JPH1122915A - Method and device therefor for burning sulfur-containing fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent sulfuric corrosion of the waterwall tube without increasing Nox in the exhaust gas in a boiler burning sulfur-containing fuel. SOLUTION: In setting burners adjacently to side walls 21, 22 on the right and left the burners themselves may be inclined in direction oppositely to the side walls for burning, or may be set with the direction of the injection vertically from the fuel nozzles of the burners 23-28 placed adjacently to the right or left side walls or in a direction oppositely to that of the side walls. It is also possible to control the direction of the injection while the boiler is in operation. Furthermore, the concentration of sulfur dioxide in the furnace is measured at two spots, which are at a burner level and above the after-air port, to see to it by regulating the direction of the injection from the fuel nozzles adjacent to the side walls that the difference in amount of signals from the two falls within a specified value. It may as well do to measure hydrogen sulfide in the furnace at a spot serving as a burner level and regulate the direction of the fuel nozzles so as to be placed within specified values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion technique for a fuel containing sulfur, and particularly to a water wall pipe without increasing NOx in exhaust gas when a fuel containing high sulfur fuel is burned. The present invention relates to a combustion method capable of preventing the corrosion of ash.

[0002]

2. Description of the Related Art It is known that boilers using fossil fuels such as coal and heavy oil generate nitrogen oxides (hereinafter referred to as NOx) by combustion. Methods for reducing this NOx include (1) lean-burn, (2) two-stage combustion,
(3) Denitration in furnace, (4) Mixing of exhaust gas, (5) Low NOx burner, (6) Arrangement of fuel injection holes of fuel nozzles, etc. have been put to practical use by a method alone or in combination.

[0003] Of the above (6), for the combustion of liquid fuel, a plurality of (in this case, six examples) fuel injection holes 32, 33 are usually provided as shown in the plan view of FIG. The fuel nozzles 31 divided into groups are used.
FIG. 14 is a side view of the fuel nozzle shown in FIG. 13, and shows fuel injection holes 32, 3 provided at positions above and below the fuel nozzle.
3, the fuel is injected from the fuel injection direction 3, and a certain or more injection angle α that does not interfere with each other is set in the injection direction as shown in the figure.

[0004] By using such a fuel nozzle, the flame generated from the fuel injection holes 32 and 33 becomes excessive in the injection direction, and a fuel-lean flame is generated in a portion away from the injection direction. In other words, by using such a fuel nozzle, it becomes a lean combustion,
As a result of the good mixing of the dispersed injected fuel and combustion air in the downstream part of the flame, NOx can be reduced.

[0005]

As a problem in using the above-mentioned fuel nozzle, there is a problem that flames of adjacent burners interfere with each other, so that the fuel cannot be completely burned and unburned matter increases. As a method to solve this problem,
Japanese Patent Publication No. 25084 discloses a method in which the fuel injection directions from the fuel nozzles of burners adjacent in the vertical and horizontal directions are different from each other in the vertical and horizontal directions.
However, although the method described in the above publication can prevent the interference of the flames of the adjacent burners, it does not consider that the flame collides with the left and right side walls.

That is, as shown in FIG. 16 and FIG. 17 which is a cross-sectional view taken along the line AA ′ of FIG. 16, the fuel nozzles of the burners 24 and 27 adjacent to the left side wall 21 or the right side wall 22 have the right and left fuel nozzle injection directions. Means that the flame 44 (see FIG. 17) collides with the left and right side walls 21 and 22. Then, the atmosphere on the surface of the left and right side wall tubes is reduced to a state of oxygen deficiency due to the flame of excess fuel, and hydrogen sulfide (H2S) is generated in the fuel containing sulfur (S). Reference numeral 43 shown in FIG. 16 denotes a portion where sulfur corrosion can occur, and reference numerals 201, 202, 203, and 204 in FIG. 17 denote burners adjacent to the side wall.

[0007] When the H2S thus generated comes into contact with the water wall pipe, sulfide corrosion occurs in the water wall pipe material. The rate of pipe wall thinning due to sulfidation corrosion varies with H2 concentration, but is problematic when using high sulfur fuels.

As a method of preventing the collision of the flame with the side wall, it is conceivable to keep a sufficient distance between the burner and the side wall. However, in this case, the furnace becomes inevitably large, and an increase in the cost of the boiler is inevitable.

