JP3843141B2

JP3843141B2 - Method and apparatus for treating flue gas desulfurization waste water

Info

Publication number: JP3843141B2
Application number: JP11511595A
Authority: JP
Inventors: 和茂川村; 明人石毛
Original assignee: Chiyoda Corp
Current assignee: Chiyoda Corp
Priority date: 1995-04-17
Filing date: 1995-04-17
Publication date: 2006-11-08
Anticipated expiration: 2021-11-08
Also published as: JPH08281296A

Description

【０００１】
【産業上の利用分野】
本発明は、硫黄過酸化物を始めとして酸化性物質を含有する排煙脱硫排水の処理方法及びその装置に関し、更に詳細には排煙脱硫排水を浄化処理する排水処理装置の性能劣化を軽減するように酸化性物質を含有する排煙脱硫排水を予め前処理する方法及びその装置に関するものである。
【０００２】
【従来の技術】
排ガスから亜硫酸ガス等の硫黄酸化物を除去するために、排ガスと吸収液とを気液接触させ、硫黄酸化物を除去する湿式排煙脱硫法が多用されている。湿式排煙脱硫方法は、大別すると、ジェットバブリング反応槽等の反応槽を設け、反応槽に収容した吸収液中に排ガスを導入して気液接触させる方式と、スプレー式吸収塔を設け、吸収塔に導入される排ガス中に吸収液をスプレーして気液接触させる方式とがある。その他、充填塔を用いる方法もある。
従来の湿式排煙脱硫方法では、反応槽又は吸収塔（以下、反応槽等と言う）の上流に除塵塔を設け、反応槽等に導入する前に除塵塔で排ガスと冷却液とを接触させて予め排ガスの冷却及び除塵を行う２塔式が採用されていたが、近年の反応槽等の性能の向上の結果、除塵塔を省略した、一塔式のいわゆるスート混合型排煙脱硫装置が多用されている。また、従来の湿式排煙脱硫方法では、反応槽等の後段に酸化塔を設け、そこで酸化処理を行っていたが、現在では、酸化を反応槽等で行う方式が一般的である。
【０００３】
使用される吸収液は、硫黄酸化物を固定化する吸収剤を水に溶解及び／又は懸濁させた液で、一般にはカルシウム化合物系の吸収剤、例えば石灰石を水に溶解及び／又は懸濁させたスラリ状水溶液を使用する。
排ガス中の硫黄酸化物は、ジェットバブリング反応槽等の反応槽に収容された吸収液或いはスプレー式吸収塔内でスプレーされた吸収液と気液接触して吸収液に化学吸収及び／又は物理吸収され、水、酸素及び石灰石と反応し、石膏となって排ガスから除去される。生じた石膏は、粒子となって晶析し、吸収液中に浮遊する。
【０００４】
晶析した石膏を濃厚に含有するスラリは、石膏分離装置に送液され、そこで石膏が分離される。図７は、従来の石膏分離装置１０の模式的フローシートである。図７に示すように、反応槽等１２の底部から排出ポンプ１４により排出され、固液分離装置又は石膏脱水機１６に送液され、そこで石膏がスラリから分離される。
次いで、母液の一部は、石灰石粉末が添加された後、吸収剤スラリとして反応槽等１２に戻されて再び排ガスと気液接触し、母液の一部は、排煙脱硫排水として排水処理装置１８へ送られ、浄化処理された後、河川等に放流される。
浄化処理する排水処理装置１８は、処理排水を河川等に放流できる程度に排煙脱硫排水を浄化する装置を言う。排水処理装置は、湿式排煙脱硫装置に付属した装置である場合もあるし、また公共の排水処理装置である場合もある。
【０００５】
【発明が解決しようとする課題】
ところで、最近、湿式排煙脱硫装置から送液される排煙脱硫排水に吸着処理及び／又は生物学的処理を施して所定の水質に排煙脱硫排水を処理する排水処理設備において、その性能の劣化が予想以上に速くしかも急激に進行することが問題にされており、その原因が湿式排煙脱硫装置から送液される排煙脱硫排水の水質にあることが判った。ここで、吸着処理とは、吸着剤による吸着のみならず、イオン交換樹脂によるイオン交換処理をも含む概念であり、生物学的処理とは、硝化菌、脱窒素菌等を使用して生物学的に排水処理することである。
その問題とは、例えば被処理排水の脱窒素工程で利用されている脱窒素菌の成長が阻害され、そのために排水処理装置から放流される処理水の窒素量が増大していることであり、また被処理排水中のＣＯＤを吸着させる吸着剤として使用されている有機物吸着樹脂の劣化が予想外に速いことである。さらに、ホウ素、フッ素を除去する樹脂についても同様の現象が起こる。
【０００６】
以上の状況に照らして、本発明の目的は、第１には排水処理装置の性能を低下させないような水質にして排煙脱硫排水を排水処理装置に送水するために排煙脱硫排水を予め前処理する方法を提供することであり、第２にはその前処理を実施するための前処理装置を提供することである。
【０００７】
【課題を解決するための手段】
本発明者らは、排水処理装置の性能低下について研究した結果、排煙脱硫装置の方式を問わず、ほとんどの装置で性能低下が起こり、特にスート混合型湿式排煙脱硫装置で低下が激しく、この方式の装置から流出する排煙脱硫排水に含まれている酸化性物質の濃度が高いことに主として原因があることを突き止めた。ここで、酸化性物質とは、排煙脱硫排水に含まれている酸化能を有する物質を意味し、その中には硫黄過酸化物、例えばＳ₂Ｏ₈ ^2-も含まれている。酸化性物質は、後述するように、例えばＤＰＤ法等による塩素換算値により定量できる。
そこで、本発明者らは、硫黄過酸化物、例えばＳ₂Ｏ₈ ^2-をＳＯ₄ ^2-に還元し、合わせてその他の酸化性物質を還元して、排煙脱硫排水中の酸化性物質濃度を低下させることにより、排水処理装置の性能低下を防止できることを実験により実証した。
ところで、排煙脱硫排水を排出する反応槽等自体において、酸化性物質が排煙脱硫排水に含まれないように排ガスを処理する方法も研究され、二、三の方法が提案されているが、加えて、排煙脱硫排水から硫黄過酸化物を除去する方法も問題解決に有力な方法であると判断し、研究を重ねた。
【０００８】
研究と実験の結果、本発明者は、活性炭を吸着剤として使用するよりも、寧ろ硫黄過酸化物を始めとする酸化性物質の酸化還元反応において還元剤として使用する方が酸化性物質の除去に関し有効であることを見い出した。更には、次に例として挙げるように、特定の条件の下では、特に活性炭の酸化還元反応が促進されることを実験により確認した。
【０００９】
第１には、排煙脱硫排水が特定のｐＨの範囲にある場合に、活性炭による酸化還元反応が促進されること。
第２には、特定の金属及びそれらの金属化合物を触媒として使用した場合に、活性炭による酸化還元反応が促進されること。また、それら金属及び金属化合物が長時間にわたり安定した触媒性能を維持できることがわかった。しかも特定金属及び低価数の金属化合物は、それ自身還元剤として有効であって、例えば硫黄過酸化物をＳＯ₄ ^2-に容易に還元できることも発見した。また、排煙脱硫排水のなかには、排煙脱硫排水のｐＨが活性炭の酸化還元反応に好適な範囲にあり、しかも触媒及び還元剤として働くＦｅ（ＯＨ）₃等の金属化合物が排煙脱硫排水中に含まれていることがあって、このような場合には、特に活性炭による酸化還元反応が促進されることも判った。
第３には、排煙脱硫排水の温度が高い程、活性炭の酸化還元反応が促進されること。
第４には、排煙脱硫排水中で活性炭を浮遊させ、活性炭の流動床を形成することが酸化還元反応に有効であること。
以下に、本発明方法の開発の過程で実施した実験例を説明する。
【００１０】
実験例１
７５cm³の椰子殻破砕炭（武田薬品（株）製の商品名白鷺ＫＬ、仕様１０メッシュ篩以下）を固定床の形態で充填した活性炭槽を作製した。
石灰石を吸収剤として使用したスート混合型湿式排煙脱硫装置により石炭焚排ガスを処理して得た排煙脱硫排水を活性炭槽に通水する原水とした。原水の酸化性物質濃度を求めたところ１２mg-cl/L −原水（塩素換算値）であった。
酸化性物質濃度の測定方法は、ＪＩＳＫ０１０２工業排水試験方法のジエチル−Ｐ−フェニレンジアミン比色法に準じ、発色時間のみを長くして安定した発色状態になった時の比色により定量する方法である。以下、この方法をＤＰＤ法と言う。尚、酸化性物質のうち硫黄過酸化物のみを定量したい場合には、例えばイオンクロマトグラフィを使用する。
次いで、原水のｐＨを調整することなく、また３価の鉄等の触媒を添加することなく、常温の原水を活性炭固定床の活性炭槽に通水した。
【００１１】
定常状態になったところで、活性炭槽出口の処理水中の酸化性物質濃度を測定して酸化性物質の除去率を算出した。その結果は、通水開始の初期には７０％の除去率であって、活性炭の酸化還元反応による酸化性物質の除去効果を確認することができた。但し、除去率は、その後徐々に低下し、３００時間経過時には１０％程度まで低下した。
【００１２】
実験例２
実験例１と同じ原水と活性炭槽を使用した。原水を所定温度に加熱し、２０ｍｇ／Ｌ−原水の添加率で鉄（３価）を原水に添加し、更に塩酸を添加してｐＨを３．０に調整しつつ、原水を０．３Ｌ／Ｈｒの流量で、即ち４．０の液空間速度で活性炭槽に送水した。定常状態になった時点で、活性炭槽出口の処理水中の酸化性物質濃度を測定して酸化性物質の除去率を算出した。更に、原水温度を種々変えて以上の実験を繰り返した。
【００１３】
その結果は、図１に示される通りであって、原水の温度が高い程、酸化性物質の除去率が高いことが判る。この実験結果から、原水の温度を３０°C 以上、好ましくは５０°C 以上にすると、８０％（この除去率は実用的には満足できる酸化性物質の除去率である）以上、場合によっては９５％以上の安定した酸化性物質除去率を得ることができる。ただし、この除去率の範囲に限定されるものではないことはいうまでもない。尚、このような高い酸化性物質の除去率を３００時間以上の長期間にわたり維持できることも確認できた。
【００１４】
また、酸化性物質濃度の測定は、ＤＰＤ法に加えて、ＪＩＳＫ０１０２よう素滴定法に準じ、かつ反応時間を長くした方法（以下、ＫＩ法と言う）、ＪＩＳＫ０１０２Ｏ−トリジン比色法に準じ、発色時間を長くした方法（以下、ＯＴ法と言う）またはフェニルアルセノオキサイド、沃化カリウムを用いた電量滴定法、アスコルビン酸による酸化還元電位滴定法又は電量滴定法を使用して行うことができる。反応が速く測定に要する時間が短い利点を有するので、アスコルビン酸による酸化還元電位滴定法又は電量滴定法が好ましい。この方法は、アスコルビン酸の還元力（電位）が検出されるまでのアスコルビン酸の滴定量を求めて、硫黄過酸化物を含む酸化性物質の濃度とするものである。これによって、酸化性物質濃度のほぼ連続的な測定ができ、リアルタイム的な検出を必要とする運転制御が可能になる。
【００１５】
実験例３
攪拌機を備えた有効容積１０００cm³の活性炭槽を用意し、その槽内に実施例１に使用したものと同じ椰子殻破砕炭を４００cm³投入した。次いで、原水として実験例１と同じ排煙脱硫排水を使用し、ｐＨを２に、温度を５０°C にそれぞれ調整し、かつ３価の鉄を２０mg/L−原水の添加率で添加した原水を２．０L/Hrの流量で活性炭槽に通水しつつ攪拌して攪拌流動床を形成した。
活性炭槽内の流動床が定常状態になったところで、活性炭槽から流出する処理水の酸化性物質濃度をＤＰＤ法により測定し、酸化性物質除去率を算出した。更に、原水に対する３価の鉄の添加量（mg/L−原水）を種々変えて以上の実験を繰り返した。
【００１６】
その結果は、図２に示される通りであって、鉄の添加量が多い程、酸化性物質の除去率が高いことが判る。この実験結果から、鉄の添加量が８〜５０mg/lの範囲にあれば、実用的には満足できる酸化性物質除去率を少なくとも２０００時間にわたり得ることができる。
また、Ｆｅに加えて、Ｃｕ、Ｍｎ及びＮｉも活性炭の酸化還元反応の触媒として有効であることを確認した。
【００１７】
実験例４
攪拌機を備えた有効容積３０００cm³の活性炭槽を用意し、その槽内に８００cm³の椰子殻破砕炭（日本カーボン社製の商品名ＡＣＧ、６０〜１２０メッシュ）を投入した。次いで、原水として実験例１と同じ排煙脱硫排水を使用し、ｐＨを所定値に、温度を５０°C にそれぞれ調整し、かつ３価の鉄を１２mg/L−原水の添加率で添加した原水を５．０L/Hrの流量で活性炭槽に通水しつつ攪拌して攪拌流動床を形成した。
活性炭槽内の流動床が定常状態になったところで、活性炭槽から流出する処理水の酸化性物質濃度をＤＰＤ法により測定し、酸化性物質除去率を算出した。更に、原水のｐＨを種々変えて以上の実験を繰り返した。
【００１８】
その結果は、図３に示される通りであって、原水のｐＨが低い程、酸化性物質の除去率が高いことが判る。この実験結果から、原水のｐＨが１．０〜４．０の範囲にあれば、実用的には満足できる酸化性物質除去率を得ることができる。
【００１９】
排煙脱硫排水の処理方法上記目的を達成するために、以上の実験結果に基づいて完成された本発明に係る排煙脱硫排水の処理方法は、酸化性物質として硫黄過酸化物を含有する排煙脱硫排水を排水処理装置で吸着処理及び／又は生物学的処理を行う前に排煙脱硫排水を予め前処理する方法であって、
Ｆｅ、Ｃｕ、Ｍｎ及びＮｉの金属並びにそれらの金属化合物のうちの少なくとも１種類を排煙脱硫排水に添加する金属添加工程と、
次いで、排煙脱硫排水に酸を添加して、ｐＨを１〜４の範囲に調整するｐＨ調整工程と、
次いで、排煙脱硫排水中の酸化性物質を活性炭との反応により還元する反応工程とを備えることを特徴とする排煙脱硫排水の処理方法。
【００２０】
本発明は、硫黄過酸化物を始めとして酸化性物質を含有する排煙脱硫排水、特に硫黄過酸化物を相対的に高濃度で含有する排煙脱硫排水、例えばスート混合型湿式排煙脱硫装置から排出される排煙脱硫排水に好適に適用される。
本発明方法で言うスート混合型湿式排煙脱硫装置は、前段の除塵塔及び別置きの酸化塔のいずれをも有しない一塔式の湿式排煙脱硫装置であって、排ガスの冷却、除塵を別置きの除塵塔で行う方式及び亜硫酸イオンの酸化を別置きの酸化塔で行う方式の湿式排煙脱硫装置のいずれをも除外する意味である。
本発明は、特に、ｐＨが１〜４の範囲にあって、触媒及び還元剤となる金属又は金属化合物、例えばＦｅ（ＯＨ）₃等を含む排煙脱硫排水の処理に好適に適用できる。
【００２１】
排煙脱硫排水のｐＨが高いときには、本発明方法は、反応工程の前に酸を添加してｐＨを１〜４の範囲に調整するｐＨ調整工程を備えることを特徴としている。これにより、活性炭による酸化還元反応が促進される。例えば、通常のスート混合型湿式排煙脱硫装置から排出される排煙脱硫排水のｐＨは、５以上であるため、特に本発明方法が好適である。
【００２２】
排煙脱硫排水中に触媒となる金属が含まれていない時には、本発明方法は、Ｆｅ、Ｃｕ、Ｍｎ及びＮｉの金属並びにそれらの金属化合物のうちの少なくとも１種類を添加する金属添加工程をｐＨ調整工程の前に備えることを特徴としている。例えば、通常のスート混合型湿式排煙脱硫装置から排出される排煙脱硫排水は、鉄の濃度が５ｍｇ／Ｌと小さいため、特に本発明方法が好適である。
【００２３】
石炭焚排ガスを処理した排煙脱硫排水に対しては、Ｃｕ及びＮｉであれば排煙脱硫排水中の濃度が３〜１５０ｍｇ／ｌの範囲になるように、Ｍｎであれば濃度が１０〜２００ｍｇ／ｌの範囲の範囲になるように、Ｆｅであれば濃度が５〜１００ｍｇ／ｌの範囲になるように各金属化合物を添加する。ここで、上述の範囲の下限値より金属添加量が少ない場合、金属の触媒効果が乏しく、上限値以上の場合、金属添加量の増大に比してその触媒効果の増大が小さく、排水処理コストが上昇する。
ｐＨ調整工程で添加する酸は、例えば塩酸、硫酸等を例として挙げることができる。ここで、ｐＨが４以上では、酸添加の効果が乏しく、逆にｐＨを１以下にすることは、酸の添加量の増大に比してその効果の増大が小さく、排水処理コストが上昇する。
金属添加工程及びｐＨ調整工程をそれぞれ別々の段階で実施することもできるし、また一つの混合槽を使用して実施することもできる。
【００２４】
本発明の好適な実施態様は、前記金属の化合物が、低価数の金属の化合物であることを特徴としている。
価数とは、イオン価と同意であって、低価数の金属の化合物、例えばＦｅ⁺²であれば、Ｆｅ⁺²がＦｅ⁺³に酸化される過程でＳ₂Ｏ₈ ^2-をＳＯ₄ ^2-に還元することができると考えられる。尚、前記金属の触媒作用に関しては、低価数の化合物である必要はない。
また、金属の化合物は、金属の硫酸塩であれば、硫酸イオンがＣａと化合して石膏を生成して、活性炭に付着し、活性炭の目詰まり或いは活性炭の活性低下を発生させるからあまり好ましくない。実際には、例えばＦｅＣｌ₂等の金属の塩化物を使用することが好ましい。
【００２５】
本発明の好適な別の実施態様は、前記反応工程の前に排煙脱硫排水を３０°C 以上に加熱することを特徴としている。
排煙脱硫排水を加熱して温度を上昇させることにより、硫黄過酸化物の除去率を高めることができる。温度と除去率とのの関係は、後述の実験例で示すように、ほぼ一次相関であるから、排煙脱硫排水の温度が高い程、硫黄過酸化物の除去率を大きくすることが出来るが、３０°C 以上であれば、実用的に満足できる除去率を達成することができる。
【００２６】
排煙脱硫排水と活性炭とを接触させる手段は、活性炭槽内に設けた活性炭の固定床に排煙脱硫排水を通水しても良く、また活性炭槽内の排煙脱硫排水に活性炭を投入し、かつ攪拌機等の攪拌手段により攪拌して排煙脱硫排水中に浮遊ないし懸濁させ、活性炭の流動床を形成しても良いが、接触効率から見て後述するように流動床の方が望ましい。流動床の形成手段としては、機械的な攪拌に加えて、更に、ノズル、多孔板等により排煙脱硫排水を活性炭槽の底部から槽内に噴出させることにより、活性炭槽内で排煙脱硫排水を流動させ、活性炭の流動床を形成することができる。
そこで、発明の好適な実施態様の反応工程では、前記反応工程では、活性炭を収容する活性炭槽に排煙脱硫排水を流入させ、排煙脱硫排水中に活性炭を浮遊ないし懸濁させる流動床を形成することを特徴としている。
【００２７】
反応工程では、反応の進行に伴い極く僅かであるが、ＣＯ₂ガス等のガスが発生することが実験により確認されている。活性炭は疎水性であるから、発生したガスは活性炭表面に付着し易く、そのため活性炭と排煙脱硫排水との固液接触が阻害される。しかも、発生ガス中には極く少量ではあるが可燃性ガスも含まれるため、ガスが活性炭表面に蓄積するのは安全上から好ましくない。従って、ガスが蓄積し易い固定床よりは、攪拌による流動床の方が反応工程の反応性及び安全性から言って好ましい。
そこで、前記反応工程において固定床の活性炭層を使用する場合には、活性炭層に排煙脱硫排水を通水しつつ活性炭層に超音波及び／又は機械的振動を与えることが好ましい。これにより、蓄積したガスを解離することができるからである。
【００２８】
また、本発明の好適な実施態様の反応工程では、前記反応工程では、排煙脱硫排水を機械的に攪拌して活性炭の流動床を形成する場合にはその攪拌強度を、又は排煙脱硫排水を流体力学的に流動させて活性炭の流動床を形成する場合にはその流動状態をそれぞれ時々間欠的に強くして、活性炭の流動床中に形成された活性炭の凝集フロックを解砕することを特徴としている。
機械的に攪拌とは攪拌機等の機械的手段で攪拌することを言い、流体力学的に流動させるとは、排煙脱硫排水をノズル等から噴出させることにより流動状態を形成することを言う。
