Application of foam technology for dust control in underground coal mine

In order to effectively control the dust in the underground coal mine,this study proposes and develops a new technology for dust control by foam,and briefly demonstrates the advantage of the foam technology for dust control,such as the good isolation performance,large contact area,high wetting ability,strong adhesion and so on.Besides,the details of the technology are introduced,including the foam agent,foam generator,and foam production process.Then the paper studies the relationship between the foaming agent concentration and liquid surface tension,and explains the principle of the foam generator.The technology is applied in heading face.The application results show that the foam has a remarkable effect on dust control in underground coal mines.

A comparative study of dust control practices in Chinese and Australian longwall coal mines

Mine dust is one of the main hazards in underground longwall mines worldwide.In order to solve the mine dust problem,a significant number of studies have been carried out regarding longwall mine dust control,both in China and Australia.This paper presents a comparative study of dust control practices in Chinese and Australian longwall mines,with particular references to statutory limits,dust monitoring methods and dust management practices,followed by a brief discussion on the research status of longwall mine dust control in both countries.The study shows that water infusion,face ventilation controls,water sprays,and deep and wet cutting in longwall shearer operations are commonly practiced in almost all underground longwall mines and that both Chinese and Australian longwall mine dust control practices have their own advantages and disadvantages.It is concluded that there is a need for further development and innovative design of more effective dust mitigation products or systems despite the development of various dust control technologies.Based on the examinations and discussions,the authors have made some recommendations for further research and development in dust control in longwall mines.It is hoped that this comparative study will provide beneficial guidance for scholars and engineers who are engaging in longwall mine dust control research and practice.

A new design of foam spray nozzle used for precise dust control in underground coal mines

In order to improve the utilization rate of foam,an arc jet nozzle was designed for precise dust control.Through theoretical analysis,the different demands of foam were compared amongst arc jets,flat jets and full cone jets when the dust source was covered identically by foam.It is proved that foam consumption was least when an arc jet was used.Foam production capability of an arc jet nozzle under different conditions was investigated through experiments.The results show that with the gas liquid ratio(GLR)increasing,the spray state of an arc jet nozzle presents successively water jet,foam jet and mist.Under a reasonable working condition range of foam production and a fixed GLR,foam production quantity increases at first,and then decreases with the increase of liquid supply quantity.When the inner diameter of the nozzle is 14 mm,the best GLR is 30 and the optimum liquid supply quantity is0.375 m^3/h.The results of field experiments show that the total dust and respirable dust suppression efficiency of arc jet nozzles is 85.8%and 82.6%respectively,which are 1.39 and 1.37 times higher than the full cone nozzles and 1.20 and 1.19 times higher than the fiat nozzles.

PARTICLE ELECTROSTATIC COAGULATION AND ITS APPLICATIONS IN DUST CONTROL

Fine particulates instead of others create particulate pollution and they are easier to escape from almost all conventional collectors of low-or medium-efficiency. It is of practical significance to take full advantages of particle coagulation by electrostatic forces to upgrade the collentors' performance. This paper investigates the main mechanisms of coagulation, an possiboie trostatic forces existing in the collectors and their effects on the particle coagulation. To make particle kinetic coagulation electrostaticaUy enhanced be a step of the conventional collectors' operations,certain conditions should be created through some modifications of the collectors. Based on that, the authors suggest that a precharger electro-cyclone technique be applied to improve the performance of common cyclones still widely used in many places. And a preliminary semi-industrial test has been carried out at Jiawang Power Station, Xuzhou, Jiangsu Province, and the results show that the modified cyclone increases its efficiency from about 800% to. 92-94%.

Remote Monitoring of Surfaces Wetted for Dust Control on the Dry Owens Lakebed, California

Extensive dust control on the dry Owens Lake mainly uses constructed basins that are flooded with shallow depths of fresh water. This dust control is mandated by law as a minimum percent of the area of each individual wetting basin. Wetted surfaces are evaluated for area and degree of wetness using the shortwave infrared (SWIR) band of Landsat TM, or similar earth observation satellite sensor. The SWIR region appropriate for these measurements lies within the electromagnetic spectrum between about 1.5 and 1.8 μm wavelengths. A threshold value for Landsat TM5 band 5 reflectance of 0.19 was found to conform with surfaces having a threshold for adequate wetting at a nascent point where rapid drying would occur following loss of capillary connection with groundwater. This threshold is robust and requires no atmospheric correction for the effects of aerosol scatter and attenuation as long as the features on the image appear clear. Monthly monitoring of surface wetting has proven accurate, verifiable and repeatable using these methods. This threshold can be calibrated for any Earth observation satellite that records the appropriate SWIR region. The monitoring program is expected to provide major input for the final phase of the dust control program that will have a focus to conserve water and resources.

Remote Monitoring of Vegetation Managed for Dust Control on the Dry Owens Lakebed, California

A monitoring program was developed to assess the cover of saltgrass managed for dust control on the saline dry Owens Lake. Although the original intent was to manage the vegetation as total cover that included green and senesced leaf and stem material, aged leaves that make up a large proportion of total cover were not differentiable spectrally from the background salt and lakebed. Hence, greenness-based indices were explored for detection of plant recruitment. Since all plant cover begins as green and growing, greenness indices provide a measure of all future cover whether living or senesced. The criteria for judging compliance were changed so that spatially variable vegetation cover measured as a milestone will need to be met in the future. A derivative of NDVI, NDVIx, calculated using scene statistics, proved highly accurate, to about 0.001 of this index and with an average signal to noise ratio of 64. This high level of accuracy allowed detection of small changes in vegetation growth and vigor. Performance according to the benchmark-as-par standard was determined through combined use of cumulative distribution functions and derivative maps.

Characteristics of dust distributions and dust control measures around road-header drivers in mining excavation roadways

In the present study,a numerical simulation method was adopted in order to examine the characteristics of dust dispersion during continuous dust release periods(CRP)and stop dust release periods(SRP).The purpose was to analyze the dust distributions and migration actions around road-header drivers in excavation roadways,and then determine effective dust control measures for underground coal mines.This study’s simulation results showed that the dust concentrations continuously increased,and then gradually reached a stability level during the CRP.During that time,the locations of the drivers were always at the intersection of the original migration dust and the backflow dust,and the drivers were invaded by these two strands dust.However,during the SRP,the dust concentrations gradually decreased under the actions of the roadway ventilation.Besides,obvious backflow phenomena were observed around the road-header during the SRP.The locations of the drivers were still within the backflow paths of the high dust concentrations.At the present time,dust separation and extraction systems have been implemented in coal mines,including vacuuming and air knife devices,which are designed to control the dust around the road-header drivers.The field applications of these systems were conducted in the 26 mechanized excavation faces of the Zhangcun Coal Mine.The results revealed that the use of these dust removal systems could effectively reduce the dust concentrations around the road-header drivers.In the present study,the dust removal rates during the CRP and SRP were determined to reach up to 88.7% and 94.6%,respectively.Therefore,the results of this research study provided effective theoretical guidance of the characteristics of dust distributions in coal mines,and introduced effective control methods for the hazardous dust concentrations around road-header drivers during the excavation process.

A Comparative Assessment of On-Site Application Effects of Mine Dust Prevention and Control Technology

Prolonged exposure to coal dust leads to various lung disorders, including incurable coal workers’ pneumoconiosis (CWP), and endangers miners’ health in underground mines. This article summarizes the latest research progress in dust control technology, including chemical dust suppressants, foam dust removal, ultrasonic atomization, magnetized water dust suppression, double curtains of wind and fog, biological nano-film, and emerging microbial dust suppressants in the field of dust. The actual application compares and analyzes the advantages and disadvantages of different dust removal technologies. The current three directions of mine dust prevention and control are pointed out: the prevention and control of respirable dust, hydrophobic dust, and secondary dust, and the prospects for future development trends. Given the treatment of respirable dust, it is necessary to strengthen the research on the dust generation mechanism under different working conditions and to explore the migration and settlement laws of respirable dust by constructing a numerical model of dust dynamics;for the treatment of hydrophobic dust, further research on the microphysical and chemical properties of coal dust is needed. The relationship between wettability and continuously optimizing the wetting agent;for the prevention and control of secondary dust in coal mines, emerging microbial dust suppression technologies need to be developed to explore the micro-action between microorganisms and coal dust molecules to achieve green prevention and control of dust.

Investigations of the effects of two typical jet crushing methods on the atomization and dust reduction performance of nozzles

Single-fuid nozzles and dual-fuid nozzles are the two typical jet crushing methods used in spray dust reduction. To distinguish the atomization mechanism of single-fuid and dual-fuid nozzles and improve dust control efciency at the coal mining faces, the atomization characteristics and dust reduction performance of the two nozzles were quantitatively compared. Results of experiments show that, as water supply pressure increased, the atomization angle of the swirl pressure nozzle reaches a maximum of 62° at 6 MPa and then decreases, but its droplet size shows an opposite trend with a minimum of 41.7 μm. The water supply pressure helps to improve the droplet size and the atomization angle of the internal mixing air–liquid nozzle, while the air supply pressure has a suppressive efect for them. When the water supply pressure is 0.2 MPa and the air supply pressure reaches 0.4 MPa, the nozzle obtains the smallest droplet size which is 10% smaller than the swirl pressure nozzle. Combined with the dust reduction experimental results, when the water consumption at the working surface is not limited, using the swirl pressure nozzle will achieve a better dust reduction efect. However, the internal mixing air–liquid nozzle can achieve better and more economical dust reduction performance in working environments where water consumption is limited.

Wetting agent investigation for controlling dust of lead-zinc ores

The purpose of this project is to control the pollution of dust,which occurred in a typical lead-zinc mine.Two kinds of surfactants and water glass were chosen as the wetting agents to study the behaviours of suppressing the dust.The performances of the wetting agents of various sizes and water content of dust and their compositions among different weting agents were investigated. Firstly,the chemical compounds,dispersity,water content,bulk density and other relevant physico-chemical properties of the choiced dust of lead-zinc ore were mensurated.A great number of down-ward penetrating tests were conducted to different partical sizes of dust and to analyze the dust wetting behaviour respectively.The optimal compositions of wetting agents were obtained in accordance with different water contents and partical sizes of the dust after analyzing and statisting the achieved experimental data. The data show that the efficiency of chemical dust suppression of weting agents is much better than that of water.The results of the research work prove that the partical size and the water content of the dust are very important factors to the dust suppression.The results are also proved validly by the dropping experiment,which takes the penetrating diameter and penetrating time as the major factors.The superfine dust is much more difficult to be wetted.Since increasing the water content of dust is the best approach to control it,the choice of wetting agents for improving dispensation is significant.

Airtight negative pressure dust-control technology and application of transpersite in the coal conveyer belt system

Presented a new coal dust control program that was airtight negative pressure dust-control technology at the transpersite,combining with analysis with the movement of air currents and numerical simulation of gas-solid flow at the transpersite,and proved the mechanism of precipitation and proliferation for coal dust-controlt in theory.The technol- ogy has made good economic results at the Heidaigou Clean Plant,not only dust concen- tration control within 10 mg/m^3 to the work site,but also substantial energy savings and cost savings.

Study on Dust-Control WaterInjection in Fully-Mchanized Top-Coal Caving Longwall Faces

Based on the analysis of the top-coal movement, the appropriate position of holes through which dustcoutrol water is injected is confirmed. And a practical test has been carried out, which has achieved good reuslts both in dust control and in the flow rate of water injected into coal.

综掘工作面混合式风流调控下的粉尘沉降研究

煤矿掘进过程中粉尘聚集严重,目前针对综掘工作面混合式风流调控下粉尘沉降规律及优化的研究还不够深入。基于混合式风流调控系统,依托陕煤集团神木柠条塔矿业有限公司综掘工作面,分析了压风口距工作面距离、压风口右偏角度、压风口口径、抽风口距工作面距离和压抽比等混合式风流调控参数对粉尘沉降规律的影响:随着压风口距工作面距离增加,司机处和回风侧行人呼吸带截面大颗粒粉尘占比先增后减再增,小颗粒粉尘占比增加;随着压风口右偏角度增加,司机处和回风侧行人呼吸带截面大颗粒粉尘占比变化明显;随着压风口口径增加,司机处截面小颗粒粉尘占比先增后减再增,回风侧行人呼吸带截面大颗粒粉尘占比先增后减;随着抽风口距工作面距离增加,司机处截面大颗粒粉尘占比先增后减,小颗粒粉尘占比先增后减再增,回风侧行人呼吸带截面粉尘粒径分布变化不大;随着压抽比增大,司机处和回风侧行人呼吸带截面小颗粒粉尘占比减小。以上述风流调控各参数为自变量,回风侧行人呼吸带全尘平均浓度和司机处呼尘平均浓度最低为优化目标,建立了粉尘沉降优化回归模型,利用粒子群优化算法求解模型,得到最优风流调控方案:压风口距工作面距离为8.9 m,压风口右偏角度为14.8°,压风口口径为0.9 m,抽风口距工作面距离为4.3 m,压抽比为1.1。搭建了风流调控下粉尘沉降实验平台,实验结果表明:测试值与粉尘沉降优化回归模型的模拟值误差在13%以内,验证了模型的准确性;优化后粒径为71~100μm的粉尘受风流调控参数影响明显,沉降在掘进机前方;优化后回风侧行人呼吸带全尘平均浓度和司机处呼尘平均浓度分别降低了47.4%和42.4%,降尘效果明显。

粒径分布对石灰岩矿爆破粉尘表面润湿特性的影响

为探究露天石灰岩矿爆破粉尘的表面润湿特性,以安徽省铜陵石灰石矿山爆破粉尘为研究对象,利用激光粒度分析仪、X射线衍射仪以及扫描电子显微镜分别测量粉尘的粒径分布、矿物成分和表面形貌,分析其对石灰岩爆破粉尘润湿特性的影响。通过对比实验数据分析,得出:亲水性粉尘(HD)平均粒径D(4,3)要比疏水性粉尘(HCD)大2.416μm,更易被湿润;两者可被人体吸入粉尘(粒径≤10μm)占比分别为24.34%,28.08%,HCD更有可能导致人们患呼吸性疾病;HD的表面形貌比HCD更光滑平整,相应的具有更好的湿润性能。

新型矿用EMI降尘剂对煤尘的润湿特性研究

随着矿井机械化开采程度的提高,煤尘产生量也随之增大。针对煤矿井下作业环境中的粉尘污染日益严重的问题,通过测定含不同质量分数绿色高效生物降尘剂(EMI)溶液的表面张力,并以不同粒径煤尘与EMI溶液的接触角、煤尘润湿速度、煤尘吸湿量及保水性为指标,研究了不同质量分数的EMI溶液对不同粒径煤尘的润湿效果。实验结果表明:随着溶液中EMI降尘剂的质量分数增大,煤尘的接触角逐渐减小,煤尘完全沉降所需时间逐渐下降,吸湿量逐渐增大,保水性逐渐增强,且失水后煤样的板结性较大。通过分析得出EMI润湿煤尘的作用机理:降低水的表面张力;增加溶液润湿性;减少水分流失;提高溶液的抗蒸发性。

阴阳离子表面活性剂对煤层自转向酸液的性能影响及优选

针对煤矿粉尘污染严重问题,研究了煤层OAPB自转向酸液均匀布酸,从而提高煤体含水率,借助黏度、荷电性、官能团等方法研究了不同阴阳离子表面活性剂对自转向酸液增黏、润湿性能的影响规律,探究了性能变化的内部原因,并根据测试结果进行了优选。结果表明:阳离子表面活性剂会直接导致自转向酸液破胶,阴离子表面活性剂的添加使自转向酸液黏度增加;SSA/SDBS润湿性能较好,表面张力最低为24.12 mN/m;SSA/SDBS-16表面张力值总体较高,自身润湿性能差,对煤体的吸附性能也较弱;通过红外实验发现在SSA/SDBS作用下OAPB分子更倾向于形成氢键,并通过三轴渗流实验验证了自转向酸液的渗流效果。

Design of a water curtain to reduce accumulations of float coal dust in longwall returns

Accumulation of float coal dust(FCD)in underground mines is an explosion hazard that affects all underground coal mine workers.While this hazard is addressed by the application of rock dust,inadequate rock dusting practices can leave miners exposed to an explosion risk.Researchers at the National Institute for Occupational Safety and Health(NIOSH)have focused on developing a water curtain that removes FCD from the airstream,thereby reducing the buildup of FCD in mine airways.In this study,the number and spacing of the active sprays in the water curtain were varied to determine the optimal configuration to obtain peak knockdown efficiency(KE)while minimizing water consumption.

双膛石灰竖窑粉尘排放特性及控制技术研究

分析了石灰双膛竖窑在泄压过程中的粉尘排放特性,初始冲击波压力过高导致烟气无法直连布袋除尘器,这是造成粉尘污染的主要原因。弄清了初始冲击波的形成、传播与演化行为特征,比对了延长直管长度、增加弯管数量、增加变径结构与泄压腔体三种方式对冲击波压力的衰减效果,提出了一种基于压块泄压阀的柔性泄压直联布袋技术,将放散烟气初始冲击波压力由8 kPa降至1 kPa,达到烟气直连布袋、环境粉尘污染得到大幅改善的效果。同时,针对粉尘在阀体和管道中易沉降的难题,提出了一种基于3通内旋阀的扇形旋塞防沉降技术,解决了粉尘在阀体与管道系统内的沉降难题。

特大型硫磺储运系统粉尘防控技术应用总结

普光天然气净化厂设计硫磺产能2.4 Mt/a,是亚洲最大的硫磺生产基地。针对该厂特大型硫磺储运系统存在的皮带输送单元落地硫磺粉尘扩散、地下廊道硫磺粉尘超标、装车单元粉尘闪爆等安全隐患,围绕固体硫磺仓储、输送、装车环节开展粉尘风险防控难题攻关,研究皮带机集成清扫、地下廊道粉尘消减及粉尘闪爆综合治理技术,形成了特大型固体硫磺储运系统全流程粉尘防控关键技术,实现了安全清洁生产,提高了装置本质安全水平。