JP2000262849A - Flue gas desulfurization equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flue gas desulfurization equipment in which scale trouble in the inside of a gas absorption device is prevented by removing gypsum from an exhaust gas-absorbing liquid containing a plenty of sulfur oxide discharged from the gas absorption device, circulating and using the exhaust gas-absorbing liquid as air-enriched water in the inside of the gas absorption device. SOLUTION: In the flue gas desulfurization equipment, sulfur oxide is removed from exhaust gas-absorbing liquid circulated in the inside of a gas- absorbing device 21. The flue gas desulfurization equipment is equipped with a means which accepts the exhaust gas-absorbing liquid discharged from the gas-absorbing device 21, and also performs agitation while replenishing and adding powdery limestone 41 and water 42 thereto, and promotes these reactions to produce gypsum, a means for settling and separating grown crystal of gypsum, a means for taking out the produced gypsum and a means for producing air-enriched liquid by blowing fine oxygen or air bubbles into absorption liquid from which gypsum has been removed. Thereby, since the exhaust gas-absorbing liquid circulated in the inside of the gas-absorbing device 21 does not contain gypsum, a fear of scale trouble in the inside of the gas-absorbing device 21 does not exist a tall, and a pump 38 can be miniturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to rationally absorb and remove sulfur dioxide, which is harmful to the human body and the natural environment, from flue gas from factories and thermal power plants or from flue gas from sulfuric acid plants and the like. To generate
Regarding the flue gas desulfurization method and device using the limestone-gypsum method, while eliminating the occurrence of scale trouble in the gas absorption device, reducing the driving force load on the processing liquid circulation pump, improving the maintainability, and reducing the cost. The purpose is to measure.

[0002]

2. Description of the Related Art As a conventionally known flue gas desulfurization means, for example, a means provided with an air blowing device for blowing air into a lower part of a gas absorption tower for absorbing exhaust gas is known as a typical means. (Japanese Patent Publication 50-17318
Reference). Specifically, as shown by a flow sheet in FIG. 3, the gas absorber main body 1 and the slurry tank 6 have a gas inlet 2 on the upper side and a gas inlet 2 on the lower side. A gas outlet 3 is provided, and a spray nozzle 4 for spraying the slurry and a grid 5 for gas-liquid contact are provided therein. Further, the slurry tank 6 is integrally attached to the lower portion of the gas absorbing device main body 1 described above, and has an opening at an upper portion, and has a stirring device 7 and an external blower device 8 for blowing air into the slurry tank 6 therein. Is installed.

Further, a suction pipe 11 for sucking the slurry in the slurry tank by a pump 10 provided outside is attached to the slurry tank 6, and the suction pipe 11 is connected to the spray of the gas absorbing device main body 1. A branch pipe 12 is connected to the nozzle 4 and between the spray nozzle 4 and the pump 10 described above. In such a configuration, the exhaust gas flows from the gas inlet 2 into the gas absorber main body 1, makes gas-liquid contact when passing through the grid 5, and is discharged from the gas outlet 3.

On the other hand, the liquid slurry S comes in contact with the exhaust gas to absorb the sulfurous acid gas in the exhaust gas, and then flows down into the slurry tank 6 from the lower part of the gas absorber main body 1 and accumulates in the slurry tank 6. Separately, limestone powder 13 and water 14 are replenished and added into the slurry tank 6, and these are reacted with the liquid slurry S by the stirring device 7. Liquid slurry S reacted with limestone powder 13 and water
Are sequentially sucked by a pump 10 and sent into the gas absorber main body 1 through a suction pipe 11, sprayed on a grid 5 by a spray nozzle 4, and thereafter circulated to a slurry tank 6 in the same manner.

[0005] In this case, a part of the liquid slurry S that has passed through the pump 10 is sent to a centrifugal separator (not shown) through a branch pipe 12 so that gypsum by-products are generated.

[0006] In addition, there is also known a method in which calcium sulfite is extracted from exhaust gas in a gas absorption tower, pH of the calcium sulfite is adjusted with sulfuric acid, and then air oxidation is performed in an oxidation tower to form gypsum. I have.

[0007]

However, in the case of the above-mentioned conventional method, limestone powder is used as a means for absorbing sulfurous acid gas in exhaust gas. However, not only limestone powder but also calcium sulfite and gypsum produced as by-products are used. As a result, it is difficult to dissolve in water, including the formation of crystals, and as a result, it must be treated as a slurry in the gas absorption device main body 1. Therefore, in order to absorb sulfur dioxide gas sufficiently, it is necessary to thicken the liquid film in the device. In addition, it is easy to cause scale trouble in this part, furthermore, it is not easy to select and control the operation of the gas absorption device, and there is a limit to the ability of the liquid slurry to absorb sulfurous acid gas, which is inevitable. It is necessary to increase the circulating usage of the liquid slurry, and the specific gravity of the liquid slurry is also heavier than water Burden takes it inevitably increased in size to the pump 10, there is a problem, such as.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention solves the above-mentioned problems in the prior art, and is versatile without any scale troubles or operation problems in the exhaust gas absorption device regardless of the size. A device for removing sulfur oxides from an exhaust gas absorbing solution circulated in a gas absorbing device, which is a device for removing a sulfur oxide from a gas absorbing device. Receiving the exhaust gas absorbing liquid of the above, and adding and adding limestone powder and water to the mixture to promote the respective reactions, thereby producing gypsum as a by-product, and means for sedimenting and separating gypsum. The present invention relates to a flue gas desulfurization apparatus comprising: means for removing gypsum; and means for blowing fine oxygen or air bubbles into an absorbent from which gypsum has been removed to form an air-enriched liquid.

Further, the present invention comprises a gas absorbing device provided with a packed bed in a passage of exhaust gas through a spray nozzle, and a gypsum separation tank provided immediately below the gas absorbing device. A top opening for receiving the exhaust gas absorbing liquid from the gypsum, a gypsum discharge port formed at the bottom, an inner bottom portion inclined toward the gypsum discharge port at an angle of at least 15 degrees so as to be gradually lowered, and A stirrer that stirs the slurry gas absorbing liquid, an air blowing device that blows fine oxygen or air bubbles into the exhaust gas absorbing liquid from which the gypsum component has been removed to turn it into an air-enriched liquid, and an exhaust gas that becomes an air-enriched liquid The present invention relates to a flue gas desulfurization device comprising a pump for extracting an absorption liquid from a gypsum separation tank and circulating the liquid to a spray nozzle in the gas absorption device.

The present invention also provides an area having a stirrer for receiving the exhaust gas absorbing solution from the gas absorbing device and stirring the slurry-like gas absorbing solution in the tank, and removing the gypsum into the gypsum separation tank. The upper and lower ends are slightly spaced between the upper opening edge and the inner bottom surface of the gypsum separation tank, respectively, between the exhaust gas absorbing liquid and the air blowing area where the fine oxygen or air bubbles are blown into the air-enriched liquid. Alternatively, the present invention also relates to a flue gas desulfurization apparatus in which an opening is provided to form a partition forming a liquid passage.

In the above configuration, the exhaust gas flows into the gas absorber main body, passes through the packed bed, and is exhausted from the exhaust gas outlet to the outside. In this process, when the exhaust gas passes through the packed bed, the exhaust gas comes into contact with the exhaust gas absorbing liquid, so-called gas-liquid contact is performed, and the sulfur dioxide gas contained in the exhaust gas is absorbed by the exhaust gas absorbing liquid. On the other hand, when the exhaust gas absorbing liquid absorbs the sulfur dioxide gas, it then flows down into the gypsum separation tank from the lower part of the absorber main body and accumulates in the gypsum separation tank. Separately, limestone powder and water are replenished and added to the gypsum separation tank, and these are reacted with the absorbing liquid by a stirrer to form gypsum, and gypsum is separated and discharged from the bottom gypsum discharge port, and gypsum is separated and removed. Fine oxygen or air is blown into the exhaust gas absorbing liquid, and the liquid is sequentially sucked by a pump and circulated through a suction pipe to a spray nozzle in the gas absorbing device main body. And then circulated into the slurry tank in the same manner.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific contents of the present invention will be described below with reference to the embodiment shown in FIGS.
21 denotes a gas absorbing device, and 27 denotes a gypsum separation tank. The gas absorbing device 21 has a vertical tower shape, and has a gas inlet 22 formed at the top, a bottom opening 24 formed at the bottom, and a gas outlet 23 formed obliquely upward from below. Further, a filling layer 25 is formed inside the gas absorbing device 21, and a spray nozzle 26 whose emission port faces the filling layer 25 is provided above the filling layer 25.

The gypsum separation tank 27 is configured as a vessel having a necessary and sufficient volume for crystal reaction of gypsum as a chemical reaction and a reaction product in the tank and sedimentation and separation of the crystallized gypsum. The gypsum discharge port is installed immediately below the gas absorbing device 21 and has an upper surface opened, and a gypsum discharge port 29 is formed at the bottom, and the gypsum discharge port is inclined so as to be gradually lowered toward the gypsum discharge port 29. An inner bottom portion 28 is formed so as to be deepest near 29. In this case, if the inclination angle α of the inner bottom is less than 15 degrees, the flow of the slurry-like gas absorbing liquid is deteriorated, and the gypsum separation tank 2 according to the present invention is used.
7 cannot sufficiently exhibit its essential function, so it is necessary to have an inclination angle of at least 15 degrees or more.

Further, in the gypsum separation tank 27, there is provided a stirrer 37 for stirring the slurry-like gas absorbing solution S1 in the tank, and the lower part of the stirrer 37 is fed from an air blower 32 installed outside. An air nozzle 34 for injecting fine air into the slurry-like gas absorbing liquid S1 is formed. Further, a partition wall 31 is formed in a portion of the gypsum separation tank 27 that is shallower than the middle of the gypsum separation tank. That is, among the gas absorbing liquids whose upper end edge is lower than the opening edge of the gypsum separation tank 27 and which remains in the tank, only the gas absorbing liquid in the portion where the supernatant liquid surface 30 exceeds the upper end edge of the partition wall 31 Can freely move over the partition wall 31 and the lower end thereof is formed on the inner bottom surface 2 of the gypsum separation tank 27.
The partition 31 separates the gypsum separation tank 27 into a deep A room (area having a stirring device) and a shallow B room. are doing.

An opening may be formed at the upper end or the lower end of the above-mentioned partition wall 31 so that the two chambers can communicate with each other. Furthermore, an air blowing device 36 facing the air nozzle 36 for blowing fine oxygen or air bubbles into an air-enriched liquid at a relatively lower portion in the B room,
A liquid extraction port 39a for taking out the exhaust gas absorbing liquid in the tank is formed in the upper part.
Is a downward hood 39 so that the air-enriched liquid containing a large amount of air bubbles can be sufficiently taken out in the room B.
b, which forms an area with an air blowing device for air-enriched liquefaction.

In the above configuration, the exhaust gas flows into the gas absorbing device 21 from the gas inlet 22, passes through the packed bed 25, and is exhausted from the gas outlet 23. When passing through the packed bed 25, gas-liquid contact is made, and the sulfurous acid gas contained in the exhaust gas is absorbed by the exhaust gas absorbing liquid near the packed bed 25. Note here reaction in the _{^{SO 2 + H 2 O ⇔ H}} + + HSO 3 - ‥‥‥‥ (1) H + + HSO 3 + 1 / 2O 2 → 2H + + SO 4 - ‥‥ (2) [ In the above formula (1), ⇔ represents an equilibrium reaction. However, although the amount of HSO ₃ ⁻ generated by the formula (1) is relatively small, a chain reaction occurs because the exhaust gas absorbing liquid contains oxygen as described above, and as a result, most of the chain reaction occurs. (2) proceeds to formula, ^2H + + _SO ^{4 -} has a form of a.

On the other hand, the exhaust gas absorbing solution S1 having absorbed the sulfurous acid gas thereafter flows down into the gypsum separation tank 27 from the lower bottom opening 24 of the absorbing device 21 and accumulates in the tank. Slurry exhaust gas absorbing liquid S1, absorbing the sulfur dioxide in the gypsum separation tank 27 to react with oxygen contained in the slurry, only a certain H ^{+ +} HSO ₃ ^{- _{is, H + + HSO 3 + 1}} / 2O ₂ → 2H ^{+ +} SO ₄ ^- is oxidized by ‥‥ (2), and is has been 2H ⁺ + SO ₄ and 2H ⁺ + SO ₄ which has accompanied the gas absorption device 21 oxide is added here along with water 42 Reacts with the limestone powder 41 to form H ₂ O + 2H ⁺ + SO ₄ ⁻⁻ + CaCO ₃ → CaSO ₄ .2H ₂ O + CO ₂ {gypsum} (3) gypsum. In this case, when the limestone powder is added in a slightly excessive amount, the above-mentioned gypsum-forming reaction (3) also partially occurs in the gas absorbing device.

Further, the air supplied from the air blower 32 is injected through a pipe 33 from an air nozzle 34 into fine air bubbles into a slurry-like exhaust gas absorbing liquid, and these are mixed with a liquid slurry by a stirring device 37. Promotes gypsum crystal growth. The gypsum produced by the reaction of the above formula (3) grows and precipitates in the gypsum separation tank 27 into the gypsum separation tank 27 while gradually growing into gypsum crystals, and gradually toward the gypsum discharge port 29 along the inclined inner bottom surface 28. And is taken out from the gypsum discharge port 29, sent to a centrifuge (not shown), and collected as a by-product.

On the other hand, the supernatant of the exhaust gas absorbing liquid from which the gypsum has been separated and removed moves from the room A to the room B across the upper end edge of the partition wall 31, and the air blower 32 and the pipe 3
5 is activated by radiating air supplied through the air nozzle 5 as fine oxygen or air by an air nozzle 36a of an air blowing device 36, and is adjusted. , And is circulated through the pipes 39 and 40 to the spray nozzle 26 in the gas absorbing device 21 and sprayed onto the packed bed 25 by the spray nozzle 26, and thereafter similarly into the gypsum separation tank 27. Is circulated.

In the above embodiment, the case where the discharged liquid from the gas absorbing device 21 and the replenished limestone powder 41 are supplied to the A room of the gypsum separation tank 27 has been described.
If a part of the discharged liquid is supplied not only to the room A but also to the room B, for example, when a part of the discharged liquid is also supplied to the room B, the gypsum separation function can be more relaxed. There is an advantage that the separation efficiency can be further improved or the gypsum separation tank can be downsized.

As another embodiment of the present invention, the above-mentioned gypsum separation tank 27 is combined with a rotary cylindrical gas absorbing device (the device disclosed in Japanese Patent Application Laid-Open No. 6-79126) which was previously developed by the present inventors. The case of combination will be described.
That is, in this case, the gas absorption device has an internal circulation type structure, has excellent gas-liquid contact properties, and can utilize oxygen in the processing gas for absorbing sulfurous acid gas in the exhaust gas. When used in combination with the gypsum separation tank 27 having the structure shown in FIG. 2, air can be supplied to the gas absorbing device in the form of air-enriched water by external circulation in addition to internal circulation. Can be expected to have a synergistic effect on sulfur dioxide gas absorption.

[0022] That is, when the reaction formula is shown for sulfur dioxide absorption by chemical reaction at each location in this case, [dioxide absorber (rotating spindle)] _{SO 2 + H 2 O → H} + + HSO 3 ^{_{- H + + HSO 3 - +}} 1 / 2O 2 → 2H + + S
O ₄ ⁻⁻ H ₂ O + 2H ⁺ + SO ₄ ⁻⁻ + CaCO ₃ → CaSO ₄
· _{2H 2} O + CO 2 [gypsum separation tank] ^{_{H + + HSO 3 - + 1}} / 2O 2 → 2H + + SO
₄ H ₂ O + 2H ⁺ + SO ₄ ⁻⁻ + CaCO ₃ → CaSO ₄
2H ₂ O + CO _2, and the sulfur dioxide gas absorption efficiency in exhaust gas is further improved.

[Comparative Example] Next, the flue gas desulfurization efficiency of the device of the present invention is compared with that of the conventional flue gas desulfurization device shown in FIG. 3. [Conventional device] [The device of the present invention] 1. Gypsum slurry water used in gas absorbers Composition of absorbent Water + air + gypsum Water + air (limestone powder) (limestone powder) * Figures in parentheses indicate the case where limestone powder is added in a slightly excessive amount. 3. 3. Useless component as absorbent gypsum None. 4. Chemical reaction mechanism Same Same Pump power Large Small * It will surely be reduced by the amount of gypsum not circulating. 6. Ventilation pressure loss Large Small 7. Wind turbine power large small * When using gypsum slurry, it is necessary to thicken the liquid film by the volume of gypsum and large crystal particles, so the ventilation cross section becomes narrow and the pressure loss increases. 8. Inappropriateness of air blowing location Inappropriate * Conventional equipment vaguely blows air into the slurry tank, and many air bubbles escape to the atmosphere or exhaust gas, and the air use efficiency is low. The air utilization efficiency is high to supply air to the section effectively. 9. Air supply capacity per cubic meter of water Small Large 10. 10. Circulating amount of absorbent large small As shown in the reliability of the gas absorption device As there is a possibility of scale trouble, low pressure loss, low power, and low price are not possible.There is no risk of scale trouble, especially low power performance, low pressure loss, and low price. In this case, a wide selection of absorbers and new development are possible. As is clear from the above comparative example, it can be understood that the invention of the present application is significantly superior to the conventional apparatus.

[0024]

As described above, the present invention is an apparatus for removing sulfur oxides from an exhaust gas absorbent circulated in a gas absorber, which receives the exhaust gas absorbent from the gas absorber. Along with this, while adding and adding limestone powder and water thereto, stirring and promoting each reaction, means for generating gypsum as a by-product, means for sedimenting and separating gypsum, means for taking out generated gypsum, and gypsum A means for blowing fine oxygen or air bubbles into the absorbing solution from which the air has been removed to form an air-enriched liquid, so that the exhaust gas absorbing solution circulated in the gas absorbing device is rich in fine air bubbles. However, since it is converted into simple air-enriched water and contains no slurry component, there is no possibility of scale trouble in the gas absorbing device. In this case, when limestone powder is excessively added, the air-enriched water can be said to be an extremely thin slurry close to water, if not pure water.

Further, since the exhaust gas absorbing liquid circulated in the gas absorbing device does not contain gypsum, the amount of the circulating liquid can be kept to a necessary minimum, and the load on the drive pump is small. In addition, power consumption can be reduced.

Further, since the inner bottom surface of the gypsum separation tank is inclined so as to be gradually lowered at an angle of at least 15 degrees toward the gypsum discharge port, the crystallized gypsum is extremely excellent in taking out property, and the gypsum is extremely easy to remove from the exhaust gas absorbing liquid. The gypsum removal efficiency has been significantly improved, and the gypsum separation tank accepts the exhaust gas absorbing liquid from the gas absorbing device,
Between an area having a stirring device for stirring the slurry-like gas absorbing solution in the tank and an air blowing device for blowing fine oxygen or air bubbles into the exhaust gas absorbing solution from which the gypsum has been removed to form an air-enriched liquid, Since the upper and lower ends are each provided with a slight gap between the upper opening edge and the inner bottom surface of the gypsum separation tank or an opening to form a partition forming a liquid passage, if only the removal capacity of gypsum is increased Without
The efficiency of making air-enriched water by blowing fine air into simple water from which gypsum has been removed is significantly improved.

Further, a downward hood is attached to the liquid extraction port, which is located above the gypsum separation tank in the upper part of the chamber B to take out the exhaust gas absorbing liquid in the tank, so that the air in the chamber B is airtight. The air-enriched liquid containing a large amount of bubbles can be more sufficiently removed.

[Brief description of the drawings]

FIG. 1 is a principle explanatory diagram of a flue gas desulfurization apparatus according to one embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of the gypsum separation tank of FIG.

FIG. 3 is a principle explanatory view schematically showing a conventionally known flue gas desulfurization apparatus.

[Explanation of symbols]

 Reference Signs List 21 gas absorbing device 22 gas inlet 23 gas outlet 24 bottom opening 25 filling layer 26 spray nozzle 27 gypsum separation tank 28 inner bottom surface 29 gypsum discharge port 30 liquid level 31 partition wall 32 air blower 33 pipe 34 air nozzle 35 pipe 36 air blowing device 36a air nozzle 37 stirrer 38 pump 39 pipe 39a liquid extraction port 39b liquid extraction port hood 40 pipe 41 limestone powder 42 water

 ──────────────────────────────────────────────────続 き Continuing from the front page (71) Applicant 599038569 Junko Sato 1-11-15 Nakashinjuku, Kashiwa-shi, Chiba Pref. Inventor Ken Kimura 742-9 Yoshizawa-cho, Mito-shi, Ibaraki F-term (reference) 4D002 AA02 AC01 AC07 BA02 CA01 CA07 CA20 DA05 DA16 EA02 EA12 FA03 GA01 GA03 GB08 GB09 GB20 HA05

Claims (4)

[Claims] An apparatus for removing sulfur oxides from an exhaust gas absorbent circulated in a gas absorber, said apparatus receiving the exhaust gas absorbent from the gas absorber and
Agitating while supplementing with limestone powder and water to promote the respective reactions, means for producing gypsum as a by-product, means for sedimenting and separating gypsum, means for removing gypsum produced, and gypsum component Means for blowing fine oxygen or air bubbles into the removed absorbent to make it an air-enriched liquid. 2. A gas absorption device provided with a packed bed in a passage of exhaust gas through a spray nozzle, and a gypsum separation tank provided immediately below the gas absorption device, wherein the gypsum separation tank is provided with a gypsum separation tank. An upper opening for receiving the exhaust gas absorbing liquid, a gypsum discharge port formed at the bottom, an inner bottom inclined at an angle of at least 15 degrees or more toward the gypsum discharge port, and a slurry in the tank. A stirrer that stirs the gas absorbing solution, an air blowing device that blows fine oxygen or air bubbles into the exhaust gas absorbing solution from which the gypsum component has been removed to turn it into an air-enriched liquid, and an exhaust gas absorbing solution that turns into an air-enriched liquid A flue gas desulfurization apparatus comprising: a pump for extracting water from a gypsum separation tank and circulating the extracted gas to a spray nozzle in the gas absorption device. 3. An area having a stirring device for receiving the exhaust gas absorbing liquid from the gas absorbing device and for stirring the slurry gas absorbing liquid in the tank, in the gypsum separation tank.
The upper and lower ends are located between the upper opening edge and the inner bottom surface of the gypsum separation tank between the exhaust gas absorbing liquid from which the slurry component has been removed and the air blowing device which blows fine oxygen or air bubbles into the air-enriched liquid. 3. The flue gas desulfurization apparatus according to claim 2, wherein a partition is formed to form a liquid passage by providing a slight gap or an opening. 4. A flue gas desulfurization device provided with an air blowing device for blowing air into a lower portion of the gas absorption tower, or the flue gas desulfurization device according to claim 1 or 2, wherein the exhaust gas is discharged as an air-enriched liquid. A flue gas desulfurization unit in which a downward hood is attached to the liquid extraction port for extracting the gas absorbing liquid from the tank, and an air blowing device is installed below the hood.