JP3053700B2 - Concentration combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentration combustion apparatus for simultaneously burning an excess fuel-air mixture and an excess air-fuel mixture to reduce NOx.

[0002]

2. Description of the Related Art Heretofore, so-called lean-burn combustion used in this type of combustion apparatus means that some of a plurality of fuel injection ports provided in a combustion burner are fuel-rich in which the air ratio of a mixture of fuel gas and air is low. The flame is burned with fuel gas and air shading by operating under conditions and other fuel lean conditions where the air ratio of the mixture of fuel gas and air is high,
This is a method of suppressing the generation of NOx.

[0003] Fig. 7 shows a schematic configuration of a generally-known rich / lean combustion apparatus. Referring to Fig. 7, an air ratio in a mixture of fuel gas and air is low (generally from an excess fuel flame port 42 of a combustion burner 40). A flame with an air ratio of <1) is blown out, and a flame with a high air ratio (in> 1) in a mixture of the fuel gas and the air is blown out of the excess air flame port 44. The oxygen (O2) concentration is insufficient at the base of the excess fuel flame blown out from the excess fuel flame port 42, and the O2 concentration is caused by the exhaust gas of the excess air flame blown out from the excess air flame port 44 in front of the excess fuel flame. Is insufficient, the generation of NOx is suppressed. On the other hand, the excess air flame blown out from the excess air flame port 44 reduces the temperature of the flame due to the lean combustion of the fuel gas and suppresses the generation of NOx. is there.

[0004] An example in which this concentration combustion apparatus is applied to, for example, a water heater will be described with reference to FIG. This figure shows a schematic configuration of a heat exchanger 48 through which water flows in a combustion chamber 46 of a water heater and a combustion burner 40 for heating the heat exchanger. An excess fuel port 42 through which a flame having a low air ratio of a mixture of air and air is blown out and an excess air port 44 through which a flame of a mixture having a high air ratio is blown out are arranged in a suitable number, respectively. The water flowing in the heat exchanger 48 is heated by the heat of the combustion gas due to the excess fuel flame and excess air flame blown out from the excess fuel flame 42 and excess air flame 44, and the excess fuel flame and excess air flame are generated. Is discharged from the combustion chamber 46. As a result, hot water is sent out from the outlet side of the heat exchanger 48.

[0005]

However, in such a lean-burn apparatus having a generally known configuration, the combustion chamber 46 has a downstream side of the excess fuel port 42 and a downstream side of the excess air port 44 in the combustion chamber 46. A temperature difference occurs. For this reason, the CH component in the mixture of fuel gas and air is not oxidized downstream of the low-temperature excess air flame outlet, and unburned gas in the combustion gas is contained. There is a possibility of causing a so-called slip phenomenon of unburned gas that is discharged. Therefore, there has been a concern that a sufficient amount of heat generated by the fuel gas cannot be obtained, resulting in a decrease in combustion efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. It is an object of the present invention to reduce NOx by rich-and-shallow combustion and at the same time to reduce air in a mixture of fuel gas and air. It is an object of the present invention to provide a lean-burn combustion apparatus which improves the combustion efficiency by reducing the unburned gas content in the low-temperature combustion gas due to the excess air flame having a high ratio and eliminating the slip phenomenon.

[0007]

In order to achieve this object, the present invention provides a lean-burn combustion apparatus in which a combustion chamber is provided with a combustion burner for burning a mixture of fuel gas and air. An excess fuel flame outlet from which an air-fuel mixture with a low air ratio is blown and an excess air flame outlet from which an air-fuel mixture with a high air ratio are blown out are respectively arranged in an appropriate number, and an excess fuel flame blown out from the excess fuel flame hole. In the downstream region of the combustion gas due to the excess fuel, a part of the heat of the combustion gas due to the excess fuel flame is taken and the taken heat is dispersed toward the downstream region of the combustion gas due to the excess air flame blown out from the excess air flame port. The gist is that a heat dispersing element is provided.

