Pulping process for quality protection including methods for hemicellulose extraction and treatment of hemicellulose-extracted lignocellulosic materials

Abstract

A method for producing pulp by extracting hemicellulosic materials from lignocellulosic materials using water in an extraction stage, wherein the extraction stage is either a single extraction or a double extraction process; treating the lignocellulosic materials with an oxidizing agent in a treatment stage, wherein the treatment stage is selected from the group consisting of a second extraction process, an agent impregnation process, and a first pretreatment process; treating the lignocellulosic materials with a reducing agent in the treatment stage, wherein the treatment stage is selected from the group consisting of the second extraction process, the agent impregnation process, and a second pretreatment process; and then subjecting the lignocellulosic materials to a modified Kraft pulping process to produce pulp.

1 . A method of protecting hemicellulose pre-extracted lignocellulosic materials against degradation in an alkaline pulping process comprising:
 a) extracting organics from lignocellulosic materials using water or steam;   b) treating the lignocellulosic materials with an oxidizing agent and a reducing agent or additive, wherein the treating further includes a second extraction; and   c) subjecting the lignocellulosic materials to a Kraft pulping process in a digester.   
     
     
         2 . The method as claimed in  claim 1 , wherein the extracting further comprises treating the lignocellulosic materials and the water at a temperature between about 120° C. and 180° C. 
     
     
         3 . The method as claimed in  claim 2 , wherein the extracted lignocellulosic materials are added with water to the second extraction, along with the oxidizing agent and the reducing agent, and treated at an elevated temperature of between about 120° C. and 180° C. 
     
     
         4 . The method as claimed in  claim 3 , wherein the double extracted lignocellulosic materials are added with water to the digester, along with sodium hydroxide and sodium sulfide to produce the pulp. 
     
     
         5 . The method as claimed in  claim 4 , wherein the oxidizing agent is selected from the group consisting of polysulfides and the reducing agent is selected from the group consisting of sodium borohydride, sodium dithionate, and in-situ hydrogen. 
     
     
         6 . A method of protecting hemicellulose pre-extracted lignocellulosic materials against degradation in alkaline pulping processes comprising:
 a) extracting organics from lignocellulosic materials using water or steam;   b) treating the lignocellulosic materials with an oxidizing agent and a reducing agent; and   c) subjecting the lignocellulosic materials to a Kraft pulping process to produce pulp in a digester.   
     
     
         7 . The method as claimed in  claim 6 , wherein the extracting further comprises treating the lignocellulosic materials and the water at a temperature between about 120° C. and 180° C. 
     
     
         8 . The method as claimed in  claim 7 , wherein the treating further comprises adding the lignocellulosic materials with additional water, along with the oxidizing agent and the reducing agent, and further treating at an elevated temperature of between about 120° C. and 180° C. 
     
     
         9 . The method as claimed in  claim 8 , wherein the treated lignocellulosic materials are added to the digester, along with sodium hydroxide and sodium sulfide to produce the pulp. 
     
     
         10 . The method as claimed in  claim 9 , wherein the oxidizing agent is selected from the group consisting of polysulfides and the reducing agent is selected from the group consisting of sodium borohydride, sodium dithionate, and in-situ hydrogen. 
     
     
         11 . A method of protecting hemicellulose pre-extracted lignocellulosic materials against degradation in alkaline pulping processes comprising:
 a) extracting organics from lignocellulosic materials using water or steam;   b) impregnating the hemicellulose extracted lignocellulosic materials with an oxidizing agent, wherein the oxidizing agent is an aqueous polysulfide ion containing solution;   c) treating the impregnated lignocellulosic materials with a reducing agent; and   d) subjecting the lignocellulosic materials to a Kraft pulping process to produce pulp in a digester to allow the lignocellulosic materials to separate into fibers.   
     
     
         12 . The method as claimed in  claim 11 , wherein the impregnating is conducted at a temperature below 180° C. 
     
     
         13 . The method as claimed in  claim 11 , wherein the impregnating is conducted at a pH of 7.0 to 13.0. 
     
     
         14 . The method as claimed in  claim 11 , wherein in either the impregnating or the treating, further comprising adding additives to increase the resulting pulp yield. 
     
     
         16 . The method as claimed in  claim 14 , wherein the additives are selected from the group consisting of: anthraquinone, anthraquinone derivatives, and reducing agents. 
     
     
         17 . The method as claimed in  claim 11 , wherein the reducing agent is selected from the group consisting of lithium aluminum hydride, alkali metal borohydride, alkali metal dithionite(hydrosulfite), alkali metal amalgam, diisobutylaluminum hydride, oxalic acid, formic acid, and/or the presence of hydrogen gas in a hydroxyl ion containing solution such as Kraft white liquor. 
     
     
         18 . The method as claimed in  claim 11 , wherein a portion of aqueous extract from the extracting is recycled back for raising the sugar content of the extract. 
     
     
         19 . The method as claimed in  claim 11 , wherein the treating is conducted at a temperature between 80° C. to 180° C. 
     
     
         20 . The method as claimed in  claim 11 , wherein the polysulfide ion containing solution is withdrawn from the impregnating to a polysulfide storage tank for recycling. 
     
     
         21 . A method of protecting hemicellulose pre-extracted lignocellulosic materials against degradation in alkaline pulping processes comprising:
 a) extracting organics from lignocellulosic materials using water or steam;   b) treating the hemicellulose extracted lignocellulosic materials with a first oxidizing agent as a first pretreatment, wherein the oxidizing agent is an aqueous polysulfide ion containing solution;   c) treating the lignocellulosic materials with a second oxidizing agent and a reducing agent as a second pretreatment; and   d) subjecting the lignocellulosic materials to a Kraft pulping process to produce pulp in a digester.   
     
     
         22 . The method as claimed in  claim 21 , wherein the first pretreatment is conducted at a temperature below 180° C. 
     
     
         23 . The method as claimed in  claim 21 , wherein the first pretreatment is conducted at a pH of 7.0 to 13.0. 
     
     
         24 . The method as claimed in  claim 21 , wherein in either the first pretreatment or the second pretreatment, further comprising adding additives to increase the resulting pulp yield. 
     
     
         25 . The method as claimed in  claim 24 , wherein the additives are selected from the group consisting of: anthraquinone, anthraquinone derivatives, and reducing agents. 
     
     
         26 . The method as claimed in  claim 21 , wherein the reducing agent is selected from the group consisting of lithium aluminum hydride, alkali metal borohydride, alkali metal dithionite(hydrosulfite), alkali metal amalgam, diisobutylaluminum hydride, oxalic acid, formic acid, and/or the presence of hydrogen gas in a hydroxyl ion containing solution such as Kraft white liquor. 
     
     
         27 . The method as claimed in  claim 21 , wherein a portion of aqueous extract from the extracting is recycled back for raising the sugar content of the extract. 
     
     
         28 . The method as claimed in  claim 21 , wherein the polysulfide ion containing solution is withdrawn from the first pretreatment to a polysulfide storage tank for recycling. 
     
     
         29 . The method as claimed in  claim 21 , wherein the first pretreatment is conducted at a temperature between 80° C. to 180° C. 
     
     
         30 . The method as claimed in  claim 21 , wherein in the second pretreatment the lignocellulosic materials are treated with Kraft white liquor containing polysulfide and reducing agent. 
     
     
         31 . The method as claimed in  claim 30 , wherein the second pretreatment is conducted at a temperature below 150° C. for at least 30 minutes. 
     
     
         32 . A system for protecting hemicellulose pre-extracted lignocellulosic materials against degradation in alkaline pulping processes, the system comprising:
 a) means for water extraction, wherein organics from the lignocellulosic materials are released;   b) means for treatment or impregnation, wherein an oxidizing agent and a reducing agent are added to the pre-extracted lignocellulosic materials to compensate for the extracted organics; and   c) a digester, wherein the lignocellulosic materials are separated into fibers to produce pulp.   
     
     
         33 . A method for producing pulp comprising the steps of:
 a) extracting hemicellulosic materials from lignocellulosic materials;   b) treating the lignocellulosic materials with an oxidizing agent by a process selected from the group consisting of an extraction process, an agent impregnation process, and a first pretreatment process;   c) treating the lignocellulosic materials with a reducing agent by a process selected from the group consisting of the extraction process, the agent impregnation process, and a second pretreatment process; and then   d) subjecting the lignocellulosic materials to a modified Kraft pulping process to produce pulp.   
     
     
         34 . The method as claimed in  claim 33 , wherein the lignocellulosic materials are treated at a temperature between about 120° C. and 180° C. in the extraction process. 
     
     
         35 . The method as claimed in  claim 34 , wherein the oxidizing agent is selected from the group consisting of polysulfides. 
     
