The Influence of Sulfur on NOx Formation in Combustion

University Of North Texas, Denton TX

Investigators

Abstract

The goal of this project is the isolation of individual elementary reactions relevant to the sulfur/nitrogen interaction in combustion systems and the characterization of their reaction kinetics over a wide range of temperature. Short-lived reactive species including atoms of nitrogen, oxygen, hydrogen, and sulfur and diatomic radicals such as NH, NH2, CN, SO, CS, and SH are generated by pulsed ultraviolet excimer-laser or flash-lamp photolysis of precursor molecules. The concentration of transient radical species are monitored with time-resolved fluorescence spectroscopy - laser-induced fluorescence for molecular radicals and vacuum-ultraviolet resonance fluorescence for atomic species - to obtain rate constants and product identification as functions of temperature and pressure. Reactions are studied under pseudo-first-order conditions with a large excess of the stable reactant. Experiments include reactions of radicals with stable molecules such as hydrogen sulfide, sulfur dioxide, and nitric oxide and also radical-radical reactions involving SO. The interaction of nitrogen and sulfur chemistry within flames and exhaust gases influences the generation of nitrogen oxides from combustion and thusly impacts acid rain, photochemical smog, and tropospheric ozone. Depending on conditions, sulfur may augment or reduce the amounts of nitrogen oxides emitted. This study investigates the underlying chemistry of this interaction. This project provides a vehicle for the participation of undergraduate and secondary-school students through the Texas Academy of Math and Science and the Upward Bound Math and Science Program.