JP3121151B2 - Combustion burner and combustion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitrogen oxide (NOx).
More specifically, the present invention relates to a lean burn combustion burner used to suppress the generation of air, and more specifically, a pilot burner is provided around a first flame port to which a lean mixed gas whose air ratio is adjusted to be high is supplied. The present invention relates to a combustion burner having a flame holding port for supplying a mixed gas for use, and a method of using the combustion burner.

[0002]

2. Description of the Related Art As a technique for reducing nitrogen oxides (NOx) generated from a combustion gas formed in a burner, a lean combustion system and a two-stage combustion system are known. The former method burns a lean mixed gas whose air ratio is adjusted to a high value, and keeps the combustion temperature lower than the NOx generation temperature to produce NOx.
This is a method of preventing generation, and as the latter method, a light-and-dark combustion method, a light-and-dark combustion method, and the like are known. In the latter case, the combustion stage is formed in two stages, and the generation of NOx is suppressed by effects such as combustion temperature control and combustion speed control. Lean-burning, which is said to have a higher NOx reduction effect, involves burning raw gas or a mixed gas with an extremely low air ratio from the periphery of the combustion gas once burned in a lean state. It is said that a reduction in NOx is realized by a reduction in combustion temperature, slow combustion, and a NOx reduction effect. However, according to recent research, the NOx reduction effect can hardly be expected, and in general lean combustion, the leaner the more, the greater the NOx reduction ability.

[0003]

In view of the above technical flow, it is preferable to increase the air ratio of the lean burn section as high as possible in order to reduce NOx generated. However, in this case, the air ratio is significantly increased, the combustion state is difficult to stabilize, and at the same time, the air ratio is far from the stoichiometric air ratio, so that the efficiency of the heating device is reduced. In lean combustion with a high air ratio, for the purpose of stabilizing combustion, a flame holding port is provided around the flame opening for performing lean combustion to constantly burn pilot gas, and forcibly and stably ignite the lean combustion gas. With this configuration, it is possible to perform lean combustion stably. However, in this configuration, if high-concentration gas is supplied from the outer peripheral portion of the lean burn in order to increase the efficiency as a combustion device (the conventional lean burn configuration),
Conversely, a high-temperature portion is generated, and the generated NOx rises rapidly,
Combustion becomes unstable. Therefore, the object of the present invention is
An object of the present invention is to obtain a combustion burner with high efficiency as a heating device in a state where NOx generated is suppressed in a burner in which a flame holding port is provided around a lean combustion flame port.

[0004]

In order to achieve the above object, a combustion burner according to the present invention is characterized in that the combustion burner is provided with the same central axis in the first flame port and is formed in the first flame port. In the combustion zone of the lean burn flame, there is provided a second flame port for supplying a low air ratio gas whose air ratio is adjusted to be low, while the characteristic means of use of the combustion burner is that A combustion burner is used in which the air ratio is set to 1.3 or more, the air ratio of the low air ratio gas is set to 0.5 or less, and the flow ratio of both gases is set to 1/10 or less in terms of energy. The operation and effect are as follows.

[0005]

In other words, in the combustion burner of the present invention, the lean combustion flame is formed at a portion between the flame holding port and the second flame port. The lean combustion flame is stably burned in a highly lean state by constantly supplying ignition energy from a pilot formed on the outer peripheral portion. On the other hand, by supplying the low air ratio gas to the lean combustion flame formed in the periphery of the second flame opening, the supplied low air ratio gas is reduced in a state where NOx generation is small in the combustion flame and the combustion exhaust gas. Oxygen, low temperature, slow burning. Therefore, stable lean combustion and low air ratio combustion occur simultaneously, and the N2 generated from these combustions
Due to the low Ox, the burner can perform high-efficiency and low-NOx combustion over the entire burner.

[0006]

Therefore, regarding the generation of NOx, it is possible to suppress the generation of NOx by causing the lean combustion which originally does not easily generate NOx and the low air ratio combustion in a predetermined state, and the combustion state on the lean combustion side. Was able to stabilize the combustion by the flame holding port. When viewed as a burner in total, the air ratio is close to the stoichiometric air ratio, so that the efficiency of the combustion device could be maintained at a high level. As an example, an average air ratio of 1.1
Below, a NOx concentration of 30 ppm (20% or less) was realized.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a combustion burner 1 according to the present invention will be described with reference to the drawings. FIG. 1 shows a longitudinal sectional view of the combustion burner of the present application.

