Method for converting carbon dioxide into SNG or LNG and storing hydrogen

Abstract

The present invention describes a method for storing electricity and producing synthetic natural gas called liquefied natural gas (LNG) or substitute natural gas (SNG), and a method for producing electricity, natural gas (NG) or synthetic natural gas (SNG) using carbon dioxide.

Description

Technical Field

[0001] Description The present invention is applicable to the use of isolated carbon dioxide and the field of manufacturing SNG and / or liquefied natural gas (LNG).

[0002] The methanation reactor requires a nearly continuous supply. In fact, frequent on / off switching not only shortens the life of the catalyst and the heat exchange train, but also requires a fairly long time to develop a heat profile to ensure the correct conversion of the reagent.

[0003] This can be avoided by producing and consuming hydrogen through methanation even during periods of energy shortage, and reducing the hydrogen demand of the reactor by turning it down.

[0004] Alternatively, it is also possible to store hydrogen produced without using energy in the form of compressed gas or liquid, which is much more suitable for large-scale storage.

[0005] To date, prior art hydrogen liquefaction requires 10 - 13 KWh / kg (source: DOE), and the lowest value is when using a low-rotational-volume compressor (efficiency 90%, reported in "Large-Scale Hydrogen Liquefaction from an Economic Perspective").

[0006] Since the lower calorific value of hydrogen is about 33.3 kWh / kg, liquefaction places a particularly heavy burden.

[0007] Regarding magnetic liquefaction, it seems to be only suitable for small-scale applications.

[0008] Attempts to achieve higher energy efficiency in liquefaction have led to replacing the pre-cooling of hydrogen with liquid nitrogen with a cooling cycle using a specific refrigerant mixture composed of light hydrocarbons and nitrogen, but some components of the mixture are at risk of freezing in cryogenic processes.

[0009] Since the Sabatier reaction is highly exothermic, there are problems with the temperature control of the methanation reactor. Usually, it is necessary to recycle a large amount of reaction products entering the first reactor using a recirculation compressor that operates at high temperatures, which is technically difficult.

[0010] The prior art document CN109943373 describes a process including the use of carbon dioxide in the hydrolysis of water and methanation, and the temperature control of the reactor is carried out by steam injection.

[0011] The prior art document Japanese Patent Application Laid-Open No. 2020-024065 describes a method for continuously supplying hydrogen to a hydrogen liquefaction system.

Summary of the Invention

[0012] Summary of the Invention The inventors of the present patent application have developed a process in which a part of the hydrogen produced (or generated; produce) by the hydrolysis of water is sent, together with carbon dioxide, to a methanation reactor for producing liquefied natural gas (LNG) or synthetic natural gas (SNG), while another part is cooled by the action of a hydrogen cooling system and optionally condensed and stored in the form of liquid and / or refrigerated compression.

[0013] Object of the Invention As a first object, the present invention describes a method for storing (or storing; store) electricity, producing liquefied natural gas (LNG) or synthetic natural gas (SNG), and using (or utilizing) carbon dioxide.

[0014] According to a preferred embodiment, the energy stored in this way is excess (or excess; excess) energy compared to the required amount.

[0015] As a second object, the present invention describes a method for producing electricity, natural gas (NG) or synthetic natural gas (SNG).

[0016] A method capable of storing electricity (or electric power), producing liquefied natural gas (LNG) or synthetic natural gas (SNG), using carbon dioxide, and producing electricity, natural gas (NG), synthetic natural gas (SNG), or alternative natural gas (SNG) according to the electricity usage situation will be described.

[0017] The present invention further relates to a plant that stores available surplus electricity, produces liquefied natural gas or synthetic natural gas, and uses carbon dioxide, and the plant can also generate power (or electric power) in the form of electricity under conditions where electricity is required.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0019] For the purpose of the present invention, the heat exchange performed in the heat exchangers (E1, E2, E3, E4, En) is carried out with an external fluid, preferably represented by air, water, etc.

[0020] The heat exchanger (denoted as “EXn”) enables heat exchange between two flows within one or more circuits as described in the present invention instead.

[0021] The method of the present invention includes the energy storage step of step A) and the chemical continuity step of step B).

[0022] For the purpose of the present invention, the storage step A) is a step in which hydrogen gas is produced that is assigned to the methanation step together with a carbon dioxide flow for producing LNG or SNG, with a part assigned for methanation and a part assigned for storage in liquid form.

[0023] An embodiment of step A) of the present invention is illustrated in FIG. 5, where switch valves SW1 and SW2 are open while SW3 is closed.

[0024] More specifically, the energy storage step A includes the following sub-steps: A1) Starting from a water flow a1, producing an oxygen gas flow a2 and a hydrogen gas flow a3 by electrolysis in an electrolyzer EL; A2) Obtaining a first hydrogen gas flow portion m1 and a second hydrogen gas flow portion l1; A3) Assigning the first hydrogen gas flow portion m1 to a methanation (or methanation) step and obtaining a condensed recycled water vapor flow W1 assigned to the methanation step; A4) Assigning the second hydrogen gas flow portion l1 to a cooling and liquefaction step to obtain a liquid hydrogen flow l16.

[0025] Therefore, for the purpose of the present invention, step A3) includes the use of carbon dioxide gas as described below.

[0026] In particular, the carbon dioxide gas flow used in the methanation step is obtained from a liquid CO2 source (CO2IN in the figure).

[0027] More specifically, the liquid CO2 flow cd0 is subjected to a first heating step to obtain a first CO2 gas flow cd1.

[0028] The first CO2 gas flow cd1 is subjected to a second heating step to obtain a methanated CO2 gas flow cd2.

[0029] According to one aspect of the present invention, a further CO2 gas flow cd1' obtained from a CO2 gas source can be added to the first CO2 gas flow cd1.

[0030] For the purpose of the present invention, the electrolysis sub-step A1) is carried out using electricity from renewable resources such as solar energy in some cases.

[0031] For this purpose, the water flow a1 is supplied to the electrolyzer EL at an appropriate pressure, for example up to 30 barg or up to 80 barg.

[0032] The obtained oxygen gas flow a2 is assigned to other purposes, liquefied, and possibly sold in some cases.

[0033] According to a preferred aspect of the present invention, the electricity used in the hydrolysis sub-step A1) is electricity that can be used in excess.

[0034] "Can be used in excess" means the amount of electricity available in the power network that is not required by the system.

[0035] For the purpose of the present invention, the sub-step A2) includes the following further sub-steps: A2a) cooling the hydrogen gas flow a3 to obtain a cooled hydrogen gas flow a4; A2b) separating a first portion wI of condensed water vapor from the cooled hydrogen gas flow a4 in a first separator S1 to obtain a partially dehydrated hydrogen flow a5; A2c) Compressing the partially dehydrated hydrogen flow a5 with a first compressor C1 to obtain a compressed hydrogen flow a6; A2d) Separating a first hydrogen gas flow portion m1 and a second hydrogen gas flow portion l1.

[0036] For the purposes of the present invention, sub-step A3) includes the following further sub-steps: A3a) Subjecting the first hydrogen gas flow portion m1 to heating in a first heat exchanger EX1 to obtain a methanated hydrogen flow m2; A3b) Subjecting the methanated hydrogen flow m2 to methanation in the presence of a methanated carbon dioxide flow cd2 to obtain a methanated product (or product) flow m7; A3c) Obtaining a partially dehydrated methanated product flow m10 and a condensed recirculated water vapor flow W1; A3d) Obtaining a further dehydrated methanated product flow m13; A3e) Subjecting the further dehydrated methanated product flow m13 to a further methanation step to thereby obtain a further methanated product flow m16; A3f) Subjecting the further methanated product flow m16 to cooling to obtain a cooled further methanated product flow m19; A3g) Subjecting the cooled further methanated product flow m19 to dehydration to obtain a dehydrated further methanated product flow m21; A3h) Subjecting the dehydrated further methanated product flow m21 to further cooling to obtain a two-phase flow m23 of a further methanated product; A3i) Obtaining a recirculated hydrogen flow h1 and a final liquid flow m26 of the methanated product.

[0037] For the purposes of the present invention, step A3b) includes the following further steps: A3b1) Subjecting the methanated hydrogen flow m2 to a first methanation step in a first methanation reactor R1 to thereby obtain a first methanated product m3; A3b2) Cooling to obtain a first cooled methanated product m4; A3b3) subjecting the first cooled methanation product m4 to a second methanation step in a second methanation reactor R2, thereby obtaining a second methanation product m5; A3b4) cooling to obtain a second cooled methanation product m6; A3b5) subjecting the second cooled methanation product m6 to a third methanation step in a third methanation reactor R3, thereby obtaining a methanation product flow m7.

[0038] For the purposes of the present invention, in the second methanation step A3b3), the first methanation CO2 portion cd3 separated from the methanation CO2 flow cd2 is employed.

[0039] For the purposes of the present invention, in the third methanation step A3b5), the second methanation CO2 portion cd4 separated from the first methanation CO2 portion cd3 is employed.

[0040] For the purposes of the present invention, step A3c) includes the following further steps: A3c1) expanding the methanation product flow m7 in a first expander EK1 capable of power generation (or with possible power production if possible), thereby obtaining an expanded methanation product flow m8; A3c2) cooling in a second exchanger E2 to obtain an expanded and cooled methanation product m9 flow; A3c3) separating a second condensed steam portion wII in a second separator S2 to obtain a partially dehydrated methanation product flow m10.

[0041] According to one aspect of the present invention, the recirculation condensed steam flow W1 is separated from the second steam portion wII separated in step A3c3) and assigned to the methanation step.

[0042] In particular, the recirculation steam flow W1 is assigned to the first and / or second methanation steps A3b3).

[0043] Advantageously, the control steam has a function of controlling the temperature of the methanation process.

[0044] According to a particular aspect of the invention, the recirculated steam flow W1 successively comprises the following: - Pumping (or pumping, or feeding; pumped) from the first pump P1 to obtain the pumped recirculated steam flow W2; - Heating in the fourth heat exchanger EX4 to obtain the pumped and heated steam flow W3; - Dividing the pumped and heated steam into a first part W4’ and a second part W4’’, each being heated, resulting in a first part W5’ and a second part W5’’ of the pumped and further heated steam, which are combined into a single pumped and further heated steam flow W6 and expanded in a turbine T1 with power generation, resulting in an expanded steam flow W7.

[0045] According to one aspect of the invention, the following are obtained from the expanded steam flow W7: - A first controlled steam portion W7’ sent to the first methanation step A3b1); - A second controlled steam portion W7’’ sent to the second methanation step A3b3); - Cooling the third steam portion W7’’’ to obtain a heat exchange water flow W8.

[0046] According to such an aspect of the invention, the heating of the first pumped and heated steam portion W4’ is carried out in the second heat exchanger EX2 by heat exchange with the first methanation product m3.

[0047] According to such an aspect of the invention, the heating of the second pumped and heated steam portion W4’’ is carried out in the third heat exchanger EX3 by heat exchange with the second methanation product m5.

[0048] For the purpose of the present invention, the step A3d) comprises the following further sub-steps: A3d1) Compressing the partially dehydrated methanation product flow m10 with a second compressor C2 to obtain a partially dehydrated and compressed methanation product flow m11; A3d2) Cooling the partially dehydrated and compressed methanation product flow m11 to obtain a partially dehydrated, compressed and cooled methanation product flow m12; A3d3) Separating a third condensed water vapor flow wIII in a third separator S3 to obtain a further dehydrated methanation product flow m13.

