Reverse water gas shift process

Abstract

Disclosed herein is a reverse water gas shift, rWGS, system comprising: a reactor configured to support a rWGS reaction; a hydrogen supply configured to supply hydrogen to the reactor; a carbon dioxide supply configured to supply carbon dioxide to the reactor, wherein the carbon dioxide supply is a separate gas supply to the reactor from the hydrogen supply; and an oxygen supply configured to supply oxygen to the reactor; wherein: the reactor is configured so that, in use, a rWGS reaction occurs in the reactor; at least some of the oxygen supplied to the reactor is converted into oxygen derived radicals in the reactor; and the oxygen derived radicals catalyse the rWGS reaction.

Description

[0001] PROCESS

[0002] FIELD

[0003] The present invention relates to the production of syngas from carbon dioxide. The syngas production may be integrated with a fuel production system.

[0004] BACKGROUND

[0005] It is commonly assumed that the greenhouse effect and the climate on earth are closely connected to human made emissions of CO2. These emissions are primarily formed by combustion of fossil coal and hydrocarbons, i.e., by generation of heat, electric power as well as use in internal combustion engines in vehicles. A desirable goal is to reduce the emission of CChto the atmosphere.

[0006] It is known art to reduce the emission of CO2 from combustion of hydrocarbons by reforming and shift technology for preparation of a mixture consisting of hydrogen and carbon dioxide. These components can be separated, where after hydrogen is used for energy generation, heat or in different types of transportation, and carbon dioxide is deposited after compression to desired pressure.

[0007] An alternative technology is to utilize syngas. Syngas is a mixture of hydrogen and CO. Syngas may be used to produce fuels, waxes and other hydrocarbons for today’s market, particularly diesel for transportation vehicles and waxes for a multitude of applications, including glues.

[0008] There is a general need to improve on known techniques for the production of hydrocarbons.

[0009] SUMMARY

[0010] Aspects of the invention are set out in the appended independent claims. Optional aspects are set out in the dependent claims. LIST OF FIGURES

[0011] Figure 1 is a schematic block diagram of a reverse water gas shift system according to a first implementation of a first embodiment;

[0012] Figure 2 is a schematic block diagram of a reverse water gas shift system according to a second implementation of the first embodiment; and

[0013] Figure 3 is a schematic block diagram of a reverse water gas shift system according to a fifth embodiment.

[0014] Figure 4 schematically shows a reactor system according to a sixth embodiment.

[0015] DESCRIPTION

[0016] Embodiments provide a system for converting carbon dioxide (CO2) into syngas. The system of embodiments may be used in a fuel generation system.

[0017] Syngas comprises carbon monoxide (CO) and hydrogen (H2). Embodiments provide a system that generates the carbon monoxide component of syngas by using the reverse(d) water gas shift reaction (rWGS / RWGS):

[0018] CO2+ H2-> co + H2O

[0019] In embodiments, an rWGS reactor receives as feed products carbon dioxide and hydrogen. The rWGS reactor converts at least some, and preferably substantially all, of the carbon dioxide and hydrogen to carbon monoxide and steam (i.e. water).

[0020] Syngas may be generated in the rWGS reactor by providing more hydrogen than required to convert the carbon dioxide to carbon monoxide. Alternatively, syngas may be generated by adding hydrogen to the output products from the rWGS reactor. The steam, and any unreacted feed products, may be removed from the output products of the rWGS reactor to generate substantially pure syngas. Alternatively, the syngas may be used together with the steam and any unreacted feed products.

[0021] The syngas may be used in any of a number of different applications. Embodiments include supplying the syngas to a Fischer-Tropsch (FT) reactor that converts the syngas into fuels. Embodiments alternatively include using the syngas in reduction processes of metal ores.

[0022] In a preferred implementation of embodiments, syngas is generated in the rWGS reactor by providing more hydrogen than required to convert the carbon dioxide to carbon monoxide. The rWGS reaction is performed at an elevated temperature and this increases the conversion of carbon dioxide to carbon monoxide.

[0023] Carbon dioxide may be the only feed product that comprises carbon. The source of carbon dioxide may be, for example, captured carbon dioxide by a carbon capture process. The rWGS reactor may be located on-site with a carbon capture process or the carbon dioxide may be transported to the rWGS reactor.

[0024] The source of hydrogen may be, for example, from a water electrolysis process that generates both hydrogen and oxygen. The electricity for the water electrolysis process may be generated by a renewable energy source, such as a hydro-electric plant. Other sources of hydrogen may include a process that generates hydrogen by steam-reforming natural gas.

[0025] Figure 1 schematically shows a system, that may be referred to as a rWGS system, according to a first implementation of a first embodiment.

[0026] The system comprises a hydrogen supply 105, a carbon dioxide supply 107, oxygen supplies 106a, 106b, a reaction product output 108 and an rWGS reactor system 101. The rWGS reactor system 101 comprises a burner 102, a gas mixing zone 103 and a reaction zone 104.

