JPH09250714A - Gas combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform further stable low NOX combustion, in a gas combustion device to perform low NOX combustion by feeding in three stages premixture gas. SOLUTION: A gas combustion device is constituted such that an injection nozzle 2 for premixture gas for primary combustion wherein a mixture ratio between air and fuel gas is constant or varied according to necessity is arranged on one end side of a combustion chamber 20a and an injection nozzle 3 for premixture gas for secondary combustion wherein a mixture ratio between air and fuel gas is varied by varying a fuel gas amount is arranged at the periphery of the injection nozzle 2, and an injection nozzle 5a for premixture gas for secondary combustion is arranged at a combustion cylinder 20. In this case, a pilot gas nozzle 50 comprising a pilot gas flow passage 51 to always feed a specified amount of fuel gas and an air flow passage 52 at the periphery of the pilot gas flow passage is arranged at the central part of the one end side of the combustion chamber 20a. Low NOX combustion of premixture gas for primary combustion is practicable and as a result, low NOX combustion is achieved regardless of a load range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas combustion device in which the nitrogen oxide (NO _x ) concentration in exhaust gas is reduced,
The present invention relates to a low NO _x gas combustion device effective as a combustor for a gas turbine.

[0002]

2. Description of the Related Art Air pollution due to NO _x has become a social problem, and reduction of NO _x discharged from a gas combustion device has also become a problem. Considering a combustor for a gas turbine as an example of a gas combustion apparatus, when diffusion combustion that can obtain stable combustion is used, combustion of fuel and air locally generates a flame temperature of around 2000 ° C., The combustion gas is mixed with air in order to lower the temperature of the combustion gas below the upper temperature limit of the metal turbine blade installed downstream of the combustor. However, due to the high temperature of the surface of the diffusion flame, the generation of so-called thermal NO _x , which is generated by the reaction between nitrogen and oxygen in the combustion air, cannot be avoided. As an effective combustion method for lowering the temperature of the flame to reduce the production of NO _x , there is a premixed combustion method in which fuel and excess combustion air for the fuel are mixed before combustion and burned as a lean premixed gas. Has been done.

As an improved gas combustor using the premixed combustion method, the applicant has provided a fuel gas ejection hole for ignition at the center of the nozzle portion and a constant mixture ratio of air and fuel gas around the hole. The premixed pre-mixed gas jet for primary combustion and the pre-mixed pre-mixed gas jet for secondary combustion in which the mixing ratio of air and fuel gas is variable are concentrically provided on the outer circumference of the pre-mixed gas jet for primary combustion. In addition, a so-called double swirler type gas combustion device has been proposed (see Japanese Patent Laid-Open No. 5-296412). Then, as a further improved version of the double swirler type gas combustion apparatus, a premixed gas combustion apparatus (double swirler multi-stage gas combustion apparatus) as shown in FIG. 340508).

In this premixed gas combustion apparatus, a combustion gas injection block 10 is supported on the upstream side (the left side in the figure) from the axial center inside the flanged cylinder 100, and is connected to the combustion gas injection block 10. A combustion cylinder 20 having a substantially constant cross-sectional area is arranged, and a combustion chamber 20a is formed inside the combustion cylinder 20. The combustion gas ejection block 10
Has an ignition fuel gas ejection hole 1 at the center thereof, and a primary combustion premixed gas ejection port having a constant mixing ratio of air and fuel gas around the ignition fuel gas ejection hole 1. 2 are formed, and around the injection port 2 of the premixed gas for primary combustion,
Premixed gas injection port for secondary combustion 3 in which the mixing ratio of air and fuel gas is made variable by making the amount of fuel gas variable
Is formed. Further, in the portion of the combustion cylinder 20, similarly, by changing the amount of fuel gas, the injection ratio 5 of the premixed gas for tertiary combustion in which the mixing ratio of air and fuel gas can be changed.
A tertiary premixing tube 5 having a is provided.

The ignition fuel gas injection hole 1 is supplied with the ignition fuel gas G via a conduit 11, and the primary combustion premixed gas injection port 2 is supplied with the primary fuel gas G ₁ via a conduit 12. The secondary fuel gas G ₂ is supplied from the conduit 13 to the secondary combustion premixed gas ejection port 3 and ejected from the gas nozzles 12a and 13a, respectively. Further, a conduit 16 penetrates through the tertiary premixing tube 5, and this conduit 16
Is tertiary fuel gas G ₃ is supplied from.

An air inlet 100a is formed on the downstream side (right side in the figure) of the cylindrical body 100, and combustion air A is supplied from this. The combustion air A is supplied from the gas nozzles 12a and 13a through swirlers 14 and 15 disposed at the ends of the primary and secondary combustion premixed gas injection ports 2 and 3 opposite to the ejection ends. The primary and secondary fuel gases G ₁ and G ₂ are mixed with each other to form a premixed gas, and the primary and secondary combustion premixed gas injection ports 2 and 3 are used to form a combustion chamber 20a.
Spouts in. Further, a part of the combustion air A is supplied to the tertiary premix pipe 5 from the conduit 16 through the tertiary fuel gas G _3.
And is injected into the combustion chamber 20a from the tertiary combustion premixed gas injection port 5a. Reference numeral 6 denotes an air hole for blowing cooling air for diluting the combustion exhaust gas and lowering the temperature to a temperature suitable for a turbine (not shown) connected to the next stage.

In the premixed gas combustion apparatus according to the above-mentioned proposal, the ignition fuel gas G is ejected from the ignition fuel gas ejection port 1 at the time of start-up to cause diffusion combustion, and at the same time, the air is ejected from the primary combustion premixed gas ejection port 2. And the primary fuel gas G ₁ have a constant mixing ratio and are pre-mixed gas to be jetted and burned. After starting, the primary pre-mixed gas G ₁ is jetted to narrow down the ignition fuel gas G and to carry out the secondary combustion. A premixed gas of air and a secondary fuel gas G ₂ having a mixing ratio corresponding to the load is jetted from the premixed gas jet port 3 for combustion and burned, and the supply amount of the secondary fuel gas G ₂ is increased as the load increases. , From the load expected to begin a significant increase in NO _x emissions,
The fuel gas G corresponding to the air and the load is supplied from the mixed gas jet port 5a for tertiary combustion with the supply amount of the secondary fuel gas G ₂ being constant.
The mixed gas with ₃ is ejected to continue combustion.

FIG. 8 shows an example of a fuel supply schedule in the above gas combustion apparatus. The primary fuel gas G ₁ is supplied in a substantially constant amount, and the load of the secondary fuel gas G ₂ and the tertiary fuel gas G ₃ is changed. Is taking the combustion method against. According to this combustion device, even if the supply amount of the primary fuel gas G _{1 that} is supplied in a fixed amount is smaller than that in the case of the conventional double swirler gas combustion device, it is possible to operate at a low load, whereby the exhaust gas Diffusion combustion with a large amount of NO _x components is only at the time of startup, and after that, it is possible to suppress the emission of NO _x while keeping the emission of unburned components low at a wide air ratio. Also in the combustion range NO _x emissions with an increase of the secondary fuel gas G ₂ was increased significantly in the secondary combustion premixed gas, can be kept significantly lower emissions NO _x,
Can NO _x emissions and unburned components in comparison with the conventional premixed combustion gas apparatus extending the combustion range shown together low.

Further, the combustion air A regardless of load fluctuations
Since the supply amount of is kept unchanged, there is an advantage that a variable mechanism for controlling the flow rate of the combustion air is unnecessary, the structure of the combustor is simplified, and the size can be reduced.

[0010]

THE INVENTION to be solved Disclosed have in the process of continued combustion experiment on the above premixed gas combustion apparatus, although NO _x discharged from the combustion device to some extent reduced the primary combustion premixed gas We found that the NO _x produced by the combustion of NOx is still present and that it is the main source of NO _x . this is,
When comparing the premixed gas for primary combustion, the premixed gas for secondary combustion, and the premixed gas for tertiary combustion, the fuel concentration of the premixed gas for primary combustion is the highest, and therefore the combustion of the premixed gas for primary combustion It is believed to be due to the generation of thermal NO _x due to the highest flame temperature. In order to reduce the NO _x , it is necessary to lower the concentration of the primary combustion premixed gas in order to lower the temperature of the primary combustion premixed gas.

However, in this type of combustion apparatus, the premixed gas for secondary combustion and the premixed gas for tertiary combustion are burned (oxidized) by stable combustion of the premixed gas for primary combustion. If the fuel concentration of the premixed gas for combustion is further diluted, the primary combustion flame will be misfired and the combustion device will be misfired.Therefore, there is a limit to the leanness of the fuel concentration of the premixed gas for primary combustion. However, it has been impossible to reduce NO _x beyond a certain level.

