WO2014089433A1 - Flow channel self-mixing flocculator for a thickener or settling tank - Google Patents

Abstract

A feed mixing system for a thickener or settling tank includes a slurry or solids/liquid feed pipe, a mixing conduit, a feedwell, and one or more flexible webs. At least a distal end portion of the slurry or solids/liquid feed pipe is disposed proximate an upstream end of the mixing conduit. The feedwell is disposed inside the thickener or settling tank, a downstream end of the mixing conduit being attached to a wall of the feedwell so that the mixing conduit communicates with the feedwell. The elongate flexible webs are disposed in the mixing conduit and extend at. least along a substantial portion of the mixing conduit. The flexible webs are provided with openings and flaps to induce an undulating or wiggling motion of the webs in response to fluid flow through the mixing conduit, thereby enhancing the mixing of the incoming slurry, diluent, and flocculent components.

Description

FLOW CHANNEL SELF-MIXING FLOCCULATOR

FOR A THICKENER OR SETTLING TANK

CROSS-REFERENCE OF RELATED APPLICATIONS

This application is an international application which claims the benefit of U.S.

Provisional Patent Application No. 61/734,607 filed on 7 December 2012.

BACKGROUND OF THE INVENTION

This invention relates to thickener/clarifier tanks used to separate liquid and solid components of an influent feed slurry and specifically relates to feedwell apparatus employed in such thickener/clarifiers to enhance the clarification process. More specifically, the invention relates to a feed mixing system that better mixes solids/liquid slurry and delivers it to a feedwell of a thickener or clarifier tank, whether or not the feed slurry has been diluted for optimum flocculation.

Thickener/clarifier tanks are used in a wide variety of industries to separate influent feed slurry comprising a solids- or particulate-containing fluid to produce a "clarified" liquid phase having a lower concentration of solids than the influent feed slurry and an underflow stream having a higher concentration of solids than the influent feed slurry. Thickener/clarifier tanks conventionally comprise a tank having a floor and a continuous wall, which define a volume within which the clarification process takes place. Thickener/clarifier tanks also include an influent feed pipe for delivering influent feed to the tank, an underflow outlet for removing settled solids from the tank and a fluid discharge outlet for directing clarified liquid away from the tank. Thickener/clarifier tanks may also include a rake assembly having rake arms for sweeping along the floor of the tank, and may include an overflow launder or bustle pipe for collecting clarified liquid near the top of the tank.

Thickener/clarifier tanks of the type described operate by introducing an influent feed stream into the volume of the tank where the influent is retained for a period long enough to permit the solids to settle out by gravity from the fluid. The solids that settle to the bottom of the tank produce a sludge bed near the bottom of the tank, which is removed through the underflow outlet. Clarified liquid is formed at or near the top of the thickener/clarifier tank and is directed away from the tank for further processing or disposal. Settling of solids may be enhanced in some applications by the addition of a flocculent or polymer that forms agglomerates that settle more readily. In many applications, an objective of fluid clarification is to enhance the settling process to achieve a high throughput of solids, and thereby enhance solids recovery.

Many thickener/clarifier tanks are constructed with a feedwell, usually centrally located within the tank, into which the influent feed stream is delivered. The feedwell generally serves the purpose of reducing the fluid velocity of the incoming influent feed stream so that the energy in the stream may be dissipated to some degree before entering the tank. Dissipation of energy in the influent feed stream lessens the disruptive effect that the incoming influent feed has on the settling rate of the solids in the tank. In other words, introduction into a thickener/clarifier of an influent feed stream under high fluid velocity tends to cause turbulence in the tank and compromises the settling rate of solids. A feedwell may be structured in a variety of ways, therefore, to create or enhance dissipation of energy in the influent feed. For example, the feedwell and influent feed pipe may be structured to introduce influent feed to the feedwell at two opposing directions and into an annular space, such as is disclosed in U.S. Pat. No. 4,278,541 to Eis, et al.

In many feedwell assemblies, the influent feed pipe is incorporated into a dilution feed system including a mixing conduit with a downstream end connected to the feedwell and an upstream end that receives both a solids/liquid stream or slurry from a feed pipe and a diluting liquid. The feed pipe is provided at its outlet end with a nozzle having a circular outlet opening located towards the upstream end of the mixing conduit. The mixing conduit may take the form of a classical submerged pipe or tube or alternatively an open channel form in which a mixing zone is open to the atmosphere. It has been observed that mixing of the incoming solids slurry with thickener overflow or dilution liquor is less complete or effective in the open channel design. It has been observed further that the dilution liquor stream flows along the wall of the mixing channel, outside of the concentrated solids jet from the feed pipe nozzle, and only partially mixes with the concentrated solids jet. This type of performance is not ideal for a mixing conduit that is mixing flocculent with a diluted slurry prior to entering a gravity thickener.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide an improved mixing conduit system for a feedwell assembly of a thickener/clarifier/settling tank.

