Electrolysis device and use thereof

Abstract

The invention relates to an electrolysis plant (1) for producing hydrogen and oxygen as product gases, comprising an electrolysis module (3) and a process unit (5), the process unit (5) having a reactant line (7) for supplying process water and a product line (9), which are each connected to the electrolysis module (3), the process unit (5) is equipped with an insulating device (11) for insulating heat, comprising an insulating material (17), in such a way that slowed cooling of the process water is achieved during shutdown operation.

Description

Technical Field

[0001] The invention relates to an electrolysis plant for producing hydrogen and oxygen as product gases, comprising an electrolysis module and a process engineering unit. The invention also relates to the use of the electrolysis plant. Background Art

[0002] Electrolysis equipment is a technical device that uses electric current to achieve the conversion of electrochemical substances in an electrolysis device (so-called electrolysis). Depending on the type of electrolysis, there are also many types of electrolysis devices, such as electrolysis devices for water electrolysis (i.e., decomposition of water as a reactant into the product gases oxygen and hydrogen).

[0003] For some time, there has been growing interest in using the surplus energy of renewable energy sources (i.e., using above-average solar or wind power) to produce valuable materials when the sun is shining and the wind is blowing abundantly. One valuable material may be hydrogen produced using water electrolysis devices in particular. For example, so-called renewable energy (EE) gas can be produced using hydrogen.

[0004] In an electrolysis device, the electrolysis device usually has a large number of electrolysis cells, which are arranged adjacent to each other and stacked together. Through water electrolysis, water is decomposed into hydrogen and oxygen in the electrolysis cell. In a PEM electrolysis device, distilled water is usually supplied to the anode side as a reactant and decomposed into hydrogen and oxygen on a proton permeable membrane (English: Proton-Exchange-Membrane, PEM). Water is oxidized to oxygen at the anode. Protons pass through the proton permeable membrane. Hydrogen is produced on the cathode side. Water is usually transported from the bottom side to the anode chamber and / or cathode chamber.

[0005] In addition to PEM electrolysis equipment operating in an acidic environment, alkaline electrolysis devices are also well known and frequently used. In addition, atmospheric pressure electrolysis devices operating at atmospheric pressure or only low operating pressures, or pressure electrolysis devices operating at high operating pressures of 35 bar and above are also known.

[0006] In an electrolysis device, individual electrolysis cells are usually stacked in the axial direction into modules comprising a plurality of single cells and installed into said modules or electrolysis modules. An electrolysis device usually has a plurality of modules, which together form a so-called electrolysis stack or simply a "stack". Thus, for example, 50 electrolysis cells can be stacked in the axial direction into a module, and then 5 modules can be stacked in the axial direction into a stack, so that such an electrolysis stack can therefore contain, for example, 250 cells in the entire axial complex.

[0007] For example, as soon as the electrolysis modules, electrolysis cells or electrolysis stacks in a PEM electrolyser are filled with water for the first time, for example after manufacture, it must be ensured that there is always water (reactant water) in the modules or a water-gas mixture during operation of the electrolyser. Dry running or drying out must be prevented in every operating phase, as this would cause irreversible damage to the electrolyser. Above all, the membrane must always remain in a moist environment, but other functional parts and components (e.g. catalysts or electrodes) must also not dry out. This also applies to the risk of frost damage during long plant shutdowns due to ambient temperatures below the freezing point of the process water being electrolyzed. Freezing must therefore also be avoided.

[0008] When an electrolyser passes from a normal operating state into an operating phase for planned and upcoming maintenance or servicing, for example for maintenance purposes, the shutdown management of the electrolyser can usually be planned well and in advance, and corresponding preventive measures and shutdown procedures can be initiated regularly and safely, so that in particular water remains in the modules after the shutdown and, if necessary, additional circulation can take place.

[0009] One source of renewable energy is wind power. In particular, large power outputs can be achieved using coastal, so-called offshore wind power plants. However, the challenge is that the large distances to the electrical consumers must be overcome, and there is no grid connection to power the auxiliary and protective systems necessary for the electrolysis device when the device is shut down. So far, it has been proven that efforts to achieve a self-sufficient power supply system to provide on-demand or preventive protection for the electrolysis device of the electrolysis device in offshore applications or remote onshore connections are very complex. In particular, in offshore electrolysis devices, special attention must be paid to preventing damage to the electrolysis device because there is usually no grid connection. Therefore, in view of this, people have found in the prior art a very complex backup system consisting of batteries and emergency power supply devices, which can at least temporarily shut down to protect the electrolysis device when the power generation device is shut down (for example, in a dark and windless period). Summary of the invention

[0010] The object of the present invention is therefore to provide an electrolysis system in which a shutdown operation can be realized in a technically simple and reliable manner, so that effective frost protection is achieved even for longer periods of time. Another object is to provide a corresponding use of the electrolysis system during shutdown operation, in which protection against frost damage is achieved even in the event of a severe risk of frost.