Further, in order to stably burn the premixed gas for primary combustion, the fuel gas G is discharged from the fuel gas injection hole 1 for ignition.
Was constantly supplied, and an attempt was made to dilute the pre-mixed gas for primary combustion by the stabilized amount.
The fuel gas G supplied from is diffuse-combusted with the relatively large amount of combustion air supplied to the primary premixed gas ejection port 2, and therefore is supplied to the primary premixed gas ejection port 2 in order to continue the ignition state. that relatively large amount of gas amount commensurate with the combustion air amount is required, it must be supplied to the ignition fuel gas injection holes more fuel gas to that end, as a result, the conventional above NO _x It resulted in discharge.

An object of the present invention is to eliminate the above-mentioned inconvenience of the premixed gas combustion apparatus of the type shown in FIG. 7 which the present applicant has already proposed, and more specifically, it has a low N ratio.
It is an object of the present invention to provide a gas combustion device that can achieve a combustion range of O _{x in} a wide load range.

[0014]

A gas combustion apparatus according to the present invention for solving the above problems and achieving the object is basically a pilot gas flow passage in a central portion, which is located at one end side of a combustion chamber. And a pilot gas nozzle composed of an air flow path around the pilot gas nozzle, and a jet port for the premixed gas for primary combustion, which is arranged around the pilot gas nozzle and in which the mixing ratio of air and fuel gas is constant or variable as necessary. And an injection port for the secondary combustion premixed gas, which is arranged around the primary combustion premixed gas injection port and in which the mixing ratio of air and fuel gas is made variable by making the fuel gas amount variable. A mixing ratio of the air and the fuel gas is made variable by arranging a fuel gas amount which is arranged at a position on the side wall of the combustion chamber at a predetermined distance from the injection port of the premixed gas for secondary combustion. Injection of premixed gas for tertiary combustion It is configured to have a mouth.

In a preferred aspect of the gas combustion apparatus of the present invention, a swirler is arranged in the air passage around the pilot gas passage. The swirling direction of the swirler is the same as the swirling direction of the swirler when the swirler is also provided in the primary combustion premixed gas passage and the secondary combustion premixed gas passage. In another preferred embodiment,
A plurality of gas ejection ports of the pilot gas flow passage are arranged in different positions in the radial direction in the surrounding air flow passage and downstream of the swirler.

Further, the gas ejection port of the pilot gas passage may be located at the same axial position as the axial position of the ejection port of the primary combustion premixed gas, and the axis of the ejection port of the primary combustion premixed gas may be set. The position may be offset to the upstream side in the direction. Further, in a preferred aspect of the gas combustion apparatus of the present invention, the cross-sectional area of the combustion chamber on the upstream side of the vicinity of the mounting position of the injection port of the premixed gas for tertiary combustion is smaller than the cross-sectional area on the downstream side thereof. It

In the gas combustion apparatus according to the present invention having the above-described structure, the pilot fuel gas is always supplied from the pilot gas passage, and at the same time, the combustion air is supplied from the air passage located around the pilot fuel gas. . That is, in the previously proposed combustion device, the ignition fuel gas ejected from the ignition fuel gas ejection hole is the air in the primary combustion premixed gas ejected from the surrounding primary combustion premixed gas ejection port. However, in the combustion apparatus according to the present invention, the pilot fuel gas mainly mixes with the air supplied from the air passage and burns. Further, since the combustion form is an intermediate form between the premixed combustion and the diffusion combustion, stable combustion can be obtained in a wider mixing range than the combustion of the premixed gas for primary combustion which is the premixed combustion. As a result, the combustion of the pilot fuel gas becomes stable, and it becomes possible to perform stable combustion up to a low fuel ratio without misfiring.

By burning the pilot fuel gas, the stable combustion state of the primary combustion premixed gas can be continued, and stable combustion can be obtained even if the primary combustion premixed gas is diluted more than ever. it can. As a result, although a certain amount of the NO _x is generated by the combustion of the pilot fuel gas, reduces the generation of the NO _x by the combustion of the primary combustion premixed gas, the total amount of the NO _x discharged from the combustion device is reduced .

