WO1998014260A1

WO1998014260A1 - Filter

Info

Publication number: WO1998014260A1
Application number: PCT/US1997/017079
Authority: WO
Inventors: Geoffrey Goodman
Original assignee: Davidson, Clifford, M.
Priority date: 1996-10-01
Filing date: 1997-09-30
Publication date: 1998-04-09
Also published as: IL119337A0; IL119337A; AU4591397A

Abstract

The invention provides a filter for separating solids from liquids. The filter includes a housing (1) having an inlet (2) for liquid to be filtered, a first outlet (3) for filtrate, and a second outlet (15) for liquid containing a high concentration of solids. The filter further includes a filter element (5) having an internal side which communicates with inlet (2) and an external side in communication with said first outlet (3). The filter further includes a rotatably mounted volume reduction device (6) located on the interior side of the filter element (5).

Description

FILTER

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a filter and, more particularly to a filter for

high quality separation of solids from liquids, the filter including a rotatable

volume reducing device for inhibiting clogging of the filter, thereby increasing its

efficiency.

Specifically, the present invention relates to filters in which an input liquid

stream containing solids is directed parallel to and along the face of the filter

element, through which it is passed in order to produce a filtrate or separation of

the desired standard. Such filters are characterized in that most of the solids

retained by the filtering process are swept to the far end of the filter, where they

tend to accumulate and settle on the filter screen, thereby causing clogging of the

filter. This may be partially prevented by periodic flushing of these retentions out

through a valve.

In U.S. Patent No. 3,862,035 the current inventor disclosed means for

minimizing accumulation of free or deposited solids in a filter, by continually

removing them, without interrupting liquid flow through the filter. Generally, the

latter invention comprised pressure-reducing means ("bleed") in communication

with the filter body or within the latter, the bleed continuously discharging a small

portion of the liquid flowing through the filter together with solids retained by the energy made available by the pressure reduction is dissipated through friction

within the discharge path or by using it for operating a hydraulic device placed

within or outside of the filter.

Various embodiments of these concepts have been utilized world-wide to

greatly increase the working cycle of filters and improve quality of filtration by

lessening eventual penetration of previously retained solids through the filter

screen. Despite these benefits, clogging could still be caused by random

movement of retained particles, particularly at the far end of the screen, by a

particularly heavy concentration of solids or by sudden spurts of these in the

incoming stream. A countervailing increase in continual discharge through the

bleed is sometimes not economic or practical.

In U.S. Patent No. 4,966,701 and associated U.S. Patent No. 5,076,942,

the current inventor presented a simple and cost-effective answer to the problems

described. These patents disclose a static volume-reduction device shaped and

disposed so as to minimize the volume of unfiltered liquid flowing between the

filtering side of the filter element and the wall of the volume-reduction device.

The volume reduction device is used in conjunction with continual bleeding out of

liquid-entrained retentions through said pressure-reducing means and with period

valve flushing. The effectiveness for cleaning of the screen, by the hydraulic

shock caused by opening of the flushing valve and by the added drag that is

caused by great increase in speed of flow while the valve is open, is considerably improved by the volume-reducing device (VRD). Thus, integration of the means

described in the above-referenced U.S. patents results in superior filtration and

often in working cycles of weeks or even months.

Despite the general effectiveness of the inventions referred to above, the presence of a considerable proportion of organic solids in the liquid to be filtered

often creates special problems. These may be caused by the composition,

shape, pliability or surface qualities (such as stickiness) of biological particles or

substances (such as mucoid exudations), alone or interacting with inorganic

materials present in the liquid. Whatever the construction or shape of its orifices,

rapid clogging of any kind of filter screen can ensue, accompanied by great

difficulties in cleaning it. Historically, these problems were met by means such as

gravity-induced or pressurized deep bed filtration or by batch induced settlement

of solids in relatively simple tank systems.

More recently, filters have been developed for such conditions, using

screens which are cleaned by one or more of several methods including scraping,

suction, brushing and jet-spraying. These usually require quite complex,

relatively expensive hydraulic and electro-mechanical engineering, which in turn

require suitable maintenance and other support. At a time when water supplies

are increasingly scarce, pollution a growing problem and capital and technical

capabilities frequently in short supply, all of these world-wide, relatively simple

solutions are also sought. Thus, various attempts have been made to provide simple and

inexpensive filters which enable efficient filtration and long working cycles even in

the presence of high concentration of organic solids in the liquid to be filtered.

