Method for the production of methanol and methane from natural gas from natural wells containing high quantities of carbon dioxide

Abstract

The present invention relates to a method that allows for the exploitation of natural gas deposits that are rich in carbon dioxide, with the production of methane and methanol.

Description

[0001] " Method for the production of methanol and methane from natural gas from natural wells containing high quantities of carbon dioxide"

[0002] DESCRIPTION

[0003] Many natural gas reserves, not yet or little exploited, contain large quantities of pollutants such as H2S and CO2.

[0004] While the former can be transformed into sulfur and used by the chemical industry, for example for the production of sulfuric acid, the latter poses serious environmental problems if it is released into the atmosphere.

[0005] As far as the exploitation of natural gas (NG) reserves is concerned, it is typical to remove pollutants, such as H2S and CO2, by means of purification technologies, such as amines, membranes or combinations of these.

[0006] The purification plants are often equipped with H2S transformation units in sulfur, while the CO2is released into the atmosphere or re-injected into the wells, where it dilutes the hydrocarbons constituting the natural gas, making it increasingly difficult to exploit the wells.

[0007] As for hydrogen production, today the possibility of replacing part of the natural gas normally transported in the pipelines with hydrogen, generated by electrolysis and, therefore, in principle, generated by renewable sources, is being considered.

[0008] The electrolytic hydrogen is produced by oxidation / reduction in an electrolytic cell, subsequently it is eventually compressed, dehydrated and mixed with natural gas. To date, various types of electrolytic cells have been developed, but the most promising for large-scale use are the Solid Oxydes Electrolitical Cells (SOEC), which hydrolyze water vapor at high temperature, with high efficiencies and large conversion factors.

[0009] Hydrogen and oxygen are obtained from the hydrolyzed steam; the latter is often considered a waste product, to the point that the electrode at which it is generated is flushed with air, in order to lower its partial pressure and reduce the voltage of the electrolytic cell, with consequent saving of electrical energy.

[0010] Alternatively, the flushing can be carried out with steam which, being easily condensable, allows for the recovery of oxygen at a high degree of purity.

[0011] Methanol synthesis

[0012] The transformation of CO2 into methanol by means of hydrogen is typically carried out in a methanol synthesis plant, in which the following reactions are performed:

[0013] -CO2+ H2→ CO + H2O

[0014] -CO + 2H2→ CH3OH

[0015] which transform CO2 and H2 into methanol and water (in the working conditions of the reactors, albeit to a very limited extent, heavier hydrocarbons are also obtained).

[0016] In a typical plant:

[0017] 1) a reagent flow, consisting mainly of CO2and H2, is combined with a compressed recirculation gas flow.

[0018] 2) The resulting flow is heated. 3) The resulting heated flow is fed to a synthesis reactor (R1), where it undergoes the reactions

[0019] -CO2+ H2→ CO + H2O

[0020] -CO + 2H2→ CH3OH.

[0021] The reactions are overall exothermic, therefore heat develops in the reactor, which is removed with a heat exchanger (Reactorexchanger) for the production of low thermal level steam (about 20 barg)

[0022] 4) A gas flow emerges from the R1 reactor, mainly containing CO2, H2, CH3OH and H2O.

[0023] 5) The current emerging from Rl is partially cooled by heat exchange with a reagent gas flow, obtaining the partially cooled gas flow emerging from Rl, recovering heat to heat the reactor inlet gas flow.

[0024] Methane synthesis

[0025] The methanation reaction is exothermic with the following reaction:

[0026] -CO2+ H2→ CO + H2O

[0027] -CO + 3H2→ CH4+ H2O.

[0028] The methanation reactor, unlike the methanol synthesis reactor, is generally adiabatic (it is not an exchanger reactor).

[0029] The transformation of carbon dioxide into methane with hydrogen is typically carried out in a methanation plant, usually consisting of several reactors placed in series, where the Sabatier reaction is carried out, which transforms carbon dioxide and hydrogen into methane and water (in the working conditions of the reactors, albeit to a very limited extent, heavier hydrocarbons are also obtained). The Lurgi plant is schematized in figure 6.

[0030] In this plant, a reagent flow, consisting mainly of carbon dioxide and hydrogen, is combined with a compressed recirculation gas flow.

[0031] The resulting flow is heated and then fed to a first methanation reactor (Rl ), where it undergoes the Sabatier reaction until it reaches equilibrium conditions.

[0032] A gas flow emerges from the Rl reactor, containing mainly carbon dioxide, hydrogen, methane and water, at a higher temperature than the incoming flow due to the heat developed in the reactor under almost adiabatic conditions.

[0033] The current emerging from Rl is partially cooled by heat exchange with a gas flow, of the same chemical composition, which continues the Sabatier reaction in a second reactor R2.

[0034] The partially cooled flow emerging from Rl is further cooled by heat exchange in a boiler, where the heat it yields produces high-pressure water vapor, thus obtaining the cooled flow emerging from Rl.

[0035] The cooled flow emerging from Rl is divided into two flows: a flow called the recirculation flow and the aforementioned flow emerging from Rl continuing the reaction, which exchanges heat and is heated by the energy transferred from the flow emerging from Rl, becoming the flow emerging from Rl that continues the reaction in the second reactor R2.

[0036] The recirculation current is compressed by means of a compressor, obtaining the compressed recirculation gas current mentioned above. The current emerging from R1 that continues the heated reaction is fed to the R2 reactor, where the Sabatier reaction continues.

[0037] The reacted gas flow emerges from R2, mainly composed of methane, water, hydrogen and carbon dioxide and possibly heavier hydrocarbons belonging to the C2+ class.

[0038] The reacted gas flow emerging from R2 is cooled in a boiler, in which high-pressure water vapor and a cooled reacted gas flow emerging from R2 are produced.

[0039] The cooling of the reacted gas flow emerging from R2 is separated, by means of a separator, into its liquid components, mainly consisting of water, and gaseous, consisting almost entirely of methane, hydrogen and carbon dioxide; the liquid phase (condensates) is removed from the system, while the gaseous phase, called SNG, is sent to purification from carbon dioxide and water to achieve the specifications required for the product.

[0040] The methanol synthesis and methanation reactors require an almost continuous supply; in fact, frequent switching on and off reduces the life of the catalysts and heat exchange trains, as well as requiring rather long times to develop the thermal profiles, which guarantee the correct conversion of the reagents.

[0041] This is avoided by producing and consuming hydrogen, in the methanol synthesis, even in periods of energy scarcity, trying to reduce the hydrogen requirement of the reactors by bringing them to the Turndown.

