KR100940430B1 - Radiant tube burner - Google Patents

Abstract

In a radiant tube burner, the amount of NOx in the combustion exhaust gas is greatly reduced, and the life of the combustion cylinder is suppressed from being lowered. Fuel gas and combustion air ejected in a straight direction from the straight jet port 21 at the tip of the fuel gas supply pipe 20 provided inside the radiant tube 10 for guiding the combustion air are opened. In the radiant tube burner which mixes and combusts in the communication 30, the radiating jet port which blows a fuel gas in the radial direction to the front-end | tip part of the fuel gas supply pipe in the back rather than the straight jet port 21 is carried out. (22) is provided, and an interference plate (23) is provided on the outer periphery of the fuel gas supply pipe in the vicinity of the rear of the radial jet port (22). In the fuel gas supply pipe 20 in the rear position, a primary ejection port 25 for ejecting fuel gas in a radial direction was provided.

Description

Radiant Tube Burner {RADIANT TUBE BURNER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube burner. In particular, a fuel gas supply pipe for supplying fuel gas is provided inside a radiant tube for guiding combustion air, and the gas is straight ahead of the fuel gas supply pipe. Radiant tubes are provided with a straight injection orifice for ejecting in the direction, and a combustion cylinder for mixing and combusting the fuel gas ejected from the straight ejection and combusting air on the front end side of the fuel gas supply pipe. It's about a burner.

A feature of the present invention is that, in the radiant tube burner, it is possible to greatly reduce the amount of NOx in combustion exhaust gas by a simple configuration, and to suppress that the combustion cylinder temperature rises and the life is reduced. There is. The NOx in the combustion exhaust gas is NOx (fuel NOx) generated by oxidizing the nitrogen content (N ₂ ) in the fuel gas, and nitrogen contained in the fuel air (unless otherwise specified). N ₂ ) and oxygen (O ₂ ) are meant to include both NOx (thermal NOx) produced by the reaction at high temperature.

Conventionally, various types of radiant tube burners have been used, and in recent years, from the viewpoint of environmental protection, in the case of burning fuel gas by a radiant tube burner, a method of reducing the amount of NOx contained in the combustion exhaust gas after combustion. This is under review.

In order to reduce the amount of NOx contained in the combustion exhaust gas, Japanese Patent Laid-Open Publication No. 63-116011 and Japanese Patent Laid-Open Publication No. 11-201417 disclose combustion for supplying combustion air in a radiant tube. A radiant tube burner having an air supply pipe and a fuel gas supply pipe for supplying fuel gas to the inside of the combustion air supply pipe is disclosed.

In this radiant tube burner, primary combustion air supplied through the combustion air supply pipe and fuel gas supplied through the fuel gas supply pipe are mixed with the fuel gas in an excessive state in the combustion cylinder to perform incomplete combustion. Thereafter, the secondary combustion air supplied through the outside of the combustion air supply pipe is mixed to be completely burned. And if it burns in two steps in this way, flame temperature will not become high and the quantity of NOx in combustion exhaust gas will be reduced.

However, in the case of separately installing a combustion air supply pipe for supplying combustion air in the radiant tube, it is very high that the production cost is increased and the combustion is carried out in multiple stages to further reduce the amount of NOx in the combustion exhaust gas. There was a problem of becoming difficult.

In addition, Japanese Patent Laid-Open No. 6-257737 and Japanese Patent Laid-Open No. 2000-146118 disclose that a combustion cylinder is provided on the tip side of a fuel gas supply pipe for supplying fuel gas, and the tip of the combustion cylinder is tapered. And a radiant tube burner having a plurality of holes provided in the combustion cylinder.

The radiant tube burner mixes the primary combustion air supplied into the combustion cylinder through the radiant tube and the fuel gas supplied through the fuel gas supply pipe in the combustion cylinder in an excess state. A portion of the gas thus mixed is led to the tapered tip of the combustion cylinder and then burned, while surplus gas not guided to the tapered tip of the combustion cylinder is passed through the hole to the outer peripheral side of the combustion cylinder. It delivers and combusts by mixing with the secondary combustion air guide | induced to the outer peripheral side of this combustion cylinder.

However, as in the radiant tube burner, the operation of contracting the tip of the combustion cylinder into a tapered shape and providing a plurality of holes in the combustion cylinder is cumbersome, resulting in a high production cost of the combustion cylinder. Moreover, when the surplus gas which is not guide | induced to the front-end | tip part is guide | induced to the outer peripheral side of a combustion cylinder, and mixes and combusts with secondary combustion air, there existed a problem that a combustion cylinder temperature rose largely and the combustion cylinder life was shortened.

