JP2000234704A - Pulverized coal combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce heat load in the vicinity of a side wall of a combustion furnace and increase the excess air ratio of a burner provided on a wall surface of the furnace, which is suitable for preventing formation of a reducing atmosphere. SOLUTION: Among coal feeding pipes 5 which connect a mill 4 and a burner 7, the radius of a coal feeding pipe 5a extending to a burner 7a which is arranged in the vicinity of a side wall 8b adjoining a furnace wall 8a of a furnace 8, where the burner 7 is located, is made smaller than that of a coal feeding pipe 5b which extends to a burner 7b at the central portion of the wall 8a. Accordingly, the amount of fuel supplied to the burner 7a is reduced compared with that supplied to the burner 7b at the central portion of the wall 8a where the burner 7 is located. Thus the excess air ratio of the burner 7a positioned adjacent to the side wall 8b is increased, the amount of air in the vicinity of the side wall 8b is increased, slagging caused by the reduction of heat load is suppressed and incomplete combustion of the fuel is suppressed to suppress production of CO. Further, the amount of sulfide produced by combustion of the fuel is suppressed by suppressing generation of uncombusted fuel and permitting reducing atmosphere in the flames to decrease, thereby preventing the wall surface of the furnace from being corroded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus for a fuel such as a particulate fuel.

[0002]

2. Description of the Related Art Nitrogen oxides (NO
In a burner in which the content of x) is reduced, that is, a so-called low NOx burner, conventionally, in order to perform denitration in a flame, the amount of air to fuel supplied to the burner (hereinafter, referred to as a burner air ratio or an air ratio) is reduced. By burning at high temperature in the initial stage of fuel combustion in the burner, oxygen consumption is promoted to create a reducing atmosphere, and NOx generated in the combustion flame is reduced.

[0003] When a reducing atmosphere due to a flame is formed near the furnace wall where the burner of the combustion furnace is disposed, the generation of hydrogen sulfide is promoted, and the side wall adjacent to the furnace wall where the burner is disposed causes reduction corrosion. there is a possibility. Further, when burning a fuel having a low ash melting point, slugging may occur when the heat load on the side wall is high.

[0004] In the present specification, the side wall means a combustion furnace wall surface adjacent to a furnace wall on which a burner is installed. And there is a possibility that corrosion may occur in the opposed combustion,
This is a portion where the flame of the side wall (furnace wall 8b of FIG. 1) collides with the wall, and the flame does not collide with the front and rear walls (furnace wall 8a of FIG. 1), so there is no risk of corrosion. Further, the vicinity of the side wall is also a region where CO generated by incomplete combustion of fuel and unburned components in combustion ash pass through.

[0005] As measures against these problems, the heat load near the side wall adjacent to the furnace wall where the burner of the combustion furnace is arranged is reduced, and the reducing atmosphere is not formed near the side wall. In addition, it is conceivable to increase the amount of air flowing near the side wall.

[0006] As a method of reducing the NOx concentration in the combustion gas, the most side wall (furnace wall adjacent to the furnace wall on which the burner is disposed) further above the burner arrangement region at the uppermost stage is described.
There is a method of providing an air supply hole between the burner and the side wall close to, and introducing air from the vicinity of the side wall into the furnace, but this removes CO in the exhaust gas and unburned components in the generated ash. It is a method that tries to remove after occurrence.

[0007] In order to suppress the generation of unburned components in hydrogen sulfide, CO and ash, the amount of air near the side wall adjacent to the furnace wall provided with a burner is increased, for example, a furnace in which a burner of a combustion furnace is disposed. It is effective to increase the burner air ratio at the burner located near the end wall side and near the adjacent side wall.

[0008]

By the way, in a conventional combustion apparatus of a system in which fuel is supplied from a plurality of burners or one mill to a plurality of burners in a combustion furnace such as one boiler, respectively, FIG. As shown in the burner arrangement diagram, burners 7 having the same capacity and the same size are all used. Also, the fuel supply pipes such as a plurality of coal supply pipes 5 for supplying a mixed fluid of fuel and primary air to each burner 7 have the same diameter in one combustion furnace 8.

In a conventional combustion apparatus of the type in which fuel is supplied from a plurality of burners 7 or a single mill 4 to a plurality of burners 7 in a combustion furnace such as the one boiler, the adjustment of the burner air ratio is not controlled. The fuel supply amount is increased or decreased for each mill 4 according to the moisture in the coal, the crushability or the combustibility of the raw coal, and the fuel supply amount is provided on the outer peripheral portion of the burner 7 as shown in the burner sectional view of FIG. This is performed by adjusting the opening degree of the damper 20 or the register provided in the secondary air flow path 18 and the tertiary air flow path 19.

