JP2011009137A - Fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for improving drainage of a fuel cell.SOLUTION: The fuel cell stack 100 includes a power generating laminated body 10S having a plurality of laminated power generating bodies 10, and a water collecting portion 50 arranged on an end portion side in a lamination direction of the power generating laminated body 10S. The power generating laminated body 10S includes a hydrogen supply manifold 11 and a hydrogen discharge manifold 12. The water collecting portion 50 includes a hollow portion 55, and the hydrogen supply manifold 11 and hydrogen discharge manifold 12 are connected through the hollow portion 55. The power generating laminated body 10S is arranged to have an inclination angle with respect to a horizontal direction so that the hydrogen discharge manifold 12 is on the downside of the hydrogen supply manifold 11 in a gravity direction, and an end portion of the hydrogen discharge manifold 12 on a water collecting portion 50 side is on the downside in the gravity direction. Liquid water generated in the hydrogen discharge manifold 12 moves by gravity and is collected in the water collecting portion 50.

Description

  The present invention relates to a fuel cell.

  The fuel cell stack usually has a stack structure in which a plurality of power generators are stacked. Each power generation body receives supply of hydrogen and oxygen as reaction gases via a manifold provided in the fuel cell stack, and generates electric power by these electrochemical reactions. Due to this electrochemical reaction, a large amount of water is generated inside the fuel cell stack. If this moisture stays in a manifold for exhaust gas, a gas flow path provided in each power generator, etc., the flow of the reaction gas is hindered, and sometimes the reaction gas flows backward.

  As described above, the retention of moisture in the fuel cell stack causes a reduction in the flowability of the reaction gas to each power generator, and increases the non-uniformity of voltage (cell voltage) for each power generator. When the non-uniformity of the cell voltage becomes significant, the power generation of the fuel cell stack itself may stop.

  Until now, various techniques for improving the drainage of the fuel cell stack have been proposed (Patent Document 1 below). However, even with these technologies, the drainage performance of the fuel cell has not been sufficiently improved.

JP 2007-141039 A JP 2007-026856 A JP-A-11-111316 JP 2003-177871 A

  An object of this invention is to provide the technique which improves the drainage property in a fuel cell.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A fuel cell stack, comprising: a power generation stack in which a plurality of power generation bodies are stacked; and a water collecting portion disposed on an end side in the stacking direction of the power generation stack, A supply manifold for supplying reaction gas to each of the plurality of power generation bodies, and a discharge manifold for discharging exhaust gas from each of the plurality of power generation bodies, each power generation section of the plurality of power generation bodies The water collection section is provided with a gas flow path for the reaction gas that connects the supply manifold and the discharge manifold, and from the discharge manifold. The power generation laminate is disposed so that the discharge manifold is below the supply manifold in the direction of gravity. Rutotomoni, an end of the water collecting portion side of the discharge manifold is such that the gravity direction lower side, are arranged with a tilt angle with respect to the horizontal direction, the fuel cell stack.
According to this fuel cell stack, liquid water generated in a gas flow path such as a discharge manifold during power generation can be guided to the water collection section using gravity and stored in the water collection section by the water retention means. it can. Therefore, it can suppress that liquid water retains in a gas channel. Further, the liquid water stored in the water collecting section can be easily discharged to the outside of the fuel cell stack, for example, directly discharged from the water collecting section or discharged together with the exhaust gas from the discharge manifold. Therefore, the drainage of the fuel cell stack can be improved.

  The present invention can be realized in various forms, for example, in the form of a fuel cell, a fuel cell system including the fuel cell, a vehicle equipped with the fuel cell system, and the like. .

Schematic which shows the structure of the fuel cell stack of 1st Example. The schematic diagram for demonstrating the water movement inside a fuel cell stack by inclining a fuel cell stack. The schematic sectional drawing which shows the structure of the water collection part of 1st Example. Schematic which shows the structure of the water collection part of 2nd Example. Schematic which shows the structure of the water collection part of 3rd Example. Schematic which shows the structure of the downstream flow-path formation site | part in the water collection part of 3rd Example. Schematic which shows the structure of the fuel cell stack of 4th Example.

