JP3799841B2 - Operating method of heating furnace - Google Patents

Operating method of heating furnace Download PDF

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JP3799841B2
JP3799841B2 JP31100298A JP31100298A JP3799841B2 JP 3799841 B2 JP3799841 B2 JP 3799841B2 JP 31100298 A JP31100298 A JP 31100298A JP 31100298 A JP31100298 A JP 31100298A JP 3799841 B2 JP3799841 B2 JP 3799841B2
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exhaust gas
combustion
air
recuperator
flue
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JP2000130745A (en
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建太 苅部
一成 安達
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JFE Steel Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

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Description

【０００１】
【発明の属する技術分野】
本発明は、蓄熱体を有して一対のバーナーを交互燃焼させる蓄熱式燃焼装置を備えた例えば連続式加熱炉の操業方法に関する。
【０００２】
【従来の技術】
従来の加熱炉の操業方法としては、例えば特開平８−１９９２３１号公報（以下、単に従来例と称す）に記載されているものが知られている。
この従来例には、予熱帯、加熱帯及び均熱帯からなる加熱炉において、予熱帯で複数の蓄熱式バーナーにより燃焼と蓄熱とを交互に繰り返して加熱し、蓄熱後の低温燃焼排ガスを空気予熱器（エアレキュペレータ）入側の高温燃焼排ガス中へ導入して燃焼排ガス温度を空気予熱器の溶損温度未満に冷却しながら操業するようにした加熱炉の操業方法が記載されている。
【０００３】
【発明が解決しようとする課題】
しかしながら、上記従来例にあっては、従来の３０℃程度のエアに代えて蓄熱燃焼装置からの蓄熱体を通過した２００℃程度の燃焼排ガスを空気予熱器の入側にダイリューションするので、エアレキュペレータの入側の高温燃焼排ガス温度をエアレキュペレータ溶損温度以下に低下させるために、エア流量に比較して多くの燃焼排ガス流量を必要とするため、エアレキュペレータ入側の排ガス流量が増大し、これによって圧損が増大することになり、その結果、加熱炉の燃焼負荷が大きい場合には煙道ドラフトが不足し、操業に支障をきたすおそれがあるという未解決の課題がある。
【０００４】
そこで、本発明は、上記従来例の未解決の課題に着目してなされたものであり、煙道ドラフトと高効率廃熱回収とを両立させた最適な加熱炉の操業方法を提供することを目的としている。
【０００５】
【課題を解決するための手段】
上記目的を達成するために、請求項１に係る加熱炉の操業方法は、炉壁に配設した所要対のバーナと、各バーナに接続された燃焼空気供給用兼排ガス排出用管の途上にそれぞれ介装した所要対の蓄熱体とを有する蓄熱式燃焼装置を燃焼室に配設し、該燃焼室の煙道にエアレキュペータ及びガスレキュペータが当該エアレキュペータを燃焼室側として配設された加熱炉の操業方法において、前記加熱炉の燃焼負荷から煙道ドラフト、煙道圧損、エアレキュペレータ溶損温度を考慮し、前記蓄熱体から排出される排ガスを前記エアレキュペレータの入側に供給する際の排ガスダイリューション量の上下限値を決定し、決定した排ガスダイリューション量の上下限範囲内で燃料原単位が最小となる最適排ガスダイリューション量を求め、求めた最適排ガスダイリューション量に基づいて排ガスダイリューション量を制御すると共に、残りの排ガスを前記ガスレキュペレータ出側の煙道に供給するようにしたことを特徴としている。
【０００６】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。
図１は本発明の一実施形態を示す概略構成図であって、図中、１は例えばウォーキングビーム２によって連続的に搬送されるフラットバー、ビームブランク等の鋼材を連続的に加熱する連続式加熱炉であって、鋼材を左側から装入し、予熱帯３、第１加熱帯４、第２加熱帯５及び均熱帯６を順次通過して加熱され、加熱を終了した鋼材が右側から抽出されて次工程に搬送される。
【０００７】
