Production of synthesis fuels from co2 with conversion of by-products into synthesis gas and separation of co2

Abstract

The invention relates to a method for converting CO 2 , comprising: treating the CO 2 (1) with H 2 (2) by means of RWGS (3) in order to produce a first synthesis gas (4); separating the first synthesis gas in order to produce a CO 2 -depleted gaseous effluent (8) and CO 2 (7) which is recycled to the RWGS unit (3); converting the CO 2 -depleted gaseous effluent by means of Fischer-Tropsch (10) in order to produce a hydrocarbon effluent (11) and a first gaseous FT effluent (13); treating the hydrocarbon effluent by means of hydroconversion (19) in order to produce at least one first C8-C22 hydrocarbon cut (20) and a second C4-C8 hydrocarbon cut (23); and converting the first gaseous FT effluent, at least in part, and the second hydrocarbon cut, at least in part, into synthesis gas (24) in a reaction unit for the conversion of by-products, in order to produce a second synthesis gas (25) which is sent for separation with the first synthesis gas.

Description

[0001] Production of synthetic fuels from CO2 with conversion of by-products into synthesis gas and CO2 separation

[0002] Technical field

[0003] The present invention relates to the production of synthetic fuels, namely gasoline, kerosene, diesel, and / or other hydrocarbon products, such as naphtha, or lubricating bases, of very high quality (essentially free of sulfur, aromatics, nitrogen). More particularly, an object of the present invention is to produce synthetic fuels from carbon dioxide (CO2) and water.

[0004] The conversion of carbon dioxide into fuel base according to the invention relates in particular to the following steps: the conversion of carbon dioxide and hydrogen into a first synthesis gas composed mainly of carbon monoxide (CO) and FL, the separation of the synthesis gases into a CO2-rich stream and a CO2-poor stream, the conversion of the CO2-poor synthesis gas into synthesis hydrocarbons by the Fischer-Tropsch (FT) process, the hydroconversion of the hydrocarbon effluent from the FT process and the conversion of products from the FT process.

[0005] Prior art

[0006] The use of the reverse water-gas shift (RWGS) process to convert a mixture of carbon dioxide and hydrogen into CO+H2 synthesis gas has been known to those skilled in the art for a very long time. The same is true for the Fischer-Tropsch synthesis process, which converts said synthesis gas into a mixture of paraffins, and / or olefins and / or oxygenates depending on the catalyst and operating conditions. In the case where paraffins are produced, it is preferable to improve certain properties to make them usable for transport applications.

[0007] Patent applications have been filed for sequences of unit operations, these sequences of unit operations aim to convert carbon dioxide into fuel base, often known as e-fuels.

[0008] For example, patent application US2010 / 0280135 A1 describes a renewable Fischer-Tropsch synthesis process for producing hydrocarbons and alcohols from wind energy, residual carbon dioxide and water. The process comprises the following unit operations: electrolysis of water to produce hydrogen and oxygen, a RWGS reactor for the production of synthesis gas, Fischer-Tropsch synthesis in a high-temperature multi-tubular reactor. Various recycling options are described (e.g. recycle after separation of unconverted carbon dioxide from RWGS, recycle carbon dioxide ex-FT to RWGS, recycle unconverted H2 and CO ex-FT to FT).

[0009] Patent application LIS2012 / 0079767 A1 describes a process and system for producing syngas by combining hydrogen and carbon monoxide from separate sources while controlling the molar ratio (H2 / CO) of the produced syngas. Hydrogen is produced by electrolysis of water. Carbon monoxide is produced by reacting carbon dioxide captured from the exhaust gases of stationary combustion engines with hydrogen in a RWGS reactor. Hydrocarbon fuels are produced from the syngas by Fischer-Tropsch synthesis.

[0010] Patent application US2007 / 0142481 A1 describes a process for synthesizing hydrocarbons comprising introducing hydrogen and carbon monoxide into a first Fischer-Tropsch reaction stage allowing the hydrogen and carbon monoxide to partially react catalytically to form hydrocarbons. At least a portion of a tail gas which comprises unreacted hydrogen and carbon monoxide, obtained from the first reaction stage, is introduced into a second Fischer-Tropsch reaction stage which is a two-phase high-temperature catalytic Fischer-Tropsch reaction stage. The hydrogen and carbon monoxide can at least partially react catalytically in the second reaction stage to form gaseous hydrocarbons. This patent application is characterized by the presence of two Fischer-Tropsch reactors in series, the second one treating the unconverted synthesis gas from the first one.There is no recycling of carbon dioxide or recycling of water.

[0011] Patent application WO2022 / 232936 A1 describes a process for increasing carbon monoxide production and recycling carbon dioxide during syngas processing using a carbon dioxide to carbon monoxide conversion unit, such as a Reverse Water Gas Shift (RWGS) reactor, converting excess CO2 from the produced syngas into additional CO, using an external source of green, renewable or low-carbon hydrogen.

[0012] Thus, the analysis of the prior art highlights that the sequence of unit operations of RWGS and Fischer-Tropsch makes it possible to produce synthetic bases for fuels from carbon dioxide and hydrogen, said hydrogen being able in certain cases to be produced by electrolysis of water with a source of electricity such as solar or wind power.

[0013] On the other hand, the prior art does not mention the possibility of integrating additional units making it possible to increase the conversion of carbon dioxide into paraffins having a carbon number between 8 and 22, and preferably essentially between 9 and 16 carbon atoms per molecule.

[0014] Summary of the invention

[0015] The invention relates to the conversion of carbon dioxide so as to produce a first synthesis gas rich in CO and H2, the separation of CO2 present in the synthesis gas, the conversion of the synthesis gas depleted in CO2 into synthesis hydrocarbons by the Fischer-Tropsch (FT) reaction, the hydroconversion of the hydrocarbon effluent of the FT process and the conversion of by-products into a second synthesis gas rich in CO and H2.

[0016] Specifically, the present invention relates to a device and a method for producing synthetic fuels from carbon dioxide and hydrogen, allowing an improved production of paraffins of 8 to 22 carbon atoms per molecule, or even essentially paraffins of 9 to 16 carbon atoms per molecule.

[0017] The present invention is based on the presence of a reverse water gas conversion reaction unit RWGS, fed by carbon dioxide and H2 and which produces a first synthesis gas rich in CO and H2.

[0018] The invention is also based on the presence of a unit for separating the carbon dioxide contained in the synthesis gases upstream of the Fischer-Tropsch reaction unit. The carbon dioxide separated from the synthesis gases is recycled to the inlet of the RWGS reaction unit. Thus, the synthesis gas sent to the Fischer-Tropsch reaction unit no longer contains significantly more carbon dioxide.

[0019] The invention is also based on the presence of a hydroconversion unit (“upgrading” according to English terminology; known to those skilled in the art), supplied by the hydrocarbon effluent from the FT process and which produces synthetic fuels compatible with use for land, air and maritime fuels.

[0020] The invention is finally based on the presence of a unit for converting by-products into synthesis gas supplied with by-products from the FT reaction unit and the hydroconversion unit to produce a second synthesis gas rich in H2 and CO. Advantageously, the second synthesis gas is returned to the inlet of the carbon dioxide separation unit, making it possible to recycle the CO2 from the RWGS and by-product conversion units into synthesis gas to the RWGS unit and to recover additional CO in the Fischer-Tropsch reaction unit.

[0021] The carbon dioxide separation unit is therefore supplied by the first synthesis gas from the RWGS unit and by the second synthesis gas from the by-product conversion unit into synthesis gas. Preferably, the hydrogen required in the process is entirely supplied by a water electrolysis unit. Advantageously, hydrogen produced by water electrolysis can be used for carbon dioxide conversion, Fischer-Tropsch synthesis and hydroconversion. Thus, the process according to the invention does not require an external supply of hydrogen, for example produced by steam reforming of natural gas. The electrolyser preferably operates with low-carbon electricity, which contributes to the renewable nature of the fuels and gases produced.In addition, the water used for hydrogen production can come at least in part from the recycling of water produced in the various stages of the process, which has the advantage of limiting the external supply of water.

[0022] Advantageously, the oxygen produced by the electrolysis of water can also feed the unit for converting by-products into synthesis gas.

[0023] According to a first aspect, the above-mentioned objects, as well as other advantages, are obtained by a method for converting a feed containing carbon dioxide, comprising the following steps: treating a feed rich in carbon dioxide with a first hydrogen source in a reverse water gas conversion RWGS reaction unit to produce a first synthesis gas rich in carbon monoxide and H2 and a first water effluent; treating the first synthesis gas in a carbon dioxide separation unit to produce a carbon dioxide-depleted gaseous effluent and a carbon dioxide-rich gaseous effluent; recycling the carbon dioxide-rich gaseous effluent to the inlet of the RWGS reaction unit;converting the depleted gaseous effluent to carbon dioxide in a Fischer-Tropsch reaction unit to produce a hydrocarbon effluent, a second water effluent, a first FT gaseous effluent rich in CO, H2, CO2 and hydrocarbons of 1 to 5 carbon atoms per molecule, and optionally a second FT gaseous effluent rich in hydrocarbons of 1 to 5 carbon atoms per molecule;treating the hydrocarbon effluent in a hydroconversion reaction unit (hydrotreatment and / or hydrocracking and / or hydroisomerization unit) with a third hydrogen source to produce at least a first hydrocarbon cut comprising paraffins having a carbon number of between 8 and 22, and preferably essentially from 9 to 16 carbon atoms per molecule, for example to the specifications for transport applications, a third gaseous effluent comprising hydrocarbons of 1 to 5 carbon atoms per molecule, and a second hydrocarbon cut comprising paraffins of 4 to 8 carbon atoms per molecule; converting at least a portion of the first FT gaseous effluent and at least a portion of the second hydrocarbon cut, in a by-product conversion reaction unit into synthesis gas, to produce a second synthesis gas rich in carbon monoxide and hydrogen;and send the second synthesis gas to the carbon dioxide separation unit.;

[0024] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas is fed at least in part with the second gaseous effluent from FT.

