JPH11333244A - Apparatus for treating discharge gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve gas treatment efficiency by promoting the extinction of residual charge between pulse streamer discharges in a gas treatment device. SOLUTION: In this apparatus, an auxiliary power source 22 for applying an auxiliary voltage VA which is smaller in an absolute value than a pulse voltage VP outputted from a pulse power source 14 is installed between an external electrode 4 and a central electrode 6 of a gas treatment device 2. Although the auxiliary voltage VA can be applied between the electrodes 4, 6 during the interval of pulse streamer discharges at least by the application of pulse voltages VP, in this example, the auxiliary power source 22 is made as a direct current power source, and the auxiliary voltage VA is applied between electrodes 4, 6 through the pulse power source 14 constantly including a period in which the pulse voltage VP is being applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, as an ozone generator, a NOx / SOx processor, a dioxin processor, a deodorizer, and the like. The gas to be treated is subjected to pulse streamer discharge (pulse generation). (Eg, ozone generation, NOx / SOx reduction, dioxin reduction,
The present invention relates to a discharge gas processing apparatus for performing deodorization and the like, and more specifically, to a means for improving the gas processing efficiency by promoting the disappearance of residual charges between discharges of pulse streamer discharge in a gas processor. .

[0002]

2. Description of the Related Art FIG. 6 shows a conventional example of this type of discharge gas processing apparatus. The discharge gas processing apparatus includes a gas processing device 2 having a cylindrical (for example, cylindrical) external electrode 4 and a linear (wire-shaped) central electrode 6 arranged on a substantially central axis thereof. and a pulse power supply 14 to be applied repeatedly high pressure pulse voltage V _P between the external electrode 4 and the center electrode 6 of the. Normally, the external electrode 4 is grounded as in this example, and a positive pulse voltage _VP is applied to the center electrode 6.

The inner diameter of the external electrode 4 is, for example, 10 to 100 m.
m, and the outer diameter of the center electrode 6 is, for example, about 0.2 to 3 mm. The magnitude of the pulse voltage V _P is for example 10 to 200
kV or so, the rise time of the pulse voltage V _P is for example 2
It is about 0 to 500 ns. However, these are merely examples, and the structure of the gas processor 2 and the gas
It may differ from this depending on the processing conditions such as the flow rate.

A gas 10 to be treated is supplied from one end of the gas processor 2 between the electrodes 4 and 6 from, for example, a gas source 8, and the gas 10 flows in the longitudinal direction of the electrodes 4 and 6. The pulse voltage _VP is repeatedly applied between the electrodes 4 and 6 from the pulse power source 14 so as to be uniform in all directions from the center electrode 6 to the external electrode 4 and in the longitudinal direction of the electrodes 4 and 6. Then, a pulse streamer discharge 16 is repeatedly generated. The gas 10 can be excited by the pulse streamer discharge 16 and the gas 10 can be subjected to a desired process such as the above-described processes such as ozone generation, NOx / SOx reduction, dioxin reduction, and deodorization. The processed gas 12 is taken out from the other end of the gas processor 2.

The technology using the pulse streamer discharge is more effective than the conventional technology using the silent discharge and the creeping discharge.
Gas processing efficiency against electric power consumed by discharge is 2
It is known to be nearly twice as high, and is attracting attention as a highly efficient gas processing technology.

[0006]

However, the above-mentioned conventional discharge gas processing apparatus has the following problems.

That is, at the time of pulse streamer discharge in the gas processor 2, for example, when the center electrode 6 is at a positive potential as in this example (ie, when the pulse voltage _VP has a positive polarity), as shown in FIG. A positive streamer 17 (a streamer having a positive charge at the tip and a negative charge at the subsequent portion) 17 extends from the center electrode 6 toward the external electrode 4. Therefore,
After the discharge is completed, as shown in FIG. 8, a donut-shaped negative residual charge 20 is generated near the center electrode 6, and a positive residual charge 18 is generated so as to surround the negative residual charge 20.
This residual charge 18 to generate an electric field E ₂ in the direction opposite to the electric field E ₁ (see FIG. 7) by the pulse voltage V _P.

[0008] When such residual charges 18, 20 remaining until the next discharge, since the electric field E ₁ by the pulse voltage V _P for the next discharge is weakened, the pulse streamer discharge is unlikely to occur . Therefore, it is difficult to efficiently input energy between the electrodes 4 and 6, and the processing efficiency of the gas 10 is reduced.

Further, in the case of a low gas flow rate where the flow rate of the gas 10 flowing into the gas processor 2 is small and a high repetition discharge operation condition in which the pulse streamer discharge 16 is generated in the gas processor 2 in a short cycle, the residual The above effects due to the charges 18 and 20 are particularly large.

For example, when this discharge gas processing apparatus is used as an ozone generator, it is necessary to generate ozone at a high concentration of, for example, about 10 ⁵ ppm in the gas processing apparatus 2. (For example, the gas residence time in the gas processor 2 is about several seconds to several tens of seconds), and the operation conditions are high repetition discharge (for example, about 1 kHz or more).

However, the diffusion time of the residual charges 18 and 20 is considered to be several milliseconds to several tens of milliseconds. When the cycle of repeated discharge is about 100 Hz or more, the diffusion time of the residual charges 18 and 20 is affected by the above. . Moreover, as the number of repetitions of the pulse streamer discharge increases, the residual charge 1
8 and 20, the residual charges 18, 20
The above effect is further enhanced. Further, in the low gas flow rate operation as described above, diffusion of the residual charges 18 and 20 due to the gas flow cannot be expected much. Therefore, the residual charges 18, 20
In particular, the above-mentioned effects due to are large.

Of course, contrary to the above-described example, the same problem as described above due to residual charges also exists when a negative pulse voltage _VP is applied to the center electrode 6.

In order to reduce the influence of the residual charge, for example, the gas flow rate is increased, the number of discharge repetitions is reduced, and the length of the gas processor 2 is shortened (however, the gas processor 2 Although it is conceivable to shorten the gas residence time (need to increase the number), in each case, the number of discharges applied to the passing gas decreases, and the gas treatment effect (for example, in the case of an ozone generator, (Generated ozone concentration).

Accordingly, an object of the present invention is to improve the gas processing efficiency by promoting the elimination of residual charges between the discharges of the pulse streamer discharge in the gas processor.

[0015]

According to a first aspect of the present invention, there is provided a discharge gas treatment apparatus comprising: an auxiliary voltage having an absolute value smaller than a pulse voltage output from the pulse power supply at least between discharges of the pulse streamer discharge. It is characterized by having an auxiliary power supply applied between the external electrode and the center electrode of the gas processor.

According to the above configuration, when an auxiliary voltage having the same polarity as the pulse voltage for the pulse streamer discharge is applied, the positive and negative residual charges immediately after the end of the pulse streamer discharge are attracted by the electric field of the auxiliary voltage. Then, they are absorbed by the center electrode or the external electrode and disappear.

Contrary to the above, when an auxiliary voltage having a polarity opposite to that of the pulse voltage is applied, the positive and negative residual charges are repelled by the electric field of the auxiliary voltage, and the positive and negative residual charges collide with each other. Neutralizes and disappears.

Therefore, in any case, the elimination of the residual charges can be promoted by applying the auxiliary voltage, so that the energy can be efficiently transferred between the electrodes of the gas processor even under the low gas flow rate and the high repetition discharge operation condition. Can be introduced, and gas processing efficiency is improved.

[0019]

FIG. 1 is a diagram showing an example of a discharge gas processing apparatus according to the present invention. Parts that are the same as or correspond to those in the conventional example of FIG. 6 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

In this embodiment, an auxiliary power supply 22 is inserted in series between the above-described pulse power supply 14 and the external electrode 4 of the gas processor 2, and from this auxiliary power supply 22, 14 through, between the external electrode 4 and the center electrode 6 of the gas processor 2, so that application of a small auxiliary voltage V _a of the absolute value than the pulse voltage V _P output from the pulse power supply 14.

The auxiliary voltage V _A applied between the electrodes 4 and 6 from the auxiliary power supply 22 is applied to the discharge of the pulse streamer discharge 16 repeated at least in the gas processor 2 in order to promote the elimination of the residual charge. And the method of connecting the auxiliary power supply 22 for this purpose is not limited to that of this embodiment. Further, the auxiliary voltage V _A, although need not be applied during the pulse voltage V _P applied, including during the pulse voltage V _P applied during the operation of the gas processor 2 may be applied at all times. When the voltage is always applied, the auxiliary power supply 22 may be a DC power supply, and the auxiliary voltage _VA may be a DC voltage. Since this configuration simplifies the configuration and connection of the auxiliary power supply 22, in this embodiment, the DC auxiliary power supply 22 is connected as described above, and the DC auxiliary voltage _VA is supplied via the pulse power supply 14. The voltage is always applied between the electrodes 4 and 6.

From the auxiliary power supply 22, the electrodes 4 of the gas processor 2,
Auxiliary voltage V _A applied between 6 to the pulse power source 14 may be a pulse voltage V _P and the same polarity applied between the electrodes 4 and 6, may be reversed polarity.

First, the case of the same polarity will be described.
The distribution of the residual charges immediately after the pulse streamer discharge in the gas processor 2 is approximately as shown in FIG. 2 as described above. This is an example of a case where a positive pulse voltage _VP is applied to the center electrode 6 as described above. Here, when the pulse voltage V _P of the same polarity as the auxiliary voltage V _A is, i.e. the center electrode 6 side auxiliary voltage V _A of the positive polarity is applied, the positive and negative residual charge 18, 20, the auxiliary voltage V _{Under the} suction effect of the electric field E ₃ of _A , the positive residual charge 18 is attracted (induced) to the external electrode 4 and the negative residual charge 20 is attracted (induced) to the center electrode 6, as indicated by arrows in FIG. hand,
Each is absorbed. Therefore, the disappearance of the positive and negative residual charges 18 and 20 can be promoted by applying the auxiliary voltage _VA .

[0024] Contrary to the above, if the auxiliary voltage V _A is the pulse voltage V _P and the opposite polarity, as shown in FIG. 3, the positive and negative residual charge 18, 20, the electric field E ₃ of the auxiliary voltage V _A , That is, as shown by the arrow in FIG.
The positive residual charge 18 receives a repulsive action from the external electrode 4, and the negative residual charge 20 receives a repulsive action from the center electrode 6. The positive and negative residual charges 18, 20 collide with each other and neutralize and disappear. Therefore, also in this case, the disappearance of the positive and negative residual charges 18 and 20 can be promoted by applying the auxiliary voltage _VA .

[0025] However, if the auxiliary voltage V _A is the pulse voltage V _P of the same polarity (i.e. the case of FIG. 2), if residual charge 18,2
0 is not excessively increased space electric field E ₂ by the positive and negative residual charges 18, 20 (see FIG. 8), but when it becomes equal to or more than the electric field E ₃ by the auxiliary voltage V _A, the electric field of the auxiliary voltage V _A In addition to the effect of promoting the disappearance of the residual charges 18 and 20 by E ₃ , the electric field E ₃ weakens the spatial electric field E ₂ for collision between the positive and negative residual charges 18 and 20, The application of the auxiliary voltage _VA may have the opposite effect.

[0026] In such a case, as in the example of FIG. 3, the pulse voltage V _P How to apply a reverse polarity of the auxiliary voltage V _A is good results. In this case, the auxiliary voltage V
_{Since the} electric field E ₃ due to _A acts in the direction of strengthening the spatial electric field E ₂ (see FIG. 8) due to the positive and negative residual charges 18 and 20, the positive and negative residual charges 18 and 20 attract each other to collide and disappear. This is because the course can be strengthened.

For example, as in the case of an ozone generator, when the operating conditions are a low gas flow rate (for example, about 1 to 5 cm / s) and a high repetition discharge (for example, about 1 kHz or more), the residual charge 18,20 especially since a large amount prone, when such operating conditions, for the reasons stated above, an auxiliary of the opposite polarity to the pulse voltage V _P voltage V _a
Is more preferable because it is possible to more reliably promote the disappearance of the residual charges 18 and 20.

In either case, the auxiliary voltage V _A
The size of the 5 to 20% of the pulse voltage V _P, more specifically about 10%, sufficient effect can be obtained. _A larger auxiliary voltage V _A is not preferable in terms of insulation design of the auxiliary power supply 22. In addition, when the auxiliary voltage _VA having the opposite polarity is constantly applied, the peak value of the pulse voltage applied to the gas processor 2 is also reduced accordingly (that is, | V _P | − | V _A |). It is not preferable for this reason.

Next, a specific example of the circuit of the pulse power supply 14 and the auxiliary power supply 22 is shown in FIG.

The pulse power source 14 is of a magnetic pulse compression circuit type in this example, and connects a high voltage charging power source 26 to a primary winding of a step-up pulse transformer 34 via an initial capacitor 30 and a time constant adjusting inductor 32. A discharge start switch 28 is connected in parallel with the high voltage charging power supply 26. The discharge start switch 28 is, for example, a discharge switch such as a thyratron or a semiconductor switch such as a thyristor. An auxiliary power supply 22 is connected between the secondary winding of the step-up pulse transformer 34 and the electrodes 4 and 6 of the gas processor 2 on the ground side.
Are connected in series, the intermediate capacitor 36, the final stage capacitor 38, and the two magnetic switches 40 and 42 are connected in a ladder shape (ladder shape). A capacitor 24 is connected in parallel to the auxiliary power supply 22.

First, the operation of only the pulse power supply 14 will be described. First, the time constant adjusting inductor 32 and the step-up pulse transformer 3 are supplied to the initial capacitor 30 from the high voltage charging power supply 26 in advance.
4, the initial charge is charged. Thereafter, when the discharge start switch 28 is turned on, the electric charge of the initial capacitor 30 is boosted through the boosting pulse transformer 34 and the intermediate capacitor 36 is charged. In this state, the magnetic switch 40 is not saturated, that is, in an off state. Near the time when the charge transfer from the initial capacitor 30 to the intermediate capacitor 36 proceeds and the voltage of the intermediate capacitor 36 becomes maximum, the magnetic switch 40 is saturated and turned on, and the intermediate capacitor 3 is turned on.
The charge of No. 6 moves to the final stage capacitor 38. Similarly, near the time when the voltage of the final-stage capacitor 38 becomes maximum, the magnetic switch 42 is saturated and turned on, and in this example, a positive-polarity pulse voltage _VP is output from the final-stage capacitor 38, and this is The voltage is applied to the center electrode 6 of the processor 2. As the charge transfer from the initial capacitor 30 to the intermediate capacitor 36, from the intermediate capacitor 36 to the final capacitor 38, and from the final capacitor 38 to the gas processor 2 progresses, the pulse width of the charge transfer is compressed. A pulse width of about 2 μs finally becomes, for example, 20 to
It is compressed to about 100 ns. The pulse voltage V _P thus compressed is applied to the gas processor 2. Peak value of the pulse voltage V _P is in the range, for example, about 10～200KV.

On the other hand, the auxiliary power source 22 is a conventional DC power supply in this example, the capacitor 24 will now auxiliary voltage V _A of the DC reversed polarity is always applied to the pulse voltage V _P. At the same time, since this auxiliary voltage _VA is a DC voltage, it is applied between the intermediate capacitor 36, the final-stage capacitor 38, and both electrodes 4 and 6 of the gas processor 2 through the step-up pulse transformer 34 and the magnetic switches 40 and 42. You. Therefore, the auxiliary voltage V _{A has the} effect of promoting the elimination of residual charges in the gas processor 2 described above.

That is, in this example, an auxiliary voltage V _{A having a} polarity opposite to that of the pulse voltage V _P is applied between the electrodes 4 and 6 of the gas processor 2.
Is always applied. Therefore, the discharge start switch 28
The size of the on and the pulse voltage applied between the electrodes 4,6 when the pulse voltage is applied V _P to the gas processing unit 2 (peak value) of _{| V P | - | V A} | become. The auxiliary power supply 22 is connected in the opposite direction to the illustrated example, and the electrodes 4 and 6 of the gas
May be applied a pulse voltage V _P of the same polarity as the auxiliary voltage V _A between the magnitude of the pulse voltage applied between the electrodes 4 and 6 in the case _{| V P | + | V A} | Becomes

The capacitor 2 connected in parallel to the auxiliary power supply 22
4 is to lower the impedance with respect to the transient current when the discharge start switch 28 is turned on to transfer the charge of the initial capacitor 30 to the intermediate capacitor 36 through the boost pulse transformer 34, and to lower the pulse voltage applied to the auxiliary power supply 22. belongs to. As the capacity of the capacitor 24 is larger than the capacity of the intermediate capacitor 36, the capacity of the capacitor 24 is larger than the voltage shared by the intermediate capacitor 36.
, The applied voltage can be prevented from being applied to the auxiliary power supply 22, and the charge can be efficiently transferred to the intermediate capacitor 36. Therefore, it is preferable that the capacity of the capacitor 24 be sufficiently larger than the capacity of the intermediate capacitor 36, for example, 100 times or more. However, the capacitor 24 in the auxiliary power supply 22
If you have a capacitor with the same or larger capacity,
Since it operates similarly to the capacitor 24, there is no need to externally attach the capacitor 24.

In order to increase the amount of the processing gas, a plurality of the above-described gas processors 2 may be provided in parallel. FIG. 5 shows such an example. In this example, a plurality of gas processors 2 are arranged side by side in a container 44, and the gas 10 to be processed flows into each of them. The container 44 is grounded, and the external electrode 4 of each gas processor 2 is
Is electrically connected to the container 44. The center electrodes 6 of the gas processors 2 may be connected in parallel to each other as in this example and connected to the pulse power supply 14, or may be connected in series and connected to the pulse power supply 14.

The external electrode 4 of the gas processor 2 is
A cylindrical shape other than the cylindrical shape, for example, a square cylindrical shape may be used. A tubular shape can be rephrased as a tubular shape.

[0037]

As described above, according to the present invention, the discharge of the pulse streamer discharge in the gas processor is controlled by the auxiliary voltage applied between the external electrode and the center electrode of the gas processor from the auxiliary power supply. Elimination of the residual charges during the period can be promoted, so that energy can be efficiently input to the gas processor, and the gas processing efficiency is improved.

If the auxiliary voltage has a polarity opposite to that of the pulse voltage for pulse streamer discharge, the residual charge can be reduced even in an operating condition in which a large amount of residual charge is generated, such as a low gas flow rate and a high repetitive discharge. Can be more reliably promoted, and the gas processing efficiency can be more reliably improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a discharge gas processing apparatus according to the present invention.

FIG. 2 shows a pulse streamer discharge between discharges.
It is a figure which shows typically the mode of the residual charge in a gas processor when an auxiliary voltage of the same polarity as a pulse voltage is applied to a gas processor.

FIG. 3 shows a pulse streamer discharge between discharges.
It is a figure which shows typically the mode of the residual charge in a gas processor when the auxiliary voltage of a polarity opposite to a pulse voltage is applied to a gas processor.

FIG. 4 is a diagram showing a specific example of a circuit of a pulse power supply and an auxiliary power supply.

FIG. 5 is a view showing another example of the discharge gas processing apparatus according to the present invention.

FIG. 6 is a diagram showing an example of a conventional discharge gas processing device.

FIG. 7 is a diagram schematically showing a state during a pulse streamer discharge in a gas processor.

FIG. 8 is a diagram schematically showing a state of residual charges immediately after a discharge of a pulse streamer discharge in a gas processor.

[Explanation of symbols]

2 gas processor 4 external electrode 6 center electrode 10 gas to be treated 14 pulse power supply 22 auxiliary power supply _VP pulse voltage _VA auxiliary voltage

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Kato 47 Nisshin Electric Co., Ltd., Umezu Takaunecho, Kyoto City, Kyoto Prefecture

Claims (2)

[Claims] 1. A gas processor having a linear central electrode substantially on the central axis of a cylindrical external electrode and supplying a gas to be processed between the two electrodes, and an external electrode of the gas processor. A pulse power supply that repeatedly applies a pulse voltage between the first electrode and the central electrode to repeatedly generate a pulse streamer discharge between the two electrodes, wherein at least a discharge between the pulse streamer discharge And an auxiliary power supply for applying an auxiliary voltage having an absolute value smaller than a pulse voltage output from the pulse power supply between an external electrode and a center electrode of the gas processing device. 2. The discharge gas processing apparatus according to claim 1, wherein the auxiliary voltage has a polarity opposite to that of the pulse voltage.