HIGH-TEMPERATURE ELECTROLYSE SYSTEM OPTIMIZED BY INCREASING THE PRESSURE AT THE ELECTROLYSE OUTLET

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of high temperature water electrolysis (HTE, or HTE for High Temperature Electrolysis, or HTSE for High Temperature Steam Electrolysis), also solid oxide (SOEC, acronym for "Solid Oxide Electrolyte Cell") and that of solid oxide fuel cells (SOFC, acronym for "Solid Oxide Fuel Cell"). It finds application particularly for optimizing the energy consumption of a SOEC electrolyzer system. STATE OF THE ART

[0002] Electrolysis of water is an electrolytic reaction that decomposes water into oxygen and hydrogen gas with the help of an electric current according to the reaction: H 2 O → H 2 + 1 / 2 O 2 .

[0003] To carry out the electrolysis of water, it is advantageous to carry it out at high temperature, typically between 600 and 950 °C, because part of the energy required for the reaction can be provided by heat, which is cheaper than electricity, and the activation of the reaction is more efficient at high temperature and does not require a catalyst. A solid oxide electrolysis cell or "SOEC" (an acronym for "Solid Oxide Electrolyte Cell") comprises in particular: - a first porous conductive electrode, or "cathode", intended to be supplied with water vapor for the production of dihydrogen, - a second porous conductive electrode, or "anode", through which the dioxygen produced by the electrolysis of the water injected onto the cathode escapes, and - a solid oxide membrane (dense electrolyte) sandwiched between the cathode and the anode, the membrane being anionically conductive for high temperatures, usually temperatures above 600 °C.By heating the cell to at least this temperature and injecting an electric current I between the cathode and the anode, a reduction of the water on the cathode occurs, which generates dihydrogen (H2) at the cathode and dioxygen at the anode.

[0004] To carry out high temperature water vapor electrolysis EHT, water vapor H2O is injected into the cathode compartment.

[0005] Under the effect of the current applied to the cell, the dissociation of water molecules in vapor form is carried out at the interface between the hydrogen electrode (cathode) and the electrolyte: this dissociation produces dihydrogen gas H2 and oxygen ions. The dihydrogen is collected and evacuated at the outlet of the hydrogen compartment. The oxygen ions migrate through the electrolyte and recombine into dioxygen O2 at the interface between the electrolyte and the oxygen electrode (anode).

[0006] For the effective implementation of electrolysis by the stack, the stack is brought to a temperature above 600°C, usually a temperature between 600°C and 950°C, the gas supply is started at a constant flow rate and an electrical power source is connected between two terminals of the stack in order to circulate the current I.

[0007] The efficiency of the electricity-to-hydrogen conversion is a key point in ensuring the technology's competitiveness. Electricity consumption occurs mainly during the electrolysis reaction itself, but nearly 30% of the electrolyzer's consumption comes from the thermal / hydraulic fluid management system. That is, the architecture external to the electrolyzer and the management of fluids and thermal energy within this architecture.

[0008] The evaporation of the water used in the electrolyzer is the largest energy consumption of this thermal / hydraulic management system. Typically, this function is performed by an electric steam generator that consumes 20% of the electrolyzer's overall consumption.

[0009] Furthermore, in general, a significant portion of energy is released into the ambient environment. For example, during the hydrogen drying and compression phase, it is necessary to significantly cool this mixture to allow condensation of the water present in the water / hydrogen mixture. This condensation takes place very largely at a temperature lower than the evaporation temperature of the water at the inlet of the electrolyser, which means that a very small portion of this condensation energy is usable.

[0010] Such systems are described in patent applications US 2013 / 126360 A1 and US 2018 / 287179 A1.

[0011] There is therefore a need to minimize this consumption by optimizing the architecture and fluid management of the electrolyzer system.

[0012] An object of the present invention is therefore to propose an optimized high-temperature electrolyzer system.

[0013] Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY OF THE INVENTION

[0014] The invention is defined by the subject matter of claim 1.

[0015] To achieve this objective, the invention provides a system comprising a high-temperature electrolyser (HTE), a first electrolyser supply line configured to supply the electrolyser with water vapor, a first electrolyser discharge line configured to discharge dihydrogen from the electrolyser, a second electrolyser discharge line configured to discharge dioxygen from the electrolyser, a first heat exchange module configured to provide heat exchange between the first water vapor supply line and the first dihydrogen discharge line, a steam generator arranged on the first water vapor supply line, upstream of the first heat exchange module, and configured to produce water vapor from liquid water,characterized in that the system comprises a module for recovering the thermal energy of the dihydrogen at the outlet of the first heat exchange module for the benefit of the first water vapor supply line, the recovery module comprising: a compressor arranged on the first dihydrogen discharge line, downstream of the first heat exchange module, and configured to compress the dihydrogen, a first heat exchanger arranged between the first water vapor supply line, upstream of the steam generator, and the first dihydrogen discharge line, downstream of the compressor, so as to transmit the thermal energy of the compressed dihydrogen to the liquid water, upstream of the steam generator.,

[0016] This arrangement makes it possible to recover the thermal energy from the dihydrogen produced by the electrolyser to participate in the evaporation of liquid water and therefore reduce the energy consumption of the system while taking into account the constraints of the components to allow the use of conventional components.

[0017] Thus, the system uses the heat of the dihydrogen at the outlet of the electrolyser, but after the first heat exchange module so that the compression of the dihydrogen raises the temperature of the dihydrogen above the evaporation temperature of liquid water and the first thermal heat exchanger is satisfied with a heat exchanger suitable for temperatures for example below 300°C therefore easily supplied commercially.

