JP3964043B2

JP3964043B2 - Waste disposal method

Info

Publication number: JP3964043B2
Application number: JP10073498A
Authority: JP
Inventors: 秀生西村; 隆文河村; 善正池田
Original assignee: Nippon Steel Corp; Nippon Steel Engineering Co Ltd
Current assignee: Nippon Steel Corp; Nippon Steel Engineering Co Ltd
Priority date: 1998-04-13
Filing date: 1998-04-13
Publication date: 2007-08-22
Anticipated expiration: 2018-04-13
Also published as: JPH11294726A

Description

【０００１】
【発明の属する技術分野】
本発明は、都市ゴミや産業廃棄物など可燃物及び不燃物から成る廃棄物の処理方法に関するものである。
【０００２】
【従来の技術】
我が国の廃棄物処理方法は、従来、ストーカ式焼却炉や流動床焼却炉により８００℃〜９００℃で焼却した後、焼却灰を埋立て処分する方法が用いられてきたが、近年、全国的な埋立地の窮迫を背景として、焼却灰の減容化及び資源化が求められている。そこで、既存の焼却炉の後段にプラズマアーク炉やバーナー燃焼炉等を設け、発生した焼却灰を溶融し、スラグ化する焼却灰処理方法が開発されているが、これらの方法は、いずれも電力、石油等の外部エネルギーが新たに必要となる欠点がある。また、既存の焼却炉は空缶等の不燃物を含む廃棄物を８００〜９００℃の高温で燃焼するため、アルミは溶融飛灰化して回収できず、また、鉄は酸化物となり再資源化できないという問題点がある。
【０００３】
これらを解決した廃棄物処理方法として、例えば「環境施設」Ｎｏ．６５、８ぺ一ジ６行目に記載されているように、廃棄物を熱分解炉にてアルミ融点の６６０℃以下で熱分解して廃棄物中の有機物を熱分解チャーと熱分解ガスにし、空缶等の不燃物を分離装置で分離した後、熱分解チャーおよび熱分解ガスを溶融炉にて空気を用いて１３００℃〜１４００℃程度の高温で完全燃焼して熱分解チャーに含まれる灰分を溶融し、溶融した灰分は排ガスと分離後、冷却、固化して水砕状のスラグとするガス化溶融方式が提案されている。ガス化溶融方式は、熱分解チャーや熱分解ガス中に含まれる炭素分を燃料として自己熱で灰分を溶融するため外部エネルギーが不要であり、また熱分解は還元雰囲気下で行われるので、不燃物中のアルミや鉄が酸化せず有価物として回収でき、資源の再利用の点からも有利である。この場合、熱分解方法として、流動層式やキルン式が提案されている。
【０００４】
【発明が解決しようとする課題】
しかしながら、これらのガス化溶融方式の抱える問題点は、適用可能な廃棄物の範囲が狭いことである。例えば都市ゴミのように含水率が高く、かっ含水率変動が大きい廃棄物を処理した場合、熱分解ガスは多量の水蒸気を含み、ガスカロリーの変動も大きいため、溶融炉温度を１３００〜１４００℃に安定維持することは困難である。これに対し、例えば「月刊地球環境」１９９７年５月号、４３べ一ジ、３０行目に記載されているように、廃棄物熱分解炉の後段に、熱分解チャーを空気にて完全燃焼して灰分を溶融する溶融炉と、熱分解ガスを空気にて完全燃焼する燃焼炉をそれぞれ設け、発熱量の安定したチャーのみを溶融炉に導入して溶融炉の安定操業を図る溶融炉−燃焼炉分離型のガス化溶融方式も提案されている。しかしながら、この方法でも低カロリーな廃棄物には適用できず、例えば発熱量が２０００kcal／kg以下程度の一般都市ゴミについては、ゴミの自己熱で溶融炉温度を灰分の溶融に必要な１３００〜１４００℃に維持することが困難である。
【０００５】
また、最近、廃棄物をエネルギー資源として有効利用することが求められており、廃棄物焼却炉は廃棄物の焼却廃熱を利用した発電装置を設置する方向にあるが、現状の廃棄物発電では１０〜１５％程度の低い発電効率しか得ることができない。現状の廃棄物発電の発電方式は、通常、高温の燃焼排ガスをボイラで蒸気回収し、回収した蒸気を蒸気タービンに供給して電力を発生する蒸気タービン発電方式が用いられているが、発電効率が低い原因は回収蒸気温度が３００℃と低いためであり、発電効率向上のためには回収蒸気温度を一般の火力発電所並みの５００〜６００℃まで上昇させる必要がある。
【０００６】
しかしながら、焼却炉では廃棄物中に含まれる塩素が燃焼時に塩酸ガスになり、また、燃焼排ガス中にはアルカリ金属等の腐食性ダストが含まれていることから、回収蒸気温度を高くするとボイラの過熱部の伝熱管の温度が高くなり、塩酸ガスや腐食性ダストによる高温腐食を受けるため、回収蒸気温度を３００℃以下に抑えなければならない。ボイラの高温腐食を抑制するため高価な耐食鋼管を使用しても、現状では回収蒸気温度は４００℃程度で発電効率は２０％程度が限界である。回収蒸気温度の更なる高温化を目的として、例えば「火力原子力発電」Ｖｏｌ．４８、Ｎｏ．１０、１２６ぺ一ジ、２４行目に記載されているように、回収蒸気温度５００℃、発電効率３０％を目差した過熱部伝熱管の材質選定研究も現在行われてはいるが、ボイラの過熱部にはさらに高価な耐食鋼管が必要となる。
【０００７】
これに対し、塩酸ガスによるボイラ腐食の抑制を狙ったガス化溶融方式として、通常の熱分解では塩素成分は熱分解ガスと熱分解チャーにほぼ均等に分配されるが、熱分解条件及び方法を工夫して塩素成分を熱分解ガスあるいは熱分解チャーの片方に集め、熱分解ガスと熱分解チャーを分離して別々に燃焼し、塩素成分の少ない方の燃焼排ガスの部分にボイラの過熱部を設置して、腐食の少ない燃焼排ガスで蒸気を過熱する方法が提案されている。例えば、「三菱重工技報」、Ｖｏｌ．３４、Ｎｏ．３、１６２ぺ一ジに記載されているように、廃棄物を３００〜４００℃で熱分解して、塩素を熱分解ガス中に移行し、塩素分の少ないチャーを燃焼して過熱蒸気を得る方法や、例えば「第二回流動層シンポジウム講演集」、１８４ペ一ジ、２１行目や、「月刊地球環境」１９９７年５月号、４３ペ一ジ、１０行目に記載されているように、消石灰等の脱塩素剤を熱分解炉に添加して５５０〜６００℃で熱分解して塩素を熱分解チャーにＣａＣｌ₂として移行させ、熱分解炉から排出された熱分解ガスとチャーをサイクロン等で分離し、塩素の少ない熱分解ガスの燃焼排ガスから過熱蒸気を得る方法が提案されている。
【０００８】
しかしながら、両者とも塩素の分離効率は９０〜９５％で完全に分離することは不可能であり、また燃焼排ガス中にアルカリ金属等の腐食性ダストは存在することから、ボイラの高温腐食を防止することは困難であり、蒸気温度の高温化のためにはボイラの過熱部への高価な材質の使用は避けられない見込みである。また、後者の消石灰等を添加する方法では添加した消石灰はスラグ排出量の増加になる欠点がある。
そこで、幅広いゴミ質の廃棄物について外部燃料なしに自己熱で灰分を溶融でき、また、ボイラの高温腐食問題を回避した高効率発電が可能な廃棄物の処理方法が望まれている。
【０００９】
本発明は、幅広いゴミ質の廃棄物について外部燃料なしに自己熱で安定に灰分を溶融して減容化及び再資源化し、不燃物中のアルミ、鉄を酸化させないで有価物として回収し、また、廃棄物のエネルギーを主に可燃性ガスとして回収することにより、回収エネルギーの用途を増やすとともに高効率発電が可能な廃棄物処理方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明は、廃棄物を熱分解するための熱分解炉の後段に廃棄物中の灰分を溶融するための溶融炉を設け、溶融炉において発熱量が安定した熱分解チャーのみを酸素または酸素富化空気を用いて部分燃焼しガス化させることにより、空気で完全燃焼する場合に比べ溶融炉発生ガス量が大幅に減少し、溶融炉温度維持のための投入エネルギーが削減され、自己熱で灰溶融可能なゴミ質範囲の拡大及び可燃性ガスの生成が可能となる。更に、溶融炉上部に溶融炉と一体型の熱分解ガス改質炉を設け、溶融炉ガスを溶融炉上部の改質炉に導入して熱分解ガスと混合させることにより、高温の溶融炉ガスの顕熱を熱分解ガス中タール分の改質に有効利用できる。また、本発明は、廃棄物からのエネルギー回収方法が、廃棄物をガス化し、可燃性ガスとして回収する方法であるため、電力を主に洗煙後の可燃性ガスによるガスタービン発電やガスエンジン発電にて得ることが可能であり、改質炉後ガスの顕熱をボイラで熱回収する際の回収蒸気温度が低くても高効率発電が可能となる。
【００１１】
本発明の要旨は、以下の（１）〜（３）の通りである。
（１）可燃物及び不燃物から成る廃棄物の処理方法において、廃棄物を加熱する熱分解炉にて廃棄物を熱分解チャーと熱分解ガスに熱分解した後、前記熱分解チャーと前記熱分解ガスを分離し、前記分離後の熱分解チャーを気流層の溶融炉にて酸素または酸素富化空気で部分燃焼して前記熱分解チャーの自己熱でガス化すると共にチャー中灰分を溶融させ、前記溶融炉でガス化したガスと前記分離後の熱分解ガスを前記溶融炉の上部に設けられてスロートを介して溶融炉と一体型の改質炉で混合して前記分離後の熱分解ガス中に含まれるタール分を分解し、可燃性ガスを生成することを特徴とする廃棄物の処理方法である。
（２）前記（１）の改質炉へ酸素または酸素富化空気を吹き込み、前記の混合したガスを部分燃焼して前記改質炉温度を調整することを特徴とする（１）記載の廃棄物の処理方法である。
（３）前記の熱分解炉を流動層とし、前記流動層の流動化ガスとして前記流動層から生成する前記熱分解ガスおよび／または前記改質炉後の可燃性ガスを使用することを特徴とする（１）記載の廃棄物の処理方法である。
【００１２】
【発明の実施の形態】
図１は、本発明の廃棄物処理方法による一実施例である。熱分解炉１、サイクロン２、溶融炉３、改質炉４、廃熱回収ボイラー５、集塵装置６、ガス洗浄装置７から構成される。
【００１３】
熱分解炉１の方式については、特に限定するところはなく、流動層方式や間接加熱キルン方式など通常使われている熱分解方式が適用できるが、本実施例では流動層方式であって、上部側方に廃棄物装入装置９、下部には流動化ガス導入管１１ａが、上部には熱分解ガスと熱分解チャーを排出する管１２が備えられている。熱分解炉の内部には、ガス分散器が設けられ、昇圧ブロア１３により吹き込まれた流動化ガスを分散して上部の流動媒体を流動化すると同時に、流動媒体を加熱し廃棄物を熱分解する。
【００１４】
流動化ガス及び流動媒体の加熱方法には、空気１０を流動化ガスとし、廃棄物を部分燃焼して流動媒体を加熱する方法のほか、熱分解炉で発生したガスまたは後段の改質炉後ガスを流動化ガスとし、これらの可燃性ガスを流動層内で燃焼して流動媒体を加熱する方法がある。流動化ガスに熱分解炉で発生したガスまたは後段の改質炉後ガスを用いた場合には、空気中窒素による熱分解ガスの希釈が減少するために、改質炉後ガスが得る発熱量が高くなる。また、熱分解チャーの発熱量が高くなり、灰分を多く含む廃棄物でも自己熱での灰溶融が可能となる。
【００１５】
熱分解ガスまたは改質炉後ガスを流動化ガスとする場合には、昇圧ブロア１３と流動化ガス導入管１１ａの代わりに、昇圧ブロア１４と流動化ガス導入管１１ｂ、または昇圧ブロア１５と流動化ガス導入管１１ｃを設ける。熱分解炉の底部には流動媒体と共に空缶、瓶等の不燃物を排出する排出口１６を設ける。排出口の後段には、流動媒体と不燃物を分離する振動篩１７を設け、不燃物分離後の流動媒体１８は熱分解炉に戻す。なお、振動篩の後段には、磁選機、金属検出器を設置して不燃物１９中の鉄、非鉄金属を分離して回収するのが好ましい。
【００１６】
溶融炉３は、気流層炉で側方にバーナー２０を設け、熱分解チャー２１を酸素又は酸素富化空気２２ａでガス化する。熱分解チャーは、熱分解炉１から熱分解ガスとともに排出され、サイクロン２で捕集し、ホッパーを経由して窒素または空気で気流搬送して、酸化剤と共にバーナー２０に供給される。溶融炉３の底部にはスラグタップ２３を設けている。溶融炉３の上部にはガス出口スロートがあり、スロートの上部には溶融炉と一体型の改質炉４を設ける。改質炉４は、下部側方に熱分解ガスと酸素を吹き込むノズル２４を、上部にはガス出口２５を設ける。
【００１７】
廃棄物は、破砕機で粉砕され熱分解炉１に装入される。熱分解炉１では、熱分解炉１の下部から吹き込まれる流動化ガスで、流動層１に事前に装入された流動媒体と廃棄物を流動化すると同時に廃棄物は加熱され、廃棄物中のプラスチック、紙等の有機物はガスと微粉のチャーに熱分解されて、熱分解炉１の上部のガス出口１２から排出される。一方、空缶、瓦礫等の大きな無機物は、流動層下部に沈降し、流動媒体と共に熱分解炉底部の排出口１６から排出される。
【００１８】
熱分解された熱分解ガスと熱分解チャーは、サイクロン２で熱分解ガス２６と熱分解チャー２１に分離され、熱分解ガスは改質炉４に装入される。一方、熱分解チャーは溶融炉３で、酸素または酸素富化ガス２２ａとともにバーナー２０から吹き込み、１３００℃以上の高温で、熱分解チャー中の有機物をＣＯ，ＣＯ₂を主体とする高温の可燃性ガスにガス化するとともに、熱分解チャー中灰分を溶融する。熱分解チャーのみを酸素または酸素富化空気で部分燃焼することにより、低カロリーチャーでも自己熱で溶融炉温度を高温に維持可能となり、チャーからの可燃性ガス生成が可能となる。
【００１９】
溶融炉で発生した高温のガスは溶融炉３の上部スロートから改質炉４に入る。熱分解チャー中の溶融した灰分は、スラグタップ２３から水中に落下し、水砕状の固形物２７になる。回収した固形物は、土木建築材料等に有効活用できる。改質炉４では、高温の溶融炉ガスとノズルから吹き込まれた熱分解ガス２６と混合して、熱分解ガス中のタールを、熱分解ガス中のＨ₂Ｏと反応してＣＯ、Ｈ₂を主とする可燃性ガスに分解する。熱分解ガス中のタール分をＣＯ、Ｈ₂を主とするガスに分解することにより、プロセス後段の冷却工程や洗浄工程の際に生じるタール分の凝縮を回避し、タール付着による配管等の閉塞を防止すると共にタールの持つエネルギーが効率良く回収できる。
【００２０】
改質炉の温度は８００℃以上の条件が必要である。改質炉の温度制御は、ノズルに酸素または酸素富化空気２２ｂを吹き込んでガスの一部を燃焼して行う。改質炉から排出されたガスは熱回収ボイラー５で蒸気回収してガスを冷却し、集塵装置６でダストを捕集し、ガス洗浄装置７でガス中の有害成分を除去して清浄なガス８を得る。
【００２１】
熱回収ボイラー５は、熱回収量が少ないことから、水噴霧冷却でガスを冷却することも可能であるが、熱回収量を増加できるボイラーによる熱回収が好ましい。熱回収ボイラーは、ガス中の塩酸等の腐食ガスを含有することから、回収蒸気温度を３００℃以下として伝熱管の腐食を防止する方が好ましい。集塵装置６はベンチュリースクラバー等の通常の集塵装置が使用でき、ガス洗浄装置７は、苛性ソーダ等のアルカリを添加した水洗塔等が利用できる。溶融炉、改質炉に使用する酸化剤は、酸素ガスの他に、酸素富化空気を使用することが可能であるが、高カロリーのガスを回収でき、回収ガス量を減少できる酸素の使用が好ましい。
【００２２】
【実施例】
（実施例１）
次に、図１に示した本発明を用いて、廃棄物を処理した実施例を示す。実施例１として、熱分解炉として流動層炉を使用し、低発熱量約２０００kcal／kgで、可燃分約４５％、水分約４５％、灰分約５％、空缶、空瓶、瓦礫等の不燃物約５％、塩素約０．５％である都市ゴミを、処理量１００ｔ／Ｄで処理した。都市ゴミは破砕機で２００mm以下に破砕して熱分解炉に装入した。熱分解炉には、空気３０００Nm³／hrを流動化ガスとして吹込み、廃棄物を部分燃焼し５００℃で熱分解した。溶融炉では、熱分解チャー５００kg／hrを酸素ガス２５０Nm³／hrを使用して１４００℃でガス化して６５０Nm³／hrのガスを得た。改質炉では、溶融炉の高温ガスに熱分解ガスと酸素４５０Nm³／hrを吹き込んで８００℃、改質炉内のガス滞留時間２．１秒で熱分解ガス中のタールを分解した。改質炉を出たガスは、廃熱ボイラーで蒸気を１ｔ／hr回収して冷却後、ガス洗浄装置でダスト、塩酸ガス等を除去して、温度３０℃、発熱量１０００kcal／Nm³の清浄ガス５５００Nm³／hrを得た。
【００２３】
この結果、ゴミ発熱量の６６％が清浄な燃料ガスで回収することができ、加熱炉、ボイラー等の燃料ガスに使用する他に、ガスタービン、ガスエンジン等の発電装置を用いて電力を回収することも可能になる。例えば、ガスタービン複合発電で効率４５％で電力に変換すれば、３０％の発電効率で電力を回収でき、既存のゴミ焼却炉の発電効率１０〜２０％に比べて高いエネルギー回収効率が得られる。
【００２４】
（実施例２）
実施例２として、熱分解炉として流動層炉を使用し、低発熱量約２１００kcal／kgで、可燃物約５５％、水分約４０％、灰分約５％、不燃物約１％、塩素約０．５％である都市ゴミを、処理量１００ｔ／Ｄで処理した。廃棄物は破砕機で２００mm以下に破砕して熱分解炉に装入した。熱分解炉の流動化ガスには熱分解炉で発生したガス２３００Nm³／hrと酸素ガス５５０Nm³／hrを使用し、流動化ガスを燃焼して４００℃で廃棄物を熱分解した。サイクロンで分離した熱分解ガスは、昇圧して４２００Nm³／hrを改質炉に送り、残りは熱分解炉の流動化ガスに使用した。溶融炉では、熱分解チャー６００kg／hrを酸素ガス３００Nm³／hrを使用してガス化し、チャーの自己熱のみで溶融炉温度を１４００℃に維持し灰分を溶融できた。改質炉では、溶融炉の高温ガスに熱分解ガスと酸素２５０Nm³／hrを吹き込んで、８００℃、改質炉内のガス滞留時間２．１秒で熱分解ガス中のタールを分解した。改質炉を出たガスは、廃熱ボイラーで蒸気を１ｔ／hr回収して冷却後、ガス洗浄装置でダスト、塩酸ガス等を除去して、温度３０℃、発熱量１７００kcal／Nm³の清浄ガス３５００Nm³／hrを得た。この結果、ゴミ発熱量の６８％が清浄な燃料ガスで回収することができた。
【００２５】
【発明の効果】
本発明は、幅広いゴミ質の廃棄物について外部燃料なしに自己熱で安定に灰分を溶融し減容化及び再資源化することが可能となる。また、不燃物中のアルミ、鉄を酸化させないで有価物として回収できる。更に、廃棄物の持つエネルギーを電力や可燃性ガスとして効率良く回収できる。
【図面の簡単な説明】
【図１】本発明の廃棄物処理方法のプロセスフロー説明図である。
【符号の説明】
１：熱分解炉
２：サイクロン
３：溶融炉
４：改質炉
５：熱回収ボイラー
６：集塵機
７：ガス洗浄装置
８：洗浄後可燃性ガス
９：廃棄物装入装置
１０：空気
１１ａ，ｌ１ｂ，１１ｃ：流動化ガス導入管
１２：熱分解ガス、熱分解チャー排出管
１３，１４，１５：昇圧ブロア
１６：不燃物排出口
１７：振動篩
１８：流動媒体
１９：不燃物
２０：バーナー
２１：熱分解チャー
２２ａ，２２ｂ：酸素または酸素富化空気
２３：スラグタップ
２４：ノズル
２５：改質炉後ガス排出口
２６：熱分解ガス
２７：冷却スラグ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating waste composed of combustible and non-combustible materials such as municipal waste and industrial waste.
