UPPDELAD ALKALITTILLSATS FOER OXYGENDELIGNIFIERING AV TJOCJMASSA

摘要

Unbleached pulp is combined with an aqueous alkaline solution while in a state of low consistency to distribute a first amount of alkaline material substantially uniformly throughout the pulp. The consistency of the pulp is then increased to above about 20%. Additional alkali is applied onto the high consistency pulp to provide a total amount of between 0.8 and 7% by weight of oven dry pulp. The high consistency alkali containing pulp is then treated with oxygen to effect delignification. High strength, low lignin pulps are formed which may be further bleached to high brightness with reduced amounts of chemicals by following the methods of the invention.