     
         36 . The method as claimed in  claim 35 , wherein the reducing agent is selected from the group consisting of lithium aluminum hydride, alkali metal borohydride, alkali metal dithionite(hydrosulfite), alkali metal amalgam, diisobutylaluminum hydride, oxalic acid, formic acid, and/or the presence of hydrogen gas in a hydroxyl ion containing solution such as Kraft white liquor. 
     
     
         37 . The method as claimed in  claim 36 , wherein the method comprises a double extraction process with water in a first extraction stage and with the oxidizing agent along with an additive in a second extraction stage or in the first pretreatment process, followed by the modified Kraft pulping process with anthraquinone in a digester. 
     
     
         38 . The method as claimed in  claim 36 , wherein the method comprises a single stage extraction process, followed by a two stage modified Kraft pulping comprising a pretreatment with the oxidizing agent. 
     
     
         39 . The method as claimed in  claim 36 , wherein the method is a single stage oxidizing agent pretreatment process for alkaline pulping of hemicellulose pre-extracted lignocellulosic materials with a polysulfide recycle. 
     
     
         40 . The method as claimed in  claim 39 , further comprising the steps of:
 a) impregnating hemicellulose extracted lignocellulosic materials with the oxidizing agent, wherein the oxidizing agent is an aqueous polysulfide ion containing solution, whereby aldehyde end groups of the hemicellulose extracted lignocellulosic materials are oxidized to carboxyl groups;   b) treating the impregnated lignocellulosic materials with a reducing agent, whereby the aldehyde end groups of the hemicellulose extracted lignocellulosic materials are reduced to alditols or thioalditols, and subsequently continuously digesting the lignocellulosic materials to allow the lignocellulosic materials to separate into fibers without much mechanical action.   
     
     
         41 . The method as claimed in  claim 40 , further comprising adding additional additives selected from the group consisting of anthraquinone, anthraquinone derivatives, and reducing agents. 
     
     
         42 . The method as claimed in  claim 41 , wherein a portion of the aqueous extract from the extracting process is recycled back to the extraction process for raising the sugar content of the hemicellulosic materials. 
     
     
         43 . The method as claimed in  claim 36 , wherein the method is a single stage dual pretreatment with an oxidizing agent and a reducing agent for alkaline pulping of hemicellulose pre-extracted lignocellulosic materials without a polysulfide recycle. 
     
     
         44 . The method as claimed in  claim 43 , further comprising the steps of:
 a) impregnating hemicellulose extracted lignocellulosic materials with the oxidizing agent, wherein the oxidizing agent is an aqueous polysulfide ion containing solution, whereby aldehyde end groups of the hemicellulose extracted lignocellulosic materials are oxidized to carboxyl groups;   b) treating the impregnated lignocellulosic materials with a reducing agent, whereby the aldehyde end groups of the hemicellulose extracted lignocellulosic materials are reduced to alditols or thioalditols, and subsequently continuously digesting the lignocellulosic materials to allow the lignocellulosic materials to separate into fibers without much mechanical action.   
     
     
         45 . The method as claimed in  claim 44 , further comprising adding additional additives selected from the group consisting of anthraquinone, anthraquinone derivatives, and reducing agents. 
     
     
         46 . The method as claimed in  claim 45 , wherein a portion of the aqueous extract from the extraction process is recycled back to the extraction process for raising the sugar content of the hemicellulosic materials. 
     
     
         47 . The method as claimed in  claim 36 , wherein the process is a two stage pretreatment process with an oxidizing agent followed by a reducing agent for alkaline pulping of hemicellulose pre-extracted lignocellulosic materials with a polysulfide recycle. 
     
     
         48 . The method as claimed in  claim 47 , further comprising the steps of:
 a) impregnating hemicellulose extracted lignocellulosic materials with the oxidizing agent, wherein the oxidizing agent is an aqueous polysulfide ion containing solution, whereby aldehyde end groups of the hemicellulose extracted lignocellulosic materials are oxidized to carboxyl groups;   b) treating the impregnated lignocellulosic materials with a reducing agent, whereby the aldehyde end groups of the hemicellulose extracted lignocellulosic materials are reduced to alditols or thioalditols, and subsequently continuously digesting the lignocellulosic materials to allow the lignocellulosic materials to separate into fibers without much mechanical action.   
     
     
         49 . The method as claimed in  claim 48 , further comprising adding additional additives selected from the group consisting of anthraquinone, anthraquinone derivatives, and reducing agents. 
     
     
         50 . The method as claimed in  claim 49 , wherein a portion of the aqueous extract from the extraction process is recycled back to the extraction process for raising the sugar content of the hemicellulosic materials.