Abstract:
A filtration system comprising a floor panel and a plurality of wall panels connected to each other to define a box, at least one filtering wall vertically inclined and supported inward of a corresponding wall panel such as to define a first free space therebetween, a filtering floor horizontally inclined and supported above the floor panel such as to define a second free space therebetween, the filtering floor being connected to the filtering wall to define a filter chamber, a plurality of openings defined in the filtering wall and the filtering floor sized to let a liquid pass through and retain at least one target solid within the filter chamber, an inlet in fluid communication with the filter chamber, and an outlet in fluid communication with the first and second free spaces. A method of filtering at least one target solid from a liquid is also provided.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to filtration systems, particularly to such systems using gravitational drainage to filter at least one target solid from a liquid for separate disposal or recovery.  
         [0003]     2. Background Art  
         [0004]     Numerous industrial processes produce waste material in the form of a sludge which is composed of a liquid and at least one solid that must be separated for disposal or recovery of the components. Examples of such waste material include waste from animal or vegetal agri-food industries, manure, industrial sludge from fabrication processes of various products, used water, wet contaminated soil, etc. Typically, the liquid is separated from the solid using a filter which will retain the solid and let the liquid pass through. Generally, the fluid can be drawn through the filter either by gravity or by the use of a vacuum produced by a pump.  
         [0005]     There exists a number of filter assemblies located within a mobile box, with a free space in the box around the filter assembly for receiving the liquid, such as is described in U.S. Pat. Nos. 4,929,353 and 6,004,461, both to Harris, and U.S. Pat. No. 6,258,268 to Lake. Although such assemblies rely on gravity to extract the liquid from the sludge through the filter bed, the side filters, which are vertical, rely mainly on capillary action to force the liquid therethrough, which is slower and less efficient.  
         [0006]     In addition, the systems presented in these patents usually require the change of filter material and/or mesh size when the nature of the material to be filtered is changed, thus preventing the manufacture of standard filter panels than can be employed with a variety of materials to be filtered.  
         [0007]     Accordingly, there is a need for a mobile gravitational filtration system with increased efficiency, which can use standard filter panels for a variety of materials to be filtered.  
       SUMMARY OF INVENTION  
       [0008]     It is therefore an aim of the present invention to provide a gravitational filtration system having an increased efficiency.  
         [0009]     It is another aim of the present invention to provide a filtration system with filtering walls using gravity to separate a liquid from at least one target solid.  
         [0010]     It is a further aim of the present invention to provide a filtration system comprising standard filtration panels adapted for a variety of materials to be filtered.  
         [0011]     Therefore, in accordance with the present invention, there is provided a filtration system for separating at least one target solid from a liquid, the filtration system comprising a floor panel, a plurality of wall panels, the wall panels being connected to each other and to the floor panel to define a box, at least one filtering wall inclined with respect to a vertical plane such that a bottom edge thereof is located inward of a top edge thereof, the at least one filtering wall being supported inward of a corresponding one of the wall panels such as to define a first free space therebetween, a filtering floor inclined with respect to a horizontal plane along a first direction and supported above the floor panel such as to define a second free space therebetween, the filtering floor being connected to the at least one filtering wall to define a filter chamber, a plurality of openings defined in the at least one filtering wall and the filtering floor, the plurality of openings being sized to let the liquid pass through and retain the at least one target solid within the filter chamber, an inlet in fluid communication with the filter chamber, and an outlet in fluid communication with the first and second free spaces, whereby the liquid and the at least one target solid enter the filter chamber through the inlet in a mixed state, the at least one target solid being retained within the filter chamber while the liquid reaches the first and second free spaces through the plurality of openings before being evacuated through the outlet.  
         [0012]     Also in accordance with the present invention, there is provided a method of filtering at least one target solid from a liquid comprising the steps of providing a box having a floor panel and a plurality of wall panels, determining the nature of the liquid and target solid, selecting a filtering floor according to the nature of the liquid and target solid, installing the filtering floor above the floor panel such as to define a first free space therebetween, selecting an inclination angle for at least one filtering wall according to the nature of the liquid and target solid, installing the filtering wall inward of a corresponding one of the wall panels and at the selected inclination angle such as to define a second free space therebetween, connecting the filtering wall to the filtering floor to define a filter chamber, and pouring the liquid and target solid in the filter chamber so that the target solid is retained therein while the liquid passes through at least one of the filtering floor and filtering wall to be collected in at least one of the first and second free spaces.  
