JP4456563B2 - Chrome-free amorphous refractory for waste melting furnace and waste melting furnace lined with this - Google Patents

Chrome-free amorphous refractory for waste melting furnace and waste melting furnace lined with this Download PDF

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JP4456563B2
JP4456563B2 JP2005504251A JP2005504251A JP4456563B2 JP 4456563 B2 JP4456563 B2 JP 4456563B2 JP 2005504251 A JP2005504251 A JP 2005504251A JP 2005504251 A JP2005504251 A JP 2005504251A JP 4456563 B2 JP4456563 B2 JP 4456563B2
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melting furnace
refractory
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waste melting
alumina
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秀行 津田
浩 北沢
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Krosaki Harima Corp
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Description

【技術分野】
【０００１】
本発明は、ガス化溶融炉、灰溶融炉等の廃棄物溶融炉の内張りに使用するクロムフリー不定形耐火物とこれを内張りした廃棄物溶融炉に関する。
【背景技術】
【０００２】
廃棄物の減容化とダイオキシン発生抑制に優れた廃棄物処理炉として、近年、廃棄物を直接溶融するガス化溶融炉あるいは廃棄物の焼却灰を溶融する灰溶融炉が出現している。
これらの廃棄物溶融炉（以下、溶融炉と称する。）のスラグ成分は、廃棄物成分に由来したアルカリを多く含み、しかも溶融炉の操業は１３００℃以上の超高温である厳しい使用条件によって、それに内張りされる耐火物の損耗が著しい。
溶融炉に使用される耐火物は、定形耐火物と不定形耐火物とに大別される。定形耐火物の施工はレンガ積み作業を伴い、重労働でしかも高度な技術を要する。そこで、近年は不定形耐火物による内張りが汎用されている。
【０００３】
従来、溶融炉用に使用されている不定形耐火物は、アルミナ−酸化クロム質（例えば特開平１０−３２４５６２号公報参照）に代表される酸化クロム含有品である。この材質は、アルミナの耐火性・容積安定性と酸化クロムの耐スラグ性とが相まって優れた耐食性を示す。しかし、耐火物成分の一部である酸化クロムが人体に有害な六価クロムに変化し、炉から排出されるスラグおよび使用後の耐火物が環境汚染をきたす問題がある。
【０００４】
そこで、溶融炉用不定形耐火物として、実質的に酸化クロム原料を含まないクロムフリー材質が提案されている。例えば、アルミナ−ジルコニア質（例えば特開２０００−２８１４５５号公報参照）、アルミナ−マグネシア質（例えば特開２００１−１５３３２１号公報参照）、アルミナ−炭化珪素質（例えば特開２０００−２０３９５２号公報参照）である。
しかし、上記従来のクロムフリー材質は溶融炉としての使用において、その耐用性は酸化クロム含有品に比べて大きく劣る。溶融炉のスラグが多アルカリのため、アルミナ−ジルコニア質あるいはアルミナ−マグネシア質は、ジルコニア成分・マグネシア成分がスラグ中に溶出し、耐食性に劣る。アルミナ−炭化珪素質は、溶融炉の操業が酸化雰囲気のため炭化珪素成分が酸化分解し、耐食性の低下が著しい。
【発明の開示】
【発明が解決しようとする課題】
【０００５】
本発明は溶融炉の内張りとして、酸化クロム含有品相当の優れた耐用性のクロムフリー質不定形耐火物と、これを内張りした溶融炉を提供することを課題とする。
【課題を解決するための手段】
【０００６】
本発明の廃棄物溶融炉用クロムフリー不定形耐火物は、耐火性原料が粒径４５μｍ以下のイットリア質原料と超微粉としての仮焼アルミナを含む主材のアルミナ質原料とからなり、化学分析値でＹ２Ｏ３：１．１〜１５質量％、Ａｌ２Ｏ３：８５質量％以上の組成を有する。
【０００７】
前記従来のクロムフリー材質は、アルミナに相当量のジルコニア、マグネシアあるいは炭化珪素を組み合わせている。これに対し本発明は、アルミナ主材の材質に特定量のイットリア質原料を含んだものである。これにより、クロムフリー材質にもかかわらず、溶融炉用の内張りとして優れた耐用性を発揮する。その理由は以下のとおりと考えられる。
【０００８】
