JPS5823056Y2 - Premix burner for reducing nitrogen oxide generation - Google Patents

Description

[Detailed description of the invention] This invention has the feature that it can perform stable and complete combustion even in a closed combustion chamber with a slight internal pressure, so it is mainly used as a burner for industrial heating furnaces and melting furnaces. The present invention relates to a premix burner configured to perform combustion by blowing combustion air toward a venturi mixer to suck and mix fuel gas supplied at low pressure into the venturi mixer.

In general, this type of premix burner has a structural form that makes it difficult to suck in secondary air from around the combustion chamber because it is capable of quantitatively low-oxygen (air) combustion. Although it is suitable as a burner for a closed combustion chamber as described above, most of the premix burners currently in use have a structure as shown in Fig. 1, and the venturi mixer 01 diffuser 01A outlet. It was of the type that burns a mixed gas with an air ratio of 1.0 or more.

Therefore, as is clear from the diagram in Figure 3,
It has the disadvantage of generating a very large amount of nitrogen oxides (hereinafter referred to as NOx), and the disadvantage that even a slight increase in combustion chamber pressure can easily cause flashback due to the high oxygen concentration at the diffuser outlet. .

In view of these circumstances, the present invention effectively utilizes structural improvement means to prevent flashback to reduce NOx through a concentrated combustion method.
The purpose of this invention is to prevent flashbacks as a whole, and to simplify the structure so that it is not a distant relative.

The premix burner for reducing NOx generation according to the present invention jets the combustion air toward the venturi mixer so that the air ratio is 1 from the tiff user outlet.
．． The secondary air for combustion blows out a mixed gas of 0 or less, and the secondary air is branched into the combustion section as insufficient air for combustion, and the flow rate ratio of the secondary air is maintained constant. When an air supply system is provided, a part of the mixed gas in the Venturi mixer is sucked in using the secondary air through an opening provided in the circumference near the outlet of the diffuser, so that the air ratio is 1. The present invention is characterized in that the mixed gas having an air ratio of 0 or more can be ejected to the combustion section in substantially the same direction as the mixed gas having an air ratio of 1.0 or less.

That is, in order to prevent backfire, which is one of the drawbacks of this type of burner, the present invention provides combustion-primary air so that the air ratio of the mixed gas at the diffuser outlet is 1.0 or less. By controlling the amount of air that is insufficient for complete combustion, the air that is insufficient for complete combustion is diverted as secondary air and separately injected into the combustion section. In other words, instead of using two Venturi mixers, a part of the mixed gas in the Venturi mixer is sucked in through a hole provided in the circumference near the diffuser outlet using divided secondary air. By separately injecting a mixed gas with a ratio of 1.0 or more (mixed gas with excess air), the third
It is possible to easily implement so-called concentration combustion, such as combustion at the air ratio shown in Figure 1 and combustion at the air ratio shown in Figure 2, and the effect of reducing NOx generation can be distantly related. Even if flashback were to occur on the branch side where a mixed gas with an air ratio of 1.0 or more is ejected, it is prevented by the openings provided on the circumference near the diffuser outlet, because:
From then on, the branch side is only secondary air, and the venturi mixer side is in a state where the air ratio is less than 1.0, making it difficult for flashback to occur. ) and on the branch side (secondary air side), it has become possible to prevent flashback.

In addition, by operating a single control valve, it is possible to simultaneously perform the desired air ratio control as well as secondary and secondary air ratio control, making control for preventing flashback and reducing NOx extremely effective. It also has the effect of simplifying things.

Hereinafter, an embodiment of the present invention will be described in detail. By jetting combustion air toward the venturi mixer 1 through a nozzle, the fuel gas G supplied at low pressure is sucked into the venturi mixer 1, and both are mixed. In a premix burner configured to carry out combustion, as shown in FIG. .0 or less (approximately 0.8 to 0.
9) A system in which a combustion air supply system 3 is provided with a valve 2 that controls the control valve 2 so that combustion air is supplied to the combustion section from a portion of the air supply system 3 downstream of this control valve 2 as secondary air. 4, and this branched secondary air supply system 4
The free end of the venturi mixer 1 is connected to an air chamber 7 formed at the base end of the burner tile 5, which has a nozzle 6 connected to the tip of the venturi mixer 1 and a nozzle 6 for blowing out excess mixed gas formed at its axial center. , a plurality of through passages 8 are formed in the circumferential direction on the outer periphery of the nozzle 6 of the burner tile 5, and a portion facing the base end of these through passages 8 is formed. is provided with a nozzle 9 for spouting secondary air A2 fed into the air chamber 7, and these nozzles 9 are provided near the nozzle 9.・・・・・・
With the ejection of secondary air from the venturi mixer 1, a portion of the excess mixed gas in the venturi mixer 1 is transferred to the through passage 8...
・Air ratio is 1.0 or more (1.2 to 1.3)
) to create an air-excessive mixed gas, diffuser 1A
An aperture 10 is provided in the circumference near the outlet, so that the gas-excess mixed gas ejected from the nozzle 6 and the air-excess mixed gas ejected from the through passage 8 are separated. The structure is such that complete combustion can be carried out while sufficiently suppressing the amount of NOx generated through combustion with concentrated combustion.

[Brief explanation of drawings]

The drawings illustrate an embodiment of the premix burner for reducing the amount of nitrogen oxides generated according to the present invention, and FIG. 1 is a schematic longitudinal sectional side view of a conventional premix burner, and FIG. 2 is a schematic longitudinal sectional view of the premix burner of the present invention. Side view, Figure 3 shows air ratio and NOx
This is a diaphragm showing the relationship with the amount of generation. 1...Venturi mixer, 1A...
・Diffuser, 3...Air supply system, 10・
...Open hole.

Claims (1)

[Scope of utility model registration request] In a premix burner configured to perform combustion by sucking and mixing fuel gas supplied at low pressure into the Venturi mixer 1 by jetting combustion air toward the Venturi mixer 1, the combustion air is
Secondary air for combustion, which is injected toward the Venturi mixer 1 and a mixed gas with an air ratio of 1.0 or less from the outlet of the tiff user 1A, and secondary air that is branched into the combustion section as insufficient air for combustion. Air supply system 3 that divides the air into secondary air and maintains the flow rate ratio of the secondary air at a constant level.
and an opening 10 provided on the periphery near the exit part of the tiff user 1A to carry the secondary air.
A part of the mixed gas in the venturi mixer 1 is sucked through the venturi mixer 1, and the mixed gas with an air ratio of 1.0 or more is combusted in approximately the same direction as the mixed gas with an air ratio of 1.0 or less. A premix burner for reducing the amount of nitrogen oxides generated, characterized in that the burner is configured to emit nitrogen oxides.