JP3653599B2

JP3653599B2 - Apparatus and method for controlling ammonia injection amount of flue gas denitration equipment

Info

Publication number: JP3653599B2
Application number: JP00158296A
Authority: JP
Inventors: 興和石黒
Original assignee: Babcock Hitachi KK
Current assignee: Mitsubishi Power Ltd
Priority date: 1996-01-09
Filing date: 1996-01-09
Publication date: 2005-05-25
Anticipated expiration: 2016-01-09
Also published as: JPH09187625A

Description

【０００１】
【発明の属する技術分野】
本発明は、高速負荷変動時にアンモニア注入量制御の追従性を高めた排煙脱硝設備のアンモニア注入量制御装置及び方法に関する。
【０００２】
【従来の技術】
図４は従来の排煙脱硝設備アンモニア注入量制御装置の構成を示すブロック図である。
本図に示すように排煙脱硝設備の排ガス流量計１からの排ガス流量信号３３と入口ＮＯｘ濃度計２からの入口ＮＯｘ濃度信号３４を乗算器７ａで乗算して入口ＮＯｘ量信号２１を得る。一方出口ＮＯｘ濃度設定器３からの出口ＮＯｘ濃度設定信号３５を引算器８ａにに入力し、入口ＮＯｘ濃度計２からの入口ＮＯｘ濃度信号３４を引算器８ａ及び割算器９に入力し、演算により必要脱硝率信号１０を得る。この必要脱硝率信号１０を関数発生器１１に入力し、演算により必要モル比信号１３を得る。出口ＮＯｘ濃度設定器３からの出口ＮＯｘ濃度設定信号３５と出口ＮＯｘ濃度計４からの出口ＮＯｘ濃度信号３６との偏差信号３７を引算器８ｂで求め、調節計１２ａで信号処理してフィードバックモル比信号１５を得る。このフィードバックモル比信号１５は現在計測した出口ＮＯｘ濃度と出口ＮＯｘ濃度設定値とから求められ偏差に基づきアンモニア必要モル比を補正し、ネガティブフィードバック的に制御するものである。必要モル比信号１３とフィードバックモル比信号１５を加算器１４ａで加算して全モル比信号１６を得て、乗算器７ａからの入口ＮＯｘ量信号２１と乗算器７ｂで乗算して必要アンモニア流量信号２２を得る。次に負荷要求信号３８を微分器１７及び二階微分器１８でそれぞれ微分演算した負荷一階微分信号３９及び負荷二階微分信号４０を加算器１４ｂに入力し、乗算器７ｂからの必要アンモニア流量信号２２と加算してアンモニア流量要求信号１９を得る。このアンモニア流量要求信号１９とフィードバック値であるアンモニア流量計６からのアンモニア流量信号４１との偏差信号４２を引算器８ｃで求め、調節計１２ｂで制御出力としての処理を行い制御信号４３をアンモニア流量調節弁２０へ出力する。制御信号４３によりアンモニア流量調節弁２０を開閉して排煙脱硝設備へのアンモニア注入量を制御し、排煙脱硝設備出口ＮＯｘ濃度を所定の値に抑制している。この制御系は基本的に入口ＮＯｘ量信号２１に対する先行値の必要モル比信号１３、出口ＮＯｘ濃度信号３６、出口ＮＯｘ濃度設定信号３５との偏差信号３７によるフィードバックモル比信号１５の補正及び負荷要求信号３８に対する動的先行値の負荷一階微分信号３９、負荷二階微分信号４０によりアンモニア注入量を制御するものである。なお、動的先行値は、アンモニア注入量の変化に対する脱硝反応を通常１０分程度補償するために設けられている。
【０００３】
最近では火力プラントの高速負荷変化率運転に伴い脱硝負荷の変動が急激になり、排煙脱硝設備の出口ＮＯｘ濃度設定値信号３５に対する出口ＮＯｘ濃度の追従性を向上させることが不可欠となっている。例えば、負荷上昇時には脱硝負荷の増加に対して負荷要求信号３８に対する動的先行制御によりアンモニアが多量注入され、出口ＮＯｘ濃度は一旦出口ＮＯｘ濃度設定値に抑制できるが、脱硝負荷が一定になるとアンモニアは過剰となり脱硝率は急上昇して出口ＮＯｘ濃度は極端に低下するものの排ガス中のリークアンモニアが問題になる。
【０００４】
【発明が解決しようとする課題】
上記従来技術は、脱硝負荷の変動が急激に変化した場合、特に負荷上昇時の動的先行制御によりアンモニアが多量に注入された後の追従性は必ずしも満足できるものではなく、必要以上にアンモニアを注入することによる排ガス中のリークアンモニアが増加したり消費量が大きくなる問題がある。
本発明の目的は、排煙脱硝設備の高速負荷変動時にアンモニア注入量制御の追従性を高めることにある。
【０００５】
【課題を解決するための手段】
上記目的は、アンモニア接触還元法による排煙脱硝設備の入口ＮＯｘ濃度と出口ＮＯｘ濃度設定値を入力しアンモニア必要モル比を演算するアンモニア必要モル比演算手段と、前記出口ＮＯｘ濃度設定値と前記排煙脱硝設備の出口ＮＯｘ濃度とアンモニア注入量を入力し、過去のアンモニアモル比と排煙脱硝設備出口ＮＯｘ濃度との因果関係を有する自己回帰モデルにより将来の排煙脱硝設備出口ＮＯｘ濃度を予測し、予測した排煙脱硝設備出口ＮＯｘ濃度を用いてアンモニアモル比補正信号を出力する予測制御手段と、前記アンモニア必要モル比と該アンモニアモル比補正信号を入力し先行値アンモニアモル比を出力する先行値アンモニアモル演算手段と、負荷要求信号と微粉炭ミル起動停止指令信号を入力して入口ＮＯｘ濃度のピークを補償する動的先行モル比信号をファジイ演算するファジイ制御手段と、前記先行値アンモニアモル比を該動的先行モル比信号により補正しアンモニア全モル比を出力する全モル比演算手段と、該アンモニア全モル比と入口ＮＯｘ量を入力し必要アンモニア量を演算する必要アンモニア量演算手段と、該必要アンモニア量と注入アンモニアフィードバック値を入力し注入アンモニア量調整弁制御量を出力する注入アンモニア量制御手段とを有することにより達成される。
