Abstract:
A feedwell comprising a plurality of holes disposed in a bottom thereof, at least some of the holes having a tube disposed thereabout which extends downward or otherwise away from an interior of the feedwell. Optionally, a large center hole can be provided and it can have a tube disposed around it. By providing a plurality of holes spread across a large portion of the bottom of the feedwell, lower velocity flow rates from the feedwell to a sedimentation chamber can be provided, thus reducing induced turbulence in the fluid within the sedimentation chamber, while still providing sufficient separation of the feedwell from the sedimentation chamber so that the contents of the feedwell can be properly and adequately mixed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of the filing of U.S. Provisional Patent Application Ser. No. 62/135,497, entitled “Thickener Feed Distributor”, filed on Mar. 19, 2015, and the specification and claims thereof are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention (Technical Field) 
         [0003]    Embodiments of the present invention relate to feedwells for mineral processing plant thickeners and clarifiers. More particularly, embodiments of the present invention relate to feedwells having a plurality of openings disposed on a lower portion thereof for more uniform distribution of fluids from the feedwell into fluids disposed in a sedimentation chamber (also known as a thickener tank) disposed there below. 
         [0004]    2. Description of Related Art 
         [0005]    Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes. 
         [0006]    For a feedwell to provide desirable results, it must permit components to be mixed and retained therein and thus have rather substantial and appropriate fluid kinetics. However, the feedwell should also isolate, to the greatest extent possible, such fluid kinetics from the contents of the sedimentation chamber, while still permitting a sufficient fluid flow rate from the feedwell to the sedimentation tank to accomplish a desired overall feed flow rate. 
         [0007]    A typical feedwell is shown and described in U.S. Patent Pub. No. 2011/0079563 (the &#39;563 application), having a single, large outlet as shown in the figures thereof (reference numeral 8). Such feedwells are common and have the characteristic downside of forcing all contents of the feedwell to escape through a single large opening in the bottom. Such a configuration enhances turbulence and creates undesirable flow patterns within the upper portion of the sedimentation chamber within which it is disposed. Although the &#39;563 application seeks to reduce such turbulence by disposing a plurality of fins into the single large opening, such fins themselves disturb the flow of the exiting fluid, thus enhancing the turbulence induced within the sedimentation chamber, which is an undesirable characteristic. 
         [0008]    Some inventions, such as that disclosed in U.S. Pat. No. 7,591,946 to Taylor, seek to minimize the induced turbulence by forcibly mixing the contents of its feedwell in a lower portion thereof and forcing the contents of the feedwell to escape therefrom at an upper opening through a Bundt pan shape. By forcing the discharge of the feedwell to be concentrated near a central bottom portion of the feedwell, the flow rate of the discharge is thus comparatively larger than would occur if Taylor instead spread the discharge of the feedwell out over a much larger area. 
         [0009]    Like other known feedwell designs, U.S. patent application Ser. No. 12/633,527 to Lake et al. also describes a feedwell with a single large opening disposed in its lower portion. Thus, this invention also suffers from the same undesirable turbulence and flow patterns that are induced in the sedimentation chamber as the other known systems. 
         [0010]    U.S. patent application Ser. No. 12/745,891 to McElvenny also discloses a feedwell with a single large opening on its bottom. The apparatus disclosed in this application, however, attempts to mitigate the disturbance to the liquid in the sedimentation chamber by placing a conical plate directly below the outlet of the feedwell so as to spread out the flow of fluid exiting the feedwell into a larger ring-shape. However, even this proposed solution does not distribute the outflow of the feedwell over a significant area, because the very plate itself blocks a significant area below the flow in which some of the outflow could travel. 
         [0011]    Other systems have also been developed which seek to make the outflow of the feedwell more uniform by incorporating a flow-shaping zone near the single large outlet of the feedwell. However, the result is still substantially the same—the entire outflow of the feedwell is concentrated in a single entry point in the sedimentation chamber, thus inducing turbulence in the contents of the sedimentation chamber. 
         [0012]    There is thus a present need for a method and apparatus which provides a feedwell that distributes the outflow of the feedwell into the sedimentation chamber over a vastly large area so as to minimize turbulence in the contents of the sedimentation chamber. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    An embodiment of the present invention relates to a feedwell having a feed inlet, a sidewall, a bottom, at least three holes disposed in the bottom of the feedwell, and a tube disposed around at least one of the holes and projecting down or otherwise away from an interior of the feedwell. Optionally, at least a majority of the holes each comprise a corresponding tube. One or more of the tubes can have a length which is greater than at least one half of the diameter of the corresponding hole about which or within which it is disposed. The feedwell can have at least 12 holes and optionally at least 36 holes disposed in its bottom. In one embodiment, the hole size can be several times the diameter of an expected floccule, thus permitting floccules to pass through the holes without being broken down. The feedwell can also include an inlet and/or at least one opening in its sidewall. Optionally, a plurality of openings can be disposed in a sidewall of the feedwell. The openings can be disposed in an upper half of the sidewall. 
         [0014]    In one embodiment, the feedwell can comprise a comparatively large opening in the center of the bottom of the feedwell. Optionally, the central opening can comprise a cross-sectional area that is two or more times larger than a cross-sectional area of one of the other holes disposed in the bottom of the feedwell. 
         [0015]    An embodiment of the present invention also relates to a feedwell having a sidewall, a bottom, a first opening in the bottom, a plurality of second openings in the bottom, each of the plurality of second openings having a cross-sectional area which is less than one-half of a cross-sectional area of said first opening; and at least some of the second openings comprising a corresponding tube disposed around the openings which projects down or away from an interior of the feedwell. Optionally, the feedwell can have a bottom that is downwardly-depending and cone-shaped. A velocity regulator and/or a flow rate regulator can be communicably coupled to one or more of the holes. 
         [0016]    An embodiment of the present invention also relates to a method for dispensing contents of a feedwell into a sedimentation chamber which includes passing the contents from within the feedwell through a plurality of openings disposed in a bottom of the feedwell, wherein the plurality of openings number at least six openings. The method can also include guiding at least some of the contents from within the feedwell to a location within the sedimentation chamber by directing them through one or more tubes disposed around at least some of the openings. Optionally, at least three openings can be disposed in the bottom of the feedwell. Preferably, the openings and tubes are consistent in design radially. 
         [0017]    Embodiments of the feedwell of the present invention permit deaeration, mixing at the right energy level, flocculation, and solids contact therein. The holes allow the feed to be evenly distributed into a sedimentation chamber in a controlled manner with little turbulence. Feedwells according to embodiments of the present invention maintain retention required for optimal mixing. The tubes connected to the holes in the bottom of the feedwell allows for instantaneous recovery of the liquid via the open channels which can be created with an off-set pattern in the layout. The liquid can be recovered very close to the feedwell underside, thereby shortcutting the typical scenario which is normally only achieved lower in the thickener. This process in known systems is often hindered by settling solids, rise rates, and other dynamics within the thickener proper. 
         [0018]    Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0019]    The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings: 
           [0020]      FIG. 1  is an elevated side-view drawing which illustrates a feedwell according to an embodiment of the present invention; 
           [0021]      FIG. 2  is a drawing which illustrates an underside of a feedwell according to an embodiment of the present invention; 
           [0022]      FIG. 3  is a side-view drawing of a feedwell according to an embodiment of the present invention; 
           [0023]      FIG. 4  is a top-view drawing of a feedwell according to an embodiment of the present invention; 
           [0024]      FIG. 5  and  FIG. 6  are elevated side-view drawings which illustrate a feedwell according to an embodiment of the present invention disposed within a sedimentation chamber; 
           [0025]      FIG. 7  is a section-view/cutaway drawing which illustrates a feedwell according to an embodiment of the present invention disposed in a sedimentation chamber; 
           [0026]      FIG. 8  is a side-view drawing of a feedwell illustrating the modular bottom floor construction according to an embodiment of the present invention; 
           [0027]      FIG. 9A  and  FIG. 9B  are side-view drawings which illustrate an embodiment of the present invention wherein a fluid-flow modification structure is disposed below the feedwell; 
           [0028]      FIG. 10A  and  FIG. 10B  are cut-away drawings which illustrate an embodiment wherein a vertical tube passes through the feedwell and wherein a fluid-flow modification structure is disposed on the lower end of the vertical tube; and 
           [0029]      FIG. 11  is a cut-away side-view drawing which illustrates an embodiment wherein a vertical tube passes through the feedwell and wherein the bottom of the feedwell has an upwardly-projecting conical shape. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Embodiments of the present invention relate to a feedwell for a thickener or clarifier, also generally referred to as a “thickener feed distributor.” The thickeners and clarifiers, used in mineral processing plants, rely on compartments or “feedwells” located at an upper center portion of a sedimentation chamber. The purpose of such feedwells is to deaerate the feed; permit introduction and mixing of slurries, flocculant, dilution water, or materials to a homogenous state; promote rapid flocculant/particle aggregate formation; capture fine and coarse particles into flocculant/particle aggregate formation through mixing at the right energy levels; prevent break-down of such flocculant/particle aggregates through excessive energy levels; and then simultaneously allow such materials to enter the sedimentation chamber with as little turbulence as possible after having been mixed so as to avoid agitating the sedimentation process. Fluid flow plays a major role in these sedimentation units and their successful operation depends, to a large extent, on having a feedwell correctly designed for the particular application. 
         [0031]    Referring now to the drawings, feedwell  10  preferably comprises sidewall  12  and bottom  14 . Bottom  14  preferably comprises a plurality of holes  16 . Holes  16  preferably comprise tubes  18  disposed around holes  16 . Tubes  18  are preferably disposed on the outside portion of feedwell  10  and thus extend away from an interior of feedwell  10 . Holes and tubes are preferably radially consistent in pattern or design. An embodiment of the present invention also relates to a method and apparatus for controlling and/or regulating the flow rate and/or exit velocity of the contents of feedwell  10  through holes  16  in bottom  14  of feedwell  10 . This can be achieved by a self-regulating or adjustable valve, a one way valve, one directional flap, a port, a diaphragm, combinations thereof, and the like, which can be incorporated into and/or attached to one or more of holes  16  and/or tubes  18  of feedwell  10 . In one embodiment, feedwell  10  comprises a generally circular shape. In an alternative embodiment, feedwell  10  does not comprise a generally circular shape. 
         [0032]    In one embodiment, in addition to a plurality of holes  16 , a large hole  20  is preferably disposed in a central portion of bottom  14  of feedwell  10 . Hole  20  also preferably has tube  22  disposed around it and tube  22  also is preferably disposed on an outside portion of feedwell  10  and thus extends away from an interior of feedwell  10 . Although a preferred embodiment provides feedwell  10  having a generally cylindrical shape, feedwell  10  need not be limited only to generally cylindrical shapes and can comprise any shape which permits materials to be mixed or clarified, including but not limited to rectangular, square and other shapes. 
         [0033]    Although holes  16  can comprise any shape, including but not limited to triangular, square, rectangular, oval, etc., in a preferred embodiment, holes  16  are most preferably circular in shape. For embodiments in which non-circular shaped holes  16  are provided, tubes  18  preferably comprise a similar shape to non-circular holes  16 . Optionally, holes  16  need not all be the same shape and size. For example, some of holes  16  can be large squares, small squares, large rectangles, small rectangles, large triangles, small triangles, large circles and small circles. Optionally, the shapes and/or sizes of holes  16  can progressively change as they approach the center of bottom  14  or they can be interspersed in patterns or randomly. For example, in one embodiment, the holes nearest sidewall  12  can comprise a diameter which is smaller than those which are near the center of bottom  14 . Although the number and spacing of holes  16  can be varied to provide specific results for a particular application and for different sizes of feedwells, in one embodiment, there are at least three holes  16 , at least 6 holes  16 , at least 12 holes  16 , at least 24 holes  16 , at least 32 holes  16 , at least 36 holes  16 , or at least 60 holes  16 . 
