Reverse water-gas shift method with individual heating of the supply flow

Abstract

The present invention relates to a method and device for producing syn gas by CO2 conversion, comprising: heating CO2(1) and H2(2) separately in a heating section (3) to produce heated CO2(11) at a first target temperature of 700°C to 1100°C and heated H2(12) at a second target temperature of 700°C to 1100°C; mixing the heated CO2 and heated H2 to produce a mixture(4) at a third target temperature greater than 760°C and less than 1100°C; introducing the heated CO2 and heated H2 into a reverse water-gas shift unit(7) before or after mixing; and processing the mixture in the reverse water-gas shift unit to produce a CO-enriched reverse water-gas shift gas(8).

Description

Technical Field

[0001] The present invention mainly relates to a method for producing synthesis gas (''syngas'') composed mainly of carbon monoxide (CO) and optionally hydrogen (H2) through a reaction between a stream containing carbon dioxide (CO2) and optionally carbon monoxide and a stream containing hydrogen.

[0002] Syngas can in that case be used to produce alcohols, especially methanol, or paraffinic hydrocarbons, such as synthetic fuels, namely gasoline, kerosene, gas oil, and / or other hydrocarbon products, such as naphtha, or lubricant bases of very high quality (essentially free of sulfur, aromatic compounds, and nitrogen).

Background Art

[0003] The use of the reverse water gas shift (RWGS) process to convert a mixture of carbon dioxide and hydrogen into syngas containing carbon monoxide and optionally H2 is known to those skilled in the art. During the RWGS reaction, carbon dioxide reacts with hydrogen to produce carbon monoxide and water (H2O): CO2 + H2 ⇔ CO + H2O. A mixture of carbon monoxide and hydrogen can be obtained by the action of excess hydrogen or by adding further hydrogen at the outlet of the reactor, and after condensation of the water, a mixture containing carbon monoxide, hydrogen and optionally unreacted carbon dioxide is obtained.

[0004] The reverse water-gas shift reaction is a reversible and endothermic reaction, which is favorable at high temperatures. In thermodynamic equilibrium, depending on the pressure and H2 / CO2 ratio, the conversion rate of carbon dioxide can reach 60% to 80% at temperatures of 800°C to 1000°C. Hydrogen can also react with carbon dioxide and / or carbon monoxide to produce methane (CH4): CO2 + 4H2 ⇔ CH4 + 2H2O; CO + 3H2 ⇔ CH4 + H2O. These reactions are exothermic and therefore unfavorable at high temperatures, but are facilitated by high hydrogen partial pressure. These reactions leading to methane formation consume large amounts of hydrogen. If the goal is to produce syngas for the production of synthetic fuels or methanol, it is necessary to limit the amount of methane present in the syngas and maximize the amount of liquid hydrocarbons synthesized. Selectivity for carbon monoxide is therefore a key concern in terms of maximizing the production of liquid hydrocarbons, limiting methane production, and thus diverting consumed hydrogen towards carbon monoxide formation.

[0005] A patent application (Patent Document 1) describes a method for converting a feed gas containing carbon dioxide and hydrogen into a gaseous product containing carbon monoxide and water, the method being as follows: - The feed gas is heated to an inlet temperature exceeding 760°C (1400°F) by a preheater outside the main reactor tank, producing heated feed gas; - A preheater uses electricity to generate heat and produce preheated supply gas; - The heated feed gas is sent to the main reactor tank; - The main reactor tank is an insulated or semi-insulated tank that minimizes heat loss; - The main reactor tank contains a catalyst that converts the heated feed gas into the product gas; - The product gas leaves the main reactor at the outlet temperature, which is lower than the inlet temperature.

[0006] The applicant has found that when a mixture of flow containing hydrogen and carbon dioxide is heated in a metal-walled tube, methane is formed, and that methane formation is promoted by temperatures below 700°C and catalyzed by nickel present in high-temperature resistant metallurgy. The presence of methane in the temperature range of 400-800°C induces the phenomenon of corrosion by metal dusting (degradation of metal alloys, e.g., iron or nickel-based metal alloys, into metal dust). In particular, metal dusting is a significant localized thickness loss, which can be generalized or take the form of pitting corrosion, which leads to the decomposition of the metal via the formation of metal particles (dust) and carbides or coke on the surface, due to the diffusion of carbon into the metal.

[0007] Furthermore, hydrogen is consumed by the formation of methane. Specifically, for every mole of carbon dioxide consumed, 4 moles of hydrogen are consumed to form 1 mole of methane, while 1 mole of hydrogen is consumed to form 1 mole of carbon monoxide. The presence of methane leads to overconsumption in the electrifier to produce the required hydrogen. Moreover, the precise concentration of the mixture during heating depends on the contact time with the metal wall, which requires control at the inlet of the RWGS reactor. For example, if the unit operates at a reduced total flow rate (the "run-down phase" during operation of industrial units), the contact time increases, and even more methane is formed.

[0008] Methane can be partially converted by catalytic steam reforming in the RWGS reactor, but the catalytic reforming reaction is slower and more endothermic than the RWGS reaction. As a result, a non-negligible concentration of methane persists at the outlet of the RWGS reactor.

[0009] The object of the present invention is to solve the problems related to the uncontrolled formation of methane and corrosion due to metal dusting in the heating system of the feedstock of an RWGS reactor. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] International Publication No. 2021 / 225643 [Overview of the project] [Means for solving the problem]

[0011] (Summary of the invention) In the context described above, the first object of this description is to overcome the problems of the prior art and to provide a method and apparatus for improving carbon monoxide production, limiting excessive hydrogen consumption, limiting methane production, and limiting corrosion by metal dusting. The second object of this description is to enable control of the gas phase composition at the inlet of the RWGS reactor, even when the unit is operating at a reduced total flow rate, and to enable the production of a syngas with a controlled composition.

[0012] According to the first aspect, the aforementioned objectives and other advantages are achieved by a method for producing syngas through the conversion of a supplying material containing carbon dioxide, the method comprising the following steps: - A process of separately heating a flow of carbon dioxide and a flow of hydrogen in a heating section; producing a heated flow of carbon dioxide with a first target temperature of 700°C to 1100°C and a heated flow of hydrogen with a second target temperature of 700°C to 1100°C; - A process of mixing a heated flow of carbon dioxide with a heated flow of hydrogen; producing a mixture with a third target temperature above 760°C and below 1100°C: - A step of introducing a heated stream of carbon dioxide and a heated stream of hydrogen into the reverse water-gas shift RWGS reaction unit before or after the mixing step; - A step of processing the mixture in a reverse water-gas shift RWGS reaction unit; producing an RWGS gas that is enriched with carbon monoxide (and water, but with significantly reduced levels of carbon dioxide and hydrogen) compared to the mixture.

[0013] According to one or more embodiments, the heated flow of carbon dioxide (11) and the heated flow of hydrogen (12) are mixed before or after being introduced into the RWGS reaction unit (7).

[0014] According to one or more embodiments, the initial temperature of the carbon dioxide stream (1) is less than 300°C, preferably less than 250°C, preferably less than 200°C, and / or the initial temperature of the hydrogen stream (2) is less than 300°C, preferably less than 200°C, preferably less than 150°C.

[0015] According to one or more embodiments, the first target temperature is 760°C to 1100°C, preferably 780°C to 1050°C, preferably 800°C to 1050°C, and / or the second target temperature is 760°C to 1100°C, preferably 780°C to 1050°C, preferably 800°C to 1050°C.

[0016] According to one or more embodiments, the third target temperature is greater than 760°C and less than or equal to 1100°C, preferably 800°C to 1100°C, preferably 880°C to 1050°C, preferably 930°C to 1050°C, and preferably 980°C to 1050°C.

[0017] According to one or more embodiments, the heating section (3) comprises at least one first furnace (17) and / or at least one first heat exchanger (9) and is suitable for separately heating a flow of carbon dioxide (1) and a flow of hydrogen (2).

[0018] According to one or more embodiments, the mixture (4) is heated in a second furnace (5) to produce a heated mixture (6), the fourth target temperature of which is 880°C to 1050°C, preferably 930°C to 1050°C, preferably 980°C to 1050°C.

[0019] According to one or more embodiments, the first furnace (17) and / or the second furnace (5) is a furnace that is at least partially supplied by electric energy and / or fuel.

[0020] According to one or more embodiments, the heating section (3) includes at least one first heat exchanger (9) and is suitable for separately heating the carbon dioxide stream (1) and the hydrogen stream (2) by the RWGS gas (8).

[0021] According to one or more embodiments, the temperature of the RWGS gas (8) is at least 700 °C, preferably at least 750 °C, and most preferably at least 800 °C when leaving the RWGS reaction unit (7).

[0022] According to one or more embodiments, after heat exchange with the RWGS gas (8), the temperature of the heated carbon dioxide stream (11) and / or the heated hydrogen stream (12) is 760 °C or higher, preferably 780 °C or higher.

[0023] According to one or more embodiments, the heating section (3) comprises: - at least one first heat exchanger (9); suitable for separately preheating the carbon dioxide stream (1) and the hydrogen stream (2) by the RWGS gas (8), generating a preheated carbon dioxide stream (18) at a first target intermediate temperature of 80 °C to 900 °C and a preheated hydrogen stream (19) at a second target intermediate temperature of 80 °C to 900 °C; and - at least one first furnace (17); suitable for separately heating the preheated carbon dioxide stream (18) and / or the preheated hydrogen stream (19), generating a heated carbon dioxide stream (11) and a heated hydrogen stream (12).

[0024] According to one or more embodiments, the RWGS gas (8) is directly cooled at the outlet from the RWGS reaction unit (7) by at least one second heat exchanger (13) to produce cooled RWGS gas (14) having a temperature of 80°C to 800°C, preferably 150°C to 600°C, preferably 250°C to 400°C, which is then sent to at least one first heat exchanger (9) to separately preheat a stream of carbon dioxide (1) and a stream of hydrogen (2) in place of the RWGS gas (8).

[0025] According to one or more embodiments, the first target intermediate temperature of the preheated flow of carbon dioxide (18) is 80°C to 300°C or 80°C to 400°C, and the second target intermediate temperature of the preheated flow of hydrogen (19) is 80°C to 300°C or 80°C to 400°C.

