US3098036A

US3098036A - Classifying apparatus

Info

Publication number: US3098036A
Application number: US50356A
Authority: US
Inventors: Neumann Willy
Original assignee: Babcock and Wilcox Ltd
Current assignee: Babcock International Ltd
Priority date: 1959-09-11
Filing date: 1960-08-18
Publication date: 1963-07-16
Anticipated expiration: 1980-07-16

Description

July 16, 1963 w. NEUMANN 3,098,036

CLASSIF'YING APPARATUS Filed Aug. 18. 1960 INVENTOR. Willy Neumann ATTORNEY United States Patent 3,098,03 CLASSIFYEVG APPARATUS Willy Neumann, Emrlen, Germany, assignor to Babcock &

Wilcox, Limited, London, England, a company of Great Britain Filed Aug. 18, 1960, Ser. No. 50,356 Claims priority, application Germany Sept. 11, 1959 3 Claims. (Cl. 209-144) The invention relates to apparatus for the separation of coarse particle-form material from its carrier medium, and more particularly to an improvement in the classification of dust-laden air, with the positive removal of coarse materials from a classifier.

It is known that a gas or air stream laden with particulate material may have the coarser particles removed by passing the stream through a classifier located in the flow path of the gas or air entrained material. In order to assure good separation of the coarser entrained particles from the carrier medium, it is customary to introduce the stream of carrier medium and entrained particles into a separator or classifier such that it will have a tangential component of motion and thereby impart a whirling motion to the stream within the separator to effect separation largely by centrifugal action. It has also been customary to construct and arrange the inlet or inlets to the separator so that the cross-sectional area and the angularity of the incoming stream or streams may be adjusted to permit regulation of the degree of separation of particles from the carrier medium.

Practice, however, has shown that a differential dust loading occurs in the discharge lines from the separator when the degree of separation is controlled. It has been impossible to obtain a uniformly distributed pickup of particles from the inside of the separator. In order to avoid this difiiculty, the present invention proposes that the internal wall of the separator be provided with an apparatus which accelerates the separation of large particles, the apparatus consisting of, for instance, insertions of blades or vanes which penetrate or protrude into the classifier or separator. It is intended to arrange these blades so they will always be below the classifier inlet and the damper supports therefor and to have them adjustable if desired. The arrangement according to the invention permits the uniform distribution of particulate material at the classifier exit and allows control of the particle size by the positioning of the blade inserts.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Of the drawings:

FIG. 1 shows a classifier having internal blades constructed in accordance with the present invention; and

FIG. 2 shows a classifier generally corresponding to the arrangement of FIG. 1 but with adjustably arranged blades.

In the illustrated embodiment of the invention as shown in FIG. l, the classifier 10 is constructed and arranged to be mounted on the top of an air-swept pulverizer (for example), such that it will have an annular stream of airborne particle material discharging upwardly through an annular passageway or chamber 11 defined by laterally spaced inner and outer inverted frusto-

conical walls

12 and 13. The inner wall 12 merges into a cylindrical wall 14 in the upper portion of the classifier. The wall 1 4 is open to the interior of the classifier and is provided 3,098,036 Patented July 16, 1963 with circumferentially, uniformly spaced vanes 15 which are pivotally positioned to impart a tangential component of motion to the stream of air-borne particle material passing therethrough.

As shown, the classifier is provided with a hollow tube 16 of circular cross section which extends throughout the length of the classifier and is coaxial therewith and which may be used for the introduction of raw material to a pulverizer (not shown) positioned beneath the classifier. A cylindrical member 17 extends downwardly through the top plate 18 of the classifier to a downwardly spaced position so as to cooperate with the tube 16 in defining an annular outlet 20 from the classifier. As shown in FIG. 1, the outlet 20 is divided into a plurality of outlet ducts 21 which may be connected with individual burners, for example, when the discharge from the classifier is utilized for combustion purposes.

The lower end of the wall 12 ends at a position laterally spaced from the tube 16, to provide an annular outlet 22 for the discharge of coarse materials separated from the carrier medium within the classifier. The outlet 22 is provided with circumferentially spaced valves 23, which may be spring loaded or counter-weighted to permit discharge only when a predetermined weight of coarse material has accumulated in the classifier. Advantageously, the coarse materials may thereafter be returned to the pulverizer for further processing or may be separately stored for later use.

