JPH1089603A - Method of stopping operation in waste heat recovery boiler - Google Patents
Method of stopping operation in waste heat recovery boilerInfo
- Publication number
- JPH1089603A JPH1089603A JP23797697A JP23797697A JPH1089603A JP H1089603 A JPH1089603 A JP H1089603A JP 23797697 A JP23797697 A JP 23797697A JP 23797697 A JP23797697 A JP 23797697A JP H1089603 A JPH1089603 A JP H1089603A
- Authority
- JP
- Japan
- Prior art keywords
- pressure
- drum
- boiler
- steam
- heat recovery
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
- F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
- F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
- F01K23/10—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle
- F01K23/101—Regulating means specially adapted therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Steam Boilers And Waste-Gas Boilers (AREA)
Abstract
Description
【発明の詳細な説明】
【0001】
【発明の属する技術分野】本発明は、脱硝装置を備えた
排熱回収ボイラの停止方法に関する。
【0002】
【従来の技術】最近の電力需要の変化に応じて、ピーク
負荷用としてガスタービンを採用する傾向が高まってい
る。このように、ガスタービンを用いた場合、ガスター
ビンに対して運動エネルギーを与えた高温ガスは排熱回
収ボイラに導かれ、当該排熱回収ボイラでは、その熱を
利用して蒸気を発生させる。発生した蒸気は蒸気タービ
ンに導かれ、これを駆動して発電を行なう。以上のよう
にして、ガスタービンと蒸気タービンによる複合サイク
ル発電が実施され、これにより省エネルギーが図られ
る。
【0003】通常、上記の排熱回収ボイラには、タービ
ンからの排ガス中に含まれる窒素酸化物(NOx)を除
去するため脱硝装置が組込まれている。この脱硝装置に
あっては、触媒が効果的に作用するのは一定の温度域に
限られ、この温度域から外れた温度では触媒の効果は大
幅に減少する。これを図により説明する。
【0004】図2は脱硝装置の脱硝有効温度範囲を示す
グラフである。図で、横軸には時間、縦軸には温度がと
ってある。図の斜線で示される範囲が脱硝有効範囲であ
り、その上限の温度がT2、下限の温度がT1で示されて
いる。温度T2は約400°Cであり、温度T1は約20
0°Cである。したがって、排ガス温度が上記斜線の温
度範囲にないと有効な脱硝は行なわれず、排煙中に多量
のNOxが含まれることとなる。
【0005】
【発明が解決しようとする課題】一方、最近のボイラ運
転においては、その高効率化を図るため、変圧運転方式
が採用されている。これを図3(a)に示す。図で、横
軸には負荷、縦軸にはドラム圧力がとってある。図に示
すように、変圧運転方式においては、負荷が小さい場合
はドラム圧力を一定の低い値とし、ある負荷点を超える
と負荷の大きさにほぼ比例してドラム圧力を変化するよ
うな運転を行なう。
【0006】このため、ボイラ停止時にはドラム圧力は
低くなる。この状態から、ボイラバンキングに入ると、
再起動時のドラム圧力は図3(b)にしめすようにさら
に低下する。図で、横軸には時間、縦軸にはドラム圧力
がとってある。図示のように、ドラム圧力はバンキング
開始から時間が経過するにつれて徐々に低下してゆき、
ドラムの再起動時には極めて低い圧力となる。1例を挙
げると、8時間のボイラバンキング中に、ドラム圧力は
約20atg降下して10atg(飽和温度183°
C)前後の残圧となる。
【0007】上述した脱硝有効温度範囲および変圧運転
方式のため、ボイラ再起動時にはボイラから排出される
排煙中に多くのNOxが含まれることとなる。即ち、ボ
イラ再起動時に排ガスがボイラに供給されるが、脱硝装
置の上流側には過熱器、蒸発器等の伝熱管群が配置され
ており、又、再起動時のドラム残圧が低いため上記伝熱
管群内の受熱媒体温度が低く、供給された排ガスはこれ
らの伝熱管群に多くの熱を奪われる。
【0008】この結果、ボイラ再起動時に脱硝装置に流
入する排ガス温度は、図2の曲線Aに示すように温度T
3(約180°C)となり、触媒が効果的に作用する温
度(以下、触媒好適温度という)以下となる。そして、
触媒好適温度に達するまでにはボイラ再起動時後相当長
時間を要することになる。したがって、ボイラ再起動時
から排ガス温度が触媒好適温度に達するまでの間、排ガ
ス中に含まれるNOxは脱硝装置において有効に除去さ
れず、この間、排煙中にNOxの量が増加することとな
る。
【0009】本発明は、このような事情に鑑みてなされ
たものであり、その目的は、上記従来の問題点を解決
し、何等特殊の装置を用いることなく、ボイラ再起動
時、ボイラから排出されるNOxを低減することができ
る排熱回収ボイラの停止方法を提供するにある。
【0010】
【課題を解決するための手段】上記の目的を達成するた
め、本発明は、主として次のような構成を採用する。
【0011】蒸気を発生するドラムと、前記ドラムの缶
水を排ガスにより加熱する蒸発器と、発生した前記蒸気
を負荷に供給する主蒸気管と、前記主蒸気管に接続され
て前記負荷をバイパスするバイパス管と、前記排ガス中
の窒素酸化物を除去する脱硝装置と、を備えた排熱回収
ボイラを停止するときに、前記ドラムの圧力をボイラ再
起動時に必要な残圧が得られる圧力に昇圧する排熱回収
ボイラの停止方法であって、前記ドラムの圧力を検出す
る圧力検出器を前記ドラムに設置し、前記圧力検出器か
らの検出信号に基づいて、前記ドラムの圧力が設計圧力
を超えないように昇圧する排熱回収ボイラの停止方法。
【0012】
【発明の実施の形態】以下、本発明を図示の実施形態に
基づいて説明する。
【0013】図4(a),(b),(c)は本発明の実
施形態に係る排熱回収ボイラの停止方法を示すタイムチ
ャートであり、図5は図4(a)乃至(c)に示す停止
方法を適用する排熱回収ボイラの系統図である。まず、
図5に示す通常の排熱回収ボイラについて説明する。図
で、1はガスタービン、2はガスタービン1からの排ガ
スGを導入する排ガスダクト、3は過熱器、4は第1の
蒸発器、5は脱硝装置、6は第2の蒸発器、7は節炭器
である。
【0014】過熱器3、第1および第2の蒸発器4,
6、脱硝装置5、節炭器7は排ガスダクト2で構成され
る排ガス流路内に配置されている。8は蒸気を発生する
ドラム、9はドラム8で発生した蒸気により駆動される
蒸気タービン、10は蒸気を凝縮して水に戻す復水器、
11は復水器10の水をドラム8に給水する復水ポンプ
である。
【0015】復水器10の水は復水ポンプ11により給
水Wとなって節炭器7で排ガスGにより予熱されてドラ
ム8内に供給される。ドラム8の水は下降管13を通っ
て下降し、管路1a,14bを経て蒸発器4,6へ導入
され管路15a,15bを経てドラム8内に戻る。この
ようにして、循環流動する間に、蒸発器4,6において
排ガスGの加熱により生じた蒸気は飽和蒸気管16によ
り過熱器3に導入され、ここで排ガスGにより加熱さ
れ、加熱蒸気として主蒸気管17を経て蒸気タービン9
へ供給される。
【0016】18は主蒸気管に接続され、蒸気タービン
9をバイパスして蒸気を直接復水器10に導くタービン
バイパス管である。又、19は蒸気タービンへの蒸気の
流量を調節する蒸気タービン加減弁、20は蒸気タービ
ン9への蒸気の供給量により蒸気のバイパス量を調節す
るタービンバイパス弁、21は排ガスダクト2のダンパ
である。上記の蒸気発生作動中、脱硝装置5は排ガスG
中のNOxを除去する動作を行なう。
【0017】ここで、図4に示すグラフに基づいて、ボ
イラ停止に伴なう本実施形態のプラント停止課程を説明
する。プラント停止の際、蒸気タービン9の停止時のメ
タル温度を高く保持して再起動時の起動時間を短縮する
ために、ガスタービン1をある負荷で保持した状態にお
いて、蒸気タービン9を先行して停止する。この状態が
図4(a),(c)に示される。
【0018】蒸気タービン9の停止は蒸気タービン加減
弁19を調節して図4(a)に示すように蒸気流量を減
少させて行なわれ、この間余剰蒸気量はタービンバイパ
ス弁20によりドラム8のドラム圧力を制御しながらタ
ービンバイパス管18を経て復水器10へダンプされ
る。図4(a)で斜線部分が余剰蒸気量となる。蒸気タ
ービン9が停止した後、図4(c)に示すように、ガス
タービン1が停止過程に入る。
【0019】従来の停止方法においては、ガスタービン
1が停止過程に入ると、これに伴なって冷却によりドラ
ム8の圧力が図4(b)の実線Cで示すように圧力P0
から低下してゆき、ガスタービン1の停止時には圧力P
1に低下する。そして、この状態でボイラ出口ダンパ2
1が全閉されてボイラバンキング状態に入る。バンキン
グ中、ボイラ自然放熱等により冷却されるので、ドラム
8の圧力は図4(b)に示すように圧力P1からさらに
低下する。したがって、ボイラ再起動時、ドラム圧力は
極めて低い圧力P2になっており、伝熱管群内の受熱媒
