JP3966103B2

JP3966103B2 - Operation method of electrodeionization equipment

Info

Publication number: JP3966103B2
Application number: JP2002197567A
Authority: JP
Inventors: 伸佐藤
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2002-07-05
Filing date: 2002-07-05
Publication date: 2007-08-29
Anticipated expiration: 2022-07-05
Also published as: JP2004033977A

Description

【０００１】
【発明の属する技術分野】
本発明は、電気脱イオン装置の運転方法に係り、特にシリカやホウ素の除去率を高めるようにした電気脱イオン装置を停止している間の該電気脱イオン装置の保守管理運転を行う方法に関する。
【０００２】
【従来の技術】
従来、半導体製造工場、液晶製造工場、製薬工業、食品工業、電力工業等の各種の産業又は民生用ないし研究施設等において使用される脱イオン水の製造には、図２に示す如く、電極（陽極１１、陰極１２）の間に複数のアニオン交換膜（Ａ膜）１３及びカチオン交換膜（Ｃ膜）１４を交互に配列して濃縮室１５と脱塩室１６とを交互に形成し、脱塩室１６にイオン交換樹脂、イオン交換繊維もしくはグラフト交換体等からなるアニオン交換体及びカチオン交換体を混合もしくは複層状に充填した電気脱イオン装置が多用されている（特許第１７８２９４３号、特許第２７５１０９０号、特許第２６９９２５６号）。なお、図２において、１７は陽極室、１８は陰極室である。
【０００３】
脱塩室１６に流入したイオンはその親和力、濃度及び移動度に基いてイオン交換体と反応し、電位の傾きの方向にイオン交換体中を移動し、更に膜を横切って移動し、すべての室において電荷の中和が保たれる。そして、膜の半浸透特性のため、及び電位の傾きの方向性のために、イオンは脱塩室１６では減少し、隣りの濃縮室１５では濃縮される。即ち、カチオンはカチオン交換膜１４を透過して、また、アニオンはアニオン交換膜１３を透過して、それぞれ濃縮室１５内に濃縮される。このため、脱塩室１６から生産水として脱イオン水（純水）が回収される。
【０００４】
なお、陽極室１７及び陰極室１８にも電極水が通液されており、一般に、この電極水としては、電気伝導度の確保のためにイオン濃度の高い濃縮室１５の流出水（濃縮水）が通液されている。
【０００５】
即ち、原水は脱塩室１６と濃縮室１５とに導入され、脱塩室１６からは脱イオン水（純水）が取り出される。一方、濃縮室１５から流出するイオンが濃縮された濃縮水は、ポンプ（図示せず）により一部が水回収率の向上のために、濃縮室１５の入口側に循環され、一部が陽極室１７の入口側に送給され、残部が系内のイオンの濃縮を防止するために排水として系外へ排出される。そして、陽極室１７の流出水は、陰極室１８の入口側へ送給され、陰極室１８の流出水は排水として系外へ排出される。
【０００６】
このような電気脱イオン装置にあっては、陽極室１７では、水解離によるＨ^＋の生成でｐＨが低下する。一方、陰極室１８ではＯＨ⁻の生成でｐＨが高くなる。このため、ｐＨが低下した酸性の陽極室１７の流出水を陰極室１８に通液することで、陰極室１８におけるアルカリを中和してスケール障害を抑制している。
【０００７】
このような電気脱イオン装置にあっては、濃縮水の影響で電気脱イオン装置の生産水の水質が影響を受ける可能性があることはこれまでに各種報告されている。また、電極室に活性炭やイオン交換樹脂を充填することは、ＵＳＰ５，８６８，９１５に示されている。
【０００８】
【発明が解決しようとする課題】
従来の電気脱イオン装置にあっては、シリカ及びホウ素の除去が若干不十分であり、例えば、シリカについては９９．９〜９９．９９％以上の除去率を得ることは困難であった。
【０００９】
本出願人は、上記従来の問題点を解決し、シリカ及びホウ素を高度に除去することができる電気脱イオン装置を特願２００１−６７８号にて提案している。
【００１０】
同号の電気脱イオン装置は、陽極を有する陽極室と、陰極を有する陰極室と、これらの陽極室と陰極室との間に複数のアニオン交換膜及びカチオン交換膜を交互に配列することにより交互に形成された濃縮室及び脱塩室とを備え、該脱塩室にイオン交換体が充填され、該濃縮室にイオン交換体、活性炭又は電気導電体が充填されている電気脱イオン装置であって、該陽極室及び陰極室にそれぞれ電極水を通水する手段と、該濃縮室に濃縮水を通水する濃縮水通水手段と、該脱塩室に原水を通水して脱イオン水を取り出す手段とを有する電気脱イオン装置において、該濃縮水通水手段が、該原水よりシリカ又はホウ素濃度の低い水を、脱塩室の脱イオン水取り出し口に近い側から該濃縮室内に導入すると共に、該濃縮室のうち脱塩室の原水入口に近い側から流出させ、この濃縮室から流出した濃縮水の少なくとも一部を系外へ排出する手段であることを特徴とする。
【００１１】
かかる同号の電気脱イオン装置によると、濃縮水として原水よりシリカ又はホウ素濃度の低い水を用い、しかも、このように水質の良好な水を、脱塩室の脱イオン水（生産水）取り出し側から原水流入側へ向かう方向に濃縮室に通水するため、シリカ、ホウ素濃度を極低濃度にまで低減した高水質の生産水を得ることができる。
【００１２】
本発明は、この特願２００１−６７８号の電気脱イオン装置の運転停止時における濃縮室から脱塩室側へのイオンの拡散を防止し、運転再開後、早期に高水質の水を生産することを可能とする電気脱イオン装置の運転方法を提供することを目的とする。
【００１３】
【課題を解決するための手段】
本発明の電気脱イオン装置の運転方法は、陽極を有する陽極室と、陰極を有する陰極室と、これらの陽極室と陰極室との間に複数のアニオン交換膜及びカチオン交換膜を交互に配列することにより交互に形成された濃縮室及び脱塩室と、該脱塩室に充填されたイオン交換体と、該濃縮室に充填されたイオン交換体、活性炭又は電気導電体と、該陽極室及び陰極室にそれぞれ電極水を通水する手段と、該濃縮室に濃縮水を通水する濃縮水通水手段と、該脱塩室に原水を通水して脱イオン水を取り出す手段とを有し、該濃縮水通水手段が、該原水よりシリカ又はホウ素濃度の低い水を、脱塩室の脱イオン水取り出し口に近い側から該濃縮室内に導入すると共に、該濃縮室のうち脱塩室の原水入口に近い側から流出させ、この濃縮室から流出した濃縮水の少なくとも一部を系外へ排出する手段である電気脱イオン装置を運転する方法であって、該原水の供給を停止して該電気脱イオン装置による脱イオン水の製造を停止しているときに、該陽極と陰極との間に電圧を印加し、該濃縮室から脱塩室へのイオンの移動を抑制することを特徴とするものである。
【００１４】
この電気脱イオン装置は、上記特願２００１−６７８号と同一構成のものであり、上記の通り、濃縮水として原水よりシリカ又はホウ素濃度の低い水を用い、しかも、このように水質の良好な水を、脱塩室の脱イオン水（生産水）取り出し側から原水流入側へ向かう方向に濃縮室に通水するため、シリカ、ホウ素濃度を極低濃度にまで低減した高水質の生産水を得ることができる。
【００１５】
本発明の電気脱イオン装置の運転方法では、該原水の供給を停止して該電気脱イオン装置による脱イオン水の製造を停止しているときに、該陽極と陰極との間に電圧を印加し、該濃縮室から脱塩室へのイオンの移動を抑制するので、運転を停止している間における濃縮室から脱塩室側へのイオンの移動が抑制され、運転再開直後から水質の良好な（即ちイオン濃度が低い）脱イオン水が脱塩室から取り出される。
【００１６】
本発明では、運転停止後に濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水と置換し、濃縮室内のイオン濃度の高い水を排出することにより、運転停止中における濃縮室側から脱塩室側へのイオンの拡散を防止することが好ましい。
【００１７】
また、濃縮室内の水がシリカ又はホウ素濃度の低い水に置換されたとしても、濃縮室内のイオン交換体からイオンが脱離し再び濃縮室内のイオン濃度が高くなってくることがあるので、運転停止後、所定時間毎に濃縮室内の水をシリカ又はホウ素濃度の低い水と置換することが望ましい。
【００１８】
なお、濃縮室内にシリカ又はホウ素濃度の低い水を供給する場合、該原水よりシリカ又はホウ素濃度の低い水を、脱塩室の脱イオン水取り出し口に近い側から該濃縮室内に導入すると共に、該濃縮室のうち脱塩室の原水入口に近い側から流出させることが好ましい。これは、濃縮室内のうち濃縮水流出側ほどイオン濃度が高くなっており、このイオン濃度の高い水をそのまま流出口から流出させて濃縮室内への拡散を防ぐためである。
【００１９】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を詳細に説明する。
【００２０】
図１は本発明の実施の形態に係る電気脱イオン装置の運転方法が適用される電気脱イオン装置の模式的な断面図である。この電気脱イオン装置は、図２に示す従来の電気脱イオン装置と同様、電極（陽極１１、陰極１２）の間に複数のアニオン交換膜（Ａ膜）１３及びカチオン交換膜（Ｃ膜）１４を交互に配列して濃縮室１５と脱塩室１６とを交互に形成したものであり、脱塩室１６には、イオン交換樹脂、イオン交換繊維もしくはグラフト交換体等からなるアニオン交換体及びカチオン交換体が混合もしくは複層状に充填されている。
【００２１】
また、濃縮室１５と、陽極室１７及び陰極室１８にも、イオン交換体、活性炭又は金属等の電気導電体が充填されている。
【００２２】
原水は脱塩室１６に導入され、脱塩室１６からは生産水が取り出される。この生産水の一部は、濃縮室１５に脱塩室１６の通水方向とは逆方向に向流一過式で通水され、濃縮室１５の流出水は系外へ排出される。即ち、この電気脱イオン装置では、濃縮室１５と脱塩室１６とが交互に並設され、脱塩室１６の生産水取り出し側に濃縮室１５の流入口が設けられており、脱塩室１６の原水流入側に濃縮室１５の流出口が設けられている。また、生産水の一部は陽極室１７の入口側に送給され、そして、陽極室１７の流出水は、陰極室１８の入口側へ送給され、陰極室１８の流出水は排水として系外へ排出される。
【００２３】
このように、濃縮室１５に生産水を脱塩室１６と向流一過式で通水することにより、生産水取り出し側ほど濃縮室１５内の濃縮水の濃度が低いものとなり、濃度拡散による脱塩室１６への影響が小さくなり、イオン除去率、特にシリカ、ホウ素の除去率を飛躍的に高めることができる。
【００２４】
また、濃縮室にイオン交換体を充填することで、濃縮室のＬＶを２０ｍ／ｈｒ以下としても、脱イオン性能を確保することができる。これは、濃縮室内がスペーサであると、濃縮室膜面におけるシリカ、ホウ素の膜面濃縮を水流により拡散させる必要があったのに対し、濃縮室にイオン交換体等を充填することで、イオン交換体を通じてイオンが拡散するため、高い通水速度（ＬＶ）を必要としないためと考えられる。
【００２５】
このように通水速度が低くても良いため、一過式で濃縮水を通水しても、水回収率は従来よりも向上させることができ、しかも、循環ポンプを用いる必要もないため、さらに経済的である。
【００２６】
濃縮室充填物は、必要電流確保のためには活性炭等でも良いが、上記イオン拡散作用の点から、イオン交換体を充填することが望ましい。
【００２７】
この図１の電気脱イオン装置では、電極室１７，１８にも生産水を供給しているが、電極室１７，１８でも濃縮室１５と同様に、電流確保のために、イオン交換体や活性炭、又は電気導電体である金属等を充填することで、水質によらず消費電圧が一定になり、超純水等の高水質の水を通水しても必要電流を確保することが可能となる。
【００２８】
なお、電極室では、特に陽極室での塩素やオゾン等の酸化剤の発生が起こるため、充填物としては、長期的にはイオン交換樹脂等を用いるよりも、活性炭を用いることが好ましい。また、電極室へ図１のように生産水を供給することは、電極室供給水にＣｌ⁻が殆ど無いため、塩素の発生を防止できるので、充填物や電極の長期安定化のためには望ましい。
【００２９】
なお、電極室は上記のような充填物を用いなくても、電極板の通水面側を多孔質状に加工し、その部分に電極水を通水できるようにしても良く、その場合、電極板と電極室が一体化できるので、組立等が簡単になる等のメリットがある。
【００３０】
ところで、濃縮水の循環を行う場合、全体で循環してしまうと濃縮室の、特に生産水流出側でのシリカ、ホウ素の温度が上がってしまうので、図３のように濃縮室を分断させ、入口側と出口側で濃度勾配をとるようにすれば、生産水質は図１の向流通水と同等のものを得ることができる。
【００３１】
図３（ａ）は本発明の電気脱イオン装置の運転方法が適用される電気脱イオン装置の他の例を示す概略的な斜視図、図３（ｂ）は同系統図である。
【００３２】
図示の如く、この電気脱イオン装置は、陽極１１と陰極１２との間に、カチオン交換膜とアニオン交換膜とを交互に配列して濃縮室１５と脱塩室１６とを交互に形成した点においては従来の電気脱イオン装置と同様の構成とされているが、濃縮室１５が仕切壁１５Ｓにより２以上（図３においては２個）の濃縮水流通部１５Ａ，１５Ｂに区画され、各濃縮水流通部１５Ａ，１５Ｂの濃縮水の通水方向が脱塩室１６内の通水方向と交叉する方向とされている点が従来の電気脱イオン装置と異なる。
【００３３】
即ち、図３において、脱塩室１６は、図３（ａ）における上側が入口側、下側が出口側であり、脱塩室１６内を水は上から下へ向かって流れる。
【００３４】
一方、濃縮室１５内には、この脱塩室１６内の通水方向と交叉する方向（図３（ａ）においては直交方向（なお、この直交方向とは必ずしも厳密なものではなく、８０〜１００゜程度の範囲を含む）に延在する仕切壁１５Ｓが設けられ、濃縮室１５内は図において上下に２段に分画され、各濃縮水流通部１５Ａ，１５Ｂの各々に図の手前側から裏側へ通水が行われる。
【００３５】
図３（ｂ）に示す如く、脱塩室から取り出された生産水の一部はポンプにより循環される濃縮水流通部１５Ｂの循環系に導入され、生産水取り出し側の濃縮水流通部１５Ｂを循環する。この循環系の循環濃縮水の一部がポンプにより循環される濃縮水流通部１５Ａの循環系に導入され、原水流入側の濃縮水流通部１５Ａを循環し、その一部は系外へ排出される。
【００３６】
この電気脱イオン装置であっても、生産水が生産水取り出し側の濃縮水流通部１５Ｂを循環した後原水流入側の濃縮水流通部１５Ａに流入して循環し、その後系外へ排出されることにより、結果的には、濃縮水は、生産水の取り出し側から原水流入側へ通水され、その後一部が系外へ排出されたことになり、図１に示す脱塩室との向流一過式通水の場合と同様の効果が奏される。
【００３７】
なお、濃縮室を仕切壁で仕切って形成する濃縮水流通部は３以上であっても良い。ただし、仕切壁の数を増やすことによる部材数の増加、装置構成の複雑化等を考慮した場合、濃縮室内を２又は３個の濃縮水流通部に区画するのが好ましい。
【００３８】
このような電気脱イオン装置において、シリカのみならず特にホウ素をも除去しようとする際には、脱塩室の厚さが小さいほど良いことが、鋭意研究の結果判明している。脱塩室の厚さは５ｍｍ以下が良く、小さいほど良いが、水の通水性や製作時の取り扱い性等を考慮すると実用上２ｍｍ以上とすることが好ましい。
【００３９】
また、電流確保を行い、濃度拡散の影響を排除することで、シリカ、ホウ素の除去率向上を図ることが本発明の目的であり、電流確保のためには、濃縮室、更には電極室に先に記したような工夫が必要となるが、シリカ、ホウ素高除去のための必要電流は、電流効率として１０％以下に相当する電流値、さらに９９．９％以上のシリカ、ホウ素除去率を得るためには望ましくは電流効率５％以下に相当する電流値が必要となる。なお、電流効率とは以下の式で示される。
電流効率（％）＝１．３１×セル当たり流量（Ｌ／ｍｉｎ）×（原水当量導電率（μＳ／ｃｍ）−処理水当量導電率（μＳ／ｃｍ））／電流（Ａ）
【００４０】
このような電気脱イオン装置では、電気脱イオン装置の原水が高比抵抗であって、この水のシリカやホウ素のみをさらに低減したい場合であっても、必要電流が確保できるので、濃縮室及び電極室のいずれか一方にでも電流が流れなければ、電気脱イオン装置全体の電流が流れなくなるという従来の問題点は解消される。
【００４１】
このため、高比抵抗の原水からさらに、シリカ、ホウ素を除去しようとする場合にも、電気脱イオン装置を用いることができ、従って、電気脱イオン装置の適用水質範囲を大きく広げることができるため、その工業的有用性は極めて大である。
【００４２】
例えば、主として半導体工場の一次純水製造装置として用いた場合、水使用が少なく、原水に生産水が戻されて循環しているような場合でも、必要電流を確保することができ、装置の立ち上げ時等にも安定に起動させることができる。
【００４３】
また、電気脱イオン装置を直列で複数段設置して多段通水するような場合の後段の電気脱イオン装置においても、必要電流を確保することができる。
【００４４】
また、超純水製造工程の二次純水システム（サブシステム）において、比抵抗１０ＭΩ・ｃｍ以上の水を原水としても、必要電流が確保できるので、デミナー（非再生式混床イオン交換装置）の代替として用いることができる。
【００４５】
本発明では、このような電気脱イオン装置の運転を停止しているときに、陽極と陰極との間に電圧を印加し、濃縮室から脱塩室へのイオン移動を抑制する。なお、この場合、陽極には正の電圧を印加し、陰極には負の電圧を印加する。
【００４６】
この運転停止後の印加電圧は、運転停止直後に陽極、陰極間に発生する残留電圧の３０〜２００％特に５０〜１５０％とすることが望ましい。電気脱イオン装置の運転を停止した直後の状態、即ち原水の通水を停止すると共に陽極、陰極間への電圧印加を停止した直後の状態にあっては、陽極側の濃縮室に高濃度に陰イオンが存在し陰極側の濃縮室には高濃度に陽イオンが存在するので、陽極と陰極との間にはイオン分極電圧に相当する電圧が存在（残留）する。本発明者の研究によると、電気脱イオン装置の運転停止後に、この残留電圧の３０〜２００％の電圧を陽極、陰極間に印加することにより、濃縮室側から脱塩室側へのイオン移動が十分に抑制されることが見出された。なお、２００％よりも高い電圧は、エネルギー効率を低下させるとともに装置構成材を損傷させる恐れがある。
【００４７】
長期運転停止の場合、運転停止直後から印加電圧を上記の範囲内で低目の電圧とすることが好ましい。
【００４８】
電気脱イオン装置停止時に印加する電圧は、連続的に印加される必要はなく断続的に印加されても同様の効果が得られる。
【００４９】
なお、イオン交換膜、イオン交換体保護のため、停止中に印加する電圧を低くすると、微量のイオンが拡散する。高純度の脱イオン水製造を目的とした場合は、この微量イオンが脱イオン水製造再開時に問題となることがある。そこで、装置再起動時に通常の運転電流より多くの電流を流すよう定常運転時の印加電圧よりも高い電圧を印加し、処理水比抵抗率、残留イオン濃度を速やかに所定の値まで到達させることが好ましい。この場合の運転再開直後の印加電圧は、定常電圧の１．１〜１．５倍程度が好ましく、また、この高い電圧を印加する時間は０．５〜２ｍｉｎ程度が好ましい。イオン移動防止用の電圧印加の電源は、商用電源である必要はない。充電池や小型発電設備を電源としてもよく、これらを用いることにより、停電時にも電気脱イオン装置内部のイオン逆拡散を防ぎ、停電時復帰時に速やかに所定の水質の脱イオン水を製造することができる。
【００５０】
