Abstract: The apparatus includes a feed box with a horizontal intake port for connection to a stoker feed and a vertical discharge port for transmitting coal to the burning zone, with a curved passage between the ports. An annular burner body has a central annular vertical delivery ring coaxial with the discharge port, a downwardly and outwardly sloped annular burner grid, and a marginal depending stabilizing flange. The ring and the flange rest on the top plate of the feed box for support and are keyed against rotation. An ash ring has an inner margin resting on the outer margin of the grid for support and rotation, and its upper surface slopes upward and outward to define with the grid surface an annular recess for retaining burning coal. A plurality of ribs on the ash ring and at least one breaker tooth on the grid cooperate to break down clinkers as the ring rotates, driven by a sprocket on the conveyor shaft.