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Conversion of char nitrogen to NO during combustion

Lookup NU author(s): Emeritus Professor Mark ThomasORCiD


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The emissions of NOx during coal combustion form a significant contribution (20%) to the total emitted in the UK. In this study, nine coals were selected as part of the UK's "DTI-NOx" programme, as typical of the rank range, worldwide origin and combustion characteristics of those used in UK power stations. These coals were pyrolysed in drop-tube reactors at 1273 K (residence time 1 s) and 1623 K (residence time 0.3 s). The microporous structures of the coals and chars were characterised by gas adsorption methods. Char morphology was studied using scanning electron microscopy. The isothermal combustion and NO gasification characteristics of the resultant chars were investigated. At high temperature, the conversion of char-N to NO tends to a constant value of approximately 0.2 in our experiments, and this value may be useful for engineering calculations of NO emissions in fixed and fluidised beds. At lower temperatures, in chemical control, the different char combustion rates could be rationalised using the approach of Smith, i.e., corrected for differences in porosity. However, the conversion of char nitrogen to NO is a complex function of the char pore structure, its development during combustion, char reactivity towards NO and char catalysis of the CO + NO reaction.

Publication metadata

Author(s): Jones JM, Pourkashanian M, Williams A, Rowlands L, Zhu Q, Thomas KM

Publication type: Article

Publication status: Published

Journal: Journal of the Energy Institute

Year: 2004

Volume: 77

Issue: 513

Pages: 82-89

ISSN (print): 1743-9671

ISSN (electronic): 1746-0220

Publisher: Maney Publishing