JP2002122302A - Boiler apparatus and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler apparatus wherein NOx in waste gas is prevented from being increased, and a water wall pipe is prevented from being corroded. SOLUTION: A soot blower 8 is disposed freely to go forward or backward with respect to a furnace from a soot blower insertion hole 7a formed in membrane bar 7. To the soot blower 8, vapor piping 1 and air piping 4 are connected, and on both piping a vapor opening/closing valve 2 and an air opening/closing valve 3 are provided. The soot blower 8 is rotated at all times with a motor 10 and a power transmitting mechanism to always supply air to the surface of a water wall pipe 6 around the soot blower 8 for bringing the surface of the water wall pipe 6 to a substantially oxidizing atmosphere. The surface of the water wall pipe 6 is prevented from being corroded with the aid of gas in a furnace including H2S. In this situation, the piping is changed over to the side of the vapor piping 1 one or two times to inject vapor with higher pressure than the foregoing air to remove ash adhering to the surface of the water wall pipe 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler apparatus for burning a sulfur-containing fuel, and more particularly to a boiler apparatus for burning water-wall pipes without increasing NOx in exhaust gas when a high-sulfur fuel is reduced. The present invention relates to a boiler device capable of preventing such a problem.

[0002]

2. Description of the Related Art It is known that boilers using fossil fuels such as coal and heavy oil generate NOx (nitrogen oxides) by combustion. There are two methods of reducing this NOx: a method of reducing the amount of NOx itself generated during combustion, and a method of decomposing and removing the generated NOx.
There are two main methods. The former is a method of reducing thermal NOx generated at high temperature and high oxygen concentration.
A combustion method using an x burner and a two-stage combustion method are considered to be effective. These methods aim to reduce the amount of NOx by generating a fuel-rich reducing gas.

In this combustion method, the inside of the furnace is in a reduced state of oxygen deficiency, and the fuel containing sulfur (S) causes the water wall pipe for cooling the furnace wall to come into contact with hydrogen sulfide (H ₂ S), resulting in severe sulfurization. Corrosion occurs. This will be described based on the Fe—SO chemical potential diagram of FIG. FIG. 5 shows the sulfur potential (pS ₂ ) on the vertical axis and the oxygen potential (pO ₂ ) on the vertical axis in a region where iron, iron oxide and iron sulfide are stably present at 500 ° C. corresponding to the metal temperature of the water wall tube. ) Is shown as a logarithm. Flames from the burners adjacent to the left and right side walls collide at 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 becomes an oxygen-deficient atmosphere. . Under such a condition, when the sulfur content in the fuel is large, the sulfur potential (pS ₂ ) increases, and as a result, the sulfur potential (pS ₂ ) is located at the point A in the potential diagram of FIG. This A
The atmosphere in which the point is located is a region where sulfides are more stable than oxides. If the atmosphere becomes inside the furnace, as described above, sulfidation corrosion occurs in the water wall tube, and rapid wall thinning occurs.

[0004] The rate of pipe wall thinning due to sulfidation corrosion varies depending on the concentration of hydrogen sulfide, but this is a major problem particularly when burning high sulfur content fuels. As a method of preventing such reduction corrosion, it is effective to change the atmosphere near the water wall to an oxidizing atmosphere or to form the water wall tube with a material having excellent corrosion resistance.

As a method of changing the atmosphere in the vicinity of the water wall tube to an oxidizing atmosphere, for example, as disclosed in Japanese Patent Application Laid-Open Nos. 57-186006 and 2-84865, air is supplied into a furnace. There is known a technique of installing a large number of air injection nozzles on a water wall pipe. Further, as a technique for making the water wall tube material excellent in corrosion resistance, for example, 50C
thermal spraying of a corrosion resistant material such as r5ONi;
A method of cladding 11 to 26% Cr steel with a thickness of 1 to 5 mm disclosed in 148259 is known.

[0006]

However, in the former method in which a nozzle is provided on the wall of the water pipe and air is supplied into the furnace, it is difficult to maintain an oxidizing atmosphere if the supply of air is insufficient. After all, reduction corrosion is performed.
Further, since a large number of air injection nozzles must be provided, the equipment cost must be increased. on the other hand,
When a corrosion-resistant material is used, the material cost naturally increases.
In particular, in the case of thermal spraying, there is a problem that reliability is lacked due to peeling due to thermal shock.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances of the prior art, and has as its object to provide a boiler apparatus capable of preventing corrosion of water wall pipes without increasing NOx in exhaust gas. Is to do.

[0008]

In order to achieve the above object, a first means is that a furnace wall is constituted by a water wall tube and a soot blower is provided for removing ash attached to the water wall tube in the furnace. In the boiler device, a steam pipe and an air pipe are respectively connected to the soot blower, and steam injection and air injection are individually performed from the soot blower.

In this case, means for extracting furnace gas in the vicinity of the soot blower to the outside of the furnace, means for analyzing the extracted gas, and air supplied from the air pipe to the soot blower according to the concentration of a predetermined component of the analyzed gas. And means for controlling the flow rate.

[0010] The concentration of the predetermined component of the gas is, for example, the H2S concentration. The means for controlling the flow rate of the air controls the supply flow rate of the air so that the H2S concentration in the furnace gas becomes 100 ppm or less.

Further, it is preferable that the soot blower is constituted by a double pipe, and cooling steam is supplied between the inner pipe and the outer pipe so that cooling can be forcibly performed. A plurality of soot blowers are provided on both side walls of the boiler between the burner level and the after-air port level.

The second means is a method for operating the boiler apparatus according to the first means, wherein the soot blower normally blows air into the furnace to keep the vicinity of the water wall tube in an oxidizing atmosphere,
Only when ash is removed, the supply of air is switched to the supply of steam, and steam is ejected from the soot blower. Note that the supply amount of the air is set according to the H ₂ S concentration in the furnace.

[0013] With the above construction, the oxygen partial pressure on the surface of the water wall tube is increased, and the vicinity of the surface of the water wall tube becomes an oxidizing atmosphere. This state corresponds to point B in FIG. When air is supplied into the furnace from the water wall tube side, the oxygen partial pressure increases, and H ₂ S in the combustion gas is oxidized and the corrosive SO ₂ is weakened.
_{Make 2} In order to make the vicinity of the surface of the water wall tube an oxidizing atmosphere, an air supply port is opened in the membrane bar between the adjacent water wall tubes and air is supplied from the air supply port to create an oxidizing atmosphere. Cannot be completely oxidized. Therefore, in the present invention, air is supplied to the vicinity of the surface of the water pipe wall by using a soot blower which has been conventionally used.

In the removal of ash, which is the original function of a soot blower, it is necessary to peel off the adhering matter, and it is necessary to eject a relatively high-pressure gas. Therefore, steam is generally used, but in order to promote the oxidation of the water wall pipe, in the present invention, air is blown out from the soot blower.

Further, since the amount of air supplied to the furnace varies depending on the H ₂ S concentration in the furnace atmosphere, the H ₂ S concentration near the water pipe wall is measured at any time, and the H ₂ S concentration at which the amount of corrosion falls below the allowable value is measured. ₂
The air flow rate is controlled so as to be S concentration, that is, 100 ppm or less. This makes it possible to cope with changes in combustion conditions such as the sulfur content in the fuel and the air ratio.

[0016]

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

<First Embodiment> FIG. 1 is a sectional view of a main part showing a schematic configuration of a soot blower installation section of a boiler apparatus according to a first embodiment of the present invention. In the figure, the side of the furnace constituting the boiler is composed of a water wall pipe 6 and a membrane bar 7 which is located between the water wall pipes 6 and connects the adjacent water wall pipes 6, and the soot blower 8 is a membrane bar 7 The soot blower insertion hole 7a formed in the furnace is installed so as to be able to advance and retreat into the furnace. The steam pipe 1 and the air pipe 4 are connected to the soot blower 8, and are provided with the steam on-off valve 2 and the air on-off valve 3, respectively. The air pipe 4 is further provided with a flow meter 5 for measuring the supply flow rate of air.
At the base end of the soot blower 8, a motor 10 and a motor 10
A transmission mechanism for transmitting power from the vehicle is provided. The soot blower 8 is constantly rotated by the motor 10 and the power transmission mechanism, and constantly supplies air 11 to the surface of the water wall pipe 6 around the soot blower 8. Thus, the surface of the water wall tube 6 is substantially in an oxidizing atmosphere, and the surface gas of the water wall tube 6 can be prevented from being corroded by the furnace gas containing H ₂ S.

Air 11 blown out from soot blower 8
Is supplied from an air pipe 4, and this air is supplied from a compressed air supply device including a compressor and a pressure tank (not shown). In addition, the supply of air does not use the thing dedicated to the soot blower 8 in this way, for example,
Air used for boiler combustion is split and soot blower 8
It can also be guided to the side.