         [0013]     Further in accordance with the present invention, there is provided a filtration system to filter a sludge, the filtration system comprising a box having impermeable bottom and side walls to form a container, at least a first filtration panel spaced from the bottom wall and defining a first plenum therebetween, the first filtration panel having a slope relative to a horizontal plane in a predetermined direction, at least a second filtration panel spaced from one of the side walls and defining a second plenum therebetween, the second filtration panel having an inward slope relative to a vertical plane, the first and second filtration panels being such as to permit a liquid from the sludge to pass through to the respective plenums while retaining a least one solid from the sludge above the filtration panels, and means for draining the liquid from the first and second plenums. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment of the present invention and in which:  
         [0015]      FIG. 1  is a perspective view of a filtration system according to a preferred embodiment of the present invention;  
         [0016]      FIG. 2  is a side view, in cross-section, of the filtration system of  FIG. 1 ;  
         [0017]      FIG. 3  is a front view, in cross-section, of the filtration system of  FIG. 1 ;  
         [0018]      FIG. 4  is a front view, in cross-section, of a filtration system according to a first alternative embodiment of the present invention;  
         [0019]      FIG. 5  is a front view, in cross-section, of a filtration system according to a second alternative embodiment of the present invention; and  
         [0020]      FIG. 6  is a front view, in cross-section, of a filtration system according to a third alternative embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Referring now to  FIGS. 1-3 , a filtration system  10  according to a preferred embodiment of the present invention is shown. The filtration system  10  comprises a box  12  receiving therein a filtering assembly  14 .  
         [0022]     The box  12  includes a floor panel  16 , a front wall panel  18 , two side wall panels  20 , a rear wall panel  22  and two top wall panel portions  24 . The wall panels  18 , 20 , 22 , top panels portions  24  and floor panel  16  are rectangular and interconnected to define a sealed enclosure  26  having a partially open top. Preferably, the wall panels  18 , 20 , 22  extend perpendicularly to the floor panel  16  and to the top wall panel portions  24 .  
         [0023]     The box  12  is preferably a truck box of a roll-off type, such as to be carried by a truck. Alternatively, the box  12  can be a trailer such as to be directly towed by a vehicle. The rear wall panel  22  is connected to the rear top wall panel portion  24  through hinges  27  such as to be openable to facilitate cleaning of the enclosure  26  and filtering assembly  14 . The rear wall panel  22  is maintained in a sealed closed position by a plurality of locks  29  engaging the side wall panels  20  and floor panel  16 . Alternatively, the rear wall panel  22  can be hingedly connected to one of the side wall panels  20  or to the floor panel  16 , or be completely removable.  
         [0024]     The rear wall panel  22  includes at least one and preferably two to four outlets  28  along a bottom part thereof, the outlets  28  being alternatively opened and closed by appropriate means such as valves or removable caps. The partially open top acts as an inlet to the box  12 . Alternatively, the box  12  can have a closed top with an inlet, such as a pipe, incorporated therein.  
         [0025]     The floor and wall panels  16 , 18 , 20 , 22 , 24  of the box  12  are preferably made of metal such as steel or aluminium.  
         [0026]     The filtering assembly comprises a filtering floor  30 , a front filtering wall  32 , and two side filtering walls  34 . The filtering walls  32 , 34  are preferably rectangular. The filtering floor  30  has a front edge  36  connected to the front filtering wall  32 , side edges  40  that are each connected to a respective one of the side filtering walls  34 , and a rear edge  38  sealingly engaged to the rear wall panel  20 . The filtering walls  32 , 34  are connected to each other and the side filtering walls  34  each have a rear edge  42  sealingly engaged to the rear wall panel  20 . Thus, a filter chamber  44  is defined by the filtering walls  32 , 34 , the filtering floor  30  and the rear wall panel  20 . It is also contemplated to provide a rear filtering wall similar to the front filtering wall  32  or to use fewer filtering walls, e.g. omitting the front filtering wall  32  and sealingly engaging a front edge of each of the side filtering walls  34  to the front wall panel  18 .  
