JP2004019961A

JP2004019961A - Once-through waste-heat boiler

Info

Publication number: JP2004019961A
Application number: JP2002171765A
Authority: JP
Inventors: Takanori Tsutsumi; 堤　孝則; Isao Moriyama; 森山　功; Keisuke Sonoda; 園田　圭介; Makoto Fujita; 藤田　真
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2002-06-12
Filing date: 2002-06-12
Publication date: 2004-01-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide a once-through waste-heat boiler which can prevent the generation of instability in flowing stability in a heating route from water supply to the generation of overheat steam and which can prevent damage to an evaporator member. <P>SOLUTION: This once-through waste-heat boiler is equipped with economizers 20a, 20b and 20c for receiving the supplied water to previously heat it, the evaporator 21 for heating the water supplied from the economizers 20a, 20b and 20c to generate the steam, and super-heaters 22a, 22b and 22c for heating more the steam from the evaporator 21 to generate the super-heated steam in a casing for leading the exhaust gas of a power generator upward from a lower part. This boiler is also equipped with a water supply control device for controlling a water supply flow rate to maintain the superheating degree of the steam in an outlet of the evaporator 21 within the predetermined range on the basis of the superheated steam temperature. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、貫流型排熱ボイラに係わり、特にガスタービン等から排出される排気ガスの排熱を利用して過熱蒸気を生成する貫流型排熱ボイラにおける給水制御装置に関する。
【０００２】
【従来の技術】
この種の貫流型排熱ボイラの一例について、図１５を参照しながら以下に説明する。
図１５において、符号１はガスタービン、符号２は貫流型排熱ボイラである。
ガスタービン１は、空気を圧縮する空気圧縮機３，圧縮された空気を用いて燃料を燃焼させる燃焼器４，燃焼器４で燃焼して膨張したガスが導入されて駆動するタービン５、後述する貫流型排熱ボイラ２からの蒸気が導入されるタービン６、および、タービン５およびタービン６の回転エネルギーから発電を行う発電機７を備えている。燃焼器４にはガバナ弁８を介して燃料が供給されている。このガバナ弁８は、負荷指令（発電装置指令）が入力されることにより、その指令値に応じた開度に調節されるようになっている。
【０００３】
次いで貫流型排熱ボイラ２の構成について具体的に説明する。同図に示す従来の貫流型排熱ボイラ２は、下方から上方へ向かってガスタービン１の排気ガスＧを導くケーシング１１と、該ケーシング１１内に上から下に向かって順番に配置された節炭器１２、蒸発器１３及び過熱器１４と、ケーシング１１の外部に設置されて節炭器１２に給水Ｗを供給する給水ポンプ１５および管寄せ１６と、ケーシング１１の外部に設置されて過熱器１４からの過熱蒸気ＳＳを取り入れる管寄せ１７とを備えて構成される。
節炭器１２、蒸発器１３および過熱器１４は、お互いの接続部を介して、管寄せ１６から管寄せ１７にかけて連続した流路をなすように構成されている。
節炭器１２は、管寄せ１６からの給水Ｗをその内部に通して予熱する役目をなし、また、蒸発器１３は、節炭器１２からの給水Ｗを加熱して蒸気Ｓを蒸発させる役目をなし、過熱器１４は、蒸発器１３からの蒸気Ｓを更に加熱して過熱蒸気ＳＳを生成する役目をなす。
この従来の貫流型排熱ボイラによれば、給水ポンプ１５を起動して給水を管寄せ１６に送り込むことにより、節炭器１２への給水が開始される。節炭器１２ではケーシング１１内を流れる排気ガスＧからの排気が管壁面を介して熱交換され、蒸発器１３に行く前の予熱が行われる。
予熱されて昇温した給水Ｗは、下方の蒸発器１３へと送り込まれ、排気ガスＧとの熱交換で更に昇温して蒸発することにより蒸気Ｓとなる。
続いて、蒸発器１３から下方の過熱器１４に向かって送り込まれる蒸気Ｓは、排気ガスＧとの熱交換で更なる加熱を受けて過熱蒸気ＳＳとなる。
このようにして生成される過熱蒸気ＳＳは、管寄せ１７を介してケーシング１１の外部へと取り出される。
【０００４】
【発明が解決しようとする課題】
ところで、上記従来の貫流型排熱ボイラでは、装置起動時や負荷変動時などの運用条件が変化する際に、蒸発器１３内に完全に給水Ｗが蒸発せずに水と蒸気とが混在した気液混合状態となり、例えば、蒸発器１３から下方の過熱器１４に向かう蒸気Ｓと共に水が流れ落ちることがあり、このような場合、過熱器１４内での蒸気の流動安定性が不安定になるおそれがあった。
また、逆に蒸発器での入熱が過多の場合、蒸発器１３で蒸発し、さらに過熱蒸気となる。蒸発器はその材質が定格運転時の飽和温度で設計されており、飽和温度を越える過度の温度の場合、蒸発器部材の焼損の危険性があった。
【０００５】
本発明は上記事情に鑑みて成されたものであり、給水から過熱蒸気生成に至る加熱経路上での流動安定性が不安定になるのを防止し、かつ蒸発器部材の焼損を防止できる貫流型排熱ボイラを提供することを目的とする。
【０００６】
【課題を解決するための手段】
請求項１に記載の発明は、他の装置から排出された排ガスを導くケーシング内に、給水を受けて該給水を予熱する節炭器と、該節炭器からの前記給水を加熱して蒸気を発生する蒸発器と、該蒸発器からの前記蒸気を更に加熱して過熱蒸気を生成する過熱器とを備えた貫流型排熱ボイラにおいて、前記節炭器によって予熱された給水の温度に基づいて、前記蒸発器出口における蒸気の過熱度を所定範囲内に保つように前記給水流量を制御する給水制御装置を備えていることを特徴とする。
【０００７】
蒸発器出口における給水の加熱が足りないと、過熱器内に流入した水によって過熱器内での蒸気の流動性が不安定になる。一方、蒸発器における加熱が大きすぎると、適正範囲を超える高温の過熱蒸気により蒸発部部材が焼損してしまう。本発明においては、給水制御装置によって過熱度が適正な範囲内に保たれる。
なお、予熱された給水の温度を検出する位置は、節炭器の出口でも良いし途中でも良い。また、排ガスを排出する他の装置としてはガスタービンを挙げることができるが、これに限定されるものではない。
【０００８】
請求項２に記載の発明は、請求項１に記載の貫流型排熱ボイラにおいて、前記給水制御装置は、前記節炭器によって予熱された給水の温度を検出する温度検出手段と、前記他の装置としてのガスタービンの負荷指令に基づいた給水温度設定を算出する給水温度設定算出器と、前記節炭器によって予熱された給水温度と給水温度設定との偏差に基づいて給水流量指令を生成する制御器とを備え、該給水流量指令に基づいて前記給水流量が制御されることを特徴とする。
【０００９】
予熱された給水の温度が設定値より低い場合、蒸発器出口での蒸発が不完全で、過熱器系統に水・蒸気の混合流体が流れ込むおそれがある。このとき、給水温度設定算出器で算出される給水温度設定と実際の蒸気温度との偏差が生じ、制御器は給水を減じさせる指令を出力する。
給水流量が減少した場合、給水の単位流量あたりの受熱量が増加し、節炭器により予熱された給水温度は上昇、蒸発器での蒸発が完全に行われるようになる。そして、給水温度設定と実際の給水温度とが一致した時点で給水量は落ち着く。また、予熱された給水の温度が設定値より高い場合、蒸発器出口での蒸発が完全に終了し、更に加熱され過熱蒸気の状態で過熱器に流れ込む。この場合、過熱器でさらに過熱され、結果として過熱器系統出口での蒸気温度が必要以上に上昇する。
このとき、給水温度設定算出器で算出される給水温度設定と実際の給水温度との偏差が生じ、制御器は給水を増加させる指令を出力する。
給水流量が増加した場合、給水の単位流量あたりの受熱量が減少し、蒸発器での蒸発が完全に行われた状態で過熱器に蒸気が流れ込むようになる。また、節炭器により予熱された給水温度は低下し、給水温度設定と実際の給水温度が一致した時点で給水量は落ち着く。
【００１０】
請求項３に記載の発明は、請求項２に記載の貫流型排熱ボイラにおいて、前記負荷指令に基づいて給水先行設定を算出する負荷基準給水先行設定算出器を備え、該給水先行設定が、前記給水流量指令に足し合わせられることを特徴とする。
【００１１】
本発明において、負荷基準給水先行設定算出器は、予め決められた負荷における排気ガス側と水・蒸気側との熱バランスにて、蒸発器出口にて給水が完全に蒸気になる給水流量を算出する。（本設定は、予め設計計画および燃焼試験等により準備される。）
これにより、本発明においては、温度偏差のずれを修正するように、制御器が動く。したがって、制御器の制御感度（ゲイン）を大きくすることができ、温度変化に対する追従性がより向上する。
【００１２】
請求項４に記載の発明は、請求項２または３に記載の貫流型排熱ボイラにおいて、前記蒸発器出口における流体圧力に対する飽和温度を計算する蒸発器出口飽和温度算出器と、該蒸発器出口飽和温度算出器により計算された飽和温度と実際の蒸発器出口における流体温度との偏差を算出する蒸発器出口側偏差演算器と、該蒸発器出口側偏差演算器により算出された前記偏差に見合った給水バイアス信号を生成する蒸発器出口側給水バイアス信号発生器とを備え、該蒸発器出口側給水バイアス信号発生器により生成された給水バイアス信号と前記給水流量指令との和と、前記給水流量指令とのいずれか大きい方に基づいて給水流量が制御されることを特徴とする。
【００１３】
本発明においては、何らかの原因で蒸発器の出口の流体（蒸気）温度が上昇した場合、給水バイアス信号によって給水流量指令を増加させ、蒸発器出口での流体温度を下げる。
【００１４】
請求項５に記載の発明は、請求項２から４いずれかに記載の貫流型排熱ボイラにおいて、前記過熱蒸気の圧力に基づいて飽和温度を計算する過熱蒸気飽和温度算出器と、該過熱蒸気飽和温度算出器により計算された飽和温度と実際の過熱蒸気温度との偏差を算出する過熱蒸気側偏差演算器と、該過熱蒸気側偏差演算器により算出された前記偏差に見合った給水バイアス信号を生成する過熱蒸気側給水バイアス信号発生器とを備え、該過熱蒸気側給水バイアス信号発生器により生成された給水バイアス信号と前記給水流量指令との和と、前記給水流量指令とのいずれか小さい方に基づいて給水流量が制御されることを特徴とする。
【００１５】
何らかの原因により過熱蒸気の温度が低下した場合、蒸発器出口流体が完全に蒸発せず、水・蒸気の混合状態にあると考えられる。本発明においては、この場合に給水バイアス信号を用いて給水流量を低下させるので、蒸発器出口で過度の過熱不足状態になることを抑えることができる。なお、過熱蒸気とは、過熱器出口でも良いし途中でも良い。
【００１６】
請求項６に記載の発明は、請求項４に記載の貫流型排熱ボイラにおいて、該蒸発器出口側偏差演算器により算出された前記偏差を比例制御した後に前記給水流量指令に足し込むことを特徴とする。
【００１７】
この発明においては、蒸発器出口の飽和温度と、実際の温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
【００１８】
請求項７に記載の発明は、請求項５または６に記載の貫流型排熱ボイラにおいて、実際の過熱蒸気温度と、ガスタービンの負荷指令に基づいた過熱蒸気温度設定との偏差を比例制御した後に前記給水流量指令に足し込むことを特徴とする。
【００１９】
この発明においては、過熱蒸気温度設定と実際の過熱蒸気温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
【００２０】
請求項８に記載の発明は、請求項１に記載の貫流型排熱ボイラにおいて、前記給水制御装置は、前記節炭器によって予熱された給水の温度を検出する温度検出手段と、前記ケーシング内に導入される排ガスによる入熱量に基づいた給水温度設定を算出する給水温度設定算出器と、前記節炭器により予熱された給水温度と給水温度設定との偏差に基づいて給水流量指令を生成する制御器とを備え、該給水流量指令に基づいて前記給水流量が制御されることを特徴とする。
【００２１】
予熱された給水の温度が設定値より低い場合、蒸発器出口での蒸発が不完全で、過熱器系統に水・蒸気の混合流体が流れ込むおそれがある。このとき、給水温度設定算出器で算出される給水温度設定と実際の蒸気温度との偏差が生じ、制御器は給水を減じさせる指令を出力する。
給水流量が減少した場合、給水の単位流量あたりの受熱量が増加し、節炭器により予熱された給水温度は上昇、蒸発器での蒸発が完全に行われるようになる。そして、給水温度設定と実際の給水温度とが一致した時点で給水量は落ち着く。また、予熱された給水の温度が設定値より高い場合、蒸発器出口での蒸発が完全に終了し、更に加熱され過熱蒸気の状態で過熱器に流れ込む。この場合、過熱器でさらに過熱され、結果として過熱器系統出口での蒸気温度が必要以上に上昇する。
このとき、給水温度設定算出器で算出される給水温度設定と実際の給水温度との偏差が生じ、制御器は給水を増加させる指令を出力する。
給水流量が増加した場合、給水の単位流量あたりの受熱量が減少し、蒸発器での蒸発が完全に行われた状態で過熱器に蒸気が流れ込むようになる。また、節炭器により予熱された給水温度は低下し、給水温度設定と実際の給水温度が一致した時点で給水量は落ち着く。
また、本発明においては、蒸気温度設定をボイラに導入される入熱量に基づいて算出することによって、より追従性の良い給水制御が可能となる。
【００２２】
請求項９に記載の発明は、請求項８に記載の貫流型排熱ボイラにおいて、前記入熱量に基づいて給水先行設定を算出する入熱基準給水先行設定算出器を備え、該給水先行設定が、前記給水流量指令に足し合わせられることを特徴とする。
【００２３】
本発明において、入熱基準給水先行設定算出器は、予め決められた入熱量における排気ガス側と水・蒸気側との熱バランスにて、蒸発器出口にて給水が完全に蒸気になる給水流量を算出する。（本設定は、予め設計計画および燃焼試験等により準備される。）
これにより、本発明においては、温度偏差のずれを修正するように、制御器が動く。したがって、制御器の制御感度（ゲイン）を大きくすることができ、温度変化に対する追従性がより向上する。
【００２４】
請求項１０に記載の発明は、請求項８または９に記載の貫流型排熱ボイラにおいて、前記蒸発器出口における流体圧力に対する飽和温度を計算する蒸発器出口飽和温度算出器と、該蒸発器出口飽和温度算出器により計算された飽和温度と実際の蒸発器出口における流体温度との偏差を算出する蒸発器出口側偏差演算器と、該蒸発器出口側偏差演算器により算出された前記偏差に見合った給水バイアス信号を生成する蒸発器出口側給水バイアス信号発生器とを備え、該蒸発器出口側給水バイアス信号発生器により生成された給水バイアス信号と前記給水流量指令との和と、前記給水流量指令とのいずれか大きい方に基づいて給水流量が制御されることを特徴とする。
【００２５】
本発明においては、何らかの原因で蒸発器の出口の流体（蒸気）温度が上昇した場合、給水バイアス信号によって給水流量指令を増加させ、蒸発器出口での流体温度を下げる。
【００２６】
請求項１１に記載の発明は、請求項８から１０いずれかに記載の貫流型排熱ボイラにおいて、過熱蒸気の圧力に基づいて飽和温度を計算する過熱蒸気飽和温度算出器と、該過熱蒸気飽和温度算出器により計算された飽和温度と実際の過熱蒸気温度との偏差を算出する過熱蒸気側偏差演算器と、該過熱蒸気側偏差演算器により算出された前記偏差に見合った給水バイアス信号を生成する過熱蒸気側給水バイアス信号発生器とを備え、該過熱蒸気側給水バイアス信号発生器により生成された給水バイアス信号と前記給水流量指令との和と、前記給水流量指令とのいずれか小さい方に基づいて給水流量が制御されることを特徴とする。
【００２７】
何らかの原因により過熱蒸気の温度が低下した場合、蒸発器出口流体が完全に蒸発せず、水・蒸気の混合状態にあると考えられる。本発明においては、この場合に給水バイアス信号を用いて給水流量を低下させるので、蒸発器出口で過度の過熱不足状態になることを抑えることができる。
【００２８】
請求項１２に記載の発明は、請求項１０に記載の貫流型排熱ボイラにおいて、該蒸発器出口側偏差演算器により算出された前記偏差を比例制御した後に前記給水流量指令に足し込むことを特徴とする。
【００２９】
この発明においては、蒸発器出口の飽和温度と、実際の温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
【００３０】
請求項１３に記載の発明は、請求項１１または１２に記載の貫流型排熱ボイラにおいて、実際の過熱蒸気温度と、入熱量に基づいた過熱蒸気温度設定との偏差を比例制御した後に前記給水流量指令に足し込むことを特徴とする。
【００３１】
この発明においては、過熱蒸気温度設定と実際の過熱蒸気温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
【００３２】
請求項１４に記載の発見は、請求項３から７いずれかに記載の貫流型排熱ボイラにおいて、前記ケーシング内に導入される排ガスによる入熱量に基づいて給水先行設定を算出する入熱基準給水先行設定算出器を備え、該給水先行設定と、前記負荷基準給水先行設定算出器によって算出された給水先行設定との偏差が、前記給水流量指令に足し合わされることを特徴とする。
【００３３】
本発明においては、給水流量先行指令に対して、負荷指令に基づく給水先行設定と、ボイラへの入熱に基づく差分を足し込むことにより、より追従性の向上が実現する。
【００３４】
【発明の実施の形態】
次に、本発明の実施形態について、図面を参照して説明する。本発明は、ガスタービン等から排出される排気ガスの排熱を利用して過熱蒸気を生成する貫流型排熱ボイラに関するものであり、その実施形態を図１〜図１４の図面を参照しながら行うが、この発明がこれらの実施形態のみに限定解釈されるものではない。図１は、本発明の第１実施形態としての貫流型排熱ボイラにおける水・蒸気の流れを示しており、高圧・中圧・低圧系の３圧力系を有する排熱ボイラであり、これら３圧力系のいずれに用いても構わない。他の実施形態についても同様である。ここでは、高圧系について説明する。
図１においては、節炭器系を符号２０，蒸発器を符号２１、過熱器系を符号２２で示してある。節炭器系２０は、３つの節炭器２０ａ、２０ｂ、２０ｃからなり、過熱器系２２は、３つの過熱器２２ａ、２２ｂ、２２ｃからなる。
【００３５】
