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    15 July 2023, Volume 52 Issue 07
    Review on the Research and Application of Water Spray Dust-reduction Technology in Mines
    JIN Longzhe, LIU Jianguo, LIN Qingxia, ZHOU Yuzhu, LI Gang, WANG Shu, WEI Yixuan, OU Shengnan, WANG Tianyang, WANG Jiahui, WANG Jiahui
    2023, 52(07):  2-17. 
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    With the advantages of simple operation,low cost and high dust removal efficiency,spray has become one of the most widely used dust-reduction technologies in underground mines. However,traditional spray technology generally has the problems of large spray particle size and low removal efficiency for respiratory dust. For the above problems,scholars have carried out extensive research on the spray dust-reduction technology in recent 20 years. However,the research and application status of this technology are rarely reviewed. Based on this situation,according to the relevant literature in recent 20 years,the research status of the mechanism of spray atomization,evaluation parameters and test methods of spray atomization effect,influencing factors of spray atomization effect,and spray dust efficiency and its influene law are summarized. The results showed that:① the evaluation parameters of spray atomization performance mainly include spray particle size,spray speed,and spray range;② Spray atomization performance is closely related to nozzle structure,air and water pressure,physical characteristics of liquid,etc. ;③ The smaller the spray droplet particle size,the faster the droplet speed,the higher the adsorption efficiency of droplet on dust. According to the research status,the current deficiencies are analyzed,and the main research directions for the future are proposed. That is,further explore the mechanism of spray atomization,improve the evaluation parameters of spray atomization performance,standardize the measurement method of spray dust removal efficiency,and pay attention to the impact of spray additives on the workers′ health and working environment.
    Present Situation and Prospect of Mine Geothermal Hazard Control Technology
    LIU Jingxian, LI Guodong, CHANG Deqiang, LI Yuanhui
    2023, 52(07):  18-27. 
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    Mine geothermal hazard is one of the important factors for deep safety mining. Effective and economical mine cooling techniques are particularly important for the safe and efficient mining of deep,high-temperature mines. The types of mine heat sources and the impact of thermal hazard on people are analyzed,and the current state of research on the principles and applications of mine cooling technologies is reviewed. The non-artificial refrigeration technology for the mine with light or shallow thermal hazard is studied,and the various artificial cooling and refrigeration technology for the mine with heavy thermal hazard and deep mine are expounded emphatically. The advantages and disadvantages of cooling technology,individual protective clothing and vortex tube combined with mine microclimate control technology and the progress of application research in the mine site are compared and analyzed. The common problems of the current cooling technologies are pointed out,and the future technical development trend of geothermal control and waste heat recovery and utilization are discussed,so as to provide certain reference for the selection of suitable deep shaft cooling technology. The results show that although the current mine cooling technology is developing rapidly,there are problems such as large energy consumption,complex refrigeration equipment systems and difficulty in maintenance,high humidity in mines that only focus on cooling,failure to fully utilize the geothermal energy value of mines,and less research on special cooling systems for non-coal mines. In view of the common problems of mine cooling systems,it is proposed to develop new energy-saving and efficient cooling technologies,focus on the development of refrigeration equipment,adhere to the principle of both cooling and dehumidification,make full use of mine geothermal energy and design mine cooling technologies for non-coal mines.
    Study Progress and Prospect Analysis of Mine Dust Control Technology Based on Knowledge Graph in China
    LI Gang, ZHOU Zhe, HU Jinhua
    2023, 52(07):  28-39. 
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    With the help of VOSviewer software,the author co-citation,keyword co-citation and other digital characteristics of 1 044 literatures collected in CNKI database from 2000 to 2022 were displayed in the form of knowledge graph. The time distribution of the development in the field of mine dust control was analyzed by bibliometrics method. The study trends and progress of mine dust control are discussed. The study results show that the research on mine dust control from 2000 to 2022 presents an overall upward trend,which can be divided into three stages according to the number of annual publications and the relative number of annual publications,namely,the germination period ( from 2000 to 2005),the rapid development period(from 2006 to 2015) and the take-off period ( since 2016). In addition,the co-citation analysis of 1 831 authors shows that five closely related academic groups have been formed. The co-occurrence analysis of 3 471 keywords shows that there have been five highly correlated keyword clusters,namely,coal mine dust control cluster,dust hazard cluster,dust control cluster, dust concentration cluster and numerical simulation cluster. On the basis of the above analysis,the paper further analyzes the shortcomings of mine dust control research in China at the present stage,namely. ① The conversion rate of dust control theoretical research results needs to be improved;② The precision monitoring technology and system of mine dust need to be further upgraded;③ Under the background of intelligent mine construction,the research and development and application of mine dust intelligent dust removal system need to be further deepened;④ Under the background of green mine construction,social environmental protection requirements are constantly strengthened,which leads to the certain restriction of the application of many traditional and effective dust suppression methods. It is believed that the key development direction of this field in the future can be summarized as:① Deepen the theoretical research on mine dust control,give full play to the advantages of interdisciplinary research,carry out joint research between schools and enterprises,increase the practical application of theories,strengthen the dialogue and combination of theory and practice,and further improve the conversion rate of scientific and technological achievements;② Strengthen the research and development of real-time monitoring and continuous monitoring systems and equipment for mine dust based on accurate dust monitoring and employee health;③ Deepen the construction of precise intelligent dust removal system,improve the accuracy of real-time monitoring of mine dust,and strengthen the depth and breadth of information application;④ Through technological breakthroughs to break the difficult coexistence of environmental protection and economy,reduce the cost of environmental protection,and improve environmental benefits.
    Study Progress and Prospect on Theory and Technology for Dust Prevention and Control in Open-pit Mine of China in the Past 20 Years
    XIAO Shuangshuang, MA Yajie, LI Weiyan, XUE Junhua, LI Kemin, MA Xurong, DING Xiaohua, ZHANG Yonggui
    2023, 52(07):  40-56. 
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    In recent years,a lot of in-depth study and practice have been carried out on the dust prevention and control in open-pit mines in China,and remarkable results have been achieved. However,it is still difficult to completely control the dust in all production links of open-pit mines,and the situation of dust occupational hazard prevention and control is still very serious. In order to further improve the theory of dust prevention and control in open-pit mines and develop emerging technologies, and improve the level and effect of dust prevention and control in open-pit mines in China,based on the study achievements of dust prevention and control theory and technology in open-pit mines in China in the past 20 years,the dust arising mechanism and migration law of each link were elaborated in detail,the prediction,monitoring and early warning technology of open-pit mine dust was systematically summarized,the study progress of dust prevention and control technology was emphatically discussed,and the development trend of dust control in open-pit mines in the future was put forward. At present,the arising mechanism of open-pit mine dust has been clarified in different production links,and the impact of various factors on dust transport has been analyzed. Various nonlinear prediction methods combined with intelligent optimization algorithms have been adopted to construct combined dust concentration prediction models. Online dust monitoring and early warning technology has been developed,gradually forming a dust monitoring cloud service platform,and multi-mode collaborative precision dust control method has been proposed. However,relevant study mainly focuses on the dust in a single production link of open-pit mines. The dust arising mechanism and migration law in each link of open-pit mines require systematic and related study. Green,efficient and economical dust suppressants suitable for various production processes in open-pit mines need to be further developed,precise dust monitoring technology in open-pit mines needs to be further improved,intelligent dust prevention and control technology and equipment urgently need to be tackled,and a dust hazard risk analysis and warning platform needs to be explored and constructed. In the future,multi-disciplinary and multi means are needed to promote the study on dust generation mechanism and migration law in all links,develop green,efficient and economic dust suppressants,develop key technologies and equipment for high-precision,wide range,pollution resistance and continuous online monitoring of dust concentration,develop precise and intelligent control technology and equipment for open-pit mine dust,and build a big data analysis and early warning platform for dust hazard risk.
