Zero emission method for producing synthesis gas

Abstract

A process for the production of synthesis gas comprising the steps of: a) combusting methane or natural gas with oxygen and optionally water vapor to produce a flue gas comprising CO2 and H2O according to: [1] CH4 + 2O2-> CO2 + 2H2Ob) cooling the flue gas from step a) by heat exchange with a water stream, thereby vaporizing the water stream; c) condensing and removing moisture in the flue gas in the step b) so as to obtain a mixture consisting essentially of CO2; d) electrolyzing the steam stream in a solid oxide electrolysis cell (SOEC) and separating the steam into oxygen and hydrogen according to the following reaction scheme: [2] H2O (g)-> H2 + 1 / 2O2e) separating and drying the hydrogen f) according to the following scheme, carrying out a reverse water gas shift reaction between CO2 from step c) and H2 from step e): [3] CO2 + H2-> CO + H2O.

Description

[0001] manual Technical Field

[0002] The present invention relates to a zero-emission method for producing synthesis gas. In particular, the present invention relates to an autothermal net zero-emission reverse water gas shift reactor with process electrification function for producing high-quality synthesis gas. Prior art

[0003] As is known, there are various ways to produce syngas. One of them is to reform natural gas through the general reaction of steam methane reforming according to the following reaction (Quirino et al., 2021, 2020):

[0004] CH4+H2O=CO+3H2

[0005] Or reforming via an autothermal pathway according to the following reaction:

[0006] CH4+0.5O2=CO+2H2

[0007] Another way to produce syngas is coal (or solid fuel) gasification, as shown in the following simplified lumped scheme:

[0008] C+H2O=CO+H2

[0009] There are other pathways and methods to produce syngas (and hydrogen), such as methanol reforming (Palo et al., 2007), ammonia decomposition (Cha et al., 2021), acid gas conversion to syngas or other sources (such as biomass, biogas, municipal solid waste, plastic waste, etc.), but none of these methods have been so widely used for mass production.

[0010] Furthermore, the integration of renewable energy sources is not yet relevant for the production of syngas and its derivatives (ammonia, methanol, dimethyl ether, etc.).

[0011] In fact, syngas is the starting source for producing hydrogen. All bio and fossil refineries reform natural gas according to the above reaction.

[0012] CH4+H2O=CO+3H2

[0013] To obtain synthesis gas, which is then converted into hydrogen according to the water-gas shift reaction:

[0014] CO+H2O=CO2+H2

[0015] If any carbon capture technology is used after the shift, the hydrogen produced will appear “blue” tagged.

[0016] However, the CO2 to be stored refers not only to the CO2 produced by the water-gas shift reactor, but also to the CO2 (mostly) released as flue gas in the combustion chamber of the steam reformer after the exothermic combustion reaction of methane with oxygen in the air.

[0017] CH4+2O2=CO2+2H2O

[0018] Heating the tubes of the steam reformer where the endothermic reforming reaction of steam occurs.

[0019] CH4+H2O=CO+3H2

[0020] Therefore, the above-mentioned known methods have two main disadvantages: first, the generation of the reactor load required for carrying out the endothermic steam reforming reaction in the steam reformer, and second, the release of flue gases. Summary of the invention

[0021] To overcome the above problems, the present invention contemplates a method and associated apparatus for producing syngas to reduce, and preferably avoid, emissions from methane (or natural gas).

[0022] Therefore, an object of the present invention is to provide a method for producing synthesis gas, comprising the following steps:

[0023] a) Combustion of methane or natural gas with oxygen and optionally water vapor to produce a flue gas comprising CO2 and H2O according to the following reaction:

[0024] [1]CH4+2O2→CO2+2H2O

[0025] b) cooling the flue gases from the previous step by heat exchange with a water stream, thereby evaporating the water stream;

[0026] c) condensing and removing moisture from the flue gas from step b) to obtain a mixture consisting essentially of CO2;

[0027] d) electrolyzing the steam stream, preferably in a solid oxide electrolysis cell (SOEC), and electrolyzing the steam into oxygen and hydrogen according to the following reaction scheme:

[0028] [2]H2O(g)→H2+1 / 2O2

[0029] e) Separate oxygen from hydrogen and dry the hydrogen

[0030] f) performing a reverse water gas shift reaction between CO 2 from step c) and H 2 from step e) according to the following scheme:

[0031] [3]CO2+H2→CO+H2O.

