Systems and methods for operation of a flexible fuel combustor

1. A method for normalizing combustion in a power production process, the method comprising:

providing a variable fuel that is subject to compositional changes during the power production process;

mixing carbon dioxide as a diluent with the variable fuel to provide a modified heating value fuel;

providing an oxidant;

mixing carbon dioxide with the oxidant to form an oxidant and carbon dioxide mixture;

inputting to a combustor with a combustion zone and a dilution zone that is downstream from the combustion zone the modified heating value fuel, the oxidant and carbon dioxide mixture; and additional carbon dioxide so that the modified heating value fuel is combusted to provide a combustor exhaust stream and at least a portion of the additional carbon dioxide is input to the dilution zone; and

passing the combustor exhaust stream through a turbine to generate power;

wherein the method also comprises implementing at least one control function such that one or more of the heating value of the modified heating value fuel, flame temperature, combustion pressure, combustor exit temperature, mass flow out of the combustor, turbine inlet flow chemistry, and turbine speed varies from a predetermined value by no greater than 10% and thus accounts for the compositional changes to the fuel during the power production process so that combustion is normalized, said control function at least including varying a ratio of the carbon dioxide as the diluent that is mixed with the variable fuel to form the modified heating value fuel, and said control function being implemented in response to receiving one or more inputs indicative of a compositional change to the variable fuel.

2. The method of claim 1 , wherein the variable fuel is a syngas, and wherein a ratio of carbon monoxide to hydrogen in the syngas varies during operation of the power production process.

3. The method of claim 1 , wherein the variable fuel is a mixture of methane, carbon monoxide, and hydrogen, and a ratio between the methane, carbon monoxide, and hydrogen varies during operation of the power production process.

4. The method of claim 1 , wherein the oxidant and carbon dioxide mixture includes 5% to 50% by mass oxygen, with the remaining portion being the carbon dioxide.

5. The method of claim 1 , wherein the oxidant and carbon dioxide mixture includes 15% to 30% by mass oxygen, with the remaining portion being the carbon dioxide.

6. The method of claim 1 , wherein a ratio of the length of the combustion zone to a length of the dilution zone is 0.25 to 1.0.

7. The method of claim 1 , wherein the control function further includes varying an amount of the carbon dioxide that is mixed with the oxidant so as to vary a ratio of the carbon dioxide to an amount of oxygen present in the oxidant.

8. The method of claim 1 , wherein the control function further includes varying a flow rate of the oxidant and carbon dioxide mixture input to the combustor.

9. The method of claim 1 , wherein the control function further includes varying a flow rate of the modified heating value fuel input to the combustor.

10. The method of claim 1 , wherein the control function further includes varying a flow rate of the additional carbon dioxide input to the combustor in the dilution zone.

11. The method of claim 1 , wherein the control function further includes one or more of: varying a temperature of the oxidant and carbon dioxide mixture input to the combustor; varying a temperature of the modified heating value fuel input to the combustor; and varying a temperature of the additional carbon dioxide input to the combustor in the dilution zone.

12. A method for normalizing combustion in a power production process, the method comprising:

inputting a fuel, an oxidant, and a diluent into a combustor so that the fuel is combusted to provide a combustor exhaust stream; and

passing the combustor exhaust stream through a turbine to generate power;

wherein the diluent comprises carbon dioxide;

wherein the fuel is a variable fuel that is subject to one or more compositional changes during the power production process and that is subject to addition of the diluent thereto;

wherein the oxidant is input to the combustor separate from the variable fuel; and

wherein the method further comprises monitoring for the one or more compositional changes to the variable fuel with a controller and, in response to receiving one or more inputs indicative of the one or more compositional changes to the variable fuel, the controller implementing at least one control function effective to change a heating value of the variable fuel being input to the combustor by varying a ratio of the diluent that is added to the variable fuel; and

wherein the implementing of the at least one control function by the controller is effective so that the variable fuel input to the combustor is adjusted to have a heating value that varies from a predetermined value by no greater than 10% and thus accounts for the compositional changes to the variable fuel during the power production process so that combustion is normalized.

13. The method of claim 12 , wherein a portion of the diluent is mixed with the oxidant prior to the oxidant being input to the combustor separate from the variable fuel.

14. The method of claim 12 , wherein the method further comprises the controller implementing at least one control function such that one or more of flame temperature, combustion pressure, combustor exit temperature, mass flow out of the combustor, turbine inlet flow chemistry, and turbine speed varies from a predetermined value by no greater than 10%.

15. The method of claim 12 , wherein the at least one control function further includes one or more of: varying a temperature of the oxidant input to the combustor; varying a temperature of the variable fuel input to the combustor; varying a flow rate of the oxidant input to the combustor; varying a flow rate of the variable fuel input to the combustor; and varying a chemistry of the diluent.