Method and apparatus for the integrated cleaning of a paper-pulp processing plant

Abstract

A method for the integrated cleaning of a paper-pulp processing plant including one or more high density cleaners comprising the steps of supplying the rejected flow ( 10 ) from one of the high density cleaners to a screening centrifugal separator ( 11 ); screening out contaminants in the separator ( 11 ) using a screen hole size of less than 3.5 mm; thickening any fibrous material accepted by the separator ( 11 ) and returning same to stock being processed in the processing plant; and recovering liquid (B) from any material (A) rejected by the separator ( 11 ) prior to disposing of the material. The invention further comprises an apparatus for performing the method.

1 . A method for the integrated cleaning of a paper-pulp processing plant including one or more high density cleaners for removing high density impurities from feed pulp, comprising the steps of:
 supplying rejected flow ( 10 ) from at least one of the high density cleaners to a screening centrifugal separator ( 11 );   screening out contaminants in the separator ( 11 ) using a screen hole size of less than 3.5 mm;   thickening any fibrous material accepted by the separator ( 11 ) and returning same to stock being processed in the processing plant; and   recovering liquid (B) from any material (A) rejected by the separator ( 11 ) prior to disposing of the material.   
   
   
       2 . A method as claimed in  claim 1 , wherein the rejected flow is from a final high density cleaner and contaminants in the separator ( 11 ) are screened using a screen hole size of approximately 2.5 mm. 
   
   
       3 . A method as claimed in  claim 2 , wherein clarified water is sprayed onto the contents of the separator ( 11 ) at a pressure in excess of 1.5 bar via nozzles having an aperture in excess of 1 mm in diameter. 
   
   
       4 . A method that is claimed in  claim 2 , wherein the material (A) rejected by the separator ( 11 ) is flushed with water at a pressure in excess of 2 bar prior to its egress from the separator ( 11 ). 
   
   
       5 . A method as claimed in  claim 1  comprising the additional step of supplying the rejected flow ( 10 ) to the separator ( 11 ) via a constant level box ( 12 ). 
   
   
       6 . A method as claimed in  claim 1  comprising the additional step of thickening any fibrous material accepted by the separator ( 11 ) prior to returning same to the stock and thickening any material (A) rejected by the separator ( 11 ) prior to its disposal. 
   
   
       7 . A method as claimed in  claim 6 , comprising the additional step of compacting the thickened material rejected by the separator ( 11 ) in order to recover the liquid (B) from the thickened material (A) prior to disposal of the thickened and compacted material (C). 
   
   
       8 . A paper-pulp processing plant including one or more high density cleaners and incorporating apparatus for the integrated cleaning of same, the apparatus comprising:
 a screening centrifugal separator ( 11 ) set up to receive the rejected flow ( 10 ) from one of the high density cleaners and adapted to screen out contaminants from the rejected flow using a screen hole size of less than 3.5 mm;   a thickener ( 15 ) for the thickening any fibrous material accepted by the separator ( 11 ) and returning same to stock being processed in the processing plant; and   apparatus for recovering liquid (B) from any material (A) rejected by the separator ( 11 ) prior to disposal of the material.   
   
   
       9 . A plant as claimed in  claim 8 , wherein the screening centrifugal separator comprises a screening basket with a screen hole size of approximately 2.5 mm. 
   
   
       10 . A plant as claimed in  claim 8  comprising a constant level box ( 12 ) to supply the rejected flow ( 10 ) to the separator ( 11 ). 
   
   
       11 . A plant as claimed in  claim 8  comprising a first inclined screw thickener ( 15 ) adapted to thicken any fibrous material accepted by the separator ( 11 ) prior to returning same to the stock, the screw thickener ( 15 ) comprising liquid filtering holes with a diameter less than 2.00 mm. 
   
   
       12 . A plant as claimed in  claim 8  wherein the means for recovering liquid (B) from the material (A) rejected by the separator ( 11 ) comprises a second inclined screw thickener ( 19 ) adapted to thicken any material rejected by the separator ( 11 ) and comprising liquid filtering holes with a diameter greater than 2.00 mm. 
   
   
       13 . A plant as claimed in  claim 8  wherein the apparatus for recovering liquid (B) from the material (A) rejected by the separator ( 11 ) also comprises a compactor press ( 20 ) adapted to compact the output from the second inclined screw thickener ( 19 ) and to release the liquid (B) therefrom. 
   
   
       14 . A plant as claimed in  claim 13 , wherein the compactor press ( 20 ) comprises a compression chamber ( 23 ) in which a ram ( 24 ) reciprocates to push material upwards into an inclined channel ( 25 ) against the force of a spring-loaded door ( 27 ) the spring loading ( 28 ) applied to the door ( 27 ) being adjustable so that the degree of compaction achieved within the press ( 20 ) can be varied as required. 
   
   
       15 . A plant as claimed in  claim 14 , wherein the spring loading ( 28 ) applied to the door ( 27 ) is equal to a constant force of around 44,000 kg.