A. First embodiment:
FIG. 1 is a schematic view showing the configuration of a fuel cell stack as one embodiment of the present invention. The fuel cell stack 100 is a polymer electrolyte fuel cell that generates power by receiving supply of hydrogen and oxygen. The fuel cell stack 100 includes a power generation stack 10 </ b> S in which a plurality of power generation bodies 10 are stacked, a water collection unit 50, and first and second end plates 21 and 22. The fuel cell stack 100 further includes a terminal, an insulator as an insulating member, and the like, but illustration and description are omitted for convenience.

  Each power generator 10 has a membrane electrode assembly in which an anode and a cathode are arranged on both sides of an electrolyte membrane that exhibits good proton conductivity in a wet state. A separator (not shown), which is a plate-like member provided with flow paths for reaction gas and refrigerant, is interposed between the power generation bodies 10. Note that the separator has conductivity and also has a function of collecting electricity generated by each power generator 10.

  The water collecting portion 50 is a substantially flat plate-like member having a hollow portion 55, and is disposed on one end side in the stacking direction of the power generation laminate 10S (hereinafter simply referred to as “stacking direction”). The hollow portion 55 of the water collecting portion 50 is connected to a pipe 61 having an open / close valve 62. The function of the water collecting unit 50 will be described later.

  The first and second end plates 21 and 22 fasten the power generation laminate 10S and the water collecting portion 50 by sandwiching them from both sides in the lamination direction. The first and second end plates 21 and 22 are provided with fastening members (not shown) for applying a fastening force to the power generation laminate 10S. In addition, the 2nd end plate 22 is arrange | positioned at the side by which the water collection part 50 is arrange | positioned. Hereinafter, in the fuel cell stack 100, the first end plate 21 side is referred to as “upper end side”, and the second end plate 22 side is referred to as “lower end side”.

  The power generation laminate 10S is provided with a hydrogen supply manifold 11 for supplying hydrogen to the anode of each power generation body 10 as a through hole along the stacking direction. Further, in the power generation stack 10S, a hydrogen discharge manifold 12 for discharging anode exhaust gas containing hydrogen that has not been subjected to an electrochemical reaction from the anode of each power generation body 10 penetrates along the stacking direction. It is provided as a hole. Each of the hydrogen supply manifold 11 and the hydrogen discharge manifold 12 is provided at a position facing each other across the power generation section provided for power generation in each power generation body 10, and through a flow path provided in the separator. Communicates with the power generation unit.

  The hydrogen supply manifold 11 is connected to a hydrogen tank (not shown) through a hydrogen supply pipe 31 connected to the first end plate 21. On the other hand, the hydrogen discharge manifold 12 is connected to a hydrogen discharge portion (not shown) for treating the anode exhaust gas via a hydrogen discharge pipe 32 connected to the first end plate 21. The fuel cell stack 100 is provided with manifolds and connection pipes for oxygen and refrigerant in the same manner as the hydrogen manifolds 11 and 12 and the two pipes 31 and 32 for hydrogen. Is omitted.

  The hydrogen supply manifold 11 and the hydrogen discharge manifold 12 are connected to the hollow portion 55 of the water collection portion 50. As a result, the hydrogen in the hydrogen supply manifold 11 flows to the hydrogen discharge manifold 12 through the hollow portion 55 of the water collection portion 50. That is, the hollow portion 55 functions as a gas flow path that connects the hydrogen supply manifold 11 and the hydrogen discharge manifold 12.

  Here, in FIG. 1, the direction of gravity is illustrated by an arrow G. When the fuel cell stack 100 is operated, the hydrogen discharge manifold 12 is disposed below the hydrogen supply manifold 11 in the direction of gravity. Further, the fuel cell stack 100 is disposed with an inclination angle with respect to the horizontal direction so that the lower end side thereof is the lower side in the gravity direction. The reason for this will be described below.

  2A to 2C are schematic views for explaining moisture movement inside the fuel cell stack 100 by arranging the fuel cell stack 100 in an inclined manner. 2 (A) to 2 (C) schematically show the state in which the liquid water W stays inside the hydrogen discharge manifold 12. 2A to 2C, illustrations other than the hydrogen discharge manifold 12 and the water collection unit 50 are omitted for convenience. 2A to 2C show an arrow G indicating the direction of gravity.

  Generally, in a fuel cell stack, a large amount of moisture is generated during power generation. In some cases, a reactive gas humidified to improve proton conductivity of the electrolyte membrane is supplied. Therefore, a large amount of water is usually present inside the fuel cell stack. If such moisture is not properly discharged with the exhaust gas and stays in the reaction gas flow path including the manifold, the flow of the reaction gas is obstructed and the power generation performance of the fuel cell stack is significantly reduced. There is a possibility that. In particular, when the operation of the fuel cell stack is stopped with moisture remaining, and the fuel cell stack is restarted below freezing point, the hydrogen remaining in the hydrogen flow path is frozen and hydrogen to some power generators This hinders the supply of the fuel cell stack and significantly reduces the startability of the fuel cell stack. Therefore, it is preferable that moisture inside the fuel cell stack, particularly moisture in the hydrogen flow path, is appropriately discharged to the outside of the fuel cell stack during the operation or after the operation is stopped.

  FIG. 2A is a perspective view showing a state in which the fuel cell stack 100 is arranged substantially horizontally without being inclined. In this arrangement, when liquid water stays in the hydrogen discharge manifold 12 of the fuel cell stack 100, the liquid water W stays at the bottom of the hydrogen discharge manifold 12 from the upper end side to the lower end side. In the fuel cell stack 100, since the hydrogen discharge manifold 12 is located below the hydrogen supply manifold 11, the liquefied water tends to stay in the hydrogen discharge manifold 12. In particular, moisture tends to stay in the hydrogen discharge manifold 12 after the operation of the fuel cell stack 100 in which the gas flow is stopped.

  FIG. 2 (B) is a perspective view showing a state in which the fuel cell stack 100 is inclined with respect to the horizontal plane by an angle θ such that the lower end side is the lower side in the direction of gravity. FIG. 2B is almost the same as FIG. 2A except that the fuel cell stack 100 is inclined and the liquid water W staying in the hydrogen discharge manifold 12 is offset downward. is there. FIG. 2C is a view of the fuel cell stack 100 of FIG.

  Thus, by arranging the fuel cell stack 100 in an inclined manner, the liquid water W staying in the hydrogen discharge manifold 12 can be moved to the water collecting section 50 using gravity. That is, it is possible to increase the amount of liquid water W that flows into the hollow portion 55 of the water collecting portion 50.

  FIG. 3A is a schematic diagram showing the internal configuration of the water collecting section 50, and shows an enlarged region A surrounded by a broken line in FIG. The bottom surface 55t of the hollow portion 55 in the water collecting portion 50 is located on the lower side in the gravitational direction than the hydrogen discharge manifold 12. As described above, by providing a step by making the bottom portion of the hydrogen discharge manifold 12 sufficiently lower than the bottom surface 55t of the hollow portion 55, it is possible to store the moisture induced in the water collecting portion 50. That is, the hollow part 55 functions also as a water retention means for holding liquid water. Note that by increasing the level difference, the water induced in the water collecting section 50 can be stored even when the inclination angle θ of the fuel cell stack 100 is relatively small (for example, 10 ° or less). .

  Here, a pipe 61 is connected to the bottom surface 55 t of the hollow portion 55. Therefore, by opening the opening / closing valve 62, the liquid water guided to and stored in the water collecting section 50 can be discharged to the outside through the pipe 61.

  FIG. 3B is a schematic diagram illustrating another configuration example of the water collecting unit 50. 3B is substantially the same as FIG. 3A except that the bottom surface 55t of the hollow portion 55 is inclined toward the connection portion of the pipe 61. FIG. By configuring the hollow portion 55 of the water collecting portion 50 in such a configuration, moisture flowing into the hollow portion 55 can be guided to the pipe 61, and the drainage performance of the fuel cell stack 100 can be further improved. Can do.

  The pipe 61 and the opening / closing valve 62 may be omitted. Even in this case, the water stored in the water collection unit 50 is vaporized by hydrogen passing through the water collection unit 50 and can be discharged to the outside of the fuel cell stack 100 together with the anode exhaust gas. Further, instead of the pipe 61 and the opening / closing valve 62, a liquid water permselective membrane (for example, an electrolyte membrane used in a PEM type fuel cell) may be provided on the bottom surface 55t of the hollow portion 55. With such a configuration, the liquid water stored in the hollow portion 55 can be discharged to the outside of the fuel cell stack 100 via the liquid water selective permeable membrane.

