JP3538207B2 - Combustion gas burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus using a commercial or industrial gas fuel, and particularly to a combustion apparatus which ensures stable combustion even when the fuel load (burner load) is significantly changed. It concerns the device.

[0002]

2. Description of the Related Art In recent years, demand for coal-fired and gas-fired boilers has rapidly increased due to instability in the price of oil fuel.
In terms of the annual average output of newly installed boilers in Japan,
It was 500 MW / can in 1975, but it increased to 1000 MW / can in 1989, and the size is increasing year by year.

Since coal-fired boilers contain ash and sulfur in the fuel, large-scale facilities are required for the subsequent treatment, and it is difficult to construct such a power generation facility around a large city due to environmental problems. It is.

[0004] On the other hand, gas-fired boilers are expected to grow steadily in the suburbs of cities in the future because they contain such impurities in the fuel and have low pollution.

[0005] Although such a clean gas-fired boiler is used, pressure pulsation (hereinafter referred to as "combustion vibration") in the furnace is apt to occur in gas combustion, and this is caused by boiler furnaces such as heat transfer tubes and TV cameras in the furnace. There is a disadvantage that the structure directly attached to the device or the device is easily damaged.

[0006] It is generally considered that the combustion oscillation phenomenon is likely to occur when the flame in the burner is unstable and constantly fluctuates (attaching to the flame stabilizer or repeating the phenomenon of blowing off). Therefore, as a conventional method of suppressing combustion oscillation, it is effective to form a stable flame of a gas burner and to locally suppress the occurrence of rapid combustion at the burner outlet (slow combustion, ie, prolonged flame). Was changed.

In any case, the combustion oscillation is likely to occur when a boiler or a combustion device is newly installed or during a trial operation after a periodic inspection. It may take a lot of manpower to complete the adjustment.

[0008] Combustion vibration in a large-sized combustion device such as a boiler causes pressure pulsation inside the furnace to affect the supply amount of burner fuel and combustion air, causing a change in heat generation rate. A column resonance phenomenon, that is, a combustion oscillation, is caused in the entire interior.

In order to suppress combustion oscillation, this pressure fluctuation,
It is necessary to suppress mutual interference of heat rate fluctuations.

FIG. 6 is a sectional view showing the structure of a conventional gas burner. Combustion air flows along the radial direction from the center of the burner, and is divided into primary air 706, secondary air 705, and tertiary air 704.
It is divided into channels and supplied into the furnace. Of which secondary air 7
The 05 and the tertiary air 704 are swirled, and have the effect of inflating the main fuel flame 711 downstream of the burner outlet. However, the bulging of the flame zone causes a distance between the flame holding flame 712 of the auxiliary fuel at the center of the burner and the main fuel flame 711 at the periphery of the burner, and the main fuel flame 711 changes when combustion conditions such as the burner air flow rate change. Induces instability of ignition.

In the figure, reference numeral 701 denotes an impeller, 702 denotes gas fuel , 708 denotes a tertiary register, 709 denotes a secondary register, 710 denotes a primary register, 713 denotes an auxiliary fuel, and 714 denotes a secondary vane.

[0012]

For example, the power generation capacity 6
In a 00MW boiler, 24 or more burners are installed, and it is difficult to adjust the combustion state of each burner in a short time.

Since combustion vibration is a column resonance phenomenon with a furnace, even a small pressure pulsation can cause energy to be accumulated and develop into large furnace vibration. Therefore, even if one of the 24 burners causes vibration, Even so, it can be a sufficient vibration source to induce combustion vibration. Therefore, it is necessary to develop a highly reliable burner that does not cause vibration even if the burner adjustment is somewhat rough.

FIG. 3 shows a basic flow around the burner relating to the ignition flame holding. The gaseous fuel is split from the gas element 402 into a main fuel 403 and an auxiliary fuel 404, resulting in a main fuel flame 405. On the other hand, the auxiliary fuel is impeller 10
1, the recirculation region 501 becomes a high-temperature zone type of ignition, and the secondary fuel flame 406
Is formed. The main fuel flame 405 is the auxiliary fuel flame 406
Fired by heat transfer from Note that 106 in FIG.
Is the primary air.