[0027] Although not shown in Figure 1, embodiments also include a heating system for heating one or more of the rWGS reactor system 101, the hydrogen supply 105, the carbon dioxide supply 107 and the oxygen supplies 106a, 106b. The heating system may be an electrical heating system, a heat exchanger, or other type of heating arrangement.

[0028] The hydrogen supply 105 is a supply of hydrogen to the burner 102 and the gas mixing zone 103. The hydrogen that is supplied to the gas mixing zone 103 is preferably fed into the gas mixing zone 103 with a high speed and in turbulent flow, or approaching turbulent flow. The turbulent flow may be generated by supplying the hydrogen with a high velocity and also forcing the hydrogen to flow through a constriction, nozzle and / or orifice as it enters the gas mixing zone 103. The turbulent flow aids the mixing of gasses in the gas mixing zone 103.

[0029] The carbon dioxide supply 107 is a supply of carbon dioxide to the gas mixing zone 103. The carbon dioxide that is supplied to the gas mixing zone 103 is preferably fed into the gas mixing zone 103 with a high speed and in turbulent flow, or approaching turbulent flow. The turbulent flow may be generated by supplying the carbon dioxide with a high velocity and also forcing the carbon dioxide to flow through a constriction, nozzle and / or orifice as it enters the gas mixing zone 103. The turbulent flow aids the mixing of gasses in the gas mixing zone 103.

[0030] The carbon dioxide supply 107 to the gas mixing zone 103 is a separate gas supply to the gas mixing zone 103 from the hydrogen supply 105. Advantageously, this avoids the risk of any reaction occurring between the hydrogen and the carbon dioxide outside of the rWGS reactor system 101. The risk of forming carbon monoxide and carbon causing corrosion and clogging in the inlet piping and equipment to the rWGS reactor system is thereby reduced.

[0031] A main oxygen supply 106a is a supply of oxygen to the burner 102. Another oxygen supply 106b, that may be an off-flow from the main oxygen supply 106a, is also arranged to supply some oxygen to the gas mixing zone 103. The oxygen supply 106b to the gas mixing zone 103 may be provided by mixing oxygen into the carbon dioxide supply 107 outside of the rWGS reactor system. An alternative embodiment to the arrangement shown in Figure 1 includes an oxygen supply directly into the gas mixing zone 103. The amount of oxygen that is mixed into the carbon dioxide supply 107 may be low, or very low. For example, the oxygen concentration in the carbon dioxide supply 107 may be less than or equal to 10 mole %, preferably less than or equal to 5 mole %, preferably less than or equal to 2 mole %, preferably less than or equal to 1 mole %. The mixture of oxygen into the carbon dioxide supply 107 is safe because there is no risk of an explosive reaction occurring between the oxygen into the carbon dioxide.

[0032] The burner 102 is arranged to support a combustion reaction between the hydrogen received from the hydrogen supply 105 and the oxygen received from the oxygen supply 106a.

[0033] The gas mixing zone 103 is arranged to mix the separately received gas streams. As described above, the hydrogen, carbon dioxide and oxygen (in low concentration) are preferably fed into the gas mixing zone 103 in turbulent flow so that the gasses in the gas mixing zone 103 are thoroughly mixed.

[0034] The reaction zone 104 is arranged to support an rWGS reaction.

[0035] The rWGS reactor system 101 may be an integrated reactor that comprises the burner 102, the gas mixing zone 103 and the reaction zone 104 as different regions within the same reactor. The same reactor therefore supports both the combustion reaction in the burner 102 and the rWGS reaction in the reaction zone 104.

[0036] The dimensions of the rWGS reactor system 101 are dependent on the specific application of the rWGS reactor system 101. The part of the burner 102 where the combustion reaction occurs is preferably separated from the part of the gas mixing zone 103 where the carbon dioxide supply 107 and / or hydrogen supply 105 are received. The separation, that is dependent on the specific application of the rWGS reactor system 101, preferably provides a high, and preferably the maximum, oxygen-radical promoted effect on the rWGS reaction. Although the separation may be any distance that achieves this, the separation may be by over 100mm, preferably by over 150mm, more preferably by over 200mm, and further preferably by over 1000mm.

[0037] The operation of the rWGS reactor system 101 is described below. The burner 102 is arranged to combust the received hydrogen and oxygen. This generates a high temperature within the rWGS reactor system 101. The gas mixing zone 103 receives hydrogen, carbon dioxide and oxygen (in low concentration) and mixes the received gasses. The gasses in the gas mixing zone 103 is heated by the combustion reaction in the burner 102.

[0038] The mixed and heated gasses in the gas mixing zone 103 flow to the reaction zone 104. The reaction zone 104 is where the rWGS reaction between the received carbon dioxide and hydrogen may mostly occur. The temperature and pressure within the gas mixing zone 103 and / or reaction zone 104 may be sufficient for at least some of the supplied oxygen to the gas mixing zone 103 to be converted into oxygen radicals. The oxygen radicals may act as a catalyst of the rWGS reaction and may substantially increase the conversion of carbon dioxide to carbon monoxide.

