DE102017202705A1 - Fuel cell stack with distribution element in the media channel and manufacturing process - Google Patents

Abstract

Technology disclosed herein relates to a fuel cell stack 100 having a plurality of fuel cells and a plurality of separator plates 110. The separator plates 110 at least partially form at least one media channel 120. The media channel 120 provides fluid communication between at least one media port 130 of the fuel cell stack 100 and the fuel cells. At least one distribution element 200 extends in the media channel 120 from a region 230 proximal to the media connection 130 to a region 220 distal to the media connection 130. The distribution element 200 is set up to influence the distribution of the medium among the plurality of fuel cells.

Description

The technology disclosed herein relates to a fuel cell stack having a distribution element disposed in a media channel. Further, the technology disclosed herein relates to a method of manufacturing a fuel cell stack.

Fuel cell stacks as such are known. Such fuel cell stacks include media channels, also called media ports, which convey media from the media ports to the individual fuel cells of the fuel cell stack. The individual fuel cells are usually designed as equal parts. Due to pressure losses, the individual fuel cells of the fuel cell stack are supplied differently with media. During the electrochemical reaction in the fuel cells i.d.R. Product water, which should be expediently discharged from the stack. If a motor vehicle has been turned off at an angle, it may happen that the product water is more difficult to remove.

It is a preferred object of the technology disclosed herein to reduce or eliminate at least one disadvantage of a previously known solution or to suggest an alternative solution. In particular, it is a preferred object of the technology disclosed here to improve the uniform distribution of the media and / or the product water discharge in the fuel cell stack, preferably without at the same time worsening the required installation space or production costs, in particular for fuel cell stacks of different power. Other preferred objects may result from the beneficial effects of the technology disclosed herein. The object (s) is / are solved by the subject matter of the independent claims. The dependent claims are preferred embodiments.

• - wobei die Separatorplatten mindestens einen Medienkanal zumindest teilweise ausbilden;
• - wobei der Medienkanal eine Fluidverbindung zwischen mindestens einem Medienanschluss des Brennstoffzellenstapels und den Brennstoffzellen herstellt;
• - wobei mindestens ein Verteilungselement sich im Medienkanal von einem zum Medienanschluss proximalen Bereich zu einem zum Medienanschluss distalen Bereich erstreckt, und wobei das Verteilungselement eingerichtet ist, die Verteilung des Mediums auf die mehreren Brennstoffzellen zu beeinflussen.

The technology disclosed herein relates to a fuel cell stack having a plurality of separator plates,

• - The separator plates form at least one medium channel at least partially;
• - wherein the media channel establishes a fluid connection between at least one media port of the fuel cell stack and the fuel cells;
• wherein at least one distribution element extends in the media channel from a region proximal to the media connection to a region distal to the media connection, and wherein the distribution element is set up to influence the distribution of the medium among the plurality of fuel cells.

The fuel cell stack comprises at least one fuel cell. The fuel cell stack is intended, for example, for mobile applications such as motor vehicles (for example passenger cars, motorcycles, commercial vehicles), in particular for providing the energy for at least one drive machine for locomotion of the motor vehicle. In its simplest form, a fuel cell is an electrochemical energy converter that converts fuel and oxidant into reaction products, producing electricity and heat. The fuel cell includes an anode and a cathode separated by an ion-selective or ion-permeable separator. The anode is supplied with fuel. Preferred fuels are: hydrogen, low molecular weight alcohol, biofuels, or liquefied natural gas. The cathode is supplied with oxidant. Preferred oxidizing agents are, for example, air, oxygen and peroxides. The ion-selective separator can be designed, for example, as a proton exchange membrane (PEM). Preferably, a cation-selective polymer electrolyte membrane is used. Materials for such a membrane are, for example: Nafion®, Flemion® and Aciplex®.

The technology disclosed herein further includes a fuel cell system having such a fuel cell stack. A fuel cell system comprises, in addition to the at least one fuel cell, peripheral system components (BOP components) which can be used during operation of the at least one fuel cell.

The fuel cell system includes an anode subsystem formed by the fuel-bearing components of the fuel cell system. The main task of the Anodensubsystems is the introduction and distribution of fuel to the electrochemically active surfaces of the anode compartment and the removal of anode exhaust gas. The fuel cell system includes a cathode subsystem. The cathode subsystem is formed from the oxidant-carrying components. The main task of the cathode subsystem is the introduction and distribution of oxidant to the electrochemically active surfaces of the cathode compartment and the removal of unconsumed oxidant.

