JPH10202048A - Treatment of stack gas from boiler plant and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and surely suppress the corrosion of structural equipment caused by SO2 by removing sulfur oxide in a waste gas in a desulfurizing equipment and charging a powdery primary alkaline agent except ammonia and a slurry like secondary alkaline agent except ammonia at an inlet and outlet of an air preheater. SOLUTION: The waste gas discharged from a boiler main body 1 is introduced into the air preheater 3 after Nox is removed in a denitrification equipment 2 and cooled by air for combustion. In such a case, the powdery primary alkaline agent except ammonia is charged into the inlet side of the air preheater 3 from a primary alkaline agent charging device 10 and the slurry like secondary alkaline agent is charged into the outlet side of the air preheater 3 from a secondary alkaline agent charging device 11. A reaction for neutralizing SO2 occurs to prevent the corrosion or the like of the element of the air preheater 3 by charging the primary alkaline agent. And by charging the secondary alkaline agent, SO2 is completely neutralized to eliminate the fear of corrosion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating flue gas in boiler equipment.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a flue gas treatment apparatus of a general boiler facility. In the figure, reference numeral 1 denotes a boiler main body, and 2 denotes a nitrogen oxide in exhaust gas discharged from the boiler main body 1. A denitration device for removing (NOx), 3 is an air preheater for heating the combustion air supplied to the boiler body 1 by the exhaust gas from which NOx has been removed in the denitration device 2, 4 is an exhaust gas passing through the air preheater 3. , A gas-gas-heater heat recovery unit for recovering the heat of the exhaust gas from which the dust has been collected in the dry-type dust collector 4, and a heat recovery unit 6 for recovering the heat of the exhaust gas from which the dust is collected in the dry-type dust collector 4. A desulfurizer for removing sulfur oxides (SOx) in the exhaust gas discharged, a wet dust collector for collecting dust remaining in the exhaust gas from which SOx has been removed in the desulfurizer 6, and a dust collector for collecting dust in the wet dust collector. Is A gas gas heater reheater that reheats the exhaust gas to a required temperature by the heat recovered by the gas gas heater heat recovery unit 5, and a chimney 9 that discharges the exhaust gas reheated by the gas gas heater reheater 8 to the atmosphere.

[0003] In the flue gas treatment apparatus for boiler equipment as described above, the exhaust gas discharged from the boiler main body 1 is first introduced into a denitration device 2, where NOx in the exhaust gas is removed, and then the air is removed. The combustion air supplied to the boiler body 1 is heated by the exhaust gas from which the NOx has been removed in the air preheater 3 where the NOx has been removed, and the exhaust gas itself is deprived of heat and cooled.

[0004] The exhaust gas cooled in the air preheater 3 is collected in a dry dust collector 4 to collect soot and dust, and then further cooled in a gas / gas heater heat recovery unit 5, guided to a desulfurization unit 6, where the waste gas is collected. The SOx in the exhaust gas is removed, and thereafter, the exhaust gas from which the SOx has been removed in the desulfurizer 6 is introduced into a wet dust collector 7,
In the gas gas heater reheater 8, the remaining dust is collected.
Reheated to the required temperature by the heat recovered in
Emitted from the atmosphere.

[0005] The wet dust collector 7 may be omitted depending on performance requirements.

When heavy oil, coal or orimulsion having a high sulfur content is used as fuel in the boiler body 1, high-concentration SO ₂ is contained in exhaust gas discharged from the boiler body 1, the amount of SO ₂ is oxidized to SO ₃ in the furnace and denitrator 2 of the boiler main body 1 is increased, since the growing more corrosive toward the downstream side, is measures to prevent the corrosion of the construction equipment in the flue gas treatment apparatus Was needed.

For this reason, conventionally, a method of injecting ammonia (NH ₃ ) for neutralizing SO ₃ into the inlet side of the air preheater 3 or the dry dust collector 4, or a method of injecting carbonic acid into the furnace of the boiler body 1. A method of introducing calcium (CaCO ₃ ) has been employed.

[0008]

However, as described above, NH ₃ is supplied to the inlet side of the air preheater 3 or the dry dust collector 4.
In the case of the method of injecting ash, clogging or corrosion of the element due to the adhesion of ammonium ammonium sulfate (NH ₄ HSO ₄ ) (so-called ammonium sulfate) in the air preheater 3 may cause a problem. A lot of N inside
Include H ₄ ⁺ salts, together with the use destination of ash handling or ash is limited, contains a large amount of NH ₄ ⁺ salts in the waste water in the desulfurization device 6, NH ₄ in the waste water treatment apparatus of the desulfurization apparatus 6 ^{+ It} is necessary to increase the salt treatment function, and the amount of NH ₄ ⁺ dust that is difficult to collect on the order of submicrons increases.
However, there is a drawback that the dust collection area becomes large, the equipment is enlarged, and the price of NH ₃ is two to four times higher than other alkaline agents.

