JP5731291B2 - Exhaust gas treatment apparatus and exhaust gas treatment method - Google Patents

Description

  The present invention relates to an exhaust gas treatment apparatus and an exhaust gas treatment method for removing exhaust gas from an exhaust gas by bringing the exhaust gas into gas-liquid contact with an absorbent containing an absorbent and reacting a specific component contained in the exhaust gas with the absorbent.

  Various methods for removing harmful substances from exhaust gas are known. Among them, the exhaust gas is brought into gas-liquid contact with an absorbent containing an absorbent and immobilized by reacting the harmful substance with the absorbent. The wet method of removing from is often used. For example, when removing environmental pollutants such as sulfurous acid gas (ie, sulfur dioxide (SO2)) from combustion exhaust gas discharged from thermal power generation facilities, sulfurous acid gas is converted to sulfate by reacting sulfurous acid gas with an absorbent. And then removed from the exhaust gas. Examples of the absorbent include an absorbent that reacts with sulfurous acid gas to generate a sulfate, such as an aqueous solution in which limestone (mainly composed of calcium carbonate (CaCO3)) is dissolved in water or a slurry in which water is suspended. used.

  Among such wet methods, the jet bubbling method in which exhaust gas is injected into the absorbing liquid and the bubbles of the exhaust gas and the absorbing liquid are in gas-liquid contact is a method that has a high removal rate of harmful substances and is economically superior. Therefore, it is widely used and used in wet flue gas desulfurization equipment. For example, Patent Document 1 discloses a jet bubbling reaction tank used in a wet flue gas desulfurization apparatus.

  In the jet bubbling reaction tank disclosed in Patent Document 1, an absorbing liquid for fixing sulfurous acid gas is accommodated in the lower part of the tank, exhaust gas containing sulfurous acid gas is injected into the absorbing liquid, and bubbles of the exhaust gas and the absorbing liquid are removed. It is a gas-liquid contact type reaction tank that reacts with an absorbent (limestone) while forming a gas-liquid contact layer (hereinafter also referred to as “floss layer”) in liquid contact and fixes sulfite gas as sulfate. The absorbent (limestone) is supplied to the lower part of the jet bubbling reaction tank as a slurry suspended in water.

  The jet bubbling reaction vessel disclosed in Patent Document 1 will be further described with reference to FIG. In the lower space of the jet bubbling reaction tank 100, a slurry in which limestone powder that reacts with sulfurous acid gas and is fixed to gypsum is suspended in water is accommodated as an absorbing liquid 120. Exhaust gas is introduced from the inlet duct 126 through the exhaust gas inlet chamber 114 through the opening of the exhaust gas dispersion pipe 130 and below the liquid level of the absorbing liquid 120, and is jetted out and rises while bubbling. As a result, a so-called floss layer 125 is formed on the upper part of the absorbing liquid 120.

  Sulfurous acid gas dissolves in the absorbent 120 and then reacts with oxygen and limestone to become gypsum and be fixed. The generated gypsum precipitates in the absorption liquid 120 as crystals, and the absorption liquid 120 becomes a slurry in which a large amount of gypsum particles are suspended (hereinafter also referred to as “gypsum slurry”). The exhaust gas from which the sulfurous acid gas has been removed passes through the communication pipe 128 and the exhaust gas outlet chamber 112 and is discharged out of the system by the outlet duct 124.

Japanese Patent Publication No. 3-70532 JP-A-8-24568

  Such a desulfurization rate of the jet bubbling reaction tank 100 can be up to about 99%. However, in recent years, it has been demanded to treat exhaust gas at a higher desulfurization rate from the viewpoint of global environmental conservation. Yes. For example, it may be required to treat high SO2 exhaust gas having a concentration of 3000 ppm, which is generated when inferior fuel with a high sulfur content, is burned, for example, at a desulfurization rate of 99.5% or more. In addition, in carbon dioxide capture and storage (CCS) that will attract attention in the future, the concentration of sulfurous acid gas in the exhaust gas after treatment is required to be, for example, 10 ppm or less.

  However, in order to achieve such a high desulfurization rate in the conventional jet bubbling reaction tank 100 as described above, the liquid surface of the absorbing liquid 120 is raised and the height (thickness) of the froth layer 125 is increased. Alternatively, since it is necessary to control the pH of the absorbent 120 to be controlled to be extremely high, there are problems in terms of an increase in power for exhaust gas treatment and the utilization rate of the absorbent (limestone).

Further, an additional process such as performing secondary desulfurization on the exhaust gas desulfurized in the froth layer 125 is necessary. As the secondary desulfurization method, there is known a method of spraying an absorption liquid on the exhaust gas desulfurized in the froth layer and bringing it into gas-liquid contact, but a large additional facility for secondary desulfurization is required. Therefore, there are problems that the facilities of the entire jet bubbling reaction tank are complicated, and that power for exhaust gas treatment is increased.
Therefore, the present invention solves the problems of the prior art as described above, and the specific components such as environmental pollutants contained in the exhaust gas are conventionally added without complicating facilities and processes and greatly increasing power. It is an object of the present invention to provide an exhaust gas treatment apparatus and an exhaust gas treatment method for removing at a higher removal rate.

  In order to solve the above-described problems, an aspect of the present invention has the following configuration as an example. That is, the exhaust gas treatment apparatus according to one aspect of the present invention removes gas from the exhaust gas by bringing the exhaust gas into gas-liquid contact with the absorbent containing the absorbent and reacting the specific component contained in the exhaust gas with the absorbent. An exhaust gas treatment apparatus comprising: a treatment tank containing a first absorption liquid; and the exhaust gas is ejected into the first absorption liquid, and the exhaust gas bubbles are disposed in an upper portion from a depth position where the exhaust gas is ejected. An exhaust gas introduction part that forms a gas-liquid contact layer in gas-liquid contact with the first absorption liquid, and a first absorption liquid from the outside of the processing tank in a portion below the gas-liquid contact layer in the processing tank A first absorption liquid replenishing section to replenish, a stirrer that stirs the first absorption liquid located below the gas-liquid contact layer and generates a flow of the first absorption liquid toward the gas-liquid contact layer; The second absorbent is directly applied to the top of the gas-liquid contact layer Kyusuru comprising a second absorbent liquid supply unit.

In such an exhaust gas treatment apparatus, the second absorption liquid supply unit is configured so that a part of the first absorption liquid positioned below the gas-liquid contact layer is used as the second absorption liquid in the gas-liquid contact layer. It can be set as the structure supplied to upper part.
Further, the second absorption liquid supply unit may be configured to spray the second absorption liquid toward the gas-liquid contact layer from above the upper surface of the gas-liquid contact layer.
Furthermore, the second absorbing liquid supply unit includes a pipe disposed in the gas-liquid contact layer and a nozzle extending upward from the pipe, and is located above the upper surface of the gas-liquid contact layer. It is preferable that the second absorbing liquid is discharged from the discharge port of the nozzle.

Further, the absorbent contained in the second absorbent supplied to the upper part in the gas-liquid contact layer, and the first supplied to the lower part in the gas-liquid contact layer by the flow of the first absorbent. The molar ratio (%) of the absorbent contained in the second absorbent supplied to the upper part of the gas-liquid contact layer with respect to the total contained in the absorbent is 5% or more. It is preferable to be within the range of 70% or less.
Furthermore, the specific component may be sulfur dioxide, and the absorbent contained in the first absorbent and the second absorbent may be calcium carbonate.

  Furthermore, the exhaust gas treatment method according to another aspect of the present invention removes gas from the exhaust gas by bringing the exhaust gas into gas-liquid contact with an absorbent containing the absorbent and reacting the specific component contained in the exhaust gas with the absorbent. The exhaust gas is ejected into the first absorption liquid accommodated in the treatment tank, and the exhaust gas bubbles, the first absorption liquid, and the upper portion from a depth position where the exhaust gas is ejected are Forming a gas-liquid contact layer in contact with the gas-liquid, replenishing the first absorption liquid from the outside of the processing tank to a portion below the gas-liquid contact layer in the processing tank, than the gas-liquid contact layer The first absorption liquid located below is agitated to generate a flow of the first absorption liquid toward the gas-liquid contact layer, and this flow supplies the first absorption liquid to the lower part in the gas-liquid contact layer. The second absorbent is directly supplied to the upper part of the gas-liquid contact layer. And wherein the door.

  Since the exhaust gas treatment apparatus and the exhaust gas treatment method according to the present invention perform exhaust gas treatment while supplying an absorbing liquid to the upper and lower parts in the gas-liquid contact layer, the facilities and processes are complicated and the power is greatly increased. It is possible to remove specific components such as environmental pollutants contained in the exhaust gas with a high removal rate.

It is typical sectional drawing explaining the structure of one Embodiment of the waste gas processing apparatus which concerns on this invention. It is an enlarged view explaining the absorption liquid supply part of the exhaust gas processing apparatus of FIG. It is an enlarged view explaining the modification of an absorption liquid supply part. It is a top view which shows the beam for grids and a grid to which an absorption liquid supply part is fixed. It is the figure which expanded and showed the part enclosed with the broken line of FIG. It is a graph which shows pH distribution of an absorption liquid. It is typical sectional drawing explaining the structure of the conventional jet bubbling reaction tank. It is a graph which shows pH distribution of the absorption liquid in the conventional jet bubbling reaction tank.

Embodiments of an exhaust gas treatment apparatus and an exhaust gas treatment method according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining the structure of the exhaust gas treatment apparatus of the present embodiment, and FIG. 2 is an enlarged view for explaining an absorbent supply unit of the exhaust gas treatment apparatus of FIG.
The exhaust gas treatment apparatus of FIG. 1 is a treatment apparatus that removes specific components such as environmental pollutants from combustion exhaust gas discharged from thermal power generation facilities, etc., and will be described below by taking a case where the specific component is sulfurous acid gas as an example. To do. Such an exhaust gas treatment apparatus can be suitably used for a wet flue gas desulfurization apparatus.

  As shown in FIG. 1, the exhaust gas treatment apparatus includes a substantially sealed treatment tank 10, and the treatment tank 10 is partitioned into three spaces. That is, in order from the top, the exhaust gas outlet chamber 12, the exhaust gas inlet chamber 14 provided so as to cross the inside of the tank, and the absorbent 20 of sulfurous acid gas (corresponding to the first absorbent that is a constituent of the present invention) And an absorption liquid storage chamber 15 for storing the liquid.

  More specifically, the exhaust gas outlet chamber 12 and the exhaust gas inlet chamber 14 are partitioned by a first partition plate 16 extending horizontally across the tank body, and the exhaust gas inlet chamber 14 and the absorbing liquid storage chamber 15 are It is partitioned by a second partition plate 18 extending in parallel to the partition plate 16. The second partition plate 18 is positioned above the liquid level of the absorbing liquid 20, and an exhaust gas outflow space 22 is formed between the second partition plate 18 and the liquid level. In addition, the absorption liquid 20 contains the slurry which suspended the powder of the limestone which is an absorber in water. The limestone concentration (ratio of limestone powder to the total amount of limestone powder and water) is not particularly limited, but may be usually 20 to 25% by mass.

  The exhaust gas outlet chamber 12 is connected to an outlet duct 24, and the lower exhaust gas inlet chamber 14 is connected to an inlet duct 26. Further, as gas risers for allowing the treated exhaust gas to flow into the exhaust gas outlet chamber 12 from the space 22, a plurality of pipe communication pipes 28 (two in the example of FIG. 1, but not limited thereto) are exhaust gas inlets. The space portion 22 and the exhaust gas outlet chamber 12 communicate with each other through the chamber 14 in the vertical direction.

  The exhaust gas dispersion pipe 30 (corresponding to the exhaust gas introduction part which is a constituent element of the present invention) is connected to the exhaust gas inlet chamber 14 at the upper end and immersed in the absorbent 20 at the lower end of the exhaust gas inlet chamber 14. It extends downward from the two-way plate 18. A plurality of small openings 30 a are provided at the lower end of the exhaust gas dispersion pipe 30, and the exhaust gas is injected into the absorbing liquid 20 from the openings 30 a. The injected exhaust gas becomes fine bubbles in the absorbing liquid 20, and a floss layer 25 is formed which is composed of the bubbles of the exhaust gas and the absorbing liquid 20 and in which both are in gas-liquid contact.

  Further, in the treatment tank 10, an absorption liquid replenishment pipe 40 for replenishing the absorption liquid from the outside of the treatment tank 10 to the absorption liquid storage chamber 15 (a portion below the floss layer 25) according to consumption of the absorbent (the present invention). The first absorption liquid replenishing section, which is a component of the absorption liquid storage chamber 15, the stirrer 32 that stirs the absorption liquid 20 stored in the absorption liquid storage chamber 15, and the absorption that directly supplies the absorption liquid to the upper part of the floss layer 25. A liquid supply unit 50 (corresponding to the second absorption liquid supply unit which is a constituent of the present invention) and an oxygen-containing gas (for example, air, oxygen) for supplying oxygen necessary for fixing gypsum of sulfurous acid gas are ejected The air supply pipe 34 provided with the jet nozzle 34a which performs and the discharge pipe 42 which discharges | emits the gypsum slurry produced by reaction to the exterior from the absorption liquid storage chamber 15 are provided.

  A rotating shaft 36 of the agitator 32 extends downward from a driving device 38 on the tank through the communication pipe 28. And the stirring blade 39 attached to the lower end of the rotating shaft 36 stirs the absorbing liquid 20 located below the floss layer 25 to generate a flow (upflow) of the absorbing liquid 20 toward the floss layer 25. It is like that. In FIG. 1, the flow of the absorption liquid 20 is indicated by an arrow in the absorption liquid storage chamber 15.

  Absorption liquid separately prepared outside the treatment tank 10 (another tank) is replenished to the absorption liquid storage chamber 15 (a part below the floss layer 25) via the absorption liquid supply pipe 40. Since the opening end portion of the replenishment pipe 40 is arranged in the vicinity of the upper part of the stirring blade 39, the new absorption liquid introduced from the opening end part of the absorption liquid replenishment pipe 40 is moved to the lower part in the froth layer 25 by the flow. Will be supplied.

Further, the ejection nozzle 34 a is arranged in the lower part of the processing tank 10, and oxygen-containing gas is ejected from the ejection nozzle 34 a into the absorbing liquid 20 in the absorbing liquid storage chamber 15. The ejected oxygen-containing gas becomes bubbles and dissolves in the absorbing liquid 20 while rising in the absorbing liquid 20, and is consumed in the reaction between the sulfurous acid gas and the limestone that is the absorbent.
Moreover, the structure of the absorption liquid supply part 50 will be specifically limited if it can supply absorption liquid (equivalent to the 2nd absorption liquid which is a structural requirement of this invention) to the upper part in the floss layer 25. is not. For example, as shown in an enlarged view in FIG. 2, the absorbent supply unit 50 includes a pipe 51 disposed in the floss layer 25 and a plurality of nozzles 52 extending upward from the pipe 51. Also good.

  As shown in FIG. 2, if the discharge port of the nozzle 52 is installed so as to be positioned above the upper surface of the floss layer 25, the absorbing liquid discharged from the discharge port of the nozzle 52 is applied to the upper surface of the floss layer 25 from above. Will be sprayed. Further, if the nozzle 52 is disposed so that the discharge port of the nozzle 52 is located in the floss layer 25, the absorbing liquid discharged from the discharge port of the nozzle 52 is supplied to the inside of the floss layer 25. However, the absorbing liquid needs to be supplied to the upper part of the floss layer 25, that is, to the upper part of the upper and lower center of the floss layer 25, and is absorbed from the upper side of the floss layer 25 toward the upper surface of the floss layer 25. It is preferable to spray the liquid.

  The pipe 51 may be fixed by using a fixing member (not shown) or the like to the grid beam 54 for fixing the grid-like grid 53 that supports the exhaust gas dispersion pipe 30. That is, as shown in FIGS. 2, 4, and 5, a lattice-like grid 53 extending horizontally across the tank body is provided in the processing tank 10. The exhaust gas dispersion pipe 30 is supported by the grid 53 by inserting the exhaust gas dispersion pipe 30 into the grid of the grid 53. The grid 53 is placed and fixed on the grid beam 54. If the pipe 51 is fixed to the grid beam 54, a plurality of nozzles 52 are arranged along the grid beam 54.

Further, as shown in an enlarged view in FIG. 3, the absorbent supply unit 50 includes a pipe 55 arranged in the space 22 above the floss layer 25 and a plurality of nozzles 56 extending downward from the pipe 55. The structure provided may be sufficient. When the absorbing liquid is discharged from the discharge ports of these nozzles 56, the absorbing liquid is sprayed toward the upper surface of the lower floss layer 25.
For example, the pipe 55 may be fixed to the lower deck support beam 58 that supports the lower deck 57 of the processing tank 10 by using a fixing member 59 or the like.

Only one of the nozzles 52 and 56 may be provided as the absorbing liquid supply unit 50, but both the nozzles 52 and 56 are provided as the absorbing liquid supply unit 50, and the nozzles 52 and 56 are provided in the floss layer 25. You may supply an absorption liquid to the upper part.
The amount of absorbing liquid discharged from these nozzles 52 and 56 and the number of nozzles 52 and 56 may be set as appropriate according to the concentration of sulfurous acid gas in the exhaust gas, the required desulfurization rate, and the like. it is preferably set to 5 to 30 m ³ / hr per nozzle, and more preferably set to 10 to 20 m ³ / hr. The latter is preferably a single nozzle horizontal area 1 to 5 m ² per froth layer 25, and more preferably to one nozzle per horizontal area 2 to 3 m ^2.

It is preferable that the absorbent supply unit 50 supply the absorbent uniformly to the entire upper surface of the floss layer 25. If there is a portion where the absorption liquid is not sufficiently supplied, the removal rate of sulfurous acid gas may be reduced in that portion.
The absorption liquid supplied to the upper part in the froth layer 25 from the absorption liquid supply part 50 is not specifically limited, The limestone slurry similar to the absorption liquid 20 accommodated in the absorption liquid storage chamber 15 can be used. . This limestone slurry may be separately prepared outside the processing tank 10 (another tank), or an absorbing liquid for replenishing the absorbing liquid storage chamber 15 from the absorbing liquid supply pipe 40 may be used. That is, a pipe of a system different from the absorbent supply pipe 40 is connected to the absorbent storage tank for replenishing the absorbent storage chamber 15 from the absorbent supply pipe 40, and this pipe is connected to the absorbent supply section 50. Alternatively, another pipe may be branched from the main pipe upstream of the absorbent supply pipe 40 and connected to the absorbent supply unit 50.

  Further, the gypsum slurry extracted from the absorption liquid storage chamber 15 (which is an absorption liquid positioned below the floss layer 25 and includes limestone as an absorbent) is transferred from the absorption liquid supply unit 50 to the floss layer 25. You may supply to upper part. In this case, the gypsum slurry may be extracted via the discharge pipe 42, and the pipe may be branched while being sent to a gypsum separator (not shown) and sent to the absorbent supply unit 50. A dedicated pipe for extracting and sending to the absorbent supply unit 50 may be separately provided in the processing tank 10.

Furthermore, as long as it reacts efficiently with sulfurous acid gas, an absorbing liquid containing an absorbent different from limestone is prepared outside the processing tank 10, and the absorbing liquid supply unit 50 is placed on the upper part in the floss layer 25. You may supply.
Hereinafter, the operation of the exhaust gas treatment apparatus will be described. In FIG. 1, a slurry in which limestone powder that reacts with sulfurous acid gas and is fixed to gypsum is suspended in water is stored as an absorbing liquid 20 in an absorbing liquid storage chamber 15 at a lower portion of the processing tank 10.

  Exhaust gas containing sulfurous acid gas reaches the exhaust gas dispersion pipe 30 from the inlet duct 26 via the exhaust gas inlet chamber 14, and is below the liquid level of the absorbent 20 (for example, 100 to 300 mm below the liquid level) from the opening 30 a of the exhaust gas dispersion pipe 30. From the position of (2), and is jetted to rise as fine bubbles having a diameter of 2 to 3 mm, for example. Thereby, it is the depth position (namely, the depth position where the opening 30a is located) in which the exhaust gas is injected among the absorbing liquid 20 accommodated in the absorbing liquid storage chamber 15, and hereinafter referred to as "immersion depth". A floss layer 25 made up of exhaust gas bubbles and the absorbing liquid 20 and in gas-liquid contact with each other is formed in the upper part from the upper part.

While the exhaust gas rises in the absorption liquid 20 as bubbles, the sulfurous acid gas in the exhaust gas dissolves in the absorption liquid 20 and reacts with dissolved oxygen and limestone as shown in the following chemical formula to become gypsum (CaSO 4 · 2H 2 O) and immobilized. Is done. The generated gypsum precipitates in the absorption liquid 20 as crystals, and the absorption liquid 20 becomes a gypsum slurry in which a large amount of gypsum particles are suspended.
SO2 (gas) + H2 O → H2 SO3 (absorption)
H2 SO3 + 1 / 2O2 → H2 SO4 (oxidation)
H2 SO4 + CaCO3 → CaSO4 + H2 O + CO2 ↑ (neutralization)
CaSO4 + 2H2 O → CaSO4 ・ 2H2 O ↓ (crystallization)

The removal rate of sulfurous acid gas can be controlled by the pH of the absorbent 20 and the immersion depth. The pH of the absorbent 20 is preferably weakly acidic, for example, 4.5 to 5.5, and the immersion depth is 100 to 300 mm (the height (thickness) of the floss layer 25 formed at this time is 0.3 to 300 mm). About 1 m).
The exhaust gas from which the sulfurous acid gas has been removed passes through the communication pipe 28 and the exhaust gas outlet chamber 12 and is discharged out of the system by the outlet duct 24. On the other hand, the gypsum slurry containing the crystallized gypsum in a concentrated manner is discharged from the discharge pipe 42. An amount of limestone slurry (new absorption liquid) corresponding to the gypsum slurry extracted from the discharge pipe 42 is continuously supplied below the floss layer 25 from the absorption liquid supply pipe 40.

  In this way, sulfurous acid gas is removed from the exhaust gas in the froth layer 25, but as the sulfurous acid gas is removed, the absorbent is consumed from the absorbent 20 in the froth layer 25, so the absorbent is abundant. It is necessary to supply the contained absorbent to the floss layer 25. In the conventional jet bubbling reaction tank 100, the flow of the absorption liquid toward the froth layer is generated using a stirrer, and thereby the absorption liquid is supplied to the lower part of the froth layer. The lower part of the floss layer was sufficiently supplied with the absorbent containing the absorbent, but the upper part of the floss layer was not sufficiently supplied with the absorbent containing the absorbent. Therefore, there is often a difference in the concentration of the absorbent in the absorbent between the upper part and the lower part in the floss layer. That is, the pH in the froth layer decreases from the bottom to the top, and the pH is the lowest at the top of the froth layer, which is the final outlet of the exhaust gas after treatment, and the equilibrium of sulfurous acid in the absorption liquid. The partial pressure increases.

  As a result, the removal performance of sulfurous acid gas is slightly lower in the upper part of the froth layer than in the lower part of the froth layer. It was difficult to do. For example, high-SO2 exhaust gas having a concentration of 3000 ppm, which is generated when inferior fuel with a high sulfur content, is burned, for example, with a desulfurization rate of 99.5% or more, carbon dioxide recovery and storage (CCS) It is difficult to achieve the sulfurous acid gas concentration of the exhaust gas after treatment, for example, 10 ppm or less, which is required by the above.

  Here, the result of measuring the pH distribution of the absorption liquid layer inside the floss layer and below the floss layer when the exhaust gas is treated by the conventional method of supplying the absorption liquid only to the lower part of the floss layer is shown in FIG. This is shown in the graph of FIG. In addition, the sulfurous acid gas density | concentration of the waste gas before a process is 1000 ppm (dry). Further, the pH of the absorbing solution slightly below the floss layer was controlled to 4.4. Further, the height ratio of the vertical axis of the graph is a ratio to the distance from the bottom of the treatment tank in which the absorption liquid is stored to the opening of the exhaust gas dispersion pipe (boundary between the floss layer and the absorption liquid layer).

As can be seen from the graph in FIG. 8, there was a large difference in pH between the upper part and the lower part in the floss layer. Moreover, the sulfurous acid gas density | concentration of the waste gas after a process was 15 ppm (dry), and the desulfurization rate was 98.7%. From this, it is considered that the pH of the uppermost part of the froth layer, which is the final outlet of the exhaust gas after treatment, is further lowered due to the low concentration of the absorbent.
On the other hand, in the exhaust gas treatment apparatus of the present embodiment, the stirrer 32 that supplies an absorbing solution rich in absorbent to the lower part of the floss layer 25 and the absorbing solution rich in absorbent in the floss layer 25. And an absorption liquid supply unit 50 that supplies the upper part of the absorption liquid. Therefore, since sufficient absorption liquid is supplied to both the upper part and the lower part in the floss layer 25, a difference in the concentration of the absorbent hardly occurs between the upper part and the lower part in the floss layer 25. All have high removal performance.

  Therefore, for example, even when a high SO2 exhaust gas having a concentration exceeding 3000 ppm, which is generated when inferior fuel having a high sulfur content, is burned, it can be processed at a desulfurization rate of 99.5% or more. In addition, it is possible to achieve a sulfur dioxide concentration of 10 ppm or less in the exhaust gas after treatment, which is required for carbon dioxide recovery storage (CCS) or the like.

  In order to remove sulfurous acid gas from exhaust gas at a higher desulfurization rate, the absorbent contained in the absorbent supplied to the upper part of the floss layer 25 and the lower part of the floss layer 25 are supplied by the flow. The molar ratio (%) of the absorbent contained in the absorbent supplied to the upper part of the floss layer 25 with respect to the total of the absorbent contained in the absorbent is within the range of 5% to 70%. Preferably, it is within a range of 10% to 50%, more preferably within a range of 20% to 40%.

  If the molar ratio is less than 5%, the effect of supplying the absorbing liquid to the upper part of the floss layer 25 may not be sufficiently obtained. On the other hand, in order to exceed the above molar ratio by 70%, it is necessary to increase the number of pipes for supplying the absorbing liquid to the upper part of the floss layer 25 or to increase the diameter, which is a problem in the device structure. May occur and the cost may increase.

  Here, the pH distribution of the absorption liquid layer inside the floss layer and below the floss layer when the exhaust gas was treated by the method of the present invention for supplying the absorption liquid to both the upper part and the lower part in the floss layer was measured. The results are shown in the graph of FIG. In addition, the sulfurous acid gas density | concentration of the waste gas before a process is 1000 ppm (dry). Further, the pH of the absorbing solution slightly below the floss layer was controlled to 4.4. Further, the height ratio of the vertical axis of the graph is a ratio to the distance from the bottom of the treatment tank in which the absorption liquid is stored to the opening of the exhaust gas dispersion pipe (boundary between the floss layer and the absorption liquid layer).

As can be seen from the graph of FIG. 6, there was no significant difference in pH between the upper part and the lower part in the floss layer. Moreover, the sulfurous acid gas density | concentration of the waste gas after a process was 10 ppm (dry), and the desulfurization rate was 99.1%.
Thus, if it processes with the exhaust gas processing apparatus of this embodiment, sulfurous acid gas can be removed from exhaust gas with a high desulfurization rate. Moreover, the exhaust gas treatment apparatus of the present embodiment only needs to add the absorbing liquid supply unit 50, and does not require a large additional equipment as in the conventional secondary desulfurization method described above. There is almost no problem that the exhaust gas treatment process becomes complicated and the cost and power of exhaust gas treatment increase significantly.

  In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, although not particularly described in the present embodiment, a spray device for spraying the absorbing liquid may be provided in one or both of the communication pipe 28 and the exhaust gas inlet chamber 14. If a spray device is provided in the exhaust gas inlet chamber 14, preliminary desulfurization can be performed on the exhaust gas before treatment, and exhaust gas can be cooled and humidified together with dust removal of the exhaust gas. On the other hand, if a spray device is provided in the communication pipe 28, secondary desulfurization can be performed on the exhaust gas desulfurized in the floss layer 25.

  In the present embodiment, sulfurous acid gas is exemplified as the specific component to be removed from the exhaust gas. However, other types of environmental pollutants can be removed using the exhaust gas treatment apparatus of the present embodiment. Other than sulfurous acid gas (SO2), acidic substances such as SO3, NO, N2 O3, NO2, N2 O4, N2 O5, CO2, HCl, HF, and alkaline substances such as ammonia can be removed.

Further, the absorbent (both the first absorbent and the second absorbent) has been described by exemplifying limestone (mainly composed of calcium carbonate), but other kinds of absorbents can also be used. When the specific component is an acidic substance as described above, the absorbent is preferably an alkali metal compound or an alkaline earth metal compound, particularly preferably calcium carbonate or calcium hydroxide. When the specific component is an alkaline substance as described above, an acidic substance such as hydrogen chloride is preferable as the absorbent.
Furthermore, in the present invention, a solution obtained by dissolving an absorbent in a solvent such as water or a slurry obtained by suspending the absorbent in a solvent such as water can be used as the absorbent.
Furthermore, the same thing may be used for a 1st absorption liquid and a 2nd absorption liquid, but a different thing may be used.

DESCRIPTION OF SYMBOLS 10 Treatment tank 12 Exhaust gas outlet chamber 14 Exhaust gas inlet chamber 15 Absorption liquid storage chamber 16 1st partition plate 18 2nd partition plate 20 Absorption liquid 22 Space part 24 Outlet duct 25 Floss layer 26 Inlet duct 28 Communication pipe 30 Exhaust gas dispersion pipe 30a Opening 32 Stirrer 34 Air supply pipe 34a Jet nozzle 40 Absorption liquid supply pipe 42 Discharge pipe 50 Absorption liquid supply part 51 Piping 52 Nozzle 55 Piping 56 Nozzle

Claims (5)

An exhaust gas treatment apparatus that removes gas from gas by liquid-gas contact with an absorbent containing an absorbent, and removes the exhaust gas by reacting a specific component contained in the exhaust gas with the absorbent,
A treatment tank containing the first absorbent,
The exhaust gas is ejected into the first absorption liquid, and a gas-liquid contact layer in which the gas bubbles of the exhaust gas and the first absorption liquid are in gas-liquid contact is formed at an upper portion from a depth position where the exhaust gas is ejected. An exhaust gas introduction part;
A first absorbent replenisher for replenishing a first absorbent from the outside of the treatment tank to a portion below the gas-liquid contact layer in the treatment tank;
A stirrer that stirs the first absorbing liquid located below the gas-liquid contact layer and generates a flow of the first absorbing liquid toward the gas-liquid contact layer;
A second absorbent supply section for directly supplying the second absorbent to the upper part in the gas-liquid contact layer;
Equipped with a,
The second absorption liquid supply unit includes a pipe disposed in the gas-liquid contact layer and a nozzle extending upward from the pipe, and the second absorbing liquid supply unit includes a nozzle that is positioned above the upper surface of the gas-liquid contact layer. exhaust gas treatment apparatus according to claim Rukoto from the discharge port discharges the second absorption liquid.   The second absorbent supply section supplies a part of the first absorbent located below the gas-liquid contact layer to the upper part of the gas-liquid contact layer as the second absorbent. The exhaust gas treatment apparatus according to claim 1.   The said 2nd absorption liquid supply part spreads said 2nd absorption liquid toward the said gas-liquid contact layer from the upper direction rather than the upper surface of the said gas-liquid contact layer, The Claim 1 or Claim 2 characterized by the above-mentioned. Exhaust gas treatment equipment. The exhaust gas according to any one of claims 1 to 3 , wherein the specific component is sulfur dioxide, and the absorbent contained in the first absorbent and the second absorbent is calcium carbonate. Processing equipment. A method for removing gas from the exhaust gas by bringing the exhaust gas into gas-liquid contact with the absorbent containing the absorbent and reacting the specific component contained in the exhaust gas with the absorbent,
The exhaust gas is ejected into the first absorption liquid accommodated in the treatment tank, and the gas in which the exhaust gas bubbles and the first absorption liquid are in gas-liquid contact with the upper portion from the depth position where the exhaust gas is ejected. Forming a liquid contact layer,
Replenishing the first absorbent from the outside of the treatment tank to the lower part of the gas-liquid contact layer in the treatment tank;
The first absorption liquid positioned below the gas-liquid contact layer is agitated to generate a flow of the first absorption liquid toward the gas-liquid contact layer. Supply the first absorbent,
An upper portion in the gas-liquid contact layer is formed by discharging a second absorbing liquid from a discharge port of a nozzle extending upward from a pipe disposed in the gas-liquid contact layer and positioned above the upper surface of the gas-liquid contact layer. An exhaust gas treatment method, wherein the second absorbent is directly supplied to the exhaust gas.

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