Device for charging and preheating granular material passing into a kiln

Abstract

Claims

3. DEVICE FOR CHARGING AND PREHEATING GRANULAR MATERIAL INTO ROTARY KILN, COMPRISING A VERTICAL SHAFT STRUCTURE HAVING OPPOSED VERTICAL WALLS, INLET MEANS AT THE BOTTOM OF SAID SHAFT FOR RECEIVING HOT GASES FROM THE KILN FOR UPWARD FLOW THROUGH THE SHAFT SPACE, MEANS AT THE TOP OF SAID SHAFT STRUCTURE FOR FEEDING SAID GRANULAR MATERIAL INTO SAID SHAFT STRUCTURE IN CONTINUOUS AND TRICKLING GRAVITY FLOW IN COUNTER-CURRENT TO SAID HOT GASES, SAID SHAFT STRUCTURE HAVING A MULTIPLICITY OF LATERAL STEP STRUCTURES PROTRUDING ALTERNATELY FROM OPPOSITE SHAFT WALLS IN MUTUALLY STAGGERED RELATION, SAID STEP STRUCTURES HAVING HORIZONAL UPPER SURFACES EXTENDING FROM A RESPECTIVE STEP-SUPPORTING WALL OF SAID SHAFT STRUCTURE AT MOST UP TO THE VERTICAL CENTER AXIS OF THE SHAFT SPACE, EACH OF SAID STEP STRUCTURES HAVING A BOTTOM SURFACE DEFINING AT LEAST ONE GENERATRIX LINE PARALLEL TO SAID HORIZONTAL UPPER SURFACE AND CURVING DOWNWARDLY TO FORM SAID BOTTOM SURFACE INTO CONCAVE CONFIGURATION, SAID BOTTOM SURFACES OF THE STEP STRUCTURES ON A RESPECTIVE ONE OF SAID OPPOSED
United States Patent O 3,164,380 DEVICE FOR CHARGING AND PREHEATlNG. GRANULAR MATERIAL PASSING INTO A KILN Rudolf Kus, Bochum, Germany, assignor to Westfalia Dinnendahl Groppel Aktiengesellschaft, Bochum, Germany, a corporation of Germany Filed Nov. 27, 196i, Ser. No. 155,135 Claims priority, application Germany Nov. 25, 196i) 3 Claims. (Cl. 263-32) My invention relates to a device for charging granular material into a rotary kiln' and Vp'reheating the,v material as it passes into the kiln. This purpose has heretofore been served, as a rule, by travelling gratings which convey the granular material- .to the k-iln, the hot waste gases from the kiln passing over the gratings. Such equipment comprises many moving machine parts as well as a drive and for that reason is expensive in manufacture, operation and maintenance. It is an object of my invention to devise a charging and preheating device of a simpler and less costly design. According to my invention, the material charging and preheating device comprises a chute or shaft structure provided with a multiplicity of lateral steps that protrude alternately from opposite sides into the shaft space and subdivide the gravity path of the material for a stepwise delay of its downward travel in counterflow to the hot kiln gases passing upwardly through lthe shaft. In general, such a shaft structure is similar to a known stair- Waytype device for downward transportation of pourable material. However, the shaft structure of a device according to the invention has its bottom opening in communication with the rotary kiln to receive the hot Waste gases therefrom and has a material inlet opening near the top, ahead of the shaft end where the gases, after heating t-he granular material, pass out of the shaft structure. The granular material, for example lime, dolomite or the like, in a grain size of approximately to 30 mm., is preferably supplied to the material inlet near the upper end of the shaft from a storage bin through a dispensing or dosage-discharging device such as a cell wheel. The hot kiln Waste gases, entering from below into the' shaft and travelling upwardly in counterflow to the material drifting downwardly, come into intimate contact therewith since the material is continuously loosened by the baille action of the steps and by the resulting whirling or stirring action. The shaft and the step structures are preferably made of masonry from refractory bricks or blocks. The drawing illustrates yan embodiment of the device according to the invention by way of example. FIG. l shows .the charging and preheating device in vertical, longitudinal section. FIG. 2 is a sectional View of part of the shaft showing one of the step structures consisting of masonry. A rotary kiln 1 has its gas outlet end, where the material to be processed is to be charged into the kiln, connected with the bottom opening of a shaft structure 2. The connection is eifected by a fixed tlue structure 1a. The annular gap between the ue la and the kiln is covered by a ring-shaped enclosure lb and is preferably sealed, inside the enclosure 1b, by a ring-type or labyrinth seal (not shown) to substantially prevent or minimize escape of gas. The shaft structure 2 is provided with steps 3 which also consist of masonry and are staggered relative to each other so as to alternately protrude from opposite sides of the shaft into the shaft space. The horizontal length of the step structures is suflicient to subdivide the gravity path of the material to cause the desired stepwise delay of its downward travel. The step structures are preferably designed as an arch of masonry as apparent from FIG. 2 and are being convex seen from trained in the waste gases issuing from the shaft. above. The shaft structure 2 may have a circular or oval inner crossV section, or a cross section with rounded corners. The upper end of the shaft communicates with the gas inlet duct of a cyclone 4 for precipitating any dust en- The cleaned waste gases leave the cyclone through an outlet conduit 5.V The precipitated dust is drained from the tip of the conical bottom portion 6 of the cyclone. Y Connected to a material inlet opening .in the upper portion of the shaft structure shortly ahead of the cyclone with respect gto the upward iloW direction of the kiln gases is the funnel-shaped bottom portion of a bin 7 provided with a dispensing and dosing device 8. The proper amount of material per unit of time is fed into the shaft from bin 7 with the aid of the dispensing device 8. The device 8 may consist of a rotatable cell wheel so that the amount of material being supplied through the shaft to the kiln can be controlled or regulated by rotating the cell wheel at a corresponding speed. In the shaft 2, the material trickles in form of a thin veil from step to step downward, each time a portion of the material being caught on the steps in accordance with the angle of repose of the particular material. The hot gases issuing from the kiln 1 travel upwardly through the shaft in intimate contact with the downward flowV of granular material thus preheating the material. I claim: 1. With a kiln having kiln outlet means for hot kiln gases, the combination of a preheating device for charging granular material into the kiln, said dew'ce compris-V ing a shaft structure extending upwardly from said kiln outlet means and communicating therewith, said shaft structure having opposed vertical walls dening a shaft space and gas outlet means at the top of the shaft space so that said shaft space is upwardly traversed by an unidirectional current of the kiln gases when in operation, charge inlet means for the granular material disposed near the top of said structure ahead of said gas outlet means for gravity flow of said material counter-current relative to the gas current flow direction, a multiplicity of vertically spaced lateral step structures having upwardly facing tlat horizontal surfaces protruding alternately from opposite shaft walls Ainto said shaft space and extending at most up to the central axis of said shaft space for subdividing the gravity path of the material, each of said step structures having a bottom surface defining at least one generatrix line parallel to said upwardly facing surface and curving downwardly to form a concave bottom surface, said bottom surface of the step structure on a respective one of said opposed vertical walls being vertically spaced from the upwardly facing horizontal surface of .the next lower step structure protruding from said one wall so as to dene togetherwith said one wall a whirling chamber for said current of gases, the open horizontal width of said chamber throughout its vertical length and measured perpendicular to said one wall being not less than the horizontal length of said step structures protruding from said one wall. 2. Inra device according to claim l, said step structures comprising masonry arches, the axis of each arch being horizontal and perpendicular to said step-supporting wall. 3. Device for charging and preheating granular material into a rotary kiln, comprising a vertical shaft structure having opposed vertical Walls, inlet means at the bottom of said shaft for receiving hot gases from the kiln for upward flow through the shaft space, means at the top o-f said shaft structure for feeding said granular material into said shaft structure in' continuous and trickling gravity llow in counter-current to said hot gases, Patented Jan. 5,1965A said shaft structure having a multiplicity of lateral step structures protruding alternately from opposite shaft walls in mutually staggered relation, said step structures having horizontal upper surfaces extending from a respective step-supporting Wall of said shaft structure at moet up to the Vertical center axis of the shaft space, each of said step structures having a bottom surface delining at least one generatriX line parallel yto said horizontal upper surface and curving downwardly to form said bottom surface into concave configuration, said bottom surfaces of 1() the step structures on a respective one of said opposed vertical walls being vertically spaced from the upwardly facing horizontal surface of the next lower step structure extending from said one wall so as to dene together with said one wall a whirling chamber for said gases, the open horizontal width of said chamber throughout its vertical length and measured perpendicular to said one wall being not less then t'ne horizontal length of said step structures extending from said one wall. References Cited in-the tile of this patent UNITED STATES PATENTS 464,784- Wilrnott Dec. 8, 1891 464,934 Dubbs Dec. 8, 1891 1,869,705 Miscampbell Aug. 2, 1932 2,824,384 Niemitz Feb. 25, 1958 2,866,625 Sylvest Dec. 30, 1958 FOREIGN PATENTS 334,048 Germany Marr. 8, 1921 536,914 Italy Dec. 12, 1955 559,822 Germany Sept. 24, 1932

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Cited By (5)

    Publication numberPublication dateAssigneeTitle
    US-3284075-ANovember 08, 1966Azbe CorpLime production
    US-3362857-AJanuary 09, 1968Textron IncContinuous heat treating system
    US-3765827-AOctober 16, 1973K BeckenbachInclined hearth kiln for the firing and sintering of material
    US-4691900-ASeptember 08, 1987Kankyo Souken Consultant, Co., Ltd.Metal melting furnace
    US-4978106-ADecember 18, 1990Kelmar John JIron reduction apparatus