JP2010129467A - Cell stack and fuel cell device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cell stack of a fuel cell capable of thinning and improving power generation performance, and to provide a fuel cell device that is equipped with the cell. <P>SOLUTION: Each cell 40 of the cell stack 20 includes an anode electrode, a cathode electrode, an electrolyte layer sandwiched between the anode electrode and the cathode electrode, an anode-side metal separator 56 arranged piled on the anode electrode, and a cathode-side metal separator 54 arranged piled on the cathode electrode. In a plurality of cells, one anode-side metal separator and one cathode-side metal separator of the other cell are laminated, while facing each other; and further, the anode-side metal separator of one cell and the cathode-side metal separator of the other adjacent cell sandwich a flame-shaped gasket 64, having a space part 64a inside and a conductive sheet which has elasticity and conductivity, is arranged inside the space part of the gasket; and further, makes the anode-side metal separator and the cathode-side metal separator conducting. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cell stack of a fuel cell used as a power source for an electronic device or the like, and a fuel cell device including the same.

  Currently, secondary batteries such as lithium ion batteries are mainly used as power sources for portable notebook personal computers (hereinafter referred to as notebook PCs) and mobile devices. In recent years, a small fuel cell with high output and no need for charging has been expected as a new power source due to an increase in power consumption accompanying the enhancement of functions of these electronic devices and a request for longer use. There are various types of fuel cells. In particular, a direct methanol fuel cell (hereinafter referred to as DMFC) using a methanol solution as a fuel is easier to handle than a fuel cell using hydrogen as a fuel. Since the system is simple, it is attracting attention as a power source for electronic devices.

  In general, a single cell in DMFC is a membrane / electrode assembly (hereinafter referred to as MEA) in which an anode and a cathode composed of a catalyst layer and carbon paper are integrated on both sides of an electrolyte layer such as an electrolyte plate or a solid polymer electrolyte membrane. Called). A cell having a fuel cell on the main surface facing the anode of the single cell, a separator having an air flow channel on the main surface corresponding to the cathode of the single cell, and a plurality of single cells stacked alternately. The stack is configured. In this case, a bipolar plate structure in which an anode and a cathode are laminated, a gas permeable membrane is placed in the anode fuel flow field, and a channel for releasing gaseous effluent is provided at a position adjacent to the gas permeable membrane. It has been proposed (for example, Patent Document 1).

Through the groove formed in the separator, fuel is supplied to the anode and oxidant is supplied to the cathode. The fuel undergoes an oxidation reaction at the anode, and methanol reacts with water and is oxidized to produce carbon dioxide, protons, and electrons. Protons pass through the polymer electrolyte membrane and move to the cathode. At the cathode, oxygen gas in the air combines with hydrogen ions and electrons and is reduced to produce water. In the process, electrons flow to the external circuit and take out current.
JP 2006-507625 A

  However, when a plurality of cells are stacked with a bipolar separator sandwiched as in the cell stack described above, the size of the stack increases and is not suitable for miniaturization. If the cooling plate is interposed between the two cell stacks, the entire cell stack becomes thick. Therefore, it becomes an obstacle to downsizing the entire fuel cell.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel cell stack capable of being thinned and improving power generation performance, and a fuel cell device including the same.

A cell stack of a fuel cell device according to an aspect of the present invention is a cell stack of a fuel cell device configured by stacking a plurality of single cells, and each single cell includes an anode electrode, a cathode electrode, and these anode electrodes. An electrolyte layer sandwiched between the anode and the cathode, an anode-side metal separator provided to overlap the anode, and a cathode-side metal separator provided to overlap the cathode. The cell is laminated with the anode side metal separator and the cathode side metal separator of another single cell facing each other,
Between the anode-side metal separator of the single cell and the cathode-side metal separator of another single cell adjacent to the frame-shaped gasket having a space inside, and having elasticity and conductivity, and the gasket A conductive sheet that is disposed in the space and conducts the anode-side metal separator and the cathode-side metal separator is sandwiched.

