On-site power generation from methane or methanol and with carbon dioxide cyclicity without connection to power grid

Abstract

The invention relates to a power plant (1) comprising two units (A) and (B), a first unit (A) and a second unit (B), located in two separate industrial sites, having:-the first unit (A) comprising a synthesis device (8) capable of producing methane or methanol (15) from hydrogen (2) and carbon dioxide (4) originating from the second unit (B), and-a second unit (B) comprising fuel cell means (5) that can be supplied with electric current (1) by methane or methanol (15) originating from the first unit (A) and an anode gas stream (6) comprising carbon dioxide, said fuel cell means being combined with collecting means (7) for collecting carbon dioxide (17) in the anode stream (6) intended for the first unit (A).

Description

[0001] The present invention relates to an apparatus for generating electricity from methane or methanol produced in another unit (hereinafter referred to as the "first unit") and recovering carbon dioxide in one unit (hereinafter referred to as the "second unit"), the two units being located at two separate industrial sites.

[0002] In particular, the present invention will be applied to the case of a first unit (preferably a land unit) connected to a conventional grid (a continental metropolitan area network) and a second unit not connected to the conventional grid.

[0003] Examples of units not connected to a conventional power grid include those located in water (sea, lake, or river), in off-grid rural areas, on islands, etc., and / or all mobile units.

[0004] For example, on a water based unit many auxiliary elements consume energy: refrigerator, navigation lights, anchor lights, VHF, interior lighting, navigation aids, water pumps, etc. This energy necessary for safety and comfort is drawn from onboard batteries which therefore need to be recharged periodically.

[0005] Water based units, such as boats, will require a lot of energy in terms of motor power.

[0006] One of the solutions that can be used to generate this energy and recharge the batteries needed for the auxiliary equipment is to use fuel cells.

[0007] Fuel cells generate electricity through an electrochemical reaction between a combustible fluid and oxygen from the air. Fuel cells are typically composed of one or more solid oxide fuel cells (SOFCs).

[0008] These cells are primarily designed for stationary applications, where the output power is in the range of 1 kW to 2 MW.In the context of the present invention, the fuel cell device will preferably provide an output power in the range of 15 MW to 100 MW.

[0009] SOFC elements are usually made of four layers, three of which are ceramic. A single cell consisting of these four stacked layers is usually only a few millimeters thick. Dozens of these cells are then stacked in series to form a cell stack.

[0010] In these cells, oxygen ions formed on the cathode side move through a solid oxide serving as a high temperature electrolyte to react with a fuel gas, such as hydrogen, on the anode side.

[0011] This electrochemical reaction results in the generation of electricity, as well as the formation of carbon dioxide and water (byproducts of the electrochemical reaction).

[0012] However, carbon dioxide CO2 is one of the main greenhouse gases, and its release into the atmosphere contributes to global warming. In order to reduce the environmental impact of fuel cells, it is therefore necessary to minimize the carbon dioxide emissions into the atmosphere.

[0013] This raises the question of how to provide a power generation plant with reduced environmental impact.

[0014] One solution of the invention is a power plant 1 comprising two units, a first unit A and a second unit B, located at two separate industrial sites, the power plant having:

[0015] a first unit A comprising a synthesis device 8 capable of producing methane or methanol 15 from hydrogen 2 and carbon dioxide 4 originating from the second unit B, and

[0016] - a second unit B comprising a fuel cell device 5 capable of being supplied with electric current 1 by methane or methanol 15 and an anode gas stream 6 containing carbon dioxide originating from the first unit A, said fuel cell device being combined with a collection device 7 for collecting carbon dioxide 17 in the anode stream 6 intended for the first unit A.

[0017] The device according to the invention may comprise one or more of the following features considered individually or in any technically possible combination:

[0018] - the first unit is connected to the mains grid and the second unit is not connected to the mains grid;

[0019] - The first unit comprises an electrolyser capable of producing hydrogen from water and electricity, and components for liquefying methane or methanol;

[0020] - the second unit comprises, upstream of the fuel cell device, means for storing liquid methane or liquid methanol originating from the first unit and means for gasifying the liquid methane or liquid methanol;

[0021] - the second unit comprises means for liquefying carbon dioxide originating from the carbon dioxide collection device;

[0022] - The second unit is selected from a vessel or a fixed or floating platform.

