JP2004136188A

JP2004136188A - Exhaust gas treatment method and exhaust gas treatment apparatus

Info

Publication number: JP2004136188A
Application number: JP2002302630A
Authority: JP
Inventors: Madoka Tanabe; 田辺　円
Original assignee: Organo Corp; Japan Organo Co Ltd
Current assignee: Organo Corp
Priority date: 2002-10-17
Filing date: 2002-10-17
Publication date: 2004-05-13
Anticipated expiration: 2022-10-17
Also published as: JP3861042B2

Abstract

<P>PROBLEM TO BE SOLVED: To remove both of fluorine and ammonia contained in an exhaust gas by means of a one-stage scrubber. <P>SOLUTION: The exhaust gas treatment apparatus used comprises a scrubber 12, a washing fluid feed mechanism 14 that feeds a washing fluid 20 into the scrubber 12, a silicon compound addition mechanism 26 that adds a silicon compound to the washing fluid 20, a pH adjusting agent addition mechanism 28 that adds a pH adjusting agent to the washing fluid 20, and an exhaust gas feed mechanism 30 that feeds an exhaust gas containing fluorine and ammonia into the scrubber 12. The exhaust gas and the washing fluid containing the silicon compound and having a pH of 3 to 6 are brought into contact with each other in the scrubber 12. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、排気中に含まれるフッ素およびアンモニアを除去する排気処理方法および装置に関する。本発明は、例えば、半導体デバイス工場の廃液乾燥設備から排出される排気の処理に使用することができる。
【０００２】
【従来の技術】
ウェハの洗浄等に使用した超純水の廃液を処理する廃液乾燥設備を備えたクローズドシステムの半導体デバイス工場では、上記廃液乾燥設備において、廃液中の水分を蒸発させて乾燥した固体廃棄物を得るとともに、乾燥排気を大気中に放出している。この場合、乾燥対象の廃液は、フッ化物イオンやアンモニウムイオンを含んでいるため、乾燥排気中には少量ではあるもののフッ素やアンモニアが含まれており、このフッ素やアンモニアが乾燥排気とともに大気中に排出されてしまう。
【０００３】
大気汚染防止法では、大気の汚染に関し、国民の健康を保護するとともに生活環境を保全することを目的として、工場および事業場からのフッ素やアンモニア等の排出基準を定めており、実際の排気中の濃度が排出基準以下を維持していることは当然のことであるが、さらに各工場および事業場における独自の環境保護活動の推進の観点から、これらの排出をできるだけ低減することが求められている。
【０００４】
そこで従来、フッ素やアンモニアを含む排気を気液接触型のスクラバで処理して、排気中に含まれるフッ素やアンモニアを除去することが提案されている。上記スクラバは、フッ素やアンモニアを含む排気と洗浄液とを接触させるもので、フッ素をフッ化物イオンとして洗浄液中に移行させ、アンモニアをアンモニウムイオンとして洗浄液中に移行させるものである。
【０００５】
この場合、フッ素はアルカリ性の洗浄液中には移行しやすいが、酸性の洗浄液中には移行しにくいという性質を有し、逆にアンモニアは酸性の洗浄液中には移行しやすいが、アルカリ性の洗浄液中には移行しにくいという性質を有する。そのため、フッ素およびアンモニアを含む排気を、アルカリ性の洗浄液を用いたスクラバおよび酸性の洗浄液を用いたスクラバの両方に順次接触させる方式を採用する必要がある。
【０００６】
【発明が解決しようとする課題】
しかし、フッ素およびアンモニアを含む排気を、アルカリ性の洗浄液を用いたスクラバおよび酸性の洗浄液を用いたスクラバの両方に順次接触させる前記方式では、２段のスクラバが必要となるため、設備および運転が複雑になって、設備コスト、運転コストが高くなるという問題があった。
【０００７】
本発明は、前述した事情に鑑みてなされたもので、排気中に含まれるフッ素およびアンモニアの両方を１段のスクラバによって除去することができ、したがって排気処理の設備および運転を簡単にして、設備コスト、運転コストを安くすることができる排気処理方法および装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明者は、前記目的を達成するために鋭意検討を行った結果、珪素化合物を含有する洗浄液にフッ素を含む排気を接触させた場合、排気中のフッ素が洗浄液中に容易に移行するようになり、洗浄液が酸性であっても排気中のフッ素が洗浄液中に移行することを見出した。
【０００９】
本発明は、上記知見に基づいてなされたもので、フッ素およびアンモニアを含む排気と、珪素化合物を含有する洗浄液とを接触させることを特徴とする排気処理方法を提供する。
【００１０】
また、本発明は、気液接触槽と、気液接触槽内に洗浄液を導入する洗浄液導入機構と、洗浄液に珪素化合物を添加する珪素化合物添加機構と、気液接触槽内にフッ素およびアンモニアを含む排気を導入する排気導入機構とを具備し、前記気液接触槽においてフッ素およびアンモニアを含む排気と珪素化合物を含有する洗浄液とを接触させることを特徴とする排気処理装置を提供する。
【００１１】
本発明では、フッ素およびアンモニアを含む排気を、珪素化合物を含有する洗浄液に接触させるので、洗浄液が酸性であっても、排気中のフッ素が洗浄液中にフッ化物イオンとして容易に移行し、排気中からフッ素が除去される。また、洗浄液を酸性とすることにより、排気中のアンモニアが洗浄液中にアンモニウムイオンとして容易に移行し、排気中からアンモニアが除去される。したがって、本発明によれば、排気中に含まれるフッ素およびアンモニアの両方を１段のスクラバ（気液接触槽）によって除去することができる。
【００１２】
本発明においては、洗浄液をｐＨ３〜６の酸性とすることが適当であり、これにより排気中のフッ素およびアンモニアを洗浄液中に確実に移行させることができる。
【００１３】
洗浄液中に含有させる珪素化合物の種類に限定はなく、水に可溶性の珪素化合物であれば全て用いることができ、代表的には珪酸アルカリ金属塩、例えば珪酸ナトリウム（水ガラス）等を用いることができる。また、施設内に市水、工業用水等の被処理水から逆浸透膜装置を用いて透過水を得る工程を有する純水あるいは超純水製造装置がある場合は、珪酸アルカリ金属塩等を系外から補給することなく、逆浸透膜装置の濃縮水をそのまま洗浄液として用いることができる。すなわち、市水、工業用水等の被処理水には５〜５０ｍｇＳｉＯ_２／Ｌの珪素化合物が含まれているが、このような原水を逆浸透膜装置で処理して脱塩水を得る場合には、珪素化合物が１００ｍｇＳｉＯ_２／Ｌ以上に濃縮された濃縮水が得られる。したがって、このような逆浸透膜装置の濃縮水は、系外から珪酸アルカリ金属塩を添加しなくとも本発明の洗浄水としてそのまま好適に用いることができる。
【００１４】
珪素化合物として珪酸アルカリ金属塩を用いる場合、洗浄液への珪酸アルカリ金属塩の添加量としては、単位時間当たりに気液接触を行う排気中のフッ素のモル数に対して、少なくともその１２分の１のモル数の量を添加する必要がある。また、６分の１のモル数の量を超えて、６分の１のモル数の量の１．５倍量程度で効果は飽和するのでそれ以上は無駄であり、洗浄液を濃縮固化する際に固体廃棄物が増加してしまうので、６分の１のモル数の量となる珪酸アルカリ金属塩を添加することが最も適正である。通常、洗浄液中の珪酸アルカリ金属塩の濃度は１００ｍｇＳｉＯ_２／Ｌ以上、特に、１００〜４００ｍｇＳｉＯ_２／Ｌとすることが、排気中のフッ素を洗浄液中に確実に移行させる点で適当である。なお、１００ｍｇＳｉＯ_２／Ｌ未満の濃度ではフッ素の洗浄水への移行速度が低下し、また４００ｍｇＳｉＯ_２／Ｌを越えた濃度では珪酸化合物が析出するおそれがある。
【００１５】
洗浄液に珪酸アルカリ金属塩等の珪素化合物を添加するとフッ素化合物の除去率が向上する理由は必ずしも明らかではないが、排気中のフッ素化合物はフッ化物イオンとして洗浄液中に捕捉されて溶存し、このとき洗浄液中に例えば珪素化合物が含まれていれば、より強い酸であるヘキサフルオロ珪酸となるので、洗浄液中に安定して陰イオンとして溶存するからと考察される（下記式参照）。
６ＨＦ　＋　ＳｉＯ_２　→　Ｈ_２ＳｉＦ_６　＋　２Ｈ_２Ｏ
【００１６】
また、フッ素化合物の除去率とともにアンモニアの除去率が向上する理由も必ずしも明らかではないが、洗浄液中に、フッ化物イオンよりも強い酸を構成するヘキサフルオロ珪酸が生成するので、アンモニアとの塩であるヘキサフルオロ珪酸アンモニウムとして安定に溶存するからと考察される（下記式参照）。
Ｈ_２ＳｉＦ_６　＋　２ＮＨ_４ＯＨ　→　（ＮＨ_４）_２ＳｉＦ_６　＋　２Ｈ_２Ｏ
【００１７】
【発明の実施の形態】
