Apparatus and method for processing gases

Abstract

The present invention relates to an apparatus and a method for processing gases.

Description

[0001] Device and method for the treatment of gases

[0002] The present invention relates to a device and a method for the treatment of gases, in particular for electrochemical hydrogen separation.

[0003] Hydrogen has a wide range of uses as an energy carrier. Hydrogen can be produced, for example, through electrolysis or by reforming hydrocarbons (e.g., methane), ethers, and alcohols (e.g., methanol), as well as by decomposing other hydrogen-containing molecules (e.g., ammonia). The hydrogen can either be used at the site of its production or transported to the site of use or energy conversion.

[0004] Fuel cells, for example, can be used to convert hydrogen into electrical energy. Some fuel cell types benefit from humidifying the anode gas and / or cathode gas supplied to the fuel cell, resulting in increased performance and / or extended service life.

[0005] To transport hydrogen from its production to its point of use, it is possible to feed the hydrogen into the natural gas grid and then separate it from the natural gas at the point of use. The hydrogen can be separated from the natural gas grid using electrochemical hydrogen separation. Unlike other purification technologies, electrochemical hydrogen separation is highly efficient at separating hydrogen from a gas mixture that contains a small proportion of hydrogen (e.g. 10 vol% H2). The hydrogen-containing gas is fed to cells. This can be pumped using a compressor or a blower, for example. By applying an electrical voltage to the cell electrodes, the hydrogen is split into protons and electrons at the anode electrodes. The protons migrate through a cell membrane.At the opposite cathode electrode, the protons and electrons are converted back into hydrogen. Since the other gas components (e.g., methane) have difficulty migrating or diffusing through the membrane, the hydrogen gas produced at the cathode electrode is very pure. The purity of the separated hydrogen is typically between 99.5% and 99.999%. If higher purity is required, the electrochemical hydrogen separation can be followed by one or more stages of electrochemical hydrogen separation or another purification stage (e.g., temperature swing adsorption, pressure swing adsorption). The remaining natural gas, which has been depleted of hydrogen to a certain extent, can be passed on for further use.This may involve applications that tolerate little or no hydrogen in natural gas, for example, engines, which have a shortened service life if a certain proportion of hydrogen is present in the natural gas. On the other hand, natural gas that has been depleted of hydrogen to a certain proportion can be fed back into the natural gas grid in whole or in part. For this to happen, the natural gas must meet the requirements of the natural gas grid operators and, for example, must not exceed a certain limit for water vapor or fall below a certain limit for odorants.

[0006] Electrochemical hydrogen separation is also useful for separating hydrogen from reformate gas. For example, hydrogen-containing reformate gas produced from the reforming of biogas or methanol can be used as feed gas. The separated hydrogen can either be used directly or further processed to achieve higher purity, for example, through additional hydrogen separation stages or other purification processes (e.g., temperature swing adsorption, pressure swing adsorption). The hydrogen can then be used, for example, for mobility applications (fuel cell vehicles).

[0007] Hydrogen transport or storage is also politically intended in the form of ammonia. If ammonia is converted back into hydrogen-containing gas, the hydrogen can be separated from the hydrogen-containing gas mixture by electrochemical hydrogen separation. The gas mixture may also contain residual ammonia.

[0008] Hydrogen can also be separated from other hydrogen-containing gases and used to produce hydrogen. For example, the hydrogen-containing gas can be obtained from fermentation, biogas, pyrolysis, decomposition, or through synthesis using bacteria. The hydrogen content can be between 1 and 50 mol%. This hydrogen can be separated by electrochemical hydrogen separation. Another application of electrochemical hydrogen separation is the separation of hydrogen from helium-containing gases, for example in the extraction of helium from gas from underground deposits. In this case, the gas originating from underground deposits or from the ground often contains both hydrogen and helium, along with many other gases such as methane, carbon dioxide, and nitrogen. Other processes (e.g.In membrane gas separation (membrane gas separation, pressure swing adsorption) the separation of hydrogen and helium is very difficult, whereas this is easily feasible for electrochemical hydrogen separation and both the valuable helium and the hydrogen can be sold or used.

[0009] For the separation of hydrogen from gases by electrochemical hydrogen separation, a proton-conducting membrane made of a polymer containing sulfonic acid groups (e.g., perfluorosulfonic acid polymer) or a polymer coated with a proton-conducting electrolyte (e.g., phosphoric acid-doped polybenzimidazole or cesium hydrogen sulfate / cesium dihydrogen phosphate) is typically used. The electrodes typically contain or are coated with a catalyst (e.g., a platinum-containing catalyst).

[0010] A fuel cell stack can be operated not only in fuel cell mode, but also in hydrogen separation mode.

[0011] During fuel cell operation, a fuel containing hydrogen atoms (e.g., methanol) or hydrogen molecules and an oxidizing agent such as atmospheric oxygen are fed into the fuel cell stack. This creates an electrical potential that can be used as electrical energy.

[0012] In hydrogen separation, as well as in electrolysis and electrochemical reforming, a substance containing hydrogen atoms or hydrogen molecules is added to the cell stack, and an electrical voltage is applied to the cell stack. This produces hydrogen at an electrode.

[0013] It is therefore possible to use an electrochemical cell stack sequentially as a fuel cell to generate electrical energy or as a hydrogen separator for electrochemical hydrogen separation.

[0014] To enable proton conduction or to increase conductivity, some membranes and electrolytes require water humidification. When cells are operated in fuel cell mode, water is produced at an electrode through the chemical reduction of supplied oxygen, which serves as an oxidant for the fuel cell reaction. Because of the water produced during fuel cell operation, some fuel cell types do not require water humidification of the supplied gases. For example, high-temperature polymer electrolyte fuel cells (HT-PEM) are generally operated without water humidification.

[0015] However, if the same or similar cells are operated in hydrogen separation mode, i.e. current is applied to the cell stack and the protons are forced through the membrane by the electrical potential, water is generally not produced. Since the membrane and / or the electrolyte is drier or completely without water when operated without humidification, this significantly impairs the hydrogen separation performance and the efficiency of the cell stack, for example when phosphoric acid is used as the electrolyte, so that operation is not or only poorly economical. If membrane electrode assemblies, which are also used for HT-PEM fuel cells and are based on phosphoric acid as the electrolyte, are used for electrochemical hydrogen separation, the phosphoric acid polymerizes or reacts at temperatures above around 110 °C, particularly at operating temperatures above 150 °C.170 °C, among other things, to polyphosphoric acid and / or diphosphoric acid, because, unlike fuel cell operation, no water is generated on the cathode, which would cause a reverse reaction of polyphosphoric acid or diphosphoric acid to form orthophosphoric acid. The resulting polyphosphoric acid and other compounds formed by condensation of phosphoric acid molecules are typically significantly less proton-conductive than orthophosphoric acid. This impairs the operation of the electrochemical hydrogen separation process, for example, in terms of efficiency, performance, and service life. This would result in increased electricity costs and thus high operating costs.

[0016] For this reason, humidification can be carried out for the operation of cells in hydrogen separation mode. The water content of the humidification can, for example, be 0.1 to 5 mol% or 0.5 to 3 mol% of the feed gas. Humidification can take place on the anode side and / or the cathode side, for example by enriching the feed gas flowing into the anode inlet or a gas flowing into the cathode inlet, which serves for purging or targeted humidification. The enrichment of the gas with water can, for example, be achieved by evaporation (e.g., heating the liquid water or flowing the gas over liquid water at approximately room temperature) or by aerosol formation (e.g., using an ultrasonic nebulizer). Cell stacks with membrane electrode assemblies with a low-temperature polymer electrolyte membrane (e.g.,Perfluorosulfonic acid polymers (perfluorosulfonic acid polymers) generally require humidification with steam to function, both in fuel cell operation and in hydrogen separation mode. Proton transport occurs primarily via the Grotthus mechanism via the water molecules. Protons are provided by the sulfonic acid groups. For cell stacks with electrolyte membranes without a liquid electrolyte at operating temperature, or for low-temperature PEM cell stacks operating at temperatures below 90°C, humidification of the gases supplied to the cell stack or the membrane is generally essential to enable proton conductivity of the membrane and thus economical operation. For high-temperature PEM cell stacks, however, humidification is not absolutely necessary but improves economic efficiency.The amount of humidification required for low-temperature PEM cell stacks is also generally significantly higher than for high-temperature PEM cell stacks. For low-temperature PEM cell stacks, the required humidification (or water content) of the gas(es) supplied to the cell stack is, for example, more than 5 mol%, more than 10 mol%, more than 20 mol%, or more than 30 mol% of water and must always be applied during operation. Suitable humidification (or water content) for high-temperature PEM cell stacks is, for example, less than 5 mol% or less than 3 mol% of water and does not always need to be applied.

[0017] If the retentate gas flowing out of a cell stack for electrochemical hydrogen separation is to be reused or, for example, fed into a natural gas pipeline or fed back into it, the water vapor from the retentate gas from the hydrogen separation must be largely removed. Drying can be achieved, for example, by temperature reduction, absorption drying (e.g., glycol drying), or adsorption drying (e.g., pressure swing adsorption or temperature swing adsorption with adsorption). This drying process is energy-intensive. The drying process can require a similar amount of energy as the hydrogen separation itself. This energy consumption significantly increases electricity costs and operating costs. If the waste heat from the cell stack is at least partially used for drying - for example, to operate a sorption device - this leads to significant energy savings.

[0018] Heat exchangers can be located before and after the cell stack. If the feed gas is significantly colder than the cell stack, the feed gas can be preheated using heat exchangers to avoid an uneven temperature distribution in the cell stack. If the feed gas is significantly warmer than the cell stack, the feed gas can be cooled using heat exchangers to avoid an uneven temperature distribution in the cell stack. To ensure that the energy of the heat flow from the feed gas is not wasted, it can be used for further heat transfer or processes. One or more heat exchangers can be located after the cell stack, which, for example, transfer the heat from the gas discharged from the cell stack to the gas being fed to the cell stack via heat transfer or to another process or another feed gas (e.g. upstream of another cell stack).A heat exchanger can also be located upstream of a compressor, for example, if the gas supplied to the compressor has a high temperature and therefore the compressor does not require high temperature resistance. A heat exchanger can also be located downstream of the compressor, for example, to dissipate generated waste heat.

[0019] The present invention can also be used, for example, for electrochemical hydrogen compression. In this case, the driving force of the electrical energy generates a higher pressure on the separated hydrogen side than on the feed gas side supplied to the cell stack. Electrical hydrogen separation and electrical hydrogen compression can be performed simultaneously using the same cell stack.

[0020] Parts of the invention can in principle also be applied to electrolyzer cell stacks or other electrochemical cell stacks or other cell stacks (e.g. cell stacks as diffusion devices or cell stacks for reforming or cell stacks as reactors) instead of to cell stacks for electrochemical hydrogen separation or electrochemical hydrogen compression as well as to fuel cell stacks.

[0021] To prevent contaminating the separated hydrogen during hydrogen separation in the event of possible pinholes in one or more membranes or other leaks within the cell stack, the pressure on the cathode side (permeate gas side, side with separated hydrogen, cathode off-stream) can be regulated higher than on the anode side (retentate gas side, anode off-stream). Gas flows through leaks, for example due to a membrane defect, would thus only flow from the permeate side to the retentate gas side, but not vice versa. The pressure difference of the gas between the anode and cathode sides can be, for example, less than 10 or 30 or 50 or 100 or 1000 or 5000 or 10000 or 30000 or 50000 mbar. The gas pressure in the cell stack can be regulated, for example, using proportional valves or mechanical pressure regulators. The feed gas pressure in front of the cell stack can also be regulated, for example, by proportional valves or pressure reducers.This is particularly relevant if a compressor is located before or after the cell stack. Temperature swing adsorption (TSA) is a long-established process for cleaning and dehumidifying gas streams. It exploits the property that different gas components adsorb to varying degrees on adsorbents (e.g. molecular sieve, silica gel, activated alumina, activated carbon, zeolite) and then desorb them again when the temperature increases. For example, unwanted gaseous substances (e.g. ammonia, water, CO2) can be removed from methane or hydrogen by adsorbing them on adsorbents in a TSA adsorber bed and, during a regeneration phase at elevated adsorber bed temperature, desorbing them again and expelling them from the adsorber by means of a regeneration gas volume flow. The regeneration gas volume flow is generally significantly lower than the process gas volume flow flowing into the adsorber for adsorption.For regeneration, either the adsorber is heated or hot gas is flowed through it. Typically, at least two adsorbers are used. For example, one adsorber can be in adsorption mode while the other is in regeneration mode. A disadvantage of TSA, however, is that it is very energy-intensive, as heat is required for regeneration.

[0022] Electrochemical hydrogen separation (EHS) is used for the energy-efficient separation of hydrogen from gas streams using electrical energy. The separated gas (here, hydrogen) is referred to as permeate gas, and the remaining gas not separated is referred to as retentate gas. The purity of the separated hydrogen depends on the feed gas composition, as some gases can diffuse through the membrane. However, the purity of the separated hydrogen, at 99.5 to 99.99%, is not pure enough for some applications. For example, strict purity specifications for automotive applications may not be met. For example, the SAE J2719 standard specifies a hydrogen concentration of over 99.97% with, among other things, less than 5 ppm water, less than 2 ppm hydrocarbons, 5 ppm oxygen, 2 ppm CO2, 0.2 ppm CO, 0.004 ppm sulfur, and 0.1 ppm ammonia.The separated hydrogen and, if applicable, the retentate gas must also be dry, i.e., water-free, for example, when fed back into the gas grid. However, electrochemical hydrogen separation is more energy-efficient if the feed gas is humidified with, for example, 0.5 to 5 vol% water. The reason for this is that, for example, within 50 hours, more and more phosphoric acid is converted to pyrophosphoric acid or polyphosphoric acids if no water is present in the MEA. This process is reversible. If the feed gas is humidified again, the pyrophosphoric acid or polyphosphoric acid is converted back to phosphoric acid, and the MEA once again has a low cell voltage during hydrogen separation, thus becoming more energy-efficient due to the humidification. Typically, the feed gas is humidified with water for this purpose (e.g., via an evaporator).

[0023] The object of the present invention is to provide a device and a method with which an efficient, cost-effective and long-lasting hydrogen separation (EHS) and / or hydrogen compression (EHC) is possible while complying with the necessary requirements for the retentate gas and / or permeate gas.

[0024] According to a first aspect of the present invention, a device for processing a hydrogen-containing feed gas is provided. This device comprises a cell stack for electrochemical hydrogen separation to form a retentate gas and a permeate gas from the feed gas, a sorption device or diffusion device connected to the cell stack via a line, and a heat transfer device that thermally couples the cell stack and the sorption device and / or the diffusion device such that the thermal energy required for processing the at least one or more gases (feed gas, retentate gas, and / or permeate gas) in the sorption device or diffusion device is provided at least partially by waste heat from the cell stack.

[0025] The technical characteristics of this aspect apply analogously to both a process and a corresponding device.

[0026] The hydrogen-containing feed gas is introduced into the cell stack, where retentate gas is usually retained and permeate gas is formed, which escapes from the cell stack in the form of hydrogen. The feed gas is thus split into retentate gas, which is retained by a membrane of the cell stack and usually escapes from the cell stack, and permeate gas, which escapes from the cell stack.

[0027] Using a cell stack for electrochemical hydrogen separation, the present invention can provide for processing or separating the feed gas. This also includes drying or removing certain substances upstream or downstream of the cell stack.

[0028] "Processing" is therefore understood to mean separating, drying, humidifying, removing substances, or cleaning. The sorption device can be one or more Temperature Swing Adsorption (TSA) systems upstream or downstream of the cell stack and / or one or more Pressure Swing Adsorption (PSA) or Vacuum (Pressure) Swing Adsorption (VSA or VPSA) systems, or Electric Swing Adsorber (ESA) with additional temperature cycling.

[0029] Alternatively, the sorption system can be an absorption system, for example. For example, carbon dioxide and / or hydrogen sulfide can be removed through amine scrubbing, or water can be removed through glycol drying. In absorption, the waste heat from the stack can also be used to regenerate the absorbent.

[0030] Utilizing the waste heat from the cell stack can save a lot of energy, as drying the retentate gas after an EHS is very energy-intensive. For example, if the retentate gas is to be fed back into the natural gas grid, it must be dry. When hydrogen is separated from helium, the helium must also be dry to be sold as a product.

[0031] The waste heat from the cell stack can also be used to clean the permeate gas after the EHS cell stack or to pre-clean the feed gas before the EHS cell stack, thus saving energy.

[0032] By cleaning the permeate gas downstream of the EHS cell stack using an adsorber, a further EHS stage (i.e. another downstream EHS cell stack) can be avoided, which is significantly more expensive than an adsorber, so costs are also lower.

[0033] The cell stack can be a high-temperature polymer electrolyte membrane cell stack (HT-PEM cell stack) operating in a temperature range of 110 to 270 °C.

[0034] Phosphoric acid can be used as the proton-conducting electrolyte for the cell stack. An alternative electrolyte is also possible, provided membranes without phosphoric acid are available. The electrolytes used in solid acid fuel cells (SAFCs), for example, consist of cesium hydrogen sulfate / cesium dihydrogen phosphate and are also operated in a high temperature range (e.g., above 230°C). If these are contained in a membrane, the SAFC cells can also be classified as high-temperature PEM cells. The heat transfer device can comprise a liquid and / or a gas, such as permeate gas or retentate gas, for heat transfer in order to heat or provide a regeneration gas; the permeate gas or retentate gas itself can also be the regeneration gas.

[0035] The thermal energy to heat the regeneration gas for the treatment or regeneration of one or more sorption devices can be provided by the waste heat of a cell stack to more than 30%, or more than 50%, or more than 70%, or more than 90%, or approximately 100%.

[0036] This means that, according to the invention, the waste heat of the high-temperature cell stack is used to a large extent or predominantly for the regeneration of one or more sorption devices.

[0037] The thermal energy for regenerating at least one sorption device can be obtained at least partially from the waste heat of a cell stack, and the waste heat of the cell stack can be transferred to the adsorber bed and / or to the regeneration gas flowing into the adsorber bed by a liquid or a gas, and / or the waste heat of the cell stack can be transferred to the adsorber bed and / or to the regeneration gas flowing into the adsorber bed by hot exhaust air or hot gas, and / or the waste heat of the cell stack can be transferred to the adsorber bed and / or to the regeneration gas flowing into the adsorber bed by thermal contact. This can also be applied to the regeneration of other types of sorption devices (e.g., absorber liquid from a glycol dryer or amine scrubber) instead of adsorber beds.

[0038] Furthermore, the thermal energy can originate from the waste heat of a sorption device regenerating at that time and / or from a regeneration gas flowing from a sorption device and / or partly from an additional energy source.

[0039] A cell stack whose waste heat is used to regenerate an adsorber bed can have an average temperature of 100 to 270 °C or 140 to 220 °C or 160 to 200 °C.

[0040] The waste heat from a cell stack used to regenerate an adsorber bed can have a temperature of 80 to 250 °C or 130 to 190 °C. After flowing through a sorption device to regenerate the corresponding adsorber bed, the regeneration gas can additionally flow through at least one additional adsorber bed of a sorption device and also regenerate this adsorber bed, or the regeneration gas can flow through three or more sorption devices in succession.

[0041] According to an advantageous embodiment, the water condensed during regeneration of the adsorber device, or a part thereof, can be fed back into the device upstream of the cell stack to humidify the cell stack.

[0042] The process of removing water is called drying, except when water is also separated or removed, where the purpose is actually to separate or remove another substance.

[0043] The waste heat of the HT-PEM cell stack can be used to operate one or more of the sorption devices, whereby the sorption device can comprise one or more Temperature Swing Adsorption (TSA) devices and / or one or more Pressure Swing Adsorption (PSA) devices and / or one or more VSA or VPSA devices.

[0044] In particular, the sorption device may comprise one or more adsorption devices upstream and / or downstream of the cell stack.

[0045] The retentate gas separated during processing in the cell stack can, for example, contain predominantly helium, nitrogen, methane or carbon dioxide or can be natural gas that can be fed back into a gas network.

[0046] The permeate gas generated in the cell stack can be separated hydrogen.

[0047] In the case of a diffusion device, the permeate gas can also be substances other than hydrogen that have a small molecular size and can therefore permeate or diffuse through the membrane (e.g., in the form of atoms or molecules). A diffusion device can, for example, comprise polymer membranes, polymer capillaries, or membranes or capillaries that contain or consist of a metal (e.g., palladium or vanadium). The molecules or atoms can, for example, be driven from the feed gas side to the permeate gas side by a pressure difference, with a higher pressure on the feed gas side than on the permeate gas side. For efficient operation, some diffusion devices must have a high temperature (e.g., over 80 °C, over 120 °C, over 200 °C, or over 300 °C). Heating for this purpose can be provided, at least in part, by the waste heat from an EHS cell stack in order to save energy.For example, operating polymer capillaries or polymer membranes at 80 to 150 °C is recommended to avoid fouling or condensation / adhesion of high-boiling components. Palladium-based membranes require high operating temperatures (e.g., over 250 °C) to achieve an economical permeability rate through the membrane.

[0048] In electrochemical hydrogen separation (EHS), on the other hand, only hydrogen (with possibly small amounts of impurities diffused through the membrane) is the permeate gas, since in EHS protons migrate through the membrane.

[0049] Preferably, the retentate gas and / or the permeate gas flowing out of the cell stack can be dried by means of a temperature swing adsorption system (TSA), which is a sorption device.

[0050] A diffusion device (e.g., pressure-driven polymer membranes or polymer capillaries) can pre-clean the feed gas flowing into an EHS cell stack. The permeate gas from the diffusion device flows into the anode inlet of the EHS cell stack.

[0051] The permeate gas flowing from a cell stack can be further purified by a diffusion device (e.g., using palladium-containing membranes). If the pressure of the permeate gas flowing from the cell stack (e.g., through electrochemical hydrogen compression) is sufficiently high (e.g., over 5, 10, 20, 30, or 40 bara), the gas may not need to be further compressed to operate the diffusion device.

[0052] If the permeate gas flowing from a cell stack operating as an electrochemical hydrogen compressor is introduced into a PSA for purification or drying, the gas may not need to be further compressed for the operation of the PSA, provided the pressure of the permeate gas flowing from the cell stack is sufficiently high (e.g., above 5 or 10 or 20 or 30 or 40 bara).

[0053] Preferably, the retentate gas and / or the permeate gas can be cooled by a cooling device arranged between the cell stack and the sorption device before flowing into the sorption device, so as not to impair adsorption in the sorption device. The feed gas can be pre-cleaned by a sorption device or diffusion device upstream of the cell stack, for example, to remove ammonia, carbon monoxide, alcohols, aldehydes, hydrogen sulfide, sulfur-containing substances such as odorants, or other pollutants such as alkenes / alkynes, or to largely separate residual gases such as methane, carbon dioxide, helium, or nitrogen. The waste heat from the cell stack can also be used for this purpose.

[0054] Alternatively, alkenes and / or alkynes can be reacted (e.g., polymerized) upstream of the cell stack, preventing them from entering the cell stack. The waste heat from the cell stack can be utilized for this purpose, possibly with the aid of a catalyst or exciting radiation.

[0055] To regenerate one or more adsorber beds of the sorption device(s), a portion of the gas cleaned and / or dried by the sorption device(s) can be removed, then optionally preheated by a heat exchanger using a gas flowing out of the sorption device(s), and then heated by waste heat from the cell stack, and optionally brought to a higher temperature level by slight reheating, whereby the gas is referred to as regeneration gas and is passed through the adsorber bed(s) to be regenerated in order to regenerate them.

[0056] When drying using a regeneration gas, pre-drying can also be carried out in a first adsorber bed at a medium-high temperature (e.g. regeneration of silica gel at 50 to 200 °C) using waste heat from a cell stack, followed by further heating to a higher temperature of the regeneration gas in order to regenerate in another adsorber bed at a high temperature (e.g. regeneration of molecular sieve at 150 to 400 °C). The high operating temperature for regenerating the adsorber bed with a high temperature (e.g. molecular sieve) can be kept significantly shorter than the operating temperature of the adsorber bed with a medium-high temperature (e.g. silica gel), since the silica gel, for example, contains the majority of the moisture, while the molecular sieve, for example, only removes the remaining residual moisture and therefore contains less water. This can save energy, since a lot of the waste heat from the cell stack can be used and yet, for example,Complete drying or very low residual moisture can be achieved using a molecular sieve. This concept can be used not only for drying but also for the removal or separation of substances.

[0057] In addition, a heat pump or an electric heating device can be provided to cool the permeate gas or retentate gas of the cell stack flowing from the cell stack into a sorption device or separation device and / or to heat the regeneration gas or an evaporation device upstream of the cell stack.

[0058] The retentate gas flowing out of the cell stack (e.g. natural gas to be fed back into the gas grid) can be further purified or dried by sorption device(s) or diffusion device(s) and / or the permeate gas flowing out of the cell stack (separated hydrogen) can be further purified or dried by sorption device(s) or diffusion device(s) in order to meet strict purity requirements of the purified gas.

[0059] The cell stack can be operated as an electrochemical hydrogen separator and / or electrochemical hydrogen compressor for at least 95% of its operating time, wherein a hydrogen-containing feed gas is supplied at the anode and hydrogen is separated or generated at the cathode of the cell stack by an electrical voltage applied to the cell stack, wherein protons migrate from the anode to the cathode through a proton-conducting membrane and / or proton-conducting layer, proton-conducting liquid, proton-conducting foil or proton-conducting plate.

[0060] Ammonia and / or alkaline substances, alcohols, methanol, aldehydes, hydrogen sulfide, carbon monoxide, odorants, sulfur-containing substances, oxygen, high boilers, alkynes, and / or alkenes can be removed or separated from the feed gas upstream of the cell stack(s) or upstream of another device via a sorption device located upstream of the cell stack(s) or upstream of another device. At least some of the waste heat from a cell stack(s) can be utilized to operate the sorption device and / or diffusion device.

[0061] Furthermore, hydrogen can be released or separated from a sorbent, sorbate or substance by means of a sorption device, and the thermal energy for releasing or separating the hydrogen can be obtained at least partially from the waste heat of a cell stack. The hydrogen obtained by releasing it from a sorbate can, for example, be further processed in a cell stack (e.g. dried / purified) and / or used as fuel for a fuel cell or for other applications. The sorbent, sorbate or substance that can release hydrogen can be a substance (solid, liquid or gas) that contains or has stored hydrogen in molecular or atomic form. For example, it can be a liquid hydrogen carrier (e.g. organic) or a metal hydride.Substances separated from the feed gas upstream of the cell stack by sorption or diffusion can be fed back into the retentate gas or permeate gas directly or indirectly downstream of this or another cell stack, whereby the fed-in substance or substances can be, for example, odorants.

[0062] The features and advantages of the device according to the invention are explained in more detail below.

[0063] The cell stack can be an HT-PEM cell stack that operates in a temperature range of 110 to 270 °C, with phosphoric acid being used as the proton-conducting electrolyte.

[0064] In the context of the present invention, the cell stack can be an HT-PEM cell stack or a cell stack of a PAFC (Phosphoric Acid Fuel Cell) or a SAFC (Solid Acid Fuel Cell) or a Solid Oxide Electrochemical Hydrogen Pump and can be used, for example, as an EHS cell stack and / or EHC cell stack.

[0065] Alternatively, an H2-permeable palladium membrane or H2-permeable polymer membrane (pressure-driven separation) can be provided in the cell stack.

[0066] A hydrogen-permeable palladium membrane or a hydrogen-permeable polymer membrane (pressure-driven separation) can also be used as the diffusion device. These require high temperatures for a high separation rate.

[0067] A sorption device, such as a TSA, is typically regenerated in a temperature range of approximately 80 to 350 °C. The temperature ranges of HT-PEM technology and TSA therefore overlap well.

[0068] Other cell stack technologies such as NT-PEM or SOFC are not suitable for combination with a TSA because the waste heat from NT-PEM is at too low a temperature level and hydrogen cannot be separated by SOFC cell stacks because they do not conduct protons.

[0069] Because the waste heat of the HT-PEM cell stack is used to operate the TSA, ideally almost no additional energy is required for its operation.

[0070] The heat transfer device can comprise a liquid and / or a gas, such as a permeate gas or a retentate gas, for heat transfer. Examples of heat transfer configurations: To utilize the waste heat from a liquid-cooled HT-PEM cell stack for the TSA, a heat transfer fluid can be circulated between the HT-PEM cell stack and the TSA system. It is also conceivable to conduct the regeneration gas from the TSA with thermal contact to the HT-PEM cell stack. In addition, the hot exhaust air from an air-cooled cell stack can be used to heat the regeneration gas or the TSA containers to be regenerated.

[0071] The waste heat of the cell stack can also be utilized by utilizing the heat from the retentate gas and / or permeate gas flowing out of the cell stack.

[0072] The thermal energy for processing or regenerating an adsorber bed can be obtained from the waste heat of a cell stack to the extent of more than 30%, more than 50%, more than 70%, more than 90% or 100%.

[0073] Phosphoric acid is preferably used as a proton-conducting electrolyte in the cell stack.

[0074] Sorption is a collective term for processes that lead to the enrichment of a substance within a phase or at an interface between two phases. Enrichment within a phase is more precisely called absorption, while enrichment at an interface is called adsorption.

[0075] The sorbing substance is called the sorbent, the sorbent, or the sorbent. The substance that has not yet been sorbed is called the sorptive, while after sorption it is called the adsorbate or absorbate. The system of the sorbed substance and the sorbent together is called the sorbate.

[0076] Sorption is usually caused by physical interactions between sorbent and sorbate. Sorption is an equilibrium process between the uptake and release (desorption) of a substance. If equilibrium does not exist, equilibrium is sought. Changes in concentration and temperature, as well as displacement reactions, influence sorption and shift the position of equilibrium. In practice, sorption processes in which certain substances are preferentially (selectively) absorbed are important. Absorption describes an equilibrium process of the incorporation (and release) of the sorbent from one phase into the volume of another phase. For example, an equilibrium is established between air (a gas phase) and water (a liquid phase), e.g. with regard to the oxygen content of both phases. Adsorption is the attachment (and deposition) of a substance from one phase to the surface (more precisely: interface) of another phase.In contrast to absorption, the internal volume of the sorbent remains unaffected and can be a solid or liquid phase. Physisorption (physical adsorption) is the general case of adsorption and is based on physical interactions between the adsorbate and the interface.

[0077] Chemisorption (chemical adsorption) is a special case of adsorption. Here, chemical bonding occurs between the adsorbate and the interface. This can lead to further chemical reactions and is an important step in heterogeneous catalysis. Chemisorption usually occurs at higher temperatures than physisorption and is limited to solid interfaces. The terms physisorption and chemisorption are usually used when describing specific processes in which a clear distinction should or can be made between chemical and physical reactions.

[0078] The waste heat of the HT-PEM cell stack can be used to operate one or more Temperature Swing Adsorption (TSA) systems and / or one or more Pressure Swing Adsorption (PSA) systems or VPSA or VSA systems.

[0079] The sorption device can be an adsorber device upstream or downstream of the cell stack.

[0080] The retentate gas (e.g. natural gas to be fed back into the gas grid) can be further purified and / or dried and / or the permeate gas (separated hydrogen) can be further purified and / or dried in order to meet strict purity requirements.

[0081] In the event that the retentate gas must be dry, i.e. largely free of water, for example in order to be allowed to feed the hydrogen-depleted retentate gas back into the natural gas network, the retentate gas can be dried using a TSA system.

[0082] The regeneration gas originates, for example, from the retentate gas dried / purified by the TSA (which flows out of the cell stack on the anode side). After flowing through an adsorber bed of the TSA for regeneration, it is cooled to condense water and discharge it as a liquid phase. The moist regeneration gas is, for example, reintroduced into the retentate gas stream flowing out of the cell stack on the anode side upstream of the TSA system. The water separated during the regeneration of the adsorber device or during drying can be fully or partially reintroduced upstream of the cell stack to humidify the incoming feed gas or the cell stack, which results in a significant reduction in the amount of water required (e.g., a much longer refill interval for a water tank). Separated or condensed electrolyte can also be recycled.

[0083] As an alternative to drying, the TSA system can be used for post-purification, provided that the retentate gas must meet certain purity criteria.

[0084] The permeate gas can be separated hydrogen, and water vapor contained therein as a result of humidification and / or temporary fuel cell operation is at least partially dried in the TSA system by means of the waste heat of the cell stack.

[0085] Alternatively, the TSA system may focus on cleaning the permeate gas (i.e. removing substances from the permeate gas).

[0086] In the event that the purity of the hydrogen separated by the EHS is insufficient (e.g., some CO2 has diffused through the cell membranes of the cell stack, resulting in 50 ppm of CO2 in the separated hydrogen), the TSA system can remove residual impurities so that the gas complies with the applicable standard (e.g., SAE J2719). For example, the CO2 content can be reduced to below 2 ppm.

[0087] The regeneration gas comes, for example, from the hydrogen purified or dried by the TSA and, after flowing through an adsorber bed of the TSA for regeneration (including small amounts of impurities), is reintroduced into the feed gas at the anode inlet of the cell stack in order to avoid wasting hydrogen.

[0088] The gas flowing from the high-temperature cell stack can be cooled by a cooler before flowing into the adsorber in order not to impair adsorption in the adsorber and to condense any electrolyte from the cell stack (e.g. phosphoric acid) and water, and feed this preferably at an anode inlet of the cell stack or into an electrolyte replenishment tank. The feed gas may contain impurities (e.g. in the case of hydrogen-containing natural gas or reformate gas as feed gas). The feed gas can be pre-cleaned using a TSA system upstream of the cell stack by removing, for example, ammonia, carbon monoxide, alcohols, aldehydes, hydrogen sulfide, sulfur-containing substances such as odorants and / or other pollutants such as high boilers or alkenes / alkynes. This is intended to improve or extend the performance, energetic efficiency and service life of the cell stack.be ensured, as these substances can impair or damage the cell stack or its operation.

[0089] To regenerate one or more adsorber beds, a portion of the gas purified by the adsorber device can be removed, subsequently preheated by a heat exchanger and then heated by the waste heat of the cell stack and, if necessary, slightly reheated to a higher temperature level for regeneration, passed through an adsorber bed to be regenerated.

[0090] A large portion of the heat is expected to come from the stack's waste heat. The contaminated regeneration gas is then introduced into the retentate gas, for example. At the end of the regeneration phase, the adsorber must be cooled. For this purpose, the purified gas is fed into the adsorber through a bypass around the heat sources, preventing heating.

[0091] If odorants have been separated from the feed gas stream using the TSA, they can be added back to the gas stream before the retentate gas stream is fed into the natural gas network.

[0092] If the feed gas is at a high pressure (e.g., a long-distance gas pipeline of a natural gas pipeline at over 20 barg), it may be advisable to reduce the pressure for operation of the cell stack upstream of the cell stack (so that the cell stack and membranes are subjected to less pressure stress) and then raise the retentate gas back to the pressure of the feed-in pipeline (e.g., a long-distance gas pipeline). The energy released when the feed gas expands is used to compress the retentate gas. Appropriate units are available for this purpose (e.g., turbines or turboexpanders).

[0093] A heat pump or an electric heating device can also be provided to cool the retentate gas or permeate gas flowing from the cell stack into the adsorber and / or to heat the regeneration gas (in addition to utilizing the waste heat from the cell stack for regeneration). A heat pump can also be used to cool the retentate gas or permeate gas exiting the cell stack, for example, to condense water, and / or to preheat the gas flowing into a cell stack and / or to utilize the thermal energy to evaporate water to humidify the cell stack.

[0094] Some odorants can be removed by chemisorption and some odorants by physisorption (e.g. TSA / PSA).

[0095] The waste heat of the cell stack can also be used to keep a non-regenerable adsorber (e.g. chemisorption) at operating temperature.

[0096] The reactor for chemisorption, e.g. for pre-cleaning the feed gas before the cell stack, requires an operating temperature of 150 °C.

[0097] Humidification of the feed gas flowing into the cell stack for electrochemical hydrogen separation can also be achieved (if necessary in addition to further humidification) by exchanging water in a diffusion device (e.g. a device with a membrane permeable to water molecules) from the retentate gas and / or permeate gas into the gas flowing into the cell stack.

[0098] Furthermore, the waste heat from a preferential oxidation (PROX) can be used for the regeneration or operation of a sorption system or, in detail, for the following processes:

[0099] In order to remove carbon monoxide from the feed gas by oxidation using oxygen that is added to the feed gas or already present in the feed gas, and thus achieve a higher efficiency of the cell stack (CO as a catalyst poison for the cells), a PROX can be installed upstream of the cell stack (or before the pre-cleaning stage). The PROX can also be used to remove oxygen (reaction of oxygen with both carbon monoxide and hydrogen to form water) if there is too much oxygen in the feed gas, which could damage the cell stack. The reactions are exothermic. The waste heat from the PROX can be used to regenerate adsorbers (e.g. TSA) or to maintain adsorbers at operating temperature (e.g. in chemisorption to remove hydrogen sulfide and / or odorants). The heat either comes solely from the PROX or is in addition to the waste heat from the cell stack.

[0100] The PROX may need to be preheated. The waste heat from the cell stack or the warm gas escaping from the PROX can be used for this purpose. The waste heat from the PROX or the waste heat from at least one cell stack can also be used to operate a water gas shift device (e.g., at 100 to 300 °C) to reduce the carbon monoxide content (e.g., upstream of the PROX).

[0101] Autothermal reforming produces waste heat that can be used to heat cell stacks and / or diffusion devices.

[0102] The cell stack can be operated as an electrochemical hydrogen separator and / or electrochemical hydrogen compressor for at least 95% of its operating time, wherein a hydrogen-containing feed gas is supplied at the anode and hydrogen is separated or generated at the cathode of the cell stack by an electrical voltage applied to the cell stack, wherein protons migrate from the anode to the cathode through a proton-conducting membrane and / or proton-conducting layer, proton-conducting liquid, proton-conducting foil or proton-conducting plate.

[0103] The permeate gas of at least one cell stack can be purified by adsorption so that the hydrogen content is at least 99.97 mol% and contains less than 0.2 micromoles per mole of carbon monoxide, less than 2 micromoles per mole of carbon dioxide and less than 2 micromoles per mole of hydrocarbons.

[0104] The permeate gas of at least one cell stack can be purified by adsorption so that the hydrogen content is at least 99.999 mol%.

[0105] The thermal energy for regenerating at least one adsorber bed can originate at least partially from the waste heat of a cell stack and from the heat of an adsorber regenerating at that time and / or regeneration gas flowing from an adsorber and / or from an additional energy source.

[0106] The waste heat of a cell stack, whose waste heat is used for the regeneration of an adsorber bed, can have a temperature of 80 to 250 °C or 130 to 190 °C.

[0107] After flowing through an adsorber bed to regenerate the adsorber bed, the regeneration gas can additionally flow through at least one further adsorber bed and also regenerate this adsorber bed, or the regeneration gas can flow through three or more adsorber beds in succession.The regeneration gas, which flows through an adsorber bed downstream of the cathode outlet of the cell stack (in the case of permeate gas) of the cell stack for the regeneration of the adsorber bed, can then flow for regeneration through a feed gas adsorber bed upstream of the cell stack and / or for regeneration through an adsorber bed downstream of the anode outlet of the cell stack (in the case of retentate gas) and / or the regeneration gas, which flows through a feed gas adsorber bed upstream of the cell stack for the regeneration, can then flow for regeneration through an adsorber bed downstream of the anode outlet of the cell stack (in the case of retentate gas) or the regeneration gas, which flows through an adsorber bed downstream of the anode outlet of the cell stack for the regeneration, can then flow for regeneration through an adsorber bed upstream of the cell stack Feed gas adsorber bed flow.

[0108] A bypass can be provided in order to be able to influence the heat exchange of the regeneration gas with the cell stack and that this bypass is opened at the end of the regeneration phase or it can be provided that the volume flow of the heat transfer medium is stopped or the thermal contact between the cell stack and the adsorber bed is interrupted in order to cool the adsorber bed or that the regeneration gas or the adsorber bed is cooled by air cooling or heat transfer fluid at the end of the regeneration phase.

[0109] It may be useful to recirculate part of the retentate gas escaping from a cell stack into the anode inlet of the cell stack (recirculation), for example to extract as much hydrogen as possible from the feed gas (e.g. helium-hydrogen mixture) or to achieve a high hydrogen recovery rate.

[0110] In the case of recirculation, a conveying device (e.g. a compressor or a pump or a blower) and, if necessary, a volume flow or mass flow measurement (e.g. mass flow meter) and, if necessary, a check valve or a controlled valve / cock / flap (to prevent gas backflow via the circuit) and, if necessary, a gas sensor (e.g. for hydrogen measurement), for example, to control the hydrogen content flowing into the cell stack by correspondingly controlling the volume flow, can be provided.

[0111] A gas sensor or gas analysis (e.g., thermal conductivity detector for determining the hydrogen concentration, an FTIR, an NDIR, a GC-MS, a gas chromatograph, a mass spectrometer, and / or another spectrometer) can be provided to continuously and / or automatically measure the composition or content of individual substances in the feed gas and / or retentate gas and / or permeate gas. For example, the purity of the permeate gas (e.g., hydrogen) may need to be determined. Or, for example, the helium content or the hydrogen fraction in the retentate gas may need to be determined to ensure a high helium concentration in the retentate gas. If the limit values ​​are exceeded or not met, automated measures can be initiated (e.g.,Changing the anode-side and / or cathode-side gas pressure, changing the temperature of the cell stack, changing the current density, changing the feed gas full flow, changing the recovery rate or stopping the operation of a cell stack or multiple cell stacks or of individual cells or cell stack compartments).

