JPH08275999A - Deodorizing method and deodorizing device by sawtooth wave corona discharge - Google Patents

Abstract

PURPOSE: To reduce the dielectric resistances of a DC high voltage generating device and a discharge gap, and attain a smaller size and a lighter weight by applying a sawtooth waveform high voltage having a discharge electrode as positive electrode and a counter electrode as negative electrode between the electrodes of a deodorizing device, and applying the following high voltage before the voltage between the electrodes is reduced less than a specified value. CONSTITUTION: In a deodorizing device 7 for performing a deodorization in a plasma space generated by a corona discharge by high voltage pulse, a high voltage pulse having a high peak, for example, 50-25kV is supplied thereto from a high voltage pulse generating device. An AC high voltage obtained by boosting the voltage of AC voltage by a high voltage transformer 3 is full- wave rectified by a high voltage rectifier 4, and the resulting DC high voltage is applied to a spark discharge gap 6 including a rotating discharge terminal in which the gap space is set to 2mm-10mm. The following sawtooth waveform high voltage is applied between electrodes 8, 9 before the high sawtooth waveform high voltage is reduced less than 1/10 of its peak value, whereby a corona discharge is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for reducing deodorization or malodor using plasma generated by streamer corona.

[0002]

2. Description of the Related Art Recently, pollution caused by bad odors is increasing, and a deodorizing method which has been widely used as a method for removing or reducing such bad odors is a method of burning or heating a catalyst to bring it into contact with gas. , A method of passing through a catalytic substance, a method of passing through plasma generated by a high-voltage pulse, or a deodorizing method combining these methods.

First, referring to FIG. 4, a general deodorizing method using a catalyst will be described.
The gas is deodorized by the action of the catalyst through the deodorizing device 22 in which the catalyst is introduced, and the deodorized gas is discharged from the conduit 23. In order to enhance the deodorizing effect, a combustion or heating device 24 for burning or heating the catalyst in the deodorizing device 22 is provided.

Next, a general method of generating plasma and deodorizing by the action of the plasma will be explained with reference to FIG. 5. The odorous gas mixed with odor is introduced into the conduit 21,
In the deodorizing device 22, a plasma space generated by corona discharge due to a high voltage pulse is formed. It is deodorized as it passes through the plasma space and is discharged through conduit 23. A high voltage pulse having a high peak of 150 to 250 kV is supplied from the high voltage pulse generator 25 into the deodorizing device 22.

This point will be described in more detail with reference to FIG. 6. The commercial AC voltage from the commercial AC power supply 1 is controlled by the voltage control device 2, and the controlled AC voltage is supplied to the high voltage transformer 3 as a predetermined AC voltage. Boosted to high voltage.
The AC high voltage is full-wave rectified by the high voltage rectifier 4,
After being smoothed by the high voltage capacitor 5, it is applied to the rotary discharge gap 6 ′. This rotating discharge gap 6 '
Has a pair of fixed discharge terminals 6'a and 6'b and a rotary discharge terminal 6'c and 6'd. Rotating discharge terminals 6'c and 6 '
When d is rotated in the direction of the arrow in the drawing, spark discharge is generated each time the rotary discharge terminals 6'c and 6'd come close to the fixed discharge terminals 6'a and 6'b, and the discharge of the deodorizing device 7 occurs. A high voltage pulse of 150 to 250 kV with the discharge electrode 8 as a positive electrode and the counter electrode 9 as a negative electrode is applied between the electrode 8 and the cylindrical counter electrode 9.

By such a high voltage pulse of 150 to 250 kV, a strong streamer corona is generated from the discharge electrode 8 toward the cylindrical counter electrode 9. The streamer portion is a plasma region in which positive and negative ions are mixed, and when the odorous gas passes through this plasma region, the odor is eliminated or reduced by the plasma chemical reaction. Therefore, in order to enhance the deodorizing effect, it suffices to increase the plasma concentration, and for that purpose, it is necessary to increase the frequency of high voltage pulse generation. For this purpose, the rotational speeds of the rotary discharge terminals 6'c and 6'd of the rotary discharge gap 6'must be practically 1500 rpm or more. To increase the frequency of high-voltage pulse generation, it is sufficient to increase the number of poles at the rotary discharge terminal, but until each ion generated in the gap is reduced to a certain level by each spark discharge, that is, the electrical insulation between the gaps is reduced. Spark discharge cannot be generated in a time interval shorter than the recovery time until recovery. However, in the case of this method, the rotary discharge terminal 6 '
The wind generated by the rotation of c and 6'd blows off a part of the ions in the gap, so that the practical high-voltage pulse is generated at a maximum frequency of about 300 times / second.