For this reason, the amount of fuel supplied to the burners 7 is determined uniformly for each mill 4, and the amount of fuel supplied cannot be determined for each of the plurality of burners 7 provided. Further, for example, when a valve (not shown) provided in the coal feed pipe 5 is throttled, the coal feed rate is reduced, and coal deposition in the coal feed pipe 5, an increase in pressure loss, and a flashback in the burner 7 may occur. Therefore, the fuel supply amount to a specific burner 7 among the burners 7 provided on the furnace wall 8a of the combustion furnace 8 cannot be limited and reduced.

Further, there is a limit in adjusting the amount of air supplied by the damper 20 or the register in the secondary air passage 18 and the tertiary air passage 19 provided on the outer peripheral portion of the burner 7, and the burner has such an effect as to be expected. It is difficult to increase the air ratio.

In order to reduce the heat load near the side wall 8b adjacent to the furnace wall 8a where the burner 7 of the combustion furnace 8 is arranged,
There is also a method in which the direction of flame emission from the burner 7 is directed toward the opposite side of the side wall 8b, that is, toward the inside of the combustion furnace 8, so that the flame does not hit the side wall 8b of the combustion furnace 8 as much as possible. The flame from the burner 7 near the side wall 8b may interfere with the flame from the burner 7 disposed inside the combustion furnace 8 from the burner 7, and the effective utilization rate of the combustion furnace 8 may be reduced.

An object of the present invention is to solve the above-mentioned problems of the prior art, to reduce the heat load near the side wall adjacent to the furnace wall where the burner of the combustion furnace is arranged, and to achieve combustion suitable for preventing the formation of a reducing atmosphere. An object of the present invention is to provide means for increasing the air ratio of a burner provided on a furnace wall.

[0014]

An object of the present invention is to provide a combustion furnace for burning fuel conveyed by primary air and a plurality of combustion furnaces for burning fuel provided on a furnace wall of the combustion furnace. In a combustion device provided with a burner and a fuel supply pipe for supplying a mixed fluid consisting of fuel and primary air to each of the burners, the burner is disposed near a side wall adjacent to a furnace wall in which the burner is provided among the plurality of burners. This problem is solved by a combustion apparatus in which the diameter of a fuel supply pipe for supplying a burner to be used is reduced as compared with the diameters of other fuel supply pipes.

In the above combustion apparatus of the present invention, a plurality of burners for burning fuel conveyed by the primary air are provided with a combustion air supply flow path for supplying secondary air and tertiary air, and The cross-sectional area of the combustion air supply flow path to be supplied to the burner arranged near the side wall adjacent to the furnace wall provided with the burner is larger than the cross-sectional area of the combustion air supply flow path to be supplied to the other burners. Is desirable.

Another object of the present invention is to provide a combustion furnace for burning fuel carried by primary air, a plurality of burners provided on a furnace wall of the combustion furnace for burning fuel, and each of the burners. A fuel supply pipe for supplying a mixed fluid consisting of fuel and primary air to a top of a furnace wall provided with the plurality of burners and near a side wall adjacent to the furnace wall. The diameter of the fuel supply pipe for supplying fuel to the burners is made smaller than the diameter of the fuel supply pipe for supplying fuel to the other burners, and the diameter of the fuel supply pipe at the top of the furnace wall where the plurality of burners are provided and not at the side near the side wall The problem is solved by a combustion apparatus in which the diameter of a fuel supply pipe for supplying a burner disposed at the upper stage is larger than the diameter of a fuel supply pipe for supplying fuel to other burners.

In the combustion apparatus having the above-described structure, a plurality of burners for burning fuel carried by the primary air are provided with a combustion air supply flow path for supplying secondary air and tertiary air, and The cross-sectional area of the combustion air supply flow path to be supplied to the burner disposed at the uppermost stage of the furnace wall provided with the burner and near the side wall adjacent to the furnace wall is the same as that of the combustion air supply path to be supplied to other burners. The cross-sectional area of the combustion air supply flow path that is larger than the cross-sectional area of the flow path and is supplied to the burner arranged at the uppermost stage of the furnace wall where the plurality of burners are provided and at the uppermost stage that is not near the side wall is The combustion air supply passage to be supplied to the other burners may be configured to have a smaller cross-sectional area.

