JPH07299476A - Descending dissolution type ozone reactor - Google Patents

Abstract

PURPOSE:To suppress the diameter of bubbles by providing a part of the descending dissolution part of a reactor with a descending mixture device to shear and mix the bubbles. CONSTITUTION:The part of descending dissolution part 1a is provided with the descending mixing device (mixing apparatus) 11. As the mixing apparatus 11, a static mixer can be used as a line mixer for shearing and mixing the bubbles. By the constitution, the bubbles are mixed and sheared to become small by the mixing apparatus. The degree is changed with the flow rate of the water to be treated 4 and the diameter of the descending dissolution part 1a. Then, the characteristic of the reactor may be fixed by the simulation with the overall mass transfer capacity coefficient optionally changed. The ozone adsorption is increased by 86-94% with the decrease of bubbles diameter by about 40%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a descending dissolution type ozone reaction tank for sterilizing water, deodorizing water, and oxidizing organic substances using ozone.

[0002]

2. Description of the Related Art In recent years, ozone is diffused in water by utilizing the characteristic that ozone has the strongest oxidizing power next to fluorine, thereby performing sterilization, decolorization, deodorization, and oxidation removal of organic or inorganic substances. Water treatment is widely used. In particular, in the water supply in the suburbs of cities, the damage of offensive odor caused by the water intake source is widespread, and the strong oxidizing power of ozone exerts a great effect in removing this offensive odor. The introduction of advanced processing using is being promoted.

An ozone treatment apparatus for reacting such ozone with water treated with ozone (hereinafter referred to as treated water) supplies an ozone generator for generating ozone mainly from electric energy and treated water. It is composed of a water supply pump, a reaction tank for advancing the reaction, and an exhaust ozone treatment facility for decomposing exhaust ozone discharged from the reaction tank in an unreacted state. The following is known as the shape of the reaction tank.

First, in the batch system, there are an ejector system in which ozone is blown into the reaction tank by an ejector, or a bubble column system in which ozone is blown out as bubbles from the lower part of the reaction tank. There are a co-current contact method that continuously supplies from the lower part, and a countercurrent contact method that supplies water to be treated from the top and opposes ozone gas.

These ozone treatment devices require a contact time for sufficiently performing an oxidation reaction on the water to be treated. Therefore, when the amount of water to be treated is large, a large-volume ozone contact tank is required, and when it is introduced into a water purification plant in a suburb of a city with a large water supply population, large-scale equipment is required. This is not preferable from the economical point of view, and is a major factor that hinders the introduction of a water treatment device using ozone. Therefore, a high ozone absorption rate and a sufficient removal efficiency are required for the ozone reaction tank.

Here, the ozone absorption rate is a rate of ozone which is consumed by being dissolved or decomposed in water to be treated in the reaction tank in the injected ozone gas, and is represented by the following formula. The removal efficiency is the ratio of water pollutants in the water to be treated that is decomposed and removed in the reaction tank, and is represented by the following formula. Typical odorants are water pollutants.

[0007] Generally, the higher the ozone absorption rate and the removal efficiency, the better the processing efficiency of the ozone reaction tank.

By the way, the amount of ozone transfer when ozone is dissolved in water is mainly determined by the overall mass transfer capacity coefficient (K _La ) and the difference between the saturated ozone concentration in water and the dissolved ozone concentration (concentration gradient). It is a factor. It is known that the saturated ozone concentration depends on the ozone concentration in the gas and the ozone distribution coefficient. Therefore, it is desirable to make the water depth of the reaction tank as deep as possible from the viewpoint of increasing ozone dissolution efficiency by utilizing the water depth pressure of the reaction tank. Since the gas had to be blown facing each other, the actual depth of the reaction tank was 6 m. A descending dissolution type ozone treatment device was conceived to cope with this.

FIG. 3 is a schematic view showing the structure of the main part of the descending dissolution type ozone processing apparatus. In FIG. 3, this device is U
The water to be treated 4 was introduced from the inlet 2 at the upper part of the letter-shaped reaction tank 1 by the water pump 3, and at the same time, the ozone gas generated by the ozone generator 5 was converted into bubbles 7 through the diffuser 6 and formed into the reaction tank 1 Inject into. The water 4 to be treated becomes a mixed flow with bubbles 7 (ozone gas), and flows down the descending dissolution part 1a of the reaction tank 1 . This mixed flow passes through the bottom of the reaction tank 1 and rises 1b.
After that, the treated water 9 can be distributed from the outlet 8 to the outside of the reaction tank 1 . The flow directions of the water to be treated 4 and the bubbles 7 are indicated by arrows. Of the injected ozone gas, unreacted ozone gas is decomposed and discharged by the exhaust ozone treatment facility 10. The U-shaped reaction tank 1 is usually smaller in diameter than the rising portion 1b in order to increase the flow velocity in the descending melting portion 1a.

Such a descending dissolution type ozone treatment apparatus is
Since the water to be treated 4 and the ozone gas are simultaneously introduced from the top of the reaction tank 1 , there is no need to blow the gas against the water depth pressure, and a reaction tank having a deeper water depth than the countercurrent contact method can be designed. .

[0011]

The ozone absorption rate is a major factor in the efficiency of the reaction tank, and the problem is how to increase the ozone absorption rate. The a represented by the above-mentioned overall mass transfer capacity coefficient K _La represents a gas-liquid contact area per unit volume, and varies depending on the shape of the reaction tank 1 . Reaction tank 1
When the amount of ozone gas blown into the same is the same, the smaller the bubble diameter, the greater the number of bubbles, and the gas-liquid contact area per unit volume,
That is, the value of a becomes large. The bubble diameter directly affects the movement of ozone, and the smaller the bubble diameter, the higher the movement efficiency.

According to the calculation formulas experimentally obtained so far,
It is generally expressed as follows. a = 87 × V _a ^1.11 V _a : Amount of gas blown in per unit volume However, the descending dissolution type ozone reaction tank 1 has a descending dissolution part 1a.
Since the ozone gas and the treated water flow as a gas-liquid mixed flow, the bubbles 7 in the treated water 4 tend to associate with each other due to a subtle difference in the flow velocity distribution between the wall surface and the central portion of the descending dissolution portion 1a. That is, even if the ozone gas injection method for reducing the bubble diameter is used, the bubble 7 grows to a certain size while descending through the descending melting portion 1a.

Therefore, in order to improve the ozone transfer efficiency, that is, the absorption efficiency, in the descending dissolution type ozone reaction tank 1 , the size of the bubbles 7 is controlled in the descending part dissolution part 1a so as to be small. Must. The present invention has been made in view of the above points, and an object thereof is to provide a descending dissolution type ozone reaction tank capable of suppressing the bubble diameter in the descending dissolution section.

[0014]

In order to solve the above problems, the descending dissolution type ozone reaction tank of the present invention is a line mixer such as a static mixer in a part of the descending dissolution part of the descending dissolution type ozone reaction tank. Is provided.

[0015]

In the down-melting type ozone reaction tank of the present invention constructed as described above, the bubbles passing through the inside of the down-melting section are sheared and mixed, and the bubble diameter can be reduced, so that the ozone absorption efficiency is improved.

[0016]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a schematic diagram showing a configuration of an essential part of an ozone processing apparatus having a descending dissolution type ozone reaction tank according to the present invention. The same reference numerals are used for the same parts as in FIG. 3, and the treated water 4 and bubbles are the same as in FIG. The flow direction of 7 is indicated by an arrow. However, here, the reaction tank is not an integrally U-shaped one, but a shape in which the descending melting part 1a is separately attached to one side surface of the lower part of the ascending part 1b is shown, but other configurations are shown in FIG. Is basically the same as that of the U-shaped reaction tank.

Regarding the present invention, FIG. 1 differs from FIG. 3 in that a descending section mixing device 11 is provided in a part of the descending melting section 1a. As the descending section mixing device 11, for example, a static mixer as a line mixer for shearing and mixing bubbles can be used. FIG. 2 is a schematic cross-sectional view showing a static mixer, in which a turbulent flow plate 14a and a turbulent flow plate 14a twisted in opposite directions are provided in a pipe 13 fixed to a flange 12.
A plurality of 4b are arranged alternately.

In this way, the size of the bubble 7 is surely reduced by the mixing and shearing by the descending mixing device 11, but the extent thereof depends on the flow rate of the water to be treated 4 and the descending dissolution part 1a.
It depends on the diameter of. Therefore, a computer was used to arbitrarily change the a of the overall mass transfer capacity coefficient K _La shown above to simulate the reaction tank characteristics at that time. The calculation was carried out by using the constants obtained from the experiment, assuming a general ozone treatment corresponding to the water treatment. The results are shown in Table 1.
Table 1 shows the relationship between the relative bubble diameter and the ozone absorptivity, which is set to 1 under normal conditions, that is, when the bubbles are not sheared.

[0019]

[Table 1] From the simulation results in Table 1, it is expected that the ozone absorption rate will increase from 86% to 94% when the bubble diameter is reduced by about 40%. This is an extremely large improvement in efficiency and contributes greatly to the improvement in the efficiency of the entire ozone treatment apparatus.

[0020]

EFFECT OF THE INVENTION In the descending dissolution type ozone reaction tank of the present invention having a descending part mixing device such as a static mixer in a part of the descending melting part, bubbles are sheared and mixed by the descending part mixing device. Since the diameter is small, the ozone absorption rate is remarkably improved, and high reactor characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main configuration of an ozone processing apparatus having a descending dissolution type ozone reaction tank of the present invention provided with a descending section mixing device.

FIG. 2 is a schematic cross-sectional view showing a static mixer used in the present invention.

FIG. 3 is a schematic diagram showing a configuration of a main part of a conventional descending dissolution type ozone processing apparatus.

[Explanation of symbols] 1 reaction tank 1a descending dissolution section 1b rising section 2 inlet 3 water pump 4 water to be treated 5 ozone generator 6 diffuser 7 bubbles 8 outlet 9 treated water 10 ozone discharge equipment 11 descending mixture Device 12 Flange 13 Tube 14a Turbulent flow plate 14b Turbulent flow plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C02F 1/50 520 B 531 R 540 A 550 B

Claims (2)

[Claims] 1. A descending melting part in which water to be treated and bubbles of ozone gas are introduced from above and a mixed flow of these flows downward, and an ascending part in which the mixed flow flows upward through a bottom part. A descending dissolution type ozone reaction tank, wherein a descending part mixing device is provided in a part of the descending dissolution part. 2. The descending dissolution type ozone reaction tank according to claim 1, wherein a line mixer for shearing and mixing bubbles is used as a descending section mixing device.