US4098639A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulosic material
Assignee: Mo och Domsjo AB
•
Filing: 1976-07-26
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Granted: 1978-07-04
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Expires: 1996-07-26
Abstract
Abstract A process is provided for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulosic material with alkaline sodium- and sulfur-containing-sulfate pulping liquor, which comprises evaporating and burning spent sulfate pulping liquor to obtain a smelt; dissolving the resulting smelt in water to form a sodium-sulfide-sodium carbonate-containing solution green liquor; regenerating pulping white liquor containing sodium sulfide and sodium hydroxide from said green liquor; and recirculating said regenerated white liquor to the pulping stage; oxidizing at least one of the resulting green and white liquors to form sodium thiosulfate therein; reacting the oxidized liquor with residual acid liquor, from the manufacture of chlorine dioxide by reduction of an alkali metal chlorate solution, to convert thiosulfate to sulfur dioxide and sulfur; removing and recovering formed sulfur dioxide; and returning the residual liquor, freed from sulfur dioxide, to the pulping.
Inventors
- 👤 Sture Erik Olof Noreus
- 👤 Lars Tage Uhlin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 03:45
CPC Classifications
D; D21; D21C; D21C11/00; D21C11/04; Y; Y10; Y10S; Y10S210/00; Y10S210/928
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
159 words
In a process for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulose material with alkaline sodium-and sulfur-containing sulfate pulping liquor; in which chemicals recovery comprises evaporating and burning spent sulfate pulping liquor to obtain a smelt; dissolving the resulting smelt in water to form a sodium sulfide-sodium carbonate-containing green liquor; regenerating pulping white liquor containing sodium sulfide-sodium hydroxide from said green liquor; and recirculating said regenerated white liquor to the pulping stage; the improvement which comprises oxidizing at least one of the green and white liquors to form sodium thiosulfate therein; reacting the oxidized liquor with residual acid liquor, from the manufacture of chlorine dioxide by reduction of an alkali metal chlorate solution, at a temperature within the range from about 30° to about 130° C. to convert thiosulfate to sulfur dioxide and sulfur; removing and recovering formed sulfur dioxide; and returning the residual acid liquor, freed from sulfur dioxide, to the pulping.
Claim 2
Dependent Claim
159 words
In a process for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulose material with alkaline sodium-and sulfur-containing sulfate pulping liquor; in which chemicals recovery comprises evaporating and burning spent sulfate pulping liquor to obtain a smelt; dissolving the resulting smelt in water to form a sodium sulfide-sodium carbonate-containing green liquor; regenerating pulping white liquor containing sodium sulfide-sodium hydroxide from said green liquor; and recirculating said regenerated white liquor to the pulping stage; the improvement which comprises oxidizing at least one of the green and white liquors to form sodium thiosulfate therein; reacting the oxidized liquor with residual acid liquor, from the manufacture of chlorine dioxide by reduction of an alkali metal chlorate solution, at a temperature within the range from about 30° to about 130° C. to convert thiosulfate to sulfur dioxide and sulfur; removing and recovering formed sulfur dioxide; and returning the residual acid liquor, freed from sulfur dioxide, to the pulping.
Claim 3
Dependent Claim
40 words
A process according to claim 1, in which the oxidized liquor is used as an alkaline scrubbing liquid for purification of combustion gases formed during said burning of spent sulfate pulping liquor, and thereafter reacted with the residual acid liquor.
Claim 4
Dependent Claim
22 words
A process according to claim 2, in which the sulfur dioxide that is removed and recovered is used to generate chlorine dioxide.
Claim 5
Dependent Claim
31 words
A process according to claim 2, in which the sulfur dioxide that is removed and recovered is converted to sulfuric acid and the sulfuric acid is used to generate chlorine dioxide.
Claim 6
Dependent Claim
27 words
A process according to claim 1, in which sulfur that is formed is separated and combined with a white liquor and/or a green liquor to form polysulfide.
Claim 7
Dependent Claim
31 words
A process according to claim 5, in which, in addition to the formed sulfur, sulfur from an external source is combined with said white liquor and/or green liquor to form polysulfide.
Claim 8
Dependent Claim
17 words
A process according to claim 1, in which sulfur that is formed is converted to sulfur dioxide.
Claim 9
Dependent Claim
39 words
A process according to claim 1, in which the residual acid liquor, after removal of sulfur dioxide, is processed to remove chloride ion, and then recycled to the pulping so that chloride ions are not added to the system.
Claim 10
Dependent Claim
54 words
A process according to claim 8, which comprises evaporating the residual acid liquor, after removal of sulfur dioxide, so that alkali metal salts contained therein, except alkali metal chloride, are precipitated out and recovered, removing the residual acid liquor containing alkali metal chloride and recycling the precipitated alkali metal salts to the pulping process.
Claim 11
Dependent Claim
32 words
A process in accordance with claim 9, which comprises reacting the recovered alkali metal chloride with sulfuric acid and using hydrogen chloride as a reduction agent in the generation of chlorine dioxide.
Claim 12
Dependent Claim
27 words
A process according to claim 1, which comprises supplying the removed and recovered sulfur dioxide to a cellulose pulp bleaching stage which contains extraction and bleaching steps.
Claim 13
Dependent Claim
27 words
A process according to claim 11, which comprises supplying the removed and recovered sulfur dioxide to one of the extraction and bleaching steps in the bleaching stage.
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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) | 1981-07-03 | 1982-01-02 | 1982-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-07-03 | 1986-01-02 | 1986-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-07-03 | 1990-01-02 | 1990-07-04 | $7700.00 | Window Closed / Lapsed |