[0025] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas is fed at least in part with the third gaseous effluent.

[0026] According to one or more embodiments, the carbon dioxide-rich feedstock and / or the carbon dioxide-rich gaseous effluent are purified, separately or after mixing, before being introduced into the RWGS reaction unit.

[0027] According to one or more embodiments, the carbon dioxide-depleted gaseous effluent is purified before being introduced into the Fischer-Tropsch reaction unit. The effluent purification steps aim to at least partially remove at least one of the following compounds: organic compounds, ionic species, sulfur compounds, nitrogen compounds, halogenated compounds, metals (e.g. heavy metals), transition metals.

[0028] According to one or more embodiments, the RWGS reaction unit comprises at least one reactor used under at least one of the following operating conditions: temperature between 700°C and 1200°C, preferably between 750°C and 1100°C, and more preferably still between 780°C and 1050°C; pressure between 0.1 MPa and 10 MPa, preferably between 0.1 MPa and 5 MPa, and more preferably between 0.1 MPa and 3.5 MPa; space velocity of the gas at the reactor inlet between 2000 NL / kg ca ta / h and 40000 NL / kg cata / h; catalyst comprising a metal or a combination of metals selected from the group consisting of the elements Ni, Cu, Fe, Co, Pt, Pd, Ru, Ag and Au. According to one or more embodiments, the catalyst for the RWGS reaction comprises a support, for example based on alumina, silica, silica-alumina, alumina-silica.

[0029] According to one or more embodiments, the carbon dioxide separation unit implements separation by chemical solvent and / or physical solvent and / or membrane and / or adsorption on a solid. According to one or more embodiments, the Fischer-Tropsch reaction unit comprises at least one reactor used under at least one of the following operating conditions: temperature between 170°C and 280°C, preferably between 190°C and 260°C and preferentially between 210°C and 240°C; absolute pressure between 1.0 MPa and 6.0 MPa, preferably between 1.5 MPa and 3.5 MPa and preferentially between 2.0 MPa and 3.0 MPa; catalyst comprising cobalt or iron, preferably cobalt, the catalyst optionally comprising a support, for example based on alumina, silica, silica-alumina, alumina-silica or titanium.

[0030] According to one or more embodiments, the method comprises supplying the Fischer-Tropsch reaction unit with a second source of hydrogen.

[0031] According to one or more embodiments, the hydroconversion reaction unit comprises at least one reactor used under at least one of the following operating conditions: temperature between 200°C and 500°C, more preferably between 280°C and 450°C, and even more preferably between 300°C and 420°C; pressure between 0.2 MPa and 15 MPa, preferably between 0.5 MPa and 12 MPa, more preferably between 1 MPa and 10 MPa; space velocity defined as the ratio of the volume flow rate of the feedstock at ambient temperature and pressure to the volume of the catalyst, between 0.1 h -1 and 10 a.m. -1 , preferably between 0.2 h -1 and 7 a.m. -1 , more preferably between 0.5 h -1 and 5 a.m. -1; hydrogen flow rate of between 70 and 2000 normal liters of hydrogen per liter of feed per hour and preferably between 150 and 1500 normal liters of hydrogen per liter of feed and more preferably between 300 and 1500 normal liters of hydrogen per liter of feed; hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprising at least one hydrogenating-dehydrogenating metal chosen from the group comprising the metals of group VIB and group VI 11 B of the periodic table and / or at least one solid which is a Bronsted acid, i.e. a solid capable of releasing one or more protons, and optionally a binder.

[0032] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas comprises at least one reactor used in at least one of the following operating conditions: absolute pressure between 0.1 MPa and 9 MPa; temperature between 600°C and 2000°C. According to one or more embodiments, the reaction unit for converting by-products into synthesis gas comprises a catalytic or non-catalytic partial oxidation unit followed by a section for cooling the synthesis gas and separating the condensed water, the partial oxidation unit comprising at least one reactor used in at least one of the following operating conditions: absolute pressure between 0.1 MPa and 9 MPa, and preferably between 0.1 MPa and

[0033] 4 MPa; temperature between 600°C and 2000°C, preferably between 800°C and 1700°C, preferably between 900°C and 1500°C or between 1100°C and 1500°C; presence of oxygen used for combustion, with an oxygenation rate between 0.2 and 0.6, preferably between 0.25 and 0.5, in order to promote the formation of carbon monoxide; presence of a catalyst containing a noble metal such as rhodium, or nickel or a nickel alloy, when the partial oxidation unit is catalytic.

[0034] According to one or more embodiments, a portion of the first FT gaseous effluent and / or at least a portion of the second FT gaseous effluent are at least partly upgraded to synthetic methane (e-methane), synthetic natural gas (e-SNG) or synthetic liquefied petroleum gas (e-LPG).

[0035] According to one or more embodiments, a portion of the first FT gaseous effluent is purged.

[0036] According to a second aspect, the above-mentioned objects, as well as other advantages, are obtained by a device for converting a feed containing carbon dioxide, comprising the following units: a reverse water gas conversion reaction unit RWGS adapted to treat a feed rich in carbon dioxide with a first hydrogen source and produce a first synthesis gas rich in carbon monoxide and H2 and a first water effluent; a carbon dioxide separation unit adapted to treat the first synthesis gas, produce a carbon dioxide-depleted gaseous effluent and a carbon dioxide-rich gaseous effluent, and recycle the carbon dioxide-rich gaseous effluent to the inlet of the RWGS reaction unit;a Fischer-Tropsch reaction unit adapted to convert the depleted gaseous effluent into carbon dioxide, and produce a hydrocarbon effluent, a second water effluent, a first FT gaseous effluent rich in CO, H2, CO2 and hydrocarbons from 1 to;

[0037] 5 carbon atoms per molecule, and optionally a second gaseous FT effluent rich in hydrocarbons of 1 to 5 carbon atoms per molecule; a hydroconversion reaction unit (hydrotreatment and / or hydrocracking and / or hydroisomerization unit) adapted to treat the hydrocarbon effluent with a third hydrogen source and produce at least a first hydrocarbon cut comprising paraffins having a carbon number of between 8 and 22, and preferably essentially from 9 to 16 carbon atoms per molecule, for example to the specifications for transport applications, a third gaseous effluent comprising hydrocarbons of 1 to 5 carbon atoms per molecule, and a second hydrocarbon cut comprising paraffins of 4 to 8 carbon atoms per molecule, and a reaction unit for converting by-products into synthesis gas adapted to convert at least a portion of the first gaseous FT effluent,at least a portion of the second hydrocarbon cut, optionally a gas stream comprising at least in part the second FT gas effluent and / or at least in part the third gas effluent, and producing a second synthesis gas rich in carbon monoxide and hydrogen which is sent to the carbon dioxide separation unit.,

[0038] Embodiments of the device and method according to the aforementioned aspects as well as other characteristics and advantages will appear on reading the description which follows, given for illustrative and non-limiting purposes only, and with reference to the following drawing.

[0039] List of figures

[0040] Figure 1 shows a schematic representation of a process according to the present invention in which the reaction unit for converting by-products into synthesis gas is fed with at least one gaseous effluent from the FT and at least one hydrocarbon cut comprising paraffins of 4 to 8 carbon atoms per molecule from the hydroconversion unit.

[0041] Description of the embodiments

[0042] Embodiments of the method and device according to the invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the method and device according to the invention. However, it will be apparent to those skilled in the art that the method and device according to the invention can be implemented without these specific details. In other cases, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0043] In this specification, the term "comprise" is synonymous with (means the same as) "include" and "contain", and is inclusive or open and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist". Furthermore, in this specification, an effluent comprising essentially, substantially, or solely a compound A corresponds to an effluent comprising at least 95% by weight, preferably at least 98% by weight, very preferably at least 99% by weight, or even 100%, of compound A.Finally, in the present description, an effluent being rich in a compound A corresponds to an effluent comprising at least 10% by weight or volume, preferably at least 30% by weight or volume, preferably at least 50% by weight or volume, preferably at least 70% by weight or volume, preferably at least 90% by weight or volume, preferably at least 95% by weight or volume, of compound A, such as at least between 50% by weight or volume and 99% by weight or volume of compound A. In the present description, an effluent being rich in a compound A may correspond to an effluent consisting of compound A (e.g. impurities less than 1000 ppm, or even less than 100 ppm).

[0044] In this description, the term "physical solvent" is synonymous with (means the same as) a solvent forming weak bonds (e.g. hydrogen bond, van der Waals bond) with the solute, a solvent not forming a strong bond (e.g. covalent bond, ionic bond) with the solute.

