Abstract: The present invention discloses a rotary grate for a solid fuel fired furnace which allows ash, cinders and clinkers to be removed from the burning fuel mass, without reducing or stopping the combustion process. A plurality of parallel water cooled rolls supports the burning fuel mass. The rolls are grouped into pairs of rolls, each pair of rolls having a drive roll and a driven roll. Each pair of rolls are geared together such that rotation of the drive roll simultaneously rotates the driven roll. Each roll has a plurality of protrusions about the circumference thereof, spaced down the length of the roll. The protrusions pass, during rotation of the rolls, the protrusions on adjacent rolls in non-contacting relationship to crush any cinders, clinkers or other tramp material. This action allows ash and the crushed material to pass between the rolls to an ash collection area beneath the rolls. Each of the drive rolls are rotated by a reversible drive mechanism which incrementally rotates the rolls.

Abstract: A particle feeding hopper having an elongate agitator positively driven around the hopper's inner surface by a reciprocating ratchet mechanism. The mechanism drivingly engages a circular chain connected to the agitator.

Abstract: A forced draft fan creates within a furnace fuel cell a pressure which is high enough to provide a pressure gradient effective to force the combustion gases from the cell all the way to the dryer. The combustion gases are provided by waste wood products which are forced by a special feeding system into the fuel cell against the resistance of the relatively high air pressure within the cell, to create a burning pile. The feeding system blocks most of the smoke and combustion gases from back-feeding through the fuel passageway, and then removes the part that is not blocked. The combustion gases during the drying process become wet. A part of these wet gases are vented at the dryer but a recirculation fan effects the return of a portion to a blending chamber where they are mixed with hot combustion gases to be again directed to the dryer. The other portion of the wet gases is directed to the combustion chamber for augmenting its operation.

Abstract: In a dry kiln, a plurality of in-tandem air control compartments and a fan between each pair of adjacent compartments. The fans are rotated in one direction only. The compartments have lateral air flow ports in which air valves are mounted. The fans are of opposite pitch and the valves are so alternately operated that although the fans blow the air unidirectionally, the air can be controlled to flow in one direction through the drying chamber of the kiln, or optionally in the opposite direction, for uniform drying purposes.