US3695173A

US3695173A - Sludge dewatering

Info

Publication number: US3695173A
Application number: US221725*A
Authority: US
Inventors: Clyde Harold Cox
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-01-28
Filing date: 1972-01-28
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

Sludge dewatering is achieved with the aid of a flow-impeding, continuous, self-cleaning, non-blinding or clogging and permanent filtering-dewatering device. The device is partly cylindrical and partly conical and comprises closely spaced rings or hoops held rigid by a frame. Inlet pressure created by a low-pressure sludge pump along with the movement of sludge through the filterdewatering unit, where squeezing and pressing takes place, forces most of the liquid or water associated with the sludge through the filtering medium or slots formed by successive closely spaced filter rings, while the solids are trapped on the inside surface before they are conveyed along the length of the filterdewatering unit and are discharged relatively dry from the solids-discharge end by a filter-cake discharger. To prevent clogging and interruption of continuous filtration or dewatering, cutter or slot-cleaning blades or brushes are secured to the outside edge of the filter-cake discharger, projecting out radially and spaced to extend into the slots or spaces between the closely spaced successive filter rings or hoops. The solids tending to clog or blind the slots or spaces pass through and out with the filtrate, or they may be forced back into the filterdewatering unit by the cutting or cleaning action of the cutterslot cleaning blades or brushes, when the leading edge of the filter cake discharger and conveyed sludge cuts and scrapes away the solids protruding within the filter-dewatering unit.

Description

United States Patent Cox [ 51 Oct. 3, 1972 SLUDGE DEWATERING [72] Inventor: Clyde Harold Cox, 35-236 Juniper Lane, Glen Ellyn, 111. 61037 [22] Filed: Jan. 28, 1972 [21] Appl. No.: 221,725

Related US. Application Data [63] Continuation-impart of Ser. No. 887,125, Dec.

22, 1969, abandoned.

[52] US. Cl. ..100/74, 100/98, 100/112, 100/117, 100/128 [51] Int. Cl. ..B30b 9/06 [58] Field of Search ..100/74, 98, 104, 126, 117, 100/127, 145, 128, 112; 210/225, 298, 414

Primary ExaminerBilly J. Wilhite Att0rney-R0bert E. Wickersham [57] ABSTRACT Sludge dewatering is achieved with the aid of a flowimpeding, continuous, self-cleaning, non-blinding or clogging and permanent filtering-dewatering device. The device is partly cylindrical and partly conical and comprises closely spaced rings or hoops held rigid by a frame. Inlet pressure created by a low-pressure sludge pump along with the movement of sludge through the filter-dewatering unit, where squeezing and pressing takes place, forces most of the liquid or water associated with the sludge through the filtering medium or slots formed by successive closely spaced filter rings, while the solids are trapped on the inside surface before they are conveyed alongthe length of the filter-dewatering unit and are discharged relatively dry from the solids-discharge end by a filter-cake discharger. To prevent clogging and interruption of continuous filtration or dewatering, cutter or slotcleaning blades or brushes are secured to the outside edge of the filter-cake discharger, projecting out radially and spaced to extend into the slots or spaces between the closely spaced successive filter rings or hoops. The solids tending to clog or blind the slots or spaces pass through and out with the filtrate, or they may be forced back into the filter-dewatering unit by the cutting or cleaning action of the cutter-slot cleaning blades or brushes, when the leading edge of the filter cake discharger and conveyed sludge cuts and scrapes away the solids protruding within the filter-dewatering unit.

29 Claims, 18 Drawing Figures PATENTEDucr 3 m2 SHEET 1 0f 5 xz k 0222:6200

ww jm PATENTEDucrs I972 SHEET 2 OF 5 FIG] FlG 6 FIG 9 PNENTEDnms 1912 3,695,173

SHEEI 3 OF 5 SLUDGE DEWATERING CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 887,125, filed Dec. 22, [969 (now abandoned).

BACKGROUND OF THE INVENTION This invention relates to sludge dewatering and particularly to an apparatus employing continuous filtration with pressure compression.

Advanced techniques of waste treatment have been able to concentrate a higher fraction of the waste impurities into sludges than formerly was possible, but they have at the same time produced more voluminous sludges. Also, because of the high cost associated with the treatment and disposal of these sludges, more emphasis has been placed on this aspect in the wastewater treatment plant.

I-I eretofore, sludge dewatering has been attempted principally by open-air bed drying, vacuum filtration, centrifugation, and mechanical separation. A brief comment on each of these techniques may be helpful to an understanding of the purpose and achievements of the present invention.

Open-air drying beds require large areas of land and are dependent on climatic conditions. They also can produce odors that are unpleasant, and winds distribute their smells over wide neighboring areas.

