JP3651871B2 - Ion exchange membrane electrolytic cell operation start method - Google Patents
Ion exchange membrane electrolytic cell operation start method Download PDFInfo
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- JP3651871B2 JP3651871B2 JP22610097A JP22610097A JP3651871B2 JP 3651871 B2 JP3651871 B2 JP 3651871B2 JP 22610097 A JP22610097 A JP 22610097A JP 22610097 A JP22610097 A JP 22610097A JP 3651871 B2 JP3651871 B2 JP 3651871B2
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- exchange membrane
- ion exchange
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Description
【０００１】
【発明の属する技術分野】
本発明は、イオン交換膜法によるアルカリ金属塩化物水溶液の電気分解方法に関し、特に、未使用のイオン交換膜を装着した電解槽の運転開始方法に関する。
【０００２】
【従来の技術】
食塩水等のアルカリ金属ハロゲン化物の水溶液をイオン交換膜電解槽において電気分解を開始する際に、イオン交換膜を装着した電解槽に、最初に通電を行う場合には、イオン交換膜の性能が発揮できるように、所定の初期運転条件によって運転を開始することが行われている。これは、イオン交換膜の電気分解性能が、運転初期に浸漬される電解液によって左右されるために、イオン交換膜を所定の電解液に浸漬した後に通電を開始することが行われている。
【０００３】
一般には、電解槽の運転開始時には、電解槽の陽極室には、電気分解で用いる飽和塩水を、また陰極室には３０重量％程度の水酸化ナトリウム水溶液をそれぞれ加熱して充填した後に、通電を開始することが行われていた。
【０００４】
ところが、このような初期運転を行っても、電気分解電圧が予想される値よりも高く、その後の定常運転においても電気分解電圧が高いという現象が多く見られていた。
【０００５】
【発明が解決しようとする課題】
本発明は、電気分解性能が高く、電気分解電圧が上昇することがないイオン交換膜電解槽の運転開始方法を提供することを課題とするものである。
【０００６】
【課題を解決するための手段】
本発明は、未使用のイオン交換膜を装着したイオン交換膜法電解槽の運転開始方法において、イオン交換膜電解槽の陽極室に、アルカリ金属濃度が２．０規定ないし４．５規定のアルカリ金属ハロゲン化物水溶液を満たし、通電を開始するイオン交換膜法電解槽の運転開始方法である。
【０００７】
陰極室には、濃度が２０重量％ないし３０重量％のアルカリ金属水酸化物水溶液を満たし、温度を６０℃ないし８５℃として、通電を開始する前記のイオン交換膜法電解槽の運転開始方法である。
【０００８】
【発明の実施の形態】
イオン交換膜電解槽において電解開始時のイオン交換膜の特性が変化する要因は多くあるが、従来、食塩水の電気分解においては、イオン交換膜電解槽への通電開始時のイオン交換膜膜の特性に影響を与える要因として、電解液の温度と陰極側の水酸化ナトリウム濃度のみが考えられていたが、本発明では、特に電気分解電圧を上昇する要因として、陽極液の濃度が大きく影響しているものを見いだしたものである。
【０００９】
陽極液の濃度を特定の濃度範囲とすることによって、電気分解電圧の上昇を防止することができる理由は明白ではないが、通電開始時に陽極液の濃度が高いと、陰極室側に移動するいわゆる浸透水の量が減少し、イオン交換膜の陰極室側に接する部分の水酸化ナトリウム濃度が上昇し、それによって含水率が低下し、イオン交換膜の電気伝導度が低下し、電気分解電圧が上昇するものではないかと推察される。そして、本発明では、陰極室側に移動する浸透水量を大きくために、陽極液の濃度を電気分解用の塩水の濃度よりも低くして、移行水の量を十分に大きくすることによって含水率が低くなることを防止し、電気分解電圧の上昇を防止するものである。
【００１０】
また、食塩水を陽極液とする場合には、陽極液中には、食塩以外に硫酸ナトリウム、塩素酸ナトリウム等も含まれていることがあり、イオン交換膜に対しては、これらの物質に由来するナトリウムも同様に影響を与えるので、陽極液中のナトリウム濃度は、それらの物質に起因するナトリウムも含めた総ナトリウムとして考慮する必要がある。
【００１１】
本発明の、イオン交換膜電解槽の運転開始時の陽極液のナトリウム濃度は、２．０規定〜４．５規定とすることが好ましく、３．５規定〜４．５規定とすることがより好ましい。
【００１２】
また、陰極液中の水酸化ナトリウム水溶液の濃度は、２０重量％〜３０重量％以下であることが好ましく、２５重量％〜３０重量％とすることがより好ましい。また、電解槽中の電解液の温度は、６０℃ないし８５℃とすることが好ましい。
【００１３】
また、イオン交換膜電解槽では、陽極液より陰極液は電解質の濃度が高く、電流の通電しない場合でも、陽極室から陰極室に水が移行する。その結果、陽極液の全ナトリウム濃度は高くなり、陰極液の水酸化ナトリウム濃度は低下する傾向がある。したがって、陽極液および陰極液の濃度が一定に保持されるように、陽極液中には、やや濃度の低い食塩水を添加し、陰極液中にはやや濃度の低い水酸化ナトリウム水溶液を供給することが好ましい。また、陽極液および陰極液の供給は、電解槽内での濃度分布および温度分布を減少させるためにも有効である。
【００１４】
本発明の方法による電解槽の運転開始方法は、未使用のイオン交換膜を装着したイオン交換膜電解槽の、組立を終え、漏れ試験を完了した電解槽の陰極室に、所定の温度および濃度に調整した水酸化ナトリウム水溶液を供給するとともに、陽極室に所定の温度および濃度に調整した塩水を供給する。電解槽を満たした水酸化ナトリウム水溶液と塩水は、供給を続けるとそれぞれの電極室から溢流するようになるが、各電極室には所定の流量で引き続き水酸化ナトリウム水溶液および塩水を供給する。次いで、電解槽の温度が所定の温度となった後に、電気分解電流の通電を開始するとともに、通常の運転用の濃厚な食塩水を供給することによって、運転を継続することができる。
【００１５】
また、本発明の方法は、イオン交換膜電解槽であれば、フィルタープレス型、箱型のいずれにも適用することができ、またイオン交換膜と電極との間隔、使用する電極の種類等の相違にかかわらず各種の電解槽にも適用することができる。
通電開始時に陽極室に供給する塩水は、食塩溶解した液を精製した食塩電解用の飽和食塩水を水で希釈して所定の濃度として使用することができ、また陰極室に供給する水酸化ナトリウム水溶液は、水酸化ナトリウムを溶解した所定の濃度の水溶液を使用することができる。
【００１６】
また、通電開始時の電解液の温度は、陽極液もしくは陰極液の少なくともいずれか一方を、熱媒体を用いた熱交換器、電気的加熱手段等によって温度調節することによって調整すれば良い。
【００１７】
【実施例】
以下に実施例を示し、本発明を説明する。
【００１８】
実施例１〜３及び比較例１〜２
実施例、比較例は、図１に示した２室式イオン交換膜電解槽を用いて実施した。電解槽１は、陽イオン交換膜２として、デュポン社ナフィオン９６２で、陽極室３と陰極室４に区画した。陽極５は、通電面積１００ｃｍ2 のチタン基体上に貴金属酸化物の被覆を形成した不溶性金属電極（ペルメレック電極製）を用い、陽極室枠体には、チタンパラジウム合金を用いた。また、陰極６には、同様の通電面積のニッケル基体上にラネーニッケルの被覆を施した活性陰極を用い、陰極室枠体には、ニッケルを用いた。
【００１９】
陽イオン交換膜の両面に陽極および陰極を接して、４０Ａの電流を通電した。また、陽極室には、陽極液貯槽７から食塩の濃度が異なる陽極液を供給し、陰極室には水８を供給するとともに、陽極室および陰極室内の電解液の温度を加熱装置９で調整した後に、電気分解を開始した。電気分解の開始とともに、陽極液のナトリウム濃度が５．２５規定の塩水を供給し、陽極室から淡塩水１０および塩素１１を取り出し、陰極室からは水酸化ナトリウム１２および水素１３を取り出した。
【００２０】
陽イオン交換膜を旭硝子製フレミオンＦ８９３とした点を除き、実施例１と同じ条件で電気分解を行いその結果を表２に示す。
【００２１】
陰極とイオン交換膜の距離を２ｍｍとした点を除き、実施例１と同様の条件で電気分解を行った。その結果を表３に示す。
【００２２】
【発明の効果】
本発明によると、運転初期より電解電圧が低く、少ない電力で所定量の水酸化ナトリウムを製造できる。また、電気分解電圧が低くなるために、発熱量の減少によって、電気分解時の熱収支が容易となり、電解槽の温度の上昇による冷却、電気分解電流の低下等の操作が不要となり、電解槽の運転管理が容易になる。
【図面の簡単な説明】
【図１】本発明の一実施例を説明する図である。
【符号の説明】
１…電解槽、２…陽イオン交換膜、３…陽極室、４…陰極室、５…陽極、６…陰極、７…陽極液貯槽、８…水、９…加熱装置、１０…淡塩水、１１…塩素、１２…水酸化ナトリウム、１３…水素[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolysis method of an aqueous alkali metal chloride solution by an ion exchange membrane method, and more particularly to a method for starting operation of an electrolytic cell equipped with an unused ion exchange membrane.
