Ozone Generator

Abstract

To provide an ozone generation device in which, when any of a plurality of discharge tubes in an ozone generator is broken, a fuse corresponding to the broken discharge tube is made to be easily blown.SOLUTION: An ozone generation device according to an embodiment comprises: a metal electrode; discharge tubes which are connected in parallel with each other; a discharge gap which is formed between the metal electrode and the discharge tubes and into which a raw material gas including oxygen flows; a fuse which is connected in series with each of the discharge tubes and which is blown on flowing of an electric current thereinto to thereby shut off electric current passage to the discharge tubes; a power source part which applies voltage to the discharge tubes to carry out discharge with the raw material gas in the discharge gap to generate ozone; and a capacitor which is connected in parallel with the discharge tubes. When abnormality occurs in any of the discharge tubes, a short-circuit current flows from the capacitor to the fuse connected in series with the discharge tubes in which the abnormality occurs, thereby blowing the fuse.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to an ozone generator. [Background technology]

[0002] Conventionally, there has been an ozone generator in which, when any of a plurality of discharge tubes in an ozone generator is damaged, a large current flows through a fuse corresponding to the damaged discharge tube, cutting off the power supply to that discharge tube while allowing ozone generation to continue using the remaining discharge tubes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5677344 [Patent Document 2] Patent No. 5439556 [Patent Document 3] Patent No. 6526581 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, for example, in the case of a small-scale ozone generator having a small number of discharge tubes, there was a problem that the current flowing through the fuse corresponding to a broken discharge tube was relatively small, making the fuse difficult to blow.

[0005] Therefore, an object of the present invention is to provide an ozone generator that, when any one of a plurality of discharge tubes in the ozone generator is broken, makes it easy to blow a fuse corresponding to the broken discharge tube. [Means for solving the problem]

[0006] An ozone generator according to an embodiment includes a metal electrode, a plurality of discharge tubes connected in parallel to each other, a discharge gap formed between the metal electrode and the discharge tubes and into which a raw material gas containing oxygen flows, a fuse connected in series to each of the discharge tubes and cutting off current to the discharge tube by cutting off the fuse when a current flows through the fuse, a power supply unit that applies a voltage to the discharge tubes to generate ozone by discharging the raw material gas in the discharge gap, and a capacitor connected in parallel to the plurality of discharge tubes. When an abnormality occurs in any of the plurality of discharge tubes, a short-circuit current flows from the capacitor to the fuse connected in series to the discharge tube in which the abnormality occurs, cutting off the fuse. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is an explanatory diagram of the operating principle of the ozone generator according to this embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a schematic configuration of the ozone generator according to this embodiment. [Diagram 3] FIG. 3 is a diagram showing the ozone generator according to this embodiment in the form of an equivalent circuit. [Figure 4] FIG. 4 is an explanatory diagram of the operation of the ozone generator according to this embodiment when the discharge tube is broken. [Diagram 5] FIG. 5 is a graph showing electrical characteristics during normal operation of the ozone generator according to this embodiment. [Figure 6] FIG. 6 is a graph showing electrical characteristics when an abnormality occurs in the ozone generator according to this embodiment. [Figure 7] FIG. 7 is a diagram showing an equivalent circuit of an ozone generator according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an example of an ozone generator according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0009] First, the operating principle of a single-tube (one discharge tube) ozone generator will be described with reference to FIG. 1, and then the schematic configuration of a multiple-tube (multiple discharge tubes) ozone generator will be described with reference to FIG.

[0010] 1 is an explanatory diagram of the operating principle of an ozone generator A according to this embodiment. The ozone generator A includes an ozone generator 1, a high-voltage power supply 2, a power supply device 3, a fuse 4, and a high-voltage power supply 5. The ozone generator 1 includes a discharge tube 10, and generates ozone by applying an AC voltage to an electrode 11 of the discharge tube 10. Specifically, the ozone generator 1 includes the discharge tube 10, an electrode 11 attached to the discharge tube 10, a metal electrode 12, a spacer 13, and a discharge gap 14.

[0011] Discharge tube 10 is formed in a cylindrical shape from a dielectric material such as glass or ceramic, with one end open and the other end U-shaped, and has electrode 11 on the inner surface of which a conductive metal (such as stainless steel) is evaporated. Electrode 11 is connected to high-voltage power supply 5.

