JP2500349B2 - Low NOx burner for high temperature combustion gas generation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner for generating a high temperature combustion gas, especially when a required gas temperature is high.
The present invention relates to a burner capable of significantly reducing the generation of Ox.

[0002]

2. Description of the Related Art A continuous combustor used for generating a high temperature combustion gas such as a gas turbine combustor, an aero propulsion engine combustor, a heating device combustor, etc.
The fuel and the air are separately supplied into the combustor, and while being mixed therein, the liquid fuel is combusted with evaporation in the liquid fuel. In this system, an area where the air is excessive and the temperature is low can be formed in the combustion chamber, while an area where the air (oxygen) is insufficient can be formed. Unburned components are mainly generated in the former, and smoke is generated in the latter. Microscopically, there is a lump of air-fuel mixture with excess fuel, but when this lump burns, it becomes a high-temperature gas lump, which is a source of NOx.

[0003]

As long as the mixing and combustion of fuel and air proceed in parallel at the same time, even if the fuel is a gaseous fuel gas, it is impossible to eliminate an excessive fuel-air mixture. It was essentially impossible and there were limits to reducing emissions of air pollutants. The fuel gas here means a general combustible gas, and in the case of not only a gaseous fuel such as natural gas but also a liquid fuel such as a jet fuel, a fuel gas obtained by gasifying this, It shall include gasification gas of coal produced by steaming coal. The most effective measure to eliminate the fuel-rich air-fuel mixture is to premix the fuel gas and air before supplying them into the combustor.
The combustion temperature in the case of the optimum ratio of fuel gas and air (mixing ratio of both fuel gas and air without excess or deficiency) achieves the maximum combustion temperature of combustion gas, but the required combustion gas temperature is higher than that. At very low temperatures, a significant reduction in NOx is possible by burning a lean fuel mixture. However, the leaner the NOx production, the more the stability of the flame is impaired and the emission of unburned components increases. If the required temperature is high,
Generation of NOx can be reduced by shortening the residence time of the combustion gas in the combustor. However, in the burner having the conventional structure, shortening the residence time increases the emission of unburned components and reduces the combustion efficiency. Furthermore, low NOx
Even in the rich / lean combustion that is expected to occur, in the burner having the conventional structure, the combustion gas and air cannot be rapidly mixed, so that a high temperature portion is generated in the mixing process. Therefore, NOx
It has not been put into practical use because the effect of suppressing the above is insufficient, and there are many unburned components and soot emissions.

In order to solve these problems, the inventor of the present invention forms a flat thin flame zone by a mixture of fuel gas and air, and injects and mixes air from a large number of pipes downstream thereof to NOx. To stop or slow down the reaction
A flat thin flame zone is formed by the fuel-rich mixture,
Immediately downstream, a method was developed to inject air from a number of tubes to rapidly burn unburned components (Japanese Patent Application No. 3-
105182). In the above invention, when the flat flame is formed by the air-fuel mixture thinner than the theoretical air-fuel mixture, and the air is made to flow in the downstream thereof, the gas temperature at the combustor outlet is necessarily higher than the combustion gas temperature of the flat flame. Will be low. Therefore, when the required combustor outlet temperature is close to the maximum combustion temperature, it becomes impossible to introduce air downstream. Also, when using a fuel-rich mixture, in order to achieve low NOx, it is necessary to introduce a considerably larger amount of air than the amount of air required to burn the unburned components in the planar flame. Becomes As a result, the combustor exit gas temperature is kept at a much lower temperature than the maximum combustion temperature. In order to obtain the combustor outlet gas temperature close to the maximum combustion temperature, it is necessary to reduce the amount of air introduced for dilution, so it is difficult to reduce NOx. The present invention has a large N ratio even when the combustion gas at a higher temperature is required as compared with the combustor outlet gas temperature which can bring about a remarkable NOx reduction effect by the above method.
The purpose is to obtain a burner that can obtain an Ox reduction effect.

