JP2004230372A

JP2004230372A - Mercury removal method from mercury-containing waste such as fluorescent tube, and apparatus therefor

Info

Publication number: JP2004230372A
Application number: JP2003154518A
Authority: JP
Inventors: Futoshi Yamamoto; 太山本; Kanetoshi Funada; 兼稔船田; Hideji Nakamoto; 秀司中本; Yoichi Kasahara; 洋一笠原
Original assignee: Daiso Co Ltd
Current assignee: Osaka Soda Co Ltd
Priority date: 2002-12-04
Filing date: 2003-05-30
Publication date: 2004-08-19

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which enables mercury to be removed easily from mercury-containing waste such as a fluorescent tube in a short time. <P>SOLUTION: The mercury removal method from the mercury-containing waste is a method including a process contacting steam with the mercury-containing waste such as the fluorescent tube. The contacting steam may be saturated steam, but preferably superheated steam. The steam is brought into contact with the mercury-containing waste, thereby generating gas such as mercury and a mercury compound. Then, the gas discharged from the process is sent to a recovery process and condensed, thereby condensation products such as condensate water, mercury and the mercury compound are generated, and the mercury and the mercury compound are recovered. One of preferable embodiments contains the steam contact process and the next process for condensing the gas discharged from the contact process and recovering mercury from the condensation products. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は蛍光管等の水銀含有廃棄物より水銀および水銀化合物を除去および回収する方法、およびその装置に関する。
【０００２】
本明細書全体を通して、「水銀含有廃棄物」とは水銀および／または水銀化合物を含む廃棄物を、「水銀回収」とは水銀および／または水銀化合物を回収すること、「水銀除去」とは水銀および／または水銀化合物を除くことを言うこととする。「蛍光管等」とは、寿命終了や故障等で廃棄される廃蛍光管や廃水銀灯、および蛍光管や水銀灯の製造工程で生じた不良品等を総称して言うこととし、「蛍光管等の水銀含有廃棄物」とは、蛍光管等の蛍光管ガラス部、口金、蛍光剤など、水銀および水銀化合物が付着している構成部材、さらにはその破砕物、および、蛍光管等の水銀回収処理に伴って発生するプレスケーキ、粉塵、水銀等を吸着したキレート添着活性炭のようなリサイクル目的もしくは廃棄目的のものも含むこととする。
【０００３】
【従来の技術】
近年、地球環境保護の見地から資源のリサイクルや環境汚染防止の要求が高まっている。蛍光管等には水銀が含まれており、リサイクルや廃棄の際、この水銀を除去し、回収することが重要である。
【０００４】
蛍光管等に封入されている水銀を除去する方法として、一般的にはこれを予め金属製の口金部とガラス製の管部に分別し、分別部分を各々破砕し、破砕物を水洗または酸性の洗浄液等で化学処理して水銀を除くかもしくは破砕物を５００〜６５０℃の高温下で焼成して水銀および水銀化合物を蒸発させて除去している。
【０００５】
蛍光管等の破砕過程で生じた微細粉や蛍光剤にも水銀が付着しているため、これらも同様に洗浄化学処理もしくは焼成して水銀および水銀化合物を除去している。
【０００６】
焼成の際、破砕物中に含まれるプラスチック成分の熱分解による焼成物の黒化や、発生した水銀蒸気の回収工程でプラスチック分解物の付着等のトラブルを防止するため、焼成容器の運転圧力を減圧とし運転温度はプラスチックの熱分解温度以下として、大部分の水銀および水銀化合物を蒸発除去した後、容器をプラスチックの熱分解温度以上に昇温し、プラスチックの分解生成物を高温空気もしくは酸素中で酸化焼成する方法が一般的である。
