JP3253350B2 - Pulverized coal burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulverized coal combustion apparatus and, more particularly, to a pulverized coal burner suitable for expanding the operation range of a load change in a combustion system operated by directly connecting a mill and a pulverized coal burner. .

[0002]

2. Description of the Related Art In recent years, in Japan, fuel has been converted from heavy oil burning to coal burning in order to correct the dependence on petroleum due to the tight supply of heavy oil. In, a large-scale coal-fired thermal power plant is being constructed.

[0003] On the other hand, as a feature of recent power demand, along with the growth of nuclear power, maximum load, most small difference also increased, there is a tendency to migrate and the boiler for thermal power generation for base load to a load adjustment, This boiler for thermal power generation is operated under variable pressure by changing the pressure according to the load, that is, a so-called super-critical pressure region in full load operation and a sub-critical pressure region in partial load operation. The power generation efficiency during operation can be improved by several percent.

[0004] For this reason, in this coal-fired thermal power,
Few boiler loads are always operated at full load, and the load is 75%, 50%, 25%, 15
% And increasing the load to the load, lowering or driving by, or at night such as stopping the operation, so-called high frequency start stop (Daily Start Stop hereinafter simply referred to D S S) coal-carrying intermediate load by performing the operation It is shifting to thermal power.

[0005] In coal-boiler for performing D S S operation, those less of operating a full load range only in the fine coal up to full load at startup, startup even the coal-boiler, during low load Light oil, heavy oil, gas, etc. other than pulverized coal are used as auxiliary fuel.

[0006] At the time of start-up, flue gas for mill warming and heated air cannot be obtained from a coal-fired boiler.
This is because the mill cannot be operated and the coal cannot be pulverized into pulverized coal.

[0007] Light oil, heavy oil, gas, and the like are used because the turndown ratio of the mill cannot be obtained at a low load and the ignitability of the pulverized coal itself is poor.

For example, when light oil or heavy oil is used as an auxiliary fuel at the time of startup, a boiler is fired using light oil as an auxiliary fuel from the time of startup up to a 15% load, and 40% from a 15% load.
Up to 40% load, the auxiliary fuel is changed from light oil to heavy oil and boiled. If the load exceeds 40%, the auxiliary fuel heavy oil and the pulverized coal of the main fuel are co-fired to gradually reduce the amount of fuel oil in the auxiliary fuel and reduce the amount of the main fuel. The amount of pulverized coal is increased and the co-firing ratio of pulverized coal is increased to shift to a substantial coal-fired combustion.

The outline of the pulverized coal-fired boiler when it is started will be described below with reference to FIGS. 6 and 7 .

FIGS. 6 and 7 are a schematic system diagram of a pulverized coal-fired boiler and an enlarged sectional view of a conventional pulverized coal burner.

[0011] When the cold start pulverized Sumi焚boiler 1 shown in FIG. 6, firstly the light oil ignition burner 2 of pulverized coal burners 7 shown in FIG. 7, raised fired up to 15% of the boiler load. Thereafter, the heavy oil starting burner 3 is ignited. And
15-35% of boiler load with only heavy oil start-up burner 3
Boil until. Then when the furnace temperature of the boiler furnace 4 has up enough, pulverized coal supply pipe 6 shown in FIG. 7 from the mill 5 shown in FIG. 6, the pulverized coal nozzle by supplying the pulverized coal fuel into pulverized coal burner 7 From 8, it is sent into the boiler furnace 4 and switched to pulverized coal only firing.

[0012] transport medium pulverized coal, the air heater 9 shown in FIG. 6, the mill 5 after being boiler exhaust gas heat exchanger
To the coal coal supplied from the coal bunker 10 to remove moisture adhering to the coal coal, and as classification air of a classifier (not shown) built in the mill 5, further pulverized coal pulverized by the mill 5 to pulverized coal. It is used as a conveying air for conveying to the burner 7.

FIG. 7 shows a pulverized coal burner 7 according to the prior art. The pulverized coal burner 7 is provided with a light oil ignition burner 2 and a heavy oil starting burner 3 to constitute the pulverized coal burner 7. ing. The air for combustion in the wind box 11 is fed into the boiler furnace 4 after being swirled by the secondary air register 12 and the tertiary air register 13. on the other hand,
The pulverized coal is sent to the pulverized coal nozzle 8 of the pulverized coal burner 7 through the pulverized coal supply pipe 6, but only passes through the venturi 14 during that time, and the boiler furnace 4 is almost in a free jet state.
It is blown in. This pulverized coal burner 7 has a flame stabilizer 15
And the swirling of the combustion air creates a backflow region, and only keeps the flame in a flow velocity region equal to or lower than the flame propagation speed. Therefore, pulverized coal particles have good diffusion,
On the one hand, the flame becomes unstable and is very susceptible to the operating conditions of the pulverized coal burner 7 on the air side. 6 is a heavy oil tank, and 17 is a light oil tank.

