JP2014504680A - In particular, an electrolytic cell for producing H2 and O2 and an assembly comprising the electrolytic cell - Google Patents

Abstract

The present invention relates to hydrogen, oxygen, chlorine or hypochlorous acid by electrolysis of pure water or water containing at least one salt, base and / or acid such as NaCl, H ₂ SO ₄ , KOH or NaOH. Or an electrolyzer for producing at least one chemical such as sodium hydroxide, the electrolyzer comprising at least a stack of first and second successive electrolysis cells, each electrolysis cell (10) comprising an anode And an ion exchange membrane (11) disposed between the anode and the cathode, the ion exchange membrane (11) of the first and second electrolysis cells on the one hand being the anode of the first electrolysis cell On the other hand, it is separated by a bipolar electrode (15) constituting the cathode of the first electrolysis cell.
[Selection] Figure 3

Description

The present invention uses an electrolytic cell provided with a plurality of electrolytic cells each having at least one ion exchange membrane disposed between an anode and a cathode, and uses pure water, NaCl, H ₂ SO ₄ , KOH, NaOH, or the like. It relates to the production of chemicals such as dihydrogen, dioxygen, chlorine, hypochlorous acid or soda by electrolysis of water containing salts, bases and / or acids.

  It is an object of the present invention to improve an electrolytic cell so as to facilitate the production of one or more substances of interest and reduce the cost thereof.

Accordingly, the present invention relates to an electrolyzer for producing dihydrogen and dioxygen or other chemicals comprising at least a stack of first and second successive electrolysis cells, each electrolysis cell comprising:
-An anode;
-A cathode;
-At least one ion exchange membrane arranged between the anode and the cathode;
The exchange membranes of the first and second electrolysis cells are separated by a bipolar electrode constituting on the one hand the anode of the first electrolysis cell and on the other hand the cathode of the second electrolysis cell.

  The electrolytic cell according to the present invention is simple to assemble compared to known electrolytic cells in which the anode and cathode of different cells are separated from each other.

  Furthermore, the current circulation in the electrolytic cell, in particular in the cell and / or between different electrolytic cells, can be improved.

This electrolytic cell is made of dihydrogen, dioxygen, chlorine, hypochlorous acid, soda by electrolysis of pure water or water containing salt, base and / or acid such as NaCl, H ₂ SO ₄ , KOH or NaOH. Can be configured to generate.

  The bipolar electrode can have a one-piece bipolar plate, which includes at least one grid or at least one perforated plate, especially one or two grids and one or two perforated plates, as required. With the plates, these grids and perforated plates can be placed on either side of the bipolar plate. Throughout this application, the term “plate” should be broadly understood to be synonymous with wall and is not limited to flat components even if a flat shape is preferred. One grid can at least partially define the anode chamber of the first cell, and the other grid can at least partially define the cathode chamber of the second cell. Each anode or cathode chamber can be delimited by a bipolar plate on the one hand and a perforated plate on the other. The perforated plate can favorably support adjacent ion exchange membranes. The perforated plate also serves as a diffuser that circulates electrolyte and gas so as to promote an electrochemical reaction. The same gasket assembled with 180 ° axis rotation provides chamber tightness to gases and electrolytes and circulation in each of the anode and cathode chambers, which are impermeable independently of each other.

  The bipolar electrode can be made entirely as a single piece, in which case the bipolar plate, grid and perforated plate are integrated with each other before being installed in the electrolytic cell.

  Bipolar electrode or at least bipolar plate is nickel, iridium, ruthenium, palladium, cadmium, molybdenum, platinum, stainless steel, titanium, tantalum, iron alloy, lead alloy and / or tantalum oxide, iridium oxide, ruthenium oxide, lead oxide , Iron oxide, platinum, platinum carbon, palladium, nickel, cadmium and / or a thin layer of molybdenum.

  Perforated plate is nickel, iridium, ruthenium, palladium, cadmium, molybdenum, platinum, stainless steel, titanium, tantalum, iron alloy, lead alloy and / or tantalum oxide, iridium oxide, ruthenium oxide, lead oxide, iron oxide, platinum , Platinum carbon, palladium, nickel, cadmium and / or a thin layer of molybdenum.

  The one or more perforated plates can include, for example, titanium whose surface adjacent to the ion exchange membrane is covered with one layer of the materials described above.

  The anode can include at least one of a thin layer of titanium, tantalum, iridium, iron alloy, lead alloy, and / or tantalum oxide, iridium oxide, ruthenium oxide, lead oxide, and / or iron oxide. This thin layer can in particular be arranged on the anode surface adjacent to the ion exchange membrane.

  The cathode is at least one of a thin layer of nickel, iridium, cadmium, molybdenum, platinum, titanium, tantalum, iron alloy, lead alloy, nickel alloy, and / or platinum, platinum carbon, palladium, nickel, cadmium and / or molybdenum. One can be included. This thin layer can in particular be arranged on the cathode surface adjacent to the ion exchange membrane.

  In particular, the entire bipolar electrode can be made of the same material, for example titanium. More precisely, the entire bipolar plate can be made of the same material, for example titanium. The entire grid or grids can also be made of the same material, for example titanium. The entire porous plate can also be made of the same material such as titanium.

  A frame and a gasket can be disposed between the electrodes. The electrolyte can circulate between the cells through holes formed in the frame and gasket and a circulation duct formed in the gasket.

  As a variant, the bipolar electrode, in particular the bipolar plate, can comprise a coating of a material such as, for example, titanium. This coating can have a thickness of 10-100 μm, for example about 50 μm.

  The ion exchange membrane preferably contains boron nitride, and more preferably contains activated boron nitride.

The purpose of “activation” of boron nitride is to increase the ionic conduction of boron nitride. In activated boron nitride, the activated “BN” crystal produces —OH, —H, —SO ₃ H, —SO ₄ H bonds on its surface, thereby producing N—H ₂ ⁺ , B A —OH ₂ ⁺ , B—SO _X H ₂ ⁺ or N—SO _X H ₂ ⁺ group is produced. Ionic conduction may also be performed by pairs available on oxygen atoms inserted into nitrogen holes in boron nitride. These nitrogen pores containing oxygen atoms may be present especially when boron nitride is obtained from B2O3 or H3BO3.

  The boron nitride used can comprise at least one, for example one or more substitution elements from boron oxide, calcium borate, boric acid, sulfuric acid. The presence of such elements can promote activation, especially when they are present in a weight ratio of 1 to 10%. For example, the presence of boric acid in the pores of boron nitride or in an amorphous form can facilitate the formation of B—OH and N—H bonds.

In order to perform the activation, boron nitride or a film including the same is supplied with H ₃ O ⁺ or SO ₄ ²⁻ ions, and B—OH and / or B—SO ₄ H, B—SO ₃ is supplied into the boron nitride. It can be exposed to a fluid to form H, N—SO ₄ H, N—SO ₃ H and / or N—H bonds. The fluid can be an acidic solution containing H ₃ O ⁺ , such as a strong or weak acid such as HCl, H ₂ SO ₄ , H ₃ PO ₄ , H ₂ S ₂ O ₇ , or is an acidic solution. Although not necessary, it can be a base solution containing, for example, OH-ions, such as a soda or potash solution. The concentration of the solution can affect the rate and level of activation obtained, i.e. the level of ionic conductivity obtained, but not the appearance of activation itself. The acid concentration is, for example, 1 to 18 mol / L, and the soda concentration can be 0.5 to 1 mol / L.

To promote the formation of bonds with [BN] crystals with —OH, —SO ₄ H, —SO ₃ H, —SO ₄ H, —SO ₃ H and / or —H, including boron nitride or this The membrane can be exposed to an electric field of, for example, 15-40,000 V / m, for example in the presence of a 1M solution of H ₂ SO ₄ acid.

This electric field can be supplied by an external generator. The applied voltage is 1.5V to 50V, for example, about 30V. The voltage source can be constant or, as a variant, non-constant. The voltage source can be configured to automatically detect the end of activation, for example, when the current density in the material increases rapidly. Intensity of the current circulating in the boron nitride in the activation is, for example, about ^{10mA / cm 2 ~1000mA / cm 2} .

  Activation by the fluid can be performed at 0-90 ° C., such as about 60 ° C., or at room temperature.

  Boron nitride can be washed after exposure to a solution and optionally dried prior to use in the manufacture of an electrolytic cell. The fluid can be removed so that its residual content is less than 2%.

  The duration of the step of exposing to the fluid can be less than 50 hours.

  In an embodiment of the invention, for example, boron nitride in powder form is activated after being activated by mixing boron nitride, for example, with 3M concentrated sulfuric acid for a predetermined time, and then washed, for example. Activated boron nitride by mixing with a polymer matrix is used to make an ion exchange membrane.

  The ion exchange membrane can include a polymer matrix. The polymer matrix may include, but is not limited to, at least one of polymers from polyvinyl alcohol (PVA), vinyl caprolactam, PTFE (Teflon), sulfonated polyethersulfone. it can. The polymer matrix can comprise, for example, PTFE from DUPONT, known under the trade name Teflon, or PTFE from another company. The ionic conduction with PTFE is as good as with other polymers and can reach 0.2 S / cm.

  The weight ratio of boron nitride in the film can exceed 50%, and can be further 95% or more, particularly in combination with PTFE. In some embodiments, this ratio is, for example, about 70%, and in other embodiments about 90%.

  The mechanical strength (mechanical strength at 300 μm) of the ion exchange membrane is sufficient even with a small amount of PTFE, for example, about 4 MPa (Young's modulus) with 5 wt% PTFE at 25 ° C., and a larger amount of PTFE. For example, at 15%, it is significantly increased to about 6 MPa.

  The temperature range in which the ion exchange membrane is used is fairly wide and can be up to 180 ° C.

  Boron nitride present in the ion exchange membrane can take the form of a powder composed of particles having a major axis dimension of 0.5 to 15 μm centered on 5 μm, for example.

  According to one hypothesis of the mechanism of action, ionic conduction in boron nitride occurs on the surface of the activated boron nitride crystals that make up this particle.

  In one embodiment, the boron nitride is composed of a powder of nanoparticles, ie, particles having a nanometer-sized single crystal, such as, for example, 10-500 nanometers.

  The ion exchange membrane can have a thickness of 50 to 500 μm, such as about 200 μm to 300 μm. With a relatively thin thickness, ion conduction can be improved. Nevertheless, if necessary, the thickness of the ion exchange membrane should be sufficient to withstand the high pressure in the electrolytic cell. In one embodiment of the invention, this pressure can reach, for example, 30 bar.

  “Material permeability” refers to an intrinsic property of the material and is a metric for the ability to pass fluids, including fluids or gases, and is independent of the porosity of the material. Dihydrogen or dioxygen dissolved in water can pass through the ion exchange membrane. This phenomenon indicates the presence of dihydrogen in the collected dioxygen and the presence of dioxygen in the collected dihydrogen.

  The presence of dihydrogen in dioxygen can be dangerous. The presence of about 4% dihydrogen in air or dioxygen corresponds to the lower explosion limit (LEL). Therefore, the LEL criterion is defined as the presence of 4% dihydrogen in dioxygen corresponding to 100% LEL.

  The permeability of dihydrogen and dioxygen through the ion exchange membrane is preferably sufficiently small so that the proportion of dihydrogen in dioxygen is less than 70% LEL at 30 bar and 90 ° C. The electrolyzer can be equipped with an alarm that is activated when this limit is exceeded. The assembly can have one or more sensors at the outlet of the cell to monitor the level of dihydrogen in dioxygen and the level of dioxygen in dihydrogen, thereby providing sufficient purity of dihydrogen Can be guaranteed. If the purity is insufficient, the operation can be stopped.

  “Porosity” refers to all of these gaps, regardless of whether the gaps in the material, which can include fluids, liquids or gases, are bonded. Porosity is a numerical value that characterizes these gaps and corresponds to the ratio of the void volume of the material divided by the total volume. The ion exchange membrane is preferably nonporous during operation so as not to allow gas to pass in the operating state. Conversely, a dry ion exchange membrane may not be nonporous. The dry ion exchange membrane may not be gas impermeable.

Each electrolytic cell can consume water, and a reaction of, for example, H ₂ O → H ₂ + 1 / 2O ₂ occurs in the electrolytic cell. This reaction can occur in an acidic medium that can facilitate the circulation of H ₃ O ⁺ ions or protons H + through the ion exchange membrane from the anode to the cathode.

  Thus, the electrolyte can include water and acid. The acid can be selected from, but not limited to, sulfuric acid, phosphoric acid, and carboxylic acid. The acid concentration can be, for example, about 5 to 20% by weight.

This reaction can also occur in a basic medium that can facilitate the circulation of OH ^- ions through the ion exchange membrane from the cathode to the anode.

  Thus, the electrolyte can include water and a base. The base can be selected from, but not limited to, potash KOH and soda NaOH. The concentration of the base can be, for example, about 5 to 30% by weight.

  Depending on the substance or substances that one wishes to produce, it may not be necessary to add an acid or base during use, for example water alone.

  In operation, the voltage at the terminals of each electrolysis cell is 1.24-5V, such as about 1.48V. In operation, the current circulating in the electrolysis cell can be 200-1000 A, such as about 500 A, for example, when the active surface is 500 cm 2.

In one embodiment, at least one cell of the stack has a single ion exchange membrane between the anode and the cathode. The cell can have two chambers: an anode chamber defined between the anode and the ion exchange membrane, and a cathode chamber between the cathode and the ion exchange membrane. In this configuration, the electrolytic cell can be used to produce H ₂ and O ₂ , Cl ₂ and NaOH, or Cl ₂ and H ₂ .

  In one embodiment, at least one cell of the stack can have two ion exchange membranes, which preferably form an intermediate chamber therebetween. This cell can have three chambers. In this configuration, the electrolyzer can be used for HClO and NaOH production, or for salt water desalination and thus pure water production.

  At least one cell can have a non-selective ion exchange membrane, such as a membrane comprising boron nitride, and a selective exchange membrane, such as a Nafion-based membrane.

  “Nonselective exchange membrane” means a membrane having the ability to conduct both anions and cations.

  There may be means for setting the circulation of the electrolyte in the intermediate chamber, especially for the purpose of taking out the material produced in the electrolytic cell during operation of the electrolytic cell.

The present invention further relates to an electrolytic assembly, the electrolytic assembly comprising:
-An electrolytic cell as defined above;
A reservoir for supplying the obtained dihydrogen at a given pressure, for example in connection with the cathode production of dihydrogen,
A reservoir for supplying the resulting dioxygen at a given pressure, for example in connection with anodic production of dioxygen;
Is provided.

  The electrolyte can be stored in each of these two reservoirs.

  The assembly can have a fluid communication between these reservoirs, particularly at the base of the two reservoirs. The assembly can comprise a device for monitoring the electrolyte level in each reservoir. As will be described later, the fluid communication portion can be controlled by a switching valve in relation to the electrolyte level in each reservoir.

  As a variant and possibly, this fluid communication can be freed to ensure a balance of electrolyte levels in the two reservoirs. In this way, when dihydrogen and dioxygen are produced by electrolysis, the ratio of the relative volume available for the gas obtained in each reservoir is always constant, resulting in the reaction stoichiometry, and thus The balance of pressure in the reservoir is respected. The advantage of having a connection between the reservoirs is that the liquid level in each reservoir can be ensured.

  The assembly can have a water supply. In one embodiment, when generating dioxygen, the water supply can be provided by a dioxygen reservoir. As a modification, the water supply unit may be provided by a dihydrogen reservoir.

  The electrolyte can contain hydroxyl ions and sulfate ions in addition to water.

  On the anode side, when voltage is present, sulfate ions convert water into gaseous oxygen and hydroxyl ions. Oxygen is recovered and hydroxyl ions pass through the membrane toward the cathode. Accordingly, this consumes water. On the cathode side, when voltage is present, hydroxyl ions are converted to hydrogen and water. The presence of sulfate ions makes it possible to maintain the concentration level of hydroxyl ions.

In an embodiment of the invention, the electrolytic cell comprises 7 consecutive electrolysis cells and the active surface per cell is 500 cm ² . In operation, such an electrolytic cell can consume 7 kW of power with 70% efficiency.

  In another embodiment, the electrolytic cell comprises 70 consecutive electrolysis cells. In operation, such an electrolytic cell can consume 70 kW of power with 70% efficiency.

Each ion-exchange membrane, for example, the dimensions of 30 cm × 35 cm, may have a total surface area, or the active surface of 500 cm ² to about 1050 cm ^2.

  The electrolytic cell can include a front end shield and a rear end shield adjacent to a continuous electrolysis cell. The front end shield and the rear end shield can include, for example, stainless steel such as stainless steel 316L.

  The assembly has a stabilizer to stabilize the pressure in the reservoir to a value of, for example, 10-30 bar when there is a gas exhaust that is not released to the atmosphere. It is also possible to operate at atmospheric pressure. This stabilizer can have an exhaust device for each reservoir to adjust the pressure in the corresponding reservoir to obtain the same pressure in each reservoir, thereby causing damage to the electrolysis cell, particularly against the ion exchange membrane Damage can be prevented.

  Each reservoir may also have a deaeration port with a control pressure sensor and a safety valve that operates in an emergency.

  Each reservoir further has an outlet valve that allows the user to collect the generated gas. The gas produced can be recovered and used directly, or it can be transported compressed for example to a value of 300 bar.

  When producing dihydrogen and dioxygen, a device containing a catalyst capable of burning residual dioxygen that may be present in the dihydrogen reservoir is provided at the outlet of the dihydrogen reservoir so that pure dihydrogen is obtained. Can do. For example, a drier can be used to remove residual moisture that may be obtained by burning dihydrogen with residual dioxygen. Thereafter, the flow rate of the obtained dihydrogen can be measured, and a sensor for confirming the purity of the obtained gas can be attached.

  The assembly controls the temperature of the electrolytic cell to maintain a substantially constant operating temperature, for example from 0 ° C. to 120 ° C., or even from 70 ° C. to 120 ° C., on the one hand in each reservoir, on the other hand. An electrolytic temperature sensor can be further included in the electrolytic cell itself. The temperature of the electrolyte can be about 70 ° C., for example. By maintaining a sufficiently high operating temperature, an electrochemical reaction can be promoted regardless of pressure selection. Conversely, temperature limits above which the risk of the assembly degrading must not be exceeded. Optionally, the assembly comprises at least one or two devices, optionally with a temperature sensor for monitoring the effectiveness of cooling, for cooling the electrolyte before it enters the electrolytic cell. You can also.

  The assembly may further comprise a heating device, for example for use in a low temperature environment, depending on the temperature difference between the operating temperature and the external temperature. The heating device includes, for example, a resistor disposed, for example, in the electrolyte in the electrolyte reservoir or close to the stack of cells. As a variant, the voltage can be increased at the start of operation to obtain a resistance loss for heating the assembly and then returned to the operating voltage.

  The assembly can also have external insulation.

  By stabilizing the temperature to the operating temperature, the efficiency and lifetime of the electrolytic cell can be improved.

  The solenoid valve can be made at least partially from PVDF.

  The electrolyzer power supply is preferably housed in an electrical cabinet with a process control computer for controlling from outlet current and voltage to current and / or voltage supplied to the stack of electrolysis cells.

  The control cabinet can also be equipped with a remote connection that allows remote maintenance of the assembly.

  The operating time of the assembly can be at least about 10,000 hours.

  Further, the assembly can comprise an electrolyte storage tank.

  The assembly can be equipped with an acidity sensor, or vice versa.

  The present invention further relates to a method for producing hypochlorous acid using an intermediate chamber electrolytic cell. The cell's anode chamber can contain water, the cathode chamber can contain water, and the intermediate chamber can contain salt water.

The present invention further relates to an electrolyzer cell, the cell comprising:
-An anode;
-A cathode;
-Two exchange membranes, in particular
A selective exchange membrane and a non-selective exchange membrane disposed between the anode and the cathode, preferably an activated boron nitride-based non-selective membrane, and preferably a Nafion-based selective membrane;
The non-selective membrane preferably protects the selective membrane from a basic environment or an acidic environment.

  A better understanding of the present invention can be obtained when the following detailed description of the embodiments is read and the accompanying drawings are considered.

1 is a perspective view of a stack of electrolysis cells according to the present invention. FIG. FIG. 2 is an exploded view of the stack of electrolysis cells of FIG. 1. It is an exploded view of an electrolysis cell. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. It is a top view of each component which comprises the stack | stuck of FIG.1 and FIG.2. FIG. 4 is a schematic partial cross-sectional view of the electrolytic cell of FIG. 3. FIG. 4 is a schematic partial cross-sectional view of the electrolytic cell of FIG. 3. Figure 2 is a perspective view of an assembly according to the present invention. Figure 2 is a perspective view of an assembly according to the present invention. Figure 2 is a perspective view of an assembly according to the present invention. FIG. 2 is a schematic diagram illustrating the operation of the assembly according to the present invention. It is a figure which shows control of electrolyte temperature. It is a figure which shows control of electrolyte temperature. FIG. 3 schematically illustrates the management of electrolyte flow in an assembly according to the invention. FIG. 3 schematically illustrates the management of electrolyte flow in an assembly according to the invention. FIG. 3 schematically illustrates the management of electrolyte flow in an assembly according to the invention. FIG. 3 schematically illustrates the management of electrolyte flow in an assembly according to the invention. FIG. 3 schematically illustrates the management of electrolyte flow in an assembly according to the invention. FIG. 3 schematically illustrates the management of electrolyte flow in an assembly according to the invention. It is a figure which shows roughly the modification of the electrolytic cell by this invention. FIG. 3 illustrates electrolyte circulation within a stack of cells according to one embodiment of the invention. FIG. 5 shows the use of holes in various elements to define circulation in various chambers.

  1 and 2 show a stack 1 of electrolysis cells according to the invention. In the example described, this stack comprises seven electrolysis cells 10 separated by six bipolar electrodes 4 and two end electrodes 4a at both ends.

  As shown in FIGS. 3 and 4 a to 4 l, each cell includes at least one ion exchange membrane 11, and porous plates 12 each surrounded by a frame 13 are arranged on both sides thereof. The two perforated plates 12 can have different sizes as shown in FIGS. 4e and 4g, with one of the perforated plates being larger than the other as shown in FIG. It can be supported on a frame around the other perforated plate to ensure good mechanical protection of the ion exchange membrane and avoid any shearing effects. Since the frame 13 has a shape corresponding to the associated perforated plate, each of the frames 13 has a different shape as shown in FIGS. 4d and 4h. The larger porous plate may be present on either the cathode side or the anode side. Each frame 13 allows the positioning of the corresponding perforated plate. This provides mechanical protection. The frame 13 can be made of titanium, for example, nylon, Teflon (registered trademark), plastic such as PFA, PEHD, or epoxy.

  On both sides of the perforated plate, grids 14 having the same size and shape are arranged as in the example described. Each grid defines an anode chamber on the one hand and a cathode chamber on the other hand. The grid 14 can be made of titanium.

  Each grid 14 is surrounded by a gasket 15. The same gasket is used for each cathode chamber and anode chamber, but placed in the opposite direction to avoid mixing the electrolyte flowing in the anode chamber with the electrolyte flowing in the cathode chamber. In the illustrated example, the gasket 15 is serrated to easily collapse so as to absorb manufacturing variations in stack thickness due to manufacturing tolerances of each component of the stack.

  Each of the grids 14 includes a protrusion 14 a configured to protrude into a circulation duct 15 a provided in the gasket 15. These protrusions 14a can support the ion exchange membrane during stack tightening to improve this level of tightness, i.e. avoid mixing of the gas produced.

  Eventually, the bipolar plate 4 will close the anode chamber of the first electrolysis cell and the cathode chamber of the second adjacent electrolysis cell. The bipolar plate can be made of titanium. The bipolar plate, together with the grid 14 and the perforated plate, forms on the one hand the anode of the first electrolysis cell and on the other hand forms the bipolar electrode 15 constituting the cathode of the second electrolysis cell, and the ion exchange membrane of the first electrolysis cell. Is separated from the ion exchange membrane of the second electrolysis cell.

  The bipolar electrode 15, in other words, the two grids, the two perforated plates, and the bipolar component constitute an assembly of five components as shown in FIG. 5, and are manufactured by diffusion bonding as an integral component such as titanium. be able to. For this purpose, the five components are placed in a mold, pressed and held in place, and then heated to a high temperature of about 1500 ° C., for example. At this time, when a bonding spot appears on the titanium, an integrated bipolar electrode can be obtained.

Below, the example of the value of the different thickness of an electrolysis cell is shown.
-Perforated plate and frame: 0.5-0.6 mm,
-Grid: 1.25mm, which can promote electrolyte circulation and avoid head loss,
-Gasket: 1.5mm, reaching 1.25mm when crushing,
-Bipolar plate: 0.5-0.6mm,
-Ion exchange membrane: 0.2-0.5 mm.

  Therefore, for example, a total cell thickness of 4.2 to 4.8 mm is obtained.

The total surface area of the ion exchange membrane can be about 1000 cm ² . The active part, i.e. the part causing the electrochemical reaction, can be only about half, for example 500 cm < ² >. A portion of the ion exchange membrane can be used as a gasket of the same size as the frame associated with the perforated plate.

  The electrolytic cell contains a catalyst for electrochemical reaction. These catalysts are preferably disposed between the ion exchange membrane and the perforated plate. The catalyst is preferably deposited on the ion exchange membrane rather than on the perforated plate.

  In one embodiment, the catalyst comprises, on the one hand, a catalyst deposited on an ion exchange membrane and on the other hand a thin layer deposited on a perforated plate forming an anode and / or cathode as described above. In this case, the perforated plate has a thin layer of catalyst material on the surface adjacent to the ion exchange membrane.

  If the cell includes a single ion exchange membrane, the ion exchange membrane can have two catalyst layers, one on each side.

  In one embodiment, if the cell includes two ion exchange membranes, each ion exchange membrane has a single catalyst layer.

In an embodiment of the present invention, the catalyst comprises platinum on one side (or one of them) on the hydrogen production side and on the other side (or one of them) on the dioxygen production side. Contains IrO ₂ .

In an embodiment of the invention, the catalyst comprises, on the one hand, platinum on the cathode side ion exchange membrane (or one of them), and on the other hand, IrO ₂ on the anode side ion exchange membrane (or one of them). including.

  Hereinafter, an example of a method for depositing a catalyst on an ion exchange membrane will be described.

  A mask having the same size as the perforated plate is used, and the catalyst is deposited on the ion exchange membrane so that the catalyst is deposited only on the portion of the ion exchange membrane covered with the porous material.

