Explosion severity of methane–coal dust hybrid mixtures in a ducted spherical vessel

甲烷-煤尘混合物在导管式球形容器中的爆炸特征

Powder Technology, Volume 323, 1 January 2018, Pages 95-102

Sazal K. Kundu, Jafar Zanganeh, Daniel Eschebach, Behdad Moghtaderi

摘要：This article reports an investigation on the explosion characteristics of methane–coal dust hybrid mixtures in a ducted spherical vessel. Methane–coal dust hybrid mixture explosion can occur in coal mines and spread into mine tunnels. While investigating the effects of methane addition to coal dust–air mixtures, the violence of coal dust explosions was found to increase significantly in the presence of methane. The energy of ignition was found to impact on the pressure rises in the vessel and in the duct. The experimental data and scientific analysis presented can assist in addressing ducted explosions originating from hybrid mixtures in process industries such as coal mines.

Laminar burning velocity and structure of coal dust flames using a unity Lewis number CFD model

基于统一路易斯数字CFD模型的煤尘火焰层流燃烧速度与结构

Combustion and Flame, Volume 190, April 2018, Pages 87-102

Chris T. Cloney, Robert C. Ripley, Michael J. Pegg, Paul R. Amyotte

摘要：Despite decades of research, predictive methods remain unavailable to estimate flame propagation in dust clouds under industrial scenarios. The complexity of scaling the fundamental processes occurring in multiphase flames to industrial geometries, and a lack of tools to explore and extend knowledge in this area, may be key factors missing in the research literature. The main objective of this work is to verify the ability of a CFD model based on a unity Lewis number assumption to explore laminar burning velocity in coal dust clouds. A second objective is to perform parametric analysis including the role of surface reactions, particle diameter, and initial system temperature. The third and final objective is to explore the impact of discrete particle combustion on flame structure and burning velocity. Despite a simplified treatment of gas phase transport properties, single-step devolatilization, and single-step surface reaction, the current model correctly captures the effects of particle diameter and initial temperature on burning velocity and demonstrates good agreement with previous investigations once preheating in the experimental results is accounted for. Furthermore, the reduced model complexity may allow future investigation by the current authors and other research groups into different combustible dusts, more detailed system geometry, and turbulent flow conditions. Lastly, the results of the current study provide a baseline that more comprehensive modeling methods may be compared to, which is currently missing in the literature.

Numerical investigation on the self-ignition behaviour of coal dust accumulations: The roles of oxygen, diluent gas and dust volume

煤尘聚集自燃特性数值研究：氧气、稀疏瓦斯和煤尘量的作用

Fuel, Volume 188, 15 January 2017, Pages 500-510

Dejian Wu, Frederik Norman, Martin Schmidt, Maarten Vanierschot, Eric Van den Bulck

摘要：Self-ignition of coal dust deposits poses a higher risk of fires in oxygen-enriched oxy-fuel combustion systems. In this work, we develop a numerical method, using the commercial software COMSOL Multiphysics, to investigate self-ignition behaviour of coal dust accumulations with a main emphasis on the roles of oxygen, diluent gas and dust volume. A one-step 2nd-order reaction kinetic model considering both coal density and oxygen density is used to estimate reaction rate using the kinetic parameters from previously conducted hot-oven tests. This model is validated to predict the transient temperature and concentration profiles of South African coal dusts until ignition. The computed self-ignition temperatures of dust volumes show a good agreement with experimental results. In addition, it is found that the inhibiting effect of carbon dioxide is comparatively small and oxygen consumption increases dramatically after ignition. Parameter analysis shows that the heating value and kinetic parameters have a comparatively pronounced effect on self-ignition temperature. The model provides a satisfactory explanation for the dependence of self-ignition behaviour on gas atmospheres, thus helping to further understand the fire risk of self-ignition in oxy-fuel combustion systems.

Preparation and characterization of a wetting-agglomeration-based hybrid coal dust suppressant

基于湿润-凝聚工艺的复合煤尘抑尘剂制备与特征化

Process Safety and Environmental Protection, Volume 113, January 2018, Pages 282-291

Tao Fan, Gang Zhou, Jiayuan Wang

摘要：Driven by the advancement of science and technology, the number of safety incidents in coal mines has been steadily declining. Nonetheless, a small-scale killer, i.e., coal dust, has become a dominating factor threatening the safe production in coal mines. Therefore, the control of coal dust has become the key to the safe and efficient production of coal mines. The present paper discusses the preparation of a type of hybrid dust suppressant by cross-linking sodium ligninsulfonate and acrylamide, which generates a type of macromolecular product. Subsequently, Fourier infrared spectroscopy, X-ray diffraction spectroscopy and scanning electron microscopy experiments are conducted to analyze the structure of the product. Moreover, the TG-DSC experiments are carried out to analyze the thermal stability of the product. It is found through a single factor experiment that the optimal synthesis condition is: the mass ratio of lignin to acrylamide is 2:7; the mass ratio of cross-linking agent to acrylamide is 3%; the optimal reaction temperature is 65 °C; an examination of the product through a high-power microscope with ultra depth of field reveals that the prepared macromolecular product can cause the coal dust particles to undergo an agglomeration process; however, the prepared product cannot sufficiently wet the coal dust; to enhance the wettability of the production, 0.15% (by mass fraction) of dodecyl dimethyl betaine (DDB) is added to the system. An experiment concerning the interaction between coal dust and the prepared product indicates that the present suppressant can effectively suppress the dispersion of coal dust through a combination of wetting and agglomeration effects.

Dust dispersion in a coal roadway driven by a hybrid ventilation system: A numerical study

基于复合通风系统的煤巷粉尘分散：数值研究

Process Safety and Environmental Protection, Volume 113, January 2018, Pages 388-400

Fan Geng, Gang Luo, Yingchao Wang, Zhengbiao Peng, Hongli Chai

摘要：Dust contamination to ventilation systems is a common issue for mine operators during underground coal mining. In the present study, dust dispersion driven by a hybrid ventilation system in an underground mine has been investigated via a computational fluid dynamics (CFD) model. Specifically, the numerical model was developed based on the Euler–Lagrange method where the trajectory of dispersed dusts was solved individually. Dust dispersion induced by turbulence was considered by a stochastic tracking model. Effects of key parameters (e.g., gas velocity and exhaust duct length) on dust dispersion characteristics throughout the coal roadway have been examined. The results showed that the distribution of dusts exhibited extreme non-uniformity with a significantly higher concentration present near the mining face, particularly on the exhaust side. The cross-sectional average dust concentration substantially decreased along the axial direction in the front part of the coal roadway. Intense circumfluence and secondary sedimentation of dusts were found to be the main mechanisms that drove the non-uniform distribution of dusts. The model is shown to be capable of reproducing the dust dispersion process captured in the experiments and the prediction results agree well with the experimental data.

Dust removal efficiency of high pressure atomization in underground coal mine

地下煤矿高压雾化除尘效率

International Journal of Mining Science and Technology, In press, corrected proof, Available online 3 March 2018

Pengfei Wang, Xuanhao Tan, Weimin Cheng, Gang Zhou, Ronghua Liu

摘要：To master theoretical calculation for dust removal efficiency of high pressure atomization in an underground coal mine, the corresponding atomization characteristics and dust removal efficiency were both comprehensively studied in theory by virtue of related theories of hydromechanics and aerosol. According to actual measurements of flow coefficients and atomization angles of X-type swirl nozzle, computational formula was derived for atomized particle sizes of such a nozzle in conjunction with relevant empirical equation. Moreover, a mathematical model for applying high pressure atomization to dust removal in underground coal mine was also established to deduce theoretical computation formula of fractional efficiency. Then, Matlab was adopted to portray the relation curve between fractional efficiency and influence factors. In addition, a theoretical formula was also set up for removal efficiency of respirable dust and total coal dust based on dust size and frequency distribution equations. In the end, impacts of dust characteristic parameters on various dust removal efficiencies were analyzed.

Experimental analysis on post-explosion residues for evaluating coal dust explosion severity and flame propagation behaviors

评估煤尘爆炸与火焰传播特征的后爆炸残渣实验分析

Fuel, Volume 215, 1 March 2018, Pages 417-428

Qingzhao Li, Chuangchuang Yuan, Qinglin Tao, Yuannan Zheng, Yang Zhao

摘要：Coal dust explosion is a major threat to coal mine and other coal processing or utilizing industries. A deep investigation and accurate knowledge of coal dust explosion mechanism are still essential for the development of safety techniques for coal dust explosion prevention. In present work, the explosion severity of coal dust/air mixture, flame propagating properties, the characteristics of gas and solid residues had been studied. And, the correlations between the residues characteristics and explosion severity had been analyzed systematically. Results show that there is a linear relationship between explosion flame propagation speed (VF) and dust concentration (Cdust). With the increasing of vitrinite reflectance (Ro,max), explosion pressure (Pm), explosion pressure rise rate (dP/dt)m, explosion index (Kst) and flame propagation speed (VF) are all presenting a first increasing and then decreasing trends. During coal dust explosion, much more solid fragments are produced by the thermal stress and blast shock impacts. Compared with raw coal dust, particle size dispersities of all residues are increased obviously. Chemical functional groups in the coal dust particles, such as aromatic CH, aromatic C  C, aliphatic CH bonds, and oxygen-containing functional groups, etc. are all involved in coal dust explosion process. Furthermore, aliphatic CH and oxygen-containing matters may be the key factors influencing on the reactivity of dust explosion. For coal dust explosion under poor dust concentration conditions, the main gas components in the mixtures are CO2 product, residual oxygen and nitrogen gas in balance. The other combustible component (CO, CH4, C2H2, C2H4, C2H6 and C3H8) is almost undetectable. However, under dust-rich conditions, the combustible components would be increased sharply. The firstly detected combustible gases (CO, CH4, C2H2, C2H4, C2H6 and C3H8) can be used as the characteristic gases to determine the maximum explosion intensity of coal dust explosion.