[0045] The present invention can be defined as a method and a device comprising a sequence of unit operations making it possible to produce synthetic hydrocarbons, such as synthetic fuels, for example gasoline, kerosene, diesel and / or naphtha or lubricating bases, preferably of very high quality from carbon dioxide.

[0046] The method and the device according to the invention are notably characterized in that they use and comprise units for reverse water gas conversion (RWGS), separation of carbon dioxide from a gaseous effluent, Fischer-Tropsch (FT) synthesis, hydroconversion (hydrotreatment, and / or hydrocracking and / or hydroisomerization) of the hydrocarbon cuts from the Fischer-Tropsch reaction unit, and conversion of hydrocarbon by-products of the process (RWGS and / or Fischer-Tropsch synthesis and / or hydroconversion) into synthesis gas.

[0047] One of the features of the present invention can be summarized as the use of carbon dioxide for the production of synthetic fuels, gasoline, kerosene, diesel and / or naphtha or very high quality lubricating bases. The present invention is based in particular on the presence of a carbon dioxide separation unit to extract carbon dioxide from the other gaseous compounds of the process and recycle it. The present invention is also based on a reaction unit for converting by-products into synthesis gas adapted to treat the hydrocarbon by-products to produce a synthesis gas rich in carbon monoxide and hydrogen in order to improve the production of the products of interest, in particular a cut comprising paraffins of 9 to 16 carbon atoms per molecule.

[0048] Thus, the combination of carbon dioxide conversion, carbon dioxide separation, FT synthesis, hydroconversion and by-product conversion into synthesis gas units makes it possible to produce fuel bases, and in particular fuel for the aviation sector, with high efficiency.

[0049] With reference to Figure 1, the process / device for converting carbon dioxide into liquid hydrocarbons uses / comprises: a RWGS reaction unit 3 adapted to at least partially convert carbon dioxide from a carbon dioxide-rich feedstock 1 with a first hydrogen source 2 and produce a first synthesis gas 4 rich in CO and H2, and a first water effluent 5 produced from the RWGS reaction; a carbon dioxide separation unit 6 adapted to treat the first synthesis gas 4 and produce a carbon dioxide-depleted gaseous effluent 8 and a carbon dioxide-rich gaseous effluent 7, and recycle the carbon dioxide-rich gaseous effluent 7 to the inlet of the RWGS reaction unit 3;a Fischer-Tropsch reaction unit 10 adapted to convert the depleted gaseous effluent into carbon dioxide 8, optionally with a second hydrogen source 9, and to produce at least one hydrocarbon effluent 11, a first gaseous FT effluent 13 rich in CO, H2, CO2 and hydrocarbons of 1 to 5 carbon atoms per molecule, optionally a second gaseous FT effluent 16 rich in hydrocarbons of 1 to 5 carbon atoms per molecule, and a second water effluent 12 produced by the Fischer-Tropsch synthesis resulting from the condensation of gaseous water under the operating conditions of the Fischer-Tropsch reaction;a hydroconversion reaction unit 19 (hydrotreatment and / or hydrocracking and / or hydroisomerization unit) adapted to treat the hydrocarbon effluent 11 with a third hydrogen source 18 and produce at least a third gaseous effluent 22 comprising hydrocarbons of 1 to 5 carbon atoms per molecule, a second hydrocarbon cut 23 comprising paraffins of 4 to 8 carbon atoms per molecule, and a first hydrocarbon cut 20 comprising paraffins of 8 to 22 carbon atoms per molecule, and preferably essentially paraffins of 9 to 16 carbon atoms per molecule;a reaction unit for converting by-products into synthesis gas 24 adapted to convert at least a portion 15 of the first gaseous effluent of FT 13, the second hydrocarbon cut 23, and optionally a gaseous stream 17 comprising at least in part the second gaseous effluent of FT 16 and / or at least in part the third gaseous effluent 22, produce a second synthesis gas 25 rich in carbon monoxide and hydrogen, and send the second synthesis gas 25 into the carbon dioxide separation unit 6.;

[0050] Process charges

[0051] According to one or more embodiments, the carbon dioxide-rich feedstock 1 may come from a carbon dioxide capture unit supplied with gaseous effluents from a refinery, an incinerator, a petrochemical unit, a chemical unit, a thermal power plant, a paper mill, an ethanol factory, a sugar factory, a cement factory, a lime production unit, or blast furnaces. According to one or more embodiments, the carbon dioxide-rich feedstock 1 comprises at least 50% by weight of CO2, preferably at least 70% by weight of CO2, at least 90% by weight of CO2, at least 95% by weight of CO2, such as at least between 50% by weight and 99% by weight of CO2. In practice, the carbon dioxide-rich feedstock 1 may consist of CO2 (e.g., impurities less than 1000 ppm, or even less than 100 ppm).

[0052] According to one or more embodiments, feedstock 1 may come from a carbon dioxide capture unit fueled by biogas, natural gas, syngas produced by gasification of biomass or other fuels, refinery gas, biomass fermentation gas, cement plant gas and blast furnace gas.

[0053] The carbon dioxide of feed 1 may also be carbon dioxide present in the air. According to one or more embodiments, the carbon dioxide-rich feed 1 may come from a direct air capture device (“Direct Air Capture” or “DAC” according to English terminology) and / or from a direct ocean capture device (“Direct Ocean Capture” or “DOC” according to English terminology).

[0054] The hydrogen (2, 9, 18) required for the process can be produced by a water electrolysis unit. Electrolyzer technologies used for water electrolysis include, for example: alkaline electrolysis, proton exchange membrane (PEM) electrolysis, solid oxide electrolysis (SOE), or anion exchange membrane (AEM) electrolysis. The operating conditions (temperature, pressure, nature of the electrolyte, electrodes and diaphragm / membrane) are then specific to each technology:

[0055] Alkaline type electrolyzer: temperature between 60°C and 90°C, pressure between 0.1 MPa and 20 MPa, preferably between 0.1 MPa and 4 MPa, electrolyte comprising KOH, electrodes comprising a metal alloy, diaphragm comprising asbestos, polytetrafluoroethylene and / or nickel oxide;

[0056] Proton exchange membrane (PEM) type electrolyzer: temperature between 50°C and 80°C, pressure between 0.1 MPa and 20 MPa, preferably between 1.8 MPa and 5.5 MPa, electrolyte comprising a polymer membrane, electrodes comprising a metal alloy; temperature between 800°C and 900°C, pressure between 0.1 MPa and 2 MPa, preferably between 0.1 MPa and 0.5 MPa, electrolyte comprising a ceramic membrane (eg perovskite type), electrodes comprising a metal alloy;

[0057] Anion exchange membrane (AEM) type electrolyser: temperature between 50°C and 70°C, pressure between 0.1 MPa and 20 MPa, preferably between 0.1 MPa and 3.5 MPa, electrolyte comprising a polymer membrane, electrodes comprising a metal alloy.

[0058] Reverse Water Gas Switching (RWGS) Reaction Unit

[0059] The RWGS reaction unit 3 produces the first synthesis gas 4, rich in CO, preferably rich in hydrogen, and containing unconverted carbon dioxide, and produces the first water effluent 5. The first source of hydrogen 2 required for the RWGS reaction may, for example, come from a water electrolysis unit.

[0060] According to one or more embodiments, the RWGS reaction unit 3 comprises at least one reactor used under at least one of the following operating conditions: temperature between 700°C and 1200°C, preferably between 750°C and 1100°C, and more preferably still between 780°C and 1050°C; pressure between 0.1 MPa and 10 MPa, preferably between 0.1 MPa and 5 MPa, and more preferably between 0.1 MPa and 3.5 MPa; space velocity of the gas at the reactor inlet between 2000 NL / kg cata / h and 40000 NL / kgcata / h; catalysts based on the elements Ni, Cu, Fe, Co or precious metals such as Pt, Pd, Ru, Ag and Au. According to one or more embodiments, the catalyst for the RWGS reaction comprises a support, for example based on alumina, silica, silica-alumina, alumina-silica.

[0061] According to one or more embodiments, the quantity of hydrogen at the inlet of the RWGS reaction unit is adjusted so that the H2 / CO molar ratio in the first synthesis gas 4 is compatible with the requirement of the Fischer-Tropsch unit, i.e. between 0.5 and 4, preferably between 1 and 3, more preferably between 1.5 and 2.5.

[0062] According to one or more embodiments, the temperature of the effluent leaving the RWGS reactor(s) is at least 700°C, preferably at least 750°C, very preferably at least 780°C.

[0063] According to one or more embodiments, the first synthesis gas 4 comprises less than 2 mol% of water.

[0064] The first synthesis gas 4 is sent to the carbon dioxide separation unit 6. According to one or more embodiments, the first synthesis gas 4 can be compressed and then optionally cooled before being sent to the carbon dioxide separation unit 6.

[0065] Carbon dioxide separation unit

[0066] In the carbon dioxide separation unit 6, the first synthesis gas 4 and the second synthesis gas 25 are treated to produce: the carbon dioxide-depleted off-gas 8; and the carbon dioxide-rich off-gas 7, relative to the carbon dioxide content of the sum of the synthesis gases 4 and 25.

[0067] For the separation of CO2 several agents can be used, such as solvents and solids. Preferably, the carbon dioxide separation unit 6 uses at least one chemical solvent based on amines, and / or at least one physical solvent such as for example based on polyethylene glycol dialkyl ether or methanol, and / or physical adsorption equipment at alternating temperature and / or a membrane.

