Hydrogen production plant including a hydrogen recirculation branch

Abstract

Installation (1) for producing dihydrogen, comprising an electrochemical device (2) and a fluid network which comprises at least one inlet conduit (11, 16, 61-64) configured to convey to the electrochemical device (2) an inlet flow comprising a fluid such as water in the gaseous state, the fluid network comprising at least one recirculation branch (RC1) configured to introduce into the at least one inlet conduit (11) a portion of an outlet flow which comprises dihydrogen, the electrochemical device (2) being configured to form the dihydrogen of the outlet flow from the inlet flow. Corresponding method for producing dihydrogen. Figure for abstract: Fig. 2

Description

Title of the invention: Hydrogen production installation comprising a hydrogen recirculation branch Technical field

[0001] The invention relates to the field of industrial production of dihydrogen.

[0002] The invention relates more specifically to installations implementing high-temperature electrolysis technologies known under the English name “Solid Oxide Electrolysis Cell (SOEC)”. State of the prior art

[0003] In the field of dihydrogen production, it is known to carry out high-temperature electrolysis, using an electrochemical device forming a reaction zone designed to convert water vapor into dihydrogen. In other words, the electrochemical device carries out vapor-phase electrolysis, with water vapor at a temperature which can be between 100°C and 850°C.

[0004] The reaction zone of a conventional electrolyser is formed by stacks of cells each having an anode, a cathode and an electrolyte. High temperature electrolysis makes it possible to decompose the water vapour so as to form, at the cathode of the cells, a flow of a fluid which comprises dihydrogen as well as unreacted water.

[0005] There is a need to improve the efficiency of hydrogen production plants and, in particular, to reduce their energy consumption and improve the steam conversion rate in the electrolyzer. Statement of the invention

[0006] The subject of the invention is a dihydrogen production installation, comprising an electrochemical device and a fluidic network which comprises: - at least one inlet conduit configured to convey to the electrochemical device an inlet flow comprising a fluid such as water in the gaseous state, - at least one recirculation branch configured to introduce into the at least one inlet conduit a portion of an outlet flow which comprises dihydrogen, the electrochemical device being configured to form the dihydrogen of the output stream from the input stream.

[0007] The electrochemical device may be a conventional electrolyser, in particular a high-temperature electrolyser, i.e. a device configured to carry out electrolysis of a fluid such as water in the vapor phase.

[0008] Such a recirculation branch makes it possible to introduce dihydrogen into the inlet flow.

[0009] It is thus possible to reduce or eliminate the risks of oxidation or premature degradation of the electrolyser, to improve the conversion rate in the electrolyser, to reduce the need for cooling and, consequently, to reduce the consumption of external energy and therefore to increase the efficiency of the installation.

[0010] The installation may comprise one or more members for processing the output flow, for example one or more members for cooling and / or compressing and / or purifying the output flow.

[0011] In a non-limiting manner, one or more of the aforementioned treatment members may be chosen from a list comprising members implementing an adsorption, absorption and / or membrane and / or distillation and / or conversion technique.

[0012] In one embodiment, the at least one recirculation branch is configured to introduce into the at least one inlet conduit a portion of the outlet flow treated by one or more of said treatment members.

[0013] According to a first variant, the at least one recirculation branch can be configured to introduce into the at least one inlet conduit a portion of the outlet flow treated by a member for purifying the outlet flow.

[0014] According to a second variant, the at least one recirculation branch can be configured to introduce into the at least one inlet conduit a portion of the outlet flow treated by a member for compressing the outlet flow.

[0015] According to a third variant, the at least one recirculation branch can be configured to introduce into the at least one inlet conduit a portion of the outlet flow treated by a member for cooling the outlet flow.

[0016] The aforementioned variants are not limiting and can of course be combined with each other. Thus, for example, the at least one recirculation branch can be configured to introduce into the at least one inlet conduit a portion of the outlet flow treated by a cooling member and / or by a compression member and / or by a member for purifying the outlet flow.

[0017] In one embodiment, the installation comprises at least one fan.

[0018] Said fan may be configured to move the output flow to one or several of said processing bodies.

[0019] In a first variant embodiment, the at least one recirculation branch is configured to take a portion of the outlet flow upstream of one or more of said treatment members, relative to a flow direction of the outlet flow.

[0020] In a second embodiment, the at least one recirculation branch is configured to take a portion of the outlet flow downstream of the fan, rela- tively to the flow direction of the outlet flow.

[0021] These variants can be combined so that the at least one recirculation branch is configured to take a portion of the outlet flow upstream of one or more of said treatment members and downstream of the fan, relative to the flow direction of the outlet flow.

[0022] In one embodiment, the installation comprises at least one ejector.

[0023] The at least one recirculation branch may comprise such an ejector.

[0024] According to a first variant embodiment in which the installation comprises an ejector, the ejector is configured to introduce into the at least one inlet conduit a portion of the outlet flow.

[0025] The ejector may in particular be configured to take this part of the output flow in the fluid network upstream of one or more of said treatment members, relative to a flow direction of the outlet flow.

[0026] According to a second variant embodiment in which the installation comprises an ejector, the ejector is configured to introduce into a second section of the at least one inlet conduit a portion of the inlet flow conveyed by a first section of the at least one inlet conduit.

[0027] These variants can be combined, the installation being able for example to comprise: - a first ejector configured to introduce into the at least one inlet conduit a portion of the outlet flow which can be taken from the fluid network upstream of one or more of said treatment members, and - a second ejector configured to introduce into a second section of the at least one inlet conduit a portion of the inlet flow conveyed by a first section of the at least one inlet conduit.

[0028] In one embodiment, the installation comprises a heat exchanger configured to transfer thermal energy from the outlet stream to the inlet stream.

[0029] According to a first variant embodiment in which the installation comprises a heat exchanger, the at least one recirculation branch is configured to introduce a portion of the outlet flow into the at least one inlet conduit upstream of the heat exchanger, relative to a flow direction of the inlet flow in the at least one inlet conduit.

[0030] According to a second variant embodiment in which the installation comprises a heat exchanger, the at least one recirculation branch is configured to introduce a portion of the outlet flow into the at least one inlet duct downstream of the heat exchanger, relative to a flow direction of the inlet flow in the at least one inlet duct.

[0031] These variants can be combined, the installation being able to comprise, in a manner non-limiting: - a first recirculation branch configured to introduce a portion of the outlet flow into the at least one inlet conduit upstream of the heat exchanger, and - a second recirculation branch configured to introduce a portion of the outlet flow into the at least one inlet conduit downstream of this heat exchanger.

[0032] Alternatively or additionally, the installation may comprise a recirculation branch configured to introduce a portion of the outlet flow into the at least one inlet conduit upstream of a first heat exchanger and to introduce another portion of the outlet flow into the at least one inlet conduit downstream of a second heat exchanger.

[0033] In one embodiment, the installation is devoid of means for introducing a sweeping gas into the electrochemical device.

[0034] Alternatively, the installation may comprise means configured to introduce into the electrochemical device a second input flow, for example in the form of a sweep gas.

[0035] In one embodiment, said output stream is a first output stream, the electrochemical device being configured to form a second output stream comprising dioxygen.

[0036] In one embodiment, the installation comprises a heat exchanger configured to transfer thermal energy from the second output stream to said input stream.

[0037] In one embodiment, the installation comprises a storage device configured to store in the gaseous state dihydrogen formed by the electrochemical device.

[0038] In one embodiment, the installation comprises one or more members for processing the second output flow, for example one or more members for cooling and / or compressing and / or purifying the output flow, and / or a storage device configured to store in the gaseous state dioxygen formed by the electrochemical device.

[0039] The invention also relates to a process for producing dihydrogen using an installation as defined above.

[0040] The method preferably comprises the following steps: - introduction into said electrochemical device, via said at least one inlet conduit, of an inlet flow comprising a fluid such as water in the gaseous state, - electrolysis of the input stream, using the electrochemical device, so as to to form an output stream comprising dihydrogen, - introduction into the inlet duct of a part of the outlet flow, via said at least one recirculation branch.

[0041] Depending on the embodiments of the installation, the method may comprise, in a non-limiting manner: - processing of the output stream, or at least one of the output streams when there are several, for example using one or more of said processing units, and / or - an introduction into the at least one inlet conduit of a part of the outlet flow, or of at least one of the outlet flows when there are several, using said ejector, or of at least one of the ejectors when there are several, and / or - a transfer of thermal energy from the output flow, or from at least one of the output flows when there are several, to said input flow.

[0042] In addition to the aforementioned advantages, the invention makes it possible to optimize the purity and pressure of the outlet flow(s) and to optimize the heat recovery of the outlet flow(s).

[0043] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows. Brief description of the drawings

[0044] The following detailed description refers to the accompanying drawings in which: - [Fig.l] is a schematic view of a hydrogen production installation in accordance with the invention; - [Fig.2] is a schematic view of an embodiment in which the installation is configured to recirculate a stream of purified cold hydrogen; - [Fig.3] is a schematic view of an embodiment in which the installation is configured to recirculate a flow of unpurified cold dihydrogen; - [Fig.4] is a schematic view of an embodiment in which the installation is configured to recirculate a flow of cold, unpurified hydrogen that has undergone an absorption refrigeration cycle; - [Fig.5] is a schematic view of an embodiment in which the installation is configured to recirculate a flow of hot dihydrogen upstream of a heat exchanger; - [Fig.6] is a schematic view of an embodiment in which the installation is configured to recirculate a flow of hot dihydrogen downstream of a heat exchanger; - [Fig.7] is a schematic view of an embodiment in which the installation is configured to recirculate a flow of hot dihydrogen upstream of a heat exchanger using an ejector; - [Fig.8] is a schematic view of an embodiment in which the installation is configured to recirculate a flow of hot dihydrogen downstream of a heat exchanger using an ejector; - [Fig.9] is a schematic view of an embodiment in which the installation is configured to recirculate a stream of hot dihydrogen downstream of a heat exchanger using an ejector, the installation being designed to operate without introducing a sweep gas into the electrolyser. Detailed description of embodiments

[0045] A plant 1 for producing dihydrogen is illustrated schematically and simplified in [Fig.l]. [Fig.l] shows different elements of the plant 1 which can be implemented in accordance with the invention, it being understood that a plant in accordance with the invention may be devoid of one or more of the elements of [Fig.l] and / or comprise one or more additional elements.

[0046] In a non-limiting manner, the installation 1 of [Fig.l] comprises: - an electrochemical device 2, - a device 3 configured to form a flow of a fluid such as water in the gaseous state, this flow also being called a “vapor flow”, - a device 4 configured to form a flow of a fluid such as a so-called sweep gas, - a device 5 configured to provide a flow of a fluid such as a so-called safety gas, - a unit 6 for processing a flow of a fluid which includes dihydrogen, this flow also being called “first outlet flow”, - a device 7 for storing said first output stream, - a unit 8 for processing a flow of a fluid which includes dioxygen, this flow also being called “second output flow”, - a device 9 for storing said second output stream, - a system 10 called thermal and fluidic integration, - a fluid network which is configured to fluidically connect the aforementioned elements to each other.