【０００７】
プラスチック類を含む破砕物をプラスチックの熱分解温度以下で減圧下で焼成すると、水銀酸化物等の水銀化合物（以下「水銀化合物」と略す）は熱分解しにくく、処理後の破砕物中の水銀含有量を規制値以下に低減することは困難である。またプラスチック含有破砕物を水銀化合物の熱分解温度以上で焼成する場合は、プラスチックの熱分解物が水銀回収工程で回収装置の内面に付着してトラブルを生じたり、プラスチックを燃焼しなければならないため排気ガス量が増大しガス中の水銀濃度が著しく低下して、冷却等により水銀を効率よく回収することが困難になる。
【０００８】
蛍光剤が管内面に塗布されている蛍光管等にあっては、製作当初に管内に微量注入される水銀が使用時間の経過とともに管内面の蛍光剤やガラス管内面等に吸着する。従来、このような形態の水銀を脱着するには高温で焼成を行ったり、水銀の化学反応性を利用して酸性洗浄液等で化学処理を行っていた。
従来、蛍光管等の水銀含有廃棄物から水銀を回収する方法としては、複数の廃蛍光灯を水銀溶解液の入った溶解処理槽内に浸漬し、浸漬した状態で各廃蛍光灯を破損させて、各廃蛍光灯の内部側に水銀溶解液を流入させ、流入した水銀溶解液で各廃蛍光灯の内面に付着していた水銀を溶解させ、水銀が溶解した水銀溶解液を水銀除去用通路の途中に設けられた水銀吸着材を通過中に、水銀吸着材で水銀が溶解した水銀溶解液から水銀を吸着除去し、水銀を吸着した水銀吸着材から水銀を分離回収するようにする方法が提案されている（特許文献１参照）。
【０００９】
また、廃蛍光管を粉砕する粉砕装置と、粉砕した廃蛍光管を燃焼して水銀を気化させるロータリキルンと、ロータリキルンから発生した水銀蒸気を冷やす冷却装置とを有した廃蛍光管処理装置を用い、粉砕装置で破砕した廃蛍光管を直接ロータリキルンに配送し、ロータリキルンの燃焼によって水銀を蒸発させ、燃焼後のガラス片を回収すると共に、蒸発した水銀を冷却回収し、これら廃蛍光管の粉砕、廃蛍光管の燃焼、水銀の回収を連続工程として行なう方法が提案されている（特許文献２参照）。
しかし、これらの方法は、水銀除去処理および水銀回収処理に長い時間を要する上に操作が繁雑であった。
【００１０】
【特許文献１】
特開２０００−３０３１２５号公報、請求項１。
【００１１】
【特許文献２】
特開２００１−２０５２４６号公報、請求項１。
【００１２】
【発明が解決しようとする課題】
本発明は、上述した実状に鑑み、蛍光管等の水銀含有廃棄物より水銀を短時間で容易に除去することができる方法を提供することを課題とする。
【００１３】
【課題を解決するための手段】
本発明者等は蛍光管等の水銀含有廃棄物を処理して水銀を回収するのに水蒸気を使用すると、ガラス部や蛍光剤等に吸着された水銀が容易に脱着されることを見出し本発明を完成した。
【００１４】
本発明による、水銀含有廃棄物からの水銀除去方法は、蛍光管等の水銀含有廃棄物に水蒸気を接触させる工程を含む方法である。
【００１５】
接触させる水蒸気は、飽和水蒸気でも過熱水蒸気でもよいが、好ましくは過熱水蒸気である。
【００１６】
水銀含有廃棄物に水蒸気を接触させることにより、水銀や水銀化合物の気体が生じ、次いでこの工程から排出される気体は回収工程へ送られここで凝縮されて凝縮水および水銀や水銀化合物の凝縮物を生じ、水銀や水銀化合物が回収される。
【００１７】
本発明による水銀除去方法の好ましい形態の１つは、上記水蒸気接触工程と、ついで、この工程から排出される気体を凝縮して凝縮物から水銀を回収する工程とを含む。
【００１８】
本発明による水銀除去方法は、より具体的には、加熱器を備えた処理容器内に蛍光管等の水銀含有廃棄物を入れ、同容器に飽和水蒸気を導入し、必要に応じて処理容器を加熱し、該水銀含有廃棄物を飽和水蒸気と接触させる工程を含むものであってもよい。
【００１９】
本発明による水銀除去方法は、加熱器を備えた処理容器内に蛍光管等の水銀含有廃棄物を入れ、同容器に過熱水蒸気を導入するか、または飽和水蒸気を導入した後加熱して過熱水蒸気とし、該水銀含有廃棄物を過熱水蒸気と接触させる工程を含むものであってもよい。
【００２０】
本発明による水銀除去方法の好ましい形態の１つは、上記処理容器での飽和水蒸気との接触工程または過熱水蒸気との接触工程と、ついで、この工程から排出される気体を凝縮して凝縮物から水銀を回収する工程とを含む。
【００２１】
水銀の脱着は、操作圧力に対応する水銀の蒸発温度（沸点）以上の温度で実施すると効率的であるが、水と蛍光剤等の化学的および物理的親和性を利用できるので脱着温度は水銀の沸点もしくは水銀化合物の分解温度以下でも構わない。
【００２２】
本発明方法では、処理容器内での水蒸気接触処理温度は大気圧下で好ましくは１００〜６５０℃、より好ましくは１００℃〜６００℃、さらに好ましくは２５０℃〜４５０℃である。この処理温度が低過ぎると水銀の脱着効果に変動があり、高過ぎると容器の熱ロスが大きく高エネルギーが必要となり、昇温、冷却に要する処理時間が長くなり経済的でない。
【００２３】
処理容器への水蒸気導入温度は好ましくは１００〜６００℃、より好ましくは１５０〜５５０℃であり、処理容器へ導入される過熱水蒸気の過熱度は好ましくは０〜５００℃、より好ましくは５０〜４５０℃である。
【００２４】
本発明方法で用いる水蒸気は飽和水蒸気でも過熱水蒸気でもよいが、処理圧力が常圧である場合は飽和水蒸気より過熱水蒸気の方が好ましい。水銀が過熱水蒸気処理によってより効率的に除去される理由は定かではないが、過熱水蒸気による水銀の脱着機構はイナートガス等によるものとは異なり、過熱水蒸気がガラス部破砕物や蛍光剤等の表面や内部に入り易く、これらに吸着している水銀を容易に脱着させるものと推測される。
