EFFECTS OF PRESSURE, GAS TEMPERATURE AND CO2 AND O-2 PARTIAL PRESSURES ON THE CONVERSION OF COAL-NITROGEN TO NO, N2O AND NO2

The effects of pressure (2-16 bar), gas temperature (800-1100 degrees C) and the partial pressures of carbon dioxide (0.01-4bar) and oxygen (0.2-2 bar) on the formation of N2O, NO and NO2 from coal-N were studied. Bituminous coal, 75-125 mu m, 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 P-CO2 increased slightly the conversion of fuel-N to N2O. The effect of P-CO2 on NO formation was too weak to be clearly detected, although a weak decrease in conversion may occur when P-CO2 is increased from 1 bar to 4 bar. The conversion of fuel-N to NO2 was weak, but increased clearly when P-O2 was increased from 1.5 bar to 2.0 bar.