JPH11132414A - Super low nox burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an interior flame holder and a bridging part from being worn out during the operation of a burner, which results in sticking of ash to these, and also to prevent the interior flame holder and the bridging part from being damaged from heat and burn during the operation shutdown of the burner, in the burner which is provided with the interior flame holder and the bridging part. SOLUTION: An outer peripheral flame holding ring 7 and an interior flame holder 8, both of which become a bluff body that is perpendicular to the pulverized coal flow in the primary passageway 1, are disposed at the outlet of a burner, so that a recirculation zone is formed at the back of the stream by the vortex of turbulent flow to involve the pulverized coal particles in. The kindling of a high temperature gas is generated by the combustion of the pulverized coal which has flown in, so as to serve to promote the ignition of the pulverized coal passing nearby. At this time, a bridging part 10 is set between the outer peripheral flame holding ring 7 and the interior flame holder 8. If the gas is ejected from a gas ejection hole at the tip of the interior flame holder 8 through the bridging part 10 and the inside of the interior flame holder 8, after introduced from a supply gas nozzle 11, the high temperature gas of 1000 deg.C or higher at the side of the outer peripheral flame holding ring positively flows in the direction of the interior flame holder 8. Thereby, a fuel combustion zone near the interior flame holder 8 is maintained in a high temperature condition stably, so as to serve to promote the ignition of fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner for combustion of pulverized solid fuel such as pulverized coal, and more particularly to a burner requiring low NOx combustion, which is suitable for burning stably at lower NOx and lower NOx. It relates to a burner for charcoal combustion.

[0002]

2. Description of the Related Art A conventional pulverized coal or other solid fuel combustion system used in a boiler includes a pulverized coal machine having a built-in classifier (hereinafter referred to as a "mill"). A combustion system for directly supplying pulverized coal having a size equal to or less than a predetermined size to a burner unit using conveying air has been put to practical use.

[0003] As a technique for reducing NOx in this pulverized coal combustion system, a two-stage combustion method is typical. The two-stage combustion method includes an external system and an internal system. The external two-stage combustion method employs an air ratio in a burner zone by all burners provided in a combustion furnace. Ratio = 1
Represents a stoichiometric equivalent) under a fuel-rich condition of 1 or less to reduce NOx generated in the combustion gas to reduce the N
In this system, Ox is formed, and for unburned fuel, air is injected from an air insertion port installed downstream of the burner zone and burned. In the internal two-stage combustion method, the secondary air or the tertiary air in the burner is swirled to ignite and burn only with the primary air (pulverized coal conveying air), and the burner jet is injected into the furnace from outside. This is a method in which mixing of secondary air or tertiary air is delayed and two-stage combustion is performed in a burner zone using individual burners, and a low NOx burner (JP-A-60-176315, JP-A-62-172105).
Gazette).

[0004] By the low NOx combustion technology of the pulverized coal burner by the combined use of the above-mentioned external and internal two-stage combustion methods, the NOx emission at the boiler outlet is about 100 to 150 ppm (fuel ratio = fixed carbon / volatile matter value). Is 2, the standard coal whose nitrogen (N) content in coal is 1.5%, and the unburned content in ash is 5
%).

[0005] However, while regulations on the amount of NOx contained in combustion exhaust gas as environmental measures have become stricter,
A low boiler outlet NOx emission concentration of 100 ppm or less is required. In addition, in Japan, where the dependence on coal imports is close to 100%, it is essential to establish a technology for stable NOx reduction combustion of pulverized coal burners regardless of coal type.

Low NOx with NOx emission of 100 ppm or less
As a countermeasure, powder solid fuel (pulverized coal) in a fuel nozzle (hereinafter sometimes referred to as a primary flow path) is aimed at further strengthening the internal two-stage combustion method in each burner section.
Method of installing an internal flame stabilizer in a direction perpendicular to the flow of a mixed fluid of a gas and a carrier gas (primary air) (Japanese Patent Laid-Open No. 8-1359)
No. 19) or a bridging portion that bridges between a flame holding ring on the outer periphery of the fuel nozzle (hereinafter, may be referred to as an outer flame holding device) and the internal flame holding device is installed to hold the fuel in the internal flame holding device. How to further enhance the flame (Japanese Patent Application No. 9-26615)
No.) is considered.

[0007] If the above-mentioned internal flame stabilizing device or bridging portion is installed in the flow of the primary air carrying pulverized coal, a high-temperature recirculation zone is formed in the subsequent flow, and the ignition and flame holding of the fuel is prevented. This promotes the expansion of the NOx reduction zone in the pulverized coal combustion zone near the burner in the furnace, thereby achieving the reduction of NOx in the combustion exhaust gas.

[0008]

In the burner structure in which the internal flame stabilizer and the bridging portion are both installed in the above-described fuel nozzle, how the negative pressure in the recirculation zone formed downstream of the internal flame stabilizer is reduced. It is important to promote the ignition and flame holding of the fuel and to expand the NOx reduction region near the burner. That is, if the negative pressure in the recirculation region becomes sufficiently large, the flow of high-temperature gas from the outer flame stabilizer to the inner flame stabilizer through the bridge portion increases, and a strong ignition flame holding is secured. This is because NOx reduction of exhaust gas is achieved.