The combustion of the pilot fuel gas and the premixed gas for primary combustion does not adversely affect the combustion of the premixed gas for secondary combustion and the premixed gas for tertiary combustion. Therefore, the double swirler multistage is used. The advantages of type gas combustion equipment are maintained.

In the gas combustion apparatus of the present invention, for example, as in the fuel supply schedule shown in FIG. 5, the pilot fuel gas and the primary fuel gas are supplied in a substantially constant amount in the entire load range up to the rated load, and the load fluctuation Is
Change the amount of secondary fuel gas and tertiary fuel gas to deal with it.
At that time, according to the experiments by the present inventors, the concentration of the mixed gas ejected from the pilot gas nozzle (hereinafter referred to as the pilot mixed gas) is equal to the concentration of the primary combustion premixed gas at a high load or the primary combustion premixed gas By making the gas concentration somewhat leaner than the mixed gas concentration, it was possible to achieve almost the same combustion efficiency as that of the conventional device and a lower NO _x production amount at the same time.

When a swirler is provided in the air flow passage around the pilot gas flow passage, a swirl can be generated in the pilot fuel gas air flow or the pilot mixed gas, thereby stabilizing the pilot mixed gas flame. Is further improved. Further, it has been experimentally found that more stable combustion can be obtained by making the swirling direction of the swirler the same as the swirling direction of the swirler provided in the primary combustion premixed gas passage and the secondary combustion premixed gas passage. Confirmed.

The position of the gas ejection port of the pilot gas flow passage is arranged at the same position as the axial position of the ejection port of the premixed gas for primary combustion or at a position displaced axially upstream thereof. If the gas outlet is arranged axially upstream of the primary combustion premixed gas outlet, the effect of the primary combustion premixed gas on the pilot fuel gas can be reduced, and less gas is used. Stable combustion is obtained with a certain amount, and the load range of the combustor is further expanded.

In the combustion apparatus of the present invention, when the gas flow outlet of the pilot gas flow passage is located at the central position and the air flow passage is arranged around it, the mixing of the pilot fuel gas and air is not actively promoted. In this state, since the pilot mixed gas is supplied to the combustion field on the downstream side, diffusion combustion is the main combustion, and stable combustion can be promoted. However, in this case, some increase in NO _x cannot be avoided. When it is particularly necessary to reduce the amount of NO _x emission, the gas is provided at different positions in the radial direction in the air flow path around the pilot gas flow path and downstream of the swirler. Arrange multiple jets. As a result, the pilot fuel gas and the air are mixed more rapidly than the above-mentioned conditions, whereby a combustion state closer to premixed combustion is achieved, and further low NO _x combustion can be achieved.

FIG. 6 is an experimental result showing NO _x emission amount during combustion in the conventional combustion apparatus shown in FIG. 7 and the combustion apparatus of the present invention when the fuel supply schedule shown in FIGS. 5 and 8 is used. Therefore, compared with the conventional combustion apparatus, the combustion apparatus according to the present invention reduces the NO _x emission amount in the entire load fluctuation range.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a gas combustion apparatus according to the present invention will be described in more detail based on an embodiment with reference to the accompanying drawings. In the gas combustion apparatus of the present invention, except for the configuration related to the pilot gas nozzle, the other configurations are the combustion apparatus previously proposed by the applicant described with reference to FIG. 7 (double swirler multi-stage gas combustion apparatus). Is basically the same as Therefore, members having the same functions as the members of the combustion apparatus shown in FIG. 7 are designated by the same reference numerals in the drawing, and detailed description thereof will be omitted. Further, at the time of combustion, in the combustion apparatus proposed above, a fixed amount of primary fuel gas is supplied as shown in FIG. 8, and the amount of secondary fuel gas and tertiary fuel gas is changed to cope with the load. The combustion method is used,
In the combustion apparatus according to the present invention, in addition to the combustion method of supplying the pilot gas and the primary fuel gas almost constantly, a constant amount of the pilot gas and the primary fuel gas is supplied at a high load, but the pilot gas and / or the low load is used. In some cases, a combustion method is used in which the primary fuel gas is variable.

