Patent US4902381A successfully refreshed from Google Patents.
US4902381A
Expired / Lapsed
US
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Method of bleaching pulp with ozone-chlorine mixtures
Assignee: Andritz Inc
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Filing: 1988-12-09
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Granted: 1990-02-20
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Expires: 2008-12-09
Abstract
Abstract Ozone and chlorine are used to bleach cellulosic fibrous material pulp in the production of kraft pulp for paper and paper products, being applied together in a mixture. When the ozone and chlorine are applied simultaneously it is possible to achieve delignification to a greater extent than is possible utilizing chlorine at any level. The total chlorinated ring compounds in the bleach plant effluent are remarkably reduced utilizing the ozone-chlorine mixture, compared to all chlorine, with resulting decrease in the fish toxicity of the bleach plant effluent. Utilizing an O3/Cl2 Eo D bleaching sequence (only three stages) it is possible to obtain pulp with 90 TAPPI Absolute, or greater, brightness.
Inventors
- 👤 Michael D. Meredith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:38
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/12; D21C9/14; D21C9/147; D21C9/153
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
83 words
A method of chlorine bleaching cellulosic fibrous material pulp at a consistency between about 1/2-15% solids during the production of kraft pulp without significantly affecting the degree of delignification produced by chlorine bleaching, comprising the step of: in the chlorine bleaching of kraft pulp at a consistency of about 1/2-15%, substituting ozone for a portion of the chlorine by providing a mixture of chlorine and ozone applied to the pulp simultaneously, the amount of ozone in the mixture being between 1-40% by volume.
Claim 2
Independent Claim
83 words
A method of chlorine bleaching cellulosic fibrous material pulp at a consistency between about 1/2-15% solids during the production of kraft pulp without significantly affecting the degree of delignification produced by chlorine bleaching, comprising the step of: in the chlorine bleaching of kraft pulp at a consistency of about 1/2-15%, substituting ozone for a portion of the chlorine by providing a mixture of chlorine and ozone applied to the pulp simultaneously, the amount of ozone in the mixture being between 1-40% by volume.
Claim 3
Dependent Claim
19 words
A method as recited in claim 1, wherein the mixture contains other materials which do not adversely affect bleaching.
Claim 4
Dependent Claim
13 words
A method as recited in claim 2 wherein the mixture also includes oxygen.
Claim 5
Dependent Claim
16 words
A method as recited in claim 1 wherein the mixture of ozone and chlorine is gaseous.
Claim 6
Dependent Claim
16 words
A method as recited in claim 1 wherein the mixture of ozone and chlorine is liquid.
Claim 7
Dependent Claim
58 words
A method as recited in claim 1 for producing 90 TAPPI Absolute, or greater, brightness kraft pulp by bleaching brown stock pulp in only three bleaching stages, the three bleaching stages comprising sequentially an O 3 Cl 2 stage in which ozone and chlorine are simultaneously applied to the pulp, an E o stage, and a D stage.
Claim 8
Dependent Claim
20 words
A method as recited in claim 6 wherein said three stage bleaching sequence is practiced in three distinct upflow reactors.
Claim 9
Dependent Claim
40 words
A method as recited in claim 7 wherein said first bleaching stage is practiced by intimately mixing the ozone-chlorine mixture with the brown stock pulp in first and second series connected mixers, and then upflowing the pulp in an upflow
Claim 10
Dependent Claim
34 words
A method as recited in claim 8 wherein the amount of ozone in the mixture of ozone and chlorine is about 7-10% by volume, and wherein the mixture consists essentially of ozone and chlorine.
Claim 11
Dependent Claim
34 words
A method as recited in claim 1 wherein the amount of ozone in the mixture of ozone and chlorine is about 7-10% by volume, and wherein the mixture consists essentially of ozone and chlorine.
References Cited (Backward Citations)
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Cited
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Cited
CA966604A
Cited
US4093506A
Cited
US4080249A
Cited
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Cited
US4372812A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-02-19 | 1993-08-21 | 1994-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-19 | 1997-08-21 | 1998-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-19 | 2001-08-21 | 2002-02-20 | $7700.00 | Window Closed / Lapsed |