Abstract:
An apparatus for filtration has a feed of sludge, containing liquid, solids and gases fed into a tank, the tank containing at least one spinning separation filter comprising a filter cone set having a filter screen, and a barrier cone, arranged roughly in parallel, and defining a conical workspace between them, the conical workspace having a peripheral opening to the tank and a central opening communicating with the interiors of one or more hollow shafts supporting the barrier cone and the filter cone, the upper shaft supporting the barrier cone having an upper axial channel for the exit of gases, the lower shaft supporting the center of the filter cone having a lower axial channel for the exit of liquid or oil, motor means for producing rotation in said at least one spinning separation filter, and a filtrate liquid reservoir located underneath the filter cone for capturing the filtrate passing through the filter screen.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/392,657, filed Jun. 6, 2016. 
     
    
     BACKGROUND 
       [0002]    Sludge dewatering filters have generally included screw and roller presses as well as filter screens, which typically require backwash cycles to prevent the filter from becoming clogged. Annular crossflow filters such as the McCutchen TriPhase Filter U.S. Pat. No. 7,757,866 (Jul. 20, 2010) feature an annular crossflow filter in at least one spinning disk, whose motion generates a shear lift effect which helps to keep the solids from clogging the filter. The faster the disk can spin, the greater will be the crossflow motion relative to the feed and the greater the shear lift effect. However, the centrifugal force from a rapidly spinning disk will make the feed move more rapidly outward across the filter surface, and reduce the time for the filtration to take place. While this approach can separate liquids, solids and gas phases, it cannot also at the same time separate a liquid oil phase. What is needed is a way to make best use of a shear lift effect for filtration from a spinning filter surface, with an increased residence time, and a simultaneous separation of solid, liquid, gas and oil phases. 
       SUMMARY 
       [0003]    A feed of sludge, containing liquid, solids and gases enters a tank containing at least one spinning separation filter comprising a filter cone set with a filter screen and a barrier cone, arranged roughly in parallel, and defining a conical workspace between them. This workspace has a peripheral opening to the tank and a central opening. The central opening communicates with the interiors of one or more hollow shafts supporting the upper barrier cone and the lower filter cone. The upper shaft supporting the barrier cone has an upper axial channel for the exit of gases, and the lower shaft supporting the center of the filter cone has a lower axial channel for the exit of liquid or oil. 
         [0004]    A filtrate liquid reservoir is located underneath the filter cone for capturing the filtrate passing through the filter screen. For a single filter cone in the tank, the outer edge of the rotating filter cone is supported by a leak-proof connection to a static cylindrical wall which circumscribes the filtrate liquid reservoir. For multiple stacked filter cone sets in the tank, the filtrate liquid reservoir is incorporated into each spinning filter cone set, with the filtrate exiting through a return pipe to the central axial shaft drain, and the underside of the filter cone set acts as the barrier cone defining the workspace for the next filter cone set farther down in the sequence. 
         [0005]    In the tank, the feed enters the tank into the feed zone, which includes the portion of the tank above the opening to the workspace. The portion opposite the workspace opening is the I/O zone, and the portion below the I/O zone is the solids zone, where the solids rejected from the filter surface are ejected by the motion of the filter cone. 
         [0006]    Vanes on the backside of the rotating barrier cone can serve to advect the feed to improve its flow into the workspace. As the feed enters the workspace, it is advected by the spinning barrier and filter disks. As the filtrate liquid falls through the filter disk into the filtrate liquid reservoir to be extracted, the rejected solids are spun outward to re-enter the tank into the solids zone, where the concentrated solids exit through a solids drain. Meanwhile, as gases are drawn inward from the workspace by low pressure and exit through the upper axial channel, liquid oil riding on the top of the feed will overflow into the lower axial channel for extraction. Thus, multiple phases of liquids, solids, gases and oil can be continuously separated. 
         [0007]    For a stacked set of filter cone sets, the filtrate exits into a central axial drain. If the tank is divided vertically into one or more stages, then the filtrate from a first stage can re-enter the next stage of the tank from the center outward, then enter from the outside in through the one or more workspaces of the next stage. The filter screens, angles or rotation characteristics of each stage can be varied, to make a sequential processing sequence, such as to screen to successively finer levels of separation. 
