Renewable power supply intermittency handling in e-fuels plant

Abstract

A process for operating an e-fuel plant is provided, comprising primary and secondary operating modes. In the secondary operating mode, the process comprises the step of feeding at least a portion of a hydrocarbon byproduct stream from a byproduct storage section to a syngas section, where it is reacted to output a syngas stream.

Description

[0001] RENEWABLE POWER SUPPLY INTERMITTENCY HANDLING IN E-FUELS PLANT

[0002] TECHNICAL FIELD

[0003] The present invention relates to a process for operating an e-fuel plant, comprising primary and secondary operating modes. The process addresses challenges related to power supply intermittency.

[0004] BACKGROUND

[0005] CO2, water / steam and renewable power are typically the only inputs to a FT-eFuels plant, also known as a power-to liquid (PtL) plant. In some regions in the world, the success of a PtL project may hinge on the operating flexibility of the process with varying power supply.

[0006] When feeds are generated via electrical means, reduced power availability can potentially limit availability of one or more sustainable feed supply (e.g. H2from electrolysis, CO2 capture from flue gas or processes, Direct Air capture (DAC) etc.). This may happen due to the unpredictability and intermittency of a renewable energy supply. As a result, feed supply can be depleted to a level where operation of the e-Fuels plant needs to be stopped. Restarting of such e-Fuels plant may take time and due to intermittency it may happen several times, eg - multiple times on the same day. Therefore, it may not be prudent to stop the operation of entire plant. It is instead, advantageous to continue operation by consuming the lowest possible sustainable feeds, preferably continuing production at least the lowest possible capacity.

[0007] One of such e-Fuels plant could be Fischer-Tropsch (FT) based transportation fuel (eg - diesel, kerosene / jet fuel etc.) production plant. Approximately 15-20 wt% of the liquid fuel products from the FT-eFuels plant are naphtha and Liquified Petroleum Gas (LPG), which have little or no market value. These byproducts are often recycled during normal operations to increase overall C and H-efficiency. However, processing of recycled byproducts as feedstock requires additional power.

[0008] Additionally, the more adaptable the process or plant is to variations in renewable power supply, the stronger the overall business case will be.

[0009] In the current invention, a novel approach is adopted by intermittent utilization of byproduct naphtha as feed to tackle the challenge of power supply intermittency in an e-Fuels plant and process. SUMMARY

[0010] It has been found by the present inventor(s) that the challenge of power supply intermittency in an e-Fuels process can be addressed using selected operating modes.

[0011] So, in a first aspect the present invention relates to a process according to claim 1.

[0012] Further details of the technology are provided in the enclosed dependent claims, figures and examples.

[0013] LEGENDS

[0014] The invention is illustrated by means of the following schematic illustrations, in which:

[0015] Figure 1 shows a simple layout of the process of the invention, in the primary operating mode.

[0016] Figure 2 shows the layout of Figure 1, in the secondary operating mode.

[0017] DETAILED DISCLOSURE

[0018] Unless otherwise specified, any given percentages for gas content are % as dry volume. All feeds are preheated / cooled, compressed and purified from any impurities, as required.

[0019] The term "synthesis gas" (abbreviated to "syngas") is meant to denote a gas comprising hydrogen, carbon monoxide, carbon dioxide and small amounts of other gasses, such as argon, nitrogen, methane, steam, etc.

[0020] In this invention, the capacity of a plant or a section or a unit is defined by the throughput. For an example - 50% plant capacity indicates that amounts of product(s) out from the plant is at 50% of the product(s) amount, for what the plant is designed. If a plant comprises more than one sections with recycle of intermediate stream(s), in a certain operating mode individual sections may operate at higher capacity, say 50%, while the plant product capacity may become lower, say 30%, due to relatively higher recycle flow of intermediate stream(s).

[0021] Operational flexibility of a plant or a section or a section or a unit, to large extent, is defined by the minimum operable capacity. The lower the minimum operable capacity is, more flexible the operation of the plant or section or section or unit would be. Typically, the minimum operable capacity of the eFuels plant lies at or below 50% of design capacity, preferably at or below 30% of the design capacity, more preferably at or below 20% of design capacity. Minimum operable capacity of individual sections, however, may differ from overall plant capacity. For example - one or more sections in eFuels plant may have minimum operable capacity at 30% of design capacity, while the overall eFuels plant may produce 20% of designed product amount and consume less sustainable feeds.

[0022] 'Normal operation' of plant or section or unit refers to a stable operating condition where the final product or effluent from the said plant or section or unit is as per approved and / or designed specification. During 'normal operation', the said plant or section or unit is operated at more than minimum operable capacity, preferably > 50%, more preferably > 75%, even more preferably at or more than 100% of its design capacity of the plant. All other operating conditions, including start-up and shutdown of the plant, fall within 'non-normal' operating mode. Plant operation with reduced power supply also falls within 'non-normal' operating mode. Typically, in this invention, "normal operation" corresponds to the first operating mode.

[0023] As noted above, processing of recycled byproducts (eg -naphtha and / or LPG for FT-eFuels) as feedstock requires additional power. As an alternative, according to the present invention, these byproduct streams can be partially or fully stored without using them, when a desired supply of renewable power is readily available.

[0024] Therefore, byproduct streams are not fully used but - instead - partially or fully stored when sufficient renewable power is available again, such as during the daytime when solar panels are generating power, or when the wind blows. This ensures that additional power consumption for byproduct processing during ’normal’ condition is avoided.

[0025] The stored byproducts may then be used as feedstock when the renewable power supply decreases and less H2is available to process CO2. Storing byproducts in this manner can allow plant operation at least at minimum capacity without stopping the operation completely. This approach ensures high overall C and H-efficiencies while providing the operational flexibility needed to manage the intermittency of renewable power supply without frequent start and stop of the plant.

[0026] A process is thus provided for operating an e-fuel plant. The e-fuel plant comprises a syngas section, a synthesis section and a byproduct storage section. Various feeds are provided to the e-fuel plant. Feeds

[0027] A first feed comprising hydrogen (i.e. an H2feed) is provided. The H2feed is hydrogen-rich meaning that the major portion of this feed is hydrogen, i.e. over 75%, such as over 85%, preferably over 90%, more preferably over 95%, even more preferably over 99% of this feed is hydrogen. Suitably, the H2feed consists essentially of hydrogen. One source of the H2feed can be one or more electrolyser units. In addition to hydrogen the H2feed may for example comprise steam, nitrogen, argon, carbon monoxide, carbon dioxide, and / or hydrocarbons. In some cases, a minor content of oxygen may be present in this feed, typically less than 100 ppm. At least a first portion of said H2feed is provided to the syngas section.

[0028] A second feed comprising carbon dioxide is provided (i.e. a CO2 feed). The CO2 feed is CO2- rich meaning that the major portion of this feed is CO2; i.e. over 75%, such as over 85%, preferably over 90%, more preferably over 95%, even more preferably over 99% of this feed is CO2. Suitably, the CO2 feed consists essentially of CO2. One source of the CO2 feed of carbon dioxide can be one or more exhaust stream(s) from one or more chemical plant(s). One source of the CO2 feed can also be carbon dioxide captured from one or more process stream(s) or from atmospheric air. Another source of the second feed could be CO2captured or recovered from the flue gas for example from fired heaters, steam reformers, power plants and / or cement plants. The CO2 feed may in addition to CO2comprise for example steam, oxygen, nitrogen, oxygenates, amines, ammonia, carbon monoxide, and / or hydrocarbons. At least a first portion of said CO2 feed is provided to the syngas section.

[0029] If H2and / or CO2feeds contain O2, higher hydrocarbons and catalyst poisons (such as S), they are converted and / or removed within the syngas section, in the presence of suitable catalysts, upfront the Reverse Water Gas Shift (RWGS) reactor(s) - see below.

[0030] The ratio of H2 / CO2provided to the syngas section inlet varies from 2.0 - 7.0. This ratio is defined as any H2and CO2in external streams (i.e. not including hydrogen and / or carbon dioxide via recycled off-gas streams). This ratio will depend upon the desired end-product in the synthesis section. For example, the desired H2 / CO-ratio of the synthesis gas will typically be around 2.0, if it is to be used in a Fischer-Tropsch synthesis. For an F-T synthesis section the H2 / CO2-ratio at the syngas section inlet (i.e. not including hydrogen and / or carbon dioxide in any recycle streams) should be in the range of 2.0-7.0 or more preferably from 3.0-6.0 and most preferably 3.0-5.0.

[0031] The syngas section is arranged to receive a hydrocarbon byproduct stream from the byproduct storage section. This will be discussed in detail below. Third stream comprising hydrocarbons

[0032] A third stream comprising hydrocarbons may be provided to the syngas stage. The third stream may be at least partially constituted by an off-gas stream from the synthesis stage. Therefore, the third stream comprising hydrocarbons may be a recycle stream from downstream in the plant. The third stream may be supplemented, as required, by an external hydrocarbon feed, such as - renewable natural gas (RNG).

