Electrolysis plant for the production of a syngas

Abstract

The invention relates to an electrolysis plant (30) comprising an electrolysis system (2) and a synthesis system (20).

Description

[0001] Electrolysis plant for producing synthesis gas

[0002] The present invention relates to an electrolysis plant for producing synthesis gas by means of an electrolysis system.

[0003] One way to reduce dependence on fossil fuels and CO2 emissions is to replace crude oil with synthetic hydrocarbons produced from carbon dioxide (CO2) and water (H2O). By applying electrical current, high-temperature electrolysis (SOE for "Solid Oxide Electrolysis") can produce a synthesis gas containing hydrogen (H2) and carbon monoxide (CO). In a subsequent synthesis process, the synthetic hydrocarbons are obtained from the synthesis gas.

[0004] The object of the present invention is to increase the efficiency of the high-temperature electrolysis described above in a cost-effective and simple manner.

[0005] The above object is achieved by an electrolysis plant having the features of claim 1.

[0006] According to the invention, an electrolysis system is provided. The electrolysis system comprises an electrolysis cell stack with a cathode section, which has a cathode supply section and a cathode discharge section, and an anode section, which has an anode supply section and an anode discharge section. Furthermore, the electrolysis system comprises an anode gas connection, fluidly coupled to the anode supply section by means of an anode supply connection, for supplying anode gas to the anode section. Furthermore, the electrolysis system comprises an anode discharge connection, fluidly coupled to the anode discharge section by means of an anode discharge connection, for discharging anode exhaust gases generated by the electrolysis cell stack. Furthermore, the electrolysis system comprises a cathode supply connection, fluidly coupled to the cathode supply section by means of a cathode supply connection, for supplying cathode gas to the cathode section.In addition, the electrolysis system has a cathode discharge connection fluidly coupled to the cathode discharge section by means of a cathode discharge connection for discharging synthesis gas generated by the electrolysis cell stack.

[0007] The synthesis system comprises a synthesis unit, which is fluidly coupled to the cathode discharge connection by means of a synthesis gas supply connection. Furthermore, the synthesis unit serves to synthesize the synthesis gas generated by the electrolysis cell stack and supplied via the synthesis gas supply connection. The synthesis unit is fluidly coupled to a residual gas supply connection by means of a residual gas discharge connection for providing residual gas. An electrolysis system according to the invention is characterized in that the residual gas supply connection is fluidly connected to at least one residual gas utilization device of the electrolysis system.

[0008] A residual gas utilization device within the meaning of the present invention serves a plant-internal use. This can be understood as the utilization of the energy stored in the residual gas. The chemical utilization of the contained substances, in particular short-chain hydrocarbons and / or carbon dioxide, are also possible components for further use in the electrolysis plant. By integrating a recycling of the residual gas for use within the electrolysis plant, an increase in operating efficiency can be achieved. In particular, it is also possible to combine different types of utilization.

[0009] In the context of the invention, an electrolysis plant is understood to mean in particular a stationary plant with an electrolysis system and a synthesis system, which, for example, produces synthetic fuels.

[0010] It can be advantageous if the electrolysis system has a recycle gas connection as a residual gas supply connection for providing recycle gas as a residual gas, which is produced as a by-product during a synthesis of the synthesis gas produced by the electrolysis cell stack in a subsequent synthesis process, wherein the recycle gas connection is connected in a fluid-communicating manner to the cathode supply connection.

[0011] For the sake of simplicity, the term "electrolysis cell stack" is used in this description. This refers to at least one electrolysis cell stack. Of course, the electrolysis system can contain multiple electrolysis cell stacks, which can be interconnected in any desired manner, e.g., connected in series or in parallel. Each cathode section and each anode section of each electrolysis cell stack is then fluidly coupled to the connections mentioned herein in the manner described herein.

[0012] For the purposes of this invention, the terms "residual gas" and "return gas" are used synonymously. Accordingly, the terms "return gas connection" and "residual gas supply connection" are also used synonymously.

[0013] The electrolysis cell stack can particularly be a solid oxide electrolyzer cell system (SOEC system). The electrolysis cell stack, preferably in the form of a co-electrolysis system, is operated to achieve the electrolysis of water (H2O) and carbon dioxide (CO2). Hydrogen gas (H2), carbon monoxide (CO), and oxygen (O2) can be produced by the electrolytes in the electrolysis cell stack. It is advantageous if the electrolysis cell stack for generating the synthesis gas is connected to a power source for providing electricity from a renewable energy source. With such a power source, which is fed from renewable energy sources, high-temperature electrolysis operation can be made ecologically sustainable. The electrolysis cell stack is particularly advantageously designed as a co-SOEC stack with a co-SOEC system.Here, water and CO2 are electrolyzed simultaneously to produce syngas. This is a mixture of CO2 and H2 that can be used in further steps to produce various synthetic fuels and chemicals.

[0014] For the reaction described above, anode gas, in particular air, especially fresh air, or oxygen, is supplied to the anode section via the anode supply connection. Cathode gas, in particular carbon dioxide, is supplied to the cathode section via the cathode supply connection. The cathode supply connection can be connected to various carbon dioxide sources. For example, it is possible to extract carbon dioxide from the air, from biogas processes, from industrial exhaust gases, etc. Water can be supplied to the cathode supply section via a first additional supply connection for supplying water. For this purpose, the first additional supply connection, which can be fluidically coupled to the cathode supply connection or the cathode supply section by means of a first additional supply connection, can supply water, preferably in the form of steam, to the cathode supply section.Alternatively or additionally, the water can be evaporated into water vapor in the electrolysis system. The water vapor can be considered part of the cathode gas because it is supplied to the cathode feed section. Any shielding gas supplied to the cathode feed connection can also be considered part of the cathode gas because it is supplied to the cathode feed section.

[0015] From the anode discharge section, the anode exhaust gases are discharged via the anode discharge connection to the anode discharge connection. The anode exhaust gases discharged via the anode discharge connection include, in particular, exhaust air or oxygen discharged from the electrolysis system, especially oxygen-enriched air, as well as catalyst exhaust gases downstream of the catalyst, i.e., combustion products of catalytic combustion. These can be released into the environment, for example, from the anode discharge connection.

[0016] From the cathode discharge section, the generated cathode offgas, which is synthesis gas containing primarily hydrogen gas and carbon monoxide, is fed to the cathode discharge port. This port is connected to a synthesis plant via a corresponding synthesis system to provide the synthetic gas for the production of synthetic hydrocarbons. In this synthesis process, typically not all of the synthesis gas can be converted, and / or short-chain hydrocarbons are produced, which are separated.

[0017] Some of the resulting hydrocarbons are unsuitable for their subsequent intended use, for example, because the chains are too short. However, the portion of the hydrocarbons that is unusable for subsequent use contains a chemically stored energy component and can be considered a carbon dioxide source. This gas component is referred to as recycle gas in the context of the present invention.