An object of the present invention is to provide a compact combustion apparatus while effectively preventing sulphation corrosion of a water wall pipe.

[0010]

In order to solve the above-mentioned problems, the present invention comprises a water wall forming a furnace and burners having split fuel nozzles attached to the water wall in multiple stages and multiple rows. In such a combustion device, flames from burners adjacent to the left and right side walls are prevented from directly hitting the side walls.

[0011] For this purpose, combustion is performed by inclining the direction of the burner itself adjacent to the left and right side walls in the direction opposite to the side wall, or changing the injection direction of the fuel nozzles of the burners adjacent to the left and right side walls in the vertical direction or the side opposite to the side wall. It is installed so as to be in the direction and burns.

[0012] In addition, adjusting the injection direction during the operation of the boiler is also a technique included in the present invention. According to this technique, the vertical position in the boiler furnace is the part of the part above the burner level and the after-air port. In at least two places, a device for measuring the sulfur dioxide concentration in the furnace is installed at the center of the left or right side wall, and when the difference in the signal amount from both exceeds a certain value, it is adjacent to the left and right side walls. Adjust the injection direction of the fuel nozzle.

Furthermore, as a similar method, a device for measuring hydrogen sulfide in the furnace is installed at the center of the left or right side wall at a position where the vertical position in the boiler furnace is at the burner level, and a signal value from the device is measured. If exceeds a certain value,
The direction of the fuel nozzles of the burners adjacent to the left and right side walls is adjusted so that the value from the above-mentioned hydrogen sulfide measuring device is equal to or less than a certain fixed value.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A number of embodiments according to the present invention will be described below with reference to FIGS. 1 to 16 and FIG.
FIG. 1 is a side view showing a basic configuration of a boiler, and FIG.
Is a horizontal sectional view of the boiler, and FIGS. 3, 7, 9 and 1
1 and 12 are furnace front views, FIGS. 4, 5, 6, 10, and 13 are plan views showing burner fuel nozzles, and FIG. 14 is a side view showing burner fuel nozzles. .

In the drawings, 1 is a furnace, 2 is a front wall, 3 is a rear wall, 4 is a lower burner on a front wall, 5 is a middle burner on a front wall, 6 is an upper burner on a front wall, 7 is a lower burner on a rear wall, and 8 is a burner on the rear wall. Rear wall middle burner, 9 upper rear wall burner, 10 front wall after air port, 11 rear wall after air port, 12 tertiary superheater, 13 secondary heater, 14 reheat Vessel, 15 is a primary superheater, 16 is a economizer, 21 is a left side wall, 22 is a right side wall,
23, 24 and 25 are lower, middle and upper burners closest to the left side wall, 26, 27 and 28 are lower, middle and upper burners closest to the right side wall, 29 is a fuel injection direction, 30 is an after air port, 31 is a fuel nozzle, 32 is a lower fuel injection hole, 33 is an upper fuel injection hole, 34 is a left fuel injection hole, 3
5 is a right fuel injection hole, 36 is a lower left fuel injection hole, 37 is an upper right fuel injection hole, 38 is a sulfur dioxide detector, 39 is a recorder, 40 is a hydrogen sulfide detector, 41 is an upper injection direction,
2 indicates a lower injection direction. 16 and 17, reference numeral 43 denotes a portion where sulfide corrosion may occur, 44 denotes a flame,
201, 202, 203 and 204 represent burners adjacent to the side walls, respectively.

The sulfide corrosion phenomenon of the ferrite-based metal material will be described with reference to the Fe.S.O. potential diagram shown in FIG. FIG. 15 focuses on 500 ° C. as a representative of the metal temperature of the boiler water wall tube, and explains the region where iron, iron oxide and iron sulfide are stably present at this temperature.

The flame from the burners adjacent to the left and right side walls collides with the center of the left and right side walls. However, in normal low NOx combustion, the air ratio is operated at about 0.8, so the colliding flame is: The atmosphere becomes oxygen deficient. At this time, if the amount of sulfur in the fuel is large, the sulfur potential (Ps2) increases,
As a result, point A in FIG. 15 is obtained. In this atmosphere, the sulfide is more stable than the oxide, and the wall thickness is reduced. To prevent this, the sulfur potential in the flame colliding with the left and right side walls may be reduced to an acceptable value or less (FIG. 15).
B point).

