JPS6342714B2 - - Google Patents
Info
- Publication number
- JPS6342714B2 JPS6342714B2 JP58041550A JP4155083A JPS6342714B2 JP S6342714 B2 JPS6342714 B2 JP S6342714B2 JP 58041550 A JP58041550 A JP 58041550A JP 4155083 A JP4155083 A JP 4155083A JP S6342714 B2 JPS6342714 B2 JP S6342714B2
- Authority
- JP
- Japan
- Prior art keywords
- electrolytic cell
- cathode chamber
- auxiliary electrode
- cathode
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 210000004027 cell Anatomy 0.000 claims description 60
- 239000007788 liquid Substances 0.000 claims description 48
- 230000007797 corrosion Effects 0.000 claims description 29
- 238000005260 corrosion Methods 0.000 claims description 29
- 238000000034 method Methods 0.000 claims description 20
- 238000000605 extraction Methods 0.000 claims description 19
- 238000005868 electrolysis reaction Methods 0.000 claims description 12
- 239000003014 ion exchange membrane Substances 0.000 claims description 11
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 9
- 239000003513 alkali Substances 0.000 claims description 8
- 210000005056 cell body Anatomy 0.000 claims description 5
- 239000000446 fuel Substances 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 7
- 239000007789 gas Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000012528 membrane Substances 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 4
- 239000003518 caustics Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 238000007747 plating Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- 229920002943 EPDM rubber Polymers 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000002048 anodisation reaction Methods 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- -1 platinum group metals Chemical class 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 235000011121 sodium hydroxide Nutrition 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
- C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
Description
本発明は塩化アルカリ水溶液のイオン交換膜法
電解に関し、詳しくは複数個の電気的直列に接続
した電解槽において各単位電解槽で生ずる腐食を
完全に防止する方法を提供するものである。
塩化アルカリ水溶液を電解して苛性アルカリと
塩素を製造する方法としてイオン交換膜をはさん
で陰、陽極を設け、陰、陽極室を形成し、塩化ア
ルカリを電解して苛性アルカリ液を得る、いわゆ
るイオン交換膜法塩化アルカリ電解方法がある。
かかる方法を用いる電解槽プラントはイオン交換
膜をはさんで単極型陰、陽極を設けた単一の単極
槽を複数個電気的に接続して構成される単極式電
解槽を電気的に直列に接続して形成されたり、或
いはイオン交換膜をはさんで複極型陰、陽極を設
けた単一の複極槽を単位電解槽としてこれを電気
的に直列に接続して構成される複極式電解槽を電
