MASSAFRAMSTAELLNINGSFOERFARANDE MED ALKALITILLSATS FOER TJOCKMASSA-OXYGENDELIGNIFIERING

摘要

Unbleached pulp (8) is combined with an aqueous alkaline solution (10, 14A) 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 18 % (12) and the high consistency alkali containing pulp is then treated with oxygen (21) to effect delignification (20). The total amount of alkaline material applied to the pulp is between 0.8 and 7 % by weight of oven dry pulp. High strength, low lignin pulps are subsequently formed which may be further bleached to high brightness with reduced amounts of chemicals.