RU2623437C1 - Electrolytic cell for producing hydrogen and oxygen from water - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to an electrolytic cell for the production of hydrogen and oxygen from water, consisting of a casing with a cathode housed therein in the form of a hollow cylinder of a porous hydrophobic material and an anode in the form of a metal tube located between them in the form of a gas-stop membrane, gas cavity between the outer wall of the cathode and the inner wall of the casing, the anode cavity inside the anode, with the anode applied to the surface and the cathode surface by the catalyst. The cell is characterized in that an anode made of perforated metal sheet attached on the outer surface of the metallic mesh coated with a catalyst, a cathode made of a porous hydrophobised material coated on its outer surface by the hydrogen cavity catalyst and the inner side with attached to it mesh coated with a catalyst gas-closing separator consists of a porous membrane of a hydrophilic material, surrounded on both sides by one or more layers of the separating material, sealing the cavity relative to the cavity hydrogen oxygen is carried out in the assembly due to the cell as a flange made of insulating material and having a ring grooves with gaskets to create a seal along the ends of the cathode at the points of contact with the flanges, and by squeezing the upper and lower ends of the separator when the electrolyser is assembled, protruding beyond the anode and the grids attached to the cathode and anode, between the outer end conical surfaces of the corresponding flanges and corresponding to the inner end conical surfaces of the cathode.

EFFECT: use of the proposed device allows to minimize energy costs for own needs and, as a result, to increase the efficiency of the claimed cell, increase the reliability of the cell operation and the purity of the produced gases.

9 cl, 3 dwg

Description

The proposed solution relates to the technology of electrochemical production, and in particular to devices for producing hydrogen and oxygen by electrolysis of water.

The known design of the electrolytic cell according to US patent for invention No. 7510633 (IPC class С25В 1/10, priority date 02.21.2003) [1] for producing hydrogen and oxygen, which consists of a tubular cathode, an anode in the form of a rod, a membrane, anode and cathode cavities, hydrogen and oxygen collector, pump for electrolyte. The cathode and anode cavities contain electrolyte.

This electrolyzer operates as follows. The electrolyte solution before starting work is fed into the anode and cathode cavities of the cell, between which a membrane is installed. Then, direct current is supplied to the anode and cathode of the electrolyzer. The electrolyte is circulated in the anode and cathode cavities using a pump. Gas bubbles formed on the electrodes during the operation of the electrolyzer, together with the electrolyte, leave the cell through the gas channels. Then, in oxygen and hydrogen containers, the gas is separated from the electrolyte, enters the cylinders or into another container, and the electrolyte is collected in one common container and is used with a pump in the electrolyte circulation system during further operation of the electrolyzer.

The disadvantages of this device are as follows:

- the use in the design of the electrolyzer of a common electrolyte collector filled with electrolyte reduces the performance of the installation as a whole, since in this case there are high leakage currents;

- the presence of distance between the electrodes (due to the anode and cathode cavities), leads to an increase in electrical resistance and unnecessary energy costs, which increases power consumption and reduces overall performance of the entire device;

- in this design of the electrolyzer requires the presence of an additional device for separating hydrogen from alkali;

- in this design of the electrolyzer, a pump is needed to circulate the electrolyte through the anode and cathode cavities.

Known electrolyzer according to the patent of the Russian Federation for invention No. 2400566 (IPC class С25В 9/00, priority date 08/24/2009, publication date 09/27/2010) [2]. The cell contains a sealed cylindrical anode body, a cathode, dielectric gaskets on both sides, mounted in the cavity of the anode body. Tubes for electrolyte inlet (aqueous electrolyte solution) and gas outlet. In this case, the cathode is made in the form of a perforated cylinder and fixed therein by dielectric perforated spacers concentrically to the anode body. The pipe for introducing electrolyte is made in the form of a diffuser with the possibility of constantly circulating electrolyte supply by a pump and spraying with a nozzle from the tank into the anode casing, the bottom of which is connected to the tank by an overflow pipe with a check valve. The gas outlet pipe is equipped with a drop catcher.

The RF patent for invention No. 2441944 “Electrolyzer” (IPC class С25В 9/00, priority date 02/17/2011, publication date 02/10/2011) [3] describes an electrolyzer for producing oxygen and hydrogen.

