US6071377A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for obtaining flue gases with low content of NOx in a black liquor recovery boiler
Assignee: Metso Fiber Karlstad AB
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Filing: 1996-12-06
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Granted: 2000-06-06
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Expires: 2016-12-06
Abstract
Abstract The invention relates to a process for combusting black liquor in recovery boilers where the intention is to obtain flue gases which have a low content of nitrogen oxides (NO x ). The invention is characterized in that ammonia is supplied to a part of the combustion air, which part is then supplied to the recovery boiler, as the final portion, at a high level, so that a reducing atmosphere is created in a very large part of the recovery boiler and for a long time, of at least 2.5-5 seconds or more. The invention also includes a recovery boiler for implementing the above mentioned process.
Inventors
- 👤 Nils Gustav Lindman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 07:55
CPC Classifications
D; D21; D21C; D21C11/00; D21C11/0085; D21C11/0092; D21C11/12; F; F23; F23G; F23G7/00; F23G7/04; F23J; F23J7/00; F23G2206/00; F23G2206/20; F23G2206/203; F23G2207/00; F23G2207/10; F23G2207/105; F23G2207/60; F23J2215/00; F23J2215/10; Y; Y02; Y02E; Y02E20/00; Y02E20/12
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
163 words
A method for combusting black liquor in a recovery boiler and producing flue gases having a low content of nitrogen oxides (NO x ), comprising: providing a recovery boiler and having a region extending from a liquor injection device to a quaternary air supply unit; supplying primary, secondary and tertiary combustion air to the recovery boiler; determining a stoichiometric requirement for a complete reduction of the nitrogen oxides present in the flue gases; supplying a quantity of gaseous ammonia to the a quaternary combustion air at an upper portion of the recovery boiler, the quantity corresponding to between about 100% and about 400% of the stoichiometric requirement for complete reduction of the nitrogen oxides present in the flue gas; mixing the gaseous ammonia with the quaternary combustion air to form a combustion air mixture; supplying the combustion air mixture to the upper portion of the recovery boiler; maintaining a reducing atmosphere in the regions for a dwell time of at least 2.5 seconds.
Claim 2
Independent Claim
163 words
A method for combusting black liquor in a recovery boiler and producing flue gases having a low content of nitrogen oxides (NO x ), comprising: providing a recovery boiler and having a region extending from a liquor injection device to a quaternary air supply unit; supplying primary, secondary and tertiary combustion air to the recovery boiler; determining a stoichiometric requirement for a complete reduction of the nitrogen oxides present in the flue gases; supplying a quantity of gaseous ammonia to the a quaternary combustion air at an upper portion of the recovery boiler, the quantity corresponding to between about 100% and about 400% of the stoichiometric requirement for complete reduction of the nitrogen oxides present in the flue gas; mixing the gaseous ammonia with the quaternary combustion air to form a combustion air mixture; supplying the combustion air mixture to the upper portion of the recovery boiler; maintaining a reducing atmosphere in the regions for a dwell time of at least 2.5 seconds.
Claim 3
Dependent Claim
29 words
The method according to claim 1 wherein the step of supplying the quantity of gaseous ammonia comprises supplying a quantity that corresponds to between about 100% and about 200%.
Claim 4
Dependent Claim
29 words
The method according to claim 1 wherein the step of supplying the quantity of gaseous ammonia comprises supplying a quantity that corresponds to between about 100% and about 300%.
Claim 5
Dependent Claim
32 words
The method according to claim 1 wherein the step of supplying the quantity of gaseous ammonia comprises supplying an ammonia that is partially generated by a mill associated with the recovery boiler.
Claim 6
Dependent Claim
22 words
The method according to claim 1 wherein the method further comprises monitoring proportions of nitrogen oxides and ammonia in the flue gases.
Claim 7
Dependent Claim
29 words
The method according to claim 1 wherein the method further comprises guiding a temperature above the quaternary air supply unit by regulating an air supply to reduce nitrogen oxides.
Claim 8
Dependent Claim
20 words
The method according to claim 1 wherein the region extends over a distance between about 10 meters and 20 meters.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-06-06 | 2003-12-06 | 2004-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-06-06 | 2007-12-06 | 2008-06-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-06-06 | 2011-12-06 | 2012-06-06 | $7700.00 | Window Closed / Lapsed |