Abstract:
An apparatus removes liquid from a liquid and solids mixture. The apparatus may include a bowl-shaped, rigid container having an upper portion, a lower portion, and a sidewall forming a chamber for receiving the liquid and solids mixture. The container includes a plurality of conduits extending radially outwardly along an inner portion of the sidewall. A filter separates the conduits from the liquid solids mixture in the chamber. Means is also provided for reducing pressure in the chamber, which causes at least liquid to be drawn from the mixture through the filter and conduits. Related systems and methods may be follow from use of the apparatus.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/810,043, filed Jun. 1, 2006, the disclosure of which is incorporated herein by reference. 
     
     COPYRIGHT STATEMENT 
       [0002]    A portion of the disclosure of this document contains material subject to copyright protection. No objection is made to the facsimile reproduction of the patent document or this disclosure as it appears in the Patent and Trademark Office files or records, but any and all rights in the copyright(s) are otherwise reserved. 
       TECHNICAL FIELD 
       [0003]    The present invention relates generally to separating a liquid from a liquid-solid mixture and, in particular, to an apparatus and methods for separating a liquid, such as water, from a waste product, such as sludge. 
       BACKGROUND OF THE INVENTION 
       [0004]    Waste products present expensive disposal problems to the industries that generate them. Unprocessed waste products typically cannot be disposed of in landfills due to regulations on water content. Even with more permissive regulations, it is much more expensive to transport and dispose of unprocessed waste products than just solid components because transportation charges correspond to weight. 
         [0005]    Additionally, the scope of potential uses of such waste products is often substantially increased by removal of the liquid component from the solid component. Typically, the value of the dry solids arises from the decrease in weight occasioned by the removal of the liquid fraction, which leads to decreased disposal and transportation costs. Additionally, the recovered dried solids may be commercially valuable, such as if they are useable in other industrial applications (e.g., as filler in concrete mixtures) or can be sold in secondary markets, such as in the case where the waste products comprise coal or mineral slurries. 
         [0006]    Unfortunately, efforts to work around the waste disposal problems often employ methods lacking environmental soundness. For example, many industries dump waste products, such as sludge, into holding ponds, which are typically enormous concrete or plastic lined, man-made pools. The waste products then sit in these sludge ponds while the solid materials settle at the bottom over time with the aid of only gravity. Aside from being a slow process, the potential for the pool lining to fail to fail or result in contamination of the surrounding environment makes this a less-than-desirable solution in terms of both efficiency and environmental impact. 
         [0007]    Industrial sludge ponds suffer from significant practical difficulties. To begin, sludge ponds have a poor resulting yield (dry solid percentage content). Being passive, it also takes a long time to separate water from solids for a given volume of sludge, as compared to devices that rely on active separation. Keeping up with the output for any given waste flow rate requires a greater area than if active separation systems are used. However, most active separation are expensive to make and are not readily scaled up or down to handle corresponding volumes of industrial waste flow rates. The lack of portability is also a significant limiting factor. 
         [0008]    Accordingly, a need is identified for fast and efficient methods and devices for actively separating water from a waste product, and also to produce a resulting solid that is sufficiently dry for use in other applications. 
       SUMMARY OF THE INVENTION 
       [0009]    In its broadest aspects, the present invention relates to apparatus and methods for separating liquids from mixtures of liquids and solids that substantially eliminate one or more of the problems arising from the limitations and disadvantages of the prior art. The invention is particularly suited for separating water or other liquids from solids in all types of waste products, including sludge wastes or slurries. Throughout this application, mixtures of solids and water may be referred to as a product or a suspension. This includes any combination of particulate matter (solids) suspended in or containing significant quantities of water or any other liquid. While it is envisioned that the primary use of the invention is to dewater waste products, it is anticipated that the device will be equally useful in any application that requires removal of liquids from any mixture of liquids and solids. 
         [0010]    The invention involves providing a bowl-shaped container for receiving and at least temporarily holding the waste product, which may flow from an effluent discharge pipe or other source. The container may comprise a chamber or compartment bounded by an interior curved sidewall having plurality of graduated, arcuate conduits associated with a filter. A cover, such as a substantially air-tight, preferably semi-permeable pliable membrane, may be placed over the compartment including the product to form a chamber. 
         [0011]    To draw liquid from the product in the container, a pressure differential is created in the chamber. In one particularly preferred embodiment, a vacuum is applied to the chamber within the container through the conduits, and the negative pressure causes the liquid component of the waste product to be forced through the filter and the conduits for recovery. The membrane may also act as a direct force or pressure on the effluent once the vacuum is applied. 
