JPH1137425A - Burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of prompt NOx by providing a tube structure which has a polygonal passage with side faces made of a porous body and making a gas flow into the passage from the outside surface of the porous body of the burner structure through the porous body, and forming a flame by the surface of the porous body which faces the passage and one of openings of the passage. SOLUTION: A premixed gas 26 which is flown into a casing 23 through a supply opening 27 is made to flow into a porous body 21 in a direction depicted by left and right arrows and a first stage flame 28 is formed on the surface of the porous body 21 which faces the passage 22. Furthermore, remaining air is supplied as secondary air 30 such that air exceeds an amount of air necessary for the complete combustion of the premixed gas 26 so as to form a second stage flame 29 at the opening 25. Due to such a construction, in a combustion of hydrocarbon-based fuel, the concentration of CH, CH2 , CH3 is lowered so that the generation of prompt NOx can be restricted. Furthermore, since the flame is separated into two stages, the temperature of flame can be controlled so that the generation of thermal NOx can be also restricted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner, particularly a low NO.
It concerns x burners.

[0002]

2. Description of the Related Art As a high-output low-NOx burner for a boiler or the like, there is a system in which a premixed gas is diffused and burned by using a ceramic particle-filled body or a porous ceramic body as a combustion chamber (Japanese Patent Laid-Open No. 8-296913). FIG.
FIG. 1 shows a configuration diagram of Japanese Patent Publication No. 813. 1 is combustion air, 2 is an inner water pipe, 3 is a water pipe fin, 4 is a fuel gas, 5 is a combustion gas passage, 6 is a flue, 7a is a ceramic granule, 7 is a combustion layer, 8
Is a premixed gas supply device, 9 is a premixed gas, and 10 is a combustion gas.

In FIG. 5, the premixed gas 9 is subjected to surface diffusion combustion in the combustion layer 7 and the heat in the combustion layer 7 and the combustion gas 10 is absorbed by the water tube fins 3 to lower the combustion temperature and reduce NOx. It is intended.

On the other hand, low output and low NO in household combustion equipment
As the x burner, a gray-scale combustion method (Japanese Patent Laid-Open No. 8-32702)
No. 8) and a multi-stage combustion system (see Japanese Utility Model Laid-Open No. 8-129) are the mainstream.

[0005] Further, the so-called all-primary Schwann burner (see Japanese Utility Model Laid-Open No. 1-11030) also has low NOx.

[0006]

In the conventional surface diffusion combustion method using a packed bed of ceramic particles as a combustion layer, relatively stable combustion is performed over a wide range of equivalent ratios, and unburned harmful substances and NOx Has the advantage of less occurrence of However, the heat capacity of the portion of the combustion layer 7, which is a packed layer of the ceramic particles 7a, is large, it takes time from ignition to steady combustion, and a pressure loss is large and a high-pressure blower is required. Need water.
For this reason, there is a problem that cannot be applied to a burner of a household combustion device.

Further, in the above-mentioned conventional lean-burning method which has been used in a household combustion device, a light flame, which is a flame of a premixed gas having an equivalent ratio of 1 or less, tends to be unstable, and C is reduced by a lift or the like.
Unburned harmful substances such as O and HC are easily generated, and a large turndown ratio of the combustion amount cannot be obtained. Further, since the burners of different shades are arranged alternately, the structure of the burner becomes complicated, and it is necessary to produce premixed gas having two different concentrations.

In the multi-stage combustion system, the number of parts is increased because the flames of each stage are separated by an independent structure, and a relatively large combustion chamber capacity is required to separate the flames. There is a problem that the first and second stage flames are not integrated to form multi-stage combustion.

[0009] All primary Schwann burners have a problem that the turndown ratio is small due to the problem that flashback occurs when the amount of combustion is reduced.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a tube structure having a polygonal or circular cross section with a porous body as a side, and gas flows in from the outer side of the porous body. In this case, a flame is formed on at least one of the surface of the porous body facing the passage and the opening of the passage after passing through the porous body.

