Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Charging and/or discharging fibrous material
Patent
1991-06-07
1995-05-02
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Charging and/or discharging fibrous material
162 65, D21C 9153
Patent
active
054116341
ABSTRACT:
In a method of bleaching medium consistency pulp with ozone using a mixer, ozone containing gas and about 6-15% consistency pulp are fed to the mixer, and then discharged in a first, preferably vertical, path. The mixture of pulp and ozone moves in a first part of the vertical path a time period of about 1-5 seconds at a velocity of about 1-5 m/s so that the gas and pulp do not separate during movement in this first part, and the vast majority of the pulp brightening reaction between the ozone and pulp takes place. This is preferably accomplished by passing the mixture upwardly in a small diameter conduit having a height of about 3-20 meters. Then the velocity of the pulp is slowed while still moving in the first path, preferably by feeding it directly to a much larger diameter (e. g. 1.5-10 times) conduit, so the height of the unit may be kept under 100 feet. The pulp flows in the large diameter conduit for about 0.5-5 minutes so that residual reactions take place.
REFERENCES:
patent: 4372812 (1983-02-01), Phillips et al.
patent: 4902381 (1990-02-01), Meredith
patent: 5034095 (1991-07-01), Kido et al.
Paper and Timber, "Effect of pulp consistency and pH in ozone bleaching", Lindholm, Feb. 1989, pp. 145, 147, 149, 150, 152, 154.
Paper and Timber "Effect of heterogeneity in pulp bleaching with ozone" Lindholm, Apr. 1986, pp. 283, 284, 286, 287, 288, 290.
"Ozone Bleaching Medium Consistency Technology and Mill Experience", Sixta et al, pp. 1-13, two drawing figures (admitted prior art).
"Medium consistency ozone bleaching", Laxen et al, 27 Mar. 1991, pp. 1-10, five drawing figures (admitted prior art).
Dunne Stephen J.
Funk Erwin D.
Greenwood Brian F.
Henricson Kaj
Phillips Joseph
Alvo Steve
Kamyr Inc.
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