Passive and active control of NOx in industrial burners

Industrial burners that use either fuel oil or natural gas are considered as candidates for implementing strategies for control of NOx. Two burners, at 20 and 800 kW burning fuel oil are installed in a tunnel furnace and subjected to active control by way of introducing pulses into the air supply. Using optical diagnostics to identify the CH radical, the imaging reveals the evolution of the vortical structures within flames: a non-premixed diffusion flame appearing in the braids of the vortex and a premixed core region. Prompt NOx mechanisms are explored, noting that thermal NOx in this case is not the predominant contributor in the fuel burner. III the case of natural gas burners, thermal NOx control is achieved passively. The burners achieve significant reductions in NOx by radically altering the fuel-air jet distribution from the normal air-surrounding Fuel ports approach: the air and fuel jets are arranged on a base circle, each low momentum fuel port alternating with high momentum air port and each type pointing away from the burner axis at a different, but constant, angle. The NOx reduction mechanism is speculated to be due to flue gas recirculation with concomitant reduction in flame temperature. The burner has been tested in both single and multiple modes in a unique multi-burner furnace. Results obtained using both active and passive control and manipulation indicate that significant enhancement of combustion can be achieved by applying modern tools and new ideas. (C) 1998 Elsevier Science Inc. All rights reserved.