D - Textiles – Paper – 21 – C
Patent
D - Textiles, Paper
21
C
D21C 9/153 (2006.01) D21C 3/00 (2006.01) D21C 9/10 (2006.01) D21C 9/147 (2006.01) D21C 9/16 (2006.01)
Patent
CA 2144825
A method of producing TCF-pulp using an ozone stage (Z) as part of the bleaching sequence does not require cooling of the pulp prior to the Z stage, and then subsequent heating of the pulp after the Z stage, since the Z stage is practiced at medium consistency and at about the same temperature as the other bleaching stages (i.e. between about 80-120°C). Chemical (or other)cellulose pulp is treated by the steps of: (a) effecting acidification, washing or pressing, oxygen delignification, peroxide bleaching, or chelation of chemical cellulose pulp at a temperature between about 80-120°C; (b) immediately after step (a), ozone bleaching the pulp at a consistency of about 8-20% at a stabilized pH of about 2-7 and at a temperature between just over 80°C and about 120°C (preferably about 90-100°C), for less than about one minute (typically less than 30 seconds); and (c) immediately after step (b) effecting acidification, washing or pressing, oxygen delignification, peroxide bleaching, or chelation of the pulp at a temperature between about 80-120°C. The pulp pH is preferably stabilized by holding the pulp in liquid at a pH between about 2-5 for at least five to ten seconds (preferably 20 seconds-100 minutes) prior to the addition of ozone to the pulp in the Z stage.
Henricson Kaj
Pikka Olavi
Ahlstrom Machinery Oy
Gowling Lafleur Henderson Llp
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