Lookup NU author(s): Emeritus Professor Mark Thomas
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The effect of pyrolysis conditions on the release of nitrogen during char combustion was investigated. A fluidized bed pyrolysis unit was used to produce several chars at different temperatures and pressures from a Spanish coal. In this way, a number of chars differing in volatile matter and specific surface area were obtained. Gas evolution profiles of CO, CO2, NO and N2 from temperature-programmed char combustion were recorded by a thermogravimetric analyser linked to a quadrupole mass spectrometer. The NO evolution profiles show two zones whose intensity depends on the volatile matter and specific surface of the chars. These zones of NO release are attributed to two different nitrogen sources. The fraction of the total nitrogen char released as NO depends on the volatile matter and the specific surface of the chars. The higher the volatile matter and the lower the surface area, the higher the NO/N ratio, i.e. the fraction of the char nitrogen that is released as NO. The nitrogen released as NO + N2 accounts for nearly all the nitrogen in chars of low surface area and high volatile matter. This is not the case for the chars of high specific surface and low volatile matter, showing that other nitrogen species, probably N2O, are formed during oxidation of such chars. The results are discussed on the basis of the mechanisms proposed in the literature for NO release that involve primary NO formation and subsequent reduction to N2 and N2O by CO and char carbon. Copyright © 1996 Elsevier Science Ltd.
Author(s): Lazaro MJ, Ibarra JV, Moliner R, De Andres AG, Thomas KM
Publication type: Article
Publication status: Published
Print publication date: 01/06/1996
ISSN (print): 0016-2361
ISSN (electronic): 1873-7153
Publisher: Elsevier Ltd
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