また、本発明では、この運転停止後に濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水と置換し、濃縮室内のイオン濃度を低下させ、これによって濃縮室から脱塩室へのイオン移動を抑制することが好ましい。さらに、このように原水よりシリカ又はホウ素濃度の低い水と置換しても、その後徐々にイオン交換体からイオンが脱離してきて再び濃縮室内のイオン濃度が高くなってくることがあるので、運転停止後、所定時間毎（例えば１日〜１０日に１回程度の割合）にて濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水と置換することが望ましい。
【００５１】
濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水と置換する場合は、該原水よりシリカ又はホウ素濃度の低い水を、脱塩室の脱イオン水取り出し口に近い側から該濃縮室内に導入すると共に、該濃縮室のうち脱塩室の原水入口に近い側から流出させることが好ましい。
【００５２】
なお、濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水よりも置換する場合、この置換水量は濃縮室内のイオン交換体の体積の４〜２０倍特に５〜１０倍程度が好ましい。
【００５３】
【発明の効果】
以上詳述した通り、本発明によれば、シリカ、ホウ素を高度に除去して高純度の生産水を製造することができる電気脱イオン装置の運転を停止し、その後運転を再開する場合、運転再開後短時間のうちに高水質の脱イオン水を生産することが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る電気脱イオン装置の運転方法が適用される電気脱イオン装置の模式的な断面図である。
【図２】従来の電気脱イオン装置を示す模式的な断面図である。
【図３】図３（ａ）は本発明方法が適用される電気脱イオン装置の他の例を示す概略的な斜視図、図３（ｂ）は同系統図である。
【符号の説明】
１１陽極
１２陰極
１３アニオン交換膜（Ａ膜）
１４カチオン交換膜（Ｃ膜）
１５濃縮室
１５Ａ，１５Ｂ濃縮水流通部
１５Ｓ仕切壁
１６脱塩室
１７陽極室
１８陰極室[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation method of an electrodeionization device, and more particularly to a method of performing maintenance management operation of the electrodeionization device while stopping the electrodeionization device designed to increase the removal rate of silica and boron. .
[0002]
[Prior art]
Conventionally, in the manufacture of deionized water used in various industries such as semiconductor manufacturing factory, liquid crystal manufacturing factory, pharmaceutical industry, food industry, electric power industry, etc. or consumer use or research facilities, as shown in FIG. A plurality of anion exchange membranes (A membranes) 13 and cation exchange membranes (C membranes) 14 are alternately arranged between the anode 11 and the cathode 12) to alternately form the concentration chambers 15 and the desalting chambers 16. An electrodeionization apparatus in which the salt chamber 16 is mixed with an anion exchanger and an cation exchanger made of an ion exchange resin, an ion exchange fiber, a graft exchanger, or the like or filled in multiple layers is used (Japanese Patent No. 17842943, Patent No. 1). 2751090, Japanese Patent No. 2699256). In FIG. 2, 17 is an anode chamber and 18 is a cathode chamber.
[0003]
The ions that flow into the desalting chamber 16 react with the ion exchanger based on their affinity, concentration and mobility, move in the ion exchanger in the direction of the potential gradient, and further move across the membrane. Charge neutralization is maintained in the chamber. The ions are reduced in the desalting chamber 16 and concentrated in the adjacent concentrating chamber 15 due to the semi-osmotic properties of the membrane and the directionality of the potential gradient. That is, cations permeate the cation exchange membrane 14 and anions permeate the anion exchange membrane 13 and are concentrated in the concentration chamber 15 respectively. For this reason, deionized water (pure water) is recovered from the desalting chamber 16 as production water.
[0004]
Electrode water is also passed through the anode chamber 17 and the cathode chamber 18, and in general, as the electrode water, effluent water (concentrated water) from the concentrating chamber 15 having a high ion concentration in order to ensure electrical conductivity. Is being passed.
[0005]
That is, raw water is introduced into the desalting chamber 16 and the concentration chamber 15, and deionized water (pure water) is taken out from the desalting chamber 16. On the other hand, the concentrated water in which the ions flowing out of the concentration chamber 15 are concentrated is partly circulated to the inlet side of the concentration chamber 15 by a pump (not shown) to improve the water recovery rate, and a part of the concentrated water is an anode. It is fed to the inlet side of the chamber 17 and the remainder is discharged out of the system as waste water to prevent the concentration of ions in the system. The outflow water from the anode chamber 17 is fed to the inlet side of the cathode chamber 18, and the outflow water from the cathode chamber 18 is discharged out of the system as waste water.
[0006]
In such an electrodeionization apparatus, in the anode chamber 17, the pH decreases due to the generation of H ⁺ by water dissociation. On the other hand, in the cathode chamber 18, the pH increases due to the generation of OH ⁻ . For this reason, by passing the effluent water of the acidic anode chamber 17 having a lowered pH through the cathode chamber 18, the alkali in the cathode chamber 18 is neutralized and the scale failure is suppressed.
[0007]
In such an electrodeionization apparatus, it has been reported so far that the quality of the production water of the electrodeionization apparatus may be affected by the concentrated water. Also, US Pat. No. 5,868,915 indicates that the electrode chamber is filled with activated carbon or ion exchange resin.
[0008]
[Problems to be solved by the invention]
In the conventional electrodeionization apparatus, the removal of silica and boron is slightly insufficient. For example, it is difficult to obtain a removal rate of 99.9 to 99.99% or more for silica.
[0009]
The present applicant has proposed in Japanese Patent Application No. 2001-678 an electrodeionization apparatus capable of solving the above-mentioned conventional problems and highly removing silica and boron.
[0010]
The electrodeionization apparatus of the same number includes an anode chamber having an anode, a cathode chamber having a cathode, and a plurality of anion exchange membranes and cation exchange membranes arranged alternately between the anode chamber and the cathode chamber. An electric deionization apparatus comprising a concentration chamber and a demineralization chamber formed alternately, wherein the demineralization chamber is filled with an ion exchanger, and the concentration chamber is filled with an ion exchanger, activated carbon or an electric conductor. A means for passing electrode water to each of the anode chamber and the cathode chamber; a concentrated water passage means for passing concentrated water to the concentration chamber; and a deionization by passing raw water to the desalting chamber. In the electrodeionization apparatus having a means for taking out water, the concentrated water flow means feeds water having a lower silica or boron concentration than the raw water into the concentration chamber from the side of the demineralization chamber close to the deionized water outlet. Introducing the raw water inlet of the desalination chamber of the concentration chamber Was allowed to escape near the side, characterized in that at least part of the concentrated water flowing out of the concentrating compartment is a means for discharging to the outside of the system.
[0011]
According to the electrodeionization apparatus of the same number, water having a silica or boron concentration lower than that of the raw water is used as the concentrated water, and water having a good water quality is taken out from the demineralization chamber in this manner. Since the water is passed through the concentrating chamber in the direction from the side toward the raw water inflow side, it is possible to obtain high quality product water in which the silica and boron concentrations are reduced to an extremely low concentration.
[0012]
The present invention prevents diffusion of ions from the concentrating chamber to the desalting chamber when the operation of the electrodeionization apparatus of Japanese Patent Application No. 2001-678 is stopped, and produces high-quality water at an early stage after the operation is resumed. It is an object of the present invention to provide an operation method of an electrodeionization apparatus that makes it possible.
[0013]
[Means for Solving the Problems]
The operation method of the electrodeionization apparatus of the present invention includes an anode chamber having an anode, a cathode chamber having a cathode, and a plurality of anion exchange membranes and cation exchange membranes arranged alternately between the anode chamber and the cathode chamber. Concentration chambers and desalting chambers formed alternately, an ion exchanger filled in the desalting chamber, an ion exchanger, activated carbon or electrical conductor filled in the concentration chamber, and the anode chamber And means for passing electrode water to the cathode chamber, concentrated water passing means for passing concentrated water to the concentration chamber, and means for passing deionized water by passing raw water to the desalting chamber. The concentrated water flow means introduces water having a silica or boron concentration lower than that of the raw water into the concentration chamber from the side close to the deionized water outlet of the demineralization chamber, and removes the concentration from the concentration chamber. Concentrate that flowed out from the side near the raw water inlet of the salt chamber A method of operating an electrodeionization apparatus, which is a means for discharging at least a part of water out of the system, wherein the supply of the raw water is stopped and production of deionized water by the electrodeionization apparatus is stopped Sometimes, a voltage is applied between the anode and the cathode to suppress the movement of ions from the concentration chamber to the desalting chamber.
[0014]
This electrodeionization apparatus has the same configuration as that of the above Japanese Patent Application No. 2001-678, and as described above, water having a lower silica or boron concentration than the raw water is used as the concentrated water, and the water quality is thus excellent. Since water is passed through the concentration chamber in the direction from the deionized water (product water) take-out side of the desalination chamber to the raw water inflow side, high-quality production water with silica and boron concentrations reduced to extremely low concentrations Obtainable.
[0015]
In the operation method of the electrodeionization apparatus of the present invention, when supply of the raw water is stopped and production of deionized water by the electrodeionization apparatus is stopped, a voltage is applied between the anode and the cathode. Since the movement of ions from the concentrating chamber to the desalting chamber is suppressed, the movement of ions from the concentrating chamber to the desalting chamber is suppressed while the operation is stopped. The deionized water (ie, the ion concentration is low) is removed from the desalting chamber.
[0016]
In the present invention, after the operation is stopped, the water in the concentration chamber is replaced with water having a lower silica or boron concentration than the raw water, and the water having a higher ion concentration in the concentration chamber is discharged. It is preferable to prevent diffusion of ions to the side.