         [0008]    For backwashing a single filter cone, a relatively static backwash hose in close proximity to the filter screen can force liquid back through the rotating filter, with, for example, a linear radial motion of the hose from one end to the other being sufficient to cover the area of the rotating filter screen. 
         [0009]    For backwashing a stacked filter set, reversal of the direction of rotation of the filter sets will serve to pump liquid or filtrate back from the central axial drain, through the return pipes and the liquid filtrate reservoir, and back through the filter screen to clean it and reject the solids outward. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a cross section of an embodiment of a biconical multiphase rotary filter. 
           [0011]      FIG. 2  shows an embodiment of a pattern for cutting a filter cone. 
           [0012]      FIG. 3  shows detail of a filter edge showing scalloped design. 
           [0013]      FIG. 4  shows a schematic half cross section of stacked filter sets. 
           [0014]      FIG. 5  shows a schematic cross section showing return channels. 
           [0015]      FIG. 6  shows a system with stacked filter sets. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Listed parts 
         [0017]      2 . Feed 
         [0018]      4 . Tank 
         [0019]      6 . Feed inlet 
         [0020]      8 . Feed zone 
         [0021]      10 . Flow pattern 
         [0022]      12 . Vanes 
         [0023]      14 . Rotating barrier cone 
         [0024]      16 . Axial upper shaft 
         [0025]      18 . Upper axial chamber 
         [0026]      20 . Direction of rotation for barrier cone 
         [0027]      22 . Upper rotation motor 
         [0028]      24 . Mechanical coupling means for upper motor 
         [0029]      26 . Upper elements 
         [0030]      28 . Holding tank with gas exit 
         [0031]      30 . Rotary seal for upper elements 
         [0032]      32 . Gas holding tank 
         [0033]      34 . Filter cone 
         [0034]      36 . Workspace between cones 
         [0035]      38 . Filter screen 
         [0036]      40 . Filtrate 
         [0037]      42 . Filtrate liquids reservoir 
         [0038]      44 . Outer cone ring 
         [0039]      46 . Support ribs 
         [0040]      48 . Center block 
         [0041]      50 . Lower axial shaft 
         [0042]      52 . Filter cone direction of rotation 
         [0043]      54 . Filter cone motor 
         [0044]      56 . Mechanical coupling means for filter cone 
         [0045]      58 . Lower elements 
         [0046]      60 . Lower axial channel 
         [0047]      62 . Rotary seal for lower elements 
         [0048]      64 . Oil holding tank 
         [0049]      66 . Pump 
         [0050]      68 . Liquids reservoir 
         [0051]      70 . Drain 
         [0052]      72 . Top of filtrate liquids reservoir wall 
         [0053]      74 . Reservoir wall 
         [0054]      76 . Inner seal strip 
         [0055]      78 . Outer seal strip 
         [0056]      80 . Danes on outer surface of outer seal strip 
         [0057]      82 . Solids zone 
         [0058]      84 . Solids outlet 
         [0059]      86 . Rejected solids stream 
         [0060]      88 . I/O zone 
         [0061]      90 . Inward stream into workspace 
         [0062]      92 . Optimal line for filling workspace 
         [0063]      94 . Gas outlet pump 
         [0064]      96 . Central space 
         [0065]      98 . Filter screen outer edge 
         [0066]      100 . Overlap seam 
         [0067]      102 . Central outlet hole 
         [0068]      104 . Cross section of cone shape 
         [0069]      106 . Scalloped pattern 
         [0070]      108 . Direction of rotation 
         [0071]      110 . Flow pattern 
         [0072]      112 . Filter cone surface 
         [0073]      114 . Feed zone flow pattern 
         [0074]      116 . Axis of rotation 
         [0075]      118 . Filtrate reservoir in stacked set 
         [0076]      120 . Return pipe 
         [0077]      122 . Return flow to central drain 
         [0078]      124 . Underside of filter cone for stacked set 
         [0079]      126 . Vent holes 
         [0080]      128 . Axial drain with closed top 
         [0081]      130 . Stacked filter set 
         [0082]    This disclosure can be applied to the filtration of a wide variety of feeds, including seawater, manure, mined material, industrial waste, food processing, polluted sediments, and wastewater. The advantages of this disclosure are the continuous nature of the process, the non-clogging nature of the rotating filter wheel, the separation of several phases at once, and the relative low cost and mechanical simplicity of this approach. 