On the other hand, in a region where the load of the mill 5 (pulverized coal burner 7) is low, the pulverized coal supplied from the mill 5—the pulverized coal concentration (C / A) in the air flow is reduced, and the ignition stability is deteriorated. . FIG. 8 shows the weight ratio (hereinafter C / A) of pulverized coal (C) and air (A) supplied from the mill 5 to the pulverized coal burner 7 with respect to the burner (mill) load on the horizontal axis and the burner (mill) load on the vertical axis.
FIG.

From FIG. 8 , it can be seen that the C / A decreases as the burner (mill) load decreases. This is a phenomenon peculiar to the mill, which is unavoidable for conveying and classifying pulverized coal. is there.

FIG. 8 shows C / A at a burner load of 15%.
As shown in FIG. 2, the pulverized coal becomes extremely lean, and the air ratio at which the primary air amount affects combustion depends on the type of coal, but in any case, exceeds 1. Therefore, in this load, only primary air causes excess air, so that secondary and tertiary air are not required. However, in practice, secondary and tertiary air burners 7 are required to prevent burnout of the pulverized coal burner 7 due to the characteristics of the fan. To supply a lot of tertiary air,
The air ratio in the vicinity of the pulverized coal burner becomes a considerably high value, and the pulverized coal particles are further diluted, so that the flame becomes unstable.

[0017]

As described above, in the pulverized coal burner using the auxiliary fuel, the usage amount of the auxiliary fuel increases every frequent start-stop operation, and the pulverized coal-air flow is directly supplied from the mill to the pulverized coal burner. When the load of the mill (burner) is low in the supplied combustion system, there is a disadvantage that the ignitability of the pulverized coal burner deteriorates and the unburned matter increases.

The present invention has been made to solve the above-mentioned conventional drawbacks, and has as its object to reduce auxiliary fuel and improve the ignition stability of a pulverized coal burner to reduce the DSS operation. An object of the present invention is to provide a pulverized coal burner capable of performing a load operation.

[0019]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a method for removing primary air and pulverized coal conveyed from a mill.
Combustion of the mixed fluid near the pulverized coal nozzle flame stabilizer
In the pulverized coal collected at the center of the pulverized coal nozzle
Primary empty with little pulverized coal
Such as a venturi, which has a constriction to generate air
First concentrating means and disposed downstream of the first concentrating means
It is, a second concentrating means having an enlarged cone, the first
Containing almost no pulverized coal produced by the enrichment means
The secondary air from the pulverized coal nozzle upstream of the second enrichment means
Air, such as the primary air bypass passage,
The air vent passage and the air vent passage according to the burner load
Adjust the amount of air to be removed.
And when the burner is under a low load,
Almost no pulverized coal produced by one concentrating means
Withdrawing primary air from the air vent channel,
Lowering the average flow velocity of the pulverized coal stream fed to the concentrating means, Ba
When the load is high, the pulverized coal
The extraction of the secondary air is regulated by the air release amount adjusting means.
It is characterized by being constituted so that .

[0020]

When the load is low, the fine particles generated by the first concentration means
Primary air containing almost no pulverized coal is extracted from the air vent channel.
To achieve high C / A, and at the same time primary
By extracting the air, the fine particles supplied to the second enrichment means are removed.
The average flow velocity of the pulverized coal stream is lowered to stabilize the flame. Sa
In addition, the second enrichment method uses inertia between pulverized coal particles and air.
Due to the difference in force, it is separated into the concentrated side and the lean side in the same tube.
A flame stabilizer is installed at the burner outlet downstream of the enrichment side of
Measure ignition stability. Therefore, depending on the difference in coal fuel ratio
The difference in ignitability at the burner outlet can be controlled by adjusting the amount of air to be removed.
Bars allow for the same range of wide load across multiple coal types
Can drive.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a pulverized coal burner according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a state of a low load state of the pulverized coal burner.
FIG. 3 is a sectional view showing a state under a high load, and FIG. 3 shows another embodiment.
Sectional view of a pulverized coal burner, FIG. 4 shows still another embodiment.
FIG. 5 is a cross-sectional view of a pulverized coal burner according to a further embodiment of the present invention.

