JP3901107B2

JP3901107B2 - Electrodeionization apparatus and operation method thereof

Info

Publication number: JP3901107B2
Application number: JP2003043701A
Authority: JP
Inventors: 伸佐藤
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2003-02-21
Filing date: 2003-02-21
Publication date: 2007-04-04
Anticipated expiration: 2023-02-21
Also published as: JP2004261648A

Description

【０００１】
【発明の属する技術分野】
本発明は、アニオン濃度の低い生産水を生産するための電気脱イオン装置及びその運転方法に関する。
【０００２】
【従来の技術】
純水、超純水等を製造する分野などにおいて電気脱イオン装置が用いられている。プレートアンドフレーム型の電気脱イオン装置は、陽極と、陰極と、該陽極、陰極間に濃縮室と脱塩室（希釈室）とを交互に形成するように交互に配置された平膜状の陽イオン交換膜及び陰イオン交換膜を有する。脱塩室にはイオン交換樹脂等のイオン交換体が充填されている。この脱塩室に脱塩処理すべき水が流通され、水中のイオンがイオン交換膜を透過して脱塩室から濃縮室に移動する。
【０００３】
特開２００２−２０５０６９号には、シリカ濃度及びホウ素濃度の低い生産水を生産するために、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、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ことが記載されている。
【０００４】
同号公報では、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ことにより、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。
【０００５】
【特許文献１】
特開２００２−２０５０６９号公報
【０００６】
【発明が解決しようとする課題】
本発明は、濃縮室からの炭酸イオン等のアニオンの濃度拡散を十分に抑制し、これにより極低炭酸濃度の生産水を得ることができる電気脱イオン装置の運転方法と電気脱イオン装置を提供することを目的とする。
【０００７】
【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、脱イオン装置の運転方法であって、被処理水を該脱塩室に流通させ、濃縮水を該濃縮室に流通させる運転方法において、該濃縮水として、アニオン除去処理手段で処理された低アニオン濃度水を、脱塩室出口に近い側から該濃縮室に流入させると共に、脱塩室入口に近い側から流出させるように該濃縮室に流通させることを特徴とするものである。
【０００８】
また、本発明の電気脱イオン装置は、陽極と陰極との間にイオン交換膜によって濃縮室と脱塩室とが区画され、被処理水が該脱塩室に流通され、濃縮水が該濃縮室に流通される電気脱イオン装置において、該濃縮水を脱塩室出口に近い側から該濃縮室に流入させると共に脱塩室入口に近い側から流出させるように濃縮水導入手段及び流出手段が設けられており、且つ、該濃縮室に流入する濃縮水からアニオンを除去する手段が設けられていることを特徴とするものである。
【０００９】
本発明では、炭酸等のアニオン濃度が著しく低い高純度の生産水の製造するために、濃縮室に供給される濃縮水の炭酸等のアニオン濃度を低くする。
【００１０】
これにより、濃縮室の出口近傍においても濃縮室から脱塩室に向うアニオン濃度勾配が比較的小さくなり、濃縮室から脱塩室への炭酸の拡散が抑制され、生産水の炭酸濃度を低くすることができる。
【００１１】
本発明では、濃縮室に流入する濃縮水の全無機炭酸濃度を５０ｐｐｂ以下とすることにより、濃縮室から脱塩室への炭酸イオンの濃度勾配による拡散を抑制し、全無機炭酸濃度が著しく低い生産水を生産することが可能となる。
【００１２】
本発明では、同様に、濃縮室に流入する濃縮水のシリカ濃度を１００ｐｐｂ以下とし、またホウ素濃度を１０ｐｐｂ以下とすることにより、これらのイオンの濃縮室から脱塩室への濃度勾配による拡散を抑制し、生産水中のシリカ濃度及びホウ素を著しく低くすることができる。
【００１３】
濃縮水に流入する濃縮水中の全無機炭酸濃度や、シリカ濃度あるいはホウ素濃度を低下させるために、脱塩室から流出する生産水の一部を濃縮水として用いてもよい。また、濃縮室に供給する水をイオン交換装置や電気脱イオン装置で処理してもよい。
【００１４】
濃縮室に流入する濃縮水中の全無機炭酸濃度を低下させるために、脱気膜装置などの脱気手段を用いてもよい。
【００１５】
本発明では、原水をアニオン除去処理した後、脱塩室に供給してもよく、これにより、生産水のアニオン濃度をさらに低下させることができる。このアニオン除去処理としては、逆浸透処理及び脱気処理が好適であり、特に多段に逆浸透処理し、さらに脱気処理することが好適である。
【００１６】
【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。
【００１７】
図１は本発明の実施の形態を示す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１０は、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。
【００１８】
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もよい。
【００１９】
被処理水は脱塩室１６に導入され、脱塩室１６からは生産水が取り出される。被処理水の一部はアニオン除去手段９に送られ、アニオン除去処理される。このアニオン除去処理手段９でアニオンが除去された水は、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。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。これにより、濃縮水は濃縮室１５に対し脱塩室出口側（図１の下側）から流入し、脱塩室入口側（図１の上側）から流出する。
【００２０】
また、アニオン除去手段９から流出した水の一部は陽極室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。なお、陽極室１７の入口水はアニオン除去手段を経ない被処理水でも良い。
【００２１】
このように、濃縮室１５にアニオン除去処理水を脱塩室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、強アニオンのみならず炭酸、シリカ、ホウ素等の弱アニオンの除去率も飛躍的に高めることができる。この電気脱イオン装置によれば、比抵抗が１８ＭΩ・ｃｍ以上の生産水を生産することが可能である。
【００２２】
なお、濃縮室に通水されるアニオン除去処理水の導電率が低く、電気脱イオン装置の電気抵抗が高くなるときには、濃縮室にイオン交換体等の導電体を充填する。これにより、濃縮水に食塩等の電解質を添加し電気抵抗を下げることが不要となる。電極室１７，１８にも、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が好ましい。これにより、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。
【００２３】
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。
【００２４】
図２は、この図１の電気脱イオン装置の脱塩室及び濃縮室への通水系統を簡略化して示したものである。図示の通り、被処理水が脱塩室１６に通水されて生産水となる。被処理水の一部がアニオン除去処理後、濃縮室１５に通水され、濃縮排水として排出される。濃縮室内の水の流れ方向は脱塩室１６内の反対（向流）である。
【００２５】
このアニオン除去手段９により、全無機炭酸濃度を５０ｐｐｂ以下好ましくは３０ｐｐｂ以下とすることにより、生産水中の全無機炭酸濃度が著しく低くなる。また、アニオン除去手段９により、シリカ濃度を１００ｐｐｂ以下好ましくは８０ｐｐｂ以下とし、ホウ素濃度を１０ｐｐｂ以下、好ましくは８ｐｐｂ以下とすることにより、生産水中のシリカ濃度及びホウ素濃度を著しく低下させることができる。
【００２６】
前記アニオン除去手段９としては、脱気膜装置、脱炭酸塔、真空脱気塔などの脱気装置のほか、逆浸透膜分離装置、電気透析装置、アニオン交換体を含むイオン交換樹脂塔等のイオン交換装置または電気脱イオン装置が例示される。
【００２７】
なお、炭酸除去のために、脱気膜、脱炭酸塔、真空脱気塔等の脱気手段を含むことが望ましい。特に真空吸引方式（例えば２０Ｔｏｒｒ以下）、または窒素等によるスイープ方式、あるいは両者を行う脱気膜処理装置は炭酸除去効率に優れている。
【００２８】