[0011] According to the invention, the purpose relating to the electrolysis device is achieved by an electrolysis device for producing hydrogen and oxygen as product gases, the electrolysis device comprising an electrolysis module and a process technology unit, wherein the process technology unit has a reactant pipeline for supplying process water and a product pipeline, which are respectively connected to the electrolysis module, wherein the process technology unit is equipped with an insulation device for thermal insulation comprising thermal insulation material, so that a slowed cooling of the process water can be achieved during shutdown operation.

[0012] The invention is based on the recognition that, in particular in the event of an interruption in the power supply for the electrolysis, reliable and efficient shutdown operation or shutdown management is required, while avoiding damage to the equipment and, therefore, absolutely avoiding damage to the electrolysis modules and electrolysis cells. If a grid connection of the electrolysis plant to the public grid is not provided or is out of service for a long period of time, the electrolysis modules and, in particular, the electrolysis cells must be protected from various hazards which could lead to damage or complete failure of sensitive components of the cells, such as membranes or electrodes or catalyst materials of PEM cells. In addition to the need to avoid dry running of the cells due to water loss or a drop in the water level in the cells, it is also necessary to avoid freezing of the process water in the electrolysis modules.

[0013] In particular, the serious risk of complete failure of the batteries due to freezing must be counteracted in areas where there is a risk of frost, where the electrolysis plant is used. This is particularly important when the electrolysis plant is installed offshore, since it cannot be connected to the public grid for energy supply during outages. It also applies to onshore applications in isolated grid operation without a public grid connection, for example in remote and underdeveloped areas.

[0014] In any case, the sensitive electrolysis cells and their components must be kept moist, that is, they must be soaked with liquid water even during idle operation or they must be flushed with water when the power supply for the electrolysis current is interrupted.

[0015] Unexpected downtime and interruptions in the power supply, especially for safety or weather reasons, such as in the direct connection of electrolysis plants to wind energy plants, in the case of a short-term or even instantaneous emergency shutdown in the event of a fault, can cause considerable problems. Therefore, the management of dark periods on the generator side has hitherto been very difficult and technically requires considerable effort, especially to prevent frost damage when the outside temperature is in the frost range, which can freeze the water in the electrolysis cells. In these application cases, the electrolysis plants must be equipped with complex and expensive battery systems, energy storage systems or emergency power generation facilities and designed to be very large in order to ensure a minimum power supply in the event of a power shortage and to keep the temperature of the process water in the electrolysis modules above the freezing point. When power shortages or dark periods occur during offshore operations for much longer than a few hours or even days, it is not possible to ensure antifreeze protection at low ambient temperatures below the freezing point of water. Frost damage occurs within a short time.

[0016] The electrolysis plant according to the invention provides an effective remedy in this case by using the thermal energy of the process water already present during operation in a simple manner to prevent the process water from freezing over a longer period of time. In this case, known auxiliary energy systems, such as battery storage for electrical heating, are not used or are used only to a limited extent. Due to the high thermal capacity of water, the process water in the process technology unit has a very high thermal energy content at an operating temperature level of about 60° C. Natural cooling results in a temperature drop from 60° C. to 40° C. within one hour after the plant is shut down.

[0017] This available heat energy in the electrolysis plant can be further utilized advantageously by providing a process technology unit with an insulation device for thermal insulation, by retaining it in the process water circuit for as long as possible and preventing the process water from cooling naturally rapidly. The insulation material of the insulation device provides a passive insulation measure to keep the heat in the system for as long as possible. This can slow down the cooling of the process water during shutdown operation and prevent frost damage in the electrolysis module. Here, heat-carrying process water at about 60° C. can be provided as a heat medium via a reactant line as an output line and a product line as a return line. Due to the thermal insulation of the process technology unit, the cooling process is significantly slowed down even under frost conditions. This provides a simple and efficient measure to advantageously keep the costs of the self-sufficient storage systems that have been common so far (such as batteries or emergency power supply systems for heating process water) low and further reduce costs compared to known systems. Due to the reduction in material costs, weight, installation space requirements, etc., lower production costs and system costs are achieved, wherein the temperature maintenance scheme of the present invention even allows the electrolysis plant to be shut down for a longer period without having to worry about damaging frost damage to the battery.

