D - Textiles – Paper – 21 – C
Patent
D - Textiles, Paper
21
C
9/16.5
D21C 3/00 (2006.01) D21C 9/10 (2006.01)
Patent
CA 1036758
ABSTRACT OF THE DISCLOSURE The present invention provides a method of delignify- ing cellulosic material with oxygen in the presence of an alkaline aqueous medium in a reaction vessel, which comprises previously dissolving said oxygen into said alkaline aqueous medium under a partial oxygen pressure of at least 4 kg/cm2 before charging the medium into the reaction vessel, contacting said alkaline medium containing dissolved oxygen with the cellulosic material in said reaction vessel at a temperature of 80 to 160°C to conduct oxidative delignification of said cellulosic material, said cellulosic material being introduced batch-wise or continuously into the reaction vessel, the con- sistency of said cellulosic material in said aqueous medium being so chosen as to form an agglomeration of the cellulosic material in the alkaline aqueous medium which agglomeration does not have any gaseous space therein, and the pressure in the reaction vessel being maintained more than the partial oxygen pressure employed in the oxygen-dissolving step, and discharging a part of the waste liquor formed during delignification from the vessel, while at the same time charging fresh alkaline aqueous medium containing dissolved oxygen into the vessel, so that the displacement of the waste liquor with the fresh alkaline aqueous medium containing dissolved oxygen is carried out continuously throughout the delignification, and so that the chosen consistency of the cellulosic material is kept substantially constant by controlling the discharging and charging volume of the alkaline aqueous medium.
210399
Miyao Saisei
Nagano Tadashi
Takeda Katsuhiko
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