[0023] Another object of the invention is a method for generating electricity using the device as defined above and comprising the steps of:

[0024] a) a step of preparing methane or methanol in the first unit from hydrogen and carbon dioxide originating from the second unit,

[0025] b) a step of generating, on a second unit, electricity and an anode gas stream comprising carbon dioxide from the methane or methanol originating from the first unit using a fuel cell device, and

[0026] c) A step of collecting carbon dioxide on a second unit to form a carbon dioxide gas stream used in step a) and a carbon dioxide-depleted anode stream.

[0027] The method according to the invention may comprise one or more of the following features considered individually or in any technically possible combination:

[0028] - the method comprises, upstream of step a), a step of preparing hydrogen by electrolysis carried out on a first unit;

[0029] - The method comprises between steps a) and b):

[0030] a step of liquefying the methanol or methane produced in step a) carried out in a first unit,

[0031] - a step of storing liquefied methanol or liquefied methane carried out on the second unit, and

[0032] - a step of gasifying the stored methanol or methane carried out in a second unit;

[0033] - the method comprises, between steps b) and c), a step of cooling and condensing the anode stream comprising carbon dioxide in order to dry said anode stream;

[0034] - the method comprises, downstream of step c), a step of recycling the carbon dioxide-depleted anode stream to the fuel cell device;

[0035] - downstream of step c), the process comprises a step of liquefying the carbon dioxide gas stream;

[0036] - In step c), the anode stream is contacted with a liquid solvent capable of absorbing carbon dioxide to form a carbon dioxide-depleted anode stream and a bottom liquid stream comprising the carbon dioxide-loaded liquid solvent.

[0037] [ Figure 1 ] Figure 1 A diagram showing a device according to the invention is shown.

[0038] The synthesis unit is preferably a "synthesis reactor".

[0039] "Two different industrial sites" preferably means two sites which are separated from each other by a distance of more than 30 km, preferably more than 100 km, even more preferably by a distance of several hundred kilometres.

[0040] The invention therefore consists in coupling a first unit for synthesizing fuel, in this case methane or methanol, with a second unit for generating electricity.

[0041] Synthetic methanol can be prepared by various methods:

[0042] -Thermocatalytic methanation: Hydrogen and CO2 are pressurized and mixed and then fed into a series of catalytic reactors to produce synthetic methane.

[0043] -Methanation by electrochemical reduction: water and CO2 are injected into an electrolyser to directly produce synthetic methane. Alternatively, the process can be carried out in two stages: a co-electrolysis stage, in which water and CO2 are converted to CO and H2 in a SOEC, followed by a thermocatalytic conversion of CO and H2 to CH4.

[0044] - Biomethanation: Synthetic methane is produced biologically, i.e. using microorganisms. H2 can be fed directly into a methanator to convert CO2 in situ. Alternatively, a dedicated bioreactor is used, which is fed with H2 and CO2 to produce methane.

[0045] The synthesis of methanol from hydrogen and carbon dioxide is represented by three macroscopic reactions:

[0046] Reaction 1: CO2+3H2→CH3OH+H2O

[0047] Reaction 2: CO2+H2→CO+H2O

[0048] Reaction 3: CO + 2H2 → CH3OH

[0049] In reaction 1, CO2 reacts with hydrogen to produce methanol and water. This is accompanied by reaction 2, the reverse water gas shift (RWGS), which consumes the same reagents but is undesirable for our purposes. The production of CO by RWGS opens another route to methanol synthesis: the hydrogenation of CO (reaction 3).

[0050] Methanol synthesis is carried out on one or more types of solid catalysts, preferably copper-based catalysts. Among them, Cu / ZnO / Al2O3 is a conventional catalyst due to its excellent activity and low price compared to other catalysts. Methanol selectivity is highest when copper is supported on alumina, while the highest methanol yield is observed on zinc oxide. They showed that alumina improves methanol selectivity because it facilitates the reduction of copper species that are believed to be responsible for methanol synthesis.

[0051] The methanol synthesis will preferably be carried out in a tubular fixed bed reactor, preferably similar to the tubular reactor described in FR3103714.

[0052] The principle behind the process of producing methanol from CO2 is very simple. A H2 / CO2 mixture (preferably preheated) is sent to a reactor, the output stream of which is directed to a separation section, where methanol (along with water and a small percentage of higher alcohols) is condensed. Unreacted gases are returned to the reactor to maximize the yield, as the conversion is typically about 20%. The methanol is finally purified by distillation.

[0053] The synthesis of methane using carbon dioxide and dihydrogen is known as the Sabatier reaction (Sabatier 1902):

[0054] Reaction 4: CO2+4H2→CH4+2H2O

[0055] The reaction is carried out in the presence of a catalyst, preferably nickel. At temperatures below 200°C, the conversion of CO2 to CH4 is negligible. Methane synthesis is best carried out at temperatures between 250°C and 700°C.

[0056] Similar to the methanol synthesis, the methane synthesis will preferably be carried out in a tubular fixed bed reactor, preferably similar to the tubular reactor described in FR3103714.

[0057] The principle behind the process of producing methane from CO2 is similar to that of methanol production. A H2 / CO2 mixture is sent to a reactor, the outlet stream of which is directed to a separation section where methane is condensed. Unreacted gases are returned to the reactor to maximize the yield. The methanol is finally purified by distillation.

[0058] The fuel cell device consists of one or more solid oxide fuel cells (SOFCs). Each fuel cell is continuously fed with a methane or methanol stream injected at the anode system (partial reforming occurs before injection at the anode) and an oxygen-rich gas stream injected at the cathode system.

[0059] Depending on the circumstances, the device according to the invention may have one or more of the following features:

[0060] - The first unit A is connected to the mains and the second unit B is not connected to the mains. As mentioned previously, examples of units not connected to the mains include units located in water (sea, lake or river), off-grid rural areas, on islands etc. and / or all mobile units.

[0061] - The first unit A and the second unit B are two land-based units;

[0062] - the first unit A is a fixed unit, preferably a land-based unit, and the second unit B is a mobile unit, preferably a water-based unit;

[0063] - The second unit is selected from a ship or a fixed or floating platform. A fixed platform is a platform anchored to the sea bed. In the case of a ship, the electricity supplied by the fuel cell device can be used as power.

[0064] - The first unit A comprises an electrolyser 8 capable of producing hydrogen 2 from water 9 and electricity 10, and means 15 for liquefying methane or methanol. Preferably, the electricity will come from renewable sources. Preferably, the methane is liquefied through a series of cryogenic cycles. Alternatively, the methane can also be liquefied in an "open cycle", i.e. by passing the methane itself through compressors and coolers so that it undergoes expansion to produce the necessary cooling.

[0065] The second unit B comprises, upstream of the fuel cell device 5 , means 14 for storing liquid methane or liquid methanol originating from the first unit A and means 11 for gasifying the liquid methane or liquid methanol.

[0066] the second unit B comprises means 12 for liquefying the carbon dioxide 17 originating from the carbon dioxide collection device 7; the second unit will preferably comprise a compressor between the carbon dioxide collection device 7 and the liquefaction means 12. The liquefied carbon dioxide 16 can then be stored at the second unit B before being sent to the first unit A, where it is then stored in the storage means 13 and finally used in the methane or methanol synthesis unit 8.

[0067] - The means 11 for gasifying liquid methane or liquid methanol and the means 12 for liquefying carbon dioxide are combined into a single heat exchange device. The carbon dioxide transfers its heat to the liquid methane or methanol and vice versa, so that the carbon dioxide is liquefied, while the methane or methanol is gasified.

[0068] The second unit comprises, upstream of the carbon dioxide collection device 7 , a post-treatment, cooling and condensation device designed to cool and dry the anode gas stream 6 to form a dry anode stream.

[0069] -The carbon dioxide collection device 7 comprises:

[0070] an absorber designed to contact the dry anode stream with a liquid solvent capable of absorbing carbon dioxide to form a carbon dioxide-depleted anode stream at the top of the absorber and a bottom liquid stream comprising the carbon dioxide-laden liquid solvent at the bottom of the absorber,

[0071] - at least one heat exchanger system for heating the bottom liquid stream to form a heated bottom liquid stream,

[0072] A vessel connected to said at least one heat exchanger system, designed to form a carbon dioxide stream at the top of the vessel and a partially regenerated liquid solvent stream at the bottom of the vessel, the partially regenerated liquid solvent stream being designed to be injected into the absorber.

