US3658182A

US3658182A - Sludge centrifuge

Info

Publication number: US3658182A
Application number: US129697A
Authority: US
Inventors: Jorgen Steen Bye-Jorgensen; Gunnar Hartvig Larsen
Original assignee: Krueger As I
Current assignee: Kruger AS
Priority date: 1971-03-31
Filing date: 1971-03-31
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25

Abstract

This invention relates to a sludge centrifuge of the type comprising a rotating drum and a conveyor worm to remove solids separated from the liquid in a drum. An improved purity of the liquid separated in the centrifuge is obtained by reducing the turbulence in the centrifuge, specifically in the separation chamber, and this is achieved by providing the centrifuge with a feed worm, by which the sludge is transported at gradually decreasing axial velocity and gradually increasing rotational velocity to the separation chamber.

Description

United States Patent Bye-Jorgensen et al.

[ 1 Apr. 25, 1972 SLUDGE CENTRIFUGE Jorgen Steen Bye-Jorgensen, Humlebaek; Gunnar l-lartvlg Larsen, Rungsted Kyst, both of Denmark I Kruger A/S, Copenhagen, Denmark Mar. 31, 1971 Inventors:

Assignee:

Filed:

Appl. No.:

Related U.S. Application Data Continuation-impart of Ser. No. 865,926, Oct. 13, 1969, abandoned.

Foreign Application Priority Data Nov. 29, 1968 Denmark ..5840

U.S. Cl ..2l0/374, 210/377 Int. Cl ..B04b 3/04 Field of Search ..2l0/374, 377; 233/7 [56] References Cited UNITED STATES PATENTS 834,043 10/1906 Berrigan ..23 3/7 I 1,806,241 5/1931 Dupuis ..233/7 3,437,209 4/1969 Evans ..2l0/374 F ORElGN PATENTS OR APPLlCATlONS 297,914 l0/l928 Great Britain ..23 3/7 Primary Examiner.lim L. De Cesare Attorney-Arnold Robinson [57] ABSTRACT This invention relates to a sludge centrifuge of the type comprising a rotating drum and a conveyor worm to remove solids separated from the liquid in a drum. An improved purity of the liquid separated in the centrifuge is obtained by reducing the turbulence in the centrifuge, specifically in the separation chamber, and this is achieved by providing the centrifuge with a feed worm, by which the sludge is transported at gradually decreasing axial velocity and gradually increasing rotational velocity to the separation chamber.

7 Claims, 1 Drawing Figure SLUDGE CENTRIFUGE This application is a continuation-in-part of copending application Ser. No. 865,926, filed Oct. 13, 1969, and now abandoned.

The present invention relates to a sludge centrifuge comprising a rotating drum containing a separating chamber for liquid and solids and a worm placed outside said chamber, for removing solids and arranged to rotate at a speed differing from the rotating speed of the drum itself, and having at least one feed conduit for sludge and at least one exit opening for liquid in one end of the chamber.

Many sludge centrifuges are known in which a worm conveyor is placed inside the centrifuge drum and rotates relative to the rotating drum. This worm conveyor may be conical and placed in a conical part of the drum so that the separated solids in more or less moist condition are discharged at the narrow end.

In a known drum centrifuge with rotating worm, the sludge containing liquid is introduced in the drum chamber at a point between its ends, the separated solids being discharged at one end and the centrifuged (and thereby partly purified) liquid being discharged at the other end. Liquid and solids are thus moving in mutual countercurrent, and this is found to give rise to so high a turbulence that the degree of liquid/solid separation is usually unsatisfactory because part of the solids return to the liquid. It is observed that such centrifuges are used, for instance, in the purification of wastewater sludge. For this purpose, it is more important that the discharged water is virtually free of sludge particles than that the solids are well drained of water, although it is desirable that the discharged solids be as well dewatered as possible. By using the drum centrifuge operating according to the above counter-current principle for separating sludge stemming from sewage or wastewater treatment plants, the centrifuged liquid may still contain about -40 percent of solids, partly in so finely dispersed form that a removal of said solids in a subsequent precipitation or centrifugation step will not yield a liquid of the desired degree of freedom from solids.

Realizing that turbulence causes such unsatisfactory results, it has been proposed to alter the described construction of the worm in such a manner that the feed conduit for the sludge debouches in part of the drum without any conveyor worm and provided with conical guiding surfaces and furthermore in such a manner that an exit for purified liquid opens from the same drum part, this drum part being constructed as one single chamber without substantial-turbulence-creating hindrances for the axial and radial movements of the solids or the liquid; hereby the sludge will slide along the conical guiding surfaces to the inlet end of the conveyor worm. A better separation effect is achieved by this type of centrifuge than by the above-mentioned counter-current centrifuge.