Vacuum filtration separates the insoluble solids from the liquid by using differential pressures to force the liquid through a porous medium carried on arotating drum. The differential pressures on the two sides of the medium are created by a vacuum pump, which is connected to the interior of the submerged portion of the drum. The solids are deposited on the outer surface of the filter medium and are subsequently scraped off. The filter medium requires washing by a substantial flow of wash water. These vacuum filters involve large equipment with many moving parts and high operating horsepower, and they are quite expensive, notonly to purchase, but also to operate and to maintain.

Centrifuges require high speeds of revolution, typically ranging from approximately 2,000 rpm to 4,500 rpm. The insoluble solids of the feed slurry or sludge centrifugally settle against the bowl wall, and the liquid flows toward and out a central discharge. The solids are typically pushed out through discharge ports and collected from the bowl. These centrifuges are conplex, and, as a result, they are expensive to purchase and also to operate and to maintain.

Mechanical separation has typically been sought by plate and frame filters, typically comprising an altemating series of empty rings that serve to contain the final filter cake. The plates are covered on both sides with cloth and are provided with drainage channels for removal of the filtrate. The frames are filled with a batch of slurry under pressure, and the filtrate escapes through the cloth and through the plate channels, while the frames are left filled with filter cake. At the end of each cycle, the press is opened and the cake is removed for further treatment or disposal. This is an intermittent or batch type of operation and therefore is associated with he high labor costs resulting from manual operation, so that the plate and frame filters are expensive to operate and very expensive also in first or capital costs.

Other mechanical separation devices have also been proposed, some of them claiming continuous, nonclogging filtration, but all of them have proved to be very complex and expensive to purchase, as well as to operate and to maintain.

BRIEF SUMMARY OF THE INVENTION The present invention provides a continuous, selfcleaning non-blinding or clogging, and permanent filter medium and is a pressure-compression device for sludge dewatering and filtration and is able to concentrate the insoluble solids in thesludge into a relatively dry mass. The apparatus is capable of low initial cost and low operating and maintenance costs, for the device is simple and compact. It can be made to serve large quantities of sludge, or can be adapted to small volumes.

An important feature of this invention is its ability to concentrate the solids into a sufficiently dry mass to enable their burning at an economical figure or their handling for land fill for earth enrichment, and to do so continuously in a filter-dewatering unit comprising a self-cleaning, nonclogging, non-blinding and permanent medium. If the sludge has too much liquid or water, burning is itself an expensive operation, for it involves a preliminary vaporization of much unwanted water.

In this invention a pressure inlet raises the feed pressure of the sludge above atmospheric, and a differential pressure is established between. the inlet flowing into the center of the separating device at a higher-than-atmospheric pressure and the water or filtrate collected from outside the device at atmospheric pressure. The sludge filtration-dewatering unit comprises a flow-impeding device with a filter medium of rings or hoops held rigid by a frame and closely spaced apart from each other, and preferably having'an initial cylindrical portion followed by a conical portion and, also, by a smaller-diameter cylindrical end portion. Inlet pressure forces the liquid or water associated with the sludge or solids through the filter medium or through slots formed by successive .closely spaced filter rings, depositing or trapping the solids on the inside surface of the filter-dewatering unit, and most of the filtration or dewateringis achieved by this differential pressure, with the liquid or filtrate draining largely from the cylindrical portion. However, during the passage through the filter-dewatering unit, the filter-cake discharger cleans and scrapes the inside surface of the filter-dewatering device and conveys the solids from the large-diameter cylindrical section to the smaller conical section with the result that there is further filtration or dewatering along the full length of the unit as well as concentration of the solids as they move along, and the filter cake discharged out through the filtercake discharge end is relatively dry. To prevent filter clogging and interruption of continuous filtration or dewatering, cutter or slot cleaning blades or brushes are secured to the outside edge of the filter cake discharger, projecting out radially and spaced to extend into the slots or spaces between the successive filter rings or hoops. The solids tending to clog or blind the slots or spaces pass through and out with the filtrate or they may be forced back into the filter by the cutting or cleaning action of the cutter blades or brushes when the leading edge of the filter cake discharger and conveyed sludge cuts and scrapes away the solids protruding within the filter-dewatering device.

Thus the invention continuously concentrates the sludge into a relatively dry mass, reduces its volume, makes it easier to handle, and achieves or approaches autogenous conditions for combustion. The apparatus is compact, simple, and inexpensive.

Other objects and advantages of the invention will appear from the following description of some preferred embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a flow diagram, only partly representational, of a sludge-dewatering system embodying the principles of the invention.

