JP4304006B2

JP4304006B2 - Steam turbine

Info

Publication number: JP4304006B2
Application number: JP2003154361A
Authority: JP
Inventors: 浩平永根; 勝也山下; 幸雄篠崎
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2003-05-30
Filing date: 2003-05-30
Publication date: 2009-07-29
Anticipated expiration: 2023-05-30
Also published as: JP2004353603A

Description

【０００１】
【発明の属する技術分野】
本発明は、蒸気タービンに係り、特に蒸気の高温化に対処してタービンノズルボックスの強度保証を高く維持させる蒸気タービンに関する。
【０００２】
【従来の技術】
蒸気の高温化は、ランキンサイクルの特性を巧みに利用するものであり、蒸気温度を高くすればする程、プラント熱効率を向上させることができるとされている。
【０００３】
このため、蒸気タービンは、ひところの比較的低温、低圧の蒸気条件から蒸気温度５３８℃／５６６℃または５３８℃／５３８℃の一段再熱にほぼ定着しつつある。
【０００４】
しかし、最近のように、ＣＯ_２やＮＯｘ等の汚染物質による温暖化現象や環境破壊等が地球規模レベルでクローズアップされている今日、蒸気タービンの分野でも燃料の消費をより一層少なくさせて単機容量を増加させる研究開発が進められており、その一つに中圧タービンを第１中圧タービンと第２中圧タービンとに区分けし、区分けした第１中圧タービンをトップタービンとして配置し、第２中圧タービンを従来と同様にボトムタービンとして配置したコンベンショナルな蒸気タービン部に組み込むとともに、第１中圧タービンにボイラの再熱器からの再熱蒸気を温度７００℃以上にして供給することが提案されている（特許文献１参照）。
【０００５】
再熱蒸気温度７００℃以上の場合、トップタービンとして配置する第１中圧タービンには、解決すべき多くの問題が残されている中で、その一つとして再熱蒸気供給管に接続するタービンノズルボックスの強度がある。
【０００６】
このタービンノズルボックスは、ボイラの再熱器から供給される再熱蒸気を再熱蒸気供給管を介してタービン段落に供給する際の蒸気室として機能をするものであるが、何分にも超高温の再熱蒸気に直接晒されるだけに高い強度保証が要求される。現在、高い強度保証を確保することに対し、模索中である。
【０００７】
【特許文献１】
特願２００３−１２５６７２号公報
【０００８】
【発明が解決しようとする課題】
従来、火力発電プラントでは、タービンノズルボックスをコンベンショナルな蒸気タービン部のうち、高圧タービンの蒸気入口側に設置し、温度５３８℃〜５６６℃の主蒸気に対処させ、高い強度を維持させていた。
【０００９】
しかし、高圧タービンに設置しているタービンノズルボックスを、そのままトップタービンとしての第１中圧タービンに設置しても、再熱蒸気の温度が７００℃以上と著しく高くなってくると、高い強度保証を維持させることが難しくなりつつある。
【００１０】
このため、蒸気タービンには、タービンノズルボックスを第１中圧タービンに設置しても強度保証を高く維持できる新たな技術の実現化が望まれており、その解決手段として蒸気による冷却の採用が進められている。
【００１１】
しかし、蒸気冷却の採用と言えども、蒸気タービンにとっては未開発の分野であり、試行錯誤を繰り返している。
【００１２】
本発明は、このような背景技術に基づいてなされたものであり、超高温の再熱蒸気に対処してタービンノズルボックスに高い強度保証を維持させる蒸気タービンを提供することを目的とする。
【００１３】
【課題を解決するための手段】
本発明に係る蒸気タービンは、上述の目的を達成するために、請求項１に記載したように、再熱蒸気供給管が接続されてボイラから再熱蒸気が供給される中圧タービンを、第１中圧タービンと第２中圧タービンとに区分けし、区分けした第１中圧タービンをトップタービンとして配置し、ボトムタービンとして配置した蒸気タービン部に前記第２中圧タービンを組み込んだ蒸気タービンにおいて、前記第１中圧タービンは、前記再熱蒸気供給管を介して供給される前記再熱蒸気をタービン段落に供給する蒸気室であるタービンノズルボックスを備え、前記タービンノズルボックスは、壁内部に設けられた冷却蒸気通路と、前記冷却蒸気通路から壁内側面に貫通させた噴出口と、前記壁内側面に前記壁内側面から離間させて設けられた遮蔽板とを備え、前記タービンノズルボックスの前記冷却蒸気通路に供給した冷却蒸気を前記噴出孔から前記遮蔽板に向かって噴出させるものである。
【００１５】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項２に記載したように、タービンノズルボックスの壁内側面を覆う遮蔽板は、前記タービンノズルボックスの壁内側面の全域を断続的に覆う構成にしたものである。
【００１６】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項３に記載したように、タービンノズルボックスの壁内側面を覆う遮蔽板は、前記タービンノズルボックスの壁内側面の全域を密閉して覆う構成にしたものである。
【００１７】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項４に記載したように、タービンノズルボックスの壁内側面を覆う遮蔽板は、平板状の耐熱板であることを特徴とするものである。
【００１８】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項５に記載したように、タービンノズルボックスの壁内側面を覆う遮蔽板は、波状板であることを特徴とするものである。
【００１９】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項６に記載したように、タービンノズルボックスの壁内側面を覆う遮蔽板は、支持部で支持させる構成にしたものである。
【００２０】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項７に記載したように、タービンノズルボックスの壁内側面を覆う遮蔽板は、前記タービンノズルボックスの壁内面に対し、層状に配置し、層状に配置した各遮蔽板間に通路を形成する構成にしたものである。
【００２１】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項８に記載したように、タービンノズルボックスの壁内側面の全域を密閉して覆う遮蔽板は、冷却蒸気を投入する冷却蒸気投入口と冷却蒸気を回収する冷却蒸気回収口とを備えたものである。
【００２２】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項９に記載したように、タービンノズルボックスの壁内側面の全域を密閉して覆う遮蔽板は、複数に区分けして配置するとともに、複数に区分けした遮蔽板毎に冷却蒸気投入口と冷却蒸気回収口とを備えたものである。
【００２３】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項１０に記載したように、タービンノズルボックスの壁内側面の全域を密閉して覆う遮蔽板は、前記タービンノズルボックスの壁内面に対し、層状に配置し、層状に配置した各遮蔽板間に通路を形成するとともに、冷却蒸気投入口から各通路に投入する冷却蒸気を回収する冷却蒸気回収口を備えたものである。
【００２４】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項１１に記載したように、タービンノズルボックスの壁内側面の全域を密閉して覆う遮蔽板は、前記タービンノズルボックスの壁内面に対し、仕切りを設けるとともに、各仕切りに冷却蒸気通過口を備えたものである。
【００２５】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項１２に記載したように、仕切りに設けた冷却蒸気通過口は、前記仕切りに対し、互い違いに蛇行して配置する構成にしたものである。
【００２６】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項１３に記載したように、冷却蒸気は、蒸気タービン部の高圧タービンの高圧タービン抽気であることを特徴とするものである。
【００２７】
また、本発明に係る蒸気タービンは、上述の目的を達成するために、請求項１４に記載したように、冷却蒸気は、トップタービンとして配置する第１中圧タービンの中圧タービン抽気であることを特徴とするものである。
【００２８】
【発明の実施の形態】
以下、本発明に係る蒸気タービンの実施形態を図面および図面に付した符号を引用して説明する。
【００２９】
本発明に係る蒸気タービンの実施形態の説明に先立ち、まず、温度７００℃以上の超高温再熱蒸気を用いる蒸気タービンプラントの実施形態を、図１を引用して説明する。
【００３０】
本実施形態に係る蒸気タービンプラントは、コンベンショナルな蒸気タービン部１のうち、中圧タービン２を第１中圧タービン２ａと第２中圧タービン２ｂとに区分けし、区分けした第１中圧タービン２ａをトップタービンとして配置し、温度７００℃以上の再熱蒸気に膨張仕事をさせるとともに、第１中圧タービン２ａに超高温再熱蒸気を供給して強度的に充分に保証できるように、ボトムタービンとして配置したコンベンショナルな蒸気タービン部１のうち、高圧タービン３の中間段落からの高圧タービン抽気を冷却蒸気として用い、この冷却蒸気を高圧タービン抽気系５を介して第１中圧タービン２ａに供給する蒸気冷却系４を設ける一方、第１中圧タービン２ａで膨張仕事を終えた中圧タービン排気を中圧タービン排気系１２を介して給水系１４の給水を加熱させる過熱器６を設けている。
【００３１】
ボトムタービンとして配置したコンベンショナルな蒸気タービン部１は、互いを軸結合させて高圧タービン３、第２中圧タービン２ｂ、複流タイプの低圧タービン７、発電機８を備え、ボイラ９から発生した主蒸気を高圧タービン３に供給し、ここで膨張仕事をさせ、膨張仕事を終えた高圧タービン排気を低温再熱系１０を介してボイラ９の再熱器１１に供給され、ここで温度７００℃以上の再熱蒸気に生成され、生成された再熱蒸気をトップタービンとしての第１中圧タービン２ａに供給している。
【００３２】
第１中圧タービン２ａは、再熱蒸気に膨張仕事をさせ、膨張仕事を終えた中圧タービン排気を中圧タービン排気系１２を介して過熱器６に供給するとともに、残りを蒸気タービン部１の第２中圧タービン２ｂに供給し、再び膨張仕事をさせ、膨張仕事を終えた中圧タービン排気を低圧タービン７に供給し、ここでも膨張仕事をさせ、その際に発生する動力で発電機８を駆動している。
【００３３】
また、本実施形態に係る蒸気タービンプラントは、復水系１３と給水系１４とを備えている。
【００３４】
復水系１３は、復水の流れに沿って順に、復水器１５、復水ポンプ１６、第１低圧給水加熱器１７、第２低圧給水加熱器１８、第３低圧給水加熱器１９、第４低圧給水加熱器２０を備え、低圧タービンからの低圧タービン排気を復水器１５で凝縮して復水にし、この復水を復水ポンプ１６で圧送させ、第１〜第４低圧給水加熱器１７，１８，１９，２０で低圧タービン７からの低圧抽気蒸気を熱源として順次、予熱（再生）させている。
【００３５】
一方、給水系１４は、給水の流れに沿って順に、脱気器２１、給水ポンプ２２、第１高圧給水加熱器２３、第２高圧給水加熱器２４、第３高圧給水加熱器２５、第４高圧給水加熱器２６、過熱器２７を備え、脱気器２１で復水系１３の第４低圧給水加熱器２０から供給される復水を蒸気タービン部１の第２中圧タービン３ｂからの中圧抽気蒸気を熱源として加熱脱気させて給水にし、この給水を給水ポンプ２２で昇圧させ、第１〜第４高圧給水加熱器２３，２４，２５，２６で蒸気タービン部１の第２中圧タービン３ｂからの中圧タービン抽気、高圧タービン３からの高圧タービン抽気、高圧タービン３からの高圧タービン排気、過熱器６からの過熱蒸気等を熱源として順次予熱させた後、ボイラ９に戻している。