    Intelligent Variable Frequency Ventilation Control System for Excavation Face Based on Collaborative Prediction of Wind Speed by Environmental Parameters
    JIANG Zhong′an, YANG Xiangdong
    2023, 52(07):  57-65. 
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    In view of the production safety problem that the working point of the traditional local fan will cause real-time deviation with the advance of the driving lane,in order to study the influence of multiple environmental parameters (dust concentration,methane concentration,temperature and humidity,etc. ) on the wind speed of the excavation roadway,explore the way of intelligent control technology to guide the local fan frequency conversion operation,and realize the real-time monitoring, collaborative prediction and frequency conversion control of the ventilation state of the driving surface,an intelligent variable frequency ventilaiton risk control system for driving face was designed. Based on the intelligent control theory,grey correlation analysis algorithm was used to extract the key factors affecting the air demand of the excavation roadway,and the genetic-neural network wind speed prediction optimization model was established with the key factors as the input layer. The monitoring program and remote control interface of Kingview host computer were developed. S7-200 SMART PLC is used to build the intelligent variable frequency pass risk control system based on proportional-integral-differential ( PID) air flow closed-loop control technology. The results show that the genetic-neural network wind speed prediction optimization model can cooperate to predict the wind speed according to the environmental parameters of different working conditions of the tunneling surface. The intelligent variable frequency ventilation control system can monitor the environmental parameters of the underground driving face in real time through the configuration interface,and also provides two remote control methods:automatic and manual. Compared with the constant power supply frequency,PID air volume closed-loop control technology can control the fan air volume by remote intelligent frequency conversion,so that the actual wind speed of the roadway can approach the predicted value continuously and stably. The intelligent variable frequency ventilation control system can be widely used in different types of mines to realize the adaptive control response of ventilation equipment.
    Structural Optimization of Mine Air Cooler Based on Enhanced Heat Transfer and Flow Resistance Characteristics
    DU Cuifeng, JIN Weibo, WANG Jiuzhu, WANG Yuan, DU Shuai
    2023, 52(07):  66-73. 
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    As the terminal equipment of underground water cooling system,mine air cooler is widely used in all kinds of high-temperature mines. In view of the low heat exchange efficiency and cooling capacity utilization of existing mining air coolers,the heat transfer process of surface air coolers is studied from the perspective of tube side and shell side by combining theoretical analysis and numerical simulation. The heat transfer performance of smooth tube air coolers and corrugated tube air coolers is compared,the influence of the wave crest height of the tube side and the arrangement of the shell side tubes on the comprehensive performance (heat transfer performance and flow resistance characteristics) of the mine air cooler is revealed. The results show that the corrugated tube air cooler has better heat transfer performance than the smooth tube air cooler. Changing the wave height can improve the heat transfer characteristics by about 24% ~ 135%,but also increase the flow resistance in the tube by about 176% ~ 767%. Among the five simulated wave crest heights,the bellows with a wave crest height of 3 mm has the best comprehensive performance,and reaches the best performance when the Reynolds number is 4 977,the comprehensive evaluation factor reaches the maximum value of 1. 27. Among the four kinds of pipe arrangement,the heat exchange can be increased by about 13% compared with the traditional in-line arrangement. The research results have certain reference significance for improving the heat transfer efficiency of mine air cooler and improving the high-temperature thermal environment underground.
    Research and Application of High-pressure Atomization Closed Dust Control and Reducing System for Cutting Dust Source of Continuous Mining Machine
    TANG Mingyun, WANG Lele, ZHOU Liang, LIN Hanyi, WANG Hongliang, JIN Jingyan
    2023, 52(07):  74-81. 
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    In order to effectively control the dust in the cutting area of the continuous mining face,aiming at the shortcomings of the traditional spray dust reduction measures of the continuous mining machine,such as poor atomization effect and small coverage,the parameter optimization experiment of the nozzle for dust reduction was carried out,and the equivalent aperture 1. 8 mm fan nozzle with sealing control characteristics and the equivalent aperture 2 mm solid cone nozzle with atomization dust capture characteristics were obtained. Based on the field conditions and continuous mining process characteristics of 15218 continuous mining face in Hongliulin Coal Mine,the dust control design of the cutting area of the continuous mining machine in the working face was carried out,and a new external spray control and dust reduction device of the continuous mining machine was developed. The adjustable ball valve was installed between the atomizing nozzle and the external spray control and dust reduction device,and the combination mode of " external spray control and dust reduction device + adjustable universal ball head + atomizing nozzle" was adopted,which not only reduced the frequent disassembly of the nozzle. The wear of the internal thread of the external spray control and dust reduction device was easy to adjust the spray direction of the atomizing nozzle to meet the dust reduction needs of the continuous mining machine. In order to improve the water pressure of the water supply pipeline of the continuous miner,through the calculation of the water consumption of each device on the continuous miner and the pressure loss along the water supply pipeline of the continuous miner,the booster pump with rated flow of 250 L / min and rated pressure of 6. 3 MPa is preferably used to supercharge the water of the continuous miner,and a high-pressure atomization closed dust control system for the cutting dust source of the continuous miner suitable for the continuous mining face of Hongliulin Coal Mine is formed. The field application shows that after using the system,the total dust reduction rate in the cutting area of the continuous miner is greater than or equal to 82. 3%,and the respirable dust reduction rate is greater than or equal to 72. 5%, which effectively reduces the dust production and overflow in the cutting area,and realizes the closed and efficient prevention and control of the cutting dust source of the continuous miner.
    Experimental Study on Dust Reduction Effect of Air-water Spray in Wet Dust Collector
    JIANG Bingyou, ZHANG Qi, ZHU Zhihui, HUANG Jinshan
    2023, 52(07):  82-90. 
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    In order to improve the dust reduction efficiency of wet dust collector in coal mine and improve the working environment of operators,a dust reduction method of installing internal mixing air atomization nozzle in wet dust collector is put forward. Firstly,based on the laser Doppler spray atomization characteristic test platform,the atomization angle and droplet average diameter D[3,2] of three air cap air atomization nozzles are compared,and the nozzle with the best atomization effect is selected. Secondly,based on the wet dust collector and air-water spray dust reduction test platform,the distance between nozzle and fan,nozzle air supply pressure,nozzle water supply pressure and fan air supply pressure are selected for single factor test, and a single optimal level is obtained. Finally,based on the orthogonal test theory,four factors and three levels of orthogonal tests are designed to carry out dust reduction experiments under different working conditions. The results show that under the same working conditions,the nozzle with 2. 0 mm aperture has the largest atomization angle and the smallest droplet size,and D [3,2] ranges from 33. 20 μm to 50. 51 μm,which is more favorable for collecting and settling fine dust. The order of significance level of dust reduction efficiency of 4 factors for total dust and exhaled dust is:distance between nozzle and fan > nozzle water supply pressure > fan air supply pressure > nozzle air supply pressure. The optimum parameters combination of dust suppression system is as follows:the distance between nozzle and fan is 2. 25 m,the air supply pressure of nozzle is 0. 4 MPa,the water supply pressure of nozzle is 0. 4 MPa,and the air supply pressure of fan is 0. 2 MPa. The dust suppression efficiency of total dust and exhaled dust can reach 90. 06% and 75. 91% respectively. This study results can provide theoretical reference for the optimization and application of mine wet dust removal system.
    Analysis of the Effect of Dust Removal Under the Regulation of Air Flow at the Pressure and Extraction ports of Continuous Mining Face
    QIU Jinwei, ZOU Yun, LÜ Yifei
    2023, 52(07):  91-98. 
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    In order to reduce the dust concentration at the continuous mining face,the effect of adding the vertical downward deflection angle of the extraction and pressure air openings on the dust reduction effect was studied. Taking the 25211 working face of Hongliulin Coal Mine as an example,six parameters,including the diameter of the pressure air cylinder d1,the horizontal deflection angle of the pressure air outlet α1,the vertical downward deflection angle of the pressure air outlet β1,the diameter of the extraction air cylinder d2,the horizontal deflection angle of the extraction air outlet α2and the vertical downward deflection angle of the extraction air outlet β2,were taken as the air flow control parameters,and the dust concentration data after different air flow control parameters were obtained through numerical simulation. Based on the response surface method and particle swarm optimization algorithm,the optimal air flow parameters of the continuous mining face were obtained with the dust concentration at the driver′s position and the height of the breathing zone as the optimization targets. The study results show that the dust concentration decreases by adding the vertical downward deflection angle of the extraction and pressure ducts, changing the pressure and extraction ratio and the position of the pressure ducts from the dust source. The dust concentration at the lower part of the tunnel is higher than that in the upper part of the tunnel in the working space between the continuous mining face and the continuous mining machine. The dust concentration shows a change trend of gradually increasing and then decreasing within 40 m from the headway. The influence of each parameter on the dust concentration at the driver′s position and the height of the breathing zone are as follows:the degree of influence of each parameter on the dust concentration at the driver′s position and the height of the breathing zone is α1 > β1 > d1 > d2 > α2 > β2, d2 > α1 > d1 > β1 > β2 > α2respectively. Based on the above analysis,the best air flow parameter of the continuous mining face is d1 = 0. 9 m, d2 = 1. 1 m, α1 = 0°, β1 = 1°, α2 = 10°, β2 = 8°. The dust concentration at the driver′s position is reduced from 297. 09 mg / m3 to 134. 98 mg / m3 after the control,a reduction of 54. 57%;The dust concentration at the height of the breathing zone is reduced from 217. 35 mg / m3 to 86. 50
    mg / m
    3,a reduction of 60. 20%. The dust concentration in the roadway is effectively reduced and the goal of efficient dust prevention and control at the continuous mining face is achieved.
    Purification Characteristics of Mine Wet Vortex Integrated Dust Collector
    HU Shengyong, SUN Jian, GUO Shuyun, LI Gang, WANG Xiaoguang, HU Bo, WANG Xiaobin
    2023, 52(07):  99-105. 
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    In order to solve the problems of poor dehydration effect and large volume of the existing wet dust collector for mine,a wet vortex integrated dust collector composed of special impeller,anti-blocking nozzle,guide vane,explosion-proof motor,first-stage dehydrator and second-stage dehydrator was developed. Through the process of five-fold dust capture and threefold dehydration,the high purification of dusty airflow is realized. The dust collector integrates three effects of high-energy air suction,cyclone dust capture and two-stage dehydration,and the special impeller is used as both the power component and the atomizing and dust collection component,so the overall structure is extremely simple and integrated. Using the experimental platform for testing the purification performance of the dust collector,the dust removal and dehydration performance tests of wet dust collector were carried out,the dehydration effect of dust collector under different water consumption and dust removal effect of different concentrations were studied. The results show that with the increase of water consumption and dust concentration,the dust removal efficiency of the dust collector first increases and then decreases,and when the water consumption is 1 m 3 / h,the average dust removal efficiency of total dust and breathing dust is the best,reaching above 95. 8% and 88. 6% respectively. With the increase of water consumption,the dehydration efficiency of the dust collector showed an increasing trend, and the average dehydration efficiency reached over 95. 5%. The study results can provide a theoretical basis for the further popularization and application of the developed wet vortex integrated dust collector.
    Test Study on the Optimization of Urea Denitrification and Dust Removal Parameters in Underground Confined Space
    CHEN Xi, LI Weichao, GE Shaocheng, DENG Cunbao, FAN Chaonan
    2023, 52(07):  106-112. 
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    With the continuous improvement of mechanization and automation of mining operations,the underground environment is becoming increasingly complex. In order to carry out mine air purification study,the effects of urea content and air supply pressure on the treatment efficiency of multiphase pollutants were explored. A small experimental bench is built independently to simulate the multiphase pollutant diffusion system in confined space. The response surface center composite experimental method was used to establish the quadratic regression equation to analyze the interaction between experimental factors and determine the best parameters. The results show that the mass fraction of urea solution has the highest influence on the denitration rate,and the dust removal rate can be improved. The air supply pressure affects the atomization effect of the nozzle and has a significant impact on the treatment of pollutants. Excessive air supply pressure will reduce the efficiency of pollutant treatment. The urea content increases,the viscosity of the solution increases,the liquid diffusion coefficient and solubility of NO and NO 2 decrease,and the denitrification efficiency is limited. However,it has a certain effect on PM10 dust control. The interaction of the two factors has different degrees of influence on pollutant control,and has a significant impact on denitration rate and PM 10 dust removal rate,and has little contribution to PM2. 5 dust removal effect. The optimal compatibility parameters determined by response surface analysis were 6. 471% urea solution mass fraction and 0. 603 MPa gas supply pressure. The treatment efficiency obtained by the test operation was basically consistent with the predicted value. This study provides theoretical reference and data support for the further purification of multiphase pollutants in confined space.
    Research on Dust Transport Law of Different Ventilation Methods in Excavation Face
    JING Deji, KAN Qisheng, ZHANG Tian, JIA Xin
    2023, 52(07):  113-119. 
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    In order to solve the problem of serious dust pollution of tunneling face,COMSOL software was used to establish the geometric modeling of 1019 tunneling face in a mine,and based on the k-ε turbulence model and fluid flow particle tracking model were used to calculate the velocity profile,airflow streamline distribution,and dust particle transport trajectory under pressure and long pressure short extraction ventilation methods. The impact of the two ventilation methods on dust particle transport was analyzed,and the dust transport law of the excavation working face was determined under the two ventilation methods. The results show that under the pressure ventilation method,fresh air is compressed into the tunnel by the pressure air duct,forcing the dust on the excavation face to be discharged from the tunnel with the airflow,causing the airflow curve in the front area of the excavation machine to be very dense and forming multiple eddies,causing dust particles to gather at the eddies. At the same time,some dust particles settle at the bottom of the tunnel,and some dust particles move towards the rear along the right tunnel wall,resulting in poor dust control effect. Under the long pressure short exhaust ventilation method,the velocity in the area ahead of the two air ducts is relatively high,and the airflow streamline between the pressure air duct and the exhaust air duct is dense. The compressed air duct blows out the airflow and carries the dust particles,while utilizing the suction effect of the exhaust duct to suck the dust particles into and out of the tunnel. Compared with the compressed ventilation method,the long pressure short suction has a better dust reduction effect.
    Research and Development of a New Drilling Dust Removal Device Based on Water Jet Injection and Dry Mist Dust Reduction Technology
    WANG Tianyang, SHI Jing, ZHOU Yuzhu, JIN Longzhe, LIU Jianguo, LI Gang, SUN Zhucong, LI Jian, CHEN Changling, DING Yao
    2023, 52(07):  120-128. 
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    In order to effectively control dust pollution during dry drilling in underground coal mines,this paper presents a newly designed and developed dust removal device. The development of this dust removal device is based on the analysis of dust diffusion characteristics and it combines the benefits of water jet injection and dry mist dust reduction technology. Theoretical analysis and laboratory experiments were conducted to study the specific structure and main performance parameters of each component of the device. Field tests were conducted in the Yangliu Coal Mine Drilling Yard to measure the dust removal rate of the device. According to the results,the new dust removal device comprises a drilling dust collecting device,water jet ejector,and dry mist dust settling device. These three parts respectively have the functions of dust source sealing,dust extraction and dust capture from drilling holes. The water flow rate,suction volume,and ejection coefficient of the water jet ejector increase linearly with increasing water pressure. The optimal operating parameters for a single dry mist nozzle are an air pressure of 0. 70 MPa and a water pressure of 0. 18 MPa. When the dry mist generator is equipped with 15 nozzles and the dry mist dust settling device is positioned 1. 2 m away from the borehole,the resulting mist field effectively covers all the borehole′s leaking points. Upon field application of the new dust removal device,the total dust removal rates were found to be 88. 9% and 87. 5% at distances of 6 m and 20 m respectively from the downwind side of the drilling rig. These results demonstrate a remarkable dust removal effect.
    Test Method of Sustained Release Performance of Dust Suppressant Components Based on Porous Materials
    LI Ming, YIN Wanjie, TANG Nade, LI Zhi, LI Gang
    2023, 52(07):  129-134. 
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    In order to effectively solve the problem of dust suppressants losing their active components due to erosion by atmospheric precipitation during outdoor use and having a short dust suppression duration,a study approach based on porous materials for the sustained release of dust suppressant components was proposed. Performance evaluation criteria were established for the adsorption rate and release rate of the dust suppressant components,and corresponding indoor standard testing methods were designed. Nylon filter cloth was used to wrap 20 g of porous material with a particle size of 30 ~ 40 mesh. After complete immersion in a 0. 5% concentration solution of polyacrylamide ( PAM) for 90 minutes,the material was dried. The percentage of the mass of adsorbed solute in the porous material to the total mass of the solute was determined as the adsorption rate. The release rate was determined by completely immersing the adsorbed solute porous material in pure water for 10 minutes,followed by drying,and calculating the ratio of the mass of the solute dissolved in the water to the total mass of the adsorbed solute. The application test was carried out by using activated carbon. The results showed that the dust suppressant components based on porous materials exhibited adsorption and sustained release capabilities. The selected criteria for adsorption rate,release rate,and their testing methods were reasonable and feasible. The standardized test procedure constructed demonstrated good operability. The test results also indicated that activated carbon has good adsorption and sustained release performance of dust suppressant.
    Study and Application of Air Fog Vortex Dust Removal Technique in Fully Mechanized Excavating Face
    SI Junhong, WANG Haoyu, HUO Xiaoquan, HU Wei, YUAN Zengyun, FAN Zhihai
    2023, 52(07):  135-141. 
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    In view of the problems of narrow space,large dust production and serious secondary dust pollution in comprehensive excavation working face,taking 42221 comprehensive excavation face of 4-2 coal seam in Chaijiagou Well of Yuhua Coal Mine as an example,the dust distribution law along the comprehensive excavation roadway is analyzed through field measurement. Based on the dust reduction theory of ventilation and gravity and the dust reduction technology of aerosol vortex in comprehensive excavation working face is put forward. Combined with gas-water spray dust reduction and centrifugal force dust reduction,an aerosol vortex generator that can be assembled in parallel is designed,and the motion law of dust with different particle sizes in the aerosol vortex generator is described. Based on the modular design idea,an aerosol vortex dust reduction device for comprehensive excavation face is designed,which is composed of six modules:air flow collection,primary filtration, aerosol agglomeration,vortex separation,gravity ash discharge and secondary mist dust suppression. The influence of water supply and air supply pressure on dust reduction efficiency in aerosol vortex dust reduction device is analyzed by experimental test method,and the relationship between dust reduction efficiency and gas-water ratio and liquid-gas ratio is studied. The results show that with the increase of the distance from the head,the dust concentration of 42221 roadways decreases gradually. The total dust reduction efficiency increases with the increase of water supply pressure and air supply pressure. The respirable dust reduction efficiency increases with the increase of water supply pressure,but it first increases and then decreases with the increase of air supply pressure. The treatment air volume increases with the increase of water supply pressure and air supply pressure. The liquid-gas ratio increases with the increase of water supply pressure,but it gradually decreases with the increase of air supply pressure. When the water supply pressure and the air supply pressure are 0. 4 MPa (the gas-water ratio is 1),or when the liquid-gas ratio is controlled at 0. 070~ 0. 075,the comprehensive performance of the aerosol vortex dust reduction device is the best. Field application results show that the average dust concentration reduction rate of the 42221 comprehensive excavation roadway is about 88%.
    Study on Flow Field Characteristics and Optimization of Metal Fiber Filter
    YAN Cuiping, LI Shilong, MAO Wenhao, JING Jie, FAN Junzhe, LI Hong
    2023, 52(07):  142-152. 
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    In industries such as mining and metallurgy,metal fiber filter are widely used due to their small size and ability to operate at higher filtration velocity. However,under high filtration velocity conditions,the internal flow field of the metal fiber filter has problems such as disordered filtration airflow and uneven distribution of flow field,leading to dust accumulation at the top of the filter bag and ineffective cleaning,which limits the stable operation and advantages of the metal fiber filter. The fluid dynamics software CFD-Fluent was used to numerically simulate the flow field in the dust collector with high filtration velocity. The results indicated that when the inlet air velocity increased from 4. 5 m / s to 8. 9 m / s,the increase in the processing air volume at the upper part of the filter bag increased from 1. 97% to 4. 76%. The distribution uniformity of flow field is poor. Accordingly,the type Ⅰ deflector ( 2 rectangular plates,aligned with the filter bag) and type Ⅱ deflector ( 3 rectangular plates,aligned with the filter bag at intervals) were designed and manufactured,and each deflector model is placed at 0°,10° and 20° with the horizontal plane. The uniformity of flow field was evaluated by comparing and analyzing the flow characteristics,the surface velocity of filter bag and the flow distribution coefficient under 6 optimization schemes. The results show that: ① The optimization effect of the installation model of type Ⅱ deflector is better than that of type Ⅰ ,with the increase of the installation angle,the impact of air flow on the bottom of the filter bag increases,and the optimization effect gradually weakens. ② Type Ⅱ -0 deflector can reduce the standard deviation of the average velocity on the surface of the filter bag to 0. 209 8,a decrease of 47. 4%,and the uneven amplitude of the comprehensive flow field to 0. 003 4,a decrease of 69. 2%. The above results provide a theoretical basis for the structural optimization design of metal fiber filters when treating flue gas at high filtration velocity.
    Development and Application of Combined Device for Air Volume Replenishment and Measurement of Mine Local Ventilator
    ZHOU Wei, LI Gang, JIA Mintao, WU Lengjun, JI Xubo, LIN Xicun, XIE Hui, YU Maojie
    2023, 52(07):  153-158. 
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    If the dust generated during excavation operations cannot be diluted and discharged in a timely manner,it is easy to accumulate and cause great harm to the physical health of the workers. A combined device for supplying and measuring the air volume of local ventilation fans suitable for metal mines has been developed and tested on a -300 m horizontal exploration single end mining face in a gold mine in Shandong Province. The test results show that after the introduction of this device, as the excavation operation progresses,without changing the original number and model of local ventilation fans,the dust exhaust wind speed of the working face is always maintained at around 0. 36 m / s by controllable compensation of the air pressure and air volume in the air duct,meeting the relevant ventilation requirements of the Safety Regulations for Metal and Non-metal Mines (GB 16423-2020). This device realizes the integration of local ventilation fan air supply and measurement,effectively solving the problems of reduced air volume delivered to the working face through flexible air ducts due to longer excavation distance and increased ventilation resistance,as well as low safety and accuracy of air volume measurement. It is of important significance for improving the underground working environment and ensuring the safety production of metal mine single head excavation.
    Study and Application of Ejection Staging Pneumatic Spray Dust Suppression Technology
    TONG Linquan, JIA Xin, SUN Kai, ZHANG Zhen, FAN Jingguang
    2023, 52(07):  159-167. 
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    In order to implement the strategy of " Healthy China" and solve the practical problems of the severe harm of underground dust in mines and the high energy consumption and low work efficiency of traditional wet-type dust removal means,this paper proposed ejection staging pneumatic spray dust suppression technology and developed an ejection grading pneumatic spray dust suppression device. The inner flow field and velocity field of the ejection grading device were analyzed with numerical simulation. The experimental platform for the ejection grading pneumatic spray dust suppression device was constructed,and both the suction air speed experiment and the dust removal experiment were performed to finally determine the spray nozzle and the ejection structure model. Meanwhile,taking suction air speed and dust-reducing effect in the experiment as a key monitoring index,the feasibility of the ejection grading pneumatic spray dust suppression device was explored. The research results showed that ejecting airflow was formed inside the ejection grading device and the air current at the suction outlet moved towards the spray nozzle;The optimal choice of the ejection grading spray dust suppression device was SV980 spray nozzle together with B-type ejection structure model,the highest air speed in the center of dust absorption port was 1. 27 m / s,and the highest air speed in the side wall of dust absorption port reached up to 1. 53 m / s;And the total dust-reducing efficiency,the first-level dust-reducing efficiency,and the second-level dust-reducing efficiency of the B-type ejection structure model reached 83. 9%,76. 6%,and 7. 4%,respectively,which were better than those of single spray nozzle and A-type ejection structure model. The field experiment revealed that the dust-reducing efficiency of total dust and respirable dust at the location of tunneller drivers was 85. 67% and 81. 02%,respectively,suggesting that the proposed device effectively reduces the dust concentration in mines and safeguards the health of staff.
    Delineation of Safety Pillars and Overlying Resource Recovery Technique in Combined Type Shafts of Hard Rock Deposits
    LIU Hailin, LI Pengcheng, WANG Yubo
    2023, 52(07):  168-175. 
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    In order to reasonably set the size of shaft safety pillar in filling mining of hard rock deposit,considering the quality grade of hard wall rock and its own deformation and failure resistance,a combined shaft safety pillar retaining scheme is proposed on the basis of the conventional rock movement angle delineation method. Based on the study background of overlying resource mining in the east main shaft of an iron mine in Shandong Province,the engineering geological zoning and rock mass quality grade evaluation are carried out through field investigation and rock mechanics test. According to the classification results,for the surrounding rocks with quality ratings of class Ⅱ ~ Ⅳ above -250 m,the blockage shape safety ore pillars were delineated by movement angle of rock layers. For the harder rock masses rated as grade -250 m,cylindrical safety pillars were defined with a maximum distance of 80 m from the shaft centerline. In addition,two backfill mining schemes for shaft overlaying resources were designed,that is,the post-filling mining with shallow boreholes and the upward horizontal layered backfill mining. The study results indicated that the displacement of inner shaft walls of the upward horizontal layered backfill mining was 80% that of the post-filling mining with shallow boreholes. However,the shaft deformation caused by the two mining schemes did not exceed the safety standard. The proposed mining scheme of the upward horizontal layered backfill mining and combined shaft safety pillar retaining scheme have been successfully applied in the mine,and the recovered ore volume is about 4 million t,which can provide reference for the mining operation of wellbore overlaying resources in other similar mines.
    Active Advanced Support Technique with Grouting Cables Instead of Hydraulic Props and Supports in Irregular Working Face
    ZHANG Min, WANG Hairui, LIANG Shun, ZHANG Yuan
    2023, 52(07):  176-184. 
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    The few people / unmanned mining operation is one of the core goals for sustained high quality development of all kinds of mines in China. The 206 working face of a mine is an irregular working face with varying face width,and the working face auxiliary transport chute originally used hydraulic brackets and monobloc pillars for overrun support. It requires 2 ~ 4 operators,the technical idea of using slurry anchor cable instead of monoblock and hydraulic bracket for active overrun support was proposed for 206 irregular working face,and the key technical parameters of slurry anchor cable support construction were selected by COMSOL finite element program. The results show that the slurry anchor cable over-supporting condition has small deformation of the surrounding rock in the auxiliary transport chute of the working face,the fissures in the surrounding rock have been effectively filled and cemented,and the anchor cable has a stable load bearing. Finally,the slurry anchor cable has completely replaced the mono-pillar and hydraulic bracket,at the same time,the advanced support section is unmanned,which has greatly facilitated the increase and decrease of hydraulic bracket in 206 irregular working face and ensured the safe and efficient production of the working face. The active advanced support technique has a good reference significance for broken roof, abnormal ore pressure area and metal mine roadway support with higher section size requirements.
    Identification Method of Microseismic Signal and Blasting Signal Based on Improved Energy Extremum Approach
    NI Bin, ZHANG Wei, LIU Xiaoming, WANG Zhao
    2023, 52(07):  185-191. 
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    Microseismic monitoring is an important auxiliary tool for safety and high efficiency mining at depth. However, the real-time data collected by the underground monitoring station network includes microseismic signals,blasting signals,drilling rigs,mine car machinery and equipment noise,and so on. Manual classification of different signals is not only time-consuming,labor-intensive,inefficient and subjective,but also causes great interference to the subsequent microseismic signal pickup and microseismic event location analysis. The signals collected by the microseismic monitoring system in a copper mine were used as the research object,firstly,the signal energy ratio curve within the moving time window was calculated based on the energy extremum method (EEV),and then the number of extremum points on energy ratio curve of different signals,the duration,and the duration between the extremum points and each other were selected as the main three indexes,finally,an automatic identification method of microseismic signals and blasting signals based on the above indexes was developed. MATLAB software was used to analyze and process the data collected at the copper mine,and the results showed that the method can accurately identify microseismic signals,quarry blast signals,excavation blast signals,the recognition accuracy of the signals collected for three consecutive months was 90. 7%,91. 8% and 95. 2%,respectively. The method proposed in this paper could be considered as an alternative tool for microseismic signal processing and has good engineering application value.
    Spatial Attitude Parameter Solving and Free Resistance Distance Blasting Warning Method for Curved Drill Holes in Open-pit Mines
    KAN Yuda
    2023, 52(07):  192-197. 
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    Blasting is an important process in open-pit mining and the analysis of spatial attitude parameters and safety warnings are essential for blasting safety and economy,so it is particularly important to investigate the solution of spatial attitude parameters for open-pit drill holes and their minimum free resistance distance blasting warnings. However,in practice,due to the natural geology and drilling process,some boreholes cannot be drilled in a straight spatial direction and deviate from the drilling track,forming arc-shaped boreholes. This paper proposes a method for solving the spatial attitude parameters of curved boreholes and their free resistance distance blasting warning based on inclinometer and UAV photogrammetry data,which shows that the method can accurately solve the spatial attitude parameters of curved boreholes and achieve free resistance distance blasting warning,which can provide technical support for the open-pit blasting industry. The study results show that the method can accurately solve the spatial attitude parameters of the arc borehole and thus achieve free resistance blasting warning,which can provide technical support to the open-pit blasting operation.
    Test Research on the Physical and Mechanical Properties of Iron Tailing Sand Improved by Clay
    TANG Jinsong, GAO Jinzhao
    2023, 52(07):  198-203. 