FIG. 2 is a longitudinal view in section of a filter-dewatering unit embodying the principles of the invention. It is on an enlarged scale with respect to FIG. 1.

FIG. 3 is an enlarged view in section taken along the line 3-3 in FIG. 2.

FIG. 4 is an enlarged fragmentary view, partly in section, of a portion of the device of FIG. 2.

FIG. 5 is a view similar to FIG. 4 of a modified form of the device.

FIG. 6 is an enlarged fragmentary view, partly in section, of a portion of FIG. 2, showing a cutter-slot cleaning blade.

FIG. 7 is a further enlarged view in perspective of one cutter-slot cleaning blade.

FIG. 8 is a view similar to FIG. 6 of a modified form of device having slot cleaning brushes conforming to the spiral-helix of filter cake discharger.

FIG. 9 is an enlarged fragmentary view, partly in section, of another form of slot cleaning brush bridging successive turns of a spiral-helix blade of the filter cake discharger.

FIG. 10 is an exploded view in perspective of the device of FIG. 2, omitting the drive unit, pillow block,

oil reservior, and distributor.

FIG. 11 is a view in perspective of a scraper having a paddle scraper for use in place of the spiral-helical blade in the cylindrical section.

FIG. 12 is an enlarged view of a filter ring showing an access slot and plug.

FIG. 13 is an enlarged view of a filter ring showing threaded pins and nuts for bolting to the support rods or frame. An access hole and a set screw therefor are also shown. I

FIG. 14 is an exploded view in perspective of a modified form of device like that of FIG. 2, except that the filter-dewatering rings and support frame are hinged to enable easy access into the unit.

FIG. 15 is an enlarged fragmentary view, of FIG. 2, showing a wearable replacable leading edge or wearable strip on the filter-cake discharger.

FIG. 16 is an enlarged view of a filter ring showing a slot-reducing or space-bridging material attached to a recessed surface or interior of the filter ring to reduce or partially close the slot opening.

FIG. 17 is a view in section taken along the line 17 17in FIG. 16.

FIG. 18 is a view similar to FIG. 2 of a modified form of device utilizing a two arm paddle scrapper preceding the filter-dewatering unit in a cylindrical section made up of a series of closely spaced rings to act as a pretreatment unit or preliminary dewatering unit.

DESCRIPTION OF PREFERRED EMBODIMENTS As shown in FIG. 1, a system embodying the principles of the invention may incorporate a variable-speed pump 20 having an inlet 21 for the sludge and an outlet 22 from which the sludge may be passed to a conditioning tank 23. At this tank 23 there may also be suitable chemical treatment. From the conditioning tank 23 the conditioned sludge flows under pressure in a conduit 24 to a filter-dewatering unit 25. The filter-dewatering unit 25 has an initial cylindrical portion 26 followed by a frustoconical portion 27, which in turnis followed by a smaller-diameter cylindrical end portion 28.

Filtrate or water associated with the sludge leaves mainly through slots or spaces 30 in the main cylindrical portion 26 and is collected outside those walls in a space 31 defined by a casing 32. Some filtrate or water also leaves through the frustoconical portion 27 and is likewise collected by the casing 32. The dry solids are carried out by a filter-cake discharge device 33 and deposited on a conveyor 34 which moves them away for disposal.

For initial start-up of the filter-dewatering unit 25, a

' start-up cap 35 is preferably utilized to plug temporarily the normally open end portion 28. The cap 35 is then screwed into position on a threaded sleeve 37 (see FIGS. 2 and 10) which is attached to the filter-cake discharge end 28 of the filtering-dewatering unit 25. After dewatered solids accumulate sufficiently in the

end portions

27 and 28, the cap 35 is removed. Usually, this takes only a few'seconds.

The filtering-dewatering unit 25 (see FIGS. 2 to 10) comprises the housing 32, a filter-dewatering structure or tubular shell 40, and a rotating member 33 which serves as a filter-cake discharging device. The shell 40 preferably comprises an initial cylindrical portion 42, a following frustoconical portion 43, and a terminal cylindrical portion 44. The shell 40 comprises a series of rings or hoops 45 separated and closely spaced from each other and held together as as single unit, as by heli-arc welds 41 or by bolting, to a longitudinally extending frame or a series of support rods 46. The rings or hoops 45 may be of various diameters and set at various spacings. I have found that one-fourth inch wide rings 45 cut from a pipe length for the cylindrical section 42 and one-fourth inch wide rings 45 for the frustoconical portion 43 cut from a formed or rolled hollow cone, held or spaced apart at 0.006 inch spacing 30 can be readily fabricated.

