Abstract:
A filter system is described which comprises a vessel ( 10 ) containing a plurality of sets of discs ( 41 ). Each set of discs ( 41 ) comprises a number of discs ( 40 ) stacked one above the other. The discs ( 40 ) have grooves ( 50 ) on their opposite sides so that media to be filtered passes through the grooves and contaminants in the media are prevented from passing through the grooves or trapped by the grooves. A backwash system ( 25 ) is provided for supplying air to force liquid in the opposite direction through the grooves to wash any contaminant out of the grooves. An air vent ( 26 ) is provided for allowing compressed air to escape from the vessel ( 10 ) and an outlet ( 16 ) is provided for discharge of contaminant.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a liquid filter system for use in relation to various environments, including oil recovery, drinking water and sewerage in which fine filtration or microfiltration of the liquid is required. For example, in the oil field environment, water needs to be filtered to remove contaminants of particle sizes above 5 to 2 microns and possibly up to one micron. 
       BACKGROUND OF THE INVENTION 
       [0002]    Enhanced oil recovery applications in oil field production or pre-treatment for membrane systems require treatment of influent water quality to 1 to 5 microns. This treatment is normally considered as fine filtration or microfiltration. Available technology to achieve this has been multimedia filter technology using granular media or membrane technologies or cartridge filters. All of these techniques require frequent media replacement and maintenance. Cartridge filters are used more of a backup or insurance after the two former methods have been implemented. Membrane technologies at the microfiltration level require a high degree of maintenance and replacement and are also expensive. These systems also have a high continuous reject rate (typically in the order of 30% of the influent). 
       SUMMARY OF THE INVENTION 
       [0003]    The object of the invention is to provide a system which improves filtration whilst reducing costs and complexity. 
         [0004]    The invention may be said to reside in a liquid filtration system comprising:
       a plurality of discs, each having a surface, an inner periphery and an outer periphery, a hole in each disc defining the inner periphery;   a support for supporting the discs one above another;   a plurality of grooves in the surface of each disc extending from the inner periphery to the outer periphery;   a vessel for containing the discs;   an inlet in the vessel for liquid to be treated so the liquid flows through the grooves in one direction, preventing or trapping contamination in the liquid from passing through the grooves in one direction;   a backwash system for providing washing fluid for flow in the opposite direction to wash and drain off any retained contaminant out of the grooves;   a vent system to remove trap air after backwash and   a filtered water outlet from the vessel.       
 
         [0013]    Depending on the size of the grooves which are employed, contaminants of very small sizes can be rejected and therefore, filtered from the liquid. Compared to microfiltration membrane type systems of an equivalent system, there is substantially no reject rate to consider. The invention provides significantly longer life cycle, reusable and smaller footprint than membrane-type equivalent systems or traditional multimedia sand filtration. The invention also requires no scouring, significantly less chemical, has no media loss through migration downstream, less backwash volume required and is reusable and recyclable as otherwise experienced with sand or multimedia filters. 
         [0014]    Preferably the surface of each disc is defined by a first surface and an opposite second surface, and a plurality of grooves are formed in both the first surface and the opposite second surface. 
         [0015]    Preferably the vessel is divided into a first chamber for receiving unfiltered liquid and a second chamber for receiving filtered liquid, the support means supporting the discs in the second chamber so that influent liquid must flow through the grooves of the disc for filtration before entering the first chamber. 
         [0016]    Preferably the support comprises a baffle having a plurality of downwardly extending support webs which are received in the holes of the discs so that liquid must flow through the grooves and then into the support webs and then into the first chamber, so that any contaminate is filtered by the discs during the passage of the fluid from the second chamber through the grooves to the first chamber. 
         [0017]    Preferably the first chamber has the liquid outlet for filtered liquid. 
         [0018]    Preferably the inlet for unfiltered liquid is located for communication with the second chamber. 
         [0019]    Preferably the support webs comprise three webs which receive the discs by the holes in the disc sliding over the webs so that the discs can be stacked on the support, the tripod being suspended from the baffle and held to the baffle by a spring assembly. 
         [0020]    Thus, liquid flows through the grooves in the discs into the spaces defined by the webs and up through those spaces into the first chamber above the baffle. 
         [0021]    Preferably the backwash system comprises a compressed air inlet for supplying compressed air to the second chamber so the compressed air forces the liquid through the first chamber and the grooves in the opposite direction to movement of the liquid being filtered to thereby push out any contaminants which are trapped in the grooves. 
         [0022]    Preferably the first chamber has an air vent for venting air from the vessel after backwash. 
         [0023]    The system may comprise a plurality of vessels, each including the said discs and the backwash system. 