As another method of obtaining a high voltage pulse for generating plasma, there is a fixed spark discharge gap method as shown in FIG. In this fixed spark discharge gap method, the fixed spark discharge gap 6 has a fixed distance, usually several tens of millimeters or more. Normally, a high DC voltage of 150 to 250 kV is applied between the gaps separated by several tens of millimeters or more, and spark discharge is intermittently generated. However, unlike the rotary discharge gap type, spark discharge is poorly cut off. Therefore, by connecting the resistor 10 across the load terminals T ₁ and T ₂ , the high voltage pulse is sharply reduced. FIG. 8 shows an example of a high-voltage pulse waveform between the discharge electrode 8 and the counter electrode 9 obtained by the rotary discharge gap type and the fixed spark discharge gap type. In the high voltage pulse waveform, the wave tail length (the time length until the peak value is reduced to half)
Many T _h is very short pulse of several tens to several hundreds of 100 [mu] s.

[0008]

However, each of the above-mentioned methods has the following drawbacks. First of all, the deodorizing method using a catalyst is not used much because the replacement or replenishment due to exhaustion of the catalyst is troublesome and the catalyst replenishment cost is very high.

Next, the deodorizing method using the spark discharge gap is as follows.
150 regardless of rotating gap type and fixed gap type
A high-voltage DC power supply device that outputs up to 250 kV is required, and the price becomes high, and at the same time, the device itself becomes large, and a large amount of cost is required for electrical insulation including safety. In addition, since the frequency of pulse generation cannot be increased so much while using the high-voltage pulse, it is not possible to maintain the plasma region at a high level that is uniform at all times, and thus the deodorization efficiency is not necessarily high. is there.

In addition, especially in the case of the rotating gap type,
While rotating the rotary discharge gap at high speed, 150-2
Since high voltage insulation of 50 kV must be done,
It has a drawback that it is not only large-sized but also has a complicated structure.

Further, in the case of the fixed gap type, since most of the electric power is consumed by the resistor, a resistor having a current capacity is required, and there is a drawback that the power efficiency becomes low. Even if the resistors are connected in this manner, once a large-current spark discharge occurs, the recovery time for recovering the electrical insulation of the air in the gap becomes long, so in practice, the maximum spark frequency is about 150. The number of times per second or less is inevitable, and the time interval between the high voltage pulses is long, so that there is a drawback that the inside of the deodorizing device cannot always be maintained in a high level plasma state.

[0012]

In order to solve the above-mentioned problems, the first aspect of the present invention provides a high voltage with a sawtooth waveform having a discharge electrode as a positive electrode and a counter electrode as a negative electrode between the electrodes of a deodorizing device. The sawtooth corona characterized in that the high voltage of the next sawtooth waveform is applied before the voltage between the electrodes is reduced to about 1/10 or less of the peak value of the high voltage of the sawtooth waveform. A deodorizing method using a discharge waveform is provided.

In order to solve the above-mentioned problems, a second aspect of the present invention is a voltage control device for controlling an AC input voltage,
A high voltage transformer for boosting the AC voltage from the voltage control device, a high voltage rectifier for converting the AC high voltage from the high voltage transformer into a DC high voltage, and between the output terminal and the load terminal of the high voltage rectifier And a spark discharge gap inserted in series to the discharge electrode of the deodorizing device connected to the load terminal, a high voltage of a sawtooth waveform formed by arc discharge intermittently generated in the spark discharge gap. The present invention provides a deodorizing device for generating plasma by applying it to reduce deodorization or bad odor, wherein the spark discharge gap has a gap interval of 2 mm or more and 10 mm or less.