According to the invention, when a flame is formed on the surface of the porous body, a violent turbulence is generated by collision of a gas such as a premixed gas with the opposite gas after passing through the porous body and after the passage.
Since the concentrations of CH, CH2, and CH3 decrease in the combustion of the hydrocarbon fuel, the generation of so-called prompt NOx can be suppressed. Further, since a flame is formed on the surface of the porous body having a high surface area and the flame temperature is suppressed, the generation of thermal NOx can also be suppressed. In addition, the flames oppose each other, stabilizing the flame in a wide equivalent ratio range and suppressing the generation of unburned substances.In addition to the flame on the surface of the porous body, a flame is formed at the opening, so the turndown ratio of the combustion amount is increased. it can. Furthermore, compared to a conventional burner using a porous body as a combustion layer, the porosity is large, the pressure loss and the heat capacity are low, so that a high-pressure blower is not required, and stable combustion is achieved in a short time after ignition. Therefore, it can be applied to a burner in a household combustion device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be embodied in the form described in each claim.
A porous structure having a passage having a polygonal or circular cross section with a porous body as a side surface, wherein gas flows in from the outer side surface of the porous body, passes through the porous body, and the porous body surface facing the passage. A flame is formed on at least one of the openings of the passage.

When a flame is formed on the surface of the porous body,
When a gas such as a premixed gas passes through the porous body and collides with an opposing gas after the passage, a violent turbulent flow is generated, and the concentration of CH, CH2, and CH3 is reduced in the combustion of the hydrocarbon-based fuel. Can be suppressed. Further, since a flame is formed on the surface of the porous body having a high surface area and the flame temperature is suppressed, the generation of thermal NOx can also be suppressed. In addition, the flames oppose each other, stabilizing the flame in a wide equivalent ratio range and suppressing the generation of unburned substances.In addition to the flame on the surface of the porous body, a flame is formed at the opening, so the turndown ratio of the combustion amount is increased. it can. Furthermore, compared to a conventional burner using a porous body as a combustion layer, the porosity is large, the pressure loss and the heat capacity are low, so that a high-pressure blower is not required, and stable combustion is achieved in a short time after ignition. Therefore, it can be applied to a burner in a household combustion device.

Further, the burner according to the second aspect has a honeycomb structure having a plurality of passages partitioned by a porous body, and one end of each of the passages is closed by a closing body so that one of the passages is closed. A gas inflow opening formed alternately, and a gas outflow opening formed alternately by closing the other end of the passage having the inflow opening with a closing body; The gas flowing in through the porous body passes through the adjacent passage and flows out of the outflow opening, and at least one of the outflow opening and the porous body surface facing the passage having the outflow opening has a flame. Is formed.

Since the porous body has a honeycomb structure, the porosity of the burner is larger than that of the first aspect of the present invention.
Even if the volume is the same, a large surface area and low pressure loss are obtained. Therefore, the size of the burner can be reduced, and NOx can be further reduced.

In the burner according to claim 3 of the present invention, the thickness of the porous body is at least three times the average porous diameter of the porous body.

Since the thickness of the porous body is made sufficiently large with respect to the average porous diameter, quenching can prevent flashback of the flame.

According to a fourth aspect of the present invention, there is provided a burner in which the porous body is made of a material having a high thermal conductivity and a high melting point. In the burner according to the fifth aspect, the material of the porous body is made of SiC.

The high heat conductivity and high melting point characteristics of SiC efficiently radiate combustion heat to the outside, and are further effective in reducing NOx and preventing flashback by suppressing the flame temperature. Crack,
Thermal degradation such as melting can be prevented.

According to the burner of the present invention, the gas passing through the porous body is a premixed gas having an equivalent ratio of 1 or more,
The first stage flame is formed on the surface of the porous body, and the second stage flame is formed at the opening by the secondary air.

No new structure is required for the second stage flame, and the first and second stage flames are formed in a direction perpendicular to each other. NOx generation can be suppressed by suppressing the flame temperature.

In the burner according to claim 7 of the present invention, the gas passing through the porous body is a premixed gas having an equivalent ratio of 1 or less,
A flame is formed on the surface of the porous body.

The entire primary flame can be formed in a wide area of the porous body, the combustion temperature is suppressed, and the NO.
The generation of x can be suppressed.

In the burner according to the present invention, the gas passing through the porous body is a premixed gas having an equivalent ratio of 1 or less,
A flame is formed at the opening.

The mixing of fuel and air proceeds due to the turbulence caused by the collision with the opposing premixed gas after passing through the porous body, and the generation of NOx and unburned harmful substances can be suppressed.

In the burner according to the ninth aspect of the present invention, a flame is formed on the surface of the porous body when the burning amount is low, and a flame is formed at the opening when the burning amount is high.