[0039] The separation between the part of the burner 102 where the combustion reaction occurs and the part of the gas mixing zone 103 where the carbon dioxide supply 107 and / or hydrogen supply 105 are received may advantageously increase the presence of oxygen radicals in the feed products to the rWGS reaction. If the part of the burner 102 where the combustion reaction occurs is too close to the part of the gas mixing zone 103 where the carbon dioxide supply 107 and / or hydrogen supply 105 are received, the oxygen radicals may be generated within the flame of the combustion process and this may decrease their effectiveness as a catalyst. The gas mixing zone 103 may be at a distance below the burner 102 that gives the maximum oxygen radical promoted effect on the rWGS reaction.

[0040] Embodiments include the above-described oxygen radicals being the only catalyst of the rWGS reaction in the rWGS reactor system 101.

[0041] The reaction products of the reactions in the rWGS reactor system 101 may flow out of the rWGS reactor system 101 through the reaction product output 108.

[0042] The temperature of the reaction products that flow out of the rWGS reactor system 101 through the reaction product output 108 may be in the range of about 1000°C to 1300°C, and is preferably in the range of about 1050°C to 1150°C. The carbon dioxide supply 107 and / or hydrogen supply 105 may be pre-heated before being fed into the gas mixing zone 103. For example, they may be pre-heated to above about 400°C, and preferably to about, or above, 800°C. They may be pre-heated by an external heat source. The external heat source may be, for example, a burner 102 or any other type of heat source, such as an electrical heat source. In a preferred implementation, the pre-heating is performed by a heat exchanger that transfers heat from the hot reaction products from the rWGS reactor system 101 to the carbon dioxide supply 107 and / or hydrogen supply 105.

[0043] The pressure within the rWGS reactor system 101 may be in the range of about 5 bara to about 40 bara or higher (such as 50 bara). In a preferred embodiment, the pressure within the rWGS reactor system 101 is about 20 to 30 bara. This allows efficient integration with an FT process that may also operate at about 20 to 30 bara. The syngas generated by the rWGS reactor system 101 may be supplied to an FT system without a substantial pressure change being required.

[0044] Embodiments include the supply of oxygen to the rWGS reactor system 101 for generating oxygen radicals being adjusted to improve the efficiency of the rWGS reaction. For example, a low concentration of oxygen, that may be, for example, 5 mol% oxygen may be mixed into the carbon dioxide supply that is injected into the gas mixing zone 103, or the same amount of oxygen may be injected directly into the gas mixing zone 103. The amount of injected oxygen may then be increased or decreased to improve the efficiency of the rWGS reaction. The efficiency may be defined as the ratio between the hydrogen flowrate injected into the rWGS reactor system 101 and the carbon monoxide flowrate out of the system (i.e. EE flowrate divided by the CO flowrate). The targeted maximum efficiency is also dependent on the intended application of the rWGS reactor system 101. For example, if the intended application is syngas production for an FT process, the ratio of hydrogen to carbon monoxide in the output products of the rWGS reactor system 101 is preferably constant and between 2.0 and 2.1. The maximum efficiency therefore occurs when the ratio between the hydrogen flowrate injected into the rWGS reactor system 101 and the carbon monoxide flowrate out of the system has reached a minimum value, with the constraint that the ratio of output hydrogen to carbon monoxide is substantially constant and between 2.0 and 2.1. The maximum efficiency may be when the outlet temperature from the rWGS reaction zone is between 1050°C and 1150°C.

[0045] Figure 2 schematically shows a second implementation of the first embodiment.

[0046] The second implementation of the first embodiment differs from the first implementation of the first embodiment by the carbon dioxide supply 107, that comprises oxygen from the oxygen supply 106b, being additionally fed into the reaction zone 104. Embodiments also include only oxygen being directly injected into the reaction zone 104 so that oxygen is both injected with the carbon dioxide supply 107 to the gas mixing zone 103 and also into the reaction zone 104 via a separate oxygen supply. The second implementation of the first embodiment may otherwise be the same as the above-described first implementation of the first embodiment.

[0047] An advantage of the second implementation of the first embodiment is that there is additional oxygen injection further away from the burner. This reduces the risk of the injected oxygen being consumed without a substantial number of oxygen radicals being generated that catalyze the rWGS reaction.

[0048] In a third implementation of the first embodiment, no oxygen is mixed with the carbon dioxide supply 107 and oxygen is directly supplied to reaction zone 104. The third implementation of the first embodiment may otherwise be the same as the above-described first implementation of the first embodiment

[0049] An advantage of the third implementation of the first embodiment is that there is oxygen injection further away from the burner 102. This reduces the risk of the injected oxygen being consumed without a substantial number of oxygen radicals being generated that catalyze the rWGS reaction.

[0050] Accordingly, the first embodiment provides a system for generating syngas from supplies of carbon dioxide, hydrogen and oxygen only. Oxygen radicals may be generated that catalyse an rWGS reaction. According to a second embodiment the rWGS reactor system 101 is substantially as described for the first embodiment but does not include the burner 102 as an integrated part of the same reactor that supports the rWGS reaction.

