DELIGNIFYING BLEACHING OF CELLULOSIC PULP USING NITROGEN OXIDES WITH ADDITION OF SODIUM NITRATE

摘要

A process is provided for delignifying bleaching lignin-containing cellulose pulp which comprises: (1) activating cellulose pulp by reacting the pulp at a pulp consistency within the range from about 20% to about 60% and at a temperature within the range from about 20 DEG to about 130 DEG C. with a gas comprising NO2 and oxygen in the presence of water, sodium nitrate in an amount of at least 0.15 g mole per kg of water, and optionally nitric acid; (2) washing the activated pulp with water or an aqueous solution; and (3) treating the activated washed pulp with an aqueous alkaline solution at a temperature within the range from about 70 DEG to about 170 DEG C., optionally in the presence of oxygen gas until the lignin content of the pulp is so reduced that the Kappa number of the pulp is within the range from about 10 to about 60% of the Kappa number of the pulp entering the activating stage (1).