The imperforate outer housing or casing 32 has a liquid or filtrate outlet 47. This housing 32 preferably surrounds the filer-dewatering structure 40, although this is not essential, since the filtrate can be collected in other ways. The housing 32 may, if desired, have an initial cylindrical portion 48, a succeeding frustoconical portion 49 and a terminal cylindrical portion 50.

The filter-dewatering shell 40, which is a closely held series of rings 45, may have its inner portion finished smooth as by grinding, to provide a flat or uniform surface 51.

As shown in FIGS. 5 and 13, bolting of a modified form of filter-dewatering rings 52 to a support frame 53 enables disassemblage. The spacing or slot openings 30 between successive rings 52 may be varied with a change of support rods or frame 53, utilizing the same filter-dewatering rings 52. FIGS. 5 and 13 show threaded filter ring pins with nuts 54 for bolting. Disassemblage also enables replacement or resurfacing of the sides or edges of the filter rings 52 when he spaces or slots 30 formed by successive rings 52 exceed an established permissible spacing.

The filter rings or hoops 52 may have threaded access holes 55, normally plugged or closed by set screws 57, as shown in FIG. 13, or, as shown in FIG. 12, rectangular access slots 56 normally plugged or closed by plugs 58. The access holes 55 or slots 56 can be used to enable access or entry into the. filter-dewatering structure 40 at each filter ring 52.

FIG. 14 shows a modified form of filter-dewatering structure or shell 60 having filter rings 61 and a support frame 62 that are hinged by hinges 63, to provide a method of access into the filter-dewatering shell 60.

As the solids are deposited, the rotating filter-cake The spring steel cutter-slot cleaning blades 70 may also be rotated and locked into cutting or cleaning position on the filter-cake discharger 33. The rotatable cutter-slot cleaning blades 70 when locked in the down or non-cleaning position enable insertion or withdrawal or disassemblage of the filter-cake discharger 33 from the filter-dewatering shell 40 without having to remove each cutter-slot cleaning blade 70 from the filter-cake discharger 33. In some circumstances, no cutter-slot cleaning blades 70 are needed, and the plain filter-cake discharger 33 is sufficient.

In the case of the wire-brush member 71 of FIGS. 8

and 9, the wires or bristles engage the spaces or slots 30 and act otherwise like the spring steel cutter-slot cleaning blades 70.

As shown in FIG. 1 1, a two-arm or a four-arm paddle scraper 80 with cutter-slot cleaning blades 70 may replace the spiral-helical blade 66 in the cylindrical discharger 33 cleans and scrapes them from the inside flat uniform surface 51 of the

rings

45, 52, or 61 and conveys the solids through the filter-dewatering unit and out the discharge end 36. A wearable replacable leading edge or wearable strip 64 (see FIG. 15) may be provided and attached to the filter-cake discharger 33, such as a Teflon or polyvinyl chloride material. The filter-cake discharger 33 may include a central shaft 65 along its axis, on which is mounted a spiral helical blade 66 which is carefully made so that it follows closely the flat inside surface 51 of the filter dewatering shell 40. The shaft 65 is attached to a suitable source of power, such as a variable speed reversing drive unit 67 (FIG. 1). A thrust bearing and pillow block 68 may be utilized for proper operation and alignment, and the other end of the shaft 65 may be supported and locked into position by a spider or a thrust bearing 69.

To prevent blinding or clogging of the closely spaced apart rings 45 52, or 61 or the slots and interruption of continuous filtration or dewatering, cutter or slot cleaning blades 70 may be secured to the outer edge of the filter-cake discharger 33 projecting out radially and spaced to extend into the spaces or'slots 30 between the successive filter rings 45, 52, or 61. See FIGS. 2, 3, 6, and 7. The solids tending to clog or blind the filterdewatering structure pass through and out with the filtrate with the cutting or cleaning action of the cutterslot cleaning blades 70 when the leading edge of the filter-cake discharger 33 and conveyed solids cuts and scrapes away the solids protruding within the filter-dewatering shell 40. The solids tending to clog or blind the filter-dewatering shell 40 may be forced back into the filter-dewatering shell 40 depending upon the angle of the cutter-slot cleaning blades 70, for further dewatering and for capture within the solids cake discharged out the filter-cake discharge end 36. The cutter-slot cleaning blades 70 may be wire or may be a wire-brush member 71 as shown in FIGS. 8 and 9, but preferably spring steel-like material is utilized for the cutter-slot cleaning blades 70, as shown in FIGS. 2, 3, 6, and 7, and is held and attached to the filter-cake discharger 33 by insertion through the filter-dewatering slots or spaces 30 and attached and locked into cutting position by a locking nut 72, with the help of an access hole 55 or an access slot 56 in the filter rings or 52.

portion 42 of the filter-dewatering structure 40.