In Patent Application No. 119,182, a method and filters are described in

which turbulence, frequently an undesirable characteristic in hydraulic systems, is

used in a deliberate and relatively controlled manner to prevent clogging and to

assist cleaning of screens both during operation and flushing. For obvious

reasons, the level of turbulence provided will be the minimum needed to achieve

the objectives in given conditions.

Embodying that method, a volume reduction device (VRD) of the kind

described above (detailed in U.S. Patent No. 4,966,701) is textured to provide

variations on its outer surface. Such a textured volume reduction device (TVRD)

may feature structural variations which are separated or continuous, regular or

irregular in shape, size, height, depth and distribution and in any number and

configuration desired. The incoming liquid stream flowing between the filter

screen and the TVRD interacts with the patterned surface of the device. The

resulting turbulence is a function of the latter and of speed of flow - similar to

when water of different speeds flows over an uneven water course. Thus, in one

of many possible embodiments of that invention, the textural variations become

more frequent toward the far end of the TVRD, though not necessarily at a

constant rate. Here, increased turbulence is more of an advantage than a disadvantage even during filtration, when the turbulence assists in keeping the

screen clear. During flushing, the TVRD causes a greatly increased and violent

turbulence, particularly at the far end of the screen where the heaviest deposits

are usually found.

The TVRD, in conjunction with a bleed device and valve flushing provides

an inexpensive and simple means of obtaining better filtration with longer working

cycles even in the presence of a high proportion of organic solids in the liquid to

be filtered. However, this may not be adequate under more difficult conditions,

particularly when long working cycles are a critical specification and when

economic conditions justify a modest further expense.

There is thus a widely recognized need for, and it would be highly

advantageous to have, a method and filter in which filtration and separation of

solids of all kinds from an in-flowing liquid stream, even when present in a high

concentration and adhesive, is made possible for long periods without clogging.

U.S. Patents Nos. 4,966,701 and 5,076,942 provide a static

volume-reducing device which enables a faster, more efficient evacuation of

filter-retained solids from within the filter, whether by way of bleed or periodic

valve flushing or both, to assist cleaning of screens during filtering and flushing.

U.S. Patent No. 3,862,035 teaches that the energy made available by

reduction in pressure of a liquid stream discharged from a filter to the atmosphere can be used to power a liquid-operated mechanical device placed within or

outside the filter housing.

Thus, it would be further advantageous to have a method and filter in

which the volume-reducing device, whether with smooth or textured surface, is

fitted so that it may be rotated by virtue of the energy derived from the constant or

periodic evacuation of liquid from within the filter to atmosphere through a

dynamic pressure-reducing device, as envisaged in U.S. Patent No. 3,862,035,

the teachings of which are incorporated herein by reference, or is rotated

electro-mechanically.

It would be further advantageous to have such a method and filter which

include a rotatable volume-reduction device bearing orifices from which clean

liquid from a high pressure source can be sprayed onto the upstream side of the

filter screen, and/or bearing brushes in contact with the screen during rotation.

It would be further advantageous to have means whereby liquid at high

pressure is used to rotate a volume-reducing device, alone or together with one

or more other sources of power.

SUMMARY OF THE INVENTION

According to the present invention there is provided a filter for efficient and

high-quality separation of solids from liquids over a substantially extended period

of time, comprising:

(a) a housing provided with an inlet for the liquid to be filtered, a first

outlet for filtrate, and a second outlet for liquid containing a high concentration of solids;

(b) a hollow filter element insertable into the housing, the filter element

having an internal side and an external side, the internal side of the filter element

being in fluid connection with the inlet and the external side of the filter element

being in fluid connection with the first outlet;

(c) a rotatabie volume reduction device inserted in the filter element

and being in a size to occupy a major portion of the hollow of the filter element; and

(d) a rotator element for rotating the volume reduction device.

According to further features in preferred embodiments of the invention

described below, the rotator element may include a hydraulic propeller element,

including: a hollow pivot element connected to the volume reduction device and

in fluid connection with the internal side of the filter element; and at least one

hollow wing having at least one aperture for evacuation of liquid therethrough, such that evacuation of liquid from within the filter through the at least one

aperture causes the propeller element to revolve, thereby revolving the volume

reduction device.

