Displacement filter apparatus and method

Abstract

A method and apparatus for filtering a slurry utilizing a displacement filtering principle. The filter apparatus desirably includes a first filter and a second filter. Both the first and second filters may be substantially annular in shape and positioned concentrically with respect to each other. A particulate collection volume is at least partially defined between the first and second filters. The method includes directing a flow of slurry into the particulate collection volume under sufficient pressure to force fluid within the particulate collection volume through one of the inner and outer filters and any particulate matter blocking a filtering surface of the inner and outer filters.

1 . A method of separating particulate matter from a slurry, comprising; 
 providing a filter apparatus comprising a pressure vessel having a first end, a second end, and a substantially cylindrical wall portion defining a longitudinal axis of said filter apparatus, said pressure vessel defining an internal space;    providing an annular first filter and an annular second filter within said internal space, said second annular filter surrounding said first annular filter, said first filter having a first surface and said second filter having a second surface facing said first surface, said first and second surfaces being substantially parallel to one another and defining a sealed annular particulate collection space therebetween,    directing a flow of said slurry into said particulate collection volume under sufficient pressure to force fluid to flow in a substantially radial direction through said first filter and through said second filter and any of said particulate matter blocking a filtering surface of said first filter and said second filter;    maintaining a fixed volume of said particulate collection space during said directing;    forming a particulate cake substantially filling said particulate collection space from a build up of said particulate matter accumulating on said first and second surfaces, a thickness of said particulate matter increasing on said first and second surfaces in a direction generally perpendicular to said first and second surfaces.    
   
   
       2 . The method of  claim 1 , additionally comprising maintaining said pressurized flow until said particulate collection space is substantially filled with said particulate matter.  
   
   
       3 . The method of  claim 1 , additionally providing a first filter media covering at least a substantial portion of said first surface and a separate second filter media covering at least a substantial portion of said second surface.  
   
   
       4 . The method of  claim 1 , wherein said pressure is at least 25 psi.  
   
   
       5 . The method of  claim 1 , wherein a concentration of particulate matter in said slurry is greater than 1000 parts per million.  
   
   
       6 . A method of separating particulate matter from a slurry, comprising: 
 providing a filter apparatus comprising an annular inner filter and an outer filter surrounding said inner filter, a first surface of said inner filter facing a second surface of said outer filter being substantially parallel to one another and defining a sealed, fixed-volume particulate collection space between them, said filter apparatus further comprising an outlet located downstream from said particulate collection space and an inlet directing fluid into said particulate collection space before said fluid passes through either of said inner filter and said outer filter;    initiating a filtering cycle comprising directing a flow of said slurry into said particulate collection space under sufficient pressure to force fluid through said inner and outer filters and any of said particulate matter blocking a filtering surface of said inner and outer filters to substantially fill said particulate collection space by a build up of said particulate matter on said first and second surfaces with a thickness of said particulate matter increasing in a direction generally perpendicular to said first and second surfaces;    initiating a drive to move said inner filter and said outer filter axially with respect to one another upon completion of said filtering cycle to empty particulate from said particulate collection space.    
   
   
       7 . The method of  claim 6 , additionally providing a first filter media covering at least a substantial portion of said first surface and a separate second filter media covering at least a substantial portion of said second surface.  
   
   
       8 . The method of  claim 6 , said filter further comprising a controller, said method further comprising initiating said drive with said controller.  
   
   
       9 . The method of  claim 6 , further comprising providing at least one annular scraper sized and shaped such that axial movement of said inner filter and said outer filter with respect to one another causes said scraper to at least substantially remove particulate from said particulate collection space.  
   
   
       10 . The method of  claim 6 , further comprising spraying at least one of said inner and outer filters with a wash liquid during said axial movement of said inner filter and said outer filter with respect to one another.