A more specific object of the present invention is to provide such a mixing conduit system which enhances mixing of a flocculent solution with an incoming slurry in a feed stream entering a feedwell. Generally, the flow velocity, especially in the feed launder channel, is mostly fairly linear in "streamlines". The mixing device of the present invention transfers linear fluid kinetic energy to fluid velocity vector components perpendicular to the main channel flow direction. These additional flow vectors increase mixing and the rate of collision between flocculating particles.

Another specific object of the present invention is to provide such a mixing conduit system which produces an improved or enhanced mixing of an incoming slurry with a flocculent without the need for the application of power from an external power supply.

A further object of the present invention is to provide components of such a mixing conduit system that may be retrofitted into almost any existing sedimentation apparatus. These and other objects of the present invention will be apparent from the drawings and description herein. Although every object of the invention is believed to be attained by at least one embodiment of the invention, there is not necessarily any one embodiment of the invention that achieves all of the objects of the invention.

SUMMARY OF THE INVENTION

A feed mixing system for a thickener or settling tank comprises, in accordance with the present invention, a slurry or solids feed pipe, a mixing conduit, a feedwell, and at least one elongate flexible web or sheet. At least a distal end portion of the slurry or solids feed pipe is disposed proximate an upstream end of the mixing conduit. The feedwell is disposed inside the thickener or settling tank, a downstream end of the mixing conduit being attached to a wall of the feedwell so that the mixing conduit communicates with the feedwell. The elongate flexible web or sheet is disposed in the mixing conduit and extends at least along a substantial portion of the mixing conduit. The flexible web or sheet is provided with structure(s) to induce an undulating or wiggling motion of the at least one flexible web or sheet in response to fluid flow through the mixing conduit.

It is to be noted that the elongate flexible web or sheet, may be provided, together with fasteners or attachment elements, as part of a kit for retrofitting existing thickeners or settling tanks to enhance flocculent mixing and slurry speed reduction. Such a kit may include a plurality of elongate flexible webs or sheets for installation into the same mixing conduit preferably in spaced relationship relative to each other. The webs or sheets may be identical or may vary in the numbers and types of motion-inducing structures. In addition, the webs or sheets may vary in stiffness or flexibility, either from one web or sheet to another or within the same web or sheet.

Pursuant to another feature of the present invention, the motion-inducing structure of an elongate flexible web or sheet for a mixing conduit includes a plurality of openings provided in the flexible web or sheet. The openings are spaced from one another in a longitudinal direction along a length of the flexible web or sheet. The openings may take various sizes and shapes, but in a preferred embodiment of the invention, the openings are rectangular and of the same size and shape.

Pursuant to a further feature of the present invention, the motion-inducing structure of an elongate flexible web or sheet for a mixing conduit may also include a plurality of flow deflectors attached to the flexible web or sheet. Again, the flow deflectors may be of different sizes and shapes, but in a preferred embodiment the flow deflectors are rectangular flaps. The flow deflectors may be attached to the flexible web or sheet proximate respective ones of the openings.

Pursuant to a further feature of the present invention, at least one of the flow deflectors extends from one major surface of the flexible web or sheet, while at least one other of the flow deflectors or guides extends from an opposing major surface of the flexible web or sheet.

Preferably, as one moves along the length of the flexible web or sheet, every other flow deflector extends from the one major surface of the web or sheet while the remaining flow deflectors extend from the opposing major surface.

It is contemplated that the flow deflectors may be geometrically identical to the respective openings, which is a natural result of a manufacturing process wherein the flow deflectors are each partially cut out of the flexible web or sheet and bent away from a plane thereof along one edge of the respective opening.

In accordance with another feature of the present invention, the flow deflectors are each provided with at least one retention member for holding the respective flow deflector in opposition to forces exerted by fluid flow on the respective flow deflector. The retention member may take the form of one or more flexible tensile members each connected at one end to the respective flow deflector and at an opposite end to the flexible web or sheet. These flexible tensile members may be made of an elastic material that naturally enhances the motion of the web or sheet. The elastic retention members may be each connected to a corner of the respective flow deflector.

Pursuant to an alternative or supplemental feature of the present invention, the retention member may take the form of a hollow rib or tube connected to pressurization source for enabling a stiffening of the hollow rib or tube. The hollow rib or tube is preferably connected to (and optionally along) a backside of the respective flow deflectors. It is contemplated that the pressurization source includes a tubular network fastened to the flexible web or sheet and communicating with the hollow rib or tube.

It is to be noted that a flexible self-undulating web or sheet of a mixing system in accordance with the present invention may in some cases omit the openings and include only a plurality of flow deflectors attached to the flexible web or sheet. Again, while congruent rectangular flaps are preferred, the flow deflectors may be of various sizes and shapes, even on a single web or sheet member. Again, the flow deflectors are disposed on opposite sides of the web or sheet and alternate along the length of the web or sheet. The flow deflectors may be each provided with at least one retention member, e.g., an elastic cord or a pressurizable hollow rib or tube, for holding the respective flow deflector in opposition to forces exerted by fluid flow on the respective flow deflector.

In a preferred embodiment of the invention, the flexible web or sheet is one of a plurality of functionally equivalent flexible webs or sheets disposed in the mixing conduit in spaced and approximate parallel relationship relative to one another. In this case, a kit in accordance with the invention includes the plurality of functionally equivalent flexible webs or sheets. "Functionally equivalent" means that while the different webs or sheets may vary in stiffness, in the shapes, sizes, numbers and distribution of openings (if any), and in the shapes, sizes, numbers, distributions, and retention elements of the flow deflectors, the flexible webs or sheets all function nonetheless to exhibit an undulating or wiggling motion in a slurry stream, thereby enhancing the mixing of flocculent and slowing down the slurry stream.

A feedwell feed mixing system and associated mixing web in accordance with the present invention improves mixing in the mixing conduit. This is of particular benefit in open-channel type mixing conduits where the invention results not only in a more even or uniform distribution of solids across the stream entering the feedwell from the mixing conduit but also serves to enhance the mixing of flocculent with the solids feed stream. In addition, the present invention may prevent a buildup of particles along the lower corners of the mixing conduit.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a vertical sectional view of a thickener/clarifier tank having a center pier supporting a rotating sludge raking structure and a feedwell assembly with a feed dilution and flocculent mixing system in accordance with the present invention.

FIG. 2 is a plan view of the thickener/clarifier tank of FIG. 1, taken on line II- II in FIG. 1.

FIG. 3 is a schematic perspective view of a feedwell assembly with a feed dilution and flocculent mixing system in accordance with the present invention.

FIG. 4 is a schematic vertical cross-sectional view of the feed dilution and flocculent mixing system of FIG. 3.

FIG. 5 is a schematic top plan view of a flexible mixing web or sheet included in the feed dilution and flocculent mixing system of FIGS. 3 and 4.

FIG. 6 is a schematic side elevational view of a set of flexible mixing webs or sheets as shown in FIG. 5 and as included in the feed dilution and flocculent mixing system of FIGS. 3 and 4. FIG. 7 is a schematic top plan view similar to FIG. 5, showing a modification of a flexible mixing web or sheet in accordance with the present invention.

FIG. 8 is a schematic top plan view similar to FIGS. 5 and 7, showing another

modification of a flexible mixing web or sheet in accordance with the present invention.

FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG. 8.

FIG. 10 is a schematic partial side elevational view of an inlet for a pressurization manifold depicted in FIG. 8.

DETAILED DESCRIPTION

As illustrated in FIGS. 1 and 2, a thickener/clarifier comprises a continuously operating thickening tank wherein a sludge raking structure 10 is supported for rotation upon a center pier 11. A drive mechanism 12 of any suitable known construction is mounted atop the pier providing the driving torque for the rake structure. The pier also supports the inner end of an access bridge 13.

Rake structure 10 comprises a central vertical cage portion or cage 14 surrounding the pier 11, and rake arms of girder like construction extending rigidly from the cage. Rake structure 10 has one pair of long rake arms 15 and 16 opposite to one another, and a pair of short rake arms 17 and 18 disposed at right angles thereto, all arms having sludge impelling or conveying blades 19 fixed to the underside thereof.

Rake structure 10 operates in a settling tank 20 to which a feed suspension or feed pulp is supplied through a feed dilution and flocculent mixing system 21 terminating in a cylindrical feedwell body 22 which surrounds the top end portion of the rake structure and is supported by pier 11.

Tank 20 may be of usual construction, comprising a bottom 24 of shallow inverted conical inclination, and formed with an annular sump 25 around the pier, to which settled solids or sludge are conveyed by rake structure 10. Scraper blades 26, unitary with rake structure 10 and substantially conforming to the profile of sump 25, move the collected sludge to a point of delivery from the sump, as by way of a discharge pipe 27.