【０００６】
上記目的は、アンモニア接触還元法による排煙脱硝設備の入口ＮＯｘ濃度と出口ＮＯｘ濃度設定値を入力してアンモニア必要モル比を演算し、前記出口ＮＯｘ濃度設定値と前記排煙脱硝設備の出口ＮＯｘ濃度とアンモニア注入量を入力して過去のアンモニアモル比と排煙脱硝設備出口ＮＯｘ濃度との因果関係を有する自己回帰モデルにより将来の排煙脱硝設備出口ＮＯｘ濃度を予測し、予測した排煙脱硝設備出口ＮＯｘ濃度を用いてアンモニアモル比補正信号を出力し、前記アンモニア必要モル比と該アンモニアモル比補正信号を入力して先行値アンモニアモル比を出力し、負荷要求信号と微粉炭ミル起動停止指令信号を入力して入口ＮＯｘ濃度のピークを補償する動的先行モル比信号をファジイ演算し、前記先行値アンモニアモル比を該動的先行モル比信号により補正してアンモニア全モル比を出力し、該アンモニア全モル比と入口ＮＯｘ量を入力して必要アンモニア量を演算し、該必要アンモニア量と注入アンモニアフィードバック値を入力して注入アンモニア量調整弁制御量を出力することにより達成される。
【０００７】
上記構成は、従来の必要アンモニア量の負荷変化率による動的先行制御に代わり、過去のアンモニアモル比と排煙脱硝設備出口ＮＯｘ濃度との因果関係をサンプリング周期毎のデータを用いて同定した自己回帰モデルにより将来の排煙脱硝設備の出口ＮＯｘ濃度を予測してアンモニア必要モル比を補正することにより、過去のデータに基づいて予測制御を行い脱硝反応の大きな遅れを補償して高速負荷変動時にもアンモニア注入量制御の追従性を高めて従来の動的先行制御によるアンモニアの大量注入を阻止し、リークアンモニア、アンモニア消費量の増加を防止することができる。予測制御により従来の出口ＮＯｘ濃度と出口ＮＯｘ濃度設定値とから求められアンモニアモル比の指標であるアンモニアフィードバックモル比を求めるフィードバックモル比手段によるネガティブフィードバック的なアンモニアモル比の補正は不要となる。
【０００８】
また、負荷要求信号と微粉炭ミル起動停止指令信号を入力して入口ＮＯｘ濃度のピークを補償するように動的先行モル比信号をファジイ演算することにより、微粉炭ミル起動停止に伴う排煙脱硝設備入口ＮＯｘ濃度のステップ状の急激な変化に対してはフィードフォワードファジイにより滑らかにアンモニア注入量を先行制御し対応することができる。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態を図により説明する。
図１は本発明の実施の形態の排煙脱硝設備アンモニア注入量制御装置の構成を示すブロック図である。
本図に示すアンモニア注入量制御装置は図４に示す排煙脱硝設備のアンモニア注入量制御装置の調節計１２ａが出力するフィードバックモル比信号１５に代わり予測制御装置３０が出力するアンモニアモル比補正信号３１を加算器１４ａへ入力し、かつ加算器１４ｂへ入力する負荷一階微分信号３９、負荷二階微分信号４０を出力する微分器１７、二階微分器１８に代わり負荷要求信号５０と微粉炭ミル起動停止指令信号５１を入力し入口ＮＯｘ濃度のピークを補償するようにファジイ演算して動的先行モル比信号５３を出力するファジイ演算器５２を設けたものである。微粉炭ミル起動停止指令信号５１は石炭焚ボイラの微粉炭ミルを起動・停止する指令であり、微粉炭ミルの起動は微粉炭ミルからボイラ火炉へ微粉炭が供給され微粉炭が燃焼して排ガスが排煙脱硝設備に流入し、脱硝負荷が急激に増加することを意味している。一方微粉炭ミルの停止は微粉炭の燃焼が停止して脱硝負荷が急激に減少することを意味している。このように微粉炭ミル起動停止指令信号５１は脱硝負荷の極めて急激な増加または急激な減少の先行信号となる。
【００１０】
予測制御装置３０には出口ＮＯｘ濃度設定器３からの出口ＮＯｘ濃度設定信号３５と出口ＮＯｘ濃度計４からの出口ＮＯｘ濃度信号３６とアンモニア流量計６からのアンモニア流量信号４１が入力され、過去のアンモニアモル比と排煙脱硝設備の出口ＮＯｘ濃度との因果関係をデータを用いて同定した自己回帰モデルにより将来のサンプリング周期毎の排煙脱硝設備の出口ＮＯｘ濃度が予測される。この将来の排煙脱硝設備出口ＮＯｘ濃度と出口ＮＯｘ濃度設定信号３５との間の制御偏差の自乗積分値とアンモニアモル比のサンプリング周期毎の変化量の自乗積分値の和を最小とするようにアンモニアモル比補正信号３１が定められる。
【００１１】
アンモニア接触還元法のようにアンモニアの触媒表面への吸着量が脱硝性能を支配するような非線形で複雑なプロセスでは、制御用のシュミレーションモデルを構築することが困難であり、ステップ応答により求められる自己回帰モデルによる手法が有効である。
【００１２】
次に予測制御装置３０におけるアンモニアモル比補正信号３１の演算について詳細に説明する。最初にアンモニアモル比（注入アンモニアモル数／入口ＮＯｘモル数）と排煙脱硝設備の出口ＮＯｘ濃度との因果関係を（１）式の自己回帰モデルで求める。
Ａ（ｚ~ ¹）ｙ（ｋ）＝Ｂ（ｚ~ ¹）ｕ（ｋ−１）……………………（１）
【００１３】
【数１】