         [0012]    The graduated design of the sidewall and conduits enable the same amount of volume at the upper portion of the apparatus as the lower portion near the drain. This results in a substantially equal vacuum pressure being applied to the entire surface area of the filter below the effluent and to the pliable, permeable or impermeable membrane above the effluent. The pliable cover acts to absorb the bulk of all vacuum pressure. By doing so, the entire force, over time, of the vacuum is applied to the effluent during the drying process. This force creates a pressurized internal processing chamber in which water evaporates at lower temperatures. With the additional application of external heat to the chamber, the apparatus can further reduce the water content of the effluent efficiently. 
         [0013]    The vacuum may be released and pulled several times in order to achieve the desired level of dryness for the solid component of the product in the container. Additionally, heat may be employed to speed the separation process, and the product may also be mixed or agitated for this reason. In one embodiment of the invention, heat and vacuum are employed to remove the liquid component from the solid component of the product or suspension in a rapid fashion. Sensors and automatic release valves may be used to ensure that the internal pressure does not reach an unacceptably high level. 
         [0014]    Once the solid component of the product in the container reaches a sufficient level of dryness, the membrane may be removed from the chamber. The dewatered or dried product should consist substantially of the solid component of the product, and may be removed from the container along with the membrane (such as by lifting the filter and any support structure (e.g., a screen or wire mesh) or vacuuming from above). Alternatively, an upper portion of the chamber may include a vacuum for drawing dried material from the lower portion of the chamber for recovery. In either case, once the recovery step is complete, the container is then once again ready to receive waste product. The removed product may then be subjected to further drying, if necessary for the proposed use. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1   a  is a schematic top view of one embodiment of the apparatus for separating liquid from a waste product forming one aspect of the invention; 
           [0016]      FIG. 1   b  is a partially cutaway side schematic view showing an exemplary arrangement of conduits associated with a container forming part of the apparatus of  FIG. 1   a;    
           [0017]      FIG. 1   c  is a partially cutaway cross-sectional view showing the manner in which a single conduit slopes in the vertical direction from an upper region or portion of the container to the lower portion; 
           [0018]      FIG. 1   d  illustrates the apparatus associated with a vehicle; 
           [0019]      FIG. 2   a  is a side schematic view illustrating in additional detail the apparatus of  FIG. 1 ; 
           [0020]      FIG. 2   b  illustrates a manner in which a system incorporating a plurality of the apparatuses for separating liquid from a waste product may be arranged; 
           [0021]      FIG. 3  is a partially cross-sectional side view of the sidewall of one possible embodiment of the container for receiving the waste product and removing water therefrom; 
           [0022]      FIG. 4  is a block diagram illustrating the possible progression of steps in the course of treating a waste product using the apparatus forming one aspect of the invention; 
           [0023]      FIG. 5  is a schematic view illustrating an embodiment of the apparatus forming another aspect of the invention; and 
           [0024]      FIG. 6  shows an apparatus formed according to one aspect of the invention in combination with a vehicle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIGS. 1   a - 1   d  depict one aspect of the invention, which includes at least one low profile, relatively compact bowl-shaped container  10  for use at an industrial site that produces a waste product, such as sludge. The container  10  may be buried in the ground or, alternatively, may be above ground and associated with a suitable support structure, if necessary, to ensure stability. Still another option is to associate the container  10  with a vehicle V, such as a flatbed truck or trailer (see  FIG. 1   d ), such that it may be easily transported from one site to another and thus becomes portable. 
         [0026]    As noted above, the container  10  is bowl-shaped, upstanding and preferably generally hemispherical with an open compartment or chamber  12  for receiving the product to be dried (i.e., dewatered). In a preferred embodiment of the invention, the chamber  12  is open at the top, and has a diameter of about ten feet or less. The container  10  can be made of any suitably strong material resistant to leaking and to reaction with the corresponding product. Examples of materials from which the container  10  may be constructed include concrete, plastic, steel, or other metal, with a preference for aluminum or stainless steel (primarily due to the superior corrosion resistance afforded). 
         [0027]    In a preferred embodiment, the container  10  is constructed of stainless steel or aluminum and, most preferably, aluminum. Specifically, the container  10  may comprise prefabricated components of a size that permits easy transport to the industrial site. The components may then be assembled at the industrial site. If warranted by the projected rate of waste product produced by the industrial site, multiple chambers may be used. This arrangement has the benefit of providing alternative receptacles for when one is full and undergoing the drying cycle, and also allows for varying filter media to be used in a graded fashion (thus allowing separation of finer particles in sequential processing applications). 
         [0028]    The container  10  includes a curved inner sidewall  14  having a plurality of conduits  16  formed therein. Preferably, the conduits  16  are generally arcuate, spaced apart grooves or channels formed in the sidewall  14  that, in view of the hemispherical nature, converge towards the bottom central region of the container  10 . As a result, and as best shown in  FIG. 1   a , the conduits  16  generally form a sunburst pattern. 