[0049] According to such an embodiment, step A3d2) is carried out in a fourth heat exchanger EX4 for heat exchange with the pumped recirculated water vapor flow W2.

[0050] For the purposes of the present invention, step A3d) can be repeated one or more times as required.

[0051] For the purposes of the present invention, before being subjected to a further methanation step A3e), the further dehydrated methanation product flow m13 is subjected to the following steps: - Compressing with a third compressor C3 to obtain a further dehydrated and compressed methanation product flow m14; - Heating with a fifth heat exchanger EX5 to obtain a dehydrated, compressed and heated methanation product M15 flow.

[0052] According to one embodiment of the present invention, the heating step is carried out in the fifth heat exchanger EX5 by heat exchange with a third vapor portion W7'''.

[0053] For the purposes of the present invention, step A3f) includes the following further steps: A3f1) Subjecting the flow m16 of the further methanation product to a first partial cooling, thereby obtaining a further methanation product flow m17 at a first partial cooling level; A3f2) Subjecting a further methanation product flow m17 at the first partial cooling level to a second partial cooling, thereby obtaining a further methanation product flow m18 at the second partial cooling level. A3f3) Subjecting a further methanation product flow m18 at the second partial cooling level to a third partial cooling in a third heat exchanger E3, thereby obtaining a cooled further methanation product flow m19.

[0054] For the purposes of the present invention, the first cooling step A3f1) is carried out in a first heat exchanger EX1 by heat exchange with a first hydrogen gas flow portion m1 assigned for methanation (step A3a described above).

[0055] For the purposes of the present invention, the second cooling step A3f2) is carried out in a sixth heat exchanger EX6 by heat exchange with a CO2 gas flow cd1, thereby obtaining a methanation CO2 flow cd2.

[0056] For the purposes of the present invention, step A3g) includes the following further steps: A3g1) Separating a fourth condensed vapor portion wIV in a fourth separator S4 to obtain a cooled and partially dehydrated further methanation product m20 flow. A3g2) Dehydrating the cooled and partially dehydrated further methanation product flow m20 in a first dehydration unit DU1, thereby obtaining a dehydrated further methanation product flow m21.

[0057] For the purposes of the present invention, step A3h) includes the following further steps: A3h1) Subjecting the flow m21 of the further methanation dehydrated product to a first cooling to obtain a cooled and dehydrated further methanation product flow m22 at the first cooling level. A3h2) Subjecting the flow m22 of the cooled and dehydrated further methanation product at the first cooling level to a second cooling in an eighth heat exchanger EX8 to obtain a two-phase flow m23 of the further methanation product.

[0058] For the purposes of the present invention, said step A3h1) is carried out in a seventh heat exchanger EX7 by heat exchange with a liquid CO2 flow cd0, whereby a first CO2 gas flow cd1 is obtained.

[0059] For the purposes of the present invention, said step A3i) comprises the following further steps: A3i1) expanding said further methanation product two-phase flow m23 by means of a first expansion valve V1, thereby obtaining an expanded two-phase flow m24; A3i2) separating from said expanded two-phase flow m24 a recycle hydrogen flow h1 from the head of a fifth separator and a methanation product enrichment flow m25; A3i3) further expanding said methanation product enrichment flow m25 with a second expansion valve V2 to obtain a final liquid flow m26 of the methanation product. The final liquid flow m26 of the methanation product is then stored in a tank for methanation product TLNG / SNG.

[0060] For the purposes of the present invention, a gas flow mh1 rich in methane and hydrogen can be drawn from the methanation product tank TLNG / SNG.

[0061] In one aspect of the present invention, said gas flow mh1 rich in methane and hydrogen is compressed by a fourth compressor C4, thereby obtaining a compressed gas flow mh2 rich in methane and hydrogen, which gas flow is sent to a further methanation step A3e) in a fourth reactor R4.

[0062] As described above, a recycle hydrogen flow h1 is also obtained from step A3i2).

[0063] For the purposes of the present invention, said recycle hydrogen flow h1 is subjected to the following steps: - obtaining a heated recycle hydrogen flow h2 by means of a first heating; - obtaining a further heated recycle hydrogen flow h3 by means of a second heating; - Obtaining a compressed recycled hydrogen flow h4 by compression of the fifth compressor C5.

[0064] According to such an embodiment of the present invention, the compressed recycled hydrogen flow h4 is sent to a further methanation step A3e) in the fourth reactor R4.

[0065] For the purposes of the present invention, in the above-described steps A3h1) and A3i2), the heat exchange in the seventh heat exchanger EX7 is also carried out by heat exchange with the heated recycled hydrogen flow h2.

[0066] For the purposes of the present invention, the heat exchange step further includes a first refrigerant fluid flow Ifr1 that circulates through a first refrigerant fluid circuit (designated as Ifr in the figure), supplies its refrigeration in the heat exchange in the seventh heat exchanger EX7, and obtains a heated first refrigerant fluid flow Ifr2.

[0067] Within the first refrigerant fluid cycle, the heated flow is cooled according to methods known in the art (not depicted in the figure) so as to provide a flow that participates in further heat exchange within the seventh heat exchanger EX7.

[0068] According to one aspect of the present invention, such a first refrigerant fluid is a fluid selected from the group consisting of propane, carbon dioxide, or a commercially available refrigerant.

[0069] In particular, for the purposes of the present invention, the steps A3h2) and A3i2) in the above-described eighth heat exchanger EX8 are carried out by heat exchange between the cooling and dehydration of the further methanation product flow m22 at the first cooling level and the recycled hydrogen flow h1.