Further, the internal flame stabilizer and the bridging portion provided for reducing the NOx of the combustion exhaust gas are in the flow of high-speed pulverized coal having a flow velocity of 20 m / s during the burner operation. There is a problem that the vessel and the bridging part are worn by the pulverized coal and ash adheres to them. In addition, in both cases when the burner is operating and when the operation is stopped, the internal flame stabilizer and the bridging portion are exposed to high temperatures due to radiant heat from the furnace at 1500 ° C. or higher. However, during the burner operation, the surface temperature of the internal flame stabilizer and the bridging part was about 8 flowing through the fuel nozzle.
The cooling effect by forced convection of the pulverized coal stream at 0 ° C. and the radiant heat shielding effect by the pulverized coal stream are about 200 to 300 ° C.

On the other hand, when the operation of the burner is stopped, the fuel nozzle (primary flow path) contains leak air due to negative pressure inside the furnace (even if there is no leak air piping,
Cooling is achieved by flowing outside air from the gap from the vicinity of the joint for absorbing the difference in thermal expansion), but the amount of leak air is not large, and the surface of the internal flame stabilizer and the bridge facing the furnace The temperature is 700-8
It is in an environment where it reaches 00 ° C and is easily burned by heat. Therefore, the internal flame stabilizer and bridging part will wear during burner operation,
There are problems such as ash adhesion, thermal burnout during operation shutdown, and ash adhesion.

Accordingly, an object of the present invention is to provide a burner having an internal flame stabilizer and a bridging portion, wherein the internal flame stabilizer and the bridging portion are worn during burner operation while reducing NOx of combustion exhaust gas. The purpose is to prevent ash from adhering to these as much as possible, and to prevent the internal flame stabilizer and the bridging portion from being thermally burned while the burner is stopped, and to prevent ash from adhering to them.

[0012]

The above object of the present invention can be attained by adopting the following constitution. That is,
Gas-solid two-phase flow consisting of solid fuel and carrier gas (pulverized coal flow)
In the burner having a primary flow path for charging the furnace with a flow path for supplying a single or a plurality of oxygen-containing gases for combustion outside the primary flow path, an outer peripheral portion of an outlet end of the primary flow path is provided. The provided outer flame stabilizer, an inner flame stabilizer provided inside the outlet end of the primary flow path, and at least one bridge between the outer flame stabilizer and the inner flame stabilizer provided between the outer flame stabilizer and the inner flame stabilizer. Two bridging parts, a gas passage for passing a gas inside the bridging part and the internal flame stabilizer, and a gas ejection hole provided in at least one of one or more bridging parts or the internal flame stabilizer. It is a low NOx burner.

As described above, a gas passage for passing a gas is provided inside the internal flame stabilizer and the bridging portion, and the air in the gas passage is provided to the gas flame outlet (FIG. 2). 16) Alternatively, the gas is ejected from the gas ejection holes (gas ejection holes 15 in FIG. 4) provided in the bridge portion.

If pulverized coal is explained as an example of the solid fuel powder, the pulverized coal conveyed by the primary air flows downstream of the external flame stabilizer (outer flame stabilizer ring 7 in FIG. 1) and the internal flame stabilizer at the burner outlet. Ignition flame holding is performed by the formed high-temperature recirculation zone, and the fuel is burned.

For example, as shown in FIG. 1, when an outer flame holding ring 7 and an inner flame stabilizer 8 which are L-shaped or U-shaped are arranged at the burner outlet with respect to the pulverized coal stream, turbulent A vortex recirculation zone 13 (see FIG. 2) is formed, entraining relatively small pulverized coal particles having a particle size of 20 μm or less,
The combustion of the pulverized coal that has flowed in becomes a high-temperature gas ignition source (high-temperature recirculation zone 13), which helps to promote the ignition of the pulverized coal passing nearby. At this time, the outer flame holding ring 7
When the bridging portion 10 is further installed at right angles to the pulverized coal flow between the inner flame stabilizer 8 and the inner flame stabilizer 8, the high-temperature gas of 1000 ° C. or more on the outer flame stabilizer ring 7 side flows toward the inner flame stabilizer 8 through the bridging portion. As a result, the fuel combustion area near the internal flame stabilizer 8 is stably maintained at a high temperature, and is useful for promoting the ignition of fuel.

At this time, when a gas such as air is blown out from the gas blowout hole (the gas blowout hole 16 in FIG. 2) provided in the internal flame stabilizer 8, the formation of the recirculation region 13 is further ensured. Further, it is desirable that the gas ejection speed from the gas ejection holes (the gas ejection holes 16 in FIG. 2) be faster than the flow rate of the pulverized coal stream.

The cross-sectional shape of the internal flame stabilizer 8 in the flow direction of the pulverized coal flow is such that its outer peripheral side has a wall surface parallel to the fuel flow direction, and its inner peripheral side has a tapered shape.
Since the outer peripheral side of the inner flame stabilizer 8 is thus cylindrical, an effect of rectifying the flow on the outer peripheral flame stabilizer ring 7 side is generated, and the ignition flame holding in the outer peripheral flame stabilizer ring 7 is further strengthened. Also, the inner peripheral side of the internal flame stabilizer 8 is tapered to gradually narrow the flow path in the flow direction of the pulverized coal stream, thereby avoiding direct impact of the pulverized coal stream at an angle to prevent wear. It has a structure. In addition, the inclination angle θ of the gas flow direction of the internal flame holding firearm
By adjusting the size of (FIG. 11), the flow rate of pulverized coal to the center of the burner can be increased, and the flow rate of pulverized coal to the outer peripheral portion can be reduced.

Further, the bridging portion 10 has a divergent shape (V-shaped cross section or U-shaped section) from the upstream side to the downstream side of the pulverized coal stream.
Shape, etc.) to prevent wear due to pulverized coal flow. Further, by increasing the surface area (projected area is the same) of the flared inclined plane of the bridging portion 10, the cooling of the inclined surface is promoted.

A gas passage 17 through which a gas (for example, air) passes is provided in both the bridging portion 10 and the internal flame holding portion 8, and a gas such as air is supplied from the gas passage 17 to the inside. A structure for discharging the gas from the gas ejection holes 16 (see FIG. 2) of the flame stabilizer 8 or a gas discharge hole 15 provided in the bridging portion
(See FIG. 4). The gas (air) entering from the bridging portion 10 is jetted toward the pulverized coal flow from the gas jet holes 16 provided in the internal flame stabilizer 8 at a plurality of gas jet holes 16 at the edge of the plane facing the furnace and in the vicinity thereof.

The gas (air) ejected from the gas ejection holes 16 accompanies the high-temperature gas in the recirculation zone 13 existing downstream of the outer flame holding ring, not only to promote the ignition of the pulverized coal, but also to recirculate it. The negative pressure in the region 13 is increased, and the differential pressure between the outer flame holding ring 7 and the inner flame stabilizer 8 is increased. Then, there is an effect that the inflow of high-temperature gas from the outer peripheral flame holding ring 7 side to the internal flame stabilizer 8 side via the bridging portion 10 is promoted. The flow rate of the gas ejected from the gas ejection holes 16 is faster than the flow rate of the pulverized coal stream,
Preferably, if it is 50 m / s or more, the entrained amount of high-temperature gas is large, and the ejected gas (air) flows through the pulverized coal stream, which is useful for igniting the pulverized coal. Increasing the gas (air) ejection speed is also effective in blowing off ash adhered to the outer flame holding ring 7 and the internal flame stabilizer 8 to prevent ash from adhering.

Further, the gas ejection holes (the gas ejection holes 1 in FIG. 2)
If the amount of gas (air) ejected from the gas ejection holes 15) of the bridging portion 10 of FIG. 6 and FIG. 4 is adjusted to be within 1 to 2% of the primary air, NO in the combustion gas due to an increase in the amount of air at the burner outlet is increased.
The increase in x concentration is suppressed.

This gas (air) is PAF (Primary Air).
A part of the air pressurized by Fan) is used, but heated gas (air) is introduced during burner operation, and unheated gas (air) is introduced when burner operation is stopped.
Heated gas (air) during burner operation is effective for ignition flame holding, and gas (air) that is not heated when burner operation is stopped
To cool the bridging part 10 and the internal flame stabilizer 8,
Helps prevent these burnouts.

Naturally, the flow of gas (air) into the internal flame stabilizer 8 and the bridging portion 10 during the operation of the burner and when the burner is stopped is controlled by the gas ejection holes 16 of the internal flame stabilizer 8.
Is also prevented from being clogged by pulverized coal or ash.

During operation of the burner of the present invention, gas is introduced from the high temperature section of the gas supply system for pulverized coal transport into the bridge section 10 or the gas introduction section flowing into the internal flame stabilizer 8 to ignite the fuel. In order to ensure the reliability and promote the combustion of the fuel, while the burner operation is stopped, the burner is supplied from the low temperature part of the gas supply system for pulverized coal transport to cool the inside of the burner. When the concentrator 19 (FIG. 10) is not inside the burner, the inside of the burner can be sufficiently cooled only by the leak air. However, when the concentrator 19 is provided, it is necessary to perform forced cooling, and the gas discharge hole 15 (FIG. 4) or Cooling gas is supplied from the gas ejection holes 16 (FIG. 2) to cool the inside of the burner.

In general, in order to guide the hot recirculating gas formed downstream of the external flame stabilizer to the center of the burner,
From the flow of the pulverized coal stream, it is necessary to sufficiently secure the pressure difference between the outer peripheral portion and the inner peripheral portion at the burner outlet. If the pressure difference between the outer and inner circumferences at the burner outlet is sufficient,
A flow from the outer peripheral portion to the inner peripheral portion occurs, and the high-temperature gas around the outer periphery of the flame stabilizer flows into the central portion of the burner, and the ignition is further improved. The distributor (the distributor 20 in FIG. 11) is installed at the end.

The distributor reduces the flow velocity in the vicinity of the outer flame holder and improves the ignitability of the pulverized coal at the outer periphery of the burner. As the difference in flow velocity between the burner outer periphery and the burner center increases, the differential pressure between the burner outer periphery and the burner center increases, and the amount of gas flowing from the burner outer periphery to the burner center increases (bridge) (Increase of action).

By setting the flow rate of the pulverized coal stream at the outer periphery of the burner to 60 to 80% of the flow rate of the pulverized coal stream at the center of the burner, when a distributor is not provided, that is, the flow rate is 100%. It was found that the NOx reduction rate in each burner zone was larger than in the case of FIG.
2).

Also, a narrow portion of the primary flow path is provided upstream of the installation portion of the internal flame stabilizer in the primary flow path, and the powder solid particles are contained in the primary flow path between the narrow portion and the internal flame stabilizer. By installing a high-temperature gas introduction pipe for introducing a gas higher in temperature than the carrier gas, the high-temperature gas gas introduced from the high-temperature gas introduction pipe flows in the primary flow path toward the center of the primary flow path. Accordingly, the flow velocity in the narrow portion into which the high-temperature gas is introduced is reduced, and the ignition and flame holding properties of the pulverized coal stream are enhanced by the same action as described above.

[0029]

Embodiments of the present invention will be described. FIG. 5 shows a combustion system diagram of a pulverized coal-fired boiler to which the burner of the present invention is applied. Coal is crushed from a coal crusher (mill) through a path (not shown) according to the load of a combustion device such as a boiler.
It is sent to 38 and crushed. The pulverized coal conveying air is pressurized by an FDF (Force Draft Fan) 31 and distributed to each of a heated air flow path 35 entering the air preheater 34 and a cold air flow path 32 not entering the air preheater 34. Then, the temperature of the heated air and the cooled air is adjusted by mixing, and
8

The air supplied to the internal flame stabilizer and the bridging section (not shown) of the pulverized coal burner section 40 of the furnace 30 of the boiler is introduced by the FDF 31, heated by the air preheater 34 and passed through the heated air flow path 35. The heated air and the cooling air passing through the cold air passage 32 that does not pass through the air preheater 34 are
Through the branch flow path 35 ′ of the heated air flow path 35 and the branch flow path 32 ′ of the cold air flow path 32, they merge at the junction where the switching valve 28 is provided. Then, it is guided to the gas supply header 12 of the burner section 40.

The mixed fluid of the pulverized coal pulverized by the mill 38 and the air for transporting the pulverized coal is transported to the pulverized coal burner 40. Air for combustion of pulverized coal enters a wind box 44 from a Force Draft Fan (FDF) 41 via a heat exchanger 34, and is conveyed to a secondary flow path and a tertiary flow path (not shown) of the burner 40.

FIG. 1A is a side sectional view of the burner section 40, and FIG. 1B is a plan view of the burner section 40 as viewed from the furnace side. A secondary flow path 2 and a tertiary flow path 3 for supplying combustion air are provided outside the primary flow path 1 through which a mixed fluid of pulverized coal and carrier air flows. A heavy oil burner 4 used at the time of starting the burner or the like is provided at the axial center of the primary flow path 1. The secondary flow path 2 is provided with a secondary air swirler 5, and the tertiary flow path 3 is provided with a tertiary air swirler 6.

An outer flame holding ring 7 is provided at the end of the outlet (tube wall) of the primary flow path 1, and an internal flame holding device 8 is provided inside the ring. A bridging portion 10 is provided between the outer flame holding ring 7 and the inner flame holder 8. In the case of the burner shown in FIG. 1, an example is shown in which four bridging portions 10 are provided radially at 90 ° intervals, but the number of bridging portions 10 and the spacing between them can be set as appropriate.

The internal flame stabilizer 8 has an annular shape when viewed from the surface facing the furnace 30 and has a burner side cross section (FIG. 1).
When viewed from (a)), the outer side of the annular shape is a cylindrical shape having a wall surface parallel to the flow direction of the fuel. To further enhance the flame holding. Further, the inner side of the annular shape of the internal flame stabilizer 8 has a shape tapered toward the burner outlet, and the flow path of the fuel fluid is gradually reduced in the tapered shape in the flow direction of the fuel fluid. The structure is such that pressure loss is not increased and wear is prevented by avoiding direct impact of the pulverized coal stream.

A supply gas nozzle 9 is provided inside the primary flow path 1, and is connected to a bridge 10. The gas passages inside the bridging part 10 and the inside of the internal flame stabilizer 8 are connected,
A plurality of gas ejection holes 16 are provided at or near the edge of the furnace side of the internal flame stabilizer 8 (see FIG. 2). Heated air (when the burner is operating) or cooling air (when the burner is stopped) enters the supply gas nozzle 9 from the supply gas pipe 11 via the gas supply header 12, and the gas flow path inside the bridge 10 shown in FIG. 17 and internal flame stabilizer 8
The gas is guided to the gas passage 17 in the inside, and is ejected from the gas ejection hole 16.

In the combustion system diagram of the pulverized coal-fired boiler shown in FIG. 5, the combustion air is heated from an FDF (Force Draft Fan) 41 to about 350 ° C. in an air preheater 34,
4 and is conveyed to the secondary flow path 2 and the tertiary flow path 3 of the pulverized coal burner section 40. The pulverized coal pulverized by the mill 38 is conveyed to the pulverized coal burner 40 by pulverized coal conveying air from a primary air fan (PAF) 31 and guided to the primary flow path 1 shown in FIG. Then, a high-temperature recirculation zone 13 formed downstream of the outer flame holding ring 7 and the internal flame stabilizer 8 at the burner outlet.
(FIG. 2) causes ignition flame holding and burns.

In the vicinity of the outer flame holding ring 7 and the inner flame stabilizer 8, there is a high-temperature recirculation region (FIG. 2 shows a high temperature recirculation region 13 near the inner flame stabilizer 8) due to turbulent turbulence in the wake. The formed pulverized coal particles having a relatively small size of 20 μm or less are entrained, and the pulverized coal flowing into the high-temperature recirculation region 13 becomes a kind of high-temperature gas by burning the pulverized coal.
Helps to promote the ignition of pulverized coal passing near. At this time, the bridging portion 10 is installed between the outer flame holding ring 7 and the inner flame stabilizer 8 so as to face the pulverized coal flow, and the flow on the outer flame holding ring 7 side is rectified, and Ignition flame is further strengthened.

Further, both the internal flame stabilizer 8 and the bridging portion 10 have gas passages 17 inside. When the burner is operated, the switching valve 28 (FIG. 5) in FIG. 5 is switched to the heating air supply side to supply the heating air in FIG. Gas piping 11 and supply gas header 1
It is introduced into the internal flame stabilizer 8 from the bridging part 10 via the supply gas nozzle 9 and 2.

As shown in FIG. 2, a recirculation zone 13 is formed downstream of the internal flame stabilizer 8, and the edge of the side of the internal flame stabilizer 8 on the recirculation zone 13 side or in the vicinity thereof A plurality of gas ejection holes 16 for ejecting gas (air) toward the pulverized coal stream are provided symmetrically in a substantially vertical direction, and the gas (air) is spouted from each gas (air) ejection hole 16 at high speed. Squirts. The gas ejection holes 16 blow out the ejection jet 14 of gas (air) in a divergent manner, increase the negative pressure in the recirculation zone 13, and also promote the inflow of high-temperature gas from the outer peripheral flame holding ring 7 side.
Hasten ignition of pulverized coal. When the burner operation is stopped, the switching valve 28 in FIG. 5 is set to the cooling air side, and cooling air is supplied to the inside of the bridging portion 10 and the internal flame stabilizer 8 to cool the bridging portion 10 and the internal flame stabilizer 8. I do.

The gas such as the heated air or the cooling air supplied to the gas ejection holes 16 is cooled by a flow control valve 27 in an amount necessary for cooling according to the pressure of the PAF 31 when the burner operation is stopped. During burner operation, about 1 to 2% of the primary air amount is introduced, and the ejection speed of the ejection jet 14 from the gas ejection hole 16 is 50 m faster than the primary pulverized coal flow.
/ S or more. This jet 14 is used for the internal flame stabilizer 8.
The negative pressure in the recirculation zone 13 in the wake is increased to promote the inflow of high-temperature gas from the outer peripheral flame holding ring 7. At the same time, the heated air or the cooling air supplied to the gas ejection holes 16 blows off the fly ash that tends to adhere to the surfaces of the internal flame stabilizer 8 and the bridging portion 10 and also helps to prevent the adhesion, and the gas ejection holes 16 made of pulverized coal are used. To prevent clogging.

In FIG. 1, only the heavy oil burner 4 is provided at the center of the primary flow path 1, but as shown in FIG. A concentrator 19 having a function of increasing the concentration of pulverized coal on the inner wall surface of the outlet of the primary flow path 1 together with the venturi section 18 may be provided on the outer peripheral portion of the heavy oil burner 4. The pulverized coal concentration on the inner wall side at the outlet of the primary flow path 1 is increased by the inclined portion on the upstream side of the pulverized coal flow of the concentrator 19, and the pulverized coal concentration on the inner wall side near the internal flame stabilizer 8 is increased. The flow of the pulverized coal flow near the outlet of the primary flow path 1 is gradually reduced by the inclined portion of the concentrator 19 on the downstream side of the pulverized coal flow, so that the pulverized coal flow is downstream of the concentrator 19. It is possible to prevent peeling from occurring between the side end wall surface.

Bridge section 1 during burner operation of the present invention
The gas passing through the gas passage 17 in the internal flame stabilizer 8 and 0 is introduced from the high temperature section of the gas supply system for conveying pulverized coal, but a part of the temperature-adjusted air supplied to the mill 38 is used instead. It is also possible to use it.

In FIG. 1, if there are a plurality of bridging portions 10, air is supplied from all bridging portions 10, passes through the internal flame stabilizer 8, and is ejected from the gas blowing holes 16 of the internal flame stabilizer 8. Although the burner is taken as an example, in the case of the burner shown in FIG. 3, gas is introduced from the supply gas pipe 11 to the gas supply header 12 through the gas supply nozzle 9 to a part of the bridging portion 10, and the internal flame stabilizer is used. After passing through 8, the gas is discharged from the remaining bridge 10 to the secondary flow path 2 via the gas discharge nozzle 15. If the gas (air) discharged into the secondary flow path 2 is heated air, the ignition of the fuel can be ensured, and the combustion of the fuel can be promoted.
When the cooling air is used, the inside of the burner can be cooled.

FIG. 4 shows that the supply gas nozzle 9 has the internal flame stabilizer 8.
The gas introduced from the supply gas inlet 11 to the internal flame stabilizer 8 via the gas supply nozzle 9 is discharged from all the bridge portions 10 to the secondary flow path 2 via the gas discharge nozzle 15. An example is shown. 3 and 4, the same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. 6 and 7 correspond to FIGS. 3 and 4, respectively, in which the supply gas is discharged into the primary flow path 1.

