JP2013174024A - Gasket for electrolysis tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasket for an electrolysis tank which suppresses elution to prevent leakage.SOLUTION: A gasket 20 for an electrolysis tank which is used for a connection part of piping through which liquid supplied to an electrolysis tank 100 or, liquid or a gas discharged from the electrolysis tank 100 passes, includes: a ring-like center member 20a; and a protection layer 20b provided at at least part of the center member 20a which comes into contact with liquid or a gas.

Description

  The present invention relates to an electrolytic cell gasket used for a connection portion of a pipe through which a liquid supplied to an electrolytic cell, or a liquid or gas discharged from the electrolytic cell passes.

  Alkali metal salt electrolysis (hereinafter referred to as electrolysis) is the production of high-concentration alkali metal hydroxide, hydrogen, chlorine, etc. by electrolyzing an aqueous alkali metal chloride solution (hereinafter referred to as electrolyte) such as saline. Is the method. As the method, electrolysis by a mercury method or a diaphragm method can be mentioned, but in recent years, an ion exchange membrane method with high power efficiency is mainly used. In the ion exchange membrane method, electrolysis is performed using an electrolytic cell in which a large number of electrolytic cells each including an anode and a cathode are arranged via an ion exchange membrane. The electrolysis cell has a structure in which a cathode chamber to which a cathode is attached and an anode chamber to which an anode is attached are arranged back to back via a partition wall.

  The electrolytic solution supplied to the electrolytic cell is supplied from a liquid supply pipe to a liquid inlet provided for each of the cathode chamber and the anode chamber, and the electrolytic solution discharged from the electrolytic cell is similarly provided for each of the cathode chamber and the anode chamber. The discharged liquid outlet is discharged into a liquid recovery pipe. Each liquid inlet, each liquid supply pipe, each liquid outlet, or each liquid recovery pipe is provided with a nozzle, and the electrolyte is supplied and discharged through a hose connected to these nozzles (see, for example, Patent Document 1). ).

  A gasket made of a ring-shaped rubber is provided at the connection portion between the nozzle and the hose to prevent leakage (see, for example, Patent Document 2).

JP 2012-158775 A JP 2006-336041 A

  However, there is a problem that the portion of the gasket in contact with the electrolytic solution is gradually eluted by the discharge generated at the nozzle. As gasket elution progresses, it may cause leaks.

  Then, an object of this invention is to provide the gasket for electrolytic vessels which can suppress elution and can prevent a leak.

  The gasket for an electrolytic cell according to the present invention is a gasket for an electrolytic cell used for a connection part of a pipe through which a liquid supplied to the electrolytic cell, or a liquid or gas discharged from the electrolytic cell passes, It is characterized by comprising a central member and a protective layer provided on at least a portion of the central member in contact with the liquid or gas.

  According to the present invention, since the protective layer is provided on at least a portion of the central member that is in contact with the electrolytic solution or the generated gas, the central member is suppressed from being eluted into the electrolytic solution, and leakage can be prevented.

  The protective layer is preferably made of tetrafluoroethylene (PTFE). Since PTFE has high chemical resistance, elution is preferably prevented.

  The thickness of the protective layer is preferably 50 μm to 800 μm. If it is thinner than 50 μm, elution cannot be sufficiently suppressed. Moreover, when it is thicker than 800 μm, it is difficult to provide a protective layer.

  ADVANTAGE OF THE INVENTION According to this invention, the gasket for electrolytic cells which can suppress elution and can prevent a leak can be provided.

It is a schematic sectional drawing explaining the structure of the electrolytic cell which concerns on this embodiment. It is a schematic sectional drawing explaining the connection structure of a nozzle and a hose.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary.

[Electrolytic cell overview]
FIG. 1 is a schematic cross-sectional view illustrating the configuration of an electrolytic cell 100 according to this embodiment. In the present embodiment, the electrolytic cell is an electrolytic cell in which a plurality of electrolytic cells 1 are arranged in series, and is called a bipolar ion exchange membrane method electrolytic cell. In FIG. 1, only one of the plurality of electrolysis cells 1 is taken out and described. In the bipolar ion exchange membrane method electrolytic cell, an ion exchange membrane is interposed between the anode chamber of the electrolysis cell 1 and the cathode chamber of the adjacent electrolysis cell to form unit electrolyzers. In contrast, electrolysis is performed by feeding power in series. In FIG. 1, the compartments of the anode chamber and the cathode chamber are omitted.

