Rotary hearth furnace with gas inlet ports in roof - providing countercurrent flow of gases and materials, e.g. coal, undergoing heat treatment

摘要

Appts. for heat treating volatile-contg. materials comprises a rotary hearth mounted in an enclosure with an inlet port for the materials at the periphery of the enclosure. Rabbles mounted in the enclosure roof progressively advance materials towards a central exit opening in the hearth floor. A plurality of concentrically arranged rows of openings are provided in the roof for the feeding of oxidant to mix with the evolved volatiles and combust in the upper portion of the enclosure. A greater no. of openings are provided at the periphery than the centre to provide a more oxidising atmosphere at the periphery. The oxidant and waste combustion gases travel radially outwardly into an exhaust manifold and the materials move progressively inwardly to the central exit simultaneously. The direction of flow of the oxidant and waste gases within the enclosure is countercurrent to the direction of travel of the materials undergoing treatment of the hearth. The temp. within the enclosure is profiled to provide a lower temp. adjacent the periphery than at the centre. The gas compsn. and temp. can be regulated by varying the no. of oxidant admitting ports in each concentric row or by varying the amt. of oxidant admitted through the ports.