[0017]
Also, even if the water in the concentrating chamber is replaced with water having a low silica or boron concentration, the ions may be desorbed from the ion exchanger in the concentrating chamber and the ion concentration in the concentrating chamber may increase again. Thereafter, it is desirable to replace the water in the concentration chamber with water having a low silica or boron concentration every predetermined time.
[0018]
In addition, when supplying water having a low silica or boron concentration into the concentration chamber, water having a lower silica or boron concentration than the raw water is introduced into the concentration chamber from the side near the deionized water outlet of the demineralization chamber, The concentration chamber is preferably discharged from the side close to the raw water inlet of the desalting chamber. This is because the ion concentration is higher on the concentrated water outflow side in the concentration chamber, and this high ion concentration water is directly discharged from the outlet to prevent diffusion into the concentration chamber.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0020]
FIG. 1 is a schematic cross-sectional view of an electrodeionization apparatus to which an operation method of an electrodeionization apparatus according to an embodiment of the present invention is applied. This electrodeionization apparatus, like the conventional electrodeionization apparatus shown in FIG. 2, has a plurality of anion exchange membranes (A membranes) 13 and cation exchange membranes (C membranes) 14 between electrodes (anode 11 and cathode 12). Are alternately arranged to form the concentration chamber 15 and the desalting chamber 16, and the desalting chamber 16 includes an anion exchanger and a cation made of an ion exchange resin, an ion exchange fiber, a graft exchanger, or the like. The exchanger is mixed or packed in multiple layers.
[0021]
The concentration chamber 15, the anode chamber 17, and the cathode chamber 18 are also filled with an electric conductor such as an ion exchanger, activated carbon, or metal.
[0022]
The raw water is introduced into the desalting chamber 16, and the production water is taken out from the desalting chamber 16. A part of this product water is passed through the concentrating chamber 15 in a counter-current and transient manner in the direction opposite to the water passing direction of the desalting chamber 16, and the outflow water of the concentrating chamber 15 is discharged out of the system. That is, in this electric deionization apparatus, the concentrating chambers 15 and the desalting chambers 16 are alternately arranged in parallel, and the inlet of the concentrating chamber 15 is provided on the product water take-out side of the desalting chamber 16. An outlet of the concentrating chamber 15 is provided on the 16 raw water inflow side. Further, a part of the production water is fed to the inlet side of the anode chamber 17, and the effluent water of the anode chamber 17 is fed to the inlet side of the cathode chamber 18, and the effluent water of the cathode chamber 18 is used as drainage. It is discharged outside.
[0023]
In this way, by passing the production water through the concentration chamber 15 in a counter-current and transient manner with the desalination chamber 16, the concentration of the concentrated water in the concentration chamber 15 becomes lower toward the production water take-out side, which is caused by concentration diffusion. The influence on the desalting chamber 16 is reduced, and the ion removal rate, particularly the removal rate of silica and boron, can be dramatically increased.
[0024]
Further, by filling the concentration chamber with an ion exchanger, deionization performance can be ensured even if the LV of the concentration chamber is 20 m / hr or less. This is because when the concentrating chamber is a spacer, it was necessary to diffuse the silica and boron membrane surfaces on the concentrating chamber membrane surface by a water flow, but by filling the concentrating chamber with an ion exchanger, etc. This is probably because ions diffuse through the exchanger so that a high water flow rate (LV) is not required.
[0025]
Since the water flow rate may be low in this way, even if the concentrated water is passed through in a transient manner, the water recovery rate can be improved as compared with the conventional one, and it is not necessary to use a circulation pump. It is more economical.
[0026]
The concentrating chamber filling may be activated carbon or the like in order to secure the necessary current, but it is preferable to fill the ion exchanger from the viewpoint of the ion diffusion action.
[0027]
In the electrodeionization apparatus of FIG. 1, the product water is also supplied to the electrode chambers 17 and 18, but in the electrode chambers 17 and 18 as well as the concentration chamber 15, an ion exchanger or activated carbon is used to secure current. Or, by filling metal or the like that is an electrical conductor, the consumption voltage becomes constant regardless of the water quality, and it is possible to secure the necessary current even when passing high quality water such as ultrapure water. Become.
[0028]
In the electrode chamber, since generation of oxidizing agents such as chlorine and ozone occurs in the anode chamber in particular, it is preferable to use activated carbon as a filling material in the long term rather than using an ion exchange resin or the like. Further, supplying the production water to the electrode chamber as shown in FIG. 1 can prevent generation of chlorine because there is almost no Cl ^{− in} the electrode chamber supply water. desirable.
[0029]
In addition, the electrode chamber may be made porous so that the water passage surface side of the electrode plate can be made porous without using the filler as described above, and in this case, the electrode water can be passed. Since the plate and the electrode chamber can be integrated, there are advantages such as easy assembly.
[0030]
By the way, when circulating the concentrated water, if it is circulated as a whole, the temperature of the silica and boron in the concentration chamber, particularly on the outflow side of the production water, will rise, so the concentration chamber is divided as shown in FIG. If the concentration gradient is taken on the inlet side and the outlet side, the quality of the produced water can be equivalent to that of the counter-flowing water shown in FIG.
[0031]
FIG. 3A is a schematic perspective view showing another example of the electrodeionization apparatus to which the operation method of the electrodeionization apparatus of the present invention is applied, and FIG. 3B is the same system diagram.
[0032]
As shown in the figure, this electrodeionization apparatus is configured such that a cation exchange membrane and an anion exchange membrane are alternately arranged between an anode 11 and a cathode 12 to alternately form concentration chambers 15 and demineralization chambers 16. However, the concentrating chamber 15 is divided into two or more (two in FIG. 3) concentrated water circulation portions 15A and 15B by the partition wall 15S. The point from which the water flow direction of the concentrated water of water distribution part 15A, 15B is made into the direction which crosses the water flow direction in the demineralization chamber 16 differs from the conventional electrodeionization apparatus.
[0033]
That is, in FIG. 3, in the desalting chamber 16, the upper side in FIG. 3A is the inlet side and the lower side is the outlet side, and water flows in the desalting chamber 16 from the top to the bottom.
