JPH1147544A - Discharge suction system gas treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress recombination loss of an active species and consumption of treatment gas while encouraging high formation efficiency of the active species. SOLUTION: In the case wherein a gas treatment apparatus is used as an ozonizer, an interior of a discharge reaction container 1 is evacuated by a vacuum pump 3, a first valve 4 is opened and closed instantaneously in order to pulsatively introduce into the discharge reaction chamber 1 a small amount of oxygen as a treatment gas and then a pulse voltage is applied between the discharge reaction chamber 1 and an electrode 2 and an oxygen atom as an active species is formed by effecting pulse discharge. Then, a second valve 5 is opened and the gas to be treated which has atmospheric pressure or a higher pressure is injected into the discharge reaction container 1 at a high speed and an ozone is formed and then discharged through the vacuum pump 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge suction type gas treatment method for treating a gas to be treated by using active species generated by electric discharge in the gas for treatment. It is used in exhaust gas treatment equipment and the like.

[0002]

2. Description of the Related Art There are various types of conventional discharge gas processing apparatuses (methods) conventionally used. FIG. 3 is a schematic diagram showing an example of a conventional direct discharge gas processing apparatus. The gas to be treated is allowed to flow through the atmospheric pressure discharge reaction vessel 1, and a high voltage is applied between the discharge reaction vessel 1 and the electrode 2,
Gas treatment is performed through a chemical reaction via active species generated by discharge (for example, IEEJ Transactions on Materials B. 113-5, P463).
(1993)). Applications include a device that removes NO _X and SO ₂ by using combustion exhaust gas as a gas to be treated, and a device that purifies contaminated air containing volatile organic substances. There is also an apparatus that uses the atmosphere as a gas to be treated and uses it as an ozonizer. However, in these apparatuses, the active species to be generated cannot be selected, and both the oxidation and reduction reactions proceed simultaneously, so that harmful reaction products may be generated.

[0003] In order to improve the selectivity of the reaction, an external injection type discharge gas treatment apparatus has been studied, and this is shown in FIG.

FIG. 4 is a schematic diagram showing an example of a conventional external injection type discharge gas processing apparatus. In this system, an active gas obtained by performing discharge processing on a processing gas is introduced into a gas to be processed. In the method of injecting, a processing gas is circulated through the discharge vessel 6, a discharge process is performed between the discharge vessel 6 and the electrode 2, then injected into the reaction vessel 7, and mixed with the gas to be processed. It is. Also in this case, the discharge is performed at the atmospheric pressure.
Specifically, the nitrogen gas used as the processing gas, discharged by generating a nitrogen atom, a method of reduction treatment NO _X by injecting into the exhaust gas has been studied (for example,
Transactions of the Japan Society of Mechanical Engineers B. 60-576.P2931 (1994)).

In order to enhance the efficiency of the discharge process, there is also a method in which the process gas is subjected to a discharge process under reduced pressure and then injected into the gas to be processed at atmospheric pressure. FIG. 5 shows a typical example of this method.

FIG. 5 is a schematic diagram showing an example of a conventional reduced pressure injection type discharge gas processing apparatus, in which the inside of a discharge vessel 6 is depressurized by a vacuum pump 3 as a pressure reducing means. After discharging under reduced pressure to generate active species,
This is a method in which the reaction vessel 7 connected to the exhaust side of the vacuum pump 3 is mixed with the gas to be treated, which is pressurized to the atmospheric pressure or higher than the atmospheric pressure. In this method, since the discharge treatment is performed under reduced pressure, the acceleration of the electrons generated by the discharge proceeds, and as a result, the generation efficiency of the active species is improved. Specifically, regarding a method of using oxygen gas as a processing gas, generating oxygen atoms by discharging, and mixing with air to generate ozone, a jet pump is used as the vacuum pump 3 to reduce the pressure of the discharge vessel 6 with the depressurized gas. A method of mixing with atmospheric pressure gas has been proposed (Transactions of the Institute of Electrical Engineers of Japan, A. 116-9, P791 (1996)). 3 to 5, the high-voltage power supply and the like of the discharging means are omitted.

[0007]

A problem with such a conventional discharge gas processing apparatus is the rate of injection and gas mixing when the active species generated by the discharge are mixed with the gas to be processed. Since the lifetime of the active species is shorter than the mixing speed of the gas, the rate at which the generated active species disappears due to a recombination reaction or the like is high. In particular, in the external injection method shown in FIGS. 4 and 5, suppression of such annihilation reaction is an important issue. For that purpose, high-speed injection and high-speed mixing into the gas to be treated are required.

However, FIG.
However, the external injection type discharge gas processing apparatus has a problem that a large amount of processing gas is required for high-speed injection, and high-speed injection is limited.

On the other hand, in the reduced pressure injection type discharge gas treatment apparatus shown in FIG. 5, which generates active species under reduced pressure, the active gas as the active species is mixed with the gas to be treated at atmospheric pressure or a pressure higher than atmospheric pressure. Once pressurized to about atmospheric pressure or higher than atmospheric pressure, mixing with the gas to be processed occurs. Therefore, also in this case, it is difficult to suppress the recombination loss of the active species.

It is an object of the present invention to solve the drawback of recombination loss while taking advantage of the selectivity of the reaction and the high production efficiency, which are the advantages of the external injection method. .

[0011]

According to the discharge suction type gas processing method of the present invention, a processing gas is supplied into a discharge reaction vessel at an atmospheric pressure or a reduced pressure, and then a pulse discharge is applied to the processing gas. Immediately after the generation of the active species, the gas to be treated is supplied into the discharge reaction vessel at a high speed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In a discharge suction type gas processing method of the present invention, a processing gas is supplied from a first valve or the like into a discharge reaction vessel depressurized by an atmospheric pressure or a vacuum pump, and the gas in the discharge reaction vessel is discharged. The processing gas is pulse-discharged by a discharge means to generate active species of the processing gas, and a gas to be processed by the active species generated in the discharge reaction vessel is supplied from a second pump or the like. Is what you do. The processed gas is discharged by a vacuum pump.

The processing gas may be oxygen or nitrogen,
Alternatively, steam, hydrogen peroxide, ammonia, hydrocarbons, or alcohols are added to air or their gases.

As described above, high-speed gas mixing can be realized by injecting the gas to be treated at a high speed immediately after the discharge. Therefore, recombination loss of active species can be significantly suppressed. Further, the consumption of the processing gas can be suppressed. In addition, if pulse discharge is performed under reduced pressure, active species can be generated with high efficiency.

[0015]

FIG. 1 is a schematic diagram showing an example of a gas processing apparatus used in a gas processing method according to an embodiment of the present invention.

The embodiment shown in FIG. 1 is different from the conventional example in that the first valve 4 which is the first supply means for supplying the processing gas into the discharge reaction vessel 1 and the processing gas is supplied into the discharge reaction vessel 1. That is, a second valve 5, which is a second supply means for supplying the use gas, is provided. Note that a high-voltage power supply and the like constituting the discharging means are omitted.

Next, the operation when the gas processing apparatus of FIG. 1 is used as an ozonizer will be described.

The first valve 4 and the second valve 5 are closed,
The pressure inside the discharge reaction vessel 1 is reduced by driving the vacuum pump 3. Next, the first valve 4 is momentarily opened and closed to introduce a small amount of oxygen as a processing gas into the discharge reaction vessel 1 in a pulsed manner. Next, a pulse voltage is applied between the discharge reaction vessel 1 and the electrode 2, which are constituent members of the discharge means, and a pulse discharge is performed to generate oxygen atoms as active species. Next, the second valve 5 is opened, and ozone is generated by injecting air pressurized to the atmospheric pressure or higher than the atmospheric pressure as the gas to be treated into the discharge reaction vessel 1 at high speed, and the ozone is discharged through the vacuum pump 3. I do. Then, the second valve 5
Is closed to complete the first step, return to the initial operation, and repeat the same steps as above.

FIG. 2 shows an example of the timing of the pulse discharge and the pulsed supply of the processing gas and the gas to be processed.

Further, the discharge suction type gas treatment method of the present invention can also be used as NO _X processing method of the combustion exhaust gas. In this case, the first valve 4 is opened and closed to supply a nitrogen gas, which is an active species, as a processing gas, and the second valve 5 is opened to inject combustion exhaust gas as a gas to be processed at a high speed to reduce NO _X. Perform processing.

Similarly, the discharge suction type gas treatment method of the present invention can also be used as a method for purifying contaminated air containing volatile organic substances and the like. In this case, the first valve 4 is opened and closed in the same manner as described above, oxygen is supplied as a processing gas, and contaminated air is supplied from the valve 5 as a gas to be processed, thereby oxidizing organic substances.

In addition, by using a gas containing water vapor, hydrogen peroxide, ammonia, hydrocarbons, and alcohols in the air as a processing gas, more reactive active species are generated, and It is also possible to increase the processing efficiency.

[0023]

As described above, according to the first aspect of the present invention,
In the invention described in (1), the recombination loss due to high-speed mixing of the active species generated by the discharge and the gas to be treated is reduced, and the required amount of the processing gas can be suppressed.

Further, the invention according to claim 2 of the present invention provides:
By performing the pulse discharge under reduced pressure, active species can be generated with high efficiency.

Further, the invention according to claim 3 of the present invention provides:
A more reactive active species can be generated, and the gas processing efficiency can be increased.

Therefore, according to the present invention, the performance of the discharge gas treatment can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a gas processing apparatus used in a gas processing method according to an embodiment of the present invention.

FIG. 2 is a timing chart of pulse discharge and pulse supply of a processing gas and a gas to be processed in the present invention.

FIG. 3 is a schematic configuration diagram showing an example of a conventional direct discharge gas treatment apparatus.

FIG. 4 is a schematic configuration diagram showing an example of a conventional external injection type discharge gas processing apparatus.

FIG. 5 is a schematic configuration diagram showing an example of a conventional reduced pressure injection type discharge gas processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge reaction container 2 Electrode 3 Vacuum pump 4 First valve 5 Second valve

Continuing from the front page (72) Inventor Mitsuji Tanimoto 1-1-4 Umezono, Tsukuba City, Ibaraki Prefecture Within the Institute of Electronics and Technology (72) Inventor Masayoshi Ishida 1-1-4 Tennodai, Tsukuba City, Ibaraki Prefecture University of Tsukuba In structural engineering

Claims (3)

[Claims] 1. A process gas is supplied and charged into a discharge reaction vessel, and a pulse discharge is performed in the discharge reaction container to generate active species of the process gas. A discharge suction type gas processing method, comprising supplying a gas to be treated and treating the gas to be treated with the active species. 2. A gas in a discharge reaction vessel is depressurized by a pressure reducing means, and a processing gas is supplied in a pulsed manner from a first supply means into the decompressed discharge reaction vessel. A pulse discharge is performed to generate an active species of the processing gas, and then a gas to be processed is supplied from a second supply unit into the discharge reaction vessel to process the gas to be processed with the active species. A discharge suction type gas processing method characterized by performing. 3. The processing gas according to claim 1, wherein the processing gas is oxygen or nitrogen, or air to which steam, hydrogen peroxide, ammonia, hydrocarbons, or alcohols are added. The discharge suction type gas treatment method described in the above.