攪拌強度は、基本的には、酸化性物質含有排水中に活性炭を浮遊ないし懸濁させて、活性炭の流動床を形成できる程度の強度で良いが、活性炭は反応の進行と共に凝集してフロックを形成し、活性炭の活性比表面積が減少して反応性が低下することがわかった。そこで、間欠的に強く攪拌して活性炭のフロックを解砕することにより、活性炭の反応性を回復させることが実用面では好ましい。
また、流体力学的に流動させる場合も、常時は、酸化性物質含有排水中に活性炭を浮遊ないし懸濁させて、活性炭の流動床を形成できる程度の流動状態で良いが、その流動状態を時々間欠的に強くして、活性炭の流動床中に形成された活性炭の凝集フロックを解砕する。
【００２９】
本発明の好適な別の実施態様は、前記反応工程を経た排煙脱硫排水中の酸化性物質の濃度を測定し、その測定値に基づき所定の関係に従って排煙脱硫排水に添加する金属化合物の量を増減する操作、排煙脱硫排水の温度を調節する操作及び活性炭の添加量を増減する操作の少なくともいずれかを行うことを特徴としている。
硫黄過酸化物濃度の測定は、ＫＩ法、ＤＰＤ法、ＯＴ法またはフェニルアルセノオキサイド、沃化カリウムを用いた電量滴定法、アスコルビン酸による酸化還元電位滴定法又は電量滴定法を使用して行えるが、測定に要する時間が短い利点を有するので、アスコルビン酸による酸化還元電位滴定法又は電量滴定法が好ましい。
【００３０】
また、更に、反応工程を経た排煙脱硫排水から活性炭を分離する活性炭分離工程を備え、
活性炭分離工程で分離した活性炭の一部を前記反応工程で再使用することもできる。この分離工程では活性炭を分離し易くするため高分子有機化合物もしくはＦｅなどの無機系凝集剤を使用することもできる。これにより、微粉化し、流出した活性炭を回収し再利用できるので活性炭の所要量を節減することができる。また、使用する活性炭としては、石炭系、石油系のものより、性能が高く、安価な椰子殻から得た椰子殻破砕炭が最適である。
【００３１】
排煙脱硫排水の前処理装置
上述の本発明方法を実施する装置として好適な本発明に係る排煙脱硫排水の前処理装置は、酸化性物質として硫黄過酸化物を含有する排煙脱硫排水を排水処理装置で吸着処理及び／又は生物学的処理を行う前に排煙脱硫排水を予め前処理する前処理装置であって、
流入する排煙脱硫排水を熱媒により加熱する加熱手段と、酸を添加する酸添加手段と、Ｆｅ、Ｃｕ、Ｍｎ及びＮｉの金属並びにそれらの金属化合物のうちの少なくとも１種類を添加する金属化合物添加手段と、添加された酸及び金属又は金属化合物と槽内に流入する排煙脱硫排水とを混合する混合手段とを備えた混合槽と、
活性炭を槽内に投入する活性炭投入手段と、混合槽を経て槽内に流入する排煙脱硫排水と投入された活性炭とを攪拌する攪拌手段とを備えた活性炭槽と
を備え、前記混合槽では、金属化合物添加手段による金属又は金属化合物の添加の後で酸添加手段による酸の添加を行うことを特徴としている。
【００３２】
混合槽の加熱手段に使用する熱媒は、発生、取扱の容易なことから、好適にはスチームであり、混合槽にスチームジャケット或いはスチームコイル管を設けることによりスチームにより容易に加熱することができる。別法として、スチームを排煙脱硫排水中に直接吹き込んでも良い。
混合手段は、混合できる限り特に限定は無く、邪魔板を混合槽内に設けて排煙脱硫排水が混合槽に流入する流速を利用しても良く、攪拌機を設けて攪拌混合しても良い。
金属化合物添加手段及び活性炭投入手段は、既知の機構を利用した手段であって、例えば粉粒状、スラリー状、液状等の金属化合物及び活性炭の形態に応じて適当なものを使用する。
【００３３】
活性炭槽に備える攪拌手段は、常用の攪拌機でも良く、また流体を噴流させる既知の噴流方式の攪拌手段でも良い。また、ガス噴き込みによる攪拌手段でもよい。
本発明の好適な実施態様は、前記攪拌手段が、混合槽を経て槽内に流入する排煙脱硫排水を活性炭槽の底部から活性炭槽内に噴出させ、活性炭投入手段から投入された活性炭の流動床を活性炭槽内に形成するようにした手段であることを特徴としている。
噴出させる手段として、ノズル、多孔板等を使用できる。
【００３４】
本発明の好適な実施態様は、攪拌強度を変える手段を前記活性炭槽の攪拌手段に備えていることを特徴としている。攪拌強度を変える手段としては、例えば攪拌機の場合にはその駆動装置を回転数可変にすること、噴流方式の場合にはその噴流の速度を可変にすることを挙げることができる。
強力に攪拌することにより、反応の進行と共に凝集してフロック状になった活性炭を分解して再度微粒子として分散させることができる。
【００３５】
本発明の好適な別の実施態様は、活性炭槽から流出した排煙脱硫排水中の酸化性物質の濃度を測定する測定装置と、
前記金属化合物添加手段により添加する金属の化合物の添加量、前記加熱手段により加熱する排煙脱硫排水の温度及び前記活性炭投入手段により投入する活性炭の投入量の少なくとも一つを前記測定値に基づき所定の相関関係に従って制御する制御装置と
を備えることを特徴としている。
【００３６】
酸化性物質の濃度測定装置としては、他の方法に比べて測定時間が短い（一回の測定に要する時間が１０分以下）ので、アスコルビン酸による酸化還元電位滴定法又は電量滴定法を利用する装置が好ましい。
本発明で使用する所定の相関関係は、予め活性炭槽から流出した排煙脱硫排水中の酸化性物質濃度と、金属化合物の添加量、排煙脱硫排水の温度及び活性炭の投入量との関係を実験により定めておくことにより設定することができる。
【００３７】
【作用】
請求項１０から１３に記載の発明では、混合槽において、流入する排煙脱硫排水を加熱手段により３０℃以上に加熱し、酸添加手段により排煙脱硫排水のｐＨを１〜４の範囲に調整し、金属化合物添加手段により金属化合物を排煙脱硫排水に添加して、活性炭槽における活性炭との酸化還元反応の促進を図っている。
また、活性炭槽から流出した排煙脱硫排水中の酸化性物質濃度を測定装置により測定し、添加手段により添加する金属の化合物の添加量、加熱手段により加熱する排煙脱硫排水の温度及び活性炭投入手段により投入する活性炭の投入量の少なくとも一つを測定値に基づき所定の相関関係に従って制御装置により調整する。これにより、処理排煙脱硫排水中の硫黄過酸化物を含む酸化性物質の濃度を所定値に制御することができる。
【００３８】
【実施例】
以下、添付図面を参照し、実施例に基づいて本発明装置をより詳細に説明する。
本発明装置の実施例１
図４は、本発明に係る排煙脱硫排水の前処理装置の好適例である実施例１の構成を示すフローシートである。
本前処理装置２０は、硫黄過酸化物を含む酸化性物質を含有する排煙脱硫排水（以下、簡単に原水と言う）に排水処理装置で吸着処理及び／又は生物学的処理を施して排水処理する前に、原水を予め前処理する前処理装置であって、図７の固液分離装置１６と排水処理装置１８との間に設けられている。本前処理装置２０は、混合槽２２と、活性炭槽２４とから構成されている。
【００３９】
混合槽２２は、排煙脱硫排水に触媒金属を添加し、かつ排煙脱硫排水の温度とｐＨを調整するための槽であって、流入する排煙脱硫排水をスチームにより加熱するスチームコイル管２６と、塩酸等の酸を混合槽２２に注入する酸注入管２８と、Ｆｅ等の金属化合物の触媒を水溶液の形で混合槽２２に投入する金属化合物添加管３０と、添加された酸及び金属化合物と槽内に流入した排煙脱硫排水とを攪拌、混合する攪拌機３２とを備えている。
スチームコイル管２６にスチームを供給する供給管３２にはスチームの流量を調節する流量調節弁３４が、また酸注入管２８には酸の注入量を調節する流量調節弁３６が、それぞれ設けてある。同じく、金属化合物添加管３０には、金属化合物の水溶液の流量を調節する流量調節弁３８が設けてある。
【００４０】
活性炭槽２４は、所定流量で流入する原水が所定の滞留時間だけ滞留できるだけの容積を備えた槽であって、活性炭槽２４の入口は、ライン４０を介して混合槽２２の出口に接続されている。
活性炭槽２４には、回転数可変の攪拌機４２と、活性炭を活性炭槽２４に投入する活性炭投入管４４とが設けてある。活性炭投入管４４には、活性炭の投入流量を調節するロータリーフィーダ等の流量調節弁４６が設けてある。
また、活性炭槽２４から流出する処理水管４８には、処理水の硫黄過酸化物濃度を測定する濃度計５０が設けてある。濃度計５０は、アスコルビン酸による滴定により酸化還元電位を測定し、測定電位に基づき所定の相関関係に従って硫黄過酸化物濃度を算出している。
【００４１】
更に、本前処理装置２０は、制御装置５２を備えていて、濃度計５０の測定値に基づき所定の相関関係に従って、流量調節弁３４を介してスチーム流量を調整することにより原水の温度を制御し、流量調節弁３６を介して酸の注入流量を調整することにより原水のｐＨを調節し、流量調節弁３８を介して触媒粉粒体の投入量を調整し、また流量調節弁４６を介して活性炭の投入量を調整する。
なお、混合槽内の液の温度、ｐＨを計測し、流量調節弁３４、流量調節弁３６の開度調整も同時に行うことは、安定運転のために好ましい。これを使用するフィードバッグ制御もできる。
【００４２】
以上の構成により、本前処理装置２０を使用して以下のようにして本発明方法を実施できる。
先ず、原水を混合槽２２に導入し、スチームコイル管２６により原水を３０℃ 以上に加熱しつつ、金属化合物添加管３０から鉄等の金属化合物、例えばＦｅＣｌ _２の水溶液を所定流量で注入し、更に酸注入管２８により酸、例えば塩酸を所定流量で注入して原水のｐＨを１〜４の範囲に調整し、攪拌機３２により攪拌、混合する。
次いで、原水は、ライン４０を経て活性炭槽２４に入る。活性炭槽２４では、活性炭、好ましくは椰子殻破砕炭を活性炭投入管４４から所定量連続的に又は断続的に原水に投入し、攪拌機４２で攪拌しながら、原水と共に活性炭の流動床を形成する。原水中の硫黄過酸化物を始めとする酸化性物質は、活性炭と酸化還元反応を行い、例えば硫黄過酸化物はＳＯ_４ ^２−に転化され、活性炭量はその反応した分だけ減少する。
【００４３】
活性炭槽２４では、活性炭が反応の進行と共に凝集してフロックを形成するので、間欠的に好ましくは定期的に攪拌機４２の回転数を上げて活性炭槽２４内を強力に攪拌して、フロックを分解して微粒の活性炭に分散させ、反応に寄与する表面積を大きくすることが好ましい。
【００４４】
本発明装置の実施例２
図５は、本発明に係る排煙脱硫排水の前処理装置の好適例である実施例２の構成を示すフローシートである。
本前処理装置６０は、図４に示す実施例１の構成に加えて、活性炭槽２４の下流に処理水から活性炭を分離する遠心分離機、シックナー等の固液分離装置６２と固液分離装置６２で分離した活性炭の一部をスラリー状としてポンプ搬送、ベルトコンベア搬送、空気搬送等により活性炭槽２４に戻すリターン設備６４と、活性炭の残部を廃棄するための配管等６６とを備えている。
本実施例では、活性炭槽２４から流出する処理水から活性炭を固液分離装置６２によって分離し、分離した活性炭の一部をリターン設備６４により活性炭槽２４に戻し、酸化還元反応に寄与させている。これにより、活性炭の所要量を節減することができる。廃棄するための配管等６６を経て、活性炭の残部をボイラ用の燃料として使用すればエネルギーとして回収できるので好ましい。
【００４５】
活性炭槽２４の改変例
図６（ａ）及び（ｂ）は、活性炭槽２４の流動床形成手段の改変例である。
改変例１の活性炭槽２４Ａは、活性炭２４の攪拌機４２に代えて、排煙脱硫排水を噴流状で活性炭槽２４Ａに流入させるノズル孔７０を多数有する供給管７２を活性炭槽２４Ａの底部に備えている。また、供給管７０は、混合槽２２からのライン４０に接続されている。これにより、排煙脱硫排水は、ノズル孔７０より噴流状で活性炭槽２４Ａ内に流入して激しく流動し、活性炭槽２４Ａ内に活性炭の流動床を形成する。
改変例２の活性炭槽２４Ｂは、活性炭２４の攪拌機４２に代えて、排煙脱硫排水を噴流状で活性炭槽２４Ｂに流入させる細孔７４を多数備えた多孔板７６を活性炭槽２４Ｂの底部に備えている。混合槽２２からのライン４０は、多孔板７６より下方の活性炭槽２４Ｂ下部に接続されている。これにより、排煙脱硫排水は、細孔７０より噴流状で活性炭槽２４Ｂ内に流入して激しく流動し、活性炭槽２４Ｂ内に活性炭の流動床を形成する。
【００４６】
【発明の効果】
請求項１から９に記載の発明によれば、活性炭を還元剤として使用して酸化還元反応により排煙脱硫排水中の酸化性物質を還元する際、例えば硫黄過酸化物をＳＯ_４ ^２−に転化する際に、排煙脱硫排水のｐＨを特定範囲に調整し、特定の金属を触媒として作用させ、また排煙脱硫排水を加熱して温度を上昇させることにより、酸化還元反応を促進して高い酸化性物質除去率を得ることができる。これにより、硫黄過酸化物を含む酸化性物質を含有する排煙脱硫排水によって従来生じていた排水処理装置の性能劣化を防止できる。
請求項１０から１３に記載の発明によれば、本発明方法を好適に実施できる装置を実現できる。
【図面の簡単な説明】
【図１】排煙脱硫排水の温度と酸化性物質除去率との関係を示すグラフである。
【図２】３価の鉄添加量と酸化性物質除去率との関係を示すグラフである。
【図３】排煙脱硫排水のｐＨと酸化性物質除去率との関係を示すグラフである。
【図４】本発明に係る排煙脱硫排水の前処理装置の実施例１のフローシートである。
【図５】本発明に係る排煙脱硫排水の前処理装置の実施例２のフローシートである。
【図６】図６（ａ）及び（ｂ）は、活性炭槽の改変例の構成を示す模式図である。
【図７】従来の石膏分離装置のフローシートである。
【符号の説明】
１０従来の石膏分離装置
１２反応槽又は吸収塔
１４排出ポンプ
１６固液分離装置又は石膏脱水機
１８排水処理装置
２０本発明に係る排煙脱硫排水の前処理装置の実施例１
２２混合槽
２４活性炭槽
２６スチームコイル管
２８酸注入管
３０金属化合物添加管
３２攪拌機
３４、３６、３８、４６流量調節弁
４０ライン
４２攪拌機
４４活性炭投入管
４８処理水管
５０濃度計
５２制御装置
６０本発明に係る排煙脱硫排水の前処理装置の実施例２
６２固液分離装置
６４リターン設備
６６活性炭の残部を廃棄するための配管等
７０ノズル孔
７２供給管
７４細孔
７６多孔板[0001]
[Industrial application fields]
The present invention relates to a method and apparatus for treating flue gas desulfurization effluent containing sulfur peroxide and other oxidizing substances, and more particularly to reducing performance deterioration of a waste water treatment apparatus for purifying flue gas desulfurization effluent. Thus, the present invention relates to a method and an apparatus for pretreating a flue gas desulfurization effluent containing an oxidizing substance.
[0002]
[Prior art]
In order to remove sulfur oxides such as sulfurous acid gas from exhaust gas, a wet flue gas desulfurization method is often used in which exhaust gas is brought into gas-liquid contact with an absorbing solution to remove sulfur oxides. The wet flue gas desulfurization method is roughly classified as follows: a reaction tank such as a jet bubbling reaction tank is provided, a method of introducing exhaust gas into the absorption liquid stored in the reaction tank and bringing it into gas-liquid contact, and a spray type absorption tower are provided. There is a method in which an absorbing liquid is sprayed into an exhaust gas introduced into an absorption tower so as to make gas-liquid contact. In addition, there is a method using a packed tower.
In the conventional wet flue gas desulfurization method, a dust removal tower is provided upstream of a reaction tank or absorption tower (hereinafter referred to as reaction tank or the like), and the exhaust gas and the cooling liquid are brought into contact with each other before introduction into the reaction tank or the like. The so-called soot-mixing type flue gas desulfurization apparatus, which is a single tower type, omits the dust removal tower as a result of the recent improvement in the performance of reaction vessels and the like. It is used a lot. Further, in the conventional wet flue gas desulfurization method, an oxidation tower is provided at the rear stage of a reaction tank or the like and oxidation treatment is performed there, but at present, a method of performing oxidation in a reaction tank or the like is common.
[0003]
The absorption liquid used is a liquid obtained by dissolving and / or suspending an absorbent for immobilizing sulfur oxides in water. Generally, a calcium compound-based absorbent such as limestone is dissolved and / or suspended in water. Use the slurry aqueous solution.
Sulfur oxides in the exhaust gas come into gas-liquid contact with the absorbing solution contained in a reaction vessel such as a jet bubbling reaction vessel or sprayed in a spray-type absorption tower, and are absorbed into the absorbing solution by chemical absorption and / or physical absorption. It reacts with water, oxygen and limestone to form gypsum and is removed from the exhaust gas. The generated gypsum crystallizes as particles and floats in the absorbent.
[0004]
The slurry containing the crystallized gypsum in a concentrated manner is fed to a gypsum separation device, where the gypsum is separated. FIG. 7 is a schematic flow sheet of the conventional gypsum separating apparatus 10. As shown in FIG. 7, it is discharged | emitted by the discharge pump 14 from the bottom part of reaction tanks etc. 12, and is sent to a solid-liquid separator or the gypsum dehydrator 16, where gypsum is isolate | separated from slurry.
Next, after the limestone powder is added, a part of the mother liquor is returned to the reaction tank or the like 12 as an absorbent slurry, and again comes into gas-liquid contact with the exhaust gas. After being sent to 18 and purified, it is discharged into a river or the like.
The wastewater treatment device 18 for purification treatment is a device that purifies the flue gas desulfurization wastewater to such an extent that the treated wastewater can be discharged into a river or the like. The wastewater treatment device may be a device attached to the wet flue gas desulfurization device, or may be a public wastewater treatment device.
[0005]
[Problems to be solved by the invention]
By the way, recently, in the wastewater treatment facility that treats the flue gas desulfurization wastewater to a predetermined water quality by subjecting the flue gas desulfurization wastewater sent from the wet flue gas desulfurization device to adsorption treatment and / or biological treatment, It has been found that deterioration is faster and more rapid than expected, and that the cause is the quality of the flue gas desulfurization effluent sent from the wet flue gas desulfurization device. Here, the adsorption treatment is a concept including not only adsorption by an adsorbent but also ion exchange treatment by an ion exchange resin, and biological treatment is biological using nitrifying bacteria, denitrifying bacteria, etc. Wastewater treatment.
The problem is that, for example, the growth of denitrifying bacteria used in the denitrification process of the wastewater to be treated is inhibited, and therefore the amount of nitrogen in the treated water discharged from the wastewater treatment device is increasing. In addition, the deterioration of the organic adsorption resin used as an adsorbent for adsorbing COD in the wastewater to be treated is unexpectedly fast. Furthermore, the same phenomenon occurs with resins that remove boron and fluorine.
[0006]
In light of the above situation, the object of the present invention is to first improve the water quality so that the performance of the wastewater treatment device is not deteriorated, and to send the flue gas desulfurization wastewater to the wastewater treatment device in advance. It is to provide a method of processing, and secondly, to provide a preprocessing apparatus for performing the preprocessing.
[0007]
[Means for Solving the Problems]
As a result of studying the performance degradation of the wastewater treatment device, the present inventors have caused a performance degradation in most devices, regardless of the type of the flue gas desulfurization device, particularly in the soot mixed type wet flue gas desulfurization device, It was found that the cause is mainly due to the high concentration of oxidizing substances contained in the flue gas desulfurization effluent discharged from the apparatus of this system. Here, the oxidizing substance means a substance having an oxidizing ability contained in the flue gas desulfurization waste water, and a sulfur peroxide such as S₂O₈ ^2-Is also included. As described later, the oxidizing substance can be quantified by, for example, a chlorine conversion value by the DPD method or the like.
Therefore, the inventors have made sulfur peroxides such as S₂O₈ ^2-SO_Four ^2-It was proved by experiments that the reduction of the performance of the wastewater treatment equipment can be prevented by reducing the concentration of oxidative substances in the flue gas desulfurization effluent by reducing other oxidative substances together and reducing other oxidative substances.
By the way, a method of treating exhaust gas so that an oxidizing substance is not included in the flue gas desulfurization wastewater in a reaction tank or the like that discharges the flue gas desulfurization wastewater itself has been studied, and a few methods have been proposed. In addition, the method of removing sulfur peroxide from flue gas desulfurization effluent was judged to be an effective method for solving problems, and research was repeated.
[0008]
As a result of research and experiment, the present inventor removed the oxidizing substance by using it as a reducing agent in the oxidation-reduction reaction of oxidizing substances such as sulfur peroxide, rather than using activated carbon as an adsorbent. Found to be effective. Furthermore, as will be described below as an example, it was experimentally confirmed that the oxidation-reduction reaction of activated carbon was promoted under specific conditions.
[0009]
First, when the flue gas desulfurization waste water is in a specific pH range, the redox reaction by activated carbon is promoted.
Second, when specific metals and their metal compounds are used as catalysts, the redox reaction by activated carbon is promoted. It was also found that these metals and metal compounds can maintain stable catalyst performance for a long time. In addition, the specific metal and the low-valent metal compound are themselves effective as a reducing agent._Four ^2-It was also found that it can be reduced easily. Further, among the flue gas desulfurization effluent, the pH of the flue gas desulfurization effluent is in a range suitable for the oxidation-reduction reaction of activated carbon, and Fe (OH) that works as a catalyst and a reducing agent._ThreeIt has also been found that a redox reaction by activated carbon is particularly promoted in such a case.
Third, the higher the temperature of the flue gas desulfurization wastewater, the more the redox reaction of the activated carbon is promoted.
Fourth, it is effective for the oxidation-reduction reaction to float activated carbon in flue gas desulfurization waste water to form a fluidized bed of activated carbon.
Hereinafter, experimental examples carried out in the course of development of the method of the present invention will be described.
[0010]
Experimental example 1
75cm^ThreeAn activated carbon tank filled with coconut shell crushed charcoal (trade name Shirakaba KL manufactured by Takeda Pharmaceutical Co., Ltd., specification 10 mesh sieve or less) in the form of a fixed bed was prepared.
The flue gas desulfurization effluent obtained by treating the coal flue gas with a soot-mixing type wet flue gas desulfurization device using limestone as an absorbent was used as raw water to be passed through the activated carbon tank. When the oxidizing substance concentration of the raw water was determined, it was 12 mg-cl / L-raw water (chlorine conversion value).
The method for measuring the concentration of the oxidizable substance is a method of quantifying by colorimetry when a stable color development state is obtained by extending only the color development time in accordance with the diethyl-P-phenylenediamine colorimetry method of JIS K0102 industrial wastewater test method. It is. Hereinafter, this method is referred to as a DPD method. In addition, when it is desired to quantify only the sulfur peroxide among the oxidizing substances, for example, ion chromatography is used.
Next, the raw water at room temperature was passed through the activated carbon tank of the activated carbon fixed bed without adjusting the pH of the raw water and without adding a catalyst such as trivalent iron.
[0011]
When the steady state was reached, the oxidizing substance concentration in the treated water at the outlet of the activated carbon tank was measured to calculate the oxidizing substance removal rate. As a result, the removal rate was 70% at the beginning of water flow, and the removal effect of the oxidizing substance by the oxidation-reduction reaction of activated carbon could be confirmed. However, the removal rate gradually decreased thereafter, and decreased to about 10% after 300 hours.