[0042] Alternatively, it is possible to accumulate the hydrogen that is not produced in the form of compressed gas (possibly at a low temperature to increase its density), or in liquid form, which is much more suitable for large accumulations.

[0043] To date, the state of the art of hydrogen liquefaction (nonmagnetic) requires from 10 to 13 KWh / kg (source DOE), where the lowest values are obtained by using volumetric compressors with a low number of revolutions ( 90% efficiency, as reported in " Large scale hydrogen liquefaction under the aspect of economic viability".

[0044] Still for the synthesis of methanol, the presence of a high quantity of methane can lead to a reduction of the partial pressure of the reaction products (CO2 and H2) with problems related to conversion.

[0045] This entails the possibility of having a high quantity of nonreacted gas ( off gas) to be recycled or burned.

[0046] Even the SOEC-type electrolyzers cannot be switched on and off cyclically, except at the cost of long waiting times, which follow the heating curves of the equipment, in order to limit its degradation.

[0047] It is therefore typical to burn fuel when renewable energies are not available ( for example, at night for a solar field) to keep both the SOEC and the methanation and methanol synthesis reactors running with the hydrogen it generates, albeit at the lower limit ( Turndown).

[0048] Since the use of a fuel implies both the production of a nonrenewable resource and the production of carbon dioxide, it is clear that this is to the detriment of the benefits provided by the use of renewable energies.

[0049] Summary of the Invention The inventors of the present patent application have developed a method that surprisingly allows a methanolation reactor ( for the synthesis of methanol) and a subsequent methanation reactor of a natural gas flow rich in carbon dioxide and methane to be kept in continuous operation by using catalytic hydrogen.

[0050] This method involves the use of an oxy-combustion system that feeds the electrolysis process in the Turndown phases, where said oxy-combustion system uses as fuel a natural gas (rich in CO2) obtained from a well.

[0051] The method of the invention is particularly suitable for the exploitation of natural gas wells rich in carbon dioxide and methane and allows the use of such wells that are not yet exhausted as storage of carbon dioxide imported from other sources.

[0052] The methanolization phase advantageously allows the reduction of the methane content to be allocated to the methanation phase; moreover, the flow sent to the methanation has a reduced carbon dioxide content and a methane and hydrogen content that act as a thermal flywheel containing the temperature at the exit from the methanation reactor (strongly exothermic).

[0053] Methanation reduces the content of carbon dioxide to be recycled / purged.

[0054] Brief Description of the Figures

[0055] Figure 1 shows the diagram of an embodiment according to the present invention in the so-called Full Run conditions.

[0056] Figure 2 shows the diagram of an embodiment according to the present invention in the so-called Turndown conditions. Figure 3 shows the diagram of a particular embodiment according to the present invention in the so-called Full Run conditions.

[0057] Figure 4 shows the diagram of a first particular embodiment according to the present invention in the so-called Turndown conditions.

[0058] Figure 5 shows the diagram of a second particular embodiment according to the present invention in the so-called Turndown conditions.

[0059] Figure 6 shows a typical Lurgi plant.

[0060] Obj ect of the invention

[0061] In accordance with a first obj ect of the present invention, a method for the production of methanol and methane in conditions of abundance of electrical energy (Full Run phase) is described.

[0062] According to a preferred aspect, this method is carried out using a natural gas obtained from a natural gas well rich in CO2 and methane.

[0063] In accordance with a second obj ect of the present invention, a method for the production of methanol and methane in conditions of scarcity of electrical energy ( Turndown phase) is described.

[0064] According to a preferred aspect, this method is carried out using electricity produced by an oxy-combustion system fed with a portion of the natural gas obtained from a natural gas well rich in CO2 and methane.

[0065] The first and second methods described, in the context of the present invention, can be considered, respectively, as a first and a second phase of a method for the continuous maintenance of the methanol and methane reactors. Detailed Description of the Invention

[0066] In accordance with a first obj ect, a method for the production of methanol and methane in conditions of abundance of electricity, i. e. at least corresponding to the needs of other utilities, is described.

[0067] The need for the method of the invention is represented by the energy required to carry out the water electrolysis phase, which, according to a preferred aspect of the present invention, is represented by renewable energy sources such as solar, wind, or nuclear electricity.

[0068] In fact, as in the following description, it is low-cost electricity due to the misalignment between production and consumption and is linked to overproduction with respect to consumption.

[0069] For the purposes of the present invention, such conditions are the conditions in which a methanol synthesis and methanation plant is in the Full Run phase.

[0070] For the purposes of the present invention, this method is carried out starting from a flow of natural gas rich in CO2 obtained from natural gas wells.

[0071] For the purposes of the present invention, this natural gas flow comprises, in addition to methane, a CO2content of about 1-70% (v / v) and preferably of about 10-50%, wherein the remaining portion is represented by methane.

[0072] For the purposes of the present invention, this natural gas flow may also include light hydrocarbons such as C1-5. In the following description, this flow of natural gas will be referred to as the "initial flow of natural gas".

[0073] According to an aspect of the present invention, such initial natural gas flow also comprises hydrogen sulphide and possibly other sulphur compounds.

[0074] The method of the invention is carried out in conditions called Full Run, i. e. of abundance of electricity, i. e. in the presence of an availability of electricity greater than that generally consumed by the network and the needs of the method itself.

[0075] According to a preferred aspect of the invention, such electrical energy is produced from renewable energy sources and is, for example, represented by solar, wind, or nuclear electrical energy.

[0076] The above method is schematically represented in Figure 1. In particular, this method for the production of methanol and methane comprises the following steps:

[0077] I ) obtaining a flow of methanol 3 from a methanolation phase carried out in a methanolation reactor R1 and a flow of methane 11 from a methanation phase carried out in a methanation reactor R2, and heat, from an initial flow of natural gas,

[0078] II ) obtaining a flow of hydrogen gas 5 and a flow of oxygen gas 8 by electrolysis.

[0079] For the purposes of the present invention, the initial natural gas flow of step I) is a natural gas flow rich in CO2 and is obtained from a natural gas well D.

[0080] In particular, as described above, said well D is a natural gas well, therefore comprising methane, rich in CO2. More specifically, said natural gas comprises, in addition to methane, CO₂ in a quantity of about 1-70% (v / v) and preferably of about 10-50% (v / v), where the remaining portion is represented by methane.