In FIGS. 1 to 5 , reference numerals 4 to 15 denote the same components as those of the prior art.

Reference numeral 18 denotes first concentrating means, which is a movable damper 2
8. Primary air bypass passage 29, closing plate 30, and interlock
It is constituted by a rod 31. 21 is a second concentration means
, Expansion cone 22, particle dispersion controller 23, reduction cone
24 and a circular tube 25. 26 is secondary sky
The air passage 27 is a tertiary air passage. First, at the time of low load, interlocking the movable damper 28 as shown in FIG. 1 bar 3
The pulverized coal particles collected at the center of the pulverized coal nozzle 8 by the venturi 14 by being pushed into the boiler furnace 4 side by 1 pass through the inside of the movable damper 28 and
At 2, it is spread to the outer peripheral portion of the pulverized coal nozzle 8, passes between the movable damper 28 and the expanded cone 22, and is supplied to the boiler furnace 4 from inside the flame stabilizer 15. A part of the primary air containing almost no pulverized coal is supplied to the primary air bypass passage 2 located between the upstream of the movable damper 28 and the downstream of the venturi 14.
9 and is separated into a secondary air flow path 26 and supplied to the boiler furnace 4 together with the secondary air. By extracting a part of the primary air from the primary air bypass passage 29 in this manner, the concentration of the pulverized coal supplied to the inside of the flame stabilizer 15 is necessary for maintaining the flame even at a low load where the C / A is low. Na C / A
Can be held.

Also, the amount of pulverized coal was removed at the same time as it was concentrated.
Because the average flow velocity of the pulverized coal stream downstream of the
The stability of ignition of the flame 15 can be strengthened. Sa
Further, in the second enrichment means 21 in the subsequent stream, pulverized coal particles and
Due to the difference in the inertial force of air, it is separated into concentrated and lean sides in the same tube.
The flame stabilizer 15 is provided at the outlet of the burner downstream of the condensing side.
It is installed and measures ignition stability. Therefore, coal fuel
The difference in the ignitability at the burner outlet due to the difference in the ratio
Can be covered by adjusting the air volume, so the same
A wide range of load operation is possible. Next, at the time of high load, as shown in FIG. 2, the upstream end of the movable damper 28 is pulled out by the interlocking rod 31 to a position corresponding to the contraction portion of the venturi 14, so that the primary air bypass passage 29
Is closed by the movable damper 28 and the primary air bypassing to the secondary air flow path 26 side is eliminated to burn.

Next, the relationship between the cross-sectional areas of the respective channels will be described. The cross-sectional area of each channel is defined as follows.

A) The cross-sectional area of a portion surrounded by the inner diameter of the pulverized coal nozzle 8 and the outer diameter of the particle dispersion controller 23: S1 b) The cross-sectional area between the movable damper 28 and the enlarged cone 22: S2c ) The cross-sectional area of the portion surrounded by the inner diameter of the movable damper 28 and the outer diameter of the circular pipe 25 around the heavy oil starting burner 3 is: S3 d) The cross-sectional area of the primary air bypass flow path 29 is: S4.

The cross-sectional area at a low load illustrated in FIG. 1, S
2 <S1 <S3, and the cross section of the flow path for controlling the pulverized coal high concentration flow is S2. The relationship between S2 and S4 also depends on the pulverized coal enrichment rate, but at a burner load of about 15%, the pulverized coal primary air amount (C / A: weight ratio) in the primary air and pulverized coal flows in the figure. ) Is about 0.08, so concentration about 3 times (C / A = 0.24) is required. So figure
In order to make the C / A of the pulverized coal high-concentration stream 0.24 to 0.24, S4 must be at least three times S2. Therefore,
The relationship between the cross-sectional areas at low load is S2 <S1 <S3 and S2
4 ≧ 3S2.

On the other hand, when the load is high, as is apparent from FIG. 2 , S4 is substantially zero because it is closed by the movable damper 28, and the primary air bypass passage 2
The amount of air bypassing from 9 to the secondary air flow path 26 is eliminated. The relationship among S1, S2 and S3 is that S1 is the smallest, and the cross-sectional area of the flow path for controlling the flow of primary air and pulverized coal is S1.
It becomes 1.