A two-arm or the four-arm paddle scraper 81 with cutter-slot cleaning blades may be utilized ahead of the filter-dewatering unit 25 in a cylindrical pretreatment section 82, as shown in FIG. 18, made up of a series of rings or hoops 83 separated and closely spaced from each other and held rigid as a single unit preceding the filter-dewatering unit 25, to act as a pre-treatment unit or preliminary dewatering unit.

For greater solids capture within the filter-dewatering unit 25, it may be desirable to reduce the actual slot space 30 formed by the successive filter rings 45, 52, or 61, by utilization of a slot-reducing or space-bridging members 85 shown in FIGS. 16 and 17. These slotreducing members 85 are capable of backward or lateral movement by the cutter-slot cleaning blades 70 enabling the cutter-slot cleaning blades 70 to pass and keep the slots or spaces 30 formed by closedly spaced successive filter rings 45, 52, or 61 clean or unclogged but the bridging or slot-reducing material 85 having the resilience to spring back to bridge or reduce the slot spaces 30 after passage of the cutter-slot cleaning blades 70.

FIGS. 16 and 17 illustrate a filter-dewatering ring 86 fabricated or machined to provide a recessed surface 87 on the interior of the filter ring 86 for attachment of the slot-reducing or space-bridging members 85 but enables a smooth and uniform inside surface, with the members 85 in place for the movement of the filtercake discharger 33 and conveyed solids. The members 85 shown to bridge or partially close the slots or spaces 30 may be stainless steel bristles; however, the disclosures and the description are purely illustrative and are not intended to be in any sense limiting. For example, another material which is utilized for slot bridging or partial closing of the spaces 30 may be rubber or plasticized polyvinyl chloride capable of partially closing or effectively reducing the slot openings 30 but enabling the passage of the cutter-slot cleaning blades 70 for cleaning or unclogging of the slots or spaces 30 but springing back to bridge or reduce the slots or spaces 30 after passage of the cutter-slot cleaning blades 70.

The use of the slot-reducing or space-bridging members or material 85, to bridge or partially close or effectively reduce the spaces 30, enables the utilization of cutter-slot cleaning blades 70 having a greater thickness and therefore stronger and tougher than what normally could be employed with actual small openings or spaces 30, while nevertheless enabling a high percentage or recovery of solids by the effective small slots or spaces 30 or small open areas between successive filter rings 45, 52, 61, or 86, produced by the slotreducing effect of the space-closing members 85.

The spacing between the filter-dewatering shell 40 and the outer housing 32 is not critical; the outer housing 32 may e held in position and by definite spacing away from the filter-dewatering shell 40 and frame or support rods 46, as by short spacer bars 88, or by outside casing supports, which enable quick and unrestricted draw-off of the filtrate. A clear plastic housing or casing 32 can be utilized for visual observation. If visual observation is not desired, the casing 32 may be metal.

The filter-dewatering structure 40 and frame or support rods 46 are firmly attached to a flange or coupling 90, which is in turn attached to the inlet feed pipe 24. A jacket closure ring 92 seals between the outside casing 32 and the flange 90. Another jacket closure ring 93 seals between the outside casing 32 and the short openend solids discharge portion 44.

Most of the dewatering occurs in the cylindrical portion 42 due to the inlet feed pressure, the back pressure being provided by the three filter-dewatering

units portions

42, 43, and 44, and by the plugging action of the sludge before cleaning or unplugging by the action of the filter-cake discharger 33 and the cutter-slot cleaning blades 70. The liquid or filtrate is forced through the filter-dewatering structure 40 mostly in the larger cylindrical portion 42, by the inlet feed pressure, and is collected and drained away by the filter outlet 47 from the outside casing 32 while depositing or trapping the solids on the inside surface of the filter-dewatering shell 40. While the filter-cake discharger 33 scrapes the inside surface 51 of the entire filter-dewatering shell 40 and during the conveying of the solids there and to and through the discharge end portion 44, squeezing and pressing of the solids takes place, so that there is dewatering during the passage of the sludge or solids through the entire filter-dewatering shell 40 and in particular through the frustoconical portion 43, when the solids are conveyed from the larger diameter portion 42 to, the smaller diameter, portion 44. This additional dewatering is very important, for it enables the dewatered solids orfiIter-cake to be discharged out the discharged end 36 in a much drier form than it would be otherwise.

Operating pressures may vary from 1 psig to 100 psig depending upon the open area provided by the slots or spaces 30 between adjacent filter rings 45, 52, 61 or 86 in the filter-dewatering shell 40, the rate of sludge input, the speed and the pitch of the filter-cake discharger 33, the use of cutter-slot cleaning blades 70, the use of slot-reducing or space-bridging material 85, the configuration of the filter-dewatering shell 40 and the nature and consistency of the sludge to be dewatered. l have found, however, that pressures only slightly above atmospheric are required when dewatering normal sewage sludge.