[0032] Advantageously, the process allows the production of synthesis gas without any methane (or natural gas) emissions. Furthermore, the CO2 produced is hydrogenated directly over a reverse water gas shift (RWGS) catalytic bed. Remarkably, in this way, the process and the apparatus enable the production of high-quality synthesis gas, thereby reducing the overall CO2 footprint. The (green) hydrogen for the RWGS process is provided directly by a solid oxide electrolyser (SOEC), which electrolyses demineralised water into hydrogen and oxygen. This electrolysis can therefore further reduce carbon source consumption (i.e. when blue and / or grey hydrogen is not required). The coupling of a SOEC and a burner unit presents several advantages:

[0033] (i) consume less fossil fuels,

[0034] (ii) CO2 hydrogenation using green hydrogen,

[0035] and

[0036] (iii) Reduce greenhouse gas (GHG) emissions to zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 : is a block flow diagram of an equipment unit according to the present invention;

[0038] Figure 2 : is a schematic diagram of a preferred embodiment of the device according to the present invention;

[0039] Figure 3 The results obtained by performing Aspen Hysys v11 simulations are reported in Table 1 Figure 2 Steam electronic data sheet for equipment.

[0040] Figure 4 The water flow compositions are reported in Table 2 and in Table 3, obtained by performing Aspen Hysys v11 simulations. Figure 2 Equipment load.

[0041] Figure 5 A schematic diagram is shown of an apparatus according to another preferred embodiment.

[0042] Figure 6 The results obtained by performing Aspen Hysys v11 simulations are reported in Table 4. Figure 5 Steam electronic data sheet for equipment.

[0043] Figure 7 The water flow compositions are reported in Table 5 and in Table 6, obtained by performing Aspen Hysys v11 simulations. Figure 5 Equipment load. DETAILED DESCRIPTION

[0044] For the purpose of the present invention, the word "comprising" does not exclude the possibility of considering other stages / elements which are not explicitly listed after the wording.

[0045] In contrast, the term “consisting of” excludes the above possibilities.

[0046] For the purposes of the present invention, the term "device" refers to an assembly comprising one or more reaction and / or operation units in fluid and / or thermal communication with each other.

[0047] For the purposes of the present invention, the term "reaction unit" refers to a plurality of reactors.

[0048] For the purposes of the present invention, the term "operating unit" refers to a plurality of heat exchangers, pumps, separators, condensers, and the like.

[0049] The present invention also relates to an apparatus for implementing the method of the present invention, comprising:

[0050] - Burner unit (OXY STEAM COMB.);

[0051] -Solid Electrolytic Cell (SOEC)

[0052] - Reverse Water Gas Shift reaction unit (RWGS).

[0053] The burner unit is connected to the RWGS reaction unit through a waste heat boiler (Boiler) and a water condensing unit (De-wa1).

[0054] The SOEC is connected to the RWGS reaction unit via a separator or separation unit (SEP) and another water condensation unit ((De-waH2)) located downstream of the SOEC.

[0055] It is noteworthy that the method and related apparatus of the present invention can be applied to all processes aimed at producing bulk organic chemicals (synthesis gas) and their derivatives (hydrogen), such as but not limited to the application fields of methanol, ammonia, dimethyl ether, acetic acid, hydrogen, polymers, methanol to olefins, hydrogenation, hydrotreating, formylation, carbonylation. Advantageously, the method and apparatus of the present invention can produce synthesis gas with zero flue gas emissions.

[0056] Advantageously, the method and apparatus of the present invention utilize an autothermal unit in step (a), avoiding the use of a combustion chamber.

