To provide a method and device for slurried coal ash pretreatment where unburned carbon is separated from slurried coal ash to be fed to flotation for removing the unburned carbon of coal ash so that the frequency of floatation can be reduced.

A scavenger, a bubbling agent, and air are fed into the slurried coal ash composed of the unburned carbon-containing coal ash and water so as to produce bubbles, and the unburned carbon is caught in the bubbles. Before the slurried coal ash 6 is fed to a floatation apparatus 2 for separating tail ash having a low unburned carbon content, ultrasonic waves are emitted thereto by an ultrasonic wave generating apparatus 8 so that the separation efficiency of the unburned carbon from the coal ash is increased.

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