本貫流型排熱ボイラには、給水制御装置２５として、以下の構成が設けられている。符号３１は、節炭器２０ｃ出口の給水温度（以下節炭器出口温度と呼ぶ）を検出する温度検出手段である。また、符号３３は、ガバナ弁８（図１５参照）への負荷指令（発電装置指令）３２に基づく節炭器出口の給水温度設定（以下節炭器出口温度設定と呼ぶ）を算出する関数演算器（給水温度設定算出器）である。符号３４は、温度検出手段３１により検出された節炭器出口温度と、関数演算器３３により算出された節炭器出口温度設定との偏差を計算する偏差演算器である。この偏差演算器３４により算出された偏差は、符号３５で示した制御器に与えられ、この制御器は、節炭器２０ｃの出口給水温度を給水温度設定にコントロールするように給水流量指令を給水ポンプ１５に指令として出力するものである。給水ポンプ１５においては、制御器３５の出力に見合う給水量をポンプ回転数またはポンプ出口に設置される給水制御弁の開度を制御することにより、ボイラにおいて必要とされる給水を供給するものである。すなわち、与えられた給水流量指令に追従する機能を含んだものであり、制御機能または制御装置を含んでいる。
関数演算器３３で算出される節炭器出口温度設定は、予め決められた負荷におけるガス側と水・蒸気側との熱バランスにて、蒸発器２１出口で給水が完全に蒸気になるために、蒸発器２１でのガスから流体への受熱量を見越した節炭器２０ｃ出口での温度設定である。（関数演算器３３にて計算に用いられる関数は、予め設定計画および燃焼試験により準備される関数である。）
【００３６】
このように構成された本実施形態においては、負荷に対して、節炭器２０ｃの出口給水温度を所定の温度に制御することにより、蒸発器２１出口での蒸発を完全に終了させ、過熱器２２系統に蒸発が完了していない混合水の流入を防止する。
具体的には、今、節炭器２０によって予熱された給水の温度が設定値より低い場合、蒸発器２１出口での蒸発が不完全で、過熱器系統に水・蒸気の混合流体が流れ込むおそれがある。このとき、関数演算器３３で算出される節炭器出口温度設定と実際の節炭器出口温度との偏差が生じ、制御器３５は給水を減じさせる指令を出力し、給水ポンプ１５は、給水量を減じるよう働く。
給水流量が減少した場合、給水の単位流量あたりの受熱量が増加し、節炭器２０により予熱された給水温度は上昇、蒸発器２１での蒸発が完全に行われるようになる。そして、節炭器出口温度設定と実際の節炭器出口温度とが一致した時点で給水量は落ち着く。
また、節炭器２０によって予熱された給水の温度が設定値より高い場合、蒸発器２１出口での蒸発が完全に終了し、更に加熱され過熱蒸気の状態で過熱器２２に流れ込む。この場合、過熱器２２でさらに過熱され、結果として過熱器系統出口での過熱蒸気温度が必要以上に上昇する。
このとき、関数演算器３３で算出される節炭器出口温度設定と実際の節炭器出口温度との偏差が生じ、制御器３５は給水を増加させる指令を出力し、給水ポンプ１５は、給水量を増加させるようにはたらく。
給水流量が増加した場合、給水の単位流量あたりの受熱量が減少し、蒸発器２１での蒸発が完全に行われた状態で過熱器２２に蒸気が流れ込むようになる。また、節炭器２０により予熱された節炭器出口温度は低下し、節炭器出口温度設定と実際の節炭器出口温度が一致した時点で給水量は落ち着く。
【００３７】
このように、適切な温度の蒸気が過熱器２２に流れ込むので、加熱経路上での流動安定性が不安定になるのを防止することができる。
【００３８】
次に、本発明の第２実施形態について図２を用いて説明する。なお、上記第１実施形態と同一の構成については同一の符号を用い、その説明を省略する。
図２において、符号３７は給水先行設定を算出する関数演算器（負荷基準給水先行設定算出器）である。この関数演算器３７は、予め決められた負荷におけるガス側と水・蒸気側との熱バランスにて、蒸発器２１出口にて給水が完全に蒸気になる給水流量を算出する。（本設定は、予め設計計画および燃焼試験等により準備される関数である。）
また、給水先行設定は、加算器３６にて制御器３５で算出された給水流量指令と足し合わされた後、上記第１実施形態と同様に給水ポンプ１５に出力される。
【００３９】
本回路によって、負荷に見合った給水がボイラに対してなされ、上記第１実施形態における温度偏差のずれを修正するように、制御器３５が動く。したがって、制御器３５の制御感度（ゲイン）を大きくすることができ、温度変化に対する追従性がより向上してより安定したボイラの運転が可能となる。
【００４０】
次に、本発明の第３実施形態について図３を用いて説明する。なお、上記第２実施形態と同一の構成については同一の符号を用い、その説明を省略する。
図３において、符号３８は蒸発器２１出口における流体圧力を測定する圧力測定手段である。３９は、圧力測定手段３８により測定された圧力に対する飽和温度を計算する蒸発器出口飽和温度算出器である。また、蒸発器２１出口における流体の実際の温度は、温度計測手段４０により計測され、前記蒸発器出口飽和温度算出器３９で算出された飽和温度と、温度計測手段４０により計測された実際の温度との偏差が、蒸発器出口側偏差演算器４１により算出される。そして、この偏差演算器４１により算出された偏差に見合った給水バイアス信号が蒸発器出口側給水バイアス信号発生器４２で生成され、この給水バイアス信号が加算器４３にて、加算器３６の出力である給水流量指令と足し合わされ、給水緊急増指令が準備される。そして、高値選択回路４４にて、加算器３６の出力である給水流量指令と加算器４３の出力である給水緊急増指令とが比較され、高値であるものが実際の給水流量指令として給水ポンプ１５に与えられる。
このように構成されていることにより、何らかの原因で蒸発器２１の出口の流体（蒸気）温度が上昇した場合、飽和温度との偏差によって給水バイアス信号が増加し、この分だけ給水流量指令が増加する。すなわち、緊急給水流量増加を行うことができ、より安定したボイラの運転が可能となる。
【００４１】
次に、本発明の第４実施形態について図４を用いて説明する。なお、上記第３実施形態と同一の構成については同一の符号を用い、その説明を省略する。
本実施形態においては、過熱器２２ａの出口における流体（蒸気）圧力を検出する圧力検出手段４５と、同温度を検出する温度検出手段４５’とが設けられている。符号４６は、圧力検出手段４５により検出された圧力における飽和温度を計算する過熱蒸気飽和温度算出器である。符号４７は、過熱蒸気飽和温度算出器４６において計算された飽和温度と、温度検出手段４５’により検出された実際の蒸気温度との偏差を求める過熱蒸気側偏差演算器である。この偏差に見合った給水バイアス信号が過熱蒸気側給水バイアス信号発生器４８により生成され、この給水バイアス信号が加算器４９にて、加算器３６の出力である給水流量指令と足し合わされ、給水緊急減指令が準備される。そして、低値選択回路５０にて、高値選択回路４４の出力である給水流量指令と加算器４９の出力である給水緊急減指令とが比較され、低値であるものが実際の給水流量指令として給水ポンプ１５に与えられる。
このように構成されていることにより、以下の効果を得ることができる。
何らかの原因により過熱器２２ａ出口の流体（蒸気）の温度が低下した場合、蒸発器２１出口流体が完全に蒸発せず、水・蒸気の混合状態にあると考えられる。本実施形態においては、飽和温度との偏差によって給水バイアス信号が減少し、この分だけ給水流量指令が減少する。すなわち、緊急給水量減少信号を発生して給水量を低下させるので、蒸発器２１出口で過度の過熱不足状態になることを抑えることができ、より安定したボイラの運転が可能となる。
【００４２】
また、他の実施形態として、図５〜図８に示す構成とすることもできる。図５〜図８は、それぞれ上記第１実施形態〜第４実施形態の変形例であり、ガスタービン排ガス温度５１とガスタービン排ガス流量５２とを乗算器５３でかけることで、排熱ボイラへの入熱量５４が算出される。図５〜図８において、符号３３’は入熱量５４に基づく節炭器出口温度設定を算出する関数演算器（給水温度設定算出器）である。また、図６〜図８において、符号５８は予め決められた入熱量におけるガス側と水・蒸気側との熱バランスにて、蒸発器２１出口にて給水が完全に蒸気になるように給水流量を算出する関数演算器（入熱基準給水先行設定算出器）である。本設定は、予め設計計画および燃焼試験等により準備される関数である。
上記温度設定と給水先行設定の作り方は、負荷指令の場合と同様であり、ガスタービン排ガスがバイパスされない限り、負荷指令と排熱ボイラへのガスタービン入熱は、基本的に同等である。
このように構成されていることにより、排熱ボイラへの入熱に従ったより追従性の良い給水制御が可能となる。
【００４３】
さらにまた、他の実施形態として、図９〜図１１に示す構成とすることもできる。図９〜図１１は、それぞれ上記第２実施形態〜第４実施形態の変形例であり、ガスタービン排ガス温度５１とガスタービン排ガス流量５２とを乗算器５３でかけることで、排熱ボイラ入熱量５４が算出される。この入熱量５４に基づいて、関数演算器（入熱基準給水先行設定算出器）５８において給水先行設定が算出される。
そして、関数演算器５８により算出された給水先行設定と、関数演算器３７により算出された給水先行設定との偏差が、偏差演算器５５で求められる。この偏差は、比例器５６を経た後、加算器５７において給水流量指令に足し合わせる。すなわち、負荷指令に基づく給水先行設定と、入熱に基づく給水先行設定との間で偏差が出た場合、その偏差によって給水流量指令を補正することにより、追従性をより向上させることができる。
【００４４】
さらに、他の実施形態として、図１２〜図１４に示す構成とすることもできる。それぞれ、図１２は図４の、図１３は図８の、図１４は図１１の制御における外乱に対する追従性の向上を図った回路である。
図１２〜図１４において、符号６１はガスタービンの負荷指令に基づいた過熱器２２ａ出口の過熱蒸気温度設定を算出する関数演算器、符号６０は関数演算器６１の出力である過熱蒸気温度設定と温度検出手段４５’により測定された実際の過熱蒸気温度の偏差を求める偏差演算器、符号６２は比例制御器、符号６３は比例制御器６２を経た偏差を給水流量指令に足し込む加算器である。
また、符号６５は蒸発器出口側偏差演算器４１により算出された偏差（蒸発器出口飽和温度算出器３９で算出された飽和温度と、温度計測手段４０により計測された実際の温度との偏差）が与えられる比例制御器であり、符号６４は比例制御器６５の出力が前記給水流量指令に足し込まれる加算器である。
【００４５】
本例では、負荷に見合った蒸発器２１に近い過熱器２２ａ出口に対する蒸気温度設定（これは関数演算器６１により算出される）と、蒸発器２１に近い過熱器２２ａ出口の実際の蒸気温度（これは温度検出手段４５’により検出される）との偏差に基づいて、比例制御器６２が連続的な制御信号（比例制御信号）を生成し、ベースとなる給水流量指令に足し込む。
これによって、外乱に対する追従性が向上する。また、低値選択回路５０で用いられる緊急給水量減少信号とは異なり、本例では給水流量指令に連続的に比例制御信号が足し込まれる。このため低値選択回路５０による緊急給水減少信号にはかからない。
また、蒸発器２１出口の飽和温度監視による蒸発器出口側偏差演算器４１により生成された温度偏差信号に基づいて比例制御器６５が連続的な制御信号（比例制御信号）を生成し、ベースとなる給水流量指令に足し込む。
これによって、外乱に対する追従性が向上する。また、高値選択回路４４で用いられる給水緊急増信号とは異なり、本例では給水流量指令に連続的に比例制御信号が足し込まれる。このため高値選択回路４４による緊急給水増信号にはかからない。
【００４６】
【発明の効果】
以上説明したように、本発明の貫流型排熱ボイラにおいては、以下の効果を得ることができる。
請求項１に記載の発明によれば、給水制御装置によって過熱度が適正な範囲内に保たれるため、給水から過熱蒸気生成に至る加熱経路上での流動安定性が不安定になるのを防止し、かつ蒸発器部材の損傷を防止することができる。
請求項２に記載の発明によれば、給水温度と給水温度設定との偏差に基づいて制御器が給水流量を制御することで、給水温度設定と給水温度とを一致させることができる。
請求項３に記載の発明によれば、温度偏差のずれを修正するように、制御器が動くため、制御器の制御感度（ゲイン）を大きくすることができ、温度変化に対する追従性がより向上する。
請求項４に記載の発明によれば、何らかの原因で蒸発器の出口の流体（蒸気）温度が上昇した場合、給水バイアス信号によって給水流量指令を増加させることにより、蒸発器出口での流体温度を下げることができる。
請求項５に記載の発明によれば、何らかの原因により過熱蒸気の温度が低下した場合、給水バイアス信号を用いて給水流量を低下させるので、蒸発器出口で過度の過熱不足状態になることを抑えることができる。
【００４７】
請求項６に記載の発明によれば、蒸発器出口の飽和温度と、実際の温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
請求項７に記載の発明によれば、過熱蒸気温度設定と実際の過熱蒸気温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
【００４８】
請求項８に記載の発明によれば、給水制御装置によって過熱度が適正な範囲内に保たれるため、給水から過熱蒸気生成に至る加熱経路上での流動安定性が不安定になるのを防止することができる。また、給水温度設定をボイラに導入される入熱量に基づいて算出することによって、より追従性の良い給水制御が可能となる。
請求項９に記載の発明によれば、温度偏差のずれを修正するように、制御器が動くため、制御器の制御感度（ゲイン）を大きくすることができ、温度変化に対する追従性がより向上する。
請求項１０に記載の発明によれば、何らかの原因で蒸発器の出口の流体（蒸気）温度が上昇した場合、給水バイアス信号によって給水流量指令を増加させることにより、蒸発器出口での流体温度を下げることができる。
請求項１１に記載の発明によれば、何らかの原因により過熱蒸気の温度が低下した場合、給水バイアス信号を用いて給水流量を低下させるので、蒸発器出口で過度の過熱不足状態になることを抑えることができる。
【００４９】
請求項１２に記載の発明によれば、蒸発器出口の飽和温度と、実際の温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
請求項１３に記載の発明によれば、過熱蒸気温度設定と実際の過熱蒸気温度との偏差に基づいて算出された制御信号が、連続的に給水流量指令に足し込まれる。これにより、外乱に対する追従性が向上する。
【００５０】
請求項１４に記載の発明によれば、給水流量先行指令に対して、負荷指令に基づく給水先行設定と、ボイラへの入熱に基づく差分を足し込むことにより、より追従性を向上させることができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態として示した貫流型排熱ボイラの構成を示した図である。
【図２】本発明の第２実施形態として示した貫流型排熱ボイラの構成を示した図である。
【図３】本発明の第３実施形態として示した貫流型排熱ボイラの構成を示した図である。
【図４】本発明の第４実施形態として示した貫流型排熱ボイラの構成を示した図である。
【図５】本発明の第１実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図６】本発明の第２実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図７】本発明の第３実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図８】本発明の第４実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図９】本発明の第２実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図１０】本発明の第３実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図１１】本発明の第４実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図１２】図４に示した第４実施形態の変形例として示した貫流型排熱ボイラの構成を示した図である。
【図１３】図８の貫流型排熱ボイラの変形例として示した貫流型排熱ボイラの構成を示した図である。
【図１４】図１１の貫流型排熱ボイラの変形例として示した貫流型排熱ボイラの構成を示した図である。
【図１５】ガスタービンと、従来の貫流型排熱ボイラとを示した図である。
【符号の説明】
３３　関数演算器（給水温度設定算出器）
３７　関数演算器（負荷基準給水先行設定算出器）
３９　蒸発器出口飽和温度算出器
４１　蒸発器出口側偏差演算器
４２　蒸発器出口側給水バイアス信号発生器
４６　過熱蒸気飽和温度算出器
４７　過熱蒸気側偏差演算器
４８　過熱蒸気側給水バイアス信号発生器
５８　関数演算器（入熱基準給水先行設定算出器）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a once-through type exhaust heat boiler, and more particularly to a feedwater control device in a once-through type exhaust heat boiler that generates superheated steam using exhaust heat of exhaust gas discharged from a gas turbine or the like.
[0002]
[Prior art]
An example of this kind of once-through type exhaust heat boiler will be described below with reference to FIG.
In FIG. 15, reference numeral 1 denotes a gas turbine, and reference numeral 2 denotes a once-through type exhaust heat boiler.
The gas turbine 1 includes an air compressor 3 that compresses air, a combustor 4 that burns fuel using the compressed air, a turbine 5 that is driven by introducing gas expanded and burned in the combustor 4, which will be described later. It is provided with a turbine 6 into which steam from the once-through type exhaust heat boiler 2 is introduced, and a generator 7 for generating electric power from the rotational energy of the turbine 5 and the turbine 6. Fuel is supplied to the combustor 4 through a governor valve 8. When a load command (power generation device command) is input, the governor valve 8 is adjusted to an opening corresponding to the command value.
[0003]
Next, the configuration of the once-through type exhaust heat boiler 2 will be specifically described. The conventional once-through type exhaust heat boiler 2 shown in FIG. 1 includes a casing 11 for guiding the exhaust gas G of the gas turbine 1 from below to above, and nodes arranged in the casing 11 in order from above to below. A charcoal unit 12, an evaporator 13 and a superheater 14, a water supply pump 15 and a header 16 installed outside the casing 11 to supply water W to the economizer 12, and a superheater installed outside the casing 11 And a header 17 for taking in the superheated steam SS from 14.
The economizer 12, the evaporator 13, and the superheater 14 are configured to form a continuous flow path from the header 16 to the header 17 via a connection part of each other.
The economizer 12 serves to preheat the feedwater W from the header 16 through the interior thereof, and the evaporator 13 serves to heat the feedwater W from the economizer 12 to evaporate the steam S. The superheater 14 serves to further heat the steam S from the evaporator 13 to generate the superheated steam SS.
According to the conventional once-through type exhaust heat boiler, the water supply to the economizer 12 is started by starting the water supply pump 15 and feeding the water to the header 16. In the economizer 12, the exhaust gas from the exhaust gas G flowing through the casing 11 exchanges heat via the pipe wall surface, and preheats before going to the evaporator 13.
The feed water W that has been preheated and raised in temperature is sent to the lower evaporator 13, where it is further heated and evaporated by heat exchange with the exhaust gas G to become steam S.
Subsequently, the steam S sent from the evaporator 13 toward the lower superheater 14 is further heated by heat exchange with the exhaust gas G and becomes the superheated steam SS.
The superheated steam SS thus generated is taken out of the casing 11 through the header 17.
[0004]
[Problems to be solved by the invention]
By the way, in the above-mentioned conventional once-through type exhaust heat boiler, when the operating conditions such as the start-up of the apparatus and the load change are changed, the water W is not completely evaporated in the evaporator 13 and water and steam are mixed. In a gas-liquid mixed state, for example, water may flow down together with the steam S flowing from the evaporator 13 to the lower superheater 14, and in such a case, the flow stability of the steam in the superheater 14 becomes unstable. There was a fear.
Conversely, when the heat input in the evaporator is excessive, the heat is evaporated in the evaporator 13 and further becomes superheated steam. The material of the evaporator is designed at the saturation temperature at the time of rated operation, and there is a danger of burning of the evaporator member at an excessive temperature exceeding the saturation temperature.
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to prevent flow stability on a heating path from water supply to generation of superheated steam from becoming unstable, and prevent burnout of an evaporator member. It is an object to provide a mold waste heat boiler.
[0006]
[Means for Solving the Problems]
The invention described in claim 1 is an energy-saving device that receives water supply and preheats the water supply in a casing that guides exhaust gas discharged from another device, and heats the water supply from the energy-saving device to generate steam. In a once-through type exhaust heat boiler comprising an evaporator for generating steam and a superheater for further heating the steam from the evaporator to generate superheated steam, based on the temperature of the feedwater preheated by the economizer. And a water supply control device that controls the flow rate of the water supply so as to keep the degree of superheat of the steam at the evaporator outlet within a predetermined range.
[0007]
If the heating of the feedwater at the evaporator outlet is insufficient, the flow of steam in the superheater becomes unstable due to the water flowing into the superheater. On the other hand, if the heating in the evaporator is too large, the evaporator member will be burned by the high-temperature superheated steam exceeding the appropriate range. In the present invention, the degree of superheat is kept within an appropriate range by the water supply control device.
The position where the temperature of the preheated feedwater is detected may be at the outlet of the economizer or at a point midway. Further, as another device for discharging the exhaust gas, a gas turbine can be cited, but it is not limited to this.
[0008]
According to a second aspect of the present invention, in the once-through type exhaust heat boiler according to the first aspect, the water supply control device includes a temperature detection unit configured to detect a temperature of the water supplied by the economizer, A feedwater temperature setting calculator for calculating a feedwater temperature setting based on a load command of a gas turbine as a device, and a feedwater flow rate command based on a deviation between the feedwater temperature preheated by the economizer and the feedwater temperature setting. And a controller, wherein the water supply flow rate is controlled based on the water supply flow rate command.
[0009]
If the temperature of the preheated feedwater is lower than the set value, evaporation at the evaporator outlet is incomplete, and a mixed fluid of water and steam may flow into the superheater system. At this time, a deviation occurs between the feed water temperature setting calculated by the feed water temperature setting calculator and the actual steam temperature, and the controller outputs a command to reduce the feed water.
When the feedwater flow rate decreases, the amount of heat received per unit flow rate of the feedwater increases, the temperature of the feedwater preheated by the economizer rises, and evaporation in the evaporator is completely performed. Then, when the water supply temperature setting matches the actual water supply temperature, the water supply amount is settled. If the temperature of the preheated feedwater is higher than the set value, the evaporation at the outlet of the evaporator is completely finished, and the heated water is further heated and flows into the superheater in a superheated steam state. In this case, the superheater further heats up, and as a result, the steam temperature at the superheater system outlet rises more than necessary.
At this time, a deviation occurs between the feed water temperature setting calculated by the feed water temperature setting calculator and the actual feed water temperature, and the controller outputs a command to increase the feed water.
When the feedwater flow rate increases, the amount of heat received per unit flow rate of the feedwater decreases, and steam flows into the superheater in a state where evaporation in the evaporator is completely performed. Also, the feedwater temperature preheated by the economizer falls, and when the feedwater temperature setting and the actual feedwater temperature match, the feedwater quantity calms down.
[0010]
According to a third aspect of the present invention, in the once-through type exhaust heat boiler according to the second aspect, a load-based water supply advance setting calculator that calculates an advance water supply setting based on the load command is provided. It can be added to the water supply flow rate command.
[0011]
In the present invention, the load-based water supply advance setting calculator calculates the water supply flow rate at which the water supply becomes completely steam at the evaporator outlet based on the heat balance between the exhaust gas side and the water / steam side at a predetermined load. I do. (This setting is prepared in advance by a design plan, a combustion test, etc.)
Thereby, in the present invention, the controller operates so as to correct the deviation of the temperature deviation. Therefore, the control sensitivity (gain) of the controller can be increased, and the ability to follow a temperature change is further improved.
[0012]
According to a fourth aspect of the present invention, in the once-through type exhaust heat boiler according to the second or third aspect, an evaporator outlet saturation temperature calculator for calculating a saturation temperature with respect to a fluid pressure at the evaporator outlet, and the evaporator outlet An evaporator outlet side deviation calculator for calculating the difference between the saturation temperature calculated by the saturation temperature calculator and the actual fluid temperature at the evaporator outlet, and matching the difference calculated by the evaporator outlet side deviation calculator. An evaporator outlet side feedwater bias signal generator for generating a feedwater bias signal, the sum of a feedwater bias signal generated by the evaporator outlet side feedwater bias signal generator and the feedwater flow command, and the feedwater flow rate. The water supply flow rate is controlled based on whichever is larger, the command.