以下、本発明につきさらに詳しく説明する。図１は本発明に係る排気処理装置の一例を示す概略図である。図中１２は気泡塔型の気液接触槽、１４は気液接触槽１２内に洗浄液を導入する洗浄液導入機構を示す。洗浄液導入機構１４は、洗浄液貯槽１６と、洗浄液貯槽１６に洗浄液を供給する洗浄液供給機構１８と、気液接触槽１２内の洗浄液２０をオーバーフローさせるとともに、この洗浄液を洗浄液貯槽１６に導入するオーバーフロー管２２と、洗浄液貯槽１６内の洗浄液を気液接触槽に導入する洗浄液導入管２４とを具備する。また、図中２６は気液接触槽１２内の洗浄液２０に珪素化合物を添加する珪素化合物添加機構、２８は気液接触槽１２内の洗浄液２０にｐＨ調整剤を添加するｐＨ調整剤添加機構、３０は気液接触槽１２内の洗浄液２０中に排気を気泡として導入する排気導入機構、３２は気液接触槽１２内の処理ガスを排出する処理ガス排出管、３４は洗浄液貯槽１６内の洗浄液を排出する排液管を示す。
【００１８】
本例の排気処理装置は、洗浄液導入機構１４によって気液接触槽１２内に洗浄液を導入し、珪素化合物添加機構２６によって気液接触槽１２内の洗浄液２０に珪素化合物を添加する。また、必要に応じｐＨ調整剤添加機構２８により気液接触槽１２内の洗浄液２０にｐＨ調整剤を添加して、洗浄液を酸性、好ましくはｐＨ３〜６の酸性に調整する。そして、排気導入機構３０により気液接触槽１２内の洗浄液２０中にフッ素およびアンモニアを含む排気を気泡として導入し、排気と洗浄液とを接触させて排気中のフッ素およびアンモニアを洗浄液２０中に移行させることにより、フッ素およびアンモニアが除去された処理ガスを得るものである。この処理ガスは、処理ガス排出管３２を通して系外に排出される。また、本例の装置では、気液接触槽内への洗浄液の導入、洗浄液への珪素化合物の添加、洗浄液へのｐＨ調整剤の添加（必要に応じ）、気液接触槽内への排気の導入、気液接触槽内の洗浄液のオーバーフロー、洗浄液貯槽への洗浄液の供給、洗浄液貯槽からの洗浄液の排出を連続的に行うようになっている。洗浄液貯槽から排出された洗浄液は、エバポレータ等によって適宜処理される。
【００１９】
なお、排気と洗浄液とを接触させる気液接触槽は本例のように気泡塔型の気液接触槽としてもよく、充填塔型等の他の方式の気液接触槽としてもよい。また、洗浄液への珪素化合物やｐＨ調整剤の添加は本例のように気液接触槽で行ってもよく、配管内や洗浄液貯槽で行ってもよい。
【００２０】
【実施例】
以下に実施例を示すが、これらの実施例は本発明の範囲を限定するものではない。なお、以下の実施例において、排気中のフッ素濃度はＪＩＳ−Ｋ−０１０５のランタン−アリザリンコンプレキソン吸光光度法によるフッ素化合物濃度（ｍｇ／ｍ^３Ｎ）であり、排気中のアンモニア濃度はＪＩＳ−Ｋ−００９９のインドフェノール吸光光度法によるアンモニア濃度（ｍｇ／ｋｇ）である。
【００２１】
（実施例１）
図１に示した排気処理装置を用いてフッ素およびアンモニアを含む排気の処理を行った。この場合、図２に示す半導体デバイス工場の超純水製造・処理システムにおける廃液乾燥設備の排気ダクトに排気導入機構３０を接続し、上記廃液乾燥設備から排出される排気の処理を行った。気液接触槽１２としては、株式会社アコー製ＷＳ−１２０−Ｐ型を用いた。洗浄液としては、ｐＨ７、珪素化合物含有量５ｍｇＳｉＯ_２／Ｌの市水を洗浄液供給機構１８により１ｍ^３／ｈｒの流量で洗浄液貯槽１６に供給し、この洗浄液貯槽１６内の市水を洗浄液導入管２４を通して気液接触槽１２内に４．２ｍ^３／ｈｒの流量で導入した。珪素化合物としては水ガラスを用い、珪素化合物添加機構２６によって９２ｍｇＳｉＯ_２／ｈｒの珪素化合物を気液接触槽１２内の洗浄液２０に添加した。また、本例ではｐＨ調整剤添加機構２８による洗浄液へのｐＨ調整剤の添加は行わなかった。
【００２２】
上記のようにして廃液乾燥設備から発生する５０００ｍ^３Ｎ／ｈｒの排気を処理した。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理後の排気（処理ガス）中に含まれるフッ素化合物濃度は１．７５ｍｇ／ｍ^３Ｎ（除去率９５％）、アンモニア濃度は３ｍｇ／ｋｇ（除去率７０％）であった。
【００２３】
（比較例１）
実施例１の条件で運転している排気処理装置において、珪素化合物添加機構２６による洗浄液への珪素化合物の添加を停止し、停止から３時間経過後に処理前の排気および処理ガスの分析を行った。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理ガス中に含まれるフッ素化合物濃度は２８ｍｇ／ｍ^３Ｎ（除去率２０％）、アンモニア濃度は４ｍｇ／ｋｇ（除去率６０％）であった。
【００２４】
（実施例２）
実施例１の条件で運転している排気処理装置において、ｐＨ調整剤添加機構２８による洗浄液へのｐＨ調整剤（硫酸）の添加を行い、気液接触槽１２内の洗浄液のｐＨを６．５、５．０、４．０、３．０の各値になるようにした。各ｐＨ値においてそれぞれ３時間運転した際に、処理前の排気および処理ガスの分析を行った。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理ガス中に含まれるフッ素化合物およびアンモニアの濃度と除去率は表１に示す通りであった。
【００２５】
【表１】

