BLEACHING MECHANICAL WOODPULP

BLEACHING MECHANICAL WOODPULP

Cellulose pulp si prepd. by refining chips, partic. a thermo-mechanical pulp prepd. from steam-preheated chips with addn. of silicate e.g. Na silicate. Bleaching takes place esp. after a pre-treatment with a complexing agent, e.g. ethylene diamine tetraacetic acid, or with CaCl2. In the initial blea...

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Bibliographische Detailangaben
Hauptverfasser: PER-OLOV LINDBLAD, GORAN ERIK ANNERGREN
Format: Patent
Sprache:eng
Schlagworte:
APPARATUS THEREFOR
PAPER-MAKING
PRODUCTION OF CELLULOSE
PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCESFROM CELLULOSE-CONTAINING MATERIALS
REGENERATION OF PULPING LIQUORS
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Zusammenfassung:Cellulose pulp si prepd. by refining chips, partic. a thermo-mechanical pulp prepd. from steam-preheated chips with addn. of silicate e.g. Na silicate. Bleaching takes place esp. after a pre-treatment with a complexing agent, e.g. ethylene diamine tetraacetic acid, or with CaCl2. In the initial bleaching phase, alkalinity of bleaching liq. is such that the liq. has a Ph of 11-12 (11.5-12) measured in pulp suspension. Quantity of silicate added to reduce buffer capacity of system is 50, esp. 30 kg/t of absolutely dry pulp, so that pH 9-10.5 (9.5-10) measured in pulp suspension is achieved during end-phase of bleaching. Brightness values of 80% SCAN are achieved.