High-efficiency rwgs fischer-tropsch process for synthesis of regenerative kerosene

Abstract

The present invention relates to a process for the synthesis of regenerative kerosene (22), comprising: carrying out (S10) a reverse water gas shift reaction in order to produce a synthesis gas stream (12); carrying out (S20) a Fischer-Tropsch reaction using the synthesis gas stream (12) in order to produce a hydrocarbon stream (14); cooling and separating (S30) the hydrocarbon stream (14) by means of a separator (30) in order to produce a syncrude stream (16); hydrocracking (S40) the syncrude stream (16) by means of a hydrocracker (40) in order to produce a paraffin stream (18); fractionating (S50) the paraffin stream (18) in order to produce a kerosene stream (22) and in order to discharge said kerosene stream as a target product stream (22), and in order to produce a by-product stream (24); reforming (S60) the by-product stream (24) by means of a pre-reformer (60) in order to produce a C1 hydrocarbon stream (26); feeding (S70) the C1 hydrocarbon stream (26) to the reverse water-gas shift reaction. The invention further relates to a system (1).

Description

[0001] Description

[0002] Highly efficient RWGS-Fischer-Tropsch process for the synthesis of regenerative kerosene

[0003] The present invention relates to a method and a plant for the synthesis of regenerative kerosene.

[0004] To produce renewable hydrocarbon products, especially renewable kerosene, it is known to first generate hydrogen by electrolysis using renewable electricity. The hydrogen is then reacted with a carbon-containing reactant, forming hydrocarbon products. The target product, kerosene, typically preferentially contains C8 to C18 hydrocarbons, i.e., with a carbon chain length in the range of 8 to 18. Known production methods include, for example, the so-called methanol route and the so-called Fischer-Tropsch route, hereinafter referred to as the "FT route" and "FT synthesis," respectively.

[0005] The FT route has the advantage of ASTM certification, which permits the blending of up to 50% by weight of so-called FT kerosene into commercial aviation fuel. A disadvantage of the FT route is that, in addition to the target product kerosene, it also yields a very wide range of byproducts, some of which require complex further processing, in the form of hydrocarbons (hereinafter abbreviated as "HC"), such as HC exhaust gases, C3 / C4 HC mixtures, and naphtha.

[0006] In the prior art, plants for the synthesis of so-called renewable kerosene are known, comprising a reverse water-gas shift (hereinafter "RWGS") reactor for generating synthesis gas, a downstream FT reactor for generating hydrocarbons, a downstream cooler and separator for cooling and separating the generated hydrocarbons to produce a syncrude stream, and a downstream hydrocracker for cracking and isomerizing the hydrocarbons and hydrogenating olefins, ultimately providing a stream of isomerized paraffins. The latter is typically fractionated in a fractionation column to extract fuels as target products and to separately utilize individual byproducts.

[0007] In such a conventional plant, hydrocarbon exhaust gas streams, originating primarily from the separator or fractionation column, are thermally utilized to provide process heat for, for example, the endothermic RWGS reaction. However, this conventional plant regularly achieves a yield of less than 40% of the target product, kerosene.

[0008] Summary of the invention

[0009] Starting from the known state of the art, it is an object of the present invention to provide a more efficient method and a more efficient plant for the synthesis of regenerative kerosene, for example with an improved yield of kerosene based on the regeneratively produced starting materials.

[0010] The problem is solved by a method with the features of claim 1. Advantageous further developments result from the dependent claims, the description and the figures.

[0011] Accordingly, a procedure is proposed comprising the following steps:

[0012] - Performing a reverse water-gas shift reaction to generate a synthesis gas stream;

[0013] - Performing a Fischer-Tropsch reaction using the synthesis gas stream to generate a hydrocarbon stream;

[0014] - Cooling and separating the hydrocarbon stream using a separator to generate a syncrude stream; - Hydrocracking the syncrude stream using a hydrocracker to generate a paraffin stream;

[0015] - Fractionation of the paraffin stream to generate a kerosene stream and to discharge this as the target product stream, and to generate a by-product stream;

[0016] - Reforming the by-product stream using a pre-reformer to produce a Cl-hydrocarbon stream;

[0017] - Feeding the Cl-hydrogen carbonate stream to the reverse water-gas shift reaction.

[0018] In this context, "synthesis gas" is understood to mean a mixture containing carbon monoxide and hydrogen. Furthermore, "hydrocarbon stream" is understood to mean a stream of substances containing hydrocarbon compounds, but also, in particular, hydrogen, water, carbon monoxide, and / or carbon dioxide. Cooling of the hydrocarbon stream can be achieved by means of a cooling unit located upstream of the separator.

[0019] Syncrude streams can contain, in particular, medium-chain and long-chain hydrocarbons. In this context, syncrude refers to a synthetic crude oil that can be produced by FT synthesis and further refined. Therefore, syncrude comprises a mixture of hydrocarbons, containing, in particular, paraffins and olefins.

[0020] In this context, "Cl-hydrocarbon stream" refers to a stream that essentially contains no hydrocarbons with a carbon chain length greater than one. "Essentially none" means that, due to process inaccuracies or fluctuations, small amounts of hydrocarbons with a chain length greater than one may be present. However, according to the technical design of the process or the corresponding plant, no carbon chain lengths greater than one are intended in the Cl-hydrocarbon stream. Furthermore, the Cl-hydrocarbon stream may contain, in addition to hydrocarbon compounds, hydrogen, water, carbon monoxide, and / or carbon dioxide. The Cl-hydrocarbon stream is, in particular, a methane-rich stream.

[0021] In this context, a "pre-reformer" refers to a reactor unit, also known as a pre-reformer in the prior art, which is typically always used in conjunction with a main reactor unit for steam reforming or autothermal reforming (ATR). Accordingly, in the pre-reformer, heavier hydrocarbons (such as naphtha or light hydrocarbons) are converted into lighter components such as methane, hydrogen, carbon monoxide, and carbon dioxide, i.e., essentially chlorine hydrocarbons.

[0022] In the course of the present invention, it was recognized that the yield of the target product, kerosene, can be drastically increased with regard to the use of regeneratively obtained feedstocks, in particular hydrogen or carbon dioxide, by foregoing purely thermal utilization of byproducts such as exhaust gases or naphtha. Thus, byproducts can be utilized materially instead of being subjected to purely thermal utilization. Furthermore, some or even all byproducts can be recycled instead of undergoing complex processing in further processes or plants.

[0023] The present disclosure proposes generating a byproduct stream during the fractionation of the paraffin stream. This byproduct stream is reformed using the pre-reformer to produce the Cl-hydrocarbon stream, which is then fed into the reverse water-gas shift (RWGS) reaction. Thus, the byproduct stream is recycled back to the input materials of the plant or process. In this way, the substances present as byproducts after fractionation are not lost to the process but can be converted into the target product, kerosene, via the cycle. In other words, the disclosed process converts hydrocarbon byproducts into synthesis gas using the pre-reformer and the RWGS reaction. This synthesis gas can then be converted into the target product, kerosene, through the downstream water-gas shift (FT) reaction and subsequent reactions. This significantly improves the kerosene yield.

[0024] By converting the by-product stream to the Cl-hydrocarbon stream via the pre-reformer, which essentially contains no hydrocarbons with a chain length of two or more, the by-products can be materially utilized while at the same time the formation of coke in the RWGS reactor can be avoided.

[0025] The byproduct stream can contain hydrocarbon exhaust, C3 hydrocarbons, C4 hydrocarbons, naphtha, and / or diesel. The byproduct stream can consist of individual substreams of the aforementioned substances, with the substreams being fractionated, i.e., separated from one another, and conveyed in separate lines from the fractionation column to the pre-reformer. For example, the hydrocarbon exhaust can be fed to the pre-reformer as a first byproduct substream in a first byproduct line. Furthermore, the C3 / C4 hydrocarbons, for example, in the form of a mixture, can be fed to the pre-reformer as a second byproduct substream in a second byproduct line. In this way, the proposed process is easily applicable to existing plants. For example, existing plants that still need to discharge specific byproducts, such as naphtha, can thus be gradually converted to the proposed process.

[0026] Furthermore, the byproduct stream can be a mixture of all hydrocarbons whose chain length is shorter than that of kerosene. In this way, the effort required for fractionation can be significantly reduced. Additionally, the step of feeding the Cl-hydrocarbon stream to the reverse water-gas shift (RWGS) reaction can take place immediately after the reforming of the byproduct stream. In particular, this can be achieved without any further intermediate steps. For example, consequently, no reactor unit for autothermal reforming can be provided between the pre-reformer and the RWGS reactor. In the course of the present invention, it was recognized that it can be more efficient for the overall process to use the pre-reformer without a downstream ATR reactor. Thus, the process can be operated with significantly less equipment.

