Abstract: An apparatus for a raking device which illustratively includes a harrow, which moves along a bridge in a reciprocating direction and which includes a mechanism for ensuring that any motion of an apex of the harrow is substantially linear as the harrow moves throughout its entire range of travel, is described. Specifically, this mechanism is comprised of a flexible tension element which forms part of a hoist and is reeved between a stationary support and the harrow such that the effective length, of the part of the flexible tension element which determines the inclination of the harrow, is adjusted in direct response to the distance through which the harrow has moved along the bridge with respect to an end point of its travel.

Abstract: This invention relates to a method for the production of anhydrous alumina having a desired .alpha.-conversion from alumina trihydrate.This method is directed to production of anhydrous alumina having a desired .alpha.-conversion from alumina trihydrate in which water is removed in a precalcining zone wherein the alumina trihydrate is heated to a temperature below 450.degree. C. Then, the precalcined dehydrated alumina is recrystallized to .alpha.-alumina in a reaction chamber by directing an oxygen containing gas to the reaction chamber, mixing and suspending the precalcined alumina and fuel in the oxygen containing gas and feeding the mixture to a combustion zone, followed by exothermal recrystallization of the alumina which is initiated by rapidly heating the precalcined alumina by burning the fuel in the oxygen containing gas in the hot combustion zone and withdrawing the recrystallized alumina from the top of the reaction chamber suspended in a combustion gas stream.

Abstract: The invention relates to a bridge scraper for raking material from a storage heap onto a belt conveyor by means of a scraper chain mounted on a bridge which also carries a carriage which feeds material from the heap to the scraper chain. The speed of the conveyor and that of the bridge, the scraper chain and the carriage is controlled by means of a bolt weigher at the outlet end of the belt conveyor which controls the speed of the belt and consequently that of the other elements of the bridge scraper so as to discharge a constant amount of material per unit time.

Abstract: A method for separating particulate material into coarse and fine fractions is disclosed by suspending the material in a conveying gas flow having a radially symmetrical flow pattern, radially surrounding the gas suspension with a band of clean gas containing substantially no particulate and directing the concentric gas flow past a vaned rotating rotor having an axis of rotation axially aligned with the concentric axis of the gases. The rotor vanes fling the coarse fraction in a radially outwardly direction while the remaining fine fraction remains in the conveying gas flow for subsequent separation from the gas. An apparatus in the form of a separator is disclosed for sorting particulate material suspended within a conveying gas into coarse and fine fractions is also disclosed.

Abstract: A vertical roller mill has a rotary grinding table (1), grinding rollers (3) and a nozzle ring (13) surrounding the table for providing an air stream to entrain ground material. Downstream of each roller is a scraper (20) with a nozzle for directing a blast of air onto the crushed material leaving the roller to break up the material so that finer fractions pass into the conveying air stream and coarser fractions are carried on the table to the next roller.

Abstract: The present invention relates to a vertical roller mill including a grinding roller which is urged against a grinding path on a grinding table by a hydraulic cylinder. The loading on the roller is measured by a transducer and the acceleration of the roller by an accelerometer. Resulting signals are combined at a controller which controls a valve through which hydraulic fluid is supplied to the hydraulic cylinder, so that the loading is compensated for the influence of the instantaneous velocity and acceleration of the roller.

Abstract: A method is disclosed for controlling the DC voltage of an electrostatic precipitator having electrodes energized by a preset DC voltage in which the preset DC voltage has pulses superimposed thereon. According to the method, the pulses are periodically turned off. Thereafter, the corona discharge current caused by the DC voltage is measured and compared against a preset value. Thereafter, the DC voltage is adjusted in dependence upon the measured corona discharge current by it being increased or decreased depending upon whether the discharge current is lower or higher than the preset value.

Abstract: An apparatus is disclosed for burning cement clinker which includes a preheater with inlet and outlet for heating gas and inlet and outlet for pulverous cement raw material, a suspension calciner with inlets for fuel, combustion air and preheated raw materials, outlet for combustion gas connected to the heating gas inlet of the preheater, and outlet for calcined material, communicating with the material inlet of a sintering furnace. The sintering furnace includes an inlet for fuel and combustion air, outlet for combustion gas communicating with the heating gas inlet of the preheater and an outlet for the sintered product connected to the material inlet of an air cooler for cooling the sintered product. The air cooler includes an air outlet connected both to the air inlet of the sintering furnace and to the air inlet of the suspension calciner.

Abstract: A method for thermally treating pulverulent material, i.e., keeping the material at a certain temperature, the treating temperature, in a desired period of time, in particular sintering, pulverulent material in a rotary kiln slightly inclined to the horizontal. The method is especially applicable for thermally treating materials which tend to become sticky at the treating temperature, in particular for sintering pulverulent materials, i.e., agglomerating these by heating without complete melting. However, the method is also useful for general thermal treatment where sintering is not intended, e.g., for burning Bauxite, Mesa and phosphate bearing ores. An example of a sintering process to which the invention is particularly applicable is the manufacture of cement clinker where the pulverulent material to be sintered is hot calcined cement raw meal. An apparatus for practicing the method of the present invention is also disclosed.

Abstract: A method for thermally treating pulverulent material, i.e., keeping the material at a certain temperature, the treating temperature, in a desired period of time, in particular sintering, pulverulent material in a cylindrical reaction chamber with an axis slightly inclined to the horizontal after the material has been heated to the treating temperature outside the reaction chamber suspended in a gas. The method is especially applicable for thermally treating materials which tend to become sticky at the treating temperature, in particular for sintering pulverulent materials, i.e., agglomerating these by heating without complete melting. However, the method is also useful for general thermal treatment where sintering is not intended, e.g., for burning Bauxite, Mesa and phosphate bearing ores. An example of a sintering process to which the invention is particularly applicable is the manufacturing of cement clinker where the pulverulent material to be sintered is hot calcined cement raw meal.

