KR20050108540A - Treating method for exhaust gas including perfluor compound using non-thermal plasma and apparatus thereof - Google Patents

Abstract

The present invention relates to a method for treating flue gas containing perfluorinated or perfluoro compounds (PFC) using a low temperature plasma, and a method for treating the same, wherein the method according to the present invention uses a magnetron to absorb microwaves of 700 to 3500 MHz in a waveguide. Irradiating and projecting into the quartz tube to produce a glow discharge in the quartz tube; And a step of removing and treating the perfluorinated compound by introducing a mixed gas in which the volume ratio of the perfluorinated compound gas and the oxygen gas is 1: 8 to 20 into the glow discharge region to generate a low temperature plasma. The apparatus according to the exhaust gas introduction pipe; At least two magnetrons; A waveguide having an exhaust gas introduction pipe passing through the center and a magnetron installed at the side, and having a microwave projection hole; And a quartz tube fixed by an inner housing and abutting a microwave projection hole.] According to the present invention, it is possible to efficiently remove various kinds of perfluorinated compound-containing exhaust gases, and to significantly reduce installation and operation costs. It is easy to install and operate, easy to install, large-capacity processing, compact and durable, and high economical efficiency, as well as general volatile organic compounds (PFC) It can be applied effectively and economically in the decontamination treatment of the compound (VOC).

Description

Method for treating flue gas containing perfluorinated compound using low temperature plasma and apparatus therefor {TREATING METHOD FOR EXHAUST GAS INCLUDING PERFLUOR COMPOUND USING NON-THERMAL PLASMA AND APPARATUS THEREOF}

The present invention relates to a method for treating flue gas containing perfluorinated or perfluoro compounds (PFC) using low temperature plasma, and a device thereof, and more particularly, to perfluorine generated from a semiconductor manufacturing facility or a liquid crystal display device manufacturing facility. The present invention relates to a method and apparatus for efficiently and economically treating exhaust gas containing a fluorination compound by glow discharge using a low temperature plasma.

Perfluorinated compounds contained in exhaust gases emitted from manufacturing processes such as semiconductor integrated circuits or liquid crystal displays are generally used in dry etching, chemical volatile deposition (CVD) processes, or chamber cleaning processes. As a gaseous phase (gaseous phase) compound to be used, for example, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , CHF ₃ , NF ₃ , SF _{6 And} the like.

Perfluorinated compound gases are stable and toxic compounds that, although their total emissions are only about a thousandth of the carbon dioxide, have a long lifetime when released into the atmosphere due to their strong binding properties, which are hardly decomposed or dissociated. Thermal incineration, which is commonly applied to common volatile organic compounds (VOCs), is difficult to handle effectively and economically.

Currently, countries around the world strictly regulate their use values. In Korea, the limit of the threshold limit value (TLV) is limited to 0.5 ppm or less, and perfluorinated compounds-based gases have a global warming index (Grobal). Since Warming Potential (GWP) is a much higher global warming substance than carbon dioxide, voluntary reduction regulations on perfluorinated compound emission are underway around the World Semiconductor Association (WSC). As expected, a considerable amount of investment is required for the construction of new semiconductor-related lines.

Conventional typical methods for the treatment of exhaust gases containing perfluorinated compounds discharged from manufacturing processes, such as semiconductor integrated circuits or liquid crystal displays, include wet treatment, combustion, pyrolysis, thermochemical treatment, and high temperature plasma treatment. have.

The wet treatment method, for example, introduces a flue gas through a wet etching, chemical vapor deposition reaction process on a wafer into a wet gas scrubber, contacts with circulating water or another solvent driven by a pump, and dissolves it. Or by reacting with the solvent to discharge together with the solvent, the method uses a large amount of solvent to discharge the solvent once used, so that the treatment efficiency is low, the problem of corrosion of the scrubber is serious, and the unreacted substance in the scrubber There is a possibility that the residual, the outlet may be blocked by the formation of the reaction solid, there is a disadvantage that the operation and maintenance costs increase because a separate purification auxiliary equipment for reprocessing the waste solvent is required.