[0018] Thus, the architecture of the system is optimized, more precisely, the thermo-hydraulic architecture external to the electrolyzer is optimized by the present invention by allowing the recovery of the fatal energy of the dihydrogen for the benefit of the system by an increase in the pressure at the electrolyzer outlet. The system comprises a second supply line of the electrolyzer configured to supply the electrolyzer with air or a gas containing oxygen.

[0019] The system comprises a third heat exchanger arranged between the first dihydrogen discharge line, downstream of the first heat exchanger of the energy recovery module, and the second air supply line.

[0020] Thus, the third heat exchanger arranged between the second air supply line and the first dihydrogen discharge line makes it possible to use the residual heat of the dihydrogen to heat the incoming air to the electrolyser. The third exchanger advantageously replaces an air cooler, conventionally used for the condensation of dihydrogen, which makes it possible to avoid the consumption of the air cooler fan, which is highly energy-intensive. BRIEF DESCRIPTION OF THE FIGURES

[0021] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which: figure 1 is a functional diagram representing the system according to the invention

[0022] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. DETAILED DESCRIPTION OF THE INVENTION

[0023] Before beginning a detailed review of embodiments of the invention, optional features that may possibly be used in combination or alternatively are set out below: According to one example, the system comprises a second heat exchanger arranged between the second oxygen discharge line and the first water vapor supply line, upstream of the steam generator, so as to transmit the thermal energy of the oxygen to the liquid water upstream of the steam generator.

[0024] Thus, this second heat exchanger helps to raise the temperature of the liquid water before the steam generator so as to limit its energy consumption by recovering the heat from the oxygen produced by the electrolyser.

[0025] According to one example, the second heat exchanger is arranged downstream of the first heat exchanger on the first steam supply line. Advantageously, the source having the energy at the lowest temperature is used first so that the one at the highest temperature is exploited to its maximum afterwards.

[0026] According to one example, the second heat exchanger and the first heat exchanger arranged on the first steam supply line, downstream of the steam generator, are combined in a three-fluid heat exchanger.

[0027] According to one example, the system comprises a second heat exchange module configured to provide heat exchange between the second air supply line and the second oxygen exhaust line.

[0028] Thus, the second heat exchange module allows the incoming air flow to be heated by the heat of the outgoing oxygen flow.

[0029] According to one example, the system comprises a compressor arranged on the second air supply line and intended to compress the air, preferably arranged upstream of the second heat exchange module and preferably downstream of the third heat exchanger of the recovery module.

[0030] Upstream and downstream, inlet, outlet, at a given point are taken in reference to the direction of circulation of the fluid.

[0031] A parameter "substantially equal / greater / less than" a given value means that this parameter is equal / greater / less than the given value, to within plus or minus 10%, or even plus or minus 5%, of this value.

[0032] The system according to the invention comprises a high temperature electrolyser 1 (EHT). Preferably, the electrolyser 1 is of the SOEC type, the English acronym for “Solid Oxide Electrolyte Cell”, i.e. solid oxide.

[0033] The system comprises several supply and discharge lines connected to the electrolyser 1. Thus, a line is understood to mean a pipe, a tube or a set of pipes or tubes which allow the transport of fluid to and from the electrolyser 1.

[0034] The system according to the invention comprises a first supply line 2 of the electrolyser 1 capable of supplying the electrolyser 1 with water vapor. According to one possibility, the first supply line 2 is configured to supply the electrolyser 1 with water vapor, by which it is meant that the first supply line 2 can supply a mixture of water vapor and other gas(es) for example air or dihydrogen or carbon dioxide. Upstream in this first supply line 2, the water vapor is not yet formed and the first supply line 2 is configured to receive liquid water. According to a preferred possibility, the first supply line 2 comprises a first portion receiving liquid water and a second portion receiving water vapor. Preferably, the first portion is located upstream of a steam generator 6 and the second portion is located downstream of said steam generator 6.

[0035] The system according to the invention comprises a first discharge line 4 capable of discharging dihydrogen (H 2 ) from the electrolyser 1. Preferably, the first discharge line 4 receives the dihydrogen. The dihydrogen is advantageously produced by the electrolyser 1. The dihydrogen is in gaseous form. The first discharge line 4 can discharge a mixture of dihydrogen and water vapour, called residual water vapour, which has not been decomposed by the electrolyser 1.

[0036] The system according to the invention comprises a second discharge line 3 capable of discharging dioxygen (O 2 ) from the electrolyser 1. Preferably, the second discharge line 3 receives the dioxygen. The dioxygen is advantageously produced by the electrolyser 1. The dioxygen is in gaseous form. The second discharge line 3 discharges, according to one possibility, a gas enriched in dioxygen, for example air enriched in dioxygen.

[0037] In the remainder of the description, the first supply line 2 is called the first water vapor supply line 2, the first discharge line 4 is called the first dihydrogen discharge line 4 and the second discharge line 3 is called the second dioxygen discharge line 3 without being limiting on the gas, fluid or mixture that can be transported in these lines.

[0038] According to the invention, the system comprises a first heat exchange module 5 configured to ensure a heat exchange between the first water vapor supply line 2 and the first dihydrogen discharge line 4. This heat exchange module is configured to transfer the calories of the dihydrogen from the electrolyser 1 to the water intended to supply the electrolyser 1. A flow of dihydrogen gas ensures the increase in temperature of the water flow while also making it possible to cool the flow of dihydrogen discharged and which is advantageously dried and / or compressed for use.

[0039] The first heat exchange module 5 comprises, according to one embodiment, at least one heat exchanger 5a configured to ensure the heat transfer of dihydrogen to water vapor. According to a preferred embodiment, the first heat exchange module 5 comprises two heat exchangers 5a, 5b arranged in series between the first supply line 2 and the first discharge line 4. This arrangement makes it possible to provide a second heat exchanger 5b adapted to the temperature of the dihydrogen at the outlet of the electrolyzer 1, conventionally of the order of 700°C, and a more usual first heat exchanger 5a adapted to the temperature of the dihydrogen after passing through a heat exchanger, i.e. conventionally of the order of 330°C. In this way, the components are optimized for the temperatures and heat transfers to be carried out.

[0040] The system according to the invention comprises a steam generator 6. The steam generator 6 is intended to produce water vapor from liquid water. The steam generator 6 is supplied with energy to ensure the increase in the temperature of the liquid water above its evaporation temperature. The steam generator 6 is a component constituting the main energy consumption of an electrolyzer system according to the state of the art. The steam generator 6 is arranged on the first water vapor supply line 2.

[0041] According to the invention, the system comprises a module for recovering thermal energy from the dihydrogen at the outlet of the heat exchange module 5 for the benefit of the first water vapor supply line 2.

[0042] According to the invention, the recovery module comprises a compressor 7. The compressor 7 is arranged on the first dihydrogen discharge line 4, preferably downstream of the first heat exchange module 5. The compressor 7 is configured to compress the dihydrogen. For example, the pressure of the dihydrogen at the outlet of the compressor 7 and in particular in the fluid connection L, is at least equal to 5 bars (500 kPa), for example 10 bars (1 Mpa). The compression of the dihydrogen circulating in the first discharge line 4 makes it possible to raise its temperature, preferably above the evaporation temperature of the water in the operating condition of the steam generator 6. The compressor 7 also participates in obtaining dry and compressed dihydrogen.The location of the compressor 7 on the first dihydrogen discharge line 4 is chosen to allow the use of a compressor and materials suitable for temperatures that are too high and therefore do not require a particular component. Indeed, the compression of the dihydrogen will increase its temperature, so it is preferred according to the invention to have a temperature of the dihydrogen at the inlet of the compressor 7, that is to say in the fluid connection K, lower than 200°C, for example between 110°C and 150°C. Thus, before compression, the dihydrogen is at a temperature too close to the evaporation temperature of water to be used. After compression, that is to say in the fluid connection L, supplying the first heat exchanger 8, the temperature of the dihydrogen is for example of the order of 450°C.

[0043] According to the invention, the recovery module comprises a first heat exchanger 8 arranged between the first water vapor supply line 2 and the first dihydrogen discharge line 4. The first heat exchanger 8 is arranged upstream of the steam generator 6 on the first supply line 2 and downstream of the compressor 7 on the first discharge line 4. The first heat exchanger 8 is configured to transmit the thermal energy of the compressed dihydrogen to the liquid water, upstream of the steam generator 6. Preferably, the first heat exchanger 8 is arranged on the first portion of the first supply line 2 receiving liquid water.

[0044] Advantageously, the compressor 7 and the first heat exchanger 8 of the recovery module allow a gain of around 5% in the overall efficiency of electricity to dihydrogen conversion.

[0045] The compressor 7 and the first heat exchanger 8 advantageously contribute to obtaining dry and compressed dihydrogen. Thus, the compressor 7 and the first heat exchanger 8 ensure compression / cooling of the dihydrogen. The cooling allows some of the water present in the dihydrogen to condense. The more the pressure increases through compression, the more liquid water can be extracted from the gaseous dihydrogen mixture. The compression causes the temperature to rise.

[0046] According to one embodiment, the system comprises a second heat exchanger 9 arranged on the first water vapor supply line 2 and on the second oxygen discharge line 3. The second heat exchanger 9 is preferably arranged on the first supply line 2 downstream of the first heat exchanger 8 and upstream of the generator 6. The second heat exchanger 9 is arranged on the first portion of the first supply line 2. This second heat exchanger 9 is configured to ensure the thermal transfer of calories taken from the flow of oxygen discharged from the electrolyzer 1 and circulating in the second discharge line 3 for the benefit of the water vapor supply line 2. The second heat exchanger 9 is configured to transmit the thermal energy of the oxygen leaving the electrolyzer 1 to the liquid water, upstream of the steam generator 6.

[0047] According to one possibility, the first heat exchanger 8 and the second heat exchanger 9 are grouped in a three-fluid heat exchanger. The three-fluid heat exchanger ensures the exchanges like the first heat exchanger 8 and the second heat exchanger 9, that is to say from the dihydrogen circulating in the first discharge line 4 to the liquid water circulating in the first supply line 2 and from the dioxygen circulating in the second discharge line 3 to the liquid water circulating in the first supply line 2.

[0048] According to the invention, the system comprises a second supply line 10 capable of supplying the electrolyser 1 with air. According to one possibility, the second supply line 10 is configured to supply air to the electrolyser 1, by which it is meant that the second supply line 10 can supply air, the air being for example a gas mixture which makes it possible to sweep the cell of the electrolyser 1 and to carry away the oxygen produced by the electrolyser 1.

[0049] According to this embodiment, it is advantageous for the system according to the invention to comprise a second heat exchange module 11 configured to ensure a heat exchange between the second air supply line 10 and the second oxygen discharge line 3. This heat exchange module 11 is configured to transfer the calories of the oxygen from the electrolyser 1 to the air intended to supply the electrolyser 1. A flow of oxygen gas ensures the increase in the temperature of the air flow, which also makes it possible to cool the flow of oxygen discharged.

[0050] The second heat exchange module 11 comprises, according to one embodiment, at least one heat exchanger 11a configured to ensure the heat transfer of the oxygen to the air. According to a preferred embodiment, the second heat exchange module 11 comprises two heat exchangers 11a, 11b arranged in series between the second supply line 10 and the second discharge line 3. This arrangement makes it possible to provide a second heat exchanger 11b adapted to the temperature of the oxygen at the outlet of the electrolyser 1, conventionally of the order of 700°C, and a more usual first heat exchanger 11a adapted to the temperature of the oxygen after passing through a heat exchanger, i.e. conventionally of the order of 330°C. In this way, the components are optimised for the temperatures and heat transfers to be carried out.

[0051] The system preferably comprises a compressor 12 arranged on the second supply line 10 intended for the air supply. The compressor 12 is preferably arranged upstream of the second heat exchange module 11, if it is present. The compressor 12 is intended to ensure the compression of the air intended to be supplied to the electrolyser 1. The compression of the air advantageously contributes to increasing the temperature of the air before it enters the electrolyser 1.

[0052] According to one embodiment, the system comprises means for treating the flow of hydrogen produced. The hydrogen produced by the electrolyser 1 and which leaves it via the first discharge line 4 initially has a very high temperature corresponding to the reaction temperature of the electrolyser 1. However, for its use, the hydrogen must preferably be brought back to a temperature close to ambient temperature. Furthermore, the hydrogen discharged from the electrolyser 1 via the first discharge line 4 may comprise water vapour carried along with the flow of hydrogen. It is therefore also preferred to separate the hydrogen from any water vapour carried along with it, by drying it.

[0053] The system according to the invention advantageously comprises for this purpose at least a first treatment stage intended for the drying and / or compression of the dihydrogen produced.

[0054] According to the invention, the first treatment stage comprises a heat exchanger. The heat exchanger is arranged on the first discharge line 4, downstream of the first heat exchange module 5 and the first heat exchanger 8. This heat exchanger is, according to a first possibility, an air cooler, i.e. a heat exchanger between a fluid and a gas, the gas being set in motion by a fan. According to another possibility, the heat exchanger is a standard cooler, i.e. without a fan, this solution being, however, less efficient. According to the invention shown in figure 1 , the heat exchanger is called third heat exchanger 16 and ensures the heat exchange between the fluid and a gas and in particular air intended for supplying the electrolyser 1.

[0055] According to a possibility which is not part of the invention, the first treatment stage comprises an air cooler, not shown in figure 1 , but arranged at the location of the third heat exchanger 16 described below at which the fluid connection 110 is removed. The first air cooler is arranged on the first discharge line 4, preferably downstream of the first heat exchange module 5 and more preferably downstream of the first heat exchanger 8 of the thermal energy recovery module. According to the invention shown in figure 1, the air cooler is replaced by a third heat exchanger 16. The system then comprises a third exchanger 16 arranged on the first dihydrogen discharge line 4 and on the second air supply line 10. In this way, the air intended to enter the electrolyser 1 is preheated by the transfer of calories from the dihydrogen. The arrangement of the third heat exchanger 16 corresponds to that of the air cooler described above, i.e. downstream of the first heat exchanger 8 of the recovery module.

[0056] The first treatment stage advantageously comprises a liquid / gas separator 17 arranged downstream of the air cooler or the third heat exchanger 16, depending on the embodiment. The separator 17 makes it possible to separate the liquid water from the gaseous dihydrogen, the liquid water resulting from the cooling of the water vapor in the air cooler or in the third heat exchanger 16 below its condensation point.

[0057] According to a preferred possibility, the system comprises a second treatment stage arranged downstream of the first treatment stage on the first discharge line 4. The second treatment stage makes it possible to complete the drying of the dihydrogen. The second treatment stage advantageously comprises a heat exchanger which, as for the first stage, can be a standard cooler, an air cooler 19 or a third heat exchanger between a fluid (dihydrogen) and the air intended to supply the electrolyser 1. The second stage comprises a liquid / gas separator 20. Preferably, the system comprises, between the first treatment stage and the second treatment stage, a compressor 18 configured to allow the second treatment by the air cooler 19 by first increasing the temperature of the mixture so as to be able to cool it again.

[0058] At the end of the first treatment stage and / or the second treatment stage, if present, the liquid water is preferentially recycled by being returned to the first steam supply line 2 by a water recycling line 21. The water recycling line is fluidically connected to the first supply line 2, preferentially upstream of the steam generator 6, preferentially upstream of the first heat exchanger 8 of the thermal energy recovery module, i.e. preferentially on the first portion of the first supply line 2. The dihydrogen is used and in particular stored after conventional treatments.

[0059] According to a possibility not shown, the air cooler 19 of the second treatment stage is replaced by a fourth exchanger. The fourth exchanger is arranged on the first dihydrogen discharge line 4, preferably downstream of the third heat exchanger 16, and on the second air supply line 10 preferably upstream of the third heat exchanger 16.

