US3368747A

US3368747A - Centrifuge

Info

Publication number: US3368747A
Application number: US585995A
Authority: US
Inventors: Andre C Lavanchy; Karl G Reed; Haresh M Desai
Original assignee: Pennsalt Chemical Corp
Current assignee: Pennwalt Corp
Priority date: 1965-10-20
Filing date: 1966-09-02
Publication date: 1968-02-13
Anticipated expiration: 1985-02-13
Also published as: DE1293089B; GB1144183A; FR1497103A

Description

Feb. 1968 A. c. LAVANCHY ETAL' 3,

CENTRIFUGE 2 Sheets-Sheet 1 Filed Sept. 2, 1966 INVENTORS ANDRE C. LAVANCHY KARL G. REED HARESH M. DESAI YQQZW/QAQM ATTORNEY Feb. 13, 1968 A. c, LAVANCHY ETAL v 3,368,747

CENTRIFUGE 2 Sheets-Sheet 2 Filed Sept. 2, 1966 INVENTORS 7 ANDRE c. LAVANCHY KARL G. REED HARESH M}, DESAI United States Patent 3,368,747 CENTRIFUGE Andre C. Lavanchy, Devon, Karl G. Reed, Wayne, and

Haresh M. Desai, Bryn Mawr, Pa., assignors to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania Continuation-impart of application Ser. No. 4%,296, Oct. 20, 1965. This application Sept. 2, 1966, Ser. No. 585,995

Claims. (Cl. 233-7) ABSTRACT OF THE DISCLOSURE In a continuous solids discharge centrifuge having a screw conveyor, feed nozzles are provided which extend out into the pond and direct the feed towards the solids discharge end of the centrifuge bowl.

This application is a continuation-in-part of application Ser. No. 498,296, filed Oct. 20, 1965, and now abandoned.

This invention relates to centrifuge feed means. More specifically this invention relates to means for delivering centrifuge feed out into the centrifugebowl in a way which minimizes the disturbance of solids already settled in the bowl. It has particular reference to continuously operating solids-discharge centrifuges.

It is old in the art to provide a solidbowl centrifuge with an axial screw conveyor adapted to move solids toward one end of the bowl for discharge. Such a centrifuge is shown in the Reed Patent 3,148,145. Conventionally in such centrifuges the feed has been delivered through anaxial feed tube to a-feed-receiving pocket inside the centrifuge conveyor. From the pocket feed has passed outwardly into the bowl through a plurality of nozzles in the conveyor. Such nozzles normally have taken the form of a straight tubular element mounted in the centrifuge conveyor and extending in a radial direction. Usually the feed nozzles have stopped short of the pond; that is, inward of the liquid level within the centrifuge bowl. In some instances, however, the feed nozzles have extended out into the pond in an effort-to reduce the turbulence created at the vapor-liquid interface by the incoming feed material.

- Under the present invention its is possible to improve the capacity of such a centrifuge while producing an efliuent of the same clarity. This is accomplished by extending thefeed nozzles out into the pondand providing their distal ends with deflecting surfaces and openings directing the incoming feed toward the solids discharge end of the bowl. Experimentation has indicated that a centrifuge equipped with nozzles embodying our invention can achieve 1.4 to 1.5 the capacity of the conventionally equipped centrifugewith the same clarity. This is a truly remarkable and unexpected performance.

Other objects of the invention will be understandable with reference to the following specification including drawings in which:

FIGURE 1 is an elevational view of a centrifuge having part of the bowl broken away to show the conveyor inside. The outline of the centrifuge is shown in phantom;

FIGURE 2 is an enlarged fragmentary sectional view on the line 2 2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary sectional view taken on the line 33 of FIGURE 2;

FIGURE 4 is a fragmentary sectional view of a modified form of feed nozzle embodying the invention;

FIGURE 5 is a fragmentary sectional view taken on the line 5-5 of FIGURE 4; 7

FIGURE 6 is a fragmentary sectional view of a further modification of a nozzle embodying the invention; and

FIGURE 7 is a sectional view taken on line 77 of FIGURE 6.

Briefly; in a continuous solids discharge centrifuge having a screw conveyor the invention is the provision of feed nozzles which extend out into the pond and 'direct the feed toward the solids discharge end of the centrifuge bowl.