Feed dilution and flocculent mixing system 21 is connected at a downstream end to feedwell body 22. Feedwell body 22 has an annular floor panel 34 (FIG. 2) with an inner edge 36 defining a circular opening 38 and an outer edge contiguous with a cylindrical sidewall 40 of the feedwell body. Feed dilution and flocculent mixing system 21 is connected to feedwell body 22 so as to deliver slurry stream 42 to flow along a circular path inside the feedwell body. Slurry stream 42 has a substantially circular inner boundary located generally above inner edge 36 and a substantially circular outer boundary located adjacent feedwell sidewall 40. The inner and outer boundaries extend parallel to the path of the slurry stream 42.

As depicted in FIG. 3 and more schematically in FIG. 4, feed dilution and flocculent mixing system 21 includes a slurry or solids/liquid feed pipe 44, a nozzle 46 attached to a downstream end of the feed pipe, and a mixing conduit 48 in the form of an open channel having lower corners 49 (only one shown). Feed dilution and flocculent mixing system 21 may be defined to further include feedwell body 22. At least a portion of nozzle 46 is disposed proximate an upstream end 50 of mixing conduit 48 for delivering a slurry or solids feed 58 thereto. A downstream end of mixing conduit 48 is attached to feedwell sidewall 40 so that the mixing conduit communicates with the feedwell. In FIG. 4, reference designation 52 represents a bed of settled solids in settling tank 20, pipe 54 being provided for removing the thickened underflow. Nozzle 46 (FIG. 4) comprises a nozzle body 92 having an inlet end 94 and an outlet end 96, the outlet end being provided with an outlet opening (not separately designated). Flocculent may be delivered via a tube 74 into the dilution fluid or supernatant flow 66 at upstream end 50 of mixing conduit 48 and additionally at points 75, 77 further downstream along the mixing conduit. As depicted in FIGS. 3-6, feed dilution and flocculent mixing system 21 includes one or more one elongate flexible webs or sheets 102 preferably made of rubber or a flexible polymeric material. Each elongate flexible web or sheet 102 is disposed in mixing conduit 48 and extends at least along a substantial portion of the mixing conduit. Each elongate flexible web or sheet 102 has an upstream end (not designated) secured to mixing conduit 48, proximate to nozzle 46, by a mounting assembly 104 including a cross-brace 106 in the form of an angle beam and at least one downwardly depending bracket member 108. Each flexible web or sheet 102 is provided with structure 110 including openings 112 (FIG. 5) and flow deflection or diversion flaps 114 to induce an undulating or wiggling motion of the respective web or sheet member 102 in response to fluid flow through mixing conduit 48. Flaps 114 may also be made of rubber or polymer or of another material that is stiffer than rubber.

The elongate flexible webs or sheets 102 may be provided, together with one or more mounting assemblies 104 or other fasteners or attachment elements, as part of a kit for retrofitting existing thickeners or settling tanks to enhance flocculent mixing and slurry speed reduction. Webs or sheets 102 may be identical to each other or may vary in such particulars as the numbers and types of motion-inducing structures 110. In addition, the webs or sheets 102 may vary in stiffness or flexibility, either from one web or sheet to another or within the same web or sheet.

As also shown in FIG. 3, one or more similar flexible web or sheet structures 60, with or without slots and respective flaps 62, in all the variations discussed herein, could also be variously attached to, most likely at their upstream end via various attachment elements such as screws, welds, rods, etc., and hung in the feedwell 22 itself where the slurry flow velocity may be less but where the web(s) or sheet(s) 60 could further, or on their own, aid in the mixing and further floe formation in and/or of the slurry. As illustrated particularly in FIG. 5, motion-inducing structure 110 of each web or sheet 102 includes a plurality of openings 112 in the flexible web or sheet. In the embodiment of FIG. 5, openings 112 are identical elongate rectangular windows oriented transversely relative to the web 102 and longitudinally spaced from one another along the length of the web. Openings or windows 112 preferably have a width of 1-3 inches, a length of about 8-11 inches, and a relative spacing of about 6-12 inches in a web 102 that is about a foot across. It is to be noted, however, that openings 102 may be provided in different sizes and shapes and at various distances from adjacent openings.

Each web 102 has a thickness of 0.1 to 0.5 inch and preferably about one-quarter inch. The width of web 102 may vary, for example, from 8 to 15 inches, but must be somewhat less that the width of mixing conduit 48. Where multiple webs 102 are disposed in the same mixing conduit, they are preferably placed one above the other each in a generally horizontal orientation and spaced apart from one another, along bracket member 108 of attachment assembly 104, by a distance of between about 4 inches and about 10 inches, preferably about 5 inches.