[0047] In this example, the electrochemical device 2 is a solid oxide electrolyser, forming a technology known under the Anglo-Saxon name “Solid Oxide Electrolysis Cell” (SOEC). In a manner known per se, such an electrolyser 2 comprises one or more stacks of cells each forming a cathode, an anode and an electrolyte, so as to constitute a reaction zone. The electrolyser 2 is here configured to carry out high-temperature electrolysis, that is to say to form said first and second output flows from the flow of water vapour having a temperature which can typically be between 100°C and 850°C. As an indication, the current density in the electrolyser 2 can be between 0.3 and 1.5 A / cm2.

[0048] In this example, the device 3 comprises a steam generator configured to form the flow of steam from water coming from a water source (not shown).

[0049] The device 4 is configured to form a flow of a sweeping gas such as air or nitrogen, or even water in the gaseous state, in order to balance the pressure in the electrolyser 2 and to facilitate the evacuation of the oxygen which accumulates there.

[0050] The device 5 is configured to form said flow of safety gas, for example during start-up and / or transient and / or interruption phases. This device 5 may comprise a tank containing the safety gas, which may typically comprise dihydrogen.

[0051] In this example, the units 6 and 8 are provided for treating respectively the first and second output streams formed by the electrolyser 2, with a view to storing them in the devices 7 and 9, respectively. In a non-limiting manner, this treatment may typically comprise operations of cooling and / or compression and / or purification of these streams, carried out by one or more corresponding treatment members.

[0052] In a non-limiting manner, the purification which is optionally carried out by the units 6 and / or 8 may implement one or more technologies chosen from adsorption, absorption, membrane, distillation and conversion technologies.

[0053] The devices 7 and 9 may comprise one or more tanks configured to store, respectively, dihydrogen in the gaseous state and dioxygen in the gaseous state, at pressures which may range from atmospheric pressure to 700 bars.

[0054] In a non-limiting manner, the thermal and fluidic integration system 10 may comprise members such as one or more heat exchangers and / or one or more pumps and / or one or more flow control valves and / or one or more heating devices and / or one or more fans and / or one or more compressors and / or one or more coolers and / or one or more reservoirs.

[0055] With reference to [Fig.l], the fluid network of the installation 1 comprises in this non-limiting example: - one or more conduits 11 fluidly connecting the device 3 to the system 10 in order to convey said flow of steam from the device 3 to the system 10, - one or more conduits 12 fluidly connecting the device 4 to the system 10 in order to convey said flow of sweeping gas from the device 4 to the system 10, - one or more conduits 13 fluidly connecting the device 5 to the system 10 in order to convey said flow of safety gas to the system 10, - one or more conduits 16 fluidly connecting the system 10 to the device 2 in order to convey said flow of steam from the system 10 to the device 2, - one or more conduits 17 fluidly connecting the system 10 to the device 2 in order to convey said flow of sweeping gas from the system 10 to the device 2, - one or more conduits 18 fluidly connecting the system 10 to the device 2 in order to convey said flow of safety gas from the system 10 to the device 2, - one or more conduits 19 fluidly connecting the device 2 to the system 10 in order to convey said first output flow from the device 2 to the system 10, - one or more conduits 20 fluidly connecting the device 2 to the system 10 in order to convey said second output flow from the device 2 to the system 10, - one or more conduits 21 fluidly connecting the system 10 to the unit 6 in order to convey said first output flow from the system 10 to the unit 6, - one or more conduits 22 fluidly connecting the unit 6 to the device 7 in order to convey said first output flow from the unit 6 to the device 7, - one or more conduits 23 fluidly connecting the system 10 to the unit 8 in order to convey said second output flow from the system 10 to the unit 8, - one or more conduits 24 fluidly connecting the unit 8 to the device 9 in order to convey said second output flow from the unit 8 to the device 9.

[0056] With respect to the electrolyser 2, the conduits 11, 12, 13, 16, 17 and 18 form inlet conduits which allow different flows to be conveyed to the electrolyser 2, while the conduits 19 to 24 form outlet conduits which allow different flows to be conveyed into the installation 1 which leave the electrolyser 2.

[0057] The architecture illustrated in [Fig.l] is not limiting, [Fig.l] mainly aiming to illustrate in a generic manner an installation 1 according to the invention as well as its general operating principle. Thus, as an example of an alternative embodiment, several inlet flows, for example said steam flow and said safety gas flow, can be conveyed to the device 2 by one or more common inlet conduits, each at respective stages of implementation of the installation 1 (see further below). For example, several of the conduits 11, 13, 16 and 18 can be replaced by one or more common conduits.

[0058] Figures 2 to 9 show non-limiting examples of architectures which implement different combinations and different arrangements of several of the elements of the generic installation of [Fig.l].

[0059] Identical or similar elements are designated by the same reference numbers in the different figures. The preceding description applies by analogy to the embodiments described below. Conversely, the following description applies by analogy to the installation of [Fig.l].

[0060] In the embodiment of [Fig. 2], the installation 1 comprises elements similar to those of the installation of [Fig. 1], the storage devices 7 and 9 however not being shown in [Fig. 2]. The installation of [Fig. 2] is essentially described in the following according to its particularities compared to [Fig. 1].

[0061] Architecture of the installation of [Fig.2]

[0062] The installation 1 of [Fig.2] comprises, in a non-limiting manner, the following elements, which form said thermal and fluidic integration system 10: heat exchangers 31, 32 and 33, heating devices 35 and 36, valves 41 to 46, coolers 51 and 52, a separation device 53, a fan 54, as well as conduits 61 to 77.

[0063] In this example, the devices 35 and 36 each comprise an electric heater powered by an external electrical energy source (not shown).

[0064] The valves 41 to 46 may be conventional flow and / or pressure regulating valves.