体温度も低く、前述のように、脱硝装置5に流入する排
ガスGの温度も低下することとなる。
【0020】しかしながら、本実施形態においては、プ
ラント停止過程において、タービンバイパス18を経て
復水器10へダンプされる蒸気量を、タービンバイパス
弁20によって絞り込む方法が採られることにより、ド
ラム8の圧力は図4(b)の2点鎖線Dに示すように上
昇し、ボイラバンキング状態に入る時点においては圧力
P3まで昇圧される。上述のように、バンキング中、ボ
イラは冷却され、ドラム8の圧力も図4(b)の2点鎖
線Dに示すように低下してゆく。
【0021】しかし、ボイラバンキング開始時に圧力P
3まで昇圧されたドラム圧力は、バンキング中の冷却に
よる圧力低下があっても、ボイラ再起動時には圧力P4
を保持し、この圧力は従来の停止方法におけるボイラ再
起動時の圧力P2より遙かに高い圧力である。この結
果、伝熱管群内の受熱媒体温度も高い温度に保持され、
ボイラ再起動時に排ガスGから奪う熱量が減少し、排ガ
スGの温度は低下せず、図2の曲線Bに示すように、触
媒好適温度に保持することができ、従来の停止方法に比
較し、排煙中のNOxの量を大幅に減少することができ
る。
【0022】ここで1例を挙げると、ボイラ停止時、ド
ラム8の圧力を60atg(P3=60atg)まで昇
圧させると、8時間のバンキングの後のドラム8の残圧
は約30atg(P4≒30atg,飽和温度約235
℃)となる。この結果、過熱器3、蒸発器4内の受熱媒
体の温度は約235℃に保持され、再起動時に導入され
る排ガスGはほとんど温度降下を生ずることなく、図2
に示す温度T4(約230℃)で脱硝装置5に流入す
る。
【0023】図6は、ボイラ再起動後のボイラから排出
されるNOx総量、排ガス量、排ガス温度の特性図であ
る。図で、横軸には時間がとってあり、又、実線はボイ
ラ再起動時のドラム残圧が30atg、一点鎖線はドラ
ム残圧が10atgの場合を示す。図から明らかによう
に、ドラム残圧が10atgの場合、ボイラから排出さ
れるNOxの量は、しばらくの間NOx規制値を大きく超
えるのに対し、ドラム残圧が30atgの場合、ボイラ
再起動時以後NOx規制値を超えることはない。したが
って、ドラム残圧を高める停止方法が、NOx低減に極
めて有効であることが判る。
【0024】図1は、図4(a)乃至(c)に示す停止
方法を適用する本発明を特徴付けている実施形態におけ
る排熱回収ボイラの系統図である。図で、図5に示す部
分と同一部分には同一符号を付して説明を省略する。な
お、排ガスダクト2内の諸装置は図5と同様であり、図
示は省略されている。
【0025】23はドラム8に取付けられてドラム圧力
を検出する圧力検出器、19’は圧力検出器23の検出
信号により制御される蒸気タービン加減弁、20’は圧
力検出器23の検出信号により制御されるタービンバイ
パス弁である。
【0026】本実施形態においては、図4(b)の2点
鎖線Dに示すように、プラント停止過程においてドラム
圧力を上昇させるが、この圧力上昇が急激であるとドラ
ム8の設計圧力を超えるおそれが生じる。図1に示すボ
イラはこのような事態を防止するもので、ドラム圧力が
一定圧力を超えると圧力検出器23がこれを検出し、信
号を蒸気タービン加減弁19’、タービンバイパス弁2
0’に出力し、これらの弁を開く方向的に制御してドラ
ム圧力の上昇を抑え、ドラム圧力を安全に昇圧すること
ができる。
【0027】本実施形態は、排熱回収ボイラの停止時に
おいて、再起動時に必要なドラム残圧を確保できるよう
にドラム圧力を昇圧させようとするものであるが、それ
と共にドラム圧力の急激な圧力上昇にも対応できるよう
に制御するものである。このような制御を行うために、
本実施形態では、具体的な構造として、ドラム圧力を検
出する圧力検出器を、発生した蒸気を蒸気タービンに供
給する主蒸気管や、前記主蒸気管のバイパス管に設ける
のではなくて、ドラムに直接設置することを特徴として
いる。
【0028】本実施形態を、圧力検出器を例えば前記バ
イパス管に設ける構造のものと比較すると、本実施形態
は次のような特有な効果を奏しうるものである。ドラム
からの蒸気は主蒸気管またはバイパス管を流通する間に
減温により減圧するようになるが、本実施形態では前記
減圧を推定してドラム圧力を決定する必要がないととも
に、バイパス管の圧力検出ではドラム圧力に対して時間
遅れが生じて急激なドラムの圧力上昇に追従できないと
いう欠陥を生じないものである。
【0029】このように本実施形態は、ドラム圧力を高
い精度で検出でき、且つドラム圧力の即応性を確保で
き、急激なドラム圧力の上昇にも対応できる制御を行う
ことができる。
【0030】更に、本実施形態では、プラントの停止過
程において、タービンバイパス弁を絞ってドラム圧力を
昇圧し、ボイラ再起動時の残圧を高めるようにしたの
で、系統中に特殊な装置を介在させたり、系統に変更を
加えたりすることなく、単に運転方法のみで、ボイラ再
起動時脱硝装置に流入する排ガス温度の低下を防止して
これを触媒好適温度内に保持することができ、ボイラか
ら排出されるNOxを大幅に低減することができる。
【0031】なお、上記実施形態の説明では、排ガス源
をガスタービンとして説明したが、ガスタービンに限る
ことはなく、排ガス源が工業炉や産業処理整備等であっ
ても適用することができる。
【0032】
【発明の効果】以上述べたように、本発明では、プラン
トの停止過程において、負荷をバイパスするバイパス管
の通過蒸気量を制御し、ドラム圧力を昇圧してボイラ再
起動時のドラム残圧を高めるようにしたので、特殊の装
置を用いることなく、ボイラ再起動時、ボイラから排出
されるNOxを低減することができる。
【0033】また、本発明では、プラントの停止過程で
ドラム圧力を昇圧してボイラ再起動時のドラムの残圧を
高める方法において、ドラムの圧力が予め定められた圧
力を超えたとき、蒸気タービン加減弁とタービンバイパ
ス弁の両方を同時に開いたドラムの圧力の上昇を抑える
ようにしたので、どのような急激な圧力上昇にも対処す
ることができ、安全に圧力上昇を行なうことができる。
【0034】更に、本発明では、ドラム圧力を検出する
圧力検出器をドラムに設置することにより、ドラム圧力
を高い精度で検出でき、且つドラム圧力の即応性を確保
でき、急激なドラム圧力の上昇にも対応できる制御を行
うことができる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stopping an exhaust heat recovery boiler provided with a denitration device. [0002] In response to recent changes in power demand, there has been an increasing tendency to employ gas turbines for peak loads. As described above, when the gas turbine is used, the high-temperature gas that has given kinetic energy to the gas turbine is guided to the exhaust heat recovery boiler, and the exhaust heat recovery boiler uses the heat to generate steam. The generated steam is guided to a steam turbine, which drives it to generate power. As described above, combined cycle power generation by the gas turbine and the steam turbine is performed, thereby achieving energy saving. [0003] Usually, the above heat recovery steam generator, the nitrogen oxides contained in the exhaust gas from the turbine (NO x) denitrator for removing is incorporated. In this denitration device, the catalyst works effectively only in a certain temperature range, and at temperatures outside this temperature range, the effect of the catalyst is greatly reduced. This will be described with reference to the drawings. FIG. 2 is a graph showing a denitration effective temperature range of the denitration apparatus. In the figure, the horizontal axis represents time, and the vertical axis represents temperature. The hatched range in the figure is the denitration effective range, and the upper limit temperature is T2 and the lower limit temperature is T1. The temperature T2 is about 400 ° C and the temperature T1 is about 20 ° C.
0 ° C. Therefore, effective denitration and the exhaust gas temperature is not in the above temperature range hatched is not performed, and may include a large amount of the NO x in the flue gas. [0005] On the other hand, in recent boiler operation, a variable-pressure operation system has been adopted in order to improve the efficiency. This is shown in FIG. In the figure, the horizontal axis represents the load, and the vertical axis represents the drum pressure. As shown in the figure, in the variable pressure operation system, when the load is small, the drum pressure is set to a constant low value, and when the load exceeds a certain load point, the operation is such that the drum pressure changes almost in proportion to the magnitude of the load. Do. For this reason, when the boiler is stopped, the drum pressure becomes low. From this state, when you enter boiler banking,
The drum pressure at the time of restarting further decreases as shown in FIG. In the figure, the horizontal axis represents time, and the vertical axis represents drum pressure. As shown in the figure, the drum pressure gradually decreases as time elapses from the start of banking,
When the drum is restarted, the pressure is extremely low. As an example, during 8 hours of boiler banking, the drum pressure drops by about 20 atg to 10 atg (saturation temperature 183 °).
C) The residual pressure before and after. [0007] For the above-described denitration effective temperature range and the transformer driving method, and thus contain many of the NO x in the flue gas discharged from the boiler at the boiler restart. That is, the exhaust gas is supplied to the boiler at the time of restarting the boiler.However, a heat transfer tube group such as a superheater and an evaporator is arranged on the upstream side of the denitration device. The temperature of the heat receiving medium in the heat transfer tube group is low, and the supplied exhaust gas takes a lot of heat from these heat transfer tube groups. As a result, when the boiler is restarted, the temperature of the exhaust gas flowing into the denitration device becomes equal to the temperature T as shown by a curve A in FIG.
3 (about 180 ° C.), which is lower than the temperature at which the catalyst works effectively (hereinafter referred to as a catalyst suitable temperature). And
It takes a considerable time after the boiler restarts to reach the catalyst suitable temperature. Thus, between the time the boiler restart until the exhaust gas temperature reaches the catalyst temperature suitable, NO x contained in the exhaust gas is not effectively removed in the denitration apparatus, during which the amount of the NO x is increased in the flue gas Becomes The present invention has been made in view of such circumstances, and an object of the present invention is to solve the above-mentioned conventional problems, and to discharge from the boiler when the boiler is restarted without using any special device. to provide a method of stopping the exhaust heat recovery boiler capable of reducing a is the NO x. In order to achieve the above object, the present invention mainly employs the following constitution. A drum for generating steam, an evaporator for heating the can water of the drum with exhaust gas, a main steam pipe for supplying the generated steam to a load, and a bypass connected to the main steam pipe for bypassing the load. When the exhaust heat recovery boiler having a bypass pipe and a denitration device for removing nitrogen oxides in the exhaust gas is stopped, the pressure of the drum is reduced to a pressure at which a residual pressure required when the boiler is restarted is obtained. A method of stopping the exhaust heat recovery boiler to increase the pressure, wherein a pressure detector for detecting the pressure of the drum is installed on the drum, and based on a detection signal from the pressure detector, the pressure of the drum decreases the design pressure. How to shut down the exhaust heat recovery boiler to increase the pressure so that it does not exceed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment. FIGS. 4A, 4B, and 4C are time charts showing a method of stopping the heat recovery steam generator according to the embodiment of the present invention, and FIG. 5 is a time chart showing FIGS. 4A to 4C. 1 is a system diagram of an exhaust heat recovery boiler to which a stop method shown in FIG. First,
The normal exhaust heat recovery boiler shown in FIG. 5 will be described. In the figure, 1 is a gas turbine, 2 is an exhaust gas duct for introducing exhaust gas G from the gas turbine 1, 3 is a superheater, 4 is a first evaporator, 5 is a denitration device, 6 is a second evaporator, 7 Is a economizer. A superheater 3, first and second evaporators 4,
The denitration device 5 and the economizer 7 are arranged in an exhaust gas flow path constituted by the exhaust gas duct 2. 8 is a drum for generating steam, 9 is a steam turbine driven by the steam generated by the drum 8, 10 is a condenser for condensing the steam and returning it to water,
Reference numeral 11 denotes a condensate pump for supplying water from the condenser 10 to the drum 8. The water in the condenser 10 is supplied as water W by a condenser pump 11, is preheated by the exhaust gas G in the economizer 7, and is supplied into the drum 8. The water of the drum 8 descends through the downcomer 13 and is introduced into the evaporators 4 and 6 via the pipes 1a and 14b, and returns into the drum 8 via the pipes 15a and 15b. In this way, during the circulation flow, the steam generated by heating the exhaust gas G in the evaporators 4 and 6 is introduced into the superheater 3 by the saturated steam pipe 16, where the steam is heated by the exhaust gas G and is mainly heated steam. Steam turbine 9 through steam pipe 17
Supplied to Reference numeral 18 denotes a turbine bypass pipe which is connected to the main steam pipe and bypasses the steam turbine 9 and directly guides the steam to the condenser 10. Reference numeral 19 denotes a steam turbine control valve for adjusting the flow rate of steam to the steam turbine, reference numeral 20 denotes a turbine bypass valve for adjusting the amount of steam bypass by the supply amount of steam to the steam turbine 9, and reference numeral 21 denotes a damper for the exhaust gas duct 2. is there. During the above steam generation operation, the denitration device 5
Performing an operation to remove NO x in. Here, based on the graph shown in FIG. 4, the process of stopping the plant according to the present embodiment accompanying the stop of the boiler will be described. When the plant is stopped, the steam turbine 9 is preceded in a state where the gas turbine 1 is held at a certain load in order to keep the metal temperature at the time of stopping the steam turbine 9 high and shorten the startup time at the time of restart. Stop. This state is shown in FIGS. 4 (a) and 4 (c). The steam turbine 9 is stopped by adjusting the steam turbine control valve 19 so as to reduce the steam flow rate as shown in FIG. 4 (a). It is dumped to the condenser 10 through the turbine bypass pipe 18 while controlling the pressure. In FIG. 4A, the hatched portion indicates the amount of excess steam. After the steam turbine 9 stops, the gas turbine 1 enters a stop process as shown in FIG. In the conventional shut-down method, when the gas turbine 1 enters a shut-down process, the pressure of the drum 8 is reduced due to the cooling as shown by the solid line C in FIG.
From the pressure P when the gas turbine 1 is stopped.
Drops to 1. Then, in this state, the boiler outlet damper 2
1 is fully closed and enters the boiler banking state. During the banking, the pressure of the drum 8 is further reduced from the pressure P1 as shown in FIG. Therefore, when the boiler is restarted, the drum pressure is extremely low P2, the temperature of the heat receiving medium in the heat transfer tube group is low, and the temperature of the exhaust gas G flowing into the denitration device 5 is also reduced as described above. Become. However, in the present embodiment, in the process of stopping the plant, the amount of steam dumped to the condenser 10 via the turbine bypass 18 is reduced by the turbine bypass valve 20, whereby the pressure of the drum 8 is reduced. Rises as shown by the two-dot chain line D in FIG. 4 (b), and is increased to the pressure P3 when the boiler banking state is entered. As described above, during the banking, the boiler is cooled, and the pressure of the drum 8 also decreases as shown by a two-dot chain line D in FIG. 4B. However, at the start of boiler banking, the pressure P
When the boiler restarts, the pressure of the drum is increased to a pressure P4 even if the pressure drops due to cooling during banking.
This pressure is much higher than the pressure P2 at the time of restarting the boiler in the conventional stop method. As a result, the temperature of the heat receiving medium in the heat transfer tube group is also maintained at a high temperature,
When the boiler is restarted, the amount of heat deprived from the exhaust gas G decreases, and the temperature of the exhaust gas G does not decrease. As shown by a curve B in FIG. 2, the catalyst can be maintained at a suitable temperature. The amount of NOx in flue gas can be greatly reduced. Here, as an example, when the pressure of the drum 8 is raised to 60 atg (P3 = 60 atg) when the boiler is stopped, the residual pressure of the drum 8 after banking for 8 hours is about 30 atg (P4 ≒ 30 atg). , Saturation temperature about 235
° C). As a result, the temperature of the heat receiving medium in the superheater 3 and the evaporator 4 is maintained at about 235 ° C., and the exhaust gas G introduced at the time of restarting hardly causes a temperature drop.
