Continuous tube reactor

Abstract

A system and method for digesting cellulosic material to extract fermentable sugars, lignin, and pulp is disclosed. One embodiment comprises a continuous digester comprising a cellulosic material feed section including a pre-steam and impregnation zone, a sugar extraction zone, a lignin extraction zone and a cooking zone, the continuous digester to impregnate the cellulosic material with a mild acid solution and continuously digest the cellulosic material to extract fermentable sugars, lignin, and pulp. Another embodiment comprises a method for receiving cellulosic material in a continuous digester, removing air from the cellulosic material, impregnating the cellulosic material with a mild acid, hydrolyzing hemicellulose in the cellulosic material to fermentable sugars, extracting the fermentable sugars from the cellulosic material, cooking the cellulosic material to extract lignin from the cellulosic material, washing the cellulosic material in a hot alcohol wash, a hot water wash, and a cold water wash, and discharging pulp.

1 . A continuous digester comprising:
 a cellulosic material feed section including a pre-steam and impregnation zone, the pre-steam and impregnation zone to remove air from cellulosic material and to impregnate the cellulosic material with a mild acid solution;   a sugar extraction zone coupled with the pre-steam and impregnation zone, the sugar extraction zone to hydrolyze hemicellulose in the cellulosic material to fermentable sugars and extract the fermentable sugars;   a cooking zone to receive the cellulosic material from the sugar extraction zone, the cooking zone to dissolve the cellulosic material and extract lignin;   a end wash zone consisting of a hot alcohol wash, a hot water wash, and a cold water wash, the end wash zone to wash the cellulosic material and discharge pulp.   
     
     
         2 . The continuous digester of  claim 1 , wherein the sugar extraction zone further includes a packing ring to extract liquid from the cellulosic material and lower the porosity of the cellulosic material in the sugar extraction zone. 
     
     
         3 . The continuous digester of  claim 2 , further comprising a positive displacement pump in fluid communication with the packing ring, the positive displacement pump to adjust the amount of liquid extracted by the packing ring. 
     
     
         4 . The continuous digester of  claim 1 , wherein the cooking zone further includes at least one packing ring to extract liquid from the cellulosic material and lower the porosity of the cellulosic material in the cooking zone. 
     
     
         5 . The continuous digester of  claim 4 , wherein the packing ring is further in fluid communication with a positive displacement pump, the positive displacement pump to adjust the amount of liquid extracted by the packing ring. 
     
     
         6 . The continuous digester of  claim 5 , wherein the cooking zone is a first cooking zone, the continuous digester further comprising at least one additional cooking zone to dissolve cellulosic material and extract lignin. 
     
     
         7 . The continuous digester of  claim 1 , further comprising at least one bleach zone between a last cooking zone and the end wash zone, the bleach zone to bleach the cellulosic material and the continuous digester to discharge bleached pulp. 
     
     
         8 . A method comprising:
 receiving cellulosic material in a continuous digester;   removing air from the cellulosic material;   impregnating the cellulosic material with a mild acid;   hydrolyzing hemicellulose in the cellulosic material to fermentable sugars;   extracting the fermentable sugars from the cellulosic material;   cooking the cellulosic material to extract lignin from the cellulosic material;   washing the cellulosic material in a hot alcohol wash, a hot water wash, and a cold water wash; and   discharging pulp.   
     
     
         9 . The method of  claim 8 , further comprising extracting liquid from the cellulosic material in the sugar extraction zone using a packing ring to lower the porosity of the cellulosic material. 
     
     
         10 . The method of  claim 9 , further comprising adjusting the amount of liquid extracted by the packing ring with a positive displacement pump in fluid communication with the packing ring. 
     
     
         11 . The method of  claim 8 , further comprising extracting liquid from the cellulosic material in the cooking zone using a packing ring to lower the porosity of the cellulosic material. 
     
     
         12 . The method of  claim 11 , further comprising adjusting the amount of liquid extracted by the packing ring with a positive displacement pump in fluid communication with the packing ring. 
     
     
         13 . The method of  claim 8 , further comprising:
 bleaching the cellulosic material after cooking and prior to washing; and   discharging bleached pulp.