Process for producing and passing hydrogen and oxygen streams to reverse water gas shift reactor

Abstract

There is described a method of generating a hydrogen stream and an oxygen stream and passing the hydrogen stream and the oxygen stream to a reverse water-gas shift reactor, the method comprising: providing a water stream to an electrolysis system configured to form: a hydrogen stream at a first pressure and an oxygen stream at a second pressure; the hydrogen stream, the carbon dioxide stream, and the oxygen stream are passed to the reverse water gas shift reactor, wherein the first pressure is lower than the second pressure.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of generating a hydrogen stream and an oxygen stream and delivering the hydrogen stream and the oxygen stream to a reverse water gas shift reactor. BACKGROUND

[0002] It is known to generate liquid hydrocarbons by performing a Fischer-Tropsch reaction on a synthesis gas comprising hydrogen and carbon monoxide. In order to increase the carbon monoxide content of the gas fed to the Fischer-Tropsch reaction to a beneficial level, it is useful to perform a reverse water gas shift reaction on a carbon dioxide stream with hydrogen gas to convert at least some of the carbon dioxide and hydrogen gas to carbon monoxide and water.

[0003] Reverse water gas shift reactors are known. Such reactors comprise a reverse water gas shift vessel containing a burner and optionally a fixed bed of reverse water gas shift catalyst. The reactor is fed with a hydrogen, carbon dioxide and oxygen stream, the oxygen stream combusting a portion of the hydrogen, thereby generating heat for the endothermic reverse water gas shift reaction.

[0004] WO2022079407A1 describes a method of synthesising hydrocarbons from synthesis gas. The method comprises using a water electrolyser to generate hydrogen and oxygen as feed to a synthesis gas unit containing a reverse water gas shift reactor. For every one oxygen molecule generated by electrolysis, two hydrogen molecules are also generated. A typical reverse water gas shift reaction uses an excess of hydrogen gas compared to oxygen on a molar basis. The nature of the reverse water gas shift reactor means that the oxygen feed experiences a higher pressure drop on entering the reactor compared to the hydrogen feed. Therefore, the oxygen feed needs to be supplied at a higher pressure (typically about 5 bar higher) than the hydrogen feed. This can be achieved by generating the hydrogen and oxygen in the electrolyser at the lower required hydrogen pressure and then using an oxygen compressor to increase the pressure of the oxygen to the higher required oxygen pressure before delivering the oxygen to the reverse water gas shift reactor. However, the use of an oxygen compressor increases the CAPEX and OPEX of the method and has safety implications. Alternatively, the hydrogen and oxygen can be generated in the electrolyser at the higher required oxygen pressure, with the hydrogen being reduced in pressure to the lower required hydrogen pressure before being delivered to the reverse water gas shift reactor. However, reducing the pressure of a large hydrogen stream reduces the efficiency of the method.

[0005] The present invention seeks to address at least some of the problems associated with the prior art or at least provide a commercially acceptable alternative solution thereto. SUMMARY

[0006] One aspect of the present disclosure relates to a method of generating a hydrogen stream and an oxygen stream and delivering the hydrogen stream and the oxygen stream to a reverse water gas shift reactor, the method comprising:

[0007] A water flow is supplied to the electrolysis system, which is configured to form:

[0008] The hydrogen gas flow under the first pressure, and

[0009] Oxygen flow under the second pressure;

[0010] The hydrogen stream, carbon dioxide stream, and oxygen stream are fed into the reverse water-gas shift reactor.

[0011] The first pressure is lower than the second pressure. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating a first embodiment of the method according to the present invention;

[0013] Figure 2 These are illustrations of the second and third embodiments of the method according to the present invention. Detailed Implementation

[0014] This disclosure relates to a method for generating a hydrogen stream and an oxygen stream and feeding the hydrogen stream and the oxygen stream to a counter-current gas shift reactor, the method comprising:

[0015] A water flow is supplied to the electrolysis system, which is configured to form:

[0016] The hydrogen gas flow under the first pressure, and

[0017] Oxygen flow under the second pressure;

[0018] The hydrogen stream, carbon dioxide stream, and oxygen stream are fed into the reverse water-gas shift reactor, wherein the first pressure is lower than the second pressure.