Abstract: A whirl chamber boiler plant for generation of steam includes a combustion chamber in which the fuel is burned in a whirl within the chamber. The bottom of the chamber slopes downwardly towards an inlet through which combustion air is admitted into the chamber. Fuel and inert material are admitted into the chamber adjacent the bottom thereof. The inlet is of a size suitable for fluidizing the inert material within the chamber. Boiler tubes built within the chamber provide for removal of heat from the chamber. Preferably the inert material is a grain-shaped ash of the type produced by the burning of the fuel. In one embodiment of the present invention, a portion of the ash contained in the gases exiting from the chamber is returned to the chamber.

Abstract: A method is disclosed for treating granular or pulverous raw material in a kiln plant including a preheater stage, a precalciner stage and a separator stage coupled to one another. Precalcined material is separated after the separator stage into a first and second material flow. The first material flow is suspended in spent cooling air and fed to a reaction zone zone for burning and melting the material therein. The melted material is fed to a cyclone for separating smoke gases therefrom and thereafter to a rotating nodulization drum. The second material flow is also fed to the rotating nudulization drum and mixed therein with the melted material so as to avoid any sticking and clogging of the melt. A kiln for practicing the method of the present invention is also disclosed. In preferred alternative embodiments, the reaction chamber can be either a shaft-like chamber or a cyclone burner.

Abstract: A substantially horizontal rotating drum mounted on roller pairs which drum is driven via some of the rollers, drive rollers, by means of a hydrostatic motor on each drive roller. In order to avoid problems, e.g., stoppage if the contact between the drum and one or more drive rollers ceases, each hydrostatic motor is part of a separate power circuit further comprising a hydrostatic pump and a squirrel-cage motor constantly ensuring essentially the same peripheral speed for drum and drive roller irrespective of the torque size.

Abstract: The present invention relates to operation of a rotary kiln plant utilizing electrostatic precipitators. Specifically, this invention is directed to a method for conditioning exhaust gases from a burning process in a rotary kiln in which mineral materials are treated by burning a fuel. The method comprises adding a water soluble alkali-metal compound to a solid fuel, at least part of which is a solid pulverized fuel, and then firing the fuel in the kiln plant, whereby the resistivity of the exhaust gases is less than about 10.sup.10 ohm cm.

Abstract: A plant for manufacturing cement clinker from cement raw material includes a preheater first stage separated by a wall into a first chamber and a second chamber. Only raw material is passed through the first chamber while only hot exit gases are permitted to pass through the second chamber. Thus the raw material including any volatile, combustion components are kept isolated from direct contact with the hot exit gases. A heat exchange system is provided to permit the transfer of heat from the hot exit gases in the second chamber to the raw material in the first chamber. The heat exchange system preferably includes self-contained heat pipes extending into both the first and second chambers. The heat pipes contain a fluid medium which aids in the heat transfer as a consequence of cylical changes of the fluid medium from a liquid to a vapor state.

Abstract: A kiln plant for burning a pulverous material such as cement, which includes a preheater string for preheating raw material and a precalciner for receiving preheated raw material, the precalciner being fired with solid fuel, and a disintegrator provided adjacent the precalciner. Within the disintegrator the solid fuel, preferably coal, is crushed and mixed with a portion of the preheated raw material before passage into the precalciner. The invention also relates to a unique method for firing in the precalcining zone of the invention kiln plant.

Abstract: A kiln plant for burning raw materials such as cement raw materials and the like includes a single-string, multi-stage suspension preheater, a suspension precalciner, a rotary kiln and a cooler. The single-string preheater includes at least a lowermost preheater stage and a penultimate preheater stage each having a gas flow inlet and outlet. The precalciner gas outlet is coupled to the gas inlet of the penultimate preheater stage. The gas outlet of the lowermost preheater stage is also coupled to the gas inlet of the penultimate preheater stage. The materials are precalcined in the precalciner solely by means of spent cooler air from the cooler while the materials are preheated in the lowermost preheater stage solely by means of kiln exhaust gases. The pressure drops arising in the two gas flows through the precalciner and the lowermost preheater stage are equalized before the union of the two gases flows entering the gas inlet of the penultimate preheater stage.

Abstract: A nozzle ring assembly for use around a circular grinding path of a roller mill of the kind comprising a grinding table which is rotatable about a vertical axis, and grinding rollers urged against the grinding table. The nozzle ring assembly comprises a nozzle ring with circumferentially spaced guide vanes for directing air, in use, over the grinding path in a direction with a component substantially tangential to the grinding path. The nozzle ring also has a set of annular guide vanes which are disposed one above the other for directing air, in use, substantially horizontally over the grinding path.

Abstract: A method is disclosed for operating a roller mill of the type having a rotating grinding path upon which one or more grinding rollers are disposed for rotatably grinding the material to be ground. In particular, a method is disclosed for maintaining a constant predetermined thickness of the grinding cushion between the grinding roller or rollers and the grinding path. More particularly, according to the invention the mean grinding pressure increases within fixed limits when the mean thickness of the grinding cushion is larger than predetermined, and decreases when the mean thickness of the grinding cushion is smaller than predetermined. The invention also pertains to an improved roller mill of the type described, for practicing the inventive method.

Abstract: A vertical roller mill includes a grinding table positioned for rotation around a vertical axis and two upright grinding rollers resting on their peripheral grinding surfaces on the grinding table for grinding material thereon. Each of the grinding rollers is rotatably mounted on a respective fixed horizontal shaft connected at one end to a common, central frame and at the other end to a draw bar. Preferably, the draw bar is regulated by a hydraulic cylinder secured in a bracket which is anchored in the mill foundation.