A fuel cell device according to another aspect of the present invention includes a cell stack, an electromotive unit that generates power by a chemical reaction, a fuel tank that contains fuel, and supplies fuel from the fuel tank to the cell stack. A fuel supply unit, and an air supply unit for supplying air to the cell stack,
The cell stack is configured by laminating a plurality of single cells, and each single cell overlaps the anode electrode with an anode electrode, a cathode electrode, and an electrolyte layer sandwiched between the anode electrode and the cathode electrode. An anode-side metal separator and a cathode-side metal separator provided to overlap the cathode electrode, and the plurality of single cells include the anode-side metal separator and a cathode-side metal separator of another single cell. Are stacked facing each other, and have a frame-like gasket having a space portion between the anode-side metal separator of a single cell and the cathode-side metal separator of another single cell, and have elasticity and conductivity. And a conductive sheet disposed in the space of the gasket and electrically conducting the anode-side metal separator and the cathode-side metal separator; There has been pinched.

  According to the above configuration, it is possible to provide a fuel cell stack capable of being thinned and improving power generation performance, and a fuel cell device including the same.

Hereinafter, a fuel cell device according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 schematically shows the configuration of a fuel cell device. As shown in FIG. 1, the fuel cell device 10 is configured as a DMFC using methanol as a liquid fuel. The fuel cell device 10 includes a cell stack 20 that constitutes an electromotive unit, a fuel tank 12, a circulation system 24 that supplies fuel and air to the cell stack 20, and a battery control unit 51 that controls the operation of the entire fuel cell device. ing.

  The fuel tank 12 has a sealed structure, and is formed as a fuel cartridge that is detachable from the fuel cell device 10. The fuel tank 12 contains high-concentration methanol as liquid fuel. When the fuel is consumed, the fuel tank 12 can be easily replaced or replenished.

  The circulation system 24 includes an anode flow path 32 that circulates fuel supplied from the fuel tank 12 through the cell stack 20, a cathode flow path 34 that circulates a gas containing air through the cell stack 20, an anode flow path, and a cathode flow. It has a plurality of auxiliary machines provided in the road. The anode channel 32 and the cathode channel 34 are each formed by piping or the like.

  2 shows a stacked structure of the cell stack 20, FIG. 3 is an exploded perspective view showing the cell stack 20, FIG. 4 is an exploded perspective view showing single cells constituting the cell stack, and FIG. FIG. 6 schematically shows a power generation reaction of each single cell.

  As shown in FIGS. 2 and 3, the cell stack 20 is configured by alternately laminating a plurality of, for example, eight single cells 40, gaskets 64 and conductive sheets 66 described later. End plates 43 are stacked at both ends in the stacking direction, and the end plates are fastened together by screws or the like, whereby a plurality of single cells 40, gaskets 64, and conductive sheets 66 are stacked between the end plates 43. Held in a state.

  As shown in FIGS. 3 to 5, the single cell 40 includes a substantially rectangular plate-like cathode electrode (air electrode) 42 and anode electrode (fuel electrode) 44 each composed of a catalyst layer and carbon paper, these cathode electrodes, A membrane / electrode assembly (hereinafter referred to as MEA) 50 is provided which is integrated with a substantially rectangular polymer electrolyte membrane 46 sandwiched between anode electrodes. In addition, the MEA 50 is integrally provided with a rectangular gas-liquid separation film 48 that is provided on the outer surface of the anode 44. The polymer electrolyte membrane 46 is formed in a larger area than the cathode electrode 42 and the anode electrode 44, and the peripheral edge thereof projects outward from the peripheral edges of the anode electrode and the cathode electrode. Rectangular frame-shaped gaskets 52a and 52b are attached to both sides of the periphery of the polymer electrolyte membrane 46 by a heat welding sheet (not shown).

  The single cell 40 has a cathode side metal separator 54 and an anode side metal separator 56 each formed in an elongated rectangular plate shape. These separators 54 and 56 are made of, for example, SUS. The cathode side metal separator 54 is laminated on the cathode electrode 42, and the anode side metal separator 56 is laminated on the anode electrode 44, here, the gas-liquid separation film 48. Accordingly, the MEA 50 is sandwiched between the cathode side metal separator 54 and the anode side metal separator 56. The MEA 50, the gaskets 52a and 52b, the cathode side metal separator 54, and the anode side metal separator 56 are joined to each other by heat welding (heating and pressurizing) with a heat welding sheet (not shown) interposed therebetween. Yes.