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    In order to investigate the influence law of different clay doping on the physical and mechanical properties of iron tailings sand. This paper takes iron tailing sand from a tailing pond in Zanhuang County,Hebei Province as the research object,and studies the influence of clay admixture on the physical and mechanical properties of iron tailing sand through compaction test,California bearing ratio test and conventional triaxial test with the help of the improvement method of external clay admixture. The results showed that:the maximum dry density of the improved soil increases and then decreases with the increase of clay admixture;The admixture of clay in iron tailings sand can effectively improve the California load bearing ratio of iron tailings sand;When the admixture of clay is near the critical point of filling the pores of iron tailings sand,the improved soil is easier to be compacted and its strength and stiffness indexes have the best overall performance.
    Study on Recovery Tests of Uranium and Boron Resources from Iron Tailings of Uranium-bearing Paigeite Ore
    LIU Feifei, LI Lixia, JIN Yuedong, XUE Xiangxin, CHENG Gongjin
    2023, 52(07):  204-212. 
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    Uranium and boron are abundant in uranium-bearing paigeite ore in Wengquangou area,Liaoning Province, which mainly exist in the form of uraninite and ascharite. The grades of U and B2O3 in the tailings of uranium-bearing paigeite ore in a concentrator are 0. 013 3% and 14. 05%. In order to improve the utilization rate of uranium and boron resources in the tailings of iron separation,through the automatic mineral identification and characterization system (AMICS) test,chemical analysis,balance calculation of uranium and boron elements and particle size analysis,the characteristics of mineral existence, particle size distribution,dissociation characteristics and element distribution in the tailings were carried out. According to the tailings properties,the separation process of " gravity-flotation combination" of " enhanced physical field preconcentration of fine uranium and boron minerals,shaking table separation,gravity tailings flotation" was formulated. The test results indicate that:by optimizing centrifugal separation,shaking table separation and flotation,the separation indexes of U grade of 0. 151 8% and U operation recovery rate of 60. 16% in uranium concentrate and B2O3 grade of 14. 76% and B2O3 operation recovery rate of 94. 84% in boron concentrate were obtained. Uranium minerals are mainly distributed in -74 μm fine grains with a U distribution rate of 77. 13%,while boron minerals are mainly distributed in - 38 μm fine grains with a B2O3 distribution rate of 84. 67%. Compared with the original process index,the recovery rates of U and B2O3 in iron tailings are improved,which can increase the benefit of enterprises. The " gravity-flotation combined process" of uranium-bearing paigeite ore iron separation tailings can effectively recover fine uranium and boron minerals,which has reference significance for the recovery of other fine minerals.
    Influencing Mechanisms of Fine Kaolinite on Pyrite Flotation with Seawater
    WANG Zhonghong, LI Yubiao, XIANG Yan, YANG Xu, LI Wanqing
    2023, 52(07):  213-218. 
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    In order to investigate the influence of clay minerals on pyrite flotation in seawater,the flotation tests of pyrite were carried out with different kaolinite content. Zeta potential,pulp foam layer and other tests were further conducted to reveal the mechanisms. The results showed that low kaolinite content did not influence pyrite flotation in seawater while high kaolinite content depressed the pyrite flotation in seawater. Further mechanisms indicated that kaolinite slime can readily cover the surface of pyrite particles or form entrainment to enter into concentrate,further reducing pyrite flotation recovery. DLVO theoretical calculation showed that the kaolinite face mainly covered pyrite surface under weakly acidic condition. Differently,kaolinite interfered with pyrite flotation by mechanical entrainment under weakly alkaline conditions. The research revealed the adverse conditions of pyrite flotation in seawater,providing importantly theoretical support to achieve an efficient flotation of pyrite in seawater,which is helpful to expand the application of high saline water such as seawater in the field of mineral flotation.
    Experimental Study on Low-alkali Separation of a Low-grade Lead-zinc Ore Containing Silver in Northeast China
    CHEN Xiong, HE Mingfei, BU Hao, TANG Youyou, JIA Min
    2023, 52(07):  219-225. 
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    In order to efficiently develop and utilize a low-grade silver-bearing lead-zinc mine in Northeast China,and solve the problems of high lead-zinc concentration,low recovery rate of associated metal silver,and difficulty in direct reuse of wastewater in the on-site separation process,a new low alkaline flotation process was studied on the basis of process mineralogy research,and the appropriate beneficiation flowsheet and reagent system were determined through the lead -zinc flotation condition tests. The results showed that for the raw ore containing lead of 1. 33%,zinc of 2. 51%,and silver of 19. 5 g / t,the leadzinc preferential flotation process was adopted. Under the condition that the grinding fineness of - 0. 074 mm accounted for 75. 42%,sodium carbonate was used as a pH regulator,zinc sulfate and sodium sulfite were used as inhibitors,and aniline+ammonium butyrate black powder was used as a collector. After one roughing,three cleaning and two scavenging lead flotation,the lead concentrate containing lead of 57. 52%,zinc of 4. 84% and silver of 585. 40 g / t were obtained with lead recovery rate of 85. 38% through clear water closed-circuit test,while the recovery of silver in lead concentrate is 57. 63%. The lead tailings were treated with copper sulfate as an activator,lime as an inhibitor,and aniline+butylamine black powder as a collector. The zinc concentrate containing zinc of 51. 85%,lead of 1. 38%,silver of 52. 20 g / t,zinc recovery rate of 90. 71%,and silver recovery rate of 11. 65% was obtained by one roughing,two cleaning and two scavenging zinc flotation. The indexes of lead and zinc using return water were similar to those in clear water. The application of aniline+butylammonium black powder as the lead-zinc flotation collector enabled conventional inhibitors to replace lime or reduce the dosage of lime,thereby achieving the low alkaline lead-zinc separation and enabling the silver enrichment in lead concentrate,and the return water can be reapplied to the production process.
    Optimization of Tower Mill Grinding Power Consumption for an Iron Ore Based on Orthogonal Test
    WANG Ziyang, HAN Cheng, HOU Ying, CHEN Laibao
    2023, 52(07):  226-231. 
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    In order to further realize the energy saving and consumption reduction of an iron ore grinding process,taking the high pressure roller grinding and preselected concentrate of an iron ore as the research object and the grinding power consumption as the evaluation index,orthogonal test method was used to optimize the grinding parameters of tower mill on the basis of single factor test. The results showed that:① The optimum grinding concentration was 60%,the rotating speed of spiral stirrer was 300 r / min,the medium filling rate was 16. 15%,the medium ratio (ϕ8 mm steel ball mass ratio) was 50%,and the ratio of material to ball was 0. 166 4. ② The orthogonal test determined that the appropriate grinding concentration was 60%,the spiral stirrer speed was 360 r / min,the medium filling rate was 20. 77%,the medium ratio (ϕ8 mm steel ball mass ratio) was 100% and the feed ball ratio was 0. 16. ③ The utilization coefficient of -0. 074 mm mill in orthogonal test is 44. 32% higher than that in single factor test,and the grinding power consumption is 9. 68% lower than that in single factor test. ④ The influence of the five factors of tower mill on grinding power consumption from large to small is the grinding concentration,spiral agitator speed,feed to ball ratio,medium filling rate and medium ratio. Orthogonal test optimization further reduces the grinding power consumption of tower mill,and the particle size distribution of grinding products is more uniform,which is conducive to improving the subsequent sorting effect.
    Test Study on Iron Removal from Leaching Solution of Sulfuric Acid Slag Containing Iron,Copper and Cobalt by Hydrolysis Precipitation Method
    CHENG Yanling, SONG Wenqiang, CHEN Guanhua, ZHANG Hanquan, YU Hong
    2023, 52(07):  232-236. 
