US4279694A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for treating refined mechanical pulp and thermo mechanical pulp with ozone
Assignee: Myrens Verksted AS
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Filing: 1979-12-07
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Granted: 1981-07-21
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Expires: 1999-12-07
Abstract
Abstract When treating refined mechanical pulp and thermo mechanical pulp with ozone, it is of great importance that the process be carried out at the most favorable conditions and with a minimum consumption of energy. According to the present invention the pulp is refined to a freeness value of at least 200 csf in a first stage refiner from which the pulp is passed to a high consistency ozonizer and maturation reactor for a time limited to maximum 30 minutes. From the reactor the pulp is passed direct to a second stage refiner, the pulp then having a solids content of approximately 8-10% and an alkaline value in the range of 7-10.
Inventors
- 👤 Bjorn H. Fritzvold
- 👤 Nicolai Soteland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 05:11
CPC Classifications
D; D21; D21D; D21D1/00; D21D1/20; D21C; D21C9/00; D21C9/10; D21C9/1073
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
180 words
In a method for continuously treating refined mechanical pulp and thermo-mechanical pulp in which the pulp is subjected to a first stage refining process, treated with ozone and subsequently treated in a second stage refining process, wherein the improvement comprises: (a) refining the pulp in said first stage refining process, by means of a single grinding step to a freeness value of at least 200 csf, and a dry substance consistency of 20-60%, (b) cooling the refined pulp to a temperature below approximately 70° C., (c) treating the cooled pulp with ozone, (d) treating the ozonized pulp in a high-consistency maturation reactor in which a material selected from the group consisting of alkali and bleaching chemicals is added for not more than 30 minutes to produce a high-consistency pulp having a solids content of between 10-40% and a pH in the range of 7-10, (e) passing the matured, high consistency pulp directly and continuously to a second stage refiner, (f) grinding the pulp in said second stage refiner by means of a single grinding step to a desired freeness value.
Claim 2
Dependent Claim
180 words
In a method for continuously treating refined mechanical pulp and thermo-mechanical pulp in which the pulp is subjected to a first stage refining process, treated with ozone and subsequently treated in a second stage refining process, wherein the improvement comprises: (a) refining the pulp in said first stage refining process, by means of a single grinding step to a freeness value of at least 200 csf, and a dry substance consistency of 20-60%, (b) cooling the refined pulp to a temperature below approximately 70° C., (c) treating the cooled pulp with ozone, (d) treating the ozonized pulp in a high-consistency maturation reactor in which a material selected from the group consisting of alkali and bleaching chemicals is added for not more than 30 minutes to produce a high-consistency pulp having a solids content of between 10-40% and a pH in the range of 7-10, (e) passing the matured, high consistency pulp directly and continuously to a second stage refiner, (f) grinding the pulp in said second stage refiner by means of a single grinding step to a desired freeness value.
Claim 3
Dependent Claim
26 words
The improvement of claim 1, wherein the pulp after being treated in the high-consistency maturation reactor of step (d) has a dry substance content of 16-25%.
Claim 4
Dependent Claim
22 words
The improvement of claim 1, wherein in step (a), the pulp is refined to a freeness value of at least 400 csf.
Claim 5
Dependent Claim
29 words
The improvement of claim 1, wherein in step (d), the treatment time of the ozonized pulp in the high-consistency maturation reactor is limited to not more than 10 minutes.
Claim 6
Dependent Claim
17 words
The improvement of claim 1, wherein in step (f), the desired freeness value is approximately 80-130 csf.
References Cited (Backward Citations)
DE2444475A1
Cited
US4123317A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-07-20 | 1985-01-19 | 1985-07-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-07-20 | 1989-01-19 | 1989-07-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-07-20 | 1993-01-19 | 1993-07-21 | $7700.00 | Window Closed / Lapsed |