WO2025093820A1

WO2025093820A1 - A method for producing a fuel product

Info

Publication number: WO2025093820A1
Application number: PCT/FI2024/050585
Authority: WO
Inventors: Fredrik NYHOLM; Jaana KANERVO; Sonja KOUVA; Valerie SAGE; Sami Toppinen; Noora VESA; Juha Visuri
Original assignee: Neste Oyj
Current assignee: Neste Oyj
Priority date: 2023-11-02
Filing date: 2024-10-31
Publication date: 2025-05-08
Anticipated expiration: 2026-05-02
Also published as: FI131465B1; FI20236223A1

Abstract

The present invention relates to a method for processing a low-temperature Fischer- Tropsch process effluent (1) into a fuel product, the method comprising fractionating the Fischer-Tropsch effluent in a first fractionation (2), separating water and oxygenates (4); and processing a fraction consisting mainly of C17 and higher hydrocarbons by a catalytic hydrocracking (21) to produce a hydrocracked liquid product (22) and a further fraction consisting mainly of C17 and higher hydrocarbons (23). Thereafter the liquid products are processed by catalytic hydroisomerisation (7) to produce a product mixture (8), which is fractionated in a second fractionation (9) and a third fractionation (14). The method further comprises directing at least some of the gases to a reverse water gas shift reaction (18); and recycling a heavy fraction consisting mainly of C17 and higher hydrocarbons to the first fractionation (2).

Description

A METHOD FOR PRODUCING A FUEL PRODUCT

FIELD

The present invention relates to a method for processing a low-temperature Fischer- Tropsch process effluent into a fuel product. The invention further relates to a system for carrying out the method.

BACKGROUND AND OBJECTS

In view of climate change and reducing the use of natural resources, for example fossil oil, there exists a need to find alternatives for the production of fuel products and fuel components. Various biomasses are currently either used as feedstock for fuel production, or studied for such use. Alternatives for sustainable biomass are thus desired, in the search of alternative energy sources.

Production of synthetic fuels from renewable hydrogen and carbon dioxide by power-to-liquids (PtL) processes is one option. However, PtL production consumes considerable amounts of electricity, and thus it would be best to use these processes for the manufacturing of liquid fuels that are difficult to replace by other sources of energy, such as electricity. One such fuel product is aviation fuel. While electricity or hydrogen may be usable in aviation, for the time being the use of electricity is limited by the weight of the batteries, while hydrogen suffers from challenges with storage.

For the moment, two PtL technologies, namely the Fischer-Tropsch (FT) and Alcohol-to-Jet (AtJ) pathways are currently accepted by the ASTM D7566-22 jet fuel standard and allowed for production of kerosene, i.e. aviation fuel. The FT synthesis, however, produces a wide range of hydrocarbons and thus exhibits a poor selectivity for the kerosene product. There is therefore a need for a good upgrading process to maximise the efficiency of the overall process as well as the yield of the desired product(s).

It is therefore an aim to provide a viable large scale (i.e. industrial size) process solution taking into account carbon efficiency and reuse of side streams, to have an overall process that is efficient in all aspects. Another aim is to provide a system for carrying out the method.

SUMMARY

The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims. According to one aspect, there is provided a method for processing a low-temperature Fischer-Tropsch process effluent into a fuel product, the method comprising

- fractionating the Fischer-Tropsch effluent in a first fractionation into at least a first mixture of gases, a first liquid product, and a first fraction consisting mainly of C17 and higher hydrocarbons;

- separating the first liquid product by decantation to obtain a second liquid product and a mixture of water and oxygenates;

- processing the fraction consisting mainly of C17 and higher hydrocarbons by a catalytic hydrocracking to produce a hydrocracked liquid product and a second fraction consisting mainly of C17 and higher hydrocarbons;

- processing the second liquid product and the hydrocracked liquid product by catalytic hydroisomerisation to produce a product mixture;

- fractionating the product mixture in a second fractionation, in the presence of water, to obtain hydrogen, a second mixture of gases at least mainly other than hydrogen, and a fractionated product mixture,

- fractionating the fractionated product mixture in a third fractionation, to obtain water and at least one fuel product;

- directing at least the first mixture of gases to a reverse water gas shift reaction; and

- recycling the second fraction consisting mainly of C17 and higher hydrocarbons to the first fractionation.

According to another aspect, there is provided a system for processing a low- temperature Fischer-Tropsch process effluent into a fuel product, comprising

- first means for fractionating the Fischer-Tropsch process effluent into at least a first mixture of gases, a first liquid product, and a first fraction consisting mainly of C17 and higher hydrocarbons; - a decanter for separating the first liquid product to obtain a second liquid product and a mixture of water and oxygenates;

- a catalytic hydrocracking reactor for processing the fraction consisting mainly of C17 and higher hydrocarbons to produce a hydrocracked liquid product and a second fraction consisting mainly of C17 and higher hydrocarbons;

- a catalytic hydroisomerisation reactor for processing the second liquid product and the hydrocracked liquid product to produce a product mixture;

- second means for fractionating the product mixture, in the presence of water, to obtain hydrogen, a second mixture of gases at least mainly other than hydrogen, and a fractionated product mixture;

- third means for fractionating the fractionated product mixture, to obtain water and at least one fuel product;

- means for directing at least the first mixture of gases to a reverse water gas shift reactor; and

- means for recycling the second fraction consisting mainly of C17 and higher hydrocarbons to the first fractionation.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a system and process according to an embodiment.

Figure 2 shows a system and process according to another embodiment.

Figure 3 shows part of a system and method according to an embodiment.

Figure 4 shows part of a system and method according to another embodiment.

Figure 5 shows another part of a system and method according to an embodiment.

Figure 6 shows a part of a system and method according to an embodiment. Figure 7 shows a part of a system and method according to an embodiment.

DETAILED DESCRIPTION

In the present description, weight percentages (wt-%) are calculated on the total weight of the material in question (typically a blend or a mixture). Any amounts defined as ppm (parts per million), are based on weight. The following abbreviations may also be used: FT for Fischer-Tropsch; HTHP for high temperature-high pressure flash; MTHP for medium temperature-high pressure flash; and LTHP for low temperature-high pressure flash.

The term “renewable” in the context of a renewable fuel component refers to one or more organic compounds derived from any renewable source (i.e., not from any fossil-based source). Thus, the renewable fuel component is based on renewable sources and consequently does not originate from or is derived from any fossilbased material.