[0018] To obtain the recycle gas, a method for separating the usable portion of the hydrocarbons is provided, described in more detail later. The recycle gas obtained in this way is then fed to the recycle gas connection of the electrolysis system and made available for recycle use in the electrolysis system. The recycle gas can be introduced into the cathode feed connection via this recycle gas connection. The recycle gas thus supplements the cathode feed gas supplied from another source, thus reducing the amount of carbon dioxide required as one of the starting materials in the production of the synthesis gas.

[0019] In other words, it becomes possible to recycle the synthesis gas converted in the synthesis process, which has been converted into an unusable portion of the hydrocarbons, back into the electrolysis system. This also allows the CO2 already converted in the synthesis process to be recycled and made available for recirculation. This increases efficiency in particular, as the recycled portion of the short-chain hydrocarbons reduces the CO2 required to operate the electrolysis system. A further advantage of this technical feature is that the short-chain and thus unusable components of the hydrocarbons, and thus the recycle gas, do not have to be disposed of separately and released into the environment.

[0020] Last but not least, another advantage is that the recycle gas is typically at a high temperature due to the high operating temperatures of the synthesis process. This high temperature can then be used to preheat the externally supplied cathode feed gases, such as the CO2 from the CO2 source. By mixing the recycle gas with the cathode feed gas, a mixed temperature is created that is already sufficient as an inlet temperature for the electrolysis system, or at least reduces the required amount of residual heat.

[0021] It can be summarized that the integration of a recycle gas connection and the associated possibility of recycling the unusable part of the production result of the synthesis process brings about an increase in efficiency in both the chemical and energetic sense.

[0022] In order to distinguish components or elements of the same kind or type from one another, such as heat exchangers, shut-off devices, partial paths or bypass paths, the components or elements of the same kind or type mentioned in this description are numbered consecutively and are referred to as first component, second component, third component (or elements), etc., for example first heat exchanger, second heat exchanger, etc. This designation based on the numbering serves solely to distinguish the components or elements of the same kind or type mentioned herein and in no way represents a limitation of the scope of protection.For example, if a claim refers to a fourth component of a kind or type, this does not necessarily presuppose a first, second and third component of that kind or type, unless the first, second and third components of that kind or type are mentioned in a claim to which the claim in question refers back.

[0023] The connections mentioned herein are fluid-conducting, particularly gas-conducting, connections. The connections can be established via various paths or lines, such as pipes or hoses, which are each coupled to one another. Various flow-influencing devices, such as those mentioned herein, can be arranged in the connections.

[0024] To the extent that reference is made herein to the arrangement of a heat exchanger in one connection and the thermal coupling of the heat exchanger to another connection, these features are to be understood as synonymous due to the function of the heat exchanger. This is because the heat exchanger exchanges the heat of two flows in the respective connections, for example, in countercurrent. In this respect, the heat exchanger is actually arranged in each of the two connections, and the heat exchanger also thermally couples both connections.

[0025] Whenever reference is made to control or monitoring, particularly in connection with a shut-off device, this refers to controlling and / or regulating. Even if not explicitly stated, appropriate control electronics and control devices beyond shut-off devices, such as flow meters, may be provided for monitoring purposes.

[0026] The shut-off devices mentioned herein serve at least to stop or allow the flow of the respective fluid, especially gas, flowing through the connections. Controlling the flow rate is also possible depending on the design of the shut-off device used. The shut-off device can be designed in a variety of ways, for example, as a valve, gate valve, shut-off cock, or butterfly valve.

[0027] It can be advantageous if, in an electrolysis system according to the invention, a reformer device is fluidly connected to the recycle gas connection upstream of the recycle gas connection for at least partially reforming the by-products from the synthesis process. The aim of this reforming is, in particular, to reform the recycle gas into carbon dioxide or at least an increased proportion of carbon dioxide in the recycle gas. This enables improved mixing and more efficient conversion in the electrolysis system of the thus increased concentration of carbon dioxide. In addition to chemical reforming and the associated advantages of recirculation to the cathode supply connection, such reforming is usually subject to an endothermic process.This means that the reforming process is usually endothermic and the necessary heat for reforming is provided, for example, by simultaneous catalytic partial oxidation.

[0028] As already explained, a certain minimum temperature for the cathode feed gas is necessary for the operation of the electrolysis system. Since the electrolysis system involves high-temperature electrolysis cells, increasing the temperature of the recycle gas is a further energy advantage. This clearly demonstrates that the integration of a reformer device also brings advantages from both a chemical and thermal, and thus energetic, perspective. In addition to complete reforming to CO2 and / or CO, or at least an increase in the CO2 concentration ratio, even a simple reduction in the chain length of the hydrocarbons can be sufficient to achieve the desired chemical and / or thermal efficiency increase.

[0029] Further advantages can be achieved if, in an electrolysis plant according to the invention, the reformer device has at least one of the following configurations:

[0030] - Steam Reformer,

[0031] Dry reformer, - CPOX reformer.

[0032] The above list is not exhaustive. Of course, it is also possible for a reformer device to have two or more different reformer modules with different reforming processes. The combination of multiple reformer modules can serve to further improve the desired reforming and, in particular, result in a greater increase in the CO2 concentration. It may even be preferable for a specific design of the reformer to be configured to completely or essentially completely reconvert the recycle gas into a carbon dioxide-containing gas.

[0033] It is also advantageous if, in an electrolysis system according to the invention, at least one controllable synthesis recycle gas connection is arranged upstream of the recycle gas connection for at least partially recirculating the recycle gas into the synthesis process. This means that, in contrast to a long recirculation into the electrolysis system, the recycle gas can also be recirculated directly into the synthesis process via a short recirculation. This can be provided in addition to or as an alternative to the recirculation gas connection into the electrolysis system. Depending on the operating situation and / or the composition of the recycle gas, it can already be advantageous to recirculate the short-chain hydrocarbons of the recycle gas directly to the inlet section of the synthesis device and thus run them through the synthesis again.In other words, the short-chain and thus unusable hydrocarbons are returned to the inlet section of the synthesis device for direct further synthesis to extend the chain length. This can be controlled flexibly, depending, for example, on the current CO2 availability for the electrolysis system, the current energy situation with regard to the need for temperature control of the electrolysis system, but also the current operating situation of the synthesis device and thus, for example, the chemical composition of the recycle gas. The possibility of recirculating the recycle gas directly into the synthesis via the synthesis recycle gas connection thus allows for flexible control with regard to a short recycle directly into the synthesis device and a long recycle back into the electrolysis system.Such control can be purely qualitative and / or quantitative. It can also be advantageous if, in an electrolysis system according to the invention, the synthesis recycle gas connection is arranged upstream of a reformer device. As already explained, reformer devices can offer advantages for adapting the recycle gas for repeated use in the electrolysis system. For recirculation of the recycle gas in the short recycle connection directly into the synthesis device, such reforming is not necessary and can even be detrimental. In particular, if, in the case of short-chain hydrocarbons in the recycle gas, the repeated synthesis is intended to lengthen the existing chains, reforming and thus further shortening the chains before this short recycle would potentially be counterproductive.According to the invention, the reformer device in this embodiment is arranged downstream of the synthesis recirculation gas connection, so that the volume flow can be branched off upstream of the reformer device and fed to the short recirculation connection, in particular with flexible and freely controllable shut-off devices, for example control valves.

[0034] It can also be advantageous if a recycle gas catalyst device is fluidly connected to the recycle gas connection upstream of the recycle gas connection. Such a recycle gas catalyst device can be integrated into a reformer device or at least partially form the same. However, it is also possible for such a recycle gas catalyst device to be integrated into an electrolysis system independently of a reformer device or even without a reformer device. The catalytic conversion of the recycle gas serves in particular to increase the temperature of the recycle gas through catalyzed chemical conversion of constituents of the recycle gas. As has already been explained several times, one aim of the present invention is to improve the energetic and in particular the thermal efficiency during operation of the electrolysis system.The use of such a recycle gas catalyst device thus supports this increase in thermal efficiency, since by increasing the temperature of the recycle gas, it can be used to preheat the externally supplied carbon dioxide. The internal recirculation of the energy contained in the recycle gas as heat to heat the recycle gas thus increases the overall efficiency during operation of the electrolysis system and the electrolysis plant in accordance with the invention. It is also advantageous if, in an electrolysis plant according to the invention, the recycle gas connection is integrated into the cathode supply connection. This is, in particular, a structural design that further reduces the overall complexity of the electrolysis system. For example, the cathode supply connection can have an integrated shut-off device that provides a controlled introduction option for the recycle gas in a quantitative and / or qualitative manner.In particular, it is possible to switch the recirculation of the recirculation gas on and off and / or even to control it in a quantifiable manner.

[0035] It is also advantageous if, in an electrolysis system according to the invention, the cathode supply connection and the recycle gas connection each have at least one control valve for controlling the volume flow of recycle gas and cathode supply gas. While purely qualitatively switching control valves would generally fulfill the purpose of controlling and thus controlling, quantitative switching using variably switchable control valves offers further advantages. Particularly when integration into a short recycle cycle using a synthesis recycle gas connection is planned, such quantitatively adjustable and thus controllable control valves can offer the advantage of flexibly and freely adapting volume flows and their relationships to one another to the respective operating situation.In other words, it is now possible to respond flexibly to the actual composition of the recycle gas, the temperature conditions in the synthesis process and in the electrolysis system, and / or the temperature conditions in the cathode feed gas. Through flexible and thus complex control of the individual volume flows, efficiency can be further increased and the core concept of the invention further improved.

[0036] It can be advantageous if, in an electrolysis plant according to the invention, the electrolysis system has at least one heat exchanger, which is arranged in the residual gas supply connection downstream of the catalyst discharge section in the flow direction, and is connected to the anode supply connection and / or the cathode supply connection for heat transfer. Furthermore, the residual gas supply connection downstream of the at least one heat exchanger is fluidly connected to the anode supply connection and / or the cathode supply connection for recirculating the catalytically combusted residual gas into the anode supply connection and / or the cathode supply connection. A significant advantage of this embodiment is the dual use of the residual gas, which can also be referred to as tail gas. A first use of the residual gas occurs through catalytic combustion and the associated thermal conversion of at least part of the chemical energy content of the residual gas.The heated residual gas can then transfer this thermal energy in the at least one heat exchanger to other process gases, in particular an anode feed gas and / or a cathode feed gas, and in this way increase the energetic efficiency during operation of the electrolysis system.

[0037] The further utilization of the residual gas depends on its chemical composition. Since residual gas typically contains carbon in the form of carbon dioxide and / or short-chain hydrocarbons, in the present invention, this carbon is returned to the electrolysis cell stack. In other words, the residual gas is converted again using the electrolysis cell stack. In addition to increasing conversion efficiency, this method can also reduce the need for externally supplied carbon dioxide.

[0038] In summary, an electrolysis system according to the invention of this embodiment thus brings about an increase in both energy and chemical efficiency. Synthesis gas can be produced with reduced energy consumption and a reduced amount of carbon dioxide. A further side effect of the multiple use of the residual gas is the reduction of the exhaust gases generated from the synthesis system. The amount of residual gas that cannot be used as useful gas from the synthesis system therefore does not need to be post-treated and released into the environment. Rather, by recirculating the residual gas into the electrolysis system, the amount of exhaust gas is reduced by this recirculation amount. In addition to the increase in efficiency, a reduction in exhaust gases is also achieved.

[0039] It can be advantageous if, in an electrolysis plant according to the invention, the residual gas supply connection has a residual gas bypass which, bypassing the at least one heat exchanger, is connected in fluid communication with the anode supply connection and / or the cathode supply connection. It can be advantageous if the heat generated by the catalytic combustion in the residual gas is not supplied separately via heat exchangers to the respective anode supply gas and / or cathode supply gas. Since operating losses are possible with heat exchangers and, in particular, a heating phase must be taken into account, the residual gas bypass can enable maximum heat input by directly mixing the heated residual gas with the anode supply gas or the cathode supply gas, particularly when maximum heat input into one of these supply gases is desired. During this mode of operation, particular attention must be paid to the gas composition of the residual gas.For example, if CO2 is present, such direct introduction into the air path is prevented. Such a residual gas bypass can be configured, for example, with the aid of a bypass valve to transfer a partial and / or the entire amount of heated residual gas into the respective feed gas. In other words, the catalytically combusted residual gas and the residual gas heated in this way are mixed directly with the respective feed gas stream via a residual gas bypass and, together with this anode feed gas or the cathode feed gas, enter the electrolysis cell stack as a mixed gas.

[0040] In an electrolysis system according to the preceding paragraph, it may be advantageous if the residual gas bypass has a bypass valve for controlling the direct fluid-communicating connection past the at least one heat exchanger. The residual gas bypass is preferably designed to form a bypass past any heat exchangers that may be present. The bypass valve can be designed as a pure control valve that can be switched between an open position and a closed position. However, a variable control valve is preferred in order to provide variable control, in particular in a quantitative manner, for the desired bypass quantity through the residual gas bypass.As already explained in the previous paragraph, in this way the desired mixing temperature in the anode feed section, provided the residual gas is free of CO2, and / or cathode feed section and thus the temperature of the resulting mixed gas can be adjusted in a controlled manner.

[0041] Further advantages can be achieved if, in an electrolysis cell stack according to the invention, the residual gas supply connection forms the anode discharge connection at least in sections. While, in principle, the residual gas aftertreatment can be designed completely separately from all other anode exhaust gas and cathode exhaust gas connections, integration is possible in this embodiment. The residual gas supply connection is integrated into the anode discharge connection here, thus also separating this anode discharge connection. This makes it possible to combine anode exhaust gas from the anode section of the electrolysis cell stack with the residual gas. This mixing of anode exhaust gas and residual gas preferably takes place upstream of the at least one catalyst, so that a mixed gas of residual gas and anode exhaust gas is fed to the catalytic combustion here.Bypasses from the supply air, i.e. the anode supply section, which will be explained later, are also conceivable in principle, in particular in order to be able to adjust the stoichiometric conditions for the catalytic combustion in a controlled manner for an optimized catalytic combustion and thus an improved energetic conversion in the catalyst device.

[0042] In an electrolysis system according to the preceding paragraph, it may be advantageous if a branch section is arranged in the anode discharge connection downstream of the at least one heat exchanger and upstream of the fluid-communicating connection to the anode supply connection and / or to the cathode supply connection. This allows, depending on the actual chemical composition in the residual gas supply connection, a portion of the catalytically combusted residual gases or mixed gases to be discharged again via the anode discharge connection via the branch section. Here, too, it is possible to flexibly respond to the different chemical and thermal gas situations depending on the operating situation of the electrolysis system and to variably adjust the volume flow, in particular for the return to the anode supply section and / or the cathode supply section.This branch section is also preferably equipped with a branch valve, which is designed either quantitatively, for example in the form of a shut-off valve, or quantitatively in the form of a variable control valve. This allows the branch section to be easily opened and closed, or to specify a defined control of a volume flow through this branch section using the quantitative control valves.

[0043] The anode gas is the gas supplied to the anode section, in particular air or oxygen. This excludes the anode off-gas, i.e., the off-gas discharged from the anode section, in particular air and / or oxygen. The cathode gas is the gas supplied to the cathode section, in particular carbon dioxide, water vapor, and / or a protective gas. This excludes the cathode off-gas, i.e., the synthetic gas discharged from the cathode section. It is also advantageous if the synthesis process is a Fischer-Tropsch process. The coupling of high-temperature electrolysis, in particular high-temperature co-electrolysis, and Fischer-Tropsch synthesis (FTS for short) has proven to be a particularly promising variant for the production of various hydrocarbons.In FTS, synthesis gas produced from high-temperature co-electrolysis is converted into hydrocarbon molecules with various chain lengths at comparatively moderate temperatures, particularly in the temperature range of 200 to 300 °C, and elevated pressures, particularly in the pressure range of 10 to 30 bar, with the help of a catalyst, particularly a Co- or Fe-based one. The FTS process is highly exothermic. In order to maintain the temperature within the specified temperature range, cooling can be carried out along the length of a reactor in the synthesis plant. Cooling can be achieved by water evaporation at the specified pressure level. The water vapor can then be used for further process steps and, as previously mentioned, for the high-temperature electrolysis itself by adding the water vapor to the cathode gas.The hydrocarbon chain length distribution resulting from FTS is described by a chain growth probability (a high chain growth probability results in large molecules, thus shifting toward liquid fuels). However, the synthesis gas is not fully converted. Depending on the chain growth probability, short-chain molecules are also produced that cannot be used as liquid fuel. The unconverted synthesis gas and the resulting short-chain hydrocarbons can be separated as the residual gas during product processing. While some of the residual gas can be recirculated into the FTS, some must be discharged. In particular, the discharged portion of the residual gas is utilized in a process.

[0044] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments are described in detail with reference to the drawings. They show schematically:

[0045] Fig. 1 shows a first embodiment of an electrolysis plant according to the invention,

[0046] Fig. 2 shows a second embodiment of an electrolysis plant according to the invention, Fig. 3 shows a third embodiment of an electrolysis plant according to the invention,

[0047] Fig. 4 shows a fourth embodiment of an electrolysis plant according to the invention,

[0048] Fig. 5 shows a fifth embodiment of an electrolysis plant according to the invention,

[0049] Fig. 6 shows a sixth embodiment of an electrolysis plant according to the invention, and

[0050] Fig. 7 shows a seventh embodiment of an electrolysis plant according to the invention.

[0051] Fig. 8 shows a further embodiment of an electrolysis plant according to the invention.

[0052] Identical or functionally equivalent elements are designated by the same reference numeral in Figures 1 to 8.

[0053] Figure 1 schematically shows an electrolysis plant 30 comprising an electrolysis system 10 with an electrolysis cell stack 100 and a synthesis system 20 with a synthesis plant 900. The electrolysis cell system 10 and the synthesis system 20 are fluidically coupled to one another, as will be explained in more detail later.

[0054] By way of example, only one electrolysis cell stack 100 is shown in Fig. 1. Nevertheless, it is possible to provide multiple electrolysis cell stacks 100. The electrolysis cell stack 100 has a cathode section 110 with a cathode supply section 112 and a cathode discharge section 114. The electrolysis cell stack 100 also has an anode section 120 with an anode supply section 122 and an anode discharge section 124. A power supply source 130, which provides power from renewable energies, is connected to the electrolysis cell stack 100. The electrolysis cell stack 100 is presently designed as a solid oxide electrolysis cell stack and is used in reverse mode for high-temperature co-electrolysis. Anode gas in the form of fresh air is provided to the electrolysis system 10 by means of an anode gas connection 202.The anode gas is supplied to the electrolysis cell stack 100 via an anode supply connection 200, which is fluidly coupled to the anode gas connection 202 and the anode supply section 122. A filter device 204, in particular in the form of an air filter, for air filtration and a fan 206 for transporting the anode gas are arranged in the anode supply connection 200.

[0055] A first heat exchanger 224 is arranged in the anode supply connection 200, downstream of the filter device 204 and the fan 206, in the flow direction of the anode gas from the anode gas connection 202 to the anode supply section 122. The first heat exchanger 224 is used for heat exchange with a warm anode exhaust gas, in particular in the form of exhaust air discharged from the anode section 120, from the electrolysis cell stack 100. For this purpose, the first heat exchanger 224 is thermally coupled to an anode discharge connection 300 upstream of a catalyst 418 in the form of an oxidation catalyst. The anode discharge connection 300 fluidically connects the anode discharge section 124 to an anode discharge connection 316.

[0056] As Figure 1 shows, a further connection, a recycle gas connection 520, is provided as a residual gas supply connection 402 as part of the electrolysis system 10. The downstream synthesis plant 900 produces production gas, which in particular has different chain lengths of hydrocarbons. With the aid of a separation device 932, shown schematically here, the produced gas is then divided into usable and unusable components, in particular with regard to the existing chain length of the hydrocarbons. Chain lengths of the hydrocarbons that are too short for the intended use are then introduced as unusable recycle gas from the separation device 932, separate from the usable portion, which can be referred to as useful gas, into the recycle gas discharge connection 930. This recycle gas discharge connection 930 is fluidly connected to the recycle gas connection 520.

[0057] The recycle gas as residual gas, i.e., the short-chain hydrocarbons, are now introduced directly into the cathode feed connection 500 and thus provide a supplement to the starting materials for carrying out the chemical process in the electrolysis cell stack 100. This ensures at least the chemical recycle as a long recycle cycle. As an alternative to direct introduction into the cathode feed connection 500, an indirect, particularly controlled, introduction can also be provided. In particular, such a controlled introduction can allow for a targeted adjustment and / or modification of the gas composition in the cathode feed connection 500.

[0058] A first bypass path 212 with a first shut-off device 214 arranged therein connects the anode supply connection 200 in the flow direction of the anode gas upstream of the first heat exchanger 224 with the anode discharge connection 300 upstream of the catalyst supply section 420 and thus allows the air content of the anode exhaust gas to be further increased before entering the catalyst 418.

[0059] In addition, a second bypass path 216 with a second shut-off device 218 is provided, which connects the anode supply connection 200 upstream of the first heat exchanger 224 in the flow direction of the anode gas with the anode supply connection 200 downstream of the first heat exchanger 224 in the flow direction of the anode gas, thereby making it possible to control the temperature of the anode exhaust gas upstream of the catalyst 418 by regulating the amount of anode gas flowing through the first heat exchanger 224. Furthermore, a third shut-off device 219 is arranged upstream of the second heat exchanger 302 and downstream of the second bypass path 216 in the flow direction.

[0060] The hot catalyst exhaust gases flow in the anode exhaust connection 300 through two individual sub-paths, into which the anode exhaust connection 300 divides in the flow direction of the catalyst exhaust gas downstream of the catalyst exhaust section 422. Located in the first sub-path is a second heat exchanger 302, which is thermally coupled to the anode supply connection 200. This allows the heat of the catalyst exhaust gas to be transferred to the anode gas upstream of the anode supply section 122. A fourth shut-off device 330 is located downstream of the second heat exchanger 302 to control the catalyst exhaust gas flow in the first sub-path.

[0061] In the second partial path, there is a third heat exchanger 304 with a fifth shut-off device 312 arranged downstream of it in the flow direction of the catalyst exhaust gas. The third heat exchanger 304 is thermally coupled to a cathode supply connection 500. The cathode supply connection 500 fluidically connects a cathode supply connection 502 to the cathode supply section 112. In the cathode supply connection 500, cathode gas, in particular carbon dioxide, is supplied from the cathode supply connection 502 to the cathode supply section 112. An ejector 504 is arranged in the cathode supply connection 500 upstream of the cathode section 110 in the flow direction of the anode gas. Furthermore, a second heating device 508, in the form of an electric heater, is arranged downstream of the ejector 504 in the flow direction of the anode gas. The third heat exchanger 310 allows the cathode gas to be heated using heat from the catalyst exhaust gas.

[0062] In the embodiment of Fig. 1, a seventh heat exchanger 340 is located in the anode discharge connection 300 downstream of the second heat exchanger 302 and the third heat exchanger 304 in the flow direction of the catalyst exhaust gas. The seventh heat exchanger 340 is thermally coupled to a first auxiliary supply connection 700, which fluidically connects a first auxiliary supply connection 702 to the cathode supply connection 500. Water or steam is provided from the first auxiliary supply connection 702 for the high-temperature co-electrolysis, which water is heated by the fourth heat exchanger 314 and flows to the cathode supply connection 500.

[0063] By means of a cathode discharge connection 600, which fluidically connects the cathode discharge section 114 to a cathode discharge connection 612, cathode exhaust gas in the form of the synthesis gas generated by the high-temperature co-electrolysis, comprising hydrogen and carbon monoxide, is discharged to the synthesis system 20. Two heat exchangers 608, 610, namely a sixth heat exchanger 608 and a seventh heat exchanger 610, are thermally arranged in the cathode discharge connection 600 and thermally coupled to the cathode supply connection 500 in order to transfer heat from the synthesis gas to the cathode gas and thus increase the efficiency of the electrolysis system 10.

[0064] A second additional supply connection 800 fluidically connects a second additional supply connection 802 for supplying a protective gas to the cathode supply connection 500. The second additional supply connection 800 is divided, for example, into two sub-paths 804, 806, namely a third sub-path 806 and a fourth sub-path 806. The third sub-path 804 leads to the anode supply connection 500 upstream of the ejector 504 and, in particular, upstream of the heat exchangers 608, 610, while the fourth sub-path 806 leads to the ejector 504. A third bypass path 602 leads from the cathode discharge section 600 to the fourth partial path 806 upstream of the ejector 504. A nozzle 604, in particular a Venturi nozzle, and a sixth shut-off device 606, in particular a valve, are arranged in the third bypass path 602.

[0065] The electrolysis cell stack 100, supplied with anode gas comprising air, and cathode gas comprising carbon dioxide, water vapor, and protective gas in the manner described above, generates the cathode exhaust gas in the form of synthesis gas comprising hydrogen and carbon monoxide, and the anode exhaust gas comprising exhaust air in reverse mode by high-temperature co-electrolysis. The anode exhaust gas is catalytically combusted by the catalyst 418, so that catalyst exhaust gases are separated from the electrolysis system 10 at the anode discharge connection 316.

[0066] The synthesis gas is provided to the synthesis system 900 of the synthesis system 20 via a synthesis gas supply connection 906, which fluidically connects a synthesis supply section 902 of the synthesis system 900 to the cathode discharge connection 612. In a reactor located there (not explicitly shown), it undergoes a synthesis process, in particular a Fischer-Tropsch synthesis process, and is converted into synthetic hydrocarbons. The hydrocarbons are discharged via a hydrocarbon discharge connection 908 fluidically connected to a synthesis discharge section 904.

[0067] Figure 2 builds on the technical solution of Figure 1. In this embodiment, however, a reformer device 522 was additionally positioned upstream of the recycle gas connection 520. Such a reformer device serves in particular to reform the recycle gas, for example, to further shorten the chain length of the hydrocarbons in the recycle gas. Reforming to an increased concentration of carbon dioxide is also conceivable here as part of the reformer device. This makes it possible, on the one hand, to improve the chemical usability in the electrolysis cell stack 100, thereby increasing the chemical efficiency. If this reforming takes place as an endothermic reforming and thus a temperature increase is necessary, catalytic oxidation can provide the necessary heat.The elevated-temperature recycle gas can now be mixed with a cathode feed gas via an external source at the cathode feed port 502. This mixing and its own elevated temperature will directly lead to an increased mixing temperature of the mixed gas as the cathode feed gas. In addition to increasing chemical efficiency, this also enables an increase in thermal efficiency.

[0068] Figure 3 also shows a further development of the embodiment of Figure 1. Here, a synthesis recycle gas connection 530 is provided, which is arranged upstream of the recycle gas connection 520. In this way, two parallel recycle options are provided. A long recycle cycle into the electrolysis system 10 and thus the electrolysis cell stack 100 is ensured via the recycle gas connection 520. Alternatively, a short recycle cycle can be operated via the synthesis recycle gas connection 530, for example, which can also be controlled with the aid of shut-off devices or control valves. In this recycle cycle, the recycle gas is recirculated, so to speak, past the electrolysis system 10 directly into the synthesis gas supply connection 906, thus serving for direct and repeated synthesis starting from the recycle gas.

[0069] Figure 4 also shows another further development of the embodiment of Figure 1. Here, a recycle gas catalyst device 524 is provided, which can, for example, at least partially carry out reforming through a catalytic chemical conversion of the recycle gas. The core idea of ​​using a recycle gas catalyst device 524, however, is to achieve an increase in the temperature of the recycle gas through the catalytic conversion of at least some components of the recycle gas. As already explained, the increased temperature, in particular the catalytically further increased temperature of the recycle gas, results in an increased mixing temperature with the externally supplied cathode feed gas, so that the thermal efficiency during operation of the electrolysis system 10 increases accordingly.

[0070] Figures 5 to 7 show three variants that allow the use of heat and chemical components in combination from the residual gas.

[0071] Figure 5 schematically shows an electrolysis plant 30 comprising an electrolysis system 10 with an electrolysis cell stack 100 and a synthesis system 20 with a synthesis plant 900. The electrolysis system 10 and the synthesis system 20 are fluidically coupled to one another, as will be explained in more detail later. By way of example, only one electrolysis cell stack 100 is shown in Figure 5. Nevertheless, it is possible to provide multiple electrolysis cell stacks 100. The electrolysis cell stack 100 has a cathode section 110 with a cathode feed section 112 and a cathode discharge section 114. Furthermore, the electrolysis cell stack 100 has an anode section 120 with an anode feed section 122 and an anode discharge section 124. A power supply source 130, which provides power from renewable energies, is connected to the electrolysis cell stack 100.The electrolysis cell stack 100 is designed as a solid oxide electrolysis cell stack and is used in reverse mode for high-temperature co-electrolysis.

[0072] Anode gas in the form of fresh air is provided to the electrolysis system 10 by means of an anode gas connection 202. The anode gas is supplied to the electrolysis cell stack 100 for electrolysis via an anode supply connection 200, which is fluidly coupled to the anode gas connection 202 and the anode supply section 122. A filter device 204, in particular in the form of an air filter, for air filtration and a fan 206 for transporting the anode gas are arranged in the anode supply connection 200.

[0073] A first heat exchanger 224 is arranged in the anode supply connection 200, downstream of the filter device 204 and the blower 206, in the flow direction of the anode gas from the anode gas connection 202 to the anode supply section 122. The first heat exchanger 224 is used for heat exchange with a warm anode exhaust gas, in particular in the form of exhaust air discharged from the anode section 120, from the electrolysis cell stack 100. For this purpose, the first heat exchanger 224 is thermally coupled to an anode discharge connection 300 upstream of a second catalyst 418 in the form of an oxidation catalyst. The anode discharge connection 300 fluidically connects the anode discharge section 124 to an anode discharge connection 308.

[0074] The second catalyst 418 is arranged in the anode discharge connection 300 downstream of the first heat exchanger 224 in the flow direction of the anode exhaust gas and is fluidly coupled to a residual gas connection 402 by means of a residual gas supply connection 400. The residual gas connection 402 receives residual gas from the synthesis plant 900, as will be described in more detail later. The residual gas provided to a second catalyst supply section 420 of the second catalyst 418, which is mixed with the anode exhaust gas in the anode discharge connection 300 at a junction of the residual gas supply connection 400 with the anode discharge connection 300 to form a residual gas-anode exhaust gas mixture, is catalytically combusted by the second catalyst 418. Hot catalyst exhaust gases with a temperature in the range of 800 to 1000 °C, in particular around 950 °C, emerge from the second catalyst discharge section 422.

[0075] A first bypass path 212 with a first shut-off device 214 arranged therein connects the anode supply connection 200 in the flow direction of the anode gas upstream of the first heat exchanger 224 with the anode discharge connection 300 upstream of the second catalyst supply section 420 and thus allows the air content of the residual gas-anode exhaust gas mixture to be further increased before entering the second catalyst 418 and the residual gas-anode exhaust gas mixture to be further cooled.

[0076] In addition, a second bypass path 216 with a second shut-off device 218 is provided, which connects the anode supply connection 200 upstream of the first heat exchanger 224 in the flow direction of the anode gas with the anode supply connection 200 downstream of the first heat exchanger 224 in the flow direction of the anode gas. This makes it possible to control the temperature of the residual gas-anode exhaust gas mixture upstream of the second catalyst 418 by regulating the amount of anode gas flowing through the first heat exchanger 224. Furthermore, a third shut-off device 219 is arranged upstream of the second heat exchanger 224 and downstream of the second bypass path 216 in the flow direction.

[0077] The hot catalyst exhaust gases of the second catalyst 418 flow from the second catalyst exhaust section 422 in the anode exhaust connection 300 through a second heat exchanger 302, which is thermally coupled to the anode supply connection 200. This allows the heat of the catalyst exhaust gas of the second catalyst 418 to be transferred to the anode gas upstream of the anode supply section 122.

[0078] In addition to the second catalyst 418, the electrolysis system 10 also includes a further catalyst 408, referred to herein as the first. The first catalyst 408 is arranged in the anode discharge connection 300 downstream of the second catalyst 418 in the flow direction, i.e., downstream of the second heat exchanger 302 and in the catalyst exhaust stream of the second catalyst 418. For this purpose, the residual gas supply connection 400 is divided into two individual sub-paths 404, 414, namely a first sub-path 404 and a second sub-path 414. A fifth shut-off device 406 is arranged in the first sub-path 404. A sixth shut-off device 416 is arranged in the second sub-path 414. In this respect, the amount of residual gas supplied to each of the two catalysts 408, 418 and thus the amount of heat released by the catalyst exhaust gases through catalytic combustion can be controlled by means of the shut-off devices 406, 416.As already explained above, upstream of the second catalyst feed section 420 of the second catalyst 418, a mixing of residual gas and anode exhaust gas occurs at the aforementioned junction point. Upstream of a first catalyst feed section 410 of the first catalyst 408, at a junction point where the anode discharge section 300 and the first partial path 404 meet, a corresponding mixing of residual gas and catalyst exhaust gases, which are also referred to herein as anode exhaust gas because they flow in the anode discharge connection 300, occurs to form a mixture, also referred to herein as a residual gas-anode exhaust gas mixture.

[0079] A third heat exchanger 304 is located in the anode discharge connection 300 downstream of the first catalyst 408 and its first catalyst discharge section 412. The third heat exchanger 304 is thermally coupled to a cathode supply connection 500. The cathode supply connection 500 fluidically connects a cathode supply connection 502 to the cathode supply section 112. In the cathode supply connection 500, cathode gas, in particular carbon dioxide, is supplied from the cathode supply connection 502 to the cathode supply section 112. A seventh shut-off device 504 and an ejector 506 are arranged in the cathode supply connection 500 upstream of the cathode section 110 in the flow direction of the anode gas. Furthermore, a second heating device 508, in the form of an electric heater, is arranged behind the ejector 506 in the flow direction of the anode gas.The third heat exchanger 304 allows the cathode gas to be heated with the heat from the catalyst exhaust gas of one or both catalysts 408, 418.

[0080] A first bypass path 208 with a first shut-off device 210 arranged therein connects the anode supply connection 200 in the flow direction of the anode gas upstream of the first heat exchanger 224, and in particular upstream of the branch to the second bypass path 212, with the anode discharge connection 300 upstream of the first catalyst supply section 410 and thus allows the air content of the residual gas-anode exhaust gas mixture to be increased before entering the first catalyst 408 and the residual gas-anode exhaust gas mixture to be cooled.

[0081] With the above-described arrangement of catalysts 408, 418 in the electrolysis system 10, it is thus possible to operate only one or both catalysts 408, 418 together, the latter being preferred. Thus, the oxygen-rich exhaust air in the anode exhaust gas can be mixed with a first amount of residual gas, which can be controlled by the sixth shut-off device 416, for controlled catalytic combustion via the second catalyst 418, which in this respect functions as the first oxidation catalyst stage, to provide the temperature at the second heat exchanger 302, which functions as an air superheater for the air in the anode gas.In turn, the still oxygen-rich catalyst exhaust gas of the second catalyst 418 can be mixed with a second amount of the residual gas, which can be controlled by means of the fifth shut-off device 406, for controlled catalytic combustion via the first catalyst 408, which in this respect functions as a second oxidation catalyst stage, to provide the temperature at the third heat exchanger 304, which functions as a reactant superheater for the cathode gas.

[0082] The two oxidation catalyst stages can ensure the same heat exchange at lower oxidation catalyst target temperatures (meaning the total mass flow through both heat exchangers 302, 304 and the same amount of enthalpy at lower temperatures), or vice versa, such as in a single-stage system with a parallel arrangement of the two heat exchangers 302, 304. Another advantage is that higher air and reactant temperatures can be achieved at the same oxidation catalyst target temperature.

[0083] As shown in Figure 5, this embodiment provides two parallel return options. One is a return to the anode feed section 200, and the other is a return to the cathode feed section 500. Embodiments with only one of these two return options are also conceivable within the scope of the present invention.

[0084] As an alternative to the arrangement shown in Fig. 5, the present interconnection of catalysts 408, 418 in the electrolysis system 10 can also be such that the third heat exchanger 304 is arranged in the catalyst exhaust stream of the second catalyst 418 and the second heat exchanger 302 is arranged in the catalyst exhaust stream of the first catalyst 408. In this respect, it is pointed out again that the designation of components or elements of the same type or kind here merely serves to distinguish them from one another and does not follow a technically necessary sequence or the like.

[0085] In the embodiment of Fig. 5, a fourth heat exchanger 306 is located in the anode discharge connection 300 downstream of the second heat exchanger 304 in the flow direction of the catalyst exhaust gas. The fourth heat exchanger 306 is thermally coupled to a first auxiliary supply connection 700, which fluidically connects a first auxiliary supply connection 702 to the cathode supply connection 500. Water or steam is provided from the first auxiliary supply connection 702 for the high-temperature co-electrolysis; this water or steam is heated by the fourth heat exchanger 306 and flows to the cathode supply connection 500.

[0086] By means of a cathode discharge connection 600, which fluidically connects the cathode discharge section 114 to a cathode discharge connection 612, cathode exhaust gas in the form of the synthesis gas generated by the high-temperature co-electrolysis, comprising hydrogen and carbon monoxide, is discharged to the synthesis system 20. Two heat exchangers 608, 610, namely a sixth heat exchanger 608 and a seventh heat exchanger 610, are thermally arranged in the cathode discharge connection 600 and thermally coupled to the cathode supply connection 500 in order to transfer heat from the synthesis gas to the cathode gas and thus increase the efficiency of the electrolysis system 10.

[0087] A fourth bypass path 602 leads from the cathode discharge section 600 to the ejector 506. In the fourth bypass path 602, a nozzle 604, in particular a Venturi nozzle, and an eighth shut-off device 606, in particular a valve, are arranged.

[0088] A second additional supply connection 800 fluidly connects a second additional supply connection 802 for supplying a protective gas to the cathode supply connection 500 in the flow direction of the cathode supply connection 500 upstream of the seventh shut-off device 504.

[0089] The electrolysis cell stack 100, supplied with anode gas comprising air, and cathode gas comprising carbon dioxide, water vapor, and protective gas in the manner described above, generates the cathode exhaust gas in the form of synthesis gas, comprising hydrogen and carbon monoxide, and the anode exhaust gas, comprising exhaust air, in reverse mode by high-temperature co-electrolysis. The anode exhaust gas is catalytically combusted by the two catalysts 408, 418 together with residual gas, so that catalyst exhaust gases are separated from the electrolysis system 10 at the anode discharge connection 308.

[0090] The synthesis gas is provided to the synthesis system 900 of the synthesis system 20 via a synthesis gas supply connection 906, which fluidically connects a synthesis supply section 902 of the synthesis system 900 to the cathode discharge connection 612. In a reactor there (not explicitly shown), it undergoes a synthesis process, in particular a Fischer-Tropsch synthesis process, and is converted into synthetic hydrocarbons. The hydrocarbons are discharged via a hydrocarbon discharge connection 908 fluidically connected to a synthesis discharge section 904. However, synthesis gas not converted during the synthesis process and short-chain hydrocarbons remain, some of which can be returned to the synthesis process and some of which can be discharged as residual gases to the residual gas supply connection 402 via a residual gas discharge connection 910, which are fluidically coupled to one another in this respect.

[0091] Figure 6 shows a modification of the embodiment of the electrolysis system 30 shown in Fig. 5. Specifically, the fourth heat exchanger 306 was omitted in Fig. 6. Instead, a fifth heat exchanger 310 was inserted in the anode discharge connection 300, downstream of the two heat exchangers 302, 304, which is thermally coupled to the anode supply connection 200, particularly downstream of the blower 206 and upstream of the first heat exchanger 224, in the flow direction of the anode gas. This allows the residual heat in the anode exhaust gas or the catalyst exhaust gas to be alternatively provided for the anode gas. However, it is of course also possible to provide both the fourth heat exchanger 306 and the fifth heat exchanger 310, either in series or in parallel with appropriate shut-off devices and bypass paths.

[0092] Furthermore, any configuration of the heat exchangers 224, 302, 304, 306, 310, 608, 610 shown is possible, which means that these heat exchangers can each be used alone or in any selection thereof in the electrolysis system 10, so that it is not necessary to equip the electrolysis system 10 with all heat exchangers 224, 302, 304, 306, 310, 608, 610. Figure 7 shows a variation of the electrolysis system 30 of the embodiment of Fig. 1, in which residual gas bypasses 430 are provided, which introduce the residual gas in the catalytically combusted form past the respective heat exchanger 304, 302 into the anode feed section 200, provided the residual gas is free of CO2, and / or the cathode feed section 500. Furthermore, the variant in Figure 3 shows the possibility of separating the anode exhaust gas and the residual gas. Thus, the anode exhaust gas can be fed directly to the anode discharge connection 308 downstream of the heat exchanger 224.By means of a branch section 440, it is possible to transfer the residual gas into the anode discharge connection 300.

[0093] Figure 8 shows an alternative embodiment. This is a variant with the sixth heat exchanger 320 in a separate path of the anode supply connection 200. This separate path can be switched qualitatively and / or quantitatively as a bypass using valves (not shown). In this way, the controllability, in particular the adjustability of the operating mode, can be further improved. This embodiment can also be applied to all other variants, in particular those shown in Figures 1 to 7.

[0094] The above explanations of the embodiments describe the present invention exclusively by way of examples.