図３は、アニオン除去手段９として電気脱イオン装置８を採用した場合の一例を示す系統図である。この電気脱イオン装置８は陽極と陰極との間にアニオン膜８ａとカチオン膜８ｃとによって脱塩室８Ｄと濃縮室８Ａ，８Ｂを形成したものである。被処理水は各室８Ａ，８Ｂ，８Ｄに並流にて流通され、脱塩室８Ｄからの脱塩水と濃縮室８Ｂからの濃縮水とが電気脱イオン装置１０の濃縮水１５の脱塩室出口側に供給され、脱塩室入口側から流出する。この電気脱イオン装置８では脱塩室８Ｄのアニオン膜８ａ側の濃縮室８Ａとカチオン膜８ｃ側の濃縮室８Ｂがあり、濃縮室８Ａに濃縮されたアニオン成分のみ排出され、カチオンが濃縮された濃縮室８Ｂは脱塩室８Ｄからの脱塩水と共に、電気脱イオン装置１０の濃縮室１５に供給される。この電気脱イオン装置８は、このようにアニオン成分のみを除去、低減するものである。
【００２９】
本発明では、脱塩室に供給される被処理水としてアニオン除去処理されたものを用いてもよく、このようにすることにより、脱塩室のアニオン負荷が軽減されるので、弱アニオン濃度がさらに低レベルとなった生産水を得ることができる。このアニオン除去処理としては、脱気処理、逆浸透処理等が好適である。活性炭により有機成分を吸着除去したり、塩素をイオン化することも好適である。
【００３０】
脱塩室への給水からアニオン除去処理により炭酸イオンを除去する場合には、アニオン除去手段として、脱気手段（特に膜脱気装置）を用いることが特に好ましい。また、脱気処理水の一部を、脱気装置入口に再循環させて炭酸除去効率を上げることが望ましい。
【００３１】
炭酸除去のための脱気処理においては、流入水を酸性好ましくはｐＨ４〜６、更に好ましくはｐＨ４〜５に調整して、炭酸除去効率を上げることが望ましい。
【００３２】
また、脱気膜のガス側を真空ポンプで吸引する場合は、真空度を５０Ｔｏｒｒ以下、更に好ましくは２０Ｔｏｒｒ以下とすることが、炭酸除去効率を上げる点で望ましい。
【００３３】
原水を逆浸透処理（以下ＲＯ処理ということがある。）する場合、多段、例えば２段に処理を行うことにより、炭酸、シリカ、ホウ素等の弱アニオン成分を十分に低減させることが望ましい。
【００３４】
この場合、１段目及び／又は２段目のＲＯ入口水をアルカリ性（ｐＨ８〜１０）とすることにより、弱アニオン成分の除去効率が向上する。
【００３５】
また、このアルカリ性とするためのアルカリ生成手段として、特開２００１−１１３２８１号で示されている脱塩室厚さ７ｍｍ以上（好ましくは１５ｍｍ）でアニオン／カチオンの混合イオン交換体を充填した電気脱イオン装置を用いてもよい。このようにすると、アルカリ生成と同時に、弱アニオン成分も低減される。このような電気脱イオン装置は、１段目と２段目のＲＯ装置の間に配置されるのが望ましい。
【００３６】
前処理としては、上記２段ＲＯ処理と脱気処理を含むことが、超高純度の超純水、例えば比抵抗１８．２ＭΩ・ｃｍ以上、シリカ濃度０．０５ｐｐｂ以下、ホウ素０．００５ｐｐｂ以下の処理水を得るには特に好適である。
【００３７】
上述の前処理装置を電気脱イオン装置１０の前段に配置した構成例を図４〜７に示す。
【００３８】
図４では、原水を脱気膜装置１によって脱気して電気脱イオン装置１０の被処理水としている。なお、脱気膜装置１の脱気処理水の一部は該装置１の上流側に返送され、繰り返し処理されている。
【００３９】
図５では、原水を活性炭吸着塔２と２段のＲＯ装置３，３に通水して被処理水としている。
【００４０】
図６では、原水を活性炭吸着塔２、第１のＲＯ装置３、電気脱イオン装置４、第２のＲＯ装置３によって処理して電気脱イオン装置１０の被処理水としている。なお、電気脱イオン装置４としては例えば特開２００１−１１３２８１号の電気脱イオン装置を用いることができるが、これに限定されるものではない。
【００４１】
図７では、原水を活性炭吸着塔２、２段のＲＯ装置３，３、脱気膜装置１によって処理し、電気脱イオン装置１０の被処理水としている。
【００４２】
本発明では、濃縮室に供給される濃縮水からアニオンを除去する手段は、電気脱イオン装置１０そのものであってもよい。即ち、図８のように、被処理水の全量を電気脱イオン装置１０の脱塩室１６に流通させ、その生産水の一部を濃縮室１５に脱塩室出口側から脱塩室入口側に向って流通させてもよい。
【００４３】
本発明では、電気脱イオン装置１０を多段に設置し、原水を多段に脱イオン処理してもよい。
【００４４】
図９は、このように電気脱イオン装置１０（１０Ａ，１０Ｂ）を多段に設置した電気脱イオンシステムの通水系統図であり、第１の電気脱イオン装置１０Ａと第２の電気脱イオン装置１０Ｂとを直列に接続している。
【００４５】
図９の電気脱イオンシステムでは、被処理水が第１の電気脱イオン装置１０Ａの脱塩室１６Ａに通水されて１次生産水となる。この１次生産水が第２の電気脱イオン装置の脱塩室１６Ｂに流通される。濃縮室１５Ａ，１５Ｂの濃縮水の流通方向は脱塩室１６Ａ，１６Ｂと向流方向である。該脱塩室１６Ｂからの２次生産水（生産水）が取り出され、その一部が濃縮室１５Ｂに供給される。第２の電気脱イオン装置２の濃縮室１５Ｂから流出する濃縮水はアニオン濃度が低いものであり、該濃縮室１５Ａに供給される。
【００４６】
第１の電気脱イオン装置１の濃縮室１５Ａからの流出水は、濃縮排水として排出される。
【００４７】
本発明では、脱塩室の厚さは２〜７ｍｍ、流速はＬＶ＝６０〜１２０ｍ／ｈ、ＳＶ＝１００〜２００／ｈが好ましい。濃縮室の厚さは２〜７ｍｍ、流速はＬＶ＝１０〜３０ｍ／ｈ、ＳＶ＝２５〜５０／ｈが好ましい。また、脱塩室、濃縮室ともにイオン交換体が充填され、特にアニオンカチオンの混合で充填されており、電流密度３００〜７００ｍＡ／ｄｍ^２で運転されることが好ましい。濃縮室に供給する水は、循環ポンプ等で濃縮室入口に再循環させずに、一過式様とすることが望ましい。
【００４８】
また、図９のように複数の脱塩室に直列に通水する場合には、特に最終段の脱塩室にて、上記となるようにすることが望ましい。
【００４９】
【発明の効果】
以上の通り、本発明の電気脱イオン装置及びその運転方法によるとアニオン濃度特に全無機炭酸濃度が著しく低い生産水を確実に生産することが可能となる。
【図面の簡単な説明】
【図１】実施の形態に係る電気脱イオン装置の模式的な断面図である。
【図２】図１の電気脱イオン装置の通水系統図である。
【図３】別の実施の形態に係る電気脱イオンシステムの通水系統図である。
【図４】さらに別の実施の形態に係る電気脱イオンシステムの通水系統図である。
【図５】異なる実施の形態に係る電気脱イオンシステムの通水系統図である。
【図６】実施の形態に係る電気脱イオンシステムの通水系統図である。
【図７】実施の形態に係る電気脱イオンシステムの通水系統図である。
【図８】実施の形態に係る電気脱イオンシステムの通水系統図である。
【図９】実施の形態に係る電気脱イオンシステムの通水系統図である。
【符号の説明】
１０電気脱イオン装置
１１陽極
１２陰極
１５，１５Ａ，１５Ｂ濃縮室
１６，１６Ａ，１６Ｂ脱塩室[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrodeionization apparatus for producing product water having a low anion concentration and an operation method thereof.
[0002]
[Prior art]
Electrodeionization apparatuses are used in the field of producing pure water, ultrapure water, and the like. The plate-and-frame type electrodeionization apparatus is a flat membrane-like arrangement in which an anode, a cathode, and a concentration chamber and a desalting chamber (dilution chamber) are alternately formed between the anode and the cathode. It has a cation exchange membrane and an anion exchange membrane. The desalting chamber is filled with an ion exchanger such as an ion exchange resin. Water to be desalted is circulated in the desalting chamber, and ions in the water pass through the ion exchange membrane and move from the desalting chamber to the concentration chamber.
[0003]
