Method for medium consistency oxygen delignification of pulp
First Claim
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1. A process for the continuous oxygen delignification of medium consistency pulp comprising the steps of:
- a. introducing pulp at a consistency of from 8 to 20% and alkaline materials into a first reaction zone and maintaining the consistency of the pulp at between 8% to 20% throughout the first and subsequent reaction zones,b. introducing gaseous oxygen into said first reaction zone to delignify said pulp and maintaining the oxygen partial pressure in the first and subsequent reaction zones from about 30 to 200 psig,c. agitating the mixture of the pulp gaseous, oxygen, and alkaline materials with a screw conveyor extending along the length of said first zone operated at from 10 to 200 rpm, andd. passing said mixture into one or more subsequent substantially horizontal reaction zones and retaining the pulp in said one or more zones for a time sufficient for further delignification to occur while agitating said pulp with a screw operating at from 0.5 to 5 rpm.
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Abstract
Medium consistency oxygen delignification of pulp is carried out in a series of tubular reaction zones. Rapid delignification is achieved by agitating the pulp by rotating a timing screw in the first reaction zone at a speed in excess of 10 rpm, modifying the flights on the timing screw to increase the amount of agitation, or a combination of the two. Primary oxygenation is carried out in the first reaction zone while subsequent zones provide the retention time needed for the delignification reaction to go to completion. A thick stock pump is used to introduce the pulp into the first reaction zone.
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13 Claims
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1. A process for the continuous oxygen delignification of medium consistency pulp comprising the steps of:
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a. introducing pulp at a consistency of from 8 to 20% and alkaline materials into a first reaction zone and maintaining the consistency of the pulp at between 8% to 20% throughout the first and subsequent reaction zones, b. introducing gaseous oxygen into said first reaction zone to delignify said pulp and maintaining the oxygen partial pressure in the first and subsequent reaction zones from about 30 to 200 psig, c. agitating the mixture of the pulp gaseous, oxygen, and alkaline materials with a screw conveyor extending along the length of said first zone operated at from 10 to 200 rpm, and d. passing said mixture into one or more subsequent substantially horizontal reaction zones and retaining the pulp in said one or more zones for a time sufficient for further delignification to occur while agitating said pulp with a screw operating at from 0.5 to 5 rpm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification