Conditioning device for a fuel cell system

Abstract

Conditioning device (10) for a fuel cell system (12) with at least one fuel cell, wherein the conditioning device (10) serves both to humidify and to temperature-control a first material stream (20, 22), wherein a first unit (41) serves to temperature-control the first material stream (20, 22) and a second unit (45) primarily serves to humidify the first material stream (20, 22), and the first unit (41) and the second unit (45) together form a building unit (40), wherein the first material stream (20, 22) is a cathode or anode input stream (20, 22), in particular the cathode input stream (20), and a second material stream (21, 23, 24) for heat transfer in the first unit (41) is a cathode or anode output stream (21, 23) or at least a partial stream of a coolant stream (24) which is in a cooling system (30) of the fuel cell system (12) is manageable, and a third material stream (21,23,24) for the release of moisture in the second unit (45) is a cathode or anode output stream (21, 23) or at least the partial stream of the coolant stream (24), characterized in that a heat exchanger (49), in particular a further shell and tube heat exchanger, is arranged in the first unit (41), wherein the heat exchanger (49) serves for temperature control, in particular for cooling, at least one partial stream (24.1, 25.1) of the second mass stream (21, 23, 24) by the third mass stream (21, 23, 24).

Description

[0001] The invention relates to a conditioning device for a fuel cell system with at least one fuel cell, wherein the conditioning device serves both to humidify and to temper a first material stream, according to the preamble of claim 1. Furthermore, the invention relates to a fuel cell system according to claim 9 and to a method according to the preamble of claim 10. State of the art

[0002] For an electrical voltage to be generated in a fuel cell through an electrochemical reaction, both an anode must be supplied with fuel from an anode input current and a cathode with an oxidizer from a cathode input current. A heated anode output current and a cathode output current with a changed chemical composition leave the fuel cell after the electrochemical reaction. For a fuel cell to operate without damaging the membrane between the anode and cathode and with high efficiency, the anode and cathode input currents must maintain a temperature within a specified range and a specified humidity level. This is particularly important for a fuel cell in which the membrane functions as a solid electrolyte, specifically a proton-conducting solid electrolyte.For this purpose, a humidification device and a temperature control device can be provided as two independent units upstream of the fuel cell. A disadvantage of this approach is that pipes must be used between the units, which creates additional flow resistance and incurs additional costs.

[0003] US Patent 6,106,964 A discloses a combined humidification and heating device in which an input stream is separated from an output stream by a water-permeable membrane. The input stream is heated and humidified by water vapor diffusing through the membrane. A disadvantage of this device is that heat is primarily transferred by the diffusing water vapor, meaning the amount of heat transfer cannot be adjusted independently of the humidification rate. Another disadvantage is that heat is transferred from a gaseous medium, so a large heat exchange surface is required to achieve sufficient heat transfer. Furthermore, the input stream must be cooler than the output stream. A warmer input stream might not be adequately cooled by the output stream itself.Furthermore, a warm incoming stream can absorb too much moisture, so the application of the device is limited to cold incoming streams with a large space requirement.

[0004] US Patent 6,013,385 A discloses that a cathode input stream is first compressed and heated in the process. Water droplets are introduced into the cathode input stream through a nozzle. The heat of vaporization of the water cools the cathode input stream. Subsequently, an enthalpy wheel, positioned between the cathode output stream and the cathode input stream, transfers water vapor, and thus heat and moisture, from the cathode output stream to the cathode input stream. Because the evaporation of the water droplets simultaneously generates cold and moisture in the cathode input stream, and heat and moisture are then transferred from the cathode output stream, achieving a temperature control rate independent of humidification is difficult. Furthermore, the enthalpy wheel must be driven by a motor and therefore requires an external energy supply.Furthermore, an enthalpy wheel is difficult to integrate due to its geometric shape.

[0005] Document AT 502 353 A1 discloses a method and a device for conditioning an O2-containing gas for the operation of a low-temperature fuel cell, comprising a supply line and a cathode-side discharge line for the cathode exhaust gas, wherein the supply line is divided into a first and a second branch line by a control valve, and one of the branch lines is guided through a humidification device exposed to cathode exhaust gas. Document US 2005 / 0053815 A1 discloses a device for regulating the temperature and humidity of a reaction gas supplied to a fuel cell stack and includes a temperature control section and a humidity control section. Disclosure of the invention

[0006] The object of the invention is to provide a compact device and a method in which a material stream, in particular an input stream of a fuel cell, is both humidified and temperature-controlled, wherein the humidification rate and the temperature control rate are to be independently adjustable. The device should preferably operate as a passive component, i.e., without an external energy supply, and in particular should also be able to serve for cooling a compressed input stream. Furthermore, the device should preferably have a small footprint.

[0007] To solve the problem, a conditioning device with the features of claim 1, in particular the characterizing part, is proposed. Advantageous embodiments of the conditioning device are specified in the dependent device claims. The problem is further solved by a fuel cell system of claim 9 and by a method according to independent claim 10. Advantageous embodiments of the method are specified in the dependent method claim. Features and details described in connection with the conditioning device according to the invention naturally also apply in connection with the method according to the invention, and vice versa. The features mentioned in the claims and in the description can be essential to the invention individually or in combination.

[0008] According to the invention, a first unit of the conditioning device serves to temper the first material stream, and a second unit of the conditioning device primarily serves to humidify the first material stream. The first and second units together form a single assembly. Because the first unit only tempers the first material stream and does not humidify it, a desired temperature of the first material stream can be set independently of the desired degree of humidification. For this purpose, the material used between the first material stream and a second material stream, which serves for heat transfer to or from the first material stream in the first assembly, is impermeable to water.Before operating the fuel cell system, the desired temperature can be predetermined by selecting the second material stream, thus enabling both heating and cooling of the first material stream in the conditioning device according to the invention. By selecting the structural features, dimensions, and materials used in the first unit, the heat transfer rate can be dimensioned independently of the humidification rate. The same applies to the second unit, where a third material stream for moisture removal can be selected and set, and the dimensions and materials of the second unit can be chosen independently of the first unit, so that humidification of the first material stream in the second unit occurs independently of the heat transfer in the first unit.The fact that the second unit primarily serves humidification means that when water enters the first stream, the temperature of the first stream also changes, for example, because warmer water vapor enters the first stream or because heat of vaporization is drawn from the first stream when liquid water evaporates. This temperature change must be taken into account when determining the temperature control rate of the first unit.

[0009] The first material stream can be a cathode input stream or an anode input stream. Since the anode input stream is often tempered and humidified by recirculating at least a portion of an anode output stream into the anode input stream, the conditioning device can be used particularly for the cathode input stream. The first material stream can be heated or cooled in the conditioning device. If the cathode input stream is taken directly from a tank or ambient air, it must be heated. If the cathode input stream is compressed, for example, if it is obtained from ambient air by compression, it must be cooled.

[0010] The second and third material streams can be the cathode output stream, the anode output stream, or at least a partial stream of a coolant stream, regardless of the choice of the first material stream. The second and third material streams can be one and the same material stream. In this case, independence of heat and moisture transfer can be achieved by selecting the physical dimensions of the first and second units. Preferably, however, two different material streams are provided as the second and third material streams in order to be able to control or regulate heat and moisture transfer independently during operation. Thus, the desired temperature of the first material stream in the first unit can be set by the flow rate and temperature of the second material stream, and the humidity in the second unit can be set by an independent flow rate of the third material stream.

[0011] In particular, the second material stream can be at least a portion of the coolant stream. Because the coolant stream consists mainly of liquid water and therefore has a high heat capacity, a significant amount of heat can be transferred per unit volume of the coolant stream. This allows for small dimensions in the first unit, resulting in a compact conditioning device. The third material stream can be, in particular, the cathode output stream, as this continuously leaves the fuel cell and contains sufficient moisture. In this case, the cathode output stream loses moisture in the second unit.

[0012] The first unit can be a shell-and-tube heat exchanger, in which the first mass flow passes through a first tube chamber and the second mass flow passes through a first shell chamber. In the second unit, the first mass flow passes through a second tube chamber and the third mass flow of the fuel cell system passes through a second shell chamber. Guiding the first mass flow through the first and second tube chambers is advantageous because individual tubes of the first tube chamber and individual tubes of the second tube chamber lie on the same axis and, in particular, can have the same tube diameter, so that the first mass flow can maintain its flow direction and velocity during the transition from the first unit to the second unit. This also allows for a simpler and more compact design of the conditioning unit.Only the material of the pipes needs to be chosen to be watertight in the first unit and water-permeable in the second. Since the coolant flow through a fuel cell consists of deionized water, the pipes of the first unit can be made of stainless steel for corrosion protection, while the pipes of the second unit can contain hollow fibers, which are also water-absorbing. Generally, however, the first fluid flow can also be routed through the first and second jacket chambers, the second fluid flow through the first chamber, and the third fluid flow through the second pipe chamber. Alternatively, a different type of heat exchanger, such as a plate or spiral heat exchanger, can be used.

