BE1031798B1 - Device for producing dihydrogen and dioxygen by electrolysis and corresponding manufacturing method - Google Patents

Abstract

Device for producing dihydrogen and dioxygen by electrolysis comprising at least one electrolyser stack and at least one gas/liquid separator of an electrolyte originating from the electrolyser stack, at least one part of the device comprising at least one wall (111) intended to be in contact with the electrolyte. According to the invention, the wall (111) is covered with a protection comprising at least one layer made of or based on organic polymer. Corresponding method.

Description

Device for producing dihydrogen and dioxygen by electrolysis and corresponding manufacturing method

The invention relates to a device for producing dihydrogen and dioxygen by electrolysis.

The invention also relates to a corresponding manufacturing method.

BACKGROUND OF THE INVENTION

To counter climate change, there is a general consensus to move towards a carbon-neutral society by 2050. Reducing greenhouse gas emissions affects not only the electricity production sector, but also industrial activities, the transport sector and residential heating.

Green dihydrogen, produced by electrolysis of water from renewable energy sources, is promoted as a major energy vector in reducing anthropogenic carbon dioxide emissions from these different sectors. In addition, electrolytic dihydrogen allows the seasonal storage of surplus renewable energy. In addition, as flexible loads, electrolysers can play a role in stabilizing electricity grids.

The production of dihydrogen by electrolysis of water consists of passing a direct current between a cathode and an anode arranged on either side of an electrolyte.

The electric current causes an electrolysis comprising a reduction reaction at the cathode which produces dihydrogen, H2, and an oxidation reaction at the anode which produces dioxygen, O2. The electrolyte can be liquid, such as a solution of potassium hydroxide, KOH, or sodium hydroxide, NaOH (commonly referred to as alkaline electrolysis), or solid, such as a proton exchange membrane (or PEM), an anion exchange membrane (or AEM) or even a ceramic (commonly referred to as a Solid Oxide Electrolysis Cell).

In the case of alkaline electrolysis, partly applicable for PEM and AEM, the production of dihydrogen is carried out by means of a device generally comprising: an electrolyzer stack in which an electrolyte is traversed by a direct current circulating between two electrodes to generate dihydrogen and dioxygen; a dihydrogen separator connected to the electrolyzer stack via a gas-liquid dihydrogen pipe to separate the gaseous dihydrogen from the liquid as well as a dioxygen separator connected to the electrolyzer stack via a gas-liquid dioxygen pipe to separate the gaseous dioxygen from the liquid.

Optionally, the device may also include a circulation pump respectively in communication with a return pipe of the dihydrogen separator and a return pipe of the dioxygen separator to return the liquid to the electrolyser stack. Alternatively, this return can be done naturally without using a pump, in particular if the device is of small dimensions.

Within the device, and in particular within the gas-liquid separators or the electrolyser stack, many parts intended to be in contact with the electrolyte are protected by a layer of nickel, commonly called “nickel plating”.

In fact, the nickel layer offers good resistance to corrosion and prevents dihydrogen or dioxygen from entering unwanted parts of the device.

It is therefore imperative that the nickel layer be as homogeneous as possible to limit any leakage of dihydrogen or dioxygen, however small, through one or more roughness(ies) of said layer, which would allow dihydrogen or dioxygen to enter unwanted parts of the device.

From a practical point of view, poor nickel plating is detected by the presence of brownish spots or by a copper sulfate test. Thus, if the copper sulfate adheres to the area normally protected by the nickel layer, this means that the nickel has not actually adhered sufficiently correctly and effectively. In both cases (detection of brownish spots or copper sulfate test), this check is carried out during the manufacture of the device, in other words when the various components of the device are assembled.

In such a context, various problems arise: — the cost of nickel continues to increase, — the size of nickel plating baths is limited, which consequently limits the size of the elements that can be subjected to nickel plating (such as gas/liquid separators or the electrolyser stack) - otherwise these elements must be constructed in several parts, each of which is subjected to nickel plating and then reassembled, which leads to the appearance of other problems, particularly in terms of manufacturing time and sealing, - nickel plating is applied to an increasingly large number of parts (gas/liquid separator tanks, filters, heat exchangers, etc.).

SUBJECT OF THE INVENTION

One aim of the invention is to propose a solution making it possible to at least partially overcome at least one of the aforementioned drawbacks.

SUMMARY OF THE INVENTION

For this purpose, a device for producing dihydrogen and dioxygen by electrolysis is provided, comprising at least one electrolyzer stack and at least one gas/liquid separator of an electrolyte originating from the electrolyzer stack, at least one part of the device comprising at least one wall intended to be in contact with the electrolyte.

According to the invention, the wall is covered with a protection, an external layer of which is made of or based on an organic polymer, the protection comprising: - at least a first layer at least partially covering the wall, the first layer being made of a material different from that of the external layer and itself being covered at least partially with a second layer forming said external layer and/or - the external layer is formed of at least one sheet applied to the wall.

Surprisingly, such protection can protect a part very well even if it comes into contact with dihydrogen, dioxygen and/or electrolyte. In particular, the wall associated with the protection proves to be well protected from possible corrosion.

Such protection also proves to be i) less expensive to apply than prior art nickel plating and ii) more advantageous with regard to the permitted sizes of walls and parts as opposed to prior art nickel plating.

Advantageously, the application of several layers limits the risk of leakage of dihydrogen, dioxygen and/or electrolyte between the protection and the associated wall.

Optionally, the sheet is made of or based on a polymer material.

Optionally, the sheet is made of or butyl based.

Optionally, the sheet is made of or based on ebonite.

Optionally, the sheet is applied directly to the wall.

By “directly” we mean that the sheet is applied to the wall without an intermediary or by means of a fixing means whose thickness is negligible compared to the thickness of the sheet (such as a layer of glue for example).

Optionally, the sheet is separated from the wall only by means of one layer.

Optionally, the thickness of the protection is between 2600 and 3700 micrometers.

Optionally, the first layer is made of or based on ceramic. 5 Optionally, the polymer of the second layer is made of or based on a thermoplastic.

Optionally, the polymer of the second layer is made of or based on polyetheretherketone.

Optionally, the thickness of the protection is between 140 and 250 micrometers.

Optionally, the device comprises at least one intermediate layer between the first layer and the second layer.

Optionally, the intermediate layer is an adhesive-based layer.

Optionally, the part belongs to the electrolyzer stack.

Optionally, the part belongs to the separation skid.

Optionally, the part belongs to the gas/liquid separator.

Optionally, the part is a connecting flange pierced by at least one orifice, an internal wall of the orifice being covered by the protection.

The invention also relates to a method of manufacturing at least one part of a device as mentioned above, comprising at least the steps of: — applying the first layer and the second layer and/or applying the at least one sheet, — polymerizing at least the external layer.

Other characteristics and advantages of the invention will emerge from reading the following description of a particular and non-limiting embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the attached drawings, among which:

Figure 1 is a flowchart illustrating a device for producing dihydrogen and dioxygen by electrolysis according to a particular embodiment of the invention;

Figure 2 is a sectional view of a part belonging to the device illustrated in Figure 1;

Figure 3 is a diagram illustrating different stages of protection of the part shown in Figure 2 according to a first possible implementation;

Figure 4 is a diagram illustrating different stages of protection of the part shown in Figure 2 according to a second possible implementation;

Figure 5 is a sectional view of parts belonging to the device illustrated in Figure 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1, a device for producing dihydrogen and dioxygen by electrolysis according to a particular embodiment of the invention is a device for producing dihydrogen and dioxygen by electrolysis of water.

The device comprises an electrolyzer stack 10, a dioxygen separator 11, a dihydrogen separator 12, and optionally a circulation pump 13 to create circulation between them.

The electrolyzer stack 10 comprises one or more electrolytic cell(s) each comprising an electrolyte reservoir containing an electrolyte in which an anode and a cathode are immersed to pass a direct current through the electrolyte and thus carry out electrolysis.

The electrolyte consists, for example, of pure water, or of an aqueous solution of KOH or NaOH, such that the passage of direct current through the electrolyte produces dihydrogen and dioxygen.

The dioxygen separator 11 and the dihydrogen separator 12 are respectively communicated with the electrolyzer stack 10 via a gas/liquid dioxygen pipeline and a gas/liquid dihydrogen pipeline. As their names indicate, the dioxygen separator 11 is arranged to perform a gas-liquid separation on the dioxygen generated by the electrolyzer stack 10; and the dihydrogen separator 12 is arranged to perform a gas-liquid separation on the dihydrogen generated by the electrolyzer stack 10. The gas-liquid separators 11, 12 are here gravity separators so that the dihydrogen and the dioxygen are separated from the liquid by the effect of the difference in weight between the gas and the liquid.

