JP2002303406A - High speed jet type diffusion combustion type burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high speed jet type diffusion combustion type burner to uniform a furnace temperature and reduce a NOx generation amount through stable combustion. SOLUTION: The high speed jet type diffusion combustion type burner comprises burner tile 12 where a primary air flow passage 14 and a secondary air flow passage 16 are formed with a given distance therebetween; wind box 18 mounted on the rear end part of the burner tile 12 and provided at an internal part with a secondary air feed pipe 26; a fuel feed pipe 28 situated in the wind box 18 and having a tip part protruding in the primary air flow passage 14; and a flame holding member 30 situated at the tip part of the fuel feed pipe 28. A direction of fuel injected through the fuel feed pipe 28 is or in parallel with inclined inwardly to a central axis 16a of a secondary air flow passage 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner which suppresses NOx and makes the furnace temperature uniform by slow mixing of fuel and combustion air.

[0002]

2. Description of the Related Art Conventionally, as a technique for suppressing NOx and making the temperature distribution in a furnace uniform, for example, as shown in FIG. 4, a burner section 51 having a fuel supply pipe 42 and a combustion air flow path 43 is provided. A regenerative direct fire burner 41 comprising a heat storage chamber 52 containing a heat storage body 52 a is provided on the furnace wall 40, and the fuel 46 and the combustion air 48 are separated from the fuel supply pipe 42 and the combustion air supply port 44. No. 30522262 discloses a low NOx combustion method for slowly burning by jetting into a furnace 50.
No. 6,086,045.

In this low NOx combustion method, the injection shaft 47 of the fuel 46 is set at a predetermined angle α (5
４５45 °), and the ejection speed of the fuel 46 is set to 60
m / sec or more, and the main streams of the combustion air 48 and the fuel 46 at a high temperature of 700 ° C. or more are jetted into the furnace 50 so that they do not overlap each other, and the mixing of the fuel 46 and the combustion air 48 is suppressed. This is a combustion method in which NOx is suppressed by maintaining a slow combustion state by self-recirculating the exhaust gas in the furnace into the respective jet flows of the fuel 46 and the combustion air 48.

[0004]

However, in the above-mentioned combustion method, before the fuel 46 and the combustion air 48 are directly mixed, the exhaust gas in the furnace is self-recirculated by the momentum of each of the fluids, so that the furnace internal space is recirculated. Burns slowly. In other words, the combustion gas intervening in the furnace space is a mixed gas composed of unreacted fuel, combustion air before contributing to combustion, intermediate products during combustion reaction, and combustion exhaust gas.
The unreacted unburned gas not only overheats the heat storage body inside the regenerative direct fire burner during the suction / exhaust operation (not shown), but also lowers the thermal efficiency. Furthermore, at a low furnace temperature of 800 ° C. or less (below the self-ignition temperature of the fuel), there is a problem that it is impossible to continue the combustion unless an auxiliary burner is provided.

[0005]

In order to solve the above-mentioned problems, a high-speed jet diffusion combustion burner according to the present invention comprises a burner tile in which a primary air passage and a secondary air passage are formed at a predetermined distance. A wind box attached to a rear end of the burner tile and having a secondary air supply pipe therein; and a fuel supply pipe provided in the wind box and having a front end protruding into the primary air flow path. And a flame holding member provided at the tip of the fuel supply pipe, and the direction of fuel ejection from the fuel supply pipe is inclined parallel or inward with respect to the center axis of the secondary air flow path. It is characterized by having.

The high-speed jet diffusion combustion burner according to the present invention comprises:
The distance between the central axes of the primary air flow path and the secondary air flow path is set to 2.0 to 3.0 times the diameter of the secondary air flow path, and the fuel ejection direction is the secondary air flow. The angle formed with respect to the center axis of the flow path may be 0 to 10 degrees.

Further, the high-speed jet diffusion combustion burner of the present invention may include an adjusting means for adjusting the primary air flow rate in the primary air flow path to 1/5 to 1/2 of a required combustion air flow rate. .

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a high-speed jet diffusion combustion burner 10 of the present embodiment.
The burner 10 is installed on the furnace wall 2, and generally includes a burner tile 12 in which a primary air flow path (also serving as a combustion chamber) 14 and a secondary air flow path 16 are formed at a predetermined distance, and a burner tile 12 behind the burner tile 12. A wind box 18 attached to an end and having a secondary air supply pipe 26 therein; and a fuel provided in the wind box 18 and having a tip protruding into a primary air flow path (also serving as a combustion chamber) 14. It comprises a supply pipe 28 and a plurality of flame holding members 30 provided at the tip of the fuel supply pipe 28.

