Methods for carbonate pretreatment and pulping of cellulosic material

Abstract

A method of pretreating comminuted fibrous material with sodium carbonate and then cooking the pretreated material in the presence of anthraquinone (AQ) is provided. The resulting pulp produced has a higher yield, enhanced strength, and better bleachability compared to pulp produced by prior art methods. AQ may also be introduced to the carbonate pretreatment stage. The method may further include an acid pretreatment providing further enhanced properties to the pulp produced.

1 . A method of treating comminuted cellulosic fibrous material comprising: 
 a) treating the cellulosic fibrous material with a substantially sulfur-free carbonate-containing solution to produce a pretreated cellulosic material; and    b) treating the pretreated cellulosic material with a pulping chemical for a sufficient time and at a sufficient temperature to produce a cellulose pulp;    wherein, in at least of one of a) and b), the cellulosic fibrous material is treated with an anthraquinone.    
   
   
       2 . The method as recited in  claim 1 , wherein the cellulosic fibrous material is treated with an anthraquinone in a).  
   
   
       3 . The method as recited in  claim 1 , wherein the pretreated cellulosic fibrous material is treated with an anthraquinone in b).  
   
   
       4 . The method as recited in  claim 1 , wherein the carbonate-containing solution comprises a sodium carbonate-containing solution.  
   
   
       5 . The method as recited in  claim 1 , wherein the carbonate-containing solution comprises an aqueous solution having a concentration of from about 1% to about 12% carbonate as Na 2 O on wood.  
   
   
       6 . The method as recited in  claim 5 , wherein the concentration comprises from about 3% to about 9% carbonate as Na 2 O on wood.  
   
   
       7 . The method as recited in  claim 1 , wherein the sulfur-free carbonate-containing solution comprises a substantially sulfur-free sodium carbonate solution.  
   
   
       8 . The method as recited in  claim 1 , wherein the pulping chemical comprises sodium hydroxide.  
   
   
       9 . The method as recited in  claim 8 , wherein the pulping chemical consists of sodium hydroxide.  
   
   
       10 . The method as recited in  claim 1 , wherein the method further comprises, prior to a), c) treating the comminuted fibrous material with an acidic solution.  
   
   
       11 . The method as recited in  claim 10 , wherein the method further comprises, after c) and before a), d) extracting at least some of the acidic solution from the cellulosic fibrous material.  
   
   
       12 . The method as recited in  claim 4 , wherein the sodium carbonate solution comprises about 1% to about 12% sodium carbonate as Na 2 O on chips.  
   
   
       13 . The method as recited in  claim 12 , wherein the sodium carbonate comprises about 2% to about 7% sodium carbonate as Na 2 O on chips.  
   
   
       14 . The method as recited in  claim 1 , wherein a) is practiced at a temperature greater than 100 degrees C.  
   
   
       15 . The method as recited in  claim 14 , wherein a) is practiced at a temperature between about 120 degrees C. and about 170 degrees C.  
   
   
       16 . The method as recited in  claim 15 , wherein a) is practiced at a temperature between about 120 degrees C. and about 150 degrees C.  
   
   
       17 . The method as recited in  claim 1 , wherein a) is practiced from about 15 minutes to about 120 minutes.  
   
   
       18 . The method as recited in  claim 1 , wherein the method produces a pulp having a lower rejects percent and a higher screened yield percent compared to a pulp produced by the method without practicing a).  
   
   
       19 . The method as recited in  claim 1 , wherein the method is practiced substantially continuously.  
   
   
       20 . The method as recited in  claim 1 , wherein the method further comprises an oxygen delignification treatment, and wherein the method produces a pulp having a lower kappa number after the oxygen delignification treatment at a predetermined screened yield compared to a pulp produced by the method without practicing a).  
   
   
       21 . The method as recited in  claim 1 , wherein the treatment with anthraquinone comprises an aqueous anthraquinone having a concentration between about 0.01 weight percent to about 0.20 weight percent on chips.  
   
   
       22 . The method as recited in  claim 21 , wherein the treatment with anthraquinone comprises an aqueous anthraquinone having a concentration between about 0.05 weight percent to about 0.10 weight percent on chips.  
   
   
       23 . The method as recited in  claim 1 , wherein the anthraquinone is introduced after a) and comprises a concentration of aqueous anthraquinone about 0.01 weight percent to about 0.20 weight percent on chips.  
   
   
       24 . The method as recited in  claim 1 , wherein treating the pretreated cellulosic material with a pulping chemical further comprises producing a liquid containing spent pulping chemical; and wherein the method further comprises: 
 treating the liquid containing spent pulping chemical to produce a carbonate-containing solution from the spent pulping chemical; and using the carbonate-containing solution produced from the spent pulping chemical as the carbonate containing solution in a).    
   
