Nitrogenous Emissions the Role of Sulphur and Equivalence Ratio

Nitrogen and sulphur are fuel constituents which contribute significantly to atmospheric pollution and to the deterioration of combustion equipment through the formation of NOx and SOx. Large concentrations of fuel-N and -S are normally present in liquid fuels of industrial interest, such as heavy or residual fuel oils. The extent to which these species interact during or after their formation can be of relevance and depend on a number of factors, such as the concentrations of nitrogen and sulphur in fuel and the equivalence ratio. In the work presented a number of heavy gas oils and an oil-water emulsion were investigated. Baseline emissions of NOx (NO plus N02) and SO2, as well as other combustion products, were measured at three equivalence ratios, namely fuel-lean (φ = 0.833), stoichiometric (φ = 1.00) and fuel-rich (φ = 1.20). The effect of sulphur on nitrogenous emissions was assessed by the addition of increasing amounts of SO2 (gaS) to the combustion system. This caused the concentrations of NO and N02 to vary in different ways according to the overall equivalence ratio of the combustion system. Sizeable increases or decreases of the emissions of nitrogenous compounds were thus observed, which were attributed to the action of sulphur compounds on NOx-forming reactions or direct reaction between SO2 and nitrogenous compounds.