[0018] This is particularly advantageous for the operation of isolated power grids in the offshore environment of the electrolysis equipment. In this way, several days of dark and windless periods or power shortages can be safely spent. Batteries or other storage systems can also be provided in the electrolysis equipment. However, due to the maintenance of the inherent temperature by the insulation device of the process technology unit, the size of the battery or other storage system can be significantly reduced and can be used for other purposes as needed, such as for operating the preferably existing circulation pump to use process water as a heat medium in the reactant pipeline or product pipeline. Therefore, the temperature maintenance for several days can be achieved and maintained by the circulation process, and the cooling is slowed down, wherein ice formation is reliably prevented. Here, partial circulation is also particularly advantageous, such as by a controllable metering valve, so that only part of the flow from the heat reservoir of the process water circulates in the insulated process technology unit in the closed loop, wherein the heat is transferred to the electrolysis module by the process water. The circulation flow required for the circulating process water is selected to be the minimum, and it is adjusted, for example, according to the external temperature and process water temperature obtained by the corresponding temperature sensor. Thus, the shutdown operation dominated by the weather is implemented in the electrolysis equipment.

[0019] Therefore, the device solution of the present invention can be used particularly advantageously in the case of an isolated grid connection and operation of an offshore wind energy plant, that is, without a connection to the public grid power supply. During the dark and windless periods of winter, the electrolysis plant may be in a shutdown state for several days without a power supply. In order to reduce the huge system costs of battery storage (the battery mass for each wind turbine is estimated to be about 76 tons), the isolation solution of the present invention is a low-cost and particularly efficient measure to purposefully slow down the cooling process of the electrolysis module and prevent freezing. The available heat in the system is utilized, and additional electric heating devices in the battery system can be completely eliminated, or the size of the battery system can be correspondingly reduced as reserve energy.

[0020] In a preferred embodiment of the electrolysis plant, the process engineering unit has a gas separator which has a thermal insulation material.

[0021] The gas separator is designed in the process technology unit for phase separation of product gas and water. Here, the electrolysis module is connected to the gas separator via a product pipeline. Hydrogen and oxygen are obtained as product gases in the water electrolysis process, which are initially in their respective mixed phases with water. Corresponding gas separators are provided in the product pipelines on the hydrogen side and the oxygen side of the electrolysis device. Advantageously, the gas separator is insulated as a component of the process technology unit for guiding process water. Therefore, the insulating device for insulation advantageously includes a gas separator with an insulating material. For example, the insulating material is applied flatly to the container wall of the gas separator from the outside. In particular, the insulating material is applied comprehensively and completely to the gas separator to ensure the best possible insulation effect for long-term shutdown operation.

[0022] In a particularly preferred embodiment of the electrolysis plant, the reactant lines and the product lines are surrounded by a thermal insulation material.

[0023] The insulating wrapping can be achieved by a tubular insulation with a suitably dimensioned wall thickness (e.g. in the form of an insulating hose or a self-adhesive insulating hose), which is guided in a tight and flush manner around the tubular reactant line or, respectively, around the product line. For the insulating tube, the outer diameter of the pipe can preferably be 20 mm to 120 mm, while the wall thickness is preferably 10 mm to 50 mm.

[0024] Preferably, in the electrolysis plant the process engineering unit has a heat exchanger, to which the thermal insulation material is applied.

[0025] It is advantageous here to wrap the heat exchanger with insulating material over a large area and all around so that the heat in the system can be stored and retained for as long as possible. During normal operation, the heat exchanger cools the process water that is heated and returned during the electrolysis process. The heat exchanger can thus form a usable heat reservoir even during standstill operation of the electrolysis plant, provided that the container is designed in a suitably insulating manner. This can be achieved, for example, by using a large number of appropriately designed thick-walled sheets made of insulating material, which can be self-adhesive.

[0026] In a particularly preferred embodiment of the electrolysis device, the thermal conductivity of the thermal insulation material is less than 0.07 W / m·K, in particular less than 0.04 W / m·K.

[0027] The lower the thermal conductivity selected, the smaller the wall thickness of the insulating material used in the thermal insulation can be designed. Therefore, high thermal insulation materials with a thermal conductivity of less than 0.04 W / m·K are particularly advantageous. Therefore, as low a thermal conductivity as possible is generally preferred in order to use less thermal insulation material and achieve better manageability when constructing the insulation in the process technology unit.

[0028] Preferably, the insulation means comprises an insulating material made from a flexible, thermally insulating barrier material.

[0029] The mechanical flexibility of the insulation material facilitates simple installation and connection and adaptation to the geometry of the surfaces of the components of the process engineering unit that need to be insulated.

[0030] Therefore, from the perspective of mechanical flexibility and assembly, an insulation layer thickness or material thickness of 9 mm to 30 mm, in particular 25 mm, is particularly advantageous for the insulation material.

[0031] Preferably, the thermal insulation material comprises or consists of an elastomeric foam based on synthetic rubber.

[0032] This material selection ensures particularly effective thermal insulation of the process technology of the electrolysis plant, in particular the insulation and protection of pipelines, containers (including pipe bends) in order to store thermal energy for shutdown operations. This saves, in particular, battery energy that would otherwise have to be reserved for electrical heating and maintaining antifreeze temperatures.

[0033] An insulating hose with a self-adhesive closure made of insulating material may be advantageous, which completely surrounds and insulates the pipe lines such as reactant lines and product lines. The size of the hose can be designed so that it can preferably be used for pipe outer diameters of 10 to 90 mm.

[0034] In a particularly preferred embodiment of the electrolysis device, the insulating device for thermal insulation is optionally designed as a hose, a self-adhesive hose, a plate, a self-adhesive plate, a tape, a pipe carrier or a combination thereof.

[0035] A preferred use of the electrolysis plant according to the invention is during standstill operation, in which a reliable protection against frost damage is achieved even in the presence of a severe risk of frost.

[0036] A particularly preferred use of such an electrolysis device is in electrical connection with an offshore wind energy installation for supplying electricity, in particular in isolated grid operation, wherein the electrolysis current is supplied from the wind energy installation to the electrolysis device.

[0037] For the described applications, a battery storage device can be used as an auxiliary energy source, by means of which additional heat can be generated as required during idle operation in order to maintain a minimum temperature for the process water.

[0038] Auxiliary energy is required here only when required and only as a supplement to the heat supply provided and available by the thermally isolated process technology.

[0039] The advantages of the electrolysis apparatus are to be regarded as advantageous embodiments of the use according to the invention and vice versa.

[0040] Further advantages, features and details of the invention are given by the following description of preferred embodiments with reference to the drawings. The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the drawings and / or shown individually in the individual figures can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the present invention are explained in more detail with reference to the accompanying drawings. Here, schematically and very simply shown:

[0042] Figure 1 A schematic diagram showing the main components of an electrolysis apparatus for producing hydrogen;

[0043] Figure 2 A section of an electrolysis plant with process engineering units and an oxygen-side circuit is shown;

[0044] Figure 3 The cooling curve of the electrolysis module during the shutdown operation of the electrolysis system is shown qualitatively.

[0045] The same reference numerals in the figures have the same meaning. DETAILED DESCRIPTION

[0046] Figure 1 A schematic or functional illustration of an electrolysis device 1 for the electrochemical decomposition of water into the product gases hydrogen and oxygen is shown. The electrolysis device 1 is, for example, a PEM electrolysis device based on a proton exchange membrane. Figure 1 Typical and basic equipment components of a hydrogen production plant based on PEM electrolysis are shown. In addition to the electrolysis unit 21 as the main component of the actual electrolysis process, auxiliary systems such as a water treatment unit 27, a gas purification unit 29 and a cooling device 31 are also provided for the operation of the electrolysis device 1. Purified and deionized water can be supplied to the electrolysis unit 21 as a reactant via a supply line 35 through the water treatment unit 27, and can be added when necessary according to process control and water requirements. The product gas obtained from the electrolysis process, such as hydrogen, can be supplied to the downstream gas purification unit 29 via a product gas pipeline 33. The gas purification unit 29 can have multiple purification stages (not shown in detail) in order to obtain high-purity hydrogen as a product gas that does not contain impurity gas components such as oxygen and other impurities. Gas purification based on catalytic recombination is usually present in the gas purification unit 29, because the catalytic purification principle has a particularly high purification efficiency and specificity, especially for oxygen as an impurity gas component in the hydrogen product gas. In the compression unit downstream of the gas purification unit 29 ( Figure 1 The hydrogen product gas may be compressed and then stored or further transported.

[0047] The actual material conversion process takes place in the electrolysis unit 21 during operation. The electrolysis unit 21 has an electrolysis module 3, a power supply unit 23 and a process technology unit 5. The electrolysis module 3 has a plurality of electrolysis cells. A plurality of electrolysis modules 3 can be electrically connected in series to form a module complex or an "electrolysis stack" or an actual electrolysis device as a reactor for the electrochemical decomposition of water. In the electrolysis device, the individual electrolysis cells are usually stacked in the axial direction into an electrolysis module 3 including a plurality of single cells, and are installed into a module or electrolysis module 3. The electrolysis device usually has a plurality of electrolysis modules 3, which together form a so-called electrolysis stack or simply a "stack". Therefore, for example, 50 electrolysis cells can be stacked axially into a module, and then, for example, 5 electrolysis modules 3 can be stacked in the axial direction into a stack, so that such an electrolysis stack can therefore contain, for example, 250 cells in the entire axial complex.

[0048] Once the electrolysis module 3, electrolysis cell or electrolysis stack in the PEM electrolysis device is filled with water for the first time, for example after manufacturing, it is necessary to ensure that water (reactant water) is always left in the module or a water-gas mixture is left during the operation of the electrolysis device. Therefore, dry operation or drying up, for example, must be prevented at each operating stage, because this will cause irreversible damage to the electrolysis device. Most importantly, the membrane must always be kept in a humid environment, but other functional components and components (such as catalysts or electrodes) must not dry out. In addition, in the event of a long interruption of the electrolysis current supplied by the power supply unit 23 or a power shortage, there is also a risk of frost damage and irreversible damage to the battery, especially to the membrane, due to freezing of the process water. In remote areas where the electrolysis device 1 is installed, or in the case of isolated grid operation that is not dependent on the grid connected to a wind energy device, long-term power shortages may occur during dark and windless periods, especially in cold winters.

[0049] In order to cope with the risk of freezing and irreversible damage to the cells and membranes, and to maintain the long-term shutdown operation of the electrolysis device 1, the process technology unit 5 is equipped with an insulation device 11 for thermal insulation. The insulation device 11 includes an insulation material 17 with a low thermal conductivity (for example, a maximum of 0.04 W / m·K), so as to achieve a good insulation effect and slow down the cooling in the shutdown state. The process technology unit 5 has a reactant pipeline 7 and a product pipeline 9, which are respectively connected to the electrolysis module 3 and are protected by the insulation device 11 together with other components of the process technology unit 5 in this case to prevent frost in particular. To this end, the insulation material 17 is applied to the outer surface of the reactant pipeline 7 and the product pipeline 9, respectively, almost completely covering it as a tubular pipeline insulation. The insulation material 17 includes a flexible, heat-insulating barrier material, such as an elastomeric foam based on synthetic rubber.

[0050] Since the process technology unit 5 is equipped with an insulation device 11 for thermal insulation, the thermal energy of the water available in the electrolysis device 1 (e.g., about 60° C.) can be further utilized advantageously during shutdown operation by keeping this heat in the process water circuit for as long as possible and preventing the process water from being subjected to rapid natural cooling. A connection to the electrolysis module 3 is provided via the reactant line 7 and the product line 9, so that the still warm process water from the process technology unit 5 can be transferred to the electrolysis module 3 and, if necessary, can be circulated in the circuit by an electrically driven and controlled circulation pump. In this way, the cooling process can be significantly slowed down without having to rely heavily on electrical auxiliary systems (e.g., battery storage 19) to maintain the temperature above the freezing point of water. Since the thermal energy in the system of the process technology unit 5 is utilized, the battery storage 19 can be designed to be smaller in size to facilitate shutdown management of the electrolysis device 1. Only when necessary, electrical energy is obtained from this additional auxiliary energy source, in particular the battery storage 19, which is used to facilitate the operation of the circulation pump during shutdown operation. In an emergency, it can also be used Figure 1 Heating elements (eg resistance heaters) not shown in detail provide additional electrically derived thermal energy in the process water circuit in order to heat the process water or to ensure that the temperature is maintained at a minimum temperature for reliable frost protection of the electrolysis module 3 .

[0051] In particular, for example, electrical consumers of the process technology unit 5, such as pumps, drives or regulating elements that generate heat during operation, as well as fittings and flanges, are not provided with an insulation layer in order to prevent these heat-generating components from accumulating heat and overheating during normal operation and to ensure that these components cool naturally by heat dissipation. In the case of fittings and flanges, they are still accessible if the thermal insulation material 17 is not applied thereto. Therefore, the thermal insulation device 11 preferably does not include these components in order to prevent overheating during operation.

[0052] Figure 2 A simplified illustration of a section of an electrolysis plant 1 with a process engineering unit 5 and an oxygen-side circuit is shown. The electrolysis plant 1 is designed for the electrolysis of water so that hydrogen and oxygen can be produced as product gases during operation. The electrolysis plant 1 shown here has, by way of example, only one circuit on the oxygen side. However, the process engineering unit 5 can be designed in a very similar manner for a corresponding second circuit on the hydrogen side. Thus, Figure 1It is a simple embodiment of an electrolysis device 1 in order to illustrate in principle the heat maintenance scheme of the present invention and the heat utilization during shutdown operation. The electrolysis device 1 has an electrolysis device 45 and an electrolysis cell stack 37, which has a plurality of electrolysis cells not shown in detail and stacked in the axial direction. Here, the anode half-cell and the cathode half-cell of the electrolysis cell are separated by a membrane not shown in detail. The membrane material contains PFSA (perfluorosulfonic acid), so that the electrolysis device 45 is implemented as a PEM device. A plurality of electrolysis cells are stacked and installed into an electrolysis module 3. A plurality of electrolysis modules 3 are connected together to form an electrolysis stack or simply referred to as a "stack", which forms an actual electrolysis device 45 or reactor for the electrochemical conversion process in the electrolysis device 1.

[0053] This simple loop is used to supply water for the electrolysis reaction to the electrolysis cell stack 37, wherein the water is also used to cool the cell during operation. As the product gas of the electrolysis, the oxygen produced is fed to the gas separator 13 for oxygen in a mixed phase together with excess water. Phase separation occurs in the gas separator 13, so that the gaseous oxygen is separated from the liquid water and leaves the loop through the product gas pipeline 33 for oxygen. In order to maintain the water circulation in the loop, a circulation pump 39 is provided in the loop, which can be driven during shutdown operation with the help of a battery 19 in an emergency (when the power is interrupted). During operation, deionized water (VE water) is supplemented from the supply line 35 through a solenoid valve 47b to compensate for the consumed water. Although it is deionized water, it may still contain a small amount of impurities in the loop. In order to cope with this effect, another solenoid valve 47a can be temporarily opened when necessary, and part of the water can be discharged from the loop through a drain pipe 41.

[0054] exist Figure 1 In the embodiment of the invention, there is no circuit on the hydrogen side of the electrolysis device 1. The prepared hydrogen is simply discharged through the product pipeline 9 for product gas and is used further, for example for subsequent compression. Usually, a pressure maintaining valve is arranged in the product gas pipeline 9 for the product gas hydrogen, but the pressure maintaining valve is not shown in detail in the embodiment. The pressure maintaining valve is used to discharge the hydrogen under a certain overpressure, which is very ideal for the further processing of the hydrogen in most applications. Since liquid water is usually produced on the hydrogen side during the PEM electrolysis process, a condensed water pipeline 43 is also provided, which is opened when a certain amount of water accumulates in order to discharge this water. This can be achieved, for example, using a buoy. Figure 1 This indicates that the water has been discarded. However, it is also possible that the water can be further used for electrolysis by returning it to the loop on the oxygen side. For large electrolysis equipment 1, this return in the process is usually an economically feasible method.

[0055] In addition, the electrolysis device 1 is also equipped with sensors 49a and 49b, which are used to monitor the quality of process water in the system on site. Sensors 49a and 49b can be used as conductivity sensors The conductivity sensors 49a, 49b are designed and installed for measuring a specific conductivity as a quality indicator. These conductivity sensors 49a, 49b can be used, for example, to determine the fluoride concentration in the water according to certain correlations. In this case, it is particularly advantageous to install the conductivity sensors 49a, 49b at a point in the system where the pressure is as high as possible, because here the degassing of dissolved hydrogen or oxygen is particularly low or unlikely to occur. Gas bubbles interfere with the precise measurement of the conductivity and distort the result. Therefore, the conductivity sensors are positioned at the geodetic low point of the electrolysis device 1 in order to take advantage of the hydrostatic pressure and thus effectively combat degassing.

[0056] The process technology unit 5 is provided with an insulation device 11, which has an insulation material 17 applied to the surface of the components of the process technology unit 5. The insulation material 17 comprises a material with a thermal conductivity that is as low as possible (maximum 0.04 W / m·K), for example, in the design and configuration of the insulation device 11, a material with the trademark Armaflex or Armaflex Ultima can be used. Elastomer foams based on synthetic rubber are particularly suitable for this purpose, so that mechanical flexibility is achieved during installation and the insulation material 17 is applied to the surfaces of selected equipment parts and components in the process technology unit 5 in a heat-tight manner. In order to insulate the process technology unit 5, at least the components that conduct or contain process heat during operation are insulated with the insulation material. Therefore, the gas separator 13 is as completely surrounded as possible by the insulation material 17, and the reactant pipeline 7 and the product pipeline 9 are also surrounded by corresponding tubular insulated hoses, which have insulation material of corresponding wall thickness. The heat exchangers 15 in the individual product gas lines 33, which are present, for example, in the process engineering units 5, are also insulated and tightly wrapped with insulation material 17. During operation, the heat exchangers 15 ensure that the product gas (hydrogen or oxygen) obtained is cooled, so that the heat exchange medium (i.e. water) is heated to a higher temperature by absorbing heat. This heat can be used additionally when the electrolysis plant 1 is in standstill operation to delay the cooling of the electrolysis modules 3 and reliably prevent the process water in the electrolysis modules 3 from freezing.

[0057] Especially in isolated grid operation, this heat maintenance concept is very economical for frost protection of the electrolysis plant 1 and is reliable for several days. Figure 1 In the embodiment of the invention, the electrical connection of the electrolysis device 1 and the feeding of the electric power and the supply of the power supply unit 23 are carried out, for example, by an offshore wind power plant in an isolated grid complex, i.e. independently of the grid connection. In this case, the electrolysis current from the wind power plant is supplied to the electrolysis device 1 and, after corresponding rectification, is supplied via the connecting line 25 (see Figure 1 ) is delivered to the electrolysis module 3. The battery storage 19 is used as an auxiliary energy source, by which additional heat is generated during shutdown operation as required, so that the minimum temperature of the process water is always maintained. However, in the current case, the auxiliary system and the storage system can be significantly reduced in size and therefore more cost-effective through the thermal management solution.

[0058] The battery 19 can usually be used for emergency power supply (UPS) to overcome short-term power shortages, for example. In isolated grid operation, the battery 19 is sometimes also needed to prevent freezing in emergency situations, but the required battery capacity is much lower for maintaining heating needs in emergency situations. During shutdown operation, the temperature is maintained above freezing and thus provides reliable antifreeze protection, which is mainly achieved by utilizing the inherent thermal energy in the process water.

[0059] In summer, if necessary and advantageous, the battery 19 can also be used for cooling. In midsummer, when the process water temperature in the water circuit is typically 60°C, overheating protection can also be achieved in combination with the insulation device 11 in the following way: for example, by means of the cooling device 31 (see Figure 1 ) to dissipate excess heat. In principle, a container solution can also be considered as a possible design of the insulation device 11, which has an insulated "container" that is cooled as required, so that the process technology unit 5 and / or the electrolysis unit 21 do not overheat in summer when installed in an insulated container such as a container. Due to the insulating effect of the insulation device 11 designed as a container, the required cooling performance in summer is also reduced.

[0060] Figure 3 The figure shows the cooling curve of the electrolysis module 3 during the shutdown operation of the electrolysis system 1 in a qualitative diagram. The electrolysis system 1 is powered by an offshore wind power system, for example on an offshore platform on the high seas, i.e. in a self-sufficient isolated grid operation. At time t=0, there is a long dark and windless period in winter, so that the power supply for electrolysis is interrupted for a correspondingly long time and there is a serious risk of frost. Figure 3 The x-axis of the graph represents time t, and the y-axis represents the change of the temperature T of the water in the electrolysis module 3 over time. At the start of the shutdown operation t=0, the temperature of the process water is, for example, T A =60℃.

[0061] In the conventional electrolysis device 1, according to the time-temperature curve T 1 (t), the cooling process takes place in a short time and, despite the additional heating of the auxiliary system using the electricity from the battery 19, only the freezing temperature T can be avoided. G= 0°C and thus avoid irreversible damage to the electrolytic cells 37 of the module 3 for a maximum of several hours. During longer dark and windless periods, despite the additional heating provided by the auxiliary system, due to the limited battery capacity, water will freeze in a relatively short time t under frost conditions during shutdown operation. G Then freeze.