         [0083]    The filter cone set and its associated parts will first be described for a single cone set arrangement, and then for an arrangement with stacked filter cone sets, to increase the effective filter surface within a compact space. 
         [0084]    In  FIG. 1 , illustrating a single filter cone set, a feed  2  enters a tank  4  though a feed inlet  6  into a feed zone  8 . Within the tank  4 , the feed in the feed zone can be advected in a flow pattern  10  by vanes  12  on the rotating barrier cone  14 . 
         [0085]    The barrier cone  14  is supported by an axial upper shaft  16 . This shaft is hollow, with an upper axial channel  18 . The barrier cone is rotated in a direction  20  by mechanical force applied to the upper shaft, such as by a rotation motor  22 , coupled to mechanical coupling means  24  for transmission of force to the shaft such as a direct coupling, or indirect means such as drive wheels, fan belts, chains or gears, with appropriate bearings and support frames. These upper rotation elements  26  should be located outside of the tank  4  for durability and to ease maintenance. The upper elements also include means for capturing any extracted gas coming out of the upper axial channel  18 , such as a holding tank with a gas exit  28 . To prevent leaks, a rotary seal  30  should be used where it exits the tank  4  and where it enters the gas holding tank  32 . 
         [0086]    Below the barrier cone  14  is the filter cone  34 . The two cones  14  and  34  are arranged to be roughly parallel, and define a workspace  36  between them. Roughly parallel includes the cases where the workspace has a changing separation distance between the disks in a radial direction from the axis to the periphery of the workspace, such as where the separation is wider at the periphery, and tapers either in a straight line or in a curved profile toward the axis. The cones can be coaxial, or they can be offset from each other, so that the workspace is wider on one side than the other. This allows for an arrangement where the workspace is wider on one side for a different pattern of inward flow of the feed and outward flow of the solids, such as where the wider workspace allows more inward and outward flow, and the narrower space has higher pressure for more filtrate to flow through the filter cone. 
         [0087]    The filter cone is primarily comprised of a filter screen  38  typically shaped into a cone. The cone shown here has a corner angle of thirty degrees. The cone shape is designed to allow for an optimal balance of forces for filtration at the filter surface. The feed  2  is first forced inward into the workspace, due to the fact that the disks are submerged, augmented by the flow pattern  10  caused by the vanes  12  on the barrier cone  14 , and optionally from relatively low pressure applied such as in the upper axial channel  18  to help suck in the feed  2 . Both the rotation of the filter cone and the shear lift effect combine to keep the solids away from the filter screen  38  surface while allowing the filtrate liquid to pass through the pores as filtrate  40  into the filtrate liquids reservoir  42 . 
         [0088]    One example support structure for the shape of the filter cone is an outer cone ring  44  connected by support ribs  46  to a center block  48  coupled to the lower axial shaft  50 , which is turned in a direction of rotation  52  by mechanical force applied to the lower shaft, such as by a motor  54 , coupled to mechanical coupling means  56  for transmission of force to the shaft such as a direct coupling or indirect means such as drive wheels, fan belts, chains or gears, together with appropriate bearings and support frames. These lower elements  58  should be located outside of the tank  4  to ease maintenance. The lower elements  58  also include means for capturing any extracted oil or overflow coming through the lower axial channel  60 . To prevent leaks, rotary seals  62  should be used where it exits the tank  4  and where it enters the oil holding tank  64 , where a pump  66  can be used to extract the oil for use. Similarly, the filtrate liquid is drained from the liquids reservoir  68  through one or more drains  70  and optional pumps. 
         [0089]    It is important to maintain an effective seal between the liquids reservoir  68  and the rest of the interior of the tank  4 , so as to prevent contamination of the filtrate. For this reason, one possible method of maintaining this separation is to have a rotary seal formed between the outer edge of the filter cone  44  and the top  72  of the cylindrical wall  74  of the liquids reservoir  68 . This can be done for example by flexible cylindrical strips of a suitable material such as vinyl or a flexible plastic which are attached to the filter cone  34  and rotate along with it. The inner seal strip  76  will tend to be forced against the reservoir wall  74  by the centrifugal force of the cone&#39;s rotation, thus maintaining the seal, and the outer seal strip  78  can also be forced inward against the wall by the addition of vanes  80  on the outer surface of the strip, which push the strip inward due to the resistance from the vanes&#39; passage through the denser material in the solids zone  82 , which lead to the solids outlet  84 . 
         [0090]    The solids zone  82  receives the rejected solids stream  86  from the filter cone  34  coming from the I/O zone  88 , while the simultaneous inward feed stream into the workspace in the I/O zone is shown at  90 . 
         [0091]    In operation, the optimal approximate line for filling the workspace is shown at  92 . This allows the maximal use of the filter surface area of the filter cone for removing the liquid, while allowing occasional overflow of any oil floating atop the feed to spill into the lower axial channel  60  for collection. To maintain this optimal line, the gas outlet pump  94  can be used to raise or lower the pressure in the upper axial channel  18  and the central space  96  to draw in or push back the feed level as needed. 
         [0092]    If backwash cleaning of the cone filter is needed, then the filtrate liquid reservoir  68  can be filled with the cleaning fluid while the workspace and the outer tank are drained down to the line of the solids zone, and the cleaning fluid forced back through the filter. As an alternative to increase the local pressure against the back side of the filter screen, the backwash fluid can be pumped through a static radial hose with an outlet slot adjacent to the backside of the rotating filter surface, to force the sediments back through the rotating screen into the workspace to be rejected into the solids zone. 
         [0093]    The filter cone can have different types of filter screens as needed for the task. For example, perforated stainless steel sheets can form the cone, with round holes in a dense pattern. The round holes have advantages for setting up swirling vortex patterns around each hole due to crossflow which help to exclude the solids, as has been shown by van Dinther et al. “High-flux membrane separation using fluid skimming dominated convective fluid flow”. Other types of filter screens or sheets can be used, made of metal plastic, ceramic or other suitable screens, and can be incorporated into the filter cone either in sections or as a large continuous surface. Microfiltration filter screen can be used, and to help force the filtrate through fine pores, the feed chamber  8  and workspace  36  can be pressurized relative to the filtrate liquid reservoir  68 . 
         [0094]    A pattern for cutting or stamping out a filter screen is shown in  FIG. 2 . The screen outer edge  98  corresponds to the outer edge of the larger dimension of the cone. The edges of a cutout with an optional overlap seam  100  are coupled to form the cone shape, including a hole for the central outlet  102 . A cross section of the resulting cone shape is shown at  104 . 
         [0095]    The flow patterns in the workspace are important for the operation of the filter cone. The form of the barrier disk can be a smooth cone, or it can have vanes or ridges, which can be stamped,  3 D printed, cast or otherwise formed in a cost-effective way. As shown in a cross section of one example in  FIG. 3 , a barrier cone in a scalloped pattern  106  when in a direction of rotation  108  will advect the feed in the workspace  36  into a flow pattern  110  that intermittently forces the feed first toward and away from the filter cone surface  112 . On the back side of the barrier cone, the feed in the feed zone will also be advected in a pattern  114 . The ridges or vanes in the barrier cone may be radial to the axis, or slanted to form advecting vanes. 
         [0096]    The direction of advection caused by the ridges or vanes on the inside of the barrier cone and the outside may be the same, or may need to be different. For example, the vanes on the outside of the barrier cone may advect the feed toward the axis, as is shown at  10  in  FIG. 1 , while the vanes facing the workspace  38  may need to advect away from the axis to sweep out the rejected solids. That means that the inside and outside surfaces of the barrier cone must have oppositely slanted vanes. 