[0073] - The carbon dioxide collection system does not have a stripping column.

[0074] The electrolyser will preferably be powered by a low-carbon energy source, preferably a renewable energy source. In the electrolyser, at the anode, water (H2O) is dissociated by an electric current to form oxygen (O2) and H+ ions; at the cathode, the H+ ions recombine to form hydrogen (H2). This hydrogen is called "green" when it is obtained from decarbonized energy.

[0075] The electrolyser will preferably be a proton exchange membrane (PEM) or a high temperature electrolyser (such as a SOEC) or an alkaline electrolyser.

[0076] Preferably, the post-treatment, cooling and condensing means also converts at least some of the carbon monoxide present in the anode gas stream into hydrogen and carbon dioxide, typically by reaction with steam. This conversion then limits oxidation of the liquid solvent used in the carbon dioxide collection means by oxidizing the carbon monoxide molecules and increases the carbon dioxide concentration in the anode gas stream to facilitate its collection in the collection means.

[0077] The apparatus according to the invention will preferably comprise means for recovering an oxygen-depleted gas stream. This oxygen-depleted gas stream will be post-treated and / or discharged to the atmosphere.

[0078] A desulfurization step would not be necessary upstream of the fuel cell, since the synthesis gas (methane or methanol) does not contain any desulfurization step.

[0079] Another object of the invention is a method for generating electricity at sea using the device according to the invention, the method comprising the following steps:

[0080] a) a step of preparing methane or methanol 15 in a first unit A from hydrogen 2 and carbon dioxide 4 originating from a second unit B,

[0081] b) a step of producing, at the second unit B, electricity 1 and an anode gas stream 6 comprising carbon dioxide from methane or methanol 15 originating from the first unit using a fuel cell device, and

[0082] c) Step 7 of collecting carbon dioxide in the second unit B to form the carbon dioxide gas stream 17 used in step a) and a carbon dioxide-depleted anode stream.

[0083] The method according to the invention may have one or more of the following features:

[0084] - it comprises, upstream of step a), a step of preparing hydrogen by electrolysis 8 carried out in a first unit A;

[0085] - which comprises between steps a) and b):

[0086] - a step of liquefying the methanol or methane produced in step a) carried out on a land-based unit,

[0087] - a step of storing 14 liquefied methanol or liquefied methane on a sea-based unit, and

[0088] - A step of gasification 11 of the stored methanol or methane carried out on a sea-based unit.

[0089] - it comprises, between steps b) and c), a step of cooling and condensing the anode stream comprising carbon dioxide in order to dry said anode stream;

[0090] - it comprises, downstream of step c), a step of recycling the carbon dioxide-depleted anode stream to the fuel cell device;

[0091] - downstream of step c), it comprises a step 12 of liquefying the carbon dioxide gas stream 17. Downstream of the collecting device 7, the carbon dioxide gas stream 17 is compressed to a pressure between 15 and 40 bar, then cooled to a temperature between -15°C and -50°C by heat exchange with liquid methane or liquid methanol, and then expanded to reach liquid CO2 storage conditions (for example: 17 bar and -28°C). The liquid CO2 16 can be stored first on a second unit, then on a first unit in the storage part 13, and then used in the methane or methanol synthesis unit 8;

[0092] - the step 11 of gasifying methane or methanol is carried out by heat exchange with a hot gas stream;

[0093] - the carbon dioxide-lean anode stream has 0 to 80 vol. %, preferably 20 vol. %

[0094] to 70% by volume, even more preferably 40% to 60% by volume of carbon dioxide content;

[0095] - in step c), contacting the anode stream with a liquid solvent capable of absorbing carbon dioxide to form a carbon dioxide-depleted anode stream and a bottom liquid stream comprising the carbon dioxide-loaded liquid solvent;

[0096] - releasing the absorbed carbon dioxide in the bottom liquid stream by heating the bottom liquid stream to form a portion of the carbon dioxide stream used in step a) and a portion of the regenerated liquid solvent stream;

[0097] - before being injected into the fuel cell device 5, the methane or methanol is heated by heat exchange with the carbon dioxide gas stream;

[0098] - recovering in the carbon dioxide gas stream at least 80%, preferably at least 90 mol%, more preferably 90 mol% to 99 mol% of the carbon dioxide produced during operation of the process.

[0099] Preferably, the apparatus according to the invention will also comprise a closed heat exchange circuit comprising a heat transfer fluid intended to exchange heat with the bottom liquid stream comprising the liquid solvent loaded with carbon dioxide at said at least one heat exchanger system on the one hand and with the anode gas stream and / or the cathode gas stream on the other hand.

[0100] Advantageously, the methane or methanol introduced into the fuel cell device will be at a pressure between atmospheric pressure and 2 bar, preferably at a temperature between 300°C and 500°C.

[0101] The hydrogen oxygen rich gas stream typically has a hydrogen oxygen content of at least 10% by volume, preferably 15% to 25% by volume of hydrogen oxygen. Advantageously, the hydrogen oxygen rich gas stream is an air stream.

[0102] Preferably, the hydrogen oxygen rich gas stream is at a pressure between atmospheric pressure and 2 bar.

[0103] Preferably, the liquid solvent used in the collecting device is selected from aqueous amine solutions capable of absorbing carbon dioxide.

[0104] Chemical absorption methods using aqueous amine solutions capable of absorbing carbon dioxide are well known to those skilled in the art and will not be further described herein. Examples of aqueous amine solutions suitable for use in the present invention include solutions consisting of one or more of the following compounds: monoethanolamine, diethanolamine, N-methyldiethanolamine, piperazine, 2-amino-2-methylpropan-1-ol, bis(2-hydroxypropyl)amine, 1-methylpiperazine, dimethylaminoethanol.

[0105] The various equipment and utilities required for the proper operation of the absorption unit are known to those skilled in the art and will not be described further in the remainder of the specification.

[0106] Upon contact with the dry anode stream, the liquid solvent absorbs carbon dioxide present in the dry anode stream to form a bottom liquid stream comprised of the carbon dioxide loaded liquid solvent and a carbon dioxide lean anode stream at the top of the absorber 200 .

[0107] The carbon dioxide-lean anode stream generally comprises 10% to 60% by volume, preferably 30% to 50% by volume, of carbon dioxide CO 2 .

[0108] The bottom liquid stream consisting of the liquid solvent loaded with carbon dioxide is then heated to form a preheated bottom stream. The preheated bottom stream 206 is then heated again so that the carbon dioxide absorbed in the liquid solvent is partially released in gaseous form. Generally, the preheated bottom stream is preferably heated to a temperature above 70° C., preferably above 80° C., specifically close to 90° C. by heat exchange. The heated bottom stream is introduced into a container to form a carbon dioxide stream at the top of the container, and a carbon dioxide-depleted liquid solvent stream is formed at the bottom of the container.

[0109] The carbon dioxide-depleted liquid solvent stream is then reinjected into the absorber for recycle.

[0110] The carbon dioxide-depleted liquid solvent stream withdrawn from the bottom of the vessel then comprises the starting liquid solvent and some absorbed carbon dioxide that was not released by expansion in vessel 216 .

[0111] Typically, at least 15%, preferably at least 35%, more preferably from 55% to 65% of the liquid solvent is still loaded with carbon dioxide.

[0112] In other words, the carbon dioxide-depleted liquid solvent stream has a carbon dioxide content greater than or equal to 0.1 mol CO2 / mol amino solvent (on a dry basis), preferably 0.15 mol to 0.4 mol CO2 / mol amino solvent (on a dry basis), and even more preferably 0.30 mol to 0.35 mol CO2 / mol amino solvent (on a dry basis).

[0113] Preferably, the carbon dioxide lean liquid solvent stream is cooled prior to reinjection into the absorber, preferably by heat exchange with a bottoms liquid stream from the absorber.

[0114] The carbon dioxide-lean liquid solvent stream may also undergo an additional cooling step before injection into the absorber, for example by passing it through a heat exchanger using an external refrigerant source.

[0115] In the solution proposed by the invention, carbon circularity is achieved: the carbon dioxide produced by the fuel cell is reused in a methane or methanol synthesis plant.