そして、予熱帯３の入側における上部には煙道７が配設され、この煙道７にエアレキュペレータ（空気予熱器）８及びガスレキュペレータ（ガス予熱器）９がその順に配設され、煙道の自由端に煙突１０が配設されている。
第１加熱帯４、第２加熱帯５及び均熱帯６には、夫々燃焼バーナが配設されているが、第１加熱帯４には、上部及び下部側に夫々少なくとも１組の蓄熱式燃焼装置１１及び１２が配設されている。
【０００８】
ここで、蓄熱式燃焼装置１１及び１２の夫々は、第１加熱帯４の側壁に並設された一対のガスバーナ１３ａ，１３ｂを有する。これらガスバーナ１３ａ，１３ｂの夫々は、その基部に燃料ガス供給口及び燃焼空気給排口（共に図示せず）が設けられ、燃焼時には燃料ガス供給口に供給される燃料ガスがガスノズルによって加熱帯４側に噴射されると共に、ガスノズルの回りに燃焼空気給排口に連通された空気ノズルから燃焼空気が噴射されるが、非燃焼時には空気ノズルから第１加熱帯４の加熱排ガスを吸引するように構成され、燃焼時には、噴射される燃料ガスがガスノズルから噴射される燃料ガスと空気ノズルから噴射される燃焼空気との合流点近傍に配設されたパイロットバーナ（図示せず）によって点火される。
【０００９】
そして、ガスバーナ１３ａ，１３ｂの燃料ガス供給口が個別の燃料遮断弁１４ａ，１４ｂを介し、さらに共通のメイン遮断弁１５、流量調節弁１６を介して燃料ガスとしてのＭガスを供給するＭガス供給源１７に接続されている。
また、ガスバーナ１３ａ，１３ｂの燃焼空気給排口が蓄熱体２０ａ，２０ｂの一端に接続され、この蓄熱体２０ａ，２０ｂの他端が分岐され、その一方の分岐部が個別の空気遮断弁２２ａ，２２ｂを介し、さらに共通の流量調節弁２３を介してエアブロア２４に接続されていると共に、他方の分岐部が個別の排ガス遮断弁２５ａ，２５ｂを介し、さらに共通の流量調節弁２６を介して排ガス吸引ファン（ＩＤＦ）２７に接続され、この排ガス吸引ファン２７で吸引された蓄熱式燃焼装置１１，１２の蓄熱帯で熱交換した後の排ガスが流量調節弁２８を介してエアレキュペレータ８の入側の煙道７にエアレキュペレータ８の溶損を防止するためのダイリューション（希釈）媒体として供給されると共に、残りの排ガスがガスレキュペレータ９の出側の煙道７に排出される。
【００１０】
また、蓄熱体２０ａ，２０ｂの夫々は、気体流通炉に沿って蓄熱媒体として例えば直径２０ｍｍのアルミナボールが９８０ｋｇ充填されており、このアルミナボールに第１加熱帯４から排出される高温（例えば１３００℃程度）の排ガスと熱交換されて蓄熱され、この顕熱がエアブロア２４から供給される低温の燃焼空気と熱交換されて放熱される。
【００１１】
そして、各蓄熱式燃焼装置１１，１２の蓄熱体２０ａ，２０ｂで熱交換された後の排ガスを煙道７におけるエアレキュペレータ８の入側にダイリューション媒体として供給する際の排ガスダイリューション量Ｖ１が以下に述べるように加熱炉の燃焼負荷から求めた最適排ガスダイリューション量Ｖ１* に制御される。
【００１２】
まず、加熱炉の燃焼負荷に応じて、排ガスダイリューション量Ｖ１（Ｎｍ3 ／Ｈ）と煙道ドラフト（ｍｍＡｑ）及び煙道圧損（ｍｍＡｑ）との関係は、図２に示すよう、煙道ドラフトは排ガスダイリューション量Ｖ１の変化にかかわらず一定であるが、煙道圧損は、排ガスダイリューション量Ｖ１が増加するにつれて増加するので、煙道圧損が煙道ドラフトに達したときの排ガスダイリューション量を排ガスダイリューション量上限値Ｖ１U として決定する。
【００１３】
一方、排ガスダイリューション量Ｖ１とエアレキュペレータ入側排ガス温度（℃）との関係は、図３に示すように、エアレキュペレータ入側排ガス温度は排ガスダイリューション量Ｖ１が増加するに応じて減少することになるため、エアレキュペレータ溶損防止温度ＴR （例えば８００℃）に達する排ガスダイリューション量Ｖ１を排ガスダイリューション量下限値Ｖ１L として決定する。
【００１４】
そして、排ガスダイリューション量Ｖ１と加熱炉燃料原単位（Ｍcal/t)の関係は、図４に示すように、排ガスダイリューション量Ｖ１が１３５００（Ｎｍ3 ／Ｈ）から増加すると加熱炉燃料原単位が減少し、排ガスダイリューション量下限値Ｖ１L を越えた２２０００（Ｎｍ3 ／Ｈ）で最小となった後に増加傾向に転じ排ガスダイリューション量上限値Ｖ１U を越えてもなお増加することになるため、操業最適条件としては、排ガスダイリューション量下限値Ｖ１L 及び排ガスダイリューション量上限値Ｖ１U 間の範囲で加熱炉燃料原単位が最小となる排ガスダイリューション量Ｖ１を最適排ガスダイリューション量Ｖ１* として決定する。
【００１５】
そして、決定された最適排ガスダイリューション量Ｖ１* に一致するように流量制御弁２８を例えばプロセスコンピュータ等の制御装置でフィードバック制御又はフィードフォワード制御することにより、煙道７におけるエアレキュペレータ８の入側に供給する排ガスダイリューション量を最適値に制御し、残りの排ガスをガスレキュペレータ９の出側の煙突１０側に排出する。
【００１６】
次に、上記実施形態の動作を説明する。
