Dust dispersion and management in underground mining faces
题名：地下开采工作面粉尘扩散与防治
International Journal of Mining Science and Technology, Volume 24, Issue 1, January 2014, Pages 39-44
Abstract: Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’ pneumoconiosis and silicosis. Major sources of dust appear of course along the mining face where the minerals are extracted. Proper control and management are required to ensure safe working environment in the mine. Here, we utilize the computational fluid dynamic (CFD) approach to evaluate various methods used for mitigating dust dispersion from the mining face and for ensuring safe level of dust concentration in the mine tunnel for safety of the operators. The methods used include: application of blowing and exhaust fans, application of brattice and combination of both. The results suggest that among the examined methods, implementation of appropriately located brattice to direct the flow from the main shaft to the mining face is the most effective method to direct dust particles away from the mining face.
Controlling the coal dust at transshipment point: A study of the foam-sol foaming device
题名：转载点的煤尘防治：泡沫溶胶发泡装置研究
International Journal of Mining Science and Technology, Volume 24, Issue 5, September 2014, Pages 625-630
Abstract: In order to effectively control the dust at the transshipment point with foam-sol, this paper attempted to study the characteristics of dust diffusion at transshipment point and the foam-sol foaming device with diffusion outlet was also designed in this paper. To study the diffusion rules of coal dust, fluent discrete phase model was utilized in the numerical simulation, as the coal dust was thrown down at a horizontal velocity of 2.5 m/s. A foam-sol foaming device was designed, through which foaming agent could be automatically sucked into the Venturi by the negative pressure. The automatic controller was also equipped, which could transform the energy of the compressed air into the constant pressure difference so that the gelling agent could be qualitatively added into the gel container. The diffusion outlet that could spray out foam-sol in a continuous, conical and 3D manner was also designed. Moreover, this paper also carried out the contrast experiments on dust removal efficiency among water, aqueous foam and foam-sol. The results clearly show that the symmetrical whirlpools appeared below the inlet where the largest whirlpool diameter was 0.52 m, and the horizontal distance from swirl range to the inlet was approximately 0.69 m. By using the self-designed foaming device, the foaming was multiplied by 30 times and the volume ratio with water and foaming agent reached 95%:5%. In this context, the gas pressure was controlled at 0.3 MPa, with gas flow at 15 m3/h and water flow at 0.5 m3/h, with water pressure controlled between 0.34 and 0.36 MPa. The foam-sol has the highest dust removal efficiency than other agents.
Collecting representative dust samples: A comparison of various sampling methods in underground coal mines
题名：典型尘样的采集：地下煤矿各种采样方法比较
Journal of Loss Prevention in the Process Industries, In Press, Corrected Proof, Available online 8 September 2014
Abstract: Former methods used in the U.S. to assess hazardous and explosible coal dust date back to the 1950s. As mining technologies advanced, so too have the hazards. Given the results of the recent coal dust particle size survey and full-scale experimental mine explosion tests, the National Institute for Occupational Safety and Health (NIOSH) recommended a new minimum standard, in the absence of background methane, of 80% total incombustible content (TIC) be required in the intake airways of bituminous coal mines, replacing the previous 65% TIC requirement. Most important to monitoring and maintaining the 80% TIC is the ability to effectively collect and analyze representative dust samples that would likely disperse and participate in dust explosion propagation. Research has shown that dust suspended on elevated surfaces is usually finer, more reactive, and more readily dispersible while floor deposits of dust are generally coarser and more difficult to disperse given the same blast of air. The roof, rib, and floor portions of the dust samples were collected and analyzed for incombustible content separately and the results were compared to a band sample of the roof, rib, and floor components. Results indicate that the roof and rib dust samples should be kept separate from floor dust samples and considered individually for analyses. The various experimental collection methods are detailed along with preferred sampling approaches that improve the detectability of potentially hazardous accumulations of explosible dust.
Physical, mineralogical and wetting characteristics of dusts from Interior Basin coal mines
题名：内陆盆地煤矿粉尘的物理、矿物学及润湿特性
International Journal of Coal Geology, Volume 127, 1 July 2014, Pages 75-87
Abstract: This paper presents physical, mineralogical and wetting characteristics for dust samples from the Interior Basin coal mines. The samples were from three sources: 1) Produced in the laboratory from bulk samples of coal and immediate roof and floor strata, 2) In-mine samples collected through gravimetric sampling of active mining areas, and 3) In-mine samples collected from wet-scrubbers on continuous miners. Particle size distribution analysis showed that about 30, 67, 68 and 60% of dust particles are in the respirable range (< 10 μm) for bulk samples of coal, and roof, and floor strata and for in-mine dust samples collected from scrubber, respectively. SEM image analysis of in-mine gravimetric dust samples showed most particles to be spherical and large number of particles to be of ≤ 1 μm. Bulk samples of roof and floor strata were determined to have varying quartz content from 6.2 to 13.7% by weight. Quartz, kaolinite, calcite, pyrite and illite were the most prevalent minerals in bulk dust samples. XRD data showed presence of quartz in un-wetted dust particles indicating the co-existence of minerals and macerals. Coal petrography analysis showed vitrinite as the dominant maceral (68–86%) in bulk coal samples.