  Here, it is assumed that the fuel cell stack 100 is mounted on a moving body such as a fuel cell vehicle. When the mobile body on which the fuel cell stack 100 is mounted is disposed at a location having an inclination angle with respect to the horizontal plane, such as a slope, the inclination angle of the fuel cell stack 100 with respect to the horizontal plane according to the inclination angle of the mobile body. Also fluctuate. For example, when the moving body is a fuel cell vehicle, the inclination angle (pitch angle) in the front-rear direction of the fuel cell vehicle may vary in a range of about ± 15 °. Further, the inclination angle (roll angle) in the left-right direction of the fuel cell vehicle may vary within a range of about ± 5 °. Therefore, in this case, in order to induce moisture to the water collecting part 50 of the fuel cell stack 100 using gravity, the inclination angle θ of the fuel cell stack 100 (FIGS. 2B and 2C). Preferably has a value larger than the absolute value of the pitch angle or roll angle.

  As described above, according to the fuel cell stack 100, during operation of the fuel cell stack 100, the water inside the fuel cell stack 100 is guided to the water collection unit 50 to collect the water, and then to the outside of the fuel cell stack 100. And can be discharged. Therefore, the drainage of the fuel cell stack 100 can be improved. In addition, since the water remaining in the fuel cell stack 100 can be guided to the water collecting section 50 even after the operation of the fuel cell stack 100 is stopped, the hydrogen flow path remains blocked by the accumulated water. Can be suppressed. Therefore, it can suppress that the starting property of the fuel cell stack 100 falls. In particular, when the fuel cell stack 100 is restarted in a low-temperature environment such as below freezing point, water remaining in the fuel cell stack 100 can be frozen in the water collecting section 50, so that a hydrogen flow path is secured. It is easy to keep.

B. Second embodiment:
FIG. 4 is a schematic view showing a configuration of a water collecting part 50A provided in a fuel cell stack as a second embodiment of the present invention. FIG. 4 is a front view of the water collecting portion 50A as viewed from the same direction as the arrow S shown in FIG. The fuel cell stack of the second embodiment is substantially the same as the fuel cell stack 100 (FIG. 1) of the first embodiment, except that the water collecting section 50A is different.

  The water collecting portion 50A is configured by a plate-like member that does not have the hollow portion 55. More specifically, the water collecting portion 50A is provided with hydrogen manifolds 11 and 12 as through-holes as in the power generation laminate 10S, and a flow for hydrogen on the surface facing the power generation laminate 10S. A road groove 51 is provided.

  The channel groove 51 is provided so as to connect the hydrogen supply manifold 11 and the hydrogen discharge manifold 12 and is formed in an inverted S shape in the drawing. In the channel groove 51, a plurality of porous water absorbing members 52 having a shape along the channel direction are arranged in parallel at intervals. Thereby, in the channel groove 51, the first channel 51a in which the water absorbing member 52 is not disposed and the second channel 51b in which the water absorbing member 52 is disposed are alternately formed. The widths of the first and second flow paths 51a and 51b may be about 0.5 to 1 mm, respectively.

  In the water collecting section 50A, the hydrogen in the hydrogen supply manifold 11 mainly flows to the hydrogen discharge manifold 12 via the first flow path 51a having a relatively low pressure loss. In the figure, the direction of hydrogen flow is indicated by white arrows. On the other hand, the liquid water that is guided and stays in the hydrogen discharge manifold 12 of the water collecting section 50A due to gravity is absorbed by the water absorbing member 52 that constitutes the second flow path 51b, and moves toward the hydrogen supply manifold 11 side. Moving. This water absorbing member 52 can be interpreted as functioning as a water retaining means for retaining the liquid water guided to the water collecting section 50A. In the figure, the moving direction of the liquid water is indicated by hatched arrows.

  Here, the hydrogen flowing through the first flow path 51 a is humidified to the saturated water vapor pressure by the water in the second flow path 51 b running side by side, and flows to the hydrogen discharge manifold 12. That is, the liquid water in the water absorbing member 52 is vaporized by the hydrogen flowing through the first flow path 51a that runs along with the second flow path 51b, and is transferred to the hydrogen discharge manifold 12 via the first flow path 51a. And flows out of the fuel cell stack.