[0027] Furthermore, this allows for savings in both energy and reactants for the operation of an ATR reactor.

[0028] Furthermore, the process cannot include a step for the purely thermal utilization of carbon compounds used in the process. In this way, the regeneratively obtained starting materials, in particular, are not lost to the overall process and can apparently be converted into the target product within the cycle.

[0029] Furthermore, the cooling and separating step can include the following sub-steps:

[0030] - Separation of a separator exhaust gas stream containing in particular CO, H2, CO2 and short-chain hydrocarbons;

[0031] - Reforming the separator exhaust gas stream using the pre-reformer.

[0032] In this way, in addition to the hydrocarbon exhaust gas obtained from fractionation, further exhaust gas can be converted into the target product in the open cycle.

[0033] Furthermore, the paraffin stream fractionation step can include: generating and diverting a diesel stream as an additional target product stream. In this way, another renewable fuel can be provided. Additionally or alternatively, the paraffin stream fractionation step can include: generating another by-product stream and feeding this additional by-product stream to the hydrocracker. In particular, this additional by-product stream can include diesel. For example, an initial portion of diesel can be diverted as the additional target product stream, and a second portion can be fed back into the cycle. In this way, a desired target quantity of diesel can be produced very easily, with the excess diesel being utilized within the cycle.This allows the amount of diesel fuel to be fed in as a further target product to be regulated, in particular by regulating valves or flow rates, without having to change any further process parameters of the reactors. For example, it is therefore not necessary to adjust the pressure and / or temperature of reactions to influence the reactions and control the diesel yield.

[0034] Furthermore, the additional byproduct stream may contain, in particular, long-chain paraffins, such as waxes. In addition, the additional byproduct stream may include separated substreams of the long-chain paraffins and the diesel in separate lines.

[0035] Furthermore, the by-product stream can consist essentially of hydrocarbons with a chain length in the range of CI to C7.

[0036] Additionally or alternatively, the further byproduct stream may contain long-chain paraffins, particularly in the form of waxes. Furthermore, the further byproduct stream may contain diesel.

[0037] Furthermore, the process can include the following step: inerting a system designed to carry out the process in order to purge air that has entered the system by means of a purge gas, wherein the purge gas is CO2, water vapor, or a sequential combination of nitrogen and methane. The air to be purged may have entered the system, in particular, during commissioning or recommissioning.

[0038] In this context, a sequential combination of nitrogen and methane is understood to mean that the system can first be purged with nitrogen and then displaced by methane. In this case, the resulting nitrogen-methane exhaust gas can be flared off.

[0039] Thanks to the inerting process described above, inert gases foreign to the process can be replaced by process-related gases. In particular, it can be ensured that any temporarily introduced inert gases, such as nitrogen, are displaced from the system before the commencement of continuous, intended operation of the corresponding plant. This prevents the accumulation of inert gases foreign to the process over time, which would hinder the complete utilization of the exhaust gas streams as described above. In other words, the risk of inert gas accumulation in the gas circuit described above can be largely eliminated.

[0040] Furthermore, the procedure may include the following steps:

[0041] - Generating electrolysis hydrogen for the reverse water-gas shift reaction using an electrolysis unit;

[0042] - Separation of a water condensate using the separator;

[0043] - Treatment of the water condensate, in particular by means of biological treatment using reverse osmosis; and

[0044] - Feeding the water condensate as deionized water to the electrolysis unit.

[0045] In this way, the ion-free water, which is in the

[0046] The wastewater generated by the separator can be used in a closed-loop system for the process or the corresponding plant. This means less water needs to be deionized specifically for operating the electrolysis unit. In this way, the process or the plant can be operated even more sustainably.

[0047] Furthermore, the process can include: transferring process heat from the Fischer-Tropsch reaction to the by-product stream, in particular by means of increasing the temperature level of the process heat using a heat pump, wherein the increase is less than 100 K, in particular less than 50 K.

[0048] Additionally or alternatively, the process can include: transferring process heat from the reverse water-gas shift reaction to the by-product stream.

[0049] Additionally or alternatively, the process can include: transferring process heat from the reverse water-gas shift reaction to a reactant side of the reverse water-gas shift reaction.

[0050] Furthermore, the Fischer-Tropsch reaction can be carried out at an FT reaction temperature between 200 and 500 °C. Specifically, the procedure can include a low-temperature mode in the range of 200–290 °C and a high-temperature mode in the range of 300–500 °C for the Fischer-Tropsch reaction.