FIG. 4 is a schematic diagram showing a flame unstable phenomenon in a conventional burner. (A) in the figure shows a state in which the main fuel 403 and the sub-fuel 404 are ejected from the gas element 402 into the furnace. Since the flame holding in the flame stabilizer (impeller) 101 is weak, the main fuel flame 405 and the auxiliary fuel flame 406 are formed at a place slightly away from the burner, that is, in a lifted state. If any pressure pulsation occurs at this time, it causes a flow velocity pulsation of the combustion air. When the flow velocity decreases, the lifted sub-fuel flame 406 is returned to the rear of the impeller 101 by the circulation of the gas inside the recirculation area 501 behind the impeller 101, and the sub-fuel flame 406 is maintained as shown in b). The fuel adheres to the flame device 101 and affects the main fuel 403, and the main fuel flame 405 also has a
02, and the main and sub fuels 403 have no lift as shown in c).

Next, when the flow velocity of the flow pulsation is high, the flame holding state of the impeller 101 returns to the state where the auxiliary fuel flame 406 has lifted. FIG. D) shows this state.
Such a periodic variation of the impeller flame holding causes a periodic variation also in the calorific value of the entire flame and induces a combustion oscillation.

That is, the mechanism of generating combustion vibration due to the instability of flame holding in the recirculation region downstream of the impeller has been described. However, if stable flame holding is possible, vibration does not occur.
As a means of stabilizing the flame holding, the contact peripheral length of the impeller forming the recirculation area with the gas is increased, the contact with the surrounding premixed auxiliary fuel gas is improved, and the maintenance around the recirculation area is performed. It is improved by stabilizing the flame.

In order to increase the contact peripheral length, there is a method of increasing the size of the impeller. However, if the burner outlet opening area is to be kept constant and the gas outlet flow velocity is to be kept constant, the inner diameter of the primary flow path must be reduced. There is a need to increase it. This causes the main fuel flame zone around the burner to expand more in the circumferential direction, and in particular, makes it difficult to propagate the flame from the flame holding part at the center of the burner to the surrounding main fuel part at low load. Become.

[0019]

SUMMARY OF THE INVENTION One of the causes of combustion oscillation is flame instability.

The flame instability phenomenon is caused by a weak flame holding state in a flame stabilizer (a downstream side of an impeller) in the center of the burner at a low load, or even if a stable flame is formed during normal combustion. Occurs when the heat generation rate near the burner changes due to external disturbance, for example, a change in the flow rate of combustion air. Even in this latter case, the main cause is that the state of flame holding in the flame holding part is weak. Therefore, even if the combustion air flow rate is disturbed, a stable flame in the flame holding section is secured, and if the fuel injection structure burns the main fuel as close to the premix burner as possible, the entire flame zone The heat generation intensity is increased, and a stable flame zone is formed that does not move even with some fluctuation, and does not develop into combustion oscillation.

Therefore, a combustion stabilizing device is provided around the outlet.
Air flow path and a plurality of fuels arranged in the air flow path
A plurality of fuel nozzles, wherein the plurality of fuel nozzles
It is located near the inner wall of the road and is gaseous upstream of the flame stabilizer.
A sub-mixture for injecting a mixture toward the inner wall of the air flow path to form a premixed air-fuel mixture
A fuel nozzle and the auxiliary fuel nozzle in the air flow path
Installed inside, parallel or circumferential to burner axis
A first main fuel nozzle for injecting gaseous fuel with
Installed inside the sub-fuel nozzle in the air flow path;
Is injected toward the primary air flow in the air flow path and
And a second main fuel nozzle forming a mixed flame
And said that you are.

[0022]

According to the present invention, a flame holding portion corresponding to the impeller is provided with one.
By installing it around the air passage for the next combustion, the auxiliary fuel blows out to the surroundings, while the main fuel blows out near the burner shaft,
The feature is that the flame holding part can be expanded without increasing the burner size. In other words, in order to obtain the same contact peripheral length in the flame holding part, the effect on the inner diameter of the burner is smaller near the inner wall than the central part of the burner cylinder, and premixing is performed by directing the main fuel to the central part of the burner. Combustion similar to a flame is enabled, and the flame stabilization is not affected by disturbance pressure pulsation. Accordingly, the gas burner does not cause combustion oscillation.