   
       25 . The method as recited in  claim 24 , wherein treating the liquid containing spent pulping chemical comprises: 
 concentrating the liquid sufficiently to support combustion;    burning the concentrated liquid to produce a smelt containing carbonate; and    introducing a liquid to the smelt to provide the carbonate-containing solution from the spent pulping chemical.    
   
   
       26 . The method as recited in  claim 24 , wherein the carbonate containing solution comprises about 2% to 7% sodium carbonate as Na 2 O on chips.  
   
   
       27 . A pulp produced from the process of  claim 1 , wherein said pulp has a greater yield than pulp produced from prior art.  
   
   
       28 . The method as recited in  claim 1 , wherein the method further comprises an oxygen delignification treatment and at least one bleaching stage, wherein the method produces a cellulose pulp having a brightness greater than 88% elrepho.  
   
   
       29 . A method of treating comminuted cellulosic fibrous material comprising: 
 a) treating the cellulosic fibrous material with an acid solution;    b) treating the cellulosic fibrous material with a carbonate-containing solution to produce a pretreated cellulosic material; and    c) treating the pretreated cellulosic material with a sulfur containing pulping chemical for a sufficient time and at a sufficient temperature to produce a cellulose pulp;    wherein, in at least of one of b) and c), the cellulosic fibrous material is treated with an anthraquinone.    
   
   
       30 . The method as recited in  claim 29 , wherein the cellulosic fibrous material is treated with an anthraquinone in b).  
   
   
       31 . The method as recited in  claim 29 , wherein the pretreated cellulosic fibrous material is treated with an anthraquinone in c).  
   
   
       32 . The method as recited in  claim 29 , wherein the carbonate-containing solution comprises a sodium carbonate-containing solution.  
   
   
       33 . The method as recited in  claim 32 , wherein the sodium carbonate-containing solution comprises kraft green liquor.  
   
   
       34 . The method as recited in  claim 29 , wherein the carbonate-containing solution comprises an aqueous solution having a concentration of from about 1% to about 12% carbonate as Na 2 O on wood.  
   
   
       35 . The method as recited in  claim 34 , wherein the carbonate containing solution comprises a aqueous solution having a concentration of from about 3% to about 9% carbonate on wood.  
   
   
       36 . The method as recited in  claim 29 , wherein the method further comprises, after a) and before b), d) extracting at least some of the acidic solution from the cellulosic fibrous material.  
   
   
       37 . The method as recited in  claim 29 , wherein b) is practiced at a temperature greater than 100 degrees C.  
   
   
       38 . The method as recited in  claim 37 , wherein b) is practiced at a temperature between about 120 degrees C. and about 170 degrees C.  
   
   
       39 . The method as recited in  claim 38 , wherein b) is practiced at a temperature between about 120 degrees C. and about 150 degrees C.  
   
   
       40 . The method as recited in  claim 29 , wherein b) is practiced from about 15 minutes to about 120 minutes.  
   
   
       41 . The method as recited in  claim 29 , wherein the method produces a pulp having a lower rejects percent and a higher screened yield percent compared to a pulp produced by the method without practicing b).  
   
   
       42 . The method as recited in  claim 29 , wherein the method is practiced substantially continuously.  
   
   
       43 . The method as recited in  claim 29 , wherein the method further comprises an oxygen delignification treatment, and wherein the method produces a pulp having a lower kappa number after the oxygen delignification treatment at a predetermined screened yield compared to a pulp produced by the method without practicing b).  
   
   
       44 . The method as recited in  claim 29 , wherein treating with anthraquinone comprises a concentration between about 0.01 weight percent to about 0.20 weight percent on chips.  
   
   
       45 . The method as recited in  claim 44 , wherein the concentration comprises between about 0.05 weight percent to about 0.10 weight percent on chips.  
   
   
       46 . The method as recited in  claim 29 , wherein the anthraquinone is introduced after b), and wherein treating with anthraquinone comprises a concentration between about 0.01 weight percent to about 0.20 weight percent on chips.  
   
   
       47 . The method as recited in  claim 29 , wherein treating the pretreated cellulosic material with a sulfur containing pulping chemical further comprises producing a liquid containing spent pulping chemical; and wherein the method further comprises: 
 treating the liquid containing spent pulping chemical to produce a carbonate-containing solution from the spent pulping chemical; and    using the carbonate-containing solution produced from the spent pulping chemical as the carbonate-containing solution in b).    
   
   
       48 . The method as recited in  claim 47 , wherein treating the liquid containing spent pulping chemical comprises: 
 concentrating the liquid sufficiently to support combustion;    burning the concentrated liquid to produce a smelt containing carbonate; and    introducing a liquid to the smelt to provide the carbonate-containing solution from the spent pulping chemical.