FIG. 1 is an axial sectional view showing an example of a gas combustion apparatus according to the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. In the figure, reference numeral 50 denotes a pilot gas nozzle, which is arranged at the upstream center of the combustion device. Around the pilot gas nozzle 50, a premixed gas outlet 2 for primary combustion is located, and a premixed gas outlet 3 for secondary combustion is located on the outer periphery thereof. Further, a tertiary premixing pipe 5 having an outlet 5a for premixed gas for tertiary combustion is provided at a substantially central position of the combustion chamber 20a of the combustion cylinder 20, and the tertiary premixing pipe 5 is provided with a conduit 16 through a tertiary fuel gas G. ₃ is supplied.

The pilot gas nozzle 50 has a central pilot gas passage 51 and an air passage 52 around it, and a swirler 53 is provided on the air introduction side of the air passage 52. The cross-sectional area of the air passage 52 is not particularly limited,
According to experiments conducted by the present inventors, it is desirable to design so that about 50% of the amount of premixed gas for primary combustion is introduced.

In this embodiment, the pilot gas flow channel 51
The closed tip portion of the above is set to a position displaced by a predetermined distance upstream of the axial position of the primary combustion premixed gas ejection port 2, and from the vicinity of the closed end in the radial direction, as shown in FIG. A plurality of (six in the illustrated example) nozzle tubes 55 extend to the air flow path 52, and the tips of the nozzle tubes 55 are also blocked. A plurality (preferably about four) of gas ejection ports 56 are formed in the portion where the nozzle pipe 55 is located in the air flow path 52.

The pilot gas G _p is fed to the pilot gas flow path 51, and the gas jet port 5 formed in the nozzle pipe 55.
6 is ejected into the air flow passage 52 located around the pilot gas flow passage 51. The air introduced into the air flow path 52 is made into a swirl flow by passing through the swirler 53, and the pilot gas G _p is rapidly mixed with the introduced air that has become the swirl flow, and diffusion combustion and premixed combustion are performed. Burning in the middle of. In this embodiment, since the gas ejection port 56 is located at a position deviated by a predetermined distance upstream of the axial position of the primary combustion premixed gas ejection port 2, the pilot mixed gas is used for the primary combustion. Its combustion is more stable without being affected by the premixed gas. Therefore, stable combustion can be continued.

The combustion air of the pilot gas is mainly the air introduced from the air flow path 52, and is not significantly affected by the primary combustion premixed gas ejected from the primary combustion premixed gas ejection port 2. Can be burned. Thereby,
The combustion can be maintained in a more stable state than the ignition fuel gas in the combustion apparatus shown in FIG. 7, and the stable combustion can be maintained up to a low combustion rate. Further, since the pilot mixed gas is in a stable and lean combustion state close to that of premixed combustion, low NO _x combustion is also maintained.

FIG. 3 is an axial sectional view showing another embodiment of the gas combustion apparatus of the present invention, and FIG. 4 is a sectional view taken along line IV-IV of FIG. In this embodiment, the combustion cylinder 20 is not a cylindrical body having the same diameter, but a first portion 21 having a small cross-sectional area located on the upstream side and a second portion 22 having a large cross-sectional area on the downstream side, It is composed of a first portion 21 and a third portion 23 connecting the second portion 22 and having a diameter increased toward the downstream side. One end of the third portion 23 is connected to the combustion chamber 20a.
A third premixing pipe 5b that is open to the outside is arranged, and the other end side of the third premixing pipe 5b extends toward the upstream side. Then, the tip of the conduit 16 is inserted into the tertiary premixing pipe 5b, and the tertiary fuel gas G ₃ is supplied from the conduit 16. The configuration for supplying the pilot fuel gas, the primary fuel gas, and the secondary fuel gas is the same as that shown in FIG.

In this embodiment, the tertiary premixing pipe 5b is connected to the first portion 2 of the combustion cylinder 20 having a small cross-sectional area.
Since the piping is provided through the first side, the thickness of the combustor can be made thinner than that of the first embodiment, and there is an advantage that the combustor can be made compact. Further, the pilot mixed gas, the primary-mixed premixed gas, and the secondary-combusted premixed gas, which are injected from the upstream side of the combustion cylinder 20, are swirled by the swirlers 53, 14, and 15 so that the swirlers 53, 14, and 15 cause centrifugal force to move to the outside. The flow velocity near the central axis of the combustion cylinder 20 is reduced by being pressed against and the flow from the downstream side to the upstream side tends to occur. Therefore, when the load is low, the tertiary combustion premixed gas (air) supplied from the tertiary premixing pipe 5b returns to the upstream side along this backflow, and the combustibility of the primary and secondary combustion premixed gases deteriorates. There is a case to let. As in this embodiment, by making the upstream portion 21 of the combustion cylinder 20 thin, the average flow velocity in the axial direction in that portion becomes high, and the premixed gas (air) flowing from the tertiary premixing pipe 5b.
There is also an advantage that it is possible to reduce the adverse effect of the gas on the combustion in the upstream portion.

