JP4252166B2

JP4252166B2 - Dust removal and harmful gas decomposition equipment

Info

Publication number: JP4252166B2
Application number: JP24784999A
Authority: JP
Inventors: 彰鳥山
Original assignee: Electric Power Development Co Ltd; Isolite Insulating Products Co Ltd
Current assignee: Electric Power Development Co Ltd; Isolite Insulating Products Co Ltd
Priority date: 1999-07-29
Filing date: 1999-07-29
Publication date: 2009-04-08
Anticipated expiration: 2019-07-29
Also published as: JP2001038117A

Description

【０００１】
【発明の属する技術分野】
本発明は特に廃棄物焼却炉、石炭等の化石燃料を使用する燃焼設備、製鉄及び冶金用各種工業炉、セメント焼成炉、耐火物焼成炉、石油精製設備、化学プラント等から排出される含塵ガス中の粉塵を除去し、同時に、窒素酸化物及び有機塩素化合物を、触媒を用いて分解し無害化する除塵兼有害ガス分解装置に関する。
【０００２】
【従来の技術】
燃焼炉からの排ガスを除塵し、窒素酸化物及びＰＣＤＤ（ポリ塩化ジベンゾダイオキシン、ＰＣＤＦ（ポリ塩化ジベンゾフラン）等の有機塩素化合物を分解し無害化する従来の方式の典型例を図３に示す。なお、バッグフィルタは、ごく一般的に普及しているポリカーボネート製織布を使用した外面集塵型バグフィルタ（キャンドルフィルタ）を使用した場合について以下に説明する。
【０００３】
燃焼炉からでた排ガスは、ダクト１０１を通り、水噴霧もしくは熱交換器を用いた減温器１０２で２００℃以下まで減温され、バグフィルタ入口１０３に入る。缶体１０４のホッパー部に流入した燃焼排ガスは、濾筒１０５の外面で集塵され、粉塵を含まないガスとなって、ガス集合部１０６を経てガス出口１０７から流出する。
【０００４】
濾筒１０５の外面に堆積した粉塵は、逆洗装置１０８にて圧縮空気を定期的に濾筒１０５の内部に噴射して濾筒１０５の内圧を高め、粉塵を剥離脱落させる。剥離脱落した粉塵はホッパー部１０９から矢印１１０の方向に落下し、図示しない切出し弁もしくはスクリューコンベアーにて系外へ排出される。
【０００５】
ガス出口１０７から出た粉塵を含まない燃焼排ガスは、加熱装置１１１にて、窒素酸化物及び有機塩素化合物の分解が最も効率良く行える温度である３００℃から３５０℃の範囲に昇温され、アンモニア注入装置１１３で注入されたアンモニアと燃焼排ガスとの混合ガスが分解装置の缶体１１４の入口部１１５に入る。以後、アンモニアと燃焼排ガスとの混合ガスは触媒を担持したハニカム群１１６、１１７、１１８を、矢印１１９、１２０、１２１の方向に順次通過し、分解装置１１４の出口１２２から矢印１２３の方向に排出される。
【０００６】
【発明が解決しようとする課題】
以上説明したように、従来の技術では、各々単一の機能を持つ除塵装置と、窒素酸化物及び有機塩素化合物分解装置の２種類の設備をシリーズに接続し、除塵と、窒素酸化物及び有機塩素化合物の分解を各々単独に行っていた。加えて、除塵装置の手前ではガス冷却器で２００℃以下まで冷却し、除塵装置を出た後は、加熱装置で３００℃から３５０℃の範囲に昇温する複雑なシステム構成となって、設備費用の増大と運転及び制御の煩雑さを招いていた。
【０００７】
バッグフィルタの濾筒材質としては、上記のポリカーボネート樹脂製織布のほか、例えばアルミナ・シリカ化合物によるセラミックス繊維の不織布が使用されている例もあるが、窒素酸化物及び有機塩素化合物分解触媒は担持されていないため、前記のポリカーボネート織布を用いたバッグフィルタの場合と同様、後流に触媒を担持したハニカム等から成る窒素酸化物及び有機塩素化合物分解設備が必要であった。
【０００８】
そこで本発明は、除塵と、燃焼排ガス中の窒素酸化物及び有機塩素化合物の分解を、１つの装置で同時に達成できる除塵兼有害ガス分解装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記の目的を解決するため、本発明による除塵兼有害ガス分解装置は、触媒を略均一に分散担持したセラミックス繊維の成形体から成る、空隙率が８０％以上９５％以下の濾筒を用いて、含塵ガス中の粉塵を除去すると同時に、含塵ガス中に含まれる窒素酸化物及び有機塩素化合物例えばＰＣＤＤ（ポリ塩化ジベンゾダイオキシン、ＰＣＤＦ（ポリ塩化ジベンゾフラン）等を分解し無害化することを特徴とする。
【００１０】
前記濾筒の形状は、両端が開放した円筒形、もしくは一端が開放し他端が閉止した円筒形（キャンドル型）の何れを使用しても良い。ただし、両端が開放した円筒形の濾筒を用いる場合は図１に示す如く、円筒の上下端部を管板で支持する構造とし、円筒の内側に含塵ガスを通し、円筒の内壁面で除塵し、粉塵を含まない燃焼排ガスが濾筒内表面から濾筒壁内部を貫通して濾筒外表面に流出する、いわゆる内面集塵方式の構成とする。
【００１１】
前記濾筒の形状が、一端が開放し他端が閉止した所謂キャンドル型の濾筒を用いる場合は、図２に示す如く、開放した円筒の上端部を管板で支持し濾筒を垂下する構造とし、円筒の外側に含塵ガスを導き、円筒の外壁面で除塵し、粉塵を含まない燃焼排ガスが濾筒外表面から濾筒壁内部を貫通して濾筒内表面に流出する、いわゆる外面集塵方式の構成とする。
【００１２】