[0068] Advantageously, the separation of carbon dioxide makes it possible to limit the carbon dioxide content in the charge of the Fischer-Tropsch reaction unit 10.

[0069] A widely used carbon dioxide separation technology relies on the phenomenon of absorption, namely the passage of a chemical species from a gas to a liquid. The gas containing the impurities, or the species to be separated, is sent to a column where it is brought into contact with a liquid solvent, the two flows being able to be implemented in different hydrodynamic configurations (co-current, cross-current or counter-current, the latter solution being preferred for reasons of favorable thermodynamic equilibrium). This absorption is carried out using an absorbent solution, comprising a chemical solvent or a physical solvent, this distinction being linked to whether or not there is a chemical reaction between the absorbed component and the solvent.

[0070] Physical absorption is preferred in order to minimize the energy cost of the process; this is particularly suitable in the case of high partial pressure of the species to be separated.

[0071] Chemical absorption is preferred in the case of high dilution and low partial pressure of the species to be separated and / or in the case where a high recovery rate of this species is desired or finally if a strict specification is desired as to the maximum admissible concentration of this species in the gas flow once washed. Thus for the separation of carbon dioxide with a high recovery rate in order to limit the carbon dioxide content in the Fischer-Tropsch 10 reaction unit, and with gaseous effluents with a low carbon dioxide concentration value, typically between 3% and 15% by volume, washing by chemical absorption, for example using an amine solvent, for example of the alkanolamine type, is well suited.

[0072] The absorbent solutions commonly used today are aqueous solutions comprising one or more reactive compounds or having a physicochemical affinity with acidic compounds. The reactive compounds may be, for example and without limitation, amines (primary, secondary, tertiary, cyclic or not, aromatic or not, saturated or not), alkanolamines, polyamines, amino acids, alkali salts of amino acids, amides, ureas, phosphates, carbonates or borates of alkali metals. According to one or more embodiments, the absorbent solution is an aqueous solution comprising one or more reactive compounds with an amine function and whose structure is described from page 6, line 1 to page 7, line 3, of patent application WO2007 / 104856.

[0073] According to one or more embodiments, the reactive compounds represent from 10% by weight to 90% by weight, preferably between 20% by weight and 50% by weight, very preferably between 25% by weight and 40% by weight, of the total weight of the absorbent solution.

[0074] Chemical absorption with amine solvents is based on acid-base equilibria, with low temperature favoring the reaction between the basic amine and acidic carbon dioxide, and high temperature favoring the reverse reaction. Thus, amine processes, using for example an aqueous phase containing 20-50% by mass of amine, use two columns (not shown) in which the solvent circulates from one to the other. In the first column, called the absorber, the stream to be washed (i.e., the sum of synthesis gases 4 and 25) is brought into contact with the amine solvent at low temperature. The amine solvent flows into the column and captures the carbon dioxide.At the bottom of the column, the amine solvent ("rich" solvent) reaches a predetermined loading rate, the ratio between the number of moles of carbon dioxide captured and the number of moles of amines; at the top of the column, the gas stream exits at predetermined specifications, namely a carbon dioxide content for example nearly 10 to 100 times lower than the initial content in the stream to be washed. The rich solvent is sent to the second column, called the regenerator, whose operation is similar to that of a distillation column, operating at high temperature. The regenerated amine solvent ("lean" solvent) can be returned to the absorber. The amine solvent thus circulates continuously in a closed loop from one column to the other, preferably passing through a load / effluent heat exchanger to cool the lean solvent and preheat the rich solvent while saving energy on the process scale.

[0075] According to one or more embodiments, the regenerator operates at a high temperature between 90°C and 250°C, preferably between 110°C and 240°C, very preferably between 120°C and 200°C at the bottom of the column.

[0076] The carbon dioxide-rich gaseous effluent 7 released from the regenerator is then returned to the RWGS reaction unit 3. According to one or more embodiments, the carbon dioxide-rich gaseous effluent 7 comprises at least 90% vol. carbon dioxide, preferably at least 95% vol. carbon dioxide, very preferably at least 98% vol. carbon dioxide. According to one or more embodiments, the carbon dioxide-rich gaseous effluent 7 has a temperature of between 20°C and 250°C, preferably between 30°C and 200°C, very preferably between 40°C and 150°C, at the outlet of the carbon dioxide separation unit 6. According to one or more embodiments, the carbon dioxide-rich gaseous effluent 7 has a pressure of between 0.1 MPa and 4 MPa, preferably between 0.1 MPa and 3.5 MPa, very preferably between 0.1 MPa and 3 MPa, at the outlet of the carbon dioxide separation unit 6.

[0077] A key aspect of solvent-based carbon dioxide separation is the regeneration step of the separating agent. Depending on the type of absorption (physical and / or chemical), regeneration by expansion, and / or distillation and / or entrainment by a vaporized gas called "stripping gas" is generally considered.

[0078] One of the main limitations of solvents commonly used today is the need to implement high flow rates of absorbent solution, which results in significant energy consumption for solvent regeneration, but also large equipment sizes (columns, pumps, etc.). This is particularly true in the case where the carbon dioxide partial pressure is low. Such energy consumption represents a considerable operating cost for the carbon dioxide separation process. The regeneration energy depends on the nature of the amines and the carbon dioxide partial pressure and is typically between 1 GJ / t and 4 GJ / t of separated carbon dioxide.

[0079] Another possible implementation is based on the principle of adsorption using a solid adsorbent with a strong chemical affinity for carbon dioxide. To ensure continuous operation, the processes operate with several reactors in parallel. The carbon dioxide is adsorbed on the solid adsorbent and the stream to be treated (i.e., the synthesis gases 4 + 25) becomes depleted as it advances through the solid bed, and, at the outlet, the stream no longer contains or contains little carbon dioxide. However, the solid adsorbent gradually becomes saturated and can no longer adsorb carbon dioxide. The stream to be treated is then sent to another reactor containing a solid adsorbent not saturated with carbon dioxide and the capture operation continues. In parallel, the reactors saturated with carbon dioxide are subject to a regeneration operation:

[0080] - by a rise in temperature, we then speak of alternating temperature adsorption (or “TSA” for “Temperature Swing Adsorption” according to Anglo-Saxon terminology); and

[0081] - by partial vacuum, we then speak of adsorption by pressure inversion (or "VPSA" for "Vacuum Pressure Swing Adsorption" according to Anglo-Saxon terminology, or simply "VSA" or "PSA", possibly in the presence of a gas promoting desorption).

[0082] The locks of TSA processes are the large amount of heat required for regeneration.

[0083] According to one or more embodiments, the solid adsorbent for carbon dioxide capture is chosen from the following compounds: activated carbon, zeolites, aluminas, silicas, synthetic fibers with or without impregnated amines, solids of the metal-organic framework type ("Metal-Organic Framework" or "MOF" according to the English terminology), supported alkali carbonates. These solid absorbents are increasingly used in the case of carbon dioxide capture from the air. The regeneration energy of absorbents with physisorption in these cases, for example on zeolites, is of the order of 0.6 to 0.9 GJ / t carbon dioxide. For amines supported on solid, the regeneration energy is between 5.4 and 7.2 GJ / t carbon dioxide.

[0084] Another possible implementation for carbon dioxide separation is membrane separation. Membrane separation processes were initially not recommended for post-combustion carbon dioxide separation, with gas-liquid absorption processes in a chemical solvent being considered the most mature and suitable technology for this operation. However, the most recent technologies allow carbon dioxide to be separated economically using membranes (dense polymers, inorganic materials, hybrid matrices, liquid membranes). Reference may be made to the journal article: Oil Gas Sci. Technol. - Rev. IFP Energies nouvelles, Volume 69, Number 6, November-December 2014. The main performance is a capture rate and carbon dioxide purity greater than 90%.

[0085] The carbon dioxide-depleted effluent gas 8 is sent to the Fischer-Tropsch reaction unit 10. The carbon dioxide-depleted effluent gas 8 may be compressed before being sent to the Fischer-Tropsch reaction unit 10.

[0086] The carbon dioxide-rich 7-gaseous effluent is sent to the RWGS reaction unit 3. The carbon dioxide-rich 7-gaseous effluent may be compressed before being sent to the RWGS reaction unit 3.

[0087] Fischer-Tropsch synthesis reaction unit

[0088] According to the invention, in the Fischer-Tropsch reaction unit 10, the carbon monoxide and hydrogen present in the carbon dioxide-depleted gaseous effluent 8 react to produce the hydrocarbon effluent 11, the first FT gaseous effluent 13 rich in CO, H2, CO2 and hydrocarbons of 1 to 5 carbon atoms per molecule, optionally the second FT gaseous effluent 16 rich in hydrocarbons of 1 to 5 carbon atoms per molecule, and a second water effluent 12.

[0089] According to one or more embodiments, the carbon dioxide-depleted gaseous effluent 8 sent to the Fischer-Tropsch reaction unit 10 comprises carbon monoxide and hydrogen with a molar ratio H2 / CO of between 0.5 and 4, preferably between 1 and 3, more preferably between 1.5 and 2.5. According to one or more embodiments, the quantity of hydrogen upstream (e.g. at the inlet) of the Fischer-Tropsch reaction unit 10 is adjusted, for example by means of the second hydrogen source 9, so that the molar ratio H2 / CO is as defined above.

