A gas turbine assembly and method for operating the gas turbine assembly are provided. The method for operating the gas turbine assembly may include compressing a process fluid containing inlet air through a compressor to produce compressed inlet air, combining fuel from a main fuel source with the process fluid, and preheating the process fluid containing the inlet air and the fuel in a warmer disposed downstream from the compressor. The method may also include heating an oxidizer by flowing the preheated process fluid from the warmer to the oxidizer, and oxidizing the process fluid containing the compressed inlet air and the fuel in the oxidizer to produce an oxidation product. The method may further include expanding the oxidation product in a turbine to generate rotational energy, and preventing the process fluid from flowing upstream to the compressor with a check valve.