System and method for oxygen delignification of pulp made for lignocellulosic material

Abstract

The system is for the oxygen delignification, in at least two reaction stages, of pulp that consists of lignocellulose-containing material having a mean concentration of 8-18% pulp consistency. The system has a first pump followed by a first oxygen mixer that is followed by a first delignification zone. The first delignification zone is followed by a second steam mixer that is followed by a second pump that is followed by a third oxygen mixer and a second delignification zone.

1 - 31 . (canceled)  
   
   
       32 . A method for the oxygen delignification of pulp, comprising: 
 providing a lignocellulose-containing pulp having a mean concentration is 8-18%;    in a first pump, pumping the pulp to a first mixer;    in the first mixer, receiving the pulp and admixing bleaching chemicals to the pulp;    in a first delignification zone, delignifying the pulp received from the first mixer, maintaining a first temperature of 75-95 C and a first pressure of 0-6 bar for 2-10 minutes;    in a second mixer, receiving the pulp from the first delignification zone and admixing steam to the pulp to increase the first temperature to a second temperature of 90-110 C;    in a second pump, receiving the pulp from the second mixer, pumping the pulp to a third mixer and increasing the first pressure to a second pressure of 8-10 bar;    in the third mixer, receiving the pulp from the second pulp and admixing bleaching chemicals to the pulp; and    in a second delignification zone, delignifying the pulp received from the third mixer for 20-100 minutes.    
   
   
       33 . The method according to  claim 32  wherein the method further comprises mechanically agitate the pulp in the first and third mixers.  
   
   
       34 . The method according to  claim 32  wherein the method further comprises adjusting a steam supply depending upon a temperature of the pulp downstream of the second mixer.  
   
   
       35 . The method according to  claim 34  wherein the method further comprises providing the second mixer with a plurality of inlet holes in a pipe wall and sending steam through the inlet holes.  
   
   
       36 . The method according to  claim 35  wherein the method further comprises providing steam at a pressure of 8-14 bar.  
   
   
       37 . The method according to  claim 32  wherein the method further comprises controlling a rotational speed of the second pump and adjusting the rotational speed depending upon a pressure in the firs delignification zone.  
   
   
       38 . The method according to  claim 32  wherein the method further comprises adding oxygen to the first and third mixers.