[0070] For the purposes of the present invention, the heat exchange further includes a second refrigerant fluid flow IIfr1 that circulates through a second refrigerant fluid circuit (designated as IIfr in the figure), supplies its refrigeration in the heat exchange in the eighth heat exchanger EX8, and obtains a heated second refrigerant fluid flow IIfr2.

[0071] According to one aspect of the present invention, the second refrigerant fluid is a fluid selected from the group consisting of ethylene, methane, ethane, nitrogen, or mixtures thereof.

[0072] As described above, in step A4), the second hydrogen gas flow portion l1 is assigned to the cooling and liquefaction process, and liquid hydrogen is obtained.

[0073] For the purpose of the present invention, step A4) of assigning the second hydrogen gas flow portion l1 to cooling and liquefaction to obtain a liquid hydrogen flow l16 includes the following sub-steps: A4a) dehydrating the second hydrogen gas flow portion l1 to obtain a second dehydrated hydrogen gas portion l4; A4b) cooling the second dehydrated hydrogen gas portion l4 to obtain a liquid hydrogen flow l16 stored in the liquid hydrogen tank TH2l. For the purpose of the present invention, step A4a) includes the following further sub-steps: A4a1) cooling the second hydrogen gas flow portion l1 in a fourth heat exchanger E4 to obtain a cooled second hydrogen gas flow portion l2; A4a2) obtaining a partially dehydrated second hydrogen gas portion l3 flow by separating a fifth condensed water vapor portion wV in a sixth separator S6; A4a3) further dehydrating the partially dehydrated portion of the second hydrogen gas portion l3 in a second dehydration unit DU2 to obtain a second dehydrated hydrogen gas portion l4.

[0074] For the purpose of the present invention, step A4b) includes one or more heat exchanges with one or more flows of a hydrogen cooling fluid (hereinafter abbreviated as "frh") circulating within a hydrogen cooling (or refrigerating) fluid cycle, said flows being characterized by different temperatures and / or pressures.

[0075] For this purpose, the heat exchange can be carried out in a ninth heat exchanger EX9 and further heat exchangers as described below.

[0076] According to one aspect of the present invention, the hydrogen cooling fluid cycle flow can involve one or more separations, stackings, expansion steps with possible power generation, mixing therebetween, compression, and heat exchange with one or more external fluids and / or one or more additional refrigerant fluids, and the heat exchange can be direct or indirect.

[0077] For example, the hydrogen cooling fluid cycle can be a Claude cycle, as described below by way of non-limiting example.

[0078] According to one aspect of the present invention, the hydrogen cooling fluid is cooled by heat exchange with a further hydrogen cooling fluid flow that circulates within a circuit of the further hydrogen cooling fluid.

[0079] For the purposes of the present invention, the further hydrogen cooling fluid is liquid air or liquid nitrogen.

[0080] In particular, in step I), a first further pumped refrigerant fluid s1 performs heat exchange to give its frigorie to the hydrogen refrigerant fluid, and as a result, a second heated further refrigerant fluid s2 is obtained.

[0081] For example, such heat exchange can be performed in a ninth heat exchanger EX9.

[0082] Subsequently, the second heated flow of the further hydrogen cooling fluid s2 is subjected to step II) of being cooled, and thus, a cooled flow of a further hydrogen cooling fluid s3 is obtained. In step III), this flow is sent to a recovery tank sS. In step IV), a liquid flow of a further hydrogen cooling fluid s4 can be drawn from the recovery tank sS. This liquid flow is pumped in step V) by a pump of a further hydrogen cooling fluid sP, and thus, a first hydrogen cooling fluid flow s1 is obtained.

[0083] Regarding step II) of cooling the second fluid flow of the further hydrogen cooling fluid s2 described above, this is carried out including a liquid air flow.

[0084] In particular, step II) is carried out by heat exchange with the pumped liquid air flow q2 in the tenth heat exchanger EX10, whereby a heated liquid air flow q3 is obtained.

[0085] On the other hand, the pumped air flow q2 is obtained by pumping the pumping air flow q1 with a pumping air pump qP.

[0086] The initial liquid air (or liquid nitrogen) flow q1 is obtained from a tank qTl in which liquid air is stored, as will be described later in connection with step B) of the method of the present invention.

[0087] According to one embodiment of the present invention, the heated liquid air flow q3 can then be expanded in a liquid air expander qEK with possible power generation, whereby an expanded air flow q4 can be obtained, and this expanded air flow q4 can be further heated by heat exchange in the tenth heat exchanger EX10, whereby a heated air flow q5 that can be discharged into the atmosphere can be obtained.

[0088] According to one embodiment of the present invention, the hydrogen cooling fluid can also perform heat exchange with one or more further flows.

[0089] In this regard, the hydrogen cooling fluid can participate in the heat exchange in the seventh heat exchanger EX7 by cooling.

[0090] Therefore, in step A) of the method of the present invention, the following can be obtained: - Oxygen gas, - LNG or SNG, - Liquid hydrogen, - Power generation, in particular, power can be generated by: - In the first expander EK1, - In any expander of the hydrogen cooling fluid circuit, - In the liquid air flow expander qEK.

[0091] However, the power generation does not exceed the amount of energy absorbed by the network, especially in the hydrolysis step A1) of water. In fact, the generated energy is mainly used for the operation of the machines implementing this method.

[0092] Therefore, in step A) of the method according to the invention, - It is possible to use surplus electricity. In particular, such energy is used in the electrolysis step A1) of water and, to a lesser extent, also for the operation of the machines (compressors and pumps).

[0093] Regarding step B) of the method according to the invention, it includes sub-step B1), in which, starting from liquid hydrogen storage, a continuous hydrogen gas flow b3 assigned to the methanation step is obtained, as a result of which LNG or SNG is obtained.

[0094] An embodiment of step B) of the invention is schematically shown in Figure 6, in which the switch valves SW1 and SW2 are closed and SW3 is open.

