To ensure combustion in the same combustor and hence safely and securely achieve combustion under low NOx in a combustor in which 4 flow passages are formed for supplying a fuel to a nozzle, and blast furnace gas and natural gas are replaceably used by properly using the flow passage in response to the kinds of the gases.
A nozzle includes a first flow passage 2 at its center, a second flow passage 4 outside the former, a third flow passage 5 further outside the former, and a fourth flow passage 6 furthermore outside the former. When a combustor 1 is used as a blast furnace combustor, blust furnace gas is supplied to the flow passage 2, the flow passage 4 is stopped, blast furnace gas is supplied to the flow passage 5, and combustion is achieved with combustion air on the flow passage 6. In contrast, when the combustor is used as a combustor for natural gas, natural gas is supplied to the flow passage 2, combustion air is supplied to the flow passages 5 and 6, and natural gas supplied to the flow pasage 4 is received from a communication hole 7 or a communication hole 9 in the flow passage 8. Hereby, premixed gas is formed which is in turn injected from nozzles 5A, 5B, and combustion is achieved with a flame in a diffusion flame region 3 and the flame is kept.
BANDAI SHIGEMI
KOMORI TOYOAKI
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