[0033] Hydrocarbon off-gas stream

[0034] The hydrocarbon off-gas stream is produced as side product from the synthesis section. In one embodiment, where the synthesis section is a Fischer-Tropsch (F-T) synthesis section, the offgas stream comprises carbon monoxide (5-40 vol. %), hydrogen (10-50 vol %), carbon dioxide (20-50 vol %), methane (10-40 vol %) and higher hydrocarbons (1-20 vol%). Additional components such as argon and nitrogen may also be present in smaller amounts. The higher hydrocarbons comprise olefins and paraffins with two or more carbon atoms.

[0035] The exact composition of the off-gas stream from the synthesis section may vary significantly depending on the process conditions and catalyst used in the synthesis section. A key parameter for making the above utilization of CO2sustainable is to recycle the hydrocarbon byproduct stream such that the carbon therein may be reintroduced in the production of the synthesis gas, thereby improving the overall carbon efficiency of the process.

[0036] A fourth feed comprising steam may be provided to the syngas stage. The fourth feed is steamrich meaning that the major portion of this feed is steam; i.e. over 75%, such as over 85%, preferably over 90%, more preferably over 95%, even more preferably over 99% of this feed is steam. Suitably, the fourth feed consists essentially of steam.

[0037] Syngas section

[0038] The syngas section receives input feeds and reacts them to provide a syngas stream. The syngas section suitably comprises one or more reverse water gas shift (RWGS) reactors. The RWGS reactors are arranged to receive the CO2 feed, the H2 feed, and any additional feeds, and to output a first syngas stream. RWGS reactors

[0039] The RWGS reactors may be non-electrical RWGS or electrical RWGS reactors. Non-electrical RWGS reactors include but are not limited to one or more fired RWGS reactors and / or autothermal RWGS reactors. For fired RWGS, any sustainable fuel, including H2, can be combusted to provide heat to the endothermic reaction. Oxygen (in the form of fifth feed comprising oxygen) is required as an additional feed when autothermal RWGS is used.

[0040] The syngas section may comprise one or more electrically heated RWGS reactors, such as a resistance heated RWGS reactor or an induction heated RWGS reactor which may be arranged in series or parallel. Resistance heated RWGS reactors are described, inter alia, in WO2019228797A1.

[0041] The RWGS catalyst can be either selective or non-selective. Selective RWGS catalyst is only active in RWGS reaction (reaction 1). While non-selective RWGS catalyst can catalyse both RWGS (reaction 1) and methanation (reaction 2) and steam reforming reactions (reverse of reaction 2). co2+ H2co + H2O (1)

[0042] CO2+ 4H2CH, + 2H2O (2)

[0043] If a selective RWGS catalyst is used in the RWGS reactor, then third stream comprising hydrocarbons needs to be processed in the presence of a separate catalyst, having steam methane reforming (opposite of reaction (2)) activity.

[0044] In one aspect, electrical RWGS reactor can comprise a structured catalyst comprising a macroscopic structure of electrically conductive material capable of catalysing both a reverse water gas shift reaction and a methanation reaction. The RWGS reactors may comprise catalysts that are active in both RWGS and methanation reactions, and / or catalysts that are active in only the RWGS reaction. The catalyst may also be active in steam reforming.

[0045] In another alternative, the RWGS section may comprise a methanation section followed by autothermal reforming section. The methanation section may comprise one or more methanation units arranged in series or parallel. Methanation units may be heated reactors or adiabatic reactors. Synthesis section

[0046] The synthesis section receives at least a portion of the syngas stream from the syngas section and reacts it to provide at least a hydrocarbon product stream and at least one hydrocarbon byproduct stream. The synthesis section suitably comprises a Fischer-Tropsch (FT) section and a product upgrade section.

[0047] At the inlet of said F-T synthesis section, the synthesis gas stream suitably has a H2 / CO ratio in the range 1.00 - 4.00; preferably in the range 1.50-2.10. In another aspect, the synthesis gas stream at the inlet of said F-T synthesis section suitably has a (H2- CO2) / (CO + CO2) ratio in the range 1.50 - 2.50; preferably 1.80 - 2.30, more preferably 1.90 - 2.20.

[0048] The hydrocarbon product stream provided by the F-T synthesis section is a raw hydrocarbon stream comprising higher hydrocarbons such as long chain hydrocarbons and olefins. The ratio between long chain hydrocarbons and olefins in the raw product from the F-T synthesis section depends on the type of catalyst, reaction temperature etc. used in the process.

[0049] In the FT section, H2 and CO feeds are reacted to provide heavy hydrocarbons in the range C5 to C60+. The heavy hydrocarbon are wax components. In the product upgrade section, the heavy hydrocarbons are reacted further by hydrocracking, hydroprocessing and isomerization to final hydrocarbon products, typically called kerosene and / or diesel and a hydrocarbon byproduct stream, e.g. naphtha. As used herein, "naphtha stream" is used interchangeably with the term "naphtha" and means a hydrocarbon product boiling in the range 30-210°C, for instance 30-160°C.

[0050] In particular, the hydrocarbon product stream may be a kerosene product stream. Such a kerosene product stream may be refined to jetfuel (SAF).

[0051] Byproduct storage section

[0052] The e-fuel plant comprises a byproduct storage section. The storage section typically comprises one or more tanks, cylinders or similar, where the hydrocarbon byproduct stream can be stored for a period of time e.g. from a few hours to a few days.

[0053] The byproduct storage section is arranged such that it can receive hydrocarbon byproduct stream from the synthesis section, and supply hydrocarbon byproduct stream to the syngas section. The hydrocarbon byproduct stream may be treated between the synthesis section and the storage section and / or between the storage section and the syngas section. Operation

[0054] The process described herein comprises a primary operating mode and a secondary operating mode. The process is carried out preferably in the primary operating mode for most of the time, and the secondary operating mode for a limited period of time. The secondary operation mode is suitably used when the supply of renewable energy used to power the e- fuels plant drops. In this manner, the plant operation can continue without significant interruption and with reduced power consumption. Suitably, the process is operated in the primary operating mode during start-up.

[0055] In the primary operating mode, the process comprises the steps of: o feeding at least a CO2 feed and an H2 and optionally, a part of the third feed comprising hydrocarbons, external to the plant, to the syngas section and reacting them to output a syngas stream; o feeding at least a portion of the syngas stream from the syngas section to the synthesis section and reacting it to provide at least a hydrocarbon product stream and at least one hydrocarbon byproduct stream; o feeding at least a portion of the hydrocarbon byproduct stream to the byproduct storage section and storing it in said byproduct storage section.

[0056] In the secondary operating mode, said process comprises the steps of: o feeding at least a portion of the hydrocarbon byproduct stream from the byproduct storage section to the syngas section, where it is reacted to output a syngas stream; and o optionally, a part of the third feed comprising hydrocarbons, external to the plant, to the syngas section and reacting them to output a syngas stream;

[0057] The recycling of the hydrocarbon byproduct stream as feed can replace the requirement for fresh first feed comprising H2 and / or second feed comprising CO2 and, optionally, third feed comprising external hydrocarbons. Thus, the consumption of the first feed comprising H2 and / or the second feed comprising CO2, provided to the syngas section, relative to the hydrocarbon production is lower in the secondary operating mode than that in the primary operating mode. Therefore, the secondary operating mode can compensate for a drop in the H2 feed. Suitably, in the first operating mode, no hydrocarbon byproduct stream is fed to the syngas section.

[0058] Suitably - in the secondary operating mode - consumption of the first feed comprising H2 relative to the hydrocarbon production is lower in the secondary operating mode than that in the primary operating mode. In one aspect, - in the secondary operating mode - substantially no H2 feed is fed to the syngas section. This may be the case when the supply of H2 generated by renewable energy is lowered or reduced to zero.

[0059] Suitably - in the secondary operating mode - consumption of the second feed comprising CO2 relative to the hydrocarbon production is lower in the secondary operating mode than that in the primary operating mode. In the secondary operating mode CO2 feed may therefore be fed to the syngas section. However, in an alternative - in the secondary operating mode - substantially no CO2 feed is fed to the syngas section.

[0060] The process may switch from said primary operating mode to said secondary operating mode in response to a decrease in the H2 and / or CO2 feeds supplied to the syngas section.

[0061] The process is of particular use wherein the e-fuel plant further comprises an electrolysis section, and wherein the process further comprises a step of electrolysing a water or steam feed in said electrolysis section so as to provide said H2 feed, preferably wherein the electrolysis section is powered by renewable electricity. In the case where the e-fuel plant further comprises an electrolysis section and wherein the process further comprises a step of electrolysing a water / steam feed in said electrolysis section so as to provide said H2 feed, the process may also switch from said primary operating mode to said secondary operating mode in response to a decrease in power supply to the electrolysis section.

[0062] The process may additionally comprise the step of feeding a fourth feed comprising steam to the syngas section. This step is particularly relevant in the secondary operation mode.

[0063] The process may additionally comprise the step of feeding a third stream comprising hydrocarbons to the syngas section. This step is particularly relevant in the primary operation mode.

[0064] The switch between primary and secondary operating modes may be manual or automatic. In one aspect, the e-fuel plant may comprise a first measurement device (110) arranged to determine a parameter of the syngas stream, preferably wherein the parameter of the syngas stream is H2 / CO ratio or the module of said syngas stream (defined as molar module

[0065] M =H2~c°2■) co+co2

[0066] The e-fuel plant may comprise a second measurement device (120) arranged to determine the flow of the first feed comprising H2 to the syngas section.

[0067] The e-fuel plant may comprise a third measurement device (130) arranged to determine the flow of electricity to the electrolysis section. The e-fuel plant may comprise a fourth measurement device (140) arranged to determine the flow of the second feed comprising CO2 to the syngas section. The e-fuel plant may comprise a fifth measurement device (150) arranged to determine the flow of the water / steam feed to the electrolysis section. The e-fuel plant may comprise a sixth measurement device (160) arranged to determine the flow of the hydrocarbon byproduct feed to the syngas section. The e-fuel plant may also comprise a seventh measurement device (170) arranged to determine the flow of the hydrocarbon byproduct from synthesis section (30) to the byproduct storage section (40) and a eighth measurement device (180) arranged to determine the flow of the hydrocarbon product from synthesis section (30).

[0068] The e-fuel plant suitably comprises regulator means arranged to regulate the flow of the hydrocarbon byproduct stream from the byproduct storage section to the syngas section. As shown in the figures, the regulator means is arranged to regulate the flow of the hydrocarbon byproduct stream from the byproduct storage section to the syngas section in response to a signal generated by at least one of said first, second, third, fourth, fifth, sixth, seventh or eighth measurement devices, and said process comprises the additional step of regulating the flow of the hydrocarbon byproduct stream from the byproduct storage section to the syngas section in response to a signal generated by at least one of said first, second, third, fourth, fifth, sixth, seventh or eighth measurement devices. For instance, a decrease in the relevant flow, detected by at least one of the first, second, third, fourth, fifth, sixth, seventh or eighth measurement devices can increase the flow of hydrocarbon byproduct stream from the byproduct storage section to the syngas section.

[0069] LEGENDS

[0070] The following references are shown in Figures 1 and 2 e-fuel plant (10) syngas section (20) synthesis section (30) byproduct storage section (40)

[0071] - CO2 feed (1)

[0072] - H2 feed (2) syngas stream (21) hydrocarbon product stream (31) hydrocarbon byproduct stream (32) to byproduct storage section (40) hydrocarbon byproduct stream feed (32a) to syngas section (40) byproduct storage section (40) electrolysis section (70) water / steam feed (4) regulator means (50) first, second, third, fourth, fifth, sixth, seventh or eighth measurement devices (110, 120, 130. 140, 150, 160, 170, 180)

[0073] Figure 1 illustrates one aspect of operation in primary operating mode of e-Fuel plant (10), where hydrocarbon product (31) is produced from CO2 feed (1) and H2 feed (2). CO2 and H2 feed flows are measured by measurement device 140 and 120, respectively. H2 feed is obtained from electrolysis (70), which uses one or more form of renewable energy, such as but not limited to - solar energy, wind energy. The electric power consumption in electrolysis is measured via measurement device 130. The syngas section converts feeds to syngas (21) flow, measured by device 110. The syngas is then fed to synthesis section (30) which comprises a FT-synthesis section and a product upgrade section. There could be internal recycle of off-gas streams synthesis section (30) to syngas section (20), which is not shown in the figure for simplification. The hydrocarbon byproduct stream (32) comprising naphtha range hydrocarbons are stored in byproduct storage section (40). The hydrocarbon byproduct flow to storage is measured by 170. In this aspect, the hydrocarbon byproduct feed (32a) stream flow to syngas section is stopped by closing regulator 50.

[0074] The syngas section (20) comprises electrically heated reactor and thus, a part of the renewable power is required for syngas section (20). Additionally, a small part of the renewable power consumption is needed for synthesis section (30).

[0075] In figure 2, secondary operating mode of the e-Fuel plant (10) is depicted, where lower availability of renewable energy is monitored in 130, causing reduction in H2 feed (2) flow, measured in 120. This necessitates reduction in e-Fuels plant capacity, measured by hydrocarbon product flow (31) and measure in 180. However, Availability of renewable power could be so low, that stopping e-Fuels plant (10) operation might be necessary. In such a situation, hydrocarbon byproduct feed (32a) regulator (50) is opened either manually or automatically to compensate reduction of renewable H2 feed flow (2) and CO2 feed flow (1) in order to maintain e-Fuels plant (10) operation with at least minimum production.