The fuel cells of the fuel cell stack usually comprise two separator plates. The ion-selective separator of a fuel cell is usually arranged in each case between two separator plates. The one separator plate forms the anode together with the ion-selective separator. The further separator plate arranged on the opposite side of the ion-selective separator, however, forms the cathode together with the ion-selective separator. In the separator plates are preferably provided gas channels for fuel or for oxidants.

The separator plates can be designed as monopolar plates and / or as bipolar plates. In other words, a separator plate expediently has two sides, one side forming an anode together with an ion-selective separator and the second side forming a cathode together with another ion-selective separator of an adjacent fuel cell.

Between the ion-selective separators and the separator plates are i.d.R. still so-called gas diffusion layers or gas diffusion layers (GDL) provided.

The plurality of separator plates of the fuel cell stack form at least one media channel. Preferably, a plurality of media channels are provided, for example for the fuel, the oxidizing agent and / or the coolant. Preferably, the media channels may be formed as inlet channels or as outlet channels. Particularly preferably, the media channel is a gas outlet channel, in particular for the fuel and / or the oxidizing agent.

According to the technology disclosed herein, the plurality of separator plates together at least partially together in the assembled state of the media channel with. For this purpose, each of the separator plates have at least one through hole. Preferably, the separator plates on a plurality of through holes, wherein the through holes each form a media channel with. Preferably, the separator plates and the corresponding through holes are of identical construction. In particular, the through holes of the separator plates have the same geometry. Preferably, therefore, the separator plates can be manufactured as equal parts. For example, the through-holes may be made by punching during the manufacture of the separator plates.

Preferably, in the stacked state of the fuel cell stack, the through holes of the individual separator plates, which together form a media channel, seen in the stacking direction and arranged in alignment with each other.

The fuel cell stack may have at least one media connection. The media connection is set up to be connected to at least one further fluid-carrying line of the fuel cell system. For example, media connections of the fuel cell stack can be connected to other components of the anode subsystem, the cathode subsystem or the cooling circuit. In particular, the media ports may be configured to be accessible from outside the fuel cell stack for coupling.

The media connection is preferably a gas outlet connection, in particular for fuel or oxidant.

According to the technology disclosed herein, the media channel may establish fluid communication between the at least one media port and the connection channels of the fuel cells or separator plates. In other words, the medium flows through the media channel to the fuel cells of the fuel cell stack. For this purpose, connecting channels can be provided in the separator plates or other elements of the individual fuel cells which branch off from the respective media channel and open into the flow field of the separator plate or the active surface of the fuel cell.

At least one distribution element can be arranged in the at least one media channel. Preferably, at least one distribution element is arranged in each media channel. The distribution element may in particular be an insert. The distribution element may extend in the media channel from a region proximal to the media connection to a region distal to the media connection. The distribution element is set up to influence the distribution of the medium to different fuel cells. Preferably, the distribution element is set up to equalize the distribution of the medium to the various fuel cells compared to the media channel without distribution element. In other words, a more uniform distribution of the medium to the various fuel cells is thus achieved when the distribution element is installed than when the distribution element has been removed.

The distribution element and the media channel can in particular be designed in such a way that a plurality of fuel cells of the fuel cell stack are supplied with the medium flowing through the medium channel substantially independently of their position in the fuel cell stack. "Essentially equal" in this context means that the deviations in the amounts of medium supplied to the various fuel cells differ only to a negligible small extent, which is irrelevant to the efficient operation of the fuel cell system, for example less than 10% mass flow deviation and particularly preferably less as 5% mass flow deviation.

For this purpose, it may be provided that the distribution element is perpendicular to the longitudinal axis of the Distribution element (or in the stacking direction of the separator plates in the mounted state) has different sized cross-sectional areas, wherein the distribution element in the distal region has a larger cross-sectional area than in the proximal region.

Alternatively or additionally, it may be provided that the connection channels are sealed to a different extent by the distribution element from the media channel to the fuel cells or to the separator plates, wherein a connection channel is less closed in the distal region than a connection channel in the proximal region.