, Referring more specifically to the drawings, a centrifuge embodying the invention is generally designated 10 in FIGURE 1. It comprises a frame F mounting a bowl 12 having a liquid discharge port 14 at one end and a solids discharge port 16 at the other end. The bowl is provided with shafts and mounted for rotation to be driven by pulley P.

Within the bowl is disposed an axial screw conveyor 18 which is journaled in bearings in the end of the bowl and adapted to be rotated at a speed different from that of the bowl by gear box G to achieve a scrolling action of the solids towards the solids discharge port 16. Speed differential may be regulated by backdrive pulley B. An axially disposed feed tube 20.extends inward through a bowl shaft and terminates inside of the conveyor (FIG. 3). Mounted transversely within the body of the conveyor 18 is a diffusion target plate 22 at which the feed is projected as it issues from the feed tube 20. The target 2211 secured to the plate directs the feed outwardly and the feed thereby forms a shallow pool within the cup 24 which is also secured to the target plate 22. Openings 26 are provided in the cup and aligned openings 28 in the body of the conveyor. Feed distributing nozzles 30 extend through these openings from outside the conveyor. The conveyor is provided with an apertured boss 32 around each opening 28 in the conveyor. The nozzles are each formed with an annular rib 34 which is received in the opening in the boss. A clamping plate 36 secured the nozzle by its rib 34 in the boss. Suitable sealing means may be provided.

At its distal end the nozzle is provided with a flat baffle 38 which deflects the feed in a rightward direction as shown in FIGURE 3. In that direction an opening 40 is formed in the tubular nozzle body. In other words the feed nozzle opening 40 and the baflie 38 direct the feed toward the rear surface of the next adjacent conveyor flight 18a. More generally the opening 40 and the baflie 38 direct the incoming feed in the direction of the end of the centrifuge bowl havingthe solids discharge port 16. This is the preferred direction. However, some of the benefits of the invention may be achieved by directing the opening in the nozzle and the baffle in a direction opposite the direction of rotation. Preferably the baflie as shown in FIGURE 3 is angled (angle a) in the range from 45 to 15 from the horizontal.

The opening 40 on the tubular feed nozzle is disposed completely outward beyondthe outermost level of the liquid discharge port 14. This provides for the submerged introduction of feed into the centrifuge pond and minimizes the disturbance caused by the introduction. However, the baflie is disposed radially inward of the distal edge of the screw flights 18a.

Actual tests using a conveyor equipped with feed nozzles as disclosed in FIGURE 1 and operating on dispersed clay indicated a 1.4 to 1.55 improvement in the capacity of a conventional machine having feed nozzles as shown in the aforementioned patent for the same clarity of discharge eflluent through the port 14.

As shown in FIGURES 4 and 5 a modified form of the invention may comprise a more open type feed nozzle arrangement. In this arrangement the conveyor body 18' having the flights 18a is provided with the target plate 22'. The wall of the conveyor body 18' is provided with an opening which is enlarged as at 52 to provide a circumferential surface 54. In this version the feed tube takes the form of a scoop-shaped nozzle 56 having an enlarged flange 58 which abuts against a shoulder on body 18' and is provided with suitable sealing means 56a in sealing engagement with the surface 54. Bolt means 60 holds the nozzle on the body. The inside surface of the scoop-shaped nozzle may be coated with an abrasive resistance surfacing. In a preferred form the surfacing may be a tungsten carbide insert sintered in suitable shape then epoxied into the nozzle opening.

The level of the pond may be at P for instance or P. When the level is at P the bulk of the feed entering through the opening of the nozzle 56 is introduced to the pond beneath the surface thereof. When the level of the pond is set at P the feed is introduced at the surface level. In either case the feed is directed toward the solids discharge end of the centrifuge toward the rear face of the flight 18a to the right of the nozzle as shown in FIGURE 4.

Within the conveyor accelerator ribs or vanes 64 promote radial acceleration of the feed.