         [0029]    Most preferably, the conduits  16  are formed such that they are generally curved in cross-section and taper from a wider dimension adjacent an upper end or top of the sidewall  14  (e.g., 10 inches) to a narrower width dimension (e.g., 2 inches) adjacent the bottom, such as near the center. Also, as perhaps best understood with reference to the partially cutaway cross-sectional view of  FIG. 1   c , the conduits  16  preferably have a depth relative to the inner surface of the wall  14  adjacent the top of the container  10  that is infinitely small (i.e., approaching zero), and increase to a greater depth (e.g., 5 inches) adjacent the bottom. In any case, the conduits  16  serve to direct any fluid (water) or fluid suspension from the product in the container  10  to an outlet or drain  18  formed at or near the bottom center of the sidewall  14  for recovery. 
         [0030]    As can be understood viewing  FIG. 1   b , which is a linear representation of the sidewall  14  (which would actually be curvilinear) to simplify illustrating the inventive concepts, a filter  20  overlies and separates the conduits  16  from the product in the chamber, and preferably also covers the opening or drain  18  through which the vacuum is drawn and the liquid recovered. This filter  20  can be any material suitable for blocking solid particulate matter from a suspension, thus holding the solid particulate matter in place, but that allows liquid from the suspension to pass through. In a preferred embodiment, the filter  20  comprises a sheet of selectively porous material, such as a synthetic polymer based fabric in the form of a woven geotextile. Other suitable filter materials useful for practicing the invention are well known to those skilled in the art, for example, any perforated or porous material. Of course, an important consideration when selecting a filter for use with this invention is the size of the particulate (solid) matter in the suspension to be separated. Finer particulate matter would require a finer mesh filter in order to prevent the particulate matter from passing through the filter with the water. The most preferred embodiment allows for micron-based filtration. 
         [0031]    To prevent the filter material  20  from overly interfering with the flow of liquid in the conduits  16 , it is also preferable to provide a rigid or semi-rigid but fluid pervious barrier material, such as a screen. This screen may be hemispherical in shape (now shown) and simply placed in the chamber  12  above or below the filter material  20 , or instead may comprise individual inserts  21  for the container  10  that engage or overlie the conduits  16  (either above or below the filter material  20 ). The underlying conduits  16  may also be coated with an inert material, such as TEFLON, to reduce wear on the surface and flow resistance. 
         [0032]    In a preferred embodiment, the container  10  including the waste product is covered in use. This covering may be accomplished using a sheet of covering material, such as a flexible or non-flexible membrane  22  to create a substantially air-tight seal with the open end of the container  10 . In a preferred embodiment, the membrane  22  is a removable, flexible, substantially impermeable membrane made, for example, of natural or synthetic rubber, neoprene, or like rubber substances. In a most preferred embodiment, the membrane  22  is semi- or selectively permeable in order to allow some gas, such as ambient air, to pass through it. Other suitable membrane materials should be readily apparent to those skilled in the art. 
         [0033]    Preferably, the membrane  22  is placed over the chamber  12  and fastened to the upper end of the sidewall  14  (which as shown may be substantially planar) using a substantially air-tight means, for example, using bolts B (see  FIG. 2   a ) or any other suitable fastening means (and possibly in further connection with seals, adhesives gaskets, or the like). The membrane  22  may also be mounted to a frame, which in turn may associated with means for positioning the membrane relative to the open end of the container  10  (such as a hydraulic lift  23  or the like for pivoting the frame and membrane together as a unit; see  FIG. 1   a ). 
         [0034]    When a pressure differential is created in the chamber  12 , such as by pulling a vacuum through the outlet or drain  18  using a pump, motor, or the like with the membrane  22  in place (see  FIG. 2   a ) the differential pressure is substantially evenly distributed across the surface of the contents through the conduits  16  as a result of the bowl-shaped design. In this way, the membrane  22  and the vacuum applied to the inside of the container  10  act together as a means to decrease pressure therein to create a differential pressure and consequently “squeeze” the contents of the chamber  12 . This applied squeezing forces liquid, such as water, from the chamber  12 , through the filter  20 , into the conduits  16 , and through the drain  18  for recovery. However, the solids for the most part are prevented from passing as the result of the filter  20  and any screen(s)  21  present. The liquid fraction recovered may then undergo further processing, such as polishing, for use in other applications, Heat may be provided for increasing the temperature of the product contained in the chamber  12 . In many applications, heating the product speeds the rate of drying by both increasing the rate of filtration and increasing the rate of evaporative drying. Furthermore, as pressure decreases the vaporization point of all liquids, the negative pressure enables low levels of induced heat to turn liquids into gas and be safely removed from the effluent. The heating element may be an electric resistive heating element, a gas heater, or any other suitable heating means. In a preferred embodiment, as shown in the partially exploded, cutaway, top view of  FIG. 3 , the heating element consists of one or more delivery lines  24  embedded in the sidewall  14  of the chamber  12 , such as between the conduits  16 , thus allowing steam or heated fluids to be circulated to elevate the temperature of the product contained therein. However, as indicated in  FIG. 2   a , the heat could also be supplied by lines positioned in and/or extending along the inside of the chamber  12 . In either case, it should be appreciated that the applied heat may further effect drying through the partial evaporation of the liquid content. 