Two approaches were used to assess dust wettability rates: 1) fixed-time wettability that attempts to simulate wetting around mining environments, and 2) absolute-time wettability that evaluates intrinsic wettability rates. Fixed-time wettability for coal dusts were in the range 57–99% (% wt.) with majority of mines having values above 90%. The middle portion of the coal seam was found to be least wettable. The contact time between dust particles and water droplets was an important factor for improving wetting of coal dust. An increase in contact time from 10 to 25 s showed 3–27% improvement in fixed time wettability. Absolute-time wettability data showed that coarser particles required more time for complete wetting. The data above is being actively used to design engineering controls for improved dust control in mines.
A new shock tube configuration for studying dust-lifting during the initiation of a coal dust explosion
题名：研究煤尘爆炸初始期间粉尘上升的新型冲击管配置
Journal of Loss Prevention in the Process Industries, Volume 29, May 2014, Pages 198-208
Abstract: The traditional defence against propagating coal dust explosions is the application of dry stone dust. This proven and effective safety measure is strictly regulated based on extensive international experience. While new products, such as foamed stone dust, offer significant practical benefits, no benchmark tests currently exist to certify their dust lifting performance in comparison to dry stone dust. This paper reviews the coal dust explosion mechanism, and argues that benchmark testing should focus on dust lifting during the initial development of the explosion, prior to arrival of the flame. In a practical context, this requires the generation of shock waves with Mach numbers ranging from 1.05 to 1.4, and test times of the order of 10's to 100's of milliseconds. These proposed test times are significantly longer than previous laboratory studies, however, for certification purposes, it is argued that the dust lifting behaviour should be examined over the full timescales of an actual explosion scenario. These conditions can be accurately targeted using a shock tube at length scales of approximately 50 m. It is further proposed that useful test time can be maximised if an appropriately sized orifice plate is fitted to the tube exit, an arrangement which also offers practical advantages for testing. The paper demonstrates this operating capability with proof-of-concept experiments using The University of Queensland's X3 impulse facility.
Experimental investigations on the roles of moisture in coal dust explosion
题名：水分在煤尘爆炸中的作用实验研究
Journal of the Taiwan Institute of Chemical Engineers, Volume 45, Issue 5, September 2014, Pages 2325-2333
Abstract: Explosion behaviors of coal dusts were systematically investigated to focus on the roles of moisture in dust explosion. It is found that, when the moisture content is lower, the explosion parameters (Pex, (dp/dt)ex and MEC) basically keep a linear relationship with the moisture content. With the further increase of moisture content, the moisture would gradually agglomerate fine particles by reducing inter-particle distance and forming liquid bridges between particles. This behavior causes the increase of effective particle size and the reduction of dust dispersibility, which would notably heighten the uncertainty of explosion tests. These results indicate that to limit the moisture content is necessary when measuring explosion parameters in practice. Considering that (dp/dt)ex is more sensitive than Pex and MEC to the particle agglomeration, for coal dusts with the particle size <125 μm, the lower moisture content of 5 wt% is proposed as the upper limit to measure (dp/dt)ex, while that of 10 wt% is proposed to measure Pex and MEC. In addition, from the perspective of inert medium, the existence of moisture would narrow the explosible concentration range of coal dusts. When the concentration of dust cloud is near to the worst case, the higher moisture content would be needed to obtain the identical inhibition level. At given conditions, compared with solid inert media, the moisture has higher inhibition level and, thus, is more effective for the inhibition of coal dust explosions. The inhibition mechanisms of moisture mainly involve four categories: heat extraction, oxygen dilution, reaction kinetic inhibition and particle agglomeration. For lower moisture content or larger particle size, the predominant mechanisms are the heat extraction and oxygen dilution. With the increase of moisture content or decrease of particle size, the predominant mechanisms would gradually transform into the reaction kinetic inhibition and particle agglomeration.
Coal dust emissions: From environmental control to risk minimization by underground transport. An applicative case-study
题名：煤尘排放：通过地下运移从环境控制到风险最小化：应用实例研究
Process Safety and Environmental Protection, Volume 92, Issue 2, March 2014, Pages 150-159
Abstract: Coal dust emission from open coal storage parks and handling plants can represent a significant part of the overall atmospheric emission contribution in different industrial activities, such as power stations or coke production plants. The emissions are strictly connected to technical characteristics of the handling system, chemico-physical properties of coal and environmental conditions. In this paper, we present a full-scale operational solution to the problem of limiting coal dust emissions during transportation from the harbor site to the final utilization plant. To this end, a simple mathematical framework is developed in order to evaluate explosion risk inside the enclosure and set-up proper technical and managerial layers of protection suitable to minimize the risk.
Numerical simulation of dilute and dense layered coal-dust explosions
题名：稀释与密层煤尘爆炸的数值模拟
Proceedings of the Combustion Institute, In Press, Corrected Proof, Available online 28 June 2014
Abstract: Multidimensional time-dependent simulations were performed to study the interaction of a shock wave and resulting shear layer with layers of coal dust. The simulations used a high-order compressible numerical method for fluid dynamics and included a Eulerian kinetic-theory-based granular multiphase model applicable over a range from dense to dilute particle volume fractions. Two cases were considered: a loose dust layer with an initial volume fraction of 1%, and a dense dust layer with an initial volume fraction of 47%. For both cases, the final result is a coupled complex consisting of a shock leading a coal-dust flame. In the simulations presented here, a shock is initially produced from remnants of a natural gas detonation, which has decayed into a shock once it passes into a region containing no gaseous fuel. This shock weakens further due to mechanical and thermal losses from lifting and entraining the coal dust. The lifted dust subsequently ignites in the shock-heated air and produces a structure similar to a mixing-limited, nonpremixed flame. The flame consists of a burning coal dust wave that follows the shock. The distance between the shock and ignition point is determined by the induction length of carbon char, which is 170 cm and 15 cm for the 47% and 1% cases, respectively. The burning of coal particles is predominantly from heterogeneous reactions with carbon char, and volatilized methane combustion is a secondary effect. Air and particles are mixed by relative velocity between the gas and solid phases. Coal particles burn and produce pressure waves that accelerate the shock from Mach 2.2 to 2.6 for the dilute layer, and from Mach 1.7 to 1.8 in the dense layer.
Comprehensive numerical modeling of ignition of coal dust layers in different configurations
题名：不同煤尘层爆炸的综合数值模型
Proceedings of the Combustion Institute, In Press, Corrected Proof, Available online 22 July 2014
Abstract: Ignition of coal dusts deposited over sufficiently hot surfaces represents a common industrial hazard. If these surfaces are above a minimum threshold temperature, then the heat transfer from them and the associated chemical heat release can cause spontaneous ignition. This ignition front can be an ignition site for nearby combustibles as well, which depends on the location of ignition and the corresponding surface temperature attained by the coal dust. A comprehensive numerical study of ignition process of coal dust layers in different configurations, by solving the coupled Navier–Stokes and energy equations, provides a clear insight of the thermal field in the coal layer as well as the flow field over the coal surface. Such study will also provide quantitative information about the convective heat transfer coefficient, which varies for different cases. In this study, ignition phenomena of coal dusts deposited over a flat plate, wedges of different angles and a 3D corner, have been analyzed using a comprehensive numerical model. The governing equations are solved using Ansys FLUENT and user defined functions. The model has been validated using experimental results and is used to study the effect of wedge angles and the direction of gravity vector on the ignition process.
Application of foam technology for dust control in underground coal mine
题名：泡沫技术在地下煤矿粉尘防治中的应用
International Journal of Mining Science and Technology, Volume 24, Issue 1, January 2014, Pages 13-16
Abstract: 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.
Experimental study on advantages of foam–sol in coal dust control
题名：泡沫溶胶在煤尘防治中的优势实验研究
Process Safety and Environmental Protection, In Press, Corrected Proof, Available online 27 November 2013
Abstract: In China, more than 2.65 million coal mine workers are exposed to coal dust. Every year, new pneumoconiosis cases amount to 25,000, among which 6000 cases die of this disease. The figure is twice the death toll in production safety accidents. Occupational diseases seriously endanger life and health of coal mine workers, and restrict the healthy growth of the coal industry.
The paper presented a study of foam–sol-based coal dust control. This was an experimental study of characteristics of foam–sol-based coal dust control, which features dust capture, suppression, and isolation. Comparative wettability experiments were carried out to determine contact angles of water, aqueous foam, and foam–sol solution. A new foam–sol generating system with a conical diffuser outlet was proposed.
The experiment results clearly showed that the foam–sol features dust capture, suppression, and isolation. The wettability of the aqueous foam solution was better than the foam–sol solution, but the foam–sol technology had the better ability to capture the airborne dust, suppress the static dust and enclose the dust source, due to the excellent surface viscosity, strong cohesiveness and less volatile property. The paper concluded that the foam–sol could greatly improve the dust control efficiency and did not have main deficiencies that the aqueous foam technology had.
Limiting oxygen concentration for coal dusts for explosion hazard analysis and safety
题名：煤尘爆炸事故分析与安全极限氧浓度
Journal of Loss Prevention in the Process Industries, Volume 26, Issue 6, November 2013, Pages 1106-1112
Abstract: Investigation of explosion characteristics of coal dust was undertaken as a part of regular research program at CSIR-CBRI, Roorkee, India, for designing explosion safety measures for coal dust handling installations. This paper presents results of detailed experimental work on determination of Limiting Oxygen Concentration (LOC) and influence of reduced oxygen levels on explosion severity data for two types of coals with varying volatile matter as 27.18% (coal A) and 19.69% (coal B) from Jharia coalfield of India determined at ambient conditions with 20-L Spherical Vessel established at CSIR-CBRI. The effects of coal particle size and moisture content were evaluated. Data presented will be used for hazard analysis, designing explosion preventive measures, and explosion severity reduction by involving the use of inert gases for installations handling pulverized coal with similar nature. The importance of ignition source energy in determining LOC data is highlighted. The data collected lead to an extension of the current data for coal dusts as found in the literature. Limiting oxygen concentrations were found as 7% for coal A and 8% for coal B for the size representative to that used in pulverized coal boilers and moisture content ∼4%.
Experimental Study on the Influence of Initial Pressure on Explosion of Methane-coal Dust Mixtures
题名：初压对甲烷-煤尘混合物爆炸影响的实验研究
Procedia Engineering, Volume 62, 2013, Pages 980-984
Abstract: Methane-coal dust explosion belongs to chemical explosion which always directly causes fire disasters. When it comes to coal mine, the gas explosion easily leads to extensive burning and forms large area stereo fire finally, due to the big blast power and many combustible materials at the scene of an accident. In order to study the explosion characteristics of methane-coal dust mixture explosion as well as to reveal the effects of initial pressure on the explosion, a rectangular explosion test vessel which is 60 cm long and with 10 cm × 10 cm cross-section was used. Different initial pressures, such as 0.2 MPa, 0.25 MPa, 0.3 MPa and 0.35 MPa were considered in this paper. The explosion pressure was measured with PCB pressure transducers, and the maximum rate of explosion pressure rise was determined based on these measured data. The results show that the maximum explosion overpressure and maximum rate of overpressure rise increase with the increasing of the initial pressures and coal dust concentration.
Methane/coal dust/air explosions and their suppression by solid particle suppressing agents in a large-scale experimental tube
题名：大型试验管道中甲烷/煤尘/空气爆炸及固体粒子阻抑剂的阻抑效果
Journal of Loss Prevention in the Process Industries, Volume 26, Issue 2, March 2013, Pages 310-316
Abstract: Methane/coal dust/air explosions under strong ignition conditions have been studied in a 199 mm inner diameter and 30.8 m long horizontal tube. A fuel gas/air manifold assembly was used to introduce methane and air into the experimental tube, and an array of 44 equally spaced dust dispersion units was used to disperse coal dust particles into the tube. The methane/coal dust/air mixture was ignited by a 7 m long epoxypropane mist cloud explosion. A deflagration-to-detonation transition (DDT) was observed, and a self-sustained detonation wave characterized by the existence of a transverse wave was propagated in the methane/coal dust/air mixtures.
The suppressing effects on methane/coal dust/air mixture explosions of three solid particle suppressing agents have been studied. Coal dust and the suppressing agent were injected into the experimental tube by the dust dispersion units. The length of the suppression was 14 m. The suppression agents examined in this study comprised ABC powder, SiO2 powder, and rock dust powder (CaCO3). Methane/coal dust/air explosions can be efficiently suppressed by the suppression agents characterized by the rapid decrease in overpressure and propagating velocity of the explosion waves.