In order to solve the above-mentioned problems, a third aspect of the present invention is a voltage control device for controlling an AC input voltage,
A high voltage transformer for boosting the AC voltage from the voltage control device, a high voltage rectifier for converting the AC high voltage from the high voltage transformer into a DC high voltage, and between the output terminal and the load terminal of the high voltage rectifier And a spark discharge gap inserted in series to the discharge electrode of the deodorizing device connected to the load terminal, a high voltage of a sawtooth waveform formed by arc discharge intermittently generated in the spark discharge gap. A device for generating plasma by applying it to reduce deodorization or malodor,
If the gap of the spark discharge gap is 2 mm or more, 1
(EN) A deodorizing device characterized by generating a sawtooth wave high voltage having a base voltage of a positive electrode at 200 times / second or more by setting it to 0 mm or less.

In order to solve the above-mentioned problems, the fourth aspect of the present invention protects the high-voltage rectifier on the DC output side of the high-voltage rectifier from the high voltage of the opposite polarity generated by the vibration of the spark discharge gap. The deodorizing device according to the second invention 1 or the third invention is provided with an inductance element.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. In FIG. 1, the same symbols as those shown in FIGS. 6 and 7 indicate corresponding members. First, a feature of the present invention is that a fixed spark discharge having a gap interval of less than 12 mm, preferably 2 to 10 mm or less. The gap is used, and by using such a fixed spark discharge gap, it is possible to apply a high voltage of a sawtooth wave that frequently occurs between the electrodes of the deodorizing device, which is significantly lower than in the past. It is possible to generate a dense plasma with a high voltage, and to improve the deodorizing effect even though the device can be made inexpensive and small.

The voltage control device 2 comprises switching elements such as thyristors connected in anti-parallel and a control circuit for controlling conduction of these elements, and applies a desired AC voltage to the primary winding of the high voltage transformer 3. The high voltage transformer 3 may generate a high voltage of several tens kV, which is significantly lower than the high voltage of 150 to 250 kV generated by the conventional high voltage transformer, on the secondary side. Therefore, the high voltage rectifier 4 and the smoothing high voltage capacitor 5 may also have a withstand voltage considering a high voltage of several tens of kV. The fixed spark discharge gap 6 has a pair of spark discharge terminals 6a and 6b, and the interval between the spark discharge terminals 6a and 6b is less than 12 mm, preferably 2 to 10 mm. If the distance between the spark discharge terminals 6a and 6b is less than 2 mm, the stepped portion of the sawtooth wave becomes small, the corona discharge weakens as the voltage decreases, and it is not possible to recover to a strong corona discharge again. However, if the distance exceeds 10 mm, and particularly exceeds 12 mm, the frequency of spark discharge becomes low and the conventional device has a problem. The fixed spark discharge gap 6 starts spark discharge when the voltage between the spark discharge terminals 6a and 6b reaches about several kV, and the secondary vibration of the high voltage transformer 3 is caused by LC oscillation of the inductance L and the capacitance C of the circuit. A voltage considerably higher than the voltage generated between the windings, for example, a voltage of about 80 kV is applied to the positive high voltage output terminal P via the high voltage capacitor 5.
The fixed spark discharge gap is much cheaper and smaller than the rotary spark discharge gap, and because the gap distance is less than 12 mm, it is cheaper and smaller than the fixed spark discharge gap used for conventional deodorization. Is.

In the deodorizing device 7 connected between the high voltage output terminals P and N, the discharge electrode 8 connected to the positive output terminal P and the inner wall connected to the negative output terminal N are preferably cylindrical. It is composed of a counter electrode 9. The counter electrode 9 also functions as a conduit for passing deodorized gas, and the discharge electrode 8 extends at the center of the cylindrical electrode 9. Therefore, when the fixed spark discharge gap 6 generates a spark discharge, a high voltage of several tens of kV or higher is applied to the discharge electrode 8 and the counter electrode 9.
Applied between. Along with this, a strong streamer corona discharge is generated from the discharge electrode 8 to the counter electrode 9, and plasma is generated and filled in the cylindrical counter electrode 9 by the streamer corona discharge. When an odorous gas is passed through the plasma-filled cylindrical counter electrode 9, the odor is decomposed by the chemical reaction of the plasma to deodorize or dilute the odor.

