Recovery process and electrochemical energy conversion system

Abstract

The present invention relates to a recovery method (200) for recovering (204) a catalyst-coated membrane (20) of an electrochemical energy conversion system (10), comprising: - flooding (202) an anode side (40) of a cell (30) of the electrochemical energy conversion system (10) with hydrogen (H2) by a flooding device (50) of the electrochemical energy conversion system (10), - Reshaping (204) the catalyst-coated membrane (20) by flooding (202) the anode side (40) with hydrogen (H2). Furthermore, the invention relates to an electrochemical energy conversion system (10) for carrying out the reshaping process (200).

Description

The present invention relates to a recovery method for recovering a catalyst coated membrane of an electrochemical energy conversion system. The invention further relates to an electrochemical energy conversion system for carrying out the recovery process.Prior ArtCell stacks from electrolysis cells of an electrochemical energy conversion system are known, which usually have bipolar plates and membrane electrode units stacked alternately one above the other. The membrane electrode units usually have a membrane, in particular a catalyst-coated membrane, which is arranged between two medium distribution devices, such as a porous transport layer and / or a gas diffusion layer.The medium distribution devices are usually arranged within a frame device and have a gap between the medium distribution devices and the frame devices. By means of the working pressure of the electrochemical energy conversion system during normal operation, the membrane can be pressed into the anode-side gap in the event of overpressure on the cathode side. This can lead to the membrane being overloaded in the region of the gap.In practice with fuel cells, flooding of anode and cathode during shutdown of the fuel cells is known. This reduces the diffusion of air and / or oxygen and thus reduces oxide formations on the catalysts of the membrane during shutdown times.Disclosure of the InventionThe invention claims a recovery method for recovering a catalyst coated membrane of an electrochemical energy conversion system having the features of independent claim 1. Features which are described in connection with the recovery method according to the invention naturally also apply in connection with the electrochemical energy conversion system according to the invention and vice versa, so that with regard to the disclosure reference is or can always be made reciprocally to the individual aspects of the invention.According to a first aspect of the invention, the invention discloses a recovery method for recovering a catalyst coated membrane of an electrochemical energy conversion system comprising:flooding an anode side of a cell of the electrochemical energy conversion system with hydrogen through a flooding device of the electrochemical energy conversion system,redoform the catalyst-coated membrane by flooding the anode side with hydrogen.The core of the recovery method according to the invention is to make it possible to recover the catalyst-coated membrane of the electrochemical energy conversion system and thus advantageously increase a service life of the membrane by virtue of harmful plastic deformations being at least partially and / or temporarily reversed during normal operation of the electrochemical energy conversion system. The recovery process is integrated into a shutdown of the electrochemical cell, in particular an electrolysis cell. Preferably, the recovery process is integrated into flooding the anode of the electrolysis cell.Unless explicitly stated otherwise, the method steps described above and in the following can be carried out individually, together, singly, multiply, in parallel in time and / or successively in any desired sequence. A designation as, for example, "first method step" and "second method step" does not require a chronological sequence and / or prioritization. A preferred sequence of the method steps provides that the method steps are carried out in the sequence listed.By way of example, the membrane is pressed by the working pressure of the electrochemical energy conversion system into a critical gap of the anode side, in particular between a porous transport layer and / or a gas diffusion layer and a frame device of the anode side. The operating pressure of the electrochemical energy conversion system is, for example, up to 40 bar H2 pressure on the cathode side of the electrochemical energy conversion system. This loading of the membrane leads to the membrane being overloaded in the region of the gap. The membrane is increasingly deformed, for example, as a function of pressure, temperature, time, flow behavior, and pressed into the anode gap.Within the scope of the recovery method according to the invention, the deformation of the catalyst-coated membrane is at least partially reversed and / or this deformation is counteracted at least temporarily. For this purpose, flooding of the anode side of at least one cell of the electrochemical energy conversion system, preferably of all cells of the electrochemical energy conversion system, takes place. Flooding is effected within the framework of the hydrogen recovery process by a flooding device of the electrochemical energy conversion system. The flooding device is, for example, a conveying device for conveying the hydrogen and / or a storage device such as a hydrogen tank for storing hydrogen. The conveying device enables conveying of the hydrogen into the anode side.Flooding the anode side allows the catalyst-coated membrane to be reformed by the hydrogen and takes place opposite to the positive pressure on the cathode side from normal operation of the electrochemical energy conversion system. The flooding of the anode side is preferably effected with at least temporarily high overpressure, with the result that harmful plastic deformations of the catalyst-coated membrane from normal operation are preferably reversed and / or at least reduced.Illustratively and exemplarily described, a membrane electrode assembly of the electrochemical energy conversion system with the catalyst coated membrane is arranged between two bipolar plates. The catalyst-coated membrane is preferably arranged in the active region between two porous transport layers and in the edge region between two frame structures. The porous transport layers and / or frame device can of course be designed differently on the anode side and on the cathode side. The normal operation of the electrochemical energy conversion system is preferably carried out with a strong overpressure on the cathode side of, for example, up to 40 bar of hydrogen pressure. The catalyst-coated membrane can be pressed into the respective gap between the frame device and the porous transport layer by the overpressure; the critical gap in normal operation is the gap on the anode side into which the catalyst-coated membrane is detrimentally pressed. Depending on the pressure, temperature, time, flow behavior, the catalyst-coated membrane is increasingly deformed and pressed into the anode gap. This may lead to failure of the catalyst coated membrane, for example due to fatigue cracking, which may result in leakage or even an electrical short circuit.The recovery method of the present invention is preferably carried out outside of normal operation of the electrochemical energy conversion system to allow flooding and recovery. The recovery method according to the invention can enable recovery of the catalyst-coated membrane in a regular, state-dependent, automated or manually triggered manner in order to advantageously increase a lifetime of the catalyst-coated membrane and of the electrochemical energy conversion system.A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the flooding of the anode side of the cell with hydrogen is effected at overpressure, in particular wherein a pressure of up to 25 bar, up to 30 bar, up to 35 bar, up to 40 bar or above 40 bar is built up at least temporarily by flooding the anode side of at least one cell with hydrogen.Flooding of the anode side with hydrogen takes place at least temporarily with high overpressure, so that harmful plastic deformations of the catalyst-coated membrane from normal operation are at least partially deformed back. Flooding may include a uniform or non-uniform, constant, and / or pulsating pressure pattern of the hydrogen on the anode side. Illustratively and exemplarily described, flooding will not always have a maximum value of the hydrogen pressure, but may only be applied briefly as peak pressure in order to enable advantageous redrawing. In particular in an embodiment of the flooding device as a hydrogen tank, the hydrogen is flooded briefly with high pressure into the anode side and is subsequently held in the anode side, for example, with increasingly decreasing pressure.A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen at overpressure, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, in a recovery method it can be provided that the flooding of the anode side of the cell with hydrogen is carried out according to a pressure-time curve, in particular wherein the pressure-time curve is adjustable by an adjustment device of the electrochemical energy conversion system. The pressure-time curve can preferably be adjusted and / or defined by means of the flooding device and / or a valve device of the flooding device. The pressure-time curve describes, in the context of the invention, preferably how long and with which pressure the hydrogen is flooded and / or held in the anode side. The adjustability of the pressure-time curve is particularly advantageous since, for example, aging of the catalyst-coated membrane can be taken into account. For example, the re-shaping of the catalyst-coated membrane requires a longer pressurization with hydrogen over time in order to achieve the desired advantageous re-shaping. By the adjustability of the pressure-time curve, an optimum recovery process can always be ensured. A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen according to the pressure-time profile curve, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the recovery method further comprises:detecting a load value of the electrochemical energy conversion system, a power value of the electrochemical energy conversion system, and / or a state of the electrochemical energy conversion system and / or the catalyst coated membrane by at least one detection device of the electrochemical energy conversion system.The recovery method is particularly advantageous when at least one load value, power value and / or state of the electrochemical energy conversion system is detected. The detection device preferably provides a measured variable which can be used for evaluating the recovery method and / or for assessing a need to carry out the recovery method. In the context of the invention, a state of the electrochemical energy conversion system and / or of the catalyst-coated membrane is to be understood, for example, as the pressure, temperature, state of expansion, state of deformation and / or medium concentration of the catalyst-coated membrane, on the anode side and / or on the cathode side of the electrochemical energy conversion system. A recovery method configured in this way is particularly advantageous since by detecting, recovery of the catalyst-coated membrane by flooding the anode side with hydrogen is advantageously made possible, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus advantageously made possible and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the flooding and / or the recovery takes place in a time-dependent manner, in a load-dependent manner, in a power-dependent manner and / or in a state-dependent manner, in particular in a manner dependent on a captured load value, power value and / or state. The recovery method is particularly preferably automated and based on a time elapsed since the last execution, operating time of the electrochemical energy conversion system and / or based on at least one detected load value, power value and / or state, in particular according to the preceding section of the description. A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane by flooding the anode side with hydrogen is made possible in a time-dependent manner, in a load-dependent manner, in a power-dependent manner and / or in a state-dependent manner, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery process that the recovery of the catalyst-coated membrane takes place as a recovery of a deformation of the catalyst-coated membrane at least in sections from a gap between a frame device and a medium distribution device. The inventive recovery method is particularly advantageous if recovery of a deformation of the catalyst-coated membrane is made possible at least in sections from a gap between a frame device and a medium distribution device of the electrochemical energy conversion system. As described above, this allows for an advantageous extension of the life of the catalyst coated membrane and thus also of the electrochemical energy conversion system. The medium distribution device is preferably to be understood as a porous transport layer for distributing media and / or as a gas diffusion layer. The frame device is preferably to be understood as a revolving frame device of the respective cell. A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane from a gap between a frame device and a medium distribution device is made possible at least in sections by flooding the anode side with hydrogen, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the recovery of the catalyst-coated membrane takes place against a direction of a working pressure of the cell. The working pressure of the cell and / or of the electrochemical energy conversion system is preferably to be understood as pressure on the catalyst-coated membrane from the cathode side. The recovery method and the recovery are particularly advantageous if flooding with hydrogen takes place counter to the working pressure of the cell and / or of the electrochemical energy conversion system and thus reverses and / or cancels a deformation of the catalyst-coated membrane by the working pressure at least in sections and / or at least temporarily. The working pressure is preferably to be understood in such a way that the working pressure is present during normal operation of the electrochemical energy conversion system, in particular is present on the cathode side. A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the recovery method further comprises:flushing the anode side of the cell with a medium, in particular water, prior to flooding by a flushing device of the electrochemical energy conversion system.Preferably, for example, between normal operation of the electrochemical energy conversion system and flooding of the anode side of at least one cell of the electrochemical energy conversion system with hydrogen by the flooding device, a flushing operation takes place with a medium, in particular water, particularly preferably pure water, in order, for example, to prevent a reaction of hydrogen with oxygen on the anode side. The oxygen is present, for example, as product on the anode side in normal operation and is removed or at least very greatly reduced by the flushing. The flushing device is preferably to be understood as a conveying device and / or as a pressurised storage device for the flushing medium. A recovery method configured in this manner is particularly advantageous since recovery of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen after a flushing operation, wherein life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the recovery method further comprises:sealing the anode side after flooding with at least one sealing device of the electrochemical energy conversion system.The closing of the anode side after flooding preferably allows the state on the anode side after flooding to be maintained at least temporarily. In practice, a closing and / or sealing of hydrogen in a volume is always not absolutely understood on account of the size and properties of hydrogen, since an at least slight leakage in the case of hydrogen is hardly avoidable. A pressure and / or a hydrogen concentration on the anode side thus decreases continuously over time even when the anode side is closed. However, the closing advantageously allows at least temporary maintenance of the state on the anode side after flooding or at least a deceleration of the state change. Described by way of example, in a preferred embodiment, the hydrogen pressure of, for example, 40 bar is still present on the anode side even after flushing, i.e. at standstill, with the anode inlet and anode outlet valves closed, so that a diffusion of air and / or oxygen into the anode during the standstill phase is prevented and / or made more difficult. The catalysts of the catalyst-coated membrane remain protected from oxidation for a longer time during shutdown.The closure device is preferably to be understood as a valve device.A recovery method configured in this way is particularly advantageous since recovery of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen through the closure device, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in a recovery method that the recovery method is carried out during a recovery method of the electrochemical energy conversion system. A recovery method of the electrochemical energy conversion system is preferably understood within the scope of the invention as a method for recovering performance parameters of the electrochemical energy conversion system. Alternatively or additionally, the recovery method is to be understood as an optimization method, recovery method, and / or recovery method of the electrochemical energy conversion system. Generally, recovery methods for electrochemical energy conversion systems are known in the art. However, it represents a particularly advantageous configuration of the recovery method to carry out this during, before and / or