【００２６】
（比較例２）
実施例２の条件で運転している排気処理装置において、珪素化合物添加機構２６による洗浄液への珪素化合物の添加を停止し、各ｐＨにおいてそれぞれ停止から３時間経過後に処理前の排気および処理ガスの分析を行った。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理ガス中に含まれるフッ素化合物およびアンモニアの濃度と除去率は表２に示す通りであった。
【００２７】
【表２】

【００２８】
（実施例３）
実施例１の条件で運転している排気処理装置において、ｐＨ調整剤添加機構２８による洗浄液へのｐＨ調整剤（硫酸）の添加を行い、気液接触槽１２内の洗浄液のｐＨを６．０に固定するとともに、珪素化合物添加機構２６による洗浄液への珪素化合物の添加量を変化させ、該添加量が５０、７０、９２、１５０、２５０、４００、６５０ｍｇＳｉＯ_２／ｈｒの各値になるようにした。各添加量においてそれぞれ３時間運転した際に、処理前の排気および処理ガスの分析を行った。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理ガス中に含まれるフッ素化合物およびアンモニアの濃度と除去率は表３に示す通りであった。
【００２９】
【表３】

【００３０】
（実施例４）
実施例１と同じ装置を用い、図３に示す半導体デバイス工場の超純水製造・処理システムにおける廃液乾燥設備から排出される排気の処理を行った。この場合、洗浄液としては、上記超純水製造・処理システムの逆浸透膜装置の濃縮水を用いた。上記逆浸透膜装置の被処理水にはスケール発生防止のため酸を添加しており、そのため逆浸透膜装置の濃縮水は酸性である。また、逆浸透膜装置の濃縮水中には被処理水に含まれていた珪素化合物が濃縮された状態で存在するため、この濃縮水中の珪素化合物濃度は高い。本例では、洗浄液（逆浸透膜装置濃縮水）の珪素化合物濃度は４００ｍｇＳｉＯ_２／Ｌ、ｐＨは５．５であった。また、気液接触槽１２内への洗浄液の導入量は１ｍ^３／ｈｒとした。
【００３１】
上記のようにして廃液乾燥設備から発生する５０００ｍ^３Ｎ／ｈｒの排気を処理した。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理ガス中に含まれるフッ素化合物濃度は１ｍｇ／ｍ^３Ｎ（除去率９７％）、アンモニア濃度は１．５ｍｇ／ｋｇ（除去率８５％）であった。
【００３２】
（実施例５）
実施例１と同じ装置を用い、図４に示す半導体デバイス工場の超純水製造・処理システムにおける廃液乾燥設備から排出される排気の処理を行った。この場合、洗浄液としては、上記超純水製造・処理システムの逆浸透膜装置の濃縮水を用いた。上記逆浸透膜装置の被処理水にはスケール発生防止のため酸を添加しており、そのため逆浸透膜装置の濃縮水は酸性である。また、逆浸透膜装置の濃縮水中には被処理水に含まれていた珪素化合物が濃縮された状態で存在するため、この濃縮水中の珪素化合物濃度は高い。本例では、洗浄液（逆浸透膜装置濃縮水）の珪素化合物濃度は４００ｍｇＳｉＯ_２／Ｌ、ｐＨは５．５であった。また、気液接触槽１２内への洗浄液の導入量は１ｍ^３／ｈｒとした。
【００３３】
上記のようにして廃液乾燥設備から発生する５０００ｍ^３Ｎ／ｈｒの排気を処理した。その結果、処理前の排気中に含まれるフッ素化合物濃度は３５ｍｇ／ｍ^３Ｎ、アンモニア濃度は１０ｍｇ／ｋｇであったのに対し、処理ガス中に含まれるフッ素化合物濃度は１ｍｇ／ｍ^３Ｎ（除去率９７％）、アンモニア濃度は１．５ｍｇ／ｋｇ（除去率８５％）であった。
【００３４】
以上の実施例より、フッ素およびアンモニアを含む排気と珪素化合物を含有する洗浄液とを接触させること、特に洗浄液をｐＨ３〜６の酸性とし、洗浄液中の珪素化合物濃度を１００ｍｇＳｉＯ_２／Ｌ以上することにより、排気中に含まれるフッ素およびアンモニアを１段の気液接触槽によって効率的に除去できることがわかる。
【００３５】
また上述のように、半導体デバイス工場の超純水製造・処理システムの逆浸透膜装置濃縮水は、酸性であるとともに、珪素化合物濃度が高い。例えば、特開平７−１６３９７９号公報には、少なくとも硬度成分及び珪素化合物を含有する被処理水を逆浸透膜処理して透過水と濃縮水とに分離する逆浸透膜処理方法において、前記濃縮水のｐＨを６以下に保って逆浸透膜処理をすることが開示されている。そのため、上記逆浸透膜装置濃縮水は、本発明における洗浄水として好適に使用することができる。したがって、本発明は、フッ素およびアンモニアを含む排気と、半導体デバイス工場等の超純水製造・処理システムの逆浸透膜装置濃縮水であって、１００ｍｇＳｉＯ_２／Ｌ以上の珪素化合物を含むｐＨ３〜６の逆浸透膜装置濃縮水とを接触させることを特徴とする排気処理方法をも提供する。
【００３６】
【発明の効果】
以上のように、本発明によれば、例えば半導体デバイス工場の廃液乾燥設備から排出される排気中に含まれるフッ素およびアンモニアの両方を１段の気液接触槽によって除去することができ、したがって排気処理の設備および運転を簡単にして、設備コスト、運転コストを安くすることができる。
【図面の簡単な説明】
【図１】本発明に係る排気処理装置の一例を示す概略図である。
【図２】半導体デバイス工場の超純水製造・処理システムの一例を示す概略図である。
【図３】半導体デバイス工場の超純水製造・処理システムの一例を示す概略図である。
【図４】半導体デバイス工場の超純水製造・処理システムの一例を示す概略図である。
【符号の説明】
１２　気液接触槽
１４　洗浄液導入機構
１６　洗浄液貯槽
１８　洗浄液供給機構
２０　洗浄液
２２　オーバーフロー管
２４　洗浄液導入管
２６　珪素化合物添加機構
２８　ｐＨ調整剤添加機構
３０　排気導入機構
３２　処理ガス排出管
３４　排液管[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust treatment method and apparatus for removing fluorine and ammonia contained in exhaust. INDUSTRIAL APPLICATION This invention can be used for the processing of the exhaust_gas | exhaustion discharged | emitted from the waste liquid drying installation of a semiconductor device factory, for example.
[0002]
[Prior art]
In a semiconductor device factory of a closed system equipped with a waste liquid drying facility for treating waste water of ultrapure water used for cleaning a wafer, etc., in the waste liquid drying facility, moisture in the waste liquid is evaporated to obtain a dried solid waste. At the same time, dry exhaust is released into the atmosphere. In this case, since the waste liquid to be dried contains fluoride ions and ammonium ions, a small amount of fluorine and ammonia are contained in the dry exhaust gas, and the fluorine and ammonia are released into the atmosphere together with the dry exhaust gas. Will be discharged.
[0003]
The Air Pollution Control Law sets forth emission standards for fluorine and ammonia from factories and business sites for the purpose of protecting the health of the people and preserving the living environment with respect to air pollution. It is a matter of course that the concentration of these substances is below the emission standard, but from the viewpoint of promoting independent environmental protection activities at each factory and business site, it is necessary to reduce these emissions as much as possible. I have.
[0004]
