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Show LNI/FDI BURNER DEVELOPMENT An LNI burner is required to perform two functions. It must operate as a conventional burner, providing a flame holder and mixing of fuel and oxidant to raise the furnace temperature above autoignition to sustain LNI combustion. It generally serves as the oxidant nozzle for LNI combustion. High velocity burners are ideally suited to both functions. In conventional firing mode, high velocity burners are inherently low N O x producers as they entrain significant cool furnace gases into the flame envelope prior to completing combustion of the fuel. The reduced port tile which is typical of high velocity burners provides an excellent oxidant nozzle for LNI combustion by entrainment of cool furnace gases with the oxidant stream prior to mixing with the fuel. Developing LNI/FDI for commercial applications requires selecting parameters of burner geometry that will provide the lowest possible N O x and C O emissions, maintain or enhance the capability of the burner(s) to heat the furnace and load, provide safe and reliable operation of the furnace, all with minimum impact on capital and operating costs. The parameters which affect the rate of N O x formation and/or the combustion zone mixing and heat release patterns for LNI/FDI combustion are: The orientation of fuel injector(s) to oxidant injector(s) (offset distance, angle, and arrangement) Oxidant velocity leaving the oxidant injector (typically the burner tile) Fuel stream velocity leaving the fuel injector The number of injectors Oxygen level in combustion products in furnace Furnace temperature Air preheat temperature Furnace geometry The first four of the above parameters are burner dependent, the last four parameters controlled by the application. The parameters interact, so application parameters can influence the selection of particular combinations of burner parameters. The variables of injector offset, angle between air and fuel injectors, air velocity, fuel velocity, and number of fuel injectors, were evaluated with the following objectives: Determine a configuration of burner and injector parameters to achieve the lowest NOx emissions with suitable combustion characteristics. Quantify the effect of the application-related parameters on N O x emissions. Quantify the effect of deviations from the optimum configuration to facilitate flexibility in application, particularly physically constrained retrofits. Also described is development work investigating potential benefits and tradeoffs in performance, packaging, and cost of inverting the first generation LNI/FDI designs which used single or multiple fuel injectors orbiting a single oxidant injector. Tokyo Gas has examined an arrangement which uses multiple air injectors around a single fuel injector in a regenerative burner package and eliminates dual mode operation. Development programs to date have produced commercial LNI/FDI products in the following categories: Ambient combustion air, natural gas fuel. Combustion air preheated by recuperator, natural gas fuel. (air preheat temperatures typically from 360 to 920 K). Oxygen enriched and pure oxygen combustion, natural gas fuel. Regeneratively preheated combustion air, natural gas, #2 and #6 fuel oil (air preheat temperatures typically from 800 to 1400 K). 3 |