US4288420A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Removal of nitrogen oxides and sulfur oxides by ammonia
Assignee: Electric Power Development Co Ltd
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Filing: 1980-08-29
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Granted: 1981-09-08
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Expires: 2000-08-29
Abstract
Abstract When exhaust gas from a coal-burning boiler containing NO x as well as SO x is subjected to NO x removal by catalytic reduction of the NO x with ammonia and the coal ashes contained in the gas are separated, the coal ashes are contaminated by a certain quantity of ammonium compounds produced from the SO x and the ammonia excessively used. The ammonium compounds in the coal ashes are decomposed into ammonia and a sulfur compound by heating by the hot gas at a temperature in the restricted range, viz. 350° to 700° C., thereby to release ammonia into the gas preferentially to the sulfur compound. The ammonia thus released is recycled to the NO x removal step.
Inventors
- 👤 Hayami Ito
- 👤 Chiaki Nagai
- 👤 Yasuyuki Nakabayashi
- 👤 Kihachiro Igarashi
- 👤 Kunihiko Mouri
- 👤 Takashi Ikeda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:08
CPC Classifications
B; B01; B01D; B01D49/00; B01D53/00; B01D53/34; B01D53/74; B01D53/86; B01D53/8637; F; F23; F23J; F23J15/00; F23J15/006
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
84 words
In a process for removing nitrogen oxides from sulfur oxides and ash containing exhaust gases from a coal-fired boiler by catalytic reduction followed by removal of the ash and ammonium-sulfur compounds from the gas, the improvement comprising contacting the ash containing ammonium-sulfur compounds with exhaust gas from said boiler at a temperature of 350° to 700° C. whereby the ammonium-sulfur compounds are decomposed, the sulfur compounds are preferentially retained in the ash and the ammonia containing exhaust gas is passed to said catalytic reduction.
Claim 2
Dependent Claim
84 words
In a process for removing nitrogen oxides from sulfur oxides and ash containing exhaust gases from a coal-fired boiler by catalytic reduction followed by removal of the ash and ammonium-sulfur compounds from the gas, the improvement comprising contacting the ash containing ammonium-sulfur compounds with exhaust gas from said boiler at a temperature of 350° to 700° C. whereby the ammonium-sulfur compounds are decomposed, the sulfur compounds are preferentially retained in the ash and the ammonia containing exhaust gas is passed to said catalytic reduction.
Claim 3
Dependent Claim
23 words
The process as claimed in claim 1 in which the temperature at which the coal ashes are heated in 350° to 500° C.
References Cited (Backward Citations)
US4141959A
Cited
JPS5517041A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-09-07 | 1985-03-09 | 1985-09-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-07 | 1989-03-09 | 1989-09-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-07 | 1993-03-09 | 1993-09-08 | $7700.00 | Window Closed / Lapsed |