[0013]
In the present invention, when the fluid (steam) temperature at the outlet of the evaporator rises for some reason, the feedwater flow command is increased by the feedwater bias signal, and the fluid temperature at the evaporator outlet is lowered.
[0014]
According to a fifth aspect of the present invention, in the once-through type waste heat boiler according to any one of the second to fourth aspects, a superheated steam saturation temperature calculator for calculating a saturation temperature based on a pressure of the superheated steam, and the superheated steam A superheated steam-side deviation calculator for calculating a deviation between the saturation temperature calculated by the saturation temperature calculator and the actual superheated steam temperature, and a feedwater bias signal corresponding to the deviation calculated by the superheated steam-side deviation calculator. A superheated steam-side feedwater bias signal generator that generates the sum of the feedwater bias signal generated by the superheated steam-side feedwater bias signal generator and the feedwater flow command, or the feedwater flow command, whichever is smaller. The water supply flow rate is controlled based on
[0015]
When the temperature of the superheated steam decreases for some reason, it is considered that the evaporator outlet fluid does not completely evaporate and is in a mixed state of water and steam. In the present invention, in this case, the feedwater flow rate is reduced by using the feedwater bias signal, so that it is possible to suppress an excessive overheating shortage state at the evaporator outlet. In addition, the superheated steam may be at the outlet of the superheater or in the middle thereof.
[0016]
According to a sixth aspect of the present invention, in the once-through type exhaust heat boiler according to the fourth aspect, the deviation calculated by the evaporator outlet deviation calculator is proportionally controlled and then added to the feedwater flow command. Features.
[0017]
In the present invention, the control signal calculated based on the difference between the saturation temperature at the evaporator outlet and the actual temperature is continuously added to the feedwater flow command. As a result, the ability to follow the disturbance is improved.
[0018]
According to a seventh aspect of the present invention, in the once-through type exhaust heat boiler according to the fifth or sixth aspect, the deviation between the actual superheated steam temperature and the superheated steam temperature setting based on the load command of the gas turbine is proportionally controlled. It is characterized in that the water supply flow rate command is added later.
[0019]
In the present invention, the control signal calculated based on the deviation between the superheated steam temperature setting and the actual superheated steam temperature is continuously added to the feedwater flow rate command. As a result, the ability to follow the disturbance is improved.
[0020]
According to an eighth aspect of the present invention, in the once-through type exhaust heat boiler according to the first aspect, the water supply control device detects a temperature of the water supply preheated by the economizer, and the inside of the casing. A feedwater temperature setting calculator that calculates a feedwater temperature setting based on the amount of heat input by the exhaust gas introduced into the exhaust gas, and a feedwater flow rate command based on a deviation between the feedwater temperature preheated by the economizer and the feedwater temperature setting. And a controller, wherein the water supply flow rate is controlled based on the water supply flow rate command.
[0021]
If the temperature of the preheated feedwater is lower than the set value, evaporation at the evaporator outlet is incomplete, and a mixed fluid of water and steam may flow into the superheater system. At this time, a deviation occurs between the feed water temperature setting calculated by the feed water temperature setting calculator and the actual steam temperature, and the controller outputs a command to reduce the feed water.
When the feedwater flow rate decreases, the amount of heat received per unit flow rate of the feedwater increases, the temperature of the feedwater preheated by the economizer rises, and evaporation in the evaporator is completely performed. Then, when the water supply temperature setting matches the actual water supply temperature, the water supply amount is settled. If the temperature of the preheated feedwater is higher than the set value, the evaporation at the outlet of the evaporator is completely finished, and the heated water is further heated and flows into the superheater in a superheated steam state. In this case, the superheater further heats up, and as a result, the steam temperature at the superheater system outlet rises more than necessary.
At this time, a deviation occurs between the feed water temperature setting calculated by the feed water temperature setting calculator and the actual feed water temperature, and the controller outputs a command to increase the feed water.
When the feedwater flow rate increases, the amount of heat received per unit flow rate of the feedwater decreases, and steam flows into the superheater in a state where evaporation in the evaporator is completely performed. Also, the feedwater temperature preheated by the economizer falls, and when the feedwater temperature setting and the actual feedwater temperature match, the feedwater quantity calms down.
Further, in the present invention, by calculating the steam temperature setting based on the amount of heat input to the boiler, it is possible to control the water supply with better tracking.
[0022]
According to a ninth aspect of the present invention, there is provided the once-through type exhaust heat boiler according to the eighth aspect, further comprising a heat input reference water supply precedence setting calculator for calculating a water supply precedence setting based on the heat input amount. And the water supply flow rate command.
[0023]
In the present invention, the heat input standard water supply advance setting calculator calculates the feed water flow rate at which the feed water becomes completely steam at the evaporator outlet based on the heat balance between the exhaust gas side and the water / steam side at a predetermined heat input amount. Is calculated. (This setting is prepared in advance by a design plan, a combustion test, etc.)
Thereby, in the present invention, the controller operates so as to correct the deviation of the temperature deviation. Therefore, the control sensitivity (gain) of the controller can be increased, and the ability to follow a temperature change is further improved.
[0024]
According to a tenth aspect of the present invention, in the once-through type exhaust heat boiler according to the eighth or ninth aspect, an evaporator outlet saturation temperature calculator for calculating a saturation temperature with respect to a fluid pressure at the evaporator outlet, and the evaporator outlet An evaporator outlet side deviation calculator for calculating the difference between the saturation temperature calculated by the saturation temperature calculator and the actual fluid temperature at the evaporator outlet, and matching the difference calculated by the evaporator outlet side deviation calculator. An evaporator outlet side feedwater bias signal generator for generating a feedwater bias signal, the sum of a feedwater bias signal generated by the evaporator outlet side feedwater bias signal generator and the feedwater flow command, and the feedwater flow rate. The water supply flow rate is controlled based on whichever is larger, the command.
[0025]
In the present invention, when the fluid (steam) temperature at the outlet of the evaporator rises for some reason, the feedwater flow command is increased by the feedwater bias signal, and the fluid temperature at the evaporator outlet is lowered.
[0026]