気的に複数個並列および／または直列に接続して
形成される。
この様な電解槽プラントを用いて塩化アルカリ
を電解して生成した苛性アルカリ水溶液は複数個
の単位電解槽間に亘つて設けられた１つの共通の
通路を通じてタンク等に集められる。また複数個
の単位電解槽への液供給についても１つの共通の
通路を通じて各々の単位電解槽へ供給される。し
かしながら、単位電解槽は電気的に直列接続され
ているため夫々の単位槽に於ける電位は異なつて
おり、電解時に単位電解槽陰極室への液供給およ
び該電解槽陰極室で生成した苛性アルカリ水溶液
を共通の通路に抜き出す際にはかかる液を通じて
電解電流の一部が漏洩する。かかる電流の漏洩の
ため電解槽陰極室本体特に陰極室本体の液供給ノ
ズルおよび生成液抜出ノズル付近はいわゆる電極
の作用をし、この部分で電解が起り、陽極として
作用する箇所では陽極酸化現象により腐食される
ことになる。
従来このような電解槽本体の腐食を防止するた
めにトラフ内に補助電極を設置し、複極式電解槽
のアノード端のセルと電気的に並列にしておくこ
とが電食防止法として提案されている（特公昭56
−44951号）。
しかしながら、この様な方法を採用した場合、
陰極室材質が純Niのような高級材料を用いた場
合に限り腐食をある程度抑えることが可能である
が、経済性、製作性、操作性等を考慮して陰極室
材質およびそれに付属するノズル類等を鉄あるい
はステンレス鋼とした場合高電位側単一電解槽に
おいては依然として自然腐食状態で腐食溶解反応
が進行し、陰極室液供給ノズルおよび生成液抜出
ノズルならびに陰極室本体の一部においては腐食
損傷のため一定時間の電解運転後にはこれを取り
換え操作或いは溶接肉盛補修等が必要となり、完
全に腐食を防止することはできない。
ここで自然腐食状態とは外部からの電圧が全く
印加されない状態を意味し、電食が全く停止した
状態を意味する。また高電位側単一電解槽とは複
極式電解槽であればアノード端に近い数個の第一
電解槽を意味し、単極式電解槽であれば、該単極
式電解槽を電気的に直列に接続して形成される電
解槽回路内の高電位側に位置する単極式電解槽を
形成する単一電解槽を意味する。
近年、電解槽浴電圧を低減するために陰極の水
素過電圧を低下させる。いわゆる活性陰極の開発
が行なわれ、一部報告されている（ソーダと塩
素、1981年８号P.427〜449）。これによると陰極
液中に重金属等の溶出イオンが存在していると活
性陰極上に電気化学的に析出し、本来の低水素過
電圧特性を失なう結果となる。すなわち単位電解
槽に活性陰極を取り付け、陰極としての低水素過
電圧特性を長期間維持するためには陰極室本体お
よび該陰極室本体に付属するノズル等で生ずる腐
食を完全に防止することが必要である。
イオン交換膜電解に使用されるイオン交換膜に
ついても同様に陰極液中に金属溶出イオンが存在
すると該イオン交換膜表面に吸着あるいは析出
し、膜過電圧特性を低下させることになる。従つ
て、このことからも陰極室本体の腐食は完全に防
止する必要性を生じる。
以上の点から本発明者は研究を重ねた結果本発
明に到達した。
すなわち、本発明は金属製の単位電解槽を複数
個電気的に直列接続して構成され、各単位電解槽
本体には電気絶縁性の陰極室液供給管および陰極
室生成液抜出管が設けられ、該陰極室液供給管お
よび／または該陰極室生成液抜室管には共通の通
路を通じて供給液および／または抜出液を集める
様にして構成される電解槽プラントにおいて該陰
極室液供給管内、該陰極室生成液抜出管内、共通
の通路内のいずれか少なくとも１箇所に補助電極
を設け、補助電極にかかる電圧が複極式電解装置
のアノード端子電圧より0.1V以上高くすること
を特徴とする塩化アルカリ電解槽の防食方法を提
供するものである。
本発明における電解槽本体とは槽を構成する部
材であり、例えば極室プール型電解槽であれば箱
体；フイルタープレス型電解槽であれば室枠がこ
れに相当する。槽を構成する部材である陽極室お
よび陽極室に付属するノズル材質としては一般に
チタン、チタン合金、タンタル、ジルコニウム、
ニオブ等が用いられ、また陰極室ならびに陰極室
に付属するノズル材質としては、鉄、軟鋼、鋳
鉄、ステンレス鋼、Ni基合金、Ni等が用いられ
る。陽陰極室に付属するノズルは溶接等により接
続されている態様が一般的である。液供給および
液抜出ノズルとしてはパイプ状のものが多く用い
られるが、その他種々の形状のものが用いられ
る。
本発明の陰極室液供給管および陰極室生成液抜
出管ならびに共通の通路は電気絶縁性であること
が望ましい。電気電導性であれば液供給管および
生成液抜出管ならびに共通の通路を通つて腐食電
流が流れる恐れがあるからである。陰極室液供給
管および陰極室生成液抜出管ならびに共通の通路
用配管材料は苛性ソーダ液、水素ガス等に対して
電解温度下で耐えて電気絶縁性であればよい。
例えば、テフロン、アスベスト、塩化ビニー
ル、アクリル樹脂、E.P.D.M.ゴムやその他のゴ
ム等が挙げられる。
本発明の補助電極は陽極として作動するので通
常用いられる陽極、例えば黒鉛ブロツク、白金族
の金属をチタン又はタンタル上に被覆されたいわ
ゆる被覆金属電極、また純Ni、Zr、Agなどが電
極として使用される。
補助電極表面では酸素ガス発生反応を伴なう場
合が多いので陰極室内への酸素ガスの混入を避け
る場合には補助電極周辺にガス分離膜を設置し、