[Electrolysis cell]
In the electrolytic cell 1 constituting the electrolytic cell 100, a cathode chamber frame attached with a cathode and an anode chamber frame attached with an anode are arranged back to back via a partition wall (back plate: not shown). The anode chamber frame and the cathode chamber frame are electrically connected. Further, the electrolytic cell 1 includes an anolyte inlet 10 for supplying an anolyte to the anode chamber, a catholyte inlet 11 for supplying the catholyte to the cathode chamber, and an anolyte for discharging the anolyte and the gas generated at the anode from the anode chamber. It has an outlet 12 and a catholyte outlet 13 for discharging the catholyte and the gas generated at the cathode from the cathode chamber. The anolyte inlet 10, the catholyte inlet 11, the anolyte outlet 12 and the catholyte outlet 13 are provided with nozzles 10a, 11a, 12a and 13a, respectively.

[Electrolyte supply pipe and electrolyte recovery pipe]
The electrolytic cell 100 of the present embodiment has an electrolytic solution supply pipe for supplying an electrolytic solution to each of a large number of electrolytic cells 1 arranged in series, and collects the electrolytic solution discharged from each electrolytic cell 1. An electrolyte recovery pipe for the purpose. Specifically, the electrolytic cell 100 includes an anolyte supply pipe 2 that supplies anolyte to the anolyte inlet 10 of each electrolysis cell, and a catholyte supply pipe that supplies catholyte to the catholyte inlet 11 of each electrolysis cell. 3. An anolyte recovery tube 4 for recovering the anolyte from the anolyte outlet 12 of each electrolysis cell, and a catholyte recovery tube 5 for recovering the catholyte from the catholyte outlet 13 of each electrolysis cell. The anolyte supply tube 2, the catholyte supply tube 3, the anolyte recovery tube 4 and the catholyte recovery tube 5 are provided with nozzles 2a, 3a, 4a and 5a, respectively.

  Further, in the electrolytic cell 100 of the present embodiment, the anolyte supply pipe 2, the catholyte supply pipe 3, the anolyte recovery pipe 4, and the catholyte recovery pipe 5 are arranged along the direction in which the electrolytic cells are connected (substantially). Arranged in parallel). The anolyte supply pipe 2 is located below the anolyte inlet 10, and the catholyte supply pipe 3 is located below the catholyte inlet 11. Further, the anolyte recovery tube 4 is positioned below the anolyte outlet 12, and the catholyte recovery tube 5 is positioned below the catholyte outlet 13. Preferably, the anolyte recovery tube 4 and the catholyte recovery tube 5 are located above the anolyte supply tube 2 and the catholyte supply tube 3.

  That is, in electrolysis, the anolyte is supplied from the anolyte supply pipe 2 to the anode chamber via the anolyte inlet 10 located at the lower part of each electrolytic cell, and the anolyte outlet located at the upper part of each electrolytic cell. 12 is recovered from the anode chamber to the anolyte recovery tube 4 via 12. On the other hand, the catholyte is supplied from the catholyte supply pipe 3 to the cathode chamber via the catholyte inlet 11 located at the bottom of each electrolysis cell, and via the catholyte outlet 13 located at the top of each electrolysis cell. Then, it is recovered from the cathode chamber to the catholyte recovery tube 5. Therefore, the electrolytic solution is supplied from below the electrolytic cell and collected from above. Note that high-concentration alkali metal hydroxide, hydrogen, chlorine, and the like generated by electrolysis are recovered from the anolyte recovery tube 4 and the catholyte recovery tube 5 which are electrolyte recovery tubes.

  That is, in the electrolytic cell 100 shown in FIG. 1, the electrolytic solution is supplied from below the electrolytic cell 1, and the discharged liquid and generated gas are collected from above the electrolytic cell 1. In the electrolytic cell 100 of the present embodiment, the electrolyte solution can be naturally recovered by discharging the gas generated in the electrolytic cell from the upper part of the electrolytic cell. It is installed below. Further, from the viewpoint of workability, the electrolyte solution recovery pipe is preferably installed above the electrolyte solution supply pipe.

