JPH0335571B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a burner used in a radiant tube for heating in a continuous annealing furnace, etc., which particularly reduces generation of thermal _NOx . Regarding.

[Conventional technology]

Generally, radiant tube burners used in continuous annealing furnaces are operated under harsh conditions at high temperatures (maximum tube temperature of about 1100℃).
Even under such combustion conditions, there are no pollution problems.
It is necessary to suppress the amount of _NO A two-stage combustion type burner, such as that disclosed in Japanese Unexamined Patent Publication No. 14106/1983, has been proposed as a burner that can meet such demands. This is low
In order to carry out _NOx combustion, combustion air is supplied to the combustion chamber through two systems, an outline of which is shown in FIGS. 7a, b, and c. Figure a is a side view with main parts cut away, figure b is a partially enlarged view of figure a, and figure c is a view taken in the direction of arrow A in figure b.

In the figure, 1 shows a part of the radiant tube, and an example of the whole is shown in FIG. 2 is a burner inserted into this radiant tube 1. Reference numeral 3 denotes a gas supply port for combustion, and gas supplied from this port to the gas chamber 4 passes through a gas lance 5 and is ejected from a gas nozzle 7 opening into a burner head 6 to be combusted. Reference numeral 8 denotes a flange of the burner head 6, which forms a ring-shaped gap between it and the radiant tube 1, and serves as a primary nozzle 9. Reference numeral 10 denotes a combustion air supply port, and the air supplied from this enters the air chamber 11, which is a space inside the radiant tube 1 defined by the burner head 6, and a part of it is supplied from the primary air nozzle 9 mentioned above. The air is blown out to perform primary combustion F ₁ together with the gas, while the air blown out from the small cylindrical secondary air nozzle 12 provided in the burner head 6 is 1
Almost complete combustion is achieved by performing secondary combustion F ₂ with the unburned gas from the next combustion F ₁ , and the resulting high-temperature combustion gas is transferred to the radiant tube 1 shown in Figure 3.
It is designed to heat the entire area.

The amount of _NOx produced in a burner with the above configuration is greatly affected by the ratio of primary air to secondary air, as shown in Figure 4, so the opening area of each air nozzle must be constant. However, it is particularly difficult to maintain the above ratio constant for the primary air nozzle 9 due to errors in the inner diameter during manufacturing of the radiant tube 1.

Therefore, in order to solve these drawbacks, the eighth
A burner as shown in the figure has been developed. (See Utility Model Application No. 63-23527). This is because the width between the radiant tube 1 and the outer periphery of the flange 8 of the burner 22 is uniform over the entire circumference so that the opening area of the primary air nozzle remains constant regardless of the inner diameter error of the radiant tube. The cylindrical body 20 is provided concentrically with the flange 8 of the burner head 6 so as to form a gap having a predetermined opening area, that is, a primary air nozzle 29. This cylindrical body 20
Unlike a radiant tube, its inner diameter can be formed with sufficiently high precision.

[Problem that the invention seeks to solve]

In the improved burner shown in FIG. 8 above, the primary air is uniformly blown out in the circumferential direction from the ring-shaped gap, so that air is generated in the combustion chamber 13 as shown in FIG. 9. Areas with high concentration and areas with low concentration (air-rich areas and gas-rich areas) should appear alternately at approximately equal rates, but in reality, ring-shaped gaps must be manufactured with high precision and uniform width. It is difficult to do so, and drifting within the gap is likely to occur. Therefore, as shown in FIG. 10, the primary air is not ejected uniformly, but varies in the circumferential direction. Therefore, in areas where the amount of air is excessive, residual air that does not participate in combustion enters the secondary combustion zone, and in areas where there is insufficient amount of air, residual gas enters the secondary combustion zone. There was a problem in that the ratio of combustion F ₂ increased and the balance between primary combustion and secondary combustion was disrupted, and optimal second-stage combustion was no longer performed, resulting in an increase in the amount of _NOx produced.

This invention has been made in view of these conventional problems, and solves the above problems by arranging a primary air nozzle at an equal distance outside or inside the gas nozzle of the burner head. The purpose is to

[Means for solving problems]

This invention relates to a radiant tube burner having a cylindrical body at the insertion part into the radiant tube, in which a disc-shaped burner head is attached to the open end of the cylindrical body so as to close the open end, and a small burner head is attached to the center of the burner head. A cylindrical secondary air nozzle is provided, and a plurality of gas nozzles are arranged on the burner head at equal intervals on the circumference of a circle concentric with the secondary air nozzle, and at positions on the outside or inside and equidistant from each of the gas nozzles. This is a radiant tube burner equipped with a number of primary air nozzles of the same shape corresponding to the gas nozzles.

[Effect]

Since the radiant tube burner according to the present invention is constructed as described above, the gas ejected from the gas nozzle performs primary combustion together with the air ejected from the primary air nozzle, while the secondary The air blown out from the air nozzle performs secondary combustion together with the unburned gas from the primary combustion.

Furthermore, since the same number of primary air nozzles as gas nozzles have the same shape, the amount of air ejected is the same, and therefore the change in air concentration related to primary combustion is uniform, and all of the primary air is consumed in primary combustion. Next, the unburned gas in the primary combustion performs secondary combustion together with the secondary air blown out from the secondary air nozzle.

As described above, this burner performs two-stage combustion with primary and secondary combustion, thereby reducing the amount of _NOx generated.

〔Example〕

The present invention will be explained below based on the drawings. FIG. 1 is a diagram showing an embodiment according to the present invention. However, the same parts as in the conventional example are given the same reference numerals, and redundant explanation will be omitted.

In the figure, 30 is a burner head, which is attached to the open end of the cylindrical body 20 so as to close it. Primary air nozzles 39 are bored at equal intervals and in the same shape along the outer periphery of the burner head 30, and are located equidistant from the plurality of gas nozzles 7, respectively. Further, in this embodiment, since four gas nozzles 7 are provided, four primary air nozzles 39 are provided correspondingly, but the number is not limited to four.

Further, the gas nozzles 7 and the secondary air nozzles 12 are provided at equal intervals on the same circumference that is concentric with the secondary air nozzles 12, as in the conventional example.

In the above configuration, the gas ejected from the gas nozzle 7 via the gas supply port 3 via the gas lance 5 is
Primary combustion occurs with air blown from the air supply port 10 through the air chamber 11 and from the primary air nozzle 39.
On the _other hand, the air blown out from the secondary air nozzle 12 performs secondary combustion F ₂ together with the unburned gas in primary combustion F ₁ .

At this time, since the plurality of primary air nozzles 39 have the same shape and are equidistant from the gas nozzle 7, the amount of ejected air is uniform as shown in the air concentration change graph in FIG. Therefore, non-uniform combustion in the circumferential direction of the buff-full surface 30a (burner head surface) does not occur, so all of the primary air is consumed in the primary combustion _F1 , and the primary combustion _F1 is the primary combustion inside the combustion chamber 13. This is completed in the combustion zone, and the unburned gas at this time performs secondary combustion _F2 in the secondary combustion zone together with the secondary air supplied from the secondary air nozzle, so that this burner 22 completely performs two-stage combustion. It becomes possible to do so.

On the other hand, in the conventional example, the primary combustion is not completed in the primary combustion area, and the amount of primary air remaining in the primary combustion area is 2. Since it is involved in the next combustion, the burners shown in FIGS. 7 and 8 do not provide complete two-stage combustion.

This appears as a difference between the embodiment and the conventional example in the amount of _NOx produced as shown in FIGS. 6 and 11. Figures 6 and 11 show _NOx generated in response to the above combustion.
This is an actual measurement diagram of the amount, with the vertical axis showing the 11% O ₂ equivalent NO _X production value and the horizontal axis showing the maximum temperature in the longitudinal direction of the radiant tube. In the conventional example shown in FIG. 11, the amount of _NOx generated at the maximum temperature in the longitudinal direction of the radiant tube of 1050° C. is 153 ppm, which exceeds the environmental standard of 150 ppm. On the other hand, in the embodiment shown in FIG. 6, in which air is uniformly blown out in the circumferential direction of the buffled surface 30a, the amount is reduced to 102 ppm.

FIG. 2 shows another embodiment.

In this case, the primary air nozzle 39 is arranged slightly inward from the outer periphery of the buttful 30 under the same conditions as the embodiment shown in Fig. 1, and all the nozzles have the same circular hole diameter, and the function as a burner is This is equivalent to the embodiment shown in FIG.

In each of the above embodiments, the secondary air nozzle, gas nozzle, and primary air nozzle are arranged outward from the center of the burner, but the primary air nozzle, secondary air nozzle, and gas nozzle may be arranged in the same order.

〔Effect of the invention〕

As explained above, according to the present invention, the amount of NO _X generated during burner combustion can be significantly reduced compared to the amount generated in the conventional example, and as a result, the environmental standards regarding the amount of NO _X generated can be fully satisfied. can get.

[Brief explanation of drawings]

Figure 1a is a side view with main parts cut away of an embodiment of the present invention, Figure 1b is a partially enlarged view of Figure 1a, Figure 1c is
2A is a side view of another embodiment; FIG. 2B is a partially enlarged view of FIG. 2A; FIG. The figure is an overall view of the radiant tube, Figure 4 is a diagram showing the amount of _NO NO _X for maximum temperature in tube longitudinal direction
7a is a side view of the first conventional example, FIG. 7b is a partially enlarged view of FIG. A side view of the second conventional example, FIG. 9b is a partially enlarged view of FIG. a, FIG. The figure shows the non-uniform primary air concentration in the conventional example, and FIG. 11 shows the amount of _NOx produced with respect to the maximum temperature in the longitudinal direction of the radiant tube in the conventional example. 1...Radiant tube, 2,22...Burner, 6,30...Burner head, 7...Gas nozzle, 9,29,39...Primary air nozzle, 12...
...Secondary air nozzle, 20...Cylindrical body.

Claims (1)

[Claims] 1. In a radiant tube burner having a cylindrical body at the insertion part into the radiant tube, a disc-shaped burner head is attached to the open end of the cylindrical body so as to close this open end, and a small cylindrical burner head is installed in the center of the burner head. A secondary air nozzle is provided, and a plurality of gas nozzles are arranged on the burner head at equal intervals on the same circumference that is concentric with the secondary air nozzle, and at positions corresponding to the gas nozzles on the outside or inside and equidistant from each gas nozzle. A radiant tube burner characterized by having a number of primary air nozzles of the same shape.