[0012]
Experimental example 2
  The same raw water and activated carbon tank as in Experimental Example 1 were used. originalThe waterWhile heating to a predetermined temperature, iron (trivalent) is added to the raw water at an addition rate of 20 mg / L-raw water, and hydrochloric acid is further added to adjust the pH to 3.0, while the raw water is adjusted to 0.3 L / Hr. Water was fed to the activated carbon tank at a flow rate, that is, a liquid space velocity of 4.0. When the steady state was reached, the oxidizing substance concentration in the treated water at the outlet of the activated carbon tank was measured to calculate the oxidizing substance removal rate. Furthermore, the above experiment was repeated with various changes in the raw water temperature.
[0013]
The result is as shown in FIG. 1, and it can be seen that the higher the temperature of the raw water, the higher the removal rate of the oxidizing substance. From this experimental result, when the temperature of the raw water is 30 ° C or higher, preferably 50 ° C or higher, it is 80% or more (this removal rate is a practically satisfactory removal rate of oxidizing substances). A stable oxidizing substance removal rate of 95% or more can be obtained. However, it is needless to say that the removal rate is not limited to this range. It has also been confirmed that such a high oxidizing substance removal rate can be maintained over a long period of 300 hours or more.
[0014]
In addition to the DPD method, the measurement of the oxidizing substance concentration is based on a method according to JIS K0102 iodine titration method and a longer reaction time (hereinafter referred to as KI method), JIS K0102 O-tolidine colorimetric method. In accordance with a method in which the color development time is extended (hereinafter referred to as OT method), a coulometric titration method using phenylarsenooxide or potassium iodide, an oxidation-reduction potential titration method or a coulometric titration method using ascorbic acid Can do. The redox potential titration method or coulometric titration method using ascorbic acid is preferable because the reaction is fast and the time required for measurement is short. In this method, a titration amount of ascorbic acid until the reducing power (potential) of ascorbic acid is detected is obtained to obtain a concentration of an oxidizing substance containing sulfur peroxide. As a result, the concentration of the oxidizing substance can be measured almost continuously, and operation control requiring real-time detection becomes possible.
[0015]
Experimental example 3
Effective volume 1000cm with stirrer^ThreeAn activated carbon tank is prepared, and the same coconut shell crushed charcoal as that used in Example 1 is 400 cm in the tank.^ThreeI put it in. Next, the same flue gas desulfurization effluent as in Experimental Example 1 was used as raw water, the pH was adjusted to 2, the temperature was adjusted to 50 ° C., and trivalent iron was added at a rate of 20 mg / L-raw water. Was stirred while passing through an activated carbon tank at a flow rate of 2.0 L / Hr to form a stirred fluidized bed.
When the fluidized bed in the activated carbon tank reached a steady state, the oxidizing substance concentration of the treated water flowing out from the activated carbon tank was measured by the DPD method, and the oxidizing substance removal rate was calculated. Furthermore, the above experiment was repeated by changing the amount of trivalent iron added to the raw water (mg / L-raw water).
[0016]
The result is as shown in FIG. 2, and it can be seen that the higher the amount of iron added, the higher the removal rate of the oxidizing substance. From this experimental result, if the amount of iron added is in the range of 8 to 50 mg / l, a practically satisfactory oxidizing substance removal rate can be obtained over at least 2000 hours.
In addition to Fe, Cu, Mn and Ni were also confirmed to be effective as catalysts for the redox reaction of activated carbon.
[0017]
Experimental Example 4
Effective volume 3000cm with stirrer^ThreeAn activated carbon tank is prepared and 800cm in the tank.^ThreeCoconut shell crushed charcoal (trade name ACG manufactured by Nippon Carbon Co., Ltd., 60 to 120 mesh) was added. Next, the same flue gas desulfurization effluent as in Experimental Example 1 was used as raw water, the pH was adjusted to a predetermined value, the temperature was adjusted to 50 ° C., and trivalent iron was added at an addition rate of 12 mg / L-raw water. The raw water was stirred while passing through an activated carbon tank at a flow rate of 5.0 L / Hr to form a stirred fluidized bed.
When the fluidized bed in the activated carbon tank reached a steady state, the oxidizing substance concentration of the treated water flowing out from the activated carbon tank was measured by the DPD method, and the oxidizing substance removal rate was calculated. Furthermore, the above experiment was repeated with various changes in the pH of the raw water.
[0018]
The result is as shown in FIG. 3, and it can be seen that the lower the pH of the raw water, the higher the removal rate of the oxidizing substance. From this experimental result, when the pH of the raw water is in the range of 1.0 to 4.0, a practically satisfactory oxidizing substance removal rate can be obtained.
[0019]
  Method for treating flue gas desulfurization wastewater In order to achieve the above object, the method for treating flue gas desulfurization waste water according to the present invention, which has been completed based on the above experimental results, is an oxidizing substance.As sulfur peroxideA method of pretreating flue gas desulfurization wastewater before performing adsorption treatment and / or biological treatment of the waste gas desulfurization wastewater containing
  A metal addition step of adding at least one of Fe, Cu, Mn and Ni metals and their metal compounds to the flue gas desulfurization waste water;
  Then, an acid is added to the flue gas desulfurization waste water to adjust the pH to a range of 1 to 4, and
  ThenReaction process to reduce oxidizing substances in flue gas desulfurization effluent by reaction with activated carbonWhenA method for treating flue gas desulfurization waste water.
[0020]
The present invention relates to flue gas desulfurization effluent containing sulfur peroxide and other oxidizing substances, in particular, flue gas desulfurization effluent containing sulfur peroxide at a relatively high concentration, for example, a soot mixed type wet flue gas desulfurization apparatus. It is suitably applied to flue gas desulfurization drainage discharged from
The soot-mixing type wet flue gas desulfurization apparatus referred to in the method of the present invention is a single tower type wet flue gas desulfurization apparatus that has neither a dust removal tower in the preceding stage nor a separate oxidation tower. It means to exclude both a method of performing in a separate dust removing tower and a wet flue gas desulfurization system of performing a method of oxidizing sulfite ions in a separate oxidation tower.
In particular, the present invention is a metal or a metal compound, such as Fe (OH), having a pH in the range of 1 to 4 and serving as a catalyst and reducing agent_ThreeThe present invention can be suitably applied to the treatment of flue gas desulfurization wastewater containing the like.
[0021]
When the pH of the flue gas desulfurization wastewater is high, the method of the present invention is characterized by including a pH adjustment step of adjusting the pH to a range of 1 to 4 by adding an acid before the reaction step. Thereby, the oxidation-reduction reaction by activated carbon is promoted. For example, the method of the present invention is particularly suitable because the pH of the flue gas desulfurization effluent discharged from a normal soot mixed type wet flue gas desulfurization apparatus is 5 or more.
[0022]
  When the flue gas desulfurization effluent does not contain a metal to be a catalyst, the method of the present invention is a metal of Fe, Cu, Mn and Ni.And at least one of those metal compoundsIt is characterized in that a metal addition step of adding is provided before the pH adjustment step. For example, the method of the present invention is particularly suitable for flue gas desulfurization effluent discharged from a normal soot-mixing type wet flue gas desulfurization device, because the iron concentration is as small as 5 mg / L.
[0023]
