Method for removal of metals from a bleach plant filtrate stream

Abstract

A method is disclosed for removal of non process elements from a Kraft bleach plant producing lyocell pulp. In the method the bleach plant filtrate is passed through at least one centrifugal cleaner. The non process elements are reduced by at least 20 percent of their original levels in the bleach plant filtrate.

1 . A method comprising the steps of: 
 providing a centrifugal cleaner,    providing an acidified bleach plant filtrate comprising non process elements,    passing said filtrate through said cleaner,    whereby each of said non process elements are reduced in the accept stream by at least 20% of their original levels in the bleach plant filtrate.    
   
   
       2 . The method of  claim 1  wherein said filtrate is a lyocell pulp bleach plant filtrate.  
   
   
       3 . The method of  claim 1  wherein the non process elements are selected from the group consisting of manganese, iron, copper, calcium and silica and mixtures thereof.  
   
   
       4 . The method of  claim 3  wherein the element is manganese.  
   
   
       5 . The method of  claim 3  wherein the element is iron.  
   
   
       6 . The method of  claim 3  wherein the element is copper.  
   
   
       7 . The method of  claim 3  wherein the element is silica.  
   
   
       8 . The method of  claim 3  wherein the element is calcium.  
   
   
       9 . The method of  claim 3  wherein manganese is reduced by at least 50% of the original level in the bleach plant filtrate.  
   
   
       10 . The method of  claim 3  wherein manganese is reduced by at least 70% of the original level in the bleach plant filtrate.  
   
   
       11 . The method of  claim 7  wherein the silica is reduced by at least 50% of the original level in the bleach plant filtrate.  
   
   
       12 . The method of  claim 7  wherein the silica is reduced by at least 70% of the original level in the bleach plant filtrate.  
   
   
       13 . The method of  claim 1  wherein the centrifugal cleaner is at least one forward cleaner.  
   
   
       14 . The method of  claim 1  where the centrifugal cleaner is a reverse cleaner.  
   
   
       15 . The accept stream of  claim 1  wherein said stream is circulated to the first bleach plant stage to wash the pulp.  
   
   
       16 . The accept stream of  claim 1  wherein said stream is circulated to any previous bleach plant stage to wash the pulp.  
   
   
       17 . The accept stream of  claim 1  wherein said stream is circulated to the last bleach plant stage to wash the pulp.