[0002]
[Prior art]
As a waste disposal method in Japan, a method of landfilling incineration ash after incineration at 800 ° C. to 900 ° C. in a stoker type incinerator or a fluidized bed incinerator has been used in recent years. Due to the tightness of landfills, it is necessary to reduce the volume and resources of incineration ash. Therefore, an incineration ash treatment method has been developed in which a plasma arc furnace, a burner combustion furnace, etc. is installed after the existing incinerator, and the generated incineration ash is melted and converted into slag. There is a disadvantage that external energy such as oil is newly required. In addition, because existing incinerators burn waste containing incombustibles such as empty cans at a high temperature of 800-900 ° C, aluminum cannot be recovered by melting into fly ash, and iron becomes oxides and is recycled. There is a problem that it is not possible.
[0003]
As a waste disposal method that solves these problems, for example, “Environmental Facility” No. As described on line 6 on pages 65 and 8, waste is pyrolyzed at a melting point of aluminum below 660 ° C in a pyrolysis furnace to convert the organic matter in the waste into pyrolysis char and pyrolysis gas. After separating incombustibles such as empty cans with a separation device, the pyrolysis char and pyrolysis gas are completely burned at a high temperature of about 1300 ° C. to 1400 ° C. using air in a melting furnace and are contained in the pyrolysis char. There has been proposed a gasification and melting method in which ash is melted and the melted ash is separated from exhaust gas and then cooled and solidified to form a crushed slag. In the gasification and melting method, ash is melted by self-heating using the carbon contained in pyrolysis char or pyrolysis gas as fuel, and no external energy is required, and since pyrolysis is performed in a reducing atmosphere, it is nonflammable. Aluminum and iron in the product are not oxidized and can be recovered as valuable resources, which is advantageous from the viewpoint of resource reuse. In this case, a fluidized bed type or a kiln type has been proposed as a thermal decomposition method.
[0004]
[Problems to be solved by the invention]
However, the problem with these gasification and melting methods is that the range of applicable waste is narrow. For example, when wastes with a high moisture content and a large variation in moisture content, such as municipal waste, are processed, the pyrolysis gas contains a large amount of water vapor and the gas calorie variation is also large, so the melting furnace temperature is 1300 to 1400 ° C. It is difficult to keep it stable. In contrast, as described in “Monthly Global Environment”, May 1997 issue, page 43, line 30, for example, the pyrolysis char is completely burned with air at the rear stage of the waste pyrolysis furnace. A melting furnace that melts ash and a combustion furnace that completely burns pyrolysis gas with air, and only introduces char with a stable calorific value into the melting furnace to achieve stable operation of the melting furnace. A combustion furnace separation type gasification melting method has also been proposed. However, even this method cannot be applied to low-calorie waste. For example, for general municipal waste with a calorific value of about 2000 kcal / kg or less, the melting furnace temperature is 1300 to 1400 required for melting ash by self-heating of the waste. Difficult to maintain at ° C.
[0005]
Recently, there has been a demand for effective use of waste as an energy resource, and waste incinerators are in the direction of installing power generation equipment that uses waste incineration waste heat. Only low power generation efficiency of about 10-15% can be obtained. The current power generation system for waste power generation is usually a steam turbine power generation system that generates steam by collecting steam from high-temperature combustion exhaust gas with a boiler and supplying the recovered steam to the steam turbine. Is because the recovered steam temperature is as low as 300 ° C., and it is necessary to raise the recovered steam temperature to 500 to 600 ° C., which is the same level as a general thermal power plant, in order to improve power generation efficiency.
[0006]
However, in an incinerator, the chlorine contained in the waste becomes hydrochloric acid gas during combustion, and the combustion exhaust gas contains corrosive dust such as alkali metals. Since the temperature of the heat transfer tube in the superheated portion becomes high and is subject to high temperature corrosion due to hydrochloric acid gas or corrosive dust, the recovered steam temperature must be suppressed to 300 ° C. or lower. Even if an expensive corrosion-resistant steel pipe is used to suppress high temperature corrosion of the boiler, the recovery steam temperature is about 400 ° C. and the power generation efficiency is about 20% at present. For the purpose of further increasing the temperature of the recovered steam, for example, “Thermal Power Generation” Vol. 48, no. As described in pages 10, 126, 24th line, the material selection research of the superheater heat transfer tube aiming at the recovered steam temperature of 500 ° C and the power generation efficiency of 30% is currently being conducted. An expensive corrosion-resistant steel pipe is required for the overheated part.
[0007]
On the other hand, as a gasification and melting method aimed at suppressing boiler corrosion by hydrochloric acid gas, chlorine components are distributed almost evenly between pyrolysis gas and pyrolysis char in normal pyrolysis. Ingeniously collect the chlorine component in one of the pyrolysis gas or pyrolysis char, separate the pyrolysis gas and pyrolysis char and burn them separately, and add the boiler superheated part to the combustion exhaust gas part with less chlorine component A method of installing and superheating steam with combustion gas with little corrosion has been proposed. For example, “Mitsubishi Heavy Industries Technical Review”, Vol. 34, no. 3, as described on page 162, pyrolyze waste at 300-400 ° C, transfer chlorine into pyrolysis gas, burn char with less chlorine and obtain superheated steam As described in the methods, for example, “The 2nd Fluidized Bed Symposium Lecture”, page 184, line 21, and “Monthly Global Environment” May 1997, page 43, line 10 In addition, a dechlorinating agent such as slaked lime is added to the pyrolysis furnace and pyrolyzed at 550 to 600 ° C. to transfer chlorine to the pyrolysis char as CaCl ₂ , and the pyrolysis gas and char discharged from the pyrolysis furnace are removed. There has been proposed a method of obtaining superheated steam from combustion exhaust gas of pyrolysis gas with little chlorine by separating with a cyclone or the like.
[0008]
However, both of them have a chlorine separation efficiency of 90 to 95% and cannot be completely separated, and corrosive dust such as alkali metals is present in the combustion exhaust gas, thus preventing high temperature corrosion of the boiler. This is difficult, and it is expected that the use of expensive materials for the superheated part of the boiler is inevitable for increasing the steam temperature. Moreover, in the latter method of adding slaked lime or the like, the added slaked lime has a drawback of increasing slag discharge.
Therefore, there is a demand for a waste treatment method capable of melting ash content of a wide range of garbage wastes by self-heating without external fuel and capable of high-efficiency power generation that avoids the hot corrosion problem of boilers.
[0009]
In the present invention, a wide range of garbage wastes are stably heated by self-heating without external fuel to reduce the volume and recycle the ash, and recover the aluminum and iron in the incombustible material as valuable resources without oxidizing them. It is another object of the present invention to provide a waste treatment method capable of increasing the use of recovered energy and performing highly efficient power generation by recovering waste energy mainly as a combustible gas.
[0010]
[Means for Solving the Problems]
The present invention is provided with a melting furnace for melting ash in waste after the pyrolysis furnace for thermally decomposing waste, and only pyrolysis char with stable calorific value in the melting furnace is oxygen or oxygen-enriched. By partially combusting using gasified air and gasifying it, the amount of gas generated in the melting furnace is greatly reduced compared to the case of complete combustion with air, the input energy for maintaining the melting furnace temperature is reduced, and the ash is generated by self-heating. It is possible to expand the range of trash that can be melted and to generate combustible gas. Furthermore, a pyrolysis gas reforming furnace integrated with the melting furnace is provided at the upper part of the melting furnace, and the melting furnace gas is introduced into the reforming furnace at the upper part of the melting furnace and mixed with the pyrolysis gas. The sensible heat can be effectively used to reform the tar content in the pyrolysis gas. Further, according to the present invention, since the energy recovery method from the waste is a method of gasifying the waste and recovering it as a flammable gas, the gas turbine power generation or the gas engine using the flammable gas mainly after washing the electric power It can be obtained by power generation, and high-efficiency power generation is possible even if the recovered steam temperature when recovering the sensible heat of the gas after the reforming furnace with a boiler is low.
[0011]
The gist of the present invention is as follows (1) to (3).
(1) In a method for treating waste composed of combustible materials and incombustible materials, after pyrolyzing the waste into a pyrolysis char and a pyrolysis gas in a pyrolysis furnace for heating the waste, the pyrolysis char and the heat The cracked gas is separated and the pyrolyzed char after the separation is partially burned with oxygen or oxygen-enriched air in a melting furnace of an air flow layer to gasify by the self-heating of the pyrolyzed char and melt the ash content in the char. pyrolysis after the separation were mixed in the reforming furnace of a melting furnace and integral provided in the upper portion and through the throat of the pyrolysis gas after the separation and gasification gas the melting furnace in the melting furnace A waste treatment method characterized by decomposing tar contained in a gas to produce a combustible gas.
(2) the blowing oxygen or oxygen-enriched air to the reforming furnace (1), the mixed gas by partial combustion and adjusting the reforming furnace temperature (1) disposal according It is a processing method of a thing.
(3) and characterized in that the pyrolysis furnace with a fluidized bed of, using said pyrolysis gas and / or flammable gas after the reforming reactor to generate from the fluidized bed as a fluidizing gas in the fluidized bed This is a waste processing method described in (1).
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment according to the waste treatment method of the present invention. It comprises a pyrolysis furnace 1, a cyclone 2, a melting furnace 3, a reforming furnace 4, a waste heat recovery boiler 5, a dust collector 6, and a gas cleaning device 7.
[0013]
The method of the pyrolysis furnace 1 is not particularly limited, and a commonly used pyrolysis method such as a fluidized bed method or an indirect heating kiln method can be applied. A waste charging device 9 is provided at the side, a fluidized gas introduction pipe 11a is provided at the lower part, and a pipe 12 for discharging the pyrolysis gas and pyrolysis char is provided at the upper part. A gas disperser is provided inside the pyrolysis furnace to disperse the fluidized gas blown by the booster blower 13 to fluidize the upper fluid medium, and at the same time, heat the fluid medium to thermally decompose the waste. .
[0014]
The heating method of the fluidizing gas and fluidizing medium includes the method of heating the fluidizing medium by partially combusting waste using air 10 as the fluidizing gas, and the gas generated in the pyrolysis furnace or after the reformer in the subsequent stage There is a method in which a fluidizing gas is used as a fluidizing gas and the combustible gas is burned in a fluidized bed to heat the fluidized medium. When the gas generated in the pyrolysis furnace or the post-reformer after the reforming furnace is used as the fluidized gas, the dilution of the pyrolysis gas with nitrogen in the air decreases, so the calorific value obtained by the post-reformer gas Becomes higher. In addition, the heat generation amount of the pyrolysis char becomes high, and it becomes possible to melt ash by self-heating even with waste containing a lot of ash.
[0015]
When the pyrolysis gas or the gas after the reforming furnace is used as a fluidizing gas, instead of the booster blower 13 and the fluidized gas introduction pipe 11a, the booster blower 14 and the fluidized gas introduction pipe 11b or the booster blower 15 and the fluid flow. A conversion gas introduction pipe 11c is provided. At the bottom of the pyrolysis furnace, a discharge port 16 is provided for discharging non-combustible materials such as empty cans and bottles together with a fluid medium. A vibrating sieve 17 for separating the fluid medium and the incombustible material is provided at the subsequent stage of the discharge port, and the fluid medium 18 after the separation of the incombustible material is returned to the pyrolysis furnace. In addition, it is preferable to install a magnetic separator and a metal detector after the vibrating sieve to separate and collect iron and non-ferrous metals in the incombustible material 19.
[0016]
The melting furnace 3 is a gas-flow-bed furnace provided with a burner 20 on the side, and the pyrolysis char 21 is gasified with oxygen or oxygen-enriched air 22a. The pyrolysis char is discharged together with the pyrolysis gas from the pyrolysis furnace 1, collected by the cyclone 2, air-flowed by nitrogen or air via a hopper, and supplied to the burner 20 together with the oxidant. A slag tap 23 is provided at the bottom of the melting furnace 3. There is a gas outlet throat at the top of the melting furnace 3, and a reforming furnace 4 integrated with the melting furnace is provided at the top of the throat. The reforming furnace 4 is provided with a nozzle 24 for blowing pyrolysis gas and oxygen on the lower side and a gas outlet 25 on the upper side.
[0017]
The waste is pulverized by a crusher and charged into the pyrolysis furnace 1. In the pyrolysis furnace 1, fluidized gas blown from the lower part of the pyrolysis furnace 1 fluidizes the fluid medium and waste previously charged in the fluidized bed 1, and at the same time the waste is heated, Organic substances such as plastic and paper are pyrolyzed into gas and fine powder char and discharged from the gas outlet 12 at the top of the pyrolysis furnace 1. On the other hand, large inorganic substances such as empty cans and debris settle in the lower part of the fluidized bed and are discharged together with the fluidized medium from the outlet 16 at the bottom of the pyrolysis furnace.
[0018]
The pyrolyzed pyrolysis gas and pyrolysis char are separated into pyrolysis gas 26 and pyrolysis char 21 by the cyclone 2, and the pyrolysis gas is charged into the reforming furnace 4. On the other hand, the pyrolysis char is blown from the burner 20 together with oxygen or oxygen-enriched gas 22a in the melting furnace 3, and the organic matter in the pyrolysis char is high temperature combustible mainly composed of CO and CO ₂ at a high temperature of 1300 ° C or higher. While gasifying into gas, ash content in pyrolysis char is melted. By partially burning only pyrolytic char with oxygen or oxygen-enriched air, the melting furnace temperature can be maintained at a high temperature by self-heating even with a low calorie char, and combustible gas can be generated from char.
[0019]
The high-temperature gas generated in the melting furnace enters the reforming furnace 4 from the upper throat of the melting furnace 3. The molten ash in the pyrolysis char falls into the water from the slag tap 23 and becomes a crushed solid matter 27. The collected solid matter can be effectively used for civil engineering and building materials. In the reforming furnace 4, the hot cracking furnace gas and the pyrolysis gas 26 blown from the nozzle are mixed, and the tar in the pyrolysis gas reacts with H ₂ O in the pyrolysis gas to react with CO, H _2. Is decomposed into combustible gas. By decomposing the tar content in the pyrolysis gas into a gas mainly composed of CO and H ₂ , condensation of the tar content that occurs during the cooling and cleaning steps in the later stage of the process is avoided, and piping is blocked due to tar adhesion. In addition, the energy of tar can be recovered efficiently.
[0020]
The temperature of the reforming furnace needs to be 800 ° C. or higher. The temperature control of the reforming furnace is performed by injecting oxygen or oxygen-enriched air 22b into the nozzle and burning a part of the gas. The gas discharged from the reforming furnace is steam recovered by a heat recovery boiler 5 to cool the gas, dust is collected by a dust collector 6, and harmful components in the gas are removed by a gas cleaning device 7 to be clean. Gas 8 is obtained.
[0021]
Since the heat recovery boiler 5 has a small amount of heat recovery, it is possible to cool the gas by water spray cooling. However, heat recovery by a boiler that can increase the heat recovery amount is preferable. Since the heat recovery boiler contains a corrosive gas such as hydrochloric acid in the gas, it is preferable to prevent the heat transfer tube from being corroded by setting the recovered steam temperature to 300 ° C. or lower. The dust collector 6 can be a normal dust collector such as a venturi scrubber, and the gas cleaning device 7 can be a water washing tower to which an alkali such as caustic soda is added. As the oxidizer used in melting furnaces and reforming furnaces, oxygen-enriched air can be used in addition to oxygen gas, but high-calorie gas can be recovered and the amount of recovered gas can be reduced. Is preferred.