Therefore, conventionally, it has been proposed to treat exhaust gas containing fluorine and ammonia with a gas-liquid contact type scrubber to remove fluorine and ammonia contained in the exhaust gas. The scrubber is for bringing exhaust gas containing fluorine or ammonia into contact with the cleaning liquid, and for transferring fluorine as fluoride ions into the cleaning liquid and transferring ammonia as ammonium ions into the cleaning liquid.
[0005]
In this case, fluorine has a property of easily migrating into an alkaline cleaning solution, but has a property of hardly migrating into an acidic cleaning solution, and conversely, ammonia easily migrates into an acidic cleaning solution, but has a property of migrating into an alkaline cleaning solution. Has the property of being difficult to migrate to. For this reason, it is necessary to employ a method in which exhaust gas containing fluorine and ammonia is sequentially brought into contact with both a scrubber using an alkaline cleaning liquid and a scrubber using an acidic cleaning liquid.
[0006]
[Problems to be solved by the invention]
However, in the above-described method in which exhaust gas containing fluorine and ammonia is sequentially contacted with both a scrubber using an alkaline cleaning solution and a scrubber using an acidic cleaning solution, a two-stage scrubber is required, so that equipment and operation are complicated. As a result, there is a problem that equipment costs and operation costs increase.
[0007]
The present invention has been made in view of the above-mentioned circumstances, and it is possible to remove both fluorine and ammonia contained in exhaust gas by a single-stage scrubber. It is an object of the present invention to provide an exhaust treatment method and apparatus capable of reducing cost and operation cost.
[0008]
[Means for Solving the Problems]
The present inventor has conducted intensive studies to achieve the above object, and as a result, when contacting exhaust containing fluorine with a cleaning liquid containing a silicon compound, fluorine in the exhaust is easily transferred into the cleaning liquid. It has been found that even if the cleaning solution is acidic, the fluorine in the exhaust gas moves into the cleaning solution.
[0009]
The present invention has been made based on the above findings, and provides an exhaust treatment method comprising contacting exhaust containing fluorine and ammonia with a cleaning solution containing a silicon compound.
[0010]
Further, the present invention provides a gas-liquid contact tank, a cleaning liquid introduction mechanism for introducing a cleaning liquid into the gas-liquid contact tank, a silicon compound addition mechanism for adding a silicon compound to the cleaning liquid, and fluorine and ammonia in the gas-liquid contact tank. An exhaust gas introduction mechanism for introducing exhaust gas containing the gas, wherein the gas-liquid contact tank makes the exhaust gas containing fluorine and ammonia come into contact with the cleaning liquid containing a silicon compound.
[0011]
In the present invention, since the exhaust gas containing fluorine and ammonia is brought into contact with the cleaning liquid containing a silicon compound, even if the cleaning liquid is acidic, fluorine in the exhaust gas easily moves as fluoride ions into the cleaning liquid, and From which fluorine is removed. Further, by making the cleaning liquid acidic, the ammonia in the exhaust gas easily moves into the cleaning liquid as ammonium ions, and the ammonia is removed from the exhaust gas. Therefore, according to the present invention, both fluorine and ammonia contained in exhaust gas can be removed by a single-stage scrubber (gas-liquid contact tank).
[0012]
In the present invention, it is appropriate to make the cleaning solution acidic at pH 3 to 6, whereby fluorine and ammonia in the exhaust gas can be surely transferred into the cleaning solution.
[0013]