[0057] Advantageously, the method and apparatus of the present invention can achieve zero environmental impact through the electrification of the production of syngas.

[0058] Advantageously, the method and apparatus of the present invention can produce pre-treated synthesis gas (usable for synthesis) without the need for any CO2 capture equipment, amine scrubbing, desulfurization or other technology.

[0059] Advantageously, the device of the present invention can be chemically and thermally integrated with existing equipment.

[0060] For the purposes of the present invention, "chemical integration" is defined as the use of part / all of the water stream leaving one unit of the inventive device as a reactant in an existing device, and vice versa. For the purposes of the present invention, "thermal integration" is defined as the use of the thermal energy generated in one unit of the inventive device for the operation of another unit of the existing problem, and vice versa.

[0061] ] Preferably, in the process of the present invention, according to reaction [1], step a) is carried out in the presence of steam to produce flue gas comprising CO2 and H2O.

[0062] In this way, the temperature of the generated flue gas can be reduced to a temperature range of 1050 to 1200°C, the mass ratio of methane, O2 and water vapor is preferably 1:4:7 to 1:4:9, more preferably 1:3.97:7.2, the pressure is 20 to 40 bar, preferably 30 bar, and the molar ratio of methane, O2 and water vapor preferably conforms to the optimal value reported by Seepana and Jayanti (Seepana and Jayanti, 2010).

[0063] Preferably, oxygen is supplied to step a) from an external oxygen source (such as an oxygen tank or an air separation unit and / or step e)).

[0064] For example, in Figure 2 In the preferred embodiment shown, the oxygen supplied in step a) originates partly from the oxygen generated in step e).

[0065] according to Figure 5 In another preferred embodiment shown, the oxygen supplied to step a) comes entirely from step e).

[0066] According to one embodiment, step b) is carried out in a waste heat boiler, wherein the hot flue gas from step a) enters the tube side, causing the feed water stream on the shell side to boil, generating medium pressure (MP) steam of 20 to 40 bar, preferably 30 bar. Specifically, the heat of the flue gas is recovered to heat the water vapor, evaporate it, and cool the flue gas for the subsequent steps.

[0067] Specifically, the medium-pressure steam leaving the waste heat boiler is divided into two streams, according to the embodiment (wherein step a) receives steam), wherein the first stream is conveyed to step a). The first stream is used to support the combustion reaction. The second medium-pressure stream is preheated to a temperature between 500-600°C, preferably 550°C, and is further divided into two streams, wherein the first stream is expanded in a turbine and the second stream is conveyed to step d).

[0068] Preferably, the second stream fed to step d) is further heated to a temperature between 800-900°C, preferably 850°C, before entering step d) to adjust the hydrogen content in the high-quality synthesis gas stream.

[0069] The method comprises step c), condensing and removing moisture from the flue gas from step b), thereby obtaining a stream consisting essentially of CO2. Preferably, in step c), the flue gas is cooled before removing moisture. Specifically, the flue gas in step c) is utilized in a dehydration unit.

[0070] The method comprises a step d) in which the steam stream is electrolyzed in a solid oxide electrolysis cell (SOEC) and the steam is separated into oxygen and hydrogen according to the reaction scheme [2]. That is, a portion of the medium pressure steam is used to generate oxygen and hydrogen. According to an alternative embodiment, the electrolysis can be carried out using known devices other than solid oxide electrolysis cells to produce oxygen and hydrogen, such as polymer electrolyte membranes (PEM) or alkaline batteries.

[0071] As expected, the oxygen generated in step d) can be fed to step a) after separation from the hydrogen to reduce the oxygen demand of the gas storage, thereby obtaining a self-sustainable combustion process. Alternatively, the hydrogen can be used in subsequent steps after step e).

[0072] Preferably, step d) is carried out at a temperature between 800 and 900° C., preferably 850° C., and at a pressure between 20 and 40 bar, preferably 30 bar.

