KR20220036828A - Scrubber, scrubber system including the same, and scrubber operating method - Google Patents

Abstract

The present invention provides a scrubber capable of preventing concentration of an arc and minimizing etching of a housing. The scrubber according to an embodiment of the present invention includes: an electrode to which a driving voltage is applied; and a housing surrounding the electrode and forming a discharge space, wherein the housing can include a discharge port for discharging plasma and an extension unit connected to the discharge port and extended outward toward a lower part.

Description

A scrubber, a scrubber system including the same, and a method of driving the scrubber

The present invention relates to a scrubber, a scrubber system, and a scrubber driving method for removing perfluorinated compounds (PFCs) or volatile organic compounds (VOCs) discharged together with a large amount of powder generated in a semiconductor manufacturing process, etc.

As is known, in order to induce a high-temperature reaction with plasma or to create a high-temperature environment, arc plasma, microwave plasma, capacitively coupled plasma, and inductively coupled plasma Plasma) is used. These technologies have advantages and disadvantages according to each technology and structural differences in the reactor for plasma generation.

An arc is formed between the electrode charged with high voltage in the scrubber and the grounded housing. If the housing is etched excessively due to the arc, the housing may be damaged and the coolant stored in the housing may leak.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scrubber capable of preventing arc concentration and minimizing the etching of the housing. Another object of the present invention is to provide a scrubber capable of stably rotating an arc. Another object of the present invention is to provide a scrubber capable of preventing the arc from escaping to the outside of the plasma generator.

A scrubber according to an embodiment of the present invention includes an electrode to which a driving voltage is applied, and a housing enclosing the electrode to form a discharge space, wherein the housing is connected to a discharge port for discharging plasma and the discharge port, and is connected to the lower side toward the outside may include an extended extension.

The scrubber according to an embodiment of the present invention may further include a magnet fixedly installed at the lower portion of the housing and rotating the arc.

An arc-maintaining protrusion protruding inwardly is formed at the lower end of the extension part according to an embodiment of the present invention, and the arc-maintaining protrusion may be formed extending in a circumferential direction of the housing.

An inner surface of the extension part according to an embodiment of the present invention may be formed to be inclined at 5 degrees to 45 degrees with respect to the central axis of the housing.

In the extension part according to an embodiment of the present invention, the arc may be inclinedly bent with respect to the central axis of the housing.

The housing according to an embodiment of the present invention may include an electrode accommodating part surrounding the electrode, an introduction part connected to a lower portion of the electrode accommodating part and narrowing toward the bottom, and an arc passage connecting the introduction part and the extension part.

The housing according to an embodiment of the present invention may further include a cooling unit in which the cooling water is accommodated, and the cooling unit may be formed extending from the arc passage to the expansion unit.

A reactive gas supply port through which a reactive gas inducing plasma is introduced and a processing gas supply port through which a processing gas containing a perfluorinated compound is introduced may be connected to the electrode receiving unit according to an embodiment of the present invention.

A diameter of the lower end of the extension part according to an embodiment of the present invention may be formed to be larger than a diameter of the electrode receiving part.

The magnet according to an embodiment of the present invention may be formed to have an inclined surface facing the extended portion and to gradually decrease in width toward the lower portion.

The magnet according to an embodiment of the present invention is inserted into the wall forming the extension portion, and may be inclined with respect to the central axis of the housing.

A scrubber system according to another embodiment of the present invention includes a scrubber that generates and discharges a plasma arc, and a wet treatment unit that receives gas from the scrubber and sprays water for wet treatment, wherein the scrubber includes a driving voltage applied thereto. An electrode, a housing enclosing the electrode to form a discharge space, and a magnet fixedly installed in the lower portion of the housing to rotate an arc, the housing being connected to a discharge port for discharging plasma and the discharge port, and moving toward the outside toward the bottom It may include an extended extension.

The inner surface of the extension part according to another embodiment of the present invention may be formed to be inclined at 5 degrees to 45 degrees with respect to the central axis of the housing.

In the extension part according to another embodiment of the present invention, the arc may be inclinedly bent with respect to the central axis of the housing.

A method of driving a scrubber according to another embodiment of the present invention includes an arc generating step of generating an arc by applying a driving voltage to an electrode, a plasma generating step of supplying a reaction gas into a housing in which the electrode is inserted to generate plasma, processing An arc extension step of increasing the rotation radius of the arc by supplying gas into the housing while rotating and flowing, extending the arc, and extending the arc to an extension portion inclinedly disposed on the central axis of the housing, and using a magnet It may include an arc rotation step of rotating the arc.

The arc extending step according to another embodiment of the present invention may extend the arc from the lower end of the extension to the arc holding protrusion protruding inward.

As described above, the scrubber, the scrubber system, and the scrubber driving method according to an embodiment of the present invention include an extension part and a magnet so that the arc is separated from the center of the housing by the extension part and the rotation radius can be increased. The Lorentz force by the magnet can be increased to stably rotate the arc. That is, according to an embodiment of the present invention, the arc can be stably rotated using the extension and the magnet, thereby remarkably reducing the etch of the housing by the arc.

1 is a view showing a scrubber system according to a first embodiment of the present invention.
2 is a cross-sectional view illustrating a scrubber according to a first embodiment of the present invention.
3 is a flowchart illustrating a method of driving a scrubber according to a first embodiment of the present invention.
4 is a cross-sectional view illustrating a scrubber according to a second embodiment of the present invention.
5 is a cross-sectional view illustrating a scrubber according to a third embodiment of the present invention.
6 is a cross-sectional view illustrating a scrubber according to a fourth embodiment of the present invention.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as 'comprising' or 'having' are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, and one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that in the accompanying drawings, the same components are denoted by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings.

Hereinafter, a scrubber system according to a first embodiment of the present invention will be described.

1 is a diagram illustrating a scrubber system according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating a scrubber according to a first embodiment of the present invention.

1 and 2 , the scrubber system 1000 according to the first embodiment may include a scrubber 100 , a wet processing unit 300 , and a wet tower 400 .

The scrubber system 1000 according to the present embodiment thermally decomposes a processing gas containing a perfluoride compound generated in a semiconductor manufacturing process by using the high-temperature plasma generated by the scrubber 100 . In addition, only the harmless gas is discharged to the outside after the water-soluble harmful gas and foreign particles contained in the pyrolyzed processing gas in the wet processing unit 300 and the wet tower 400 are collected.

The wet treatment unit 300 may include a nozzle and a water tank, and collect and dissolve impurities such as hydrogen fluoride contained in the gas by spraying water to the gas delivered from the scrubber 100 . The wet tower 400 collects and dissolves impurities by spraying water to the additionally delivered gas, including a filter and a nozzle.

The scrubber 100 decomposes the processing gas using the high-temperature plasma formed by the arc and the reaction gas. The scrubber 100 includes an electrode 120 charged with a driving voltage and a housing 110 that surrounds the electrode 120 and provides a discharge space in which an arc is generated, and a reactor 160 connected to the lower end of the housing 110 and A magnet 141 fixed to a lower portion of the housing 110 may be included.

The electrode 120 has a rod shape, and a coolant passage 121 through which coolant moves may be formed. Power is connected to the electrode 120 , and a driving voltage may be applied to the electrode 120 . Here, the power may be not only AC power but also DC power, and the driving voltage may be a voltage sufficient for arc formation.

The electrode 120 is inserted into the housing 110 to extend in the height direction of the housing 110 , and a cooling water port 123 for supplying cooling water into the electrode 120 may be formed in the electrode 120 . there is.

The housing 110 may have a cylindrical shape having an inner space, and a discharge gap G1 is formed between the outer surface of the electrode 120 and the inner surface of the housing 110 . The housing 110 may be electrically grounded, and for this purpose, an insulating member 117 made of ceramic may be installed on the housing 110 . A discharge port 118 through which the processing gas is discharged is formed in the lower portion of the housing 110 .

The housing 110 is connected to the electrode receiving portion 111 surrounding the electrode 120 and the lower portion of the electrode receiving portion 111, and an arc passage formed at the lower portion of the introduction portion 112 and the introduction portion 112 that is narrower toward the bottom ( 113) and the arc passage 113 may include an extended portion 114 formed in the lower portion. The electrode accommodating part 111 has a cylindrical shape and is spaced apart from the electrode 120 with a discharge gap G1. The introduction part 112 is connected to the lower part of the electrode receiving part 111 and may be formed to gradually decrease in diameter toward the lower part. The arc passage 113 is made of a circular tube and connects the introduction part 112 and the expansion part 114 .

The extended part 114 is formed at the lower part of the housing 110 and the discharge port 118 is formed at the lower end of the extended part. The extended part 114 is formed to expand outward toward the lower part so that the inner diameter of the extended part 114 gradually increases toward the lower part. In addition, the inner surface of the extension 114 is inclined to have an inclination angle A1 with respect to the central axis X1 of the housing 110 . Here, the inclination angle A1 may be 5 degrees to 45 degrees. If the inclination angle A1 is smaller than 5 degrees, there is a problem in that the arc AC is not separated by a sufficient distance from the central axis of the housing 110, and when the inclination angle A1 is greater than 45 degrees, the lower end of the arc AC The arc point formed in the can not move to the lower part of the extension part, and may be located at a corner where the extension part 114 and the arc passage 113 are connected.

The diameter D2 of the lower end of the extension part 114 may be formed to be larger than the diameter D1 of the electrode receiving part 111, so that the arc AC can be sufficiently spaced apart from the center of the housing 110. there is. In addition, the length of the extension 114 may be formed to be longer than 1/2 of the length of the arc passage 113 , and the length of the extension 114 may be formed to be longer than the length of the arc passage 113 . there is. When the extended portion 114 is formed to be sufficiently long, the arc AC may be increased in length to improve efficiency, and the arc AC may be spaced apart from the center of the housing 110 further.

The housing 110 may further include a cooling unit 116 in which the cooling water is accommodated, and the cooling unit 116 may be formed outside the expansion unit 114 in the introduction unit 112 . The cooling unit 116 is formed on the outside of the introduction unit 112 , the arc passage 113 , and the expansion unit 114 to cool the housing 110 . A cooling water inlet 138 and a cooling water outlet 139 are formed in the housing 110 , and the cooling water inlet 138 and the cooling water outlet 139 are connected to the cooling unit 116 . When the cooling unit 116 extends to the extended unit 114 , it is possible to stably cool the extended unit 114 in which the arc point is located.

In addition, a reaction gas passage 131 , a reaction gas injection hole 132 , and a reaction gas supply port 136 may be formed in the housing 110 . The reactive gas supply port 136 is connected to the electrode receiving unit 111 , and supplies a reactive gas for plasma generation to the housing 110 . Here, the reactive gas may be formed of an inert gas such as nitrogen or carbon dioxide, and the reactive gas forms plasma through an arc discharge process.

The reaction gas passage 131 is formed to extend in the circumferential direction of the electrode receiving part 111 , and the reaction gas injection hole 132 connects the reaction gas passage to the inner space of the housing 110 . The plurality of reaction gas injection holes 132 are spaced apart from each other in the circumferential direction of the housing, and the reaction gas injection holes 132 may lead in an eccentric direction with respect to the center of the housing 110 to induce rotational flow.

The magnet 141 is installed in the lower portion of the housing 110 and rotates the arc AC. The magnet 141 may be formed of a permanent magnet, and may be formed in a ring shape or a plurality of magnets 141 may be spaced apart from each other in the circumferential direction of the housing 110 . In addition, the magnet 141 may be located below the cooling unit 116 outside the expansion unit 114 .

The arc AC is formed between the first introduction part 112 or the electrode receiving part 111 and the electrode 120 , and may gradually extend according to the movement of the gas to move to the extended part 114 . In the extension 114 , the arc AC is inclined with respect to the central axis of the housing 110 , and accordingly, the distance between the arc AC and the central axis X1 of the housing 110 increases.

The Lorentz force acts on the arc AC by the magnet 141, and as the radius of the arc AC increases, a greater force acts on the arc AC. If the extension 114 is not formed, the rotation radius of the arc AC may be small or close to zero, so that the arc AC may not rotate and concentrate, and the housing 110 may be excessively etched. However, when the extended portion 114 is formed as in the first embodiment, the rotation radius r1 of the arc AC increases, so that the arc AC can rotate more stably. In addition, if only the extended part 114 is formed and the magnet 141 is not installed, the arc AC cannot rotate even if the rotation radius r1 increases, so excessive etching cannot be avoided, but according to this embodiment, the extended part ( Since the 114 is formed and the magnet 141 is installed, the arc AC stably rotates to minimize damage caused by the arc AC.

The reactor 160 has a substantially cylindrical shape and is connected to the outlet 118 . Although the first embodiment illustrates that the reactor 160 is connected to the lower portion of the housing 110, the present invention is not limited thereto, and when the housing 110 is formed to be sufficiently long, the reactor 160 may be omitted. may be In this case, the housing 110 is directly connected to the wet processing unit 300 .

The reactor 160 provides a space in which the processing gas is decomposed, and a processing gas supply port 137 through which the processing gas is supplied may be formed in the reactor. Here, the process gas means a gas to be decomposed including perfluorinated compounds. The high-temperature plasma discharged from the housing 110 heats the processing gas to form a flame, and the processing gas may be decomposed inside the reactor 160 . The gas discharged from the reactor 160 moves to the wet processing unit 300 . A cooling unit for cooling the reactor may be formed outside the reactor 160 .

3 is a flowchart illustrating a method of driving a scrubber according to a first embodiment of the present invention.

Referring to FIGS. 2 and 3 , the scrubber driving method according to the first embodiment includes an arc generating step (S101) of generating an arc (AC) by applying a driving voltage to the electrode 120, and a reaction gas to the electrode Plasma generation step (S102) of generating plasma by supplying it into the housing 110 in which 120 is inserted, supplying the processing gas into the housing 110 while rotatingly flowing, extending the arc AC, and extending the extension part 114 ) to extend the arc AC to increase the radius of rotation of the arc AC (S103), and an arc rotation step (S104) of rotating the arc AC using the magnet 141 (S104). can

In the arc generating step S101 , an arc AC is generated between the outer circumferential surface of the electrode 120 and the inner circumferential surface of the housing 110 using the electrode 120 charged with a high voltage and the grounded housing 110 .

In the plasma generating step ( S102 ), a reactive gas such as nitrogen is supplied into the housing 110 to generate high-temperature plasma.

In the arc extension step S103 , the arc AC is extended to the extension 114 formed in the lower portion of the housing 110 so that the lower portion of the arc AC is obliquely bent with respect to the central axis of the housing 110 . Accordingly, the radius of rotation of the lower portion of the arc AC may increase in the arc extension step S103 . In the arc extension step S103 , one arc point may be located at the lower end of the electrode 120 , and the other arc point may be located at the lower end of the extension part 114 .

In the arc rotation step S104 , a Lorentz force is applied to the arc AC using the magnet 141 installed in the housing 110 to rotate the arc AC. Accordingly, it is possible to prevent the housing 110 from being excessively etched by the rotation of the arc AC.

Hereinafter, a scrubber according to a second embodiment of the present invention will be described. 4 is a cross-sectional view illustrating a scrubber according to a second embodiment of the present invention.

4, since the scrubber 100 according to the present embodiment has the same structure as the scrubber according to the first embodiment, except for the arc maintaining protrusion 151, redundant description of the same configuration is omit

An arc maintaining protrusion 151 protruding inwardly is formed at the lower end of the extended part 114 . The arc maintaining protrusion 151 is formed to extend in the circumferential direction of the housing 110 and may protrude obliquely toward the center and the lower portion of the housing 110 . The arc holding protrusion 151 is formed in a ring shape and may be detachably coupled to the housing 110 .

When the arc holding protrusion 151 is formed in this way, an arc point is formed on the arc holding protrusion 151 to prevent the arc AC from escaping to the outside of the extension part 114 . In addition, since the arc holding protrusion 151 is formed thicker than other portions, damage to the housing 110 can be minimized. In addition, since the arc holding protrusion 151 is detachably coupled, if the arc holding protrusion 151 is damaged, only the arc holding protrusion 151 can be removed and replaced.

Meanwhile, the scrubber driving method according to the second embodiment may include an arc generating step, a plasma generating step, an arc extending step, and an arc rotating step, and in the arc extending step and the arc rotating step, the lower end of the arc is an arc holding protrusion It can be located on (151).

Hereinafter, a scrubber according to a third embodiment of the present invention will be described. 5 is a cross-sectional view illustrating a scrubber according to a third embodiment of the present invention.

Referring to FIG. 5 , the scrubber 100 according to this embodiment has the same structure as the scrubber according to the first embodiment except for the magnet 142 and the processing gas supply port 137 , so the same A redundant description of the configuration will be omitted.

The magnet 142 is fixedly installed at the lower portion of the housing 110 and rotates the arc AC. The magnet 142 may be formed of a permanent magnet, and may be formed in a ring shape or a plurality of magnets 142 may be spaced apart from each other in the circumferential direction of the housing 110 . In addition, the magnet 142 may be located below the cooling unit 116 outside the expansion unit 114 .

The magnet 142 may have an inclined surface 142a facing the extension 114 and may be formed to gradually decrease in width toward the bottom. Accordingly, the magnet 142 may be in close contact with the extension 114 to provide a greater rotational force to the arc AC.

Meanwhile, a processing gas supply port 137 , a processing gas passage 134 , and a processing gas injection hole 135 may be formed in the housing 110 . The processing gas supply port 137 is connected to the electrode receiving part 111 under the processing gas supply port 136 . Here, the process gas means a gas to be decomposed including perfluorinated compounds. The processing gas passage 134 is formed in a circumferential direction of the electrode receiving part 111 , and the processing gas injection hole 135 connects the processing gas passage 134 and the inner space of the housing 110 . The plurality of processing gas injection holes 135 are spaced apart from each other in the circumferential direction of the housing 110 , and the processing gas injection holes 135 lead in an eccentric direction with respect to the center of the housing 110 to induce rotational flow. can

Since the processing gas injection hole 135 injects the processing gas toward the outer circumferential surface of the electrode 120, the processing gas flows into a high-temperature region and comes into contact with the plasma, compared to the case in which the processing gas is supplied to a conventional reactor, and the processing gas is heated to a high temperature. As the time in the zone is increased, the process gas can be decomposed more efficiently. In addition, since the processing gas and the reaction gas are supplied while causing rotational motion, the rotational force of the arc can be increased by the processing gas and the injection gas, and the length of the arc is stable because the amount of gas discharged to the discharge port 118 is large. can be maintained as

Hereinafter, a scrubber according to a fourth embodiment of the present invention will be described. 6 is a cross-sectional view illustrating a scrubber according to a fourth embodiment of the present invention.

Referring to FIG. 6 , the scrubber 100 according to this embodiment has the same structure as the scrubber according to the first embodiment except for the magnet 143 , the cooling unit 116 , and the reactor 160 . Therefore, redundant description of the same configuration will be omitted.

The magnet 143 is fixedly installed in the lower portion of the housing 110 and rotates the arc AC. The magnet 143 may be formed of a permanent magnet, and may be formed in a ring shape or a plurality of magnets 143 may be spaced apart from each other in the circumferential direction of the housing 110 .

The magnet 143 may be fixedly installed inside the wall forming the extension 114 and inclined with respect to the central axis X1 of the housing 110 . The cooling unit 116 may extend to the lower portion of the expansion unit 114 and may be formed to the outside of the magnet 143 . Accordingly, the distance between the magnet 143 and the arc AC may be close, and the cooling unit 116 may sufficiently cool the lower portion of the housing 110 .

Meanwhile, the processing gas supply port 137 is connected to the outer wall of the reactor 160 , and a processing gas passage 134 extending in the circumferential direction of the reactor 160 may be formed outside the reactor 160 . In addition, a processing gas injection hole 135 connecting the processing gas passage 134 and the inner space of the reactor 160 is formed in the reactor 160 , and the processing gas injection hole 135 is configured to induce rotational flow. It may lead in an eccentric direction with respect to the center of the reactor 160 . Accordingly, the processing gas may be injected while forming a swirl in the reactor 160 .

In the above, an embodiment of the present invention has been described, but those of ordinary skill in the art can add, change, delete or add components within the scope that does not depart from the spirit of the present invention described in the claims. It will be possible to variously modify and change the present invention by, etc., which will also be included within the scope of the present invention.

1000: scrubber system 100: scrubber
110: housing 111: electrode receiving part
112: introduction 113: arc passage
114: extension 116: cooling unit
117: insulating member 118: outlet
120: electrode 121: coolant passage
123: coolant port 131: reaction gas passage
132: reaction gas injection hole 134: process gas passage
135: processing gas injection hole 136: reaction gas supply port
137: processing gas supply port 141, 142, 143: magnet
151: arc maintenance projection 160: reactor
300: wet processing unit 400: wet tower

Claims (17)

an electrode to which a driving voltage is applied;
a housing surrounding the electrode and forming a discharge space; and
including,
The housing comprises a discharge port for discharging plasma and an extension part connected to the discharge port and extending outward toward the bottom. According to claim 1,
The scrubber is fixed to the lower portion of the housing and further comprises a magnet for rotating the arc. According to claim 1,
An arc holding protrusion protruding inward is formed at the lower end of the extension, and the arc holding protrusion is formed in a circumferential direction of the housing. According to claim 1,
The inner surface of the extension portion is a scrubber, characterized in that formed inclined at 5 to 45 degrees with respect to the central axis of the housing. According to claim 1,
In the expanded portion, the arc is a scrubber, characterized in that it is bent obliquely with respect to the central axis of the housing. According to claim 1,
The housing further comprises an electrode accommodating portion surrounding the electrode, an introduction portion connected to a lower portion of the electrode accommodation portion and narrowing toward the bottom, and an arc passage connecting the introduction portion and the extension portion. 7. The method of claim 6,
The housing further includes a cooling unit in which the cooling water is accommodated, and the cooling unit is formed extending from the arc passage to the expansion unit. 7. The method of claim 6,
Scrubber, characterized in that the electrode receiving portion is connected to a reactive gas supply port through which a reactive gas inducing plasma flows and a processing gas supply port through which a processing gas containing a perfluorinated compound is introduced. 7. The method of claim 6,
The diameter of the lower end of the extension portion is a scrubber, characterized in that formed larger than the diameter of the electrode receiving portion. 3. The method of claim 2,
The magnet has an inclined surface facing the extended portion, and the scrubber, characterized in that formed so as to gradually decrease in width toward the lower portion. 3. The method of claim 2,
The magnet is inserted into the wall forming the extension, the scrubber, characterized in that disposed inclined with respect to the central axis of the housing. a scrubber generating and discharging a plasma arc;
It includes a wet treatment unit and a wet tower for receiving the gas from the scrubber and spraying water for wet treatment,
The scrubber is
an electrode to which a driving voltage is applied, and
a housing enclosing the electrode to form a discharge space;
including,
The housing includes a discharge port for discharging plasma and an extension part connected to the discharge port and extending outward toward a lower portion. 13. The method of claim 12,
The scrubber system is fixed to the lower portion of the housing and further comprises a magnet for rotating the arc. 13. The method of claim 12,
The inner surface of the extension portion is a scrubber system, characterized in that formed inclined at 5 to 45 degrees with respect to the central axis of the housing. 13. The method of claim 12,
The scrubber system, characterized in that the arc in the extension is bent obliquely with respect to the central axis of the housing. an arc generating step of generating an arc by applying a driving voltage to the electrode;
a plasma generating step of supplying a reaction gas into the housing into which the electrode is inserted to generate plasma;
an arc extending step of supplying a processing gas into the housing while rotatingly flowing to extend the arc, and extending the arc to an extension portion inclinedly disposed on a central axis of the housing to increase a rotation radius of the arc; and
Arc rotation step of rotating the arc using a magnet
A method of driving a scrubber comprising a. 17. The method of claim 16,
The arc extension step is a method of driving a scrubber, characterized in that extending the arc from the lower end of the extension to the arc holding projection protruding inward.

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