Combustion method introduces exhaust gas into the combustion chamber, and then burns the exhaust gas using methane (CH ₄ ) or hydrogen (H ₂ ) as a fuel under the introduction of oxygen (O ₂ ) to improve combustion efficiency. a method for processing by using the wet gas scrubbers as described above, because direct combustion of a flammable-gas has a problem in safety, and various types of combustion by-products, such as HF, NO _x, CO ₂ produced as a by-product of the combustion As a result, accurate evaluation of decontamination efficiency (performance) is difficult, and since a wet gas scrubber is used, the above-described problems with the wet treatment method are accompanied.

Pyrolysis method is a method of heating and treating the exhaust gas at a temperature of about 800 ~ 1200 ℃ by using a heater, which is advantageous in terms of stability in the treatment of flammable exhaust gas because of the use of a heater, but uses more energy and is corrosive. There is a high risk of corrosion of the hot wire due to the contact with the strong exhaust gas, the performance of the controller of the heater element, such as the performance degradation due to the heat fade phenomenon, there is a fear of disconnection of the heater, and the efficiency of removal is not high. have.

Thermochemical treatment is pyrolysis method and, like in which the thermal decomposition by heating the exhaust gas to the heater, and then, how to handle harm-elimination for the exhaust gas is passed through the resin adsorbent, or a catalyst such as a cage or the filter cartridge, or the method has a low treatment efficiency, a high stability CF ₄ In addition to the difficulty in processing such as the above, there is a fear of secondary contamination by the filter cartridge, and there is a disadvantage in that it is accompanied with all the problems of the above-described pyrolysis method.

The high temperature plasma treatment is a method of removing perfluorinated compounds using high temperature plasma by exposing the process gas under high pressure in a state of molecular plasma of about 10,000 K, and then quenching it. There is a problem of electrode deterioration due to burning phenomenon, and when using a high temperature thermal plasma, the processing gas must be heated or maintained at a high temperature of at least 600 ° C., which entails a considerable amount of additional energy consumption. Compared to the cost and the cost, the throughput and performance were not satisfactory enough.

In addition, as another treatment method, a method of removing the perfluorinated compound in the exhaust gas with aluminum to form AlF ₃ is proposed. There is a problem in terms of maintenance and maintenance of the overall treatment facilities, such as the need for facilities.

Accordingly, the development of a method and apparatus capable of efficiently and economically treating flue gas containing various kinds of perfluorinated compounds emitted in a large amount in a manufacturing process such as a semiconductor integrated circuit or a liquid crystal display device have been in the field for a long time. Has been requested.

Therefore, the first object of the present invention is to efficiently perfluorinate the exhaust gas containing various kinds of perfluorinated compounds exhausted in a large amount in the manufacturing process such as semiconductor integrated circuit or liquid crystal display device. It is to provide a compound-containing flue gas treatment method.

A second object of the present invention is to provide an economical perfluorinated compound-containing flue gas treatment method which is easy to install and operate, and which is economical and capable of large-volume treatment.

It is a third object of the present invention to provide a perfluorinated compound-containing flue gas treatment apparatus capable of compacting and having excellent durability for smoothly implementing the first and second objects described above.

According to one preferred aspect of the present invention for smoothly achieving the first and second objects of the present invention, a magnetron is used in a waveguide at 700 to 3500 MHz, preferably 1500 to 2800 MHz, more preferably. Irradiating microwave at 2400-2500 MHz and causing a glow discharge in the quartz tube by projecting it through a microwave projection hole into a quartz tube abutting it; The glow discharge in the above-described quartz tube is a mixture gas of perfluorinated compound-containing exhaust gas and oxygen gas whose volume ratio of the perfluorinated compound gas and oxygen gas is adjusted to 1: 8-20, preferably 1: 14-18. Provided is a method for treating perfluorinated compound-containing flue gas using a low-temperature plasma, which comprises introducing into a zone to produce a low-temperature plasma to remove and treat the above-mentioned perfluorinated compound.

According to a preferred aspect of the present invention for smoothly achieving the third object of the present invention, there is provided an exhaust gas introduction tube having an inlet opening and an outlet opening; At least two magnetrons; A waveguide having a microwave projection hole in a region through which the exhaust gas introduction pipe passes through the center and the magnetron is installed on the side, and through which the discharge opening of the exhaust gas introduction pipe passes; The exhaust gas inlet pipe is inserted into the discharge opening, and the outer circumferential surface is fixed by the inner housing, and consists of a quartz tube positioned in contact with the microwave projection hole. A perfluorinated compound-containing flue gas treatment apparatus is provided using a low temperature plasma in which the perfluorinated compound introduced therefrom is removed in a low temperature plasma state.

Hereinafter, the present invention will be described in detail.

In the low temperature plasma used in the present invention, electrons generated by high-pressure electric discharges collide with flue gas molecules to change the outer electron state of the flue gas molecules. Accordingly, radicals, excitation molecules, ions, etc., which are highly reactive chemically active species, are positive or It is a negatively charged, electrically neutral gas, and a plasma with only a high electron temperature.

Since the low temperature plasma has only a high electron temperature, the gas temperature is the temperature of the exhaust gas, and is generally applicable to materials or conditions that are difficult to apply at high temperatures, the apparatus is simple, and various chemical reactions can be induced.

In the discharge forming the low temperature plasma, a pulse streamer discharge generating a streamer discharge by applying a pulsed high voltage having a rise time of several tens of ns and a duration of about 1 ms or less is sandwiched between an insulator between parallel electrodes having a number of pores. Silent discharge, which causes pulsed discharge by applying alternating current high voltage, Metal mesh electrodes are installed on both sides of the filler of ceramic pellets with a particle diameter of several mm, and partial discharge, which applies alternating current high voltage, is generated during inequality. Corona discharge in which light is produced, microwave discharge using a magnetron, etc. are mentioned.

However, in the present invention, among the various discharge forms capable of generating the above-mentioned low temperature plasma, homogeneous plasma generation is possible over a relatively wide volume range, and easy-to-control microwave discharge is applied, and low temperature plasma by such microwave discharge is applied. It is most effective for the decontamination treatment of the perfluorinated compound.

The microwave discharge is applied by the magnetron of the klystron, the magnetron, the traveling wave, the backward wave, etc., and irradiates the microwave of 700 to 3500 MHz, preferably 1500 to 2800 MHz, more preferably 2400 to 2500 MHz in the waveguide. The glow discharge generated in the quartz tube is utilized by projecting it through the microwave projection hole into the quartz tube abutting it.

On the other hand, in the method for treating perfluorinated compound-containing flue gas using the low temperature plasma according to the present invention, it is not sufficient to remove the perfluorinated compound by removing the low temperature plasma, and oxygen gas is supplied at a specific volume ratio to the perfluorinated compound gas. It is necessary to apply the mixed gas mixed.

In the present invention, the mixing ratio (volume ratio) of the perfluorinated compound gas to oxygen gas is generally in the range of 1: 8 to 20, preferably in the range of 1:14 to 18. When the volume ratio of the oxygen gas to the perfluorinated compound gas exceeds 1: 8, the decontamination efficiency is lowered to less than 50%, which is not preferable, and conversely, when the volume ratio is less than 1:20, Not only is it difficult to expect an increase in decontamination efficiency, but a decrease in treatment efficiency due to an increase in the gas flow rate to be treated may be a problem, which is also undesirable.

When the mixing ratio (volume ratio) of the perfluorinated compound gas to oxygen gas is 1:15, 99% or more of CF ₄ which is the most stable form of perfluoride is removed.

According to a preferred example of the present invention, at least 99.3% of CF ₄ , at least 99.8% of C ₂ F ₆ , at least 99.3% of C ₃ F ₈ , at least 99.4% of C ₄ F ₈ , C ₅ F ₈ At least 99.1% of, at least 99.5% of CHF ₃ , at least 99.9% of NF ₃ , at least 99.6% of SF ₆ , and at least 99.7% of CH ₂ F ₂ are removed.

On the other hand, the perfluorinated compound-containing exhaust gas discharged from a manufacturing process such as a semiconductor integrated circuit or a liquid crystal display device contains a large amount of nitrogen gas as a relatively inert and economical carrier gas.

As used herein, the term 'abatement' broadly refers to a wide variety of toxic and additionally flammable perfluorinated compounds as described above, which are harmless to the human body or to solvents such as water. It needs to be understood to mean converting into a chemical species that can be collected by known means, such as being collected, adsorbed on a filter or the like, or converted into a harmless substance by a chemical reaction cartridge. Most of the perfluorinated compounds such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , C ₅ F ₈ , CHF ₃ , NF ₃ , SF ₆ , CH ₂ F ₂ are decomposed, or It can be understood to mean a state that is converted and does not exist.

The method for treating perfluorinated compound-containing flue gas using a low temperature plasma according to the present invention includes the following steps.

(A) Glow discharge in a quartz tube by using a magnetron to irradiate a microwave of 700 to 3500 MHz, preferably 1500 to 2800 MHz, more preferably 2400 to 2500 MHz in the waveguide and project it through a microwave projection hole into a quartz tube that is in contact with it. Causing; And

(B) The quartz tube described above is a mixed gas of perfluorinated compound-containing exhaust gas and oxygen gas in which the volume ratio of the perfluorinated compound gas and the oxygen gas is 1: 8 to 20, preferably 1:14 to 18. Decontaminating said perfluorinated compound by introducing it into a glow discharge region within said to produce a low temperature plasma.

Optionally, the first decontamination flue gas via step (B) described above is further subjected to at least one or more times again in succession with the same step as step (B) described above. Complete decontamination may be performed, in which case it is not necessary to inject oxygen gas again, but if necessary, oxygen gas may be supplemented and supplied so that the first decontamination flue gas: oxygen has a volume ratio of 1: 0.08 to 0.20. have.

In the present invention, as an optional step, if necessary, flashing the vaporized neutralizer or water before, after or simultaneously with the above step (B) for pH control and decontamination assistance of the perfluorinated compound-containing exhaust gas. Step (C) may also be carried out, and in step (B), the emission state of the low-temperature plasma is analyzed by polarization to monitor the reaction state of the exhaust gas using a spectrometer, and accordingly to control the microwave frequency of the magnetron. And the control step (D) can also be performed in parallel.

The exhaust gas introduced into the exhaust gas introduction pipe in the above step (B) may be introduced by, for example, a booster pump, and the decontaminated gas may be performed by, for example, a dry pump, and optionally also required. It is also possible to include a drain pipe and an exhaust duct.

Next, an apparatus according to the present invention for efficiently and economically carrying out the above-described method for treating perfluorinated compound-containing flue gas using a low temperature plasma according to the present invention will be described with reference to the accompanying drawings.

1 is a cross-sectional view of a perfluorinated compound-containing flue gas treatment device 1 using a low temperature plasma according to the present invention, wherein the device 1 includes an flue gas introduction pipe having an inlet opening 2a and an outlet opening 2b. 2), at least two magnetrons 10 and the exhaust gas introduction pipe 2 pass through the center, and the magnetron 10 is installed on the side, and the discharge opening of the exhaust gas introduction pipe 2 is A waveguide (3) having a microwave projection hole (3b) and an exhaust gas introduction tube (2b) toward the discharge opening (2b) are inserted in an area through which 2b) penetrates, and an outer peripheral surface thereof is fixed by an inner housing (6). It consists of the quartz tube 4 which abuts on the said microwave projection hole 3b.

The magnetron 10 is provided with at least two or more, for example, in mutually opposite positions, in order to increase the waveguide efficiency and to prevent the attack of the electromagnetic waves while also allowing the microwaves to be highly uniformly distributed. can do.

Also, optionally, the above-described quartz tube 4 is used as the main, and the auxiliary quartz tube 5 having a thinner tube thickness is formed to extend outwardly therefrom, thereby increasing the length of the glow discharge generating region, thereby increasing the exhaust gas. The low-temperature plasma state of the off-gas containing the perfluorinated compound discharged from the inlet pipe 2 can also be extended. The auxiliary quartz tube 5 is accommodated in a relatively large diameter outer housing 7 located outside the housing 6 (ie, inner housing), and extends from the outer housing 7. 7a) can be securely detachable.

The exhaust gas introduction pipe 2 penetrates the center of the waveguide 3, and one end of the introduction opening 2a is located outside the waveguide, and the through portion (not shown) is sealed so that microwaves do not leak. The discharge opening 2b at the other end is inserted into the main quartz tube 4 through the microwave projection hole 3b formed on the opposite surface of the penetrating portion.

The waveguide 3 may be cylindrical or rectangular in cross section, and the material may be made of silver plated or stainless steel of an inner wall of a copper or brass tube. The diameter of the microwave projection hole 3b is larger than the diameter of the flue gas introduction pipe 2 penetrating through it, and the outer periphery thereof is formed by the inclined portion 3c that extends toward the inside of the waveguide 3 so that the waveguide 3 The microwaves within can be formed so that they can be easily projected into the main quartz tube 4 inserted in the inner housing 6. An opening 3a is formed in at least one outside of the waveguide 3, and the magnetron 10 is mounted so that the electromagnetic tube 11 (microwave tube) protrudes into the waveguide 3 through the opening 3a. do. The number of magnetrons 10 described above is not limitative and arbitrary in the present invention.

Here, reference numeral 12 denotes a power line connector.

On the other hand, the inner circumferential surface of the inner housing 6 provided in contact with the microwave projection hole 3b of the waveguide 3 and the outer circumference of the discharge opening 2b side of the exhaust gas introduction pipe 2 are main quartz. In contact with the tube 4, the discharge opening 2b is located in the main quartz tube 4 described above. In addition, the outer end of the main quartz tube 4 may be formed as the enlarged portion 4a so that the low temperature plasma generation region due to the glow discharge can be smoothly extended to the "B" region as well as the "A" region. have. By such a structure, the retention time during which the flue gas forms a low temperature plasma can be effectively extended.

For reference, the inner housing 6 or the whole including the inner housing 6 and the outer housing 7 may be referred to as a waveguide.

The above apparatus according to the present invention has sufficient utility even as a single apparatus, but if necessary, it is possible to increase decontamination processing capacity by connecting a plurality of the apparatus in parallel, and also by removing a plurality of the apparatus in series. Maximization of the efficiency is possible, and if necessary, it is also possible to install and use a plurality of combinations of the above-mentioned devices in parallel and in series.

Hereinafter, the present invention will be described in more detail with reference to Examples, which are intended to illustrate the present invention but are not intended to limit the present invention.

Examples 1-6 and Comparative Examples 1-5

The exhaust gas was removed under the following conditions by using a perfluorinated compound-containing flue gas treatment apparatus using a low-temperature plasma as shown in FIG. 1 and using CF ₄ , which is the most stable form of the perfluorinated compound, as an index. The treatment was carried out and the results are shown in Table 1 below.

* Power: AC220V, 5A

* Magnetron Frequency: 2450MHz

* Equipped with two commercial magnetrons

* Low Temperature Plasma Generating Path Length: 15cm

* Total flow rate: 81 L / min ~ 101 L / min

* Treatment flue gas composition (ℓ): CF ₄ 1ℓ / min, N ₂ 80ℓ / min, O ₂ 0 ~ 20ℓ / min

* The gas chromatography was used for the measurement of the concentration of CF ₄ after decontamination treatment.

* Detector: electrical cooled MCT

CF ₄ before treatment (ℓ) O ₂ Usage (ℓ) N ₂ Volume (ℓ) CF ₄ volume after treatment (cc) Decontamination efficiency (%) Low temperature plasma Comparative Example 1 One 0 80 1000 ─ off Comparative Example 2 One 0 80 635.9 36.4 on Comparative Example 3 One One 80 642.4 35.7 on Comparative Example 4 One 3 80 602.0 39.8 on Comparative Example 5 One 5 80 580.0 42.0 on Example 1 One 7 80 510.0 49.0 on Example 2 One 10 80 132.7 86.7 on Example 3 One 13 80 21.5 97.9 on Example 4 One 15 80 8.2 99.2 on Example 5 One 18 80 9.1 99.1 on Example 6 One 20 80 9.7 99.0 on

As described above, according to the method and apparatus for treating perfluorinated compound-containing flue gas using a low-temperature plasma according to the present invention, various types of perfluorinated compounds discharged in a large amount in a manufacturing process such as a semiconductor integrated circuit or a liquid crystal display device are contained. Since the exhaust gas can be removed very efficiently, it is possible to meet the requirements of future flue gas-containing flue gas regulation legislation, and can significantly reduce the installation and operation costs, and the installation and operation work are simple, easy and large-volume treatment. High compactness, compactness, durability, and the like, the method and apparatus of the present invention are not only decontamination treatment for perfluorinated compounds (PFCs) but also general volatile organic compounds (VOCs). It is effective and effective in removing It may be widely applied to expulsion.

1 is a cross-sectional view of a perfluorinated compound-containing exhaust gas treatment apparatus using a low temperature plasma according to the present invention.

-Explanation of symbols for the main parts of the drawings-

1: Low temperature plasma processing apparatus of the present invention

2: exhaust gas introduction pipe 2a: introduction opening

2b: discharge opening 3: wave guide

3a: aperture 3b: microwave projection hole

3c: slope 4: (main) quartz tube

4a: part 5: auxiliary quartz tube

6: (inside) housing 7: outer housing

7a: support

10: magnetron

11: electron tube (microwave tube) 12: power line

Claims (8)

Method for treating flue gas containing perfluorinated or perfluoro compounds (PFC) using a low temperature plasma consisting of the following steps: (A) generating a glow discharge in the quartz tube by irradiating a microwave of 700 to 3500 MHz in the waveguide using a magnetron and projecting it through a microwave projection hole into a quartz tube abutting it; And (B) A low-temperature plasma was introduced by introducing a mixed gas of a perfluorinated compound-containing exhaust gas and an oxygen gas having a volume ratio of the perfluorinated compound gas and oxygen gas 1: 3 to 20 into the glow discharge region in the quartz tube. Treating the above-mentioned perfluorinated compound to produce an abatement. The method for treating perfluorinated compound-containing exhaust gas using a low-temperature plasma according to claim 1, wherein the microwave has a frequency of 1500 to 2800 MHz and a volume ratio of the perfluorinated compound gas and oxygen gas is 1: 14-18. 2. The perfluorine using the low temperature plasma according to claim 1, wherein the exhaust gas treated through step (B) is subjected to at least one re-treatment of the same decontamination step (C) as in step (B). Process for treating flue gas containing fluorinated compounds. The method for treating perfluorinated compound-containing flue gas using a low-temperature plasma according to claim 3, wherein the flue gas subjected to the first decontamination treatment in step (C) is supplemented with oxygen gas so that the volume ratio of oxygen is 1: 0.08-0.20. . The method according to any one of claims 1 to 4, wherein in step (B), the emission state of the low-temperature plasma is polarized to monitor the reaction state of the exhaust gas using a spectrometer, and thus the microwave frequency of the magnetron is monitored. A method of treating perfluorinated compound-containing flue gas using a low temperature plasma that performs controlling monitoring and control step (D). An exhaust gas inlet tube having an inlet opening and an outlet opening; At least two magnetrons; A waveguide having a microwave projection hole in a region through which the exhaust gas introduction pipe passes through the center and the magnetron is installed on the side, and through which the discharge opening of the exhaust gas introduction pipe passes; The discharge opening side exhaust gas introduction tube is inserted and the outer circumferential surface is fixed by the inner housing and consists of a quartz tube positioned in contact with the microwave projection hole: The perfluorinated or perfluoro compounds (PFCs) introduced from the flue gas introduction tube by the glow discharge in the quartz tube by microwaves are ablated in a low temperature plasma state. An apparatus for treating exhaust gas containing perfluorinated compound using low temperature plasma. 7. The apparatus for treating perfluorinated compound-containing flue gas using low temperature plasma according to claim 6, wherein the auxiliary quartz tube extends outward from the quartz tube and is accommodated in the outer housing by the support portion. The method according to claim 6 or 7, wherein the outer periphery of the microwave projection hole is formed with an inclined portion that is wider toward the inside of the waveguide, and an extension is formed at the outer end of the quartz tube, The wall is a flue gas-containing flue gas treatment apparatus using a low-temperature plasma thinner than the wall of the quartz tube described above.