US3831764A

US3831764A - Pusher-type centrifuge

Info

Publication number: US3831764A
Authority: US
Inventors: D Humphrey
Original assignee: Pennwalt Corp
Current assignee: Alfa Laval AB
Priority date: 1973-06-05
Filing date: 1973-06-05
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: JPS5021369A; JPS5713344B2

Abstract

Annular structure is provided outwardly of the accelerator vanes in the annular feed passageway of a pusher centrifuge. The annular structure recombines into an annular stream the subdivided feed streams flowing outwardly of the accelerator vanes, thereby reducing abrasive wear on the screen of the inner rotor.

Description

United States Patent [191 Hum hre Au 27 1974 P g y PUSHER-TYPE CENTRIFUGE Primary Examiner-Roy Lake hr [75] Inventor Eg Edson Hump ey Ldnsdale Assistant Exammer-DeWalden W. Jones Attorney, Agent, or FirmEdward A. Sager, Esq. [73] Assignee: Pennwalt Corporation, Philadelphia,

[22] Filed: June 5, 1973 [57] ABSTRACT Appl. No.: 367,274

US. Cl. 210/376, 137/804 Int. Cl. B0ld 33/02 Field of Search 210/376, 374; 137/804,

References Cited UNITED STATES PATENTS 6/1964 Gooch 210/376 Annular structure is provided outwardly of the accelerator vanes in the annular feed passageway of a pusher centrifuge. The annular structure recombines vinto an annular stream the subdivided feed streams flowing outwardly of the accelerator vanes, thereby reducing abrasive wear on the screen of the inner rotor.

10 Claims, 3 Drawing Figures PATENTEB 2 71974 SIEHIUFZ PUSHER-TYPE CENTRIFUGE This invention relates to centrifuge apparatus of the pusher type for separating solids and liquid from a mix- .ture thereof. Such centrifuge apparatus comprises a BACKGROUND OF THE INVENTION An example of pusher-type centrifuges to which the present invention is applied is shown and described in US. Pat. No. 3,136,722, which issued June 9, I964 to Fred P. Gooch. Such centrifuges are provided with an annular passageway of frusto-conical configuration for conducting feed outwardly of the rotational axis of the inner rotor toward the small end of a tapered portion of the inner rotor. Accelerator vanes in the passageway rotate with the inner rotor to impart angular acceleration to the feed as it moves outward.

The feed flows toward the accelerator vanes as an annular stream and it is subdivided into a number of radially outwardly directed streams by the accelerator vanes. In a conventional pusher centrifuge having a conical screen for drainage, the subdivided streams jet against the screen surface of the inner rotor. Since such streams contain solids, usually crystals, the same spaced portions of the rotor screen are always abraded by the feed streams. As a result, the screen of the conventional inner rotor wears away rapidly and must be replaced frequently.

The present invention is directed to an improvement which delivers the feed to the inner rotor as a more uniformly distributed, recombined annular stream which is less abrasive to the screen of the inner rotor. Longer screen life is thereby achieved.

BRIEF SUMMARY OF THE INVENTION According to the invention an annular structure is provided outwardly of the accelerator vanes in the annular feed passageway. It is the function of the annular structure to intercept the subdivided streams of feed as they jet radially outwardly of the vanes and to recombine the subdivided streams as an annular feed stream, after which they overflow the annular structure and are evenly distributed against the screen of the inner rotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view, partly in vertical section, of apparatus embodying the invention;

FIG. 2 is an enlarged sectional view of a portion of the apparatus shown in FIG. I; and

FIG. 3 is a horizontal sectional view of the apparatus,

taken on line 3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION In the drawings, there is shown in FIG. 1 an apparatus embodying the invention and generally designated 10. The apparatus includes a base 12 adapted to be secured to a floor. The base 12 carries a pair of spaced brackets 14 to which a shaft housing 16 is mounted. Within the shaft housing 16 are a pair of aligned ball bearing units 18, the center races of which are affixed to a tubular outer rotor drive shaft 20. On the right hand end of shaft 20, as shown, is mounted adriving pulley 22 which is driven through suitable belts 24 by a motor M. I

Connected to the left hand end of the tubular outer shaft is an outer rotor 26. The connection is made to the smaller end of a frusto-conical tapered section 28 of the outer rotor 26.The taperedsection 28 has a plurality of large drain openings 30 formed therein. The larger end of the frusto-conical portion 28 mounts a basket or perforated cylinder 32 comprising the main portion of the outer rotor 26. Formed in the basket 32 are a plurality of evenly spaced radial holes 34 communicating with a plurality of annular grooves 36 on the inner surface thereof. A screen 38 (not visible in the drawings) is secured on the inner face of the cylinder 32 Mounted for coaxial rotation with the tubular shaft 20 is the drive shaft 40 of the inner rotor 42. The

shafts

20 and 40 are connected for rotation together, preferably by frictionalengagement but optionally by a suitable key (not shown). The inner rotor 42 comprises a frusto-conical hub 44 and a tapered portion 46.