The 14C-isotope content can be used as evidence of the renewable or biological origin of a feedstock or product. Carbon atoms of renewable material comprise a higher number of unstable radiocarbon (14C) atoms compared to carbon atoms of fossil origin. Therefore, it is possible to distinguish between carbon compounds derived from biological sources, and carbon compounds derived from fossil sources by analysing the ratio of 12C and 14C isotopes. Thus, a particular ratio of said isotopes can be used to identify and quantify renewable carbon compounds and differentiate those from non-renewable i.e. fossil carbon compounds. The isotope ratio does not change in the course of chemical reactions. Example of a suitable method for analysing the content of carbon from biological sources is ASTM D6866- 20 (2020). An example of how to apply ASTM D6866-20 to determine the renewable content in fuels is provided in the article of Dijs et al., Radiocarbon, 48(3), 2006, pp 315-323. For the purpose of the present invention, a carbon-containing material, such as a feedstock or product is considered to be of renewable origin if it contains 90 % or more modern carbon (pMC), such as about 100 % modern carbon, as measured using ASTM D6866-20.

In the present case, the feedstock fed to the Fischer-Tropsch process may also comprise components of fossil origin and/or recycled components. The recycled components may be of fossil or renewable origin.

According to one aspect, there is provided a method for processing a low- temperature Fischer-Tropsch process effluent into a fuel product, the method comprising - fractionating the Fischer-Tropsch effluent in a first fractionation into at least a first mixture of gases, a first liquid product, and a first fraction consisting mainly of C17 and higher hydrocarbons;

In the FT synthesis H2, CO2 and, if needed, O2 are first heated and fed to a reverse water gas shift (RWGS) reactor. Water is separated from the outlet stream and syngas from the RWGS is fed to the FT reactor. The effluent, i.e. product, obtained from FT is also called “syncrude”, and the present method thus upgrades the “syncrude” produced with the low-temperature Fischer-Tropsch synthesis into synthetic paraffinic kerosene, which can be used as a blend stock for jet fuel, and a small naphtha fraction as a by-product.

Typically, the process effluent from the FT synthesis includes, in addition to the paraffins, some further compounds in small amounts, such as H2, CO, CO2, O2, H2O, N2, C1 , C2, C3 and C4 (straight chain and branched) hydrocarbons; mainly C2 to C30 olefins with a carbon-carbon double bond and optionally some C30+ olefins; C2-C22 alcohols, such as CH3OH, C2H6O, Ci 2^H26O> C22H46O; and C1- C22 acids, such as HCOOH, C2H4O2, C12H24O2, £22^4402-

The method thus allows for refining of FT syncrude into liquid fuels, with a jet fuel component, such as e-kerosene as the main product and a small fraction of e- naphtha as by-product. Indeed, with the present method, a major part of the FT syncrude is treated to produce liquid fuels, thus leading to a high yield of e-kerosene. By “major part of the FT syncrude” is meant all of the FT syncrude except gases, water and oxygenates dissolved in the water.

The method concentrates on maximising the carbon efficiency as well as minimising waste, as both the feedstock and the products of the process are of high value. This is mainly achieved through the presently disclosed processing scheme with suitable re-circulations and suitable process conditions, as explained in more detail below. The present method thus maximises the production of synthetic paraffinic kerosene from Fischer-Tropsch syncrude with two reactors. The configuration of the process and system is simple, relatively economical and can also be used on a small scale. For example, no naphtha splitter distillation column may be needed. Further, light gases are recycled back to FT synthesis to enhance the kerosene yield of the process.

Reverse water gas shift

The feedstock and various recycle streams are first converted into syngas in a reverse water gas shift (RWGS) process. Wastewater from the RWGS is separated and typically sent to wastewater treatment.

The pressure of the synthesis section is propagated forward from the feed streams through the reactors and heat exchangers. The RWGS reactor converts the feed streams (such as H2 and CO2) into syngas (mainly CO and H2, with H2O as a byproduct). Shorter hydrocarbons (C1 -C4) can also be recycled back into the reactor, which then acts as a reformer to convert them to syngas. Alternatively, the shorter hydrocarbons can be processed by partial oxidation to carbon monoxide and carbon dioxide, which are then fed to the RWGS. All or part of the recycled gas stream may also pass through a purge, in case there are any inert impurities in the feed that would otherwise accumulate.

A feed preheater heats up the gas feeds to the RWGS reactor temperature. Maximum outlet temperature of preheater is typically 800-1100 °C, such as 1000 °C. The RWGS reactor can be for example an electrically heated RWGS reactor. It may also be an isothermal equilibrium reactor.

Low-temperature Fischer Tropsch process

The FT process is known per se, thus it is discussed here only generally. A description of the FT process can be found for example in the PhD (chemical engineering) thesis by Arno de Klerk, University of Pretoria, South-Africa, February 2008, titled Fischer-Tropsch Refining, the contents of which are herein incorporated by reference.

The FT process is affected by reactor size, temperature, pressure, feed H2/CO-ratio and water content. In the FT process, the syngas from RWGS is synthesised into hydrocarbons, to produce syncrude. The produced syncrude is sent downstream to the present method.

Either the FT process or the RWGS process typically comprises a syngas cooler to cool the syngas to condense and separate the water generated by the RWGS reaction. Thereafter the syngas can be re-heated by an FT feed preheater, which thus sets the FT reactor temperature. The FT reactor generates hydrocarbon chains through the Fischer-Tropsch synthesis, using for example a cobalt catalyst.

H2 and CO are consumed in the reactor, while any other components in the feed are typically inert. Water has an effect on the reaction rate. The FT process typically generates a continuous paraffin distribution, preferably mostly in the C1 -C30 range, while the effluent may comprise up to C100 paraffins. The paraffin distribution follows the Anderson-Schulz-Flory distribution, with a rate correction for methane. The chain growth probability is influenced by the reactor temperature and partial pressures of CO and H2O. Olefin distribution is determined in a similar manner as the paraffins, with a rate correction for ethylene. The cobalt-catalysed FT also produces small amounts of alcohols and carboxylic compounds. Additionally, aldehydes, ketones and esters may be formed.

According to an embodiment, the FT effluent comprises 20-50 wt-% of hydrocarbons, 20-40 wt-% of water and 20-40 wt-% of other gases (as water is in gaseous form at the outlet of the FT reactor).

According to an embodiment, the low temperature Fischer-Tropsch process takes place at 170-270 °C, preferably 210-230 °C. The pressure in the FT reactor is typically in the range of 1 -5 MPa, preferably 1 -3 MPa, more preferably 1 .9-2.8 MPa, such as 2.0-2.2 MPa. The H2 feed is adjusted to keep the molar H2/CO ratio in the feed at 2. The length of the reactor is typically such that 75 % of the carbon monoxide fed to the reactor is converted.

Operation of the low temperature FT aims to maximise the yield of longer chain hydrocarbons, which are easier to upgrade into liquid fuel products. A high once- through conversion of CO2 is beneficial for reducing the size of the recirculated stream.

As examples, it can be mentioned that the CO2 feed can have a temperature of 30 °C and a pressure of 2.2 MPa, while the recycled gases from the FT itself are typically mixed with the CO2 feed prior to feeding it to the RWGS and, consequently, the FT reactor. Additional gases from the syncrude section, reformed to syngas in a separate reformer, can be mixed with the feed to the FT reactor. The H2 feed may be at a temperature of 60 °C, and a pressure of 2.2 MPa.

First fractionation

The product from the low-temperature FT process, i.e. its effluent, the syncrude is fractionated in a first fractionation. The first fractionation may, and preferably does, comprise several steps. In this first fractionation, the effluent is split into at least four fractions, namely a first mixture of gases, a mixture of water and oxygenates, a fraction consisting mainly of C17 and higher hydrocarbons (i.e. a wax fraction), and a fraction consisting mainly of C5-C16 hydrocarbons. The first mixture of gases consists mainly of unreacted or inert gases, but also contains some lighter hydrocarbons. This fraction is directed back upstream to the reverse water-gas shift reactor (RWGS), where it is reformed to syngas, and preferably synthesised in the low-temperature FT reactor again into syncrude. The mixture of water (generated in the FT process) and oxygenates may consist of over 98 wt-% of water and can also contain some dissolved gases and oxygenates, along with traces of olefins and some paraffins. The remaining fractions, namely the fraction consisting mainly of C17 and higher hydrocarbons, and the fraction consisting mainly of C5-C16 hydrocarbons, are directed to the next step of the process.

The first fractionation may be, for example, a sequence of flashes. According to an embodiment, the first fractionation comprises

- separating C17 and higher hydrocarbons from a first remaining part of the effluent in a first high temperature flash;

- lowering the temperature of the first remaining part of the effluent in a heat exchanger; and

- separating the first mixture of gases from the first liquid product in a second low temperature flash.

The advantage of first separating the fraction consisting mainly of C17 and higher hydrocarbons is that heat of the stream is thus conserved, and practical issues with solidifying wax at low temperatures are avoided.

The temperature in the high temperature flash is typically 170-270 °C, preferably 210-230 °C. The temperature is thus preferably identical or very close to the temperature at the FT reactor. A small pressure drop, for example of about 30 kPa, typically occurs due to the flash, but pressure is preferably not otherwise lowered between the FT reactor and the first flash, similarly between the first and eventual second flash.

A heat exchanger to lower the temperature of the first remaining part of the effluent is then preferably used to cool down the temperature of the remaining hot gas stream, such as to a temperature of 35 °C or 120 °C, depending on the temperature of the flash used next. In one embodiment, the cooled stream is flashed again in a low temperature flash, with again a small pressure drop, for example of 30 kPa. According to an embodiment, the temperature in the low temperature flash is 20-70 °C. This separates the water and distillate range hydrocarbons (C5-C16 hydrocarbons), i.e. the first liquid product, from the lighter gases.

According to another embodiment, the first fractionation comprises

- lowering the temperature of the first remaining part of the effluent in a heat exchanger;

- separating remaining C17 and higher hydrocarbons from the first remaining part of the effluent in a medium temperature flash, to obtain a remaining part of the effluent;

- lowering the temperature of the remaining part of the effluent; and

In another embodiment, after the high temperature flash, the gases (i.e. effluent other than the C17+ hydrocarbons) are cooled down to a higher temperature than above, such as to a temperature 120 °C in order to withdraw the remaining heavier components above the desired kerosene range. This temperature can be used to control how much heavy material bypasses the first fractionation. According to an embodiment, the temperature in the medium temperature flash is 100-140 °C.

In this embodiment, the cooled stream is flashed in the medium temperature-high pressure (MTHP) flash with a pressure drop of about 30 kPa. This vessel separates the remaining heavy hydrocarbon fraction, along with most of the water, from the syncrude.

A good control of the fractionation is advantageous to control the heavy end of the product while still conserving the thermal energy of the streams

The gases from this medium temperature flash are then cooled again, preferably to 35 °C, to condense the remaining water and distillates in a low temperature flash and separate these from the lighter gases. This temperature can be used to control the amount of recirculated lighter distillates. The liquid from the medium temperature flash is further fractionated by separating the aqueous phase from the heavy distillate hydrocarbons in a decanter at the same conditions as in the medium temperature flash.

This heavy hydrocarbon stream is mixed with the heavy hydrocarbon stream from the high temperature flash and sent to the catalytic hydrocracking.

The gases from the second flash, be it low or medium temperature flash, are preferably pressurised by a recycle gas compressor and returned to the RWGS reactor for reforming back into syngas.

Decantation

The first liquid product is fed to a decanter to separate the mixture of water and oxygenates from the fraction consisting mainly of C5-C16 hydrocarbons, i.e. the second liquid product. The decanter is preferably a low temperature decanter, operated in the same conditions as the low temperature flash.

The resulting aqueous phase is sent to wastewater treatment, while the hydrocarbon stream, i.e. the second liquid product, is sent to the catalytic hydroisomerisation.

Hydrocracking

The purpose of the hydrocracking is to break down the wax and heavy distillate from the first fractionation, i.e. the C17 and higher hydrocarbons, into components in the desired product range. The reactions typically crack paraffinic and isomer compounds to shorter chain lengths and generate 1-, 2- or 3-methylated isomers. Hydrocracking of tribranched isomers is by far the fastest reaction compared to hydrocracking of lower isomers, which means higher degrees of branching would be very rare as the tribranched species do not get to build up in meaningful quantities before rapidly undergoing hydrocracking. Methyl branches are most abundant. According to an embodiment, any lighter components may be still separated from the feed by a wax fractionator to avoid unnecessary cracking of product range components. Gas range components from the wax fractionator top are recycled to the RWGS reactor, while the liquid range components are mixed with the second liquid product from the decanter before being sent to the hydroisomerisation.

In this embodiment, the wax fractionator is preferably preceded by a heat exchanger to set a suitable temperature level for the feed stream. This feed stream may also comprise any recycled streams. The temperature in the wax fractionator may be for example about 220 °C.

The wax fractionator may be for example a column that separates the heavy distillate and wax fraction from the lighter components. Its bottoms rate is adjusted to ensure a mass purity of 99 % for the column top stream. All material up to and including C18 is considered as product. This determines how much of the column feed stream is sent to the hydroisomerisation and how much is to be sent to the hydrocracking. The column may have a partial-vapor-liquid condenser at the top and its pressure can be set so that the bottom temperature is kept below 300 °C, in order to avoid thermal cracking. A 2 % fraction of the distillate is typically set to vaporise in the condenser. The gaseous stream from the column top is preferably pressurised and recycled to the RWGS reactor. The liquid top product is preferably mixed with the middle distillate fraction from the first fractionation, i.e. the first liquid product, before being fed to the hydroisomerisation.