In the embodiment shown in FIGS. 8, 10 and 11, a venturi 18 and a concentrator 19 are provided in the heavy oil burner 4 in the primary flow path. Of these, in the example shown in FIG. A distributor 20 is provided at the upstream end of the primary channel 1 of the flame 8.
Is attached, and the flame holding at the burner outlet is further improved. The role of the distributor 20 is to increase the flow rate of the pulverized coal stream to the center of the burner and to reduce the flow rate of the pulverized coal stream to the outer peripheral portion.

Generally, in order to guide the high-temperature recirculated gas formed on the downstream side of the outer flame holding ring 7 to the center of the burner, the outer peripheral portion at the burner outlet and the inner peripheral portion at the burner outlet are introduced by the flow of the pulverized coal flow. It is necessary to ensure a sufficient differential pressure between the parts,
If the differential pressure between the outer peripheral portion and the inner peripheral portion at the burner outlet can be sufficiently ensured, a flow from the outer peripheral portion to the inner peripheral portion occurs, and the high-temperature gas around the outer peripheral flame holding ring 7 flows into the burner central portion,
Ignition is better.

The installation of the distributor 20 reduces the flow velocity near the outer flame holding ring 7 and improves the ignitability of the pulverized coal at the outer periphery of the burner. As the difference in flow velocity between the burner outer periphery and the burner center increases, the differential pressure between the burner outer periphery and the burner center increases, and the amount of gas flowing from the burner outer periphery to the burner center increases (bridge) (Increase of action). As shown in the enlarged view of the burner outlet portion in FIG. 11 in FIG. 11, the flow rate of pulverized coal to the center of the burner is adjusted to be increased by the angle of inclination θ in the gas flow direction of the internal flame stabilizer 8. Can be. However, the pulverized coal is directly sent to the outer peripheral portion because the pulverized coal concentration on the inner wall surface side of the outlet of the primary flow path 1 is increased by the inclined portion of the concentrator 19 on the upstream side of the pulverized coal flow. FIG. 9 shows the relationship between the bending angle of the end portion of the internal flame stabilizer of the burner of FIG. 8 on the primary flow path side and the wear rate.

As shown in FIG. 12, in the present invention, the difference in the flow rate of the pulverized coal flow between the outer peripheral portion of the burner and the central portion of the burner increases as the flow speed of the pulverized coal flow in the primary flow path 1 decreases. As a result, the differential pressure also increases, the amount of high-temperature gas flowing from the outer peripheral portion of the burner to the central portion of the burner increases, the reduction combustion region expands, and low NOx combustion can be performed. From the results shown in FIG. 12, when the flow rate of the pulverized coal stream at the outer peripheral portion of the burner is 60 to 80% of the flow rate of the pulverized coal stream at the central portion of the burner, the case where the distributor 20 is not provided, , The flow rate is 1
The NOx reduction rate becomes larger than the case of 00%. Here, the NOx value is measured by a NOx meter installed at the boiler outlet. The primary flow rate is divided by the area of the diameter of the primary flow path 1 where the primary flow rate is fixed, excluding the oil burner 4 at the center, and the mill outlet temperature is defined as 0 ° C.
And temperature-corrected.

In the burner shown in FIG. 10, a high-temperature gas pipe 22 for introducing a high-temperature gas from the downstream side of the venturi section 18 of the primary flow path 1 is further provided. It expands in the flow path 1 to reduce the flow velocity, and the same action as described above enhances the ignition and flame holding of the pulverized coal stream.

As described above, the external flame holding ring 7,
The burner provided with the internal flame stabilizer 8, the bridging portion 10, and the distributor 20 can significantly reduce NOx and unburned fuel as compared with the conventional burner.

Although not shown, in the burner of the present invention shown in FIGS. 1, 3, 4, 6, 7, 8 and 10, the pulverized coal stream of the bridging portion 10 and the internal flame stabilizer 8 is formed. May be coated with a highly wear-resistant refractory material. Examples of the wear-resistant substance include (1) thermal spray coating (self-fluxing alloy, thermal spray coating with 13 chrome steel or ceramics), and (2) aluminum diffusion treatment.

Further, the bridging portion 10 and the portion of the internal flame stabilizer 8 facing the flame of the furnace 30 may be coated with a refractory material having high wear resistance. Ceramics and the like are used as the refractory substance. When ceramics are used, the types of ceramics are classified into oxides such as alumina, magnesia and zirconia and non-oxides such as silicon oxide and silicon nitride. Table 1 shows the types and characteristics of ceramics.

[Table 1]

When these refractory materials are coated on a portion facing the flame or a portion facing the pulverized coal flow of a member provided in the primary flow path 1, how to join the base metal is a problem. As a method of attaching to a member installed in the primary flow channel 1, there are two types of a chemical bonding method of directly attaching with an adhesive and a mechanical joining method such as bolting. The mechanical joining method is an effective method that can withstand severe conditions by devising measures such as preventing stress concentration or rattling on ceramics. Also, in the chemical bonding method, there are problems such as generation of strain due to a difference in thermal expansion between the material and the adhesive under high heat, separation from the material, and a heat resistant temperature of the adhesive. This can be improved by using an inorganic adhesive as a main component and interposing a heat-resistant cloth that absorbs strain between the adhesives.