Alternatively or additionally, it can be provided that the distribution element has a greater porosity in the distal region than in the proximal region. A greater porosity is associated with the fact that the medium can flow comparatively easily through the distribution element to the respective connecting channel in the distal region, whereas the lower porosity in the proximal region represents a greater flow resistance. Thus, by variation of the flow resistance through the distribution element, a uniform distribution of the medium to the different fuel cells of the fuel cell stack is obtained.

It can preferably be provided that for two fuel cell stacks each having a different total number of separator plates in the respective fuel cell stack, different distribution elements are provided in the at least one media channel of the respective fuel cell stack, and wherein the two fuel cell stacks simultaneously have the same separator plates. It can preferably be provided that the length and the cross-sectional area in a direction perpendicular to the longitudinal axis of the distribution element over the length of the distribution element varies with the total number of separator plates in the fuel cell stack. The distribution elements for the two different fuel cell stacks differ, for example, in their length and / or in their cross-sectional area profile in the direction of the longitudinal axis. Likewise, the flow cross-section to the connecting channels and / or the porosity of the distribution element could be varied in order to achieve a better uniform distribution for fuel cell stacks of different lengths. Advantageously, fuel cell stacks of different power can thus be provided, which are optimized with regard to their media distribution to the individual fuel cells, without the need for different fuel cells or separator plates. Thus, the Separatorplatten can be designed as a common part for different fuel cell stack, which can contribute significantly to the reduction of manufacturing costs.

The proximal region is an area which is arranged at a smaller distance from the media connection than the distal region. Preferably, the proximal region is immediately adjacent the media port of the fuel cell stack, which is typically provided in the end plate or adjacent to an end plate. Preferably, the distal region is disposed immediately adjacent to the end of the fuel cell stack to which the media port is not provided. In other words, the medium can not drain away at this end.

At least one delivery channel can be provided in the distribution element. The distribution element may be arranged and configured such that the delivery channel conveys liquid and / or medium from the distal region to the proximal region. An advantage of such a configuration is that even with an unfavorable arrangement of the fuel cell stack, for example in an inclined position of the fuel cell stack compared to its normal installation position, any product water can be removed. If, for example, a motor vehicle is operated in an extreme inclined position, the product water can still be transported away during operation of the fuel cell system through the channel. For this purpose, the product water can flow, for example, at the distal end adjacent to the end plate into the conveying channel, which then conveys the product water to the proximal end at the media connection, preferably at the media outlet from the stack. The media channel can be formed for example by an open channel on the back of the distribution element. In this case, then form the wall of the media channel and the distribution element from the conveyor channel. In a further embodiment, the delivery channel can be completely formed in the distribution element. If the product water is discharged completely, the frost start behavior may improve.

Particularly preferably, a jet pump or venturi nozzle is formed in the proximal region on the distribution element. A jet pump generally comprises a pipe section with a cross-sectional constriction, for example by two oppositely directed cones, which are united at the point of their smallest diameter. At this constricted point or adjacent thereto ends here the delivery channel. The end of the conveyor channel is flowed around with the medium of the media channel, which then acts as a propellant. With such a jet pump, the flow energy contained in the exhaust gas can advantageously be used to convey the liquid. Such a jet pump is comparatively cheap, failsafe and requires comparatively little space.

The fuel cell stack disclosed herein may further include a heater that is set up to heat the conveyor channel. Particularly preferably, the heating device is provided in the distribution element. Particularly preferably, the heating device is an electrical heating device. Such a heater has the advantage that any frozen water can be thawed more easily. For this purpose, for example, a heating coil can be arranged concentrically to the delivery channel. But other design are conceivable.

The distribution element preferably has such a low conductivity that it can not lead to short-circuit currents between adjacent separator plates. Preferably, the distribution element is arranged so that it does not vibrate or slip in the media channel. Preferably, the distribution element is designed and arranged such that no product water can accumulate between a wall of the media channel and the back of the distribution element.

The technology disclosed herein further includes a method of manufacturing a fuel cell stack. The method comprises the step of arranging at least one distribution element in at least one media channel formed by a plurality of separator plates before, during, and / or after stacking a plurality of fuel cells into a fuel cell stack, preferably the interconnect element disclosed herein, the separator plates disclosed herein, and is the media channel disclosed here.

1. a) Bereitstellen des Verteilungselements; und
2. b) Stapeln der mehreren Brennstoffzellen des Brennstoffzellenstapels; wobei das Verteilungselement die zu stapelnden Brennstoffzellen während des Stapelns positioniert.

The method disclosed herein may include the steps of:

1. a) providing the distribution element; and
2. b) stacking the plurality of fuel cells of the fuel cell stack; wherein the distribution member positions the fuel cells to be stacked during stacking.

The technology disclosed herein further includes a method of manufacturing two different fuel cell stacks, wherein for two fuel cell stacks having a different total number of separator plates in the fuel cell stack, different distribution elements are provided in the at least one media channel, and wherein the two fuel cell stacks have the same separator plates.

In other words, the technology disclosed herein involves introducing a particular nonconducting element into the port of an assembled fuel cell stack to match the cross section across the cell planes such that each cell is distributed equally with media, regardless of their position in the fuel cell stack Cell is advantageously a common part.

In particular, the port diameter of the media port can be varied depending on the position of the cell. The insert (= distribution element) can be supported on the contour of the port and / or the end plates so that vibration or slippage is excluded. Alternatively or additionally, the insert may be designed such that it reduces or at least partially prevents the flow of at least one passage opening to the flow field of a single cell or a separator plate. Thus, the distribution of fluxes between cells can be more accurately influenced.

The insert may be configured so that little or preferably no liquid can collect between the insert and the seal lines. In particular, the back of the insert can press against the separator plate. Preferably, the rear side can be formed so deformable that the contours formed by the cells or separator plates are closed at least partially.

Preferably, the insert has a low and, in comparison to the separator plates, lower thermal mass. Advantageously, the formation of condensation can thus be reduced or avoided. Advantageously, at least one surface of the insert can be designed such that the likelihood of formation reduces or avoids liquid film formation. For this purpose, for example, a hydrophobic layer / material may be provided.

Suitably, the insert has an electrical conductivity which is so low that short-circuit currents between separator plates are prevented.

The insert can be introduced in one embodiment during the stacking process and / or thereafter in the port. Advantageously, the distribution element can be jammed in the port and / or locked. Alternatively or additionally, the distribution element can also be materially connected, for example by means of an adhesive. Appropriately, the distribution element can be inserted through the media connection. Further advantageous for this purpose, the media channel is formed substantially straight and undercut substantially. "Essentially" in this context means that negligible curvatures or undercuts are irrelevant for the general flow guidance and for insertion. The distribution element can be advantageously used here additionally as a guide of the cells during the stack. So it serves as an internal stop, which remains in the stack.

Alternatively or additionally, it can be provided that the distribution element is designed and arranged such that it serves as an assembly aid during the stack of the fuel cell stack and in particular as a positioning element for the elements to be stacked (eg separator plates, etc.). Likewise, a material can be arranged on the rear wall of the distribution element that expands or swells over time. Thus, the support can be improved and / or a build-up of liquid between the rear wall of the distribution element and the wall can be reduced by the media channel.

The insert may include an electrical heating element to remove ice at temperatures below 0 ° C. Furthermore, a water return channel can be introduced in the insert. This can discharge accumulated water from the opposite end (terminal end plate) via the channel on the media plate. Preferably, a Venturi nozzle can be provided for this purpose.

• 1 eine schematische Querschnittsansicht durch einen Brennstoffzellenstapel 100 entlang der Schnittlinie A-A der 2; und
• 2 eine schematische Querschnittsansicht durch einen Brennstoffzellenstapel 100 entlang der Schnittlinie B-B der 1.

The technology disclosed herein will now be explained with reference to the figures. Show it:

• 1 a schematic cross-sectional view through a fuel cell stack 100 along the section line AA of 2 ; and
• 2 a schematic cross-sectional view through a fuel cell stack 100 along the section line BB of 1 ,

The 1 schematically shows a cross-sectional view through the fuel cell stack 100 along the line AA the 2 , Such a fuel cell stack 100 may for example be part of a fuel cell powered vehicle. Between the end plates 150, a plurality of fuel cells are arranged here, of which only the separator plates 110 are shown. Between the end plates 150 and the fuel cells are pantographs here 140 intended. The end plates 150 as well as the pantographs 140 can be designed arbitrarily. Other components, such as the tie rods of the bracing system and other media channels have been omitted here simplistic.

In this sectional view are two media channels 120 shown. The upper media channel is, for example, a first media channel 120 and the lower media channel is, for example, a second media channel 120 , The location of these media channels 120 Within the fuel cell stack, ie, top or bottom, is only a preferred location and is in no way to be considered limiting. The media channels 120 extend here substantially in the longitudinal direction or stacking direction Z of the fuel cell stack 100 , The media channels 120 extend from a proximal area 230 to a distal area 220 , The proximal area 230 is closer to the media connection 130 arranged as the distal area 220 , The distal area 220 is here immediately adjacent to the end plate 150 arranged, in which not the media connection 130 of the media channel 120 is arranged here in the 1 So the right end plate 150.

The first media channel and the second media channel are formed here as gas channels 120. The oxidant O2 flows here into the media connection 130 or in the first media channel 120 one. In the proximal area 230 the oxidant O2 has a comparatively high pressure. Would not be a distribution element 200 provided in the media channel 120, the pressure of the oxidant O2 would gradually decrease opposite to the stacking direction Z. Due to the distribution element of 200, however, the pressure here remains substantially constant in the opposite direction to the stacking direction Z, so that essentially the same amount of oxidizing agent O 2 flows into the connection channels 122 (see. 2 ) of the individual fuel cells flows. In the embodiment shown here, the distribution element 200 in the stacking direction Z on a continuously decreasing cross-sectional area perpendicular to the fuel cell longitudinal axis Z. This cross-sectional area profile causes a reduction of the flow channel cross-section for through the first media channel 120 flowing oxidizing O2, which goes hand in hand with an at least partial pressure medium loss compensation by flowing in the proximal region in the fuel cell oxidant O2. The second media channel 120 points in the proximal area 230 a jet pump 212 on. The jet pump 212 is here by the distribution element 200 with trained. For this purpose, a delivery channel provided in the distribution element 200 is provided 210 at the proximal end of the distribution element 200 designed so above that it can be flowed around by all sides of the oxidant O2. Such a configuration has the advantage that the jet pump 212 Particularly good may promote any product water, which is located in the distal region 220 of the fuel cell stack 100 has accumulated. The oxidant O2 thus serves as a propellant for the jet pump 212 , Further, to achieve the venturi effect, there is a restriction in the end plate 150 intended. Such a jet pump 212 is particularly cost-effective, space-neutral, lightweight and fail-safe. The product water is here by the delivery channel shown in dashed lines 210 discharged. The conveyor channel 210 is formed here by a groove (see. 2 ) extending across the back and over the side wall of the distribution element 200 extends. The front of the distribution element 200 Here is the gas flow area of the media channel 120 facing. The surface of the front side may preferably be substantially water-repellent, so as to avoid film formation. Also, the cross-sectional area profile in the stacking direction Z of the distribution element of the 200 of the second media channel 120 is designed to favor the equal distribution of the media. Due to the increasing in the stacking direction Z cross-section, which is traversed by the oxidant O2, there is a certain suction in the second media channel 120 which can favor the equal distribution. Through the media connection 130 of the second media channel as 120, the exhaust gas flows out of the fuel cell stack after the electrochemical reaction. Even with a tilt of the fuel cell stack can thus be safely discharged product water. Furthermore, a more uniform electrochemical reaction in the plurality of fuel cells of the fuel cell stack can be achieved by the more uniform supply of media 100 be achieved. This can increase the overall performance and efficiency of the fuel cell stack.

Not shown here is the heating device, for example, adjacent to a wall of the conveyor channel 210 can be provided. The heater may be an electric heater integral with the distribution member 200 can be trained. In general, the distribution element becomes 200 be formed of an electrical insulator, which can also have comparatively good thermal insulation property in at the same time. For example, the distribution element 200 be made of a plastic. Now is the heater directly in the distribution element 200 provided, the heat can be produced directly where it is needed to thaw product water. Furthermore, such a heater can also be well manufactured and assembled. The electrical connections for the electric heater can, for example, through the media connection 130 be led out.