連続式加熱炉１の操業を開始する際に、所定の初期化処理を行って炉内温度を予め設定された目標温度ＴT （例えば１３００℃）まで昇温する昇温処理を実行し、目標温度ＴT に達したとき第１加熱帯４内に配設した燃焼空気温度センサ（図示せず）の温度検出値に基づいて燃焼バーナの切換えタイミングを決定して燃焼バーナの切換えを行う定常切換制御処理を行う。
【００１７】
このとき、一方のガスバーナ１３ａが燃焼状態にあり、他方のバスバーナ１３ｂが非燃焼状態にあるものとすると、この状態では、燃焼状態のガスバーナ１３ａに対しては、外気からエアブロア２４によって圧送される冷風状態（例えば２０℃）の燃焼空気が流量調節弁２３、空気遮断弁２２ａを介して蓄熱体２０ａに供給され、この蓄熱体２０ａで蓄熱されたアルミナボールと熱交換されて１０００℃以上に予熱された状態でガスバーナ１３ａの燃焼空気給排口に供給され、ガスノズルから噴射される燃料ガスと混合されて燃焼されて炉内を加熱する。
【００１８】
これと同時に、他方の非燃焼状態のガスバーナ１３ｂでは、燃焼空気給排口が蓄熱体２０ｂ、排ガス遮断弁２５ｂ、共通流量調節弁２６を介して排ガス吸引ファン２７に連通され、この排ガス吸引ファン２７によって炉内の排ガスが吸引されて蓄熱体２０ｂを通って排出され、蓄熱体２０ｂ内のアルミナボールと熱交換することにより、蓄熱体２０ｂの蓄熱温度が徐々に上昇される。
【００１９】
このとき、ガスバーナ１３ａが燃焼状態に、ガスバーナ１３ｂが非燃焼状態に夫々切換えられた直後であるものとすると、燃焼状態のガスバーナ１３ａ側の蓄熱体２０ａの温度は、図５で実線図示の特性曲線Ｌa で示すように、蓄熱体２０ａの飽和温度例えば１２００℃であり、一方、非燃焼状態のガスバーナ１３ｂの蓄熱体２０ｂの温度は、一点鎖線図示の特性曲線Ｌb で示すように、前回の燃焼時に放熱された設定下限温度ＴL である１０００℃となっており、ガスバーナ１３ｂ側の排ガス遮断弁２５ｂの出側の温度は、図５の特性曲線Ｌc で示すように、露点温度（１７０℃前後）より高い例えば１９０℃程度になっている。
【００２０】
この状態でガスバーナ１３ａでの燃焼状態が継続されると共に、ガスバーナ１３ｂでの排ガス回収状態が継続されるが、ガスバーナ１３ａに供給される燃焼空気の温度ＴDaは、図５の特性曲線Ｌa で示すように、時間の経過と共に徐々に低下する一方、ガスバーナ１３ｂ側の蓄熱体２０ｂの温度が図５の特性曲線Ｌb で示すように徐々に上昇し、これに伴って排ガス遮断弁２５ｂの出側温度も図５の特性曲線Ｌc に示すように、徐々に上昇する。
【００２１】
その時、時点ｔ1 でガスバーナ１３ａに供給される燃焼空気温度ＴDaが下限設定温度ＴL に達すると、これによってガスバーナ１３ａが非燃焼状態の排ガス回収状態に切換えられると共に、他の非燃焼状態のガスバーナ１３ｂに高温の蓄熱体２０ｂで予熱された燃焼空気を供給する燃焼準備状態に移行し、その後所定時間経過した後ガスバーナ１３ｂを燃焼状態に切換える。
【００２２】
このように、ガスバーナ１３ｂが燃焼状態に切換わると、時間の経過と共に図５の特性曲線Ｌb で示すように、燃焼空気温度ＴDbが徐々に低下し、逆にガスバーナ１３ａで回収された排ガスによって蓄熱体２０ａの温度が徐々に上昇され、これに応じて排ガス遮断弁２５ａの出側の排ガス温度が特性曲線Ｌd で示すように、徐々に上昇する。
【００２３】
そして、このガスバーナ１３ｂの燃焼状態が、燃焼空気温度ＴDbが下限設定温度ＴL 以下となるまで継続され、燃焼空気温度ＴDbが加減設定温度ＴL 以下となると、ガスバーナ１３ｂが燃焼状態から非燃焼状態に、逆にガスバーナ１３ａが非燃焼状態から燃焼状態に切換えられる。その後、燃焼状態のガスバーナ１３ｉ（ｉ＝ａ，ｂ）に供給される燃焼空気温度ＴDiが下限設定温度ＴL 以下となる毎に燃焼バーナの切換えが行われる。
【００２４】
このようにして、蓄熱式燃焼装置１１及び１２の各バーナ１３ａ及び１３ｂが交互に切換燃焼されることにより、第１加熱帯４の炉温を設定温度に維持することができるものであるが、この間に蓄熱式燃焼装置１１及び１２の蓄熱体２０ａ又は２０ｂを通過して排ガス吸引ファン２７によって吸引排出された排ガスは、前述したように、最適排ガスダイリューション量Ｖ１* に制御されて、煙道７におけるエアレキュペレータ８の入側に導入されると共に、残りがガスレキュペレータ９の出側に排出される。
【００２５】
そして、最適排ガスダイリューション量Ｖ１* は、前述したように、加熱炉の燃焼負荷から、先ず、煙道ドラフト、煙道圧損及びエアレキュペレータ溶損防止温度を考慮して、蓄熱式燃焼装置１１，１２の蓄熱体２０ａ，２０ｂで熱交換後に排出される排ガスを煙道７におけるエアレキュペレータ８の入側にダイリューション媒体として供給する際の排ガスダイリューション量の下限値Ｖ１L 及び上限値Ｖ１U を決定し、決定された排ガスダイリューション量の上下限値の範囲内で燃料原単位が最小となる排ガスダイリューション量として求められるので、この最適排ガスダイリューション量となるように流量調節弁２８で排ガスダイリューション量Ｖ１を制御することにより、蓄熱式燃焼装置を使用した加熱炉操業の最適化を図ることができる。
【００２６】
すなわち、操業条件として、鋼材の挿入温度を４００℃、抽出温度を１１４４℃としたときに、排ガスダイリューションの上限値Ｖ１U が２５０００Ｎｍ3 ／Ｈ、下限値Ｖ１L が１７０００Ｎｍ3 ／Ｈ、最適値Ｖ１* が２２０００Ｎｍ3 ／Ｈとなり、排ガスダイリューション量を流量調節弁２８で最適排ガスダイリューション量Ｖ１* となるように制御することにより、加熱能力限界は従来例では２５０t/H であったものが本発明では排ガスダイリューションにより、ダイリューションエアが不要になることで煙道の圧損が低減されて２８０t/H に大幅に向上させることができ、燃料原単位が従来法では２４０Ｍcal/t であったものが本発明では２１５Ｍcal/t に大幅に低減することができた。
【００２７】
なお、上記実施形態においては、第１加熱帯４にのみ蓄熱式燃焼装置１１，１２を設けた場合について説明したが、これに限定されるものではなく、３組以上の蓄熱式燃焼装置を設置するようにしてもよく、あるいは蓄熱式燃焼装置１１，１２に複数対のバーナー及び蓄熱体を設けるようにしてもよく、また、第２加熱帯５や均熱帯６にも蓄熱式燃焼装置を設けるようにしてもよく、さらには、各燃焼帯で蓄熱式燃焼装置と通常バーナーによる燃焼装置とを混在させるようにしてもよく、要は蓄熱式燃焼装置の蓄熱体２０ａ，２０ｂを通過して排出される排ガスを煙道７のエアレキュペレータ８の入側にその排ガス温度を溶損防止温度に冷却するダイリューション媒体として供給する場合に、本発明を適用し得るものである。
【００２８】
また、上記実施形態においては、第１及び第２の加熱帯４及び５を有する場合について説明したが、これに限定されるものではなく、加熱帯が１つ又は３以上である場合であっても、各帯に配設した蓄熱式燃焼装置の排ガスを排ガス吸引ファンで吸引した後、最適排ガスダイリューション量Ｖ１* に制御することにより最適な加熱炉操業を行うことができる。
【００２９】
さらに、上記実施形態においては、蓄熱式燃焼装置１１，１２に供給する燃料としてＭガスを使用する場合について説明したが、これに限定されるものではなく、他の燃料ガスや重油等の液体燃料を使用することができる。
さらにまた、上記実施形態においては蓄熱式燃焼装置１１，１２におけるガスバーナ１３ａ，１３ｂに対する燃焼空気の供給及び排ガスの排出を個別の空気遮断弁２２ａ，２２ｂ及び排ガス遮断弁２５ａ，２５ｂで行う場合について説明したが、これらに限らずエアシリンダ等によって流路を切換える方向切換片や、特開平１−２１９４１１号公報に開示されているように流体力学的にコアンダ効果を利用して切換機構を構成するようにしてもよい。
【００３０】
【発明の効果】
以上説明したように、請求項１に係る発明によれば、燃焼室の煙道にエアレキュペータ及びガスレキュペータがエアレキュペータを燃焼室側として配設された加熱炉で、加熱炉の燃焼負荷から煙道ドラフト、煙道圧損、エアレキュペレータ溶損温度を考慮し、前記蓄熱体から排出される排ガスを前記エアレキュペレータの入側に供給する際の排ガスダイリューション量の上下限値を決定し、決定した排ガスダイリューション量の上下限範囲内で燃料原単位が最小となる最適排ガスダイリューション量を求め、求めた最適排ガスダイリューション量に基づいて排ガスダイリューション量を制御すると共に、残りの排ガスをガスレキュペレータ出側の煙道に供給するようにしたので、煙道ドラフトと高効率廃熱回収とを両立させた最適な加熱炉操業を実現することができるという効果が得られる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す概略構成図である。
【図２】排ガスダイリューション量と煙道ドラフト及び圧損との関係を示す特性線図である。
【図３】排ガスダイリューション量とエアレキュペレータ入側排ガス温度との関係を示す特性線図である。
【図４】排ガスダイリューション量と加熱炉燃料原単位との関係を示す特性線図である。
【図５】燃焼バーナの切換えによる蓄熱体の前後の温度変化及び排ガス温度変化を示すタイムチャートである。
【符号の説明】
１ 連続式加熱炉
３ 予熱帯
４ 第１加熱帯
５ 第２加熱帯
６ 均熱帯
７ 煙道
８ エアレキュペレータ
９ ガスレキュペレータ
１１，１２ 蓄熱式燃焼装置
１３ａ，１３ｂ ガスバーナ
２０ａ，２０ｂ 蓄熱体
２５ａ，２５ｂ 排ガス遮断弁
２７ 排ガス吸引ファン
２８ 流量調節弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating, for example, a continuous heating furnace including a heat storage combustion apparatus that includes a heat storage body and alternately burns a pair of burners.
[0002]
[Prior art]
As a conventional method for operating a heating furnace, for example, a method described in JP-A-8-199231 (hereinafter simply referred to as a conventional example) is known.
In this conventional example, in a heating furnace consisting of a pretropical zone, a heating zone, and a soaking zone, combustion and heat storage are alternately and repeatedly heated by a plurality of regenerative burners in the pretropical zone, and the preheated low-temperature combustion exhaust gas is preheated to the air. A method of operating a heating furnace is described in which operation is performed while cooling the flue gas temperature below the melting temperature of the air preheater by introducing it into the high-temperature flue gas on the inlet side of the heater (air recuperator).
[0003]
[Problems to be solved by the invention]
However, in the above conventional example, instead of the conventional air of about 30 ° C., the combustion exhaust gas of about 200 ° C. that has passed through the heat storage body from the heat storage combustion device is diluted to the inlet side of the air preheater. In order to lower the high-temperature combustion exhaust gas temperature on the inlet side of the air recuperator below the air recuperator melting temperature, a larger amount of combustion exhaust gas flow is required compared to the air flow rate, so the exhaust gas flow rate on the inlet side of the air recuperator As a result, the pressure loss increases, and as a result, when the combustion load of the heating furnace is large, there is an unsolved problem that the flue draft is insufficient and the operation may be hindered.
[0004]
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and provides an optimum heating furnace operating method that achieves both flue draft and high-efficiency waste heat recovery. It is aimed.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a method for operating a heating furnace according to claim 1 includes a required pair of burners arranged on the furnace wall and a combustion air supply / exhaust gas discharge pipe connected to each burner. Operation of a heating furnace in which a regenerative combustion apparatus having a required pair of regenerators interposed therein is disposed in a combustion chamber, and an air recuperator and a gas recuperator are disposed on the combustion chamber side in the flue of the combustion chamber. In the method, considering flue draft, flue pressure loss, and air recuperator melting temperature from the combustion load of the heating furnace, exhaust gas when supplying the exhaust gas discharged from the heat storage body to the inlet side of the air recuperator The upper and lower limits of the dilution amount are determined, and the optimum exhaust gas dilution amount that minimizes the fuel consumption rate within the upper and lower limits of the determined exhaust gas dilution amount is determined. Controls the exhaust gas dilution amount based on the gas dilution volume, is characterized in that the remaining gas was then supplied to the flue of the gas recuperator outlet side.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, 1 is a continuous type for continuously heating a steel material such as a flat bar and a beam blank continuously conveyed by a walking beam 2, for example. It is a heating furnace, and the steel material is charged from the left side, heated through the pre-tropical zone 3, the first heating zone 4, the second heating zone 5 and the soaking zone 6 in order, and the heated steel material is extracted from the right side. And conveyed to the next process.
[0007]
A flue 7 is disposed at the upper part of the entrance side of the pre-tropical zone 3, and an air recuperator (air preheater) 8 and a gas recuperator (gas preheater) 9 are disposed in this order in the flue 7. A chimney 10 is disposed at the free end of the flue.
Combustion burners are disposed in the first heating zone 4, the second heating zone 5, and the soaking zone 6, respectively. In the first heating zone 4, at least one set of regenerative combustion is provided on the upper and lower sides, respectively. Devices 11 and 12 are arranged.
[0008]
Here, each of the regenerative combustion apparatuses 11 and 12 has a pair of gas burners 13 a and 13 b arranged side by side on the side wall of the first heating zone 4. Each of the gas burners 13a and 13b is provided with a fuel gas supply port and a combustion air supply / exhaust port (both not shown) at the base thereof, and the fuel gas supplied to the fuel gas supply port during combustion is heated by the gas nozzle 4 by the gas nozzle. The combustion air is injected from the air nozzle connected to the combustion air supply / exhaust port around the gas nozzle, and the heated exhaust gas in the first heating zone 4 is sucked from the air nozzle during non-combustion. Thus, at the time of combustion, the fuel gas to be injected is ignited by a pilot burner (not shown) disposed in the vicinity of the junction of the fuel gas injected from the gas nozzle and the combustion air injected from the air nozzle.
[0009]
The fuel gas supply ports of the gas burners 13a and 13b are supplied with M gas as fuel gas through the individual fuel cutoff valves 14a and 14b, and further through the common main cutoff valve 15 and the flow rate control valve 16. Connected to source 17.
Further, the combustion air supply / exhaust ports of the gas burners 13a and 13b are connected to one ends of the heat storage bodies 20a and 20b, the other ends of the heat storage bodies 20a and 20b are branched, and one of the branch portions is an individual air cutoff valve 22a, 22b, and is connected to the air blower 24 via a common flow rate control valve 23. The other branch portion is connected to individual exhaust gas shut-off valves 25a and 25b, and is further connected to a common flow rate control valve 26 for exhaust gas. The exhaust gas connected to the suction fan (IDF) 27 and sucked by the exhaust gas suction fan 27 and having undergone heat exchange in the tropics of the heat storage combustion devices 11 and 12 enters the air recuperator 8 via the flow rate control valve 28. Is supplied to the side flue 7 as a dilution medium for preventing the air recuperator 8 from being melted, and the remaining exhaust gas is supplied to the gas recuperator 9. It is discharged to the flue 7 of the side.
[0010]
Each of the heat storage bodies 20a and 20b is filled with 980 kg of alumina balls having a diameter of 20 mm, for example, as a heat storage medium along the gas flow furnace, and the alumina balls are discharged from the first heating zone 4 at a high temperature (for example, 1300). The sensible heat is heat-exchanged with the low-temperature combustion air supplied from the air blower 24 and is radiated.
[0011]
And exhaust gas dilution when supplying the exhaust gas after heat exchange by the heat storage bodies 20a, 20b of the respective heat storage combustion apparatuses 11, 12 as a dilution medium to the inlet side of the air recuperator 8 in the flue 7 The amount V1 is controlled to the optimum exhaust gas dilution amount V1 * obtained from the combustion load of the heating furnace as described below.
[0012]
First, according to the combustion load of the heating furnace, the relationship between the exhaust gas dilution amount V1 (Nm 3 / H), the flue draft (mmAq), and the flue pressure loss (mmAq) is as shown in FIG. Although the draft is constant regardless of the change in the exhaust gas dilution amount V1, flue pressure drop, since the exhaust gas dilution amount V1 is increased with the increase, when the flue pressure loss reaches the flue draft determining the exhaust gas dilution amount as exhaust gas dilution amount upper limit value V1 U.
[0013]
On the other hand, as shown in FIG. 3, the relationship between the exhaust gas dilution amount V1 and the air recuperator inlet side exhaust gas temperature (° C.) corresponds to the increase of the exhaust gas dilution amount V1. to become a reducing Te, determines the exhaust gas dilution amount V1 reaching the air recuperator erosion prevention temperature T R (e.g. 800 ° C.) as the exhaust gas dilution amount lower limit value V1 L.
[0014]
As shown in FIG. 4, when the exhaust gas dilution amount V1 increases from 13500 (Nm 3 / H), the relationship between the exhaust gas dilution amount V1 and the heating furnace fuel intensity (Mcal / t) is as follows. After the basic unit decreased and became the minimum after 22000 (Nm 3 / H) exceeding the exhaust gas dilution amount lower limit value V1 L , it turned to an increasing trend, and even if the exhaust gas dilution amount upper limit value V1 U was exceeded, it still increased Therefore, as the optimum operation condition, the exhaust gas dilution amount V1 at which the heating furnace fuel unit becomes the minimum in the range between the exhaust gas dilution amount lower limit value V1 L and the exhaust gas dilution amount upper limit value V1 U. Is determined as the optimum exhaust gas dilution amount V1 * .
[0015]
Then, the flow control valve 28 is feedback-controlled or feed-forward controlled by a control device such as a process computer so as to coincide with the determined optimum exhaust gas dilution amount V1 * , whereby the air recuperator 8 in the flue 7 is controlled. The amount of exhaust gas dilution supplied to the inlet side is controlled to an optimum value, and the remaining exhaust gas is discharged to the chimney 10 side of the outlet side of the gas recuperator 9.
[0016]
Next, the operation of the above embodiment will be described.
When the operation of the continuous heating furnace 1 is started, a temperature increase process for performing a predetermined initialization process to raise the furnace temperature to a preset target temperature T T (for example, 1300 ° C.) is performed. constant switching performing the first switching of the combustion burner to determine the switching timing of the combustion burner based on the temperature detection value of the combustion air temperature sensor disposed in the heating zone 4 (not shown) when it reaches a temperature T T Perform control processing.
[0017]
At this time, assuming that one gas burner 13a is in a combustion state and the other bus burner 13b is in a non-combustion state, in this state, the cool air blown by the air blower 24 from the outside air to the combustion gas burner 13a. Combustion air in a state (for example, 20 ° C.) is supplied to the heat storage body 20a via the flow rate adjusting valve 23 and the air shutoff valve 22a, and is heat-exchanged with the alumina balls stored in the heat storage body 20a and preheated to 1000 ° C. or higher. In this state, the gas is supplied to the combustion air supply / exhaust port of the gas burner 13a, mixed with the fuel gas injected from the gas nozzle and burned to heat the inside of the furnace.
[0018]
At the same time, in the other non-combustion gas burner 13b, the combustion air supply / exhaust port communicates with the exhaust gas suction fan 27 via the heat storage body 20b, the exhaust gas cutoff valve 25b, and the common flow rate control valve 26. As a result, the exhaust gas in the furnace is sucked and discharged through the heat storage body 20b, and the heat storage temperature of the heat storage body 20b is gradually increased by exchanging heat with the alumina balls in the heat storage body 20b.
[0019]
At this time, assuming that the gas burner 13a is immediately after being switched to the combustion state and the gas burner 13b is switched to the non-combustion state, the temperature of the heat storage body 20a on the gas burner 13a side in the combustion state is the characteristic curve shown in FIG. as shown by L a, a saturation temperature for example 1200 ° C. regenerator 20a, while the temperature of the regenerator 20b of the gas burner 13b of the non-combustion state, as shown by the characteristic curve of one-dot chain line shown L b, the previous The set lower limit temperature TL radiated at the time of combustion is 1000 ° C., and the temperature on the outlet side of the exhaust gas shutoff valve 25b on the gas burner 13b side is the dew point temperature (170) as shown by the characteristic curve L c in FIG. For example, the temperature is about 190 ° C.
[0020]
With the combustion state in the gas burner 13a is continued in this state, the exhaust gas recovery state in the gas burner 13b is continued, the temperature T Da of the combustion air supplied to the gas burner 13a is a characteristic curve L a in FIG. 5 as shown, while gradually decreases with time, the temperature of the regenerator 20b of the gas burner 13b side rises gradually as shown by a characteristic curve L b in FIG. 5, out of the exhaust gas shutoff valve 25b in accordance with this side temperature, as shown by the characteristic curve L c of FIG. 5 increases gradually.
[0021]
At that time, when the combustion air temperature T Da supplied to the gas burner 13a at the time point t 1 reaches the lower limit set temperature T L , the gas burner 13a is thereby switched to the non-burning exhaust gas recovery state and other non-burning state The gas burner 13b is switched to a combustion preparation state in which combustion air preheated by the high-temperature heat storage body 20b is supplied to the gas burner 13b, and after a predetermined time has elapsed, the gas burner 13b is switched to the combustion state.
[0022]
Thus, when the gas burner 13b is switched to the combustion state, as shown by the characteristic curve L b in FIG. 5 over time, gradually decreases the combustion air temperature T Db, was recovered by a gas burner 13a Conversely exhaust gas the temperature of the regenerator 20a is gradually increased, the exhaust gas temperature of the outlet side of the exhaust gas shutoff valve 25a in response to this, as shown by the characteristic curve L d, gradually increases by.
[0023]
Then, the combustion state of the gas burner 13b is, the combustion air temperature T Db is continued until less than the lower limit set temperature T L, when the combustion air temperature T Db is less acceleration set temperature T L, a gas burner 13b is non from the combustion state Conversely, the gas burner 13a is switched from the non-combustion state to the combustion state. Thereafter, the combustion burner is switched each time the combustion air temperature T Di supplied to the gas burner 13i (i = a, b) in the combustion state becomes equal to or lower than the lower limit set temperature T L.
[0024]
In this way, the furnace temperature of the first heating zone 4 can be maintained at the set temperature by alternately switching and burning the burners 13a and 13b of the regenerative combustion apparatuses 11 and 12. During this time, the exhaust gas sucked and discharged by the exhaust gas suction fan 27 after passing through the heat storage body 20a or 20b of the heat storage combustion devices 11 and 12 is controlled to the optimum exhaust gas dilution amount V1 * as described above. The air is introduced to the inlet side of the air recuperator 8 in the road 7 and the rest is discharged to the outlet side of the gas recuperator 9.
[0025]
As described above, the optimum exhaust gas dilution amount V1 * is determined from the combustion load of the heating furnace in consideration of the flue draft, flue pressure loss and air recuperator melting prevention temperature, as described above. 11 and 12 of the regenerator 20a, the lower limit value V1 L and the exhaust gas dilution amount when supplying the exhaust gas discharged after heat exchange entrance side of the air recuperator 8 in flue 7 as dilution medium 20b The upper limit value V1 U is determined, and is determined as the exhaust gas dilution amount that minimizes the fuel consumption rate within the range of the upper and lower limit values of the determined exhaust gas dilution amount. Thus, by controlling the exhaust gas dilution amount V1 with the flow rate control valve 28, it is possible to optimize the heating furnace operation using the regenerative combustion apparatus. .
[0026]
That is, as operating conditions, when the steel material insertion temperature is 400 ° C. and the extraction temperature is 1144 ° C., the exhaust gas dilution upper limit value V1 U is 25000 Nm 3 / H, and the lower limit value V1 L is 17000 Nm 3 / H, which is optimal. The value V1 * is 22000 Nm 3 / H, and the heating capacity limit is 250 t / H in the conventional example by controlling the exhaust gas dilution amount to be the optimum exhaust gas dilution amount V1 * with the flow control valve 28. In the present invention, the exhaust gas dilution eliminates the need for dilution air, thereby reducing the pressure loss of the flue and greatly improving it to 280 t / H. The fuel consumption rate is 240 Mcal in the conventional method. What was / t could be greatly reduced to 215 Mcal / t in the present invention.
[0027]
In addition, in the said embodiment, although the case where the thermal storage type combustion apparatuses 11 and 12 were provided only in the 1st heating zone 4 was demonstrated, it is not limited to this, Three sets or more of thermal storage type combustion apparatuses are installed. Alternatively, a plurality of pairs of burners and heat storage bodies may be provided in the regenerative combustion apparatuses 11 and 12, and a regenerative combustion apparatus is also provided in the second heating zone 5 and the soaking zone 6. In addition, in each combustion zone, a regenerative combustion apparatus and a combustion apparatus using a normal burner may be mixed. In short, the heat storage body 20a, 20b of the regenerative combustion apparatus passes through and is discharged. The present invention can be applied when supplying the exhaust gas to be supplied to the inlet side of the air recuperator 8 of the flue 7 as a dilution medium for cooling the exhaust gas temperature to the melting prevention temperature.
[0028]
Moreover, in the said embodiment, although the case where it has the 1st and 2nd heating zones 4 and 5 was demonstrated, it is not limited to this, It is a case where a heating zone is 1 or 3 or more. In addition, after the exhaust gas of the regenerative combustion apparatus arranged in each zone is sucked by the exhaust gas suction fan, the optimum heating furnace operation can be performed by controlling the optimum exhaust gas dilution amount V1 * .
