Steam production system for high-temperature electrolyzer including an absorption chiller

Abstract

Preheating of a feed fluid for a high-temperature electrolyzer (6) using a system (1) comprising an absorption heat transformer (12). Figure for the abstract: Fig. 5

Description

Title of the invention: Steam production system for a high-temperature electrolyzer comprising an absorption machine technical field

[0001] The present invention relates to the field of industrial heat production techniques, particularly in the form of steam.

[0002] The invention is of particular interest for hydrogen production installations by vapor phase electrolysis, also called "high temperature electrolysis", which may typically require water vapor with a temperature between 600°C and 850°C. State of the art

[0003] Vapor phase electrolysis technologies, in particular solid oxide electrolyzers known by the Anglo-Saxon name "Solid Oxide Electrolysis Cell (SOEC)", classically use steam produced by generators which use electricity or fossil fuels as an energy source.

[0004] There is a need to reduce the ecological impact of such technologies, as well as the cost of hydrogen production. Description of the invention

[0005] The invention relates to a system for treating a first fluid, comprising: - a first circuit configured to convey said first fluid from an inlet of the system to an outlet of the system, - a second circuit configured to conduct a second fluid from a heat source, - a heat exchanger connected to the first circuit and the second circuit in order to transfer heat from said second fluid to said first fluid, - an absorption heat transformer comprising an absorber connected to said first circuit in order to be able to transfer to said first fluid the heat generated by the absorber.

[0006] Said first fluid may be water.

[0007] Said second fluid may be a heat transfer fluid such as water.

[0008] By way of non-limitation, the system may be intended to treat said first fluid in order to supply an electrochemical device, in particular a high-temperature electrolyzer to produce hydrogen.

[0009] The invention makes it possible to valorize a source of waste heat, in particular when it has a temperature below 100°C, while increasing the heat input to said first fluid.

[0010] The use of waste heat typically makes it possible to reduce the electrical consumption of the system by about 15% to preheat said first fluid when it is used to power said electrochemical device.

[0011] When the system is used to supply an electrochemical device, the invention thus makes it possible to reduce the need to use ancillary techniques, for example an electric boiler, to finalize the conditioning of said first fluid at the inlet of the electrochemical device.

[0012] In addition, an absorption heat transformer, or absorption machine, makes it possible to produce heat with lower electrical consumption, in particular compared with conventional heat pumps, and can be implemented with fluids that do not contribute to the destruction of the ozone layer or to the increase of the greenhouse effect.

[0013] The invention thus makes it possible to recover waste heat, in particular at low temperature, to power the absorption machine, which can thus be used to preheat the water required for the electrolysis reaction of an electrolyzer to a temperature which is higher than that which would be obtained by directly recovering the waste heat source with a heat exchanger.

[0014] In one embodiment, the first circuit includes a conduit connecting the heat exchanger and the absorber to each other in order to convey said first fluid from the heat exchanger to the absorber.

[0015] In one embodiment, the first circuit includes a conduit connecting the heat exchanger to a condenser of the transformer in order to convey said first fluid from said condenser to the heat exchanger.

[0016] In one embodiment, the transformer includes a generator connected to the second circuit in order to be able to transfer heat from said second fluid to said generator.

[0017] In one embodiment, the transformer includes an evaporator connected to the second circuit in order to be able to transfer heat from said second fluid to said evaporator.

[0018] In one embodiment, the second circuit includes a conduit connecting the heat exchanger and the generator to each other in order to convey said second fluid from the generator to the heat exchanger.

[0019] In one embodiment, the second circuit includes a conduit connecting the heat exchanger and the evaporator to each other in order to convey said second fluid from the evaporator to the heat exchanger.

[0020] In one embodiment, the system includes a means for cooling the condenser.

[0021] By way of non-limitation, said cooling means may include a component of the system such as an air heater and / or an external source such as a water table or a river.

[0022] The invention also relates to an installation comprising a system as defined above and an electrochemical device.

[0023] In one embodiment, the electrochemical device includes a high-temperature electrolyzer.

[0024] Said system output is preferably fluidly connected to an input of the electrochemical device.

[0025] In one embodiment, the installation includes the aforementioned heat source, that is to say the source from which said second fluid originates.

[0026] In one embodiment, said heat source is a waste heat source rejected at a temperature below 120°C, preferably below 110°C, more preferably below 100°C.

[0027] By way of non-limitation, this waste heat can be released by an agri-food industry, a paper and cardboard industry, a chemical industry, a waste incinerator, a data center, or even a wastewater treatment plant.

[0028] The invention also relates to a method for treating a fluid such as water, in particular said first fluid, using a system as defined above.

[0029] The process includes a step of transferring to the fluid, in particular to said first fluid, heat generated by the absorber of the transformer of the system.

[0030] Alternatively or in addition, depending on the embodiment, the process may include one or more of the following steps: - heat transfer from said second fluid to said first fluid by means of said heat exchanger, and / or - heat transfer to said second fluid in said generator, and / or - heat transfer of said second fluid to said evaporator, and / or - cooling of said condenser using said cooling means.

[0031] According to a first variant, the process can be implemented to treat said fluid in order to supply an electrochemical device of an installation as defined above.

[0032] According to a second variant, the process can be implemented to treat said fluid in order to provide industrial steam.

[0033] Regardless of the use of the fluid treated by the system of the invention, the process can be implemented to change or not the state of the fluid.

[0034] Thus, according to a first alternative, the process can be implemented to increase the temperature of said fluid while maintaining it in a liquid state.

[0035] According to a second alternative, the process can be implemented to increase the temperature of said fluid by changing it from a liquid state to a gaseous state.

[0036] Other advantages and features of the invention will become apparent from the following detailed, non-limiting description. Brief description of the figures

[0037] The following detailed description refers to the attached drawings on which: - Fig. 1 schematically illustrates a system configured to thermally treat a fluid such as water using an external heat source; - [Fig.2] schematically shows an installation, comprising a system such as that of [Fig.1] as well as an electrochemical device supplied by the fluid treated by the system; - [Fig.3] is a schematic view of a system such as that of [Fig.1], in an embodiment in which the system includes a heat exchanger and an absorption machine, each configured to transfer thermal energy to the fluid to be treated; - [Fig.4] is a schematic view of an absorption machine comprising a generator, a condenser, an evaporator, an absorber, a heat exchanger, two pumps, an expansion valve and fluidic circuits, forming a single-effect absorption heat transformer; - [Fig.5] is a schematic view of an installation comprising on the one hand a system such as that of [Fig.3], this system integrating an absorption machine as illustrated in [Fig.4] and, on the other hand, an electrochemical device supplied by the fluid treated by the system.

[0038] Common references are used on the different figures to designate identical or analogous elements. Detailed description of implementation methods

[0039] With reference to [Fig. 1], the invention generally relates to a system 1 for treating a first fluid, in particular for raising the temperature of this first fluid, using heat contained in a second fluid. The system 1 comprises for this purpose a fluid circuit 2 for introducing the second fluid into the system 1, and a fluid circuit 3 for extracting the first fluid from the system 1.

[0040] In the non-limiting embodiment illustrated in [Fig. 2], the system 1 of the invention is implemented within an installation 5 which is equipped with a device electrochemical 6 intended for the production of hydrogen. The invention is of course not limited to the production of hydrogen.

[0041] Circuit 3 of installation 5 is configured to establish fluid communication between an output of system 1 and an input of device 6, in order to introduce into device 6 said first fluid treated by system 1.

[0042] In this example, the electrochemical device 6 comprises solid oxide electrolytic cells for carrying out vapor-phase electrolysis, forming a technology known in English as a "Solid Oxide Electrolysis Cell". In a manner known per se, such an electrolyzer 6 comprises one or more stacks of cells, each forming a cathode, an anode, and an electrolyte, so as to constitute a reaction zone.

[0043] In the example of [Fig. 2], the device 6 is configured to perform high-temperature electrolysis in order to produce hydrogen from said first fluid. By way of example, in the part of the circuit 3 connecting the outlet of system 1 to the inlet of device 6, this fluid can typically comprise water vapor at a temperature between 100°C and 850°C.

[0044] In an alternative embodiment of the invention, not shown, the system of the invention may form, or be part of, an installation lacking such an electrochemical device. For example, system 1 of [Fig. 1] may be used as an industrial heat production unit.

[0045] In the context of the examples presented here, said second fluid is a heat transfer fluid transporting heat from a source which is preferably an industrial waste heat source.

[0046] More specifically and without limitation, the second fluid can transport waste heat at a temperature below 100°C, which can typically be discharged by an agri-food industry, a paper and cardboard industry, a chemical industry, a waste incinerator, a data center, or even a wastewater treatment plant.

[0047] Fig. 3 shows a system 1 according to the invention, which can be implemented in the installation 5 of Fig. 2, or in a different installation.

[0048] In the embodiment of [Fig.3], the system 1 includes a heat exchanger 11, an absorption machine 12, conduits 2A and 2B forming the circuit 2 to convey said second fluid, in this example from a waste heat source, and conduits 3A, 3B and 3C forming the circuit 3 which is configured to convey said first fluid.