         [0035]    The process of pulling a vacuum for a time, then releasing the vacuum, may be repeated several times as required until the remaining solids are sufficiently dry for their intended purpose. If a drier product is required, the process may need to be repeated for some time. Often, however, some remaining moisture is desirable, especially for products containing finer particulate matter, so that the fine solids can be unloaded and transported with minimal spillage (that is, the remaining moisture serves as a binder). Before initiating the any vacuum, it is also of course possible to allow for gravity to effect naturally some initial liquid separation, which of course saves energy. 
         [0036]    Sensors and pressure release valves may be associated with the chamber  12  to prevent dangerous internal pressure levels from occurring. These valves may be set electronically depending on the substances being processed and their combustion point. For instance, in municipal waste processing, methane within the effluent that is under direct pressure and heat may become volatile at certain levels. The pressure sensors may be used to detect this and trigger the release valves to open and reduce the internal pressure. 
         [0037]    Once the product is sufficiently dried, it may be removed from the chamber  12 . This may be accomplished by removing the membrane  22  and then simply scooping out the product. However, the compact, low-profile nature of the bowl-shaped container  10  of the invention also allows for it to simply be lifted for dumping out the dried contents using an adjacent means, such as a hydraulic lifter  26  associated with a pivot axis  28 . In such case, the arrangement of the drain  18  would be such that it may be easily detached or otherwise disconnected from any associated line(s) for the vacuum or liquid takeaway. 
         [0038]    In order to speed the drying process, a system including at least one of the containers  10  may include a dryer  30  for drying the remaining product once a substantial portion of the liquid is removed. In the embodiment shown in the drawing figures, the dryer  30  is associated with a conveyor  32  on which the remaining substantially dried product is placed, and may pass through a heater  34 . Preferably, the infeed end of the conveyor  32  is positioned such that the product can be dumped directly on it as a result of the reorientation of the container  10  using the lifter  26 . 
         [0039]    In another system, and as shown with reference to  FIG. 2   b , two of the apparatus  10 ,  100  may be used in series. As shown, the containers  12 ,  112  may be in communication with common vacuum source, as well as possibly with one or more additional downstream vacuum sources (pump or motor), as shown in  FIG. 2   b . As noted above, an array or series of the containers  10  may also be used as necessary to simultaneously process a large amount of waste product in parallel, each operating independently. 
         [0040]    In an alternate embodiment, as shown in  FIG. 5 , the bowl-shaped container  10  may be of a clamshell design, formed of two hemispherical bowl-shaped upper and lower portions  10   a ,  10   b , and thus forming a generally spherical body. The upper bowl portion  10   a  serving as the cover in this embodiment would have direct valves into the lower bowl portion  10   b  through any membrane  22 , thus allowing for a closed system. When the valve is open, a vacuum may also be applied to the upper bowl portion  10   a  to remove dry materials from the lower portion  10   b , while smaller blowers associated with the side walls circulate the dry material in a cyclone-like fashion while the vacuum is applied from the top. If used, the semi-permeable membrane  22  would thus allow some hot, dry air (note action arrows A) to pass into the lower bowl portion  10   b  when the vacuum is applied thereto. 
         [0041]    With reference to  FIG. 5 , it is also shown that a mixer M or agitator, such as a rotatable mixing blade, may be provided to churn the dried yield in the lower bowl portion  10   b . The upper bowl portion  10   a  may then be used as the vacuum point to remove the dried and loosened yield for recovery. In lieu of a mechanical mixer, it is possible in this or any of the embodiments disclosed to agitate the contents by reversing the vacuum motor in order to cause air to flow back through the conduits  16 , the filter material  20 , and any screen(s)  21  present (which may or may not require opening a pressure release valve, depending on the relative permeability of the membrane  22  used). This would essentially provide a sparging function to the container  12 . 
         [0042]    The foregoing description provides illustration of the inventive concepts. The descriptions are not intended to be exhaustive or to limit the disclosed invention to the precise form disclosed. Modifications or variations are also possible in light of the above teachings. For example, a positive pressure may be used to create the differential pressure in the chamber of the container, such as by pressurizing the space between the liquid-solid product and the cover (membrane). Additional modifications to the bowl-shaped container  10  can also be made, as disclosed in U.S. Published Patent Application No. 2002/0113014, the disclosure of which is incorporated herein by reference. The embodiments described above were chosen to provide the best application to thereby enable one of ordinary skill in the art to utilize the inventions in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention.