JP3974534B2

JP3974534B2 - Electric melting furnace operation method

Info

Publication number: JP3974534B2
Application number: JP2003034626A
Authority: JP
Inventors: 吉司松田; 考太郎加藤
Original assignee: Takuma Co Ltd
Current assignee: Takuma Co Ltd
Priority date: 2003-02-13
Filing date: 2003-02-13
Publication date: 2007-09-12
Anticipated expiration: 2023-02-13
Also published as: JP2004245475A

Description

【０００１】
【発明の属する技術分野】
本発明は都市ごみや都市ごみの焼却残滓等を溶融処理するアーク溶融炉やプラズマアーク溶融炉（以下電気溶融炉と呼ぶ）の運転方法に関するものであり、特に電気溶融炉の冷間立上げ時の主電極と補助電極間の通電操業方法に改良を加えることにより、絶縁性固形物の溶融を大幅に促進させ、前記冷間立上げ時の通電操業時間の大幅な短縮を可能とした電気溶融炉の運転方法に関するものである。
【０００２】
【従来の技術】
都市ごみや都市ごみの焼却残滓等の溶融処理には、従前からアーク溶融炉やプラズマアーク溶融炉が多く利用されている。
図５は、従前のプラズマアーク溶融炉の一例を示すものである。即ち、炉本体１の天井壁に主電極２と補助電極３とが、また、炉本体１の底面に炉底電極４が夫々設けられており、直流電源装置５から主電極３と炉底電極４間へ直流電圧を印加して主電極２と溶融スラグＢ間にプラズマアーク６を発生させることにより、その発生熱によって炉本体１内へ供給されて来る焼却残滓等の被溶融物Ｃを順次溶融させて行く。
【０００３】
尚、図５に於いてＡは被溶融物Ｃが溶融された溶融スラグ（溶融物）、Ｂは金属等の溶融された溶融メタル、７は炉電電極４を構成する集電板、８は被溶融物Ｃの投入口、９は溶融スラグＡの隘流口、１０は溶融メタルＢの抜出孔、１１は主電極２を上・下位置調整可能に保持する主電極支持装置、１２は補助電極３を上・下動位置調整可能に保持する補助電極支持装置、１３は電力用配電盤である。
【０００４】
而して、都市ごみ焼却残滓等の被溶融物Ｃの溶融物である溶融スラグＢは電気的に導電性であるため、プラズマアーク溶融炉の定常運転時には、前記プラズマアーク６は比較的安定した状態に保持されることになり、投入された被溶融物Ｃは順次プラズマアーク熱によって溶融されて行く。
【０００５】
一方、何等かの事情で溶融炉の運転を一時的に停止したような場合には、熱源を失うために必然的に内部の溶融スラグＡは固形化することになる。この残留した溶融スラグＡの一部が固形化した状態にある電気溶融炉を再運転するような場合（以下、電気溶融炉の冷間立上げと呼ぶ）には、溶融スラグＡが固形化することによって絶縁性となるため、主電極２と炉底電極４間に存続する絶縁性固形物により両電極２、５間の通電性が極端に低下し、アーク若しくはプラズマアークの発生が困難になったり、或いは万一アーク若しくはプラズマアークを発生することができても、その安定維持が不可能となる。
【０００６】
そのため、電気溶融炉の冷間立上げに於いては、通常先ず主電極２と補助電極３間へ通電して両電極２、３間にアーク若しくはプラズマアークを発生させ、当該主電極２と補助電極３により発生させたアーク若しくはプラズマアークの熱を利用して絶縁性固形物Ａ′を融解させることによりその導電性を回復させ、主電極２と炉底電極４間の通電が可能な状態になってから、主電極２と炉底電極４間への通電に切換えるようにしている。
【０００７】
具体的には、図６に示すように、先ず補助電極３を下降させてその先端を絶縁性固形物Ａ′へ接触させ、次に、主電極２の先端を絶縁性固形物Ａ′の上面より一定距離だけ上方の位置まで下降させて主電極２と絶縁性固形物Ａ′間にアーク若しくはプラズマアーク６を発生させる。更に、前記プラズマアーク６等の発生熱によって絶縁性固形物Ａ′の溶解が進行すると、これに合わせて主電極２を徐々に上方へ引き上げ、アーク若しくはプラズマアークの安定化を図りつつ絶縁性固形物Ａ′を順次溶解させて行き、絶縁性固形物Ａ′の溶解によって主電極２と炉底電極４間の導電性が回復されると、一旦電源を切り、前述の通り補助電極３を上方へ引き上げて主電極２と炉底電極４間の通電に切換えるようにしている。
【０００８】
尚、上記の如き電気溶融炉の構成や被溶融物Ｃの定常的な溶融運転及び冷間立上げ時の運転操作等は公知の技術であるため、ここではその詳細な説明を省略するものとする。
【特許文献１】
特開２００１−５０５２８号公報
【０００９】
【発明が解決しようとする課題】
上記従前のプラズマアーク溶融炉やアーク溶融炉等の電気溶融炉は、焼却残滓等の被溶融物Ｃを安定に溶融処理することができ、優れた実用的効用を有するものである。
しかし、従前の溶融炉にも解決すべき問題が多く残されており、その中でも前記冷間立上げ時に於ける絶縁性固形物Ａ′の溶解に長時間を必要とし、電気溶融炉の操業効率の向上を図れないと云う点が、解決すべき問題点として残されている。
【００１０】