[0073] The method includes a step e) of separating and drying hydrogen. Specifically, step e) can separate the oxygen and hydrogen generated in step d). The oxygen stream is transported to step a) for the combustion step, and the hydrogen stream is transported to step f) for producing synthesis gas. Specifically, the hydrogen stream is pretreated by a dehydration unit to reduce the moisture content. It is worth noting that in order to optimize the removal of moisture, the hydrogen stream is first cooled. In addition, the heat of the hydrogen stream is used to generate high-pressure steam of about 30 bar, which is used in the method and / or integrated device of the present invention to produce energy or other products.

[0074] Preferably, the hydrogen gas stream generated in step e) to be fed to step f) is almost pure hydrogen (more than 99.5%).

[0075] The method comprises step f), wherein according to scheme [3], a reverse water gas shift reaction is carried out between CO2 from step c) and H2 from step e). Specifically, in step f), wet syngas is produced due to the reaction [3] between H2 from step e) and CO2 from step c). Specifically, the reverse water gas shift reaction reduces CO2 to CO to obtain wet syngas.

[0076] According to one embodiment, the reverse water gas shift reaction in step f) is carried out in a catalytic tube bundle at a temperature between 800 and 900° C., preferably 850° C., and a pressure between 20 and 40 bar, preferably 30 bar. That is, in step f) the CO2 and H2 streams are mixed and heated in the temperature range of 800 to 900° C., preferably 850° C. Preferably, the heat to reach the reaction temperature in step f) can be derived from the exothermic reaction in step a).

[0077] Preferably, in step f), hydrogen is fed in a molar ratio relative to CO2, preferably between 3.0 and 5.5, more preferably between 3.1 and 5.0.

[0078] According to one embodiment, the method comprises a step g) of dehydrating the wet syngas from step e) to separate H2O from the syngas. Preferably, the H2 / CO ratio of the dry syngas is between 3.0 and 5.5, preferably between 3.1 and 5.0. It is worth noting that a cooling step may also be performed before step g) so as to generate 30 bar high-pressure steam through a heat exchanger to recover the enthalpy of the wet syngas. The cooled wet syngas is conveyed to the dehydration unit of step g) to reduce the moisture content.

[0079] Another object of the present invention is to provide an apparatus for producing synthesis gas, which can implement the method of the present invention. It is worth noting that it is clear from the context in which unit the steps of the method are carried out.

[0080] The apparatus comprises a burner unit configured to perform step a). Preferably, the burner unit comprises a furnace. The burner unit is configured to receive methane or natural gas, oxygen and preferably steam. That is, the burner unit can be in fluid communication with a methane or natural gas production facility, with an oxygen source (such as a gas storage and / or an oxygen production unit) and with a steam source (such as another unit that generates steam).

[0081] The apparatus comprises a waste heat boiler comprising a plurality of tubes surrounded by a shell. The waste heat boiler is configured to perform step b). Specifically, the waste heat boiler is directly connected to the burner unit to receive flue gas on the tube side, and is directly connected to the source water unit to receive water flow on the shell side. In this way, the waste heat boiler can perform heat exchange.

[0082] The apparatus comprises a water condensing unit connected to the burner unit via a waste heat boiler. The water condensing unit is configured to perform step c) to produce a mixture consisting essentially of CO2. Preferably, the first water condensing unit may be connected to the first heat exchange unit to cool the flue gas before or during dehydration.

[0083] The solid oxide electrolysis cell is configured to perform step d) to generate an oxygen stream and a hydrogen stream. Specifically, when generating the oxygen stream and the hydrogen stream, the solid oxide electrolysis cell is configured to deliver the oxygen stream to the burner unit and deliver the hydrogen stream to the reverse water gas shift reactor unit.

[0084] It is worth noting that the solid oxide electrolysis cell is preferably connected to a first separation unit and a further water condensation unit, which are configured to separate the oxygen gas flow and the hydrogen gas flow, and then dehydrate the hydrogen gas flow to be delivered to the reverse water gas shift reactor unit. That is, in a solid oxide electrolysis cell provided with a separation unit and a further dehydration unit, step d) and step e) of the method of the present invention can be carried out.

[0085] It is worth noting that the device may include a heat exchange unit for cooling the moist hydrogen from the separation unit and before entering the dehydration unit, thereby obtaining pure hydrogen.

[0086] Furthermore, the heat exchanger uses a water flow as a cooling fluid, which is converted into high-pressure steam in the heat exchanger.

[0087] Preferably, the device comprises a second separation unit configured to separate the medium-pressure steam from the waste heat boiler into a first steam flow to be sent to the burner unit and a second steam flow to be sent to the SOEC. The device also comprises a second heating unit configured to heat the second flow before it reaches the solid oxide electrolysis cell. Preferably, the device comprises a third separation unit, which can be configured to split the second flow into a first flow to be sent to the turbine and a second flow to be sent to the solid oxide electrolysis cell. More preferably, the device comprises a third heating unit, which is configured to heat the second steam flow before it reaches the solid oxide electrolysis cell.

[0088] The apparatus comprises a reverse water gas shift reactor unit directly connected to the first water condensation unit and the solid oxide electrolysis unit. The reverse water gas shift reactor unit is configured to perform step f) to produce synthesis gas. Specifically, the reverse water gas shift reactor unit is configured to heat the mixture to a reaction temperature, thereby converting CO2 into CO and generating water.

[0089] According to one embodiment, the apparatus comprises a second dehydration unit directly connected to the reverse water-gas shift reactor unit. The second dehydration unit is configured to perform step g), receiving the wet syngas, thereby separating H2O from the syngas.

[0090] Preferably, the apparatus comprises a fourth heat exchange unit configured to act on the synthesis gas produced by the reverse water gas shift reactor unit before the synthesis gas enters the second water condensing unit.The fourth heat exchange unit is configured to produce high pressure steam.

[0091] It is noteworthy that the high pressure steam generated in the plant and the energy from the turbine can be used in the plant itself to achieve self-sufficiency and / or reduce resource usage and / or support other methods and apparatus related to the present invention.

[0092] Example 1

[0093] Figure 2 A preferred embodiment of the device according to the invention is described in detail in . In addition to the energy / process integration, the layout also includes all relevant unit operations and reactions. Methane (CH4_fuel), steam (Steam_in) and oxygen (O2_in) are burned in the furnace burner (OXY-STEAM COMB) and steam-regulated oxygen-rich combustion (SMOC) occurs. The relative ratios between these three streams reflect the optimal values ​​reported by Seepana and Jayanti (Seepana and Jayanti, 2010). The heat of the exhausted flue gas (FlueGas) is recovered in a waste heat boiler, in which pressurized water (stream 6) is evaporated at 30 bar (a). The cooled flue gas (ColdFG) is then cooled in a dehydration unit (DeWat1), where almost dry CO2 leaves the unit (CO2). In the first separator (TEE-101), a portion of the saturated steam (Steam1) is directly recycled to the burner to maintain SMOC,

[0094] The remaining part (steam to be separated, Steam_to_split) is further heated to 550°C. In the second separator (TEE-100), the superheated steam is divided into two streams: one part (SHSteam highP) is expanded into the turbine (K-110), while the complementary part (ToSH2) is further preheated to 850°C in the economizer (E-105). The latter stream (ToSH2) is selected to adjust the hydrogen content in the high-quality synthesis gas stream (RWGS synthesis gas, RWGS_syngas). The superheated steam (ToSOEC) is then separated in the SOEC. Figure 2In the diagram, the SOEC electrolyzer is a shift reactor (SOEC) and a universal separator (X-100). Pure oxygen (O2SOEC) can be recycled to the furnace burner, thereby further reducing the oxygen demand, while the hydrogen-rich stream (H2SOEC) is cooled (E-102) and then dried in the dehydration vessel (DewatH2). Almost pure hydrogen (99.85%) leaves the dehydration flash unit. The recovered heat is used to produce 30 bar high-pressure steam (HPS) (Steam 2, Steam2). Pure CO2 and hydrogen (H2) are mixed and the resulting stream (stream 1, stream 1) is preheated to 850°C. The RWGS reaction is carried out in a catalytic tube bundle, and heat is provided by the exothermic SMOC. The wet syngas mixture (Wet_syngas) is cooled. The heat exchanger (E-103) can recover the wet syngas enthalpy by producing HPS at a pressure of 30 bar. The cooled gas stream (Wet_syngas_out) is sent to the dehydration process to reduce the moisture content (DeWat2). The final dry high-quality syngas (RWGS_syngas) presents the best composition for synthesizing methanol (SN=2.05 and H2 / CO>3) ( et al., 2001).

