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|Title:||The stoichiometry and kinetics of carbon combustion at low temperature: A surface complex approach|
|Citation:||Proceedings of the Combustion Institute, 2009; 32(Part 2):1981-1988|
|Publisher:||The Combustion Institute|
|Abstract:||The stoichiometry and rate of carbon combustion at low temperature (673 K) were investigated. Oxidation and TPD experimental data provide quantification of gaseous products and stable surface complexes over a broad range of conversion. Our analysis distinguishes between surface complexes forming CO and CO2 and has assumed a certain fraction of each complex type decomposes instantaneously upon formation, leaving the remainder on the surface as stable complexes, C(O) and C(O2). This analysis suggests that a maximum of 25% of CO-complexes and 89% of CO2-complexes are unstable upon formation. At low conversion, unstable complex formation is the dominant pathway for the CO product. As conversion increases, decomposition of stable CO-complexes eventually becomes the main source of CO. Formation of unstable CO2-complexes is the dominant pathway for the CO2 product at all times. The combustion rate is initially high due to a high availability of vacant active sites, decreases sharply as these sites are filled with stable complexes, and gradually increases as the stable complexes promote CO2-complex formation, in turn, driving their decomposition. The dynamics of formation and decomposition of C(O) and C(O2) dictates their ratio on the carbon surface at any moment, which may be measured by TPD. This work may help in developing new kinetic models of carbon combustion which can predict the stoichiometry as well as the rate.|
|Keywords:||Char; Reactivity; Primary product ratio; Surface oxides|
|Description:||Copyright © 2009 Elsevier Inc. All rights reserved.|
|Appears in Collections:||Chemical Engineering publications|
Environment Institute publications
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