         [0027]     As can be best seen in  FIG. 3 , the filtering floor  30  includes two vertically inclined filtering panels  46 , each having a bottom edge forming one of the side edges  40  of the filtering floor  30 . The filtering panels  46  are inclined toward each other with top edges thereof connected by a filtering strip  48 . It is also contemplated to have the top edges of the filtering panels  46  directly connected to each other.  
         [0028]     The filtering floor  30  is supported above the floor panel  16 , such as by metal channels, to define a first free space  50 , or plenum, under the filter chamber  44 , between the filtering floor  30  and floor panel  16 . The first free space  50  is in fluid communication with the outlets  28  defined in the rear wall panel  22 . As can be best seen in  FIG. 2 , the filtering floor  30  is inclined with respect to a horizontal plane (shown in broken lines) to improve filtration by minimizing stagnation of solid waste on the filtering floor  30 . The front edge is  36  preferably higher than the rear edge  38  to facilitate cleaning of the filter chamber  44  through the open rear wall panel  22 . A preferred inclination is represented by a height difference between the front edge  36  and the rear edge  38  of between 19.05 and 50.8 millimeters (¾ inch and 2 inches, respectively), for a filtering floor having a length of 8.5 meters (28 feet).  
         [0029]     Referring to  FIG. 3 , each of the side filtering walls  34  extends inward of a respective one of the side wall panels  20  such as to define a second free space  52 , or plenum, therebetween. The side filtering walls  34  are vertically inclined, with a bottom edge  54  thereof located inward of a top edge  56  thereof. Preferably, the top edge  56  is connected to the corresponding side wall panel  20 . A preferred inclination is represented by the filtering side wall  34  forming an angle of about  10  degrees with the vertical side wall panel  20 . As seen in  FIG. 2 , the front filtering wall  32  similarly extends inward of the front wall panel  18  in a vertically inclined position, the second free space  52  thus being defined around the front and sides of the filter chamber  44 . The second free space  52  is in fluid communication with the outlets  28  through the first free space  50 .  
         [0030]     The filtering floor and walls  30 , 32 , 34  are preferably made of an outer structural frame  58  (see FIG. l) supporting a wire mesh  60  (see  FIG. 3 ) which, in turn, supports a filtering membrane  62  (see  FIG. 3 ) forming the inner surface of the filter chamber  44 . The structural frame  58  is preferably composed of metal channels. The wire mesh  60  is preferably metallic, with openings having a size between 6.35 and 25.4 millimeters (¼ and 1 inch). Preferred metals for the structural frame  58  and wire mesh  60  are stainless steel and aluminium. The filtering membrane  62  is preferably made of Textilene™, with openings having a diameter between 0.1 to 1 millimeter. The structural frame  58 , wire mesh  60  and filtering membrane  62  are interconnected through means well known in the art, one example being the use of flat metal strips  64  (see  FIG. 3 ) placed over the membrane  62  and screwed into the frame  58  such as to sandwich the membrane  62  and mesh  60  therebetween.  
         [0031]     In operation, and with the rear wall panel  22  closed, a mix of a liquid and at least one solid is poured into the filter chamber  44  through the inlet or partially open top of the box  12 . Under the action of gravity, the liquid passes through the filtering membrane  62  of the filtering floor and walls  30 , 32 , 34  to reach the first and second free spaces  50 , 52 . The liquid accumulates in the bottom of the box  12 , in the first free space  50 , and is removed from the box  12  through the outlets  28 . The solid is retained by the filtering membrane  62  within the filter chamber  44  where it is accumulated. As stated above, the angle of the filtering floor  30  with respect to the horizontal minimizes stagnation of the solid waste, thereby reducing clogging of the membrane  62  and improving the flow of liquid therethrough. The angle of the filtering walls  34  with respect to the vertical increases the filtering efficiency by allowing the use of gravity to force the liquid therethrough, instead of relying mainly on capillary action.  