In JP-A-2002-205069, in order to produce production water having a low silica concentration and a boron concentration, water having a lower silica or boron concentration than the raw water is used as the concentrated water, close to the deionized water outlet of the demineralization chamber. It is described that it is introduced into the concentrating chamber from the side, is allowed to flow out of the concentrating chamber from the side near the raw water inlet of the desalting chamber, and at least part of the concentrated water that has flowed out of the concentrating chamber is discharged out of the system. ing.
[0004]
In this publication, water having a lower silica or boron concentration than the raw water is used as the concentrated water, and water having a good water quality is transferred from the deionized water (product water) extraction side of the desalting chamber to the raw water inflow side. By passing water through the concentrating chamber in the direction to go, it is possible to obtain high-quality product water in which the silica and boron concentrations are reduced to an extremely low concentration.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-205069
[Problems to be solved by the invention]
The present invention provides an operation method of an electrodeionization apparatus and an electrodeionization apparatus capable of sufficiently suppressing concentration diffusion of anions such as carbonate ions from a concentration chamber, thereby obtaining production water having an extremely low carbonate concentration. The purpose is to do.
[0007]
[Means for Solving the Problems]
The operation method of the electrodeionization apparatus of the present invention is an operation method of the deionization apparatus, wherein the water to be treated is circulated to the demineralization chamber and the concentrated water is circulated to the concentration chamber. As described above, the low anion concentration water treated by the anion removal treatment means is allowed to flow into the concentration chamber from the side close to the desalting chamber outlet and to the concentration chamber so as to flow out from the side close to the desalting chamber inlet. It is characterized by this.
[0008]
In the electrodeionization apparatus of the present invention, the concentration chamber and the desalination chamber are partitioned by an ion exchange membrane between the anode and the cathode, the water to be treated is circulated through the desalination chamber, and the concentrated water is concentrated. In the electrodeionization apparatus circulated through the chamber, the concentrated water introducing means and the outflow means are arranged so that the concentrated water flows into the concentrating chamber from the side close to the desalting chamber outlet and flows out from the side close to the desalting chamber inlet. It is provided and a means for removing anions from the concentrated water flowing into the concentration chamber is provided.
[0009]
In the present invention, in order to produce high-purity production water having a remarkably low concentration of anions such as carbonic acid, the concentration of anions such as carbonic acid in concentrated water supplied to the concentration chamber is lowered.
[0010]
As a result, even in the vicinity of the outlet of the concentrating chamber, the anion concentration gradient from the concentrating chamber to the desalting chamber is relatively small, so that the diffusion of carbon dioxide from the concentrating chamber to the desalting chamber is suppressed, and the carbonate concentration of the production water is lowered. be able to.
[0011]
In the present invention, the concentration of the total inorganic carbonate in the concentrated water flowing into the concentration chamber is set to 50 ppb or less, so that diffusion due to the concentration gradient of carbonate ions from the concentration chamber to the desalting chamber is suppressed, and the total inorganic carbonate concentration is extremely low. Production water can be produced.
[0012]
In the present invention, similarly, by setting the silica concentration of the concentrated water flowing into the concentration chamber to 100 ppb or less and the boron concentration to 10 ppb or less, diffusion of these ions from the concentration chamber to the desalting chamber is caused by the concentration gradient. It is possible to significantly reduce the silica concentration and boron in the production water.
[0013]
In order to reduce the total inorganic carbonic acid concentration, the silica concentration or the boron concentration in the concentrated water flowing into the concentrated water, a part of the production water flowing out from the desalting chamber may be used as the concentrated water. Moreover, you may process the water supplied to a concentration chamber with an ion exchange apparatus or an electrodeionization apparatus.
[0014]
In order to reduce the total inorganic carbonic acid concentration in the concentrated water flowing into the concentration chamber, a degassing means such as a degassing membrane device may be used.
[0015]
In the present invention, the raw water may be supplied to the desalting chamber after anion removal treatment, whereby the anion concentration of the production water can be further reduced. As the anion removal treatment, reverse osmosis treatment and deaeration treatment are suitable, and it is particularly preferred to perform reverse osmosis treatment in multiple stages and further deaeration treatment.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a schematic cross-sectional view of an electrodeionization apparatus showing an embodiment of the present invention. The electrodeionization apparatus 10 includes a plurality of anion exchange membranes (A membranes) 13 and cation exchange membranes (C membranes) 14 arranged alternately between electrodes (anode 11 and cathode 12), and a desiccant chamber 15 and a desalting salt. The chambers 16 are alternately formed, and the desalting chamber 16 is mixed or filled with an anion exchanger and a cation exchanger made of an ion exchange resin, an ion exchange fiber, a graft exchanger, or the like. .
[0018]
The concentration chamber 15, the anode chamber 17, and the cathode chamber 18 may also be filled with an electric conductor such as an ion exchanger, activated carbon, or metal.
[0019]
The water to be treated is introduced into the desalting chamber 16, and the production water is taken out from the desalting chamber 16. A part of the water to be treated is sent to the anion removal means 9 and subjected to anion removal treatment. The water from which the anion has been removed by the anion removal treatment means 9 is passed through the concentrating chamber 15 in a counter-current transient manner in the direction opposite to the water passing direction of the desalting chamber 16, and the outflow water from the concentrating chamber 15 is the system. It is discharged outside. 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 raw water inflow side. Thus, the concentrated water flows into the concentration chamber 15 from the desalting chamber outlet side (lower side in FIG. 1) and flows out from the desalting chamber inlet side (upper side in FIG. 1).
[0020]
A part of the water flowing out from the anion removing means 9 is fed to the inlet side of the anode chamber 17, and the effluent water from the anode chamber 17 is fed to the inlet side of the cathode chamber 18. The effluent is discharged out of the system as wastewater. The inlet water of the anode chamber 17 may be treated water that does not go through the anion removing means.
[0021]
Thus, by passing the anion-removed treated water through the concentration chamber 15 in a countercurrent and transient manner with the desalting chamber 16, the concentration of the concentrated water in the concentration chamber 15 becomes lower as the product water is removed. The influence of the diffusion on the desalting chamber 16 is reduced, and the removal rate of not only strong anions but also weak anions such as carbonic acid, silica, and boron can be dramatically increased. According to this electrodeionization apparatus, it is possible to produce production water having a specific resistance of 18 MΩ · cm or more.
[0022]
In addition, when the electrical conductivity of the anion removal treatment water passed through the concentration chamber is low and the electric resistance of the electrodeionization device is high, the concentration chamber is filled with a conductor such as an ion exchanger. Thereby, it becomes unnecessary to add an electrolyte such as salt to the concentrated water to lower the electrical resistance. It is preferable to fill the electrode chambers 17 and 18 with an ion exchanger, activated carbon, a metal which is an electric conductor, or the like in order to secure a current. This makes it possible to secure the necessary current even when high-quality water such as ultrapure water is passed.
[0023]
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 the filler 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.
[0024]
FIG. 2 shows a simplified water flow system to the demineralization chamber and the concentration chamber of the electrodeionization apparatus of FIG. As shown in the figure, the water to be treated is passed through the desalting chamber 16 to produce product water. A part of the water to be treated is passed through the concentration chamber 15 after the anion removal treatment and discharged as a concentrated waste water. The direction of water flow in the concentrating chamber is the opposite (counterflow) in the desalting chamber 16.
[0025]
By making the total inorganic carbonic acid concentration 50 ppb or less, preferably 30 ppb or less by the anion removing means 9, the total inorganic carbonic acid concentration in the production water is remarkably lowered. Further, the silica concentration in the production water and the boron concentration can be remarkably lowered by setting the silica concentration to 100 ppb or less, preferably 80 ppb or less and the boron concentration to 10 ppb or less, preferably 8 ppb or less by the anion removing means 9.
[0026]
Examples of the anion removing means 9 include a degassing device such as a degassing membrane device, a decarbonation tower, and a vacuum degassing tower, a reverse osmosis membrane separation device, an electrodialysis device, and an ion exchange resin tower including an anion exchanger. An ion exchange device or an electrodeionization device is exemplified.
[0027]
In order to remove carbonic acid, it is desirable to include degassing means such as a degassing membrane, a decarbonation tower, and a vacuum degassing tower. In particular, a degassing membrane treatment apparatus that performs a vacuum suction method (for example, 20 Torr or less), a sweep method using nitrogen or the like, or both has excellent carbonation removal efficiency.
[0028]
FIG. 3 is a system diagram showing an example when the electrodeionization apparatus 8 is employed as the anion removing means 9. In this electrodeionization apparatus 8, a demineralization chamber 8D and concentration chambers 8A and 8B are formed between an anode and a cathode by an anion membrane 8a and a cation membrane 8c. The water to be treated is circulated to each of the chambers 8A, 8B, and 8D in parallel flow, and the desalted water from the desalting chamber 8D and the concentrated water from the concentrating chamber 8B are demineralized in the concentrated water 15 of the electrodeionization apparatus 10. It is supplied to the outlet side and flows out from the inlet side of the desalination chamber. This electrodeionization apparatus 8 has a concentration chamber 8A on the anion membrane 8a side and a concentration chamber 8B on the cation membrane 8c side of the desalination chamber 8D, and only the anion component concentrated in the concentration chamber 8A is discharged and the cations are concentrated. The concentration chamber 8B is supplied to the concentration chamber 15 of the electrodeionization apparatus 10 together with the desalted water from the desalting chamber 8D. This electrodeionization apparatus 8 removes and reduces only the anion component in this way.
[0029]
In the present invention, water to be treated with anions may be used as the water to be treated supplied to the desalting chamber. By doing so, the anion load in the desalting chamber is reduced, so that the weak anion concentration is reduced. Further, the production water can be obtained at a low level. As this anion removal treatment, deaeration treatment, reverse osmosis treatment and the like are suitable. It is also preferable to adsorb and remove organic components with activated carbon or to ionize chlorine.
[0030]
When removing carbonate ions from the feed water to the desalting chamber by anion removal treatment, it is particularly preferable to use a deaeration means (particularly a membrane deaeration device) as the anion removal means. In addition, it is desirable to recycle part of the degassed treated water to the deaerator inlet to increase the carbonation removal efficiency.
[0031]
In the deaeration treatment for removing carbonic acid, it is desirable to adjust the influent water to acidic, preferably pH 4-6, more preferably pH 4-5, to increase the carbonic acid removal efficiency.
[0032]
Further, when the gas side of the degassing membrane is sucked with a vacuum pump, it is desirable that the degree of vacuum is 50 Torr or less, more preferably 20 Torr or less in order to increase the carbonation removal efficiency.
[0033]
When the raw water is subjected to reverse osmosis treatment (hereinafter sometimes referred to as RO treatment), it is desirable to sufficiently reduce weak anion components such as carbonic acid, silica, boron, etc. by performing treatment in multiple stages, for example, two stages.
[0034]
In this case, the removal efficiency of the weak anion component is improved by making the first-stage and / or second-stage RO inlet water alkaline (pH 8 to 10).
[0035]
In addition, as an alkali generating means for making this alkaline, an electrodeionization method in which a desalting chamber thickness of 7 mm or more (preferably 15 mm) disclosed in JP-A-2001-113281 is filled with an anion / cation mixed ion exchanger. An ion device may be used. If it does in this way, a weak anion component will also be reduced simultaneously with alkali production. Such an electrodeionization apparatus is preferably arranged between the first-stage and second-stage RO apparatuses.
[0036]
The pretreatment includes the above-described two-stage RO treatment and deaeration treatment. Ultra-pure ultrapure water, for example, having a specific resistance of 18.2 MΩ · cm or more, a silica concentration of 0.05 ppb or less, and boron of 0.005 ppb or less. It is particularly suitable for obtaining treated water.
[0037]
4 to 7 show configuration examples in which the above-described pretreatment apparatus is arranged in the front stage of the electrodeionization apparatus 10.
[0038]
In FIG. 4, raw water is deaerated by the deaeration membrane device 1 to be treated water of the electrodeionization device 10. A part of the degassed water of the degassing membrane device 1 is returned to the upstream side of the device 1 and repeatedly processed.
[0039]
In FIG. 5, raw water is passed through the activated carbon adsorption tower 2 and the two-stage RO apparatuses 3 and 3 to be treated water.
[0040]
In FIG. 6, raw water is treated by the activated carbon adsorption tower 2, the first RO device 3, the electrodeionization device 4, and the second RO device 3 to be treated water of the electrodeionization device 10. As the electrodeionization device 4, for example, an electrodeionization device disclosed in JP-A-2001-113281 can be used, but the electrodeionization device 4 is not limited to this.
[0041]
In FIG. 7, raw water is treated by the activated carbon adsorption tower 2, the two-stage RO devices 3, 3, and the degassing membrane device 1 to be treated water of the electrodeionization device 10.
[0042]
