JP2001180916A - Ozonizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ozonizer allowing its discharge tube to be cleaned easily. SOLUTION: An ozonizer, having a tank 1, the piping system 11, 12 for supplying feed gas to the tank and sending out the produced ozone gas, and a discharge tube 10A to produce ozone gas from feed gas, is also provided with argon purge means 16, 17, 18, 19. This system carries out the argon gas purge by supplying argon gas to the tank 1, after the supply of feed gas to the tank 1 via the piping system 11, 12 and also the flow of the ozone gas from the tank 1 have been stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozone generator installed in a water purification plant or the like and used for water treatment and the like.
The present invention relates to an easy-to-maintain ozone generator for removing a substance attached to a discharge tube due to generation of ozone gas.

[0002]

2. Description of the Related Art Today, the functions required of water treatment processes are gradually changing, and there is an increasing demand for high-quality water from simply drinking water to delicious water, and further to safe water. Along with this, existing water treatment processes are being reviewed and operated.

[0003] Among them, chlorination of drinking water has been regarded as essential for disinfecting pathogenic bacteria, but due to its oxidizing power, there are concerns about trihalomethanes and all organic chlorine compounds.
It is inferred from the toxicity and accumulation properties of HC, DDT, PCB and the like. Even if chlorination of natural water is performed, organic chlorinated compounds are also produced. Therefore, as a method of reducing these even a little, ozone treatment has been reviewed as advanced treatment of drinking water.

[0004] Attempts to apply ozone to water treatment are said to begin in France around 1886. Then in 1906, one of Nice's Bon Voyage.
It has been put to practical use at a water purification plant of 90,000 tons / day, and has reached today.
In 1916, there were 49 ozone water purification plants, 29 of which were said to have been in France. There were 119 places in 1940, and around 1977, Rice reported about 1,000 places.

[0005] It is said that the application to water purification operations in Japan began around 1972, but interest in the use of ozone became common in the mid-1950s, and thereafter, in the mid-1960s, mainly in the Kansai region. The first issue was the drinking water odor problem, which was taken up as one of the treatment methods when examining the solution, and examined through pilot plant scale experiments.

[0006] In recent years, the problem of unpleasant tastes of tap water, especially musty odor, has spread nationwide with the progress of eutrophication due to pollution of water sources, and various tap waters that meet the needs of consumers who are seeking safe and delicious water. Businesses are struggling with such measures.

At present, 2-methylisoborneol and diosmin are known as causative substances of musty odor, and it has been found that certain cyanobacteria are involved in odor generation. The odor is generated mainly in summer from April, when the water temperature rises, and mold odor cannot be removed by the rapid filtration system that is the usual water purification treatment. Therefore, powdery activated carbon is generally added to raw water for adsorption treatment. It is carried out.

[0008] However, this powdered activated carbon alone has a limit as a deodorizing measure, and cannot be completely deodorized when the odor is strong. In addition, drastic measures against odor removal, such as injecting powdered activated carbon throughout the year, such as algae odor other than musty odor and other odors, have become necessary.

Therefore, while conducting various studies on methods for removing off-flavors and the like, attention has been paid to the introduction of an ozone treatment system.

Although ozone exerts a strong decomposing and removing effect on not only the musty odor that could not be dealt with by the coagulation, sedimentation, and rapid filtration treatments that have been carried out so far, but also trace organic substances, new ozone As a function of the compound, synergistic effects at the time of composite treatment, such as an increase in biodegradability of organic substances, an increase in oxidizing power by combined use with other oxidizing agents (composite oxidation), and an improvement in cohesiveness, are also increasing.

At present, a typical treatment flow of a water treatment plant using ozone is “pre-ozone treatment” such as ozone + coagulation / precipitation + rapid filtration, coagulation / precipitation + ozone + rapid filtration or coagulation / precipitation. + "Rapid filtration + ozone +" medium ozone treatment "such as granular activated carbon, coagulation / precipitation / filtration + ozone, or" coagulation / sedimentation / filtration + post-ozone treatment "such as ozone (+ granular activated carbon), medium ozone treatment The treatment method is selected in consideration of the characteristics of the raw water to be treated, the substance to be removed, and the like, such as the combined use of post treatment and post-ozone treatment.