According to an eleventh aspect of the present invention, in the once-through type exhaust heat boiler according to any one of the eighth to tenth aspects, a superheated steam saturation temperature calculator that calculates a saturation temperature based on a pressure of the superheated steam, A superheated steam-side deviation calculator for calculating a deviation between the saturation temperature calculated by the temperature calculator and the actual superheated steam temperature, and a feedwater bias signal corresponding to the deviation calculated by the superheated steam-side deviation calculator are generated. A superheated steam-side feedwater bias signal generator, the sum of the feedwater bias signal generated by the superheated steam-side feedwater bias signal generator and the feedwater flow command, or the feedwater flow command, whichever is smaller. The water supply flow rate is controlled on the basis of this.
[0027]
When the temperature of the superheated steam decreases for some reason, it is considered that the evaporator outlet fluid does not completely evaporate and is in a mixed state of water and steam. In the present invention, in this case, the feedwater flow rate is reduced by using the feedwater bias signal, so that it is possible to suppress an excessive overheating shortage state at the evaporator outlet.
[0028]
According to a twelfth aspect of the present invention, in the once-through type waste heat boiler according to the tenth aspect, the deviation calculated by the evaporator outlet deviation calculator is proportionally controlled and then added to the feedwater flow command. Features.
[0029]
In the present invention, the control signal calculated based on the difference between the saturation temperature at the evaporator outlet and the actual temperature is continuously added to the feedwater flow command. As a result, the ability to follow the disturbance is improved.
[0030]
According to a thirteenth aspect of the present invention, in the once-through type exhaust heat boiler according to the eleventh or twelfth aspect, the water supply is performed after proportionally controlling a deviation between an actual superheated steam temperature and a superheated steam temperature setting based on a heat input amount. It is characterized in that it is added to the flow rate command.
[0031]
In the present invention, the control signal calculated based on the deviation between the superheated steam temperature setting and the actual superheated steam temperature is continuously added to the feedwater flow rate command. As a result, the ability to follow the disturbance is improved.
[0032]
A discovery according to claim 14 is a heat-input standard water supply in which the advance water-supply setting is calculated based on an amount of heat input by the exhaust gas introduced into the casing in the once-through type exhaust heat boiler according to any one of claims 3 to 7. A preceding setting calculator is provided, and a deviation between the preceding water supply setting and the preceding water supply setting calculated by the load-based preceding water supply setting calculator is added to the above-mentioned water supply flow rate command.
[0033]
In the present invention, the follow-up performance can be further improved by adding the water supply advance setting based on the load command and the difference based on the heat input to the boiler to the feed water flow advance command.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. The present invention relates to a once-through type exhaust heat boiler that generates superheated steam by using exhaust heat of exhaust gas discharged from a gas turbine or the like, and an embodiment thereof will be described with reference to FIGS. 1 to 14. However, the present invention is not construed as being limited to only these embodiments. FIG. 1 shows the flow of water and steam in a once-through type exhaust heat boiler as a first embodiment of the present invention. The exhaust heat boiler has three high-pressure, medium-pressure, and low-pressure systems. It may be used for any of the pressure systems. The same applies to other embodiments. Here, the high-pressure system will be described.
In FIG. 1, the economizer system is indicated by reference numeral 20, the evaporator is indicated by reference numeral 21, and the superheater system is indicated by reference numeral 22. The economizer system 20 includes three economizers 20a, 20b, and 20c, and the superheater system 22 includes three superheaters 22a, 22b, and 22c.
[0035]
The following configuration is provided as the water supply control device 25 in the once-through type exhaust heat boiler. Reference numeral 31 denotes temperature detecting means for detecting the feedwater temperature at the outlet of the economizer 20c (hereinafter referred to as economizer outlet temperature). Reference numeral 33 denotes a function calculation for calculating a feedwater temperature setting at the outlet of the economizer based on a load command (generator command) 32 to the governor valve 8 (see FIG. 15) (hereinafter referred to as an economizer outlet temperature setting). (A feed water temperature setting calculator). Reference numeral 34 denotes a deviation calculator for calculating a deviation between the economizer outlet temperature detected by the temperature detector 31 and the economizer outlet temperature setting calculated by the function calculator 33. The deviation calculated by the deviation calculator 34 is given to a controller indicated by reference numeral 35, and the controller issues a water supply flow rate command to control the outlet water supply temperature of the economizer 20c to the water supply temperature setting. This is output to the pump 15 as a command. The water supply pump 15 supplies water required in the boiler by controlling the amount of water supply corresponding to the output of the controller 35 by controlling the pump rotation speed or the opening of a water supply control valve installed at the pump outlet. is there. That is, it includes a function of following a given water supply flow rate command, and includes a control function or a control device.
The economizer outlet temperature setting calculated by the function calculator 33 is such that the feedwater becomes completely steam at the outlet of the evaporator 21 by the heat balance between the gas side and the water / steam side at a predetermined load. The temperature is set at the outlet of the economizer 20c in anticipation of the amount of heat received from the gas to the fluid in the evaporator 21. (The function used for calculation in the function calculator 33 is a function prepared in advance by a setting plan and a combustion test.)
[0036]
In the present embodiment configured as above, by controlling the feed water temperature at the outlet of the economizer 20c to a predetermined temperature with respect to the load, the evaporation at the outlet of the evaporator 21 is completely terminated, and the superheater The mixture water whose evaporation has not been completed is prevented from flowing into the 22 systems.
Specifically, if the temperature of the feedwater preheated by the economizer 20 is lower than the set value, evaporation at the evaporator 21 outlet is incomplete, and a mixed fluid of water and steam may flow into the superheater system. There is. At this time, a deviation occurs between the economizer outlet temperature setting calculated by the function calculator 33 and the actual economizer outlet temperature, the controller 35 outputs a command to reduce the water supply, and the water supply pump 15 Work to reduce the amount.
When the flow rate of the feedwater decreases, the amount of heat received per unit flow rate of the feedwater increases, the temperature of the feedwater preheated by the economizer 20 rises, and the evaporator 21 completely evaporates. Then, when the economizer outlet temperature setting matches the actual economizer outlet temperature, the amount of water supply calms down.
When the temperature of the feedwater preheated by the economizer 20 is higher than the set value, the evaporation at the outlet of the evaporator 21 is completely terminated, and the water is further heated and flows into the superheater 22 in a superheated steam state. In this case, the superheater 22 is further heated, and as a result, the superheated steam temperature at the superheater system outlet rises more than necessary.
At this time, a deviation occurs between the economizer outlet temperature setting calculated by the function calculator 33 and the actual economizer outlet temperature, the controller 35 outputs a command to increase the water supply, and the water supply pump 15 Work to increase the amount.
When the feedwater flow rate increases, the amount of heat received per unit flow rate of the feedwater decreases, and the steam flows into the superheater 22 in a state where the evaporation in the evaporator 21 is completely performed. Also, the economizer outlet temperature preheated by the economizer 20 decreases, and when the economizer outlet temperature setting matches the actual economizer outlet temperature, the amount of water supply calms down.