[0065] In this example, the conduit 11 connected to the device 3 is divided into two branches. A first branch of the conduit 11 is fluidically connected to an inlet of the valve 41, while a second branch of the conduit 11 is fluidically connected to an inlet of the valve 42.

[0066] The conduit 61 is configured to fluidically connect an outlet of the valve 41 to a first inlet of the exchanger 31.

[0067] The conduit 62 is configured to fluidically connect an outlet of the valve 42 to a first inlet of the exchanger 32.

[0068] The conduit 63 is configured to fluidly connect a first outlet of the exchanger 31 to an inlet of the heating device 35. The outlet of the heating device 35 is fluidly connected to a first inlet of the electrolyser 2 by a conduit which corresponds to both the conduit 16 and the conduit 18 of the installation of [Fig.l].

[0069] The conduit 64 is configured to fluidically connect a first outlet of the exchanger 32 to a branch of the conduit 63.

[0070] The conduit 12 is configured to fluidically connect the device 4 to a first inlet of the exchanger 33.

[0071] The conduit 71 is configured to fluidly connect a first outlet of the exchanger 33 to the heating device 36. The outlet of the heating device 36 is fluidly connected to a second inlet of the electrolyser 2 by the conduit 17.

[0072] The conduit 19 is configured to fluidically connect a first outlet of the electrolyser 2 to a second inlet of the exchanger 31.

[0073] The conduit 21 is configured to fluidically connect a second outlet of the exchanger 31 to the unit 6.

[0074] The conduit 65 is configured to fluidically connect an outlet of the unit 6 to an inlet of the valve 45.

[0075] The conduit 66 is configured to fluidically connect an outlet of the valve 45 to a branch of the conduit 11, in this example upstream of the valve 4L.

[0076] The conduit 20 is configured to fluidically connect a second outlet of the electrolyser 2 on the one hand to a second inlet of the exchanger 32 via the conduit 67 and, on the other hand, to a second inlet of the exchanger 33 via the conduit 68.

[0077] The conduits 69 and 70 are configured to fluidically connect a second outlet of the exchanger 32 and 33, respectively, to the valve 43 and 44, respectively.

[0078] The conduit 23 is configured to fluidically connect the unit 8 to the valve 43 via a first branch of this conduit 23 and to the valve 44 via a second branch of this conduit 23.

[0079] In this example, the exchangers 31, 32 and 33 are configured to circulate the flows they receive counter-currently. Thus, the flow arriving in the exchanger 31 via its first inlet passes through the exchanger 31 counter-currently to the flow arriving in the exchanger 31 via its second inlet. The same applies to the exchangers 32 and 33.

[0080] In this example, the conduit 13 is configured to fluidly connect the device 5 to said first inlet of the exchanger 31, and said second outlet of the exchanger 31 is fluidly connected to a branch of the conduit 13 by the conduits 72 to 77, which connect in series the coolers 51 and 52, the separation device 53, the fan 54 and the valve 46.

[0081] The conduits 65 and 66 thus form a recirculation branch RC1 which makes it possible to introduce into the inlet conduit 11 a part of the flow leaving the unit 6, this flow coming from the electrolyser 2 and arriving at the unit 6 via the conduits 19 and 21 passing through the exchanger 31.

[0082] Similarly, the conduits 76 and 77 form a recirculation branch which makes it possible to introduce into the inlet conduit 13 a part of the flow leaving the fan 54, this flow coming from the electrolyser 2 and arriving at the fan 54 via the conduits 19, 72, 73 and 74 passing through the exchanger 31, the coolers 51 and 52 and the separation device 53.

[0083] Operation of the installation of [Fig.2]

[0084] In this non-limiting example, the installation 1 of [Fig.2] can be selectively placed in several configurations, including a di-hydrogen production configuration and a standby configuration.

[0085] First of all, a non-limiting example of operation of the installation 1 of [Fig.2] placed in the hydrogen production configuration will be described, which is a normal implementation configuration of this installation.

[0086] The device 3 is implemented to form a flow of water in the gaseous state, that is to say to form said flow of steam, at a pressure which can typically be between 1.5 bara and 3.5 bara and at a temperature which can typically be between 150°C and 750°C, preferably between 150°C and 250°C.

[0087] The steam flow leaving the device 3, also called “primary flow”, is conveyed to said first inlet of the electrolyser 2 via the conduits 11, 61, 62, 63, 64 and 16.

[0088] More precisely, a first fraction of the vapor flow is mixed in the conduit 11 with a fraction of a dihydrogen flow produced by the electrolyzer 2, that is to say a fraction of said first outlet flow, which is introduced into the conduit 11 by the recirculation branch RC1. This fraction of the first outlet flow is here called “recirculated fraction”.

[0089] The mixture formed by said first fraction of the vapor flow and said recirculated fraction of the first outlet flow is herein called “upstream mixed flow”.

[0090] The upstream mixed flow is conveyed to said first inlet of the exchanger 31 via the valve 41 and the conduit 61, so as to pass through the exchanger 31 to exit through its first outlet via the conduit 63. Said upstream mixed flow is reheated within the exchanger 31 by the first outlet flow conveyed to said second inlet of the exchanger 31 via the conduit 19.

[0091] A second fraction of the steam flow is conveyed to said first inlet of the exchanger 32 via the valve 42 and the conduit 62, so as to pass through the exchanger 32 to exit through its first outlet via the conduit 64 and be introduced into the conduit 63 to be mixed with said upstream mixed flow.

[0092] The mixture formed by said upstream mixed flow and said second fraction of the first vapor flow is herein called “downstream mixed flow”.

[0093] Said downstream mixed flow is conveyed to the heating device 35, then to said first inlet of the electrolyser 2 via the conduit 16, so as to form a first inlet flow for the electrolyser 2.

[0094] On leaving the exchanger 31, the first outlet flow is conveyed to the unit 6 via the conduit 21. In this example, the unit 6 carries out steps of cooling, compression and purification of the first outlet flow.

[0095] A first fraction of the first output flow thus treated by the unit 6 forms said recirculated fraction which leaves the unit 6 via the recirculation conduit 65 to be reinjected into the fluid network of installation 1 and mixed with said first fraction of the steam flow, depending on the quantity of dihydrogen desired in said first inlet flow.

[0096] In this non-limiting example, the installation 1 is implemented so that the first inlet flow enters the electrolyser 2 with a temperature between 650°C and 850°C and comprising a percentage of dihydrogen between 1% and 20% by mole.

[0097] For information purposes, the first outlet flow may typically contain a percentage of dihydrogen of between 60% and 80% by mole at the outlet of the exchanger 31.

[0098] A second fraction of the first output stream may typically exit the unit 6 through another of its outputs for storage (see conduit 22 and storage device 7 in [Fig.l]).

[0099] By passing through the exchanger 32, said second fraction of the steam flow is heated by a first fraction of a flow of dioxygen produced by the electrolyser 2, that is to say a fraction of said second outlet flow, which leaves the electrolyser 2 through its second outlet and which is conveyed to the exchanger 32 by the conduits 20 and 67. This first fraction of the second outlet flow leaves the exchanger 32 through its second outlet, after having transferred a part of its thermal energy to said second fraction of the steam flow, to be conveyed to the unit 8 through the conduits 69 and 23 passing through the valve 43.

[0100] A second fraction of the second outlet flow is extracted from the conduit 20 to be conveyed to said second inlet of the exchanger 33 via the conduit 68. This fraction leaves the exchanger 33 via its second outlet, after having transferred part of its thermal energy to the flow of sweeping gas (see below), being conveyed to the unit 8 via the conduits 70 and 23 via the valve 44.

[0101] In this example, unit 8 carries out steps of cooling, compression and purification of the mixture arriving via line 23. Unit 8, which is optional, typically makes it possible to remove impurities such as water, nitrogen, argon, carbon monoxide, or carbon dioxide. All or part of the flow of oxygen thus treated can be stored (see line 24 and storage device 9 in [Fig.l]).

[0102] The device 4 is used to form the flow of sweeping gas, in this example with air, at a pressure which can typically be between 1.5 bara and 3.5 bara and at a temperature which can typically be between 20°C and 750°C.

[0103] This flow of sweeping gas forms a second inlet flow which is conveyed to said second inlet of the electrolyser 2 by the conduits 12, 71 and 17, passing through the exchanger 33 and the heating device 36.

[0104] The flow of sweeping gas is heated within the exchanger 33 by said second fraction of the second outlet flow which arrives in this exchanger 33 via the conduit 68, then optionally by the heating device 36, so as to reach a temperature which can typically be between 650°C and 850°C at said second inlet of the electrolyser 2.

[0105] In the configuration which has just been described, the installation 1 of [Fig.2] makes it possible to recirculate part of a flow of dihydrogen which is produced by the electrolyser 2, in this example after cooling and purification within the unit 6.

[0106] Such recirculation makes it possible to introduce dihydrogen into the steam flow, in this example upstream of the exchanger 31, which in particular makes it possible to reduce or eliminate the risks of oxidation or premature degradation of the electrolyser 2.

[0107] The inventors estimate that the embodiment of [Fig.2] makes it possible to achieve an energy efficiency of the order of 88.9%, an energy consumption level of the order of 37.5 kWh / kg of dihydrogen, and a percentage of dihydrogen at the inlet of unit 6 greater than 70% by mole.

[0108] A non-limiting example of operation of the installation 1 of [Fig. 2] in standby configuration will now be described, which is a configuration that can typically be implemented when starting or stopping the installation 1, or in transient interruption phases. In standby configuration, the electrolyser 2 generally does not produce dihydrogen.

[0109] In this example, the device 3 and the exchanger 32 are not implemented when the installation 1 is in standby configuration.

[0110] With reference to the elements shown in dotted lines in [Fig.2], the device 5 is implemented so as to form a flow of safety gas comprising in this example dihydrogen and dinitrogen, this flow being conveyed to said first inlet of the exchanger 31 via the conduit 13.

[0111] In this example, the installation 1 in standby configuration is implemented so as to supply the electrolyser 2 with a flow of safety gas comprising a mixture which can typically comprise 4% dihydrogen and 96% nitrogen.

[0112] The safety gas flow makes it possible to avoid oxidation of the cells of the electrolyser 2 and to maintain them at temperatures which can typically be between 650°C and 850°C, while avoiding the risks linked to the presence of oxygen.

[0113] In standby configuration, the flow leaving the electrolyser 2 through its first outlet is routed to said second inlet of the exchanger 31 and leaves through its second outlet so as to pass through the conduits 72 to 77, the coolers 51 and 52, the separation device 53, the fan 54 and the valve 46, to then be introduced into conduit 13 and thus mixed with the safety gas flow.

[0114] The description relating to the operation of the installation 1 in the hydrogen production configuration applies by analogy to its operation in the standby configuration.

[0115] The embodiment of [Fig. 3] is described only in terms of its differences from that of [Fig. 2]. The preceding description applies by analogy.

[0116] The installation 1 of [Fig. 3] comprises a series of additional members 81 to 84 which are configured to process said first output flow downstream of the exchanger 31 and upstream of the unit 6, in particular when the installation 1 is in the hydrogen production configuration.

[0117] These additional members comprise in this example two cooling devices 81 and 82, a separation device 83 and a fan 84, which are fluidically connected to each other as well as to the exchanger 31 and the unit 6 by conduits 91 to 95 (see [Fig.3]).

[0118] The cooling devices 81 and 82 are configured to lower the temperature of the first outlet flow, which in this example typically allows it to reach a temperature of between 5°C and 20°C. Optionally, heat recovered by one or more of the devices 81 and 82 may be supplied to the device 3 (not shown).

[0119] The separation device 83 is configured to remove water present in the first outlet flow, in this case downstream of the device 82. For information purposes, the separation device 83 typically makes it possible to obtain at its outlet a composition of said first outlet flow which comprises more than 98% dihydrogen by mole. Optionally, the water recovered by the separation device 83 can feed the device 3 (not shown).

[0120] The fan 84 is generally configured to move the first output flow towards the unit 6 by increasing its pressure, which in particular makes it possible to avoid pressure jumps.

[0121] Unlike the embodiment of [Fig.2] in which the recirculation branch RC1 is connected to an outlet of the unit 6, the recirculation branch RC1 of the installation 1 of [Fig.3] is connected to the conduit 96 upstream of the unit 6 and, in this non-limiting example, downstream of the fan 84.

[0122] The installation 1 of [Fig.3] thus makes it possible to recirculate a fraction of the first output flow not treated by the unit 6, another fraction of this flow being directed towards the unit 6 to be treated there with a view to its storage.

[0123] In this example, the recirculated fraction of the first outlet flow is introduced into the steam flow in a manner analogous to the embodiment of [Fig.2], which also makes it possible to reduce or eliminate the risks of oxidation or degradation. premature failure of electrolyzer 2.

[0124] The inventors estimate that the embodiment of [Fig.3] makes it possible to achieve an energy efficiency of the order of 84.8%, an energy consumption level of the order of 39.3 kWh / kg of dihydrogen, and a percentage of dihydrogen at the inlet of unit 6 greater than 98% by mole.

[0125] The embodiment of [Fig.4] is described only in terms of its differences from that of [Fig.3]. The preceding description applies by analogy.

[0126] The installation 1 of [Fig.4] comprises an absorption refrigeration system 100 having a first inlet fluidically connected to the conduit 91 and a first outlet fluidically connected to the conduit 93, in place of the devices 81 and 82 and the conduit 92 of the installation of [Fig.3].

[0127] The device 100 further comprises a second inlet fluidly connected to the conduit 11 and a second outlet fluidly connected to a conduit 11B, the conduit 11B forming said first branch connected to the valve 41 as well as said second branch connected to the valve 42.

[0128] The system 100 is configured to cool the first output flow which arrives in the system 100 via the conduit 91 and which leaves it via the conduit 93, using the flow of steam produced by the device 3, this flow of steam arriving in the system 100 via the conduit 11 and leaving it via the conduit 11B.

[0129] In a non-limiting manner, the system 100 may use a heat transfer fluid comprising, for example, a mixture of water and ammonia, or a mixture of water and lithium bromide, the water forming a cooling medium.

[0130] In a manner known per se, the system 100 is implemented to carry out at least one absorption refrigeration cycle. In this example, the corresponding coefficient of performance can typically be between 0.6 and 0.8.

[0131] For information purposes, the system 100 typically makes it possible to obtain at its outlet a composition of said first outlet stream which comprises more than 98% of dihydrogen by mole, at a temperature between 5°C and 20°C.

[0132] The embodiment of [Fig.5] is described only in terms of its differences from that of [Fig.2]. The preceding description applies by analogy.

[0133] In the installation 1 of [Fig.5], the conduit 65 is fluidically connected to a branch of the conduit 21 so as to extract from the conduit 21 a fraction of said first outlet fluid.

[0134] By distinction with the recirculation branch RC1 shown in [Fig.2] which comprises only the conduits 65 and 66 and the valve 45, the recirculation branch RC2 of the installation of [Fig.5] comprises an additional member 105 and conduit 106.

[0135] In a non-limiting manner, the member 105 may comprise a fan and / or a pump and / or a compressor.

[0136] The member 105 comprises an inlet fluidly connected to the conduit 66 and an outlet fluidly connected to one end of the conduit 106, the other end of the conduit 106 being fluidly connected to said first branch of the conduit 11.

[0137] The recirculation branch RC2 thus makes it possible to take a first fraction of the first outlet flow, in this example downstream of the exchanger 31 and upstream of the unit 6, and to reintroduce this fraction into the conduit 11 to mix it with the steam flow.

[0138] A second fraction of the first output flow can be conveyed to unit 6 via conduit 21.

[0139] In this example, the member 105 is a fan, making it possible in particular to increase the pressure of the recirculated fraction while avoiding pressure jumps.

[0140] The installation 1 of [Fig.5] makes it possible to recirculate part of a flow of di-hydrogen which is produced by the electrolyser 2 and, thus, to reduce or cancel the risks of oxidation or premature degradation of the electrolyser 2.

[0141] The inventors estimate that the embodiment of [Fig.5] makes it possible to achieve an energy efficiency of the order of 90.5%, an energy consumption level of the order of 36.8 kWh / kg of dihydrogen, and a percentage of dihydrogen at the input of unit 6 greater than 70% by mole.

[0142] In a variant not shown of the embodiment of [Fig.5], said second fraction of the first outlet flow can be cooled by an additional cooling member, for example to reach a temperature between 5°C and 20°C, making it possible to remove from this fraction the water that it contains upstream of the unit 6.

[0143] Such a separation, which can be carried out by a separation member of the same type as the device 53, typically makes it possible to obtain at the inlet of the unit 6 an outlet flow comprising more than 98% of dihydrogen by mole.