The exact nature an consistency of the sludge to be dewatered will determine the requirement for the cutter-slot cleaning blades 70 or wire brushes 71, or the employment of a slot-reducing material 85 between successive or adjacent filter rings.

When a very dry filter cake results, I have found it advisable to lubricate the last portion of the frustoconical portion 43. As shown in FIGS. 1 and 2, this lubrication may be accomplished by a reservoir 95 for oil or other lubricant, with a conduit 96 leading through the casing 32 to a distributor 97. The distributor 97 may comprise a small arcuate hollow member with a perforate lower surface close to the filter-dewatering shell 40. The lubrication is effective in reducing the load on the drive unit 67 of the solids or filter-cake discharger 33, and does not interfere with burning or combustion of the filter cake, if that be desired. A very dry sludge cake may prohibit the discharge from the filter-dewatering unit 25 even with a lubrication oil. A reversing variable speed drive unit 67 for the filter-cake discharger 33 along with by-pass or return piping may be provided. Provision for water or lubrication fluid to thin the dry sludge cake and otherwise make less viscous may also be provided. As an example of feasible operating conditions and the results obtainable from the sludge dewatering unit 25 of FIG. 2, the following examples are given. An apparatus like that of FIG. 2, with the cutter-slot cleaning blades 70, had a cylindrical portion 42 25 inches long and a frustoconical portion 43 14 inches long. The portion 42 was 6 inches in inside diameter and the portion 44, 2 V4 inches in inside diameter. The cylindrical filter rings 45 were one-fourth inch in width and they were cut from a pipe length having one-eighth inch wall thickness. The conical filter rings 45 were three-sixteenth inch in width and they were formed individually from threesixteenth inch diameter wire, ground smooth inside to one-half as thick as the diameter of the original wire, providing a smooth or flat uniform surface 51 and a series of diverging slots or spaces 30 between adjacent rings 45. The filter rings 45 in both the cylindrical portion 42 and the frustoconical portion 43 were spaced at 0.008 inch. The cutter-slot cleaning blades and access holes 55 with set screws 57 were utilized in the cylindrical portion 42 of the filter-dewatering shell 40. The data as to sizes used in this example form no limitation on the invention, for a very wide range of sizes can be used, depending mainly on the quantity of material to be handled. Two different types of sludge were used and processed under the conditions shown below in Table I with the results there given. All the sludge was preconditioned with ferric chloride and lime. A startup end cap 35 utilized.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

l. A device for dewatering sludge, including in combination:

a filter-dewatering shell having an initial portion comprising a series of longitudinally and closely spaced-apart circular rings that are identical in size, presenting a smooth cylindrical inner surface interrupted only by the space between successive rings,

said filter-dewatering shell having a succeeding portion comprising a series of longitudinally closely spaced-apart circular rings that gradually diminish in size to provide a smooth frustoconical inner surface,

support means aligning and retaining all said rings in place,

filtrate collection means outside said shell for collecting filtrate and spaced therefrom,

a central shaft along the axis of said filter-dewatering shell, 1

wiping and filter-cake discharging means secured to said shaft in both said initial and succeeding portions, and wiping both said cylindrical and said frustoconical inner surfaces, and

power means for rotating said shaft.

2. The device of claim 1 wherein said rings are semicircular in cross section with the arc thereof facing outwardly to provide outwardly flaring spaces between adjacent rings.

3. The device of claim 1 wherein said rings are rectangular in cross-section.

4. The device of claim 1 wherein said rings have access openings enabling access into the filter-dewatering shell, and means normally closing said openings during operation.

5. The device of claim 1 wherein said rings are bolted to said support means, thereby enabling disassemblage, replacement, resurfacing, and variation in ring spacing.

6. The device of claim 1 wherein said rings and said support means comprise a pair of sections hinged together to provide access into the filter-dewatering shell.

7. The device of claim 1 having a wearable replacable edge strip attached to the wiping surface of said wiping and filter-cake discharging means.

8. The device of claim 1 wherein said wiping and filter-cake discharging means has a seriesof projecting cleaning blades attached thereto projecting out radially and spaced to engage the spaces between successive rings, to prevent filter clogging and interruption of continuous filtration or dewatering.

9. The device of claim 8 wherein said rings have access openings therethrough and means for normally closing said access openings, so that 7 said cleaning blades can be inserted through said spaces and attached and locked into cutting position on said wiping and filter-cake discharging means, by means of said access openings.