The circulation pump 13 is respectively in communication with a dihydrogen-side return pipeline connected to the bottom of the dihydrogen separator 12 and a dioxygen-side return pipeline connected to the bottom of the dioxygen separator 11, and is used to supply the liquid from the dihydrogen separator 12 and the liquid from the dioxygen separator 11 to the electrolyzer stack 10 for recycling. The circulation flow generated by the circulation pump 13 causes the discharge from the electrolyzer stack 10 of dihydrogen and dioxygen generated in the electrolyzer stack 10 and the electrolytic solution to the dihydrogen separator 12 and the dioxygen separator 11.

The oxygen separator 11, the hydrogen separator 12, the circulation pump 13, the electrolyte filter (lye filter) and the electrolyte heat exchanger (lye cooler) form a separation module ensuring: - the separation of the liquid-gaseous oxygen mixture from the electrolyzer stack 10 to produce gaseous oxygen; - the separation of the liquid-gaseous hydrogen mixture from the electrolyzer stack 10 to produce gaseous hydrogen;

- the recirculation of liquids from the gas-liquid separators to the electrolyser stack 10 to reconstitute the electrolyte.

The dioxygen separator 11 has an outlet at the top which communicates with the atmosphere via a dioxygen side control device having a dioxygen outlet 110.

The oxygen outlet 110 is connected to the inlet of a first three-way valve 34. The first three-way valve 34 has a first outlet communicated with the atmosphere for direct discharge, and a second unrestricted outlet. The first three-way valve 34 may be a pneumatic ball valve.

The dioxygen side control device comprises a dioxygen control valve 16 and manual ball bypass valves 17 which are connected in parallel to both ends of the dioxygen control valve 16. The dioxygen separator 11 is provided with a dioxygen hydrogen analyzer 20, a dioxygen pressure sensor 21, and a dioxygen differential pressure sensor 22. The dioxygen differential pressure sensor 22 and the dioxygen pressure sensor 21 are connected to the dioxygen separator 11 via a first valve 26 and a second valve 29, respectively. In this embodiment, the first valve 26 and the second valve 29 are both flow control valves.

The dihydrogen separator 12 has an outlet at the top which is connected to a dihydrogen gas storage tank 14 via a dihydrogen side control device having an outlet 35 connected to said dihydrogen gas storage tank 14. The dihydrogen outlet of the dihydrogen side control device is connected to an inlet of a second three-way valve 33. A first outlet of the second three-way valve 33 communicates with the atmosphere, and the second outlet of the first three-way valve 33 is connected to the dihydrogen storage tank 14. The second three-way valve 33 may be a pneumatic ball valve.

The dihydrogen side control device comprises a back pressure valve 18 and third automatic ball bypass valves 19 which are connected in parallel to both ends of the back pressure valve 18. The back pressure valve 18 is selected according to the desired gas production quantity, the pressure and the operating requirements of the device. The back pressure valve 18 is preset to a set pressure according to the operating requirements of the device and the pressure of the hydrogen gas storage tank 14. The hydrogen separator 12 is provided with a hydrogen level sensor 23 and a hydrogen differential pressure sensor 24. A hydrogen pressure sensor 25 is provided on the hydrogen outlet 35 upstream of the second three-way valve 33. Both ends of the hydrogen differential pressure sensor 24 are connected to the hydrogen separator 12 via a third valve 27 and a fourth valve 28, respectively. The hydrogen pressure sensor 25 is connected to the hydrogen outlet 35 via a fifth valve 30. In this embodiment, the third valve 27 and the fourth valve 28 are both flow control valves.

In the device thus described, numerous parts are in contact with the electrolyte and/or the dihydrogen and/or the dioxygen. Preferably, these parts are thus covered with at least one protection 100 with respect to the electrolyte and/or the dihydrogen and/or the dioxygen.

Such a part is for example a part belonging to the stack of the electrolyser 10 or a part belonging to the separation unit better known under the term of "separation skid". The separation skid actually comprises all of the elements that have been previously described apart from the electrolyser stack 10. In particular

bind, the separation skid comprises the dioxygen separator 11 as well as the dihydrogen separator 12.

If the part belongs to the separation skid, the said part can thus be the gas-liquid separator tank (i.e. the gas-liquid separator tank - also sometimes called "shell") or the electrolyte filter of the gas-liquid separator or the heat exchanger of the gas-liquid separator or any other pressurized equipment belonging to the separation skid.

If the part belongs to the stack of the electrolyser 10, said part can thus be a bottom plate or a distribution plate or any other constituent element of said stack of electrolyser 10.

In Figure 2 is illustrated such a part which here belongs to the gas-liquid dihydrogen separator 12 or to the gas-liquid dioxygen separator 11. Said part is a flange 200 which makes it possible to connect a pipe to the gas/liquid separator (whether it is the dihydrogen separator 12 or the dioxygen separator 11) or to another element of the separation skid.

The flange 200 is provided with a central orifice 201 passing through it from side to side, the electrolyte flowing in service through this orifice 201.

In the case of this flange 200, the internal wall of the flange 200 defining the orifice 201 is covered with a protection 100. In the present case, the entire internal wall is covered with such a protection 100.

This is of course a non-limiting example and other walls of this part and/or other parts of the device may be covered with protection 100.

For example, only one area of such a wall can also be covered with such protection 100.

For example, with reference to FIG. 5, several successive parts may be covered with such protection 100: the flange 200 and/or one of the pipes 300 to which it is connected and/or a tank 400 associated with such a flange or such a pipe, etc.

For this purpose, and with reference to FIG. 3, according to a first implementation, during a first step 101 the wall 111 to be protected (that of the flange 200 or of another part) is covered with a first main layer 112.

For example, a liquid or semi-liquid material (varnish, paint, resin, etc.) is applied to the wall 111 before hardening to form the first main layer 112 on the wall 111.

Optionally, the liquid or semi-liquid material is sprayed onto the wall 111.

Optionally, hardening is done naturally or forced (drying, heating, etc.).

Optionally, the first main layer 112 is made of or based on aluminum oxide and/or boron nitride.

During a second step 102, the first main layer 112 is covered with an intermediate layer 113. The intermediate layer 113 is made of a different material from the first main layer 112.

The intermediate layer 113 is preferably an adhesive layer.

For example, a liquid or semi-liquid material (varnish, paint, resin, etc.) is applied to the first main layer 112 to form the intermediate layer 113.

Optionally, the liquid or semi-liquid material is sprayed onto the first main layer 112.

During a third step 103, the intermediate layer 113 is covered with a second main layer 114.

For example, a liquid or semi-liquid material is applied to the intermediate layer 113 to form the second main layer 114.

Optionally, the liquid or semi-liquid material is sprayed onto the wall 111.

The second main layer 114 is in a second material different from that of the first main layer 112 and that of the intermediate layer 113.

The second material is made of or based on organic polymer.

Preferably, the second material is in or based on a thermoplastic organic polymer.

Preferably, the second material is in or based on a thermoplastic organic polymer.

For example, the second material is made of or based on polyetheretherketone (e.g. marketed under the name PEEK — registered trademark).

In a fourth step 104, the protection 100 is here polymerized in a forced manner. For this purpose, the part is heated which causes a chemical polymerization of the protection 100.

The part is here placed in an oven: heating the part ensures polymerization of at least the second main layer 114.

The heating allows: - good adhesion of the first main layer 112 to the part, and/or - good adhesion of the intermediate layer 113 to the first main layer 112, and/or - good adhesion of the second main layer 114 to the intermediate layer 113, and/or — good uniformization of the second main layer 114.

At the end of the manufacturing process of the protection 100, it has a thickness of between 140 and 250 micrometers.

The protection 100 here only comprises the three aforementioned layers 112, 113, 114.

The second main layer 114 is the one intended to be in contact with the electrolyte and/or the dihydrogen and/or the dioxygen. This is particularly advantageous because the second material of the second main layer 114 has very good compatibility with the electrolyte.

The second main layer 114 thus forms the outer layer of the protection 100.

Furthermore, the adhesive layer 113 makes it possible to reinforce the cohesion between the two main layers 112, 114.

In addition, the first main layer 112 makes it possible to limit a risk of leakage of dihydrogen and/or dioxygen and/or electrolyte under the protection 100, between the protection 100 and the part itself.

Protection 100 is therefore of very good quality.

With reference to figure 4, according to a second implementation, during a first step 131 the wall 111 to be protected (that of the flange 200 or another part) is covered with a single main layer 112.

For this purpose, at least one sheet of a first material is applied to the wall 111 to form the main layer 112 either directly or by means of fixing means (such as glue for example).

The leaves here are in the same material.

In this way, the main layer 112 is here formed from the material which is made of or based on organic polymer material.

The material is for example made of or based on butyl and for example made of or based on butyl rubber.

During a second step 132, the protection 100 is here polymerized in a forced manner. For this purpose, the part is heated which causes a chemical polymerization of the protection 100.

The part is here placed in an oven: heating the part ensures polymerization of the main layer 112 and/or good adhesion of the main layer 112 on the part and/or good uniformization of the main layer 112.

At the end of the manufacturing process of the protection 100, it has a thickness of between 2600 and 3700 micrometers.

The protection 100 here only comprises the aforementioned layer 112 (apart from the tiny layer of glue to place the aforementioned layer 112 on the wall).

The main layer 112 is the one intended to be in contact with the electrolyte. This is particularly advantageous because the material of the main layer 114 has very good compatibility with the electrolyte.

The main layer 112 thus forms the outer layer of protection.

In addition, the main layer 112 makes it possible to limit a risk of hydrogen and/or oxygen and/or electrolyte leakage under the protection 100, between the protection 100 and the part itself.

Protection 100 is therefore of very good quality.

According to a variant of this second implementation, the material of the main layer 112 may be different from what has been indicated.

For example, the material is made of or based on organic polymer.

For example, the material is in or based on thermoplastic organic polymer.

For example, the material is in or based on ebonite.

With regard to the second implementation, and whatever the variant considered, the sheet making up the main layer 112 is arranged so that the largest dimension of said sheet extends substantially along the largest dimension of the wall to which it is applied.

This allows to maximize the coverage of the part considered.

For example, if the part is a balloon 400 of the separation skid (more precisely of one of the separators of the separation skid), at least one of the sheets can be applied so that its length extends along the corresponding length of one of the walls to be protected of the balloon 400 and for example extends along the length of the lower wall of the gas-liquid separator.

Preferably, depending on the wall 111 to be protected, the protective layer 112 will not be made of the same material.

For example, the protection associated with the orifice 201 of the flange 200 may be made of or based on ebonite.

This will allow it to withstand seating pressure from the associated sealing gasket(s).

For example, the protection at the balloon 400 or at the pipe 300 can be made of or based on butyl.

Preferably, the flat walls are thus covered with a protection made of or based on butyl rather than made of or based on ebonite.

Two different implementations were thus proposed to protect the parts, simple and inexpensive implementations.

Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

Thus, although here the device comprises a circulation pump, the device may not comprise a circulation pump or may comprise a greater number of pumps and for example comprise at least two pumps (one for each of the gas/liquid separators).

The device may include more elements than those indicated. For example, the device may include at least one gas cooler to cool the gases and/or at least one scrubber (make-up water injection point).

The protection may include a different number of layers than indicated.

The protection may include materials other than those indicated.

If one of the layers of the protection is formed by sheets, depending on the surface of the wall to be covered, several sheets will potentially have to be used to be able to cover the entire surface with possible overlapping areas to ensure that no area of the surface is free of protection. Outside the overlapping area, said layer may consist of a single sheet or a stack of at least two sheets.

The manufacturing method may include one or more additional steps. For example, in the case of the first implementation, the method may include an intermediate step between the deposition of the intermediate layer 113 and the deposition of the second main layer 114, such as, for example, a heating step (at a lower temperature than the temperature of the polymerization step).

Claims (7)

17 BE2023/5587 CLAIMS 1. Device for producing dihydrogen and dioxygen by electrolysis comprising at least one electrolyser stack and at least one gas/liquid separator of an electrolyte originating from the electrolyser stack, at least one part of the device comprising at least one wall (111) intended to be in contact with the electrolyte, characterised in that the wall is covered with a protection (100), the protection comprising at least a first layer (112) at least partly covering the wall (111), an intermediate layer (113) and a second layer (114), the intermediate layer (113) being arranged between the first layer (112) and the second layer (114) so that the second layer covers the first layer, the second layer forming an external layer of the protection and being made of a material made of or based on an organic polymer, the second layer being made of a material different from that of the first layer, the polymer of the second layer (114) being made of or based on a thermoplastic, the polymer of the second layer (114) is made of or based on polyetheretherketone. 2. Device according to claim 1, in which the first layer (112) is made of or based on ceramic. 3. Device according to one of claims 1 to 2, in which the thickness of the protection (100) is between 140 and 250 micrometers. 4. Device according to one of claims 1 to 3, in which the intermediate layer (113) is an adhesive-based layer. 5. Device according to one of the preceding claims, in which the part belongs to the electrolyser stack or to the separation skid. 6. Device according to one of the preceding claims, in which the part is a connection flange (200). 18 BE2023/5587 pierced by at least one orifice (201), an internal wall of the orifice being covered by the protection (100). 7. Method for manufacturing at least one part of a device according to one of the preceding claims, comprising at least the steps of: — applying the first layer (112) and the second layer (114), - polymerizing at least the external layer.