To jet heated dry air into fly ash in a reserving tank, to forcibly exhaust the air, and to keep the fly ash dry, in relation to a reserving method of the fly ash for preventing the fly ash from generating a bridge in the reserving tank in discharging the fly ash that is conveyed from a conveying machine, guided into the reserving tank, and stored in the reserving tank for a predetermined period, and contains a component having moisture absorbing property.

The heated dry air is jetted into the deliquescent fly ash, and moisture absorbed into the fly ash is forcibly exhausted with the air out of the system, thereby providing the effects: (1) the heated dry air is simply jetted to decrease temperature of the fly ash and not to cause a condensation phenomenon, (2) the moisture contained in the fly ash is transferred to the heated dry air to be exhausted out of the reserving tank, and (3) the heated dry air intrudes among fly ash particles to increase fluidity of the fly ash, and smoothly exhausting the fly ash without generating the bridge.