A liquid fuel injector includes a cylindrical primary fuel injecting body having a central axis; an annular shroud concentrically placed radially outside; and an annular secondary fuel injecting body placed concentrically with the primary fuel injecting body and the shroud between the primary fuel injecting body and the shroud. A plurality of inner swirlers placed at equal intervals in a circumferential direction are provided in an annular inner air passage formed between the primary fuel injecting body and the secondary fuel injecting body, and a plurality of outer swirlers placed at equal intervals in the circumferential direction are provided in an annular outer air passage formed between the secondary fuel injecting body and the shroud. The primary fuel injecting body is formed as a pressure spray-type injector, and the secondary fuel injecting body and the inner and outer air passages cooperatively constitute an airblast-type injector.

A method for heating a heating chamber to a temperature below the spontaneous ignition temperature of the fuel that is used, wherein fuel and air are reacted in flameless oxidation in a non-stoichiometric mixture ratio in a combustion chamber. The air ratio λ is at least lower than the stoichiometric ratio λ=1 such that the temperature in the combustion chamber does not exceed the temperature at which thermal nitrous oxide generation begins. Otherwise, λ is established such that the spontaneous ignition temperature of the fuel is exceeded. This results in two permissible air ratio ranges, between λ.sub.min and λ.sub.1 in sub-stoichiometric operation, and λ.sub.2 to λ.sub.max in superstoichiometric operation of the combustion chamber. The still-reactive gases released from the combustion chamber are made to react in the heating chamber, preferably by flameless oxidation. This avoids thermal nitrous oxide generation in the heating chamber.

A plugging resistant, highly stable free-jet burner and method which provide Ultra-Low NO.sub.x emissions using (a) large free-jet ejection ports, (b) a wide tip-to-tip spacing, and (c) auxiliary stabilization tips in the throat of the burner which are highly resistant to plugging and also produce very low levels of NO.sub.x emissions.

A cylindrical burner apparatus and method which produce low NO.sub.x emissions and low noise levels without being dependent upon a blower, or natural draft, for providing air flow or flue gas recirculation. A flow of combustion air is induced into the initial tube pass of the burner by discharging a gas fuel from a plurality of discharge ports located in the initial tube pass. At the same time, a flow of recycled flue gas is induced through a bypass duct between a subsequent tube pass of the burner and the initial tube pass by discharging one or more jets of gas fuel through the bypass duct.

A reverse-jet swirl pulverized coal burner with multi-stage recirculations includes a pre-combustion housing, a primary coal-air structure, a rich-lean output structure, an inner secondary air structure, and an outer secondary air structure. The pre-combustion housing has a pre-combustion chamber and a housing outlet. The primary coal-air structure is configured to separate a primary coal-air flow into a fuel-rich coal-air flow and a fuel-lean coal-air flow. The rich-lean output structure is configured to output the fuel-lean coal-air flow and block the fuel-rich coal-air flow to make the fuel-rich coal-air flow reversely flow to the pre-combustion chamber. The inner secondary air structure is configured to introduce an inner secondary air into the pre-combustion chamber, thereby forming a first-stage recirculation zone in the pre-combustion chamber and forming a second-stage recirculation zone. The outer secondary air structure is configured to form a third-stage recirculation zone at the housing outlet.

A burner includes an oxidant feed passage, a fuel feed passage surrounding the oxidant feed passage, an air feed surrounding the fuel feed passage, a movable air flow diverter and, optionally, a flame nozzle. The movable air flow diverter and/or flame nozzle are independently configured to create one or a plurality of gas recirculation regions adjacent the downstream tip of the burner to improve the mixing and reaction of the fuel and oxidant, and overall combustion process efficiency. A related furnace and method for generating a stable flame with the burner are also provided.

A cylindrical burner apparatus and method which produce low noise levels and are not dependent upon a blower, or natural draft, for providing combustion air flow. A flow of combustion air is induced into a rearward end of a burner tube and a swirling flame is produced in the tube by discharging a gas fuel from a plurality of discharge ports located in the tube.

A burner and methods of using the burner. The burner produces a flame from combustion air and fuel gas. Flue gas, also produced, can be withdrawn and recycled to the burner. A cooling or condition gas, such as ambient air, may be mixed with the flue gas to reduce its temperature. The burner may also utilize a stage injection so that a portion of the produced flue gas is recycled internally.

Embodiments of the present invention include high-temperature staged recirculating burners and radiant tube burner assemblies that provide high efficiency, low NOx and CO emissions, and uniform temperature characteristics. One such staged recirculating burner includes a combustion tube having inside and outside helical fins forming opposing spiral pathways for combustion gases and products of combustion, a combustion nozzle coupled to the combustion tube, a gas tube running axially into the combustion tube, and a staging gas nozzle coupled to the gas tube, where the staging gas nozzle includes radial exit holes into the combustion tube and an axial gas staging tube extending into the combustion nozzle to stage combustion.

A cylindrical burner apparatus and method which produce low NO.sub.x emissions and low noise levels without being dependent upon a blower, or natural draft, for providing air flow. A flow of combustion air is induced into a cylindrical burner lube by discharging a gas fuel from a plurality of discharge ports located inside the rearward end of the tube. At least some of the discharge ports are oriented to direct jets of the gas fuel toward flame stabilization structures positioned downstream of the discharge ports.