EP4357439A1 - Method for producing a target product and corresponding facility - Google Patents

Abstract

A method (100, 200, 300, 400, 500, 600, 700, 800) for producing a target product is proposed, in which a synthesis gas (103) is subjected to a Fischer-Tropsch synthesis, wherein a product mixture (110) of the Fischer-Tropsch synthesis is separated to obtain a tail gas (105) and a crude product (106), wherein a first portion (115) of the tail gas (105) is fed back to the Fischer-Tropsch synthesis in a composition unchanged from the tail gas (105), and wherein a second portion (125) of the tail gas (105) is returned to one or more provision steps used to provide the synthesis gas (103). A corresponding system is also the subject of the present invention.

Description

The invention relates to a process for producing a target product comprising a Fischer-Tropsch synthesis and to a corresponding plant.

background

The Fischer-Tropsch synthesis is well known and extensively described in the specialist literature. Instead of referring to many examples, the article by Arno de Klerk, "Fischer-Tropsch Process" in the Kirk-Othmer Encyclopedia of Chemical Technology, 2013 edition , referred to.

The Fischer-Tropsch synthesis comprises a series of chemical reactions in which a mixture of carbon monoxide and hydrogen, known as synthesis gas or water gas, is converted into liquid hydrocarbons. These reactions take place in the presence of metal catalysts, typically at temperatures of 150 to 300°C and absolute pressures of 1 to 30 bar. As a process of so-called C1 chemistry, the Fischer-Tropsch synthesis is used both in coal liquefaction and in gas-to-liquids processes for the production of liquid hydrocarbons.

Cobalt or iron catalysts are typically used in Fischer-Tropsch synthesis. In available reactor types, the catalysts are present as fixed bed, slurry, fluidized bed, circulating fluidized bed or microstructured. A product mixture from a Fischer-Tropsch synthesis contains a variety of components ranging from short-chain gaseous hydrocarbons to long-chain waxes. The product spectrum includes saturated and unsaturated compounds (e.g. alkanes, alkenes and oxygenates).

The product mixture is cooled and separated into a gaseous stream, a liquid hydrocarbon stream, a waste water stream and a stream with a high wax content. The cooling can be carried out in several stages, with a liquid wax phase already occurring in the reactor and being withdrawn from it can. A so-called high-temperature separator can be connected to separate further waxes. This can be followed by a so-called low-temperature separator or a three-phase separator. The liquid hydrocarbons and waxes are then combined and referred to as crude. The gaseous fraction containing short-chain hydrocarbons, unreacted reactants and inert gases is referred to as tail gas. In the following, inert gases are understood not only to mean the gas components widely known as such, such as nitrogen and noble gases, but also all gas components that are inert or essentially inert in a corresponding process, including carbon dioxide and methane.

The term "essentially inert" is to be understood as meaning that the corresponding gas components are not converted or are converted only to a small extent, which does not have a significant effect on the overall process. A gas component that is "essentially inert" is typically converted to no more than 5%, 1%, 0.5% or 0.1%.

Carbon monoxide and hydrogen, or synthesis gas, the starting materials for the Fischer-Tropsch synthesis, can be produced by gasification from coal or biomass. The production of synthesis gas from natural gas is also known. The production of synthesis gas is described, for example, in the article " Gas Production" in Ullmann's Encyclopedia of Industrial Chemistry, online edition 15 December 2006, DOI 10.1002/14356007.a12_169.pub2 , described. For the conversion of natural gas to synthesis gas on an industrial scale, for example, autothermal reforming, partial oxidation, steam reforming or combinations of these processes can be used.

Recently, Fischer-Tropsch processes (FT processes) based on carbon dioxide as a carbon source have been developed. For example, hydrogen and carbon dioxide can be converted to synthesis gas by a reverse water gas shift or water gas conversion, as in H. Yang et al., Catal. Sci. Technol., 2017, 7, 4580-4598 and G. Centi, Energy Environ. Sci., 2013, 6, 1711-1731 In the reverse water gas shift, a molecule of carbon dioxide is converted endothermically with a molecule of hydrogen to form a molecule of carbon monoxide and a molecule of water. A co-electrolysis of water and carbon dioxide in a High-temperature electrolysis processes, such as R. Küngas, J. Electrochem. Soc. 2020, 167, 044508 can be used in this context. The hydrogen required can be obtained from any hydrogen source, the present invention is not limited in this respect. For example, "green" or "blue" hydrogen from an electrolysis process can be used, but also hydrogen from an ammonia cracker or from a pipeline.