  For flue gas desulfurization effluent treated with coal soot exhaust gas, if Cu and Ni, the concentration in the flue gas desulfurization effluent is in the range of 3 to 150 mg / l, and if Mn, the concentration is 10 to 200 mg. Each metal compound is added so that the concentration is in the range of 5 to 100 mg / l in the case of Fe so as to be in the range of / l. Here, when the metal addition amount is less than the lower limit value of the above range, the catalytic effect of the metal is poor, and when the metal addition amount is equal to or more than the upper limit value, the increase in the catalytic effect is small compared to the increase in the metal addition amount, and the wastewater treatment cost. Rises.
  Examples of the acid added in the pH adjustment step include hydrochloric acid and sulfuric acid. Here, when the pH is 4 or more, the effect of acid addition is poor, and conversely, when the pH is 1 or less, the increase in the effect is small compared to the increase in the amount of acid added, and the wastewater treatment cost increases. .
  The metal addition step and the pH adjustment step can be carried out in separate steps, or a single mixing tank can be used.RealIt can also be applied.
[0024]
A preferred embodiment of the present invention is characterized in that the metal compound is a low-valent metal compound.
The valence is the same as the ionic valence, and is a low-valence metal compound such as Fe.⁺²Then, Fe⁺²Is Fe⁺³In the process of being oxidized to S₂O₈ ^2-SO_Four ^2-It is thought that it can be reduced. It should be noted that the metal catalysis need not be a low valence compound.
Further, if the metal compound is a metal sulfate, sulfate ions combine with Ca to form gypsum and adhere to the activated carbon, causing clogging of the activated carbon or reducing the activity of the activated carbon. . In practice, for example, FeCl₂It is preferable to use metal chlorides such as
[0025]
Another preferred embodiment of the present invention is characterized in that the flue gas desulfurization waste water is heated to 30 ° C. or more before the reaction step.
By heating the flue gas desulfurization waste water to raise the temperature, the removal rate of sulfur peroxide can be increased. Since the relationship between the temperature and the removal rate is almost linear as shown in the experimental examples described later, the higher the temperature of the flue gas desulfurization wastewater, the greater the removal rate of the sulfur peroxide. If it is 30 ° C. or higher, a practically satisfactory removal rate can be achieved.
[0026]
As a means for bringing the flue gas desulfurization wastewater into contact with the activated carbon, the flue gas desulfurization wastewater may be passed through a fixed bed of activated carbon provided in the activated carbon tank, and activated carbon is introduced into the flue gas desulfurization wastewater in the activated carbon tank. In addition, it may be suspended or suspended in the flue gas desulfurization waste water by stirring with a stirring means such as a stirrer to form a fluidized bed of activated carbon, but a fluidized bed is preferable as will be described later in view of contact efficiency. . As a means for forming a fluidized bed, in addition to mechanical stirring, flue gas desulfurization wastewater is further ejected into the tank from the bottom of the activated carbon tank by a nozzle, a perforated plate, etc. To form a fluidized bed of activated carbon.
Therefore, in the reaction step of a preferred embodiment of the invention, in the reaction step, flue gas desulfurization effluent is introduced into an activated carbon tank containing activated carbon, and a fluidized bed is formed that floats or suspends the activated carbon in the flue gas desulfurization effluent. It is characterized by doing.
[0027]
In the reaction process, it is very slight as the reaction proceeds, but CO₂Experiments have confirmed that gas such as gas is generated. Since activated carbon is hydrophobic, the generated gas tends to adhere to the surface of the activated carbon, so that solid-liquid contact between the activated carbon and the flue gas desulfurization waste water is hindered. Moreover, since the generated gas contains a flammable gas even though it is a very small amount, it is not preferable from the viewpoint of safety that the gas accumulates on the surface of the activated carbon. Therefore, a fluidized bed by stirring is preferable to a fixed bed that easily accumulates gas in terms of reactivity and safety of the reaction process.
Therefore, when a fixed bed activated carbon layer is used in the reaction step, it is preferable to apply ultrasonic waves and / or mechanical vibrations to the activated carbon layer while passing the flue gas desulfurization waste water through the activated carbon layer. This is because the accumulated gas can be dissociated.
[0028]
Further, in the reaction step according to a preferred embodiment of the present invention, in the reaction step, when the flue gas desulfurization waste water is mechanically stirred to form a fluidized bed of activated carbon, the stirring strength or the flue gas desulfurization waste water is obtained. In order to form a fluidized bed of activated carbon by fluidizing the fluid, it is necessary to intermittently strengthen the fluid state from time to time to break up the activated flocs flocs formed in the fluidized bed of activated carbon. It is a feature.
Stirring mechanically refers to stirring by mechanical means such as a stirrer, and fluidizing fluidically refers to forming a fluidized state by ejecting flue gas desulfurization wastewater from a nozzle or the like.
The stirring strength is basically sufficient to float or suspend activated carbon in waste water containing oxidizing substances to form a fluidized bed of activated carbon, but the activated carbon aggregates and flocates as the reaction proceeds. It was found that the active specific surface area of the activated carbon decreased and the reactivity decreased. In view of this, it is practically preferable to recover the reactivity of the activated carbon by pulverizing the floc of the activated carbon by intermittently stirring it.
In addition, when fluidizing fluidically, the fluidized state may always be such that the activated carbon is suspended or suspended in the oxidizing substance-containing waste water to form a fluidized bed of activated carbon. Strengthen intermittently to break up the activated carbon flocs formed in the fluidized bed of activated carbon.
[0029]
According to another preferred embodiment of the present invention, the concentration of the oxidizing substance in the flue gas desulfurization waste water that has undergone the reaction step is measured, and the metal compound added to the flue gas desulfurization waste water according to a predetermined relationship based on the measured value. It is characterized by performing at least one of an operation of increasing / decreasing the amount, an operation of adjusting the temperature of the flue gas desulfurization waste water, and an operation of increasing / decreasing the amount of added activated carbon.
The sulfur peroxide concentration can be measured using the KI method, DPD method, OT method or coulometric titration method using phenylarsenooxide or potassium iodide, redox potential titration method or coulometric titration method using ascorbic acid. However, since it has the advantage that the time required for the measurement is short, an oxidation-reduction potential titration method or a coulometric titration method using ascorbic acid is preferable.
[0030]
In addition, an activated carbon separation process for separating activated carbon from the flue gas desulfurization effluent after the reaction process is provided,
A part of the activated carbon separated in the activated carbon separation step can be reused in the reaction step. In this separation step, an inorganic flocculant such as a high molecular organic compound or Fe can be used to facilitate separation of the activated carbon. As a result, the activated carbon that has been pulverized and flowed out can be recovered and reused, so that the required amount of activated carbon can be reduced. As the activated carbon to be used, coconut shell crushed coal obtained from coconut shell, which has higher performance and is cheaper than coal-based and petroleum-based ones, is optimal.
[0031]
Pretreatment equipment for flue gas desulfurization drainage
  The pretreatment device for flue gas desulfurization drainage according to the present invention suitable as a device for carrying out the above-described method of the present invention is an oxidizing substanceAs sulfur peroxideA pretreatment device for pretreating the flue gas desulfurization wastewater before the adsorption treatment and / or biological treatment of the flue gas desulfurization wastewater containing
  Heating means for heating the inflowing flue gas desulfurization wastewater with a heating medium, acid addition means for adding acid, and metals of Fe, Cu, Mn and NiAnd at least one of those metal compoundsMeans for adding metal compound, and added acid and metalOr metalA mixing tank comprising a mixing means for mixing the compound and the flue gas desulfurization wastewater flowing into the tank;
  An activated carbon tank provided with activated carbon charging means for charging activated carbon into the tank, and an agitation means for stirring the flue gas desulfurization effluent flowing into the tank through the mixing tank and the charged activated carbon,
  WithIn the mixing tank, the addition of the acid by the acid addition means is performed after the addition of the metal or the metal compound by the metal compound addition means.It is characterized by that.
[0032]
The heating medium used for the heating means of the mixing tank is preferably steam because it is easy to generate and handle, and can be easily heated by steam by providing a steam jacket or a steam coil tube in the mixing tank. . Alternatively, steam may be blown directly into the flue gas desulfurization effluent.
The mixing means is not particularly limited as long as it can be mixed, and a baffle plate may be provided in the mixing tank to use a flow rate at which the flue gas desulfurization wastewater flows into the mixing tank, or a stirrer may be provided to perform stirring and mixing.
The metal compound addition means and the activated carbon charging means are means utilizing a known mechanism, and for example, an appropriate one is used depending on the form of the metal compound and activated carbon such as powder, slurry, and liquid.
[0033]
The stirring means provided in the activated carbon tank may be a conventional stirring machine or a known jet type stirring means for jetting a fluid. Further, stirring means by gas injection may be used.
In a preferred embodiment of the present invention, the stirring means causes the flue gas desulfurization wastewater flowing into the tank through the mixing tank to be ejected from the bottom of the activated carbon tank into the activated carbon tank, and the flow of activated carbon charged from the activated carbon charging means It is a means that the floor is formed in an activated carbon tank.
A nozzle, a perforated plate, etc. can be used as the means for ejecting.
[0034]
A preferred embodiment of the present invention is characterized in that means for changing the stirring intensity is provided in the stirring means of the activated carbon tank. As means for changing the stirring intensity, for example, in the case of a stirrer, the drive device can be made variable in the number of rotations, and in the case of a jet type, the speed of the jet can be made variable.
By vigorously stirring, the activated carbon aggregated into a floc form with the progress of the reaction can be decomposed and dispersed again as fine particles.
[0035]
Another preferred embodiment of the present invention is a measuring device for measuring the concentration of an oxidizing substance in flue gas desulfurization effluent discharged from an activated carbon tank,
Based on the measured value, at least one of the addition amount of the metal compound added by the metal compound addition means, the temperature of the flue gas desulfurization waste water heated by the heating means, and the input amount of activated carbon supplied by the activated carbon input means is predetermined. A control device that controls according to the correlation of
It is characterized by having.
[0036]
As the concentration measuring apparatus for oxidizing substances, the measurement time is shorter than other methods (the time required for one measurement is 10 minutes or less), so the oxidation-reduction potential titration method or coulometric titration method using ascorbic acid is used. An apparatus is preferred.
The predetermined correlation used in the present invention is the relationship between the oxidizing substance concentration in the flue gas desulfurization effluent that has flowed out from the activated carbon tank in advance, the amount of metal compound added, the temperature of the flue gas desulfurization effluent, and the input amount of activated carbon. It can be set by setting by experiment.
[0037]
[Action]
  Claim10From13In the mixing tank, in the mixing tank, the flue gas desulfurization waste water is heated to 30 ° C. or higher by the heating means, the pH of the flue gas desulfurization waste water is adjusted to a range of 1 to 4 by the acid addition means, and the metal compound is added. The metal compound is added to the flue gas desulfurization effluent by means to promote the redox reaction with the activated carbon in the activated carbon tank.
  Also, measure the oxidizing substance concentration in the flue gas desulfurization effluent flowing out from the activated carbon tank, add the amount of metal compound added by the addition means, the temperature of the flue gas desulfurization effluent heated by the heating means, and input the activated carbon At least one of the charged amounts of activated carbon charged by the means is adjusted by the control device according to a predetermined correlation based on the measured value. Thereby, the density | concentration of the oxidizing substance containing the sulfur peroxide in process flue gas desulfurization waste_water | drain can be controlled to a predetermined value.
[0038]
【Example】
Hereinafter, the present invention device will be described in more detail based on embodiments with reference to the accompanying drawings.
Embodiment 1 of the device of the present invention
FIG. 4 is a flow sheet showing the configuration of Example 1, which is a preferred example of the pretreatment device for flue gas desulfurization waste water according to the present invention.
This pretreatment device 20 performs an adsorption treatment and / or biological treatment on a flue gas desulfurization waste water (hereinafter simply referred to as raw water) containing an oxidizing substance containing a sulfur peroxide by a waste water treatment device. A pretreatment device that pretreats raw water before treatment, and is provided between the solid-liquid separation device 16 and the waste water treatment device 18 of FIG. The pretreatment device 20 is composed of a mixing tank 22 and an activated carbon tank 24.
[0039]
The mixing tank 22 is a tank for adding a catalyst metal to the flue gas desulfurization waste water and adjusting the temperature and pH of the flue gas desulfurization waste water, and the steam coil pipe 26 that heats the flowing flue gas desulfurization waste water with steam. An acid injection pipe 28 for injecting an acid such as hydrochloric acid into the mixing tank 22, a metal compound addition pipe 30 for introducing a metal compound catalyst such as Fe into the mixing tank 22 in the form of an aqueous solution, and the added acid and metal A stirrer 32 is provided for stirring and mixing the compound and the flue gas desulfurization effluent flowing into the tank.
The supply pipe 32 for supplying steam to the steam coil pipe 26 is provided with a flow rate adjusting valve 34 for adjusting the flow rate of steam, and the acid injection pipe 28 is provided with a flow rate adjusting valve 36 for adjusting the amount of injected acid. . Similarly, the metal compound addition pipe 30 is provided with a flow rate adjusting valve 38 for adjusting the flow rate of the aqueous solution of the metal compound.
[0040]
The activated carbon tank 24 is a tank having a volume that allows raw water flowing in at a predetermined flow rate to stay for a predetermined residence time. The inlet of the activated carbon tank 24 is connected to the outlet of the mixing tank 22 via a line 40. Yes.
The activated carbon tank 24 is provided with a stirrer 42 with variable rotation speed and an activated carbon charging pipe 44 for charging the activated carbon into the activated carbon tank 24. The activated carbon charging pipe 44 is provided with a flow rate adjusting valve 46 such as a rotary feeder for adjusting the charging flow rate of activated carbon.