[0076] Recycle of hydrocarbon byproduct feed (32a) would require some pretreatment steps, which are included in syngas section (20). The steps might include purification and higher hydrocarbon conversion. The use of fourth feed comprising steam (not shown in the figure) relative to hydrocarbon product might increase during secondary mode of operation. A small part of the first feed comprising H2is needed for product upgrading in synthesis section (30), which is not shown in the figure.

[0077] Examples

[0078] The following examples are for e-Fuels plant to produce primarily the Sustainable Aviation Fuel (SAF) using H2feed and CO2feed via Fischer-Tropsch (FT) synthesis process. Thus, the capacity of the e-Fuels plant is defined as production rate of SAF. The syngas for FT synthesis is produced via electrically heated reverse water gas shift (RWGS) reactor system in syngas section. Hydrocarbon byproduct comprises naphtha range hydrocarbons. In all operating modes, light hydrocarbons and off-gases are recycled within e-fuels plant.

[0079] In secondary operating mode, for each scenario, the aim is to keep the total power consumption of maximum 40% of that in full SAF capacity in primary operating mode, while maintaining at least 30% SAF production capacity and operating H2and CO2feed sections above the minimum operable capacity of 20%.

[0080] It is assumed that H2comes from alkaline electrolysis, using renewable electricity, and CO2feed comes as point source. Moreover, any byproduct naphtha produced in secondary operating mode is also consumed.

[0081] Scenario 1

[0082] Table 1 Primary operating mode for 8 hours and secondary operating mode operation for 16 hours

[0083] In scenario 1, e-Fuels plant (10) operation split of 8 hours in primary operating mode and 16 hours in secondary operating mode are considered. In other words, most of the naphtha byproduct is first accumulated for 8 hours during primary operating mode. Then, the stored naphtha byproduct is used uniformly over 16 hours in secondary operating mode. As shown in Table 1, the e-Fuels plant (10) has run in primary operating mode for 8 hours at 100% SAF capacity. During primary operating mode, most of the naphtha byproduct is stored in byproduct storage section (40) and not used in syngas section (20). During secondary operating mode, plant capacity is reduced to 50% SAF ensuring minimized power consumption without compromising e-Fuels plant operation and continuous SAF production at reduced rate. Such flexibility would allow continuing e-Fuels plant operation with 38% total power consumption of that in full e-Fuels plant capacity. The reduced power can be attributed to reduced H2and CO2feed flows. The productivity of SAF relative to energy input to the e-Fuels plant gets improved by 31%.

[0084] Scenario 2 Table 2 Primary operating mode for 12 hours and secondary operating mode operation for 12 hours In scenario 2, e-Fuels plant (10) operation split of 12 hours in primary operating mode and 12 hours in secondary operating mode are considered. In other words, most of the naphtha byproduct is first accumulated for 12 hours during primary operating mode. Then, the stored naphtha byproduct is used uniformly over 12 hours in secondary operating mode. Compared to scenario 1, more naphtha byproduct gets accumulated due to longer operating hours in primary operating mode. Moreover, shorter operating hour in secondary operating mode allows use of higher naphtha byproduct feed flow rate, resulting in further reduction in H2and CO2feed flows. Consequently, overall power consumption is further reduced without compromising e-Fuels plant capacity during secondary operating mode. As shown in Table 2, renewable power consumption reduction to 32% of that in full e-Fuels plant capacity is shown. Importantly, the productivity of SAF relative to energy input to the e-Fuels plant gets further improved by 56%.

[0085] Scenario 3

[0086] Table 3 Primary operating mode for 16 hours and secondary operating mode operation for 8 hours

[0087] In scenario 3, e-Fuels plant (10) operation split of 16 hours in primary operating mode and 8 hours in secondary operating mode are considered. In other words, most of the naphtha byproduct is first accumulated for 16 hours during primary operating mode. Then, the stored naphtha byproduct is used uniformly over 8 hours in secondary operating mode.

[0088] Compared previous scenarios, more naphtha byproduct gets accumulated due to longer operating hours in primary operating mode. Moreover, shorter operating hour in secondary operating mode allows use of higher naphtha byproduct feed flow rate, resulting in further reduction in H2and CO2feed flows. Consequently, overall power consumption is further reduced without compromising e-Fuels plant capacity during secondary operating mode. As shown in Table 3, renewable power consumption reduction to 29% of that in full e-Fuels plant capacity can be achieved.