In the present invention, the means for removing anions from the concentrated water supplied to the concentration chamber may be the electrodeionization apparatus 10 itself. That is, as shown in FIG. 8, the entire amount of water to be treated is circulated through the desalting chamber 16 of the electrodeionization apparatus 10, and a part of the product water is passed from the desalting chamber outlet side to the desalting chamber inlet side to the concentrating chamber 15. May be distributed toward the market.
[0043]
In the present invention, the electrodeionization apparatus 10 may be installed in multiple stages, and the raw water may be deionized in multiple stages.
[0044]
FIG. 9 is a water flow diagram of the electrodeionization system in which the electrodeionization devices 10 (10A, 10B) are installed in multiple stages as described above, and the first electrodeionization device 10A and the second electrodeionization device. 10B is connected in series.
[0045]
In the electrodeionization system of FIG. 9, the water to be treated is passed through the desalination chamber 16A of the first electrodeionization apparatus 10A to become primary production water. This primary production water is circulated to the demineralization chamber 16B of the second electrodeionization apparatus. The flow direction of the concentrated water in the concentration chambers 15A and 15B is the counter-current direction to the desalting chambers 16A and 16B. Secondary production water (production water) is taken out from the desalting chamber 16B, and a part thereof is supplied to the concentration chamber 15B. The concentrated water flowing out from the concentration chamber 15B of the second electrodeionization apparatus 2 has a low anion concentration and is supplied to the concentration chamber 15A.
[0046]
The outflow water from the concentration chamber 15A of the first electrodeionization apparatus 1 is discharged as concentrated waste water.
[0047]
In the present invention, the thickness of the desalting chamber is preferably 2 to 7 mm, and the flow rate is preferably LV = 60 to 120 m / h and SV = 100 to 200 / h. The thickness of the concentration chamber is preferably 2 to 7 mm, and the flow rate is preferably LV = 10 to 30 m / h and SV = 25 to 50 / h. Further, both the desalting chamber and the concentrating chamber are filled with an ion exchanger, particularly filled with an anion cation, and preferably operated at a current density of 300 to 700 mA / dm ² . It is desirable that the water supplied to the concentrating chamber is in a transient manner without being recirculated to the concentrating chamber inlet by a circulation pump or the like.
[0048]
In addition, when water is passed through a plurality of desalting chambers in series as shown in FIG. 9, it is desirable that the above be achieved particularly in the final desalting chamber.
[0049]
【The invention's effect】
As described above, according to the electrodeionization apparatus and the operation method thereof of the present invention, it is possible to reliably produce product water having a remarkably low anion concentration, particularly the total inorganic carbonic acid concentration.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an electrodeionization apparatus according to an embodiment.
FIG. 2 is a water flow diagram of the electrodeionization apparatus of FIG.
FIG. 3 is a water flow diagram of an electrodeionization system according to another embodiment.
FIG. 4 is a water flow diagram of an electrodeionization system according to yet another embodiment.
FIG. 5 is a water flow diagram of an electrodeionization system according to different embodiments.
FIG. 6 is a water flow diagram of the electrodeionization system according to the embodiment.
FIG. 7 is a water flow diagram of the electrodeionization system according to the embodiment.
FIG. 8 is a water flow diagram of the electrodeionization system according to the embodiment.
FIG. 9 is a water flow diagram of the electrodeionization system according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Electrodeionization apparatus 11 Anode 12 Cathode 15, 15A, 15B Concentration chamber 16, 16A, 16B Desalination chamber