The dust-air mixture entering the classifier along the direction indicated by arrow 24 passes through the classifier inlet vanes 15 to the interior of the classifier wherein the heavy dust particles, such as grains and coarse particles, are projected against the wall 12 of the inner cone of the classifier, and then would tend, in prior structures, to slide downwardly in a circular direction toward the outlet valves 23 which close off the lower portion of the inner cone. The flow of the heavy dust particles will ordinarily be largest at the area where the resistance and pressure are lowest on the exit dampers 23. This produces a differential dust loading in the burner ducts 21 since it formerly was impossible to have a uniform particle return by means of such an arrangement.

According to the invention, the installation of ribs, bafile plates, or blades 25 controls the movement of coarse particles along the separator inner cone toward exit Valves 23, [thereby attaining uniform removal of the heavier dust particles from the inner cone of the classifier. Because of this, the fine particle dust discharge from the pulverizer classifier outlets 21 will also have a more uniform fineness distribution in the individual outlet ducts 21. The blades 25 are circumferentially spaced about the internal surface of the wall 12 and extend longitudinally thereof from positions spaced from the opposite ends of the wall.

A close adjustment of the finesness distribution of the product may be attained by arranging the battle blades 25 so that each blade may be rotated around its lower horizontal axis 26 (see FIG. 2). This makes it possible to vary the free flow area and thus vary the rotational velocity of the dust-air stream to improve the fines classification of the dust. At the same time, this reduces or eliminates the need for adjusting the classifier vanes '15. The adjustment of the blades 25' may occur by means of an arrangement 27 which actuates a ring 28 connecting the blades 25. It is often possible to attain good results with the insertion of only three blades although it may be found advantageous to install a larger or smaller number within the classifier.

Upon entering the classifier, the dust laden air passes through chamber 11, enters vanes 15 and is discharged with a tangential component of motion to be whirled downward in a generally helical flow path through the chamber 19. The larger and heavier particles move outwardly towards the wall "12 as a result of the centrifugal forces acting in the larger masses of particulate material. As the whirling stream enters the frusto-conical portion of the classifier defined by the wall 12, the whirling outer layers of the stream encounters the longitudinally extending blades 25 which interrupt this portion of the stream, and form eddy currents, arresting the circular motion so that the coarser particles drop out of suspension and gravitate downwardly along the wall 12 and blades 25 to discharge through the valves 23. While the peripheral layers of the whirling stream are subjected to eddy currents, the inner layers will tend to retain a smooth generally helical flow pattern and will turn to discharge through the annular outlet 20 formed between the tube 16 and member 17. Changing the eifective height of the blades 25 will change the depth of the whirling stream affected by the eddy currents and thus change the classifying action.

It is to be understood that the word air as used in the claims has a generic connotation and can mean any gaseous medium.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form and mode of operation of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. Apparatus for separating the coarse particles from an air-borne stream of mixed fine and coarse particle materials which comprises a separator having a cylindrical wall forming an upper end portion merging with the base of an inverted frusto-conical wall forming a lower portion thereof, said cylindrical and inverted frusto-conical wall portions having a common substantially upright axis, a cylindrical outlet duct coaxial with and of lesser diameter than the cylindrical portion of said separator, said outlet duct extending through the cylindrical portion and opening into the frusto-conical portion of said separator, means for the admission of said air-borne material into said separator with a tangential component of motion to effect a whirling motion therein, means for interrupting the peripheral portions of said whirling stream of air-borne material only in and to direct the coarser particles of said material only along the wall of said frustoconical portion and out of the whirling stream of the finer air-borne material moving toward said outlet duct, and annular sealing discharge means at the lower end of said inverted frusto-conical portion for the discharge of coarse material from said separator.

