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Emissions of nitrogen oxides (NO x ) from combustion sources are significant contributors to a number of detrimental atmospheric environmental effects, including acidic deposition processes and production of photochemical smog. 1 Combustion of coal, both in pulverized-fuel fired furnaces and, increasingly, in fluidized-bed combustors, is an important anthropogenic source of NO x , 1 and in the latter case of nitrous oxide (N 2 O), which has a large greenhouse warming potential. The predominant source of these emissions is the nitrogen bound in the organic structures present in all coals. 2 A significant proportion of coal-bound nitrogen is released during the initial stages (devolatilisation) of combustion as simple gas-phase species (HCN, NH 3 ) and in more complex organics, which are categorized as tar molecules. [3][4][5][6] Oxidation of these nitrogen-containing species results in the conversion of some coal-bound N to NO and some to N 2 . Proportions of NO and N 2 formed are a function of the overall stoichiometry, and the chemistry of this volatile-N is relatively well understood, based on extant models of fuel-N chemistry. 7 However, not all coal-N is volatile, and, depending on the coal, varying amounts are retained in the char matrix, and only released during burnout of the char. The fate of this char-N is much more uncertain. This is although, under staged combustion conditions such as those found in low-NO x burners, it is probable that it is the major source of NO x .Molecular nitrogen (N 2 ), NO, and N 2 O are generally agreed to be the most significant products of char combustion. In fact, for many reported experiments, only two of these products have been measured, and it is assumed that the third product (usually N 2 ) completes the mass balance.

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