Claims

An operation method of an electrodeionization apparatus in which a concentration chamber and a desalination chamber are partitioned by an ion exchange membrane between an anode and a cathode,
In the operation method of circulating the water to be treated to the desalination chamber and circulating the concentrated water to the concentration chamber,
As the concentrated water, the low anion concentration water treated by the anion removing treatment means flows into the concentrating chamber from the side close to the desalting chamber outlet and flows out from the side close to the desalting chamber inlet. A method of operating an electrodeionization apparatus, characterized in that

2. The method of operating an electrodeionization apparatus according to claim 1, wherein the total inorganic carbonic acid concentration of the low anion concentration water treated by the anion removal treatment means is 50 ppb or less.

3. The operation method of an electrodeionization apparatus according to claim 1, wherein the silica concentration of the low anion concentration water treated by the anion removal treatment is 100 ppb or less.

The operation method of the electrodeionization apparatus according to any one of claims 1 to 3, wherein the boron concentration of the low anion concentration water treated by the anion removal treatment is 10 ppb or less.

The operation method of the electrodeionization apparatus according to any one of claims 1 to 4, wherein a part of the production water flowing out from the demineralization chamber is supplied to the concentration chamber.

6. The method of operating an electrodeionization apparatus according to any one of claims 1 to 5, wherein the anion removal treatment means includes a deaeration means.

6. The operation method of an electrodeionization apparatus according to any one of claims 1 to 5, wherein the anion removal processing means includes an ion exchange apparatus or an electrodeionization apparatus.

The operation method of the electrodeionization apparatus according to any one of claims 1 to 7, wherein the raw water is subjected to anion removal treatment, and the treated water is supplied to the demineralization chamber as treated water.

9. The operation method of an electrodeionization apparatus according to claim 8, wherein the raw water is subjected to anion removal treatment by reverse osmosis treatment and deaeration treatment.

A concentration chamber and a desalination chamber are partitioned by an ion exchange membrane between the anode and the cathode,
In the electrodeionization apparatus in which treated water is circulated to the demineralization chamber and concentrated water is circulated to the concentration chamber,
Concentrated water introducing means and outflow means are provided so that the concentrated water flows into the concentrating chamber from the side close to the desalting chamber outlet and flows out from the side close to the desalting chamber inlet,
An electrodeionization apparatus characterized in that means for removing anions from the concentrated water flowing into the concentration chamber is provided.

11. The electrodeionization apparatus according to claim 10, wherein the means for removing the anion is such that the total inorganic carbonate concentration after the anion removal treatment is 50 ppb or less.

The electrodeionization apparatus according to claim 10 or 11, further comprising means for removing anions from water supplied to the demineralization chamber.