【００１４】
【数２】

【００１５】
【数３】

【００１６】
ｕ（ｋ−１），・・・・，ｕ（ｋ−ｎ）……………………………（１０）
ｙ（ｋ），・・・・・・，ｙ（ｋ−ｎ）……………………………（１１）
次に（１２）式の評価関数を考える。
【００１７】
【数４】

【００１８】
ここで、
Ｒ：設定値
ｈ：重み係数
Ｍ：予測サンプリング数
である。
【００１９】
（１２）式を最小にする解は（１３）式で与えられる。
【００２０】
【数５】

【００２１】
このようにして（１３）式よりアンモニアモル比補正信号３１が求められる。
次にファジイ演算器を説明する。
負荷要求信号５０と微粉炭ミル起動停止指令信号５１を入力し以下のファジイ演算を行う。
制御ルールの前件部としては、負荷要求信号５０と微粉炭ミル起動停止指令信号５１を信号処理し、負荷変化率と微粉炭ミル起動停止指令後の経過時間とする。即ち、ｋ時刻点における負荷要求信号をｘ（ｋ）、微粉炭ミル起動停止指令後の経過時間をｚ（ｋ）とすると、負荷変化率信号Δｘ（ｋ）は次式となる。
【００２２】
Δｘ（ｋ）＝（ｘ（ｋ）−ｘ（ｋ−１））・Ｓｘ…………………（１４）
ここでＳｘはスケーリングファクタである。
【００２３】
同様にｚ（ｋ）についてもスケーリングを行う。
【００２４】
ｚ´（ｋ）＝ｚ（ｋ）・Ｓｚ…………………………………………（１５）
図２は本発明の実施の形態のメンバシップ関数の例を示す図表である。
【００２５】
本図においてファジイ変数を分割するファジイ集合の数は以下のような１３個であり、これらの集合にそれぞれラベルを付加する。ラベルは−６から１つ刻みに＋６までの整数で表す。
【００２６】
｛−６，・・・，−１，０，１，・・・，６｝＝｛NAL,NVL,NL,NM,NS,NVS,ZE,PVS,PS,PM,PL,PVL,PAL｝……………（１６）
ここで、
ＮＡＬ：Negative Absolutely Large
ＮＶＬ：Negative Very Large
ＮＬ：Negative Very
ＮＭ：Negative Medium
ＮＳ：Negative Small
ＮＶＳ：Negative Very Small
ＺＥ：Zero
ＰＶＳ：Positive Very Small
ＰＳ：Positive Small
ＰＭ：Positive Medium
ＰＬ：Positive Large
ＰＶＬ：Positive Very Large
ＰＡＬ：Positive Absolutely Large
である。
【００２７】
図３は本発明の実施の形態のアンモニア注入モル比を定めるルールを示す図表である。
【００２８】
本図に示すように横方向の数列は負荷変化率信号Δｘ（ｋ）であり、縦方向の数列は微粉炭ミル起動停止指令後の経過時間をｚ´（ｋ）についてスケーリングを行ったものである。この数表からΔｘ（ｋ）とｚ´（ｋ）の状況により公知のＭｉｎ−Ｍａｘ重心法を用いてアンモニア注入モル比Ｈ（ｋ）を求める。求められたアンモニア注入モル比Ｈ（ｋ）に制御ゲインＫを乗算して制御入力ｕ´を得る。
【００２９】
ｕ´（ｋ）＝Ｋ・Ｈ（ｋ）…………………………………………（１７）
この制御入力ｕ´により動的先行モル比信号５３が与えられる。
【００３０】
予測された出口ＮＯｘ濃度に基づいて定められたアンモニアモル比補正信号３１により必要モル比信号１３が補正され予測的にアンモニアモル比が確定する。アンモニアモル比補正信号３１は加算器１４ａへ図４と同様に定められた必要モル比信号１３と共に入力され先行値モル比信号３２が出力される。先行値モル比信号３２と動的先行モル比信号５３が加算器１４ｂへ入力され全モル比信号１６が出力される。全モル比信号１６は乗算器７ｂで入口ＮＯｘ量信号２１と乗算され、アンモニア流量要求信号１９が出力される。全モル比と入口ＮＯｘ量の乗算により要求されるアンモニア流量は得られる。図４に示す従来技術ではアンモニア流量を動的先行値により補正し、本実施の形態ではアンモニアモル比を動的先行モル比により補正した後に全モル比と入口ＮＯｘ量からアンモニア流量を得ているが両者の間に基本的な相違は無い。本実施の形態のようにアンモニアモル比の段階で動的先行補正する方がファジイ演算ルールを定める上で容易となる。アンモニア流量要求信号１９とアンモニア流量計６からのアンモニア流量信号４１を引算器８ｃへ入力し、偏差信号４２を求めて調節計１２ｂでＰＩＤ等の制御処理を行い、制御信号４３をアンモニア流量調節弁２０へ出力してアンモニア注入量を制御し、排煙脱硝設備出口ＮＯｘ濃度を所定値に抑制する。
【００３１】
このように本実施の形態の制御装置は、必要モル比信号１３、アンモニアモル比補正信号３１、動的先行モル比信号５３を組み合わせたものであり、必要モル比信号１３は制御入力のベースを与えアンモニアモル比補正信号３１は出口ＮＯｘ濃度設定値に対するフィードバック補正であり、動的先行モル比信号５３は微粉炭ミル起動停止に伴う排煙脱硝設備入口ＮＯｘ濃度のピークを補償する。
【００３２】
従って現時点より１，２，・・・Ｍサンプリング数後の将来の排煙脱硝設備出口ＮＯｘ濃度を予測してアンモニア注入量をフィードバック補正すると共に、微粉炭ミル起動停止により排煙脱硝設備入口ＮＯｘ濃度のステップ状の急激な変化に対してはフィードフォワードファジイにより滑らかにアンモニア注入量を先行制御し、脱硝反応の大きな遅れを補償して高速負荷変動時にもアンモニア注入量制御の追従性を高めることができる。
【００３３】
【発明の効果】
本発明によれば、過去のアンモニアモル比と排煙脱硝設備出口ＮＯｘ濃度との因果関係を同定した自己回帰モデルにより将来の排煙脱硝設備出口ＮＯｘ濃度を予測してモル比を補正し、排煙脱硝設備入口ＮＯｘ濃度のステップ状の急激な変化に対してはフィードフォワードファジイによりアンモニア注入量を制御することにより、脱硝反応の大きな遅れを補償して高速負荷変動時にもアンモニア注入量制御の追従性を高めて排煙脱硝設備出口ＮＯｘ濃度を所定の値に抑制すると同時にリークアンモニア、アンモニア消費量の増加を防止する効果が得られる。
【図面の簡単な説明】
【図１】本発明の実施の形態の排煙脱硝設備アンモニア注入量制御装置の構成を示すブロック図である。
【図２】本発明の実施の形態のファジイ演算器メンバシップ関数例を示す図表である。
【図３】本発明の実施の形態のアンモニア注入モル比を定めるルールを示す図表である。
【図４】従来のアンモニア注入量制御装置の構成を示すブロック図である。
【符号の説明】
１排ガス流量計
２入口ＮＯｘ濃度計
３出口ＮＯｘ濃度設定器
４出口ＮＯｘ濃度計
６アンモニア流量計
７乗算器
７ａ乗算器
７ｂ乗算器
８ａ引算器
８ｂ引算器
８ｃ引算器
９割算器
１０必要脱硝率信号
１１関数発生器
１２ａ調節計
１２ｂ調節計
１３必要モル比信号
１４ａ加算器
１４ｂ加算器
１５フィードバックモル比信号
１６全モル比信号
１７微分器
１８二階微分器
１９アンモニア流量要求信号
２０アンモニア流量調節弁
２１入口ＮＯｘ量信号
２２必要アンモニア流量信号
３０予測制御装置
３１アンモニアモル比補正信号
３２先行値モル比信号
３３排ガス流量信号
３４入口ＮＯｘ濃度信号
３５出口ＮＯｘ濃度設定信号
３６出口ＮＯｘ濃度信号
３７偏差信号
３８負荷要求信号
３９負荷一階微分信号
４０負荷二階微分信号
４１アンモニア流量信号
４２偏差信号
４３制御信号
５０負荷要求信号
５１微粉炭ミル起動停止指令信号
５２ファジイ演算器
５３動的先行モル比信号[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ammonia injection amount control apparatus and method for a flue gas denitration facility that improves the followability of ammonia injection amount control when a high-speed load fluctuates.
[0002]
[Prior art]
FIG. 4 is a block diagram showing a configuration of a conventional flue gas denitration facility ammonia injection amount control device.