In an actual field test in the plant of a corn processor two identical screw centrifuges were set up side by side. In one of the machines the four feed nozzles were conventional as shown in the US. Patent 3,148,145. In the other the nozzles were directional of the type shown in FIGURES 4 and 5, the openings of the nozzles being directed toward the solids discharge end of the centrifuge. To both machines was led a feed of distillers slops, or stillage, for dewatering. The fine fiber insoluble solids were present in the feed to a degree indicated in the table below and the feed rate for each machine ranged between 25 to 40 gallons per minute. A series of readings were taken, readings on both machines for each of a number of feed input rates. In the table below the electrical load on the machine fairly represents the feed rate since both machines had identical no load readings. The results provide a direct comparison between operation with the conventional nozzles and the directional nozzles.

Insoluble solids in discharges, percent wJw. Insoluble Amperage From the above table it can be seen that there was a marked reduction in the solids content of the efiluent. The solids content of the effluent of the machine having the conventional nozzles varied in the range from roughly 4 to 16 times the solid content of the effluent of the directional nozzle machine for the same feed.

With the same set-up, the two machines being in sideby-side comparison, a series of readings were then taken on a feed comprising a slurry of fine fibers from wet corn milling. The feed was in the range of 25 to 50 gallons per minute. The results may be tabulated:

Insoluble solids in discharges, percent w.lw.

Insoluble Amperage Data not available.

From the above it can be seen generally that in using directional nozzles the liquid efliuent contained in each case is roughly a tenth of the insoluble solids of the screw centrifuge having conventional nozzles.

Other direct comparisons were made of the same type machine, one having conventional nozzles and the other directional nozzles of the type shown in FIGURES 4 and 5. For instance, the soft flocky non-packing solids in underflow from a settling basin containing activated domestic sewage were centrifugally dewatered in the two machines. With the directional nozzle machine as shown in FIGURES 4 and 5 a reasonable settling in the bowl could be achieved employing an economical level of polyelectrolyte coagulant. Using the screw machine with the conventional feed nozzles, on the other hand, the amount of polyelectrolyte necessary to effect a reasonable separation was economically prohibitive. The advantage of the directional nozzlesis abundantly clear.

A modified feed nozzle is shown in FIGURES 6 and 7. The conveyor body 18" formed with the flight 18a is provided with an opening 70 communicating with the feed supply on the inside of the conveyor. The opening is reinforced with a collar 72 to which is secured by bolt means 74 a clamping ring 76. The clamping ring is undercut as shown to hold tightly the flange 78 of the nozzle proper 80. The opening through the nozzle 80 terminates upwardly as shown in FIGURES 6 and 7 in a fiat mouth 82 directed toward the solids discharge end of the centrifuge. The mouth is connected to the body of the nozzle 80 by a transition element 84.

In the preparation of this application the following art was considered: US. 3,148,145, 2,600,372, 775,320, and 750,668.

The present invention may be embodied in other specific forms without departing from the spirit or central attributes thereof and, accordingly, reference should be made to the appended claims rather than the foregoing specification as indicating the scope of the invention.

We claim:

1. In a centrifuge comprising a hollow bowl having a solids discharge port at one end and a liquid discharge port at the other end and outward from the solids discharge port, a conveyor having screw flights and mounted on the axis of the bowl for moving solids toward the solids discharge port, means for rotating the bowl and the conveyor at different speeds, and feed means including a feed pipe extending axially into the conveyor, the conveyor having a feed receiving pocket and at least one feed nozzle extending outward from the conveyor into the bowl, the distal end of the feed nozzle having an opening facing toward the solids discharge port and adapted to direct feed mixture in that direction and toward the rear surface of the adjacent screw flight, there being clear space between the latter and said opening.

2. A centrifuge as described in claim 1 wherein the feed nozzle extends to a point located at a greater radius than the liquid discharge port and having an opening to deliver feed to the bowl at a level radially outward from the liquid discharge port.

3. A centrifuge as described in claim 2 wherein the distal end of the feed nozzle is disposed inward of the distal edges of the screw flights.

4. A centrifuge as described in claim 1 wherein the inside of the nozzle is coated with a hard surfacing material.

5. A centrifuge as described in claim 1 wherein the feed nozzle has an enlarged portion of its base which abuts against an outwardly facing shoulder about an opening in the conveyor and a clamping plate holds the portion inward against the shoulder.

References Cited UNITED STATES PATENTS Van Kirk 2337 Milliken et a1. 2337 Millard 233-47 Lyons 2337 Fitzsimmons 23347 Reed 2337 Moore 51-11 HENRY T. KLINKSIEK, Primary Examiner.