[0002]
[Prior art]
When electrolysis of an aqueous solution of an alkali metal halide such as saline in an ion exchange membrane electrolytic cell is performed for the first time, the performance of the ion exchange membrane is reduced. The operation is started under predetermined initial operation conditions so that the operation can be performed. This is because, since the electrolysis performance of the ion exchange membrane depends on the electrolyte immersed in the initial stage of operation, energization is started after the ion exchange membrane is immersed in a predetermined electrolyte.
[0003]
In general, at the start of the operation of the electrolytic cell, the anode chamber of the electrolytic cell is heated and filled with saturated salt water used for electrolysis and the sodium chloride aqueous solution of about 30% by weight is charged into the cathode chamber. It was done to start.
[0004]
However, even when such an initial operation is performed, many phenomena have been observed in which the electrolysis voltage is higher than expected and the electrolysis voltage is high even in the subsequent steady operation.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for starting operation of an ion exchange membrane electrolytic cell that has high electrolysis performance and does not increase the electrolysis voltage.
[0006]
[Means for Solving the Problems]
The present invention provides an operation start method for an ion exchange membrane electrolytic cell equipped with an unused ion exchange membrane, and an alkali chamber having an alkali metal concentration of 2.0 to 4.5 normal in an anode chamber of the ion exchange membrane electrolytic cell. This is an operation start method for an ion exchange membrane electrolytic cell that fills a metal halide aqueous solution and starts energization.
[0007]
The cathode chamber is filled with an alkali metal hydroxide aqueous solution having a concentration of 20 wt% to 30 wt%, the temperature is set to 60 ° C. to 85 ° C., and the ion exchange membrane method electrolytic cell starting operation is started. is there.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the ion exchange membrane electrolytic cell, there are many factors that change the characteristics of the ion exchange membrane at the start of electrolysis. Conventionally, in the electrolysis of saline solution, the ion exchange membrane membrane at the start of energization to the ion exchange membrane electrolytic cell Only the temperature of the electrolyte and the sodium hydroxide concentration on the cathode side were considered as factors affecting the characteristics. However, in the present invention, the concentration of the anolyte is greatly influenced as a factor that particularly increases the electrolysis voltage. It is what you have found.
[0009]
The reason why the increase in the electrolysis voltage can be prevented by setting the concentration of the anolyte to a specific concentration range is not clear, but if the concentration of the anolyte is high at the start of energization, it moves to the cathode chamber side. The amount of permeated water decreases, the concentration of sodium hydroxide in the portion of the ion exchange membrane that contacts the cathode chamber increases, thereby reducing the water content, reducing the electrical conductivity of the ion exchange membrane, and reducing the electrolysis voltage. It is presumed that it will rise. In the present invention, in order to increase the amount of permeated water moving to the cathode chamber side, the water content is increased by making the concentration of the anolyte lower than the concentration of salt water for electrolysis and sufficiently increasing the amount of transition water. Is prevented, and an increase in the electrolysis voltage is prevented.
[0010]
In addition, when using saline as the anolyte, the anolyte may contain sodium sulfate, sodium chlorate, and the like in addition to sodium chloride. Since the derived sodium also has an effect, the sodium concentration in the anolyte needs to be considered as total sodium, including sodium originating from those substances.
[0011]
The sodium concentration of the anolyte at the start of operation of the ion exchange membrane electrolytic cell of the present invention is preferably 2.0 to 4.5 and more preferably 3.5 to 4.5. preferable.
[0012]
The concentration of the sodium hydroxide aqueous solution in the catholyte is preferably 20% by weight to 30% by weight and more preferably 25% by weight to 30% by weight. The temperature of the electrolytic solution in the electrolytic cell is preferably 60 ° C to 85 ° C.
[0013]
Further, in the ion exchange membrane electrolytic cell, the concentration of the electrolyte in the catholyte is higher than that in the anolyte, and water moves from the anode chamber to the cathode chamber even when no current is applied. As a result, the total sodium concentration of the anolyte tends to increase and the sodium hydroxide concentration of the catholyte tends to decrease. Therefore, a slightly lower concentration saline solution is added to the anolyte so that the concentrations of the anolyte and the catholyte are kept constant, and an aqueous sodium hydroxide solution having a slightly lower concentration is supplied to the catholyte. It is preferable. The supply of the anolyte and the catholyte is also effective for reducing the concentration distribution and temperature distribution in the electrolytic cell.
[0014]
The method of starting the electrolytic cell according to the method of the present invention is that an ion exchange membrane electrolytic cell equipped with an unused ion exchange membrane is assembled at a predetermined temperature and concentration in the cathode chamber of the electrolytic cell after completion of the leak test. A sodium hydroxide aqueous solution adjusted to 1 is supplied, and salt water adjusted to a predetermined temperature and concentration is supplied to the anode chamber. The sodium hydroxide aqueous solution and the salt water filling the electrolytic cell overflow from the respective electrode chambers when the supply is continued, but the sodium hydroxide aqueous solution and the salt water are continuously supplied to each electrode chamber at a predetermined flow rate. Next, after the temperature of the electrolytic cell reaches a predetermined temperature, the operation can be continued by starting energization of the electrolysis current and supplying concentrated saline for normal operation.
[0015]
In addition, the method of the present invention can be applied to either a filter press type or a box type as long as it is an ion exchange membrane electrolytic cell. Also, the distance between the ion exchange membrane and the electrode, the type of electrode to be used, etc. It can be applied to various electrolytic cells regardless of the difference.
The salt water supplied to the anode chamber at the start of energization can be used as a predetermined concentration by diluting a saturated saline solution for salt electrolysis obtained by purifying a solution in which salt is dissolved, with water supplied to the cathode chamber. As the aqueous solution, an aqueous solution having a predetermined concentration in which sodium hydroxide is dissolved can be used.
[0016]
The temperature of the electrolytic solution at the start of energization may be adjusted by adjusting the temperature of at least one of the anolyte or the catholyte with a heat exchanger using a heat medium, an electric heating means, or the like.
[0017]
【Example】
The following examples illustrate the invention.
[0018]
Examples 1-3 and Comparative Examples 1-2
Examples and Comparative Examples were carried out using the two-chamber ion exchange membrane electrolytic cell shown in FIG. The electrolytic cell 1 was divided into an
[0019]
An anode and a cathode were in contact with both surfaces of the cation exchange membrane, and a current of 40 A was applied. Further, an anolyte having a different salt concentration is supplied from the
[0020]
Table 2 shows the results of electrolysis under the same conditions as in Example 1 except that the cation exchange membrane was Flemion F893 manufactured by Asahi Glass.
[0021]
Electrolysis was performed under the same conditions as in Example 1 except that the distance between the cathode and the ion exchange membrane was 2 mm. The results are shown in Table 3.
[0022]
【The invention's effect】
According to the present invention, a predetermined amount of sodium hydroxide can be produced with low electric power and lower power than the initial stage of operation. In addition, since the electrolysis voltage is low, the heat balance during electrolysis becomes easy due to the reduction in the amount of heat generation, and operations such as cooling due to a rise in the temperature of the electrolyzer and a decrease in electrolysis current are not required. Operation management becomes easier.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electrolytic cell, 2 ... Cation exchange membrane, 3 ... Anode chamber, 4 ... Cathode chamber, 5 ... Anode, 6 ... Cathode, 7 ... Anolyte storage tank, 8 ... Water, 9 ... Heating apparatus, 10 ... Fresh salt water, 11 ... chlorine, 12 ... sodium hydroxide, 13 ... hydrogen
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22610097A JP3651871B2 (en) | 1997-08-22 | 1997-08-22 | Ion exchange membrane electrolytic cell operation start method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22610097A JP3651871B2 (en) | 1997-08-22 | 1997-08-22 | Ion exchange membrane electrolytic cell operation start method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1161476A JPH1161476A (en) | 1999-03-05 |
| JP3651871B2 true JP3651871B2 (en) | 2005-05-25 |
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| JP22610097A Expired - Lifetime JP3651871B2 (en) | 1997-08-22 | 1997-08-22 | Ion exchange membrane electrolytic cell operation start method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105951119B (en) * | 2016-07-04 | 2018-07-06 | 宁波镇洋化工发展有限公司 | A kind of method for preparing sodium hydroxide |
| EP3670706B1 (en) * | 2018-12-18 | 2024-02-21 | Covestro Deutschland AG | Method for the membrane electrolysis of alkali chloride solutions with gas diffusion electrode |
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| JPH1161476A (en) | 1999-03-05 |
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