JP2007254223A - Ozone generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ozone generating apparatus having good ozone generation (power) efficiency, and more specifically to provide an ozone generating apparatus which can reduce the amount of cooling water and is simple in the construction of the power source, and in which a stable operation is possible. <P>SOLUTION: In an ozone generating apparatus which has a plasma generation part provided with a pair of opposing electrodes 2, 2' and solid dielectric layers 3, 3' that are arranged on the opposing surface of at least one of the electrodes of the pair of electrodes 2, 2', and which generates ozone from a raw material gas 6 by supplying the raw material gas 6 that contains oxygen into the space 10 between the pair of electrodes 2, 2', and by using discharge generated by impressing pulsed voltage between the pair of electrodes 2, 2', the ozone generating apparatus uses a gap between the pair of electrodes 2, 2' of not larger than 0.4 mm, a pulse duration of the pulsed voltage of not longer than 10 μsec, and a value of input power/gas flow volume of at least 30 W×min/NL. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ozone generator having good generation efficiency (power efficiency), and more particularly to an ozone generator that reduces cooling water, has a simple power supply configuration, and is capable of stable operation.

  Conventionally, ozone generators have been used for applications such as bleaching, sterilization, and sterilization by generating ozone from plasma generated in a space. As methods for generating ozone, methods described in Patent Document 1 and Patent Document 2 are known.

  In Patent Document 1, a dielectric barrier discharge type using a high-frequency power source is described. In this method, the current waveform is a sine wave, and a large amount of heat is generated because the power consumed in the discharge space and the dielectric increases. Further, when the temperature of the raw material gas rises due to heat generation, ozone is decomposed by heat and the yield of ozone is reduced. In order to prevent a decrease in the yield of ozone due to this heat generation, it is necessary to increase the discharge area in order to reduce the power density, leading to an increase in the size of the apparatus.

Patent Document 2 discloses a current type inverter system. In this method, since the rising steepness of the generated voltage is low, the ozone generation efficiency is low. Further, since the pulse width is long (cannot be shortened), there is a problem that ozone generation efficiency is low. Furthermore, since the number of semiconductor elements used in the inverter circuit is large, there are problems that the power loss is large and the power supply efficiency is low, and that the switching element is likely to be destroyed when an arc occurs.
Japanese Patent No. 3545257 Japanese Patent No. 3971100

  The present invention has been made in view of such conventional problems. The purpose is to provide an ozone generator with good generation efficiency (power efficiency). More specifically, an ozone generator with reduced cooling water, simple power supply configuration and stable operation is provided. There is to do.

  As a result of intensive studies to solve the above problems, the following ozone generator is provided.

[1] A plasma generation unit including a pair of electrodes facing each other and a solid dielectric layer disposed on a facing surface of at least one of the pair of electrodes, and between the pair of electrodes In an ozone generator for generating ozone from a source gas using a discharge generated by supplying a source gas containing oxygen into the space and applying a pulsed voltage between the pair of electrodes, a gap between the electrodes The ozone generator is characterized in that: 0.4 mm or less, pulse duration of the pulse voltage is 10 μsec or less, and input power / gas flow rate is 30 W · min / NL or more.

[2] The ozone generator according to [1], wherein an induction accumulation type pulse power source is used as the pulse power source for generating the pulse voltage.

[3] The ozone generator according to [2], wherein an electrostatic induction thyristor element is used as a switching element of a pulse power source for generating the pulse voltage.

  The ozone generator of the present invention is excellent in ozone generation efficiency (power efficiency), has the effect of reducing the amount of cooling water required when ozone is generated and reducing the size of the cooling device, and has a simple power supply configuration. It has an excellent effect that stable operation is possible.

  Next, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments, and the knowledge of those skilled in the art can be used without departing from the scope of the present invention. It goes without saying that various changes, modifications, and improvements can be added based on the above.

  FIG. 1 is a schematic explanatory view showing the configuration of an embodiment (Example 1) of an ozone generator according to the present invention. In FIG. 1, reference numeral 1 denotes a pulse power supply, and a voltage is applied to the two metal electrodes 2 and 2 ′ opposed to each other by the pulse power supply 1. There is a space 10 between the metal electrodes 2 and 2 ′ with the dielectrics 3 and 3 ′ interposed therebetween, and the source gas 6 passes through the space 10. At that time, plasma is generated in the space 10 by the voltage applied to each electrode 2, 2 ′. This plasma reacts with the source gas 6 to generate an ozonized gas 7. At this time, the heat generated by the electric power applied to the metal electrodes 2 and 2 'is cooled by the water-cooled heat sinks 5 and 5' provided with the insulating plates 4 and 4 'interposed therebetween.

