Claims
- 1. In a method of combustion of a fuel/air mixture in a combustor having a catalytic combustion system containing a catalyst unit and wherein a portion of the fuel is combusted in a homogeneous combustion wave (HC Wave) downstream of said catalyst unit, said HC Wave being located in a post-catalyst reaction zone, said combustion producing hot combustion gases from which energy is extracted, the improvement comprising:
a) controlling the location of said HC Wave in said post-catalyst reaction zone to reduce the time at which said hot gas is retained in said post-catalyst reaction zone before extraction of energy therefrom to reduce the NOx produced in said post-catalyst reaction zone.
- 2. A reduced NOx combustion process as in claim 1 wherein said NOx is reduced to below about 3 ppm in hot combustion gases having a temperature in the range of above about 1450° C. while maintaining the CO within the range of below about 100 ppm.
- 3. A reduced NOx combustion process as in claim 2 wherein said combustor is part of a gas turbine system that includes a compressor upstream of said combustor providing compressed air to said combustor.
- 4. A reduced NOx combustion process as in claim 1 wherein said controlling step includes monitoring at least one condition of at least one of said fuel/air mixture and said hot combustion gas.
- 5. A reduced NOx combustion process as in claim 4 wherein said condition monitoring includes sensing at least one of fuel amount, fuel feed rate, fuel/air temperature, gases temperature, NOx, and CO.
- 6. A reduced NOx combustion process as in claim 5 wherein said NOx and CO is monitored and the location of said HC Wave is controlled to reduce NOx while maintaining CO within a predetermined range.
- 7. A reduced NOx combustion process as in claim 1 wherein said controlling step includes adjusting the catalyst outlet gas temperature to control the delay time for ignition of the fuel in the HC Wave.
- 8. A reduced NOx combustion process as in claim 7 wherein said catalyst outlet gas temperature is adjusted by controlling the temperature of the fuel/air mixture entering the catalyst.
- 9. A reduced NOx combustion process as in claim 8 wherein said combustor includes a preburner upstream of said catalyst unit and said temperature of at least one of said fuel/air mixture and outlet gas is controlled by at least one of:
a) adjusting the fraction of air bypassing the catalyst; b) adjusting the fuel supplied to said combustor by proportioning the fuel supplied between said catalyst and said preburner; c) adjusting air input to said preburner; d) changing the composition of the fuel by introduction of components that affect the ignition delay time; and e) addition of water in at least one of upstream of said combustor and in said combustor.
- 10. A reduced NOx combustion process as in claim 9 wherein the temperature of said hot combustion gas is maintained in a predetermined range for energy extraction and the fuel supplied to said prebumer is controlled to move said HC Wave to a location to reduce NOx while maintaining CO to within a predetermined range of below about 50 ppm in said hot gas.
- 11. A reduced NOx combustion process as in claim 3 wherein said controlling step includes developing an empirical model of the operation of said combustor under a range of operating parameters, calculating the location of the HC Wave in the post-catalyst reaction zone as said parameters change, and setting system operating controls to selectively position the location of the HC Wave.
- 12. Apparatus for control of NOx produced during combustion of a fuel/air mixture in a combustor having a catalytic combustion system disposed medially therein and a post-catalyst combustion zone extending downstream of the catalyst of said catalytic combustion system, and a portion of the fuel is combusted in a homogeneous combustion wave (HC Wave) in said post-catalyst combustion zone, said combustion producing hot combustion gases from which energy is extracted, the improvement comprising:
a) at least one sensor mounted in association with said post-catalyst combustion zone, said sensor outputting a signal responsive to at least one of said HC Wave, NOx, temperature and CO; and b) a controller receiving and processing said signal to control the location of the HC Wave to reduce the NOx produced in said post-catalyst combustion zone while maintaining CO levels to within a predetermined range in said hot gas.
- 13. NOx control apparatus as in claim 12 wherein said combustor is part of a gas turbine system that includes a compressor upstream of said combustor providing compressed air to said combustor and said NOx is reduced to below about 3 ppm in hot combustion gases having a temperature in the range of above about 1450° C., and CO is maintained below about 100 ppm.
- 14. NOx control apparatus as in claim 12 wherein said controller adjusts the temperature of the catalyst inlet fuel/air mixture to control the location of said HC Wave.
- 15. NOx control apparatus as in claim 12 wherein said sensors are disposed in an array along at least a portion of said post-catalyst reaction zone to provide a profile of the sensed value in said zone.
- 16. NOx control apparatus as in claim 12 that includes at least one said sensor disposed in association with said combustor upstream of said catalyst.
- 17. NOx control apparatus as in claim 12 wherein said at least one sensor is selected from at least one of a flame sensor, a UV sensor, an ion sensor, a CO sensor, and a temperature sensor.
- 18. NOx control apparatus as in claim 17 wherein at least one sensor is oriented to look at the downstream end of said catalyst.
- 19. NOx control apparatus as in claim 14 wherein said controller effects positioning of said HC Wave by:
a) adjusting the fraction of air bypassing the catalyst; b) proportionally feeding fuel supplied, between said catalyst and a preburner upstream of said catalyst in said combustor; c) adjusting air input to said preburner; d) feeding fuel into said combustor having components that selectively affect the ignition delay time; and e) addition of water in at least one location selected from upstream of said combustor and in said combustor.
- 20. NOx reduction apparatus as in claim 13 wherein said controller includes an a control algorithm derived from an empirical model of the operation of said combustor under a range of operating parameters, said algorithm including calculated locations of the HC Wave in the post-catalyst reaction zone in relation to change in said parameters, and said controller sets system operating controls to selectively position the location of the HC Wave in response to at least one of selected hot combustion gas output temperature, NOx upper limit, and CO upper limit.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the Regular U.S. Application of our earlier-filed Provisional Application entitled METHOD OF NOx REDUCTION IN CATALYTIC COMBUSTION SYSTEMS, Ser. No. 60/244,019 filed Oct. 27, 2000. This application is related to co-pending Ser. No. 09/942,976 filed Aug. 29, 2001 by us entitled CONTROL STRATEGY FOR FLEXIBLE CATALYTIC COMBUSTION SYSTEM. The benefits of the filing and priority dates of these applications are hereby claimed under 35 U.S. Code, §§119 and 120.
Provisional Applications (1)
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Number |
Date |
Country |
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60244019 |
Oct 2000 |
US |