【００３６】
他方、ボトムタービンとして配置したコンベンショナルな蒸気タービン部１に対し、トップタービンとして配置した第１中圧タービン２ａには、蒸気タービン部１の高圧タービン３の中間段落から抽気する冷却蒸気として使用する高圧タービン抽気が低温再熱系１０、蒸気冷却系４を介して供給されている。
【００３７】
また、第１中圧タービン２ａは、図２に示すように、外部ケーシング３２と内部ケーシング３３との２重ケーシング構造にするとともに、再熱蒸気管２７から供給される超高温の再熱蒸気を一旦集め、集めた再熱蒸気を内部ケーシング３３に収容するタービンロータ３４の軸方向に沿って多段落に設けたタービンノズル２９とタービン動翼３０とで構成するタービン段落２８に噴出させるタービンノズルボックス３１を備えている。
【００３８】
このタービンノズルボックス３１は、図３および図４に示すように、一側面を再熱蒸気管２７に接続し、タービン段落２８に臨む他側面を、ノズル口（絞り口）３５を備えた蒸気室３６を形成するとともに、蒸気室３６を形成する壁３７の内部に設けた冷却蒸気通路３８と、冷却蒸気通路３８からの冷却蒸気を壁３７の壁内側面に向って噴出させる噴出口３９と、支持部４０で支持され、壁面３７の壁内側面全体を断続的に覆い、冷却蒸気流出口４５を備えた遮蔽板４１とで構成される。
【００３９】
この遮蔽板４１は、例えば、平板状の耐熱板、具体的には耐酸化性に優れたオーステナイト系合金ＳＵＳ３１０等が使用される。
【００４０】
このような構成を備える第１中圧タービン２ａにおいて、タービンノズルボックス３１には、図１に示すように、蒸気タービン部１の高圧タービン３の中間段落から抽気する高圧タービン抽気が高圧タービン抽気系５、蒸気冷却系４を介して冷却蒸気として供給される。なお、冷却蒸気は、高圧タービン抽気を用いたが、これに限らず第１中圧タービン２ａの中圧タービン抽気でもよく、またはボイラで加熱中の蒸気でもよい。
【００４１】
タービンノズルボックス３１に供給された冷却蒸気は、図３および図４に示すように、壁３７の内部に形成する冷却蒸気通路３８を流れる間に壁３７を冷却させた後、噴出口３９から遮蔽板４１に向って噴出し、ここからさらに冷却蒸気流出口４５を介して蒸気室３６に向って噴出する。
【００４２】
図１４は、タービンノズルボックス３１に超高温の再熱蒸気が供給されたときの遮蔽板４１を設けた場合の壁３７に与える温度分布線図で、横軸にタービンノズルボックス３１の壁３７、壁３７の内面側の遮蔽板４１のそれぞれの各位置を模式的に示し、縦軸に温度を示している。
【００４３】
この図から、遮蔽板４１があるために、タービンノズルボックス３１の壁３７に超高温の再熱蒸気から与えられる熱が少なくなっていることがわかった。
【００４４】
このように、本実施形態は、タービンノズルボックス３１の壁３７の内部に冷却蒸気を流す冷却蒸気通路３８を形成し、超高温の再熱蒸気とタービンノズルボックス３１の壁３７との温度差を少なくさせるとともに、タービンノズルボックス３１の壁内側面を遮蔽板４１で断続的に覆い、タービンノズルボックス３１の壁３７への超高温の再熱蒸気から与えられる熱を遮蔽させる構成にしたので、タービンノズルボックス３１の壁３７に発生する熱応力等を少なくさせることができ、高い強度保証を維持させて蒸気タービンに安定運転を行わせることができる。
【００４５】
なお、本実施形態では、タービンノズルボックス３１の外側を覆う遮蔽板４１を平板状の耐熱板を用いたが、この例に限らず、例えば、図５に示すように、遮蔽板４２を伸縮材で作製された波状板を用いてもよい。熱移動を効果的に吸収する点で有効である。
【００４６】
また、本実施形態では、タービンノズルボックス３１の壁内側面を断続的に覆う遮蔽板４１を、壁３７の内面から同じ高さにして支持部４０で支持させているが、この例に限らず、例えば、図６に示すように、支持部４１を他の支持部４０ｂ，４０ｃよりも高くし、タービンノズルボックス３１の壁３７の壁内側面と遮蔽板４１との空間部４３をより広く確保して噴出口３９から噴出する冷却蒸気の圧力を回復させてもよく、さらに、例えば、図７に示すように、遮蔽板４１ａ，４１ｂ，４１ｃ，…を支持する支持部４０ａ，４０ｂ，４０ｃ，…を順次、タービンノズルボックス３１の壁内側面から蒸気室３６に向って高くし、層状に配置した遮蔽板４１ａ，４１ｂ，４１ｃ，…で通路４４ａ，４４ｂ，…を形成し、遮蔽板４１ａ，４１ｂ，４１ｃ，…の内径側、外径側の両面に冷却蒸気を流して冷却させてもよい。
【００４７】
図８および図９は、本発明に係る蒸気タービンに適用するタービンノズルボックス３１の第２実施形態を示す断面図である。
【００４８】
本実施形態に係る蒸気タービンは、タービンノズルボックス３１の壁３７の壁内側面全域を遮蔽板４１で密閉にして覆い、密閉にした遮蔽板４１を支持部４０で支持させるとともに、タービンノズルボックス３１の壁３７の内部に設けた冷却蒸気通路３８と遮蔽板４１との間に形成する空間部４７に冷却蒸気通路３８からの冷却蒸気を噴出させる噴出口４ｂと、噴出させた冷却蒸気を再び冷却蒸気通路３８に回収させる回収口４８とを備えたものである
このように、本実施形態は、タービンノズルボックス３１の壁３７の壁内側面全域を密閉にして覆う遮蔽板４１を設けるとともに、密閉した空間部４７と冷却蒸気通路３８との間に冷却蒸気の噴出と回収とのそれぞれを行わせる噴出口４６と、回収口４８とを備え、タービンノズルボックス３１の壁３７に超高温の再熱蒸気から与えられる熱を遮蔽させる構成にしたので、タービンノズルボックス３１に発生する熱応力を低く抑えることができ、蒸気タービンに安定運転を行わせることができる。
【００４９】
なお、本実施形態に係る蒸気タービンは、タービンノズルボックス３１の壁３７の壁内側面全域を覆う遮蔽板４１を密閉形にし、密閉した空間部４７と冷却蒸気通路３８との間に冷却蒸気の噴出と回収とのそれぞれを行わせる噴出口４６と、回収口４７とを備えたが、この例に限らず、例えば、図１０に示すように、タービンノズルボックス３１の壁３７の壁内側面全域を遮蔽板４１で密閉にして覆い、その密閉する遮蔽板４１を第１遮蔽板４１ａ、第２遮蔽板４１ｂ、…と細く複数に区分けし、区分けした遮蔽板４１ａ，４１ｂ，…のそれぞれに形成する空間部４７ａ，４７ｂ，…と冷却蒸気通路３８との間に噴出口４６と回収口４８とを設けてもよく、さらに、例えば、図１１に示すように、遮蔽板４１ａ，４１ｂ，４１ｃ，…を支持する支持部４０ａ，４０ｂ，４０ｃ，…を順次タービンノズルボックス３１の壁３７の壁内側面から蒸気室３６に向って高くし、層状に配置した遮蔽板４１ａ，４１ｂ，４１ｃ，…で通路４４ａ，４４ｂ，…を形成し、遮蔽板４１ａ，４１ｂ，４１ｃ，…の内径側、外径側の両面に冷却蒸気を流して冷却させてもよい。
【００５０】
図１２は、本発明に係る蒸気タービンに適用するタービンノズルボックス３１の第３実施形態を示す一部切欠概念図である。
【００５１】
本実施形態に係る蒸気タービンは、タービンノズルボックス３１の壁３７の壁内側面全域を遮蔽板４１で密閉にして覆い、密閉にした遮蔽板４１に、例えば図１に示した高圧タービン３からの高圧タービン抽気を冷却蒸気として供給する冷却蒸気供給口４９と、タービンノズルボックス３１の壁３７を冷却させた後の冷却蒸気を、例えば、第１中圧タービン２ａの中間段落に回収させる冷却蒸気回収口５０とを設けたものである。なお、遮蔽板４１は、支持部４０で支持される。
【００５２】
このように、本実施形態は、遮蔽板４１で密閉するタービンノズルボックス３１の壁３７の壁内側面に冷却蒸気を直接供給して冷却させるので、比較的圧力損失を少なくさせてタービンノズルボックス３１の壁３７を良好に冷却させることができる。
【００５３】
なお、本実施形態は、タービンノズルボックス３１の壁３７の壁内側面全域を密閉にして覆う遮蔽板４１に冷却蒸気供給口４９と冷却蒸気回収口５０とを設け、タービンノズルボックス３１の壁３７に、直接、冷却蒸気を供給したが、この例に限らず、例えば、図１３に示すように、タービンノズルボックス３１の壁３７の壁内側面全域を遮蔽板４１で密閉にして覆うとともに、密閉にした空間部分に仕切り５１，５１，…を複数設け、各仕切り５１，５１，…の互い違いの蛇行位置に冷却蒸気通過口５２，５２，…を設け、冷却蒸気を蛇行させてタービンノズルボックス３１の壁３７を冷却させてもよい。
【００５４】
【発明の効果】
以上の説明のとおり、本発明に係る蒸気タービンは、タービンノズルボックスの壁の壁内側面全域を遮蔽板で覆うとともに、タービンノズルボックスの壁を遮蔽板で覆って形成する空間部分に冷却蒸気を直接供給し、タービンノズルボックスの壁に超高温の再熱蒸気からの熱を直接与えない構成にしたので、超高温の再熱蒸気の熱に基づく過度な熱応力等の発生もなく、タービンノズルボックスに高い強度保証を維持させることができる。
【図面の簡単な説明】
【図１】中圧タービンを第１中圧タービンと第２中圧タービンとに区分けし、区分けした第１中圧タービンをトップタービンとして配置し、第１中圧タービンに超高温の再熱蒸気を供給する蒸気タービンプラントの概略系統図。
【図２】図１で示した第１中圧タービンの概略縦断面図。
【図３】本発明に係る蒸気タービンに適用するタービンノズルボックスの第１実施形態を示す概略断面図。
【図４】図３のＸ部の部分拡大断面図。
【図５】図３におけるタービンノズルボックスの第１変形例を示す部分断面図。
【図６】図３におけるタービンノズルボックスの第２変形例を示す部分断面図。
【図７】図３におけるタービンノズルボックスの第３変形例を示す部分断面図。
【図８】本発明に係る蒸気タービンに適用するタービンノズルボックスの第２実施形態を示す概略断面図。
【図９】図８のＹ部の部分拡大断面図。
【図１０】図９におけるタービンノズルボックスの第１変形例を示す概念図。
【図１１】図９におけるタービンノズルボックスの第２変形例を示す概念図。
【図１２】図９におけるタービンノズルボックスの第３変形例を示す概念図。
【図１３】図９におけるタービンノズルボックスの第４変形例を示す概念図。
【図１４】タービンノズルボックスの壁内側面を遮蔽板で覆った場合、再熱蒸気のタービンノズルボックス壁に与える温度分布線図。
【符号の説明】
１蒸気タービン部
２中圧タービン
２ａ第１中圧タービン
２ｂ第２中圧タービン
３高圧タービン
４蒸気冷却系
５高圧タービン抽気系
６過熱器
７低圧タービン
８発電機
９ボイラ
１０低温再熱系
１１再熱器
１２中圧タービン排気系
１３復水系
１４給水系
１５復水器
１６給水ポンプ
１７第１低圧給水加熱器
１８第２低圧給水加熱器
１９第３低圧給水加熱器
２０第４低圧給水加熱器
２１脱気器
２２給水ポンプ
２３第１高圧給水加熱器
２４第２高圧給水加熱器
２５第３高圧給水加熱器
２６第４高圧給水加熱器
２７再熱蒸気管
２８タービン段落
２９タービンノズル
３０タービン動翼
３１タービンノズルボックス
３２外部ケーシング
３３内部ケーシング
３４タービンロータ
３５ノズル口
３６蒸気室
３７壁
３８冷却蒸気通路
３９噴出口
４０，４０ａ，４０ｂ… 支持部
４１，４１ａ，４０ｂ… 遮蔽板
４２遮蔽板
４３空間部
４４ａ，４４ｂ… 通路
４５冷却蒸気流出口
４６噴出口
４７空間部
４８回収口
４９冷却蒸気供給口
５０冷却蒸気回収口
５１仕切り
５２冷却蒸気通過口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steam turbine, and more particularly, to a steam turbine that can maintain high strength assurance of a turbine nozzle box by coping with high steam temperatures.
[0002]
[Prior art]
The high temperature of the steam skillfully utilizes the characteristics of the Rankine cycle, and it is said that the higher the steam temperature, the more the plant thermal efficiency can be improved.
[0003]
For this reason, steam turbines are becoming nearly established from the relatively low temperature and low pressure steam conditions to single-stage reheating of steam temperatures of 538 ° C / 566 ° C or 538 ° C / 538 ° C.
[0004]
However, as recently, global warming and environmental destruction caused by pollutants such as CO ₂ and NOx have been raised on a global scale, and even in the field of steam turbines, fuel consumption has been reduced to a single unit. Research and development to increase the capacity is underway, one of which is dividing the intermediate pressure turbine into a first intermediate pressure turbine and a second intermediate pressure turbine, and arranging the divided first intermediate pressure turbine as a top turbine, The second intermediate pressure turbine is incorporated in a conventional steam turbine section arranged as a bottom turbine as in the conventional case, and the reheat steam from the boiler reheater is supplied to the first intermediate pressure turbine at a temperature of 700 ° C. or higher. Has been proposed (see Patent Document 1).
[0005]
When the reheat steam temperature is 700 ° C. or higher, the first intermediate pressure turbine arranged as the top turbine still has many problems to be solved, and as one of them, the turbine connected to the reheat steam supply pipe There is strength of the nozzle box.
[0006]
This turbine nozzle box functions as a steam chamber when supplying reheated steam supplied from a boiler reheater to a turbine stage through a reheated steam supply pipe. A high strength guarantee is required only by direct exposure to high-temperature reheat steam. Currently, we are exploring ways to ensure high strength.
[0007]
[Patent Document 1]
Japanese Patent Application No. 2003-125672 [0008]
[Problems to be solved by the invention]
Conventionally, in a thermal power plant, a turbine nozzle box is installed on the steam inlet side of a high-pressure turbine in a conventional steam turbine section to cope with main steam at a temperature of 538 ° C. to 566 ° C. to maintain high strength.
[0009]
However, even if the turbine nozzle box installed in the high-pressure turbine is installed in the first medium-pressure turbine as the top turbine as it is, if the temperature of the reheat steam becomes extremely high at 700 ° C or higher, a high strength guarantee is provided. Is becoming difficult to maintain.
[0010]
For this reason, it is desired for the steam turbine to realize a new technology capable of maintaining a high strength guarantee even when the turbine nozzle box is installed in the first intermediate pressure turbine. It is being advanced.
[0011]
However, adoption of steam cooling is an undeveloped field for steam turbines, and trial and error are repeated.
[0012]
The present invention has been made based on such a background art, and an object of the present invention is to provide a steam turbine that copes with extremely high-temperature reheat steam and maintains a high strength guarantee in a turbine nozzle box.
[0013]
[Means for Solving the Problems]
Steam turbine according to the present invention, in order to achieve the above object, as described in claim 1, and reheat steam supply pipe is connected to pressure turbine in the reheat steam is supplied from the boiler, the In a steam turbine in which a first intermediate pressure turbine is divided into a first intermediate pressure turbine, the divided first intermediate pressure turbine is disposed as a top turbine, and the second intermediate pressure turbine is incorporated in a steam turbine portion disposed as a bottom turbine. The first intermediate pressure turbine includes a turbine nozzle box which is a steam chamber for supplying the reheat steam supplied through the reheat steam supply pipe to a turbine stage, and the turbine nozzle box is disposed inside the wall. A provided cooling steam passage, a jet port penetrating from the cooling steam passage to the inner wall surface, and a shielding plate provided on the inner wall surface away from the inner wall surface Provided is a cooling steam supplied to the cooling steam passage of the turbine nozzle box which is ejected toward the shield plate from the ejection hole.
[0015]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claim 2, the shielding plate for covering the wall inner surface of the turbine nozzle box wall inner surface of the turbine nozzle box The entire area is intermittently covered.
[0016]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claim 3, the shield plate covering the wall inner surface of the turbine nozzle box wall inner surface of the turbine nozzle box The entire area is hermetically covered.
[0017]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claim 4, the shielding plate for covering the wall inner surface of the turbine nozzle box, that the plate-shaped heat plate It is a feature.
[0018]
Further, the steam turbine relating to the present invention, to achieve the object, as described in claim 5, the shielding plate for covering the wall inner surface of the turbine nozzle box, characterized in that a corrugated plate Is.
[0019]
Moreover, in order to achieve the above-mentioned object, the steam turbine according to the present invention is configured such that the shielding plate covering the inner wall surface of the turbine nozzle box is supported by the support portion as described in claim 6. It is.
[0020]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claim 7, the shielding plate for covering the wall inner surface of the turbine nozzle box to wall inner surface of the turbine nozzle box These are arranged in layers, and a passage is formed between the shielding plates arranged in layers.
[0021]
Further, in order to achieve the above object, the steam turbine according to the present invention, as described in claim 8 , is provided with a shielding plate that seals and covers the entire area of the inner surface of the wall of the turbine nozzle box. And a cooling steam recovery port for recovering the cooling steam.
[0022]
In order to achieve the above object, the steam turbine according to the present invention has a shielding plate that covers and seals the entire area of the inner surface of the wall of the turbine nozzle box, as described in claim 9. And provided with a cooling steam inlet and a cooling steam recovery port for each of the shielding plates divided into a plurality of sections.
[0023]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claim 1 0, shielding plate covering seals the entire region of the wall inner surface of the turbine nozzle box, the turbine nozzle Arranged in layers with respect to the inner wall of the box, and formed a passage between the shield plates arranged in layers, and provided with a cooling steam recovery port for recovering the cooling steam that enters the passage from the cooling steam input port It is.
[0024]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claim 1 1, shielding plate covering seals the entire region of the wall inner surface of the turbine nozzle box, the turbine nozzle A partition is provided on the inner wall surface of the box, and each partition is provided with a cooling steam passage port.
[0025]
The steam turbine according to the present invention, in order to achieve the above object, as described in claim 1 2, the cooling steam passage port formed in a partition, compared the partition, and alternately meandering arrangement It is the structure which does.
[0026]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claims 1 to 3, the cooling steam is characterized by a high-pressure turbine extraction of the high-pressure turbine of the steam turbine unit Is.
[0027]
Further, the steam turbine according to the present invention, in order to achieve the above object, as described in claims 1 to 4, the cooling steam is a pressure turbine extraction in the first intermediate-pressure turbine disposed as a top turbine It is characterized by this.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a steam turbine according to the present invention will be described with reference to the drawings and reference numerals attached to the drawings.
[0029]
Prior to the description of the embodiment of the steam turbine according to the present invention, first, an embodiment of a steam turbine plant using ultra-high temperature reheated steam having a temperature of 700 ° C. or higher will be described with reference to FIG.
[0030]
In the steam turbine plant according to the present embodiment, in the conventional steam turbine unit 1, the intermediate pressure turbine 2 is divided into a first intermediate pressure turbine 2a and a second intermediate pressure turbine 2b, and the divided first intermediate pressure turbine 2a is divided. Is arranged as a top turbine, and the reheated steam having a temperature of 700 ° C. or higher is caused to perform expansion work, and the superheated reheated steam is supplied to the first intermediate pressure turbine 2a to sufficiently guarantee the strength. Among the conventional steam turbine sections 1 arranged as follows, the high-pressure turbine bleed from the middle stage of the high-pressure turbine 3 is used as cooling steam, and this cooling steam is supplied to the first intermediate-pressure turbine 2 a via the high-pressure turbine bleed system 5. While providing the steam cooling system 4, the intermediate pressure turbine exhaust that has finished the expansion work in the first intermediate pressure turbine 2 a is passed through the intermediate pressure turbine exhaust system 12. It is provided superheater 6 for heating a feed water feed water system 14.
[0031]
A conventional steam turbine unit 1 arranged as a bottom turbine includes a high-pressure turbine 3, a second intermediate-pressure turbine 2 b, a double-flow type low-pressure turbine 7, and a generator 8 that are axially coupled to each other, and main steam generated from a boiler 9. Is supplied to the high-pressure turbine 3, where the expansion work is performed, and the high-pressure turbine exhaust that has finished the expansion work is supplied to the reheater 11 of the boiler 9 through the low-temperature reheat system 10. The generated reheat steam is supplied to the first intermediate pressure turbine 2a as the top turbine.
[0032]
The first intermediate-pressure turbine 2a causes the reheat steam to perform expansion work, supplies the intermediate-pressure turbine exhaust that has completed the expansion work to the superheater 6 via the intermediate-pressure turbine exhaust system 12, and the remainder to the steam turbine unit 1 Is supplied to the second intermediate pressure turbine 2b, and the expansion work is performed again. The intermediate pressure turbine exhaust which has completed the expansion work is supplied to the low pressure turbine 7, and the expansion work is performed here, and the generator is generated by the power generated at that time. 8 is driven.
[0033]
The steam turbine plant according to this embodiment includes a condensate system 13 and a water supply system 14.
[0034]
The condensate system 13 includes a condenser 15, a condensate pump 16, a first low-pressure feed water heater 17, a second low-pressure feed water heater 18, a third low-pressure feed water heater 19, and a fourth in order along the condensate flow. A low-pressure feed water heater 20 is provided, and the low-pressure turbine exhaust from the low-pressure turbine is condensed by the condenser 15 to be condensed water, and this condensate is pumped by the condensate pump 16. , 18, 19 and 20 are sequentially preheated (regenerated) using the low-pressure extracted steam from the low-pressure turbine 7 as a heat source.
[0035]
On the other hand, the feed water system 14 is in the order of the flow of feed water, in the order of the deaerator 21, feed water pump 22, first high pressure feed water heater 23, second high pressure feed water heater 24, third high pressure feed water heater 25, fourth. A high-pressure feed water heater 26 and a superheater 27 are provided, and the degasifier 21 supplies the condensate supplied from the fourth low-pressure feed water heater 20 of the condensate system 13 to the intermediate pressure from the second intermediate-pressure turbine 3 b of the steam turbine unit 1. The extracted steam is heated and degassed as a heat source to supply water, the water supply is pressurized by the water supply pump 22, and the first to fourth high-pressure water heaters 23, 24, 25, 26 are used for the second intermediate pressure turbine of the steam turbine unit 1. The medium pressure turbine bleed air from 3b, the high pressure turbine bleed air from the high pressure turbine 3, the high pressure turbine exhaust from the high pressure turbine 3, the superheated steam from the superheater 6 and the like are sequentially preheated as heat sources and then returned to the boiler 9.
[0036]
On the other hand, in contrast to the conventional steam turbine section 1 arranged as a bottom turbine, the first intermediate pressure turbine 2a arranged as a top turbine has a high pressure used as cooling steam extracted from an intermediate stage of the high-pressure turbine 3 of the steam turbine section 1. Turbine bleed air is supplied via a low-temperature reheat system 10 and a steam cooling system 4.
[0037]
Further, as shown in FIG. 2, the first intermediate pressure turbine 2 a has a double casing structure of an outer casing 32 and an inner casing 33, and the super high-temperature reheat steam supplied from the reheat steam pipe 27. A turbine nozzle box that once collects and recharges the collected reheated steam to a turbine stage 28 composed of turbine nozzles 29 and turbine blades 30 provided in multiple stages along the axial direction of the turbine rotor 34 that accommodates the inner casing 33. 31 is provided.
[0038]
As shown in FIGS. 3 and 4, the turbine nozzle box 31 has one side connected to the reheat steam pipe 27 and the other side facing the turbine stage 28 is a steam chamber provided with a nozzle port (throttle port) 35. 36, a cooling steam passage 38 provided inside a wall 37 forming the steam chamber 36, and a jet outlet 39 for jetting the cooling steam from the cooling steam passage 38 toward the inner wall surface of the wall 37, It is supported by the support portion 40 and includes a shielding plate 41 that intermittently covers the entire inner wall surface of the wall surface 37 and includes a cooling steam outlet 45.
[0039]
As the shielding plate 41, for example, a flat heat-resistant plate, specifically, an austenitic alloy SUS310 having excellent oxidation resistance is used.
[0040]
In the first intermediate pressure turbine 2a having such a configuration, as shown in FIG. 1, a high pressure turbine bleed air extracted from an intermediate stage of the high pressure turbine 3 of the steam turbine section 1 is provided in the turbine nozzle box 31 in a high pressure turbine bleed system. 5. It is supplied as cooling steam through the steam cooling system 4. The cooling steam used is high-pressure turbine extraction, but is not limited to this, and may be medium-pressure turbine extraction of the first intermediate-pressure turbine 2a, or steam being heated by a boiler.
[0041]
As shown in FIGS. 3 and 4, the cooling steam supplied to the turbine nozzle box 31 cools the wall 37 while flowing through the cooling steam passage 38 formed inside the wall 37, and is then shielded from the jet outlet 39. It ejects toward the plate 41, and further ejects from here toward the steam chamber 36 via the cooling steam outlet 45.
[0042]
FIG. 14 is a temperature distribution diagram given to the wall 37 when the shielding plate 41 is provided when the super-high-temperature reheated steam is supplied to the turbine nozzle box 31, and the horizontal axis shows the wall 37 of the turbine nozzle box 31, Each position of the shielding plate 41 on the inner surface side of the wall 37 is schematically shown, and the vertical axis indicates the temperature.
[0043]
From this figure, it was found that due to the shielding plate 41, the heat given to the wall 37 of the turbine nozzle box 31 from the superheated reheat steam is reduced.
[0044]
As described above, in the present embodiment, the cooling steam passage 38 through which the cooling steam flows is formed inside the wall 37 of the turbine nozzle box 31, and the temperature difference between the super high temperature reheat steam and the wall 37 of the turbine nozzle box 31 is reduced. Since the inner wall surface of the turbine nozzle box 31 is intermittently covered with the shielding plate 41 and the heat given from the super high-temperature reheat steam to the wall 37 of the turbine nozzle box 31 is shielded. The thermal stress etc. which generate | occur | produce on the wall 37 of the nozzle box 31 can be decreased, a high intensity | strength guarantee can be maintained, and a steam turbine can be performed stably.
[0045]
In this embodiment, the shield plate 41 that covers the outside of the turbine nozzle box 31 is a flat heat-resistant plate. However, the present invention is not limited to this example. For example, as shown in FIG. You may use the corrugated board produced by (1). This is effective in effectively absorbing heat transfer.
[0046]
In the present embodiment, the shielding plate 41 that intermittently covers the inner wall surface of the turbine nozzle box 31 is supported at the same height from the inner surface of the wall 37 by the support portion 40. However, the present invention is not limited to this example. For example, as shown in FIG. 6, the support part 41 is made higher than the other support parts 40 b and 40 c, and a wider space part 43 is secured between the inner wall surface of the wall 37 of the turbine nozzle box 31 and the shielding plate 41. Then, the pressure of the cooling steam ejected from the ejection port 39 may be recovered, and further, for example, as shown in FIG. 7, support portions 40a, 40b, 40c, which support the shielding plates 41a, 41b, 41c,. Are sequentially raised from the inner wall surface of the turbine nozzle box 31 toward the steam chamber 36, and the passages 44a, 44b,... Are formed by the shielding plates 41a, 41b, 41c,. 41b, 1c, ... inner diameter side of, may be cooled by flowing cooling steam to both sides of the outer diameter side.
[0047]
8 and 9 are cross-sectional views showing a second embodiment of a turbine nozzle box 31 applied to a steam turbine according to the present invention.
[0048]
In the steam turbine according to the present embodiment, the entire inner wall surface of the wall 37 of the turbine nozzle box 31 is hermetically covered with the shielding plate 41, and the sealed shielding plate 41 is supported by the support portion 40, and the turbine nozzle box 31. The cooling steam passage 38 formed between the cooling steam passage 38 and the shielding plate 41 provided in the wall 37 and ejecting the cooling steam from the cooling steam passage 38 into the space 47 and cooling the jetted cooling steam again. As described above, the present embodiment is provided with the recovery port 48 for recovery to the steam passage 38. In this embodiment, the shielding plate 41 is provided so as to cover the entire inner surface of the wall 37 of the wall 37 of the turbine nozzle box 31 and seal the sealing. A turbine nozzle box having a recovery port 48 and a recovery port 48 for performing ejection and recovery of cooling steam between the space 47 and the cooling steam passage 38. Since the heat applied from the ultra-high-temperature reheated steam is shielded by the one wall 37, the thermal stress generated in the turbine nozzle box 31 can be kept low, and the steam turbine can be operated stably. .
[0049]
In the steam turbine according to the present embodiment, the shielding plate 41 that covers the entire inner side surface of the wall 37 of the turbine nozzle box 31 is sealed, and the cooling steam flows between the sealed space 47 and the cooling steam passage 38. Although the ejection port 46 for performing each of ejection and recovery and the recovery port 47 are provided, the present invention is not limited to this example. For example, as shown in FIG. Is sealed with a shielding plate 41, and the shielding plate 41 is hermetically divided into a plurality of first shielding plates 41a, second shielding plates 41b,... And formed on each of the divided shielding plates 41a, 41b,. .. And the cooling steam passage 38 may be provided with a jet outlet 46 and a recovery port 48. Further, as shown in FIG. 11, for example, shielding plates 41a, 41b, 41c, Supports… The support portions 40a, 40b, 40c,... Are sequentially raised from the inner surface of the wall 37 of the turbine nozzle box 31 toward the steam chamber 36, and the passages 44a, 44b are formed by the shielding plates 41a, 41b, 41c,. ,... May be formed and cooled by flowing cooling steam on both the inner and outer diameter sides of the shielding plates 41a, 41b, 41c,.
[0050]
FIG. 12 is a partially cutaway conceptual view showing a third embodiment of a turbine nozzle box 31 applied to a steam turbine according to the present invention.
[0051]
The steam turbine according to the present embodiment covers the entire inner side surface of the wall 37 of the turbine nozzle box 31 with a shielding plate 41 and covers the sealed shielding plate 41 from, for example, the high-pressure turbine 3 shown in FIG. Cooling steam recovery for recovering the cooling steam after cooling the cooling steam supply port 49 for supplying the high-pressure turbine bleed gas as cooling steam and the wall 37 of the turbine nozzle box 31 to the intermediate stage of the first intermediate pressure turbine 2a, for example. A mouth 50 is provided. The shielding plate 41 is supported by the support portion 40.
[0052]
As described above, in the present embodiment, the cooling steam is directly supplied to the wall inner surface of the wall 37 of the turbine nozzle box 31 that is sealed by the shielding plate 41 to cool the turbine nozzle box 31. Therefore, the turbine nozzle box 31 is relatively reduced in pressure loss. The wall 37 can be cooled well.
[0053]
In the present embodiment, a cooling steam supply port 49 and a cooling steam recovery port 50 are provided in the shielding plate 41 that covers and covers the entire inner wall surface of the wall 37 of the turbine nozzle box 31, and the wall 37 of the turbine nozzle box 31 is provided. However, the present invention is not limited to this example. For example, as shown in FIG. 13, the entire inner side surface of the wall 37 of the turbine nozzle box 31 is covered with a shielding plate 41 and sealed. Are provided with a plurality of partitions 51, 51,... In the meandering space, and cooling steam passage ports 52, 52,... Are provided at alternate meandering positions of the partitions 51, 51,. The wall 37 may be cooled.
[0054]
【The invention's effect】
As described above, the steam turbine according to the present invention covers the entire inner side surface of the wall of the turbine nozzle box with the shielding plate, and supplies the cooling steam to the space portion formed by covering the wall of the turbine nozzle box with the shielding plate. Since it is configured to supply directly and heat from the ultra-high temperature reheat steam is not directly applied to the wall of the turbine nozzle box, there is no occurrence of excessive thermal stress etc. due to the heat of the ultra-high temperature reheat steam, and the turbine nozzle The box can maintain a high strength guarantee.
[Brief description of the drawings]
FIG. 1 shows that a medium-pressure turbine is divided into a first medium-pressure turbine and a second medium-pressure turbine, the divided first medium-pressure turbine is arranged as a top turbine, and an ultrahigh-temperature reheat steam is disposed in the first medium-pressure turbine. The schematic system diagram of the steam turbine plant which supplies
FIG. 2 is a schematic longitudinal sectional view of the first intermediate pressure turbine shown in FIG.
FIG. 3 is a schematic cross-sectional view showing a first embodiment of a turbine nozzle box applied to a steam turbine according to the present invention.
4 is a partial enlarged cross-sectional view of a portion X in FIG. 3;
FIG. 5 is a partial sectional view showing a first modification of the turbine nozzle box in FIG. 3;
6 is a partial cross-sectional view showing a second modification of the turbine nozzle box in FIG. 3;
7 is a partial cross-sectional view showing a third modification of the turbine nozzle box in FIG. 3;
FIG. 8 is a schematic cross-sectional view showing a second embodiment of a turbine nozzle box applied to a steam turbine according to the present invention.
9 is a partially enlarged cross-sectional view of a Y portion in FIG.
10 is a conceptual diagram showing a first modification of the turbine nozzle box in FIG. 9;
11 is a conceptual diagram showing a second modification of the turbine nozzle box in FIG. 9;
12 is a conceptual diagram showing a third modification of the turbine nozzle box in FIG.
13 is a conceptual diagram showing a fourth modification of the turbine nozzle box in FIG. 9. FIG.
FIG. 14 is a temperature distribution diagram of reheat steam given to the turbine nozzle box wall when the inner surface of the wall of the turbine nozzle box is covered with a shielding plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steam turbine part 2 Medium pressure turbine 2a 1st intermediate pressure turbine 2b 2nd intermediate pressure turbine 3 High pressure turbine 4 Steam cooling system 5 High pressure turbine bleed system 6 Superheater 7 Low pressure turbine 8 Generator 9 Boiler 10 Low temperature reheat system 11 Heater 12 Medium pressure turbine exhaust system 13 Condensate system 14 Water supply system 15 Condenser 16 Feed water pump 17 First low pressure feed water heater 18 Second low pressure feed water heater 19 Third low pressure feed water heater 20 Fourth low pressure feed water heater 21 Deaerator 22 Water supply pump 23 First high pressure feed water heater 24 Second high pressure feed water heater 25 Third high pressure feed water heater 26 Fourth high pressure feed water heater 27 Reheat steam pipe 28 Turbine stage 29 Turbine nozzle 30 Turbine blade 31 Turbine nozzle box 32 External casing 33 Internal casing 34 Turbine rotor 35 Nozzle port 36 Steam chamber 37 Wall 38 Cooling steam passage 39 Jet Ports 40, 40a, 40b ... Support portions 41, 41a, 40b ... Shield plate 42 Shield plate 43 Space portions 44a, 44b ... Passage 45 Cooling steam outlet 46 Spout 47 Space 48 Recovery port 49 Cooling steam supply port 50 Cooling steam Recovery port 51 Partition 52 Cooling steam passage port

Claims

The intermediate pressure turbine to which the reheat steam supply pipe is connected and the reheat steam is supplied from the boiler is divided into a first intermediate pressure turbine and a second intermediate pressure turbine, and the divided first intermediate pressure turbine is used as a top turbine. In the steam turbine in which the second intermediate pressure turbine is incorporated in the steam turbine section disposed as a bottom turbine,
The first intermediate pressure turbine includes a turbine nozzle box which is a steam chamber for supplying the reheat steam supplied via the reheat steam supply pipe to a turbine stage,
The turbine nozzle box includes a cooling steam passage provided in a wall, a jet port penetrating the cooling steam passage from the cooling steam passage to an inner wall surface, and a shield provided on the inner wall surface away from the inner wall surface. With a board,
A steam turbine, wherein the cooling steam supplied to the cooling steam passage of the turbine nozzle box is jetted from the jet port toward the shielding plate .

The steam turbine according to claim 1, wherein the shielding plate covering the inner wall surface of the turbine nozzle box is configured to intermittently cover the entire inner wall surface of the turbine nozzle box.

The steam turbine according to claim 1, wherein the shielding plate that covers the inner wall surface of the turbine nozzle box is configured to cover and cover the entire inner wall surface of the turbine nozzle box.

The steam turbine according to claim 1, wherein the shielding plate covering the inner wall surface of the turbine nozzle box is a flat heat-resistant plate.

The steam turbine according to claim 1, wherein the shielding plate covering the inner wall surface of the turbine nozzle box is a corrugated plate.

The steam turbine according to claim 1, wherein the shielding plate that covers the inner surface of the wall of the turbine nozzle box is supported by a support portion.

The shielding plate that covers the inner surface of the wall of the turbine nozzle box is arranged in layers with respect to the inner surface of the wall of the turbine nozzle box, and a passage is formed between the shielding plates arranged in layers. Item 2. The steam turbine according to Item 1.

Shielding plate covering seals the entire region of the wall inner surface of the turbine nozzle box, according to claim 3, characterized in that a cooling steam recovery port for recovering the cooling steam and the cooling steam inlet for introducing cooling steam Steam turbine.

The shielding plate that covers and covers the entire area of the inner wall surface of the turbine nozzle box is divided into a plurality of parts, and a cooling steam inlet and a cooling steam recovery port are provided for each of the divided shielding plates. The steam turbine according to claim 3 .

The shielding plate that seals and covers the entire area of the inner surface of the wall of the turbine nozzle box is arranged in layers on the inner surface of the wall of the turbine nozzle box, and forms a passage between the shielding plates arranged in layers, and cooling steam. The steam turbine according to claim 3, further comprising a cooling steam recovery port that recovers the cooling steam input to each passage from the input port.

The shielding plate that covers and covers the entire area of the inner surface of the wall of the turbine nozzle box is provided with a partition on the inner surface of the wall of the turbine nozzle box, and each partition is provided with a cooling steam passage port. 3. The steam turbine according to 3 .

Cooling steam passage port formed in a partition, it compared the partition, the steam turbine of claim 1 1, wherein it has a structure in which disposed alternately meanders.

The cooling steam, the steam turbine of claim 1 or 8, wherein it is a high-pressure turbine extraction of the high-pressure turbine of the steam turbine unit.

Cooling steam, the steam turbine of claim 1 or 8, wherein it is a pressure turbine extraction in the first intermediate-pressure turbine disposed as a top turbine.