         [0097]    The filter and barrier cones may be co-rotating, or counter-rotating, as shown in  FIG. 1 . The cone pairs may also be stacked, as long as each cone pair has its own workspace, and the filter disk has its own filtrate liquid reservoir. For example, another cone pair can be located in the filtrate liquid reservoir  68 , with a smaller diameter to fit within the filtrate liquid reservoir  68 , and a second filtrate liquid reservoir under the second filter cone for the re-filtered filtrate. 
         [0098]    An integrated stacked filter set design is shown in a schematic half cross section in  FIG. 4 . The axis of rotation is shown at  116  and a representation of the tank is at  4 . In this design, there are multiple stacked filter sets, each set having a filtrate liquid reservoir  118  beneath the filter screen  38 , and a return pipe  120 . The motion of rotation of the filter set  130  serves to force the filtrate out of the filtrate reservoir  118  through the return tube in a flow  122  which brings the filtrate inward to a central axial drain  124 . The underside surface of the filter cone  126  in this case is designed to act as a barrier cone for the filter set below. 
         [0099]    An example of this stacked filter set  130  is seen from below with the barrier cone surface  126  removed in  FIG. 5 . The motion of rotation of the filter set  132  serves to force the filtrate out of the filtrate reservoir  118  through the return tube in a flow  122  which brings the filtrate inward to a central axial drain  124 . Vent holes in the central support between the return pipes are shown at  134  which allow gases to escape vertically at the top of the workspaces of the stacked filter sets. 
         [0100]    A view of the apparatus with stacked filter sets is shown in  FIG. 6 . The stack is shown enclosed in a tank  4  with the barrier cone  14  at the top rotated by an upper rotation motor  22 , and the stacked filter sets rotated by a bottom rotation motor  54 . The relative rotations can be counter-rotation, co-rotations or rotations at different speeds. The return pipe  120  in each stacked filter set  130  returns the filtrate to a central drain  124 , where a filtrate pump  66  aids in extraction, especially then the top of the drain pipe is closed, as is shown here, so suction through the return pipe can be created. To backflush the filter screens, the filtrate pump can be reversed to force the filtrate back through the filter screens, and this can be aided by a reversal of the direction of rotation of the filter sets also will help force the filtrate back through the return pipes in the opposite direction. The rejected solids, or the backwashed solids from the filter screens, will concentrate in the tank to be extracted through drains, which can include components such as filters, or devices such as screw conveyors. 
         [0101]    If the tank and the central drain is divided vertically into one or more stages, then the filtrate from a first stage can re-enter the next stage of the tank from the center outward, then enter from the outside in through the one or more workspaces of the next stage. The filter screens, angles or rotation characteristics of each stage can be varied, to make a sequential processing sequence, such as to screen to successively finer levels of separation. 
         [0102]    For backwashing a single filter cone as shown in  FIG. 1 , a relatively static backwash hose in close proximity to the filter screen can force liquid back through the rotating filter, with, for example, a linear radial motion of the hose from one end to the other being sufficient to cover the area of the rotating filter screen. 
         [0103]    The tank should be of a suitable size and shape for long operation and low cost. It can be cylindrical, which could produce symmetrical inlet and outlet flow patterns in the I/O zone  88  relative to the edges of the disks. Or it can be rectangular or square, which could produce relative “dead zones” in the corners which aid in the settling of the solids in the solids zone  82 . One example is the Den Hartog ST0120-32 120 gallon polyethylene tank, which roughly in the shape of a tall cube, and has fluted sides, which increase its strength and also can further disrupt the motion of the feed and encourage settling in the lower corners, where the drain outlets are located. 
         [0104]    The frames to support the tank and the mechanical components on the top and bottom should be mated to the tank and designed for durability and easy maintenance. 
         [0105]    This simple and scalable approach to filtration should have many applications. For example, filtration down to 0.5 microns (the width of the rod of a cholera virus) would protect water supplies, including the ballast water on ships. Dewatering sludge, including agriculture and industrial waste, allows the water to be recycled while the solids can into products by means such as the applicant&#39;s Shear Retort (U.S. Pat. No. 9,011,646) for pyrolysis. 
         [0106]    While the present embodiments have been particularly shown and described above, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present embodiments as defined by the following claims.