The effects of fragmentation on devolatilization of large coal particles

Stubington, John F.; Linjewile, Temi M.

doi:10.1016/0016-2361(89)90316-5

Cited by 60 publications

(15 citation statements)

References 7 publications

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“…The measures taken to reduce emissions from coal combustion are not necessarily effective for high-volatile fuels. Feng et al [64] [65] have noted that inefficient in-bed combustion of volatile matter results in undesirably high freeboard temperatures, which facilitates the need for larger heat transfer surfaces in the freeboard region. The evolution of volatiles within the bed is dependent on the mixing of the coal particles [17,66] and progress of devolatilization of the particles from the time of entry to the fluidized bed to the completion of devolatilization.…”

Section: Implications Of Devolatilization In Fluidized Bed Pyrolysismentioning

confidence: 98%

A review on devolatilization of coal in fluidized bed

Borah

Ghosh

Rao

2011

Int. J. Energy Res.

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SUMMARYDevolatilization is an important step in fluidized bed combustion and gasification of coal. 'Devolatilization' is a general term that signifies the removal of volatile matters from the coal matrix. It is an extremely important step because the combustion of volatile matter can account for 50% of the specific energy of fluidized bed combustion of a high-volatile coal. Significant insights into the complex physicochemical phenomena that occur during devolatilization have been obtained in the recent years. This review focuses on the devolatilization of coal in an inert gas, air, and oxygen-enriched air, with emphasis on the effects of the operating parameters (e.g. temperature, heating rate, pressure, and gas velocity) on the yield of volatile matter. Particle size, oxygen content of the fluidizing gas, volatile content of coal and specific heat are some of the other important parameters for the devolatilization of coal. This review also explains the development and application of structural and empirical models. The structural models (e.g. FG-DVC and CPD models) are fairly complex. However, they can accurately predict the yields of gas and tar. It is observed from the review of the literature that the mechanism of coal devolatilization needs further study. Although the shrinking-core model can describe the devolatilization in the beginning and toward the end of the process, major deviations are often observed. The economic studies reveal that the capital cost of fluidized bed combustion reduces upon doubling the capacity. Some problems associated with bubbling fluidized bed combustion (e.g. the increase in freeboard temperature) have been explained with the present knowledge of devolatilization.

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Section: Implications Of Devolatilization In Fluidized Bed Pyrolysismentioning

confidence: 98%

A review on devolatilization of coal in fluidized bed

Borah

Ghosh

Rao

2011

Int. J. Energy Res.

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“…When connected to the issue of the reduction of tar through a secondary reaction, it is clear that the size of the particles used in the pyrolysis should be designed to provide sufficient residence time to proceed into a secondary reaction. Stubington and Linjewile [34] also mentioned that secondary reactions occured outside the coal particles (external secondary reaction) when the density of the particles in the pyrolysis process was high enough or the particle and/or product residence time in the hot zone was long enough. In this case, according to Stubington and Linjewile, [34] the influence of external secondary reaction will be higher compared to the effect of internal secondary reactions.…”

Section: Effect Of Temperature On Coal Pyrolysismentioning

confidence: 99%

Numerical simulation of coal pyrolysis with Tar and Gas products prediction

Sasongko

Arifpin

Rasrendra

et al. 2015

Asia-Pacific J Chem Eng

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Coal pyrolysis products can vary both in species and composition that are influenced by internal coal properties and process parameters, including temperature and heating rate during the pyrolysis process. In order to accurately predict the composition of the pyrolysis products, a mathematical model with correct formulation of heat transfer inside the coal particle is necessary to be developed. In this report, the inclusion of heat transfer term to the recent development of fragmentation and diffusion (FD) model is discussed and used to determine the coal pyrolysis products in various operating conditions. Derived from the model result, it concludes that the increment of reaction temperature led to higher rate of secondary reactions and suppress the production of tar. Taking the lignite-type coal pyrolysis of Zap North Dakota (average particle radius of 30 µm) as the sample, at temperature of 600°C, 96.4% of primary tar was produced by the primary reaction and diffused outward, while at temperature of 950°C, 49.9% of primary tar undergo secondary reactions.

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“…Ragland and Weiss, 1979;Sundback et al, 1984;Chirone and Massimilla, 1988,;Ragland and Pecson, 1988;Dakic et al, 1989;Stubington and Linjewile, 1989;Arena et al, 1992Arena et al, , 1994Dacombe et al, 1994;Stanmore et al, 1996;Dacombe et al, 1999;Lee, 2001;Lee et al, 2002;Zhang et al, 2002;Lee et al, 2003). The results of earlier studies have been extensively reviewed by .…”

Section: Introductionmentioning

confidence: 96%

An Experimental Investigation into the Fragmentation of Coal Particles in a Fluidized-Bed Combustor

Kosowska-Galacbowska

Luckos

2009

Proceedings of the 20th International Conference on Fluidized Bed Combustion

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Abstract:The fragmentation of coal plays a significant role in combustion in fluidized-bed boilers because it accelerates combustion and influences the distribution of particle sizes in the bed. Fine char particles produced by comminution can be carried out and increase the heat loss due to incomplete carbon conversion. The thermal fragmentation depends on the initial structure of the coal and how this structure changes with an increase in temperature when the particle is dropped into the combustion chamber. Experiments with nine Polish coals were carried out to quantify the fragmentation of burning coal particles. A bench-scale bubbling fluidized bed combustor was used to determine the degree of fragmentation for spherical coal particles during devolatilization and combustion. The effects of bed temperature, particle size and coal properties on the extent of primary and secondary fragmentation have been determined. It has been found that the combination of low porosity and high volatile content is the main factor responsible for the observed extent of fragmentation.

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The effects of fragmentation on devolatilization of large coal particles

Cited by 60 publications

References 7 publications

A review on devolatilization of coal in fluidized bed

A review on devolatilization of coal in fluidized bed

Numerical simulation of coal pyrolysis with Tar and Gas products prediction

An Experimental Investigation into the Fragmentation of Coal Particles in a Fluidized-Bed Combustor

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