         [0024]    Actuators may be provided for controlling valves to, in turn, control the supply of compressed air, the air vent, the outlet of filtered liquid, the inlet of unfiltered liquid, and the contamination outlet for discharge of contaminants from the system. 
         [0025]    Preferably the system includes a pressure differential measuring means for measuring the pressure differential between the inlet and the outlet, and for actuating the backwash system when the pressure differential reaches a predetermined level. 
         [0026]    Preferably the pressure differential measuring means comprises a differential pressure indicating switch located in a bypass line connecting the inlet to the outlet. 
         [0027]    Preferably a controller is provided for controlling the actuators and for controlling the backwash system upon receipt of a signal from the switch indicating that the predetermined pressure differential level has been reached. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    A preferred embodiment of the invention will be described, by way of example, with reference to the accompanying drawings in which: 
           [0029]      FIG. 1  is a view of the system of the preferred embodiment; 
           [0030]      FIG. 2  is a detailed view of part of  FIG. 1 ; 
           [0031]      FIG. 3  is a plan view of a disc used in the embodiment of  FIG. 1 ; 
           [0032]      FIG. 4  is a detailed view of the circled part of the disc labelled A in  FIG. 3 ; 
           [0033]      FIG. 5  is a view along the line B-B of  FIG. 3 ; 
           [0034]      FIG. 6  is view along the line A-A of  FIG. 5 ; 
           [0035]      FIG. 7  is a detailed view of a disc assembly according to the preferred embodiment of the invention; and 
           [0036]      FIG. 8  is a view of a vessel in a filtration plant according to the preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    With reference to  FIG. 1 , a vessel  10  is provided which has an inlet  12  for unfiltered liquid (such as sea water in this embodiment of the invention). The inlet  12  is controlled by a control valve  14 . The vessel  10  has an outlet  16  controlled via valve  18  for discharge of contaminant and an outlet  20  controlled via valve  22  for the discharge of filtered liquid (such as sea water). A compressed air inlet  24  and an air vent  26  are provided, each controlled by respective valves  25  and  27 . 
         [0038]    Arranged within the vessel  10  is a wall or baffle having a plurality of holes  29 , each of which receive a candle  31 . The candle  31  comprises a support web  32  and a plurality of discs  40  (which form a disc assembly  41 ) stacked on the web  32 . The baffle  29  divides the vessel  10  into a first chamber  33  for filtered sea water and a second chamber  34  for unfiltered sea water. As is best shown in  FIG. 7 , the plurality of discs  40  are stacked one above the other on the support web  32  and the support web  32  is supported in place by a retainer spring assembly  43  which rests on the baffle  29  (see  FIG. 7 ). 
         [0039]    The discs  40  have a central hole  45  where they slip over the support web  32  and are defined by a first surface  46 , a second opposite surface  47 , an inner periphery  48  which defines the hole  45  and an outer periphery  49 . 
         [0040]    As is best shown in  FIG. 3 , a plurality of grooves extend from the inner periphery  48  in each of the surfaces  46  and  47  to the outer periphery  49 . 
         [0041]      FIG. 4  is a detailed view of part of the disc of  FIG. 3  showing two grooves  50   a  and  50   b . As is apparent from  FIG. 4 , the grooves are not perfectly radial, but rather are arranged at an angle of say about 30° to the radius of the disc  40 . 
         [0042]    The dimensions of the discs  40  may be as follows:
       outer diameter defined by outer periphery  49 : 35 to 40 mm   inner diameter defined by inner periphery  48 : 24 to 28 mm   thickness of the disc between 0.5 to 0.75 mm   groove  50  having a normal rating size of about 5 to 2 micron   distance between centres of cavities  50  from 5 micron to 25 microns.       
 
         [0048]    The discs  40  may be formed from any suitable material including polypropylene, polyvinylidene fluoride, polyvinyl chloride or polytetrafluoroethylene. 
         [0049]    Again with reference to  FIGS. 1 and 2 , when it is desired to filter sea water, the valve  14  is controlled to allow the sea water to enter the chamber  34 . The sea water is able to pass up beside the discs  40  and can travel through the grooves  50  of the discs to the support web  32 , and then from the support web  32  into the chamber  33 . The passing of the water through the grooves filters large colloidal material and other larger solids, thereby trapping that material so that filtered sea water can exit the outlet  20  when the valve  22  is opened. 
         [0050]    Each of the discs therefore provides a predetermined flow rate and the effluent flow rate through the vessel  10  is determined by the number of discs and the number of stacks of discs which are employed. 