[0018]

The burner in the vicinity of the side wall adjacent to the furnace wall where the burner of the combustion furnace is disposed has a burner throat diameter smaller than that of the other burners, and the diameters of the secondary air and tertiary air supply passages are different. If the size is the same as that of the burner, the supply amounts of the secondary air and the tertiary air are larger than those of the other burners.
Therefore, in the burner arranged near the side wall, the air ratio in the furnace width direction can be increased to about 0.95 as compared with the case where the air ratio in the furnace width direction is uniform at 0.90 when the burner air ratio is not adjusted. To increase.

Further, the flame of the burner disposed near the side wall adjacent to the furnace wall in which the burner of the combustion furnace is disposed is smaller than the flame obtained by other burners, and the oxygen concentration at the time of fuel combustion also increases. I do.

At this time, the capacity of the burner from the center of the furnace wall is made larger than that of all the burners in the prior art boiler compared to the same size, so that the burner is located near the side wall adjacent to the furnace wall where the burner is arranged. It is possible to compensate for the decrease in fuel supply to a certain burner.

In this manner, slagging can be suppressed by reducing the heat load, CO generation is suppressed by suppressing incomplete combustion of fuel, furthermore, generation of unburned fuel is suppressed, and reducing atmosphere in flame is reduced. By reducing the amount of sulfide, the amount of sulfide generated by combustion of the fuel is suppressed, and the wall of the combustion furnace can be prevented from being corroded.

[0022]

1 is a combustion system diagram of a pulverized coal combustion boiler according to an embodiment of the present invention. FIG. 2 is a burner arrangement diagram of the boiler of FIG. 1. FIG. 3 is a sectional view of a combustion furnace. 4 is a cross-sectional view of a burner in which the burner throat diameter is reduced, and FIG. 6 shows a burner air ratio in a width direction of a furnace wall where a burner is disposed in a combustion furnace.

In FIG. 1, the coal includes a plurality of coal bunker 1
And is sent from each coal bunker 1 to the mill 4 via the coal supply pipe 2 and the coal feeder 3 according to the load of the boiler which is the combustion furnace 8. Further, the coal pulverized in each mill 4 is transferred as pulverized coal to the corresponding burner 7 provided on the furnace wall 8a of the combustion furnace 8 through the coal feed pipe 5, but the primary ventilation 12 , And preheated by the air preheater 10, the primary air supplied through the air passage 13 is used.

The secondary and tertiary air for fuel combustion is preheated by an air ventilator 11 from an air preheater 10 and then supplied to a wind box 6 via a wind path 13. In addition, the combustion exhaust gas is supplied to the air preheater 10 from the combustion furnace 8 via the flue 9.

Conventionally, as shown in FIGS. 7 and 8, all burners 7 and coal feed pipes 5 of one boiler have the same capacity and the same size. For this reason, as shown by the straight line 21 in FIG. 6, the air ratio of each burner 7 has the same value in a plurality of burners 7 arranged along the width direction of a specific furnace wall 8a of a normal combustion furnace (furnace) 8. have.

When the flow rates of the secondary air and the tertiary air are adjusted by the register 20 (FIG. 8), the air ratio of the burner 7 near the side wall 8b adjacent to the furnace wall 8a among the burners 7 arranged on the furnace wall 8a Is the furnace wall 8a on which the burner 7 of the combustion furnace 8 is arranged
It is possible to increase the air ratio in comparison with the air ratio of the burner 7 near the center.

However, in the adjustment by the register 20, FIG.
The maximum air ratio of the burner 7 near the furnace wall 8b is 0.92 compared to the case where the air ratio in the furnace width direction shown in FIG.
Can only increase up to.

On the other hand, as shown in FIG. 2, in the embodiment of the present invention, of the coal feed pipe 5 connecting the mill 4 and the burner 7, the side wall in the burner 7 arranged on the furnace wall 8a of the combustion furnace 8 is used. 8b
Feed pipe 5 to burner 7a arranged at a position adjacent to
The diameter of a is smaller than the diameter of the coal feed pipe 5b reaching the burner 7b from the center of the furnace wall 8a, and the amount of fuel to be conveyed is from the center of the furnace wall 8a to the burner 7b. It decreases compared to the supply amount.