[0008]

According to the present invention having such a configuration, the flame of the air-fuel mixture having a low air-fuel ratio from the fuel gas is emitted from the excess fuel port of the combustion burner disposed in the combustion chamber. The flame of the air-fuel mixture having a high air-ratio of fuel gas and air is blown out from the excess air flame outlet, but the downstream region of the high temperature combustion gas due to the excess fuel flame blown out from the excess fuel flame outlet. The heat dissipator disposes a part of the heat of the combustion gas due to the excess fuel flame, and the heat dissipated by the heat disperser dissipates the excess air blown out from the excess air flame outlet by the heat disperser. The combustion gas is dispersed toward the downstream region. Therefore, the relatively low temperature combustion gas due to the excess air flame is reheated by the heat dispersed by the heat dispersing element, and the unburned gas component in the combustion gas is assisted by the heat of dispersion, so that the combustion gas as a whole is The unburned gas content therein is reduced.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a lean-burn combustion apparatus according to a first embodiment of the present invention. This embodiment shows an example in which the present invention is applied to heating water passed through a heat exchanger by the heat of combustion exhaust gas from a combustion burner in a burning appliance such as a water heater.

As shown, in this embodiment, the combustion chamber 10
A combustion burner 12 for burning an air-fuel mixture of the fuel gas and air is disposed on an upstream side where the combustion gas flows therein, and a heat collection fin 1 is provided on a water pipe 16 through which water flows on the downstream side of the combustion gas.
A heat exchanger (heat collector) 14 in which a large number of 8 are arranged is provided. The combustion burner 12 has a fuel excess flame port 20 through which a mixture of fuel gas and air having a low air ratio is blown out.
And a large number of excess air ports 22 from which a mixture of fuel gas and air having a high air ratio is blown out. This excess fuel port 20 and excess air port 2
Although the adjustment of the air ratio of the air-fuel mixture blown out from 2 is not shown, for example, the fuel gas supply pipe connected to the fuel gas cylinder is branched and led to the excess fuel flame port 20 and excess air flame port 22, respectively. It is performed by adjusting the opening degree of the provided valve.

Thus, in the first embodiment, the combustion chamber 1
An appropriate number of heat dispersing elements 24 are disposed at a position in the downstream of the flame blown out from each excess fuel flame port 20 between the combustion burner 12 and the heat exchanger 14. This heat dispersion 2
As shown in FIGS. 2 (a) and 2 (b), a gas pipe 26 having both ends opened in a direction in which a high-temperature combustion gas due to an excess fuel flame blown out from an excess fuel flame port 20 flows through as shown in FIGS. A radial heat collecting fin 28 is provided on the inner peripheral wall surface. A relatively low temperature combustion gas due to excess air flame blown out from the excess air flame port 22 passes through the outer peripheral portion of the gas pipe 26 of the heat dispersing element 24 as shown in the figure.

Regarding the air ratio of the air-fuel mixture of the fuel gas and the air in the above embodiment, the following three types are supposed, but any of them can be applied. The first is that the air ratio of the mixture of fuel gas and air blown from the excess fuel flame port 20 is less than 1.0 and the air of the mixture of fuel gas and air blown from the excess fuel flame port 22 is air. This is the case when the ratio is 1.0 or more. Desirably, the excess fuel flame port 2
The air ratio of the air-fuel mixture blown from 0 is about 0.8 or less,
It is preferable that the air ratio of the air-fuel mixture blown out from the excess air outlet 22 be about 1.3 or more.

The second is that the air ratio of the mixture of the fuel gas and the air blown out from the excess fuel flame port 20 is the air ratio of the mixture of the fuel gas and the air blown out from the excess fuel flame port 22. The air-rich state is smaller than 1.0 but not less than 1.0, and the air ratio of the air-fuel mixture blown out from the excess air flame port 20 is higher than the air ratio of the air-fuel mixture blown out from the excess fuel flame port 20. In this case, the fuel excess flame port 20
The air ratio of the air-fuel mixture blown out of the nozzle may be as high as about 1.2 to 1.4.
If the air ratio of the air-fuel mixture blown out of the fuel-excess flame port side is 1.2, it is sufficient that the air ratio is 1.3 or more.

The third is to mix secondary air with the air-fuel mixture in each of the above two examples. Examples of these will be described later specifically with reference to the drawings. According to the thus configured lean-burn combustion apparatus, the high-temperature combustion gas of the excess fuel flame blown out from the excess fuel flame port 20 of the combustion burner 12 passes through the gas pipe 26 of the heat dispersion medium 24. When the heat is removed, the heat is taken away by the heat collecting fins 28, the temperature is lowered slightly, and the heat is exhausted after flowing through the heat exchanger 14 in contact with the heat exchanger 14. 26 is radiated from the outer peripheral wall surface.