[0051] A gas mixing zone 103 receives separate supplies of carbon dioxide and hydrogen. As described for the first embodiment, the supply of carbon dioxide may comprise a low concentration of oxygen, or there may be a separate oxygen supply to the gas mixing zone 103. For example, the oxygen concentration in the carbon dioxide supply 107 and / or gas mixing zone 103 may be less than or equal to 10 mole %. The gas mixing zone 103 has the purpose of thoroughly mixing the received gasses. The mixed gasses then flow to the reaction zone 104 where the rWGS reaction mainly occurs.

[0052] To provide heat for the rWGS reaction, an external heat source may indirectly heat the reaction zone 104 and / or the gas mixing zone 103. The external heat source may be, for example, a burner for supporting the combustion of hydrogen and oxygen, a burner of other products, or any other type of heat source.

[0053] The carbon dioxide supply 107 and / or hydrogen supply 105 may be pre-heated before being fed into the gas mixing zone 103. For example, they may be pre-heated to about 400°C, or to about, or above, 800°C. They may be pre-heated by an external heat source. The external heat source may be, for example, a burner for supporting the combustion of hydrogen and oxygen, a burner of other products, or any other type of heat source such as an electrical heat source. In a preferred implementation, the pre-heating is performed by a heat exchanger that transfers heat from the hot reaction products from the rWGS reactor system 101 to the carbon dioxide supply 107 and / or hydrogen supply 105.

[0054] The second embodiment is similar to the first embodiment in that it provides a system for generating syngas from supplies of carbon dioxide, hydrogen and a low concentration of oxygen only. Oxygen radicals may be generated that catalyse the rWGS reaction.

[0055] According to a third embodiment the rWGS reactor system 101 is used in an FT system.

[0056] The syngas generated by the rWGS reactor system 101 is supplied to an FT reactor that performs an FT process in dependence on the received syngas. The output products of the FT reactor include fuels generated by the FT process as well as unreacted feed products and / or other reaction products. One or more separation processes may be performed to generate one or more fuel streams that comprise at least some, and preferably all, of the carbonaceous fuels in the output products of the FT reactor. The one or more separation processes may also remove the substantial part of constituents such as water. The one or more separation processes may also generate a recycle stream that comprises at least some, and preferably substantially all, of the carbonaceous output products from the FT process that were not separated into the one or more fuel streams. The recycle stream may comprise, for example, one or more of carbon monoxide, carbon dioxide, light hydrocarbons such as methane and other carbonaceous products. The recycle stream may also comprise any hydrogen that did not react in the FT process.

[0057] In the third embodiment, the rWGS reactor system 101 may differ from the rWGS reactor system 101 of the first and second embodiments by further comprising an inlet into the gas mixing zone 103 and / or an inlet into the reaction zone 104. The inlet(s) supply the recycle stream that has been generated from the output products of the FT process back into the rWGS reactor system 101. Alternatively, the recycle stream may be mixed with any of the other gas streams supplied to the rWGS reactor system 101 so that separate gas inlet(s) to the rWGS reactor system 101 for the recycle stream are not required.

[0058] Within the rWGS reactor system 101, a partial oxidation (POX) process, and / or other processes such as a steam methane reforming (SMR) process and / or a dry reforming process, may convert at least some of the gasses in the recycle stream to carbon monoxide and hydrogen. This increases the carbon usage efficiency of the overall process.

[0059] In a preferred implementation of the third embodiment, the rWGS reactor system 101 comprises a first zone and a second zone. A POX process is performed on the recycle stream in a first zone of the rWGS reactor system 101. In the second zone, an rWGS process is performed on the output products of the first zone.

[0060] The first zone may be, or comprise some or all of, the gas mixing zone 103. Preferably, most of the carbon dioxide supply 107 is received by the first zone so that it is heated by the exothermic POX process. Oxygen radicals may also be generated in the first zone.

[0061] The temperature of the gasses that flow out of the first zone may be above about 1350°C so that the hydrocarbons in the recycle stream, that may be mostly methane, are substantially converted to carbon monoxide and so that the temperature is high enough for the rWGS process.

[0062] The second zone receives at least the gasses that flow out of the first zone and supports a rWGS process. The second zone may be, or comprise some or all of, the reaction zone 104. Preferably, there is a gas inlet for supplying hydrogen directly to the second zone so that most of the hydrogen is injected into the second zone where the rWGS process is performed. The reaction zone 104 may comprise a further gas inlet for injecting hydrogen into the second zone.

[0063] The rWGS reactor system 101 of the third embodiment may otherwise be substantially the same as the rWGS reactor system 101 of either the first or the second embodiments.

[0064] The third embodiment advantageously provides an integrated syngas generation system and FT system with a high carbon usage efficiency. At least some, and preferably substantially all, of the carbon that is not converted into a fuel by the FT process is fed back to the rWGS reactor for re-use in syngas and / or fuel generation processes.

[0065] According to a fourth embodiment, the rWGS reactor system 101 of any of the first to third embodiments is used in a one of the fuel generation systems as described in the International patent application PCT / EP2021 / 056733 (with publication number WO 2021 / 185869) or described in the International patent application PCT / EP2022 / 080525 (with publication number WO 2023 / 083661). The entire contents of PCT / EP2021 / 056733 and PCT / EP2022 / 080525 are incorporated herein by reference. Both PCT / EP2021 / 056733 and PCT / EP2022 / 080525 disclose systems in which a reactor receives a recycle stream comprising carbonaceous output products from an FT process.