At this time, the capacity of the burners 7b from the center of the furnace wall 8a is the same as that of FIG.
The capacity is larger than the capacity of the conventional burner shown in FIG. This is to compensate for the decrease in the amount of coal supplied to the burner 7a disposed adjacent to the side wall 8b.

FIG. 4 is a side sectional view of a burner 7a located at a position adjacent to the side wall 8b in the burner 7 arranged on the furnace wall 8a of the combustion furnace 8 shown in FIG. Burner 7a
Is smaller than that of the other burner 7b, but the diameters of the secondary air supply passage 18 and the tertiary air supply passage 19 provided on the outer periphery of the burner 7a are the same as those of the other conventional burners 7. Therefore, the supply amounts of the secondary air and the tertiary air increase. Therefore, as shown in FIG.
Can increase the burner air ratio to about 0.95. Thus, the side wall 8b of the combustion furnace 8
4, the burner air ratio increases, and the air amount near the side wall 8b increases.

FIG. 3 is a plan view of a boiler portion including the combustion furnace 8 shown in FIG. 2. The burner is located at a position adjacent to a side wall 8b of a furnace wall 8a on which the burner 7 of the combustion furnace 8 is arranged. The flame 14a of 7a is a flame 1 obtained by another burner 7b.
4b, and the oxygen concentration during fuel combustion also increases.

As a result, the generation of slugging is suppressed due to the reduction of the heat load, the formation of a reducing atmosphere in the vicinity of the side wall 8b of the combustion furnace 8 can be prevented, and the incomplete combustion of fuel is suppressed. Generation is suppressed. In addition, the generation of unburned fuel is suppressed, and the reducing atmosphere in the flame is reduced, so that the amount of sulfide generated by the combustion of the fuel is suppressed and the furnace wall 8b of the combustion furnace 8 is prevented from corroding. it can.

It is to be noted that corrosion may occur in the opposed combustion at a portion where the flame collides with the flame on the side wall (furnace wall 8b) and the flame does not collide with the front and rear walls (furnace wall 8a). There is no risk of corrosion. Therefore, the effect of preventing corrosion of the furnace wall 8a is unnecessary.

The structure of the burner 7 of the present invention is, as shown in FIG. 5, at a position adjacent to the side wall 8b of the combustion furnace 8 in the coal feed pipe 5 connected to the mill 4, and at the end of the combustion furnace 8. Even if the diameter of the coal feed pipe 5c connected to only the burner 7c arranged in the upper stage and the burner throat diameter are smaller than the diameter of the coal feed pipes 5d and 5e connected to the other burners 7d and 7e and the burner throat diameter. good.

In the example shown in FIG. 5, the capacity of the burner 7d arranged at the uppermost stage and not adjacent to the side wall 8b of the combustion furnace 8 is larger than that of the burner 7e arranged at a position other than the uppermost stage. This is because the burner 7d inside the uppermost stage compensates for the decrease in the amount of coal supplied by the uppermost stage burner 7c disposed adjacent to the side wall 8b of the combustion furnace 8.

Since the burner throat diameter increases in the following order, the coal supply also increases in the same order. Uppermost burner 7c adjacent to combustion furnace side wall 8b <non-topmost burner 7e <topmost burner 7d not adjacent to combustion furnace side wall 8b

The amount of fuel supplied to the uppermost burner 7c adjacent to the side wall 8b of the furnace wall 8a of the combustion furnace 8 is smaller than the amount of fuel supplied to the other burners 7d and 7e. The secondary air and the tertiary air supplied from the ventilator 11 to the uppermost burner 7c via the wind box 6 are supplied in the same amount as the other burners 7d and 7e, so that the burner air ratio increases.

Burner 7e arranged at a position other than the uppermost stage
Have the same burner size and the same diameter of the coal supply pipe 5e connected to the burner 7e, so that all the burners 7e are supplied with the same amount of coal, and there is no difference in the amount of coal supplied to each burner 7e. Is also uniform between the burners 7e.

Incomplete combustion substances and reducing substances generated from the fuel burned by the burners 7e other than the uppermost row tend to slip through the vicinity of the joint between the furnace wall 8a and the side wall 8b of the combustion furnace 8, but the combustion furnace 8 Since the inside of the combustion furnace 8 near the uppermost burner 7c, which is located at a position adjacent to the side wall 8b, is under an air-rich condition, the combustion is performed here. In this way, the incomplete combustion material and the reducing material are removed from the side wall 8 of the combustion furnace 8.
It can be prevented from slipping in the vicinity of b.

