Patent ID: 8051985

Claim:
A method of removing unburned carbon from coal ash, comprising the steps of; mechanically separating the unburned carbon from the coal ash using a dry type classifying unit; grinding or crushing the coal ash from which the unburned carbon has been partially removed by the dry type classifying unit by means of a dry type grinding unit; slurrying by adding water to the coal ash grinded or crushed by the dry type grinding unit; adding a collector to the slurried coal ash; selectively making the collector attach to the unburned carbon in the coal ash by applying shearing force to the slurry to which the collector is added; adding a frother to the slurry after having made the collector attach to the unburned carbon; and separating the foam and the unburned carbon from the slurry after having added the frother thereto through flotation thereof.