JP4449204B2 - Boiler feed water treatment apparatus and boiler feed water treatment method - Google Patents

Boiler feed water treatment apparatus and boiler feed water treatment method Download PDF

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JP4449204B2
JP4449204B2 JP2000333246A JP2000333246A JP4449204B2 JP 4449204 B2 JP4449204 B2 JP 4449204B2 JP 2000333246 A JP2000333246 A JP 2000333246A JP 2000333246 A JP2000333246 A JP 2000333246A JP 4449204 B2 JP4449204 B2 JP 4449204B2
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water
boiler
alkali
supply
feed water
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JP2002136994A (en
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信博 織田
史郎 田家
高 川村
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Kurita Water Industries Ltd
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Kurita Water Industries Ltd
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Description

【0001】
【発明の属する技術分野】
本発明はボイラ給水処理装置及びボイラ給水の処理方法に係り、特に、スケール防止剤、防食剤、更にはボイラ給水処理のための装置の再生剤等の薬剤を必要とすることなく、ボイラへの給水を行えるボイラ給水処理装置及びボイラ給水の処理方法に関する。
【0002】
【従来の技術】
従来、一般産業用のボイラの給水系においては、ボイラのスケール障害及び腐食障害を防止するために、陽イオン交換樹脂を用いた軟化処理と、スケール防止剤(清缶剤)、防食剤としてのアルカリ剤及び脱酸素剤の薬剤処理が行われている。アルカリ剤は、シリカスケールの生成防止、腐食抑制に有効であり、また、脱酸素剤は、酸素に起因する腐食防止に有効である。清缶剤としては、リン酸系の薬剤と、非リン酸系の薬剤とがあるが、最近では、閉鎖性水域の富栄養化防止の観点から、非リン酸系の薬剤が主に使用されており、なかでも、ポリマー系の薬剤、具体的にはアクリル酸ポリマー系の薬剤が用いられている。このアクリル酸ポリマー系の薬剤はスケール生成抑制効果に優れるものの、水中の微量の硬度成分にしか有効でないことから、従来においては、軟水器による軟水処理も必要となっている。この軟水器では、陽イオン交換樹脂の再生用の食塩が必要となる。
【0003】
また、発電ボイラーなどの高圧ボイラでも、ボイラ給水には、純水装置によるスケール成分の除去処理、アンモニアによる高pH処理、ヒドラジンによる脱酸素処理が行われており、ボイラ給水に直接添加されるアンモニア等の薬剤の他、苛性ソーダや塩酸等の純水装置の再生剤が必要とされている。
【0004】
【発明が解決しようとする課題】
このように従来においては、ボイラのスケール障害や腐食障害を防止するために、ボイラ給水に直接添加するスケール防止剤や防食剤等の薬剤の他、水処理装置の再生剤としての薬剤が必要とされており、このため、薬剤の運搬、調製、貯留、補充等の手間を要する上に、作業環境の悪化、更には薬剤成分を含む排水の処理といった様々な問題があった。
【0005】
本発明は上記従来の問題点を解決し、ボイラ給水への添加薬剤やボイラ給水の処理装置の再生剤といった薬剤を使用することなく、ボイラのスケール障害及び腐食障害を防止することができるボイラ給水処理装置及びボイラ給水の処理方法を提供することを目的とする。
【0006】
【課題を解決するための手段】
本発明のボイラ給水処理装置は、原水を処理してボイラに給水するボイラ給水装置において、原水中の硬度成分を除去する逆浸透膜分離装置と、原水中の溶存酸素を除去する脱酸素装置と、ボイラブロー水中のアルカリ成分を回収し、回収したアルカリ成分を該逆浸透膜分離装置の透過水に供給するアルカリ回収・供給装置とを備えてなることを特徴とする。
【0007】
本発明のボイラ給水の処理方法は、原水を処理してボイラに給水するボイラ給水の処理方法において、逆浸透膜分離装置により原水中の硬度成分を除去する工程と、脱酸素装置により原水中の溶存酸素を除去する工程と、ボイラブロー水中のアルカリ成分を回収して逆浸透膜分離装置の透過水に供給する工程とを備えてなることを特徴とする。
【0008】
本発明では、逆浸透(RO)膜分離装置において、ボイラ給水の硬度成分を十分に除去することにより、スケール障害を防止する。これにより、ポリマー系のスケール防止剤を不要とする。
【0009】
また、脱酸素装置により溶存酸素(DO)を除去することで、酸素による腐食を防止する。これにより、脱酸素剤を不要とする。
【0010】
更に、ボイラブロー水中のアルカリ成分を回収してボイラ給水に供給することでアルカリ剤の添加も不要となる。
【0011】
即ち、ボイラに供給された水(缶水)は加熱され、蒸気を生産すると共に缶水は濃縮される。生産された蒸気は任意の用途に直接使用されたり、間接的に使用され、一部又は全部が復水として給水タンクに返送され、給水として循環使用される。缶水は所定の電気伝導度に維持されるように、一部はブロー水としてボイラから排出される。
【0012】
通常、ボイラ缶水は、腐食抑制、シリカスケール抑制の目的でボイラ給水に添加されたアルカリ性に保持され、この調整pHはボイラによって異なるが、通常、缶水pH9〜12とされ、軟水給水の場合はpH11〜12に調整されることが多い。
【0013】
従って、このような缶水から一部ブローされるボイラブロー水も高pHのアルカリ性であるので、本発明では、従来廃棄していたブロー水からアルカリ成分を回収して再度給水に添加する。
【0014】
本発明で用いるRO膜分離装置は再生剤不要であり、また、脱酸素装置としては、真空脱気装置、窒素脱気装置、脱脱気装置、触媒樹脂脱酸素装置、加熱脱気装置などがあるが、これらの脱酸素装置も、再生剤等の薬剤は不要である。
【0015】
更に、アルカリ回収・供給装置としても、弱酸性カチオン交換樹脂塔、電気透折器、活性炭電極脱塩装置などを用いることができるが、これらの装置についても再生剤は不要であり、従って、後述のボイラの運転開始時のアルカリ剤以外は薬剤を全く必要とすることなく、ボイラ給水の処理を行える。
【0016】
本発明においては、逆浸透膜分離装置の透過水の全硬度成分濃度が0.5mg/L以下となるように、また、脱酸素装置の脱酸素処理水のDO濃度が0.1mg/L以下となる処理を行うのが好ましい。
【0017】
本発明において、脱酸素装置としては、真空脱気装置、窒素脱気装置、膜脱気装置、触媒樹脂脱酸素装置又は加熱脱気装置を用いることができ、また、アルカリ回収・供給装置としては、弱酸性カチオン交換樹脂塔、電気透折器又は活性炭電極脱塩装置を用いることができる。
【0018】
このアルカリ回収・供給装置から排出されたボイラブロー水は装置の入口側へ循環することが好ましい。
【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は本発明のボイラ給水処理装置の実施の形態を示す系統図であり、図2,3,4は本発明に係るアルカリ回収・供給装置の実施の形態を示す系統図である。
【0021】
図1のボイラ給水処理装置では、井水、水道水、工業用水等の原水は、まず、配管11を経てポンプPによりRO膜分離装置1に導入され、含有される硬度成分が除去される。
【0022】
RO膜分離装置1のRO膜としては、原水中の硬度成分を除去できるものであれば良く、全塩類を除去するRO膜であっても、硬度成分を主として除去するRO膜であっても良い。また、原水水質によって、高脱塩率のRO膜でも低脱塩率の膜、例えば、ルーズRO膜、ナノフィルトレーション膜と呼ばれるRO膜であっても良い。
【0023】
また、膜の形式、材質、膜装置の形式は任意であり、ポリスルホン膜、芳香族ポリアミド膜、セルロース膜等の管型モジュール、平膜型モジュール、スパイラル型モジュール、中空糸型モジュール等を用いることができる。
【0024】