[0019] This method can be performed using an electrolysis system comprising a single electrolysis unit, the single electrolysis unit including a single type of electrolytic cell providing a hydrogen flow at a first pressure and an oxygen flow at a second pressure. The single type of electrolytic cell can include multiple electrolysis sub-units, each operating in the same manner to perform electrolysis. Preferably, the method is performed using an electrolysis system including a first electrolysis unit and a second electrolysis unit, each electrolysis unit including one or more electrolytic cells. Therefore, the present invention includes a method comprising:

[0020] Provide the first and second water flows;

[0021] The first water flow is sent to the first electrolysis unit to form a first oxygen flow and a first hydrogen flow at a first pressure;

[0022] The second water flow is sent to the second electrolysis unit to form a second hydrogen flow and a second oxygen flow under a second pressure;

[0023] The first hydrogen gas stream and the second hydrogen gas stream are combined to form a combined hydrogen gas stream; and

[0024] The combined hydrogen stream, carbon dioxide stream, and second oxygen stream are fed into the reverse water-gas shift reactor.

[0025] Unless expressly indicated otherwise, each aspect or embodiment as defined herein may be combined with any other aspect or embodiment. Specifically, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

[0026] Advantageously, the method of the present invention avoids the need to compress the oxygen stream before it is delivered to the reverse water-gas shift reactor. This improves the efficiency and safety of the method. Furthermore, there is no need to reduce the pressure of the hydrogen stream before it is delivered to the reverse water-gas shift reactor. Therefore, the efficiency of the method can be increased.

[0027] The countercurrent water-gas shift reactor is known in the art. During the countercurrent water-gas shift reaction, carbon dioxide and hydrogen are converted as follows:

[0028]

[0029] WO2022079408A1 discloses a typical reverse-flow gas shift reactor. This reactor typically converts a portion of carbon dioxide and a portion of hydrogen into carbon monoxide and water. It should be understood that not all hydrogen is converted. This is because the resulting syngas needs to contain hydrogen to undergo, for example, a subsequent Fischer-Tropsch reaction. A typical reverse-flow gas shift reactor may comprise a refractory-lined long-neck forged vessel. The feed gas is typically introduced into the combustion zone via a distributor to ensure uniform flow and thus uniform mixing. At the top of the vessel in the combustion zone, oxygen is added to the hydrogen-rich environment through burner nozzles. The long-neck design and the use of a high-momentum oxidizer jet burner provide the catalyst bed with a mixed, combusting, and homogeneous feed gas. This ensures good reaction energy and physical stability of the catalyst. The high mass and momentum transfer rates generate a relatively short, well-defined flame front, which minimizes radiation returning to the burner tip, thus preventing overheating. The lower section of the reactor comprises a fixed catalyst bed in which an endothermic reverse water-gas shift reaction occurs. This fixed catalyst bed is situated above a refractory dome, commonly referred to as a "refractory arch." The refractory arch is slotted to allow outlet gas passage, and a catalyst bed of alumina spheres is present to prevent catalyst loss through the arch slots. An internal refractory lining is used to contain the high temperatures within the reactor and is mounted within a supporting shell. The shell is enclosed in a boiler feed water jacket, which maintains the shell temperature near 100°C through water evaporation, thus removing any heat loss. Maintaining the shell temperature at 100°C minimizes thermal expansion and keeps the refractory material compressed.

[0030] The method involves supplying a water stream to the electrolyzer system. This water stream can be provided in the form of liquid water or steam.