[0062] In contrast, the time-temperature curve T 2 (t) shows the advantages of the heat storage and heat utilization solution of the present invention: since the process technology unit 5 is equipped with the insulation device 11, the heat energy provided by the operation in the electrolysis equipment 1 can be advantageously continued to be used during the shutdown period by keeping it in the process water circuit for as long as possible, instead of letting the process water cool naturally as before. Effective passive insulation measures are ensured by the insulation material 17 of the insulation device 11 to retain and utilize the available heat energy in the system for as long as possible. As a result, the cooling of the process water is significantly slowed down during the shutdown period, and frost damage in the electrolysis module 3 is reliably and long-term avoided. As a result, the time-temperature curve T 2 (t) can be reliably and almost asymptotically maintained at the freezing point of water, T G = Values ​​ΔT above 0°C - only as an alternative, additional heat can be brought in by the battery 19, for example by a resistance heating device, in the case of additional demand. For this purpose, basically, at the beginning, i.e. at t=0, heat-carrying process water at about 60°C is provided as heat storage and heat medium via the reactant line 7 as an output line and the product line 9 as a return line as well as in other containers of the process technology unit 5. Compared with known measures, by the targeted insulation of the process technology unit 5 with the insulating material 17, the cooling process can be significantly slowed down even under frost conditions and last for at least several days, and advantageously even longer. In this way, longer dark and windless periods can be spent in isolated offshore operation without having to worry about frost damage. The electrolysis device 1 can also be provided with a battery 19 or other storage system. However, since the inherent temperature is maintained by the insulation device 11 of the process technology unit 5, the size of the battery or other storage system can be designed to be significantly smaller and, if necessary, can also be used for purposes other than heating purposes, such as for operating a preferably existing circulation pump ( -or Zirkulationspumpe) 39, in order to use process water as a heat medium in the reactant line 7 or the product line 9. In this way, temperature maintenance for several days can be achieved and maintained by a circulation process, and cooling can be slowed down, wherein freezing is reliably prevented. Partial circulation is also particularly advantageous here, for example, by means of a controllable metering valve, so that only a part of the flow from the heat reservoir of the process water circulates in the insulated process technology unit 5 in a closed loop, wherein the heat is transferred to the electrolysis module 3 in a targeted manner by the process water as a heat carrier. As a result, the water remains liquid and the sensitive membrane remains immersed in water or remains moist. Once the dark and windless period ends after a period of time and the power supply can be restored again, from time point t s The shutdown operation is ended, and the electrolysis device 1 is started again and put into normal operation, so that the time-temperature curve T of the process water 3 (t) shows an increasing curve until it reaches about T again A = Normal operating temperature of 60°C.

Claims

1. An electrolysis plant (1) for producing hydrogen and oxygen as product gases, comprising an electrolysis module (3) and a process technology unit (5), in, The process technology unit (5) has a reactant pipeline (7) and a product pipeline (9) for supplying process water, wherein the reactant pipeline and the product pipeline are respectively connected to the electrolysis module (3), wherein the process technology unit (5) is equipped with an insulating isolation device (11) comprising an insulating material (17) for thermal insulation, so that the process water can be cooled slowly during shutdown operation.

2. The electrolysis device (1) according to claim 1, in, The process engineering unit (5) has a gas separator (13) which has the thermal insulation material.

3. The electrolysis device (1) according to any one of the preceding claims, in, The reactant pipeline (7) and the product pipeline (9) are wrapped by the thermal insulation material (17).

4. The electrolysis device (1) according to any one of the preceding claims, in, The process engineering unit (5) has a heat exchanger (15) to which the thermal insulation material (17) is applied.

5. The electrolysis device (1) according to one of the preceding claims, in, The thermal conductivity of the thermal insulation material (17) is less than 0.07 W / m·K, in particular less than 0.04 W / m·K.

6. The electrolysis device (1) according to any one of the preceding claims, in, The insulation device (11) has a heat-insulating material (17) made of a flexible, heat-insulating barrier material.

7. The electrolysis device (1) according to claim 6, in, The thermal insulation material (17) comprises an elastomeric foam based on synthetic rubber.

8. The electrolysis device (1) according to any one of the preceding claims, in, The insulating device (11) for thermal insulation is optionally designed as a hose, a self-adhesive hose, a plate, a self-adhesive plate, a tape, a pipe support or a combination thereof.

9. Use of an electrolysis device (1) according to any of the preceding claims, which is electrically connected to an offshore wind energy plant for supplying electricity, in particular in isolated grid operation, in, The electrolysis current comes from the wind energy installation and is supplied to the electrolysis installation (1).

10. The use according to claim 9, in, A battery storage (19) is used as an auxiliary energy source, by which additional heat is generated as required during standstill operation, thereby maintaining the minimum temperature of the process water.

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