RO膜分離装置1は、ボイラ5内でスケール化する硬度成分を除去するためのものであり、ボイラ5内のスケール障害を確実に防止するためには、RO膜分離装置1の透過水(RO透過水)の全硬度成分濃度を0.5mg/L以下とすることが好ましい。
【0025】
RO膜分離装置1により、全硬度成分濃度0.5mg/L以下のRO透過水を得るためには、原水水質に応じて、適当な脱塩率のRO膜を選択使用しても良いが、水質の変動にかかわらず、安定して全硬度成分濃度0.5mg/L以下の透過水を得ることができることから、RO膜分離装置1の水回収率を制御して透過水側に透過する硬度成分濃度を調節するのが好ましい。
【0026】
即ち、一般にRO膜分離装置は水回収率80%程度で運転される場合が多いが、この場合、透過水の全硬度成分濃度は1〜2mg/L程度である。このような全硬度成分濃度のボイラ給水ではボイラにスケール障害が発生する。しかし、RO膜分離装置の水回収率を低減することにより透過水の全硬度成分濃度を下げることができる。
【0027】
RO膜分離装置1の水回収率を調整することにより、全硬度成分濃度0.5mg/L以下の透過水を得るには、図1に示す如く、RO膜分離装置1の濃縮水排出配管14に全硬度計、電気伝導度計等のセンサSを設け、濃縮水の全硬度成分を検出し、演算器6において、濃縮水の全硬度成分濃度検出値と原水水質や組成から、透過水の全硬度成分濃度を算出し、この濃度が0.5mg/L以下となるように、図1に示す如く、原水側に戻す濃縮水量と排出する濃縮水量とを、濃縮水を原水側に戻す配管13の弁V−1と、濃縮水排出配管14の弁V−2の開度操作により調整して水回収率を調整するのが好ましい。このように高濃度の濃縮水の全硬度成分濃度を検出して透過水の全硬度成分濃度を算出する方が、希薄な透過水の全硬度成分濃度を検出するよりも、精度良く測定することができ、的確な制御を行える。
【0028】
なお、RO膜分離装置1では、硬度成分をできるだけ多く除去することが好ましいが、Na,Kなどの1価のカチオンは完全に脱塩する必要はなく、僅かに透過水側にリークして透過水中に含有されていることが好ましい。このようにすることにより、後段のアルカリ回収・供給装置2でのボイラブロー水からのアルカリ成分の回収が十分でない場合に、透過水中にリークした1価のカチオンがNa等のアルカリ成分としてアルカリ回収・供給装置2で回収され、ボイラ給水へのアルカリ成分の補給に寄与するようになり、好ましい。
【0029】
RO膜分離装置1の透過水はアルカリ回収・供給装置2を経て給水タンク3に送給されるが、図1の装置では、このRO透過水の一部がアルカリ回収・供給装置2の弱酸性カチオン交換樹脂塔2Aに通水され、残部は直接給水タンク3に送給され、各々の流量を調整することにより、ボイラ給水のpHが所定のpHとなるように構成されている。
【0030】
即ち、RO透過水の一部は弁V−4を備える配管11、弱酸性カチオン交換樹脂塔2A及び配管15,16を経て給水タンク3に送給され、残部は弁V−3を備える配管12及び配管16を経て直接給水タンク3に送給される。配管16にはpHセンサSが設けられており、演算器7にて、pHセンサSのpH測定値に基いて、弁V−3,V−4の開度を調整することにより、給水タンク3に送給されるボイラ給水のpHを所定のpH値に維持している。
【0031】
通常の場合、ボイラ給水のpHは9以上、特に11〜11.8となるように制御することで、アルカリによるシリカスケールの防止、腐食抑制効果を得ることができる。
【0032】
図1の装置では、アルカリ回収・供給装置2として、弱酸性カチオン交換樹脂塔2A,2Bを用い、一方の弱酸性カチオン交換樹脂塔2AでRO透過水を処理してRO透過水にアルカリを供給し、他方の弱酸性カチオン交換樹脂塔2Bでボイラ5からのボイラブロー水を処理してボイラブロー水からアルカリを回収し、このアルカリの供給を行う弱酸性カチオン交換樹脂塔とアルカリの回収を行う弱酸性カチオン交換樹脂塔とを交互に入れ換えることにより、再生剤を必要とすることなく、アルカリの回収・供給を行う。
【0033】
以下に、このアルカリ回収・供給装置2について図2を参照して説明する。なお、図2(a),(b)において、黒ぬりの弁は閉状態であることを示し、白ぬきの弁は開状態であることを示す。
【0034】
弱酸性カチオン交換樹脂は、アルカリ性の水を通水するとアルカリ(Na,K等の陽イオン)を捕捉し、酸性水や中性水を通水すると、この捕捉しているアルカリを放出する。アルカリ回収・供給装置2は、この原理を利用するものであり、まず、図2(a)に示す如く、弁V,V,V,V開、弁V,V,V,V閉として、RO透過水を弱酸性カチオン交換樹脂塔2A(以下「A塔」と称す。)に通水し、ボイラブロー水を弱酸性カチオン交換樹脂塔2B(以下「B塔」と称す。)に通水する。なお、通水開始時において、RO透過水を通水するA塔の弱酸性カチオン交換樹脂はNa形、ボイラブロー水を通水するB塔の弱酸性カチオン交換樹脂はH形としておく。
【0035】
RO透過水は、A塔のNa形弱酸性カチオン交換樹脂に接触すると、下記反応でNaイオンがNa形弱酸性カチオン交換樹脂から放出され、アルカリ水となる。
R−COONa+HO→R−COOH+NaOH
Naイオンを放出した弱酸性カチオン交換樹脂はH形弱酸性カチオン交換樹脂となる。
【0036】
一方、ボイラブロー水(このボイラブロー水はpH11以上のアルカリ水である。)はB塔のH形弱酸性カチオン交換樹脂に接触すると、下記反応でNaイオンが弱酸性カチオン交換樹脂に取り込まれる。
R−COOH+NaOH→R−COONa+H
Naイオンを取り込んだH形弱酸性カチオン交換樹脂はNa形弱酸性カチオン交換樹脂となる。
【0037】
通水を継続することにより、A塔はNa形弱酸性カチオン交換樹脂からH形弱酸性カチオン交換樹脂が多くなり、B塔はH形弱酸性カチオン交換樹脂からNa形が多くなり、A塔ではNaイオンが放出されなくなり、B塔ではNaイオンの捕捉ができなくなるので、その前に、RO透過水とボイラブロー水の通水する塔を入れ替える。即ち、図2(b)に示す如く、弁V,V,V,V開、弁V,V,V,V閉として、RO透過水をB塔に、ボイラブロー水をA塔にそれぞれ通水する。これにより、ボイラブロー水からアルカリを回収してNa形となったB塔において、RO透過水にアルカリの供給が行われ、また、RO透過水にアルカリを供給することでH形となったA塔において、ボイラブロー水からのアルカリの回収を行える。
【0038】
RO透過水を通水する塔と、ボイラブロー水を通水する塔との切り替えは、タイマー制御で行っても良く、また、各塔の流出水のpHを検出し、その検出値に基いて行っても良い。
【0039】
このように、通水する弱酸性カチオン交換樹脂塔の切り替えを繰り返し行うと共に、アルカリ回収・供給装置2に通水するRO透過水の水量を調節することにより、pH9以上のアルカリ性のボイラ給水を給水タンク3に安定に送給することができる。
【0040】
給水タンク3内のボイラ給水は、配管17よりポンプPで抜き出され、配管20よりボイラ5に送給されるが、図1の装置では、その一部が配管18より脱酸素装置4に送給され、DOが除去された後、配管19より給水タンク3に戻される。
【0041】
脱酸素装置4は、被処理水に含まれるDOを除去するためのものであり、脱酸素装置4でDOを除去することにより、ボイラ5内でのDOによる腐食を抑制する。ボイラ5内でのDOによる腐食を確実に抑制するためには、ボイラ給水のDOを0.1mg/L以下にすることが好ましい。
【0042】
脱酸素装置4としては、任意の装置を用いることができ、例えば、次のような膜脱気装置、真空脱気装置、窒素脱気装置、触媒樹脂脱酸素装置、加熱脱気装置などの1種を単独で或いは2種以上を組み合わせて用いることができる。
(i) 真空脱気装置:内部を真空化(減圧)した脱気塔内に被処理水を噴霧して水中のDOを除去する装置
(ii) 窒素脱気装置:被処理水に窒素ガスを吹き込み、DOを窒素ガス中に取り込んで除去する装置
(iii) 膜脱気装置:気体分離膜の一側に被処理水を供給し、他側の気相室を減圧して、水中のDOを気相室に移行させて除去する装置
(iv) 触媒樹脂脱酸素装置:パラジウムなどの触媒を担持させた樹脂に、水素ガスを供給しながら被処理水を接触させ、DOを水素と反応させて除去する装置
(v) 加熱脱気装置:被処理水を加熱して気体溶解度を低下させてDOを除去する装置
このような脱酸素装置を用いることにより、亜硫酸塩、ヒドラジン、糖類などの化学薬品を成分とした脱酸素剤を使用することなく、DOの除去を行える。
【0043】
このような脱酸素装置はRO膜分離装置の後段に設けるのが好ましいが、RO膜分離装置の前段であっても良い。RO膜分離装置の後段に設けることにより、原水中の汚染物質がRO膜分離装置で除去された透過水が脱酸素装置に流入するため、脱酸素装置でのファウリングが防止され、好ましい。
【0044】