When the combustion rate is low, the flow rate of the premixed gas is low, and a flame is formed on the surface of the porous body. On the other hand, when the combustion rate is high, the flow rate of the premixed gas is large, and the flame leaves the porous body surface and opens. Since a flame is formed, it is difficult to continuously vary the amount of combustion, but the turndown ratio can be increased.

In the burner according to the tenth aspect of the present invention, a flame is formed at the opening by the ignition means provided near the opening, and thereafter, the flow rate of the premixed gas is reduced to form the flame on the surface of the porous body. Things.

Even if there are a large number of passages in which a flame is to be formed, the flame can be returned to the upstream side by narrowing the flow rate of the premixed gas after ignition at the opening of the burner, and the entire passage can be ignited.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a view showing a burner according to Embodiment 1 of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. Claims 1, 3, 4, and 5 will be described in this embodiment.

In FIGS. 1 and 2, reference numeral 21 denotes a porous body having a communicating hole, preferably having a thickness of at least 10 mm and an average porous diameter of preferably 100 to 500 μm. The thickness is three times or more.
The material of the porous body 21 is preferably carborundum (SiC). In this embodiment, four porous bodies 21 are connected to one passage 2.
2 to form a tube structure. Porous body 2
1 is fixed to the casing 23. 24 is a passage 22
Is a closing body for closing one end of the opening, and 25 is an opening. 26
Is a premixed gas of fuel and air, and the equivalent ratio is set to 1 or more so as to perform so-called two-stage combustion. 27 is a supply port of the premixed gas, 28 is a first-stage flame formed on the surface of the porous body 21 facing the passage 22, and 29 is a second-stage flame formed by the opening 25. 30 is secondary air.

Next, the operation and operation will be described. The premixed gas 26 flowing into the casing 23 from the premixed gas supply port 27 flows into the porous body 21 as indicated by left and right arrows in FIG. A first stage flame 28 is formed. Here, the premixed gas 26 becomes violent turbulence generated when passing through the porous body 21 and colliding with the opposed first-stage flame 28, and a rapid oxidation reaction is performed. In the combustion of the hydrocarbon fuel, CH, CH
2. The concentration of CH3 drops, so-called prompt NOx
Can be suppressed. Then, the remaining air is supplied as secondary air 30 so that the amount of air is equal to or more than the air amount necessary for complete combustion of the premixed gas, and a second-stage flame 29 is formed at the opening 25. Since the first-stage flame 29 is formed over a wide area on the surface of the porous body 21 and the flame is separated into two stages, the flame temperature is suppressed, and the generation of so-called thermal NOx can be suppressed. Furthermore, since the first stage flame 28 is opposed, the flame is stabilized in a wide equivalent ratio range, and the generation of unburned substances can be suppressed. Further, by arranging the porous body 21 to form the passage 22 to form a burner, the porosity of the burner per volume determined by the outer shape is large, and low pressure loss and low heat capacity are obtained. Therefore, a high-pressure blower is not required, and stable combustion can be performed in a short time after ignition, so that it can be used as a burner in a household combustion device.

The second stage flame 29 is formed by the opening 25 and does not require a new structure. Further, the formation directions of the first stage flame 28 and the second stage flame 29 are orthogonal, and they do not interfere with each other in a wide range of combustion amount, and form a two stage combustion. Further, the average porous diameter and the thickness are set so that the thickness of the porous body 21 is sufficiently larger than the average porous diameter of the porous body 21 (three times or more). Therefore, quenching can prevent flashback of the flame and stabilize the flame. Further, the material of the porous body 21 is SiC having characteristics of high thermal conductivity (commonly known as cordierite and mullite 10 times or more) and high melting point (2000 ° C. or more).
The porous body efficiently radiates combustion heat to the outside, and is more effective in reducing NOx and preventing flashback by suppressing the flame temperature. In addition, the temperature distribution of the porous body 21 is made uniform, and heat such as cracks and melting is generated. Deterioration can be prevented.

(Embodiment 2) FIG. 3 is a sectional view showing a main part of a burner according to Embodiment 2 of the present invention, and FIG.
It is B sectional drawing. Claims 2, 6, 7, 8 and 9 will be described in this embodiment.