Corresponding high-temperature electrolysis processes can be carried out in particular using solid oxide electrolysis cells (SOEC) and proton-conducting high-temperature materials. Solid oxide electrolysis cells in particular comprise doped zirconium dioxide or doped rare earth oxides, which become conductive at more than 800°C, and in newer designs even at 600°C.

The tail gas can be at least partially returned to the Fischer-Tropsch process without any processing being carried out (so-called internal recirculation). However, it is also possible to at least partially return the tail gas to the Fischer-Tropsch process and subject the returned part to certain processing steps (so-called external recirculation). Processing steps can include, for example, a liquid gas recovery step, a return circuit to an upstream reforming process, acid gas removal, hydrogenation and pressure swing adsorption (PSA) to provide hydrogen for downstream processes.

In order to achieve high energy, hydrogen and carbon efficiency, it is advantageous to use both internal and external recirculation of the tail gas from the Fischer-Tropsch synthesis. In addition to hydrogen and carbon monoxide, this tail gas also contains carbon dioxide, inert gases, methane and higher hydrocarbons. There is a need for a solution as to how this recirculation can be included in the reverse water gas shift and/or co-electrolysis, because the combustion of this electricity or export as fuel alone leads to an inefficient and costly process with high carbon dioxide emissions.

Disclosure of the invention

This object is achieved by a method which comprises a Fischer-Tropsch synthesis and a corresponding plant having the features of the respective independent patent claims. Embodiments are the subject of the dependent patent claims and the following description.

Embodiments of the present invention relate in particular to variants of a return of a tail gas from a Fischer-Tropsch synthesis. In embodiments of the invention, in addition to a direct return of a portion of the tail gas (also referred to here as the "first portion"), an indirect return of a further portion of the tail gas (also referred to here as the "second portion") takes place. A further portion of the tail gas (also referred to here as the "third portion") can be discharged from the process (as purge gas), whereby inert components can be removed from the circuit. Alternatively, such a third portion can also be used for energy by thermal combustion or in a solid oxide fuel cell (SOFC), whereby inert components can be transferred into an exhaust gas and thus also removed from the circuit.

When using a reverse water gas shift, the second portion can in certain cases be fed directly back into the latter. However, if the second portion contains saturated and unsaturated hydrocarbons with two or more carbon atoms, which may have a damaging effect on the process (e.g. coking of heat exchangers flowing through them when heated) or the catalyst (used for the reverse water gas shift), it may be advantageous to subject the second portion to conventional processing steps before a reverse water gas shift. Such processing steps may include adsorption and/or hydrogenation steps in which gas mixtures are formed, which in turn can be fed back. Combustion, if carried out, can be used to heat other plant components (e.g. the water gas shift, a reforming plant, a steam generator or a high-temperature electrolysis or co-electrolysis plant). Energy use can also be used to generate electricity and/or heat, e.g. in a high-temperature solid oxide fuel cell. In addition, part of the external recycle can be fed to a reforming plant or dry reforming plant and synthesis gas formed there can be included in the Fischer-Tropsch synthesis, whereby appropriate System components can be installed in particular parallel to the reverse water gas shift. At least part of the external return to the cathode and/or anode side of a co-electrolysis or the anode side of an electrolysis can also take place using a solid oxide fuel cell. When returning to the cathode side of the co-electrolysis, pretreatment, e.g. pre-reforming the return stream, can be advantageous in order not to introduce components that damage the electrolysis cell, such as long-chain hydrocarbons, into the cathode side. At least some of these embodiments and aspects thereof can be combined in any way, resulting in particularly advantageous embodiments.

The recirculation concepts proposed in the context of embodiments of the invention can be combined with an (at least partially) electrically heated reverse water gas shift and/or steam reforming. In addition, the pressureless exhaust gas or exhaust gases from further downstream process steps (e.g. hydrocracking) can be used by incorporating them into the synthesis gas production for the Fischer-Tropsch synthesis.