[0066] According to the fourth embodiment, the configurations disclosed in PCT / EP2021 / 056733 and PCT / EP2022 / 080525 are adapted to additionally include the rWGS reactor system 101 according to any of the first to third embodiments. As described for the first to third embodiments, the rWGS reactor system 101 may receive a stream of substantially pure carbon dioxide. The syngas generated by the rWGS reactor system 101 may be used in an FT reactor. The FT reactor may be either an additional FT reactor to that used in either PCT / EP2021 / 056733 or PCT / EP2022 / 080525, or alternatively it may be the same FT reactor as that used in either PCT / EP2021 / 056733 or PCT / EP2022 / 080525. A recycle stream comprising carbonaceous output products from the FT process may be generated, as described for the third embodiment and / or as described in either PCT / EP2021 / 056733 or PCT / EP2022 / 080525.

[0067] When the rWGS reactor system 101 is according to the first or second embodiments, the recycle stream may be supplied to a carbon monoxide generation reactor, or FT reactor, as described in PCT / EP2021 / 056733 or PCT / EP2022 / 080525.

[0068] When the rWGS reactor system 101 is according to the third embodiment, the recycle stream may be supplied back to the rWGS reactor system 101 as described for the third embodiment and / or supplied to a carbon monoxide generation reactor, or FT reactor, as described in PCT / EP2021 / 056733 or PCT / EP2022 / 080525.

[0069] Advantageously, in the fourth embodiment, the systems in PCT / EP2021 / 056733 or PCT / EP2022 / 080525 are adapted so that they can efficiently perform the rWGS process.

[0070] Embodiments include the use of alternative plasma’s to oxygen for catalyzing the rWGS process.

[0071] Figure 3 schematically shows a fifth embodiment of an rWGS reactor system 101 in which a plasma torch 110 is used to provide free radicals within the reaction zone 104. The plasma torch 110 is powered by a high voltage supply 109. The plasma torch 110 generates plasma including free radicals. The plasma may be generated within the plasma torch and supplied to the reaction zone 104 and / or generated within the reaction zone 104. Apart from the plasma torch 110, the rWGS reactor system 101 may otherwise be substantially the same as described for previous embodiments (as indicated by the corresponding reference signs in Figure 3 to those in Figures 1 and 2). Embodiments include the plasma torch 110 generating any type of free radicals for catalyzing the rWGS reaction. For example, hydroxyl radicals may be generated as described here: https: / / www.researchgate.net / figure / Configuration-of-the-dc-water- plasma-torch_figl_230971146 (as viewed on 25 November 2024), or here: https: / / www.researchgate.net / publication / 366900420_Generation_and_delivery_of_firee_h ydroxyl_radicals_using_a_remote_plasma (as viewed on 25 November 2024).

[0072] In a first implementation of the fifth embodiment, the plasma torch 110 is the only source of free radicals in the rWGS reactor system 101. Alternative to what is shown in Figure 3, there is no oxygen supply 106b to the carbon dioxide supply 107. The carbon dioxide supply 107 may be to the gas mixing zone 103 or both the gas mixing zone 103 and the reaction zone 104. Most of the carbon dioxide supply 107 may be to the gas mixing zone 103 and only a small fraction of the carbon dioxide supply may be to the reaction zone 104. An advantage of having an additional carbon dioxide supply to the reaction zone 104 is that it may increase the mixing of the gasses and the free radicals in the reaction zone 104. The carbon dioxide may be injected into the reaction zone 104 through a jet nozzle to generate turbulence. Similarly, the hydrogen supply 105 may be to the gas mixing zone 103 or both the gas mixing zone 103 and the reaction zone 104.

[0073] In a second implementation of the fifth embodiment, the plasma torch 110 is the main source of free radicals in the rWGS reactor system 101. However, some oxygen may still be mixed into the carbon dioxide supply 107 as shown in Figure 3. The carbon dioxide supply 107, that comprises a low concentration of oxygen that may be as described for the previous embodiments, may be to the gas mixing zone 103 or both the gas mixing zone 103 and the reaction zone 104. The substantial proportion of the carbon dioxide may be supplied to the gas mixing zone 103 and only a small fraction of the carbon dioxide supplied to the reaction zone 104. The carbon dioxide may be injected into the reaction zone 104 through a jet nozzle to generate turbulence. The oxygen in the carbon dioxide supply 107 may combust with hydrogen in the gas mixing zone 103 and / or the reaction zone 104 of the rWGS reactor system 101. This combustion may be used to control the temperatures within the rWGS reactor system 101. Alternative to what is shown in Figure 3, there may be separate carbon dioxide supplies to the gas mixing zone 103 and the reaction zone 104. This allows different concentrations of oxygen in the carbon dioxide supplies to the gas mixing zone 103 and the reaction zone 104. Oxygen in the carbon dioxide supply may also be converted into free radicals that are in addition to the free radicals from the plasma torch 110.