【００２５】
本発明方法において、被処理物内部を水蒸気と効率よく接触させ水銀を効率よく短時間で除去するには、蛍光管等の水銀含有廃棄物を撹拌もしくは混合できる機能を備えた処理容器を使用することが好ましい。このような処理容器としては、例えば回転式容器および／または攪拌羽根を備えた容器が使用できる。攪拌羽根はロータリーキルン式の処理容器の内面に固定されたものであっても良い。
【００２６】
また、本発明の水銀除去方法および水銀除去回収装置は、水銀含有廃棄物を処理容器に連続的に供給し、水銀を除去回収する方法およびその装置とすることも可能である。
【００２７】
蛍光管等の破砕物中にはプラスチック類が含まれており、窒素ガス等のイナートガス中ではプラスチック類の熱分解は約２９０℃で始まるが、水蒸気、特に過熱水蒸気の使用により、分解温度を約４５０℃以上まで上昇させることができ、高温でのプラスチックの分解を防止できる。加えて、水蒸気、特に過熱水蒸気の使用により蛍光管等の破砕物からの水銀除去が容易となる。水銀を含む破砕物の処理排気ガスは、イナートガス使用の場合、水銀濃度の希薄なガスとなり、水銀を凝縮しにくいが、本発明方法では水蒸気を使用するので、水蒸気の凝縮により排気ガス中の水銀濃度を高く維持することができ、凝縮工程で水銀および水銀化合物の凝縮物を効率良く回収することができる。
【００２８】
本発明方法は、水銀回収処理に伴って生ずる水銀含有廃棄物にも適用できる。水銀回収処理に伴って生ずる水銀含有廃棄物とは、蛍光管等の水銀を除去する処理装置で生じる廃棄物であり、具体例としては、水銀を含有する蛍光管等の破砕過程で生じる微細粉、またはこのような微細粉を含むスラリーもしくは含水ケーキ、水銀を含む排気ガスや排水を処理するのに用いられて水銀を化学的または物理的に吸着したキレート添着活性炭や、排水処理設備の濾過剤等が挙げられるが、これらに限定されない。
【００２９】
水銀を吸着したキレート添着活性炭から水銀を除去するのに、キレート添着活性炭をイナートガス雰囲気中で５００℃以上の高温で加熱処理すると、キレートの熱分解が起こり排気ガスからの水銀回収が困難になる。本発明方法ではイナートガスの代わりに水蒸気、好ましくは過熱水蒸気を使用するので、キレート添着活性炭に吸着された水銀の脱着がイナートガス使用時の脱着温度より低い温度で起こり、添着キレートの熱分解は比較的少なく水銀および水銀化合物を容易に回収することができる。
【００３０】
本発明は、また、水銀含有廃棄物からの水銀回収装置を提供する。本発明による水銀回収装置は、過熱水蒸気を発生させるための水蒸気加熱器と、同加熱器に過熱水蒸気導入管を介して接続され、かつ過熱水蒸気を蛍光管等の水銀含有廃棄物に接触させる処理容器と、同容器に水蒸気排出管を介して接続され、かつ、処理容器から排出される気体を凝縮する凝縮器とを具備するものである。処理容器は、好ましくは加熱器を備えた容器である。
【００３１】
【発明の実施の形態】
以下、本発明を実施例、比較例により具体的に説明する。ただし、本発明はこれら実施例に限定されるものではない。
【００３２】
実施例１
図１は、この実施例で処理容器として使用する回転式加熱容器の概略を示す。処理容器（１）は中央の大径胴部（１ａ）と、その前側にテーパ部（１ｂ）を介して連設された小径入口部（１ｃ）と、大径胴部（１ａ）の後側にテーパ部（１ｄ）を介して連設された小径出口部（１ｅ）とからなる。大径胴部（１ａ）には加熱器（２）が外装されている。入口部（１ｃ）の上流端には入口蓋（３）が、出口部（１ｅ）の下流端には出口蓋（４）がそれぞれ設けられている。入口蓋（３）には水蒸気導入管（５）が、出口蓋（４）には水蒸気排出管（６）がそれぞれ配設されている。水蒸気導入管（５）に第１温度計（７）が、大径胴部（１ａ）と加熱器（２）の間に第２温度計（８）が、出口部（１ｅ）に第３温度計（９）が、それぞれ設けられている。水蒸気導入管（５）には第１温度計（７）の上流にバルブ（１０）が設けられている。処理容器（１）は図示省略の回転駆動装置により回転され、これにより内部の被処理物が攪拌される。
【００３３】
図２は実施例１の概略フローを示す。まず、入口蓋（３）を開け、入口部（１ｃ）から大径胴部（１ａ）に被処理物として蛍光管口金の破砕物（プラスチック類を含む）を投入し、処理容器（１）を回転させながら第２温度計（８）が第３温度計（９）の所定温度に昇温されるように大径胴部（１ａ）を加熱器（２）で加熱した。次いで、水蒸気導入管（５）のバルブ（１０）を開いて大気圧下で処理容器（１）内へ飽和水蒸気を注入し、処理容器（１）から排出される気体を水蒸気排出管（６）を通して凝縮器（１１）に導いてここで凝縮させ、凝縮物を得た。
【００３４】
排出水蒸気温度を示す第３温度計（９）の温度が所定値に達した後、この温度を一定時間保った。その後、加熱器（２）による加熱を停止し、処理容器（１）の温度が下がった後、容器内の焼成物を取り出した。
【００３５】
被処理物から環境庁告示第１３号に従い分析用の試料を調製し、ＪＩＳＫ０１０２６６．１に従い還元気化原子吸光法により試料中の水銀濃度を測定し、水銀溶出濃度とした。
【００３６】
大径胴部（１ａ）での処理温度を変動させ、排出水蒸気温度を示す第３温度計（９）の温度を所定値にした点を除いて、上記と同じ操作を繰り返し、水銀溶出濃度を求めた。
【００３７】
これらの測定結果を表１にまとめて示す。いずれの処理物にもプラスチック分解によるタールの発生および処理後の破砕物の黒化現象は無かった。第３温度計（９）の温度２７０℃以上で水銀の溶出濃度は規制値（０．００５ｍｇ／Ｌ）以下となった。
【００３８】
【表１】