[0012]

[0005] A silent discharge method is generally used for mass production of ozone. The silent discharge ozone generator includes a tank, a piping system for supplying a raw material gas into the tank and flowing out the generated ozone gas, and a discharge phenomenon acting on the raw material gas provided in the tank to generate the ozone gas. And a discharge tube to be generated.

In this ozone generator, the raw material gas processed by the raw material gas pretreatment device is passed through a piping system into a tank, and a high frequency (up to 1000 Hz) is applied between a discharge tube formed by sputtering stainless steel on a glass tube and a ground electrode. ) And a high voltage (6 to 20 kV) to generate ozone.

The source gas used for generating ozone has a dew point of-
Use very dry air at 60 ° C., but about 80 watts of nitrogen
The ratio of t% and oxygen 20 wt% does not change.

Therefore, nitrogen contained in the raw material gas stays in the tank as a nitrogen oxide or a nitrite gas. Further, a metal in stainless steel sputtered by applying a high frequency and a high voltage as described above, for example, iron,
The tin and the like are excited and combined with nitrogen and oxygen in the raw material gas, and also with the above-mentioned nitrogen oxide and nitrite gas to generate metal oxide, metal nitrate, metal nitrite and the like.

Since the raw material gas hardly contains moisture, these metal oxides, metal nitrates, metal nitrites and the like do not adhere to the discharge tube, but remain in the discharge tube.

However, as the accumulated amount increases, the generation of ozone is hindered. Therefore, it is necessary to clean the inside of the tank by opening the tank as a periodic inspection, and particularly to clean the discharge tube.

In order to clean the discharge tube, first, it is necessary to extract the discharge tube from the tank, but the gap (discharge gap) between the tank and the discharge tube is very small, about 0.5 to 1.5 mm. The average is about 1.2 mm, and is narrow to about 0.6 mm when the source gas is oxygen. For this reason, a skilled technique is required even if the discharge tube is simply extracted. After that, the discharge tube extracted from the tank is cleaned with alcohol after wiping the outside with water.

On the other hand, the tank side is also cleaned with alcohol after wiping the stainless steel ground electrode side with water. Since the length of the discharge tube is about 1500 mm, complicated work is required for cleaning the tank side.

The problem here is the moisture in the air. Moisture in the air enters the tank by opening the tank. As described above, metal oxides, metal nitrates, metal nitrites, and the like generated by the generation of ozone do not adhere to the discharge tube, but remain in the tank. But,
Deliquescence occurs due to the incorporation of moisture in the air. Deliquescence refers to a phenomenon in which a metal or a metal compound and moisture are combined.
As a result, harmful gases such as nitrogen oxides and nitrate gas are generated from the metal nitrates, metal nitrites, and the like that have accumulated in the tank.

When the tank is opened, if ozone stays in the tank, there is a concern that the ozone may be adversely affected. Therefore, ozone purging is performed to purge the inside of the tank with the raw material gas. This purging causes the tank to be filled with nitrogen gas, and this nitrogen and moisture in the air combine to generate harmful gases such as nitrogen oxides and nitric gas. Furthermore, a nitric acid solution of the metal is generated due to moisture in the air, nitrogen oxides, metal compounds, and the like.

As described above, when the tank is opened, nitrogen oxides and nitrate gas are generated, and a metal nitrate solution is generated, and these adhere to the surface of the discharge tube. Is a very difficult task.

[0023] In addition, the above-mentioned complicated discharge tube and the insertion of the extracted discharge tube into the tank require a lot of skill to make the discharge gap uniform (discharge gap). The bias becomes the bias of the discharge). It is said that the damage to the discharge tube due to the work in cleaning the discharge tube amounts to 10 to 20% of the total number.

That is, it is considered important to consider cleaning the discharge tube without opening the tank as the most important item.

An object of the present invention is to provide an ozone generator capable of easily cleaning a discharge tube.

[0026]

In order to achieve the above-mentioned object, the invention according to claim 1 comprises a tank for supplying a source gas and an outflow of generated ozone gas, and a tank provided in the tank for supplying the source gas. An ozone generator having a discharge tube that generates an ozone gas by causing a discharge phenomenon,
Argon gas purging means for stopping supply of the raw material gas into the tank and stopping outflow of ozone gas from the tank and supplying argon gas into the tank to perform argon gas purging. .

