KR100434940B1 - Catalyst Reactor Activated for Treating Hazardous Gas with Nonthermal Plasma and Dielectric Heating and Method Treating thereof - Google Patents

Abstract

The present invention provides a reactor for treating harmful gases and a method of treating the same, which can improve the removal rate of harmful gases and the selectivity of a reaction process by simultaneously using a dielectric heat and a catalyst by low temperature plasma. The reactor includes a body having a predetermined internal volume; A flat plate electrode disposed in parallel at regular intervals in a body thereof, the plurality of flat plate electrodes being connected to an AC power source to one flat plate electrode repeatedly and the other flat plate electrodes adjacent to ground; And a power supply device for applying an AC frequency voltage to each of the flat plate electrodes. Hazardous gas treatment method using this reactor comprises the steps of preparing a reactor in a hazardous gas treatment device; Applying an alternating current voltage of alternating current frequency to each plate-shaped electrode of the reactor to generate low temperature plasma and dielectric heat; Supplying harmful gas to the inside of the reactor; And simultaneously performing a plasma reaction and a catalytic reaction on the noxious gas.

Description

Catalytic Reactor Activated for Treating Hazardous Gas with Nonthermal Plasma and Dielectric Heating and Method Treating Technical Field

The present invention relates to a reactor for treating noxious gases using low temperature plasma and dielectric heat, and more particularly, to a dielectric heat and catalyst by low temperature plasma in a noxious gas treatment process using both low temperature plasma and a catalyst simultaneously. The present invention relates to a reactor for treating harmful gases and a method of treating the same, which can improve the removal rate of harmful gases and the selectivity of the reaction process by using the same.

In general, most of the volatile organic compounds (VOCs) that are inevitably emitted from industrial processes are not only harmful to the human body but also cause light smog in the atmosphere, and thus, countries have strict regulations on them. Meanwhile, international agreements are stepping up restrictions on emissions of global warming materials, perfluorocarbons (PFCs) and chlorofluorocarbons (CFCs), which are expected to be implemented in 2002, for example. Accordingly, many efforts have been made to develop technologies for treating such harmful substances or gases, and generalized treatment techniques include incineration, catalytic, adsorption, or biological filtration. However, it is known that such a conventional method cannot sufficiently satisfy emission regulations for harmful gases which will be strengthened in the future. For example, incineration and catalysts require a high temperature heat source, but in a business process such as an ultra clean semiconductor process in which harmful gases are intermittently discharged, a high temperature heat source cannot be continuously maintained and high costs are required to maintain it. There is a problem.

On the other hand, there is a harmful gas treatment method using a low-temperature plasma as a technique for decomposing or oxidizing harmful gas without using a high temperature heat source. One such hazardous gas treatment is disclosed in US Pat. No. 5,236,627. According to this patent, a low-temperature plasma composed of electrons and ions under atmospheric pressure is generated by applying high voltage alternating current in a plasma reactor filled with electrical dielectric and ferroelectric pellets or beads of several mm in diameter, where Some of the energy generated is used to treat harmful gases through chemical reactions using high electrons. However, such a noxious gas treatment method has a high power cost required for the treatment process, and the aerosol-type by-products generated during the treatment process may cause clogging in the reactor or worsen the electrical characteristics, thereby preventing continuous operation of the process. There is a problem that the practical practical use and commercialization is difficult.

In addition, similar to the US Patent No. 5,236,672, US Patent No. 4,954,320 discloses a noxious gas treatment method for filling a reactor with precious metal catalyst beads, alumina beads or adsorbents to simultaneously adsorb or catalyze a low temperature plasma. Doing. In addition, US Pat. No. 5,843,288 discloses transition metal catalysts such as lead (Pt), palladium (Pd), and cobalt (Pt) on the surface of ferroelectric beads to reduce gaseous by-products in reactors and alternating current power devices disclosed in such patents. Co), nickel (Ni) and the like has been proposed a technique for coating.

As described above, the reactor for treating noxious gases using low temperature plasma to date is based on a structure or shape in which a tube or body is filled with pellets or beads having dielectric properties, and the catalytic process is performed at a low temperature. When used simultaneously with the plasma forms a catalyst coating on the surface of the dielectric pellets or beads filled in the reactor. However, when these methods are applied to a process that actually emits harmful gases, pressure loss occurs due to the dielectric filled in the reactor, and the presence of particulate materials in the exhaust gas can easily clog the reactor. If the reactor is inevitably applied to a transport engine that generates vibration, the contact surface between pellets or beads may be grounded, and in order to process a large amount of exhaust gas, it is necessary to bundle or collectively bundle several tubular reactors. There are problems such as excessively large scale of the gas treatment system.

In particular, if the volume or volume of the reactor is large, it is not only a practical problem but also the performance of the catalyst activated by the heat cannot be expected because the dielectric heat generated by the AC power is not concentrated in the reaction space. There is a problem that the efficiency is significantly reduced.

Therefore, the development of a technology that does not disturb the flow of gas while having a small-volume reactor structure that can effectively utilize the dielectric heat generated when generating low temperature plasma is an important solution in the process using both low temperature plasma and catalytic process simultaneously. It is raised as a task.

Accordingly, the present invention has been made to solve the above problems and problems, it is an object of the present invention to provide a reactor for treating harmful gases using low-temperature plasma and dielectric heat to prevent pressure loss and clogging.

Another object of the present invention is to provide a reactor for treating harmful gases using low temperature plasma and dielectric heat, which can reduce the overall volume without using pellets or beads.

Still another object of the present invention is to provide a reactor for treating harmful gases capable of treating a large amount of gas in a small space.

It is still another object of the present invention to concentrate heat generated by plasma generation in a narrow space so that the catalyst coated on the electrode surface can be effectively activated by heat, thereby reducing operating power and by-products in liquid and solid state. It is to provide a reactor for treating harmful gases that can suppress the occurrence of.

Another main object of the present invention is to provide a method for treating noxious gas using the reactor described above.

According to the present invention, the volatile organic compounds (VOCs), perfluorocarbons (PFCs), chlorofluorocarbons (CFCs), dioxins and other inorganic gases used in a hazardous gas treatment system using a low-temperature plasma and a catalyst simultaneously to treat harmful gases. The present invention relates to a reactor and a method for manufacturing the same, which can effectively reduce power required for operation by effectively utilizing a dielectric heat and a catalyst, which was not conventionally used in a low temperature plasma reactor, in a reaction process, and suppress generation of by-products in liquid and solid phases. You can do it.

1 is a perspective view schematically showing a reactor for treating harmful gases using a low temperature plasma according to the present invention;

2 is a block diagram showing the arrangement of the plate electrode in the reactor of FIG.

3 is a perspective view showing the configuration of the electrode of FIG. 2 in detail; And

3 is a graph showing the results of the efficiency of low temperature plasma and catalyst in a reactor according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: body 14: flow distributor

16: Plate Electrode 18: Dielectric Plate

20: thin metal film 22: catalyst

24: AC power supply 26: ground

28: power supply

Such objects include a low temperature plasma and a reactor for treating noxious gases using dielectric heat generated when the low temperature plasma is generated, the body having a predetermined internal volume; A plurality of flat plate electrodes arranged in parallel on the body at regular intervals, the plurality of flat plate electrodes being connected to the ground to one of the plate electrodes continuously connected to an AC power source, and to another adjacent plate electrode; And a power supply device for applying a voltage of an AC frequency to each of the plate electrodes connected to the AC power source.

Objects according to the invention also include the steps of preparing a reactor in a noxious gas treatment device; Generating a low temperature plasma and dielectric heat by applying an alternating current voltage of alternating current frequency to each plate-shaped electrode of the reactor; Supplying harmful gas to the inside of the reactor; And it can be achieved by a harmful gas treatment method comprising the step of performing a plasma reaction and a catalytic reaction for the harmful gas at the same time.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a reactor for a noxious gas treatment apparatus using a low temperature plasma and dielectric heat and a noxious gas treatment apparatus using the reactor according to the present invention will be described in detail.

1 and 2, a reactor for a noxious gas treatment apparatus using low temperature plasma and dielectric heat according to the present invention basically includes a cube-shaped body 10 having a predetermined space, such as a rectangle or a square. In front of the body 10 is a flow distributor 14 having an inlet 12 for introducing harmful gas into the body 10.

In particular, the body 10 includes one or a plurality of plate electrodes 16. Each plate electrode 16 is preferably formed in a rectangle or a square. In addition, as shown in FIG. 3, the plate electrode 16 includes two dielectric plates 18 formed of a material such as ceramic, glass, and quartz having both electrical insulation and dielectric properties. Each of these dielectric plates 18 may be, for example, 0.1 to 2 mm thick. In addition, the size of each dielectric plate 18 may be arbitrarily set according to the capacity of the entire reactor, for example, the lengths of the vertical and horizontal sides may be several mm to several hundred mm, respectively.

One side of each dielectric plate 18 is coated with a metal coating material or a metal thin film 20 so as to allow electricity, while the other side is preferably coated with a catalyst 22 or an adsorbent.

On the other hand, each flat electrode 16 is completed by bringing the two dielectric plates 18 into close contact with each other. That is, by adhering one side on which the metal thin film 20 of one dielectric plate 18 is applied and one side on which the metal thin film 20 of the other dielectric plate 18 is applied to each other, The electrode 16 is completed.

Alternatively, the plate electrode may be formed by inserting a metal thin film between two dielectric plates, in which case it is not necessary to apply the metal thin film to all of the mutual bonding surfaces of the respective dielectric plates.

Each of the plate electrodes 16 thus completed is arranged in parallel in the body of the reactor, as shown in FIG. Although only seven flat electrodes are shown in the figure, the number can be arbitrarily set according to the capacity or volume of the reactor. In this way arranged in parallel, one is connected to the AC power source 24 and the other is connected to the ground in a continuous repeating arrangement. At this time, the distance between each electrode is preferably maintained to about 1 to 6mm. In addition, the plate electrodes 16 may be arranged in parallel in several pairs, tens, or hundreds, depending on the flow rate of the gas to be treated or the capacity of the reactor. Although not shown in the drawings, it is preferable that the body forming the outer shape of the reactor is formed of a material such as ceramic to have electrical insulation and withstand high temperatures.

Of course, the power supply 28 connected to each of the plate electrodes 16 of the reactor supplies an alternating voltage of 5 kV to 20 kV at a specific frequency of, for example, several tens to tens of thousands of Hz, and impedance matching with the reactor. Inductance and charging circuits (not shown) are preferably installed between the power supply and the reactor.

In addition, the catalyst coated on each dielectric plate 18 is one or more of metal catalysts such as Ni, Cu, Co, as well as precious metal catalysts such as Pt, Rd, and Pd, which are known to be activated by heat. Can be selected and used. In addition, each of these metal catalysts is first coated with a γ-alumina, silica, or zeolite with a large surface area on a smooth ceramic plate of the dielectric plate 18 so as to increase the contact area with the reactant body, and then on the coated surface. It is preferred to be coated.

In addition, the adsorbent coated on the dielectric plate 18 may be γ-alumina or zeolite. Here, the zeolite is preferably a molecular sieve (Molecular Sieve (MS)) 3A or 5A, it was shown that it is possible to use a catalyst in which the alkaline earth metal, which is an alkali metal, is substituted for these molecular sieves.

According to the reaction process of the reactor configured as described above, first, when the power source device 28 is operated to apply electric power to the reactor, electric discharge occurs between the plate electrodes 16 to generate electrons and ions. The electrons generated here are O, OH, HO ₂ , N radicals generated by directly decomposing the gas molecules to be treated, or by the air supplied with the harmful gas to be treated or the added gas molecules collide with the electrons. Or oxidized or reduced by ions. The above reaction process is a process principle using a general low temperature plasma.

In addition, the reactor according to the present invention can be easily achieved by increasing the temperature in the reactor using the dielectric heating, low temperature plasma reaction by using the elevated temperature in the reactor to activate the catalyst through the dielectric heating It is possible to obtain the combined effect of the catalytic reaction. For example, when the combined effect of low temperature plasma reaction and catalysis is compared with the existing low temperature plasma or catalytic process, the following technical advantages have been shown.

That is, when oxidizing noxious gas through a catalyst as in the prior art, it is necessary to heat the catalyst above a certain temperature. However, when the low temperature plasma and the catalyst are used simultaneously as in the present invention, the temperature at which the catalyst can be activated is lowered due to the low temperature. The execution of the process is also possible. This is because the harmful gas or the oxidizing agent (for example, oxygen, moisture or additives) is converted into a state where a reaction is likely to occur in the low temperature plasma space.

In addition, as in the conventional low temperature plasma reaction, although a particular reaction is less likely to occur selectively, selectivity in the reaction may be increased when the catalyst is used together with the low temperature plasma as in the present invention. For example, when toluene is removed by only low-temperature plasma, more than half of toluene is polymerized and converted into an aerosol form, and these materials may adhere to the surface of the electrode, preventing long-term operation or clogging in the reactor. When activated by the catalyst, the final output can be more easily proceeded to the oxidation reaction of carbon dioxide and water.

Hereinafter, the mode of operation and the effect of the specific embodiment according to the present invention will be described in detail.

Example 1

The size of the plate electrodes 16 is 76mm × 76mm × 1mm, the size of the inner metal thin film 20 is 60mm × 60mm × 0.1mm, the number of the plate electrodes 16 is 15, and each of the plate electrodes 16 The distance between the two is set to 2mm, 14 stages reaction space is formed in the reaction flow cross-sectional area 60mm × 60mm. Then, AC power with an average voltage of 11 kV and a frequency of 60 Hz was supplied to the reactor to generate a low temperature plasma. At this time, the power supply lasted for 5 to 6 hours and repeated experiments were performed 10 times, but no fatal damage due to dielectric breakdown was found in the reactor. Meanwhile, as the dielectric plate of the plate electrode used at this time, a plate formed by coating a gamma-alumina and platinum on an alpha-alumina plate, an alpha-alumina plate, a plate formed by coating a zeolite on an alpha-alumina plate, a quartz plate, etc. Material may be selected and used.

Example 2

Injecting and flowing air into the reactor configured as in Example 1 and applying power by increasing the frequency of the power supply device from 60 Hz to 10 kHz, the power input to the reactor increases as the frequency is increased and discharged from the temperature in the reactor and the rear end of the reactor. It has been shown that the temperature of the air is increased. On the other hand, while the actual total area of the electrode where the low-temperature plasma is generated in the reactor is 6 cm × 6 cm × 14 × 2 = 1008 cm 2, the contact area with the outside can be calculated as 6 cm × 6 cm × 6 = 216 cm 2. . That is, the area of contact with the outside that can generate heat loss is significantly smaller than the area of the electrode where dielectric heat is generated, so that the generated heat can be effectively used in the reaction process. On the other hand, in the conventional tubular reactor, since the contact area between the electrode area and the outside is high, a lot of heat loss is generated, and thus the heat required for the reaction cannot be effectively used.

Example 3

When the air is injected into the reactor configured as in Example 1 and flowed, and the pressure loss was measured at the front and rear ends of the reactor, when the catalyst beads or pellets were filled in the existing tubular reactor and flowed through the air, In comparison, the pressure loss was significantly reduced. Therefore, the reactor according to the present invention can be effectively used in a process having a high flow rate, and it has been shown that clogging does not occur even in the presence of particulate matter or such particles during the reaction process.

For example, when the air containing tens to hundreds of ppm of toluene is supplied to the reactor for a long time, some of the toluene is transformed into small particulate carbon compounds instead of undergoing an oxidation process, and is attached to the electrode. At this time, the attached by-products cause problems in power supply by changing the electrical characteristics of the electrodes. However, when the platinum catalyst causing the oxidation process is coated on the electrode plate as in the present invention, the generation of by-products of particles and liquids is significantly reduced, and after a certain time, only the air is periodically injected to remove the attached carbon compound. It turns out that you can.

Comparative Example 1

In order to examine the effect of catalyst and heat on the removal performance in the actual treatment of harmful gases, 300 ppm of toluene was supplied to the reactor together with air as a noxious gas, and immediately afterwards, 11kV of AC power was supplied to the reactor at a frequency of 60 Hz. After the addition, the concentration of toluene discharged from the rear end of the reactor was measured. Here, for clarity of comparison, 1) a flat electrode using alpha-alumina plate, 2) a flat electrode coated with gamma-alumina on alpha-alumina plate, 3) gamma-alumina and platinum on alpha-alumina plate Comparative experiments were carried out by dividing the case into a coated electrode. In addition, in order to examine how the temperature rise affects the reaction process in the oxidation process of volatile organic compounds such as toluene, the operation temperature (air supplied to the reactor and ambient temperature of the reactor) for each plate electrode It was performed by setting at room temperature, 60 ℃ and 100 ℃, respectively.

The results of the experiment under the set experimental conditions are shown in the graph of FIG. 4. According to this graph, although the power consumption was equally consumed, the removal rate of the toluene (the removed concentration relative to the initial concentration) of the harmful gas increased in the order of alpha-alumina, gamma-alumina, and platinum catalyst. On the other hand, in each case, when the operating temperature is increased, the removal rate of toluene increases in common, indicating that the increase in temperature has a significant positive effect on the reaction process.

Comparative Example 2

In experiments in which the PFCs NF ₃ and CF ₄ are treated with the reactor according to the present invention with respect to harmful gases containing toluene, these gases are added to the low temperature plasma process as well as toluene, and the removal rate by the temperature rise in the reactor is increased. Was observed. In particular, since NF ₃ is a substance that is simply decomposed by heat when the temperature in the reactor is 400 ° C. or higher, an increase in the removal rate by the reactor was observed even when the catalytic process was not used together.

On the other hand, since pyrolysis of CF ₄ is possible only at 1200 ° C to 1800 ° C or higher, a platinum-coated electrode, which is a noble metal catalyst, was required. When using such a platinum catalyst, the temperature in the reactor was maintained at a temperature of 300 ° C to 400 ° C at a low temperature. When plasma occurs, full-fledged CF ₄ decomposition begins.

In addition, even in the decomposition experiments of organic compounds containing Cl, such as trichloroethylene (TCE: trichloroethylene), increasing the reaction temperature was shown to accelerate the oxidation of harmful substances. Accordingly, it is understood that the technique of raising the reaction temperature by the reactor according to the present invention can be widely applied not only to VOCs such as toluene but also to decomposition of inorganic substances such as dioxins, PFCs, CFCs, and nitrogen oxides.

As described above, according to the reactor for treating harmful gases using low temperature plasma and dielectric heat according to the present invention and a method of treating the same, the process of reacting dielectric heat generated when generating low temperature plasma through an AC power source and a dielectric electrode is performed. It can be used in conjunction with the catalyst has the effect of improving the reaction efficiency. In addition, the pressure loss in the reactor is reduced, maintenance such as cleaning and replacement of the electrode is easy, and the volume of the reactor is small, so that there is an advantage that the practicality is improved.

In the above, preferred embodiments of the present invention have been described, but it will be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the appended claims.

Claims (8)

A reactor for processing harmful gases using low-temperature plasma and dielectric heat generated during the generation of low-temperature plasma, comprising: a body having a predetermined internal volume for accommodating noxious gas, a plurality of plate electrodes disposed on the body; In the reactor for the treatment of harmful gases using low-temperature plasma and dielectric heat having a power supply for applying a voltage to each of the plate electrodes, Each of the plate electrodes is disposed in parallel, and one plate electrode is continuously connected to an AC power source and the other plate plate electrode is connected to ground; Each of the plate electrodes is formed by bonding one side of each of the two thin plates to be in contact with each other so that the metal thin film is coated with a metal thin film on one side and a catalyst is applied on the other side to allow electricity to pass therethrough; Each dielectric plate has a thickness of 0.1 mm to 2.0 mm and is selected from one of glass, ceramic, and quartz; The catalyst is a reactor for the treatment of harmful gases using low-temperature plasma and dielectric heat, characterized in that one selected from the group of metallic catalysts including platinum, Pd, V, Rh and TiO ₂ photocatalyst groups. delete delete delete The reactor for treating noxious gas according to claim 1, wherein the power supplied to the plate electrode by the power supply device is an alternating voltage of 1 kV to 30 kV at a frequency of 50 Hz to 100 kHz. Using one or more hazardous gas treatment reactors according to claim 1 or 5, at least one harmful component selected from the group consisting of VOCs (Volatile Organic Compounds), PFCs (Perfluorocarbons), CFCs (Chlorofluorocarbons), TCE (trichloroethylene), Dioxin In the method of processing the harmful gas containing, Preparing the reactor in a hazardous gas treating apparatus; Generating a low temperature plasma and dielectric heat by applying an alternating current voltage of alternating current frequency to each plate-shaped electrode of the reactor; Supplying harmful gas to the inside of the reactor; And Toxic gas treatment method comprising the step of performing a plasma reaction and a catalytic reaction to the harmful gas at the same time. The method of claim 6, further comprising periodically supplying clean air or oxygen to the reactor after a long time in order to remove solid and liquid by-products that may be formed inside the reactor. . delete