As shown in the figure, the exhaust gas flow rate signal 33 from the exhaust gas flow meter 1 of the flue gas denitration facility and the inlet NOx concentration signal 34 from the inlet NOx concentration meter 2 are multiplied by a multiplier 7a to obtain an inlet NOx amount signal 21. On the other hand, the outlet NOx concentration setting signal 35 from the outlet NOx concentration setting device 3 is input to the subtractor 8a, and the inlet NOx concentration signal 34 from the inlet NOx concentration meter 2 is input to the subtractor 8a and the divider 9. The necessary denitration rate signal 10 is obtained by calculation. This required denitration rate signal 10 is input to the function generator 11 and a required molar ratio signal 13 is obtained by calculation. A deviation signal 37 between the outlet NOx concentration setting signal 35 from the outlet NOx concentration setting device 3 and the outlet NOx concentration signal 36 from the outlet NOx concentration meter 4 is obtained by the subtractor 8b, signal processed by the controller 12a, and fed back to the feedback mole. A ratio signal 15 is obtained. This feedback molar ratio signal 15 is obtained from the currently measured outlet NOx concentration and outlet NOx concentration set value, and corrects the required ammonia molar ratio based on the deviation, and is controlled in a negative feedback manner. The required molar ratio signal 13 and the feedback molar ratio signal 15 are added by an adder 14a to obtain a total molar ratio signal 16, which is multiplied by an inlet NOx amount signal 21 from the multiplier 7a by a multiplier 7b and required ammonia flow rate signal. Get 22. Next, the load first derivative signal 39 and the load second derivative signal 40 obtained by differentiating the load request signal 38 with the differentiator 17 and the second differentiator 18 are input to the adder 14b, and the necessary ammonia flow rate signal 22 from the multiplier 7b is input. To obtain an ammonia flow rate request signal 19. A deviation signal 42 between the ammonia flow rate request signal 19 and the ammonia flow rate signal 41 from the ammonia flow meter 6 as a feedback value is obtained by the subtractor 8c, and the control signal 43 is processed by the controller 12b as a control output. Output to the flow control valve 20. The ammonia flow control valve 20 is opened and closed by the control signal 43 to control the amount of ammonia injected into the flue gas denitration facility, and the NOx concentration at the exhaust gas denitration facility outlet is suppressed to a predetermined value. This control system basically corrects the feedback molar ratio signal 15 by the deviation signal 37 from the required molar ratio signal 13 of the preceding value with respect to the inlet NOx amount signal 21, the outlet NOx concentration signal 36, and the outlet NOx concentration setting signal 35, and the load request. The amount of ammonia injection is controlled by the first-order load differential signal 39 and second-order load differential signal 40 of the dynamic leading value with respect to the signal 38. The dynamic leading value is usually provided to compensate for the denitration reaction with respect to the change of the ammonia injection amount for about 10 minutes.
[0003]
Recently, the fluctuation of the denitration load has become abrupt with the high-speed load change rate operation of the thermal power plant, and it has become essential to improve the followability of the outlet NOx concentration with respect to the outlet NOx concentration set value signal 35 of the flue gas denitration equipment. . For example, when the load rises, a large amount of ammonia is injected by dynamic advance control with respect to the load request signal 38 in response to an increase in the denitration load, and the outlet NOx concentration can be temporarily suppressed to the outlet NOx concentration set value. However, although the NOx removal rate rapidly increases and the outlet NOx concentration decreases extremely, leaked ammonia in the exhaust gas becomes a problem.
[0004]
[Problems to be solved by the invention]
In the above prior art, when the fluctuation of the denitration load changes abruptly, the followability after a large amount of ammonia is injected by the dynamic advance control especially when the load is increased is not always satisfactory. There is a problem that leakage ammonia in the exhaust gas due to the injection increases or the consumption amount increases.
An object of the present invention is to improve the followability of the ammonia injection amount control when the flue gas denitration equipment changes at a high speed load.
[0005]
[Means for Solving the Problems]
The purpose is to input ammonia NOx concentration and outlet NOx concentration set values of the flue gas denitrification facility by the ammonia catalytic reduction method, and to calculate ammonia required molar ratio calculation means for calculating the ammonia required molar ratio, the outlet NOx concentration set value and the exhaust gas. Enter the NOx concentration at the outlet of the smoke denitrification facility and the ammonia injection amount, and predict the future NOx concentration at the outlet of the flue gas denitrification facility by an autoregressive model that has a causal relationship between the past ammonia molar ratio and the NOx concentration at the exhaust flue gas removal facility. A predictive control means for outputting an ammonia molar ratio correction signal using the predicted NOx concentration at the exhaust gas denitrification facility, and an input for inputting the ammonia required molar ratio and the ammonia molar ratio correction signal and outputting the preceding value ammonia molar ratio. Value ammonia mole calculation means, load request signal and pulverized coal mill start / stop command signal are input, and the peak of inlet NOx concentration is Fuzzy control means for fuzzy calculation of the dynamic leading molar ratio signal to be compensated, total mole ratio calculating means for correcting the leading value ammonia molar ratio by the dynamic leading molar ratio signal and outputting the ammonia total molar ratio, and the ammonia Necessary ammonia amount calculation means for calculating the required ammonia amount by inputting the total molar ratio and the inlet NOx amount, and injected ammonia amount control means for inputting the required ammonia amount and the injected ammonia feedback value and outputting an injection ammonia amount adjustment valve control amount Is achieved.
[0006]
The purpose is to calculate the required ammonia molar ratio by inputting the inlet NOx concentration and the outlet NOx concentration set value of the flue gas denitrification facility by the ammonia catalytic reduction method, and the outlet NOx concentration set value and the outlet NOx concentration of the flue gas denitration facility. Enter the concentration and ammonia injection amount, and predict the future NOx concentration at the exhaust flue gas denitrification facility using the autoregressive model that has a causal relationship between the past ammonia molar ratio and the NOx concentration at the flue gas denitrification facility. Output ammonia mole ratio correction signal using equipment outlet NOx concentration, input the required ammonia mole ratio and ammonia mole ratio correction signal, output preceding value ammonia mole ratio, load request signal and pulverized coal mill start / stop Fuzzy calculation is performed on the dynamic leading molar ratio signal that compensates for the peak of the inlet NOx concentration by inputting the command signal, and the leading ammonia phase ratio is Correct by the preceding molar ratio signal and output the total ammonia molar ratio, input the total ammonia molar ratio and the inlet NOx amount, calculate the required ammonia amount, input the required ammonia amount and the injected ammonia feedback value, and inject This is achieved by outputting an ammonia amount adjusting valve control amount.
[0007]
In the above configuration, instead of the conventional dynamic advance control based on the load change rate of the required ammonia amount, the self-identification in which the causal relationship between the past ammonia molar ratio and the NOx concentration at the flue gas denitrification facility is identified using the data for each sampling period. By predicting the outlet NOx concentration of the flue gas denitration facility in the future using the regression model and correcting the required molar ratio of ammonia, predictive control is performed based on past data to compensate for large delays in the denitration reaction and during high-speed load fluctuations. In addition, it is possible to improve the followability of the ammonia injection amount control and to block the large amount of ammonia injection by the conventional dynamic advance control, and to prevent the increase of leakage ammonia and ammonia consumption. It is not necessary to perform negative feedback correction of the ammonia molar ratio by the feedback molar ratio means for obtaining the ammonia feedback molar ratio, which is obtained from the conventional outlet NOx concentration and the outlet NOx concentration set value by predictive control and is an indicator of the ammonia molar ratio.
