PURPOSE: To reduce the generation of NOx, and to reduce the corrosion of furnace walls, which is caused with H2S, by a method wherein pulverized coal burners for normal air ratio and pulverized coal burners for low air ratio are alternately arranged lengthwise and crosswise, and pulverized coal is burnt by regulating the air ratio of the pulverized coal burners.

CONSTITUTION: Pulverized coal burners 3, of which the air ratio is normal and is about 0.8, and pulverized coal burners 3, of which the air ratio is low and is about 0.5, are alternately arranged lengthwise and crosswise. For that reason, the temperature of pulverized coal combustion flames discharged from the pulverized coal burners 3 for low air ratio does not become low by radiant-heat transfer from the pulverized coal combustion flames of the pulverized coal burners 3 for normal air ratio, the pulverized coal burners 3 for the low air ratio are stably ignited, and intermediate reduction substance such as HCN and NHi is made easy to produce. Furthermore, burnt gases from both kinds of pulverized coal burners 3 are sufficiently mixed, and a reaction to be shown by the mixture of the intermediate reduction substance and NO discharged from the pulverized coal burners 3 for the normal air ratio is made easy to cause. In this way, the generation of NOx can be reduced and the corrosion of furnace walls 2, which is caused with H2S, can be reduced.