FR3142477A1 - Production of synthetic fuels from CO2 with partial oxycombustion of by-products and CO2 separation - Google Patents

Abstract

CO2 capture/conversion device/method, comprising/using a CO2 capture unit (2) producing CO2 (3), a water electrolysis unit (5) converting water (4) into oxygen (6) and hydrogen (7), an RWGS unit (8) treating CO2 with hydrogen and producing an RWGS gas (9) enriched with CO and water, an FT unit (13) converting the RWGS gas and producing an effluent FT (14), a first separation unit (15) treating the FT effluent and producing a hydrocarbon effluent (17) and a gaseous effluent (33), a second separation unit (34) separating the gaseous effluent into a gas depleted in CO2 (18) and a gas rich in CO2 (35) sent to the RWGS unit, a partial oxycombustion unit (28) oxidizing the gas depleted in CO2 and producing CO sent to the FT unit, a unit with hydrogen (20) treating the hydrocarbon effluent to produce hydrocarbon cuts (21). Figure 1 to be published

Description

Production of synthetic fuels from CO2 with partial oxycombustion of by-products and CO2 separation

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 (CO ₂ ) and hydrogen (H ₂ ).

The capture and conversion of carbon dioxide into a fuel base according to the invention comprises two successive steps: the conversion of carbon dioxide and hydrogen into synthesis gas composed mainly of CO+ _H2 , then the conversion of the synthesis gas into synthesis hydrocarbons by the Fischer-Tropsch (FT) process. The properties of the products resulting from the Fischer-Tropsch process can be adjusted by suitable post-treatment operations to obtain the desired fuel specifications.

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 depending on the catalyst and operating conditions. In the case where paraffins are produced, it is preferable to improve certain properties thereof to make them usable for transport applications.

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

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, a Fischer-Tropsch synthesis in a high-temperature multitubular 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).

On the other hand, patent application US2010/0280135 A1 does not mention the possibility of advantageously integrating the unit operations with a carbon dioxide capture process. Nor is there any mention of thermal integration between the different sources of calories generated by the unit operations.

Patent application US2007/0244208 A1 relates to a process for producing high-octane fuel from carbon dioxide and water. The raw material is industrial carbon dioxide and water. The end product may be high-octane gasoline, high-cetane diesel or other liquid hydrocarbon mixtures suitable for driving conventional combustion engines or hydrocarbons suitable for further industrial processing or commercial use. Products, such as dimethyl ether or methanol, may also be removed from the production line. The heat generated by the exothermic reactions in the process is fully utilized, as is the heat generated by the production process, as well as the heat generated by the reprocessing of hydrocarbons that are not suitable for liquid fuel.

In contrast, US2007/0244208 A1 does not mention the possibility of advantageously integrating unit operations with a carbon dioxide capture process. Nor is there any mention of recycling from the Fischer-Tropsch reactor to maximize fuel production.

Patent application US2012/0079767 A1 describes a process and system for producing syngas by combining hydrogen and carbon monoxide from separate sources while controlling the molar ratio (H ₂ /CO) of the syngas produced. Hydrogen is produced by electrolysis of water. Carbon monoxide is produced by reacting carbon dioxide captured from the exhaust gas of stationary combustion engines with hydrogen in a RWGS reactor. Hydrocarbon fuels are produced from the syngas by Fischer-Tropsch synthesis.

In contrast, patent application US2012/0079767 A1 does not mention the possibility of advantageously integrating unit operations with a carbon dioxide capture process. Nor is there any mention of recycling from the Fischer-Tropsch reactor to maximize fuel production.

Patent application US2007/0142481 A1 describes a process for the synthesis of 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 comprising 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 treating the unconverted synthesis gas from the first. There is no recycling of carbon dioxide and no recycling of water.

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.

However, these documents do not provide any information on the possibility of integrating, with an unexpected positive result, unit operations with the carbon dioxide capture process which provides the raw material containing the carbon source to produce fuels.

In the context described above, a first object of the present description is to overcome the problems of the prior art and to capture and recover carbon dioxide in the form of synthetic fuels usable for transport applications.

The invention relates to the capture and conversion of carbon dioxide, so as to produce a synthesis gas CO+H ₂ , and to the conversion of said synthesis gas into synthesis hydrocarbons by the Fischer-Tropsch reaction. The characteristics of the effluents resulting from the Fischer-Tropsch synthesis can then be adjusted by a post-treatment process ("upgrading" according to the English terminology; known to those skilled in the art) so that they are compatible with use for land, air and maritime fuels. The gases produced at the outlet of the Fischer-Tropsch reactor can also be upgraded to synthetic methane (e-methane), synthetic natural gas SNG (e-SNG) or LPG (e-LPG).

Specifically, the present invention relates to a device and a method for producing synthetic fuels from carbon dioxide and hydrogen, allowing improved production of products of interest. Advantageously, the method also makes it possible, by original thermal integration, to minimize the energy requirements for the production of said fuels.

The present invention is based on the presence of a partial oxycombustion unit (called "POX" for Partial Oxidation which is carried out with pure oxygen in substoichiometry to produce a _H2 /CO mixture). Advantageously, the gaseous effluent is returned to the inlet of the Fischer-Tropsch reaction unit, making it possible to recover additional CO in the Fischer-Tropsch reaction unit.

The invention is also based on the presence of a unit for separating the carbon dioxide contained in the gaseous effluent from the Fischer-Tropsch reaction section, the carbon dioxide separated from this gaseous effluent is recycled to the inlet of the RWGS reaction unit. Thus the gaseous effluent which can be sent to the partial oxycombustion unit essentially no longer contains carbon dioxide.

Advantageously, additional energy integration of the process makes it possible to use the heat release generated in the partial oxycombustion unit to supply calories to other units of the process, such as the RWGS reaction unit and/or the carbon dioxide capture unit, which limits the external supply of calories required.

The energy integration of the process also makes it possible to produce electricity from heat recovery. This heat converted into electricity provides energy for both water electrolysis and/or the RWGS reactor and/or the capture unit which converts carbon dioxide and hydrogen into synthesis gas.

Advantageously, hydrogen produced by water electrolysis can be used for carbon dioxide conversion, Fischer-Tropsch synthesis and post-treatment. Preferably, the hydrogen required in the process is entirely provided by a water electrolysis unit. 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 will preferably operate with low-carbon electricity, which will contribute 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 the water produced in the various stages of the process, which has the advantage of limiting the external supply of water.

Advantageously, the oxygen produced by the electrolysis of water can supply the partial oxycombustion section.

According to a first aspect, the aforementioned objects, as well as other advantages, are obtained by a device for capturing and converting a charge containing carbon dioxide, comprising the following units:
- a unit for capturing carbon dioxide from the feedstock using, for example, at least one amine-based solvent, at least one physical solvent such as, for example, based on polyethylene glycol dimethyl ether, and/or physical adsorption equipment operated by alternating temperature adsorption, and being suitable for producing an effluent rich in carbon dioxide;
- a water electrolysis unit suitable for converting water to produce oxygen and hydrogen;
- a reverse water gas conversion RWGS reaction unit adapted to treat the carbon dioxide-rich effluent with hydrogen and produce a RWGS gas enriched in carbon monoxide and water;
- a Fischer-Tropsch reaction unit adapted to: convert the RWGS gas and produce an FT effluent, and optionally generate a first water vapor, generated for example by the vaporization of water in an exchanger located inside the Fischer-Tropsch reaction unit, to supply thermal energy to the carbon dioxide capture unit;
- a first separation unit adapted to treat at least in part the FT effluent and produce: a hydrocarbon effluent, a first water effluent optionally recycled at least in part to the inlet of the water electrolysis unit, and a first gaseous effluent;
- a second separation unit adapted to treat the first gaseous effluent, produce a gaseous effluent depleted in carbon dioxide optionally recycled in part in the Fischer-Tropsch reaction unit, and send at least in part a gaseous effluent rich in carbon dioxide in the RWGS reaction unit;
- a partial oxycombustion reaction unit adapted to partially oxidize at least a portion of the carbon dioxide-depleted gaseous effluent, produce an oxycombustion effluent comprising carbon monoxide, hydrogen, carbon dioxide and water, and send the oxycombustion effluent to the Fischer-Trospch reaction unit; and
- a hydrogen reaction unit (hydrotreatment and/or hydrocracking and/or hydroisomerization unit) adapted to treat the hydrocarbon effluent and produce at least one hydrocarbon cut, for example to specifications for transport applications.

According to one or more embodiments, the partial oxycombustion reaction unit is adapted to produce heat used to supply calories to the RWGS reaction unit and/or the carbon dioxide capture unit (via a feed line), for example by heat exchange to heat the carbon dioxide-rich effluent and/or the carbon dioxide-rich gaseous effluent and/or the hydrogen, or by integrating the reaction section of the RWGS reaction unit within the chamber of the partial oxycombustion unit.

According to one or more embodiments, a portion of the hydrogen is supplied downstream of the RWGS reaction unit and upstream of the Fischer-Tropsch reaction unit.

According to one or more embodiments, a load/effluent heat exchange makes it possible to use the heat available in the RWGS effluent to preheat the gases entering the RWGS reaction unit (gases rich in _CO2 and _H2 ).

According to one or more embodiments, the device comprises a first heat exchanger adapted to generate a second water vapor by heat exchange between water and the RWGS gas which can be used for example to supply thermal energy to the carbon dioxide capture unit.

According to one or more embodiments, the device comprises a first turbine for treating at least a portion of the carbon dioxide-depleted gaseous effluent separated by the first separation unit to produce electricity.

According to one or more embodiments, a second turbine is adapted to process at least in part the first water vapor and/or the second water vapor to produce electricity.

According to one or more embodiments, electricity is used to supply calories to the RWGS reaction unit and/or the carbon dioxide capture unit and/or the water electrolysis unit.

According to one or more embodiments, electricity is used to provide calories to the regeneration section of the carbon dioxide capture unit.

According to one or more embodiments, the water electrolysis unit treats water from a make-up line and/or RWGS gas and/or FT effluent.

According to one or more embodiments, the water from the RWGS gas is at least partially or substantially completely separated by a third separation unit to be sent to the water electrolysis unit.

According to one or more embodiments, the carbon dioxide-rich effluent and/or the carbon dioxide-rich gaseous effluent are purified, separately or after mixing, before being introduced into the RWGS reaction unit. According to one or more embodiments, the RWGS gas is purified before being introduced into the Fischer-Tropsch reaction unit, upstream or downstream of the third separation unit. According to one or more embodiments, the first water effluent is purified before being introduced into the water electrolysis unit. The effluent purification steps aim to at least partially eliminate sulfur compounds, nitrogen compounds, halogens, heavy metals and transition metals. The main gas purification technologies are: adsorption, absorption, catalytic reactions.

According to a second aspect, the aforementioned objects, as well as other advantages, are obtained by a process for capturing and converting carbon dioxide, comprising the following steps:
- treat the load in a carbon dioxide capture unit to produce an effluent rich in carbon dioxide;
- converting water in a water electrolysis unit to produce oxygen and hydrogen;
- treating the carbon dioxide-rich effluent with hydrogen in a reverse water gas conversion RWGS reaction unit to produce a CO and water-enriched RWGS gas;
- convert the RWGS gas in a Fischer-Tropsch reaction unit to produce an FT effluent;
- optionally generate a first water vapor in the Fischer-Tropsch reaction unit to supply thermal energy to the carbon dioxide capture unit;
- treating the FT effluent in a first separation unit to produce at least one hydrocarbon effluent, a first water effluent and a first gaseous effluent;
- treating the first gaseous effluent in a second separation unit to produce a carbon dioxide-depleted gaseous effluent and a carbon dioxide-rich gaseous effluent which is recycled to the inlet of the RWGS section;
- partially oxidizing at least a portion of the carbon dioxide-depleted gaseous effluent after optional expansion in a turbine, in a partial oxycombustion reaction unit to produce an oxycombustion effluent comprising carbon monoxide and water;
- send the oxycombustion effluent into the FT reaction unit; and
- treating the hydrocarbon effluent in a hydrogen reaction unit to produce at least one hydrocarbon cut, for example to the specifications required for transport applications.

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 800°C and 1100°C, and more preferably still between 850°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;
- gas space velocity at the reactor inlet between 5000 NL/kg _cata /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.

According to one or more embodiments, the FT 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.

According to one or more embodiments, the partial oxycombustion reaction unit comprises at least one reactor used under at least one of the following operating conditions:
- absolute pressure between 0.1 MPa and 9 MPa, preferably between 1 MPa and 4 MPa;
- temperature between 600°C and 2000°C, preferably between 800°C and 1700°C and more preferably between 1100°C and 1500°C.

According to one or more embodiments, the second separation unit is a unit for separating carbon dioxide by membrane and/or by absorption in a solvent and/or by adsorption on a solid.

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.

List of figures

There shows a schematic representation of a device according to the present invention in which the oxycombustion effluent is in particular sent into the reaction unit FT.

Embodiments of the device according to the first aspect and the method according to the second aspect 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 device. However, it will be apparent to those skilled in the art that the device 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.

In this description, the term “comprising” 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 “comprising” includes the exclusive and closed term “consist”. Furthermore, in this description, an effluent comprising essentially 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, of compound A.

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.

The present invention can be defined as a device and a method 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 from a capture unit.

The device and the method according to the invention are notably characterized in that they comprise and use units for capturing carbon dioxide, for reverse water gas conversion (RWGS), for Fischer-Tropsch (FT) synthesis, and for hydrogen treatment (hydrotreatment, and/or hydrocracking and/or hydroisomerization) of the hydrocarbon cuts from the FT reaction unit, for separating carbon dioxide from the gaseous effluents from the Fischer-Tropsch process, and for partial oxycombustion of the gaseous hydrocarbon by-products of the process (RWGS and Fischer-Tropsch synthesis and post-treatment) after separating the carbon dioxide therefrom. Advantageously, the necessary hydrogen can be produced by a water electrolysis unit, said water being able to come from the RWGS and Fischer-Tropsch reaction units. Advantageously, the oxygen required for partial oxycombustion can be produced by electrolysis of water to feed the partial oxycombustion section, and optionally by another unit such as an air separation unit.

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 and recycle carbon dioxide from the other gaseous hydrocarbon by-products of the process. The present invention is also based on a partial oxycombustion unit adapted to treat the gaseous hydrocarbon by-products depleted in carbon dioxide to produce a gaseous effluent rich in carbon dioxide in order to improve the production of products of interest.

In addition, the heat release generated by the partial combustion can advantageously be used to supply calories to the RWGS reaction unit and/or the carbon dioxide capture unit. This supply of calories can be done for example by heat exchange with:
- the oxycombustion gas within the oxycombustion chamber; and/or
- the high temperature gaseous effluent downstream of the oxycombustion chamber; and/or
- water vapor generated by the partial oxycombustion reaction unit and/or by heat exchange with the oxycombustion gas effluent.

According to one or more embodiments, the present invention also makes it possible to minimize the amount of carbon energy external to the process and therefore the impact on the environment, by means of an original energy integration based on the use of heat at the outlet of the Fischer-Tropsch reaction unit and optionally of the RWGS reaction unit, to desorb carbon dioxide, for example complexed with amine in the carbon dioxide capture unit and more particularly in a solvent regeneration unit.

According to one or more embodiments, electricity can also be produced by a turbine powered by an effluent from the Fischer-Tropsch reaction unit and/or by water vapor (e.g. produced at the outlet of the Fischer-Tropsch reaction unit and/or the RWGS reaction unit), this electricity making it possible, for example, to supply calories to the device according to the invention, for example to the RWGS reaction unit.

Thus, the combination of carbon dioxide capture and chemical conversion units, preferably with original thermal integration, makes it possible to produce bases for fuels, and in particular for fuel for the aviation sector, while minimizing the environmental impact of the process.

Preferably, the use of the water electrolysis unit to treat the water produced by the RWGS reaction unit and/or the Fischer-Tropsch unit further helps to minimise the environmental impact of the process.

In reference to the , the device for converting carbon dioxide into liquid hydrocarbons comprises:
- a carbon dioxide capture unit 2 adapted to treat a load 1 containing carbon dioxide and produce an effluent (gaseous) rich in carbon dioxide 3 ( i.e., enriched in carbon dioxide compared to load 1);
- a water electrolysis unit 5 adapted to treat water 4 (fresh or recycled) to produce oxygen 6 and hydrogen 7;
- a RWGS 8 reaction unit adapted to at least partially convert the carbon dioxide of the carbon dioxide-rich effluent 3 into a CO-rich RWGS 9 gas (i.e., synthesis gas enriched in CO (and water) relative to the carbon dioxide-rich effluent 3);
- a Fischer-Tropsch (FT) reaction unit 13 adapted to convert the RWGS gas 9 and produce a Fischer-Tropsch (FT) effluent 14, and optionally adapted to generate a first water vapor 22, generated for example by the vaporization of water in an exchanger located inside the FT reaction unit 13, to supply thermal energy to the carbon dioxide capture unit 2;
- a first separation unit 15 adapted to treat at least in part the FT effluent 14 and produce: at least one hydrocarbon effluent 17, a first gaseous effluent 33 (off-gas), and a first water effluent 16 produced by the Fischer-Tropsch synthesis resulting from the condensation of gaseous water under the operating conditions of the Fischer-Tropsch reaction;
- a second separation unit 34 for producing a carbon dioxide-depleted gaseous effluent 18 and a carbon dioxide-rich gaseous effluent 35 from the first gaseous effluent 33, and recycling the carbon dioxide-rich gaseous effluent 35 to the inlet of the RWGS section 8;
- a partial oxycombustion reaction unit 28 adapted to oxidize at least a portion 24 of the carbon dioxide-depleted gaseous effluent 18 separated by the second separation unit 34, produce an oxycombustion effluent 29 comprising carbon monoxide and water, and send the oxycombustion effluent 29 into the FT reaction unit 13;
- a hydrogen reaction unit 20 (hydrotreatment and/or hydrocracking and/or hydroisomerization unit) adapted to treat the hydrocarbon effluent 17 with hydrogen 7 and separate at least one hydrocarbon fraction 21 comprising for example at least one of the following fractions: naphtha, gasoline, kerosene, diesel, and lubricating base;
- optionally at least one heat exchanger 31 adapted to generate a second water vapor 23 by heat exchange between water and the RWGS gas 9, which can be used for example to supply thermal energy to the carbon dioxide capture unit 2; and
- preferably a separation unit 10 adapted to treat the RWGS gas 9 to produce a water-depleted RWGS gas 12 (relative to the RWGS gas 9), sent to the FT reaction unit 13 in place of the RWGS gas 9, and send a second water effluent 11 to the water electrolysis unit 5.

Advantageously, the reaction unit FT 13 and optionally the first heat exchanger 31 are adapted to produce water vapor by heat exchange. Advantageously, the use of water vapor makes it possible to supply energy to the carbon dioxide capture unit 2, for example by regenerating an amine-based solvent (or a physical solvent) loaded with carbon dioxide in a regeneration unit of the carbon dioxide capture unit 2, or by supplying alternating temperature adsorption equipment.

To avoid unnecessarily complicating the description and the figures, it will be apparent to those skilled in the art that the water supplies to the FT reaction unit 13 and to the heat exchanger 31 for generating water vapor have not been described in detail. The same applies to the water outlet from the carbon dioxide capture unit 2.

Carbon Dioxide Capture Unit

The carbon dioxide capture unit 2 makes it possible to separate the carbon dioxide from the remainder of the feedstock 1. Such a carbon dioxide capture unit conventionally makes it possible to provide CO ₂ which can be compressed for recovery or for storage. According to one or more embodiments, the feedstock 1 comprises at least 0.04% Vol. of carbon dioxide, preferably at least 2% Vol. of carbon dioxide, very preferably at least 10% Vol. of carbon dioxide.

According to one or more embodiments, the feedstock 1 comprises or consists of combustion fumes. According to one or more embodiments, the feedstock 1 comprises gaseous effluents from at least one unit selected from the group consisting of: a refinery, an incinerator, a petrochemical unit, a chemical unit, a thermal power plant, a paper mill, an ethanol factory, a sugar factory. According to one or more embodiments, the feedstock 1 comprises gaseous effluents from a cement plant, and/or gaseous effluents from a lime production unit, and/or gaseous effluents from blast furnaces. According to one or more embodiments, the combustion fumes come from a combustion chamber (e.g. from a boiler) adapted to burn a fuel, such as coal, natural gas, fuel oil, biogas, biomass, organic waste, urban waste, with an oxidant, generally air.

According to one or more embodiments, feedstock 1 comprises or consists of biogas, natural gas, synthesis gas, refinery gas, biomass fermentation gas, cement plant gas and/or blast furnace gas.

The carbon dioxide may also be carbon dioxide present in the air. According to one or more embodiments, the load 1 comprises or consists of air. For example, the carbon dioxide capture unit 2 may comprise a direct air capture device (“Direct Air Capture” or “DAC” according to English terminology).

For the capture, several agents can be used, such as solvents and solids. According to the invention, the carbon dioxide capture unit 2 uses at least one amine-based solvent, and/or at least one physical solvent such as for example based on polyethylene glycol dimethyl ether), and/or (physical adsorption) equipment for alternating temperature adsorption.

A widely used carbon dioxide capture technology is based on the phenomenon of absorption, i.e. 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 according to 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 the fact that there is or is not a chemical reaction between the absorbed component and the solvent.

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.

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 capture of carbon dioxide on (industrial) fumes with a low carbon dioxide concentration value, typically between 3 and 15% by volume (typically in low pressure gases), washing by chemical absorption, for example using an amine solvent, for example of the alkanolamine type, is well suited.

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.

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.

Chemical absorption with amine solvents is based on acid-base equilibria, with low temperature promoting the reaction between the basic amine and the acidic carbon dioxide, and high temperature promoting the reverse reaction. Thus, amine processes, using for example an aqueous phase with 20-50% by mass of amine(s), can use two columns (not shown) in which the solvent circulates from one to the other. In the first column, called the absorber, the flow to be washed (i.e., feed 1) 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 (the “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, i.e. a carbon dioxide content for example nearly 10 times lower than the initial content in the fumes. The rich solvent is sent to the second column, called the regenerator, which operates in a similar way to a distillation column, operating at high temperature. The regenerated amine solvent (the “lean” solvent) can be sent back 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 a process scale.

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.

The carbon dioxide released from the regenerator can then be optionally compressed and recovered. According to one or more embodiments, the carbon dioxide-rich effluent 3 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 effluent 3 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 capture unit 2. According to one or more embodiments, the carbon dioxide-rich effluent 3 has a pressure of between 0.20 MPa and 4 MPa, preferably between 0.30 MPa and 3.5 MPa, very preferably between 0.4 MPa and 3 MPa, at the outlet of the carbon dioxide capture unit 2.

A key aspect of industrial fume treatment operations using solvents is the regeneration step of the separation agent. Depending on the type of absorption (physical and/or chemical), regeneration by expansion, and/or by distillation and/or by entrainment by a vaporized gas called "stripping gas" is generally considered.

One of the main limitations of the 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 capture process. The regeneration energy depends on the nature of the amines and the carbon dioxide partial pressure and is typically between 2 GJ/t and 4 GJ/t of captured carbon dioxide. New capture processes tend to reduce this energy in order to tend towards values lower than 2 GJ/t of carbon dioxide. In the context of air treatment, since carbon dioxide concentrations are very low, the energy consumed is very high, of the order of 5 GJ/t of carbon dioxide to 7.5 GJ/t of carbon dioxide.

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 flow to be treated (i.e., feed 1) becomes depleted as it advances through the solid bed, and, at the outlet, the flow no longer contains or contains little carbon dioxide. However, the solid adsorbent gradually becomes saturated and can no longer adsorb carbon dioxide. The flow 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:
– by a rise in temperature, we then speak of temperature swing adsorption (or “TSA” for “Temperature Swing Adsorption” according to Anglo-Saxon terminology); and
– 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).

The bottlenecks of TSA processes are the large amount of heat required for regeneration. The thermal integration proposed in the present invention allows this bottleneck to be lifted.

According to one or more embodiments, the solid adsorbent for capturing carbon dioxide is selected 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 adsorbents are increasingly used in the case of capturing carbon dioxide from the air. The regeneration energy of the adsorbents with physisorption in these cases, for example on zeolites, is of the order of 0.6 to 0.9 GJ/t of carbon dioxide. For amines supported on solid, the regeneration energy is between 5.4 and 7.2 GJ/t of carbon dioxide.

Advantageously, the energy required for the regeneration of the amine solvent and/or the temperature increase of the solid adsorbent can be provided at least partially by the first water vapor 22 and optionally the second water vapor 23. This supply of energy to the carbon dioxide capture unit 2 makes it possible to maximize the energy efficiency of the process.

According to one or more embodiments, the temperature of the water vapor 22 and/or 23 is at least 110°C, preferably at least 120°C, very preferably at least 130°C, for example at the outlet of the heat exchanger 31 and/or the reaction unit FT 13. According to one or more embodiments, the temperature of the water vapor 22 and/or 23 is between 110°C and 270°C, preferably between 120°C and 260°C, very preferably between 130°C and 220°C, for example at the outlet of the heat exchanger 31 and/or the reaction unit FT 13. According to one or more embodiments, the water vapor 22 and/or 23 has a pressure of between 0.1 MPa and 4 MPa, preferably between 0.1 MPa and 4 MPa. and 3.5 MPa, very preferably between 0.1 MPa and 1.7 MPa, for example at the outlet of the heat exchanger 31 and/or the reaction unit FT 13.

Water electrolysis unit

The water electrolysis unit 5 treats water 4 coming from: a make-up line and/or the optional third separation unit 10 and/or the first separation unit 15.

According to one or more embodiments, the water electrolysis unit 5 comprises a pre-treatment section adapted to extract oxygenated compounds from the water 4, for example from the first water effluent 16.

According to one or more embodiments, the water electrolysis unit 5 comprises at least one alkaline electrolyzer. Other electrolyzer technologies may be used for the water electrolysis unit, such as 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.

According to one or more embodiments, the water electrolysis unit 5 comprises at least one reactor used in at least one of the following operating conditions:
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;
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;
Solid Oxide Electrolyzer (SOE):
- 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;
Anion exchange membrane (AEM) type electrolyzer:
- 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.

According to one or more embodiments, the oxygen 6 produced by the water electrolysis unit 5 comprises between 99.0% by weight and 99.8% by weight of O ₂ (after drying).

According to one or more embodiments, the hydrogen 7 produced by the water electrolysis unit 5 comprises between 99.5% by weight and 99.999% by weight of H ₂ (after drying).

Advantageously, oxygen 6 is used for partial oxycombustion. Oxygen 6 produced by the water electrolysis unit 5 can be used for this purpose. According to one or more embodiments, oxygen 6 can be purified if necessary and compressed if the oxycombustion is carried out at a pressure higher than the pressure at which oxygen 6 is produced in the water electrolysis unit 5.

Thus, the invention makes it possible to generate heat by recovering the oxygen 6 produced by the water electrolysis unit 5 within the oxycombustion unit, the oxycombustion effluent 29 produced being able to be directly introduced into the reaction unit FT 13. Thus, part of the energy used for the electrolysis can be reintroduced into the system in the form of heat via the oxygen 6 as an energy vector. This represents an advantage over the conventional oxycombustion operation which requires producing pure oxygen from the separation of oxygen from the air, a step that is costly in terms of energy.

According to one or more embodiments, the water electrolysis unit 5 is based on a solid oxide electrolyser (SOE) technology for which at least part of the water 4 can be in the form of steam provided at least partially by the first water vapour 22 and optionally the second water vapour 23. This supply of energy to the electrolysis unit 5 makes it possible to improve the energy efficiency of the process.

RWGS Reaction Unit

The reaction unit RWGS 8 produces a RWGS 9 gas (synthesis gas) enriched in CO (and depleted in hydrogen) compared to the total effluents rich in carbon dioxide 3 and 35 and containing unconverted carbon dioxide and water. The hydrogen 7 required for the RWGS reaction comes from the water electrolysis unit 5.

According to one or more embodiments, the RWGS reaction unit 8 comprises at least one reactor used under at least one of the following operating conditions:
- temperature between 700°C and 1200°C, preferably between 800°C and 1100°C, and more preferably still between 850°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;
- gas space velocity at the reactor inlet between 5000 NL/kg _cata /h and 40000 NL/kg _cata /h;
- catalyst 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.

According to one or more embodiments, the quantity of hydrogen at the inlet of the reaction unit of RWGS 8 is adjusted so that the molar ratio H₂/CO at the outlet of the reaction unit of RWGS 8 is compatible with the need of the FT unit, i.e. 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 RWGS 9 gas has an outlet temperature from the RWGS 8 reaction unit of at least 700°C, preferably at least 750°C, very preferably at least 800°C.

According to one or more embodiments, at least a portion of the RWGS gas 9 supplies energy to the regeneration unit of the carbon dioxide capture unit 2, by means of the first heat exchanger 31 producing the second water vapor 23 by heat exchange (indirect) between water (not shown) and the RWGS gas 9, preferably directly at the outlet of the RWGS reaction unit 8.

The gas from RWGS 9 is preferably sent to the third separation unit 10.

Fischer-Tropsch reaction unit

According to the invention, in the reaction unit FT 13, the carbon monoxide and the hydrogen present in the RWGS gas 9 (preferably depleted in water) react to produce a stream comprising an effluent FT 14 comprising unconverted synthesis gas, carbon dioxide, gaseous and liquid hydrocarbon products and water.

According to one or more embodiments, the RWGS 9 gas (preferably depleted in water) sent to the FT reaction unit 13 comprises carbon monoxide and hydrogen with a molar ratio H ₂ /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 amount of hydrogen upstream (eg at the inlet) of the FT reaction unit 13 is adjusted, for example by means of an optional hydrogen supply, so that the molar ratio H ₂ /CO is as defined above.

The FT 13 reaction unit 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.

According to one or more embodiments, the FT 13 reaction unit uses one or more bubble column type 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 loss.

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.

According to one or more embodiments, the reaction unit FT 13 comprises at least one reactor used in at least one of the following operating conditions:
- temperature between 170°C and 280°C, preferably between 190°C and 260°C and preferably 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 preferably between 2.0 MPa and 3.0 MPa.

The effluent FT 14 is sent to the first separation unit 15. According to one or more embodiments, the effluent FT 14 has an outlet temperature from the reaction unit FT 13 of at least 170°C, preferably at least 190°C, very preferably at least 210°C.

According to one or more embodiments, the reaction unit FT 13 is adapted to produce the first water vapor 22 and supply thermal energy to the carbon dioxide capture unit 2. The first water vapor 22 is generated for example by the vaporization of water (not shown) in a heat exchanger located inside the reaction unit FT 13 making it possible to eliminate the calories from the Fischer-Tropsch reaction, an exothermic reaction.

First separation unit

In the first separation unit 15, at least a (first) part of the effluent FT 14 is treated to produce:
- hydrocarbon effluent 17 (depleted in water compared to effluent FT 14),
- the first gaseous effluent 33, and
- the first water effluent 16.

According to one or more embodiments, a second part of the effluent FT 14 is sent directly into the hydrogen reaction unit 20. Preferably, said second part of the effluent FT 14 is a liquid fraction, preferably containing little or no water.

At the outlet of the first separation unit 15, the hydrocarbon effluent 17 is sent to the hydrogen reaction unit 20, and the first water effluent 16 is optionally sent to the water electrolysis unit 5 by means of a first recycle line.

According to one or more embodiments, the hydrocarbon effluent 17 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 17 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 first water effluent 16 is produced from the Fischer-Tropsch synthesis resulting from the condensation of gaseous water under the operating conditions of the Fischer-Tropsch reaction.

According to one or more embodiments, the first gaseous effluent 33 comprises unconverted synthesis gas, carbon dioxide and gaseous hydrocarbons such as C1 to C4 paraffins (predominantly), C2 to C4 olefins, and C1 to C3 oxygenated compounds.

Second separation unit

In the second separation unit 34, the first effluent 33 from the first separation unit 15 is treated to produce:
- the gaseous effluent depleted in carbon dioxide 18; and
- the gaseous effluent rich in carbon dioxide 35, relative to the carbon dioxide content of the first gaseous effluent 33.

According to a first embodiment, the second separation unit 34 is a membrane separation unit. Membrane separation processes were initially not recommended for capturing carbon dioxide in post-combustion, gas-liquid absorption processes in a chemical solvent being considered the most mature and most suitable technology for performing this operation. However, the most recent technologies make it possible to separate carbon dioxide economically with 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 purity of carbon dioxide greater than 90%.

According to a second embodiment, the second separation unit 34 is a carbon dioxide capture unit based on the absorption of carbon dioxide in a solvent.

According to a third embodiment, the second separation unit 34 is a carbon dioxide capture unit based on the adsorption of carbon dioxide on a solid.

According to one or more embodiments, a (first) portion 19 of the carbon dioxide-depleted gaseous effluent 18 is sent to the FT reaction unit 13 by means of a second recycle line.

According to one or more embodiments, at least a (second) portion 24 of the carbon dioxide-depleted gaseous effluent 18 is treated by the first turbine 26 to produce electricity, the gas 27 leaving the first turbine 26 is sent to the partial oxycombustion reaction unit 28.

According to one or more embodiments, a (third) portion of the carbon dioxide-depleted gaseous effluent 18 is recycled into the RWGS reaction unit 8 (not shown) in order to be converted into synthesis gas and thus improve the mass efficiency of the process chain.

According to one or more embodiments, a (fourth) part of the gaseous effluent depleted in carbon dioxide 18 is sent to an independent synthesis gas production unit (not shown), for example of the type:
- partial oxidation (or “POx” for “Partial oxidation” according to Anglo-Saxon terminology);
- steam methane reforming (or “SMR” for “Steam Methane Reforming” in Anglo-Saxon terminology);
- autothermal reforming (or “ATR” for “Autothermal Reforming” according to Anglo-Saxon terminology);
- enhanced heat transfer reforming (or “EHTR” for “Enhanced Heat Transfer Reformer” according to Anglo-Saxon terminology).
According to one or more embodiments, said synthesis gas produced in the independent unit is recycled to the inlet or outlet of the RWGS reaction unit 8.

Partial oxycombustion reaction unit

According to the invention, at least a portion 24 of the gaseous effluent 18 is sent to the partial oxycombustion reaction unit 28, in which the hydrocarbon compounds, carbon monoxide and hydrogen present (i.e., CO, H ₂ , paraffins and olefins of 1 to 7 carbon atoms per molecule, and alcohol compounds of 1 to 3 carbon atoms per molecule) are converted at least partially into carbon dioxide and water in the presence of oxygen 6, to produce an oxycombustion gas comprising (essentially) carbon dioxide and water (and optionally CO and H ₂ if partial oxycombustion).

Total oxycombustion is a common process in the glass, cement and steel industries. The main difference with conventional combustion in the presence of air is that the fuel is burned in the presence of pure oxygen. Pure oxygen (O ₂ ) (i.e. at least 95% by weight, preferably at least 98% by weight, very preferably at least 99% by weight) can be produced by an air separation unit that removes atmospheric nitrogen (N ₂ ) from the oxidant stream or by electrolysis of water. A flue gas, called oxycombustion effluent 29, having a high concentration of carbon dioxide and water vapor (compared to the gaseous effluent 18) is then produced at the oxycombustion outlet. Oxycombustion technologies are well known to those skilled in the art, for example, reference may be made to: Int. J. Energy Res., 2017, 41, p. 1670–1708; Energies 2021, 14, p. 4333 and WO 2006/013290.

Partial oxycombustion (POX), sometimes called gasification technology, is a slightly exothermic process that can be used as an alternative to methane steam reforming to produce syngas or hydrogen. This reaction can be applied to hydrocarbons (light, heavy, asphalts, petroleum coke) but also to coal and biomass (e.g. wood, green waste, etc.). Partial oxycombustion is preferably carried out at high temperature (e.g. between 1100°C and 1500°C) and pressure (e.g. between 1 MPa and 9 MPa or more), in the presence of pure oxygen and without a catalyst. The reaction corresponds to partial oxidation itself. It is a reaction that brings the gas mixture to a temperature ranging from, for example, 1000°C to 1400°C, by preheating to, for example, 300°C. The industrial process of partial oxycombustion 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.

In the case of a partial oxycombustion operation, this will preferably be carried out at oxygen stoichiometry so as to obtain the oxidation of the mixture of hydrocarbons, hydrogen and carbon monoxide, and so as to have a maximum concentration of carbon monoxide in the oxycombustion effluent 29.

To control the adiabatic flame temperature, which can rise from 1900°C with air to 2800°C with 95% _O2 , an inert gas can be used, such as water vapor or carbon dioxide.

According to one or more embodiments, in order to have an oxycombustion temperature within the desired range, a portion of the effluent rich in carbon dioxide 3 is introduced into the partial oxycombustion unit 28. This introduction can be done directly into the partial oxycombustion unit 28 or after prior mixing with the at least one second portion 24 of the gaseous effluent 18 or after mixing with the oxygen 6. According to one or more embodiments, the oxygen flow rate is adjusted to obtain a target temperature in the oxycombustion chamber and to minimize the light hydrocarbon content in the oxycombustion effluent 29.

According to one or more embodiments, the partial oxycombustion reaction unit 28 comprises 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 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
- presence of oxygen used for combustion, with an oxygenation rate between 0.3 and 0.8, preferably between 0.4 and 0.7, 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.

According to one or more embodiments, a so-called “light” hydrocarbon cut (not shown) from the hydrogen reaction unit 20 is sent at least in part to the partial oxycombustion reaction unit 28 (not shown). According to one or more embodiments, the hydrocarbon cut comprises gaseous hydrocarbons such as C1 to C4 paraffins (predominantly), C2 to C4 olefins, and C1 to C3 oxygenated compounds.

According to one or more embodiments, the oxycombustion gas produced in the partial oxycombustion reaction unit 28 has a temperature of between 600°C and 2000°C and preferably between 800°C and 1700°C and more preferably between 900°C and 1500°C, and an absolute pressure of between 0.1 MPa and 9 MPa, preferably between 1 MPa and 4 MPa.

The oxycombustion gas produced in the partial oxycombustion reaction unit 28 being at high temperature allows, via the supply line 32, to supply part of the necessary calories to the RWGS reaction unit 8 and/or the carbon dioxide capture unit 2.

The supply of calories can be done for example by a heat exchange with water vapor produced by the partial oxycombustion reaction unit 28 and/or a heat exchange within the oxycombustion chamber of the partial oxycombustion reaction unit 28.

Advantageously, the partial oxycombustion reaction unit 28 makes it possible to convert into CO substantially all of the hydrocarbon by-products of the process, and therefore to recover them in the form of the desired products. Thus the yield of desired products of the process according to the invention is improved.

The oxycombustion effluent 29 at the outlet of the partial oxycombustion reaction unit 28 is recycled to the inlet of the FT reaction unit 13.

Hydrogen reaction unit

The hydrocarbon effluent 17 is sent to the hydrogen reaction unit 20 to undergo a hydrotreatment and/or hydrocracking and/or hydroisomerization reaction, in which one or more hydrocarbon cuts 21 can be recovered, in particular 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). A possible option is the production of paraffinic cuts, base 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 the Anglo-Saxon terminology), or waxes for various industrial applications.

According to one or more embodiments, the hydrogen reaction unit 20 comprises at least one reactor used under at least one of the following operating conditions:
- temperature between 250°C and 450°C, more preferably between 280°C and 450°C, and even more preferably between 320°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 feed at ambient temperature and pressure to the volume of the catalyst, between 0.1 h ^-1 and 10 h ^-1 , preferably between 0.2 h ^-1 and 7 h ^-1 , more preferably between 0.5 h ^-1 and 5 h ^-1 ;
- hydrogen flow rate between 100 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.

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 VIB and group VIIIB of the periodic table and at least one solid which is a Bronsted acid, i.e. a solid capable of releasing one or more protons, and optionally a binder.

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.

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 an alumina, silica-alumina, alumina-silica, silica.

According to one or more embodiments, the hydrotreatment and/or hydrocracking and/or hydroisomerization catalyst comprises at least one base metal from group VIIIB chosen from nickel and cobalt in combination with at least one metal from group VIB chosen from molybdenum and tungsten, used alone or as a mixture, and preferably used in their sulfurized form.

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 is between 0.01% and 5% by weight, preferably between 0.05% and 4% by weight and very preferably between 0.10% and 2% by weight, relative to the total weight of the catalyst.

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 VIB in combination with at least one non-noble metal from group VIII chosen from nickel and cobalt, the content of metal from group VIB in said catalyst is comprised in oxide equivalent between 5% and 40% by weight, preferably between 10% and 35% by weight, and the content of metal from group VIIIB in said catalyst is comprised in oxide equivalent between 0.5% and 15% by weight, preferably between 1% and 10% by weight, preferably between 1% and 8% by weight, and very preferably between 1.5% and 6% by weight, relative to the total weight of the catalyst.

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.

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.

Third separation unit

In the third separation unit 10, the RWGS gas 9 is treated, for example by condensation, to produce the water-depleted RWGS gas 12 (compared to the RWGS gas 9) and to recycle, for example, the second water effluent 11 to the water electrolysis unit 5.

According to one or more embodiments, the water-depleted RWGS gas 12 comprises less than 1 mol% water, preferably less than 0.5 mol% water, most preferably less than 0.25 mol% water.

The water-depleted RWGS gas 12 is sent to the FT reaction unit 13.

Turbine

In reference to the , according to one or more embodiments, the present invention makes it possible to recover energy in the form of electricity by means of at least one turbine 26.

