Combustion – Flame holder having protective flame enclosing or flame... – Tubular member delineates flame
Patent
1987-05-25
1989-03-21
Focarino, Margaret A.
Combustion
Flame holder having protective flame enclosing or flame...
Tubular member delineates flame
431186, 126 91A, F23D 1502
Patent
active
048138673
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiant tube burner in which a nozzle of a gas burner is coaxially placed in a combustion tube located in a radiant tube so that the burner can be moved in the axial direction, fuel gas issuing from the gas burner undergoes primary combustion by primary air supplied through the annular space between the gas burner and the combustion tube and further undergoes secondary combustion by secondary air supplied through the annular space between the combustion tube and the radiant tube and, more particularly to a radiant tube burner used for heat treatment furnaces or the like. The newly invented burner is capable of reducing the amount of NOx contained in the exhaust gas discharged from the radiant tube.
2. Description of the Prior Art
There has been a proposal in the design of radiant tube burners in which a damper is provided at the inlet of the primary air admitted into the combustion tube, for example, to restrain the generation of NOx, thereby making it possible to change the primary and the secondary air ratio. (See Japanese Utility Model Laid-open No. Sho 52-21036)
However, it has been found out that the amount of generated Nox cannot be sufficiently reduced only by adjusting the primary and the secondary air ratio.
Further, there has been known another proposal in which a steam tube is provided in the fuel gas nozzle to eject steam into the flame formed by burner combustion, to make it possible to reduce the flame temperature to restrain the generation of NOx (See Japanese Patent Laid-open No. Sho 52-29007).
When comparing the case of ejecting steam with that of atomizing water, the latter is more effective in reducing the flame temperature, thus leading to higher reduction of Nox. However, an adverse effect on the radiant tube and instability of the flame may be expected due to the relatively large particle size of atomized water so that the practical use has been considered to be impossible.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a radiant tube burner in which high heat load primary combustion is caused to happen in satisfactory and stable way by swirling the primary air and soft secondary combustion takes place in a radiant tube, thereby making it possible to obtain low NOx.
In order to attain the first object, according to the present invention, a divergent flame type nozzle is installed movably in the axial direction, while swirling vanes are provided on the outer periphery thereof and air dampers for adjusting the primary and the secondary air ratio are provided on the outside of a primary air supply tube.
Another object of the present invention is to provide a radiant tube burner in which the flame temperature is reduced by means of adding atomized water into the combustion flame, thereby making it possible to obtain low NOx, while high heat load combustion is going on in satisfactory and stable way owing to the two-stage combustion described above.
In order to attain the second object, a water spray nozzle is placed at the center of the divergent flame type nozzle, said nozzle being connected to an atomized water generator capable of supplying pressurized gas and additive water through an additive water transfer tube installed in the gas burner.
Further, as a different advantageous means according to the present invention, the atomized water generator is composed of a cylinder having a conical hole to be connected to the additive water transfer tube, a recessed disk having grooves for injecting pressurized gas and additive water thereinto and fitted to said cylinder and a housing for accommodating said cylinder and said disk.
It is also another object of the present invention to provide a radiant tube burner in which, in addition to the aforementioned features, the exhaust gas is used as atomizing medium, thereby accomplishing enhanced reduction of NOx while high heat load and low NOx combustion occurs due to the swirling of the primary air and addition of atomized water int
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Atarashiya Kenji
Hashime Toshiyuki
Hyodo Kaneaki
Oomori Nobuyoshi
Shiraishi Norihisa
Focarino Margaret A.
Kawasaki Seitetsu Kabushiki Kaisha
Mitsubishi Jukogyo Kabushiki Kaisha
Nihon Nensho System Kabushiki Kaisha
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