This invention makes it a subject to solve the above various problems of the conventional radiant tube burner.

That is, this invention makes it a subject to suppress that the temperature of a combustion cylinder rises and a life falls, while the quantity of NOx in combustion exhaust gas can be greatly reduced by a simple structure.

In order to solve the above problems, the present invention provides a fuel gas supply pipe (20) for supplying fuel gas into a radiant tube for guiding combustion air, and provides fuel gas at the tip of the fuel gas supply pipe (20). Combustion cylinder 30 for providing a straight jet port 21 for ejecting in a straight direction and mixing and combusting the fuel gas ejected from the straight jet port 21 and combustion air on the tip side of the fuel gas supply pipe 20. In the radial tube burner provided with the fan, a radial jet port 22 is provided at the tip of the fuel gas supply pipe 20 at the rear side of the straight jet port 21 in a radial direction, and the radial jet port is provided. An interference plate 23 is provided on the outer periphery of the fuel gas supply pipe 20 in the vicinity of the rear of the 22, and at the fuel gas supply pipe 20 at a position rearward from the interference plate 23. The primary injection port 25 which ejects fuel gas in a radial direction was provided.

Here, in the radial tube burner, in ejecting the fuel gas in the radial direction from the primary ejection port 25 provided in the fuel gas supply pipe, the fuel gas ejected from the primary ejection port is properly combusted and burned. In order to be guided to the inside, it is preferable to eject the fuel gas ejected in the radial direction from the primary ejection port 25 so as to incline forward.

In addition, in order to reduce the amount of NOx in the combustion exhaust gas and to prevent the temperature of the combustion cylinder from significantly increasing, the amount of the combustion gas ejected from the primary ejection port 25 is 5-30 vol% of the total fuel gas. It is preferable to set it as the range of.

In addition, in the radiant tube burner, in order to allow the combustion of the fuel gas ejected from the radiant jet port 22 and the primary jet port 25 to be performed uniformly inside the radiant tube 10, a radiant jet port is provided in the fuel gas supply pipe. It is preferable to provide a plurality of the primary jet ports 25 and 22, and to alternate between the circumferential positions of the radial jet ports 22 and the circumferential positions of the primary jet ports 25, respectively.

Further, in the radiant tube burner of the present invention, since the fuel gas and combustion air mixed in the combustion cylinder do not need to be guided to the combustion cylinder outer circumferential side as in the prior art, the combustion cylinder tip is shrunk to a tapered shape as in the prior art. Alternatively, it is not necessary to provide a plurality of holes in the combustion cylinder, and the combustion cylinder can be formed into a cylindrical shape having a substantially constant diameter.

In the radiant tube burner of the present invention, the combustion air guided into the radiant tube 10 is mixed with the fuel gas jetted from the primary jet port provided in the fuel gas supply pipe, and the oxygen concentration of the combustion air is lowered. do. Then, the combustion air whose oxygen concentration is lowered is led to the outer peripheral side of the tip of the fuel gas supply pipe beyond the interference plate, mixed with the fuel gas ejected from the radial ejection outlet provided in the fuel gas supply pipe, and combusts on the outer side of the combustion cylinder. In addition, combustion air having a lower oxygen concentration is led to the combustion cylinder tip side. Subsequently, in the state where the combustion air guided into the said combustion cylinder is small, fuel gas is introduce | transduced into this combustion cylinder from the straight spout provided in the fuel gas supply line front end, and fuel gas is guided to the tip of this combustion cylinder in incomplete combustion state. This fuel gas is mixed with combustion air guided from the outer circumferential side of the combustion cylinder to combust.

Thus, in the radiant tube burner of the present invention, the fuel gas ejected from the primary ejection outlet, the fuel gas ejected from the radial ejection outlet, and the fuel gas ejected from the straight ejection outlet are burned in three stages. It is further suppressed that the flame temperature is higher than the radiant tube burner, and the amount of NOx in the combustion exhaust gas is further reduced. In addition, since the amount of fuel gas combusted on the outer side of the combustion cylinder can be adjusted to suppress the increase in the temperature of the combustion cylinder, the life of the combustion cylinder can be extended.

EMBODIMENT OF THE INVENTION Below, the radiant tube burner which concerns on embodiment of this invention is demonstrated concretely based on an accompanying drawing. In addition, the radiant tube burner which concerns on this invention is not limited to what was shown to the following embodiment, It can change and implement suitably in the range which does not change the summary of invention.