The 2 shows a schematic cross-sectional view along the section line BB of 1 , The cross-sectional area A200 of the distribution element 200 narrows considerably here the cross section of the media channel 120 , From the media channel 120 occurs here, the oxidant O2 in the connecting channel 122 above. The connection channel 122 Here is a pre-manifold structure that distributes the oxidant O2 on the different channels of the flow field (shown here in broken lines). After the electrochemical reaction in the flow field of the separator plate 110 the exhaust gas flows over the connection channel 122 in the second media channel 120 , In the second media channel 120 is also a distribution element 200 arranged. On the back of the distribution element is here a delivery channel 210 educated. The conveyor channel 210 is through a groove in the distribution element 200 and the wall of the media channel 120 educated. The areas dotted here are further through holes for other media channels, which will not be discussed here.

For the sake of legibility, the term "at least one" has been omitted for simplicity. If a feature of the technology disclosed herein is described in singular form (eg, the / a fuel cell stack, the separator plate, the media channel, the media port, the distribution element, the delivery channel) Heater, the / a gas outlet channel, the / a jet pump, the / a connecting channel) so should also be at the same time be disclosed (eg, the at least one fuel cell stack, the at least one separator plate, the at least one media port, the at least one media port, the at least a distribution element, the at least one delivery channel, the at least one heating device, the at least one gas outlet channel, the at least one jet pump, the at least one connecting channel, etc.). In the embodiments shown here are each two distribution elements 200 intended. It is also conceivable that distribution elements are provided in the various media channels for oxidant and fuel. Similarly, it is conceivable that only one connecting element in the anode subsystem or in the cathode subsystem 200 in a media channel 120 is provided, for example, respectively on the exhaust side and exhaust side.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Claims (10)

A fuel cell stack (100) having a plurality of fuel cells and a plurality of separator plates (110), - wherein the separator plates (110) at least partially form a media channel (120); - wherein the media channel (120) establishes a fluid connection between at least one media port (130) of the fuel cell stack (100) and the fuel cells; wherein at least one distribution element (200) extends in the media channel (120) from a region (230) proximal to the media connection (130) to a region (220) distal to the media connection (130), and wherein the distribution element (200) is set up, to influence the distribution of the medium on the several fuel cells. Fuel cell stack (100) after Claim 1 wherein at least one delivery channel (210) is provided in the distribution member (200), and wherein the distribution member (200) is arranged and configured to deliver fluid from the distal region (220) to the proximal region (230). Fuel cell stack (100) after Claim 1 or 2 wherein the media channel (120) is a gas outlet channel (120). Fuel cell stack (100) after Claim 2 or 3 , wherein in the proximal region (230) a jet pump (212) from the distribution element (200) is formed. Fuel cell stack (100) according to one of the previous Claims 2 to 4 further comprising a heater (240) configured to heat the delivery channel (210). Fuel cell stack according to one of the preceding claims, wherein the distribution element (200) and the media channel (120) are formed such that a plurality of fuel cells of the fuel cell stack (100), regardless of their position in the fuel cell stack are supplied substantially equal to the medium. Fuel cell stack according to one of the preceding claims, wherein the distribution element (200) perpendicular to the longitudinal axis of the distribution member (200) has different sized cross-sectional areas (A200); wherein the distribution member (200) has a larger cross-sectional area (A200) in the distal region (220) than in the proximal region (230); and / or wherein connection channels are sealed differently from the media channel (120) to the fuel cells by the distribution element (200), whereby a connection channel (122) in the distal region (220) is closed less than a connection channel (122) in the proximal region (230). ; and / or wherein the distribution element (200) has a greater porosity in the distal region (220) than in the proximal region (230). A method of manufacturing a fuel cell stack (100), the method comprising the step of arranging at least one distribution element (200) in at least one media channel (120) formed by a plurality of separator plates (100) before, during, and / or after stacking a plurality of fuel cells to a fuel cell stack (100. Method according to Claim 8 further comprising the steps of - providing the distribution element (200); and - stacking the plurality of fuel cells of the fuel cell stack; wherein the distribution member (200) positions the fuel cells to be stacked during stacking. Method according to one of the preceding claims, wherein in two fuel cell stacks (100) with different total number of separator plates (110) each different distribution elements (200) in each case in two fuel cell stacks (100) identically formed media channels (120) are provided, and wherein the two fuel cell stack (100) have the same separator plates (110).

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