[0060] According to one possibility, the system comprises at least one additional heat source configured to heat the water vapor entering the electrolyser 1 to a predefined target temperature. The additional heat source is advantageously arranged on the first water vapor supply line 2, preferably downstream of the first heat exchange module 5. The additional heat source is for example an electric heater 14.

[0061] According to one possibility, the system comprises at least one additional heat source configured to heat the air entering the electrolyser 1 to a predefined target temperature. The additional heat source is advantageously arranged on the second air supply line 10, preferably downstream of the second heat exchange module 11. The additional heat source is for example an electric heater 13.

[0062] According to one embodiment, the system comprises at least one pump 15 arranged on the first steam supply line 2 configured to set the liquid water in motion in the first portion of the first supply line 2 upstream of the steam generator 6.

[0063] The system preferably comprises a pump 22 on the water recycling line 21. The pump 22 is configured to set in motion the liquid water circulating in the water recycling line 21 and coming from the gas / liquid separator 20.

[0064] Electrolyzer 1 receives water vapor and air and releases dihydrogen and dioxygen.

[0065] The electrolyser 1 is fluidically connected to the first steam supply line 2. The first steam supply line 2 provides the fluidic connection of components arranged upstream of the electrolyser 1 on said first supply line 2. The following description is made starting upstream of the electrolyser 1 and following the direction of circulation in the first supply line 2.The first supply line 2 ensures the fluidic connection of the first heat exchanger 8 of the recovery module to the second heat exchanger 9 of the recovery module, then the fluidic connection of the second heat exchanger 9 of the recovery module to the steam generator 6, then the fluidic connection of the steam generator 6 to the first heat exchange module 5, preferably to the first heat exchanger 5a, then the fluidic connection of the first heat exchanger 5a to the second heat exchanger 5b, then the fluidic connection of the second heat exchanger 5b to the electric heater 14, then the fluidic connection of the electric heater 14 to the electrolyser 1.

[0066] The electrolyser 1 is fluidically connected to a first hydrogen discharge line 4. The first discharge line 4 ensures the fluidic connection of components arranged downstream of the electrolyser 1 on said first discharge line 4. The following description is made starting from the electrolyser 1 and following the direction of circulation in the first discharge line 4 from the electrolyser 1.The first discharge line 4 ensures the fluid connection of the electrolyser 1 with the first heat exchange module 5, more preferably with the second heat exchanger 5b, then the fluid connection of the second heat exchanger 5b to the first heat exchanger 5a, then the fluid connection of the first heat exchanger 5a to the compressor 7, then the fluid connection of the compressor 7 to the first exchanger 8 of the recovery module then the fluid connection of the first exchanger 8 of the recovery module to the third heat exchanger 16 or air cooler, then the fluid connection of the third heat exchanger 16 to the liquid / gas separator 17, then the fluid connection of the liquid / gas separator 17 to the compressor 18, then the fluid connection of the compressor 18 to the air cooler 19, then the fluid connection of the air cooler 19 to the liquid / gas separator 20.

[0067] The electrolyser 1 is fluidically connected to a second oxygen discharge line 3. The second discharge line 3 ensures the fluidic connection of components arranged downstream of the electrolyser 1 on said second discharge line 3. The following description is made starting from the electrolyser 1 and following the direction of circulation in the second discharge line 3 from the electrolyser 1. The second discharge line 3 ensures the fluidic connection of the electrolyser 1 with the second heat exchange module 11, more preferably with the second heat exchanger 11b, then the fluidic connection of the second heat exchanger 11b to the first heat exchanger 11a, then the fluidic connection of the first heat exchanger 11a to the second heat exchanger 9 of the recovery module.

[0068] The electrolyser 1 is fluidically connected to the second air supply line 10. The second supply line 10 ensures the fluidic connection of components arranged upstream of the electrolyser 1 on said second supply line 10. The second supply line ensures the fluidic connection of the compressor 12 to the first heat exchanger 11a, then the fluidic connection of the first heat exchanger 11a to the second heat exchanger 11b, then the fluidic connection of the second heat exchanger 11b to the electric heater 13, then the fluidic connection of the electric heater 13 to the electrolyser 1. According to one possibility, upstream of the compressor 12, the second supply line ensures the fluidic connection of the third heat exchanger 16 to the compressor 12.

[0069] The system includes fluid connections described below and forming part of the various supply lines 2, 10 and discharge lines 3, 4 of the system.

[0070] Concerning the first supply line 2, it advantageously comprises a fluid connection A connected to the inlet of the pump 15.

[0071] Advantageously, the first supply line 2 comprises a fluid connection B connected between the outlet of the pump 15 and the inlet of the first heat exchanger 8.

[0072] Advantageously, the first supply line 2 comprises a fluid connection C connected between the outlet of the first heat exchanger 8 and the second heat exchanger 9.

[0073] Advantageously, the first supply line 2 comprises a fluid connection D connected between the outlet of the second heat exchanger 9 and the inlet of the steam generator 6.

[0074] Advantageously, the first supply line 2 comprises a fluid connection E connected between the outlet of the steam generator 6 and the inlet of the first heat exchanger 5a of the heat exchange module 5.

[0075] Advantageously, the first supply line 2 comprises a fluid connection F connected between the outlet of the first heat exchanger 5a and the inlet of the second heat exchanger 5b.

[0076] Advantageously, the first supply line 2 comprises a fluid connection J connected between the outlet of the second heat exchanger 5b and the inlet of the electric heater 14.

[0077] Advantageously, the first supply line 2 comprises a fluid connection H connected between the outlet of the electric heater 14 and the inlet of the electrolyser 1.

[0078] Concerning the first evacuation line 4, it advantageously comprises a first fluid connection I between the outlet of the electrolyser 1 and the inlet of the second heat exchanger 5b of the first heat exchange module 5.

[0079] Advantageously, the first discharge line 4 comprises a fluid connection J between the outlet of the second heat exchanger 5b of the first heat exchange module 5 and the inlet of the first heat exchanger 5a of the first heat exchange module 5.

[0080] Advantageously, the first discharge line 4 comprises a fluid connection K between the outlet of the first heat exchanger 5a and the inlet of the compressor 7.

[0081] Advantageously, the first discharge line 4 comprises a fluid connection L between the outlet of the compressor 7 and the inlet of the first heat exchanger 8 of the recovery module.

[0082] Advantageously, the first discharge line 4 comprises a fluid connection M between the outlet of the first heat exchanger 8 and the third heat exchanger 16, which can be replaced by an air cooler.

[0083] Advantageously, the first discharge line 4 comprises a fluid connection N between the outlet of the third heat exchanger 16 which can be replaced by an air cooler and the inlet of the separator 17.

[0084] Advantageously, the first discharge line 4 comprises a fluid connection O between the outlet of the separator 17 and the inlet of the compressor 18.

[0085] Advantageously, the first discharge line 4 comprises a fluid connection P between the outlet of the compressor 18 and the inlet of the air cooler 19.

[0086] Advantageously, the first discharge line 4 comprises a fluid connection Q between the outlet of the air cooler 19 and the separator 20.

[0087] Advantageously, the first evacuation line 4 comprises a fluid connection R ensuring the exit of dihydrogen from the separator 20.

[0088] Concerning the second oxygen evacuation line 3, it advantageously comprises a fluid connection 100 between the outlet of the electrolyser 1 and the inlet of the second heat exchanger 11 b of the second heat exchange module 11.

[0089] Advantageously, the second discharge line 3 comprises a fluid connection 101 between the outlet of the second heat exchanger 11b and the inlet of the first heat exchanger 11a of the second heat exchange module 11.

[0090] Advantageously, the second discharge line 3 comprises a fluid connection 102 between the outlet of the first heat exchanger 11a and the inlet of the second heat exchanger 9.

[0091] Advantageously, the second discharge line 3 comprises a fluid connection 103 between the outlet of the second heat exchanger 9 and the exterior.

[0092] Concerning the second air supply line 10, it advantageously comprises a fluid connection 110 between the outlet of the third heat exchanger 16 and the inlet of the compressor 12.

[0093] Advantageously, the second supply line 10 comprises a fluid connection 111 between the outlet of the compressor 12 and the inlet of the first heat exchanger 11a of the second heat exchange module 11.

[0094] Advantageously, the second supply line 10 comprises a fluid connection 112 between the outlet of the first heat exchanger 11a and the inlet of the second heat exchanger 11b of the second heat exchange module 11.

[0095] Advantageously, the second supply line 10 comprises a fluid connection 113 between the outlet of the second heat exchanger 11 b and the inlet of the electric heater 13.

[0096] Advantageously, the second supply line 10 comprises a fluid connection 114 between the outlet of the electric heater 13 and the inlet of the electrolyser 1.

[0097] In operation, the liquid water arrives in the first water vapor supply line 2, more precisely in the first portion via the fluid connection A. The fluid connection A is advantageously connected to the inlet of the pump 15 which sets the liquid water in motion and advantageously ensures pressurization of the first supply line 2. The water recycling line 21 is advantageously fluidically connected to the first supply line 2 via the fluid connection B ensuring the fluid connection of the pump outlet 15 to the inlet in the first heat exchanger 8 of the recovery module via the fluid connection B. The recycled water and the liquid water enter the first heat exchanger 8 of the recovery module. The temperature of the water increases by recovering the calories from the dihydrogen circulating in the first heat exchanger 8.The heated water leaves the first heat exchanger 8 via the fluid connection C and enters, preferably directly, i.e. without an intermediate member, the second heat exchanger 9. The temperature of the water increases by recovering the calories from the oxygen circulating in the second heat exchanger 9. The hot liquid water leaves the second heat exchanger 9 via the fluid connection D at a temperature advantageously close to the evaporation temperature, i.e. at + / -5°C and, preferably, enters directly into the steam generator 6. The liquid water is transformed into steam by the steam generator 6.

[0098] According to the invention, the energy to be supplied by the steam generator 6 for the transformation of liquid water into water vapor is reduced thanks to the thermal energy recovery module and in particular to the first heat exchanger 8 and advantageously also to the second heat exchanger 9 ensuring an increase in the temperature of the liquid water by recovery of thermal energy from the dihydrogen and dioxygen produced by the electrolyzer 1.

[0099] The water vapor leaves the steam generator 6 through the fluid connection E and enters, preferably directly, the first heat exchange module 5, preferably the first heat exchanger 5a. The water vapor is heated in the first heat exchanger 5a by recovering the calories from the hydrogen circulating in the first heat exchanger 5a. The superheated water vapor leaves the first heat exchanger 5a through the fluid connection F and enters, preferably directly, the second heat exchanger 5b. The water vapor is heated again in the second heat exchanger 5b by recovering the calories from the hydrogen circulating in the second heat exchanger 5b. The superheated water vapor leaves the second heat exchanger 5b through the fluid connection F and enters, preferably directly, the electric heater 14 if necessary.The electric heater 14 provides the final temperature rise that may be necessary for the water vapor to reach a predefined target temperature for entering the electrolyzer 1. The water vapor leaves the electric heater 14 via the fluid connection H and enters, preferably directly, the electrolyzer 1.

