JP2001132912A - Premixing burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a premixing burner capable of preventing a back fire and a natural ignition without increasing a cost and using high temperature preheated air. SOLUTION: The premixing burner 10 for burning a premixed gas 38 obtained by premixing a fuel with air comprises a combustion nozzle 13 for burning the gas 38, and a narrow channel part 17 having a narrow channel 16 connected to the nozzle 13. Thus, the channel 16 accelerates the flowing velocity of the gas 38 to a burning speed or more. The channel 16 is perforated at a solid cylindrical metal to form the part 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a premix burner used in a heating zone such as a continuous annealing facility for steel sheets and a continuous galvanizing facility.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional premix burner 50 which mixes fuel and air in advance and supplies and burns. The premix burner 50 has a combustion cylinder 52 and a combustion nozzle 53 at the tip of a burner main body 51, and blows out a premixed gas 54 supplied into the burner main body 51 from the combustion nozzle 53 into the combustion cylinder 52, and the flame F Is formed. In FIG. 8, reference numeral 55 denotes an ignition plug tube having a tip passing through the axial portion of the burner main body 51 and a leading end positioned at a blowing portion of the combustion nozzle 53, reference numeral 56 denotes a perforated plate for assisting mixing of the premixed gas 54, and reference numeral 57 denotes a mounting plate. A flange, 60 is a furnace wall, 61 is a heat-resistant material of the furnace wall, and 62 is a material to be heated.

[0003]

When the premixed gas 54 is a mixed gas of propane gas and air, the premixed gas 5
The combustion speed S, which is the speed at which the flame propagates in 4, is as follows: premixed gas temperature combustion speed S 30 ° C. S = approximately 0.40 m / sec 250 ° C. S = approximately 0.94 m / sec. In the premix burner 50 described above, the combustion nozzle 53
The flow rate of the premixed gas 54 flowing out of the burner is set so as to be equal to or higher than the combustion speed S, thereby preventing the flame F from returning to the burner.

However, such a premix burner 50 has the following problems. (1) In order to adjust the combustion load (thermal calorie amount%) of the premix burner 50, the flow rate of the premix gas 54 is reduced so that the flow rate of the premix gas 54 at the combustion nozzle 53 becomes lower than the combustion speed S. In such a case, the flame F may flash back into the premix burner 50 and burn the burner body 51. Further, when the flashback reaches the pipe connected to the premix burner 50, there is a problem that the premix gas 54 explodes in the pipe.

(2) The above phenomenon is caused by the premix burner 50
Changes in the pressure inside the furnace to which the
4 is generated even by a slight pulsation, so when adjusting the combustion load (thermal calorie content%) of the premix burner 50,
The flow rate of the premixed gas 54 in the combustion nozzle 53 could not be reduced to less than three times the combustion speed S. here,
When the premix burner 50 is used for a propane-fired burner capable of burning at a minimum combustion load of 5%, the flow rate VBmi of the premix gas 54 in the combustion nozzle 53 at the time of the minimum combustion load of 5%.
n is the premixed gas temperature, the combustion nozzle flow rate VBmin 30 ° C. VBmin = 3 × S = 1.2 m / sec 250 ° C. VBmin = 3 × S = 2.82 m / sec The combustion nozzle flow rate VBmax at a load of 100% is as follows: Premixed gas temperature Combustion nozzle flow rate VBmax 30 ° C. VBmax = 3 × S × 100/5 = 24 m / sec 250 ° C. VBmax = 3 × S × 100/5 = 56.4 m / , The combustion nozzle flow rate VBmi at the time of the minimum combustion load of 5%
There is a problem that an excessively high flow velocity is required as compared with n, and the pressure loss when the premixed gas 54 passes through the combustion nozzle 53 increases. Further, in this case, the premix burner 50
The premixed gas 54 to be supplied to the fuel cell needs an excessive flow rate, so that the capacity of the blower for feeding the premixed gas 54 to the combustion nozzle 53 needs to be increased, and these costs are reduced. It was bulky.

(3) The heat in the furnace and the flame F is transmitted from the combustion nozzle 53 to the burner main body 51, so that the temperature of the burner main body 51 near the combustion nozzle 53 becomes high. The spontaneous ignition may cause the burner main body 51 to burn out. In addition, there is a possibility that the mixed gas explodes in the pipe, including when the flashback reaches the pipe connected to the premix burner 50.

(4) As the temperature of the supplied premixed gas 54 increases, the combustion speed S increases, and the burner main body 51 becomes hot and there is a risk of spontaneous ignition. It is difficult to use preheated air, and even when preheated air is used, about 250 ° C. has been regarded as the limit of preheating.

(5) For the reasons described above, the premix burner 5
In order to prevent explosion occurring in the piping due to flashback from zero, it is necessary to provide an expensive flame arrestor or rupture hole device in the piping, and there has been a problem that these costs are high.

The present invention has been made in view of the above circumstances, and has as its object to prevent flashback and spontaneous ignition without increasing the cost and to enable the use of high-temperature preheated air. Things.

[0010]

The present invention employs the following means in order to solve the above-mentioned problems. The premixed combustion burner according to claim 1 is a premixed burner that burns a premixed gas in which fuel and air are premixed, and is connected to a combustion nozzle that burns the premixed gas and the combustion nozzle. A narrow flow path portion formed by perforating a solid cylindrical metal with a narrow flow path for setting the flow rate of the premixed gas to a combustion speed or higher.

According to such a premixed combustion burner, since the narrow channel portion is formed in the solid cylindrical metal having excellent heat transfer characteristics, the area of the upstream end face and the cross-sectional area contributing to heat conduction increase. Convection cooling performance with preheated air is improved. For this reason, the temperature gradient from the combustion nozzle side where the temperature becomes high can be increased, so that the nozzle wall surface temperature at the premixed gas inlet portion (the temperature of the upstream end surface of the narrow flow passage portion) can be reduced.

According to a second aspect of the present invention, there is provided a premixed combustion burner for burning a premixed gas obtained by premixing fuel and air, wherein the combustion nozzle burns the premixed gas and the combustion nozzle. And a heat insulating layer formed between the combustion nozzle and the narrow flow passage portion, wherein the narrow flow passage portion is connected to the combustion nozzle and sets the flow rate of the premixed gas to a combustion speed or more. It is.

According to such a premixed combustion burner, since the upstream side of the combustion nozzle, which becomes high in temperature due to radiant heat, is insulated by the heat insulating layer, the amount of heat transmitted to the narrow flow path side is suppressed, and The temperature of itself can be lowered. Therefore, the nozzle wall temperature at the premixed gas inlet can also be reduced.

According to a third aspect of the present invention, there is provided a premixed combustion burner for burning a premixed gas in which fuel and air are premixed, wherein the combustion nozzle is made of ceramics for burning the premixed gas. A narrow flow path portion connected to the combustion nozzle for setting the flow rate of the premixed gas to a combustion speed or higher, and the ceramic combustion nozzle is elastically supported in the axial direction. . In this case, it is preferable that the ceramic combustion nozzle be divided into a central portion and an outer peripheral portion.

According to such a premixed combustion burner, the use of a combustion nozzle made of ceramics improves heat resistance and makes it possible to increase the furnace temperature and the premixed gas temperature. Further, since the stress can be absorbed by being elastically supported in the axial direction, the relatively fragile ceramic combustion nozzle is less likely to crack. Furthermore, if the ceramic combustion nozzle is divided into a central part and an outer peripheral part,
Stress cracking due to a temperature difference between inside and outside can also be prevented.

In the above-mentioned premixed combustion burner, it is preferable that the inside of the nozzle flow passage leading from the narrow flow passage portion to the combustion nozzle has a recess structure.
The propagation of the flame to the upstream side can be suppressed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a premix burner according to the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view showing an embodiment of a premixing burner according to the present invention, FIG. 2 is an exploded view of a main part of FIG. 1, FIG. 3 is an enlarged view of the vicinity of a combustion nozzle of FIG. 1, and FIG. 3 is a sectional view taken along line AA of FIG. 3, showing the shape of the combustion nozzle, FIG. 6 is a sectional view of a principal part showing an elastic support structure of the combustion nozzle, and FIG. 7 is a sectional view of a principal part showing a recess structure. It is.

In FIG. 1, a premix burner 10 has a burner main body 11, a ceramic combustion cylinder 12 provided at the end of the burner main body 11, and a combustion nozzle 13 housed in the combustion cylinder 12. Here, reference numeral 14 denotes a plurality of combustion nozzle holes provided in the combustion nozzle 13, and reference numeral F denotes a flame ejected from the premixing nozzle 10,
61 is a refractory material of the furnace wall 60 to which the premix burner 10 is attached, and 62 is a material to be heated which is heated by the flame F.

The burner main body 11 has a plurality of ignition plug pipes 15 arranged at the axial center and reaching the combustion nozzle 13, and a plurality of burner main bodies 11 arranged around the ignition plug pipe 15 and communicating with the combustion nozzle holes 14 of the combustion nozzle 13. And a narrow channel 16. The narrow channel 16 is made of a solid cylindrical metal such as SUS310, and is formed in the axial direction by machining using a drill or the like. Has a function of accelerating the combustion speed to be higher than the combustion speed. Hereinafter, the solid cylindrical metal part in which such a narrow channel 16 is formed is referred to as a narrow channel section 17. Further, the narrow flow path portion 17 has a length of 1/5 or more of the thickness of the refractory material 61 of the furnace wall 60, in order to suppress the heat in the furnace and the flame F from being transmitted to the burner main body 11 side. Preferably, the length is set to 1/3 or more.

As shown in FIG.
It is a porous cylindrical metal in which a plug tube hole 18 for passing the ignition plug tube 15 is formed in the center of the cross section, and a large number of narrow channels 16 are formed in the outer periphery thereof at equal pitches. In the illustrated example, a total of 12
Although the narrow channels 16 are arranged at a pitch of 30 degrees, it goes without saying that the design can be changed as appropriate. In addition, as shown in FIG.
6 is preferably wound and covered with a stainless steel wire. The combustion nozzle 13 is disposed downstream of the narrow flow path portion 17 via a heat insulating layer 19. As the heat insulating layer 19, an irregular refractory material such as a ceramic fiber filler is used. The narrow channel 16 in the heat insulating layer 19
Sleeves 20 and 21 made of alumina, mullite, or the like are used as a heat insulating material support ring at a connection portion with the plug tube hole 18 so that a hole or a passage in the heat insulating layer 19 can be reliably secured. I have.

The combustion nozzle 13 is preferably made of ceramics having excellent heat resistance. As specific heat-resistant ceramics, silicon carbide and silicon nitride are suitable. The combustion nozzle 13 is a substantially disk-shaped member having an appropriate thickness.
As shown in the figure, a structure in which a central part 13a and an outer peripheral part 13b are divided into two parts is adopted. One central portion 13a is shown in FIG.
As shown in (a), the whole is a member having a substantially convex cross section, and a plug hole 22 for an ignition plug is provided through the center. The other outer peripheral portion 13b is shown in FIG.
As shown in (b), the central portion 13 a is a donut-shaped member fitted to the central portion, and a large number of nozzle holes 14 are formed in a narrow channel so as to be located on the outer periphery of the plug hole 22. The same number as 16 (12 in the illustrated example) penetrates and is provided. As shown in FIG. 5 (c), each of the nozzle holes 14 penetrates in a state where the inlet 14a and the outlet 14b are eccentric and inclined in the circumferential direction, so that the premixed gas is swirled and discharged. It has become.

The central plug hole 22 communicates with the plug tube hole 18 of the narrow flow passage 17 through the sleeve 21 in the assembled state. Each nozzle hole 14 communicates with the narrow flow path 16 of the narrow flow path portion 17 via the sleeve 20, and forms a nozzle flow path of the premixed gas supplied to the burner main body 11. . This nozzle flow passage has a recessed structure at a portion connecting the narrow flow passage portion 17 to the combustion nozzle 13, specifically, a connection portion between the sleeve 20 having the same diameter as the narrow flow passage 16 and the nozzle hole. That is, the sleeve 2
0 and the inner diameter D2 of the narrow channel 16
The step 23 is provided with a smaller diameter, and a vortex is generated in the premixed gas flowing in the nozzle flow path at the step 23.

The above-described combustion nozzle 13 is housed in the combustion cylinder 12 and is elastically supported in the axial direction. Explaining this elastic support structure, the combustion nozzle 13 is connected to the burner main body 1.
1 is sandwiched, via a heat insulating layer 19, between the distal end surface of the narrow flow path portion 17 fixed to 1 and the combustion cylinder 12 whose distal end portion is tapered. On the inner surface of the combustion cylinder 12, a step surface 24 (see FIG. 3) is provided on the upstream side near the taper start portion.
The stepped surface 24 is configured to press the outer peripheral portion of the downstream end surface of the combustion nozzle 13 toward the burner main body 11.