[0051] In the high-temperature mode, the FT reaction can produce a distribution with more shorter hydrocarbon chains and fewer longer ones. This results in lower proportions of diesel and waxes, and significantly reduces the effort required for hydrocracking. While the proportion of hydrocarbon chains in the kerosene range (C8 to C18) decreases, this disadvantage is more than offset by the closed-loop approach of this disclosure, especially since the savings in hydrocracking, in terms of investment and / or operating costs, outweigh the additional effort required for the closed-loop approach.

[0052] In low-temperature mode, particularly in the 200–250 °C range, the FT reaction can yield a distribution with more long hydrocarbon chains and fewer shorter ones. This advantageously results in lower naphtha content in the FT reactor. While the proportion of diesel and waxes increases, making the hydrocracking effort comparatively high, the hydrocracking of the long diesel and wax chains produces a relatively large fraction of the target product, kerosene. Furthermore, the shorter hydrocarbon chains, such as naphtha and lighter hydrocarbons, can be utilized within the process or plant using the open-loop approach and ultimately converted into the target product.

[0053] The problem stated above is further solved by a plant with the features of claim 10. Advantageous embodiments of the plant are described in the dependent claims, the description, and the figures. Accordingly, a plant for the synthesis of renewable kerosene is proposed, comprising a reverse water-gas shift reactor, a Fischer-Tropsch reactor, a separator, a hydrocracker, and a fractionation column. The plant also includes a pre-reformer for reforming a by-product stream. An inlet side of the pre-reformer is connected to an outlet side of the fractionation column via a by-product line. A reactant side of the reverse water-gas shift reactor is connected to an outlet side of the pre-reformer via a feed line.

[0054] In particular, a cooling unit for cooling the hydrocarbon stream can be connected upstream of the separator.

[0055] The definitions, technical effects, and advantages explained above for the disclosed process apply equally to the proposed plant. In particular, the chemical and structural components and technical units described in the context of the process correspond to the chemical and structural components and technical units of the same name described in the context of the proposed plant.

[0056] Furthermore, the plant can have at least one target product discharge and a substantially closed loop for carbon-containing byproducts. As can already be seen from the preceding disclosure, a byproduct is understood here to be a substance that is not discharged from the technical process or plant in the form of a target product. In this context, the term "substantially" means that the loop for carbon-containing byproducts is to be considered closed in the sense of the technical design, whereby marginal losses do not preclude this. Marginal losses can result, for example, from inaccuracies or leaks that are typical for technical processes or plants.

[0057] Furthermore, the system may include a heat exchanger for transferring process heat from the reverse water-gas shift reactor to the pre-reformer. In particular, the system may include a heat pump to increase the temperature level of the process heat.

[0058] Furthermore, the system can include an electrolysis unit, with the separator being connected to the electrolysis unit to supply the electrolysis unit with deionized water.

[0059] Brief description of the characters

[0060] Exemplary embodiments of the invention are explained in more detail by the following description of the figures. Figure 1 schematically shows a flow diagram of a process for the synthesis of renewable kerosene according to a first embodiment;

[0061] Figure 2 shows a flowchart of the procedure according to further implementation forms;

[0062] Figure 3 shows an embodiment of a plant for the synthesis of renewable kerosene according to a first embodiment; and

[0063] Figure 4 shows another embodiment of the system from Figure 3.

[0064] Detailed description of application examples

[0065] The following section describes individual examples of implementation with reference to the figures. Identical, similar, or equivalent elements in the different figures are marked with identical reference symbols, and repeated descriptions of these elements are sometimes omitted to avoid redundancy.

[0066] For better understanding, the process steps described in connection with Figures 1 and 2 are additionally shown with corresponding reference symbols in Figures 3 and 4.

[0067] Figure 1 schematically shows a flow diagram of a process for the synthesis of renewable kerosene according to a first implementation. As can be seen from Figures 1 and 3, the process comprises the following steps:

[0068] - Performing S 10 a reverse water-gas shift reaction to generate a synthesis gas stream 12;

[0069] - Performing S20 a Fischer-Tropsch reaction using the synthesis gas stream 12 to generate a hydrocarbon stream 14;

[0070] - Cooling and separating S30 of the hydrocarbon stream 14 by means of a separator 30 to generate a syncrude stream 16, wherein the syncrude stream 16 contains in particular medium-chain and long-chain hydrocarbons; - Hydrocracking S40 of the syncrude stream 16 by means of a hydrocracker 40 to generate a paraffin stream 18;

[0071] - Fractionating S50 of the paraffin stream 18 to generate a kerosene stream 22 and to discharge this as target product stream 22, and to generate a by-product stream 24;

[0072] - Reforming S 60 of the by-product stream 24 using a pre-reformer 60 to generate a Cl-hydrocarbon stream 26;

[0073] - Feeding S70 of the Cl-hydrogen carbonate stream 26 to the reverse water-gas shift reaction.

