D - Textiles – Paper – 21 – C
Patent
D - Textiles, Paper
21
C
D21C 9/16 (2006.01) D21C 9/10 (2006.01) D21C 11/00 (2006.01)
Patent
CA 2325738
A method in bleaching of pulp is described, in which the pulp is subjected to a peroxide bleaching step, whereupon the pulp is washed and the washing liquid from the washing is separated from the pulp in the form of a filtrate. The method is characterised in that the filtrate is treated with an aluminium compound, such as aluminium sulphate or polyaluminium sulphate, for precipitation of interfering substances, such as oxygen-demanding organic material and metals, that the precipitated material is removed from the filtrate, that the aluminium content of the filtrate after precipitation of interfering substances is adjusted to at most 20 ppm, and that the filtrate is then recirculated to the peroxide bleaching step. By the method, a reduced consumption of hydrogen peroxide in the peroxide bleaching step is achieved.
L'invention concerne un procédé de blanchiment de la pâte selon lequel on soumet la pâte au blanchiment au peroxyde puis on la lave et l'on sépare de la pâte le liquide de lavage obtenu, qui prend la forme d'un filtrat. Le procédé est caractérisé en ce que suit: on traite le filtrat avec un composé d'aluminium tel que le sulfate d'aluminium ou le sulfate de polyaluminium pour précipiter les substances interférentes, par exemple, les métaux et les matières organiques ayant besoin d'oxygène; on évacue du filtrat les substances précipitées; on règle la teneur du filtrat en aluminium afin qu'elle ne dépasse pas 20 ppm après la précipitation des substances interférentes; et l'on réinjecte le filtrat au stade de blanchiment au peroxyde. Ce procédé permet de limiter la consommation de peroxyde d'hydrogène lors du blanchiment au peroxyde.
Nilsson Margareta
Olsson Anette
Rampotas Christos
Svensson Jessica
Terelius Hans
Fetherstonhaugh & Co.
Kemira Kemi Ab
LandOfFree
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