Abstract: In a combustion system for particulate fuel including a combustion chamber with an opening at the base of the combustion chamber and a vertical discharge duct pushing the particulate fuel through the opening there is provided a hopper spaced from the combustion chamber and a transportation duct for carrying the particulate fuel from hopper to the discharge duct. In the transportation duct there is provided an auger shaft with a first long auger flight rotated to carry the material from the hopper to the discharge duct. A second shorter flight is arranged on a side of the discharge duct opposite to the hopper in a short tube portion and is rotated in the direction to feed the material back toward the discharge duct. The two flight portions cooperate in pushing the material into the vertical discharge duct as the shaft of the flight is rotated.