[0095] Step B further includes manufacturing a liquid air storage. More specifically, sub-step B1 includes the following further sub-steps: B1a) Drawing a continuous liquid hydrogen flow b1 from the liquid hydrogen tank TH2l; B1b) Pumping up said flow with a liquid hydrogen pump PH2l to obtain a pumped-up continuous liquid hydrogen flow b2; B1c) Heating said pumped-up continuous liquid hydrogen flow b2 to obtain a continuous hydrogen gas flow b3 and allocating it to the methanation step described above.

[0096] If necessary, said continuous hydrogen gas flow b3 forms the first part of said hydrogen gas flow m1.

[0097] Regarding step B1d), such heating is carried out in the eleventh heat exchanger EX11 by heat exchange with a first carrier fluid flow fv1 circulating within the carrier fluid cycle.

[0098] For the purpose of the present invention, the carrier fluid is nitrogen or oxygen-depleted air.

[0099] In particular, after heat exchange with the continuous expanding hydrogen flow b3, a second cooled carrier fluid fv2 is obtained, which is collected in the carrier fluid tank fvS.

[0100] A third carrier fluid fv3 is drawn therefrom and pumped by a pump of the carrier fluid fvP to become a fourth carrier fluid fv4, and is heated by heat exchange to become a first carrier fluid fv1.

[0101] In particular, the heating of the fourth carrier fluid flow fv4 is obtained in a twelfth heat exchanger EX12 for heat exchange with one or more heat exchange air flows assigned for producing liquid air storage, as will be described later.

[0102] In particular, the initial ambient air flow p1 is subjected to the following steps: - Compression and cooling capable of separating condensed water vapor - Dehydration Thereby, a dehydrated air flow p5 is obtained.

[0103] In particular, the initial ambient air flow p1 is compressed by a first ambient air compressor pC1 to obtain a compressed ambient air flow p2.

[0104] Such a compressed ambient air flow p2 is cooled in a first ambient air exchanger pE1 to obtain a compressed and cooled ambient air flow p3.

[0105] Condensed water vapor is separated in the ambient air separator pS to obtain a sixth condensed water vapor portion wVI and a partially dehydrated ambient air flow p4.

[0106] The steps of compression and cooling can be repeated as necessary.

[0107] The partially dehydrated atmospheric air flow is further dehydrated in the air dehydration device pDU, and a dehydrated air flow p5 is obtained.

[0108] A part of the dehydrated air p6 is separated from the dehydrated air flow p5.

[0109] Such a dehydrated air portion p6 is involved in a heat exchange process performed with the fourth carrier fluid flow fv4 in the twelfth heat exchanger EX12.

[0110] Regarding the dehydrated air flow p5, a heat exchange dehydrated air flow p9 is obtained through processes of compression and cooling, and this air flow p9 further undergoes heat exchange with the fourth carrier fluid flow fv4 in the twelfth heat exchanger Ex12.

[0111] In particular, the dehydrated air flow p5 is compressed by the dehydrated air compressor pC2 to become a compressed dehydrated air flow p8, and is cooled by the dehydrated air heat exchanger pE2 to become a heat exchange dehydrated air flow p9.

[0112] The heat exchange dehydrated air flow p9 and the dehydrated air portion p6 are two heat exchange air flows as described above. Actually, both flows are cooled by heat exchange with the fourth carrier fluid flow fv4 in the twelfth heat exchanger EX12, and from this, a first liquid air flow p10 and a second liquid air flow p7 are obtained.

[0113] Next, the first liquid air flow p10 is depressurized by the first air valve pV1, and as a result, a depressurized flow of the first liquid air flow p11 is obtained.

[0114] The depressurized flows of the first liquid air flow p11 and the second liquid air flow p7 are combined into a single liquid air flow p12 and sent to the liquid air tank pTl.

[0115] For the purpose of the present invention, the continuous liquid hydrogen flow b1 in step B1a) is drawn from the liquid hydrogen tank TH2l containing the liquid hydrogen stored during the above-described step A4).

[0116] Next, the methanation step is carried out with a hydrogen gas flow obtained from the liquid hydrogen stored in the above-described step A4), and is used in step B) in a situation where electricity is required, in other words, in a situation where electricity cannot be used in excess (for carrying out the hydrolysis step A1)).

[0117] For the purpose of the present invention, the tank in which the liquid air pTl is stored in step B) is the tank from which the initial liquid air flow q1 is drawn, and when this liquid air flow q1 is pumped up, it generates a pumped-up liquid air flow q2 that participates in heat exchange in the tenth heat exchanger EX10 of step A).

[0118] Example of step A4b) As described above, step A4b) includes cooling and liquefying the second dehydrated hydrogen gas portion l4 to obtain a liquid hydrogen flow l16 and storing this in a liquid hydrogen tank TH2l.

[0119] Such cooling can be carried out by a cycle of a hydrogen cooling fluid (abbreviated as "frh") according to various modes known in the art.

[0120] One of the modes described below by way of example is the Claude cycle (referred to as step C) shown in FIG. 5 for convenience.

[0121] According to such a mode, the cooling is carried out by the first heat exchanger of the cycle rFH rEX1 (such a heat exchanger corresponds to the ninth heat exchanger EX9 described in the above step A).

