JPH09303714A - Boiler equipment and operating method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the concentration of SO3 at a boiler, furnace outlet at a low value even in the case when fuel of a high sulfur content is used. SOLUTION: An SO2 gas analyzer 12 is provided at a boiler furnace outlet 18 and a gas analyzer 13 of SO2 in combustion gas is provided at a portion positioned on the upstream side of the gas analyzer 12, in the vicinity of an upper-stage coil 8 of a low-temperature superheater, for instance. The difference between measured values of the two gas analyzers 12 and 13 is monitored during the operation of a boiler, and when the difference between the concentrations of the SO2 in the combustion gas at the two spots becomes a certain prescribed value or above, an ash removing device such as a soot blower 14 is operated. This is based on the finding that the rate of conversion of the SO2 into SO3 has a close relationship with the portion of sticking of ashes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler that burns fossil fuels such as coal and petroleum, and more particularly to a boiler apparatus suitable for reducing the concentration of anhydrous sulfuric acid in boiler exhaust gas and a method for operating the boiler apparatus.

[0002]

2. Description of the Related Art Sulfur compounds contained in coal, heavy oil, etc.
Most of what is burnt or the like becomes sulfur dioxide (hereinafter referred to as SO ₂ ), and a part thereof becomes sulfur trioxide or sulfuric anhydride (hereinafter referred to as SO ₃ ) in the reaction of the formula (1).

SO ₂ + 1 / 2O ₂ = SO ₃
(1) There are both cases where SO ₃ is produced in combustion flames and cases where it is produced by metal oxides such as V ₂ O ₅ that come into contact with combustion gas, but SO ₃ in exhaust gas is combined with moisture. It becomes sulfuric acid, which condenses on the surface of the equipment material and causes corrosion.
Further, since sulfuric acid also has a function of solidifying dust, it also causes clogging of the device. The problem due to such SO ₃ is a device having a relatively low temperature such as an air preheater, an exhaust gas duct, and a dust collector.

[0004] condensation temperature (acid dew point) of the SO ₃ is to increase with increasing SO ₃ concentration in the exhaust gas, the vanadium to catalyze the oxidation of the fuel and SO ₂ high sulfur content in SO ₃ (V) When a large amount of fuel, for example, heavy oil, is used in the boiler, the boiler exhaust gas contains a high concentration of SO ₃ . The SO ₃ concentration is 10 ppm or less in the exhaust gas in general C heavy oil, but may increase to several tens to 100 ppm in heavy oil fuel containing high sulfur and vanadium. Therefore, when burning such high-sulfur and high-vanadium fuels, measures against the increase in SO ₃ concentration in the exhaust gas are indispensable.

Conventional methods for reducing the concentration of SO _{3 in} exhaust gas include (1) a method of chemically neutralizing SO ₃ in gas, (2)
A method of lowering the oxygen concentration in gas is known and is actually used.

[0006]

Of the above-mentioned conventional techniques,
As the method (1), a method of adding an alkaline earth metal component such as magnesium (Mg) or calcium (Ca) to the fuel or injecting it into the furnace separately from the fuel is used. In this case, in addition to combustion ash, magnesium sulfate (MgSO ₄ ) and the like generated by reaction with SO ₂ are simultaneously attached to the heat transfer tube, which causes an increase in the ash and ash quantity adhering to the heat transfer tube.

Ammonia (NH ₃ ) is injected at the entrance of a dust collector or the like to convert SO ₃ into ammonium sulfate ((NH ₄ ) ₂ SO ₄ ).
However, in this case, additional ammonia injection equipment and NH ₃ purchase costs are required, which increases the running cost of the plant. Also,
There is also a problem of ash clogging due to the precipitation of ammonium sulfate.

In the method (2), SO ₂ is replaced with SO ₃
Conversion to carbon monoxide (C
O) Concentration may increase.

Therefore, there is a drawback that another problem is newly generated when the SO ₃ concentration in the boiler exhaust gas is reduced by the above-mentioned conventional technique.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to use a fuel having a high sulfur content.
It is an object of the present invention to provide a boiler device capable of maintaining a low SO ₃ concentration at the boiler furnace outlet and an operating method thereof.

[0011]

The above object of the present invention is achieved by the following constitution. That is, in a boiler device that burns fossil fuel to heat a boiler heat transfer tube group provided in a boiler furnace, in a boiler furnace outlet and at least two points on the upstream side thereof, sulfur oxides in combustion gas the concentration measurement, SO ₃ of SO ₂ based on the difference between the measured value
It is a method of operating a boiler device that monitors the conversion rate to water.

