Facility for producing dihydrogen

Abstract

The invention relates to a facility (2) for producing dihydrogen, comprising: • a heating system (6) configured to provide at least one heated-water stream (8); and • an electrochemical system (4) which has a plurality of stacks (10), each configured to produce an outlet gas stream (12) from a respective heated-water stream; the heating system comprising: • a primary heating device (18) configured to bring the inlet water stream to an intermediate temperature, so as to form an intermediate water stream (22); and • a plurality of secondary heating devices (20), each being connected at the outlet of the primary heating device (18) so as to receive a respective fraction of the intermediate water stream, and being configured to bring the fraction received to a nominal operating temperature of a corresponding stack (10), so as to form the heated-water stream (8) supplying the stack (10).

Description

Dihydrogen production facility

[0001] The present invention relates to a hydrogen production installation.

[0002] The invention applies to the field of industrial production of dihydrogen, and in particular to installations implementing solid oxide electrolysis cells. State of the art

[0003] In the field of dihydrogen production, it is classically known to use electrolysis systems employing a proton exchange membrane (or PEM, from the English "Proton Exchange Membrane"), an anion exchange membrane (or AEM, from the English "Anion Exchange Membrane"), or even an alkaline technology.

[0004] More recently, systems called SOE (from the English "Solid Oxide Electrolysis", or solid oxide electrolysis), which offer better efficiency than conventional systems, have emerged.

[0005] Typically, such electrolysis systems comprise stacks of electrochemical cells within which electrolysis reactions take place.

[0006] In general, the efficiency of an electrolysis system is defined as the electrical energy consumed by the electrolysis system for one kilogram of dihydrogen produced.

[0007] More specifically, an SOE electrolysis system has an efficiency greater than 80%, which is about 30% better performance than PEM electrolysis systems.

[0008] Such an improvement in efficiency is, in large part, due to the implementation, in SOE electrolysis systems, of high-temperature hydrolysis reactions (generally between 700°C and 800°C), which reduces the electrical energy required to split water molecules (steam) into hydrogen and oxygen.

[0009] However, state-of-the-art SOE electrolysis systems do not provide complete satisfaction.

[0010] Indeed, the water injected into the electrolysis system needs to be heated to a sufficient temperature for hydrolysis reactions to occur. However, such a temperature increase, from ambient temperature to the operating temperature (on the order of 700°C to 800°C), requires an energy input that could compromise the overall efficiency of the electrolysis system.

[0011] Furthermore, within the same electrolyzer, disparities between electrochemical cells are likely to lead to different optimal working temperatures from one stack to another.

[0012] One object of the present invention is to remedy at least one of the drawbacks of the prior art.

[0013] Another aim of the invention is to propose an SOE electrolysis system which has a better yield than conventional systems, despite the optimal working temperature differences between stacks.

[0014] To this end, the invention relates to an installation of the aforementioned type, comprising: a heating system configured to receive an inlet water flow having an initial temperature and to provide, at the outlet, at least one heated water flow having a temperature higher than the initial temperature; and an electrochemical system fluidly connected at the outlet of the heating system to receive each heated water flow, the electrochemical system comprising a plurality of stacks of electrochemical cells, each stack being configured to produce at least one outlet gas flow from a respective heated water flow, the at least one outlet gas flow comprising dihydrogen; the installation being characterized in that the heating system comprises: a primary heating device configured to raise the inlet water flow to an intermediate temperature higher than the initial temperature, to form an intermediate water flow;and a plurality of secondary heating devices, each associated with a corresponding stack of the plurality of stacks, each secondary heating device being fluidly connected at the outlet of the primary heating device to receive a respective fraction of the intermediate water flow, and being configured to raise said respective received fraction to a final temperature equal to a nominal operating temperature of the corresponding stack, higher than the intermediate temperature, to form the heated water flow supplying said stack.;

[0015] Indeed, thanks to the invention, the water intended for each stack is heated in two stages. More precisely, thanks to the single primary heating device, the incoming water flow is first brought to a temperature lower than the nominal temperature of each stack.

[0016] Then, through each secondary heating device, the fraction of the intermediate water flow intended for each stack is brought to the nominal temperature of said stack.

[0017] In this way, the water temperature intended for each stack is adjusted to said stack, thanks to a single heating system.

[0018] This results in optimal efficiency for each stack, as well as low complexity of the heating system.

[0019] Advantageously, the installation according to the invention has one or more of the following characteristics, taken individually or in any technically feasible combination:

[0020] the primary heating device is a passive heating device configured to provide heat exchange between the inlet water flow and at least one outlet gas flow;

[0021] the electrochemical system comprises, for at least one stack of the plurality of stacks, a respective thermally insulating enclosure forming an individual hot box, said stack and the corresponding secondary heating device being arranged in said individual hot box;

[0022] the primary heating device is arranged outside each individual hot box;

[0023] the electrochemical system includes, for at least two stacks of the plurality of stacks, a corresponding common thermally insulating enclosure, forming a collective hot box, said at least two stacks and each corresponding secondary heating device being arranged in said collective hot box;

[0024] Each stack of the collective hot box is arranged, together with the associated secondary heating device, in a respective enclosure located in the corresponding collective hot box;

[0025] the primary heating system is arranged outside the collective hot box;

[0026] Each secondary heating device comprises: a pipe for the circulation of the respective fraction of the intermediate water flow; and a heating element configured to transform a first energy source into thermal energy, and to apply the thermal energy produced to the pipe;

[0027] the heating element comprises an electrical resistance wound around a sleeve arranged around the corresponding pipe, the sleeve being preferably made of ceramic;

[0028] the electrochemical system is a solid oxide electrolyzer, each heated water stream comprising water in the vapor phase. Brief description of the figures

[0029] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0030] laest a general schematic representation of an installation according to the invention;

[0031] laest a schematic representation of an electrochemical cell of an electrochemical system of the installation of the ;

[0032] This is a schematic representation of a first embodiment of the installation of the; and

[0033] This is a schematic representation of a second embodiment of the installation of the.

[0034] It is understood that the embodiments described below are by no means exhaustive. 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.

[0035] In particular, all the variants and embodiments described can be combined with each other if there are no technical obstacles to this combination.

[0036] In the figures and in the rest of the description, elements common to several figures retain the same reference. Detailed description

[0037] A hydrogen production installation 2 according to the invention is illustrated by the.

[0038] Installation 2 includes an electrochemical system 4 and a heating system 6.

[0039] The heating system 6 is configured to provide, at the outlet, at least one flow of heated water 8.

[0040] In addition, the electrochemical system 4 is fluidically connected at the outlet of the heating system 6 to receive each flow of heated water 8.

[0041] For the purposes of this invention, the expression "A fluidically connected / linked / connected to B" means that "A is in fluidic connection with B", but does not exclude the presence of one or more organ(s) between A and B.

[0042] The electrochemical system 4 is configured to produce dihydrogen from each heated water stream 8.

[0043] Preferably, electrochemical system 4 is a solid oxide electrochemical system.

[0044] For example, electrochemical system 4 is a gas-phase electrolyzer, designed for the production of dihydrogen from a stream of water vapor and electrical energy. In this case, the heated water stream 8 includes water in the vapor phase.

[0045] In a classical way, the electrochemical system 4 comprises a plurality of stacks 10 of electrochemical cells.

[0046] Preferably, each stack 10 comprises a plurality of electrochemical cells 11 and interconnectors staged alternately.

[0047] Each stack 10 is arranged to receive a respective flow of heated water 8.

[0048] Furthermore, each stack 10 is configured to produce at least one outlet gas stream 12 from a respective heated water stream 8. More precisely, at least one outlet gas stream 12 produced by any given stack 10 contains dihydrogen.

[0049] Each stack 10 has a corresponding nominal operating temperature, at which the transformation of the respective heated water flow 8 into dihydrogen has the greatest efficiency.

[0050] As is known, and as illustrated by the, each electrochemical cell 10 comprises two electrodes 116 and 118, forming respectively an anode and a cathode, as well as an electrolyte 120 disposed between the electrodes 116 and 118.

[0051] In addition, each interconnector, here bearing the numerical reference 112A or 112B, includes a machined or stamped plate to allow the circulation of fluid(s), or a plurality of superimposed plates to give the same properties to the interconnector 112.

[0052] In particular, in the case of operation as an electrolyzer, the electrochemical cell 10 is configured to dissociate water molecules into dihydrogen and dioxygen by redox reaction. To do this, water vapor 122 (from the heated water stream 8) is introduced, via a first interconnector 112A, at the cathode 118 which ensures the electrochemical reduction reaction resulting in the production of dihydrogen 124 in gaseous form and superoxide ions 126. A potential difference is imposed between the anode 116 and the cathode 118, creating an electric field which causes the superoxide ions 126 to migrate from the cathode 118 to the anode 116 through the electrolyte 120. At the anode 116, the superoxide ions 126 are oxidized, resulting in the production of dioxygen 128 in gaseous form, which is discharged via a second interconnector 112B.

[0053] The at least one outlet gas stream 12 mentioned above includes, in particular, one and / or the other of the streams 124, 128.

