Mechanism of solid-partical combustion with simultaneous gas-phase volatiles combustion

Howard, Jack B.; Essenhigh, Robert H.

doi:10.1016/s0082-0784(67)80164-4

Cited by 82 publications

(38 citation statements)

References 3 publications

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“…For each type of solid fuel, the efflux rate of the volatile was found to vary with the particle sizes. For example, Howard and Essenhigh reported that coal particles larger than 65 m do not react heterogeneously during the rapid devolatilization process [49]. Furthermore, according to the predicted results, the peak temperature for TB2 consisting of uniform particle sizes of 0.1 mm, 0.2 mm, and 0.3 mm is 1984 °C, 1881 °C, and 1582 °C, respectively, which indicates that a small particle is quickly combusted completely.…”

Section: Effect Of Particle Size On Flamementioning

confidence: 70%

Flame characteristics of pulverized torrefied-biomass combusted with high-temperature air

Biagini

Yang

et al. 2013

Combustion and Flame

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This version is available at https://strathprints.strath.ac.uk/53528/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Abstract:In this work, the flame characteristics of torrefied biomass were studied numerically under hightemperature air conditions to further understand the combustion performances of biomass.Three torrefied biomasses were prepared with different torrefaction degrees after by releasing 10%, 20%, and 30% of volatile matter on a dry basis and characterized in laboratory with standard and high heating rate analyses. The effects of the torrefaction degree, oxygen concentration, transport air velocity, and particle size on the flame position, flame shape, and peak temperature are discussed based on both direct measurements in a laboratory-scale furnace and CFD simulations. The results primarily showed that the enhanced drag force on the biomass particles caused a late release of volatile matter and resulted in a delay in the ignition of the fuelair mixture, and the maximum flame diameter was mainly affected by the volatile content of the biomass materials. Furthermore, oxidizers with lower oxygen concentrations always resulted in a larger flame volume, a lower peak flame temperature and a lower NO emission. Finally, a longer flame was found when the transport air velocity was lower, and the flame front gradually moved to the furnace exit as the particle size increased. The results could be used as references for designing a new biomass combustion chamber or switching an existing coal-fired boiler to the combustion of biomass.

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Section: Effect Of Particle Size On Flamementioning

confidence: 70%

Flame characteristics of pulverized torrefied-biomass combusted with high-temperature air

Biagini

Yang

et al. 2013

Combustion and Flame

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“…Single particle combustion modes were discussed comprehensively in previous studies [4,5,20]. In summary, Howard and Essenhigh [20] studied the combustion phenomena of coal particles and proposed a model to assess whether the burning of the volatiles and char takes place sequentially or simultaneously.…”

Section: Combustion Modementioning

confidence: 99%

“…In summary, Howard and Essenhigh [20] studied the combustion phenomena of coal particles and proposed a model to assess whether the burning of the volatiles and char takes place sequentially or simultaneously. Khatami et al [4,5] employed that model to a number of coals from different ranks in a variety of oxygen-nitrogen and oxygen-carbon dioxide environments.…”

Section: Combustion Modementioning

confidence: 99%

Single particle ignition and combustion of anthracite, semi-anthracite and bituminous coals in air and simulated oxy-fuel conditions

Riaza

Khatami

Levendis

et al. 2014

Combustion and Flame

188

111

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A fundamental investigation has been conducted on the combustion behavior of single particles (75-150 μm) of four coals of different ranks: anthracite, semi-anthracite, medium-volatile bituminous and high-volatile bituminous. A laboratory-scale transparent laminar-flow drop-tube furnace was used to burn the coals, electricallyheated to 1400 K. The experiments were performed in different combustion atmospheres: air (21%O 2 /79%N 2 ) and four simulated dry oxy-fuel conditions: 21%O 2 /79%CO 2 , 30%O 2 /70%CO 2 , 35%O 2 /65%CO 2 and 50%O 2 /50%CO 2 . The ignition and combustion of single particles was observed by means of three-color pyrometry and high-speed high-resolution cinematography to obtain temperature-time histories and record combustion behavior. On the basis of the observations made with these techniques, a comprehensive examination of the ignition and combustion behavior of these fuels was achieved. Higher rank coals (anthracite and semi-anthracite) ignited heterogeneously on the particle surface, whereas the bituminous coal particles ignited homogeneously at the gas phase. Moreover, deduced ignition temperatures increased * Corresponding author: Tel.: 001 (617) 373-3806; Fax: 001 (617) 373-2921 E-mail address: y.levendis@neu.edu 2 with increasing coal rank and decreased with increasing oxygen concentrations.Strikingly disparate combustion behaviors were observed depending on the coal rank.The combustion of bituminous coal particles took place in two phases. First, volatiles evolved, ignited and burned in luminous enveloping flames. Upon extinction of these flames, the char residues ignited and burned. In contrast, the higher rank coal particles ignited and burned heterogeneously. The replacement of the background N 2 gas of air with CO 2 (i.e., changing from air to an oxy-fuel atmosphere) at the same oxygen mole fraction impaired the intensity of combustion. It reduced the combustion temperatures and lengthened the burnout times of the particles. Increasing the oxygen mole fraction in CO 2 to 30-35% restored the intensity of combustion to that of air for all the coals studied. Volatile flame burnout times increased linearly with the volatile matter content in the coal in both air and all oxygen mole fractions in CO 2 . On the other hand, char burnout times increased linearly or quadratically versus carbon content in the coal, depending on the oxygen mole fraction in the background gas.

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“…In closing discussion, it may be informative to note that there exists another critical size for particles, defined whether the volatile-matter flame lifts from the particle surface or not, as examined by Howard and Essenhigh [65]. Since it has nothing to do with the critical particle size examined in the present study, it is strongly requested for readers not to confuse it with the present one, related to the activation of the surface reaction.…”

Section: Remarks Relevant To the Combustion Ratementioning

confidence: 78%

Critical condition related to the activation of solid fuel particles; comparisons with experimental results for char combustion in a quiescent environment

Makino

Shintomi

2015

Combustion and Flame

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Mechanism of solid-partical combustion with simultaneous gas-phase volatiles combustion

Cited by 82 publications

References 3 publications

Flame characteristics of pulverized torrefied-biomass combusted with high-temperature air

Flame characteristics of pulverized torrefied-biomass combusted with high-temperature air

Single particle ignition and combustion of anthracite, semi-anthracite and bituminous coals in air and simulated oxy-fuel conditions

Critical condition related to the activation of solid fuel particles; comparisons with experimental results for char combustion in a quiescent environment

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