Abstract: Bulk materials containing volatile constituents are calcined in a two-stage process comprising a first heating stage at de-volatilizing temperature but below calcining temperature during which the material is turned over and mixed to accelerate its bulk heating rate without substantially accelerating local heating rate. The first heating stage is followed by a second heating stage at calcining temperature. A rotary hearth furnace adapted for the above process is divided into outer and inner connecting annular heating zones and has rabble means for turning over and mixing the charge in the outer zone and rabble means for transporting the charge through both zones.

Abstract: Apparatus for drying and heating wet particulate materials comprises a furnace with stationary circular hearth and sidewalls and a rotating roof. The hearth is perforated to receive hot gases from a plenum chamber below it, which gases are drawn off from the hearth through conduit openings out of its sidewalls, the major portion of the gases are externally heated, and are returned to the hearth through the plenum chamber. A feed bin is positioned on the roof at its center and through a conveyor feeds charged material onto the hearth through an opening in the roof near its outside edge. Rabbles are mounted in the roof to move the charge toward the center of the hearth as the roof rotates. From the center of the hearth a soaking pit extending through the plenum chamber discharges the heated material.

Abstract: Bulk materials containing volatile constituents are calcined in a two-stage process comprising a first heating stage at de-volatilizing temperature but below calcining temperature during which the material is turned over and mixed to accelerate its bulk heating rate without substantially accelerating local heating rate. The first heating stage is followed by a second heating stage at calcining temperature. A rotary hearth furnace adapted for the above process is divided into outer and inner connecting annular heating zones and has rabble means for turning over and mixing the charge in the outer zone and rabble means for transporting the charge through both zones.

Abstract: A process for the simultaneous production of metallized ores and a char. A carbonaceous material such as coal is mixed on a weight ratio basis of about 1/2 coal to about 1 iron ore to about 11/2 or more coal to about 1 iron ore. The coal is mixed on a weight ratio basis with the iron ore within the ratios defined above and the mixture subjected to a heat treatment of between 1800.degree. F. to about 2200.degree. F. within a substantially air tight enclosure wherein in oxidizing atmosphere is provided in the upper portion of the enclosure and a reducing atmosphere is maintained about the materials on the floor of the enclosure. The floor of the enclosure comprises a travelling imperforate hearth with the speed of travel thereof variable so as to vary the residence time of the materials on the floor of the enclosure from the time of deposit of the materials on the hearth to the time of removal of the materials from the floor.

Abstract: Method and apparatus for feeding an oxidant such as air and/or a fuel rich gas within the confines of a substantially air tight enclosure employed in the heat treatment of volatile containing materials which are deposited on the floor of a rotary hearth mounted within the enclosure. A larger number of air and/or fuel rich gas inlet ports are provided in the roof of the enclosure at the outer periphery thereof than at the central or intermediate areas of the enclosure to thus provide a more oxidizing atmosphere at the outer peripheral area of the enclosure than at the central and intermediate areas of the enclosure. The oxidant is admitted into the furnace enclosure through concentrically arranged rows of inlet openings formed in the roof of the enclosure.

Abstract: Method and apparatus for the heat treatment of volatile containing materials in a rotary hearth type furnace wherein the flue gases emanating from the calciner are employed to create either a positive or negative pressure within the calciner hearth as well as the soaking pit area of the said calciner.