Patent US4013430A successfully refreshed from Google Patents.
US4013430A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for regenerating absorbing solution used for exhaust gas purification
Assignee: JNC Engineering Co Ltd
•
Filing: 1975-12-29
•
Granted: 1977-03-22
•
Expires: 1995-12-29
Abstract
Abstract In the process wherein industrial exhaust gases containing nitrogen oxides and SO 2 are treated with an absorbing solution containing an iron chelate complex and a sulfite to remove nitrogen oxides and SO 2 , the absorptivity of the solution is reduced sometimes on account of dithionate formed during the treatment. The absorptivity-reduced absorbing solution is regenerated by heat-treating the solution at a pH of 3.0 or lower and a temperature of 80° C or higher whereby the dithionate is decomposed.
Inventors
- 👤 Keiji Adachi
- 👤 Tokio Gorai
- 👤 Kazuaki Ohami
- 👤 Takehiko Takahashi
- 👤 Takayoshi Mizukami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:33
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/46; B01D53/60; Y; Y02; Y02A; Y02A50/00; Y02A50/20
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
164 words
In the process for treating industrial exhaust gased containing nitrogen oxides and SO 2 with an absorbing solution containing an iron chelate complex salt and a sulfite in an absorbing zone to remove nitrogen oxides and SO 2 from the industrial exhaust gases, the improvement which comprises regenerating and recirculating the absorbing solution by a. cooling the absorbing solution withdrawn from said absorbing zone during or after the absorption treatment, at a pH of 3.0 or lower and a temperature of about 0° C, to precipitate and remove the chelating agent constituting said iron chelate complex salt contained in the absorbing solution; b. heating the resulting absorbing solution at a temperature of 80° C or higher, to decompose dithionate, imidodisulfate and amidosulfate contained in the absorbing solution; c. removing SO 2 liberated from the absorbing solution, and removing ammonium sulfate by evaporating the absorbing solution to crystallize out and remove ammonium sulfate; and d. recirculating the resulting regenerated absorbing solution to said absorbing zone.
Claim 2
Dependent Claim
164 words
In the process for treating industrial exhaust gased containing nitrogen oxides and SO 2 with an absorbing solution containing an iron chelate complex salt and a sulfite in an absorbing zone to remove nitrogen oxides and SO 2 from the industrial exhaust gases, the improvement which comprises regenerating and recirculating the absorbing solution by a. cooling the absorbing solution withdrawn from said absorbing zone during or after the absorption treatment, at a pH of 3.0 or lower and a temperature of about 0° C, to precipitate and remove the chelating agent constituting said iron chelate complex salt contained in the absorbing solution; b. heating the resulting absorbing solution at a temperature of 80° C or higher, to decompose dithionate, imidodisulfate and amidosulfate contained in the absorbing solution; c. removing SO 2 liberated from the absorbing solution, and removing ammonium sulfate by evaporating the absorbing solution to crystallize out and remove ammonium sulfate; and d. recirculating the resulting regenerated absorbing solution to said absorbing zone.
Claim 3
Dependent Claim
26 words
A process according to claim 1 wherein the absorbing solution is maintained at a pH of 0-1 in the regeneration step by adding sulfuric acid thereto.
Claim 4
Dependent Claim
18 words
A process according to claim 1 wherein said heating step is carried out at 120-140° C under pressure.
Claim 5
Dependent Claim
18 words
A process according to claim 1 wherein the chelating agent constituting said iron chelate complex salt is ethylenediaminetetraacetate.
Claim 6
Dependent Claim
32 words
A process according to claim 1 wherein said sulfite is ammonium sulfite, and ammonium sulfate formed by the decomposition of dithioate is separated in advance of the recirculation of the absorbing solution.
References Cited (Backward Citations)
DE1251900B
Cited
US3556722A
Cited
US3503185A
Cited
US3653812A
Cited
US3644087A
Cited
US3923954A
Cited
US3933993A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-03-21 | 1980-09-20 | 1981-03-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-21 | 1984-09-20 | 1985-03-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-21 | 1988-09-20 | 1989-03-22 | $7700.00 | Window Closed / Lapsed |