New Technics for NOx Emission Reduction

As environmental regulations become more stringent, especially with regards to NOx emissions, researchers and engineers are developing new combustion techniques, or modifying traditional ones, in order to lover these pollutant emissions. In a recent publication CHARON et ale (1990) indicated that combustion of a gaseous fuel using pure oxygen as comburant could, if properly managed, be by itself a lov NOx combustion technique. Up to nov, a important part of the effort in minimizing NOx from pure oxygen combustion operations has been focused on the design of the burner. The use of gas recirculation, to induce dilution and partial quenching of the flame, has shovn limited results vhen applied to very high temperature processes such as glass melting furnace. The technique herein described is based on the pulsation of at least one of the gaseous feeds (natural gas and oxygen) and is applicable to any existing or nevly designed burner or furnace. Tests have been performed to evaluate the effect of a) firing rate (20 and 50 kV), b) N2 contained in natural gas and c) flue gas temperature (up to 1500C), on NOx emissions. In all cases, reductions in NOX emissions were observed which ranged between 40% and 90% of the NOx emitted by their respectively equivalent not-pulsated flames. The equipment used in generating the pulsation of the gas is briefly dfescribed.