系外に抜き出す方法が採用される。
本発明における補助電極にかかる電圧は複極式
電解装置のアノード端子電圧より0.1V以上であ
る。0.1V未満であれば陰極室本体および陰極室
に付属するノズル等の腐食防止効果が小さい。従
つて0.1V以上が望ましい。好ましくは2V以上で
ある。
補助電極に電圧をかける方法としては複極式電
解装置電解用電源のアノード端子にバツテリーあ
るいは燃料電池等を電気的に直列接続させて補助
電極に連結させるか、或いはアノード端子と補助
電極との回路間に補助整流路を入れるか等いろん
な方法が採用される。補助整流路としては例えば
シリコンサイリスター、又はシリコンダイオード
等の素子が使用される。
本発明の補助電極設置箇所としては、特に限定
されないが、操作上の観点からまた腐食を防止す
る効率の点から陰極室液供給管内、陰極室生成液
抜出管内、共通の通路内のいずれか少なくとも１
箇所に設けることが好ましい。
本発明を用いる場合、特に電解生成液が苛性ア
ルカリであるときは供給管および／または抜出管
と該管の共通の通路との接続位置との間に更に液
を液滴として液を通じて電流漏洩を防止する様な
滴断器を設けることが好ましい。滴断器を設置す
ることにより少ない電流でもつて防食でき、エネ
ルギーロスを少なくでき、効率よく電解槽の防食
が達成される。
本発明によれば陰極室液供給管内、陰極室生成
液抜出管内、共通の通路内のいずれか少なく１箇
所に補助電極を設置し、補助電極にかかる電圧が
複極式電解装置のアノード端子電圧より0.1V以
上高くすることにより電解槽本体および電解槽本
体に付属する金属製ノズルの腐食を完全に防止す
ることができる。このため電解槽の寿命は著しく
長くなり、特に電解槽材料として高価な金属を用
いる場合は経済的な面でも有利である。更に従来
の方法に比べメンテナンスが軽減できる。
本発明の方法を用いると陰極室供給液および該
陰極室抜出液中に溶出金属イオンの量が皆無に等
しいから低水素過電圧特性を有する活性陰極を用
いた場合においても活性陰極上に溶出金属イオン
の吸着、析出反応することによる劣化を起こすこ
となく長期間安定な電解運転を持続して行なうこ
とができる。
また、溶出金属イオンがないので同時にイオン
交換膜に対する悪影響すなわちイオン交換膜の性
能低下を起こすことなく驚異的な寿命を維持する
ことができる。
次に本発明の実施例について説明する。
実施例 １
陽極はルテニウムオキサイドとチタニウムオキ
サイドをコーテイングしたチタニウムのエキスパ
ンドメタル、陰極はNiのエキスパンドメタルか
らなる複極式電極を有し、本体は陽極室がチタニ
ウム、陰極室がSUS304ステンレス鋼よりなる通
電面積200dm2（幅２ｍ×高さ１ｍ）のセルユニ
ツトを用いた。
上記のセルユニツト25対に陽イオン交換膜
Nafion901（商品名デユポン社製）を隔膜として
はさみ込み第１図に示すような複極式電解槽１を
作つた。電解槽陰極室本体にはフツ素樹脂製の液
供給管２および生成液抜出管３を設置した。また
夫々のセルユニツトに設けられた液供給管２およ
び抜出管３には夫々１つの共通の通路４，５を接
続し、次に夫々の共通の通路内には夫々１枚の
Ni製補助電極６を設け、補助電極６は複極式電
解槽電解用電源のアノード端子と電気的に接続
し、その回路内に夫々シリコン整流器７を設置し
た。また第２図に示すように補助電極近傍にはテ
フロン製ガス分離膜８およびガス抜き管９を設置
した。次に食塩の電解を電流密度30A／ｄm2、電
解温度90℃で行なつた。その際、陰極室生成液抜
出ノズル付近にSUS304ステンレス鋼製のテスト
ピースを取り付け、補助電極回路整流器電圧を変
化させ、整流器電圧に対するSUS304の腐食速度
を測定した。得られた結果を第１表に示した。
The present invention relates to ion-exchange membrane electrolysis of aqueous alkali chloride solutions, and more specifically, provides a method for completely preventing corrosion occurring in each unit electrolytic cell in a plurality of electrolytic cells electrically connected in series. As a method for producing caustic alkali and chlorine by electrolyzing an aqueous alkali chloride solution, a negative and anode are provided with an ion exchange membrane sandwiched between them, forming a negative and anode chamber, and the alkali chloride is electrolyzed to obtain a caustic alkaline solution. There is an ion exchange membrane method and an alkali chloride electrolysis method.
An electrolytic cell plant using this method is a monopolar electrolytic cell constructed by electrically connecting a plurality of single monopolar cells each having a monopolar cathode and an anode across an ion exchange membrane. A single bipolar cell with a bipolar cathode and an anode sandwiched between ion exchange membranes is connected electrically in series as a unit electrolytic cell. It is formed by electrically connecting a plurality of bipolar electrolytic cells in parallel and/or series. A caustic alkaline aqueous solution produced by electrolyzing alkali chloride using such an electrolytic cell plant is collected in a tank or the like through one common passage provided between a plurality of unit electrolytic cells. Also, liquid is supplied to each of the plurality of unit electrolytic cells through one common passage. However, since the unit electrolytic cells are electrically connected in series, the potential in each unit cell is different. When an aqueous solution is drawn into a common path, a portion of the electrolytic current leaks through the aqueous solution. Due to this current leakage, the electrolytic cell cathode chamber body, especially the vicinity of the liquid supply nozzle and produced liquid extraction nozzle of the cathode chamber body, acts as a so-called electrode, and electrolysis occurs in this part, and an anodization phenomenon occurs in the part that acts as an anode. It will be corroded by Conventionally, in order to prevent corrosion of the electrolytic cell body, installing an auxiliary electrode in the trough and electrically paralleling it with the cell at the anode end of a bipolar electrolytic cell was proposed as a method to prevent electrolytic corrosion. (Tokuko Showa 56)
−44951). However, if such a method is adopted,
Corrosion can be suppressed to some extent only if the cathode chamber is made of high-grade material such as pure Ni, but the material of the cathode chamber and the nozzles attached to it must be carefully selected in consideration of economic efficiency, manufacturability, operability, etc. When iron or stainless steel is used, the corrosion and dissolution reaction still progresses in a state of natural corrosion in the single electrolytic cell on the high potential side, and the corrosion and dissolution reaction proceeds in the cathode chamber liquid supply nozzle, produced liquid extraction nozzle, and part of the cathode chamber main body. Due to corrosion damage, it is necessary to replace it or repair it by welding after a certain period of electrolytic operation, and corrosion cannot be completely prevented. Here, the natural corrosion state means a state where no external voltage is applied, and means a state where electrolytic corrosion has completely stopped. In addition, a single electrolytic cell on the high potential side means several first electrolytic cells near the anode end in the case of a bipolar electrolytic cell, and in the case of a monopolar electrolytic cell, the single electrolytic cell is means a single electrolytic cell that is connected in series to form a monopolar electrolytic cell located on the high potential side of an electrolytic cell circuit. In recent years, the hydrogen overvoltage of the cathode has been reduced to reduce the electrolyzer bath voltage. A so-called active cathode has been developed and some reports have been made (Soda and Chlorine, No. 8, 1981, pp. 427-449). According to this, if eluted ions such as heavy metals are present in the catholyte, they will electrochemically precipitate on the active cathode, resulting in the loss of the original low hydrogen overvoltage characteristics. In other words, in order to install an active cathode in a unit electrolytic cell and maintain the low hydrogen overvoltage characteristics of the cathode for a long period of time, it is necessary to completely prevent corrosion that occurs in the cathode chamber body and the nozzles attached to the cathode chamber body. be. Similarly, in the case of ion exchange membranes used in ion exchange membrane electrolysis, if metal ions are present in the catholyte, they will be adsorbed or deposited on the surface of the ion exchange membrane, reducing the membrane overvoltage characteristics. Therefore, this also creates the need to completely prevent corrosion of the cathode chamber body. In light of the above points, the present inventor has completed the present invention as a result of repeated research. That is, the present invention is constructed by electrically connecting a plurality of unit electrolytic cells made of metal in series, and each unit electrolytic cell body is provided with an electrically insulating