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Pulverized Coal (pulverized + coal)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

A dimensionless factor characterizing the ignition of pulverized coal flow: Analytical model, experimental verification, and application

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2009
Qulan Zhou
Abstract An analytical model describing the ignition process of pulverized coal is proposed, and a dimensionless condition number (Ncom) is obtained to describe the comprehensive effect of factors governing the ignition of pulverized coal flow, such as the initial temperature of flow, the sectional heat load of the furnace, and the flux of primary air, secondary air and recirculation flue gas. An optimized concentration of pulverized coal flow is derived explicitly, upon which the earliest ignition of pulverized coal flow is possible. The model is verified in a hot furnace experiment, where it is shown that the derived criterion (Ncom) can be used for different kinds of coal and different types of burner. For given coal and sectional heat load of furnace, when the value of Ncom increases, the condition of ignition is improved and both unburned carbon and NOx emission are reduced. The employment of Ncom in the optimization of burner operating conditions is demonstrated through two applications. In practice, the criterion Ncom can be used to guide the selection of the concentration and type of pulverized coal, as well as the choice of burner and desired aerodynamic field, so as to achieve an optimized performance. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Numerical modelling and simulation of pulverized solid-fuel combustion in swirl burners

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
H. Ettouati
Abstract A finite-volume numerical model for computer simulation of pulverized solid-fuel combustion in furnaces with axisymmetric-geometry swirl burner is presented. The simulation model is based on the k,,,, single phase turbulence model, considering the presence of the dispersed solid phase via additional source terms in the gas phase equations. The dispersed phase is treated by the particle source in cell (PSIC) method. Solid fuel particle devolatilization, homogenous and heterogeneous chemical reaction processes are modelled via a global combustion model. The radiative heat transfer equation is also resolved using the finite volume method. The numerical simulation code is validated by comparing computational and experimental results of pulverized coal in an experimental furnace equipped with a swirl burner. It is shown that the developed numerical code can successfully predict the flow field and flame structure including swirl effects and can therefore be used for the design and optimization of pulverized solid-fuel swirl burners. On présente un modèle numérique de volumes finis pour la simulation par ordinateur de la combustion de combustibles solides pulvérisés dans des fours munis de brûleur à tourbillon axisymétrique. Le modèle de simulation repose sur le modèle de turbulence monophasique k,,,,, et décrit la présence de la phase solide dispersée par le biais de termes-sources additionnels dans les équations de la phase gazeuse. La phase dispersée est traitée par la méthode PSIC. La dévolatilisation des particules combustibles solides et les procédés de réaction chimique homogène et hétérogène sont modélisés à l'aide d'un modèle de combustion global. L'équation de transfert de chaleur radiatif est également résolue par la méthode des volumes finis. Le code de simulation numérique a été validé en comparant les résultats des calculs par ordinateur avec des expériences pour du charbon pulvérisé dans un four expérimental équipé d'un brûleur à tourbillon. On montre que le code numérique peut prédire avec succès le champ d'écoulement et la structure de flamme y compris les effets tourbillonnaires et qu'il peut donc servir à la conception et à l'optimisation des brûleurs à tourbillons pour les combustibles solides pulvérisés. [source]

Transformation behaviors of excluded pyrite during O2/CO2 combustion of pulverized coal

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010
Changdong Sheng
Abstract The article was addressed to the transformation of excluded pyrite during O2/CO2 combustion of pulverized coal. Raw pyrite mineral was added to a pulverized coal sample, which was density fractionated to remove the excluded minerals, to simulate the excluded pyrite present in coal. The mixed sample was burned in a drop tube furnace in O2/CO2 and O2/N2 conditions to generate the residue ash, which was characterized by Mössbauer spectroscopic and size analyses. It was found that, in comparison with O2/N2 combustion at the same oxygen concentration, slightly less iron glass silicate was formed from excluded pyrite and silicates although the transformation of pyrite to oxides was slowed in O2/CO2 combustion, different from the behaviors of included pyrite in pulverized coal those were observed in previous study. Additionally, less fragmentation of excluded pyrite particles was also observed in O2/CO2 combustion. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

SCT reaction kinetics model and diffusion for p.c. combustion in TGA

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010
Pei-Fang Fu
Abstract Recently, the process of char burnout is extensively concerned. Global model used widely cannot predict the extent of char burnout at the later burning stage. For the need of predicting the burnout degree in industrial pulverized coal (p.c.) fired furnace by making use of the experimental data from such as thermogravimetry analysis (TGA) and drop tube furnace, based on the simple collision theory (SCT) of chemical reaction kinetics, the SCT model is educed. The p.c. combustion is considered as the results of strike and oxidation of oxygen molecules on the surface of p.c. particles, and the frequency of effective strike was determined by Boltzmann factor. Strike and oxidation occur on the oxygen accessible specific surface area (OASA). Chemical regime controlled is at temperature below 1200 K, and molecules diffusion regime controlled is at the temperature above 1600 K, at which OASA corresponds to the specific surface area with pore diameter more than 38 nm of p.c particles in coal-fired boiler. The OASA of p.c. particles increases with the char burning, for the particles swells, shrinks and cracks. The burning rates calculated based on SCT model have shown good correspondence with experimental data reported. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]