[0122] According to such an embodiment, the dehydrated hydrogen gas flow l4 is subjected to the following steps: C1) Performing a first cooling with the first heat exchanger rEX1 of the cycle rFH to obtain a hydrogen flow l5 at a first cooling level, C2) Obtain a first portion l6’ and a second portion l6’’ of the hydrogen flow at the first cooling level, subject each of them to ortho / para allotropic conversion in a first converter CONV1 and a second converter CONV2 respectively to obtain a converted first portion l7’ and a converted second portion l7’’, and combine these into a converted single flow l8. C3) The converted single flow l8 is cooled by heat exchange and further converted within a special conversion section of the first exchanger rEX1c of the cycle frh to obtain a hydrogen flow l9 at the second cooling level. C4) Perform cooling and conversion in the second heat exchanger rEX2 of the cycle frh to obtain a hydrogen flow l10 at the third cooling level. C5) Perform cooling and conversion in the third heat exchanger rEX3 of the hydrogen cooling cycle to obtain a hydrogen flow l11 at the third cooling level. C6) Perform cooling and conversion in the fourth heat exchanger rEX4 of the cycle frh to obtain a hydrogen flow l12 at the fourth cooling level. C7) Perform cooling and conversion in the fifth heat exchanger rEX5 of the cycle frh to obtain a hydrogen flow l13 at the fifth cooling level. C8) Expand the hydrogen flow l13 at the fifth cooling level by means of a third expansion valve V3 to obtain an expanded hydrogen flow l14 at the fifth cooling level. C9) Combine it with the recirculating hydrogen flow H2r to produce a single hydrogen flow l15. C10) It is cooled and converted in the sixth heat exchanger rEX6 of the cycle frh to obtain a liquid hydrogen flow l16, which is stored in a liquid hydrogen tank TH2l.

[0123] The recirculating hydrogen flow H2r is obtained from the head of such a tank TH2l and can be combined with the expanded hydrogen flow at the fifth cooling level l14 as described in step C9) above.

[0124] Each hydrogen flow cooling step is carried out in the presence of a suitable catalyst within an appropriate section of the heat exchanger, as a result of which the hydrogen is converted from the ortho-isomer to the para-isomer and stabilized.

[0125] Therefore, each cooling process is also a conversion and stabilization process.

[0126] Regarding the hydrogen cooling fluid cycle, when represented by a Claude cycle, it can be described starting from the first hydrogen cooling fluid flow r1 (abbreviated as the refrigerant fluid and denoted by the reference symbol "r"). This hydrogen cooling fluid flow r1 is cooled by heat exchange in the seventh heat exchanger EX7, thereby obtaining the second refrigerant fluid flow r2.

[0127] The second flow frh r2 is cooled by heat exchange in the first exchanger rEX1 of the cycle frh, obtaining the third flow frh r4.

[0128] The third flow frh r3 is cooled in the second exchanger rEX2 of the cycle frh, obtaining the fourth flow frh r4.

[0129] The fourth flow frh r4 is cooled in the third exchanger rEX3 of the cycle frh, obtaining the fifth flow frh r5.

[0130] The fifth flow frh r5 is cooled in the fourth exchanger rEX4 of the cycle frh, obtaining the sixth flow frh r6.

[0131] The sixth flow frh r6 is cooled in the fifth exchanger rEX5 of the cycle frh, obtaining the seventh flow frh r7.

[0132] The seventh flow frh r7 is expanded in the first expander rEK1 of the cycle frh where power generation is possible, obtaining the eighth flow frh r8.

[0133] The eighth flow frh r8 is further expanded by the second valve rV2 of the cycle rfh, obtaining the ninth flow frh r9.

[0134] In the separator of the cycle frh rS, the twelfth liquid flow frh r12 and the tenth gas flow frh r10 are obtained from the ninth flow frh r9.

[0135] The 10th gas flow frh r10 is heated by the heat exchange of the 6th heat exchanger rEX6 of the cycle frh, and the 11th gas flow frh r11 is obtained.

[0136] The 12th flow r12 is heated by the heat exchange of the 6th heat exchanger rEX6 of the cycle frh, the 13th flow frh r13 is obtained, and the 11th flow frh r11 is combined with this.

[0137] The 13th flow r13 is heated by the heat exchange in the 5th heat exchanger frh rEX5, and the 14th flow frh r14 is obtained.

[0138] The 14th flow frh r14 is heated by the heat exchange in the 4th heat exchanger rfh rEX4, and the 15th flow r15 is obtained.

[0139] The 15th flow frh r15 is heated by the heat exchange in the 3rd heat exchanger frh rEX3 to obtain the 16th flow frh r16.

[0140] The 16th flow r16 is heated by the heat exchange in the 2nd heat exchanger frh rEX2 to obtain the 17th flow frh r17.

[0141] The 17th flow frh r17 is heated by the heat exchange in the 1st heat exchanger frh rEX1 to obtain the 18th flow frh r18.

[0142] The 18th flow frh r18 is compressed by the 1st compressor of the cycle of frh rC1 to become the 19th flow frh r19, and this flow is cooled by the 7th exchanger of the cycle frh rE7 to become the 20th flow frh r20.

[0143] Optionally, the compression and cooling steps can be repeated as necessary.

[0144] According to a possible embodiment, the portion r4' is separated from the fourth flow frh r4, which is expanded by the power generation possible with the second expander of the cycle frh rEK2, and a further fourth flow frh r4'' is obtained.

[0145] According to a possible embodiment, the portion r5' is separated from the fifth flow frh r5, which is expanded by the power generation possible with the third expander of the cycle frh rEK3, and a further fifth flow frh r5'' is obtained.

[0146] The said further fifth flow frh r5'' is heated by heat exchange in the fourth heat exchanger frh rEK4 of the cycle, and as a result, the 21st flow frh r21 is obtained.

[0147] The 21st flow frh r21 is heated by heat exchange in the third heat exchanger rEX3 to obtain the 22nd flow frh r22.

[0148] The 22nd flow r22 frh is heated by heat exchange in the second heat exchanger rEX2 to obtain the 23rd flow r23 frh.

[0149] The 23rd flow frh r23 is heated by heat exchange in the first heat exchanger rEX1 to obtain the 24th flow frh r24, which is compressed by the second compressor frh rC2 of the cycle to obtain the 25th flow frh r25.

[0150] The said 25th flow rfh r25 is combined with the 27th flow rfh r20, thus obtaining the 26th flow rfh r26, which is compressed by the third compressor frh rC3 of the cycle, thus obtaining the 27th flow rfh r27, which is cooled by the eighth cooler rEX8, thus obtaining the first hydrogen cooling fluid flow r1.

[0151] The present invention further relates to a plant that stores available surplus electricity, produces liquefied natural gas or synthetic natural gas, and uses carbon dioxide, which can also produce power in the form of electricity under conditions where electricity is required.

[0152] In particular, such a plant includes the following: - A module (M1) for producing hydrogen by electrolysis of water, - A module (M2) for methanation and power generation as required, - A first refrigerant fluid cycle and optionally a second refrigerant fluid cycle (M3) for liquefying the methanation product, - A module (M4) for liquefying hydrogen gas and generating electricity, - A module (M5) for gasifying liquid hydrogen, - A module (M6) for liquefying air, - Valves for allocating the hydrogen flow obtained by electrolysis to methanation or liquefaction, and valves for allocating the hydrogen flow gasified from liquefied hydrogen to methanation, - Tanks for storing liquid hydrogen (TH2l), liquid methanation products (TLNG / SNG), and liquid air (pTl),

[0153] For the purposes of the present invention, the module for producing hydrogen by electrolysis of water also produces oxygen.

[0154] For the purposes of the present invention, the module for producing hydrogen by electrolysis of water can also use surplus electricity as described above.

[0155] According to one aspect of the present invention, the methanation module includes one or more methanation reactors.

[0156] According to one aspect of the present invention, the methanation module includes a system for dehydrating the methanation product and recycling at least a part of the separated water to the methanation reactor itself.

[0157] According to one aspect of the present invention, the methanation module uses gaseous or gasified carbon dioxide.

[0158] According to one aspect of the present invention, a module that liquefies hydrogen gas to produce power includes a circuit for an additional hydrogen cooling fluid.

[0159] According to one aspect of the present invention, a liquid hydrogen gasification module includes a cycle of a carrier fluid.

[0160] According to one aspect of the present invention, the carrier fluid cycle is also part of a liquid air circuit.

[0161] For the purposes of the present invention, the described plant includes valves in an open configuration for sending a portion of the hydrogen gas obtained by water electrolysis to a methanation module (M2) and for sending a portion of the hydrogen gas obtained by water electrolysis to a hydrogen liquefaction module (M4), while the valve for sending the liquefied hydrogen to a hydrogen gasification module (M5) is closed.

[0162] The advantages provided by the present invention will become immediately apparent from the above description.

[0163] First, the method uses carbon dioxide isolated from the environment or other sources (exhaust gas) for the production of combustible gas and can supply it to the natural gas network.

[0164] Furthermore, although not a secondary advantage, the method enables the continuous supply of hydrogen and carbon dioxide to the methanation reactor (chemical continuity), ensuring the continuity of the process.

[0165] This continuity enables the avoidance of reactor shutdown even when there is a shortage of electricity used for the hydrolysis of water.

[0166] Overall, this method stabilizes the electrical network, absorbs surplus power when it is generated, and stores it for use in case of shortages.

[0167] In addition, by vaporizing the liquefied natural gas obtained by the method of the present invention, the gas network can be partially supplied and the gas network can be stabilized.

[0168] Part of the produced oxygen gas, LNG and / or SNG, and hydrogen gas may be salable.

[0169] More specifically, the method of the present invention activates reaction control by using separate steam in the method itself to optimize the methanation process.

[0170] Furthermore, this can eliminate the reaction gas recirculation compressor that is usually used in the methanation section and is technically quite a burden due to severe operating conditions. This is achieved by injecting steam in place of recirculation of the reaction gas.

[0171] In the method of the present invention, a large amount of hydrogen can be stored beyond the daily and / or seasonal available energy amount, and the amount of energy lost by cooling the hydrogen can be limited. This means that the conversion ability from CO2 to SNG is large.

[0172] The surplus energy is converted into SNGLNG and used in other power generation systems and transportation systems.

Claims

1. A method for storing electricity, producing liquefied natural gas (LNG) or synthetic or alternative natural gas (SNG), and using carbon dioxide, comprising the following steps: A1) Starting with a water flow a1, oxygen gas flow a2 and hydrogen gas flow a3 are produced by electrolysis in an electrolytic cell EL. A2) To obtain a first hydrogen gas flow portion m1 and a second hydrogen gas flow portion l1, A3) In the presence of carbon dioxide gas, the first hydrogen gas flow portion m1 is allocated to the methane process, and a condensed recirculated water vapor flow W1 is obtained for the methane process, and methane is carried out. A4) A method comprising allocating the second hydrogen gas flow portion l1 to a cooling and liquefaction process to obtain a liquid hydrogen flow l16 and storing it in a liquid hydrogen tank TH2l.

2. The method according to claim 1, wherein step A1) is carried out using electricity from available surplus electricity and / or renewable resources.

3. The method according to claim 1 or 2, wherein the carbon dioxide gas in step A3) is obtained from liquid carbon dioxide.

4. The method according to claim 1 or 2, wherein step A3) includes the following further sub-steps: A3a) The first hydrogen gas flow portion m1 is heated in the first heat exchanger EX1 to obtain a methane hydrogen flow m2. A3b) The hydrogen methane flow m2 is subjected to methanation in the presence of the methanated carbon dioxide flow cd2 to obtain the methanated product flow m7. A3c) To obtain a partially dehydrated methane product flow m10 and a condensed recirculated steam flow W1. A3d) To obtain a further dehydrated methane product flow m13, A3e) The further dehydrated methane product flow m13 is subjected to a further methane process to obtain a further methane product flow m16. A3f) The further methane product flow m16 is subjected to cooling to obtain the cooled further methane product flow m19. A3g) The cooled further methane product flow m19 is subjected to dehydration to obtain the dehydrated further methane product flow m21. A3h) The dehydrated further methane product flow m21 is subjected to further cooling to obtain a further two-phase methane product flow m23. A3i) Obtain the recirculated hydrogen flow h1 and the final liquid flow m26 of the methane product.