At a temperature T4 (approximately 230 ° C.) shown in FIG. [0023] Figure 6, NO x amount exhausted from the boiler after the boiler restart, the amount of exhaust gas is a characteristic diagram of the exhaust gas temperature. In the drawing, the horizontal axis represents time, the solid line represents the case where the drum residual pressure at the time of restarting the boiler is 30 atg, and the dashed line represents the case where the drum residual pressure is 10 atg. As apparent from the figure, when the drum residual pressure of 10Atg, the amount of the NO x discharged from the boiler, while greatly exceed a while NO x regulation value, if the drum residual pressure of 30Atg, boiler re After the start-up, the NO x regulation value will not be exceeded. Therefore, stopping method of increasing the drum residual pressure, it can be seen that is very effective in NO x reduction. FIG. 1 is a system diagram of an exhaust heat recovery boiler according to an embodiment characterizing the present invention to which the stop method shown in FIGS. 4A to 4C is applied. In the figure, the same parts as those shown in FIG. The various devices in the exhaust gas duct 2 are the same as those in FIG. 5 and are not shown. Reference numeral 23 denotes a pressure detector which is attached to the drum 8 and detects a drum pressure. Reference numeral 19 'denotes a steam turbine control valve controlled by a detection signal of the pressure detector 23. Reference numeral 20' denotes a pressure detector by the detection signal of the pressure detector 23. A controlled turbine bypass valve. In this embodiment, as shown by the two-dot chain line D in FIG. 4B, the drum pressure is increased in the process of stopping the plant. There is a fear. The boiler shown in FIG. 1 prevents such a situation. When the drum pressure exceeds a certain pressure, the pressure detector 23 detects the pressure, and outputs a signal to the steam turbine control valve 19 ′ and the turbine bypass valve 2.
The pressure is output to 0 ', and these valves are controlled in the opening direction to suppress an increase in the drum pressure, and the drum pressure can be safely increased. In this embodiment, when the exhaust heat recovery boiler is stopped, the drum pressure is increased so as to secure the necessary drum residual pressure at the time of restarting. The control is performed so as to cope with the pressure rise. In order to perform such control,
In the present embodiment, as a specific structure, a pressure detector for detecting drum pressure is not provided in a main steam pipe for supplying generated steam to a steam turbine or a bypass pipe of the main steam pipe. It is characterized by being installed directly in When this embodiment is compared with a structure in which a pressure detector is provided in, for example, the bypass pipe, this embodiment has the following unique effects. Although the steam from the drum is decompressed by temperature reduction while flowing through the main steam pipe or the bypass pipe, in this embodiment, it is not necessary to estimate the decompression and determine the drum pressure, and the pressure of the bypass pipe is reduced. In the detection, there is no defect that a time delay occurs with respect to the drum pressure and it is impossible to follow a sudden increase in the drum pressure. As described above, according to the present embodiment, the drum pressure can be detected with high accuracy, the responsiveness of the drum pressure can be ensured, and control can be performed to cope with a sudden increase in the drum pressure. Further, in this embodiment, in the process of stopping the plant, the turbine pressure is increased by narrowing the turbine bypass valve to increase the residual pressure when the boiler is restarted. It is possible to prevent the temperature of exhaust gas flowing into the denitration apparatus at the time of restarting the boiler from decreasing and maintain the temperature within a suitable temperature for the catalyst by simply operating the system without changing the system or changing the system. NO x discharged from the fuel cell can be greatly reduced. In the description of the above embodiment, the exhaust gas source is described as a gas turbine. However, the present invention is not limited to a gas turbine, and the present invention can be applied to a case where the exhaust gas source is an industrial furnace or an industrial treatment facility. As described above, in the present invention, in the process of stopping the plant, the amount of steam passing through the bypass pipe that bypasses the load is controlled, the drum pressure is increased, and the drum at the time of restarting the boiler is controlled. since so as to increase the residual pressure, without using a special device, when the boiler restart, it is possible to reduce the NO x discharged from the boiler. Further, according to the present invention, in the method for increasing the drum pressure in the process of stopping the plant to increase the residual pressure of the drum at the time of restarting the boiler, when the pressure of the drum exceeds a predetermined pressure, the steam turbine Since the increase in the pressure of the drum with both the control valve and the turbine bypass valve opened at the same time is suppressed, any sudden increase in the pressure can be dealt with, and the pressure can be increased safely. Further, according to the present invention, by installing a pressure detector for detecting the drum pressure on the drum, the drum pressure can be detected with high accuracy, and the responsiveness of the drum pressure can be ensured. Can be controlled.