The method of introducing CaCO ₃ into the furnace of the boiler body 1 has a disadvantage that the SO ₃ removing effect is extremely small.

In view of the above circumstances, the present invention can efficiently and reliably suppress the corrosion of components due to SO ₃ with an alkali agent other than ammonia, and reduce clogging of elements of an air preheater. Another object of the present invention is to provide a method and an apparatus for treating flue gas in boiler equipment, which can prevent the generation of NH ₄ ⁺ dust and can further reduce the cost of an alkali agent for neutralizing SO _3. It is.

[0011]

According to the present invention, nitrogen oxides in exhaust gas discharged from a boiler body are removed by a denitration device, and the exhaust gas from which the nitrogen oxides have been removed in the denitration device is heated by an air preheater. This is a flue gas treatment method for boiler equipment that removes sulfur oxides in exhaust gas in a desulfurization device after replacement. And charging the slurry-like secondary alkali agent to the outlet side of the air preheater.

Further, the present invention provides a method for removing nitrogen oxides in exhaust gas discharged from a boiler body in a denitration device, and exchanging heat in the exhaust gas from which nitrogen oxides have been removed in the denitration device in an air preheater. A flue gas treatment device for a boiler facility for removing sulfur oxides in exhaust gas in a desulfurization device, and a primary alkali agent charging device for charging a powdery primary alkali agent other than ammonia to an air preheater inlet side,
A secondary alkaline agent introducing device for introducing a slurry-like secondary alkaline agent other than ammonia to the outlet side of the air preheater.

According to the above means, the following effects can be obtained.

When a powdery primary alkaline agent other than ammonia is introduced into the air preheater inlet side, a reaction for neutralizing SO ₃ occurs, and the production of ammonium acid sulfate is suppressed in the air preheater. Element clogging and corrosion due to adhesion do not occur.

In the components downstream of the air preheater, the corrosive conditions become more severe due to the temperature drop due to the heat exchange of the exhaust gas in the air preheater. However, a slurry-like secondary alkali agent other than ammonia is used. When put into the outlet side of the air preheater, the slurry-like secondary alkali agent can be evenly sprayed on the exhaust gas, so that the SO ₃ is thoroughly neutralized, and there is no need to worry about corrosion. If the temperature of the exhaust gas is lower than the melting point of the ammonium sulfate by the slurry-like secondary alkali agent, the ammonia ammonium sulfate generated when ammonia for the denitration is injected at the denitration apparatus inlet is solidified, and the downstream components Adhesion to the surface is also avoided.

In addition, since ammonia is not used as an alkaline agent, a large amount of NH ₄ ⁺
No salt is contained, and the increase in the NH ₄ ⁺ salt treatment function in the waste water treatment device of the desulfurization device becomes unnecessary, and almost no NH ₄ ⁺ dust which is difficult to collect on the submicron order is almost eliminated. _{(3) The} cost of the alkaline agent for neutralization can be reduced.

Regarding the primary alkali agent and the secondary alkali agent, those which are brought into the desulfurization unit with respect to the excess charge, including those used for neutralization of SO ₃ , are also used as desulfurization agents, and are used for desulfurization. This contributes to savings in the desulfurization agent in the desulfurization unit, and increases the economic efficiency.

[0018]

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

FIG. 1 shows an example of an embodiment of the present invention. In the drawing, the portions denoted by the same reference numerals as those in FIG. 2 represent the same components, and a powdery primary alkaline agent (other than ammonia) For example, CaCO ₃ , CaO, Ca (OH) ₂ , Na ₂
CO ₃ or the like is charged into the inlet side of the air preheater 3 by the primary alkali agent charging device 10, and a slurry-like secondary alkali agent other than ammonia (for example, CaCO ₃ , CaO, Ca (O)
H) ₂ , Na ₂ CO _3, etc.) and a secondary alkali agent charging device 11
Thus, the air preheater 3 is supplied to the outlet side.

In addition, the primary alkali agent charging device 10 includes:
The powdered primary alkaline agent is injected from a powder nozzle disposed in an exhaust gas duct on the inlet side of the air preheater 3 by high-pressure air supplied from a blower or a compressor (not shown). In addition, the secondary alkaline agent charging device 11 supplies a slurry-like secondary alkaline agent from a slurry nozzle disposed in an exhaust gas duct on the outlet side of the air preheater 3 by operating a pump (not shown). It is designed to inject.

As described above, the primary alkaline agent charging device 10
When the primary alkali agent other than ammonia is put into the inlet side of the air preheater 3, for example, when the primary alkali agent is CaCO ₃ , CaCO ₃ + SO ₃ → CaSO ₃ + CO ₂ + 1 / 2O ₂ CaCO ₂ A reaction for neutralizing SO ₃ such as ₃ + SO ₃ → CaSO ₄ + CO ₂ occurs, and the air preheater 3
In this case, generation of ammonium ammonium sulfate is suppressed, and clogging or corrosion of the element due to the adhesion of the ammonium sulfate does not occur.