The upper portion of the wind box 18 communicates with a combustion air supply port 22 through a regulating valve 20 (hereinafter, referred to as a regulating valve 20) for regulating a ratio between primary air and secondary air.
The opening of the regulating valve 20 is adjusted by the control motor 24, thereby controlling the distribution ratio of the combustion air to the primary air and the secondary air. For example, when the furnace temperature is lower than the self-ignition temperature of the fuel (for example, 800 ° C.), the distribution ratio is adjusted to 50:50, and when the furnace temperature is higher than the self-ignition temperature of the fuel, the distribution ratio is adjusted to 20:80. . In addition, the control motor 2 is supplied from a furnace temperature controller (not shown).
4, the distribution ratio may be automatically adjusted by transmitting an opening signal.

A distal end of a secondary air supply pipe 26 branched from between the combustion air supply port 22 and the regulating valve 20 is connected to the secondary air flow path 16 of the burner tile 12.

The fuel supply pipe 28 has a leading end protruding into the primary air flow path (also serving as a combustion chamber) 14 of the burner tile 12. The ejection speed of the fuel is appropriately set for each type of fuel. For example, 50 m / sec for LPG-based fuel gas, which is an example of fuel, and 80 m / sec for LNG-based fuel gas.
/ Sec, 120 g / sec for by-product gases such as COG.

A flame-holding member 30 is fixed to the outer periphery of the front end of the fuel supply pipe 28 located in the primary air flow path 14. The flame holding member 30 includes a swirling blade, a stabilizer, and the like, and has a function of vortexing the primary air ejected from the primary air flow path 14.

As shown in FIG. 2, a fuel outlet hole 29 is formed at the tip of the fuel supply pipe 28. Fuel outlet 2
The central axis 29 a of the fuel supply pipe 9, that is, the direction in which the fuel is ejected is inclined by a predetermined angle α with respect to the central axis 28 a of the fuel supply pipe 28. The central axis 28a of the fuel supply pipe 28 and the central axis 14a of the primary air flow path 14 are on the same axis. Therefore, as shown in FIG. 1, the direction in which fuel is ejected from the fuel supply pipe 28 is inclined at a predetermined angle α inward with respect to the central axis 16 a of the secondary air flow path 16.

The reason for limiting the numerical values of the high-speed jet diffusion combustion burner 10 having the above-described configuration will be described below. Central axes 14a, 16a of the primary air passage 14 and the secondary air passage 16
The distance L between 2.0 and 2.0 of the diameter d of the secondary air flow path 16.
The reason for increasing the ratio to 3.0 times is that if the ratio is less than 2.0 times, the fuel and the combustion air (primary air and secondary air) rapidly mix before entraining the exhaust gas in the furnace near the burner.
If the amount of x generation increases remarkably, and if it exceeds 3.0 times, the fuel and the combustion air are hardly mixed in the furnace similarly to the problem in the low NOx combustion method of the prior art described above. Therefore, the combustion becomes unstable, and unburned components such as CO increase.

When the inclination angle α of the fuel ejection direction is
The reason for setting it to 0 degrees is that if it is formed inward of 10 degrees, the fuel and the combustion air mix rapidly before entraining the exhaust gas in the furnace near the burner, so that the amount of generated NOx increases remarkably. On the other hand, when the temperature exceeds 0 degree, as in the above-described problem of the low NOx combustion method of the prior art, the fuel and the combustion air become difficult to mix in the furnace, so that combustion becomes unstable and CO This is because the unburned components such as are increased. Note that the inclination angle of the fuel ejection direction of 0 degree means that the ejection direction of the fuel is parallel to the central axis 16a of the secondary air flow path 16, and that the inclination angle exceeding 0 degree means that the fuel ejection direction is This means that the direction is inclined outward with respect to the center axis 16a of the secondary air flow path 16.

The primary air flow rate is set to one of the required combustion air flow rates.
The reason why the temperature can be adjusted to ５〜 to １ ／ is that, from the viewpoint of suppressing NOx and making the temperature distribution in the furnace uniform, the primary air and the secondary air are not separated when the furnace is started and when the temperature in the furnace reaches a predetermined temperature. This is because the distribution ratio of the secondary air is different. For example, at a low furnace temperature of 800 ° C. or lower (below the self-ignition temperature of the fuel gas), the primary air flow rate is adjusted to の of the required combustion air flow rate. Adjust to 1/5 of the air flow. When adjusting the temperature distribution in the furnace, if it is desired to increase the temperature near the burner, for example, the distribution ratio may be set to 40:60 and the primary air flow rate may be increased to promote combustion near the burner. To increase the temperature far from the burner, for example, the distribution ratio is set to 2
At 0:80, the primary air flow rate may be reduced to increase the secondary air ejection momentum, that is, the secondary air flow rate may be increased to allow the combustion gas to reach a distant place.