[0022]
【Example】
Example 1
Next, the Example which processed the waste using this invention shown in FIG. 1 is shown. As Example 1, a fluidized bed furnace is used as a pyrolysis furnace, with a low calorific value of about 2000 kcal / kg, combustible content about 45%, moisture content about 45%, ash content about 5%, empty cans, empty bottles, rubble, etc. Municipal waste that is about 5% incombustibles and about 0.5% chlorine was treated at a treatment rate of 100 t / D. Municipal waste was shredded to 200 mm or less with a crusher and charged into a pyrolysis furnace. In the pyrolysis furnace, 3000 Nm ³ / hr of air was blown as a fluidized gas, and the waste was partially burned and pyrolyzed at 500 ° C. The melting furnace to obtain a 650 nm ³ / hr of gas to the pyrolysis char 500 kg / hr and gasified at 1400 ° C. using an oxygen gas 250 Nm ³ / hr. In the reforming furnace, pyrolysis gas and oxygen 450 Nm ³ / hr were blown into the high-temperature gas of the melting furnace to decompose tar in the pyrolysis gas at 800 ° C. and a gas residence time of 2.1 seconds in the reforming furnace. The gas exiting the reforming furnace is recovered by 1t / hr of steam with a waste heat boiler and cooled, then dust, hydrochloric acid gas, etc. are removed with a gas scrubber and cleaned at a temperature of 30 ° C and a calorific value of 1000 kcal / Nm ³ A gas of 5500 Nm ³ / hr was obtained.
[0023]
As a result, 66% of the amount of generated heat can be recovered with clean fuel gas, and in addition to being used as fuel gas for heating furnaces, boilers, etc., power is recovered using power generators such as gas turbines and gas engines. It is also possible to do. For example, if the gas turbine combined power generation is converted into electric power with an efficiency of 45%, the electric power can be recovered with an electric power generation efficiency of 30%, and a higher energy recovery efficiency can be obtained as compared with the electric power generation efficiency of an existing refuse incinerator. .
[0024]
(Example 2)
In Example 2, a fluidized bed furnace was used as the pyrolysis furnace, with a low calorific value of about 2100 kcal / kg, combustible material about 55%, moisture content about 40%, ash content about 5%, incombustible material about 1%, chlorine about 0 .5% municipal waste was processed at a processing rate of 100 t / D. The waste was crushed to 200 mm or less with a crusher and charged into a pyrolysis furnace. The fluidizing gas of the pyrolysis furnace using gas 2,300 Nm ³ / hr and oxygen gas 550Nm ³ / hr generated in the pyrolysis furnace, waste was pyrolyzed at combustion to 400 ° C. The fluidizing gas. The pyrolysis gas separated by the cyclone was pressurized and sent to the reforming furnace at 4200 Nm ³ / hr, and the rest was used as the fluidizing gas for the pyrolysis furnace. In the melting furnace, 600 kg / hr of pyrolysis char was gasified using 300 Nm ³ / hr of oxygen gas, and the ash content could be melted by maintaining the melting furnace temperature at 1400 ° C. only by the self-heating of the char. In the reforming furnace, pyrolysis gas and oxygen 250 Nm ³ / hr were blown into the high-temperature gas of the melting furnace, and tar in the pyrolysis gas was decomposed at 800 ° C. and a gas residence time of 2.1 seconds in the reforming furnace. The gas exiting the reforming furnace is recovered by 1t / hr of steam with a waste heat boiler and cooled, then dust and hydrochloric acid gas are removed with a gas scrubber and cleaned at a temperature of 30 ° C and a calorific value of 1700kcal / Nm ³ A gas of 3500 Nm ³ / hr was obtained. As a result, 68% of the waste heat generation amount could be recovered with clean fuel gas.
[0025]
【The invention's effect】
The present invention makes it possible to melt and reduce the volume and recycling of ash for a wide range of waste-like wastes with no external fuel and with stable self-heating. Moreover, it can collect | recover as valuables, without oxidizing the aluminum and iron in an incombustible material. Furthermore, the energy of waste can be efficiently recovered as electric power or combustible gas.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a process flow of a waste treatment method of the present invention.
[Explanation of symbols]
1: pyrolysis furnace 2: cyclone 3: melting furnace 4: reforming furnace 5: heat recovery boiler 6: dust collector 7: gas cleaning device 8: combustible gas 9 after cleaning 9: waste charging device 10: air 11a, l1b 11c: Fluidized gas introduction pipe 12: Pyrolysis gas, pyrolysis char discharge pipes 13, 14, 15: Booster blower 16: Incombustible discharge port 17: Vibrating sieve 18: Fluid medium 19: Noncombustible substance 20: Burner 21: Pyrolysis chars 22a and 22b: oxygen or oxygen-enriched air 23: slag tap 24: nozzle 25: gas outlet after reforming furnace 26: pyrolysis gas 27: cooling slag

Claims

In a method for treating waste consisting of combustible and non-combustible materials, after pyrolyzing the waste into pyrolysis char and pyrolysis gas in a pyrolysis furnace for heating the waste, the pyrolysis char and pyrolysis gas are It separated, pyrolysis char after the separation to melt the char ash content as well as gasification self heat by partial combustion with oxygen or oxygen-enriched air at melting furnace of air flow layer the pyrolytic char, the molten the pyrolysis gas after the separation and gasification gas to the pyrolysis gas after the separation were mixed in the reforming furnace of a melting furnace and integral through the throat provided at an upper portion of the melting furnace in the furnace A method for treating waste, comprising decomposing a tar content and generating a combustible gas.

The blowing oxygen or oxygen-enriched air to the reforming furnace, the processing method according to claim 1 waste wherein the mixed gas by partial combustion and adjusts the reformer temperature.

Claim 1, the thermal cracking furnace as a fluidized bed, characterized by the use of the pyrolysis gas and / or flammable gas after the reforming reactor to generate from the fluidized bed as a fluidizing gas in the fluidized bed The waste disposal method described.