Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain

Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.

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 collertors' performance. This paper investigates the main mechanisms of coagulation, all possible electrostatic forces existing in the collectors and their effects on the particle coagulation. To make particle kinetic coagulation electrostatically enhanced be a step of the conventional collectors. operations,certain conditions should be created through some medifications 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 80% to 92~94%.

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.

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.

Development of dust collection and removal technology of comprehensive mechanized excavation face

To solve the problem of excavation face dust control,the theory of dust removal after collection was put forward.Through a large number of theoretical and experimental researches,a new wind screen dust-collection system which was applied to comprehen- sive excavation face was developed.To set a wind dam in jet stream box,achieve the function of multi-stage and multiple-level regulation,lots of experimentation was carried out to obtain higher jet stream velocity with the minimum loss of energy.Experiments show that the slit width in the exports of wind screen dust-collection system should be 10 to 15 mm.For the general excavation roadway,after wind attenuation,the velocity can be greater than 3 m/s at the roof which meets the requirements of respirable dust control.

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.

A computational fluid dynamics investigation of a novel flooded-bed dust scrubber with vibrating mesh

This work proposes a vibrating mesh screen as an alternative to the static mesh screen currently used in conventional flooded-bed dust scrubbers for removing airborne coal mine dust in the continuous mining environment.Fundamental assessments suggest that a vibrating screen may improve the dust collection efficiency of scrubber systems and mitigate the clogging issues associated with the conventional design.To evaluate this hypothesis,computational fluid dynamics(CFD)simulations were carried out to assess the effects of vibration conditions(i.e.,frequency and amplitude)on the dust particle-mesh interaction and mesh wetting conditions,which are the two decisive factors in determining the dust collection efficiency.The results suggest that the vibrating mesh screen can enhance dust particle collision opportunities on the mesh and increase mesh wetted area as compared to the static mesh screen.The effects of mesh screen aperture,coal dust concentration,and spray nozzle flow rate on the performance of the vibrating mesh are also evaluated.Finally,a simplified three-phase flow simulation including airflow,dust particles,and water droplet spray is performed,and the results reflect a significant improvement of dust collection efficiency in the liquid-coated vibrating mesh screen.

Feasibility of micro-organisms in soil bioremediation and dust control

Detrimental impacts of dust caused by mine tailings have yielded to several studies on the efficiency of different soil stabilizers.Bacterial stabilization has been recognized as a reality within recent decades,where bacteria could get adhesion to the grains and stabilize the soil particles.However,these bacteria are prone to be destroyed while exposed to the normal environmental conditions.In this study,the effects of microcapsules containing two types of bacterial freeze-dried spores(B.Subtilis Natto LMG 19457 and B.ESH)have been investigated on the mine tailing stability in terms of two parts.The first part of the study is dedicated to the fabrication of microcapsules within the two bacteria and identification of the characteristics of these microcapsules to set the time of microcapsules break and release in the soil.The urea-formaldehyde microcapsules containing tung oil were synthesized using microencapsulation method and at the following,the bacterial spores of B.Subtilis Natto LMG 19457 and B.ESH which had the high durability and the capability to grow in the silicon oil,were added to the microcapsules.The microcapsules effect on MT specimens and the viability of encapsulated spores were determined.The characteristics of the capsules were analyzed by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and thermo-gravimetric thermal analysis(TGA).In the second part,wind tunnel tests were conducted to study the effects of microorganism stabilizers on mine tailings.The results indicated that the dust erosion reduced from 16%-using water as a stabilizer-to the 0.2%while using microcapsules containing B.Subtilis Natto LMG 19457 and 0.8%while using microcapsules containing ESH.The results showed the high efficiency of microcapsules containing bacteria in stabilizing the MTs.This phenomenon was proved by SEM imaging in which the voids were bounded significantly while using the bacteria.

ControlLogix系统在煤气站的应用

为了改善操作条件,保证设备安全运行,设计了煤气站集中控制系统。利用ControlLogix系统,实现了18台煤气发生炉的集中控制。该系统采用3个处理器、2层网络结构,实现了集中控制、自动加煤、自动出灰、炉底饱和空气温度自动控制和电收尘等的控制。多个安全联锁措施和严谨的自动整流方案的应用,保证了电收尘的安全运行。

半煤岩巷快速掘进工作面粉尘综合治理技术及装备研究

快速掘进工作面由于掘进速度快、产尘强度高导致粉尘污染严重,特别是岩巷以及半煤岩巷道,粉尘污染程度更高。以袁大滩煤矿半煤岩快速掘进工作面为研究对象,设计了新型的滚筒下部喷雾、大臂喷雾、滚筒底部喷雾、滚筒上部喷雾及转载喷雾,同时设计了配套机载控除尘系统。经过现场实测,采用综合降尘措施后,总粉尘和呼吸性粉尘降尘效率最高分别达到91.37%和85.49%以上,降尘效果显著。