In the present invention, these refractory materials are used in the internal flame stabilizer 8.
And other parts of the primary flow path 1 facing the flame can be prevented from being damaged by flame radiation in the primary flow path 1 even when the operation of the burner is suspended. it can. Although the present invention has mainly described the measures against burning due to the radiation of the flame in the furnace 30, the consideration for the wear of the pulverized coal particles is opposed to the pulverized coal flow of the member installed in the primary flow path 1 as described above. This is done by coating the parts with a wear-resistant substance, but this is also reflected in the structure of the members installed in the primary flow path 1. That is, in the pulverized coal burner according to the embodiment of the present invention shown in the drawings, the internal flame stabilizing unit 8, the bridging unit 10, and the distributor 20 all have a divergent shape that becomes wider from the upstream of the primary flow to the downstream. And the inclination angle is 4 with respect to the flow direction of this pulverized coal stream.
By setting the temperature to 5 ° C. or lower, the structure can withstand wear caused by particles such as pulverized coal.

The shape of the inner flame stabilizer 8 and the bridging portion 10 at the end of the cross section can be a) V-shaped, b) U-shaped, c) U-shaped, and d) semicircular. In addition, bridging part 10
Is a divergent shape having a V-shaped or U-shaped cross section from the upstream side to the downstream side of the flow of the solid-gas mixed fluid (pulverized coal flow) to prevent wear due to pulverized coal.

[0056]

According to the present invention, it is possible to reduce the amount of NOx in the burner section, which cannot be achieved by a conventional pulverized coal burner, and at the same time, eliminate the burning of the internal flame stabilizer and the adhesion of ash. Also low NOx
Thus, ammonia consumption in the exhaust gas denitration device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an ultra-low N gas in which a gas is supplied from a bridging portion according to an embodiment of the present invention and the gas is jetted by an internal flame stabilizer.
It is an Ox burner sectional view.

FIG. 2 is an enlarged cross-sectional view and a perspective view of an internal flame stabilizer portion showing a gas ejection state from a gas ejection hole of the internal flame stabilizer portion of the burner in FIG. 1;

FIG. 3 is a cross-sectional view of an ultra-low NOx burner in which gas is supplied from some bridges and discharged from another bridge to a secondary flow passage through an internal flame stabilizer according to an embodiment of the present invention. .

FIG. 4 is a cross-sectional view of an ultra-low NOx burner for supplying gas from the internal flame stabilizer and discharging the gas from the bridging portion to the secondary flow channel according to the embodiment of the present invention.

FIG. 5 is a system diagram of a pulverized coal combustion device.

FIG. 6 is a cross-sectional view of an ultra-low NOx burner that supplies gas from some bridges and passes through an internal flame stabilizer and discharges from another bridge into a primary flow channel according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view of an ultra-low NOx burner for supplying gas from the internal flame stabilizer and discharging the gas from the bridging portion into the primary flow channel according to the embodiment of the present invention.

FIG. 8 is a cross-sectional view of an ultra-low NOx burner provided with an internal flame stabilizer coated with a refractory material for supplying gas from a bridge portion and jetting the gas with an internal flame stabilizer according to an embodiment of the present invention and a bridge portion. It is a figure and a front view.

9 is a view showing a relationship between a bending angle and a wear rate of a primary flow path side end portion of the internal flame stabilizer of the burner of FIG. 8;

FIG. 10 is a view showing a state in which gas is supplied from several bridges according to an embodiment of the present invention, a distributor is arranged at the upstream end of the internal flame stabilizer, and further, from the downstream side of the venturi section of the primary flow path. It is a sectional view and a front view of an ultra-low NOx burner into which a high-temperature gas is introduced.

FIG. 11 is an enlarged partial cross-sectional view of FIG. 10;

12 is a diagram showing the relationship between the primary flow velocity of the pulverized coal flow of the burner of FIG. 8 and the NOx concentration (relative value) of the combustion gas.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Primary flow path 2 Secondary flow path 3 Tertiary flow path 4 Heavy oil burner 5 Secondary air swirler 6 Tertiary air swirler 7 Peripheral flame holding ring 8 Internal flame holding device 9 Supply gas nozzle 10 Bridge section 11 Supply gas pipe 12 Gas Supply header 13 High temperature recirculation area 14 Jet jet 15 Gas exhaust hole 16 Gas (air)
Outlet 17 Gas passage 18 Venturi section 19 Concentrator 20 Distributor 22 High-temperature gas pipe 27 Flow control valve 28 Switching valve 30 Furnace 31 FDF 32 Cold air flow path 34 Air preheater (heat exchanger) 35 Heated air flow path 38 Mil 40 Pulverized coal burner 41 FDF 44 Wind box

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[Procedure amendment]

[Submission date] November 5, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 13

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 14

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] Claim 15

[Correction method] Change

[Correction contents]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Claim 16

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noboru Takayama 3-36 Takaracho, Kure-shi, Hiroshima Pref. Inside the Kure Laboratory (72) Miki Mori Inventor 3-36 Takaracho Kure-shi, Hiroshima Pref. Babcock Hitachi, Ltd. Inside the Kure Research Institute (72) Inventor Toshihiko Mine 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside Kure Laboratory, Babcock Hitachi Co., Ltd. (72) Inventor Shunichi Tsumura 6-9 Takara-cho, Kure City, Hiroshima Prefecture Inside Babcock Hitachi Kure Factory ( 72) Inventor Hironobu Kobayashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (16)

