Fragmentation of small coal particles under fluidized-bed combustor conditions

Stanmore, B. R.; Brillard, Alain; Gilot, P.; Delfosse, L.

doi:10.1016/s0082-0784(96)80173-1

Cited by 18 publications

(15 citation statements)

References 4 publications

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“…It means if a fuel particle has irregularities in structure and composition, then with the increase in particle size, the nonhomogeneity gets compounded, resulting in increased thermal stress. 33 Finally, the particle tends to crack severely and produce daughter fragments. If the particle is more homogeneous, the effect of particle size is less pronounced.…”

Section: Energy and Fuelsmentioning

confidence: 99%

Primary Fragmentation Behavior of Indian Coals and Biomass during Chemical Looping Combustion

Pragadeesh

Sudhakar

2018

Energy Fuels

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Devolatilization and fragmentation are important physical phenomena occurring during solid fuel chemical looping combustion (CLC). Primary fragmentation during devolatilization strongly affects the rate of fuel conversion, emissions, and fine particulates generation in a fuel reactor of a fluidized bed CLC unit, thus forming a critical design input. The present study focuses on investigating the primary fragmentation behavior of large coal and biomass (wood) particles during the devolatilization phase of CLC. Three types of coals (two Indian coals, one Indonesian coal) and one type of Casuarina wood of three sizes in the range of 8–25 mm, at different fuel reactor bed temperatures (800, 875, and 950 °C) are studied for primary fragmentation. Iron ore with 64% Fe is used as the oxygen carrier bed material, with steam as the fluidizing medium in the fuel reactor. The fragmentation behavior is expressed in terms of the number of fragments, fragmentation index, frequency of fragmentation, and particle size distribution of fragments at different residence times of coal during devolatilization in the fuel reactor. Under the conditions of study, the number of fragments increases with an increase in particle size and temperature, for all fuels studied. Also, it is found that the number of fragments increases with the decrease in compressive strength of both coal and biomass particles. The Indian coals are found to fragment in the earlier stages of devolatilization, while the Indonesian coal and the biomass particles begin to fragment in the later stages of devolatilization. The maximum fragmentation index is found with Indian coal - IC1, which has the highest fixed carbon content among the fuels studied, and the least value is observed in biomass. Different modes of fragmentation exhibited by each fuel type is discussed. Indian coals do not show any volumetric changes as such, whereas Indonesian coal indicates some degree of volumetric expansion.

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Section: Energy and Fuelsmentioning

confidence: 99%

Primary Fragmentation Behavior of Indian Coals and Biomass during Chemical Looping Combustion

Pragadeesh

Sudhakar

2018

Energy Fuels

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“…Marban et al [10] haben für Anthrazitpartikel eine kritische Partikelgröße von 0,68 mm festgestellt. Stanmore et al [16] berichteten, dass für verschiedene Steinkohlepartikel eine drastische Verringerung des Fragmentierungsfaktors unterhalb des Schwellwertes von 1,5 mm auftritt.…”

Section: Einfluss Der Partikelgrößeunclassified

“…Als mögliche Ursachen für die stark sinkende Fragmentierungsintensität mit geringer werdender Partikelgröße kommen kürzere Wege für den Abtransport der freigesetzten flüchtigen Bestandteile und/oder geringere thermische Spannungen, welche durch Temperaturgradienten im Kohlepartikel hervorgerufen werden, in Frage [16].…”

Section: Einfluss Der Partikelgrößeunclassified

Experimental Investigation of Primary Fragmentation of Coal Particles in a Drop‐DSC

Friedemann¹,

Baitalow²,

Ceia³

et al. 2014

Chemie Ingenieur Technik

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Experimental Investigation of Primary Fragmentation of Coal Particles in a Drop-DSCIn the presented work, the fragmentation behavior of 18 coals was investigated under high temperature conditions in a drop calorimeter. It was shown that the fragmentation intensity strongly depends on the coals used but tends to increase with increasing coal rank. Furthermore, it was determined that the fragmentation ratio increases with increasing temperature and particle size. As a requirement, a critical value for temperature and particle size has to be exceeded.

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“…Two phenomena have been reported as the causes for the primary fragmentation of coal: rapid change of the temperature and the formation of volatiles within the particle. Some authors have given priority to the mechanical stress generated by the pressure of volatiles, ,− whereas others prioritized the thermal stress. ,− Reduced primary fragmentation of pretreated coal (mildly prepyrolyzed anthracite in work of Chirone et al and devolatilized Chinese coals done by Zhang et al) indicated that the quantity and pressure of volatiles contribute to the particle breakage. On the other hand, experiments designed to show the influence of the FB temperature and the size of coal particles ,,,, testify to the role of thermal stress.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Coal Primary Fragmentation and Char Particle Size Distribution in Fluidized Bed

et al. 2013

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The combination of temperature gradient and volatile release has been identified as the main cause for primary fragmentation (breakage of fuel particles during devolatilization). A mathematical model of the primary fragmentation in a fluidized bed has been developed, incorporating both causes. It takes into account the type of the coal, size of the coal particles, and the fluidized bed temperature. The model simulates fragmentation of a batch of coal particles. For each particle in the batch, the model follows propagation and merging of cracks, starting from randomly distributed pre-existing pores, leading to possible breakage of the particle. The model calculates volume of the fragmented particles and volume diameters, classifying them into size classes. For each size class, the number of particles is counted, and the mass fraction is calculated. The results are the distribution of mass and number of char particles after the devolatilization and the primary fragmentation parameters.

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Fragmentation of small coal particles under fluidized-bed combustor conditions

Cited by 18 publications

References 4 publications

Primary Fragmentation Behavior of Indian Coals and Biomass during Chemical Looping Combustion

Primary Fragmentation Behavior of Indian Coals and Biomass during Chemical Looping Combustion

Experimental Investigation of Primary Fragmentation of Coal Particles in a Drop‐DSC

Prediction of Coal Primary Fragmentation and Char Particle Size Distribution in Fluidized Bed

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