Method for continuously producing a multiphase fluid stream

Abstract

The present invention relates to a method for continuously preparing a multiphase fluid flow, in particular in the operation of a fuel cell, the method comprising the steps of: a) providing a multiphase fluid flow having a gas phase and a liquid phase, wherein the gas phase has a carrier material and a process material, and wherein the liquid phase has a process material, b) introducing the multiphase fluid flow into a continuously operable rotating separator, c) at least partially separating the liquid phase from the multiphase fluid flow with the aid of the rotating separator to produce a prepared fluid flow having a prepared gas phase, wherein the prepared gas phase has a carrier material and a process material, and wherein the material quantity proportion of the process material in the prepared gas phase is 50% or more of the material quantity proportion of the process material in the gas phase of the multiphase fluid flow.

Description

Technical Field

[0001] The present invention relates to a method for continuously producing a multiphase fluid flow, a rotating separator for use in a corresponding method, and a fuel cell system for carrying out the corresponding method. Furthermore, the use of a corresponding rotating separator for the continuous production of a multiphase fluid flow is disclosed. Background Art

[0002] For years, the use of fuel cells in the automotive industry has been considered a promising option for reducing dependence on fossil fuels, such as oil. Fuel cells represent one of the most important alternatives to batteries, such as lithium-ion batteries. Fuel cell technology offers significant advantages over battery technology, particularly in terms of practical handling of fuel, storage capacity, and refilling times, as well as the potential for utilizing existing wiring and storage infrastructure.

[0003] In fuel cells, oxygen and fuel, such as hydrogen, methane, or methanol, are converted into water and, if necessary, other reaction products under controlled reaction conditions. The reaction steps of the redox reaction are spatially separated. For this purpose, a fuel cell comprises an anode and a cathode, which are separated from each other by an electrolyte, such as an electrolyte membrane.

[0004] During operation, reactants are continuously supplied to the fuel cell, with the fuel usually being used in an overstoichiometric manner. Therefore, a separate system for the fluid lines is required for smooth operation of the fuel cell. To ensure the most efficient possible operation of the fuel cell and high utilization of the materials used, it is particularly necessary to recirculate the fluid flow discharged from the fuel cell, in particular the overstoichiometrically used fuel, at least partially back into the fuel cell. However, this is associated with significant practical problems, particularly because the fluid flow discharged from the fuel cell typically contains reaction products of chemical conversions, mostly water, which are at least partially present in condensed form. Recirculation of the discharged operating gas is generally intended to prevent the water produced in the fuel cell and condensed to a large extent from also being directed back into the fuel cell, where, for example, the fuel cell stack could otherwise flood unexpectedly.

[0005] For this reason, water separators are often used in fluid line systems for recirculation use or at least in fluid line systems associated with anode use.

[0006] In the prior art, passive water separators are used for this purpose. However, according to the inventors, these systems can be associated with significant disadvantages. For example, they can lead to undesirable stagnation pressures or pressure drops in the fluid line system. Furthermore, such systems have a poor separation efficiency with respect to condensed water, especially when the fuel cell is operated at low load and the fluid flow exiting the fuel cell stack is therefore relatively weak. In principle, the separation performance of the passive systems known from the prior art is often considered insufficient.

[0007] The inventors of the present invention have now realized that the problems known from the prior art can be solved by using a rotating separator, in particular when the separator is driven, for example, by a separate electric motor and thus not only removes condensed by-products from the fluid flow with excellent separation performance, but also actively ensures a sufficient flow in the fluid line system by its rotation, similar to that of a turbine.

[0008] However, the inventors have discovered that the fundamentally advantageous use of rotating separators for the continuous production of multiphase fluid flows can also be associated with disadvantages that can be disadvantageous for certain applications, particularly in fluid line systems in fuel cells. In this inherently extremely advantageous configuration, the inventors' own experiments have resulted in individual unexpected and unpredictable effects that have led to unexpected power losses in the fuel cell.

[0009] Without being bound by this theory, the inventors hypothesize that these fuel cell power losses may be a result of the exceptionally high effective power of the rotating separator, which occurs particularly when the rotating separator is operated at particularly high rotational speeds or separation powers. In this case, the effective water separation by the rotating separator can function so effectively that the water content in the gas phase discharged from the rotating separator is significantly reduced. At the same time, the fuel cell's now very dry carrier gas is supplied by the rotating separator at sufficient pressure and circulated through the fuel cell even under low load. However, for smooth fuel cell operation, it is often necessary to keep the electrolyte membrane separating the electrodes moist to ensure adequate ion transport. Without being bound by this theory, the inventors based their conclusion on the fact that the inherently advantageous use of a rotating separator in a fuel cell, particularly in the fluid line system connected to the anode, increases the risk of insufficient membrane moisture in the electrolyte membrane compared to conventional separators. Summary of the Invention

[0010] The object of the present invention is to eliminate the above-mentioned problems and to provide a method for the use of a rotating separator in a fuel cell system which is extremely advantageous and innovative in its design, said method being particularly suitable for continuously preparing a multiphase fluid flow, in particular during the operation of a fuel cell, and thereby avoiding the above-mentioned disadvantages and enabling efficient operation of the fuel cell.

[0011] The method to be specified for continuously producing a multiphase fluid flow, in particular during operation of a fuel cell, should make it possible to obtain a produced fluid flow, even when using a rotating separator, with which unintentional drying of the electrolyte membrane can be prevented.

[0012] The inventors of the present invention have now realized that in order to achieve the above-mentioned task, the method for continuously preparing a multiphase fluid flow must be designed in such a way that, in the inherently advantageous use of a rotating separator, the material quantity share of the process material in the prepared gas phase does not decrease by more than 50% relative to the initial gas phase.

[0013] The aforementioned objects are correspondingly achieved by a method according to the invention for the continuous preparation of a multiphase fluid stream or by a rotary separator and use as disclosed below.

[0014] The features of the technical solution according to the invention, which are described below as preferred, are combined in particularly preferred embodiments with other features, which are described below as preferred. A combination of two or more of the embodiments described below as particularly preferred is therefore particularly preferred. Also preferred are embodiments in which a feature, which is described below as preferred, is combined with one or more other features, which are described below as preferred. The features of the preferred rotary separator and application are derived from the features of the preferred method.

[0015] The invention relates to a method for continuously producing a multiphase fluid flow, in particular in the operation of a fuel cell, comprising the steps of:

[0016] a) providing a multiphase fluid flow having a gas phase and a liquid phase, wherein the gas phase comprises a carrier material and a process material, wherein the liquid phase comprises the process material,

[0017] b) introducing the multiphase fluid flow into a continuously operable rotating separator, wherein the rotating separator is preferably operated continuously or at intervals, particularly preferably continuously,

[0018] c) at least partially separating the liquid phase from the multiphase fluid flow by means of the rotating separator in order to produce a prepared fluid flow having a prepared gas phase,

[0019] The prepared gas phase comprises a carrier material and a process material, wherein the material amount proportion of the process material in the prepared gas phase is 50% or more of the material amount proportion of the process material in the gas phase of the multiphase fluid flow.

[0020] The method according to the invention is particularly suitable for use in the operation of fuel cells, in particular polymer electrolyte fuel cells, i.e., fuel cells that use a polymer membrane as the electrolyte. The use of the method according to the invention in the fluid conduit system on the anode side of the fuel cell is preferred.

[0021] However, the inventors of the present invention have come to the assessment that the insights gained in the optimization of fuel cells for the continuous preparation of multiphase fluid flows using rotating separators are also relevant in principle for other areas of application that require careful control of the concentration of process material in the gas phase, because, for example, downstream devices and components require a specific minimum amount of process material.

[0022] In step a) of the method according to the invention, a multiphase fluid flow having a gas phase and a liquid phase is provided. A corresponding multiphase fluid flow can be formed, for example, in a fuel cell, where water is formed by a redox reaction and is discharged from the fuel cell in condensed form together with excess fuel.

[0023] In the inventor's opinion, although it is in principle possible for a multiphase fluid flow to contain solid-phase contaminants, such as particles, in certain applications, this is less preferred for most applications and should generally be avoided, particularly in the operation of fuel cells. In any case, an advantage of the method according to the invention is that any particulate contaminants present in the fluid flow can be automatically and completely separated using a rotating separator.

[0024] The multiphase fluid flow provided according to the present invention comprises a process material in the liquid phase. Within the scope of the present invention, the process material is a compound whose concentration must be carefully controlled in the method according to the present invention. In the most relevant applications, especially in the preferred use of the method according to the present invention in polymer electrolyte fuel cells, the process material is water.

[0025] In addition to the liquid phase, the process material is also present in the gaseous phase, wherein the phase equilibrium of the process material between the gaseous and liquid phases is usually regulated as a function of the temperature and the prevailing pressure, or wherein the multiphase system at least strives to achieve this state.

[0026] In addition to the gaseous process material, the gas phase also contains a carrier material. Simply put, the term carrier material refers to all gaseous components that are not process material. In the method according to the present invention, the carrier material primarily serves to provide a sufficient gas volume and enable the transport of process material in liquid and gaseous form through the fluid line system. In practice, especially when used in fuel cells, the carrier material is usually a fuel or a mixture containing fuel that is delivered in a superstoichiometric manner, for example in combination with nitrogen.

[0027] In accordance with the above-described embodiments, the provided multiphase fluid flow is introduced into a continuously operable rotating separator in step b) of the method according to the present invention. Continuously operable rotating separators are generally known to those skilled in the art from other fields of application and are distinguished from other rotating separators, such as centrifuges, which are not capable of continuous operation. Those skilled in the art refer to such separators as rotating separators, which have one or more elements whose rotation causes or promotes the separation action.

[0028] With the aid of the rotating separator, the liquid phase, i.e. the phase containing liquid process material, is at least partially separated from the multiphase fluid flow in step c), wherein in principle a separation of 98% by weight or more of the liquid phase, particularly preferably 99% by weight or more of the liquid phase, is preferred.

[0029] Through this working step c), a prepared fluid stream is obtained, which has at least one prepared gas phase. Considering the above embodiments, it can be understood that the prepared fluid stream can potentially have a liquid phase and a gas phase, so that the prepared fluid stream can also be a multiphase system, which can even be particularly preferred in some cases, as will be disclosed below.

[0030] It is now essential for the method according to the invention that the prepared gas phase contains not only carrier material but also process material, i.e., process material in gaseous form. According to the inventors, it is essential that the mass fraction of the process material in the prepared gas phase, i.e., the gas phase of a prepared fluid stream such as that discharged from a continuously operable rotating separator, does not decrease significantly despite the effective power of the rotating separator. A halving of the mass fraction of the process material in the gas phase relative to the mass fraction of the same process material in the gas phase of the multiphase fluid stream can be identified as a meaningful limit value with which, in particular in the operation of polymer electrolyte fuel cells, excellent performance can be achieved over a range of parameters and under a wide variety of operating conditions.

[0031] It has proven particularly advantageous to operate the method according to the invention in such a way that the smallest possible differences in the relative composition of the prepared gas phase relative to the gas phase of the multiphase fluid flow are maintained. This allows reliable operation over extended periods of time, particularly of fuel cells that are operated at low load and produce relatively little water, wherein the fluid flow in the fluid line system can be provided with the required pressure by a rotating separator. Therefore, a method according to the invention is preferred in which the mass fraction of the process material in the prepared gas phase is 80% or more, preferably 90% or more, particularly preferably 95% or more, and most particularly preferably 95% to 105% of the mass fraction of the process material in the gas phase of the multiphase fluid flow.

[0032] This relationship between the composition of the gas phase before and after the rotating separator can also be expressed, consistent with the understanding of a person skilled in the art, by the ratio of the partial pressures of the carrier material and the process material. Alternatively, a method according to the invention is provided in which the ratio of the partial pressure of the process material to the partial pressure of the carrier material decreases by 50% or less from the gas phase of the multiphase fluid flow to the prepared gas phase. Similarly, a method according to the invention is preferably provided in which the ratio of the partial pressure of the process material to the partial pressure of the carrier material decreases by 20% or less, preferably by 10% or less, particularly preferably by 5% or less, and even more particularly preferably does not decrease substantially at all from the gas phase of the multiphase fluid flow to the prepared gas phase.

[0033] To determine the change in the amount of process material in the gas phase before and after the rotating separator, a person skilled in the art can use conventional determination methods, in which they select a suitable determination method depending on the method parameters, particularly the process material. For organic process materials, a person skilled in the art can, for example, remove a sample and analyze it using gas chromatography. For water, which is often particularly relevant as a process material, the determination can be performed using a conventional hygrometer, which, in a preferred embodiment, can be placed before and after the rotating separator. Depending on the selected measurement method, the total pressure of the gas phase is also suitably determined, for example, in order to calculate the partial pressure of the process material.

[0034] In accordance with the understanding of a person skilled in the art, the determination of the material quantity proportions or partial pressures is carried out under the process conditions, ie the temperatures and pressures prevailing during operation of the method according to the invention.

[0035] The material quantity fractions or partial pressures are clearly defined at each instant and are not dependent on the measurement method itself, which only influences the accuracy of the determination. In other words, a person skilled in the art can freely choose the measurement method to use, especially when the determined change is so far from a defined limit value that the limit value is not reached even when measurement errors are taken into account. Generally, a person skilled in the art only needs to use a more accurate measurement method when the distance from the defined limit value is so great that the measurement is unreliable.

[0036] The inventors of the present invention have identified various options for achieving the maximum change in the mass fraction of the process material in the gas phase to be adjusted in the method according to the present invention, as well as preferred values for this change. According to the inventors' assessment, condensation of process material contained in the gas phase, which reduces the mass fraction of this process material in the gas phase, can be prevented or at least reduced to a certain extent, particularly in a rotating separator, by suitable structural and process-related measures. This presents a particular challenge, as rotating separators at least partially remove the liquid phase of a multiphase fluid flow from equilibrium, thereby facilitating condensation.

[0037] In methods known from the prior art other than fuel cells operated with rotating separators, this problem is hardly relevant, since in these applications it is usually preferred that the condensed process material can be separated as completely as possible together with the remaining fraction to be removed.

[0038] The options identified by the inventors for controlling the partial pressure changes described below can be selected and combined in a suitable manner by a person skilled in the art, according to the inventors' assessment, to obtain a method that is compatible with the configurations used by a person skilled in the art. In the inventors' opinion, it has proven particularly advantageous to combine two or more, preferably three or more, and particularly preferably four or more of the options described below, with the use of all of the options described below being particularly preferred.

[0039] Many rotary separators used in the prior art have elements, such as drying mechanisms or refrigeration dryers, that are used for physicochemical binding of water, with the goal of purifying the gas flow as completely as possible. However, according to the inventors, the rotary separator to be used in the method according to the present invention should not have any of these elements. Therefore, a method according to the present invention is preferred in which the rotary separator does not have mechanisms for removing gaseous process materials from the gas phase, in particular by chemical binding and / or adsorption of the process materials. This design also has the advantage that the corresponding rotary separator requires less maintenance and eliminates the need for frequent replacement of the desiccant.

[0040] In addition to dispensing with special devices for drying the gas phase, the inventors have identified a particularly effective way to influence the change in the material quantity. In principle, it is intuitively desirable to separate the liquid phase in a multiphase fluid flow as largely as possible, so as to thereby achieve the lowest possible mass fraction of the liquid phase in the prepared fluid flow of 1% or less, preferably 0.5% or less, particularly preferably 0.1% or less, which may also be preferred for certain applications.

[0041] However, the inventors of the present invention have recognized that unintended condensation of gaseous process material from the gas phase can be particularly effectively avoided if, despite the potentially high efficiency of the rotary separator, the liquid phase is not completely removed from the fluid flow, so that the prepared fluid flow still contains a residual liquid phase that is in equilibrium with the gas phase. This method-based regulation is advantageously particularly simple to implement by specifically controlling the power of the rotary separator or its inherent separation efficiency for water. It has proven particularly suitable here if the remaining portion of condensed process material in the liquid phase is in the form of small particles with an average droplet size of 1 μm or less.

[0042] The inventors have identified a particularly suitable range for the conflicting objectives between the greatest possible separation and the retention of a liquid phase to ensure the smallest possible changes in the material quantity proportion of the process material, within which the method according to the invention can be operated particularly advantageously, in particular in the operation of polymer electrolyte fuel cells. Specifically, a method according to the invention is preferred in which the separation in step c) is carried out such that the prepared fluid stream has a mass fraction of the liquid phase of 0.05% to 2%, preferably 0.1% to 1%, and particularly preferably 0.2% to 0.5%, based on the mass of the prepared fluid stream.

[0043] While considering how to prevent the unintended separation of process material from the gas phase, the inventors of the present invention have recognized that it is advantageous to regulate the temperature of the rotating separator in order to reduce the extent of unintended condensation in the rotating separator. As understood by those skilled in the art, the temperature of the inner walls of the working chamber, i.e., the space through which the multiphase fluid flow is conducted, is relevant. In particular, combined with targeted power control to regulate the residual content of the liquid phase, this approach has proven to be an excellent solution for providing a prepared fluid flow that enables long-term, error-free operation, for example, in fuel cells comprising polymer electrolyte membranes. For easier operation, the rotating separator can be covered with thermal insulation, which is preferred for many applications. It is particularly preferred to equip the rotating separator with a heating device so that the temperature of the rotating separator can be controlled during the method. Therefore, the method according to the present invention is preferred in which the inner walls of the working chamber of the rotating separator have a temperature of 60°C or higher, preferably 70°C or higher, and particularly preferably 80°C or higher.

[0044] In particular, in conjunction with a temperature-controlled rotating separator and / or when using a heated fluid flow, it has also proven advantageous to provide a reservoir for the liquid process material in the rotating separator, the gas space of which is in fluid-conducting connection with the working chamber. This allows the preferably temperature-controlled liquid in the reservoir to additionally saturate the gas phase with the process material, which suppresses unintended condensation. Advantageously, the reservoir can be fed directly from the separated liquid phase. This embodiment has therefore proven particularly advantageous because it allows for minimal saturation of the gas phase with the process material.

[0045] According to the inventors, another option for controlling changes in the mass fraction of the process material in the gas phase is to appropriately select the type of rotary separator. This is because, due to the general operating principle of the rotary separator, particularly selected rotary separators can more easily avoid excessively strong changes in the mass fraction of the process material, or the method parameters can be particularly easily adapted to suppress excessively strong changes. A method according to the invention is preferred in which the rotary separator is a fluid machine, a rotary filter, a rotary channel separator, or a disc separator, preferably a disc separator. Disc separators are therefore also preferred because they can generally be operated particularly energy-efficiently, so that the method according to the invention saves energy compared to the prior art.

[0046] According to the inventors, the use of disc separators is particularly preferred among the aforementioned rotating separators. The method according to the present invention can be particularly advantageously performed using disc separators in particular in fluid conduit systems of fuel cells comprising polymer electrolyte membranes, particularly because disc separators are well suited for ensuring a continuous fluid flow.

[0047] According to the inventors, the use of a disc separator is therefore also advantageous because the extent of unintended condensation of process material from the gas phase can be particularly well controlled in such a disc separator by means of structural measures. The inventors have recognized that it is particularly advantageous to select the distance between the discs of the disc separator to be not excessive. Specifically, a method according to the invention is preferred in which the rotating separator is a disc separator and the distance between the discs is less than 0.6 mm, preferably less than 0.3 mm, and particularly preferably less than 0.2 mm.

[0048] Furthermore, the inventors propose to use disks with particularly smooth surfaces to reduce unintended condensation, which can be achieved, for example, by suitable surface treatment during the manufacturing process. Without wishing to be bound by this theory, the inventors based their conclusion on the fact that particularly smooth surfaces act to a lesser extent as condensation nuclei, thereby reducing the degree of condensation. Therefore, a method according to the invention is preferred in which the rotating separator is a disk separator, wherein the disks have an average surface roughness Rz according to DIN EN ISO 1302:2002 of 25 μm or less, preferably 10 μm or less, and particularly preferably 6.3 μm or less.

[0049] The inventors of the present invention believe that it is particularly advantageous to construct the disks from a material that repels the process material, or to coat the surfaces with a corresponding material, in a departure from the conventional design of the prior art. In the case of water as the process material, this can be, for example, a hydrophobic material such as polytetrafluoroethylene or another perfluorocarbon. Without wishing to be bound by this theory, the inventors of the present invention based their conclusion on the fact that a corresponding repelling surface only allows a small degree of condensation of the process material. Therefore, a method according to the present invention is preferred in which the rotating separator is a disk separator, in which at least one of the disks, preferably all of the disks, and particularly preferably all of the components of the disk separator that come into contact with the fluid flow, are made from a material that repels the process material or are coated with a material that repels the process material, wherein the process material has a contact angle on the repelling material in the range of 70° or greater, preferably 80° or greater, particularly preferably 90° or greater, and most particularly preferably 100° or greater.

[0050] Furthermore, the inventors consider it expedient to avoid cooling of the gas by expansion, which could promote condensation of process material from the gas phase. Accordingly, the inventors propose to design or operate the rotary separator in such a way that an isenthalpic pressure drop, which could lead to cooling via the Joule-Thomson effect, does not occur. Therefore, a method according to the invention is preferred in which the difference in total pressure between the gas phase of the multiphase fluid stream upstream of the rotary separator and the prepared gas phase of the prepared fluid stream downstream of the rotary separator is less than 1%, preferably less than 0.5%, and particularly preferably less than 0.1%.

[0051] The method according to the invention can advantageously be implemented in such a way that the separated liquid phase and / or the prepared gas phase from the method can be fed back into a working device for providing a multiphase fluid flow. A corresponding method according to the invention can thus be operated in a circuit, in particular a closed circuit.

[0052] It is possible, for example, to feed the separated liquid phase to a working device in which the multiphase fluid flow provided in step a) is generated. This can be, for example, a steam engine or the like. A method according to the invention is preferred in which the liquid phase separated in step c) is at least partially fed to a working device in which the multiphase fluid flow provided in step a) is generated.

[0053] However, the above-described method is generally not worth pursuing for use in the operation of a fuel cell. That is, in a fuel cell, the removed liquid phase should be fed to a discharge system, with which the separated liquid phase is removed from the fuel cell system in order to prevent undesired flooding of the fuel cell. However, as explained above, it is particularly advantageous and suitable for use in a fuel cell to guide the prepared fluid flow generated in step c) back into the fuel cell. Therefore, a method according to the invention is preferred, in which the processed fluid flow generated in step c) is at least partially fed to a working device, in which the multiphase fluid flow provided in step a) is generated. It is clear from the above-described embodiments that such a method according to the invention is preferred, in which the working device is a fuel cell, in particular a polymer electrolyte fuel cell.

[0054] The inventors of the present invention have recognized that operating the method according to the present invention at very low and very high temperatures, in particular in conjunction with fuel cell operation, can be particularly challenging. Controlling the change in the amount of process material in the gaseous component according to the present invention in this extreme temperature range is particularly challenging. Accordingly, the inventors of the present invention have proposed specific temperature ranges within which the method according to the present invention can be carried out particularly effectively. Preferred in this context is a method according to the present invention in which the multiphase fluid flow and / or the prepared fluid flow has a temperature in the range of -40 to 120° C., preferably in the range of 0 to 110° C.

[0055] As explained above, a particularly advantageous aspect of the present invention is to control the change in the material quantity fraction of the process material in the gas phase by controlling the power of a rotating separator, wherein the separator can intentionally pass a certain portion of the liquid phase. For this purpose, it has proven particularly advantageous to equip the rotating separator with an electric motor so that the separator can be controlled by the power of the motor. Therefore, a method according to the present invention is preferred in which the rotating separator is driven by an electric motor, wherein the electric motor is preferably installed in a housing that is impermeable to the carrier material and / or the process material, and wherein the conveying power and / or separation power of the rotating separator can preferably be controlled by the power of the electric motor.

[0056] As explained above, an advantageous design is to operate the rotating separator in such a way that a small portion of the liquid phase remains in the prepared fluid flow. However, this can lead to problems in the further use of the fluid flow. For example, it is possible that condensation of process material occurs before the rotating separator and that this material separates on the walls of the fluid line system. Such a separation can be coupled with the fluid flow, resulting in undesirable fluctuations in the liquid intake into the rotating separator, which can then lead to an unexpectedly high proportion of the liquid phase in the prepared fluid flow. To prevent this, a simpler, non-rotating pre-separator can be provided, which prevents such condensates from entering the rotating separator. Correspondingly, a method according to the invention is preferred, in which the multiphase fluid flow is guided through a preferably non-rotating pre-separator before being introduced into the continuously operable rotating separator.

[0057] Depending on the design of the fluid line system, further condensation can also occur after the rotating separator. It is also not ruled out that the liquid phase content after passing through the rotating separator is still too high for a particular application. In these cases, it is appropriate to use a reseparator, which can advantageously be arranged directly before the inlet of the working device in order to reduce the liquid phase content to the desired level in questionable cases. Therefore, a method according to the invention is preferred in which the treated fluid flow is passed through a preferably non-rotating reseparator.

[0058] The inventors of the present invention were able to identify, based on the collected knowledge and the basic inventive idea, particular operating parameters with which the method according to the present invention can be operated particularly advantageously.

[0059] Preference is given to a method according to the invention in which the rotating separator has a separation degree of 70% or more, preferably 80% or more, particularly preferably 90% or more, with respect to liquid particles having a diameter of less than 1 μm.

[0060] Preferred is also a method according to the invention, wherein the multiphase fluid flow is an aerosol, wherein the liquid phase in the multiphase fluid flow is preferably present as liquid particles having a diameter d50 of less than 10 μm, preferably less than 5 μm, particularly preferably less than 2 μm.

[0061] The inventors believe that methods according to the invention are particularly advantageous in which the gas phase comprises a multi-material system as a carrier material. With regard to process efficiency, it is particularly advantageous if the carrier material used dissolves as little as possible in the liquid phase of the multiphase fluid flow. In other words, methods according to the invention are preferred in which the gas phase comprises two or more different materials as carrier materials. Also preferred are methods according to the invention in which the combined mass fraction of all carrier materials in the liquid phase of the multiphase fluid flow is less than 5%, preferably less than 3%, and particularly preferably less than 1%, relative to the mass of the liquid phase of the multiphase fluid flow.

[0062] The inventors of the present invention have also been able to identify particularly suitable carrier materials. Specifically, preference is given to a method according to the invention in which the carrier material is selected from the group consisting of helium, neon, argon, nitrogen, oxygen, hydrogen, and mixtures of these materials, wherein the carrier material is preferably selected from the group consisting of nitrogen, hydrogen, and mixtures of these materials.

[0063] The inventors have also identified a particularly suitable mixture for the carrier material for use in the operation of a fuel cell according to the method of the invention. In this case, a method according to the invention is preferred in which the carrier material in the gas phase of the multiphase fluid flow has a mass fraction of 30% to 100%, preferably a mass fraction of 50% to 95%, of hydrogen and a mass fraction of 0% to 70%, preferably a mass fraction of 5% to 50%, of nitrogen, based on the mass of the gas phase.

[0064] With regard to the above embodiments, it will be apparent to a person skilled in the art that the method according to the present invention is particularly suitable for use in fuel cells, in particular polymer electrolyte fuel cells, and in particular in their anode-side fluid conduit systems or fluid management systems. In this application, the relevant process material is water, the concentration of which should be specifically controlled. Consequently, a method according to the present invention is preferred in which the process material is water. Also particularly preferred is a method according to the present invention in which the multiphase fluid flow is generated in step a) by a working device, wherein the working device is preferably a fuel cell, in particular a polymer electrolyte fuel cell.

[0065] The inventors have been able to identify particularly suitable ranges for the absolute material proportions in the prepared gas stream for the operation of the process material water and polymer electrolyte fuel cells. Specifically, a method according to the invention is preferred in which the material proportion of the process material in the prepared gas phase is in the range of 10% to 40%, preferably 13% to 35%, and particularly preferably 16% to 30%.

[0066] A person skilled in the art will recognize, with reference to the above embodiments, that the present invention also relates to a rotary separator. The present invention therefore also relates to a rotary separator for use in the method according to the present invention, wherein the rotary separator is continuously operable, wherein the rotary separator is designed to at least partially separate a liquid phase of a multiphase fluid flow containing process material from a gaseous phase containing carrier material and process material, so that the resulting prepared gaseous phase contains carrier material and process material, and the material quantity fraction of the process material in the prepared gaseous phase is 50% or more of the material quantity fraction of the process material in the gaseous phase of the multiphase fluid flow.

[0067] The rotary separator according to the invention is particularly preferred because the method according to the invention can be implemented particularly efficiently with it. A preferred design of the rotary separator according to the invention is given below, which is used to implement the preferred method according to the invention and can be considered particularly advantageous for these reasons.

[0068] The rotary separator according to the invention is therefore preferred, wherein the rotary separator is a fluid machine, a rotary filter, a rotary channel separator or a disk separator, wherein the rotary separator is preferably a disk separator.

[0069] Also preferred is a rotating separator according to the invention, wherein the rotating separator has a heating device for temperature control of the inner wall of the working chamber.

[0070] Likewise preferred is a rotating separator according to the invention, wherein the rotating separator is a disk separator, wherein the distance between the disks is less than 0.6 mm, preferably less than 0.3 mm, particularly preferably less than 0.2 mm.

[0071] Furthermore, preference is given to a rotating separator according to the invention, wherein the rotating separator is a disk separator, wherein the disks have an average surface roughness Rz of 25 μm or less, preferably 10 μm or less, particularly preferably 6.3 μm or less.

[0072] Furthermore, a rotating separator according to the invention is preferred, wherein the rotating separator is a disk separator, wherein at least one of the disks, preferably all of the disks, particularly preferably all of the components of the disk separator that are in contact with the fluid flow are made of a material that repels the process material or are coated with a material that repels the process material, wherein the process material has a contact angle on the material that repels the process material in the range of 70° or more, preferably 80° or more, particularly preferably 90° or more, and more particularly preferably 100° or more.

[0073] Likewise preferred is a rotating separator according to the invention with a non-rotating pre-separator and / or a non-rotating after-separator.

[0074] Furthermore, preference is given to a rotary separator according to the invention, wherein the rotary separator has a separation degree of 70% or more, preferably 80% or more, particularly preferably 90% or more, with respect to liquid particles having a diameter of less than 1 μm.

[0075] In connection with the present invention, the use of such a rotating separator is also disclosed for continuously preparing a multiphase fluid flow during the operation of a fuel cell, in particular a polymer electrolyte fuel cell, in order to extend the service life of the fuel cell when operating at a power of less than 20%, preferably less than 10% of the maximum power.

[0076] Finally, the present invention also relates to a fuel cell system, in particular a polymer electrolyte fuel cell system, having a fluid line system for supplying fluid to at least one electrode of the fuel cell, in particular an anode, wherein such a rotating separator is arranged in at least one fluid line for continuously preparing a multiphase fluid flow.

[0077] The corresponding fuel cell system according to the present invention is advantageous because the method according to the present invention can be implemented therein and the fuel cell can be operated for extended periods even at low load, thereby preventing drying out of the electrolyte membrane. Furthermore, the rotating separator advantageously enables sufficient supply of recirculated fuel to the fuel cell even at low loads and correspondingly low power. This advantageously achieves high operational reliability and a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Next, the present invention and preferred embodiments of the present invention will be further explained and described with reference to the accompanying drawings. In the drawings, it is shown:

[0079] Figure 1 A schematic diagram shows a particularly preferred embodiment of the rotary separator according to the invention, with which the method according to the invention can be carried out in a preferred design. DETAILED DESCRIPTION

[0080] Figure 1 A schematic diagram of a rotary separator according to the invention is shown in a particularly preferred embodiment.

[0081] The rotating separator 10 shown is suitable and designed for use in the method according to the invention and is a continuously operable disc separator.

[0082] according to Figure 1 The rotating separator 10 is arranged in a fluid line system (not shown) on the anode side of a polymer electrolyte fuel cell system and serves therein to continuously produce a multiphase fluid stream, in particular comprising hydrogen and water.

[0083] exist Figure 1 In the example shown, the rotary separator 10 is designed to at least partially separate a liquid phase, in particular water, of a multiphase fluid flow from a gas phase comprising hydrogen, water, and optionally nitrogen. This can advantageously be accomplished using the rotary separator 10 according to the invention such that the resulting prepared gas phase comprises hydrogen and water, and the mass fraction of water in the prepared gas phase is 50% or more of the mass fraction of water in the gas phase of the multiphase fluid flow, i.e., before preparation.

[0084] The multiphase fluid flow enters the rotating separator 10 from below, as indicated by the solid arrows. A conveying device, located below the working chamber 16, ensures fluid transport through the rotating separator 10. The rotating separator 10 includes a disk stack comprising a plurality of disks 12, which is driven in rotation by an electric motor 14. The electric motor 14 allows for adjustment of the separation power. Separation occurs via the disk stack, with the separated liquid phase being discharged at the right edge in the example shown, as indicated by the non-solid arrows.

[0085] The prepared gas phase, which, in addition to the carrier material hydrogen, also contains gaseous water, is conducted away in the opposite direction to the left in the schematic diagram and is recirculated to the fuel cell.

[0086] according to Figure 1 The rotating separator 10 has a heating device (not shown) for controlling the temperature of the inner wall of the working chamber 16 and has a distance of 0.25 mm between the disks 12. The average surface roughness of the surfaces of the disks 12 is 6.3 μm. The disks 12 of the rotating separator 10 are made of polytetrafluoroethylene, and the inner wall of the working chamber 16 is coated with polytetrafluoroethylene.

[0087] according to Figure 1 The exemplary rotary separator 10 has a separation degree of 70% or more with respect to liquid particles having a diameter of less than 1 μm.

[0088] Reference Signs List

[0089] 10 Rotating separator

[0090] 12 plates

[0091] 14 electric motors

[0092] Studio 16

Claims

1. A method for continuously producing a multiphase fluid flow during operation of a fuel cell, the method comprising the steps of: a) providing a multiphase fluid stream having a gas phase and a liquid phase, wherein, The gas phase comprises a carrier material and a process material, wherein the liquid phase comprises the process material, the process material being water, b) introducing the multiphase fluid flow into a continuously operable rotating separator (10), c) at least partially separating the liquid phase from the multiphase fluid stream by means of the rotary separator (10) to produce a prepared fluid stream with a prepared gas phase, 98% by weight or more of the liquid phase being separated, The prepared gas phase comprises a carrier material and a process material, wherein the material amount proportion of the process material in the prepared gas phase is 50% or more of the material amount proportion of the process material in the gas phase of the multiphase fluid flow.

2. The method according to claim 1, wherein The separation in step c) is carried out such that the prepared fluid stream has a liquid phase with a mass fraction of 0.05% to 2%, based on the mass of the prepared fluid stream.

3. The method according to claim 1 or 2, wherein: The rotating separator (10) has a temperature of 60°C or higher on the inner wall of the working chamber (16).

4. The method according to claim 1 or 2, wherein The rotating separator (10) is a fluid machine, a rotating filter, a rotating channel separator or a disc separator.

5. The method according to claim 4, wherein The rotating separator (10) is a disc separator, wherein the disc (12) has an average surface roughness Rz of 25 μm or less.

6. The method according to claim 4, wherein The rotating separator (10) is a disc separator, wherein the distance between the discs (12) is less than 0.6 mm.

7. The method according to claim 4, wherein: The rotating separator (10) is a disc separator, wherein at least one of the discs (12) is made of or coated with a material that repels the process material, wherein the process material has a contact angle of 90° or more on the material that repels the process material.

8. The method according to claim 1 or 2, wherein: The rotating separator (10) is driven by an electric motor (14).

9. The method according to claim 2, wherein: The separation in step c) is carried out such that the prepared fluid stream has a liquid phase with a mass fraction of 0.1% to 1% relative to the mass of the prepared fluid stream.

10. The method according to claim 2, wherein: The separation in step c) is carried out such that the prepared fluid stream has a liquid phase with a mass fraction of 0.2% to 0.5%, relative to the mass of the prepared fluid stream.

11. The method according to claim 3, wherein The rotating separator (10) has a temperature of 70°C or higher on the inner wall of the working chamber (16).

12. The method according to claim 3, wherein: The rotating separator (10) has a temperature of 80°C or higher on the inner wall of the working chamber (16).

13. The method according to claim 5, wherein: The disk (12) has an average surface roughness Rz of 10 μm or less.

14. The method according to claim 5, wherein The disk (12) has an average surface roughness Rz of 6.3 μm or less.

15. The method according to claim 6, wherein The distance between the discs (12) is less than 0.3 mm.

16. The method according to claim 6, wherein The distance between the discs (12) is less than 0.2 mm.

17. The method according to claim 7, wherein: The entire disc (12) is made of or coated with a material that repels the process material.

18. The method according to claim 7, wherein: All components of the disc separator that are in contact with the fluid flow are made of or coated with a material that repels the process material.

19. The method according to claim 7, wherein: The process material has a contact angle of 100° or greater on the material that repels the process material.

20. The method according to claim 8, wherein The electric motor (14) is mounted in a housing which is impermeable to the carrier material and / or the process material.

21. The method according to claim 8, wherein The delivery capacity and / or separation capacity of the rotating separator (10) can be controlled by the power of the electric motor (14).

22. A rotary separator (10) for use in a method according to any one of claims 5 to 8, wherein: The rotating separator (10) is capable of continuous operation, wherein the rotating separator (10) is designed to at least partially separate a liquid phase of a multiphase fluid flow containing process material from a gas phase containing carrier material and process material, so that the prepared gas phase obtained contains carrier material and process material and the material amount share of the process material in the prepared gas phase is 50% or more of the material amount share of the process material in the gas phase of the multiphase fluid flow, the rotating separator (10) is a disc separator, and the disc (12) has an average surface roughness Rz of 25 μm or less.

23. A fuel cell system comprising a fluid line system for supplying a fluid to at least one electrode of the fuel cell, wherein: A rotating separator according to claim 22 is arranged in at least one fluid line for the continuous production of a multiphase fluid flow.

24. The fuel cell system according to claim 23, wherein: The fuel cell system is a polymer electrolyte fuel cell system.

25. The fuel cell system according to claim 23, wherein: The fuel cell system has a fluid line system for supplying fluid to the anodes of the fuel cell.

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