【００３９】
実施例２
この実施例では、図３に概略フローを示すように、水蒸気導入管（５）に第１温度計（７）の上流に水蒸気加熱器（１２）を設け、飽和水蒸気を水蒸気加熱器（１２）で予め加熱し、得られた加熱水蒸気を処理容器（１）に供給した。
【００４０】
その他の点は実施例１と同じ操作を繰り返し、被処理物中の水銀溶出濃度を求めた。
【００４１】
また、被処理物を蛍光管のガラス部破砕物、蛍光剤にそれぞれ替えた点を除いて上記と同じ操作を繰り返し、水銀溶出濃度を求めた。
【００４２】
これらの測定結果を表２にまとめて示す。いずれの処理物にもプラスチック分解によるタールの発生および処理後の破砕物の黒化現象は無かった。また、第３温度計（９）の温度２９０℃以上で水銀の溶出濃度はいずれも規制値（０．００５ｍｇ／Ｌ）以下であった。
【００４３】
【表２】

【００４４】
実施例３
図４は、この実施例の概略フローを示す。この実施例では処理容器（１３）は保温材で構成された固定式の箱型容器であり、水平の多孔板（１４）を内装し、その上に設けられた多孔区画（１５）内に被処理物を充填するものである。水蒸気導入管（５）は処理容器（１３）の底壁に配設され、水蒸気排出管（６）は処理容器（１３）の頂壁に配設され、処理容器（１３）内の多孔区画（１５）の上方に第４温度計（１６）が設置されている。水蒸気導入管（５）に第１温度計（７）の上流に水蒸気加熱器（１２）が設けられている。その他の構成は図２に示す実施例１のものと同じである。
【００４５】
まず、多孔区画（１５）内に被処理物として蛍光管ガラス部の破砕物を入れた。次いで飽和水蒸気を水蒸気加熱器（１２）で予め３９０℃まで加熱し、得られた加熱水蒸気を処理容器（１３）内に除々に注入し、底部から上向きに通過させた。
【００４６】
排出水蒸気温度を示す第４温度計（１６）の温度が３３０℃に達した後、この温度を６０分間保った。その後、実施例１と同様な操作で処理容器（１３）から排出される気体を冷却し、凝縮物を得、異なる２つの凝縮物試料についてそれぞれ水銀溶出濃度を求めた。
【００４７】
これらの測定結果を表３にまとめて示す。水銀の溶出濃度はいずれも規制値（０．００５ｍｇ／Ｌ）以下となった。
【００４８】
【表３】

【００４９】
表３から分かるように、固定式の処理装置では被処理物は攪拌されないため処理に比較的長時間を要し、分析値のバラツキが大きいが、加熱窒素ガス使用の場合（後述する比較例２）より低温での水銀の除去が可能であった。
【００５０】
実施例４
この実施例では、水銀を含む排気ガスや排水を処理するのに用いられて水銀を化学的または物理的に吸着したキレート添着活性炭を被処理物とした。処理装置および操作は実施例１と同様に行った。
【００５１】
被処理物から環境庁告示第１３号に従い分析用の試料を調製し、ＪＩＳＫ０１０２６６．１に従い還元気化原子吸光法により分析用試料中の水銀濃度を測定し、水銀含有量とした。
【００５２】
大径胴部（１ａ）での処理温度を変動させ、排出水蒸気温度を示す第３温度計（９）の温度を所定値にした点を除いて、上記と同じ操作を繰り返し、水銀含有量を求めた。
【００５３】
これらの測定結果を表４にまとめて示す。いずれの処理物でも活性炭に添着しているキレート剤の分解は少なく、水銀の除去率も第３温度計（９）の温度３２０℃以上で９９％以上となった。
【００５４】
【表４】

【００５５】
比較例１
図５は、比較例１の概略フローを示す概略図である。過熱水蒸気の代わりに加熱窒素ガスを用いた点を除いて、実施例１と同様な操作で蛍光管の破砕物（プラスチック類を含む）を処理し、被処理物中の水銀溶出濃度を求めた。
【００５６】
また、処理容器（１）内の圧力を減圧にして上記操作を繰り返した。すなわち、処理容器（１）内へ予め破砕物を投入した後、吸引ポンプ（１７）にて容器内圧を減圧にし、この減圧状態を保ちながら加熱窒素ガスを処理容器（１）内へ注入した。
【００５７】
プラスチック類を含む破砕物を高温で処理すると、生じたプラスチック分解生成物が容器出口、容器から凝縮器への配管および凝縮器の排気導入部の内壁に付着し、連続運転は不可能であった。また容器内に残った焼成物は黒化し、タールが付着し、その粘着性のためハンドリングが困難であり、かつ高温処理にも拘らず溶出水銀濃度は低下しなかった。
【００５８】
表５は、操作条件および加熱処理後の溶出水銀濃度を示す。常圧、減圧いずれの条件下でも溶出水銀濃度を規制値（０．００５ｍｇ／Ｌ）以下とするには、排出窒素ガス温度を示す第３温度計（９）の温度を約３４０℃以上にする必要があった。
【００５９】
また、プラスチック類の熱分解を防止するには排出窒素ガス温度を２４０℃以下にする必要があるので、この温度では溶出水銀濃度を規制値以下とすることはできなかった。
【００６０】
【表５】

【００６１】
比較例２
過熱水蒸気の代わりに加熱窒素ガス（４００℃と５００℃）を用いた点を除いて、実施例３と同様な操作を繰り返し、被処理物中の水銀溶出濃度を求めた。この測定結果を表６に示す。
【００６２】
【表６】