It has now been found, however, that it is possible to obtain the result that the liquid, especially the water from wastewater sludge, is discharged from the centrifuge in a still more purified condition that it is possible by means of the constructions described above. This can be obtained if, according to the invention, the inlet for the sludge is situation at the opposite end of the separation chamber through openings in a feed worm placed coaxially with respect to the centrifuge drum and running in a chamber outside the separation chamber. It has been found that by this construction it is possible to achieve an extraordinarily high purity of the liquid discharged, with as little as 0.02 percent solids, if the feed liquid is wastewater sludge, in which case the conventional centrifuges often give contents of solids in the discharged liquid of 0.5-1 percent. Moreover, it has been found that the centrifuge construction thus suggested can give this improved result with a centrifugal effect in the order of 5001,000 g, whereas conventional centrifuges usually operate at 2,000-3,000 g. This clearly results in significant savings in the construction of the centrifuge.

The drum may be arranged in various ways, and the conveyor worm and the feed worm may also be mounted in various manners. 1f the drum is substantially conical with an outlet for solids at the narrow end, the most simple construction is obtained if, according to the invention, the feed worm is arranged for working in contact with a surface fixedly connected to the conveyor worm, and for rotating at a speed differing from that of the conveyor wonn. Thus, the number of rotating parts is kept as low as possible. In this embodiment, the feed worm may be arranged so as to rotate at the same rotation speed as the drum itself. In this way, the mounting and driving of the various parts, especially the feed screw, become as simple and sturdy as possible.

In the following the centrifuge according to the invention will be described more in detail with reference to the drawing, showing a preferred embodiment thereof. A conical drum 11 is placed on a suitable support 14 by the aid of shafts, bearings 12 and rods 13. The drum 11 is mounted on a hollow shaft 15, which, in a suitable manner, e.g., by means of a pulley 16, is mounted to be driven at a desired speed of rotation n,. The power source, which may be of known or conventional type, is not shown. On a body 17, which is not necessarily solid, is mounted a conveyor worm 18 which includes convolutions 19. The body 17 and thus the conveyor won'n 18 is fixedly connected to a shaft 20, which, for instance by the aid of a pulley 21 and a driving motor (not shown), is arranged to rotate at a speed of rotation n differing from the speed of n of drum 11. The relative rotation between the drum 11 and the conveyor worm l8 scraping the drum wall should be such that the solids deposited in the centrifuge are carried towards an exit opening 22 for solids and from there are discharged through a channel 23 in the direction shown by an arrow. The

pulleys

16 and 21 might be replaced by a gear mechanism driven from one motor and giving the desired difference in revolution speed of the two shafts l5 and 20.

Sludge is conducted to the drum from a conduit 24 through a channel 25 in the shaft 20. The channel 25 debouches in openings 26 into a chamber 51 in which is placed a feed worm 53. In the embodiment shown, the openings 26 lead through a fixed coupling 27, the shaft 20 at this place being divided into two parts mutually fixedly connected by the aid of the coupling 27, but the shaft 20 may also be continuous. Moreover, there is in the shown embodiment a channel 28 at the left end of the shaft 20 (the orientation of the figure); it is in connection with a conduit 29 and debouches in the drum space with openings 30. Through conduit 29, channel 28 and openings 30 there may, if desired, be fed chemicals for treatment of the feed sludge in order to facilitate the separation. The inlets may also be interchanged, so that sludge-containing liquid is fed through conduit 29 and a solution or a suspension and chemicals through the conduit 24. Chemicals may also be added in any other known manner.

The feed wonn 53 is mounted on a body 34 which is not necessary solid and which is fixedly connected to the shaft 15, to which shaft the drum 11 too is fixedly connected. During the operation of the centrifuge, the body 34 consequently rotates at the speed n, of the drum ll. Feed worm 53, being mounted on the body 34, also rotates at the speed n,. When sludge is fed through the conduit 24, the channel 25 and the openings 26, it can only continue through the chamber 51 by passing the feed worm 53. As shown in the drawing, the feed worm 53 has an outer diameter which increases as the feed wonn 53 extends along the length of body 34 from feed chamber 51 to separation chamber 31. The sludge which is transported by feed worm 53 in an axial direction from feed chamber 51 to separation chamber 31 undergoes a gradual decrease in axial velocity due to increased cross-section while simultaneously being subjected to increasing tangential velocity as a consequency of the gradually varied velocities. Turbulence within wonn 53 is greatly reduced, and therefore the sludge enters the separation chamber 31 in a state of insignificant turbulence. The lack of turbulence in the separation chamber 31 is maintained due to the absence of any moving members in that chamber, thereby enabling the settling out even of fine solid particlesv Feed worm 53 scrapes against the inside 33 of the body'17, that is in practice against the inside of the conveyor worm 18, which rotates at the speed n (slightly different from speed n,) and has transport direction from left to right (in the orientation of the drawing). Through openings 55 the feed worm delivers the sludge conveyed by it into the separation chamber 31 at the right end of the drum (in the orientation of the drawing). In the embodiment shown, the chamber 31 is in one end limited by the feed work 53 and the body 34, at the other end by the end wall of the drum. in this end wall there are openings 36 for discharging separated liquid. From the chamber 31 there is also entrance to the intake end 39 of the conveyor worm 18, through which intake end the separated solids pass. Thus, the liquid leaves the drum through openings 36, the size and exact placing of which may be adjustable, e.g., by aid of an opening having variable size. The place of the openings 36 determines the liquid surface in the centrifuge, suggested by the two broken lines 37.

