KR101077145B1 - Gas scrubber - Google Patents

Abstract

The present invention relates to a gas scrubber, and an embodiment of the present invention is provided with a gas inlet through which a processing gas is introduced, and a burning chamber for burning the introduced processing gas, and at least one burning chamber installed at one side of the burning chamber. The preheating chamber for supplying the combustion air preheated to the chamber and the gas guide tube installed in the lower side of the burning chamber and guiding the processing direction of the processing gas are installed therein, and the processing gas is cooled and the harmful gas contained in the processing gas. At least one absorber is embedded to filter the material, and on one side there is a cooling chamber provided with a gas discharge line for discharging the cooled processing gas, and one side of the cooling chamber further cools the first cooled processing gas. And an auxiliary cooling chamber to be installed above the cooling chamber and an injection nozzle disposed at an end portion to allow the cooling water to be injected into the cooling chamber. 1 is installed on the lower side of the circulation pipe and the cooling chamber and installed on one side of the circulation pipe and the cooling chamber to discharge the cooling water injected into the cooling chamber and the cooling water discharged by the circulation pipe through the first circulation pipe to the upper portion of the cooling chamber. Cooling water circulation system equipped with a second circulation pipe for injecting the cooling water into the auxiliary cooling chamber by the injection nozzle installed at the other end is installed in the auxiliary cooling chamber and the other side is connected to the circulation pump and the other side is drawn up to the circulation pump It provides a gas scrubber comprising a.

According to one embodiment of the present invention, it is possible to process a large amount of gas by connecting to a plurality of manufacturing equipment at a time, and to reduce the cost by recycling the cooling water used, inducing the complete combustion of the processing gas to improve the combustion efficiency Can be improved.

Gas Scrubber, Burning Chamber, Preheat Chamber, Cooling Chamber, Absorber, Coolant

Description

Gas Scrubber {GAS SCRUBBER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas scrubber for purifying and exhausting a process gas, particularly an exhaust gas containing a ignitable gas or a toxic gas generated in a semiconductor manufacturing process.

That is, the present invention efficiently removes various harmful gases containing acid gas components such as hydrogen chloride, hydrogen fluoride, sulfur oxides, nitrogen oxides, hydrogen sulfide, and sulfurous acid gas generated in the chemical industry, semiconductor or LCD manufacturing industry and many other industrial fields. A gas scrubber for combustion and removal.

In the process of producing a semiconductor device, there are many processes for emitting toxic gases. For example, SiH ₄ , SiH ₂ , NO, AsH ₃ , PH ₃ , NH ₃ , N used in Chemical Vapor Deposition (CVD) process, ion implantation process, etching process, diffusion process, etc. Gases such as ₂ O and SiH ₂ Cl ₂ are used, and the gases released through the process contain various types of toxic substances.

These toxic gases are not only harmful to the human body but also flammable and corrosive, causing fires and other accidents.

In addition, the release of these toxic gases into the atmosphere causes serious environmental pollution, so that the gas passes through a gas scrubber to purify the gas before it is released into the atmosphere.

Gas scrubbers are roughly classified into a wetting method and a burning method.

Wetting scrubber is a structure that cleans and cools exhaust gas by using water, and has a relatively simple structure, so that it is easy to manufacture and large-capacity. However, insoluble gas cannot be treated, and particularly ignitable There is an inadequate problem in the treatment of exhaust gas containing hydrogen groups.

The burning scrubber has a structure in which an exhaust gas passes directly through a burner such as a hydrogen burner, or is burned indirectly by forming a high temperature chamber using a heat source and passing the exhaust gas therein.

Such a burning scrubber has an excellent effect on the treatment of ignitable gases, but is inadequate for the treatment of poorly burned earth gas.

On the other hand, the reaction process using a ignition gas such as hydrogen and earthwork gas such as silane (SiH ₄ ), for example, the semiconductor manufacturing process is carried out at a high temperature higher than room temperature, so the exhaust gas at the same time purifying the toxic gas in the exhaust gas treatment It is necessary to cool.

Therefore, in the semiconductor manufacturing process, a mixed gas scrubber combining a wetting scrubber and a burning scrubber is used.

The mixed gas scrubber first has a structure in which the exhaust gas is first burned in the combustion chamber to remove the ignition gas and the explosive gas, and then secondarily contained in the water tank to melt the water-soluble toxic gas in the water.

However, conventional mixed gas scrubbers generally have a limited processing capacity, for example, by using one scrubber per set of one CVD chamber.

In addition, the conventional scrubber uses compressed air at room temperature for combustion, wherein the air at room temperature also serves to burn the process gas in the combustion chamber, but also rapidly lowers the temperature in the combustion chamber. After ignition at the bottom of the tank, it passes through the tank before complete combustion.

Accordingly, in the case of H2 may be in a state that can be exploded at the gas outlet due to incomplete combustion, in the case of NH3 has a problem in that a large cost is consumed in the waste water treatment by making Tn dissolved in water.

In addition, the cost is excessively consumed as a large amount of cooling water is required, and the gas that can be treated using a heater in the combustion chamber is only a low temperature gas such as PH ₃ , SiH ₄ , H ₂ , and CH ₄ , PFC gas, which has a fatal effect on global warming such as C ₂ F ₆ and NF ₃ , is difficult to treat.

The present invention has been made to solve the problems described above, according to one embodiment of the present invention, it is possible to purify the processing gas of a large capacity, and the effect of productivity improvement due to cost reduction and increased combustion efficiency, etc. Gas scrubber is provided.

According to an embodiment of the present invention, the present invention relates to a gas scrubber, and an embodiment of the present invention is a burning chamber for forming a gas inlet through which a processing gas is introduced and burning the introduced processing gas, At least one side is installed at one side and a preheating chamber for supplying combustion air preheated to the burning chamber, and a gas guide tube installed at the lower side of the burning chamber and guiding the processing direction of the processing gas and cooling the processing gas. At least one absorber is embedded to filter the harmful substances contained in the processing gas and a cooling chamber is provided at one side with a gas discharge line for discharging the cooled processing gas, and is installed at one side of the cooling chamber. The inside of the cooling chamber by an auxiliary cooling chamber for further cooling the primary cooled processing gas and an injection nozzle installed at an end of the auxiliary cooling chamber. The first circulation pipe and the lower side of the cooling chamber to allow the cooling water is injected into the furnace and the circulation pipe to discharge the cooling water injected into the cooling chamber and one side of the cooling chamber and the cooling water discharged by the circulation pipe to the first circulation Circulation pump that is pulled up to the upper part of the cooling chamber through the pipe and one side is connected to the circulation pump, the other side is installed in the auxiliary cooling chamber and the second circulation to inject the coolant into the auxiliary cooling chamber by the injection nozzle installed at the end Provided is a gas scrubber comprising a cooling water circulator equipped with a pipe.

In this case, an inlet pipe having a plurality of inlet ports may be connected to the gas inlet port.

In addition, one side of the gas inlet may be provided with a combustion gas supply device for supplying at least one combustion gas selected from H ₂ , LNG, LPG to the burning chamber.

In addition, one side of the cooling chamber, a drain chamber for storing the moisture generated during the process may be provided.

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In addition, on the inner circumferential surface of the auxiliary cooling chamber, a dust collecting absorber is formed so that a plurality of inclined jaws projecting downwardly are staggered from each other.

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According to the gas scrubber according to an embodiment of the present invention, the inlet pipe having a plurality of inlet port is provided, it is possible to purify the processing gas generated in a large number of equipment in one gas scrubber.

In addition, by supplying the preheated combustion air into the burning chamber to induce the complete combustion of the processing gas, it is possible to reduce the processing cost due to incomplete combustion, and by installing a cooling water circulation system to enable reuse of the cooling water, Can reduce the cost.

In addition, it is possible to improve productivity by reducing maintenance costs and time, and also to treat PFC gas, which has been difficult to treat conventionally.

Hereinafter, a preferred embodiment of a gas scrubber according to an embodiment of the present invention will be described with reference to the accompanying drawings. In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description.

In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention or custom of the user, the operator. Therefore, definitions of these terms should be made based on the contents throughout the specification.

In addition, the following examples are not intended to limit the scope of the present invention but merely illustrative of the components set forth in the claims of the present invention, which are included in the technical spirit throughout the specification of the present invention and constitute the claims Embodiments that include a substitutable component as an equivalent in the element may be included in the scope of the present invention.