[0012] Metal electrode 12 is a cylindrical electrode made of, for example, stainless steel and coaxial with electrode 11. Metal electrode 12 has a plurality of spacers 13 for forming a discharge gap 14 between electrode 11 and metal electrode 12. Spacers 13 are protrusions that form discharge gap 14 having a width of, for example, about 0.3 to 1.3 mm. A raw material gas containing oxygen flows into discharge gap 14.

[0013] The high-voltage power supply 2 inputs an AC voltage from a commercial power supply, and applies a high AC voltage to the power supply device 3. When a high-frequency high voltage is applied from the power supply device 3 to the discharge tube 10, a dielectric barrier discharge occurs in the discharge gap 14, and ozone is generated from the source gas. In addition, the heat generated by the dielectric barrier discharge is absorbed by the cooling water W.

[0014] Here, Fig. 2 is a diagram showing an example of a schematic configuration of an ozone generator A according to this embodiment. In order to increase the amount of ozone generated compared to the single-tube configuration shown in Fig. 1, a configuration in which multiple tubes are provided in one housing is often used as shown in Fig. 2. Oxygen or dry air, which is a raw material gas, is introduced into the housing 112 from the raw material gas inlet 21a and fills the gas inlet side space 111a.

[0015] The source gas is then introduced into the discharge gap 14 formed by the discharge tube 10, the end plate 151 (metal electrode), etc., where oxygen molecules are dissociated into oxygen atoms by the dielectric barrier discharge and are converted into ozonized gas by combining with other oxygen molecules. The ozonized gas passes through the discharge gap 14 and fills the outlet side space 111b formed by the housing 113 and the end plate 152, and is taken out from the ozonized gas outlet 21b.

[0016] A fixed electrode 18 is provided inside the discharge tube 10 via stainless steel wool 19. A fuse 4 is provided corresponding to each discharge tube 10. A high-frequency high voltage is applied to the fuse 4 from the power supply device 3, and a voltage equal to or higher than the discharge voltage is applied to the discharge gap 14 by this high-frequency high voltage, thereby generating a dielectric barrier discharge in the discharge gap 14. Heat generated by the dielectric barrier discharge is introduced from the cooling water inlet 21c and absorbed in the closed space 17 by the cooling water. The cooling water is then discharged to the outside from the cooling water outlet 21d. In this way, the temperature rise of the raw material gas in the discharge gap 14 is suppressed, and ozone can be obtained at a high concentration and a high yield. The generated ozone is used for water treatment, such as deodorization, decolorization, and sterilization of the water to be treated.

[0017] The fuse 4 cuts off the overcurrent when the corresponding discharge tube 10 is damaged by dielectric breakdown. Then, by disconnecting the damaged discharge tube 10, it becomes possible to continue operation without stopping, and a stable supply of ozone can be achieved.

[0018] Next, an equivalent circuit of the ozone generator A according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram showing the ozone generator A according to this embodiment in the form of an equivalent circuit. The power supply device 3 includes a converter 31, a capacitor Cs, an inverter 32, a transformer Tr, a coil Lr, and a capacitor Cp.

[0019] The converter 31 converts the high AC voltage received from the high voltage power supply 2 into a DC voltage. The capacitor Cs is disposed between the converter 31 and the inverter 32, and serves to perform a role of rectification and the like.

[0020] The inverter 32 converts the DC voltage into an AC voltage of a preset frequency (for example, about 1 kHz to 5 kHz) and outputs it. The coil Lr is disposed between the transformer Tr and the ozone generator 1, and plays a role of compensation, etc. The transformer Tr boosts the AC voltage output from the inverter 32 to a high voltage.

[0021] The fuses 4 are connected in series to the respective discharge tubes 10, and cut off the current to the discharge tubes 10 by blowing them when a current flows through them.

[0022] In the equivalent circuit of the ozone generator 1, the capacitances Cg (Cg1 to Cg3) of the electrodes 11 of the discharge tube 10 and the capacitances Co (Co1 to Co3) of the discharge gap 14 are connected in series. The discharge gap voltage Vo is the discharge sustaining voltage V * When the discharge voltage exceeds 1 V, a barrier discharge occurs in the discharge gap 14. Since the barrier discharge has a constant voltage characteristic, the discharge sustaining voltage V * This characteristic is that the breakdown voltage of the Zener diode is the sustaining discharge voltage V * Since this is equivalent to the characteristic that the discharge section has a capacitance of 1, the equivalent circuit of the discharge section is represented by a Zener diode 15. Since the discharge section is a capacitive load, in order to bring the power factor closer to 1, the coil Lr is connected in series or parallel to cancel the capacitance of the discharge section.

[0023] If the discharge tube 10 is damaged, that is, if a pinhole with a diameter of about 1 mm is formed in the discharge tube 10, a short-circuit current will flow, and first, the electric charge stored in the capacitance Co and capacitance Cg of the other normal, undamaged discharge tubes 10 will flow into the damaged discharge tube 10. In a large-capacity ozone generator A (i.e., many discharge tubes 10), this will cause an overcurrent to flow, causing the fuse 4 connected to the damaged discharge tube 10 to melt and automatically disconnect the damaged discharge tube 10.

[0024] However, in an ozone generator A with a small capacity (i.e., a small number of discharge tubes 10), this short-circuit current alone may not be sufficient to blow the fuse 4, and a current flow from the power supply device 3 may be necessary. Also, a protection circuit provided in the power supply device 3 may suppress the current flow from the power supply device 3, making it impossible to blow the fuse 4. Conventionally, in such cases, it has been difficult to operate the ozone generator A without stopping it, and there has been a problem in that stable operation is not possible.

[0025] This point will be explained with reference to Fig. 7. Fig. 7 is a diagram showing an equivalent circuit of an ozone generator A' according to a comparative example (prior art). Fig. 7 differs from Fig. 3 in that it does not have the capacitor Cp. In this case, as described above, in an ozone generator A' having a particularly small capacity (i.e., a small number of discharge tubes 10), when a discharge tube 10 is damaged, the short-circuit current from the other discharge tubes 10 alone may not be sufficient to blow the fuse 4.

[0026] Therefore, hereinafter, a technique for making it easier to cut the fuse 4 corresponding to a damaged discharge tube 10 when any of the multiple discharge tubes 10 in the ozone generator 1 is damaged will be described.

[0027] 3, a capacitor Cp is connected in parallel to a plurality of discharge tubes 10. When any of the plurality of discharge tubes 10 is damaged, a short-circuit current automatically flows from the capacitor Cp to the fuse 4 corresponding to the damaged discharge tube 10, cutting the fuse 4, thereby enabling ozone to be generated stably and reliably.

[0028] In recent years, the cost of ozone generator A has been reduced, and the discharge power density has been increased from the conventional 1.5 kW / m 2 From 2.5 to 4kW / m 2 In recent years, the number of discharge tubes 10 has been reduced by increasing the rated current to 0.3 A. Accordingly, the current value flowing through each discharge tube 10 has become higher. For this reason, while conventional fuses 4 have a rated current of 0.3 A, fuses 4 with a rated current of 0.7 to 1 A have recently become necessary. To prevent fuses 4 from melting at the rated current, measures have been taken such as making the element of fuse 4 (hereinafter also referred to as "fuse element") thicker.

[0029] When the discharge tube 10 is broken, the fuse element of the fuse 4 melts due to the short-circuit current, and the metal of the fuse element melts to generate arc plasma. At the moment when the current of the power supply frequency becomes zero voltage, the arc voltage rises and the fuse 4 is cut.

[0030] The energy Uft required to melt the fuse element is expressed by the following equation (1): Uft = C ρ πr 2 ·L·(T m -T r )...Equation (1)

[0031] C: Specific heat of the fuse element ρ: Density of the fuse element π: Pi r: Radius of the cross section of the thin wire part of the fuse element L: Length of thin wire of fuse element T m : Melting point of fuse element T r : The temperature of the fuse element during normal operation of the ozone generator

[0032] Equation (1) is for the case where the fuse element is one type of thin wire. On the other hand, in order to cut off a large current, the fuse 4 may be configured by combining two or more types of fuse elements. In other words, in a relatively small ozone generator A, the fuse element is melted at the thin wire portion, but in a relatively large ozone generator A, the combined thicker fuse element is melted to gain distance, and the arc discharge of the metal vapor of the fuse element is extinguished at the zero current point. In that case, the energy Uft required to melt the fuse element is expressed by the following equation (2). Uft = Ra / R C ρ πr 2 ·L·(T m -T r )...Equation (2)

[0033] Ra: The total resistance of the fuse element consisting of the thick and thin wire parts R: Resistance of the thin wire of the fuse element

[0034] If the fuse element is a single type of thin wire portion, Ra=R, so Ra / R=1, and equation (2) becomes the same as equation (1).

[0035] In addition, the fuse element may be configured to use two or more thin wires in parallel instead of one thin wire section. In this case, if the number of parallel thin wire sections is n, the energy Uft required to melt the fuse element is expressed by the following formula (3). Uft = Ra / R C ρ n πr 2 ·L·(T m -T r )...Equation (3)

[0036] If the fuse element has a single thin wire, n = 1, and formula (3) becomes the same as formula (2). There are also cases where the thin wire of the fuse element is divided and a thicker wire is also divided and combined, in which case the total length of the divided thin wires should be taken as L.

[0037] Moreover, the damage to the discharge tube 10 is due to dielectric breakdown of the glass or ceramic that is the material of the discharge tube 10. Dielectric breakdown occurs when the voltage is high, so dielectric breakdown occurs when the high frequency voltage is close to the zero-peak voltage Vop.

[0038] Ozone Generator A C L (VQ (applied voltage V: transferred charge Q) Lissajous figure slope) and I 2 The relationship between current and time (I: current value, t: time) is expressed by the following formula. Generally, I 2 The value of t is 1 / (√3)Io if the temperature rise over time is exponential. 2 Here, Io is the peak value of the inrush current to the fuse 4, and to is the time constant of the decay waveform. Conventionally, this formula has been used to evaluate the blowing of the fuse 4.

[0039] 4 is an explanatory diagram of the operation when the discharge tube 10 in the ozone generator A according to this embodiment is broken. By providing a capacitor Cp in parallel with the ozone generator 1 for the output of the high-voltage power supply 2, it becomes possible to blow the fuse 4 corresponding to the broken discharge tube 10. As shown in FIG. 4, when one discharge tube 10 (marked with an x ​​in FIG. 4) is broken, the short-circuit current is added with the current flowing in from the capacitor Cp in addition to the current flowing in from the healthy discharge tube 10, so that it becomes possible to blow the fuse 4 even in a small-capacity ozone generator A in which the fuse 4 cannot be blown by the current flowing in from the healthy discharge tube 10 alone.

[0040] If the capacitance of the capacitor Cp connected in parallel is Cp, the total electrostatic energy Uo is given by equation (4). Uo=1 / 2(C L +C p )V op 2 -1 / 2(C t +C p )V arc 2 ...Equation (4)

[0041] C t: Series capacitance of the dielectric capacitance Cg of the discharge tube and the capacitance Co of the discharge gap V arc : Arc voltage of fuse element vapor when fuse melts

[0042] By designing the capacitor Cp so that Uo is greater than Uft, it becomes possible to reliably blow the fuse 4 in the event that the discharge tube 10 is damaged. In other words, it is sufficient to satisfy the following formula (5). 1 / 2(C L +Cp)V op 2 -1 / 2(C t +C p )V arc 2 > Ra / R C ρ n πr 2 ·L·(T m -T r )...Equation (5)

[0043] In addition, the capacitance C p The larger the capacitance C, the more the current capacity of the inverter 32 needs to be increased. p I want to make it as small as possible. Also, V arc is several kV from actual measurements, and V op is, for example, about 11 kV as a voltage at which abnormal discharge does not occur at the end of the discharge tube 10.

[0044] In this manner, according to the ozone generator A of this embodiment, the fuse 4 can be reliably blown, enabling stable generation of ozone.

[0045] Fig. 5 is a graph showing the electrical characteristics of the ozone generator A according to this embodiment during normal operation. Fig. 5 shows the voltage and current waveforms when a resonant circuit is used for the high-voltage power supply 2. The voltage waveform is approximately a sine wave because a reactor (coil Lr) is provided in series as a resonant circuit to cancel the electrostatic capacitance of the load, which acts as a filter and amplifies only the frequency component of the resonant frequency. The current waveform has corners due to the current flowing through the capacitor Cp connected in parallel to the load of this embodiment.

[0046] Fig. 6 is a graph showing the electrical characteristics of the ozone generator A according to this embodiment when an abnormality occurs. As shown in Fig. 6, when the discharge tube 10 is broken (time t0), a short-circuit current flows, and the voltage drops as a result, resulting in a waveform with a reduced voltage. Even if a short circuit occurs, it can be seen that the current is limited by the impedance of ωL due to L of the reactor (coil Lr) provided for resonance. For the pulse-like waveform that appears in the current waveform, 1 / (√3)Io 2 The power of to flows into fuse 4. By appropriately selecting the capacitance Cp of the capacitor Cp connected in parallel with the load, fuse 4 can be melted and the circuit can be broken. Note that after time t0, the voltage becomes 0 at time t1.

[0047] In a circuit using a resonant circuit to which this embodiment is applied, the energy to melt the fuse 4 should be supplied from the capacitance of the ozone generator A and the stored energy of the added capacitor Cp. The electrostatic energy Uc of a healthy discharge tube 10 in a small-capacity ozone generator A is expressed by the following formula (6). Uc=1 / 2C L V op 2 -1 / 2C t V arc 2 ...Equation (6)

[0048] In large-capacity ozone generator A, Uc is larger than Uft, so if a discharge tube 10 is damaged, fuse 4 melts down due to the short-circuit current flowing from many healthy discharge tubes 10, and the current of the damaged discharge tube 10 is cut off. However, in small-capacity ozone generator A, without capacitor Cp, Uc is smaller than Uft, and the short-circuit current is small, so fuse 4 may not melt down due to the current from healthy discharge tubes 10 alone.

[0049] Thus, according to the ozone generator A of this embodiment, by providing the capacitor Cp in parallel with the ozone generator 1, when any of the multiple discharge tubes 10 in the ozone generator 1 is damaged, a large current flows through the fuse 4 corresponding to the damaged discharge tube 10, making it easy to blow the fuse. This makes it possible to automatically blow the fuse 4 when the discharge tube 10 is damaged, enabling stable ozone generation.

[0050] Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. This embodiment is included in the scope and gist of the invention, and is included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0051] 1... ozone generator, 2... high voltage power supply, 3... power supply device, 4... fuse, 5... high voltage power supply, 10... discharge tube, 11... electrode, 12... metal electrode, 13... spacer, 14... discharge gap, 17... closed space, 18... fixed electrode, 19... stainless steel wool, 112... housing, 113... housing, 151... end plate, 152... end plate, A... ozone generator

Claims

1. A metal electrode; A plurality of discharge tubes connected in parallel to each other; a discharge gap formed between the metal electrode and the discharge tube, into which a raw material gas containing oxygen is introduced; a fuse connected in series to each of the discharge tubes and cutting off current to the discharge tubes by causing a current to flow through the fuse; a power supply unit that applies a voltage to the discharge tube in order to generate ozone by discharging the raw material gas in the discharge gap; a capacitor connected in parallel with the plurality of discharge tubes, storing energy by a voltage applied by the power supply unit, and supplying the stored energy to the fuse connected in series to the discharge tube in which an abnormality occurs, when an abnormality occurs in any of the plurality of discharge tubes; The capacitor has a capacitance sufficient to store the energy required to blow the fuse.

2. An ozone generator as described in claim 1, wherein the capacitance of the capacitor satisfies the following formula. 1 / 2(C Ｌ +C ｐ )V ｏｐ ２ -1 / 2(C ｔ +C ｐ )V ａｒｃ ２ > R / R・C・ρ・n・πr ２ ・L・(T ｍ -T ｒ ) C Ｌ : VQ (applied voltage V: transferred charge Q) slope of Lissajous figure C ｐ : Capacitance of the capacitor V ｏｐ : Zero-peak voltage of applied voltage C ｔ :Serial capacitance of the capacitance Cg of the dielectric of the discharge tube and the capacitance Co of the discharge gap V ａｒｃ : Arc voltage of fuse element vapor when fuse melts Ra: Total resistance of the fuse element consisting of the thick wire portion and the thin wire portion R: Resistance of the thin wire of the fuse element C: Specific heat of the fuse element ρ: Density of the fuse element n: Number of thin wires in the fuse element π: pi r: Radius of the cross section of the thin wire part of the fuse element L: Length of the thin wire part of the fuse element T ｍ : Melting point of fuse element T ｒ : Temperature of the fuse element during normal operation of the ozone generator

3. An ozone generator as described in claim 1, wherein the capacitance of the capacitor satisfies the following formula. 1 / 2 (C L +C p )V op 2 -1 / 2 (C t +C p )V arc 2 > C・ρ・πr 2 ・L・(T m −T r ) C L : VQ (applied voltage V: transferred charge Q) slope of Lissajous figure C p : Capacitor capacitance V op : Zero-peak voltage of applied voltage Ct: Series capacitance of the capacitance Cg of the dielectric of the discharge tube and the capacitance Co of the discharge gap V arc : Arc voltage of the fuse element vapor when the fuse melts C: Specific heat of the fuse element ρ: Density of the fuse element π: pi r: Radius of the cross section of the thin wire part of the fuse element L: Length of the thin wire part of the fuse element Tm: melting point of the fuse element Tr: Temperature of the fuse element during normal operation of the ozone generator

4. An ozone generator as described in claim 1, wherein the capacitor is circuit-arranged so that, if an abnormality occurs in any of the plurality of discharge tubes, the stored energy is automatically supplied to the discharge tube in which the abnormality occurs.

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