JPH10318504A - High capacity pulverized solid fuel burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate firing and combustion of a pulverized solid fuel by providing an inner circumferential flame holder coupled with an outer circumferential flame holder, in addition to the outer circumferential flame holder, at a rich burner section for burning the high concentration pulverized solid fuel and interposing an intermediate flame holder between the inner circumferential flame holder and the outer circumferential flame holder. SOLUTION: A fuel, i.e., pulverized coal, is carried on the primary air through a pulverized coal supply pipe 8 and separated into a rich flow and a lean flow through an internal concentrator 27. The rich flow is jetted from a rich burner section 1 into a furnace. In this regard, a low speed pulverized coal circulating region is formed in the downstream of an outer circumferential flame holder 17 and the circulating pulverized coal is fired by receiving radiation heat from high temperature gas in the furnace to produce a flame. A circulating region is also formed in the downstream of a flame holding plate 24 and since it is coupled with the outer circumferential flame holder 17, the flame in the downstream of the outer circumferential flame holder 17 propagates to the circulating region in the downstream of a flame holder 24. Furthermore, flame is formed in the circulating region formed in the downstream of an intermediate flame holder 32 and an inner circumferential flame holder 23 coupled through the plate 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-capacity pulverized solid fuel combustion apparatus used for a boiler or the like, and more particularly to a burner for burning pulverized solid fuel represented by pulverized coal.

[0002]

2. Description of the Related Art Due to recent changes in fuel situations, coal-fired boilers using coal as a main fuel are increasing in commercial boilers such as large-scale boilers for thermal power generation. The coal-fired boiler employs a combustion system in which a pulverized and pulverized coal is directly supplied to a combustor, that is, a burner, mainly using a coal pulverizer (hereinafter referred to as a mill) having a built-in classifier. .

FIG. 12 shows an example of a conventional burner for pulverized coal (Japanese Patent Laid-Open No. 63-320). The conventional pulverized coal burner mainly includes a pulverized coal supply pipe 8 that conveys pulverized coal with primary air and supplies the pulverized coal to the furnace as fuel, and a secondary air pulverized around the pulverized coal supply pipe 8 and provided in the furnace. And a tertiary flow path formed around the secondary flow path and feeding tertiary air 21 into the furnace. And the pulverized coal supply pipe 8 has a venturi 26 on its inner wall,
Downstream of the venturi 26, a plug 2 slidable on the core shaft 3
The fuel is separated downstream of the plug 28 so that the pulverized coal has a higher concentration near the inner surface of the pipe wall and has a lower concentration near the center of the pipe. An internal concentrator 27 including a rich burner unit 1 for burning and a lean burner unit 2 for burning a lean fuel having a low pulverized coal concentration is installed, and furthermore, an outer periphery of a leading end opening of the pulverized coal supply pipe 8, that is, a rich burner. On the outer periphery of the distal end of the portion 1, an outer peripheral flame stabilizer 17 composed of a flange that is approximately widened is installed. Also, a secondary air register 13 is provided in the secondary flow path.
However, a tertiary air register 14 is provided in each of the tertiary flow paths.

[0004] Coal as fuel is pulverized by a mill into pulverized coal, and pulverized coal supply pipe 8 is conveyed together with conveying air (primary air).
Through the furnace. At this time, a circulating flow 25 in which the pulverized coal circulates at a low speed is formed downstream of the outer peripheral flame stabilizer 17 attached to the tip of the pulverized coal supply pipe 8. The pulverized coal in this circulation area receives radiant heat from the high-temperature gas in the furnace and ignites. In this manner, the flame can be stably held by the outer flame stabilizer 17. On the other hand, secondary air 2 of combustion air
The secondary and tertiary air 21 are swirled by the secondary air register 13 and the tertiary air register 14, respectively, and are injected into the boiler furnace. By separating the mixture of primary air and pulverized coal from secondary and tertiary air, a reduction zone is formed near the burner in the furnace, and the generation of NOx can be suppressed.

When the burner is operated at a low load where the C / A concentration (ratio of pulverized coal to air) in the fuel supply pipe 8 of the burner is low, the plug 28 is moved to the inside of the furnace. Plug 28
Is moved to the inside of the furnace, and the pulverized coal is collected on the outer peripheral side in the primary flow path by inertia, so that the pulverized coal concentration of the outer burner (rich burner portion 1) increases. Thus, even if the C / A concentration of the entire burner becomes low at a low load, the C / A concentration can be locally increased by the concentrator, so that a stable flame can be formed.

[0006]

In recent years, commercial boilers have been increasing in size, and 1000 MW coal-fired boilers have been put to practical use. In addition, plans for a 1500 MW class boiler are underway. One way to increase the capacity of the boiler is to increase the number of burners. However, this requires an increase in the number of fuel pipes, air pipes, and the like, which increases the manufacturing cost.

As another method for increasing the capacity of a boiler, there is a method of increasing the capacity of a burner. When the size of the pulverized coal burner is increased, the diameter of the pulverized coal burner increases as the capacity increases, and the thickness of the pulverized coal stream increases. For this reason, the main flame which holds the flame by the outer flame stabilizer 17 and ignites the pulverized coal stream cannot propagate to the inside of the pulverized coal stream. For this reason, the pulverized coal passing through the inside is ejected into the furnace without being ignited, and even if the flame is ignited stably, there is a problem that unburned components increase. In order to burn the unburned portion generated in the burner section, it is necessary to increase the size of the furnace, which increases the production cost of the boiler.

In addition, since unignited pulverized coal passes through the center of the burner, oxygen consumption at the center of the burner is delayed, the reducing flame becomes extremely small, the temperature of the reducing flame itself decreases, and the pulverized coal is heated. As the rate of release of N in the fuel from the fuel decreases, the amount of NOx generated increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a large-capacity fine-powder solid fuel combustion apparatus which maintains a stable flame near a burner and has excellent NOx characteristics and unburned component characteristics.

[0010]

In order to achieve the above object, a first large-capacity fine solid fuel combustion apparatus according to the present invention is provided.
A first flow path having an annular cross section, a second flow path surrounded by the first flow path, and an outer peripheral flame stabilizer formed of a ring at a tip of an outer peripheral wall of the first flow path; In addition to the conventional combustion device that supplies a solid-gas two-phase flow composed of a finely divided solid fuel and a carrier gas into the furnace through a passage and a second flow passage, the first flow passage is provided at the end of the inner peripheral wall of the first flow passage. An inner peripheral flame stabilizer formed of a ring extending to the outer peripheral flame stabilizer and an inner peripheral flame stabilizer are provided, and at least one intermediate member composed of a ring is provided between the outer peripheral flame stabilizer and the inner peripheral flame stabilizer. The flame stabilizer is provided so as to be connected to the flame stabilizer.

The first flow path is a rich burner for supplying a solid-gas two-phase flow having a high concentration of finely divided solid fuel into the furnace,
The second flow passage preferably functions as a lean rich burner for supplying a solid-gas two-phase flow having a low concentration of the finely divided solid fuel into the furnace. Further, it is preferable to provide the inner flame stabilizer on the upstream side of the solid-gas two-phase flow from the outer flame stabilizer. Further, it is preferable that the intermediate flame stabilizer and the inner flame stabilizer are sequentially arranged closer to the upstream side of the solid-gas two-phase flow than the outer flame stabilizer.

By installing an inner flame stabilizer in addition to the conventionally known outer flame stabilizer of the pulverized coal burner, pulverized coal as solid fuel ignited downstream of the inner flame stabilizer increases. The ignition energy (caloric value, temperature) for the mainstream pulverized coal increases. However, with this alone, if unburned low-temperature and high-concentration pulverized coal flows between the inner flame stabilizer and the outer flame stabilizer due to the enlargement of the burner, the radiant heat from the high-temperature combustion flame in the furnace and the outer flame flame It becomes difficult for the ignition heat energy from the heater to reach. For this reason, the heat energy required to ignite the pulverized coal inside the burner may be insufficient, and the ignition may not be achieved. Therefore, in order to supply thermal energy to the pulverized coal in the circulating area downstream of the inner flame stabilizer, a flame holding plate is provided as a flame stabilizer that bridges the inner flame stabilizer and the outer flame stabilizer.

By installing the flame holding plate, a circulating zone in which pulverized coal circulates at a low speed is also formed downstream of the flame holding plate. Since this circulation area is connected to the circulation area formed by the outer flame stabilizer and the inner flame stabilizer, the high-temperature gas ignited and flamed in the circulation area downstream of the outer flame stabilizer directly passes the pulverized coal in the circulation area. Since the thermal energy is transmitted to the pulverized coal, the pulverized coal downstream of all the flame holding plates is ignited and the flame is stably held.