cathode chamber liquid supply pipe and a cathode chamber produced liquid extraction pipe. In an electrolytic cell plant configured such that the cathode chamber liquid supply pipe and/or the cathode chamber produced liquid withdrawal pipe collect the feed liquid and/or the withdrawn liquid through a common passage, the cathode chamber liquid supply pipe is Provide an auxiliary electrode in at least one location within the tube, in the cathode chamber product liquid extraction tube, or in the common passage, and make sure that the voltage applied to the auxiliary electrode is 0.1 V or more higher than the anode terminal voltage of the bipolar electrolyzer. The present invention provides a method for preventing corrosion of an alkali chloride electrolytic cell. The electrolytic cell main body in the present invention is a member constituting the cell, and for example, in the case of an electrode pool type electrolytic cell, the box body corresponds to this; in the case of a filter press type electrolytic cell, the chamber frame corresponds to this. The anode chamber and the nozzle attached to the anode chamber, which are the members that make up the tank, are generally made of titanium, titanium alloy, tantalum, zirconium,
Niobium or the like is used, and iron, mild steel, cast iron, stainless steel, Ni-based alloy, Ni, or the like is used as the cathode chamber and the nozzle material attached to the cathode chamber. The nozzles attached to the anode and cathode chambers are generally connected by welding or the like. Although pipe-shaped nozzles are often used as liquid supply and liquid extraction nozzles, various other shapes can also be used. It is desirable that the cathode chamber liquid supply pipe, the cathode chamber product liquid extraction pipe, and the common passage of the present invention be electrically insulating. This is because if the pipe is electrically conductive, there is a possibility that a corrosive current will flow through the liquid supply pipe, the produced liquid extraction pipe, and the common passage. The cathode chamber liquid supply pipe, the cathode chamber produced liquid discharge pipe, and the piping material for the common passage only need to be electrically insulating and withstand against caustic soda solution, hydrogen gas, etc. at electrolytic temperatures. Examples include Teflon, asbestos, vinyl chloride, acrylic resin, EPDM rubber, and other rubbers. Since the auxiliary electrode of the present invention operates as an anode, commonly used anodes such as graphite blocks, so-called coated metal electrodes in which platinum group metals are coated on titanium or tantalum, pure Ni, Zr, Ag, etc. can be used as electrodes. be done. Oxygen gas generation reactions often occur on the surface of the auxiliary electrode, so if you want to prevent oxygen gas from entering the cathode chamber, install a gas separation membrane around the auxiliary electrode.
A method is adopted to extract it from the system. The voltage applied to the auxiliary electrode in the present invention is 0.1 V or more higher than the anode terminal voltage of the bipolar electrolyzer. If it is less than 0.1V, the effect of preventing corrosion of the cathode chamber main body and the nozzle attached to the cathode chamber is small. Therefore, 0.1V or more is desirable. Preferably it is 2V or more. The method of applying voltage to the auxiliary electrode is to connect a battery or fuel cell electrically in series to the anode terminal of the power supply for electrolysis in a bipolar electrolyzer and connect it to the auxiliary electrode, or to connect the anode terminal and the auxiliary electrode to the anode terminal. Various methods are adopted, such as inserting an auxiliary rectifying path in between. Elements such as silicon thyristors or silicon diodes are used as the auxiliary rectifying path. The location for installing the auxiliary electrode of the present invention is not particularly limited, but from the viewpoint of operation and efficiency in preventing corrosion, it is possible to install the auxiliary electrode in the cathode chamber liquid supply pipe, in the cathode chamber product liquid extraction pipe, or in a common passage. at least 1
It is preferable to provide it at a location. When using the present invention, especially when the electrolytically produced liquid is caustic, current leaks through the liquid in the form of droplets between the supply pipe and/or the extraction pipe and the connection position with the common passage of the pipe. It is preferable to provide a drip breaker to prevent this. By installing a drip breaker, corrosion protection can be achieved even with a small amount of current, energy loss can be reduced, and corrosion protection of the electrolytic cell can be achieved efficiently. According to the present invention, an auxiliary electrode is installed in at least one of the cathode chamber liquid supply pipe, the cathode chamber produced liquid extraction pipe, and the common passage, and the voltage applied to the auxiliary electrode is applied to the anode terminal of the bipolar electrolyzer. Corrosion of the electrolytic cell body and the metal nozzle attached to the electrolytic cell body can be completely prevented by increasing the voltage by 0.1 V or more. For this reason, the life of the electrolytic cell is significantly extended, which is also economically advantageous, especially when expensive metals are used as the material for the electrolytic cell. Furthermore, maintenance can be reduced compared to conventional methods. When the method of the present invention is used, the amount of eluted metal ions in the cathode chamber supply liquid and the cathode chamber effluent is almost completely eliminated. Stable electrolytic operation can be maintained for a long period of time without causing deterioration due to ion adsorption or precipitation reactions. Furthermore, since there are no eluted metal ions, an amazing lifespan can be maintained without causing any adverse effects on the ion exchange membrane, ie, deterioration in the performance of the ion exchange membrane. Next, examples of the present invention will be described. Example 1 The anode has a bipolar electrode made of expanded titanium metal coated with ruthenium oxide and titanium oxide, and the cathode is made of expanded Ni metal.The main body is a current-carrying device with an anode chamber made of titanium and a cathode chamber made of SUS304 stainless steel. A cell unit with an area of 200 dm 2 (width 2 m x height 1 m) was used. A cation exchange membrane is added to the 25 pairs of cell units above.
A bipolar electrolytic cell 1 as shown in FIG. 1 was made by inserting Nafion 901 (trade name, manufactured by DuPont) as a diaphragm. A liquid supply pipe 2 and a produced liquid extraction pipe 3 made of fluororesin were installed in the main body of the electrolytic cell cathode chamber. Further, one common passage 4, 5 is connected to each of the liquid supply pipe 2 and extraction pipe 3 provided in each cell unit, and then one sheet is connected to each common passage.
An auxiliary electrode 6 made of Ni was provided, and the auxiliary electrode 6 was electrically connected to the anode terminal of a power source for bipolar electrolytic cell electrolysis, and a silicon rectifier 7 was installed in each of the circuits. Further, as shown in FIG. 2, a Teflon gas separation membrane 8 and a gas vent pipe 9 were installed near the auxiliary electrode. Next, the salt was electrolyzed at a current density of 30 A/dm 2 and an electrolysis temperature of 90°C. At that time, a test piece made of SUS304 stainless steel was attached near the cathode chamber produced liquid extraction nozzle, the auxiliary electrode circuit rectifier voltage was varied, and the corrosion rate of SUS304 relative to the rectifier voltage was measured. The results obtained are shown in Table 1.
【表】
表より明らかなように補助電極にかかる電圧が
0VではNo.１セルノズルに取り付けたSUS304が激
しく腐食された。本発明の方法により補助電極に
かかる電圧をアノード端子電圧より0.1V以上高
くするとSUS304の腐食は著しく軽減され、特に
1V以上では完全に防食が達成された。
実施例 ２
実施例１において補助電極設置箇所を第３図に
示すように液供給管内および同様な方法で液抜出
管内に付け変えた。補助電極６としては板状のも
のが取り付けにくいこともあり、Ni製円筒型の
ものを用い、補助電極回路整流器電圧に対する
SUS304の腐食速度の関係を調べた。
その結果は第１表の示した値と全く同一であ
り、本発明の方法は電解槽の腐食を完全に防止す
る手段として驚異的な方法であることが証明され
た。
実施例 ３
実施例１において陰極を以下のような電気メツ
キ処理したエキスパンドメタルに取り換え、電解
運転を行なつた。
（電気メツキ条件）
１ メツキ浴組成
硫酸ニツケル 1.0M／
チオ尿素 0.2M／
ホウ酸 0.3M／
２ メツキ条件
浴 温 40℃
電流密度 0.5A／ｄm2
メツキ時間 １時間
その結果、セル電圧は第２表に示すようにほと
んど経時変化することなく約3.10Vの一定値を示
した、１年間電解運転後、電解槽を解体し、腐食
状況を調査してみたが、電解槽内部での腐食は全
く認められず、また陰極上への析出物も全く検出
されなかつた。[Table] As is clear from the table, the voltage applied to the auxiliary electrode is
At 0V, the SUS304 attached to No. 1 cell nozzle was severely corroded. When the voltage applied to the auxiliary electrode is made higher than the anode terminal voltage by 0.1V or more using the method of the present invention, corrosion of SUS304 is significantly reduced, especially
Corrosion protection was completely achieved above 1V. Example 2 In Example 1, the auxiliary electrode was installed inside the liquid supply pipe as shown in FIG. 3, and in the same manner as inside the liquid withdrawal pipe. As the auxiliary electrode 6 may be difficult to install in the form of a plate, we used a cylindrical Ni cylindrical electrode, which is suitable for the auxiliary electrode circuit rectifier voltage.