[0008]
Also, by inputting the load request signal and the pulverized coal mill start / stop command signal and fuzzy calculation of the dynamic leading molar ratio signal so as to compensate for the peak of the inlet NOx concentration, flue gas denitration accompanying the pulverized coal mill start / stop is performed. A sudden change in the NOx concentration at the facility inlet can be handled by controlling the ammonia injection amount smoothly by feedforward fuzzy.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a flue gas denitration facility ammonia injection amount control apparatus according to an embodiment of the present invention.
The ammonia injection amount control device shown in this figure is an ammonia molar ratio correction signal output by the prediction control device 30 in place of the feedback molar ratio signal 15 output by the controller 12a of the ammonia injection amount control device of the flue gas denitration equipment shown in FIG. 31 is input to the adder 14a and input to the adder 14b. The load request signal 50 and the pulverized coal mill are activated instead of the load first-order differential signal 39, the differentiator 17 that outputs the load second-order differential signal 40, and the second-order differentiator 18. A fuzzy calculator 52 is provided which inputs a stop command signal 51 and performs a fuzzy calculation so as to compensate for the peak of the inlet NOx concentration and outputs a dynamic leading molar ratio signal 53. The pulverized coal mill start / stop command signal 51 is a command for starting / stopping the pulverized coal mill of the coal fired boiler. The pulverized coal mill is activated by supplying pulverized coal from the pulverized coal mill to the boiler furnace and burning the pulverized coal. Flows into the flue gas denitration facility, which means that the denitration load increases rapidly. On the other hand, the stop of the pulverized coal mill means that the combustion of the pulverized coal is stopped and the denitration load is rapidly reduced. In this way, the pulverized coal mill start / stop command signal 51 is a preceding signal for an extremely rapid increase or a rapid decrease in the denitration load.
[0010]
The predictive control device 30 is inputted with an outlet NOx concentration setting signal 35 from the outlet NOx concentration setting device 3, an outlet NOx concentration signal 36 from the outlet NOx concentration meter 4, and an ammonia flow signal 41 from the ammonia flow meter 6. The auto-regression model that identifies the causal relationship between the ammonia molar ratio and the outlet NOx concentration of the flue gas denitrification facility using data predicts the outlet NOx concentration of the flue gas denitrification facility for each future sampling period. The sum of the square integral value of the control deviation between the future NOx concentration at the exhaust gas denitrification facility and the outlet NOx concentration setting signal 35 and the square integral value of the change amount for each sampling period of the ammonia molar ratio is minimized. An ammonia molar ratio correction signal 31 is determined.
[0011]
In a non-linear and complex process where the amount of ammonia adsorbed on the catalyst surface dominates the denitration performance as in the ammonia catalytic reduction method, it is difficult to construct a simulation model for control, and the self-requirement required by the step response A method based on a regression model is effective.
[0012]
Next, the calculation of the ammonia molar ratio correction signal 31 in the predictive control device 30 will be described in detail. First, the causal relationship between the ammonia molar ratio (number of moles of injected ammonia / number of moles of inlet NOx) and the outlet NOx concentration of the flue gas denitration facility is determined by the autoregressive model of equation (1).
A (z ~ ¹ ) y (k) = B (z ~ ¹ ) u (k-1) ……………… (1)
[0013]
[Expression 1]

[0014]
[Expression 2]

[0015]
[Equation 3]

[0016]
u (k-1),..., u (k-n) ... (10)
y (k), ..., y (k-n) ........................ (11)
Next, consider the evaluation function of equation (12).
[0017]
[Expression 4]

[0018]
here,
R: Set value h: Weight coefficient M: Predicted sampling number.
[0019]
The solution that minimizes equation (12) is given by equation (13).
[0020]
[Equation 5]

[0021]
In this way, the ammonia molar ratio correction signal 31 is obtained from the equation (13).
Next, the fuzzy computing unit will be described.
The load request signal 50 and the pulverized coal mill start / stop command signal 51 are input, and the following fuzzy calculation is performed.
As the antecedent part of the control rule, the load request signal 50 and the pulverized coal mill start / stop command signal 51 are signal-processed to obtain the load change rate and the elapsed time after the pulverized coal mill start / stop command. That is, when the load request signal at the time point k is x (k) and the elapsed time after the pulverized coal mill start / stop command is z (k), the load change rate signal Δx (k) is expressed by the following equation.
[0022]
Δx (k) = (x (k) −x (k−1)) · Sx (14)
Here, Sx is a scaling factor.
[0023]
Similarly, scaling is performed for z (k).
[0024]
z ′ (k) = z (k) · Sz ………………………………………… (15)
FIG. 2 is a chart showing an example of the membership function according to the embodiment of the present invention.
[0025]
In this figure, the number of fuzzy sets into which fuzzy variables are divided is 13 as follows, and a label is added to each of these sets. Labels are expressed as integers from -6 to +6 in increments of 1.
[0026]
{−6,..., −1, 0, 1,..., 6} = {NAL, NVL, NL, NM, NS, NVS, ZE, PVS, PS, PM, PL, PVL, PAL}… ………… (16)
here,
NAL: Negative Absolutely Large
NVL: Negative Very Large
NL: Negative Very
NM: Negative Medium
NS: Negative Small
NVS: Negative Very Small
ZE: Zero
PVS: Positive Very Small
PS: Positive Small
PM: Positive Medium
PL: Positive Large
PVL: Positive Very Large
PAL: Positive Absolutely Large
It is.
[0027]
FIG. 3 is a chart showing rules for determining the ammonia injection molar ratio according to the embodiment of the present invention.
[0028]
As shown in this figure, the horizontal sequence is the load change rate signal Δx (k), and the vertical sequence is the scaled time for z ′ (k) after the pulverized coal mill start / stop command. is there. From this numerical table, the ammonia injection molar ratio H (k) is obtained using the known Min-Max centroid method according to the situation of Δx (k) and z ′ (k). A control input u ′ is obtained by multiplying the determined ammonia injection molar ratio H (k) by the control gain K.
[0029]
u ′ (k) = KH (k) ………………………………………… (17)
This control input u ′ gives a dynamic leading molar ratio signal 53.
[0030]
The required molar ratio signal 13 is corrected by the ammonia molar ratio correction signal 31 determined based on the predicted outlet NOx concentration, and the ammonia molar ratio is determined in a predictive manner. The ammonia molar ratio correction signal 31 is input to the adder 14a together with the required molar ratio signal 13 determined in the same manner as in FIG. 4, and the preceding value molar ratio signal 32 is output. The preceding molar ratio signal 32 and the dynamic leading molar ratio signal 53 are input to the adder 14b and the total molar ratio signal 16 is output. The total molar ratio signal 16 is multiplied by the inlet NOx amount signal 21 by the multiplier 7b, and an ammonia flow rate request signal 19 is output. The required ammonia flow rate is obtained by multiplying the total molar ratio by the inlet NOx amount. In the prior art shown in FIG. 4, the ammonia flow rate is corrected by the dynamic leading value, and in this embodiment, the ammonia flow rate is obtained from the total molar ratio and the inlet NOx amount after the ammonia molar ratio is corrected by the dynamic leading mole ratio. There is no fundamental difference between the two. As in this embodiment, it is easier to perform dynamic advance correction at the ammonia molar ratio stage in order to determine fuzzy calculation rules. The ammonia flow rate request signal 19 and the ammonia flow rate signal 41 from the ammonia flow meter 6 are input to the subtractor 8c, the deviation signal 42 is obtained, the controller 12b performs control processing such as PID, and the control signal 43 is adjusted to the ammonia flow rate. Output to the valve 20 to control the ammonia injection amount, and suppress the NOx concentration at the exhaust gas denitration facility outlet to a predetermined value.
[0031]
As described above, the control device of the present embodiment is a combination of the required molar ratio signal 13, the ammonia molar ratio correction signal 31, and the dynamic preceding molar ratio signal 53. The required molar ratio signal 13 is the base of the control input. The given ammonia molar ratio correction signal 31 is a feedback correction for the outlet NOx concentration set value, and the dynamic leading molar ratio signal 53 compensates for the peak of the NOx concentration at the inlet of the flue gas denitrification facility accompanying the start and stop of the pulverized coal mill.
[0032]
Therefore, the NOx concentration at the exhaust gas denitration facility outlet is predicted by predicting the future NOx concentration at the exhaust gas denitrification facility after the number of

samplings

1, 2,... In order to prevent sudden changes in the step, the ammonia injection amount can be controlled smoothly by feed-forward fuzzy to compensate for large delays in the denitration reaction, and the follow-up of ammonia injection amount control can be improved even during high-speed load fluctuations. it can.
[0033]
【The invention's effect】
According to the present invention, the NOx concentration in the future flue gas denitrification equipment is predicted by the autoregressive model that identifies the causal relationship between the past ammonia molar ratio and the flue gas denitrification equipment exit NOx concentration, and the molar ratio is corrected. By controlling the ammonia injection amount by feed-forward fuzzy for the stepwise rapid change in NOx concentration at the inlet of the smoke denitrification facility, the ammonia injection amount is controlled by feedforward fuzzy to compensate for a large delay in the denitration reaction and follow the ammonia injection amount control even during high-speed load fluctuations. As a result, the NOx concentration at the outlet of the flue gas denitration facility is suppressed to a predetermined value, and at the same time, an effect of preventing an increase in leakage ammonia and ammonia consumption is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a flue gas denitration facility ammonia injection amount control apparatus according to an embodiment of the present invention.
FIG. 2 is a chart showing an example of a fuzzy computing unit membership function according to the embodiment of the present invention.
FIG. 3 is a chart showing rules for determining an ammonia injection molar ratio according to the embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a conventional ammonia injection amount control device.
[Explanation of symbols]
1 Exhaust gas flow meter 2 Inlet NOx concentration meter 3 Outlet NOx concentration setter 4 Outlet NOx concentration meter 6 Ammonia flow meter 7 Multiplier 7a Multiplier 7b Multiplier 8a Subtractor 8b Subtractor 8c Subtractor 9 Divider 10 Required denitration rate signal 11 Function generator 12a Controller 12b Controller 13 Required molar ratio signal 14a Adder 14b Adder 15 Feedback molar ratio signal 16 Total molar ratio signal 17 Differentiator 18 Second-order differentiator 19 Ammonia flow rate request signal 20 Ammonia flow rate Control valve 21 Inlet NOx amount signal 22 Required ammonia flow rate signal 30 Predictive control device 31 Ammonia molar ratio correction signal 32 Advancing value molar ratio signal 33 Exhaust gas flow rate signal 34 Inlet NOx concentration signal 35 Outlet NOx concentration setting signal 36 Outlet NOx concentration signal 37 Deviation Signal 38 Load request signal 39 Load first derivative signal 40 Load second derivative signal 4 Ammonia flow rate signal 42 error signal 43 the control signal 50 the load demand signal 51 pulverized coal mill start stop command signal 52 fuzzy arithmetic unit 53 dynamically preceding molar ratio signal

Claims

A required ammonia molar ratio calculating means for inputting the inlet NOx concentration and the outlet NOx concentration set value of the flue gas denitrification facility by the ammonia catalytic reduction method and calculating the required ammonia molar ratio;
By inputting the outlet NOx concentration set value, the outlet NOx concentration of the flue gas denitrification facility, and the ammonia injection amount, a future exhaust gas is calculated by an autoregressive model having a causal relationship between the past ammonia molar ratio and the flue gas denitrification facility outlet NOx concentration. A predictive control means for predicting the NOx concentration at the outlet of the smoke denitrification facility and outputting an ammonia molar ratio correction signal using the predicted NOx concentration at the exit of the flue gas denitrification facility;
A preceding value ammonia mole calculating means for inputting the ammonia required mole ratio and the ammonia mole ratio correction signal and outputting the preceding ammonia mole ratio;
A fuzzy control means for fuzzy calculation of a dynamic leading molar ratio signal that compensates for the peak of the inlet NOx concentration by inputting a load request signal and a pulverized coal mill start / stop command signal;
A total molar ratio calculating means for correcting the preceding ammonia molar ratio by the dynamic leading molar ratio signal and outputting an ammonia total molar ratio;
Necessary ammonia amount calculating means for inputting the total ammonia molar ratio and the inlet NOx amount and calculating the required ammonia amount;
An ammonia injection amount control device for flue gas denitrification equipment, comprising: an injection ammonia amount control means for inputting the required ammonia amount and an injection ammonia feedback value and outputting an injection ammonia amount adjustment valve control amount.

Calculate the required ammonia molar ratio by inputting the inlet NOx concentration and outlet NOx concentration set value of the flue gas denitrification equipment by the ammonia catalytic reduction method,
By inputting the outlet NOx concentration set value, the outlet NOx concentration of the flue gas denitrification facility, and the ammonia injection amount, the future exhaust gas is calculated by an autoregressive model having a causal relationship between the past ammonia molar ratio and the flue gas denitrification facility outlet NOx concentration. Predict the NOx concentration at the outlet of the smoke denitrification facility, and output the ammonia molar ratio correction signal using the predicted NOx concentration at the exit of the exhaust smoke denitrification facility,
Input the required ammonia molar ratio and the ammonia molar ratio correction signal to output the preceding ammonia molar ratio,
Fuzzy calculation of the dynamic leading molar ratio signal that compensates for the peak of the inlet NOx concentration by inputting the load request signal and the pulverized coal mill start / stop command signal,
Correcting the preceding ammonia molar ratio by the dynamic preceding molar ratio signal to output the total ammonia molar ratio;
Calculate the required ammonia amount by inputting the total ammonia molar ratio and the amount of inlet NOx,
An ammonia injection amount control method for a flue gas denitrification facility, wherein the required ammonia amount and an injection ammonia feedback value are input and an injection ammonia amount adjustment valve control amount is output.