In the present invention, the direction of the burner itself adjacent to the left and right side walls is inclined in the direction opposite to the side wall, and the fuel injection direction from the fuel nozzle of the burner adjacent to the left and right side walls is limited to the vertical direction or the opposite side wall direction. By doing, H2S
Is prevented from colliding with the left and right side walls, so that the water wall pipe hardly undergoes sulfurization corrosion.

Further, in the present invention, the H2S concentration of the left and right side walls at the burner level is measured directly or indirectly, and the fuel nozzle injection direction of the burners adjacent to the left and right side walls is adjusted so that the value becomes less than an allowable value. However, this makes it possible to more reliably prevent the flame containing H2S from colliding with the right and left side walls, thereby effectively preventing the sulfurization corrosion.

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 show an embodiment of the present invention. FIG. 1 is a side view of the boiler, and FIG. 2 is a sectional view taken along the line AA ′ of FIG. In this embodiment, three burners are provided before and after the can in three stages. In FIG. 2, the burners 201, 202, 203 and 204 adjacent to the left and right side walls are installed so that the directions thereof are opposite to the side walls. Therefore, the flame formed by the burners 201, 202, 203 and 204 is prevented from directly hitting the side wall.

In this case, if the inclination α between the burner 201 and the side wall 21 is smaller than 10 °, the collision of the flame with the side wall cannot be prevented.

(Embodiment 2) FIG. 3 shows a second embodiment of the present invention. In the first embodiment, the direction of the burner itself is adjusted, but in the present embodiment, the injection direction of the fuel nozzle of the burner is adjusted. In the case of the present embodiment as well, three burners are provided before and after the can in three stages × 7.
FIG. 4 is a front view of the fuel nozzle used in FIG.
As shown in FIGS. 5 and 6, each is a two-split type.
FIG. 4 shows the fuel injection holes 32 and 33 arranged vertically, FIG. 5 shows the fuel injection holes 32 and 33 arranged vertically, and FIG.

An arrow (→) 29 in FIG. 3 indicates a fuel injection direction at each fuel nozzle. As is apparent from the figure, the fuel nozzles of the burners 23 to 28 adjacent to the left and right side walls are arranged in such a manner that the flame does not collide with the left and right side walls in the vertical direction. On the other hand, the injection directions of the fuel nozzles of the other burners are arranged so as to be different from the injection directions of the fuel nozzles of the adjacent burners, and are arranged so as to avoid interference of the flame.

(Embodiment 3) FIGS. 7 and 8 show a third embodiment of the present invention. In the case of the first embodiment, the flame of the middle burner 24 adjacent to the left and right side walls interferes with the flame from the upper burner 25 and the lower burner 23, and the unburned component may increase slightly.

Therefore, in the present embodiment, the injection direction of the middle burner fuel nozzle is slightly adjusted from the up-down direction to the left-right direction so as to suppress the increase in unburned components and prevent the side wall pipe from being sulfided. .

When adjusting the position of the injection hole of the injection nozzle,
As shown in FIG. 8, the angle β between the injection direction 29 and the vertical axis of the boiler is shown.
Is larger than 45 degrees, the flame may collide with the side wall, so β needs to be 45 degrees or less.

In other words, in a vertical section parallel to the side wall, 4
Included is one that is tilted to 5 degrees or less, further includes one that is tilted to 45 degrees or less in a vertical section perpendicular to the side wall, and further includes the inclination of the former two vector components.

(Embodiment 4) FIG. 9 shows a fourth embodiment of the present invention. In the present embodiment, the fuel injection direction of the burners other than the burners adjacent to the left and right side walls is the same as that of the first embodiment, but, of the burners adjacent to the left and right side walls, the injection direction of the middle burners 24 and 27 is changed to the right or left. Only the minus direction.

According to the present embodiment, there is an advantage that the interference of the flame can be completely prevented and the collision of the flame with the side wall can be prevented as compared with the first and second embodiments. As shown in FIG. 10, the position of the injection hole of the injection nozzle
4 has an injection hole only in the right direction.

(Embodiment 5) FIG. 11 shows a fifth embodiment of the present invention. The injection direction of each burner in this embodiment is the same as that of the second embodiment, but the sulfur dioxide (SO2) concentration is measured at a total of four places above the middle burners 24 and 27 on the left and right side walls and the after-air port 30. A sulfur dioxide detector 38 is provided.