[0013] Preferably, the first unit is positioned upstream of the second unit in the direction of flow of the first mass stream, so that temperature control occurs first, followed by humidification. This ensures that the first mass stream absorbs only the amount of moisture appropriate to its desired temperature. Otherwise, a first mass stream that is too warm could, for example, initially absorb too much water, which could then condense when the first mass stream cools and clog the flow path.

[0014] To achieve the highest possible heat transfer over a small area, the first and second material streams in the first unit can be arranged to flow in counterflow. Similarly, for high moisture exchange, the first and third material streams in the second unit can also flow in counterflow.

[0015] Due to the compact design and integration of the first and second units into a single unit, and because the second and third material streams are preferably two separate streams, it is also conceivable that the second and third material streams can condition each other, for example, that the second or third material stream is tempered, humidified, and / or deionized by the other. For example, at least one partial stream of the second material stream can be tempered by the third. "At least one partial stream" means that the entire second material stream can also be tempered. In particular, a partial stream of the coolant flow heated by heat transfer in the first unit can be cooled by a colder third material stream.This increases the available cooling capacity of the fuel cell system, which is particularly important during full-load operation, since prior art fuel cell systems suffer from a cooling capacity deficit under full load, necessitating a power limitation of the fuel cell system. In the fuel cell system according to the invention, the power limitation of the fuel cell stack can be shifted by cooling the partial flow. Such full-load operation can occur when the fuel cell system is used in a motor vehicle, both during uphill driving and at top speed.

[0016] A heat exchanger is arranged in the first or second unit of the conditioning unit to temper the partial flow. This heat exchanger can be another shell-and-tube heat exchanger, but the other heat exchanger designs listed above are also conceivable. The partial flow can flow into a third jacket chamber and the third fluid flow through a third tube chamber, or vice versa. It is also possible to design the heat exchanger so that ions from the partial flow are transferred into the third flow. In this case, at least part of the heat exchanger can function as an electrical deionization device. This may be necessary because the coolant flow through the fuel cell must be deionized to prevent a short circuit in the fuel cell.

[0017] The conditioning device thus set up is a passive component in the fuel cell system that does not require its own power supply or a motor.

[0018] The conditioning device can be used with all fuel cells that require the humidification of a solid electrolyte. This includes, for example, polymer electrolyte membrane fuel cells using hydrogen as fuel or direct methanol fuel cells. A fuel cell stack can also be used instead of a single fuel cell. The fuel cell can be used to power a motor vehicle.

[0019] The object of the invention is also solved by a method for tempering and humidifying the first material stream, wherein the first material stream is tempered and humidified in a single unit, but the level of heat transfer from or into the first material stream can be adjusted independently of the degree of humidification.

[0020] Further improvements to the invention will become apparent from the following description of exemplary embodiments of the invention, which are schematically illustrated in the figures. All features and / or advantages arising from the claims, the description, or the drawings, including design details, spatial arrangement, and process steps, can be essential to the invention, both individually and in various combinations. The figures show: Fig. 1A a first fuel cell system according to the invention with a conditioning device according to the invention, Fig. 1B a second fuel cell system according to the invention with a conditioning device according to the invention, which is installed at a different location Fig. 2 a conditioning device according to the invention in longitudinal section, Fig. 3 the conditioning device according to the invention in a cross-section according to line II of the Fig. 2 and Fig. 4 another embodiment of the conditioning device according to the invention with an electrical deionization device.

[0021] In Fig. Figure 1A shows a first embodiment of a fuel cell system 12 according to the invention, comprising a fuel cell stack 11. To operate the fuel cell stack 11, hydrogen is supplied to the fuel cell stack 11 as fuel in an anode input current 22, as indicated by arrow 28. An anode output current 23, reduced by the amount of reacted hydrogen, leaves the fuel cell stack 11, as indicated by arrow 28'. Oxygen-containing air from the environment 19 is supplied to the fuel cell stack 11 in a cathode input current 20 as an oxidizing agent for the electrochemical reaction. The air is first compressed in a compressor 13, then passes through a conditioning device 10 according to the invention, and reaches the fuel cell stack 11 at a pre-temperature and humidified state, as indicated by arrows 27.A heated cathode output stream 21 with reduced oxygen content and enriched with water leaves the fuel cell stack 11 according to arrows 27' and passes through the conditioning device 10.

[0022] The fuel cell system 12 also includes a cooling system 30. A coolant flow 24 passes through the fuel cell stack 11 in a main flow path 24'. The coolant flow 24 flows in the direction indicated by arrow 29. The coolant flow 24 is circulated by a pump 15. In a cooler 17, a first partial flow 24.1 of the coolant flow 24, after being heated by the fuel cell stack 11, can be cooled again. The first partial flow 24.1, which flows through the cooler 17, can be adjusted by a control valve 16, whereby a first portion 24.2 of the coolant flow 24 can flow through a bypass 26. The coolant flow 24 passes through the conditioning device 10 according to the invention to cool the cathode input flow 20. The coolant flow temperature is controlled by three temperature sensors 18, 18', 18" in front of and behind the fuel cell stack 11 and behind the cooler 17.A coolant flow temperature control based on the measurement of the coolant flow temperature, which can adjust an electrical power of the coolant pump 15, an opening degree of the control valve 16 and / or an electrical power of a radiator fan 17', also regulates the heat transferred in the conditioning device 10.

[0023] In Fig. In section 1A, the conditioning device 10 is arranged such that a first branch 70 is located within the conditioning device 10, leading to the first partial flow 24.1 and the first component 24.2. The first partial flow 24.1 can be cooled in the conditioning device 10 by the cathode output flow 21 in a heat exchanger 49, so that the heat exchanger 49 and the cooler 17 can be understood as two cooling devices connected in series, whereby the power of the cooler fan 17' can be reduced by pre-cooling the first partial flow 24.1 in the heat exchanger 49.

[0024] In Fig. Figure 1B shows a second embodiment of a fuel cell system 12 according to the invention, wherein the same reference numerals are used for the same components and arrows. Fig. 1B differs from Fig. 1A by arranging the conditioning device 10 upstream of the fuel cell stack 11. Within the conditioning device 10, the coolant flow 24 can be secondly branched into a second partial flow 25.1 and a second component 25.2 of the coolant flow 24. The second partial flow 25.1 can be cooled by the cathode output flow 21 and returned to the radiator 17 via a partial flow path 25' upstream of the control valve 16. In the second embodiment, the first partial flow 24.1 is not cooled by the conditioning device 10. The temperature sensor 18" is located between the control valve 16 and the point 14 where the first partial flow 24.1 and the second partial flow 25.1 meet. The level of the second partial flow 25.1 is therefore dependent on the opening degree of the control valve 16 and is thus adjustable.This is advantageous because, at high cooling capacity, the control valve 16 is set such that both the first partial flow 24.1 of the coolant flow 24, cooled by the cooler 17, and the second partial flow 25.1 increase. Alternatively, the partial flow path 25' can also terminate with its own control valve after the control valve 16 and before the pump 15 (not shown). The second portion 25.2 of the coolant flow 24, which flows through the fuel cell stack 11, is slightly heated by the heat transfer from the cathode inlet flow 20 in the conditioning device 10, so that a coolant flow inlet temperature into the conditioning device 10 is maintained slightly below a coolant flow temperature at a fuel cell inlet by means of the coolant flow temperature control.

[0025] In both embodiments, a first partial flow 24.1 or a second partial flow 25.1 of the coolant flow 24 is additionally cooled by the conditioning device 10, so that the cooling fan 17' requires less electrical power than without additional cooling. The available cooling capacity of the fuel cell system 12 is also increased by the additional cooling, although the overall heat input into the cooling system by the conditioning device 10 increases. Advantages of the first embodiment according to Fig. 1A compared to the second embodiment according to Fig. 1B are that in the first embodiment the entire coolant flow 24 delivered by the pump 15 flows through the fuel cell stack 11, that no additional partial flow path 25' is necessary and that the in Fig. The temperatures shown in the first embodiment are advantageous.

[0026] In the case of a cold start of the fuel cell system 12, both in the embodiment according to Fig. 1A as well as in the embodiment according to Fig. 1B The coolant flow 24 in the conditioning unit 10 is heated by the cathode input flow 20 such that the coolant flow 24 can in turn heat the fuel cell stack 11. It is advantageous that existing heat in the fuel cell system 12, generated during the compression of the cathode input flow 20, is used to heat the fuel cell stack 11. Therefore, according to the invention, separate heating plates in the fuel cell stack 11 or separate heating devices for the coolant flow 24 can be eliminated or reduced in size.

[0027] In Fig. 1A and Fig. In 1B, the entire main flow 24 passes through the conditioning device 10. However, it is also conceivable that only a partial flow of the coolant flow 24 passes through the conditioning device 10. For this purpose, an additional bypass is routed around the conditioning device 10 (not shown). This bypass could have an additional control valve to separately regulate the flow of the coolant flow 24 through the conditioning device 10.

[0028] In another embodiment not shown, the entire coolant flow passing through the conditioning device 10 can flow through the heat exchanger 49 and be cooled. In this case, the conditioning device 10 is preferably arranged in the first partial flow 24.1 downstream of the branch 70. The partial flow path 25' is omitted.

[0029] In Fig. Figure 2 shows a conditioning device 10 according to the invention. In the conditioning device 10, a first unit 41 for tempering the cathode input stream 20 and a second unit 45, primarily for humidifying the cathode input stream 20, are combined in a single assembly 40. The cathode input stream 20 is distributed in a distribution chamber 53 to the individual tubes of a first tube chamber 42 of the first unit 41. The cathode input stream 20 flows through the tubes of the first tube chamber 42, of which only two are shown by way of example in Figure 2. Fig. Figure 2 shows the process according to arrows 27. Here, the cathode inlet flow 20 transfers heat to the coolant flow 24 according to arrows 31, with the coolant flow 24 flowing counter-currently through a first jacket chamber 43 of the first unit 41 according to arrows 29. Deflector plates may be provided in the first jacket chamber 43 (not shown). The cathode inlet flow 20, which has been heated by the compressor 13, is thus cooled in the first unit 41 without being humidified. Pipes of the second tube chamber 46 of the second unit 45 connect to the pipes of the first tube chamber 42 in the same direction and with the same diameter, so that the cathode inlet flow 20 can maintain its velocity and pressure when flowing through the second tube chamber 46 and experiences no significant flow resistance. Only two of the pipes of the second tube chamber 46 are shown as examples.

[0030] In the second unit 45, the tubes of the second tube chamber 46 are made of hollow fibers so that they can absorb moisture from the cathode output flow 21. For this purpose, the cathode output flow 21 flows counter-currently through the second unit 45 in a second jacket chamber 47, as indicated by arrows 27'. Liquid water droplets from the cathode output flow 21 are absorbed by the hollow fibers of the second tube chamber 46 and evaporated into the cathode inlet flow 20. The heat of vaporization released during this process cools both the cathode output flow 21 and the cathode inlet flow 20. This further cooling of the cathode inlet flow 20 should be taken into account when adjusting the heat transfer 31 in the first unit 41. Baffle plates may also be provided in the second jacket chamber 47 of the second unit 45 (not shown).A humidified and cooled cathode input current 20, approximately at the operating temperature of the fuel cell stack 11, leaves the second unit 45 according to arrows 27 to a merging chamber 54 and is forwarded to the fuel cell stack 11.

[0031] The transition from the first tube chamber 42 to the second tube chamber 46 results in a compact design for the conditioning device 10, allowing it to be referred to as a single unit 40. A further advantage of this compact design is that a first jacket 44, surrounding the first jacket chamber 43, and a second jacket 48, surrounding the second jacket chamber 47, can be made of a single piece and a single material. The first unit 41 and the second unit 45 are separated from each other only by a bottom 55 to separate the coolant flow 24 from the cathode output flow 21. If the same fluid flow is used for both humidification and temperature control, the bottom 55 is omitted. The conditioning device 10 according to the invention is easy to integrate into the fuel cell system 12, for example, by soldering, welding, or crimping.

[0032] By integrating the first unit 41 and the second unit 45 into a single assembly 40, and by the resulting spatial proximity of the cathode output flow 21 and the coolant flow 24, it is possible for these two flows to also condition each other. The cathode output flow 21, which is significantly cooled by the heat of vaporization occurring in the second unit 45, can be used to cool at least the first partial flow 24.1 in the case of the first embodiment, or the second partial flow 25.1 in the case of the second embodiment, of the coolant flow 24, which has been slightly heated by the heat transfer in the first unit 41. For this purpose, the cathode output flow 21 must have a lower temperature than the heated coolant flow 24. A heat exchanger 49 can be integrated into the first unit 41 for cooling the first or second partial flow 24.1, 25.1.The coolant flow 1 flows through a third jacket chamber 51 according to arrows 29' and is cooled by the cathode output flow 21, which flows through a third tube chamber 50 of the heat exchanger 49 according to arrows 27'. The first jacket chamber 43 and the third jacket chamber 51 are separated from each other by a third jacket 52, so that the first or second partial flow 24.1, 25.1 can be diverted from the coolant flow 24, wherein a first portion 24.2, in the case of the first embodiment, leaves the conditioning device 10 uncooled to flow through the bypass 26, or a second portion 25.2, in the case of the second embodiment, leaves the conditioning device uncooled to flow through the fuel cell stack 11. The reference numerals for the second embodiment are in . Fig. 2 in parentheses. As the electrical power of the fuel cell stack 11 increases, both the heat of reaction and the heat of vaporization in the second unit 45 also increase. Therefore, coupling the heat of vaporization, which indirectly cools the first or second partial flow 24.1, 25.1, with the heat of reaction from the fuel cell stack 11, which is to be dissipated by the coolant flow 24, is particularly advantageous.

[0033] Possible temperatures of the individual streams at different locations according to the first embodiment are shown in Fig. Figure 2 is shown without brackets; possible temperatures according to the second embodiment are shown in Fig. The number 2 is shown in parentheses. The temperature specifications are only examples and should not be considered restrictive.

[0034] In Fig. Figure 3 shows a cross-section through the first unit 41 along line II. In contrast to Fig. Figure 2 shows a plurality of tubes of the first tube chamber 42, arranged in circular tube rows, with the tube rows lying radially one behind the other. The first jacket chamber 43 is bounded by the first jacket 44. To separate the first jacket chamber 43 from the third jacket chamber 51, the third jacket 52 is provided. Several tubes of the third tube chamber 50 are also shown. The heat transfer can be dimensioned for the first tube chamber 42, and for the third tube chamber 50, based on the number, inner diameter, materials, and surface finish of the tubes, at the expected temperatures and heights of the cathode inlet flow 20 and the coolant flow 24, at the expected temperatures and heights of the cathode outlet flow 21 and the first or second partial flow 24.1, 25.1.

[0035] In Fig.Figure 4 shows the first unit 41 again along the same section line II. Instead of a shell-and-tube heat exchanger as the heat exchanger 49, a spiral-shaped electrical deionization device 60 is shown. The electrical deionization device 60 also serves to transfer heat from the heated first or second partial current 24.1, 25.1 to the cooled cathode output current 21. In addition, the electrical deionization device 60 is designed so that ions from the first or second partial current 24.1, 25.1 pass into the anode output current 21 and thus deionize the first or second partial current 24.1, 25.1. A cathode 61 is arranged in the center of the deionization device 60. An anode 62 forms an outer boundary of the deionization device 60 in place of the third sheath 52. The anode 62 and the cathode 61 are supplied with a direct current voltage, for example from the fuel cell stack 11.Between cathode 61 and anode 62, both a cation-selective membrane 63 and an anion-selective membrane 64 are wound spirally, such that the cation-selective membrane 63 and the anion-selective membrane 64 alternate radially. The ion-donating first or second partial current 24.1, 25.1 is guided in the spaces between the anion- and cation-selective membranes 63, 64 such that it is limited by the cation-selective membrane 63 towards the cathode 61 and by the anion-selective membrane 64 towards the anode 62. The ion-accepting cathode output current 21, on the other hand, is guided such that it is limited by the cation-selective membrane 63 towards the anode 62 and by the anion-selective membrane 64 towards the cathode 61. This ensures that cations migrating towards the cathode 61 are removed from the first or second partial current 24.1, 25.1. Cations migrate through the cation-selective membrane 63 into the cathode output current 21, while the cations from the cathode output current 21 cannot pass through the anion-selective membrane 64 into the first or second partial current 24.1, 25.1. Similarly, anions from the first or second partial current 24.1, 25.1 can migrate towards the anode 62 through the anion-selective membrane 64 into the cathode output current 21, while the anions from the cathode output current 21 cannot pass through the cation-selective membrane 63 towards the anode 62 into the first or second partial current 24.1, 25.1. This causes the first or second partial current 24.1, 25.1 to be deionized even against a concentration gradient in the direction of the cathode output current 21, while the cathode output current 21 is enriched with ions.

[0036] To improve ion release, an ion exchange bed can be provided in the first or second partial current 24.1, 25.1 (not shown). Furthermore, spacers can be provided (not shown) to better separate the cation-selective membrane 63 and the anion-selective membrane 64. Instead of the spiral-shaped embodiment of the electrical deionization device 60, an embodiment with parallel, adjacent cation- and anion-selective membranes 63, 64 can also be provided.

Images