Sustainable Mining and Metallurgy

Abstract:The aluminum industry is the largest source of carbon dioxide emissions in the non-ferrous industry, so reducing carbon emissions in the aluminum industry is an important guarantee for China to achieve carbon peak and carbon neutralization. Based on the carbon emission redution targets of no-ferrous industry and international aluminum industry, combined with the carbon emission status of China’s aluminum industry, China’ s aluminum industry is expected to achieve carbon peak in 2025. The carbon emissions of aluminum industry in China are mainly from raw aluminum production, and the proportion of CO₂ emissions from energy consumption is the largest. There is a large proportion of coal power in the production of electrolytic aluminum in China’s aluminum industry, and the space for the reduction of energy consumption indexes of electrolytic aluminum and alumina is limited. There are still bottlenecks in key carbon reduction technologies, and the production capacity of recycled aluminum is relatively low. In view of the above problems, technical paths such as improving energy utilization efficiency, optimizing industrial structure, optimizing energy structure, and promoting zero-carbon technology innovation are proposed.

Abstract:A large amount of hydrogen-enriched COG will be produced during the coking process of iron and steel plants. To tackle the low utilization rate of the hydrogen-enriched tail gas, a hybrid process combining membrane separation and pressure swing adsorption (PSA) is proposed for hydrogen recovery and is used in the production unit of a large iron and steel complex. Based on the simulation and optimization of the hybrid process with Aspen HYSYS, the effects of membrane feed pressure upon membrane area, hydrogen recovery rate, total power consumption of compressor and annual economic profitability are studied. The study shows that as the increase of membrane feed pressure, the membrane area is gradually reduced, the total power consumption of compressor is ever increasing, the annual economic profit is on the decline, while the hydrogen recovery rate has not been affected. Under the operation pressure of 2500kPa, the membrane area is 550m², the hydrogen recovery rate is 81.1%, the purity of hydrogen product is 99.9%, and the annual economic profit is 5.89×106CNY. By adopting the hybrid process, the hydrogen in COG can be recovered at a high rate and with high purity.

Abstract:The application progress of secondary lead pyrometallurgical process in China was introduced. The principles and process flow of pyrometallurgical processes were detailed, including conventional pyrometallurgical process (such as reverberatory furnace smelting and blast furnace smelting), short kiln smelting, combined smelting, side-blowing bath smelting, bottom-blowing bath smelting, top-blowing bath smelting, etc., and a systematic comparison among these processes in terms of advantages and disadvantages was made. Moreover, a representation was given that the modern intensified bath smelting technology has become a development trend of secondary lead metallurgy in China and has pushed the technical upgrade of secondary lead metallurgical process in China. Side-blowing smelting, bottom-blowing smelting and top-blowing smelting process have become the preferred process of new secondary lead smelting project.

Abstract:Based on study of the space of intensified current and the effect of current intensification on cell heat balance and stability，the current intensification practiced on the 500kA electrolytic cell line of an electrolytic aluminum enterprise in China was done，and the necessary measures to be taken after current intensification were discussed. During the production, by adjustment of process parameters, and the measures such as using “intelligent shelling+slot control” double control system, optimizing voltage, keeping low molecular ratio, high liquid aluminum level, low liquid aluminum temperature and superheat, the current of 500kA cell was increased to 518kA, and the current density was increased from 0.804A/cm² to 0.833A/cm², with good heat balance and stability, energy consumption was reduced by 152kW·h, which demonstrated the feasibility of intensified current applied on the cell.

Abstract:The leachate of the residue from filtration of cyanidation tailings contains high concentration of total cyanide and can’t meet the requirement of relevant technical specification. Therefore, the NaHSO₃-air method is proposed for treating cyanidation tailings. In this paper, the optimal reaction conditions of the NaHSO₃-air method were studied based on test. The study showed that the best cyanide removal effect occurs under such conditions as NaHSO₃ dosage 6.00kg/t, initial pH value 9.5, CuSO₄·5H₂O dosage 300mg/L, no aeration, reaction lasting 2h and reaction temperature at 19℃. After 13 times of closed-circuit circulation under the optimal reaction conditions, the total cyanide in the toxic leachate was less than 5mg/L, meeting the cyanidation tailings treatment standard of TSF in the technical specification.

Abstract:In order to make the smelting flue gas emissions of the four industrial silicon production lines in Yonglong Company of Mangshi meet the current national and local air pollutant emission standards, based on the silicon smelting process, the limestone-gypsum process was used for desulfurization transformation. The cores of desulfurization system were SO₂ absorption system, the limestone slurry preparation and storage system, and the gypsum dehydration system. The flue gas parameters before and after desulfurization were compared. The results showed that the concentration of SO₂ and NO_x in exhaust gas was less than 150mg/Nm³, which was better than the emission requirements of pollutants in key areas. The dust emission was less than 50mg/Nm³, which meet the national and local pollution emission standards.

