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Title	Modelling of Coal Pyrolysis and Combustion
Creator	Saastamoinen, J.
Publisher	Digitized by J. Willard Marriott Library, University of Utah
Date	1988
Spatial Coverage	presented at Pittsburgh, Pennsylvania
Abstract	A coal particle combustion model starting from the devolatilization to the final char combustion is presented. The most serious shortcoming of modelling the coal devolatilization by means of Arrhenius kinetics is the failure to account for the apparently asymptotic yield of volatiles that depends on the temperature. A coal devolatilization model that is based on the temperature dependent asymptotic yield of volatiles is presented. This model applies well for the usual non-isothermal coal particle pyrolysis. Three different char combustion models are compared to measurements presented in the literature. Intra-particle heat transfer during the drying and the pyrolysis stage of the combustion is considered. The spatial temperature differences during the char combustion stage are usually insignificant, but there is a significant spatial temperature distribution inside the particle during the drying and the devolatilization even the particle is small. This paper is based on three larger unpublished reports /1,2,3/ that are available on request from Domestic Fuel Laboratory.
Type	Text
Format	application/pdf
Language	eng
Rights	This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
Conversion Specifications	Original scanned with Canon EOS-1Ds Mark II, 16.7 megapixel digital camera and saved as 400 ppi uncompressed TIFF, 16 bit depth.
Scanning Technician	Cliodhna Davis
ARK	ark:/87278/s6bv7k6m
Setname	uu_afrc
ID	5083
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6bv7k6m

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Title	Page 6
Format	application/pdf
OCR Text	Show - 6 - Fig. 3. Devolatilization M/Mo 1 of a particle. e(T) o ~------~~--~--------~ T PARTICLE TEMPERATURE t TIME (nonlinear scale) The mass loss curve of the particle coincides with the curve e(T) and the transient mass of the particle is uniquely defined by the transient particle temperature, when the devolatilization is limited by the heat transport. The total model for small particles is based on the numerical solution of the energy equation for the particle d dT d dp pCG dt + Ip G dt = (5 ) where the first term on the left side is due to the heat storage and the second term accounts for the heat of pyrolysis reactions. The first term on the right side is due to the convection from the surrounding gas or flame and the second term is due to the radiation to the walls. The corresponding equation for a large particle is discussed later. The density p of the particle decreases during the devolatilization. Tef is the temperature of the atmosphere if it is inert or before the ignition of the volatiles. After ignition the effective flame temperature is /9/ (6 ) The heat transfer coefficientho is calculated from the correlation 1/3 Nu = 2 + O.6iRe Pr (7 ) The heat transfer coefficient is reduced due to the volatiles efflux according to h/h o = 1/{St(exp(1/St)-1)}.
Setname	uu_afrc
ID	5063
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6bv7k6m/5063