Abstract:
There is provided method and apparatus for creating a longitudinally disposed, sharp pulse of liquid, useful for pulseback renewal of liquid-entry faces of a panel-bed liquid filter or a panel-bed liquid-powder contactor. Perforations are disposed along the wall of a tank in a path generally parallel to the tank&#39;s axis. Stoppers are provided for stoppering the perforations. With the perforations so stoppered, a liquid is introduced at high pressure into the tank. Thereafter, a quick unstoppering of the perforations releases the liquid from the tank in form of a longitudinally disposed, sharp pulse of liquid moving in a direction perpendicular to the tank&#39;s axis. If the tank is placed vertically alongside or within a space that in normal operation receives liquid from a panel bed, the sharp pulse can effectively pulseback the panel bed.

Description:
This application claims the benefit of priority of U.S. Provisional Application having Ser. No. 61/215,074 filed May 1, 2009, which is herein incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to the renewal of fluid-entry faces in a panel bed of a loose granular solid material employed for intimate contacting of liquid and the solid material for purpose of chemically or physically treating the liquid or the granular solid (or both of these), for example: to filter fine particulate matter (“dirt”) from the liquid; to effect a chemical change in liquid or solid; to remove a chemical constituent of the liquid by absorption, adsorption, or chemical reaction. Renewal of liquid-entry faces is accomplished by employment of pulseback: i.e., by subjecting the bed to a sharp pulse of a liquid in a direction reverse to the “forward” flow of the liquid that earlier entered the bed for treatment. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,000,066 (Dec. 28, 1976) broadly discusses two significant uses of a panel bed of granular material: (1) for filtering powdery matter from a liquid, the filtration being assisted by an accumulation of powdery matter deposits (filter cakes) upon fluid-entry faces of the granular material; (2) for countercurrent contacting of the granular material with a liquid. See also “Granular-bed filtration assisted by filter-cake formation: 5. Treating a liquid in a panel bed with pulseback renewal of liquid-entry granular-bed faces,” by J.-S. Yang, D. R. Whitmire, and A. M. Squires,  Powder Technology, vol.  155, pp. 134-138, 2005. 
     The referenced patent discloses means for renewing liquid-entry faces of a panel bed of a granular material in which vertically disposed louvers (resembling slats of a Venetian blind) support the material: i.e., to provide a “reverse” surge flow of liquid toward the liquid-entry faces (a “pulseback”). This surge flow produces a body movement of the granular material toward the faces, spilling moieties of the material from the faces and concomitantly exposing previously underlying material, thereby renewing the faces. 
     SUMMARY OF THE INVENTION 
     In experiments at a small scale, pulsebacks have been delivered, originating from the top of the space receiving treated liquid in normal operation, and producing relatively uniform spills of granular material from each of a panel&#39;s liquid-entry surfaces. For operation at a significant commercial scale, installation of tall, wide panel beds is required. Without expensive experimentation, involving set-up and study of equipment at a large scale, one cannot be certain that a pulseback originating of the top of the aforementioned space will produce a sufficiently near uniformity of spills, an especially important requirement for a panel bed intended for countercurrent contacting of liquid and a granular material. Accordingly, there is need for improved method and apparatus for supplying pulseback liquid to the tall, wide panel beds that are advantageously specified for the commercial scale. 
     A primary object of the invention is to provide improved, inexpensive method and apparatus for renewing liquid-entry faces of a large panel bed of granular material. 
     Another object is to eliminate ducts for carrying pulseback liquid to a space receiving liquid from a panel bed during its normal treatment of “forwardly” flowing liquid. 
     Another object is to provide pulseback method and apparatus inherently guaranteeing substantially uniform spills of granular material from a multiplicity of liquid-entry surfaces of a tall panel bed. 
     The present invention relates to a method for producing a longitudinally disposed, sharp pulse of liquid. A tank filled with the liquid is provided with perforations disposed longitudinally along a path generally parallel to the tank&#39;s axis. The perforations are stoppered, substantially preventing passage of the liquid there through, and liquid in the tank is elevated in pressure. The perforations are quickly unstoppered, thereby suddenly releasing the liquid in form of a longitudinally disposed, sharp pulse moving in a direction perpendicular to the tank&#39;s axis. 
     The invention also relates to an apparatus for producing a longitudinally disposed, sharp pulse of liquid. The apparatus comprises a tank filled with the liquid and provided with perforations disposed longitudinally along a path generally parallel to the tank&#39;s axis; stoppers capable of a first movement into a set of positions whereby the perforations are stoppered, and the stoppers are also capable of a quick, second movement into a second set of positions whereby the perforations are unstoppered; a source of liquid at elevated pressure; a connection between the source and the interior of the tank; and in the connection a valve the opening of which, when the stoppers are in the first set of positions, causes liquid in the tank to assume substantially the elevated pressure, so that the quick, second movement releases liquid from the tank in a longitudinally disposed, sharp pulse of liquid moving in a direction perpendicular to the tank&#39;s axis. 
     Two quick-opening valves of prior art should be mentioned as background for the instant invention. First, the Big Blaster Air Cannon (marketed by Martin Engineering Co., U.S. Route 34, Neponset, Ill. 61345) can provide a sudden release of gas from a chamber at high pressure. A piston separates a small zone and a large chamber, each at the high pressure; fast release of gas from the small zone causes the piston to move smartly into the zone, opening a port for sudden release of gas from the large chamber. Second, U.S. Pat. No. 5,048,568 (17 Sep. 1991) discloses a valve comprising two concentric, perforated, water-filled tubes. While the tubes&#39; perforations are out of registry, an elevated pressure is imposed upon a zone of water that surrounds the tubes. A mechanical arrangement then moves one of the tubes in a motion that brings the tubes&#39; perforations into registry, thereby producing a sharp inward pulse of water capable of launching a projectile from the inner tube. Neither of these prior-art valves is capable of creating the extended, longitudinally disposed, sharp pulse of liquid provided by the instant invention. 
     Exploiting this extended, longitudinal disposition, the invention also relates to an improved method and apparatus for renewal of a plurality of faces across which liquid enters a panel bed of granular solid material provided for contacting the liquid and the granular material With each other. First, “forward” flow of liquid that undergoes contacting is interrupted. Next, the sharp pulse flow of liquid created by the instant invention is directed, without using a duct to carry the flow, into a space that previously received contacted liquid from the panel. This sharp pulse flow creates a “pulseback” of the granular material, which causes the material to move bodily toward the faces, thereby causing moieties of granular material to fall away from the faces with concomitant exposure of previously underlying granular material, renewing the faces. 
     In the design of panel beds for use at a commercial scale, an attractive option is an arrangement of two panel beds in a module in which they face “outward”: i.e., they receive forwardly flowing liquid to be contacted from a space external to the module; contacted liquid, exiting the two panel beds, enters an interior space bounded by the two beds and two side closures. The interior space could be said to be “vertical”: advantageously, its height is considerably greater than the width dimension separating the interiorly-facing sides of the two panel beds. 
     An attractive arrangement, permitting a designer to specify a panel-bed module much taller than any considered hitherto, is to place the tank of the instant invention vertically alongside the vertical interior space. A preferred pattern for the tank&#39;s perforations is a series of holes equally spaced from one another and disposed along a line parallel to the tank&#39;s axis, their orientation being such that, when unstoppered, they direct a sharp pulse of liquid moving horizontally into the vertical interior space along this space&#39;s entire height. Inherently, with this arrangement, the action of pulseback creates substantially uniform spills from the multiplicity of liquid-entry faces of the module&#39;s two panel beds. 
     A panel-bed module design, however, may employ more than two beds, these cooperatively enclosing an interior space that receives contracted liquid. For example, four panel beds could be arranged to enclose a vertical square space; six beds, a vertical hexagonal space; etc. In such designs, the tank, positioned vertically, could occupy a central location within the interior space; and cylinder perforations could advantageously be disposed in a spiral pattern (or in a pattern of other, more complex form). 
     Renewing liquid-entry faces of a panel bed and further other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 
     These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more particularly described in conjunction with the following drawings wherein: 
         FIG. 1  illustrates a mechanical arrangement suitable for practice of the invention. 
         FIG. 2A  is a section at A-A of  FIG. 1 . 
         FIG. 2B  is a section at B-B of  FIG. 1 . 
         FIG. 2C  is a section a C-C of  FIG. 2B . 
         FIG. 3  illustrates use of the arrangement of  FIG. 1  to accomplish the pulseback of two panel-bed modules, each comprising two outwardly facing panel beds. 
         FIGS. 4A and 4B  are each a section at D-D of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In all the figures, like reference numerals refer to like parts having like functions. 
       FIG. 1  illustrates, in vertical cross-section, an arrangement suitable for stoppering and unstoppering perforations disposed longitudinally along the side of a tank immersed longitudinally within a liquid. Tank  1  comprises relatively long cylinder  2  and end plates  3  and  4 . In a lower portion of cylinder  2 , entirely surrounded by the liquid, equally spaced perforations  5  are disposed along a straight line substantially parallel to the cylinder&#39;s axis. Fitting snugly within this portion of cylinder  2 , cylinder  6  is slightly smaller in diameter than cylinder  2 . Cooperatively, cylinder  6 , lower plate  4 , and upper plate  7  enclose space  8 . Notice that cylinder  6  is open at the end opposite to plate  7 . As will be described shortly, in normal operation of the arrangement of  FIG. 1 , space  8  is filled with the same liquid as that which surrounds the lower portion of cylinder  2 . Perforations  9  in cylinder  6 , seen in the cross-sectional drawing  FIG. 2A  of Section A-A of  FIG. 1 , have the same dimensions as perforations  5  and are disposed vertically at the same spacing and along a straight line parallel to the line followed by perforations  5 . The two sets of perforations, as drawn in  FIG. 1 , are out of registry, so that portions of cylinder  6  effectively act as stoppers of perforations  5 . A rotational motion of cylinder  6  (counterclockwise, as seen in the drawing  FIG. 2A  of Section A-A) can bring perforations  5  and  9  into registry. 
     An upper portion of cylinder  2  extends beyond liquid surface  29 . Partial cylinder  10  is an upward extension of a major part of cylinder  6  (as best seen in the cross-sectional drawing  FIG. 2B  of Section B-B of  FIGS. 1 and 2C  of Section C-C). A stationary wall  11  occupies a radius of the upper portion of cylinder  2 . Plate  13  articulates with the wall of partial cylinder  10  and occupies a radius of this partial cylinder. At the central point of partial cylinder  10 , plate  13  articulates with plate  14 , which (as drawn in  FIG. 2B  Section B-B of  FIG. 1 ) fits closely against plate  11 . Cooperatively, partial cylinder  10 , plate  13 , and major portions of plates  3  and  7  enclose space  12 . Cooperatively, plates  11  and  13  and minor portions of plates  3  and  7  enclose space  15 , which is much smaller than space  12 . Spaces  12  and  15  contain a gas. 
     Pipe  17  enters space  8  across plate  4  and connects this space via valve  18  with source  19  of liquid at elevated pressure. Pipe  16  enters space  15  across plate  11  and connects this space via valve  23  with the ambient. Pipe  20  connects pipe  16  via valve  21  with source  22  of a gas at elevated pressure. Opening valve  21  quickly elevates gas pressure in space  15 ; flow of gas through hole  116  in plate  13  elevates the pressure in space  12 , more slowly. Opening valve  18  places liquid in space  8  at an elevated pressure. With all three spaces ( 8 ,  12 , and  15 ) at elevated pressures, opening valve  23  quickly releases gas from space  15  to the ambient, as indicated by arrow  24 . The pressure difference that arises between spaces  12  and  15  drives plate  13  against plate  11 , extinguishing space  15  and rotating both partial cylinder  10  and cylinder  6  (counterclockwise as drawn in  FIG. 1 ), thereby bringing perforations  5  and  9  (seen in drawing  FIG. 2A  of Section A-A of  FIG. 1 ) into registry, and producing a longitudinally disposed, sharp pulse of liquid from space  8  in a direction perpendicular to the axis of tank  1 . Connections  25 ,  26 , and  27  permit controls  28  to govern opening or closing of valves  18 ,  21 , and  23  respectively. 
     Notice that the stoppering of perforations  5 , as seen in  FIG. 1 , need not be absolutely liquid tight. A significant leakage of liquid can be permitted from space  8  after liquid pressure therein has increased, if operation of the arrangement is such that space  8  is held at this pressure for only a relatively short time. 
