US4081509A
Expired / Lapsed
US
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Method for removing nitrogen oxides from flue gas by absorption
Assignee: Hitachi Ltd
•
Filing: 1976-03-19
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Granted: 1978-03-28
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Expires: 1996-03-19
Abstract
Abstract Nitrogen oxides are removed from a flue gas by wet process, where the flue gas is contacted with a solution of transition metal complex compounds capable of reacting with oxygen in the presence of oxygen, thereby forming oxygen complexes, and the nitrogen oxides are oxidized and absorbed by the oxygen complexes.
Inventors
- 👤 Yukio Hishinuma
- 👤 Hidetoshi Akimoto
- 👤 Ryuichi Kaji
- 👤 Fumito Nakajima
- 👤 Yoshijiro Arikawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:22
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/46; B01D53/54; B01D53/56
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
118 words
A method for removing nitrogen oxides comprising nitrogen monoxide from a flue gas by absorption, which comprises contacting in the presence of oxygen a flue gas containing nitrogen oxides comprising nitrogen monoxide with an aqueous solution comprising a transition metal complex compound of a transition metal and a ligand, wherein said transition metal complex compound forms a complex with oxygen, where said transition metal is selected from the group consisting of divalent cobalt and divalent chromium and where a ligand of said transition metal complex compound is selected from the group consisting of ammonia, an amine, and an imidazole derivative retaining the imidazole moiety whereby nitrogen monoxide is oxidized and absorbed as nitrous acid in said aqueous solution.
Claim 2
Independent Claim
118 words
A method for removing nitrogen oxides comprising nitrogen monoxide from a flue gas by absorption, which comprises contacting in the presence of oxygen a flue gas containing nitrogen oxides comprising nitrogen monoxide with an aqueous solution comprising a transition metal complex compound of a transition metal and a ligand, wherein said transition metal complex compound forms a complex with oxygen, where said transition metal is selected from the group consisting of divalent cobalt and divalent chromium and where a ligand of said transition metal complex compound is selected from the group consisting of ammonia, an amine, and an imidazole derivative retaining the imidazole moiety whereby nitrogen monoxide is oxidized and absorbed as nitrous acid in said aqueous solution.
Claim 3
Independent Claim
115 words
A method for removing nitrogen oxides comprising nitrogen monoxide from a flue gas by absorption, which comprises contacting a flue gas containing oxygen and nitrogen oxides comprising nitrogen monoxide with an aqueous solution of a transition metal complex compound of a transition metal and a ligand, wherein said transition metal complex compound forms a complex with oxygen, where said transition metal is selected from the group consisting of divalent cobalt and divalent chromium and where a ligand of said transition metal complex compound is selected from the group consisting of ammonia, an amine, and an imidazole derivative retaining the imidazole moiety whereby nitrogen monoxide is oxidized and absorbed as nitrous acid in said aqueous solution.
Claim 4
Independent Claim
115 words
A method for removing nitrogen oxides comprising nitrogen monoxide from a flue gas by absorption, which comprises contacting a flue gas containing oxygen and nitrogen oxides comprising nitrogen monoxide with an aqueous solution of a transition metal complex compound of a transition metal and a ligand, wherein said transition metal complex compound forms a complex with oxygen, where said transition metal is selected from the group consisting of divalent cobalt and divalent chromium and where a ligand of said transition metal complex compound is selected from the group consisting of ammonia, an amine, and an imidazole derivative retaining the imidazole moiety whereby nitrogen monoxide is oxidized and absorbed as nitrous acid in said aqueous solution.
Claim 5
Dependent Claim
11 words
A method according to claim 1, wherein said ligand is ethanolamine.
Claim 6
Dependent Claim
11 words
A method according to claim 1, wherein said ligand is histidine.
Claim 7
Dependent Claim
26 words
A method according to claim 1, wherein, said oxygen is 0.1 to 20 % by volume on the basis of total volume of the flue gas.
Claim 8
Dependent Claim
13 words
A method according to claim 1, wherein said transition metal is divalent cobalt.
Claim 9
Dependent Claim
11 words
A method according to claim 1 wherein said ligand is ammonia.
Claim 10
Dependent Claim
25 words
A method according to claim 2, wherein said oxygen is 0.1 to 20% by volume on the basis of total volume of the flue gas.
Claim 11
Dependent Claim
24 words
A method according to claim 2, wherein said aqueous solution is a 0.05 M to 0.5 M solution of said transition metal complex compound.
Claim 12
Dependent Claim
17 words
A method according to claim 2, wherein said flue gas is washed countercurrently with said aqueous solution.
Claim 13
Independent Claim
100 words
A method for removing nitrogen oxides comprising nitrogen monoxide from a flue gas by absorption, which comprises contacting a flue gas containing oxygen and nitrogen oxides comprising nitrogen monoxide with an aqueous solution of a transition metal complex compound of a transition metal and a ligand, wherein said transition metal complex compound forms a complex with oxygen, where said transition metal is divalent cobalt and where said ligand is selected from the group consisting of ammonia, an amine, and an imidazole derivative retaining the imidazole moiety, whereby nitrogen monoxide is oxidized and absorbed as nitrous acid in said aqueous solution.
Claim 14
Independent Claim
100 words
A method for removing nitrogen oxides comprising nitrogen monoxide from a flue gas by absorption, which comprises contacting a flue gas containing oxygen and nitrogen oxides comprising nitrogen monoxide with an aqueous solution of a transition metal complex compound of a transition metal and a ligand, wherein said transition metal complex compound forms a complex with oxygen, where said transition metal is divalent cobalt and where said ligand is selected from the group consisting of ammonia, an amine, and an imidazole derivative retaining the imidazole moiety, whereby nitrogen monoxide is oxidized and absorbed as nitrous acid in said aqueous solution.
Claim 15
Dependent Claim
11 words
A method according to claim 11, wherein said ligand is ethanolamine.
Claim 16
Dependent Claim
11 words
A method according to claim 11, wherein said ligand is histidine.
Claim 17
Dependent Claim
11 words
A method according to claim 11, wherein said ligand is ammonia.
Claim 18
Dependent Claim
25 words
A method according to claim 11, wherein said oxygen is 0.1 to 20% by volume on the basis of total volume of the flue gas.
Claim 19
Dependent Claim
24 words
A method according to claim 11, wherein said aqueous solution is a 0.05 M to 0.5 M solution of said transition metal complex compound.
Claim 20
Dependent Claim
17 words
A method according to claim 11, wherein said flue gas is washed countercurrently with said aqueous solution.
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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) | 1981-03-27 | 1981-09-26 | 1982-03-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-03-27 | 1985-09-26 | 1986-03-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-03-27 | 1989-09-26 | 1990-03-28 | $7700.00 | Window Closed / Lapsed |