例えば容量９４００ＫＶＡ、被処理物の処理量７０ｔ／日、被溶融物Ｃがごみ焼却残滓のプラズマアーク溶融炉に於いて、当該プラズマアーク溶融炉の運転停止から１００Ｈｒ後の溶融スラグＡの固形物層の厚さが約２００ｍｍの時、当該プラズマアーク溶融炉の冷間立上げに必要とする時間（補助電極３と主電極２間の通電から主電極２と炉底電極４間の通電に切換えするまでの時間）は約半日程度であり、且つこの時の溶解すべき絶縁性固形物Ａ′の総容積は約１．５ｍ³程度となる。
【００１１】
本願発明は電気溶融炉の前記冷間立上げ時の主電極２と補助電極３間の通電操業に於ける上述の如き問題を解決せんとするものであり、従前の冷間立上げ時の主電極２と補助電極３間の通電操作では絶縁性固形物Ａ′の溶解の進行と共に電極を上昇させる方向に移動するようにしているが、本発明では従前の操作とは逆に、主電極２と補助電極３の両方を絶縁性固形物Ａ′の溶解の進行と共に連続的又は間欠的に下降させ、両電極２、３を絶縁性固形物Ａ′へ密着させた状態で両電極２、３間へ通電することにより、冷間立上げ時の絶縁性固形物Ａ′の溶解時間の大幅な短縮を可能にした電気溶融炉の運転方法を提供するものである。
【００１２】
【課題を解決するための手段】
上記目的を達成するため、本願請求項１の発明は、主電極と補助電極と炉底電極とを備えた都市ごみやごみ焼却残滓の溶融用電気溶融炉の内部に溶融スラグの絶縁性固形物が存在する状態下で溶融炉を運転する溶融炉の冷間立上げ運転に於いて、先ず前記主電極と補助電極を下降させて両電極の先端を炉本体の内部に存在する溶融スラグの絶縁性固形物の上面へ接触させ、次に両電極間の絶縁性固形物の上に冷間立上用導電物を配設したあと、両電極間に通電することにより前記絶縁性固形物の一部を溶解させ、更に前記絶縁性固形物の一部が溶解すると両電極を下降させると共に、電気溶融炉の主電極支持装置及び補助電極支持装置に付設した主電極下降限度位置規制機構及び補助電極下降限度位置規制機構により、主電極及び補助電極の下降時に両電極をその先端が絶縁性固形物の上面へ接当する位置に自動的に保持しつつ両電極間に通電をし、両電極間の溶融スラグの絶縁性固形物を所定の厚みに亘って溶解させたあと、主電極と炉底電極間に通電をするようにしたことを発明の基本構成とするものである。
【００１３】
請求項２の発明は、請求項１の発明に於いて、電気溶融炉をプラズマアーク溶融炉又はアーク溶融炉とするようにしたものである。
【００１７】
【発明の実施の形態】
以下、図面に基づいて本発明の実施形態を説明する。
図１は本発明の実施に係るプラズマアーク溶融炉の概要を示すものであり、プラズマアーク溶融炉自体の構成は、後述する主電極及び補助電極の電極下降限度位置規制機構を主電極支持装置及び補助電極支持装置に備えている点を除いて、従前のプラズマアーク溶融炉の場合と略同一である。
【００１８】
図１に於いて、１は炉本体、２は主電極、３は補助電極、４は炉底電極、５は直流電源装置、６はプラズマアーク、７は集電板、８は被溶融物投入口、９は溶融スラグＡの隘流口、１０は溶融メタルの抜出孔、１１は主電極支持装置、１２は補助電極支持装置、１３は電力用配電盤、Ａ″は冷間立上げ時に炉本体内へ導入された立上げ用の導電物である。
また、主電極２は直流電源装置５の＋極に、補助電極３及び炉底電極４を形成する集電板６は−極に夫々接続されている。
【００１９】
本発明の実施に係る主電極支持装置１１及び補助電極支持装置１２には、主電極下降限度位置規制機構１４及び補助電極下降限度位置規制機構１５が夫々設けられている。即ち、後述するように、主電極支持装置１１及び補助電極支持装置１２の支持枠体１６にワイヤ１９を介して吊下げ支持された各電極２、３が下降され、電極２、３の先端部（下端部）が溶融スラグＡの絶縁性固形物Ａ′に接当すると、ワイヤ１９が若干弛み、各電極２、３は自重によりその先端部を溶融スラグの絶縁性固形物Ａ′へ密着状に接触させた状態に保持されると共に、ワイヤ１９の弛みがロードセル２１やワイヤ弛み検出器２３によって検知され、これによって電極昇降装置１８の駆動が停止される。
【００２０】
その後、両電極２、３間に通電されることにより、前記先きに介存せしめた冷間立上げ用の導電物Ａ″を介して通電され、固形物Ａ′の溶解が開始される。
また、固形物の溶解が進行して、各電極２、３の先端が固形物Ａ′から離れると、電極２、３が重力によって下降し、ワイヤ１９の弛みが無くなると後述するロードセル２１等によってそれが検出され、各電極２、３の位置が検出されると共に必要な場合には、引き続きワイヤ１９を繰り出してワイヤ１９に弛みを与え、各電極２、３の先端を固形物Ａ′の上面へ下降接当させるようにする。
【００２１】
上述の如き操作を繰り返すことにより、固形物Ａ′はその厚み方向に順次溶解されて行き、主電極２と炉底電極４間の通電性が確保されるようになると、各電極２、３は上方へ引き上げられ、主電極２のみによる定常運転状態に電気炉の運転操作が切換えられる。
【００２２】
図４は、前記主電極支持装置１１の概要を示す側面図であり、補助電極支持装置１２の方も当該主電極支持装置１１と同一の構成を有している。
図４に於いて、２は主電極、１６は枠体、１７は電極棒把持体、１８は電極昇降駆動装置、１９は電極吊下げワイヤ、２０はロータリエンコーダ、２１はロードセル、２２は電極落下防止装置、２３はワイヤ弛み検出器、２４は給電接続導体である。
【００２３】
