Mo Och Domsjo Aktiebolag

John R Bergstrom

Jonas A Lindahl

Bengt G Hultman

Sten L Haggstrom

Astrid T Dalborg

A method for delignifying and/or bleaching cellulose pulp adds to the cellulose pulp a liquid which contains chlorine dioxide, causes the pulp to react with the chlorine dioxide over a selected period of time, and then reduces the amount of available active chlorine, optionally to a negligible amount, either by reducing the amount of liquid accompanying the cellulose pulp and/or by displacing such liquid with a newly supplied liquid containing no active chlorine or at most only a small amount of active chlorine; the displaced liquor can be replenished with chlorine and optionally with chlorine dioxide, and then added mainly to fresh cellulose pulp in the same bleaching stage, and/or to cellulose pulp in another bleaching stage.

Method for delignifying or bleaching cellulose pulp wherein chlorine is

A process is provided for the recovery of sulfur dioxide liberated in the chemical pulping of lignocellulosic material, which comprises

Process for recovery of sulfur dioxide liberated in the chemical pulping

A method is provided for controlling the supply of delignifying and/or bleaching chemicals in the continuous delignification and/or bleaching of lignocellulosic material such as wood and pulp in a through flow delignification and/or bleaching stage which commprises admixing the lignocellulosic material with delignifying and/or bleaching chemicals and flowing the lignocellulosic material under delignifying and/or bleaching conditions through the stage while controlling the addition of the delignifying and/or bleaching chemicals according to the ratio of the quantity of delignifying and/or bleaching chemicals consumed to the quantity of delignifying and/or bleaching chemicals originally charged, referred to hereinafter as relative consumption, the time and the temperature in a manner to maintain substantially constant the relative consumption of delignifying and/or bleaching chemicals at a predetermined time by the lignocellulosic material during flow through the stage.

Process for controlling the supply of delignifying and/or bleaching

A method is provided for controlling the addition of active chemical for delignifying and/or bleaching cellulose pulp suspended in an aqueous liquor containing at least one chemical reactive with such active chemical, which comprises determining the amount of active chemical consumed by the chemical reactive with the active chemical in the liquor; adding the active chemical to the cellulose pulp suspension; and then after a predetermined time interval determining the amount of active chemical consumed by the chemical and cellulose pulp reactive with the active chemical in the liquor; from these determinations determining the amount of active chemical consumed by the pulp; and then carrying out the delignification and/or bleaching with an amount of active chemical adjusted according to the amount of active chemical consumed by the pulp.

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Domsjo, Sweden

John R Bergstrom