Abstract:
A nut shell filter allows the shell filter media to be scrubbed without being removed from the filter vessel. In order to protect the vessel from pressure surges which can occur during the scrubbing cycle, pressure applied during the beginning of the scrubbing cycle is contained within a scrubber tube such that the filter vessel is not subjected to pressure surges which occur at the beginning of the scrubbing cycle. The scrubber tube and scrubber filter tube may either be disposed within the filter vessel or outside of the filter vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     U.S. Provisional Application No. 61/273,484 for this invention was filed on Aug. 4, 2009 for which application this inventor claims domestic priority. 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to the removal of contaminants or debris from a flowing liquid stream. The present invention more specifically relates to various embodiments of an apparatus which employs a filter media comprised of particulate filter matter in which the filter media may be backwashed to clean the captured contaminants from the filter media. 
     Removal of contaminants or debris from a flowing liquid stream by the employment of a filter media comprised of particulate filter material is known. Various prior U.S. patents teach the advantages of using various different sizes of various different particulate filter material. Many of the described filter systems require that the filter media be removed from the filter vessel each time it becomes necessary to scrub the contaminant from the media, thereby enabling the media to be used many times. 
     As stated in U.S. Pat. No. 4,496,464 (the “&#39;464 patent”) these prior art systems require a considerable amount of additional space, and complicated plumbing must be connected between the various pumps, valves, and other mechanical members in order to interconnect the scrubbing vessel and filtering vessel so that various different predetermined flow patterns are attained. A substantial amount of equipment is required in order to return the filter media to the filter vessel. In addition to the added cost and the required additional space considerations, all of the external plumbing presents a continued maintenance problem; and, the numerous additional mechanical connections involved therein greatly increase the likelihood of leakage occurring from the different components of the filter system. 
     The &#39;464 patent, which is incorporated herein in its entirety by this reference, provides additional explanation of the problems associated with filter systems which required transfer of the filter media from the filter vessel into a scrubber vessel. In an effort to solve these problems, the &#39;464 patent discloses a filter system wherein the filter media remains within the filter vessel for the entire life of the media, and wherein the filter media is scrubbed or rejuvenated without removing the filter media to a second vessel. 
     One drawback of the apparatus disclosed in the &#39;464 patent is that the entire interior of the separator vessel is continually subjected to higher pressure during the scrubbing cycle imposed by the scrubbing pump. As noted in the example described in the &#39;464 patent, the initial pressure drop across the filter media may change from a low of 3-5 psi to a pressure drop of 15-25 psi 18 hours later, at which time the scrubbing cycle is initiated. During the scrubbing cycle, the pressure at the discharge nozzle must be sufficiently high to force the liquid into a guide means and to the bottom of the vessel, setting up a flow pattern in which the filter media is “intimately admixed with the liquid contained in the vessel” such that the flow follows a geometrical flow path which is in the form of a toroid having a central vortex which coincides with the axial centerline of the vessel. Achieving this flow pattern requires the repeated application of pressures during the scrubbing mode which are typically higher than the pressures to which the vessel is exposed during the filtering mode. As stated above, for the example provided in the &#39;464 patent, this cycle is repeated approximately every 18 hours, such that the vessel is subjected to a continual stress cycle in which the maximum pressure may substantially exceed the normal operating pressure of the vessel during the filtering cycle. In addition, during the scrubbing cycle, the interior scrubber of the &#39;464 patent is subjected to exterior forces for which the interior scrubber must be designed to resist collapse. 
     It should be further noted that the apparatus disclosed in the &#39;464 patent has screens at the bottom of the vessel through which the filtered liquid is discharged to an outlet header. It should be appreciated that the lower screens can be subjected to very high loads. If the backwash pump comes on while the separator vessel is already at a relatively high pressure, the vessel pressure can increase by 25 psi or more. The lower screens are thus subjected to the increased pressure, as well as the hydrostatic pressure of the fluid in the separator vessel and the media bed overlying the lower screens. Therefore, when the backwash pump comes on, the lower screens can be exposed to relatively high transient loads, which have, with the prior art designs, resulted in catastrophic damage to the lower screens. 
