Method for producing pulp and products from high silica content agricultural waste materials

Abstract

A method of producing a high quality paper pulp slurry from high silica content lignocellulosic agricultural waste materials is provided. The method includes combining the agricultural waste materials with a chemical composition to form a mixture, sautéing the mixture, and grinding the sautéed mixture to provide the pulp slurry. The method results in greater than 55 percent solids recovery in the pulp slurry relative to the starting lignocellulosic agricultural waste materials, and removes substantially none of the lignin from the agricultural waste materials.

What is claimed is:  
     
         1 . A method for producing a pulp slurry comprising the steps of: 
 a) providing a lignocellulosic material having a silica content of at least 1% by weight on a dry solids basis;    b) combining said lignocellulosic material with a chemical composition to form a mixture, said chemical composition comprising 0.4-4.8 weight percent base reckoned as alkali hydroxide, 0.2-4 weight percent bleaching agent, 0.1-10 weight percent alkali metal silicate, and 0.001-10 weight percent chelating agent, all on a dry solids basis relative to said lignocellulosic material;    c) sautéing said mixture; and    d) comminuting said sautéed mixture to produce said pulp slurry.    
     
     
         2 . A method according to  claim 1 , further comprising adding water to said mixture after said sautéing step to provide said pulp slurry with a total solids content of 0.02-5 weight percent.  
     
     
         3 . A method according to  claim 1 , said bleaching agent being hydrogen peroxide.  
     
     
         4 . A method according to  claim 1 , said alkali metal silicate being sodium silicate.  
     
     
         5 . A method according to  claim 1 , said mixture being sautéed at a temperature of 100-300° C.  
     
     
         6 . A method according to  claim 1 , said mixture being sautéed at a temperature of about 200° C.  
     
     
         7 . A method according to  claim 1 , said pulp slurry having greater than 55 percent solids recovery relative to said lignocellulosic material.  
     
     
         8 . A method according to  claim 1 , said pulp slurry having at least a 60 percent solids recovery relative to said lignocellulosic material.  
     
     
         9 . A method according to  claim 1 , said lignocellulosic material having an initial lignin content, wherein lignin is not substantially removed from said lignocellulosic material to produce said pulp slurry, said pulp slurry comprising substantially all of said initial lignin content of said lignocellulosic material.  
     
     
         10 . A method according to  claim 1 , being performed at substantially atmospheric pressure.  
     
     
         11 . A method according to  claim 1 , said lignocellulosic material having a moisture content of 1-30 weight percent, balance solids, said chemical composition being solvated in water supplied from said moisture content of said lignocellulosic material.  
     
     
         12 . A method according to  claim 1 , wherein no additional water is supplied to said mixture during or prior to said sautéing step besides the water supplied from said moisture content of said lignocellulosic material.  
     
     
         13 . A method according to  claim 1 , said lignocellulosic material having a moisture content of about 10 weight percent, balance solids.  
     
     
         14 . A method according to  claim 1 , further comprising adding water to said mixture during or prior to said sautéing step to provide a total moisture content, relative to said lignocellulosic material, of about 50 percent by weight.  
     
     
         15 . A method according to  claim 1 , performed on a continuous basis at steady-state.  
     
     
         16 . A method according to  claim 1 , further comprising: 
 a) providing a pulping apparatus, said pulping apparatus comprising a cooker unit and a milling unit, said cooker unit including an agricultural waste material passage having an inlet and an outlet, and a conveying device located within said agricultural waste material passage, said milling unit having a first grinding plate and a second grinding plate;    b) providing said mixture into said inlet of said agricultural waste material passage;    c) conveying said mixture through said agricultural waste material passage by operation of said conveying device;    d) sautéing said mixture at a temperature of 100-300 degrees Celsius as said mixture is conveyed through said agricultural waste material passage; and    e) delivering said mixture into said milling unit, said comminuting step being performed by grinding between said first and second grinding plates to produce said pulp slurry.    
     
     
         17 . A method according to  claim 16 , said lignocellulosic material being sautéed in juices supplied from a moisture content of said lignocellulosic material, said chemical composition being dissolved or solvated at least in part in water from said moisture content.  
     
     
         18 . A method according to  claim 16 , further comprising moving or shearing at least one of said first and second grinding plates relative to the other grinding plate to provide a shearing grinding force between adjacent surfaces of said first and second grinding plates to comminute said mixture to produce said pulp slurry.  
     
     
         19 . A method according to  claim 1 , said chelating agent being selected from the group consisting of alkali earth sulfates.  
     
     
         20 . A method according to  claim 1 , said chelating agent being magnesium sulfate.  
     
     
         21 . A method for producing a pulp slurry comprising the steps of: 
 a) providing a lignocellulosic material having an initial lignin content and a silica content of at least 1% by weight on a dry solids basis;    b) combining said lignocellulosic material with a chemical composition to form a mixture;    c) sautéing said mixture; and    d) comminuting said sautéed mixture to produce said pulp slurry, said pulp slurry comprising substantially all of said initial lignin content of said lignocellulosic material.    
     
     
         22 . A method according to  claim 21 , said pulp slurry having greater than 55 percent solids recovery relative to said lignocellulosic material.  
     
     
         23 . A method according to  claim 21 , further comprising adding water to said mixture after said sautéing step to provide said pulp slurry with a total solids content of 0.02-5 weight percent.  
     
     
         24 . A method according to  claim 21 , further comprising adding water to said mixture during or prior to said sautéing step to provide a total moisture content, relative to said lignocellulosic material, of 30-70 percent by weight.