System and method for diffusion combustion with oxidant-diluent mixing in a stoichiometric exhaust gas recirculation gas turbine system

1. A method, comprising:

injecting first, second, third, and fourth flows separately into a chamber of a turbine combustor of a system through a diffusion fuel nozzle to produce a diffusion flame, wherein the turbine combustor is without a premix fuel nozzle;

wherein the first flow is routed through a first passage of the diffusion fuel nozzle, and the first flow comprises a first fuel;

wherein the second flow is routed through a second passage of the diffusion fuel nozzle that is separate from the first passage, and the second flow comprises a first oxidant and a first diluent;

wherein the third flow is routed through a third passage of the diffusion fuel nozzle that is separate from the first passage and the second passage, wherein the third flow comprises a second fuel, a second diluent, or a second oxidant;

wherein the fourth flow is routed through a fourth passage of the diffusion fuel nozzle that is separate from the first passage, the second passage, and the third passage, wherein the fourth flow comprises a third fuel, a third diluent, or a third oxidant;

wherein the system comprises a turbine engine comprising the turbine combustor, an exhaust gas compressor, and a control system;

driving the turbine with combustion products from the diffusion flame, and outputting an exhaust gas;

recirculating the exhaust gas along an exhaust recirculation path to the exhaust gas compressor;

compressing and routing the exhaust gas from the turbine to the turbine combustor along an exhaust gas recirculation path, wherein the first diluent comprises exhaust gas; and

controlling, using the control system, the first flow, the second flow, or both the first flow and the second flow into the chamber to produce the diffusion flame during steady state operation.

2. The method of claim 1 , wherein the first diluent comprises a portion of the exhaust gas, steam, nitrogen, another inert gas, or any combination thereof.

3. The method of claim 1 , comprising injecting a diluent flow into the chamber downstream from the first diffusion fuel nozzle.

4. The method of claim 3 , comprising injecting the diluent flow through a plurality of openings in a liner of the turbine combustor, and the diluent flow comprises a portion of the exhaust gas.

5. The method of claim 3 , comprising injecting the diluent flow through a plurality of diluent injectors extending through at least one wall of the turbine combustor, and the diluent flow comprises a portion of the exhaust gas, steam, nitrogen, or another inert gas.

6. The method of claim 1 , comprising treating the exhaust gas with a first catalyst unit along the exhaust recirculation path, wherein treating comprises controlling concentration levels of carbon monoxide, carbon dioxide, and unburnt hydrocarbons in the exhaust gas.

7. The method of claim 1 , comprising adjusting one or more operating parameters in response to sensor feedback to control an equivalence ratio or emissions levels in the exhaust gas, wherein adjusting the one or more operating parameters comprises maintaining the equivalence ratio between 0.95 and 1.05.

8. A system, comprising:

a turbine combustor comprising a first diffusion fuel nozzle, the turbine combustor being without a premix nozzle, wherein the first diffusion fuel nozzle comprises:

first and second passages that separately inject respective first and second flows into a chamber of the turbine combustor to produce a diffusion flame, wherein the first flow comprises a first fuel, and the second flow comprises a first oxidant and a first diluent;

a third passage separate from the first and second passages, the third passage being configured to inject a third flow into the chamber separately from the first and second flows, the third flow comprising a second fuel, a second diluent, or a second oxidant; and

a fourth passage separate from the first, second, and third passages, wherein the fourth passage is configured to inject a fourth flow into the chamber separately from the first, second, and third flows, the fourth flow comprising a third fuel, a third diluent, or a third oxidant;

a turbine driven by combustion products from the diffusion flame in the turbine combustor;

an exhaust gas compressor, wherein the exhaust gas compressor is configured to compress and route an exhaust gas from the turbine to the turbine combustor along an exhaust recirculation path, wherein the first diluent comprises the exhaust gas; and

a control system configured to control the first flow, the second flow, or both the first flow and the second flow through the first diffusion fuel nozzle and into the chamber to produce the diffusion flame during steady state operation.

9. The system of claim 8 , wherein the first passage has a first outlet and the second passage has a second outlet, the first outlet and the second outlet are disposed along a downstream end of the first diffusion fuel nozzle, and the first and second passages are isolated from one another along the first diffusion fuel nozzle.

10. The system of claim 8 , wherein the first and second passages are disposed in a concentric arrangement.

11. The system of claim 8 , wherein the first passage extends around the second passage.

12. The system of claim 8 , wherein the second passage extends around the first passage.

13. The system of claim 8 , wherein the turbine combustor comprises a diluent injection system disposed downstream from the first diffusion fuel nozzle and configured to inject a portion of the exhaust gas, steam, nitrogen, or another inert gas, or a combination thereof, into the chamber downstream from the first diffusion fuel nozzle.

14. The system of claim 8 , wherein the control system is configured to receive sensor feedback and to adjust one or more operating parameters based on the sensor feedback to control an equivalence ratio or emissions levels in the exhaust gas, wherein the one or more operating parameters comprise an oxidant flow rate and/or a fuel flow rate to the turbine combustor, and wherein the control system is configured to maintain the equivalence ratio between 0.95 and 1.05.

15. The system of claim 8 , wherein the first diffusion fuel nozzle is configured to produce only the diffusion flame.

16. The system of claim 8 , wherein the first diffusion fuel nozzle receives the first diluent from a first source during startup operation of the turbine combustor and from a second source during steady state operation of the turbine combustor.

17. The system of claim 8 , comprising a catalyst heat and recovery system disposed along the exhaust recirculation path, wherein the catalyst heat and recovery system comprises a catalyst unit configured to adjust a composition of the exhaust gas.

18. The system of claim 17 , comprising an exhaust gas extraction system configured to extract a portion of the exhaust gas and direct the portion of the exhaust gas to an enhanced oil recovery system.

19. The system of claim 8 , wherein the exhaust gas compressor is coupled to the first diffusion fuel nozzle via a conduit, wherein the conduit is configured to route the exhaust gas from the exhaust gas compressor to the second passage of the first diffusion fuel nozzle.