     SUMMARY OF THE INVENTION 
     The embodiments of the apparatus disclosed herein provide a solution to the problems identified above. The apparatus comprises a vessel within which there is enclosed a filter media comprised of particles of particulate filter material. Lateral screens are positioned at the lower end of the vessel and below most of the filter media, where the lateral screens comprise a screened surface for retaining the filter media within the vessel, and each lateral screen member is connected to a clean water outlet for discharge of the filtered water. The lateral screens of the present invention, because of the rectangular construction of the screens having a solid side wall, have additional structural strength. The upper end of the vessel provides a liquid and scrubbing space, with there being a contaminated water inlet, whereby flow of dirty or contaminated water is conducted into the upper end of the vessel, proceeds down through the filter media, where the filter media removes the contaminants from the flowing liquid, whereupon the clean water flows through the screened surface of the lateral supports, through the outlet, and away from the vessel, leaving the contaminants and filter media within the vessel. 
     From time to time, as the removed contaminants progressively accumulate within the filter media, it is necessary to scrub the filter media, thereby re-establishing the original filter efficiency. The scrubbing of the media is accomplished by introducing the backwash liquid into the vessel through a backwash filter tube, with the scrub liquid flowing through the inside diameter of the backwash filter tube and exiting through a nozzle disposed at the bottom of the tube. The nozzle comprises an orifice which may be utilized to control backpressure and to reduce the pressure to which the separator is subjected during the backwash cycle, particularly high transient pressures which occur when the backwash pump initially comes on. The backwash filter tube is enclosed within a scrubber tube. The scrubber tube and enclosed backwash filter tube may either be enclosed within the filter vessel, or attached to the outside of the vessel. 
     During the first phase of the backwash cycle, the scrubbing liquid flows through the nozzle at the bottom of the backwash filter tube, through an opening in the scrubber tube, and into the media bed located beneath the scrubber tube, causing great agitation of the media, to thereby translocate the removed contaminants from the media into the scrubbing liquid. It should be noted that during the backwash cycle, as opposed to the interior scrubber of the &#39;464 patent which is subjected to exterior pressure and must resist collapse, the backwash filter tube of the present invention is subjected to internal pressure and must resist burst as opposed to collapse. As appreciated by those skilled in the art, a tube has greater resistance to burst pressure than to collapse pressure, such that flow of the backwash liquid on the inside of the backwash filter screen is preferred to flow on the outside. 
     During the second phase of the backwash cycle, the contaminated scrubbing liquid is discharged through the screen openings of the backwash filter tube, into the annular space of the scrubber tube and discharged through an outlet on the side of the scrubber and discharged from the scrubber. Also during this second phase, relatively clean make-up water may be added to the filter vessel. 
     Following the two phases of the backwash cycle, the filter media is reset or repositioned into the lower end of the vessel by shutting down all systems which causes the media to gravitate to the bottom. Thereafter, the various flow lines are cleaned by flowing filtered liquid from the vessel, along a closed circuit, and back into the vessel, thereby separating any residual contaminants from the liquid. The filter system is placed back on stream and used until the contaminant load on the media again increases to a magnitude which justifies undertaking another cleaning cycle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an embodiment of the disclosed filter system in the filtering mode. 
         FIG. 2  depicts an embodiment of the disclosed filter system in the scrubbing cycle 
         FIG. 3  shows a second embodiment of the disclosed filter system in the filtering mode, showing how the scrubber tube may be disposed outside of the main filter vessel. 
         FIG. 4  shows side view of an embodiment of a scrubber tube. 
         FIG. 5  shows a backwash filter tube which is utilized with the scrubber tube depicted in  FIG. 4 . 
         FIG. 6  shows a top view of an embodiment of lateral screens which are disposed in the lower end of the filter vessel. 
         FIG. 7  shows a bottom oblique view of the lateral screens shown in  FIG. 6 , showing a configuration of discharge piping which may be utilized with the lateral screens. 
