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Low NOx combustion technologies for gas turbines, such as lean premixedflame combustion, have been developed and used for commercial gas turbines to meet stringent NOx regulations. However, lower NOx is required for themore severe regulations in some areas.For developing a practical catalytic combustor, intensive studies have been carried out for the screening of a favourable catalyst, the optimization of monolith sizes, the research of pressureeffects on performances and the confirmation of the effectiveness of a catalytic pilot flame.With these results, an ultra low NOx combustor for a gas turbine, which is based on a catalytic pilot flame and a lean premixed main flame, has been developed and achieved NOx of less than 10 ppm on high pressure combustion tests.High temperature gas, produced by catalytic combustion, is used as a pilot for flame holding of premixed main flames. This manner of combustion has some advantages compared with previous combustion technologies. These advantages are, besides less NOx from catalytic pilot than from diffusion flame pilot, less pressure drop on the setting catalytic pilot in parallel with main flames and high reliability by using smaller catalyst.The catalyst endurance tests are now under being carried out for the practical applications of this ultra low NOx combustor for gas turbines.