The treatment water pipe 48 flowing out from the activated carbon tank 24 is provided with a concentration meter 50 for measuring the sulfur peroxide concentration of the treatment water. The densitometer 50 measures a redox potential by titration with ascorbic acid, and calculates a sulfur peroxide concentration according to a predetermined correlation based on the measured potential.
[0041]
Further, the present pretreatment device 20 includes a control device 52, and controls the temperature of the raw water by adjusting the steam flow rate via the flow rate adjustment valve 34 in accordance with a predetermined correlation based on the measured value of the densitometer 50. Then, the pH of the raw water is adjusted by adjusting the acid injection flow rate via the flow rate adjusting valve 36, the input amount of the catalyst particles is adjusted via the flow rate adjusting valve 38, and the flow rate adjusting valve 46 is used. Adjust the input amount of activated carbon.
In addition, it is preferable for stable operation to measure the temperature and pH of the liquid in the mixing tank and simultaneously adjust the opening degree of the flow rate control valve 34 and the flow rate control valve 36. The feedback control using this can also be performed.
[0042]
  With the above configuration, the method of the present invention can be implemented as follows using the pretreatment apparatus 20.
  First, the raw water is introduced into the mixing tank 22, and the raw water is heated to 30 ° C. or more by the steam coil pipe 26.Metal compound such as iron, for example FeCl, from the metal compound addition tube 30 ₂ Is injected at a predetermined flow rate, and an acid, for example, hydrochloric acid is injected at a predetermined flow rate through the acid injection pipe 28 to adjust the pH of the raw water to a range of 1-4,Stir and mix with stirrer 32.
  Next, the raw water enters the activated carbon tank 24 via the line 40. In the activated carbon tank 24, activated carbon, preferably coconut shell crushed charcoal, is continuously or intermittently charged into the raw water from the activated carbon charging pipe 44, and a fluidized bed of activated carbon is formed together with the raw water while stirring with the stirrer 42. Oxidizing substances such as sulfur peroxide in raw water undergo an oxidation-reduction reaction with activated carbon. For example, sulfur peroxide is SO₄ ^2-The amount of activated carbon is reduced by the amount of reaction.
[0043]
In the activated carbon tank 24, the activated carbon aggregates and forms a floc as the reaction proceeds. Therefore, the inside of the activated carbon tank 24 is vigorously stirred by intermittently and preferably periodically increasing the rotational speed of the activated carbon tank 24 to decompose the floc. Then, it is preferable to disperse in fine activated carbon to increase the surface area contributing to the reaction.
[0044]
Embodiment 2 of the device of the present invention
FIG. 5 is a flow sheet showing the configuration of Example 2, which is a preferred example of the pretreatment device for flue gas desulfurization waste water according to the present invention.
In addition to the configuration of the first embodiment shown in FIG. 4, the pretreatment device 60 includes a solid-liquid separation device 62 such as a centrifuge or thickener that separates activated carbon from treated water downstream of the activated carbon tank 24, and a solid-liquid separation device. A return facility 64 for returning a part of the activated carbon separated in 62 to the activated carbon tank 24 as a slurry by pump conveyance, belt conveyor conveyance, air conveyance, and the like, and a pipe 66 for discarding the remainder of the activated carbon are provided.
In the present embodiment, the activated carbon is separated from the treated water flowing out from the activated carbon tank 24 by the solid-liquid separation device 62, and a part of the separated activated carbon is returned to the activated carbon tank 24 by the return equipment 64 to contribute to the oxidation-reduction reaction. . Thereby, the required amount of activated carbon can be saved. It is preferable that the remainder of the activated carbon is used as boiler fuel through a pipe 66 for disposal, etc., because it can be recovered as energy.
[0045]
Modified example of activated carbon tank 24
6A and 6B are modified examples of the fluidized bed forming means of the activated carbon tank 24. FIG.
The activated carbon tank 24A of the modified example 1 is provided with a supply pipe 72 having a number of nozzle holes 70 through which the flue gas desulfurization wastewater flows into the activated carbon tank 24A in the form of a jet instead of the stirrer 42 of the activated carbon 24 at the bottom of the activated carbon tank 24A. Yes. The supply pipe 70 is connected to the line 40 from the mixing tank 22. As a result, the flue gas desulfurization wastewater flows into the activated carbon tank 24A in a jet form from the nozzle hole 70 and flows violently to form a fluidized bed of activated carbon in the activated carbon tank 24A.
The activated carbon tank 24B of the modified example 2 is provided with a porous plate 76 provided with a large number of pores 74 for allowing the flue gas desulfurization drainage to flow into the activated carbon tank 24B in the form of a jet instead of the stirrer 42 of the activated carbon 24 at the bottom of the activated carbon tank 24B. ing. The line 40 from the mixing tank 22 is connected to the lower part of the activated carbon tank 24 </ b> B below the perforated plate 76. Thereby, the flue gas desulfurization waste water flows into the activated carbon tank 24B in a jet form from the pores 70 and flows violently to form a fluidized bed of activated carbon in the activated carbon tank 24B.
[0046]
【The invention's effect】
  From claim 19According to the invention described in the above, when reducing an oxidizing substance in flue gas desulfurization wastewater by an oxidation-reduction reaction using activated carbon as a reducing agent, for example, sulfur peroxide is converted to SO.₄ ^2-When converting to, the pH of flue gas desulfurization wastewater is adjusted to a specific range, a specific metal acts as a catalyst, and the flue gas desulfurization wastewater is heated to raise the temperature, thereby promoting the oxidation-reduction reaction. And high oxidizing substance removal rate can be obtained. Thereby, the performance degradation of the waste water treatment apparatus conventionally produced by the flue gas desulfurization waste water containing the oxidizing substance containing sulfur peroxide can be prevented.
  Claim10From13According to the invention described in the above, it is possible to realize an apparatus that can suitably execute the method of the present invention.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the temperature of flue gas desulfurization waste water and the oxidizing substance removal rate.
FIG. 2 is a graph showing the relationship between the amount of trivalent iron added and the oxidizing substance removal rate.
FIG. 3 is a graph showing the relationship between the pH of the flue gas desulfurization waste water and the oxidizing substance removal rate.
FIG. 4 is a flow sheet of Example 1 of the pretreatment device for flue gas desulfurization waste water according to the present invention.
FIG. 5 is a flow sheet of Example 2 of the pretreatment device for flue gas desulfurization waste water according to the present invention.
6 (a) and 6 (b) are schematic views showing the configuration of a modified example of the activated carbon tank.
FIG. 7 is a flow sheet of a conventional gypsum separation device.
[Explanation of symbols]
10 Conventional gypsum separator
12 Reaction tank or absorption tower
14 Discharge pump
16 Solid-liquid separator or gypsum dehydrator
18 Wastewater treatment equipment
20 Example 1 of a pretreatment device for flue gas desulfurization waste water according to the present invention
22 Mixing tank
24 Activated carbon tank
26 Steam coil tube
28 Acid injection tube
30 Metal compound tube
32 Stirrer
34, 36, 38, 46 Flow control valve
40 lines
42 Stirrer
44 Activated carbon injection tube
48 treated water pipe
50 Densitometer
52 Control device
60 Example 2 of a pretreatment device for flue gas desulfurization waste water according to the present invention
62 Solid-liquid separator
64 return equipment
66 Piping for disposing the remaining activated carbon
70 Nozzle holes
72 Supply pipe
74 pores
76 perforated plate

