Continuous cooking with a two-stage cool impregnation

Details Continuous cooking with a two-stage cool impregnation Continuous cooking with a two-stage cool impregnation

1997-08-07

1999-09-28

Nguyen, Dean T.

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Continuous chemical treatment or continuous charging or...

162 39, 162 62, D21C 326

Patent

active

059581816

ABSTRACT:
A method of treating wood chips allows chemical pulp (e. g. kraft pulp) to be produced having enhanced fiber strength properties. In a first zone or stage the chips are cool impregnated (e. g. a temperature of about 60-120.degree. C.) with a first alkali-containing liquid (25-35 g/l expressed as NaOH). In the top of a continuous digester in a second zone or stage the chips are then treated with a second alkali-containing liquid having an alkali concentration at least 5 g/l less than the first liquid (e. g. 10-20 g/l) and a temperature of between about 120-160.degree. C. (e. g. 130-150.degree. C.). An extraction typically takes place to effect the change in treatment zones. After the second zone the chips are cooked at about 140-180.degree. C. (e. g. 150-170.degree. C.), and higher than in the second zone.

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