Motion-inducing structure 110 also includes a plurality of flow deflector flaps 114 (FIGS. 5 and 6) which are variously attached to opposing sides or major surfaces 116 and 118 of each flexible web or sheet 102. As shown in FIGS. 5 and 6, every other flow deflector flap 114 is attached to the same major surface 116 or 118, the other flaps 114 being attached to the other major surface 118 or 116. Flow deflector or guide flaps 114 may have a common width of 2-4 inches, a length of about 10-12 inches and a mutual spacing of about 12 inches. Like openings 12, flow deflector flaps 114 may be of different sizes and shapes, but in the preferred embodiment of FIG. 5 are rectangular flaps. Flaps 114 are attached to web 102 in sufficient proximity to respective openings 112 to deflect at least some current flow 120 (FIG. 6) through the openings. Flow deflectors or flaps 114 are provided with tensile retention elements 122 each connected at one end to the body of the respective web or sheet 102 and at an opposite end to an edge or corner 124 of a flow deflector flap 114. Tensile retention elements 122 serve at least in part to define a maximum angle a in the range of about 120 degrees, preferably at about 45 degrees, of the respective flow deflection flap 114 relative to web or sheet 102. Tensile retention elements 122 may be elastic cords that enable flow deflector flaps 114 to bend back towards web 102 in response to forceful currents, with the retention elements 122 elastically returning the flaps 114 to positions angled towards the incoming fluid flow, as shown in FIGS. 5 and 6. Elastic cords 122 stretch, temporarily slowing or capturing incoming fluid, then suddenly release the fluid, which increases wiggling motion of the mixing web 102.

As pulp or slurry 58 traverses mixing conduit 48, the divergent forces exerted on a web 102 by the moving fluid or currents 120, 126 (FIG. 6), especially via flaps 114, induces an undulating motion or wiggling of the web, represented by the various curvilinear aspects of webs 102 in FIG. 6. The induced undulating motion or wiggling of web 102 accelerates and enhances the mixing of flocculent and dilution fluid or supernatant flow 66 with the slurry or solids feed 58.

FIG. 7 depicts a modified mixing web or sheet 202 having openings 212 that are geometrically substantially identical to respective flow deflection flaps 214. Flaps 214 are each partially cut out of web or sheet 202 and bent away from a plane thereof (plane of the drawing sheet) along one edge 215 of the respective opening 212. The mixing web 202 of FIG. 7 is thus a result of a simplified manufacturing process, in contrast to that of mixing web 102 wherein flaps 114 are connected to the web via adhesive bonding, ultrasonic welding, heat treatment, rivets, or other means. Flow deflection or diversion flaps 214 are provided with elastic retaining or position-limiting cords 222 each secured at one end to web 202 and at an opposite end to an edge or corner 224 of a respective flap 214. Web 202 is mounted to mixing conduit 48 via an attachment assembly 204 like assembly 104.

FIGS. 8 and 9 show another modified mixing web or sheet 302 having openings 312 and flow deflection or diversion flaps 314. Mixing web 302 is provided with a flap control or retention mechanism 315 comprising a pressure manifold or tubular network 317 connected to and communicating with a plurality of hollow ribs or tubes 319 each attached along a backside of a respective flow deflection or diversion flap 314. Pressure manifold 317 carries a pressurization fluid, e.g., air or water, that pressurizes or inflates ribs 319, to support and reinforce flaps 314. An increase in the pressure of the pressurization fluid also serves to rigidify pressure manifold 317, particularly including longitudinally extending main pressure lines 321, 323 thereof, which results in a stiffer web 302, thereby reducing the undulating movements thereof.

Pressurization manifold 317 may be connected to an external pressure source (not shown) or in some cases may be automatically operated by the incoming slurry stream 58 and/or the incoming dilution fluid or supernatant flow 66. To that end, as depicted in FIG. 10, an upstream end of each main pressure line 321 and 323 may be provided with a funnel inlet 325 that varies the degree of pressurization of manifold 317 and ribs 319 depending on the rate of flow through mixing conduit at an upstream end thereof, upstream of webs 302. Such a pressurized, flow responsive system may further comprise an open or closed system, the closed system type possibly including a master and slave type hydraulic and/or piston type arrangement.

It is to be noted that a flexible self-undulating web or sheet 102, 202, 302 of a mixing system may in some cases omit openings 112, 212, 312 and include only flow deflector flaps 114, 214, 314. Openings 112, 212, 312 and flow deflectors 114, 214, 314 may be of various sizes and shapes and spaced by different distances from one another, even on the same web or sheet member 102, 202, 302. Flow deflectors 114, 214, 314 may be replaced by flow diversion elements having different geometrical shapes, such as wedge-shaped or arcuate, which may not require separate position retention or position limiting members.

