To reduce NOx and unburnt carbon by keeping low-air-ratio combustion for a long time with the supply of primary air and secondary air.
A device comprises a primary nozzle 2 for injecting mixed fluid 1 of pulverized coal and primary air for conveying the pulverized coal fuel, to a furnace 15, and a secondary air channel 10 and a tertiary air channel 11 which are annularly arranged at the outer periphery of the primary nozzle 2. An angle of an air jet streamline from the secondary air channel 10 and the tertiary air channel 11 with respect to the center axis of the primary nozzle 2 is rendered to exceed 0° but not more than 40°. Further, there is provided a division plate 21 so as to divide, in a circumferential direction, an air jet exit at the tip of the tertiary air channel 11. Joining of tertiary air 11 and secondary air 10 is delayed to accelerate air-shortage combustion and keep low-air-ratio combustion for a long time, thereby reducing NOx. The tertiary air 11 is joined after the progress of low-NOx combustion in the vicinity of a burner, which fact effectively works on reducing unburnt carbon in comparison with the case where two-step combustion is employed.
TSUMURA SHUNICHI
KURAMASU KIMIHARU
