A system comprising: an oxidant compressor comprising an ac_inlet and an ac_outlet; a compressor comprising a compressor inlet and a compressor outlet; wherein the compressor operates independently of the oxidant compressor; at least one combustion system that operatively generates a working fluid and comprises a head end and a discharge end, wherein the at least one combustion system is fluidly connected to: the ac_outlet, the compressor outlet, and a first fuel supply; a first turbine section operatively connected to the compressor, wherein the turbine section comprises a PT_inlet which receives the working fluid from the at least one combustion system, a PT_outlet that discharges the working fluid; at least one secondary flow circuit being operatively connected to the first turbine section for cooling and sealing portions of the first turbine section; a secondary combustion system fluidly connected downstream of the first turbine section, wherein the secondary combustion system receives fuel from a second fuel supply; a second turbine section connected downstream of the secondary combustion system; an exhaust section fluidly connected to an outlet of the second turbine section; an exhaust gas recirculation system fluidly connected between a discharge of the exhaust section and the compressor inlet such that the working fluid exiting the exhaust section is ingested by the compressor inlet; wherein the EGR system comprises a control device for adjusting a physical property of the working fluid; an extraction from the first turbine section that removes a portion of the working fluid; and a secondary fluid source fluidly connected to the at least one secondary flow circuit, wherein the secondary fluid source supplies a substantially oxygen-free fluid to the at least one secondary flow circuit. an oxidant compressor comprising an ac_inlet and an ac_outlet; a compressor comprising a compressor inlet and a compressor outlet; wherein the compressor operates independently of the oxidant compressor; at least one combustion system that operatively generates a working fluid and comprises a head end and a discharge end, wherein the at least one combustion system is fluidly connected to: the ac_outlet, the compressor outlet, and a first fuel supply; a first turbine section operatively connected to the compressor, wherein the turbine section comprises a PT_inlet which receives the working fluid from the at least one combustion system, a PT_outlet that discharges the working fluid; at least one secondary flow circuit being operatively connected to the first turbine section for cooling and sealing portions of the first turbine section; a secondary combustion system fluidly connected downstream of the first turbine section, wherein the secondary combustion system receives fuel from a second fuel supply; a second turbine section connected downstream of the secondary combustion system; an exhaust section fluidly connected to an outlet of the second turbine section; an exhaust gas recirculation system fluidly connected between a discharge of the exhaust section and the compressor inlet such that the working fluid exiting the exhaust section is ingested by the compressor inlet; wherein the EGR system comprises a control device for adjusting a physical property of the working fluid; an extraction from the first turbine section that removes a portion of the working fluid; and a secondary fluid source fluidly connected to the at least one secondary flow circuit, wherein the secondary fluid source supplies a substantially oxygen-free fluid to the at least one secondary flow circuit.