The above description is only a description of some embodiments of the gas combustion device according to the invention, and many variants exist. For example, it is not essential that the tip of the pilot gas flow channel 51 is closed, and the flow channel may have an open tip. In that case, the air that flows in from the air flow path 52 and the pilot gas G _P move to the combustion field on the downstream side in a state where the mixing is not actively performed, and combustion close to diffusion combustion is performed, A more stable combustion state can be obtained. Further, the swirler 53 provided in the air flow path is not always essential and may be omitted. In that case, the degree of mixing of air and pilot gas decreases, which is effective for expanding the load range, but on the other hand, diffusion combustion increases and low NO _x combustion becomes somewhat difficult.

[0034]

As described above, according to the present invention, the pilot gas nozzle provided with the air flow passage around the pilot gas flow passage is arranged at the center of the premixed gas ejection port, and therefore, it has been previously proposed. Combustion device in which the premixed gas is supplied in three stages (Japanese Patent Laid-Open No. 5-340)
No. 508), lower NO _x combustion becomes possible.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing an example of a gas combustion apparatus according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is an axial sectional view showing another example of the gas combustion apparatus according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a graph showing an example of a fuel schedule of the gas combustion device according to the present invention.

FIG. 6 is a graph showing a comparison of NO _x production amounts.

FIG. 7 is an axial sectional view showing a premixed gas combustion device according to the above proposal.

8 is a graph showing an example of a fuel schedule of the premixed gas combustion device shown in FIG.

[Explanation of symbols]

20 ... Combustion cylinder, 20a ... Combustion chamber, 50 ... Pilot gas nozzle, 51 ... Pilot gas flow path, 52 ... Air flow path,
55 ... Nozzle tube, 56 ... Gas ejection port, 53 ... Swirler,
G _p ... pilot gas G ₁ ... primary fuel gas, G ₂ ... secondary fuel gas, G ₃ ... tertiary fuel gas, 2 ... primary combustion premixed gas ports, 3 ... secondary combustion premixed gas ports 5a
… Premixed gas jet for tertiary combustion

Claims (6)

[Claims] 1. A pilot gas nozzle, which is located on one end side of a combustion chamber and has a central pilot gas passage and an air passage around it, and a mixing ratio of air and fuel gas around the pilot gas nozzle. Of the premixed gas for primary combustion whose constant value is constant or variable as necessary, and a mixture of air and fuel gas by making the amount of fuel gas around the premixed gas outlet for primary combustion variable. A premixed gas for secondary combustion with a variable ratio and an outlet for premixed gas for secondary combustion, and a variable amount of fuel gas, which is located at a predetermined distance from the jet port for premixed gas for secondary combustion on the side wall of the combustion chamber. The gas combustion device is characterized by further comprising: an injection port for premixed gas for tertiary combustion, in which the mixing ratio of air and fuel gas is variable. 2. The gas combustion apparatus according to claim 1, wherein a swirler is arranged in an air flow path of the pilot gas nozzle. 3. The plurality of gas ejection holes of the pilot gas flow passage are arranged in different positions in the radial direction in the surrounding air flow passage and downstream of the swirler. The gas combustion device described. 4. The gas ejection hole of the pilot gas flow passage is located at a position displaced upstream of the axial position of the ejection port for the primary combustion premixed gas. 4. The gas combustion device according to any one of 3 to 3. 5. The cross-sectional area of the combustion chamber on the upstream side of the vicinity of the attachment position of the injection port of the premixed gas for tertiary combustion is smaller than the cross-sectional area on the downstream side thereof. The gas combustion device according to any one of 1 to 4. 6. A swirler is also provided in the primary combustion premixed gas passage and the secondary combustion premixed gas passage, and the swirler and the swirler arranged in the air passage of the pilot gas nozzle are The gas combustion apparatus according to claim 2, wherein the gas combustion apparatus has the same turning direction.