Staged gradual oxidation
Described herein are embodiments of systems and methods for oxidizing gases. In some embodiments, a reaction chamber is configured to receive a fuel gas and maintain the gas at a temperature within the reaction chamber that is above an autoignition temperature of the gas. The reaction chamber may also be configured to maintain a reaction temperature within the reaction chamber below a flameout temperature. In some embodiments, heat and product gases from the oxidation process can be used, for example, to drive a turbine, reciprocating engine, and injected back into the reaction chamber.
1. A method for oxidizing fuel comprising:
gradually oxidizing a first fuel, in a first gas mixture, in a first reaction chamber that is configured to maintain gradual oxidation of the first fuel within the first reaction chamber without a catalyst;
introducing flue gas, comprising heated product gas from oxidation of the first fuel in the first reaction chamber, into a second reaction chamber;
introducing a second fuel into the second reaction chamber; and
oxidizing the second fuel in the second reaction chamber in a gradual oxidation process without a catalyst;
wherein a first internal temperature within the first reaction chamber is maintained beneath a flameout temperature of the first fuel;
wherein a second internal temperature within the second reaction chamber is maintained beneath a flameout temperature of the second fuel, higher than the flameout temperature of the first fuel.
2. The method of claim 1 , wherein the second internal temperature within the second reaction chamber is maintained beneath the flameout temperature of the second fuel by controlling an amount of the flue gas relative to an amount of the second fuel in the second reaction chamber.
3. The method of claim 2 , further comprising reducing the second internal temperature within the second reaction chamber by increasing an amount of the flue gas relative to an amount of the second fuel second reaction chamber when an adiabatic temperature within the second reaction chamber (i) is lower than and approaches or (ii) exceeds the flameout temperature of the second fuel within the second reaction chamber.
4. The method of claim 3 , wherein reducing the second internal temperature comprises removing heat from the second reaction chamber.
5. The method of claim 2 , wherein the flameout temperature of the second fuel is higher than the flameout temperature of the first fuel.
6. The method of claim 1 , further comprising reducing the first internal temperature within the first reaction chamber when an adiabatic temperature within the first reaction chamber (i) is lower than and approaches or (ii) exceeds the flameout temperature of the first fuel within the first reaction chamber.
7. The method of claim 6 , wherein reducing the first internal temperature comprises removing heat from the first reaction chamber.
8. The method of claim 1 , further comprising determining a first inlet temperature of the gas mixture at the first reaction chamber inlet.
9. The method of claim 8 , further comprising increasing the first inlet temperature when the first inlet temperature (i) is higher than and approaches or (ii) drops below an autoignition temperature of the first fuel within the first reaction chamber, such that the first inlet temperature is maintained above the autoignition temperature.
10. The method of claim 1 , further comprising determining a second inlet temperature at a second reaction chamber inlet.
11. The method of claim 10 , further comprising increasing the second inlet temperature when the second inlet temperature (i) is higher than and approaches or (ii) drops below an autoignition temperature of the second fuel within the second reaction chamber, such that the second inlet temperature is maintained above the autoignition temperature.
12. The method of claim 11 , wherein increasing the second inlet temperature comprises introducing the flue gas to mix with the second fuel at or near the second reaction chamber inlet.
13. A method for oxidizing fuel comprising:
gradually oxidizing a first fuel, in a first gas mixture, in a first reaction chamber that is configured to maintain gradual oxidation of the first fuel within the first reaction chamber without a catalyst;
introducing flue gas, comprising heated product gas from oxidation of the first fuel in the first reaction chamber, into a second reaction chamber configured to maintain gradual oxidation without a catalyst;
determining, with a processor, an oxygen content level within the second reaction chamber;
introducing a second fuel into the second reaction chamber;
oxidizing the second fuel in the second reaction chamber in a gradual oxidation process without a catalyst;
maintaining a first internal temperature within the first reaction chamber beneath a flameout temperature of the first fuel; and
maintaining a second internal temperature within the second reaction chamber beneath a flameout temperature of the second fuel, higher than the flameout temperature of the first fuel.
14. The method of claim 13 , wherein an amount and distribution within the second chamber of the introduction of flue gas into the second chamber is based on the determined oxygen content level.
15. The method of claim 13 , further comprising reducing the second internal temperature within the second reaction chamber when an adiabatic temperature within the second reaction chamber (i) is lower than and approaches or (ii) exceeds the flameout temperature of the second fuel within the second reaction chamber.
16. The method of claim 15 , wherein reducing the second internal temperature comprises removing heat from the second reaction chamber.
17. The method of claim 13 , further comprising reducing the first internal temperature within the first reaction chamber when an adiabatic temperature within the first reaction chamber (i) is lower than and approaches or (ii) exceeds the flameout temperature of the first fuel within the first reaction chamber.
18. The method of claim 17 , wherein reducing the first internal temperature comprises removing heat from the first reaction chamber.
19. The method of claim 13 , further comprising determining a first inlet temperature of the gas mixture at the first reaction chamber inlet.
20. The method of claim 19 , further comprising increasing the first inlet temperature when the first inlet temperature (i) is higher than and approaches or (ii) drops below an autoignition temperature of the first fuel within the first reaction chamber, such that the first inlet temperature is maintained above the autoignition temperature.
21. The method of claim 13 , further comprising determining a second inlet temperature at a second reaction chamber inlet.
22. The method of claim 21 , further comprising increasing the second inlet temperature when the second inlet temperature (i) is higher than and approaches or (ii) drops below an autoignition temperature of the second fuel within the second reaction chamber, such that the second inlet temperature is maintained above the autoignition temperature.
23. The method of claim 22 , wherein increasing the second inlet temperature comprises introducing the flue gas to mix with the second fuel at or near the second reaction chamber inlet.