[0089] In scenario 3 secondary operating mode, e-Fuels plant capacity is increased (to 60%) compared to scenario 1 and scenario 2 (with e-Fuels plant capacity 50%) to maintain operation of H2and CO2the feed systems in syngas section (20) above their turn down capacity (the lowest possible controllable capacity). This would also allow continuing operation without frequent start-up and shut-down of a part of the e-Fuels plant while shifting from secondary operating mode to primary operating mode, when sufficient renewable energy is available. Resultingly, remarkable improvement in SAF productivity per energy input is obtained, where more than 2 times SAF production seems achievable with same energy input.

[0090] The shorter the duration of the secondary operating mode is the higher the capacity of e-Fuels plant would be during secondary operating mode. Shorter duration of secondary operating mode would allow continuous use of at least a part of the hydrocarbon byproduct also during primary operating mode.

Claims

CLAIMS1. A process for operating an e-fuel plant (10), said e-fuel plant (10) comprising a syngas section (20), a synthesis section (30) and a byproduct storage section (40), wherein: in a primary operating mode, said process comprises the steps of: o feeding at least a CO2 feed (1) and an H2 feed (2) to the syngas section (20) and reacting them to output a syngas stream (21); o feeding at least a portion of the syngas stream (21) from the syngas section to the synthesis section (30) and reacting it to provide at least a hydrocarbon product stream (31) and at least one hydrocarbon byproduct stream (32); o feeding at least a portion of the hydrocarbon byproduct stream (32) to the byproduct storage section (40) and storing it in said byproduct storage section (40); wherein in a secondary operating mode, said process comprises the steps of: o feeding at least a portion of the hydrocarbon byproduct stream (32) from the byproduct storage section (40) to the syngas section (20), where it is reacted to output a syngas stream (21), and wherein the H2 feed (2) and / or the CO2 feed (1) provided to the syngas section (20) is / are lower in the secondary operating mode than in the primary operating mode,2. The process according to claim 1, wherein - in said primary operating mode - only a CO2 feed (1) and an H2 feed (2) are fed to the syngas section (20) and reacted to output syngas stream (21).

3. The process according to claim 1, wherein - in said primary operation mode - at least a portion of the hydrocarbon byproduct stream (32) is fed to the syngas section (20) and reacted to output a syngas stream (21) and wherein the flow of the hydrocarbon byproduct stream (32) as feed to the syngas section (20) is higher in the secondary operating mode than in the primary operating mode.

4. The process according to any one of claims 1 to 3, wherein a third-stream comprising hydrocarbon(s), external to the plant, is fed to the syngas section (20), where it is reacted to output a syngas stream (21), in one or both of primary and secondary operating mode(s).

5. The process according to any one of the preceding claims, wherein the hydrocarbon product stream (31) is a kerosene product stream and wherein the at least one hydrocarbon byproduct stream (32) is a naphtha-containing stream.

6. The process according to any one of the preceding claims, wherein - in the secondary operating mode - H2 feed (2) is fed to the syngas section (20).

7. The process according to any one of claims 1-6, wherein - in the secondary operating mode - substantially no H2 feed (2) is fed to the syngas section (20).

8. The process according to any one of the preceding claims, wherein - in the secondary operating mode - CO2 feed (1) is fed to the syngas section (20).

9. The process according to any one of claims 1-7, wherein - in the secondary operating mode - substantially no CO2 feed (1) is fed to the syngas section (20).

10. The process according to any one of the preceding claims, wherein the process is arranged to switch from said primary operating mode to said secondary operating mode in response to a decrease in the H2 feed (2) and / or the CO2 feed (1).

11. The process according to any one of the preceding claims, wherein the process is arranged to switch from said secondary operating mode to said primary operating mode in response to an increase in the H2 feed (2).

12. The process according to any one of the preceding claims, wherein the e-fuel plant (10) further comprises an electrolysis section (70) and wherein the process further comprises a step of electrolysing a water / steam feed (4) in said electrolysis section (70) so as to provide said H2 feed (2), preferably wherein the electrolysis section (70) is powered by renewable electricity.

13. The process according to claim 12, wherein the process is arranged to switch from said primary operating mode to said secondary operating mode in response to a decrease in in power supply to the electrolysis section.

14. The process according to any one of the preceding claims, wherein the e-fuel plant (10) comprises a first measurement device (110) arranged to determine a parameter of the syngas stream (21), preferably wherein the parameter of the syngas stream (21) is the module of said syngas stream (21).1815. The process according to any one of the preceding claims, wherein the e-fuel plant (10) comprises a second measurement device (120) arranged to determine the flow of the H2 feed (2) to the syngas section (20).

16. The process according to any one of claims 9-13, wherein the e-fuel plant (10) comprises a third measurement device (130) arranged to determine the flow of electricity to the electrolysis section (70).

17. The process according to any one of the preceding claims, wherein the e-fuel plant (10) comprises a fourth measurement device (140) arranged to determine the flow of the CO2 feed to the syngas section (20).

18. The process according to any one of claims 9-15, wherein the e-fuel plant (10) comprises a fifth measurement device (150) arranged to determine the flow of the water / steam feed (4) to the electrolysis section (70).

19. The process according to any one of the preceding claims, wherein the e-fuel plant (10) comprises a sixth measurement device (160) arranged to determine the flow of the hydrocarbon byproduct stream (32) as feed to the syngas section (20).

20. The process according to any one of the preceding claims, wherein the e-fuel plant (10) comprises regulator means (50) arranged to regulate the flow of the hydrocarbon byproduct stream (32) from the byproduct storage section (40) to the syngas section (20), such that when the measured flow of the H2 feed and / or the measured power to the electrolysis section falls below a predetermined threshold the flow of the hydrocarbon byproduct stream is increased to maintain the is H2 / CO ratio or the module of said syngas stream defined as molar module M = cHo2~+cc°o22within 1.90 to 2.20 and / ' or to maintain hydrocarbon production at or above turn down capacity.

21. The process according to claim 18, wherein the regulator means (50) is arranged to regulate the flow of the hydrocarbon byproduct stream (32) from the byproduct storage section (40) to the syngas section (20) in response to a signal generated by at least one of said first, second, third, fourth, fifth or sixth measurement devices (110, 120, 130. 140, 150, 160), and said process comprises the additional step of regulating the flow of the hydrocarbon byproduct stream (32) from the byproduct storage section (40) to the syngas section (20) in response to a signal generated by at least one of said first, second, third, fourth, fifth or sixth measurement devices (110, 120, 130, 140, 150, 160).1922. The process according to any one of the proceeding claims, wherein the syngas section (20) comprises one or more electrically heated reverse water gas shift (RWGS) reactors, such as a resistance heated RWGS reactor or an induction heated RWGS reactor, in which reaction of CO2 feed (1), H2 feed (2) and optionally hydrocarbon byproduct stream (32) takes place.

23. The process according to any one of the preceding claims, wherein the syngas section (20) comprises one or more non-electrical RWGS reactors, such as an autothermal RWGS reactor, in which reaction of CO2 feed (1), H2 feed (2) and optionally hydrocarbon byproduct stream (32) takes place, said process further comprising feeding a fifth feed (5) comprising oxygen to said autothermal RWGS reactor.

24. The process according to any of claims 20-21, wherein the RWGS reactors comprise catalysts that are active in both RWGS and methanation reactions, and / or catalysts that are active in only RWGS reaction.

25. The process according to any one of the proceeding claims, wherein the synthesis section (30) comprises a Fischer-Tropsch (FT) section and a product upgrade section, and wherein the product upgrade section provides said hydrocarbon product stream (31) and said hydrocarbon byproduct stream (32).

26. The process according to any one of the proceeding claims, wherein process is operated in the primary operating mode during start-up.

27. An e-fuel plant (10) comprising :- a syngas section (20),- a synthesis section (30) and a- byproduct storage section (40), the syngas section (20) being arranged to receive a CO2-comprising feed (1), a hydrogen-containing feed (2) and optionally a third feed comprising hydrocarbon(s) external to the plant, to output a synthesis gas stream (21),20 the synthesis section (30) being arranged to convert at least a portion of the synthesis gas stream (21) into a hydrocarbon product stream (31) and a hydrocarbon byproduct stream (32), the byproduct storage section (40) being fluidly connected to receive and store at least a portion of the hydrocarbon byproduct stream (32) and to supply a byproduct-derived hydrocarbon feed (32a) to the syngas section (20), and a control system operatively connected to a flow regulator (50) in a line conveying the byproduct-derived hydrocarbon feed (32a) from the byproduct storage section (40) to the syngas section (20) and to at least one measurement device (110, 120, 130, 140, 150, 160) configured to provide a signal indicative of an availability of the hydrogen-containing feed (2) and / or of electrical power to equipment (70) for generating the hydrogen-containing feed (2), the control system being configured to increase a flow of the byproduct-derived hydrocarbon feed (32a) to the syngas section (20) in response to the signal indicating a reduction in said availability so as to sustain operation of the plant (10) at or above turn down capacity of the plant, wherein said plant additionally comprises a seventh measurement device (170) arranged to determine the flow of the hydrocarbon byproduct from synthesis section (30) to the byproduct storage section (40) and a eighth measurement device (180) arranged to determine the flow of the hydrocarbon product from synthesis section (30).

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