[0081] According to an aspect of the present invention, the initial natural gas flow 1 may be a flow 1 ' ' enriched in carbon dioxide.

[0082] For such a purpose, a flow of natural gas enriched in carbon dioxide 1 ' ' is obtained by inj ecting an additional flow of carbon dioxide 4.

[0083] Said flow of CO2 4 can be represented by a flow of liquid or pumped carbon dioxide obtained by pumping a flow of liquid CO₂ stored in a tank of liquid CO₂ TCO2l by means of a pump of liquid CO₂ PCO2l.

[0084] For the purposes of the present invention, in step I ), a flow of methanol 3 and a head flow 10 of unreacted products are obtained from the methanolation, from which a flow of methane CO₂ and H₂ 11 is obtained, which are sent to the methanation reactor for the conversion of CO₂ to methane.

[0085] For the purposes of the present invention, step II ) is carried out on a vapor flow 7 obtained from a first water flow 6 vaporized by the heat developed in step I ) of methanolation and methanation.

[0086] For the purposes of the present invention, the hydrogen gas flow 5 obtained in step II ) is sent to step I ) of methanolation and methanation.

[0087] According to an embodiment of the invention, before being subj ected to step I ) of methanolation, the initial natural gas flow can be subj ected to a purification step in a purifier P. In particular, such step 0) is a purification step from sulfur compounds.

[0088] According to a preferred aspect, the purification step 0) eliminates the sulfur compounds present in the initial natural gas flow 1.

[0089] In particular, said purification removes these sulfur compounds up to a concentration suitable for the production of methanol and methanation, and less than 50 ppm.

[0090] According to an embodiment of the invention, the desulphurization can be carried out by means of an absorption column.

[0091] According to an embodiment of the invention, the desulphurization can be carried out using an aqueous solution of a tertiary amine.

[0092] If sulfur compound contents are required, after absorption with amines, adsorption with oxides such as ZnO₂ can be used, with the formation of ZnS.

[0093] According to an aspect of the present invention, the purification phase can also comprise a phase of removing heavy metals, in order to prevent the so-called poisoning of the methanation catalysts.

[0094] According to an embodiment of the invention, the removal of heavy metals can be carried out by means of activated carbon filters.

[0095] The initial purified natural gas flow 1 ' thus obtained is then sent to phase I ) of methanolation and methanation.

[0096] Therefore, the initial natural gas flow of phase I ) can be a purified initial natural gas flow 1 '. For the purposes of the present invention, the electrolysis phase II ) is carried out in an electrolyzer E (or water splitter).

[0097] According to an aspect of the present invention, the electrolysis phase II ) is carried out using a first energy source el.

[0098] According to a preferred aspect of the present invention, said first energy source el is represented by a renewable energy source, such as, for example, solar energy, wind energy or nuclear energy.

[0099] In fact, as in the following description, it is low-cost electricity linked to the misalignment between production and consumption and is linked to overproduction with respect to consumption.

[0100] For the purposes of the present invention, the gaseous oxygen flow 8 obtained from the electrolysis phase II ) is liquefied in a phase III ) in an oxygen liquefaction unit OL, obtaining a liquid oxygen flow 9, which is stored in a liquid oxygen tank TO2l.

[0101] In particular, the liquefaction phase is carried out using a second energy source e2.

[0102] According to a preferred aspect of the present invention, said second energy source e2 is represented by a renewable energy source, such as, for example, solar energy, wind energy or nuclear energy.

[0103] For the purposes of the present invention, the obtained methanol flow 2 is sent to storage in a special storage tank TMeoH.

[0104] According to an embodiment of the invention, before being accumulated, said methanol flow 2 may be subj ected to a dehydration phase. In particular, such dehydration reduces the water content below the permitted limits suitable for distillation.

[0105] For the purposes of the present invention, a methane flow 11 is also obtained from phase I ).

[0106] In accordance with a second obj ect of the present invention, a method for the production of methanol and methane in conditions of scarcity of electrical energy is described, i. e. in the presence of a reduced availability of electrical energy, i. e. lower than the needs of the other utilities with respect to the needs of the method of the invention.

[0107] This need of the method is represented by the energy necessary to carry out the water electrolysis phase, which, according to a preferred aspect of the present invention, is obtained from discontinuous renewable energy sources such as solar, wind, or nuclear electricity.

[0108] For the purposes of the present invention, these conditions are the conditions in which a methanol and methane plant is in the Turndown phase.

[0109] According to a preferred aspect, this method is therefore carried out using electrical energy produced in an oxy-combustion phase fed with a portion of the initial natural gas flow 1.

[0110] For the purposes of the present invention, this method is carried out starting from a natural gas flow 1 obtained from natural gas wells.

[0111] For the purposes of the present invention, such natural gas flow comprises, in addition to methane, carbon dioxide in a quantity of approximately 1-70% (v / v) and preferably of approximately 10-50% (v / v), where the remaining portion is represented by methane.

[0112] For the purposes of the present invention, such natural gas flow may also include light hydrocarbons, for example C₁₋₅.

[0113] For the purposes of the present invention, such natural gas flow also comprises hydrogen sulphide and possible other sulphur compounds.

[0114] The aforementioned method is schematically represented in Figure 2.

[0115] In particular, such method for the production of methanol and methane in conditions of scarcity of electricity from renewable sources includes the phase of:

[0116] IV) carrying out an oxy-combustion step obtaining a third (e3) energy source, a fourth energy source (e4 ), a steam flow from oxy-combustion (w7 ) a first carbon dioxide flow from oxy-combustion (28, 68 ), a second carbon dioxide flow from oxy-combustion (29, 69) and a third carbon dioxide flow from oxy-combustion (30, 70).

[0117] According to an aspect of the present invention, the oxycombustion step IV) can also be carried out in the presence of a portion of the initial natural gas flow 21 ' ' ', preferably of a portion of the initial purified natural gas flow 21ivobtained from step 0) (to avoid obtaining sulfur derivatives).

[0118] The products of step IV) of oxycombustion and represented by: a third (e3) energy source, a fourth energy source (e4 ), a flow of steam from oxycombustion (w7 ) a first flow of carbon dioxide from oxycombustion (28, 68 ), a second flow of carbon dioxide from oxycombustion (29, 69) and a third flow of carbon dioxide from oxycombustion (30, 70), can be used depending on the activity carried out in the Turndown step.

[0119] According to a first aspect of the invention, in the Turndown phase, the methanoling and methanation are carried out at a minimum rate, and the electrolysis is also carried out at a minimum rate.

