JPH05309229A - Semi-dry or dry desulfurizer - Google Patents

Abstract

PURPOSE:To provide semi-dry or dry desulfurizer which is compact and maintenance-free and where water consumption is remarkably decreased, and simultaneously, the corrosion of equipment due to exhaust gas is prevented and desulfurizing efficiency is stabilized. CONSTITUTION:A combustion furnace 1 where limestone powder is received and sulfur dioxide generated on coal combustion is given primary desulfurization by the limestone powder and a cooling reactor 2 where residual sulfur dioxide in exhaust gas is given secondary desulfurization by sprayed slaked lime slurry S, while exhaust gas flowing in from the combustion furnace 1 is cooled to a temp. at which exhaust gas does not undergo dew condensation are provided. A cyclone 3 for removing dust in exhaust gas when the exhaust gas flowing in from the cooling reactor 2 is passed through it, a slaked lime slurry preparation tank 4 where the dust removed by the cyclone 3 and makeup water W are each received to prepare slaked lime slurry S of a prescribed concentration and a pump 5 for feeding and spraying the slaked lime slurry S prepared in the slaked lime slurry preparation tank 4 to the cooling reactor 2 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desulfurization apparatus for desulfurizing combustion gas of coal, and more particularly to a semi-dry type and dry desulfurization apparatus capable of saving space and saving water.

[0002]

2. Description of the Related Art As a conventional desulfurization apparatus of this kind, for example, a limestone supply device and a sulfur oxide such as sulfurous acid gas generated when coal is burned by receiving limestone powder from the limestone supply device is used. A boiler that receives primary desulfurization and exhaust gas from the boiler via a gas air heater, sprays water and cools the exhaust gas with spray water to remove sulfur oxides and perform secondary desulfurization. A semi-dry type simple desulfurization device provided with a cooler and a dust collector for removing dust from exhaust gas from a spray cooler is known ("Industrial Machinery", January 1992, pp. 19-23).
Page, published by the Japan Industrial Machinery Manufacturers Association).

In the boiler of the above-mentioned semi-dry type simple desulfurization apparatus, primary desulfurization is carried out by a reaction according to the following chemical formulas 1 and 2.

[Chemical formula 1] CaCO ₃ → CaCO + CO ₂ (800 ° C or higher)

Embedded image CaO + SO ₂ + 1 / 2O ₂ → CaSO ₄ (800 to 1200 ° C.)

Further, in the spray cooler of the above-mentioned semi-dry type simple desulfurization apparatus, secondary desulfurization is performed by the reaction according to the following chemical formulas 3 to 6, and as a result, the following chemical formulas 7 to 7 are obtained. Desulfurization according to That is, in the secondary desulfurization, water is sprayed on the exhaust gas in the spray cooler that passes through the gas air heater, and desalination is performed near the dew point of the water by using quicklime that remains unreacted in the primary desulfurization. Calcium sulfite generated later is removed in the dust collector on the downstream side.

[Chemical Formula 3] CaO + H ₂ O → Ca (OH) ₂

Embedded image Ca (OH) ₂ + SO ₂ → CaSO ₃ · 1 / 2H ₂ O + 1 / 2H ₂ O

Embedded image SO ₂ + H ₂ O → H ₂ SO ₃

[Chemical Formula 6] H ₂ SO ₃ + CaO → CaSO ₃ · 1 / 2H ₂ O + 1 / 2H ₂ O

[Chemical formula 7] SO ₂ + CaO + 1 / 2H ₂ O → CaSO ₃ 1 / 2H ₂ O

Particularly, in the secondary desulfurization, the desulfurization efficiency is improved by appropriately controlling the amount of spray water in the spray cooler and cooling the outlet gas temperature of the spray cooler to a temperature (60 to 70 ° C.) close to the dew point of water. There is.

As another conventional desulfurization device,
For example, a device for injecting limestone fine powder of several μm into a combustion furnace for burning coal to perform dry desulfurization (Japanese Patent Publication No. 3-129).
No. 26), or an apparatus for performing dry desulfurization in a combustion furnace for burning coal and then treating the quicklime produced by this desulfurization with a wet mill to reuse it.
4902 publication).

