Feed systems and methods for rotary screen separators

Abstract

A rotary screen separator includes a screen having a substantially cylindrical shape extending from a feed end to a discharge end along a horizontal longitudinal axis. The screen is perforated in a plurality of discrete regions. The regions including at least a first perforation region wherein the screen is perforated in a first perforation pattern and a second perforation wherein the screen is perforated in a second perforation pattern. The first perforation pattern is sized to allow liquid and finer particulate matter to pass through the perforations and the second perforation pattern is sized to allow liquid and coarser particulate matter to pass through the perforations in the second perforation pattern. A first vane structure is helically shaped at a first vane depth having a first vane pitch and handedness selected to advance feedstock within the screen as the screen is rotated in operation.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A rotary screen separator comprising:
 a cylindrical screen having a substantially cylindrical shape extending from a feed end to a discharge end along a longitudinal axis, the longitudinal axis being oriented to be substantially horizontal, about which a drive assembly rotates the screen in operation, the screen being perforated in a plurality of discrete regions, the regions including at least:
 a first perforation region extending from the feed end a first perforation distance, the screen being perforated through substantially all of the first perforation region and being characterized by a first perforation pattern, and 
 a second perforation region extending from the discharge end a second perforation distance, the screen being perforated through substantially all of the second perforation region and being characterized by a second perforation pattern, the first perforation pattern being sized to allow liquid and finer particulate matter to pass through the perforations in the first perforation region and the second perforation pattern being sized to allow liquid and coarser particulate matter to pass through the perforations in the second perforation pattern; 
   a first vane structure rigidly affixed to an inner surface of the screen, the first vane structure being helically shaped, having a first vane depth and extending substantially the first perforation distance from the feed end and having a first vane pitch and handedness selected to advance feedstock within the screen as the screen is rotated in operation; and   a second vane structure rigidly affixed to the inner surface of the screen, the second vane structure extending the second perforation length from the discharge end being helically shaped with the same handedness and both of a second vane depth greater than the first vane depth and a second vane pitch less than the first vane pitch;   a first collection structure located beneath the first perforation region to collect the liquid and the finer particulate matter after it should pass through the perforations in the first perforation region; and   a second collection structure located beneath the second perforation region to collect the liquid and the coarser particulate matter after it should pass through the perforations in the second perforation pattern.   
     
     
         2 . The rotary screen separator of  claim 1  further comprising:
 a third perforation region extending the first and the second perforation regions for a third perforation distance, the screen being perforated through substantially all of the third perforation region and being characterized by a third perforation pattern configured to pass liquid and particulate matter finer than the coarse matter the second perforation region allows through the screen and coarser than the fine matter the first perforation region allows through the screen; 
 a third vane structure rigidly affixed to the inner surface of the screen, the third vane structure extending the third perforation length extending between the first and second perforation regions, the third vane structure being helically shaped with the same handedness of the first and second vane structure and both of a third vane depth greater than the first vane depth and lesser than the second vane depth and a third vane pitch less than the first vane pitch but greater than the second vane pitch; and 
 a third collection structure located beneath the third perforation region to collect liquid and such particulate matter as should pass through the perforations in the third perforation pattern. 
 
     
     
         3 . The rotary screen separator of  claim 1  further comprising:
 an overflow collection structure defining an overflow material chamber located generally at the feed end at a height beneath that screen and arranged to collect liquids overflowing the first vane structure and exiting the screen at the feed end. 
 
     
     
         4 . The rotary screen separator of  claim 1 , further comprising:
 an infeed structure to deposit feed material onto the first perforation region of the inner surface of the screen.   
     
     
         5 . The rotary screen separator of  claim 4 , further comprising:
 receiving feed material at an infeed structure which includes a feed chamber for receiving the feed material to convey it for deposit on the first perforation region through an inlet opening the feed end defines, the feed chamber further defining an outlet opening extending downward to an upper edge of a side wall the feed chamber comprises, the upper edge of the side wall being located at the overflow height, Y1; and   urging a feed lid rotatably attached to the feed housing to rotate from a closed position to feed material flowing from the feed chamber over the upper edge of the side wall, the feed lid having a feed lid weight bearing onto the flow of feed material.   
     
     
         6 . A method for dewatering feed material, the feed material comprising an admixture of liquid and solid matter into a rotary screen separator, the solid matter comprising both fine and coarse particulate the method comprising:
 feeding the feed material through an inlet opening a feed housing enclosing a feed chamber defines;   receiving the feed material at a feed end of a cylindrical screen having a substantially cylindrical shape extending from the feed end to a discharge end along a longitudinal axis, the longitudinal axis being oriented to be substantially horizontal, about which a drive assembly rotates the screen in operation, the screen being perforated in a plurality of discrete regions, the regions including at least:
 a first perforation region extending from the feed end a first perforation distance, the screen being perforated through substantially all of the first perforation region and being characterized by a first perforation pattern, and 
 a second perforation region extending from the discharge end a second perforation distance, the screen being perforated through substantially all of the second perforation region and being characterized by a second perforation pattern, the first perforation pattern being sized to allow liquid and finer particulate matter to pass through the perforations in the first perforation region and the second perforation pattern being sized to allow liquid and coarser particulate matter to pass through the perforations in the second perforation pattern; 
   motivating the feed material by means of a first vane structure rigidly affixed to an inner surface of the screen, the first vane structure being helically shaped, having a first vane depth and extending substantially the first perforation distance from the feed end and having a first vane pitch and handedness selected to advance feedstock within the screen as the screen is rotated in operation;   receiving, at a first collection structure located beneath the first perforation region, the liquid and the finer particulate matter after it should pass through the perforations in the first perforation region;   motivating the feed material out of the discharge end by means of a second vane structure rigidly affixed to the inner surface of the screen, the second vane structure extending the second perforation length from the discharge end being helically shaped with the same handedness and both of a second vane depth greater than the first vane depth and a second vane pitch less than the first vane pitch; and   receiving, at a second collection structure located beneath the second perforation region, the liquid and the coarser particulate matter after it should pass through the perforations in the second perforation pattern.   
     
     
         7 . The method of  claim 6  further comprising:
 receiving the feed material from the first vane structure at a third perforation region extending the first and the second perforation regions, the third perforation region extending for a third perforation distance, the screen being perforated through substantially all of the third perforation region and being characterized by a third perforation pattern configured to pass liquid and particulate matter finer than the coarse matter the second perforation region allows through the screen and coarser than the fine matter the first perforation region allows through the screen; 
 motivating the feed material along the third perforation region by means of a third vane structure rigidly affixed to the inner surface of the screen, the third vane structure extending the third perforation length extending between the first and second perforation regions, the third vane structure being helically shaped with the same handedness of the first and second vane structure and both of a third vane depth greater than the first vane depth and lesser than the second vane depth and a third vane pitch less than the first vane pitch but greater than the second vane pitch; and 
 collecting, in a third collection structure located beneath the third perforation region liquid and such particulate matter as should pass through the perforations in the third perforation pattern. 
 
     
     
         8 . The method of  claim 6  further comprising:
 receiving, at an overflow collection structure defining an overflow material chamber located generally at the feed end at a height beneath that screen such liquids as might overflow the first vane structure by overtopping the first vane structure and exiting the screen at the feed end. 
 
     
     
         9 . The method of  claim 6 , further comprising:
 depositing the feed material from an infeed structure onto the first perforation region of the inner surface of the screen.   
     
     
         10 . The method of  claim 9 , wherein:
 Infeed structure includes a feed chamber for receiving the feed material to convey it for deposit on the first perforation region through an inlet opening, the feed chamber further defining an outlet opening extending downward to an upper edge of a side wall the feed chamber comprises, the upper edge of the side wall being located at the overflow height, Y1; and   urging a feed lid rotatably attached to the feed housing to rotate from a closed position to feed material flowing from the feed chamber over the upper edge of the side wall, the feed lid having a feed lid weight bearing onto the flow of feed material.