Ignition of coal particles: A review

Essenhigh, Robert H.; Misra, Mahendra K.; Shaw, David W.

doi:10.1016/0010-2180(89)90101-6

Cited by 280 publications

(112 citation statements)

References 30 publications

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“…Figure 9 depicts the ignition temperatures at different particle diameter for three tested coal particles at μ-g and 1-g respectively. Consistent with previous studies (e.g., Essenhigh et al 1989;Katalambula et al 1997b), present experiments show that at both μ-g and 1-g, ignition temperature decreases with the particle size for a given coal. For the mm-sized particles, ignition occurs homogeneously, especially at μ-g, depending on the volatile matter concentration surrounding the particles.…”

Section: Ignition Of Single Mm-sized Particles At μ-Gsupporting

confidence: 92%

“…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%

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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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Section: Ignition Of Single Mm-sized Particles At μ-Gsupporting

confidence: 92%

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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“…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%

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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“…This is followed by ignition of the char. The heterogeneous coal ignition mechanism involves the direct attack of oxygen on the whole coal particles and, in this case, the rates of heat generation due to combustion reactions are much higher than the rates of heat removal [7][8][9].…”

Section: Introductionmentioning

confidence: 99%