3 and 4, the porous body 4 having a communication hole
The first embodiment differs greatly from the first embodiment in that the first embodiment has a honeycomb structure having many passages 42. The average porous diameter of the porous body 41 is preferably 20 to 100 μm, and the thickness is preferably 0.2 to 100 μm.
1 mm. The material is preferably SiC. Reference numeral 43 denotes an outer peripheral wall of the porous body 41 having a honeycomb structure, through which gas does not pass. 44 is a casing, 45 is a porous body 4 having a honeycomb structure
1 is a holding means. Reference numeral 46 denotes an inflowing premix gas. In this embodiment, the equivalent ratio is set to 1 or less so as to perform so-called primary combustion. Reference numeral 47a denotes an inflow opening of a gas such as the premixed gas 46, and one end of the passage 42 is closed.
The inflow openings 47a are formed alternately by being closed by every other by 8a. Reference numeral 47b denotes an outflow opening. The other end of the passage 42 having the inflow opening 47a is closed by a closing body 48b, so that the outflow opening 47b is formed.
Are formed every other. 49 is a flame a formed on the surface of the porous body 41 facing the passage 42 having the outflow opening 47b, and 50 is a flame b formed at the outflow opening 47b. 51 is an ignition means.

Next, the operation and operation will be described. In this embodiment, the porous body 41 having the honeycomb structure is a burner. As compared with Example 1, the porosity of the burner is increased, the surface area per volume is significantly increased, and the pressure loss is reduced. This is effective in reducing the size of the burner. When the burner has a low combustion amount, the premixed gas 46 flowing into the passage 42 from the inflow opening 47a passes through the porous body 41 to form a flame a49. The exhaust gas after combustion is discharged from the outflow opening 47b. Here, when the flame a49 is ignited, a flame b50 is formed at the outflow opening 47b by the ignition means 51 provided near the outflow opening 47b, and thereafter, the flow rate of the premixed gas 46 is reduced to cause the flame b50 to flash back, A flame a49 is formed on the surface of the porous body 41 of all the passages 42 having the outflow openings 47b. As a result, the entire primary flame is formed in a wide area of the porous body 41, and the flame temperature is suppressed. Further, since the generation of the prompt NOx is originally small in the entire primary flame, NOx can be further reduced as compared with the first embodiment.

When the combustion amount is high, the flow rate of the premixed gas 46 increases, so that the flame a49 separates from the surface of the porous body 41,
This time, a flame b50 divided at the outflow opening 47b is formed. Here, the mixing of the fuel and the air proceeds by violent turbulence caused by the collision with the opposed premixed gas 46 after passing through the porous body 41, and thus the generation of NOx and unburned harmful substances can be suppressed. Further, since the flame form switches naturally like the flame a49 and the flame b50 according to the combustion amount,
Although it is difficult to continuously vary the amount of combustion, the turndown ratio of the amount of combustion can be increased.

Although the porous body is made of SiC in each of the above embodiments, it is not limited to this. For example, a burner can be formed by rolling a plate-shaped porous metal body into a roll shape to form a hollow tube having a circular cross section.

In Example 1, the equivalent ratio of the premixed gas was set to 1
Although the two-stage combustion method set as described above and Example 2 are described as the all-primary combustion method in which the equivalent ratio is set to 1 or less, the combustion method is not limited to these. For example, all the primary combustions can be performed by the configuration shown in the first embodiment.

In the first embodiment, a burner having four passages 21 and one passage 22 is described. However, the number of the porous bodies is not limited to this, and a part of the porous body may be non-porous. It can be replaced with a porous body.

[0042]

As described above, according to the first aspect of the present invention, when a flame is formed on the surface of the porous body, the gas such as the premixed gas passes through the porous body and faces the gas after the passage. Violent turbulence is generated by collision with gas, and the concentration of CH, CH2, and CH3 is reduced in the combustion of the hydrocarbon-based fuel, so that the generation of so-called prompt NOx can be suppressed.
Further, since a flame is formed on the surface of the porous body having a high surface area and the flame temperature is suppressed, the generation of thermal NOx can also be suppressed. In addition, the flames oppose each other, stabilizing the flame in a wide equivalent ratio range and suppressing the generation of unburned substances.In addition to the flame on the surface of the porous body, a flame is formed at the opening, so the turndown ratio of the combustion amount is increased. it can. Furthermore, compared to a conventional burner using a porous body as a combustion layer, the porosity is large, the pressure loss and the heat capacity are low, so that a high-pressure blower is not required, and stable combustion is achieved in a short time after ignition. Therefore, it can be applied to a burner in a household combustion device.