     As will be described more fully below, the arrangement of  FIG. 1  can be employed to subject a panel bed to pulseback, or, preferably, two “back-to-back” panel beds that constitute a module, the liquid-exit sides of these beds cooperating with end plates to enclose a space for receiving exit liquid. During normal operation of the panel-bed module (treating a liquid, or a granulated solid material, or both of these), valves  18 ,  21 , and  23  are closed. When controls  28  sense that pulseback will soon be required, these direct valve  21  to open. Rising pressure in line  16  drives plate  13  into the position shown in the drawing  FIG. 2B  of Section B-B, creating space  15 . When controls  28  sense that pressures in spaces  12  and  15  are approaching stable values, controls  28  first direct valve  18  to open, elevating the pressure of liquid in space  8 ; next, close valves  18  and  21 ; and then open valve  23 , creating the sharp pulse of liquid required for an effective pulseback. 
     In  FIG. 1 , elements  105  and  109  ( FIG. 2A ) are optional; they function as already described for elements  5  and  9 , respectively. Presence of the optional elements allows the arrangement of  FIG. 1  to pulseback two back-to-back panel beds arranged in a panel-bed module (as will be described more fully below). 
     In a schematic, horizontal cross-sectional drawing, the upper drawing in  FIG. 3  illustrates use of the arrangement depicted in  FIG. 1  (including optional elements  105  and  109 ) to accomplish the simultaneous pulseback of panel-bed modules  31  and  131 . Each module comprises two outwardly facing panel beds ( 32  and  33  in  31 ;  132 ′ and  133  in  131 ). In normal operation of the two panel bed modules, beds  32  and  132  receive liquid for contacting from external space  37 ; beds  33  and  133  receive liquid from space  38 . Beds  32  and  33  discharge liquid into space  36 , bounded by liquid-exit sides of beds  32  and  33  and end plates  34  and  35 . Beds  132  and  133  discharge liquid into space  136 , bounded by liquid-exit sides of beds  132  and  133  and end plates  134  and  135 . To accomplish pulseback of the two modules, longitudinally disposed, sharp pulses of liquid  39  and  139  from perforations  5  and  105  enter spaces  36  and  136  respectively. 
     The two drawings  FIGS. 4A and 4B  of Section D-D in  FIG. 3  partially illustrate alternative vertical cross-sectional designs of panel bed  32 , each at the moment of pulseback. Each drawing displays how action of pulseback creates a body movement of granular material toward the panel bed&#39;s liquid-entry surfaces, causing granular bed spills  140  and  150  to fall away from the outer edges of supporting plates in the upper  FIG. 4A  and lower  FIG. 4B  at D-D of  FIG. 3 , respectively. 
     The upper D-D drawing  FIG. 4A  illustrates a preferred panel bed arrangement  40  for filtering powdery matter from a “dirty” liquid, the filtration being assisted by accumulation of filter cakes resting upon granular material liquid-entry faces. Plates  41  and  42  support bed  44  of granular material. In normal operation of panel bed  40 , liquid from space  37  enters a bed  44  across a liquid-entry face  43 . Liquid entering the bed  44  flows laterally into a bed  45 , supported by a plate  46 . From the bed  45 , liquid flows into vertical supply column  47 , situated between the interior edges of plates  46  and retention wall  48 , which comprises a panel of narrowly spaced, horizontal louvers. Liquid flowing across wall  48  enters space  36 . During pulseback, granular material lost in spill  140  is made good from supply column  47 . Plates  46  and beds  45  are supplied to prevent, following a pulseback, the rapid descent of granular material in column  47  from pulling material downward from those spaces  44  that occupy positions toward the top of panel bed  40 . 
     The lower D-D drawing,  FIG. 4B  illustrates a preferred panel bed arrangement  50  for countercurrent contacting of a liquid and a granular material. Elements  41 - 44 ,  47 , and  48  serve the same functions as in the upper D-D drawing,  FIG. 4A . Liquid flows from bed  44  flows laterally into bed  145  supported by plate  146 . Bed  145  serves as a zone for countercurrent contacting of liquid and the granular material. Following a pulseback, fresh material entering  145  (making good the loss in spill  150 ) together with the forward flow of liquid in normal operation achieve a countercurrent contacting of the liquid and the material. 
     An example of the application of the arrangement of the lower D-D drawing in  FIG. 4B  is for service to bring water containing hydrocarbonaceous pollutants into countercurrent contacting with granules of activated carbon, thereby removing the pollutants. Conventional installations for this purpose use deep beds of carbon in an intermittent service in which absorption of pollutants alternates with their desorption, regenerating the carbon for repeated usage. For these absorption and desorption steps, two panel beds can be mounted, one above the other. An advantage of the panel-bed arrangement is its much smaller footprint and inventory of expensive carbon. 
     While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.