[0005]

A low NOx burner for generating high temperature combustion gas according to the present invention is provided with a large number of first flow paths through which a mixture of fuel gas and air flows in a wall of a combustion chamber and the fuel gas and air.
A plurality of second flow paths through which the air-fuel mixture flows, and the second flow paths are arranged so as to surround each other .
1 through a flat flame formed downstream of the end faces of many flow paths
And extends downstream, and a large number of
A hole is formed, and the second channel is mixed from the plurality of holes.
Air is injected and mixed into the fuel gas in the flat flame zone
The above problems are solved by the technical means characterized by
We were able to. The outlet end of the first flow path and the second end
If the axial distance to the flow path hole of the
Both unburned components and NOx emissions can be suppressed over
Therefore, it is desirable. In addition, the first flow path is, for example,
The large number of holes provided in the plate in which the second flow path is arranged
It can be constructed with a simple structure. Further
The air-fuel mixture on the wall surface of the first and / or second flow path.
If a catalyst that accelerates the reaction of
Or even if a rich air-fuel mixture is formed, the formation of a flat flame is acceptable.
It is easier to obtain a larger NOx reduction effect.
Wear.

[0006]

As described above, when the fuel gas or the air-fuel mixture of the fuel gas and the air is injected and mixed into the combustion gas from the flat flame, the temperature thereof is lowered and the NOx generation reaction is stopped or Be slowed down. Furthermore, when the injected air-fuel mixture contains a large amount of fuel, some of the NOx produced in the planar flame was reduced to harmless nitrogen by the fuel. confirmed. The NOx produced by the combustion of the injected fuel has a rational burner structure that allows for uniform mixing, which makes it difficult to generate local high-temperature parts, and the oxygen concentration causes a flat flame. Since it is lower in the downstream than in the air, it is suppressed. The injected fuel gas or the fuel in the air-fuel mixture has a high temperature after mixing with the combustion gas of the flat flame, and therefore can be easily burned.

FIG. 1A shows the generation of high temperature combustion gas according to the present invention.
2 is a cross-sectional view showing the configuration of a low NOx burner for a combustion chamber 8
A mixture of fuel gas and air into the first channel 1 and the second channel
It is supplied separately in two channels, the channel 5 . A large number of mixed air streams are provided from the first flow path 1 in which a lean air-fuel mixture of a part of the fuel gas and air is uniformly distributed on the flat plate 3 forming the wall of the combustion chamber 8 on the first side. It is supplied into the combustion chamber through a hole 2 which is a passage. This air-fuel mixture forms a flame zone 4 that spreads in a planar shape downstream of the flat plate 3. The tip of the second channel 5 is
As shown in FIG. 2, the flat plate 3 is evenly distributed and penetrates,
The remaining mixture of fuel gas and air supplied from the flow path 5 is formed by the hole 2 and a large number of tubes 6 arranged so as to surround each other, and a hole provided near the tip of the tube 6. From 7 in the radial direction, it is injected into the flow of the combustion gas in the flat flame zone 4 and mixed and burned.

Since the temperature of the air-fuel mixture injected from the holes 7 is lower than the combustion gas temperature of the flat flame, the NOx production reaction downstream of the flat flame is stopped or slowed down by this mixing. It Further, when the fuel concentration of the injected air-fuel mixture is high, a part of NOx generated in the flat flame is reduced to harmless nitrogen. Since the temperature of the mixed gas generated by mixing the injected mixed gas with the combustion gas of the flat flame is sufficient to start the oxidation reaction of the fuel, the reaction starts, the gas temperature rises, and the combustion The maximum temperature is reached at the outlet. This situation is shown in FIG. 1B as a temperature distribution in the combustion chamber.

Low NOx bar for high temperature combustion gas generation of the present invention
The design is not limited to the above embodiment, and various design changes are possible.
It For example, instead of the flat plate 3 provided with a large number of holes 2 in the above-mentioned embodiment , even if thin tubes are bundled to form a flow path of the air-fuel mixture, a flat flame zone can be formed downstream of the lower end surface thereof. , A similar effect is obtained. In addition, the above-mentioned first flow path and / or
If a catalyst that promotes the reaction of the air-fuel mixture is carried on the wall surface of the second flow path, it becomes easier to form a flat flame zone even for a fuel-lean or rich air-fuel mixture, and a larger N
Ox reduction effect can be obtained. Furthermore, if the flat plate 3 and the pipe 6 are not fixed to each other and the relative axial positions of the two are variable according to the operating conditions (temperature, fuel concentration, required gas temperature, etc.) of the combustor, unburned over a wide operating range. Both the components and NOx emissions can be suppressed.

[0010]

EFFECT OF THE INVENTION A low NOx bar for producing high temperature combustion gas according to the present invention.
As described above, since the flame held by the air-fuel mixture that is subdivided and formed forms a thin planar flame zone as a whole, and immediately after that, the air-fuel mixture is effectively mixed, The combustion gas temperature is lowered within an extremely short time after combustion, and the NOx production reaction can be stopped or significantly reduced. Moreover, the reduction effect of the fuel gas of the air-fuel mixture injected from the second flow path can effectively suppress the emission of NOx, and the NOx can be injected from the second flow path.
By mixing the injected mixture with the combustion gas in the flat flame zone,
Then, the oxidation reaction of the fuel gas begins and the combustion gas temperature
First, it rises, reaches the maximum temperature at the combustor outlet, and emits low NOx.
The temperature at the combustor outlet is the highest at the same time
A combustion gas close to the temperature can be obtained. Further, the mixture injected to the downstream of the combustion gas is preheated by mixing with the combustion gas, so that the discharge of unburned components is suppressed, the mixing is uniform, and the oxygen concentration is low, so that the generation of NOx is also suppressed. . Besides, the combustion gas reaches the maximum temperature at the combustor outlet
Therefore, even when higher temperature combustion gas is required , the temperature of the combustion gas in the upstream part of the combustion chamber can be kept considerably lower than the temperature at the combustor outlet, and the flame radiation is also small, so the burner part and the combustion chamber The requirements for cooling and heat resistance can be relaxed.
Further, the first flow path and the second flow path are connected to the operating condition of the combustor.
Relative axis according to (temperature, fuel concentration, required gas temperature, etc.)
If the directional position is variable, unburned over a wide operating range.
Both burning components and NOx emissions can be suppressed. Even more
In addition, a catalyst that accelerates the reaction of the air-fuel mixture is supported on the wall surface of the flow path.
By doing so, for a fuel-lean or rich mixture,
Also facilitates the formation of a flat flame zone, resulting in larger NOx.
A reduction effect can be obtained.

[Brief description of drawings]

FIG. 1A is a sectional view conceptually showing the structure of one embodiment of a burner of the present invention, and FIG. 1B is a view showing a change in combustion temperature in a combustion chamber.

FIG. 2 is a front view showing a distribution of air-fuel mixture supply ports of the embodiment of the burner.

[Explanation of symbols]

1 Mixture channel 2, 7 holes
3 Flat plate 4 Planar flame zone 5 Mixture or fuel gas 6 Tube 8 Combustion chamber

Claims (4)

(57) [Claims] 1. A plurality of first flow paths through which a mixture of fuel gas and air flows in a combustion chamber wall, and a lean mixture of fuel gas and air.
A large number of second flow passages through which the air-fuel mixture flows are arranged so as to surround each other, and the second flow passages are formed in a flat flame zone downstream of the end faces of the first plurality of flow passages. A number of holes on the side wall of the flow path near the downstream end.
Is formed, and the air-fuel mixture in the second flow path is formed from the large number of holes.
Is injected into and mixed with the combustion gas in the flat flame zone , and a low NOx burner for producing high-temperature combustion gas. 2. The axial distance between the outlet ends of a large number of first flow paths and the holes of the second flow paths in which the mixture of the fuel gas and air flows is variable. Claim 1
Low NOx burner for generating high temperature combustion gas 3. A large number of first flow passages through which the mixture of combustion gas and air flows and a second flow passage downstream of the planar flame zone through which a mixture of fuel gas and air flows. 2. A multiplicity of holes provided in a plate provided therein.
Or a low NOx burner for generating high temperature combustion gas according to 2 . 4. The wall surface of the first and / or second flow path ,
The low N for high temperature combustion gas generation according to claim 1, 2 or 3 , wherein a catalyst that promotes a reaction of the air-fuel mixture is supported.
Ox burner.