[0034]
On the other hand, in the concentrating chamber 15, the direction intersecting with the water flow direction in the desalting chamber 16 (the orthogonal direction in FIG. 3A (note that this orthogonal direction is not necessarily strict, Partition wall 15S extending in a range (including a range of about 100 °), and the inside of the concentrating chamber 15 is divided into two stages in the upper and lower parts in the figure, and each of the concentrated water circulation parts 15A and 15B has a front side in the figure. Water is carried from one side to the other side.
[0035]
As shown in FIG. 3 (b), a part of the product water taken out from the desalination chamber is introduced into the circulation system of the concentrated water circulation part 15B circulated by a pump, and the concentrated water circulation part 15B on the production water take-out side is introduced. Circulate. A part of the circulated concentrated water in this circulatory system is introduced into the circulatory system of the concentrated water circulation part 15A circulated by the pump, circulates through the concentrated water circulation part 15A on the raw water inflow side, and a part thereof is discharged out of the system. The
[0036]
Even in this electrodeionization apparatus, the production water circulates through the concentrated water circulation section 15B on the production water take-out side, then flows into the concentrated water circulation section 15A on the raw water inflow side, circulates, and is then discharged out of the system. As a result, the concentrated water is passed from the product water take-out side to the raw water inflow side, and then a part of the concentrate is discharged out of the system. The same effect as in the case of flow-through water flow is achieved.
[0037]
In addition, the concentration water circulation part formed by partitioning the concentration chamber with a partition wall may be three or more. However, considering the increase in the number of members by increasing the number of partition walls, the complexity of the apparatus configuration, and the like, it is preferable to partition the concentration chamber into two or three concentrated water circulation portions.
[0038]
In such an electrodeionization apparatus, when it is attempted to remove not only silica but also boron in particular, it has been found as a result of intensive studies that the thickness of the demineralization chamber is better. The thickness of the desalting chamber is preferably 5 mm or less, and the smaller the better, but in view of water permeability, handling at the time of production, etc., it is preferably 2 mm or more in practice.
[0039]
Further, it is an object of the present invention to improve the removal rate of silica and boron by securing the current and eliminating the influence of concentration diffusion. In order to secure the current, the concentration chamber and further the electrode chamber are used. Although the devices described above are required, the current required for high removal of silica and boron is a current value equivalent to 10% or less as a current efficiency, and further silica and boron removal rate of 99.9% or more. In order to obtain this, a current value corresponding to a current efficiency of 5% or less is required. The current efficiency is expressed by the following formula.
Current efficiency (%) = 1.31 × flow rate per cell (L / min) × (raw water equivalent conductivity (μS / cm) −treated water equivalent conductivity (μS / cm)) / current (A)
[0040]
In such an electrodeionization apparatus, even if the raw water of the electrodeionization apparatus has a high specific resistance and it is desired to further reduce only the silica and boron of the water, the necessary current can be secured, If the current does not flow in any one of the electrode chambers, the conventional problem that the current of the entire electrodeionization apparatus does not flow is solved.
[0041]
For this reason, even when trying to remove silica and boron from raw water having a high specific resistance, an electrodeionization device can be used, and therefore the applicable water quality range of the electrodeionization device can be greatly expanded. The industrial utility is extremely large.
[0042]
For example, when it is used mainly as a primary pure water production device in a semiconductor factory, the required current can be secured even when the production water is returned to the raw water and circulated. It can be activated stably even when it is raised.
[0043]
In addition, the necessary current can be ensured also in the latter-stage electrodeionization apparatus in which the electrodeionization apparatus is installed in a plurality of stages in series and multistage water flow is performed.
[0044]
In addition, in the secondary pure water system (subsystem) of the ultrapure water production process, the necessary current can be secured even if water with a specific resistance of 10 MΩ · cm or more is used as the raw water, so the deminer (non-regenerative mixed bed ion exchange device) Can be used as an alternative.
[0045]
In the present invention, when the operation of such an electrodeionization apparatus is stopped, a voltage is applied between the anode and the cathode to suppress ion movement from the concentration chamber to the demineralization chamber. In this case, a positive voltage is applied to the anode and a negative voltage is applied to the cathode.
[0046]
The applied voltage after the operation is stopped is preferably 30 to 200%, particularly 50 to 150% of the residual voltage generated between the anode and the cathode immediately after the operation is stopped. In a state immediately after the operation of the electrodeionization apparatus is stopped, that is, in a state immediately after the flow of raw water is stopped and the voltage application between the anode and the cathode is stopped, the concentration chamber in the anode side has a high concentration. Since anions are present and cations are present at a high concentration in the cathode-side concentration chamber, a voltage corresponding to the ion polarization voltage exists (residual) between the anode and the cathode. According to the research of the present inventor, after the operation of the electrodeionization apparatus is stopped, by applying a voltage of 30 to 200% of the residual voltage between the anode and the cathode, the ion movement from the concentration chamber side to the demineralization chamber side. Has been found to be sufficiently suppressed. Note that a voltage higher than 200% may reduce the energy efficiency and damage the device constituent materials.
[0047]
In the case of long-term operation stop, it is preferable to set the applied voltage to a lower voltage within the above range immediately after the operation stop.
[0048]
The voltage applied when the electrodeionization apparatus is stopped need not be applied continuously, and the same effect can be obtained even when applied intermittently.
[0049]
In order to protect the ion exchange membrane and the ion exchanger, a small amount of ions diffuses when the voltage applied during the stop is lowered. For the purpose of producing high-purity deionized water, these trace ions may cause problems when resuming production of deionized water. Therefore, apply a voltage higher than the applied voltage during steady operation so that more current than normal operation current flows when the device is restarted, so that the specific resistance of the treated water and the residual ion concentration can quickly reach the predetermined values. Is preferred. In this case, the applied voltage immediately after resuming operation is preferably about 1.1 to 1.5 times the steady voltage, and the time for applying this high voltage is preferably about 0.5 to 2 minutes. The power supply for voltage application for preventing ion migration need not be a commercial power supply. Rechargeable batteries and small power generation facilities may be used as power sources, and by using these, it is possible to prevent ion back-diffusion inside the electrodeionization device even during a power failure, and to quickly produce deionized water with a predetermined water quality upon recovery from a power failure Can do.