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    In order to recover copper and cobalt from the leaching solution of sulfuric acid slag containing valuable metals such as iron and copper and cobalt,a hydrolysis precipitation method was proposed to remove iron from the leaching solution with high concentration of iron ions. The effects of the amount of oxidizing agent H2O2,oxidation time,titration temperature,pH value of titration end point and stirring time on the iron removal rate and the loss rate of copper and cobalt were systematically studied. The results showed that the optimal conditions for iron precipitation are H2O2 dosage of 5 mL,oxidation time of 2 h,titration temperature of 70 ℃ ,titration end pH value of 3. 0,stirring time of 1. 0 h. At this time,the removal rate of iron in the leaching solution is 91. 97%,and the loss rate of copper and cobalt are 12. 20% and 12. 04%,respectively. SEM-EDS and XRD analysis results showed that the calcium carbonate iron precipitation residue has a single phase,and the surface of the product is smooth with rod shape and irregular sheet. The main substances of the product are calcium sulfate dihydrate and goethite. In the process of iron removal,a small amount of Cu and Co are adsorbed by the precipitate,resulting in the loss of Cu and Co.
    Experimental Study on Recycling Indium and Zinc from Tin Flue Dust by Using Sulfuric Acid Curing Immersion and Leaching at Atmospheric Pressure
    KE Jingjing, JIN Yan
    2023, 52(07):  237-241. 
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    A tin dust contains Sn of 37. 43%,Zn of 8. 82% and In of 0. 56%,which has a high comprehensive recovery value. The valuable metals indium and zinc were recovered by sulphuric acid-atmospheric leaching process,while tin was effectively enriched in the slag. The optimum parameters were determined by the experimental conditions as curing temperature of 140 ℃ ,curing holding time of 40 min,mass ratio of sulfuric acid to tin smoke and dust of 0. 7 ∶1,leaching time of 1. 5 h,leaching temperature of 90 ℃ ,leaching liquid-solid ratio of 4 ∶1 mL / g. Under these conditions,the average leaching rates of indium and zinc reached 96. 68% and 97. 70% respectively,and the average leaching rates of tin decrease to 0. 52%. Compared with the atmospheric acid leaching process,the leaching rate of indium and zinc can be significantly increased by sulfuric acid curing atmospheric pressure leaching process,and the leaching rate of tin can be significantly reduced,which realizes the efficient separation of indium,zinc and tin.
    Effects of Underflow Orifice Diameter on Density Effect During Classification Process of Multi-component Iron Ore
    ZHANG Caie, SHI Jihong, ZHANG Mingyu, SUN Yicheng, PAN Chengyao, LU Shuaishuai
    2023, 52(07):  242-247. 
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    Aiming at the problem of density effect in the process of cyclone classification of iron ore,according to the lowgrade characteristics of iron ore resources in China,quartz-magnetite (1 ∶1) artificial mixed ore were taken as the research object,and hydrocyclone with diameter 100 mm was used to carry out physical experiments. The influences of changes of the underflow orifice diameter on the particle density effect in the classification process were systematically investigated. The results showed that the recovery to underflow of high-density magnetite component is larger,and the difference of recovery to underflow between high-density magnetite component and quartz component is the most obvious near the middle particle size (45 μm). With the increase of underflow orifice diameter,the difference of recovery to underflow decreases to about 10%. Increasing the diameter of underflow orifice can reduce the difference in cut size and classification sharpness caused by the density effect,and weaken the interaction of different density components due to the density effect. The fine particles (d≤ 20 μm) misplaced into underflow products are mainly composed of high-density fine-grained magnetite component,while the coarse (d>20 μm) particles misplaced into overflow products are mainly composed of low-density coarse-grained quartz component. The research results could provide a theoretical basis for weakening the influence of particle density effect in the classification process.
    Path Planning of Mine Inspection Robot Based on Optimal Genetic Algorithm and Variable Step Size Ant Colony Algorithm
    NIE Xiuzhen, JIAO Yingxue, ZHANG Xia
    2023, 52(07):  248-253. 
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    As an important industrial production base,mine plays an important role in ensuring production safety and improving production efficiency. Traditional mine inspection mainly relies on manual inspection,which has some shortcomings such as high labor cost,low inspection efficiency and safety risk. Therefore,it is of great significance to study path planning algorithm of autonomous inspection robot for mine inspection to improve the technical level of mine inspection. In this paper,a road stiffness planning method of mine inspection robot is proposed,which combines optimal genetic algorithm and variable step size ant colony algorithm. Firstly,genetic algorithm is used to optimize the robot path,and then the optimized path is adopted as the initial path for ant search. In the process of ant search,the step size of ants is adjusted according to the change of current path length to adapt to the search of different path lengths. At the same time,the heuristic information and pheromone updating strategy are introduced to enhance the local and global search ability of ant search. The study results show that the proposed method can find the optimal solution faster,and has better robustness and stability than a single algorithm. By combining the advantages of variable step size ant colony algorithm and genetic algorithm,this method can quickly converge to the global optimal solution,and at the same time improve the search accuracy and convergence speed,which has certain significance for improving the path rule efficiency of mine inspection robots and ensuring the safe and efficient production of mines.
    Isolation of an SRB Strain and It′s Application in Remediation of Coal Gangue Acidification Pollution
    CAI Yun, ZHU Qi, HU Zhenqi
    2023, 52(07):  254-260. 
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    The high salinity acid drainage caused by the oxidation of coal gangue are one of the pollution sources that seriously harm the environmental quality of coal mine area. The use of sulfate-reducing bacteria for biological sulfur fixation can effectively control the acid production and pollution caused by the oxidation of coal gangue. In view of the problem that most of the known sulfate reducing bacteria are strict anaerobic bacteria,depending on external carbon source,and difficult to be applied to open coal gangue mountain,a facultative anaerobic sulfate reducing bacteria was isolated and screened from the soil around the acid coal gangue yard. The 16S rDNA gene sequence,morphology,physiological and biochemical characteristics of isolated strain were investigated,and the column leaching experiments was used to analyze the repair effect of the strain on coal gangue acidification pollution. The results showed that the strain had 99. 93% homology with Bacillus subtilis,and its shape was rod-shaped,with size (0. 4~ 0. 6) μm×0. 2 μm. The optimal growth temperature range of the strain was 25~ 35 ℃ ,and it grew well with pH of 4~ 8. In the absence of any additional carbon source,the pH value of the acidified coal gangue was raised from 3. 09 to 4. 62 after inoculation of the strain for 18 days,and 48. 25% sulfate ions and more than 88. 40% heavy metal were removed,effectively controlling the generation of high-salt acidic wastewater in the coal gangue yard.
    Evaluation of Heavy Metal Contamination and Dietary Health Risk Analysis in the Cultivation Area of Morchella
    ZENG Qinglan, WU Di, YANG Zhen, PU Fumin, XIANG Mei, LIU Xiaoyuan
    2023, 52(07):  261-267. 
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    In order to understand the heavy metal pollution status of morchella and planting areas,soil and morchella fruit samples were collected from Guizhou morchella planting area,the content of Pb,Cd,Cu,Zn,Cr,Hg and As in the samples was measured,and the degree of heavy metal pollution in the soil in the morchella planting area was evaluated by using the one-factor pollution index,the Nemero comprehensive pollution index and the Hakanson potential ecological index. The dietary health risk of heavy metals in morchella was then assessed using the target hazard quotient. The results showed that there were different degrees of heavy metal accumulation and exceeding the standard in the soil and morels in the soil and morels in the three planting areas. The comprehensive pollution index of Nemero showed that 12. 09%,4. 57% and 7. 20% of the planting areas of A,B and C are at the level of mild pollution respectively. The results of the Hakanson potential ecological index showed that the A and C planting areas belong to the medium potential risk level,and the A planting area belongs to the slight potential ecological risk level. The target hazard quotient indicated that the consumption of morchella in the three planting areas will not pose a dietary health risk to adults,but there will be certain As health risks for children eating it in the A planting area. Children in the C planting area consume it,there will be certain Hg health risks. The subsequent planting of morchella in morchella planting areas should pay attention to the control of soil heavy metal pollution,and strengthen the attention and management of the surrounding environment of the planting area.