In any case, the injection air pressure needs to be the air pressure required to keep the H ₂ S concentration in the combustion gas below a certain value. In order to make the wall thinning rate of the water wall pipe 6 equal to or less than the allowable value of 0.1 mm per year, according to the experimental results of the inventor,
The H ₂ S concentration needs to be 100 ppm or less. Further, if the air pressure is too high, the combustion ash is entrained in the spray air flow, and the water wall pipe is worn down, so that the air pressure needs to be set so as not to be worn. This pressure varies depending on the abrasion properties of the ash and the H2S concentration in the combustion gas.
It is used in the range of kg / cm ² .

However, it is difficult to remove the ash adhering to the surface of the water wall pipe 6 with this amount of air. Therefore, the air is switched to the steam pipe 1 once or twice a day, and a pressure higher than the air (about At 7 kg / cm ² ), steam is jetted to remove ash attached to the surface of the water wall pipe 6.

FIG. 2 shows a soot blower 8 according to this embodiment.
It is a figure which shows the arrangement state to a boiler. In the present embodiment, ten soot blowers 8 are arranged on the left and right side walls 18 of the boiler B, respectively. In this embodiment,
The soot blower 8 is located between the upper burner 13 and the upper part of the after-air port 12, but the number and location of the soot blowers vary depending on the boiler structure, size, fuel properties, and the like. The position is not particularly limited.

In FIG. 2, reference numerals 14 and 15 indicate a middle burner and a lower burner, respectively, reference numeral 16 indicates a front wall, and reference numeral 17 indicates a rear wall.

<Second Embodiment> FIG. 3 is a sectional view of a main part showing a schematic configuration of a soot blower installation section of a boiler apparatus according to a second embodiment. In this embodiment, a gas sampling nozzle 23 is inserted into the furnace from the membrane bar 7 with respect to the first embodiment, and the water sampling tube 23 is inserted from the gas sampling nozzle 23 into the furnace.
The gas in the furnace in the vicinity is sampled, the gas is analyzed, and the amount of air blown out from the soot blower 8 is controlled. That is, in this embodiment, the gas in the vicinity of the water wall pipe 6 is sampled from the gas sampling nozzle 23 by the pump 24 and guided to the H ₂ S analyzer 22, and the H ₂ S concentration in the gas is detected. The detected concentration is determined by the control unit 2
The controller 25 calculates the amount of air to be supplied based on the detection data and controls the opening of the flow control valve 26 based on the determined amount of air. The flow control valve 26 is provided on the downstream side of the air opening / closing valve 3 and on the upstream side of the flow meter 5, so that the flow rate after the flow rate adjustment can be confirmed by the flow meter 5. The other components are configured in the same manner as in the first embodiment, and a duplicate description will be omitted.

The controller 25 has at least an interface for outputting a drive signal to the CPU, ROM, RAM and the flow control valve 26, and a drive (opening) signal of the flow control valve 26 based on data input from the analyzer 22. Is output to the flow control valve 26. The CPU performs predetermined processing based on a program stored in the ROM in advance,
The ROM stores programs to be processed by the CPU, and also stores static data used by the CPU. The RAM stores dynamic data to be processed by the CPU and functions as a work area for the CPU. Although not shown here, the flow rate measured by the flow meter 5 can be fed back to the control device 25 to further adjust the opening of the flow control valve 26. In addition, more precise control becomes possible.

According to the second embodiment, an optimum amount of air can be supplied into the furnace in accordance with the H ₂ S concentration in the furnace gas that changes in various ways, so that it is higher than the first embodiment. A corrosion inhibiting effect can be obtained. The sampling of the H ₂ S gas and the measurement of the concentration may be performed continuously or at predetermined intervals, and the measurement timing and the air flow timing are not particularly limited.

<Third Embodiment> FIG. 4 is a sectional view showing a schematic configuration of a soot blower of a boiler apparatus according to a third embodiment. The soot blower 8 according to this embodiment includes the inner tube 3
4 and the outer tube 31 have a double-tube structure, and steam is allowed to flow through the space between the inner tube 34 for ejecting air into the furnace and the outer tube 31 located outside the inner tube 34. Things. That is, in this embodiment, since the soot blower 8 is always inserted into the furnace, the outer tube 31 of the soot blower 8 is always exposed to the high-temperature combustion gas. For this reason,
If the combustion gas temperature is high, the outer tube 31 may be burned. Therefore, since the steam pipe 1 is connected,
Steam is supplied to the inside of the outer tube 31 to prevent burning of the outer tube 31 by steam cooling. Other configurations are the same as those of the first and second embodiments.
Duplicate description will be omitted.

