Process for reforming the fly ash

A process for reforming a fly ash by heating a raw fly ash powder that contains a unburned carbon and thereby decreasing a content of the unburned carbon, characterized in that:

• a:
• as means for heating the raw fly ash powder, use is made of a heating unit that heats said raw fly ash powder by passing it through a heated medium-fluidized bed;
• b:
• a high-temperature gas stream is passed through said heating unit to form the heated medium-fluidized bed and to fluidize and convey said raw fly ash powder that is thrown into said medium-fluidized bed;
• c:
• a flow rate of said high-temperature gas stream is so set that a superficial velocity in a column is not less than 0.6 m/sec. and not more than 3 m/sec. and that said raw fly ash powder thrown into said heating unit is all heated in said medium-fluidized bed and is taken out from a take-out port provided at an upper part of said heating unit but that the particulate medium forming said medium-fluidized bed is not discharged from said take-out port;
• d:
• a fly ash powder after heated and discharged from the take-out port of said heating unit is introduced into an air classifier where it is separated into a fine powder and a coarse powder;
• e:
• a fine powder separated by said air classifier is recovered as the reformed fly ash;
• and
• f:
• a coarse powder separated by said air classifier is measured for its content of the unburned carbon and when the measured value is larger than a predetermined threshold value, said coarse powder is introduced again into said heating unit so as to be heated again and when said measured value is smaller than the threshold value, the powder is recovered as the reformed fly ash;
• wherein a classification point of said air classifier is set to lie in a range of 100 to 150 μm.