Claims
- 1. A nitrogen oxides decreasing combustion method which comprises:
- a first step of mixing a fuel and air with each other;
- a second step of bringing the mixture obtained in the first step into contact with a packed catalyst such that only catalytic combustion occurs; and
- a third step of adding a fresh supply of the fuel to a stream obtained from the second step to form a mixed gas and causing the mixed gas to undergo non-catalytic thermal combustion, the temperature of said packed catalyst being lower than the ignition temperature of the mixture and the adiabatic flame temperature of said mixed gas being lower than a temperature at which the nitrogen oxides occur.
- 2. The method according to claim 1, wherein the temperature of the catalyst ranges from 300.degree. to 900.degree. C.
- 3. The method according to claim 1, wherein the third step comprises allowimg the mixed gas stream to back-flow or stagnate.
- 4. The method according to claim 1, wherein the third step comprises exposing said mixed gas to an ignition source.
- 5. The method according to claim 1, wherein the catalyst is comprised of palladium.
- 6. The method according to claim 1, wherein the fuel to be added in the third step is supplied through one or more pipes arranged through the catalyst bed.
- 7. The method according to claim 1, wherein the length of the catalyst in the gas stream direction ranges from 3 to 15 cm.
- 8. The method according to claim 1, wherein the temperature of the gas at a catalyst inlet ranges from 250.degree. to 500.degree. C.
- 9. The method according to claim 1, wherein the gas flow velocity at a catalyst inlet ranges from 15 to 40 m/sec.
- 10. The method according to claim 1, wherein the fuel concentration in the first step is controlled to give a temperature of 700.degree. to 1300.degree. C. as adiabatic flame temperature when the fuel has been burnt.
- 11. The method according to claim 1, wherein the fuel added in the third step is further added with steam.
- 12. The method according to claim 1, wherein the third step comprises passing said mixed gas over a swirl-forming or gyration-forming means.
- 13. The method according to claim 12, wherein the swirl-forming means comprises a non-streamline body.
- 14. The method according to claim 12, wherein the swirl-forming means comprises a swirler.
- 15. The method according to claim 12, wherein the swirl-forming means comprises at least one swirl-forming nozzle.
- 16. The method according to claim 1, wherein the third step comprises subjecting said mixed gas to a dust-collection means.
- 17. The method according to claim 1, wherein the third step comprises passing said mixed gas through a back-fire preventive means.
- 18. The method according to claim 1, wherein the third step comprises passing said mixed gas through a flame-holding means equipped with a plurality of flow passages.
- 19. The method according to claim 1, wherein the catalyst in the second step comprises a plurality of catalysts arranged in parallel to one another.
- 20. The method according to claim 1, wherein the catalyst comprises a heat-resistant carrier supporting a silica-alumina mixture containing a noble metal and an oxide of a rare earth element.
- 21. The method according to claim 20, wherein the catalyst comprises a former-stage catalyst and a latter-stage catalyst, and the particle size of the noble metal and the pore size of the silica-alumina carrier is controlled within the range of 50 to 200 .ANG. in the former-stage catalyst and within the range of 1000 to 2000 .ANG. in the latter-stage catalyst.
- 22. The method according to claim 20, wherein the catalyst comprises a former-stage catalyst and a latter-stage catalyst, and the rare earth element comprises cerium contained in the former-stage catalyst and lanthanum contained in the latter-stage catalyst.
- 23. The method according to claim 1, wherein the catalyst comprises a heat-resistant carrier supporting a noble metal and fine aluminum particles comprised of an oxide represented by the following formula:
- MAl.sub.2 O.sub.3
- wherein M represents a rare earth element selected from the group consisting of samarium, gadolinium, cerium, lanthanum, praseodymium and neodymium.
- 24. The method according to claim 1, wherein the catalyst comprises a heat-resistant carrier and an alumina supported on the heat-resistant carrier and containing a noble metal, which has been subjected to a quenching treatment.
- 25. The method according to claim 24, wherein the catalyst contains a rare earth metal selected from the group consisting of yttrium, cesium, lanthanum, neodymium, samarium and gadolinium, in the state of an alloy.
Priority Claims (4)
Number |
Date |
Country |
Kind |
58-229967 |
Dec 1983 |
JPX |
|
59-31363 |
Feb 1984 |
JPX |
|
59-41909 |
Mar 1984 |
JPX |
|
59-59431 |
Mar 1984 |
JPX |
|
Parent Case Info
This application is a continuation, of application Ser. No. 930,977, filed Nov. 13, 1986 (abandoned), which is a continuation of Ser. No. 676,936 filed Nov. 30, 1984 (abandoned).
US Referenced Citations (8)
Foreign Referenced Citations (4)
Number |
Date |
Country |
9523 |
Apr 1980 |
EPX |
2179019 |
Nov 1973 |
FRX |
2382584 |
Sep 1978 |
FRX |
1570180 |
Jun 1980 |
GBX |
Non-Patent Literature Citations (1)
Entry |
Lew, H. G. et al, American Society of Mechanical Engineers, Paper No. 79-GT-150, 1979, "Experimentally Determined Catalytic Reactor Behavior and Analysis for Gas Turbine Combustors". |
Continuations (2)
|
Number |
Date |
Country |
Parent |
930977 |
Nov 1986 |
|
Parent |
676936 |
Nov 1984 |
|