Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Treatment with particular chemical
Patent
1989-02-23
1990-07-03
Chin, Peter
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Treatment with particular chemical
162 26, 162 37, 162 56, 162 72, 162 80, 162 82, D21B 116, D21D 120
Patent
active
049388428
ABSTRACT:
A process is provided for the bleaching of wood pulp with hydrogen or sodium peroxide. The process includes the steps of adding to a wood pulp a bleach liquor having an effective amount of hydrogen or sodium peroxide bleaching agent and, by weight of the diluted wood pulp, 0.5 to 6% sodium hydroxide, 0 to 5% sodium silicate, 0 to 1%, preferably 0.02 to 0.05%, magnesium sulphate, and a chelating agent in an amount sufficient to sequester heavy metal ions in the pulp, to produce a pulp consistency of 1 to 16% at a temperature in the range of the bleach liquor freezing point to 25.degree. C., uniformly mixing the bleach liquor with the wood pulp, and immediately thickening the diluted wood pulp to a consistency in the range of 20 to 70% for bleaching of the thickened wood pulp. The wood pulp can be subjected to a preliminary treatment by the addition of a chelating agent in an amount sufficient to sequester chelatable heavy metals including manganese at a pulp consistency of 1 to 10%, and dewatering said pulp to a consistency of 20 to 70% to remove the sequestered manganese to less than 10 ppm.
REFERENCES:
patent: 4294653 (1981-10-01), Lindahl et al.
patent: 4599138 (1986-07-01), Lindahl
Fairbank Martin G.
MacEwen Hollis D.
McLellan Fraser
Rhodes Adele M.
Whiting Philip
Abitibi-Price Inc.
Chin Peter
Dang Thi
Fors Arne I.
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