Process for peroxide bleaching of chemical pulp in a pressurized

Details Process for peroxide bleaching of chemical pulp in a pressurized Process for peroxide bleaching of chemical pulp in a pressurized

1996-11-04

2000-11-21

Alvo, Steve

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Charging and/or discharging fibrous material

162 65, 162 76, 162 78, D21C 9153, D21C 916

Patent

active

061497665

ABSTRACT:
A process for chlorine-free bleaching of chemical pulp in association with the production thereof, where a suspension of the pulp preferably has a concentration exceeding 8% of cellulose-containing fiber material and where the pulp entering into a bleaching line is preferably fed continuously through at least one bleaching vessel in the bleaching line, is treated with at least one acid for adjusting the pH to a value below 7, and with a chelating agent, and is subsequently bleached in at least one stage to a brightness exceeding 75% ISO, preferably exceeding 80%, with hydrogen peroxide or the corresponding quantity of another peroxide, employed in a quantity exceeding 5 kg/BDMT, where the peroxide bleaching takes place at elevated temperature and at a pressure in the bleaching vessel which exceeds 2 bar and where the cross-sectional area of the bleaching vessel exceeds 3 m.sup.2 and the area of the metal surface exposed towards the interior of the bleaching vessel is less than 4V m.sup.2, where V indicates the volume in m.sup.3.

REFERENCES:
patent: 3619110 (1968-10-01), Borzee
patent: 3719552 (1973-03-01), Farley
patent: 4732650 (1988-03-01), Michalowski et al.
patent: 4756798 (1988-07-01), Lachenal et al.
Singh, "The Bleaching of Pulp"; Tappi Press, Atlanta, GA, p. 543, 1979.
Lachenal et al; "The Potential of H2O2 as Delignifying and Bleaching Agent", 1992 Pacific Pulp & Paper Conf., p. 33-38.

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