Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Continuous chemical treatment or continuous charging or...
Patent
1995-11-13
1997-06-03
Czaja, Donald E.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Continuous chemical treatment or continuous charging or...
162 29, 162 33, 162 38, 162 39, 162 42, 162 47, D21C 326
Patent
active
056350260
ABSTRACT:
Chemical (typically kraft) pulp having enhanced intrinsic fiber strength and bleachability compared to pulp produced using conventional or modified kraft cooking is produced by using high alkali and/or pH cooking. After being impregnated with a first cooking liquor (e.g. white liquor) having low effective alkali, the first liquor is extracted from the pulp, and it is impregnated with a second cooking liquor having an effective alkali concentration of at least 25 g/l and cooked at cooking temperature (e.g. 140.degree.-190.degree. C.) to produce a spent second cooking liquor having a residual effective alkali concentration of at least about 15 g/l, which is then extracted from the pulp. The spent second liquor may be used to preheat incoming white liquor, and then flashed and used as the first liquor. The pH of the first liquor is typically less than about 13.0, and the residual pH of the spent second liquor is about 13.0 or more.
REFERENCES:
patent: 5138535 (1992-08-01), Tikka
patent: 5575890 (1996-11-01), Prough et al.
"Modified continuous kraft pulping--now a reality", Johansson et al Svensk Papperstidning, nr 10, 1984, pp. 30-35.
"Extended delignification in kraft cooking through improved selectivity", Sjoblom et al, Paperi Ja Puu--Paper and Timber, No. 4, 1983, pp. 227-240.
"Improved modified kraft cooking--Part 1. Pretreatment with a sodium sulfide solution", Mao et al, Paperi Ja Puu--Paper and Timber, vol. 74, No. 6, 1992, pp. 491-494.
"Extended delignification in kraft cooking through improved selectivity--Part II. The Effects of Dissolved Lignin", Sjoblom et al, Paperi Ja Puu--Paper and Timber, vol. 70, No. 5, 1988, pp. 452-460.
"Improved modified kraft cooking--Part 3: Modified vapor-phase polysulfide cooking", Mao et al, TAPPI Journal, vol. 77, No. 11, Nov. 1994, pp. 149-153.
"Improved modified kraft cooking--Part 4. Modified cooking with improved sulfide and lignin profiles", Mao et al, Paperi Ja Puu--Paper and Timber, vol. 77, No. 6-7, 1995, pp. 419-422.
"Modified Kraft Pulping--Fundamentals and Applications in Continuous Cooking" by Jiang, Manager, R&D Laboratory, Kamyr, Inc., Glens Falls, NY 12801, Beijing Seminar, 1994 Aug. 29,
Henricson Kaj O.
Jiang Jian E.
Kettunen Auvo K.
Marcoccia Bruno S.
Vilpponen Aki H.
Ahlstrom Machinery Inc.
Czaja Donald E.
Leavitt Steven B.
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