         FIG. 8  shows a close up view of an embodiment of the nozzle of the scrubber tube. 
         FIG. 8A  shows a sectional view of the nozzle taken along line A-A of  FIG. 8 . 
         FIG. 9  shows a close up view of an embodiment of the nozzle of the scrubber tube. 
         FIG. 9A  shows a sectional view of the nozzle taken along line A-A of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring now to the figures,  FIG. 1  shows an embodiment of the disclosed filtering system  10 . The system comprises a filter vessel  12 . The filter vessel  12  has an upper end  14 , which generally extends from inlet  16  to the enclosed top  18  of the vessel. Contaminated liquid flows into the filter vessel  12  through inlet  16 . The filter vessel  12  has a lower end  20  which generally comprises about the lower axial third of the vessel to the enclosed bottom  22  of the vessel. The filter vessel  12  is adapted to hold a quantity of particulate filter material  24 . The filter material  24  may comprise various nutshell or other organic materials, including walnut shells, pecan shells, coconut shells, peach pits, apricot pits, and olive seeds. Acceptable filter material should be sufficiently strong as to resist rupture but also have a sufficiently high elastic modulus to resist deformation and to recover its size and shape after deformation. The filter material  24  will preferably have a depth of about four feet within filter vessel  12 . 
     The disclosed filtering system  10  has at least one lateral screened enclosure  26  supported within the lower end  20  of the vessel  12 . The lateral screened enclosure  26  may have rigid side walls  28  to provide additional structural strength. As shown in the Figures, the disclosed filtering system may have a plurality of lateral screen enclosures which are placed within the vessel at the lower end  20  at approximately the same axial position within the vessel  12 . Each lateral screened enclosure  26  may comprise an outlet  30  through which filtered liquid can exit the enclosure into a header  32 . Outlets  30  may be piped together, as shown in detail in  FIG. 7 , to header  32  for discharge out of vessel  12  through vessel outlet  34 . 
     While other type of screening materials may be utilized, the top of lateral screen enclosure  26  is preferably of wedge wire construction, while the sides and bottoms may be fabricated from solid plate to provide additional structural strength to the screen enclosures. Wedge wire screens are superior for retaining media, filtering, and sizing. In comparison with wire mesh and perforated metal, wedge wire continuous slot screens have more open area, have very precise openings, are stronger and more durable, are virtually non-clogging and reduce media abrasion. The screen material utilized on lateral screen enclosure  26  should be corrosion resistant, and fabricated from corrosion resistant alloys such as type 304, 316, 316L, 321, and 410S stainless steels, or from nickel alloys. The slot widths of the screen material should be sized smaller than the particle size of the filter material  24  and are preferably 15 thousands of an inch. 
     The disclosed apparatus further comprises a scrubber apparatus connected to vessel  12 . The scrubber apparatus provides the means for cleaning the filter material  24  to remove the matter deposited by the water passing through the filter material. The scrubber apparatus comprises some form of pump means, such as pump  36 , which provides for circulation of scrub water through the vessel, allowing for the cleaning of the filter material  24 . Pump  36  has a suction  38  and a discharge  40 . The scrubber apparatus further comprises a scrubber tube  42  which has an enclosed top  44  and an enclosed bottom  46 . Scrubber tube  42  is generally a cylindrical in shape. Scrubber tube  42  has an inlet  48  generally located at the top of the scrubber tube, where flow from the pump discharge  40  is received. Toward the bottom end of the scrubber tube  42  is an outlet  50  through which flow is discharged from the scrubber tube. 
     The scrubber apparatus further comprises a filter tube  52  which is contained within the scrubber tube  42 . An annulus  54  is defined between the scrubber tube  42  and the filter tube  52 . As with the scrubber tube  42 , the filter tube  52  is generally cylindrical in shape. The filter tube  52  has an inner passage  56  which receives flow from the inlet  48 . Flow through inner passage  56  is controlled by a control valve (not seen) connected to vessel outlet  58 . When flow is allowed through vessel outlet  58  by the opening of the control valve, water flowing through inner passage  54  will pass through the screen openings of the filter tube  52 , which extend from the inner passage to the exterior of the filter tube, into annulus  54  and the dirty water discharged through vessel outlet  58 . Various means may be utilized to control back pressure, including a control valve, orifice plate or piping design, causing flow through inner passage  56  to be discharged through nozzle  60  which discharges into vessel  12 . The nozzle  60 , comprises a conical tube  63  and an orifice  61  which may be utilized to control backpressure and to reduce the pressure to which the separator is subjected during the backwash cycle, particularly high transient pressures which occur when the backwash pump initially comes on. As shown in  FIG. 1 , the scrubber tube  42  has an enclosed top  44  and bottom  46 , a scrubber tube inlet  48  at the top for receiving flow from the pump discharge, a scrubber tube outlet  50  in a sidewall of the scrubber tube, and a scrubber tube opening at the bottom  46  through which a nozzle  60  extends so flow is discharged outside of the scrubber tube  42 . The filter tube  52  includes a conical tube having an upper end and a lower end, wherein the upper end of the conical tube has an outer diameter that is larger than an outer diameter of the lower end of the conical tube, wherein the upper end of the conical tube is connected to a lower end of the filter tube  52  and a lower end of the conical tube is hydraulically connected to the nozzle  60 . The nozzle  60  includes a flow restricting orifice that is hydraulically connected to the inner passage  56  of the filter tube  52  via the conical tube, wherein the flow restricting orifice reduces a pressure to which the vessel is subjected during a backwash cycle and discharges filter material and water into the vessel  12 . 
     As with the apparatus disclosed in the &#39;464 patent, the scrubbing cycle preferably is achieved by disposing the suction  38  and discharge  40  of pump  36  within the upper end  14  of the vessel  12 . However, instead of being directed towards a circulation guide means as taught in the &#39;464 patent, the pump  36  discharges into the inside of the backwash filter tube  52 . As with the apparatus disclosed in the &#39;464 patent, pump suction  38  takes liquid from the upper end  14  of the vessel  12 . As backwash water is discharged from the nozzle  60  located at the bottom of the backwash filter tube  52 , the backwash water is directed towards the bottom of the filter vessel  12 . This action sets up a desirable flow pattern wherein the filter media  24  becomes intimately admixed with the liquid contained within the vessel  12  and great agitation of the individual particles of the media achieves an unusually efficient cleaning and scrubbing action. As with the &#39;464 apparatus, the flow at this time follows a geometrical flow path which is in the form of a toroid having a central vortex which coincides with the axial centerline of the filter vessel  12 , with the outer upward flowing part of the vortex being confined by the inner peripheral wall surface of the vessel. 
       FIGS. 4 and 5  depict the scrubber tube  42  and filter tube  52 , with the filter tube removed from the scrubber tube. It is to be noted that scrubber tube  42  comprises a bottom outlet  62  through which nozzle  60  extends. Filter tube  52  may comprise an upper flange  62  which sits within seat  64  of the scrubber tube  42 . Filter tube  52  may further comprise lifting tabs  66  which may be utilized for lifting the filter tube from the scrubber tube  42 . Filter tube  52  comprises wire screen  68  which, as with lateral screened enclosure  26  is preferably of wedge wire construction. Wedge wire screen utilized for wire screen  68  should have slot widths of approximately 20 thousands of an inch. 
       FIG. 3  depicts an alternative embodiment of the disclosed filtering system  100 . The alternative embodiment of the system comprises a filter vessel  112 . The filter vessel  112  has an upper end  114 , which generally extends from inlet  116  to the enclosed top  118  of the vessel. Contaminated liquid flows into the filter vessel  112  through inlet  116 . The filter vessel  112  has a lower end  120  which generally comprises about the lower axial third of the vessel to the enclosed bottom  122  of the vessel. The filter vessel  112  is adapted to hold a quantity of particulate filter material  124 . As with the embodiment discussed above, the filter material  124  may comprise various nutshell or other organic materials, including walnut shells, pecan shells, coconut shells, peach pits, apricot pits, and olive seeds. 