[0037]
As described above, since the steam having the appropriate temperature flows into the superheater 22, it is possible to prevent the flow stability on the heating path from becoming unstable.
[0038]
Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 2, reference numeral 37 denotes a function calculator (load-based water supply precedence setting calculator) for calculating the water supply precedence setting. The function calculator 37 calculates the feed water flow rate at which the feed water becomes completely steam at the outlet of the evaporator 21 based on the heat balance between the gas side and the water / steam side at a predetermined load. (This setting is a function prepared in advance by a design plan, a combustion test, and the like.)
Further, the water supply precedence setting is added to the water supply flow rate command calculated by the controller 35 by the adder 36, and then output to the water supply pump 15 as in the first embodiment.
[0039]
With this circuit, the water supply corresponding to the load is supplied to the boiler, and the controller 35 operates so as to correct the deviation of the temperature deviation in the first embodiment. Therefore, the control sensitivity (gain) of the controller 35 can be increased, and the followability to a temperature change is further improved, so that a more stable boiler operation can be performed.
[0040]
Next, a third embodiment of the present invention will be described with reference to FIG. The same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 3, reference numeral 38 denotes pressure measuring means for measuring the fluid pressure at the outlet of the evaporator 21. Reference numeral 39 denotes an evaporator outlet saturation temperature calculator for calculating a saturation temperature with respect to the pressure measured by the pressure measuring means 38. Further, the actual temperature of the fluid at the outlet of the evaporator 21 is measured by the temperature measuring means 40, and the saturated temperature calculated by the evaporator outlet saturation temperature calculator 39 and the actual temperature measured by the temperature measuring means 40. Is calculated by the evaporator outlet-side deviation calculator 41. Then, a water supply bias signal corresponding to the deviation calculated by the deviation calculator 41 is generated by the evaporator outlet side water supply bias signal generator 42, and this water supply bias signal is output by the adder 43 at the output of the adder 36. A certain water supply flow rate command is added to prepare a water supply urgent increase command. Then, the high value selection circuit 44 compares the water supply flow rate command output from the adder 36 with the water supply emergency increase command output from the adder 43. Given to.
With this configuration, if the fluid (steam) temperature at the outlet of the evaporator 21 rises for some reason, the feedwater bias signal increases due to the deviation from the saturation temperature, and the feedwater flow command increases accordingly. I do. That is, the emergency water supply flow rate can be increased, and more stable operation of the boiler can be achieved.
[0041]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The same components as those in the third embodiment are denoted by the same reference numerals, and description thereof will be omitted.
In the present embodiment, a pressure detecting means 45 for detecting the fluid (steam) pressure at the outlet of the superheater 22a and a temperature detecting means 45 'for detecting the same temperature are provided. Reference numeral 46 denotes a superheated steam saturation temperature calculator for calculating the saturation temperature at the pressure detected by the pressure detection means 45. Reference numeral 47 denotes a superheated steam side deviation calculator for calculating a deviation between the saturation temperature calculated by the superheated steam saturation temperature calculator 46 and the actual steam temperature detected by the temperature detecting means 45 '. A feedwater bias signal corresponding to this deviation is generated by a superheated steam side feedwater bias signal generator 48, and this feedwater bias signal is added by an adder 49 to a feedwater flow rate command output from the adder 36, and an emergency feedwater reduction is performed. A command is prepared. Then, in the low value selection circuit 50, the water supply flow rate command output from the high value selection circuit 44 is compared with the water supply emergency decrease command output from the adder 49, and the low value is used as the actual water supply flow rate command. The water supply pump 15 is provided.
With this configuration, the following effects can be obtained.
When the temperature of the fluid (steam) at the outlet of the superheater 22a decreases for some reason, it is considered that the fluid at the outlet of the evaporator 21 does not completely evaporate and is in a mixed state of water and steam. In the present embodiment, the feedwater bias signal decreases due to the deviation from the saturation temperature, and the feedwater flow command decreases accordingly. That is, since the urgent water supply amount decrease signal is generated to reduce the water supply amount, it is possible to suppress an excessive overheating shortage state at the outlet of the evaporator 21 and to operate the boiler more stably.
[0042]
Further, as another embodiment, the configuration shown in FIGS. FIGS. 5 to 8 are modified examples of the first to fourth embodiments, respectively. The gas turbine exhaust gas temperature 51 and the gas turbine exhaust gas flow rate 52 are multiplied by a multiplier 53 so as to be input to the exhaust heat boiler. The amount of heat 54 is calculated. In FIG. 5 to FIG. 8, reference numeral 33 ′ denotes a function calculator (feed water temperature setting calculator) that calculates the economizer outlet temperature setting based on the heat input amount 54. 6 to 8, reference numeral 58 denotes a water supply flow rate such that the water supply becomes completely steam at the outlet of the evaporator 21 based on the heat balance between the gas side and the water / steam side at a predetermined heat input amount. Is a function calculator (heat input reference water supply advance setting calculator). This setting is a function prepared in advance by a design plan, a combustion test, and the like.
The method of making the temperature setting and the water supply advance setting is the same as in the case of the load command. Unless the gas turbine exhaust gas is bypassed, the load command and the gas turbine heat input to the exhaust heat boiler are basically the same.
With such a configuration, it is possible to perform water supply control with better followability according to the heat input to the exhaust heat boiler.
[0043]
Further, as another embodiment, the configuration shown in FIGS. 9 to 11 can be adopted. FIGS. 9 to 11 are modified examples of the second to fourth embodiments, respectively. The multiplier 53 multiplies the gas turbine exhaust gas temperature 51 and the gas turbine exhaust gas flow rate 52 to obtain a heat input amount 54 of the exhaust heat boiler. Is calculated. Based on this heat input amount 54, a water supply advance setting is calculated by a function calculator (heat input reference water supply advance setting calculator) 58.
Then, a deviation between the water supply precedence setting calculated by the function calculator 58 and the water supply precedence setting calculated by the function calculator 37 is obtained by the deviation calculator 55. This deviation is added to the water supply flow rate command in the adder 57 after passing through the proportional unit 56. That is, when a deviation occurs between the water supply advance setting based on the load command and the water supply advance setting based on the heat input, the followability can be further improved by correcting the water supply flow rate command based on the deviation.
[0044]
Further, as another embodiment, the configuration shown in FIGS. 12 is a circuit of FIG. 4, FIG. 13 is a circuit of FIG. 8, and FIG. 14 is a circuit of the control of FIG.
