process and system for the production of hydrogen with improved energy efficiency

Abstract

The invention relates to a process for producing hydrogen by steam electrolysis, using the heat from a hot effluent (204) discharged by an industrial installation. The process comprises: the production of steam, and the electrolysis, in an electrolysis unit (100), of at least a portion of said steam. The steam production comprises: a vaporization step, using heat recovered from said hot effluent (204), of a preheated water stream (208), and a preheating step of a liquid water stream (206) to obtain said preheated water stream (208), using heat recovered from said hot effluent (204) obtained at the outlet of said vaporization step. It also relates to a system (200) implementing such a process. See Figure 2.

Description

Title of the invention: Process and system for the production of hydrogen with improved energy efficiency

[0001] The present invention relates to a process for producing hydrogen by high-temperature electrolysis of steam with reduced electrical consumption. It also relates to a system for producing hydrogen by high-temperature electrolysis of steam implementing such a process.

[0002] The field of the invention is generally the field of hydrogen production by steam electrolysis, and in particular by high-temperature steam electrolysis, and in particular in a high-temperature solid oxide electrolyzer. State of the art

[0003] Several techniques for producing hydrogen currently exist. One of these techniques is the electrolysis of steam in a solid oxide electrolyzer (SOEL). In summary, water is heated to produce steam at a temperature above 150°C. The steam is introduced into an electrolysis unit maintained at a temperature between 700°C and 850°C and supplied with an electric current to decompose the water vapor molecule H2O into H2 and O2 molecules, thus obtaining, at the outlet of the electrolysis unit, a stream rich in hydrogen (H2) and a stream rich in oxygen (O2).

[0004] This solution requires an external energy input for the production of water vapor at the desired temperature. This degrades the overall efficiency of hydrogen production, particularly with regard to its electricity consumption.

[0005] One object of the present invention is to remedy at least one of the drawbacks of the prior art.

[0006] Another object of the invention is to propose a solution for the production of hydrogen by electrolysis of water vapor with improved overall efficiency, and in particular with reduced electrical consumption. Description of the invention

[0007] The invention proposes to achieve at least one of the aforementioned objectives by means of a process for producing hydrogen by electrolysis of steam, using the heat from a hot effluent discharged by an industrial installation, said process comprising: - the production of steam from liquid water, and - electrolysis, in an electrolysis unit, of at least a portion of said water vapor to provide a first output stream rich in hydrogen and a second output stream rich in oxygen; in which the production of steam includes: - a vaporization stage, using heat recovered from said hot effluent, of a preheated water stream, and - a preheating step of a liquid water stream, to obtain said preheated water stream, with heat recovered from said hot effluent obtained at the outlet of said vaporization step.

[0008] Thus, in a conventional manner, the process according to the invention proposes to produce hydrogen from steam introduced into an electrolysis unit powered by an electric current. Such an electrolysis operation is conventionally known to those skilled in the art and will not be described in further detail here.

[0009] In an innovative way, the invention proposes to use at least part of the waste heat from a hot effluent discharged by an industrial site to produce steam. More specifically, the invention proposes using the waste heat from the same effluent to, firstly, preheat liquid water, and secondly, vaporize the preheated liquid water to obtain steam. Thus, the invention makes it possible to maximize the recovery of the waste heat from the hot effluent, and this: - firstly, during the vaporization stage of a preheated water stream, - then during the preheating stage to obtain a flow of preheated liquid water ready to be vaporized. In other words, the invention makes it possible to carry out two heat recovery steps from the same hot effluent to produce water vapor from a liquid water stream, for example at ambient temperature.

[0010] Consequently, the invention makes it possible to produce hydrogen with a higher overall efficiency than current solutions since it makes it possible to reduce, or even eliminate, the electricity consumption required for the production of water vapor, depending on the temperature of the hot effluent discharged by the industrial installation.

[0011] In this application, "hot effluent" means a gaseous effluent, or a liquid effluent, discharged by an industrial installation. For example, hot effluent may be a hot gaseous effluent, such as steam, combustion fumes, or hot air, discharged by a nuclear installation, a cement production plant, a metallurgical installation, etc. As another example, hot effluent may be a hot liquid effluent, such as oil or hot water produced by an industrial installation.

[0012] According to embodiment examples, the hot discharged effluent can have a temperature of around 150°C to 900°C.

[0013] According to some embodiments, the vaporization step can be carried out by a first heat exchange circuit comprising: - a first heat exchanger performing a heat exchange between the hot effluent and a first heat transfer fluid; and - a second heat exchanger performing a heat exchange between said first heat transfer fluid and the preheated water flow.

[0014] In this case, the transfer of heat from the hot effluent to the preheated water stream to vaporize said preheated water stream is not carried out directly but via the first heat transfer fluid.

[0015] This embodiment has the advantage of providing greater flexibility in carrying out the vaporization step, particularly in terms of the temperature of the resulting steam. This embodiment also allows for greater flexibility in responding to fluctuations in the hot effluent in terms of temperature and / or flow rate.

[0016] The first heat transfer fluid can be any type of heat transfer fluid.

[0017] Preferably, the first heat transfer fluid can be liquid.

[0018] For example, the first heat transfer fluid can be an oil, for example Therminol 66 ®.

[0019] According to embodiments, the preheating step can preheat the liquid water up to the saturation temperature of the water at the operating pressure of the electrolysis unit, in particular to 113°C.

[0020] According to embodiments, the preheating step can preheat the liquid water to a temperature lower than the saturation temperature of the water at the operating pressure of the electrolysis unit.

[0021] According to embodiments, the preheating step can preheat the liquid water without vaporizing said liquid water.

[0022] For example, the preheating step can preheat the liquid water to the saturation temperature of the water at the operating pressure of the electrolysis unit.

[0023] The preheating step can be carried out by any technique using part of the heat from the hot effluent obtained at the outlet, or downstream, of the vaporization step.

[0024] According to embodiments, the preheating step of the liquid water stream can be carried out in a heat exchanger performing a heat exchange between the hot effluent obtained at the outlet of the vaporization step and the liquid water stream.

[0025] In this case, the heat exchanger receives, on the one hand, the liquid water to be preheated, and on the other hand, the hot effluent from the vaporization stage. A portion of the heat from the hot effluent is transferred to the liquid water stream, thereby increasing the temperature of said liquid water stream. In this case, there is a direct heat exchange from the hot effluent to the liquid water stream.

[0026] This embodiment has the advantage of being inexpensive.

[0027] The exchanger can be any type of heat exchanger known to a person skilled in the art.

[0028] According to some embodiments, the preheating step of the liquid water flow can be carried out by a second heat exchange circuit. This second heat exchange circuit may comprise: - a third heat exchanger performing heat exchange between the hot effluent exiting the vaporization stage and a second heat transfer fluid; and - a fourth heat exchanger performing a heat exchange between said second heat transfer fluid and said liquid water flow.

[0029] In this case, the transfer of heat from the hot effluent to the water flow is not carried out directly but via the second heat transfer fluid.

[0030] This embodiment has the advantage of providing greater flexibility in carrying out the preheating step, particularly with regard to the temperature of the preheated water. This embodiment also allows for greater flexibility in responding to fluctuations in the hot effluent in terms of temperature and / or flow rate.

[0031] The second heat transfer fluid can be any type of heat transfer fluid.

[0032] Preferably, the second heat transfer fluid can be liquid.

[0033] For example, the second heat transfer fluid can be pressurized water, or an oil.

[0034] According to embodiments, the first circuit may include at least one means for adjusting the flow rate of the first heat transfer fluid in particular as a function of the temperature of said first heat transfer fluid.

[0035] For example, the first circuit may be equipped with a valve allowing the flow rate of the first fluid to be decreased or increased. Alternatively, the first circuit may be equipped with a first fluid circulation pump whose flow rate is adjustable, allowing the flow rate of the first fluid to be decreased or increased.

[0036] For example, the flow rate of the first fluid can be adjusted according to the temperature of said first fluid. To do this, the first circuit can be equipped with a temperature sensor measuring the temperature of the first heat transfer fluid.

[0037] According to embodiments, the second circuit may include at least one means for adjusting the flow rate of the second heat transfer fluid in particular as a function of the temperature of said second heat transfer fluid.

[0038] For example, the second circuit may be equipped with a valve allowing the flow rate of the second fluid to be decreased or increased. Alternatively, the second circuit may be equipped with a second fluid circulation pump whose flow rate is adjustable, allowing the flow rate of the second fluid to be decreased or increased.

[0039] For example, the flow rate of the second fluid can be adjusted according to the temperature of said second fluid. To do this, the second circuit can be equipped with a temperature sensor measuring the temperature of the second heat transfer fluid.

[0040] According to embodiments, the process according to the invention may include a step of adjusting, in particular reducing, the temperature of the hot effluent.

[0041] Indeed, when the hot effluent has too high a temperature, it may be appropriate to reduce said temperature in order to carry out the vaporization and preheating steps.

[0042] Such an adjustment can be achieved by mixing said hot effluent with a fluid that is comparatively colder.

[0043] For example, adjusting the temperature of the hot effluent can be achieved by mixing cooler air with the hot effluent, particularly when the hot effluent is gaseous. For example, adjusting the temperature of the hot effluent can be achieved by mixing cooler water with the hot effluent, particularly when the effluent is liquid.

[0044] The mixing can be carried out by any mixing means known to a person skilled in the art, such as for example by a valve installed in bypass on the hot effluent supply line.

[0045] The mixing can be carried out in a controlled manner so that it can be adjusted, for example according to the temperature of the hot effluent.

[0046] According to another aspect of the present invention, a system for producing hydrogen by electrolysis of steam is proposed, using the heat from a hot effluent discharged by an industrial installation, said system comprising: - a unit for producing steam from liquid water, and - at least one electrolysis unit for at least a portion of said vapor of water, to provide a first output stream rich in hydrogen and a second output stream rich in oxygen; said steam production unit comprising: - a vaporization stage, with heat recovered from said hot effluent, from a preheated water stream, and - a preheating stage for a liquid water stream, to obtain said preheated water stream, with heat recovered from said hot effluent obtained at the outlet of said vaporization stage.

[0047] The system according to the invention has the same advantages as those described above with reference to the method according to the invention and which will not be repeated here for the sake of brevity.

[0048] Furthermore, the system according to the invention may include, in terms of hardware component(s) and / or software component(s), at least one, or any combination of at least two, of the optional features described above with reference to the method according to the invention, and which are not all repeated in detail in the following, for the sake of brevity.

[0049] According to some embodiments, the vaporization stage may include a first heat exchange circuit comprising: - a first heat exchanger performing a heat exchange between the hot effluent and a first heat transfer fluid; and - a second heat exchanger performing a heat exchange between said first heat transfer fluid and the preheated water flow.

[0050] In particular, the preheating stage may include a heat exchanger carrying out a heat exchange, in particular a direct one, between the hot effluent obtained at the outlet, or downstream, of the vaporization stage and the liquid water flow.

[0051] Alternatively, the preheating stage may include a second heat exchange circuit comprising: - a third heat exchanger performing a heat exchange between the hot effluent at the outlet, or downstream, of the vaporization stage and a second heat transfer fluid; and - a fourth heat exchanger performing a heat exchange between said second heat transfer fluid and said liquid water flow.

[0052] According to embodiments, the electrolysis unit may include at least one high-temperature steam electrolyzer, for example an electrolyzer operating, i.e. carrying out steam electrolysis, at a temperature between 700°C and 850°C.

[0053] According to embodiments, the electrolysis unit may include at least one solid oxide electrolyzer.

[0054] In particular, the electrolysis unit may include several solid oxide electrolyzers arranged in series or in parallel.

[0055] At least one electrolyzer may comprise one or more stacks, or stacks, of solid oxide electrolysis cells. Description of the figures and methods of realization

[0056] Other advantages and features will become apparent upon examination of the detailed description of non-limiting embodiments and the accompanying drawings, in which: - Figure 1 is a schematic representation of an example of a hydrogen production system according to the prior art; and - FIGURES 2 and 3 are schematic representations of non-limiting examples of embodiments of a system according to the invention.

[0057] It is understood that the embodiments described below are in no way limiting. In particular, variants of the invention may be conceived comprising only a selection of the features described below, isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one preferably functional feature without structural details, or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0058] In particular, all the variants and embodiments described are combinable with each other if there is no technical obstacle to this combination.

[0059] In the figures and in the rest of the description, elements common to several figures retain the same reference.

[0060] Fig. 1 is a schematic representation of an example embodiment of a hydrogen production unit that can be implemented in the present invention.

[0061] Unit 100 of [Fig.1] can be used to produce hydrogen by electrolysis of water vapor, in particular at high temperature, for example at a temperature between 700°C and 850°C.

[0062] The electrolysis unit 100 may comprise one or more stacks of electrolysis cells (not shown). The stacks may be arranged in parallel or in series.

[0063] To carry out the electrolysis of water vapor, the electrolysis unit 100 is alternated by an electric current denoted I on the [Fig.1].

[0064] During operation, the electrolysis unit 100 receives at its inlet a first inlet stream 102, entirely, or mainly, composed of water vapor, H2OV. In the case of high-temperature electrolysis of water vapor in a solid oxide electrolysis unit, the first inlet stream 102 is supplied to the electrolysis unit 100 at a temperature above the saturation temperature of water at the operating pressure of the electrolysis unit, in particular at 113°C. The water vapor is then heated to a temperature between 700°C and 850°C in the electrolysis unit 100 to be electrolyzed.

[0065] Optionally, the electrolysis unit 100 can also receive a second inlet flow 104. This second inlet flow serves to regulate the pressures in the electrolysis unit 100, and in particular the stack(s) located in said electrolysis unit 100. This second inlet flow 104 is intended to circulate in the stack(s) of cells located in the electrolysis unit 100, without mixing with the first inlet flow 102. The second inlet flow 104 can be a flow of air, neutral gas, etc.

[0066] In the electrolysis unit 100, and in particular in the stack of electrolysis cells (not shown), the electrolysis of water vapor in the first stream 102 produces hydrogen and oxygen according to the following relationship:

[0067] 2 H2O 2 H2 + O2

[0068] Thus, the electrolysis unit 100 provides, at its outlet, a first output stream 106 essentially composed of hydrogen, H2, and possibly including undecomposed water vapor. In the case of high-temperature electrolysis of water vapor in a solid oxide electrolysis unit, the first output stream 106 exits the cell stack(s) located in the electrolysis unit 100 at a temperature between 700°C and 850°C.

[0069] The electrolysis unit 100 provides, at the output, a second output stream 108 essentially composed of oxygen, O2, and other components, in particular when using the second input stream 104. In the case of high-temperature electrolysis of water vapor in a solid oxide electrolysis unit, the second output stream 108 exits the cell stack(s) located in the electrolysis unit 100 at a temperature between 700°C and 850°C.

[0070] As mentioned above, the electrolysis unit 100 is supplied by a first stream 102 consisting solely or primarily of water vapor, H2OV. The generation of water vapor is generally achieved by vaporizing liquid water, which requires a significant heat input, and therefore substantial energy consumption that must be taken into account in the energy balance of the electrolysis unit 100.

[0071] The invention proposes to reduce this energy balance by using the waste heat from a hot effluent discharged by an industrial installation.

[0072] Fig. 2 is a schematic representation of a non-limiting example embodiment of a hydrogen production system according to the invention.

[0073] The system 200 of [Fig.2] can be used to produce hydrogen by electrolysis of water vapor in particular at high temperature, for example at a temperature between 700°C and 850°C.

[0074] System 200 of [Fig.2] includes a steam electrolysis unit, and in particular electrolysis unit 100 of [Fig.1].

[0075] The system 200 further includes a steam production unit 202 using part of the heat from a hot effluent 204 discharged by an industrial installation (not shown) to vaporize a stream of liquid water 206.

[0076] The steam production unit 202 receives, on the one hand, the hot effluent 204 discharged by the industrial installation, which may be a nuclear installation, a metallurgical installation, etc. The hot effluent 204 may be gaseous, liquid, or a gas-liquid mixture. For example, without loss of generality, the hot effluent 204 may be at a temperature of 210°C.

[0077] Unit 202 also receives a flow of liquid water 206. The liquid water 206 may, for example, be at ambient temperature. Of course, the liquid water 206 may be at a temperature other than ambient temperature.

[0078] The steam production unit 202 comprises - a stage 230 for preheating the liquid water 206 and providing a flow of preheated liquid, or mainly liquid, water 208; and - a stage 210 for vaporizing liquid water 208 supplied by the preheating stage 230, to provide the flow of water vapor 102; using at least some of the heat from the hot effluent 204.

[0079] In the example of [Fig.2], the vaporization stage 210 comprises, or consists of, a first heat exchange circuit 212 comprising: - a first heat exchanger 214 performing a heat exchange between the hot effluent 204 and a first heat transfer fluid; and - a second heat exchanger 216 performing a heat exchange between said first heat transfer fluid and the flow of preheated liquid water supplied by the preheating stage 230. Thus, calories without transfer from the hot effluent 204 entering the steam production unit 202 to the preheated liquid water stream 208 supplied by the preheating stage 230, to vaporize it.

[0080] In the non-limiting example shown in [Fig.2], the preheated water 208 supplied to the vaporization stage 210 may have a temperature less than or equal to the saturation temperature of water at the operating pressure of the electrolysis unit, in particular 113°C, and the water vapor 102 supplied by the vaporization stage may have a temperature of around 140°C.

[0081] Optionally, the first heat exchange circuit 212 can be equipped with a first temperature sensor 218 to measure the temperature of the first heat transfer fluid circulating in said first circuit 212.

[0082] Optionally, the first heat exchange circuit 212 can be equipped with a first flow sensor 220 to measure the flow rate of the first heat transfer fluid circulating in said first circuit 212.

[0083] Optionally, the first heat exchange circuit 212 can be equipped with a first means 222, for example a first controllable recirculation pump allowing adjustment of the flow rate of the first heat transfer fluid of said first circuit 212 in order, for example, to adapt to fluctuations in temperature and / or flow rate of the hot effluent 204.

[0084] In the example of [Fig.2], the preheating stage 230 comprises, or consists of, a second heat exchange circuit 232 comprising: - a third heat exchanger 234 performing a heat exchange between the hot effluent 204 from the vaporization stage 210 and a second heat transfer fluid; and - a fourth heat exchanger 236 carrying out a heat exchange between said second heat transfer fluid and the liquid water flow 206 entering the steam production unit 202. Thus, calories without transfer from the hot effluent 204 coming from the vaporization stage 210 to the liquid water 206 to be preheated.

[0085] In the non-limiting example shown in [Fig. 2], the liquid water 206 supplied to the preheating stage 230 may be at ambient temperature. Furthermore, the preheated water 208 supplied by the preheating stage 230 may be at a temperature lower than or equal to the saturation temperature of water at the operating pressure of the electrolysis unit.

[0086] Optionally, the second heat exchange circuit 232 can be equipped with a second temperature sensor 238 to measure the temperature of the second heat transfer fluid circulating in said second circuit 232.

[0087] Optionally, the second heat exchange circuit 232 can be equipped with a second flow sensor 240 to measure the flow rate of the second heat transfer fluid circulating in said second circuit 232.

[0088] Optionally, the second heat exchange circuit 232 can be equipped with a means 242, for example a controllable recirculation pump, allowing adjustment of the flow rate of the second heat transfer fluid of said circuit 232 in order, for example, to adapt to fluctuations in temperature and / or flow rate of the hot effluent 204.

[0089] Fig. 3 is a schematic representation of a non-limiting example embodiment of a hydrogen production system according to the invention.

[0090] The system 300 of [Fig.3] can be used to produce hydrogen by electrolysis of water vapor, in particular at high temperature, for example at a temperature between 700°C and 850°C.

[0091] The system 300 of [Fig.3] includes a steam electrolysis unit, and in particular the electrolysis unit 100 of [Fig.1].

[0092] The system 300 further includes a steam production unit 302 102 using part of the heat from a hot effluent 204 discharged by an industrial installation to vaporize liquid water 206.

[0093] The steam production unit 302 includes the vaporization stage 210 described with reference to [Fig.2].

[0094] In addition, the steam production unit 302 includes a liquid water preheating stage 304 206.

[0095] In the example of [Fig. 3], the preheating stage 304 comprises, or consists of, a heat exchanger 306. The heat exchanger 306 receives: - on the one hand, the flow of liquid water 206, and - on the other hand, the hot effluent 204 coming from, or leaving, the vaporization stage 210. Thus, the heat exchanger 306 performs a heat exchange between the liquid water stream 206 and the hot effluent 204 to preheat said liquid water stream 206.

[0096] Thus, unlike the system 200 of [Fig.2], in the system 300, the preheating stage 304 comprises only a heat exchanger 306 which performs the heat exchange directly between the hot effluent 204 downstream of the vaporization stage 210 and the liquid water flow 206 without using an intermediate heat transfer fluid.

[0097] According to embodiments not shown, the system according to the invention may optionally include a means for adjusting, in particular reducing, the temperature of the hot effluent 204, upstream of the steam production unit 202 or 302.

[0098] Such an adjustment means may include a mixing means, such as a bypass valve installed on the hot effluent supply line, mixing said hot effluent with a colder fluid, such as air at ambient temperature for example.

[0099] Of course, the invention is not limited to the examples just described.

Claims

Demands

1. A process for producing hydrogen by electrolysis of steam, using the heat from a hot effluent (204) discharged by an industrial installation, said process comprising: - a production of steam from liquid water (206), and - an electrolysis, in an electrolysis unit (100), of at least a portion of said steam to provide a first output stream (106) rich in hydrogen and a second output stream (108) rich in oxygen; in which the production of steam comprises: - a vaporization step, with heat recovered from said hot effluent (204), of a preheated water stream (208), and - a preheating step of a liquid water stream (206), to obtain said preheated water stream (208), with heat recovered from said hot effluent (204) obtained at the outlet of said vaporization step.

2. A process according to the preceding claim, characterized in that the vaporization step is carried out by a first heat exchange circuit (212) comprising: - a first heat exchanger (214) carrying out a heat exchange between the hot effluent (204) and a first heat transfer fluid; and - a second heat exchanger (216) carrying out a heat exchange between said first heat transfer fluid and the preheated water stream (208).

3. The method according to the claim, characterized in that the first heat transfer fluid is an oil, and in particular Therminol 66 ®.

4. A method according to any one of the preceding claims, characterized in that the preheating step preheats the liquid water (206) to the saturation temperature of the water at the operating pressure of the electrolysis unit, in particular to 113°C.

5. A method according to any one of the preceding claims, characterized in that the preheating step of the liquid water stream (206) is carried out in a heat exchanger (306) performing a heat exchange between the hot effluent (204) obtained at the outlet of the vaporization step and said liquid water stream (206).

6. A method according to any one of claims 1 to 4, characterized in that the preheating step of the liquid water stream (206) is carried out by a second heat exchange circuit (232) comprising: - a third heat exchanger (234) carrying out a heat exchange between the hot effluent (204) at the outlet of the vaporization step and a second heat transfer fluid; and - a fourth heat exchanger (236) carrying out a heat exchange between said second heat transfer fluid and said liquid water stream (206).

7. The method according to the claim, characterized in that the second heat transfer fluid is pressurized water, or an oil.

8. A method according to any one of claims 4 to 7, characterized in that the first circuit (212), respectively the second circuit (232), comprises at least one means (222,242) for adjusting the flow rate of the first heat transfer fluid, respectively of the second heat transfer fluid, in particular as a function of the temperature of said heat transfer fluid.

9. A method according to any one of the preceding claims, characterized in that it comprises a means for adjusting, in particular reducing, the temperature of the hot effluent (204).

10. System (200;300) for producing hydrogen by electrolysis of steam, using the heat from a hot effluent (204) discharged by an industrial installation, said system (200;300) comprising: - a unit (202;302) for producing steam from liquid water (206), and - at least one electrolysis unit (100) of at least a portion of said steam, to provide a first output stream (106) rich in hydrogen and a second output stream (108) rich in oxygen; said steam production unit (202;302) comprising: - a vaporization stage (210), with heat recovered from said hot effluent (204), of a preheated water stream (208), and - a preheating stage (230) of a liquid water stream (206), to obtain said preheated water stream (208), with heat recovered from said hot effluent (204) obtained at the outlet of said vaporization stage (210).

11. System (200;300) according to claim 10, characterized in that the vaporization stage (210) comprises a first heat exchange circuit (212) comprising: - a first heat exchanger (214) carrying out a heat exchange between the hot effluent (204) and a first heat transfer fluid; and - a second heat exchanger (216) carrying out a heat exchange between said first heat transfer fluid and the preheated water stream (208).

12. System (300) according to any one of claims 10 or 11, characterized in that the preheating stage (304) comprises a heat exchanger (306) carrying out a heat exchange between the hot effluent (204) obtained at the outlet of the vaporization stage (210) and the liquid water stream (206).

13. System (200) according to any one of the preceding claims 10 or 11, characterized in that the preheating stage (230) comprises a second heat exchange circuit (232) comprising: - a third heat exchanger (234) carrying out a heat exchange between the hot effluent (204) at the outlet of the vaporization stage (210) and a second heat transfer fluid; and - a fourth heat exchanger (236) carrying out a heat exchange between said second heat transfer fluid and said liquid water flow (206).

14. System (200;300) according to any one of claims 10 to 13, characterized in that the electrolysis unit (100) comprises at least one solid oxide electrolyzer.