System and method for load control with diffusion combustion in a stoichiometric exhaust gas recirculation gas turbine system

A system, comprising:

• a turbine combustor comprising a first diffusion fuel nozzle, wherein the first diffusion fuel nozzle is configured to produce a diffusion flame;
• 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;
• and
• a control system configured to control flow rates of at least one oxidant and at least one fuel to the turbine combustor in a stoichiometric control mode and a non-stoichiometric control mode, wherein the stoichiometric control mode is configured to change the flow rates and provide a substantially stoichiometric ratio of the at least one fuel with the at least one oxidant, and the non-stoichiometric control mode is configured to change the flow rates and provide a non-stoichiometric ratio of the at least one fuel with the at least one oxidant.

A method, comprising:

• injecting at least one oxidant and at least one fuel into a chamber of a turbine combustor, wherein the at least one oxidant and the at least one fuel mix and combust as a diffusion flame to generate combustion products;
• driving a turbine with the combustion products and outputting an exhaust gas;
• recirculating the exhaust gas along an exhaust recirculation path to an exhaust gas compressor;
• compressing and routing the exhaust gas to the turbine combustor.
• controlling flow rates of the at least one oxidant and the at least one fuel to the turbine combustor in a stoichiometric control mode, wherein the stoichiometric control mode is configured to change the flow rates and provide a substantially stoichiometric ratio of the at least one fuel with the at least one oxidant;
• and
• controlling flow rates of the at least one oxidant and the at least one fuel to the turbine combustor in a non-stoichiometric control mode, wherein the non-stoichiometric control mode is configured to change the flow rates and provide a non-stoichiometric ratio of the at least one fuel with the at least one oxidant.

A method, comprising:

• introducing an oxidant to at least one oxidant compressor to produce a compressed oxidant stream;
• introducing a recirculated gas stream to a compressor section of a gas turbine engine to produce a compressed recirculated gas stream;
• introducing a first portion of the compressed oxidant stream with a first compressed oxidant flow rate and a fuel stream with a first fuel flow rate in a substantially stoichiometric ratio to at least one turbine combustor;
• mixing the compressed oxidant stream and the fuel stream at the point of combustion and combusting the mixture of the compressed oxidant stream and the fuel stream;
• introducing a first portion of the compressed recirculated gas stream with a compressed recirculated gas flow rate to the at least one turbine combustor and mixing it with the combusting streams of compressed oxidant and fuel after the point of combustion to produce a combustion products stream;
• introducing the combustion products stream to an expander section of the gas turbine engine and expanding the combustion products stream to produce a first mechanical power and an exhaust gas stream at a first exhaust gas flow rate and a first emissions level;
• using a first portion of the first mechanical power to drive the compressor section of the gas turbine engine;
• using a second portion of the first mechanical power to drive at least one of:
• a generator, the at least one oxidant compressor, or at least one other mechanical device;
• recirculating the exhaust gas stream in a recirculation loop from an outlet of the expander section to an inlet of the compressor section of the gas turbine engine to produce the recirculated gas stream;
• extracting at least a second portion of the compressed recirculated gas stream from the gas turbine engine and delivering the at least a second portion of the compressed recirculated gas stream to a first oxidation catalyst unit to produce a first product stream having a second emissions level that is lower than the first emissions level;
• reducing the first fuel flow rate and the first compressed oxidant flow rate to a second fuel flow rate and a second compressed oxidant flow rate, respectively, while maintaining the substantially stoichiometric ratio, to produce a second mechanical power that is less than the first mechanical power and a second product stream having a third emissions level that is within a target range;
• reducing the second fuel flow rate and the second compressed oxidant flow rate to a third fuel flow rate and a third compressed oxidant flow rate, respectively, while maintaining the substantially stoichiometric ratio, to produce a third mechanical power that is less than the second mechanical power and a third product stream having a fourth emissions level that is at a limit of a target range;
• and
• reducing the third fuel flow rate and the third compressed oxidant flow rate to a fourth fuel flow rate and a fourth compressed oxidant flow rate, respectively, such that fuel lean combustion occurs, to produce a fourth mechanical power that is less than the third mechanical power and a fourth product stream having a fifth emissions level that is higher than the target range.