主電極２（又は補助電極３）は電極棒把持体１７をワイヤ１９を介して電極昇降駆動装置１８により巻き上げ（又は巻き降し）することにより、枠体１６に沿って昇降動されるように構成されており、主電極２の先端が固形物Ａ′に接当している場合には、前記ワイヤ１９に僅かな弛みが生じている。その結果、固形物Ａ′の溶解が進行すると、ワイヤ１９の弛み分だけ主電極２の先端は下降することになる（即ち、固形物Ａ′の溶解に追随して主電極２の先端が下降することになる）。
【００２４】
また、ワイヤ１９の先端と電極棒把持体１７との間にはロードセル２１が介設されており、主電極２の先端が固形物Ａ′に当接してワイヤ１９が弛むと、ロードセル２１によつてその弛みが検出され、これによって主電極２の固形物Ａ′への当接が検出される。
【００２５】
更に、当該ロードセル２１は電極棒把持体１７の昇降作動の保護装置としての機能をも果しており、何等かの原因で設定値以上の荷重がロードセル２１にかかると、電極昇降駆動装置１８の作動が停止される。
【００２６】
同様に、ワイヤ１９の巻上量や伸長量等はロータリーエンコーダ２０によって検出され、制御装置（図示省略）へ入力されている。
また、ワイヤ１９の弛み量はワイヤ弛み検出器２３によって検出され、制御装置（図示省略）へ入力されることによりワイヤ弛み量が設定値に規制されている。
【００２７】
尚、本実施形態では、主電極支持装置１１及び補助電極支持装置１２を前記図４に示したようなワイヤ吊下げ機構を主体とする構造のものにしているが、各支持装置１１、１２を枠体１６に上・下方向へスライド自在に支持した電極棒把持体１７と、電極棒把持体１７を上・下方向へスライド駆動させるねじ機構（図示省略）と、ねじ機構を回転駆動させる駆動用モータ（図示省略）とから構成すると共に、各電極２、３の先端部が溶融スラグの固形物Ａ′の上面へ接当した際に生ずるねじ機構の回転駆動用モータの負荷電流の変化を検出し、当該負荷電流の急増を検出することにより電極棒把持体１７の下降動作を停止させ、各電極２、３の先端を溶融スラグの固形物Ａ′へ接当させた状態に保持する構成とすることも可能である。
【００２８】
更に、前記主電極下降限度位置規制機構１４や補助電極下降限度位置規制機構１５の構成は、如何なるものであってもよいことは勿論であり、例えば、電極棒把持体１７に圧電素子（図示省略）を取り付け当該圧電素子を介して電極棒把持体１７に下方向への駆動力（押圧力）を加えると共に、圧電素子の歪起電力の変化から電極先端と溶融スラグ固形物Ａ′の接当を検出して前記電極棒把持体１７の下方への移動を停止させ、その先端を溶融スラグの固形物Ａ′の上面へ接当させた状態で電極２、３を保持する構成とすることも可能である。
【００２９】
次に、本発明に係る電気溶融炉の運転方法について説明する。
図１を参照して、何等かの原因により、電気溶融炉の運転を炉本体１内に溶融スラグＡを残留せしめた状態で一時的に停止し、その後内部の溶融スラグＡが固形化した状態の炉本体１を起動する場合（以下、電気溶融炉の冷間立上げと呼ぶ）には、先ず主電極２及び補助電極３の両方を下降させ、その各先端を溶融スラグＡの固形物Ａ′（絶縁性固形物Ａ′）の上面へ密着状に接当させる。また、図１のＡ″に示すように両電極２、３間の固形物Ａ′上に鉄くずや炭素粉等の導電物Ａ″を置いて、両電極２、３間の導電性を確保する。
【００３０】
その後、補助電極３及び炉底電極４を直流電源装置５の＋側に、主電極２を直流電源装置５の＋側へ接続し、各電極２、３、４間へ直流電圧を印加する。
直流電圧の印加により、補助電極３と主電極２間の絶縁性固形物Ａ′の外表面近傍にプラズマアークが発生し、この発生したアーク熱により絶縁性固形物Ａ′の表層部の一部が図２に示す如き状態に融解され、導電性の溶融スラグＡが形成される。
【００３１】
絶縁性固形物Ａ′の一部が融解されて溶融スラグＡが形成されると、図３に示すように主電極２及び補助電極３の先端を下降させ、両電極２、３の先端部を絶縁性固形物Ａ′の表面に密着状に接触させ通電を継続する。
尚、主電極２及び補助電極３の下降は、前記主電極支持装置１１及び補助電極支持装置１２を介して自動的に行なわれる。また、各電極２、３の下端面の位置は、前記主電極支持装置１１及び補助電極支持装置１２に設けた主電極下降限度位置規制機構１４及び補助電極下降限度位置規制機構１５によって夫々規制されており、両電極２、３の下端面が絶縁性固形物Ａ′の外表面へ密着状に接当した状態の位置で、各電極２、３は自動的に保持される。
【００３２】
前記両電極２、３の下降操作は、溶解による溶融スラグＡの形成と同期して連続的に行なうのが望ましいが、一定時間毎（例えば３０分毎に）に間欠的に、形成された溶融スラグＡ内へ両電極２、３の先端を下降させて行くようにしてもよい。
【００３３】
尚、図３のように、両電極２、３の先端を形成された溶融スラグＡの内部に位置せしめた状態で両電極２、３間へ通電をした場合でも、両電極２、３間に発生するプラズマアークの発生熱が主体となって絶縁性固形物Ａ′が順次溶解されて行くことが判明している。即ち、両電極２、３間への通電により多量のジュール熱が発生するが、現実には両電極２、３間にアークも発生しており、この発生アークにより生じたプラズマガスによって電極２、３間の溶融スラグ液面が押し付けられて拡散し、この拡散によって生じた空間部でアークが形成され、成長して行くことが確認されている。
【００３４】
上述の如き両電極２、３の下降と両電極２、３間への通電を繰り返し行なうことにより、絶縁性固形物Ａ′は順次溶解され、主電極２と炉底電極４間の絶縁性固形物Ａ′が、その厚み方向寸法に略１００％程度溶解されると、主電極２と補助電極３間の電流よりも主電極２と炉底電極４間に流れる電流が支配的となる。
【００３５】
前記の従来例との対比のために、容量９４００ＫＶＡ、被処理量７０ｔ／日、被処理物Ｃがごみ焼却炉残滓のプラズマアーク溶融炉に於いて、当該プラズマアーク溶融炉の運転停止から１００Ｈｒ後の溶融スラグＡの固形物層の厚さが約２００ｍｍの時、当該プラズマアーク溶融炉の冷間立上げに必要とする時間（補助電極３と主電極２間の通電から、主電極２と炉底電極３間の通電に切換えるまでの時間）は約４時間３０分であり、且つこの時の溶解した絶縁性固形物Ａ′の総容積は約１．５ｍ³となった。
尚、上記実施例の冷間立上げ運転に於ける両電極２、３の下降回数は、約１０回であった。
【００３６】
本発明と従来例との冷間立上げに必要とする時間を対比して見ると、本発明の場合には冷間立上げに必要とする時間が従来例の約３０〜４０％位い（４．５ｈ／１２ｈ）となり、それだけ電気溶融炉の操業率を高めることが可能となる。
【００３７】
尚、前記実施形態に於いては、主としてアーク放電により発生したプラズマを溶融熱とするようにした型式のプラズマアーク溶融炉へ本発明を適用した場合について述べたが、本発明は通常のアーク溶融炉へも適用できることは勿論である。
また、前記実施形態に於いては、主電極２及び補助電極３の下降を間欠的に行なう場合について述べたが、両電極を絶縁性固形物Ａ′の溶解と連動させて自動的に連続下降させるようにしてもよいことは勿論である。
【００３８】
【発明の効果】
本発明に於いては、都市ごみやごみ焼却残滓の溶融用電気溶融炉に於いて、電気溶融炉の冷間立上げ運転を主電極と補助電極の先端を溶融スラグの絶縁性固形物の上面へ密着させた状態で両電極間へ通電し、これ等の操作を連続的又は間欠的に行なうことにより絶縁性固形物を所定の厚みに亘って溶解させる構成としている。
その結果、従前のこの種電気溶融炉に於ける冷間立上げ運転方法の場合に比較して、冷間立上げに必要とする作業時間の短縮を図ることが可能となり、電気溶融炉の操業率を大幅に向上させることが可能となる。
また、本発明に於いては、主電極支持装置と補助電極支持装置に、主電極下降限度位置規制機構と補助電極下降限度位置規制機構を設けることにより、これ等を利用して主電極と補助電極を、その各下端が絶縁性固形物の表面へ常時密着した状態に固定保持することができる。その結果、冷間立上げ時に於ける両電極の下降と両電極間への通電を絶縁性固形物の溶解と連動して自動的に連続して行なうことができ、冷間立上げ時の電気溶融炉の運転操作が著しく容易になる。
本発明は上述の通り優れた実用的効用を奏するものである。
【図面の簡単な説明】
【図１】本発明の実施対象であるプラズマアーク溶融炉の全体構成を示す断面概要図である。
【図２】本発明の実施により、炉本体内の絶縁性固形物の一部が溶融し出した状態を示すプラズマアーク溶融炉の断面概要図である。
【図３】本発明の実施により、炉本体内の絶縁性固形物の一部が溶融をしたため、主電極及び補助電極を更に下降せしめて通電をしている状態を示すプラズマアーク溶融炉の断面概要図である。
【図４】本発明の実施に用いたプラズマアーク溶融炉の主電極支持装置の側面概要図である。
【図５】従前のプラズマアーク溶融炉を示す断面概要図である。
【図６】従前のプラズマアーク溶融炉に於ける冷間立上げ時の通電状態を示すプラズマアーク溶融炉の断面概要図である。
【符号の説明】
Ａは溶融スラグ、Ａ′は溶融スラグの固形物（絶縁性固形物）、Ｂは溶融メタル、Ｃは被溶融物、１は炉本体、２は主電極、３は補助電極、４は炉底電極、５は直流電源装置、６はプラズマアーク、７は集電板、８は被溶融物投入口、９は溶融スラグＡの隘流口、１０は溶融メタルの抜出孔、１１は主電極支持装置、１２は補助電極支持装置、１３は電力用配電盤、１４は主電極下降限度位置規制機構、１５は補助電極下降限度位置規制機構、１６は枠体、１７は電極棒把持体、１８は電極昇降駆動装置、１９は電極吊下げワイヤ、２０はロータリエンコーダ、２１はロードセル、２２は電極落下防止装置、２３はワイヤ弛み検出器、２４は給電接続導体である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operating method of an arc melting furnace or a plasma arc melting furnace (hereinafter referred to as an electric melting furnace) for melting and processing municipal waste or municipal waste incineration residue, and particularly at the time of cold start-up of an electric melting furnace. By improving the current-carrying operation method between the main electrode and the auxiliary electrode, the melting of insulating solids is greatly promoted, and the current-carrying time during the cold start-up can be greatly shortened. The present invention relates to a furnace operation method.
[0002]
[Prior art]
Conventionally, arc melting furnaces and plasma arc melting furnaces are often used for melting treatment of municipal waste and municipal waste incineration residue.
FIG. 5 shows an example of a conventional plasma arc melting furnace. That is, the main electrode 2 and the auxiliary electrode 3 are provided on the ceiling wall of the furnace body 1, and the furnace bottom electrode 4 is provided on the bottom surface of the furnace body 1. By applying a DC voltage between 4 and generating a plasma arc 6 between the main electrode 2 and the molten slag B, the melted material C such as incineration residue that is supplied into the furnace body 1 by the generated heat is sequentially applied. Let it melt.
[0003]
In FIG. 5, A is a molten slag (melt) obtained by melting the melt C, B is a molten metal such as metal, 7 is a current collector plate constituting the furnace electrode 4, and 8 is An inlet for molten material C, 9 is an inlet for molten slag A, 10 is an outlet for molten metal B, 11 is a main electrode support device for holding the main electrode 2 so that the upper and lower positions can be adjusted, and 12 An auxiliary electrode support device 13 that holds the auxiliary electrode 3 so that the up / down movement position can be adjusted, and 13 is a power distribution board.
[0004]
Thus, since the molten slag B, which is a melt of the melt C such as municipal waste incineration residue, is electrically conductive, the plasma arc 6 is relatively stable during steady operation of the plasma arc melting furnace. The molten material C that has been charged is sequentially melted by the plasma arc heat.
[0005]
On the other hand, when the operation of the melting furnace is temporarily stopped for some reason, the internal molten slag A is inevitably solidified in order to lose the heat source. When the electric melting furnace in which a part of the remaining molten slag A is solidified is restarted (hereinafter referred to as cold starting of the electric melting furnace), the molten slag A is solidified. Therefore, the insulating solid material existing between the main electrode 2 and the furnace bottom electrode 4 significantly reduces the electrical conductivity between the electrodes 2 and 5, making it difficult to generate an arc or plasma arc. Even if an arc or plasma arc can be generated, the stable maintenance is impossible.
[0006]
For this reason, in the cold start-up of the electric melting furnace, first, the main electrode 2 and the auxiliary electrode 3 are first energized to generate an arc or plasma arc between the electrodes 2 and 3, and the main electrode 2 and the auxiliary electrode 3 are auxiliary. The electric conductivity between the main electrode 2 and the furnace bottom electrode 4 can be restored by melting the insulating solid A ′ using the heat of the arc or plasma arc generated by the electrode 3 to restore its conductivity. After that, switching to energization between the main electrode 2 and the furnace bottom electrode 4 is performed.
[0007]
Specifically, as shown in FIG. 6, first, the auxiliary electrode 3 is lowered to bring its tip into contact with the insulating solid A ′, and then the tip of the main electrode 2 is brought into contact with the upper surface of the insulating solid A ′. An arc or plasma arc 6 is generated between the main electrode 2 and the insulating solid A ′ by lowering to a position above a certain distance. Further, when the melting of the insulating solid A ′ progresses due to the heat generated by the plasma arc 6 or the like, the main electrode 2 is gradually pulled upward in accordance with this, and the insulating solid is stabilized while stabilizing the arc or plasma arc. When the electrical conductivity between the main electrode 2 and the furnace bottom electrode 4 is restored by melting the insulating solid A ′, the power is turned off and the auxiliary electrode 3 is moved upward as described above. The current is switched between the main electrode 2 and the furnace bottom electrode 4.
[0008]
In addition, since the construction of the electric melting furnace as described above, the steady melting operation of the melt C, the operation operation at the time of cold start-up, and the like are known techniques, detailed description thereof will be omitted here. To do.
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-50528
[Problems to be solved by the invention]
The conventional electric melting furnaces such as the plasma arc melting furnace and the arc melting furnace can stably melt the material to be melted C such as incineration residue and have an excellent practical utility.
However, there are still many problems to be solved in the conventional melting furnace. Among them, it takes a long time to dissolve the insulating solid A ′ at the cold start-up, and the operation efficiency of the electric melting furnace is increased. The point that the improvement cannot be achieved remains as a problem to be solved.
[0010]
For example, in a plasma arc melting furnace having a capacity of 9400 KVA, a processing amount of 70 tons / day, and a melting target C of waste incineration residue, a solid layer of molten slag A 100 hours after the operation of the plasma arc melting furnace is stopped. When the thickness of the plasma arc furnace is about 200 mm, the time required for cold start-up of the plasma arc melting furnace (switching from energization between the auxiliary electrode 3 and the main electrode 2 to energization between the main electrode 2 and the furnace bottom electrode 4 is switched. Time) is about half a day, and the total volume of the insulating solid A ′ to be dissolved at this time is about 1.5 m ³ .
[0011]
The present invention is intended to solve the above-described problems in the energization operation between the main electrode 2 and the auxiliary electrode 3 during the cold start-up of the electric melting furnace. In the energization operation between the electrode 2 and the auxiliary electrode 3, the electrode is moved in the direction of ascending with the progress of dissolution of the insulating solid A ′. In the present invention, however, the main electrode 2 is contrary to the previous operation. Both the auxiliary electrode 3 and the auxiliary electrode 3 are continuously or intermittently lowered with the progress of dissolution of the insulating solid A ', and both electrodes 2, 3 are brought into close contact with the insulating solid A'. It is intended to provide a method of operating an electric melting furnace that can significantly reduce the melting time of the insulating solid A ′ at the time of cold start-up by energizing the gap.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is directed to an insulating solid material of molten slag in an electric melting furnace for melting municipal waste and refuse incineration residue comprising a main electrode, an auxiliary electrode, and a furnace bottom electrode . there in cold start-up operation of the melting furnace operating a melting furnace in a state that is present, first insulating molten slag present the tip of the electrodes lowers the said main and auxiliary electrodes in the interior of the furnace body The insulating solid material is brought into contact with the upper surface of the insulating solid material, and then a cold-rise conductive material is disposed on the insulating solid material between the electrodes. When the part of the insulating solid is dissolved, both electrodes are lowered, and the main electrode lower limit position regulating mechanism and auxiliary electrode attached to the main electrode supporting device and auxiliary electrode supporting device of the electric melting furnace Due to the lower limit position regulation mechanism, the main electrode and auxiliary electrode The upper surface and automatically held while current between the electrodes at a position Setto to a predetermined thickness of insulating solid slag between the two electrodes of the both electrodes the tip insulating solids when descending The basic configuration of the invention is to energize between the main electrode and the furnace bottom electrode after being dissolved.
[0013]
The invention of claim 2 is the invention of claim 1, wherein the electric melting furnace is a plasma arc melting furnace or an arc melting furnace.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of a plasma arc melting furnace according to an embodiment of the present invention. The configuration of the plasma arc melting furnace itself includes an electrode lowering limit position regulating mechanism for a main electrode and an auxiliary electrode, which will be described later, Except for the point provided in the auxiliary electrode support device, it is substantially the same as the case of the conventional plasma arc melting furnace.
[0018]
In FIG. 1, 1 is a furnace body, 2 is a main electrode, 3 is an auxiliary electrode, 4 is a furnace bottom electrode, 5 is a DC power supply, 6 is a plasma arc, 7 is a current collector plate, and 8 is a material to be melted. Numeral 9 is a flow outlet for molten slag A, 10 is a molten metal outlet, 11 is a main electrode support device, 12 is an auxiliary electrode support device, 13 is a power distribution board, and A ″ is a furnace during cold start-up. This is a starting conductive material introduced into the body.
The main electrode 2 is connected to the positive electrode of the DC power supply device 5 and the current collector plate 6 forming the auxiliary electrode 3 and the furnace bottom electrode 4 is connected to the negative electrode.
[0019]
The main electrode support device 11 and the auxiliary electrode support device 12 according to the embodiment of the present invention are provided with a main electrode lower limit position restriction mechanism 14 and an auxiliary electrode lower limit position restriction mechanism 15, respectively. That is, as will be described later, the electrodes 2 and 3 suspended and supported by the support frame 16 of the main electrode support device 11 and the auxiliary electrode support device 12 via the wire 19 are lowered, and the tips of the electrodes 2 and 3 are lowered. When the (lower end) contacts the insulating solid A ′ of the molten slag A, the wire 19 is slightly loosened, and the electrodes 2, 3 are in close contact with the insulating solid A ′ of the molten slag by their own weight. In addition, the slack of the wire 19 is detected by the load cell 21 and the wire slack detector 23, thereby stopping the driving of the electrode lifting device 18.
[0020]
Thereafter, when the electrodes 2 and 3 are energized, they are energized through the cold starting conductive material A ″ previously provided, and the dissolution of the solid A ′ is started.
Further, when the solid matter is dissolved and the tips of the electrodes 2 and 3 are separated from the solid matter A ′, the electrodes 2 and 3 are lowered by gravity, and when the looseness of the wire 19 is eliminated, the load cell 21 or the like described later is used. When it is detected, the positions of the electrodes 2 and 3 are detected, and if necessary, the wire 19 is continuously drawn out to give the wire 19 a slack, and the tips of the electrodes 2 and 3 are placed on the upper surface of the solid A ′. So that it touches down.
[0021]
By repeating the operation as described above, the solid A ′ is sequentially dissolved in the thickness direction, and when the conductivity between the main electrode 2 and the furnace bottom electrode 4 is ensured, each electrode 2, 3 becomes The operation of the electric furnace is switched to a steady operation state with only the main electrode 2 pulled up.
[0022]
FIG. 4 is a side view showing an outline of the main electrode support device 11, and the auxiliary electrode support device 12 has the same configuration as the main electrode support device 11.
In FIG. 4, 2 is a main electrode, 16 is a frame, 17 is an electrode rod gripping body, 18 is an electrode lifting drive device, 19 is an electrode suspension wire, 20 is a rotary encoder, 21 is a load cell, and 22 is an electrode drop. The prevention device, 23 is a wire slack detector, and 24 is a feed connection conductor.
[0023]
The main electrode 2 (or the auxiliary electrode 3) is moved up and down along the frame 16 by winding up (or unwinding) the electrode rod gripping body 17 with the electrode lifting / lowering driving device 18 via the wire 19. When the tip of the main electrode 2 is in contact with the solid A ′, the wire 19 is slightly slackened. As a result, as the dissolution of the solid A ′ proceeds, the tip of the main electrode 2 descends by the amount of looseness of the wire 19 (that is, the tip of the main electrode 2 descends following the dissolution of the solid A ′). Will do).
[0024]
Further, a load cell 21 is interposed between the tip of the wire 19 and the electrode rod gripping body 17, and when the tip of the main electrode 2 comes into contact with the solid material A ′ and the wire 19 is loosened, the load cell 21 Thus, the slack is detected, whereby the contact of the main electrode 2 with the solid A ′ is detected.
[0025]
Further, the load cell 21 also functions as a protection device for the lifting operation of the electrode rod gripping body 17, and the operation of the electrode lifting drive device 18 is activated when a load exceeding a set value is applied to the load cell 21 for some reason. Stopped.
[0026]
Similarly, the winding amount and the extension amount of the wire 19 are detected by the rotary encoder 20 and input to a control device (not shown).
Further, the amount of slackness of the wire 19 is detected by the wire slackness detector 23 and is input to a control device (not shown) so that the amount of slackness of the wire is regulated to a set value.
[0027]
In the present embodiment, the main electrode support device 11 and the auxiliary electrode support device 12 have a structure mainly composed of a wire suspension mechanism as shown in FIG. An electrode rod gripping body 17 supported on the frame 16 so as to be slidable upward and downward, a screw mechanism (not shown) for slidingly driving the electrode rod gripping body 17 upward and downward, and a drive for rotating the screw mechanism And a change in load current of the rotational drive motor of the screw mechanism that occurs when the tips of the electrodes 2 and 3 come into contact with the upper surface of the solid material A ′ of the molten slag. Detecting and detecting a sudden increase in the load current, the descent operation of the electrode rod gripping body 17 is stopped, and the tips of the electrodes 2 and 3 are held in contact with the solid material A ′ of the molten slag. It is also possible.
[0028]
Furthermore, the main electrode lower limit position restricting mechanism 14 and the auxiliary electrode lower limit position restricting mechanism 15 may be of any configuration. For example, a piezoelectric element (not shown) is provided on the electrode rod gripping body 17. ) Is applied to the electrode rod gripping body 17 via the piezoelectric element, and a contact force between the electrode tip and the molten slag solid A ′ is applied from the change in the electromotive force of the piezoelectric element. It is also possible to stop the electrode rod gripping body 17 from moving downward and hold the electrodes 2 and 3 with their tips in contact with the upper surface of the solid material A ′ of the molten slag. Is possible.
[0029]
Next, an operation method of the electric melting furnace according to the present invention will be described.
Referring to FIG. 1, for some reason, the operation of the electric melting furnace is temporarily stopped with the molten slag A remaining in the furnace body 1, and then the molten slag A inside is solidified. When starting the furnace main body 1 (hereinafter referred to as cold start-up of the electric melting furnace), first, both the main electrode 2 and the auxiliary electrode 3 are lowered, and the respective ends thereof are solids A of the molten slag A. ′ (Insulating solid A ′) is brought into close contact with the upper surface. Also, as shown in FIG. 1A ″, a conductive material A ″ such as iron scrap or carbon powder is placed on the solid material A ′ between the electrodes 2 and 3 to ensure conductivity between the electrodes 2 and 3. To do.
[0030]
Thereafter, the auxiliary electrode 3 and the furnace bottom electrode 4 are connected to the + side of the DC power supply device 5, the main electrode 2 is connected to the + side of the DC power supply device 5, and a DC voltage is applied between the electrodes 2, 3 and 4.
When a DC voltage is applied, a plasma arc is generated near the outer surface of the insulating solid A ′ between the auxiliary electrode 3 and the main electrode 2, and a part of the surface layer portion of the insulating solid A ′ is generated by the generated arc heat. Is melted in a state as shown in FIG. 2 to form a conductive molten slag A.
[0031]
When a part of the insulating solid A ′ is melted to form the molten slag A, the tips of the main electrode 2 and the auxiliary electrode 3 are lowered as shown in FIG. The surface of the insulating solid A ′ is brought into close contact with the surface to continue energization.
The main electrode 2 and the auxiliary electrode 3 are automatically lowered via the main electrode support device 11 and the auxiliary electrode support device 12. The positions of the lower end surfaces of the electrodes 2 and 3 are respectively regulated by a main electrode lower limit position restriction mechanism 14 and an auxiliary electrode lower limit position restriction mechanism 15 provided in the main electrode support device 11 and the auxiliary electrode support device 12, respectively. The electrodes 2 and 3 are automatically held at positions where the lower end surfaces of the electrodes 2 and 3 are in close contact with the outer surface of the insulating solid A ′.
[0032]
The lowering operation of the electrodes 2 and 3 is preferably performed continuously in synchronism with the formation of the molten slag A by melting, but the melt formed intermittently at regular intervals (for example, every 30 minutes). The tips of the electrodes 2 and 3 may be lowered into the slag A.
[0033]
As shown in FIG. 3, even when power is applied between the electrodes 2 and 3 with the tips of the electrodes 2 and 3 positioned inside the molten slag A formed, It has been found that the insulating solid A ′ is sequentially dissolved mainly by the heat generated by the generated plasma arc. That is, a large amount of Joule heat is generated by energization between the electrodes 2 and 3, but in reality, an arc is also generated between the electrodes 2 and 3, and the electrodes 2 and 3 are generated by the plasma gas generated by the generated arc. It has been confirmed that the molten slag liquid surface between 3 is pressed and diffused, and an arc is formed and grows in the space produced by this diffusion.
[0034]
By repeating the lowering of both electrodes 2 and 3 and the energization between both electrodes 2 and 3 as described above, the insulating solid A ′ is sequentially dissolved, and the insulating solid between the main electrode 2 and the furnace bottom electrode 4 is dissolved. When the object A ′ is dissolved by about 100% in the dimension in the thickness direction, the current flowing between the main electrode 2 and the furnace bottom electrode 4 becomes more dominant than the current between the main electrode 2 and the auxiliary electrode 3.
[0035]
For comparison with the above-described conventional example, in a plasma arc melting furnace with a capacity of 9400 KVA, a processing amount of 70 t / day, and a processing object C that is a residue of a refuse incinerator, 100 hours after the operation of the plasma arc melting furnace is stopped. When the thickness of the solid layer of the molten slag A is about 200 mm, the time required for cold start-up of the plasma arc melting furnace (from energization between the auxiliary electrode 3 and the main electrode 2 to the main electrode 2 and the furnace The time until switching to energization between the bottom electrodes 3) was about 4 hours 30 minutes, and the total volume of the dissolved insulating solid A ′ at this time was about 1.5 m ³ .
In the cold start operation of the above example, the number of times the electrodes 2 and 3 were lowered was about 10 times.
[0036]
When comparing the time required for cold start-up between the present invention and the conventional example, in the case of the present invention, the time required for cold start-up is about 30 to 40% of the conventional example ( 4.5h / 12h), and the operation rate of the electric melting furnace can be increased accordingly.
[0037]
In the above embodiment, the case where the present invention is applied to a plasma arc melting furnace of a type in which the plasma generated by the arc discharge is mainly used as the melting heat has been described. Of course, it can also be applied to a furnace.
In the above embodiment, the case where the main electrode 2 and the auxiliary electrode 3 are intermittently lowered has been described. However, both the electrodes are automatically continuously lowered in conjunction with the dissolution of the insulating solid A ′. Of course, it is also possible to make them.
[0038]
【The invention's effect】
In the present invention, in the electric melting furnace for melting municipal waste and garbage incineration residue, the cold start-up operation of the electric melting furnace is carried out with the tips of the main electrode and the auxiliary electrode at the top surface of the insulating solid of the molten slag. In this state, electricity is passed between both electrodes in a state of being in close contact with each other, and these operations are continuously or intermittently performed to dissolve the insulating solid material over a predetermined thickness.
As a result, compared to the conventional cold start-up operation method in this type of electric melting furnace, it is possible to shorten the work time required for cold start-up, and to operate the electric melting furnace. The rate can be greatly improved.
In the present invention, the main electrode supporting device and the auxiliary electrode supporting device are provided with the main electrode lower limit position restricting mechanism and the auxiliary electrode lower limit position restricting mechanism. The electrode can be fixed and held in a state in which each lower end thereof is always in close contact with the surface of the insulating solid. As a result, the two electrodes can be lowered and energized between the two electrodes at the time of cold startup automatically and continuously in conjunction with the dissolution of the insulating solid. The operation of the melting furnace is remarkably facilitated.
The present invention has excellent practical utility as described above.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the overall configuration of a plasma arc melting furnace which is an object of the present invention.
FIG. 2 is a schematic cross-sectional view of a plasma arc melting furnace showing a state in which a part of the insulating solid in the furnace body is melted out by implementing the present invention.
FIG. 3 is a cross-sectional view of a plasma arc melting furnace showing a state where the main electrode and the auxiliary electrode are further lowered and energized because a part of the insulating solid in the furnace body is melted by the practice of the present invention. FIG.
FIG. 4 is a schematic side view of a main electrode support device for a plasma arc melting furnace used in the practice of the present invention.
FIG. 5 is a schematic cross-sectional view showing a conventional plasma arc melting furnace.
FIG. 6 is a schematic cross-sectional view of a plasma arc melting furnace showing an energized state during cold start-up in a conventional plasma arc melting furnace.
[Explanation of symbols]
A is a molten slag, A 'is a molten slag solid (insulating solid), B is a molten metal, C is a molten material, 1 is a furnace body, 2 is a main electrode, 3 is an auxiliary electrode, 4 is a furnace bottom Electrode, 5 DC power supply, 6 plasma arc, 7 current collector, 8 melt input port, 9 slag A inlet, 10 molten metal outlet, 11 main electrode Support device, 12 is an auxiliary electrode support device, 13 is a power distribution board, 14 is a main electrode lower limit position restriction mechanism, 15 is an auxiliary electrode lower limit position restriction mechanism, 16 is a frame body, 17 is an electrode rod gripping body, and 18 is An electrode lifting drive device, 19 is an electrode suspension wire, 20 is a rotary encoder, 21 is a load cell, 22 is an electrode drop prevention device, 23 is a wire slack detector, and 24 is a power supply connection conductor.

Claims

Cooling of a melting furnace that operates a melting furnace in the presence of an insulating solid material of molten slag in an electric melting furnace for melting municipal waste and waste incineration residue having a main electrode, an auxiliary electrode, and a furnace bottom electrode In the intermittent operation, the main electrode and the auxiliary electrode are first lowered to bring the tips of both electrodes into contact with the upper surface of the insulating solid material of the molten slag present inside the furnace body, and then between the electrodes . After disposing a conductive material for cold rising on the insulating solid, a part of the insulating solid is dissolved by energizing between both electrodes, and further a part of the insulating solid is When melting, both electrodes are lowered, and when the main electrode and auxiliary electrode are lowered by the main electrode lower limit position restriction mechanism and auxiliary electrode lower limit position restriction mechanism attached to the main electrode support device and auxiliary electrode support device of the electric melting furnace. Both electrodes have their tips on top of the insulating solid Automatically the held while current between the electrodes to those positions, after dissolving the insulating solid slag between the two electrodes for a predetermined thickness, current between the main electrode and the furnace bottom electrode A method for operating an electric melting furnace, characterized in that:

The method for operating an electric melting furnace according to claim 1, wherein the electric melting furnace is a plasma arc melting furnace or an arc melting furnace.