Green liquor pretreatment of lignocellulosic material

Abstract

A continuous process for producing a chemical grade pulp, the process comprising the steps of: (a) steaming lignocellulosic material for a first period of time between 1 and 60 minutes; (b) after steaming, impregnating the steamed lignocellulosic material in an impregnation vessel with green liquor for a second period of time up to 5 minutes and at a temperature between 110° C. and 150° C.; and (c) after impregnation, continuously cooking the lignocellulosic material in a digester to produce a chemical grade pulp.

1 . A continuous process for producing a chemical grade pulp, the process comprising the steps of:
 (a) steaming lignocellulosic material for a first period of time between 1 and 60 minutes;   (b) after steaming, impregnating the steamed lignocellulosic material in an impregnation vessel with green liquor for a second period of time up to 5 minutes and at a temperature between 110° C. and 150° C.; and   (c) after impregnation, continuously cooking the lignocellulosic material in a digester to produce a chemical grade pulp.   
     
     
         2 . The continuous process of  claim 1 , wherein the lignocellulosic material comprises wood chips. 
     
     
         3 . The continuous process of  claim 1 , wherein step (a) occurs in the presence of water vapor and in the absence of white liquor, green liquor, and black liquor. 
     
     
         4 . The continuous process of  claim 1 , wherein the first period of time lasts approximately 15 minutes. 
     
     
         5 . The continuous process of  claim 1 , wherein step (a) occurs at atmospheric pressure. 
     
     
         6 . The continuous process of  claim 1 , wherein step (a) occurs at a pressure up to 10 bar. 
     
     
         7 . The continuous process of  claim 1 , wherein step (b) occurs for a period of time of up to 2 minutes. 
     
     
         8 . The continuous process of  claim 1 , wherein step (b) occurs for a period of time of up to 1 minute. 
     
     
         9 . The continuous process of  claim 1 , wherein step (b) occurs at a pressure up to 10 bar. 
     
     
         10 . The continuous process of  claim 1 , wherein step (b) occurs at a pressure up to 6 bar. 
     
     
         11 . The continuous process of  claim 1 , further comprising the step of removing free green liquor between step (b) and step (c).