In the method for operating the boiler apparatus of the present invention, the difference between the measured value of the sulfur oxide concentration at the boiler furnace outlet and the measured value of the sulfur oxide concentration on the upstream side of the boiler furnace is not less than a predetermined value. Then, by operating the ash removal device provided in the boiler heat transfer tube group, the SO ₃ concentration at the boiler furnace outlet can be maintained at a low value. In the present invention, the concentration of SO ₂ or SO _{3 in} the combustion gas is measured as the concentration of sulfur oxides.

The above object of the present invention can be achieved by the following constitution. That is, in a boiler device that burns fossil fuel to heat a group of boiler heat transfer tubes provided in a boiler furnace, in a boiler furnace outlet and in a boiler furnace on the upstream side of the boiler furnace, at least two places in the combustion gas Is installed in the boiler heat transfer tube group, and further, the measured value of the sulfur oxide concentration meter at the boiler furnace outlet and the inside of the boiler furnace on the upstream side of the boiler furnace outlet The boiler device is provided with a control device that activates the ash removal device when the difference between the measurement values of the sulfur oxide concentration meter provided in the above is greater than or equal to a predetermined value.

In the boiler apparatus of the present invention described above, a pair of sulfur oxide concentration meters and an ash removing device are provided for each of the plurality of boiler heat transfer tubes, and the measured values of the sulfur oxide concentration meters at the boiler furnace outlet and the respective sulfur are measured. The difference from the measured value of the oxide concentration meter,
It is possible to provide a control device for activating the ash removal device corresponding to each sulfur oxide concentration meter when the value exceeds a predetermined value. An SO ₂ concentration meter or an SO ₃ concentration meter can be used as the sulfur oxide concentration meter. A soot blower type or an acoustic type device can be used as the ash removing device.

In a boiler apparatus for burning fossil fuels such as coal and petroleum, the SO ₂ concentration or SO ₃ in the combustion gas should be present at least at the two locations of the boiler furnace outlet and the upstream thereof, for example, the low temperature superheater inlet. A device for measuring the concentration is installed, and the difference between the two is monitored during operation, and when the difference between the SO ₂ concentration or SO ₃ concentration in the combustion gas at the two locations becomes a certain value or more, an ash removal device such as soot blower. The operation is to operate.

SO ₃ is produced by the reaction of SO ₂ and oxygen in the combustion gas, and the in-furnace ash containing vanadium (V) and iron (Fe), which act as an oxidation catalyst, is converted into SO _3. It is easily inferred that it will affect the change of. However, the relationship between the property of deposits in the boiler furnace and the SO ₃ conversion rate has not been known so far. Therefore, as a result of various examinations by the present inventors, S
It was found that the conversion rate of O ₂ to SO ₃ is closely related to the attachment site of ash.

That is, as shown in FIG. 6, ash attached to various places of a boiler using high sulfur and high vanadium content fuel was sampled and the SO ₃ conversion rate was measured. That is, it was found that the ash attached to the low temperature superheater and the economizer has a very high SO ₃ conversion rate.

As a mechanism for increasing the SO ₃ conversion rate in the ash attached to the low temperature portion of the boiler, it is considered that the amount and form of V in the ash and the amount of sulfate radical (SO ₄ ²⁻ ) are large. . The SO ₃ conversion was 500 ppm SO ₂ -3% O ₂ -bal. While flowing N ₂ gas at 1 liter / min, the SO ₂ concentration of the adhering ash before and after was measured, and the difference was taken as the SO ₃ concentration.

According to the present invention, it is possible to reduce the SO ₃ conversion rate at the boiler furnace outlet by efficiently removing the ash attached to the low temperature superheater and the economizer.

In the present invention, the S in the combustion gas at the boiler furnace outlet and at least at two locations in the boiler furnace on the upstream side of the boiler furnace outlet.
When the O ₂ concentration or SO ₃ concentration difference exceeds an allowable value, a device that removes ash attached to the heat transfer tube, such as a soot blower or an acoustic ash removal device, is activated to remove the ash attached to the heat transfer tube group. And SO ₃ from SO ₂ at the boiler furnace outlet
The conversion rate was set to be below the allowable value. As a result, it is possible to effectively prevent corrosion and dust adhesion of the air preheater and the electrostatic precipitator installed downstream of the boiler furnace.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 An example of the present invention will be described below with reference to the drawings.
FIG. 1 is a side view of a boiler to which an embodiment of the present invention is applied. In FIG. 1, the combustion ash burned by the burner 1 follows the flow of the combustion gas, the Plato superheater 4, the screen tube 5, the high temperature superheater 6, the high temperature reheater 7, and the low temperature superheaters 8 to 10.
And the boiler furnace outlet 18 via the economizer 11. The exhaust gas discharged from the boiler furnace passes through a denitration device 19, an air preheater 20, a dust collector 21, and a desulfurization device 22, and then a chimney 23.
Emitted from. Devices 12 and 13 for measuring the SO ₂ concentration in the combustion gas are installed at the boiler furnace outlet 18 and upstream of the low temperature superheater upper stage 8, and a plurality of soot blowers 14 are installed in each heat transfer tube group.