According to a second aspect of the present invention, in the ozone generator according to the first aspect, a liquid supply means for supplying a liquid in which a substance adhering to the discharge tube is dissolved with the generation of the ozone gas into the tank is further provided. Have.

The invention according to claim 3 is the ozone generator according to claim 1 or 2, further comprising a showering means for removing a substance attached to the discharge tube by showering. 2. The ozone generator according to 2.

According to a fourth aspect of the present invention, in the ozone generator according to any one of the first to third aspects, ultrasonic waves for ultrasonically cleaning the discharge tube provided in the tank are generated. An ultrasonic transducer is further provided.

According to the first aspect of the present invention, during the maintenance of the ozone generator, in particular, during the cleaning of the discharge tube, the deposits on the surface of the discharge tube, that is, nitrogen gas, nitrate gas, etc. The cleaning step, which has been complicated due to the toxic gas, is facilitated, and the cleaning of the discharge tube can be performed without having to insert and remove the discharge tube which requires a skilled technique.

According to the second aspect of the invention, in addition to the first aspect, the maintenance can be performed without opening the tank, so that moisture in the air does not enter the tank. Therefore, no toxic gas such as nitrogen gas or nitrate gas is generated.

According to the third aspect of the present invention, in addition to the first or second aspect of the present invention, the nitrogen oxides, the nitrate metal salts, By dissolving nitrate metal salts, metal oxides, and the like in a liquid such as water, deliquescent phenomenon due to moisture in the air does not occur.

According to a fourth aspect of the present invention, in addition to the first aspect of the present invention, the tank further comprises a nitrogen oxide, a nitrate metal salt, and a zinc oxide. When dissolving a nitrate metal salt, a metal oxide, or the like in a liquid such as water, ultrasonic cleaning is performed, so that the dissolving effect is enhanced.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of an ozone generator according to the present invention will be described below with reference to FIG. The ozone generator of the present embodiment includes a tank 1 having a door (not shown), a source gas inflow pipe 11 for supplying a source gas into the tank 1, a source gas inlet valve 12,
A discharge tube (10A) (not shown) that is provided in the tank 1 and generates an ozone gas by causing a discharge phenomenon to act on the supplied source gas, an ozone gas outlet pipe 13 that outputs the ozone gas, an ozone gas outlet valve 14, a source gas, As a purge gas supply system for stopping the supply to the inside of the tank and stopping the outflow of ozone gas from inside the tank and supplying argon gas into the tank to perform argon gas purging,
It has a pipe 16 connected to the raw material gas inflow pipe 11, a purge gas inlet valve 17, a flow control valve 18, and an argon gas container 19 filled with argon gas.

This embodiment has the above-described configuration, and has the following operation. First, the maintenance of the ozone generator will be described. That is, the first cause of the maintenance is that nitrogen is contained in the raw material gas supplied into the tank 1 to generate ozone by silent discharge. This nitrogen stays in the tank 1 as a nitrogen oxide or a nitrite gas. Further, metals in stainless steel sputtered on the discharge tube, such as iron and tin, are excited, and combined with nitrogen and oxygen in the raw material gas, and also with the above-mentioned nitrogen oxide and nitrite gas to form a metal oxide. , Metal nitrates and metal nitrites.

In some cases, oxygen is used as the source gas instead of air. In order to increase the ozone concentration, the source gas may be oxygen. However, from the viewpoint of safety of the source gas and high cost, it is not preferable to use the source gas as oxygen. Also, even when oxygen is used as a source gas, a metal in a sputtered stainless steel, for example, iron or tin, is excited by applying a high frequency and a high voltage to the discharge tube, and combines with oxygen to generate a metal oxide. .

Since the raw material gas contains almost no water, not limited to air and oxygen, these metal oxides, metal nitrates, metal nitrites and the like do not adhere to the discharge tube and remain in a state of stay. . Over time, the amount of stagnation increases and the inspection windows in the tank of the ozone generator are filled with fine particles presumed to be metal oxides, metal nitrates, metal nitrites, etc. Can be visually confirmed. This phenomenon causes a reduction in the efficiency of ozone generation. A huge amount of energy (1k ozone)
Since about 20 kWh per g is required, maintenance of the ozone generator is very important in order to prevent a decrease in ozone generation efficiency due to such a phenomenon.

In the conventional maintenance method, as described above, the tank 1 is opened, and the inside of the tank 1 and the discharge tube are cleaned. Here, what matters is moisture in the air. Moisture in the air enters the tank by opening the tank. As described above, metal oxides, metal nitrates, metal nitrites, and the like generated by the generation of ozone do not adhere to the discharge tube, but remain in the tank.
However, deliquescence occurs due to mixing of moisture in the air. As a result, harmful gases such as nitrogen oxides and nitrate gas are generated from the metal nitrates, metal nitrites, and the like that have accumulated in the tank. In addition, a nitric acid solution of a metal is generated due to moisture in the air, nitrogen oxides, metal compounds, and the like.

As described above, by opening the tank, nitrogen oxides and nitrate gas are generated, and a metal nitrate solution is generated, and these adhere to the discharge tube surface.

In order to prevent such a phenomenon from occurring, a maintenance method for the ozone generator that cleans the discharge tube without opening the tank is possible with the ozone generator of the present embodiment. That is, the ozone generator according to the present embodiment can employ a purge method performed as preparation for maintenance. Although it has been performed at the time of conventional maintenance, if ozone stays in the tank 1, there is a concern that the ozone may be adversely affected. Therefore, ozone purging has been performed in the tank 1 with a raw material gas. This purge causes the tank 1 to be filled with nitrogen gas, and this nitrogen and moisture in the air combine to generate a vicious cycle in which harmful gases such as nitrogen oxides and nitrate gas are generated. .

In addition, a part of the nitrogen oxide, nitrate metal salt, nitrite metal salt, metal oxide, etc., which fills the tank 1 by this purge is moved from the generator to the pipe at the subsequent stage. Such a substance may accumulate in the piping and cause clogging of the piping.

In this embodiment, purge gas supply systems 16 to 18 are provided. Purge with argon gas is performed using the purge gas supply systems 16 to 18. With argon gas, nitrogenous compounds and metal oxides are not generated as before.

In order to prevent the ozone purged by the purge gas supply systems 16 to 18 from leaking, there are also provided piping systems 19, 20, and 21 for connection to an exhaust ozone treatment device.

When an ozone generator is installed in the water treatment, a piping system 19, 2
The pipes 0 and 21 are preferably connected to a waste ozone treatment apparatus, but similarly to the conventional method, nitrogen oxides, nitrate metal salts, nitrite metal salts, metal oxides, etc., which fill the tank 1 are used. Is moved from the tank 1 to the pipe at the subsequent stage. Since such substances are expected to accumulate in the pipes and cause clogging of the pipes, it is preferable that the pipes be connected to the exhaust ozone treatment apparatus separately from the pipes that are always used.

Further, by introducing the purge gas through a separate pipe, the gas flow rate can be adjusted.

In the configuration shown in FIG. 1, purging with argon gas is performed. That is, the raw material gas inlet valve 12,
The ozone gas outlet valve 14 is closed, and then the purge gas inlet valve 17 and the outlet valve 20 are opened. The tank 1 was filled with argon gas for purging from the container 15. The ozone generated by the ozone generator used at this time was 10 kg / h, and the required flow rate of the raw material gas was 500 Nm ³ / h (operating at an ozone injection rate of 0.5 ppm).

When purging with argon gas, the flow control valve 1
At 8, the argon gas flow rate was adjusted to 500 Nm ³ / h. The gas detector 21 measured the ozone concentration, the nitrogen concentration, and the oxygen concentration in the gas, respectively, and confirmed the progress of the purge. The result is shown in FIG.

According to FIG. 2, the oxygen concentration was 0 g in about 6 hours.
/ Nm ^3, the nitrogen concentration of 0 g / Nm ³ to about 9 hours, about 18
The ozone concentration became 0 g / Nm ^{3 over} time.

By purging with argon gas, ozone, oxygen, and nitrogen are eliminated from the generator, thereby suppressing the production of metal oxides, metal nitrates, metal nitrites, and the like.

(Second Embodiment) Next, a second embodiment of the ozone generator according to the present invention will be described with reference to FIG. The ozone generator of the present embodiment includes a showering device separately or additionally from the configuration of the first embodiment.

The showering device is disposed in the cleaning tank 23 for storing a cleaning liquid 23 such as ion-exchanged water, acetone, alcohol, etc., a cleaning liquid supply pipe 24, a pump 25, a cleaning liquid inlet valve 26, and the tank 1. The nozzle 23 includes a nozzle 27 for spraying a cleaning liquid shower stored in the tank 23 onto the discharge tube 10A, a cleaning liquid discharge pipe 28, a cleaning liquid outlet valve 29, and a drain tank 30.

This embodiment has the above-described configuration, and has the following operation. First, the treatment of metal oxides, metal nitrates, metal nitrites and the like generated with the generation of ozone and retained in the tank will be described. These become metal hydroxides by the deliquescence phenomenon, and at that time, harmful gases such as nitrogen oxides and nitric gas are generated. Since this adheres to the surface of the discharge tube, the cleaning process is a very complicated operation. Furthermore, when the discharge tube is complicated to extract and when the extracted discharge tube is inserted into the tank, a great skill is required to make the discharge gap uniform. In this case, since the source gas uses very dry air, the deliquescent phenomenon does not occur if the ozone generator is in a closed state. For this reason, metal oxides, metal nitrates,
A metal nitrite or the like is previously brought into contact with water or a liquid effective for dissolving them, for example, an organic solvent such as alcohol or acetone.

At this time, the showering device is installed in the tank 1 so that the water and the like can be spread over the entire area in the tank. The cleaning liquid shower uniformly contacts the metal oxides, metal nitrates, metal nitrites, and the like staying in 1. Metal oxides, metal nitrates, metal nitrites, and the like come into contact with water, alcohol, acetone, and the like, and dissolve.

The waste liquid after such washing is supplied to the washing pipe 2.
8 to take out of the generator. By repeating washing by the showering device and draining by the washing pipe, metal oxides, metal nitrates, metal nitrites, and the like that have accumulated in the tank 1 are taken out of the generator together with the washing waste liquid.

After purging in the first embodiment, treatment of metal oxides, metal nitrates, metal nitrites and the like remaining in the tank 1 is performed by the showering device shown in FIG.

First, showering cleaning using water is performed.

In preparation for washing, the washing pipe outlet valve 29 is closed and the inlet valve 26 is opened. As the water used for cleaning, ion exchange water is used to prevent corrosion in the tank 1. The cleaning ion-exchanged water 23 stored in the container 22 is sent to the nozzle 27 of the showering device in the tank 1 using the pump 25. The pump discharge pressure at this time was 1.5 kg / cm ² . After performing showering cleaning for 30 seconds, the pump 25 was stopped, and the cleaning pipe outlet valve 29 was opened. The waste liquid was collected in the drain tank 30, and the composition of the waste liquid was analyzed. The washing and draining described above are repeated, and each time,
Table 1 shows the results of the waste liquid analysis.

[0058]

[Table 1]

According to Table 1, No. 11, iron, tin,
It can be seen that detection of metal components such as zinc, nitrate and nitrogenous substances has been eliminated.

Next, showering cleaning using acetone was performed.

The washing-draining step was the same as in the case of water, and the use of a 10% acetone solution as a substitute for water was examined to increase the washing efficiency. Repeat washing and draining, each time
Table 2 shows the results of the waste liquid analysis.

[0062]

[Table 2]

According to Table 2, no. 6, it can be seen that detection of metal components such as iron, tin, and zinc, nitrate substances, and nitrogen substances has been eliminated. It was found that the use of the 10% acetone solution increased the washing efficiency as compared with water.

Further, showering cleaning using alcohol was performed.

In this case, 10% methyl alcohol was used. The washing results are shown in Table 3.

[0066]

[Table 3]

According to Table 3, no. 8, it can be seen that detection of metal components such as iron, tin and zinc, nitrate substances, and nitrogen substances has been eliminated.

As described above, the cleaning effect of the three cleaning solutions is 10%.
It was found that the order was acetone solution> 10% methyl alcohol> ion-exchanged water.

By repeating washing with the shower ring as described above, metal oxides, metal nitrates, metal nitrites and the like staying in the tank 1 can be removed out of the generator. It was found that it is most efficient to use a 10% acetone solution as the washing liquid at this time, and that reducing the number of washings leads to a reduction in the amount of waste liquid.

(Third Embodiment) Next, a third embodiment of the ozone generator according to the present invention will be described with reference to FIG. In the ozone generator of the present embodiment, an ultrasonic oscillator 30 is provided in the tank 1 separately or additionally from the first embodiment, or in addition to the configuration of the second embodiment.

This embodiment has the above-described configuration, and has the following operation. In the present embodiment, the above-described cleaning step can be performed more efficiently. That is, in the showering cleaning with water or the like in the second embodiment, the inside of the tank 1 is cleaned by repeating the cleaning-draining process. To improve the cleaning efficiency, ultrasonic cleaning is also used. After the inside of the tank 1 is filled with water, alcohol, acetone, or the like, ultrasonic waves are generated using the ultrasonic vibrator 30 inside the tank 1 to perform efficient cleaning. Since ultrasonic cleaning is used in combination, the number of cleaning-draining steps is reduced.
It also leads to the reduction of waste liquid.

Here, a magnetostrictive vibrator (nickel / ferrite) was used as the ultrasonic vibrator 30. As shown in FIG. 4, the vibrators 30 were installed at two upper and lower locations in the tank 1.
During cleaning, a high frequency of 50 to 80 kHz is applied at 5 kHz.
Ultrasonic irradiation was performed for 60 sec while changing to z / 10 sec.

At the time of ultrasonic cleaning, the inside of the tank 1 is filled with water or the like by a showering device as in the second embodiment, and thereafter, ultrasonic cleaning is performed. This ultrasonic cleaning was continuously performed in the drainage process. In the waste liquid analysis, the composition of the waste liquid was analyzed in the same manner as in Embodiment 2, and the results are shown in Table 4.

[0074]

[Table 4]

According to Table 4, No. 3 shows that detection of metal components such as iron, tin, and zinc, nitrate substances, and nitrogen substances has been eliminated.

As described above, it was found that the cleaning effect was further enhanced by the ultrasonic irradiation.

[0077]

As described above, according to the present invention, during maintenance, particularly during cleaning of the discharge tube, the toxic gas such as nitrogen gas or nitrate gas adheres to the discharge tube surface, which is complicated. Cleaning can be facilitated, and an ozone generator can be provided that can perform cleaning of the discharge tube without taking in and out of the discharge tube that requires a skilled technique.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an ozone generator according to the present invention.

FIG. 2 is a view showing characteristics of an argon gas purge in the embodiment.

FIG. 3 is a configuration diagram showing a second embodiment of the ozone generator according to the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the ozone generator according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tank, 10A ... Discharge tube, 11 ... Raw material supply piping, 1
2 ... material inlet valve, 13 ... ozone outlet pipe, 14 ... ozone outlet valve, 15 ... argon gas container, 16 ... argon gas supply pipe, 17 ... argon gas inlet valve, 18 ... flow rate control valve, 19 ... purge gas discharge pipe, Reference Signs List 20: purge gas outlet valve, 21: gas detector, 22: cleaning liquid tank, 23: cleaning liquid, 24: cleaning liquid supply pipe, 25: pump, 26: cleaning liquid inlet valve, 27: nozzle, 28: cleaning liquid discharge pipe, 2
9: Cleaning liquid outlet valve, 30: Ultrasonic vibrator.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Takase 1-1-1, Shibaura, Minato-ku, Tokyo F-term in Toshiba head office (reference) 4D050 AA03 AB06 AB07 BB02 BD04 4G042 CA01 CC10 CC15

Claims (4)

[Claims] 1. An ozone generator comprising: a tank for supplying a source gas and flowing out a generated ozone gas; and a discharge tube provided in the tank for generating an ozone gas by causing a discharge phenomenon to act on the source gas. An argon gas purging means for stopping supply of the source gas into the tank and stopping outflow of ozone gas from inside the tank and supplying argon gas into the tank to perform argon gas purging. Ozone generator. 2. The ozone generator according to claim 1, further comprising liquid supply means for supplying a liquid in which a substance attached to the discharge tube is dissolved with the generation of the ozone gas into the tank. 3. The ozone generator according to claim 1, further comprising showering means for removing a substance attached to said discharge tube by showering. 4. The ozone generator according to claim 1, further comprising an ultrasonic vibrator provided in said tank for generating ultrasonic waves for ultrasonically cleaning said discharge tube.