Multiple flexible mixing webs 102, 202, 302 of any type or variation described herein may be provided in a kit together with attachment assemblies 104, as mentioned above.

"Functionally equivalent" means that while the different webs or sheets may vary in stiffness, in the shapes, sizes, numbers and distribution of openings (if any), and in the shapes, sizes, numbers, distributions, and retention elements of the flow deflectors, the flexible webs or sheets all

function nonetheless to exhibit an undulating or wiggling motion in a slurry stream, thereby

enhancing the mixing of flocculent and slowing down the slurry stream.

A contractor or other entity may provide a mixing conduit system for a feedwell assembly of a thickener/clarifier/settling tank having a feedwell assembly with a mixing conduit system or operate a thickener/clarifier/settling tank apparatus in whole, or in part, as shown and described. For instance, the contractor may receive a bid request for a project related to designing or operating a

thickener/clarifier/settling tank, or the contractor may offer to design such a system or a process for a client. Or the contractor may receive a bid request for a project related to redesigning a mixing conduit system or retrofitting an existing mixing conduit system. The contractor may then provide, for example, multiple mixing webs 102, 202, 302 as shown and/or described in the embodiments discussed above. The contractor may provide such mixing webs 102, 202, 302 optionally with attachment devices 104, for example in kit form, by selling or offering to sell those mixing webs optionally with attachment devices 104, optionally in kit form. The contractor may provide various embodiments that are sized, shaped, and/or otherwise configured to meet the design criteria of a particular client or customer. The contractor may subcontract the fabrication, delivery, sale, or installation of the mixing webs and/or attachment devices disclosed, or of other devices used to provide said devices. The contractor may also survey a site and design or designate one or more storage areas for storing the webs 102, 202, 302, etc., and related attachment devices 104. The contractor may also maintain, modify, or upgrade the provided mixing webs 102, 202, 302 and devices. The contractor may provide such maintenance or modifications by subcontracting such services or by directly providing those services or components needed for said maintenance or modifications, and in some cases, the contractor may modify a preexisting

thickener/clarifier/settling tank, or parts thereof with a "retrofit kit" to arrive at a modified

thickener/clarifier/settling tank comprising one or more method steps, devices, components, or features of the systems and processes discussed herein.

Elongate flexible mixing webs 102, 202, 302, etc., may have different cross-sections, for instance, triangular, corrugated, wave-formed, and/or different dimensions, for example, different thicknesses, widths and/or lengths. Mixing webs 102, 202, 302 may be solid or hollow, textured or smooth, perforated or imperforate.

The present invention lends itself well to retrofit installations. Accordingly, the invention is directed in part to a method for constructing or retrofitting a thickener/clarifier/settling tank and particularly a slurry infeed, dilution and/or flocculent mixing conduit thereof. The method includes providing elongate flexible mixing webs or sheets 102, 202, 302 and placing, disposing or installing the mixing webs within the mixing conduit 48.

The placing, disposing or installing of the mixing webs 102, 202, 302 may include

attaching one end of each web 102, 202, 302 to structure in the mixing conduit, for instance,

brackets 108 and extending the elongate flexible mixing webs 102, 202, 302 in a downstream

direction away from an inlet end of the mixing conduit 48.

Although the invention has been described in terms of particular embodiments and

applications, one of ordinary skill in the art, in light of this teaching, can generate additional

embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. It is believed that the invention is useful in virtually any type of feedwell assembly, with or without the addition of flocculent, with or without slurry dilution by eduction, with singular or multiple infeed paths, with or without spill lips (i.e., annular bottom panels or shelves in the feedwell bodies), etc.

Mixing webs 102, 202, 302 may also be disposed vertically inside mixing conduit 48, rather than horizontally, although horizontal is the preferred orientation. Mixing webs 102, 202, 302 may also be fastened to mixing conduit 48 also at their downstream ends, for instance, via elastic cords (not shown) that will accommodate the multifarious transverse and wave-like motions of the mixing webs while still holding the webs in rough parallel relationship to one another and preventing unlikely entanglement or entrainment.

Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.

Claims

WHAT IS CLAIMED IS:

1. A feed mixing system for a thickener or settling tank, comprising:

a slurry feed pipe;

a mixing conduit, at least a distal end portion of said slurry feed pipe being disposed proximate an upstream end of said mixing conduit;

a feedwell disposed inside the thickener or settling tank, a downstream end of said mixing conduit being attached to a wall of said feedwell so that said mixing conduit communicates with said feedwell; and

at least one elongate flexible web or sheet disposed in said mixing conduit and extending at least along a substantial portion of said mixing conduit, said at least one flexible web or sheet being provided with structure to induce an undulating or wiggling motion of said at least one flexible web or sheet in response to fluid flow through said mixing conduit.