[0144] The inventors estimate that such an embodiment variant makes it possible to achieve an energy efficiency of the order of 85.4%, an energy consumption level of the order of 39.0 kWh / kg of dihydrogen, and a percentage of dihydrogen at the inlet of unit 6 greater than 98% by mole.

[0145] The embodiment of [Fig.6] is described only in terms of its differences from that of [Fig.2]. The preceding description applies by analogy.

[0146] The installation 1 of [Fig.6] comprises a recirculation branch RC2 comprising a member 110 and conduits 111 and 112.

[0147] In a non-limiting manner, the member 110 may comprise a fan and / or a pump and / or a compressor.

[0148] The conduit 111 is configured to fluidically connect an inlet of the member 110 to a bifurcation of conduit 19.

[0149] The conduit 112 is configured to fluidically connect an outlet of the member 110 to a bifurcation of the conduit 16.

[0150] The recirculation branch of the installation 1 of [Fig.6] thus makes it possible to take a first fraction of the first outlet flow, in this example upstream of the exchanger 31, and to reintroduce this fraction into the conduit 16 to mix it with the steam flow in order to form said first inlet flow.

[0151] A second fraction of the first outlet flow is conveyed to said second inlet of the exchanger 31 via the conduit 19.

[0152] In this example, the member 110 is a fan, making it possible in particular to increase the pressure of the recirculated fraction while avoiding pressure jumps.

[0153] The installation 1 of [Fig.5] makes it possible to recirculate part of a flow of di-hydrogen produced by the electrolyser 2 whose temperature is typically between 650°C and 850°C and, thus, to reduce or cancel the risks of oxidation or premature degradation of the electrolyser 2.

[0154] In a variant not shown of the embodiment of [Fig.6], said second fraction of the first outlet flow can be cooled, downstream of the exchanger 31 and upstream of the unit 6, by an additional cooling member, for example to reach a temperature of between 5°C and 20°C, making it possible to remove from this fraction the water that it contains upstream of the unit 6.

[0155] Such a separation, which can be carried out by a separation member of the same type as the device 53, typically makes it possible to obtain at the inlet of the unit 6 an outlet flow comprising more than 98% of dihydrogen by mole.

[0156] In a variant not shown of the embodiment of [Fig.6], the conduit 111 can be fluidically connected not to the conduit 16 but to the conduit 63, that is to say upstream of the heating device 35. On the one hand, this makes it possible to benefit from a relatively higher pressure level of the steam flow and, consequently, to reduce the energy consumption of the member 110. On the other hand, this makes it possible to bring the heating device 35 closer to the electrolyser 2 and to promote the increase in temperature of the first inlet flow before its arrival in the electrolyser 2.

[0157] In summary, the embodiments of figures 2 to 6, as well as their variants and combinations, make it possible to recirculate a fraction of a flow of dihydrogen produced by the electrolyser 2 to mix it with a flow of steam, forming an inlet flow injected into the electrolyser 2. This inlet flow thus comprises dihydrogen in a controlled quantity, which makes it possible in particular to reduce or eliminate the risks of oxidation or premature degradation of the electrolyser 2.

[0158] In a non-limiting manner, the recirculated fraction can thus be formed with a flow cold outlet (see for example embodiments of figures 2 and 3) and / or hot (see for example embodiments of figures 4 and 5) and / or purified (see for example embodiment of [Fig.2]) and / or having undergone an absorption refrigeration cycle (see for example embodiment of [Fig.4]). The recirculated fraction can be injected upstream of a heat exchanger such as the exchanger 31 (see for example embodiments of figures 2 to 5) and / or downstream of such an exchanger (see for example embodiment of [Fig.6]).

[0159] Figures 7 and 8 illustrate non-limiting variants of the embodiments of Figures 5 and 6, respectively, in which at least one ejection device, also called an “ejector”, is implemented.

[0160] The embodiments of Figures 7 and 8 are described only as they differ from those of Figures 5 and 6, respectively. The foregoing description applies by analogy.

[0161] In the example of [Fig.7], an ejector 120 comprises a first inlet fluidly connected to one end of the conduit 66, the other end of the conduit 66 being fluidly connected to the valve 45.

[0162] In this example, the ejector 120 comprises a second inlet fluidly connected to one end of the conduit 61, the other end of the conduit 61 being fluidly connected to the valve 4L

[0163] The ejector 120 comprises an outlet fluidly connected to one end of a conduit 125, the other end of the conduit 125 being fluidly connected to said first inlet of the exchanger 31.

[0164] The installation 1 of [Fig.7] thus makes it possible to convey to the first inlet of the ejector 120 a fraction of said first outlet flow leaving the exchanger 31, via the recirculation conduits 65 and 66. The conduits 11 and 61 make it possible to convey to the second inlet of the ejector 120 a portion of the steam flow formed by the device 3, which is in this example used as motive steam within the ejector 120.

[0165] In the example of [Fig.8], an ejector 130 comprises a first inlet fluidly connected to a bifurcation of the conduit 19 by the conduit 111 and a second inlet fluidly connected to one end of the conduit 16, the other end of the conduit 16 being fluidly connected to the heating device 35.

[0166] The ejector 130 comprises an outlet fluidly connected to one end of a conduit 135, the other end of the conduit 135 being fluidly connected to said first inlet of the electrolyser 2.

[0167] The installation 1 of [Fig.8] thus makes it possible to route towards the first inlet of the ejector 130 a fraction of said first output flow leaving the electrolyser 2 via the conduit 19. The conduit 16 makes it possible to route towards the second inlet of the ejector 130 the steam flow formed by the device 3, which is in this example used as motive steam within the ejector 130.

[0168] In a variant not shown of the embodiment of [Fig.8], the ejector 130 may be arranged not downstream but upstream of the heating device 35. In other words, according to this variant, said second inlet of the ejector 130 may be fluidically connected to an outlet of the conduit 63 and the conduit 135 may be connected on the one hand to the outlet of the ejector 130 and on the other hand to the inlet of the heating device 35. This allows the ejector 130 to benefit from a relatively higher pressure level of the steam flow injected therein and to bring the heating device 35 closer to the electrolyser 2 to promote the increase in temperature of the first inlet flow before its arrival in the electrolyser 2.

[0169] In each of the embodiments of figures 7 and 8 and their variants, the ejectors 120 and 130 make it possible to recycle dihydrogen formed by the electrolyser 2, so as to obtain a first inlet flow which comprises a chosen quantity of dihydrogen (see above), while eliminating or reducing pressure jumps.

[0170] The foregoing description is not limiting, the invention being generally defined by the claims. In particular, the embodiments described above may be combined with each other. Thus, the installation may comprise several recirculation branches, combining for example the principles of the embodiments of Figures 2 and 5 or more generally several of the embodiments described above.

[0171] In alternative embodiments, a portion of said first output flow formed by the electrolyser 2 may be conveyed to the device 5 to constitute all or part of the safety gas stored therein (not shown). The device 5 and / or all or part of the elements relating thereto (in dotted lines in the figures) are however optional and / or may be replaced by another technology.

[0172] Several elements of the installations described above are optional, including, but not limited to, the heating devices 35 and 36, or the elements for supplying said second input flow.

[0173] Thus, in alternative embodiments, the installation 1 of the invention may in particular be devoid of the device 4 and / or the conduits 12 and / or 17 and / or 71, and / or the heating device 36 and / or the exchanger 33.

[0174] [Fig.9] illustrates in a non-limiting manner such an embodiment, which constitutes a variant of the embodiment of [Fig.8].

[0175] The installation 1 of [Fig.9] differs from that of [Fig.8] in that: - it is devoid of the device 4, the exchanger 33, the heating device 36, the valve 44 and the conduits 12, 17, 68, 70 and 71, - it comprises a device 4B configured to maintain the required static pressure in the electrolyser 2 and forming a flow of a fluid such as a so-called sweeping gas, a valve 150, a conduit 151 fluidly connecting the device 4B to an inlet of the valve 150, and a conduit 152 fluidly connecting the valve 150 to a branch of the conduit 69: these additional elements are in this example intended to be implemented in production and standby configurations, in order to maintain the required static pressure in the electrolyser 2.

[0176] The description of figures 1 to 8 applies by analogy to the example of [Fig.9].

Claims

Claims

1. Installation (1) for producing dihydrogen, comprising an electrochemical device (2) and a fluid network which comprises: - at least one inlet conduit (11, 16) configured to convey to the electrochemical device (2) an inlet flow comprising a fluid such as water in the gaseous state, - at least one recirculation branch (RC1, RC2) configured to introduce into the at least one inlet conduit (11, 16) a part of an outlet flow which comprises dihydrogen, the electrochemical device (2) being configured to form the dihydrogen of the outlet flow from the inlet flow.

2. Installation (1) according to claim 1, comprising one or more members (6, 81, 82, 83, 84, 100) for treating the outlet flow, for example one or more members for cooling and / or compressing and / or purifying the outlet flow, the at least one recirculation branch (RC1) being configured to introduce into the at least one inlet conduit a part of the outlet flow treated by one or more of said treatment members.

3. Installation (1) according to claim 2, comprising a fan (84) configured to move the outlet flow towards one or more of said treatment members (6, 81, 82, 83, 84, 100), the at least one recirculation branch (RC1) being configured to take a portion of the outlet flow upstream of one or more of said treatment members and / or downstream of the fan, relative to a flow direction of the outlet flow.

4. Installation (1) according to any one of claims 1 to 3, comprising an ejector (120, 130), the ejector (120, 130) being configured to: - introduce into the at least one inlet conduit a portion of the outlet flow which is preferably taken from the fluid network upstream of one or more of said treatment members of an installation (1) according to claim 2 or 3, relative to a flow direction of the outlet flow, and / or - introduce into a second section (125, 135) of the at least one inlet conduit a portion of the inlet flow conveyed by a first section (11, 16, 61-64) of the at least one inlet conduit.

5. Installation (1) according to any one of claims 1 to 4, comprising a heat exchanger (31) configured to transfer thermal energy from the outlet flow to the inlet flow.

6. Installation (1) according to claim 5, in which the at least one recirculation branch (RC1, RC2) is configured to introduce a portion of the outlet flow into the at least one inlet duct upstream and / or downstream of the heat exchanger (31), relative to a flow direction of the inlet flow in the at least one inlet duct.

7. Installation (1) according to any one of claims 1 to 6, this installation (1) being devoid of means for introducing a sweeping gas into the electrochemical device (2).

8. Installation (1) according to any one of claims 1 to 7, wherein: - said output flow is a first output flow, - the electrochemical device (2) is configured to form a second output flow comprising dioxygen, - the installation (1) comprises a heat exchanger (32) configured to transfer thermal energy from the second output flow to said input flow.

9. Installation (1) according to any one of claims 1 to 8, comprising a storage device (7) configured to store in the gaseous state dihydrogen formed by the electrochemical device (2).

10. A method of producing dihydrogen using a plant (1) according to any one of claims 1 to 9, comprising the following steps: - introducing into said electrochemical device (2), via said at least one inlet conduit, an inlet flow comprising a fluid such as water in the gaseous state, - electrolysis of the inlet flow, using the electrochemical device (2), so as to form an outlet flow comprising dihydrogen, - introducing into the inlet conduit a portion of the flow of output, via said at least one recirculation branch (RC1, RC2).

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