Study of Interaction of Entrained Coal Dust Particles in Lean Methane-Air Premixed Flames
TL;DR: In this article, the interaction of micron-sized coal particles entrained into lean methane-air premixed flames was investigated and the effects of different coal dust concentrations (10−300g/m 3 ) entrained in the mixture of methane-Air at three lean equivalence ratios, ϕ, of 0.75, 0.80 and 0.85, on the laminar burning velocity were studied experimentally.
About: This article is published in Combustion and Flame.The article was published on 2012-07-01 and is currently open access. It has received 51 citations till now. The article focuses on the topics: Coal dust & Coal.
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TL;DR: In this article, the Hybrid Flame Analyzer (HFA) is used to measure burning velocity of gas, dust, and hybrid (gas and dust) premixed flames in premixed CH 4 -air.
66 citations
TL;DR: In this article, the minimum explosion concentration (MEC), over pressure rise (OPR), deflagration index for gas and dust hybrid mixtures (K st ) and explosive region of hybrid fuel mixtures present in Ventilation Air Methane (VAM) were investigated.
Abstract: Deflagration explosions of coal dust clouds and flammable gases are a major safety concern in coal mining industry. Accidental fire and explosion caused by coal dust cloud can impose substantial losses and damages to people and properties in underground coal mines. Hybrid mixtures of methane and coal dust have the potential to reduce the minimum activation energy of a combustion reaction. In this study the Minimum Explosion Concentration (MEC), Over Pressure Rise (OPR), deflagration index for gas and dust hybrid mixtures (K st ) and explosive region of hybrid fuel mixtures present in Ventilation Air Methane (VAM) were investigated. Experiments were carried out according to the ASTM E1226-12 guideline utilising a 20 L spherical shape apparatus specifically designed for this purpose. Results obtained from this study have shown that the presence of methane significantly affects explosion characteristics of coal dust clouds. Dilute concentrations of methane, 0.75–1.25%, resulted in coal dust clouds OPR increasing from 0.3 bar to 2.2 bar and boosting the K st value from 10 bar m s −1 to 25 bar m s −1 . The explosion characteristics were also affected by the ignitors’ energy; for instance, for a coal dust cloud concentration of 50 g m −3 the OPR recorded was 0.09 bar when a 1 kJ chemical ignitor was used, while, 0.75 bar (OPR) was recorded when a 10 kJ chemical ignitor was used. For the first time, new explosion regions were identified for diluted methane-coal dust cloud mixtures when using 1, 5 and 10 kJ ignitors. Finally, the Le-Chatelier mixing rule was modified to predict the lower explosion limit of methane-coal dust cloud hybrid mixtures considering the energy of the ignitors.
64 citations
TL;DR: In this article, a series of palladium doped cobalt spinel catalysts was synthesized via solution combustion synthesis plus incipient wetness impregnation and tested in lean CH 4 oxidation.
53 citations
TL;DR: In this article, the influence of dilute coal dust concentrations on the deflagration of methane in a hybrid form was investigated and two concentrations of coal dust were introduced to the methane deflagrations, which were 10gm −3 and 30gm−m−3.
47 citations
References
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Book•
22 Aug 2013
TL;DR: In this paper, the authors discuss coal processes and properties, basic reaction processes of coal particles, including coal devolatilization, char oxidation, and volatiles combustion, and fundamental equations and background for turbulent combustion systems.
Abstract: The book is divided into five major topic areas: general characteristics of coal processes and properties; basic reaction processes of coal particles, including coal devolatilization, char oxidation, and volatiles combustion; practical fossil combustion flames; fundamental equations and background for turbulent combustion systems; the approach and theory for the interactions between chemistry and turbulence in reacting systems encompassing gaseous flames, particle-laden systems, and pollutant formation in these systems.
608 citations
Book•
01 Jun 1991
TL;DR: In this article, a comprehensive account of the existing practical and theoretical knowledge of the origin, development, prevention and mitigation of dust explosions in the process industries is presented, along with an up-to-date evaluation of prevalent activities, testing methods, design measures and safe operating techniques.
Abstract: This work is a comprehensive account of the existing practical and theoretical knowledge of the origin, development, prevention and mitigation of dust explosions in the process industries. It offers an up-to-date evaluation of prevalent activities, testing methods, design measures and safe operating techniques in a detailed and comprehensive critique of all the significant phases relating to the hazard and control of a dust explosion. This should be a useful reference work for design, production, maintenance and safety engineers in the process industries, safety consultants and students.
586 citations
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01 Jan 2012
TL;DR: In this paper, an experimental system was designed to stabilize steady counterflow methane diffusion flames at elevated pressures, up to 3 MPa, and the replacement of nitrogen with helium as inert was found to be critical to stabilize well behaved flames with respect to steadiness, laminarity, adiabaticity, one dimensionality and flame thickness.
Abstract: An experimental system was designed to stabilize steady counterflow methane diffusion flames at elevated pressures, up to 3 MPa. In contrast with the much more common coflow configuration, the counterflow one is advantageous for the following reasons: the suppression of buoyancy instabilities that typically plague coflow flames at high pressures; the one-dimensionality of the flame, that enables computational modeling with very large chemical kinetic mechanisms; and the high level of control that it provides on soot loading. Above 0.8 MPa, the replacement of nitrogen with helium as inert was found to be critical to stabilize well behaved flames with respect to steadiness, laminarity, adiabaticity, one-dimensionality and flame thickness. Scaling and experimental considerations allowed for the identification of acceptable operating conditions in terms of pressure and strain rate and yielded a synthetic representation of a domain of diffusion flames of good quality. Such a graph can inform the design of a high-pressure counterflow system with respect to the selection of burner geometry, diagnostic techniques and experimental conditions, allowing for the experimentalist to sidestep costly and time consuming trial and error. Measurements by thin-filament pyrometry and numerical simulations confirmed the proposed scaling.
246 citations
"Study of Interaction of Entrained C..." refers background or methods in this paper
...[8], 4 CH h ∆ is the heat of combustion of methane, and the volume of the devolatilization zone is the conical space with a thickness of δ as shown in Fig....
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.../ )sin( Utr = α δ (5) The devolatilization time is used to estimate the total mass of released volatiles per unit volume during the passage of dust particles through δ and is given by: .rvv tmm ′′′=′′′ (6) This additional fuel is assumed to be CH4 for simplicity as suggested by Seshadri et al. [8] and added to the original gaseous mixture to obtain a new equivalence ratio....
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...Seshadri et al. [8] used the expression below to predict devolatilization rate of coal particles, ,4 2 nssv TrAnm π=′′′ (2) where the unit of vm ′′′ is mass of gaseous fuel vaporized per unit volume per second....
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...Or devolatilization rate can be estimated based on a temperature depended power-law relation as proposed by Seshadri et al [8]....
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...[8] and added to the original gaseous mixture to obtain a new equivalence ratio....
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228 citations
"Study of Interaction of Entrained C..." refers background in this paper
...[1] have shown that adding combustible liquid droplets to a gas flame can increase the burning velocity under certain conditions....
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...8 for conveying are pulverized coal, ash, food grains, sand particles and dry chemicals [1]....
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TL;DR: In this article, the structure of premixed flames propagating in combustible systems, containing uniformly distributed volatile fuel particles, in an oxidizing gas mixture, is analyzed in the asymptotic limit, where the value of the characteristic Zeldovich number, based on the gas-phase oxidation of the gaseous fuel, is large.
138 citations