The signals from these detectors are connected to a recorder 39 and monitored as needed. The signal amount from the detector 38 installed in the middle burner of the left or right side wall is the SO2 amount at the burner level, and the signal amount of the detector 38 installed above the after-airport 30 has completely burned. Since this is the amount of SO2 in the furnace, the difference between the two signal amounts corresponds to the amount of H2S generated at the time of the side wall collision of the flame.

Therefore, while monitoring the difference between the above signal amounts, the injection direction of the middle burner fuel nozzles adjacent to the left and right side walls is adjusted so that the difference becomes equal to or less than a preset value.

The corrosion rate of the water wall decreases as the H2S concentration decreases, but its absolute value changes depending on the material of the water wall and the metal temperature. For this reason, the set value is not particularly limited, but when the water wall pipe is made of a low alloy steel of 1 to 2% Cr-Mo (for example, STBA20), the set value is set to 200.
It is preferable that the content be about ppm or less.

Since the horizontal position of the side wall where the flame from the burner adjacent to the side wall is most likely to collide is the center of the side wall,
Preferably, the detector is located at the center of the side wall.

According to the present embodiment, it is possible to more completely prevent the collision of the flame with the side wall than in the case of the first and second embodiments. It is also efficient to make adjustments at startup or when the fuel changes.

(Embodiment 6) FIG. 12 shows a sixth embodiment of the present invention. The injection direction of each burner in the present embodiment is the same as that of the second embodiment, but hydrogen sulfide detectors 40 for measuring the H2S concentration are installed at two places on the middle burners 24 and 27 on the left and right side walls. The injection direction of the middle burner adjacent to the left and right side walls is adjusted so that the signal amount from the detector 40 becomes equal to or less than a predetermined value.

In this embodiment, similarly to the fifth embodiment,
It is possible to more completely prevent the collision of the flame than in the case of the first and second embodiments. Also, in the case of the present embodiment, similarly to the second embodiment, the adjustment may be performed at the time of starting or when the fuel changes, and it is not necessary to constantly monitor.

The embodiment described above is an example in which burners having two divided fuel nozzles are arranged in three stages × seven rows. However, in the present invention, the number of burners and the number of rows are not particularly limited. . The fuel used in the present invention includes not only liquids such as oil but also fuels such as gas and pulverized coal.

[0040]

As described above, according to the present invention, even if a fuel containing a large amount of sulfur is burned, the flame does not collide with the left and right side walls, so that the burner operation for reducing the generation of NOx is performed. Also eliminates the risk of sulfidation corrosion of water wall pipes,
The generation of harmful gas from the boiler is suppressed, and the reliability of the boiler is improved.

Further, since the distance between the burner and the left and right side walls and the burner can be reduced, a compact combustion device can be realized.

[Brief description of the drawings]

FIG. 1 is a side view of a boiler showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view (AA ′ cross section of FIG. 1) of the furnace showing the first embodiment of the present invention.

FIG. 3 is a furnace front view showing a second embodiment of the present invention.

FIG. 4 is a front view of a fuel nozzle in which a fuel injection direction is up and down in a second embodiment.

FIG. 5 is a front view of a fuel nozzle in which a fuel injection direction is left and right in a second embodiment.

FIG. 6 is a front view of the fuel nozzle according to the first embodiment, in which the fuel injection direction is the upper right and lower left directions.

FIG. 7 is a furnace front view showing a third embodiment of the present invention.

FIG. 8 is a diagram illustrating the injection direction of a middle burner adjacent to the left side of the third embodiment.

FIG. 9 is a diagram showing a fourth embodiment of the present invention.

FIG. 10 is a front view of a fuel nozzle of a middle burner adjacent to a left side wall according to a fourth embodiment.

FIG. 11 is a diagram showing a fifth embodiment of the present invention.

FIG. 12 is a diagram showing a sixth embodiment of the present invention.

FIG. 13 is a front view of a two-split type fuel nozzle.

FIG. 14 is a side view of the fuel nozzle shown in FIG.

FIG. 15 is an Fe—SO potential diagram at 500 ° C.

FIG. 16 is a furnace front view showing a position where sulfide corrosion may occur.