[0095] Figure 3 Table 1 in reports the results obtained by performing Aspen Hysys v11 simulations Figure 2 The steam spreadsheet for the plant. Table 2 shows the water flow composition and Table 3 illustrates the results obtained by performing an Aspen Hysys v11 simulation. Figure 4 Reported load.

[0096] Example 2

[0097] Figure 5 Another preferred embodiment of the device according to the present invention is shown, which is the same as that in the SOEC part. Figure 2 The reported embodiments are different. In fact, the SOEC electrolyzer produces the total oxygen required by the SMOC system. Therefore, the oxygen produced is directly supplied to the burners in the furnace. This means that an external oxygen supplier (i.e., an oxygen tank or an air separation unit) is no longer required. The recovery of the internal complete oxygen demand is reflected in the increase in the final hydrogen content. Although the final dry synthesis gas is not optimized for methanol production, it is closer to the composition of conventional industrial mixtures.

[0098] Figure 6 Table 4 in reports the results obtained by performing Aspen Hysys v11 simulations Figure 5 Steam electronic data sheet for equipment. Figure 7, Table 5 describes the water flow compositions; and Table 6 describes the loads obtained by performing Aspen Hysys v11 simulations.

[0099] References

[0100] Bassani,A.,Pirola,C.,Maggio,E.,Pettinau,A.,Frau,C.,Bozzano,G.,Pierucci,S.,Ranzi,E.,Manenti,F.,2016.Acid Gas to Syngas(AG2S TM ) technology applied to solid fuel gasification:Cutting H2S and CO2 emissions by improving syngas production.Appl.Energy 184,1284–1291.https: / / doi.org / https: / / doi.org / 10.1016 / j.apenergy.2016.06.040

[0101] Cha,J.,Park,Y., B.,Lee,B.,Lim,D.,Lee,T.,Jeong,H.,Kim,Y.,Sohn,H., H.,Lee,KM,Nam,DH,Lee,KB,Lim,H.,Yoon,CW,Jo,YS,2021.Anefficient process for sustainable and scalable hydrogen production from greenammonia.Renew.Sustain.Energy Rev.152.https: / / doi.org / 10.1016 / j.rser.2021.111562

[0102] Palo,D.R.,Dagle,R.A.,Holladay,J.D.,2007.Methanol steam reforming forhydrogen production.Chem.Rev.107,3992–4021.https: / / doi.org / 10.1021 / cr050198bQuirino,P.P.S.,Amaral,A.,Pontes,K.V.,Rossi,F.,Manenti,F.,2021.Impact ofkinetic models in the prediction accuracy of an industrial steam methanereforming unit.Comput.Chem.Eng.152,107379.https: / / doi.org / 10.1016 / j.compchemeng.2021.107379

[0103] Quirino,P.P.S.,Amaral,A.,Pontes,K.V.,Rossi,F.,Manenti,F.,2020.Modeling and Simulation of an Industrial Top-Fired Methane SteamReforming Unit.Ind.Eng.Chem.Res.59,11250–11264.https: / / doi.org / 10.1021 / acs.iecr.0c00456

[0104] I., M.,Olsvik,O.,Hertzberg,T.,2001.Estimation of adeactivation model for the methanol synthesis catalyst from historic processdata,in:Gani,R., S.B.B.T.-C.A.C.E.(Eds.),European Symposium onComputer Aided Process Engineering-11.Elsevier,pp.219–224. https: / / doi.org / https: / / doi.org / 10.1016 / S1570-7946(01)80032-8Seepana,S.,Jayanti,S.,2010.Steam-moderated oxy-fuel combustion.Energy Convers.Manag.51,1981–1988.https: / / doi.org / 10.1016 / j.enconman.2010.02.031.