[0023]

FIG. 5 shows a fuel and air supply system diagram of a gas fired boiler. LNG, the main fuel, is stored in the LNG storage tank 6
From 01 is sent to the thermal power plant by pipeline. It is gasified by the vaporizer 602 in the power plant,
After the pressure is adjusted in step 3, the pressure is supplied to the burner. The gas pressure at the burner inlet is usually set in the range of 1 atg to 3 atg, but there is no such regulation value. From the viewpoint of suppressing combustion oscillation, in order to suppress feedback of pressure pulsation in the boiler furnace 605 to the fuel system, Higher gas pressure is desirable.
At least when the pressure is 1 atg or more, the flow velocity of the gas ejection reaches the sonic speed, the feedback of the pressure pulsation of the boiler furnace 605 is small, and it is considered that the influence on the combustion vibration is small.

On the other hand, after the combustion air is pressurized by an FDF (indentation ventilator), the temperature is raised to about 300 ° C. by an air preheater and supplied to wind boxes 604 provided at each stage of the boiler furnace 605. The air volume is adjusted by a damper at the entrance of the wind box 604, divided into three primary, secondary and tertiary flow paths inside the burner, and the secondary and tertiary are turned and sent to the boiler furnace 605. Can be However, regarding the air pressure in the wind box 604, feedback of pressure pulsation in the boiler furnace 605 is likely to occur because the pressure loss in the burner is small. Therefore, if the flame holding at the burner outlet is weak, the pulsation of the combustion air that has received the feedback leads to a change in the heat generation rate, and the possibility of developing the combustion oscillation is sufficiently considered.

FIG. 1 shows a side view of a gas fuel combustion apparatus according to an embodiment of the present invention.

At the outlet of the cylindrical tube 10 serving as a primary combustion air flow path, a flame holding projection 1 for flame holding is installed in the peripheral portion of the inner wall in a direction perpendicular to the flow. To form In order to prevent the release of the high-temperature gas and heat in the recirculation area to the secondary combustion air side and to guide the secondary swirl flow in the circumferential direction, the flame holding guard 2 is circumferentially provided. is set up.

The gas fuel is divided and supplied from the gas fuel supply header 3 into the main fuel 12 and the auxiliary fuel 11. Of these, the auxiliary fuel 11 is injected in the circumferential direction of the inner wall from the auxiliary fuel nozzle 20 near the inner wall of the burner primary air flow path to form a premixed gas upstream of the flame holding section, Forms a flame. here,
The flame holding projection 1 installed on the inner wall side has less influence on the inner diameter of the primary air cylindrical tube 10 as long as it is located on the inner wall peripheral portion, as compared with the impeller at the center of the conventional burner. A large flame stabilizer contact peripheral length can be ensured, and a sufficient air-auxiliary fuel mixture can be established to facilitate the ignition of the air-fuel mixture. It promotes the flow of fuel into the recirculation zone and creates a hot zone.

On the other hand, the main fuel 12 is also installed inside the sub-fuel gas element 13 in the primary air flow path, and has a structure in which a premixed flame can be more easily formed. Specifically, of the plurality of main fuel gas elements, a part 14 is injected from the multi-hole nozzle 21 in a direction perpendicular to the primary air flow to promote mixing with the primary air 6 to form a premixed flame. . In the remaining main fuel gas element 15, the fuel is injected from the main fuel nozzle 22 at an angle parallel to the burner axis or at an angle in the outer circumferential direction to form a diffusion flame. And operation in a wide range of loads becomes possible.

Although not shown in the figure, the primary combustion air flow path is a gas burner having a flame stabilizing protrusion installed around the inner wall of the cylindrical pipe. And at a right angle to the premixed flame, or conversely, if it has the same or some angle as the flow but the main fuel pipe forms a diffusion flame, there is no distinction between the main fuel and the auxiliary fuel, The fuel jets from the perforated nozzles of all fuel pipes can also form a premix in a direction perpendicular to the flow.