The operation of the electrolyzer is as follows. The electrolyzer tank is charged with electrolyte, and a constant current regulated by the control unit is supplied to its electrodes, the anode and cathode, separated by a diaphragm. With a pump from an electrolyte tank, the electrolyte is continuously fed through a metering device and sprayed through a nozzle into a diffuser nozzle. In the diffuser nozzle, due to the fact that it is sprayed by a nozzle in the form of fog from the lower dielectric perforated insert, it is sprayed vertically upward and enters the perforated cathode cylinder, which makes it possible to contact the electrolyte with the entire surface of the electrolysis electrodes, while the water present in the electrolyte decomposes into oxygen and hydrogen. The diaphragm, permeable to ions, but preventing the mixing of oxygen and hydrogen, separates the cathode cavity of the cell from the anode cavity. The oxygen and hydrogen obtained as a result of electrolysis pass through the upper perforated insert, each part of the insert in the droplet separator, is cleaned of droplets of electrolyte and supplied to the consumer through the corresponding nozzles with cutoffs. The electrolyte condensed in the bottom of the cavity of the anode body through an overflow pipe with a check valve is discharged into the electrolyte tank and reused.

The disadvantages of the cells according to the patents of the Russian Federation for inventions No. 400566 and 2441944 is that in these designs of cells:

- requires a constantly working alkaline pump to spray through the electrolyte nozzle into the water electrolysis zone, which creates additional energy costs and does not ensure uniform operation of the electrolysis cell over the entire area, which in turn reduces its efficiency of the entire cell;

- the use of a constantly working mechanical unit (pump) reduces the reliability of the electrolysis unit;

- the use of the droplet separation unit, justified by the need to obtain oxygen and hydrogen purified from electrolyte as a result of the operation of the device.

Known electrolyzer according to the patent of the Russian Federation for invention No. 2501890 "Electrolyzer for producing hydrogen and oxygen from water" (IPC class С25В 9/10, С25В 1/10, priority date 05/11/2012, publication date 12/20/2013) [4], the closest to the proposed technical solution and therefore adopted as a prototype.

This electrolyzer consists of a housing and placed in it connected in series with each other cells. The anode of each cell is made in the form of a tube of mesh material, and the cathode is in the form of a hollow cylinder of porous hydrophobized material. The anode and cathode of each cell are placed close to the gas-tight membrane with the formation of a cathode gas cavity between the outer side of the cathodes and the housing. The cathode gas cavity is connected to a water trap capacity, an alkaline electrolyte capacity, and a device for separating hydrogen from water vapor and alkali. The cells are connected by anode cavities with a heat exchanger and with an alkaline electrolyte capacity, which, in turn, is connected to a device for separating oxygen from water vapor and alkali and a water supply system. The catalysts are deposited on the surface of the anode and the inner surface of the cathode of the cells. Porous hydrophobized nickel was used as the cathode material of the cells. The anode may be made of nickel mesh.

The disadvantage of the electrolyzer of this design is that:

- the design of the electrolyzer uses several electrolysis cells, which creates the need for consistent sealing of the gas cavities of the electrolysis unit;

- the presence of a heat exchanger in the anode circuit;

- the need to use a device for separating gases from water vapor and alkali;

- the presence of a pump for circulating electrolyte in the anode cavity.

The objectives of the proposed design of the electrolyzer to produce hydrogen and oxygen from water are to minimize energy costs for their own needs and, as a result, increase the efficiency of the proposed electrolyzer, increase the reliability of the electrolyzer and the purity of the produced gases.

The tasks are solved due to the fact that in the proposed electrolyzer for producing oxygen and hydrogen, consisting of a housing with a cathode placed in it in the form of a hollow cylinder made of porous hydrophobized material and an anode in the form of a pipe, a separator from the gas-sealing membrane placed closely between them, with the formation cathode gas cavity between the outer wall of the cathode and the inner wall of the housing, the anode cavity inside the anode, with catalysts deposited on the surface of the anode and cathode surface, according to the proposal According to the technical solution, the anode is made of a perforated metal sheet with a metal mesh attached over the entire outer surface of the pipe with a catalyst deposited on it, the cathode is made of porous hydrophobized material with a catalyst deposited on its outer surface from the side of the hydrogen cavity, and attached to it from the inside mesh with a catalyst deposited on it, the separator consists of a gas barrier membrane of a porous hydrophilic material surrounded on both sides with one or more layers of separation material, the hydrogen cavity is sealed relative to the oxygen cavity when the electrolyzer is assembled, both due to flanges made of electrical insulation material and having annular grooves with gaskets to create a seal at the ends of the cathode at the points of contact with the flanges, and due to crimping ( seals) during the assembly of the electrolyzer of the upper and lower ends of the separator, protruding beyond the anode and grids attached to the cathode and anode, between the end cone GOVERNMENTAL surfaces of the respective flanges and respective end cone-shaped surfaces of the cathode.

The design of the proposed cell for producing hydrogen and oxygen from water is characterized by FIG. 1 is a sectional general view of the electrolyzer, FIG. 2 is an enlarged sectional view of the oxygen and hydrogen cavities and the cell body (view A), FIG. 3 is an enlarged view of the sealing element between the oxygen and hydrogen cavities (view B).

The electrolyzer for producing hydrogen and oxygen from water of the proposed design, shown in FIG. 1, consists of a housing (1), for example a cylindrical one, inside which there are cavities of hydrogen (2) and oxygen (3). The hydrogen cavity (2) is organized between the inner wall of the housing (1) and the outer wall of the cathode (4).

The cathode (4) is a hollow cylinder made of porous hydrophobized material, for example, porous sintered nickel, with a catalyst deposited on its surface from the outside (from the hydrogen cavity), and a grid, for example, nickel, is connected to the inside of the cylinder, for example, supported catalyst.

The oxygen cavity (3) is formed inside the anode (5), made in the form of a perforated metal pipe, for example, in the form of a cylinder with a mesh, for example nickel, attached to it from the outside, for example, nickel, with a catalyst deposited on it.

Over the entire area of the inner surface of the cathode (4) and the outer surface of the anode (5), between them and adjacent to them, a separator (6) is placed, consisting of a gas barrier membrane made of a porous hydrophilic material and adjacent to the gas barrier membrane on both sides of the separation material, for example , in the form of one or more layers of a film of polymeric microporous material.

At the bottom of the housing (1) of the proposed electrolyzer is located the lower insulating flange (7) with a fitting for supplying an aqueous electrolyte solution (8). The outlet fitting of the electrolyte (9), which has fallen into the hydrogen cavity and the water formed, is located below the hydrogen cavity of the electrolyzer. To seal the insulating flange (7), sealing gaskets (10) are used, for example, annular ones. To seal the nozzle for supplying an aqueous electrolyte solution (8), sealing gaskets (11), for example ring ones, are used.

On the side of the housing (1) of the electrolyzer is a fitting for the removal of hydrogen (12) produced as a result of the operation of the electrolyzer, the sealing of which is carried out using sealing gaskets (13), for example, annular ones.

In addition, for example, from the side, the proposed electrolyzer has a minus current lead (14) in contact with the cathode wall (4) using a current-conducting plate (15), for example, nickel, which is welded to the cathode. The negative current lead is isolated from the housing (1) of the electrolyzer using bushings (16) made of electrical insulation material and gaskets (17), for example ring ones.

In the upper part of the cell there is an upper insulating flange (18), sealed against the metal flange (19) located on top of it by means of sealing gaskets (20), for example, annular ones. In turn, the metal flange (19) is sealed relative to the inner wall of the housing (1) of the electrolyzer using gaskets (21), for example ring, and a union nut (22).

A fitting (23) is located in the upper insulating flange (18) for circulating the electrolyte and removing oxygen resulting from the operation of the electrolyzer, which is sealed with gaskets (24), for example, annular ones. In addition, there is a plus current lead (25) in contact with the anode wall using a current-conducting plate (26), which is sealed with gaskets (27), for example ring ones.

In view A (Fig. 2), an enlarged view is a fragment of a section of the oxygen and hydrogen cavities located between the separator and the electrolyzer body.

The hydrogen cavity (2) is located between the inner surface (28) of the housing (1) and the outer wall of the cathode (4). The cathode (4) consists of a porous hollow cylinder (29) of hydrophobized material deposited on the porous hollow cylinder (29) from the side of the hydrogen cavity of the catalyst layer (30) and mesh (31) is applied on the opposite surface of the porous hollow cylinder (29) with the applied on her catalyst.

The oxygen cavity (3) is formed inside the anode (5), made in the form of a perforated metal pipe with a grid with a catalyst attached to its outer surface (32).

Between the cathode (4) and the anode (5) over the entire surface of their surfaces, a separator (6) is placed close to them, consisting of a gas-tight membrane made of porous hydrophilic material (33) and adjacent to the gas-tight membrane on both sides of the separation material (34), for example , in the form of one or more layers of a film of polymeric microporous material.

In FIG. 3 shows an enlarged fragment of the seal between the hydrogen cavity (2) and the oxygen cavity (3) in the proposed electrolyzer (type B).

The seal between the hydrogen (2) and oxygen (3) cavities of the proposed cell, eliminating the flow of oxygen from the oxygen cavity into the hydrogen cavity and vice versa, is organized as follows.

The lower insulating flange (7) has an annular groove (35), in which, when assembling the electrolyzer, an annular sealing gasket (36) is placed. The outer surface (37) at the end of the lower insulating flange (7) is conical, for example, at an angle of 5 ° to 20 °. The inner surface (38) at the end of the cathode (4) is also conical, for example, at an angle of 5 ° to 20 °. The separator (6) has such a length that its ends above and below protrude beyond the anode (5) and grids (31 and 32).

The sealing of the hydrogen cavity relative to the oxygen cavity in the proposed design of the cell during its assembly, for example, in the lower part of the cell is carried out as follows:

- firstly, due to compression of the lower end (39) of the separator (6) in the gap between the outer conical surface (37) of the lower insulating flange (7) and the corresponding inner conical surface (38) of the lower part of the cathode (4), since in the assembly of the cell, the lower end of the separator is located in the gap between them and during assembly of the cell is compressed between them.

- secondly, at the end of the cathode (4) due to compression of the gasket (36) located in the annular groove (35) of the lower insulating flange (7) during assembly of the electrolyzer.

Similarly, the sealing of the hydrogen cavity of the electrolyzer relative to the oxygen cavity is organized in the upper part of the electrolyzer between the upper insulating flange (18), the upper end of the separator (6) and the upper part of the cathode (4).

An example of a specific application.

The electrolyzer for producing hydrogen and oxygen from water of the proposed design consisted of a metal case (1) made of stainless steel 12X18H10T (GOST 5632-72) [5]; cathode (4) in the form of a hollow cylinder made of sintered porous nickel grade NP2 (GOST 492-73) [6] hydrophobized [7] with fluoroplastic grade F-4D (TU 6-05-1246-81), on the outside of which a platinum rhodium catalyst is applied (30), and a mesh (31) of NP2 grade nickel with a platinum rhodium catalyst deposited on it is baked to its inner wall; anode (5) made of perforated nickel sheet, grade of NP2 sheet material in the form of a cylinder with a grid baked to it (32) of nickel of grade NP2 with a platinum rhodium catalyst deposited on it; separator (6), consisting of a gas barrier membrane (33) of a porous hydrophilic material, namely asbestos (eK0.023.709 TU) [8], and adjacent to the gas barrier membrane (33) on both sides of the separation material (34), laid in two layer of a film of polypropylene microporous PORP-A1-22-114 (TU 6-00001-94) [9].

The lower (7) and upper (18) insulating flanges are made of fluoroplast grade 4-C (GOST 10007-80) [10]. O-rings in the form of rings are made of a mixture of rubber RP-2043 (TU 38.005924-2002) [11].

The outer surface (37) at the end of the lower insulating flange (7) was conical at an angle of 10 °; similarly, the outer surface was made at the end of the upper insulating flange (18). The inner surface (38) at both ends of the cathode (4) is also conical at an angle of 10 °. Isolation of the hydrogen cavity (2) from the oxygen cavity (3) was carried out during the assembly of the cell as described above.

The work of the proposed electrolyzer to produce hydrogen and oxygen from water is as follows.

A voltage of 2.4 V is supplied to the electrolyzer, while the DC current is ≈38 A.

The electrolyte, an aqueous seven normal KOH solution enters from below, through the nozzle for supplying an aqueous electrolyte solution (8) to the oxygen (anode) cavity (3) and fills it completely. When voltage is applied to the current leads “minus” (14) and “plus” (25), electrolysis of water in the electrolyte occurs. Oxygen is generated in the oxygen cavity (3) on the anode (5), and hydrogen is released on the inner side of the cathode (4), which, passing through the porous hydrophobized hollow cylinder (29) of the cathode (4), enters the hydrogen cavity (2) and is removed from it through a fitting for the removal of hydrogen (12). Since the cathode (4) is hydrophobized, the alkali practically does not pass into the hydrogen cavity. The electrolyte, which can sometimes seep into the hydrogen cavity (2) through the hydrophobized hollow porous cylinder (29) of the cathode (4), is removed from it through the electrolyte drain fitting (9).

The oxygen released at the anode through the fitting for circulating the electrolyte and oxygen removal (23) is removed from the electrolyzer.

