The ignition of pulverized coal is an important preliminary step in the coal combustion process, due to its influence on flame stability, the formation and emission of pollutants and flame extinction. In recent years there has been an increasing utilization of coal blends for combustion, but information on the changes of coal flame during ignition process is scarce. In this work the ignition behavior of a series of coal blends, made up from four coals of different rank was studied in a drop-tube furnace. A new method of oscillation frequency based on empirical mode decomposition is introduced. The Ignition feature of oscillation frequency was obtained from the coals studied; the feature proved well in distinguishing ignition mechanisms from homogeneous, hetero-homogeneous to heterogeneous in the ignition section of a drop-tube furnace. The different ignition mechanisms of coal blends were observed depending on the blends mass proportion and inclined to the characteristic of the coal consisted of higher volatile.
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