The type of the silicon compound to be contained in the cleaning liquid is not limited, and any silicon compound soluble in water can be used. Typically, an alkali metal silicate, for example, sodium silicate (water glass) or the like is used. it can. If the facility has a pure water or ultrapure water production system that has a process of obtaining permeated water from the water to be treated such as city water or industrial water using a reverse osmosis membrane device, the alkali metal silicate etc. The concentrated water of the reverse osmosis membrane device can be used as it is as a washing liquid without external replenishment. In other words, city water, although the water to be treated, such as industrial water contains silicon compounds 5~50mgSiO 2 / _L, if such raw water is treated with a reverse osmosis membrane apparatus to obtain a demineralized water Thus, concentrated water in which the silicon compound is concentrated to 100 mg SiO ₂ / L or more is obtained. Therefore, the concentrated water of such a reverse osmosis membrane device can be suitably used as washing water of the present invention without adding an alkali metal silicate from outside the system.
[0014]
When an alkali metal silicate is used as the silicon compound, the amount of the alkali metal silicate added to the cleaning solution is at least one-twelfth of the number of moles of fluorine in the exhaust gas that is subjected to gas-liquid contact per unit time. Need to be added. In addition, the effect is saturated when the amount exceeds the 1/6 mole number and is about 1.5 times the 1/6 mole number, so that the effect is wasteful, and when the washing liquid is concentrated and solidified. Therefore, it is most appropriate to add an alkali metal silicate in an amount of 1/6 of the number of moles since the amount of solid waste increases. Normally, the concentration of the alkali metal silicate in the cleaning liquid is preferably 100 mg SiO ₂ / L or more, particularly preferably 100 to 400 mg SiO ₂ / L, in order to surely transfer the fluorine in the exhaust gas into the cleaning liquid. If the concentration is less than 100 mg SiO ₂ / L, the transfer rate of fluorine to the cleaning water decreases, and if the concentration exceeds 400 mg SiO ₂ / L, a silicate compound may be precipitated.
[0015]
It is not always clear why the addition of a silicon compound such as an alkali metal silicate to the cleaning solution improves the removal rate of the fluorine compound.However, the fluorine compound in the exhaust gas is trapped and dissolved in the cleaning solution as fluoride ions. If the cleaning solution contains, for example, a silicon compound, it becomes hexafluorosilicic acid, which is a stronger acid, and is considered to be stably dissolved as an anion in the cleaning solution (see the following formula).
_{_{6HF + SiO 2 → H 2 SiF}} 6 + 2H 2 O
[0016]
Further, it is not always clear why the ammonia removal rate is improved together with the fluorine compound removal rate, but hexafluorosilicic acid, which is an acid stronger than fluoride ions, is generated in the cleaning solution. It is considered that it is stably dissolved as a certain ammonium hexafluorosilicate (see the following formula).
H ₂ SiF ₆ + 2NH ₄ OH → (NH ₄ ) ₂ SiF ₆ + 2H ₂ O
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail. FIG. 1 is a schematic view showing an example of an exhaust treatment device according to the present invention. In the figure, reference numeral 12 denotes a gas-liquid contact tank of a bubble column type, and reference numeral 14 denotes a cleaning liquid introduction mechanism for introducing a cleaning liquid into the gas-liquid contact tank 12. The cleaning liquid introduction mechanism 14 includes a cleaning liquid storage tank 16, a cleaning liquid supply mechanism 18 that supplies the cleaning liquid to the cleaning liquid storage tank 16, and an overflow pipe that causes the cleaning liquid 20 in the gas-liquid contact tank 12 to overflow and introduces the cleaning liquid into the cleaning liquid storage tank 16. 22 and a cleaning liquid introduction pipe 24 for introducing the cleaning liquid in the cleaning liquid storage tank 16 into the gas-liquid contact tank. In the figure, 26 is a silicon compound addition mechanism for adding a silicon compound to the cleaning liquid 20 in the gas-