[0120] In these conditions, therefore, the method includes the additional steps of:

[0121] Va) obtaining a flow of methanol (3, 57 ) from a methanolation phase carried out in a methanolation reactor R1 and a flow of methane ( 11, 66) from a methanation phase carried out in a methanation reactor R2, and heat, from an initial flow of natural gas ( 1, 21, 51 ), Via) obtaining a hydrogen gas flow (5, 24, hl ) and an oxygen gas flow ( 8, 25, ol ) by electrolysis,

[0122] In such situation, the resumption of the methanolation reactor R1 and the methanation reactor R2, as well as the electrolyzer in the Full Run phase, will be advantageously faster.

[0123] According to an aspect of the present invention, prior to phase IV), the initial natural gas flow 21 may be subj ected to a purification phase 0) in a purifier P.

[0124] In particular, such phase 0) is a phase of purification from sulfur compounds.

[0125] In particular, such purification removes these sulfur compounds up to a concentration suitable for the production of methanol and methanation, and less than 50 ppm.

[0126] According to an embodiment of the invention, the desulphurization can be carried out through an absorption column. According to an embodiment of the invention, desulphurization can be carried out using an aqueous solution of a tertiary amine.

[0127] In the event that sulfur compound contents are required, downstream of the absorption with amines, it is possible to use adsorption with oxides such as ZnO₂ with the formation of ZnS.

[0128] According to an aspect of the present invention, the purification phase can also include a phase of removing heavy metals, in order to prevent the so-called poisoning of the methanation catalysts.

[0129] According to an embodiment of the invention, the removal of heavy metals can be carried out by means of activated carbon filters.

[0130] The purified natural gas flow 21 ' thus obtained is then sent to the oxycombustion phase IV).

[0131] For the purposes of the present invention, phase Via) is carried out on a vapor flow 23 obtained from a first water flow 6 vaporized by the heat developed in phase Va).

[0132] For the purposes of the present invention, said hydrogen gas flow 24 obtained from step Via) can be sent to step Va).

[0133] For the purposes of the present invention, said gaseous oxygen flow 25 obtained from step Via) can be sent to step IV) of oxycombustion, possibly in a liquefied and pumped form.

[0134] For the purposes of the present invention, the oxy-combustion phase IV) can be carried out in the presence of a liquid oxygen flow 26.

[0135] In particular, said flow of liquid oxygen 26 is obtained from a liquid oxygen storage tank TO2l. For the purposes of the present invention, said third source of energy e3 obtained from step IV) is used to carry out the electrolysis step Via), in place of the first source of energy el if not available.

[0136] For the purposes of the present invention, said fourth source of energy e4 obtained from step IV) (not shown in the figures) is used to carry out the liquefaction of gaseous oxygen, in place of the second source of energy e2 if not available.

[0137] According to a preferred aspect of the present invention, the liquid oxygen flow 26 used in the oxycombustion step IV) and obtained from a liquid oxygen storage tank TO2lis obtained according to the method of the present invention described above, carried out in conditions of abundance of electrical energy (so-called Full Run).

[0138] The flow of steam from oxy-combustion 27 obtained from step IV) can be sent to the electrolysis step Via) in the form of one or more flows (not shown in the figure).

[0139] The first flow of carbon dioxide from oxy-combustion 28, partly in liquid form and partly in gaseous form obtained by cooling and liquefaction by heat exchange with the flows inside the oxy-combustion unit, can be sent to a liquefied carbon dioxide tank TCO2l.

[0140] The second flow of carbon dioxide from oxy-combustion 29 can be re-injected into a suitable well.

[0141] The third flow of carbon dioxide from oxy-combustion 30 can be sent to step Va).

[0142] In a second aspect of the invention, in the Turndown phase, the methanolation and methanation are suspended and possibly also the electrolysis and the methanolation reactor Rl, the methanation reactor R2 and the electrolyzer E are in stand by.

[0143] In these conditions, therefore, instead of steps Va) and Via), the method instead comprises the steps of:

[0144] Vb) flushing the methanolation reactor Rl and the methanation reactor R2 with the third flow of carbon dioxide from oxy-combustion 30,

[0145] VIb) flushing the electrolyzer E with the flow of steam from oxy-combustion 27 (not shown in the figure).

[0146] Advantageously, such situation allows a faster restart of the methanolation reactor Rl and of the methanation reactor R2, as well as of the electrolyzer in the Full Run phase.

[0147] A particular embodiment of the method of the present invention for the production of methanol and methane is schematized in Figure 3.

[0148] As described above, these conditions can be indicated as Full Run conditions of a methanol and methane synthesis plant.

[0149] For the purposes of the present invention, such method is carried out starting from a flow of natural gas obtained from natural gas wells.

[0150] For the purposes of the present invention, such natural gas flow comprises, in addition to methane, CO2 in a quantity of approximately 1-70% (v / v) and preferably of approximately 10-50% (v / V).

[0151] For the purposes of the present invention, such natural gas flow may also include light hydrocarbons such as C1-5. According to one aspect of the present invention, such natural gas flow also comprises hydrogen sulphide and possibly other sulphur compounds.

[0152] The method of the invention is carried out in conditions of abundance of electrical energy, that is, in the presence of an availability of electrical energy superior to the needs of the method itself.

[0153] According to a preferred aspect of the invention, this electrical energy is produced from renewable energy sources and is, for example, represented by solar, wind, or nuclear energy.

[0154] In fact, as in the following description, it is low-cost electricity linked to the misalignment between production and consumption and is linked to overproduction with respect to consumption.

[0155] In particular, an initial natural gas flow 51 is obtained from a natural gas well D, which can be preliminarily compressed by a natural gas compressor KI.

[0156] In a Purification Unit P, said initial natural gas flow 51 can optionally be purified from sulfur compounds, obtaining a purified initial natural gas flow 52.

[0157] Said initial natural gas flow 51 or said purified initial natural gas flow 52 can be enriched in carbon dioxide.

[0158] For this purpose, a flow of liquid carbon dioxide 70 obtained from a tank of liquid carbon dioxide TCO21 is pumped by a pump of liquid carbon dioxide PCO21, obtaining a pumped flow of liquid carbon dioxide 71, which can be combined with the initial flow of natural gas 51 or said purified initial natural gas flow 52. Said initial natural gas flow 51 or said purified initial natural gas flow 52, possibly enriched in carbon dioxide, is heated in a first heat recovery unit EXI, obtaining an initial natural gas flow 53, possibly purified, and heated, which is destined for the methanoling phase in the reactor R1.

[0159] For the purposes of the present invention, said initial natural gas flow (possibly purified) is heated to a temperature such as to guarantee sufficient reaction kinetics and a thermal profile that is not too high in the methanolation reactor Rl; typically 250°C.

[0160] A flow of hydrogen gas from methanolation h11 is sent to the methanolation reactor Rl as described below.

[0161] The following exothermic reaction takes place in the methanol synthesis reactor Rl:

[0162] C02+ 3 H2"> CH3OH + H20

[0163] The heat developed during the reaction is partially removed in the exchanger reactor with the production of steam (about 20 barg).

[0164] A gaseous flow of methanol 54 is obtained from the methanolation.

[0165] For the purposes of this invention, said gaseous methanol flow 54 is a flow with a prevalent methanol content; in fact, it also includes water, unreacted natural gas, carbon dioxide, and hydrogen.

[0166] Said gaseous flow of methanol 54 is cooled in the first heat exchanger EXI by heat exchange with the initial natural gas flow 51, possibly purified 52, which is heated, obtaining a cooled gaseous flow of methanol 55. Said cooled methanol gaseous flow 55 is further cooled in a first heat exchanger TE1, obtaining the condensation of the further cooled methanol flow in a mixed phase flow 56.

[0167] For the purposes of the present invention, said first heat exchanger TE1 operates by means of a refrigerant fluid represented by air or water.

[0168] In a first separator SI, said mixed flow 56 is separated into an overhead flow 58 containing mainly unreacted carbon dioxide and hydrogen and unreacted methane, and a final methanol bottom flow 57, which is stored in a methanol tank TMeOH, and which can possibly be subj ected to distillation to enrich it in methanol.

[0169] Advantageously, the methane content in the overhead flow 58, acting as an inert in the methanation phase, allows to avoid the recirculation of carbon dioxide to the methanation phase in order to contain its temperature.

[0170] In turn, the overhead flow 58 is heated in a second heat exchanger EX2, obtaining a preliminary heated methanation flow 59, preferably at a temperature of 200-250°C, to which a hydrogen flow from methanation h12 is mixed, obtaining a flow from methanation 60.

[0171] For the purposes of the present invention and as described below, said hydrogen flow from methanation h12 is obtained by electrolysis.

[0172] The reacted gas flow exiting the reactor R is cooled in the WHB ( Waste Heat Boiler) exchanger with the production of water vapor.

[0173] A first methane flow 62 is obtained from the methanation reactor R2, which is cooled in the second heat exchanger EX2 for heat exchange with the overhead flow 58, obtaining a first cooled methane flow 63, indicatively at a temperature of about 70-100°C.

[0174] Said first cooled methane flow 63 is further cooled in a second heat exchanger TE2, obtaining a first further cooled methane flow 64, which is sent to a second separator S2, from the bottom of which a first portion of dehydration water wwl is obtained and from the head of which a methane flow to be dehydrated 65 is obtained.

[0175] In a Dehydration Unit DU, said methane flow to be dehydrated 65 is dehydrated, obtaining a final methane flow 66, which can be sent to the network or re-injected into the well.

[0176] Advantageously, said final methane flow 66 comprises less than 100 ppm of carbon dioxide.

[0177] As described above, for the purposes of the present invention, respective flows of hydrogen gas obtained by electrolysis are sent to the methanolation phase and to the methanation phase.

[0178] According to a preferred aspect of the invention, such electrolysis is carried out using energy obtained from renewable (discontinuous) sources, such as, for example: solar energy, wind energy, or nuclear energy.

[0179] For the purposes of this invention, said steam flow to be subj ected to electrolysis has a temperature of approximately 700°C.

[0180] Said steam flow to be subj ected to electrolysis is sent to an electrolyzer El for an electrolysis phase.

[0181] In particular, a first flow of water wl represented by a flow of boiler feed water is vaporized in the first WHB1 ( Waste Heat Boiler) of the methanolation reactor Rl, obtaining a first flow of saturated steam w2. In particular, a further first flow of water wl ' represented by a second flow of boiler feed water is vaporized in the second WHB ( Waste Heat Boiler 2 ) of the methanation reactor R2, obtaining a further first flow of saturated steam w2 ', which is combined with the first flow of saturated steam w2.

[0182] Said first flow of saturated steam w2 (comprising the further first flow of saturated steam w2 ' ) is superheated in a third heat recovery unit EX3, obtaining a further superheated steam flow w3, which can be sent to an electrolyzer E for an electrolysis phase.

[0183] In an embodiment of the present invention, a portion w5 of the saturated steam flow is cooled in a fifth heat exchanger EX5, obtaining a portion w6 of the saturated steam flow at an adjusted temperature, which is combined with the further superheated steam flow w3, obtaining a steam flow to be electrolyzed w4.

[0184] Said further superheated steam flow w3 or said steam flow to be electrolyzed w4 is sent to an electrolyzer El for an electrolysis phase.

[0185] For the purposes of this invention, the electrolyzer El is represented by a Solid Oxides Electrolytic Cell (SOEC) electrolyzer.

[0186] From the electrolysis phase there are obtained a first flow of hydrogen gas hl and a first flow of oxygen gas ol.

[0187] The first hydrogen gas flow hl has a temperature of approximately 800°C.

[0188] For the purposes of the present invention, said hydrogen gas flow hl comprises a water content of approximately 50% (v / v). For the purposes of the present invention, said gaseous oxygen flow ol comprises oxygen in a concentration of approximately 99% (v / v).

[0189] For the purposes of the present invention, said hydrogen gas flow hl is cooled, obtaining a first cooled hydrogen gas flow h2.

[0190] In particular, the hydrogen gas flow hl is cooled from approximately 800°C to approximately 440°C.

[0191] In particular, said cooling is obtained in the third heat exchanger EX3 by heat exchange with the further superheated steam flow w3.

[0192] The cooled hydrogen gas flow h2 is further cooled in a fourth heat exchanger EX4, obtaining a further cooled hydrogen gas flow h3.

[0193] In particolare, the further cooled hydrogen gas flow has a temperature of about 300°C.

[0194] Said further cooled hydrogen gas flow h3 is subj ected to one or more compression and cooling steps, obtaining a compressed and further dehydrated hydrogen flow h8.

[0195] In particular, said further cooled hydrogen gas flow h3 is cooled in a third heat exchanger TE3, obtaining a hydrogen flow at a first cooling level h4, from which a second portion of dehydration water ww2 is separated in a third separator S3, obtaining a hydrogen gas flow at a first dehydration level h5.