In the radiant tube burner of this embodiment, as shown in FIG. 1, the combustion air supply port 11 which supplies combustion air into the radiant tube 10 to the rear side of the radiant tube 10 is shown. ) And a fuel gas supply pipe 20 for supplying fuel gas to the center of the radiant tube 10.

In addition, a straight jet port 21 for ejecting fuel gas in a straight direction is provided at the front end of the fuel gas supply pipe 20, and fuel is provided at the tip of the fuel gas supply pipe 20 behind the straight jet port 21. A plurality of radiation ejection openings 22 which eject gas in a radial direction are provided. Further, the fuel gas ejected in the radial direction from the radial ejection port 22 can be ejected in the radial direction inclined at an appropriate angle in the front-rear direction.

In addition, on the outer circumference of the fuel gas supply pipe 20 in the vicinity of the rear of the spinneret 22, an interference plate 23 for preventing the combustion air from being directly led to the spinneret 22 is provided. In addition, an ignition means 12 such as a spark plug or a pilot burner is provided so as to protrude forward from the interference plate 23 and to be located near the radiation ejection opening 22. In addition, a hole (not shown) may be formed in the interference plate 23 to guide a small amount of combustion air.

Moreover, the projection part 24 which is slightly larger in diameter is provided in the fuel gas supply line 20 in the position back than the said inhibition plate 23, and blows out so that fuel gas may incline forward in a radial direction to this projection part 24. FIG. A plurality of primary jet holes 25 are provided. As a result, the fuel gas is suitably ejected along the primary ejection port 25.

In addition, in this embodiment, although the primary blower outlet 25 was inclined forward in the radial direction in order to send the fuel gas ejected from the primary blower outlet 25 to the front appropriately as mentioned above, it is not necessary to necessarily make it blow forward. It is also possible to blow out so that it may incline backward. Moreover, it is also possible to provide the primary injection port 25 directly in the fuel gas supply pipe 20, without providing the protrusion part 24 as mentioned above.

Moreover, in the radiant tube burner of this embodiment, as shown in FIG. 1 and FIG. 2, the cylindrical combustion cylinder 30 into which the fuel gas blown off from the said straight blower outlet 21 is introduce | transduced is the said inhibitor board 23. ) Is maintained at the tip side of the fuel gas supply pipe 20 by a plurality of attachment members 26 extending from the tip side to provide a sufficient space between the inhibitor 23 and the combustion cylinder 30. have. In addition, in this embodiment, although the combustion cylinder 30 was hold | maintained by the attachment member 26 which consists of three flat bars extended from the interference plate 23, the attachment which hold | maintains the combustion cylinder 30 is carried out. The number and types of the members 26 are not particularly limited, and may be other forms.

In addition, in this embodiment, the said combustion cylinder 30 is what consists of a cylindrical shape of substantially constant diameter.

Then, the radiant tube burner configured as described above is projected in the heating furnace 1, and the radiant tube burner is attached to the wall surface 1a of the heating furnace 1.

In the radiant tube burner, when the fuel gas is mixed with combustion air and combusted, the combustion air is introduced into the radiant tube 10 through the combustion air supply port 11, and the fuel gas The fuel gas guided through the supply pipe 20 is blown into the radiant tube 10 from the primary jet 25, the radial jet 22, and the straight jet 21 into a radiant tube 10, and the fuel gas is discharged from the combustion air. Mix. And it ignites by the said ignition means 12 provided in the radiation ejection opening 22, and it combusts.

At this time, the temperature in the radiant tube 10 is low at first when the fuel gas is mixed with combustion air and combusted, but when the temperature in the radiant tube 10 rises by burning as described above, the primary jet port The combustion is performed at a position where the fuel gas blown out from (25) is mixed with the combustion air, so that the oxygen concentration of the combustion air is lowered.

Then, the combustion air having a lower oxygen concentration is led to the outer circumferential side of the tip of the fuel gas supply pipe 20 beyond the interference plate 23, and the radiation jet port 22 provided at the tip of the fuel gas supply pipe 20. The combustion air, which is mixed with the fuel gas ejected from the combustion chamber 30 and is combusted at the outer circumferential side of the combustion cylinder 30, further has an oxygen concentration lowered and is led to the combustion cylinder 30 front end side.