[0031] In some arrangements, the electrolysis system comprises a single electrolysis unit including an electrolytic cell of a single type. In such an arrangement, the single electrolysis unit may include an electrolytic cell having an anode that generates an oxygen stream at a pressure higher than that of the cathode that generates the hydrogen stream. However, this arrangement may generate excess pressurized oxygen, which will need to be safely depressurized before being sent to other processes. Additionally, a single electrolytic cell configuration may result in more or larger equipment rated for higher oxygen pressures, leading to higher manufacturing costs. Therefore, the electrolysis system preferably includes a first electrolysis unit and a second electrolysis unit, each including one or more electrolytic cells, and the method includes the following steps:

[0032] Provide the first and second water flows;

[0033] The first water flow is sent to the first electrolysis unit to form a first oxygen flow and a first hydrogen flow at a first pressure;

[0034] The second water flow is sent to the second electrolysis unit to form a second hydrogen flow and a second oxygen flow under a second pressure;

[0035] The first hydrogen gas stream and the second hydrogen gas stream are combined to form a combined hydrogen gas stream; and

[0036] The combined hydrogen stream, carbon dioxide stream, and second oxygen stream are fed into the reverse water-gas shift reactor.

[0037] The method includes providing one or more, preferably a first electrolysis unit and a second electrolysis unit. Electrolysis units are known in the art. The electrolysis unit typically comprises a single type of electrolytic cell and associated auxiliary equipment. Suitable electrolysis units include, for example, alkaline electrolytic cells, polymer electrolyte membrane electrolytic cells (including proton exchange membrane electrolytic cells and anion exchange membrane electrolytic cells – also known as alkaline exchange membrane electrolytic cells), and solid oxide electrolytic cell unit electrolytic cells, wherein the membrane can be proton-conducting or oxygen-ion-conducting.

[0038] In the presence of a single electrolysis unit, a single polymer electrolyte membrane electrolyzer (such as a proton exchange membrane electrolyzer or anion exchange membrane electrolyzer) operating in differential pressure mode (where the anode operates at a higher pressure than the cathode) can be used to generate hydrogen and oxygen at the pressure required by the reverse water gas shift reactor.

[0039] In the presence of a first electrolysis unit and a second electrolysis unit, the first electrolysis unit and the second electrolysis unit can be of the same type. Alternatively, the first electrolysis unit and the second electrolysis unit can be of different types. In such an arrangement, the pressures at the anode and cathode in the electrolyzer can be the same or different, but the electrolyzer is operated to provide a flow of hydrogen and an flow of oxygen at a first pressure and a second pressure.

[0040] In the electrolysis unit, electricity is used to decompose water into hydrogen and oxygen, that is:

[0041]

[0042] The electrolysis system is preferably operated at temperatures ranging from ambient temperature to 1000°C, depending on the type of electrolysis unit used. For example, polymer electrolyte membrane electrolyzers are typically used at temperatures ranging from 20°C to 100°C, while solid oxide electrolyzer units can be used at temperatures ranging from 400°C to 1000°C, preferably from 450°C to 900°C.

[0043] The method involves feeding water into an electrolysis system to generate a hydrogen stream at a first pressure and an oxygen stream at a second pressure. To avoid the need for pressurizing the hydrogen, the first pressure is preferably the pressure at which the hydrogen stream is fed into the reverse water-gas shift reactor.

[0044] In the arrangement including a first electrolysis unit and a second electrolysis unit, there are two combined hydrogen gas flows, and a first oxygen flow and a second oxygen flow at different pressures. The first oxygen flow is not fed to the reverse water-gas shift reactor. This is because the first oxygen flow needs to be compressed before being fed to the reverse water-gas shift reactor, and the second oxygen flow provided at the higher second pressure already meets the oxygen requirements. The first oxygen flow can be formed at the first pressure or at a pressure lower than the first pressure.

[0045] In an arrangement including a first electrolysis unit and a second electrolysis unit, the method includes feeding a second water stream into the second electrolysis unit to form a second hydrogen stream at or above a first pressure and a second oxygen stream at a second pressure.

[0046] In an arrangement including a first electrolysis unit and a second electrolysis unit, the method includes merging a first hydrogen stream and a second hydrogen stream to form a merged hydrogen stream. When the first pressure is the pressure required for hydrogen to enter the reverse water-gas shift reactor, the second hydrogen stream can be depressurized to the first pressure before merging the first and second hydrogen streams. This ensures that the pressure of the merged hydrogen stream is the pressure required for hydrogen to enter the reverse water-gas shift reactor. A second oxygen stream is fed into the reverse water-gas shift reactor. The first oxygen stream can be vented to the atmosphere, used for combustion outside this process, or used as an oxidant in a separate chemical process requiring oxygen at lower pressures.

[0047] Alternatively, when using a single electrolysis unit containing a single electrolyzer type, the cathode in the electrolyzer generates all the hydrogen required for the reverse-flow gas shift reactor at a first pressure, and the anode generates the oxygen required for the reverse-flow gas shift reactor at a second pressure. Excess oxygen not sent to the reverse-flow gas shift reactor can be used for combustion outside of this method, or as an oxidant in a separate chemical process where oxygen is required or the pressure is reduced and sent outside the battery limit.

[0048] The hydrogen stream or combined hydrogen stream fed into the reverse water gas shift reactor is preferably purified in a hydrogen purification unit upstream of the reverse water gas shift reactor.

[0049] Preferably, the oxygen stream fed into the reverse water gas shift reactor is purified in an oxygen purification unit upstream of the reverse water gas shift reactor.

[0050] The purification step can be performed in an electrolysis system or electrolysis unit downstream of one or more electrolyzers to remove any water / vapor and oxygen from the hydrogen stream and water / vapor and hydrogen from the oxygen stream to prevent the potential explosive gas mixture from being carried downstream.

[0051] Alternatively or additionally, contaminants can be removed from the hydrogen and / or oxygen streams in a purification unit located downstream of the electrolysis system or electrolysis unit and upstream of the reverse water-gas shift reactor. The carbon dioxide stream fed to the reverse water-gas shift reactor can also undergo one or more purification stages.

[0052] The method involves feeding hydrogen and oxygen streams, along with carbon dioxide streams from an electrolysis system, into a reverse-flow gas shift reactor. The hydrogen stream from the electrolysis system is supplied at a pressure suitable for entry into the reverse-flow gas shift reactor.

[0053] The carbon dioxide stream can be mixed with the hydrogen stream from the electrolysis system, or it can be fed separately into the reverse water-gas shift reactor.

[0054] The first pressure of hydrogen entering the reverse water-gas shift reactor from the electrolysis system is lower than the second pressure of oxygen entering the reverse water-gas shift reactor from the electrolysis system, for example, at least 1 bar lower.

[0055] In a preferred embodiment, the reverse water gas shift reactor is a catalytic reverse water gas shift reactor. The use of a catalyst can increase the rate and / or yield and / or selectivity of the reverse water gas shift reaction. In an alternative preferred embodiment, the reverse water gas shift reactor is a non-catalytic reverse water gas shift reactor.

[0056] Preferably, the reverse-flow gas shift reactor includes a reverse-flow gas shift catalyst bed downstream of the burner; a reverse-flow gas shift reactor adjacent to the burner and upstream of the catalyst bed; and an oxygen flow to the burner. This arrangement can be particularly effective for the reverse-flow gas shift reactor. Furthermore, with this arrangement, the pressure drop experienced by the oxygen flow can be significantly greater than that experienced by the hydrogen flow.

[0057] In an arrangement including a first electrolysis unit and a second electrolysis unit, the amount of hydrogen contained in the first hydrogen stream fed to the reverse water-gas shift reactor, by volume or molar, is preferably 1.1 to 12 times the amount of hydrogen contained in the second hydrogen stream fed to the reverse water-gas shift reactor. For embodiments in which hydrogen from the second electrolyzer is generated at a pressure greater than the first pressure, this results in a smaller amount of hydrogen requiring depressurization, thereby improving the efficiency of the method compared to a single electrolyzer system containing a single electrolyzer operating at a second pressure to provide hydrogen and oxygen streams.

[0058] The pressure of the hydrogen gas fed from the electrolysis system into the reverse water-gas shift reactor (first pressure) is lower than the pressure of the oxygen gas entering the reactor (second pressure). The first pressure is preferably 1 to 20 bar lower than the second pressure, more preferably 2 to 8 bar lower. This pressure difference is typical of the decompression difference experienced by the hydrogen and oxygen gas streams as they enter the reverse water-gas shift reactor.

[0059] Preferably, the first pressure is 10 bar to 55 bar, and / or the second pressure is 11 bar to 60 bar. Such pressures are required for the hydrogen and oxygen streams to enter the reverse water-gas shift reactor, respectively.

[0060] In an arrangement including a first electrolysis unit and a second electrolysis unit, where the pressure of the second hydrogen gas stream is greater than the first pressure, the method preferably further includes: reducing the pressure of the second hydrogen gas stream to the first pressure to form a reduced-pressure second hydrogen gas stream; and introducing the reduced-pressure second hydrogen gas stream into the first hydrogen gas stream to form a combined hydrogen gas stream, and then conveying the combined hydrogen gas stream to the reverse water-gas shift reactor. This ensures that the combined hydrogen gas stream enters the reverse water-gas shift reactor at the desired pressure.

[0061] The electrolysis system may include an alkaline electrolyzer, a polymer electrolyte membrane electrolyzer, or a solid oxide electrolysis unit electrolyzer. In an arrangement including a first electrolysis unit and a second electrolysis unit, the first electrolysis unit and / or the second electrolysis unit preferably includes an alkaline electrolyzer, a polymer electrolyte membrane electrolyzer, or a solid oxide electrolysis unit, more preferably an alkaline electrolyzer or a polymer electrolyte membrane electrolyzer. Such electrolyzers are known in the art. These electrolyzers are particularly suitable for generating hydrogen and oxygen streams at pressures suitable for entry into a reverse water-gas shift reactor.

[0062] In a preferred embodiment, both the first electrolytic cell and the second electrolytic cell are alkaline electrolytic cells, wherein the first electrolytic cell generates hydrogen and oxygen under a first pressure, and the second electrolytic cell generates oxygen and hydrogen under a second pressure.

[0063] In an alternative embodiment, the first and second electrolyzers can be any combination of an alkaline electrolyzer, an SOEC electrolyzer, or a polymer electrolyte membrane electrolyzer operating in balanced or differential mode. In this embodiment, the first electrolyzer generates hydrogen at a first pressure, and the second electrolyzer generates oxygen at a second pressure. In one arrangement, the first electrolysis unit includes a solid oxide electrolysis unit, and the first hydrogen stream is pressurized before being fed to the reverse water-gas shift reactor; and

[0064] The second electrolysis unit includes an alkaline electrolyzer or a polymer electrolyte membrane electrolyzer operating in a balanced pressure or differential pressure mode.

[0065] When using a solid oxide electrolysis unit, the generated hydrogen and oxygen streams can exceed 450°C and can therefore be usefully fed directly into a reverse-flow gas shift reactor. If desired, the hydrogen and / or oxygen streams can undergo one or more cooling stages to below this temperature within or downstream of the electrolysis system or unit, and upstream of the reverse-flow gas shift reactor. Cooling can be performed by heating one or more process streams, for example, by generating steam.

[0066] The electrolysis system or electrolysis unit is preferably powered by renewable energy. This makes the method more environmentally friendly.

[0067] In another aspect, the present invention provides a method for generating hydrocarbon products, the method comprising:

[0068] The method described herein is used to generate a hydrogen stream and an oxygen stream and to send the hydrogen stream and the oxygen stream to a reverse water gas shift reactor, wherein the hydrogen stream and the oxygen stream are sent to the reverse water gas shift reactor together with a carbon dioxide stream and a carbon monoxide-rich syngas is formed in the reverse water gas shift reactor.

[0069] The carbon monoxide-rich syngas is fed to the Fischer-Tropsch unit to form hydrocarbon products, tail gas, and a water-containing stream; and

[0070] Recover hydrocarbon products.

[0071] The advantages and preferred features of the first aspect also apply to this aspect.

[0072] The term "hydrocarbon product" has its usual meaning in the art. As used herein, the term can encompass substances formed from carbon and hydrogen, including those that are liquid at room temperature and pressure. Hydrocarbon products typically contain alkanes and generally contain 5 to 100 or more carbon atoms per molecule. This invention is particularly applicable to processes for synthesizing liquid hydrocarbon fuels such as gasoline, diesel, and kerosene.