  A cathode inflow passage 58a and an anode inflow passage 58b through which air and fuel respectively pass are formed at one end in the longitudinal direction of the cathode side metal separator 54, the anode side metal separator 56, and the gaskets 52a and 52b, respectively. Are formed with a cathode outflow passage 60a and an anode outflow passage 60b through which reaction products on the cathode side and the anode side are respectively discharged.

  In the cathode-side metal separator 54, a groove-like air channel 54 a that supplies air to the cathode electrode 42 is formed on the wall surface facing the cathode electrode 42. The air flow path 54a extends in a bellows shape from the cathode inflow path 58a to the cathode outflow path 60a.

  In the anode-side metal separator 56, a groove-like fuel flow path 56 a for supplying fuel to the anode electrode 44 is formed on the wall surface facing the anode electrode 44. The fuel flow path 56a extends in a bellows shape from the anode inflow path 58b to the anode outflow path 60b. The anode-side metal separator 56 has a plurality of exhaust holes 56 b through which gas separated by the gas-liquid separation membrane 48, here, carbon dioxide containing water vapor is discharged to the outside of the single cell 40. The exhaust holes 56b are formed through the anode-side metal separator 56, and are provided along the fuel flow path 56a. Each exhaust hole 56 b faces the gas-liquid separation membrane 48.

  As shown in FIGS. 2, 3, and 5, the plurality of single cells 40 configured as described above are stacked side by side in series. That is, the plurality of single cells 40 are stacked such that the cathode side metal separator 54 of one single cell 40 and the anode side metal separator 56 of another adjacent single cell 40 face each other. The cathode-side metal separator 54 and the anode-side metal separator 56 facing each other are each formed of a metal plate, and the rigid body and the rigid body have a high contact resistance, resulting in insufficient electrical contact. Therefore, a frame-shaped gasket 64 having a space portion 64a between the cathode-side metal separator 54 and the anode-side metal separator 56 of the adjacent single cell 40, and a conductive material disposed in the space portion 64a of this gasket. The sheet 66 is sandwiched. The conductive sheet 66 has elasticity and conductivity, and is in close contact with the anode-side metal separator 56 and the cathode-side metal separator 54 to electrically connect them.

  The gasket 64 is formed of, for example, a material having elasticity, and has a hardness and dimensions such that the conductive sheet 66 is in close contact with the cathode side metal separator 54 and the anode side metal separator 56 of the single cell 40. A cathode inflow passage 58a and an anode inflow passage 58b through which air and fuel respectively pass are formed at one end in the longitudinal direction of the gasket 64, and reaction products on the cathode side and the anode side are discharged at the other end in the longitudinal direction, respectively. A cathode outflow passage 60a and an anode outflow passage 60b are formed.

  The conductive sheet 66 is formed of, for example, a carbon non-woven fabric and has hydrophilicity or water retention. The conductive sheet 66 is disposed to face the exhaust hole 56 b of the anode side metal separator 56. Carbon dioxide and water vapor exhausted from the exhaust holes 56 b pass through the conductive sheet 66, and a part of the water vapor is absorbed by the conductive sheet 66. The remaining water vapor and carbon dioxide pass through the exhaust groove 64b formed in the gasket 64 and are discharged to the cathode outflow passage 60a.

  As shown in FIGS. 2, 3, and 5, the cell stack 20 is configured by alternately stacking eight single cells 40, gaskets 64, and conductive sheets 66. End plates 43 are stacked at both ends in the stacking direction, and the end plates are fastened together by screws or the like, whereby a plurality of single cells 40, gaskets 64, and conductive sheets 66 are stacked between the end plates 43. Held in a state. The cathode inflow passage 58a and anode inflow passage 58b of the plurality of single cells 40 and the cathode inflow passage 58a and anode inflow passage 58b of the gasket 64 are in communication with each other. Similarly, the cathode outflow passage 60a and the anode outflow passage 60b of the plurality of single cells 40 and the cathode outflow passage 60a and the anode outflow passage 60b of the gasket 64 are in communication with each other.

  The cathode inflow path 58 a and the cathode outflow path 60 a of the cell stack 20 are connected to the cathode flow path 34 of the circulation system 24. The anode inflow path 58 b and the anode outflow path 60 b of the cell stack 20 are connected to the anode flow path 32 of the circulation system 24.

  As shown in FIG. 2, the cathode-side metal separator 54 of the single cell 40 located on one end side in the stacking direction is provided with a cathode terminal 71 for taking out power, and the single cell 40 positioned on the other end side in the stacking direction. The anode side metal separator 56 is provided with an anode terminal 72 for taking out electric power.

In each single cell 40 of the cell stack 20 configured as described above, as shown in FIGS. 5 and 6, fuel (methanol aqueous solution) is supplied to the anode electrode 44 through the fuel flow path 56a on the anode side, A reaction occurs, carbon dioxide is released, and e − (electrons) are generated to conduct the anode side metal separator 56 forming the fuel flow path 56a. At this time, H ^{+ is} also generated, which passes through the polymer electrolyte membrane 46 and is supplied to the cathode electrode 42 side. On the other hand, on the cathode side, e− conducted through the cathode side metal separator 54, H ⁺ passing through the polymer electrolyte membrane 46, and oxygen in the air supplied from the air flow path 54 a chemically react on the cathode electrode 42. Form water. In this process, electrons can flow between the anode 44 and the cathode 42, that is, between the anode-side metal separator 56 and the cathode-side metal separator 54, and current can be taken out.

  During a series of reactions, carbon dioxide generated at the anode 44 is separated into gas (carbon dioxide, water vapor) and liquid (unreacted fuel) in the MEA 50 by the gas-liquid separation membrane 48, and carbon dioxide Passes through the exhaust hole 56b of the anode side metal separator 56 and is discharged from the exhaust groove 64b of the gasket 64 to the cathode outflow passage 60a. As described above, the carbon dioxide that passes through the exhaust hole 56 b and is released to the outside contains water vapor, and at least a part of this water vapor is absorbed by the conductive sheet 66. Thereby, the conductive sheet 66 is in a state containing moisture.

  As shown in FIG. 1, the upstream end 34a and the downstream end 34b of the cathode channel 34 are each in communication with the atmosphere. The cathode flow path 34 is connected to the cathode inflow path 58 a and the cathode outflow path 60 a of the cell stack 20. The auxiliary machine provided in the cathode channel 34 includes an air supply pump 38 connected to the cathode channel 34 on the upstream side of the cell stack 20. The air supply pump 38 constitutes an air supply unit that supplies air to the cathode electrode 42 of the cell stack 30.

  The anode flow path 32 is connected to the anode inflow path 58b and the anode outflow path 60b of the cell stack 20 to form a closed loop. The auxiliary equipment provided in the anode flow path 32 includes a fuel pump 14 connected to the fuel supply port of the fuel tank 12, a mixing tank 16 connected to the output portion of the fuel pump 14 via the piping, and the mixing tank 16. A liquid feed pump 17 connected between the output unit and the inflow side of the cell stack 20 is provided. The mixing tank 16 together with the fuel tank 12 constitutes a part of the fuel tank in the present invention.

  The output part of the liquid feed pump 17 is connected to the anode inflow path 58 b of the cell stack 20 through the anode flow path 32. The fuel pump 14 and the liquid feed pump 17 constitute a fuel supply unit that supplies fuel to the cell stack 20. The output side of the anode outflow passage 60 b of the cell stack 20 is connected to the input portion of the mixing tank 16 via the anode passage 32.

  The battery control unit 51 is connected to the cathode terminal 71 and the anode terminal 72 of the cell stack, takes out the electric power generated in the cell stack 20, supplies it to the electronic device 53, and measures the voltage of each single cell 40 of the cell stack 20, and the cell Controls the current drawn from the stack.