Within the scope of the present invention, a process for producing a target product is proposed in which a synthesis gas is subjected to a Fischer-Tropsch synthesis, wherein a product mixture of the Fischer-Tropsch synthesis is separated to obtain a tail gas and a crude product, wherein a first portion of the tail gas is fed back to the Fischer-Tropsch synthesis in a composition unchanged from the tail gas, and wherein a second portion of the tail gas is returned to one or more provision steps used to provide the synthesis gas.

The present invention and its embodiments propose advantageous concepts for the reuse of a Fischer-Tropsch tail gas, through which the carbon efficiency can be increased in a special way. The tail gas stream is partially recycled internally without further gas processing steps. The amount of internal recycling is limited by the content of the gas components carbon dioxide, methane, nitrogen and argon, since these gas components reduce the hydrogen and carbon monoxide partial pressure in the Fischer-Tropsch synthesis. If the content of undesirable gas components is too high, the Conversion of carbon monoxide may decrease and a larger reactor volume may be required. This can be avoided by partial external recirculation within the scope of embodiments of the invention.

Remaining tail gas is therefore recycled externally, including any processing steps (e.g. adsorption, hydrogenation), or used as fuel gas. In some configurations, a purge stream is formed to remove inert materials. Carbon efficiencies of 47 to 95% and power efficiencies of 45 to 50% (calculated as the lower heating value of the Fischer-Tropsch crude product divided by the energy consumption) can be achieved. If no processing steps are included in the external recycling and this takes place directly into the burner to heat the reverse water gas shift, an efficiency of up to 40% and more can still be achieved.

The synthesis gas used in the context of the present invention contains hydrogen, carbon monoxide and carbon dioxide, whereby the term "contains", as is usual, does not describe the components of a gas mixture exhaustively, but leaves open further components in a corresponding gas mixture. The measures proposed according to the invention make it possible to avoid an enrichment of the carbon dioxide, which leads to the negative effects explained, and at the same time to use a synthesis gas containing carbon dioxide.

The tail gas can in particular contain hydrogen, carbon monoxide, carbon dioxide, methane, one or more hydrocarbons with two, three and/or four carbon atoms and one or more inert gases. Higher hydrocarbons with five or more carbon atoms can also be present in small quantities, typically in the ppm range. By using embodiments of the present invention, advantageous use of this is possible.

In a group of embodiments of the present invention, the one provision step or one of the several provision steps is a reverse water gas shift, wherein hydrogen and carbon dioxide are supplied to the reverse water gas shift, and wherein in the reverse water gas shift a part of the hydrogen is reacted with a part of the carbon dioxide to form carbon monoxide and water. A reverse water gas shift can be carried out using different sub-steps known type, for example a reverse high and a reverse low temperature shift, and corresponding apparatus. In general, temperatures of 600 to 1000 °C or 400 to 600 °C can be used. The present invention is not restricted to a specific embodiment.

In embodiments of the present invention, the reverse water gas shift can further be supplied with up to 10, 20, 30, 40 or 50 mole percent steam, whereby coking can be prevented in a particularly advantageous manner.

Feeding the second portion of the tail gas into the reverse water gas shift enables the recovery of further carbon monoxide from the recycled carbon dioxide with hydrogen, which is also contained in the tail gas.

In one embodiment of the present invention, it can be provided that the second portion of the end gas is fed to the reverse water gas shift in a composition that is unchanged from that of the end gas. This can also result in advantages over the prior art, which in particular include the advantageous further conversion of the carbon dioxide.

In a further embodiment of the present invention, however, it can also be provided that one of the several provision steps (which are provided in this case), in addition to the reverse water gas shift, is a hydrogenation step, wherein the second portion of the end gas is subjected to the hydrogenation step to obtain a subsequent mixture, and wherein at least a portion of the subsequent mixture is fed to the reverse water gas shift. Such an embodiment is particularly advantageous because it saturates the unsaturated hydrocarbons. When heated, unsaturated hydrocarbons can lead to coking of the heat exchangers through which they flow or damage the reverse water gas shift catalyst.

In alternative embodiments of the present invention, it can be provided that one of the several provision steps (which are provided in this case) is an adsorption step, wherein the second portion of the end gas is supplied to the Adsorption step, and wherein at least part of the pressure product is fed to the reverse water gas shift. In this way, the hydrogen in particular can be selectively recovered and advantageously used in the reverse water gas shift to obtain carbon monoxide. Such a design is particularly advantageous if a direct return of the external recycle and a supply of a stream after a hydrogenation step to the reverse water gas shift would damage it.

Embodiments of the present invention may include a carbon dioxide removal step. In other words, in such embodiments, one of the several provision steps (which are provided in this case) is a carbon dioxide removal step, to which at least part of a gas mixture formed in the reverse water gas shift is fed, and using which the synthesis gas is provided, wherein carbon dioxide separated in the carbon dioxide removal step is at least partially returned to the reverse water gas shift. This carbon dioxide can thus be subjected to further conversion without the Fischer-Tropsch synthesis being burdened with the negative effects explained. The return to the reverse water gas shift is particularly advantageous in order to increase the ratio of hydrogen to carbon monoxide and to achieve a higher conversion of carbon dioxide. When considering the reaction equation of the reverse water gas shift, which represents an equilibrium reaction, a return of carbon dioxide means the increase in the reactants on the left-hand side of the reaction equation. Thus, more carbon monoxide can be formed. The ratio of hydrogen to carbon monoxide at the reactor outlet thus decreases due to the return of carbon dioxide.

In embodiments of the present invention, one of the several provision steps (which are provided in this case) can be a high-temperature electrolysis step, wherein in the high-temperature electrolysis step electrolysis hydrogen is formed (and in particular water in the form of steam, but no other starting materials are electrolyzed), wherein at least a portion of the electrolysis hydrogen is fed together with carbon dioxide to the reverse water gas shift. This embodiment enables a particularly advantageous and decoupled provision of the synthesis gas, for example using renewably generated electrical current, wherein in the high-temperature electrolysis For example, the externally recycled portion of the tail gas can be used thermally on the anode side.

In all embodiments of the present reverse water gas shift can be carried out using combustion heat, with a third portion of the end gas being used to provide the combustion heat. If the reverse water gas shift is carried out using electrical heat, a third portion of the end gas can instead be discharged from the process in a composition unchanged from the end gas or can be used thermally on the anode side in high-temperature electrolysis or energetically in a solid oxide fuel cell.

In embodiments of the present invention, it can be provided that the one provision step or one of the several provision steps (which are provided in this case) is a high-temperature co-electrolysis step, wherein in the high-temperature co-electrolysis step carbon dioxide and water are co-electrolyzed to obtain a gas mixture used to provide the synthesis gas. In such a high-temperature electrolysis, a corresponding portion of the end gas, which in this case is fed to the high-temperature co-electrolysis step, can be used in a particularly advantageous manner on the cathode side, as mentioned possibly after a pretreatment step, since the high-temperature co-electrolysis allows the conversion of carbon dioxide into further carbon monoxide. Feeding on the cathode and/or anode side is also possible. On the anode side, the third portion of the end gas can also be thermally utilized.

In embodiments of the present invention, the provision of the synthesis gas can include separating carbon dioxide from at least part of the gas mixture obtained in the high-temperature co-electrolysis step and returning it to the high-temperature co-electrolysis step. In this way, it can be converted and does not burden the Fischer-Tropsch synthesis.

A plant for producing a target product, which is designed to subject a synthesis gas to a Fischer-Tropsch synthesis, to separate a product mixture of the Fischer-Tropsch synthesis to obtain a tail gas and a crude product, to process a first portion of the tail gas in a form unchanged from the tail gas, The present invention also provides for recycling the final gas composition to the Fischer-Tropsch synthesis and for recycling a second portion of the final gas to one or more preparation steps used to provide the synthesis gas.

For further features and advantages of a corresponding system and embodiments thereof, express reference is made to the above explanations concerning the method proposed according to the invention and its embodiments, since these apply to this in the same way.

The same applies to a system which, according to an embodiment of the invention, is designed to carry out a method according to any embodiment of the present invention.

Short description of the drawing

• Figuren 1 bis 8 Verfahren gemäß unterschiedlicher Ausgestaltungen der vorliegenden Erfindung veranschaulichen, und
• Figur 9 Details von Verfahren gemäß unterschiedlicher Ausgestaltungen der vorliegenden Erfindung veranschaulicht.

Embodiments of the invention are described below purely by way of example with reference to the accompanying drawings, in which

• Figures 1 to 8 illustrate methods according to different embodiments of the present invention, and
• Figure 9 Details of methods according to different embodiments of the present invention are illustrated.

Embodiments of the invention

The embodiments described below are described solely for the purpose of assisting the reader in understanding the features claimed and previously discussed. They are merely representative examples and are not intended to be exhaustive and/or limiting with respect to the features of the invention. It is to be understood that the advantages, embodiments, examples, functions, features, structures and/or other aspects described above and below are not to be construed as limitations on the scope of the invention as defined in the claims or as limitations on equivalents to the claims, and that other embodiments may be utilized and changes may be made without departing from the scope of the claimed invention.

Different embodiments of the invention may include, have, consist of, or consist essentially of other useful combinations of the described elements, components, features, parts, steps, means, etc., even if such combinations are not specifically described herein. Moreover, the disclosure may include other inventions that are not currently claimed, but that may be claimed in the future, particularly if they are included within the scope of the independent claims.

Explanations relating to devices, apparatus, arrangements, systems, etc. according to embodiments of the present invention may also apply to methods, processes, methods, etc. according to the embodiments of the present invention and vice versa. Elements, method steps, etc. that are identical, act in the same way, correspond to one another in terms of their function, are structurally identical or comparable may be indicated with identical reference symbols.

In Figure 1 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 100.

The method 100 comprises the use of a synthesis unit 10 set up for Fischer-Tropsch synthesis and a shift unit 20 set up for a reverse water gas shift. Hydrogen 101 and carbon dioxide 102 are fed to the shift unit (separately or in a gas mixture). A synthesis gas can also be used which already contains carbon monoxide in addition to these components, as explained at the beginning. Any mixtures of different material streams are also possible.

In the shift unit 20, (further) carbon monoxide is formed from hydrogen and carbon dioxide by reverse water gas shift. This is an equilibrium reaction, so that a gas mixture 103 taken from the shift unit 20 contains hydrogen, carbon monoxide and carbon dioxide. This gas mixture 103 is combined with a tail gas portion 115 from an internal recirculation to form a feed mixture 104, which is fed into the synthesis unit 10. In the Fischer-Tropsch synthesis in the synthesis unit 10, which in the example illustrated is also assigned a corresponding separation unit, the tail gas 105, a crude product 106 and waste water 107 are formed.

In the example illustrated here, the tail gas is divided into the internally recirculated portion 115, an externally recirculated portion 125 and a purge gas portion 135, for the reasons mentioned several times previously.

In Figure 2 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 200.

As in Figure 2 with a dashed line around the shift unit, this is heated by means of a heating unit 21, which comprises one or more burners, using a fuel gas 108. A hydrogenation unit 30 is provided in which the externally recycled portion 125 of the end gas 105 is hydrogenated to obtain a follow-up stream 145, which is fed into the shift unit 20. A purge gas 135 according to Figure 1 The corresponding portion, which is also designated 135 here, is also supplied as fuel gas to the heating unit 21. Inert components can therefore be transferred into an exhaust gas stream 109.

In Figure 3 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 300.

The procedure 300 according to Figure 3 represents in particular a variant of the method 200 according to Figure 2 , in which, however, an electric heating unit 22 is used instead of the heating unit 21 operated by means of one or more burners. Therefore, no fuel gas 108 is provided here. A portion of the end gas 105, also designated 135 here, is therefore discharged here as purge gas from the process 300 to remove the inert substances, essentially as in the process 100 described in Figure 1 is illustrated.

In Figure 4 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 400.

