JP3250116B2 - Combustion device using gas fuel - 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 device using a commercial or industrial gas fuel, and more particularly to a gas fuel capable of achieving stable combustion over a wide range even when the fuel load is significantly changed. It relates to the combustion device used.

[0002]

2. Description of the Related Art In recent years, demand for coal-fired boilers has been rapidly increasing due to instability of oil fuel prices. Coal-fired boilers contain ash and sulfur in the fuel,
After that, large-scale equipment is required for processing, and it is difficult to construct such a power generation facility around a large city due to environmental problems.

[0003] 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. By the way, although such a clean gas-fired boiler is used, gas fuel has good flammability, but easily causes pressure pulsation in the furnace (hereinafter referred to as combustion oscillation), and heat transfer tubes and TVs in the furnace.
There are drawbacks such as cameras and other structures that are directly attached to the boiler furnace and that can easily damage the equipment.

[0004] The combustion oscillation phenomenon is generally caused by (1) a case in which the heating rate distribution inside the furnace is localized near the furnace wall (fuel burning speed is high and burns out near the burner outlet) or (2) flames are generated. It is said that it is likely to occur when it is unstable and constantly fluctuates (adhering to the flame stabilizer or repeating the phenomenon of blowing off). Therefore, the conventional combustion vibration suppression is effective in improving the stability of the flame of the gas burner and suppressing the rapid combustion (slow combustion: lengthening the flame), and has responded by changing the burner structure.

[0005] In addition, even when the instability of the flame is not a direct cause (for example, when the gap between the air flow velocity and the fuel injection velocity is large, the mixture is rapidly mixed, and a high heat generation area exists near the burner), the combustion oscillation also occurs. Easy to induce. Normal combustion vibration is likely to occur when a boiler is newly installed or during a test run after periodic inspection.In each case, since the operation is started immediately, the time given to these combustion adjustments is small, and therefore the combustion vibration phenomenon occurs once In order to find the cause in a short period of time and to take countermeasures, a lot of manpower was required.

In terms of the annual average output of a newly installed boiler in Japan, the output was 500 MW / can in 1975, but it has increased to 600 MW / can in 1989 and is increasing year by year. For example, in a boiler having a power generation capacity of 600 MW, 24 or more burners are installed, and it is difficult to adjust the combustion state of each burner in a short time.

[0007] Since the combustion vibration is an air column resonance phenomenon with the furnace, even a small pressure pulsation may accumulate energy and develop into large furnace vibration. Even if one of the 24 burners is the cause of the vibration, it can be a sufficient vibration source to induce combustion vibration. Therefore, it is necessary to develop a reliable burner that has a stable combustion range and does not cause vibration even if the burner adjustment is somewhat crude.

FIG. 4 is a sectional view of a main portion showing the principle of flame stabilization of a conventional gas burner, and shows a basic flow around the burner relating to ignition flame holding. Gas fuel is gas element 4
02 is divided into a main fuel 403 and an auxiliary fuel 404, and as a result, a main fuel flame 405 is formed. The auxiliary fuel 404 is blown into the downstream side of the flame stabilizer (impeller) 401, so that an auxiliary fuel flame 406 is formed in a circulation region thereof. Main fuel flame 4
Numeral 05 can be stably ignited by radiant heat from the auxiliary fuel flame 406.

FIG. 7 shows a sectional view of a conventional gas burner structure. The flow rate of the air supplied to each burner stage is adjusted by a damper provided at the entrance of the wind box. After that, it is sent to each burner, turned, and then supplied into the furnace. That is, the combustion air is divided into three flow paths in the radial direction from the center of the burner and supplied to the furnace as primary air 114, secondary air 113, and tertiary air 112. The secondary air 113 is swirled by an axial swirler (swirl vane) 71, and the tertiary air 112 is swirled.
Is turned by the register 72. Due to the swirling effect of the combustion air, a large circulation region is formed behind the burner, which greatly contributes to the ignition stability of the gas fuel.

[0010]

FIG. 5 describes the mechanism of flame instability of a conventional gas burner. FIG.
(A) shows a state in which the main fuel 403 and the sub fuel 404 are ejected from the gas element 402 into the furnace. The main fuel flame 405 and the auxiliary fuel flame 406 are formed at a position slightly away from the burner, that is, in a lifted state. The high-temperature gas from the auxiliary fuel flame 406 is supplied to the impeller 10
1 is returned to the rear of the impeller 101 by the circulation of the gas inside the recirculation region 501 formed behind the first impeller 101, and FIG.
As shown in (2), the auxiliary fuel flame 406 is attached to the flame stabilizer 101. Further, the main fuel 403 is ignited from the vicinity of the element by the radiant heat from the sub-fuel flame 406, and both the main fuel 403 and the sub-fuel 404 are ignited as shown in FIG. In this state, the O ₂ partial pressure inside the impeller 101 decreases, and the auxiliary fuel flame 406 lifts. FIG. 5D shows this state. When the flame lifts, O ₂ is also replenished inside the impeller 101, and FIG.
It returns to the state of (a). Therefore, there is a problem that the flame repeats a periodic change and cannot suppress the combustion oscillation.

One of the causes of the combustion oscillation is the instability of the flame as described above. The flame instability phenomenon is that even if the flame is stable during normal combustion, if the flame blows off due to some disturbance, for example, a change in the flow rate of combustion air, the heat rate near the burner changes due to the effect, and the inside of the furnace Pressure changes.
One of the causes of such flame instability is turbulence caused by a speed difference between fuel and air. It has been found that rapid mixing contributes to improving flammability, but has a large effect on flame fluctuations and fluctuations.

An object of the present invention is to provide a combustion apparatus using gaseous fuel in which the flame is stabilized even when the combustion conditions such as the flow rate of combustion air change.

[0013]

In order to achieve the above object, a flame stabilizer (impeller) always provided at the center of the burner so that the flame is stabilized even when combustion conditions such as the flow rate of combustion air change. A nozzle for injecting auxiliary fuel is installed near the flame stabilizer so that the fuel can flow stably.

That is, according to the present invention, gas fuel is injected into a furnace.
A gas element to be discharged, and burning the gas fuel
Provide a central flow path for supplying combustion air and outside
Flow path and a front end in the central flow path inside the furnace.
A combustion device having a flame stabilizer provided as
Place the gas element in the outer channel and the central channel.
And the gas fuel is provided in the outer flow path.
Spouts from the furnace into the furnace and is installed in the central channel
From the gas element to the upstream side of the flame stabilizer.
A combustion device using gaseous fuel,
It is composed .

Further, as a combustion device using gas fuel,
A gas element for injecting gas fuel into the furnace;
Central flow to supply combustion air to burn gaseous fuel
Channel and a channel provided outside thereof, and the central portion channel
With a flame stabilizer provided at the tip of the inside facing the furnace
In the combustion device, the gas element may be connected to the outer passage.
Inside and in the central channel, respectively, and the gas fuel
Spouts into the furnace from the gas element provided in the outer channel
The main fuel flame is formed by the
From the element to the upstream side of the flame stabilizer
To be supplied to the downstream side as a premixed state with
Combustion device using gas fuel characterized by the following
It is.

[0016]

[Function] Combustion oscillation is a furnace column resonance phenomenon in a furnace. Pressure pulsations inside the furnace affect the amount of fuel and combustion air supplied to the burner, causing the heat rate to change over time, and a feedback loop between them. In many cases. FIG. 3 shows a simple block diagram of this mechanism. It can be seen that the pressure fluctuation and the heat generation rate fluctuation influence each other to form a feedback loop.
In order to suppress combustion oscillation, this pressure fluctuation, heat rate fluctuation,
It suffices to break one of the feedback loops. The present invention improves the ignition flame holding property of the gas burner,
The purpose is to suppress the change in the heat generation rate.

That is, according to the present invention, as one means of flame stabilization, the main fuel and the auxiliary fuel are supplied by separate elements, and an element for the auxiliary fuel is arranged near the impeller so that the auxiliary fuel is supplied to the primary air for combustion. And in a premixed state. In addition, in order to stabilize the heat generation rate near the impeller with time, sufficient mixing time with the air of the auxiliary fuel is taken to make the local air ratio uniform .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. First, the overall structure will be outlined with reference to FIG. FIG. 6 shows a system diagram of the gas combustion air supply device. Liquefied natural gas (LNG), which is the main fuel, is sent from the LNG storage tank 61 at the receiving terminal to the thermal power plant via a pipeline. The gas is gasified by a vaporizer (vaporizer) 62 in the power plant, and the pressure is adjusted by a flow control valve 63, and then supplied to each burner. Normally, the gas pressure at the burner inlet is set in the range of 1 atg to 3 atg at the time of maximum load, but there is no particular pressure regulation value. However, from the viewpoint of suppressing combustion oscillation, it is preferable to increase the burner inlet pressure as high as possible so that the pressure pulsation in the furnace is not easily fed back to the fuel side. However, if the pressure exceeds 1 atg, the gas flow velocity reaches the sonic velocity at the nozzle outlet, and it is unlikely that the pressure pulsation of the furnace directly affects the pressure fluctuation of the fuel. On the other hand, after the combustion air is pressurized by an FDF (indentation ventilator) 64, the temperature is raised to about 330 ° C. by an air preheater 66, and then a wind box which is a supply duct of combustion air provided at each stage of the furnace is provided. 65.

FIG. 1 is a sectional view of a combustion apparatus using gas fuel according to the present invention. The gas fuel is supplied from the gas fuel supply header 110 by being divided into a main fuel 107 and an auxiliary fuel 108. Of these, the auxiliary fuel 108 is the impeller 101
Upstream of the impeller 101 to create a premixed gas inside the
Fuel supply element 106 in the primary air flow path on the side
Injected from. On the other hand, the main fuel 107 is injected from the main fuel supply element 103. The combustion air for burning the gas fuel includes the primary air 114, the secondary air 1
13, the primary air 114 is removed from the air flow path divided into three parts, that is, the primary air 114, and the swirl is supplied to the furnace 102. The swirling of the secondary air 113 and the tertiary air 112 is performed by adjusting the opening of the secondary air register 105 and the tertiary air register 104. These swirls create a large recirculation zone, so that the flame ignites stably.

The fuel distribution ratio between the main fuel 107 and the auxiliary fuel 108 is set to 3: 1 or more so that heat is not generated so much near the impeller 101. The primary air amount adjusting damper 109 is changed so that the primary air flow amount for premixing the primary air 114 is proportional to the fuel flow amount of the auxiliary fuel 108. It should be noted that the main fuel 107 is wrapped with an inert gas having a low O ₂ concentration so as not to generate heat near the burner. This inert gas is obtained by recirculating the furnace outlet gas. The supply method is as follows: a part of the exhaust gas pressurized by the recirculation fan is supplied to the exhaust gas supply header 1.
11 and supplied into the furnace through an exhaust gas passage 116 having a cylindrical shape. FIG. 2 shows a plan sectional view of FIG. In FIG. 2, the case where the number of fuel injection holes of the main fuel supply element 103 is one is introduced, but there may be a plurality of cases. FIG. 8 shows the structure of the main fuel supply element 103. This is the case of a single-hole nozzle. In the case of a double-hole nozzle, a plurality of injection holes are formed in the nozzle end face 82.

FIG. 9 is a structural view of the auxiliary fuel supply element 106. Here, the auxiliary fuel 108 and the primary air 1
In order to maintain a good mixture with the secondary fuel injection holes 91,
Are opened so as to be injected in a direction perpendicular to the flow direction of the primary air 114. Now, in order to adjust the local air ratio behind the impeller 101, an optical fiber 117 is inserted into the impeller 101, and this impeller 1
01 rearward in the flame of OH, CH, and detecting the emission intensity of the radical, such as C _2, to obtain the information of the heating rate and air ratio. Based on this information, the control unit 119 adjusts and suppresses the burner local air ratio with the primary air flow rate. Here, the local air ratio of the auxiliary fuel is preferably maintained at 0.8 or less or 1.2 or more. As described above, these measurement and analysis are performed by the control unit 119 which is a heat rate / air ratio measurement / evaluation apparatus provided outside the burner connected to the optical fiber 117.
The opening degree of the primary air flow adjustment damper 109 is changed. This device is a primary air flow adjustment damper 1
As in 09, no adjustment is required during normal operation, and the adjustment is performed during boiler test operation and after periodic inspection. Therefore, the optical fiber 117 has a structure that can be easily attached and detached, and is detached during normal operation.