liquid contact tank

12, 28 is a pH adjuster addition mechanism for adding a pH adjuster to the cleaning liquid 20 in the gas-liquid contact tank 12, Reference numeral 30 denotes an exhaust introduction mechanism for introducing exhaust gas into the cleaning liquid 20 in the gas-liquid contact tank 12 as bubbles, 32 a processing gas discharge pipe for discharging the processing gas in the gas-liquid contact tank 12, and 34 a cleaning liquid in the cleaning liquid storage tank 16. 2 shows a drain pipe for draining water.
[0018]
In the exhaust processing apparatus of this example, a cleaning liquid is introduced into the gas-liquid contact tank 12 by the cleaning liquid introduction mechanism 14, and a silicon compound is added to the cleaning liquid 20 in the gas-liquid contact tank 12 by the silicon compound addition mechanism 26. Further, if necessary, a pH adjusting agent is added to the cleaning liquid 20 in the gas-liquid contact tank 12 by the pH adjusting agent adding mechanism 28 to adjust the cleaning liquid to be acidic, preferably pH 3 to 6. Then, an exhaust gas containing fluorine and ammonia is introduced as bubbles into the cleaning liquid 20 in the gas-liquid contact tank 12 by the exhaust introducing mechanism 30, and the exhaust gas and the cleaning liquid are brought into contact with each other to transfer the fluorine and ammonia in the exhaust gas into the cleaning liquid 20. By doing so, a process gas from which fluorine and ammonia have been removed is obtained. This processing gas is discharged out of the system through the processing gas discharge pipe 32. Further, in the apparatus of this example, introduction of the cleaning liquid into the gas-liquid contact tank, addition of a silicon compound to the cleaning liquid, addition of a pH adjuster to the cleaning liquid (if necessary), and exhaustion of gas into the gas-liquid contact tank. The introduction, the overflow of the cleaning liquid in the gas-liquid contact tank, the supply of the cleaning liquid to the cleaning liquid storage tank, and the discharge of the cleaning liquid from the cleaning liquid storage tank are continuously performed. The cleaning liquid discharged from the cleaning liquid storage tank is appropriately processed by an evaporator or the like.
[0019]
The gas-liquid contact tank for bringing the exhaust gas into contact with the cleaning liquid may be a bubble-column type gas-liquid contact tank as in this example, or may be another type of gas-liquid contact tank such as a packed tower type. Further, the addition of the silicon compound or the pH adjuster to the cleaning liquid may be performed in a gas-liquid contact tank as in this example, or may be performed in a pipe or a cleaning liquid storage tank.
[0020]
【Example】
Examples are shown below, but these examples do not limit the scope of the present invention. In the following examples, the fluorine concentration in the exhaust gas is the concentration of a fluorine compound (mg / m ³ N) determined by lanthanum-alizarin complexone spectrophotometry according to JIS-K-0105, and the ammonia concentration in the exhaust gas is JIS-K. This is the ammonia concentration (mg / kg) of K-0099 as determined by indophenol absorption spectrophotometry.
[0021]
(Example 1)
Exhaust gas containing fluorine and ammonia was treated using the exhaust treatment device shown in FIG. In this case, the exhaust introduction mechanism 30 was connected to the exhaust duct of the waste liquid drying facility in the ultrapure water production / treatment system of the semiconductor device factory shown in FIG. 2, and the exhaust gas discharged from the waste liquid drying facility was treated. As the gas-liquid contact tank 12, a model WS-120-P manufactured by Accor Corporation was used. As the cleaning liquid, city water having a pH of 7 and a silicon compound content of 5 mg SiO ₂ / L is supplied to the cleaning liquid storage tank 16 at a flow rate of 1 m ³ / hr by the cleaning liquid supply mechanism 18, and the city water in the cleaning liquid storage tank 16 is supplied with the cleaning liquid introduction pipe 24. And introduced into the gas-liquid contact tank 12 at a flow rate of 4.2 m ³ / hr. Water glass was used as the silicon compound, and 92 mg of SiO ₂ / hr of the silicon compound was added to the cleaning liquid 20 in the gas-liquid contact tank 12 by the silicon compound addition mechanism 26. Further, in this example, the pH adjusting agent was not added to the cleaning liquid by the pH adjusting agent adding mechanism 28.
[0022]
The exhaust of 5000 m ³ N / hr generated from the waste liquid drying equipment was treated as described above. As a result, while the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, the concentration of the fluorine compound contained in the exhaust gas (the treatment gas) after the treatment was The concentration was 1.75 mg / m ³ N (removal rate 95%), and the ammonia concentration was 3 mg / kg (removal rate 70%).
[0023]
(Comparative Example 1)
In the exhaust treatment apparatus operating under the conditions of Example 1, the addition of the silicon compound to the cleaning solution by the silicon compound addition mechanism 26 was stopped, and three hours after the stop, the exhaust gas and the processing gas before the treatment were analyzed. . As a result, the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, whereas the concentration of the fluorine compound contained in the treatment gas was 28 mg / m ³ N ( The removal rate was 20%), and the ammonia concentration was 4 mg / kg (removal rate 60%).
[0024]
(Example 2)
In the exhaust treatment apparatus operating under the conditions of the first embodiment, the pH adjusting agent (sulfuric acid) is added to the cleaning liquid by the pH adjusting agent adding mechanism 28 to adjust the pH of the cleaning liquid in the gas-liquid contact tank 12 to 6.5. , 5.0, 4.0, and 3.0. When the system was operated for 3 hours at each pH value, the exhaust gas and the processing gas before the processing were analyzed. As a result, while the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, the concentration and the removal rate of the fluorine compound and the ammonia contained in the treatment gas were As shown in Table 1.
[0025]
[Table 1]

[0026]
(Comparative Example 2)
In the exhaust treatment apparatus operating under the conditions of Example 2, the addition of the silicon compound to the cleaning liquid by the silicon compound addition mechanism 26 was stopped, and after 3 hours from the stop at each pH, the exhaust gas and the processing gas before the treatment were removed. Analysis was carried out. As a result, while the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, the concentration and the removal rate of the fluorine compound and the ammonia contained in the treatment gas were As shown in Table 2.
[0027]
[Table 2]

[0028]
(Example 3)
In the exhaust treatment apparatus operating under the conditions of the first embodiment, the pH adjusting agent (sulfuric acid) is added to the cleaning solution by the pH adjusting agent adding mechanism 28, and the pH of the cleaning solution in the gas-liquid contact tank 12 is adjusted to 6.0. And the amount of the silicon compound added to the cleaning solution by the silicon compound addition mechanism 26 is changed so that the amount of addition becomes 50, 70, 92, 150, 250, 400, and 650 mg SiO ₂ / hr. did. When the operation was performed for 3 hours at each addition amount, the exhaust gas and the processing gas before the processing were analyzed. As a result, while the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, the concentration and the removal rate of the fluorine compound and the ammonia contained in the treatment gas were As shown in Table 3.
[0029]
[Table 3]

[0030]
(Example 4)
Using the same apparatus as in Example 1, the exhaust gas discharged from the waste liquid drying equipment in the ultrapure water production / treatment system of the semiconductor device factory shown in FIG. 3 was treated. In this case, the concentrated water of the reverse osmosis membrane device of the ultrapure water production / treatment system was used as the cleaning liquid. An acid is added to the water to be treated in the reverse osmosis membrane device in order to prevent scale generation, and thus the concentrated water in the reverse osmosis membrane device is acidic. Further, since the silicon compound contained in the water to be treated is present in a concentrated state in the concentrated water of the reverse osmosis membrane device, the concentration of the silicon compound in the concentrated water is high. In this example, the concentration of the silicon compound in the cleaning liquid (concentrated water of the reverse osmosis membrane device) was 400 mg SiO ₂ / L, and the pH was 5.5. The amount of the cleaning liquid introduced into the gas-liquid contact tank 12 was 1 m ³ / hr.
[0031]
The exhaust of 5000 m ³ N / hr generated from the waste liquid drying equipment was treated as described above. As a result, while the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, the concentration of the fluorine compound contained in the treatment gas was 1 mg / m ³ N ( The removal rate was 97%), and the ammonia concentration was 1.5 mg / kg (85% removal rate).
[0032]
(Example 5)
Using the same apparatus as in Example 1, the exhaust gas discharged from the waste liquid drying facility in the ultrapure water production / treatment system of the semiconductor device factory shown in FIG. 4 was treated. In this case, the concentrated water of the reverse osmosis membrane device of the ultrapure water production / treatment system was used as the cleaning liquid. An acid is added to the water to be treated in the reverse osmosis membrane device in order to prevent scale generation, and thus the concentrated water in the reverse osmosis membrane device is acidic. Further, since the silicon compound contained in the water to be treated is present in a concentrated state in the concentrated water of the reverse osmosis membrane device, the concentration of the silicon compound in the concentrated water is high. In this example, the concentration of the silicon compound in the cleaning liquid (concentrated water of the reverse osmosis membrane device) was 400 mg SiO ₂ / L, and the pH was 5.5. The amount of the cleaning liquid introduced into the gas-liquid contact tank 12 was 1 m ³ / hr.
[0033]
The exhaust of 5000 m ³ N / hr generated from the waste liquid drying equipment was treated as described above. As a result, while the concentration of the fluorine compound contained in the exhaust gas before the treatment was 35 mg / m ³ N and the concentration of the ammonia was 10 mg / kg, the concentration of the fluorine compound contained in the treatment gas was 1 mg / m ³ N ( The removal rate was 97%), and the ammonia concentration was 1.5 mg / kg (85% removal rate).
[0034]
According to the above examples, the exhaust containing fluorine and ammonia is brought into contact with the cleaning liquid containing a silicon compound, in particular, the cleaning liquid is made acidic to pH 3 to 6, and the concentration of the silicon compound in the cleaning liquid is made 100 mg SiO ₂ / L or more. It can be seen that fluorine and ammonia contained in the exhaust gas can be efficiently removed by the single-stage gas-liquid contact tank.
[0035]
Further, as described above, the concentrated water of the reverse osmosis membrane device of the ultrapure water production / treatment system at the semiconductor device factory is acidic and has a high silicon compound concentration. For example, Japanese Patent Application Laid-Open No. 7-163979 discloses a reverse osmosis membrane treatment method in which water to be treated containing at least a hardness component and a silicon compound is treated with a reverse osmosis membrane and separated into permeated water and concentrated water. It is disclosed that a reverse osmosis membrane treatment is performed while maintaining the pH of the solution at 6 or less. Therefore, the concentrated water of the reverse osmosis membrane device can be suitably used as the washing water in the present invention. Therefore, the present invention is directed to an exhaust gas containing fluorine and ammonia and a concentrated water of a reverse osmosis membrane device of an ultrapure water production / treatment system such as a semiconductor device factory, which has a pH of ₃ to 6 containing a silicon compound of 100 mg SiO ₂ / L or more. The present invention also provides an exhaust treatment method characterized by contacting the concentrated water of the reverse osmosis membrane device with the above.
[0036]
【The invention's effect】
As described above, according to the present invention, for example, both fluorine and ammonia contained in exhaust gas discharged from waste liquid drying equipment of a semiconductor device factory can be removed by a single-stage gas-liquid contact tank, and Processing equipment and operation can be simplified, and equipment costs and operation costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an exhaust treatment device according to the present invention.
FIG. 2 is a schematic diagram showing an example of an ultrapure water production / treatment system at a semiconductor device factory.
FIG. 3 is a schematic diagram showing an example of an ultrapure water production / treatment system at a semiconductor device factory.
FIG. 4 is a schematic view showing an example of an ultrapure water production / treatment system at a semiconductor device factory.
[Explanation of symbols]
12 Gas-liquid contact tank 14 Cleaning liquid introduction mechanism 16 Cleaning liquid storage tank 18 Cleaning liquid supply mechanism 20 Cleaning liquid 22 Overflow pipe 24 Cleaning liquid introduction pipe 26 Silicon compound addition mechanism 28 pH adjuster addition mechanism 30 Exhaust introduction mechanism 32 Processing gas discharge pipe 34 Drain pipe

Claims

An exhaust treatment method comprising contacting exhaust containing fluorine and ammonia with a cleaning solution containing a silicon compound.

The exhaust treatment method according to claim 1, wherein the cleaning solution is made acidic at pH 3 to 6.

3. The exhaust treatment method according to claim 1, wherein the silicon compound is an alkali metal silicate.

Exhaust treatment method according to claim 3 in which the alkali metal silicate concentration in the cleaning liquid, characterized in that at 100mgSiO 2 / _L or more.

Exhaust gas containing fluorine and ammonia and concentrated water of a reverse osmosis membrane device of an ultrapure water production / treatment system such as a semiconductor device factory, wherein the concentration of the reverse osmosis membrane device having a pH of 3 to 6 and containing a silicon compound of 100 mg SiO ₂ / L or more. An exhaust treatment method comprising contacting with water.

A gas-liquid contact tank, a cleaning liquid introduction mechanism for introducing a cleaning liquid into the gas-liquid contact tank, a silicon compound addition mechanism for adding a silicon compound to the cleaning liquid, and an exhaust gas for introducing exhaust containing fluorine and ammonia into the gas-liquid contact tank. An exhaust treatment device comprising an introduction mechanism, wherein the exhaust gas containing fluorine and ammonia is brought into contact with a cleaning solution containing a silicon compound in the gas-liquid contact tank.

The exhaust treatment apparatus according to claim 6, further comprising a pH adjusting agent addition mechanism for adding a pH adjusting agent to the cleaning liquid to make the cleaning liquid acidic to pH 3 to 6.