According to one or more embodiments, the first turbine 26 is adapted to treat at least a portion 24 of the gaseous effluent depleted in carbon dioxide 18 to produce electricity.

According to one or more embodiments, a second turbine (not shown) is adapted to process at least in part the first water vapor 22 and/or the second water vapor 23 to produce electricity (not shown).

According to one or more embodiments, electricity is used to supply calories to the RWGS reaction unit 8 and/or to the carbon dioxide capture unit 2 and/or to the water electrolysis unit 5. According to one or more embodiments, electricity 25 is used to supply calories to the RWGS reaction unit 8. According to one or more embodiments, electricity 25 can be used to power an electric furnace for preheating the charge of the RWGS reaction unit 8.

Carbon dioxide separation unit

According to one or more embodiments, the device further comprises a unit for separating carbon dioxide and optionally methane (not shown), compounds potentially present in the RWGS gas 9. Advantageously, the carbon dioxide can be recycled into the RWGS reaction unit 8.

According to one or more embodiments, the carbon dioxide separation unit is arranged between the RWGS reaction unit 8 and the FT reaction unit 13. Advantageously, the size of the FT reaction unit 13 can thus be reduced.

According to one or more embodiments, the carbon dioxide separation unit is arranged at the outlet of the reaction unit FT 13.

Additional oxycombustion unit

According to one or more embodiments, the oxygen 6 from the water electrolysis unit is recovered in an additional oxycombustion unit (partial or total oxidation), for example to convert the methane formed present in the RWGS 9 gas separated by the carbon dioxide separation unit.

Effluent purification units

According to one or more embodiments, the carbon dioxide-rich effluent 3 and/or the carbon dioxide-rich gaseous effluent 35 are purified, separately or after mixing, before being introduced into the RWGS reaction unit 8. According to one or more embodiments, the RWGS gas 9 is purified before being introduced into the FT reaction unit 13, upstream or downstream of the third separation unit 10. According to one or more embodiments, the first water effluent 16 is purified before being introduced into the water electrolysis unit 5. The effluent purification steps 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.

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 D.R. 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 IUPAC classification; group VIB according to the CAS classification corresponds to the metals of column 6 according to the new IUPAC classification.

The various examples concern sequences, in accordance or not with the invention, the objective of which is to produce a hydrocarbon cut from fumes containing 21% by weight of carbon dioxide. The flow rate of fumes to be treated is 3641 kg/h for all the examples.

Example 1 not in accordance with the invention

Example 1 illustrates the operation of the chain with the recovery of part 24 of the carbon dioxide-depleted gaseous effluent 18 to an air combustion unit in order to generate heat for the RWGS reaction unit 8. The carbon dioxide-depleted gaseous effluent 18 comes from the second separation unit 34, making it possible to eliminate a part of the carbon dioxide from the effluent 33 coming from the first separation unit 15. The carbon dioxide-rich gaseous effluent 35 is directed to the RWGS reaction unit 8. Part 24 of the carbon dioxide-depleted gaseous effluent 18 is directed to the combustion unit. The combustion effluent from the combustion unit is directed to the carbon dioxide capture unit 2.

The flue gas flow rate feeding the carbon dioxide capture unit 2 is 3641 kg/h to which must be added the flue gas flow rate of the combustion effluent from the combustion unit, which gives a total flow rate of load 1 of 5332 kg/h. The flow rate of the carbon dioxide-rich effluent 3 from the carbon dioxide capture unit 2 is mixed with the carbon dioxide-rich gaseous effluent 35, and their total flow rate amounts to 1352 kg/h sent to the RWGS reaction unit 8.

1403 kg/h of water 4 feeds the water electrolysis unit 5 of which 709 kg/h is fresh water. The electricity consumption of the water electrolysis unit 5 is 6.6 MWe.

The amount of first water vapor 22 generated by the FT reaction unit 13 is 1377 kg/h. The heat exchanger 31 generates 1332 kg/h of second water vapor 23 out of the 2392 kg/h required for the operation of the carbon dioxide capture unit 2 and the second separation unit 34. The steam requirements of the reboiler of the carbon dioxide capture unit 2 and the second separation unit 34 are covered.

The production of hydrocarbon cut 21 is 186 kg/h.

Table 1 summarizes the inlet and outlet flow rates of the process units.

- Entrance Exit - 3+35 4 6 11 16 24 21 Flow rate in kg/h 1352 1403 1273 377 317 601 186

Needs:
- consumption of water electrolysis unit 5: 6.6 MWe;
- heat consumed by the RWGS 8 reaction unit at 864°C: 0.2 MWth;
- heat requirement to preheat the load (3+35+7) of the RWGS unit to 864°C: 0.8 MWth;
- steam at the reboiler of carbon dioxide capture unit 2: 2002 kg/h;
- steam in the reboiler of the second separation unit 34: 390 kg/h.

Energy recovery:
- heat released by the combustion reaction unit in air at 1200°C (with an excess of air of 20%): 0.56 MWth;
- heat recovered during cooling of the fumes at the outlet of the combustion reaction unit in air from 1200°C to 150°C: 0.7 MWth (to partially preheat the load (3+35+7) at the inlet of unit 8);
- steam produced at heat exchanger 31: 1332 kg/h;
- steam produced in the FT 13 reaction unit: 1377 kg/h;
- electricity production at the first turbine 26: 3.5 kWe.

Example 2 in accordance with the invention

Example 2 illustrates the operation of the sequence with the recovery of part 24 of the carbon dioxide-18-depleted gaseous effluent to the oxygen partial oxidation reaction unit 28 in order to generate heat for the RWGS reaction unit 8. The carbon dioxide-18-depleted gaseous effluent comes from the second separation unit 34, making it possible to eliminate part of the carbon dioxide from the effluent 33 coming from the first separation unit 15. The carbon dioxide-rich gaseous effluent 35 is directed to the RWGS reaction unit 8. Part 24 of the carbon dioxide-18-depleted gaseous effluent is directed to the oxygen partial oxidation reaction unit 28. The partial oxycombustion effluent 29 from the oxygen partial oxidation reaction unit 28 is directed to the RWGS reaction unit 8. Fischer-Trospch 13.

The total flow rate of flue gases feeding the carbon dioxide capture unit 2 is 3641 kg/h. The addition of the carbon dioxide-rich gaseous effluent 35 (from the second separation unit 34) to the carbon dioxide-rich effluent 3 makes it possible to achieve a CO ₂ flow rate at the inlet of the RWGS reaction unit 8 of 987 kg/h.

The partial oxycombustion effluent 29 is mixed with the RWGS gas 9 from the RWGS reaction unit 8 before the heat exchanger 31.

1230 kg/h of water 4 feeds the water electrolysis unit 5 of which 504 kg/h is fresh water. The electricity consumption of the water electrolysis unit 5 is 5.4 MWe.

The quantity of first water vapor 22 generated by the reaction unit FT 13 is 1880 kg/h. The heat exchanger 31 generates 1660 kg/h (23) of second water vapor 23 out of the 1355 kg/h required for the operation of the unit 2 and 32. The steam requirements of the reboiler of the carbon dioxide capture unit 2 and of the unit 32 are covered.

The flow rate of oxygen 6 at the inlet of the partial oxidation reaction unit with oxygen 28 is 126 kg/h, which corresponds to an oxygenation rate defined as the ratio of the molar flow rate of injected oxygen to the theoretical oxygen flow rate for complete oxidation of all hydrocarbons present (methane, ethane, propane, butane, etc.) of 0.52. This ratio was adjusted in order to convert all the methane and limit or even avoid the conversion of other molecules, in particular CO.

With the same quantity of fumes treated as example 1, the production of hydrocarbon cut is 230 kg/h instead of the previous 186 kg/h.

Table 2 summarizes the inlet and outlet flow rates of the process units.

- Entrance Exit - 3+35 4 27 6 11 16 21 Flow rate in kg/h 987 1230 390 1116 336 390 230

Needs:
- consumption of water electrolysis unit 5: 5.4 MWe;
- heat consumed by the RWGS 8 reaction unit at 864°C: 0.17 MWth;
- heat requirement to preheat the load (3+35+7) of the RWGS unit to 864°C: 0.7 MWth;
- steam at the reboiler of carbon dioxide capture unit 2: 1025 kg/h;
- steam at the reboiler of the carbon dioxide capture unit 32: 330 kg/h.

Energy recovery:
- heat released by the partial oxidation reaction unit with oxygen 28 at 1200°C: 0.00 MWth;
- steam produced at heat exchanger 31: 1660 kg/h;
- steam produced in the FT 13 reaction unit: 1880 kg/h;
- electricity production at the first turbine 26: 4.3 kWe.

Claims (15)

Device for capturing and converting a charge containing carbon dioxide, comprising the following units:
- a carbon dioxide capture unit (2) from the feedstock (1) adapted to produce an effluent rich in carbon dioxide (3);
- a water electrolysis unit (5) adapted to convert water (4) to produce oxygen (6) and hydrogen (7);
- a reverse water gas conversion reaction unit RWGS (8) adapted to treat the carbon dioxide-rich effluent (3) with hydrogen (7) and produce a RWGS gas (9) enriched in carbon monoxide and water;
- a Fischer-Tropsch reaction unit (13) adapted to: convert the RWGS gas (9) and produce an FT effluent (14);
- a first separation unit (15) adapted to at least partially treat the FT effluent (14) and produce: a hydrocarbon effluent (17), a first water effluent (16), and a first gaseous effluent (33);
- a second separation unit (34) adapted to treat the first gaseous effluent (33) and produce a gaseous effluent depleted in carbon dioxide (18) and send at least in part a gaseous effluent rich in carbon dioxide (35) into the RWGS reaction unit (8);
- a partial oxycombustion reaction unit (28) adapted to partially oxidize at least a portion of the carbon dioxide-depleted gaseous effluent (18), produce an oxycombustion effluent (29) comprising carbon monoxide and water, and send the oxycombustion effluent (29) to the Fischer-Trospch reaction unit (13); and
- a hydrogen reaction unit (20) adapted to treat the hydrocarbon effluent (17) and produce at least one hydrocarbon cut (21). Device according to claim 1, in which the partial oxycombustion reaction unit (28) is adapted to produce heat used to supply calories to the RWGS reaction unit (8) and/or the carbon dioxide capture unit (2). Apparatus according to claim 1 or claim 2, wherein the partial oxycombustion reaction unit (28) is adapted to produce heat used to supply calories to the RWGS reaction unit (8). Apparatus according to any preceding claim, wherein the partial oxycombustion reaction unit (28) is adapted to heat the carbon dioxide-rich effluent (3) and/or the carbon dioxide-rich gaseous effluent (35) and/or the hydrogen (7), or to integrate the reaction section of the RWGS reaction unit (8) within an oxycombustion chamber. Device according to any one of the preceding claims, in which the Fischer-Tropsch reaction unit (13) is adapted to generate a first water vapor (22) to supply thermal energy to the carbon dioxide capture unit (2). Device according to any one of the preceding claims, comprising a first heat exchanger (31) adapted to generate a second water vapor (23) by heat exchange between water and the RWGS gas (9). Device according to any one of the preceding claims, comprising a first turbine (26) for treating at least in part the carbon dioxide-depleted gaseous effluent (18) to produce electricity. Device according to claim 7, wherein the electricity is used to supply calories to the RWGS reaction unit (8) and/or the carbon dioxide capture unit (2) and/or the water electrolysis unit (5). Apparatus according to any preceding claim, wherein the water electrolysis unit (5) treats water from a make-up line and/or RWGS gas (9) and/or FT effluent (14). Device according to any one of the preceding claims, wherein the water from the RWGS gas (9) is at least partly separated by a third separation unit (10) to be sent to the water electrolysis unit (5). A process for capturing and converting carbon dioxide, comprising the following steps:
- treating the load (1) in a carbon dioxide capture unit (2) to produce an effluent rich in carbon dioxide (3);
- converting water (4) in a water electrolysis unit (5) to produce oxygen (6) and hydrogen (7);
- treating the carbon dioxide-rich effluent (3) with hydrogen (7) in a reverse water gas conversion RWGS reaction unit (8) to produce a CO and water-enriched RWGS gas (9);
- converting the RWGS gas (9) in a Fischer-Tropsch reaction unit (13) to produce an FT effluent (14);
- treating the FT effluent (14) in a first separation unit (15) to produce at least one hydrocarbon effluent (17), a first water effluent (16) and a first gaseous effluent (33);
- treating the first gaseous effluent (33) in a second separation unit (34) to produce a gaseous effluent rich in carbon dioxide (35) and a gaseous effluent depleted in carbon dioxide (18);
- sending at least part of the carbon dioxide-rich gaseous effluent (35) into the RWGS reaction unit (8);
- partially oxidizing at least a portion (24) of the carbon dioxide-depleted gaseous effluent (18), after optional expansion in a turbine (26), in a partial oxycombustion reaction unit (28) to produce an oxycombustion effluent (29) comprising carbon monoxide and water;
- sending the oxycombustion effluent (29) into the FT reaction unit (13); and
- treating the hydrocarbon effluent (17) in a hydrogen reaction unit (20) to produce at least one hydrocarbon cut (21). The method of claim 11, wherein the RWGS reaction unit (8) comprises at least one reactor used under at least one of the following operating conditions:
- temperature between 700°C and 1200°C, preferably between 800°C and 1100°C, and more preferably still between 850°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;
- gas space velocity at the reactor inlet between 5000 NL/kg _cata /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. A method according to claim 11 or claim 12, wherein the FT reaction unit (13) 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. A method according to any one of claims 11 to 13, wherein the partial oxycombustion reaction unit (28) comprises at least one reactor used under at least one of the following operating conditions:
- absolute pressure between 0.1 MPa and 9 MPa, preferably between 1 MPa and 4 MPa;
- temperature between 600°C and 2000°C, preferably between 800°C and 1700°C and more preferably between 1100°C and 1500°C. Method according to any one of claims 11 to 14, in which the second separation unit (34) is a unit for separating carbon dioxide by membrane and/or by absorption in a solvent and/or by adsorption on a solid.