Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With agitation or forced circulation
Patent
1983-01-31
1985-09-24
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With agitation or forced circulation
162 60, 162 65, 162 89, D21C 906, D21C 910, D21C 914
Patent
active
045431558
ABSTRACT:
Wood pulp is bleached in a process which includes passing pulp slurry from a chlorine tower through a washer to a downflow extraction tower which is open to the ambient atmosphere. Caustic and steam are supplied to the extraction tower as is dilution water which is introduced into the lower portion thereof. Oxygen is dissolved in the dilution water which may be at least partially comprised of recycled washer filtrate. This addition of oxygen to the dilution zone of an extraction stage enables the consumption of chemicals such as hypochlorite and/or chlorine dioxide to be reduced while still meeting required levels of pulp brightness and strength. Oxygen may be added to the extraction or other alkaline stages of a bleaching process.
REFERENCES:
patent: 3884752 (1975-05-01), Campbell et al.
patent: 3966542 (1976-06-01), Oldshue
patent: 4274913 (1981-06-01), Kikuiri et al.
patent: 4451332 (1984-05-01), Annergren et al.
Nasman et al., "Medium Consistency Oxygen Bleaching" Tappi, vol. 63, No. 4, Apr. 1980.
Alvo Steve
Cassett Larry R.
Rae David L.
The BOC Group Inc.
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