岩巷综掘面高效控除尘系统关键工艺参数研究

针对岩巷综掘工作面粉尘扩散严重、治理难度大的问题,提出了一套岩巷综掘工作面控除尘方法。通过数值模拟对控除尘关键参数与工作面颗粒物运动规律进行了研究,得出了不同条件下工作面粉尘颗粒物的运动规律,基于数值模拟研究结果搭建了现场试验系统,对工作面降尘效果进行了现场试验研究,得出工作面高效控除尘关键工艺参数,实现了对工作面产粉尘的高效治理,解决了综掘工作面粉尘带来的危害问题。

车载式多功能公路吹扫降尘设备的研发与应用

传统的吸尘车借助负压形成真空,大气压强差把杂物反推进去,因此耗油量大,成本高,功能单一,长时间清扫路面灰尘比较多,进气管道容易堵塞。车载式公路吹扫降尘车是一种具有构造简单,清扫效果明显,适用范围广,作用面积大,动力充足,直接作用于路面杂物、积雪、浮雪的便捷式吹扫设备,实现了高效作业,节约了劳动消耗,并且燃油经济性较高,成为环兰高速公路路面日常保洁模式。

大型铸造工厂除尘系统设计与应用

钢铁制造业是消耗能源的大户,更是大气污染的重点行业。因此,控制工业粉尘对环境的污染破坏以及人身的健康危害是现阶段急需解决的问题。根据铸造工厂的车间实际情况,阐述除尘系统的最优设计方案以及智能控制的应用。

光伏组件表面积灰监控系统设计与实现

光伏组件表面积灰会影响组件的发电效率,降低光伏电站运行的经济性。为了能够监测光伏电站中组件表面的积灰状态,进而基于监测数据进行光伏电站清洗运维优化方法的研究,提出一种光伏电站组件表面积灰监控系统。该系统中,下位机采用STM32F407微处理器扩展ADS1256模数转换器采集与积灰相关的多种传感器信号,并通过无线传输模块将数据传给上位机监控软件。基于LabVIEW开发的上位机监控软件通过串口接收数据,处理并存储数据后,根据相应数据对光伏电站的清洗时间进行优化。经过实验测试,本系统能够准确地采集、传输、处理和储存数据,监测光伏电站组件表面的积灰状态并实现电站清洗时间的规划,对光伏电站清洗运维优化有重要意义。

电石储运系统的粉尘治理及回收利用创新技术

在电石储运系统中的卸车、破碎、储存及输送等工段,设备运行中会产生大量粉尘,影响环境安全、设备的使用寿命及操作人员的身体健康。通过采用区域封闭的卸车除尘系统、安全可靠的筒仓储存、封闭的破碎及输送设备、安全环保的粉尘回收系统,实现粉尘的有效治理及回收利用。

焦化企业粉尘来源与防治措施探讨

针对焦化企业因“以煤产焦”生产特性导致职工粉尘职业病危害的问题,通过分析焦炭生产过程中备煤阶段、炼焦阶段、干熄焦阶段的粉尘来源,介绍焦炭生产现场除尘治理地实践,以及防护用品发放及使用、粉尘危害防治与管理、防尘宣传和专题培训、职业健康监护与职业卫生档案管理4个方面的焦化企业粉尘防治管理实践进行探讨,通过以上方面在企业中的实践,使得焦化企业粉尘治理效果提高明显,为实现清洁生产,保护职工身体健康,为焦化企业的粉尘治理提供参考。

大断面综掘巷道机载除尘系统研究

山西省A煤矿通过在3307运输巷引进先进的MB670-Ⅰ型掘锚一体机+液压锚杆钻车实现了大断面巷道快速掘进,但是巷道掘进期间迎头高浓度粉尘成为制约巷道快速掘进的不利因素之一。结合3307运输巷现场条件、掘进设备生产工艺等对现有粉尘治理措施存在的问题进行了分析,并提出通过增设机载除尘系统实现粉尘高效治理。具体在MB670-Ⅰ型掘锚一体机上增设KCS-450D-Ⅰ型除尘器,在供风风筒靠近出风口增设附壁风筒,通过除尘器与附壁风筒相互配合将掘进迎头高浓度粉尘控制在迎头位置,减少粉尘外溢量,利用KCS-450D-Ⅰ型除尘器处理能力强、效率高等优势对迎头高浓度粉尘气流进行集中处理,降低巷道粉尘质量浓度。工程应用后,巷道掘进迎头呼吸性粉尘、全尘质量浓度最大分别为29.52、89.73 mg/m^(3),粉尘治理效果显著。