In the components downstream of the air preheater 3, the corrosion conditions become more severe due to the temperature drop due to the heat exchange of the exhaust gas in the air preheater 3. When a slurry-like secondary alkaline agent other than ammonia charged into the air preheater 3 outlet side, because the slurry-like secondary alkaline agent can be uniformly sprayed against the exhaust gas, neutralization of sO ₃ is When the temperature of exhaust gas is lower than the melting point of ammonium ammonium sulphate due to the slurry-like secondary alkali agent, ammonia for denitrification is introduced at the inlet of the denitration device 2 The generated ammonium ammonium sulfate solidifies, is efficiently collected in the dry dust collector 4, and is prevented from adhering to downstream components.

Moreover, since ammonia is not used as an alkaline agent, a large amount of NH ₄ ⁺ salt is not contained in the collected ash in the dry dust collector 4, so that the ash treatment or the use destination of the ash is not limited, and the desulfurizer 6 A large amount of NH ₄ ⁺ salt is not contained in the waste water, so that it is not necessary to increase the NH ₄ ⁺ salt treatment function in the waste water treatment device of the desulfurization device 6, and it is difficult to collect NH ₄ ⁺ in the submicron order. Since the system dust is almost eliminated, it is possible to omit the dry dust collector 4 and to construct a system in which the dust is collected by the desulfurizer 6 and the wet dust collector 7, and furthermore, the alkali for SO ₃ neutralization can be constructed. The cost of the agent is low.

[0024] Of the primary alkali agent and the secondary alkali agent, those that have reached the desulfurization unit 6 without being collected by the dry dust collector 4 are also used as desulfurization agents in the desulfurization unit 6. If the dry dust collector 4 is omitted as described above and dust collection is carried out by the desulfurizer 6 and the wet dust collector 7, all of the primary alkaline agent and the secondary alkaline agent are desulfurized in the desulfurizer 6. As a result, the desulfurization device 6 can be saved, and the desulfurization agent can be saved.

In this way, the corrosion of the components due to SO ₃ can be efficiently and reliably suppressed by an alkali agent other than ammonia, the clogging of the elements of the air preheater 3 can be reduced, and NH ₄ ⁺ It is possible to prevent the generation of system dust, further reduce the cost of an alkali agent for neutralizing SO _{3, and} use the primary alkali agent and the secondary alkali agent as desulfurization agents in the desulfurization device 6. Thus, the desulfurization device 6 can save the desulfurizing agent and improve the economic efficiency.

It should be noted that the method and apparatus for treating flue gas of a boiler facility according to the present invention are not limited to the illustrated examples described above, and various modifications can be made without departing from the scope of the present invention. It is.

[0027]

As described above, according to the method and the apparatus for treating flue gas of a boiler facility of the present invention, the corrosion of components caused by SO ₃ can be efficiently and reliably suppressed by an alkali agent other than ammonia. Can reduce the clogging of the elements of the air preheater, can prevent the generation of NH ₄ ⁺ dust, and can further reduce the cost of the alkaline agent for neutralizing SO ₃ , In addition, the primary alkali agent and the secondary alkali agent can be utilized as desulfurizing agents in the desulfurizing device, and an excellent effect that the desulfurizing device can save the desulfurizing agent and improve the economic efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is an overall schematic configuration diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler main body 2 Denitration device 3 Air preheater 6 Desulfurization device 10 Primary alkali agent charging device 11 Secondary alkaline agent charging device

Claims (2)

[Claims] A nitrogen oxide in exhaust gas discharged from a boiler body is removed by a denitration device, and the exhaust gas from which the nitrogen oxide has been removed in the denitration device is subjected to heat exchange in an air preheater. A flue gas treatment method for boiler equipment for removing sulfur oxides in exhaust gas, wherein a powdery primary alkali agent other than ammonia is charged into the air preheater inlet side, and a slurry-like secondary alkali agent other than ammonia is added. Boiler equipment, wherein the waste gas is supplied to an outlet of an air preheater. 2. The nitrogen oxides in the exhaust gas discharged from the boiler main body are removed in a denitration device, and the exhaust gas from which the nitrogen oxides have been removed in the denitration device is subjected to heat exchange in an air preheater, and then the heat is removed in a desulfurization device. A flue gas treatment device for a boiler facility for removing sulfur oxides in exhaust gas, comprising a primary alkali agent charging device for charging a powdery primary alkali agent other than ammonia to an air preheater inlet side, and a slurry other than ammonia. And a secondary alkaline agent introduction device for introducing a secondary alkaline agent in the form of an outlet to an air preheater outlet side.