12 to 14, reference numeral 61 denotes a function calculator for calculating the superheated steam temperature setting at the outlet of the superheater 22a based on the load command of the gas turbine, and reference numeral 60 denotes a superheated steam temperature setting which is an output of the function calculator 61. A deviation calculator for calculating a deviation of the actual superheated steam temperature measured by the temperature detecting means 45 ', a reference numeral 62 is a proportional controller, and a reference numeral 63 is an adder for adding the deviation passed through the proportional controller 62 to the feed water flow rate command. .
Reference numeral 65 denotes a deviation calculated by the evaporator outlet side deviation calculator 41 (a deviation between the saturation temperature calculated by the evaporator outlet saturation temperature calculator 39 and the actual temperature measured by the temperature measuring means 40). The reference numeral 64 denotes an adder for adding the output of the proportional controller 65 to the feed water flow rate command.
[0045]
In this example, the steam temperature setting for the outlet of the superheater 22a near the evaporator 21 corresponding to the load (this is calculated by the function calculator 61) and the actual steam temperature at the outlet of the superheater 22a near the evaporator 21 ( The proportional controller 62 generates a continuous control signal (proportional control signal) based on the deviation from the temperature detection means 45 ') and adds it to the base water supply flow rate command.
As a result, the ability to follow a disturbance is improved. Also, unlike the emergency water supply amount decrease signal used in the low value selection circuit 50, in this example, a proportional control signal is continuously added to the water supply flow rate command. For this reason, the emergency water supply decrease signal by the low value selection circuit 50 is not affected.
Further, the proportional controller 65 generates a continuous control signal (proportional control signal) based on the temperature deviation signal generated by the evaporator outlet deviation calculator 41 by monitoring the saturation temperature at the outlet of the evaporator 21, Add the water supply flow rate command.
As a result, the ability to follow a disturbance is improved. Also, unlike the water supply urgent increase signal used in the high value selection circuit 44, in this example, a proportional control signal is continuously added to the water supply flow rate command. For this reason, the emergency water supply increase signal by the high value selection circuit 44 does not start.
[0046]
【The invention's effect】
As described above, the following effects can be obtained in the once-through type exhaust heat boiler of the present invention.
According to the first aspect of the present invention, since the degree of superheat is kept within an appropriate range by the feedwater control device, the flow stability on the heating path from the feedwater to the generation of superheated steam becomes unstable. This can prevent the evaporator member from being damaged.
According to the invention described in claim 2, the controller controls the feedwater flow rate based on the deviation between the feedwater temperature and the feedwater temperature setting, so that the feedwater temperature setting and the feedwater temperature can be matched.
According to the third aspect of the present invention, since the controller moves so as to correct the deviation of the temperature deviation, the control sensitivity (gain) of the controller can be increased, and the follow-up property to the temperature change is further improved. I do.
According to the fourth aspect of the invention, when the fluid (steam) temperature at the outlet of the evaporator rises for some reason, the fluid temperature at the outlet of the evaporator is increased by increasing the feedwater flow command by the feedwater bias signal. Can be lowered.
According to the fifth aspect of the present invention, when the temperature of the superheated steam decreases for some reason, the feedwater flow rate is reduced using the feedwater bias signal, so that an excessive overheat shortage state at the evaporator outlet is suppressed. be able to.
[0047]
According to the invention described in claim 6, the control signal calculated based on the difference between the saturation temperature at the evaporator outlet and the actual temperature is continuously added to the feedwater flow rate command. As a result, the ability to follow the disturbance is improved.
According to the seventh aspect of the invention, the control signal calculated based on the difference between the superheated steam temperature setting and the actual superheated steam temperature is continuously added to the feedwater flow rate command. As a result, the ability to follow the disturbance is improved.
[0048]
According to the invention described in claim 8, since the degree of superheat is kept within an appropriate range by the water supply control device, the flow stability on the heating path from the supply water to the generation of superheated steam becomes unstable. Can be prevented. In addition, by calculating the feedwater temperature setting based on the amount of heat input to the boiler, feedwater control with better tracking becomes possible.
According to the ninth aspect of the present invention, since the controller moves so as to correct the deviation of the temperature deviation, the control sensitivity (gain) of the controller can be increased, and the responsiveness to a temperature change is further improved. I do.
According to the invention described in claim 10, when the fluid (steam) temperature at the outlet of the evaporator rises for some reason, the fluid temperature at the evaporator outlet is increased by increasing the feed water flow rate command by the feed water bias signal. Can be lowered.
According to the eleventh aspect of the present invention, when the temperature of the superheated steam decreases for some reason, the feedwater flow rate is reduced using the feedwater bias signal. be able to.
[0049]
According to the twelfth aspect of the invention, the control signal calculated based on the deviation between the saturation temperature at the evaporator outlet and the actual temperature is continuously added to the feedwater flow command. As a result, the ability to follow the disturbance is improved.
According to the thirteenth aspect, the control signal calculated based on the deviation between the superheated steam temperature setting and the actual superheated steam temperature is continuously added to the feedwater flow rate command. As a result, the ability to follow the disturbance is improved.
[0050]
According to the fourteenth aspect of the present invention, the follow-up performance can be further improved by adding the water supply advance setting based on the load command and the difference based on the heat input to the boiler to the feed water flow rate advance command. it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a second embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a third embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a fourth embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the first embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the second embodiment of the present invention.
FIG. 7 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the third embodiment of the present invention.
FIG. 8 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the fourth embodiment of the present invention.
FIG. 9 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the second embodiment of the present invention.
FIG. 10 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the third embodiment of the present invention.
FIG. 11 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the fourth embodiment of the present invention.
FIG. 12 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the fourth embodiment shown in FIG.
FIG. 13 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the once-through type exhaust heat boiler of FIG.
FIG. 14 is a diagram showing a configuration of a once-through type exhaust heat boiler shown as a modification of the once-through type exhaust heat boiler of FIG. 11;
FIG. 15 is a diagram showing a gas turbine and a conventional once-through type exhaust heat boiler.
[Explanation of symbols]
33 Function calculator (water supply temperature setting calculator)
37 Function calculator (load-based water supply advance setting calculator)
39 Evaporator outlet saturation temperature calculator
41 Evaporator outlet deviation calculator
42 Evaporator outlet side feedwater bias signal generator
46 Superheated steam saturation temperature calculator
47 Superheated steam side deviation calculator
48 Superheated steam side feedwater bias signal generator
58 Function calculator (heat input standard water supply advance setting calculator)

