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Continuous digester for cellulose pulp including method and recirculation system for such digester: Kontinuerlig kokare förfarande för drift av kontinuerlig kokare och återföringssystem för kokvätska i en kontinuerlig kokare
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-2900-4713
2001 (Swedish)Patent (Other (popular science, discussion, etc.))
Abstract [en]

The invention relates to a continuous digester for producing chemical pulp, to a process for operating this digester and to a feedback system for the cooking liquid. By means of implementing cooking zones 1st, 2nd, 3rd, 4th and 5th down through the digester, having a successively decreasing liquid-to-wood ratio, it is possible to obtain a more uniform alkali profile during the cooking. The alkali which is totally available is kept high at the beginning by means of a high liquid-to-wood ratio, typically well over 6:1, which well exceeds conventional liquid-to-wood ratios, which are normally around 3.5-5.0:1. In combination with digester liquid from subsequent cooking zones being fed back to the top of the digester, the alkali concentration can be kept low at the beginning of the cooking, typically within 20-35 g/l when cooking softwood. This is achieved with essentially all the alkali, i.e. more than 80 %, being added at the beginning of the cooking. A more uniform alkali profile is favourable for the cooking process and gives an improved pulp quality.

Place, publisher, year, edition, pages
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-49245OAI: diva2:459432
SE 518542-C2 (2002-10-22)

US 7285179 B2 (2007-10-23); JP 2004522873 A (2004-07-29); EP 1383955 (2010-01-27)

Available from: 2011-11-25 Created: 2011-11-25 Last updated: 2013-08-09Bibliographically approved

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Mikael, Lindström
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Fibre and Polymer Technology
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