The separator (6) has gas shut-off properties, i.e. in a soaked state, it does not pass gases through itself. The gas-shutoff properties of the separator are such that it is impassable for gases at pressures up to 0.4 MPa, and due to these properties, the resulting oxygen does not penetrate into the hydrogen cavity through it (2).

In order to ensure the safe operation of the electrolyzer and to obtain cleaner hydrogen, the cathode (4) is coated on the outside with a catalyst, on which, in the case of the penetration of an insignificant amount of oxygen through the cathode, it reacts with hydrogen on the surface of the catalyst, resulting in water with excess alkali is removed through the electrolyte outlet fitting (9).

Using the anode (5) made of a metal sheet with perforation over its entire area and rolled into a cylinder during assembly of the electrolyzer in the proposed design of the electrolyser, allows due to the elastic properties of the material of the cylinder to tightly connect (press) the cathode (4), the separator (6) ) and the anode (5) to reduce ohmic losses, which leads to an increase in the efficiency of the electrolyzer.

As a result of the operation of the electrolyzer of the proposed design, hydrogen was obtained with a purity higher than 99.99%.

Using the proposed technical solution allows you to:

- minimize energy costs for the operation of the electrolyzer and, as a result, increase the efficiency of the installation;

- a method of manufacturing the anode and cathode, as well as a method of sealing them allows you to get working gases of high pressure without the use of gas compression devices;

- maximize the efficiency of the electrolysis cell by changing the design of the anode and cathode.

- increase safety through the use of separation materials and the use of a catalyst on the outer surface of the cathode;

- increase the purity of the gases emitted.

Information sources

1. US patent for the invention No. 7510633.

2. RF patent for the invention No. 2400566 "Electrolyzer".

3. RF patent for the invention No. 2441944 "Electrolyzer".

4. RF patent for the invention No. 2501890 "Electrolyzer for producing hydrogen and oxygen from water."

5. GOST 5632-72 "High-alloy steels and corrosion-resistant, heat-resistant and heat-resistant alloys."

6. GOST 492-73 "Nickel, nickel and copper-nickel alloys processed by pressure."

7. TU 6-05-1246-81 "Fluoroplastic suspension F-4D, F-4DV."

8. eK0.023.709 TU “Asbestos fiber”.

9. TU 6-00001-94.

10. GOST 10007-80 "Ftoroplast-4. Technical conditions. "

11. TU 38.005924-2002 "Special rubber mixtures."

Claims (9)

1. An electrolyzer for producing hydrogen and oxygen from water, consisting of a housing with a cathode placed in it in the form of a hollow cylinder made of porous hydrophobized material and an anode in the form of a metal pipe, a separator between them in the form of a gas-separation membrane, with the formation of a cathode gas cavity between the outer wall of the cathode and the inner wall of the housing, the anode cavity inside the anode, with a catalyst deposited on the surface of the anode and the surface of the cathode, characterized in that the anode is made of perforated metal cathode is made of a porous hydrophobized material with a catalyst deposited on its outer surface from the side of the hydrogen cavity, and on the inside with a grid attached with a catalyst deposited on it, a separator consists of a gas shut-off membrane of a porous hydrophilic material surrounded on both sides by one or more layers of separation material, sealing the cavity of the water kind with respect to the oxygen cavity is carried out during the assembly of the electrolyzer both due to flanges made of electrical insulating material and having annular grooves with gaskets to create seals at the ends of the cathode at the points of contact with the flanges, and due to compression during assembly of the electrolyzer of the upper and lower ends of the separator outside the anode and grids attached to the cathode and the anode, between the outer end conical surfaces of the respective flanges and the corresponding inner ends mi conical surfaces of the cathode. 2. The electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that the outer surface at the ends of the lower and upper insulating flanges is conical at an angle of 5 to 20 °. 3. An electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that the inner surfaces at both ends of the cathode are conical at an angle of 5 to 20 °. 4. The electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that the casing and the anode are made of stainless steel grade 12X18H10T. 5. The electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that the cathode is made of sintered porous nickel grade NP2. 6. An electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that a platinum rhodium catalyst is used as a catalyst. 7. An electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that a nickel mesh of the NP2 grade is used. 8. An electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that the gas-barrier membrane consists of asbestos. 9. An electrolyzer for producing hydrogen and oxygen from water according to claim 1, characterized in that a polypropylene microporous film PORP-A1-22-114 is used as a separation material.

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