Alternatively, the rotator element may include a hydraulic propeller element in fluid connection with an external high-pressure liquid source.

Alternatively, the rotator element may include an external

electro-mechanical supplier connected to the volume reduction device.

A filter of the present invention may preferably be in fluid connection with a

static pressure reduction device as disclosed in U.S. Pat. No. 3,862,085, and with

a discharge valve operated manually or automatically.

According to additional features of the described preferred embodiments,

the volume reduction device may include two closed ducts running its length just

beneath its surface, each placed diametrically opposite to the other, each of the

ducts featuring a plurality of micro-vents so as to allow spraying of fluid at high

pressure over the internal side of the filter element.

Such embodiment may further include a pipe installed centrally through

the pivot of the propeller element, the pipe being in fluid connection with the ducts

and with an external high pressure liquid source.

Further, the volume reduction device may feature two slots along its length

wherein thin brushes are mounted, each placed opposite the other and being free

to move towards and away from the filter element.

According to the present invention there is further provided a method for

inhibiting the clogging of a filter during separation of solids from liquids, including

the step of rotating a volume reduction device mounted within the filter so as to

create deliberate turbulence within the narrow space between the filter screen

and the outer wall of the volume reduction device so as to facilitate cleaning of

the filter screen.

The rotation of the volume reduction device may be accomplished by

evacuation of fluid from within the filter through a hollow hydraulic propeller

connected to the volume reduction device so as to revolve the propeller, thereby

revolving the volume reduction device.

Alternatively, the rotation of the volume reduction device may be

accomplished by using an external electro-mechanical source or an external

high-pressure liquid source. Alternatively, the volume reduction device may be

rotated manually.

According to still further features of the described preferred embodiments,

a method according to the present invention may further include the steps of: (a)

injecting fluid at high pressure through ducts running the length of the volume

reduction device and spraying said fluid over the upstream surface of the filter

screen through micro-vents placed along the ducts; and (b) cleaning the filter screen by means of brushes mounted within slots running the length of the

volume reduction device.

The present invention successfully addresses the shortcomings of the

presently known filter designs by providing a filter and method in which filtration

and separation of solids of all kinds, including adhesive organic materials, from

an in-flowing liquid stream is made possible for long periods without clogging of

the filter, and without the need to interrupt the filtration process.

The present invention discloses a novel filter and method in which a

volume reduction device is rotated by virtue of the energy derived from the

constant or periodic evacuation of liquid from within the filter to atmosphere

through a dynamic pressure-reducing device and/or a discharge valve.

Further, the present invention provides a rotatable volume-reduction

device bearing orifices from which clean liquid from a high pressure source can

be sprayed onto the upstream side of the filter screen, and/or bearing brushes in

contact with the screen during rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference

to the accompanying drawings, wherein: FIG. 1 is a longitudinal cross-section through a filter being one

embodiment of the invention, wherein discharge devices for solids are shown in

schematic form;

FIG. 2 is a longitudinal cross-section through a filter being another

embodiment of the invention, wherein is incorporated a high pressure liquid

spraying means and wherein discharge devices for solids are shown in schematic form;

FIG. 3 is a cross-section (A - A) through the body of the filter shown in

FIG. 2; and

FIG. 4 is a cross-section (B - B) through the body of the filter shown in

FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a filter and method for efficient and high quality

separation of solids from liquids.

Specifically, the present invention enables continuous and efficient

removal of solid particles, including adhesive organic particles, from within the

filter without the need to interrupt the filtration process, thereby allowing long

working cycles without clogging of the filter. ^' The principles and operation of a device according to the present

invention may be better understood with reference to the drawings and the

accompanying description.

Referring now to the drawings, FIG. 1 illustrates a filter according to the

present invention. As shown in the figure, the filter includes a filter housing 1

made in two parts 1a and 1b for convenience of assembly, the parts being of

conventional design. Housing 1 contains an insertable hollow cylindrical filter

element 5 featuring an internal side and an external side and bearing numerous

orifices. Further, housing 1 contains a rotatable volume-reducing device (RVRD)

6 having a near end, a far end, and an outer surface. Preferably, RVRD 6 is of a

substantially cylindrical shape and occupies the major portion of the internal

volume of filter element 5. RVRD 6 may be substantially hollow or solid, and its

outer surface may be smooth or textured. Preferably, filter housing 1 features an

inlet 2, a first outlet 3 for filtrate and second 15 and third 16 outlets for discharge

of retained solids.

The near end of RVRD 6 includes a spindle 7 preferably held by a spider

centering ring 7a within which spindle 7 can rotate, and a hydrodynamically

shaped plug 7b. Spider centering ring 7a is connected to or made as an integral

part of an input connector 8 which defines inlet 2.

According to the embodiment shown in Fig. 1 , the base 9 at the far end of

RVRD 6 is preferably integral with the pivot 30 of a hollow hydraulic propeller 13. Pivot 30 is held by, and can rotate within, that end of filter housing 1, through

which all retained solids are discharged. A passage 17 for fluids and entrained

solids provides a fluid connection between the liquid external to RVRD 6 and

hollow pivot 30. On propeller pivot 30 is mounted a at least one, and preferably

two, hollow wings of hydraulic propeller 13, the wings being set in a housing 11

which is connected to filter housing 1, or alternatively being an integral but

separate part of housing 1. Each of the two propeller wings has one of two

contra-positioned fluid outlets 14. For convenience of assembly, the propeller

housing 11 preferably bears a lid 12 which in turn carries a propeller pivot cap 10

within which the pivot can rotate. Evacuation of solids-containing liquid from the

internal side of the filter through fluid outlets 14 located at the hollow propeller 13

wings causes propeller 13 to revolve, thereby revolving RVRD 6. Preferably,

fluid outlets 14 of propeller 13 are confluent with a valve 15a and a static

pressure-reducing device 15b as described in U.S. Pat. No. 3,862,035., and with

a discharge valve 16. Vaives 15a and 16 may be operated manually or

automatically.

According to another embodiment (not shown), an external

electro-mechanical rotator element may be fitted and connected to RVRD 6 so as

to turn it electro-mechanically.

Alternatively, the volume reduction device may be rotated manually. Another possible embodiment of a filter according to the present invention

is shown in Figs. 2 and 3. Preferably, such embodiment is substantially as

described above except that the RVRD is solid and through its length run at least

one and preferably two diametrically-opposed fluid ducts 19. Ducts 19 bear many

spaced micro-vents 20 for providing fluid connection between ducts 19 and the

annular liquid passage 32 between RVRD 6 and filter element 5. The base 9 at

the far end of RVRD 6 preferably features a distribution well 18 from which liquid

at high pressure is distributed to ducts 19. Preferably, a metal high pressure pipe

22 is placed centrally through hollow propeller pivot 30 and held at one end with a

centering and retaining ring 23 seated in well 18 and at the other end with pivot

cap 10. Thus, pipe 22 rotates together with RVRD 6 whilst supplying high

pressure fluid from an external source (not shown) through an inlet 34 defined by

a pressurized liquid connector 21 to distribution well 18. When RVRD 6 is

connected to the external source and liquid at a high pressure is applied,

micro-vents 20 spray the internal side of filter element 5 helping to clean it, in

conjunction with the additional drag caused by the turbulence created by the

rotation and surface configuration of RVRD 6, and by the increased flow caused

by the opening of flushing valve 16. Preferably, each of ducts 19 features a

different distribution pattern of micro-vents 20 along its longitudinal axis such that

each of ducts 19 is confluent with different sections of passage 32, thereby allowing more efficient spraying of the internal side of filter element 5. The

spraying fluid may be heated and special cleaning materials may be added to it

so as to improve the cleaning of the filter element.

As shown in FIG. 4, such embodiment may include at least one and

preferably two diametrically-opposed filter screen brushes 24 mounted in slots on

RVRD 6, at an angle of 90 degrees or any other angle to micro-vents 20.

Preferably, brushes 24 are free to move towards or away from filter element 5,

and feature bristles of the length suited to be in light but firm contact with the

internal side of the filter element.

The embodiments shown in Figs. 1-4 may further feature fluid connection

between the wings of propeller 13 and an external high pressure liquid source, so

that propeller 13 is motored by said external source.

While using a filter according to the present invention, the fluid to be

processed is fed into inlet 2 of filter housing 1 from where it proceeds along the

narrow annular passage 32 between the outer surface of RVRD 6 and the

internal side of filter element 5. The greater portion of the liquid passes through

the perforations of filter element 5 and then out through first outlet 3 of filter

housing 1. Solid particles too large to pass through filter element 5 will either

accumulate on the inner face thereof or will be carried by that portion of the liquid

which flows towards passage 17 and then to optional static pressure-reducing

device 15b. the perforations of filter element 5 and then out through first outlet 3 of filter

which flows towards passage 17 and then to optional static pressure-reducing

device 15b.

When fluids for processing contain large quantities of solids, the flow caused by the operation of static pressure-reducing device 15b (i.e., bleed flow),

may not be sufficient to prevent gradual clogging of filter element 5. Particularly in

the case of biological retentions, even the combination of the hydraulic shock and

of the drag caused by the flow resulting from operation of valve 16 and of the

additional turbulence provided by configuration of the surface of the volume

reducing device, as described in the concurrent patent application, may not be

adequate to remove the caked solids which bleeding alone did not prevent.

However, while using a filter according to the present invention, continual

or periodic opening of valve 16, manually or automatically, leads to a large

discharge flow through outlets 14 of hydraulic propeller 13, causing it and thereby

RVRD 6 to revolve. Rotation adds much to the cleaning effect of a smooth

surfaced RVRD. Rotation of a textured RVRD is even more effective.

While using the embodiment shown in Figs. 2 and 3, cleaning is greatly

facilitated by high pressure spraying of the internal side of filter element 5 by

liquid forced through micro-vents 20 during rotation of RVRD 6. It will be clear As will be realized, the present invention provides the basis for a solution

to problems not solved by the discharge of liquid-entrained, filter-retained solids

using a pressure-reducing device as described in U.S. Pat. No. 3,862,035 and by

the incorporation of a volume-reduction device in filters as described in U.S. Pats.

No. 4,966,701 and 5,076,942. Furthermore, it will be clear that the current

invention, together with the concurrent application (No. 119, 182) and the above-

referenced patents provide independent or integrated practical and economic

answers to a wide range of problems in liquid filtration and separation, by

providing means for reducing costs associated with regular maintenance,

pressure loss, filter shut-down and investment in backup filtration, particularly in

conditions where biological materials cause clogging and short filtering cycles

between cleanings.

The degree of efficiency afforded by the invention also makes it very

suitable for liquid and/or solid recovery in cost-conscious industrial separations in

continuous processing with critical cut-off specifications.

While the invention has been described with respect to a limited number of

embodiments, it will be appreciated that many variations, modifications and other

applications of the invention may be made.

Claims

WHAT IS CLAIMED IS:

1. A filter for separating solids from liquids, comprising:

(a) a housing provided with: an inlet for the liquid to be filtered; a first

outlet for filtrate; and a second outlet for liquid containing a high

concentration of solids;

(b) a hollow filter element inserted into said housing, the filter element

having an internal side and an external side, said internal side of

said filter element being in fluid communication with said inlet and

said external side of said filter element being in fluid communication

with said first outlet; said internal side of said filter element defining

a chamber.

(c) a rotatable volume reduction device inserted in said filter element

and being of a size so as to occupy a portion of said chamber, said

volume reduction device having an outer surface, said outer

surface of said volume reduction device and said internal side of

said filter element defining a space within said housing; and

(d) a rotator element for rotating said volume reduction device.

2. The filter of claim 1, wherein said rotator element includes a hydraulic

propeller element, the propeller element including: a hollow pivot element connected to said volume reduction device and in fluid communication with said

internal side of said filter element; and at least one hollow wing in fluid

communication with said pivot element, said at least one wing featuring at least

one aperture for evacuation of liquid therethrough,

such that evacuation of liquid from said narrow space within said housing

through said at least one aperture causes the propeller element to revolve,

thereby revolving said volume reduction device.

3. The filter of claim 1 , wherein said rotator element includes an external

electro-mechanical source.

4. The filter of claim 1, wherein said rotator element includes a hydraulic

propeller element and an external high-pressure liquid source, the high-pressure

liquid source being in fluid communication with said propeller element.

5. The filter of claim 1 , wherein said outer surface of said volume reduction

device is smooth.

6. The filter of claim 1 , wherein said outer surface of said volume reduction

device is textured.

7. The filter of claim 1, wherein said volume reduction device is substantially

cylindrical in shape.

8. The filter of claim 1, wherein said volume reduction device is substantially

solid.

9. The filter of claim 1, wherein said volume reduction device is substantially

hollow.

10. The filter of claim 2, wherein said propeller element is placed in a separate

chamber within said housing.

11. The filter of claim 2, wherein said propeller element is placed within a

separate housing.

12. The filter of claim 2, wherein said pivot element is an integral part of said

volume reduction device.

13. The filter of claim 2, wherein said pivot element is detachably connected to

said volume reduction device.

14. The filter of claim 1, wherein said second outlet of said filter is in fluid communication with a static pressure reduction device.

15. The filter of claim 1, wherein said second outlet of said filter is in fluid

communication with a discharge valve.

16. The filter of claim 15, wherein said discharge valve is manually operated.

17. The filter of claim 15, wherein said discharge valve is automatically

operated.

18. The filter of claim 1, wherein said volume reduction device includes at

least one closed duct, said at least one duct featuring a plurality of micro-vents in

fluid communication with said outer surface of said volume reduction device, and

with an external high pressure liquid source.

19. The filter of claim 18, wherein said volume reduction device includes two

closed ducts, each placed diametrically opposite the other.

20. The filter of claim 2, wherein said volume reduction device includes at

fluid communication with said outer surface of said volume reduction device, and wherein said propeller element features a pipe installed centrally through said

pivot element, said pipe being in fluid communication with said at least one duct

and with an external high pressure liquid source.

21. The filter of claim 20, wherein said volume reduction device further

features a distribution well in fluid connection with said pipe and said at least one

duct.

22. The filter of claim 1 , wherein said volume reduction device features at

least one slot along its length wherein at least one brush is mounted, said at least

one brush being free to move towards and away from said filter element.

23. The filter of claim 22, wherein said volume reduction device includes two

slots wherein two thin brushes are mounted, each placed opposite the other.

24. The filter of claim 1 , wherein said volume reduction device is rotated

manually.

25. A method for inhibiting clogging of a filter during separation of a solid and

liquid constituent from a solid-entrained liquid, the method comprising the steps of: (a) inserting the solid-entrained liquid into an inlet of a housing;

(b) flowing the solid-entrained liquid from said inlet into a narrow space

formed in said housing between a filter element and a rotatable volume reduction device; and

(c) rotating the volume reduction device so as to facilitate cleaning of said filter element.

26. The method of claim 25, wherein said rotation of said volume reduction

device is accomplished by evacuation of the solid constituent and the liquid in

which it is entrained from said narrow space in said housing through a hollow

hydraulic propeller element connected to said volume reduction device, thereby

causing the propeller element to revolve, thereby revolving said volume reduction device.

27. The method of claim 25, wherein said rotation of said volume reduction

device is accomplished by using an external electro-mechanical source.

28. The method of claim 25, wherein said rotation of said volume reduction

device is accomplished by using an external high-pressure liquid source.

29. The method of claim 25, further comprising the step of evacuating the solid

constituent and the liquid in which it is entrained from said narrow space in said housing through a static pressure reducing device.

30. The method of claim 25, further comprising the step of evacuating the solid

constituent and the liquid in which it is entrained from said narrow space in said

housing through a discharge valve.

31. The method of claim 25, further comprising the step of injecting fluid at

high pressure through ducts running the length of said volume reduction device

and spraying said fluid over said internal side of said filter element through

micro-vents placed along said ducts.

32. The method of claim 31 , wherein said fluid is heated so as to facilitate

cleaning of said filter element.

33. The method of claim 31 , wherein said fluid contains cleaning materials so

as to facilitate cleaning of said filter element;

34. The method of claim 25, further comprising the step of cleaning said filter

element by means of brushes mounted within slots running the length of said

volume reduction device.

35. The method of claim 34, wherein said brushes are free to move towards

and away from said filter element.

36. The method of claim 25, wherein said volume reduction device is rotated manually.