[Claims] 1. A primary flow path for introducing a solid-gas two-phase flow composed of a solid fuel and a carrier gas into a furnace, and a single or a plurality of oxygen-containing gases for combustion supplied outside the primary flow path. In a burner having a flow path, an outer flame stabilizer provided on an outer peripheral portion of an outlet end of a primary flow path, an inner flame stabilizer provided inside an outlet end of a primary flow path, and At least one bridging part provided between the vessel and the internal flame stabilizer, and at least one bridging part, and a gas passage for passing gas inside the bridging part and the internal flame stabilizer, and one or more bridging parts or An ultra-low NOx burner, characterized in that at least one of the internal flame stabilizers is provided with the gas ejection hole. 2. A gas passage is provided so that gas flows from at least one bridging portion toward the internal flame stabilizing device. A solid-gas gas jetted from a burner into the furnace is provided at a portion of the internal flame stabilizing device on the furnace side. 2. The ultra-low NOx burner according to claim 1, further comprising an ejection hole for ejecting a gas flowing inside the internal flame stabilizer toward the phase flow. 3. The gas passage is provided so as to be introduced from at least one bridging portion so that the gas flows toward the internal flame stabilizer, and the gas flowing inside the internal flame stabilizer is a portion other than the bridging portion into which the gas is introduced. The flow path provided with a gas ejection hole is provided in the bridging section so as to be discharged to the primary flow path or the oxygen-containing gas flow path for combustion via the bridging section. Ultra low NOx burner. 4. An exhaust hole for injecting a gas flowing inside the internal flame stabilizer toward a solid-gas two-phase flow from a burner into the furnace is provided in a portion of the internal flame stabilizer on the furnace side. An ultra-low NOx burner according to claim 3. 5. The gas passage is provided so as to be introduced from the internal flame stabilizer and discharged to the primary flow passage or the oxygen-containing gas flow passage for combustion through all bridge portions. 2. The ultra-low NOx burner according to 1. 6. The cross-sectional shape of the upstream portion of the bridging portion and the internal flame stabilizer in the flow direction of the solid-gas two-phase flow is divergent toward the downstream side. Ultra low NOx burner. 7. The cross-sectional shape of the internal flame stabilizer in the flow direction of the solid-gas two-phase flow is such that its outer peripheral side has a wall surface parallel to the fuel flow direction, and its inner peripheral side has a tapered shape. 7. The ultra-low NOx burner according to claim 6, wherein: 8. A plurality of gas ejection holes provided in the internal flame stabilizer are provided at a furnace side portion of the internal flame stabilizer so as to form a divergent gas ejection flow. Ultra low NOx burner as described. 9. A gas flow passage from a low-temperature section or a high-temperature section of a gas supply system for conveying solid fuel powder is connected to a bridge section or a gas introduction section flowing into a gas passage inside the internal flame stabilizer. The ultra-low NOx burner according to claim 1, wherein: 10. A solid fuel carrier is supplied to a gas flow path from a low temperature part or a high temperature part of a gas supply system for conveying a solid fuel powder, which is connected to a bridge part or a gas introduction part flowing into a gas passage inside an internal flame stabilizer. 10. A switching means for switching and supplying any gas from a low temperature section or a high temperature section of the gas supply system for use to the bridging section or the introduction section of the internal flame stabilizer gas. Ultra low NOx burner. 11. The ultra-low NOx burner according to claim 1, wherein a portion of the internal flame stabilizer or the bridge portion facing the flow direction of the solid-gas two-phase flow is coated with a material having wear resistance. 12. The ultra-low NOx burner according to claim 1, wherein a portion of the internal flame stabilizer or the bridging portion facing the flame in the furnace is coated with a refractory substance. 13. A gas from a high-temperature section of a gas supply system for conveying pulverized coal during the operation of the ultra-low NOx burner according to claim 10, wherein the gas is supplied to a bridge section or an introduction section of a gas flowing to an internal flame stabilizer. The method for operating an ultra-low NOx burner, wherein a gas is supplied from a low-temperature portion of a gas supply system for pulverized coal transport during the pause of the burner operation. 14. The flow rate of the solid-gas two-phase flow at the outer peripheral portion of the cross section of the primary flow passage at the upstream end of the primary flow passage in the gas flow direction of the internal flame stabilizer, 2. The ultra-low NOx burner according to claim 1, further comprising a distributor for distributing the solid-gas two-phase flow so as to be slower than the solid-gas two-phase flow. 15. A narrow portion of the primary flow path is provided on the upstream side in the gas flow direction of the installation portion of the internal flame stabilizer in the primary flow path, and a primary flow path between the narrow portion and the internal flame stabilizer is provided. 15. The ultra-low NOx burner according to claim 14, further comprising a high-temperature gas introduction pipe for introducing a gas higher in temperature than the carrier gas for the powder solid particles. 16. The ultra-low NOx burner according to claim 14, wherein the high-temperature gas introduction pipe is connected to a supply path of combustion air for powdered solid fuel.