The hub is carried on the left hand end of inner shaft 40 and is secured, thereto by an axially tapered nut 48. The hub 44 inclines to the right, or tapers axially to the left, as shown, and mounts the tapered portion 46 by its smaller end. Although the tapered portion 46 is imperforate from intermediate (approximately midway), the ends thereof and the small end thereof, the remainder or imperforate section 49 of the tapered portion 46 is provided with radial drain holes 50 communicating with annular grooves 52 on its inner surface. A screen 53 of frusto-conical shape is secured to the inner rotor 42 on its inner surface for the length of the perforate portion of the tapered portion 46..

At the right hand end of the inner drive shaft 40 is a double-acting piston 54 which reciprocates the inner rotor 42 relative to the outer rotor 26 in axial direction, as shown by the arrows 56. The piston 54 reciprocates within a cylinder 58 under fluid driving pressure. Any suitable means for controlling and delivering driving fluid to the cylinder 58, for example, that disclosed in US. Pat. application of A. G. Doak and L. Shapiro, Ser. No. 248,876, filed May I, 1972, which is incorporated herein by reference. The cited Doak et al. application is assigned to the assignee of the present application.

Surrounding the outer rotor 26 and anchored to the frame 12 is a cover 60. Extending inwardly from the cover 60 are a plurality of annular partitions 62 compartmenting the zone inwardly of the cover into the desired number of drain zones, each provided with a drain outlet 64. Further provided is a solids discharge outlet 66 and a liquid discharge outlet 68.

From the top of the cover 60 an. L-shaped feed tube 70 extends downwardly and then axially, terminating in a reduced portion further provided with an outlet having an outwardly flared distal end flange 72. The flange 72 and the nut 48 are in spaced relationship, defining between them an outwardly and axially directed annular orifice 74 for the discharge of feed to an annular passageway 76.

As used herein, the term acceleration shall mean tangential acceleration unless otherwise indicated.

Feed flowing outwardly through passageway 76 is accelerated by annularly spaced, axially extending accelerator vanes 78. Such acceleration helps to bring the feed up to the speed of the

rotors

26 and 42 before it contacts the small end of the tapered portion 46. As the feed is advanced along the screen 53, liquid drains through the openings thereof, thence through the holes 50 and the openings and out the liquid discharge outlet 68.

Partly deliquified solids then advance to the cylinder 32 and are advanced to the open end thereof by the action of the pusher surface 80 of the reciprocating inner rotor 42. As the solids advance, they are rinsed by a plurality of washing heads 82 which are supported on a pipe 84 extending through an end wall 86 of the cover 60. Each head 82 is arranged to direct rinse liquid toward the cylinder 32 over its associated drain zone. The rapidly rotating and advancing solids shed the rinse liquid and are further deliquified by centrifugal action. The solids exit the outer rotor 26 by the open end of the cylinder 32 and discharge through the outlet 66.

An annular seal 88 is disposed between the shaft housing 16 and the outer drive shaft 20 in order to keep process material out of the bearings 18. Baffle surface 90 also helps to distribute feed; and baffle 92 is provided to level the solids advancing along the screen surfaces as desired.

The invention will now be described in greater detail with reference especially to FIGS. 2 and 3.

In accordance with the invention an annular structure or ring 94, radially spaced from the vanes 78, is installed in the passageway 76. Preferably it is formed integrally with the feed distribution shell 96. The latter is spaced from the hub 44 to define the frusto-conical passageway 76 and is connected by bolts 98 to the inner rotor 42 for rotation therewith. The inwardly facing surface 100 of the ring 94 is smoothly finished, that is. it has no bumps, objects or other flow-impeding surfaces thereon. The surface of the shell 96 facing the passageway 76 is also smoothly finished outwardly of the vanes 78. Feed accelerated by the vanes 78 is directed radially outwardly toward the inclined surface of the feed distribution shell 96. The feed at this point is subdivided into a plurality of streams by the vanes 78. However, with the present invention the feed streams collect on the surface 100 of the ring 94 and there recombine into an annular stream. Next the feed stream overflows the lip of the ring 94 in radial direction toward the imperforate section 49 of the tapered portion 46 of the inner rotor 42. Such imperforate section 49 is also smoothly finished to function like the ring 94 to provide second stage reconbining of the feed into an annular stream. In like manner the hub surface 102 outwardly of the vanes 78 and facing the passageway 76 is smoothly finished.

