Plural stage mixing and thickening oxygen bleaching process

Details Plural stage mixing and thickening oxygen bleaching process Plural stage mixing and thickening oxygen bleaching process

1979-12-10

1981-03-31

Bashore, S. Leon

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

With regeneration, reclamation, reuse, recycling or...

162 56, 162 60, 162 65, D21C 902, D21C 910, D21C 918

Patent

active

042591503

ABSTRACT:
A method and apparatus for the treatment of fiber material by oxygen bleaching. Digested cellulosic fiber material is treated with oxygen to reduce the Kappa number thereof further to about 15 or below. The reaction products are removed immediately after formation, and during the oxygen bleaching process. The fiber material is at a first consistency of about 8 to 15% consistency, and treatment with oxygen is accomplished by mixing the pulp with O.sub.2, NaOH solution, and water to thereby form an integral mixture of pulp with oxygen at a second consistency, thickening the integral mixture to return it to generally its first consistency, and repeating the mixing and thickening until pulp of a desired Kappa number (15 or below) is reached. The pulp is then washed and may be subsequently treated to reduce the Kappa number thereof to any desired value. A thickener is used which can thicken pulp at superatomspheric pressures and at a temperature greater than 100.degree. C.

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Kleppe et al., "Oxygen/Alkali Delignification at Kamyr Digester Blowline Consistency-A Status Report", TAPPI , vol. 59, No. 11; Nov. 1976.
Coetee; Pulp and Paper Magazine of Canada; "Continuous Saporal Bleaching Operating Experience"; vol. 75, No. 6, Jun. 1974.

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