[0074] In a preferred implementation of the fifth embodiment, the rWGS reactor system 101 is as described for the third embodiment and it receives the recycle stream of an FT process. As described for the third embodiment, the rWGS reactor system 101 preferably comprises a first zone and a second zone. A POX process is performed on the recycle stream in a first zone of the rWGS reactor system 101. In the second zone, an rWGS process is performed on the output products of the first zone. The first zone may be, or comprise some or all of, the gas mixing zone 103. The second zone receives at least the gasses that flow out of the first zone and supports an rWGS process. The second zone may be, or comprise some or all of, the reaction zone 104. There is preferably a gas inlet to the second zone so that most of the hydrogen may be injected directly into the second zone.

[0075] Figure 4 schematically shows a reactor system 400 that generates syngas according to a sixth embodiment. The reactor system 400 may differ from those of the previous embodiments to the extent that it is characterized by being a single reactor that comprises a first zone 401 in which a POX process is performed and a second zone 402 in which an RWGS process is performed.

[0076] The reactor system 400 of the sixth embodiment is used in an FT system. The syngas generated by the reactor system, which is syngas stream 409, is supplied to an FT reactor that performs an FT process using on the received syngas stream 409. The output products of the FT reactor include fuels generated by the FT process as well as unreacted feed products and / or other reaction products. One or more separation processes may be performed to generate one or more fuel streams that comprise at least some, and preferably all, of the carbonaceous fuels in the output products of the FT reactor. The one or more separation processes may also remove the substantial part of constituents such as water. The one or more separation processes may also generate a recycle stream 403 that comprises at least some, and preferably substantially all, of the carbonaceous output products from the FT process that were not separated into the one or more fuel streams. The recycle stream 403 may comprise, for example, one or more of carbon monoxide, carbon dioxide, light hydrocarbons such as methane and other carbonaceous products. The recycle stream 403 may also comprise any hydrogen that did not react in the FT process.

[0077] The reactor system 400 comprises a first zone 401 and a second zone 402. The first zone 401 receives the recycle stream 403, a hydrogen stream 404, an oxygen stream 405 and a carbon dioxide stream 406. These gasses may all be mixed together in a gas single stream, or one or more of the gasses may supplied to first zone 401 in separate streams.

[0078] An exothermic POX process is performed on the recycle stream in the first zone 401. The exothermic POX process may be a substantial heat source of the reactor system 400. The reactor system may comprise the burner 102 as described for the earlier embodiments but this is not necessarily required. Other heat sources may also be present such as electrical heat sources.

[0079] Preferably, the first zone 401 receives the substantial proportion of a carbon dioxide supply to the reactor system so that the carbon dioxide is heated by the exothermic POX process. Oxygen radicals are generated in the first zone 401. The temperature of the gasses that flow out of the first zone 401 may be above about 1350°C so that the hydrocarbons in the recycle stream 403, that may be mostly methane, are substantially converted to carbon monoxide and so that the temperature is high enough for the rWGS process.

[0080] The second zone 402 receives the gasses that flow out of the first zone 401 and supports an rWGS process. In the second zone 402, most of the hydrogen is injected in hydrogen stream 408 and some carbon dioxide is injected by carbon dioxide stream 407. These gasses may all be mixed together in a gas single stream, or one or more of the gasses may supplied to second zone 402 in separate streams.

[0081] In the second zone 402 the rWGS reaction becomes the dominant performed process. Small controlled amounts of oxygen may be supplied to the second zone 402 to further promote the rWGS reaction. The oxygen may be mixed into the carbon dioxide stream 407 or supplied as a separate stream. The oxygen supply may fine tune the ratio of output hydrogen and carbon monoxide from the second zone 402 in the output stream 409. The oxygen supply may also regulate the temperature of the output stream 409 from the second zone 402. Carbon dioxide may be supplied to the second zone 402 to increase the mixing efficiency in the second zone 402 because it has higher density than hydrogen. The substantial constituents of the output stream 409 of the second zone 402 may be carbon monoxide and hydrogen so that the output stream 409 is syngas. The output stream 409 is supplied to the FT process.

[0082] The use of a recycle stream 403, increases the carbon usage efficiency of the overall FT process.

[0083] In the present embodiment, an SMR and / or a dry reforming process may additionally, or alternatively, occur in the first zone 401 for converting at least some of the gasses in the recycle stream 403 to carbon monoxide and hydrogen.

[0084] The reactor system 400 may be the two-zone reactor that receives the recycle stream from an FT process as described in PCT / EP2021 / 056733, or the reactor as described in PCT / EP2022 / 080525.

[0085] Embodiments include a number of modifications and variations to the above-described techniques.

[0086] Embodiments include using a number of different concentrations of oxygen for radical generation. For example, embodiments include the oxygen concentration in the carbon dioxide supply 107 being less than or equal to 1 mole %, or less than or equal to 2 mole %, or less than or equal to 5 mole %, or less than or equal to 10 mole %, or less than or equal to 30 mole %.

[0087] Embodiments describe the generation and use of oxygen radicals. These include oxygenderived free radicals such as OH radicals. In the third embodiment the rWGS reactor system 101 supplies syngas to an FT system. Embodiments also include the rWGS reactor system 101 alternatively supplying syngas to a different type of system, such as a metal reduction system. A carbonaceous recycle stream may be generated from the output products of the system and supplied back to rWGS reactor system 101.

[0088] In embodiments, the main described carbonaceous feedstock is carbon dioxide. Embodiments include the use of additional, or alternative carbonaceous feedstocks. In particular, the feedstock may be, or comprise, one or more of biomethane, biogas (that contains about 40 % carbon dioxide) and fossil natural gas. The rectors of at least the third and or sixth embodiments may be configured to perform a POX process, and / or SMR and / or a dry reforming process, on the hydrocarbons in the feedstock. Embodiments include the only received hydrocarbons by the reactors being from their feedstock. Alternatively, the reactors may also receive hydrocarbons from a recycle stream as described for the third and sixth embodiments.

[0089] The sixth embodiment provides a single reactor with two zones respectively for a POX process, and / or SMR process, and / or a dry reforming process, and an rWGS process. Embodiments also include the described reaction processes being performed in a single reactor with a single reaction zone for a POX process and / or a SMR process and / or a dry reforming process, and an rWGS process.

[0090] Although not always specifically described, embodiments include using one or more heat exchangers, compressors, pumps, coolers, heaters, cleaning sections, water removal sections and / or other components in a syngas generation process.

[0091] Any flow charts and descriptions thereof herein should not be understood to prescribe a fixed order of performing the method steps described therein. Rather, the method steps may be performed in any order that is practicable. Although the present invention has been described in connection with specific exemplary embodiments, it should be understood that various changes, substitutions, and alterations apparent to those skilled in the art can be made to the disclosed embodiments without departing from the spirit and scope of the invention as set forth in the appended claims.

Claims

CLAIMS1. A reverse water gas shift, rWGS, system comprising: a reactor configured to support a rWGS reaction; a hydrogen supply configured to supply hydrogen to the reactor; a carbon dioxide supply configured to supply carbon dioxide to the reactor, wherein the carbon dioxide supply is a separate gas supply to the reactor from the hydrogen supply; and an oxygen supply configured to supply oxygen to the reactor; wherein: the reactor is configured so that, in use, a rWGS reaction occurs in the reactor; at least some of the oxygen supplied to the reactor is converted into radicals in the reactor; and the radicals catalyse the rWGS reaction.

2. The rWGS system according to claim 1, wherein: the reactor comprises a reaction zone and a gas mixing zone; the hydrogen supply is configured to supply hydrogen to the gas mixing zone of the reactor; the carbon dioxide supply is configured to supply carbon dioxide to the gas mixing zone of the reactor; the oxygen supply is configured to supply oxygen to the gas mixing zone of the reactor and / or the reaction zone of the reactor; the gas mixing zone is configured to mix the received gasses; and in use, at least the reaction zone is arranged to support the rWGS reaction in the reactor; the rWGS system optionally further comprising: a first constriction, first nozzle and / or first orifice in the hydrogen supply to the reactor that, in use, is configured to generate turbulence in flow of hydrogen into the reactor; anda second constriction, second nozzle and / or second orifice in the carbon dioxide supply to the reactor that, in use, is configured to generate turbulence in flow of carbon dioxide into the reactor.

3. The rWGS system according to any preceding claim, wherein the oxygen supply is configured to supply oxygen to the carbon dioxide supply.

4. The rWGS system according to any preceding claim, wherein the concentration of oxygen in the carbon dioxide supply, and / or the reactor, is less than or equal to 10 mole %, and preferably less than or equal to 5 mole %, and preferably less than or equal to 2 mole %, and preferably less than or equal to 1 mole %.

5. The rWGS system according to any preceding claim, further comprising a heat source arranged to heat the hydrogen, carbon dioxide and oxygen in the reactor.

6. The rWGS system according to claim 5, wherein the heat source is a burner and the system further comprises a hydrogen supply to the burner; and an oxygen supply to the burner; wherein the burner is arranged to support a combustion reaction between the hydrogen and oxygen received by the burner.

7. The rWGS system according to claim 5 or 6, wherein the heat source is external from the reactor and the heat source is arranged to indirectly heat the hydrogen, carbon dioxide and oxygen in the reactor.

8. The rWGS system according to claim 6, when dependent on claim 2, wherein the burner is comprised by the reactor and arranged to directly heat the hydrogen, carbon dioxide and oxygen in the gas mixing zone of the reactor.

9. The rWGS system according to claim 8, wherein the part of the burner where the combustion reaction occurs is separated from the gas mixing zone by over 100mm, preferably by over 150mm, more preferably by over 200mm, and further preferably by over 1000mm.