上記何れの方式を採用する場合も、燃焼ガスが濾筒壁内部を貫通する際に、燃焼ガス中に含まれる窒素酸化物及び有機塩素化合物は、濾筒壁内部に分散担持された触媒によって分解され、無害化される。
【００１３】
なお、窒素酸化物を分解する目的の場合は、本発明による除塵兼有害ガス分解装置の含塵ガス入口配管の上流側配管に、窒素酸化物の還元剤であるアンモニアを注入する設備と、注入されたアンモニアを燃焼排ガス中に均一に分散させるための混合ゾーンが必要である。ただし、有機塩素化合物のみを分解する目的であれば、アンモニアの注入は不要である。
【００１４】
濾筒を構成するセラミックス繊維は、少なくとも５００℃以上の耐熱性があり、燃焼排ガスに対する耐食性があって、成形体を形成できるものであれば如何なるセラミックス繊維も使用することができる。アルミナ、シリカ、チタニア、マグネシア、ガラス、炭化珪素、窒化珪素の何れかの単一成分から成る繊維、もしくはこれらの化合物から成る繊維、もしくはこれら繊維の複合組成からなるセラミックス繊維は耐熱性、耐食性及び市場性の点で特に好ましい。
【００１５】
触媒を担持したセラミックス繊維成形体から成る濾筒は、その繊維径が１〜１０ミクロンの範囲でかつ繊維長さが少なくとも１０ｍｍ以上あるセラミックス繊維が少なくとも全体の５０％以上を占めるセラミックス繊維から成り、少なくとも１０ｍｍ以上の厚さを有する成形体の中に、五酸化バナジウム又は三酸化タングステン、もしくは両者の混合物からなる平均粒径２０ミクロン以上８０ミクロン以下の粉末状触媒を略均一に分散担持させて濾筒を形成する。
【００１６】
前記濾筒を構成するセラミックス繊維径が１ミクロン以下の場合は繊維の製造技術上の困難さを伴い、又、繊維径が１０ミクロンを越える場合は繊維の靭性が低下して折れ易くなり、濾筒を構成することが困難となって好ましくない。
【００１７】
前記濾筒を構成する触媒を担持したセラミックスス繊維成形体の厚みは、濾筒内部に分散担持した触媒と、濾筒を通過するガスとが十分に接触し、窒素酸化物及び有機塩素化合物を環境排出基準値以下に低減する上で、１０ｍｍ以上の厚みを確保し、ガスの濾筒中の滞留時間を少なくとも０．５秒以上確保することが必要である。なお、濾筒に構造体としての強度を持たせる上でも１０ｍｍ以上の厚みが必要である。
【００１８】
前記セラミックス繊維成形体から成る濾筒中に担持される粉末状触媒は、平均粒径２０ミクロン以上８０ミクロン以下で、かつ、濾筒の全重量の内、５重量％以上２５重量％以下の範囲であることが望ましい。
【００１９】
その理由は、触媒の平均粒径が２０ミクロン以下では、触媒としての活性が低下することに加え、特に触媒粉末とセラミックス繊維との混合液を濾過して濾筒を製造する場合に、触媒が濾過体に捕捉されずに通過し、結果として廃棄される触媒が増加して触媒の歩留まりが低下することによる。又、触媒の平均粒径が８０ミクロン以上では、触媒の単位重量当りの比表面積が減少し、触媒の重量当りの効率が低下することに加え、特に触媒粉末とセラミックス繊維との混合液を濾過して濾筒を製造する場合に、混合液中に触媒が充分に分散浮遊せずに沈降して容器底に溜まり、結果として廃棄される触媒が増加して触媒の歩留まりが低下することによる。
【００２０】
前記セラミックス繊維成形体から成る濾筒中に担持される粉末状触媒は、濾筒の重量に占める粉末状触媒の割合が５重量％以下になると、濾筒壁を貫通して流れる燃焼排ガス中の窒素酸化物及び有機塩素化合物が、触媒と十分に接触せずに通過してしまうため、分解されずに排出される割合が多くなり好ましくない。又、濾筒に占める粉末状触媒の割合が２５重量％以上では、セラミックス繊維から成る成形体中に占める粉末状物質の割合が多くなって、濾筒２の機械的強度が低下するため好ましくない。
【００２１】
又、前記濾筒に分散担持される触媒は、予め、五酸化バナジウム及び三酸化タングステンとの親和性に優れた酸化チタンを担体とした粉末状触媒に成形したものを使用することもできる。
【００２２】
更に、触媒を担持したセラミックス繊維成形体から成る濾筒の空隙率は８０％以上９５％以下であることが望ましい。その理由は、８０％未満の空隙率では、単位容積当りのセラミックス繊維の充填密度が過大となって、濾筒壁を通過するガスの圧力損失が増大し、燃焼排ガス系統の吸引送風機もしくは燃焼器への押込送風機動力の増大を招き、一方、９５％を超える空隙率では、単位容積当りのセラミックス繊維の充填密度が過少となって、濾筒の機械的強度が不足し、除塵装置として構成することが不可能になるためである。
【００２３】
なお、触媒を分散担持させたセラミックス繊維製濾筒を製造する方法としては、例えば、アルミナゾル、シリカゾル、チタンゾル等の金属ゾルの何れか単一成分もしくは複合成分と、澱粉等の界面活性剤から成る水溶液中に触媒の粉末を加えて攪拌しつつ、セラミックス繊維を順次投入して触媒とセラミック繊維とのスラリー状混合液を作り、その後、固形分のみを捕捉し液体成分を透過することのできる鋳型に流し込んで成形し、乾燥処理の後、鋳型から取外し、焼成処理をして成形体を得ることができる。
【００２４】
又は、前記金属ゾル、界面活性剤、触媒から成る混合溶液中により多くのセラミックス繊維を投入し、触媒とセラミック繊維から成る可塑性のゲル状素材とし、その後、押出し成形もしくはプレス成形し、乾燥処理及び焼成処理をして成形体を得ても良い。
【００２５】
以上説明した窒素酸化物及び有機塩素化合物の分解が、同時に実現可能であることを検証すべく、実際のダイオキシンとの分解特性の相関が得られている擬似ダイオキシンであるモノクロロベンゼン（ＭＣＢ）を用いて、窒素酸化物及び有機塩素化合物の分解特性確認試験を実施した。
【００２６】
試験に供したセラミックス繊維成形体及び触媒要目と、これらの材料を用いて実施した試験条件及び試験結果を表１及び表２に示す。
【表１】