In this hydrocracking step, the C17 and higher hydrocarbons or the heavy bottoms from the wax fractionator, if used, are hydrocracked. According to a preferred embodiment, the feed to the hydrocracker is first pressurised, for example in three stages, by feed pumps, which raise the feed pressure to an adequate level for the hydrocracker. A hydrogen compressor is also preferably used to pressurise the recycle and make-up H2 to the hydrocracker pressure. The heavy hydrocarbon stream and hydrogen are fed then to the hydrocracker, which may be an adiabatic reactor that also converts olefins and oxygenates in the feed to their corresponding paraffins. Some heating of the hydrocracker feed may also be required, as the hydrogen is typically fed to the reactor at a lower temperature which cools the stream. The feed temperature to the hydrocracker reactor can be set to for example about 320 °C, so that a few mol-% of the hydrotreated stream would still remain in liquid form. The make-up H2 feed can be adjusted to keep the H2 feed to the reactor at a suitable level, for example at 110 kg H2/ton feed oil.

The hydrocracker product is cooled, so that only a minimal amount of C17+ components are flashed to the gas phase in high temperature-high pressure (HTHP) flash. This temperature could be used as a handle for adjusting the amount of heavy isomers in the final product by bypassing the recirculation to the wax fractionator. The HTHP flash vessel isobarically flashes the hydrocracker product. The resulting heavy liquid stream is recirculated to the wax fractionator for a sharper fractionation. The gases from HTHP flash are cooled to condense all but the lightest components and to separate these from the gas in an isobaric low temperature-high pressure (LTHP) flash vessel. This is to prevent valuable naphtha and kerosene range components from unnecessarily being recycled to the RWGS reactor. This temperature could be used as a handle to control the amount of light material that is sent to the upgrading instead of being reformed in the RWGS reactor. The upper limit of allowable temperature is set by the membrane, which realistically is operated at a relatively low temperature.

According to an embodiment, the hydrocracking is carried out at a temperature of 260-400 °C, preferably 300-380 °C, pressure of 3-7 MPa, weight hourly space velocity of 0.5-2.0 /h. These conditions can be chosen independently from one another, while a person skilled in the art knows how they affect one another. The conditions also depend on the catalyst used, and are tailored to obtain an optimal yield of the desired product, here preferably hydrocarbons in the kerosene range.

According to an exemplary embodiment, the hydrocracking is carried out at a temperature of about 320 °C and a pressure of about 5 MPa.

This method step takes place in a single reactor, preferably using sulphur free catalyst(s), such as noble metal catalyst(s), on a support. The single reactor may have only one catalyst bed or several catalyst beds (such as two, three, four, five or more catalyst beds), with the same or different catalysts. The catalyst in the hydrocracking is preferably selected from a group consisting of noble metals on a support. More preferably, the noble metals are selected from Pt, Rh, Pd, most preferably Pt. The support may preferably be selected from zeolite, such as betazeolite, alumina, silica or mixtures thereof. A noble metal catalyst is preferred for easier recycling of the gaseous effluents.

The hydrocracked product is preferably cooled, so that only a minimal amount of any remaining C17+ components are flashed to the gas phase in a high temperature flash after cooling. This temperature could be used as a handle for adjusting the amount of heavy isomers in the final product by bypassing the recirculation to a steam stripper. The high temperature flash isobarically flashes the hydrocracked product, to produce a heavy liquid stream and a gas stream. The heavy liquid stream is recirculated to the wax fractionator arranged before the hydrocraker, which splits out any remaining distillate range compounds and sends the heavy fraction back to hydrocracking.

The resulting heavy liquid stream may also be first recirculated to a steam stripper for a sharper fractionation. The gas stream is cooled to condense all but the lightest components and separate these from the gas, for example in an isobaric low temperature flash. The gases may also pass through a hydrogen membrane from which the permeate is circulated to the hydrocracker and the retentate is sent to the RWGS reactor. This helps to prevent valuable naphtha and kerosene range components from unnecessarily being recycled to the RWGS reactor. This temperature could be used as a handle to control the amount of light material that is sent to hydroisomerisation instead of being reformed in the RWGS reactor. The upper limit of allowable temperature is set by the membrane, which is operated at a relatively low temperature.

The cooled stream is then flashed again, for example in an isobaric low temperature flash. The flash gases are sent to the hydrogen membrane and consequently, a pressure drop in this flash should be avoided to the extent possible, as there typically already is a significant pressure drop over the membrane to the permeate side. An excessive drop in pressure would lead to additional costs in compression of the recycle H2. The permeate pressure may be set to drop from 4000 kPa to 2200 kPa to match the make-up H2 feed. The retentate pressure is preferably throttled by a valve to match the pressure level of the other recycle gas streams before mixing with these and being returned to the RWGS reactor for reforming.

According to an embodiment, a pre-hydrotreating with an excess H2 may be used to convert the olefins and any remaining oxygenates to paraffins, before the actual hydrocracking. By excess hydrogen it is here meant for example from five- to twentyfold excess compared to the chemical consumption. Pre-hydrotreating the feed is beneficial for the operation of the hydrocracking, as the oxygenate compounds may have an adverse effect on its performance. The conditions in this prehydrotreatment may be for example a temperature of 280-320 °C, such as 300 °C and a pressure of 3-7 MPa, such as 5 MPa.

The liquid product obtained is mixed with the other feed streams and fed to the hydroisomerisation.

Hydroisomerisation

The second liquid product and the hydrocracked liquid product, as well as any minor streams from any of the above fractionation that contain at least mainly hydrocarbons in the range of C5-C16 is hydroisomerised in the presence of a catalyst, to lead to a product mixture.

This method step takes preferably place in a single reactor, preferably using sulphur free catalyst(s), such as noble metal catalyst(s). The single reactor may have only one catalyst bed or several catalyst beds (such as two, three, four, five or more catalyst beds), with the same or different catalysts. The hydroisomerisation catalyst comprises SAPO-11 , SAPO-41 , ZSM-12, ZSM-22, ZSM-23, EU-2 or fernerite, and Pt, Pd or Ni, and AI2O3 or SiO2- Typical hydroisomerisation catalysts are, for example, Ni/SAPO-11/AI₂O₃, Ni/ZSM-23/AI₂O₃, Pt/ZSM-23/AI₂O₃, Pt/ZSM- 12/AI₂O₃, Pt/SAPO-11/AI₂O₃, Pt/ZSM-22/AI₂O₃, Pt/ZSM-23/AI₂O₃, Pt/EU- 2/AI2O3 and Pt/SAPO-11/SiO2- Most of these catalysts require the presence of hydrogen to reduce the catalyst deactivation.

This step thus upgrades the hydrocarbons by branching the hydrocarbon chains to produce an isomerised product. The hydrocarbons are treated to improve the cold flow properties. The product mixture comprises multibranched, such as 1 -, 2- and 3-methylated isomers or even longer branches, i.e. an isomerised product.

The hydroisomerisation saturates any remaining olefins, dehydrates the oxygenates and primarily causes branching of the hydrocarbons. Hydrocracking can also be induced, to some degree, by adjusting the reactor temperature. The feed to the hydroisomerisation typically does not contain any heavier hydrocarbons or waxes, as these are already dealt with in the separate hydrocracking. As such, there is thus no need for a heavy hydrocarbon recycle to the reactor feed.

The different fractions and streams are preferably combined before feeding them to the reactor.

The feed to the hydroisomerisation is preferably pressurised to the required pressure, by a feed pump. Each stream may also have their own feed pump to equalise the pressures before the streams are mixed. The system may also comprise a hydrogen compressor to pressurise the recycle and make-up H2 to required pressure before being preferably mixed with the liquid feed.

The feed may thereafter be heated to a feed temperature, and the feed temperature can be used to control the degree of isomerisation.

According to an embodiment, the hydroisomerisation is carried out at a temperature of 160-350 °C, such as 160-300 °C, such as 185-270 °C, for example 185-230 °C. The pressure in the reactor is typically 2-7 MPa, preferably 3-7 MPa, more preferably 4-5 MPa. The pressure is preferably at a slightly raised level in an attempt to prevent excessive vaporisation of the feed and to allow raising of the temperature. Preferably, the hydroisomerisation is carried out at a temperature of about 185 to 200 °C, such as 190 °C, and a pressure of about 4 MPa. The weight hourly space velocity (WHSV) can be 0.5-1 .5 /h, such as 0.6-1 .2 /h, for example 0.9 /h. The make- up H2 feed is adjusted to keep the H2 feed to the reactor at a desired level, for example at 110 kg H2/ton feed oil, while the temperature of the H2 feed can be for example 60 °C, and its pressure 2.2 MPa.

The method may further comprise a pre-hydrotreatment with an excess H2 before the hydroisomerisation. By excess hydrogen it is here meant for example from five- to twenty-fold excess compared to the chemical consumption. The conditions in this pre-hydrotreatment may be for example a temperature of 150-170 °C, such as 160 °C and a pressure of 3-5 MPa, such as 4 MPa.

Second and third fractionation

The hydroisomerised product is then directed to a second fractionation, followed by a third fractionation, to obtain at least one fuel product.

The second fractionation of the product mixture is carried out in the presence of water, to obtain hydrogen, a second mixture of gases at least mainly other than hydrogen, and a fractionated product mixture. In the third fractionation, the fractionated product mixture is fractionated again, to obtain water and at least one fuel product. Often two fuel products are obtained, a small portion of naphtha and a main portion of kerosene.

According to an embodiment, the second fractionation comprises

- lowering the temperature of the hydroisomerised product in a heat exchanger;

- separating a gas stream from the hydroisomerised product in a flash;

- separating hydrogen from the gas stream with a membrane; and

- stripping the hydroisomerised product with steam.

This type of second fractionation thus allows separating unreacted H2 from the gas stream. Preferably, the H2 is returned to either the hydrocracker or the hydroisomerisation.

The lowering of the temperature of the product mixture aims at lowering the temperature to a suitable level for the H2 membrane. This also helps to prevent unwanted flashing of valuable product range components, in particular in case a high pressure flash vessel is used, which adiabatically flashes the stream. The membrane permeate pressure may be set to drop from 3 MPa to 2.2 MPa, matching the pressure needed in the make-up H2 feed. Temperature of the product mixture entering the flash may be for example around 60-90 °C.

The flash gas is preferably sent to the H2 membrane, a separation block splitting out 100 % of the hydrogen with a pressure drop from 3000 kPa to 2200 kPa on the permeate side, for H2 separation. The separated hydrogen is mixed with the makeup H2 and recirculated to the hydrocracking or hydroisomerisation.

The liquid stream from the flash then goes to a steam stripper, in which steam is adjusted to remove the remaining light end components in the liquid stream from the flash, such as 90-95 % of C4 from the stream, resulting in the fractionated product mixture. In this second fractionation, non-condensable gases are thus flashed and the lightest hydrocarbons are steam stripped away, while unreacted hydrogen is recovered. The remaining fraction from the second fractionation consists mainly of hydrocarbons and possibly some condensed steam from the stripper. This stream is sent to third fractionation where it is preferably split to a naphtha and a kerosene stream.

The steam stripper may be a column without a condenser or reboiler. It preferably uses a separate steam feed stream to separate the remaining light components from the hydrocarbon stream. The steam feed and the conditions of the steam stripper can be used to adjust the light end of the product distribution and the amount of naphtha produced.

Conditions in the steam stripper may be, for example, temperature at the top around 92 °C, temperature at the bottom around 100 °C, pressure about 1 MPa. The used steam may have a temperature of 250 °C and a pressure of 1 MPa.

The fractionated product mixture is thus fractionated again in a third fractionation. According to an embodiment, the third fractionation comprises at least one distillation column. Using only one column can save on the number of equipment, but the column design and operation may be more complex. According to another embodiment, the third fractionation comprises two distillation columns, in which case the first column separates a naphtha fraction and the second one separates a kerosene and possibly a heavy bottoms fraction, consisting mainly of C17 and higher hydrocarbons. This heavy bottom fraction is recycled to the hydrocracking. Ideally, this second column is not needed as the product mixture does not contain any significant amount of C17 and higher hydrocarbons, and the kerosene thus meets the specifications. The latter goal is achieved mainly through controlling the distillation column and the hydroisomerisation. An important function of this third fractionation is thus to do the final adjustment of the properties of the kerosene product so that they are on-spec, which is mainly achieved through controlling the distillation column(s), or other fractionation methods as used.

The liquid stream from the steam stripper of the second fractionation may thus be sent to a distillation column, called naphtha splitter. It separates a naphtha fraction from the kerosene fraction. The flash point of the kerosene product is typically set by adjusting the distillate rate of the naphtha splitter. The reflux ratio of the column is preferably adjusted to give a sharp cut point and minimise the loss of kerosene range material to the naphtha stream. All material up to and including C8 is considered as product for the naphtha splitter and the purity target is typically set to 99 %.

In one embodiment, the liquid feed enters at the middle of the column. The column has a total condenser at the top, which also does a separation to split out any condensed water from the steam stripper. In order to avoid thermal cracking, the column works at atmospheric pressure. As the freeze point of the kerosene product is already set by adjusting the hydroisomerisation temperature, the flash point is taken care of by adjustment of the distillate rate and the other measured product properties have fulfilled their specs once the freeze point and flash point specs have been satisfied, the bottom stream from the column is ready kerosene product.

The distillation column typically operates at pressures 5-300 kPa, such as 80-200 kPa, and top/bottom temperatures 45/140 - 90/230 °C, such as 67/177 °C. As an example, the temperature at the top may be about 67 °C, temperature at its bottom about 177 °C, and pressure 0.1 MPa. In an embodiment, the product slate is for example 86 % kerosene and 14 % naphtha and the kerosene product fulfils the requirements for FT-SPK defined in ASTM D7566-22. Any remaining water may be split from the naphtha stream in a decanter.

Recycling

As explained also above, recycling of various side products from the different steps is performed, to increase carbon efficiency and overall efficiency of the present method. In addition to the recycling mentioned above, some further embodiments increase the recycling within the present method.

According to an embodiment, the method further comprises directing the second mixture of gases and water to reforming or to the reverse water gas shift reaction. Optionally, when directing the second mixture of gases and water to reforming, at least syngas and carbon dioxide are obtained, and these are then recycled to the Fischer-Tropsch process. By recycling the gases, loss of feedstock material to a gaseous product can be avoided.

Further, in this embodiment, the reforming of the second mixture of gases and water is carried out by a method selected from steam reforming, dry reforming, electric reforming, autothermal reforming, partial oxidation, and catalytic partial oxidation.

Gases from the flash and stripper of the second fractionation may thus be sent via a steam reformer to the FT reactor. A stream of steam is fed to the reformer, which mainly produces syngas, CO2 and methane.

The separated H2 from the second fractionation is preferably fed back to the hydroisomerisation or hydrocracking, while the remaining gas stream, i.e. the retentate from the hydrogen membrane can be mixed with the gases from the steam stripper for further processing. The gases may be pressurised to the required level by a recycle gas compressor. The hydrogen may also be fed to the pre- hydrotreatment(s) with an excess H2 before the hydrocracking, if used. The steam reformer may be an isothermal equilibrium reactor, similar to the RWGS reactor. It converts the recycle stream mainly into syngas, CO2 and methane with the help of an additional steam stream. The reformed stream is sent to the FT reactor. The reformer temperature is in the range 800-1100+ °C, such as 950 °C. The pressure may be 2200 kPa.

The various wastewater streams generated for example by the RWGS, FT and distillation condenser are preferably gathered in a flash, which adiabatically flashes these at low temperature and atmospheric pressure. This causes a small stream of dissolved hydrocarbons and oxygenates to vaporise from the water. The water stream can then be sent on to a wastewater treatment facility. The gas stream may be flared or recycled. For a large scale facility, or for a process generating more dissolved oxygenates, the wastewater and flash gas can be sent to a work-up section to recover and valorise the dissolved compounds. Such wastewater flash may work for example at a temperature of about 87 °C and a pressure of about 101 kPa.

System

The present method can be carried out in a system for processing a low-temperature Fischer-Tropsch process effluent into a fuel product, comprising

- first means for fractionating the Fischer-Tropsch process effluent into at least a first mixture of gases, a first liquid product, and a first fraction consisting mainly of C17 and higher hydrocarbons;

- a decanter for separating the first liquid product to obtain a second liquid product and a mixture of water and oxygenates;

- second means for fractionating the product mixture, in the presence of water, to obtain hydrogen, a second mixture of gases at least mainly other than hydrogen, and a fractionated product mixture; - third means for fractionating the fractionated product mixture, to obtain water and at least one fuel product;

- means for recycling the fraction consisting mainly of C17 and higher hydrocarbons to the first fractionation.

The various embodiments and options described above in connection with the process apply mutatis mutandis to the system.

The first means for fractionating may comprise

- a high temperature flash;

- a heat exchanger arranged downstream of the first high temperature flash; and

- a low temperature flash arranged downstream of the heat exchanger.

According to another embodiment, the first means for fractionating comprises

- a high temperature flash;

- a first heat exchanger arranged downstream of the high temperature flash;

- a medium temperature flash arranged downstream of the first heat exchanger;

- a second heat exchanger arranged downstream of the medium temperature flash; and

- a low temperature flash arranged downstream of the second heat exchanger.

According to an embodiment, the second means for fractionating comprises

- a heat exchanger;

- a flash arranged downstream of the heat exchanger;

- a hydrogen separator with membrane arranged downstream the flash; and

- a steam stripper arranged downstream of the flash.

The third means for fractionating may comprise at least one distillation column. The number of distillation columns is selected according to the aimed purity of the final product, and is preferably one, two, three or four.

The different flashes, heat exchanger, decanters and phase separation means, as well as strippers and distillation columns are known perse to a person skilled in the art. Typically, when a flash is mentioned, be it a high temperature, medium temperature or low temperature, it is operated at high pressure. When heat exchangers are mentioned, it is naturally also possible to use any other kind of device for either lowering or raising the temperature of the stream. Most preferably recovered heat is re-used in the method.

The system may still further comprise means for directing the second mixture of gases and water to a reformer or to the reverse water gas shift reactor. These means may comprise pipes, heat exchangers and pumps, as need be. The reformer is typically selected from steam reformer, dry reformer, electric reformer, partial oxidation reactor, and catalytic partial oxidation reactor.

The system may also comprise a pre-hydrotreatment reactor arranged before the hydrocracking reactor and/or before the hydroisomerisation reactor.

Obtained product

The product obtained by the present method and system fulfils the requirements of the standard ASTM D7566-22 for hydroprocessed synthetic blendstock for aviation fuels.

It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a process according to an embodiment. In this process, a Fischer- Tropsch effluent 1 is directed to a first fractionation 2, wherein it is fractionated into a first mixture 3 of gases, a first liquid product 6, and a first fraction 5 consisting mainly of C17 and higher hydrocarbons. Thereafter the first liquid product 6 is separated by decantation 19 to obtain a second liquid product 20 and a mixture of water and oxygenates 4.

The fraction 5 consisting mainly of C17 and higher hydrocarbons is then catalytically hydrocracked 21 to produce a hydrocracked liquid product 22 and a second fraction consisting mainly of C17 and higher hydrocarbons 23. The second liquid product 20 and the hydrocracked liquid product 22 are then catalytically hydroisomerised 7 to produce a product mixture 8, while the fraction consisting mainly of C17 and higher hydrocarbons 23 is recycled to the first fractionation 2.

The product mixture 8 is fractionated in a second fractionation 9, in the presence of water 10, to obtain hydrogen 11 , a second mixture 12 of gases at least mainly other than hydrogen, and a fractionated product mixture 13. The fractionated product mixture 13 is fractionated in a third fractionation 14, to obtain water 15 and at least one fuel product 16, 16’. The first mixture 3 of gases is recycled to a reverse water gas shift reaction 18.

Figure 2 shows a process according to another embodiment. In this embodiment, the second mixture 12 of gases and water is directed to reforming 24 to obtain a mixture 25 of at least syngas and carbon dioxide, which are recycled to the Fischer- Tropsch reactor 26. The reforming may take place in the presence of water 27.

