Kvaerner Pulping Technologies Ab

Erik Nilsson

Petter Tibbling

Lars-Ove Larsson

Anders Bergqvist

Lars Ove Larsson

Ulla Ekstrom

Ulla Ekstroom

Method of bleaching pulp without using chlorine chemicals in a (QP)Z bleaching sequence

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.

Process for peroxide bleaching of chemical pulp in a pressurized

Process for peroxide bleaching of chemical pulp in a pressurized bleach

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Väse, Sweden

Erik Nilsson