Method of bleaching cellulose pulp and bleaching line therefore

Abstract

The method is for bleaching cellulose pulp in a bleach line that has at least two bleaching steps. The filtrate distribution is led up through the bleaching line counter-currently to the flow of cellulose pulp established in the bleaching line. A single joint main conduit is used for the bleaching steps. Wash filtrates obtained from the wash steps, used after or before the bleaching step, are led in conduits to branch locations on the main conduit that are positioned downstream of the branch location for drawing off of wash and/or dilution liquor for the wash step in question. All branch points in the joint main conduit are in fluid communication with one another along the main conduit.

1 - 26 . (canceled)  
   
   
       27 . A method of bleaching cellulose pulp in a bleaching line, comprising: 
 providing a bleaching line having a first and a second wash apparatus, conducting cellulose pulp in a first flow direction through the bleaching line, the first wash apparatus being downstream of the second wash apparatus in the bleaching line;    providing a main continuous conduit extending passed both the first and second wash apparatuses;    conducting a wash liquor in a second flow direction through the main conduit, the second flow direction being opposite the first flow direction, conveying a wash liquor through the main continuous conduit;    establishing a continuous liquid volume in the main conduit;    conveying a first portion of the wash liquor from the main continuous conduit to the first wash apparatus;    bleeding out a first filtrate from the first wash apparatus; and    conveying the first filtrate to the same main continuous conduit; and    mixing the first filtrate with a second portion of wash liquor in the main conduit to form a mixture, and using at least a part of the mixture as wash liquor in the second wash apparatus.    
   
   
       28 . The method according to  claim 27  wherein the method further comprises conveying all wash liquor to the first wash apparatus via a first branch conduit connected to the main continuous conduit.  
   
   
       29 . The method according to  claim 27  wherein the method further comprises conveying the first portion of the wash liquor via a first branch conduit to the first wash apparatus, the first branch conduit being connected directly to the main conduit.  
   
   
       30 . The method according to  claim 27  wherein the method further comprises conveying the first filtrate to the main conduit in a second branch conduit.  
   
   
       31 . The method according to  claim 27  wherein the method further comprises connecting the second branch conduit to the main conduit downstream of a connection of the first branch conduit to the main conduit.  
   
   
       32 . The method according to  claim 27  wherein the method further comprises conveying the cellulose pulp in the bleaching line in a first flow direction and conveying the wash liquor in the main conduit in a second flow direction that is opposite the first flow direction.  
   
   
       33 . The method according to  claim 31  wherein the method further comprises conveying a second portion of the wash liquor to the second wash apparatus.  
   
   
       34 . The method according to  claim 33  wherein the method further comprises providing a third wash apparatus and a fourth wash apparatus in the bleaching line, the fourth wash apparatus being upstream of the third and the second wash apparatuses and bleeding of a second filtrate from the second wash apparatus and conveying the second filtrate to the main conduit via a fourth branch conduit.  
   
   
       35 . The method according to  claim 34  wherein the method further comprises withdrawing a third portion of the wash liquor from the main conduit and conveying the third portion of the wash liquor in a fifth branch conduit to the fourth wash apparatus and bleeding off a third filtrate from the third wash apparatus and conveying the third filtrate to an outlet portion of the fourth wash apparatus without passing through the main conduit.  
   
   
       36 . The method according to  claim 27  wherein the method further comprises feeding acidic liquor to the cellulose pulp adjacent to the first wash apparatus.  
   
   
       37 . The method according to  claim 27  wherein the method further comprises feeding alkaline liquor to cellulose pulp adjacent to the second wash apparatus.  
   
   
       38 . The method according to  claim 27  wherein the method further comprises conveying the filtrate in the second branch conduit directly to the main conduit.  
   
   
       39 . The method according to  claim 27  wherein the method further comprises conveying the first filtrate to an end of the main continuous conduit disposed adjacent to the beginning portion of the bleaching line.