Effects of pressure, gas temperature and CO2 and O2 partial pressures on the conversion of coal-nitrogen to NO, N2O and NO2

The effects of pressure (2–16 bar), gas temperature (800–1100°C) and the partial pressures of carbon dioxide (0.01–4 bar) and oxygen (0.2–2 bar) on the formation of N2O, NO and NO2 from coal-N were studied. Bituminous coal, 75–125 μm, was burned as a dilute pressurized suspension in an electrically heated pressurized entrained-flow reactor.
Nitrogen oxides were analysed by an on-line FT-i.r. The experimental conditions differed from those of an earlier study in that high concentrations of CO2 (up to 80 vol.%) and higher oxygen partial pressures and especially concentrations (up to 50 vol.%) were used. The results were analysed by a partial-least-squares method. Increase of pressure decreased the conversion of fuel-nitrogen to NO, and had a weak effect on its conversion to N2O.
Increase of PCO2 increased slightly the conversion of fuel-N to N2O. The effect of PCO2 on NO formation was too weak to be clearly detected, although a weak decrease in conversion may occur when PCO2 is increased from 1 bar to 4 bar.
The conversion of fuel-N to NO2 was weak, but increased clearly when PCO2 was increased from 1.5 bar to 2.0 bar.