         [0051]    When the amount of solids filtered by the discs has built up to a predetermined level, a backwash system comprised of the compressed air inlet  25  and air vent  27  is operated. Compressed air is supplied to the chamber  33  from the inlet  24  and passes in the opposite direction to the flow which performs the filtration so that any colloids or solids trapped in the grooves of the discs are blown out of the grooves or discs back into the chamber  34  where they can be discharged via the outlet  16 . 
         [0052]    The air vent  26  can be opened to vent any remaining air in the system out of the vessel  10  before the next use of the system. 
         [0053]    The backwash operation can continue for a predetermined period of time before normal filtration occurs. 
         [0054]    As is best shown in  FIG. 7 , each disc assembly  41  is supported on one of the support webs  32  which is formed from a central core  50  from which extends three web arms  51 ,  52  and  53 . The central core  50  and arms  51 ,  52 ,  53  can be formed from angle iron with the arms  51 ,  52  and  53  disposed at an angle of 120° with respect to one another. The periphery of the arms  54  is matched to fit the inner periphery of the discs  40 . Typically, the support web  32  may carry as many as 1000 filter discs  40 . The bottom of the support web  32  is provided with a block or retainer  55  so the discs  40  cannot simply slide off the end of the support web  32 . 
         [0055]    The support web  32  passes through a hole  37  in baffle  29 . The baffle  29  may be provided with as many holes as is desired and with as many candles  31  as is required to provide the required filtration flow. Typically a baffle can be provided with a predetermined number of holes  37  and if the holes are not provided with candles  31 , the holes are simply blocked. 
         [0056]    The space between the inner periphery  48  of the discs and the web arms  51 ,  52  and  53  form channels  38  which are generally wedge-shaped in cross-section so that liquid can flow up the channels  38  through the openings  29  and into the chamber  33  for exit through filtered sea water outlet  20 . 
         [0057]    Each of the support webs  32  is held in place by wave spring  56 , a retaining washer  57  and a retaining ring  59 . Thus, the liquid is able to flow through the spring  56 , washer  57  and retaining ring  59  into the chamber  33  from the channels  34  between the inner periphery  48  of the discs  40  and the web arms  51 ,  52  and  53 . 
         [0058]      FIG. 8  is a schematic view of the vessel shown in  FIG. 1  in more detail. Inlet sea water is provided via line  12  through strainer  81 . The valve  14  controls inflow of liquid into the vessel  10  so that the liquid can flow through the various disc assemblies  41  previously described into chamber  33  and out through filter outlet  20 . Inlet  12  and outlet  20  are connected to a control box  86  which monitors the flow and if a sufficiently large pressure differential is detected indicative of the fact that the discs  40  are becoming blocked with contaminants, the backwash system is operated. The backwash system includes the air supply line  24  which connects to the vessel  10  via valve  25  and vent  26  which connects to the vessel  10 . The drain outlet  16  having the valve  18  is connected to the control box  86 . When the pressure differential is determined, the valves  25  and  18  are opened and the valves  14  in the line  12  and  22  in line  20  are closed. Thus, air is pushed into the vessel  10  when valve  25  in line  24  opens, thereby forcing the liquid out in the reverse direction through the discs  40  and the drain  16 . The operation of the backwash system can occur upon determination of a significant pressure differential, as detected by the control box  86 , or may simply be timed to operate at predetermined time intervals. When the backwash has completed and air has blown through the discs  40 , the valves  18  and  25  are closed. The valves  14  in line  12  and  27  in the vent line  26  are opened so that incoming water through the line  12  can push air trapped in the vessel out through the vent outlet  26 . When all the air has escaped, the valve  27  is closed and the vessel  10  continues its normal operation by filtering water coming through line  12  and outletting the filtered water through line  20 . 
         [0059]    In embodiments where the backwash system is operated automatically when high pressure differential across the filter is reached indicating the filter being “clogged”. The inlet  12  connected to valve  92  and the outlet  20  connecting to valve  94  respectively provides the pressure impulses in line  91  to the differential pressure indicating switch  96 . This switch  96  provides an indication of the difference in pressure between the inlet  12  and the outlet  20  and when this differential is at a predetermined high level, indicating that the filter is clogged, the backwash sequence is triggered by a signal to the controller  86 . 
         [0060]    The valves  14 ,  18 ,  22 ,  25  and  27  are operated by actuators  97  under the control of controller  86  to operate the filtration system and also the backwash system. 
         [0061]    In preferred embodiments of the invention, a number of the vessels  10  may be connected together to form a filtration plant with the required inlet and outlet lines, drains and backwash systems so that a particular flow rate of filtered water is provided, as is required. 
         [0062]    In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise”, or variations such as “comprises” or “comprising”, is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 
         [0063]    Since modifications within the spirit and scope of the invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hereinabove.