At this time, a relatively low temperature combustion gas due to excess air flame blown out from the excess air flame port 22 of the combustion burner 12 flows through the outer peripheral region of the gas pipe 26 of the heat disperser 24. The low-temperature combustion gas is supplied to the heat dispersing element 24.
Is heated by the heat dissipated from the The low-temperature combustion gas due to the excess air flame contains unburned gas containing unburned CH components. This unburned gas is heated by the heat dissipated from the heat dispersing member 24 to assist combustion. The fuel gas flows through the heat exchanger 14 as a higher temperature combustion gas and is discharged.

Therefore, the heat exchanger 14 is heated not only by the combustion gas due to the excess fuel flame, but also by the combustion gas due to the excess air flame whose combustion temperature, which has a low unburned gas content, has been raised. At that time, the temperature of the combustion gas due to the excess fuel flame is lowered by the heat dispersing element 24, and the temperature of the combustion gas due to the excess air flame is raised by burning the unburned gas. The gas flows through the heat exchanger 14 and the outer peripheral surface of the heat exchanger 14 is uniformly heated.

FIG. 3 shows another embodiment of the heat dispersion in the embodiment shown in FIG. The heat dispersing element 24a shown in FIG. 3 has a configuration in which radial radiating fins 28a are provided on the outer peripheral wall of a gas pipe 26a through which high-temperature combustion gas due to excess fuel flame passes.

The heat disperser 24a shown in FIG. 3 also removes the heat of the high-temperature combustion gas due to the excess fuel flame due to contact with the inner wall surface of the gas line 26a, and the heat is dissipated by the radiating fins 28a. The low-temperature combustion gas due to the excess air flame which is radiated to the outer peripheral area of the pipe 26a and flows through the outer peripheral area of the gas pipe 26a of the heat dispersing body 24a is reheated by the dissipated heat. Fire CH
The unburned gas content is reduced by heating and burning the components.

Therefore, according to this embodiment, part of the heat of the high-temperature combustion gas due to the excess fuel flame is also transferred to the heat disperser 24.
Therefore, the heat exchanger 14 heats the low-temperature combustion gas due to the excess air flame and converts the combustion gas into a combustion gas having a higher combustion temperature with less unburned gas. It is efficiently heated by the combustion gas having a large amount of heat.

The heat dispersers 24 and 24a may be variously modified. For example, although not shown, if the heat collecting fins 28 are provided on the inner peripheral wall surfaces of the gas pipes (26 and 26a). At the same time, a radiation fin 28a may be provided on the outer peripheral wall surface of the gas pipeline (26, 26a), or a modification such as a star-shaped tube instead of the fin-type heat radiator as in the above-described embodiment may be appropriately made. Can be selected.

FIG. 4 shows a schematic configuration of a concentration combustion apparatus according to a second embodiment of the present invention. In this example,
Combustion burner 12 and heat exchanger (heat collector) 1 in combustion chamber 10
A red-hot body 30 is provided as a heat dispersing body disposed between the red-hot body 4 and the red-hot body 4. As a material of the red heat body 30, a mullite material having a low coefficient of thermal expansion is preferable, but a ceramic material such as a cordierite material and a silicon carbide (SiC) material formed in a porous and air-permeable form may be used. Alternatively, a metal material such as a stainless material (for example, SUS430) may be used. Further, regarding the ventilation shape of the combustion exhaust gas, in addition to the grid-shaped or honeycomb-shaped red-hot body 30a as shown in FIG.
May be used, and the shape is not particularly limited.

According to the embodiment shown in FIGS. 4 and 5 (a) and 5 (b), the combustion gas of the excess fuel flame and the combustion gas of the excess air flame are both red hot bodies 30 (30a, 30a).
b), but the heat of the high-temperature combustion gas of the excess fuel flame is then transferred to the red hot body 30 (30a, 30b).
Passed at lower temperature. On the other hand, the removed heat is dispersed and propagated in the red hot body 30 (30a, 30b), and the low-temperature combustion gas of the excess air flame flowing through the red hot body 30 (30a, 30b) is reheated by the dispersed heat, The unburned gas in the combustion gas is burned.

As a result, the combustion gas of the excess fuel flame slightly lowers the temperature, but the combustion gas of the excess air flame emits the red heat 30 (3).
0a, 30b), the temperature is increased, and the heat collector 1 has a substantially uniform temperature distribution as a whole, and has a calorific value larger than that of the unburned gas due to the combustion of the unburned gas.
4 for heating.

At this time, FIGS. 4 and 5 (a),
The glowing body 30 (30a, 3a) in the embodiment shown in FIG.
0b) is preferably between the combustion burner 12 and the heat collector 14, and if it is disposed closer to the heat collector 14 at that time, the heat collector 14 is heated only by direct heating by the combustion exhaust gas. Instead, it is also heated by radiant heating by the red-hot body 30 (30a, 30b), and the heating effect is large.

FIG. 6 is an embodiment showing the case where secondary air is supplied to the combustion chamber 10. As shown in the drawing, a secondary air supply port 32 is provided separately from the excess fuel port 20 and the excess air port 22 of the combustion burner 12, and the fuel is supplied from the excess fuel port 20 and the excess air port 22 into the combustion chamber 12. A flame of a mixture of gas and air is introduced, and secondary air is introduced from a secondary air supply port 32.

Therefore, by adopting such a configuration, the air ratio on the excess air flame side can be set lower, and the flame of the excess air flame is stabilized, and fresh air comes into contact with a part of the excess fuel flame side. By doing so, the flame of the excess fuel flame is stabilized.

It is needless to say that various improvements and modifications can be made without departing from the spirit of the present invention as described in the above embodiments. The present invention is not understood by the above-described embodiments. In other words, in the case of rich / lean combustion, part of the heat of the high-temperature combustion gas due to the excess fuel flame is taken out and the heat is used to generate the relatively low-temperature combustion gas due to the excess air flame. To combust the unburned gas contained in the fuel gas to eliminate the slip phenomenon of the unburned gas. Thus, the calorific value possessed by the fuel gas is sufficiently exhibited to increase the combustion efficiency. In addition, it avoids poor combustion and contributes to the reduction of dust.

[0028]

As is apparent from the above description of the embodiment, according to the concentration combustion apparatus of the present invention, part of the heat of the high temperature combustion gas due to the excess fuel flame having a low air ratio is utilized. Heating and burning unburned gas components such as CH components in the combustion gas at a relatively low temperature due to the excess air flame with a high air ratio eliminates the concern of slipping of the unburned gas and further improves combustion efficiency. Can be improved. Also, the combustion gas temperature is made uniform, and it is extremely useful to apply this concentration combustion apparatus to various kinds of combustion appliances in combination with the reduction in NOx.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of a concentration combustion apparatus according to a first embodiment of the present invention.

2 (a) is an enlarged cross-sectional view of the vicinity of a heat dispersion body of the concentration combustion apparatus shown in FIG. 1, and FIG. 2 (b) is a perspective view of the heat dispersion body itself.

FIG. 3 is a perspective view according to another embodiment of the heat dispersion body shown in FIG. 2;

FIG. 4 is a cross-sectional view illustrating a schematic configuration of a concentration combustion apparatus according to a second embodiment of the present invention.

5 (a) is a view showing a structure according to an embodiment of a red-hot body which is a heat dispersion body of the concentration combustion apparatus shown in FIG. 4,
(B) is a diagram showing a structure according to another embodiment.

FIG. 6 is a schematic configuration diagram of an embodiment showing a configuration in which secondary air is taken into a combustion chamber in the concentration combustion apparatus shown in FIGS. 1 to 5;

FIG. 7 is a diagram shown to explain a schematic configuration of a conventional lean-burn combustion apparatus.

FIG. 8 is a diagram showing a state in which the concentration combustion device shown in FIG. 7 is applied to, for example, a combustion device of a water heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Combustion chamber 12 Combustion burner 14 Heat exchanger (heat collector) 20 Excess fuel flame 22 Excess air flame 24, 24a Heat dispersion 30, 30a, 30b Heat dispersion (red heat)

Claims (1)

(57) [Claims] A combustion burner for burning a mixture of fuel gas and air is provided in a combustion chamber, and the combustion burner has a high fuel ratio and an excess fuel port through which a mixture having a low air ratio is blown out. An appropriate number of excess air flame outlets from which the air-fuel mixture is blown are arranged, and a portion of the heat of the combustion gas due to the excess fuel flame is provided in a downstream region of the combustion gas due to the excess fuel flame blown from the excess fuel flame opening. And a heat dispersing device for distributing the heat taken by the heat dispersing element toward a downstream region of the combustion gas due to the excess air flame blown out from the excess air flame port.