[0050]
In the present invention, after the operation is stopped, the water in the concentrating chamber is replaced with water having a lower silica or boron concentration than the raw water, and the ion concentration in the concentrating chamber is lowered, thereby moving ions from the concentrating chamber to the desalting chamber. It is preferable to suppress. Furthermore, even if the silica or boron having a lower concentration than the raw water is replaced in this way, ions may gradually be desorbed from the ion exchanger and the ion concentration in the concentration chamber may increase again. After stopping, it is desirable to replace the water in the concentration chamber with water having a lower silica or boron concentration than the raw water every predetermined time (for example, about once every 1 to 10 days).
[0051]
When replacing the water in the concentrating chamber with water having a lower silica or boron concentration than the raw water, water having a lower silica or boron concentration than the raw water is introduced into the concentrating chamber from the side near the deionized water outlet of the desalting chamber. At the same time, it is preferable that the concentration chamber is discharged from the side close to the raw water inlet of the desalting chamber.
[0052]
In addition, when substituting the water in a concentration chamber rather than the water whose silica or boron concentration is lower than raw | natural water, the amount of this replacement water is 4-20 times the volume of the ion exchanger in a concentration chamber, and about 5-10 times are preferable.
[0053]
【The invention's effect】
As described above in detail, according to the present invention, when the operation of the electrodeionization apparatus capable of producing high-purity product water by highly removing silica and boron is stopped, and then the operation is resumed, High-quality deionized water can be produced within a short time after resumption.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an electrodeionization apparatus to which an operation method of an electrodeionization apparatus according to an embodiment of the present invention is applied.
FIG. 2 is a schematic cross-sectional view showing a conventional electrodeionization apparatus.
FIG. 3 (a) is a schematic perspective view showing another example of an electrodeionization apparatus to which the method of the present invention is applied, and FIG. 3 (b) is a similar system diagram.
[Explanation of symbols]
11 Anode 12 Cathode 13 Anion exchange membrane (A membrane)
14 Cation exchange membrane (C membrane)
15 Concentration chambers 15A, 15B Concentrated water circulation section 15S Partition wall 16 Desalination chamber 17 Anode chamber 18 Cathode chamber

Claims

陽極を有する陽極室と、
陰極を有する陰極室と、
これらの陽極室と陰極室との間に複数のアニオン交換膜及びカチオン交換膜を交互に配列することにより交互に形成された濃縮室及び脱塩室と、
該脱塩室に充填されたイオン交換体と、
該濃縮室に充填されたイオン交換体、活性炭又は電気導電体と、
該陽極室及び陰極室にそれぞれ電極水を通水する手段と、
該濃縮室に濃縮水を通水する濃縮水通水手段と、
該脱塩室に原水を通水して脱イオン水を取り出す手段とを有し、
該濃縮水通水手段が、該原水よりシリカ又はホウ素濃度の低い水を、脱塩室の脱イオン水取り出し口に近い側から該濃縮室内に導入すると共に、該濃縮室のうち脱塩室の原水入口に近い側から流出させ、この濃縮室から流出した濃縮水の少なくとも一部を系外へ排出する手段である電気脱イオン装置を運転する方法であって、
該原水の供給を停止して該電気脱イオン装置による脱イオン水の製造を停止しているときに、該陽極と陰極との間に電圧を印加し、該濃縮室から脱塩室へのイオンの移動を抑制することを特徴とする電気脱イオン装置の運転方法。An anode chamber having an anode;
A cathode chamber having a cathode;
A concentration chamber and a desalting chamber alternately formed by alternately arranging a plurality of anion exchange membranes and cation exchange membranes between the anode chamber and the cathode chamber;
An ion exchanger filled in the desalting chamber;
An ion exchanger, activated carbon or electrical conductor filled in the concentrating chamber;
Means for passing electrode water through the anode chamber and the cathode chamber,
Concentrated water flow means for passing concentrated water through the concentration chamber;
Means for passing raw water through the desalting chamber and taking out deionized water;
The concentrated water flow means introduces water having a silica or boron concentration lower than that of the raw water into the concentration chamber from the side close to the deionized water outlet of the demineralization chamber. A method of operating an electrodeionization apparatus, which is a means for draining at least part of the concentrated water flowing out from the side close to the raw water inlet and out of the system,
When supply of the raw water is stopped and production of deionized water by the electrodeionization apparatus is stopped, a voltage is applied between the anode and the cathode, and ions from the concentration chamber to the demineralization chamber The operation method of the electrodeionization apparatus characterized by suppressing the movement of the ionization apparatus.

請求項１において、前記運転停止後に前記濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水と置換することを特徴とする電気脱イオン装置の運転方法。2. The operation method of an electrodeionization apparatus according to claim 1, wherein after the operation is stopped, the water in the concentration chamber is replaced with water having a lower silica or boron concentration than the raw water.

請求項２において、運転停止後、所定時間毎に前記濃縮室内の水を原水よりシリカ又はホウ素濃度の低い水と置換することを特徴とする電気脱イオン装置の運転方法。3. The operation method of an electrodeionization apparatus according to claim 2, wherein after the operation is stopped, the water in the concentration chamber is replaced with water having a lower silica or boron concentration than the raw water every predetermined time.

請求項２又は３において、前記置換を行うときに、該原水よりシリカ又はホウ素濃度の低い水を、脱塩室の脱イオン水取り出し口に近い側から該濃縮室内に導入すると共に、該濃縮室のうち脱塩室の原水入口に近い側から流出させることを特徴とする電気脱イオン装置の運転方法。4. When performing the substitution according to claim 2, water having a lower silica or boron concentration than that of the raw water is introduced into the concentration chamber from the side close to the deionized water outlet of the demineralization chamber, and the concentration chamber The operation method of the electrodeionization apparatus characterized by making it flow out from the side near the raw | natural water inlet of a desalination chamber among these.