図1の実施の形態では、脱酸素装置4を給水タンク3の循環ラインに設けているが、給水タンク3からボイラ5への給水配管17,20に設けても良く、この場合には、脱酸素処理水が空気と触れることによる酸素や炭酸ガスの再溶解が防止され、好ましい。
【0045】
給水タンク3から配管17,20を経てボイラ5に送給されたボイラ給水は、ボイラ5で蒸気となり、配管21を経て需要箇所に送給され、復水は配管22より給水タンク3に戻される。
【0046】
ボイラ5のボイラブロー水は配管23よりアルカリ回収・供給装置2でアルカリが回収された後、配管24で原水側に戻され、ボイラ給水として再利用される。
【0047】
即ち、本発明のボイラ給水処理装置により、このようにアルカリ成分を回収した後のブロー水は、従来のように、給水処理のための薬剤を含まず、更にアルカリ成分も除去されているために、塩類や有機物を殆ど含まない清澄な水であるので、図示の如く、原水側に戻し、ボイラ給水の原水として回収再利用することが望ましい。このようなボイラブロー水の回収により、ボイラ給水処理のための薬品添加を必要としない効果と共に、排水量及び使用水量を著しく削減できるという効果も奏される。
【0048】
なお、図1のボイラ給水処理装置には、アルカリ回収・供給装置として弱酸性カチオン交換樹脂塔を用いたものであるが、アルカリ回収・供給装置は弱酸性カチオン交換樹脂塔に限らず、電気透折器又は活性炭電極脱塩装置であっても良い。また、弱酸性カチオン交換樹脂塔、電気透折器、活性炭電極脱塩装置のうちの2種以上を組み合わせて用いても良い。
【0049】
図3はアルカリ回収・供給装置としての電気透折器8を示すものである。電気透折器8は、電解槽内に陰極8Aを有する陰極室と陽極8Bを有する陽極室とがイオン交換膜(本実施例ではカチオン交換膜)8Cで仕切られたものであり、陽極室にアルカリ水を、陰極室に中性水を通水して両極8A,8B間に電圧を印加すると、陰極室のアルカリ(Naイオン等の陽イオン)がカチオン交換膜8Cを透過して陰極室側へ移行する。この電気透折器8では、イオン交換膜としてカチオン交換膜を設けているため、陰極室側から陽極室側への陰イオンの透過はない。
【0050】
従って、このような電気透折器8の陽極室側へアルカリ性のボイラブロー水を通水し、陰極室側へRO透過水を通水することにより、ボイラブロー水中のアルカリを陰極室のRO透過水側へ移行させることができ、ボイラブロー水からのアルカリの回収と、RO透過水への回収したアルカリの供給を行える。
【0051】
なお、この電気透折器8に印加する電圧は、1.2V以上の直流電圧であることが好ましい。
【0052】
図4は、アルカリ回収・供給装置としての活性炭電極脱塩装置9A,9Bを示すものである。活性炭電極脱塩装置は、金属、黒鉛等の集電極に接した活性炭電極が電気絶縁性で透水性のセパレータを介して1対向い合って配置しているものであり、電極間に直流電圧を印加しながら、イオンを含む水を通水すると、水中の陽イオンは陰極側へ、陰イオンは陽極側へ吸着することで、水中のイオンが除去される。そして、このイオンの吸着が飽和に達する前に、両極を短絡させるか、逆接続することにより、吸着したイオンが脱離される。
【0053】
本発明では、この原理を利用して、活性炭電極脱塩装置を2塔設置し、一方の活性炭電極脱塩装置に電極間を短絡又は逆接続した状態でRO透過水を通水して、活性炭電極からアルカリを溶離させ、他方の活性炭電極脱塩装置に電極間に直流電圧を印加してボイラブロー水を通水してアルカリを吸着除去し、このアルカリの溶離と吸着除去を行う活性炭電極脱塩装置を切り替える。
【0054】
即ち、図4に示す如く、2塔の活性炭電極脱塩装置9A,9Bを並設する。この活性炭電極脱塩装置9A,9Bは、アルカリ(陽イオン)のみの吸着、溶離を行うため、陽極9b側には比表面積の小さい活性炭電極又は炭素電極のみとし、陰極9a側は通常の活性炭電極とし、これらの電極9a,9bが非導電性透水性セパレータ9sで仕切られている。
【0055】
まず、活性炭電極脱塩装置9Aに電極間を短絡又は逆接続した状態でRO透過水を通水して、活性炭電極からアルカリを溶離させ、他方の活性炭電極脱塩装置9Bに電極間に0.5〜2V程度の直流電圧を印加してボイラブロー水を通水してアルカリを吸着除去する。なお、通水開始時においては、RO透過水を通水する活性炭電極脱塩装置9Aの活性炭電極にアルカリを吸着させておく。
【0056】
活性炭電極脱塩装置9Aの活性炭電極からのアルカリの溶離がなくなり、また、活性炭電極脱塩装置9Bの活性炭電極へのアルカリの吸着が飽和に達する前に、両活性炭電極脱塩装置9A,9Bの通水を切り替え、活性炭電極脱塩装置9Bに電極間を短絡又は逆接続した状態でRO透過水を通水して、活性炭電極からアルカリを溶離させ、活性炭電極脱塩装置2Aに電極間に0.5〜2V程度の直流電圧を印加してボイラブロー水を通水してアルカリを吸着除去する。以降、この切り替えを繰り返す。
【0057】
このような通水の切り替えは、前述の図2に示す弱酸性カチオン交換樹脂塔2A,2Bの通水の切り替えと同様に弁の開閉操作で行うことができる。
【0058】
これにより、ボイラブロー水のアルカリを回収して、RO透過水に供給することができる。
【0059】
なお、このようなアルカリ回収・供給装置では、通常運転中はボイラブロー水から回収したアルカリをRO透過水に供給することで、アルカリ薬剤を添加することなく、ボイラ給水のpH調整を行える。ただし、ボイラ稼動初期においては、給水タンク3内のpHを所定値にするために、アルカリ薬剤が必要とされる。また、運転中において、ボイラブロー水からの回収アルカリが不足する場合においても、アルカリ薬剤を補給することとなる。また、RO透過水が通水される弱酸性カチオン交換樹脂塔や活性炭電極脱塩装置に予めアルカリを吸着させておくために薬剤が必要となる場合もあるが、pH調整した給水タンク3内のボイラ給水を通水して弱酸性カチオン交換樹脂塔をNa形にしたり、活性炭電極脱塩装置にアルカリを吸着させるようにしても良い。
【0060】
図2〜4のアルカリ回収・供給装置では、ボイラブロー水から回収したアルカリを直接RO透過水に供給するが、このアルカリ水は、貯槽に一旦貯留して、必要量を任意の箇所に供給しても良い。
【0061】
このようなアルカリ回収・供給装置によるボイラ給水へのアルカリの供給は、RO膜分離装置の出口からボイラに至る任意の箇所で行うことができるが、給水タンク3が大気と連通している場合、給水タンク3内の水がアルカリ性になると、大気中の炭酸ガスを吸収してしまい、アルカリ成分を消費する恐れがあることから、この場合には、給水タンク3の下流側でアルカリの供給を行うのが望ましい。
【0062】
ただし、給水タンク3内のボイラ給水には、空気中の酸素が溶解するのを防止するために、通常、水面に遮蔽材が設けられ大気と遮断されており、この場合には炭酸ガスの溶解も防止されるため、図1に示す如く、給水タンク3の上流側でアルカリの供給を行ってもこのような問題を生じることはない。
【0063】
【実施例】
以下に実施例及び比較例を挙げて本発明をより具体的に説明する。
【0064】
なお、実施例及び比較例でボイラ給水の処理を行ったボイラは蒸発量1m/hr、最高圧力2MPaの水管ボイラであり、ボイラブロー水量は0.05m/hr、缶水pHは11となるようにした。
【0065】
実施例1
図1に示す装置で全硬度成分濃度25〜50mg/Lに変動する水道水を原水として処理を行った。
用いた各装置の仕様は次の通りである。
<RO膜分離装置>
日東電工(株)製ES20,4インチ
モジュール24本
給水圧力0.8MPa
<アルカリ回収・供給装置>
三菱化学(株)製弱酸性カチオン交換樹脂「ダイアイオンWK11」を25L充填した弱酸性カチオン交換樹脂塔
RO透過水を通水する弱酸性カチオン交換樹脂塔はNa形のものを充填し、ボイラブロー水を通水する弱酸性カチオン交換樹脂塔にはH形のものを通水した。
<脱酸素装置>
大日本印刷(株)製脱気膜SEPAREL EF−040 φ180×615mm1本を用いて2m/Hrで給水タンクに循環処理した。操作真空圧は2kPaで運転した。
【0066】
RO膜分離装置1では、濃縮水の全硬度成分濃度が100mg/Lとなるように水回収率80〜50%で運転した。その結果、水回収率70%の運転では、原水の全硬度が30mg/L以下の時は処理水の全硬度が0.5mg/L以下であったが、30mg/L以上の場合は0.5mg/L以上となった。原水硬度が50mg/Lの時は約0.9mg/Lにもなったが、本実施例では水回収率を調整することにより、安定して全硬度成分濃度0.5mg/L以下のRO透過水を得た。
【0067】
このRO膜分離装置の透過水の一部はNa形弱酸性カチオン交換樹脂塔2Aに通水し、残部は直接給水し、給水タンク3に送給されるボイラ給水のpHが9となるように両通水量を制御した。また、ボイラブロー水はH形弱酸性カチオン交換樹脂塔2Bに通水し、このRO透過水とボイラブロー水の通水を弱酸性カチオン交換樹脂塔2Aと2Bとで切り替え、この切り替えを繰り返し行った。
【0068】
また、脱酸素装置では、給水タンクで2m/Hr循環通水することにより、給水タンク3内のDO濃度を0.1mg/L以下とした。
【0069】
実施例2
実施例1において、アルカリ回収・供給装置として弱酸性カチオン交換樹脂塔の代りに下記仕様の電気透折器を用いたこと以外は同様にして処理を行った。
<電気透折器>
電極面積2dm
カチオン交換膜はトクヤマ(株)製「ネオセプタCM1」
この電気透折器の陽極室にボイラブロー水を0.05m/hrで通水すると共に、陰極室にRO透過水を同流量で通水し、給水タンク3に送給されるボイラ給水のpHが9となるように、3〜5Vの範囲で電圧を調整して直流電圧を印加した。電流は1.5〜2Aであった。
【0070】
実施例3
実施例1において、アルカリ回収・供給装置として、下記仕様の活性炭電極脱塩装置を2塔用いたこと以外は同様にして処理を行った。
<活性炭電極脱塩装置>
クラレ製活性炭繊維クラアクティブCH−20(正極はCH−10)を2m、集電極として日本カーボン(株)製ニカフィルムFL−400(厚み0.4mm)、セパレータはポリプロピレン製不織布0.2mmを用いて活性炭電極脱塩セルを組み立てた。
【0071】
運転開始に当っては、RO透過水を通水する活性炭電極脱塩装置には、NaOHを予め負荷した。
【0072】
一方の活性炭電極脱塩装置にRO透過水を通水すると共に電極を短絡させ、他方の活性炭電極脱塩装置にボイラブロー水を通水すると共に直流電圧0.8〜1.2Vを印加し、このRO透過水とボイラブロー水の通水を2塔の活性炭電極脱塩装置で切り替え、この切り替えを繰り返し行った。
【0073】
実施例1と同様に通水量の制御で給水タンク3に送給されるボイラ給水のpHが9となるように調整した。
【0074】
比較例1
実施例1において、アルカリ回収・供給装置と脱酸素装置を用いず、RO膜分離装置における水回収率を70%の一定条件とし、薬剤として下記のものを添加したこと以外は同様にして処理を行った。
<添加薬剤及び添加量>
ポリマー(ポリアクリル酸ソーダ)系スケール防止剤:5〜50mg/L
リン酸(POイオン)系スケール防止剤:1〜50mg/L
アルカリ(苛性ソーダ):4〜10mg/L
脱酸素剤(亜硫酸ナトリウム):70〜90mg/L
上記薬剤の添加によりボイラ給水のCODは10〜100mg/Lとなった。
【0075】
上記実施例1〜3及び比較例1の処理で1ヶ月運転した後、ボイラを開缶してスケール付着量及び腐食量を調べたところ、いずれの場合も、
スケール付着量:0.05mg/cm/日
腐食量(孔食深さ):0.05〜1mm/年
と同等の結果が得られ、実施例1〜3では薬剤不使用で良好なスケール防止、腐食防止効果が得られたことが確認された。
【0076】
また、実施例1〜3では、アルカリ回収後のボイラブロー水として
Pアルカリ:5mg/L以下
COD:2mg/L以下
の清浄度の高い水が得られ、この水は、ボイラ給水の原水として再使用することができたが、比較例1では、薬剤を添加したために、ボイラブロー水の水質は、
Pアルカリ:約40〜100mg/L
COD:約400mg/L
であり、このようなボイラブロー水(0.05m/hr)の中和のために25%硫酸約10〜20mL/minが必要となった。
【0077】
【発明の効果】
以上詳述した通り、本発明によれば、リン酸、アルカリ剤、ポリマー等のスケール防止剤や脱酸素剤等のボイラ給水への添加薬剤やボイラ給水の処理装置の再生剤といった薬剤を使用することなく、ボイラのスケール障害及び腐食障害を防止することができる。
【0078】
このため、薬剤の運搬、調製、貯留、補充等の手間が不要となる上に、作業環境の悪化、更には薬剤成分を含む排水の処理といった薬剤使用に起因する様々な問題が解消される。
【図面の簡単な説明】
【図1】本発明のボイラ給水処理装置の実施の形態を示す系統図である。
【図2】本発明に係るアルカリ回収・供給装置の実施の形態を示す系統図である。
【図3】本発明に係るアルカリ回収・供給装置の実施の形態を示す系統図である。
【図4】本発明に係るアルカリ回収・供給装置の実施の形態を示す系統図である。
【符号の説明】
1 RO膜分離装置
2 アルカリ回収・供給装置
2A,2B 弱酸性カチオン交換樹脂塔
3 給水タンク
4 脱酸素装置
5 ボイラ
6,7 演算器
8 電気透折器
9A,9B 活性炭電極脱塩装置
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a boiler feedwater treatment apparatus and a boiler feedwater treatment method, and in particular, to a boiler without requiring a chemical such as a scale inhibitor, an anticorrosive, and a regenerant for a boiler feedwater treatment apparatus. TECHNICAL FIELD The present invention relates to a boiler water supply processing apparatus and a boiler water supply processing method capable of supplying water.
[0002]
[Prior art]
Conventionally, in a boiler water supply system for general industries, in order to prevent scale failure and corrosion failure of the boiler, softening treatment using a cation exchange resin, scale inhibitor (cleaning agent), and anticorrosive agent Chemical treatment of alkaline agent and oxygen scavenger is performed. The alkali agent is effective in preventing the formation of silica scale and suppressing corrosion, and the oxygen scavenger is effective in preventing corrosion caused by oxygen. There are two types of cleansing agents: phosphate-based drugs and non-phosphate-based drugs. Recently, non-phosphate-based drugs are mainly used from the viewpoint of preventing eutrophication in closed waters. Among them, polymer drugs, specifically, acrylic acid polymer drugs are used. Although this acrylic acid polymer-based drug is excellent in the effect of inhibiting scale formation, it is effective only for a very small amount of hardness component in water. Therefore, conventionally, soft water treatment with a water softener is also required. In this water softener, salt for regeneration of the cation exchange resin is required.
[0003]
Even in high-pressure boilers such as power generation boilers, boiler feedwater is treated with removal of scale components by a pure water device, high pH treatment with ammonia, deoxygenation treatment with hydrazine, and ammonia added directly to boiler feedwater In addition to chemicals such as these, there is a need for regenerants for pure water devices such as caustic soda and hydrochloric acid.
[0004]
[Problems to be solved by the invention]
Thus, conventionally, in order to prevent scale failure and corrosion failure of boilers, in addition to chemicals such as scale inhibitors and anticorrosives added directly to boiler feedwater, chemicals as regenerants for water treatment devices are required. For this reason, there are various problems such as the trouble of transportation, preparation, storage, replenishment and the like of the drug, the deterioration of the working environment, and the treatment of the waste water containing the drug component.
[0005]
The present invention solves the above-described conventional problems, and boiler feed water that can prevent boiler scale failure and corrosion failure without using chemicals such as chemicals added to boiler feed water or regenerants for boiler feed water treatment devices. It aims at providing the processing method and the processing method of boiler feed water.
[0006]
[Means for Solving the Problems]
The boiler feed water treatment device of the present invention is a boiler feed water device that treats raw water and feeds it to a boiler, a reverse osmosis membrane separation device that removes hardness components in raw water, and a deoxygenation device that removes dissolved oxygen in raw water And an alkali recovery / supply device for recovering the alkali component in the boiler blow water and supplying the recovered alkali component to the permeated water of the reverse osmosis membrane separation device.
[0007]
The boiler feed water treatment method of the present invention is a boiler feed water treatment method that treats raw water and feeds it to the boiler. A process for removing hardness components from the raw water by a reverse osmosis membrane separator, and a deoxygenator to remove the raw water from the raw water. It is characterized by comprising a step of removing dissolved oxygen and a step of recovering alkali components in boiler blow water and supplying them to the permeate of the reverse osmosis membrane separation device.
[0008]
In the present invention, in the reverse osmosis (RO) membrane separator, scale failure is prevented by sufficiently removing the hardness component of boiler feed water. This eliminates the need for a polymer-based scale inhibitor.
[0009]
Further, by removing dissolved oxygen (DO) with a deoxygenation device, corrosion due to oxygen is prevented. This eliminates the need for oxygen scavengers.
[0010]
Furthermore, the alkali component in the boiler blow water is recovered and supplied to the boiler feed water, so that it is not necessary to add an alkali agent.
[0011]
That is, the water (canned water) supplied to the boiler is heated to produce steam and the canned water is concentrated. The produced steam is directly used for any application or indirectly, and a part or all of the steam is returned to the water supply tank as condensate and recycled for use as water supply. A portion of the can water is discharged from the boiler as blow water so as to maintain a predetermined electrical conductivity.
[0012]
Usually, boiler can water is maintained in the alkali added to the boiler feed water for the purpose of inhibiting corrosion and silica scale, and this adjusted pH varies depending on the boiler, but is usually can water pH 9-12. Is often adjusted to pH 11-12.
[0013]
Accordingly, since the boiler blow water partially blown from such can water is alkaline with high pH, in the present invention, the alkaline component is recovered from the blow water that has been conventionally discarded and added to the feed water again.
[0014]
The RO membrane separation apparatus used in the present invention does not require a regenerant, and examples of the deoxygenation apparatus include a vacuum degassing apparatus, a nitrogen degassing apparatus, a degassing apparatus, a catalyst resin deoxygenating apparatus, and a heating degassing apparatus. However, these deoxygenation apparatuses also do not require a chemical such as a regenerative agent.
[0015]
Furthermore, a weak acid cation exchange resin tower, an electric folding device, an activated carbon electrode demineralizer, etc. can be used as an alkali recovery / supply device, but a regenerant is not necessary for these devices, and will be described later. The boiler feed water can be treated without requiring any chemicals other than the alkaline agent at the start of operation of the boiler.
[0016]
In the present invention, the total hardness component concentration of the permeated water of the reverse osmosis membrane separation device is 0.5 mg / L or less, and the DO concentration of the deoxygenated water of the deoxygenation device is 0.1 mg / L or less. It is preferable to perform the following process.
[0017]
In the present invention, as the deoxygenating device, a vacuum degassing device, a nitrogen degassing device, a membrane degassing device, a catalyst resin deoxygenating device or a heating degassing device can be used, and as an alkali recovery / supply device, A weakly acidic cation exchange resin tower, an electric folding device, or an activated carbon electrode desalting apparatus can be used.
[0018]
The boiler blow water discharged from the alkali recovery / supply device is preferably circulated to the inlet side of the device.
[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 system diagram showing an embodiment of a boiler feed water treatment apparatus of the present invention, and FIGS. 2, 3 and 4 are system diagrams showing an embodiment of an alkali recovery / supply apparatus according to the present invention.
[0021]
In the boiler feed water treatment apparatus of FIG. 1, raw water such as well water, tap water, and industrial water is first pumped through a pipe 11.1Is introduced into the RO membrane separation apparatus 1 and the contained hardness component is removed.
[0022]
The RO membrane of the RO membrane separation apparatus 1 may be any RO membrane that can remove the hardness component in the raw water, and may be an RO membrane that removes all salts or an RO membrane that mainly removes the hardness component. . Further, depending on the raw water quality, an RO membrane having a high desalting rate or a membrane having a low desalting rate, such as an RO membrane called a loose RO membrane or a nanofiltration membrane, may be used.
[0023]
In addition, the form of the membrane, the material, and the form of the membrane apparatus are arbitrary, and a tube type module such as a polysulfone membrane, an aromatic polyamide membrane, or a cellulose membrane, a flat membrane type module, a spiral type module, a hollow fiber type module, etc. should be used. Can do.
[0024]
The RO membrane separation device 1 is for removing hardness components to be scaled in the boiler 5, and in order to reliably prevent scale failure in the boiler 5, the permeated water (RO The total hardness component concentration of the permeated water is preferably 0.5 mg / L or less.
[0025]
In order to obtain RO permeated water having a total hardness component concentration of 0.5 mg / L or less by the RO membrane separation device 1, an RO membrane with an appropriate desalination rate may be selected and used according to the raw water quality. Since the permeated water having a total hardness component concentration of 0.5 mg / L or less can be stably obtained regardless of fluctuations in water quality, the hardness permeating to the permeate side by controlling the water recovery rate of the RO membrane separation device 1 It is preferable to adjust the component concentration.
[0026]
That is, in general, the RO membrane separator is often operated at a water recovery rate of about 80%. In this case, the total hardness component concentration of the permeated water is about 1 to 2 mg / L. In such boiler water supply with a total hardness component concentration, scale failure occurs in the boiler. However, the total hardness component concentration of the permeated water can be lowered by reducing the water recovery rate of the RO membrane separation device.
[0027]
In order to obtain permeated water having a total hardness component concentration of 0.5 mg / L or less by adjusting the water recovery rate of the RO membrane separation device 1, as shown in FIG. 1, the concentrated water discharge pipe 14 of the RO membrane separation device 1. Sensors S such as total hardness tester and electrical conductivity meter1The total hardness component of the concentrated water is detected, and the calculator 6 calculates the total hardness component concentration of the permeated water from the detected value of the total hardness component concentration of the concentrated water and the quality and composition of the raw water. As shown in FIG. 1, the valve V-1 of the pipe 13 for returning the concentrated water to the raw water side and the concentrated water discharge pipe 14 for returning the concentrated water to the raw water side as shown in FIG. It is preferable to adjust the water recovery rate by adjusting the opening degree of the valve V-2. In this way, it is more accurate to detect the total hardness component concentration of permeated water by detecting the total hardness component concentration of concentrated water than to detect the total hardness component concentration of diluted permeated water. Can be controlled accurately.
[0028]
In the RO membrane separation device 1, it is preferable to remove as much of the hardness component as possible.+, K+Monovalent cations such as these do not need to be completely desalted and are preferably slightly leaked to the permeate side and contained in the permeate. By doing in this way, when recovery of the alkali component from the boiler blow water in the subsequent alkali recovery / supply device 2 is not sufficient, the monovalent cation leaked into the permeated water becomes Na.+It is preferably recovered as an alkali component such as the alkali recovery / supply device 2 and contributes to the supply of the alkali component to the boiler feed water.
[0029]
The permeated water of the RO membrane separation device 1 is supplied to the water supply tank 3 through the alkali recovery / supply device 2. In the device of FIG. 1, a part of this RO permeate is weakly acidic in the alkali recovery / supply device 2. Water is passed through the cation exchange resin tower 2A, and the remainder is directly fed to the feed water tank 3, and the pH of the boiler feed water is set to a predetermined pH by adjusting the flow rate of each.
