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.

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.

Effects of proper drilling control to reduce respirable dust during roof bolting operations

Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.

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.

Development of a roof bolter drilling control process to reduce the generation of respirable dust

The drilling operation in the roof bolting process,especially in hard rock,generates excessive respirable coal and quartz dusts,which could expose the roof bolting operator to continued health risks.Previous research has shown that the amount of respirable dust produced is dependent on the main drilling parameters,specifically the drilling rotational and penetration rate.In this paper,a roof bolter drilling control process was proposed to reduce the generation of respirable dust.Based on the analysis of laboratory drilling test results,a rational drilling control process(adjusting rotational and penetration rates)to achieve the optimal drilling parameter for different rock types was proposed.In this process,the ratio between specific energy and rock uniaxial compressive strength was used as the index to determine the optimal operation point.The recommended drilling operation range for the rock type used in the experiment was provided,and the reduction in respirable dust generation was demonstrated.By following this control process,the drilling efficiency can be monitored in real time,so the system can stay in a relatively high-energy efficiency with less respirable dust production from the drilling source.This algorithm is targeted to be incorporated into the current roof bolter drilling control system for drilling automation so that a safe and productive drilling operation can be conducted in a healthy working environment.

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.

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.

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.

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.

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.

不同采高综采工作面液压支架封闭控尘装置系列化研究

为了解决不同采高综采面液压支架降柱移架粉尘污染问题,开展了液压支架封闭控尘装置系列化研究。基于降柱移架产尘特点和液压支架结构,研发了适用于4 m以下、4~6 m、6 m、6 m以上采高综采面的架间喷雾引射抽尘净化装置和拉簧式、扭簧式、滑移式液压支架防尘装置,在源头降低支架产尘90%以上。该系列装置在国能集团、陕煤集团下属多个矿井推广应用,受到矿方一致好评。

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.

The design of a laboratory apparatus to simulate the dust generated by longwall shield advances

A laboratory apparatus (shield dust simulator) was designed and constructed to simulate the dust generated during the advance of longwall hydraulic roof supports,or shields.The objective of the study was to develop a tool that could be used to test the hypothesis that foam applied to a mine roof prior to a shield advance could be used to reduce the respirable dust generated during shield advances.This paper will outline the design parameters for the development of thesystem,as well as describe baseline testing of coal and limestone dust.Results show that the average instantaneous respirable dust concentrated during simulated shield advance.Confidence intervals were calculated from the instantaneous respirable dust data to determine the repeatability of the data produced by the device.

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.

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。

Erosion resistance of treated dust soils based on the combined enzymatically induced carbonate precipitation and polyacrylic acid

The majority of cities worldwide are grappling with the challenge of dust pollution.Recently,the application potential of enzymatically induced carbonate precipitation(EICP),a novel environmentally friendly method,for dust control has been convincingly demonstrated.However,the long-term durability of EICP treatment is consistently a significant concern,particularly in regions prone to recurrent erosion caused by rainfall.As a result,the erosion durability of the EICP-treated dust soils requires further investigation.To address this,Polyacrylic acid(PAA)was added to the cementation solution in this study as the combined PAA and EICP treatment for dust control.The results showed that the addition of PAA slightly affected urea degradation;however,the combined PAA and EICP treatment significantly improved surface strength from 300 kPa to 500 kPa,especially for the wind-erosion resistance compared with the EICP treatment alone.The surface strength of samples treated with the combined PAA and EICP still exhibited a decrease due to repeated rainfall erosion,along with a reduction in calcium carbonate(CaCO_(3))contents.Nevertheless,the decreasing slopes of surface strength(k=13.434,14.002,or 14.186)in response to repeated rainfall for EICP-PAA-treated slopes were much smaller than those for EICP-treated samples(k=14.271),as well as the decreasing slopes of CaCO_(3)contents,which suggested the slopes with the combined treatment had significantly improved durability.By comparing the cementation effect and the influence of repeated rainfalls on treated dust samples,the EICP-PAA(50 g/L)treatment achieved better dust control effects.Overall,the combined treatment of EICP-PAA shows promising potential for effectively suppressing dust generation and enhancing erosion durability.