The SO ₂ concentration measuring device 12 at the boiler furnace outlet 18, the SO ₂ concentration measuring device 13 upstream of the upper coil 8 of the low-temperature superheater, and the flow control valve 15 of the soot blower 14 are connected to the computer 17, and each SO ₂ concentration is measured. The computer 17 opens and closes the flow rate adjusting valve 15 of each sootblower 14 and adjusts the flow rate according to signals input from the concentration measuring devices 12 and 13 to the computer 17.

Next, the operation method in the present embodiment configured as described above will be explained. FIG. 2 shows the relationship between the difference between the SO ₂ concentration upstream of the low temperature superheater upper coil 8 and the SO ₂ concentration at the boiler furnace outlet 18 (= SO ₃ concentration at the boiler furnace outlet) and the operating time. At the start of the operation (a), the surface of each heat transfer tube group is clean and the SO ₃ concentration is almost zero, but as the operation starts, the combustion ash gradually begins to adhere to each heat transfer tube group, and SO ₃
The concentration increases. When this SO ₃ concentration exceeds a certain set value A, the flow rate control valve 15 of the soot blower 14 opens and steam or air is supplied into the boiler furnace 2 (b). As a result, the ash attached to the heat transfer tube is removed and S
The O ₃ concentration begins to drop. When the SO ₃ concentration falls below a certain set value A, the flow control valve 1 of the soot blower 14
5 is closed (c). By repeating this operation,
It is possible to always keep the SO ₃ concentration at the boiler furnace outlet 18 below a certain set value A.

Devices 12 and 13 used for SO ₂ concentration measurement
A commercially available device such as an infrared gas analyzer or a gas chromatograph is used. Especially, the infrared gas analyzer is 10 ppm to 1
It is possible to measure a wide range of SO ₂ concentrations up to 00%,
In addition, since the response is relatively fast at 0.1 to 20 seconds, it is a suitable method when used almost continuously as in this embodiment.

Setting SO ₃ for activating the soot blower 14
Since the concentration needs to be variously changed depending on the material used and the operating temperature of the device installed in the downstream of the boiler furnace 2,
It is not particularly limited.

Embodiment 2 FIG. 3 shows another embodiment according to the present invention. In the present embodiment, the SO ₂ measuring device 13 is an example positioned at the middle of each stage of the low-temperature superheaters 8 to 10, the upper stage of the low-temperature superheater 8, the middle of the economizer 11, and the boiler furnace outlet 18 at a total of 5 positions. . Figure 4 shows the change in operating time due to the difference between the SO ₂ measuring device at each part and the outlet of the economizer. In the figure, B is the upper stage of the low temperature superheater upper coil 8 and C
Is an intermediate between the low temperature superheater upper coil 8 and the middle coil 9, D is an intermediate between the low temperature superheater middle coil 9 and the lower coil 10, and E is an SO ₂ installed between the low temperature superheater lower coil 10 and the economizer 11. Concentration measuring device 13 and boiler furnace outlet 1
8 is a line showing a difference between the SO ₂ concentration measuring devices 12 installed in FIG. Since the temperature, the amount of ash deposited, and the ash composition differ depending on the position of the heat transfer tube group, the conversion rate of SO ₂ to SO ₃ also changes depending on each part.

Therefore, in this embodiment, SOs at a plurality of positions are set.
By monitoring the change in the conversion rate of ₂ to SO ₃ , a plurality of soot blowers 14 are individually operated (b) and stopped (c).
The SO ₃ concentration at the boiler furnace outlet 18 is set to be the set value A or less.

The second embodiment is different from the first embodiment in SO
_{2 Although} the installation cost of the concentration measuring device 13 is high, the running cost of the soot blower 14 is low because only the minimum necessary soot blower 14 is operated, and the SO ₃ concentration at the boiler furnace outlet 18 is controlled. It has the advantage of improving accuracy.

The SO ₂ concentration measuring device 1 of this embodiment
The number of 3 is 4 but the number of installations and the installation locations need to be changed depending on the size and structure of the boiler.
It is not particularly limited. However, boiler furnace outlet 1
At least _two of the SO ₂ concentration measuring device 12 and the SO ₂ concentration measuring device 13 arranged at least one position on the upstream side of the SO ₂ concentration measuring device 8 are required.

