JPS6082684A - Method for remodeling alkali chloride electrolytic cell - Google Patents

Abstract

PURPOSE:To remodel effectively an electrolytic cell for electrolyzing alkali chloride by a mercury process into an electrolytic cell provided with ion exchange membranes by placing plural vertical cathodes on the bottom plate and putting each vertical anode wrapped with a cation exchange membrane between the cathodes. CONSTITUTION:Many vertical cathodes 3a are placed on the bottom plate 3 of an electrolytic cell for electrolyzing alkali chloride by a mercury process at prescribed intervals. Each vertical anode 2a wrapped with a cation exchange membrane 6 is put between the cathodes 3a, and the membrane 6 is attached to the cover 5 of the cell with a gasket. Since the bottom plate 3 of the electrolytic cell is utilized as it is, the term of works required to remodel the cell into an electrolytic cell provided with ion exchange membranes can be considerably shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for effectively converting a mercury iodochloride alkali electrolytic cell into an ion exchange membrane electrolytic cell.

Conventionally, mercury electrolysis has been mainly used to produce chlorine, hydrogen, and caustic alkali by electrolyzing an aqueous alkali chloride solution. Mercury electrolysis has the advantage of maintaining high current efficiency and directly producing a highly pure and highly concentrated caustic alkaline solution.

However, due to the problem that mercury used as a medium may cause environmental pollution, the mercury law is gradually being abolished in Japan. For this purpose, a diaphragm method is used in which a liquid-permeable asbestos diaphragm is attached to the surface of a bag-shaped cathode wire mesh to form a cathode seedling inside, and an anode is inserted outside the asbestos diaphragm to form a positive seedling. Although asbestos diaphragm electrolysis has the advantage of not using mercury at all, the current efficiency is lower than that of mercury electrolysis, and in particular, the generated caustic alkaline solution contains many cans of salt. Because the concentration of caustic alkali is extremely low, large-scale concentration equipment is required, and salt still remains in the concentrated solution from which a large amount of common salt has been separated, making it difficult to manufacture caustic alkali that requires high quality. It had the fatal flaw of being inappropriate. Recently, so-called ion-exchange dehydration electrolysis, which uses a cation exchange membrane instead of an asbestos diaphragm, has been attracting attention.This method has a lower concentration than the mercury method, but a higher concentration than the asbestos diaphragm method, and also eliminates salt. Since it is possible to obtain a much smaller amount of high-quality caustic alkaline solution and has a high current efficiency, it has been increasingly adopted and industrialized in place of the mercury method and asbestos diaphragm method with recent advances in film forming technology. Therefore, when converting mercury electrolysis equipment, conventionally the asbestos diaphragm method was used, but recently there has been a trend towards converting to the ion exchange membrane method. The method for this conversion is to remove the mercury method electrolysis equipment and install a new ion exchange membrane electrolysis equipment, or
Another method is to install new ion-exchange membrane electrolysis equipment and then remove the mercury electrolysis equipment. However, while this method has the advantage of allowing the ion-exchange membrane electrolytic cell to be installed freely, it also requires a huge amount of expense due to the need to completely replace the equipment, and in the case of the former, operation may have to be suspended.
It is necessary to consider the distance between IJs. Therefore, if a part of the mercury electrolytic cell can be used to convert it into an ion exchange membrane cell, the area of the equipment can be used effectively and the cost required for this can be greatly reduced. Such a proposal is already known in JP-A-58-71381, but in both of these proposals a horizontal ion exchange membrane is provided parallel to the bottom plate of the electrolytic cell, instead of the usual vertical ion exchange membrane. Compared to exchange membrane electrolyzers, the electrolysis area is limited by the size of the bottom plate, so the production volume is lower than the mercury method, and installation of the exchange membrane requires maintenance or special processing of the bottom plate. There is a problem with this.

The present invention is intended to solve the above problems,
That is, a plurality of vertical cathode plates are installed in parallel at predetermined intervals on the cathode bottom plate of a mercury iodochloride alkali electrolytic cell, and a vertical anode body wrapped with a cation exchange membrane is inserted between the vertical cathode plates. This is a method for modifying an alkali chloride electrolyzer for converting from a mercury method to an ion exchange membrane method.

To explain the embodiment of the present invention, the tank lid (1), side wall (4) and anode (2) of the mercury method electrolytic cell shown in FIG.
Remove the bottom plate (3) to expose it. Next, as shown in FIG. 2, a large number of vertical cathode plates (3a) are placed on the bottom plate (3) by means such as welding at predetermined intervals.

J.Pull the side wall (4a). Vertical cathode plate (3).
As shown in Fig. 4, the shape of a) is as follows: iron shade 4~lead plate (3b) is built in the width direction of the bottom plate, and a steel mesh (3C) is installed on this.
), it does not have a large structure. Next, as shown in Figure 3, a vertical anode (
Insert 2a) between each shadow 4ffl (3a).

The shape of the vertical anode (2a) is as shown in FIG.
), and a net-shaped metal anode (<20) is attached to both sides of the anode lead rod (2b), and the net-shaped metal anode (2C) has a cation exchange membrane (6) on its surface. wrapped. Cation exchange membrane <6) is also compatible with 5)
and the frame (7) by gaskets 1-. Note that (8) is a main pipe that supplies and circulates salt water to the anode chamber partitioned by the cation exchange membrane (6), and the branch pipe (9) is connected to the lower part of the anode chamber (6110). A water supply pipe and a supply/discharge pipe (none of which are shown) for circulating the generated caustic solution are inserted into the cathode from the outside so as to keep the cathode liquid level constant. <10) is a hydrogen gas exhaust pipe.

As explained above, the ion exchange membrane electrolytic cell formed by the method of the present invention is essentially a comb-type electrolyzer (11), and a large number of vertical unit cells can be installed by using the bottom plate of the mercury method electrolytic cell. I can do it.

The advantages of the method of the present invention are as follows: 1) Since the bottom plate of the mercury electrolytic cell can be used as is, the foundation, support stand, etc. of the cell can also be used as is.

11) The copper strips (busbars) that electrically connect each column of the mercury method electrolyzer in series can also be used as is.

111) In order to stop the mercury method electrolyzer one by one, the switch installed between the copper strips can be used as is, so it is possible to short-circuit each tank, and there is no limit to the number of tanks to be stopped.

In addition to the economic advantages mentioned above, conversion can be done by simply modifying the bottom plate, so the conversion period can be shortened by a huge amount, and since it is extremely easy to convert one tank at a time, production volume can be reduced even during the conversion period. There is an advantage that the decrease in eyelidness can be stopped at 1d microphthalmia.

In particular, since the ion-exchange membrane electrolytic cell formed by this method is a vertical cell, it has a single-area human exchange membrane, similar to the horizontal type ion-exchange membrane electrolytic cell that was previously proposed as a modification method of this type. Since chlorine gas and hydrogen gas generated from the anode and cathode can be easily discharged without the need for a
In addition, it is extremely easy to replace the exchange membrane and the anode section, which has practical value.

Example mercury iodochloride alkaline electrolyte TM tank (14 (IX 550x2
3ci) on the bottom plate as shown in Figures 4 and 5.
Sixteen reticulated iron cathode plates (100×100 cm) were placed with a spacing of 10.6 cIl each. Next, a circular ion exchange membrane (Nafion 901, manufactured by Yubon Co., Ltd., trade name) (wrapped net-like negative metal coated titanium plate (100 x 1
00cm> respectively as shown in the drawing, the distance between poles 2
F was inserted between the cathode plates to maintain the in
The RP lining was attached to an iron tank lid and suspended. The height of the side wall that holds the tank lid is 110mm (i), and the salt water inlet/outlet pipe, chlorine scum discharge chamber, caustic alkaline solution inlet/outlet pipe, and hydrogen gas outlet pipe are of the flow rate of a known comb-shaped ion exchange membrane electrolytic cell. Piping was done according to the operating conditions: cathode current density 20A/d
11', Saturated saline flow fj"t O, 8 m'/hr
, water injection m 701 / l + r, and as a result of performing 120-mouth electrolysis, a caustic soda solution with a NaOH content of 32% by weight was produced, the current efficiency was 94-96%, and the electrolysis voltage was 3.1-3.2V. Met.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a mercury method electrolytic cell before modification, FIG. 2 is a schematic diagram showing an electrolytic cell being modified into an ion exchange deprocessing electrolytic cell, and FIG. 3 is a schematic diagram showing an ion exchange membrane electrolytic cell after modification. Figure 4 is a partial vertical cross-sectional view showing the cathode part of the ion exchange membrane electrolytic cell after modification, and the left diagram in Figure 5 shows the cathode part of the modified ion exchange membrane electrolytic cell.
A partial vertical cross-sectional view showing the structure of the anode part, and the fifth fixed view is a partial vertical cross-sectional view taken from the A-A'' section in the left figure. (1) (5) ...Iso cover , (2>(2a) ・
・・Anode, (2b) ・・Anode lead rod, (3)・
・・Cathode bottom plate, (3b) ・・Cathode lead plate, (3C)・
...Reticular cathode, (4)...Side wall (6)...Cation exchange membrane. Applicant: Osaka Kaedatsu Co., Ltd. Agent: Patent Attorney: Kadota Procedures for writing amendments) 1. Indication of matter A9 Patent Application No. 190295 of 1982 2, Title of the invention Method for modifying an alkali chloride electrolytic cell 3, Relationship with the case of the person making the amendment Patent applicant 3 Ko Ta Noso Yuki Representative Yoko ff, L Noriyuki 4. Agent Address: Osaka Soda Co., Ltd., 1-10-8 Edobori, Nishi-ku, Osaka 550 January 118, 1959 (lli (24159)
(Sent January 318R) 7, Contents of the amendment (1> Mei 111819, line 8, "5th fixed figure" has been changed to "Figure 5(a-)", line 10, "5th fixed figure is on the left. ``Figure'' to ``
Figure 5(b) is corrected to ``Figure 5(a).'' (2) Correct the second leaf of the drawing as shown in the attached sheet. Ward α Akira

Claims (1)

[Claims] A plurality of vertical cathode plates are installed in parallel at predetermined intervals on the cathode bottom plate of an alkaline mercury iodochloride electrolytic cell, and a vertical anode body wrapped with a cation exchange membrane is inserted between the vertical cathode plates. A method for modifying an alkali chloride electrolytic cell for converting from a mercury method to an ion exchange membrane method.