     The disclosed filtering system  100  has at least one lateral screened enclosure  126  supported within the lower end  120  of the vessel  112 . As shown in the Figures, the disclosed filtering system may have a plurality of lateral screen enclosures  126  which are placed within the vessel at the lower end  120  at approximately the same axial position within the vessel  112 . Each lateral screened enclosure  126  may comprise an outlet  130  through which filtered liquid can exit the enclosure into a header  32 . Outlets  130  may be piped together to header  132  for discharge out of vessel  112  through vessel outlet  134 . 
     The disclosed apparatus further comprises a scrubber apparatus connected to the side of vessel  112 . The scrubber apparatus provides the means for cleaning the filter material  124  to remove the matter deposited by the water passing through the filter material. The scrubber apparatus comprises some form of pump means, such as pump  136 , which provides for circulation of scrub water through the vessel, allowing for the cleaning of the filter material  124 . Pump  136  has a suction  138  and a discharge  140 . The scrubber apparatus further comprises a scrubber tube  142  which has an enclosed top  144  and an enclosed bottom  146 . Scrubber tube  142  is generally a cylindrical in shape. Scrubber tube  142  has an inlet  148  generally located at the top of the scrubber tube, where flow from the pump discharge  140  is received. Toward the bottom end of the scrubber tube  142  is an outlet  150  through which flow is discharged from the scrubber tube. 
     The scrubber apparatus further comprises a filter tube  152  which is contained within the scrubber tube  142 . An annulus  154  is defined between the scrubber tube  142  and the filter tube  152 . As with the scrubber tube  142 , the filter tube  152  is generally cylindrical in shape. The filter tube  152  has an inner passage  156  which receives flow from the inlet  148 . Flow through inner passage  156  is controlled by pressure control means (not shown) such as a control valve, orifice plate or piping design connected to outlet  150 . When flow is allowed through outlet  150  by the opening of the control valve, water flowing through inner passage  154  will pass through the screen openings of the filter tube  152 , which extend from the inner passage to the exterior of the filter tube, into annulus  154  and the dirty water discharged through outlet  150 . The control valve, orifice plate, or other back pressure control means may be manipulated to apply back pressure and cause flow through inner passage  156  to be discharged through nozzle  160  which discharges into vessel  112 . The nozzle  160  comprises an orifice  161  which may be utilized to control backpressure and to reduce the pressure to which the separator is subjected during the backwash cycle, particularly high transient pressures which occur when the backwash pump initially comes on. Scrubbing of the filter material  124  for this embodiment of the filtering system  100  accomplished in a similar fashion as that discussed for the embodiment of the filtering system  10  discussed above. As shown in  FIG. 3 , the scrubber tube  142  includes an enclosed top  144  and an enclosed bottom  146 , a scrubber tube inlet  148  at the top for receiving flow, a first scrubber tube outlet  150  in a bottom of the scrubber tube, and a second scrubber tube outlet in a sidewall of the scrubber tube, wherein the second scrubber tube outlet is hydraulically connected to an inlet of a nozzle  160  located within the vessel  112  via a connecting pipe. The filter tube  152  includes a conical tube having an upper end and a lower end, wherein the upper end of the conical tube has an outer diameter that is larger than an outer diameter of the lower end of the conical tube, and wherein the upper end of the conical tube is connected to a lower end of the filter tube  152  and a lower end of the conical tube is connected to the second scrubber tube outlet. The nozzle  160  includes a flow restricting orifice hydraulically connected to the inner passage  156  of the filter tube  152  via the conical tube, the second scrubber tube outlet, and the connecting pipe, wherein the flow restricting orifice reduces a pressure to which the vessel is subjected during a cleaning cycle. 
     While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. For example, the size, shape, and/or material of the various components may be changed as desired. Thus the scope of the invention should not be limited by the specific structures disclosed. Instead the true scope of the invention should be determined by the following appended claims.