JPS632884B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for generating ozone using a glow discharge generated by applying a pulse voltage between opposing metal electrodes.

In recent years, treatments such as disinfection, bleaching, and oxidation using ozone gas have been widely carried out, and industrial-scale ozone generators are being used.

In this type of industrial-scale ozone generator, the silent discharge method has conventionally been used exclusively. In the silent discharge method, as shown in the basic configuration diagrams of FIGS. 1 to 3, a dielectric material 2 is placed between a high voltage electrode 1 and a ground electrode 3 that face each other with a gap 4 in between. In this method, a high alternating current voltage is applied between the electrode 3 and the ground electrode 3 by a power source 5 to generate a silent discharge in the gap 4, and gas containing oxygen is passed through the gap 4 to generate ozone.

FIG. 4 is a fragmented cross-sectional view of a dielectric electrode used in the silent discharge with the application of an AC high voltage.

In FIG. 4, a thin film high-voltage electrode 1 is formed by adhering to the inner surface of a dielectric material 2 such as a glass tube, using carbon paint, aluminum sputtering, metal vapor deposition, or the like. FIG. 5 is a fragmentary sectional view of an ozone generator provided with the required number of dielectric electrodes 6 described above. In FIG. 5, the dielectric electrode 6
is inserted into a tubular ground electrode 3 made of a stainless steel tube, and both end portions of the ground electrode 3 are attached through the tube sheet 13, and are formed by the ground electrode 3, the housing 12, and the tube sheet 13. In the space where
Cooling water is supplied from a cooling water inlet 8 at the bottom of the housing 12, and drained from a cooling water outlet 9 at the top of the housing 12, thereby cooling the ground electrode 3 with water. The dielectric electrode 6 is connected to a high voltage bushing 14 from an AC power source (not shown).
An AC high voltage is applied through the power supply jig 7 and a silent discharge is generated between the power supply jig 7 and the ground electrode 3. The heat generated by the silent discharge is removed by the cooling water, and the temperature rise in the gap 4 and the dielectric electrode 6 is suppressed. A gas containing oxygen, for example dry air, is supplied from the gas inlet 10 to be treated, is ozonated while passing through the discharge gap 4, and is ozonated at the ozone gas outlet 11.
taken from.

In the above-mentioned method of using silent discharge by applying high AC voltage, the equipment becomes very expensive, and furthermore, since a dielectric material is used to stabilize the discharge, that is, to prevent migration of the arc, the applied voltage cannot be increased. Therefore, if the distance between the electrodes (gap) is wider than a few millimeters, discharge cannot be obtained with a low applied voltage, and the reaction volume is forced to be narrow, which is not optimal for an industrial-scale device. Furthermore, since the trigger electrons for the discharge are incidental electrons generated by the ionization effect of ultraviolet rays and cosmic rays in the atmosphere, it is necessary to increase the electric field strength. Therefore, an intense streamer discharge in which positive and negative charges are mixed locally occurs due to the overvoltage, and nearly 95% of the discharge energy becomes heat, resulting in a state unsuitable for ozone generation.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide an ozone generation method that is easy to handle and has a large reaction volume.

The present invention removes the dielectric material from the gap between the main discharge electrodes of an ozone generator, expands the gap between the electrodes, and externally supplies initial electrons that trigger the discharge.
It is characterized by causing a uniform glow-like discharge in the entire space between the electrodes.

Hereinafter, embodiments of the ozone generation method according to the present invention will be described with reference to the drawings.

Example 1 FIG. 6 shows a basic configuration diagram of an ozone generator. In Figure 6, a metal negative electrode (high voltage electrode)
A groove is provided at intervals between the discharge electrodes 41, and in this groove, a third electrode 42 made of wire as shown in the partial cross-sectional view of FIG.
3 is buried, and the third electrode 42 is connected to the same potential as the positive electrode 44 via a capacitor 46. A flat positive electrode (ground electrode) 44 is provided across a gap 45 from the negative electrode 41 . When a negative impulse is applied to the negative electrode (high-voltage electrode) 41 from the pulse generator 47, the voltage between the negative electrode 41 and the positive electrode 44 through which the gas to be treated flows increases, and the voltage between the third electrode 42 and the positive electrode 44 increases. A preliminary discharge begins between the negative electrode 41 and the vicinity of the negative electrode 41 becomes electron-rich, and when the voltage further increases, a main discharge occurs between the negative electrode 41 and the positive electrode 44. Since the timing of the preliminary discharge by the third electrode 42 is controlled by the capacitor 46, this main discharge becomes an extremely uniform glow-like discharge. In this case, the gas to be treated contains He, which is said to be more effective in preventing discharge concentration than normal dry air, and N ₂ and CO ₂ , which promote the action of He.
It is preferable to flow a mixed gas of O ₂ to prevent a violent transition from glow-like discharge to arc. Also,
Of course, when the negative electrode 41 side is grounded, the positive electrode 44 becomes high voltage, and a positive impulse is applied from the pulse generator 47.