[0030]
That is, a part of the RO permeate is supplied to the feed water tank 3 through the pipe 11 provided with the valve V-4, the weak acid cation exchange resin tower 2A and the pipes 15 and 16, and the remainder is supplied through the pipe 12 provided with the valve V-3. And, it is fed directly to the water supply tank 3 through the pipe 16. The pipe 16 has a pH sensor S.2Is provided, and the computing unit 7 uses the pH sensor S.2The pH of the boiler feed water fed to the feed water tank 3 is maintained at a predetermined pH value by adjusting the opening of the valves V-3 and V-4 based on the measured pH value.
[0031]
Usually, the pH of boiler feed water is controlled to be 9 or more, particularly 11 to 11.8, whereby the silica scale can be prevented by alkali and the effect of inhibiting corrosion can be obtained.
[0032]
In the apparatus of FIG. 1, weak acid cation exchange resin towers 2A and 2B are used as alkali recovery / supply apparatus 2, and RO permeate is treated in one weak acid cation exchange resin tower 2A to supply alkali to RO permeate. In the other weakly acidic cation exchange resin tower 2B, the boiler blow water from the boiler 5 is treated to recover the alkali from the boiler blow water, and the weak acid cation exchange resin tower for supplying the alkali and the weak acid for recovering the alkali. By alternately replacing the cation exchange resin tower, alkali is recovered and supplied without the need for a regenerant.
[0033]
Hereinafter, the alkali recovery and supply device 2 will be described with reference to FIG. 2A and 2B, the blackening valve is in a closed state, and the whitening valve is in an open state.
[0034]
Weakly acidic cation exchange resins are alkaline (Na) when alkaline water is passed through.+, K+And the like, and when acidic water or neutral water is passed through, the captured alkali is released. The alkali recovery / supply device 2 utilizes this principle. First, as shown in FIG.2, V3, V6, V7Open, valve V1, V4, V5, V8As closed, the RO permeate is passed through the weak acid cation exchange resin tower 2A (hereinafter referred to as “A tower”), and the boiler blow water is passed through the weak acid cation exchange resin tower 2B (hereinafter referred to as “B tower”). Pass water. At the start of water flow, the weakly acidic cation exchange resin of the A tower that passes RO permeated water is Na type, and the weakly acidic cation exchange resin of the B tower that passes boiler blow water is H type.
[0035]
When RO permeated water comes into contact with the Na-type weakly acidic cation exchange resin in the A tower,+Ions are released from the Na-type weakly acidic cation exchange resin and become alkaline water.
R-COONa + H2O → R-COOH + NaOH
Na+The weakly acidic cation exchange resin from which ions have been released becomes an H-type weakly acidic cation exchange resin.
[0036]
On the other hand, when boiler blow water (this boiler blow water is alkaline water having a pH of 11 or more) comes into contact with the H-type weakly acidic cation exchange resin in the B tower, Na+Ions are incorporated into the weakly acidic cation exchange resin.
R-COOH + NaOH → R-COONa + H2O
Na+The H-type weakly acidic cation exchange resin into which ions are incorporated becomes Na-type weakly acidic cation exchange resin.
[0037]
By continuing the water flow, the tower A increased from Na-type weakly acidic cation exchange resin to H-type weakly acidic cation exchange resin, and the tower B increased from H-type weakly acidic cation exchange resin to Na-type. Na+Ions are no longer released and Na in the B tower+Since it becomes impossible to capture ions, the tower through which RO permeated water and boiler blow water are passed is replaced. That is, as shown in FIG.1, V4, V5, V8Open, valve V2, V3, V6, V7As closed, the RO permeate water is passed through the B tower and the boiler blow water is passed through the A tower. Thereby, in the B tower which became Na form by recovering the alkali from the boiler blow water, the alkali was supplied to the RO permeated water, and the A tower became H form by supplying the alkali to the RO permeated water. Can recover alkali from boiler blow water.
[0038]
Switching between the tower that passes the RO permeate and the tower that passes the boiler blow water may be performed by timer control, and the pH of the effluent of each tower is detected and the detected value is used. May be.
[0039]
As described above, the weakly acidic cation exchange resin tower to be passed is repeatedly switched and the amount of RO permeate to be passed to the alkali recovery / supply device 2 is adjusted to supply alkaline boiler feed water having a pH of 9 or more. The tank 3 can be fed stably.
[0040]
Boiler feed water in the feed water tank 3 is pumped from a pipe 1721, and is supplied to the boiler 5 from the pipe 20. In the apparatus of FIG. 1, a part of the apparatus is supplied from the pipe 18 to the deoxidizer 4, and after DO is removed, water is supplied from the pipe 19. Returned to tank 3.
[0041]
The deoxygenation device 4 is for removing DO contained in the water to be treated. By removing DO with the deoxygenation device 4, corrosion due to DO in the boiler 5 is suppressed. In order to reliably suppress corrosion due to DO in the boiler 5, it is preferable to set the DO of boiler feed water to 0.1 mg / L or less.
[0042]
As the deoxygenation device 4, any device can be used. For example, the following membrane degassing device, vacuum degassing device, nitrogen degassing device, catalytic resin deoxygenating device, heating degassing device, etc. Species can be used alone or in combination of two or more.
(i) Vacuum degassing device: A device that removes DO in water by spraying water to be treated into a degassing tower whose inside is evacuated (reduced pressure).
(ii) Nitrogen degassing device: A device that blows nitrogen gas into the water to be treated and removes DO by taking it into the nitrogen gas.
(iii) Membrane deaerator: A device that supplies treated water to one side of a gas separation membrane, depressurizes the gas phase chamber on the other side, and transfers DO in the water to the gas phase chamber for removal.
(iv) Catalytic resin deoxygenation device: An apparatus for removing DO by reacting DO with hydrogen by bringing water to be treated into contact with a resin carrying a catalyst such as palladium while supplying hydrogen gas.
(v) Heat deaerator: A device that removes DO by heating the water to be treated to lower the gas solubility.
By using such a deoxygenation device, it is possible to remove DO without using an oxygen scavenger composed of chemicals such as sulfite, hydrazine, and saccharides.
[0043]
Such a deoxygenation device is preferably provided in the subsequent stage of the RO membrane separation apparatus, but may be in the previous stage of the RO membrane separation apparatus. By providing it in the subsequent stage of the RO membrane separation device, the permeated water from which the contaminants in the raw water have been removed by the RO membrane separation device flows into the deoxygenation device, which is preferable because fouling in the deoxygenation device is prevented.
[0044]
In the embodiment of FIG. 1, the deoxygenation device 4 is provided in the circulation line of the water supply tank 3, but may be provided in the water supply pipes 17 and 20 from the water supply tank 3 to the boiler 5. Re-dissolution of oxygen and carbon dioxide gas due to contact of oxygen-treated water with air is prevented, which is preferable.
[0045]
Boiler feed water fed from the feed water tank 3 to the boiler 5 through the pipes 17 and 20 becomes steam in the boiler 5 and is fed to the demand point through the pipe 21, and the condensate is returned to the feed water tank 3 through the pipe 22. .
[0046]
The boiler blow water of the boiler 5 is recovered from the pipe 23 by the alkali recovery / supply device 2 and then returned to the raw water side through the pipe 24 and reused as boiler feed water.
[0047]
That is, the blow water after the alkali component is recovered in this way by the boiler feed water treatment apparatus of the present invention does not contain a chemical for the feed water treatment and the alkali component is further removed as in the conventional case. Since it is a clear water containing almost no salt or organic matter, it is desirable to return to the raw water side and recover and reuse it as raw water for boiler feed water as shown in the figure. By collecting such boiler blow water, there is an effect that the amount of waste water and the amount of water used can be remarkably reduced together with the effect of not requiring the addition of chemicals for boiler feed water treatment.
[0048]
The boiler feed water treatment apparatus of FIG. 1 uses a weakly acidic cation exchange resin tower as an alkali recovery and supply apparatus. However, the alkali recovery and supply apparatus is not limited to a weakly acidic cation exchange resin tower. A folding device or an activated carbon electrode desalting apparatus may be used. Moreover, you may use combining 2 or more types among a weak acidic cation exchange resin tower, an electric folding device, and an activated carbon electrode desalination apparatus.
[0049]
FIG. 3 shows an electric folding device 8 as an alkali recovery / supply device. The electric folding device 8 has a cathode chamber having a cathode 8A and an anode chamber having an anode 8B in an electrolytic cell separated by an ion exchange membrane (cation exchange membrane in this embodiment) 8C. When alkaline water is passed through the cathode chamber and neutral voltage is applied between the electrodes 8A and 8B, the alkali (Na+Cations) pass through the cation exchange membrane 8C and migrate to the cathode chamber side. In the electric folding device 8, since a cation exchange membrane is provided as an ion exchange membrane, there is no permeation of anions from the cathode chamber side to the anode chamber side.
[0050]
Accordingly, by passing alkaline boiler blow water to the anode chamber side of the electric folding device 8 and RO permeate water to the cathode chamber side, the alkali in the boiler blow water is supplied to the RO permeate side of the cathode chamber. The alkali can be recovered from the boiler blow water and the recovered alkali can be supplied to the RO permeated water.
[0051]
In addition, it is preferable that the voltage applied to this electric folding device 8 is a DC voltage of 1.2 V or more.
[0052]
FIG. 4 shows activated carbon electrode desalting apparatuses 9A and 9B as alkali recovery and supply apparatuses. The activated carbon electrode demineralizer is a device in which activated carbon electrodes that are in contact with a collector electrode such as metal or graphite are arranged to face each other through an electrically insulating and permeable separator, and a DC voltage is applied between the electrodes. When water containing ions is passed while applying, cations in the water are adsorbed to the cathode side and the negative ions are adsorbed to the anode side, so that the ions in the water are removed. And before adsorption | suction of this ion reaches saturation, the adsorbed ion is desorbed by short-circuiting both electrodes or reversely connecting them.
[0053]
In the present invention, using this principle, two activated carbon electrode desalting apparatuses are installed, and RO permeate is passed through the activated carbon electrode desalting apparatus in a state where the electrodes are short-circuited or reversely connected. Activated carbon electrode demineralization that elutes and removes the alkali by eluting the alkali from the electrode, applying a DC voltage between the electrodes to the other activated carbon electrode desalting apparatus and passing the boiler blow water to adsorb and remove the alkali. Switch devices.
[0054]
That is, as shown in FIG. 4, two towers of activated carbon electrode desalting apparatuses 9A and 9B are provided side by side. Since the activated carbon electrode desalting apparatuses 9A and 9B perform adsorption and elution only of alkali (cation), only the activated carbon electrode or carbon electrode having a small specific surface area is provided on the anode 9b side, and the normal activated carbon electrode is provided on the cathode 9a side. These electrodes 9a and 9b are partitioned by a non-conductive water-permeable separator 9s.
[0055]
First, RO permeated water is passed through the activated carbon electrode desalting apparatus 9A in a state where the electrodes are short-circuited or reversely connected, and the alkali is eluted from the activated carbon electrode. A direct current voltage of about 5 to 2 V is applied to pass boiler blow water to adsorb and remove alkali. In addition, at the time of a water flow start, an alkali is made to adsorb | suck to the activated carbon electrode of 9 A of activated carbon electrode desalination apparatuses which flow RO permeated water.
[0056]
Alkaline elution from the activated carbon electrode of the activated carbon electrode desalting apparatus 9A is eliminated, and before the adsorption of alkali to the activated carbon electrode of the activated carbon electrode desalting apparatus 9B reaches saturation, both activated carbon electrode desalting apparatuses 9A and 9B Water is switched, RO permeate is passed through the activated carbon electrode desalinator 9B with the electrodes short-circuited or reversely connected, and the alkali is eluted from the activated carbon electrode. Apply a DC voltage of about 5 to 2 V and pass boiler blow water to adsorb and remove alkali. Thereafter, this switching is repeated.
[0057]
Such switching of water flow can be performed by opening and closing the valve in the same manner as switching of water flow in the weakly acidic cation exchange resin towers 2A and 2B shown in FIG.
[0058]
Thereby, the alkali of boiler blow water can be collect | recovered and it can supply to RO permeated water.
[0059]
In such an alkali recovery / supply device, during normal operation, the alkali recovered from the boiler blow water is supplied to the RO permeated water, so that the pH of the boiler feed water can be adjusted without adding an alkaline agent. However, in the initial stage of boiler operation, alkaline chemicals are required to bring the pH in the feed water tank 3 to a predetermined value. In addition, during operation, even when the recovered alkali from the boiler blow water is insufficient, the alkaline chemical is replenished. In addition, a chemical may be required to preliminarily adsorb the alkali to the weakly acidic cation exchange resin tower or the activated carbon electrode desalting apparatus through which RO permeate is passed, but the pH is adjusted in the water supply tank 3. Boiler feed water may be passed to make the weakly acidic cation exchange resin tower Na-shaped, or alkali may be adsorbed by an activated carbon electrode desalting apparatus.
[0060]
2-4, the alkali recovered from the boiler blow water is directly supplied to the RO permeated water. This alkaline water is temporarily stored in a storage tank, and the required amount is supplied to an arbitrary location. Also good.
[0061]
The supply of alkali to the boiler feed water by such an alkali recovery and supply device can be performed at any location from the outlet of the RO membrane separation device to the boiler, but when the water supply tank 3 communicates with the atmosphere, If the water in the water supply tank 3 becomes alkaline, carbon dioxide in the atmosphere is absorbed and there is a risk of consuming alkaline components. In this case, alkali is supplied downstream of the water supply tank 3. Is desirable.
[0062]
However, in order to prevent the oxygen in the air from dissolving in the boiler feed water in the feed water tank 3, a shielding material is usually provided on the surface of the water so as to be shut off from the atmosphere. Therefore, as shown in FIG. 1, such a problem does not occur even if the alkali is supplied upstream of the water supply tank 3.
[0063]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0064]
In addition, the boiler which processed the boiler feed water in an Example and a comparative example is 1 m in evaporation amount3/ Hr, water tube boiler with a maximum pressure of 2 MPa, boiler blow water volume is 0.05m3/ Hr, the can water pH was set to 11.
[0065]
Example 1
With the apparatus shown in FIG. 1, the tap water which fluctuates to 25-50 mg / L of total hardness component concentration was processed as raw water.
The specifications of each device used are as follows.
<RO membrane separator>
Nitto Denko Corporation ES20, 4 inches
24 modules
Supply water pressure 0.8MPa
<Alkali recovery and supply device>
Weakly acidic cation exchange resin tower filled with 25 L of weakly acidic cation exchange resin “Diaion WK11” manufactured by Mitsubishi Chemical Corporation
The weakly acidic cation exchange resin tower for passing RO permeate was filled with Na type, and the weakly acidic cation exchange resin tower for passing boiler blow water was passed with H form.
<Deoxygenation device>
2m using one degassing membrane SEPAREL EF-040 φ180 × 615mm made by Dai Nippon Printing Co., Ltd.3Circulated to the water supply tank at / Hr. The operating vacuum pressure was operated at 2 kPa.
[0066]
The RO membrane separator 1 was operated at a water recovery rate of 80 to 50% so that the total hardness component concentration of the concentrated water was 100 mg / L. As a result, in the operation with a water recovery rate of 70%, the total hardness of the treated water was 0.5 mg / L or less when the total hardness of the raw water was 30 mg / L or less. It became 5 mg / L or more. When the raw water hardness was 50 mg / L, it was about 0.9 mg / L, but in this example, by adjusting the water recovery rate, the RO permeation with a total hardness component concentration of 0.5 mg / L or less was stabilized. Got water.
[0067]
A part of the permeated water of this RO membrane separator is passed through the Na-type weakly acidic cation exchange resin tower 2A, the remaining part is directly fed, and the pH of the boiler feed water fed to the feed water tank 3 becomes 9. Both water flows were controlled. Further, the boiler blow water was passed through the H-type weak acid cation exchange resin tower 2B, and the RO permeate water and boiler blow water were switched between the weak acid cation exchange resin towers 2A and 2B, and this switching was repeated.
[0068]
Also, in the deoxygenation device, 2m in the water tank3The DO concentration in the water supply tank 3 was set to 0.1 mg / L or less by circulating / Hr.
[0069]
Example 2
In Example 1, the treatment was carried out in the same manner except that an electroreflective device having the following specifications was used in place of the weakly acidic cation exchange resin tower as the alkali recovery / supply device.
<Electrical folding device>
Electrode area 2dm2
The cation exchange membrane is "Neocepta CM1" manufactured by Tokuyama Corporation.
Boiler blow water is 0.05m in the anode chamber of this electric folding device.3In addition to passing water at / hr, the RO permeated water is passed through the cathode chamber at the same flow rate, and the voltage is adjusted in the range of 3 to 5 V so that the pH of the boiler feed water fed to the feed water tank 3 is 9. Then, a DC voltage was applied. The current was 1.5-2A.
[0070]
Example 3
In Example 1, the treatment was carried out in the same manner except that two towers of activated carbon electrode desalting apparatus having the following specifications were used as the alkali recovery and supply apparatus.
<Activated carbon electrode desalination system>
2m of Kuraray activated carbon fiber Kuraactive CH-20 (positive electrode is CH-10)2An activated carbon electrode desalting cell was assembled using Nika Film FL-400 (thickness 0.4 mm) manufactured by Nippon Carbon Co., Ltd. as the collector electrode and 0.2 mm nonwoven fabric made of polypropylene as the separator.
[0071]
At the start of operation, NaOH was loaded in advance on the activated carbon electrode desalting apparatus for passing RO permeate.
[0072]
The RO permeated water is passed through one activated carbon electrode desalting device and the electrode is short-circuited. The boiler blow water is passed through the other activated carbon electrode desalting device and a DC voltage of 0.8 to 1.2 V is applied. The RO permeated water and the boiler blow water were switched with two towers of activated carbon electrode desalting apparatus, and this switching was repeated.
[0073]
As in Example 1, the pH of boiler feed water fed to the feed water tank 3 was adjusted to 9 by controlling the amount of water flow.
[0074]
Comparative Example 1
In Example 1, the alkali recovery / supply device and the deoxygenation device were not used, the water recovery rate in the RO membrane separation device was set to a constant condition of 70%, and the treatment was performed in the same manner except that the following were added as chemicals. went.
<Additives and amounts added>
Polymer (sodium polyacrylate) scale inhibitor: 5 to 50 mg / L
Phosphoric acid (PO4Ion) scale inhibitor: 1-50 mg / L
Alkali (caustic soda): 4 to 10 mg / L
Oxygen absorber (sodium sulfite): 70 to 90 mg / L
The COD of boiler feed water became 10 to 100 mg / L by adding the above chemicals.
[0075]
After operating for 1 month in the processing of Examples 1 to 3 and Comparative Example 1, the boiler was opened and the amount of scale adhered and the amount of corrosion were examined.
Scale adhesion amount: 0.05mg / cm2/Day
Corrosion amount (pitting corrosion depth): 0.05 to 1 mm / year
It was confirmed that in Examples 1 to 3, good scale prevention and corrosion prevention effects were obtained without using chemicals.
[0076]
Moreover, in Examples 1-3, as boiler blow water after alkali recovery
P alkali: 5 mg / L or less
COD: 2 mg / L or less
Water of high cleanliness was obtained, and this water could be reused as raw water for boiler feedwater. However, in Comparative Example 1, since the chemical was added, the quality of the boiler blow water was
P alkali: about 40 to 100 mg / L
COD: about 400 mg / L
And such boiler blow water (0.05m3/ Hr) required about 10-20 mL / min of 25% sulfuric acid for neutralization.
[0077]
【The invention's effect】
As described in detail above, according to the present invention, chemicals such as phosphoric acid, alkali agents, polymers and other scale inhibitors, oxygen scavengers, and other chemicals added to boiler feed water and boiler feed water treatment devices are used. Therefore, scale failure and corrosion failure of the boiler can be prevented.
[0078]
For this reason, troubles such as transportation, preparation, storage, and replenishment of the medicine are not required, and various problems caused by the use of the medicine such as deterioration of the working environment and treatment of waste water containing the medicine component are solved.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a boiler feed water treatment apparatus of the present invention.
FIG. 2 is a system diagram showing an embodiment of an alkali recovery / supply device according to the present invention.
FIG. 3 is a system diagram showing an embodiment of an alkali recovery and supply apparatus according to the present invention.
FIG. 4 is a system diagram showing an embodiment of an alkali recovery / supply device according to the present invention.
[Explanation of symbols]
1 RO membrane separator
2 Alkali recovery and supply equipment
2A, 2B Weakly acidic cation exchange resin tower
3 Water supply tank
4 Deoxygenation device
5 Boiler
6,7 arithmetic unit
8 Electric Folding Machine
9A, 9B Activated carbon electrode desalination equipment

Claims (7)

原水を処理してボイラに給水するボイラ給水装置において、原水中の硬度成分を除去する逆浸透膜分離装置と、
原水中の溶存酸素を除去する脱酸素装置と、
ボイラブロー水中のアルカリ成分を回収し、回収したアルカリ成分を該逆浸透膜分離装置の透過水に供給するアルカリ回収・供給装置とを備えてなることを特徴とするボイラ給水処理装置。
In a boiler water supply apparatus that processes raw water and supplies water to the boiler, a reverse osmosis membrane separation device that removes hardness components in the raw water,
A deoxygenation device that removes dissolved oxygen in the raw water,
A boiler feed water treatment apparatus comprising: an alkali recovery / supply device that recovers an alkali component in boiler blow water and supplies the recovered alkali component to the permeated water of the reverse osmosis membrane separation device.
請求項1において、逆浸透膜分離装置の透過水の全硬度成分濃度が0.5mg/L以下であり、脱酸素装置の脱酸素処理水の溶存酸素濃度が0.1mg/L以下であることを特徴とするボイラ給水処理装置。2. The total hardness component concentration of the permeated water of the reverse osmosis membrane separation device is 0.5 mg / L or less, and the dissolved oxygen concentration of the deoxygenated water of the deoxygenation device is 0.1 mg / L or less. Boiler feed water treatment device characterized by the above. 請求項1又は2のいずれか1項において、該脱酸素装置が真空脱気装置、窒素脱気装置、膜脱気装置、触媒樹脂脱酸素装置又は加熱脱気装置であることを特徴とするボイラ給水処理装置。3. The boiler according to claim 1, wherein the deoxygenating device is a vacuum degassing device, a nitrogen degassing device, a membrane degassing device, a catalyst resin deoxygenating device, or a heating degassing device. Water supply treatment device. 請求項1ないし3のいずれか1項において、該アルカリ回収・供給装置が弱酸性カチオン交換樹脂塔、電気透折器又は活性炭電極脱塩装置であることを特徴とするボイラ給水処理装置。The boiler feed water treatment apparatus according to any one of claims 1 to 3, wherein the alkali recovery / supply apparatus is a weakly acidic cation exchange resin tower, an electric folding apparatus, or an activated carbon electrode desalting apparatus. 請求項1ないし4のいずれか1項において、該アルカリ回収・供給装置から排出されたボイラブロー水を装置の入口側へ循環する手段を備えることを特徴とするボイラ給水処理装置。The boiler feed water treatment apparatus according to any one of claims 1 to 4, further comprising means for circulating the boiler blow water discharged from the alkali recovery / supply apparatus to the inlet side of the apparatus. 原水を処理してボイラに給水するボイラ給水の処理方法において、
逆浸透膜分離装置により原水中の硬度成分を除去する工程と、
脱酸素装置により原水中の溶存酸素を除去する工程と、
ボイラブロー水中のアルカリ成分を回収して逆浸透膜分離装置の透過水に供給する工程とを備えてなることを特徴とするボイラ給水の処理方法。
In the boiler water supply processing method of processing raw water and supplying water to the boiler,
Removing the hardness component in the raw water with a reverse osmosis membrane separator;
Removing the dissolved oxygen in the raw water with a deoxygenation device;
And a step of recovering an alkaline component in boiler blow water and supplying it to the permeated water of the reverse osmosis membrane separation device.
請求項6において、逆浸透膜分離装置の透過水の全硬度成分濃度が0.5mg/L以下であり、脱酸素装置の脱酸素処理水の溶存酸素濃度が0.1mg/L以下であることを特徴とするボイラ給水の処理方法。7. The total hardness component concentration of the permeated water of the reverse osmosis membrane separation device is 0.5 mg / L or less, and the dissolved oxygen concentration of the deoxygenated water of the deoxygenation device is 0.1 mg / L or less. A method for treating boiler water supply.
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