PURPOSE: To be able to utilize waste sawdust as fuel by placing ventilating boxes which are placed on an air supply box having a number of small ventilating holes on its upper surface and have ventilating holes communicating with the air supply box on their sides and are able to discharge air passing through the ventilating holes into a furnace and also have barriers preventing the ventilating holes from being clogged with sawdust.

CONSTITUTION: Sawdust 32 is supplied to a hopper 4 through a supply pipe 5 by a scraper placed at the bottom of a sawdust tank 31 and falls down on an air supply box 6 and an upper and a lower ventilating boxes 14 and 9. Air transferred through a blast pipe 22 is spouted partially through ventilating small hole groups 7 formed on the upper surface of the box 6. A part of the air which flows into the lower ventilating box 9 from a path hole 8 and passes through ventilating hole groups 10 is discharged into a furnace in the condition that ventilating hole groups are not clogged with accumulated sawdust because of barriers 11. Further, a part of the air transferred to the box 9 flows into the upper box 14 from a path hole 13 and is discharged into the furnace in the same way as before.