after a recovery method in order to enable a particularly efficient operation of the electrochemical energy conversion system.According to a second aspect of the invention, the invention discloses an electrochemical energy conversion system comprising at least one cell having an anode side, a cathode side and a flooding device. The electrochemical energy conversion system is configured to perform the recovery method according to the first aspect.The described electrochemical energy conversion system has all the advantages already described with respect to the recovery method according to the first aspect of the invention.An electrochemical energy conversion system configured in this way is particularly advantageous since a redeformation of the catalyst-coated membrane is made possible by flooding the anode side with hydrogen, wherein a service life and stability of the catalyst-coated membrane and of the electrochemical energy conversion system is thus made possible advantageously and with particularly simple means.According to a preferred development of the invention, it can be provided in an electrochemical energy conversion system that the electrochemical energy conversion system comprises a flushing device, a closure device, a detection device and / or an adjustment device.A recovery method according to the invention and an electrochemical energy conversion system are explained in more detail below with reference to drawings. They show in each case schematically: FIG. 1 is a cross-sectional side view of an electrochemical energy conversion system having a catalyst coated membrane, FIG. 2 is a perspective view of an electrochemical energy conversion system having a plurality of cells; and FIG. 3 shows a flow chart of an embodiment of the recovery method according to the invention.Elements with the same function and mode of operation are provided with the same reference numerals in each of FIGS. 1 to 3.FIG. 1 schematically shows a sectional side view of an electrochemical energy conversion system 10 having a catalyst-coated membrane 20. The electrochemical energy conversion system 10 is shown during normal operation, where a working pressure 28 produces a deformation of the catalyst coated membrane. The electrochemical energy conversion system 10 is configured to flood 202 (not shown) an anode side 40 of a cell 30 of the electrochemical energy conversion system 10 with hydrogen H 2 through a flooding device 50 of the electrochemical energy conversion system 10. Flooding 202 (not shown) occurs outside of normal operation. The electrochemical energy conversion system 10 is further configured to re-shape 204 (not shown) the catalyst coated membrane 20 by flooding 202 (not shown) the anode side 40 with hydrogen H2. Flooding 202 (not shown) of the anode side 40 of the cell 30 with hydrogen H2takes place at superatmospheric pressure, with a pressure of up to 40 bar being built up at least temporarily by flooding 202 (not shown) of the anode side 40 of the cell 30 with hydrogen H2. The re-forming 204 (not shown) of the catalyst coated membrane 20 is performed as a re-forming 204 (not shown) of a deformation of the catalyst coated membrane 20 from a gap 22 between a frame device 24 and a medium distribution device 26.FIG. 2 schematically shows a perspective view of an electrochemical energy conversion system 10 having a plurality of cells 30. The electrochemical energy conversion system 10 is configured to flood 202 (not shown) the respective anode side 40 of the cells 30 of the electrochemical energy conversion system 10 with hydrogen H 2 through a flooding device 50 of the electrochemical energy conversion system 10. The electrochemical energy conversion system 10 is further configured to re-shape 204 (not shown) the catalyst coated membrane 20 by flooding 202 (not shown) the anode sides 40 with hydrogen H2. The electrochemical energy conversion system 10 comprises an adjustment device 90 for adjusting a pressure-time curve, wherein flooding 202 (not shown) of the anode side 40 of the cell 30 with hydrogen H2is carried out according to the pressure-time curve. The electrochemical energy conversion system 10 comprises two detection devices 80 each for detecting 206 (not shown) a load value of the electrochemical energy conversion system 10, a power value of the electrochemical energy conversion system 10 and / or a state of the electrochemical energy conversion system 10 and / or the catalyst-coated membrane 20. The electrochemical energy conversion system 10 includes a flushing device 60 for flushing 208 (not shown) the anode side 40 of the cell 30 with a medium M prior to flooding 202 (not shown). The electrochemical energy conversion system 10 includes a closure device 70 for closing 210 (not shown) the anode side 40 after flooding 202 (not shown).FIG. 3 schematically shows a flow chart of an embodiment of the recovery method 200 according to the invention. For improved clarity, only the reference numerals of the method steps are indicated in FIG. 3. The recovery method 200 comprises, in a first method step, flooding 202 an anode side 40 of a cell 30 of the electrochemical energy conversion system 10 with hydrogen H2by a flooding device 50 of the electrochemical energy conversion system 10. The recovery method 200 comprises, in a further method step, recovering 204 the catalyst-coated membrane 20 by flooding 202 the anode side 40 with hydrogen H2. The recovery method 200 comprises, in a further method step, the detection 206 of a load value of the electrochemical energy conversion system 10, a power value of the electrochemical energy conversion system 10 and / or a state of the electrochemical energy conversion system 10 and / or of the catalyst-coated membrane 20 by at least one detection device 80 of the electrochemical energy conversion system 10. The recovery method 200 comprises, in a further method step, the flushing 208 of the anode side 40 of the cell 30 with a medium M before flooding 202 by a flushing device 60 of the electrochemical energy conversion system 10.

Claims

A recovery method (200) for recovering (204) a catalyst coated membrane (20) of an electrochemical energy conversion system (10) comprising: - flooding (202) an anode side (40) of a cell (30) of the electrochemical energy conversion system (10) with hydrogen (H2) by a flooding device (50) of the electrochemical energy conversion system (10), - recovering (204) the catalyst coated membrane (20) by flooding (202) the anode side (40) with hydrogen (H2).The recovery method (200) according to claim 1, characterized in that flooding (202) of the anode side (40) of the cell (30) with hydrogen (H2) is effected with overpressure, in particular wherein a pressure of up to 25 bar, up to 30 bar, up to 35 bar, up to 40 bar or above 40 bar is built up at least temporarily by flooding (202) of the anode side (40) of at least one cell (30) with hydrogen (H2).The recovery method (200) according to any one of the preceding claims, characterized in that the flooding (202) of the anode side (40) of the cell (30) with hydrogen (H2) is carried out according to a pressure-time curve, in particular wherein the pressure-time curve is adjustable by an adjustment device (90) of the electrochemical energy conversion system (10).The recovery method (200) according to any one of the preceding claims, characterized in that the recovery method (200) further comprises: - detecting (206), by at least one detecting device (80) of the electrochemical energy conversion system (10), a load value of the electrochemical energy conversion system (10), a power value of the electrochemical energy conversion system (10) and / or a state of the electrochemical energy conversion system (10) and / or the catalyst coated membrane (20).The recovery method (200) according to any one of the preceding claims, characterized in that the flooding (202) and / or the recovery (204) takes place in a time-dependent manner, in a load-dependent manner, in a power-dependent manner and / or in a state-dependent manner, in particular in a manner dependent on a captured load value, power value and / or state.The reshaping method (200) according to any one of the preceding claims, characterized in that the reshaping (204) of the catalyst-coated membrane (20) takes place as a reshaping (204) of a reshaping of the catalyst-coated membrane (20) at least in sections out of a gap (22) between a frame device (24) and a medium distribution device (26).The recovery method (200) according to any one of the preceding claims, characterized in that the recovery (204) of the catalyst-coated membrane (20) takes place against a direction of a working pressure (28) of the cell (30).The recovery method (200) according to any one of the preceding claims, characterized in that the recovery method (200) further comprises: - flushing (208) the anode side (40) of the cell (30) with a medium (M), in particular water, prior to flooding (202) by a flushing device (60) of the electrochemical energy conversion system (10).The recovery method (200) according to any one of the preceding claims, characterized in that the recovery method (200) further comprises: - closing (210) the anode side (40) after flooding (202) with at least one closing device (70) of the electrochemical energy conversion system (10).The recovery method (200) according to any one of the preceding claims, characterized in that the recovery method (200) is performed during a recovery process of the electrochemical energy conversion system (10).An electrochemical energy conversion system (10) comprising at least one cell (30) having an anode side (40), a cathode side (42) and a flooding device (50), characterized in that the electrochemical energy conversion system (10) is configured to carry out the recovery method (200) according to any one of the preceding claims.Electrochemical energy conversion system (10) according to claim 11, characterized in that the electrochemical energy conversion system (10) comprises a flushing device (60), a closure device (70), a detection device (80) and / or an adjustment device (90).

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