Method for high temperature, high consistency quick bleaching of

Details Method for high temperature, high consistency quick bleaching of Method for high temperature, high consistency quick bleaching of

1989-06-23

1990-03-20

Alvo, Steve

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Waste paper or textile waste

162 6, 162 7, 162 26, 162 56, 162 57, D21B 116, D21B 132, D21C 910, D21C 918

Patent

active

049099000

ABSTRACT:
The bleaching chemicals are added to the pulp immediately after heating of the raw pulp thickened to more than 20% by weight and immediately prior to a dispersing process. This is carried out in a high-speed, high-efficiency disperser, where the heated, thickened pulp is forced through a plurality of narrow slits in a disperser lining and is exposed to strong shearing, impact and kneading stresses. In this way, the dispersing process is reduced to a time period less than 3 seconds, preferably about 1 second or less. As a result, the total time required for reductive bleaching is reduced to less than 15 seconds and no further measures are required for displacing and excluding air from the system. The method can also be advantageously used with oxidative bleaching at reduced reaction time requirements. A high dispersing temperature in the region of 40.degree. C. to 110.degree. C., preferably about 95.degree. C. is possible and there are essentially simultaneously carried out the bleaching and dispersing actions without the need for separate dispersing stages and large reaction towers and pumps.

REFERENCES:
patent: 3467574 (1969-09-01), West
patent: 4339206 (1982-07-01), Ahs
patent: 4381969 (1983-05-01), Cuester et al.
patent: 4390395 (1983-06-01), Cuester et al.

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