[0112] The hydrogen content of the feed gas supplied to the cell stack may not be constant, but fluctuates. For example, the hydrogen content of the feed gas may sometimes be zero, close to zero, or relatively low. Or the feed gas volume flow may sometimes be low, close to zero. To prevent the EHS cell stack from cooling down at these times (since little current density can be drawn due to the low supplied hydrogen mass flow, and thus little or no waste heat is generated), the hydrogen produced on the cathode side (i.e., the permeate gas of the cell stack) can be recirculated to the anode inlet of the cell stack at these times, so that operation at high current density (and thus regular waste heat generation) can be maintained. A switching device (e.g., a valve or valves) can be provided for this purpose.

[0113] The lifetime of the cell stack, for example in high-temperature PEM cell stacks, can be limited or reduced by the discharge of electrolyte (e.g. phosphoric acid or another acid or an ionic liquid or cesium dihydrogen phosphate or cesium hydrogen sulfate or boron phosphate), for example by evaporation during operation or droplet / aerosol discharge during start-stop cycles.

[0114] In order to achieve the longest possible service life of the cell stack, electrolyte can be supplied to or returned from the cell stack or the electrodes and / or membranes. This can take place in the gas phase, liquid phase or as a solid. For example, the electrolyte can be supplied to the electrodes and / or membranes as a liquid, or it can be supplied via the gas supplied to the cell stack in the form of smoke (e.g. phosphorus pentoxide, which can be generated from the oxidation / combustion of phosphorus and reacts with water to form ortho-phosphoric acid), or it can be supplied via the gas supplied to the cell stack as a gaseous electrolyte or as an aerosol. In this case, a device for generating gas, vapor and / or aerosol can be installed upstream of the cell stack, through which device the feed gas and / or a purge gas is charged with acid or electrolyte and flows into the cell stack.For example, an ultrasonic nebulizer can be provided to generate an aerosol containing an electrolyte, or bubbling can be provided through an electrolyte-containing solution or through electrolyte liquid at room temperature or at an elevated temperature of, for example, over 80, 100, 130, 150, 170, 200, 250 or 300 °C. Enriching the feed gas flowing into the cell stack with a small amount of gaseous acid or electrolyte can result in at least less acid or electrolyte being evaporated or discharged from the cells, in particular if the feed gas is completely or at least partially saturated with the electrolyte at the operating temperature of the cell stack. The cell stack can also contain elements or sacrificial cells for evaporating acid or electrolyte, through which the feed gas and / or purge gas flows or past and through which the feed gas and / or purge gas is saturated with acid orElectrolyte is applied within the cell stack and flows into one or more cells of the cell stack. For example, acid or electrolyte can be supplied to these elements or sacrificial cells for evaporation of acid or electrolyte from outside the cell stack (e.g., from a reservoir).

[0115] An effective method for supplying electrolyte is to supply the electrolyte in liquid form directly to the gas diffusion electrodes and / or membranes via channels in the cell stack.

[0116] For this purpose, a device for extending the service life of a cell stack, for example a high-temperature PEM cell stack, which is used for example for electrochemical hydrogen separation and / or for electrochemical hydrogen compression, can be provided, wherein a cell of the stack is constructed according to the following sequence: a supply plate with anode channel structure, an anode gas diffusion electrode, an electrolyte-containing polymer membrane, a cathode gas diffusion electrode, a supply plate with a cathode channel structure, characterized in that at least one acid reservoir or electrolyte reservoir filled or fillable with acid or electrolyte or aA fillable storage container is provided, which is connected to a distribution channel extending in the supply plates approximately perpendicular to the channel structures, wherein the distribution channel is connected to at least one of the gas diffusion electrodes and / or the polymer membrane of at least one of the cells of the cell stack in such a way that acid or electrolyte can be supplied to at least one of the gas diffusion electrodes and / or the polymer membrane of at least one of the cells of the cell stack. The acid reservoir or electrolyte reservoir can be designed, for example, as a pocket or cavity or channel or container.

[0117] The storage container can be a container (e.g. made of plastic or metal) or a hollow space.

[0118] In the acid reservoir or electrolyte reservoir and / or in the storage container, for example, phosphoric acid, sulfuric acid, an ionic liquid, a liquid polymer with acid groups or another electrolyte or electrolyte-containing mixture (e.g. with water and / or a solvent and / or with high boilers and / or with surfactant and / or with other electrolytes) is at least temporarily contained or arranged.

[0119] The distribution channel is connected, for example, to at least one of the gas diffusion electrodes and / or the polymer membrane of at least one of the cells of the cell stack via a connecting means, such as capillaries, a feed channel, a feed element, a transport aid, a reservoir or a channel-like structure.

[0120] For example, a connecting channel formed in the plane of the channel structure branches off from the distribution channel, which is connected to a supply channel located in the same plane, which forms a supply acid reservoir or supply electrolyte reservoir, whereby acid or electrolyte can be supplied to the cell via these channels.

[0121] A reservoir can be integrated into the connecting channel and / or the supply channel.

[0122] The distribution channel may be formed from distribution channel sections of each cell, wherein the distribution channel is connected to the acid reservoir or electrolyte reservoir.

[0123] A supply device for supplying acid or electrolyte from an external storage container, which is the acid reservoir or electrolyte reservoir, into the distribution channel may be provided.

[0124] In the cell stack, distribution channel sections for supplying and removing acid or electrolyte can be configured such that the acid or electrolyte can be circulated through the cell by means of a circulation device. The supply device and / or the circulation device can be controlled by a control device such that a controlled supply of acid or electrolyte to the cells of the cell stack occurs.

[0125] The feed element can be connected to the acid reservoir or electrolyte reservoir and the electrolyte-containing polymer membrane and / or the gas diffusion electrode in such a way that acid or electrolyte can be fed from the acid reservoir or electrolyte reservoir to the polymer membrane and / or the gas diffusion electrode, wherein the feed element is arranged between the polymer membrane and the gas diffusion electrode or in a region adjacent to one of the two.

[0126] The supply element can be designed as a wick or a net or made of fibers, as a capillary between polymer film(s) and / or membrane or as an absorbent body, e.g. with a high diffusion resistance and a suitable porosity, so that the acid or electrolyte can be released slowly from the body.

[0127] The feed element can be arranged in the feed acid reservoir or feed electrolyte reservoir and / or in the feed channel.

[0128] The distribution channel section can be designed as a self-contained, limited space in the supply plate and define an acid reservoir or electrolyte reservoir.

[0129] It can be a method for extending the service life of a high-temperature polymer electrolyte membrane cell stack, in which acid or electrolyte is supplied from an acid reservoir or electrolyte reservoir and / or storage container filled or fillable with acid or electrolyte via a distribution channel extending approximately perpendicular to the channel structures of a supply plate to one of the gas diffusion electrodes and / or a polymer membrane of at least one cell of a cell stack.

[0130] The supply can be carried out in such a way that the acid or the electrolyte enters the electrode layer of a gas diffusion electrode and from there into the polymer matrix of the polymer membrane and the acid or the electrolyte is distributed over the electrode layer and / or over the membrane or its boundary layer and a part of it is released to the opposite gas diffusion electrode.

[0131] The supply can be effected by means of gravity in such a way that the acid or electrolyte is supplied slowly, whereby entry of acid or electrolyte into the supply channels is prevented by arranging the reservoir or storage container below or at the level of the supply channel and thus the force acting on the acid or electrolyte is lower and the acid flow or electrolyte flow is slower.

[0132] Such or a similar cell stack has been published for use as a fuel cell in the application "EP3365935 - DEVICE AND METHOD FOR EXTENDING THE LIFESPAN OF HT-PEM FUEL CELLS" by Siqens. This concept is also intended to be applied to cell stacks for electrochemical hydrogen separation. The nomenclature and figures or illustrations can be found in the aforementioned publication.

[0133] The device for extending the service life of a cell stack by supplying acid or electrolyte can also be designed without an acid reservoir or electrolyte reservoir.

[0134] The electrolyte supply can, for example, take place alternately on the anode side of the membrane electrode assembly and on the cathode side of the membrane electrode assembly.

[0135] During the electrolyte supply, the electrolyte can be circulated through the cell stack (e.g. for less than 10 or 30 minutes or for less than 1 or 10 hours), either during operation or during a break in operation (e.g. when the cell stack is hot or cold) and, for example, after the supply, the lines / channels of the electrolyte supply can be flushed with permeate gas, feed gas or retentate gas in order to expel residual electrolyte from the lines / channels in order to avoid uncontrolled uptake of electrolyte by individual cells of the cell stack.

[0136] A channel can be connected to a reservoir filled with electrolyte or acid and should be connected to at least one of the gas diffusion electrodes and / or the polymer membrane of at least one of the cells of the cell stack in such a way that acid or electrolyte can be supplied to at least one of the gas diffusion electrodes and / or the polymer membrane of at least one of the cells of the cell stack.

[0137] The distribution channel does not necessarily have to extend approximately perpendicular to the channel structures of the supply plates, but can also or exclusively extend in other directions (e.g. parallel to the channel structures of the supply plates). High-temperature PEM membrane electrode assemblies usually contain a frame (subgasket) made of an acid- or electrolyte-resistant material that is temperature-resistant up to at least 150° or 200°C (e.g. polyimide, FEP, PFA, PTFE, PVDF, PPS, PSU, PESU, PPSU, PES, PEEK). This frame (subgasket) serves to mechanically stabilize the polymer membrane in the edge region, for example to prevent cracks in the polymer membrane. This subgasket is, for example, between 10 and 200 micrometers thick and can extend in the edge region of the gas diffusion electrode between the gas diffusion electrode and the polymer membrane or between the gas diffusion layer and the catalyst-coated membrane (CCM).Unfortunately, this area is not available for the active area of ​​the membrane electrode assembly (a smaller active area can mean a higher number of cells and thus higher costs for the cell stack). Nevertheless, this area can at least be used for the supply of acid or electrolyte. In this case, the supply channel, supply element, connecting channel, and / or the reservoir on the gas diffusion electrode or gas diffusion layer are located above the area where the subgasket is located on the polymer membrane or CCM, i.e., in an area that is not part of the active area of ​​the high-temperature PEM membrane electrode assembly. The acid or electrolyte can still pass through the gas diffusion layer or gas diffusion electrode to the polymer membrane (e.g., via capillary forces).

[0138] The acid or electrolyte can be fed in actively from a storage container, for example, via a pump or feed device. One or more valves can be provided to prevent gas or liquid flow at times when there is no supply, or to prevent leaks of the media or gases from the cell stack towards the storage container and / or to the outside. The electrolyte can, for example, be introduced into the cell stack at one or more points and led out at one or more points. Acid or electrolyte can be fed to all or some of the cells in series (i.e. one after the other). The feed can take place through the cell stack, so that the acid or electrolyte exits again at another point in the cell stack. As soon as the remaining acid or electrolyte has been used, the electrolyte can be fed in again.Electrolyte exits the cell stack again, it is ensured that all cells and / or gas diffusion electrodes and / or polymer membranes connected to the affected channels have been contacted with acid and / or electrolyte and ideally absorb the same amount of acid and / or electrolyte. This is of great importance because, for example, if the cells are fed in parallel without residual acid or electrolyte escaping, it is difficult to ensure a uniform supply or absorption of electrolyte to / through the cells and / or gas diffusion electrodes and / or polymer membranes. The channel exiting the cell stack (electrolyte outlet channel) can, for example, contain a light barrier or a sensor to detect the flow / presence of acid or electrolyte. The electrolyte outlet channel can, for example, be a hose (e.g.Made of an acid-resistant and temperature-resistant material such as PFA, PTFE, FEP, PVDF, or polypropylene, it can be at least slightly transparent to allow the functionality of an attached light barrier. The acid or electrolyte exiting the electrolyte outlet channel can either be returned to the storage tank or directed to another tank (electrolyte outlet tank).

[0139] The acid or electrolyte can be supplied to the gas diffusion electrodes and / or polymer membranes on the anode side and / or cathode side.

[0140] All channels and containers connected to acid or electrolyte (e.g., storage tanks, electrolyte outlet tanks, distribution channels, connecting channels, feed channels, etc.) can be designed to be largely gas-tight to the outside. This is intended to prevent any leakage of gas (e.g., feed gas, permeate gas, retentate gas) or acid or electrolyte to the outside. Furthermore, the channels and containers connected to acid or electrolyte can be designed to be pressure-resistant up to at least 0.1 barg, 0.5 barg, 1 barg, 2 barg, 5 barg, 10 barg, 20 barg, 30 barg, 50 barg, 70 barg, 100 barg, 150 barg, or 200 barg.

[0141] This is particularly relevant, for example, when the acid or electrolyte is supplied to the gas diffusion electrodes and / or polymer membranes on the permeate or cathode side of the cells, which are intended to generate hydrogen pressure (electrochemical hydrogen compression). If the feed gas and / or retentate gas is also at a high pressure level (e.g., feed gas from a long-distance pipeline of a hydrogen-containing natural gas network at over 20 barg), the pressure resistance of the channels and containers connected to the acid or electrolyte on the retentate or anode side is relevant.

[0142] The reservoir can be located above the cells and / or supply channels and / or connecting channels and / or distribution channels, so that at times when acid or electrolyte is to be supplied, the acid or electrolyte can flow by gravity into the cells or to the gas diffusion electrodes and / or polymer membranes. The supply can be controlled, for example, via a valve or a pump or supply device. The supply can be active and / or passive.

[0143] For example, acid or electrolyte can be pumped from the storage container into a container or reservoir (intermediate electrolyte reservoir) equipped with a level sensor (e.g., light barrier or capacitive) until the upper level sensor detects that the intermediate electrolyte reservoir is full. During the supply times, a valve can be opened so that acid or electrolyte can flow from the intermediate electrolyte reservoir via the supply channels and / or supply elements and / or connecting channels and / or distribution channels to the cells or gas diffusion electrodes and / or polymer membranes of the cell stack.

[0144] For example, the supply may occur always or less frequently than every 10 or 50 or 100 or 300 or 500 or 1000 or 3000 or 5000 or 8000 or 10 000 or 15 000 operating hours.

[0145] The supply can take place during operation of the cell stack or after the operation of the cell stack has been switched off (e.g. when the cell stack is still close to its operating temperature) and / or after the cell stack has cooled down.

[0146] Liquid acid or electrolyte can also be supplied via the flowfield channels. For example, at times when the cell stack is not operating for the purpose of supplying acid or electrolyte (e.g., still at operating temperature or cooled down). In this case, the flowfield channels (anode and / or cathode flowfields) can be connected to a reservoir filled with acid or electrolyte. In addition, valves can close the supply and / or discharge lines for feed gas, purge gas, permeate gas, and / or retentate gas for the purpose of supplying acid and / or electrolyte.

[0147] If the HT-PEM cell stack is refilled with electrolyte (e.g., phosphoric acid) to extend its service life, a downstream TSA may also be useful, for example, if the mixture being refilled contains water or a solvent. This would escape from the stack during or after the electrolyte refill and contaminate the permeate or retentate gas. This water or solvent can be separated from the retentate or permeate gas stream by the TSA.

[0148] The electrolyte (e.g., phosphoric acid) can be removed after the anode outlet or after the cathode outlet of the cell stack, i.e., from the permeate gas or from the retentate gas. The electrolyte can, for example, be corrosive or caustic (e.g., phosphoric acid), meaning that the electrolyte could damage components, piping, and / or equipment. Furthermore, it typically has a very high boiling point and would accumulate in piping and / or instrumentation. Furthermore, purity requirements for the permeate gas and / or retentate gas may have to be met, which may prohibit the inclusion of an electrolyte component. If the permeate gas or retentate gas is fed directly or indirectly into a low-temperature PEM cell stack, the electrolyte contained in the gas can poison the electrodes of the cells in the low-temperature PEM cell stack.For example, the catalysts of low-temperature PEM cells are poisoned by phosphoric acid at low operating temperatures (e.g., 70 °C) (phosphate adsorption on platinum), which can lead to very poor performance and service life. TSA adsorbers are also depleted more quickly by adsorbed electrolyte, as this desorbes poorly, and some adsorbents may be attacked by the electrolyte. For example, some adsorbents are not acid-resistant. Therefore, the electrolyte must be removed from the permeate gas and / or retentate gas after the cell stack or, in a multi-stage cell stack configuration, at least after the last high-temperature PEM cell stack.

[0149] The electrolyte can be removed from the gas by condensation (e.g. by cooling), by leaching or absorption (e.g. bubbling through liquid or flowing past liquid), by physisorption (e.g. by a molecular sieve or silica gel), or by chemisorption (e.g. by activated carbon impregnated with potassium carbonate, potassium hydroxide, calcium hydroxide, calcium carbonate and / or sodium hydroxide). Since, for example, only less than 3 or 2 or 1 or 0.5 kilograms of electrolyte per cell stack are removed over 10,000 hours, an adsorbent intended for electrolyte removal does not necessarily have to be regenerated regularly, but can be replaced, for example, once a year. The electrolyte can also be removed, for example, by condensation within a cooled heat exchanger or a downstream separator.If the remaining electrolyte residues are to be largely removed, an adsorbent (e.g., physisorption or chemisorption) is suitable. The electrolyte can be returned to the cell stack.

[0150] The retentate gas and / or permeate gas and / or feed gas can also be purified by a particle filter. For example, to remove carbon dust emitted from the electrodes or graphite-containing monopolar plates and / or bipolar plates of the EHS cell stack, preventing the dust from causing damage.

[0151] The separated hydrogen from the HT-PEM cell stack can also be fed to an LT-PEM cell stack to further purify the hydrogen and, if necessary, simultaneously achieve an efficient pressure increase as an electrochemical hydrogen pump. However, the LT-PEM cell stack must be constantly humidified so that the LT-PEM membranes (e.g., Nafion) retain their conductivity. To comply with hydrogen purity standards, the hydrogen must be dried from the LT-PEM cell stack after separation. Drying the hydrogen using conventional methods would require significant energy consumption. By means of the described invention, the waste heat from the HT-PEM cell stack is to be used to dry the hydrogen gas stream emerging from the downstream LT-PEM cell stack without high energy costs, thereby meeting hydrogen purity standards.

[0152] According to a second aspect of the present invention, a method for processing gases is provided. This method comprises a plurality of cell stacks, wherein the gas exiting from the anode side of a cell stack is guided into at least one further cell stack and / or wherein the gas exiting from the cathode side of a cell stack is guided into at least one further cell stack, and wherein gaseous water is removed from at least one gas stream exiting from at least one cell stack or a portion of the gas stream directly or indirectly downstream of the at least one cell stack, such that the water content of the gas is less than 0.1 mol%, and / or wherein electrolyte expelled from at least one cell stack or a portion of the gas stream directly or indirectly downstream of the at least one cell stack is removed, such that the electrolyte content of the gas is less than 0.5 micromoles per mole and / or wherein at least a portion of at least one gas stream emerging from at least one cell stack is recirculated directly or indirectly after the at least one cell stack into the gas flowing into this at least one cell stack or is fed into the gas flowing into at least one cell stack upstream of this at least one cell stack.

[0153] The technical characteristics of this aspect apply analogously to both a process and a corresponding device.

[0154] The cascading and / or recirculating of several EHS cell stacks serves either to

[0155] - to produce even purer H2 (PERMEAT gas from the first stack flows into the anode inlet of the next stack) to meet purity standards or

[0156] - to extract as much H2 as possible from the feed gas (retentate gas from the first stack flows into the anode inlet of the next stack). This is very important, for example, for H2 separation from helium, since helium is actually the main product, which should be as hydrogen-free as possible. Helium and hydrogen cannot be separated using other technologies (e.g., PSA, polymer membrane), or only with considerable energy expenditure, because they have similar physical properties.

[0157] The phosphoric acid or water escaping from the cell stack in gaseous form must be removed from the gases in order to avoid damage to downstream components or to meet gas purity standards.

[0158] Due to the removal of electrolyte after a cell stack (e.g. HT-PEM), it is possible that the downstream cell stack is a different cell stack type that does not tolerate contamination of the supplied gas with this electrolyte (e.g. NT-PEM cell stack).

[0159] Separated water and electrolyte can be recycled.

[0160] If the stack is used for electrochemical hydrogen compression (EHC): For the permeate-side downstream connection of an EHS cell stack, even higher pressure can be generated or the pressure is distributed across two stacks, meaning that the MEAs have to withstand less differential pressure and can therefore be produced more cost-effectively.

[0161] If the second cell stack serves to further purify the hydrogen (permeate gas from the first stack flows into the anode inlet of the next stack), then the advantage is that, unlike palladium membranes or adsorbers, for example, the purity of the hydrogen remains constant throughout its lifetime (even with pinhole formation) and does not decrease, as is the case with adsorbers (adsorbent breakthrough) or palladium membranes (crack formation -> feed gas contaminates H2, which has a lower pressure). The reason for this is that in the EHS or EHC, the pressure on the permeate side should be regulated higher than on the feed gas side.

[0162] Gas emerging from at least one cell stack on the cathode side and / or the anode side after a device for removing water can have a water content of less than 500 micromoles per mol or less than 100 micromoles per mol or less than 50 micromoles per mol or less than 10 micromoles per mol or less than 5 micromoles per mol or less than 1 micromole per mol.

[0163] Gas emerging from at least one cell stack on the cathode side and / or the anode side after a device for removing electrolyte can have an electrolyte content of less than 2 micromoles per mol or less than 0.5 micromoles per mol or less than 0.2 micromoles per mol or less than 0.1 micromoles per mol or less than 0.01 micromoles per mol or less than 0.001 micromoles per mol.

[0164] Electrolyte can be removed from a retentate gas or permeate gas exiting a high-temperature PEM cell stack using an electrolyte removal device by adsorption (e.g., chemisorption), absorption, and / or condensation before flowing into a low-temperature PEM cell stack for hydrogen extraction.

[0165] From a hydrogen-containing feed gas, a large part of the hydrogen can be extracted, preferably by several stages of successive processes for extracting hydrogen from this feed gas, and the gas can be reduced by a certain percentage of hydrogen content per stage, and that each stage contains a cell stack or a cell stack compartment (wherein each cell stack compartment consists of cells supplied with gas in parallel within a cell stack and can optionally have its own electrical current density through additional power connections) or a group of cell stacks through which the gas flows in parallel for the extraction of hydrogen, and that the retentate gas of the cell stack or the cell stack compartment or the group of cell stacks can flow into the anode inlet of the cell stack or the cell stack compartment or the group of cell stacks of the next stage, and that at least two, three, four,five, six or seven stages of sequential processes for the extraction of hydrogen are present.

[0166] The feed gas from which hydrogen is to be extracted can contain at least 0.5, 1, 3, 5, 10, 30, 40, 60, 70, 90 or 95 mol% helium.

[0167] A portion of the retentate gas emerging from each or at least one stage is recycled into the gas flowing on the anode side into at least one cell stack of that respective stage, to which that cell stack or group of cell stacks or that cell stack compartment belongs, or of another stage by means of a conveying device, and at least 10, 20, 40, 60, 80 or 90 percent of the respective retentate gas is recirculated, so that the recirculation of the retentate gas results in a greater reduction in the hydrogen content per stage.

[0168] Gaseous water can be removed from the retentate gas flowing from the last stage of the cell stack or the group of cell stacks or the cell stack compartment, so that the water content of the gas is less than 0.1 or 0.01 or 0.001 or 0.0001 mol% and / or that electrolyte expelled from the cell stack or cell stacks directly or indirectly after the cell stack or after the cell stacks can be removed, so that the electrolyte content of the gas is less than 1 or 0.1 or 0.01 micromol per mole and / or the content of hydrogen or helium or residual gases in the retentate gas and / or permeate gas is measured after the last stage in order to stop the operation of at least one cell stack or cell stack compartment if a limit value is exceeded or not met, or to adjust the feed gas supply, the current density, the temperature, the anode gas pressure and / or the cathode gas pressure of at least one cell stack or cell stack compartments.

[0169] For successive stages, the current density of the cell stack or group of cell stacks or cell stack compartment may decrease from stage to stage with the unit amperes per square centimeter for electrochemical hydrogen separation, so that the current density of the cell stack or group of cell stacks or cell stack compartment of a stage is less than 80, 60, 40, 30 or 20 percent of the cell stack or group of cell stacks or cell stack compartment of the previously flowed through stage.

[0170] For successive stages, the number of cell stacks or the total number of cells of all cell stacks or the total number of cells of the cell stack compartment per stage may decrease from stage to stage.

[0171] For successive stages, a hydrogen recovery rate per stage may decrease from stage to stage.

[0172] The permeate gas of a high-temperature cell stack can flow into the anode compartments of a low-temperature cell stack, wherein the high-temperature cell stack has a temperature of 110 to 270 °C, or 140 to 220 °C, or 160 to 200 °C, and the low-temperature cell stack has a temperature below 100 °C, and wherein both cell stacks are operated in hydrogen separation mode, or wherein the high-temperature cell stack is operated in hydrogen separation mode and the low-temperature cell stack is operated in hydrogen compression mode. The high-temperature cell stack can be an HT-PEM cell stack, while the low-temperature cell stack is an LT-PEM cell stack.

[0173] The permeate gas of the high-temperature cell stack can be humidified or water can be generated in the cathode compartments of the cell stack, thereby humidifying the anode compartments of the downstream cell stack, so that the proton conductivity of the cells of the downstream cell stack is maintained or increased.

[0174] At least two different types of electrochemical membrane electrode assemblies can be used within at least one cell stack, and the permeate gas from the cathode of cells with a high platinum content of the membrane electrode assemblies is passed into the anode compartments of cells with a lower platinum content of the membrane electrode assemblies and / or that the permeate gas from the cathode of cells with a high operating temperature (e.g. HT-PEM MEAs) is passed into the anode compartments of cells with a lower operating temperature (e.g. NT-PEM MEAs).

[0175] For each stage of a cell stack, group of cell stacks, or cell stack compartment, for example, a power supply can be connected to this cell stack, group of cell stacks, or cell stack compartment, or to individual cell stacks per stage, so that a separate electrical current or current density can be regulated for each stage. In general, all cell stacks can be connected to a separate power supply, and the electrical current or current density can be regulated separately for each cell stack.

[0176] The permeate gas of a high-temperature cell stack can flow into the anode compartments of a low-temperature cell stack, wherein the high-temperature cell stack has a temperature of 110 to 270 °C or of 140 to 220 °C or of 160 to 200 °C and the low-temperature cell stack has a temperature below 100 °C and wherein both cell stacks are operated in hydrogen separation mode or wherein the high-temperature cell stack is operated in hydrogen separation mode and the low-temperature cell stack is operated in hydrogen compression mode.

[0177] The high-temperature cell stack can be an HT-PEM cell stack and the low-temperature cell stack can be an NT-PEM cell stack.

[0178] The permeate gas of the high-temperature cell stack can be humidified or water can be generated in the cathode compartments of the cell stack, thereby humidifying the anode compartments of the downstream cell stack, so that the proton conductivity of the cells of the downstream cell stack is maintained or increased.

[0179] At least two different types of electrochemical membrane electrode assemblies can be used within a cell stack, whereby the permeate gas or retentate gas from the cathode or anode of higher-temperature cells (e.g., HT-PEM MEAs) can be directed into the anode compartments of lower-temperature cells (e.g., NT-PEM MEAs). Such a cell stack then contains several cell stack compartments due to the multi-stage flow through the cells, each of which has different types of membrane electrode assemblies.

[0180] The high-temperature cell stack can have a pressure of 1 - 100 bar(a) on the anode side and a similar or slightly higher pressure on the cathode side, and the low-temperature cell stack can have a pressure on the anode side corresponding to the cathode side of the high-temperature cell stack, and the permeate gas can have a higher pressure, e.g. 500 bar(a), on the cathode side of the low-temperature cell stack.

[0181] The permeate gas of the high-temperature cell stack can be humidified or water can be generated in the cathode compartments of the cell stack, thereby humidifying the anode compartments of the downstream cell stack, so that the proton conductivity of the cells of the downstream cell stack is maintained or increased.

[0182] The high-temperature cell stack can be an HT-PEM cell stack and the low-temperature cell stack can be an NT-PEM cell stack.

[0183] During the start and stop of the entire system and / or during the phase of switching at least one cell stack from hydrogen separation mode to fuel cell mode and from fuel cell mode to hydrogen separation mode, the supply pipes and / or anode and / or cathode chambers of the at least one cell stack can be flushed with a non-combustible inert gas (e.g. nitrogen, helium or carbon dioxide) in order to prevent degradation of the at least one cell stack.

[0184] According to a third aspect of the present invention, devices and methods for discontinuous humidification of a cell stack are provided. A corresponding method or device for discontinuous humidification of a cell stack comprises the following features and steps: a cell stack to whose cells water-containing gas or water is supplied for less than 50 percent of the operating time, or water is generated at the anode and / or cathode electrode for less than 50 percent of the operating time, and for more than 50 percent of the operating time, all gases supplied to the stack contain less than 2 mol% water and no water is supplied, and wherein a device which removes water from at least one escaping gas stream is connected directly or indirectly downstream of the cell stack, so that directly or indirectly this respective escaping gas or a portion of the escaping gas contains less than 0.1 mol% of water and / or wherein at least one gas stream emerging from the cell stack is diverted, stopped, recirculated or discharged indirectly or directly after the cell stack during the time of water supply or water generation via a switching device.

[0185] The technical characteristics of this aspect apply analogously to both a process and a corresponding device.

[0186] According to the invention, the method and the corresponding device are designed for discontinuous humidification only. This significantly reduces the energy required for humidification and drying of escaping gases.

[0187] Drying the separated hydrogen or the retentate gas is associated with very high energy costs, presumably on a similar scale to those for the hydrogen separation itself. Discontinuous humidification therefore requires only infrequent humidification, thus saving a large portion of the energy costs required for drying. This would not be possible for NT-PEM cell stacks, as the NT-PEM membrane must always be humidified. With HT-PEM, humidification is only occasionally required, so that only a small amount of the orthophosphoric acid polymerizes to poly- or pyrophosphoric acid (poor proton conductivity) or reverts to orthophosphoric acid (good proton conductivity) (equilibrium reaction).

[0188] If the humidified gas is recirculated back into the cell stack after flowing through it during the humidification period, very little water needs to be added (as this accumulates in the circuit) or very little water needs to be dried from the escaping gas, thus resulting in further energy cost savings. If a low current density is used during the humidification period or very little feed gas is added, very little water needs to be added (as this accumulates in the circuit) or very little water needs to be dried from the escaping gas, thus resulting in further energy cost savings.

[0189] Humidification through fuel cell operation (e.g., 1 hour of fuel cell operation, 9 hours of EHS operation) has the advantage that no water supply is required (e.g., no water refueling is necessary). Furthermore, the electricity generated during fuel cell operation can be utilized. Especially in locations without a power grid (e.g., off-grid natural gas wells with H2 content in the natural gas), power generation through fuel cell operation can enable environmentally friendly self-sufficiency.

[0190] The cell stack is preferably a device for processing gases, in particular for electrochemical hydrogen separation.

[0191] The cell stack is preferably an HT-PEM cell stack with high-temperature polymer electrolyte membrane electrode units, which operates in a temperature range of 105 to 250 °C and is used for the electrochemical separation of hydrogen (EHS) or the electrochemical compression of hydrogen (EHC).

[0192] The cells of the cell stack can be supplied with water-containing gas or water for less than 0.5, 2, 5, 10, 20, 30, 40 or 50 percent of the operating time, or water can be generated at the anode and / or cathode electrode for less than 2, 5, 10, 20, 30, 40 or 50 percent of the operating time, and for more than 50, 60, 70, 80, 90, 95, 98 or 99.5 percent of the operating time, all gases supplied to the stack contain less than 2 or 1 or 0.5 or 0.3 or 0.1 or 0.005 or 0.001 or 0.0001 or 0.000001 mol% water and no water is supplied.

[0193] The time during which all gases supplied to the stack contain less than 2 mol% water and no water supply takes place can be more than 15 minutes or 30 minutes or 1 hour or 5 hours or 24 hours or 50 hours or 100 hours.

[0194] The gas exiting the cell stack on the cathode and / or anode sides can be recirculated to the respective cathode and / or anode inlet of the cell stack via a gas conveying device, with gaseous water being added or enriched in the gas in the respective circuit. The gas exiting the cell stack on the cathode and / or anode sides can, after a water removal device, have a water content of less than 500 micromoles per mol, or less than 100 micromoles per mol, or less than 50 micromoles per mol, or less than 10 micromoles per mol, or less than 5 micromoles per mol, or less than 1 micromole per mol.

[0195] Preferably, all cell stacks are cell stacks for electrochemical hydrogen separation and / or cell stacks for electrochemical hydrogen compression.

[0196] A method and apparatus for separating and purifying hydrogen from gas mixtures or generating hydrogen pressure by means of electrochemical hydrogen separation comprises one or more cell stacks, wherein a cell stack (or at least one cell of the cell stack) is discontinuously humidified by temporarily switching from separation mode to fuel cell mode.

[0197] Furthermore, according to the invention, a method is provided for, in particular discontinuously, humidifying a cell stack, in particular an EHS, by producing water on the cathode side of the cell stack during fuel cell operation, by adding atmospheric oxygen to the cathode of the cell stack and enabling an electric current to flow through a consumer.

[0198] For example, the cell stack is operated in electrochemical hydrogen separation mode most of the time. Periodically (e.g., every 50 hours), the stack is operated briefly (e.g., for 30 minutes) in fuel cell mode to generate water at the cathode by reacting with atmospheric oxygen, thereby converting the pyrophosphoric acid and polyphosphoric acid contained in the cells back into phosphoric acid, which has a significantly higher proton conductivity and thus leads to a significant improvement in cell voltage. During short-term fuel cell operation, air is supplied, and instead of applying voltage to the cell stack as in EHS mode, the electrical energy is converted or stored via a consumer.

[0199] This operation in fuel cell mode can be carried out cyclically over the entire stack or over a section at a time, e.g. every 1 - 75 hours for 5 - 30 minutes each.

[0200] At least one cell of at least one cell stack can be humidified by temporarily switching from separation mode to fuel cell mode. The cathode and anode sides can be alternated during fuel cell operation, so that sometimes water is generated at one electrode of the membrane electrode assemblies during fuel cell operation, and sometimes water is generated at the other electrode of the membrane electrode assemblies during fuel cell operation. This means that the electrodes that were previously supplied with hydrogen-containing gas during fuel cell operation are alternately supplied, or sometimes also supplied with air during fuel cell operation.This is intended to ensure that on both electrode sides per membrane electrode unit, a high water content during water generation in fuel cell operation allows polyphosphoric acid and / or pyrophosphoric acid to react with water again to form orthophosphoric acid, which is a better proton conductor.

[0201] A cell stack can be operated in hydrogen separation mode and / or hydrogen compression mode for at least 95% of its operating time and in fuel cell mode for a maximum of 5%.

[0202] The device can be characterized in that the electrical energy generated in the fuel cell mode is used at least partially as an electrical energy source in the hydrogen separation mode and / or hydrogen compression mode for operating the electrochemical hydrogen separation or electrochemical hydrogen compression, wherein the electrical energy generated in the fuel cell mode is either stored or made available to other cell stacks.

[0203] Water supplied or generated for humidification can be separated by sorption from the permeate gas and / or the retentate gas of at least one cell stack, wherein the thermal energy for regenerating at least one sorption device is at least partially obtained from the waste heat of a cell stack.

[0204] When switching from EHS operation to fuel cell operation and back, the anode channels / flow fields can be purged with inert gas to prevent a flammable hydrogen-air mixture in the channels or to prevent cell degradation. To prevent contaminating the retentate gas and / or permeate gas, the cathode air and inert gas must be removed during fuel cell operation or during switching.

[0205] The stack can also be constructed in such a way that a part of the stack is supplied with air due to a corresponding channel structure and is operated as a fuel cell (possibly driving the EHS) and its moist cathode exhaust gas is fed to the feed gas of the other part of the stack (EHS area).

[0206] The structure can also consist of two different stacks, one (e.g., an HT-PEM stack) operating in fuel cell mode and the other in EHS mode. Between the parts or stacks, a device can be located that reduces or separates residual oxygen from the fuel cell cathodes (e.g., by adding H2) before the moist gas is at least temporarily fed into the feed gas of the anode compartments of the EHS stack.

[0207] The air supply can have a cathode lambda oxygen content of 2. The lambda refers to the desired electrical current or proton current. Ideally, however, to keep the oxygen concentration in the feed gas of the anode of the next cell stack (EHS cell stack) low, the oxygen lambda is significantly lower, e.g., 1.0 - 1.3.

[0208] If a cathode lambda of less than 1 is used for the air supply in fuel cell operation, this results in mixed operation of a fuel cell operation and an electrochemical hydrogen separation, which should be maintained in the desired voltage range via an external voltage source in the event of a decreasing cell potential (e.g. negative cell potential).

[0209] Devices for removing oxygen are possible.

[0210] According to the invention, a method for discontinuous humidification is provided, wherein for humidification purposes, the fuel cell operation is repeatedly switched over in order to form water on the cathode side by the hydrogen reacting with oxygen from the air and thus to achieve humidification of the MEA.

[0211] The invention also provides a method for humidifying a cell stack, wherein oxygen is added to the feed gas or is already present in the feed gas, which reacts, for example, with the hydrogen or natural gas on a catalyst (e.g., platinum-based) to form water, thereby humidifying the feed gas. It is also possible to oxidize hydrogen or feed gas / retentate gas outside the feed gas stream in order to obtain water and add it to the feed gas stream for humidification. Water can be produced on the cathode of the cell stack during fuel cell operation by adding atmospheric oxygen to the cathode of the cell stack and enabling an electrical current to be drawn through a consumer.

[0212] This operation can be performed cyclically across the entire stack or across a specific section, e.g., every 25-75 hours for 5-30 minutes each. When switching from EHS operation to fuel cell operation and back, the anode channels / flow fields must be purged with inert gas to prevent a flammable hydrogen-air mixture in the channels or to prevent cell degradation. To prevent contaminating the retentate gas and / or permeate gas, the cathode air and inert gas must be removed during fuel cell operation or during switching.

[0213] According to the invention, a device for discontinuous humidification is provided, wherein a cell stack is also constructed in such a way that a part of the stack is supplied with air due to a corresponding channel structure and is operated as a fuel cell (possibly driving the EHS) and its moist cathode exhaust gas is fed to the feed gas of the other part of the stack (EHS region).

[0214] Two different cell stacks can be provided, one (e.g. HT-PEM stack) being operated in fuel cell mode and the other in EHS mode.

[0215] Between the parts or stacks there may be a device that reduces (e.g. by adding H2) or separates residual oxygen from the fuel cell cathodes before the moist gas is added to the feed gas of the anode compartments of the EHS stack.

[0216] The air supply can have a cathode lambda of oxygen content of 2. The lambda refers to the desired electrical or proton current. Ideally, however, to keep the oxygen concentration in the anode feed gas (EHS stack) low, the oxygen lambda is significantly lower, e.g., 1.0 - 1.3.

[0217] If the cathode lambda of the air supply is set to less than 1, this results in a mixed operation of a fuel cell and electrochemical hydrogen separation, which must be maintained within the desired voltage range via an external voltage source in the event of a falling cell potential (e.g., negative cell potential). Devices for removing the oxygen are available. An LT-PEM cell stack is located upstream of the TSA system. LT-PEM cell stacks must be constantly humidified, otherwise the LT-PEM membrane would dry out and exhibit drastically lower proton conductivity. Therefore, this TSA system serves to dry the hydrogen so that it meets the applicable hydrogen purity standards (e.g., SAE J2719: less than 5 ppm H2O).

[0218] Before the gas flowing from the cell stack flows into the adsorber, it is cooled by a cooler in order not to impair adsorption in the adsorber and to condense out any water (and to return it to the anode circuit of the NT-PEM cell stack by evaporation).

[0219] Discontinuous HUMIDIFICATION UA (e.g. fuel cell operation) feed gas humidification (before EHS cell stack) membrane humidification

[0220] According to the invention, a device for discontinuously humidifying a cell stack is provided, comprising a cell stack to whose cells water-containing gas or water is supplied for less than 50 percent of the operating time or water is generated at the anode and / or cathode electrode for less than 50 percent of the operating time and all gases supplied to the stack contain less than 0.5 mol% water for more than 50 percent of the operating time, and wherein a device which removes water from at least one exiting gas stream is connected directly or indirectly downstream of the cell stack, so that directly or indirectly this respective exiting gas or a part of the exiting gas contains less than 0.1 mol% water and / or

[0221] At least one gas flow exiting the cell stack can be diverted or discharged indirectly or directly after the cell stack during the time of water supply or water generation via a switching device and / or wherein at least one gas volume flow exiting the cell stack is stopped indirectly or directly after the cell stack for the time of water supply or water generation.

[0222] Gas exiting the cell stack on the cathode and / or anode sides can be recirculated to the respective cathode and / or anode inlet of the cell stack via a gas conveying device, and in the process, gaseous water is added or enriched in the gas in the respective circuit. Gas exiting the cell stack on the cathode and / or anode sides can have a water content of less than 500 micromoles per mol, or less than 100 micromoles per mol, or less than 50 micromoles per mol, or less than 10 micromoles per mol, or less than 5 micromoles per mol, or less than 1 micromole per mol in a water removal device.

[0223] Furthermore, the invention provides a device for separating and purifying hydrogen from gas mixtures, or for generating hydrogen pressure by means of electrochemical hydrogen separation. This device comprises one or more cell stacks, wherein a cell stack (or at least one cell of the cell stack) is humidified by temporarily switching from separation mode to fuel cell mode.

[0224] A cell stack can be operated in hydrogen separation mode and / or hydrogen compression mode for at least 95% of its operating time and in fuel cell mode for a maximum of 5%.

[0225] In temporary fuel cell mode, water produced at the cathode of a cell stack can be at least partially stored and fed to the anode gas and / or cathode gas of a cell stack in electrochemical hydrogen separation mode and / or hydrogen compression mode.

[0226] Electrical energy generated in fuel cell mode can be used at least partially as an electrical energy source for operating the electrochemical hydrogen separation or electrochemical hydrogen compression in hydrogen separation mode and / or hydrogen compression mode, wherein the electrical energy generated in fuel cell mode is either stored or made available to other cell stacks.

[0227] Water condensed during the regeneration of an adsorber system can be fed back into the cell stack for humidification.

[0228] This is particularly important so that no or only a small amount of water needs to be stored or supplied externally for humidification.

[0229] Humidification can be achieved discontinuously by adding H2O or O2. For example, for 1 hour every 20 hours. During this time, the adsorber at the anode outlet and, if applicable, the adsorber at the cathode outlet should dry the retentate gas or permeate gas using the waste heat from the cell stack.

[0230] Note: LT-PEM stacks require continuous humidification. For HT-PEM stacks, however, repeated humidification is sufficient, as the pyrophosphoric acid and polyphosphoric acid formed from phosphoric acid during dry operation through polymerization should react back to phosphoric acid upon humidification to restore good membrane conductivity.

[0231] Humidification of the feed gas can be achieved by introducing water into this heat exchanger (into the feed gas stream).

[0232] The permeate gas of the high-temperature cell stack can be humidified or water can be generated in the cathode compartments of the cell stack, thereby humidifying the anode compartments of the downstream cell stack, so that the proton conductivity of the cells of the downstream cell stack is maintained or increased.

[0233] In temporary fuel cell mode, water produced at the cathode of a cell stack can be at least partially stored and fed to the anode gas and / or cathode gas of a cell stack in electrochemical hydrogen separation mode and / or hydrogen compression mode.

[0234] Water can be added to the anode gas and / or the cathode gas of a cell stack and / or water can be produced from the reaction of oxygen with hydrogen or a fuel and / or water can be generated in the cell stack so that more than 99.9% of this water is removed from the retentate gas and / or permeate gas flowing out of the cell stack, wherein more than 50% of this water is separated by at least one adsorber bed, the thermal energy for regeneration of which is obtained at least 50% from the waste heat of a cell stack.

[0235] The invention can also be useful for fuel cells or fuel cell systems:

[0236] The cell stack can be a fuel cell that is operated exclusively in fuel cell mode or is operated in fuel cell mode for more than 50% of the operating time, and the thermal energy for regenerating at least one adsorber bed is obtained at least partially from the waste heat of the fuel cell stack, and this adsorber bed is used to remove ammonia, and / or alkaline substances, methanol, alcohols, aldehydes, hydrogen sulfide, carbon monoxide, odorants, sulfur-containing substances, oxygen, high boilers, alkynes and / or alkenes from the feed gas of a fuel cell stack and / or hydrogen separation cell stack and / or hydrogen compression cell stack or another application.

[0237] Fuel cells and fuel cell systems are often sensitive to certain pollutants in the gases supplied to the anode or cathode side of the cell stack (e.g., reformate gas or hydrogen or hydrogen-containing gas on the anode side and air or oxygen on the cathode side). These pollutants can reduce the performance of the fuel cell stack and thus lead to lower efficiency, lower energy output and / or higher costs (e.g., due to the need for more cells). Furthermore, pollutants can increase reversible or irreversible degradation. This can significantly reduce the service life of the fuel cell stack and, consequently, potentially the entire fuel cell system. In fuel cell systems in which the cell stack is an HTPEM fuel cell stack and which are fueled with reformate gas resulting from the reforming (e.g.,For plants supplied with methanol (e.g., steam reforming), the following substances in the reformate gas or in the supplied air are harmful: methanol, ammonia, and / or alkaline substances, alcohols, aldehydes, hydrogen sulfide, carbon monoxide, sulfur-containing substances, high boilers, alkynes, and / or alkenes. These include, in particular, methanol and carbon monoxide, which may be present in the reformate gas due to incomplete reforming, and ammonia, which may be formed on the anode side when nitrogen is introduced, or which may be present in the air on the cathode side.

[0238] Furthermore, a high hydrogen concentration in the reformate gas is beneficial for fuel cell performance and energy efficiency. Thus, a lower carbon dioxide content and, conversely, a higher hydrogen content are also beneficial. Furthermore, an excessively high water content (e.g., over 5, over 7, over 10, over 15, or over 20 mol%) in the reformate gas or in the air supplied on the cathode side can cause faster degradation. Reducing the carbon dioxide content in the reformate gas can also lead to a higher rate of hydrogen used for the fuel cell reaction, for example, in the case of anode-side recirculation (see Siqens patents), and thus also to a higher energy efficiency of the fuel cell system.The pollutants mentioned (methanol, ammonia, and / or alkaline substances, alcohols, aldehydes, hydrogen sulfide, carbon monoxide, sulfur-containing substances, high boilers, alkynes and / or alkenes) as well as carbon dioxide and water can be removed by a sorption device and / or diffusion device.

[0239] Methanol and / or water can also be recovered and recycled using a sorption device and / or diffusion device (e.g., from the feed gas or reformate gas, or from the gas exiting the anode or cathode side). This allows the methanol and / or water, for example, to be converted into hydrogen in the reformer and converted into electrical energy in the fuel cell stack instead of remaining unused. Particularly at low reforming temperatures (e.g., with internal reforming in the fuel cell stack in separate reformer chambers, see Siqens patent applications), the methanol content in the reformate gas supplied to the fuel cell stack can be high (e.g., over 0.1 mol%, over 0.5 mol%, over 1 mol%, over 3 mol%, over 5 mol%, over 10 mol%, over 30 mol%).

[0240] Electrolyte (e.g. phosphoric acid) leaked from the fuel cell stack can also be recovered by a sorption device and / or diffusion device and returned to the cell stack or to the electrodes or membranes of the cell stack.

[0241] Furthermore, a high oxygen content in the air or gas supplied to the cathode side results in a significant improvement in performance or efficiency. A sorption device and / or diffusion device can separate oxygen or nitrogen from the air, resulting in an increase or enrichment of the oxygen content. Thus, an oxygen content of over 22, over 25, over 30, over 40, over 50, over 70, or over 90 mol% can be achieved. This gas with a high oxygen content can be supplied to the fuel cell stack on the cathode side and results in a significantly higher energy efficiency or a significantly higher electrical output of the fuel cell stack.

[0242] However, a sorption device or diffusion device requires a lot of energy. In a fuel cell system that is operated autonomously, for example, electrical energy is precious because the total cost of ownership is very high compared to electricity from the power grid. This is due to the high investment costs, the limited service life of the fuel cell stack or fuel cell system, and high fuel costs, among other things. It is therefore a great advantage if the waste heat from the cell stack is used, at least in part, to operate the sorption device and / or diffusion device. The sorption device could, for example, be a TSA system (and possibly in combination with a pressure swing). The thermal energy required to desorb the adsorber bed should come largely from the waste heat of the fuel cell stack.

[0243] The use of waste heat from a high-temperature PEM fuel cell stack to operate a sorption device or diffusion device is possible because the average operating temperature of the cell stack is above 100 °C, above 120 °C, above 140 °C, above 150 °C, above 160 °C, above 170 °C, above 180 °C, or above 210 °C. For a low-temperature fuel cell stack, this would be impossible or very difficult (cost-intensive, low efficiency, large installation space, and weight).

[0244] The use of the waste heat of the fuel cell stack for the operation of a sorption device or diffusion device (e.g. through thermal coupling) can therefore result in the following advantages: longer service life, higher energy efficiency or higher electrical output of the fuel cell stack, lower investment costs by saving cells and / or by saving on separate heating of the sorption device or diffusion device and smaller installation space by saving on separate heating of the sorption device or diffusion device.

[0245] Thus, a device or a method can be characterized in that the cell stack is a fuel cell which is operated exclusively in fuel cell mode or is operated in fuel cell mode for more than 50% of the operating time, and the thermal energy for regenerating at least one adsorber bed is obtained at least partially from the waste heat of the fuel cell stack and this adsorber bed is used to remove ammonia and / or alkaline substances, methanol, alcohols, aldehydes, hydrogen sulfide, carbon monoxide, odorants, sulfur-containing substances, oxygen, high boilers, alkynes and / or alkenes from the feed gas of a fuel cell stack and / or hydrogen separation cell stack and / or hydrogen compression cell stack or another application.

[0246] The present invention will be described in more detail below with reference to exemplary embodiments illustrated in the figures. These show: Figure 1 is a schematic circuit diagram of a device according to the invention according to a first exemplary embodiment,

[0247] Figure 2 is a schematic circuit diagram of the device according to the invention according to a second embodiment,

[0248] Figure 3 is a schematic circuit diagram of an anode-side piping system "Retentate gas of a first cell stack flows into the anode inlet of the further cell stack" with recirculation, e.g. for the production of hydrogen-free helium according to a first embodiment, and

[0249] Figure 4 is a schematic circuit diagram of an anode-side piping system "retentate gas of a first cell stack flows into the anode inlet of another cell stack" with recirculation, e.g. for the production of hydrogen-free helium according to a first embodiment,

[0250] The technical features of the present inventions are disclosed above and can be seen from the figures.

[0251] Figure 1 shows a high-temperature EHS cell stack 1 with TSA pre-cleaning 2, TSA hydrogen cleaning 3, and TSA drying 4 of the retentate gas, as well as with fuel cell mode for temporary humidification. The device also includes a heat exchanger 5 for utilizing waste heat from the cell stack 1 for the regeneration of the TSA adsorber beds 2, 3, and 4 with hot gases.

[0252] In the event of impurities in the feed gas, TSA System 1 can be used for pre-cleaning or removing impurities (e.g., ammonia, methanol, hydrogen sulfide, odorants, carbon monoxide, etc.) from the feed gas (e.g., hydrogen-containing natural gas or reformate gas). This TSA System 1 serves to protect the cell stack from contaminants that could degrade it.

[0253] To regenerate the adsorber beds of the TSA systems, a small portion of the purified gas is diverted, preheated by a heat exchanger, then heated by the stack waste heat. If necessary, it is slightly reheated to a higher temperature level for ideal regeneration. The gas is then passed through the adsorber to be regenerated. A large portion of the heat should come from the stack waste heat. The contaminated regeneration gas is then introduced into the retentate gas, for example, after the drying TSA system 4. At the end of the regeneration phase, the adsorber must be cooled. For this purpose, the purified gas is fed into the adsorber through a bypass around the heat sources, so that no heating occurs.

[0254] High-temperature cell stack 1, for example, is an HT-PEM cell stack. It is operated in electrochemical hydrogen separation mode most of the time. Periodically (e.g., every 50 hours), the stack is operated briefly (e.g., for 30 minutes) in fuel cell mode to generate water at the cathode by reacting with atmospheric oxygen, thereby converting the pyrophosphoric acid and polyphosphoric acid contained in the cells back into phosphoric acid, which has a significantly higher proton conductivity and thus leads to a significant improvement in cell voltage. During short-term fuel cell operation, air is supplied, and instead of applying voltage to the cell stack as in EHS mode, the electrical energy is converted or stored via a consumer.The electrical energy generated in fuel cell mode can, after intermediate storage, also be used to apply electrical energy to the cell stack in EHS operation.

[0255] The high-temperature cell stack 1 generates waste heat in both EHS and fuel cell operation. This waste heat is used to power the regeneration of the TSA systems 2, 3, and 4. The flow diagram shows, for example, finned tubes 5 through which the regeneration gas for the TSA systems is conducted and which are positioned in the hot cell stack exhaust air stream. As a result, the fluids used to heat the regeneration gases are heated by the stack's waste heat (e.g., to 150 °C). If liquid or oil cooling is provided for cooling the cell stack, the stack's waste heat can be fed via the heated oil to the heat exchanger to heat the TSA's regeneration gas.

[0256] In both cases, especially with oil cooling, a heat sink independent of the TSA is provided for heat dissipation from the cooling medium of the stack (not shown).

[0257] In the event that the purity of the hydrogen separated by the EHS is insufficient (e.g., some CO2 has diffused through the membranes of the cells in the cell stack, resulting in 50 ppm of CO2 in the separated hydrogen), residual impurities can be removed by the TSA system 3 so that the gas complies with the applicable standard (e.g., SAE J2719). For example, the CO2 content can be reduced to below 2 ppm. Before the gas flowing from the high-temperature cell stack 1 flows into the adsorber, it is cooled by a cooler 6 to avoid impairing adsorption in the adsorber and to condense any electrolyte from the stack (e.g., phosphoric acid) and water (and feed it at the anode inlet or into the electrolyte replenishment tank).

[0258] The TSA system's regeneration largely relies on waste heat from the high-temperature cell stack. The regeneration gas, for example, comes from the purified hydrogen and, after the adsorber has been regenerated (along with minor amounts of impurities), is reintroduced into the process gas at the anode inlet, thus avoiding hydrogen waste.

[0259] In cases where the retentate gas must be dry, i.e., free of water, for example, to allow the hydrogen-depleted retentate gas to be fed back into the natural gas grid, the retentate gas can be dried using a TSA system 4. Alternatively, the TSA system can be used for post-purification, provided the retentate gas must meet certain purity criteria.

[0260] Before the gas flowing from the high-temperature cell stack 1 flows into the adsorber 4, it is cooled by a cooler 6 in order not to impair the adsorption in the adsorber and to condense out any electrolyte from the stack (e.g. phosphoric acid) and water (and to feed it at the anode inlet or into the electrolyte replenishment tank).

[0261] The waste heat from the high-temperature cell stack 1 is largely used for the regeneration of TSA plant 4. The regeneration gas originates, for example, from the dried / purified retentate gas and is cooled after adsorber regeneration to condense water and discharge it as a liquid phase. The moist regeneration gas is reintroduced into the retentate gas stream upstream of the TSA plant.

[0262] Furthermore, an air supply 7 is provided for short-term fuel cell operation. Other components required for fuel cell operation, such as an electrical consumer, are not shown here.

[0263] In addition, a phosphoric acid feed / electrolyte supply 8 to the cell stack is provided

[0264] Figure 2 shows a high-temperature EHS cell stack 1 with TSA pre-purification 2, with an LT-PEM hydrogen compressor (cell stack) 9 for purification and pressure boosting, with TSA drying 10 of the hydrogen and with TSA drying 4 of the retentate gas, as well as with fuel cell mode for temporary humidification. Furthermore, a heat exchanger 5 is installed to utilize the cell stack's waste heat for the regeneration of the TSA adsorber beds using hot gases. The LT-PEM cell stack 9 is located upstream of the TSA system 10. LT-PEM cell stacks must be constantly humidified, otherwise the LT-PEM membrane would dry out and exhibit drastically lower proton conductivity. Therefore, this TSA system serves to dry the hydrogen so that it meets the applicable hydrogen purity standards (e.g., SAE J2719: less than 5 ppm H2O).

[0265] Before the gas flowing from the cell stack 9 flows into the adsorber 10, it is cooled by a cooler 6 in order not to impair the adsorption in the adsorber and to condense out any water (and to feed it back into the anode circuit of the NT-PEM cell stack by evaporation).

[0266] The waste heat from high-temperature cell stack 1 is largely used for the regeneration of the TSA system. The regeneration gas comes, for example, from the dried permeate gas and is recycled after the adsorber regeneration, for example, in the anode circuit of the LT-PEM cell stack.

[0267] The permeate gas from the high-temperature cell stack 1 flows into the LT-PEM cell stack 9, which is operated in EHS mode. The LT-PEM cell stack serves, on the one hand, to further purify the hydrogen through hydrogen separation within the cell stack. On the other hand, the LT-PEM cell stack can also be operated as an electrochemical hydrogen compressor (EHC), or electrochemical hydrogen pump (EHP), to pressurize the hydrogen with high energy efficiency to, for example, 700 bar. Several LT-PEM products are already available on the market as EHCs. The materials used for LT-PEM cell stacks allow operation at high pressure.

[0268] The NT-PEM cell stack must be constantly humidified, otherwise the NT-PEM membrane would dry out and have a drastically lower proton conductivity.

[0269] The water for this purpose is generated, for example, by the recurring short-term fuel cell mode of the upstream high-temperature cell stack. This water is condensed downstream during the fuel cell mode of the high-temperature cell stack by cooling the gas, and the water is then stored in a tank. The water can be introduced as water vapor, for example, into the cathode of the high-temperature cell stack during EHS operation and then flows into the anode circuit of the LT-PEM cell stack with the permeate gas stream of the high-temperature cell stack. In addition, the water condensed downstream of the LT-PEM cell stack or separated by the TSA system is returned to the anode circuit of the LT-PEM cell stack.The water produced by the fuel cell operation of the high-temperature cell stack is used in EHS operation to humidify both the cathode of the high-temperature cell stack and the anode of the NT-PEM cell stack.

[0270] During start-up and stop-up of the entire system, the pipelines are purged with a non-flammable inert gas (e.g. nitrogen) to prevent degradation of the cell stacks and to avoid the risk of explosion.

[0271] For some applications, the depletion of hydrogen from a gas is paramount (Figure 3). For example, the retentate gas may be the main product, while hydrogen may be produced only as a byproduct. For example, helium is many times more expensive than hydrogen, so when extracting hydrogen from helium-containing gas, a cost-effective and efficient method for reducing the hydrogen content in the helium or helium-containing gas is essential.

[0272] The following processes or devices can be used for this purpose:

[0273] A two-stage extraction or depletion of hydrogen from a gas can be carried out. The feed gas (which contains hydrogen and, for example, helium) is fed into the anode inlet of a cell stack 11, and a large portion of the hydrogen is extracted in the cell stack. To ensure that as much hydrogen as possible can be extracted, a portion of the retentate gas flowing from the cell stack is fed back (i.e., recirculated) into the anode inlet of this cell stack using a conveying device 13. This gives some of the hydrogen molecules contained in the retentate gas another chance to be extracted by the EHS cell stack or EHC cell stack. This allows a high degree of hydrogen depletion of the retentate gas downstream of this cell stack with anode circuit. Thus, a first stage of hydrogen depletion has been completed.To achieve further hydrogen depletion of the retentate gas, the retentate gas is fed into another EHS cell stack 12 or EHC cell stack on the anode side. There, hydrogen is extracted again. After this cell stack, a portion of the retentate gas flowing from this cell stack is also fed back into the anode inlet of this cell stack (recirculated 14) in order to achieve the greatest possible hydrogen depletion. With the help of this second cell stack 12, a second stage of hydrogen depletion was thus completed. This process, consisting of cell stacks flowing through one after the other on the anode side with a separate anode circuit around each cell stack, can be repeated many times, e.g., three, four, five, six, seven, eight times (not shown in the figure), in order to achieve the specified low amount of hydrogen in the retentate gas.Downstream of the cell stack of the final stage, i.e., here, downstream of the second cell stack, a device 15 can be located for removing electrolyte expelled or evaporated from the cell stacks, ensuring that this cannot cause damage to downstream piping or instrumentation. This can be, for example, a cooling system with a condenser, a scrubber for absorption, an adsorber with potassium carbonate-impregnated activated carbon for chemisorption, or with a molecular sieve for physisorption. Alternatively or additionally, a device for removing water from the retentate gas can be located downstream of the cell stack of the final stage. This can, for example, be a system for TSA, PSA, or glycol drying, or a system for drying using a water-permeable membrane.Additionally or alternatively, a gas sensor 16 or a gas analysis device may be located after the last cell stack in order to continuously measure, for example, the hydrogen or helium content and to take automated measures if limit values ​​are exceeded or undershot.

[0274] Reference symbol list

[0275] 1 EHS cell stack

[0276] 2 TSA pre-cleaning

[0277] 3 TSA hydrogen cleaning

[0278] 4 TSA drying retentate gas

[0279] 5 heat exchanger (device)

[0280] 6. Cooler (cooling device)

[0281] 7 Air supply (device)

[0282] 8 Electrolyte supply

[0283] 9 cell stacks

[0284] 10 TSA-Drying-Hydrogen

[0285] 11 cell stacks

[0286] 12 cell stacks

[0287] 13 Conveyor system

[0288] 14 Conveyor system

[0289] 15 Device for removing an electrolyte

[0290] 16 Gas sensor

Claims

Patent claims 1. A device for processing a hydrogen-containing feed gas comprising a cell stack for electrochemical hydrogen separation in order to form a retentate gas and a permeate gas from the feed gas, a sorption device or diffusion device connected to the cell stack via a line, and a heat transfer device which thermally couples the cell stack and the sorption device and / or the diffusion device such that the thermal energy required for "processing" the at least one or more gases (feed gas, retentate gas and / or permeate gas) in the sorption device or diffusion device is provided at least partially by waste heat from the cell stack.

2. Device according to claim 1, characterized in that the cell stack is a high-temperature polymer electrolyte membrane cell stack (HT-PEM cell stack) which operates in a temperature range of 110 to 270 °C.

3. Device according to claim 1 or 2, characterized in that the heat transfer device comprises a liquid and / or a gas, such as the permeate gas or the retentate gas, for heat transfer in order to heat up or provide a regeneration gas, wherein the permeate gas or the retentate gas itself can also be the regeneration gas.

4. Device according to one of claims 1 to 3, characterized in that the thermal energy for heating the regeneration gas for processing or regenerating one or more sorption devices is provided to more than 30% or more than 50% or more than 70% or more than 90% or approximately 100% by the waste heat of a cell stack.

5. Device according to one of claims 1 to 4, characterized in that the thermal energy for regenerating at least one sorption device is at least partially obtained from the waste heat of a cell stack and the waste heat of the cell stack is transferred by a liquid or a gas to the adsorber bed and / or to the regeneration gas flowing into the adsorber bed and / or the waste heat of the cell stack is transferred by a hot exhaust air or hot gas to the adsorber bed and / or to the regeneration gas flowing into the adsorber bed and / or the waste heat of the cell stack is transferred by thermal contact to the adsorber bed and / or to the regeneration gas flowing into the adsorber bed, and / or,that the thermal energy for regenerating at least one sorption device originates at least partly from the waste heat of a sorption device regenerating at that time and / or from a regeneration gas flowing from a sorption device and / or partly from an additional energy source.

6. Device according to one of claims 1 to 5, characterized in that the regeneration gas, after flowing through a sorption device for regenerating the corresponding adsorber bed, additionally flows through at least one further adsorber bed of a sorption device and also regenerates this adsorber bed, or that the regeneration gas flows through three or more sorption devices in succession.

7. Device according to one of claims 1 to 6, characterized in that the waste heat of the HT-PEM cell stack is used to operate one or more of the sorption devices, wherein the sorption device comprises one or more Temperature Swing Adsorption (TSA) systems and / or one or more Pressure Swing Adsorption (PSA) systems and / or one or more Vacuum Pressure Swing Adsorption (VPSA) systems and / or one or more Vacuum Swing Adsorption (VSA) systems, which also undergo temperature changes.

8. Device according to one of claims 1 to 7, characterized in that the sorption device comprises one or more adsorber devices upstream and / or downstream of the cell stack.

9. Device according to one of claims 1 to 8, characterized in that that the retentate gas retained in the cell stack during processing and discharged from the cell stack contains predominantly or to a large extent, for example, helium, nitrogen, methane or carbon dioxide or is natural gas to be fed back into a gas network.

10. Device according to one of claims 1 to 9, characterized in that the permeate gas generated in the cell stack is separated hydrogen.

11. Device according to one of claims 1 to 10, characterized in that the retentate gas flowing from the cell stack and / or the permeate gas is dried by means of a temperature swing adsorption system (TSA), which is a sorption device.

12. Device according to one of claims 1 to 11, characterized in that the retentate gas and / or permeate gas flowing from the high-temperature cell stack is cooled by a cooling device arranged between the cell stack and the sorption device before it flows into the sorption device, in order not to impair the adsorption in the sorption device.

13. Device according to one of claims 1 to 12, characterized in that the feed gas is pre-cleaned by means of a sorption device or diffusion device upstream of the cell stack in order to remove, for example, ammonia, carbon monoxide, alcohols, aldehydes, high boilers, hydrogen sulfide, sulfur-containing substances such as odorants or other pollutants such as alkenes / alkynes or to largely separate residual gases such as methane, carbon dioxide, helium or nitrogen and that at least part of the waste heat of the cell stack is used in the process.

14. Device according to one of claims 1 to 13, characterized in that for the regeneration of one or more adsorber beds of the sorption device(s), a part of the gas purified by the sorption device(s) is removed, then optionally preheated by a heat exchanger using a gas flowing out of the sorption device(s) and then heated by waste heat of the cell stack and if necessary, brought to a higher temperature level by slight reheating, whereby the gas is referred to as regeneration gas and is passed through the adsorber bed(s) to be regenerated in order to regenerate them.

15. Device according to one of claims 1 to 14, characterized in that a heat pump or an electric heating device is provided to cool the permeate gas or retentate gas of the cell stack flowing from the cell stack into a sorption device or separation device and / or to heat the regeneration gas or an evaporation device upstream of the cell stack.

16. Device according to one of claims 1 to 15, characterized in that the retentate gas flowing out of the cell stack (e.g. natural gas to be fed back into the gas network) is subsequently purified or dried by sorption device(s) or diffusion device(s) and / or that the permeate gas flowing out of the cell stack (separated hydrogen) is subsequently purified or dried by sorption device(s) or diffusion device(s) in order to also meet strict purity requirements of the purified gas.

17. Device according to one of claims 1 to 16, characterized in that the cell stack is operated for at least 95% of its operating time as an electrochemical hydrogen separator and / or electrochemical hydrogen compressor, wherein a hydrogen-containing feed gas is supplied to the anode and hydrogen is separated or generated at the cathode of the cell stack by an electrical voltage applied to the cell stack, wherein protons migrate from the anode to the cathode through a proton-conducting membrane and / or proton-conducting layer, proton-conducting liquid, proton-conducting foil or proton-conducting plate.

18. Device according to one of claims 1 to 17, characterized in that ammonia, and / or alkaline substances, alcohols, methanol, aldehydes, hydrogen sulfide, carbon monoxide, carbon dioxide, odorants, sulfur-containing substances, oxygen, high boilers, alkynes and / or alkenes are adsorbed by a sorption device upstream of the cell stack or the cell stacks or upstream of another application. removed or separated from the feed gas upstream of the cell stack or cell stacks or upstream of another device, or hydrogen is released or separated from a sorbent, sorbate or substance by means of a sorption device, and wherein the thermal energy for regenerating at least one adsorber bed or for releasing or separating hydrogen is obtained at least partially from the waste heat of this or another cell stack.

19. Device according to one of claims 1 to 18, characterized in that substance or substances separated by adsorption from the feed gas upstream of the cell stack are fed back into the retentate gas or permeate gas directly or indirectly downstream of this or another cell stack, the substance or substances fed in being, for example, odorants.

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