JP2011011106A - Plasma reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma reactor stably generating plasma discharge in a discharge space at a predetermined place at specified even time intervals using a plasma reacting structural body comprising a dielectric and a palisade electrode, and in addition facilitating the fabrication of the palisade electrode to decrease the manufacturing cost.SOLUTION: In the plasma reactor, the palisade electrodes 1, 2 are formed by a plurality of bars 6 and electric conductors 7 connecting them, and the bars 6 of the palisade electrodes 1, 2 facing each other are extended in different directions, and intersected. A plurality of plasma reacting structural bodies 5 each of which is formed by inserting the dielectric 3 between the palisade electrodes 1, 2 are arranged in parallel to form one layer or more of discharge spaces 10 capable of streaming gas G. The gas G is streamed in the discharge spaces 10 between the palisade electrodes 1, 2 and the dielectrics 3 or between the dielectrics 3 covering the palisade electrodes 1, 2 while generating plasma discharge by applying a voltage between the palisade electrodes 1, 2 to react the gas G.

Description

  The present invention relates to a plasma reactor that generates a plasma discharge.

  Diesel engines have high thermal efficiency, and as a result, the spread of diesel vehicles will contribute to the prevention of global warming. In addition, harmful substances such as carbon-based particulate matter (PM), NOx, and organic compounds emitted from diesel engines are harmful to the human body, and in recent years they have been regulated to further reduce their emissions. Yes. Because the temperature of exhaust gas discharged from diesel vehicles is low, the technology for reducing harmful substances by plasma reaction is said to be effective for removing PM. Most of the plasma reactors used for reducing the PM by the plasma reaction are generally reactors of a type through a dielectric barrier. Conventionally developed and used plasma reactors have different electrodes and dielectric shapes.

  In a conventional plasma reactor, electrodes having a plate shape, a tubular shape, a spherical shape, a net shape, a porous shape, and an uneven shape are used. In addition, a dielectric material having a plate shape, a tubular shape, a spherical shape, a porous shape, or an uneven shape is used.

  A conventionally known exhaust gas purification method purifies NOx in exhaust gas under plasma using an adsorbent that increases NOx adsorption under a plasma generated in a reducing agent-containing exhaust gas atmosphere. Yes, when the temperature of the reducing agent-containing exhaust gas is equal to or lower than the operating temperature of the NOx purification catalyst, discharge is performed near the surface of the NOx adsorbent under plasma, and plasma is generated in the reducing agent-containing exhaust gas atmosphere to generate NOx under the plasma. When NOx is adsorbed by the adsorbent and the temperature is equal to or higher than the operating temperature, the discharge is stopped and the NOx adsorbed by the NOx adsorbent under the plasma is guided to the NOx purification catalyst to purify NOx (for example, Patent Documents). 1).

  Further, as an under-plasma NOx adsorbent, a material comprising a porous carrier carrying a base component and having a property of increasing the adsorbability under plasma is known (for example, see Patent Document 2).

  As an exhaust purification device, one that efficiently purifies exhaust gas containing PM is known. The exhaust emission control device includes a charging means for charging particulate matter contained in the exhaust gas of an internal combustion engine, a grounding electrode provided on the exhaust downstream side of the charging means, and charging between the charging means and the grounding electrode. And a filter for collecting the particulate matter thus formed (see, for example, Patent Document 3).

  Conventionally known plasma reactors have a case body having a plasma generating electrode and a gas flow path containing a predetermined component inside, and when the gas is introduced into the gas flow path of the case body, the plasma reaction is performed. The predetermined component contained in the gas reacts with the plasma generated by the generator electrode. The plasma generating electrode includes two or more plate-like unit electrodes opposed to each other, can generate plasma by applying a voltage between the unit electrodes, and the unit electrode is a ceramic that is a dielectric. A body, a conductive film disposed on one surface of the ceramic body, and a first protective film composed of a metal film disposed to cover the exposed surface of the conductive film Yes (see, for example, Patent Document 4).

  Further, as an exhaust gas purification device, a device using plasma discharge capable of detecting PM deposition is known. The exhaust gas purifying apparatus has an insulating honeycomb structure, a case which is disposed on the outer peripheral portion thereof and functions as an outer peripheral electrode, a rod-like discharge electrode which is held on the central axis of the case, and a particulate matter detection electrode The particulate matter detection electrode forms a circuit with the case, and the particulate matter is deposited on the electrode to form an electrical continuity with the case, and the particulate matter is detected by detecting the electrical continuity. It can be grasped that it has accumulated (for example, refer to patent documents 5).

  In addition, as a method for producing a plasma electrode, a plasma electrode for producing plasma by applying a voltage is prepared by having an electrode body and a dielectric. Glass is coated on the electrode body by dip coating to form a dielectric. A body is formed (for example, refer to Patent Document 6).

  A reaction control device that efficiently reforms gas in a low temperature region is known. The reaction control device includes a first electrode, a second electrode disposed opposite to the first electrode, and a dielectric layer laminated on either the first electrode or the second electrode on the opposite surface side of each electrode. And grooves or pores are formed at a predetermined periodic interval on at least one surface of the electrode or dielectric on the opposite surface side of each electrode (see, for example, Patent Document 7).

JP 2001-182525 A JP 2001-232185 A JP 2003-269134 A Japanese Patent Laying-Open No. 2005-93107 JP 2007-90255 A JP 2009-117175 A JP 2005-138098 A

  By the way, in order to remove PM by the plasma reactor, it is necessary to efficiently contact and react the active oxygen species generated by the plasma with the PM. In the plasma reactor, it was necessary to generate a plasma discharge in a predetermined place in the discharge space. The concavo-convex plasma reactors developed so far are suitable for removing PM. For example, as shown in Patent Document 7, it is expensive to produce a dielectric in a concavo-convex shape. The removal technology has been difficult to put into practical use.

  An object of the present invention is to solve the above-mentioned problem, and to stably generate a plasma discharge in a predetermined place in a discharge space by using a plasma reaction structure in which a dielectric and a fence-like electrode are combined. It is also possible to provide a plasma reactor which can be manufactured at a low cost and can be remarkably reduced in cost.

The present invention has a plasma reaction structure composed of two conductive electrodes facing each other and a dielectric inserted between the conductive electrodes, and a plasma reaction is performed by applying a voltage to the conductive electrodes. In a plasma reactor consisting of generating
A plurality of the plasma reaction structures are arranged in parallel, and the conductive electrode is formed as a fence-shaped electrode from a plurality of fences spaced apart from each other and a conductor that connects the fences to each other. The directions of the fences of the opposing fence-like electrodes are different from each other, and the gas flows between the opposite of the fence-like electrode and the dielectric or between the opposite of the dielectric covering the fence-like electrode. The present invention relates to a plasma reactor characterized in that one or more discharge spaces which can pass through and have an inlet and an outlet for the gas are provided.

  Further, in this plasma reactor, the fence of the fence-like electrode has a width of 0.1 mm to 10 mm, a length of 1 mm to 1000 mm, a thickness of 0.001 mm to 10 mm, and a distance between the fences of 0. The range is from 5 mm to 100 mm. Further, the plurality of fences in the fence-like electrode are connected to the conductors with the same size at predetermined equal intervals. It is preferable that the fences of the fence-like electrodes are configured with the same size and at predetermined equal intervals, so that plasma discharge can be generated in a regular state with equal intervals.

  In the plasma reactor, the conductor of the fence-like electrode is formed into a frame-like conductor, and at least one end of the fence is fixed to the frame-like conductor, and the frame-like conductors are opposed to each other. The discharge space is formed between the fence-like electrodes facing each other with a spacer interposed therebetween.

  In addition, one or more dielectrics inserted between the fence-like electrodes can be provided.

  The dielectric is formed into a plate shape, a cylindrical shape, or a spherical shape from one or more materials selected from metal oxide, plastic, rubber, and glass. Within the range of 1 mm to 10 mm. The fence-like electrode is connected to a lead wire to which a voltage can be applied, and can pass electricity, such as iron, copper, stainless steel, zinc, aluminum, titanium, metal oxide such as indium tin oxide, zinc oxide, conductive Plastic.

  In the plasma reactor, a catalyst for promoting a chemical reaction is supported on the surface of the dielectric and / or the fence-like electrode in contact with the discharge space.

  The plasma reactor uses an oxygen-containing gas as the gas supplied from the inlet of the discharge space, generates ozone gas by a plasma reaction generated in the discharge space, and generates the ozone gas from the outlet of the discharge space. Can be applied to an ozone generator capable of recovering water. Alternatively, the plasma reactor uses a gas containing harmful substances such as particulate matter, nitrogen oxides, organic compounds, and sulfur oxides as the gas supplied from the inlet of the discharge space, and is generated in the discharge space. The present invention can be applied to an exhaust gas purifying apparatus that can eliminate the harmful substance by the plasma reaction and recover the purified gas from the outlet of the discharge space.

  In this plasma reactor, as described above, the directions of the opposing fences in the fence-like electrodes intersect with each other, so that the intersection areas of the many fences in the fence-like electrodes are the shortest distance where the fences are closest to each other. The plasma discharge is first generated at the shortest distance between the electrodes, and the plasma discharge is reliably and stably generated at the crossing region of the fence, and the discharge state progresses to the discharge space. In addition, since the conductive electrode has a simple shape of many fences, the manufacture of the fence-like electrode is simplified, and the plasma reactor is simplified by alternately laminating the fence-like electrodes extending in different directions. The manufacturing cost is low.

It is a top view which shows the fence-like electrode from which the fence which comprises the plasma reactor by this invention is extended in one direction. It is a top view which shows the fence-like electrode from which the fence which comprises the plasma reactor by this invention is extended in the other direction. The assembly process of the plasma reaction structure which comprises the plasma reactor by this invention is shown, (A) shows the assembly process of the fence-like electrode and dielectric which the fence is extended in one direction, (B) is the fence It is a perspective view which shows the assembly process of the fence-shaped electrode and dielectric material which are extended in the other direction. It is a top view which shows the plasma reaction structure which consists of a pair of fence-like electrode and dielectric material (not shown) which comprise the plasma reactor by this invention. It is explanatory drawing which shows the site | part which a plasma discharge generate | occur | produces in the plasma reaction structure which comprises the plasma reactor by this invention. It is sectional drawing which shows the plasma reaction structure which consists of the fence-shaped electrode in the plasma reactor by this invention and one fence-shaped electrode covered with a pair of dielectrics. It is sectional drawing which shows the plasma reaction structure in which the fence-shaped electrode in the plasma reactor by this invention was each covered with a pair of dielectric material. FIG. 7 is a cross-sectional view showing a state in which a plurality of plasma reaction structures shown in FIG. 6 are stacked. FIG. 8 is a cross-sectional view showing a state in which a plurality of plasma reaction structures shown in FIG. 7 are stacked. It is a perspective view which shows the assembly process which laminates | stacks the several plasma reaction structure which comprises the plasma reactor by this invention. It is a perspective view which shows the state which accommodated the plasma reactor by this invention in the container, and shows an example applicable to an ozone generator or an exhaust-gas purification apparatus. It is explanatory drawing which shows the example which can apply the plasma reactor by this invention to an exhaust-gas purification apparatus.

Embodiments of a plasma reactor according to the present invention will be described below with reference to the drawings.
The plasma reactor generally has a plasma reaction structure 5 composed of two conductive electrodes 1 and 2 facing each other and a dielectric 3 inserted between the conductive electrodes 1 and 2. The plasma reaction is generated by applying a voltage to the electrodes 1 and 2. In the plasma reactor according to the present invention, in particular, a plurality of plasma reaction structures 5 are arranged in parallel, and a plurality of fences 6 in which conductive electrodes 1 and 2 have spaces 4 are spaced from each other, and the fences 6 are connected. Are formed on the fence-like electrodes 1 and 2 from the conductor 7 and the opposing fence-like electrodes 1 and 2 extend in different directions from each other so that the opposite fences cross each other, The gas G can pass between the facing of the body 3 or the facing of the dielectric 3 covering the fence-like electrodes 1 and 2, and has at least one discharge space 10 having an inlet 8 and an outlet 9 for the gas G It has the feature in being.

  In this plasma reactor, the waveform of the voltage applied to the plurality of fence-like electrodes 1 and 2 can be AC, DC, pulse, or arbitrary wave. This plasma reactor can control the chemical reaction by discharge by controlling the output of the high-voltage power supply according to the nature of the processing gas such as exhaust gas or oxygen-containing gas. Further, all or a part of the plasma reactor 20 can be installed in an electric furnace or a cooling device to control the temperature of the plasma reactor or the temperature of the gas G introduced into the plasma reactor.

  In this plasma reactor, the fence 6 of the fence-like electrodes 1 and 2 has a width of 0.1 mm to 10 mm, a length of 1 mm to 1000 mm, and a thickness of 0.001 mm to 10 mm. The distance between 6, that is, the separation space 4 is configured to be in a range of 0.5 mm to 100 mm.

  Further, in this plasma reactor, as shown in FIG. 10, the conductors 7 of the fence-like electrodes 1 and 2 are formed on the frame-like conductor 7, and both ends of the fence 6 are fixed to the frame-like conductor 7. The discharge space 10 is formed between the opposing fence-like electrodes 1 and 2 with a spacer 14 interposed between the opposing frame-like conductors 7. Further, the dielectric 3 inserted between the fence-like electrodes 1 and 2 can be provided as a single layer as shown in FIG. 6, or as two layers as shown in FIG. In this plasma reactor, the fence 6 in the fence-like electrodes 1 and 2 is formed so as to extend on the frame-like conductor 7 at equal intervals, so that the plasma discharge can be performed at a predetermined regular interval in the discharge space 10, that is, at regular intervals. It can be generated similarly and is preferred.

  In this plasma reactor, the dielectric 3 is formed into a plate shape, a cylindrical shape, or a spherical shape from at least one material selected from metal oxide, plastic, rubber, and glass. Further, the thickness of the dielectric 3 is in the range of 0.1 mm to 10 mm. The fence-like electrodes 1 and 2 are connected to a lead wire 11 to which a voltage can be applied, and can pass electricity, such as metal such as iron, copper, stainless steel, zinc, aluminum and titanium, metal oxide such as indium tin oxide and zinc oxide. Made of conductive plastic.

  Further, in this plasma reactor, it is preferable that the surface of the dielectric 3 and / or the fence-like electrodes 1 and 2 exposed in the discharge space 10 carry a catalyst 12 that promotes a chemical reaction with the gas G. is there.

  Further, this plasma reactor uses an oxygen-containing gas G as a gas G supplied from the inlet 8 of the discharge space 10, generates ozone gas by a plasma reaction generated in the discharge space 10, and generates ozone gas from the outlet 9 of the discharge space 10. Can be applied to an ozone generator capable of recovering water.

  Alternatively, the plasma reactor is configured to emit exhaust gas containing harmful substances such as particulate matter, nitrogen oxides, organic compounds, and sulfur oxides discharged from an engine or the like as the gas G supplied from the inlet 8 of the discharge space 10. The present invention can be applied to an exhaust gas purification device that can be used to remove harmful substances by reaction incineration by a plasma reaction generated in the discharge space 10 and recover the purified gas from the outlet 9 of the discharge space 10. Further, when this plasma reactor is applied to an exhaust gas purification device, although not shown, a catalyst layer or an adsorption layer can be provided behind the plasma reactor 20 to promote a chemical reaction. Further, another gas, liquid, or solid powder can be introduced into the discharge space 10 in the plasma reactor 20 or behind the discharge space 10 to promote the chemical reaction. Furthermore, the output voltage and frequency of the high-voltage power source can be controlled in response to information such as an electrical signal corresponding to the measured value obtained by measuring the rotational speed, exhaust temperature, pressure, etc. of the diesel engine 15.

  Next, the plasma reactor will be specifically described. 1 and 2 show examples of flat plate-like shapes of the stainless steel fence-like electrodes 1 and 2. 3 and 4 show a plasma reaction structure 5 which is a basic structure composed of a pair of fence-like electrodes 1 and 2 and a flat plate-like alumina dielectric 3. 6 to 9 show structural examples when the plasma reaction structure 5 is stacked. The fences 6 of the fence-like electrodes 1 and 2 are inclined at 45 ° and 135 ° with respect to the horizontal axis direction (X direction), respectively, but are not limited to this inclination angle.

  FIG. 6 shows a plasma reaction structure 5A which is a basic structure composed of two fence-like electrodes 1 and 2 and a pair of dielectrics 3. As shown in FIG. However, the fence-like electrode 2 is installed so that a space is formed between the surface of the dielectric 3 and a discharge is performed under the dielectric 3 in contact with the fence-like electrode 1. A fence-like electrode 2 is provided so as to form a space 10. When the inclination angles of the fences 6 of the two fence-like electrodes 1 and 2 extend in opposite directions to each other, the fences 6 on both sides of the dielectric 3 intersect each other. When a voltage is applied between the fence-like electrodes 1 and 2 through the lead wire 11, it exists in the discharge space 10 formed between the surface of the dielectric 3 in contact with the fence-like electrode 1 and the fence-like electrode 2. A chemical reaction occurs by generating a plasma discharge in the plasma gas. FIG. 8 shows a state in which a large number of plasma reaction structures 5A shown in FIG. 6 are stacked.

  FIG. 7 also shows a plasma reaction structure 5B, which is a basic structure comprising a pair of fence-like electrodes 1 and 2 and two pairs of dielectrics 3, and a discharge is generated between the dielectrics 3 located in the middle part. A space 10 is formed. When the inclination angles of the fences 6 of the two fence-like electrodes 1 and 2 extend in opposite directions to each other, the fences 6 on both sides of the dielectric 3 intersect each other. FIG. 9 shows a state in which a large number of plasma reaction structures 5B shown in FIG. 7 are stacked.

  In FIG. 5, when a voltage is applied between the plasma reaction structures 5 </ b> A and 5 </ b> B, a discharge occurs in the discharge space 10 in the intersecting region 25 (see FIG. 4) where the fence-like electrodes 1 and 2 are separated. A discharge location 26 and a non-discharge location 27 that is not discharged are shown. When the discharge location 26 was verified, it was found that the locations of the fence 6 of the opposing fence electrodes 1 and 2 coincided with the intersection. That is, the region where the fences 6 intersect is the case where the fences 6 are evenly spaced and fixed to the continuous conductor, that is, the frame-like conductor 7. Has been confirmed to be uniformly distributed at equal intervals. In addition, the active species generated by the discharge contribute to the chemical reaction in the discharge space 10 in the discharge location 26, but the active species develop or diffuse to the non-discharge location 27 where no discharge occurs, and the plasma further undergoes a chemical reaction. In other words, it is possible to effectively contribute to the generation of the plasma reaction in the entire region of the discharge space 10 based on the active species generated by the discharge.

Next, the process of assembling this plasma reactor will be described with reference to FIG.
FIG. 3 shows an assembly process of this plasma reactor with the fence-like electrodes 1 and 2 and the dielectric 3. In (A), the fence-like electrode 1 installed on the dielectric 3 and the dielectrics 3 and 3 are shown. And (B) shows a step of bonding the fence-like electrode 2 and the dielectric 3 installed on the dielectric 3 with an adhesive 24 attached to the outer periphery of the dielectric 3. In FIG. 10, a spacer 14 is inserted between the plasma reaction structures 5B composed of the fence-like electrodes 1 and 2 sandwiched between the dielectrics 3, and these are sequentially stacked. As a result, a discharge space 10 is formed by the spacers 14 between the plasma reaction structures 5B.

  Next, FIG. 11 shows a plasma reactor 20 that can be applied to an ozone generator or an exhaust gas purifier incorporating a large number of plasma reaction structures 5. As shown in FIG. 10, in the process of manufacturing the plasma reactor 20, the plasma reaction structure 5 </ b> B and the spacer 14 are sequentially laminated and set in a stainless steel container 13. The stainless steel container 13 has an inlet 8 and an outlet 9. A gas G containing gas, liquid and / or solid is introduced into the inlet 8 and flows out from the outlet 9 through the discharge space 10 formed by the spacer 14. After the stacked fence-like electrodes 1 and 2 are connected by the electrode connecting line 21, an external high voltage power source is connected by the lead wire 22. The lead wire 22 and the stainless steel container 13 are insulated by an insulating tube 23.

  FIG. 12 shows an example in which the plasma reactor 20 is used to remove particulate matter (PM) discharged from the diesel engine 15. The exhaust gas G from the diesel engine 15 is introduced into the plasma reactor 20 through the exhaust pipe 16. PM contained in the exhaust gas G reacts and is incinerated and removed by a chemical reaction generated by discharge in the plasma reactor 20. The exhaust gas G from which PM has been removed is discharged from the exhaust pipe 16 to the atmosphere. The plasma reactor 20 is connected to the high voltage power source 17 by a lead wire 22. Plasma discharge is generated in the discharge space 10 in the plasma reactor 20 by the electric power supplied from the high-voltage power supply 17. The output of the high-voltage power source 17 is controlled by the control unit 18 by taking in electrical signals corresponding to the rotational speed of the diesel engine 15, the exhaust gas temperature and the pressure. The high-voltage power source 17 is driven by being connected to a generator or external power provided in the diesel engine 15 via a line 19. The PM removal effect was measured by a predetermined method. As a result, it was confirmed that the PM in the exhaust gas G can be removed by using the plasma reactor 20.

  The plasma reactor according to the present invention disappears by oxidizing or burning soot, black smoke, and solid particulate matter floating in the environment contained in exhaust gas from hydrocarbon combustion engines such as diesel engines. It can be applied to ozone generators that generate oxygen using oxygen-containing gas, and it can also be applied to air purifiers that react and incinerate and remove harmful substances such as fine particles in the air. is there.

DESCRIPTION OF SYMBOLS 1 Fence electrode 2 Fence electrode 3 Dielectric 5, 5A, 5B Plasma reaction structure 6 Fence 7 Frame conductor 8 Inlet 9 Outlet 10 Discharge space 11 Lead wire 12 Catalyst 13 Container 14 Spacer 20 Plasma reactor 25 Opposed Fence area G gas

Claims (10)

Having a plasma reaction structure composed of two conductive electrodes facing each other and a dielectric inserted between the conductive electrodes, and generating a plasma reaction by applying a voltage to the conductive electrodes In a plasma reactor consisting of
A plurality of the plasma reaction structures are arranged in parallel, and the conductive electrode is formed as a fence-shaped electrode from a plurality of fences spaced apart from each other and a conductor that connects the fences to each other. The directions of the fences of the opposing fence-like electrodes are different from each other, and the gas flows between the opposite of the fence-like electrode and the dielectric or between the opposite of the dielectric covering the fence-like electrode. A plasma reactor characterized in that at least one layer of discharge space that can pass through and has an inlet and an outlet for the gas is provided.   The fence of the fence-like electrode has a width of 0.1 mm to 10 mm, a length of 1 mm to 1000 mm, a thickness of 0.001 mm to 10 mm, and a distance between the fences of 0.5 mm to 100 mm. The plasma reactor according to claim 1.   3. The plasma reactor according to claim 1, wherein a plurality of the fences in the fence-like electrode are connected to the conductors with the same size and at equal intervals.   The conductor of the fence-like electrode is formed in a frame-like conductor, and at least one end of the fence is fixed to the frame-like conductor and faces each other with a spacer interposed between the opposed frame-like conductors. The plasma reactor according to any one of claims 1 to 3, wherein the discharge space is formed between the fence-like electrodes.   The plasma reactor according to any one of claims 1 to 4, wherein the dielectric inserted between the fence-shaped electrodes is one or more layers.   The dielectric is formed into a plate shape, a cylindrical shape, or a spherical shape from one or more materials selected from metal oxide, plastic, rubber, and glass, and the thickness of the dielectric is 0.1 mm to The plasma reactor according to claim 1, wherein the plasma reactor is within a range of 10 mm.   The fence-like electrode is connected to a lead wire to which voltage can be applied, and can pass electricity, such as iron, copper, stainless steel, zinc, aluminum, titanium, metal oxide such as indium tin oxide, zinc oxide, conductive plastic, etc. The plasma reactor according to any one of claims 1 to 6, wherein   The plasma according to any one of claims 1 to 7, wherein a catalyst for promoting a chemical reaction is supported on a surface of the dielectric and / or the fence-like electrode in contact with the discharge space. Reactor.   An oxygen-containing gas is used as the gas supplied from the inlet of the discharge space, ozone gas is generated by a plasma reaction generated in the discharge space, and the ozone gas is recovered from the outlet of the discharge space. The plasma reactor according to any one of claims 1 to 8.   The gas supplied from the inlet of the discharge space is a gas containing a harmful substance such as particulate matter, nitrogen oxide, organic compound, or sulfur oxide, and the harmful substance is generated by a plasma reaction generated in the discharge space. The plasma reactor according to claim 1, wherein the purified gas is recovered from the outlet of the discharge space.

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