  When the fuel cell device 10 having the above configuration is used as a power source for the electronic device 53, first, the fuel tank 12 containing methanol is mounted and connected to the circulation system 24 of the fuel cell device 10. In this state, power generation of the fuel cell device 10 is started. In this case, the fuel pump 14, the liquid feed pump 17, and the air feed pump 38 are operated under the control of the battery control unit 51. High-concentration methanol is supplied from the fuel tank 12 to the mixing tank 16 through the anode flow path 32 by the fuel pump 14, mixed with water in the mixing tank, and diluted to a predetermined concentration. The aqueous methanol solution diluted in the mixing tank 16 is sent from the anode flow path 32 to the anode inflow path 58 b in the cell stack 20 by the liquid feed pump 17. Further, the methanol aqueous solution passes through the fuel flow path 56 a of each anode side metal separator 56 and is supplied to the anode electrode 44 of the single cell 40. Thereafter, the unreacted aqueous methanol solution is sent to the anode outflow passage 60 b of the cell stack 20, and further returned to the mixing tank 16 through the anode passage 32.

  On the other hand, the air pump 38 sucks air, that is, air, into the cathode channel 34 from the upstream end 34 a of the cathode channel 34. This air passes through an intake filter (not shown), and then is supplied to the cathode inflow path 58a of the cell stack 20 through the cathode flow path 34, and further passes through the air flow path 54a of each cathode-side metal separator 54. It is supplied to the cathode electrode 42. The air that has reacted with the cathode electrode 42 and contained moisture is sent to the cathode outflow passage 60a of the cell stack 20, and further exhausted to the outside through the cathode passage. The carbon dioxide separated by the gas-liquid separation membrane 48 of the single cell 40 is exhausted to the outside through the cathode outflow passage 60 a and the cathode passage 34.

  The aqueous methanol solution and air supplied to the cell stack 20 undergo an electrochemical reaction at the polymer electrolyte membrane 46 provided between the anode electrode 44 and the cathode electrode 42, whereby the anode electrode 44 and the cathode electrode 42 are Electric power is generated between them. The electric power generated in the cell stack 20 is drawn from the cell stack by the battery control unit 51 and supplied to the electronic device 53.

According to the fuel cell device configured as described above, the cell stack 20 can be stacked with the anode / cathode integrated cell as a minimum unit. Therefore, the stack size can be reduced as compared with a conventional stack using bipolar plates. By sandwiching the conductive sheet 66 having elasticity and conductivity between the single cells 40, the electrical resistance between the single cells can be lowered, and the output reduction of the cell stack 20 can be suppressed. As a result, a thin cell stack with improved power generation performance and a fuel cell device including the cell stack can be obtained. Further, the conductive sheet 66 has hydrophilicity or water retention, and can absorb the vapor discharged from the exhaust hole, thereby further reducing the electrical resistance between the single cells 40.
The contact resistance between the single cells was compared with and without the conductive sheet 66 having elasticity, conductivity, and hydrophilicity between the adjacent single cells 40. When the conductive sheet 66 was sandwiched, the electrical resistance between the single cells 40 was 78 mΩ, whereas when there was no conductive sheet, the electrical resistance between the single cells 40 was 89 mΩ. It was confirmed that when the conductive sheet 66 is present, the electrical resistance is reduced by 11 mΩ as compared with the case without the conductive sheet, and the conductivity between the single cells 40 is improved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  For example, in the cell stack, the number of single cells to be stacked is not limited to eight and can be increased or decreased as necessary. The shape, material, and the like of each constituent element are not limited to the above-described embodiment, and can be selected as appropriate. The fuel cell device may omit the air supply pump and supply air to the cell stack by air diffusion and convection. The fuel cell device according to the present invention can also be applied to power supplies of various electronic devices such as personal computers, mobile devices, and portable terminals, and other devices.

FIG. 1 is a block diagram schematically showing the configuration of a fuel cell device according to an embodiment of the present invention. FIG. 2 is a perspective view showing a cell stack of the fuel cell device. FIG. 3 is an exploded perspective view showing the cell stack in an exploded manner. FIG. 4 is an exploded perspective view showing a single cell of the cell stack in an exploded manner. FIG. 5 is a cross-sectional view of the cell stack taken along line AA of FIG. FIG. 6 is a diagram schematically showing a power generation reaction of the single cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell apparatus, 12 ... Fuel tank, 14 ... Fuel pump, 16 ... Mixing tank,
17 ... Liquid feed pump, 20 ... Cell stack, 24 ... Circulation system, 32 ... Anode flow path,
34 ... Cathode flow path, 40 ... Single cell, 42 ... Cathode electrode, 43 ... End plate,
44 ... anode electrode, 46 ... polymer electrolyte membrane, 48 ... gas-liquid separation membrane, 50 ... MEA,
51 ... Battery control unit, 54 ... Cathode side metal separator, 54a ... Air flow path,
56 ... anode side metal separator, 56a ... fuel flow path, 56b ... exhaust hole,
64 ... Gasket, 64a ... Space part, 66 ... Conductive sheet

Claims (10)

A cell stack of a fuel cell device configured by stacking a plurality of single cells,
Each single cell is provided with an anode electrode, a cathode electrode, an electrolyte layer sandwiched between the anode electrode and the cathode electrode, an anode side metal separator provided on the anode electrode, and an electrode layer on the cathode electrode. A cathode-side metal separator,
The plurality of single cells are laminated such that the anode side metal separator and the cathode side metal separator of another single cell face each other.
Between the anode-side metal separator of the single cell and the cathode-side metal separator of another single cell adjacent to the frame-shaped gasket having a space inside, and having elasticity and conductivity, and the gasket A cell stack of a fuel cell device, which is disposed in a space and sandwiches a conductive sheet that conducts the anode side metal separator and the cathode side metal separator.   The gasket is formed of an elastic material, and has a hardness and a dimension that allow the conductive sheet to be in close contact with the anode-side metal separator of another single cell adjacent to the anode-side metal separator of the single cell. 2. A cell stack of the fuel cell device according to 1.   The anode-side metal separator has a groove-shaped fuel flow path for supplying fuel to the anode electrode, and the cathode-side metal separator has a groove-shaped air flow path for supplying air to the cathode electrode. The cell stack of the fuel cell device according to claim 1.   Each single cell has a gas-liquid separation membrane that is laminated between the anode electrode and the anode-side metal separator and separates gas and liquid, and the anode-side metal separator is separated by the gas-liquid separation membrane. The cell stack of the fuel cell device according to claim 3, wherein the cell stack has an exhaust hole through which the discharged gas is discharged to the outside of the single cell.   5. The cell stack of a fuel cell device according to claim 4, wherein the conductive sheet is positioned opposite to an exhaust hole of the anode side metal separator and has hydrophilicity or water retention.   The cell stack of the fuel cell device according to claim 5, wherein the conductive sheet is formed of a carbon nonwoven fabric. An electromotive unit having a cell stack and generating power by a chemical reaction;
A fuel tank containing fuel;
A fuel supply unit for supplying fuel from the fuel tank to the cell stack;
An air supply unit for supplying air to the cell stack,
The cell stack is configured by stacking a plurality of single cells,
Each single cell is provided with an anode electrode, a cathode electrode, an electrolyte layer sandwiched between the anode electrode and the cathode electrode, an anode side metal separator provided on the anode electrode, and an electrode layer on the cathode electrode. A cathode-side metal separator,
The plurality of single cells are laminated such that the anode side metal separator and the cathode side metal separator of another single cell face each other.
Between the anode-side metal separator of the single cell and the cathode-side metal separator of another single cell adjacent to the frame-shaped gasket having a space inside, and having elasticity and conductivity, and the gasket A fuel cell device in which a conductive sheet that is disposed in the space and conducts the anode side metal separator and the cathode side metal separator is sandwiched.   The anode-side metal separator has a groove-shaped fuel flow path for supplying fuel to the anode electrode, and the cathode-side metal separator has a groove-shaped air flow path for supplying air to the cathode electrode. The fuel cell device according to claim 7.   Each single cell has a gas-liquid separation membrane that is laminated between the anode electrode and the anode-side metal separator and separates gas and liquid, and the anode-side metal separator is separated by the gas-liquid separation membrane. The fuel cell device according to claim 8, further comprising an exhaust hole through which the discharged gas is discharged to the outside of the single cell.   10. The fuel cell device according to claim 9, wherein the conductive sheet is positioned opposite to an exhaust hole of the anode-side metal separator and has hydrophilicity or water retention.

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