〔hose〕
In the electrolytic cell 100 of this embodiment, the nozzle 10a of the anolyte inlet 10 of the electrolytic cell 1 and the nozzle 2a of the anolyte supply pipe 2 are connected by a hose 6, and the nozzle of the catholyte inlet 11 of the electrolytic cell 1 11a and the nozzle 3a of the catholyte supply pipe 3 are connected by a hose 7, and the nozzle 12a of the anolyte outlet 12 of the electrolytic cell 1 and the nozzle 4a of the anolyte recovery pipe 4 are connected by a hose 8. The nozzle 13 a at the catholyte outlet 13 of the electrolytic cell 1 and the nozzle 5 a of the catholyte recovery tube 5 are connected by a hose 9.

  As a material for the above hoses 6 to 9, since a chlorine or alkaline solution flows in the hose, a fluororesin is preferable from the viewpoint of corrosion resistance. Examples of the fluororesin include, for example, tetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and vinylidene fluoride. (PVDF). Among these, PFA or PTFE is preferable from the viewpoint of corrosion resistance. Also, the surface inside the hose should be smooth so that the liquid flow is not disturbed.

  Moreover, it is preferable that the thickness of the hose is a thickness that does not rupture at a pressure of 0.4 MPa or more. If the thickness is 0.4 MPa or more and does not rupture, even if pressure is applied in the electrolysis cell 1, it does not rupture and the contents do not leak (burst pressure resistance), and safety is improved. More preferably, the thickness is such that it does not burst at a pressure of 0.6 MPa or more.

  Specifically, the wall thickness of the hose is more preferably 0.5 mm to 3 mm. If the wall thickness is 0.5 mm or more, the bursting pressure resistance is sufficient, and the safety is further improved. If the wall thickness is 3 mm or less, the bent portion of the hose has a sufficient degree of freedom. More preferably, the thickness is 1 mm to 2 mm.

[Connection between nozzle and hose]
FIG. 2 is a schematic cross-sectional view illustrating a connection structure between the nozzle 4a and the hose 8. As shown in FIG. Here, only the connection portion between the nozzle 4a of the catholyte recovery tube 4 and the hose 8 is taken out as a connection portion of the pipe through which the liquid supplied to the electrolytic cell 100 or the liquid discharged from the electrolytic cell 100 passes. As will be described, the connecting portion between the nozzle and the hose other than this in the electrolytic cell 100 has the same structure.

  The base end of the nozzle 4a is attached to the catholyte recovery tube 4 by welding. A ring-shaped recess 4b that opens in a direction opposite to the base end is formed at the tip of the nozzle 4a. The bottom of the ring-shaped gasket 20 is fitted and fixed in the recess 4b. A flange 8a formed at the end of the hose 8 is attached to the tip of the nozzle 4a via a gasket 20. The hose 8 is fastened and fixed to the tip of the nozzle 4a by a cap nut 21 that is screwed into the nozzle 4a.

〔gasket〕
As shown in FIG. 2, the gasket 20 is disposed at a connection portion between the nozzle 4 a and the hose 8 to prevent leakage. The gasket 20 is configured such that a protective layer 20b is coated on a ring-shaped central member 20a having a flat bottom at the bottom in contact with the nozzle 4a and a rounded top at the bottom in contact with the hose 8. The protective layer 20b is only required to be provided at least on the part of the gasket 20 that is in contact with the electrolytic solution or the generated gas, and may be provided up to the bottom as necessary. The protective layer 20b can be formed by welding and wrapping the central member 20a with a protective film. In addition, it sets as the state which wrapped the center member 20a with the protective film without welding, and is good also as the protective layer 20b.

  As the central member 20a, for example, a sulfur (S) vulcanized product or a peroxide (PO) crosslinked product of ethylene / propylene / diene rubber (EPDM rubber) or ethylene / propylene rubber (EPM rubber) is used.