【００６３】
表６から分かるように、固定式の処理装置で被処理物を加熱窒素ガスで処理すると、被処理物が攪拌されないため分析値のバラツキが大きい上に、低温での水銀の除去が不可能であった。
【００６４】
【発明の効果】
本発明によれば、蛍光管等の水銀含有廃棄物に含まれる水銀を従来法に比べ低い温度で、短時間に除去し、容易に回収することができる。また、同廃棄物がプラスチック類を含んでいても、プラスチックが熱分解により装置内面に付着し水銀除去を阻害する恐れがなく、この点でも水銀を効率的に回収できる。
【図面の簡単な説明】
【図１】図１は、この実施例で処理容器として使用する回転式加熱容器の概略を示す概略図である。
【図２】図２は、実施例１の概略フローを示す概略図である。
【図３】図３は、実施例２の概略フローを示す概略図である。
【図４】図４は、実施例３の概略フローを示す概略図である。
【図５】図５は、比較例１の概略フローを示す概略図である。
【符号の説明】
（１）：処理容器
（２）：加熱器
（５）：水蒸気導入管
（６）：水蒸気排出管
（７）：第１温度計
（８）：第２温度計
（９）：第３温度計
（１１）：凝縮器
（１２）：水蒸気加熱器
（１３）：処理容器
（１６）：第４温度計[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and apparatus for removing and recovering mercury and mercury compounds from mercury-containing waste such as fluorescent tubes.
[0002]
Throughout this specification, “mercury-containing waste” refers to waste containing mercury and / or mercury compounds, “mercury recovery” refers to the recovery of mercury and / or mercury compounds, and “mercury removal” refers to mercury. And / or exclude mercury compounds. The term "fluorescent tube, etc." is a generic term for waste fluorescent tubes and waste mercury lamps that are discarded due to their end of life or failure, and defective products, etc., generated in the manufacturing process of fluorescent tubes and mercury lamps. "Mercury-containing waste" refers to fluorescent glass parts such as fluorescent tubes, bases, fluorescent materials, and other components to which mercury and mercury compounds are attached, as well as crushed materials and mercury recovery from fluorescent tubes and other materials. It also includes those for recycling or disposal such as chelate-impregnated activated carbon that adsorbs press cake, dust, mercury, etc. generated during the treatment.
[0003]
[Prior art]
In recent years, demands for resource recycling and environmental pollution prevention have been increasing from the viewpoint of global environmental protection. Fluorescent tubes and the like contain mercury, and it is important to remove and recover this mercury during recycling or disposal.
[0004]
As a method of removing mercury sealed in a fluorescent tube or the like, generally, the mercury is separated into a metal base and a glass tube in advance, the separated portions are crushed, and the crushed material is washed with water or acid. Or a crushed material is fired at a high temperature of 500 to 650 ° C. to evaporate and remove mercury and mercury compounds.
[0005]
Since mercury also adheres to the fine powder and the fluorescent agent generated during the crushing process of the fluorescent tube and the like, the mercury and the mercury compound are also removed by cleaning chemical treatment or firing similarly.
[0006]
During firing, reduce the operating pressure of the firing vessel to prevent blackening of the fired material due to the thermal decomposition of the plastic components contained in the crushed material and adhesion of the plastic decomposed material in the recovery process of the generated mercury vapor. After reducing most of the mercury and mercury compounds by evaporating and removing the mercury and mercury compounds by reducing the pressure and setting the operating temperature below the plastic decomposition temperature, the container is heated to the plastic decomposition temperature or higher, and the plastic decomposition products are heated in hot air or oxygen. Is generally carried out by oxidizing and firing.
[0007]
When crushed materials containing plastics are fired under reduced pressure at a temperature not higher than the thermal decomposition temperature of plastics, mercury compounds such as mercury oxides (hereinafter abbreviated as “mercury compounds”) are less likely to be thermally decomposed, and mercury in the crushed materials after treatment is reduced. It is difficult to reduce the content below the regulation value. Also, when crushing plastic-containing crushed products at a temperature equal to or higher than the thermal decomposition temperature of the mercury compound, the pyrolyzed products of plastic adhere to the inner surface of the recovery device during the mercury recovery process, causing trouble or burning the plastic. The amount of exhaust gas increases and the concentration of mercury in the gas decreases significantly, making it difficult to efficiently recover mercury by cooling or the like.
[0008]
In a fluorescent tube or the like in which a fluorescent agent is applied to the inner surface of a tube, a small amount of mercury injected into the tube at the beginning of manufacture adsorbs to the fluorescent agent on the inner surface of the tube, the inner surface of the glass tube, or the like as time passes. Conventionally, in order to desorb such a form of mercury, baking is performed at a high temperature, or a chemical treatment is performed using an acidic cleaning solution or the like utilizing the chemical reactivity of mercury.
Conventionally, as a method of recovering mercury from mercury-containing waste such as fluorescent tubes, a plurality of waste fluorescent lamps are immersed in a dissolution tank containing a mercury solution, and each of the waste fluorescent lamps is damaged while immersed. Then, a mercury solution is flowed into the interior of each waste fluorescent lamp, the mercury adhering to the inner surface of each waste fluorescent lamp is dissolved by the mercury solution flowing in, and the mercury solution in which mercury is dissolved is used for mercury removal. A method in which mercury is adsorbed and removed from a mercury solution in which mercury is dissolved by a mercury adsorbent while passing through a mercury adsorbent provided in the middle of a passage, and mercury is separated and recovered from the mercury adsorbent that adsorbs mercury. Has been proposed (see Patent Document 1).
[0009]
Further, a waste fluorescent tube processing device having a crushing device for crushing the waste fluorescent tube, a rotary kiln for burning the crushed waste fluorescent tube to vaporize mercury, and a cooling device for cooling mercury vapor generated from the rotary kiln is provided. The waste fluorescent tubes crushed by the pulverizer are delivered directly to the rotary kiln, the mercury is evaporated by the combustion of the rotary kiln, the burned glass fragments are collected, and the evaporated mercury is cooled and collected, and these waste fluorescent tubes are collected. There has been proposed a method in which pulverization, burning of waste fluorescent tubes, and recovery of mercury are performed as a continuous process (see Patent Document 2).
However, these methods require a long time for the mercury removal treatment and the mercury recovery treatment and are complicated in operation.
[0010]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-303125, Claim 1.
[0011]
[Patent Document 2]
JP-A-2001-205246, Claim 1.
[0012]
[Problems to be solved by the invention]
An object of the present invention is to provide a method capable of easily removing mercury from mercury-containing waste such as a fluorescent tube in a short time in view of the above situation.
[0013]
[Means for Solving the Problems]
The present inventors have found that when water vapor is used to treat mercury-containing waste such as a fluorescent tube and recover mercury, mercury adsorbed on a glass part, a fluorescent agent, and the like is easily desorbed. Was completed.
[0014]
The method for removing mercury from mercury-containing waste according to the present invention is a method including a step of bringing water vapor into contact with mercury-containing waste such as a fluorescent tube.
[0015]
The steam to be contacted may be saturated steam or superheated steam, but is preferably superheated steam.
[0016]
Contacting water vapor with mercury-containing waste produces gaseous mercury and mercury compounds, and the gas discharged from this process is sent to the recovery process where it is condensed and condensed, and condensate of mercury and mercury compounds And mercury and mercury compounds are recovered.
[0017]
One preferred form of the method for removing mercury according to the present invention includes the above-mentioned step of contacting with water vapor, and then the step of condensing the gas discharged from this step to recover mercury from the condensate.
[0018]
More specifically, the method for removing mercury according to the present invention is to put a mercury-containing waste such as a fluorescent tube into a processing vessel equipped with a heater, introduce saturated steam into the vessel, and, if necessary, remove the processing vessel. The method may include a step of heating and bringing the mercury-containing waste into contact with saturated steam.
[0019]
In the method for removing mercury according to the present invention, a mercury-containing waste such as a fluorescent tube is placed in a processing vessel provided with a heater, and superheated steam is introduced into the vessel, or heated after introducing saturated steam, and then heated. And a step of contacting the mercury-containing waste with superheated steam.
[0020]