[0054] In the case of operation in a fuel cell, the reverse reactions take place (in particular, oxidation of an incoming flow of dihydrogen), resulting, in particular, in the production of electrical energy.

[0055] According to a first embodiment, illustrated by the figure, the electrochemical system 4 further comprises, for at least one stack 10 of the plurality of stacks 10, a respective thermally insulating enclosure 14, referred to as an "individual hot box". In this case, each stack 10 is arranged in said respective individual hot box 14.

[0056] Heating system

[0057] The heating system 6 is configured to receive an inlet water flow 16 with an initial temperature. Furthermore, the heating system 6 is configured to provide, at the outlet from the inlet water flow 16, at least one heated water flow 8 mentioned previously. More specifically, each heated water flow 8 has a temperature higher than the initial temperature.

[0058] The heating system 6 comprises a primary heating device 18 and a plurality of secondary heating devices 20 arranged downstream of the primary heating device 18 with respect to a direction of water flow.

[0059] Primary heating device

[0060] The primary heating device 18 is configured to raise the inlet water flow 16 to an intermediate temperature higher than the initial temperature, to form an intermediate water flow 22.

[0061] The intermediate water flow 22 has a temperature strictly lower than the nominal temperature of each stack 10.

[0062] Preferably, the intermediate water flow 22 has a temperature greater than or equal to 700°C, for example between 700°C and 800°C.

[0063] Preferably, the primary heating device 18 is arranged outside each individual hot box 14. Even more preferably, the primary heating device 18 is further arranged in a respective thermally insulating enclosure (not shown).

[0064] Advantageously, the primary heating device 18 is a passive heating device, such as a heat exchanger, configured to provide heat exchange between the inlet water flow 16 and a flow of a second fluid having a temperature higher than the initial temperature, in particular greater than or equal to the intermediate temperature.

[0065] In particular, the second fluid flow includes one or more outlet gas flows 12. Such a feature is advantageous, as it improves efficiency by exploiting the heat carried by each outlet gas flow 12.

[0066] Secondary heating devices

[0067] Each secondary heating device 20 is associated with a corresponding stack 10 of the plurality of stacks 10.

[0068] In addition, each secondary heating device 20 is fluidly connected at the outlet of the primary heating device 18 to receive a respective fraction 24 of the intermediate water flow 22.

[0069] Each secondary heating device 20 is further configured to bring the respective fraction 24 received from the intermediate water flow 22 to a final temperature equal to the nominal operating temperature of the corresponding stack 10, to form the heated water flow 8 supplying said stack 10.

[0070] Preferably, the temperature rise induced by a given heating device 20 is between 20°C and 120°C.

[0071] As illustrated by the, each secondary heating device 20 is arranged in a corresponding individual hot box 14, together with the associated stack 10.

[0072] Each secondary heating device 20 is an active heating device. Alternatively, at least one secondary heating device 20 is a passive heating device, such as a heat exchanger, configured to provide heat exchange between the respective fraction 24 of the intermediate water flow 22 and at least one outlet gas flow 12 available at the outlet of the corresponding stack 10.

[0073] Preferably, each secondary heating device 20 includes a pipe 26 associated with a heating element 28.

[0074] More specifically, for each secondary heating device 20, the pipe 26 is a circulation pipe for the respective fraction 24 of the intermediate water flow 22.

[0075] In addition, the heating element 28 is configured to transform a first energy source (preferably electrical) into thermal energy, and to apply the thermal energy produced to the associated pipe 26, in order to increase the temperature of the fraction 24 of the intermediate water flow 22 circulating in said pipe 26.

[0076] Preferably, the heating element 28 comprises an electrical resistance wound around a ceramic sleeve arranged around the pipe 26 associated with said heating element 28.

[0077] A second embodiment of an installation according to the invention is illustrated by the.

[0078] Installation 32 differs from installation 2 in that the electrochemical system 4 comprises, for at least two stacks 10 of the plurality of stacks, a common thermally insulating enclosure 34, referred to as the "collective hot box". In this case, said at least two stacks 10 and each corresponding secondary heating device 20 are arranged within said collective hot box 34.

[0079] The collective hot box 34 has the function of maintaining a high ambient temperature and ensuring efficient thermal insulation to reduce energy losses from the heating system.

[0080] Advantageously, in this case, each stack 10 of the collective hot box 34 is arranged, together with the associated secondary heating device 20, in a respective enclosure 36 disposed in the collective hot box 34.

[0081] The use of such an enclosure is advantageous, insofar as it results in the temperature in the vicinity of each stack 10 remaining close to the corresponding nominal temperature.

[0082] In this second embodiment, the heating system 6 is likely to include, in addition, an intermediate heating device (not shown), disposed in the collective hot box 34, and fluidly connected between the primary heating device 18 and each secondary heating device 20 for the circulation of the intermediate water flow 22.

[0083] Such an intermediate heating device is configured to raise the temperature of the intermediate water flow 22 to a new intermediate temperature higher than the intermediate temperature at the inlet of the intermediate heating device.

[0084] Preferably, the intermediate heating device is an active heating device. In this case, each secondary heating device 20 is preferably a passive heating device.

[0085] Obviously, a combination of these two embodiments is conceivable. For example, within the same installation, a first part of the stacks 10 (as well as the respective secondary heating devices 20) could be arranged in individual hot boxes, while a second part of the stacks 10 could be arranged jointly (as well as the respective secondary heating devices 20) in a collective hot box 34.

[0086] Functioning

[0087] In operation, the primary heating device 18 receives the inlet water flow 16, which has an initial temperature.

[0088] The primary heating device 18 raises the inlet water flow 16 to an intermediate temperature, higher than the initial temperature, to form the intermediate water flow 22.

[0089] Preferably, the intermediate water flow 22 has a temperature greater than or equal to 700°C, for example between 700°C and 800°C.

[0090] For each stack 10, the corresponding secondary heating device 20 receives a respective fraction 24 of the intermediate water flow 22.

[0091] Furthermore, each secondary heating device 20 raises the respective fraction 24 received from the intermediate water flow 22 to the final temperature, i.e., the nominal operating temperature of the corresponding stack 10. The heated water flow 8 supplying said stack 10, for the production of dihydrogen, is thus formed.

[0092] Preferably, the temperature rise induced by each given heating device 20 is between 20°C and 120°C.

[0093] Of course, the invention is not limited to the examples that have just been described.

Claims

Installation (2) for the production of dihydrogen comprising: a heating system (6) configured to receive an inlet water stream (16) having an initial temperature and to provide, at the outlet, at least one heated water stream (8) having a temperature higher than the initial temperature; and an electrochemical system (4) fluidly connected at the outlet of the heating system (6) to receive each heated water stream (8), the electrochemical system (4) comprising a plurality of stacks (10) of electrochemical cells (11), each stack being configured to produce at least one outlet gas stream (12) from a respective heated water stream, the at least one outlet gas stream comprising dihydrogen;the installation (2) being characterized in that the heating system comprises: a primary heating device (18) configured to raise the inlet water flow to an intermediate temperature higher than the initial temperature, to form an intermediate water flow (22); and a plurality of secondary heating devices (20), each associated with a corresponding stack (10) of the plurality of stacks, each secondary heating device (20) being fluidly connected at the outlet of the primary heating device (18) to receive a respective fraction of the intermediate water flow, and being configured to raise said respective received fraction to a final temperature equal to a nominal operating temperature of the corresponding stack (10), higher than the intermediate temperature, to form the heated water flow (8) supplying said stack (10). Installation (2) according to claim 1, wherein the primary heating device (18) is a passive heating device configured to provide heat exchange between the inlet water flow (16) and at least one outlet gas flow (12). Installation (2) according to claim 1 or 2, wherein the electrochemical system (4) comprises, for at least one stack of the plurality of stacks, a respective thermally insulating enclosure forming an individual hot box (14), said stack (10) and the corresponding secondary heating device (20) being arranged in said individual hot box (14). Installation (2) according to claim 3, wherein the primary heating device (18) is arranged outside each individual hot box (14). Installation (2) according to any one of claims 1 to 4, wherein the electrochemical system (4) comprises, for at least two stacks of the plurality of stacks, a corresponding common thermally insulating enclosure, forming a collective hot box (34), said at least two stacks (10) and each corresponding secondary heating device (20) being arranged in said collective hot box (34). Installation (2) according to claim 5, wherein each stack of the collective hot box (34) is arranged, together with the associated secondary heating device (20), in a respective enclosure (36) disposed in the corresponding collective hot box (34). Installation (2) according to claim 5 or 6, wherein the primary heating device is arranged outside the collective hot box (34). Installation (2) according to any one of claims 1 to 7, wherein each secondary heating device (20) comprises: a conduit (26) for the circulation of the respective fraction of the intermediate water flow; and a heating element (28) configured to transform a first energy source into thermal energy, and to apply the thermal energy produced to the conduit. Installation (2) according to claim 8, wherein the heating element (28) comprises an electrical resistance wound around a sleeve arranged around the corresponding conduit, the sleeve being preferably made of ceramic. Installation (2) according to any one of claims 1 to 9, wherein the electrochemical system (4) is a solid oxide electrolyzer, each heated water stream comprising water in vapor phase.

Images