According to the third embodiment, the soot blower 8 installed at the part exposed to the high-temperature combustion gas is steam-cooled, and the soot blower 8 installed at the part does not burn.

[0028]

As described above, according to the present invention, the steam pipe and the air pipe are respectively connected to the soot blower, and the steam injection and the air injection can be performed individually from the soot blower. An oxidizing atmosphere can be provided in the vicinity of the water wall pipe in the furnace, whereby the corrosion of the water wall pipe can be minimized. According to the present invention, the furnace gas in the vicinity of the soot blower is taken out of the furnace and analyzed, and the flow rate of air supplied from the air pipe to the soot blower is controlled in accordance with the analysis result. it can.

Further, according to the present invention, the H 2 S
Since the supply air flow rate is controlled based on the concentration, the corrosion of the water wall pipe by H2S can be suppressed.

Further, according to the present invention, since the soot blower is formed of a double pipe and steam is supplied between the inner pipe and the outer pipe to forcibly cool the soot blower, burning of the soot blower can be prevented. .

According to the present invention, the soot blower normally blows air into the furnace to keep the vicinity of the water wall tube in an oxidizing atmosphere, and switches the air supply to the steam supply only when ash is removed. Since the steam is blown out from the boiler, one soot blower normally functions to set the oxidizing atmosphere, and only when the ash is removed, the steam is supplied to separate the ash, so that the boiler is operated in a stable state for a long time. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a schematic configuration of a soot blower installation section of a boiler device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state in which a soot blower is arranged in a boiler according to the first embodiment.

FIG. 3 is a sectional view of a main part showing a schematic configuration of a soot blower installation part of a boiler device according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a structure of a soot blower according to a third embodiment of the present invention.

FIG. 5 is a graph showing the sulfur potential (pS ₂ ) on the vertical axis and the oxygen potential (pO ₂ ) on the vertical axis in a region where iron, iron oxide and iron sulfide are stably present at 500 ° C. corresponding to the metal temperature of the water wall tube. FIG. 2 is a state diagram showing the logarithm of ( ₂ ).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steam piping 2 Steam on-off valve 3 Air on-off valve 4 Air piping 5 Air flow meter 6 Water wall tube 7 Membrane bar 8 Soot blower 9 Nozzle 10 Motor 11 Jet air 12 After air port 18 Side wall 22 H2S analyzer 23 Furnace gas suction nozzle 24 air pump 25 controller 26 flow control valve 31 outer pipe 32 steam 34 inner pipe

Claims (8)

[Claims] 1. A boiler device in which a furnace wall is formed of a water wall tube and has a soot blower for removing ash attached to the water wall tube in the furnace, wherein a steam pipe and an air pipe are connected to the soot blower, respectively. Boiler device, wherein steam injection and air injection are individually performed from a soot blower. 2. A means for taking out furnace gas in the vicinity of a soot blower out of the furnace, a means for analyzing the taken out gas, and a means for supplying air to the soot blower from an air pipe according to the concentration of a predetermined component of the analyzed gas. The boiler apparatus according to claim 1, further comprising: means for controlling a flow rate. 3. The boiler apparatus according to claim 2, wherein the concentration of the predetermined component of the gas is an H ₂ S concentration. 4. The boiler apparatus according to claim 2, wherein the means for controlling the flow rate of the air controls the supply flow rate of the air such that the H ₂ S concentration in the furnace gas becomes 100 ppm or less. . 5. The boiler apparatus according to claim 1, wherein the soot blower is formed of a double pipe, and supplies cooling steam between the inner pipe and the outer pipe. 6. The boiler apparatus according to claim 1, wherein a plurality of soot blowers are provided on both side walls of the boiler between a burner level and an after-air port level. 7. The method for operating a boiler device according to claim 1, wherein the soot blower normally blows air into the furnace to keep the vicinity of the water wall tube in an oxidizing atmosphere, and A method for operating a boiler apparatus, characterized in that the supply of air is switched to the supply of steam only during removal, and steam is ejected from a soot blower. 8. The method for operating a boiler according to claim 7, wherein the supply amount of the air is set according to the H ₂ S concentration in the furnace.