Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...
Patent
1992-07-20
1994-08-23
Jones, W.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With regeneration, reclamation, reuse, recycling or...
162 29, 162 301, 162 3011, 162 90, D21C 1112
Patent
active
053404408
ABSTRACT:
Chemicals are recovered during the production of cellulose pulp by forming two different sulfidity melts in two different sections of a soda recovery boiler, and then producing cooking liquors from different melts in dissolving tanks. The liquors may be causticized and/or oxidized, or may be utilized uncausticized. Uncausticized green liquor having a sulfidity of about 70-90% may be used early in a kraft cooking cycle, followed by treatment with low sulfidity oxidized and causticized white liquor. In the continuous digestion of cellulosic pulp, oxygen may be added to the recirculation loops below the black liquor withdrawal to enhance the alkalinity of the slurry and to assist in delignification. Oxidized cooking liquor with low sulfidity can be added to oxygen bleaching and alkali extraction stages downstream of the digester, and a portion of the high sulfidity cooking liquor can be used to produce acid used in an ozone bleaching stage.
REFERENCES:
patent: 4929307 (1990-05-01), Kiiskila et al.
Ayala et al, "Evaluation of Oxidized White Liquor as an Alkali Source", Tappi Oxygen Delig. Symposium, Oct. 1990.
K. Baczynska, "Use of White & Green Liquors as Alkalis in the Oxygen Stage of Kraft Pulp," Przeglad Papier, Miczy 35 No. 6:193-195 (Jun. 1979).
A. Ahlstrom Corporation
Jones W.
Nguyen Dean T.
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