Self-cleaning Centrifugal Separator

Abstract

Fluid controlled pulsations of one or several elastic and or pliable annular membrane linings in a centrifugal separator, preferably of the "Decanter"-type, to transport precipitated sludge and solids to ejection openings.

Description

BACKGROUND OF THE INVENTION

The present invention relates to new fluid controlled annular membrane linings to be used in particular but not exclusively in connection with a centrifugal separator with conical bowl and usually supported in a horizontal position where the precipitated sludge of a fluid-sludge mixture is conveyed to the narrow end of the bowl to one or several ejection openings, while the fluid phase leaves the bowl via the wide end. It is known in the art to employ centrifugal separators with a bowl of a generally conical shape and incorporating a conveyor screw in a coaxial position. Bowl and screw rotate at different speeds, and thus the peripheral windings of the screw scrape most of the sludge along the inner surface of the bowl towards one or several ejection openings at the narrow end of the bowl. This construction suffers from several serious drawbacks such as:

1. the conveyor screw is a very expensive part to fabricate;

2. the peripheral edge of the conveyor screw is worn away relatively quickly resulting in expensive work stoppage and repairs;

3. the difference in speeds of bowl and conveyor screw respectively demands expensive and damage prone differential gears or equivalent mechanical means;

4. because of the necessary gap between the wall of the bowl and the periphery of the conveyor screw not all the sludge is moved but a thin compressed layer of solids is always left behind prone to bacterial contamination and unwanted chemical processes;

5. the conveyor screw stirs up already settled sludge and smashes advantageous coagulations; and

6. this kind of machine works at a very high noise level.

SUMMARY OF THE INVENTION

The object of the present invention is to eliminate conveyor screw and differential gears, and to substitute instead one or several membrane linings of a suitably resilient and or pliable material capable to generate pulsating movements in a predetermined direction and able to propel precipitated sludge and solids in a predetermined direction.

Another object of the invention is to provide a centrifugal bowl furnished with adjacent open annular grooves which in connection with the annular membrane linings or lining form annular pockets for sludge and solids when deflated, and profilated chambers with slanting outer surfaces when inflated by a control fluid respectively.

A further object of the invention is to provide an advantageous hydraulic system incorporated in the bowl and or the membrane lining to generate predetermined pulsation sequences.

These and other novel features and advantages of the present invention will be described and defined in the following specification and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagrammatic vertical sectional view of a centrifugal separator furnished with a membrane lining of the present invention, shown only in the upper half of the bowl in connection with suitably shaped adjacent open annular grooves of the present invention, the latter being shown without membrane lining in the lower half of the bowl;

FIG. 2 is an enlarged diagrammatic detail in vertical sectional view of the bowl with membrane lining illustrating by way of example a way of securing the lining to the bowl;

FIG. 3 is a diagrammatical sectional view of a special type of lining attached to a bowl without said annular grooves; and

FIG. 4 is a diagrammatical sectional view of another embodiment according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring more specifically to the drawing in FIG. 1 is shown a centrifugal separator bowl 1 with end sections 2 and 3 which are furnished with hollow shafts 4 and 5 respectively, said bowl and shafts 1, 2, 3 rotating in connection with suitable bearings, supports and driving means not shown in the drawing.

The inner surface of bowl 1 is furnished with adjacent open annular grooves 6 each being covered by an annular membrane lining 7. All linings will preferably be integrated into one single membrane lining 8 as indicated in the drawing made of a suitably pliable and or elastic material. In the drawing, the individual membrane linings 7 are shown alternatingly in a deflated and in an inflated condition, thus either forming a kind of annular pocket together with grooves 6 or forming inflated chambers under the influence of a control fluid injected through channels 9 belonging to control fluid conduits 10 or 11 which are connected to annular fluid chambers 12 and 13 respectively which in turn are supplied through stationary pipes 14 and 15 respectively inserted through hollow shaft 4. Fluid conduits 10 and 11 are also furnished with evacuation valves 16 and 17 respectively. The sludge-fluid mixture to be separated enters the bowl 1 through a stationary pipe 18 projecting through hollow shaft 5. Pipes 14, 15 and 18 need no expensive means of tightening such as packings. The clean phase leaves the bowl 1 through openings 19 while the sludge is ejected through openings 20. When under the influence of the control fluid linings 7 will be inflated to form outer surfaces 21 which slant downwardly in the direction of ejection openings 20.

FIG. 2 exemplifies means of securing membrane linings 7 or lining 8 to the bowl 1. At every top of grooves 6 a further narrow groove is provided to house a suitably formed part or lip of linings 7 or 8 respectively under the pressure of an expandable ring 22 of steel or other suitably resilient and strong material. Rings 22 may have advantageous slanting outer surfaces.

