Paper making and fiber liberation – Apparatus – Digester
Patent
1985-09-24
1987-09-15
Alvo, Steve
Paper making and fiber liberation
Apparatus
Digester
162246, 162248, 162251, 2103231, D21C 326, D21C 714
Patent
active
046937854
ABSTRACT:
Comminuted cellulosic fibrous material, such as wood chips, are treated in a continuous digester to produce paper pulp or the like in a manner providing completely uniform treatment of the chips. The chips are introduced in a feed liquid slurry into the top of the digester having a plurality of annular screen systems each set vertically spaced from the other sets. At each screen set a plurality of nozzles are provided circumferentially spaced around the digester, each nozzle cooperating with only a particular radial segment of the screens. Withdrawal of liquid through the nozzles is practiced so that liquid is being withdrawn substantially through only one nozzle at a time, and it is being withdrawn at the same radial segment of the digester at each screen set at any particular point in time, with progressive switching in a circumferential sequence of the nozzles through which liquor is being withdrawn. Treatment liquors are introduced through a vertical conduit in the digester concentric with the digester shell, and discharge of treated chips (i.e. pulp) is provided at the bottom of the digester utilizing sluicing liquor and a rotating outlet which are designed to be substantially opposite the radial segment through which liquid withdrawal is being practiced at any particular time. The vertical conduit has a relatively large diameter so that treatment liquid is introduced with a relatively low velocity. A plurality of rotating valve elements and a common driven shaft preferably provide the mechanism for effecting liquid withdrawal in the desired sequence, and a rotatable shaft synchronized with the valve shaft provides for the introduction of sluicing liquid and positioning of the rotatable outlet.
REFERENCES:
patent: 2414062 (1947-01-01), Richter
patent: 2695232 (1954-11-01), Richter
patent: 3811994 (1974-05-01), Ostberg
patent: 4193839 (1980-03-01), Sherman
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