JPH0838850A - Gas blowing-in apparatus - Google Patents

Abstract

PURPOSE:To blow-in even a large quantity of a gas as fine bubbles by installing a recovering part for a dropping liquid in a liquid sump, installing a descending pipe whose cross-section surface area is smaller than that of the recovering part in the lower part of the recovering part, and blowing a gas into the pipe. CONSTITUTION:As a liquid sump to sump an absorption liquid, a liquid sump tank 4 is installed in the inner lower part of an absorption tank 1. A cylindrical recovering part 11 whose upper part is opened is installed above the liquid surface in the liquid sump tank 4. A descending 12 is connected coaxially with the lower part of the recovering part 11 and the diameter d2 of the descending pipe 12 is made to be smaller than the diameter d1 of the recovering part 11. A funnel is composed of the recovering part 11 and descending pipe 12 and a portion of a spray liquid from a spray nozzle 6 is recovered in the recovering part 11, and then the liquid is made to descend in the descending pipe 12 due to self-weight and guided to the lower part of the liquid saving tank 14. An air blowing-in pipe 13 to blow in air is connected with the descending pipe 12, a blowing-in inlet 14 is formed along the flow direction of the descending pipe 12, and bubbles descend following the descending current and ascend from the lower part of the tank 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas blowing device for blowing a gas into a liquid.

[0002]

2. Description of the Related Art A gas blowing device blows gas into a liquid and is provided in, for example, a wet flue gas desulfurization device for desulfurizing exhaust gas from a combustion device.

In a wet flue gas desulfurization apparatus, exhaust gas is desulfurized by bringing the exhaust gas and an absorbent such as a slurry-like absorbent containing calcium carbonate into contact with each other in the absorption tower to absorb the sulfur oxide in the gas into the absorbent. A gas blowing device is used when oxidizing the absorbent after desulfurization in order to recover the absorbent that has absorbed the sulfur oxides as gypsum. In this gas blowing device, a plurality of air blowing pipes are arranged on the entire surface (in the absorbing liquid) where the absorbing liquid after desulfurization treatment is stored, and the air is blown into the absorbing liquid from the blowing port of the blowing pipe. With a pipe blowing type, as shown in FIG.
Blade 2 of a lateral stirrer 20 for stirring the absorbent after desulfurization treatment
There is a stirrer suction side air-blowing type that blows air to the suction side (rear side) of No. 1 (Japanese Patent Publication No. 4-69089, etc.), which allows the absorbing liquid to react with oxygen in the air. Gypsum deposits.

[0004]

In the gas blowing device described above, in the case of the former pipe blowing type, gas is simply blown into the liquid through the blowing ports of a plurality of blowing pipes. When bubbles are blown in, the bubbles become large and the efficiency of oxidation of the absorbing liquid deteriorates. In the latter agitator suction side air blowing type, since air is jetted to the suction side of the blade and the air is decomposed into fine bubbles by the blade, the blade and air are in contact with each other, so cavitation is likely to occur and gas is generated. There is a limit to the blowing amount.

Therefore, the present invention has been made in consideration of such circumstances, and an object thereof is to provide a gas blowing device capable of blowing even a large volume of gas as fine bubbles. .

[0006]

In order to achieve the above-mentioned object, the present invention is a device for blowing gas into a liquid that has been dropped and stored, in a liquid collecting part for receiving the falling liquid. A downcomer having a smaller cross-sectional area than the recovery section is connected to the lower part of the recovery section to guide the liquid in the recovery section to the lower side of the liquid storage section by its own weight, and a gas injection port for blowing gas into the downcomer is connected. It is provided. Further, it is preferable that the flow velocity of the liquid flowing down in the downcomer is 1 m / s or more.

[0007]

The liquid dropped and recovered by the recovery unit flows down in the downcomer. Since gas is blown in the middle of this descending flow, the gas is blown into the flowing portion of the liquid, so that it is entrained in the turbulent flow of the liquid and the bubbles are miniaturized. Since the multiphase flow in which the air bubbles are mixed is guided below the liquid reservoir, there is no fear of causing cavitation even if the amount of gas is increased. Also,
Since gas is blown into the liquid reservoir as a multiphase flow mixed with liquid, the inertial force at the time of jetting is stronger than when jetting only gas, and thus bubbles easily diffuse in the liquid. Furthermore, multiphase flow (bubble flow) in which bubbles are mixed using the falling liquid
Therefore, no power is required to create a bubbly flow.
Therefore, even a large volume of gas can be blown into the liquid as fine bubbles, and power for creating a bubble flow is not required, and the bubbles can be easily diffused into the liquid.

The flow velocity of the liquid flowing down the downcomer is 1
By making it m / s or more, it is possible to surely miniaturize the bubbles.

[0009]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In this embodiment, a case where the gas blowing device of the present invention is applied to an absorption tower of a wet type flue gas desulfurization device will be described.

In FIG. 1, reference numeral 1 denotes a cylindrical absorption tower for desulfurizing exhaust gas from a combustion device such as a boiler, and a gas introduction port 2 for exhaust gas is provided below a side portion of the absorption tower 1.

The absorption tower 1 is connected with an absorption liquid supply pipe 3 for supplying a slurry-shaped absorption liquid in which an absorption agent such as calcium carbonate for absorbing the sulfur content of sulfur oxides in exhaust gas is dissolved. In addition, a liquid storage tank 4 as a liquid storage portion for storing the absorbing liquid is provided below the inside thereof. Also,
A transfer pipe 7 is connected to the liquid reservoir tank 4 of the absorption tower 1 to transfer a part of the absorbed liquid in the tank 4 to a spray nozzle 6 provided above the tower 1 by a circulation pump 5. Absorption liquid (spray liquid) sprayed from 6 and tower 1
The exhaust gas rising in the interior is brought into countercurrent contact with the sulfur content in the gas to be absorbed and removed by the absorption liquid, and the exhaust gas is desulfurized.

Further, in the absorbing liquid in the liquid storage tank 4 of the absorption tower 1, a propeller-shaped side stirring blade 8 for stirring the absorbing liquid in the tank 4 by rotating to generate a discharge flow is provided near the side wall. It is rotatably installed. The stirring blade 8 is attached to a shaft 10 of a motor 9 provided through the side wall of the stirring blade 8 and is rotated by the drive of the motor 9 to generate a discharge flow in the liquid. The stirring blade 8 (the shaft 1
0) should be rotatably supported.

Further, in the liquid storage tank 4, a cylindrical recovery body (recovery section) 11 having an open top is arranged coaxially above the liquid surface. A downcomer pipe 12 is coaxially connected to the lower part of the recovery body 11, and the other end of the downcomer pipe 12 is arranged below the tank 4 and a diameter d ₂ of the recovery body 11 is reduced.
Is formed to be smaller than the diameter d ₁ . That is, a kind of funnel is formed by the collection body 11 and the downcomer 12, and a part of the spray liquid sprayed and dropped from the spray nozzle 6 is collected and collected by the collection body 11, and the collected liquid is attached by its own weight. The liquid flows down in the downcomer pipe 12 and is guided below the liquid storage tank 4.

An air blow-in pipe 13 for blowing air is connected to the downcomer 12, and a blow-in port 14 of the air blow-in pipe 13 is arranged so as to blow out the air along the flow direction of the downcomer 12 so as to blow the air. The air, that is, the bubbles from the port 14 rides on the descending flow of the liquid in the descending pipe 12 and descends, and rises from below the liquid reservoir tank 4. The connection position of the air blowing pipe 13 to the downcomer pipe 12 is arbitrarily determined as long as air is blown into the downcomer pipe 12, but it is preferably set to a position as high as possible in consideration of oxidation.

The size (diameter) of the recovery body 11 and the downcomer pipe 12 is such that the air (bubbles) from the blow-in port 14 of the air blowing pipe 13 descends in the downcomer pipe 12 and a good bubble state (fine bubbles) is obtained. Arbitrarily set to be, that is, downcomer 1
The liquid velocity in 2 is set to be 1 m / s or more. Specifically, the diameter d ₂ of the downcomer pipe 12 is determined by the spray nozzle 6
Since the spray liquid from No. 1 is uniformly sprayed into the absorption tower 1, and the amount of this spray liquid is large, the cross-sectional area may be 10% of that of the absorption tower 1. For example, if the diameter of the absorption tower 1 is D, it is 0.33D. And The diameter d ₁ of the recovery body 11 is required to make the ratio of the spray liquid collected and collected by the recovery body 11 to the total spray liquid higher than the cross-sectional ratio of the downcomer pipe to the total cross-section of the tank, and is set to 0.50D, for example. . In this way, by setting the diameter d ₁ of the recovery body 11 to 0.50 D and the diameter d ₂ of the downcomer pipe 12 to 0.33 D, the liquid velocity in the downcomer pipe 12 becomes 1 m / s or more, and The air is blown into the flowing part of the liquid and is entrained in the turbulent flow to form fine bubbles.

The reason why the liquid velocity is set to 1 m / s or more is as follows.

First, sodium sulfite (Na ₂ SO ₃ )
Was oxidized with air using a liquid having a Na ₂ SO ₃ concentration of 1% while changing the liquid velocity and the amount of air. The result is shown in Figure 2.
Shown in From the results shown in FIG. 2, it can be seen that the bubble flow in a good state (fine bubble flow) cannot be performed unless the liquid velocity is to some extent, and if the liquid velocity is 1 m / s or more, the bubble flow in a good state can be surely obtained. It was found that a fine bubbly flow) can be formed. That is, the more liquid and the less air, the better the bubbly flow obtained. Further, the oxidation rate was examined by changing the liquid amount while keeping the air constant, and the results are shown in FIG. As a result, as shown in the figure, the oxidation rate improves when the liquid-air ratio is 1.0 or more. That is, if the liquid-air ratio is not 1.0 or more, a good bubbly flow (fine bubbly flow) cannot be obtained. Therefore, in the case of an absorption tower of a wet flue gas desulfurization device, it absorbs and oxidizes sulfur oxides in exhaust gas (the absorbent is calcium carbonate (Ca
CO ₃ ): CaCO ₃ + SO ₂ + 1/2 · O ₂ +
2H ₂ O → CaSO ₄ · 2H ₂ O + CO ₂ ) Therefore, the amount of air is determined by the amount of sulfur oxide absorbed, so the amount of air can be small, so if the liquid velocity is set to 1 m / s or more, fine bubbles will be generated. As a result, air can be blown in to reliably oxidize the absorbing liquid. Since the ascending speed of the bubbles is about 0.4 to 0.5 m / s, if the liquid velocity is 1 m / s or more, the bubbles hardly rise in the downcomer pipe.

Next, the operation of this embodiment will be described.

Exhaust gas is introduced into the absorption tower 1 through the gas introduction port 2 and rises in the tower 1. A slurry-like absorption liquid in which an absorption agent such as calcium carbonate is dissolved is introduced into the absorption tower 1 through the absorption liquid supply pipe 3 and is accumulated in the liquid storage tank 4. A part thereof is transferred to the spray nozzle 6 via the transfer pipe 7 by the circulation pump 5, and is sprayed from the nozzle 6 into the tower 1. The absorbing liquid and the gas come into gas-liquid contact with each other, the sulfur oxide in the gas is absorbed by the absorbing liquid, and the gas to be treated is desulfurized. The desulfurized gas is discharged from the upper part of the tower 1 and guided to another system.

After the desulfurization treatment, the absorbing liquid drops into the liquid storage tank 4, and a part of the absorbing liquid is collected by the collecting body 11 and collected in the center of the tank 4. Since the ratio of the absorbing liquid collected by the recovery body 11 to the total falling absorbing liquid (total spray liquid) is higher than the cross-sectional ratio of the downcomer pipe 12 to the entire cross-section of the tank 1, it flows down in the downcomer pipe 12.

Air is blown into the absorbing liquid flowing down in the downcomer pipe 12 through the blow-in port 14 of the air blow-in pipe 13. Since air is blown into the flowing portion of the liquid, not in the stationary tank, the bubbles are made fine by the turbulent flow. The liquid containing the bubbles (mixed-phase flow of bubbles and liquid) is guided from the downcomer pipe 12 to the lower side of the tank 4, and then reverses and rises on the outer periphery of the downcomer pipe to diffuse throughout the tank 4. As described above, the air becomes fine bubbles and flows down with the liquid in the downcomer 12 and is guided to the lower side of the tank 4, and ascends to reach the liquid surface. Therefore, when the air retention time is simply blown in, It will be longer than that. Further, when the bubbles become fine, the surface area becomes large and the contact area increases, so that the absorbing liquid and the air come into sufficient contact with each other. In this way, since the contact between the absorbing liquid and air is performed efficiently,
After the desulfurization treatment, the oxidation reaction of the absorbing solution progresses well, the absorbing solution can be efficiently oxidized, and the amount of air blown into the absorbing solution can be reduced.

Further, since the mixed phase flow in which the gas and the liquid are mixed is blown out from the downcomer 12, the inertial force at the time of ejection is stronger than that when only gas is ejected, so that the bubbles are absorbed in the liquid storage tank 4 (absorption). It spreads far into the liquid and is easily and uniformly dispersed in the absorbing liquid. At this time, when the stirring blade 8 is rotationally driven by the motor 9, the liquid on the back surface (suction side) of the blade 8 is pushed out in front of the blade and a discharge flow occurs, causing a liquid flow in the tank 4. The absorption liquid is agitated. As a result, the fine bubbles can be more surely uniformly dispersed in the absorbing liquid, and the uniform oxidation reaction can be promoted. Also,
It is also possible to prevent SS from settling in the absorbent.

Therefore, a descending flow of the absorbing liquid is created by utilizing the falling absorbing liquid, air is blown into the flowing portion of the absorbing liquid, and this is guided (blown out) below the tank 4, so that the stirring blade 8 Since air is not blown into the vicinity, that is, the air and the blade 8 do not come into contact with each other, cavitation does not occur even if a large amount of air is blown.
In addition, since the bubbly flow is created using the falling liquid of the spray,
No power is needed to create the bubbly flow. Furthermore, since the position of the gas blowing pipe 13 is at a high position, the pressure of the air is small, and the power of the gas compressor (power at the time of blowing air)
Is less.

[0025]

In summary, the present invention has the following excellent effects.

(1) Even a large volume of gas can be made into fine bubbles, and the power for creating a bubble flow is not necessary, and the bubbles can be easily diffused in the liquid.

(2) The flow velocity of the liquid flowing down the downcomer is 1 m.
By setting it to be / s or more, it is possible to surely miniaturize the bubbles.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an apparent air velocity and an apparent liquid velocity of a bubbly flow state.

FIG. 3 is a diagram showing a relationship between a liquid-air ratio and an oxidation rate.

FIG. 4 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 4 Liquid Reservoir (Liquid Reservoir Tank) 11 Recovery Part (Recovery Body) 12 Downcomer 14 Gas Inlet

Claims (2)

[Claims] 1. A device for blowing gas into a liquid that has fallen and stored, wherein a collecting part for receiving the falling liquid is provided in the liquid reservoir part, and the liquid in the collecting part is self-weighted under the collecting part. A gas injecting device, characterized in that a downcomer having a smaller cross-sectional area than the recovering part is connected so as to be guided below the liquid reservoir, and a gas injecting port for injecting gas is provided in the downcomer. 2. The flow velocity of the liquid flowing down in the downcomer is 1
2. The ratio is set to m / s or more.
The described gas blowing device.