  Thus, according to the water collecting part 50A of the second embodiment, the liquid water collected in the water collecting part 50A is absorbed by the water absorbing member 52 and vaporized by hydrogen passing through the water collecting part 50A. , Discharge outside the fuel cell stack. Therefore, the drainage of the fuel cell stack can be improved.

C. Third embodiment:
FIG. 5 is a schematic diagram showing the configuration of a water collecting part 50B used in the fuel cell stack as the third embodiment of the present invention. 5 is substantially the same as FIG. 4 except that a flow channel 51B is provided in place of the flow channel 51 and a plate-like water absorbing member 53 is disposed on the flow channel 51B. is there. The fuel cell stack of the third embodiment is substantially the same as the fuel cell stack 100 (FIG. 1) of the first embodiment, except that the water collecting part 50B is different.

  The flow channel 51 </ b> B of the water collecting unit 50 </ b> B is a flow channel for hydrogen that connects the hydrogen supply manifold 11 and the hydrogen discharge manifold 12. In the figure, the channel groove 51B is provided so as to constitute an inverted S-shaped channel. Hereinafter, in the flow channel 51B, the hydrogen supply manifold 11 side is referred to as “upstream side”, and the hydrogen discharge manifold 12 side is referred to as “downstream side”. A porous plate-like water absorbing member 53 is laminated on the flow channel 51B so as to cover the entire flow channel 51. In addition, the water collection part 50B is good also as a thing in which the recessed part for arrange | positioning the plate-shaped water absorption member 53 is formed. A downstream-side channel forming portion 54 is provided on the downstream side of the channel groove 51B.

  FIG. 6 is a schematic view showing the configuration of the downstream side flow path forming portion 54, and is a schematic cross-sectional view of the water collecting portion 50B in the AA cut shown in FIG. The downstream flow path forming portion 54 is provided with a plurality of rectangular flow path walls 54 a that run parallel to the plate-shaped water absorbing member 53. As a result, a plurality of hydrogen flow paths 54 b running side by side and surrounded by the flow path wall 54 a and the plate-like water absorbing member 53 are formed in the downstream flow path forming portion 54. Each hydrogen flow path 54b is formed to have such a small width that the liquid water staying in the hydrogen discharge manifold 12 can be guided upstream by capillary action.

  In the fuel cell stack of the third embodiment, after the operation is stopped, the liquid water staying at the lower end side of the hydrogen discharge manifold 12 is guided to the channel groove 51B by the hydrogen channel 54b of the downstream channel formation portion 54. And absorbed by the plate-like water absorbing member 53. This suppresses the flow path for hydrogen inside the fuel cell stack from being blocked by moisture remaining in the fuel cell stack. Moisture absorbed by the plate-like water absorbing member 53 is vaporized by high-temperature (for example, about 80 ° C.) hydrogen passing through the water collection part 50B when the fuel cell stack is restarted, and the hydrogen discharge manifold 12 is made to flow. To the outside of the fuel cell stack.

  Thus, according to the water collecting part 50B of the third embodiment, after the operation of the fuel cell stack is stopped, the water staying in the hydrogen discharge manifold 12 is absorbed by the plate-like water absorbing member 53 arranged in the water collecting part 50B. I can leave it to you. Therefore, the flow path for hydrogen provided in the fuel cell stack can be prevented from being blocked by moisture remaining in the fuel cell stack, and the startability of the fuel cell stack can be prevented from being lowered.

D. Fourth embodiment:
FIGS. 7A to 7C are schematic views showing the configurations of fuel cell stacks 100Ca, 100Cb, and 100Cc, respectively, as a fourth embodiment of the present invention. These fuel cell stacks 100Ca, 100Cb, and 100Cc are different from each other in the position where the water collecting section 50 is disposed.

  FIG. 7A shows the first and second terminals 71 and 72 between the first end plate 21 and the power generation laminate 10S and between the second end plate 22 and the water collecting section 50, respectively. 1 is substantially the same as FIG. 1 except that is interposed. In FIG. 7A, the fuel cell stack 100Ca is illustrated so that its stacking direction is substantially horizontal to the paper surface. However, the fuel cell stack 100Ca is the same as the fuel cell stack 100 of FIG. Inclined.