10. A reverse water gas shift, rWGS, system comprising: a reactor configured to support a rWGS reaction; a hydrogen supply configured to supply hydrogen to the reactor; a carbon dioxide supply configured to supply carbon dioxide to the reactor, wherein the carbon dioxide supply is a separate gas supply to the reactor from the hydrogen supply; and a source of free radicals, such as oxygen or a plasma torch, configured such that, in use, free radicals are present in the reactor; wherein: the reactor is configured such that, in use, a rWGS reaction occurs in the reactor; and the free radicals catalyse the rWGS reaction11. A fuel generation system comprising: a Fischer-Tropsch (FT) reactor system; and the rWGS system according to any preceding claim; wherein the rWGS system and FT system are configured so that the input products to the FT system comprise output products from the rWGS system.

12. The fuel generation system according to claim 11, wherein a recycle stream comprising output products from the FT reactor system is supplied to the reactor of the rWGS system.

13. The fuel generation system according to claim 12, wherein the rWGS system comprises: a first zone for supporting one or more of a partial oxidation reaction, a steam methane reforming reaction and a dry reforming reaction; and a second zone for supporting the rWGS reaction.

14. A reverse water gas shift, rWGS, process comprising: supplying hydrogen to a reactor; supplying carbon dioxide to the reactor in a separate gas supply to the reactor from the hydrogen supply; supplying oxygen to the reactor; performing a rWGS reaction in the reactor; and converting at least some of the oxygen supplied to the reactor into free radicals that catalyse the rWGS reaction in the reactor.

15. The rWGS process according to claim 14, wherein: the reactor comprises a reaction zone and a gas mixing zone; the hydrogen is supplied to the gas mixing zone of the reactor; the carbon dioxide is supplied to the gas mixing zone of the reactor; and the oxygen supply is supplied oxygen to the gas mixing zone of the reactor and / or the reaction zone of the reactor; the process further comprising mixing the received gasses in the gas mixing zone; and performing the rWGS reaction in at least the reaction zone;the rWGS process optionally further comprising supplying the hydrogen and carbon dioxide to the reactor in turbulent fluid flows.

16. The rWGS system process according to any of claims 14 or 15, wherein the oxygen supply is mixed into the carbon dioxide supply; and wherein the concentration of oxygen that is in the carbon dioxide supply, and / or the reactor, is less than or equal to 30 mole %, and preferably less than or equal to 10 mole %, and preferably less than or equal to 5 mole %, and preferably less than or equal to 2 mole %, and preferably less than or equal to 1 mole %.

17. The rWGS process according to any of claims 14 to 16, further comprising using a heat source to heat the hydrogen, carbon dioxide and oxygen in the reactor.

18. The rWGS process according to claim 17, wherein the heat source is a burner and the process further comprises: supplying hydrogen to the burner; supplying oxygen to the burner; combusting the supplied hydrogen and oxygen in the burner.

19. The rWGS process according to claim 17 or 18, wherein the heat source is external from the reactor and the heat source indirectly heats the hydrogen, carbon dioxide and oxygen in the reactor.

20. The rWGS process according to claim 18, when dependent on claim 15, wherein the burner is comprised by the reactor and directly heats the hydrogen, carbon dioxide and oxygen in the gas mixing zone of the reactor.

21. The rWGS process according to any of claims 14 to 20, wherein: the rWGS reaction converts at least some of the carbon dioxide in the reactor to carbon monoxide; and the hydrogen supply to the reactor supplies more hydrogen than is required for the rWGS reaction such that the output products of the reactor comprise both hydrogen and carbon monoxide.

22. The rWGS process according to any of claims 14 to 21, wherein the pressure in reactor is in the range of about 5 bara to about 50 bara, preferably about 20 bara to about 30 bara.

23. The rWGS process according to any of claims 14 to 22, wherein the temperature of the output products from the reactor is in the range of about 1000°C to 1300°C, and is preferably about in the range of about 1050°C to 1150°C.

24. A reverse water gas shift, rWGS, process comprising: supplying hydrogen to a reactor; supplying carbon dioxide to the reactor in a separate gas supply to the reactor from the hydrogen supply; and performing a rWGS reaction in the reactor that is catalyzed by free radicals in the reactor.

25. A fuel generation process comprising: performing the rWGS process according to any of claims 14 to 24; andusing output products of the rWGS process in a Fischer-Tropsch (FT) process.

26. The fuel generation process according to claim 25, further comprising supplying a recycle stream comprising output products from the FT process to the rWGS process.

27. The fuel generation process according to claim 26, further comprising performing one or more of a partial oxidation reaction, a steam methane reforming reaction and a dry reforming reaction in a first zone of a reactor; wherein the rWGS process is performed in a second zone of the reactor.

28. A system comprising: a reactor with a first zone and a second zone; a hydrogen supply configured to supply hydrogen to the reactor; a carbon dioxide supply configured to supply carbon dioxide to the reactor; and an oxygen supply configured to supply oxygen to the reactor; wherein: the reactor is configured so that, in use, one or more of a partial oxidation reaction, a steam methane reforming reaction and a dry reforming reaction occurs in the first zone of the reactor and a rWGS reaction occurs in the second zone of the reactor; at least some of the oxygen supplied to the reactor is converted into radicals in the reactor; and the radicals catalyse the rWGS reaction.25

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