[0029]
Furthermore, in the said embodiment, although the case where M gas was used as a fuel supplied to the thermal storage combustion apparatus 11 and 12 was demonstrated, it is not limited to this, Liquid fuels, such as other fuel gas and heavy oil Can be used.
Furthermore, in the above embodiment, the case where the combustion air is supplied to the gas burners 13a and 13b and the exhaust gas is discharged by the individual air cutoff valves 22a and 22b and the exhaust gas cutoff valves 25a and 25b in the regenerative combustion apparatuses 11 and 12 will be described. However, the present invention is not limited thereto, and a direction switching piece that switches the flow path by an air cylinder or the like, or a switching mechanism that uses the Coanda effect hydrodynamically as disclosed in Japanese Patent Laid-Open No. 1-219411. It may be.
[0030]
【The invention's effect】
As described above, according to the first aspect of the present invention, in the heating furnace in which the air recuperator and the gas recuperator are disposed in the combustion chamber flue with the air recuperator as the combustion chamber side, the flue draft from the combustion load of the heating furnace, Taking into account flue pressure loss and air recuperator melting temperature, the upper and lower limit values of the exhaust gas dilution amount when supplying exhaust gas discharged from the heat storage body to the inlet side of the air recuperator were determined and determined. The optimum exhaust gas dilution amount that minimizes the fuel consumption rate within the upper and lower limits of the exhaust gas dilution amount is obtained, and the exhaust gas dilution amount is controlled based on the obtained optimum exhaust gas dilution amount. Since the exhaust gas is supplied to the flue at the outlet side of the gas recuperator, the optimum furnace operation that combines the flue draft and high-efficiency waste heat recovery is achieved. Effect that can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a characteristic diagram showing the relationship between exhaust gas dilution amount, flue draft and pressure loss.
FIG. 3 is a characteristic diagram showing a relationship between an exhaust gas dilution amount and an exhaust gas temperature on the inlet side of the air recuperator.
FIG. 4 is a characteristic diagram showing a relationship between an exhaust gas dilution amount and a heating furnace fuel consumption rate.
FIG. 5 is a time chart showing temperature changes before and after a heat storage body and exhaust gas temperature changes due to switching of a combustion burner.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Continuous heating furnace 3 Pre-tropical 4 1st heating zone 5 2nd heating zone 6 Soaking zone 7 Flue 8 Air recuperator 9 Gas recuperator 11, 12 Thermal storage combustion apparatus 13a, 13b Gas burner 20a, 20b Thermal storage body 25a 25b Exhaust gas shut-off valve 27 Exhaust gas suction fan 28 Flow control valve

Claims (1)

炉壁に配設した所要対のバーナと、各バーナに接続された燃焼空気供給用兼排ガス排出用管の途上にそれぞれ介装した所要対の蓄熱体とを有する蓄熱式燃焼装置を燃焼室に配設し、該燃焼室の煙道にエアレキュペータ及びガスレキュペータが当該エアレキュペータを燃焼室側として配設された加熱炉の操業方法において、前記加熱炉の燃焼負荷から煙道ドラフト、煙道圧損、エアレキュペレータ溶損温度を考慮し、前記蓄熱体から排出される排ガスを前記エアレキュペレータの入側に供給する際の排ガスダイリューション量の上下限値を決定し、決定した排ガスダイリューション量の上下限範囲内で燃料原単位が最小となる最適排ガスダイリューション量を求め、求めた最適排ガスダイリューション量に基づいて排ガスダイリューション量を制御すると共に、残りの排ガスを前記ガスレキュペレータ出側の煙道に供給するようにしたことを特徴とする加熱炉の操業方法。A regenerative combustion apparatus having a required pair of burners disposed on the furnace wall and a required pair of heat storage bodies respectively disposed in the middle of a combustion air supply / exhaust gas discharge pipe connected to each burner. In a method of operating a heating furnace in which an air recuperator and a gas recuperator are arranged in the combustion chamber flue with the air recuperator as the combustion chamber side , a flue draft, flue pressure loss, air recuperation is detected from the combustion load of the heating furnace. In consideration of the melting temperature of the pelletizer, the upper and lower limit values of the exhaust gas dilution amount when the exhaust gas discharged from the heat storage body is supplied to the inlet side of the air recuperator are determined, and the determined exhaust gas dilution amount is determined. The optimum exhaust gas dilution amount that minimizes the fuel consumption rate within the upper and lower limits is obtained, and the exhaust gas dilution amount is calculated based on the obtained optimum exhaust gas dilution amount. With Gosuru, operating method of a heating furnace, characterized in that it has to supply the rest of the exhaust gas flue of the gas recuperator outlet side.
JP31100298A 1998-10-30 1998-10-30 Operating method of heating furnace Expired - Fee Related JP3799841B2 (en)

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KR101020358B1 (en) 2003-07-07 2011-03-08 재단법인 포항산업과학연구원 Waste heat recovery Apparatus for reheating furnace
KR101420652B1 (en) 2007-12-21 2014-07-21 재단법인 포항산업과학연구원 Waste gas temperature control method for recuperator in reheating furnace system

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