FIG. 3 illustrates the employment of an outer lining 23 preferably of the same material as the membrane linings 7 or 8 respectively, these parts being bonded together by way of example by welding along seams 24. The outer lining 23 needs only to be fastened at its ends near end sections 2 and 3. Thus, the inside of bowl 1 needs no expensive machining.

Returning to FIG. 1, bowl 1 is shown to include an alternative fluid conduit 25 which is in direct connection with the first channel 9 and from there through a short length of conduit 11 to chamber 13. A bowl of this type has neither chamber 12, conduit 10 with its channels 9 and valve 16 nor the rest of conduit 11. Pipe 14 is not needed. Conduits 25 may be holes interconnecting grooves 6 or open channels milled through the tops of the grooves.

OPERATION

Regardless of whether the embodiment of the invention is as shown in FIG. 1 or FIG. 3, the centrifugal separator may work as follows:

When bowl 1 rotates at full speed control fluid is injected through both fluid systems at the same time. Thus, all linings 7 will be inflated and will act as accelerators on the sludge-fluid mixture fed through pipe 18 provided the supply of control fluid exceeds the constant losses through valves 16 and 17. At a certain moment, the supply of control fluid is stopped for example through pipe 14 as shown in FIG. 1 causing the fluid in conduit 10 and its channels 9 to leave through valve 16. As a result, the particular membrane linings 7 subside into their grooves 6 forming annular pockets to receive sludge sliding down from slanting surfaces 21 in addition to the sludge already deposited therein. After a suitable interval, this procedure is reversed, the fluid supply through pipe 15 is stopped, the fluid pressure falls through valve 17 and pipe 14 is opened. In this manner, the sludge deposited in the subsided membrane lining pockets will be lifted up by the expanding membrane 7 and transferred into the annular pocket next to it. In this manner, all sludge will be propelled through the length of the bowl 1 towards openings 20.

In FIG. 4, the bowl 1 incorporates only control fluid conduit 26 with one channel 25 and part of conduit 10 with chamber 12 and supply pipe 15, the transportation of the sludge will be obtained by intermittent opening and closing of pipe 15. As pipe 15 is opened, the control fluid will run through said conduits into the first groove 6. Conduits 26 must be dimensioned in such a manner that the first membrane lining is expanded entirely before the adjacent membrane lining changes considerably from its pocket shape inside groove 6. In this manner, membrane linings 7 will expand one after the other like a wave rolling through the length of bowl 1 propelling all the deposited sludge before it towards openings 20.

When the control fluid supply is closed, the hydrostatic pressure inside the fluid conduits will be evacuated through valve 17, and all the members linings 7 will subside into the grooves 6. This procedure can be repeated at predetermined intervals. The scope of the present invention is not necessarily limited to parallel annular grooves 6. Especially in connection with said wave-principle propulsion, it is possible to use one single groove spiralling through the length of the bowl beginning in connection with channel 9 and ending blindly near openings 20. This feature applies also to the embodiment shown in FIG. 3. The scope of the present invention also embraces the employment of a membrane lining which is inflatable in a rolling wave fashion without any grooves either in the wall of the bowl or integrated in outer lining 23. In that case, the lining will have suitably elastic and or pliable parts either parallel and adjacent to each other or in the shape of a spiral acting as a rolling wave by expanding progressively under the influence of the progressively advancing control fluid as described above.

While the preferred embodiments of the present invention have been shown and described herein, it is obvious that many structural details may be changed without departing from the spirit and scope of the appended claims .

Claims

What is claimed is:

1. A centrifugal separator comprising a conical bowl having an inner surface presenting a wide end and a narrow end opposite thereto, means for delivering a fluid-sledge mixture into said bowl, in which the bowl is provided with discharge opening means at said wide end for discharging fluid phase of said mixture and discharge means at said narrow end for discharging a precipitated sludge of said fluid-sludge mixture while the fluid phase leaves the bowl via the wide end, a plurality of ring-shaped elastic membrane sections covering said inner wall of the bowl, means engaging opposite ends of said sections in fluid tight relation to said inner surface for allowing said sections to be inwardly flexed therebetween, the bowl being provided with an opening below each membrane section, and means connected with said openings for the supply and the withdrawal of a pressure fluid to flex and release said sections and including means for controlling the supply and withdrawal of the pressure fluid such that when supplying pressure fluid the membrane section are flexed away from the wall of the bowl in a predetermined sequence which progresses from the wide toward the narrow end of the bowl thereby to effect discharge of said sludge while the mixture is still being delivered to the bowl and the fluid phase is being discharged, said membrane sections being detailed in design so that at least a part of the surface of each ring-shaped membrane section when flexed is slanted toward said narrow end of the bowl where the precipitated sludge is ejected.

2. Centrifugal separator according to claim 1 in which the inner surface of the bowl is provided with adjacent open annular grooves, said membrane sections being in fluid tight connection with the rims of the grooves, the membrane sections following the shape of the grooves when the membrane is not pressurized.

3. Centrifugal separator according to claim 1 in which the ring-shaped sections are divided in two or more groups, each group being connected with a common supply for pressure fluid, such that the groups can be pressurized at will.

4. Centrifugal separator according to claim 1 characterized in that only the membrane section lying at the end remote from the end where the precipitated sludge is ejected is directly connected with the supply for pressurized fluid, each section communicating with the adjacent section through a duct with a flow restriction.

5. Centrifugal separator according to claim 1 in which the several membrane sections are combined to one single membrane extending through the whole length of the bowl of the separator.

6. Centrifugal separator according to claim 5 in which the membrane between the ring-shaped sections is connected with the wall of the bowl.

7. Centrifugal separator according to claim 5 in which the membrane between the ring-shaped membrane sections has a portion which is less elastic than the material of the membrane sections themselves.

8. Centrifugal separator according to claim 5 in which the separator consists of ring-shaped segments which are combined to centrifugal units of predetermined length.

9. A centrifugal separator comprising, in combination:

a horizontally elongate drum and means for supporting said drum for rotation about its longitudinal axis, said drum having an interior surface defining a chamber which decreases in diameter from one end of the drum to the opposite end thereof;

fluid outlet means at said one end of the drum;

solids outlet means at said opposite end of the drum;

means for introducing a fluid-solids mixture into said chamber;

membrane means on said interior surface of the drum; and

means for periodically deforming said membrane means to work centrifugally separated solids toward said opposite end of the drum.

10. The centrifugal separator as defined in claim 9 wherein said means for periodically deforming said membrane means comprises a pressure fluid-conveying system communicating with the interface between said interior surface and said membrane means, and means for periodically conveying pressure fluid to such interface.

11. The centrifugal separator as defined in claim 10 wherein said pressure fluid-conveying system includes means for conveying pressure fluid to different longitudinal sections of said drum in time-delayed relation from said one end of the drum to said opposite end thereof.

12. The centrifugal separator as defined in claim 10 wherein the interior surface of said drum is formed as a series of frusto-conical sections.

13. The centrifugal separator as defined in claim 12 wherein said pressure fluid-conveying system communicates with interfaces at alternate ones of said frusto-conical sections.

14. The centrifugal separator as defined in claim 10 wherein said pressure fluid conveying system includes inlet means, discharge means having a restricted opeining, and means for introducing pressure fluid through said inlet means alternately at rates exceeding and less than the rate at which pressure fluid escapes through said restricted opening.

15. The centrifugal separator as defined in claim 9 including anchoring means spaced longitudinally of said drum for anchoring said membrane means to the interior surface of said drum, said interior surface of the drum and those portions of the membrane means between said anchoring means being detailed in design to allow said solids to be worked toward and discharged from said opposite end of the drum without affecting the normal centrifugal separating action of the separator.

16. The centrifugal separator as defined in claim 15 wherein said means for periodically deforming said membrane means comprises a pressure fluid-conveying system communicating with the interfaces between said portions of the membrane means between said anchoring means and said interior surface of the drum.

17. The centrifugal separator as defined in claim 16 wherein said pressure fluid-conveying system includes means for conveying pressure fluid to different longitudinal sections of said drum in time-delayed relation from said one end of the drum to said opposite end thereof.

18. The centrifugal separator as defined in claim 16 wherein said pressure fluid-conveying system includes means for conveying pressure fluid to different longitudinal sections of said drum in time-delayed relation from said one end of the drum to said opposite end thereof.

19. The centrifugal separator as defined in claim 15 wherein the interior surface of said drum is formed as a series of frusto-conical sections.

20. The centrifugal separator as defined in claim 15 wherein each of said portions of the membrane means is of annular form and of V-shaped cross section.

21. The centrifugal separator as defined in claim 9 wherein said membrane means comprises a plurality of annular sections each of generally V-shaped cross section, and including anchoring means attaching the opposite edges of each such annular section to the interior surface of said drum.

22. The centrifugal separator as defined in claim 21 wherein said means for periodically deforming said membrane means comprises a pressure fluid-conveying system communicating with the interfaces between said portions of the membrane means between said anchoring means and said interior surface of the drum.

23. The centrifugal separator as defined in claim 22 wherein said pressure fluid-conveying system includes means for conveying pressure fluid to different longitudinal sections of said drum in time-delayed relation from said one end of the drum to said opposite end thereof.

24. The centrifugal separator as defined in claim 21 wherein said interior surface of the drum is formed as a series of frusto-conical sections mating with said V-shaped annular sections of the membrane means.

25. A centrifugal separator as defined in claim 9 wherein said means for introducing said fluid-solids mixture continuously maintains a body of fluid in said chamber which terminates short of said opposite end thereof whereby separation of said solids from said fluid phase and discharge of said fluid phase occur continuously and discharge of said solids occurs during such continuous separation and such continuous discharge of fluid phase.