[0007]

However, in the conventional simple dry type desulfurization apparatus, it is necessary to lower the exhaust gas temperature to near the dew point temperature of water having a high desulfurization rate to increase the secondary desulfurization efficiency as described above. Therefore, a large amount of water is consumed in the spray cooler, and the exhaust gas in the device is below the dew point (60 to 80 ° C) due to the spray of water. Therefore, acid gas in the spray cooler, the dust collector, and the flue is reduced. However, there is a problem in that they condense and corrode them. Further, in the above-mentioned conventional simple dry desulfurization device, the desulfurization rate is unstable due to fluctuations in the exhaust gas temperature because the temperature of the exhaust gas is lowered below its dew point by the spray amount of water supplied to the spray cooler. There was a problem of becoming.

Further, in the dry desulfurization apparatus described in Japanese Patent Publication No. 3-12926, the particle size of limestone is as small as several μm, so that the cost is high when such fine powder is industrially produced. In addition, quick lime on the surface of the fine powder generated by firing the limestone fine powder reacts with sulfur oxide to form calcium sulfate, which may hinder the desulfurization reaction, which in turn lowers the desulfurization efficiency. There was a challenge to let it do.

Further, in the desulfurization apparatus described in Japanese Patent Application Laid-Open No. 3-244902, since wet lime is reused by using a wet mill, the wet mill is worn and there is a problem in maintenance. ..

The present invention has been made in order to solve the above problems, and can drastically reduce the consumption of water and prevent corrosion of the equipment due to exhaust gas, and it is compact and stable in desulfurization efficiency. It is an object of the present invention to provide maintenance-free semi-dry and dry desulfurization equipment.

[0011]

A semi-dry desulfurization apparatus according to claim 1 of the present invention comprises a combustion furnace which receives limestone powder and primarily desulfurizes sulfur oxides generated during combustion of coal with the limestone powder, A cooling reactor that secondary desulfurizes residual sulfur oxides in the exhaust gas while cooling the exhaust gas flowing from the combustion furnace to a temperature at which it does not condense with slaked lime slurry that has been sprayed, and the exhaust gas that flows in from the cooling reactor First dust collector that collects and removes the dust contained in the exhaust gas when passing through, and slaked lime that receives the dust and makeup water removed by the first dust collector to prepare a slaked lime slurry of a predetermined concentration It comprises a slurry preparation tank and a slaked lime slurry supply device for feeding and spraying the slaked lime slurry prepared in the slaked lime slurry preparation tank to the cooling reactor.

The semi-dry desulfurization apparatus according to claim 2 of the present invention is the semi-dry desulfurization apparatus according to claim 1, wherein
The limestone powder collected in the cooling reactor is configured to be fed back to the combustion furnace.

A semi-dry desulfurization apparatus according to a third aspect of the present invention is the semi-dry desulfurization apparatus according to the first or second aspect, wherein a second dust collector is provided downstream of the first dust collector. A device is provided, and while the second dust collector is maintained at a temperature at which the exhaust gas does not condense, the exhaust gas flowing from the first dust collector passes through the second dust collector to collect dust from the exhaust gas. The residual dust collected and removed is accumulated to form a dust accumulation layer, and the exhaust gas passing through the dust accumulation layer is subjected to third desulfurization with slaked lime in the dust accumulation layer.

Further, the dry desulfurization apparatus according to the fourth aspect of the present invention receives the limestone powder and carries out the primary desulfurization of the sulfur oxides generated at the time of combustion of coal with the limestone powder and the inflow from the combustion furnace. A cooling reactor that secondary desulfurizes residual sulfur oxides in the exhaust gas while cooling the exhaust gas to a temperature at which the exhaust gas does not condense with the desulfurizing agent sprayed, and collects dust in the cooling reactor and removes this dust. And a fluidized bed for regenerating the quick lime by fluidizing it, and the quick lime regenerated in the fluidized bed is supplied to the combustion furnace.

The dry desulfurization apparatus according to a fifth aspect of the present invention is the dry desulfurization apparatus according to the fourth aspect, in which the exhaust gas flowing from the cooling reactor is maintained at a temperature at which dew condensation does not occur. A dust collector that collects and removes the dust contained in the exhaust gas in a state of being heated, and an ash recovery preparation tank that heats and regulates the dust removed by the dust collector and prepares this dust as the desulfurizing agent. And is configured to feed and spray the desulfurizing agent prepared in the ash recovery preparation tank to the cooling reactor.