[0100] The electrolyser 1 is supplied with electric current at a predefined voltage and intensity to ensure electrolysis and therefore the production of dihydrogen and dioxygen.

[0101] The hydrogen leaves the electrolyser 1 through the first discharge line, through the fluid connection I and enters, preferably directly, the first heat exchange module 5, preferably in the second heat exchanger 5b. The hydrogen leaves the electrolyser in the hot gaseous state; it is necessary to lower its temperature to use and / or store it. The calories from the hydrogen are therefore recovered by the first supply line and more precisely the steam circulating therein. In the second heat exchanger 5b, the temperature of the hydrogen is lowered by transfer of calories to the benefit of the water vapor circulating in the second heat exchanger 5b. The cooled hydrogen leaves the second heat exchanger 5b through the fluid connection J and enters, preferably directly, the first heat exchanger 5a.In the first heat exchanger 5a, the dihydrogen sees its temperature lowered again by transfer of calories to the benefit of the water vapor circulating in the first heat exchanger 5a. The cooled dihydrogen leaves the first heat exchanger 5a via the fluid connection K and enters, preferably directly, the compressor 7. Passing through the compressor 7, the dihydrogen is compressed and sees its temperature increase, preferably above the evaporation temperature of the water. The dihydrogen leaves the compressor 7 via the fluid connection L and enters, preferably directly, the first heat exchanger 8 of the recovery module. The dihydrogen heated by compression sees its temperature lowered by transfer of calories to the benefit of the liquid water circulating in the first heat exchanger 8.The dihydrogen leaves the first heat exchanger 8 via the fluid connection M at a temperature of the order of that at which it left the first heat exchange module 5 via the fluid connection K. The dihydrogen then passes into the third heat exchanger 16 or the air cooler ensuring the cooling of the dihydrogen and advantageously the heating of the air which can circulate in the second supply line 10 and be intended to be introduced into the electrolyser 1. The dihydrogen leaves the third heat exchanger 16 via the fluid connection N and enters, preferably directly, the liquid / gas separator 17 ensuring the condensation of the dihydrogen. The dihydrogen leaves the liquid / gas separator 17 via the fluid connection O and undergoes, if necessary, a new compression with a view to a new condensation.In this case, the dihydrogen leaves the liquid / gas separator 17 via the fluid connection O and enters, preferably directly, the compressor 18 from where it leaves via the fluid connection P and enters, preferably directly, the air cooler 19 or a heat exchanger ensuring the cooling of the dihydrogen and advantageously the heating of the air which may be intended to be introduced into the electrolyser 1. The dihydrogen leaves the air cooler 19 or a heat exchanger via the fluid connection Q and enters, preferably directly, the liquid / gas separator 20 ensuring the condensation of the dihydrogen. The condensed dihydrogen leaves the liquid / gas separator 20 via the fluid connection R and can be used or stored. The condensed liquid water recovered from the liquid / gas separator 17, 20 can be recycled in the first water vapour supply line 2 via a fluid connection with the water recycling line 21.

[0102] The oxygen produced by the electrolyser leaves through the second discharge line 3, through the fluid connection 100 and enters, preferably directly, the second heat exchange module 11, preferably the second heat exchanger 11b. The oxygen leaves the electrolyser in the hot gaseous state; it is necessary to lower its temperature for discharge into the air. The calories from the oxygen are therefore advantageously recovered by the second supply line 10 and more precisely the air circulating therein. In the second heat exchanger 11b, the oxygen sees its temperature lowered by transfer of calories to the benefit of the air circulating in the second heat exchanger 11b. The cooled oxygen leaves the second heat exchanger 11b through the fluid connection 101 and enters, preferably directly, the first heat exchanger 11a.In the first heat exchanger 11a, the oxygen temperature is again lowered by transfer of calories to the benefit of the air circulating in the first heat exchanger 11a. The cooled oxygen leaves the first heat exchanger 11a via the fluid connection 102 and advantageously enters, preferably directly, the second heat exchanger 9 of the recovery module. Passing through the second heat exchanger 9, the oxygen temperature is again lowered by transfer of calories to the benefit of the liquid water circulating in the second heat exchanger 9. The air leaves the second heat exchanger via the fluid connection 103 and is discharged into the air.

[0103] According to one possibility, air is supplied to the electrolyser 1. The air arrives via the second supply line 10. The air passes through the third heat exchanger 16 and recovers calories from the dihydrogen circulating in the heat exchanger. This first heat exchange ensures a first heating of the air. The air leaves the heat exchanger 16 via the fluid connection 110 and enters, preferably directly, the compressor 12. The air is compressed by the compressor 12 and its temperature increases. The air leaves the compressor 12 via the fluid connection 111 and enters, preferably directly, the second heat exchange module 11, preferably the first heat exchanger 11a. The air is heated in the first heat exchanger 11a by recovering calories from the dioxygen circulating in the first heat exchanger 11a.The superheated air leaves the first heat exchanger 11a via the fluid connection 112 and enters, preferably directly, the second heat exchanger 11b. The air is heated again in the second heat exchanger 11b by recovering the calories from the oxygen circulating in the second heat exchanger 11b. The superheated air leaves the second heat exchanger 11b via the fluid connection 113 and enters, preferably directly, the electric heater 13 if necessary. The electric heater 13 provides the final temperature rise that may be necessary for the air to reach a predefined target temperature for entering the electrolyser 1. The air leaves the electric heater 13 via the fluid connection 114 and enters, preferably directly, the electrolyser 1. Fluid connection Temperature °C Bar pressure A 20 B 20 1,8 C 115 D 115 E 112 F 300 G 614 H 700 I 700 J 330 K 117 L 460 M 120 N 45 O P 370 10 Q 41 R 100 700 101 450 102 230 110 111 65 1,55 112 350 113 670 114 700

[0104] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the claims. LIST OF REFERENCES

[0105] 1 Electrolyzer 2 First steam supply line 3 Second oxygen exhaust line 4 First hydrogen exhaust line 5 a First heat exchanger of the first heat exchange module 5 b Second heat exchanger of the first heat exchange module 6 Steam generator 7 Compressor 8 First heat exchanger of the recovery module 9 Second heat exchanger 10 Second air supply line 11 a First heat exchanger of the second heat exchange module 11 b Second heat exchanger of the second heat exchange module 12 Compressor 13 Electric heater 14 Electric heater 15 Pump 16 Third heat exchanger 17 Liquid / Gas separator 18 Compressor 19 Dry cooler 20 Liquid / Gas separator 21 Water recycling line 22Pump AFluid connection entering pump 15 BFluid connection between pump 15 and the first heat exchanger CFluid connection between the first heat exchanger 8 and the secondheat exchanger 9 D Fluid connection between the second heat exchanger 9 and the steam generator 6 E Fluid connection between the steam generator 6 and the first heat exchanger 5a F Fluid connection between the first heat exchanger 5a and the second heat exchanger 5b G Fluid connection between the second heat exchanger 5b and the heater 14 H Fluid connection between the heater 14 and the electrolyzer 1 I Fluid connection between the electrolyzer 1 and the second heat exchanger 5b J Fluid connection between the second heat exchanger 5b and the first heat exchanger 5a K Fluid connection between the first heat exchanger 5a and the compressor 7 L Fluid connection between the compressor 7 and the first heat exchanger 8 M Fluid connection between the first heat exchanger 8 and the third heat exchanger 16 N Fluid connection between the third heat exchanger 16 and the separator 17 O Fluidic connectionbetween the separator 17 and the compressor 18 P Fluid connection between the compressor 18 and the air cooler 19 Q Fluid connection between the air cooler 19 and the separator 20 R Fluid connection leaving the separator 20 100 Fluid connection between the electrolyser 1 and the second heat exchanger 11 b 101 Fluid connection between the second heat exchanger 11 b and the first heat exchanger 11a 102 Fluid connection between the first heat exchanger 11a and the second heat exchanger 9 110 Fluid connection between the third heat exchanger 16 and the compressor 12 111 Fluid connection between the compressor 12 and the first heat exchanger 11a 112 Fluid connection between the first heat exchanger 11a and the second heat exchanger 11 b 113Fluid connection between the second heat exchanger 11 b and the heater 13 114Fluid connection between the heater 13 and the electrolyser 1

Claims

1. System comprising - a high temperature electrolyser (1) (HTE), - a first supply line (2) of the electrolyser configured to supply steam to the electrolyser (1), - a first electrolyser discharge line (4) configured to discharge dihydrogen from the electrolyser (1), - a second electrolyser discharge line (3) configured to discharge dioxygen from the electrolyser (1), - a first heat exchange module (5) configured to provide heat exchange between the first steam supply line (2) and the first dihydrogen discharge line (4), - a steam generator (6) arranged on the first steam supply line (2), upstream of the first heat exchange module (5), and configured to produce steam from liquid water, characterised in that the system comprises a module for recovering the thermal energy of dihydrogen at the output of the first heat exchange module (5) for the benefit of the first steam supply line (2), the recovery module comprising: o a compressor (7) arranged on the first dihydrogen discharge line (4), downstream of the first heat exchange module (5), and configured to compress the dihydrogen, o a first heat exchanger (8) arranged between the first steam supply line (2), upstream of the steam generator (6), and the first dihydrogen discharge line (4), downstream of the compressor (7), so as to transmit the thermal energy of the compressed dihydrogen to the liquid water, upstream of steam generator (6), and that the system comprises a second electrolyser supply line (10) configured to supply air to the electrolyser (1) and a third heat exchanger (16) arranged between the first dihydrogen discharge line (4), downstream of the first heat exchanger (8) of the energy recovery module, and the second air supply line (10).

2. System according to the preceding claim comprising a second heat exchanger (9) arranged between the second dioxygen discharge line (3) and the first steam supply line (2), upstream of the steam generator (6), so as to transmit the thermal energy of the dioxygen to the liquid water upstream of the steam generator (6).

3. System according to the preceding claim, wherein the second heat exchanger (9) is arranged downstream of the first heat exchanger (8) on the first steam supply line (2).

4. System according to any one of the two preceding claims, wherein the second heat exchanger (9) and the first heat exchanger (8) arranged on the first steam supply line (2), upstream of steam generator (6), are associated in a three-fluid heat exchanger.

5. System according to any one of the preceding claims comprising a second heat exchange module (11) configured to provide a heat exchange between the second air supply line (10) and the second dioxygen discharge line (3).

6. System according to any one of the preceding claims comprising a compressor (12) arranged on the second air supply line (10) and intended for compressing air.