【図面の簡単な説明】
【図1】本発明の実施形態に係る排熱回収ボイラの系統
図である。
【図2】脱硝有効温度範囲を示すグラフである。
【図3】変圧運転方式におけるドラム圧力の特性図であ
る。
【図4】排熱回収ボイラの停止方法を示すタイムチャー
トである。
【図5】通常の排熱回収ボイラの系統図である。
【図6】ボイラから排出されるNOx総量を示すグラフ
である。
【符号の説明】
1 ガスタービン
2 排ガスダクト
3 過熱器
4,6 蒸発器
5 脱硝装置
8 ドラム
9 蒸気タービン
17 主蒸気管
18 タービンバイパス管
19,19’ 蒸気タービン加減弁
20,20’ タービンバイパス弁
23 圧力検出器BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram of an exhaust heat recovery boiler according to an embodiment of the present invention. FIG. 2 is a graph showing a denitration effective temperature range. FIG. 3 is a characteristic diagram of drum pressure in a variable pressure operation mode. FIG. 4 is a time chart showing a method of stopping the exhaust heat recovery boiler. FIG. 5 is a system diagram of a normal exhaust heat recovery boiler. FIG. 6 is a graph showing the total amount of NOx discharged from the boiler. [Description of Signs] 1 Gas turbine 2 Exhaust gas duct 3 Superheater 4, 6 Evaporator 5 Denitration device 8 Drum 9 Steam turbine 17 Main steam pipe 18 Turbine bypass pipe 19, 19 'Steam turbine control valve 20, 20' Turbine bypass valve 23 Pressure detector
Claims (1)
スにより加熱する蒸発器と、発生した前記蒸気を負荷に
供給する主蒸気管と、前記主蒸気管に接続されて前記負
荷をバイパスするバイパス管と、前記排ガス中の窒素酸
化物を除去する脱硝装置と、を備えた排熱回収ボイラを
停止するときに、前記ドラムの圧力をボイラ再起動時に
必要な残圧が得られる圧力に昇圧する排熱回収ボイラの
停止方法であって、 前記ドラムの圧力を検出する圧力検出器を前記ドラムに
設置し、 前記圧力検出器からの検出信号に基づいて、前記ドラム
の圧力が設計圧力を超えないように昇圧することを特徴
とする排熱回収ボイラの停止方法。[Claims] 1. A drum that generates steam, an evaporator that heats the drum water with exhaust gas, a main steam pipe that supplies the generated steam to a load, and a bypass pipe that is connected to the main steam pipe and bypasses the load. And a denitration device for removing nitrogen oxides in the exhaust gas, when the exhaust heat recovery boiler is stopped, the pressure of the drum is increased to a pressure at which a residual pressure required when the boiler is restarted is obtained. A method for stopping a heat recovery boiler, wherein a pressure detector for detecting a pressure of the drum is installed on the drum, and a pressure of the drum does not exceed a design pressure based on a detection signal from the pressure detector. A method for stopping an exhaust heat recovery boiler, characterized in that the pressure is increased.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9237976A JP2951294B2 (en) | 1997-09-03 | 1997-09-03 | How to stop the waste heat recovery boiler |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9237976A JP2951294B2 (en) | 1997-09-03 | 1997-09-03 | How to stop the waste heat recovery boiler |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP59195745A Division JPH0619201B2 (en) | 1984-09-20 | 1984-09-20 | How to stop the exhaust heat recovery boiler |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH1089603A true JPH1089603A (en) | 1998-04-10 |
JP2951294B2 JP2951294B2 (en) | 1999-09-20 |
Family
ID=17023273
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP9237976A Expired - Fee Related JP2951294B2 (en) | 1997-09-03 | 1997-09-03 | How to stop the waste heat recovery boiler |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2951294B2 (en) |
-
1997
- 1997-09-03 JP JP9237976A patent/JP2951294B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JP2951294B2 (en) | 1999-09-20 |
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