FIG. 2 shows a voltage waveform between the discharge electrode 8 and the counter electrode 9. A strong streamer corona discharge occurs at a point corresponding to each peak value of the waveform, and when the voltage drops to a certain value due to the occurrence of the corona discharge, the fixed spark discharge gap 6 again generates a spark discharge. Repeat this.
Therefore, the fluctuation of the plasma density in the space between the discharge electrode 8 and the counter electrode 9 is smaller than in the conventional case, and is maintained at a high level on average. If the frequency of spark discharge in the fixed spark discharge gap 6 exceeds 200 times / second, especially 300 times / second,
Since the next spark discharge is generated before the voltage between the discharge electrode 8 and the counter electrode 9 is sufficiently lowered, the plasma density in the space between the discharge electrode 8 and the counter electrode 9 can be always maintained at a high level, and thus deodorization can be performed. The effect is factory.

In FIG. 2, T on the horizontal axis is 1 of the commercial frequency.
/ 2 cycle period, which corresponds to 10 ms when the AC power source is 50 Hz. Since the gap of the fixed spark discharge gap 6 is 2 to 10 mm or less, which is narrower than the conventional one,
The heat generated by the spark discharge is small, and the discharge voltage between the gaps is low, so that the recovery time of the gap is short, and the frequency of repeating the sawtooth wave can be increased to about 600 times / sec. Further, by blowing gas into the fixed spark discharge gap 6, the recovery time of the gap can be shortened, and as a result, the repetition frequency of the sawtooth wave can be increased to about 700 times / second or more. As described above, when the recovery time of the fixed spark discharge gap 6 becomes short, the voltage between the discharge electrode 8 and the counter electrode 9 becomes lower than 1/4 to 1/10 of the peak value of the sawtooth wave voltage. Since the next sawtooth wave voltage is generated, a voltage of a certain value or more is always applied between the discharge electrode 8 and the counter electrode 9, which means that the plasma density inside the cylindrical counter electrode 9 is increased. It helps to keep the value above a certain value. That is, when the spark discharge in the fixed spark discharge gap 6 occurs at a frequency of 200 times / second, preferably 300 times / second, the voltage between the discharge electrode 8 and the counter electrode 9 is 1 of the peak value of the sawtooth voltage. Since the next strong streamer corona discharge occurs before the pressure drops below / 4 to 1/10, the plasma density inside the cylindrical counter electrode 9 can be maintained at a high level.

Since the fixed spark discharge gap 6 is narrower than the conventional one, that is, 2 to 10 mm or less, the voltage applied to both ends of the gap is as low as several kV to several tens of kV, and the fixed spark discharge gap is small. Even if 6 is provided on the negative electrode side of the ground side, the same effect can be obtained. As a result of being able to install the fixed spark discharge gap 6 on the ground side, electrical insulation can be significantly reduced compared to the conventional fixed spark discharge gap, so it is possible to make it considerably smaller and lighter, and at the same time reduce costs. is there.

The high-voltage capacitor 5 can be omitted. In this case, the DC output voltage waveform of the high-voltage rectifier 4 is a single-phase full-wave rectification waveform, and the fixed spark discharge gap 6 is a single-phase full-wave. Since a spark discharge occurs when the rectified waveform voltage exceeds several kV, the voltage applied between the discharge electrode 8 and the counter electrode 9 of the deodorizing device 7 through the fixed spark discharge gap 6 also becomes a single-phase full-wave rectified waveform. Therefore, the voltage waveform between the discharge electrode 8 and the counter electrode 9 of the deodorizing device 7 is a combination of the single-phase full-wave rectified waveform and the sawtooth wave voltage as shown in FIG. 3 due to the corona discharge generated between them. Becomes Also in FIG. 3, T on the horizontal axis indicates a period of 1/2 cycle of the commercial frequency, and 10 ms when the AC power source is 50 Hz.
Equivalent to.