At the rear end side of the combustion cylinder 12, a flange 12a projecting in the outer peripheral direction is provided, and the flange 12a is engaged with a fixing ring 27 of a clamp 26 via a ceramic wool blade 25. . The clamp 26 is formed by fixing three rods 28 extending in the axial direction in an assembled state to a fixing ring 27, and a thread 28 a is formed at an end of each rod 28. On the other hand, the flange portion 29 on the burner main body 11 side is provided with a boss hole 30 in which an internal thread is cut at a position corresponding to the screw portion 28 a of the clamp 26. A boss 31 having a through hole 31 a having a diameter larger than that of the rod 28 is screwed and fixed to the boss hole 30. A rod 28 is inserted into the boss 31, and a nut 34 is screwed into a tip thread portion 28 a of the rod 28 that passes through a spring 32 and a washer 33 provided inside the boss 31, and tightened.
As a result, the spring 32 is compressed by the boss 31, and one of the springs 32 is restricted from moving by the boss 31, so that the rod 28 is connected to the flange 2 via the washer 33 and the nut 34.
9 is urged in a direction away from 9. It should be noted that reference numeral 35 in FIG.
Is a plug that is screwed with the boss 31 to close the inside of the boss.

The above-described urging force acts as a force in a direction in which the clamp 26 pulls the combustion cylinder 12 toward the burner main body 11, and the combustion cylinder 12 receiving this force moves the combustion nozzle 13 in the axial direction by the elasticity of the spring 32. It is pressed and supported. In other words, the combustion nozzle 13 due to thermal deformation or the like.
The force acting in the axial direction with respect to the spring 32 can be absorbed by the elasticity of the spring 32.

Now, the burner main body 11 is connected through a conduit (not shown).
The premixed gas 38 supplied to the gas flow chamber 37 in the inside is dispersed in each narrow channel 16 in the narrow channel section 17. The premixed gas 38 is a mixture of fuel and air in advance, and the fuel used here is propane, LNG, COG (Coke (Coke)).
Over Gas) and LPG. Since the total cross-sectional area of the cross-sectional areas of the narrow channels 16 is set to be smaller than the cross-sectional area of the gas flow chamber 37, the flow rate of the premixed gas 38 is accelerated when passing through the narrow channels 16. . In this case, when the premix burner 10 is burned with the minimum combustion load, the narrow flow path 16
The gas flow velocity Vc of the premixed gas 38 is set to be higher than the combustion speed S of the premixed gas 38.

In such a premix burner 10,
Since the premixed gas 38 is jetted from the common flow chamber 37 of the burner main body 11 through each narrow flow path 16 into the combustion cylinder 12 from the combustion nozzle hole 14 of the combustion nozzle 13, the ignition plug tube 1
5, the premixed gas 38 is ignited to form a flame F, and the flame F directly heats the material to be heated 62 in front of the combustion tube 12. At this time, the gas flow velocity Vc is
Is maintained to be greater than the combustion speed S of
There is no flashback.

When the combustion of the premixed gas 38 and the direct heating are continued in this manner, the tip of the combustion nozzle 13 rises in temperature by receiving radiant heat from the furnace and from the flame F. Therefore,
The combustion nozzle 13 itself is made of ceramics that can withstand high temperatures. For this reason, it is possible to set a high furnace temperature or a high premixed gas temperature by using high-temperature preheated air. Setting the temperature inside the furnace or the temperature of the premixed gas high is effective for improving the furnace efficiency. Further, since the temperature of the combustion nozzle 13 can be increased, the flame holding property of the flame F can be improved.

Further, the combustion nozzle 13 which is heated to a high temperature has a combustion nozzle hole 14 provided on the outer peripheral side and a plug tube hole 18.
Is provided, there is a possibility that a large temperature difference occurs between the inside and the outside, and cracks may occur due to thermal stress. In particular, since ceramics are more brittle than metals, they tend to crack. In view of this, the combustion nozzle 13 made of ceramics has a structure in which the central portion 13a having a relatively low temperature is separated from the peripheral portion 13b having a high temperature, and the central portion 13a and the peripheral portion 13b are divided into two. For this reason, thermal stress generated between the central portion 13a and the outer peripheral portion 13b can be absorbed, and thermal stress cracking of the combustion nozzle 13 can be prevented. In this case, it is particularly effective for absorbing thermal stress in the radial direction, but it is also possible to absorb thermal stress in the axial direction due to the presence of the stepped surface.