2. The feed mixing system defined in claim 1 wherein said structure includes a plurality of openings provided in said at least one flexible web or sheet, said openings being spaced from one another in a longitudinal direction along a length of said at least one flexible web or sheet.

3. The feed mixing system defined in claim 2 wherein said structure further includes a plurality of flow deflectors attached to said at least one flexible web or sheet.

4. The feed mixing system defined in claim 3 wherein said flow deflectors are attached to said at least one flexible web or sheet so as to direct slurry through said openings.

5. The feed mixing system defined in claim 4 wherein at least one of said flow deflectors extends from one major surface of said at least one flexible web or sheet, at least one other of said flow deflectors or guides extending from an opposing major surface of said at least one flexible web or sheet.

6. The feed mixing system defined in claim 5 wherein adjacent ones of said flow deflectors extend from different ones of said one major surface and said opposing major surface of said at least one flexible web or sheet.

7. The feed mixing system defined in claim 3 wherein said flow deflectors are each provided with at least one retention member for holding the respective flow deflector in opposition to forces exerted by fluid flow on the respective flow deflector.

8. The feed mixing system defined in claim 7 wherein said at least one retention member is a flexible tensile member connected at one end to the respective flow deflector and at an opposite end to said at least one flexible web or sheet.

9. The feed mixing system defined in claim 8 wherein said flexible tensile member is elastic.

10. The feed mixing system defined in claim 7 wherein said at least one retention member is a hollow rib or tube connected to pressurization source for enabling a stiffening of said hollow rib or tube.

11. The feed mixing system defined in claim 11 wherein said hollow rib or tube is connected to a backside of the respective one of said flow deflectors.

12. The feed mixing system defined in claim 10 wherein said pressurization source includes a tubular network fastened to said at least one flexible web or sheet and communicating with said hollow rib or tube.

13. The feed mixing system defined in claim 1 wherein said structure includes a plurality of flow deflectors attached to said at least one flexible web or sheet.

14. The feed mixing system defined in claim 13 wherein at least one of said flow deflectors extends from one major surface of said at least one flexible web or sheet, at least one other of said flow deflectors or guides extending from an opposing major surface of said at least one flexible web or sheet.

15. The feed mixing system defined in claim 14 wherein a plurality of said flow deflectors extend from said one major surface and another plurality of said flow deflectors extend from said opposing major surface.

16. The feed mixing system defined in claim 13 wherein said flow deflectors are each provided with at least one retention member for holding the respective flow deflector in opposition to forces exerted by fluid flow on the respective flow deflector.

17. The feed mixing system defined in claim 16 wherein said retention member is a flexible tensile member connected at one end to the respective flow deflector and at an opposite end to said at least one flexible web or sheet.

18. The feed mixing system defined in claim 17 wherein said flexible tensile member is elastic.

19. The feed mixing system defined in claim 16 wherein said retention member is a hollow rib or tube connected to a pressurization source for enabling a stiffening of said hollow rib or tube.

20. The feed mixing system defined in claim 19 wherein said hollow rib or tube is connected to a backside of the respective one of said flow deflectors.

21. The feed mixing system defined in claim 19 wherein said pressurization source includes a tubular network fastened to said at least one flexible web or sheet and communicating with said hollow rib or tube.

22. The feed mixing system defined in claim 1 wherein said at least one flexible web or sheet is one of a plurality of flexible webs or sheets disposed in said mixing conduit.

23. The feed mixing system defined in claim 22 wherein said flexible webs or sheets are disposed in approximate parallel relationship to one another.

24. The feed mixing system defined in claim 22 wherein said flexible webs or sheets have different degrees of elasticity or stiffness.

25. The feed mixing system defined in claim 1 wherein said mixing conduit is an open channel.

26. A kit for retrofitting a feed mixing system for a thickener or settling tank to enhance mixing of flocculent, said thickener or settling tank having a feedwell disposed inside the thickener or settling tank, a mixing conduit having a downstream end attached to a wall of said feedwell so that said mixing conduit communicates with said feedwell, a slurry feed pipe extending proximate an upstream end of said mixing conduit, said kit comprising;

at least one elongate flexible web or sheet disposable in a mixing conduit of the thickener or settling tank so as to extend at least along a substantial portion of said mixing conduit, said at least one flexible web or sheet being provided with structure to induce an undulating or wiggling motion of said at least one flexible web or sheet in response to fluid flow through said mixing conduit; and

at least one attachment element configured for securing at least an upstream end of said at least one elongate flexible web or sheet to said mixing conduit.