The combustion burner 1 according to the present invention has an outer cylinder 2 (inner diameter 140 mm) and an intermediate cylinder 3 (inner diameter 10
6 mm) and a triple tube having an inner cylinder 4 (inner diameter 10 mm), and a flame holding port 5 (opening gap 5 m)
m), which is provided with double combustion flame ports 6 and 7 on its inner side. That is, the pilot gas mixture is supplied to the flame holding port 5 from the first gas passage 8 sandwiched between the outer cylinder 2 and the intermediate cylinder 3, and the intermediate cylinder 3, A dilute mixed gas is supplied from a second gas passage 9 sandwiched between the inner cylinders 4. Further, a low air ratio gas is supplied to the second flame port 7 (opening gap 5 mm) from a third gas channel 10 formed in the inner cylinder 4. Then, in the first flame port 6, a ring-shaped lean combustion flame is formed, and the main combustion of the combustion burner 1 is performed. The axial end of the inner cylinder 4 protrudes outward by about 10 mm from the end of the intermediate cylinder 3 in the axial direction.
The end face 40 of the inner cylinder 4 is closed, and a ring-shaped flame port extending outward in the radial direction is formed in the vicinity of the end, which is the second flame port 7 described above. This second flame 7
Is an opening for supplying a low air ratio gas (raw gas or a dense gas having an air ratio of 0.5 or less) into the lean combustion flame (into the reducing flame) from this portion.

The flame-holding port 5 will be described. The end of the outer cylinder 2 forming the above-described flame-holding port 5 is located at substantially the same axial position as the end of the intermediate cylinder 3 (the intermediate cylinder 3 is 11 is slightly overhanged for extension) and the end 2
Reference numeral 0 extends in the radial direction toward the intermediate cylinder 3. The extension portion 21 is configured as a fixing screw mounting seat portion of the wire net 11 stretched over the flame holding port 5 and the first flame port 6. Here, the wire mesh 11 has a 24-mesh wire diameter of about 0.45 mm. The wire mesh 11 improves the mixing state of the diluted mixed gas supplied to the first flame port 6, makes the gas distribution uniform, It is employed for stabilizing the transfer of fire to the combustion flame formed in the flame outlet 6.

Hereinafter, the combustion operation of the combustion burner 1 will be described. As described above, the lean mixed gas (air ratio λ = 1.3 or more) flows through the first flame port 6, and the pilot mixed gas (air ratio λ = 0.5 to 0.6) flows through the flame holding port 5. hand,
The combustion is always performed, the lean mixed gas is forcibly ignited, and stable combustion is performed. As a result, the lean mixed gas can be burned in an extremely lean state, and the NOx generation amount is low (about 30 ppm). Further, raw gas or gas having an extremely low air ratio (λ = 0.5 or less) (referred to as low air ratio gas) is supplied to the second flame port 7 in the direction of the lean mixed gas sent out from the first flame port 6. Inject at a minute speed.
The injection direction of the low air ratio gas is about 60 degrees.

In the case of employing such a combustion configuration, the lean burn portion is stable even in a highly lean state of λ = 1.5 or more, because ignition energy is always supplied from a pilot formed on the outer peripheral portion. Burn. Second fire port 7
By introducing a lower air ratio gas and causing low oxygen, low temperature, and slow combustion in the combustion exhaust gas on the inner peripheral side of the first flame port 6, the average air ratio can be suppressed while suppressing generation of NOx. . As a result, the efficiency of the combustion device is improved.

Hereinafter, the effect of reducing NOx in the above-described combustion burner 1 will be described with reference to FIG. In the figure, the vertical axis indicates the amount of NOx (p
pm), and the horizontal axis is the total air-fuel ratio of the combustion burner of the present application (air-fuel ratio of the entire combustion equipment in consideration of all of the pilot mixed gas, the lean mixed gas, and the low air ratio gas).
It is shown. The figure shows the case where the secondary gas which is a low air ratio gas is not mixed (solid line), the case where the secondary gas of 2000 kcal / h is mixed (dashed line), and the case where the secondary gas is 2000 kcal / h.
The case where the secondary gas of h is mixed (dashed line) is shown respectively. Other combustion conditions are as follows. Main gas (lean combustion gas) Gas flow 80,000 kcal / h Air-fuel ratio λ = 1.6 Pilot gas Gas flow 2,200 kcal / h Air-fuel ratio λ = 0.55 Secondary gas (low air ratio gas) Gas flow 2, 000 and 6000 kca
1 / h Air-fuel ratio λ = Adjustment