One preferred embodiment of the method for removing mercury according to the present invention is a step of contacting with saturated steam or a step of contacting with superheated steam in the processing vessel, and then condensing a gas discharged from this step to form a condensate. Recovering mercury.
[0021]
It is efficient to carry out the desorption of mercury at a temperature equal to or higher than the evaporation temperature (boiling point) of mercury corresponding to the operating pressure. However, since the chemical and physical affinity of water and a fluorescent agent can be used, the desorption temperature is mercury. , Or below the decomposition temperature of the mercury compound.
[0022]
In the method of the present invention, the temperature of the steam contact treatment in the treatment vessel is preferably 100 to 650 ° C, more preferably 100 to 600 ° C, and further preferably 250 to 450 ° C under the atmospheric pressure. If the treatment temperature is too low, the effect of desorbing mercury fluctuates. If the treatment temperature is too high, the heat loss of the container is large and high energy is required, and the treatment time required for heating and cooling is long, which is not economical.
[0023]
The temperature of introducing steam into the processing vessel is preferably 100 to 600 ° C, more preferably 150 to 550 ° C, and the degree of superheating of the superheated steam introduced into the processing vessel is preferably 0 to 500 ° C, more preferably 50 to 450 ° C. ° C.
[0024]
The steam used in the method of the present invention may be saturated steam or superheated steam, but when the processing pressure is normal pressure, superheated steam is preferred over saturated steam. The reason why mercury is more efficiently removed by superheated steam treatment is unknown, but the mechanism of desorption of mercury by superheated steam is different from that by inert gas, etc. It is presumed that they easily enter the interior and easily desorb mercury adsorbed on them.
[0025]
In the method of the present invention, in order to efficiently contact the inside of the object to be treated with water vapor and remove mercury efficiently and in a short time, use a processing vessel having a function of stirring or mixing mercury-containing waste such as a fluorescent tube. Is preferred. As such a processing container, for example, a rotary container and / or a container equipped with a stirring blade can be used. The stirring blade may be fixed to the inner surface of a rotary kiln type processing vessel.
[0026]
Further, the mercury removal method and the mercury removal / recovery device of the present invention can be a method and a device for continuously supplying mercury-containing waste to a treatment container to remove and recover mercury.
[0027]
Plastics are contained in crushed materials such as fluorescent tubes, and in inert gas such as nitrogen gas, thermal decomposition of plastics starts at about 290 ° C. However, the use of steam, especially superheated steam, reduces the decomposition temperature to about 290 ° C. The temperature can be raised to 450 ° C. or higher, and decomposition of plastic at high temperatures can be prevented. In addition, the use of steam, particularly superheated steam, facilitates the removal of mercury from crushed materials such as fluorescent tubes. In the case of using inert gas, the exhaust gas for the treatment of crushed products containing mercury is a gas having a low mercury concentration and is unlikely to condense mercury.However, in the method of the present invention, steam is used. The concentration can be kept high, and condensates of mercury and mercury compounds can be efficiently recovered in the condensation step.
[0028]
The method of the present invention can also be applied to mercury-containing waste generated in the mercury recovery treatment. The mercury-containing waste generated by mercury recovery processing is waste generated by a processing device such as a fluorescent tube that removes mercury. Specific examples include fine powder generated during the crushing process of a fluorescent tube that contains mercury. , Or a slurry or hydrated cake containing such fine powder, chelated impregnated activated carbon that is used to treat exhaust gas or wastewater containing mercury and that chemically or physically adsorbs mercury, or a filtering agent for wastewater treatment equipment And the like, but not limited thereto.
[0029]
If the chelated impregnated activated carbon is heated at a high temperature of 500 ° C. or more in an inert gas atmosphere to remove mercury from the chelated impregnated activated carbon adsorbing mercury, thermal decomposition of the chelate occurs and it becomes difficult to recover mercury from exhaust gas. In the method of the present invention, steam, preferably superheated steam, is used in place of the inert gas. A small amount of mercury and mercury compounds can be easily recovered.
[0030]
The present invention also provides a device for recovering mercury from mercury-containing waste. The mercury recovery device according to the present invention includes a steam heater for generating superheated steam, a process connected to the heater via a superheated steam introduction pipe, and a process for bringing the superheated steam into contact with mercury-containing waste such as a fluorescent tube. The apparatus includes a container, and a condenser connected to the container via a steam discharge pipe and condensing gas discharged from the processing container. The processing container is preferably a container provided with a heater.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.
[0032]
Example 1
FIG. 1 schematically shows a rotary heating vessel used as a processing vessel in this embodiment. The processing vessel (1) has a central large-diameter body (1a), a small-diameter inlet (1c) connected in front of the large-diameter body (1b) via a tapered part (1b), and a rear side of the large-diameter trunk (1a). And a small-diameter outlet (1e) connected continuously through a tapered portion (1d). The large diameter body (1a) is provided with a heater (2). An inlet cover (3) is provided at an upstream end of the inlet (1c), and an outlet cover (4) is provided at a downstream end of the outlet (1e). The inlet lid (3) is provided with a steam inlet pipe (5), and the outlet lid (4) is provided with a steam outlet pipe (6). A first thermometer (7) is provided in the steam introduction pipe (5), a second thermometer (8) is provided between the large diameter body (1a) and the heater (2), and a third temperature is provided in the outlet (1e). A total of (9) is provided. The steam introduction pipe (5) is provided with a valve (10) upstream of the first thermometer (7). The processing container (1) is rotated by a rotation driving device (not shown), and thereby the object to be processed is stirred.
[0033]
FIG. 2 shows a schematic flow of the first embodiment. First, the entrance lid (3) is opened, and a crushed fluorescent tube cap (including plastics) is put into the large-diameter body (1a) as an object to be treated from the entrance (1c), and the processing vessel (1) is opened. While rotating, the large-diameter body (1a) was heated by the heater (2) so that the second thermometer (8) was heated to a predetermined temperature of the third thermometer (9). Next, the valve (10) of the steam introduction pipe (5) is opened, saturated steam is injected into the processing vessel (1) under atmospheric pressure, and the gas discharged from the processing vessel (1) is discharged into the steam discharge pipe (6). To a condenser (11), where it was condensed to obtain a condensate.
[0034]
After the temperature of the third thermometer (9) indicating the temperature of the discharged steam reached a predetermined value, this temperature was maintained for a certain period of time. Thereafter, the heating by the heater (2) was stopped, and after the temperature of the processing vessel (1) was lowered, the fired product in the vessel was taken out.
[0035]
A sample for analysis was prepared from the object to be treated in accordance with the Notification of the Environment Agency No. 13, and the concentration of mercury in the sample was measured by a reduced vaporization atomic absorption method in accordance with JIS K0102 66.1, which was taken as the mercury elution concentration.
[0036]
The same operation as above was repeated except that the treatment temperature in the large diameter body (1a) was changed and the temperature of the third thermometer (9) indicating the discharged steam temperature was set to a predetermined value, and the mercury elution concentration was reduced. I asked.
[0037]
Table 1 summarizes the measurement results. None of the processed products generated tar due to decomposition of the plastic and no blackening phenomenon of the crushed product after the processing. At a temperature of 270 ° C. or higher of the third thermometer (9), the elution concentration of mercury was below the regulation value (0.005 mg / L).
[0038]
[Table 1]

[0039]
Example 2
In this embodiment, a steam heater (12) is provided in the steam inlet pipe (5) upstream of the first thermometer (7) as shown in FIG. And heated steam obtained was supplied to the processing vessel (1).
[0040]
In other respects, the same operation as in Example 1 was repeated, and the mercury elution concentration in the object to be treated was determined.
[0041]
In addition, the same operation as above was repeated, except that the object to be treated was changed to the crushed glass part of the fluorescent tube and the fluorescent agent, respectively, to determine the mercury elution concentration.
[0042]
Table 2 summarizes the measurement results. None of the processed products generated tar due to decomposition of the plastic and no blackening phenomenon of the crushed product after the processing. Further, at a temperature of 290 ° C. or higher of the third thermometer (9), the elution concentration of mercury was all below the regulation value (0.005 mg / L).
[0043]
[Table 2]

[0044]
Example 3
FIG. 4 shows a schematic flow of this embodiment. In this embodiment, the processing container (13) is a fixed box-shaped container made of a heat insulating material, has a horizontal perforated plate (14) inside, and is covered in a perforated section (15) provided thereon. This is for filling the processed material. The steam introduction pipe (5) is disposed on the bottom wall of the processing vessel (13), and the steam discharge pipe (6) is disposed on the top wall of the processing vessel (13). Above 15), a fourth thermometer (16) is provided. A steam heater (12) is provided in the steam inlet pipe (5) upstream of the first thermometer (7). Other configurations are the same as those of the first embodiment shown in FIG.
[0045]
First, a crushed material of a fluorescent tube glass part was placed as an object to be treated in the porous section (15). Next, the saturated steam was heated to 390 ° C. in advance with a steam heater (12), and the obtained heated steam was gradually injected into the processing vessel (13) and passed upward from the bottom.
[0046]
After the temperature of the fourth thermometer (16) indicating the temperature of the discharged steam reached 330 ° C., this temperature was maintained for 60 minutes. Thereafter, the gas discharged from the processing vessel (13) was cooled by the same operation as in Example 1 to obtain a condensate, and the mercury elution concentration was determined for each of two different condensate samples.
[0047]
Table 3 summarizes the measurement results. The elution concentrations of mercury were all below the regulation value (0.005 mg / L).
[0048]
[Table 3]

[0049]
As can be seen from Table 3, in the case of the fixed processing apparatus, the processing object takes a relatively long time because the processing object is not agitated, and the analysis value varies widely. However, when the heating nitrogen gas is used (Comparative Example 2 described later) 3.) Mercury removal at lower temperatures was possible.
[0050]
Example 4
In this example, a chelate-impregnated activated carbon which is used for treating exhaust gas and wastewater containing mercury and which chemically or physically adsorbs mercury was used as an object to be treated. The processing apparatus and operation were the same as in Example 1.
[0051]
A sample for analysis was prepared from the object to be treated in accordance with the notification of the Environment Agency No. 13, and the mercury concentration in the sample for analysis was measured by a reduced vaporization atomic absorption method in accordance with JIS K0102 66.1, and was determined as the mercury content.
[0052]
The same operation as above was repeated except that the treatment temperature in the large-diameter body part (1a) was varied and the temperature of the third thermometer (9) indicating the discharged steam temperature was set to a predetermined value, and the mercury content was reduced. I asked.
[0053]
Table 4 summarizes these measurement results. In each of the treated products, the decomposition of the chelating agent attached to the activated carbon was small, and the mercury removal rate was 99% or more at a temperature of 320 ° C. or more of the third thermometer (9).
[0054]
[Table 4]

[0055]
Comparative Example 1
FIG. 5 is a schematic diagram showing a schematic flow of Comparative Example 1. Crushed fluorescent tubes (including plastics) were treated in the same manner as in Example 1, except that heated nitrogen gas was used instead of superheated steam, and the concentration of mercury eluted in the object was determined. .
[0056]
Further, the above operation was repeated while the pressure in the processing vessel (1) was reduced. That is, after the crushed material was previously charged into the processing vessel (1), the internal pressure of the vessel was reduced by the suction pump (17), and heated nitrogen gas was injected into the processing vessel (1) while maintaining the reduced pressure.
[0057]
When crushed materials containing plastics were treated at high temperatures, the resulting plastic decomposition products adhered to the vessel outlet, the piping from the vessel to the condenser, and the inner wall of the condenser exhaust inlet, making continuous operation impossible. . Further, the calcined product remaining in the container was blackened, tar adhered thereto, and its tackiness made handling difficult, and the concentration of eluted mercury did not decrease despite high-temperature treatment.
[0058]
Table 5 shows the operating conditions and the eluted mercury concentration after the heat treatment. In order to keep the dissolved mercury concentration below the regulation value (0.005 mg / L) under both normal pressure and reduced pressure conditions, the temperature of the third thermometer (9) indicating the temperature of the discharged nitrogen gas should be about 340 ° C or more. Needed.
[0059]
Further, in order to prevent the thermal decomposition of plastics, the temperature of the discharged nitrogen gas must be kept at 240 ° C. or less, so that at this temperature, the concentration of eluted mercury could not be kept below the regulation value.
[0060]
[Table 5]

[0061]
Comparative Example 2
The same operation as in Example 3 was repeated, except that heated nitrogen gas (400 ° C. and 500 ° C.) was used instead of superheated steam, to determine the concentration of mercury eluted in the object. Table 6 shows the measurement results.
[0062]
[Table 6]

[0063]
As can be seen from Table 6, when the object to be treated is heated with a fixed-type treatment apparatus and heated with nitrogen gas, the object to be treated is not agitated. there were.
[0064]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, mercury contained in mercury-containing wastes, such as a fluorescent tube, can be removed at a lower temperature than a conventional method in a short time, and can be easily collect | recovered. In addition, even if the waste contains plastics, there is no risk that the plastics will adhere to the inner surface of the apparatus due to thermal decomposition and hinder the removal of mercury. In this respect, mercury can be recovered efficiently.
[Brief description of the drawings]
FIG. 1 is a schematic view schematically showing a rotary heating vessel used as a processing vessel in this embodiment.
FIG. 2 is a schematic diagram illustrating a schematic flow of the first embodiment;
FIG. 3 is a schematic diagram illustrating a schematic flow of a second embodiment;
FIG. 4 is a schematic diagram illustrating a schematic flow of a third embodiment;
FIG. 5 is a schematic diagram showing a schematic flow of Comparative Example 1.
[Explanation of symbols]
(1): Processing container (2): Heater (5): Steam introduction pipe (6): Steam discharge pipe (7): First thermometer (8): Second thermometer (9): Third thermometer (11): Condenser (12): Steam heater (13): Processing vessel (16): Fourth thermometer

Claims

A method for removing mercury from mercury-containing waste, comprising a step of bringing water vapor into contact with mercury-containing waste such as a fluorescent tube.

A step of bringing water vapor into contact with mercury-containing waste such as a fluorescent tube, and then a step of condensing a gas discharged from this step and recovering mercury from the condensate; Mercury removal method.

3. The method for removing mercury according to claim 1, wherein the steam to be contacted is superheated steam.

A mercury-containing waste such as a fluorescent tube is placed in a processing vessel equipped with a heater, saturated steam is introduced into the vessel, and the processing vessel is heated as necessary to bring the mercury-containing waste into contact with the saturated steam. A method for removing mercury from mercury-containing waste, comprising the steps of:

A mercury-containing waste such as a fluorescent tube is placed in a processing vessel equipped with a heater and superheated steam is introduced into the vessel, or saturated steam is introduced and then heated to superheated steam. A method for removing mercury from mercury-containing waste, comprising a step of contacting with superheated steam.

A mercury-containing waste such as a fluorescent tube is placed in a processing vessel equipped with a heater, saturated steam is introduced into the vessel, and the processing vessel is heated as necessary to bring the mercury-containing waste into contact with the saturated steam. A method for removing mercury from mercury-containing waste, comprising: a step of condensing a gas discharged from the step and recovering mercury from the condensate.

A mercury-containing waste such as a fluorescent tube is placed in a processing vessel equipped with a heater and superheated steam is introduced into the vessel, or saturated steam is introduced and then heated to superheated steam. A method for removing mercury from mercury-containing waste, comprising: a step of contacting with superheated steam; and a step of condensing a gas discharged from this step to recover mercury from a condensate.

The steam contact treatment temperature in the processing vessel is 100 to 650 ° C, the steam introduction temperature to the processing vessel is 100 to 600 ° C, and the degree of superheat of the superheated steam introduced to the processing vessel is 0 to 500 ° C. The method for removing mercury from mercury-containing waste according to any one of claims 4 to 7, wherein:

The method for removing mercury from mercury-containing waste according to any one of claims 4 to 8, wherein the mercury-containing waste such as a fluorescent tube is stirred in a processing vessel.

10. The method for removing mercury from mercury-containing waste according to claim 9, wherein the processing container is a container having a function of stirring or mixing the internal object.

A steam heater for generating superheated steam, a processing vessel connected to the heater via a superheated steam introduction pipe and for bringing the superheated steam into contact with mercury-containing waste such as a fluorescent tube, and discharging steam to the vessel. A mercury-removing and recovering device for mercury-containing waste, comprising: a condenser connected through a pipe to condense gas discharged from the processing container.

The apparatus for removing and collecting mercury from mercury-containing waste according to claim 11, wherein the processing vessel is a vessel provided with a heater.