[0049] The heat exchanger 11 is connected to circuits 2 and 3 so as to be able to transfer heat from said second fluid to said first fluid.

[0050] In the following description, the terms "upstream" and "downstream" are used with reference to a direction of fluid flow when system 1 is in operation.

[0051] In the example of [Fig.3], a downstream end of conduit 2A is fluidly connected to a first inlet of the heat exchanger 11, an upstream end of conduit 2B is fluidly connected to a first outlet of the heat exchanger 11, a downstream end of conduit 3A is fluidly connected to a second inlet of the heat exchanger 11, and an upstream end of conduit 3B is fluidly connected to a second outlet of the heat exchanger 11.

[0052] By way of non-limitation, the heat exchanger 11 and the circuits 2 and 3 are configured here to circulate the first fluid and the second fluid in counter-current flow within the exchanger 11. Of course, in an alternative embodiment not shown, the heat exchanger 11 and the circuits 2 and 3 can be configured to circulate the first fluid and the second fluid in co-current flow within the exchanger 11.

[0053] With reference to [Fig.3], a downstream end of conduit 3B is fluidly connected to an inlet of machine 12, while an upstream end of conduit 3C is fluidly connected to an outlet of machine 12.

[0054] System 1 of [Fig.3] thus allows the introduction into machine 12 of said first fluid after it has recovered part of the heat transported by said second fluid.

[0055] Fig. 4 shows an absorption machine 12 that can be implemented in a system according to the invention, in particular in system 1 of figures 1 to 3.

[0056] The machine 12 is a thermal machine operating in heat production mode which is classically called an "absorption heat transformer", or "absorption heat transformer" ("Absorption Heat Transformer" in English).

[0057] With reference to [Fig.4], the machine 12 comprises a generator 21, a condenser 22, an evaporator 23, an absorber 24, an internal heat exchanger 25, an expansion valve 26, two pumps 27 and 28, as well as internal fluid circulation conduits 31, 32, 33, 34, 41, 42, 43, 51, 52 and 53, forming in a manner known per se a single-effect absorption heat transformer.

[0058] More specifically, in this example, the conduits 31 to 34 are configured to circulate a refrigerant from the generator 21 to the absorber 24, via the condenser 22, the pump 28 and the evaporator 23. The conduits 41 to 43 and 51 to 53 form a circuit configured to circulate a refrigerant-absorbent solution between the absorber 24 and the generator 21, via the exchanger 25, the expansion valve 26 and the pump 27 (see [Fig.4]).

[0059] By way of non-limitation, the refrigerant may be ammonia and the absorbent may be water.

[0060] In a manner known as such, the generator 21 generates refrigerant vapor at a relatively low pressure, by means of a thermal energy input 61. The condenser 22 condenses this vapor, releasing thermal energy 62, typically to the atmosphere. The pump 28 increases the refrigerant to a relatively high pressure, where it is evaporated by the evaporator 23 under the action of a thermal energy input 63. The refrigerant vapor exiting the evaporator 23 is conveyed to the absorber 24 via the conduit 34 to be absorbed into the refrigerant-absorbent solution.This exothermic absorption generates thermal energy 64, providing a useful heat source, and reduces the solution from conduit 53 from a relatively high absorbent concentration to a relatively low absorbent concentration. The absorbent-rich solution exits absorber 24 through conduit 4L. The expansion valve 26 lowers the pressure of the solution exiting absorber 24 before it enters generator 21. The solution exiting generator 21 through conduit 51, which has been enriched in absorbent within generator 21, is compressed by pump 27 before entering absorber 24. The heat exchanger 25 allows heat transfer between the absorbent-rich solution and the absorbent-poor solution in the circuit formed by conduits 41-43 and 51-53.

[0061] Of course, the invention can be implemented using a machine different from that illustrated in [Fig. 4]. By way of non-limiting example, the machine 12 can be without the internal heat exchanger 25.

[0062] Cleverly, the thermal energy 64 produced at the level of the absorber 24 of the machine 12 can be transferred to a fluid, in particular said first fluid when the machine 12 is implemented in a system as described above with reference to Figures 1 to 3, for example as illustrated in the embodiment of [Fig. 5],

[0063] Figure 5 shows an installation 5 according to the invention, combining the principles described above with reference to Figures 1 to 4.

[0064] In this particular example, the installation 5 of [Fig. 5] comprises a system 1 and an electrolyzer 6 coupled to each other according to the principle illustrated in [Fig. 2]. The system 1 of this installation 5 comprises a heat exchanger 11 and an absorption chiller 12 coupled to each other according to the principle illustrated in [Fig. 3]. The absorption chiller 12 of the installation 5 is similar to that of [Fig. 4].

[0065] It is understood that the entire preceding description applies by analogy to the embodiment of [Fig.5], which is described below mainly in order to specify coupling modes which do not appear directly on Figures 1 to 4.

[0066] With reference to [Fig. 5], circuit 2 comprises the aforementioned conduits 2A and 2B as well as conduits 2C1, 2C2 and 2D. Circuit 3 comprises the aforementioned conduits 3A, 3B and 3C, as well as conduits 3D, 3E and 3F.

[0067] Installation 5 of [Fig.5] further includes an air heater 70.

[0068] The conduits 3E and 3F are configured to circulate said first fluid between the condenser 22 and the air heater 70 so as to transfer to the air heater 70 the thermal energy 62 produced by the condenser 22, which allows the condenser 22 to be cooled.

[0069] The duct 3D is configured to introduce into system 1, in this case at the level of the duct 3E, the said first fluid which, in this example, comes from a relatively cold source. By way of example, the first fluid can arrive in the duct 3D with a temperature that can be between 0°C and 30°C, for example a temperature of around 15°C.

[0070] An upstream end of the conduit 3A is fluidically connected to an outlet of the condenser 22 in order to convey a portion of the first fluid to the heat exchanger 11, within which its temperature is increased (see [Fig.4] and corresponding description).

[0071] By way of non-limitation, the condenser 22 may include a plate heat exchanger or a shell and tube type heat exchanger.

[0072] Regarding circuit 2 of installation 5 in [Fig. 5], conduits 2C1 and 2C2 are both configured in this example to carry the second fluid, originating from a waste heat source, to their downstream end. For illustrative purposes, the second fluid may arrive in conduits 2C1 and 2C2 at a temperature between 60°C and 100°C, for example, a temperature of around 80°C.

[0073] The downstream end of the conduit 2C1 is fluidically connected to an inlet of the evaporator 23, while an upstream end of the conduit 2A is fluidly connected to an outlet of the evaporator 23, so that the second fluid can provide the evaporator 23 with the thermal energy input 63 necessary for its operation.

[0074] The downstream end of conduit 2C2 is fluidly connected to an inlet of generator 21, while an upstream end of conduit 2D is fluidly connected to an outlet of generator 21, so that the second fluid can supply generator 21 with the thermal energy input 61 necessary for its operation.

[0075] A downstream end of the 2D conduit is fluidly connected to said first inlet of the heat exchanger 11.

[0076] In the example of [Fig. 5], the thermal energy 64 rejected at the level of the absorber 24 is used to increase the temperature of said first fluid passing through the absorber 24 by the conduits 3B and 3C. The absorber 24 is thus connected to the circuit 3 in order to be able to transfer heat 64 to said first fluid.

[0077] Two non-limiting modes of operation of the installation 5 of [Fig.5] will now be described.

[0078] In each of these modes of operation, the first fluid is water which is introduced into system 1 at a temperature of around 15°C, the second fluid is water introduced into system 1 with a temperature of around 80°C, and the first fluid exits system 1 at a temperature of around 105°C in order to produce the electrolysis reaction in device 6.

[0079] In the first mode of operation, the installation 5 is implemented so that the fluid exiting the system 1 through the conduit 3C is in a liquid state, the fluid being vaporized within the device 6. In other words, the system 1 is configured to preheat the first fluid by maintaining it in a liquid state.

[0080] This first mode of operation can typically be implemented when the device 6 is a relatively high power electrolyzer, consuming in this example a maximum of 0.83 kg of water per second and requiring a power of 2.2 MW to obtain a temperature and water pressure sufficient for the electrolysis reaction.

[0081] The inventors estimated that in this first mode of operation, the absorption machine 12 transfers 0.318 MW of power to the water, i.e. 15% of the total power required, and provides a thermal coefficient of performance (COP) of 0.79 and an electrical COP of 12.4. By comparison, an installation using only a heat exchanger in an analogous configuration would transfer 0.153 MW of power to the water, i.e. only 6% of the total power required.

[0082] In the second operating mode, the installation 5 is implemented so that the fluid exiting system 1 through conduit 3C is in a gaseous state. In other words, system 1 is configured to preheat the first fluid by changing it from a liquid to a gaseous state.

[0083] This second mode of operation can typically be implemented when the device 6 is a relatively low power electrolyzer, consuming in this example a maximum of 0.1 kg of water per second and requiring a power of 0.27 MW to obtain a temperature and water pressure sufficient for the electrolysis reaction.

[0084] The inventors estimated that in this second operating mode, the absorption chiller 12 transfers 0.264 MW of power to the water, representing 98% of the total power required, and achieves a thermal COP of 0.61 and an electrical COP of 5.3. By comparison, an installation using only a A heat exchanger in a similar configuration would allow the transfer of 0.019 MW of power to the water.

[0085] These examples illustrate the possibility of preheating the feedwater of the electrolyzer 6 from 15°C to 105°C, with or without phase change, using the absorption chiller 12 powered by a heat source at 80°C. In addition to the increase in the final temperature of the preheated water, the addition of such an absorption chiller 12 makes it possible to transfer significantly more power from the source to the feedwater of the electrolyzer 6, compared to an installation comprising only a heat exchanger utilizing a waste heat source at 80°C. The data provided above indicate that the invention makes it possible to increase the power transferred by approximately twofold in the case of a high-power electrolyzer and by approximately fourteenfold in the case of a low-power electrolyzer.The invention thus makes it possible to reduce electrical energy consumption since an increase in the amount of power transferred reduces the amount of electrical energy needed to complete the conditioning of the feed water.

[0086] The foregoing description is not limiting, as many variations can be envisaged within the scope of the invention. For example, the absorption machine can use a refrigerant and absorption fluid pair H2O-LiBr instead of NH3-H2O.

[0087] By way of further, non-limiting examples, the air heater 70 of the installation 5 in [Fig. 5] can be replaced by another means of cooling the condenser 22, in particular by an abundant external cooling source such as groundwater or river water. It is thus possible to eliminate the air heater 70 and further improve the energy performance of the installation, typically increasing the electrical COP tenfold.

Claims

Demands

1. System (1) for treating a first fluid, such as water, comprising: - a first circuit (3) configured to convey said first fluid from an inlet of the system (1) to an outlet of the system (1), - a second circuit (2) configured to conduct a second fluid from a heat source, - a heat exchanger (11) connected to the first circuit (3) and to the second circuit (2) in order to be able to transfer heat from said second fluid to said first fluid, - an absorption heat transformer (12) comprising an absorber (24) connected to said first circuit (3) in order to be able to transfer heat (64) generated by the absorber (24) to said first fluid.

2. System (1) according to claim 1, wherein the first circuit (3) comprises a conduit (3B) connecting the heat exchanger (11) and the absorber (24) to each other in order to convey said first fluid from the heat exchanger (11) to the absorber (24).

3. System (1) according to claim 1 or 2, wherein the first circuit (3) comprises a conduit (3A) connecting the heat exchanger (11) to a condenser (22) of the transformer (12) in order to convey said first fluid from said condenser (22) to the heat exchanger (11).

4. System (1) according to any one of claims 1 to 3, wherein: - the transformer (12) includes a generator (21) connected to the second circuit (2) in order to be able to transfer heat (61) from said second fluid to said generator (21), and / or - the transformer (12) includes an evaporator (23) connected to the second circuit (2) in order to be able to transfer heat (63) from said second fluid to said evaporator (23).

5. System (1) according to any one of claims 1 to 4, wherein: - the second circuit (2) comprises a conduit (2D) connecting the heat exchanger (11) and the generator (21) to one another to the other in order to convey said second fluid from the generator (21) to the heat exchanger (11), and / or - the second circuit (2) includes a conduit (2A) connecting the heat exchanger (11) and the evaporator (23) to each other in order to convey said second fluid from the evaporator (23) to the heat exchanger (11).

6. System (1) according to any one of claims 1 to 5, comprising a means (70) for cooling the condenser (22), said cooling means (70) comprising an element of the system (1) such as an air heater and / or an external source such as a water table or a river.

7. Installation (5) comprising a system (1) according to any one of claims 1 to 6 and an electrochemical device (6) such as a high-temperature electrolyzer, said output of the system (1) being fluidly connected to an input of the electrochemical device (6).

8. Installation (5) according to claim 7, comprising said heat source from which said second fluid is derived, this heat source preferably being a waste heat source discharged at a temperature below 100°C, for example by a food processing industry, a paper and cardboard industry, a chemical industry, a waste incinerator, a data center, or a wastewater treatment plant.

9. A method for treating a fluid such as water using a system (1) according to any one of claims 1 to 6, for example to supply an electrochemical device (6) of an installation (5) according to claim 7 or 8, or to supply industrial steam, the method comprising a step of transferring to the fluid heat generated by the absorber (24) of the transformer (12) of the system (1).

10. A method according to claim 9, wherein the system (1) is configured to increase the temperature of said fluid by maintaining it in a liquid state, or by changing it from a liquid state to a gaseous state.

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