Abstract:A large amount of high temperature off-gas will be produced during the smelting and thermal insulation of gas-fired aluminum alloy smelting furnace. The off-gas is characterized by a high temperature, large fluctuation and frequent discontinuity, causing severe energy wastage. Based on a comprehensive understanding about the operation characteristics of smelting furnace, a new type of waste heat recovery technology is adopted to recover the off-gas of smelting furnace. This paper discussed the operation characteristics of off-gas collection device for the smelting furnace and design requirements of recovery technology on the off-gas recovery flue and waste heat boiler (WHB) unit. The application of a new waste heat recovery device in an aluminum parts manufacturing company in Nanjing suggested that the new type of waste heat recovery technology can recover the sensible heat of off-gas previously discharged into the atmosphere by the smelting furnace, while the produced steam can be used in corporate production and life so as to achieve the purpose of saving energy and cleaning production environment in the plant, thus realizing efficient and sustainable development of enterprise manufacturing aluminum alloy parts.

Abstract:The operation mode of SO₂ fan for acid-making in Yunnan Tin Company 100000t/a copper smelting project was of soft start on power frequency, which has some problems such as low efficiency, high failure rate and large energy loss. Based on the direct relationship between the rotation speed and the frequency of power supply of asynchronous motor, high voltage frequency converter was selected to carry out speed regulation and energy-saving transformation of SO₂ fan for acid-making. After transformation, the SO₂ fan for acid-making was controlled by high voltage frequency converter, featured by stable and reliable performance. The annual electricity saving was 4260000kW·h, the annual economic benefit was over 1.5million CNY, indicating remarkable energy saving effect.

Abstract:Combining with the features of non-ferrous metal processing industry, this paper discussed the transformer loss and its calculation method. The total active power loss, reactive power loss and active energy loss of SCB11, SCB12 and SCB13 transformers were calculated. Taking SCB11 as baseline, this paper also calculated the payback period of the excess cost of selecting SCB12 and SCB13 transformers. Taking SCB9 as an example, the power saved through replacing high energy consumption transformer to SCB11, SCB12 and SCB13 were also calculated. The calculation results showed that the latest energy-saving transformer should be selected for new construction projects in high electricity price areas; in low electricity price areas, the latest energy-saving transformers should be selected as much as possible if available. Replacing high energy consumption transformer can save a lot of electric energy every year, and the larger the transformer capacity, the more electric energy can be saved. It was suggested that enterprises should replace the high energy consumption transformer with the latest energy-saving transformer with the opportunity of technical transformation and upgrading or site relocation in combination with enterprise development planning.

Abstract:This paper reviewed the development history of hazardous waste industry in China, analyzed the advantages and disadvantages of current industrial hazardous waste disposal technology and highlighted the principle and core development of SCC independently developed by China ENFI as well as its promotion and application in the hazardous waste disposal industry. SSC refers to the injection of oxygen-enriched air and fuel into the bath through the side-blowing lance at an approximately sound velocity, making the fuel fully burnt in the bath and providing energy for the reaction. Meanwhile, the gas injected by lance and produced from combustion stirs the bath and accelerates the heat and mass transfer in the bath. The core equipment for industrial hazardous waste treatment is the comprehensive recovery treatment furnace. SSC is characterized by advantages of strong adaptability of raw materials, high availability, good safety, low dust yield and high recovery date of valuable metals, which can achieve hazard-free disposal of industrial hazardous waste and comprehensive resources recovery.

Abstract:As regards a large amount of sludge produced, undesirable processing effect, low product quality and ineffective realization of waste emulsion recycling concerning the current waste emulsion treatment process, the ultra-filtration plus vacuum flashing process is proposed. This paper introduced pretreatment, process and treatment effect of ultra-filtration and vacuum flashing process, discussed the impact of raw material properties, operation pressure and temperature and vacuum degree on the process, and analyzed the per ton cost of handling waste emulsion. It showed that the greater the COD content of waste emulsion, the smaller the effluent flux of ultra-filtration membrane. As the operating pressure increases, the effluent flux increases, until the operating pressure reaches 0.45MPa, the effluent flux no longer increases. In the actual production, the operating temperature should be controlled at 25-45℃, and the vacuum degree should be appropriately increased. The vacuum ultra-filtration and vacuum flashing process for waste emulsion treatment is characterized by the advantages of low disposal cost, free of additional waste and high product quality, and the waste emulsion can be recycled and utilized to prepare fuel oil.

Abstract:Salt-bearing wastewater from non-ferrous smelter is characterized by a high salt content, complex composition and easy scaling, etc. With a lack of green, efficient and low-cost treatment technology and device, the conventional treatment technology confronts the problems of high energy consumption, limited processing capacity, high operation cost and easy scaling inside the equipment, etc. LTE technology, with exhaust steam as the heat source, is suitable for high salt, high calciumand high ammonia nitrogen waste water treatment. This paper studied the high-salt wastewater (TDS＞100g/L) from a non-ferrous smelter and built a set of LTE equipment with a treatment capacity of 10m³/d, and the pilot test was done. The pilot test result showed that the single-effect LTE evaporation and concentration equipment boasted a processing capacity of 0.32-0.45m³/h, the evaporation capacity was 0.20-0.31m³/h, water yield was larger than 60% and the conductivity of yielded water was stable and less than 60us/cm. The yielded water with a high quality meet the standard of softened water. LTE technology realizes the high-quality recycling of wastewater, characterized by a low operation cost and anti-scale of heat exchange pipe and other advantages.

Abstract:The effluent of a gold mine in Shandong has high COD and cyanide content. To remove/reduce these substances, a pilot test was carried out to compare the oxidation effect of hydrogen peroxide, sodium hypochlorite, and ozone, and the potency of ozone was verified. Then the effect of pH, ozone dosage, reaction temperature and duration upon the oxidation process were studied and optimization was conducted. The study showed that when ozone is injected at 1.5L/min, with pH=11, reaction temperature at 45℃ and reaction lasting 90min, the removal efficiency of COD and CN^- can reach 95.7% and 96.2% respectively, which satisfied the effluent reuse requirements.

Abstract:The process effluent of a ternary precursor manufacturer mainly comes from its extraction system and synthesis system: the sodium sulfate effluent from the synthesis system has high alkalinity, and contains almost no heavy metals or organics; the extraction effluent is more complex, containing impurity organics and ions, including Ni²⁺、Mn²⁺、Zn²⁺、F^-、Cl^-. The impurities, organics, and pH value of the feed solution have a considerable effect on the evaporative crystallization process. Therefore, in the pre-evaporative crystallization treatment process, a series of unit operations were conducted by the manufacturer to remove the organics, heavy metals, and regulate the pH value of the feed solution. The issues in these unit operations were analyzed and suggestions for optimizing the process were made accordingly.

Abstract:The bean processing effluent is a highly bio-degradable organic effluent containing large amounts of substances that can be degraded by microbes, such as plant protein, oxalic acid, and collagen. To facilitate the operation of a bean made noodle plant, a small effluent treatment system needs to be built. The system can process 100m³/d of effluent, following the flotation+UASB+A²/O process. The process design, main structures, and design parameters were described, and process features and parameter controls were analyzed. The process is a mature process, and makes good use of the plant space. The treated effluent can constantly meet the quality standard, and both the capital costs and plant footprint are saved.

Abstract:The structure and function of the refractory of Al-smelting holding furnace, and the characteristics of the refractory failure were described, and the causes of the failure were analyzed in eight aspects, including refractory surface condition, heat impact, static pressure, impurities, mechanic agitation, solid furnace charge, and furnace cleaning. Then suggestions were made on extending the service life of the refractory, including adopting appropriate furnace dimensions, using low-impurity refractory material, improving furnace refractory installation quality, developing an appropriate furnace heat-up curve, using pre-fabricated furnace refractory, controlling the dosage of refining agent and slag cleaning agent, improving the method of charging solids, and improving the operation of agitation and slag removal, establishing an appropriate furnace cleaning regime, and reducing the heat impact of hot aluminum electrolyte on the refractory.

Abstract:The oil film of primary and secondary tilting bearing bush of SVK12-3S centrifugal air compressor in smelting plant of a smelter was studied. After adjusting the boundary conditions, the oil film temperature, pressure and flow rate under different oil inlet temperatures were simulated by modeling and finite element simulation. The simulation results showed that: 1) There were pressure concentration areas in the oil film of the bearing bush, but the pressure distribution of the oil film of the primary bearing bush was all positive pressure, while the oil film of the secondary bearing bush has obvious positive and negative concentration areas, and the pressure difference was large, so it was predicted that the oil film of the secondary bearing bush was easy to break; 2) The change trend of oil film temperature of the primary and secondary bearing bush was basically the same, and the oil film temperature difference of the secondary bearing bush was slightly larger; 3) The oil film velocity of the primary and secondary bearing bushes was basically constant, which was 13.1m/s and 82.0m/s respectively; 4) Compared with the previous three overhauls of a plant, the damage of the secondary bearing bush was worse, which was consistent with the simulation results and verified the reliability of the model. According to relevant research experience, some suggestions were proposed to improve the bearing bush operation, such as monitoring the main parameters such as oil pressure and oil temperature, strictly following the operation rules during start-up, etc.

Abstract:Aiming at the problem of heavy data calculation and accounting load when designers prepare chemical process package, this paper introduced a method of compiling process package by using VBA in cooperation with AspenPlus, AutoCAD and Excel, and took the processing pipe of PID as an example to show how to use VBA program to realize mutual reading, calculation and writing of data among AspenPlus, AutoCAD and Excel. This method can automatically compile the data tables of various enhanced block objects, which saves a lot of time for designers and makes designers focus on the design and optimization of process flow. It not only improves labor efficiency, but also improves design quality, and saves a lot of expenses for purchasing commercial software.