JPH08950A - Gas blowing device - Google Patents

Abstract

PURPOSE:To blow in even a large volume of gas in a form of fine foams by forming a turbulence on the way of a liquid circulating flow path, blowing gas into a turbulent zone to form a mixed phase flow of foams and liquid. CONSTITUTION:A circulating pipe 12 as a circulating flow path with an extraction pump 11 for extracting a part of absorbing solution in a liquid storage tank 4 is connected with a lower section of the tank 4. A turbulence is formed in the pipe 12 on the downstream side of the extraction pump 11 of the circulating pipe 12, and gas is blown into the turbulent zone, and a mixing section 13 forming a mixed phase flow of foams and liquid is formed. As gas is blown into a section where liquid is moving and turbulence is formed, foams are entrapped into the turbulence to turn the foams into fine forms. As the mixed phase flow mixed with the foams is returned to the liquid, cavitation are not formed even when gas is generated in a large amount.

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 provided on the entire surface of the tower (in the absorbing liquid) where the desulfurized absorbing liquid is stored, and air is blown into the absorbing liquid from the blowing port of the blowing pipe. Pipe blower type and agitator suction side air blower type that blows air to the suction side of the blade of a side stirrer that stirs the absorption liquid after desulfurization treatment (Japanese Patent Publication No. 4-69089 etc.) This causes the absorption liquid to react with oxygen in the air to precipitate gypsum.

[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 air intake type of the agitator suction side, gas is jetted to the suction side of the blade and the air is decomposed into fine bubbles by the blade, so the blade and air come into contact with each other, which easily causes cavitation and the amount of gas blown. Is limited.

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 object, the present invention is a device for injecting a gas into a liquid, in which a part of the liquid is extracted, and is circulated by returning the liquid to the liquid, A turbulent flow is generated, a gas is blown into this turbulent flow portion, and a mixing section that forms a mixed-phase flow of bubbles and liquid is provided.

Further, in an apparatus for blowing a gas into a liquid, a mixing section for extracting a part of the liquid and mixing the gas therein is arranged above the liquid surface of the liquid, and the fluid from the mixing section is discharged. A circulation channel for blowing into the liquid is provided.

[0008]

A part of the liquid is withdrawn, passes through the circulation channel, and flows through the mixing section. At this time, turbulent flow occurs in the mixing section, and gas is blown into this section. As a result, the gas is blown into the flowing part of the liquid and also into the part where the turbulent flow is generated, so that the gas is entrained in the turbulent flow and the bubbles are miniaturized. Since the multiphase flow mixed with the bubbles is returned to the liquid, there is no fear of causing cavitation even if the amount of gas is increased. Further, since the multiphase flow in which the gas and the liquid are mixed is jetted to the liquid, the inertial force at the time of jetting is stronger than the case where only the gas is jetted, so that the bubbles easily diffuse in the liquid. Therefore, even a large volume of gas can be blown into the liquid as fine bubbles and the bubbles can be easily diffused into the liquid.

Further, a part of the liquid is taken out and a mixing part for mixing the gas into the liquid is arranged above the liquid surface of the liquid, so that the blowing part at the time of blowing the fluid from the mixing part into the liquid. The gas injection pressure becomes low and the gas supply power becomes low. Further, since the gas blowing section is located below the mixing section, the bubbles mixed in the mixing section are reduced in pressure,
Can be miniaturized. Therefore, even a large volume of gas can be made fine and dispersed in the entire liquid, and the gas feeding power can be reduced.

[0010]

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 inlet 2 for the 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 for storing the absorbing liquid is provided below the inside thereof. A transfer pipe 7 is connected to the liquid storage 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, The absorption liquid sprayed from the spray nozzle 6 and the exhaust gas rising in the tower 1 are countercurrently contacted with each other, and the sulfur content in the gas is absorbed and removed by the absorption liquid, so that 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.

In addition, below the liquid reservoir tank 4, the tank 4
A circulation pipe 12, which is a circulation flow path, having an extraction pump 11 for extracting a part of the absorbing liquid therein is connected. The circulation pipe 12 is connected to the upper side surface of the stirring blade 8 of the tank 4, and the liquid is jetted from the circulation pipe 12 to the tank 4. The circulation pipe 12 is connected to the tank at an angle deviated from the center by a predetermined angle similarly to the discharge flow, and the circulation pipe 12
An agitated flow is generated in the tank 4 by the jet flow from.

On the downstream side of the withdrawal pump 11 of the circulation pipe 12, a turbulent flow is generated in the pipe 12, and a gas is blown into this turbulent flow portion, and a mixing portion 13 for forming a multiphase flow of bubbles and liquid is interposed. It is set up. The mixing section 13 may have any structure as long as it produces a turbulent flow and blows a gas into this turbulent flow section. For example, there is a mixing section having a structure as shown in FIGS. 1 and 3. The mixing portion 13 has an air supply pipe 14 penetrating the circulation pipe 12 at right angles to its axis, and an air outlet 15 that blows out air in the fluid flow direction coaxially with the circulation pipe 12 of the air supply pipe 14. Is provided, the flow path in the circulation pipe 12 is narrowed by the air supply pipe 14, and a turbulent flow is generated on the downstream side of the air supply pipe 14, and the air outlet 15 is located at this turbulent flow portion. Air is entrained in the turbulent flow from the outlet 15 to make bubbles fine. The diameter d of the air supply pipe 14 varies depending on the flow velocity in the circulation pipe 12 by the extraction pump 11, but when the flow velocity is 2 to 3 m / s, for example, in the range of 0.3D to 0.7D (D: circulation pipe 12 The diameter of the circulation pipe 12 is preferably half (0.5D). Within this range, a turbulent flow occurs and the air from the air outlet 15 is entrained in the turbulent flow to form fine bubbles. The flow rate of the absorbing liquid flowing through the circulation pipe 12 and the supply amount of air are, for example, 10 m ³ N / h and 6 m ³ N / h.

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. The liquid after desulfurization is the liquid storage tank 4
Accumulated in the tank 4, oxidized in the tank 4 and appropriately extracted and processed.

A part of the absorption liquid in the liquid storage tank 4 is extracted by the extraction pump 11, flows through the circulation pipe 12, and reaches the mixing section 13. Then, the flow path of the circulation pipe 12 is narrowed by the penetrating air supply pipe 14, and when liquid flows through this portion, a turbulent flow is generated on the downstream side of the air supply pipe 14, and the air outlet is formed in this turbulent portion. Air is blown from 15. As a result, the air is blown into the part where the liquid is flowing and the turbulent flow is generated. Therefore, the air is entrained in the turbulent flow and the bubbles are miniaturized. Liquid containing bubbles (mixed-phase flow of bubbles and liquid)
Are jetted from the circulation pipe 12 to the tank 4. At this time, since the jet flow is directed in a direction deviating from the center of the tank 4 by a predetermined angle, a swirling flow occurs and the absorbing liquid is agitated.
Since this jet flow is a multiphase flow in which a gas and a liquid are mixed, the inertial force at the time of jetting is stronger than when jetting only gas, so that the bubbles can reach far inside the liquid storage tank 4 (absorption liquid). Spreads and is easily and uniformly dispersed in the absorbent.
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. Further, it is possible to prevent SS from settling in the absorbent.

As described above, since the air is blown into the absorbing liquid in advance and the liquid is jetted to the tank 4, the air is not blown near the stirring blade 8, that is, the air and the blade 8 do not come into contact with each other. Therefore, even if a large amount of air is blown, the bubbles can be made fine without causing cavitation. 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. Therefore, the oxidation reaction of the absorbing liquid progresses well, and the amount of air can be reduced.

Specifically, sodium sulfite (Na ₂ S
A test of oxidizing O ₃ ) with air is carried out by the premixing method according to the present invention,
The pipe blowing and the air blowing method on the suction side of the stirrer were performed, and the oxidation rate was measured. The results are shown in Table 1. The conditions are as shown below.

Test equipment Tank: φ 800 mm × Height 2000 mm Liquid level: 1500 mm Stirrer: Stirrer blade φ 140 mm, 3 propeller blades Test conditions Air volume: 10 m ³ N / h Temperature: 50 ° C. Na ₂ SO ₃ concentration: 1%

[0023]

[Table 1]

As can be seen from the results shown in Table 1, the premixing type according to the present invention has a much higher oxidation rate than the pipe blowing type and the agitator suction side air blowing type.

FIG. 4 is a constitutional view showing another embodiment of the present invention. The characteristic feature of this embodiment is that the mixing section for mixing gas with the extracted liquid is arranged above the liquid surface of the liquid. The description of the same structure as that of the above embodiment is omitted and the same reference numerals are given.

That is, as shown in FIG. 4, a circulation pipe 18 which is a circulation passage having a withdrawal pump 17 for withdrawing a part of the absorbing liquid in the tank 4 is connected to the lower portion of the liquid reservoir tank 4. There is. The circulation pipe 18 is connected to a side surface below the liquid surface of the absorbing liquid in the tank 4 through a mixing portion 19 provided above the liquid surface of the absorbing liquid in the tank 4, and the blowing angle from the circulation pipe 18 is a horizontal plane. It is blown into the tank 4 at an angle which is above and a predetermined angle from the center of the tank 4. As a result, the jet flow from the circulation pipe 18 causes a stirring flow in the tank 4.

The mixing section 19 may have any structure as long as it blows air into the absorbing liquid, and may have the structure of the above embodiment, for example.

By arranging the mixing portion 19 above the liquid surface of the absorbing liquid in this way, a large volume of air can be made fine and dispersed in the entire tank 4.

That is, a part of the absorbing liquid in the liquid storage tank 4 is withdrawn by the withdrawing pump 17 and flows through the circulation pipe 18 to reach the mixing section 19, where air is mixed and contains bubbles. A saliva (multiphase flow of bubbles and liquid) is formed. Then, this bubble flow (mixed-phase flow of bubbles and liquid) is ejected from the circulation pipe 18 to the tank 4.

At this time, since the mixing section 19 is arranged above the liquid surface of the tank 4, the gas injection pressure at the injection section when the bubble flow (multiphase flow) from the mixing section 19 is decreased, The air supply power of gas becomes low. In addition, since the blowing section is located below the mixing section 19, the bubbles mixed in the mixing section 19 become smaller due to the pressure, and it is possible to achieve miniaturization.

Furthermore, since the jet flow is directed in a direction deviating from the center of the tank 4 by a predetermined angle, a swirling flow occurs,
The absorption liquid is agitated. Since this jet flow is a multiphase flow in which a gas and a liquid are mixed, the inertial force at the time of jetting is stronger than the case of jetting only gas, and therefore bubbles are generated in the liquid storage tank 4.
It spreads far into the (absorption liquid) and is easily and uniformly dispersed in the absorption liquid. At this time, by rotating the stirring blade 8 by the motor 9, the back surface of the blade 8 (suction side)
Liquid is pushed out to the front of the blades and a discharge flow occurs,
A liquid flow is generated inside and 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. Further, it is possible to prevent SS from settling in the absorbent.

As described above, the air is blown into the absorbing liquid in advance, and the absorbing liquid is jetted to the tank 4. Therefore, the air is not blown near the stirring blade 8, that is, the air and the blade 8 do not come into contact with each other. Therefore, even if a large amount of air is blown, the bubbles can be made fine without causing cavitation. 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. Therefore, the oxidation reaction of the absorbing liquid progresses well, and the amount of air can be reduced.

Therefore, even a large volume of air can be finely divided and dispersed in the entire absorbing liquid, and the air supply power (power of the blown air source) can be reduced.

When performing maintenance on the mixing section 19, since the mixing section 19 is arranged on the liquid surface,
If the supply of the liquid or gas is stopped, the liquid only reaches the liquid level in the tank 4, that is, the liquid does not reach the mixing section 19, so that it can be easily performed.

In this embodiment, the mixed-phase flow mixed with bubbles is directly injected into the absorbing liquid to diffuse the bubbles. However, if the bubbles contained in the mixed-phase flow are diffused, the multi-phase flow reservoir tank It may be supplied by any method, for example, it may be supplied in front of the side stirring blade and the bubbles may be diffused by the discharge flow due to the rotation of the stirring blade. Further, the fluid (liquid containing bubbles (mixed-phase flow of bubbles and liquid)) from the mixing portion is ejected from the circulation pipe into the liquid reservoir tank from one location, but may be ejected from a plurality of locations. With this configuration, it becomes possible to reliably disperse the air bubbles in the entire liquid storage tank even if the liquid storage tank becomes large.

[0036]

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

(1) Since a turbulent flow is generated in the circulation flow path and a mixing section for blowing gas into the turbulent flow section is provided, even a large volume of gas can be made into fine bubbles. It can easily diffuse into a liquid.

(2) Since the mixing section for mixing the gas with the liquid is arranged above the liquid surface of the liquid, even a large volume of gas can be made fine and dispersed throughout the liquid, and the gas feeding power can be reduced. .

[Brief description of drawings]

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

FIG. 2 is a view taken along the line AA in FIG.

FIG. 3 is a diagram showing an example of a mixing unit of the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

 12 Circulation flow path 13 Mixing section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 10/00 104 0821-4D B01D 53/34 125 E

Claims (2)

[Claims] 1. A device for injecting gas into a liquid, wherein a turbulent flow is generated in a circulation flow path in which a part of the liquid is extracted and jetted back to the liquid, and the gas is blown into the turbulent flow part to generate bubbles. And a liquid mixing unit for forming a multiphase flow of liquid. 2. A device for blowing gas into a liquid, wherein a mixing portion for extracting a part of the liquid and mixing the gas therein is provided above the liquid surface of the liquid, and a fluid from the mixing portion is supplied. A gas blowing device comprising a circulation flow path for blowing into the liquid.