【表２】

上記の試験結果から、本発明による除塵と、窒素酸化物及び有機塩素化合物の分解が、触媒を担持したセラミックス繊維成形体から成る濾筒により実現できることが明らかとなった。
【００２７】
【発明の実施の形態】
以下本発明の実施の形態を図面に基づき詳細に説明する。図1は、本発明による除塵装置兼有害ガス分解装置の１実施例で、両端が開放した円筒形の濾筒を用いた所謂内面集塵型の除塵装置兼有害ガス分解装置で、その構成は、缶体１と、両端が開放した円筒形状のセラミックス繊維からなる成形体の濾筒中に、五酸化バナジウム又は三酸化タングステンもしくは両者の混合物からなる粉末状の触媒を濾筒の板厚方向に略均一に分散担持して成る複数の濾筒２と、該濾筒の両端部を支持する１対の管板３及び４からなるフィルタユニット５と、該フィルタユニットに連通する前記缶体に接続された含塵ガス入口管６と、前記フィルタユニットで除塵された粉塵を集合して排出する為に前記缶体の下部空間に設けられた粉塵ホッパー７と、前記フィルタユニットの濾筒壁を通過して得られた清浄ガスを、缶体外部に取出す清浄ガス出口管８と、前記濾筒表面に付着した粉塵を払い落とす逆洗装置９と、含塵ガス入口管６に接続する配管１０の途中に設けたアンモニア注入装置１１から成ることを特徴とする。
【００２８】
図２は、本発明による除塵装置兼有害ガス分解装置の他の実施例で、一端が開放し、他端が閉止した円筒形の濾筒を用いた所謂外面集塵型の除塵装置兼有害ガス分解装置で、缶体１と、上端が開放し下端が閉止した円筒形状のセラミックス繊維からなる成形体の濾筒中に、五酸化バナジウム又は三酸化タングステンもしくは両者の混合物からなる粉末状の触媒を濾筒の板厚方向に略均一に分散担持して成る複数の濾筒２と、該濾筒の上端部を支持し、濾筒を垂下するための管板３からなるフィルタユニット５と、該フィルタユニットに連通する前記缶体に接続された含塵ガス入口管６と、前記フィルタユニットで除塵された粉塵を集合して排出する為に前記缶体の下部空間に設けられた粉塵ホッパー７と、前記フィルタユニットの濾筒壁を通過して得られた清浄ガスを、缶体外部に取出す清浄ガス出口管８と、前記濾筒表面に付着した粉塵を払い落とす逆洗装置９と、含塵ガス入口管６に接続する配管１０の途中に設けたアンモニア注入装置１１から成ることを特徴とする。なお、図中の記号の内、図１と同一機能のものは図1と同じ符号を付してある。
【００２９】
図１及び図２に示す何れの方式の除塵装置兼有害ガス分解装置においても、窒素酸化物及び有機塩素化合物を含む燃焼排ガスは、ガスダクト１０を通り、アンモニア注入装置１１から注入されたアンモニアと混合し、有害ガス分解装置入口６から装置内に導かれ、触媒を担持したセラミックス繊維成形体から成る濾筒２のガス流入側壁面１２で除塵され、濾筒壁内部に流入する。濾筒壁内部に流入したガスは、濾筒壁内部に分散担持された触媒の働きにより、窒素酸化物及び有機塩素化合物が分解され、無害化されて、濾筒のガス流出側壁面１３から流出する。濾筒２から流出した無害化されたガスは、集合部１４を経て、装置出口８から矢印１５の方向に排出される。
【００３０】
図１に示す内面集塵型の除塵装置兼有害ガス分解装置においては、逆洗装置９により定期的に圧縮空気を噴射して清浄ガス集合部１３の内圧を高め、濾筒内面１２に堆積した粉塵を剥離・脱落させ、下部ホッパーに落下せしめる。下部ホッパーに落下した粉塵１４は図示しない粉塵切出し弁もしくはスクリューコンベアーにより矢印１５の方向に排出される。
【００３１】
又、図２に示す外面集塵型の除塵装置兼有害ガス分解装置においては、逆洗装置９により定期的に圧縮空気を噴射して清浄ガス集合部１３の内圧を高め、濾筒外面１６に堆積した粉塵を剥離・脱落させ、下部ホッパーに落下せしめる。下部ホッパーに落下した粉塵１４は図示しない粉塵切出し弁もしくはスクリューコンベアーにより矢印１５の方向に排出される。
【００３２】
なお、有機塩素化合物を分解する目的のみに本装置を使用する場合は、アンモニアを注入する必要はない。
【００３３】
又、図１及び図２に示す何れの方式の除塵装置兼有害ガス分解装置においても、装置に流入する燃焼排ガス温度は２００℃以上４００℃以下の範囲で制御することが望ましい。その理由は、２００℃以下の温度では、燃焼排ガス中に含まれる硫黄酸化物と、排ガス中に注入されたアンモニアとが反応し、硫酸アンモニウム塩となって触媒が被毒する可能性が高まるからである。
【００３４】
更に、ガス温度が２００℃以下の場合、主として廃棄物焼却炉等からの排ガス中に含まれる塩素ガス及び炭化水素が、飛灰中に含まれる銅などの金属酸化物の触媒作用によって、有機塩素化合物が再合成（デノボ合成）され、除塵された灰中の有機塩素化合物濃度が高まる。従って、有機塩素化合物が再合成しても、それらが気体の状態に留まっている２００℃以上の温度、望ましくは３５０℃前後の温度域で、除塵された灰に吸着されることなく濾筒表面の灰堆積層を透過し、濾筒材内部に分散担持された触媒により効果的に分解せしめる上で、燃焼排ガス温度は２００℃以上４００℃以下の範囲に制御することが望ましい。
【００３５】
一方、装置に流入する燃焼排ガス温度が４００℃を越える場合は、触媒による排ガス中の窒素酸化物及び有機塩素化合物の分解能が低下することに加え、排ガスの容積流量が増大することによる濾筒の必要濾過面積の増大を招き、装置が大型化するため好ましくない。
【００３６】
【発明の効果】
以上説明したように、本発明による除塵兼有害ガス分解装置を使用すれば、特に廃棄物焼却炉、石炭等の化石燃料を使用する燃焼設備、製鉄及び冶金用各種工業炉、セメント焼成炉、耐火物焼成炉、石油精製設備、化学プラント等から排出される含塵ガス中の粉塵を濾筒表面で除去し、同時に、窒素酸化物及び有機塩素化合物を、濾筒内部に分散担持した触媒を用いて分解し無害化することができるので、従来、それぞれ異なる機能を有する装置をシリーズに接続し、それぞれ異なる入口ガス温度に制御していた方式に比べ、装置の系統が単純化され、設備費用及びメンテナンス費用を大幅に低減できるのみならず、運転及び制御も簡素化されて信頼性及び運用性の何れも大幅に向上することが期待できる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る第１の実施例を示す組立断面図兼系統図である。