5. The method according to claim 4, wherein step A3b) includes the following further steps: A3b1) The hydrogen methane flow m2 is subjected to a first methane step in a first methane reactor R1 to obtain a first methane product m3. A3b2) Cool to obtain the first cooled methane product m4. A3b3) The first cooled methane product m4 is subjected to a second methane step in a second methane reactor R2 to obtain a second methane product m5. A3b4) Cool to obtain a second cooled methane product m6. A3b5) The cooled second methane product m6 is subjected to a third methane step in a third methane reactor R3 to obtain a methane product flow m7, where In the second methane step A3b3), methane CO ２ First methane CO separated from flow cd2 ２ Part cd3 is adopted, here In the third methane step A3b5), the first methane CO ２ Second methane CO separated from partial cd3 ２ Partial cd4 is adopted.

6. The method according to claim 4, wherein step A3c) further includes the following steps: A3c1) The methane product flow m7 is expanded with a first expander EK1 capable of generating electricity to obtain the expanded methane product flow m8. A3c2) Cool the second exchanger E2 to obtain the expanded and cooled methane product flow m9. A3c3) Separate the second condensed water vapor portion wII in the second separator S2 to obtain a partially dehydrated methane product flow m10.

7. The method according to claim 6, wherein step A3d) includes the following further steps: A3d1) The partially dehydrated methane product flow m10 is subjected to compression by the second compressor C2 to obtain a partially dehydrated and compressed methane product flow m11. A3d2) Cool the partially dehydrated and compressed methane product flow m11 to obtain a partially dehydrated, compressed and cooled methane product flow m12. A3d3) Separating the third condensed water vapor flow wIII in the third separator S3 to obtain a dehydrated methane product flow m13.

8. The method according to claim 7, wherein the condensed recirculating steam flow W1 is employed in the first and / or second methane step.

9. The method according to claim 1 or 2, wherein step A4) includes the following sub-steps: A4a) Dehydrate the second hydrogen gas flow portion l1 to obtain a second dehydrated hydrogen gas portion l4. A4b) Cool the second dehydrated hydrogen gas portion l4 to obtain a liquid hydrogen flow l16 and store it in the liquid hydrogen tank TH2l, here Step A4b) includes one or more heat exchanges with one or more hydrogen cooling fluid flows.

10. The method according to claim 9, wherein the hydrogen cooling fluid is sequentially cooled by heat exchange with a further hydrogen cooling fluid flow circulating in a circuit of further hydrogen cooling fluids, and is liquid air or liquid nitrogen.

11. A method for producing electricity, natural gas (NG), or synthetic natural gas or alternative natural gas (SNG), including sub-step B1), comprising starting from liquid hydrogen storage, obtaining a continuous hydrogen gas flow b3, assigning it to a methane step, and obtaining LNG or SNG.

12. The method according to claim 11, wherein step B1) includes the following further sub-steps: B1a) To draw a continuous liquid hydrogen flow b1 from the liquid hydrogen tank TH2l, B1b) The flow is pumped up using a liquid hydrogen pump PH2l to obtain the pumped-up continuous liquid hydrogen flow b2. B1c) Heat the pumped continuous liquid hydrogen flow b2 to obtain a continuous hydrogen gas flow b3, and allocate it to the methane process.

13. The method according to claim 12, wherein step B1c) is carried out by heat exchange with a first carrier fluid flow fv1 circulating within a carrier fluid cycle.

14. The method according to claim 13, wherein the carrier fluid performs heat exchange with one or more heat exchange air flows for producing liquid air.

15. The method according to claim 14, wherein the continuous liquid hydrogen flow b1 of step B1a) is drawn from a liquid hydrogen tank TH2l containing liquid hydrogen stored during step A4) of the method according to claim 1).

16. A method for storing electricity, producing liquefied natural gas (LNG) or synthetic or alternative natural gas (LNG or SNG), and using carbon dioxide to produce electricity, natural gas (NG) or synthetic or alternative natural gas (SNG), the method comprising the step of carrying out the method according to claim 1 or 2.

17. A plant that stores usable surplus electricity, produces liquefied natural gas or synthetic natural gas, and uses carbon dioxide, and which, under conditions where electricity is required, can generate power in the form of electricity, and which includes the following: - Module (M1) that produces hydrogen by electrolysis of water. - Methane generation module (M2) and, if necessary, power generation module. - A first refrigerant fluid cycle for liquefying methane products and, if necessary, a second refrigerant fluid cycle (M3), - A module (M4) that generates electricity by liquefying hydrogen gas. - Module for gasifying liquid hydrogen (M5) - Module for liquefying air (M6), - Tanks for storing liquid hydrogen (TH2l), liquid methane products (TLNG / SNG), and liquid air (pTl). - A valve for allocating the hydrogen flow obtained by electrolysis to methane (SW1) or liquefaction (SW2), and a valve (SW3) for allocating the hydrogen flow gasified from liquefied hydrogen to methane, where The valves (SW1, SW2) are configured to be open to send a portion of the hydrogen gas obtained by water electrolysis to the methane module (M2) and a portion of the hydrogen gas obtained by water electrolysis to the hydrogen liquefaction module (M4), while the valve (SW3) for sending liquefied hydrogen to the hydrogen gasification module (M5) is either closed or vice versa.

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