Abstract:
A belt filter press for deliquifying a material comprises two endless filter belts disposed adjacent each other so that a portion of the belts travel together and converge towards one another and between which a material is progressively compressed, and a belt washer for cleaning the belt of residual material, wherein the belt washer has at least one wiper holder and at least one belt wiper, wherein the at least one belt wiper is disposed against a first surface of one of the belts and removably retained thereagainst by the at least one wiper holder.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/287,895, filed May 1, 2001. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to belt filter presses for removing liquid from a mixture of liquid and solid material. In one aspect, the invention relates to an improved belt washing apparatus for a belt filter press.  
           [0004]    2. Description of the Preferred Embodiment  
           [0005]    Belt filter presses are utilized to remove liquid from a mixture of liquid and solid material, leaving a relatively dry, solid “cake” for disposal or further processing. The belt filter press comprises a frame and an assembly of rollers that support and drive an upper continuous belt and a lower continuous belt that are in operable communication with each other. The belts are permeable to allow the extrusion of the liquid therethrough. The mixture is first placed on the lower belt, then “sandwiched” between the upper and lower belts. The belts and the retained mixture then pass through a wedge section where the mixture is evenly distributed between the belts, and an initial volume of liquid is removed. The belts then pass through a series of progressively smaller diameter rollers where the retained mixture is compressed for further liquid removal. The belts are then separated and the dry “cake” is removed from the belts, generally by a scraping apparatus. The belts are then washed to remove any remaining cake, after which the process is repeated. The liquids from the extrusion and belt washing processes are collected for disposal.  
           [0006]    Belt washers are used to clean the residual cake from the belts. These belt washers typically utilize scrapers to assist in the removal of the residue and any wash water adhering to the belts. The scrapers are typically fixedly mounted in the belt washers, necessitating a shutdown of the filter press when the scrapers must be maintained or replaced.  
         SUMMARY OF INVENTION  
         [0007]    The invention comprises a belt washer assembly for a belt filter press for removing liquid from a mixture of liquid and solid material. The belt filter press comprises two endless filter belts disposed adjacent each other so that a portion of the belts travel together and converge towards one another and move together in a compression zone where material is compressed, and a belt washer for cleaning one of the belts of residual material. The belt washer has at least one wiper holder and at least one belt wiper, wherein the at least one belt wiper is disposed against a first surface of one of the belts and removably retained thereagainst by the at least one wiper holder. The at least one wiper holder is a clip and the at least one belt wiper is slidably retained in the clip. The at least one belt wiper is made of rubber or soft polyethylene. At least one scraper is disposed against a second surface of one of the belts opposite the at least one belt wiper, and the at least one scraper presses the belt against the at least one belt wiper. In one embodiment, the at least one belt wiper comprises a plurality of belt wipers, and each belt wiper is disposed from the first belt wiper in the direction of belt travel. In another embodiment, the belt washer is provided with a first pair of belt wipers and a second pair of belt wipers, with a sprayer disposed therebetween. In yet another embodiment, the belt washer is provided with a plurality of scrapers equal to the number of belt wipers. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]    In the drawings:  
         [0009]    [0009]FIG. 1 is a side elevational view of a schematic of a belt filter press comprising a curved wedge section, primary and secondary rollers, and a belt washer assembly according to the invention.  
         [0010]    [0010]FIG. 2 is an exploded perspective view of the belt washer assembly of the belt filter press of FIG. 1.  
         [0011]    [0011]FIG. 3 is a sectional view of a portion of the belt washer assembly of the belt filter press of FIG. 1 taken perpendicular to the longitudinal axis of the belt washer assembly.  
         [0012]    [0012]FIG. 4 is a perspective view of a portion of the belt washer assembly of the belt filter press of FIG. 1 showing a washer spray head assembly. 
     
    
     DETAILED DESCRIPTION  
       [0013]    Referring now to FIG. 1, a belt filter press  10  according to the invention comprises a frame  12 , an upper belt  14 , a lower belt  16 , a waste placement apparatus  18 , liquid catch pans  20 , belt washers  22 , a wedge section  24 , a primary roller  26 , secondary rollers  28 , upper belt guide rollers  38 , and lower belt guide rollers  32 . It will be readily understood by one skilled in the art that the belt filter press of FIG. 1 will also comprise suitable belt tensioning devices, belt drives, and controls, which for purposes of this disclosure will not be described herein. As with a conventional belt filter press, the belt filter press  10  of FIG. 1 extrudes liquid from a mixture of solid and liquid material by “sandwiching” the mixture between the two belts  14 ,  16 , in a compression zone, passing the belts over the wedge section  24  and around the primary and secondary rollers  26 ,  28 , and discharging the dewatered solids upon separation of the belts  14 ,  16 .  
         [0014]    After the dewatered material has been expelled from the belt filter press, the belts are typically washed of any residual solid material adhering thereto. Adequate washing of the belts typically requires relatively large volumes of water, which must then be removed in order to avoid adding water to the mixture and reducing the efficiency of the dewatering process. Referring to FIGS. 2 and 3, a belt washer  22  according to the invention comprises a lower box  70 , an upper box  72 , and a washer assembly  76 . The lower box  70  is an elongated container comprising two parallel ends  78 , two parallel sides  80 , and a bottom  90 . Each end  78  terminates in an outwardly extending flange  82 , provided with apertures  92  extending therethrough. The upper box  72  is an elongated container comprising two parallel ends  114 , two parallel sides  116 , and a top  150 . Each end  114  of the upper box  72  terminates in an outwardly extending flange  118 , provided with apertures  120  extending therethrough. The length of each box  70 ,  72  is generally equal to the width of the belts  14 ,  16 .  
         [0015]    The lower box  70  is provided with a pair of parallel outside wiper clips  84  and a pair of parallel inside wiper clips  86  extending longitudinally along the sides  80 . Each parallel outside wiper clip  84  comprises a pair of parallel clip sides  94  and a clip bottom  96  defining a narrow channel slot  98 . In the preferred embodiment, each clip  84  comprises a pair of narrow, elongated bars rigidly attached to the side  80  and extending along the length of the side  80 . Each parallel inside wiper clips  86  comprises a pair of parallel clip sides  100  and a clip bottom  102  rigidly connected to define a narrow channel  104 . In the preferred embodiment, each inside wiper clip  86  is rigidly attached to the ends  78  parallel to the outside wiper clips  84 , preferably by welding. Channel braces  88  are regularly spaced along the clips  84 ,  86  and rigidly attach the inside wiper clips  86  to the outside wiper clips  84 , such as by welding. Wipers  74  comprise flexible, elongated blades adapted to be slidably retained in the clips  84 ,  86 , and to extend longitudinally from one end  78  to the other. Suitable materials for the wipers  74  include rubber and soft polyethylene.  
         [0016]    Each side  116  of the upper box  72  terminates in a scraper edge  122 . An inside scraper  124  comprises a rigid, narrow, elongated blade with a scraper edge  125 . A pair of scrapers  124  is rigidly attached to the ends  114 , such as by welding parallel to the sides  116  so that the edges  122 ,  125  define a fixed elevation. Scraper braces  126  are regularly spaced along the scrapers  122 ,  124  and rigidly attach the inside scrapers  124  to the sides  116 , such as by welding, in order to eliminate lateral deflection of the inside scrapers  124 . The lower flange apertures  92  and the upper flange apertures  120  are adapted to be in axial alignment when the upper box  72  and the lower box  70  are assembled into the washer  22 . The alignment of the apertures  92 ,  120  enables the upper box  72  and the lower box  70  to be fixedly connected, such as by conventional bolted connections. The sides  116 , the scrapers  124 , and the clips  84 ,  86  are adapted so that, when the upper box  72  and the lower box  70  are assembled into the washer  22 , the wipers  74  retained in the clips  84 ,  86  will extend toward the scrapers  122 ,  124 , respectively, and the belts  14 ,  16  will be in contact with both the wipers  74  and the edges  122 ,  125 .  
         [0017]    One end  78 ,  114  of the lower box  70  and the upper box  72 , respectively, is provided with a washer aperture  128  therethrough. The washer aperture  128  comprises a circular section  130  and a slot section  132 . Proximate to the slot section  132  is a washer mounting aperture  134  adapted to receive and retain a threaded fastener, such as a machine screw. The other end  78 ,  114  is provided with a tube support  144  comprising a circular aperture therethrough.  
         [0018]    Referring to FIG. 4, a washer assembly  76  comprises a washer tube  136  and a plurality of spray heads  138 . The washer tube  136  comprises a hollow tube which is sealed at a distal end and provided with a suitable fitting  146  at a proximal end for connection to a water supply. The tube  136  is also provided with a mounting plate  140  adapted to extend over the slot section  132 . The mounting plate  140  is rigidly attached to the tube  136 , such as by welding, so that the plane of the plate  140  is orthogonal to the longitudinal axis of the tube  136 . The plate  140  is provided with a mounting plate aperture  142 . The spray heads  138  comprise generally circular projections extending longitudinally along the outer surface of the tube  136 . Each spray head  138  is provided with a center aperture  139  adapted to disperse water in a spray pattern. The center aperture  139  is in fluid communication with the interior of the washer tube  136 . Water supplied under pressure to the washer tube  136  will flow from the spray heads  138  in a dispersed pattern.  
         [0019]    Each belt washer  22  comprises two washer spray head assemblies  76 . One washer spray head assembly  76  is inserted into the lower box  70  and the other washer spray head assembly  76  is inserted into the upper box  72 . The spray tube  136  is inserted through the washer aperture  128  by aligning the spray heads  138  with the slot section  132 . The distal end of the spray tube  136  is inserted into the tube support  144 . The mounting plate aperture  142  is aligned with the washer mounting aperture  134  and the washer spray head assembly  76  is secured to the boxes  70 ,  72  by use of a threaded fastener inserted therethrough. In the preferred embodiment, the spray heads  138  are aligned so that the spray is directed against the travel of the belt  14 ,  16 . The lower box  70  is provided with a suitable drain  148  for removing the liquid from the washing process.  
         [0020]    In use, the lower box  70  with installed washer spray head assembly  76  is mounted to the frame  12  through suitable connectors so that the belt  14 ,  16  is in contact with the wipers  74 . The lower box  70  is oriented so that the longitudinal axis of the box  70  is orthogonal to the direction of travel of the belt  14 ,  16 . The upper box  72  with installed washer spray head assembly  76  is attached to the lower box  70  by aligning the upper flange apertures  120  with the lower flange apertures  92  and inserting a threaded fastener, such as a bolt or machine screw, therethrough. The scrapers  122 ,  124  will be in contact with the belt  14 ,  16  to maintain the belt  14 ,  16  in contact with the wipers  74 . The washer spray head assemblies  76  are connected to a pressurized water supply (not shown) and the drain  148  is connected to a suitable external drainage system (not shown). Water entering the washer spray head assemblies  76  will be sprayed from the spray heads  138  onto the belt  14 ,  16 , removing residual cake from the belt  14 ,  16 . The wash water will be removed from the belt  14 ,  16  by the wipers  74  and the edges  122 ,  125 , and will be collected in the lower box  70  to be removed through the drain  148 .  
         [0021]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing description and drawings without departing from the spirit of the invention.