Rotary calciner

In a rotary kiln suitable for calcining normally solid carbonaceous material wherein the combustion gases and solid materials to be calcined travel countercurrently in the kiln during calcination, said kiln including, at its lower discharge end, a firing crown equipped with means for admitting combustible gases or liquids and air;

• a feeding means for such solid carbonaceous material to be calcined adapted to the upper end of the kiln;
• at least one series of at least two tuyeres passing through the wall of the kiln spaced symmetrically to and at about the middle one-half of the longitudinal axis of the kiln, each tuyere terminating within the kiln through a nozzle which is located on the side of the tuyere at a sufficient height above the bed of the carbonaceous material being calcined in the kiln to permit the discharge of exterior oxidizing gases passing through the nozzle;
• at least one shroud which surrounds the kiln in the tuyere area and which is movably mounted with respect to the kiln wall, thereby allowing the kiln but not the shroud to rotate;
• said tuyeres terminating on the outside of the kiln and within the shroud;
• and means to cause air or other oxygen-containing gases to flow into the shroud through the tuyeres and into the kiln, the improvement which comprises:
• 1. locating the nozzle in said tuyeres perpendicular to the radius of the kiln and pointing them at an acute angle from the longitudinal axis of the kiln in substantially the same direction toward the upper end of the kiln in order to direct the oxidizing gases toward said end and to provide a vortex flow pattern for said gases;
• and
• 2. means at the junction of each tuyere with the interior surface of the kiln lining to cause forced movement of the carbonaceous material being calcined past the tuyeres as the kiln rotates.