Next, a description will be given of a combustion operation of the high-speed jet diffusion combustion burner 10, that is, an operation method from a low furnace temperature to a predetermined furnace temperature. For example, 13A city gas (hereinafter, referred to as fuel gas), which is an example of fuel, is supplied to a fuel supply pipe 28, and a fuel ejection hole 29 at the tip thereof.
Thus, the air is ejected in a direction inclined, for example, three degrees inward with respect to the center axis 16a of the secondary air flow path 16.

The combustion air is supplied from the combustion air supply port 22, and the distribution ratio between the primary air and the secondary air is adjusted by the regulating valve 20 to 50:50. That is, the primary air adjusted to 所 要 of the required combustion air flow rate flows from the wind box 18 to the primary air flow path 14, is swirled by the flame stabilizing member 30, and is ejected from the fuel supply pipe 28. The gas flows out so as to cover the periphery of the gas, and is ignited by ignition means such as a pilot burner (not shown), and then stable combustion is continued. At this time, for example, the primary air is ejected into the furnace from the primary air passage 14 while being gradually attracted to the fuel gas ejected at 80 m / sec. Very low diffusion. As a result, the primary combustion becomes local, and as a result, many unburned portions remain in the primary combustion flame ejected from the primary air flow path 14 into the furnace, and the carbon component thermally decomposed therein contains the flame. Will be improved.

The primary combustion flame ejected from the primary air passage 14 reacts with the secondary air ejected from the secondary air passage 16 to perform secondary combustion. When the furnace temperature reaches a predetermined temperature, for example, 800 ° C., the adjusting valve 20 adjusts the distribution ratio between the primary air and the secondary air to 20:80. That is, since the primary air is reduced to 1/5 of the required combustion air flow rate and the ratio of the secondary air is increased, the ejection speed of the secondary air is 100 m / s.
ec or more. The secondary air reacts while contacting each other after the primary combustion flame and the secondary air sufficiently entrain the exhaust gas in the furnace while stirring the atmosphere in the furnace.
As a result, the secondary combustion becomes slow, the volume of the flame itself increases, and the radiant intensity from the flame increases. As a result, uniform combustion with a small temperature gradient and a small concentration gradient can be formed, and the temperature distribution in the furnace can be improved. And the amount of NOx generated can be significantly reduced. The term "small concentration gradient" refers to a state in which oxygen, exhaust gas, and unreacted fuel are present in the flame at a constant partial pressure ratio.

In the high-speed jet diffusion combustion burner 10 of the present embodiment, the direction in which the fuel gas is ejected from the tip of the fuel supply pipe 28 is inclined inward with respect to the central axis 16 a of the secondary air flow path 16. Therefore, the primary combustion flame formed by the reaction between the fuel gas and the primary air reliably reacts with the secondary air ejected from the secondary air passage 16 to perform secondary combustion, thereby sooting. Stable combustion can be performed without generation of gas.

FIG. 3 shows a result of analyzing the combustion reaction when the high-speed jet diffusion combustion type burner 10 of this embodiment is burned under the following conditions by using the following software and calculation method. As is apparent from FIG.
The maximum temperature of the flame appears at a distance of m. this is,
Because the injection speed of the secondary air is as high as 100 m / sec or more, the primary combustion flame and the secondary air each sufficiently entrain the exhaust gas in the furnace while agitating the furnace atmosphere, and then contact each other to react. As a result, the secondary combustion becomes slow, the volume of the flame itself increases, and the total radiation increases in conjunction with the increase in the radiation intensity from the flame, thereby reducing the temperature gradient and the concentration gradient. It suggests that the combustion is uniform.

-Software name: Fluent 4.32-Calculation method: Finite Volume Method Flow (turbulent) k-ε model High Reynolds Standard Combustion Probability Density Function-Fuel: 13A city gas (gas temperature 30 ° C)-Combustion air temperature: 400 ° C. ・ Air ratio: m = 1.1 ・ Primary / secondary air flow distribution ratio: 20:80 ・ Combustion capacity: 1163 kw (100 × 10 ⁴ kcal / h)

In the high-speed jet diffusion burner 10 of the present embodiment, the fuel ejection direction is inclined inward with respect to the center axis 16a of the secondary air flow passage 16, but the fuel ejection direction is changed to the secondary direction. Parallel to the central axis 16a of the air flow path 16 (when the angle α is 0)
The same operation and effect can be obtained even when the degree is set to (degree).