【図２】本発明の実施の形態に係る第２の実施例を示す組立断面図兼系統図である。
【図３】従来技術の燃焼排ガスを浄化するプロセスの１例を示す系統図である。
【符号の説明】
１缶体
２触媒を担持した濾筒
３上部管板
４下部管板
５フィルターユニット
６含塵ガス入口管
７粉塵ホッパー
８清浄ガス出口管
９逆洗装置
１０含塵ガス入口ダクト配管
１１アンモニア注入装置
１２触媒を担持した濾筒の内壁面
１３清浄ガス集合部
１４粉塵
１５粉塵排出方向
１６触媒を担持した濾筒の外壁面[0001]
BACKGROUND OF THE INVENTION
The present invention particularly includes waste incinerators, combustion facilities using fossil fuels such as coal, various industrial furnaces for iron and metallurgy, cement firing furnaces, refractory firing furnaces, petroleum refining facilities, chemical plants, etc. The present invention relates to a dust removal and harmful gas decomposition apparatus that removes dust in gas and simultaneously decomposes and detoxifies nitrogen oxides and organic chlorine compounds using a catalyst.
[0002]
[Prior art]
Fig. 3 shows a typical example of a conventional method for removing dust from a combustion furnace and decomposing and detoxifying nitrogen oxides and organic chlorine compounds such as PCDD (polychlorinated dibenzodioxin and PCDF (polychlorinated dibenzofuran)). As for the bag filter, a case where an outer surface dust collecting type bag filter (candle filter) using a woven fabric made of polycarbonate, which is very popular, will be described below.
[0003]
Exhaust gas discharged from the combustion furnace passes through the duct 101, is reduced in temperature to 200 ° C. or less by a temperature reducer 102 using water spray or a heat exchanger, and enters the bag filter inlet 103. The combustion exhaust gas that has flowed into the hopper portion of the can body 104 is collected on the outer surface of the filter tube 105, becomes a gas that does not contain dust, and flows out from the gas outlet 107 through the gas collecting portion 106.
[0004]
The dust accumulated on the outer surface of the filter tube 105 is periodically sprayed with compressed air into the filter tube 105 by the backwash device 108 to increase the internal pressure of the filter tube 105, and the dust is peeled off. Dust that has fallen off is dropped from the hopper 109 in the direction of arrow 110 and is discharged out of the system by a not-shown cut-off valve or screw conveyor.
[0005]
Combustion exhaust gas that does not contain dust discharged from the gas outlet 107 is heated to a temperature in the range of 300 ° C. to 350 ° C., which is the temperature at which nitrogen oxides and organochlorine compounds can be most efficiently decomposed, by the heating device 111, and ammonia A mixed gas of ammonia and combustion exhaust gas injected by the injection device 113 enters the inlet 115 of the can 114 of the decomposition device. Thereafter, the mixed gas of ammonia and combustion exhaust gas sequentially passes through the

honeycomb groups

116, 117, and 118 carrying the catalyst in the directions of arrows 119, 120, and 121, and is discharged from the outlet 122 of the decomposition apparatus 114 in the direction of arrow 123. Is done.
[0006]
[Problems to be solved by the invention]
As described above, in the conventional technology, two types of equipment, a dust removing device having a single function and a nitrogen oxide and organochlorine compound decomposing device, are connected in series to remove dust, nitrogen oxide, and organic. The decomposition of the chlorine compounds was carried out independently. In addition, before the dust removal device, it is cooled to 200 ° C or less with a gas cooler, and after exiting the dust removal device, it becomes a complicated system configuration in which the temperature is raised from 300 ° C to 350 ° C with a heating device. This increased the cost and complicated operation and control.
[0007]
In addition to the above-mentioned polycarbonate resin woven fabric, there are examples in which a nonwoven fabric of ceramic fibers made of alumina / silica compound is used as the material for the filter tube of the bag filter, but nitrogen oxide and organochlorine compound decomposition catalysts are supported. Therefore, as in the case of the bag filter using the polycarbonate woven fabric, a nitrogen oxide and organochlorine compound decomposition facility comprising a honeycomb or the like carrying a catalyst in the downstream is required.
[0008]
Therefore, an object of the present invention is to provide a dust removal and harmful gas decomposition apparatus that can simultaneously achieve dust removal and decomposition of nitrogen oxides and organic chlorine compounds in combustion exhaust gas with one apparatus.
[0009]
[Means for Solving the Problems]
In order to solve the above-described object, the dust removal and harmful gas decomposition apparatus according to the present invention uses a filter tube having a porosity of 80% or more and 95% or less, which is formed of a ceramic fiber molded body in which a catalyst is substantially uniformly dispersed and supported. In addition to removing dust in the dust-containing gas, it simultaneously decomposes and detoxifies nitrogen oxides and organochlorine compounds such as PCDD (polychlorinated dibenzodioxin, PCDF (polychlorinated dibenzofuran)) contained in the dust-containing gas. And
[0010]
The shape of the filter tube may be either a cylindrical shape with both ends open, or a cylindrical shape (candle type) with one end open and the other end closed. However, when using a cylindrical filter tube with both ends open, as shown in FIG. 1, the upper and lower ends of the cylinder are supported by a tube plate, dust-containing gas is passed inside the cylinder, and the inner wall surface of the cylinder is used. The so-called inner surface dust collection system is configured in which dust is removed and combustion exhaust gas that does not contain dust flows from the inner surface of the filter tube through the inside of the filter tube wall and flows out to the outer surface of the filter tube.
[0011]
When using a so-called candle type filter tube whose one end is open and the other end is closed, as shown in FIG. 2, the upper end of the open cylinder is supported by a tube plate and the filter tube is suspended. It is structured so that dust-containing gas is guided to the outside of the cylinder, dust is removed on the outer wall surface of the cylinder, and combustion exhaust gas that does not contain dust flows out from the outer surface of the filter tube to the inner surface of the filter tube, so-called, The external dust collection system is used.
[0012]
In any of the above methods, when the combustion gas penetrates the inside of the filter cylinder wall, the nitrogen oxides and organochlorine compounds contained in the combustion gas are decomposed by the catalyst dispersedly supported inside the filter cylinder wall. And detoxified.
[0013]
For the purpose of decomposing nitrogen oxides, equipment for injecting ammonia, which is a reducing agent of nitrogen oxides, into the upstream pipe of the dust-containing gas inlet pipe of the dust removal and harmful gas decomposition apparatus according to the present invention, A mixing zone is required to uniformly disperse the released ammonia in the combustion exhaust gas. However, it is not necessary to inject ammonia for the purpose of decomposing only the organic chlorine compound.
[0014]
Any ceramic fiber may be used as long as it has a heat resistance of at least 500 ° C. and corrosion resistance to combustion exhaust gas and can form a molded body . A fiber composed of a single component of alumina, silica, titania, magnesia, glass, silicon carbide, silicon nitride, a fiber composed of these compounds, or a ceramic fiber composed of a composite composition of these fibers has heat resistance, corrosion resistance and This is particularly preferable in terms of marketability.
[0015]
A filter cylinder made of a ceramic fiber molded article carrying a catalyst is composed of ceramic fibers in which the fiber diameter is in the range of 1 to 10 microns and the fiber length is at least 10 mm or more occupies at least 50% of the total, In a molded body having a thickness of at least 10 mm or more, a powdered catalyst having an average particle size of 20 microns or more and 80 microns or less composed of vanadium pentoxide, tungsten trioxide, or a mixture of both is dispersed and supported substantially uniformly. Form a tube.
[0016]
