Abstract: A method of calcining mineral components such as bituminous limestone in which heat is recovered from the calcining process and is used to liberate volatilizable substances within the mineral matter before the latter is subjected to calcination. The volatilized and pyrolytically decomposed substances form a fuel which is burned to produce the calcining gas mixture.

Abstract: A method of and an apparatus for cooling white cement clinker from a rotary kiln wherein the clinker is classified into at least two and preferably more particle-size fractions which are quenched with water with residence times staggered so as to increase as the particle size range increases. The cooling is effected to a temperature of below 1200.degree. C. but without excessively cooling the clinker so that all fractions retain sufficient sensible heat to drive off water picked up during the quenching process and resulting in completely dry clinker.

Abstract: A method of firing granular carbonate minerals, for example a cement-calcine-forming meal, in which the comminuted solids are preheated in a fluidized bed or by like entrainment in a hot gas and then subjected to decarbonation in a precalcinator before entering a rotary kiln from which the cement clinker is discharged into a cooler for heat exchange between the hot clinker and air. According to the invention, the meal is suspended in the precalcinator, which forms an upright shaft at the inlet end of the kiln, so that the particles do not pass into the kiln directly from the precalcinator but rather can be entrained by the gases in the precalcinator, separated therefrom in a cyclone and delivered to the kiln. Fuel is mixed with the kiln exhaust gases just ahead of the zone at which the meal is suspended so that the sensible heat of the exhaust gas vaporizes the fuel or gasifies the latter.

Abstract: A method and device for sintering materials and, in particular, limestone gravel, of very different granular size in the granular range of 5 to 50 mm, in a rotary shaft kiln with a shaft preheater and shaft cooler, are provided wherein the sintering charge of the original gravels are crushed into two or more granular fractions and are fed in a low band width to the furnace system periodically and alternately, and wherein the process gases flow through the filling or charge layers of the sintering materials. The filling layers are automatically changed in the shaft preheater and the shaft cooler in their thickness, so that the flow through resistance thereof remains constant.

Abstract: A centrifuge for sifting granular material, ranging in particle size from a few microns to several hundred microns, for example, comprises an upwardly concave frustoconical disk rotatable about a horizontal axis and provided with a similarly shaped cover defining therewith a narrow annular gap of outwardly converging radial cross-section. Air, or some other gaseous or liquid fluid, is axially introduced from above into that gap together with the granular material to be centrifuged, the fluid stream imparting to the smaller particles an added acceleration making the velocities of all particles substantially equal at the disk periphery.