Process and Device to Manufacture Cellulose Pulp

Abstract

Process and device to manufacture and dewater cellulose pulps in which defibered cellulose is screened to remove shives, fractionated in to at least three fractions ( 10, 3, 12 ), which fractions are treated each by itself and then are brought together completely or partly, and that the fractionation is done according to specific surface, preferably with hydrocyclones, and that the process comprises process stages ( 6,7 ) that fractionates out fibers with high specific surface, preferably thin-walled fibers, and that the process comprises process stages ( 2 ) that fractionates out fibers that have lower specific surface, preferably fibers with thicker fiber wall, and that one or several fiber fractions ( 3, 3 a ) are treated, to be split, fibrillated and permanently collapsed, preferably with a refiner, ball mill or similar.

1 . A process for manufacturing cellulose pulps, the process comprising: 
 screening defibered cellulose to remove shives;    fractionating the defibered cellulose, according to specific surface, with a device comprising hydrocylones, the step of fractionating comprising;    fractionating out fibers with high specific surfaces;    fractionating out fibers having lower specific surface, and    fractionating the defibered cellulose into at least three fractions;    treating the at least three fractions individually;    bringing the at least three fractions together completely or partly, and    using a device that comprises a comminution device, to split, fibrillate and permanently collapse at least one of the at least three fractions.    
   
   
       2 . The process according to  claim 1 , wherein the fractions treated in the comminution device comprise fibers with a z-value between 0.3 and 0.8.  
   
   
       3 . The process according to  claim 1 , wherein the comminution device permanently collapses the fibers of the fractions treated therein by inducing cracks in a fiber wall of the fibers.  
   
   
       4 . The process according to  claim 1 , wherein the comminution device is configured to refine at a pulp consistency in the interval 0.8%-14%.  
   
   
       5 . The process according to  claim 1 , wherein the comminution device comprises a refiner configured to run at an energy input of 10-800 kWh/t.  
   
   
       6 . The process according to  claim 1 , wherein the fraction that comprises the fibers with high specific surface leaves from a base of a hydrocyclone stage.  
   
   
       7 . The process according to  claim 1 , wherein the fraction with lower specific surface leaves from a base of a hydrocyclone stage.  
   
   
       8 . The process according to  claim 1 , wherein the fraction enriched in a fines material and comprising the fibers with high specific surface is bleached by a bleaching agent in a non alkaline environment.  
   
   
       9 . The process according to  claim 8 , wherein the pH at the bleaching is less than 9.  
   
   
       10 . The process according to  claim 8 , wherein the bleaching agent is a reducing bleaching agent.  
   
   
       11 . The process according to  claim 8 , wherein the bleaching agent comprises dithionite.  
   
   
       12 . The process according to  claim 1 , wherein the fraction with fibers with lower specific surface is bleached with an oxidative bleaching agent.  
   
   
       13 . The process according to  claim 12 , wherein the bleaching agent comprises hydrogen peroxide.  
   
   
       14 . The process according to  claim 12 , wherein the bleaching agent comprises ozone.  
   
   
       15 . The process according to  claim 1 , wherein a device for treatment comprising a comminution device is provided for peeling off fiber walls of fibers in the fraction that remains after previous process stages and which has the lowest specific surface.  
   
   
       16 . The process according to  claim 15 , wherein the device for treatment comprises refining at greater than 14% consistency.  
   
   
       17 . The process according to  claim 1 , wherein the fraction with fibers with lower specific surface, after treatment is mixed with the fraction with fibers with high specific surface to improve the dewatering properties.  
   
   
       18 . The process according to  claim 1 , wherein the fraction with fibers with lower specific surface, is dewatered alone to a higher consistency than the finally wanted consistency of a mix of the fractions, so that the fraction with the fibers with high specific surface only needs to be dewatered partly or not at all.  
   
   
       19 . The process according to  claim 1 , wherein the fractions comprising the fibers with high and lower specific surface, after treatment, are brought together to a pulp stream with a pulp that has been produced with lower input of energy and bleaching agents than in a conventional factory for wood containing printing grades of pulp, news-print pulp, SC, LWC, SC A++ pulp and other pulps.  
   
   
       20 . A device for improving properties of cellulose pulps, the improved properties concerning properties such as, light scattering, tensile index, tear index, surface roughness, bleaching chemicals consumption, energy consumption, the device comprising: 
 a first hydrocyclone device for receiving the cellulose pull and dividing therefrom a first base fraction and a first apex fraction;    a second hydrocyclone device for receiving the first apex fraction from the first hydrocyclone and dividing therefrom a second base fraction and a second apex fraction, and    a refiner for receiving and treating the second base fraction at a consistency between 1-14%.    
   
   
       21 . The device according to  claim 20 , wherein the device is configured to bleach the first base fraction with a non alkaline reducing bleaching agent.  
   
   
       22 . The device according to  claim 20 , wherein the device is configured to bleach the second base fraction with an oxidizing bleaching agent.  
   
   
       23 . The device according to  claim 20 , further comprising: 
 a third hydrocylcone device for dividing the second apex fraction into a third base fraction and a third apex fraction; and    a second refiner for treating the third base fraction after dewatering at a consistency between 1-14%.    
   
   
       24 . The device according to  claim 23 , wherein the device is configured to bleach the third base fraction with an oxidizing bleaching agent.  
   
   
       25 . The device according to  claim 20 , wherein the device is configured to bring together the first base fraction and the second base fraction to a common pulp stream with improved properties.  
   
   
       26 . The device according to  claim 20 , wherein the device continues cleaning the third apex fraction with a fourth hydrocyclone that removes heavy impurities.  
   
   
       27 . The device according to  claim 26 , wherein the device is configured to refine a fourth base fraction from the fourth hydrocyclone at a consistency greater than 5%.  
   
   
       28 . A process for producing and dewatering cellulose pulps, the process comprising: 
 screening defibered cellulose to remove shives;    fractionating the defibered cellulose into at least three fractions, according to specific surface, with a device comprising hydrocylones, the step of fractionating comprises: 
 fractionating out fibers with high specific surface, and  
 fractionating out fibers having lower specific surface;  
   dewatering the fraction having lower specific surface to a given consistency, and    mixing the fraction having lower specific surface with at least one of the other fractions.