Figure 3 shows part of a system and method according to an embodiment. In this part, one embodiment of the first fractionation is illustrated. It comprises a first high temperature flash 28 to separate C17 and higher hydrocarbons 5 from a first remaining part of the effluent 29 and a heat exchanger 30 to lower the temperature of the first remaining part of the effluent. Further, the first fractionation comprises a second low temperature flash 31 to separate the first mixture of gases 3 from the first liquid product 6.

Figure 4 shows another embodiment of a part of the system and method, namely the first fractionation. In this embodiment, after a first high temperature flash 28 to separate C17 and higher hydrocarbons 5 from a first remaining part of the effluent 29, a heat exchanger 30 is arranged thereafter to lower the temperature of the first remaining part of the effluent to a temperature of for example 120 °C. A medium temperature flash 32 is then used to separate remaining C17 and higher hydrocarbons 33 from the first remaining part of the effluent to obtain a remaining part of the effluent 34. The temperature of this remaining part of the effluent is thereafter lowered in a heat exchanger 35, before directing it to a second low temperature flash 31 to separate the first mixture of gases 3 from the first liquid product 6.

Figure 5 shows another part of a system and method according to an embodiment, namely the second fractionation and one embodiment of the third fractionation. The second fractionation comprises a heat exchanger 36 to lower the temperature of the product mixture 8; a flash 41 to separate a gas stream 42 from the product mixture; a membrane 37 to separate hydrogen 11 from the gas stream 42; and a steam stripper 38 for stripping the product mixture. In this embodiment, the third fractionation 14 comprises one distillation column 39.

Figure 6 shows a part of a system and method according to an embodiment. In this embodiment, a pre-hydrotreatment reactor 40 is arranged before the hydrocracking 21. Figure 7 shows an embodiment wherein a pre-hydrotreatment reactor 41 is arranged before the hydroisomerisation 7.

EXAMPLES

The following describes how to carry out the method.

Syncrude is produced by first feeding CO2 and H2 to an eRWGS reactor (pressure 2.2 MPa), which is an isothermal equilibrium reactor, after having been heated to the reactor temperature, namely 1000 °C. The feed stream is converted into syngas and cooled in a syngas cooler/condenser to condense and separate the water generated by eRWGS. Temperature in the cooler/condenser is set to 35 °C. The obtained syngas is then preheated by an FT feed preheater to set it to the FT reactor temperature, i.e. 220 °C. Pressure in the FT reactor is 2.2 MPa, and the residence time 0.07 h.

The obtained syncrude is then fractionated in a first fractionation, namely in a first high temperature flash (temperature 220 °C, pressure 2.17 MPa), whereafter the heavy distillate (C17 and higher) is directed to the hydrocracker, while the rest is directed to a heat exchanger and a medium temperature flash (temperature 120 °C, pressure 2.14 MPa). From this second flash, the gases are directed, via a heat exchanger, to a low temperature flash (temperature 35 °C, pressure 2.11 MPa). From this third flash, gases are directed to FT gas recycle via a recycle gas compressor, and the rest to a second decanter, which is operated at the same conditions as the low temperature flash. The aqueous phase (water and oxygenates) are directed to wastewater treatment, and the rest to the hydroisomerisation.

The second flash separated also a small amount of heavy hydrocarbons, which are directed to a decanter to remove any water contained therein (which is then directed to wastewater treatment), and the heavy hydrocarbons are directed to hydrocracking.

The feed to the hydrocracker is first heated in a heater (although it could also be cooled if need be), and thereafter fractionated once more to remove any lighter components (C16 and below). This fractionation takes place in a distillation column (condenser temperature 88 °C, reboiler temperature 301 °C, pressure 0.03 MPa). A 2 % fraction of the distillate is set to vaporise in the condenser. The partial condenser is needed to avoid excessive cooling of the distillate, which is directed to the hydroisomerisation. The rest of the stream (i.e. the main part of the stream) is directed to a pre-hydrotreatment via pumps to increase its pressure. The prehydrotreater is operated at a temperature of 303 °C and a pressure of 5 MPa. The pre-hydrotreated effluent is then directed to a hydrocracker via a heater, and the hydrocracker is operated at a temperature of 320 °C, pressure 5 MPa and WHSV 0.7/h. The catalyst used is Pt/A^O .

The hydrocracked product is cooled down and flashed twice, first with a HTHP flash (220 °C, 4 MPa) and then an LTHP flash (30 °C, 4 MPa), preceded by a cooler. Any heavy liquid products from the HTHP flash are mixed with the uncracked feed and recirculated to the distillation column. Gases are treated with a hydrogen membrane and recirculated in the process.

The liquid hydrocarbons from the LTHP flash are directed to hydroisomerisation. Prior to the hydroisomerisation, the feed is pressurised and heated. A further prehydrotreatment is also used, operated at a temperature of 160 °C and a pressure of 4 MPa. After heating up the feed, it is directed to the hydroisomerisation reactor, operated at a temperature of 188 °C, pressure 4 MPa and WHSV 0.9 /h. The catalyst used is Pt/ZSM-23/AI₂O₃.

After the hydroisomerisation, the product mixture is fractionated in a second and third fractionation as follows.

First, the product mixture is cooled down and thereafter sent to a high pressure flash (90 °C, pressure 3 MPa) to make a first separation of the light gases from the rest of the product mixture. These gaseous compounds are passed through a membrane that separates the hydrogen to be fed back into the reactor from the rest of the gas stream. This is followed by a steam stripper, operated at a temperature of 92 °C at the top and 100 °C at the bottom, pressure 1 MPa (stripper steam at 250 °C, pressure 1 MPa). The separated gases are combined with the retentate light gases from the hydrogen membrane. The combined gas stream continues to a steam reformer, operated at 950 °C and a pressure of 2.2 MPa. The obtained syngas is recirculated back to the FT reactor.

The fractionated product mixture is then directed to a distillation column (condenser temperature 67 °C, reboiler temperature 177 °C, pressure 0.1 MPa). Naphtha and kerosene are retrieved and water directed to wastewater treatment. The wastewater treatment comprises also a wastewater flash, operated at 87 °C and a pressure of 0.1 MPa.

The yield of kerosene is 3458 kg/h while the yield of naphtha is 549 kg/h, i.e. a very large amount of kerosene was obtained. The obtained kerosene fulfills the requirements of the ASTM D7566-22 for jet fuel. The overall yield of the process is about 86 wt-% of kerosene, on a carbon efficiency basis. The product slate consists of 86 wt-% of kerosene and 14 wt-% of naphtha.

Claims

1 . A method for processing a low-temperature Fischer-Tropsch process effluent (1 ) into a fuel product, the method comprising

- fractionating the Fischer-Tropsch effluent in a first fractionation (2) into at least a first mixture of gases (3), a first liquid product (6), and a first fraction consisting mainly of C17 and higher hydrocarbons (5);

- separating the first liquid product by decantation (19) to obtain a second liquid product (20) and a mixture of water and oxygenates (4);

- processing the fraction consisting mainly of C17 and higher hydrocarbons by a catalytic hydrocracking (21 ) to produce a hydrocracked liquid product (22) and a second fraction consisting mainly of C17 and higher hydrocarbons (23);

- processing the second liquid product and the hydrocracked liquid product by catalytic hydroisomerisation (7) to produce a product mixture (8);

- fractionating the product mixture in a second fractionation (9), in the presence of water (10), to obtain hydrogen (11 ), a second mixture of gases at least mainly other than hydrogen (12), and a fractionated product mixture (13),

- fractionating the fractionated product mixture in a third fractionation (14), to obtain water (15) and at least one fuel product (16, 16’);

- directing at least the first mixture of gases (3) to a reverse water gas shift reaction (18); and

- recycling the second fraction consisting mainly of C17 and higher hydrocarbons to the first fractionation (2).

2. The method according to claim 1 , wherein the low temperature Fischer-Tropsch process has taken place at 170-270 °C.

3. The method according to any of the preceding claims, wherein the first fractionation comprises

- separating C17 and higher hydrocarbons (5) from a first remaining part of the effluent (29) in a first high temperature flash (28);

- lowering the temperature of the first remaining part of the effluent in a heat exchanger (30); and - separating the first mixture of gases (3) from the first liquid product (6) in a second low temperature flash (31 ).

4. The method according to claim 1 or 2, wherein the first fractionation comprises

- lowering the temperature of the first remaining part of the effluent in a heat exchanger (30);

- separating remaining C17 and higher hydrocarbons (33) from the first remaining part of the effluent, in a medium temperature flash (32), to obtain a remaining part of the effluent (34);

- lowering the temperature of the remaining part of the effluent in a heat exchanger (35); and

- separating the first mixture of gases (3) from the first liquid product (6) in a second low temperature flash (31 ).

5. The method according to any of the claim 3 or 4, wherein the temperature in the high temperature flash is 170-270 °C, preferably 210-230 °C.

6. The method according to any one of the claims 3-5, wherein the temperature in the low temperature flash is 20-70 °C.

7. The method according to any one of the claims 4-6, wherein the temperature in the medium temperature flash is 100-140 °C.

8. The method according to any of the preceding claims, wherein the hydrocracking is carried out at a temperature of 260-400 °C, pressure of 3-7 MPa, weight hourly space velocity of 0.5-2.0 /h.

9. The method according to any of the preceding claims, wherein the hydroisomerisation is carried out at a temperature of 160-350 °C, pressure of 2-7 MPa, weight hourly space velocity of 0.5-1 .5 /h.

10. The method according to claim 8 or 9, wherein the hydrocracking is carried out at a temperature of 320 °C and a pressure of 5 MPa.

11 . The method according to any of the claims 8-10, wherein the hydroisomerisation is carried out at a temperature of 190 °C and a pressure of 4 MPa.

12. The method according to any of the preceding claims, wherein the catalyst in the hydrocracking is selected from a group consisting of noble metals on a support, preferably Pt, Rh or Pd on zeolite, alumina, silica or mixtures thereof.

13. The method according to any of the preceding claims, wherein the catalyst in the hydroisomerisation is selected from a group consisting of catalysts comprising

- SAPO-11 , SAPO-41 , ZSM-12, ZSM-22, ZSM-23, EU-2 or fernerite,

- Pt, Pd or Ni,

- on AI2O3 or SiC>2 support, preferably Ni/SAPO-11/AI₂O₃, Ni/ZSM-23/AI₂O₃, Pt/ZSM-23/AI₂O₃, Pt/ZSM- 12/AI₂O₃, Pt/SAPO-11/AI₂O₃, Pt/ZSM-22/AI₂O₃, Pt/ZSM-23/AI₂O₃, Pt/EU- 2/AI₂O₃ or Pt/SAPO-11/SiO₂.

14. The method according to any of the preceding claims, wherein the second fractionation comprises

- lowering the temperature of the product mixture (8) in a heat exchanger (36);

- separating a gas stream (42) from the product mixture in a flash (41 );

- separating hydrogen (11 ) from the gas stream with a membrane (37); and

- stripping the product mixture in a steam stripper (38).

15. The method according to any of the preceding claims, wherein the third fractionation (14) comprises distillation in at least one distillation column (39).

16. The method according to any of the preceding claims, further comprising directing the second mixture of gases and water (12) to reforming (24) or to the reverse water gas shift reaction (18).

17. The method according to claim 16, comprising directing the second mixture of gases and water (12) to reforming (24) to obtain at least syngas and carbon dioxide

(25); and recycling the syngas and carbon dioxide to the Fischer-Tropsch process

18. The method according to claim 16 or 17, wherein the reforming of the second mixture of gases and water (12) is carried out by a method selected from steam reforming, dry reforming, electric reforming, autothermal reforming, partial oxidation, and catalytic partial oxidation.

19. The method according to claim 16, comprising directing the second mixture of gases and water (12) to the reverse water gas shift reaction (18).

20. The method according to any of the preceding claims, further comprising a prehydrotreatment with an excess H2 before the hydrocracking and/or before the hydroisomerisation.

21. A system for processing a low-temperature Fischer-Tropsch process effluent into a fuel product, comprising

22. The system according to claim 21 , wherein the first means for fractionating comprises

- a high temperature flash (28);

- a heat exchanger (30) arranged downstream of the first high temperature flash; and

- a low temperature flash (31 ) arranged downstream of the heat exchanger.

23. The system according to claim 21 , wherein the first means for fractionating comprises

- a high temperature flash (28);

- a first heat exchanger (30) arranged downstream of the high temperature flash;

- a medium temperature flash (32) arranged downstream of the first heat exchanger;

- a second heat exchanger (35) arranged downstream of the medium temperature flash; and

- a low temperature flash (31 ) arranged downstream of the second heat exchanger.

24. The system according to any one of the claims 21 -23, wherein the second means for fractionating comprises

- a heat exchanger (36);

- a flash (41 ) arranged downstream of the heat exchanger;

- a hydrogen separator (37) with membrane (31 ) arranged downstream the flash; and

- a steam stripper (38) arranged downstream of the flash.

25. The system according to any one of the claims 21 -24, wherein the third means for fractionating comprises at least one distillation column (39).

26. The system according to any one of the claims 21-25, further comprising means for directing the second mixture of gases and water to a reformer or to the reverse water gas shift reactor.

27. The system according to claim 25, wherein the reformer is selected from steam reformer, dry reformer, electric reformer, partial oxidation reactor, and catalytic partial oxidation reactor.

28. The system according to any one of the claims 21 -27, further comprising a prehydrotreatment reactor arranged before the hydrocracking reactor and/or before the hydroisomerisation reactor.