Claims

1. A method for producing synthesis gas, comprising the following steps: a) Combustion of methane or natural gas with oxygen and optionally water vapor to produce a flue gas comprising CO2 and H2O according to the following reaction: [1]CH4+2O2-→CO2+2H2O b) cooling the flue gases from the previous step by exchanging heat with a water stream, thereby evaporating the water stream; c) condensing and removing moisture from the flue gas in step b) to obtain a mixture consisting essentially of CO2; d) electrolyzing the steam stream, preferably in a solid oxide electrolysis cell (SOEC), and separating the steam into oxygen and hydrogen according to the following reaction scheme: [2]H2O(g)→H2+1 / 2O2 e) Separate oxygen from hydrogen and dry the hydrogen f) performing a reverse water gas shift reaction between CO 2 from step c) and H 2 from step e) according to the following scheme: [3]CO2+H2→CO+H2O.

2. The method according to claim 1, wherein the O2 supplied to step a) comes partly from an external oxygen source and the remainder comes from step e).

3. The method according to claim 1, wherein the O2 All from step e).

4. The method according to any one of claims 1 to 3, wherein step a) is carried out in the presence of steam, and in step a), steam-regulated oxygen-enriched combustion is carried out in a temperature range of 1050 to 1200° C., wherein the mass ratio of methane, O2 and water vapor is 1:4:7 to 1:4:9, preferably 1:3.97:7.

2.

5. The method according to any one of claims 1 to 4, wherein step b) is carried out in a waste heat boiler, wherein the hot flue gases from step a) enter the tube side, causing the feed water stream on the shell side to boil, producing medium pressure (MP) steam of 20 to 40 bar, preferably 30 bar.

6. A method according to claim 5, wherein the medium-pressure steam leaving the waste heat boiler is divided into two streams, of which the first stream is conveyed to step a), and the second medium-pressure stream preheated to a temperature between 500-600° C., preferably 550° C., is further divided into two streams, of which the first stream is expanded in a turbine and the second stream is conveyed to step d).

7. The process according to any one of claims 1 to 6, wherein step d) is carried out at a temperature between 800 and 900°C, preferably 850°C, and at a pressure between 20 and 40 bar, preferably 30 bar.

8. The process according to any one of claims 1 to 7, wherein the reverse water gas shift reaction in step f) is carried out in a catalytic tube bundle at a temperature between 800 and 900°C, preferably 850°C, and at a pressure of 20 to 40 bar, preferably 30 bar.

9. The process according to any one of claims 1 to 8, wherein in step f), hydrogen is fed in a molar ratio relative to CO2 of between 3 and 5.5, preferably between 3.1 and 5.

0.

10. The method according to any one of claims 1 to 9, wherein the method comprises a step g) of dehydrating the wet synthesis gas of step e) to separate H2 from the synthesis gas.

11. The method according to claim 10, wherein the H2 / CO ratio of the dry syngas is between 3.0 and 5.5, preferably between 3.1 and 5.

0.

12. An apparatus for producing synthesis gas according to the method according to any one of claims 1 to 11, comprising: - Burner unit (OXY STEAM COMB.); -Solid Electrolytic Cell (SOEC) - Reverse Water Gas Shift Reactor (RWGS), in, i. The burner unit (OXY STEAM COMB.) is connected to the reverse water gas shift reaction unit (RWGS) via a waste heat boiler (Boiler) and a water condensing unit (De-wa1), ii. The solid electrolysis cell unit (SOEC) is connected to the reverse water gas shift reaction unit (RWGS) via an oxygen separation unit (SEP) in wet hydrogen and another water condensation unit (De-waH2) located downstream of the SOEC.

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