Example

1 is a cross-sectional view showing a gas scrubber according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a burning chamber of FIG. 1, FIG. 3 is a cross-sectional view showing a cooling chamber of FIG. 1, FIG. IV-IV cross-sectional view, Figure 5 is a cross-sectional view showing an embodiment of the auxiliary cooling chamber of Figure 1, Figure 6 is a schematic configuration diagram of the combustion gas supply device of Figure 1, Figure 7 is a gas scrubber according to another embodiment of the present invention It is a cross-sectional view.

As shown in FIG. 1, the gas scrubber 100 according to an embodiment of the present invention supplies a burning chamber 200 and a preheated air to the burning chamber 200 for burning a toxic or explosive process gas. The preheat chamber 300, and a cooling chamber 400 for cooling the burned process gas.

Here, the burning chamber 200 is formed in a substantially cylindrical shape, as shown in Figs. 1 and 2, the gas inlet 210 is formed so that the processing gas, such as toxic gas or explosive gas flows in the upper side.

At this time, the gas inlet 210 is preferably connected to the inlet pipe 240 having a plurality of inlet port 241, each inlet port 241, such as a CVD chamber (not shown) for generating a processing gas The semiconductor manufacturing equipment is connected to each other, and the processing gas discharged from the plurality of semiconductor manufacturing equipment is introduced into the gas inlet 210 through the inlet pipe 240.

At this time, the number of the inlet port 241 may be appropriately selected in consideration of the processing capacity of the gas scrubber 100, it is preferable that 1 to 30 inlet port 241 is provided in the inlet pipe 240.

A pipe 220 having a predetermined diameter is installed inside the burning chamber 200, and a heater 230 providing a sufficient amount of heat (800 ° C. or more in this embodiment) is provided between the burning chamber 200 and the pipe 220. Is installed.

That is, a heater 230 is provided on the inner surface of the burning chamber 200 in order to burn and decompose the process gas induced through the pipe 220, and the process gas combusted by the heating of the heater 230 is installed. Is guided to the lower side of the burning chamber 200 is discharged.

Therefore, when the gas scrubber 100 is operated, various processing gases used in the semiconductor manufacturing process are introduced into the burning chamber 200, wherein the burning chamber 200 is provided by the heater 230 installed on the outer surface thereof. The process gas heated to a high temperature and introduced into the burning chamber 200 is heated while reacting with air.

In this case, by-products such as water and harmful substances are generated in the process gas, for example, hydrogen or ammonia gas, which is heated. That is, 2H ₂ O + O ₂ → H ₂ O, 4NH ₃ + 5O ₂ → 6H ₂ O + 4NO.

At least one preheating chamber 300 is installed at one side of the burning chamber 200.

The preheating chamber 300 serves to preheat the compressed air at room temperature to 800 ° C. and to supply the burning chamber 200 with combustion air, and the heater is provided around the pipe 310 through which the compressed air passes. It is made of a cylindrical 320 is installed, the air at room temperature introduced into the inlet pipe 311 of the lower preheating chamber 300 is preheated to 800 ℃ by the heater 320 while passing through the preheating chamber 300, preheating The supplied air is supplied into the burning chamber 200 through the air inlet 250 of the top of the burning chamber 200 via the outlet pipe 312 of the upper end of the preheating chamber 300.

As such, since the preheated compressed air is supplied to the burning chamber 200, the heating zone formed in the burning chamber 200 becomes relatively longer than the conventional one, and the complete combustion rate of the processing gas is improved. At this time, the size and number of the preheating chamber 300 can be appropriately selected according to the processing capacity of the gas scrubber 100.

Meanwhile, it is preferable that a combustion gas supply device 260 is installed at one side of the gas inlet 210, and the combustion gas supply device 260 is a combustion gas such as H ₂ , LNG, or LPG through the gas inlet 210. It serves to supply the burning chamber 200.

Therefore, the gas that can be treated using a heater in the conventional gas scrubber is only low temperature gas such as PH ₃ , SiH ₄ , H ₂ , and has a fatal effect on global warming such as CH ₄ , C ₂ F ₆ , NF ₃ . Since the PFC gas is pyrolyzed at 1200 ° C. or more, there is a problem in that it is difficult to process, but the gas scrubber 100 according to the exemplary embodiment of the present invention has a temperature of 800 ° C. in the burning chamber 200 by the heater 230. After raising to, the combustion gas such as H ₂ , LNG, LPG is supplied to ignite, so that the temperature rises rapidly and the PFC gas can be treated.

The combustion gas supply device 260 may be a known gas supply device, for example, connecting the combustion gas storage tank and the gas inlet 210 of the burning chamber 200 to the gas supply pipe, one side of the pipe It can be easily configured by providing an on-off valve.

As shown in FIG. 3, the cooling chamber 400 has a cylindrical shape and is connected to the lower side of the burning chamber 200.

A gas guide tube 410 is installed at a predetermined interval inside the cooling chamber 400 to guide the movement path of the processing gas, and water cooling is provided around the wall of the cooling chamber 400 to store the cooling water for cooling the processing gas. Jacket 420 is provided.

At this time, the length of the gas guide tube 410 is formed so as not to touch the bottom surface of the cooling chamber 400. Therefore, a predetermined gap is formed between the cooling chamber 400 and the gas guide tube 410, and the gap serves as a duct to serve as a movement path of the processing gas.

At this time, the first absorber 430 is installed at a position corresponding to the lower end of the gas guide tube 410 to cool the processing gas and to filter the by-products contained in the processing gas.

And, the gas discharge line 450 is connected to one side of the cooling chamber 400, the cooled and purified processing gas is introduced between the cooling chamber 400 and the gas guide pipe 410 is discharged to the gas discharge line 450 do.

In addition, a second absorber 440 is installed above a predetermined height of the bottom surface of the cooling chamber 400 to increase the cooling effect of the processing gas and to re-filter toxic gas contained in the processing gas.

According to one embodiment of the invention, as shown in Figures 1, 3, 4, the drain chamber 500 is installed on one side of the cooling chamber 400.

The drain chamber 500 stores the converted water and by-products while the process gas such as hydrogen or ammonia reacts with the air during the process, and the drain chamber 500 detects the water level of the water stored therein. 510 is preferably mounted, and a drain pump 520 is installed at one side of the drain chamber 500 so that water, including by-products stored in the drain chamber 500, may be discharged to the outside when the water is out of an appropriate level. .

As shown in FIG. 1, one side of the cooling chamber 400 further includes an auxiliary cooling chamber 600 provided with a gas cooling line 610 connected to the gas discharge line 450, and an auxiliary cooling chamber 600. The gas cooling line 610 connected to the gas discharge line 450 is installed in a zig-zag several times.

In more detail, as shown in FIG. 5, the gas cooling line 610 is zigzag-circulated several times in a vertical direction in the auxiliary cooling chamber 600 having a sufficient internal volume.

When the processing gas flows into the auxiliary cooling chamber 600 through the gas discharge line 450 connected to the gas cooling line 610, the processing gas is heat-exchanged by the cooling water contained in the auxiliary cooling chamber 600. After the gas is sufficiently cooled, the process gas is sufficiently purged and cooled and then discharged to the outside through the exhaust port 611 formed at the top of the gas cooling line 610.

To this end, a coolant supply line 620 is installed at one side of the auxiliary cooling chamber 600, and a coolant discharge line 630 is installed at the other side.

Hereinafter, the operation of the gas scrubber 100 according to an embodiment of the present invention will be described.

For example, the toxic or explosive process gas generated in the reactor of the semiconductor manufacturing equipment is introduced into the burning chamber 200 through the gas inlet 210, each connected to the inlet port 241 of the inlet pipe 240 Process gases can be introduced in large quantities from many semiconductor manufacturing equipment.

At the same time as the processing gas is introduced, the air preheated from the preheating chamber 300 flows into the burning chamber 200, and the processing gas evenly diffused in the burning chamber 200 while being properly mixed with air is heated while passing through the heater 230. do.

That is, since the ceramic heater 230 is built into the burning chamber 200 and heated to a temperature of about 800 ° C., the processing gas acquires sufficient heat while passing through the heater 230, and as a result, the burning chamber ( All combustible ignitable gases or explosive gases such as hydrogen groups are combusted in 200.

On the other hand, when processing PFC gas such as CH ₄ , C ₂ F ₆ , NF ₃ , combustion gas such as H ₂ , LNG, LPG is supplied from the combustion gas supply device 260, and the burning chamber is ignited by the combustion gas. The internal temperature is rapidly increased to decompose the PFC gas.

FIG. 6 is a diagram schematically illustrating a method in which combustion gas is automatically supplied when PFC gas is introduced. For example, when the PFC gas is used for chamber cleaning of the CVD equipment 10, a pneumatic valve may be used. As the pneumatic valve 20 is opened, the PFC gas is supplied to the CVD equipment 10, and at this time, the pressure sensor 40 connected to the pneumatic valve driving air line 30 senses this and the solenoid. The valve 50 is operated to open the combustion gas supply valve 60.

As such, the processing gas from which the explosive and ignition gases are removed while passing through the burning chamber 200 flows into the cooling chamber 400 at the lower portion.

The processing gas introduced into the cooling chamber 400 first flows into the center of the first absorber 430, and then rises to the upper side of the cooling chamber 400 by the gas guiding pipe 410 constituting the duct structure. Discharged to 450.

At this time, the high-temperature process gas is appropriately cooled by the heat exchange action of the cooling water contained in the first and second absorbers 440 and the water cooling jacket 420, and hydrogen or ammonia contained in the process gas is oxygen in this process. Reacts with and is converted into water and flows into the drain chamber 500.

Next, the processing gas introduced into the auxiliary cooling chamber 600 filled with the cooling water through the gas discharge line 450 passes through a plurality of gas cooling lines 610 in a vertical direction, thereby contacting the cooling water. The longer the path, the greater the cooling effect of the process gas. In this process, the process gas and oxygen react with each other and are converted into water, and are introduced into the drain chamber 500 through the drain line 530 connected to the gas cooling line 610.

Therefore, the process gas finally passed through the first and second absorbers 430 and 440 is a gas from which all ignition or explosive gases are removed, and the exhaust gas is cooled by the cooling chamber 400 and the auxiliary cooling chamber 600. Through 611 to the atmosphere.

On the other hand, if the amount of by-products including the water contained in the drain chamber 500 exceeds an appropriate height, the water level sensor 510 detects this and sends a signal to the drain pump 520, the drain pump 520 The level is maintained continuously by operating and discharging to the outside.

7 illustrates a gas scrubber 100 ′ according to another embodiment of the present invention.

As shown in FIG. 7, the gas scrubber 100 ′ according to another embodiment of the present invention includes the burning chamber 200, the preheating chamber 300, and the cooling chamber 400. Similar to the embodiment, the cooling chamber 400 and the auxiliary cooling chamber 600 is provided with a cooling water circulator 700, respectively, to circulate the reused cooling water through the circulation pipe 710 and gas cooling Instead of installing the line, there is a difference in that the dust collector absorber 640 is installed on the upper inner peripheral surface of the auxiliary cooling chamber 600.

Hereinafter, different points from the above-described embodiment will be described in detail.

A first circulation pipe 720 is installed across the cooling chamber 400 on the upper portion of the cooling chamber 400. The cooling water flows through the first circulation pipe 720, and the first circulation pipe 720 is formed. Cooling water is injected into the cooling chamber 400 through the plurality of injection nozzles 721 provided at one end.

On the other hand, the circulation pipe 710 is connected to one side of the lower end of the cooling chamber 400, the cooling water injected into the cooling chamber 400 to be introduced into the circulation pipe 710, the circulation pump 740 is the cooling chamber 400 It is installed on one side of the), the cooling water introduced into the circulation pipe 710 is pulled back to the upper portion of the cooling chamber 400 through the first circulation pipe (720).

At this time, the circulation pipe 710 is branched while passing through the circulation pump 740, the first circulation pipe 720 connected to the upper portion of the cooling chamber 400, and the second cooling chamber 600 is connected to one side of the auxiliary cooling chamber (600). The circulation pipe 730 is divided into.

That is, some of the cooling water flowing into the circulation pipe 710 is injected into the cooling chamber 400 through the first circulation pipe 720, and the rest is injected through the injection nozzle 731 of the second circulation pipe 730. It is injected into the auxiliary cooling chamber 600 to cool the processing gas. As such, by circulating and reusing the cooling water, the cost consumed by the cooling water can be reduced, and the installation of the water cooling jacket in the cooling chamber 400 can be eliminated.

In this case, it is preferable that absorbers 490 and 690 are respectively installed in the cooling chamber 400 and the auxiliary cooling chamber 600 in which the coolant is injected, so that the processing gas is filtered, and the drain chamber is located at one side of the cooling chamber 400. It is also possible, of course, to install 500 to discharge the cooling water to the outside without further recycling.

On the other hand, the dust collecting absorber 640 is installed on the upper portion of the second circulation pipe 730 connected to the auxiliary cooling chamber 600 to inject the coolant into the auxiliary cooling chamber 600, the dust collecting absorber 640 is shown in FIG. As shown in FIG. 7, a plurality of inclined jaws 641 protruding downwardly along the inner circumferential surface thereof are staggered from each other, and by-products are additionally filtered while the processing gas passes through the dust collecting absorber 640.

That is, according to the gas scrubber 100 ′ according to another embodiment of the present invention, the processing gas is cooled by the cooling water injected from the cooling chamber 400 and the auxiliary cooling chamber 600, wherein the cooling water is a circulation pump. 740 is circulated so as to be reused, and by-products are filtered by absorbers 490 and 690 respectively installed in the cooling chamber 400 and the auxiliary cooling chamber 600. The dust collector absorber 640 is installed and undergoes one more filtration process before being discharged to the atmosphere through the exhaust port 611.

1 is a cross-sectional view showing a gas scrubber according to an embodiment of the present invention.

FIG. 2 is a sectional view of the burning chamber of FIG. 1. FIG.

3 is a cross-sectional view of the cooling chamber of FIG.

4 is a cross-sectional view taken along the line IV-IV of FIG. 3.

5 is a cross-sectional view showing an embodiment of the auxiliary cooling chamber of FIG.

6 is a schematic configuration diagram of the combustion gas supply device of FIG. 1.

7 is a sectional view showing a gas scrubber according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100, 100 ': gas scrubber

200: Burning Chamber

240: incoming piping

300: preheat chamber

400: cooling chamber

500: drain chamber

600: auxiliary cooling chamber

640: dust collector

700: cooling water circulation device

Claims (10)

A gas inlet through which a processing gas is introduced, and a burning chamber configured to burn the introduced processing gas; At least one preheating chamber installed at one side of the burning chamber and supplying combustion air preheated to the burning chamber; And It is installed on the lower side of the burning chamber, there is a gas guide tube for guiding the traveling direction of the processing gas therein, at least one or more absorbers for cooling the processing gas and filtering harmful substances contained in the processing gas A cooling chamber which is internally formed and has a gas discharge line for discharging the cooled processing gas on one side; An auxiliary cooling chamber installed at one side of the cooling chamber to further cool the first cooled processing gas; And A first circulation pipe installed at an upper side of the cooling chamber and configured to spray cooling water into the cooling chamber by an injection nozzle disposed at an end thereof, and cooling water sprayed inside the cooling chamber and installed below the cooling chamber; A circulation pipe for discharging, a circulation pump installed at one side of the cooling chamber and pulling the cooling water discharged through the circulation pipe to the upper portion of the cooling chamber through the first circulation pipe, and one side is connected to the circulation pump The other side of the gas scrubber, characterized in that it comprises a cooling water circulator equipped with a second circulation pipe which is installed inside the auxiliary cooling chamber and the cooling water is injected into the auxiliary cooling chamber by the injection nozzle installed at the end. The method according to claim 1, A gas scrubber, characterized in that the inlet pipe having a plurality of inlet port is connected to the gas inlet. The method according to claim 1 or 2, One side of the gas inlet gas scrubber, characterized in that the combustion gas supply unit for supplying at least one combustion gas selected from H ₂ , LNG, LPG to the burning chamber is installed. delete The method according to claim 1 or 2, One side of the cooling chamber, the gas scrubber, characterized in that the drain chamber for storing the moisture generated during the process is installed. delete delete The method according to claim 1 or 2, Gas scrubber, characterized in that the dust collection absorber is formed on the inner circumferential surface of the sub-cooling chamber is formed so that the plurality of inclined jaw projecting downward inclined. delete delete

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