10. The device of claim 8 wherein said cleaning blades are rotatably attached to said wiping and filtercake discharging means so that they may be locked into their cleaning position after insertion of said wiping and filter-cake discharging means into said shell and may be rotated into a down, non-cleaning position for insertion and removal of said wiping and filter-cake discharging means into said shell.

11. The device of claim 1 wherein there is spacebridging means at each space between adjacent rings, for greater solids capture by reducing or partially closing said space while enabling passage of and operation by the cleaning blades to keep the spaces clear and unclogged, said bridging means having resilience for springing back to bridge or reduce said spaces after passage of the cleaning blades.

12. The device of claim 1 having a wire-brush wiper secured to said wiping and filter-cake discharging means to penetrate into the spaces between successive rings and keep those spaces unplugged.

13. The device of claim 1 wherein said wiping and filter-cake discharge means is a spiral-helical blade. v

14. The device of claim 1 wherein said wiping and filter-cake discharge means is a paddle scraper in the cylindrical section and a spiral-helical blade in the frustoconical section.

15. The device of claim 1 wherein said filter-dewatering shell has a terminal small-diameter cylindrical portion secured to said frustoconical portion, said wiping and filter-cake discharging means having a cylindrical portion for wiping it.

16. The device of claim 15 having a removable plug for closing the end of said shell during start-up, the plug being removed after start-up.

17. The device of claim 15 having lubrication means in the last part of said frustoconical portion of said shell.

18. A device for dewatering sludge, including in combination:

a filter-dewatering shell having an initial portion comprising a series of longitudinally and closely spaced-apart rings that are identical in size and are semicircular in cross section, presenting a smooth cylindrical inner surface interrupted only by the space between successive rings, said space in each instance flaring outwardly due to the circular section of the outer portions of the successive rings,

said filter-dewatering shell having a succeeding portion comprising a series of longitudinally closely spaced-apart rings that gradually diminish in size and are semicircular in cross section to provide a smooth frustoconical inner surface, with similar outwardly flaring spaces,

an outer housing surrounding said shell and spaced therefrom and having a filtrate outlet,

a central shaft along the axis of said filter-dewatering shell,

a spiral-helical blade secured to said shaft in both said initial and succeeding portion, said blade wiping both said cylindrical and said frustoconical inner surfaces, and

power means for rotating said shaft.

19. The device of claim 18 wherein a wire-brush wiper is secured to said spiral-helical blade, bridging successive turns thereof at the outer periphery, to

penetrate into the spaces between successive rings and keep them unplugged.

20. The device of claim 18 wherein a wire-brush wiper is secured to said spiral-helical blade, following the helix of the blade, to penetrate into the spaces between successive rings and keep them unplugged.

21. The device of claim 18 wherein said spiral-helical blade has a series of projecting cleaning blades attached to it and projecting out radially and spaced to engage the spaces between successive rings to prevent filter clogging and interruption of continuous filtration and dewatering.

22. The device of claim 21 wherein the cleaning blades are rotatably attached to said spiral-helical blade, to enable insertion and removal of said spiralhelical blade.

23. The device of claim 21 wherein said rings have access openings and means for normally plugging said openings, said access openings enabling access into the filter-dewatering shell at each ring and wherein the cleaning blades are capable of attachment to the spiralhelical blades by insertion through the spaces between rings and by nuts inserted through the access openings.

24. The device of claim 21 wherein space bridging means is secured within said filter-dewatering shell at each space between adjacent rings for greater solids capture by reducing or partially closing said space, said bridging means being capable of movement by said cleaning blades, so that said cleaning blades keep the spaces clear and unclogged, said bridging means having resilience for springing back to bridge or reduce said spaces after passage of said cleaning blades.

25. The device of claim 18 having a pre-treatment portion ahead of said cylindrical portion having a cylindrical section made up of a series of closely spaced rings and having a paddle scraper wiping them.

26. The device of claim 25 having cleaning blades on the paddle scraper.

27. The device of claim 25 having cleaning brushes on the paddle scraper.

28. The device of claim 18 wherein said filter-dewatering shell, has a terminal small-diameter cylindrical portion secured to said frustoconical portion, and said spiral helical blade wipes this small-diameter cylindrical portion also, and a removable plug for closing the normally open end of said shell during start-up, said plug being removed after start-up.

29. The device of claim 18 having lubrication means in the last part of the frustoconical portion of the filterdewatering shell.