[0074] Figure 3 shows an embodiment of plant 1 for the synthesis of renewable kerosene. Plant 1 comprises a reverse water-gas shift reactor 10 for carrying out step S10; a Fischer-Tropsch reactor 20 for carrying out step S20; a cooling unit (not shown) and the separator 30 for carrying out step S30; the hydrocracker 40 for carrying out step S40; a fractionation column 50 for carrying out step S50; a pre-reformer 60 for carrying out step S60; and, for carrying out step S70, a feed line 70 which connects a reactant side 10a of the RWGS reactor 10 with an output side 60b of the pre-reformer 60.

[0075] To avoid repetition, reference is made to the preceding description regarding technical effects as well as the definitions and abbreviations used. The procedure and Annex 1 are explained below, first with reference to Figures 1 to 3.

[0076] The RWGS reaction according to step S 10 is endothermic and can be carried out at an RWGS temperature in the range of 800 to 1000 °C. In this way, the RWGS equilibrium can be shifted towards the desired RWGS product CO, according to the following equation (1): CO2 + H2CO + H2O. On the reactant side, H2 in molar excess and CO2, for example in a ratio of approximately 3:1, are supplied to the RWGS reactor 10. On the product side, the unreacted CO2 and the excess H2 remain after the RWGS reactor 10, so that a synthesis gas stream 12 generated by the RWGS reactor 10 contains a gas mixture containing CO2, H 2fIt contains CO and H2O. Condensed water can optionally be removed.

[0077] The synthesis gas stream 12 is fed to an FT reactor 20 for step S20, in which a hydrocarbon stream 14 is generated at an FT temperature in the range of 250 to 300 °C on a heterogeneous catalyst. The heterogeneous catalyst can be, in particular, a cobalt- or iron-based catalyst. The hydrocarbon stream 14 is a mixture of hydrocarbons, especially olefins and paraffins, with a typically very broad distribution of hydrocarbon chains for the FT reaction. In addition to the paraffin-olefin mixture, the hydrocarbon stream 14 also contains residues of the unreacted gases CO2, H2, and CO, as well as water of reaction formed.

[0078] The following equations (2) and (3) describe the product formation in the FT reactor 20, respectively according to step S20:

[0079] Olef inbildung: nCO + 2nH2 (CH2)n + nH20 (2)

[0080] Paraffinbildung: n CO + (2n+l) H2 H- (CH2)nH + nH2O (3)

[0081] In step S30, the hydrocarbon stream 14 is cooled by means of a cooling unit (not shown) and separated by means of a separator 30. This means that water, as well as medium-chain and long-chain hydrocarbons, are condensed out by cooling the gaseous hydrocarbon stream 14. In contrast, the unreacted reactants remain gaseous. The mixture of condensed substances decomposes into two phases, which are separated in the separator 30. A water condensate 42 can be drawn off from the bottom of the separator 30 due to its higher density. Since the water condensate 42 is deionized, it can be processed in step S35 and fed to an electrolysis unit 38 in step S36, so that electrolysis hydrogen is produced in step S 8 for step S 10, which uses deionized water from the cycle of the disclosed process or plant 1 (see Figures 2 and 3).The processing can be carried out using a processing plant, for example biological processing in conjunction with reverse osmosis.

[0082] With reference again to step S30, the mixture of medium-length and long-chain hydrocarbons in the form of the syncrude stream 16 is obtained as a further liquid phase in the separator 30.

[0083] The syncrude stream 16 is now fed to the hydrocracker 40 together with gaseous hydrogen. During hydrocracking S40, long-chain hydrocarbons, especially those with a chain length >C20, such as waxes, are split into shorter and medium-length hydrocarbons.

[0084] Furthermore, in the hydrocracker 40, the hydrocarbon chains produced in unbranched form in the FT reactor 20 are isomerized by introducing side chains. Additionally, the olefins are hydrogenated. Consequently, a mixture of isomerized paraffins with shorter and medium-length chains is produced, which is fed as paraffin stream 18 to a fractionation column 50. The paraffin stream 18 also contains waxes, i.e., long-chain hydrocarbons, since their conversion during cracking in the hydrocracker 40 is not complete.

[0085] In step S50, the paraffin stream 18 is separated into fractions by distillation. Apparently, at least the kerosene stream 22 and the by-product stream 24 are produced as fractions. The by-product stream 24 can consist essentially of hydrocarbons with a chain length in the range of C1 to C7. According to the above definition of "essentially," hydrocarbons with a chain length of C8 or more may also be present, either individually or in negligible amounts.

[0086] In addition, a further by-product stream 34 comprising long-chain paraffins, in particular waxes, can be produced (step S54), which can be fed to the syncrude stream 16 or the hydrocracker 40 (step S56), so that the further by-product stream 34 is again subjected to a hydrocracker S40 and thus remains in the cycle of the process or plant 1.

[0087] As shown in Figure 3, an outlet 50b of the fractionation column 50 is connected to an inlet 60a of the pre-reformer 60 via a by-product line 50a. The by-product stream 24 is fed to the pre-reformer 60 via the by-product line 50a to carry out step S 60.

[0088] Furthermore, as described above, the output side 60b of the pre-reformer 60 is connected to the reactant side 10a of the RWGS reactor 10 via the feed line 70. The Cl-hydrogen carbonate stream 26 generated by the pre-reformer 60 is fed to the RWGS reactor 10 via the feed line 70 to carry out step S 10.

[0089] As further shown in Figure 3, additional reactor units can be omitted along the by-product line 50a and along the feed line 70. In other words, reactor units that are interposed between the distillation column 50 and the pre-reformer 60, or between the pre-reformer 60 and the RWGS reactor 10, can be omitted. However, units for transferring process heat may be interposed, which in this context are not considered reactor units (see Figure 4). Thus, the by-product line 50a essentially serves to convey the by-product stream 24 directly from the fractionation column 50 to the pre-reformer 60. The feed line 70 essentially serves to convey the Cl-hydrocarbon stream directly from the pre-reformer 60 to the RWGS reactor 10.

[0090] In this way, a process-technically particularly simple procedure or plant 1 is provided, whereby the by-product stream 24 is returned to the RWGS reactor 10 via lines 50a and 70 in a cycle and can be materially converted back into the target product in the process or plant 1.

[0091] In the pre-reformer 60, the by-product stream 24 is reacted with the addition of steam at temperatures between 250 and 500 °C on the heterogeneous catalyst according to the following equation (4) (step S60):

[0092] Pre-referring: C n H m + x H2O CH4 / CO / CO2 / H2 / H2O (4)

[0093] Optionally, a separator exhaust stream 28 is separated in separator 30 (step S32). This separator exhaust stream 28 contains, in particular, CO, H2, CO2, and short-chain hydrocarbons, and is optionally fed to pre-reformer 60 and reformed (step S62). In this way, the yield of the target product can be further increased.

[0094] Nickel-based catalysts can be used in the Pre-Reformer 60. The steam-carbon ratio is 2:1 to 3:1, for example, 2.5:1 to 3:1. The reaction pressures range from 1 to 40 bar, particularly between 10 and 30 bar, for example, between 15 and 25 bar.

[0095] The present disclosure further takes advantage of the fact that in the RWGS reactor 10 CH4 can be converted to CO or to CO2 according to the following equations (5) and (6):

[0096] CH4+ H2O CO + 3 H2(5) CH4+ 2 H20 C02+ 4 H2( 6 )

[0097] Thus, steps S 60 and S70, or the apparent arrangement of the pre-reformer 60 between the fractionation column 50 and the RWGS reactor 10, provide a utilization of the by-product stream 24 that is both efficient in terms of yield and simple and robust, since the Cl-hydrocarbon stream 26 can be readily and harmlessly converted by the RWGS reactor 10. In particular, the RWGS reaction can be heterogeneously catalyzed at 800–1000 °C using a nickel-based catalyst deposited on ceramic supports.

[0098] Figure 2 schematically shows a flowchart of the procedure according to further implementation forms. In particular, Figure 2 illustrates individual further developments that can be applied alone or in combination for the disclosed procedure or Annex 1.

[0099] The exemplary further development of the recycling of the deionized water condensate 42 from the separator 30 according to steps S33, S35, S36, S8 and S10 has already been described with reference to Figure 3. The same applies to the exemplary further development of the recycling of the further by-product stream 34 according to steps S50, S54, S56 and S40, which has also been described with reference to Figure 3. The same applies to the exemplary further development of the recycling of the separator exhaust gas stream 28 according to steps S30, S32, S62 and S70, which has also been described with reference to Figure 3.

[0100] According to a further exemplary development, as a sub-step of step 50 fractionation in step S52, a diesel stream 32 is generated and discharged from the process or plant 1 in the form of a further target product stream 32. Alternatively, the diesel stream 32 can be generated in the fractionation column 50 and fed completely or partially, in particular by means of a controllable branch, to the further by-product stream 34.

[0101] In this way, a desired quantity of diesel can be produced as a further target product, with any excess diesel being utilized within the cycle. Thus, the amount of diesel fed in can be regulated without having to change any further process parameters of the reactors in Plant 1.

[0102] Figure 2 also shows the following further training courses, which can each be applied individually or in combination and are explained in more detail with reference to Figure 4:

[0103] - Transferring S22 of process heat from the FT reaction to the by-product stream 24, in particular by means of an increase in the temperature level of the FT process heat 45a using a heat pump 46, wherein the increase is less than 100 K, in particular less than 50 K;

[0104] - Transfer S 12 of process heat from the RWGS reaction to the by-product stream 24 ;

[0105] - Transferring S 13 of process heat from the RWGS reaction to a reactant side 10a of the RWGS reaction .

[0106] Figure 4 shows another embodiment of the system 1 from Figure 3, focusing on heat recovery according to steps S22, S12, and S13. According to a first exemplary embodiment, the system 1 includes a heat exchanger in the form of the FT heat exchanger 44a for carrying out step S22. Optionally, the system 1 includes a heat pump 46 for increasing the temperature level of the FT process heat 45a according to step S22.

[0107] The reforming of S 60 in the pre-reformer 60 according to the reaction equation ( 4) above proceeds endothermically or exothermically, depending on the product ratio. More precisely, the reaction is weakly endothermic if more CO than CO2 is formed alongside CH4; conversely, it is slightly exothermic if more CO2 than CO is formed alongside CH4. The pre-reformer 60 can, in particular, be operated adiabatically. Thus, in the case of an exothermic reaction, a reacting gas mixture heats up, and in the case of an endothermic reaction, it cools down.

[0108] In particular, in the case of an endothermic reaction in the pre-reformer 60, the by-product stream 24 on the inlet side 60a of the pre-reformer 60 can be heated thanks to the FT process heat 45a provided by the FT heat exchanger 44a of the exothermic FT reaction. Thus, for example, no additional oxygen addition is required to generate heat of oxidation.

[0109] If the temperature level of the FT process heat 45a is lower than the desired temperature on the input side 60a of the pre-referrer 60, the FT process heat 45a can be raised to a higher temperature level by means of the heat pump 46.

[0110] According to the first exemplary further development, the system 1 also includes an additional heat exchanger in the form of the RWGS heat exchanger 44b for carrying out step S 13, i.e., for transferring process heat 45b of the RWGS reaction to a reactant side 10a of the RWGS reaction. In this way, electrical energy can be saved, in particular for heating the reactant side 10a of the RWGS reactor 10.

[0111] Additionally or alternatively, the above step S 12 can be implemented using heat exchanger 44b or another heat exchanger, i.e., transferring process heat 45c from the RWGS reaction to the by-product stream 24 on the input side 60a of the pre-former 60. Due to the high energy requirement for heating the reactant side 10a of the RWGS reactor, the process heat flow 45b can be larger, in particular many times larger, than the process heat flow 45c.

[0112] Where applicable, all individual features shown in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention.

Claims

Patent claims 1. Method for the synthesis of regenerative kerosene (22) , comprising the following steps: - Performing (S10) a reverse water-gas shift reaction to generate a synthesis gas stream (12); - Performing (S20) a Fischer-Tropsch reaction using the synthesis gas stream (12) to generate a hydrocarbon stream (14); - Cooling and separating (S30) the hydrocarbon stream (14) by means of a separator (30) to generate a syncrude stream (16), wherein the syncrude stream (16) contains in particular medium-chain and long-chain hydrocarbons; - Hydrocracking (S40) of the syncrude stream (16) by means of a hydrocracker (40) to generate a paraffin stream (18); - Fractionation (S50) of the paraffin stream (18) to generate a kerosene stream (22) and to discharge this as the target product stream (22), and to generate a by-product stream (24); characterized by - Reforming (S60) the by-product stream (24) using a pre-reformer (60) to generate a Cl-hydrocarbon stream (26); - Feeding (S70) the Cl-hydrocarbon stream (26) to the reverse water-gas shift reaction .

