NITROUS-OXIDE EMISSIONS FROM UK POWER-STATIONS

Nitrous oxide (N2O) was measured in the flue gas at a number of large (500 and 660 MW) coal- and oil-fired power station boilers. Measurements were made on-line by non-dispersive infrared spectrometry, and off-line by gas chromatography on samples collected in gas sampling bags. N2O concentrations in flue gas from all boiler types were low; generally in the range < 1 to < 5 ppm. The N2O concentrations measured were affected by the sampling conditions at the individual stations. The most satisfactory sampling conditions gave the lowest N2O values, and the true values for N2O concentrations in flue ps are likely to lie at the low end of the measured range, at 1-2 ppm or less. Within the resolution of the measurements, no dependence of N2O emissions on boiler (wall-fired or comer-fired) or burner type (standard or low NO(x)) was detected. Both coal- and oil-fired boilers gave similarly low emissions of N2O. The greenhouse impact of N2O from conventional fossil-fuelled plants is < 1 % of that contributed by the corresponding CO2 emissions.