[0073] In this method, hydrogen, oxygen, and carbon dioxide streams are all fed into a reverse water-gas shift reactor. The carbon dioxide stream can be any type of carbon dioxide stream. Carbon dioxide can be recovered from the combustion gases, or it can be included in or separated from a process stream such as a syngas stream or biogas stream. Carbon dioxide can also be recovered from the air or from seawater via direct air capture. The carbon dioxide stream may contain small amounts of substances other than carbon dioxide, such as carbon monoxide, hydrogen, and water.

[0074] This method involves feeding carbon monoxide-rich syngas into a Fischer-Tropsch unit to form hydrocarbon products, tail gas, and a water-containing stream. Fischer-Tropsch reactors are known in the art. The temperature of the Fischer-Tropsch reactor is preferably between 150°C and 300°C. Lower temperatures may result in unfavorable low levels of hydrocarbon products. Higher temperatures increase the energy cost of the method without a significant increase in the level of hydrocarbon products produced, and there is a risk of thermal damage to the catalyst. The Fischer-Tropsch reactor preferably contains a catalyst comprising cobalt, iron, and / or ruthenium. Such a catalyst may be particularly effective in catalyzing the Fischer-Tropsch reaction and / or enables the reaction to proceed advantageously at low temperatures and / or in high yields. The molar ratio of hydrogen to carbon monoxide in the syngas is preferably between 1.8 and 2.2, as this is close to the stoichiometric ratio of about 2 for the Fischer-Tropsch reaction.

[0075] Exhaust gas may contain one or more of C1 to C4 hydrocarbons, water, and unreacted substances such as hydrogen, carbon monoxide, and carbon dioxide.

[0076] A Fischer-Tropsch unit may include a downstream reforming unit in which hydrocarbon products from the Fischer-Tropsch reactor are typically converted into useful liquid hydrocarbon products, such as kerosene, diesel, and naphtha, as well as byproducts of liquefied petroleum gas (LPG) and non-condensable waste gas, through hydrogenation treatment with hydrogen gas.

[0077] The aqueous stream generated in the Fischer-Tropsch unit can be purified and recycled to the first and / or second aqueous streams. Alternatively or additionally, process condensate recovered from the syngas downstream of the reverse-flow gas shift reactor can be purified and recycled to the electrolysis system. This reduces the amount of water required by the method. The aqueous stream is preferably at least partially purified before being fed to the electrolysis system. For example, hydrocarbons, ammonia, and dissolved gases can be removed from the aqueous stream. Impurities such as hydrocarbons can clog the electrolysis unit and / or poison the catalyst contained in the cathode and / or anode of the electrolysis unit.

[0078] Example

[0079] Figure 1A diagram illustrating a first embodiment of the method according to the invention is shown. A single water stream 10 is fed into an electrolysis system comprising a single electrolysis unit of type 12 containing a single electrolyzer, which forms a hydrogen stream 13 at a pressure of 25 bar and a flow rate of 300 kmol / h at the cathode and an oxygen stream 14 at a pressure of 30 bar and a flow rate of 150 kmol / h at the anode. The oxygen stream 14 is split into a stream 15 at a flow rate of 120 kmol / h and a stream 16 at a flow rate of 30 kmol / h. The single electrolyzer unit comprises a polymer membrane electrolyte electrolyzer operating in differential mode (where the anode operates at a pressure greater than that of the cathode). The hydrogen stream 13, the oxygen stream 16, and the carbon dioxide stream 17 are fed into a reverse water-gas shift reactor 18. The oxygen stream 15 may undergo depressurization (upstream or downstream of the equilibrium of the facility unit) and be transported outside the boundary area. In the reverse-flow gas shift reactor 18, a portion of hydrogen 13 is combusted with oxygen 16, and a hot gas mixture containing carbon dioxide 17 is passed through a reverse-flow gas shift catalyst bed to form a synthesis gas containing carbon monoxide and hydrogen, which is recovered from the reactor 18 via line 19. The synthesis gas from line 19 is converted into hydrocarbon products in a Fischer-Tropsch unit (not shown).

[0080] Figure 2A second and third embodiment of the method according to the invention using a first electrolysis unit and a second electrolysis unit are depicted. In the second embodiment, a water stream 20 is split and fed into a first electrolysis unit 21 and a second electrolysis unit 22. The first electrolysis unit 21 forms a hydrogen stream 23 at a pressure of 25 bar and a flow rate of 240 kmol / h, and an oxygen stream 24 at a pressure of 25 bar and a flow rate of 120 kmol / h. The second electrolysis unit 22 forms another hydrogen stream 25 at a pressure of 30 bar and a flow rate of 60 kmol / h, and another oxygen stream 26 at a pressure of 30 bar and a flow rate of 30 kmol / h. Electrolysis units 21 and 22 each include one or more alkaline electrolysis cells. The hydrogen stream 25 from electrolysis unit 22 is depressurized to 25 bar (upstream or downstream of the equilibrium of the facility unit) and merged with the hydrogen stream 23 from electrolysis unit 21 to form a merged hydrogen stream 27, which is then conveyed to a reverse water-gas shift reactor 28. Oxygen stream 24 from electrolysis unit 21 may undergo depressurization (upstream or downstream of the facility unit's equilibrium) and be conveyed outside the boundary area. Oxygen stream 26 from electrolysis unit 22 is conveyed to reverse-flow gas shift reactor 28. Carbon dioxide stream 29 is also fed into the reverse-flow gas shift reactor. In the reverse-flow gas shift reactor 28, a portion of the combined hydrogen stream 27 is combusted with oxygen 26, and the hot gas mixture containing carbon dioxide 29 is passed through a reverse-flow gas shift catalyst bed to form a synthesis gas containing carbon monoxide and hydrogen, which is recovered from reactor 28 via line 30. The synthesis gas from line 30 is converted into hydrocarbon products in a Fischer-Tropsch unit (not shown).

[0081] The third embodiment differs from the second embodiment in that the electrolysis unit 21 includes an alkaline electrolyzer, a polymer electrolyte membrane electrolyzer operating in equilibrium or differential mode, or a solid oxide electrolyzer. When using a solid oxide electrolyzer, the hydrogen flow 23 may require an additional compression stage before merging with the hydrogen flow 25. If the polymer electrolyte membrane electrolyzer is used in differential mode (where the cathode operates at a higher pressure than the anode), the oxygen flow 24 may not require depressurization. Additionally, the electrolysis unit 22 may include an alkaline electrolyzer or a polymer electrolyte membrane electrolyzer operating in equilibrium or differential mode (where the anode operates at a higher pressure than the cathode). If the polymer electrolyte membrane electrolyzer is used in differential mode (where the anode operates at a higher pressure than the cathode), the hydrogen flow 25 may not require depressurization before merging with the hydrogen flow 23.

[0082] The detailed description above has been provided by way of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A method for generating a hydrogen stream and an oxygen stream and feeding the hydrogen stream and the oxygen stream to a countercurrent water gas shift reactor, the method comprising: A water flow is supplied to an electrolysis system, which is configured to form: The hydrogen gas flow under the first pressure, and Oxygen flow under the second pressure; The hydrogen stream, carbon dioxide stream, and oxygen stream are fed into the reverse water-gas shift reactor. The first pressure is lower than the second pressure.

2. The method of claim 1, wherein the electrolysis system comprises a single electrolysis unit containing a single type of electrolytic cell having an anode that generates the oxygen flow at a higher pressure than the cathode that generates the hydrogen flow.

3. The method according to claim 1, wherein the electrolysis system comprises a first electrolysis unit and a second electrolysis unit, each electrolysis unit comprising one or more electrolytic cells, the method comprising: Provide the first and second water flows; The first water flow is sent to the first electrolysis unit to form a first oxygen flow and a first hydrogen flow under the first pressure; The second water flow is sent to the second electrolysis unit to form a second hydrogen flow and a second oxygen flow under the second pressure; The first hydrogen gas flow and the second hydrogen gas flow are combined to form a combined hydrogen gas flow; and The combined hydrogen stream, carbon dioxide stream, and second oxygen stream are fed into the reverse water gas shift reactor.

