Kraft-Pulping of Hot Water Extracted Woodchips

Abstract

The method of the present invention is directed towards a method to increase the pulp yield of a lignocellulosic material, or increasing pulp bulk and/or pulp viscosity. This method comprises the following steps; preparing a lignocellulosic material, contacting the lignocellulosic material in a vessel with hot water or steam for a predetermined time, producing acetic acid from the reaction of the hot water or steam and the lignocellulosic material, lowering the pH to less than about 4, removing lignocellulosic material extracts including a large percentage of hemicellulose, acetic acid and metal ions, exposing contacted lignocellulosic material to pulping chemicals in a pulping reactor, forming a contacted lignocellulosic material pulp with a kappa number below about 19 after about 90 minutes of contact with the pulping chemicals, exposing the contacted lignocellulosic material pulp to whitening agents, and producing a whitened hot water contacted lignocellulosic material pulp.

1 . A method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material, the method comprising the steps of:
 a. preparing a lignocellulosic material;   b. contacting the lignocellulosic material in a vessel with hot water or steam for a predetermined time;   c. lowering the pH to less than about 5 by producing acetic acid from the reaction of the hot water or steam and the lignocellulosic material;   d. removing lignocellulosic material extracts including a percentage of hemicellulose, acetic acid and metal ions from the vessel;   e. exposing contacted lignocellulosic material to pulping chemicals in a pulping reactor;   f. forming a contacted lignocellulosic material pulp with a kappa number below about 19 after about 90 minutes of contact with the pulping chemicals;   g. exposing the contacted lignocellulosic material pulp to whitening agents; and   h. producing a whitened hot water contacted lignocellulosic material pulp.   
     
     
         2 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the hot water in the vessel is between about 20° C. and about 200° C. 
     
     
         3 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 2 , wherein the hot water in the vessel is about 150° C. 
     
     
         4 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the lignocellulosic material is contacted for between about 1 minute and 7 days. 
     
     
         5 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 4 , wherein the lignocellulosic material is contacted for about 90 minutes. 
     
     
         6 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the pH is lowered to about 3.5. 
     
     
         7 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the acetic acid reaches a concentration of about 0.06 M. 
     
     
         8 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the lignocellulosic material extracts are between about 2% and about 25% of the mass of the prepared lignocellulosic material. 
     
     
         9 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the lignocellulosic material extracts are between about 8% and about 15% of the mass of the prepared lignocellulosic material. 
     
     
         10 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the pulping chemicals are consumed by about 80% within about 60 minutes by the contacted lignocellulosic material. 
     
     
         11 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the residual concentration of pulping chemical in the contacted lignocellulosic material prior to exposing the contacted lignocellulosic material to whitening agents is about 10% of initial concentration within the pulping reactor. 
     
     
         12 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 9 , wherein the pulping chemicals comprise sodium hydroxide and sodium sulfide. 
     
     
         13 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 10 , wherein the pulping chemicals comprise sodium hydroxide and sodium sulfide. 
     
     
         14 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the contacted lignocellulosic material pulp has a kappa number about 90% lower than a pulp which has not undergone hot water contact. 
     
     
         15 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 13 , wherein the pulping chemicals are sodium hydroxide at a concentration of 16% and sodium sulfide at a concentration of 18%. 
     
     
         16 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 13 , wherein the pulping reactor is heated to between about 150° C. and 180° C. 
     
     
         17 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the contacted lignocellulosic material pulp has a bulk of at least about 2.00 cm 3 /g after about 210 minutes of contact with pulping chemicals. 
     
     
         18 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the contacted lignocellulosic material pulp has a bulk higher than an un-contacted lignocellulosic material pulp. 
     
     
         19 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 16 , wherein the pulping chemicals are sodium hydroxide at a concentration of 16% and sodium sulfide at a concentration of 18%. 
     
     
         20 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 16 , wherein the pulping reactor is heated to between about 150° C. and 180° C. 
     
     
         21 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein about 50% of the hemicellulose content of the lignocellulosic material is extracted from the vessel during the removal of lignocellulosic material extracts step. 
     
     
         22 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the hot water contacted lignocellulosic material has a residual chemical concentration from about 25% to about 33% of the residual chemical concentration of a non hot water contacted lignocellulosic material. 
     
     
         23 . The method of treating lignocellulosic material to increase pulp yield, pulp bulk and pulp viscosity of hot-water extracted lignocellulosic material of  claim 1 , wherein the pulping chemicals comprise sodium hydroxide.