Further, in a combustion technique typified by an exhaust gas reburning gas-fired boiler, a combustion exhaust gas is mixed with combustion air, and a gas having a low oxygen partial pressure of 14% to 18% is blown to the primary flow path. Is also possible.

[0031]

The present invention relates to the basic structure of a gas burner which suppresses combustion oscillation as described above. Combustion oscillation is a phenomenon that occurs as a result of interaction not only with the burnability of the burner but also with pressure pulsation in the furnace and oscillation characteristics, and improvement with only the burner structure is not completely cut off. However, development of gas column resonance in a furnace requires a very large amount of energy, and there is no doubt that the calorific value fluctuation of the gas fuel is the energy source.

Therefore, according to the present invention, stable flame holding in a wide range of burner operating conditions such as air flow rate and air ratio,
The burner structure that enables the securing of the flame suppresses fluctuations in the amount of heat generated in a wide range of operating conditions and does not cause combustion oscillation, shortening the combustion adjustment of a gas-fired boiler, and furthermore, over a wide range of loads. An effect is brought about in that variation and the like are enabled.

In the exhaust gas reburning gas boiler technology,
In particular, in an atmosphere mixed with combustion air and having a low oxygen partial pressure, the ignitability naturally deteriorates, and the flame holding becomes unstable, resulting in low cost. Even in such a case, the burner structure according to the present invention is effective.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a combustion gas burner according to the present invention.

FIG. 2 is a front view of the gas burner.

FIG. 3 is a diagram showing a fuel injection and flame structure of a conventional gas burner.

FIG. 4 is a diagram showing a mechanism of a periodic flame instability phenomenon.

FIG. 5 is a diagram showing a combustion system diagram of a gas-fired boiler.

FIG. 6 is a view showing a cross-sectional structure of a conventional gas burner.

[Explanation of symbols]

1 flame holding protrusion 2 Flame guard 4 Tertiary air 5 Secondary air 6 Primary air 10 Cylindrical tube for primary combustion air flow path 11 Secondary fuel 12 Main fuel 13 Auxiliary fuel gas element 14,15 Main fuel gas element 20 Auxiliary fuel nozzle 21,22 Main fuel nozzle

Continuing from the front page (72) Inventor Hiromi Ikeda 3-36 Takara-cho, Kure-shi, Hiroshima Prefecture Bab Kotsuk Hitachi Ltd. Inside the Kure Research Laboratory (72) Kunio Okiura 3-36 Takara-cho Kure-shi, Hiroshima Prefecture Babkotsuk Kure Corporation In the laboratory (72) Inventor Shigeki Morita 6-9 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Factory, Babkotsuk Hitachi Ltd. (56) References JP-A-60-213719 (JP, A) JP-A-2-50011 (JP) , A) Real opening 61-63521 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23D 14/22-14/24 F23D 14/74-14/76

Claims (2)

(57) [Claims] (1) Combustion air with a flame stabilizer around the outlet
A flow path and a plurality of fuel nozzles arranged in the air flow path
With the door, the plurality of fuel nozzles is arranged near the inner wall of the air passage, before the flameholder
Premixing by injecting gas fuel in the direction of the inner wall of the air flow path
A sub-fuel nozzle for producing air, and
And parallel to the burner axis or at an angle in the circumferential direction.
A first main fuel nozzle for injecting fuel gas, and a first fuel nozzle installed inside the air flow path from the sub fuel nozzle.
Is injected toward the primary air flow in the air flow path and
And a second main fuel nozzle forming a mixed flame
A combustion gas burner. 2. A combustion air flow provided with a flame stabilizer around an outlet.
And a fuel nozzle disposed in the air flow path.
e, The fuel nozzle is It is arranged near the inner wall of the air flow path and in front of the flame stabilizer.
Premixing by injecting gas fuel in the direction of the inner wall of the air flow path
A combustion gas bar characterized by being a fuel nozzle for producing air
Huh.