As a result, by mixing secondary gas, it becomes possible to perform combustion while keeping the air-fuel ratio close to the stoichiometric ratio while suppressing NOx generation to a low level. Therefore, as a combustion burner, the air ratio as a whole is close to the stoichiometric air ratio, the efficiency as a combustion device is high, and the device can be made compact.

[Alternative Embodiment] In the above embodiment, the gas supplied to the flame holding port 5, the first flame port 6, and the second flame port 7 is
Although the air-fuel ratio is supplied while adjusting the air-fuel ratio independently, the second and third gas passages 9 and 10 may be configured as shown in FIG. That is, while the throttle portion 90 is provided in the second gas flow path 9 connected to the first flame port 6, the oxygen-containing gas for combustion which opens to the narrow portion 90 in the tube wall of the inner pipe 4 and flows to the first flame port 6. In the supply state, a low air ratio gas supply opening 100 that guides a part of the low air ratio gas in the inner pipe to the first flame port 6 may be provided. When this configuration is adopted, the gas in the third gas passage 10 is sucked out by the suction of the air in the second gas passage 9, and the mixed state of the lean mixed gas is improved.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the accompanying drawings.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a combustion burner of the present application.

FIG. 2 is a diagram showing the effect of reducing NOx in the combustion burner of the present application.

FIG. 3 is a diagram showing another configuration on the fuel supply side of the combustion burner of the present application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion burner 2 Outer cylinder 3 Intermediate cylinder 4 Inner cylinder 5 Flame holding port 6 First flame port 7 Second flame port 8 First gas flow path 9 Second gas flow path 10 Third gas flow path 90 Throttle section 100 Low air Opening for specific gas supply

Continuation of front page (56) References JP-A-53-49337 (JP, A) JP-A-4-190007 (JP, A) JP-A-6-82015 (JP, A) JP-A-6-294505 (JP, A) , A) JP-A-3-247908 (JP, A) JP-A-52-84031 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23D 14/02-14/10 F23D 14/74 F23C 11/00 329-330

Claims (4)

(57) [Claims] 1. A combustion burner (1) provided with a flame holding port (5) for supplying a pilot mixed gas around a first flame port (6) to which a lean mixed gas whose air ratio is adjusted to a high level is supplied. 1)
Wherein the air ratio is adjusted to be low within the combustion zone of the lean burn flame formed in the first flame port (6) and having the same central axis and formed in the first flame port (6). A two-stage combustion type combustion burner provided with a second flame port (7) for supplying a selected low air ratio gas. 2. A concentric cylindrical outer cylinder (2), an intermediate cylinder (3), and an inner cylinder (4), and a first gas between the outer cylinder (2) and the intermediate cylinder (3). In the cylindrical triple pipe provided with the second gas flow path (9) between the intermediate pipe (3) and the inner pipe (4), the flame holding port (5) is formed by the flow path (8). The first gas flow path (8) at the axial end of the cylindrical triple pipe;
In addition, the first flame port (6) is a ring flame port connected to the second gas flow path (9) at an axial end of the cylindrical triple tube, and the second flame port (7). 2. The combustion burner according to claim 1, wherein) is a ring-shaped flame port formed at an axial end of said inner cylinder. 3. A throttle section (90) is provided in the second gas flow path (9) connected to the first flame port (6), and the throttle section (90) is provided on a wall of the inner cylinder (4). With the opening and supply of the oxygen-containing gas for combustion to the first flame port (6), a part of the low air ratio gas in the inner cylinder (4) is supplied to the first flame port (6). Low air ratio gas supply opening (10
3. The combustion burner according to claim 2, wherein 0) is provided. 4. The air ratio of the lean mixed gas is set to 1.3 or more, the air ratio of the low air ratio gas is set to 0.5 or less, and the flow ratio of both gases is reduced to 1/1 in terms of energy. A combustion method using the combustion burner according to claim 1, set at 10 or less.