Although the combustion air is distributed and supplied to the primary air and the secondary air by using the regulating valve 20, the primary air flow path 14 and the secondary air flow path 16 are respectively provided through flow control valves. A primary air supply pipe and a secondary air supply pipe connected to each other may be provided, and the respective flow rates of the primary air and the secondary air may be set by adjusting the respective flow control valves.

[0025]

In the high-speed jet diffusion combustion burner of the present invention, the direction in which fuel is ejected from the tip of the fuel supply pipe located in the primary air flow path is relative to the center axis of the secondary air flow path. Because it is inclined in parallel or inward, the primary combustion flame formed by the reaction between the fuel and the primary air and the secondary air ejected from the secondary air flow path surely react to perform secondary combustion. Thus, stable combustion can be performed without generating soot.

Further, since the primary air flow path and the secondary air flow path are formed at a predetermined distance, the primary flame and the secondary air do not react rapidly, and the primary combustion flame and the secondary air flow do not. Since each of them reacts by contacting each other after the exhaust gas in the furnace is sufficiently involved, the secondary combustion becomes slow, the volume of the flame itself increases, and the radiation intensity increases.
As a result, uniform combustion with a small temperature gradient and a small concentration gradient can be formed, and the temperature distribution in the furnace can be made uniform and the amount of NOx generated can be significantly reduced.

Further, the primary air flowing so as to cover the outer peripheral surface of the jet flow of the fuel is ejected from the primary air passage while being gradually attracted by the fuel, so that the mutual diffusion at the contact surface between the primary air and the fuel is reduced. Very few. As a result, the primary combustion becomes local, and as a result, many unburned portions remain in the primary combustion flame ejected into the furnace from the primary air flow path (also serving as the combustion chamber), and the primary combustion flame is decomposed therein. The carbon component improves the brightness of the flame and increases the radiation intensity from the flame.

When the furnace temperature is equal to or lower than the self-ignition temperature of the fuel, the primary air flow rate is set to １ ／ of the required combustion air flow rate.
If it is adjusted to, the stable combustion can be continued by the vortex of the primary air formed by the flame holding member without providing the auxiliary burner.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a high-speed jet diffusion combustion burner.

FIG. 2 is an enlarged cross-sectional view of a tip portion of a fuel supply pipe.

FIG. 3 is an analysis diagram of a combustion state.

FIG. 4 is a view for explaining an example of a conventional low NOx combustion method.

[Explanation of symbols]

10 high-speed jet diffusion combustion burner, 12 burner tile, 14 primary air flow path, 16 secondary air flow path, 18
Wind box, 20: regulating valve for adjusting the ratio of primary air and secondary air, 22: combustion air supply port, 24: control motor, 26: secondary air supply pipe, 28: fuel supply pipe, 2
9: fuel ejection hole, 30: flame holding member.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Susumu Takasaki 2-4-7 Kyomachibori, Nishi-ku, Osaka-shi, Osaka F-term in Chugai Furnace Industry Co., Ltd. (Reference) 3K017 CA06 CB02 3K019 AA06 BA02 BA04 BB01 3K065 TA01 TB01 TB09 TE01 TE09 TH06

Claims (3)

[Claims] A burner tile having a primary air flow path and a secondary air flow path formed at a predetermined distance, and a wind box attached to a rear end of the burner tile and having a secondary air supply pipe therein. A fuel supply pipe provided in the wind box and having a leading end projecting into the primary air flow path; and a flame holding member provided at a leading end of the fuel supply pipe. A high-speed jet diffusion combustion burner, characterized in that the direction in which fuel is injected from the fuel cell is inclined parallel or inward with respect to the center axis of the secondary air flow path. 2. A distance between central axes of the primary air flow path and the secondary air flow path is set to a value of 2.0 to a diameter of the secondary air flow path.
2. The high-speed jet diffusion combustion according to claim 1, wherein the fuel injection direction is 3.0 times, and an angle between the fuel injection direction and a central axis of the secondary air flow path is 0 to 10 degrees. Expression burner. 3. The high-speed device according to claim 1, further comprising an adjusting unit that adjusts a primary air flow rate in the primary air flow path to ５〜 to の of a required combustion air flow rate. Jet diffusion burner.