[0095] List of reference symbols

[0096] 10 Electrolysis system

[0097] 20 Synthesis system

[0098] 30 electrolysis plant

[0099] 100 electrolysis cell stacks

[0100] 110 Cathode section

[0101] 112 Cathode feed section

[0102] 114 Cathode discharge section

[0103] 120 anode section

[0104] 122 Anode feed section

[0105] 124 Anode discharge section

[0106] 130 Power source

[0107] 200 Anode feed connection

[0108] 202 Anode gas connection

[0109] 204 Filter device

[0110] 206 blowers

[0111] 212 first bypass path

[0112] 214 first shut-off device

[0113] 216 second bypass path

[0114] 218 second shut-off device

[0115] 219 third shut-off device

[0116] 220 first heating device

[0117] 224 first heat exchanger

[0118] 300 anode discharge connection

[0119] 302 second heat exchanger

[0120] 304 third heat exchanger

[0121] 306 fourth heat exchanger

[0122] 308 anode discharge connection

[0123] 310 fifth heat exchanger

[0124] 312 fifth shut-off device

[0125] 316 anode discharge connection

[0126] 320 heat exchangers

[0127] 330 fourth shut-off device

[0128] 340 Heat exchanger residual gas supply connection residual gas supply connection partial path

[0129] shut-off device

[0130] catalyst

[0131] Catalyst feed section Catalyst discharge section

[0132] Partial path

[0133] shut-off device

[0134] catalyst

[0135] Catalyst feed section Catalyst discharge section

[0136] Residual gas bypass

[0137] branch section

[0138] Cathode feed connection Cathode feed connection

[0139] shut-off device

[0140] Ejector second heating device

[0141] Residual gas supply connection reformer device

[0142] Recycle gas catalyst device Synthesis recycle gas connection Cathode discharge connection

[0143] Bypass path

[0144] nozzle

[0145] shut-off device

[0146] heat exchanger

[0147] heat exchanger

[0148] Cathode discharge connection first additional feed connection first additional feed connection second additional feed connection second additional feed connection third sub-path fourth sub-path

[0149] Synthesis plant

[0150] Synthesis feed section

[0151] Synthesis discharge section

[0152] Synthesis gas supply connection

[0153] Hydrocarbon discharge connection

[0154] Residual gas discharge connection

[0155] Cooling device third additional supply connection

[0156] Residual gas discharge connection

Claims

Patent claims 1. Electrolysis plant (30) with an electrolysis system (10) and a synthesis system (20), wherein the electrolysis system (10) has - at least one electrolysis cell stack (100) with a cathode section (110) having a cathode supply section (112) and a cathode discharge section (114), and an anode section (120) having an anode supply section (122) and an anode discharge section (124), - an anode gas connection (202) fluidly coupled to the anode supply section (112) by means of an anode supply connection (200) for supplying anode gas to the anode section (120), - an anode discharge connection (308, 316) fluidly coupled to the anode discharge section (124) by means of an anode discharge connection (300) for discharging anode exhaust gases generated by the electrolysis cell stack (100), - a cathode supply connection (502) fluidly coupled to the cathode supply section (112) by means of a cathode supply connection (500) for supplying cathode gas to the cathode section (110), and - a cathode discharge connection (612) fluidly coupled to the cathode discharge section (114) by means of a cathode discharge connection (600) for discharging synthesis gas generated by the electrolysis cell stack (100), and wherein the synthesis system (20) comprises - a synthesis plant (900) which is fluidically coupled to the cathode discharge connection (612) by means of a synthesis gas supply connection (906), the synthesis plant (900) for the synthesis of synthetic hydrocarbons from the electrolysis cell stack (100) produced and by means of the Synthesis gas supply connection (906) supplied synthesis gas, and - the synthesis plant (900) is fluidically coupled to a residual gas supply connection (402) by means of a residual gas discharge connection (910, 930) for providing residual gas, characterized in that the residual gas supply connection (402) is fluidly connected to at least one residual gas utilization device of the electrolysis system (10).

2. Electrolysis plant (30) according to claim 1, characterized in that the electrolysis system (10) has as a residual gas utilization device: - a recycle gas connection (520) as a residual gas supply connection (402) for providing recycle gas as residual gas, which is produced in a subsequent synthesis process for producing synthetic hydrocarbons from the synthesis gas generated in the electrolysis cell stack (100), wherein the recycle gas connection (520) is fluidly connected to the cathode supply connection (500).

3. Electrolysis plant (30) according to claim 2, characterized in that upstream of the recycle gas connection (520) a reformer device (522) is fluidly connected to the recycle gas connection (520) for at least partial reforming of the by-products from the synthesis process.

4. Electrolysis plant (30) according to claim 3, characterized in that the reformer device (522) has at least one of the following configurations: - Steam Reformer - Dry Reformer CPOX Reformer 5. Electrolysis plant (30) according to claims 2 to 4, characterized in that upstream of the recycle gas connection (520) at least one controllable synthesis recycle gas connection (530) is arranged for at least partial recirculation of the recycle gas into the synthesis process.

6. Electrolysis plant (30) according to claim 5, characterized in that the synthesis recycle gas connection (530) is arranged upstream of a reformer device (522).

7. Electrolysis plant (30) according to claim 2 to 6, characterized in that upstream of the recirculation gas connection (520) a recirculation gas catalyst device (524) is fluidly connected to the recirculation gas connection (520).

8. Electrolysis plant (30) according to claim 2 to 7, characterized in that the return gas connection (520) is integrated into the cathode supply connection (502).

9. Electrolysis plant (30) according to claims 2 to 7, characterized in that the cathode supply connection (502) and the recirculation gas connection (520) each have at least one control valve for controlling the volume flow of recirculation gas and cathode gas.

10. Electrolysis plant (30) according to one of the preceding claims, characterized in that the electrolysis system (10) has as a residual gas utilization device: - at least one catalyst (408, 418) fluidically coupled to the residual gas supply connection (402) by means of a residual gas supply connection (400) for the catalytic combustion of the residual gas, - at least one heat exchanger (302, 304, 306, 310) which is arranged in the residual gas supply connection (400) downstream of the catalyst discharge section (412, 422) in the flow direction and is connected to the anode supply connection (200) and / or the cathode supply connection (500) in a heat-transfer manner, - wherein the residual gas supply connection (400) downstream of the at least one heat exchanger (302, 304, 306, 310) is fluidly connected to the anode supply connection (200) and / or the cathode supply connection (500) for returning the catalytically combusted residual gas to the anode supply connection (200) and / or the cathode supply connection (500).

11. Electrolysis plant (30) according to claim 10, characterized in that the residual gas supply connection (400) has a residual gas bypass (430) which is connected to the anode supply connection (200) and / or the cathode supply connection (500) in fluid communication past the at least one heat exchanger (302, 304, 306, 310).

12. Electrolysis plant (30) according to claim 11, characterized in that the residual gas bypass (430) has a bypass valve for controlling the direct fluid-communicating connection past the at least one heat exchanger (302, 304, 306, 310).

13. Electrolysis plant (30) according to one of claims 10 to 12, characterized in that the residual gas supply connection (400) forms at least in sections the anode discharge connection (300) 14. Electrolysis plant (30) according to one of claims 10 to 13, characterized in that a branching section (440) is provided downstream of the at least one heat exchanger (304, 310, 314, 320) and upstream of the fluid-communicating connection to the anode supply connection (200) and / or the cathode supply connection (500), wherein the anode discharge connection (300) branches off downstream of the heat exchanger (224).

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