FIG. 3 is a sectional view of a pulverized coal burner showing another embodiment. 1 and 2 is that the movable damper 28 is arranged on the inner surface of the pulverized coal nozzle 8 and the interlocking rod 31 for controlling the movable damper 28 is installed in the secondary air passage 26. It is. In FIG. 3 , when the movable damper 28 is located at the position indicated by the solid line, it indicates a state under high load, and when it is located at the position indicated by the broken line, it indicates the state under low load. During high load, the primary air bypass passage 29 as is apparent from FIG. 3 may be the same combustion to that of closed by a movable damper 28 Figure 2.

On the other hand, when the load is low, the high-concentration pulverized coal collected at the center of the pulverized coal nozzle 8 by the venturi 14 and the primary air are supplied to the inside of the closing plate 30 of the movable damper 28 and the enlarged cone of the second enrichment means 21. While being supplied to the boiler furnace 4 from the inside of the flame stabilizer 15 through the space between the outer wall 22 and
A part of the primary air containing almost no pulverized coal passes between the outside of the closing plate 30 of the movable damper 28 and the venturi 14, and is extracted from the primary air bypass flow path 29 to the secondary air flow path 26. The effect of this embodiment is that the interlocking rod 31 for controlling the movable damper is provided in the secondary air passage 26,
Wear due to pulverized coal is reduced.

[0032] Next will be described another embodiment with reference to FIG.

FIG. 4 differs from the pulverized coal burner of FIGS. 1 to 3 in that a primary air bypass extraction passage 32 is provided around the outer periphery of the pulverized coal nozzle 8, and a combustion air damper 33 and a secondary air passage 26 are provided in the secondary air passage 26. A combustion air control interlocking rod 34 is provided, and the other description is the same as that of FIGS. 1 to 3 .

First, when the load is low as shown in FIG. 4 , the movable damper 28 is pushed into the boiler furnace 4 as shown by a solid line, so that the pulverized coal particles collected at the center of the pulverized coal nozzle 8 by the venturi 14 are removed. It passes through the inside of the movable damper 28, spreads outward with the enlarged cone 22 of the second concentrating means 21, passes between the movable damper 28 and the enlarged cone 22 a, and is supplied to the boiler furnace 4 from inside the flame stabilizer 15. Also,
Part of the primary air containing almost no pulverized coal enters the primary air bypass extraction passage 32 through the primary air bypass passage 29 from between the upstream of the movable damper 28 and the venturi 14, and enters the boiler furnace 4. Supplied. In this case, the combustion air damper 3 provided on the upstream side of the primary air bypass extraction passage 32, that is, in the middle of the secondary air passage 26.
3 is closed, and the air extracted from the primary air bypass channel 29 flows through the primary air bypass extraction channel 32.

As described above, even when the load is low and the C / A is low, the concentration of the pulverized coal supplied from the inside of the flame holder 15 can be surely concentrated to the C / A necessary for holding the flame.

Next, at the time of high load, by pulling the movable damper 28 to a position corresponding to contraction of the venturi 14 as shown by a broken line in FIG. 4 by the interlocking rod 31, the movable damper a primary air bypass passage 29 The primary air bypass passage 28 is closed by the primary air bypass extraction passage 32, and the primary air bypassed is eliminated.

On the other hand, the primary air bypass extraction passage 32
By opening the combustion air damper 33 located upstream of the primary air bypass, the combustion air flows from the secondary air passage 26 into the primary air bypass extraction passage 32.

[0038] Next will be described another embodiment with reference to FIG.

[0039] Figure 5 of the pulverized coal burner and different points pulverized coal burner of FIG. 4, but in that of Figure 4 is provided with a venturi 14 in the pulverized coal nozzle 8, this venturi 14 in that of FIG. 5 The difference is that a current contractor 35 is provided instead.

In FIG. 5 , when the movable damper 28 is located at the position indicated by the solid line, the combustion air damper 33 is in a high load state.
Is located at the position indicated by the broken line, indicating a state at the time of low load.

When the load is high, the pulverized coal and the primary air collected at the center of the pulverized coal nozzle 8 by the flow constrictor 35 are
The air flows between the pulverized coal nozzle 8 and the second concentrating means 21, and the combustion air from the secondary air flow path 26 flows through the primary air bypass extraction flow path 32 around the nozzle.

On the other hand, when the load is low, the high-concentration pulverized coal and primary air collected at the center of the pulverized coal nozzle 8 by the flow constrictor 35 are supplied to the downstream side of the movable damper 28 and the particle dispersion controller 23.
A part of the primary air which is supplied to the boiler furnace 4 from the inside of the flame stabilizer 15 and contains little pulverized coal through the space between the expanded cone 22 and the outer wall of the condensate cone 22 and the upstream of the movable damper 28 From the primary air bypass channel 29 between
After entering the primary air bypass extraction passage 32, the flame stabilizer 15
Is supplied to the boiler furnace 4 from outside. At this time, the combustion air damper 33 is closed, and only the primary air extracted from the primary air bypass passage 29 flows through the primary air bypass passage 29. Primary air can be extracted from the

The effect of this embodiment is that the length of the pulverized coal burner 7 can be shortened and the production cost can be greatly reduced because the venturi 14 is changed to the current contractor 35.

[0044]

According to the present invention, when the load is low , the first concentration is performed.
Primary air substantially free of pulverized coal produced by means
High C / A by extracting air from the air vent channel
At the same time as the primary air
The average flow rate of the pulverized coal stream supplied to the
Measure stabilization. Further, in the second concentration means,
Due to the difference in inertial force between pulverized coal particles and air,
Separated to the lean side and kept at the burner outlet downstream of the concentrated side
A firearm is installed to measure ignition stability. Therefore, coal
Difference in ignitability at the burner outlet due to the difference in fuel ratio
Because it can be covered by adjusting the amount of air to be pulled out,
Wide-range load operation in the same range.

[Brief description of the drawings]

FIG. 1 shows a low load state of a pulverized coal burner according to an embodiment of the present invention .
It is sectional drawing which shows the state of.

FIG. 2 is a cross-sectional view showing a state of the pulverized coal burner under a high load.
FIG.

FIG. 3 is a sectional view of a pulverized coal burner according to another embodiment.
You.

FIG. 4 is a sectional view of a pulverized coal burner according to still another embodiment.
It is.

FIG. 5 is a sectional view of a pulverized coal burner according to still another embodiment.
It is.

FIG. 6 is a schematic system diagram of a pulverized coal-fired boiler.

FIG. 7 is an enlarged sectional view of a conventional pulverized coal burner.

FIG. 8 is a characteristic curve diagram showing a burner load on a horizontal axis and a weight ratio between pulverized coal (C) and air (A) on a vertical axis.

[Explanation of symbols]

5 Mill 8 Pulverized Coal Nozzle 14 Venturi 15 Flame Holder 18 First Concentrating Means 21 Second Concentrating Means 22 Expansion Cone 23 Particle Dispersion Controller 24 Reduction Cone 25 Circular Tube 26 Secondary Air Flow Path 27 Tertiary Air Flow Path 28 Movable damper 29 Primary air bypass passage 30 Closing plate 31 Interlocking rod

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Baba 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Laboratory Co., Ltd. (72) Inventor Hiromi Ikeda 3-36 Takara-cho Kure City, Hiroshima Prefecture Babkotsuk Date Inside Kure Research Laboratories Co., Ltd. (72) Inventor Shigeki Morita 6-9 Takaracho, Kure City, Hiroshima Pref. Inside Kure Plant, Babkotsuk Ltd. (72) Hironobu Kobayashi 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (56) References JP-A-61-285306 (JP, A) JP-A-4-20702 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23D 1/00

Claims (1)

(57) [Claims] 1. A method of burning a mixed fluid of primary air and pulverized coal conveyed from a mill in the vicinity of a flame stabilizer of a pulverized coal nozzle, wherein pulverized coal is collected and concentrated at a central portion of the pulverized coal nozzle.
Both produce primary air with little pulverized coal
A first concentrating means having a contraction section, and disposed on the downstream side of the first concentrating means,
A second enrichment means having a pulverized coal generated by the first enrichment means.
Pulverized coal upstream of the second enrichment means
The air bleed passage for extracting from the nozzle and the amount of air bleed from the air bleed passage according to the burner load
Adjusting means for adjusting the amount of air removed, and when the burner is under a low load , the air is generated by the first concentrating means.
The primary air that contains almost no pulverized coal
Withdrawn from the flow path and supplied to the second concentration means
Lowers the average flow rate of the pulverized coal stream and hardly contains the pulverized coal when the burner is under heavy load
The removal of primary air is regulated by the air removal amount adjusting means.
A pulverized coal burner, characterized in that the burner is configured to be controlled .