[0090] The Fischer-Tropsch reaction unit 10 is implemented in a reaction unit comprising one or more suitable reactors, the technology of which is known to those skilled in the art. This may be, for example, one or more multitubular fixed bed reactors, or one or more slurry bubble column reactors, or one or more microchannel reactors.

[0091] According to one or more embodiments, the Fischer-Tropsch reaction unit uses one or more bubble column reactors. Since the synthesis is highly exothermic, this embodiment makes it possible, among other things, to improve the thermal control of the reactor and to create little pressure drop. The catalyst used in this Fischer-Tropsch synthesis is generally any catalytic solid known to those skilled in the art for carrying out the Fischer-Tropsch synthesis. According to one or more embodiments, the catalyst used in the Fischer-Tropsch synthesis comprises cobalt or iron, preferably cobalt. The catalyst used is generally a supported catalyst. The support may be, for example, based on alumina, silica, silica-alumina, alumina-silica or titanium.

[0092] According to one or more embodiments, the Fischer-Tropsch reaction unit 10 comprises at least one reactor used under at least one of the following operating conditions: temperature between 170°C and 280°C, preferably between 190°C and 260°C and preferentially between 210°C and 240°C, absolute pressure between 1.0 MPa and 6.0 MPa, preferably between 1.5 MPa and 3.5 MPa and preferentially between 2.0 MPa and 3.0 MPa.

[0093] According to one or more embodiments, the Fischer-Tropsch reaction unit 10 is adapted to produce steam by vaporizing water (not shown) in a heat exchanger located inside the Fischer-Tropsch reaction unit 10 making it possible to eliminate the calories from the Fischer-Tropsch reaction, an exothermic reaction.

[0094] According to one or more embodiments, an FT effluent obtained at the outlet of the FT reactor is separated in a first step, e.g. vapor-liquid-liquid separation, to produce the first FT gaseous effluent 13 and the second water effluent 12 as well as a liquid effluent, the latter being separated in a second step, e.g. by distillation, to produce the hydrocarbon effluent 11 and the second FT gaseous effluent 16. According to one or more embodiments, an FT effluent obtained at the outlet of the FT reactor is separated in one step to produce the first FT gaseous effluent 13, the second water effluent 12 as well as the hydrocarbon effluent 11.

[0095] According to one or more embodiments, the hydrocarbon effluent 11 comprises: n-paraffins, olefins and oxygenated compounds resulting from the condensation of gaseous hydrocarbons under the operating conditions of the Fischer-Tropsch reaction. According to one or more embodiments, the hydrocarbon effluent 11 comprises hydrocarbon compounds comprising at least 5 carbon atoms per molecule, preferably at least 6 carbon atoms.

[0096] According to one or more embodiments, the hydrocarbon effluent 11 comprises less than 5% by weight of water, preferably less than 2% by weight of water, very preferably less than 1% by weight of water. According to one or more embodiments, the second water effluent 12 is produced by Fischer-Tropsch synthesis and is derived from the condensation of gaseous water under the operating conditions of the Fischer-Tropsch reaction.

[0097] According to one or more embodiments, the first gaseous effluent of FT 13 comprises unconverted synthesis gas, carbon dioxide and gaseous hydrocarbons such as C1 to C5 paraffins (majority - eg at least 50% by weight of the gaseous hydrocarbons), C2 to C5 olefins, and C1 to C5 oxygenated compounds.

[0098] At least a portion 15 of the first gaseous effluent of FT 13 is sent to the reaction unit for converting by-products into synthesis gas 24. According to one or more embodiments, a portion 14 of the first gaseous effluent of FT 13 is purged to avoid the accumulation of inert compounds, such as nitrogen for example, in the process.

[0099] According to one or more embodiments, at least a portion of the second gaseous effluent of FT 16 is sent to the reaction unit for converting by-products into synthesis gas 24, via the gaseous stream 17. According to one or more embodiments, the gaseous stream 17 comprises predominantly (i.e., at least 50% by weight) hydrocarbons such as paraffins of 1 to 5 carbon atoms per molecule. According to one or more embodiments, at least a portion of the second gaseous effluent of FT 16 is extracted from the process, for example to produce energy.

[0100] Hydroconversion reaction unit (hydrotreatment and / or hydrocracking and / or hydroisomerization unit)

[0101] In the hydroconversion reaction unit 19, the hydrocarbon effluent 11 and the third hydrogen source 18 react to produce at least: the third gaseous effluent 22 comprising hydrocarbons of 1 to 5 carbon atoms per molecule, the second hydrocarbon cut 23 comprising paraffins of 4 to 8 carbon atoms per molecule, the first hydrocarbon cut 20 comprising paraffins of 8 to 22 carbon atoms per molecule, and preferably essentially paraffins of 9 to 16 carbon atoms per molecule, and optionally a third water effluent 21.

[0102] The hydrocarbon effluent 11 is sent to the hydroconversion reaction unit 19 to undergo a hydrotreatment and / or hydrocracking and / or hydroisomerization reaction. At the outlet of the hydroconversion reaction unit 19, the first hydrocarbon cut 20 can be upgraded, in particular into synthetic fuels, namely gasoline, kerosene, diesel, and / or other hydrocarbon products, such as naphtha, or very high-quality lubricating bases (essentially free of sulfur, aromatics, nitrogen). One possible option is the production of paraffinic cuts, basic products for petrochemical processes, for example the production of a C10-C13 cut intended for the production of linear alkyl benzene (or "LAB" for "Linear Alkyl Benzene" according to English terminology), or even waxes for various industrial applications.

[0103] According to one or more embodiments, the first hydrocarbon fraction 20 mainly comprises hydrocarbons of 8 to 22 carbon atoms per molecule (eg at least 50% by weight, preferably at least 70% by weight, very preferably at least 90% by weight), such as C9 to C16 paraffins, linear and / or branched.

[0104] According to one or more embodiments, the third gaseous effluent 22 mainly comprises hydrocarbons of 1 to 5 carbon atoms per molecule (e.g. at least 50% by weight, preferably at least 70% by weight, very preferably at least 90% by weight), such as linear and / or branched C1 to C5 paraffins. According to one or more embodiments, at least a portion of the third gaseous effluent 22 is sent to the reaction unit for converting by-products into synthesis gas 24 via the gas stream 17. According to one or more embodiments, at least a portion of the third gaseous effluent 22 is extracted from the process, for example to produce energy.

[0105] According to one or more embodiments, the second hydrocarbon cut 23 mainly comprises hydrocarbons of 4 to 8 carbon atoms per molecule (e.g. at least 50% by weight, preferably at least 70% by weight, very preferably at least 90% by weight), such as C4 to C8 paraffins, linear and / or branched. At least a portion of the second hydrocarbon cut 23 is sent to the reaction unit for converting by-products into synthesis gas 24.

[0106] According to one or more embodiments, the hydroconversion reaction unit 19 comprises at least one reactor used under at least one of the following operating conditions: temperature between 200°C and 500°C, more preferably between 280°C and 450°C, and even more preferably between 300°C and 420°C; pressure between 0.2 MPa and 15 MPa, preferably between 0.5 MPa and 12 MPa, more preferably between 1 MPa and 10 MPa; space velocity defined as the ratio of the volume flow rate of the feedstock at ambient temperature and pressure to the volume of the catalyst, between 0.1 h -1 and 10 a.m. -1 , preferably between 0.2 h -1 and 7 a.m. -1 , more preferably between 0.5 h -1 and 5 a.m. -1; hydrogen flow rate between 70 and 2000 normal liters of hydrogen per liter of charge per hour and preferably between 150 and 1500 normal liters of hydrogen per liter of charge and more preferably between 300 and 1500 normal liters of hydrogen per liter of charge.

[0107] According to one or more embodiments, the hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises at least one hydrogenating-dehydrogenating metal chosen from the group comprising the metals of group VI B and group VI 11 B of the periodic table and / or at least one solid which is a Bronsted acid, i.e. a solid capable of releasing one or more protons, and optionally a binder.

[0108] In this description, the groups of chemical elements are given by default according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIIIB according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IIIPAC classification; group VI B according to the CAS classification corresponds to the metals of column 6 according to the new IIIPAC classification.

[0109] According to one or more embodiments, the hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises at least one noble metal from group VIIIB chosen from ruthenium, rhodium, palladium, osmium, iridium and platinum, taken alone or as a mixture, and preferably from platinum and palladium taken alone or as a mixture, and preferably used in their reduced form.

[0110] According to one or more embodiments, the hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises: at least one metal chosen from nickel, molybdenum, tungsten, cobalt, ruthenium, indium, palladium, platinum; at least one support chosen from aluminas, boron oxides, magnesias, zirconias, titanium oxides, clays. According to one or more embodiments, the support is chosen from an alumina, silica-alumina, alumina-silica, silica and zeolite.

[0111] According to one or more embodiments, the hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises at least one metal from group VIIIB chosen from nickel and cobalt and / or at least one metal from group VI B chosen from molybdenum and tungsten, and preferably used in their sulfurized form.

[0112] According to one or more embodiments, in the case where said hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises at least one noble metal from group VIIIB, the noble metal content of said catalyst, expressed as an element, is between 0.01% and 5% by weight relative to the finished catalyst, preferably between 0.05% and 4% by weight and very preferably between 0.10% and 2% by weight.According to one or more embodiments, in the case where said hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises at least one metal from group VI B and / or at least one non-noble metal from group VIII chosen from nickel and cobalt, the content of metal from group VI B in said catalyst is comprised in oxide equivalent between 5% and 40% by weight relative to the finished catalyst, preferably between 10% and 35% by weight, and the content of metal from group VI II B in said catalyst is comprised in oxide equivalent between 0.5% and 15% by weight relative to the finished catalyst, preferably between 1% and 10% by weight, preferably between 1% and 8% by weight, and very preferably between 1.5% and 6% by weight.

[0113] According to one or more embodiments, the hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprises or consists of at least one noble metal and a support comprising or consisting of at least one zeolite and at least one binder.

[0114] According to one or more embodiments, the zeolite-based hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst is advantageously of the bifunctional type, that is to say that it has a hydro-dehydrogenating function and a hydro-isomerizing function.

[0115] Reaction unit for converting by-products into synthesis gas

[0116] According to the invention, at least a portion 15 of the gaseous effluent 13 from the Fischer-Tropsch reaction unit and of the second hydrocarbon cut 23 resulting from the hydroconversion are sent to the reaction unit for converting by-products into synthesis gas 24, in which the hydrocarbon compounds (i.e., paraffins, olefins, oxygenates) are converted at least partially, to produce the second synthesis gas 25 comprising (preferably mainly, or even essentially) carbon monoxide and hydrogen. According to one or more embodiments, a fourth water effluent (not shown in the figures) is produced by the reaction unit for converting by-products into synthesis gas 24.

[0117] Various catalytic and non-catalytic processes, known to those skilled in the art, may be used to convert the by-products present in the first gaseous effluent of FT 13 and the second hydrocarbon cut 23 and produce the second synthesis gas 25: steam reforming (“Steam methane reforming” or “SMR” according to English terminology); partial oxidation (“Partial oxidation” or “POX” according to English terminology), which may be catalytic or thermal; autothermal reforming (“Autothermal reforming” or “ATR” according to English terminology); combined reforming (“Combined reforming” or “CR” according to English terminology); and dry reforming (“Dry reforming of methane” or “DRM” according to English terminology).

[0118] Steam reforming (SM R)

[0119] Steam reforming (SM R) consists of reacting a hydrocarbon feedstock (gas, naphtha) on a catalyst in the presence of excess water vapor to obtain a synthesis gas rich in CO and H2. This reaction is endothermic and balanced and can be summarized as 1 CH4 and 1 H2O producing 1 CO and 3 H2 (in the case of methane for example).

[0120] Steam reforming is typically carried out by circulating the feedstock with added steam through tubes filled with catalyst, generally a nickel catalyst, for example comprising from 5 to 30% by weight of nickel deposited on a support comprising mainly (i.e., at least 50% by weight) alumina, or a mixture of alumina and one or more other refractory compounds. The tubes are typically heated by radiation in tube furnaces.

[0121] Excess steam is used to limit carbon deposits and increase conversion.

[0122] This process is well suited to gaseous feedstocks, particularly natural gas, but also naphtha. The steam reforming reaction is favored by high temperatures and is generally carried out in a furnace. The heat required for the reaction is produced by the combustion of a fuel (e.g., natural gas or the hydrocarbon feedstock) with air in the steam reforming furnace.

[0123] The synthesis gas obtained by the steam reforming reaction contains mainly (i.e., at least 50% by weight) hydrogen, carbon monoxide, carbon dioxide, as well as water vapor and unconverted hydrocarbon feedstock.

[0124] Steam reforming is typically carried out at a temperature between 600°C and 900°C and at a pressure of up to 2.5 MPa, but can also be carried out at a temperature above 900°C.

[0125] The synthesis gas leaving the steam reforming furnace is then cooled and the condensed water is separated from the synthesis gas. Cooling of the synthesis gas leaving the steam reforming furnace can be done in an exchanger that produces steam.

[0126] Other technical elements relating to the steam reforming process can be found in the reference work: “Conversion processes”, P. Leprince, Editions Technip, 2001, Paris 15 ème, pages 455-495. According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a steam reforming unit and a section for cooling the synthesis gas and separating condensed water, the steam reforming unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 Mpa and 4 Mpa, and preferably between 1 Mpa and 3 Mpa; temperature between 600°C and 1500°C, preferably between 700°C and 900°C; and the presence of a catalyst comprising nickel.

[0127] Partial oxidation (POX), sometimes called partial oxidation gasification, is combustion with less than stoichiometric amounts of oxygen to form carbon dioxide and steam. Partial oxidation is slightly exothermic and can be used as an alternative to steam methane reforming to produce syngas. Partial oxidation can process light and heavy hydrocarbon feedstocks, asphalts, petroleum coke, but also coal and biomass (e.g. wood, green waste, etc.). Partial oxidation is preferably carried out at high temperature (e.g. between 1100°C and 1500°C), pressure between 1 MPa and 9 MPa or more, in the presence of near-pure oxygen (purity greater than 98% by volume). The partial oxidation reaction itself corresponds to the reaction between 1 ChL and 0.5 O2 to produce 1 CO and 2 H2 (in the case of methane for example).Partial oxidation is a reaction that brings the gas mixture to a temperature between 1100°C and 1500°C, by preheating the feedstock and oxygen, for example to 250°C. A high temperature allows almost all of the feedstock to be converted and prevents soot formation. The amount of oxygen typically used corresponds to 35% of the stoichiometric oxygen required for complete oxidation to CO2 and water.

[0128] To control the adiabatic flame temperature, which can reach 1900°C with air and 2800°C with 95% O2, an inert gas can be used, such as water vapor or carbon dioxide. The addition of water vapor will increase the molar ratio of H2 to CO in the produced syngas, while the addition of carbon dioxide will reduce the molar ratio of H2 to CO in the produced syngas.

[0129] The synthesis gas leaving the partial oxidation reactor is then cooled and the condensed water is separated from the synthesis gas. Cooling of the synthesis gas leaving the partial oxidation reactor can be done in an exchanger that produces steam. The industrial process of partial oxidation is well known to those skilled in the art, a process marketed by Shell, Texaco, BASF-Lurgi, Air Liquide, etc. See, for example, the chapters Hydrogen, 2. Production (p. 249 vol. 18) and Carbon Monoxide (p. 679 vol. 6) of Ullmann's Encyclopedia of Industrial Chemistry.

[0130] Other technical elements relating to the partial oxidation process can be found in the reference work: "Conversion processes", P. Leprince, Editions Technip, 2001, Paris 15 ème , pages 455-495.

[0131] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a partial oxidation unit preferably operated at oxygen stoichiometry so as to obtain the oxidation of the hydrocarbon mixture and so as to have a maximum concentration of carbon monoxide in the second synthesis gas 25.

[0132] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a partial oxidation unit operated with an oxygen flow rate adjusted to have the desired temperature in the partial oxidation chamber and to minimize the content of light hydrocarbons in the second synthesis gas 25.

[0133] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a non-catalytic partial oxidation unit followed by a section for cooling the synthesis gas and separating the condensed water, the partial oxidation unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 9 MPa, and preferably between 1 MPa and 4 MPa; temperature between 600°C and 2000°C, preferably between 800°C and 1700°C, preferably between 1100°C and 1500°C; and the presence of oxygen used for combustion, with an oxygenation rate between 0.2 and 0.6, preferably between 0.25 and 0.5, in order to promote the formation of carbon monoxide. The oxygenation rate is defined as the ratio of the molar flow rate of injected oxygen to the theoretical oxygen flow rate for complete oxidation of all hydrocarbons.

[0134] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a catalytic partial oxidation unit followed by a section for cooling the synthesis gas and separating the condensed water, the partial oxidation unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 9 MPa, and preferably between 0.1 MPa and 4 MPa; temperature between 600°C and 2000°C, preferably between 800°C and 1700°C, preferably between 900°C and 1500°C; and the presence of oxygen used for combustion, with an oxygenation rate between 0.2 and 0.6, preferably between 0.25 and 0.5, in order to promote the formation of carbon monoxide.The oxygenation rate is defined as the ratio of the molar flow rate of injected oxygen to the theoretical oxygen flow rate for complete oxidation of all hydrocarbons; presence of a catalyst containing a noble metal such as rhodium, or nickel or a nickel alloy.

[0135] Autothermal reforming (ATR), also known as catalytic partial oxidation, consists of partial oxidation immediately followed by catalytic steam reforming in adiabatic conditions at high temperatures, for example in the outlet temperature range 900°C -1000°C. Autothermal reforming can tightly control the final composition of the syngas by combining non-catalytic partial oxidation with catalytic steam reforming in a single reactor. It consumes less oxygen than partial oxidation, but requires a catalytic bed. As with steam reforming, autothermal reforming can only process light feedstocks (gas, naphtha). The autothermal reforming reaction corresponds to the reaction between 1 ChL, 0.25 O2 and 0.5 H2O to produce 1 CO and 2.5 H2 (in the case of methane for example).In the autothermal reforming process, the hydrocarbon feedstock is mixed with steam and then optionally heated in a furnace before being introduced into an autothermal reactor. Oxygen is also introduced into the autothermal reactor. The heat required for the reaction is provided by the partial combustion of the feedstock with oxygen. The feedstock arrives at a pressure typically between 3 MPa and 10 MPa.

