NOVELTY - The oxidizer (224) has a reaction chamber including an inlet to accept a gas mixture comprising high-energy-content (HEC) fuel gas (210) e.g. propane. The mixture is provided at initial temperature below auto-ignition temperature of the mixture. A first flow path directs the mixture entering an inlet through a medium that is hotter than the autoignition temperature of the mixture until the mixture reaches temperature above the autoignition temperature of the mixture. A second flow path directs an oxidizing gas mixture to an outlet. The second flow path is opposite to the first flow path.    USE - Oxidizer for oxidizing fuel e.g. hydrogen, methane, ethane, ethylene, natural gas, propane, propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane, acetylene, hexane and carbon monoxide (all claimed), to perform industrial process e.g. power generation process, steam generation process and thermally driven chemical process.    ADVANTAGE - The oxidizer allows a heat controller that increases the temperature of the mixture above the autoignition temperature of the mixture, thus permitting the mixture to autoignite and to maintain the temperature of the mixture below flameout temperature, while the autoignited mixture oxidizes. The oxidizer allows excess flue gas such as carbon dioxide and hydrogen mono-oxide, and a reduced amount of oxygen such that reduced oxygen concentration delays autoignition, thus permitting the mixture of the fuel with the air-flue gas mixture to reach a generally homogeneous composition in an effective manner. The oxidizer allows an injection of steam in gradual oxidation process within the oxidizer to reduce emissions of criteria pollutants, while burning near-stoichiometric air-fuel ratios in an improved manner. The oxidizer allows cooler compressor inlet temperature to reduce an amount of work or power used to compress gas, thus leaving more shaft power available to drive a generator. The oxidizer can dispose low-energy-content (LEC) fuel i.e. methane, that evolves from landfills, while minimizing undesirable component e.g. carbon monoxide and mono-nitrogen oxide, in an exhaust, thus decreasing expense of the fuel.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for operating an oxidizer.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a pre-mix oxidation system.    Gas-collection piping system (204)    Homogenized oxidant-diluent-fuel mixture (206e)    HEC fuel gas (210)    Compressor or blower (222)    Oxidizer (224)