  As the material of the protective layer 20b, a fluororesin is preferable from the viewpoint of corrosion resistance because it contacts with chlorine or an alkali solution. Examples of the fluororesin include, for example, tetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and vinylidene fluoride. (PVDF). Among these, PTFE or PFA is preferable from the viewpoint of corrosion resistance. The thickness of the protective layer 20b is preferably 50 μm to 800 μm, and is preferably formed by welding and wrapping the central member 20 a with a protective film. If it is thinner than 50 μm, elution cannot be sufficiently suppressed. Moreover, when it is thicker than 800 μm, it is difficult to provide the protective layer 20b. More preferably, it is 100 micrometers-500 micrometers.

  By providing the protective layer 20b within this thickness range, not only the elution of the central member 20a is suppressed and leakage is prevented, but also the amount of compressive strain of the gasket 20 during use is reduced and the amount of plastic deformation is reduced. , Can suppress crushing and enable long-term use. In addition, a connecting portion of a pipe used for supplying or collecting the anolyte, for example, a connecting portion between the nozzle 12a of the anolyte outlet 12 and the hose 8 or a connecting portion of the nozzle 4a of the anolyte recovery tube 4 and the hose 8 is used. In the gasket 20 to be arranged, chlorine gas may permeate the protective layer 20b and chlorinate the surface of the central member 20a, and chlorinated substances may be precipitated inside the protective layer 20b. If it is a range, the damage of the protective layer 20b can be suppressed.

  In this embodiment, a case where a gasket is applied to a connection portion between each nozzle and a hose as a connection portion of a pipe through which liquid supplied to the electrolytic cell 100 or liquid or gas discharged from the electrolytic cell 100 passes. Although described, it is a connection part of piping through which the liquid supplied to the electrolytic cell 100, or the liquid or gas discharged from the electrolytic cell 100 passes, and can be applied to other connection parts. Further, the gasket 20 has been described as a shape having a flat bottom portion and a rounded top portion, but may have other shapes, for example, a shape having a round or square cross section. Good.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

Example 1
A ring-shaped EPDM rubber gasket having an outer diameter of 44 mm, an inner diameter of 31 mm, and a thickness of about 7 mm is used as a central member, and a protective layer is formed by welding and enclosing a 200 μm-thick PTFE film on the surface. did.

(Example 2)
Using a ring-shaped EPDM rubber gasket having an outer diameter of 32 mm, an inner diameter of 20 mm, and a thickness of about 7 mm as a central member, a protective layer is formed by welding and encapsulating a 200 μm-thick PTFE film on the surface. did.

(Comparative Example 1)
As a central member, a ring-shaped EPDM rubber gasket having an outer diameter of 44 mm, an inner diameter of 31 mm, and a thickness of about 7 mm was used.

(Comparative Example 2)
As a central member, a ring-shaped EPDM rubber gasket having an outer diameter of 32 mm, an inner diameter of 20 mm, and a thickness of about 7 mm was used, and a protective layer was not formed, and a gasket of Comparative Example 2 was obtained.

[Airtight test]
The gasket of Example 1 was assembled in a pressure test apparatus with a connecting portion between the nozzle and hose of the electrolyte recovery pipe attached. In a state where the gasket was pressed at a surface pressure of 7.5 kg / cm ² , the connecting portion was immersed in water at 90 ° C. and pressurized with nitrogen gas at an internal pressure of 0.1 MPa. No gas leak was confirmed by visual observation. The surface pressure was 40 kg / cm ² and the press was continued for 3 days, and then the gasket was taken out and observed. The thickness of the gasket was the same as before the test. As a result of conducting a test under the same conditions for the gasket having no protective layer of Comparative Example 1, no gas leak was confirmed, and no change in the thickness of the gasket after pressing for 3 days was confirmed.

[Measurement of compression strain]
Table 1 shows the results of measuring the height from the bottom of the gasket to the top of the gasket of Example 1 and the gasket having no protective layer of Comparative Example 1 by changing the press surface pressure. The gasket of Example 1 had a smaller amount of compressive strain than the gasket of Comparative Example 1.

[Electrolysis test]
In the electrolysis cell 1, the gasket of Example 1 was used as a connection portion between the nozzle 4 a and the hose 8 of the anolyte recovery tube 4, a connection portion between the nozzle 12 a and the hose 8 of the anolyte outlet 12, and a nozzle of the catholyte recovery tube 5. 5a and the hose 9 and the nozzle 13a of the catholyte outlet 13 and the hose 9 are respectively attached, and the gasket of Example 2 is connected to the nozzle 2a of the anolyte supply pipe 2 and the hose 6. Attached to the connecting portion between the nozzle 10a of the anolyte inlet 10 and the hose 6, the connecting portion between the nozzle 3a and the hose 7 in the catholyte supply pipe 3, and the connecting portion between the nozzle 11a and the hose 7 in the catholyte inlet 11. Then, an electrolysis test was conducted.

The electrolytic area of the electrolytic cell 100 was 1200 mm × 2400 mm. As the anode, a titanium-made expanded metal having a thickness of 1 mm was prepared by coating an anode active material made of an oxide containing ruthenium, iridium, and titanium as components. As the cathode, the one produced by plasma spraying a cathode active material mainly composed of nickel oxide on the surface of a nickel expanded metal was used. A cation exchange membrane Aciplex (registered trademark) F6801 was sandwiched between the anode and the cathode via a frame gasket, and the electrolytic cell 100 was assembled. 300 g / liter of salt water is supplied to the anode chamber side of the electrolytic cell 100 as an anolyte so that the concentration of salt water at the outlet of the electrolysis cell is 200 g / liter. Diluted caustic soda was supplied so that the caustic soda concentration would be 32% by weight, and it was continuously operated for 30 days at an electrolysis temperature of 90 ° C. and a current density of 4 to 6 kA / m ² . As a result of taking out and observing the gasket after continuous operation, the protective layer was not cracked, and the gaskets of Example 1 and Example 2 did not change.

  An electrolytic cell 1 having the same structure was prepared except that the gasket of Example 1 was changed to the gasket of Comparative Example 1 and the gasket of Example 2 was changed to the gasket of Comparative Example 2, and the continuous electrolytic test was performed under the same conditions. did. As a result of taking out and observing the gasket after the continuous operation, the connecting part of the pipe for supplying and collecting the anolyte, that is, the connecting part of the nozzle 4a of the anolyte recovery pipe 4 and the hose 8, the nozzle 12a of the anolyte outlet 12 Electrolytic solution or generated gas of a gasket used for a connection portion between the nozzle 2a and the hose 6 of the anolyte supply pipe 2 and a connection portion of the nozzle 10a and the hose 6 of the anolyte inlet 10 Precipitation of chlorinated products was observed in the part in contact with the surface. On the other hand, the connecting portion of the piping for supplying and collecting the catholyte, that is, the connecting portion of the nozzle 5a and the hose 9 of the catholyte collecting tube 5, the connecting portion of the nozzle 13a and the hose 9 of the catholyte outlet 13, the catholyte supply A portion of the gasket 3 used in the connection portion between the nozzle 3a and the hose 7 of the tube 3 and the connection portion between the nozzle 11a and the hose 7 of the catholyte inlet 11 is slightly fuzzed. Black powder adhered to the finger when rubbed with the finger.

DESCRIPTION OF SYMBOLS 1 ... Electrolytic cell, 2 ... Anolyte supply tube, 3 ... Catholyte supply tube, 4 ... Anolyte recovery tube, 5 ... Catholyte recovery tube, 6-9 ... Hose, 10 ... Anolyte inlet, 11 ... Catholyte inlet , 12 ... anolyte outlet, 13 ... catholyte outlet, 20 ... gasket, 100 ... electrolytic cell

Claims (3)

A gasket for an electrolytic cell used for a connection part of a pipe through which a liquid supplied to an electrolytic cell, or a liquid or gas discharged from the electrolytic cell passes,
A ring-shaped central member;
And a protective layer provided on at least a portion of the central member in contact with the liquid or gas.   2. The electrolytic cell gasket according to claim 1, wherein the protective layer is made of tetrafluoroethylene (PTFE).   The thickness of the said protective layer is 50 micrometers-800 micrometers, The gasket for electrolytic cells of Claim 1 or 2 characterized by the above-mentioned.

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