[0136] The autothermal reforming reactor comprises two successive zones: a first zone corresponding to a combustion chamber and a second zone with a catalytic bed. In the combustion chamber, partial oxidation of the hydrocarbon feedstock takes place with oxygen burners. In the second zone, the synthesis gas produced in the combustion chamber passes through a catalytic bed in which the steam reforming reaction takes place.

[0137] The synthesis gas leaving the autothermal reforming reactor is then cooled and the condensed water is separated from the synthesis gas. Cooling of the synthesis gas leaving the autothermal reforming reactor can be done in an exchanger that produces steam. Other technical elements relating to autothermal reforming processes can be found in the reference work: "Conversion processes", P. Leprince, Editions Technip, 2001, Paris 15 ème , pages 455-495.

[0138] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises an autothermal reforming unit followed by a section for cooling the synthesis gas and separating the condensed water, the autothermal reforming unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 10 MPa, and preferably between 1 MPa and 4 MPa; temperature between 800°C and 1100°C, preferably between 900°C and 1000°C; and the presence of a catalyst based on a noble metal, nickel or nickel alloy.

[0139] Combined reforming (CR), or two-stage reforming, involves a first tubular steam reformer (steam reformer furnace) combined in series with a second autothermal reformer (reforming reactor) to which oxygen is added. A fraction of the feedstock may be sent directly to the second autothermal reformer.

[0140] As with steam reforming, the feedstock is mixed with steam and then preheated to approximately 500°C before entering the steam reforming furnace. The synthesis gas leaving the reforming furnace, rich in unconverted feedstock, is mixed with oxygen and sent to the autothermal reforming reactor. The synthesis gas leaving the autothermal reforming reactor has a temperature between 900°C and 1000°C. The synthesis gas leaving the autothermal reforming reactor is then cooled and the condensed water is separated from the synthesis gas. Cooling of the synthesis gas leaving the autothermal reforming reactor can be done in an exchanger that produces steam.

[0141] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a combined reforming unit followed by a section for cooling the synthesis gas and separating the condensed water, the combined reforming unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 10 MPa, and preferably between 1 MPa and 4 MPa; temperature between 800°C and 1100°C, preferably between 900°C and 1000°C; and the presence of a catalyst based on a noble metal, nickel or dry nickel alloy.

[0142] Dry reforming, also called carbon dioxide reforming, corresponds to the reaction between 1 CH4 and 1 CO2 to produce 2 CO and 2 H2 (in the case of methane for example). The name carbon dioxide reforming comes from the fact that carbon dioxide replaces the steam in conventional steam reforming. Dry reforming is particularly interesting if you are looking for a synthesis gas with a low H2 to CO molar ratio, around 1. Dry reforming operates at a temperature generally between 900°C and 1000°C and at an operating pressure between 0.1 MPa and 4 MPa. The catalysts used are noble metal catalysts, nickel or nickel alloy.

[0143] The synthesis gas leaving the dry reforming reactor is then cooled and the condensed water is separated from the synthesis gas. Cooling of the synthesis gas leaving the dry reforming reactor can be done in an exchanger that produces steam.

[0144] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 comprises a dry reforming unit followed by a section for cooling the synthesis gas and separating the condensed water, the dry reforming unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 10 MPa, and preferably between 0.1 MPa and 4 MPa; temperature between 800°C and 1100°C, preferably between 900°C and 1000°C; and the presence of a catalyst based on a noble metal, nickel or nickel alloy.

[0145] According to one or more embodiments, the second synthesis gas 25 produced in the reaction unit for converting by-products into synthesis gas 24, has an absolute pressure of between 0.1 MPa and 9 MPa, preferably between 0.1 MPa and 4 MPa.

[0146] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 provides the necessary calories to the RWGS reaction unit 3 and / or the carbon dioxide separation unit 6 via one or more heat exchanges.

[0147] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 is adapted to produce water vapor by (indirect) heat exchange between water (not shown) and an effluent leaving a reactor for converting by-products into synthesis gas, to optionally supply thermal energy to the carbon dioxide separation unit 6. According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 is supplied by a flow of oxygen, for example obtained by electrolysis of water or separation of air.

[0148] According to one or more embodiments, the reaction unit for converting by-products into synthesis gas 24 is supplied with water vapor and / or carbon dioxide.

[0149] Advantageously, the reaction unit for converting by-products into synthesis gas 24 makes it possible to convert substantially all of the hydrocarbon by-products of the process into CO, and therefore to recover them in the form of the desired products. Thus, the yield of desired products from the process according to the invention is improved.

[0150] The second synthesis gas 25 at the outlet of the reaction unit for converting by-products into synthesis gas 24 is sent to the carbon dioxide separation unit 6. The second synthesis gas 25 can be compressed and then optionally cooled before being sent to the carbon dioxide separation unit 6.

[0151] Effluent purification units (optional)

[0152] According to one or more embodiments, the carbon dioxide-rich feedstock 1 and / or the carbon dioxide-rich gaseous effluent 7 are purified, separately or after mixing, before being introduced into the RWGS reaction unit 3.

[0153] According to one or more embodiments, the carbon dioxide-depleted gaseous effluent 8 is purified before being introduced into the Fischer-Tropsch reaction unit 10.

[0154] The effluent purification stages aim to at least partially remove sulfur compounds, nitrogen compounds, halogens, heavy metals and transition metals. The main gas purification technologies are: adsorption, absorption, catalytic reactions.

[0155] Examples

[0156] The various examples concern sequences, in accordance or not in accordance with the invention, the objective of which is to produce paraffins of 9 to 16 carbon atoms per molecule from a carbon dioxide charge with a flow rate of 37.3 tonnes per hour.

[0157] Example 1 not in accordance with the invention

[0158] Example 1 is not in accordance with the invention according to Figure 1. Example 1 illustrates a CO2 conversion device comprising: a RWGS reaction unit 3, supplied with CO2 1 and the first hydrogen source 2, and which produces the first synthesis gas 4 rich in CO and H2 and the first water effluent 5; a carbon dioxide separation unit 6 which produces the CO2-depleted gaseous effluent 8 and the CO2-rich gaseous effluent 7 from the synthesis gases 4 and 25, the CO2-rich gaseous effluent 7 is recycled to the inlet of the RWGS reaction unit 3; a Fischer-Tropsch reaction unit 10 supplied by the CO2-depleted gaseous effluent 8 and the second hydrogen source 9, and which produces the hydrocarbon effluent 11, the second water effluent 12, the first FT gaseous effluent 13 rich in CO, H2, CO2 and hydrocarbons, and the second FT gaseous effluent 16 rich in hydrocarbons;a hydroconversion reaction unit 19 (hydrotreatment and / or hydrocracking and / or hydroisomerization unit), supplied by the hydrocarbon effluent 11 and the third hydrogen source 18, and which produces the first hydrocarbon cut 20, the third water effluent 21, the third gaseous effluent 22, and the second hydrocarbon cut 23; a reaction unit for converting by-products into synthesis gas 24 of the partial oxidation type supplied by oxygen, by the part 15 of the first gaseous effluent of FT 13 and by the gaseous flow 17 comprising the mixture of the gaseous effluents 16 and 22, and which produces the second synthesis gas 25 which is sent to the inlet of the carbon dioxide separation unit 6.;

[0159] In example 1, the second hydrocarbon cut 23 comprising paraffins of 4 to 8 carbon atoms per molecule is not sent to the reaction unit for converting by-products into synthesis gas 24 of the partial oxidation type.

[0160] Table 1 summarizes the inlet and outlet flow rates of the overall process.

[0161] Table 1

[0162] The flow rate of paraffins with 9 to 16 carbon atoms per molecule produced in example 1 is 8.9 tonnes / h, i.e. a yield of 24% by weight relative to the CO2 charge.

[0163] Example 2 in accordance with the invention

[0164] Example 2 is in accordance with the invention according to Figure 1. Example 2 illustrates a CO2 conversion device comprising: a RWGS reaction unit 3, supplied with CO2 1 and the first source of hydrogen 2, and which produces the first synthesis gas 4 rich in CO and H2 and the first water effluent 5; a carbon dioxide separation unit 6 which produces the CO2-depleted gaseous effluent 8 and the CO2-rich gaseous effluent 7 from the synthesis gases 4 and 25, the CO2-rich gaseous effluent 7 is recycled to the inlet of the RWGS reaction unit 3; a Fischer-Tropsch reaction unit 10 supplied by the CO2-depleted gaseous effluent 8 and the second hydrogen source 9, and which produces the hydrocarbon effluent 11, the second water effluent 12, the first FT gaseous effluent 13 rich in CO, H2, CO2 and hydrocarbons, and the second FT gaseous effluent 16 rich in hydrocarbons;a hydroconversion reaction unit 19 (hydrotreatment and / or hydrocracking and / or hydroisomerization unit), fed by the hydrocarbon effluent 11 and the third hydrogen source 18, and which produces the first hydrocarbon cut 20, the third water effluent 21, the third gaseous effluent 22, and the second hydrocarbon cut 23; a reaction unit for converting by-products into synthesis gas 24 of the partial oxidation type fed by oxygen, by the part 15 of the first gaseous effluent of FT 13, by the gaseous flow 17 comprising the mixture of the gaseous effluents 16 and 22, by the second hydrocarbon cut 23 and which produces the second synthesis gas 25 which is sent to the inlet of the carbon dioxide separation unit 6.;

[0165] Unlike example 1, in example 2 the second hydrocarbon cut 23 is sent to the reaction unit for converting by-products into synthesis gas 24 of the partial oxidation type to be converted into CO and H2, preferably mainly into CO and H2 to produce a second synthesis gas 25 comprising at least 50% by weight of CO and H2.

