Kvaerner Pulping Technologies Ab

Kvaerner Pulping Aktiebolag

Petter Tibbling

Erik Nilsson

Lars-Ove Larsson

Anders Bergqvist

Soren Gustavsson

Ewa W Johansson

Christer Fahlgren

Ulla Ekstrom

Lars Ove Larsson

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

A method of manufacturing chemical pulp out of comminuted cellulosic fiber material comprising digesting the fiber material with digestion liquid without preceding peroxide stage. According to the invention the comminuted fiber material is treated in at least one stage prior to said digestion, in the presence of a liquid containing at least one compound having the ability to form complexes with metals existing naturally in the fiber material.

Pulp production

Process for peroxide bleaching of chemical pulp in a pressurized bleach

Growing community of inventors

V.ang.lberg, Sweden

Petter Tibbling