廃棄物溶融炉は操業中にアルカリ（Ｎａ２Ｏ＋Ｋ２Ｏ）：１．５〜１５質量％を含むスラグが炉内を通過する。溶融炉スラグは、前記のとおり多アルカリでしかも炉操業温度が超高温であることによって、溶融時の粘性がきわめて低い。また、アルカリは耐火物に対し激しい侵食作用をもつ。従来のクロムフリー不定形耐火物は、溶融炉スラグは粘性が低いことで耐火物組織にアルカリ成分が深く浸透し、耐火物の耐用性を大きく低下させる。
【０００９】
これ対し本発明の耐火物は、特定量のイットリア質原料と、アルミナ質原料との組み合わせにより、耐火物使用中の高温下でイットリア質原料のＹ２Ｏ３成分がアルミナ質原料のＡｌ２Ｏ３成分と反応し、分子量の大きなＹＡＧ（イットリウム・アルミニウム・ガーネット：Ｙ３Ａｌ５Ｏ１２）を生成させ、耐火物のマトリックスを緻密化する。
【００１０】
さらに本発明の耐火物は、イットリア質原料のＹ２Ｏ３成分が溶融炉スラグとの反応により、耐火物稼動面と接するスラグの粘性が高くなってスラグ浸透が防止され、しかもスラグと耐火物の反応速度が遅くなることで、耐火物の侵食が抑制される。
【００１１】
耐火物の耐用性向上の要素には耐食性の他、耐スポーリング性がある。溶融炉の操業温度は１３００℃以上の超高温で、しかも溶融炉の炉壁は一般に水冷構造が採用されている。このため耐火物は使用時において、炉壁厚さ方向に対する温度勾配がきわめて大きくなり、スポーリングが生じ易い。
【００１２】
本発明の耐火物は、Ａｌ２Ｏ３含有量が８５質量％以上と多いためにＡｌ２Ｏ３成分自身がもつ容積安定性に優れている。しかも、前記したＹＡＧの生成によるマトリックスを緻密化によって耐火物組織が低気孔率化し、熱伝度率が高い。これにより、本発明の耐火物は使用時において炉壁厚さ方向に対する温度勾配が小さくなり、耐スポーリング性においても優れた効果を発揮する。
【００１３】
また、本発明の耐火物に含むイットリア質原料からのＹ２Ｏ３成分は、多アルカリの溶融炉スラグに対して溶解度が低い性質がある。このため、耐火物マトリックスからのＹ２Ｏ３成分の過度の溶出がなく、Ｙ２Ｏ３成分によるスラグ粘性向上による耐食性向上の効果が持続する。
【００１４】
スラグ粘性の向上によるスラグ浸透防止の効果は、従来のアルミナ−酸化クロム質耐火物おける酸化クロム成分と同じである。しかし、酸化クロム成分はイットリア質原料と違って環境汚染の問題があり、本発明のクロムフリー材質としての環境汚染防止の効果は得られない。
【００１５】
本発明は、イットリア質原料として富イットリウム混合希土酸化物を使用してもよい。この富イットリウム混合希土酸化物が化学成分値で、主成分のＹ２Ｏ３以外に、Ｇｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３から選ばれる一種以上を５〜３５質量％含む場合は、溶融炉特有の多アルカリスラグに対する耐食性および耐スラグ浸透性が一段と向上する。これは以下の理由によるものと考えられる。
【００１６】
耐火物使用中の高温下において、富イットリウム混合希土酸化物中のＧｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３の成分はＹ２Ｏ３と同様にアルミナ原料のＡｌ２Ｏ３成分と反応し、分子量の大きなガーネット構造をとるＹ３Ａｌ５Ｏ１２，Ｅｒ３Ａｌ５Ｏ１２，Ｄｙ３Ａｌ５Ｏ１２，Ｙｂ３Ａｌ５Ｏ１２を生成する。また、Ｇｄ２Ｏ３はＡｌ２Ｏ３との反応でペロブスカイト構造をとるＧｄ２Ａｌ２Ｏ６となる。そして、この分子量の大きなガーネット構造あるいはペロブスカイト構造は耐火物組織を緻密化させ、しかもＧｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３自身が耐アルカリ性に優れていることによって、耐食性を向上させる。
【００１７】
また、主成分のＹ２Ｏ３以外に、Ｇｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３から選ばれる一種以上を５〜３５質量％含むこの富イットリウム混合希土酸化物は、Ｙ２Ｏ３純度の高いイットリアに比べてアルミナ原料のＡｌ２Ｏ３成分との反応が早く、耐火物は使用時の温度が低い稼動面後方の組織をも十分に緻密化し、耐スラグ浸透性がより一層向上する。
【００１８】
本発明に使用するイットリア質原料の具体例は以上のイットリア、富イットリウム混合希土酸化物などから選ばれる一種以上である。Ｙ２Ｏ３純度は限定されるものではなく、例えばＹ２Ｏ３純度が７０質量％程度のものであっても特段の弊害成分を含んでいなければ使用できるが、品質の安定した高純度品の使用が好ましい。Ｇｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３から選ばれる一種以上を５〜３５質量％含む富イットリウム混合希土酸化物では、Ｙ２Ｏ３純度の下限は例えば５０質量％でもよい。
【００１９】
イットリア質原料の使用量は、不定形耐火物組成全体の化学成分値でＹ２Ｏ３：１．１〜１５質量％となるように調整する。Ｙ２Ｏ３の割合がこれより少ないと本発明の耐食性、耐スラグ浸透性、耐スポーリング性の効果が得られず、多過ぎるとＹ２Ｏ３とＡｌ２Ｏ３との反応生成物が増え、緻密化が過多となって耐スポーリング性が低下する。
【００２０】
化学成分値でＹ２Ｏ３の割合をこの範囲にするには、イットリア質原料の使用量とＹ２Ｏ３純度との調整で行うことができる。高純度イットリアを使用した場合は、実質的にイットリア質原料の使用量そのままが化学成分値でのＹ２Ｏ３の割合となる。
【００２１】
富イットリウム混合希土酸化物はＹ２Ｏ３以外にＧｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３から選ばれる一種以上を含む原料である。合成品、粗精希土類酸化物より得ることができるが、経済面で粗精希土類酸化物が好ましい。
【００２２】
粗精希土類酸化物は、希土類鉱石から希土類元素を精製する途中過程の原料である。例えば、ゼノタイム〔Ｙ（ＰＯ４）〕等のＹ２Ｏ３を主成分とした希土類鉱石を酸、アルカリ処理により、燐、アルカリ土類金属等を除去して得たものである。
【００２３】
富イットリウム混合希土酸化物は、化学成分値でＧｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３から選ばれる一種以上を５〜３５質量％、さらに好ましくは１０〜３０質量％含むことが好ましい。Ｇｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３から選ばれる一種以上が５質量％未満では耐食性、耐スラグ浸透性においてＹ２Ｏ３純度の高いイットリアの使用と特に変わりなく、３５質量％を超えるとＹ２Ｏ３の割合が少なくなるために耐食性に劣る。
【００２４】
富イットリウム混合希土酸化物において、Ｙ２Ｏ３の割合は５０質量％以上が好ましく、さらに好ましくは６０質量％以上である。Ｙ２Ｏ３の上限割合はＧｄ２Ｏ３、Ｅｒ２Ｏ３、Ｄｙ２Ｏ３、Ｙｂ２Ｏ３が占める割合から自ずから定まり、特に限定するものではないが、例えば９５質量％、あるいは９０質量％とする。
【００２５】
また、粗精希土酸化物は鉱石から不可避的にＮｄ２Ｏ３、Ｌａ２Ｏ３、ＣｅＯ２の成分が含まれることがある。この成分は不定形耐火物施工時の施工水と反応し、施工体乾燥時に消化に伴う膨張によって耐火物組織のぜい弱化の原因となる。一方、ＣｅＯ２は多アルカリの溶融炉スラグに溶解しやすい。そこで、粗精希土酸化物はＮｄ２Ｏ３、Ｌａ２Ｏ３、ＣｅＯ２の一種以上が１５質量％以下であることが好ましい。
【００２６】
イットリア質原料の粒径はアルミナとの反応性を高めるために４５μｍ以下とする。耐火性原料組成の主材となるアルミナ質原料は、超微粉としての仮焼アルミナを含む。それ以外は、電融アルミナ、焼結アルミナ、ボーキサイト、あるいはこれらを主原料とした耐火物のリサイクル品のいずれでもよい。これらを粗粒、中粒、微粒に適宜調整して使用する。
【００２７】
アルミナ質原料の使用量は、不定形耐火物組成全体に占める化学分析値でＡｌ２Ｏ３：８５質量％以上になるように調整する。Ａｌ２Ｏ３の割合がこの範囲より少ないと本発明の耐食性および耐スポーリング性の効果が得られない。Ａｌ２Ｏ３のさらに好まし割合は９０〜９９．７質量％である。
【００２８】
アルミナ質原料のＡｌ２Ｏ３成分を前記の割合にするのは、主としてアルミナ質原料のＡｌ２Ｏ３純度とその使用割合とによって定めることができる。例えば高純度アルミナを使用した場合は、実質的にアルミナ質原料の使用量そのままが化学成分値でのＡｌ２Ｏ３割合となる。
【００２９】
後述する結合剤に、アルミナセメントを使用した場合は、わずかではあるがアルミナセメントからもＡｌ２Ｏ３成分が供給される。アルミナセメントは一般にＡｌ２Ｏ３：５５〜８０質量％含んでいる。本発明で規定するＡｌ２Ｏ３の割合は不定形耐火物組成全体に占めるものであり、このアルミナセメントからのＡｌ２Ｏ３成分量も含めての数値である。
結合剤と必要により添加する分散剤は、従来材質に使用されるものと特に変わりない。結合剤は前記したアルミナセメント以外にも、リン酸塩、珪酸塩等が挙げられる。施工体強度の面からアルミナセメントが好ましい。この結合剤の使用量は、耐火性原料組成と結合剤との合計量１００質量％に占める割合で１〜１０質量％が好ましい。
【００３０】
分散剤は不定形耐火物施工時の流動性を付与する効果をもつ。分散剤の材質は従来から種々のものが提案されている。分散剤の種類は限定されるものではなく、例えばトリポリリン酸ソーダ、ヘキサメタリン酸ソーダ、ウルトラポリリン酸ソーダ、酸性ヘキサメタリン酸ソーダ、ホウ酸ソーダ、炭酸ソーダ、ポリメタリン酸塩などの無機塩、クエン酸ソーダ、酒石酸ソーダ、ポリアクリル酸ソーダ、スルホン酸ソーダ、ポリカルボン酸塩、β−ナフタレンスルホン酸塩類、ナフタレンスルホン酸、カルボキシル基含有ポリエーテル系分散剤等である。その添加量は耐火性原料と結合剤の合計量１００質量部に対し、０．０１〜１質量部が好ましい。
【００３１】
施工には以上の不定形耐火物組成１００質量部に対し水分を３〜７質量部程度添加して混練し、型枠を用いて流し込み施工する。流し込みの際には振動を付与して充填を図る。施工後は養生・乾燥させる。この施工は炉に直接流し込み施工する他、別の場所で流し込み施工して得た成形体を炉に内張するプレキャスト施工でもよい。また流し込み施工とプレキャスト施工の組み合わせでも良い。
【００３２】
なお、本発明でいうクロムフリーとは、酸化クロムを実質的に含まないことを意味する。従来一般的な酸化クロム含有品は酸化クロムを５〜６０質量％含んでいる。酸化クロムは例え１質量％以下でも環境汚染の問題が生じる。クロムフリーの効果を得るには、酸化クロムを不可避的以外に含まないことが好ましい。
【００３３】
溶融炉は一般に冷却装置が設けられる。冷却装置は例えば水冷管、水冷ジャケット、空冷ジャケット、散水装置などの配設である。本発明による不定形耐火物は、その耐スポーリング性の効果によって、特にこの冷却装置を備えた溶融炉の内張りとして好適である。
【発明を実施するための最良の形態】
【００３４】
以下に本発明実施例およびその比較例を説明する。同時に各例の試験結果を示す。表１は各例で使用した耐火性原料の化学成分、表２は本発明実施例、表３はその比較例である。
【００３５】
【表１】

Figure 0004456563
【００３６】
【表２】
Figure 0004456563
【００３７】
【表３】
Figure 0004456563
【００３８】
各例は、表２、表３に示す不定形耐火物組成をミキサーにて混練した後、金属製の型枠に流し込んだ。流し込みの際には型枠に振動を付与し、施工体の充填を促進した。ついで２４時間養生し、脱型後、さらに１１０℃×２４時間乾燥した。
【００３９】
耐食性は、前記条件で２３０ｍｍ×１１４ｍｍ×６５ｍｍの並形れんがサイズに施工して得た成形体を試料とし、回転侵食試験で行った。侵食剤として化学成分値がＳｉＯ２：４２．８質量％、ＣａＯ：３１．７質量％、Ａｌ２Ｏ３：１２．４質量％、Ｆｅ２Ｏ３：４．８質量％、Ｎａ２Ｏ：３．７質量％、Ｋ２Ｏ：１．１質量％、Ｃｌ：０．９質量％、（ＣａＯ／ＳｉＯ２：０．７４）のガス化溶融炉スラグを使用した。１６００℃×３０時間侵食させた後、侵食寸法を測定した。
【００３９】
耐スポーリング性は、前記と同様、並形れんがのサイズに施工して得た成形体を試料とした。長さ方向に対する片面を電気炉にて１４００℃×１５分間加熱した後、強制空冷し、この加熱−冷却を１０回繰り返した後、試料の亀裂発生状況から次の４段階で評価した。◎…亀裂殆どなし。○…微細亀裂の発生。△…亀裂が大きい。×…亀裂が極めて大きいか又は剥離。
【００４０】
実機試験として、一日あたりのごみ処理量が１００ｔの、側壁に水冷装置を備えたガス化溶融炉に内張りした。１２ヶ月間の使用後において損耗速度（ｍｍ／月）を測定した。操業温度は約１４００℃。
【００４１】
試験結果が示すとおり、本発明の実施例による不定形耐火物はいずれも耐食性、耐スポーリング性共に優れている。表には示していないが、稼動面でのスラグ浸透が少なく、これも耐食性向上の効果に寄与していると思われる。また、イットリア質原料として富イットリウム混合希土酸化物を使用した実施例は、耐食性において一段と優れている。
【００４２】
これに対し、イットリア質原料を含まない比較例１はスラグ浸透が大きく、耐食性に劣る。Ｙ２Ｏ３成分が本発明の限定範囲より多い比較例２及び比較例４はいずれも耐食性および耐スポーリング性に劣る。アルミナ含有量の少ない比較例３と、Ａｌ２Ｏ３含有量が本発明で限定した範囲より少なく、しかもイットリア質原料を含まない比較例５についても耐食性、耐スポーリング性に劣る。
【００４３】
ジルコニアを含みＡｌ２Ｏ３含有量が本発明の限定範囲より少ない比較例６、炭化珪素を含みＡｌ２Ｏ３含有量が本発明の限定範囲より少ない比較例７は、いずれも耐食性に大きく劣る。
【００４４】
比較例８は酸化クロムを多量に含むことで耐食性に優れるものの、六価クロムの生成の問題があり、環境上の問題からクロムフリーとしての本発明の効果が得られない。また、耐スポーリング性に劣ることで側壁に水冷装置を備えた溶融炉への使用はスポーリング損傷が懸念される。
【００４５】
実機試験において、本発明実施例１、５は比較例６のアルミナ−ジルコニア質、比較例７のアルミナ−炭化珪素質に比べ、耐用性が格段に優れている。
【００４６】
本発明実施例１、５は、比較例８のアルミナ−酸化クロム質に対して耐食性に若干劣るが、耐スポーリング性に優れるためか、実機試験での耐用性は大差がない。
【００４７】
図１は実施例１の不定形耐火物組成をベースに成形体のＹ２Ｏ３成分の量を変化させ（Ｙ２Ｏ３量に合わせてＡｌ２Ｏ３を増減）、Ｙ２Ｏ３量と耐火物の耐食性との関係を示したグラフである。このグラフ結果から、Ｙ２Ｏ３の割合が本発明の範囲内のものが耐食性に優れていることが確認される。
【００４８】
廃棄物処理炉は焼却炉と違って高温操業であり、しかもその耐火物の損耗機構は廃棄物成分に由来する多アルカリスラグに起因した廃棄物処理炉特有のものである。本発明の不定形耐火物は以上の実施例の試験結果が示すように、廃棄物処理炉用の不定形耐火物として、クロムフリー材質であるにもかかわらず、酸化クロム含有品に匹敵する耐用性を発揮する。
【産業上の利用可能性】
【００４９】
廃棄物溶融炉はガス化溶融炉あるいは灰溶融炉が知られている。本発明にかかるクロムフリー不定形耐火物は、この廃棄物溶融炉の内張り材として使用する。
【図面の簡単な説明】
【００５０】
【図１】不定形耐火物組成に占めるＹ２Ｏ３量と、不定形耐火物の耐食性との関係を示したグラフである。【Technical field】
[0001]
The present invention relates to a chromium-free amorphous refractory used for the lining of a waste melting furnace such as a gasification melting furnace or an ash melting furnace, and a waste melting furnace with the lining thereof.
[Background]
[0002]
In recent years, gasification melting furnaces for directly melting waste or ash melting furnaces for melting incineration ash of waste have emerged as waste processing furnaces excellent in volume reduction of waste and suppression of dioxin generation.
The slag component of these waste melting furnaces (hereinafter referred to as melting furnaces) contains a large amount of alkali derived from the waste components, and the operation of the melting furnace is extremely high temperature of 1300 ° C. or higher due to severe use conditions. The wear of the refractory lining it is significant.
The refractories used in the melting furnace are roughly classified into regular refractories and irregular refractories. The construction of regular refractories involves brickwork and is labor intensive and requires advanced technology. In recent years, therefore, lining with an irregular refractory has been widely used.
[0003]
Conventionally, amorphous refractories used for melting furnaces are chromium oxide-containing products represented by alumina-chromium oxide (see, for example, JP-A-10-324562). This material exhibits excellent corrosion resistance in combination with the fire resistance and volume stability of alumina and the slag resistance of chromium oxide. However, there is a problem that chromium oxide, which is a part of the refractory component, is changed to hexavalent chromium harmful to the human body, and the slag discharged from the furnace and the refractory after use cause environmental pollution.
[0004]
Then, the chromium free material which does not contain a chromium oxide raw material substantially as an amorphous refractory for melting furnaces is proposed. For example, alumina-zirconia (see, for example, JP-A-2000-281455), alumina-magnesia (see, for example, JP-A-2001-153321), alumina-silicon carbide (see, for example, JP-A-2000-203952) It is.
However, the above-mentioned conventional chromium-free material is greatly inferior in durability to a chromium oxide-containing product when used as a melting furnace. Since the slag of the melting furnace is multi-alkali, the alumina-zirconia or alumina-magnesia is inferior in corrosion resistance because the zirconia component / magnesia component is eluted in the slag. In the case of alumina-silicon carbide, since the operation of the melting furnace is an oxidizing atmosphere, the silicon carbide component is oxidatively decomposed and the corrosion resistance is remarkably lowered.
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0005]
It is an object of the present invention to provide an excellent durable chromium-free amorphous refractory equivalent to a chromium oxide-containing product as a lining of a melting furnace and a melting furnace lining the same.
[Means for Solving the Problems]
[0006]
Waste melting furnace for chrome-free monolithic refractory of the present invention, the refractory material consists of an alumina raw material of the main material containing calcined alumina as yttria material and ultrafine powder having a particle size 45 [mu] m, chemical analysis It has a composition of Y 2 O 3 : 1.1 to 15% by mass and Al 2 O 3 : 85% by mass or more.
[0007]
In the conventional chromium-free material, a considerable amount of zirconia, magnesia or silicon carbide is combined with alumina. On the other hand, the present invention includes a specific amount of yttria-based material in the material of the alumina main material. This demonstrates excellent durability as a lining for the melting furnace despite the chromium-free material. The reason is considered as follows.
[0008]
During the operation of the waste melting furnace, slag containing alkali (Na 2 O + K 2 O): 1.5 to 15% by mass passes through the furnace. As described above, the melting furnace slag has a very low viscosity at the time of melting because it is multi-alkali and has an extremely high furnace operating temperature. Alkali also has a severe erosion effect on refractories. In the conventional chrome-free amorphous refractory, the melting furnace slag has a low viscosity, so that the alkali component penetrates deeply into the refractory structure, greatly reducing the durability of the refractory.
[0009]
On the other hand, the refractory of the present invention is a combination of a specific amount of yttria raw material and alumina raw material, so that the Y 2 O 3 component of the yttria raw material is Al 2 O of the alumina raw material at a high temperature while using the refractory. It reacts with the three components to generate YAG (yttrium / aluminum / garnet: Y 3 Al 5 O 12 ) having a large molecular weight, thereby densifying the refractory matrix.
[0010]
Furthermore, the refractory according to the present invention is such that the Y 2 O 3 component of the yttria-based raw material reacts with the melting furnace slag to increase the viscosity of the slag in contact with the refractory operating surface and prevent slag infiltration, and the slag and refractory Since the reaction rate of is slow, erosion of the refractory is suppressed.
[0011]
In addition to corrosion resistance, spalling resistance is one of the factors that improve the durability of refractories. The operation temperature of the melting furnace is an ultra-high temperature of 1300 ° C. or more, and the furnace wall of the melting furnace generally adopts a water cooling structure. For this reason, when the refractory is used, the temperature gradient with respect to the thickness direction of the furnace wall becomes extremely large, and spalling is likely to occur.
[0012]
Since the refractory according to the present invention has an Al 2 O 3 content as high as 85% by mass or more, the Al 2 O 3 component itself has excellent volume stability. In addition, the refractory structure has a low porosity by densifying the matrix formed by the above-described YAG, and the thermal conductivity is high. As a result, the refractory according to the present invention has a small temperature gradient with respect to the thickness direction of the furnace wall during use, and exhibits excellent effects in spalling resistance.
[0013]
In addition, the Y 2 O 3 component from the yttria raw material included in the refractory of the present invention has a property of low solubility with respect to a multi-alkali melting furnace slag. For this reason, there is no excessive elution of the Y 2 O 3 component from the refractory matrix, and the effect of improving the corrosion resistance by improving the slag viscosity by the Y 2 O 3 component is sustained.
[0014]
The effect of preventing slag penetration by improving the slag viscosity is the same as the chromium oxide component in the conventional alumina-chromium oxide refractory. However, unlike yttria-based materials, the chromium oxide component has a problem of environmental pollution, and the effect of preventing environmental pollution as the chromium-free material of the present invention cannot be obtained.
[0015]
In the present invention, a yttrium rich rare earth oxide may be used as a yttria-based raw material. This yttrium-rich rare earth oxide has a chemical component value, and in addition to Y 2 O 3 as a main component, 5 or more selected from Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 When it is contained in an amount of 35% by mass, the corrosion resistance and slag penetration resistance to the multi-alkali slag unique to the melting furnace are further improved. This is thought to be due to the following reasons.
[0016]
The components of Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 in the yttrium-rich mixed rare earth oxide are the same as Y 2 O 3 at a high temperature while using the refractory. It reacts with the Al 2 O 3 component to produce Y 3 Al 5 O 12 , Er 3 Al 5 O 12 , Dy 3 Al 5 O 12 , Yb 3 Al 5 O 12 having a large molecular weight garnet structure. Gd 2 O 3 becomes Gd 2 Al 2 O 6 having a perovskite structure by reaction with Al 2 O 3 . The garnet structure or perovskite structure having a large molecular weight densifies the refractory structure, and Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 itself are excellent in alkali resistance. , Improve corrosion resistance.
[0017]
In addition to Y 2 O 3 as a main component, this yttrium rich rare earth oxidation containing 5 to 35% by mass of one or more selected from Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 and Yb 2 O 3 Compared to yttria with a high purity of Y 2 O 3 , the product reacts faster with the Al 2 O 3 component of the alumina raw material, and the refractory has sufficiently refined the structure behind the working surface where the temperature during use is low. Slag permeability is further improved.
[0018]
Specific examples of the yttria-based raw material used in the present invention are one or more selected from the above yttria, yttrium-rich mixed rare earth oxides, and the like. The purity of Y 2 O 3 is not limited. For example, even if the purity of Y 2 O 3 is about 70% by mass, it can be used as long as it does not contain any special harmful components. The use of products is preferred. In the yttrium-rich mixed rare earth oxide containing 5 to 35% by mass of one or more selected from Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 , the lower limit of Y 2 O 3 purity is, for example, 50 It may be mass%.
[0019]
The amount of the yttria-based material used is adjusted so that the chemical component value of the entire amorphous refractory composition is Y 2 O 3 : 1.1 to 15% by mass. If the proportion of Y 2 O 3 is less than this, the effects of the corrosion resistance, slag penetration resistance and spalling resistance of the present invention cannot be obtained, and if it is too much, a reaction product of Y 2 O 3 and Al 2 O 3 is produced. Increased, densification becomes excessive, and spalling resistance decreases.
[0020]
In order to make the ratio of Y 2 O 3 within this range in terms of chemical component values, it can be carried out by adjusting the amount of yttria raw material used and the Y 2 O 3 purity. When high-purity yttria is used, the used amount of the yttria-based raw material is substantially the ratio of Y 2 O 3 in terms of chemical component values.
[0021]
The yttrium-rich rare earth oxide is a raw material containing at least one selected from Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 and Yb 2 O 3 in addition to Y 2 O 3 . Although it can be obtained from a synthetic product or a crude rare earth oxide, a crude rare earth oxide is preferred in terms of economy.
[0022]
Crude rare earth oxide is a raw material in the middle of refining rare earth elements from rare earth ores. For example, a rare earth ore mainly composed of Y 2 O 3 such as xenotime [Y (PO 4 )] is obtained by removing phosphorus, alkaline earth metal, and the like by acid and alkali treatment.
[0023]
The yttrium-rich rare earth oxide is 5 to 35% by mass, more preferably 10 to 30% of one or more selected from Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 and Yb 2 O 3 in terms of chemical component values. It is preferable to contain the mass%. If at least one selected from Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 is less than 5% by mass, it is particularly different from the use of yttria having high Y 2 O 3 purity in corrosion resistance and slag penetration resistance. If the amount exceeds 35% by mass, the proportion of Y 2 O 3 decreases, resulting in poor corrosion resistance.
[0024]
In the yttrium-rich rare earth oxide, the proportion of Y 2 O 3 is preferably 50% by mass or more, and more preferably 60% by mass or more. The upper limit ratio of Y 2 O 3 is naturally determined from the ratio of Gd 2 O 3 , Er 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 , and is not particularly limited. For example, 95% by mass or 90% by mass %.
[0025]
The crude rare earth oxide may inevitably contain components of Nd 2 O 3 , La 2 O 3 , and CeO 2 from the ore. This component reacts with the construction water at the time of construction of the irregular refractory, and causes a weakening of the refractory structure due to expansion accompanying digestion when the construction body is dried. On the other hand, CeO 2 is easily dissolved in a multi-alkali melting furnace slag. Accordingly, the crude rare earth oxide preferably contains 15% by mass or less of one or more of Nd 2 O 3 , La 2 O 3 , and CeO 2 .
[0026]
The particle size of the yttria-containing material to 45μm or less in order to enhance the reactivity with alumina. The alumina raw material that is the main material of the refractory raw material composition includes calcined alumina as ultrafine powder. Other than that, any of fused alumina, sintered alumina, bauxite, or recycled refractories using these as main raw materials may be used. These are used by appropriately adjusting to coarse grains, medium grains and fine grains.
[0027]
The amount of the alumina raw material used is adjusted so that the chemical analysis value in the entire amorphous refractory composition is Al 2 O 3 : 85% by mass or more. When the proportion of Al 2 O 3 is less than this range, the effects of the corrosion resistance and spalling resistance of the present invention cannot be obtained. A more preferable ratio of Al 2 O 3 is 90 to 99.7% by mass.
[0028]
The ratio of the Al 2 O 3 component of the alumina raw material can be determined mainly by the Al 2 O 3 purity of the alumina raw material and its use ratio. For example, when high-purity alumina is used, the used amount of the alumina raw material is substantially the Al 2 O 3 ratio in terms of chemical component values.
[0029]
When alumina cement is used for the binder described later, the Al 2 O 3 component is also supplied from the alumina cement, though only slightly. Alumina cement generally contains Al 2 O 3 : 55-80% by mass. The proportion of Al 2 O 3 specified in the present invention is a value including the amount of Al 2 O 3 component from the alumina cement, which occupies the entire amorphous refractory composition.
The binder and the dispersant added if necessary are not particularly different from those used for conventional materials. Examples of the binder include phosphate and silicate in addition to the above-mentioned alumina cement. Alumina cement is preferable from the viewpoint of the strength of the construction body. The amount of the binder used is preferably 1 to 10% by mass in a proportion of 100% by mass of the total amount of the refractory raw material composition and the binder.
[0030]
The dispersant has the effect of imparting fluidity during construction of the irregular refractory. Various materials for the dispersant have been proposed. The type of the dispersant is not limited. For example, sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate, sodium carbonate, polymetaphosphate, etc., sodium citrate, Examples thereof include sodium tartrate, sodium polyacrylate, sodium sulfonate, polycarboxylate, β-naphthalenesulfonate, naphthalenesulfonate, a carboxyl group-containing polyether dispersant, and the like. The addition amount is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the total amount of the refractory raw material and the binder.
[0031]
For the construction, about 3 to 7 parts by mass of water is added to 100 parts by mass of the above-mentioned amorphous refractory composition, and the mixture is kneaded and cast using a mold. When pouring, filling is performed by applying vibration. Curing and drying after construction. This construction may be performed by pouring directly into the furnace, or may be precast construction in which a molded product obtained by casting at another place is lined in the furnace. Also, a combination of casting construction and precast construction may be used.
[0032]
The term “chromium-free” as used in the present invention means that chromium oxide is not substantially contained. Conventionally, a general chromium oxide-containing product contains 5 to 60% by mass of chromium oxide. Even if chromium oxide is 1% by mass or less, there is a problem of environmental pollution. In order to obtain a chromium-free effect, it is preferable not to contain chromium oxide other than unavoidable.
[0033]
A melting furnace is generally provided with a cooling device. The cooling device is, for example, a water cooling tube, a water cooling jacket, an air cooling jacket, a watering device, or the like. The amorphous refractory according to the present invention is particularly suitable as a lining of a melting furnace equipped with this cooling device because of its spalling resistance effect.
BEST MODE FOR CARRYING OUT THE INVENTION
[0034]
Examples of the present invention and comparative examples thereof will be described below. At the same time, the test results of each example are shown. Table 1 shows chemical components of the refractory raw materials used in each example, Table 2 shows examples of the present invention, and Table 3 shows comparative examples.
[0035]
[Table 1]
Figure 0004456563
[0036]
[Table 2]
Figure 0004456563
[0037]
[Table 3]
Figure 0004456563
[0038]
In each example, the amorphous refractory compositions shown in Tables 2 and 3 were kneaded with a mixer and then poured into a metal mold. When pouring, the formwork was vibrated to promote the filling of the construction body. Subsequently, it was cured for 24 hours, and after demolding, it was further dried at 110 ° C. for 24 hours.
[0039]
Corrosion resistance was measured by a rotary erosion test using a molded product obtained by constructing 230 mm × 114 mm × 65 mm parallel bricks under the above conditions as a sample. Chemical component values as the erodant are SiO 2 : 42.8 mass%, CaO: 31.7 mass%, Al 2 O 3 : 12.4 mass%, Fe 2 O 3 : 4.8 mass%, Na 2 O: A gasification melting furnace slag of 3.7% by mass, K 2 O: 1.1% by mass, Cl: 0.9% by mass, (CaO / SiO 2 : 0.74) was used. After erosion at 1600 ° C. for 30 hours, the erosion dimension was measured.
[0039]
As for the spalling resistance, a molded body obtained by applying to the size of an ordinary brick was used as a sample as described above. One side in the length direction was heated at 1400 ° C. for 15 minutes in an electric furnace, then forced air cooling was performed, and this heating-cooling was repeated 10 times. ◎… There are almost no cracks. ○: Generation of fine cracks. Δ: Large cracks. X: Cracks are extremely large or peeling.
[0040]
As an actual machine test, the lining was placed in a gasification melting furnace having a water-cooling device on the side wall with a daily waste treatment amount of 100 t. The wear rate (mm / month) was measured after 12 months of use. The operating temperature is about 1400 ° C.
[0041]
As the test results show, the amorphous refractories according to the examples of the present invention are excellent in both corrosion resistance and spalling resistance. Although not shown in the table, there is little slag penetration on the operation side, which seems to contribute to the effect of improving corrosion resistance. Moreover, the Example which uses a yttrium rich rare earth oxide as a yttria quality raw material is much more excellent in corrosion resistance.
[0042]
On the other hand, the comparative example 1 which does not contain a yttria-like raw material has large slag penetration, and is inferior to corrosion resistance. Both Comparative Example 2 and Comparative Example 4 having more Y 2 O 3 components than the limited range of the present invention are inferior in corrosion resistance and spalling resistance. Comparative Example 3 having a low alumina content and Comparative Example 5 having an Al 2 O 3 content less than the range defined in the present invention and also containing no yttria-based material are also inferior in corrosion resistance and spalling resistance.
[0043]
Al 2 O 3 content less Comparative Example 6 than the limited range of the present invention comprises zirconia, Al 2 O 3 content less Comparative Example 7 than the limited range of the present invention comprises a silicon carbide are all significantly inferior in corrosion resistance .
[0044]
Although Comparative Example 8 contains a large amount of chromium oxide and is excellent in corrosion resistance, there is a problem of hexavalent chromium formation, and the effect of the present invention as chromium-free cannot be obtained due to environmental problems. Moreover, since it is inferior in spalling resistance, there is a concern that spalling damage is caused when it is used in a melting furnace having a water cooling device on the side wall.
[0045]
In the actual machine test, Examples 1 and 5 of the present invention have much superior durability compared to the alumina-zirconia of Comparative Example 6 and the alumina-silicon carbide of Comparative Example 7.
[0046]
Inventive Examples 1 and 5 are slightly inferior in corrosion resistance to the alumina-chromium oxide of Comparative Example 8, but the durability in the actual machine test is not much different because of excellent spalling resistance.
[0047]
1 (or decrease the Al 2 O 3 in accordance with the Y 2 O 3 amount) monolithic refractory composition based on varying amounts of Y 2 O 3 component of the molded product of Example 1, Y 2 O 3 amount It is the graph which showed the relationship between the corrosion resistance of refractories. From this graph result, it is confirmed that the Y 2 O 3 ratio within the range of the present invention is excellent in corrosion resistance.
[0048]
Unlike the incinerator, the waste treatment furnace is a high-temperature operation, and the wear mechanism of the refractory is unique to the waste treatment furnace due to the multi-alkali slag derived from the waste components. As shown by the test results of the above examples, the amorphous refractory of the present invention is an amorphous refractory for a waste treatment furnace. Demonstrate sex.
[Industrial applicability]
[0049]
As the waste melting furnace, a gasification melting furnace or an ash melting furnace is known. The chromium-free amorphous refractory according to the present invention is used as a lining material for this waste melting furnace.
[Brief description of the drawings]
[0050]
FIG. 1 is a graph showing the relationship between the amount of Y 2 O 3 in an amorphous refractory composition and the corrosion resistance of an amorphous refractory.

Claims (4)

耐火性原料が粒径４５μｍ以下のイットリア質原料と超微粉としての仮焼アルミナを含む主材のアルミナ質原料とからなり、化学分析値でＹ２Ｏ３：１．１〜１５質量％、Ａｌ２Ｏ３：８５質量％以上の組成を有する廃棄物溶融炉用クロムフリー不定形耐火物。The refractory material is composed of an yttria material having a particle size of 45 μm or less and a main material alumina material including calcined alumina as ultrafine powder, and the chemical analysis value is Y 2 O 3 : 1.1 to 15% by mass, Al 2 O 3 : A chromium-free amorphous refractory for a waste melting furnace having a composition of 85% by mass or more. イットリア質原料がイットリア、富イットリウム混合希土酸化物から選ばれる１種以上である請求項１記載の廃棄物溶融炉用クロムフリー不定形耐火物。  The chromium-free amorphous refractory for a waste melting furnace according to claim 1, wherein the yttria-based material is at least one selected from yttria and yttrium-rich mixed rare earth oxides. 廃棄物溶融炉が操業中に、アルカリ（Ｎａ２Ｏ＋Ｋ２Ｏ）：１．５〜１５質量％を含むスラグが炉内を通過する廃棄物溶融炉である、請求項１または請求項２記載の廃棄物溶融炉内張り用クロムフリー不定形耐火物。 3. The waste melting furnace according to claim 1, wherein a slag containing alkali (Na 2 O + K 2 O): 1.5 to 15% by mass passes through the furnace while the waste melting furnace is in operation. Chrome-free amorphous refractory for waste melting furnace lining. 請求項１ないし請求項３のいずれかに記載のクロムフリー不定形耐火物を流し込み施工および／またはプレキャスト施工にて内張りしてなる廃棄物溶融炉。  A waste melting furnace formed by lining the chrome-free amorphous refractory according to any one of claims 1 to 3 by pouring and / or precasting.
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