FIGS. 10 to 13 show other embodiments. FIG. 10 shows an example in which the main fuel supply element 103 is inserted into the flow path of the tertiary air 112 for combustion. Note that FIG.
FIG. 11 is a front view of FIG. 10. In this structure, since the gas element of the main fuel 107 is inserted into the flow path of the tertiary air 112 for combustion, the air flow path width of each of the primary air 114, the secondary air 113, and the tertiary air 112 is sufficiently set. The structure is basically similar to the existing gas burner structure. Therefore, there is an advantage that the existing burner can be easily modified.

FIG. 12 shows the effect of injecting the auxiliary fuel 108 in the opposite direction to the primary air 114 to promote the mixing of the auxiliary fuel 108 and the primary air 114. In addition,
FIG. 13 shows a front view of the burner shown in FIG.

[0024]

According to the present invention , the outside of the central flow path is provided.
The main fuel from the gas element provided in the flow path is injected into the furnace.
From the gas element installed in the central flow path
The source was injected to the upstream side of the flame stabilizer,
The stability of the burner
In addition, the furnace design becomes easier. Furthermore, from the central channel
The main fuel from the gas element provided in the outer channel is
From the gas element provided in the central channel
Pre-mixed with air upstream of the flame stabilizer,
The auxiliary fuel is supplied to the flame stabilizer,
Allows sufficient time for mixing fuel and air,
The heat generation rate in the vicinity of the vessel can be stabilized over time.

[Brief description of the drawings]

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

FIG. 2 is a front view of FIG.

FIG. 3 is an explanatory view showing a mechanism of combustion oscillation.

FIG. 4 is a sectional view of a main part showing the principle of flame stabilization of a conventional gas burner.

5 (a) to 5 (d) are cross-sectional views showing a conventional flame instability phenomenon mechanism of a conventional example.

FIG. 6 is a schematic configuration diagram showing a combustion system of a gas-fired boiler.

FIG. 7 is a sectional view showing the structure of a conventional burner.

8 shows a main fuel supply element of the combustion device according to the present invention, wherein (a) is a side view, (b) is a plan view, and (c) is a front view.

FIG. 9 is a side view showing an auxiliary fuel supply element according to the present invention.

FIG. 10 is a cross-sectional view illustrating another embodiment of the present invention, in which a main fuel supply element is inserted into a tertiary air flow path.

FIG. 11 is a front view of FIG. 10;

FIG. 12 is a cross-sectional view showing another embodiment of the present invention, in which the method of supplying the auxiliary fuel is changed.

FIG. 13 is a front view of FIG.

[Explanation of symbols]

 Reference Signs List 101 flame stabilizer (impeller) 102 furnace 103 main fuel supply element 104 tertiary air register 105 secondary air register 106 auxiliary fuel supply element 107 main fuel 108 auxiliary fuel 109 primary air amount adjustment damper 112 tertiary air 113 secondary air 114 Primary air 115 Exhaust gas 116 Exhaust gas channel 117 Optical fiber 118 Burner throat 119 Control unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichiro Nomura 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Institute (72) Inventor Toshio Uemura 6-9 Takara-cho Kure City, Hiroshima Prefecture Babcock Date Kure Factory Co., Ltd. (56) References JP-A-1-121610 (JP, A) JP-A-57-52831 (JP, A) JP-A-6-88609 (JP, A) JP-A-1-51721 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23D 14/22 F23C 11/00

Claims (2)

(57) [Claims] A gas element for injecting gas fuel into a furnace.
And a combustion air for burning the gaseous fuel.
A flow path in the center and a flow path provided outside the flow path,
A protection provided at the end of the central flow path facing the furnace
A combustion device having a flame device;
Are provided in the outer channel and the central channel, respectively.
The gas fuel is supplied from a gas element provided in the outer passage.
Gas element blown out into the furnace and installed in the central channel
From the upstream side of the flame stabilizer.
Combustion apparatus using a gas fuel to symptoms. 2. A gas element for injecting gas fuel into a furnace.
And a combustion air for burning the gaseous fuel.
A flow path in the center and a flow path provided outside the flow path,
A protection provided at the end of the central flow path facing the furnace
A combustion device having a flame device;
Are provided in the outer channel and the central channel, respectively.
The gas fuel is supplied from a gas element provided in the outer passage.
Spouts into the furnace to form a main fuel flame,
From the gas element provided at the upstream side of the flame stabilizer
And supply it to the downstream side as premixed with the center air
A combustion device using gas fuel, characterized in that: