Method for ozone treatment of used paper

Abstract

The invention concerns a novel method for ozone treatment of used paper which consists in transforming used paper into pulp in an aqueous medium, screening then de-inking said paper by liquid flotation, the method further comprising an ozone treatment step carried out at latest prior to the liquid flotation step.

1 - 12 . (canceled)  
     
     
         13 . A method for treating used paper comprising: 
 a) pulping said paper in an aqueous medium;    b) screening said pulp at least once to remove coarse particles;    c) deinking said pulp with at least on flotation; and    d) performing an ozonization step prior to said flotation.    
     
     
         14 . The method of  claim 13 , wherein said ozonization step is performed at a used paper pulp consistency of between about 0.5% and about 5%.  
     
     
         15 . The method of  claim 14 , wherein said consistency is between about 0.5% and about 3%.  
     
     
         16 . The method of  claim 13 , further comprising performing said method in water, without adding chemicals other than ozone.  
     
     
         17 . The method of  claim 13 , further comprising performing said method in the presence of caustic soda NaOH, hydrogen peroxide H 2 O 2 , and sodium silicate Na 2 SiO 3 .  
     
     
         18 . The method of  claim 13 , wherein said ozonization is performed after said screening.  
     
     
         19 . The method of  claim 13 , wherein said ozonization further comprises being performed in a two-phase tubular contactor, wherein said contactor comprises a gas-liquid type.  
     
     
         20 . The method of  claim 19 , further comprising performing said ozonization in said contactor in wave mode.  
     
     
         21 . The method of  claim 19 , further comprising performing said ozonization in said contactor in plug mode.  
     
     
         22 . The method of  claim 13 , further comprising performing said ozonization with a gas mixture wherein said mixture comprises between about 50 g and about 200 g of ozone per m 3  of gas mixture.  
     
     
         23 . The method of  claim 13 , further comprising performing said ozonization with a gas mixture wherein said mixture comprises at least one member selected from the group consisting of: 
 a) an air-ozone gas mixture; and    b) an oxygen-ozone gas mixture.    
     
     
         24 . The method of  claim 19 , further comprising: 
 a) introducing said ozone in a gas mixture at a rate greater than about 0.5 m/s and less than or equal to about 10 m/s;    b) introducing said pulp at a rate greater than about 0.5 m/s and less than or equal to about 10 m/s.    
     
     
         25 . The method of  claim 24 , wherein: 
 a) said gas mixture rate is between about 0.5 m/s and about 2 m/s; and    b) said pulp rate is between about 0.5 m/s and about 2 m/s.    
     
     
         26 . The method of  claim 25 , wherein said gas mixture comprises at least one member selected from the group consisting of: 
 a) an air-ozone mixture;    b) an oxygen-ozone gas mixture; and    c) a nitrogen-ozone mixture.