[0016]

According to the semi-dry desulfurization apparatus according to the first aspect of the present invention, when the limestone powder is received in the combustion furnace, the sulfur oxides are removed from the limestone powder during the combustion of coal to perform the primary desulfurization. When the exhaust gas after desulfurization flows from the combustion furnace into the cooling reactor, it is supplied from the slaked lime slurry preparation tank and is sprayed, and the exhaust gas is cooled to a predetermined temperature at which no condensation occurs and residual sulfur oxidation in the exhaust gas occurs. The substance reacts with slaked lime to be secondarily desulfurized and flows into the first dust collector,
While collecting and removing the dust in the exhaust gas with the dust collector, the dust and makeup water from the first dust collector were respectively supplied to the slaked lime slurry preparation tank to prepare a slaked lime slurry with a predetermined concentration The slaked lime slurry can be sprayed and supplied to the cooling reactor by the slaked lime slurry supply device for secondary desulfurization.

Further, according to the semi-dry desulfurization apparatus according to claim 2 of the present invention, the unreacted limestone powder is reused by feeding back the limestone powder recovered in the cooling reactor to the combustion furnace. be able to.

Further, according to the semi-dry desulfurization apparatus of the third aspect of the present invention, the exhaust gas flows into the second dust collecting apparatus from the first dust collecting apparatus in a state where the exhaust gas is kept at a temperature where dew condensation does not occur. The residual dust from the exhaust gas is collected by the second dust collector,
During the removal, the dust can be accumulated in the second dust collector to form the dust accumulation layer, and the slaked lime in the dust accumulation layer can be used for the third desulfurization.

Further, according to the dry desulfurization apparatus according to the fourth aspect of the present invention, when the limestone powder is received in the combustion furnace, the sulfur oxide is removed from the limestone powder during the combustion of coal to perform the primary desulfurization, When the exhaust gas after primary desulfurization flows from the combustion furnace into the cooling reactor, it is cooled to a predetermined temperature in the cooling reactor where the exhaust gas does not condense, and the residual sulfur oxide in the exhaust gas is sprayed with a desulfurizing agent. While it reacts and is secondarily desulfurized and flows into the dust collector, the cooling reactor collects the dust in the exhaust gas and causes the collected dust to flow in the fluidized bed. After regenerating, the regenerated quick lime can be returned to the combustion furnace for reuse.

Further, according to the dry desulfurization apparatus according to the fifth aspect of the present invention, the dust from the exhaust gas flowing from the cooling reactor into the dust collector is kept in a state where the exhaust gas is kept at a temperature at which dew condensation does not occur. The dust removed by the dust collector is collected in the ash recovery preparation tank, and the recovered dust is heated and conditioned in the ash recovery preparation tank to prepare a desulfurizing agent. Then, this desulfurizing agent can be fed to the cooling reactor and sprayed to be subjected to secondary desulfurization.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiment shown in FIG. 1 is a perspective view showing the entire system of an embodiment of the semi-dry desulfurization apparatus according to the present invention, and FIG. 2 is a diagram showing the limestone injection rate and the desulfurization rate in the combustion furnace in the semi-dry desulfurization apparatus shown in FIG. FIG. 3 is a graph showing an example of the relationship, FIG. 3 is a graph showing an example of the relationship between the blowing rate of slaked lime and the total desulfurization rate of secondary and tertiary desulfurization in the semi-dry desulfurization apparatus shown in FIG. 1, and FIG. It is a block diagram which shows the whole system of one Example of a desulfurization apparatus.

As shown in FIG. 1, the semi-dry desulfurization apparatus of this embodiment receives a limestone powder and produces sulfur oxides such as sulfur dioxide generated during combustion of coal (hereinafter represented by "sulfurous acid gas"). Combustion furnace 1 for primary desulfurization with limestone powder, and secondary desulfurization of residual sulfur dioxide in the exhaust gas while cooling the exhaust gas flowing from the combustion furnace 1 to a temperature at which the exhaust gas is not condensed by the sprayed slaked lime slurry S Cooling reactor 2;
A first dust collecting device 3 that removes dust and water when the exhaust gas flowing from the cooling reactor 2 passes, and a dust and makeup water W removed by the first dust collecting device 3 are respectively received to obtain a predetermined concentration. It is provided with a slaked lime slurry preparation tank 4 for preparing the slaked lime slurry S, and a slaked lime slurry supply device (pump) 5 for feeding and spraying the slaked lime slurry S prepared in the slaked lime slurry preparation tank 4 to the cooling reactor 2. Has been done.

