Abstract: A shrouded rabble includes a blade having an active face and a backface with a shroud extending from the backface along a lower edge of the blade. The rabble is suspended above a perforated hearth for urging charge materials on the hearth from one location to another in response to relative rotation between the hearth and the rabble. The action of the rabble on the charge materials causes breakdown of the charge materials and accumulation of fines on the perforated hearth. The shroud defines a shroud chamber behind the blade and screens charge materials from the shroud chamber to expose accumulated fines on the perforated hearth. The charge fines thus become fluidized in an upflowing heating gas and exit the shroud chamber through at least one opening in the shroud, facilitating the flow of heating gas through the perforated hearth and into the charge materials. The opening may simply comprise one end of the shroud being open, or it may include a plurality of holes in the shroud itself.

Abstract: The furnace has a hearth which rotates inside a stationary closed chamber and is supported therein on vertical cylindrical conduit which extends through the furnace floor and is supported by a single center bearing. The charge is deposited through the furnace roof on the rim of the hearth as it rotates and is moved toward the center of the hearth by rabbles. Externally generated hot gases are introduced into the furnace chamber below the hearth and rise through perforations in the hearth and up through the charge. Exhaust gases are withdrawn through the furnace roof. Treated charge drops from a center outlet on the hearth into the vertical cylindrical conduit which extends downwardly through the furnace floor to which it is also sealed.

Abstract: The furnace has a hearth which rotates inside a stationary closed chamber and is supported therein on circumferentially spaced rollers the shafts of which extend outside the furnace and are cantilevered in bearings. The shafts are sealed to the furnace wall by mechanical and pressurized gas sealing means. The charge is deposited through the furnace roof on the rim of the hearth as it rotates and is moved toward the center of the hearth by rabbles. Externally generated hot gases are introduced into the furnace chamber below the hearth and rise through perforations in the hearth and up through the charge. Exhaust gases are withdrawn through the furnace roof. Treated charge drops from a center outlet on the hearth into a soaking pit which extends downwardly through the furnace floor to which it is also sealed.

Abstract: Metal strip in coils is heat-treated by impinging jets of a temperature-controlled gaseous medium on the ends of the coils which are positioned with the coil axis horizontal. The medium is recirculated through heat exchangers. A rotating hearth furnace for such heat-treating has an annular hearth which carries coils in intermittent movement through successive stations in which the gaseous medium is directed on the coils.

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: The furnace is circular in plan and comprises an annular charge space charged through chutes in its top wall. Effluent gas offtakes are provided in the furnace outer wall and the level of the charge bed is maintained above the chute bottoms but below those offtakes. Hot gases generated externally of the furnace pass into it through an opening in its bottom wall or hearth and travel upwardly through the charge. Solids are discharged downwardly through the same opening in counterflow. A vertical axle is journalled centrally in an upper wall of the annular furnace chamber spaced above the opening in the hearth, and a plow affixed to the lower end of the axle rotates in an open space between the hearth of the annular furnace chamber and its inside wall, so scraping heated charge solids into the discharge opening. The axle is pressure sealed to the wall through which it passes, and that seal is the only rotating seal required for the furnace.

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 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.