  The solid dielectric layer used in the ozone generator of the present invention and shown as dielectrics 3 and 3 ′ in FIG. 1 may have a dielectric constant of about 10 to 20, such as alumina, zirconia, cordierite, etc. It is not limited to these. The thickness of the solid dielectric layer is not particularly limited, but is about 0.2 to 3 mm, for example.

In the ozone generator of the present invention,
(1) The gap between the two metal electrodes 2 and 2 'facing each other up and down is 0.4 mm or less, preferably 0.3 mm or less,
(2) The pulse duration of the applied pulse voltage is 10 μsec or less,
(3) The value of the power / gas flow rate, which is the ratio between the input (applied) power and the gas flow rate, is 30 W · min / NL or more,
It is characterized by satisfying these three conditions.

  Thus, in the present invention, ozone can be efficiently generated by configuring the gap (interval) between the electrodes in the barrier discharge to be very narrow. In addition, since the pulse duration (pulse width) is narrowed, power loss is low and heat generation is suppressed, so that it is not necessary to increase the electrode area as in the conventional ozone generator. Thus, the device can be reduced in size.

Moreover, it is preferable to use an induction storage type pulse power supply as a pulse power supply of the ozone generator of the present invention.
A pulse power supply using an SI thyristor will be described with reference to FIG. 2 are a DC power supply 13, a load 11, a high voltage 12, a capacitor 18, a diode 17, a pulse transformer 8, an SI thyristor 9, and an FET 10, and an SI thyristor anode 14 and a cathode, respectively. 15 means the gate 16.

  In the pulse power source of the ozone generator according to the present invention, the high voltage 12 can be obtained by accumulating and releasing energy in the inductive component of the pulse transformer 8. Further, as shown in FIG. 2, by using the SI thyristor 9, the current resistance can be increased as compared with the prior art, and a pulse waveform with high agility can be obtained. Further, in addition to the fact that the SI thyristor 9 itself is not easily broken, the number of elements is reduced, and the circuit itself can be simply assembled, and the stability of operation is further increased.

Next, it demonstrates still more concretely using an Example.
(Example 1)
An ozone generator having the configuration shown in FIG. 1 was used.
1. Ozone generating part Two alumina plates (dielectrics 3, 3 ′, dimensions: 90 × 50 × 1 mm) having a silver metallized layer (metal electrodes 2, 2 ′) formed on one surface were used. Although not shown, two spacers (dimensions: 10 × 50 mm) for adjusting the discharge gap (interval) were used. The spacers were made of Teflon (registered trademark), and five types with thicknesses of 0.1 / 0.2 / 0.3 / 0.5 / 1.0 mm were prepared in order to adjust the gap (interval).

A structure in which insulating plates (made of alumina) 4, 4 ′ and water-cooled heat sinks 5, 5 ′ are sandwiched between both outer sides of the pair of metal electrodes 2, 2 ′.
The gap space 10 was sealed, and piping for introducing and discharging the source gas 6 was attached to the outside.

2. Source gas High purity oxygen gas (purity: 99.999%) was used. The gas flow rate was 1 to 5 NL / min, and the gas pressure was 0.25 MPa.

3. Discharge Power Supply An inductive accumulation type pulse power supply as shown in FIG. 2 was used as the pulse power supply 1 for discharge. The SI thyristor element 9 is used as the main switch element of this dielectric storage type pulse power supply.

  The pulse width was about 1 μsec as shown in FIG. However, the pulse width referred to here is defined by the half width of the voltage peak value. The pulse frequency was set to 30 kHz at maximum.

  The maximum input power was 300 W (one pulse energy: 10 mJ × 30 kHz). The pulse voltage is 8 kV.

  Under the above conditions, the ozone concentration of the exhaust gas was measured with an ozone concentration meter (EG-600 manufactured by Ebara Corporation).

  FIG. 4 shows the result of ozone concentration with respect to (input power / gas flow rate). From this result, it was found that high-concentration ozone can be obtained under conditions where the input power / gas flow rate is large and the gap between electrodes is narrow. In particular, high-concentration ozone can be obtained under conditions where the input power per unit gas flow rate is 30 W · min / NL or more and the gap interval is 0.3 mm or less. Regarding the input power, if it is 400 W · min / NL or more, the calorific value becomes large, and therefore, a smaller value is preferable. The narrower the gap (interval) between the electrodes, the higher the generated ozone concentration with respect to the input power / gas flow rate. However, the minimum value of the interelectrode gap (interval) is 0.05 mm in the design of the apparatus.

(Example 2)
In Example 1, since it was found that high-concentration ozone can be obtained by narrowing the gap (interval) between the electrodes, the gap (interval) between the electrodes was set to 0.1 mm and the unit time per unit time when the pulse width was changed. The amount of ozone generated was confirmed.
Among the ozone generators, as the ozone generation part structure, one type (dimension: 10 × 50 × 0.1 mm) having a thickness of 0.1 mm was used as two spacers for adjusting the discharge gap (interval). Except this, it was the same as Example 1. The purity, gas flow rate, and gas pressure of the used raw material gas were the same as those in Example 1.

  As the discharge power source, an inductive accumulation type pulse power source as shown in FIG. 2 was used in the same manner as in Example 1, but the pulse transformer primary side inductance was adjusted to set the pulse width to 1 μsec and 10 μsec. Further, the amount of ozone generation was measured under the conditions of pulse widths of 50 μsec and 100 μsec using a closing circuit type pulse power supply whose circuit configuration is shown in FIG. An IGBT element 21 was used as a switching element of the closing circuit type pulse power supply of FIG.

Pulse widths of about 1 μsec, 10 μsec, 50 μsec, and 100 μsec were used. The maximum pulse frequency was 30 kHz.
The input power was 300 W maximum (1 pulse energy: 10 mJ × 30 kHz), and the pulse voltage was 8 kV.

  FIG. 6 shows a result of “ozone generation amount with respect to pulse width” when the input power is 300 W. From this result, it was found that the amount of ozone generation increased under the condition of a short pulse width. In particular, a high ozone generation amount can be obtained under the condition of a pulse width of 10 μsec or less. The smaller the pulse width, the larger the amount of ozone generated, which is preferable. However, the lower limit of the pulse width is about 0.05 μsec for circuit design.

  The ozone generator of the present invention has high ozone generation efficiency (power efficiency), can reduce cooling water, has a simple power supply configuration and can be stably operated, and thus has great industrial utility value. is there.

It is typical explanatory drawing which shows the structure of one Example (Example 1) of the ozone generator which concerns on this invention. FIG. 3 is a circuit diagram showing a configuration of a pulse power supply used in Example 1. 3 is a graph showing a pulse waveform in Example 1. It is a graph which shows the ozone concentration in Example 1, and the relationship of (input electric power / gas flow rate). It is a circuit diagram which shows the structure of the closing system pulse power supply used for Example 2. FIG. It is a graph which shows the relationship between the pulse width in the ozone generator of Example 2, and the amount of ozone generation.

Explanation of symbols

1: pulse power source, 2, 2 ′: a pair of metal electrodes, 3, 3 ′: dielectric, 4, 4 ′: insulating plate, 5, 5 ′: water-cooled heat sink, 6: source gas, 7: ozonized Gas, 8: Pulse transformer, 9: SI thyristor, 10: FET, 11: Load, 12 ,: High voltage, 13: DC power supply, 14: Anode, 15: Cathode, 16: Gate, 17: Diode, 18: Capacitor , 19: load, 20: capacitor, 21: IGBT, 22: high-voltage power supply.

Claims (3)

A plasma generation unit including a pair of electrodes facing each other and a solid dielectric layer disposed on a facing surface of at least one of the pair of electrodes, and in a space between the pair of electrodes; In an ozone generator for generating ozone from a source gas using a discharge by supplying a source gas containing oxygen and applying a pulsed voltage between the pair of electrodes,
An ozone generator having a gap between the electrodes of 0.4 mm or less, a pulse duration of the pulse voltage of 10 μsec or less, and a value of input power / gas flow rate of 30 W · min / NL or more.   2. The ozone generator according to claim 1, wherein an induction storage type pulse power source is used as the pulse power source for generating the pulse voltage.   The ozone generator according to claim 2, wherein an electrostatic induction thyristor element is used as a switching element of a pulse power source for generating the pulse voltage.

Images