Further, in the semi-dry desulfurization device, as shown in FIG. 1, a second dust collecting device 6 is provided on the downstream side of the first dust collecting device 3, and from the first dust collecting device 3 When the inflowing exhaust gas passes through the second dust collector 6, the dust in the exhaust gas is collected and the residual dust removed is accumulated to form a dust accumulation layer (cake layer) described below, and the dust accumulation layer passes through this cake layer. The slaked lime in the cake layer is subjected to third desulfurization from the exhaust gas, and a part of the dust removed by the second dust collector 6 is supplied to the slaked lime slurry preparation tank 4.

The combustion furnace 1 is additionally provided with a coal storage tank (not shown) and a limestone storage tank 7 for storing limestone powder prepared in advance to have a particle size of about 10 to 300 μm. The combustion furnace 1 automatically receives coal from the coal storage tank on the grate to burn the coal, and receives limestone blown from the limestone storage tank 7 through the pipe 8 to burn the coal. The sulfurous acid gas generated at the time of coal combustion is desulfurized with quicklime gradually generated on the surface of limestone powder at (800 to 1200 ° C). At the time of this desulfurization, the blowing rate of the limestone powder, that is, the blowing rate when blowing an equivalent amount of limestone with respect to the sulfurous acid gas in the gas is 100%.
The relationship between the blowing rate of limestone and the primary desulfurization rate in such a case varies depending on the model of the combustion furnace 1, but in the present example, when the average particle size of the limestone powder is 12 μm, the relationship shown in FIG. 2 is obtained. Was given. According to the figure, the injection rate of limestone powder is 2
A primary desulfurization rate of 30 to 50% was obtained at 00%,
Considering the subsequent secondary and tertiary desulfurization, the practical blowing rate is preferably in the range of 200 to 300%. In particular, when the combustion furnace 1 is a fluidized bed, the residence time of the limestone powder in the combustion furnace 1 is long, and while the limestone powder stays, the quicklime on the surface is sequentially scraped and the quicklime is updated successively. 60 ~
A desulfurization rate of 70% can be obtained. Then, the exhaust gas after the primary desulfurization flows into the cooling reactor 2 through the duct 9.

In the cooling reactor 2, the slaked lime slurry S blown by the pump 5 from the slaked lime slurry preparation tank 4 through the pipe 10 is scattered all over the inside to generate exhaust gas from around 180 ° C. The temperature is set to a temperature at which no dew condensation occurs, that is, 90 to 150 ° C., and the slaked lime undergoes a reaction of the following chemical formula 8 with the residual sulfur dioxide in the exhaust gas for secondary desulfurization. The blowing rate of the slaked lime slurry S at the time of desulfurization is represented by the molar ratio (Ca / S) of the slaked lime of the slaked lime slurry S and the sulfurous acid gas in the exhaust gas. The relationship shown in FIG. 3 was obtained between the secondary desulfurization rate and the total desulfurization rate of the tertiary desulfurization rate. According to the figure, slaked lime slurry S
The blowing rate is preferably in the range of 1 to 3 where a desulfurization rate of 90% or more can be obtained when the exhaust gas temperature is in the range of 90 to 150 ° C. Then, the exhaust gas after the secondary desulfurization flows into the first dust collector 3 through the duct 11, and the limestone powder collected in the hopper 12 of the cooling reactor 2 is transferred to the pipe 13
The pump 14 feeds back to the combustion furnace 1 via the.

[Image Omitted] Ca (OH) ₂ + SO ₂ → CaSO ₃ · 1 / 2H ₂ O + 1 / 2H ₂ O

The first dust collector 3 is composed of a cyclone, and the cyclone 3 is composed of dust such as quick lime, calcium sulfate, calcium sulfite and limestone while the exhaust gas after the secondary desulfurization flows through the inside. Dust was removed and accumulated as a cake layer. The cake layer accumulated in the cyclone 3 is completely removed at a predetermined time and is supplied to the slaked lime slurry preparation tank 4 described below in a semi-dried state for the slaked lime slurry S through the pipe 15. Then, the exhaust gas dedusted by the cyclone 3 flows into the second dust collector 6 via the pipe 16.

Further, the second dust collector 6 is operated while being kept at a temperature at which exhaust gas does not condense, and is provided with a bag filter made of non-woven fabric as a filter material. While removing the dust that remains in the exhaust gas while flowing through to form the above-mentioned cake layer dust adhered to the inner surface of the bag filter, so that the third desulfurization while this exhaust gas passes through the cake layer. There is. That is, in the cake layer, in addition to unreacted limestone, a large amount of slaked lime is contained together with calcium sulfate and calcium sulfite, and while the exhaust gas passes through the cake, residual sulfite gas in the exhaust gas contains the cake. 80% of it is removed by reacting with slaked lime in the layer,
As a whole, including this tertiary desulfurization, 90% or more desulfurization can be performed as described above. In addition, the second dust collector 6 prevents the sulfurous acid gas in the exhaust gas from dew condensation.
The exhaust gas, which is maintained at 150 ° C. and is dust-removed, is exhausted to the flue 18 on the downstream side by the blower 17. Thus, the bag filter preferably has a pressure difference between the inside and the outside of the exhaust gas of 50 to 150 mm in water column, and if the cake layer formed on the bag filter is 3 to 8 mm, The cake layer is automatically removed, and a part of the cake layer is supplied in a semi-dried state to the slaked lime slurry preparation tank 4 for the slaked lime slurry S via the pipe 19, and the remaining cake is supplied to the outside via a pipe 20. The material is discharged to the recovery tank 21. Further, the permeation speed of the exhaust gas in the cake layer is usually preferably 1 to 1.5 m / min.

The slaked lime slurry preparation tank 4 is equipped with a stirrer 22, and part of the cake of the cyclone 3 and the cake layer of the second dust collector 6 and makeup water W from the pipe 23.
The slaked lime slurry S containing 2 to 6% of slaked lime is prepared by producing slaked lime from the quick lime in each cake by agitating with a stirrer 22 according to the following chemical formula 9. And the slaked lime slurry S prepared in the slaked lime slurry preparation tank 4
As described above, the slaked lime slurry S is sprayed onto the cooling reactor 2 by the pump 5 through the pipe 10 as described above, and the combustion furnace 1
The exhaust gas from the above is cooled from around 180 ° C to 90 to 150 ° C.

Embedded image CaO + H ₂ O → Ca (OH) ₂

Next, the operation of the semi-dry desulfurizer will be described. When the combustion furnace 1 receives the limestone powder from the limestone storage tank 7, the sulfurous acid gas generated by the combustion of coal reacts with the quick lime generated on the surface of the limestone powder by the heat of combustion to generate calcium sulfate. Primary desulfurization of gas.

The exhaust gas from the combustion furnace 1 after the primary desulfurization is
The slaked lime slurry S that has flowed into the cooling reactor 2 and has been sprayed from the slaked lime slurry preparation tank 4 into the inside of the slaked lime slurry preparation tank 4 via the pipe 10 by the pump 5 from about 180 ° C. to 90 to 150 ° C.
Is cooled to. At this time, the slaked lime reacts with the sulfurous acid gas remaining in the exhaust gas to generate calcium sulfite, thereby secondary desulfurizing the exhaust gas.

The exhaust gas after the secondary desulfurization from the cooling reactor 2 flows into the cyclone 3, and in the cyclone 3, the dust and water composed of calcium sulfate and the like in the exhaust gas are collected from the exhaust gas and dehydrated. The exhaust gas that has been collected and dehydrated further flows into the second dust collecting device 6, and inside this, the residual dust that has not been removed by the cyclone 3 is collected from the exhaust gas. The collected dust adheres to and accumulates on the inner surface of the bag filter of the second dust collector 6 to form a cake layer, and while the exhaust gas passes through the cake layer, residual sulfurous acid gas in the exhaust gas is The exhaust gas is thirdly desulfurized by reacting with slaked lime contained in the cake layer to generate calcium sulfate.