Further, a combustion nozzle 13 made of ceramics
Is elastically supported in the axial direction, so that it has a support structure that does not easily cause stress cracking. The premix burner 10
When each member is thermally deformed due to a rise in temperature, the combustion nozzle 1
The force acting in the axial direction of No. 3 also changes. However, since the above-described elastic support structure using the spring 32 is employed, a change in stress acting in the axial direction can be absorbed by the elasticity of the spring 32 to prevent stress cracking. As described above, since measures have been taken against thermal stress and stress changes caused by thermal deformation of peripheral members, even if the ceramic combustion nozzle 13 having the characteristic of being able to withstand high temperatures as compared with metal, but having the characteristic of being brittle, is used. , High durability and reliability can be obtained. In addition, due to measures taken against thermal stress,
The combustion nozzle 13 made of ceramics can be used at a higher temperature.

The combustion nozzle 1 thus heated to a high temperature
3 increases the temperature of the inner wall surface of the burner body 11 by heat conduction. However, since the heat insulating layer 19 is provided between the combustion nozzle 13 and the narrow flow passage 17, heat conduction between the combustion nozzle 13 and the narrow flow passage 17 is suppressed, and a large temperature difference is provided. be able to. In addition, the narrow channel portion 1
7 is made of a solid cylindrical metal, the contact area with the premixed gas 38 on the upstream end face and the cross-sectional area contributing to heat transfer are increased, and the heat transfer property is excellent. Convection cooling is efficiently performed by the supplied premixed gas 38. Thus, a large temperature gradient can be applied to the narrow flow path portion 17 from the combustion nozzle 13 to the gas flow chamber 37, and as a result, the upstream side (the gas flow chamber 3
The temperature on the side 7) can be set considerably lower than that of the high-temperature combustion nozzle 13. Since this temperature varies depending on the length of the narrow flow passage portion 17, the air preheating temperature, and the like, it may be appropriately adjusted to be equal to or lower than the ignition temperature of the premixed gas 38 which differs depending on the fuel. Can be prevented from spontaneously ignited in the burner main body 11.

By the way, the combustion nozzle 1 made of ceramics
In the case of No. 3, since the upstream side is insulated by the heat insulating layer 19, the temperature rises, and even in the case of room temperature air, it is considered that self-ignition occurs in this portion. However, if the self-ignition point does not move to the upstream side and the temperature does not rise in the narrow metal channel section 17, there is no problem in heat resistance of the burner. In order to prevent the flame F from propagating from the ceramic combustion nozzle 13 to the upstream side, a recess structure shown in FIG. 7 is employed in the nozzle flow path.

Here, a preferred inner diameter D1 of the combustion nozzle hole 14 and an inner diameter D2 of the upstream sleeve 20 and the narrow passage 16 which differ depending on the fuel are shown. For example, if the burner capacity is 1
When the premixed gas temperature is set to 350 ° C. at 40 Kw, the result is as follows. When propane is used as fuel, D1 is set to 8.1 to 12.3 mm, and D2 is set to 6.5 to 9.8.
mm, and it is particularly preferable that D1 = 10 mm and D2 = 8 mm. When COG, which is a by-product gas of an ironworks, is used as a fuel, D1 may be set to 8.6 to 12.9 mm and D2 may be set to 6.9 to 10.3 mm.
It is preferable that 1 = 10.5 mm and D2 = 8.4 mm.
When LNG and LPG are used as fuel, it is preferable that the diameter is approximately equal to that of propane.

As described above, in the premix burner 10, even when the combustion load is adjusted, the mixed gas flow velocity Vc in the narrow passage 16 is set to the combustion speed unless the combustion load becomes equal to or less than the set minimum combustion load. Since it is held at S or more, the flame F does not flash back into the premix burner 10. For this reason, the danger of burning of the burner main body 11 and explosion of the mixed gas 38 in the piping can be eliminated.

Further, due to the pressure loss generated in the narrow flow path 16, the inside of a pipe (not shown) for supplying the premixed gas 38 to the burner main body 11 increases the static pressure. Therefore, even under a slight fluctuation of the furnace pressure or a slight pulsation of the premixed gas 38,
A predetermined flow velocity can be maintained in the narrow channel 16. Therefore, the flame F does not flash back into the premix burner 10. Further, the length of the narrow channel 16 is set to, for example, 1/5 or more of the thickness of the refractory material 61 of the furnace wall 60,
If the portion where the premixed gas 38 flows at the flow velocity Vc is extended,
The convective cooling performance in the narrow flow path 16 is improved, and the effect of preventing the flame F from flashing back can be dramatically improved.
Therefore, the flammable range of the combustion load of the premix burner 10 can be expanded. As a result, the combustion load of the premix burner 10 can be reduced to a maximum of 1/20.

By maintaining the premixed gas flow velocity Vc in the narrow flow passage section 16 at the combustion speed S or more, even if the inner wall temperature of the narrow flow passage 16 reaches the spontaneous ignition temperature of the premixed gas 38, the narrow flow passage No flame is formed in the inside 16, and it is possible to prevent the occurrence of flashback in the narrow channel 16. Therefore, it becomes possible to arrange the combustion nozzle 13 close to the high-temperature furnace. Further, since the common flow chamber 37 of the burner 11 main body can be arranged behind the refractory material 61 of the furnace wall 60 by the narrow flow path 16, the flow chamber 37 becomes high temperature and spontaneously ignites the mixed gas. Danger can be avoided.

As a result, flashback from the premix burner 10
In addition, the necessity of providing an expensive flame arrester and a rupture hole device in the piping to prevent explosion in the piping has been eliminated.

By improving the effect of preventing backfire as described above, it becomes possible to raise the temperature of the premixed gas 38 to near the spontaneous ignition temperature by preheating. For example, even when the premix burner 10 using propane gas is used at a high furnace temperature of 1400 ° C. or more, the preheating temperature of the combustion air is set to about 47 ° C. for the ignition temperature of propane gas of 520 ° C.
It is possible to increase the temperature to about 0 to 500 ° C.

Further, since the high-temperature premixed gas 38 can be used, the premixed gas 38 can be preheated by using the exhaust gas to improve the heat recovery rate, and the operating cost can be reduced. Further, since a high-temperature premixed gas 38 can be used, a flame having a combustion temperature of 2200 ° C. or more can be obtained by premixed combustion. As a result, the ability to rapidly raise the temperature of the material to be heated 62 can be dramatically improved. like this,
The molecules of the combustion gas are ionized by the premixed high-temperature flame,
An air ratio of 0.
Reduction heating of the material to be heated 62 can be performed in a wide range of 9 or less.

[0040]

According to the premix burner of the present invention, the following effects can be obtained. (1) Since a narrow channel portion formed by machining a solid metal to form a narrow channel is employed, convection cooling performance by preheated air can be increased. For this reason, even if the furnace temperature is set to a high temperature, the temperature at the inlet of the premixed gas can be reduced to a value equal to or lower than the spontaneous ignition temperature by taking a large thermal gradient,
Flashback due to spontaneous ignition of the premixed gas can be prevented. (2) Since the heat insulating layer is provided between the combustion nozzle and the narrow flow passage portion, heat conduction from the combustion nozzle, which becomes hot, to the narrow flow passage portion is suppressed, and a large temperature difference can be provided. Therefore, it is possible to prevent the metal narrow channel portion from being burned,
The flame ignited in the combustion nozzle can be prevented from moving upstream. (3) Since the combustion nozzle is made of ceramics, it can withstand high temperatures, and the furnace temperature and the premixed gas temperature can be set higher than before, which has a great effect on improving furnace efficiency. Further, since the combustion nozzle can withstand high temperatures, the flame holding property of the flame can be improved. (4) Since the combustion nozzle made of ceramics, which is resistant to high temperatures as compared with metals, has a two-part structure, and has a support structure elastically supported in the axial direction, cracks due to thermal stress and support stress can be prevented. . Accordingly, it is possible to use the ceramic combustion nozzle at a higher temperature, and it is possible to improve durability and reliability. (5) By employing the recess structure, it is possible to suppress the flame from propagating from the combustion nozzle to the upstream side, so that burning of the narrow metal channel can be prevented. Therefore, metal can be used without water cooling, which is advantageous in cost.

As described above, the flow rate of the premixed gas in the narrow flow path is maintained at the combustion speed or higher, and the temperature of the premixed gas inlet can be set at the spontaneous ignition temperature or lower. Therefore, the risk of burnout of the burner body and explosion of the mixed gas in the piping can be eliminated. Therefore, it is not necessary to provide an expensive flame arrestor and a rupture hole device in the piping, and it is not necessary to increase the capacity of the blower for feeding the premixed gas to the combustion nozzle. This can be achieved without increasing operating costs.

Since a large temperature gradient can be obtained from the combustion nozzle to the upstream side, even if a ceramic nozzle is used and the furnace temperature is set high, the preheating of the premixed gas can be increased to near the spontaneous ignition temperature. By improving the furnace efficiency, there is a great effect on energy saving and reduction of carbon dioxide emission. If the fuel is propane, the conventional 250
The temperature can be raised from about 0 ° C to at least about 470 ° C, which is at least about 50 ° C lower than the auto-ignition temperature (about 520 ° C).

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a premix burner of the present invention.

FIG. 2 is an exploded view of a main part of FIG.

FIG. 3 is an enlarged view showing a periphery of a combustion nozzle of FIG. 1;

FIG. 4 is a sectional view taken along the line AA of FIG. 3, showing a sectional shape of the narrow flow passage portion.

5A and 5B are diagrams showing an example of the shape of a combustion nozzle divided into two parts, in which FIG. 5A is a longitudinal sectional view of a central part, FIG. 5B is a longitudinal sectional view of an outer peripheral part, and FIG. FIG.

FIG. 6 is a sectional view of a main part showing an elastic support structure of the combustion nozzle.

FIG. 7 is a sectional view of a main part showing a recess structure of a nozzle flow path.

FIG. 8 is a sectional view showing a conventional premix burner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Premix burner 11 Burner main body 12 Combustion cylinder 13 Combustion nozzle 13a Central part 13b Outer peripheral part 14 Combustion nozzle hole 14a Inlet 14b Exit 15 Ignition plug tube 16 Narrow channel 17 Narrow channel 18 Plug tube hole 19 Insulating layer 20, 21 Sleeve 22 Plug hole 23 Step portion 24 Step surface 25 Ceramic wool blade 26 Clamp 27 Fixing ring 28 Rod 28a Thread portion 29 Flange portion 30 Boss hole 31 Boss 31a Through hole 32 Spring 33 Washer 34 Nut 35 Plug 36 Ceramic paper 37 Gas flow chamber 38 Premixed gas 60 Furnace wall 61 Refractory material 62 Heated material F Flame

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Shinya 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Shigeru Horie Kannon-Shimmachi 4 in Nishi-ku, Hiroshima-shi, Hiroshima No. 6-22, F-term in Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (Reference) 3K017 AA01 AA05 AB07 AB09 AC01 AD01 AD11 AE01 AE02 AF03 AG05 CA03 CA05 CB02 CB04 CB11 CD02 CD05 CF01 CF02 CG03 CH04

Claims (5)

[Claims] 1. A premix burner for burning a premix gas obtained by premixing fuel and air, comprising: a combustion nozzle for burning the premix gas; and a flow rate of the premix gas connected to the combustion nozzle. And a narrow flow passage portion formed by perforating a solid cylindrical metal with a narrow flow passage for setting the combustion speed to a combustion speed or more. 2. A premix burner for burning a premix gas in which fuel and air are premixed, a combustion nozzle for burning the premix gas, and a flow rate of the premix gas connected to the combustion nozzle. A premixing burner comprising: a narrow passage portion that sets the combustion speed to be equal to or higher than a combustion speed; and a heat insulating layer formed between the combustion nozzle and the narrow passage portion. 3. A premix burner for burning a premix gas obtained by premixing fuel and air, comprising: a combustion nozzle made of ceramics for burning the premix gas; A premixing burner comprising: a narrow flow path portion for setting a gas flow rate to a combustion speed or more; and a ceramic combustion nozzle elastically supported in an axial direction. 4. The premix burner according to claim 3, wherein said combustion nozzle is divided into a central portion and an outer peripheral portion. 5. The premix burner according to claim 1, wherein an inside of a nozzle passage connected to the combustion nozzle from the narrow passage portion has a recess structure.