IrO ₂ deposition is accomplished by mixing IrO ₂ in powder form with liquid proton conductors used as adhesives, such as activated boron nitride mixed with ethanol and Nafion®, or PTFE. Done. The resulting liquid can be placed in a sonotrode to break up the granules and then sprayed onto one side of the membrane. The membrane can be heated to a temperature of about 50 ° C. immediately after injection or during injection to promote the evaporation of ethanol present in the mixture.

  The same procedure can be used with platinum by adding activated carbon to the mixture. In one embodiment, a catalyst deposited on a perforated plate is used.

In one embodiment, 1 mg / cm ² of platinum and 2 mg / cm ² of iridium oxide are deposited.

  In the example to be studied, the cells are assembled at the same time, and are clamped and held between the end shields 2a and 2b by the flexible washer 5. In one embodiment, these washers form a spring rather than flat, and the pressure experienced by the stack of electrolysis cells can be adjusted so that the resulting pressure is substantially constant. This pressure can be, for example, about 100 bar. A washer stack can be used to increase the stiffness constant. The clamping of the electrolysis cell stack can be performed in a controlled manner by calculating the appropriate clamping torque.

  The stack can have bipolar plates 4 all of the same shape. In particular, all bipolar plates can be flat.

  As a variant, the stack comprises a flat bipolar plate 4 arranged between the ion exchange membranes and two different forms of bipolar plates 4a, called the anode current collector and the cathode current collector, at both ends. it can. These bipolar plates are each configured to contact a copper part 7 having a sleeve 8 to fit in a central hole in the corresponding end shield 2a, 2b, to allow power supply to the stack. be able to. The copper part 7 can be insulated from the end shield by a seal (not shown) and surrounded by a gasket 9 to ensure hermeticity and stress distribution. The sleeve 8 can be surrounded by a Teflon insert to protect the electricity supply.

  The electrolyzer further comprises a fluid connector defining two inlets and two outlets, more precisely a cathode end chamber inlet 3a and outlet 3b, and an anode end chamber inlet 3c and outlet 3d. The cathode chamber and the anode chamber in between communicate with each other. Each fluid connector can have an intermediate insert made of, for example, titanium.

  The front end shield 2a, also shown in FIG. 4k, has an electrolyte inlet and outlet, more precisely an electrolyte inlet 3a on the dioxygen production side, an outlet 3b for an electrolyte containing dioxygen, and an electrolyte on the dihydrogen production side. It contains an inlet 3c and finally an outlet 3d for an electrolyte containing dihydrogen.

  The electrolyte circulates between the electrolytic cells in the electrolytic cell according to the shape of the gasket 15 arranged around the grid.

  Hereinafter, referring to FIG. 7a, FIG. 7b and FIG. 8, the electrolytic cell, the dihydrogen reservoir 21 for supplying the obtained dihydrogen and the dioxygen reservoir 22 for supplying the obtained dioxygen will be described. The provided electrolytic assembly 20 will be described. In the example considered, the cross-sectional area of the dihydrogen reservoir is twice that of the dioxygen reservoir, but this need not be the case.

Electrolyte circulation is controlled by solenoid valves V ₁ , V ₂ , V ₃ and V ₄ and is supplied, for example, “all or zero” by pumps P ₁ and P ₂ .

The electrolyte used in the examples can be demineralized water containing 10 wt% H ₂ SO ₄ .

The electrolyte is stored in each of a dihydrogen reservoir and a dioxygen reservoir, and the assembly has a switching valve EV at the base of the two reservoirs to balance the electrolyte level and acidity level in these reservoirs. A fluid communication between two reservoirs controlled by ₁ ;

Considering the reaction to generate dihydrogen and dioxygen, there is a H ₃ O ⁺ ion flux that passes through the membrane. Furthermore, considering that the membrane can conduct both anions and cations, there is a sulfate ion flux that passes through the membrane. In this way, the concentration of sulfate ions decreases on the dihydrogen generation side and increases on the dioxygen generation side. In fact, in contrast to ion exchange membranes containing Nafion®, ion exchange membranes containing boron nitride are non-selective ion exchange membranes. Thus, this causes the sulfate ions to circulate through the membrane, and their concentration may differ on both sides of the membrane in the chamber. Therefore, it is desirable to adjust this density. For this purpose, the assembly comprises a switching valve EV ₁ , a feed water pump P ₃ , a discharge device DEV1 on the dihydrogen outlet side and a DEV2 on the dioxygen outlet side.

The electrolyte level in the dioxygen and dihydrogen reservoirs is maintained between high and low in normal operation. Accordingly, while the electrolyte level is maintained between the high level and the low level, the supply pump P ₃ and the switching valve EV ₁ remain inactive as shown in FIG.

Results through the membrane during normal operation of the electrolyzer water naturally moves, two of hydrogen electrolyte liquid level in the reservoir exceeds high, the electronic switching valve EV ₁ is open emitting device of dihydrogen gas outlet DEV1 By controlling the pressure, depending on the amount of electrolyte remaining in the assembly, the liquid will reach either the high level of the oxygen reservoir as shown in FIG. 11a or the low level of the dihydrogen reservoir as shown in FIG. 11b. It becomes possible to rebalance the position.

If all the available water has been consumed and the electrolyte level in both reservoirs is low, the supply pump P ₃ is activated as shown in FIG. Fill with water from.

It should be noted that during normal operation of the electrolytic cell, the actual membrane operation causes an acid concentration imbalance between the dihydrogen reservoir and the dioxygen reservoir. Dioxygen reservoir anion side, to recover the vast majority of the ^2-sulfate ion SO _4, ^2-sulfate ion SO ₄ depleted from hydrogen reservoir. After the dioxygen reservoir is filled, it is possible to rebalance the concentration of sulfate ion SO ₄ ²⁻ between the two reservoirs by bi-directional movement between the two reservoirs, as shown in FIGS. 12b and 12c. become. This cycle therefore depends on the amount of water consumed between the high and low levels. The same adjustment can be applied when less electrolyte is used, except that the movement is reversed.

  The assembly may also comprise two condensers 24 for recovering essentially water vapor and optionally electrolyte that may be released from the reservoir.

Outlet pressure of the reservoir 21 can be controlled by the release device DEV ₁ and DEV _2. The pressure can be adjusted to be the highest pressure on the dihydrogen production side, in which case the pressure difference can be positive and up to 10 bar on the dihydrogen production side. For this purpose, taking into account this pressure difference, it is possible to use a larger size perforated plate on the dihydrogen generation side and a smaller size perforated plate on the other side. This makes it possible to advantageously obtain higher purity hydrogen over a longer period of time.

  Needless to say, reversing the size of the porous plate is also included in the scope of the present invention.

The user can select the operating pressure. The pressure in the reservoir can be controlled by a loop composed of two pressure sensors PH ₂ and PO ₂ and two discharge devices DEV ₁ and DEV ₂ . This control loop allows the gas flow to be adjusted to adjust the pressure in the reservoir.

  Each of the reservoirs 21, 22 can further include a safety valve 25 and an opening 26 for initially filling the reservoir.

  The outlets of the reservoirs 21 and 22 are also provided with a dryer 27 for removing residual moisture that may be generated by, for example, dihydrogen burning with residual dioxygen.

  The flow rate of the obtained dihydrogen and the flow rate of dioxygen can be measured at 28 and a sensor for confirming the purity of the obtained gas can be provided at 29.

  The assembly controls the temperature of the electrolytic cell, for example maintaining a substantially constant operating temperature of a value between 70 and 120 ° C., on the one hand the temperature of the electrolyte in each reservoir and on the other hand the temperature of the electrolytic cell itself. 30 may further be provided. By maintaining a sufficiently high operating temperature, an electrochemical reaction can be promoted regardless of the selected pressure. However, the temperature limit above which there is a risk of degradation of the assembly must not be exceeded. Optionally, the assembly comprises at least one or two devices, optionally with temperature sensors for monitoring the effectiveness of cooling, for cooling the electrolyte before it enters the electrolytic cell. You can also.

  In the illustrated example, the assembly comprises two cooling devices 50 each for cooling the electrolyte received from the dihydrogen reservoir and the electrolyte received from the dioxygen reservoir. In the illustrated example, as shown in FIG. 9 a, each cooling device 50 includes three elements: a cooling pump 51, a liquid-liquid heat exchanger 52 that receives a high-temperature electrolyte, and a gas-liquid heat exchanger 53.

  Thus, this cooling device can have two levels of operation as shown in FIG. 9b. In the first level 55, cooling is performed only by the operation of the cooling pump, the electrolyte is circulated in the gas-liquid exchanger, and then the cooled electrolyte is returned to the cell stack. At the second level 56, the cooling pump and gas-liquid exchanger fan can be operated simultaneously. Finally, if this is insufficient, the system is configured to automatically reduce the current at 57. The temperature threshold that determines the level to use can be determined as appropriate according to the operating temperature desired for the assembly. Specifically, the threshold shown in FIG. 9b is only a guideline.

  Finally, the electrolyzer power supply is housed in an electrical cabinet 40 with a process control computer for controlling from outlet current and voltage to current intensity and / or voltage supplied to the stack of electrolysis cells. .

  The control cabinet may also be provided with a remote connection 41 that allows remote maintenance of the assembly.

  In the example described, the power used to generate dihydrogen and dioxygen is 5 kW. Needless to say, the case where the power consumption is different and the case where the size of the assembly is large or small are also included in the scope of the present invention. As an example, FIG. 7c shows an assembly configured for 1 kW power consumption.

  The present invention is not limited to the production of dihydrogen and dioxygen.

  The invention also applies to the production of other substances, in particular hypochlorous acid.

  The present invention is not limited to having one exchange membrane per cell.

  Thus, according to one aspect of the invention, the cell includes at least two exchange membranes 11 defining an intermediate chamber I between the anode and the cathode.

  An example of such a cell is shown in FIG.

  In such a cell, two membranes 11 are arranged between the anode and cathode of the cell and can further comprise all the elements described above.

  Thus, this cell uses two membranes 11 instead of a single membrane 11 and the stack shown in FIG. 3 except that these membranes are separated by a frame to form an intermediate chamber I. Can be included. Furthermore, an additional fluid communication part can also be provided.

  For example, as shown in FIGS. 14 and 15, an inlet 3 g and an outlet 3 f can be added to allow electrolyte circulation in the intermediate chamber I.

  Thus, in an embodiment in which one membrane per cell is replaced with two membranes that define an additional circulation chamber I, the electrolyser can have three inlets and three outlets. In this case, a third reservoir (not shown) for receiving the electrolyte can be provided.

  The electrolyte circulation in the anode chamber A, the cathode chamber C, and the intermediate chamber I can be performed as shown in FIG.

  When producing hypochlorous acid, for example, water circulates in one or more anode chambers, for example, water circulates in one or more cathode chambers, for example, salt water in one or more intermediate chambers I. (Eg water / NaCl) circulates to recover hypochlorous acid in one or more intermediate chambers and soda in one or more cathode chambers.

4 Bipolar plate 10 Electrolysis cell 11 Ion exchange membrane 12 Perforated plate 13 Frame 14 Grid 15 Gasket

Claims (19)

Dihydrogen, dioxygen, chlorine or hypochlorous acid, or soda by electrolysis of pure water or water containing at least one salt such as NaCl, H ₂ SO ₄ , KOH or NaOH, base and / or acid An electrolytic cell for producing at least one chemical substance, such that the electrolytic cell comprises a stack of at least first and second successive electrolytic cells, each electrolytic cell (10) comprising:
-An anode;
-A cathode;
-At least one ion exchange membrane (11) arranged between the anode and the cathode;
The ion exchange membranes (11) of the first and second electrolysis cells comprise on the one hand the anode of the first electrolysis cell and on the other hand constitute the cathode of the first electrolysis cell Separated by a bipolar electrode (15)
An electrolytic cell characterized by that. The bipolar electrode (15) comprises a monolithic bipolar plate (4), optionally with at least one grid (14) and at least one perforated plate (12),
The electrolytic cell according to claim 1. The bipolar electrode (15) is an integral part as a whole, and the bipolar plate (4), the grid (14) and the porous plate (12) are integrated with each other before being installed in the electrolytic cell. The
The electrolytic cell according to claim 1 or 2, characterized in that The bipolar electrode (15) is nickel, iridium, ruthenium, palladium, cadmium, molybdenum, platinum, stainless steel, titanium, tantalum, iron alloy, nickel alloy, lead alloy, and / or tantalum oxide, iridium oxide, ruthenium oxide, Comprising at least one of a thin layer of lead oxide, iron oxide, platinum, platinum carbon, palladium, nickel, cadmium and / or molybdenum,
The electrolytic cell according to any one of claims 1 to 3, wherein the electrolytic cell is characterized. The anode includes at least one of a thin layer of titanium, tantalum, iridium, iron alloy, lead alloy, and / or tantalum oxide, iridium oxide, ruthenium oxide, lead oxide and / or iron oxide.
The electrolytic cell of any one of Claims 1-4 characterized by the above-mentioned. The cathode is a thin layer of nickel, iridium, palladium, cadmium, molybdenum, platinum, titanium, tantalum, iron alloy, lead alloy, nickel alloy and / or platinum, platinum carbon, palladium, nickel, cadmium and / or molybdenum. Including at least one of them,
The electrolytic cell of any one of Claims 1-5 characterized by the above-mentioned. Said ion exchange membrane (11) comprises boron nitride, in particular activated boron nitride,
The electrolytic cell of any one of Claims 1-6 characterized by the above-mentioned. Said ion exchange membrane (11) comprises a polymer matrix, in particular a PTEF-based polymer matrix,
The electrolytic cell of any one of Claims 1-7 characterized by the above-mentioned. The ion exchange membrane (11) has a thickness of 100 to 500 μm,
The electrolytic cell according to any one of claims 1 to 8, wherein the electrolytic cell is characterized. The electrolyte includes water and acid, water and base, or water and salt.
The electrolytic cell according to claim 9. One cell includes a single ion exchange membrane between the anode and the cathode;
The electrolytic cell of any one of Claims 1-10 characterized by the above-mentioned. At least one cell of the stack comprises two ion exchange membranes (11), preferably the two membranes form an intermediate chamber (I) between them,
The electrolytic cell according to any one of claims 1 to 8, wherein the electrolytic cell is characterized. At least one cell comprises a non-selective ion exchange membrane, such as a membrane comprising boron nitride, and a selective exchange membrane, such as a Nafion-based membrane;
The electrolytic cell according to any one of claims 1 to 8, wherein the electrolytic cell is characterized. Means for setting the circulation of the electrolyte in the intermediate chamber (I), in particular for the purpose of taking out substances produced in the electrolytic cell during operation of the electrolytic cell;
The electrolytic cell according to claim 12, wherein: An electrolytic assembly comprising:
-An electrolytic cell (1) according to any one of claims 1 to 14;
A reservoir, in particular a dihydrogen reservoir (21) for storing the resulting dihydrogen,
A reservoir, in particular a dioxygen reservoir (22) for storing the obtained dioxygen;
An assembly comprising: The electrolyte is stored in each of the two reservoirs;
The assembly of claim 15. Between the two reservoirs, preferably at the base of the two reservoirs, and more preferably controlled by a switching valve (EV ₁ ), to maintain a balance of the electrolyte levels in the two reservoirs Having a fluid communication section of
The assembly of claim 16. Using the electrolyzer of claim 12, the anode chamber of the cell preferably comprises water, the cathode chamber comprises water, and the intermediate chamber comprises brine.
A method for producing hypochlorous acid characterized by the above. -An anode;
-A cathode;
Two exchange membranes (11), in particular
A selective exchange membrane and a non-selective exchange membrane (11) arranged between the anode and the cathode, preferably an activated boron nitride-based non-selective membrane (11), and preferably a Nafion-based membrane A selective membrane;
Preferably the non-selective membrane protects the selective membrane from a basic or acidic environment,
An electrolytic cell characterized by that.