Development of Nitrogen Stable Isotope Ratio Measurements to Apportion Fuel and Thermal NO_x in Coal Combustion

The main aim of the project was to develop a nitrogen-stable isotope measurement technique for NO_x and to ascertain whether it can be used to determine the relative contributions of fuel and thermal NO_x during coal combustion. The specific objectives were to:

• To design suitable substrates for adsorbing NO_x in flue gases.
• To establish the isotopic values for fuel and thermally-derived NO_x with samples from test rigs.
• T >o apply the experimental approach to larger facilities and to assess the data obtained for improving existing combustion models.

Suitable substrates for adsorbing sufficiently high concentrations of NO_x from flue gas streams to facilitate the reliable measurement of the nitrogen stable isotope ratios were developed, the substrates encompassing both manganese oxide supported on zirconia (MnO_y-ZrO₂) and iron supported on active carbon (Fe/AC).

Nitrogen stable isotope measurements were conducted on a number of thermal/prompt (diesel) and actual (coal) PF NO samples collected from >the 1 MW test facility at Powergen and fuel NO_x samples from the fluidised-bed (FB) combustor at the Caledonian paper mill in Ayrshire, together with measurements on a range of pyrolysis and combustion chars obtained from a drop-tube reactor. The nitrogen stable isotope ratios ( ¹⁵N) of the thermal/prompt NO samples analysed occur across a relatively narrow range with a mean below 0 (the value for atmospheric nitrogen), although reliable backgroundcorrect ions could no >t be applied at this stage.

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Development of Stable Isotopic Ratio Measurement - Apportioning of Fuel and Thermal NOx

Nitrogen Isotope Ratio Measurements Apportioning Of Fuel And Thermal Nox: Project Summary