US1996076A - Centrifugal separating apparatus - Google Patents

Description

A ril 2,1935. M. A. ,LIss MANQ- 6,

CENTRIFUGAL SEPARATING APPARATUS Filed Ju1y 2a, 1952 2 Sheets-Sheet 2 INVENTOR M c'aLAllssna/v mmemMz imga w/ Patented Apr. 2, 1935 UNITED STATES e 1,996,056. WGAL SEPABA'IING APPARATUS lfareelmllissmam'lemniccliacallfsaaslgnor to International Precipitation Angeles, Calif.. a corporation company, In of California Application July as, 1932, semi No. $25,3 9

' This invention relates to an improvement in centrifugal classifiers or apparatus for separate ing divided materials of different size. The main object of the invention is to provide apparatus of this character which will have large capacity and at the same. time will effect a sharp separation between the coarser particles of the material .and the finer portions thereof. The invention is particularly intended and adapted for separation from coarser material of extremely fine material as hereinafter set forth.

In the usual types of classifiers-it'has bee found difilcult to effect a sharp separation between the constituents of different size inthe material to be operated upon and the .operation a of such a classifier. generally results in the production of a coarser fraction having more or less fines mixed with it and a finer fraction containing some of the coarser material. To avoid this dimculty my invention provides for subjecting the material to be treated to the action of a moving body of air in a suitable casing in such manner that the fines are forcibly removed from adherence to the coarser particles and are sharply separated therefrom by the counteractions of centrifugal force and gas entrainment, and the finer particles are then removed from the body of gas under such conditions as to minimize the passage of" coarser particles therewith. The invention may be employed for separation of materials of different sizes or densities from a .body of gas in which such materials are suspended, either by forcible distribution into such gas of material to'be classified, or by the operations of furnaces, mills, or other apparatus which result in production of gas having materials of different sizes or densities dispersed therein.

The accompanying drawings illustrate my invention and referring thereto:

Fig. 1 is a vertical section of one form of the invention.

Fig. 2 is a section on line 2-2 in Fig. l. Fig. 3 is a section on line 3-4 in Fig. 1,.

Fig. 4 is a vertical section of another form of.

modifitends therefrom through the casing l to a suit- Fig. 10 is a vertical section of a further modification.

' The form ofmy invention shown in Figs. 1 to 3 comprises a casing I, an impeller or fan 2 mounted'within said casing, means indicated at 3 for 5 supplying to the interior of the casing the material to be treated, deflector means mounted within the casing for guiding the air or gas currents therein in such manner as to effect the desired separation, and suitable outlet means for the 10' coarse material and for the 'ifi'ne material respec tively. The coarse material outlet means, shown at i6, is preferably disposed, adjacent the opposite end of the casing from the impeller 2.

The casing I is of substantially circular cross- 15 section, and is preferably cylindrical although it may be tapered slightly in a longitudinal direction, and is preferably mounted with its axis vertical, although ifdesired, it may be mounted in any other suitable manner.

The impeller or fan'=2 is shown in Fig. 1 as positioned at the lower portion of the casing i or adjacent to the bottom of said casing and is driven by a suitable motor 5 whose shaft 5' extends through the bottom of the casing and carries the blades of the fan 2.

The deflector means comprises a suction tube or cylindrical partition member 6 mounted coaxially in casing l and having at its upper end an upwardly flaring cone or frusto-conical deflector means I spaced at its upper edge from the top 8 of the casing I and from the side walls of said casing, said deflector means being supported by brackets 9, secured, for example'to the top member 8. Ah additional partition or deflector means I0 is provided around the lower portion of the member 6, said means l0 consisting preferably of a cylindrical member mounted coaxially with the member 6 and connected thereto at the lower end thereof by a transverse web It, so as to form an annular space or chamber l2 between the members 6 and Ill, said space being cl ed at the bottom and open at the top as she sat l2, so as to establish communication of I d annular space with the interior of the casing/l through the open upper end if at..a position longitudinally intermediate the impeller 2 and the coarse material outlet means It. A fines outlet conduit It leads tangentially from this annular space I! and exable point of delivery. Said fines outlet conduit opens into the annular space through an opening ll which is preferably located at a position longitudinally removed from the open end 12' of said space, for example, near the bottom thereof.

interior of the casing I through ports or passages 16. In some cases it is desirable to provide for adjustment of these passages and for this purpose a regulating or closure plate I! may be mounted to slide on the outside of the casing l by means of bolts l8 engaging in suitable holes in the member l1, said plate l'lbeing provided with ports l1 adapted to register with the ports l6 aforesaid to a greater or less extent according to adjustment of the plate H. A hand hole 20 may be provided in one side of the box I 6 to facilitate access to the interior thereof, for example, for adjustment of the closure plate H. The coarse material may be discharged from bin I5 through a rotating pocket feeder 2| which-prevents passage of air and thence through conduit 2| to storage means or to any other suitable means for further treatment or handling.

In this form of my invention, provision is made for introducing a certain amount of gas or air, hereinafter referred to as breathing air, into the casing I along with the material to be classified,- said material being introduced into a hopper or funnel 3 which extends through the top 8 of the casing I and is of sufiicient size topermit a certain amount of air or gas to be drawn into the casing along with such material. The operation of the fan or impeller results in production of a radial outward pressure within-the casing in such manner that a flow of gas through the apparatus is produced, involving inflow of air or gas through thematerial inlet 3 and outflow of such air or gas through the fines outlet l3.- In addition to this through fiow of gas, there is an internal circulation produced within the casing in the manner hereinafter described, resulting in the effective separation and classification of the material.

The operation is as follows: The material to be classified is introduced into casing l at 3, to-- gether with asmall amount of breathing air.

The fan impeller 2, actuated by the means 5, keeps the air within casing I; whirling at a high rate. The maximum rate of whirling takes place in the plane of the fan, the minimum occurs at the top end of casing I, furthest away from the source of energy, the reduction in whirling rate being due to frictional .and eddy losses. Thus, the integrated pressure increase from the axis to the periphery of casing l due to the radial acceleration 'ergy losses in frictionandeddies encountered by the gas stream in making a circuit. Immediately adjacent the cylindrical walls'of casing I is a region of strong eddies where energy is dissipated rapidly, due to the high rate of shear in the gas stream on account of the relative velocity between the main gas stream and the stationary wall. This zone of intense eddies disintegrates the material to be classified, and causes an air emulsion to be formed with the finer fractions. Radially inward from this zone of strong eddies,

there is a region where the stream lines of 'the rapidly whirling gas are smoothed out. In this region of smooth stream lines, the radial accelera-' tion is kept very high, several hundred times that of gravity, due to the whirling of the gas maintained by'the action of the fan. Opposed to this strong radial acceleration outward there is a small inward component of the gas stream towards the entrance I 2'to annular space l2, and thence to the breather outlet tube entrance at l3, which inward flow will entrap sumciently fine particles. This inward component of motion can be varied by varying the volume 01' breather air, without affecting the whirling or recirculation volume from the fan. Thus, the fines reach the breather outlet, where they may be collected, if desired, by any suitable means.

The heavier particles always remain adjacent to the cylindrical walls of casing l,'and finally reach holes l6 leading into the oversize bin I 5.

By regulating the number or size of the holes Ii leading into this bin, it is possible to regulate the dispersion or washing action to which this over-- size material is subjected by changing the number of complete circuits which this oversize will make .before passing through said holes.

The form of my invention shown in Fig. 41s similar to'that above described except that the breather outlet tube indicated at 22 is open at its lower end and closed at its upper end, the outlet pipe 23 for fines opening tangentially into thev ing 25' to both ends of the fines-receiving space between said tube 22' and the suction tube 24'. Said tube 22' may be supported in any suitable manner, as for example by supporting arms or brackets secured to suction tube 24'. The fines outlet pipe 23, as'before, communicates tangentially with the annular space between the tubes 22 and 24', preferably at a level intermediate the ends of said space, for example adjacent the midheight thereof.

If desired, the fan or impeller may be located at the upper end ofthe casing as in the form of apparatus shown in Figs. 5 and 6, wherein the fan 30 and its driving motor 3| are shown as mounted on the top plate 32 of the cylindrical casing 33. In this case the inlet for breather air or gas is shown as a pipe 34 opening into the top of 33 and provided with means indicated at 8 for feeding or supplying thereto the material to be classified. The suction tube 36 is mounted coaxially within the casing 33 and is provided at its lower end with a deflector cone 3'! extending adjacent to the bottom 38 of casing 33 and to the side wall of said casing. In order to insure picking up of the'fines from the bottom portion of the space within the casing 33, a deflector cone 39 is provided within the cone 31 so as to maintain a as it of casing 33 adjacent the cylindrical wall thereof for discharging the coarse material into a suitable bin or receiving means 43. and in order to regulate the rate of discharge closure means may be provided for said openings consisting, for example, of a ring 46 having openings 41 adapted to register with the openings 45, said ring being adjusted in any suitable manner. for example, by

means of a pinion 48 engaging a-rack 49 on the ring 48, said pinion being carried by a shaft 50 mounted on the casing 33 and having an operating handle 52. Forcontinuous operation, bin 43 may be provided with suitable means such as indicated at SI for discharging coarse material therefrom without permitting appreciable inflow or outflow of air through said bin.

In case the breather air, or the through flow of gas, is of very considerable volume, the fines outlet pipe extending across the space between the breather outlet tube and the outer casing would,

.in some cases, oifer objectionable resistance to the whirling movement of the gas within the casing and in such cases the construction shown in Figs. 7 to 9 may be used. In this form of my invention the casing 54 is preferably relatively short as compared with the forms above described and the material and breather air inlet tube 55 extends coaxially with the casing 54 from the upper part thereof into proximity with the fan 56 which is adjacent the lower end 51 of the casing, the driving motor 58 for said fan being mounted on the bottom of the casing. The fines. outlet pipe 60 in this case opens tangentially or by an involute connection 6! from a cylindricaloutlet chamber 6| disposed coaxially about the tube 55 and extending through the top 62 of the casing 54 to a suitable height intermediate the fan 56and the top of said casing. In order to adjust" this height for most effective operation, the member 6| may be slidably mounted in an annular flange 63 on the top of casing 54 and may be adjustably secured in any desired position by screw 64. In order to adjust the material and breather air inlet tube 55 independently of the adjustment of the outlet member 6! said member 55 may be mounted to slide vertically in an annular flange 65 on member GI and may be fastened by screw 65.

A coarse material outlet opening 68 discharging into a bin 10 is provided in the casing 54 adjacent the top thereof and a regulating plate 69 may be provided therefor similar to. that shown in Fig. l.

In this form of the invention, the inner recirculation is especially vigorous and increases with any increase in the rate of feed of the material to be classified. The integrated pressure increase from the axis to the periphery of casing 54 is maximum at the fan end and minimum at the top of the casing away from the fan. The resulting pressure differential at the walls in'an axial dipensate for the energy lost in friction and eddies encountered by the gas streamin making a. circuit. As part of the gas stream in the inner vortex is withdrawn through tube 5| to the breathing air outlet 80, there results a component of motion radially inward. Particles beyond a certain definite size are not stable in the inner vortex as the component of motion vradially inward is not sumcient vigorous to overcome the outward radial acceleration due to the high rate of whirling of the gas stream. These larger particles therefore move radially outward into the outer vortex. Thus, the oversize particles repeat again and again a small circuit towards the top .end of casing 54. As this region is quite closely coupled to the fan, a high rate of whirling of the gas stream is maintained by the fan, nd this causes strong eddies close to the walls no to the high' rate of shear in the gas stream caused by the relative velocity between the whirling gas stream and the stationary walls. These strong eddies wash oil the fines adhering to the larger particles causing an air emulsion to be formed which is removed with the breathing air carrying the fines in suspension. The oversize particles finally ing. This material constantly picked up by the whirling air stream, causing friction and eddy losses. The increased pressure differential causes an increased rate of recirculation through the fan, thus withdrawing energy from the fan at a higher rate to maintain a high rate of" whirling tent from the rate of feed of the material to be classified.

In this form of the invention the material to be separated is introduced along with the breather air or'gas through the inlet pipe 55, it being in the dispersion zone, independent to a large exunderstood that such material may consist of finely divided solid material, for example, suspended in 'such air or gas either by distribution of such material into such air or gas by suitable dispersion means or by reason of the presence of such suspended material in air or gas coming from industrial operations in furnaces, mills or other apparatus.

The operation of this form of my invention is as follows: A breather air or gas is drawn through the inlet pipe 55 into the separating chamber 55 by the operation of the centrifugal fan 56 and a vortical motion of the air or gas is produced within said chamber 54 by the operation of said centrifugal fan with the result that the heavier or coarser solid particles are eventually discharged through the outlet means 68 and the finer or lighter solid particles are eventually dischargedthrough the breather outlet 60.

In case a closer or sharper separation is desired so that only extremely fine particles will be allowed to pass to the breather outlet, the construction shown in Fig. l0 may be adopted. This construction is similar to that shown in Fig. '7, except that the tubular member 6| leading to the breather outlet is provided at its lower end with an inwardly tapering frusto-co'nical deflector ll approaching sufliciently close to the inlet tube 55' for gas and suspended material to restrict the passage of fine material to the breather outlet to the extent desired. To assist in this selective operatiomthe lower end of the breather inlet tube 55' may be provided with an outwardly and downwardly flaring flange 12. The construction and operation may beotherwise as described in connection with Fig. 'l.

I claim: v

- l. A centrifugal separating apparatus comprising a casing of circular cross-section, centrif ugal impeller means within said casing adjacent one end thereof, means for rotating said im-- peller means, outlet opening means for coarse material in open communication with the'inte rior of said casing adjacent the other end of said casing and adjacent the periphery thereof,

means for supplying to the interior of the casing adjacent the axis thereof gaseous medium together with material to be separated, and tuthe axis of the casing and the zone of maximum pressure at the periphery of the casing, and flnesoutlet means communicating with said fines-receiving'space.

2. A centrifugal separating apparatus as set forth in claim 1, and also comprising a coarse material-receiving chamber communicating with said coarse material outlet means, said chamber being substantially closed against outflow of gas so as to substantially prevent passage of gaseous medium through said coarse material outlet opening means. t

3. A centrifugal separating apparatus as set forth. in claim 1, and also comprising a coarse material-receiving chamber communicating with said coarse material outlet opening means, said chamber being substantially closed against outflow of gas so as to substantially prevent passage of gaseous medium through said coarse material outlet opening means, and means for adjusting the size of said coarse material outlet opening means so as to regulate the discharge of coarse material from the interior of said casing into said receiving chamber.

4. A construction as set forth in claim 1, in which the tubular deflector means is provided at one end with a flaring frusto-conlcal portion extending outwardly nearly to the periphery of the cylindrical casing and nearly to the end wall of said casing adjacent said coarse material outlet means.

5. Centrifugal separating apparatus comprising a substantially cylindrical casing, centrifugal impeller means located near one end of said casinsfltubular means within said chamber coaxially with the centrifugal impeller means, deflector means extending within the cylindrical casing and around said tubular means and forming a fines-outlet chamber between said tubular means and said deflector means, a fines-outlet communicating with said fines-outlet chamber, and coarse material outlet opening means in open communication with the interior of said casing at the periphery of said casing and at the end thereof remotefrom the centrifugal impeller.

6. A construction as set forth in claim 5, in which the outlet from the fines-outlet chamber extends tangentially from said chamber.

7. A construction as set forth in claim 5, in which the fines-outlet chamber. communicates with the interior of the casing at a position disposed longitudinally intermediate the centrifugal impeller and the coarse material outlet opening means. i 1

8. A construction as set forth in claim 5, said tubular member being open at one end toward said centrifugal impeller means and open at the other end toward said end of the casing remote from said impeller means, so as to provide for recirculation of gas within said casing-through said tubular means.

9. A construction as set forth in claim 5, said tubular means being-open at one end toward said centrifugal impeller means and extending at its other end through said end of the casing remote MARCEL A. LISSMAN.

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