[0196] For the purposes of the present invention, said third heat exchanger TE3 operates by means of a refrigerant fluid represented by air or water.

[0197] Subsequently, said hydrogen gas flow at a first level of dehydration h5 is compressed in a second compressor K2, obtaining a hydrogen gas flow at a first level of dehydration and a first level of compression h6.

[0198] Said hydrogen gas flow at a first level of dehydration and at a first level of compression h6 is further cooled in a fourth heat exchanger TE4, obtaining a hydrogen gas flow at a first level of dehydration and at a first level of compression h7, from which, in a fourth separator S4, a third portion of dehydration water ww3 is separated, obtaining the compressed and further dehydrated hydrogen flow h8.

[0199] For the purposes of the present invention, the cooling, separation and compression phases can be repeated n times according to operational needs.

[0200] Said flow of compressed and further dehydrated hydrogen h8 is compressed in a third compressor K3, obtaining a flow of further dehydrated and further compressed hydrogen h9.

[0201] Said further dehydrated and further compressed hydrogen flow h9 is heated in the fourth heat exchanger EX4 by heat exchange with said cooled hydrogen gas flow h2, obtaining a hydrogen flow h10 for methanolation and methanation, from which the hydrogen gas flow for methanolation h11 and the hydrogen gas flow for methanation h12 are obtained, respectively.

[0202] For the purposes of the present invention, said hydrogen flow h10 for methanoling and methanation preferably has a temperature of about 250°C.

[0203] As for the gaseous oxygen flow ol, this is first subj ected to a heat exchange phase in the fifth recuperator EX5, obtaining a cooled gaseous oxygen flow o2, which is subsequently liquefied in a liquefaction unit (LU), obtaining a first liquefied oxygen flow to be stored o3, which is stored in a liquid oxygen tank TO2l.

[0204] In particular, the liquefaction can be carried out with a fourth source of energy e4 obtained from the oxy-combustion phase.

[0205] A particular embodiment of the method of the present invention for the production of methanol and methane is schematized in Figure 4.

[0206] In particular, said method is carried out in conditions of scarcity of electrical energy, i. e. in the presence of a reduced availability of electrical energy, as it is lower than the needs of the method itself.

[0207] As described above, these conditions can be indicated as Turndown conditions of a methanol synthesis and methanation plant.

[0208] According to a preferred aspect of the invention, this electrical energy is scarcely available, as it is produced from renewable (discontinuous) energy sources such as solar, wind, or nuclear energy.

[0209] For the purposes of the present invention, this method is carried out starting from a natural gas flow obtained from natural gas wells.

[0210] For the purposes of the present invention, this natural gas flow comprises, in addition to methane, CO2 in a quantity of approximately 1-70% (v / v) preferably 10-50%.

[0211] For the purposes of the present invention, this natural gas flow may also comprise light hydrocarbons such as Cl-5.

[0212] T1 According to an aspect of the present invention, this natural gas flow also comprises hydrogen sulphide and possibly other sulphur compounds.

[0213] In particular, an initial natural gas flow 51 is obtained from a natural gas well D, which can be preliminarily compressed by a natural gas compressor KI.

[0214] In a Purification Unit P, said initial natural gas flow 51 can optionally be purified of sulfur compounds, obtaining the purified initial natural gas flow 52.

[0215] Said initial natural gas flow 51 or said purified initial natural gas flow 52 can be enriched in carbon dioxide.

[0216] For this purpose, a flow of liquid carbon dioxide 70 obtained from a tank of liquid carbon dioxide TCO21 is pumped by a pump of liquid carbon dioxide PCO21, obtaining a flow of pumped liquid carbon dioxide 71, which can be combined with the initial natural gas flow 51 or said purified initial natural gas flow 52.

[0217] Said initial natural gas flow 51 or said purified initial natural gas flow 52, possibly enriched in carbon dioxide, is heated in a first heat recovery unit EXI, obtaining a purified and heated initial natural gas flow 53, which is destined for the methanoling phase.

[0218] For the purposes of the present invention, said purified initial natural gas flow 52 can be heated up to a temperature that guarantees sufficient reaction kinetics and a thermal profile that is not too high in the methanoling reactor; typically around 250°C.

[0219] From the methanolation, a final flow of methanol 57 is obtained, as described below. More specifically, a gaseous flow of methanol 54 is obtained from the initial purified and heated natural gas flow 53 sent to a methanolation reactor R1.

[0220] Said gaseous flow of methanol 54 is cooled by heat exchange with the purified initial natural gas flow 52 in the first heat recovery unit EXI, obtaining a cooled gaseous flow of methanol 55.

[0221] Said cooled methanol gaseous flow 55 is further cooled in a first heat exchanger TE1, obtaining the condensation of the further cooled methanol flow in a mixed phase flow 56.

[0222] For the purposes of the present invention, said first heat exchanger TE1 operates by means of a refrigerant fluid represented by air or water.

[0223] In a first separator SI, said mixed flow 56 is separated into an overhead flow 58 containing mainly unreacted carbon dioxide and hydrogen and unreacted natural gas, and a final methanol bottom flow 57, which is stored in a methanol tank TMeOH, and which can possibly be subj ected to distillation to enrich it in methanol.

[0224] In turn, the overhead flow 58 is heated in a second heat exchanger EX2, obtaining a preliminary flow to be methanated containing CO 2, H2 and CH4 (in the next reactor, the CO2 is eliminated with the methanation) heated 59, preferably at a temperature of 200-250°C, to which a hydrogen flow is mixed to be sent to the methanation h12, obtaining a flow 60 to be sent to the methanation.

[0225] Electrolytic hydrogen is possibly added to the flow to be sent to methanation 60, obtaining a flow 61 in input to the methanator. For the purposes of the present invention and as described below, said hydrogen flow from methanation h12 is obtained by electrolysis.

[0226] The reacted gas flow exiting the reactor R2 is cooled in the exchanger WHB ( Waste Heat Boiler) with the production of water vapor.

[0227] A first methane flow 62 is obtained from the methanation reactor R2, which is cooled in the second heat exchanger EX2 for heat exchange with the head flow 58, obtaining a first cooled methane flow 63, indicatively at a temperature of about 70-100°C.

[0228] Said first cooled methane flow 63 is further cooled in a second heat exchanger TE2, obtaining a first further cooled methane flow 64, which is sent to a second separator S2, from the bottom of which a first portion of dehydration water wwl is obtained and from the head of which a methane flow to be dehydrated 65 is obtained.

[0229] In a Dehydration Unit DU, said methane flow to be dehydrated 65 is dehydrated, obtaining a final methane flow 66, which can be sent to the network or re-injected into the well.

[0230] Advantageously, said final methane flow 66 comprises less than 100 ppm of carbon dioxide.

[0231] As described above, for the purposes of the present invention, respective flows of hydrogen gas obtained by electrolysis are sent to the methanolation phase and to the methanation phase.

[0232] According to a preferred aspect of the invention, this electrolysis is carried out using energy obtained from renewable sources, such as, for example: solar energy, wind energy, or nuclear energy. For the purposes of the present invention, said flow of steam to be subj ected to electrolysis has a temperature of approximately 700°C.

[0233] Said steam flow to be subj ected to electrolysis is sent to an electrolyzer El for an electrolysis phase.

[0234] According to a preferred aspect of the invention, such electrolysis is carried out using a third source of energy e3 obtained from an oxy-combustion step, which, therefore, replaces the energy offered by renewable energy sources if not available.

[0235] In particular, a first flow of water wl represented by a flow of boiler feed water is vaporized in the first WHB1 ( Waste Heat Boiler) of the methanolation reactor Rl, obtaining a first flow of saturated steam w2.

[0236] In particular, a further first flow of water wl ' represented by a second flow of boiler feed water is vaporized in the second WHB ( Waste Heat Boiler 2 ) of the methanation reactor R2, obtaining a further first flow of saturated steam w2 ', which is combined with the first flow of saturated steam w2.

[0237] Said first flow of saturated steam w2 (comprising the further first flow of saturated steam w2 ' ) is superheated in a third heat recovery unit EX3, obtaining a further superheated steam flow w3, which can be sent to an electrolyzer El for an electrolysis phase.

[0238] In an embodiment of the present invention, a portion w5 of the saturated steam flow is cooled in a fifth heat recovery unit EX5, obtaining a portion w6 of the saturated steam flow at an adjusted temperature, which is combined with the further superheated steam flow w3, obtaining a steam flow to be electrolyzed w4. Said further superheated steam flow w3 or said steam flow to be electrolyzed w4 are sent to an electrolyzer El for an electrolysis phase.

[0239] For the purposes of this invention, the electrolyzer El is represented by a Solid Oxides Electrolytic Cell (SOEC) electrolyzer.

[0240] From the electrolysis phase thre are obtained a first hydrogen gas flow hl and a first oxygen gas flow ol.

[0241] The first hydrogen gas flow hl has a temperature of approximately 800°C.

[0242] For the purposes of the present invention, said hydrogen gas flow hl comprises a water content of approximately 50% (v / v).

[0243] For the purposes of the present invention, said gaseous oxygen flow ol comprises oxygen in a concentration of approximately 99% (v / v).

[0244] For the purposes of the present invention, said hydrogen gas flow hl is cooled, obtaining a first cooled hydrogen gas flow h2.

[0245] In particular, the hydrogen gas flow hl is cooled from approximately 800°C to approximately 440°C.

[0246] In particular, said cooling is obtained in the third heat exchanger EX3 for heat exchange with the further superheated steam flow w3.

[0247] The cooled hydrogen gas flow h2 is further cooled in a fifth heat exchanger EX5, obtaining a further cooled hydrogen gas flow h3.

[0248] In particolare, il flusso di idrogeno gassoso ulteriormente raffreddato h3 ha una temperatura di circa 300°C. Said further cooled hydrogen gas flow h3 is subj ected to one or more compression and cooling phases, obtaining a compressed and further dehydrated hydrogen flow h8.

[0249] In particular, said further cooled hydrogen gas flow h3 is cooled in a third heat exchanger TE3, obtaining a hydrogen flow at a first cooling level h4 from which a second portion of dehydration water ww2 is separated in a third separator S3, obtaining a hydrogen gas flow at a first dehydration level h5.

[0250] For the purposes of the present invention, said third heat exchanger TE3 operates by means of a refrigerant fluid represented by air or water.

[0251] Subsequently, said hydrogen gas flow at a first level of dehydration h5 is compressed in a second compressor K2, obtaining a hydrogen gas flow at a first level of dehydration and a first level of compression h6.

[0252] Said hydrogen gas flow at a first level of dehydration and at a first level of compression h6 is further cooled in a fourth heat exchanger TE4, obtaining a hydrogen gas flow at a first level of dehydration and at a first level of compression h7, from which, in a fourth separator S4, a third portion of dehydration water ww3 is separated, obtaining the compressed and further dehydrated hydrogen flow h8.

[0253] For the purposes of the present invention, the cooling, separation and compression phases can be repeated n times according to operational needs. Said flow of fully dehydrated hydrogen h8 is compressed in a third compressor K3, obtaining a flow of fully dehydrated and compressed hydrogen h9.

[0254] Said flow of fully dehydrated and compressed hydrogen h9 is heated in the fourth heat exchanger EX4 by heat exchange with said cooled hydrogen gas flow h2, obtaining a flow of hydrogen from methanoling and methanation h10.

[0255] The hydrogen flow from methanolation and methanation h10 is used to obtain, respectively, the hydrogen flow from methanolation h11 and the hydrogen flow from methanation h12.

[0256] For the purposes of the present invention, said hydrogen flow from methanation preferably has a temperature of approximately 250°C.

[0257] The gaseous oxygen flow ol is sent to an Oxycombustion Power Plant (OPP) for the oxycombustion phase.

[0258] In particular, the gaseous oxygen flow ol obtained from the electrolysis phase is first cooled in the fourth heat exchanger EX4 for heat exchange with the portion w5 of the first superheated steam flow, obtaining a cooled gaseous oxygen flow o2.

[0259] Said cooled gaseous oxygen flow o2 is liquefied in a Liquefaction Unit (LU) obtaining a liquefied oxygen flow to be stored o3, which is stored in a liquid oxygen tank TO2l.

[0260] For the purposes of the present invention, a flow of liquefied oxygen o4 can be obtained from the liquid oxygen tank TO2land pumped by a liquefied oxygen pump PO2l, obtaining a pumped liquefied oxygen flow o5. Said liquefied oxygen flow o4 or said pumped liquid oxygen flow o5 is sent to an Oxycombustion Unit (OPP) for the oxycombustion phase.

[0261] In particular, said liquefied oxygen flow o4 is obtained from the liquefied oxygen storage tank TO2I.

