A method of providing flameless combustion includes forming a pre-heated reactant stream in a primary reaction zone by reacting a first stream of fuel and a first stream of undiluted oxidant and maintaining a combustible air/fuel ratio within flammability limits of the fuel. Forming a combustion stream by reacting a first stream of diluted oxidant, a second stream of fuel, and the pre-heated reactant stream in at least one secondary reaction zone downstream of the primary reaction zone. The combustion stream is maintained at a bulk combustion temperature below an auto-ignition temperature of the combustion stream. A composition of the combustion stream and the bulk combustion temperature are adjusted to maintain combustion marginally above a lower ignition limit boundary of the combustion stream. Upon the composition and the bulk combustion temperature reaching pre-determined flameless combustion conditions, the bulk combustion temperature is increased above an auto-ignition temperature of the combustion stream.

A method of generating a flame from combustion of a fuel, includes moving an oxidant feed through an oxidant feed passage; moving a fuel feed through a fuel feed passage surrounding the oxidant feed passage; moving an air feed containing oxidant within an air feed region surrounding the fuel feed passage along the fuel feed passage; creating a gas recirculation region immediately downstream from the air feed and the fuel feed passage; diverting the air feed for proportioning the air feed around the fuel feed passage for controlling flame stabilization in the gas recirculation region; and igniting a resulting gas mixture.

A furnace heating device comprising one or more radiant tubes that are configured in one or more zones of a furnace chamber; one or more burners that are coupled to the one or more radiant tubes and one or more burner control units; a programmable controller that is configured to determine one or more estimated radiant tube temperatures that respectively correspond to the one or more radiant tubes, generate one or more control signals based on the one or more estimated radiant tube temperatures with respect to a threshold temperature, wherein the one or more control signals instruct the one or more burners to operate in a flame combustion operation or a flameless combustion operation, and provide the one or more control signals to the one or more burner control units to enable flameless combustion at furnace chamber temperatures that are below a minimum temperature for flameless combustion.