Hoechst Celanese Corporation

Abitibi-price, Inc.

Martin G Fairbank

Philip Whiting

Arnold E Willoughby

Jeffrey Nye

Fraser McLellan

Hollis D MacEwen

Adele M Rhodes

A method for eliminating the formation of sulfur dioxide in a refiner bleaching process is disclosed wherein a selected amount of a carbonate is added to the refiner contents at approximately the same time that sodium dithionite is added.

Method for reduced sulfur dioxide formation in refiner bleaching

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.

High consistency peroxide bleaching

Growing community of inventors

Milton, Canada

Martin G Fairbank