The effects of the particle sizes of pulverized coal on the flame structure in a coal fire plant were studied experimentally. This study mainly focused on the inner recirculation zone (IRZ) and exhaust tube vortex (ETV), which are major parameters for a reduction of NO,, in swirl-stabilized pulverized coal combustion. To clarify the effects of the coal particle size, three different sized Glencore particles were prepared, namely, under 90 mu m (GC(90 down arrow)), under 150 mu m (GC(150 down arrow)), and between 90 and 150 mu m (GC(90-150)). The temperature of the coal particles, the intensity of the OH chemiluminescence, and the pulverized coal flame structure were compared with the particle sizes of pulverized coal. In a pulverized coal flame, the temperature and OH radical intensity were shown to decrease with an increase in the coal particle size, and the IRZ and ETV increase with a decrease in the particle size. The residence time of the coal particles increase in the IRZ and ETV, which creates a reduction environment and a fuel-rich condition, leading to a reduction of NOx emissions.