The presence of the feed worm 53 causes a quiet, turbulence-free flow to the separation chamber 31 and causes the liquid to depart from that chamber through openings 36 in an extremely pure condition.

The entire machine may be encased in a housing and the liquid from the openings 36 may depart through a channel 38 in the direction shown by an arrow.

If desired, the embodiment shown may be altered so that the body 34 and thereby the feed worm 53 rotates at a rotation speed differing from both that of drum l1 and that of the conveyor worm 18, but that gives a somewhat more complicated suspension and requires a third shaft coaxial to the other two

shafts

15 and 20.

The advantages of the present invention, as well as certain changes and modifications of the disclosed embodiment thereof, will be readily apparent to those skilled in the art. It is the applicants intention to cover all those changes and modifications which could be made to the embodiment of the invention herein chosen for the purpose of the disclosure without departing from the spirit and scope of the invention.

What is claimed is:

l. A centrifuge for separating water from wastewater sludge and comprising:

l. rotatably mounted drum means with a horizontal shaft and having an imperforate side wall and an end wall;

2. conveyor worm means rotatably and c'oaxially mounted within said drum means;

3. feed worm means rotatably and coaxially mounted within said conveyor worm means;

4. a feed chamber within said conveyor worm means;

5. a separation chamber formed between said end wall of said drum means and said conveyor worm means and said feed worm means, said separation chamber being free of turbulence-creating obstructions and having at least one outlet formed in said end wall for the removal of liquid therefrom, said conveyor wonn means being operative to remove dewatered sludge from said separation chamber by rotating relative to said drum means;

6. conduit means operative to introduce said sludge into said feed chamber, from which said mixture is transported into said separation chamber at decreasing axial velocity and increasing tangential velocity by said feed worm means; and

7. support means for mounting said drum means, conveyor means, and feed worm means,

2. The centrifuge according to claim 1 wherein said drum means is generally conical in shape, and said horizontal shaft is hollow.

3. The centrifuge according to claim 2 wherein said conveyor worm means is generally cortical in shape, and further includes a second hollow shaft to enable said conveyor worm means to be rotatably driven.

4. The centrifuge according to claim 3 wherein said second hollow shaft is coaxially disposed within said first hollow shaft for at least a portion of its length.

5. The centrifuge according to claim 3 wherein said conveyor worm means has a hollow larger end. said feed worm means being mounted within said hollow larger end and being mounted on said first hollow shaft.

6. The centrifuge according to claim 3 wherein said second hollow shaft includes said conduit means.

7. The centrifuge according to claim 1 wherein said feed worm means comprises a feed worm increasing in diameter as it extends from said feed chamber to said separation chamber.

Claims

1. A centrifuge for separating water from wastewater sludge and comprising: 1. rotatably mountEd drum means with a horizontal shaft and having an imperforate side wall and an end wall; 2. conveyor worm means rotatably and coaxially mounted within said drum means; 3. feed worm means rotatably and coaxially mounted within said conveyor worm means; 4. a feed chamber within said conveyor worm means; 5. a separation chamber formed between said end wall of said drum means and said conveyor worm means and said feed worm means, said separation chamber being free of turbulencecreating obstructions and having at least one outlet formed in said end wall for the removal of liquid therefrom, said conveyor worm means being operative to remove dewatered sludge from said separation chamber by rotating relative to said drum means; 6. conduit means operative to introduce said sludge into said feed chamber, from which said mixture is transported into said separation chamber at decreasing axial velocity and increasing tangential velocity by said feed worm means; and 7. support means for mounting said drum means, conveyor means, and feed worm means.

2. conveyor worm means rotatably and coaxially mounted within said drum means;

3. The centrifuge according to claim 2 wherein said conveyor worm means is generally conical in shape, and further includes a second hollow shaft to enable said conveyor worm means to be rotatably driven.

4. a feed chamber within said conveyor worm means;

5. The centrifuge according to claim 3 wherein said conveyor worm means has a hollow larger end, said feed worm means being mounted within said hollow larger end and being mounted on said first hollow shaft.

5. a separation chamber formed between said end wall of said drum means and said conveyor worm means and said feed worm means, said separation chamber being free of turbulence-creating obstructions and having at least one outlet formed in said end wall for the removal of liquid therefrom, said conveyor worm means being operative to remove dewatered sludge from said separation chamber by rotating relative to said drum means;

7. support means for mounting said drum means, conveyor means, and feed worm means.