The transient ignition of isolated coal particle

Du, Xiaoxu; Annamalai, K.

doi:10.1016/0010-2180(94)90025-6

Cited by 98 publications

(48 citation statements)

References 14 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%

“…However, this might not be accurate since that homogeneous ignition occurred at the location away from the particle surface. Consequently, a new criterion defined as oT or r¼a ¼ 0ða > r p Þ was proposed by Du and Annamalai [5]. In this study, this criterion was adopted, coupled with the new model considering thermal conduction inside the coal particle.…”

Section: Resultsmentioning

confidence: 99%

“…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%

“…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. Obviously, this kind of manipulation, though convenient, could induce noticeable discrepancy, especially for large coal particles with diameter larger than 1 mm [5,8]. One important reason to cause this mismatch was due to lack of experimental data at l-g. As introduced, experimental data, even with questionable accuracy were only available after 1990s.…”

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: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Pulverized Coal‐Fired Boilers

Zhang

2010

Handbook of Combustion

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The sections in this article are Introduction PC Combustion and PC Fired Boiler Physical Properties of PC Particles Conventional Layout of a PC Boiler Heating Surfaces and Water‐Vapor Path in a PC Boiler Heat Transfer Calculation Procedure of a PC Boiler Some Theories Theoretical Air and Coefficient of Excess Air Heat Balance and Efficiency of a PC Boiler Ignition of PC Particles Char Combustion NO x Formation Mechanisms Thermal NO Fuel NO PC Fired Furnace Furnace Layout and Firing Type Cross‐Section Heat Release Rates Selection Volumetric Heat Release Rates Selection Empirical Heat Transfer Calculation in the Furnace General Introduction Heat Input to the Furnace Emissivity of the Flame and the Furnace Empirical Heat Transfer Calculation in the Furnace PC Fired Burners General Introduction Arrangement of Burners Low NO x burners ( LNB ) Examples of LNBs Boat‐Shaped Bluff‐Body Burner Double PA Channel Burner DRB Burner WR Burner PM Burner and Vertical Rich/Lean Louver Damper Burner and Bias Combustion In‐Furnace HTAC Burner Outlook Summary

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