Methods of processing lignocellulosic pulp with cavitation

Abstract

Methods of treating lignocellulosic pulp with cavitation are disclosed. The methods include delignifying a slurry comprising lignocellulos pulp in the presence of cavitation and bleaching a delignified pulp in the presence of cavitation. Delignification can be done by contacting a lignocellulosic pulp slurry with an oxidizing agent in a cavitation zone. Bleaching can be carried out by contacting a delignified pulp slurry with a bleaching agent in a cavitation zone.

1 . A method of processing lignocellulosic pulp comprising: 
 producing a delignified pulp slurry; and    contacting a bleaching agent with the delignified pulp slurry in a first cavitation region to produce a bleached, delignified pulp.    
     
     
         2 . The method of  claim 1 , wherein the slurry contains about 15% or less by weight dry pulp material.  
     
     
         3 . The method of  claim 1 , wherein the first cavitation region comprises a plurality of cavitation zones, each cavitation zone having a void zone adjacent thereto.  
     
     
         4 . The method of  claim 1 , wherein the first cavitation region comprises a chamber having a rotor formed with a plurality of irregularities.  
     
     
         5 . The method of  claim 1 , wherein the delignified pulp slurry is produced by contacting a slurry comprising lignocellulosic pulp with at least one oxidizing agent.  
     
     
         6 . The method of  claim 5 , wherein the slurry and oxidizing agent are contacted in a second cavitation region.  
     
     
         7 . The method of  claim 6 , wherein the second cavitation region comprises a plurality of cavitation zones, each cavitation zone having a void zone adjacent thereto.  
     
     
         8 . The method of  claim 6 , wherein the second cavitation region comprises a chamber having a rotor formed with a plurality of irregularities.  
     
     
         9 . The method of  claim 5 , wherein the slurry further comprises black liquor.  
     
     
         10 . The method of  claim 7 , wherein the oxidizing agent comprises an oxygen-containing material.  
     
     
         11 . The method of  claim 10 , wherein the oxygen-containing material is air, ozone, molecular oxygen, sodium hydroxide, hydrogen peroxide, or any combination thereof.  
     
     
         12 . A method according to  claim 1 , wherein the bleaching agent is air, oxygen, ozone, hydrogen peroxide, sodium hydrosulfite, chlorine, chlorine dioxide, or any combination thereof.  
     
     
         13 . A method according to  claim 1 , wherein the delignified pulp slurry contains about 15% or less dry pulp material by weight.  
     
     
         14 . The method of  claim 1 , wherein the lignocellulosic pulp is produced by mechanical pulping, chemical pulping, or semichemical pulping.  
     
     
         15 . The method of  claim 1 , wherein the lignocellulosic pulp is a secondary pulp.  
     
     
         16 . A method of processing lignocellulosic pulp comprising: 
 contacting a bleaching agent with a slurry comprising lignocellulosic pulp in a first cavitation region to produce a bleached pulp.    
     
     
         17 . The method of  claim 16 , wherein the first cavitation region comprises a plurality of cavitation zones, each cavitation zone having a void zone adjacent thereto.  
     
     
         18 . The method of  claim 16 , wherein the first cavitation region comprises a chamber having a rotor formed with a plurality of irregularities.  
     
     
         19 . The method of  claim 16 , wherein the slurry further comprises black liquor.  
     
     
         20 . A method according to  claim 16 , wherein the bleaching agent is air, oxygen, ozone, hydrogen peroxide, sodium hydrosulfite, chlorine, chlorine dioxide, or any combination thereof.  
     
     
         21 . The method of  claim 16 , wherein the slurry contains about 15% or less dry pulp material by weight.  
     
     
         22 . The method of  claim 16 , wherein the lignocellulosic pulp is produced by mechanical pulping, chemical pulping, or semichemical pulping.  
     
     
         23 . The method of  claim 16 , wherein the lignocellulosic pulp is a secondary pulp.  
     
     
         24 . The method of  claim 16 , wherein 
 a first handsheet is produced from the lignocellulosic pulp and a second handsheet is produced from the bleached pulp;    the first handsheet exhibits a first tear strength and the second handsheet exhibits a second tear strength; and    the second tear strength is at least 10% greater than the first tear strength.    
     
     
         25 . The method of  claim 16 , wherein 
 a first handsheet is produced from the lignocellulosic pulp and a second handsheet is produced from the bleached pulp;    the first handsheet exhibits a first tensile strength and the second handsheet exhibits a second tensile strength; and    the second tensile strength is at least 15% greater than the first tensile strength.    
     
     
         26 . A process to produce a paper product from wood comprising: 
 (a) providing wood chips;    (b) pulping the wood chips to produce a lignocellulosic pulp slurry;    (c) delignifying the lignocellulosic pulp slurry to produce a delignified pulp slurry;    (d) bleaching the delignified pulp slurry by contacting a bleaching agent with the delignified pulp slurry in the presence of cavitation to produce a bleached, delignified pulp;    (e) forming the bleached, delignified pulp into a paper product.