[0262] According to a preferred aspect of the present invention, the liquefied oxygen flow o4, possibly pumped o5, obtained as described above, can also be sent to the oxycombustion step VI).

[0263] For the purposes of the present invention, the oxycombustion phase can be carried out in the presence of a portion of the initial natural gas flow 51 ', possibly compressed by a natural gas compressor PNG, or of a portion of the initial purified natural gas flow 52 ', as described above in relation to the method of the present invention.

[0264] As shown in Figure 5, a flow of methanol for oxycombustion 72 obtained from the methanol tank TMeOHcan also be sent to the oxycombustion stage.

[0265] One or more of the following are therefore obtained from the oxycombustion phase:

[0266] - a flow of steam from oxy-combustion w7, which can be sent to the electrolysis phase or used for flushing the electrolyzer to keep it warm;

[0267] - a first flow of carbon dioxide from oxy-combustion 68, having a temperature of about 500°C, which can be mixed with the flow of hydrogen from methanoling and from methanation h10 in order to keep the methanoling and methanation reactors warm; - a second flow of carbon dioxide from oxy-combustion 69, which can be inj ected into a well D;

[0268] - a flow of liquefied carbon dioxide from oxy-combustion 70, which can be sent to the liquefied carbon dioxide tank TCO2l.

[0269] ~ ~ ~

Claims

CLAIMS1. A method for the production of methanol ( 3, 57 ) and methane ( 11, 66 ) comprising the steps of:I ) obtaining a flow of methanol ( 3, 57 ) from a methanolation phase carried out in a methanolation reactor R1 and a flow of methane ( 11, 66 ) from a methanation phase carried out in a methanation reactor R2, and heat, from an initial flow of natural gas ( 1, 21, 51 ),I I ) obtaining a flow of hydrogen gas ( 5, 24, hl ) and a flow of oxygen gas ( 8, 25, ol ) by electrolysis in an electrolyzer E, wherein said electrolysis phase I I ) is carried out on a vapor flow ( 7, 23, w2 ) obtained from a first water flow and / or from a further first water flow ( 6, wl, wl ' ) vapori zed by the heat produced in phase I ),wherein a flow of methanol ( 3, 57 ) and a head flow ( 10 ) are obtained from the methanolation of phase I ), said head flow ( 10, 58 ) being subj ected to said methanation phase for the production of a flow of methane ( 11, 66 ),characteri zed by the fact that said initial natural gas flow has a CO2content of approximately 1 -70% (v / v) and preferably of approximately 10-50%.

2. The method for the production o f methanol ( 3, 57 ) and methane ( 11, 66 ) according to the preceding claim, wherein said initial natural gas flow is a natural gas enriched ( 1 ' ', 21 ' ', 52 ) in carbon dioxide by inj ection of an additional flow of carbon dioxide ( 4,3. The method for the production o f methanol ( 3, 57 ) and methane ( 11, 66 ) according to claim 1 or 2, wherein said electrolysis phase I I ) is carried out using a first available energy source ( el ).

4. The method for the production o f methanol ( 3, 57 ) and methane ( 11, 66 ) according to any one of the preceding claims, wherein said electrolysis phase I I ) is carried out using a first available renewable energy source ( el ).

5. The method for the production o f methanol ( 3, 57 ) and methane ( 11, 66 ) according to any one of the preceding claims, comprising the step I I I ) of liquefying said gaseous oxygen flow ( 8, 25, ol ) obtaining a liquid oxygen flow to be stored ( 9, 26, o3 ).

6. A method for the production of methanol ( 3, 57 ) and methane ( 11, 66 ) comprising the steps of:IV) carrying out an oxy-combustion phase obtaining a third ( e3 ) energy source and a fourth ( e4 ) energy source, a flow of steam from oxy-combustion (w7 ) a first flow of carbon dioxide from oxy-combustion ( 28, 68 ), a second flow of carbon dioxide from oxy-combustion ( 29, 69 ) and a third flow of carbon dioxide from oxy-combustion ( 30, 70 );Va ) obtaining a flow of methanol ( 3, 57 ) from a methanolation phase carried out in a methanolation reactor R1 and a flow of methane ( 11, 66 ) from a methanation phase carried out in a methanation reactor R2, and heat, from an initial flow of natural gas ( 1, 21, 51 ), Via ) obtaining a hydrogen gas flow ( 5, 24, hl ) and an oxygen gas flow ( 8, 25, ol ) by electrolysis,wherein a flow of methanol ( 3, 57 ) and a head flow ( 10 ) are obtained from the methanolation of phase Va ), said head flow ( 10, 58 )being subj ected to said methanation phase for the production of a flow of methane ( 11, 66),wherein said electrolysis step Via) is performed on a vapor flow to be subj ected to electrolysis (7, 23, w3) obtained from a first water flow and / or from a further first water flow ( 6, wl, wl ) vaporized by heat produced in step Va), by said third energy source (e3) obtained in step IV) and whereinsaid oxycombustion step IV) is carried out by means of a portion (21iv, 51 ' ) of a natural gas flow having a CO2content of about 1-70% (v / v) and preferably of about 10-50%.

7. The method for the production of methanol (3, 57 ) and methane ( 11, 66) according to the preceding claim, wherein said first flow of carbon dioxide from oxy-combustion (28, 68 ) is sent to step Va).

8. The method for the production of methanol (3, 57 ) and methane ( 11, 66) according to claim 6 or 7, wherein a flow of liquefied oxygen ( 9, 26, o4 ) obtained from the flow of oxygen to be stored ( 9, 26, o3) obtained according to the method of claim 4 is sent to said oxy-combustion step IV).

9. The method for producing methanol (3, 57 ) and methane ( 11, 66) according to any one of claims 6 to 8, wherein to said oxycombustion step IV) there is also sent a flow of methanol (72 ) for oxycombustion obtained from step Va).

10. The method for producing methanol (3, 57 ) and methane ( 11, 66) according to any one of claims 6 to 9, wherein said third flow of carbon dioxide from oxy-combustion (30, 70) is sent to step Va).

11. The method for the production of methanol (3, 57 ) and methane ( 11, 66) according to any one of claims 6 to 10, wherein said steps Va) and Via) are replaced respectively by the steps of:Vb) flushing said methanolation reactor R1 and said methanation reactor R2 with said third flow of carbon dioxide from oxy-combustion (30, 70),VIb) flushing said electrolyzer E with said first flow of steam from oxy-combustion (w7 ).

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