FIG. 17 is a furnace sectional view (AA ′ section in FIG. 16) showing a position where sulfide corrosion may occur.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Furnace 2 Front wall 3 Rear wall 4 Front wall lower burner 5 Front wall middle burner 6 Front wall upper burner 7 Rear wall lower burner 8 Rear wall middle burner 9 Rear wall upper burner 10 Front wall after air port 11 Rear wall after air port Air port 12 Tertiary superheater 13 Secondary superheater 14 Reheater 15 Primary superheater 16 Economizer 21 Left side wall 22 Right side wall 23 Lower burner closest to left side wall 24 Middle burner closest to left side wall 25 Upper burner closest to left side wall 26 Lower burner closest to right side wall 27 Middle burner closest to right side wall 28 Upper burner closest to right side wall 29 Fuel injection direction 30 After air port 31 Fuel nozzle 32 Lower fuel injection hole 33 Upper fuel injection hole 34 Left fuel injection hole 35 Right fuel injection hole 36 Left lower fuel injection hole 37 Right upper fuel injection hole 38 Sulfur dioxide detector 3 Burners adjacent to the recorder 40 hydrogen sulfide detector 41 the upper spray direction 42 lower injection direction 43 sulfide site 44 flame 201, 202, 203, 204 the side wall

Claims (7)

[Claims] In a combustion apparatus in which a furnace wall is formed of a water-cooled wall tube and burns a sulfur-containing fuel, the direction of a burner body adjacent to left and right side walls is adjusted, or the fuel injection direction of a burner fuel nozzle is adjusted. A combustion device for a sulfur-containing fuel, wherein the flame does not directly hit the side wall. 2. A combustion apparatus in which a furnace wall is constituted by a water-cooled wall tube and which burns a sulfur-containing fuel, wherein a direction of a burner main body adjacent to right and left side walls is maintained at an angle of 10 degrees or more with respect to the side walls. An apparatus for burning a sulfur-containing fuel. 3. A combustion apparatus in which a furnace wall is constituted by a water-cooled wall tube and which burns a sulfur-containing fuel, wherein a fuel injection direction of an injection hole split type burner fuel nozzle adjacent to left and right side walls is set to a vertical direction. Combustion device for sulfur-containing fuel. 4. A combustion device in which a furnace wall is constituted by a water-cooled wall tube and which burns a sulfur-containing fuel, wherein the upper and lower injection hole split type burner fuel nozzles adjacent to the left and right side walls have a vertical fuel injection direction. An apparatus for burning sulfur-containing fuel, characterized in that a fuel injection direction of a middle injection hole split type burner fuel nozzle adjacent to the left and right side walls is inclined within 45 ° from the vertical direction. 5. A combustion device in which a furnace wall is constituted by a water-cooled wall tube and combusts a sulfur-containing fuel, wherein the upper and lower injection hole split type burner fuel nozzles adjacent to the left and right side walls have a vertical fuel injection direction. An apparatus for burning sulfur-containing fuel, characterized in that the injection hole split type burner fuel nozzle adjacent to the left side wall or the right side wall has only one fuel injection direction on the right or left side. 6. A combustion apparatus in which a furnace wall is formed of a water-cooled wall tube and which burns a sulfur-containing fuel, by controlling a fuel injection direction of burner fuel nozzles adjacent to left and right side walls to prevent a flame from directly hitting the side walls. A method for burning a sulfur-containing fuel, comprising: measuring the sulfur dioxide concentration in the furnace on the left and right side walls at at least two places: a burner level part in the furnace and a part above the after-airport; If the difference between the measured values exceeds a predetermined value, the injection direction of the burner fuel nozzle is adjusted so that the difference between the measured values of the sulfur dioxide concentration is within the predetermined value. How to burn fuel. 7. A combustion apparatus in which a furnace wall is formed of a water-cooled wall tube and which burns a sulfur-containing fuel, a fuel injection direction of burner fuel nozzles adjacent to right and left side walls is adjusted to prevent a flame from directly hitting the side walls. A method for burning sulfur-containing fuel, wherein hydrogen sulfide in the furnace is measured on left and right side walls at a burner level portion in the furnace, and when the measured value in the portion exceeds a predetermined value, the burner fuel is burned. A method for burning a sulfur-containing fuel, comprising adjusting an injection direction of a nozzle so that a measured value of the hydrogen sulfide is within the predetermined value.