Devolatilization and char burning of coal particles in a fluidized bed combustor

Jia, Lei; Becker, H. A.; Code, R. K.

doi:10.1002/cjce.5450710103

Cited by 24 publications

(6 citation statements)

References 11 publications

(8 reference statements)

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“…It can be seen that the fluidization velocity does not play a noticeable role on devolatilization time of the oil sludge pellet in air atmosphere. This is consistent with the study by Jia et al [23], who undertook experiments on pyrolysis and combustion of several coals in FB reactor, and found that superficial gas velocity play a little role on release and burnout of volatiles.…”

Section: Influence Of Fluidization Velocity On Devolatilizationsupporting

confidence: 90%

Devolatilization of oil sludge in a lab-scale bubbling fluidized bed

Liu

Jiang

Han

2011

Journal of Hazardous Materials

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Section: Influence Of Fluidization Velocity On Devolatilizationsupporting

confidence: 90%

Devolatilization of oil sludge in a lab-scale bubbling fluidized bed

Liu

Jiang

Han

2011

Journal of Hazardous Materials

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“…There are very few reports in the literature on devolatilization time in oxygen-enriched air [46,56,57]. A summary of these results is presented in Table IV.…”

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confidence: 71%

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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“…Jia et al discussed the importance of studies on larger coal particles and reported devolatilization times of coal of various sizes up to 36 mm. However, a review on devolatilization of coals in fluidized beds by Borah et al points out that there are only a few devolatilization studies in conventional FB combustors that focus on larger particles as used in commercial units.…”

Section: Introductionmentioning

confidence: 99%

“…The use of large (mm-sized) fuel particles can also be beneficial in the CLC systems for the following other reasons: (i) reduction in auxiliary power consumption by cutting down energy usage in pulverizing fuel particles 20 and the power consumption reduces further upon using heavily fragmenting high-carbon coals under FB conditions; (ii) use of large coal particles aids in slow release of volatiles and other combustible gases, resulting in reduced levels of uncombusted gases at the exit of fuel reactor (thus cutting down the oxygen requirement for oxygen-polishing step) and also avoiding additional requirement of oxygen carrier inventory in the system. Jia et al 21 discussed the importance of studies on larger coal particles and reported devolatilization times of coal of various sizes up to 36 mm. However, a review on devolatilization of coals in fluidized beds by Borah et al 22 points out that there are only a few devolatilization studies in conventional FB combustors that focus on larger particles as used in commercial units.…”

Section: Introductionmentioning

confidence: 99%

Color Indistinction Method for the Determination of Devolatilization Time of Large Fuel Particles in Chemical Looping Combustion

Pragadeesh

Sudhakar

2019

Energy Fuels

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Chemical looping combustion (CLC) is one of the promising fuel conversion technologies for carbon capture with low energy penalty. Devolatilization is an important physical phenomenon occurring during solid fuel CLC. Devolatilization behavior influences fragmentation, combustion rate, emission, and particulates generation in fluidized bed CLC (FB-CLC), thus a critical input for its design. Existing visual techniques for determining devolatilization time cannot be applied in CLC conditions because of its flameless combustion nature. In the present study, a new, simple, and quick technique called “color indistinction method” (CIM) is proposed for the determination of devolatilization time (τd) in FB-CLC, where the end of devolatilization is inferred from the disappearance of fuel particle in a hot fluidized bed. Single-particle devolatilization studies in FB-CLC are conducted to determine the devolatilization time using CIM for two types of fuels, viz., coal and biomass (Casuarina equisetifolia wood), of size range 8–25 and 10–20 mm, respectively, at three different fuel reactor bed temperatures (800, 875, and 950 °C) and one fluidization velocity. The proposed technique is validated in three ways: (i) the measurement of residual volatiles present in char by thermogravimetric analysis; (ii) mass loss history of the fuel during devolatilization; and (iii) diagnostics using particle center temperature measurements. The results of CIM experiments, in terms of degree of error involved, are compared with an established flame extinction technique (FET) and a more accurate particle center temperature (PCT) method. The amount of volatiles released during devolatilization, as determined by CIM, is 91.3% for coal and 98.9% for biomass. These values compare very well with the results of the established FET, in which the volatile release is 90.7% for coal and 99.1% for biomass samples. The devolatilization times determined using CIM are in line with particle center temperature measurements with an acceptable error range of −7.57 to +3.70%. The proposed CIM is successful in establishing the devolatilization time of different fuels in CLC conditions and can also be applied in other flameless combustion conditions.

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Devolatilization and char burning of coal particles in a fluidized bed combustor

Cited by 24 publications

References 11 publications

Devolatilization of oil sludge in a lab-scale bubbling fluidized bed

Devolatilization of oil sludge in a lab-scale bubbling fluidized bed

A review on devolatilization of coal in fluidized bed

Color Indistinction Method for the Determination of Devolatilization Time of Large Fuel Particles in Chemical Looping Combustion

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