JPH0138203B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a low NOx burner.

As a conventional low NOx oil burner, as shown in FIG. 1, an inner cylinder 2 surrounding a central burner gun 1 is provided concentrically to form a passage 3 for primary air for combustion, and a burner throat 4 is installed outside the inner cylinder 2. are arranged concentrically to form a secondary air passage 5, and the amount of exhaust gas mixed into the primary air can be adjusted separately from the amount of exhaust gas mixed into the secondary air.

In the conventional low NOx oil burner with such a configuration, the flame 6 made of primary air and the flame 7 made of secondary air have a composite shape as shown in Fig. 1, and combustion is performed long and dispersed in the direction of the flame axis. Since the surface area of the entire flame increases, it becomes easier to cool down, lowering the combustion temperature, and slowing down the combustion, so the temperature peak of the flame is as low as 8, making it flat as a whole, and NOx also decreases. It gets lower.
This tendency becomes more pronounced as the amount of exhaust gas mixed into the primary air increases, but in burners where the swirling force of the primary air is weak, if the oxygen concentration of the primary air becomes low, the flame will blow away from the burner or ignite again. This can result in a long flame and poor combustion.
In fact, if the primary air swirl is too strong, the mixture of primary air and fuel will move away from the burner shaft and enter the secondary air flow, causing intense combustion near the burner and causing the flame temperature peak to disperse. zu, low
It has the drawback of producing results that cannot be called NOx.

Therefore, when mixing a considerable amount of exhaust gas into the primary air to reduce the amount of NOx generated, the swirling force described above must be strengthened, and the mixture of primary air and fuel should come into contact with the secondary air near the burner. It is necessary to have a burner structure that does not cause mixing.

In addition, in conventional pulverized coal burners, swirling blades are provided at the primary air (air for pulverized coal transport) outlet to stabilize the flame. However, in this case the pulverized coal (which is ejected with the primary air) enters the secondary air stream and burns rapidly, resulting in increased NOx production. For this reason, conventional low NOx pulverized coal burners do not have the above-mentioned swirl vanes to prevent pulverized coal from rapidly burning in the secondary air. However, according to this method, the pulverized coal flows downward due to gravity, resulting in undesirable concentration imbalance.

Furthermore, some conventional pulverized coal burners mix exhaust gas into the primary air. In this case, if the amount of exhaust gas mixed into the primary air is increased, flame stability and ignition will become poor. If the above-mentioned swirling blade is abolished, this tendency will become stronger and become more inconvenient.

The one shown in Fig. 2 mixes exhaust gas into the primary air and secondary air so that the amount of each exhaust gas mixed can be adjusted separately, and there is no swirl vane in the primary air port. In this burner, the flame is primary flame 1 as shown in the figure.
6 and secondary flame 17, the combustion is slow and the flame surface area is large and cools well, resulting in a low flame temperature as shown in the figure.
It becomes NOx. But with this burner,
As mentioned above, pulverized coal drifts due to gravity, resulting in unbalanced combustion, and if the amount of exhaust gas mixed into the primary air is increased to reduce NOx, ignition and combustion become unstable.

An object of the present invention is to provide a low NOx burner having a structure for solving the problems of the conventional low NOx oil or pulverized coal burners.

Hereinafter, details of the low NOx burner of the present invention will be explained with reference to illustrated embodiments.

In FIG. 3, reference numeral 3 indicates primary air (pulverized coal) surrounding the burner gun 1 by a double-structured tapered cylinder formed by the inner cylinder 2 and the tapered inner cylinder 9. The case is a passage for a mixture of primary air and pulverized coal). Reference numeral 4 denotes a tapered burner throat provided concentrically on the outside of the double-structured tapered cylindrical body, forming a secondary air passage 12 oriented on an extension of the axial center line of the burner gun 1.
In addition, 13 in the figure is a swirl vane.

In this embodiment configured as described above, the secondary air is supplied at a suitable distance from the mixture 11 of primary air and fuel, so that the mixing of the fuel and secondary air is delayed and combustion becomes slow.

In the above embodiment, a plurality of swirling blades 1 are installed near the primary air outlet, as shown in FIG.
3 to exert the effect of the turning action, and
The turning angle can be adjusted.

The swirler 13 is fixed by a bar 15 that is rotatably held on the outer periphery of the burner gun 1, and by rotating the swirler 13 from the outside at a desired angle, the primary air jet rotation angle can be adjusted freely. It is possible to change it.

It is known that the flame is stabilized by giving appropriate swirl to the primary air, but the degree of swirl is determined by the axial speed of the primary air, the diameter of the primary air outlet, the amount of exhaust gas mixed into the primary air, and the amount of exhaust gas mixed into the primary air. The amount of exhaust gas surrounding the secondary air, its ejection speed, the penetration length, the amount of exhaust gas mixed into the secondary air, the ejection direction and speed of the secondary air, the penetration length, etc. is extremely difficult. Therefore, it is more desirable to have a structure that allows the angle of rotation to be adjusted freely.

In addition, by providing the swirling blade 13 also in the secondary air outlet 12, it is possible to adjust the position where the secondary air surrounding the primary air contacts and mixes with the primary air. However, as a practical matter, installing such swirling blades at all jet ports would result in high costs, so in practice, several types of blades with fixed angles should be prepared, and tests would be conducted to determine the One method is to select an appropriate one from among them.

Figure 4b shows the swirler blade 13 in a pulverized coal burner.
An example is shown below. Reference numeral 15 denotes a holding portion for the swirler 13.

As mentioned above, according to the low NOx burner of the present invention,
The secondary air is supplied at a suitable distance from the mixture of primary air and fuel, and combustion is dispersed in the direction of the flame axis and combustion is slow, resulting in a low flame temperature peak and a burner with low NOx emissions. is obtained.
In addition, by providing a variable-angle swirling vane at the primary air outlet and appropriately swirling the primary air, it is possible to maintain a stable flame.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view of the main parts of a conventional low NOx burner, flame shape, and flame temperature distribution. Figure 2 is a schematic sectional view of the main parts of a conventional low NOx pulverized coal burner, flame shape, and flame temperature distribution. 3A and 3B show a schematic cross-sectional view of main parts and a flame shape showing an embodiment of the low NOx burner of the present invention. Figure 4 a and b are the lower parts of Figure 3.
FIG. 3 is a schematic cross-sectional view showing a method of attaching a swirler to a NOx burner. 1... Burner gun, 2... Inner cylinder, 3... Primary air passage, 4... Tapered burner throat, 9...
Tapered inner cylinder, 12...Secondary air passage.

Claims (1)

[Claims] 1 A low-temperature system that allows the amount of exhaust gas mixed into the primary air to be adjusted separately from the amount of exhaust gas mixed into the secondary air.
In a NOx burner, a primary air passage is formed by surrounding a burner gun with a double-structured tapered cylinder formed by an inner cylinder and a tapered inner cylinder, and the double-structured tapered cylinder described above. A low NOx burner consisting of a primary air passage consisting of a body, and a secondary air passage oriented on an extension of the axial center line of the burner gun, which is formed by providing a concentrically tapered burner throat on the outside of the primary air passage.