JPH11188255A - Gas-liquid mixing tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the production efficiency of the water contg. dissolved gas or the decomposition efficiency of the component to be treated in a gas by a feed gas in a gas-liq. mixing tank for mixing the water to be treated and the small bubbles of gas to dissolve the gas in the water or to react the gas with the water by suppressing the liberation of the dissolved gas component from a gas-liq. interface in the mixing tank. SOLUTION: The floats 1 as many as to almost cover the gas-liq. interface 26 are floated on the water 22 to be treated. The water 22 injected under the water surface while the floats 1 are floated from a water feed pipe 8 is mixed with the small bubbles of a gas 25 supplied from a gas pipe 32 and a diffuser 23. Besides, the float 1 is hollowed, liq. and gas are introduced into the hollow part to control the sp.gr. of the float 1 to 1/2 of that of the water 22, and the upper half of the float 1 is floated in a gas phase 2 and the lower half positioned in the water 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-liquid mixing tank used in a water treatment system for service water or waste water.

[0002]

2. Description of the Related Art A gas-liquid mixing tank for dissolving gas components used in a water treatment system into water to be treated.
Alternatively, FIG. 4 shows a conventional example of a gas-liquid mixing tank for reacting a dissolved component and a gas component in the water to be treated.

In the mixing tank 20, the water to be treated 22 supplied from a water supply pipe 31 by a pump 21 is pumped by a compressor 24 and installed below the inside of the mixing tank 20 via an air supply pipe 32. Gas-liquid mixing is performed with the gas 25 supplied as small bubbles from the air diffuser 23.

The gas 25 of small bubbles moves upward by buoyancy while dissolving or reacting in the water 22 to be treated, and is released to the gas phase 27 through the gas-liquid boundary surface 26, and is discharged to the exhaust pipe 28. It is exhausted outside through the system. The treated water 29 in which the gas 25 is dissolved or reacted is supplied to the drain pipe 3
Transported through 0.

In the above-mentioned conventional gas-liquid mixing tank, when there is no reaction between the water to be treated 22 and the components of the gas 25, that is, when the components of the gas 25 to be supplied are used for dissolving in the water to be treated 22, Gas 25 in the water to be treated 22
Rate of increase in dissolved gas concentration C _A of the components is in accordance with equation (1).

[0006] _{dC A / dt = k L a} 1 (C X -C) ··· (1) C X: dissolved gas concentration becomes balanced with respect to the gas phase concentration of the gas supplied C: Dissolved gas concentration

[0007] (1) As apparent from the equation (wherein, referred to as C _A.) Dissolved concentration of the gas 25 increase rate (wherein the, d
Notation C _A / dt. ) Is proportional to the liquid-side overall mass transfer coefficient (denoted as k _{L in the} formula) and the gas-liquid contact area per unit volume (denoted as a _{1 in the} formula). Note that the gas-liquid contact area a ₁ shown here corresponds to the sum of the surface areas of the bubbles of the gas 25 contained in the unit volume of the water 22 to be treated.

Further, in parallel with this, the components of the gas 25 dissolved in the water to be treated 22 diverge from the gas-liquid boundary surface 26 in the mixing tank 20 to the gas phase 27, and the gas 25 in the water to be treated 22 reducing the dissolved gas concentration C _a of the component. Incidentally, the rate of decrease in the dissolved concentration C _B due to divergence follows a (2).

[0009] _{dC B / dt = k L a} 2 (C-C Y) ··· (2) C: Dissolved gas concentration C _Y: to the gas phase concentration of the feed gas collected in the gas phase of the gas-liquid boundary surface top Dissolved gas concentration at equilibrium

As apparent from the equation (2), the dissolved gas 2
Dissolved gas concentration due to divergence of 5 (wherein, referred to as C _B.) Decreasing speed (in the formula, referred to as dC _B / dt.) Of the liquid side overall mass transfer coefficient k _L and the gas-liquid contact per unit volume area (in the formula, referred to as a _2.) proportional to. The gas-liquid contact area a ₂ shown here can be approximated to a value obtained by dividing the surface area of the gas-liquid boundary surface 26 by the volume of the water to be treated 22 stored in the mixing tank 20.

Therefore, the components of the gas 25 are
In a conventional gas-liquid mixing tank to be used for the purpose of dissolving in 2, the dissolved concentration C and increasing the dissolved concentration C _A by dissolution of the components of the gas 25 obtained by the small aerated, due to the divergence from the gas-liquid boundary surface 26 The decrease in _B occurs in parallel, and the dissolved concentration of the component of the gas 25 in the treated water 29 is determined by both these phenomena and the supply amount of the treated water 22.

[0012] Next, the components of the gas 25 to be supplied for reacting with the water to be treated 22, the rate of decrease in the dissolved gas concentration C _C in the treated water 22, according to equation (3).

[0013] _{dC C / dt = k L a} 3 (C-C Y) + kC ··· (3) k: reaction rate constant of the component to be treated in the gas component in solution

When a reaction occurs in the mixing tank 20, as is apparent from the equation (3), the components of the dissolved gas 25 dissolved in the water to be treated 22 are different from the components to be treated in the water 22 to be treated. (Represented by kC in the formula) and by divergence from the gas-liquid interface 26 (k _{L in the} formula)
a ₃ (C-C _Y ). ), The dissolved concentration (where C
Notation _C ) Occurs.

[0015] Thus, the dissolved concentration due to the divergence of the dissolved gases 25 C _C reduction k _L a ₃ of (C-C _Y), the gas-liquid contact area per unit volume (in the formula, referred to as a _3.), That is, it is proportional to a value obtained by dividing the surface area of the gas-liquid boundary surface 26 by the volume of the water 22 to be stored in the mixing tank 20, and is the same as the case where there is no reaction between gas and liquid shown in the above equation (2). Show the trend.

[0016]

In the above-mentioned conventional gas-liquid mixing tank, when the components of the gas 25 are dissolved in the water 22 to be treated, and the components of the gas 25 react with the components in the water 22 to be treated. In any case, the divergence of the dissolved gas 25 from the gas-liquid interface 26 causes a reduction in efficiency. Therefore, the supply of an excessive amount of gas 25 and the mixing tank 2
The processing performance is improved by extending the residence time at 0. For this reason, it is necessary to provide a supply source of the gas 25 having excessive performance and to reduce the water 22 to be treated.

Therefore, the present invention suppresses the emission of dissolved gas components from the gas-liquid interface in the gas-liquid mixing tank, thereby improving the production efficiency of the gas-dissolved water and the decomposition efficiency of the components to be treated in the liquid by the supply gas. The purpose is to improve.

[0018]

In order to achieve the above object, according to the present invention, water to be treated is supplied into a mixing tank, and gas is supplied as small bubbles into the water to be treated. In the gas-liquid mixing tank in which the gas is dissolved or reacted, and a gas phase of the gas is formed above the water to be treated, a spherical float is floated on the entire surface of the water to be treated, The upper half of the float is located in the gas phase and the lower half is located in the water to be treated. Thereby, since most of the gas-liquid boundary surface in the mixing tank is shielded by the float, the gas-liquid boundary area that is deeply involved in the amount of the dissolved gas component diverged can be significantly reduced. That is, waste of the dissolved gas component due to divergence can be suppressed.

Further, it is preferable that the float is formed hollow. Thereby, regardless of the material of the float, the upper half of the float can be located in the gas phase and the lower half can be located in the water to be treated.

Further, it is preferable that the float has a hollow portion in which liquid and gas are stored. Thereby, the material of the float can be reduced.

The water supply pipe for supplying the water to be treated is
It is preferable that the gas phase is introduced into the mixing tank from the position of the gas phase, and that the tip is positioned in the water to be treated below the float. Thereby, the turbulence does not occur on the surface of the water to be treated, and the effect of shielding the gas-liquid boundary surface by the float can be stabilized.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 3. FIG. In these figures, the float 1 is made of a material that is not easily affected by the water to be treated 22 and the gas 25, for example, a resin such as polyethylene or polypropylene, and is made of a smooth outer wall 2.
Is formed in a spherical shape having Depending on the use conditions, it is preferable to improve the corrosion resistance by coating the outer surface of the outer wall 2 with a fluororesin.

The float 1 is suspended in the water 22 so that the upper half is located in the gas phase 27 and the lower half is located in the water 22. The whole water surface, that is, the gas-liquid boundary surface 26 is floated in such a quantity that it is almost hidden by the float 1. That is, by forming the specific gravity of the float 1 to be approximately half the specific gravity of the water 22 to be treated, the upper half of the float 1 is located in the gas phase 27 and the lower half thereof is located in the water 22 to be treated. Can be.

In this case, when the specific gravity of the material of the float 1 is about 1/2 of the specific gravity of the water 22 to be treated, the float 1 may be formed into a spherical shape using only the material. When the float 1 is formed of a resin such as polypropylene, the specific gravity of these resins is substantially equal to the specific gravity of the water to be treated 22 and is considerably larger than 1/2, so that a hollow portion may be formed in the outer wall 2. .

As shown in FIG. 1, a part of the hollow portion accommodates a liquid 3 such as water to be treated 22 or water which does not react with the outer wall 2, and the remaining portion includes the outer wall 2 and the liquid 3. If a stable gas 4 that does not react with the liquid 3 is stored, for example, an inert gas such as air, nitrogen, or argon, the outer wall 2 can be made thinner, so that the material of the float 1 can be reduced.

The water supply pipe 8 for supplying the water to be treated 22
Is introduced into the mixing tank 20 from the position of the gas phase 27, and the leading end thereof is lowered so that the water 2 to be treated below the float 1 is removed.
2 are disposed. Since the other parts are configured in exactly the same manner as the conventional gas-liquid mixing tank, the same reference numerals are given and the description thereof is omitted.

In the gas-liquid mixing tank of the present invention, the water 22 to be treated is supplied to the gas-liquid interface 26 by the external water supply pump 21 via the water supply pipe 8 without disturbing the gas-liquid interface 26. It is injected into the to-be-treated water 22 below. The gas 25 to be dissolved or reacted with the water to be treated 22 is supplied by an external compressor 24 to an air supply pipe 32 and a diffuser 2.
3 and supplied as small bubbles into the water 22 to be treated.

The gas 25 of the small bubbles moves upward by buoyancy while dissolving or reacting in the water to be treated 22, and the undissolved or unreacted gas 25 moves to the gas-liquid interface 26 where the float 1 floats. To reach. The water to be treated 22 is gas 2
After being mixed with the gas 5, it is drained to the outside as treated water 29 via a drain pipe 30.

FIG. 3 shows a state in which the undissolved or unreacted gas 25 is released from the water to be treated 22 to the gas phase 27 at the gas-liquid boundary surface 26. Undissolved or unreacted small gas bubbles 25 move along the outer wall 2 of the float 1 toward the gas-liquid interface 26 and a slight gas-liquid contact surface formed between adjacent floats 1. From 15 is released to the gas phase 27.

If there is not enough gas-liquid contact surface 15 to release gas 25, undissolved or unreacted small gas 25 becomes accumulated pool 17 and pushes float 1 to the gas phase. Released to 27. At this time, since the float 1 that is displaced floats so that the upper half is positioned in the gas phase 27 and the lower half is positioned in the water 22 to be treated, the float 1 can be easily lifted from the gas-liquid interface 26. However, the gas-liquid interface 15 is pushed back while rotating in the direction of the arrow 18 and returns to the original position together with the discharge of the air pocket 17, so that the gas-liquid boundary surface 26 is always kept on the float 1 without the useless gas-liquid contact surface 15 being formed. Will be shielded.

Therefore, the gas 2 in the mixing tank 20
In the case of performing the dissolution or gas-liquid reaction of No. 5, the gas-liquid boundary which is deeply involved in the concentration decrease due to the emission of the component of the dissolved gas 25 from the gas-liquid boundary surface 26 shown in the equations (2) and (3) The surface areas a ₂ and a ₃ of the surface 26 can always be kept small. That is, the dissolved gas 25 from the gas-liquid interface 26
Divergence of the component can be suppressed.

[0032]

As described above, in the gas-liquid mixing tank of the present invention, the float is floated over the entire surface of the gas-liquid interface, so that the dissolved gas component diverging from the gas-liquid interface to the gas phase. , The dissolved gas component can be used efficiently, and the gas supply amount can be reduced and the processing performance can be improved.

Also, since the upper half of the float is located in the gas phase and the lower half is located in the water to be treated, the gas in the water to be treated is discharged from the gas-liquid interface to the gas phase. Since the float does not rise and a large amount of gas is not released at a time, gas divergence can be suppressed. Further, since the contacts of the plurality of adjacent floats are located on the center line of the sphere and coincide with the gas-liquid boundary surface, the gas-liquid contact surface can be minimized, and the number of floats can be minimized. .

[Brief description of the drawings]

FIG. 1 is a view showing a cross section of a float used in a gas-liquid mixing tank of the present invention.

FIG. 2 is a diagram showing a cross section of the gas-liquid mixing tank of the present invention.

FIG. 3 is a diagram showing a degassed state of an undissolved gas at a gas-liquid boundary surface inside a gas-liquid mixing tank of the present invention.

FIG. 4 is a diagram showing a cross section of a conventional gas-liquid mixing tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Float 2 Outer wall 3 Liquid 4 Gas 8 Water supply pipe 20 Mixing tank 22 Water to be treated 25 Gas 26 Gas-liquid interface 27 Gas phase

Claims (4)

[Claims] 1. A method for supplying water to be treated into a mixing tank, supplying gas as small bubbles into the water to be treated, dissolving or reacting the gas in the water to be treated, and In a gas-liquid mixing tank in which a gas phase of the gas is formed, a spherical float is floated on the entire surface of the water to be treated, and an upper half of the float is in the gas phase and a lower half. Are located in the for-treatment water, respectively. 2. The gas-liquid mixing tank according to claim 1, wherein the float is formed hollow. 3. The gas-liquid mixing tank according to claim 2, wherein the float has a liquid and a gas stored in a hollow portion. 4. A water supply pipe for supplying the water to be treated is introduced into the mixing tank from the position of the gas phase, and a tip of the water supply pipe is located in the water to be treated below the float. The gas-liquid mixing tank according to any one of claims 1 to 3, wherein: