water treatment, and coagulation pretreatment is one of the effective technologies to control ultrafiltration membrane fouling. In this paper, the characteristics and influencing factors of Bisphenol A (BPA) removal by coagulation, ultrafiltration and coagulation-ultrafiltration were studied. The results show that the removal of BPA by aluminum sulfate coagulation is limited. When the dosage of aluminum sulfate is 15mg/L and pH value is 7, the removal rate of BPA is the highest, and the Zeta potential is close to the isoelectric point. Increasing humic acid concentration is not conducive to BPA removal. In the study of influencing factors of ultrafiltration, the smaller the initial BPA concentration and the smaller the pore size of ultrafiltration membrane , the higher the removal efficiency of BPA. When the pH value is close to the acid dissociation constant of BPA, the removal effect of BPA becomes worse. Compared with the single coagulation or ultrafiltration process, the removal rate of BPA of the combined coagulation-ultrafiltration process is higher, which indicates coagulation preteatment has good effect and is beneficial for reducing membrane fouling. With the increase of aluminum sulfate dosage, the removal effect of BPA by coagulation-ultrafiltration combined process is enhanced. With the increase of initial concentration of pollutants, the removal rate of BPA decreased.

Abstract:As the critical infrastructure of the new electrical power system with new energy playing a leading role, energy storage is a requisite for large-scale application of new energy and thus carbon neutrality. Among all current energy storage technologies, lithium battery storage is seen as the most likely to accomplish large-scale commercialization. This paper analyzed the status quo of lithium battery storage industry, studied the trend and market share of this industry, and put forward countermeasures to promote its sound development.

Abstract:In this paper, the functions of main elements and compositions of the concentrate fed for ISA copper smelting were studied; based on production practice, a comparison was made between two blending modes for their influence on ISA copper smelting, so as to find a more suitable and favorable blending mode for ISA copper smelting. The two modes are respectively as blending with sulfide ore only and blending with sulfide ore and oxide ore. The comparison results show that adding a proper proportion of copper oxide ore in copper sulfide concentrate can make the Fe, S and SiO₂ content in the feed closer to the production process requirements and result in lower consumption of auxiliaries, increased smelting and converting efficiency, improved production capacity and process balance rate, reduced heat energy waste in smelting and reduced energy consumption.

Abstract:Many electrolytic aluminum enterprises use a large number of alumina rich in Li and K for production. Li and K enrichment significantly change some physical and chemical properties of the electrolyte, affecting electrolysis production. This paper discussed the effects of LiF and KF on the physical and chemical properties of electrolyte phase, primary crystal temperature, conductivity, density, dissolution loss of aluminum and dissolution of alumina, as well as the influence on aluminum electrolysis production. In view of the influence of Li and K enrichment on aluminum electrolysis production, relevant production technical measures were summarized.

Abstract:Carbon dross is a hazardous solid waste produced in aluminum electrolytic cell production. A combustion test of carbon dross in Muffle furnace has been conducted. The test results show that when no covering material is added, carbon dross is barely combustible at the temperature of below 500℃; at 500℃, carbon dross starts to be combusted; at 600℃, it takes 5h for full combustion of carbon dross; at the temperature of above 700℃, only 2h is needed for full combustion of carbon dross, and the electrolyte in carbon dross is molten and becomes coked after cooling. In case of adding covering material, both carbon dross and covering material have no change at the temperature of below 500℃; at 550℃ with the combustion lasting 8h, carbon dross takes on grey white and is completely combusted; at the temperature of above 600℃, carbon dross speeds up combustion and is fully combusted after 5h; at the temperature of above 700℃ with the combustion lasting for more than 3h, carbon dross and covering material are molten and bond with each other, resulting in lower oxygen concentration and hindering carbon combustion. The pre-baked anode of electrolytic cell can provide the temperature and oxygen conditions required for carbon dross combustion. Carbon dross on the replaced anode can be combusted completely by using the heat energy released by the anode. The practical application in high and low lithium salt electrolyte system aluminum electrolysis series has proved that zero discharge of carbon dross can be realized by carbon dross combustion.

Abstract:Based on production practice, this paper expounded structural features of furnace profile, process technical indicators and process control of the continuous copper smelting practice using three furnaces in Yantai, China, and point out the difference between this process and the traditional copper smelting process. This process truly accomplishes continuous copper smelting, featuring more reasonable furnace profile and structure, optimized production indicators, lower one-off costs, higher degree of intelligence, greater safety and environmental protection.

Abstract:Two on-line oxygen concentration analyzers were installed respectively at the waste heat boiler outlet and the electrostatic precipitator (ESP) outlet of a company s smelting dust collection system. In this paper, the influence of oxygen concentration on the sulfur content in the white dust collected by the ESP, the dust discharge and electric field operation of the ESP, the efficiency of arsenic recoverer and the amount of waste acid resulting from non-ferrous smelting were analyzed; the application of oxygen concentration analyzers was introduced. Production practice shows that the grayness of white dust and detected oxygen concentration data can be based on to realize accurate adjustment of process parameters, guarantee a stable sulfur content in the white dust collected by the ESP, and control the ESP voltage within an optimal range. As a result, the dust collection efficiency is improved significantly, the purity of the dust collected in downstream arsenic recovery process is increased efficiently, and waste acid amount from the acid-making system and waste acid treatment cost are reduced.

Abstract:The heavy metals in dilute acid were removed and recovered by the vulcanization method. The hydrogen sulfide was prepared by the reaction of sodium hydride and sulfuric acid. The by-product sodium sulfate solution was prepared into sodium sulfate solid by evaporation crystallization device. In view of the problems existing in the existing three-effect evaporation device, such as pipeline blockage, high salt content of evaporative condensate water, too fine crystal particle size, and mother liquor running and mixing, the equipment structure and process flow were optimized: the salt leg was designed at the bottom of the primary and three-effect separators,and each effect circulating pump was changed to the axial flow pump with large flow rate and low head, and the storage volume of the crystal evaporation chamber was increased. After the optimization, the evaporation crystallization system runs continuously and stably, the driving rate is improved, and the salt content of condensate water is less than 0.1g/L.

Abstract:This paper elaborates on the process control of large-plate lead electrolysis, including impurity control in the early stage of large anode plate preparation, quality requirements for starter sheet preparation process, loading large plates into the cell and the electrolyte, control over the circulation speed and temperature of electrolyte, and purification of anode slime washing water. This process control can reduce the impact of impurities, improve the quality and quantity of precipitated lead, lower DC power consumption and thus achieve energy conservation and consumption reduction.

Abstract:A wastewater treatment plant in northern China adopted the AAO process in the past to ensure that the outlet water was in compliance with the first-level A standard regulated in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant. Now, to reduce pollution to water body, indicators of COD_Cr, NH₃-N and TP in the outlet water should be improved to comply with the Grade V water standard stipulated in Environmental Quality Standards for Surface Water. Due to the improvement of effluent standards, the sewage plant needs to be upgraded. Comparison of influent and effluent indexes showed that NH₃-N and TP should be focused on. Without adding new structures, MBBR packing is applied to partial gallery of the original oxic tank and AAO tanks were rezoned for 5-stage AO process. In the meantime, the blower room, aeration system, sludge dewatering system and other systems were also upgraded. After upgrade, After the transformation, the indexes of the effluent reached the standard stably, indicating that the process had strong stability and impact resistance.

Abstract:China’s relevant standards stipulate that the volume of the main control temperature zone in the incinerator furnace should meet the requirements that the residence time of flue gas above 850℃ is greater than or equal to 2s under the most unfavorable conditions. At present, the main control temperature zone of mechanical grate furnace in domestic waste incineration power generation industry mainly has two types: single flue and main and auxiliary flue. In this paper, by studying the relevant specifications and combining the characteristics of these two types of furnaces, the calculation of flue gas residence time of single flue and main and auxiliary flue was discussed, especially for how to meet the requirements of 850℃/2s for the flue gas residence time of the incinerator with the main and auxiliary flue, the starting point of the calculation was analyzed and studied, and the solution to the controversial point was given.

Abstract:As rectifier units are crucial equipment to provide energy for the Cu electrolysis plant, the reasonable selection of such units bears on the reliability and cost-effectiveness of corporate production. This paper expounded the determination of all important parameters of rectifier units, including primary side voltage of rectifier transformer, DC voltage of rectifier, the number of rectifier phase, the form of rectifier circuit, the connection mode of rectifier transformer and rectifier, and the capacity of rectifier transormer. In addition, this paper took a Cu electrolysis project as an example to conduct selection and parameter calculation of rectification devices.

Abstract:In the 300000t/a production area of the electrolysis plant in a certain metallurgical plant, the compressed air system is confronted with such issues as high moisture content in air supplied by compressor units, high power consumption and high failure rate of air compressors. By optimizing the equipment, pipeline, management mode of the compressed air system, the issue of water entrained in compressed air was addressed, and the equipment failure rate and energy consumption were reduced.

Abstract:Taking the distributed photovoltaic power generation project with installed capacity of 36MWp as an example, this paper introduced the available access voltage level scheme, and according to the influence of distributed photovoltaic power supply access to the distribution network on the voltage rise of the grid connection point, 10kV voltage level was selected to connect to the grid, and a distributed power supply access system scheme was given, and the conductor cross section was verified. Finally, combined with the actual work, the primary design points of distributed photovoltaic power supply were summarized, including the main wiring design，the selection of high voltage side fuse and low voltage side circuit breaker.