JP3889259B2 - Wet flue gas desulfurization equipment - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a wet flue gas desulfurization apparatus that removes sulfur oxide (SO ₂ ) in exhaust gas discharged from a combustion apparatus such as a boiler, and in particular, wet exhaust gas in which oxidation of sulfurous acid species in an absorbent is efficiently performed. The present invention relates to a smoke desulfurization apparatus and an oxidized air supply apparatus.
[0002]
[Prior art]
An outline of a spray type absorption tower is shown in FIG. 13 as an example of a wet flue gas desulfurization device that removes sulfur oxides in flue gas generated by combustion of fossil fuel in a thermal power plant or the like. This wet flue gas desulfurization apparatus mainly includes an absorption tower body 1, an inlet duct 2, an outlet duct 3, an absorbent circulation pump 4, a circulation tank 6, a stirrer 7, an air supply pipe 8, a mist eliminator 9, and an absorbent extraction pipe 10. , A circulation pipe 11, a spray header 12, a spray nozzle 13, a suction pipe 14, and the like.
[0003]
The exhaust gas discharged from the boiler is introduced into the absorption tower body 1 from the inlet duct 2 and discharged from the outlet duct 3 provided at the top of the tower. During this time, the absorption liquid 5 containing calcium carbonate sent from the absorption liquid circulation pump 4 is jetted from the spray nozzle 13, and the gas-liquid contact between the absorption liquid 5 and the exhaust gas is performed. At this time, the absorbing solution 5 absorbs SO ₂ in the exhaust gas, SO ₃ ²⁻ is generated, and reacts with calcium carbonate to generate calcium sulfite Ca (HSO ₃ ) ₂ . The injected absorbent 5 once drops to the circulation tank 6 and is stirred by the oxidizing stirrer 7 during the stay, and Ca (HSO ₃ ) ₂ is oxidized by oxygen in the oxidized air supplied from the air supply pipe 8. , Produces calcium sulfate (gypsum).
[0004]
An example of an oxidized air supply device provided on the wall surface of the conventional circulation tank 6 is shown in FIGS.
[0005]
In the example shown in FIG. 14, an air jet pipe 18 is provided around the rotation axis of the stirrer 7, and the stirrer propeller 16 is rotated from the back side (stirrer 7 side) of the stirrer propeller 16 through the air jet pipe 18. In particular, the oxidized air 15 was supplied into the absorbent 5. Further, in the example shown in FIG. 15, the oxidized air is constantly supplied from below the back of the stirrer propeller 16 (the stirrer 7 side) through the air jet pipe 18 regardless of the rotational position of the stirrer propeller 16.
[0006]
[Problems to be solved by the invention]
As the load of the desulfurizer increases with the amount of exhaust gas treated and the sulfur content in the fuel, the amount of oxidized air necessary for the oxidation of Ca (HSO ₃ ) _{2 in} the absorbent also increases.
[0007]
In any of the above-described oxidized air supply devices, when the amount of oxidized air supplied increases, the amount of discharged absorbent from the stirrer 7 becomes insufficient compared to the amount supplied, and the oxidized air hardly reaches the center of the circulation tank 6. There was a trend. Accordingly, since the oxidation of Ca (HSO ₃ ) ₂ is insufficient at the central portion of the circulation tank 6, excessively oxidized air is supplied or absorbed from the oxidized air supply device such as the air ejection pipe 18 to compensate for this. It was necessary to lengthen the residence time of the liquid 5 in the circulation tank 6, and there was a tendency that the power for supplying the oxidizing air and the capacity of the circulation tank increased.
[0008]
The object of the present invention is to reduce the power for supplying oxidized air by efficiently oxidizing calcium sulfite Ca (HSO ₃ ) ₂ with a small amount of oxidized air, and to perform wet operation with a small capacity of the absorbent circulation tank. An object is to provide a flue gas desulfurization apparatus and an oxidized air supply apparatus.
[0009]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations. The invention according to claim 1 is an absorption tower in which exhaust gas is introduced and brought into contact with an absorption liquid containing calcium carbonate, and an absorption liquid in which sulfur oxides in the exhaust gas are absorbed by the absorption tower is stored and oxidized in the absorption liquid. In a wet flue gas desulfurization apparatus equipped with a circulation tank for blowing air, a stirrer propeller and a spindle having a rotating shaft for discharging the absorbing liquid are provided on the wall surface of the circulation tank, and at a position facing the negative pressure side surface of the stirrer propeller. An air chamber for supplying oxidized air that supports the rotating shaft of the agitator propeller is provided, and the air outlet or air ejection slit and the air ejection opening or air ejection slit are opened and closed on the negative pressure side surface of the agitator propeller of the air chamber. It is a wet type flue gas desulfurization device provided with a rotary valve or a shutter-like object.
[0010]
The above-mentioned subject of the present invention is achieved by the following composition. The invention according to claim 4 is an absorption tower for introducing exhaust gas into contact with an absorption liquid containing calcium carbonate, and storing an absorption liquid in which the sulfur oxide in the exhaust gas is absorbed in the absorption tower to oxidize the absorption liquid. In a wet flue gas desulfurization apparatus provided with a circulation tank for blowing air, a stirrer propeller having a rotating shaft for discharging the absorption liquid to the wall surface of the circulation tank, and a stirrer propeller at a position facing the negative pressure side surface of the stirrer propeller An air chamber for supplying oxidized air that supports a rotating shaft is provided, and a rotating portion is provided in the air chamber, and an air jet pipe that faces the circulating tank from the rotating portion along the rotating shaft of the stirrer propeller is provided, It is a wet type flue gas desulfurization apparatus provided with the oxidation air supply apparatus in which the air jet outlet of the front-end | tip of an air jet pipe was installed in the discharge side peripheral part of the agitator propeller.
[0011]
[Action]
FIG. 4 is a view for explaining the behavior of the oxidized air supply port provided on the wall surface of the circulation tank and the agitator propeller 16 of the present invention, in the case where the specific propeller 16 of the agitator is rotated by a predetermined distance. A sectional view of the propeller 16 (cross section on the plane S shown in FIG. 3) is schematically shown, and the mechanism of the present embodiment is described in comparison with the prior art.
[0012]
Ca (HSO ₃ ) ₂ In order to efficiently oxidize the air, the air supplied from the air supply pipe is refined by the stirrer and dispersed in the circulation tank together with the discharge flow by the stirrer. In the prior art, when the increase in the discharge amount of the absorbent slurry is reduced as compared with the increase rate of the air supply amount due to the increase in the air supply amount, the bubbles rise to the liquid level of the absorption liquid immediately after being discharged from the stirrer propeller 16 and absorbed. With the liquid discharge flow, the number of bubbles reaching the center of the circulation tank is reduced, and it cannot be said that effective gas-liquid contact is performed. Such a decrease in the absorption liquid discharge flow can be explained with reference to FIG.
[0013]
FIG. 4A shows the state of discharge of the slurry in the vicinity of the propeller 16 of the stirrer when oxidizing air is not supplied. When the agitator starts to rotate, the fluid mass (slurry) B of the absorbing liquid on the back surface (motor side) of the propeller 16 moves relatively to the discharge side. Therefore, the slurry C that has been on the discharge side is discharged from the propeller 16. At the same time, a negative pressure is generated on the motor side of the propeller 16 and the slurry A is sucked into the propeller 16 side. When air is not supplied, the slurry C is continuously discharged from the propeller 16 in this manner.
[0014]
At this time, when the air from the air jet pipe 18 is supplied from behind the propeller 16, in the prior art shown in FIG. 4B, the air A ′ is sent from the air jet pipe 18 instead of the slurry A shown in FIG. Sucked into the propeller 16 side. Therefore, after the slurry C existing on the discharge side of the propeller 16 and the slurry B existing on the back side are discharged from the propeller 16, it is not the slurry but the air A ′ that is discharged from the propeller 16. Is extremely reduced.
[0015]
On the other hand, in the present invention shown in FIG. 4C, the oxidation air D ejected from the air ejection pipe 18 is selectively supplied to the discharge side surface of the propeller 16, whereby the oxidation supplied to the discharge side of the propeller 16. The slurry C on the discharge side of the propeller 16 together with the air D is pushed out into the absorbing liquid in the circulation tank, and the slurry A is sucked into the negative pressure side (motor side) of the propeller 16 generated thereafter.
[0016]
Thus, by selectively supplying the oxidized air D to the discharge side surface of the propeller 16, the slurry is continuously sucked into the negative pressure side of the propeller 16, and the discharge flow rate of the slurry discharged from the propeller 16 does not decrease. .
[0017]
Accordingly, a sufficient slurry discharge flow rate is obtained from the propeller 16, and the fine air bubbles also reach the center of the circulation tank along with the slurry discharge flow. However, in order to always supply the oxidized air to the discharge side of the propeller 16 in this way, the oxidized air ejection pipe 18 must also rotate together with the rotation of the propeller 16.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
A wet flue gas desulfurization apparatus according to an embodiment of the present invention is shown in FIGS . 1 , 3, and 4, but only the configuration near the agitator propeller is different from the wet flue gas desulfurization apparatus shown in FIGS. 13 and 14. The other configuration is substantially the same as the wet flue gas desulfurization apparatus shown in FIG.
[0020]
Figure 1 is Ru der shows a schematic cross-sectional view of a desulfurization apparatus having an absorption column provided with an air supply port on the surface of the discharge side of the agitator propeller 16. FIG. 2 is a reference example of the present invention, and FIG. 3 is a perspective view of the propeller 16 of the agitator 7.
[0021]
The exhaust gas discharged from the boiler is introduced into the absorption tower body 1 from the inlet duct 2 and discharged from the outlet duct 3 provided at the top of the tower. During this time, the absorption liquid 5 containing calcium carbonate sent from the absorption liquid circulation pump 4 is jetted from the spray nozzle 13, and the gas-liquid contact between the absorption liquid 5 and the exhaust gas is performed. At this time, the absorbing solution 5 absorbs SO ₂ in the exhaust gas, SO ₃ ²⁻ is generated, and reacts with calcium carbonate to generate calcium sulfite Ca (HSO ₃ ) ₂ . The absorbing liquid 5 sprayed from the spray nozzle 13 once descends to the circulation tank 6 and is stirred by the oxidizing stirrer 7 during the staying, while being oxidized by the oxygen in the oxidized air supplied from the air supply pipe 8 to Ca (HSO ₃ ) _2. Is oxidized to produce calcium sulfate (gypsum).
[0022]
The present embodiment is characterized in that an oxidized air supply port is provided on the agitator propeller 16 that discharges the absorbent into the absorbent stored in the absorbent circulation tank 6.
[0023]
The operation and effect peculiar to the present embodiment with such a configuration is as described with reference to FIG.
[0024]
That is, as shown in FIG. 4C, the absorbent slurry is continuously supplied to the negative pressure side of the propeller 16 by selectively supplying the oxidized air D ejected from the air ejection pipe 18 to the discharge side surface of the propeller 16. Thus, the flow rate of the slurry discharged from the propeller 16 is not reduced, and a sufficient flow rate of the slurry is obtained from the propeller 16, and the fine air bubbles are also accompanied by the slurry discharge flow to the circulation tank 6 To the center of At this time, in order to always supply the oxidized air to the discharge side of the propeller 16, it is necessary to rotate the air ejection pipe 18 along with the rotation of the propeller 16.
[0025]
As shown in FIG. 2, the stirrer propeller 16 in FIG. 2 of the stirrer 7 is shown with the discharge side surface being white and the motor side surface being hatched .
An air chamber 17, which is a reservoir for air supplied from the air supply pipe 8, is provided at the attachment portion of the stirrer 7 on the side wall of the circulation tank 6. A rotating shaft 7 a of the propeller 16 extends toward the inside of the circulation tank 6 through the air chamber 17. An air jet pipe 18 supported by a rotary portion 17b provided on the front surface 17a of the air chamber 17 on the tank side is provided along the rotary shaft 7a, and a propeller 16 is provided at the tip of the air jet pipe 18. An air outlet 18a for ejecting oxidized air 15 is provided on the discharge side.
[0026]
Further, the rotating portion 17b of the air chamber 17 is fixed to the rotating shaft 7a of the stirrer 7 and rotates together with the rotating shaft 7a. A seal 19 is installed at the joint between the air chamber 17 and the rotating portion 17b. The oxidized air in 17 is prevented from leaking into the circulation tank 6.
[0027]
Oxidizing air is sent from the air supply pipe 8 to the air chamber 17 by the configuration of the agitator 7, and is oxidized from the air chamber 17 to the tip of the air jet pipe 18 rotating in the same manner as the rotating shaft 7 a of the propeller 16. Air is sent. Since the air outlet 18 a at the tip of the air ejection pipe 18 is always on the discharge side of the propeller 16, the oxidized air is ejected from the surface on the discharge side of the propeller 16 into the absorbing liquid in the circulation tank 6.
[0028]
By supplying oxidized air to the discharge side of the propeller 16 as described above, the slurry discharge flow rate is reliably obtained by the mechanism shown in FIG. 4 (c), and the refined bubbles circulate as shown in FIG. The air reaches the vicinity of the center of the tank 6 and the bubbles are uniformly dispersed throughout the circulation tank 6. Prior art and compared to oxidation air 13 spreads enough in the absorbing liquid by the bubbles which is reduced to reach the vicinity of the central portion of the circulation tank 6 shown in FIG. 1, effectively rows oxidation of calcium sulfite Is called.
[0029]
FIG. 5 shows the amount of air required for the oxidation of SO ₃ ^{2− in} a conventional flue gas desulfurization apparatus that treats exhaust gas having an SO ₃ concentration of 3,000 ppm and an exhaust gas flow rate of 750,000 m ³ N / hr per unit time. It is the figure compared with the present invention by setting technology as "1".
[0030]
By applying the implementation method of the embodiment by oxidation air supply of the present invention, the gas-liquid contact is performed efficiently uniformly oxidized air in the absorbing solution in the circulating tank 6 is dispersed, the conventional 2/3 It can be seen that sufficient SO ₃ ²⁻ oxidation is possible with a supply air amount of the order.
[0031]
For this reason, the blower for supplying oxidized air into the circulation tank 6 can also be made smaller than before. Furthermore, since the amount of oxidized air supplied into the circulation tank 6 is smaller than that in the prior art, the amount of bubbles sucked into the circulation pump 4 together with the absorbing liquid 5 is reduced, and the amount of bubbles sucked into the circulation pump 4 is reduced. It is possible to prevent a reduction in the amount of circulating fluid and a reduction in the exhaust gas desulfurization rate that occur when there is a large amount of gas.
[0032]
The reference example shown in FIG. 6 differs from the reference example shown in FIG. 2 in that the rotating shaft 7a of the stirrer 7 is hollow and serves also as the air ejection pipe 18. Oxidized air supplied from the air supply pipe 8 and stored in the air chamber 17 passes through an air ejection pipe 18 in a hollow portion provided in the rotating shaft 7a of the stirrer 7 and is provided on the discharge side of the propeller 16. It is supplied to the absorption liquid in the circulation tank 6 from the jet outlet 18a. By making the rotating shaft 7a of the stirrer 7 hollow, it is not necessary to separately provide the air ejection pipe 18 shown in FIG. 2, and the apparatus becomes simpler. A seal 19 is installed between the outer periphery of the rotating shaft 7 a of the stirrer 7 and the wall surface of the air chamber 17.
[0033]
In the embodiment shown in FIG. 7, the air outlet 18a of the air outlet pipe 18 is installed on the edge of the propeller 16, and a plurality of air outlets 18a are provided, and a plurality of air outlets 18a are provided. This is different from the reference example shown in FIGS. In the configuration shown in FIG. 7, the air ejection pipe 18 provided in the rotating portion 17 b of the air chamber 17 rotates together with the rotation shaft 7 a of the propeller 16, so that the oxidized air sent to the air chamber 17 is in the air ejection pipe 18. It is ejected from the air jet outlet 18a at the tip. Since the air spout 18 a is installed at the edge of the propeller 16, the oxidized air is ejected from the vicinity of the discharge side of the propeller 16 into the absorbing liquid in the circulation tank 6. Further, since the oxidized air supplied from the air outlet 18a to the absorbing liquid in the circulation tank 6 is dispersed throughout the propeller 16, finer bubbles are generated as compared with the reference examples shown in FIGS. . The rotating portion 17b of the air chamber 17 and the air chamber front surface 17a are sealed with a seal 19.
[0034]
In the above embodiments and reference examples , the air jet outlet 18a of the air jet pipe 18 is provided at any position of the propeller 16, but the air jet outlet of the air jet pipe 18 on the spindle 21 of the agitator propeller 16 is shown. 18a may be provided. In this case, it is desirable to open near the base of the side surface in the propeller rotation direction.
[0035]
In another embodiment of the present invention shown in FIG. 8 (schematic cross-sectional view) and FIG. 9 (perspective view), the oxidized air is supplied continuously or intermittently in synchronization with the rotation of the agitator propeller 16 that discharges the absorbing liquid. It is characterized in that means for performing the above is provided. As means for continuously or intermittently supplying the oxidized air, an air jet 17c or an air jet slit (not shown) is provided on the air chamber front surface 17a, and the air jet 17c or the air jet slit is opened and closed. The rotary valve 20 for performing the above, a shutter-like object (not shown), and the like are provided.
[0036]
8 and 9, the air chamber 17 is provided around the rotating shaft 7a of the stirrer propeller 16, and the air outlet 17c is provided on the front surface 17a on the propeller 16 installation side. The back surface of the front surface 17a of the air chamber 17 is provided. The rotary valve 20 is provided on the rotary shaft 7a so as to be in contact with the air jet port 17c and close the air jet port 17c. The air chamber 17 is fixed to the wall surface of the circulation tank 6.
[0037]
The rotary valve 20 rotates in synchronization with the stirrer propeller 16 while being in contact with the front surface 17a, and as shown in FIG. 10 (view of the stirrer propeller 16 as viewed from the front), an opening angle region (profile) is provided at the air outlet 17c. Oxidized air is supplied when θA matches, and is shut off when the closed angle region (profile) θB matches.
[0038]
The opening / closing profile of the rotary valve 20 is such that the open angle region (profile) θA is close to the region A (shown as 16a among the three propellers 16a to 16c) near the leading edge in the rotational direction of the agitator propeller 16; Area B (profile) is set for each of the agitator propellers 16a to 16c.
[0039]
Thus, as possible out to ensure that the oxidation air ejected from the air ejection port 17c is supplied to the pressure side of the propeller 16A～16a (region A in the rotation direction front edge closer).
[0040]
The number and shape of the air jets 17c are not limited to those shown in the figure.
[0041]
The effect peculiar to the present embodiment shown in FIGS. 8, 9 and 10 is that it is not necessary to rotate the thin air ejection pipe 18 as shown in the embodiment of FIG. 7 at the same speed as the agitator propeller 16. It is easy to maintain the strength, and it becomes a highly safe device.
[0042]
Further, as shown in FIG. 11, by installing the guide vane 22 at the base of the spindle 21 on the positive pressure side of the propellers 16a to 16c, it becomes possible to supply the oxidized air to the discharge side of the agitator propeller 16 more reliably. .
[0043]
The reference example shown in FIG. 12 uses an existing air jet pipe 18 that supplies oxidized air from the wall surface of the circulation tank 6 only below the stirrer propeller 16 of the prior art as shown in FIG. In this configuration, the air for oxidization is supplied. By modifying the existing oxidized air jet pipe 18 and the stirrer 7 shown in FIG. 15 as they are, the configuration shown in FIG. 12 can be obtained. In this case, the existing air supply line is changed. There is no need.
[0044]
【The invention's effect】
According to the present invention, the oxidized air bubbles can be uniformly dispersed in the absorbing liquid in the circulation tank, and efficient gas-liquid contact is possible. Since it is possible to oxidize SO ₃ ^2- in the absorbent sufficiently with a small amount of supply air, the power for supplying oxidized air can be reduced.
[0045]
Further, the efficient gas-liquid contact according to the present invention can shorten the residence time of the absorption liquid in the circulation tank, thereby reducing the capacity of the circulation tank.
[Brief description of the drawings]
FIG. 1 is a side view of an absorption tower in which an air supply port is provided on a discharge side surface of a stirrer propeller according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a desulfurization apparatus provided with an absorption tower provided with an air supply port on a discharge side surface of a stirrer propeller, which is a reference example of the present invention .
3 is a view showing a cross-sectional position described in FIG. 4 of the stirrer propeller of the flue gas desulfurization apparatus of FIG. 1;
4 is a diagram illustrating a discharge mechanism of oxidized air and slurry of a stirrer propeller of the flue gas desulfurization apparatus of FIG. 1 in comparison with the prior art.
FIG. 5 shows the present invention assuming that the prior art is 1 for the amount of air required for the oxidation of SO ₃ ^2- in a flue gas desulfurization apparatus for treating exhaust gas with an exhaust gas flow rate of 750,000 m ³ N / hr and an SO ₂ concentration of 3,000 ppm. It is the figure compared with.
FIG. 6 is a reference example of the present invention, and is an enlarged view of a stirrer portion when the agitator rotating shaft is hollow and also serves as an air ejection pipe.
FIG. 7 is an enlarged view of an oxidation stirrer part in the case where an air outlet of an air outlet pipe according to an embodiment of the present invention is installed at an edge of a propeller blade and a plurality of air outlets are provided.
FIG. 8 is an enlarged view of the agitator portion when the air outlet is opened and closed so that air is selectively supplied to the discharge side of the propeller by a rotary valve that rotates in the same manner as the propeller in the air chamber of the embodiment of the present invention. FIG.
9 is a perspective view of the agitator portion of FIG. 8. FIG.
10 is a front view of the agitator portion of FIG. 8. FIG.
11 is a perspective view showing an embodiment in which guide vanes in the stirrer portion of FIG. 9 are installed. FIG.
12 is a reference example of the present invention, and an existing air jet pipe that supplies oxidizing air only below the stirrer propeller of the prior art as shown in FIG. 15 is used to supply oxidizing air to the air chamber. It is the figure which expanded the stirrer part in the case of doing.
FIG. 13 is a side view of an absorption tower in a conventional wet flue gas desulfurization apparatus.
14 is an enlarged view of the stirrer portion of FIG.
FIG. 15 is a view showing a modification of the stirrer portion of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Absorption tower body 2 Inlet duct 3 Outlet duct 4 Absorbing liquid circulation pump 5 Absorbing liquid 6 Circulating tank 7 Stirrer 7a Rotating shaft 8 Air supply pipe 13 Spray nozzle 15 Oxidized air 16 Propellers 16a, 16b, 16c Propeller 17 Air chamber 17a Front of air chamber 17b Rotating part 17c Air outlet 18 Air outlet pipe 8a Air outlet 19 Seal 20 Rotating valve 22 Guide vane

Claims (4)

An absorption tower for introducing exhaust gas into contact with an absorption liquid containing calcium carbonate; and a circulation tank for storing an absorption liquid that has absorbed sulfur oxides in the exhaust gas in the absorption tower and blowing oxidized air into the absorption liquid. In wet flue gas desulfurization equipment,
An agitator propeller having a rotating shaft for discharging the absorbing liquid and a spindle are provided on the wall surface of the circulation tank, and an oxidizing air supply air chamber for supporting the rotating shaft of the agitator propeller is provided at a position facing the negative pressure side surface of the agitator propeller. And provided with an oxidized air supply device provided with a rotary valve or shutter-like object for opening and closing the air outlet or air ejection slit and the air ejection outlet or air ejection slit on the negative pressure side surface of the agitator propeller of the air chamber Wet flue gas desulfurization device characterized by that.   2. The wet flue gas desulfurization apparatus according to claim 1, further comprising means for supplying oxidized air continuously or intermittently in synchronism with rotation of a stirrer propeller or spindle for discharging the absorption liquid.   2. The wet flue gas desulfurization apparatus according to claim 1, wherein a guide vane for supplying oxidized air to the absorption liquid discharge side of the propeller is provided at a spindle base portion on the positive pressure side of the agitator propeller for discharging the absorption liquid. An absorption tower for introducing exhaust gas into contact with an absorption liquid containing calcium carbonate; and a circulation tank for storing an absorption liquid that has absorbed sulfur oxides in the exhaust gas in the absorption tower and blowing oxidized air into the absorption liquid. In wet flue gas desulfurization equipment,
A stirrer propeller having a rotating shaft that discharges the absorbing liquid on the wall surface of the circulation tank, and an air chamber for supplying oxidized air that supports the rotating shaft of the stirrer propeller at a position facing the negative pressure side surface of the stirrer propeller, The air chamber is provided with a rotating portion, and an air ejection pipe is provided along the rotation axis of the agitator propeller from the rotating portion into the circulation tank, and an air outlet at the tip of the air ejection pipe is a peripheral edge on the discharge side of the agitator propeller. A wet flue gas desulfurization apparatus comprising an oxidizing air supply apparatus installed in a section.

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