[0040]

According to the present invention, as the air ratio of the burner arranged near the side wall adjacent to the furnace wall where the burner of the combustion furnace is arranged increases, the amount of air near the combustion furnace side wall increases, and the combustion rate increases. The heat load on the furnace side wall is reduced, and slagging of ash is suppressed. Furthermore, the formation of a reducing atmosphere due to an increase in the amount of oxygen supplied during combustion is suppressed, and the effects of reducing corrosion inhibition and promoting safe combustion are obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram of a combustion device according to an embodiment of the present invention.

FIG. 2 is a layout diagram of burners according to the embodiment of the present invention.

FIG. 3 is a plan view of a furnace in which the burner shown in FIG. 2 is used.

FIG. 4 is a sectional view of the burner in which the burner throat diameter shown in FIG. 2 is reduced.

FIG. 5 is a layout diagram of burners according to the embodiment of the present invention.

FIG. 6 is a diagram showing a burner air ratio in a furnace width direction.

FIG. 7 is a burner arrangement diagram of a boiler using a burner according to the related art.

FIG. 8 is a sectional view of a burner according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coal bunker 2 Coal supply pipe 3 Coal feeder 4 Mill 5 Coal supply pipe 6 Wind box 7 Burner 8 Combustion furnace 9 Flue 10 Air preheater 11 Push-in ventilator 12 Primary ventilator 13 Wind path 14 Flame 18 Secondary air flow path 19 Tertiary air flow path 20 Damper

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Keiji Ishii 2-4-1 Hamamatsucho, Minato-ku, Tokyo Inside Babcock Hitachi Co., Ltd. (72) Inventor Shigenobu Ohashi 2-4-2 Hamamatsucho, Minato-ku, Tokyo No. 1 Babcock Hitachi F-term (reference) 3K065 TA01 TA04 TB08 TB13 TC01 TD01 TD07 TE01 TF02 TH04 TH12 TH14 TH18

Claims (4)

[Claims] 1. A combustion furnace for burning fuel conveyed by primary air, a plurality of burners provided on a furnace wall of the combustion furnace for burning fuel, and each burner is provided with fuel and primary air. A fuel supply pipe for supplying each of the mixed fluids, wherein the diameter of the fuel supply pipe for supplying to a burner arranged in the vicinity of a side wall adjacent to a furnace wall provided with the burner among the plurality of burners is selected. A combustion apparatus characterized in that the diameter is reduced as compared with the diameter of a fuel supply pipe for supplying fuel to another burner. 2. A plurality of burners for burning fuel conveyed by the primary air are provided with a combustion air supply passage for supplying secondary air and tertiary air, and a furnace wall provided with the plurality of burners is provided. The cross-sectional area of the combustion air supply passage for supplying to a burner disposed near the side wall adjacent to the burner is larger than the cross-sectional area of the combustion air supply passage for supplying to other burners. 2. The combustion device according to 1. 3. A combustion furnace for burning fuel conveyed by primary air, a plurality of burners provided on a furnace wall of the combustion furnace for burning fuel, and a fuel and primary air are supplied to each of the burners. A fuel supply system comprising: a fuel supply pipe for supplying a mixed fluid, wherein fuel is supplied to a burner disposed at an uppermost stage of a furnace wall provided with the plurality of burners and near a side wall adjacent to the furnace wall. The diameter of the pipe is made smaller than the diameter of a fuel supply pipe for supplying fuel to the other burners, and the burner is arranged at the highest level of the furnace wall where the plurality of burners are provided and not at the side near the side wall. A combustion apparatus characterized in that the diameter of a fuel supply pipe for supplying fuel to other burners is larger than the diameter of a fuel supply pipe for supplying fuel to other burners. 4. A plurality of burners for burning fuel conveyed by the primary air are provided with a combustion air supply passage for supplying secondary air and tertiary air, and a furnace wall provided with the plurality of burners is provided. The cross-sectional area of the combustion air supply flow path to be supplied to the burner arranged at the uppermost stage and near the side wall adjacent to the furnace wall is smaller than the cross-sectional area of the combustion air supply flow path to be supplied to the other burners. The cross-sectional area of the combustion air supply flow path to be supplied to the burner arranged at the uppermost stage of the furnace wall provided with the plurality of burners and at the uppermost stage which is not near the side wall is supplied to other burners. 4. The combustion apparatus according to claim 3, wherein the cross-sectional area of the combustion air supply passage is smaller than the cross-sectional area.