  In the fuel cell stack 100Ca, the water collection unit 50 is disposed between the second terminal 72 and the power generation laminate 10S. Therefore, in order to form a conductive path between the power generation laminate 10 </ b> S and the second terminal 72, it is preferable that the water collection unit 50 is configured with a conductive member. In addition, when the water collection part 50 is comprised with a nonelectroconductive member, between the electric power generation laminated body 10S and the 2nd terminal 72, it is good also as what should provide a conductive path separately.

  FIG. 7 (B) is substantially the same as FIG. 7 (A) except that the water collecting section 50 is disposed between the second terminal 72 and the second end plate 22. In the fuel cell stack 100Cb, since the second terminal 72 and the power generation laminate 10S are in direct contact with each other, the water collection unit 50 may be configured of a non-conductive member. In this case, it is possible to make the water collection part 50 function as an insulator. In the fuel cell stack 100Cb, the second terminals 72 are provided with the manifolds 11 and 12 for hydrogen similarly to the power generation laminate 10S.

  FIG. 7C is substantially the same as FIG. 7B except that the water collection unit 50 is disposed outside the second end plate 22. In the fuel cell stacks 100Ca and 100Cb of FIGS. 7A and 7B described above, since the water collecting part 50 is disposed inside the second end plate 22, the water collecting part 50 also has a power generation laminate. A fastening force is applied similarly to 10S. Therefore, it is preferable that the water collecting part 50 used in the fuel cell stacks 100Ca and 100Cb has a strength that can withstand the fastening force. However, in the fuel cell stack 100Cc of FIG. 7C, the water collecting portion 50 can avoid applying fastening force from the first and second end plates 21 and 22, and therefore has a relatively low strength. Can be configured. Therefore, the water collecting part 50 can be reduced in weight and size by the amount of low strength. In the fuel cell stack 100Cc, hydrogen manifolds 11 and 12 are provided on the second terminal 72 and the second end plate 22 in the same manner as the power generation laminate 10S.

  Thus, in the case of the fuel cell stacks 100Ca, 100Cb, 100Cc of the fourth embodiment, the drainage performance of each is improved by the water collecting portion 50 arranged on the lower end side. Moreover, the water collection part 50 can change the arrangement | positioning place suitably like these fuel cell stacks 100Ca, 100Cb, and 100Cc. The fuel cell stacks 100Ca, 100Cb, and 100Cc may use the water collection units 50A and 50B of the second and third embodiments instead of the water collection unit 50.

DESCRIPTION OF SYMBOLS 10 ... Power generation body 10S ... Power generation laminated body 11 ... Hydrogen supply manifold 12 ... Hydrogen discharge manifold 21 ... First end plate 22 ... Second end plate 31 ... Hydrogen supply pipe 32 ... Hydrogen discharge pipe 50, 50A , 50B ... Water collecting part 51, 51B ... Channel groove 51a ... First channel 51b ... Second channel 52 ... Water absorbing member 53 ... Plate-like water absorbing member 54 ... Downstream channel forming part 54a ... Channel wall 54b ... Hydrogen flow channel 55 ... Hollow part 55t ... Bottom 61 ... Pipe 62 ... Open / close valve 71 ... First terminal 72 ... Second terminal 100, 100Ca, 100Cb, 100Cc ... Fuel cell stack W ... Liquid water

Claims (1)

A fuel cell stack,
A power generation laminate in which a plurality of power generation bodies are laminated;
A water collecting portion disposed on an end side in the stacking direction of the power generation laminate,
With
The power generation laminate includes a supply manifold for supplying a reaction gas to each of the plurality of power generation bodies, and a discharge manifold for discharging exhaust gas from each of the plurality of power generation bodies. Provided at positions facing each other across each power generation section of the power generation body,
The water collection section is provided with a gas flow path for the reaction gas that connects the supply manifold and the discharge manifold, and has water retention means for holding moisture from the discharge manifold. And
The power generation laminate is arranged such that the discharge manifold is located below the supply manifold in the direction of gravity, and the end of the discharge manifold on the side of the water collecting portion is positioned below the direction of gravity. The fuel cell stack is disposed with an inclination angle with respect to the horizontal direction.

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