[0026] According to the second aspect, the aforementioned objectives and other advantages are achieved by an apparatus for producing syngas through the conversion of a supplying material containing carbon dioxide, comprising the following steps: - Heating section; suitable for separately heating carbon dioxide and hydrogen flows, producing a heated carbon dioxide flow with a first target temperature of 700°C to 1100°C and a heated hydrogen flow with a second target temperature of 700°C to 1100°C; - Reverse water-gas shift RWGS reaction unit; suitable for processing mixtures containing heated flows of carbon dioxide and heated flows of hydrogen, producing an RWGS gas that is rich in carbon monoxide (and water, but with significantly reduced levels of carbon dioxide and hydrogen) compared to the mixture, with a third target temperature of above 760°C and below 1100°C, and the heated flows of carbon dioxide and hydrogen are mixed before or after being introduced into the reverse water-gas shift RWGS reaction unit.

[0027] Embodiments of the apparatus and method according to the aspects described above, as well as other features and advantages, will be revealed by reading the following description, which is given for illustrative purposes only and without limitation, with reference to the following drawings. [Modes for carrying out the invention]

[0028] (List of drawings) Figure 1 is a simplified schematic diagram of the method according to the present invention, in which the flow of the supply material is heated separately.

[0029] Figure 2 is a simplified schematic diagram of the method according to the present invention, in which the feedstock flows are heated separately, and then the mixture of the feedstock flows is heated.

[0030] Figure 3 is a simplified schematic diagram of the method according to the present invention, in which the feed material flow is heated separately by heat exchange with the RWGS effluent, and then the mixture of the feed material flow is heated in a furnace.

[0031] Figure 4 is a simplified schematic diagram of the method according to the present invention, in which the feed material flow is heated separately by heat exchange with the RWGS effluent, and then the feed material flow is heated separately by a furnace.

[0032] Figure 5 is a simplified schematic diagram of the method shown in Figure 4, where the RWGS spill is cooled.

[0033] (Description of the embodiment) Embodiments of the method according to the first aspect and the apparatus according to the second aspect are described in detail below. Numerous specific details are presented in the following detailed description to convey a deeper understanding of the apparatus. However, it will be apparent to those skilled in the art that the apparatus may be used without these specific details. In other cases, well-known features are not described in detail to avoid unnecessarily complicating the explanation.

[0034] In this description, the term "to comprise" is synonymous with "to include" and "to contain," and is inclusive or open, not excluding other elements not mentioned. The term "to comprise" is understood to include the exclusive and closed term "to consist of." In this description, a spill primarily comprising compound A corresponds to a spill containing at least 50% by weight of compound A. In this description, a spill containing compound A essentially or alone corresponds to a spill containing at least 95% by weight, preferably at least 98% by weight, and very preferably at least 99% by weight of compound A.

[0035] The present invention can be defined as a method and apparatus comprising a series of operations that enable the production of syngas, which consists mainly of carbon monoxide (CO), via the conversion of carbon dioxide (CO2) in the presence of hydrogen (H2). In particular, the method and apparatus for producing syngas from carbon dioxide and hydrogen makes it possible to guarantee the quality of the resulting syngas. The method and apparatus according to the present invention makes it possible to reduce the amount of methane present in the syngas.

[0036] The methods and apparatus according to the present invention are characterized in that they comprise and utilize at least one furnace and / or at least one feedstock / fluid heat exchanger and a reverse water-gas shift (RWGS) unit.

[0037] The required carbon dioxide can be supplied by a unit for separating carbon dioxide-containing flows (e.g., flue gas) or by a unit for capturing carbon dioxide (e.g., carbon dioxide present in the air).

[0038] The hydrogen required for the conversion of carbon dioxide can be produced by a unit for electrolyzing water, which can come from the effluent of the RWGS reaction unit, and possibly from a downstream unit (e.g., Fischer-Tropsch (FT) or alcohol synthesis unit). Preferably, the use of a water electrolysis unit to treat the water produced by the RWGS reaction unit can minimize the environmental impact of this method. Therefore, the method according to the present invention does not require an external supply of hydrogen, such as that produced by steam reforming of natural gas. The electrolyzer can preferably be operated with low-carbon electricity, which contributes to the renewable nature of syngas and, in that case, the hydrocarbons produced from this syngas. In addition, the water used for hydrogen production can, at least in part, originate from recycled water produced by the RWGS reaction, which has the advantage of limiting the external supply of water.

[0039] Referring to Figure 1, according to the first aspect, a method for producing syngas through the conversion of a carbon dioxide-containing feedstock includes the following steps: - A process of separately heating a flow of carbon dioxide (1) and a flow of hydrogen (2) in a heating section (3); generating a heated flow of carbon dioxide (11) with a first target temperature of 700°C to 1100°C and a heated flow of hydrogen (12) with a second target temperature of 700°C to 1100°C; - A step of mixing a heated stream of carbon dioxide (11) and a heated stream of hydrogen (12); producing a mixture (4) with a third target temperature above 760°C and below 1100°C; - A step of introducing a heated stream of carbon dioxide (11) and a heated stream of hydrogen (12) into the reverse water-gas shift (RWGS) reaction unit (7) before or after the mixing step; - A step of processing the mixture (4) in the RWGS reaction unit (7); producing RWGS gas (8); the RWGS gas (8) is richer in carbon monoxide (and water, but with significantly reduced levels of carbon dioxide and hydrogen) compared to the mixture (4).

[0040] In this application, when the carbon dioxide stream (1) (or the hydrogen stream (2)) is heated to a first (or second) temperature of 760°C or lower, the hydrogen stream (2) (or the carbon dioxide stream (1)) is heated to a second (or first) temperature of over 760°C, and the mixture (4) is understood to be at a third target temperature of over 760°C.

[0041] Figure 1 shows that the heated carbon dioxide stream (11) and the heated hydrogen stream (12) are mixed before being introduced into the RWGS reaction unit (7). It is understood that the method according to the present invention also relates to the separate introduction of the heated carbon dioxide stream (11) and the heated hydrogen stream (12) into the RWGS reaction unit (7), and then to the introduction of a mixture of the heated carbon dioxide stream (11) and the heated hydrogen stream (12).

[0042] According to one or more embodiments, the initial temperature of the carbon dioxide stream (1) (before the first step of separate heating) is less than 300°C, preferably less than 250°C, preferably less than 200°C. According to one or more embodiments, the initial temperature of the carbon dioxide stream (1) is -50°C to 300°C, preferably 0°C to 250°C, preferably 0°C to 200°C.

[0043] According to one or more embodiments, the initial temperature of the hydrogen stream (2) (before the first step of separate heating) is less than 300°C, preferably less than 200°C, preferably less than 150°C. According to one or more embodiments, the initial temperature of the hydrogen stream (2) is 10°C to 300°C, preferably 10°C to 200°C, preferably 10°C to 150°C.

[0044] According to one or more embodiments, the first target temperature is 760°C to 1100°C, preferably 780°C to 1050°C, and preferably 800°C to 1050°C. According to one or more embodiments, the second target temperature is 760°C to 1100°C, preferably 780°C to 1050°C, and preferably 800°C to 1050°C.

[0045] According to one or more embodiments, the third target temperature is greater than 760°C and less than or equal to 1100°C, preferably 800°C to 1100°C, preferably 880°C to 1050°C, preferably 930°C to 1050°C, and preferably 980°C to 1050°C.

[0046] According to one or more embodiments, the heating section (3) comprises at least one first furnace (17) suitable for separately heating a flow of carbon dioxide (1) and a flow of hydrogen (2).

[0047] With reference to Figure 2, according to one or more embodiments, for example, when the third target temperature is greater than 760°C and less than 880°C, the mixture (4) is heated in a second furnace (5) to produce a heated mixture (6) with a fourth target temperature of 880°C to 1050°C, preferably 930°C to 1050°C, preferably 980°C to 1050°C. The heated mixture (6) can be sent to the RWGS reaction unit (7) in place of the mixture (4).

[0048] According to one or more embodiments, the first furnace (17) and / or the second furnace (5) are furnaces supplied at least in part by electrical energy. According to one or more embodiments, the first / second furnace is supplied at least in part by fuel. According to one or more embodiments, the first / second furnace is supplied in a hybrid manner by electrical energy and fuel. Preferably, the first furnace (17) and / or the second furnace (5) are furnaces supplied essentially or entirely by electrical energy.

[0049] Advantageously, existing electric furnace technology makes it possible to reach the target temperature. According to one or more embodiments, the first / second electric furnace is a tube (of the technology), and each flow to be heated flows through one or more tubes, and the tubes can be heated by either a system of electrical resistors or impedance. According to one or more embodiments, the first / second electric furnace consists of electrical resistors immersed in the flow to be heated. Advantageously, the supply of thermal energy is caused either by each flow flowing through one or more metal tubes via impedance, or by the flow flowing through the metal tubes by electrical resistors that may or may not be in direct contact with the flowing flow. The metallurgy of the metal tubes can be adapted to the nature of the flow to be heated and the target temperature.

[0050] In cases where the first / second furnace is at least partially supplied by fuel, the first / second furnace is preferably supplied by an oxygen source (air and / or oxygen produced by an electrifier) ​​and by at least one of the following fuels: - Gaseous hydrocarbon effluents ("off-gas"), e.g., effluents from FT units that process RWGS gas (8), or effluents from units for hydrocracking, hydrotreatment or hydroisomerization of paraffins produced by FT units, or effluents from methanol synthesis units; and / or - Hydrogen, for example, hydrogen produced by an electrifier.

[0051] According to one or more embodiments, the hydrocarbon off-gas comprises at least one of the following elements: unconverted RWGS gas (8), carbon dioxide, gaseous hydrocarbons, e.g., C1-C4 paraffins, C2-C4 olefins, and / or C1-C3 oxygen-containing compounds. According to one or more embodiments, when the first / second furnace is supplied with hydrocarbon off-gas, the first / second furnace is a partial oxidation unit, which in particular allows to produce an effluent rich in carbon monoxide, preferably consisting essentially of carbon monoxide, but optionally containing carbon dioxide, hydrogen, and water.

[0052] With reference to Figure 3, according to one or more embodiments, the heating section (3) comprises at least one first heat exchanger (9). According to one or more embodiments, the at least one first heat exchanger (9) comprises one or more heat exchangers (e.g., a train-arranged heat exchanger) suitable for separately heating, for example, each of the flows at the outlet of the RWGS reaction unit (7) directly by heat exchange with the RWGS gas (8) to produce cooled RWGS gas (10). According to one or more embodiments, the at least one first heat exchanger (9) is suitable for heating a carbon dioxide flow (1) and a hydrogen flow (2) in parallel. For example, the RWGS gas (8) may be divided into two flows, one of which heats a carbon dioxide flow (1) by one or more heat exchangers, and the other heats a hydrogen flow (2) by another heat exchanger or other heat exchangers. According to one or more embodiments, at least one first heat exchanger (9) comprises at least one multifunctional heat exchanger, i.e., a heat exchanger suitable for heating at least two separate fluids in parallel. According to one or more embodiments, at least one first heat exchanger (9) is suitable for successively heating a flow of carbon dioxide (1) and a flow of hydrogen (2), for example, RWGS gas (8) is heated by one or more heat exchangers to heat the flow of carbon dioxide (1) and then the flow of hydrogen (2), or the flow of hydrogen (2) and then the flow of carbon dioxide (1). According to one or more embodiments, at least one first heat exchanger (9) comprises at least one plate heat exchanger (e.g., for temperatures below 400°C) and / or at least one shell-and-tube heat exchanger (e.g., for temperatures above 400°C).

[0053] According to one or more embodiments, the temperature of the RWGS gas (8) upon leaving the RWGS reaction unit (7) is lower than the third target temperature, at a minimum of 700°C, preferably at a minimum of 750°C, and very preferably at a minimum of 800°C, for example, the temperature is 800°C to 1050°C, preferably at a minimum of 800°C to 1000°C, and very preferably at a minimum of 800°C to 900°C. According to one or more embodiments, the temperature difference between the gas (mixture (4) or heated mixture (6)) entering the RWGS reaction unit (7) and the RWGS gas (8) is at a minimum of 10°C, preferably at a minimum of 40°C, and very preferably at a minimum of 50°C, for example, the temperature difference is 50°C to 200°C, preferably at a minimum of 60°C to 195°C, and very preferably at a minimum of 80°C to 190°C. It is understood that the temperature of the gas entering the RWGS reaction unit (7) is higher than the temperature of the RWGS gas (8).

[0054] According to one or more embodiments, the temperature of the heated flow of carbon dioxide (11) and / or the heated flow of hydrogen (12) is 760°C or higher, preferably 780°C or higher, after heat exchange with the RWGS gas (8).

[0055] With reference to Figure 4, according to one or more embodiments, the heating section (3) includes the following: - At least one first heat exchanger (9); suitable for separately preheating a carbon dioxide flow (1) and a hydrogen flow (2); producing a preheated carbon dioxide flow (18) with a first target intermediate temperature of 80°C to 900°C, for example, 280°C or higher, preferably 380°C or higher, and a preheated hydrogen flow (19) with a second target intermediate temperature of 80°C to 900°C, for example, 280°C or higher, preferably 380°C or higher; and - At least one first furnace (17); suitable for separately heating a preheated flow of carbon dioxide (18) and / or a preheated flow of hydrogen (19); to produce a heated flow of carbon dioxide (11) and a heated flow of hydrogen (12). It is understood that the first target intermediate temperature is lower than the first target temperature and the second target intermediate temperature is lower than the second target temperature. It is also understood that, in the embodiment shown in Figure 4, it is possible to use a second furnace (5) to heat the mixture (4) and produce the heated mixture (6) described above.

[0056] Referring to Figure 5, according to one or more embodiments, the RWGS gas (8) is cooled directly at the outlet of the RWGS reaction unit (7) by at least one second heat exchanger (13) to produce cooled RWGS gas (14). For example, at least one second heat exchanger (13) may be used to produce steam (16) from feedwater (15). According to one or more embodiments, the temperature of the cooled RWGS gas (14) (e.g., the temperature when it leaves the second heat exchanger (13)) is 80°C to 800°C, preferably 150°C to 600°C, preferably 250°C to 400°C. According to one or more embodiments, the temperature of the steam (16) (e.g., the temperature when it leaves the second heat exchanger (13)) is 120°C to 400°C, preferably 130°C to 350°C, preferably 130°C to 300°C.

[0057] Advantageously, cooled RWGS gas (14) may be used instead of RWGS gas (8) sent to the first heat exchanger (9) to preheat the carbon dioxide flow (1) and the hydrogen flow (2) separately, producing a preheated flow of carbon dioxide (18) with a first target intermediate temperature of 80°C to 300°C or 80°C to 400°C, and a preheated flow of hydrogen (19) with a second target intermediate temperature of 80°C to 300°C or 80°C to 400°C.

[0058] Advantageously, it is possible to use a first furnace (17) suitable for processing one or more feedstocks whose temperature upon entry into the first furnace (17) is 300°C or less or 400°C or less, and at least one furnace (17) is suitable for heating (separately) a preheated flow of carbon dioxide (18) and / or a preheated flow of hydrogen (19), thereby producing a heated flow of carbon dioxide (11) and a heated flow of hydrogen (12). It is also understood that, in embodiments such as those shown in Figure 5, it is possible to use a second furnace (5) which heats the mixture (4) as described above and produces a heated mixture (6).

[0059] According to one or more embodiments, the RWGS reaction unit (7) comprises at least one reactor used under at least one of the following operating conditions: - Temperature: 700℃~1200℃, preferably 800℃~1100℃, and even more preferably 850℃~1050℃; - Pressure: 0.1 MPa to 10 MPa, with a preference for 0.1 MPa to 5 MPa, and a higher preference for 0.1 MPa to 3.5 MPa; - Space velocity of gas at the reactor inlet: 2000 NL / kg cata / h~40,000NL / kg cata / h; - The catalyst is based on the elements Ni, Cu, Fe, Co, or noble metals, such as Pt, Pd, Ru, Ag, and Au. According to one or more embodiments, the catalyst for the RWGS reaction includes a support, such as a carrier based on alumina, silica, silica-alumina, or siliceous alumina. According to one or more embodiments, the catalyst is in the form of a ring or cylinder. Advantageously, the RWGS reaction unit (7) is equipped with a catalyst bed that allows for a carbon dioxide conversion rate of at least 60%, preferably at least 65%, preferably at least 67%.

[0060] According to one or more embodiments, at least one reactor of the RWGS reaction unit (7) is an adiabatic reactor. Advantageously, low heat loss, or even no heat loss, in an adiabatic reactor is ensured by any means of thermal insulation known to those skilled in the art. For example, an adiabatic reactor may be insulated via the outer surface of the metal wall of the adiabatic reactor, in this case being made of metallurgy resistant to temperature and gases containing CO, hydrogen, and water, and may be covered with an anti-coking and anti-metal dusting coating (e.g., a layer <1 mm thick) (e.g., an Al, Cr, or Si-based coating), which is then oxidized in situ to form an Al2O3 oxide layer. For example, an adiabatic reactor may be insulated via one or more layers of insulating material via the inner surface of the metal wall of the adiabatic reactor.

[0061] According to one or more embodiments, the amount of hydrogen at the inlet of the RWGS reaction unit (7) is adjusted so that the H2 / CO molar ratio at the outlet of the RWGS reaction unit (7) is suitable for the needs of a downstream FT unit (not described) or alcohol synthesis unit (not described). According to one or more embodiments, the amount of hydrogen at the inlet of the RWGS reaction unit (7) is controlled so that the H2 / CO molar ratio at the outlet of the RWGS reaction unit (7) is 0.5 to 4, preferably 1 to 3, more preferably 1.5 to 2.5. According to one or more embodiments, some of the hydrogen required for FT synthesis or alcohol synthesis may be supplied downstream of the RWGS reaction unit (7), for example, by mixing a supplement hydrogen source with the RWGS effluent ((8), (10), or (14)) before or after heat exchange with the feedstock flow of the RWGS reaction unit (7). Hydrogen may be added downstream of a water separation unit (defined below) suitable for separating water contained in the RWGS effluent, for example. Advantageously, hydrogen is added upstream of the FT unit or the alcohol synthesis unit.

[0062] According to one or more embodiments, the RWGS gas ((8), (10), or (14)), preferably cooled RWGS gas (10), is sent to a water separation unit (not described) to separate, at least partially or completely, the water present in the RWGS gas, resulting in a water-depleted RWGS gas. Advantageously, the water-depleted RWGS gas essentially contains carbon monoxide, optionally (residual) carbon dioxide, and optionally hydrogen (if hydrogen is in excess). For example, the RWGS gas may be cooled to a condensation temperature that allows for the condensation of water present in the RWGS gas.

[0063] According to one or more embodiments, the water electrolysis unit at least partially processes water separated from the RWGS gas, which is drastically depleted of water, and / or water separated from effluents from downstream units (e.g., units for the production of paraffinic hydrocarbons or alcohols) to at least partially generate a hydrogen stream (2). The water electrolysis unit may optionally process some or all of the water coming from a supply line.

[0064] According to one or more embodiments, the water electrolysis unit 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. Operating conditions (temperature, pressure, electrolyte, electrode and diaphragm / membrane properties) are in that case specific to each technology.

[0065] According to one or more embodiments, the water electrolysis unit comprises at least one reactor used under at least one of the following operating conditions: Alkaline Electrizer: - Temperature: 60℃~90℃, - Pressure: 0.1 MPa to 20 MPa, preferably 0.1 MPa to 4 MPa. - The electrolyte contains KOH. - The electrodes contain a metal alloy. - The diaphragm contains asbestos, polytetrafluoroethylene, and / or nickel oxide; Proton exchange membrane (PEM) electrifier: - Temperature: 50℃~80℃, - Pressure: 0.1 MPa to 20 MPa, preferably 1.8 MPa to 5.5 MPa. - The electrolyte contains a polymer membrane. - The electrodes contain a metal alloy; Solid oxide electrifier (SOE): - Temperature: 800℃~900℃, - Pressure: 0.1 MPa to 2 MPa, preferably 0.1 MPa to 0.5 MPa. - The electrolyte contains a ceramic (e.g., perovskite) membrane. - The electrodes contain a metal alloy; Anion exchange membrane (AEM) electrifier: - Temperature: 50℃~70℃, - Pressure: 0.1 MPa to 20 MPa, preferably 0.1 MPa to 3.5 MPa. - The electrolyte contains a polymer membrane. - The electrodes contain a metal alloy.

[0066] According to one or more embodiments, the hydrogen flow (2) generated by the water electrolysis unit contains 99.5% to 99.999% by weight of hydrogen (after drying).

[0067] According to one or more embodiments, the carbon dioxide-rich effluent (1) is purified before being introduced into the RWGS reaction unit (7). According to one or more embodiments, the carbon dioxide-rich effluent (1) is purified in the heating section (3). For example, the carbon dioxide-rich effluent (1) may be purified before or after being introduced into the first heat exchanger (9). It is preferable that the carbon dioxide-rich effluent (1) is purified before being introduced into the first furnace (17) or the second furnace (5). According to one or more embodiments, the carbon dioxide-rich effluent (1) is purified before being introduced into the heating section (3).

[0068] According to one or more embodiments, the RWGS gas (8) is purified, for example, upstream or downstream of a water separation unit located between the RWGS reaction unit (7) and the paraffinic hydrocarbon or alcohol synthesis reaction unit, before being introduced into the paraffinic hydrocarbon or alcohol synthesis reaction unit. According to one or more embodiments, the water effluent recovered by separation from the RWGS gas (8) is purified before being introduced into a water electrolysis unit.

[0069] The effluent purification process aims to at least partially remove sulfur-containing and nitrogen-containing compounds, halogens, heavy metals, and transition metals. The main techniques for purifying the gas are: adsorption, absorption, and catalytic reactions.

[0070] (Examples) (Example 1: Not conforming to the present invention - shared heating) In Example 1 (which does not conform to the present invention), 1000 kg / h of carbon dioxide and 88.6 kg / h of hydrogen are mixed at a low temperature (15°C) to produce RWGS gas with an H2 / CO ratio of 2.1. The mixture is then heated to a mixture temperature of 1000°C. The thus heated mixture is sent to the reactor of the RWGS reaction unit.

[0071] As shown in Table 1, 350.2 kg / h of carbon monoxide, 271.6 kg / h of water, and 20.6 kg / h of methane are produced at the reactor outlet. The RWGS gas also contains 393.2 kg / h of carbon dioxide and 53.0 kg / h of unconverted hydrogen.

[0072] [Table 1]

[0073] The production of 1 mole of methane consumes 3 to 4 moles of hydrogen. In other words, to produce 20.6 kg / h of methane, 7.7 kg / h to 10.3 kg / h of hydrogen is consumed. This corresponds to an additional power consumption of over 0.5 MW (compared to the case without methane production) for conventional electrifiers, such as PEM-type electrifiers, and for a total consumption of 5 MW, it generates 88.6 kg / h of hydrogen, or 10% of the power consumption.

[0074] (Example 2: Conforms to the present invention - Separate heating across the entire range) In Example 2 (which is consistent with the present invention), 1000 kg / h of carbon dioxide and 97.2 kg / h of hydrogen are supplied to the reactor of the RWGS reaction unit to produce RWGS gas with an H2 / CO ratio of 2.1. To do this, the carbon dioxide stream (1) and the hydrogen stream (2) are heated separately to reach a first target temperature of 1000°C and a second target temperature of 1000°C. The heated carbon dioxide stream (11) and the heated hydrogen stream (12) are then mixed to produce a mixture (4) with a third target temperature of 1000°C. The mixture (4) is supplied to the reactor of the RWGS reaction unit.

[0075] As shown in Table 2, 424.9 kg / h of carbon monoxide, 286.3 kg / h of water, and 5.8 kg / h of methane are produced at the reactor outlet. The RWGS gas also contains 316.5 kg / h of carbon dioxide and 64.2 kg / h of unconverted hydrogen.

[0076] [Table 2]

[0077] In this Example 2, the carbon dioxide stream (1) and the hydrogen stream (2) were heated separately to 1000°C. No reaction occurred between carbon dioxide and hydrogen below 1000°C. This indicates that the line and equipment were not degraded by metal dusting.

[0078] The production of 1 mole of methane consumes 3 to 4 moles of hydrogen. In other words, to produce 5.8 kg / h of methane, 2.2 kg / h to 2.9 kg / h of hydrogen is consumed, which corresponds to a net additional 0.15 MW of power consumption (compared to the case without methane production) for a given PEM-type electrifier, and for a total consumption of 5.5 MW, this results in 97.2 kg / h of hydrogen, or 3% of the power consumption.

[0079] In Example 2, the total electrifier consumption was 10% higher than in Example 1, and the production of RWGS gas (with an H2 / CO ratio of 2.1) was 20% higher. Therefore, it is preferable to limit the interaction between carbon dioxide and hydrogen before reaching a temperature suitable for the RWGS reaction, thereby improving carbon monoxide production, limiting excessive power consumption of the electrifier, limiting methane production, and limiting metal dusting. [Brief explanation of the drawing]

[0080] [Figure 1] This is a simplified schematic diagram of the method according to the present invention, in which the flow of the supply material is heated separately. [Figure 2] This is a simplified schematic diagram of the method according to the present invention, in which the feed streams are heated separately, and then the mixture of the feed streams is heated. [Figure 3] This is a simplified schematic diagram of the method according to the present invention, in which the feed material flow is heated separately by heat exchange with the RWGS effluent, and then the mixture of the feed material flow is heated in a furnace. [Figure 4]This is a simplified schematic diagram of the method according to the present invention, in which the feed material flow is heated separately by heat exchange with the RWGS effluent, and then the feed material flow is heated separately by a furnace. [Figure 5] Figure 4 is a simplified schematic diagram of the method, in which the RWGS outflow is cooled.

Claims

1. A method for producing syngas through the conversion of a carbon dioxide-containing feedstock, comprising the following steps: - A process of separately heating a carbon dioxide flow (1) and a hydrogen flow (2) in a heating section (3); generating a heated carbon dioxide flow (11) with a first target temperature of 700°C to 1100°C and a heated hydrogen flow (12) with a second target temperature of 700°C to 1100°C; - A step of mixing a heated stream of carbon dioxide (11) and a heated stream of hydrogen (12); producing a mixture (4) with a third target temperature above 760°C and below 1100°C: - A step of introducing a heated stream of carbon dioxide (11) and a heated stream of hydrogen (12) into the reverse water-gas shift reaction unit (7) before or after the mixing step; - A step of treating the mixture (4) in a reverse water-gas shift reaction unit (7); producing a reverse water-gas shift gas (8) enriched with carbon monoxide compared to the mixture (4).

2. The method according to claim 1, wherein a heated flow of carbon dioxide (11) and a heated flow of hydrogen (12) are mixed before being introduced into a reverse water-gas shift reaction unit (7).

3. The method according to claim 1 or 2, wherein the initial temperature of the carbon dioxide stream (1) is less than 300°C, preferably less than 250°C, preferably less than 200°C, and / or the initial temperature of the hydrogen stream (2) is less than 300°C, preferably less than 200°C, preferably less than 150°C.

4. The method according to any one of claims 1 to 3, wherein the first target temperature is 760°C to 1100°C, preferably 780°C to 1050°C, preferably 800°C to 1050°C, and / or the second target temperature is 760°C to 1100°C, preferably 780°C to 1050°C, preferably 800°C to 1050°C.

5. The method according to any one of claims 1 to 4, wherein the third target temperature is 800°C to 1100°C, preferably 880°C to 1050°C, preferably 930°C to 1050°C, and preferably 980°C to 1050°C.

6. The method according to any one of claims 1 to 5, wherein the heating section (3) comprises at least one first furnace (17) and / or at least one first heat exchanger (9), and is suitable for separately heating a flow of carbon dioxide (1) and a flow of hydrogen (2).

7. The method according to any one of claims 1 to 6, wherein the mixture (4) is heated in a second furnace (5) to produce a heated mixture (6) with a fourth target temperature of 880°C to 1050°C, preferably 930°C to 1050°C, preferably 980°C to 1050°C.

8. The method according to claim 6 or 7, wherein the first furnace (17) and / or the second furnace (5) are furnaces supplied at least in part by electrical energy and / or fuel.

9. The method according to any one of claims 1 to 8, wherein the heating section (3) comprises at least one first heat exchanger (9) and is suitable for separately heating a flow of carbon dioxide (1) and a flow of hydrogen (2) with a reverse water-gas shift gas (8).

10. The method according to claim 9, wherein the temperature of the reverse water-gas shift gas (8) is at least 700°C, preferably at least 750°C, and very preferably at least 800°C when it leaves the reverse water-gas shift reaction unit (7).

11. The method according to claim 9 or 10, wherein, after heat exchange with the reverse water-gas shift gas (8), the temperature of the heated flow of carbon dioxide (11) and / or the heated flow of hydrogen (12) is 760°C or higher, preferably 780°C or higher.

12. The heating section (3) comprises the following, according to any one of claims 1 to 11: - At least one first heat exchanger (9); suitable for separately preheating a carbon dioxide flow (1) and a hydrogen flow (2) with a reverse water-gas shift gas (8); producing a preheated flow of carbon dioxide (18) with a first target intermediate temperature of 80°C to 900°C and a preheated flow of hydrogen (19) with a second target intermediate temperature of 80°C to 900°C; and - At least one first furnace (17); suitable for separately heating a preheated flow of carbon dioxide (18) and / or a preheated flow of hydrogen (19); producing a heated flow of carbon dioxide (11) and a heated flow of hydrogen (12).

13. The reverse water-gas shift gas (8) is directly cooled at the outlet of the reaction unit (7) by at least one second heat exchanger (13) to produce cooled reverse water-gas shift gas (14) having a temperature of 80°C to 800°C, preferably 150°C to 600°C, preferably 250°C to 400°C, and the cooled reverse water-gas shift gas (14) is sent to at least one first heat exchanger (9) to separately preheat the carbon dioxide stream (1) and the hydrogen stream (2) in place of the reverse water-gas shift gas (8). The method according to claim 12.

14. The method according to claim 13, wherein the first target intermediate temperature of the preheated flow of carbon dioxide (18) is 80°C to 300°C or 80°C to 400°C, and the second target intermediate temperature of the preheated flow of hydrogen (19) is 80°C to 300°C or 80°C to 400°C.

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