METHOD AND SYSTEM FOR OXYGEN DELIGNIFICATION OF CELLULOSE PULP

The invention relates to an improved oxygen delignification stage located between 2 wash positions (W1， W2) in a fiberline producing bleached qualities of cellulose pulp. The inventive method and system divide the oxygen stage into at least 2 phases， and after the first phase is the pulp suspension effectively depressurized and vented to atmosphere in order to vent away the bulk volume of inert gases formed during the first phase. The partial pressure of oxygen added to final phase may thus be increased and the amount of oxygen dissolved in the liquid phase is increased enabling better delignification of the cellulose pulp in the final phase. The invention relates to an improved oxygen delignification stage located between 2 wash positions (W1， W2) in a fiberline producing bleached qualities of cellulose pulp. The inventive method and system divide the oxygen stage into at least 2 phases， and after the first phase is the pulp suspension effectively depressurized and vented to atmosphere in order to vent away the bulk volume of inert gases formed during the first phase. The partial pressure of oxygen added to final phase may thus be increased and the amount of oxygen dissolved in the liquid phase is increased enabling better delignification of the cellulose pulp in the final phase.