[0116] Thus, the main benefit is the reduction of the carbon footprint associated with the recycling of carbon dioxide. Since the amount of CO2 required for methanogenesis is significant and biogenic CO2 resources are limited, CO2 circularity helps to reduce emissions in the chain.

Claims

1. A power generation device (1), comprising two units, a first unit (A) and a second unit (B), said units being located at two separate industrial sites, said power generation device having: - said first unit (A) comprising a synthesis device (8) capable of producing methane or methanol (15) from hydrogen (2) and carbon dioxide (4) originating from said second unit (B), and - said second unit (B) comprising a fuel cell device (5) capable of supplying electric current (1) from methane or methanol (15) originating from said first unit (A) and from an anode gas stream (6) containing carbon dioxide, said fuel cell device being combined with a collection device (7) for collecting carbon dioxide (17) in the anode stream (6) intended for said first unit (A).

2. The power generation device according to claim 1, characterized in that The first unit (A) is connected to the main grid and the second unit (B) is not connected to the main grid.

3. The power generation device according to claim 1, characterized in that The first unit (A) comprises an electrolyser (8) capable of producing hydrogen (2) from water (9) and electricity (10), and methane or methanol liquefaction means (15).

4. The power generation device according to one of claims 1 to 3, characterized in that The second unit (B) comprises, upstream of the fuel cell device (5), means (14) for storing liquid methane or liquid methanol from the first unit (A) and means (11) for gasifying the liquid methane or liquid methanol.

5. The power generation device according to one of claims 1 to 4, characterized in that The second unit (B) comprises means (12) for liquefying the carbon dioxide (17) originating from the carbon dioxide collection device (7).

6. Offshore power generation plant according to one of claims 1 to 5, characterized in that The second unit (B) is selected from a vessel or a fixed or floating platform.

7. A method for generating electricity using a device according to one of claims 1 to 6, the method comprising the following steps: a) a step of producing methane or methanol (15) in the first unit (A) from hydrogen (2) and carbon dioxide (4) originating from the second unit (B), b) a step of generating, on said second unit (B), electricity (1) and an anode gas stream (6) comprising carbon dioxide from methane or methanol (15) originating from said first unit using said fuel cell device, and c) In said second unit (B), a step (7) of collecting carbon dioxide to form a carbon dioxide gas stream (17) and a carbon dioxide-depleted anode stream used in step a).

8. The method for generating electricity according to claim 7, characterized in that Said process comprises, upstream of step a), a step (8) of producing hydrogen by electrolysis carried out in said first unit (A).

9. A method for generating electricity according to one of claims 7 or 8, characterised in that The method comprises between steps a) and b): - a step of liquefying the methanol or methane (15) produced in step a) carried out in said first unit (A), - a step (14) of storing said liquefied methanol or said liquefied methane carried out on said second unit, and - A step (11) of gasifying the stored methanol or methane carried out on said second unit.

10. Method for generating electricity according to one of claims 7 to 9, characterized in that The method comprises, between steps b) and c), a step of cooling and condensing the anode stream comprising carbon dioxide in order to dry the anode stream.

11. Method for generating electricity according to one of claims 7 to 10, characterized in that The method comprises, downstream of step c), the step of recycling the carbon dioxide-depleted anode stream to the fuel cell device.

12. Method for generating electricity according to one of claims 7 to 11, characterised in that The method comprises, downstream of step c), a step of liquefying (12) the carbon dioxide gas stream (17).

13. Method for generating electricity according to one of claims 7 to 12, characterised in that The carbon dioxide-lean anode stream has a carbon dioxide content of 0 to 80% by volume, preferably 20 to 70% by volume, even more preferably 40 to 60% by volume.

14. A method for generating electricity according to any one of claims 7 to 13, characterised in that In step c), the anode stream is contacted with a liquid solvent capable of absorbing carbon dioxide to form the carbon dioxide-lean anode stream and a bottom liquid stream comprising the carbon dioxide-loaded liquid solvent.

15. Method for generating electricity according to one of claims 7 to 14, characterised in that At least 80%, preferably at least 90 mol%, more preferably 90 mol% to 99 mol% of the carbon dioxide produced during operation of the process is recovered in the carbon dioxide gas stream.

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