2. The method of claim 1, wherein the step of feeding (S70) the Cl-hydrocarbon stream (26) to the reverse water-gas shift reaction takes place directly, in particular without any further intermediate step, after the reforming (S60) step of the by-product stream (24), and / or wherein the method does not include a step for the thermal utilization of carbon compounds used in the process.

3. The method of claim 1 or 2, wherein the cooling and separation step (S30) comprises the following sub-steps: - Separation (S32) of a separator exhaust gas stream (28) which contains in particular CO, H2, CO2 and short chain hydrocarbons; - Reforming (S62) the separator exhaust stream (28) by means of the pre-reformer (60) .

4. Method according to one of the preceding claims, wherein the step of fractionating (S50) the paraffin stream (18) includes: - Generating and venting (S52) a diesel stream (32) as a further target product stream (32); and / or - Generating (S54) another by-product stream (34) and feeding (S56) the further by-product stream to the hydrocracker (40) .

5. A method according to any of the preceding claims, wherein the by-product stream (24) consists essentially of hydrocarbons with a chain length in the range of CI to C7, and / or wherein the further by-product stream (34) contains long-chain paraffins, in particular in the form of waxes, and optionally diesel.

6. A method according to any of the foregoing claims, further comprising: Inerting (S5) a plant (1) which is set up to carry out the process in order to flush out air which has entered the plant (1) by means of a purge gas, in particular during commissioning or recommissioning of the plant (1), wherein the purge gas is CO2, water vapor or a sequential combination of nitrogen and methane.

7. A method according to any of the foregoing claims, further comprising: - Generating (S8) electrolysis hydrogen for the reverse water-gas shift reaction using an electrolysis unit ( 38 ); - Separation (S33) of a water condensate (42) using the separator ( 30 ); - Treatment (S35) of the water condensate (40), in particular by means of biological treatment using reverse osmosis; and - Feeding (S36) the water condensate (42) as deionized water to the electrolysis unit (38) .

8. A method according to any of the foregoing claims, further comprising: - Transferring (S22) process heat of the Fischer-Tropsch reaction to the by-product stream (24) , in particular by means of an increase in the temperature level of the process heat using a heat pump (46) , wherein the increase is less than 100 K, in particular less than 50 K; - optional: Transfer (S12) of process heat from the reverse water-gas shift reaction to the by-product stream (24) ; - optional: Transfer (S13) of process heat from the reverse water-gas shift reaction to a reactant side (10a) of the reverse water-gas shift reaction.

9. A method according to any of the preceding claims, wherein the Fischer-Tropsch reaction is carried out (S20) at an FT reaction temperature between 200 and 500 °C, in particular wherein the method comprises a low-temperature mode in the range of 200-290 °C and a high-temperature mode in the range of 300-500 °C for the Fischer-Tropsch reaction.

10. Plant (1) for the synthesis of renewable kerosene (22) , comprising a reverse water-gas shift reactor (10) , a Fischer-Tropsch reactor (20) , a separator (30) , a hydrocracker (40) and a fractionation column (50) , characterized by a pre-reformer (60) for reforming a by-product stream (24) wherein an inlet side (60a) of the pre-reformer (60) is connected to an outlet side (50b) of the fractionation column (50) by means of a by-product line (50a), and wherein a reactant side (10a) of the reverse water-gas shift reactor (10) is connected to an outlet side (60b) of the pre-reformer (60) by means of a feed line (70).

11. Plant (1) according to claim 10, comprising at least one target product discharge (22, 32) and a substantially closed cycle for carbon-containing by-products.

12. Plant (1) according to claim 10 or 11, comprising a heat exchanger (44a) for transferring process heat from the Fischer-Tropsch reactor (20) to the pre-reformer (60), wherein the plant (1) optionally includes a heat pump (46) for increasing the temperature level of the process heat.

13. Plant (1) according to one of claims 10 to 12, comprising an electrolysis unit (38) wherein the separator (30) is connected to the electrolysis unit (38) to supply the electrolysis unit (38) with deionized water.

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