PC3-1050 UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORRECTION Patent No. 3,695,173 Dated October 3, 1972 Inventor(s) Clvde Harold COX It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' C0lumn 1, line 51, "conplex" should read com lax-; line 66,

"he" should read --the--. Column 5, line 32, surface 51" should read surfaces 51-. Column 6, line 37, "closedly" should read --closely--. Column 7, line 3, "or recovery" should read of recover line 9, "may e held" should read may be held--; line 63, 'an" should read --and--. Column 8, Table 1 beginning at line 50, there should be no line space between "Filter Cake" and "Moisture,%" so that the fourth item should read Filter Cake Moisture,% 71 66--;

Table I before "Discharger Speed, rpm" insert --Filter-Cake-- so that the last item should read --Fi1ter-Cake Discharger Speed, rpm 30 30--.

Signed and sealed this 13th. da of March 1973.

(SEAL) Attest:

EDWARD M FLETCHER JP. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

1. A device for dewatering sludge, including in combination: a filter-dewatering shell having an initial portion comprising a series of longitudinally and closely spaced-apart circular rings that are identical in size, presenting a smooth cylindrical inner surface interrupted only by the space between successive rings, said filter-dewatering shell having a succeeding portion comprising a series of longitudinally closely spaced-apart circular rings that gradually diminish in size to provide a smooth frustoconical inner surface, support means aligning and retaining all said rings in place, filtrate collection means outside said shell for collecting filtrate and spaced therefrom, a central shaft along the axis of said filter-dewatering shell, wiping and filter-cake discharging means secured to said shaft in both said initial and succeeding portions, and wiping both said cylindrical and said frustoconical inner surfaces, and power means for rotating said shaft.

3. The device of claim 1 wherein said rings are rectangular in cross-section.

8. The device of claim 1 wherein said wiping and filter-cake discharging means has a series of projecting cleaning blades attached thereto projecting out radially and spaced to engage the spaces between successive rings, to prevent filter clogging and interruption of continuous filtration or dewatering.

9. The device of claim 8 wherein said rings have access openings therethrough and means for normally closing said access openings, so that said cleaning blades can be inserted through said spaces and attached and locked into cutting position on said wiping and filter-cake discharging means, by means of said access openings.

10. The device of claim 8 wherein said cleaning blades are rotatably attached to said wiping and filter-cake dischaRging means so that they may be locked into their cleaning position after insertion of said wiping and filter-cake discharging means into said shell and may be rotated into a down, non-cleaning position for insertion and removal of said wiping and filter-cake discharging means into said shell.

11. The device of claim 1 wherein there is space-bridging means at each space between adjacent rings, for greater solids capture by reducing or partially closing said space while enabling passage of and operation by the cleaning blades to keep the spaces clear and unclogged, said bridging means having resilience for springing back to bridge or reduce said spaces after passage of the cleaning blades.

13. The device of claim 1 wherein said wiping and filter-cake discharge means is a spiral-helical blade.

18. A device for dewatering sludge, including in combination: a filter-dewatering shell having an initial portion comprising a series of longitudinally and closely spaced-apart rings that are identical in size and are semicircular in cross section, presenting a smooth cylindrical inner surface interrupted only by the space between successive rings, said space in each instance flaring outwardly due to the circular section of the outer portions of the successive rings, said filter-dewatering shell having a succeeding portion comprising a series of longitudinally closely spaced-apart rings that gradually diminish in size and are semicircular in cross section to provide a smooth frustoconical inner surface, with similar outwardly flaring spaces, an outer housing surrounding said shell and spaced therefrom and having a filtrate outlet, a central shaft along the axis of said filter-dewatering shell, a spiral-helical blade secured to said shaft in both said initial and succeeding portion, said blade wiping both said cylindrical and said frustoconical inner surfaces, and power means for rotating said shaft.

19. The device of claim 18 wherein a wire-brush wiper is secured to said spiral-helical blade, bridging successive turns thereof at the outer periphery, to penetrate into the spaces between successive rings and keep them unplugged.

22. The device of claim 21 wherein the cleaning blades are rotatably attached to said spiral-helical blade, to enable insertion and removal of said spiral-helical blade.

23. The device of claim 21 wherein said rings have access openings and means for normally plugging said openings, said access openings enabling access into the filter-dewatering shell at each ring and wherein the cleaning blades are capable of attachment to the spiral-helical blades by insertion through the spaces between rings and by nuts inserted through the access openings.

26. The device of claim 25 having cleaning blades on the paddle scraper.

27. The device of claim 25 having cleaning brushes on the paddle scraper.

28. The device of claim 18 wherein said filter-dewatering shell has a terminal small-diameter cylindrical portion secured to said frustoconical portion, and said spiral helical blade wipes this small-diameter cylindrical portion also, and a removable plug for closing the normally open end of said shell during start-up, said plug being removed after start-up.

29. The device of claim 18 having lubrication means in the last part of the frustoconical portion of the filter-dewatering shell.