Abstract: A method is described for reducing NOx emissions and improving energy efficiency during mineral processing in a rotary kiln. The method comprises injection of air with high velocity/high kinetic energy into the kiln to reduce or eliminate stratification of kiln gases. The method can be applied to mix gases in a rotary kiln vessel or in a preheater/precalciner vessel.

Abstract: A method and apparatus is described for environmentally sound usage of combustible hazardous waste as supplemental fuel in operating rotary cement kilns. The apparatus comprises an open port in the rotary vessel at a point where during cement kiln operation the in-process mineral material is in a calcining state and where kiln gas temperatures are sufficient to decompose volatile components of the waste fuel. A drop tube extending from the port into the kiln is provided to prevent in-process mineral from escaping through the port during rotation of the rotary vessel. Combustible solids are delivered through the port under the force of gravity and air is continuously drawn into the rotary vessel through the open port during kiln operation. The apparatus and method allow efficient usage of combustible solid waste as a supplemental fuel for cement kiln operation.