27. The kit defined in claim 26 wherein said structure includes a plurality of openings provided in said at least one flexible web or sheet, said openings being spaced from one another in a longitudinal direction along a length of said at least one flexible web or sheet.

28. The kit defined in claim 27 wherein said structure further includes a plurality of flow deflectors attached to said at least one flexible web or sheet.

29. The kit defined in claim 28 wherein said flow deflectors are attached to said at least one flexible web or sheet proximate respective ones of said openings so as to selectively direct slurry flow through said openings.

30. The kit defined in claim 29 wherein at least one of said flow deflectors extends from one major surface of said at least one flexible web or sheet, at least one other of said flow deflectors or guides extending from an opposing major surface of said at least one flexible web or sheet.

31. The kit defined in claim 28 wherein said flow deflectors are each provided with at least one retention member for holding the respective flow deflector in opposition to forces exerted by fluid flow on the respective flow deflector.

32. The kit defined in claim 31 wherein said retention member is a flexible tensile member connected at one end to the respective flow deflector and at an opposite end to said at least one flexible web or sheet.

33. The kit defined in claim 32 wherein said flexible tensile member is elastic.

34. The kit defined in claim 31 wherein said retention member is a hollow rib or tube connected to pressurization source for enabling a stiffening of said hollow rib or tube.

35. The kit defined in claim 34 wherein said hollow rib or tube is connected to a backside of the respective one of said flow deflectors.

36. The kit defined in claim 35 wherein said pressurization source includes a tubular network fastened to said at least one flexible web or sheet and communicating with said hollow rib or tube.

37. The kit defined in claim 26 wherein said structure includes a plurality of flow deflectors attached to said at least one flexible web or sheet.

38. The kit defined in claim 37 wherein at least one of said flow deflectors extends from one major surface of said at least one flexible web or sheet, at least one other of said flow deflectors or guides extending from an opposing major surface of said at least one flexible web or sheet.

39. The kit defined in claim 48 wherein a plurality of said flow deflectors extend from said one major surface and another plurality of said flow deflectors extend from said opposing major surface.

40. The kit defined in claim 37 wherein said flow deflectors are each provided with at least one retention member for holding the respective flow deflector in opposition to forces exerted by fluid flow on the respective flow deflector.

41. The kit defined in claim 40 wherein said retention member is a flexible tensile member connected at one end to the respective flow deflector and at an opposite end to said at least one flexible web or sheet.

42. The kit defined in claim 41 wherein said flexible tensile member is elastic.

43. The kit defined in claim 40 wherein said retention member is a hollow rib or tube connected to a pressurization source for enabling a stiffening of said hollow rib or tube.

44. The kit defined in claim 43 wherein said hollow rib or tube is connected to a backside of the respective one of said flow deflectors.

45. The kit defined in claim 43 wherein said pressurization source includes a tubular network fastened to said at least one flexible web or sheet and communicating with said hollow rib or tube.

46. The kit defined in claim 26 wherein said at least one flexible web or sheet is one of a plurality of flexible webs or sheets disposable in said mixing conduit.

47. The kit defined in claim 46 wherein said flexible webs or sheets have different degrees of elasticity or stiffness.

48. A feed mixing system for a thickener or settling tank, comprising:

a slurry feed pipe; a mixing conduit, at least a distal end portion of said slurry feed pipe being disposed proximate an upstream end of said mixing conduit;

a feedwell disposed inside the thickener or settling tank, a downstream end of said mixing conduit being attached to a wall of said feedwell so that said mixing conduit communicates with said feedwell; and

at least one elongate flexible web or sheet disposed in said feedwell, said at least one flexible web or sheet being provided with structure to induce an undulating or wiggling motion of said at least one flexible web or sheet in response to fluid flow through said feedwell.

49. A kit for retrofitting a feed mixing system for a thickener or settling tank to enhance mixing of flocculent, said thickener or settling tank having a feedwell disposed inside the thickener or settling tank, a mixing conduit having a downstream end attached to a wall of said feedwell so that said mixing conduit communicates with said feedwell, a slurry feed pipe extending proximate an upstream end of said mixing conduit, said kit comprising;

at least one elongate flexible web or sheet disposable in a feedwell of the thickener or settling tank, said at least one flexible web or sheet being provided with structure to induce an undulating or wiggling motion of said at least one flexible web or sheet in response to fluid flow through said mixing conduit; and

at least one attachment element configured for securing at least an upstream end of said at least one elongate flexible web or sheet to said feedwell.