COMBUSTION DEVICE FACILITY

PURPOSE:To reduce NOx and provide a stable pre-mixed flame by a method wherein fuel and combustion air are mixed in a substantially uniform manner. CONSTITUTION:The first and second pre-mixing burners 22 and 24 having annular injection ports therein are arranged in a concentric manner. They are arranged with positions of the injection ports in up-stream and down-stream directions being substantially coincided to each other. A pilot burner 21 is arranged at a substantially central part of the annular first pre-mixing burner 22 in such a way as the position of the injection port in an up-stream or down- stream direction may be substantially coincided with the position of the injection port of the first pre-mixing burner 22. A flame holder 30 for forming a circulation flow of combustion gas at its own down-stream side is arranged at a down- stream end of an interface wall 26 between the pre-mixing burners 22 and 24 in such a way as the pre-mixing burners 22 and 24 may have it together. In addition, flow rate adjusting means 35, 36, 37 and 40 for adjusting a flow rate of fuel supplied to the first and second pre-mixing burners 22 and 24 and a flow rate of fuel supplied to the pilot burner 21 for every burners are provided.