Claims

An evaporator that receives water and preheats the water in a casing that guides exhaust gas discharged from another device, an evaporator that generates steam by heating the water from the economizer, And a superheater that further heats the steam from the vessel to generate superheated steam.
A feedwater control device for controlling the feedwater flow rate based on the temperature of the feedwater preheated by the economizer, so as to keep the superheat degree of the steam at the evaporator outlet within a predetermined range. Once-through waste heat boiler.

The once-through type exhaust heat boiler according to claim 1,
The feedwater control device includes a temperature detection unit that detects a temperature of feedwater preheated by the economizer, and a feedwater temperature setting calculator that calculates a feedwater temperature setting based on a load command of a gas turbine as the other device. And a controller that generates a feedwater flow rate command based on a deviation between the feedwater temperature preheated by the economizer and the feedwater temperature setting, wherein the feedwater flow rate is controlled based on the feedwater flow command. Characteristic once-through type waste heat boiler.

The once-through type waste heat boiler according to claim 2,
A once-through type exhaust heat boiler, comprising: a load reference water supply advance setting calculator that calculates a water supply advance setting based on the load command, wherein the water supply advance setting is added to the feedwater flow rate command.

The once-through heat boiler according to claim 2 or 3,
An evaporator outlet saturation temperature calculator for calculating a saturation temperature with respect to the fluid pressure at the evaporator outlet, and calculating a deviation between the saturation temperature calculated by the evaporator outlet saturation temperature calculator and the actual fluid temperature at the evaporator outlet. Evaporator outlet-side deviation calculator, and an evaporator outlet-side water-supply bias signal generator that generates a water-supply bias signal corresponding to the deviation calculated by the evaporator outlet-side deviation calculator. Wherein the feedwater flow rate is controlled based on the larger of the sum of the feedwater bias signal generated by the side feedwater bias signal generator and the feedwater flow rate command or the feedwater flow rate command. Thermal boiler.

The once-through heat boiler according to any one of claims 2 to 4,
A superheated steam saturation temperature calculator that calculates a saturation temperature based on the pressure of the superheated steam, and a superheated steam side deviation that calculates a deviation between the saturation temperature calculated by the superheated steam saturation temperature calculator and the actual superheated steam temperature. A superheated steam side water supply bias signal generator that generates a water supply bias signal corresponding to the deviation calculated by the superheated steam side deviation calculator, and is generated by the superheated steam side water supply bias signal generator. A feed water flow rate is controlled based on the smaller of the feed water flow signal and the sum of the feed water bias signal and the feed water flow command, wherein the once-through type exhaust heat boiler is controlled.

The once-through type exhaust heat boiler according to claim 4,
A once-through type exhaust heat boiler, wherein the deviation calculated by the evaporator outlet side deviation calculator is proportionally controlled and then added to the feedwater flow command.

The once-through type exhaust heat boiler according to claim 5 or 6,
A once-through type exhaust heat boiler, wherein a deviation between an actual superheated steam temperature and a superheated steam temperature setting based on a load command of a gas turbine is proportionally controlled and then added to the feedwater flow rate command.

The once-through type exhaust heat boiler according to claim 1,
The water supply control device includes a temperature detection unit configured to detect a temperature of the water supply preheated by the economizer, and a water supply temperature setting calculator configured to calculate a water supply temperature setting based on an amount of heat input by exhaust gas introduced into the casing. And a controller that generates a feedwater flow rate command based on a deviation between the feedwater temperature preheated by the economizer and the feedwater temperature setting, wherein the feedwater flow rate is controlled based on the feedwater flow command. Characteristic once-through type waste heat boiler.

The once-through type waste heat boiler according to claim 8,
A once-through type exhaust heat boiler, further comprising a heat input reference water supply advance setting calculator that calculates an advance water supply setting based on the amount of heat input, wherein the advance water supply setting is added to the water supply flow rate command.

The once-through type exhaust heat boiler according to claim 8 or 9,
An evaporator outlet saturation temperature calculator for calculating a saturation temperature with respect to the fluid pressure at the evaporator outlet, and calculating a deviation between the saturation temperature calculated by the evaporator outlet saturation temperature calculator and the actual fluid temperature at the evaporator outlet. Evaporator outlet-side deviation calculator, and an evaporator outlet-side water-supply bias signal generator that generates a water-supply bias signal corresponding to the deviation calculated by the evaporator outlet-side deviation calculator. Wherein the feedwater flow rate is controlled based on the larger of the sum of the feedwater bias signal generated by the side feedwater bias signal generator and the feedwater flow rate command or the feedwater flow rate command. Thermal boiler.

The once-through type exhaust heat boiler according to any one of claims 8 to 10,
A superheated steam saturation temperature calculator that calculates a saturation temperature based on the pressure of the superheated steam, and a superheated steam side deviation calculation that calculates a deviation between the saturation temperature calculated by the superheated steam saturation temperature calculator and the actual superheated steam temperature. And a superheated steam-side feedwater bias signal generator that generates a feedwater bias signal corresponding to the deviation calculated by the superheated steam-side deviation calculator. The superheated steam-side feedwater bias signal generator generates the feedwater bias signal. A once-through type exhaust heat boiler characterized in that the feedwater flow rate is controlled based on the smaller of the sum of the feedwater bias signal and the feedwater flow rate command or the feedwater flow rate command.

The once-through type exhaust heat boiler according to claim 10,
A once-through type exhaust heat boiler, wherein the deviation calculated by the evaporator outlet side deviation calculator is proportionally controlled and then added to the feedwater flow command.

In the once-through type exhaust heat boiler according to claim 11 or 12,
A once-through type exhaust heat boiler, wherein a deviation between an actual superheated steam temperature and a superheated steam temperature setting based on a heat input amount is proportionally controlled and then added to the feedwater flow rate command.

The once-through type exhaust heat boiler according to any one of claims 3 to 7,
A heat input reference water supply precedence setting calculator for calculating a water supply precedence setting based on an amount of heat input by the exhaust gas introduced into the casing, wherein the water supply precedence setting and the water supply calculated by the load reference water supply precedence setting calculator A once-through type exhaust heat boiler, wherein a deviation from a preceding setting is added to the feed water flow rate command.