A theory on transition of ignition phase of coal particles

Annamalai, K.; Durbetaki, P.

doi:10.1016/0010-2180(77)90107-9

Cited by 113 publications

(31 citation statements)

References 21 publications

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“…For all testing coals, the ignition temperature decreases when initial coal particle size increases from 1.5 to 2.0 mm. The results confirmed the literatures ones obtained by various kinds of experimental methods and modeling [2][3][4][5][6]10], indicating that to reach the same volatile matter concentration for ignition, higher temperature is needed for smaller particles. Shown in Fig.…”

Section: Mathematic Modelingsupporting

confidence: 88%

“…For simplification, single-particle studies were often taken [e.g., [1][2][3][4][5][6][7][8][9][10][11]. Some of them experimentally obtained a large amount data on the ignition temperature and ignition time, and some of them developed ignition models.…”

Section: Introductionmentioning

confidence: 99%

“…Various models of coal ignition have been developed [e.g., [1][2][3][4][5][6]11,14]. However, nearly all of them neglected the influence of natural convection while the results were directly compared with experimental data obtained at 1-g in the presence of natural convection.…”

Section: Introductionmentioning

confidence: 99%

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Ignition of single coal particle in a hot furnace under normal- and micro-gravity condition

Zhu

Zhang

Gen-tu

et al. 2009

Proceedings of the Combustion Institute

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An experimental study on ignition and combustion of single particles was conducted at normal gravity (1-g) and microgravity (l-g) for three high volatile coals with initial diameter of 1.5 and 2.0 mm, respectively. The non-intrusive twin-color pyrometry method was used to retrieve the surface temperature of the coal particle through processing the images taken by a color CCD camera. At the same time, a mathematical model considering thermal conduction inside the coal particle was developed to simulate the ignition process.Both experiments and modeling found that ignition occurred homogeneously at the beginning and then heterogeneously for the testing coal particles burning at l-g. Experimental results confirmed that ignition temperature decreased with increasing volatile content and increasing particle size. However, contradicted to previous studies, this study found that for a given coal with certain particle size, ignition temperature was about 50-80 K lower at l-g than that at 1-g.The model predictions agreed well with the l-g experimental data on ignition temperature. The criterion that the temperature gradient in the space away from the particle surface equaled to zero was validated to determine the commence of homogeneous ignition. Thermal conduction inside the particle could have a noticeable effect for determining the ignition temperature. With the consideration of thermal conduction, the critical size for the phase transient from homogeneous to heterogeneous is about 700 lm at ambient temperature 1500 K and oxygen concentration 0.23.

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Section: Mathematic Modelingsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Ignition of single coal particle in a hot furnace under normal- and micro-gravity condition

Zhu

Zhang

Gen-tu

et al. 2009

Proceedings of the Combustion Institute

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“…Most arc described in the review by Essenhigh et al (21 The ignition behavior of clouds of pulverized fuel is of greatest interest to those concerned with the prevention of dust explosions (in coal mines or grain elevators, for example) and with flame stabiliry in coal-fired combustors (3)(4)(5).…”

Section: Introducfionmentioning

confidence: 99%

Laser ignition of pulverized coals

Chen

Taniguchi

Narato

et al. 1994

Combustion and Flame

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We present a novel experiment to study the ignition of pulverized ooal. A dilute stream of panicles is dropped inlo a laminar, upward-flow wind lunnel with a quartz lest section. lbc gas stream is not preheated, A single pulse from a Nd:YAG laser is fotused through the tunnel and ignites the fuel. The transparent test section and cool walls allow for optical detection of the ignition process. In this article we describe the experiment and demonstrate ilS capabilities by ohserving the ignition behavior of spherical, amorphous-"', oxygen consumption (mol C mol O 2 -t) h convective heat transfer coefficient, evaluated in the limit whereR condition at particle surface, r -R k particle thennal conductivity (W m-free-stream or environment condition K-1 ) thermal conductivity of the gas in the Greek Symbols boundary layer (W m-l K-1 ) molecular weight of carbon (g mol-I) a constant derived from the correlation order of reaction (-) for the binary diffusion coefficient of pressure (Pa) oxygen = 9.25 x to-IO (m 2 S-l K-US ) rate of heat generation (W)Ii H, heat of reaction per mass of carbon rate of heat loss (W) consumed (J kg-I)

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“…Previous studies showed that this process is influenced by a few factors, including coal type (Annamalai and Durbetaki 1977;Karcz et al 1980;Tognotti et al 1985;Gieras et al 1986a, b;Essenhigh et al 1989;Gururajan et al 1990;Du and Annamalai 1994;Zhang and Wall 1994;Chen et al 1994;Davini et al 1996;Katalambula et al 1996Katalambula et al , 1997aYang et al 2005), particle size (Annamalai and Durbetaki 1977;Karcz et al 1980;Tognotti et al 1985;Gieras et al 1986a, b;Essenhigh et al 1989;Gururajan et al 1990; Du and Annamalai 1994;Zhang and Wall 1994;Chen et al 1994;Davini et al 1996;Katalambula et al 1996Katalambula et al , 1997a, oxygen concentration (Annamalai and Durbetaki 1977;Karcz et al 1980;Tognotti et al 1985;Gieras et al 1986a, b;Essenhigh et al 1989;Gururajan et al 1990;Zhang and Wall 1994;Chen et al 1994), heating rate (Gieras et al 1986b;Essenhigh et al 1989;Gururajan et al 1990;Du and Annamalai 1994;Zhang and Wall 1994;Katalambula et al 1997b;…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Ignition Process of Single Coal Particles at Microgravity

Gen-tu

Zhang

Zhu

et al. 2008

Microgravity Sci. Technol.

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In this paper, the first Chinese microgravity (μ-g) experimental study on coal combustion was introduced. An experimental system used to study the ignition process of single coal particles was built up, complying with the requirements of the 3.5 s drop tower in the National Microgravity Laboratory of China (NMLC). High volatile bituminous and lignite coal particles with diameter of 1.5 and 2.0 mm were tested. The ignition and combustion process was recorded by a color CCD and the particle surface temperature before and at the ignition was determined by the RGB colorimetric method. Comparative experiments were conducted at normal gravity (1-g). The experiments revealed that at different gravity levels, the ignition of all tested coal particles commenced in homogeneous phase, while the shape, structure, brightness and development of the flames, as well as the volatile matter release during the ignition process are different. At μ-g, the part of volatile was released as a jet, while such a phenomenon was barely observed at 1-g. Also, after ignition, flames were more spherical, thicker, laminated and dimmer at μ-g. It was confirmed that ignition temperature decreased as the particle size or volatile content increased. However, contradicted to existing experimental results, provided other experimental conditions except gravity level were the same, ignition temperature of coal particles was about 50-80 K lower at μ-g than that at 1-g.

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A theory on transition of ignition phase of coal particles

Cited by 113 publications

References 21 publications

Ignition of single coal particle in a hot furnace under normal- and micro-gravity condition

Ignition of single coal particle in a hot furnace under normal- and micro-gravity condition

Laser ignition of pulverized coals

Experimental Study on the Ignition Process of Single Coal Particles at Microgravity

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