Method and arrangement for treating pulp

Abstract

The present invention relates to a method and arrangement for treating pulp. The method and arrangement according to the invention are suitable for use in production of chemical pulp in situations, where gas must be separated from the pulp and the pulp must be diluted. A characterizing feature of the method and arrangement for treating pulp according to the invention, in which method pulp is transferred from a first pulp treatment apparatus ( 5 ) treating pulp in a higher consistency, to a second pulp treatment apparatus ( 50 ) treating pulp in a lower consistency, is that gas is separated from the pulp in a consistency higher than said second consistency, pulp is pumped by means of a pump ( 26 ) to a second treatment performed in low consistency, with the pulp being diluted with an apparatus ( 28 ) located after the pump ( 26 ) to said second consistency prior to treatment in said consistency.

1 . A method of degassing, pumping and diluting pulp, in which method pulp is transferred from a first, at least so-called medium consistency to a treatment in a second, lower consistency, characterized in that 
 a) gas is separated from the pulp in a consistency higher than said second consistency,    b) pulp is pumped to the treatment taking place in the second, lower consistency, and    c) in the last step, pulp is diluted to said second consistency prior to the treatment in said consistency.    
   
   
       2 . A method according to  claim 1 , characterized in that pulp is diluted from said first consistency to a consistency higher than the second consistency in step a).  
   
   
       3 . A method according to  claim 2 , characterized in that pulp is diluted from the discharge consistency of the press to medium consistency.  
   
   
       4 . A method according to  claim 1 , characterized in that said first consistency is the discharge consistency of a washing apparatus.  
   
   
       5 . A method according to  claim 1 , characterized in that said consistency higher than the second consistency is medium consistency.  
   
   
       6 . A method according to  claim 1 , characterized in that the treatment taking place in low consistency is screening ( 50 ).  
   
   
       7 . A method according to  claim 1 , characterized in that in step c) the pulp is diluted to a consistency of about 1-3%.  
   
   
       8 . A method according to  claim 1 , characterized in that step a) is performed by means of a turbulence-forming rotor ( 32 ).  
   
   
       9 . A method according to  claim 1 , characterized in that steps a) and b) are performed by means of a so-called MC™ pump.  
   
   
       10 . A method according to  claim 2 , characterized in that said dilution is performed with the assistance of a bottom scraper ( 22 ).  
   
   
       11 . A method according to  claim 1 , characterized in that the treatment taking place in low consistency is washing, pressing, dewatering or filtering ( 55 ).  
   
   
       12 . An apparatus for treating pulp, the apparatus comprising at least a first pulp treatment apparatus, from which the pulp is discharged in a first, at least so-called medium consistency, a second pulp treatment apparatus ( 50 ) the operation of which requires a second consistency lower than the discharge consistency of the first pulp treatment apparatus, and a pump ( 26 ) for transferring pulp to the second pulp treatment apparatus ( 50 ), characterized in that both an apparatus for degassing the pulp at first consistency and an apparatus ( 28 ) for diluting pulp to the consistency required by the second pulp treatment apparatus ( 50 ) is arranged between the pump ( 26 ) and the second pulp treatment apparatus ( 50 ).  
   
   
       13 . A pulp treating arrangement according to  claim 12 , characterized in that an apparatus ( 26 ;  32 ) for separating gas from pulp in higher consistency than the treatment consistency of the second pulp treatment apparatus ( 50 ) is arranged between the first pulp treatment apparatus ( 5 ) and a second pulp treatment apparatus ( 50 ).  
   
   
       14 . A pulp treating arrangement according to  claim 12 , characterized in that said pump ( 26 ) is a gas separating pump.  
   
   
       15 . A pulp treating apparatus according to  claim 13 , characterized in that said gas separating apparatus is a turbulence-forming rotor ( 32 ) arranged in the drop leg ( 30 ) prior to the pump ( 26 ).  
   
   
       16 . A pulp treating arrangement according to  claim 12 , characterized in that said pump ( 26 ) is a so-called MC™ pump.  
   
   
       17 . A pulp treating arrangement according to  claim 12 , characterized in that said first pulp treatment apparatus ( 5 ) is a washing apparatus, such as a pressurized drum washer, suction drum washer, wire press or a wash press.  
   
   
       18 . A pulp treating arrangement according to  claim 12 , characterized in that the second pulp treatment apparatus ( 50 ) is a screening apparatus.  
   
   
       19 . A pulp treating arrangement according to  claim 12 , characterized in that said dilution apparatus is a rotary or static mixer ( 28 ).  
   
   
       20 . A pulp treating arrangement according to  claim 12 , characterized in that said dilution apparatus is a centrifugal pump.  
   
   
       21 . A pulp treating arrangement according to  claim 12 , characterized in that the second pulp treatment apparatus ( 55 ) is a pressurized drum washer, suction drum washer, wire press or a wash press.