         [0032]     When the filter chamber  44  is full of solid waste, and the liquid has been removed through the outlets  28 , the box  12  can be appropriately mounted on a truck (not shown) to be moved to a dump site, where the solid can be removed from the filter chamber  44  through the open rear wall panel  22 . The cleaning process can be facilitated if the truck has means to incline the box  12  by elevating a front end thereof, as is well known in the art.  
         [0033]     Applicants have found that although the filtering system  10  is adapted to filter a variety of materials, preferable uses therefor include the filtration of waste from animal agri-food industries and wet contaminated soil.  
         [0034]     Now referring to  FIGS. 4-6 , three alternative embodiments of the present invention are shown. Most of the elements of these alternative filtration systems are similar to the elements of the filtration system  10  of  FIGS. 1-3 , and as such are represented by the same reference numerals. The difference between the alternative filtration systems and the first filtration system  10  resides in the shape of the filtering floor.  
         [0035]     Referring to  FIG. 4 , the filtering floor  130  of the first alternative filtration system  110  is composed of a single filtering panel  146  which is semi-circular in shape. The filtering panel  146  is curved so that its lowest points are located along the side edges  140  of the filtering floor  130 . This embodiment is preferably used for filtering waste such as pig manure or industrial sludge.  
         [0036]     Referring to  FIG. 5 , the filtering floor  230  of the second alternative filtration system  210  is composed of a single filtering panel  246  which is flat. This embodiment is preferably used for rapid filtration processes, such as the filtration of used water or waste from vegetal agri-food industries.  
         [0037]     Referring to  FIG. 6 , the filtering floor  330  of the third alternative filtration system  310  is composed of two flat filtering panels  346 , each flat filtering panel  346  having one longitudinal edge forming the side edge  340  of the filtering floor  330  and another longitudinal edge connected to a vertically inclined filtering panel  347 . The inclined filtering panels  347  are inclined toward each other with top edges thereof connected by a filtering strip  348 . It is also considered to have the top edges of the inclined filtering panels  347  directly connected to each other. The first free space  350  extends under the filtering floor  330  and between the filtering panels  347 . This embodiment is preferably also used for rapid filtration processes such as the filtration of used water or waste from vegetal agri-food industries, and for slower filtration processes such as the filtration of waste from animal agri-food industries.  
         [0038]     All of these alternative embodiments  110 , 210 , 310  function following the operational steps described above for the filtration system  10 . Like the filtering floor  30 , the filtering floors  130 , 230 , 330  are preferably composed of an outer structural frame supporting a wire mesh supporting a filtering membrane. Also like the filtering floor  30 , the filtering floors  130 , 230 , 330  are supported above the floor panel  16  such as to define a first free space therebetween, and are inclined with respect to a horizontal plane.  
         [0039]     Before installation within the box  12 , the type of filtering floor and the inclination of the filtering walls  32 , 34  are thus selected according to the nature of the material to be filtered. For materials that are more difficult or slower to filter (e.g. materials with a high grease content, a high density, etc), the selected inclination of the filtering walls  32 , 34  will be more pronounced, such as to have a greater portion of the gravitational force perpendicular to the filtering wall  32 , 34  forcing the liquid therethrough. A filtering floor such as shown in  FIGS. 3-4  is also preferred for such materials that are more difficult to filter. The proper combination of floor type and wall inclination can be determined by testing with a sample of the material to be filtered.  
         [0040]     Adapting the inclination of the filtering walls and the type of filtering floor to the material to be filtered allows for a same filtering membrane to be used for different materials, i.e. the size of the filter openings in the filtering walls can be kept constant. This allows for standard filtering wall panels to be manufactured, a specific filtration system being assembled for a specific material to be filtered by choosing the appropriate type of filtering floor and inclination angle of the filtering walls.  
         [0041]     The embodiments of the invention described above are intended to be exemplary. Those skilled in the art will therefore appreciate that the foregoing description is illustrative only, and that various alternatives and modifications can be devised without departing from the spirit of the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.