Embodiment 3 FIG. 5 shows another embodiment according to the present invention. In this embodiment, the installation position of the SO ₂ measuring device 13 is the same as that of the first embodiment, but the ash removing method uses an acoustic ash removing device 24 instead of the soot blower 14 used in the first or second embodiment. are doing.

The ash removing device 24 removes the ash attached to the heat transfer tube by vibrating the combustion gas in the furnace with a sound wave.
The ash removing device 24 of this system is difficult to remove ash that is strongly adhered to the heat transfer tube, but can effectively remove ash that has a weak adhesive force in the low temperature bank. The advantage of this method is that the equipment cost is lower than the soot blower method,
In addition, running costs can be reduced because no gas such as steam or air is used.

[0032]

According to the present invention, the SO ₃ concentration at the boiler furnace outlet, which is a problem when burning high-sulfur fuel, can be significantly reduced. Therefore, an air preheater installed downstream of the boiler or It is possible to prevent corrosion of the electrostatic precipitator and clogging due to ash. Further, the addition of NH ₃ at the entrance of the electrostatic precipitator is not used, and the running cost of the plant can be reduced. Furthermore, in the present invention, since the ash removing device is operated as necessary, it is possible to reduce the wear of the heat transfer tube due to the vapor containing the ash, as compared with the case of operating the ash removing device at all times. The steam used can be saved.

[Brief description of drawings]

FIG. 1 is a side view of a boiler device according to an embodiment of the present invention.

2 is a diagram showing a soot blower operation of the boiler of FIG. 1. FIG.

FIG. 3 is a side view of a boiler device according to an embodiment of the present invention.

FIG. 4 is a diagram showing a soot blower operation of the boiler of FIG.

FIG. 5 is a side view of a boiler device according to an embodiment of the present invention.

FIG. 6 is a diagram showing the SO ₃ conversion rate of ash attached to each bank (heat transfer tube group) when burning high-sulfur fuel.

[Explanation of symbols]

1 burner 2 furnace 3 water wall 4 Plato superheater 5 screen 6 high temperature superheater 7 reheater 8 low temperature superheater upper coil 9 low temperature superheater middle coil 10 low temperature superheater lower coil 11 economizer 12 boiler boiler outlet SO ₂ concentration Measuring instrument 13 SO ₂ concentration measuring instrument 14 Soot blower 15 Flow rate control valve 16 Steam piping 17 Computer 18 Furnace outlet 19 Denitration device 20 Air preheater 21 Dust collector 22 Desulfurization device 23 Chimney 24 Acoustic ash removal device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F23N 5/24 107 F23N 5/24 107Z

Claims (7)

[Claims] 1. A boiler apparatus for burning fossil fuel to heat a group of boiler heat transfer tubes provided in a boiler furnace, comprising: a boiler furnace outlet; and at least two points on the upstream side of the boiler furnace. A method for operating a boiler device, comprising measuring the concentration of sulfur oxides and monitoring the conversion rate of sulfur dioxide to sulfur trioxide based on the difference between the measured values. 2. The boiler heat transfer tube group is provided when the difference between the measured value of the sulfur oxide concentration at the boiler furnace outlet and the measured value of the sulfur oxide concentration on the upstream side of it exceeds a predetermined value. The method for operating a boiler device according to claim 1, wherein the ash removing device is operated. 3. The method for operating a boiler device according to claim 1, wherein the concentration of sulfur dioxide or sulfur trioxide in the combustion gas is measured as the concentration of sulfur oxides. 4. A boiler apparatus for burning a fossil fuel to heat a group of boiler heat transfer tubes provided in a boiler furnace, wherein the boiler furnace outlet and the boiler furnace on the upstream side of the boiler furnace have at least two locations. A sulfur oxide concentration meter in the combustion gas is provided, and an ash removal device is provided in the boiler heat transfer tube group.Furthermore, the measurement value of the sulfur oxide concentration meter at the boiler furnace outlet and the upstream side of the boiler furnace outlet are provided. A boiler device comprising a control device for activating an ash removal device when a difference between measured values of a sulfur oxide concentration meter provided in a boiler furnace exceeds a predetermined value. 5. A pair of sulfur oxide densitometers and an ash removal device are provided for each of the plurality of boiler heat transfer tubes, and the measured values of the sulfur oxide densitometers at the boiler furnace outlet and the respective sulfur oxide densitometers are measured. The boiler apparatus according to claim 4, further comprising a control device that operates an ash removing device corresponding to each sulfur oxide concentration meter when the difference from the value exceeds a predetermined value. 6. The boiler device according to claim 4, wherein the sulfur oxide concentration meter is a device for measuring the concentration of sulfur dioxide or sulfur trioxide in the combustion gas. 7. The ash removing device is a soot blower type or an acoustic type device.
The boiler device according to any one of 1.