The relationship between the corrosion rate of SUS304 was investigated. The results were exactly the same as the values shown in Table 1, proving that the method of the present invention is an amazing method for completely preventing corrosion of electrolytic cells. Example 3 In Example 1, the cathode was replaced with an electroplated expanded metal as described below, and electrolytic operation was carried out. (Electroplating conditions) 1 Plating bath composition Nickel sulfate 1.0M / Thiourea 0.2M / Boric acid 0.3M / 2 Plating conditions Bath temperature 40℃ Current density 0.5A/dm 2 Plating time 1 hour As a result, the cell voltage was As shown in the table, after one year of electrolytic operation, which showed a constant value of approximately 3.10V with almost no change over time, the electrolytic cell was disassembled and the corrosion situation was investigated, but no corrosion was found inside the electrolytic cell. No deposits were detected on the cathode.
【表】
比較例 １
実施例３において補助電極を取りはずし、電解
運転を行なつた。その結果電解運転初期浴電圧が
3.10Vであつた。しかしながら数日経過後から浴
電圧の上昇がみられ、20日経過後には鉄陰極を用
いた場合と同じ約3.50Vの浴電圧を示すに至つ
た。30日電解運転後、電解槽を解体してみた所、
電解槽の液供給ノズルおよび液抜出ノズル内部は
もちろんのこと、これらノズル付近の電解槽内部
においても激しい腐食が認められ、また陰極上に
もかなりの量のFeの析出が起つていた。
比較例 ２
実施例２において補助電極と複極式電解槽電解
用電源のアノード端子の間に何も取り付けずに電
気的に接続して、電解運転を行なつた。
その結果比較例１に比べると浴電圧の上昇速度
は遅かつたが、約60日経過後には約3.40Vの浴電
圧を示すに至つた。
このことからも本発明の方法が電解槽の完全腐
食防止方法として非常に有効であるばかりでな
く、省エネルギーの観点からもすぐれた電解性能
を維持できる方法であることが明らかとなつた。[Table] Comparative Example 1 In Example 3, the auxiliary electrode was removed and electrolysis operation was performed. As a result, the initial bath voltage during electrolysis operation is
It was 3.10V. However, after several days had passed, an increase in bath voltage was observed, and after 20 days, the bath voltage reached approximately 3.50 V, the same as when using an iron cathode. After 30 days of electrolytic operation, I disassembled the electrolytic cell and found
Severe corrosion was observed not only inside the liquid supply nozzle and liquid extraction nozzle of the electrolytic cell, but also inside the electrolytic cell near these nozzles, and a considerable amount of Fe was precipitated on the cathode. Comparative Example 2 In Example 2, electrolysis operation was carried out by electrically connecting the auxiliary electrode and the anode terminal of the bipolar electrolytic cell electrolysis power source without attaching anything. As a result, although the rate of increase in bath voltage was slower than in Comparative Example 1, it reached a bath voltage of about 3.40 V after about 60 days. From this, it has become clear that the method of the present invention is not only very effective as a method for completely preventing corrosion of electrolytic cells, but also a method that can maintain excellent electrolytic performance from the viewpoint of energy saving.