4. The method according to any of the preceding claims, wherein the reverse water gas shift reactor is a catalytic or non-catalytic reverse water gas shift reactor.

5. The method according to any of the preceding claims, wherein: The reverse-flow gas shift reactor includes a reverse-flow gas shift catalyst bed downstream of the burner; The hydrogen stream is delivered to the reverse-flow gas shift reactor, which is adjacent to the burner and upstream of the reverse-flow gas shift catalyst bed; and the oxygen stream is delivered to the burner.

6. The method according to any one of claims 3 to 5, wherein the amount of hydrogen contained in the first hydrogen stream fed to the reverse water gas shift reactor is 1.1 to 12 times the amount of hydrogen contained in the second hydrogen stream fed to the reverse water gas shift reactor.

7. The method according to any of the preceding claims, wherein the first pressure is 1 bar to 20 bar lower than the second pressure, preferably 2 bar to 8 bar.

8. The method according to any of the preceding claims, wherein the first pressure is 10 bar to 55 bar, and / or the second pressure is 11 bar to 60 bar.

9. The method according to any one of claims 3 to 8, wherein the pressure of the second hydrogen gas flow is greater than the first pressure, and the method further comprises: The second hydrogen gas flow is reduced to the first pressure to form a reduced-pressure second hydrogen gas flow; as well as The depressurized second hydrogen gas flow is introduced into the first hydrogen gas flow to form the combined hydrogen gas flow, and then the combined hydrogen gas flow is conveyed to the reverse water gas shift reactor.

10. The method according to any of the preceding claims, wherein a hydrogen stream is fed into a hydrogen purification unit upstream of the reverse water gas shift reactor.

11. The method according to any of the preceding claims, wherein an oxygen stream is fed into an oxygen purification unit upstream of the reverse-flow gas shift reactor.

12. The method according to any of the preceding claims, wherein the electrolysis system comprises an alkaline electrolyzer, a polymer electrolyte membrane electrolyzer, or a solid oxide electrolysis unit electrolyzer, preferably an alkaline electrolyzer or a polymer electrolyte membrane electrolyzer.

13. The method according to claims 3 to 12, wherein the first electrolysis unit and the second electrolysis unit each comprise an alkaline electrolytic cell.

14. The method according to claims 3 to 12, wherein the first electrolysis unit and / or the second electrolysis unit comprises an alkaline electrolyzer or a polymer electrolyte membrane electrolyzer operating in a balanced pressure mode or a differential pressure mode.

15. The method according to any of the preceding claims, wherein the oxygen stream is not compressed before being conveyed to the reverse-flow gas shift reactor.

16. The method according to any one of claims 3 to 12, wherein: The first electrolysis unit includes a solid oxide electrolysis cell, and the first hydrogen gas stream is pressurized before being fed to the reverse water gas shift reactor; and The second electrolysis unit includes an alkaline electrolyzer or a polymer electrolyte membrane electrolyzer operating in a balanced pressure or differential pressure mode.

17. The method according to any of the preceding claims, wherein the electrolysis system is powered by a renewable energy source.

18. The method according to any of the preceding claims, wherein the process condensate recovered from the syngas downstream of the reverse-flow gas shift reactor is purified and recycled back to the electrolysis system.

19. A method for producing a hydrocarbon product, the method comprising: A hydrogen stream and an oxygen stream are generated, and the hydrogen stream and the oxygen stream are fed to a reverse water gas shift reactor using the method according to any of the preceding claims, so as to form carbon monoxide-rich syngas in the reverse water gas shift reactor. The carbon monoxide-rich syngas is fed to the Fischer-Tropsch unit to form hydrocarbon products, tail gas, and a water-containing stream. as well as The hydrocarbon products are recovered.

20. The method of claim 19, wherein the aqueous stream generated in the Fischer-Tropsch unit is purified and recycled to the electrolysis system.

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