During this period, the cake removed by the cyclone 3 and a part of the cake layer removed by the second dust collector 6 and the makeup water W are supplied to the slaked lime slurry preparation tank 4 at appropriate times, and the quick lime in each cake and After slaked lime is generated from water and prepared as a slaked lime slurry S containing 2 to 6% of slaked lime, it is supplied to the cooling reactor 2 via the pipe 10 as described above by the pump 5, and limestone is circulated and used.

As described above, according to the semi-dry desulfurization apparatus of this embodiment, a desulfurization rate of 90% or more can be obtained by the primary desulfurization or the tertiary desulfurization in a compact apparatus, and water is circulated for reuse. Only the make-up water W necessary for preparing the slaked lime slurry S is required, and the water can be remarkably saved as compared with the conventional desulfurization device, and it can be suitably used in an area where water resources are scarce. Further, in the present embodiment, even if the combustion furnace 1 is small and primary desulfurization is not performed effectively, the lack of desulfurization can be supplemented by the secondary and tertiary desulfurization. Since the exhaust gas temperature is operated at 90 to 150 ° C throughout, stable operation can be performed easily and easily, and there is no condensation of exhaust gas to prevent corrosion of the device itself and prolong the life of the device. can do. Further, according to the semi-dry desulfurization apparatus of the present embodiment, since the desulfurization process does not include mechanical treatment, the apparatus can be operated almost maintenance-free.

Further, as shown in FIG. 4, the dry desulfurization apparatus of the present embodiment is a combustion furnace 31 for receiving limestone powder and primarily desulfurizing sulfur oxides generated during combustion of coal with the limestone powder.
And a cooling reactor 32 for secondary desulfurization of residual sulfur oxides in the exhaust gas while cooling the exhaust gas flowing from the combustion furnace 31 to a temperature at which the exhaust gas is not condensed by the desulfurizing agent sprayed.
And a cyclone 33 for collecting dust in the cooling reactor 32
And a fluidized bed 34 that regenerates quicklime by flowing the dust collected by the cyclone 33, and is configured to supply the quicklime regenerated in the fluidized bed 34 to the combustion furnace 31 via a pipe 35. There is.

Further, as shown in FIG. 4, the dry desulfurization apparatus collects dust from the exhaust gas while the exhaust gas flowing from the cooling reactor 32 is kept at a temperature at which the exhaust gas is not condensed. An ash recovery preparation tank 37 is provided, which includes a dust collector 36 for removing the dust and an ash recovery preparation tank 37 for heating and conditioning the dust composed of limestone, quick lime, calcium sulfate and the like removed by the dust collector 36 to prepare a desulfurizing agent. The desulfurizing agent prepared in the tank 37 is supplied to the cooling reactor 3 through the pipe 38.
2 is configured to be fed and sprayed. As the dust collecting device 36, for example, a device provided with a bag filter or a conventionally known device such as a cyclone can be used.

A blower 39 is arranged on the downstream side of the dust collector 36, and the exhaust heat gas of the dust collector 36 is sent to the humidity control sprayer 41 through the pipe 40 by the blower 39. .. Further, pipes 42 and 43 are connected to the humidity control sprayer 41, and these pipes 42 and 43 are connected.
The exhaust gas is heated and humidified as a heat treatment gas by sending water and preheated air into the humidity control sprayer 41 through the ash recovery preparation tank 37, and the ash recovery preparation tank is already heated by the heat treatment gas. The dust stored in 37 is heat-treated to be prepared as a desulfurizing agent containing slaked lime according to Chemical Formula 3 above. The blower 39 communicates with the bottom of the fluidized bed 34 via a pipe 44. The blower 39 sends the exhaust gas from the bottom of the fluidized bed 34 to flow the dust collected in the fluidized bed 34. The lime is then regenerated.

Next, the operation of the dry desulfurizer will be described. When the combustion furnace 31 receives the limestone powder, the sulfurous acid gas generated by the combustion of coal reacts with the quick lime generated on the surface of the limestone powder by the heat of combustion to generate calcium sulfate according to the above chemical formulas 1 and 2. By doing so, the combustion gas is primarily desulfurized.

The exhaust gas after the primary desulfurization from the combustion furnace 31 is a temperature at which the exhaust gas is not condensed by the desulfurizing agent sprayed from the ash recovery preparation tank 37 in the cooling reactor 32, that is, about 180 ° C.
The secondary sulfur oxide in the exhaust gas is secondarily desulfurized in accordance with the above chemical formula 4 while being cooled to about 90 to 150 ° C., and a desulfurization rate of 80 to 90% or more is achieved as a whole. The exhaust gas after the secondary desulfurization flows from the cooling reactor 32 into the dust collector 36, while the unreacted quicklime powder in the exhaust gas is collected together with the dust by the cyclone 33 and the fluidized bed 34.
The unreacted quicklime powder is fluidized in the fluidized bed 34 to scrape off secondary desulfurization products such as calcium sulfate adhering to the surface thereof to regenerate the quicklime powder, and the regenerated quicklime powder is supplied to the pipe 35. It is fed back to the combustion furnace 31 and reused.

Further, the exhaust gas after the secondary desulfurization from the cooling reactor 32 flows into the dust collecting device 36 as described above, and in the dust collecting device 36, limestone, quick lime, sulfuric acid made of calcium sulfate etc. in the exhaust gas. Dust composed of powder of calcium or the like is collected from the exhaust gas and collected in the ash collection tank 37. On the other hand, during this period, the blower 3
The exhaust gas sent through the pipe 40 at 9 is the pipe 4
Water and preheated air sent via 2, 43 are heated and humidified to generate a heat treatment gas, and the heat treatment gas is sprayed from the humidity control sprayer 41 to the ash recovery preparation tank 37 to be recovered. Dust inside is heat-treated to prepare desulfurizing agent containing slaked lime from dust containing quick lime. The prepared desulfurizing agent is sprayed from the ash recovery preparation tank 37 into the cooling reactor 32 through the pipe 38 and is used for secondary desulfurization. Further, the exhaust gas after dust collection in the dust collector 36 is discharged as it is, but a part of the exhaust gas is discharged through the pipe 44.
To regenerate the quick lime, and then to the combustion furnace 31 to disperse the limestone powder.

As described above, according to the dry desulfurization apparatus of this embodiment, quicklime regenerated in the fluidized bed 34 is used in the combustion furnace 31.
Since it is reused in the primary desulfurization in the above, the consumption amount of limestone powder can be saved similarly to the above semi-dry desulfurization device, and the exhaust gas after dust collection is used for spraying limestone powder in the combustion furnace 31. Therefore, the combustion furnace 31 is used more than the conventional case in which the limestone powder is sprayed by using the outside air.
The combustion efficiency can be improved, and since fresh external air is not introduced into the combustion furnace 31, an increase in nitrogen oxides can be eliminated. In addition, in the present embodiment, it is possible to achieve an effect similar to that of the above semi-dry desulfurization apparatus.

The present invention is not limited to the above-mentioned embodiments, and in the case of the above semi-dry desulfurization apparatus, the range of 65-
In areas where 70% desulfurization rate is acceptable, second dust collector 6
Can be omitted to make a more compact device.

[0042]

As described above, according to the present invention, it is possible to significantly reduce the amount of water consumption and prevent corrosion of the equipment due to exhaust gas, and to stabilize desulfurization efficiency, and to make it compact and maintenance-free. Semi-dry and dry desulfurization equipment can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing the entire system of an embodiment of a semi-dry desulfurization apparatus according to the present invention.

2 is a graph showing an example of a relationship between a limestone injection rate and a desulfurization rate in a combustion furnace in the semi-dry desulfurization apparatus shown in FIG.

FIG. 3 is a graph showing an example of the relationship between the blowing rate of slaked lime and the total desulfurization rate of secondary and tertiary desulfurization in the semi-dry desulfurization apparatus shown in FIG.

FIG. 4 is a configuration diagram showing an entire system of an embodiment of a dry desulfurization apparatus according to the present invention.

[Explanation of Codes] 1 combustion furnace 2 cooling reactor 3 cyclone (first dust collector) 4 slaked lime slurry preparation tank 5 pump (slaked lime slurry supply device) 6 second dust collector 31 combustion furnace 32 cooling reactor 34 fluidized bed 36 Dust collector 37 Ash recovery and preparation tank

 ─────────────────────────────────────────────────── ─── Continuation of front page (71) Applicant 000173809 Central Research Institute of Electric Power Industry 1-6-1, Otemachi, Chiyoda-ku, Tokyo (71) Applicant 000133032 Takuma Co., Ltd. 1-3, Dojimahama, Kita-ku, Osaka-shi, Osaka No. 23 (71) Applicant 592120173 Japan-China Technology Resources Trading Co., Ltd. 1-12-17 Fujimidai, Nerima-ku, Tokyo (72) Inventor Hidefumi Ikegami 1-2-7 Nishi-Shimbashi, Minato-ku, Tokyo Engineering Promotion Association (72) Inventor Masayuki Masakata 7-3 Hongo, Bunkyo-ku, Tokyo Department of Chemical Engineering, Faculty of Engineering, Tokyo University (72) Inventor Masao Matsumura 4-2-11 Ginza, Chuo-ku, Tokyo Stock Exchange Company Ishii Iron Works (72) Inventor Yoshimi Ishihara 1-6-1, Otemachi, Chiyoda-ku, Tokyo Inside Central Research Institute of Electric Power Industry (72) Inventor Inazumi 1-32 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture Takuma Co., Ltd. (72) Inventor Shizuo Kataoka 1-3-23, Dojimahama, Kita-ku, Osaka City, Osaka Prefecture (72) Inventor Masaaki Tamayama Tokyo 1-12-17 Fujimidai, Nerima-ku, Tokyo Within Japan-China Technology Resources Trading Co., Ltd.

Claims (5)

[Claims] 1. A combustion furnace which receives limestone powder and performs primary desulfurization of sulfur oxides generated during combustion of coal with limestone powder, and a slaked lime slurry in which exhaust gas flowing from the combustion furnace is sprayed does not cause dew condensation. A cooling reactor for secondary desulfurization of residual sulfur oxides in exhaust gas while cooling to a temperature, and a first collection for collecting and removing dust contained in the exhaust gas when passing through the exhaust gas flowing from the cooling reactor. The dusting device, a slaked lime slurry preparation tank for respectively receiving the dust and makeup water removed by the first dust collector to prepare a slaked lime slurry having a predetermined concentration, and the slaked lime slurry prepared in the slaked lime slurry preparation tank for the above cooling reaction A semi-dry desulfurization device comprising: a slaked lime slurry supply device for feeding and spraying to a vessel. 2. The semi-dry desulfurization apparatus according to claim 1, wherein the limestone powder recovered in the cooling reactor is fed back to the combustion furnace. 3. A second dust collecting device is provided on the downstream side of the first dust collecting device, and the second dust collecting device flows from the first dust collecting device in a state where the second dust collecting device is maintained at a temperature at which exhaust gas does not condense. When the exhaust gas passing through the second dust collecting device accumulates residual dust collected and removed from the exhaust gas to form a dust accumulation layer, the exhaust gas passing through the dust accumulation layer forms slaked lime in the dust accumulation layer. 3. The semi-dry desulfurization apparatus according to claim 1 or 2, wherein the third desulfurization is carried out. 4. A combustion furnace that receives limestone powder and performs primary desulfurization of sulfur oxides generated during combustion of coal with limestone powder, and a desulfurizing agent sprayed with the exhaust gas flowing from the combustion furnace does not condense exhaust gas. A cooling reactor for secondary desulfurization of residual sulfur oxides in the exhaust gas while cooling to a temperature, and a fluidized bed for recovering dust in the cooling reactor and flowing this dust to regenerate quicklime, A dry desulfurization device characterized in that quick lime regenerated on the floor is supplied to the combustion furnace. 5. A dust collector that collects and removes the dust contained in the exhaust gas while keeping the exhaust gas at a temperature at which dew condensation does not occur during passage of the exhaust gas flowing from the cooling reactor. An ash recovery preparation tank that heats and controls the humidity of the removed dust and prepares this dust as the desulfurization agent is provided, and the desulfurization agent prepared in the ash recovery preparation tank is fed to the cooling reactor and sprayed. The dry desulfurization apparatus according to claim 4, wherein