Chemistry and emissions of nitrogen oxides (NO, NO2, N2O) in combustion ofsolid fuels II. Heterogeneous reactions - N2O

Nitrous oxide (N2O) volume fractions in atmosphere increase at an estimated rate 0.7-0.8 ppb per year. Potential anthropogenic sources of N2O include fertilization, combustion, mobile (car) sources, and atmospheric transforma tion of NOx to N2O. Combustion of solid fuels and waste at lower temperatur es (750-900 degrees C) presents a significant source of N2O. During stages of a coal particle combustion (pyrolysis-devolatilization and char combusti on) both volatile N and char N are mainly transformed to N-2 + NO and partl y to N2O. HCN was recognized as the main precursor of N2O in volatile combu stion. Char-N conversion to N2O (through various mechanisms) is affected by in seiu reduction of N2O by carbon surface and CO. Temperature has the most important effect on N2O emissions. At temperatures over 1000 degrees C the N2O emissions are negligible. Char and CaO are in practical combustion systems the most effective catalysts for thermal decom position of N2O.