If an intermediate flame stabilizer is provided between the inner flame stabilizer and the outer flame stabilizer, a circulating zone in which pulverized coal circulates at a low speed is formed downstream of the intermediate flame stabilizer. Since the thermal energy of the high-temperature gas held in the circulating area downstream of the flame stabilizer is transmitted, the pulverized coal ignites and can stably hold the flame, so that the capacity of the burner can be increased. Will be possible.

As described above, by installing the inner flame stabilizer, the flame stabilizer plate and the intermediate flame stabilizer that connect the inner flame stabilizer and the outer flame stabilizer, the energy required for ignition is supplied from inside and outside the rich fluid. Therefore, it is possible to provide a fine-powder solid fuel combustion device capable of performing low unburned fuel and low NOx combustion over a wide load even when the capacity is increased.

Further, by arranging the inner flame stabilizer and the intermediate flame stabilizer upstream of the burner from the outer flame stabilizer, the ignition of the pulverized coal is accelerated, and the consumption of oxygen in the primary air is accelerated. The range becomes wider and NOx will be further reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a wide-area load type pulverized coal large-capacity burner according to a large-capacity pulverized solid fuel combustion apparatus according to a first embodiment of the present invention, and FIG. 2 is a view taken along the line AA in FIG. This burner is a burner in which the capacity of a built-in concentrator type burner described in the section of the prior art with reference to FIG. 11 is increased, and is shown in FIG. 11 except for a flame holding portion at the tip of the burner described later in detail. It is composed of the same elements as

The burner is provided with a pulverized coal supply pipe 8 for supplying pulverized coal, which is pulverized solid fuel, to carrier air and sending it into the furnace as a solid-gas two-phase flow. Pulverized coal supply pipe 8
Is provided with an internal concentrator 27 therein, in which the concentration of the pulverized coal is increased by the internal concentrator 27, and the separated concentrated stream is supplied to the dense burner section 1, while the diluted stream having the reduced concentration of the pulverized coal is supplied to It is configured to feed to the lean burner section 2. Each of the rich burner section 1 and the lean burner section 2 has a ring-shaped cross section,
It has a double structure in which the flow path of the lean burner section 2 is provided inside the flow path of the rich burner section 1. At the end of the outer peripheral wall (also the pipe wall of the pulverized coal supply pipe 8) of the rich burner section 1, an outer peripheral flame stabilizer 17 is installed, which is arranged in a substantially ring shape in the shape of a flared part. , Rich burner part 1
A ring-shaped inner flame stabilizer 23 projecting toward the flow path side of the dense burner portion 1 at the tip of the inner peripheral wall, and a ring-shaped intermediate flame stabilizer 32 between the outer flame stabilizer 17 and the inner flame stabilizer 23; Further, a flame stabilizing plate 24 is provided for connecting the flame stabilizers 17, 32, 23 in the radial direction.

The distance between the outer flame stabilizer 17 and the intermediate flame stabilizer 32 and the distance between the intermediate flame stabilizer 32 and the inner flame stabilizer 23 (referred to as the width of the outflow hole) are determined based on the following experimental results. Was. FIG. 3 shows that the width D of the outlet hole from which pulverized coal flows out is changed.
The result of measuring the unburned matter in the ash sampled downstream of the burner is shown. It can be seen that when the width D of the outflow hole exceeds a certain value A, the amount of unburned components starts to increase. Then, the intermediate flame stabilizing device 32 was installed so that the width D of the outflow hole became a certain value A or less. The relationship between the width D of the outlet hole from which pulverized coal flows out and the amount of unburned fuel shown in FIG. 3 changes as shown by broken lines a and b depending on the properties of the fuel used and the C / A concentration. That is, the width D of the outlet hole needs to be changed depending on the fuel used and the C / A concentration.

The operation of each part of the large capacity, wide area load type pulverized coal burner according to the first embodiment will be described below. The pulverized coal as the fuel is conveyed in the pulverized coal supply pipe 8 by the primary air, and separated into a rich stream and a lean stream by the internal concentrator 27. The rich flow is blown out of the rich burner 1 into the furnace. At this time, a circulation zone 25 in which pulverized coal circulates at a low speed is formed downstream of the outer peripheral flame stabilizer 17 (see FIG. 6). The pulverized coal in the circulation zone 25 ignites to receive radiant heat from the high-temperature gas in the furnace, and forms a flame. Further, a circulation area is formed downstream of the flame holding plate 24. Since the flame stabilizer 24 and the outer flame stabilizer 17 are connected, the flame downstream of the outer flame stabilizer 17 propagates to the circulation area downstream of the flame stabilizer 24. Further, similarly, a flame is also formed in a circulation region formed in the downstream of each of the intermediate flame stabilizer 32 and the inner peripheral flame stabilizer 23 connected via the flame stabilizer 24. By installing the inner peripheral flame stabilizer 23, the intermediate flame stabilizer 32 and the flame stabilizer 24, a flame can be formed over the entire area of the dense burner 1 even if the capacity is increased,
The amount of pulverized coal spouted into the furnace before ignition was greatly reduced.

Further, a high-temperature reducing flame can be formed in the vicinity of the burner in the furnace, and the NOx reduction can be similarly realized by introducing the secondary air 22 and the tertiary air 21 in multiple stages from around the rich burner section 1.

Further, the inner flame holder 23 is connected to the dense burner 1
And the lean burner section 2, and the air ejected from the lean burner section 2 is taken into the circulation region. for that reason,
In the furnace, oxygen in the lean burner section 2 is consumed in the vicinity of the burner, and the reduction region is widened, which is effective in reducing NOx.

FIG. 4 and FIG. 5 show an example of the NOx and unburned portion characteristics of the large capacity burner according to the present invention. In FIG. 4, the broken lines indicate the unburned components and NOx of a conventional burner with a concentrator.
The solid line shows the above characteristics of a conventional burner with a concentrator and a large-capacity burner with the same structure. It can be seen that in the conventional burner, due to the effect of the internal concentrator 27, the unburned portion is low even in the low load range, and combustion is performed with NOx kept low. If the burner is increased in capacity with the conventional structure, the amount of unburned matter released increases when the burner load decreases. This is because the thick flow becomes thicker due to the increase in capacity, and the outer flame stabilizer 17 provided outside the rich flow
Because the radiant heat from the high-temperature gas in the wake does not easily reach the inside of the rich flow, the pulverized coal that passed through the inside of the rich flow was released into the furnace without ignition, and the unburned content increased. Conceivable. Further, since unignited pulverized coal passes, the oxygen consumption at the center of the burner is delayed, and the NOx generation amount is increasing.

In FIG. 5, the broken lines indicate the unburned matter and NOx characteristics of the burner whose capacity has been increased in the conventional structure, and the solid lines indicate those of the burner whose capacity has been increased by the structure according to the present invention shown in FIGS. The characteristics of Comparing the unburned portion and NOx characteristics of the burner according to the present invention with the conventional structure, it can be seen that the burner according to the present invention has a small increase in unburned portion and a small amount of NOx generated even when the load is reduced. Thus, by providing the structure of the present invention, that is, by providing the inner peripheral flame stabilizer 23, the intermediate flame stabilizer 32, and the flame stabilizer 24, a burner capable of suppressing NOx and unburned components even when the capacity is increased can be realized.

FIG. 6 shows a combustion apparatus in which the inner flame stabilizer 23 and the intermediate flame stabilizer 32 are installed on the upstream side of the burner from the outer flame stabilizer 17. Although the inner flame stabilizer 23, the intermediate flame stabilizer 32, and the outer flame stabilizer 17 are installed on the same plane in FIG.
From the viewpoint of realization, it is preferable to install at least the inner flame stabilizer 23 upstream of the burner from the outer flame stabilizer 17 as shown in FIG. By arranging the inner peripheral flame stabilizer 23 on the upstream side of the burner, the ignition of the pulverized coal is accelerated, and the consumption of oxygen in the primary air is accelerated. Therefore, there is an effect that the reduction region is widened and NOx can be further reduced.

In order to realize such an effect, a flame holding plate 24 for connecting the outer flame stabilizer 17 and the inner flame stabilizer 23 according to the present invention is provided, and an intermediate flame stabilizer 32 is further provided. That is, when the flame stabilizing plate 24 and the intermediate flame stabilizing device 32 are not provided, the flame held by the outer flame stabilizing device 17 flows backward because the inner flame stabilizing device 23 is located on the upstream side of the outer flame stabilizing device 17. It does not propagate to the peripheral flame holder 23. However, by providing a flame holding plate 24 that connects the inner flame holding device 23 and the outer flame holding device 17, the flame held by the outer flame holding device 17 can be reduced.
, And can propagate to the inner peripheral flame stabilizer, and a flame can be formed in the inner peripheral flame stabilizer 23. However, when the capacity is increased, the propagation of the flame through the flame holding plate 24 from the outer flame stabilizer 17 to the inner flame stabilizer 23 side becomes longer, so that the propagation length becomes longer.
Not enough. For this reason, by providing the intermediate flame stabilizer 32 on the flame stabilizer 24 connecting the outer flame stabilizer 17 and the inner flame stabilizer 23, the ignition region is formed stably on the downstream side of the intermediate flame stabilizer 32, and Propagation of the flame to the inner peripheral flame stabilizer can also be performed stably. Therefore, the pulverized coal is ignited more upstream, and the consumption of oxygen in the primary air is accelerated. Therefore, the reduction region is widened, and the generation of NOx can be reduced.

(Another embodiment of the present invention) FIG. 7 shows an example in which the capacity of a burner having a structure in which air flows in from the inside of a pulverized coal channel is increased. In this burner, the rich burner section 1
In addition to the outer flame stabilizer 17 provided at the tip of the outer peripheral wall, an inner flame stabilizer 23 at the tip of the inner peripheral wall of the rich burner portion 1, a flame stabilizer 24 connecting the flame stabilizers 17 and 23 in the radial direction, An intermediate flame stabilizer 32 is provided. As described above, the burner having the structure in which the air is supplied from the shaft center also has the effect of reducing the unburned fuel and the NOx similarly to the burner of the first embodiment.

FIG. 8 shows an example in which a burner having a structure in which pulverized coal is ejected from a rectangular hole is increased in capacity. In addition to the outer peripheral flame stabilizer 17 provided on the upper side of the rectangular hole of the dense burner section 1, a dense burner is provided. An inner peripheral flame stabilizer 23 is provided on the lower side of the part 1, and further, a flame stabilizer 24 connecting the hole flame stabilizers 17 and 23, and an intermediate flame stabilizer 3
2 are provided. Even in such a structure, the present invention has the same effect as the burner of the first embodiment.

The above is an example in which the present invention is applied to a pulverized coal burner with a concentrator. However, the present invention is also effective in increasing the capacity of a burner without a concentrator. FIG. 13 shows a conventional example of a pulverized coal combustion apparatus of the type that does not use a concentrator (Japanese Patent Application Laid-Open No. 60-171307). When the burner is increased in capacity, a similar problem occurs in that the thickness of the pulverized coal stream increases and the main flame is not propagated to the inside of the pulverized coal stream.
FIG. 9 shows an example in which the present invention is applied to this type of burner. By installing the inner peripheral flame stabilizer 23 and the intermediate flame stabilizer 32 based on the results shown in FIG. 4, the unignited pulverized coal stream does not occur inside the pulverized coal stream, and the amount of unburned components and NOx generated is reduced. It can be kept low.

FIG. 10 shows a case where the capacity of the burner shown in FIGS. 1 and 2 is further increased. Two intermediate flame stabilizers 32 are provided to make the width of the pulverized coal flow path equal to or less than A obtained from FIG.

FIG. 11 shows an example in which, instead of using the intermediate flame stabilizer 32, the number of flame stabilizers 24 for bridging the outer flame stabilizer 17 and the inner flame stabilizer 23 is increased.

[0032]

According to the present invention, in addition to the conventional outer flame stabilizer, the inner flame stabilizer connected to the outer flame stabilizer via the flame holding member is added to the rich burner section for burning the high-concentration fine solid fuel. Since the intermediate flame stabilizer is provided between the outer flame stabilizer and the inner flame stabilizer, the energy of the high-temperature gas maintained by the outer flame stabilizer is transferred to the intermediate flame stabilizer through the flame stabilizer. The flame holding area is transmitted to the perimeter flame stabilizer and the flame holding area is expanded, making it easier to ignite and burn the fine powder solid fuel. Therefore, even if the burner is increased in capacity, the generation of unburned components and NOx can be suppressed low.
Wide area load combustion becomes possible. Therefore, the capacity of the boiler can be increased at a lower cost than before.

Further, the burner of the present invention is excellent in ignitability, so that it is also effective when burning flame-retardant coal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a large-capacity fine-powder solid fuel combustion device according to a first embodiment of the present invention.

FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;

FIG. 3 is a diagram showing a relationship between the width of a pulverized coal passage in a burner and unburned components.

FIG. 4 is a diagram showing unburned components and NOx characteristics of a conventional combustion device and a combustion device obtained by simply enlarging the device.

FIG. 5 shows unburned components and NOx characteristics of the combustion device of the present invention and a combustion device in which the conventional structure is simply enlarged.

FIG. 6 is a cross-sectional view showing a combustion device in which an inner flame stabilizer is installed upstream of an outer flame stabilizer.

FIG. 7 is a diagram illustrating an example in which an inner flame stabilizer is applied to a burner provided with a concentrator and supplying secondary air from a shaft center portion.

FIG. 8 is a diagram showing an example in which an inner flame stabilizer is applied to a burner having a rectangular outlet with a concentrator.

FIG. 9 is a diagram showing an example in which an inner flame stabilizer and an intermediate flame stabilizer are applied to a pulverized coal burner without a concentrator.

FIG. 10 is a front view of a pulverized coal burner including an inner flame stabilizer and two intermediate flame stabilizers.

FIG. 11 is a front view of a pulverized coal burner in which the number of flame stabilizing plates connecting an outer flame stabilizer and an inner flame stabilizer is increased.

FIG. 12 shows a pulverized coal burner with a concentrator having a conventional structure.

FIG. 13 shows a conventional pulverized coal burner of the type without a concentrator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rich burner part 2 Lean burner part 3 Heavy oil start-up burner 8 Pulverized coal supply pipe 13 Secondary air register 14 Tertiary air register 17 Outer flame holder 20 Fuel pipe 21 Tertiary air 22 Secondary air 23 Inner circumference flame holder 24 Flame stabilizer 25 Circulation area 26 Venturi 27 Internal concentrator 28 Plug 30 Cyclone concentrator 31 Concentration adjusting drive 32 Intermediate flame stabilizer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noriyuki Oyatsu 3-36 Takaracho, Kure-shi, Hiroshima Pref. Inside the Kure Research Laboratory (72) Inventor Akira Baba 3-36 Takaracho, Kure-shi Hiroshima Pref. Babcock Hitachi, Ltd. Inside Kure Research Laboratory (72) Inventor Hidehisa Yoshimiwa 3-36 Takaracho, Kure City, Hiroshima Pref. Babcock Hitachi Co., Ltd.

Claims (4)

[Claims] 1. A first flow path having an annular cross section, a second flow path surrounded by the first flow path, and an outer flame stabilizer formed of a ring at an end of an outer peripheral wall of the first flow path. In a large-capacity fine-powder solid fuel combustion apparatus for supplying a solid-gas two-phase flow composed of finely divided solid fuel and a carrier gas through a first flow path and a second flow path into a furnace, a tip of an inner peripheral wall of the first flow path is provided. A flame holding member connecting the outer flame stabilizer and the inner flame stabilizer is provided, and a ring is further provided between the outer flame stabilizer and the inner flame stabilizer. At least one consisting of
A large-capacity fine-powder solid fuel combustion device comprising two intermediate flame stabilizers connected to a flame retaining member. 2. A first flow path having an annular cross section, a second flow path surrounded by the first flow path, and an outer flame holder formed of a ring at a tip of an outer peripheral wall of the first flow path. The first flow path is a rich burner section that supplies a solid-gas two-phase flow with a high concentration of finely divided solid fuel into the furnace, and the second flow path is a solid-gas two-phase flow with a low concentration of finely divided solid fuel. In a large-capacity fine-powder solid fuel combustion device having a lean burner section to be supplied into a furnace, an inner flame stabilizer formed of a ring projecting toward the first flow path is provided at a tip of an inner peripheral wall of a first flow path, and an outer flame stabilizer is provided. A flame holding member connecting the inner flame stabilizer and the inner flame stabilizer, and at least one intermediate flame stabilizer consisting of a ring is provided between the outer flame stabilizer and the inner flame stabilizer connected to the flame stabilizer. Large capacity fine powder solid fuel combustion device. 3. The large-capacity fine-powder solid fuel combustion apparatus according to claim 1, wherein the inner flame stabilizer is provided on the upstream side of the solid-gas two-phase flow from the outer flame stabilizer. 4. The large flame holding device according to claim 4, wherein the intermediate flame holding device and the inner flame holding device are sequentially arranged closer to the upstream side of the solid-gas two-phase flow than the outer flame holding device. Capacity fine solid fuel combustion device.