Embodiment 2 FIG. 8 is a diagram showing the basic configuration of an ozone generator that uses impulse irradiation with strong ultraviolet rays instead of the preliminary discharge of Embodiment 1. In FIG. 8, a negative electrode 61 made of, for example, metal mesh is provided and grounded to facilitate the passage of ultraviolet rays emitted from an ultraviolet generator 69, and a positive electrode 64 is placed opposite to the negative electrode 61 with a gap 65 in between. The pulse generator 67 is connected to the pulse generator 67 . In this device, an impulse voltage is applied between the negative electrode 61 and the positive electrode 64, and in synchronization with the rise of this voltage, an intense ultraviolet ray 68 with a wavelength of 2000 Å or less is emitted from an ultraviolet generator 69 into the sky 65 for the purpose of preliminary discharge. It is irradiated impulsively as
Thereafter, the voltage between the main electrodes rises sufficiently to generate a uniform glow discharge in the gap 65, and the gas to be treated containing oxygen flowing through the gap 65 is ozonated. In this apparatus, the gas to be treated can also be ozonated by irradiation with radiation instead of ultraviolet rays.
Further, even if the ultraviolet ray generator is provided on the side surface of the metal electrode, initial electrons can be supplied.

In the present invention, the time from the preliminary discharge or ultraviolet irradiation to the main discharge is a very important parameter in order to obtain a glow-like discharge without arcing. In order to obtain a stable glow-like discharge, it is necessary to adjust the impulse waveform so that the time interval is several microseconds or less, although it depends on the initial supply amount of electrons.

According to the present invention, since a dielectric material is not interposed between the main electrodes, it is possible to apply a high voltage, and the gap between the main electrodes can be reduced to 10 times or more than in the case of silent discharge, that is, 5 cm.
This makes it possible to obtain a large reaction volume. Due to the initial supply of electrons, the interelectrode voltage is very low compared to the size of the interelectrode gap, for example, a gap of 2 cm.
Glow discharge can be obtained at 17kV for
There is no risk of arc discharge caused by applying 60kV. Furthermore, the device can be operated by abundantly supplying initial electrons through preliminary discharge or ultraviolet irradiation, and a stable glow-like discharge can be obtained. Therefore, it is easy to use as an ozone generator, has a large reaction volume, and
It is possible to provide a high-yield ozone generation method that has performance superior to conventional silent discharge devices, such as low voltage drive and highly efficient ozone generation. In the above embodiments, the application of high voltage was explained using direct current application, but it goes without saying that alternating current application is also possible by providing the third electrode on both electrode sides.

[Brief explanation of the drawing]

Figures 1 to 3 are basic configuration diagrams of a conventional ozone generator, Figure 4 is a fractured cross-sectional view of a dielectric electrode of a conventional ozone generator, and Figure 5 is a fracture of a conventional ozone generator. A cross-sectional view, FIG. 6 is a basic configuration diagram of Example 1 of the ozone generator according to the present invention, FIG. 7 is a partial cross-sectional view of the third electrode of Example 1, and FIG.
The figure is a diagram showing the principle configuration of Example 2 according to the present invention. 41, 61... negative electrode, 42... third electrode, 4
4,64...Positive electrode, 45,65...Gap, 47,
67...Pulse generator.

Claims (1)

[Claims] 1. A method for generating ozone by applying a pulsed voltage between main electrodes disposed opposite each other to generate a glow discharge, and passing a gas containing oxygen between the electrodes, A method for generating ozone, characterized in that initial electrons are supplied from a third electrode in synchronization with a voltage rise between the main electrodes arranged to face each other to cause a preliminary discharge. 2. In the method described in claim 1,
Initial electron supply was achieved by supplying a divided voltage between the main electrodes via a coupling capacitor to an electrically insulating tubular third electrode buried in multiple grooves provided near the surface of one of the main electrodes. An ozone generation method characterized by: 3. In the method described in claim 1,
The third electrode is a mesh-shaped electrode, and an ultraviolet ray generator installed behind the third electrode irradiates ultraviolet rays in pulses in synchronization with the rise of the voltage between the main electrodes to cause a preliminary discharge. Characteristic ozone generation method.