         [0034]    In one embodiment, bottom  14  of feedwell  10  can be flat or at least substantially flat. However, in a preferred embodiment, at least a portion of bottom  14  comprises a concave or conical shape, such as that illustrated in the figures. Optionally, a portion of bottom  14  nearest sidewall  12  can be flat while the rest of bottom  14  can have a concave shape (see for example  FIGS. 1 and 2 ). If the feed to the feedwell is tangential to a nearest sidewall, a flat portion of the bottom of the feed inlet nearest the sidewall is preferably proportional in width to the feed flow rate. In one embodiment, the flat portion of the feedwell is preferably below the bottom of the feed inlet by approximately the feed inlet height. 
         [0035]    Tubes  18  can optionally comprise a length which is uniform to each of holes  16 . Optionally, however, some of tubes  18  can have a length which is longer or shorter than other tubes  18 . For example, in one embodiment, tubes  18  of holes  16  nearest sidewall  12  can have a length which is short in relation to tubes  18  of holes  16  which are nearest the center of bottom  14 . Optionally, the length of tubes  18  can be varied in a consistent manner—for example, the tubes nearest sidewall  12  can be long and each tube nearer to a center of bottom  14  can be progressively larger such that tubes  18  nearest the bottom are longer than tubes  18  which are nearest sidewall  12  (or vice-versa). Alternatively, the length of tubes  18  can be varied in some predetermined pattern or can be varied randomly. In one embodiment, wherein feedwell  10  comprises holes  16  with varying diameters, the length of tubes  18  can also vary as their diameters vary—optionally, the length of a tube  18  can relate directly to the diameter of its accompanying hole  16 . In one embodiment, the length of a tube is preferably at least half of the diameter of its accompanying hole. For example, if a first hole  16  is small and a second hole  16  is large, the length of the tube on the small first hole can be short and the length of the tube on the large second hole can be long. Optionally, tubes  18  can be connected to bottom  14  such that they project down or otherwise away from an interior of feedwell  10  in a desired and predetermined direction. For example, in one embodiment, wherein feedwell  10  comprises a flat bottom, tubes  18  nearest sidewall  12  can have their proximal end cut at an angle, such as for example 45 degrees. This outer ring of tubes can be oriented such that they project down or otherwise away from a center of bottom  14  at a 45 degree angle, and a row of tubes  18  further away from sidewall  12  can have their proximal ends cut at some other angle, for example, 30 degrees, etc. In such a configuration, the outer-most tubes  18  can be directed in a direction different from that of other tubes. Of course these are merely illustrative examples that one or more of tubes  18  can be made to point in a different direction than other tubes  18 . In one embodiment, tubes  18  can be arranged in a radially consistent pattern. 
         [0036]    Optionally, all or some of tubes  18  can be made long and can comprise one or more bends. For example, in one embodiment, tubes  18  nearest sidewall  12  can comprise a bend and can be extended such that they project radially just below sidewall  12 . Further, providing tubes  18  connected to one or more of holes  16  permit a user to design a specific-purpose feedwell system which permits fluids to exit feedwell  10  and be piped directly to any desired location within a sedimentation chamber. In one embodiment, the hole and tube arrangement is preferably radially consistent in pattern for a round sedimentation chamber. 
         [0037]    In one embodiment, tubes  18  can connect to bottom  14  via a removable connection. For example, tubes  18  can screw onto short nipples or other fittings such that a user can selectively connect tubes of different lengths, shapes, and/or sizes about any of holes  16 . Optionally, placement, size, and/or shape of holes  16  can be determined based on computer modeling for a particular application. In one embodiment, each of holes  16  comprise a corresponding tube  18 . In an alternative embodiment, a majority of holes  16  comprise a corresponding tube  18 . In yet a further embodiment, only one or some of holes  16  comprise a corresponding tube  18 . In an alternative embodiment, none of holes  16  comprise a corresponding tube  18 . 
         [0038]    In one embodiment, central hole  20  can be significantly larger than any of holes  16 . Alternatively, however, hole  20  can be slightly larger, the same size as, or even smaller than any of holes  16 . In a further embodiment, hole  20  and/or tube  22  are not provided. Tube  22  can have the same length as tubes  18  or it can be shorter or longer than tubes  18 . As with tubes  18 , tube  22  can also comprise any desired length and can be shaped in a number of ways such as concave-shape or cone shape and can connect to a connector, including but not limited to a nipple, which is attached to bottom  14  of feedwell  10 . Optionally tubes  18  and/or  22  can comprise one or more structures disposed therein which promote a laminar flow therefrom. For example, an array of smaller diameter tubes can be packed or otherwise formed within tubes  18  and/or  22 . 
         [0039]    Fluid preferably enters feedwell  10  via inlet  24 . Optionally, a plurality of inlets  24  can be provided. Inlet  24  is preferably positioned on sidewall  12  and is most preferably positioned such that fluid entering feedwell  10  enters tangentially. Alternatively, however, inlet  24  can be disposed such that fluid enters into the open top of feedwell  10 . Also, inlet  24  can be positioned such that fluid does not enter tangentially into feedwell  10 . In one such embodiment, the feed can be introduced to feedwell  10  so that a radially inward or outward flow pattern is created. In a further embodiment, more than one inlet  24  can be provided. For example, in one embodiment, a first inlet can be configured to force incoming fluid to enter feedwell  10  in a counter-clockwise manner and a second inlet can be configured to also enter feedwell  10  in a counter-clockwise manner but at a location on an opposite side of feedwell  10  from the first inlet, thus promoting circulation. Alternatively, however, in some applications where increased turbulence is desired within feedwell  10 , the second inlet can be configured to enter feedwell  10  in a clockwise direction, thus forcing the incoming fluid streams to collide against one another. Like tubes  18  and  22 , one or more structures can be disposed or formed within inlet  24  which promote a laminar flow or any other flow pattern desired for a particular application. 
         [0040]    In one embodiment, sidewall  12  can comprise a solid structure. In an alternative embodiment, sidewall  12  is not provided at all. In this embodiment, bottom  14  can be conical or otherwise downwardly-depending and inlet  24  can simply enter into the downwardly-depending bottom structure. In one embodiment, feed dilution can be carried out before the introduction of the feed to feedwell  10 . In an alternative embodiment, however, one or more openings  26  (see  FIG. 1 ) can be provided in sidewall  12 , or of the conical or downwardly-depending structure, for embodiments which do not comprise a sidewall. Openings  26  can comprise any shape or combination of shapes and can be disposed in a predetermined pattern or at random. In a preferred embodiment, however, openings  26  are disposed near an upper edge of sidewall  12 , or an upper half of sidewall  12 , or the conical or downwardly-depending structure, for embodiments which do not comprise a sidewall, such that supernatant or dilution liquid can easily pass into the upper portion of feedwell  10  to dilute the contents thereof. In one embodiment, openings  26  are positioned near a top portion of sidewall  12  at a location which is left of inlet  24 . Optionally, one or more openings  26  can comprise a damper or other closable structure which reduces the size of openings  26  so that a user can adjust the size and number of openings  26  to meet a desired dilution rate. 
         [0041]    In one embodiment, feedwell  10  can be disposed such that it hangs just above or slightly into a surface of fluid in sedimentation chamber  28 . In a preferred embodiment, however, feedwell  10  is most preferably positioned such that a significant portion of it is submerged within the fluid contained in sedimentation chamber  28  (see  FIGS. 5-7  which illustrate a most preferred placement of feedwell  10  with regard to sedimentation chamber  28 ). 
         [0042]    Optionally, as best illustrated in  FIG. 8 , the bottom of the feedwell can be formed from a plurality of individual sections  30  that can be welded, bolted, or otherwise connected together. Sections  30  can be made from a urethane material, carbon or stainless steel, rubber-coated steel, rubber, fiber glass, aluminum, other metals, other composites, other plastics including but not limited to nylon, materials that provide desired wear and/or wear-resistance characteristics, materials that provide desired corrosion and/or corrosion resistance characteristics, combinations thereof and the like. Optionally, sections  30  can have a wedge or pie shape, or any other shape which is capable of forming a bottom of a feedwell. Thus, when one or more sections  30  wear out, they can quickly and easily be replaced. 
         [0043]    In one embodiment, feedwell bottom  14  preferably comprises a conical or otherwise downwardly-depending shape rather than a flat or upward-projecting shape as more typical feedwells have. Because of the downward-depending shape of bottom  14 , the total volume of feedwell  10  is increased without requiring the diameter of feedwell  10  to be increased. Thus, compared to an upwardly-projecting bottom of a conventional feedwell, embodiments of the present invention provide a feedwell having a similar overall weight and diameter, but with significantly more internal volume—thus increasing the amount of retention, mixing, and floccule growth for the same size of footprint. 
         [0044]    As best illustrated in  FIGS. 9A, 9B, 10A, and 10B , in one embodiment, one or more structures  32  can be disposed on a lower portion of, or directly below feedwell  10 . Structures,  32  preferably promote further fluid flow modifications to achieve desired objectives for particular applications of feedwell  10 . Although the one or more structures  32  can comprise any shape which is useful for achieving a particular objective for a given application of feedwell  10 , in one embodiment, structures  32  can include, but are not limited to, an inverted cone, radially placed blades, combinations thereof, and the like. In one embodiment, one or more structures  32  can be incorporated into or otherwise communicably coupled to tube  22  disposed around hole  20 , which can be disposed in a central location of bottom  14  of feedwell  10  (see  FIGS. 9A and 9B ). 
         [0045]    In an alternative embodiment, as is best illustrated in  FIG. 10A , one or more structures  32  can be disposed around tube  34  which extends upwardly through feedwell  10 . In another embodiment, as illustrated in  FIG. 10B , tube  34 , which extends upwardly through feedwell  10 , can be communicably coupled to tube  22  disposed around hole  20 , which can be disposed in a central location of bottom  14  of feedwell  10 . Thus, in one embodiment, tube  34  can be disposed in an at least substantially central portion of feedwell  10 . Optionally, as illustrated in  FIGS. 10A, 10B, and 11 , one or more openings  38  can be provided such that an interior of tube  34  is communicably coupled to an exterior thereof, and thereby an interior of tube  34  can be communicably coupled to an interior of feedwell  10 . Tube  34  can be disposed within an interior of feedwell  10 . In one embodiment, tube  34  can extend from the top of feedwell  10  to bottom  14  of feedwell  10 . The one or more openings  38  are most preferably disposed near an upper portion of tube  34 , but can optionally be disposed at one or more locations at any position along the length of tube  34  to promote further fluid flow modifications including feed dilution, fines capture, and recirculation to achieve desired objectives for particular applications. Elongated member  36 , which can comprise a rotating shaft, one or more hydraulic hoses, or any other elongated structure, can optionally pass through or be disposed at least partially within tube  34 . 
         [0046]    As best illustrated in  FIG. 11 , bottom  14  of feedwell  10  can comprise an upwardly-projecting conical shape. As with other embodiments of feedwell  10 , tube  34  can extend from a position above a top of feedwell  10  and can extend to bottom  14 . 
         [0047]    Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.