KR20030030387A - noxious gas purification system using non-thermal plasma reactor and control method therefor - Google Patents

Abstract

PURPOSE: Provided are system for controlling noxious gas using non thermal plasma reactor with multi-layer flat panel electrodes, and a control method therefor. CONSTITUTION: The method comprises the steps of introducing polluted air containing harmful gas into a plasma reactor(10); starting the plasma reactor(10) for purifying the polluted air; introducing clean air with hydrogen peroxide into the plasma reactor(10); and starting the plasma reactor(10) for cleaning inside of the plasma reactor(10) using the clean air.

Description

Noxious gas purification system using non-thermal plasma reactor and control method therefor}

The present invention relates to a hazardous gas treatment system using a low temperature plasma reactor, and more particularly, to a hazardous gas treatment using a low temperature plasma reactor capable of quickly regenerating contaminated electrodes of a low temperature plasma reactor and preventing arc discharge. It relates to a system and a control method thereof.

Hazardous gases are emitted into the atmosphere from various industrial processes such as wastewater treatment plants, chemical processes, semiconductor processes, and combustion facilities or from contaminated soil. Hazardous gases such as volatile organic compounds (VOCs), perfluorocarbons (PFCs), chlorofluorocarbons (CFCs), dioxin, odors, and other minerals are not only harmful to the human body, but are also known to cause light smog in the atmosphere. Regulations are in force in each country. In recent years, regulations on certain industrial wastes have been tightened. Particularly, global warming substances, PFCs and CFCs, have been gradually phased out by international agreements, and total regulations will be implemented from 2002.

At present, an incineration method, a catalyst method, an adsorption or a biological filtration method and the like have been put into practical use as treatment technologies for harmful gases. However, it is known that these existing technologies alone cannot fully satisfy the tightening regulations. For example, incineration and catalytic processes require a high temperature heat source in any way, but it is known that there is a technical and economic difficulty to continuously maintain a high temperature heat source in an ultra clean semiconductor process in which harmful gases are intermittently discharged.

On the other hand, there is a low temperature plasma method as a technique for decomposing or oxidizing harmful gases even without a high temperature heat source. The low temperature plasma process supplies a high voltage alternating current power to a reactor composed of an electrical dielectric to generate a low temperature plasma composed of electrons and ions at atmospheric pressure, and to generate a chemical reaction with a noxious gas using some high energy electrons generated therein. To deal with harmful gases.

US Patent 4,954,320 "REACTIVE BED PLASMA AIR PURIFICATION," issued August 17, 1993, to Joseph G. Birmingham et al. US Pat. No. 5,236,672 issued to Carlos M. Nunez et al, "CORONA DESTRUCTION OF VOLATILE ORGANIC COMPOUNDS AND TOXICS," US Patent 5,609,736 to Toshiaki Yamamoto, dated March 11, 1997. " METHODS AND APPARATUS FOR CONTROLLING TOXIC COMPOUNDS USING CATALYSIS-ASSISTED NON-THERMAL PLASMA. "

The above-mentioned prior arts use pulse power to generate low temperature plasma, or fill catalyst or ferroelectric beads in the reactor to reduce gaseous secondary contaminants that may be generated after the reaction and improve reaction efficiency. Are proposing. However, the above-mentioned prior arts prevent the continuous operation of the process by aerosol by-products generated during the process attached to the reactor or the pipe, causing clogging or deteriorating the electrical characteristics of the reactor. Very few cases are in operation.

Most of the reactors used in the low temperature plasma process proposed so far have a structure in which a circular cylinder is used as an electrode and a thin line or a small diameter tube in the cylinder is used as the other electrode. The reactor having such a shape is similar to the commercially available medium-large ozone generator, which has an advantage in lowering the operating temperature by discharging heat generated in the reactor to the outside, but has a disadvantage in that the reactor becomes larger than the flow rate of the gas to be treated.

On the other hand, in the case of a small ozone generator using the plasma generation principle, the electrode in the reactor may be composed of a multilayer plate. Multi-layered flat electrodes have a well-known electrode shape, the biggest characteristic of which is that the heat generated in the reactor is difficult to transfer to the outside compared to the reactor structure having a cylindrical cylinder structure, thereby increasing the operating temperature. Therefore, the reactor having a multi-layered flat electrode may be advantageous for a harmful gas removal process in which the removal rate of harmful gas increases as the operating temperature increases, or the process of oxidizing and removing the by-products attached in the reactor may be accelerated.

However, unlike ozone generators that generate ozone from relatively clean air or oxygen, arc discharge may occur in the process of treating harmful gases and exhaust gases containing a large amount of moisture and particulate matter. There is a problem in that the reactor can be fatally damaged. Therefore, there is a need for a low temperature plasma reactor having a multi-layered flat electrode capable of stably generating a low temperature plasma even in a gas containing moisture and particulate matter.

Accordingly, an object of the present invention has been proposed to solve the above-mentioned problems, the harmful gas treatment system using a low temperature plasma reactor that can effectively remove the aerosol attached to the inner wall of the low temperature plasma reactor and the electrode plate during the harmful gas treatment process. To provide.

Another object of the present invention is to provide a noxious gas treatment system using a low temperature plasma reactor and a control method thereof, which can continuously perform a noxious gas treatment process using a low temperature plasma reactor.

It is still another object of the present invention to provide a multi-layered flat electrode for a low temperature plasma reactor capable of preventing arc discharge and a method of manufacturing the same.

1 is a block diagram schematically showing the configuration of a noxious gas treatment system according to a preferred embodiment of the present invention;

2 is a block diagram schematically showing the configuration of a noxious gas treatment system having a plurality of low temperature plasma reactors;

3 is a perspective view of a multilayer plate electrode for the low temperature plasma reactor of the present invention;

4 is an exploded perspective view of the unit plate electrode of FIG. 3;

5 shows a flat surface electrode with aerosol attached after treating contaminated air; And

6 illustrates a plate electrode regenerated through a regeneration process.

* Description of the symbols for the main parts of the drawings *

10, 20, 22: low temperature plasma reactor 18, 28: valve system

12, 21, 23: high frequency oscillator 30: multilayer plate electrode

31 ceramic plate electrodes 31a and 31b: ceramic plate

31c: electrode plate 31d: electrode protrusion

31e: electrode plate insertion area 31f: electrode plate insertion hole

32a, 32b: ceramic spacer

According to an aspect of the present invention for achieving the object of the present invention as described above, the harmful gas treatment system for purifying the polluted air containing harmful gases using a low temperature plasma reactor is contaminated in the treatment step of contaminated air The prepared air is introduced into a low temperature plasma reactor and purified by a low temperature plasma reaction. The low temperature plasma reactor contaminated in the regeneration step receives non-contaminated air containing no harmful gas and regenerates the low temperature plasma reactor itself contaminated by the low temperature plasma reaction.

In this embodiment, when it is necessary to perform the purification treatment process continuously, at least two low temperature plasma reactors constitute a noxious gas treatment system so that the at least two low temperature plasma reactors alternately perform a purification treatment and a regeneration treatment step. The entire purification process is continued. When the purification treatment process may be carried out discontinuously, the hazardous gas treatment system is constituted by a single low temperature plasma reactor, and the purification treatment step and the regeneration treatment step are alternately performed.

According to another feature of the invention, a noxious gas treatment system for purifying contaminated air containing noxious gases using a low temperature plasma reactor comprises at least one low temperature plasma reactor, a valve system having a plurality of valves, and at least one unit. The above high frequency generator is provided. The valve system provides contaminated air to a low temperature plasma reactor that performs a process for purifying contaminated air and non-contaminated air to a low temperature plasma reactor that performs a process for regenerating the contaminated low temperature plasma reactor itself. do. And at least one high frequency generator provides high frequency power, respectively, to at least one low temperature plasma reactor.

According to still another aspect of the present invention, a multi-layered flat electrode installed in a low temperature plasma reactor and receiving high frequency power from a high frequency generator to generate a low temperature plasma discharge has a non-conductive plate having an electrode plate insertion region therein and an electrode plate insertion. It consists of a plurality of plate electrodes arranged in a multilayer having a conductive electrode plate inserted into the region and a plurality of spacers positioned between each ceramic plate electrode such that a hole is formed between the multilayer plate electrodes.

In this embodiment, the non-conductive plate and the spacer are made of ceramic. The plurality of plate electrodes have a shape of a substantially square plate, and an electrode plate insertion hole is provided at one side thereof, and the plurality of plate electrodes are alternately arranged in opposite directions with the electrode plate insertion holes of neighboring plate electrodes.

According to still another aspect of the present invention, there is provided a method of manufacturing a multi-layered flat plate electrode, which is installed in a low-temperature plasma reactor and receives high-frequency power from a high-frequency generator, to generate a low-temperature plasma discharge. An electrode plate is inserted into one surface of a first ceramic plate. Forming a region; Performing a first high temperature heat treatment to join the first ceramic plate and the second ceramic plate into one plate electrode such that the electrode plate insertion region is inward; Inserting an electrode plate in the electrode plate insertion region; Arranging a plurality of flat plate electrodes in a multi-layer, and performing a second high temperature heat treatment to bond the plurality of flat plate electrodes and the ceramic spacers with ceramic spacers so as to form holes therebetween.

In this embodiment, the first and second high temperature heat treatments are performed at a high temperature of about 1450 ° C. to 1800 ° C. for about 0.5 to 4 hours.

The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. This embodiment is provided to explain more clearly the present invention to those skilled in the art. Accordingly, the shape of the elements in the drawings and the like are exaggerated to emphasize a clearer description.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In general, unlike the technique of generating ozone by injecting uncontaminated air or oxygen into the reactor, a large amount of particulate matter is formed as a result of the plasma reaction in treating contaminated substances such as odorous substances, VOCs, PFCs, and CFCs with low temperature plasma. Material may be generated. These particulate matters adhere to the reactor inner wall and the electrode, causing clogging or change of the electrical characteristics of the reactor, making long time continuous operation impossible.

On the other hand, the inventors found that by-products attached to the reactor inner wall supply clean air and operate the plasma reactor at the same time, the by-products are gradually removed to clean the contaminated reactor inner wall and the electrode, and furthermore, such a reactor Process technology that allows the regeneration process to proceed more quickly and efficiently has been specifically invented as described below.

The noxious gas treatment system of the present invention includes a low temperature plasma reactor having a multi-layered flat electrode. The low temperature plasma reactor is alternately carried out with a noxious gas treatment process and an electrode regeneration process, and if two or more low temperature plasma reactors are provided to alternately perform the noxious gas treatment process, the overall noxious gas treatment process can be continuously performed. It can be done. In particular, by forming a low temperature plasma reactor with a multi-layered electrode plate and staggering the electrode insertion holes of the multi-layered plate electrodes in opposite directions to prevent an arc discharge from occurring during the process, it is possible to prevent damage to the electrode plate and the reactor. Can be.

1 is a block diagram schematically showing the configuration of a noxious gas treatment system according to a preferred embodiment of the present invention. Referring to the drawings, the harmful gas treatment system of the present invention is a low-temperature plasma reactor 10, a high-frequency generator 12 for providing a high frequency power to a multi-layer flat electrode (not shown, described later in detail) installed in the low-temperature plasma reactor 10 And a valve system 18 consisting of first and second valves 14, 16 providing noxious gas or clean air to the low temperature plasma reactor 10. The high frequency generator 12 uses a high voltage AC power in the range of about 2 ~ 20KV, and the frequency of the AC power is used in the range of about 50 ~ 10Khz.

The noxious gas treatment system opens the first valve 14 to purify the polluted air, thereby introducing the polluted air containing the noxious gas into the low temperature plasma reactor 10. The low temperature plasma reactor 10 receives high frequency power from the high frequency generator 12 to generate low temperature plasma to purify and discharge the polluted air.

After the hazardous gas treatment process is performed for a predetermined time, the noxious gas treatment system shuts off the first valve 14 to prevent contaminated air from entering the low-temperature plasma reactor 10 and opens the second valve to introduce clean air. The electrode regeneration process is performed. When clean air flows into the low temperature plasma reactor 10 through the second valve 16 in the electrode regeneration process, high frequency power is again supplied from the high frequency generator 12 to generate a low temperature plasma to contaminate the electrode (not shown) and the low temperature. The aerosol attached to the inside of the plasma reactor 10 is removed.

In this manner, the noxious gas treatment system alternately performs the noxious gas treatment process and the electrode regeneration process while alternately opening / closing the first valve 14 and the second valve 16. This case can be used when the hazardous gas treatment process may be performed discontinuously. However, when two or more low temperature plasma reactors are used, a continuous process of harmful gas treatment is possible.

2 is a block diagram schematically showing the configuration of a noxious gas treatment system having a plurality of low temperature plasma reactors.

As shown in the figure, there are two low temperature plasma reactors 20 and 22 and two high frequency oscillators 21 and 23 respectively connected to them to provide high frequency power. The valve system 28 has first to fourth valves 24, 25, 26, 27, the first and third valves 24, 26 for providing contaminated air and the first for providing clean air. And second and fourth valves 25 and 27.

The two low temperature plasma reactors 20 and 22 alternately perform harmful gas treatment processes. That is, while one reactor proceeds with the noxious gas treatment process, the other reactor performs the electrode regeneration process, and the reactor that has completed the electrode regeneration process is stopped and is in the atmospheric environment. If the inner wall and the electrode of the reactor undergoing the noxious gas treatment process are contaminated by the adhesion of by-products and the electrical characteristics change or the performance is deteriorated, the noxious gas treatment process is stopped and the regeneration process is carried out while accepting fresh air. The other reactor receives the polluted air and proceeds with the noxious gas treatment process.

More specifically, the specific method for regenerating a contaminated low temperature plasma reactor is as follows.

The polluted reactor is supplied with clean air free of noxious gas, and the flow rate of the clean air is reduced to 1/2 or less than the amount of polluted air that has been treated so far. In this case, the operation temperature of the reactor may be increased, thereby facilitating a process of oxidizing and removing byproducts attached to the inner wall of the reactor and the electrode. In addition, the frequency of the high frequency power supplied to the reactor is supplied 2 to 10 times higher than during the noxious gas treatment process so that the temperature inside the reactor is increased by dielectric heating.

In order to finish the regeneration process in a shorter time, supplying a small amount of hydrogen peroxide to the reactor in the regeneration process can reduce the regeneration time, this technique is a method that can be selected and used for the purpose of regenerating the reactor in a short time. Another way to shorten the regeneration time is to coat noble metal catalysts (Pt, Pd, Rh, etc.) on the inner wall of the reactor, which can be used selectively or simultaneously with the method using hydrogen peroxide. In addition, in order to obtain a higher regeneration effect, the smaller the volume of the low-temperature plasma reactor can be expected to have an additional effect of increasing the operation temperature and increasing the removal rate of harmful gas.

Next, with reference to the accompanying drawings, Figures 3 and 4 will be described in detail a preferred embodiment of a multi-layered flat electrode for the low temperature plasma reactor of the present invention. 3 is a perspective view of a multi-layered flat electrode for the low temperature plasma reactor of the present invention, and FIG. 4 is an exploded perspective view of the unit flat electrode of FIG. 3, respectively.

Referring to the drawings, the multilayer plate electrode 30 includes a plurality of ceramic spacers 32a and 32b in which a plurality of ceramic plate electrodes 31 form a multilayer and holes are formed between the ceramic plate electrodes 31. It is composed. The ceramic plate electrode 31 has a pair of non-conductive ceramic plates 31a and 31b having an electrode plate insertion region 31e therein and a conductive electrode plate 31c inserted into the electrode plate insertion region 31e. It consists of.

The plurality of ceramic plate electrodes 31 has a substantially rectangular flat plate shape, and an electrode plate insertion hole 31f is provided at one side thereof, and the plurality of plate electrodes 31 have electrode plate insertion holes of the plate electrodes adjacent to each other. And are staggered in opposite directions. The electrode protrusions 31d of the electrode plates 31c arranged in the same direction are connected in parallel to one terminal of the high frequency generator 40 in the same manner. Air contaminated by the through holes of the multilayer flat electrode 30 configured as described above is passed through and purified by low temperature plasma discharge.

As shown in FIG. 4, when a pair of ceramic plates 31a and 31b are simply overlapped or bonded to each other with a general ceramic adhesive, high voltage may be supplied between extremely small gaps or pores, thereby causing arc discharge. Therefore, the present invention provides a manufacturing method for completely sealing the pair of ceramic plates 31a and 31b to prevent this.

Specifically, the pair of ceramic plates 31a and 31b is formed by using an alumina plate having a thickness of about 1 mm and having good processability at a relatively low temperature, and using a ceramic plate processed on one side and a ceramic plate not processed on one side. do.

First, one electrode plate 31b is formed with an electrode plate insertion region 31e to a depth of about 0.1 mm. This is for later insertion of the electrode plate 31c having a thickness of about 0.1 mm. Subsequently, it is pasted into another ceramic plate 31a and placed in a high temperature heat treatment furnace (not shown), and then heat treatment is performed at a temperature of about 1450 ° C. to 1800 ° C. for 0.5 to 4 hours. The pair of ceramic plates 31a and 31b are bonded through the heat treatment process, and after completion, the electrode plates 31c are inserted into the grooves previously dug.

As such, when the plurality of ceramic plate electrodes 31 are completed, as illustrated in FIG. 3, the plurality of ceramic spacers 32a having a diameter of about 1-10 mm to allow fluid to flow between the plurality of ceramic plate electrodes 31. 32b). At this time, the electrode plate protrusions 31d are staggered so as to be opposite to each other. The above-described heat treatment process is performed once again to complete the multilayer flat electrode 30. The present inventors produced the electrode by such a manufacturing method and tested the test to 18 KV, and no arc discharge occurred.

5 is a view showing a flat electrode with an aerosol attached after treating contaminated air, and FIG. 6 is a view showing a flat electrode regenerated through a regeneration process.

As shown in FIG. 5, after a long time operation of the low temperature plasma reactor, by-products are attached and contaminated on the inner plate electrode surface. As shown in FIG. 6, by-products attached to the surface of the electrode through the regeneration process are removed through the oxidation process. The present inventors found that by-products of 1,000 ppm toluene-containing air were purified by generating a plasma at low temperature for 10 hours using the noxious gas treatment system of the present invention, so that by-products were attached to the surface of the electrode which was originally white, turning brown. Then, when plasma was generated in the reactor by adding hydrogen peroxide to clear air containing no toluene, it was found that after about 30 minutes, the contaminated electrode surface was cleanly regenerated.

As described above, the configuration and operation of the noxious gas treatment system using the low temperature plasma reactor according to the preferred embodiment of the present invention are illustrated according to the above description and the drawings, but these are merely described as examples and the technical features of the present invention. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the scope of the invention.

According to the present invention as described above, it is possible to prevent the arc discharge of the low-temperature plasma reactor to prevent damage to the electrode and the inner wall of the reactor, it is possible to process the continuous harmful gas and rapid electrode regeneration. And it is possible to increase the efficiency of the treatment of harmful gases relative to the volume of the reactor.

Claims (15)

A control method of a noxious gas treatment system for purifying polluted air containing noxious gases using a low temperature plasma reactor: Introducing contaminated air containing noxious gas into the low temperature plasma reactor, and operating the low temperature plasma reactor to purify the contaminated air; And And introducing non-contaminated air that does not contain harmful gas into the low temperature plasma reactor and operating the low temperature plasma reactor to regenerate the polluted low temperature plasma reactor itself. The method of claim 1, The noxious gas treatment system consists of at least two low temperature plasma reactors, At least two low-temperature plasma reactors alternately perform a purification treatment step and a regeneration treatment step so that the polluted air purification treatment is generally performed in a continuous process. The method of claim 1, The noxious gas treatment system consists of a single low temperature plasma reactor, The single low temperature plasma reactor alternately performs a purification treatment step and a regeneration treatment step, and thus, the polluted air purification process is performed in a discontinuous process as a whole. The method of claim 1, A control method of a noxious gas treatment system, characterized by including a predetermined amount of hydrogen peroxide in uncontaminated air provided to a low temperature plasma reactor undergoing a regeneration treatment step. The method of claim 1, The inner wall of the low-temperature plasma reactor is a control method of the noxious gas treatment system, characterized in that the noble metal catalyst is coded. The method of claim 1, And the amount of non-contaminated air provided to the low temperature plasma reactor in the regeneration treatment step is about 1/2 or less than the amount of the contaminated air provided to the low temperature plasma reactor in the purification treatment step. The method according to claim 1 or 6, The high frequency power for plasma discharge provided to the low temperature plasma reactor in the regeneration treatment step has a frequency higher than the frequency of the high frequency power provided in the purification treatment step. In a noxious gas treatment system using a low temperature plasma reactor to purify contaminated air containing noxious gases: At least one low temperature plasma reactor; A plurality of low temperature plasma reactors providing contaminated air to a low temperature plasma reactor performing a process for purifying contaminated air, and a low temperature plasma reactor performing a process for regenerating the contaminated low temperature plasma reactor itself are provided. A valve system having valves; And And at least one high frequency generator for providing high frequency power to at least one low temperature plasma reactor. The method of claim 8, The noxious gas treatment system consists of at least two low temperature plasma reactors, The at least two low temperature plasma reactors alternately undergo a purification process and a regeneration treatment step so that the polluted air purification process of the noxious gas treatment system is generally performed in a continuous process. The method of claim 8, The noxious gas treatment system consists of a single low temperature plasma reactor, The single low temperature plasma reactor alternately performs a purification treatment step and a regeneration treatment step so that the polluted air purification process is performed in a discontinuous process as a whole. In a multilayer flat electrode installed in a plasma reactor and receiving high frequency power from a high frequency generator to generate a low temperature plasma discharge: A plurality of flat electrodes arranged in a multi-layer having a non-conductive plate having an electrode plate insertion region therein and a conductive electrode plate inserted into the electrode plate insertion region; And And a plurality of spacers positioned between each ceramic plate electrode such that a hole is formed between the plurality of plate electrodes. The method of claim 11, The non-conductive plate and the spacer is a multilayer plate electrode for a low temperature plasma reactor, characterized in that consisting of a ceramic. The method of claim 11, The plurality of plate electrodes may have a substantially rectangular plate shape, and an electrode plate insertion hole may be provided on one side thereof, and the plurality of plate electrodes may be alternately arranged in opposite directions with the electrode plate insertion holes of neighboring plate electrodes. A multilayer plate electrode for a low temperature plasma reactor. In the method of manufacturing a multi-layered flat electrode, which is installed in a low temperature plasma reactor, receives a high frequency power from a high frequency generator and generates a low temperature plasma discharge: Forming an electrode plate insertion region on one surface of the first ceramic plate; Performing a first high temperature heat treatment to join the first ceramic plate and the second ceramic plate into one plate electrode such that the electrode plate insertion region is inward; Inserting an electrode plate in the electrode plate insertion region; And arranging a plurality of plate electrodes in a multi-layer, and performing a second high temperature heat treatment to bond the plurality of plate electrodes and the ceramic spacers with ceramic spacers so as to form holes therebetween. Process for the production of multilayer plate electrodes for reactors. The method of claim 14, The first and second high temperature heat treatments are performed for about 0.5 to 4 hours at a high temperature of about 1450 ° C to 1800 ° C.