Surface physical properties and its effects on the wetting behaviors of respirable coal mine dust
题名：呼吸性煤矿粉尘表面物理特性以及其对润湿特性的影响
Powder Technology, Volume 233, January 2013, Pages 137-145
Abstract: In the present research work, coal dust physical properties as well as its wetting behaviors were analyzed systemically. The influences of different surfactants on coal dust's wetting behaviors were also investigated and compared with deionized water. Research results show that the finer the coal particle sizes, the more complex the coal particle micro structures are, which may cause the poor wetting abilities. Among the three different coal dust samples, the wetting performance is poor for the coal with higher volatile content due to the easier release of volatile matter and the easier formation of gas film around the particle. The fractal dimension and contact angles are presenting perfect correlations. With the increase of the fractal dimension, the contact angle would increase correspondingly, which indicates a poor wetting performance. The wetting behaviors of coal dust could be greatly improved by adding surfactant in the deionized water. However, the species of surfactant and its contents in the solvent are the two important factors for dust wetting abilities enhancement. For the two selected surfactants, sodium dodecyl sulfate (SDS) may be a better choice and 0.2% concentrations are recommended during coal dust suppression applications. Based on the experimental results, a wetting dynamic model was built to simulate coal dust wetting process. The calculated values agreed well with the experimental results.
Influence of coal dust on premixed turbulent methane–air flames
题名：煤尘对预混合甲烷-空气复合火焰的影响
Combustion and Flame, Volume 160, Issue 3, March 2013, Pages 635-640
Abstract: This study discusses the design of a new experimental platform, the Hybrid Flame Analyzer (HFA) to measure burning velocity of gas, dust, and hybrid (gas and dust) premixed flames. The HFA is used to analyze a particle–gas–air system of coal dust particles (75–90 μm and 106–120 μm) in a premixed CH4–air (ϕg = 0.8, 1.0 and 1.2) flame. Experimental results show that particles usually increase the turbulent burning velocity. Smaller particle sizes and larger concentrations (>50 g/m3) increase turbulent burning velocity compared with larger particle sizes and lower concentration ranges. The experimental data is used to develop a correlation similar to turbulent gas flames to help modeling of the complex behavior.
Participation of large particles in coal dust explosions
题名：大粒子在煤尘爆炸中的作用
Journal of Loss Prevention in the Process Industries, Volume 27, January 2014, Pages 49-54
Abstract: Float coal dust is produced during the coal mining process in underground mines. If it is entrained, the float coal dust presents a dangerous explosion hazard to miners when it reaches the minimum explosible concentration and is ignited. However, coal dust can be inerted if properly mixed with generous amounts of pulverized rock dust such as limestone to result in a homogeneous dust mixture with a total incombustible content (TIC) ≥80%. In the United States, it is mandatory for the rock dust to be 100% passing through a 20 mesh (841 μm) sieve and 70% or more passing through a 200 mesh (75 μm) sieve. Laboratory experiments have been conducted using the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) 20-L and the Fike Corporation 1-m3 explosion chambers. Coal and rock dust samples were prepared by sieving and were used to investigate the effect of particle size on explosibility and inerting effectiveness.
The results from both chambers show that large coal particles >60 mesh (>250 μm) do not explode/ignite at dust concentrations up to 600 g/m3, and limestone rock dust particles >200 mesh (>75 μm) require a significantly higher TIC of 90% to inert Pittsburgh pulverized coal (PPC). This data illustrates the significance of particle size for preventing coal dust explosions and the importance of measuring particle size as well as TIC (which includes moisture as well as incombustibles) to determine the true explosibility of a dust sample.
Dust fall and elemental flux in a coal mining area
题名：采煤区粉尘沉降及基本流量
Journal of Geochemical Exploration, Volume 144, Part C, September 2014, Pages 443-455
Abstract: Air is a very essential part for the existence of humans and other living organisms. To know the quantum of atmospheric dust fall and their mineral and morphological characteristics, dust samples were collected at monthly intervals from three different sites (commercial, residential, and control) of the Jharia coal mining area, India. Samples were analysed for heavy metals, minerals, and morphological features by ICP-AES, XRD, and SEM respectively. The yearly average dust fall was higher for the commercial site (15.5 t/km2/month) than the residential site (10.7 t/km2/month) of Jharia coal mining area. The dust deposition rate was highest during summer (March–June), followed by winter (October–February) and lowest in the monsoon season (July–September). The elemental fall was higher for Zn followed by Pb > Sr > Cu > V > Cr > Ni > Co. The major minerals in dusts from Jharia mining area were quartz, kaolinite, pyrite, albite, and magnesiohornblende. The SEM-EDS analysis showed the dust in commercial sites has contributions from coal, and soil. In the residential site, soot particles from domestic coal burning; and in control site, soot particles from biomass burning were observed in SEM. Overall the intensity of dust pollution is more in the commercial sites of the coal mining area.
