A gas-fired atmospheric pressure steam humidifier having high efficiency and ultra-low NOx(3) emissions is disclosed. In some examples, the gas-fired humidifier can have an efficiency of greater than 90 percent and a NOx(3) output of less than 20 parts per million (ppm). In one aspect, the humidifier includes a secondary heat exchanger having a first heat exchange section for pre-heating combustion air and a separate second heat exchange section for pre-heating make-up water, wherein the first and second heat exchange sections are in heat transfer communication with exhaust gases generated by the gas-fired burner and combustion blower assembly. In some examples, the first heat exchange section includes orifices for enabling flue gas recirculation.

A burner operating with flameless combustion, comprising a system for sucking the recycling flue gases directly from the combustion chamber by means of an ejector fed with the comburent, a heat exchange system positioned between the recycling flue gases and the comburent, a system for injecting the fuel directly into the recycling flue gases, the latter comprising or not comprising the comburent with formation of a mixture of fuel-recycling flue gases-comburent in the zone around the outlet of the comburent ejector and following introduction of the mixture into the combustion chamber.

A method for reducing nitrogen oxide NOx emissions during combustion of a gaseous fuel in a burner intended for a naked-flame or controlled-atmosphere reheating furnace, for reheating steel products or for continuous coating and/or annealing of metal strips, wherein a first dilution is carried out by mixing combustion air with combustion products upstream from or in the body of the burner, and a second dilution is carried out directly at the level at which the gaseous fuel reacts with the combustion air, mixing the fuel with a recirculated portion of the flame or products of partial combustion, the double dilution enabling the physical and chemical properties of the gas to be modified in order for the burner to operate with low oxygen rates and obtain a flame that produces a very low level of NOx production regardless of the temperature of the enclosure in which the combustion takes place.

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 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.

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 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.

The invention relates to a device (2) and a method for supplying combustion air and for recirculating exhaust gas for a burner (1) comprising a combustion chamber (10) and to a burner (1) comprising a device (2) for supplying combustion air and for recirculating exhaust gas. Multiple drive nozzles (21) distributed about a central axis (A) are used to supply combustion air to a mixing chamber (22) arranged downstream of the drive nozzles (21) by suctioning exhaust gases out of the combustion chamber (10); the combustion air exiting the drive nozzles (21) is mixed with exhaust gases in the mixing chamber (22) in order to form a combustion air/exhaust gas mixture, said exhaust gases flowing out of the combustion chamber (10) and being backflushed by means of the drive nozzles (21); and the combustion air/exhaust gas mixture is supplied to a reaction zone downstream of the mixing chamber (22).

Disclosed is an air heating apparatus including a burner configured to cause a combustion reaction, a heat exchanging device configured to receive heat from combustion gas generated by the combustion reaction and heat water, a heating heat exchanger configured to receive the water heated by the heat exchanging device and exchange heat with the air for heating, a main passage, in which the heat exchanging device and the heating heat exchanger are disposed, and configured such that the water flows therethrough while circulating, and a fan configured to blow the air to the heating heat exchanger.

A recuperative burner having a burner base and a combustion chamber tube in which at least one burner nozzle is positioned. An exhaust gas recirculation device has a jet pump operated by combustion air and comprises a jet nozzle. A jet pump annular gap is provided for the intake of exhaust gases from outside the combustion chamber tube via an annular driving jet. The exhaust gas recirculation device being configured upstream of the mixing plane of the fuel gases flowing into the combustion chamber tube, between the burner base and the combustion chamber tube and comprises at least one endless exhaust gas intake opening and/or a peripheral, self-contained arrangement of a plurality of exhaust gas intake openings, from which at least one flow path leads into the interior of the combustion chamber tube. A recuperator is arranged upstream of the combustion chamber tube and has a heat transfer body.