Fragmentation on batches of coke or char particles during fluidized bed combustion

Pinho, Carlos

doi:10.1016/j.cej.2005.10.001

Cited by 12 publications

(7 citation statements)

References 7 publications

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“…One is the freezing of the reaction that is achieved by replacing the fluidization air by nitrogen and, subsequently, cooling the bed, with the char particles being collected and analyzed. This method was studied by several authors. − It is a time-consuming method adopted in fundamental scientific studies. The other process, which was used in this work, assesses the degree of fragmentation of the particles through the experimental values of the Sherwood number and reaction rate constant, which were obtained through combustion experiments involving the mechanically stronger and weaker pellets.…”

Section: Resultsmentioning

confidence: 99%

“…The fragmentation study conducted with Acacia char pellets was based on a model developed by Pinho . Using this model and the experimental values of the Sherwood number and reaction rate constant obtained in the fluidized bed combustion, the fragmentation ratio σ can be determined.…”

Section: Mathematical Modelsmentioning

confidence: 99%

“…The main purpose of this work is to study the fragmentation phenomenon of Acacia dealbata char pellets burning in a laboratory-scale fluidized bed reactor. A previously developed fragmentation model was used to determine the fragmentation ratio through the analysis of kinetic and diffusive data, obtained from the combustion experiments of mechanically stronger and weaker pellets of the above-mentioned species.…”

Section: Introductionmentioning

confidence: 99%

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Simple Methodology To Quantify the Fragmentation on Batches of Char Pellets During Fluidized Bed Combustion

et al. 2017

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A simple technique is used to determine the degree of fragmentation during the fluidized bed combustion of biochar pellets. From the analysis of the evolution of the overall resistance of combustion of batches of particles, composed alternatively by robust and fragile particles, kinetic and diffusive data for both types of particles were obtained. Subsequently, through the obtained combustion information, the degree of fragmentation of the fragile particles was determined. The experiments were carried out for bed temperatures of 700 and 800 °C, using Acacia dealbata char pellets.

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Section: Resultsmentioning

confidence: 99%

Section: Mathematical Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simple Methodology To Quantify the Fragmentation on Batches of Char Pellets During Fluidized Bed Combustion

et al. 2017

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“…Each plot has two sets of data points for that particular char, but only 10% of the registered points are shown in each plot. U-type curves are quite common for fluidized bed batch combustion experiments of cokes and chars, as referred to by many authors. ,,,, …”

Section: Resultsmentioning

confidence: 99%

Determination of Fluidized Bed Combustion Kinetic and Diffusive Data of Four Wood Chars from the Central Region of Portugal

Pereira

Pinho

2013

Energy Fuels

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The fluidized bed reactor is suitable for the combustion of biomass solid fuels because of its advantages in terms of pollution control. At the same time it is a useful laboratory tool to determine kinetic and diffusive combustion data in operating conditions similar to those found in industrial systems. Because of the heterogeneous nature of biomass, available information on its combustion is still limited. During the combustion of ligneous biomass, the burning of the solid carbonaceous residues formed after the initial steps of drying and volatiles release is the time-consuming step. In the present work, kinetic and diffusive data from the fluidized bed combustion of chars produced from four Portuguese wood speciesQuercus ilex (holm oak), Eucalyptus globulus (eucalyptus), Pinus pinaster (maritime pine), and Quercus suber (cork oak)were obtained in the 750–900 °C temperature range. Subsequently, activation energies and pre-exponential factors were calculated from the Arrhenius plot of the kinetic data. The obtained activation energies from 38 to 121 kJ/mol are coherent with results obtained for other wood chars and demonstrate that the fluidized bed technology is a fruitful and reliable methodology to achieve a collection of results of real and industrial interest. The main goal of the present work is to widen the information on the kinetic and diffusive data of wood chars in order to better understand the mechanisms of ligneous biomass combustion, and the data now published increases the range of available kinetic data on wood char combustion.

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“…Many researchers have studied the fragmentation phenomenon in both particle models [5,9,[20][21][22][23][24] and in reactors models, laminar flow reactors [25] or fluidized beds [26,27]. Such models can be classified in three distinct approaches:…”

Section: Introductionmentioning

confidence: 99%

Impact of peripheral fragmentation on the steam gasification of an isolated wood charcoal particle in a diffusion-controlled regime

Golfier¹,

Steene

Salvador

et al. 2009

Fuel

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This study focuses on the effect of peripheral fragmentation during gasification of an isolated wood charcoal particle in the regime of diffusional limitations. In fact, all the models available in the literature fail to reproduce the specific changes in biomass charcoals for which conversion increases quasi linearly versus time, whatever the particle size. We assumed this discrepancy is partly due to the fragmentation phenomenon, i.e. the detachment of fragments from the surface of the particle, which is not usually taken into account in models. The classical assumption in percolation models is a critical value of porosity beyond which fragmentation occurs. We compared our model results with experimental data. We demonstrated that in the diffusion-limited regime, the direct extrapolation of such a method to a continuum model is not satisfying. A new criterion of fragmentation based on a critical porosity and a critical porosity gradient is proposed which considerably improves modelling of gasification charcoal particles.

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Fragmentation on batches of coke or char particles during fluidized bed combustion

Cited by 12 publications

References 7 publications

Simple Methodology To Quantify the Fragmentation on Batches of Char Pellets During Fluidized Bed Combustion

Simple Methodology To Quantify the Fragmentation on Batches of Char Pellets During Fluidized Bed Combustion

Determination of Fluidized Bed Combustion Kinetic and Diffusive Data of Four Wood Chars from the Central Region of Portugal

Impact of peripheral fragmentation on the steam gasification of an isolated wood charcoal particle in a diffusion-controlled regime

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