According to the second aspect of the present invention, since the porous body has a honeycomb structure, the porosity of the burner is larger than that of the first aspect of the present invention. Become. For this reason, the burner can be downsized, and N
Ox can be further reduced.

According to the third aspect of the present invention, since the thickness of the porous body is made sufficiently large with respect to the average porous diameter, flashback of the flame can be prevented by quenching.

According to the fourth and fifth aspects of the present invention, the porous body is made of a material having a high thermal conductivity and a high melting point, in particular, SiC, so that the combustion heat is efficiently radiated to the outside and low NOx is suppressed by suppressing the flame temperature. It is further effective in preventing the occurrence of flashback and flashback, and since the temperature distribution of the burner can be made uniform, thermal deterioration such as cracking and melting can be prevented.

According to the sixth aspect of the present invention, a new structure for the second stage flame is not required, and the first and second stage flames are formed in a direction perpendicular to each other. Thus, two-stage combustion can be realized, and generation of NOx can be suppressed by suppressing the flame temperature.

According to the seventh aspect of the present invention, the entire primary flame can be formed in a wide area of the porous body, the combustion temperature can be suppressed, and the generation of NOx can be further suppressed as compared with the above invention.

According to the eighth aspect of the present invention, mixing of fuel and air proceeds due to turbulence caused by collision with the opposing premixed gas after passing through the porous body and generation of NOx and unburned harmful substances. Can be suppressed.

According to the ninth aspect of the present invention, when the combustion amount is low, the flow rate of the premixed gas is small, and a flame is formed on the surface of the porous body. Since a flame is formed at the opening away from the surface of the porous body, it is difficult to continuously vary the amount of combustion, but the turndown ratio can be increased.

According to the tenth aspect of the present invention, even if there are a large number of passages in which a flame is to be formed as in the second aspect, after the flame is ignited at the burner opening, the flow rate of the premixed gas is reduced to move the flame upstream. And all the passages can be ignited.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a burner according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view showing a burner according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along the line BB of FIG. 1;

FIG. 5 is a sectional view showing a conventional burner.

[Explanation of symbols]

 21, 41 Porous body 22, 42 Passage 25 Opening 47a Inflow opening 47b Outflow opening 48a, 48b Closure body 51 Ignition means

Claims (10)

[Claims] 1. A tubular structure having a passage having a polygonal or circular cross section having a porous body as a side surface, wherein gas flows in from an outer side surface of the porous body, passes through the porous body, and faces the passage. A burner in which a flame is formed on at least one of the surface of the porous body and the opening of the passage. 2. A honeycomb structure having a plurality of passages partitioned by a porous body, wherein one end of each of the passages is closed by a closing body, and alternately formed with an inflow opening of a gas. A gas outflow opening formed alternately by closing the other end of the passage having the inflow opening with a closing body, and allowing the gas flowing from the inflow opening to pass through the porous body. And a burner that flows out of the outflow opening through the adjacent passage and at least one of the outflow opening and the porous body surface facing the passage having the outflow opening. 3. The burner according to claim 1, wherein the thickness of the porous body is at least three times the average porous diameter of the porous body. 4. The burner according to claim 1, wherein the porous body is made of a material having a high thermal conductivity and a high melting point. 5. The burner according to claim 4, wherein the porous body is made of carborundum. 6. A gas passing through a porous body is a premixed gas having an equivalent ratio of 1 or more, forms a first-stage flame on the surface of the porous body, and forms a second-stage flame at an opening by secondary air. The burner according to claim 1, wherein the burner is formed. 7. The burner according to claim 1, wherein the gas passing through the porous body is a premixed gas having an equivalent ratio of 1 or less, and a flame is formed on the surface of the porous body. 8. The burner according to claim 1, wherein the gas passing through the porous body is a premixed gas having an equivalent ratio of 1 or less, and a flame is formed at the opening. 9. The burner according to claim 7, wherein a flame is formed on the surface of the porous body when the combustion amount is low, and a flame is formed at the opening when the combustion amount is high. 10. A flame is formed at an opening by an ignition means provided in the vicinity of the opening, and thereafter, the flow rate of the premixed gas is reduced to form a flame on the surface of the porous body.
Burner described.