Abstract: The heat treatment of fine-grained material wherein two quantities of fuel are delivered to a precalcination zone at two different levels. The first quantity of fuel is delivered at a lower level nearer the combustion zone and the oxygen content of the gases passing through this region of the precalcination zone are such that in this region a substoichiometric combustion takes place and a CO content between 0.05% and 1% is established. As a result a reducing decomposition of the NO.sub.x content of the exhaust gases from the combustion zone takes place.

Abstract: Apparatus for the heat treatment of fine material comprises a multi-stage cyclone preheater, a rotary kiln and a calciner supplied with tertiary air from a cooler for precalcination of the preheated fine material. The tertiary air pipe is narrowed at the point where it joins into the calciner. In this way an intensification of the mixing together of material, fuel and gas is achieved as well as an improved combustion, particularly fuels which are slow to react.

Abstract: A grate cooler arranged at right angles to a rotary kiln and having its vertical longitudinal central plane spaced a distance between 10 and 150 cm from the discharge end of the rotary kiln. The zone of the grate cooler lying below the material discharge end of the rotary kiln has more stationary grating plates and more unventilated grating plates per unit area than the laterally adjacent zones of the material receiving end and in the remaining region of the cooler. This results in good protection of the grating plates at the material receiving end and an even distribution of the material over the whole width of the cooler by means of a distribution cone which is kept in motion.

Abstract: A rotary drum having a toothed rim arranged on the drum casing and supported at several peripheral points on the drum casing by evenly distributed bridge members. Each bridge member includes two clips axially spaced from one another and welded to the drum casing and a cross plate which connects the clips and is radially spaced from the drum casing. Each cross plate is rigidly connected to one clip and slideably connected in the axial direction to the other clip so that differing degrees of thermal expansion and resulting deformation of the cross plates and further strain on the cross plates, clips and connection points can be compensated for.

Abstract: The apparatus comprises a main drive including a main motor and main gearing disposed between the main motor and the unit being driven; an auxiliary drive including an auxiliary motor and auxiliary gearing disposed between the auxiliary motor and the main gearing; a clutch between the auxiliary gearing and the main gearing; and a centrifugal brake connected to the auxiliary drive. A further centrifugal brake is connected to the main drive.

Abstract: A rotary kiln has at one end circumferentially spaced apart outlet openings into each of which extends a sleeve establishing communication between the interior of the kiln and a planetary cooling tube. Encircling the inner end of each sleeve is a refractory collar that is flush with the surface of the kiln's lining. Between each tube and the edge of the associated outlet is a thermally insulative packing.

Abstract: Fine-grained material adapted to be fired in a furnace is discharged from a preheater into a gas conduit extending from the furnace to the preheater and through which a stream of hot gases pass. The conduit is shaped to deflect the gas stream and concentrate it along one side of the conduit in the area of introduction of the material to the conduit. Below the area of introduction of material to the conduit fuel burners provide a heating zone through which the material falls. The concentration of the gas stream along one side of the conduit assures entrainment of the material in the gas stream and passage of the material again through the heating zone. Above the area of introduction of material to the conduit the latter is shaped to deconcentrate the gas stream and permit some of the material entrained therein again to fall downwardly through the heating zone, following which such material is reentrained in the gas stream.

Abstract: Fine-grained material such as raw ground cement adapted to be fired in a rotary tube furnace is introduced to a vertical preheater and falls through a heating zone located at a level below the level at which the material enters the preheater. A stream of air enters the preheater at a level below the heating zone and passes upwardly at sufficient velocity to entrain the material that has passed through the heating zone, thereby causing such material to pass again through the heating zone. From the preheater the material is delivered to the furnace for final firing.

Abstract: A rotary kiln having a row of planetary cooler tubes disposed around its outer periphery and carried by individual metal mountings on the kiln casing, adjacent mountings abutting against each other in their areas bordering on the kiln casing and being spaced apart in their areas remote from the kiln casing, for minimizing changing temperature induced stresses imparted therefrom to the kiln casing during operation.

Abstract: A rotary kiln has a cylindrical casing interrupted along its length by annular members which are welded into and constitute part of the casing and which are provided with outwardly projecting, profiled webs adapted for attachment to the mounting structure of cooler tubes which are arranged in planetary manner about the casing.

Abstract: A plurality of cooling tubes are arranged in planetary fashion about the periphery of the kiln. An inlet for each cooling tube includes a transition member extending from one end of each tube, which transition member comprises the wall of an inclined frustum whose base lies on the end of the cooling tube in a plane perpendicular to the axis of the tube. An inlet tube has one end intersecting the wall of the kiln and its other end intersecting the wall of the transition member, two surface lines of the transition member being tangent to the inlet tube.

Abstract: This invention relates to a rotary drum having a bearing ring mounted on the drum casing and movable relative thereto in the peripheral direction, said ring being supported by support plates affixed to the drum casing at constant intervals.

Abstract: Fine-grained material such as raw ground cement adapted to be fired in a rotary tube furnace is introduced to a vertical perheater and falls through a heating zone located at a level below the level at which the material enters the preheater. A stream of air enters the preheater at a level below the heating zone and passes upwardly at sufficient velocity to entrain the material that has passed through the heating zone, thereby causing such material to pass again through the heating zone. From the preheater the material is delivered to the furnace for final firing.