On the other hand, in the combustion cylinder 30, the combustion air is inhibited by the inhibition plate 23, and the combustion air introduced into the combustion cylinder 30 is reduced. In the state where the combustion air is reduced in this way, the fuel gas is introduced into the combustion cylinder 30 from the straight jet port 21 provided at the tip of the fuel gas supply pipe 20 so that the fuel gas is in an incomplete combustion state. (30) Guided to the tip, the fuel gas in the incomplete combustion state is mixed with the combustion air guided from the outer circumferential side of the combustion cylinder 30 to be combusted.

As a result of the combustion of the fuel gas in three stages as described above, the increase in the flame temperature is suppressed and the amount of NOx in the combustion exhaust gas is reduced.

Here, in the radiant tube burner of the above embodiment, the number of the radial jet ports 22 and the primary jet ports 25 provided in the fuel gas supply pipe 20 and the position in the circumferential direction thereof are not particularly limited. For example, in the case where three radiation ejection openings 22 and one primary ejection opening 25 are respectively provided in the fuel gas supply pipe 20, as shown in FIG. 3, the radiation ejection opening in the circumferential direction of the fuel gas supply pipe 20 is shown. It is preferable to stagger the position of (22) and the primary jet port (25). In other words, when the positions of the radial jet port 22 and the primary jet port 25 in the circumferential direction of the fuel gas supply pipe 20 are alternated, the circumferential direction in which the fuel gas jetted from the primary jet port 25 is combusted is burned. Position and the position in the circumferential direction where the fuel gas ejected from the radiating jet port 22 is burned are different, and combustion is performed in a wide position in the circumferential direction, so that the temperature difference in the circumferential direction inside the radiant tube 10 is small. Lose. As a result, the temperature of a part in the radiant tube 10 rises significantly, and the generation amount of NOx is increased or the combustion cylinder 30 is prevented from deteriorating.

In addition, in order to eject fuel gas from the primary jet port 25, the radial jet port 22, and the straight jet port 21 provided in the fuel gas supply pipe 20 as mentioned above, the primary jet port 25 or the radial jet port 22 When the ratio of the fuel gas blown out from the ()) is large, the temperature of the combustion cylinder 30 becomes too high and the combustion cylinder 30 easily deteriorates. On the other hand, when there are few fuel gases ejected from the primary jet port 25 or the radial jet port 22 and many fuel gases are ejected from the straight jet port 21 and combusted at the tip of the combustion cylinder 30, the flame temperature by this combustion Is so high that NOx is easily generated.

For this reason, the volume ratio with respect to the total fuel gas of the fuel gas blown out from the said primary injection port 25 with respect to the total fuel gas is 5-30 vol%, and the volume ratio with respect to the total fuel gas of the fuel gas blown out from the radial injection port 22 is 5 It is preferable to adjust to -30 vol%, and to blow off the remainder from the said straight jet nozzle 21.

In the radiant tube burner, as a fuel gas, a simulated COG (coke gas) containing 50 Vol% of hydrogen and 20 Vol% of methane is used, and the combustion capacity is 137000 kcal / h and the furnace temperature is about 940 ° C. , The volume ratio of the fuel gas ejected from the radial ejection outlet 22 is 17.5 vol% under the condition of an air ratio 1.15, and the volume ratio of the fuel gas ejected from the primary ejection outlet 25 and the straight ejection outlet 21. The experiment was performed to change and burn. In addition, since the simulation COG does not contain nitrogen content, the amount of generation of the fuel NOx is 0 vol%. For this reason, the amount of NOx produced in this experiment is the amount of thermal NOx generated by combustion.

Then, the change in the concentration of NOx in the combustion exhaust gas and the change in the temperature of the combustion cylinder according to the change in the volume ratio of the fuel gas ejected from the primary injection port 25 were investigated, and the results are shown in FIG. 4. In addition, in FIG. 4, the change of the concentration of NOx is shown by the solid line, and the change of the temperature of a combustion cylinder is shown by the broken line. In addition, the density | concentration of NOx in combustion exhaust gas was shown by the value converted so that oxygen concentration might be 11vol%.

As a result, as the volume ratio of the fuel gas ejected from the primary ejection port 25 increases, the concentration of NOx in the combustion exhaust gas decreases, while the temperature of the combustion cylinder increases. When the volume ratio of the fuel gas blown out from the primary jet port 25 is in the range of 5 to 30 vol%, the concentration of NOx decreases and the temperature rise of the combustion cylinder is not particularly a problem. It is preferable to make the volume ratio of the fuel gas blown out from the primary injection port 25 into the range of 8-18 volume%.

In addition, when the simulated COG (coke gas) containing 50 vol% of hydrogen and 20 vol% of methane is used as the fuel gas, in the conventional radiant tube burner, the NOx concentration is usually 120 to 150 volppm. Radiant tube burners showed a significant effect of reducing NOx concentration to approximately 52 volppm.

In addition, about fuel NOx, "the description of a combustion apparatus" (Daily Kogyo Shimbun, Japan burner research meeting, P211-213) describes that two-stage combustion is effective for suppressing fuel NOx, The radiant of this invention Even in the tube burner, it is obvious that it is effective for suppressing fuel NOx.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic cross section explanatory drawing which shows the state which attached the radiant tube burner which concerns on one Embodiment of this invention to a heating furnace.

Fig. 2 is a schematic explanatory view showing a state in which a combustion cylinder is held by an attachment member consisting of three flat steel bars extending from an interference plate in a radiant tube burner according to the same embodiment.

Fig. 3 is a cross-sectional explanatory diagram showing a positional relationship in the circumferential direction of a radial jet port provided in a fuel gas supply pipe and a primary jet port in a radiant tube burner according to the same embodiment.

Fig. 4 shows the change in the concentration of NOx (thermal NOx) in the combustion exhaust gas and the temperature change in the combustion cylinder according to the change in the volume ratio of the fuel gas ejected from the primary ejection opening in the experiment using the radiant tube burner according to the same embodiment. Schematic diagram showing the relationship of.

* Explanation of symbols for the main parts of the drawings

1: heating furnace

1a: wall panel

10: radiant tube

11: combustion air supply

12: ignition means

20: fuel gas supply pipe

21: straight spout

22: radiation outlet

23: Inhibitor

24: protrusion

25: primary outlet

26: attachment member

30: combustion cylinder

Claims (9)

A fuel gas supply pipe 20 for supplying fuel gas is provided inside a radiant tube 10 for guiding combustion air, and a fuel gas is provided at a tip of the fuel gas supply pipe 20. In addition, a straight jet port 21 for ejecting in a straight direction is provided, and a combustion cylinder 30 for mixing and combusting the fuel gas ejected from the straight jet port 21 and combustion air on the front end side of the fuel gas supply pipe 20. In the radial tube burner provided with), a radial jet port 22 is provided at a tip end of the fuel gas supply pipe 20 behind the straight jet port 21 to radiate fuel gas in a radial direction. A disk-shaped interfering plate 23 which prevents the combustion air from being directly led to the radial jet port 22 on the outer circumference of the fuel gas supply pipe 20 in the vicinity of the rear side 22. On this attachment member 26 In addition, it is provided so as to hold the combustion cylinder 30, and a primary jet port 25 for ejecting fuel gas in a radial direction is provided in the fuel gas supply pipe 20 at a position rearward from the inhibition plate 23. Radiant tube burner characterized in that. According to claim 1, wherein the primary injection port 25 is formed to be inclined forward or rearward in the fuel gas supply pipe 20, the fuel gas ejected in the radial direction from the primary injection port 25 to the front or rear Radiant tube burner, characterized in that ejected obliquely. The method of claim 1 or claim 2, characterized in that the amount of fuel gas ejected from the primary ejection port 25 is in the range of 5 to 30 vol% of the total fuel gas supplied to the radiant tube 10. Radiant Tube Burners. The said fuel gas supply pipe 20 is provided with two or more radiation blower outlets 22 and the primary blower outlets 25, The circumferential position of the said spinneret outlet 22, The said 1 A radial tube burner, characterized in that the circumferential positions of the vehicle jet ports (25) are shifted from each other. The radiant tube burner according to claim 1 or 2, wherein the combustion cylinder (30) has a cylindrical shape having a constant diameter. 4. The fuel gas supply pipe (20) according to claim 3, wherein a plurality of radiation ejection openings (22) and primary ejection openings (25) are provided, respectively, and the circumferential position of the radiation ejection openings (22) and the primary ejection openings (25) are provided. Radial tube burner, characterized in that the position in the circumferential direction of the () is shifted from each other. The radiant tube burner according to claim 3, wherein the combustion cylinder (30) has a cylindrical shape having a constant diameter. The radiant tube burner according to claim 4, wherein the combustion cylinder (30) has a cylindrical shape having a constant diameter. The radiant tube burner according to claim 6, wherein the combustion cylinder (30) has a cylindrical shape having a constant diameter.

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