The procedure 400 according to Figure 4 again involves the use of a heating unit operated by one or more burners, which is therefore comparable to Figure 2 or the process 200 is designated with 21. As there, fuel gas 108 is therefore supplied and exhaust gas 109 is formed. An adsorptive separation unit 40, for example a pressure swing adsorption unit, is provided here to process the externally recycled portion 125 of the end gas 105. In the adsorptive separation unit, a pressure product 155 that is enriched in hydrogen compared to the end gas 105, which can also be essentially pure hydrogen, and a low-pressure product 165 that is depleted in hydrogen compared to the end gas 105 can be formed. In the example illustrated here, the pressure product 155 is supplied to the shift unit 20, the low-pressure product 165 can be burned in the heating unit 21, so that inert substances can be discharged in this way.

In Figure 5 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 500.

As in Figure 5 illustrated, in order to provide an insert designated here as 111, to which carbon dioxide 102 can be fed, an electrolysis unit 50 set up for high-temperature electrolysis can be provided, into which air 112 and steam 113 are fed, and from which an electrolysis exhaust gas 114 is taken in addition to the hydrogen 111. As illustrated here, an externally recycled portion 125 of the end gas can be fed into the electrolysis unit 50 on the anode side. In this way, components of the end gas 105 can be used thermally in the electrolysis unit 50. A portion 135 is designed as a purge gas.

In Figure 6 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 600.

As in Figure 6 illustrated, in order to provide a gas mixture as previously designated 103, which contains hydrogen, carbon monoxide and carbon dioxide, a co-electrolysis unit 60 set up for the high-temperature co-electrolysis of water and carbon dioxide can be provided, into which air 112, steam 113 and carbon dioxide 102 are fed. Here too, an externally recycled portion 125 of the end gas can be fed into the co-electrolysis unit 60 on the anode side and/or the cathode side (if necessary with pretreatment). In this way, components of the end gas 105 can be used in the co-electrolysis unit 60. A portion 135 is designed as purge gas, which can also be fed to the co-electrolysis on the anode side.

In Figure 7 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 700.

As in some of the previously described embodiments, a shift unit 20 is provided here, but this is followed by a carbon dioxide removal unit 70. Carbon dioxide 122 separated in this can be returned to the shift unit 20 and converted into further carbon monoxide. The gas mixture 103 is thus provided with a reduced carbon dioxide content. It is then possible to increase the internal recycling. For the sake of simplicity, no provision steps are shown in stream 125, but these can also be carried out as in processes 200 and 300 according to Figure 2 and 3 be provided.

In Figure 8 a method according to an embodiment of the present invention is illustrated using a simplified schematic flow chart or system plan and is designated overall by 800.

As in the Figure 6 In the method 600 illustrated, a co-electrolysis unit 60 is provided here, which, however, is comparable to the method 700 according to Figure 7 a carbon dioxide removal unit 70 is connected downstream. Carbon dioxide 122 separated in this can be returned to the co-electrolysis unit 60 and converted into further carbon monoxide. The gas mixture 103 is thus provided with a reduced carbon dioxide content. The external Recirculation of the portion 125 can be optionally provided here if not all of the tail gas 105 is recirculated internally.

As in the Figures 7 and 8 illustrated in the form of dashed arrows, in certain embodiments of the invention, if a corresponding carbon dioxide removal unit 70 is designed for this purpose, a return of the stream 115 or a portion thereof to a position upstream of the carbon dioxide removal unit 70 can also be provided.

In Figure 9 Details of a synthesis unit 10 according to an embodiment of the present invention are illustrated using a simplified schematic flow or system plan. The synthesis unit 10 can be used in any of the previously explained embodiments.

As in Figure 9 As illustrated, the synthesis unit 10 shown with a dashed line can comprise one or more synthesis reactors 11 and a separation device 12 with one or more stages (not shown here for the sake of clarity). A liquid wax phase can also arise in the synthesis gas reactor(s) 11, which is also not shown here for the sake of clarity. A product mixture 110 is taken from the synthesis reactor(s) 11, which is separated in the separation device 12 into the previously explained fractions of end gas 105, crude product 106 and waste water 107.

Claims (15)

Method (100, 200, 300, 400, 500, 600, 700, 800) for producing a target product, in which a synthesis gas (103) is subjected to a Fischer-Tropsch synthesis, wherein a product mixture (110) of the Fischer-Tropsch synthesis is separated to obtain a tail gas (105) and a crude product (106), wherein a first portion (115) of the tail gas (105) is fed back to the Fischer-Tropsch synthesis in a composition unchanged compared to the tail gas (105), and wherein a second portion (125) of the tail gas (105) is returned to one or more provision steps used to provide the synthesis gas (103). The process (100, 200, 300, 400, 500, 600, 700, 800) of claim 1, wherein the synthesis gas (103) contains hydrogen, carbon monoxide and carbon dioxide. A process (100, 200, 300, 400, 500, 600, 700, 800) according to claim 1 or claim 2, wherein the tail gas (105) contains hydrogen, carbon monoxide, carbon dioxide, methane, one or more hydrocarbons having two, three and/or four carbon atoms and one or more inert gases. Method (100, 200, 300, 400, 500, 700) in which the one provision step or one of the several provision steps is a reverse water gas shift, wherein hydrogen and carbon dioxide are supplied to the reverse water gas shift, and wherein in the reverse water gas shift a part of the hydrogen is reacted with a part of the carbon dioxide to form carbon monoxide and water. Method (100) according to claim 4, wherein the second portion (125) of the tail gas is fed to the reverse water gas shift in a composition unchanged compared to the tail gas (105). The method (200, 300) of claim 4, wherein one of the plurality of providing steps is a hydrogenation step, wherein the second portion (125) of the tail gas (105) is subjected to the hydrogenation step to obtain a subsequent mixture (145), and wherein at least a portion of the subsequent mixture (145) is fed to the reverse water gas shift. The method (400) of claim 4, wherein one of the plurality of providing steps is an adsorption step, wherein the second portion (125) of the tail gas (105) is subjected to the adsorption step to obtain a pressure product (155) enriched in hydrogen compared to the tail gas (105) and a low-pressure product (165) depleted in hydrogen compared to the tail gas (105), and wherein at least a portion of the pressure product (155) is fed to the reverse water gas shift. Method (700) according to claim 4 or 5, wherein one of the plurality of provision steps is a carbon dioxide removal step to which at least a portion of a gas mixture formed in the reverse water gas shift is supplied and using which the synthesis gas is provided, wherein carbon dioxide separated in the carbon dioxide removal step is at least partially returned to the reverse water gas shift. The method (500) of claim 4, wherein one of the plurality of providing steps is a high temperature electrolysis step, wherein electrolysis hydrogen is formed in the high temperature electrolysis step, wherein at least a portion of the electrolysis hydrogen is supplied to the reverse water gas shift together with carbon dioxide. Method (100, 200, 300, 400, 500, 700) according to one of claims 4 to 9, in which the reverse water gas shift is carried out using heat of combustion, wherein a third portion (135) of the tail gas (105) is used to provide the heat of combustion, or in which the reverse water gas shift is carried out using electrical heat, wherein a third portion (135) of the tail gas (105) is discharged from the method (300) in a composition unchanged compared to the tail gas (105). Method (600, 800) according to one of claims 1 to 3, wherein the one provision step or one of the plurality of provision steps is a high-temperature co-electrolysis step, wherein in the high-temperature co-electrolysis step carbon dioxide and water are co-electrolyzed to obtain a gas mixture used to provide the synthesis gas (103). Method (600, 800) according to claim 11, wherein the second portion (125) of the tail gas is fed to the high-temperature co-electrolysis step on the anode and/or cathode side. The method (800) of claim 11, wherein the provision of the synthesis gas (103) comprises separating carbon dioxide from at least a portion of the gas mixture obtained in the high-temperature co-electrolysis step and recycling it to the high-temperature co-electrolysis step. Plant for producing a target product, which is designed to subject a synthesis gas (103) to a Fischer-Tropsch synthesis, to separate a product mixture (110) of the Fischer-Tropsch synthesis to obtain a tail gas (105) and a crude product (106), to re-feed a first portion (115) of the tail gas (105) to the Fischer-Tropsch synthesis in a composition unchanged from the tail gas (105), and to return a second portion (125) of the tail gas (105) to one or more provision steps used to provide the synthesis gas (103). Installation according to claim 14, which is arranged to carry out a method (100, 200, 300, 400, 500, 600, 700, 800) according to one of claims 1 to 13.

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