Claims

A method for pretreating flue gas desulfurization wastewater prior to adsorption treatment and / or biological treatment of the flue gas desulfurization wastewater containing sulfur peroxide as an oxidizing substance,
A metal addition step of adding at least one of Fe, Cu, Mn and Ni metals and their metal compounds to the flue gas desulfurization waste water;
Then, an acid is added to the flue gas desulfurization waste water to adjust the pH to a range of 1 to 4, and
Then, the processing method of the waste water of flue gas desulfurization which the oxidizing agent in the waste water of flue gas desulfurization; and a reaction step of reducing by reaction with activated carbon.

The method for treating flue gas desulfurization waste water according to claim 1 , wherein the metal compound is a low-valence metal compound.

The method for treating flue gas desulfurization waste water according to claim 1 or 2 , wherein the flue gas desulfurization waste water is heated to 30 ° C or more before the reaction step.

In the reaction step, any of the preceding claims, characterized in that providing the waste water of flue gas desulfurization ultrasound and / or mechanical vibrations in the activated carbon layer while passed through the activated carbon layer formed as a fixed bed 3 The method for treating flue gas desulfurization waste water according to item 1.

Wherein in the reaction step, the activated carbon allowed to flow into waste water of flue gas desulfurization in reactor housing the out from claim 1 and forming a fluidized bed to float or suspended activated carbon 3 in the waste water of flue gas desulfurization The processing method of flue gas desulfurization waste water of any one of these.

In the reaction step, when the flue gas desulfurization waste water is mechanically stirred to form a fluidized bed of activated carbon, the strength of stirring is formed, or the flue gas desulfurization waste water is fluidized to form a fluidized bed of activated carbon. The flue gas desulfurization drainage according to claim 5 , wherein the flue gas flocs formed in the activated carbon fluidized bed are crushed by intermittently strengthening the fluidity of each of the fluidized states. Processing method.

The operation of measuring the concentration of the oxidizing substance in the flue gas desulfurization wastewater that has undergone the reaction step, and increasing or decreasing the amount of acid added according to a predetermined relationship based on the measured value, the amount of the metal compound added to the flue gas desulfurization wastewater The exhaust gas according to any one of claims 3 to 6, wherein at least one of an operation of increasing / decreasing, an operation of adjusting the temperature of the flue gas desulfurization waste water, and an operation of increasing / decreasing the amount of added activated carbon is performed. Smoke desulfurization wastewater treatment method.

Furthermore, it has an activated carbon separation process for separating activated carbon from the flue gas desulfurization effluent after the reaction process,
The method for treating flue gas desulfurization waste water according to any one of claims 1 to 3 and 5 to 7 , wherein a part of the activated carbon separated in the activated carbon separation step is reused in the reaction step.

The method for treating flue gas desulfurization waste water according to any one of claims 1 to 8 , wherein the activated carbon is coconut shell crushed coal.

A pretreatment device for pretreating flue gas desulfurization wastewater before the adsorption treatment and / or biological treatment of the flue gas desulfurization wastewater containing sulfur peroxide as an oxidizing substance in the wastewater treatment device,
Heating means for heating inflowing flue gas desulfurization wastewater with a heating medium, acid addition means for adding acid, metal of Fe, Cu, Mn and Ni and metal compound for adding at least one of those metal compounds A mixing tank comprising an adding means, and a mixing means for mixing the added acid and metal or metal compound with the flue gas desulfurization effluent flowing into the tank;
Activated carbon dosing means for introducing activated carbon into the vessel, through the mixing tank and a charcoal tank equipped with a stirring means for stirring the activated carbon having been put the waste water of flue gas desulfurization which flows into the tank, said in the mixing tank A pretreatment device for flue gas desulfurization waste water, wherein acid is added by acid addition means after addition of metal or metal compound by metal compound addition means .

The agitation means jets the flue gas desulfurization drainage flowing into the tank through the mixing tank from the bottom of the activated carbon tank into the activated carbon tank, and forms a fluidized bed of activated carbon charged from the activated carbon charging means in the activated carbon tank. The pretreatment device for flue gas desulfurization waste water according to claim 10 , wherein

The pretreatment device for flue gas desulfurization waste water according to claim 10 or 11 , wherein means for changing the stirring intensity is provided in the stirring means of the mixing tank.

A measuring device for measuring the concentration of oxidizing substances in the flue gas desulfurization effluent discharged from the activated carbon tank;
Based on the measured value, at least one of the addition amount of the metal compound added by the metal compound addition means, the temperature of the flue gas desulfurization waste water heated by the heating means, and the input amount of activated carbon supplied by the activated carbon input means is predetermined. The pretreatment device for flue gas desulfurization wastewater according to any one of claims 10 to 12 , further comprising: