A rotary kiln for burning and calcining a waste oil, sludge or slurry to form gases and residual solids which comprises
- a pair of tubes each of which is formed by an enclosing side wall,
- a first tube oriented with its rearward end raised above its forward end, the forward end being closed by an end wall,
- a second tube concentric with and mounted inside said first tube having a diameter sufficiently small to provide an annular passageway between the side walls of said pair of tubes, said annular passageway sloping downwardly from its rearward end toward its forward end, the forward side wall end of said second tube having circumferential openings which communicate the forward end of said annular passageway with the opening extending through said second tube, said second tube being extended downwardly from its forward end to its rearward end in a direction opposite that of said connecting annular passageway formed between the two tubes,
- a burner box formed by enclosing side and end walls, located at the rearward end of said first tube, within the forward side wall of which a terminal end of said first tube is mounted, and rotatably sealed such that the annular passageway between said pair of tubes is in open communication therewith, and a rearward portion of said second tube is mounted and rotatably sealed within the rearward end wall of said burner box, and its terminal end extended therethrough,
- waste oil, sludge or slurry feed means mounted with its feed discharge end extending into the rearward end of said first tube for introducing a waste oil, sludge or slurry into the annular passageway located between the side walls of said pair of tubes,
- one or more burners mounted within the walls of the burner box from which burning gases are emitted into said annular passageway for igniting and burning said waste oil, sludge or slurry introduced into the annular passageway, the burning residue of said waste oil, sludge or slurry moving concurrently with the burning gases from said burners downwardly to the forward end of the annular passageway where the residue is collected and piled,
- elevator means located within the forward end of said first tube interfacing with said annular passageway for lifting and elevating the piled residue and introducing same via the circumferential side wall openings into the axial opening extending through said second tube,
- one or more burners extending through the enclosing end wall of said first tube into the forward end of said second smaller diameter tube from which burning gases are emitted, the solids and vapors within the axial opening of said second tube being contacted and calcined by the burning gases while moving cocurrently downwardly therewith to the opposite lower end of said second tube wherefrom both the burned gases and calcined solids are discharged,
- a chimney within a forward wall of which the rearward terminal end of said second tube is sealed and rotatably contained, the chimney being provided with a lower solids discharge outlet and stack, such that the gases and solids discharged from the rearward end of said second tube therein are separated, the gases passing upwardly through the stack and the solids being discharged via said solids outlet, and
- means for rotating said pair of tubes while a waste oil, sludge or slurry is being introduced via the waste oil, sludge or slurry feed means into the rearward end of said first tube, burned, and the burned solids residue passed concurrently with the flow of gas through the continuous passageways formed by the annular passageway between the two tubes and axial opening through the second tube, and discharged into the chimney.