第１図から第３図は本発明における補助電極な
らびに補助整流器回路を付設した塩化アルカリ溶
液の複極式電解装置の各態様を模式的に示した説
明図である。各図において
１は複極式電解槽、２は陰極室液供給管、３は
陰極室生成液抜出管、４は陰極室液供給管の共通
の通路、５は陰極室生成液抜出管の共通の通路、
６は補助電極、７はシリコン整流器、８はガス分
離膜、９はガス抜き管。
1 to 3 are explanatory diagrams schematically showing various aspects of a bipolar electrolyzer for alkaline chloride solution equipped with an auxiliary electrode and an auxiliary rectifier circuit according to the present invention. In each figure, 1 is a bipolar electrolytic cell, 2 is a cathode chamber liquid supply pipe, 3 is a cathode chamber liquid extraction pipe, 4 is a common passage for the cathode chamber liquid supply pipe, and 5 is a cathode chamber liquid extraction pipe. common passage,
6 is an auxiliary electrode, 7 is a silicon rectifier, 8 is a gas separation membrane, and 9 is a gas vent pipe.
Claims (1)
続して構成され、各単位電解槽本体には電気絶縁
性の陰極室液供給管および陰極室生成液抜出管が
設けられ、該陰極室液供給管および／または該陰
極室生成液抜出管には共通の通路を通じて供給液
および／または抜出液を集める様にして構成され
る電解槽プラントにおいて、該陰極室液供給管
内、該陰極室生成液抜出管内、共通の通路内のい
ずれか少なくとも１箇所に補助電極を設け、補助
電極にかかる電圧が複極式電解装置のアノード端
子電圧より0.1V以上高くすることを特徴とする
塩化アルカリ電解槽の防食方法。 ２ 補助電極と複極式電解装置電解用電源のアノ
ード端子間に補助整流器を設け、それらが電気的
に直列接続されていることを特徴とする特許請求
の範囲第１項記載の方法。 ３ 補助電極と複極式電解装置用電源のアノード
端子間にバツテリーまたは燃料電池を設け、それ
らが電気的に直列接続されていることを特徴とす
る特許請求の範囲第１項記載の方法。 ４ 単位電解槽がイオン交換膜を隔膜とした塩化
アルカリ電解槽であることを特徴とする特許請求
の範囲第１項から第３項のいずれかの項に記載の
方法。[Scope of Claims] 1. Consisting of a plurality of metallic unit electrolytic cells electrically connected in series, each unit electrolytic cell body has an electrically insulating cathode chamber liquid supply pipe and cathode chamber produced liquid extraction pipe. In an electrolytic cell plant configured such that the cathode chamber liquid supply pipe and/or the cathode chamber product liquid extraction pipe collect the supply liquid and/or the withdrawn liquid through a common passage, the cathode An auxiliary electrode is provided in at least one of the chamber liquid supply pipe, the cathode chamber produced liquid extraction pipe, and the common passage, and the voltage applied to the auxiliary electrode is 0.1 V or more higher than the anode terminal voltage of the bipolar electrolyzer. A method for preventing corrosion of an alkaline chloride electrolytic cell. 2. The method according to claim 1, characterized in that an auxiliary rectifier is provided between the auxiliary electrode and the anode terminal of the power source for electrolysis in a bipolar electrolyzer, and these are electrically connected in series. 3. The method according to claim 1, wherein a battery or a fuel cell is provided between the auxiliary electrode and the anode terminal of the power source for the bipolar electrolyzer, and these are electrically connected in series. 4. The method according to any one of claims 1 to 3, wherein the unit electrolytic cell is an alkali chloride electrolytic cell using an ion exchange membrane as a diaphragm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58041550A JPS59170280A (en) | 1983-03-15 | 1983-03-15 | Method for preventing corrosion of alkali chloride electrolytic cell |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58041550A JPS59170280A (en) | 1983-03-15 | 1983-03-15 | Method for preventing corrosion of alkali chloride electrolytic cell |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59170280A JPS59170280A (en) | 1984-09-26 |
| JPS6342714B2 true JPS6342714B2 (en) | 1988-08-25 |
Family
ID=12611530
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP58041550A Granted JPS59170280A (en) | 1983-03-15 | 1983-03-15 | Method for preventing corrosion of alkali chloride electrolytic cell |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59170280A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5426229A (en) * | 1977-07-30 | 1979-02-27 | Sumitomo Metal Ind | Mold for continuous casting |
-
1983
- 1983-03-15 JP JP58041550A patent/JPS59170280A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5426229A (en) * | 1977-07-30 | 1979-02-27 | Sumitomo Metal Ind | Mold for continuous casting |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59170280A (en) | 1984-09-26 |
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