GREEN LIQUOR PRETREATMENT OF LIGNOCELLULOSIC MATERIAL
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).