Furthermore, it is preferable to provide an inductance element 10 such as an air-core reactor for protecting the high voltage rectifier 4 as shown by a chain line in FIG. As described above, when the fixed spark discharge gap 6 causes the spark discharge, the LC of the circuit causes vibration, and a large positive oscillating voltage is applied between the discharge electrode 8 and the electrode 9 of the deodorizing device 7. In the next half cycle, a large negative oscillating voltage may be applied to the high voltage rectifier 4, and the high voltage rectifier 4 may be destroyed by overvoltage. By imposing this large negative oscillating voltage on the inductance element 10, the magnitude of the reverse voltage applied to the high-voltage rectifier 4 can be suppressed. In the above embodiments, the counter electrode has a cylindrical shape, but it may have a polygonal shape such as a hexagonal shape or a flat plate shape.

[0024]

As described above, according to the present invention, the voltage of the high-voltage power supply for generating plasma in the deodorizing device is reduced to 1/2 to 1/4 as compared with the conventional voltage. The DC high voltage generator and the fixed spark discharge gap can have a low electrical insulation resistance, and therefore can be significantly reduced in size and weight, and a very inexpensive deodorizing device can be provided. Further, since a sawtooth wave high voltage having a higher frequency than that of the conventional one is applied between the discharge electrode of the deodorizing device and the counter electrode, the space between the discharge electrode of the deodorizing device and the counter electrode can be maintained at a high plasma density, and therefore the deodorizing can be performed. The effect can be enhanced.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a deodorizing device according to the present invention.

FIG. 2 is a diagram showing a voltage waveform between both electrodes of the deodorizing device of the present invention.

FIG. 3 is a diagram showing another voltage waveform between both electrodes of the deodorizing device of the present invention.

FIG. 4 is a diagram for explaining an example of a deodorizing device.

FIG. 5 is a diagram for explaining another example of the deodorizing device.

FIG. 6 is a diagram for explaining an example of a conventional deodorizing device.

FIG. 7 is a diagram for explaining another example of the conventional deodorizing device.

FIG. 8 is a diagram showing a voltage waveform between electrodes of a conventional deodorizing device.

[Explanation of symbols]

 1 ... Commercial AC power supply 2 ... Voltage control device 3 ... High-voltage transformer 4 ... High-voltage rectifier 5 ... High-voltage capacitor 6 ... ..Fixed spark discharge gap 7 Deodorizer 8 Discharge electrode 9 Counter electrode

Claims (4)

[Claims] 1. A high voltage of a sawtooth waveform having a discharge electrode as a positive electrode and a counter electrode as a negative electrode is applied between electrodes of a deodorizing device, and the voltage between the electrodes is about the peak value of the high voltage of the sawtooth waveform. A deodorizing method using a sawtooth corona discharge, characterized in that a high voltage having the following sawtooth waveform is applied before the voltage drops to 1/10 or less. 2. A voltage controller for controlling an AC input voltage, a high voltage transformer for boosting the AC voltage from the voltage controller, and an AC high voltage from the high voltage transformer converted to a DC high voltage. A high voltage rectifier, comprising a spark discharge gap inserted in series between the output terminal and the load terminal of the high voltage rectifier, and having a sawtooth waveform formed by arc discharge intermittently generated in the spark discharge gap A device for applying a high voltage to a discharge electrode of a deodorizing device connected to the load terminal to generate plasma to reduce deodorization or bad odor, wherein the spark discharge gap has a gap interval of 2 mm or more and 10 mm or less. A deodorizing device using a saw-tooth wave corona discharge. 3. A voltage controller for controlling an AC input voltage, a high voltage transformer for boosting the AC voltage from the voltage controller, and an AC high voltage from the high voltage transformer converted to a DC high voltage. A high voltage rectifier, comprising a spark discharge gap inserted in series between the output terminal and the load terminal of the high voltage rectifier, and having a sawtooth waveform formed by arc discharge intermittently generated in the spark discharge gap A device for applying a high voltage to a discharge electrode of a deodorizing device connected to the load terminal to generate plasma to reduce deodorization or malodor, wherein the spark discharge gap has a gap interval of 2 mm or more and 10 mm or less. By doing so, a sawtooth wave high voltage having a base voltage of the positive electrode is generated 200 times / sec or more, and a deodorizing device by sawtooth corona discharge. 4. An inductance element for protecting the high-voltage rectifier from a high-voltage rectifier having a reverse polarity generated by vibration of the spark discharge gap is provided on a DC output side of the high-voltage rectifier. Alternatively, the deodorizing device using the sawtooth wave corona discharge according to claim 2.