2. Apparatus for separating coarse particles from an air-borne stream of mixed fine and coarse particle materials which comprises an outer wall, an inverted frustoconical inner wall coaxial with and spaced from said outer Wall, said walls defining an annular passageway for upward movement of an air-borne stream of said mixed materials therethrough, means for discharging said mixed particle materials from said annular passageway into the upper end portion of said inner wall with a tangential component of motion and to effect a whirling motion of said materials therein, a centrally located air-borne material outlet duct in the upper portion of said separator, annular sealing means for removing coarse material from the lower end of said frusto-conical portion, a plurality of circumferentially spaced vanes pivotably attached at their lower end portions on the inner surface of said frusto-conical wall for interrupting the peripheral portions of said whirling stream of air-borne material in and to direct the coraser particles of said material along the wall of said frusto-conical portion and out of the whirling stream of the finer air-borne material moving toward said outlet duct, and means for radially adjusting said vanes above said pivotable attachment relative to the inner surface of said frusto-conical wall to change the thickness of the interrupted peripheral portions of said whirling stream.

3. Apparatus for separating the coarse particles from an air-borne stream of mixed fine and coarse particle materials which comprises an upright separator of circular cross-section having a cylindrical wall forming an upper end portion merging with the base of an inverted frusto-conical wall forming a lower portion thereof, a cylindrical outlet duct coaxial with and of lesser diameter than the cylindrical portion of said separator, said outlet duct extending through the cylindrical portion and opening into the frusto-conical portion of said separator, duct means coaxial with said outlet duct extending through said separator and being of lesser diameter than said outlet duct, circumferentially spaced vanes positioned in the cylindrical wall of said separator for the admission of said air-borne material with a tangential component of motion to said separator and to effect a whirling motion therein, axially extending vanes positioned on the inner surface of said frusto-conical wall for interrupting the peripheral portions of said whirling stream of air-borne material and to direct the coarser particles of said material along the wall of said frusto-conical portion out of the whirling stream of the finer air-borne material moving toward said outlet duct, and means forming an annular coarse material outlet from said separator positioned between the lower end portion of said frusto-conical separator portion and said duct means.

References Cited in the file of this patent UNITED STATES PATENTS 505,977 Fletcher Oct. 3, 1893 1,721,908 Heist July 23, 1929 2,168,091 Butler Aug. 1, 1939 2,917,131 Evans Dec. 15, 1959 FOREIGN PATENTS 27,130 Great Britain 1913

Claims

1. APPARATUS FOR SEPARATING THE COARSE PARTICLES FROM AN AIR-BORNE STREAM OF MIXED FINE AND COARSE PARTICLE MATERIALS WHICH COMPRISES A SEOPARATOR HAVING A CYLINDRICAL WALL FORMING AN UPPER END PORTION MERGING WITH THE OF AN INVERTED FRUSTO-CONCIAL WALL FORMING A LOWER PORTION THEREOF, SAID CYLINDRICAL AND INVERTED FRUSTO-CONCILA WALL PORTIONS HAVING A COMMON SUBSTANTIALLY UPRIGHT AXIS, A CYLINDRICAL OUTLET DUCT COAXIAL WITH AND OF LESSER DIAMETER THAN THE CYLINDRICAL PORTION OF SAID SEPARATOR, SAID OUTLET DUCT EXTENDING THROUGH CYLINDRICAL PORTION AND OPENING INTO THE FRUSTO-CONCIAL PORTION OF SAID SEPARATOR, MEANS FOR THE ADMISSION OF SAID AIR-BORNE MATERIAL INTO SAID SEPARATOR WITH A TANGENTIAL COMPONENT OF MOTION TO EFFECT A WHIRLING MOTION THEREIN, MEANS FOR INTERRUPTING THE PERIPHERAL PORTIONS OF SAID WHIRLING STREAM OF AIR-BORNE MATERIAL ONLY IN AND TO DIRECT THE COARSER PARTICLES OF SAID MATERIAL ONLY ALONG THE WALL OF SAID FRUSTOCONICAL PORTION AND OUT OF THE WHIRLING STREAM OF THE FINER AIR-BORNE MATERIAL MOVING TOWARD SAID OUTLET DUCT, AND ANNULAR SEALING DISCHARGE MEANS AT THE LOWER END OF SAID INVERTED FRUSTO-CONCIAL PORTION FOR THE DISCHARGE OF COARSE MATERIAL FROM SAID SEPARATOR.