When the diameter of the ceramic fiber constituting the filter tube is 1 micron or less, there are difficulties in fiber manufacturing technology, and when the fiber diameter exceeds 10 microns, the toughness of the fiber is lowered and the fiber is easily broken. It is not preferable because it is difficult to configure the cylinder.
[0017]
The thickness of the ceramic fiber molded article carrying the catalyst constituting the filter cylinder is such that the catalyst dispersed and supported inside the filter cylinder and the gas passing through the filter cylinder are in sufficient contact with each other so that the nitrogen oxides and the organic chlorine compounds are contained. In order to reduce it below the environmental emission standard value, it is necessary to secure a thickness of 10 mm or more and to secure a residence time of gas in the filter tube of at least 0.5 seconds or more. In addition, the thickness of 10 mm or more is required also in order to give the filter cylinder strength as a structure.
[0018]
The powdered catalyst supported in the filter cylinder made of the ceramic fiber molded body has an average particle diameter of 20 microns to 80 microns, and within the range of 5% to 25% by weight of the total weight of the filter tube. It is desirable to be.
[0019]
The reason is that when the average particle size of the catalyst is 20 microns or less, the activity as a catalyst is lowered, and in particular, when a filter tube is produced by filtering a mixed solution of catalyst powder and ceramic fibers, This is because the catalyst that passes without being captured by the filter body and is discarded as a result increases and the yield of the catalyst decreases. In addition, when the average particle size of the catalyst is 80 microns or more, the specific surface area per unit weight of the catalyst is reduced, the efficiency per unit weight of the catalyst is lowered, and in particular, the mixed liquid of the catalyst powder and the ceramic fiber is filtered. Thus, when producing a filter cylinder, the catalyst does not sufficiently disperse and float in the mixed solution and settles and accumulates at the bottom of the container, resulting in an increase in the amount of catalyst discarded and a decrease in catalyst yield.
[0020]
When the ratio of the powdered catalyst to the weight of the filter tube is 5% by weight or less, the powdered catalyst supported in the filter tube made of the ceramic fiber molded body is nitrogen in the combustion exhaust gas flowing through the filter tube wall. Since the oxide and the organic chlorine compound pass through without sufficiently contacting with the catalyst, the ratio of being discharged without being decomposed increases, which is not preferable. In addition, if the proportion of the powdered catalyst in the filter tube is 25% by weight or more, the proportion of the powdery material in the molded body made of ceramic fibers increases, and the mechanical strength of the filter tube 2 decreases, which is not preferable. .
[0021]
The catalyst dispersed and supported on the filter tube may be a catalyst formed in advance into a powdered catalyst using titanium oxide having excellent affinity with vanadium pentoxide and tungsten trioxide as a carrier.
[0022]
Further, it is desirable that the porosity of the filter cylinder made of the ceramic fiber molded body supporting the catalyst is 80% or more and 95% or less. The reason for this is that when the porosity is less than 80% , the packing density of ceramic fibers per unit volume becomes excessive, the pressure loss of the gas passing through the filter cylinder wall increases, and the suction blower or combustor of the combustion exhaust gas system On the other hand, when the porosity exceeds 95%, the packing density of ceramic fibers per unit volume is too low, and the mechanical strength of the filter tube is insufficient, so that it is configured as a dust removing device. This is because it becomes impossible.
[0023]
As a method for producing a ceramic fiber filter tube in which a catalyst is dispersed and supported, for example, a single component or a composite component of a metal sol such as alumina sol, silica sol, or titanium sol and a surfactant such as starch are used. A mold that can add catalyst powder to an aqueous solution and stir it, and then sequentially add ceramic fibers to make a slurry-like mixture of catalyst and ceramic fibers, and then capture only the solids and permeate the liquid components. The molded product can be obtained by pouring into a mold, removing it from the mold after the drying process, and performing a firing process.
[0024]
Alternatively, a larger amount of ceramic fiber is put into a mixed solution composed of the metal sol, surfactant, and catalyst to form a plastic gel material composed of the catalyst and the ceramic fiber, and then extrusion molding or press molding, drying treatment, and You may obtain a molded object by baking processing.
[0025]
In order to verify that the decomposition of nitrogen oxides and organochlorine compounds described above can be realized at the same time, monochlorobenzene (MCB), which is a pseudo-dioxin that has a correlation with the decomposition characteristics of actual dioxins, is used. Thus, a test for confirming the decomposition characteristics of nitrogen oxides and organochlorine compounds was conducted.
[0026]
Tables 1 and 2 show the ceramic fiber molded bodies and catalyst points subjected to the test, and test conditions and test results performed using these materials.
[Table 1]

[Table 2]

From the above test results, it became clear that the dust removal according to the present invention and the decomposition of nitrogen oxides and organochlorine compounds can be realized by a filter tube made of a ceramic fiber molded body carrying a catalyst.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a dust removal apparatus and harmful gas decomposition apparatus according to the present invention, which is a so-called inner surface dust collection type dust removal apparatus and harmful gas decomposition apparatus using a cylindrical filter tube having both ends open. , substantially a can body 1, in濾筒of the molded body made of ceramic fiber cylindrical with both ends open, a powdery catalyst consisting of vanadium pentoxide, or tungsten trioxide or a mixture thereof in the thickness direction of the濾筒A plurality of filter tubes 2 uniformly dispersed and supported, a filter unit 5 comprising a pair of

tube plates

3 and 4 that support both ends of the filter tube, and the can connected to the filter unit The dust-containing gas inlet pipe 6, the dust hopper 7 provided in the lower space of the can body for collecting and discharging the dust removed by the filter unit, and the filter cylinder wall of the filter unit. The clean gas obtained from From a clean gas outlet pipe 8 to be taken out of the can body, a backwashing device 9 for removing dust adhering to the surface of the filter cylinder, and an ammonia injection device 11 provided in the middle of a pipe 10 connected to the dust-containing gas inlet pipe 6 It is characterized by comprising.
[0028]
FIG. 2 shows another embodiment of the dust removing apparatus / hazardous gas decomposition apparatus according to the present invention, which is a so-called external dust collecting type dust removing apparatus / hazardous gas using a cylindrical filter tube having one end opened and the other end closed. In a decomposition apparatus, a powdered catalyst composed of vanadium pentoxide or tungsten trioxide or a mixture of both is filtered into the filter body of the can body 1 and a cylindrical ceramic fiber having an open upper end and a closed lower end. A filter unit 5 comprising a plurality of filter tubes 2 that are substantially uniformly dispersed and supported in the thickness direction of the tube, a tube plate 3 that supports the upper end of the filter tube and hangs down the filter tube, and the filter A dust-containing gas inlet pipe 6 connected to the can body communicating with a unit; a dust hopper 7 provided in a lower space of the can body for collecting and discharging dust removed by the filter unit; Through the filter wall of the filter unit. The clean gas outlet pipe 8 for taking out the clean gas obtained outside the can body, the backwashing device 9 for removing dust adhering to the surface of the filter cylinder, and the pipe 10 connected to the dust-containing gas inlet pipe 6 It consists of the ammonia injection apparatus 11 provided in the middle. Of the symbols in the figure, those having the same functions as in FIG. 1 are given the same reference numerals as in FIG.
[0029]
1 and 2, the combustion exhaust gas containing nitrogen oxides and organochlorine compounds is mixed with ammonia injected from the ammonia injection device 11 through the gas duct 10 in any type of dust removal device and harmful gas decomposition device. Then, the gas is introduced from the inlet 6 of the harmful gas decomposition apparatus into the apparatus, is removed by the gas inflow side wall surface 12 of the filter tube 2 made of a ceramic fiber molded body carrying the catalyst, and flows into the filter wall. The gas that has flowed into the filter cylinder wall is decomposed and detoxified by the action of the catalyst dispersedly supported inside the filter wall, and flows out from the gas outlet side wall surface 13 of the filter cylinder. To do. The detoxified gas flowing out from the filter tube 2 passes through the collecting portion 14 and is discharged from the apparatus outlet 8 in the direction of the arrow 15.
[0030]
In the inner surface dust collection type dust removing apparatus and harmful gas decomposition apparatus shown in FIG. 1, compressed air is periodically injected by the backwashing device 9 to increase the internal pressure of the clean gas collecting portion 13 and accumulate on the inner surface 12 of the filter cylinder. Remove and drop off the dust and drop it onto the lower hopper. The dust 14 falling on the lower hopper is discharged in the direction of arrow 15 by a dust cutting valve or a screw conveyor (not shown).
[0031]
Further, in the outer surface dust collecting type dust removing apparatus and harmful gas decomposition apparatus shown in FIG. 2, the backwashing apparatus 9 periodically injects compressed air to increase the internal pressure of the clean gas collecting section 13, The accumulated dust is peeled off and dropped and dropped onto the lower hopper. The dust 14 falling on the lower hopper is discharged in the direction of the arrow 15 by a dust cutting valve or a screw conveyor (not shown).
[0032]
In addition, when this apparatus is used only for the purpose of decomposing the organic chlorine compound, it is not necessary to inject ammonia.
[0033]
Further, in any type of dust removing apparatus and harmful gas decomposition apparatus shown in FIGS. 1 and 2, it is desirable to control the temperature of combustion exhaust gas flowing into the apparatus in a range of 200 ° C. or more and 400 ° C. or less. The reason is that at a temperature of 200 ° C. or lower, the sulfur oxide contained in the combustion exhaust gas reacts with the ammonia injected into the exhaust gas to increase the possibility that the catalyst becomes poisoned as an ammonium sulfate salt. is there.
[0034]
Furthermore, when the gas temperature is 200 ° C. or lower, chlorine gas and hydrocarbons contained mainly in the exhaust gas from a waste incinerator etc. are converted into organic chlorine by the catalytic action of metal oxides such as copper contained in the fly ash. The compound is re-synthesized (de novo synthesis), and the concentration of organochlorine compound in the ash from which dust is removed increases. Therefore, even when organochlorine compounds are re-synthesized, the surface of the filter cylinder is not adsorbed by the dedusted ash at a temperature of 200 ° C. or higher, preferably around 350 ° C. It is desirable to control the combustion exhaust gas temperature in the range of 200 ° C. or more and 400 ° C. or less in order to allow the catalyst to pass through the ash accumulation layer and be effectively decomposed by the catalyst dispersedly supported inside the filter cylinder material.
[0035]
On the other hand, when the temperature of the combustion exhaust gas flowing into the apparatus exceeds 400 ° C., the resolution of nitrogen oxides and organochlorine compounds in the exhaust gas by the catalyst is lowered, and the filter tube is increased by increasing the volume flow rate of the exhaust gas. This is not preferable because the required filtration area is increased and the apparatus is enlarged.
[0036]
【The invention's effect】
As described above, if the dust removal and harmful gas decomposition apparatus according to the present invention is used, incinerators for waste, combustion facilities using fossil fuels such as coal, various industrial furnaces for iron and metallurgy, cement firing furnaces, fireproofing Dust contained in dust-containing gas discharged from a product firing furnace, oil refining equipment, chemical plant, etc. is removed on the surface of the filter cylinder, and at the same time, a catalyst in which nitrogen oxides and organochlorine compounds are dispersed and supported inside the filter cylinder is used. Compared with the conventional method of connecting devices with different functions to the series and controlling them to different inlet gas temperatures, the system of the devices is simplified, and the equipment costs and It can be expected that not only maintenance costs can be greatly reduced, but also operation and control are simplified, and both reliability and operability are greatly improved.
[Brief description of the drawings]
FIG. 1 is an assembly cross-sectional view and system diagram showing a first example according to the embodiment of the present invention;
FIG. 2 is an assembly sectional view and system diagram showing a second example according to the embodiment of the present invention;
FIG. 3 is a system diagram showing an example of a conventional process for purifying combustion exhaust gas.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Can body 2 Filter cylinder 3 which supported the catalyst Upper tube sheet 4 Lower tube sheet 5 Filter unit 6 Dust containing gas inlet pipe 7 Dust hopper 8 Clean gas outlet pipe 9 Backwash apparatus 10 Dust containing gas inlet duct piping 11 Ammonia injection apparatus 12 Inner wall surface of filter cylinder carrying catalyst 13 Clean gas collecting part 14 Dust 15 Dust discharge direction 16 Outer wall surface of filter cylinder carrying catalyst

Claims

And the can body, the interior of the molded body made of ceramic fiber cylindrical with both ends open, is formed by substantially uniformly dispersed and supported powdery catalyst composed of vanadium pentoxide or tungsten trioxide or a mixture thereof, porosity A filter unit comprising a plurality of filter tubes of 80% or more and 95% or less, a pair of tube plates that support upper and lower ends of the filter tube provided at both ends provided in the can body, and communicates with the filter unit A dust-containing gas inlet pipe connected to the can body, a dust hopper provided in a lower space of the can body for collecting and discharging dust removed by the filter unit, and a filter cylinder of the filter unit a clean gas outlet pipe to take out the can body outside the clean gas obtained by passing through the said characterized in that it consists of a backwash device shake off dust adhering to the濾筒surface, supporting a catalyst ceramic Dust and harmful gas decomposition apparatus having a濾筒consisting hex fiber molded body.

A powdered catalyst made of vanadium pentoxide or tungsten trioxide or a mixture of both is dispersed and uniformly distributed in a can and a formed body made of a cylindrical ceramic fiber having one end closed and the other end opened. A plurality of filter tubes having a porosity of 80% or more and 95% or less, and one tube that supports the upper end of the filter tube that is closed at one end and opened at the other end, and hangs down the filter tube A filter unit composed of a plate, a dust-containing gas inlet pipe connected to the can body communicating with the filter unit, and a lower space of the can body for collecting and discharging dust removed by the filter unit A dust hopper provided, a clean gas outlet pipe for taking out the clean gas obtained by passing through the filter cylinder of the filter unit to the outside of the can body, and a backwash device for removing dust adhering to the surface of the filter cylinder To make The symptom, catalyst dust and harmful gas decomposition apparatus having a濾筒consisting loaded with ceramic fiber molded body.

The catalyst having an average particle diameter of 20 microns or more and 80 microns or less is contained in the filter tube in a range of 5% by weight or more and 25% by weight or less based on the weight of the filter tube. 2. A dust removing and harmful gas decomposition apparatus according to 2 .

The powdered catalyst is a powdered catalyst having an average particle size of 20 microns or more and 80 microns or less composed of vanadium pentoxide, tungsten trioxide, or a mixture of both with titanium oxide as a support. 2. A dust removing and harmful gas decomposition apparatus according to 2 .

The ceramic fiber is a fiber composed of a single component of any one of alumina, silica, titania, magnesia, glass, silicon carbide, and silicon nitride, a fiber composed of these compounds, or a ceramic fiber composed of a composite composition of these fibers. 3. The dust removal according to claim 1, wherein the ceramic fibers are composed of ceramic fibers having an average fiber diameter in a range of 1 to 10 microns and a fiber length of at least 10 mm or more and occupying 50% or more of the whole. Cumulative gas decomposition equipment .

The filter tube is a single component or a plurality of components of metal sol such as alumina sol, silica sol, titanium sol, etc., and adheres the ceramic fibers to each other and the ceramic fibers and the catalyst, and then performs drying and firing treatment, The dust removal and harmful gas decomposition apparatus according to claim 1 or 2 , wherein the dust removal and harmful gas decomposition apparatus is a ceramic fiber molded body in which ceramic fibers and ceramic fibers and a catalyst are firmly bonded.

The dust removal / hazardous gas decomposition apparatus according to claim 1 or 2 , wherein the dust removal / hazardous gas decomposition apparatus passes a combustion exhaust gas containing dust of 200 ° C to 400 ° C.

The upstream gas pipe connected to the combustion exhaust gas inlet of the dust removal and harmful gas decomposition apparatus is provided with an ammonia injection device and a mixing zone for uniformly mixing the injected ammonia and the combustion exhaust gas. The dust removal and harmful gas decomposition apparatus according to claim 1 or 2 .