Since most of the imperforate section 49 of the tapered portion shown in H6. 2 is generally parallel to the rotational axis (as is the surface 100) the stepped surfaces designated 104 and 106 in FIG. 2 defining the overflow lip of this section are also smoothly finished.

As shown, the ring 94 and the imperforate section 49 of the tapered portion 46 are in axially overlapping relationship to ensure that feed will overflow the ring 94 into the section 49. It is also preferred that the ring 94 project axially in the general direction of angular inclination of the passageway 76 to ensure that feed streams will be collected and recombined as an annular stream, that is, a stream of annular cross section. The outwardly facing surface of the ring 94 is in mutually facing and radially spaced relationship with the surface of the section 49 to provide an annular passage leading from the passageway 76 to the screen 53.

Thus, where a screen 53 would previously be subjected to concentrated abrasive action by the solids contained in annularly spaced .feed streams, and where a screen would wear out rapidly under such action, an annular stream now has the abrasive solids therein more evenly distributed throughout the annulus. As a result of the present invention screen wear is greatly reduced and screen life is appreciably extended.

The smooth surfaces previously descirbed tend to recombine the feed subdivided by the vanes into a single annular stream so that it has substantially uniform thickness throughout by the time it strikes the screen 53.

The improved distribution of feed reduces unbalance conditions which have been noted in conventional apparatus, expecially when more than 20 percent of the solids are -l00 mesh particle size or smaller.

One of the most important advantages resulting from improved feed distribution is the improved drainage ability by full use of the screen surface, with attendant increase in feed handling capacity.

I claim:

1. In a pusher centrifuge having inner and outer rotors arranged on a common axis for rotation at the same speed, with means for reciprocating said inner rotor relative to said outer rotor in axial direction; said outer rotor including a perforated cylinder open at one end and a perforated, tapered section connected to the other end of said cyliner, said tapered section tapering in a first axial direction away from the open end of said cylinder; said inner rotor comprising a hub at the end of said centrifuge opposite the open end of said cylinder, a tapered portion of perforate construction disposed within the tapered section of said inner rotor, said tapered portion tapering in said first axial direction and being connected at its small end to said hub, means for delivering feed for centrifugation into the interior of said inner rotor to a zone adjacent the center of said hub, an annular passageway entending outwardly from said zone to the small end of the tapered portion of said inner rotor, and a plurality of annularly spaced and axially extending vanes in said passageway for accelerating feed flowing therethrough; that improvement comprising annular structure carried on said inner rotor outwardly of said accelerator vanes and extending in axial direction into said passageway in the flow path of feed, said annular structure having at least one annular surface, whereby feed flowing through said passageway and subdivided into several streams by said accelerator vanes is reformed as an annular stream by said annular structure before flowing from the small end to the large end of the tapered portion of said inner rotor, thereby reducing wear on said tapered portion.

2. A pusher centrifuge according to claim 1 wherein said annular structure extends in said first axial direction.

3. A pusher centrifuge according to claim 1 wherein said annular surface of said annular structure is smoothly finished. I

4. A pusher centrifuge according to claim 1 wherein the end portion of said tapered portion is disposed outwardly of said annular structure at the outer end said passageway, said end portion of said tapered portion being smoothly finished and imperforate to provide a second annular surface facing said axis for reforming said feed as an annular stream.

5. A pusher centrifuge according to claim 4 wherein said annular structure and said end portion of the tapered portion are in axially overlapping relationship.

6. A pusher centrifuge according to claim 1 wherein said passageway is frusto-conical.

7. A pusher centrifuge according to claim 6 wherein said passageway tapers in a direction opposite to said first axial direction.

8. A pusher centrifuge according to claim 1 wherein the means for delivering feed to said zone is a pipe extending through the open end of said cylinder, further including a shaft in driving relation to said hub, and a conical element on the end of said shaft for deflecting feed from said zone into said passageway.

9. A pusher centrifuge according to claim 1 wherein said annular structure is radially spaced from said accelerator vanes.

10. A pusher centrifuge according to claim 1 wherein said tapered portion includes a frustro-conical screen on the inner surface thereof extending from its large end to adjacent its small end, and said annular structure has an outwardly facing annular surface in mutually facing and spaced relationship with the small end of said tapered portion to define between them an annular passage extending from the outer end of said passageway toward said screen.

Claims

3. A pusher centrifuge according to claim 1 wherein said annular surface of said annular structure is smoothly finished.