    Study on Preparation,Properties and Coagulation Mechanism of Composite Polysilicate Ferric Coagulant
    LI Lihui, CONG Zhongkui, CHEN Jianshe, LI Binchuan, LIU Kuiren, HAN Qing
    2023, 52(07):  268-274. 
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    In order to find out the effect of ferrosilicon mole ratios on the coagulation effect of ferrosilicate,six kinds of ferrosilicate were prepared with Na2SiO3· 5H2O and Fe2(SO4)3· 7H2O as raw materials,and the phase and microscopic morphology of ferrosilicate were characterized by XRD,SEM and FTIR. The effects of ferric polysilicate dosage,pH value,stirring time and other process parameters on COD removal rate were systematically studied. The results showed that:① Ferric polysilicate has a polycrystalline phase structure. With the increase of the material ratio of ferric silicate,the surface morphology changes from hollow tubular to sheet. ② With the increase of ferrosilicon mole ratios,the content of Fe(Ⅲ ) free ion and mononuclear hydroxyl complex in ferrosilicate decreased,and the electric neutralization ability of ferrosilicate decreased;The adsorption and bridging capacity of ferric polysilicate was improved with the increase of silicate polymer content. ③ For the water samples prepared by sodium butyl xanthate and No. 2 oil,the removal rate of COD could reach 48% when the dosage of ferric silicate is 4 mmol / L,the pH value is 5. 0 and the stirring time is 20 min. Compared with Fe2(SO4)3· 7H2O and polysilicic acid,the coagulability of polysilicic iron is obviously improved,and the electric neutralization and adsorption bridge work together during the coagulation process.
    Effect of CeO2 Doping on the Structure and Properties of CMAS Glass-ceramics
    XU Wence, CAO Zhao, MA Rui, OUYANG Shunli
    2023, 52(07):  275-282. 
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    Resource utilization of solid waste is an effective way to promote sustainable social development and environmental protection, the CaO-MgO-Al2O3-SiO2 ( CMAS) system glass-ceramics was prepared by conventional and microwave treatment using iron tailing and fly ash as the main raw materials. The effects of different CeO2 contents on the crystallization kinetic parameters,crystallization behavior and properties of glass-ceramics were investigated. The results showed that the improvement of CeO2 content led to the enhancement of the stability and polymerization of the glass and the gradual improvement of the crystallization temperature. However,CeO2-independent crystallization appeared in the conventionally treated samples with 4% CeO 2 content. Raman spectroscopy analysis revealed that the microwave treatment increased the [CeO4]content in the glass,which prompted the coupling of [CeO4]with metal cations and inhibited ion diffusion. The mechanical property tests revealed that the strength and toughness of glass-ceramics were enhanced when the doping amount of CeO2 was 2%. However,the mechanical properties of the glass-ceramics decreased as the CeO2 content increased.
    Study on Rheological Properties and Mechanical Properties of Cement Grouting Material Prepared by Gold Tailing Sand
    WANG Changjun, HU Zhigang, XU Dandan, JI Tianhong, SUN Zhihua
    2023, 52(07):  283-290. 
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    The cement grouting material with excellent rheological properties was prepared by gold tailing sand with a fineness modulus lower than 0. 7 to improve the performance of the grouting material and to realize the resource utilization of solid waste in response to the problems of high cost and unstable volume of underground space plugging grout. The particle distribution,chemical composition,mineral composition and particle morphology of gold tailing sand were determined, and the effects of additive admixture and water-binder ratio on the rheological properties and mechanical properties of gold tailing sand cement grouting material were investigated systematically by single-factor test,and the influence of water-binder ratio on mechanical properties was revealed by SEM analysis. The results showed that the fine-grained and angular gold tailing sand with quartz as the main mineral,and the flow degree of cement grouting material can reach up to 335 mm when the surface of the tailing sand is modified by admixture,the fixed cement sand ratio is 1 ∶1. 5 and the control water-binder ratio is 0. 35. The maximum flexural strength of the cement grouting material was reached at a controlled water-binder ratio of 0. 31,with flexural strengths of 6. 87,8. 87 and 10. 5 MPa at 3,7 and 28 d,respectively,and the compressive strength of the cement grouting material reached the maximum at a water-binder ratio of 0. 32,with compressive strengths of 43. 1,59. 0,and 69. 0 MPa at 3,7 and 28 d,respectively;The brittleness coefficient of gold tailing sand cement grouting material decreases with the increase of waterbinder ratio,and the lowest 28 d brittleness coefficient is 5. 58. The SEM analysis showed that with the increase of water-binder ratio,the calcium alumina ( Aft) phase increases,the brittleness coefficient decreases and the toughness increases,but too much Aft phase led to the loosening of the structure and the decrease of strength.
    Study on Electrical Properties of Graphite Solid Waste-Based Electric Heating Plates
    ZHANG Qiankun, REN Zijie, LIU Yuhang, GAO Huimin, LÜ Yang, LI Xiangguo
    2023, 52(07):  291-295. 
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    Adding graphite to the cement mortar system can make a heating plate with better performance. In order to explore the relationship between heating and volume resistivity of graphite electric heating plates under different external electric fields,different humidity and temperature conditions,graphite solid waste,graphite beneficiation tailings and spherical graphite tailings were used to prepare electric heating plates,and different methods such as experiments and statistical analysis were used. The results showed that the AC voltage has a better heating effect on the graphite electric heating plate,and the resistivity and heating performance of the electric heating plate are stable after the addition of spherical graphite tailings reaching the percolation threshold (9% graphite content). In the range of ambient temperature 10~ 30 ℃ and ambient humidity 20% ~ 80%, the resistivity is maintained at about 2. 5 Ω· m,which is not easily affected by factors such as ambient temperature and humidity,and is low in cost and easy to apply.
    Effect of Iron Tailings Content on the Anti-deterioration Performance of Concrete under the Combined Action of Freeze-thaw Cycles and Sulfate Corrosion
    CHEN Yueyu, GUO Haiyan
    2023, 52(07):  296-300. 
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    In order to study the deterioration mechanism of concrete under the freeze-thaw cycle of sodium sulfate,the loss rate of mass,compressive strength and relative dynamic elastic modulus of iron tailings concrete were tested,and a freezethaw damage model based on Weibull distribution was established. The results show that when the replacement rate of iron tailings is 60%,the quality loss of iron tailings concrete is 1. 7% after 150 freeze-thaw times. The compressive strength loss rate of iron tailings concrete increases with the increase of freezing and thawing times. After 60 freeze-thaw cycles,the compressive strength loss rate of IC15 iron tailings concrete and IC45 iron tailings concrete is significantly lower than that of ordinary concrete. The relative dynamic elastic modulus loss of IC30 group iron tailings concrete is the smallest,while the relative dynamic elastic modulus loss of IC60 group iron tailings concrete is the largest. When the freeze-thaw cycle is 0~ 30 times,the relative dynamic elastic modulus decreases slowly and the loss is small. When the replacement rate of iron tailings is 30%,the relative dynamic elastic modulus loses the least,and the freeze resistance and sulfate resistance are the best. The freeze-thaw damage model of iron tailings concrete under the combined action of freeze-thaw cycle and sulfate erosion accords with Weibull distribution,and the correlation coefficient R2 is greater than 0. 96.