[0166] Table 2 summarizes the inlet and outlet flow rates of the overall process.

[0167] Table 2 The flow rate of paraffins with 9 to 16 carbon atoms per molecule produced in example 2 according to the invention is 11.8 tonnes / h, an increase of 33% compared to example 1 and a yield of 32% by weight compared to the CO2 feedstock.

Claims

Claims 1. A method for converting a feedstock containing carbon dioxide, comprising the following steps: treating a feedstock rich in carbon dioxide (1) with a first hydrogen source (2) in a reverse water gas conversion RWGS reaction unit (3) to produce a first synthesis gas (4) rich in carbon monoxide and H2 and a first water effluent (5); treating the first synthesis gas (4) in a carbon dioxide separation unit (6) to produce a carbon dioxide-depleted gaseous effluent (8) and a carbon dioxide-rich gaseous effluent (7); recycling the carbon dioxide-rich gaseous effluent (7) to the inlet of the RWGS reaction unit (3);converting the depleted carbon dioxide gas effluent (8) in a Fischer-Tropsch reaction unit (10) to produce a hydrocarbon effluent (11), a second water effluent (12), a first FT gas effluent (13) rich in CO, H2, CO2 and hydrocarbons of 1 to 5 carbon atoms per molecule, and optionally a second FT gas effluent (16) rich in hydrocarbons of 1 to 5 carbon atoms per molecule;treating the hydrocarbon effluent (11) in a hydroconversion reaction unit (19) with a third hydrogen source (18) to produce at least a first hydrocarbon cut (20) comprising paraffins having a carbon number between 8 and 22, and preferably essentially from 9 to 16 carbon atoms per molecule, a third gaseous effluent (22) comprising hydrocarbons of 1 to 5 carbon atoms per molecule, and a second hydrocarbon cut (23) comprising paraffins of 4 to 8 carbon atoms per molecule, converting at least a portion (15) of the first FT gaseous effluent (13) and at least a portion of the second hydrocarbon cut (23), in a reaction unit for converting by-products into synthesis gas (24), to produce a second synthesis gas (25) rich in carbon monoxide and hydrogen; and sending the second synthesis gas (25) into the carbon dioxide separation unit (6).; 2. Method according to claim 1, in which the reaction unit for converting by-products into synthesis gas (24) is fed at least in part with the second gaseous effluent from FT (16).

3. Method according to claim 1 or claim 2, in which the reaction unit for converting by-products into synthesis gas (24) is fed at least in part with the third gaseous effluent (22).

4. A process according to any preceding claim, wherein the carbon dioxide-rich feedstock (1) and / or the carbon dioxide-rich gaseous effluent (7) are purified, separately or after mixing, before being introduced into the RWGS reaction unit (3).

5. A method according to any one of the preceding claims, wherein the carbon dioxide-depleted gaseous effluent (8) is purified before being introduced into the Fischer-Tropsch reaction unit (10).

6. Process according to any one of the preceding claims, in which the RWGS reaction unit (3) comprises at least one reactor used under at least one of the following operating conditions: temperature between 700°C and 1200°C, preferably between 750°C and 1100°C, and more preferably still between 780°C and 1050°C; pressure between 0.1 MPa and 10 MPa, preferably between 0.1 MPa and 5 MPa, and more preferably between 0.1 MPa and 3.5 MPa; space velocity of the gas at the reactor inlet between 2000 NL / kg ca ta / h and 40000 NL / kg cata / h; catalyst comprising a metal or a combination of metals selected from the group consisting of the elements Ni, Cu, Fe, Co, Pt, Pd, Ru, Ag and Au.

7. Method according to any one of the preceding claims, in which the carbon dioxide separation unit (6) implements separation by chemical solvent and / or physical solvent and / or membrane and / or adsorption on a solid.

8. Method according to any one of the preceding claims, in which the Fischer-Tropsch reaction unit (10) comprises at least one reactor used under at least one of the following operating conditions: temperature between 170°C and 280°C, preferably between 190°C and 260°C and preferentially between 210°C and 240°C; absolute pressure between 1.0 MPa and 6.0 MPa, preferably between 1.5 MPa and 3.5 MPa and preferentially between 2.0 MPa and 3.0 MPa; catalyst comprising cobalt or iron, preferably cobalt, the catalyst optionally comprising a support, for example based on alumina, silica, silica-alumina, alumina-silica or titanium.

9. A method according to any one of the preceding claims, wherein the method comprises supplying the Fischer-Tropsch reaction unit (10) with a second source of hydrogen (9).

10. A process according to any one of the preceding claims, wherein the hydroconversion reaction unit (19) comprises at least one reactor used under at least one of the following operating conditions: temperature between 200°C and 500°C, more preferably between 280°C and 450°C, and even more preferably between 300°C and 420°C; pressure between 0.2 MPa and 15 MPa, preferably between 0.5 MPa and 12 MPa, more preferably between 1 MPa and 10 MPa; space velocity defined as the ratio of the volume flow rate of the feedstock at ambient temperature and pressure to the volume of the catalyst, between 0.1 h -1 and 10 a.m. 1 , preferably between 0.2 h -1 and 7 a.m. -1 , more preferably between 0.5 h -1and 5 a.m. 1 ; hydrogen flow rate of between 70 and 2000 normal liters of hydrogen per liter of feed per hour and preferably between 150 and 1500 normal liters of hydrogen per liter of feed and more preferably between 300 and 1500 normal liters of hydrogen per liter of feed; hydrotreatment and / or hydrocracking and / or hydroisomerization catalyst comprising at least one hydrogenating-dehydrogenating metal chosen from the group comprising the metals of group VI B and group VI II B of the periodic table and / or at least one solid which is a Bronsted acid, i.e. a solid capable of releasing one or more protons, and optionally a binder.

11. Method according to any one of the preceding claims, in which the reaction unit for converting by-products into synthesis gas (24) comprises at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 9 MPa; temperature between 600°C and 2000°C.

12. Process according to any one of the preceding claims, in which the reaction unit for converting by-products into synthesis gas (24) comprises a catalytic or non-catalytic partial oxidation unit followed by a section for cooling the synthesis gas and separating the condensed water, the partial oxidation unit comprising at least one reactor used under at least one of the following operating conditions: absolute pressure between 0.1 MPa and 9 MPa, and preferably between 0.1 MPa and 4 MPa; temperature between 600°C and 2000°C, preferably between 800°C and 1700°C, preferably between 900°C and 1500°C or between 1100°C and 1500°C; presence of oxygen used for combustion, with an oxygenation rate between 0.2 and 0.6, preferably between 0.25 and 0.5, in order to promote the formation of carbon monoxide;presence of a catalyst containing a noble metal such as rhodium, or nickel or a nickel alloy, when the partial oxidation unit is catalytic.; 13. A method according to any one of the preceding claims, wherein a portion of the first FT gaseous effluent (13) and / or at least a portion of the second FT gaseous effluent (16) are at least partly upgraded to synthetic methane, synthetic natural gas or synthetic liquefied petroleum gas.

14. A method according to any preceding claim, wherein a portion (14) of the first FT gaseous effluent (13) is purged.

15. Device for converting a feed containing carbon dioxide, comprising the following units: a reverse water gas conversion reaction unit RWGS (3) adapted to treat a feed rich in carbon dioxide (1) with a first hydrogen source (2) and produce a first synthesis gas (4) rich in carbon monoxide and H2 and a first water effluent (5); a carbon dioxide separation unit (6) adapted to treat the first synthesis gas (4), produce a gaseous effluent depleted in carbon dioxide (8) and a carbon dioxide-rich gaseous effluent (7), and recycling the carbon dioxide-rich gaseous effluent (7) to the inlet of the RWGS reaction unit (3); a Fischer-Tropsch reaction unit (10) adapted to convert the depleted gaseous effluent into carbon dioxide (8), and produce a hydrocarbon effluent (11), a second water effluent (12), a first FT gaseous effluent (13) rich in CO, H2, CO2 and hydrocarbons of 1 to 5 carbon atoms per molecule, and optionally a second FT gaseous effluent (16) rich in hydrocarbons of 1 to 5 carbon atoms per molecule; a hydroconversion reaction unit (19) adapted to treat the hydrocarbon effluent (11) with a third hydrogen source (18) and produce at least a first hydrocarbon cut (20) comprising paraffins having a carbon number between 8 and 22, and preferably essentially from 9 to 16 carbon atoms per molecule,for example to specifications for transport applications, a third gaseous effluent (22) comprising hydrocarbons of 1 to 5 carbon atoms per molecule, and a second hydrocarbon fraction (23) comprising paraffins of 4 to 8 carbon atoms per molecule, and a reaction unit for converting by-products into synthesis gas (24) adapted to convert at least a portion (15) of the first FT gaseous effluent (13), at least a portion of the second hydrocarbon fraction (23), optionally a gaseous stream (17) comprising at least in part the second FT gaseous effluent (16) and / or at least in part the third gaseous effluent (22), and produce a second synthesis gas (25) rich in carbon monoxide and hydrogen which is sent to the carbon dioxide separation unit (6).,