JP4627611B2

JP4627611B2 - Ammonia injection amount control method and apparatus for denitration apparatus and ammonia injection amount correction device

Info

Publication number: JP4627611B2
Application number: JP2001201849A
Authority: JP
Inventors: 孝裕竹友; 宏権藤
Original assignee: Babcock Hitachi KK
Current assignee: Mitsubishi Power Ltd
Priority date: 2001-07-03
Filing date: 2001-07-03
Publication date: 2011-02-09
Anticipated expiration: 2021-07-03
Also published as: JP2003010645A

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling an NH3 injection amount to a nitrogen oxide removal apparatus so as to prevent excess nitrogen oxide removal and leakage of NH3 and avoid deviation from a regulated value of the NOx concentration at an outlet due to insufficient injection amount of NH3 . SOLUTION: The method for controlling ammonia injection amount comprises steps of calculating an inlet NOx amount from the quantity of an object waste gas to be treated and an inlet NOx concentration; calculating the NH3 mole ratio necessary to the NOx amount based on the prescribed values and the measured values of the inlet NOx concentration and an outlet NOx concentration; calculating correcting bias signals for NH3 adsorption amount remaining in a catalyst based on the injected NH3 flow rate, the amount of the object waste gas to be treated, the inlet and outlet NOx concentrations, and the NH3 flow rate leaking from the apparatus; correcting the necessary NH3 flow rate signals based on the correcting bias signals; and operating an NH3 flow rate control apparatus based on the deflection between the corrected necessary NH3 flow rate signal and the practically measured NH3 flow rate signal.

Description

【０００１】
【発明の属する技術分野】
本発明は、脱硝装置へのアンモニア注入量制御方法および装置ならびにそれらに使用するアンモニア注入量補正装置に係り、特にボイラなどの燃焼装置から排出される排ガス中の窒素酸化物（ＮＯｘ）をアンモニア（ＮＨ₃）の注入によって還元・除去する脱硝装置へのアンモニア注入量制御方法および装置ならびにこれらに使用するアンモニア注入量補正装置であって、触媒に吸着されるＮＨ₃量を考慮し、かつ出口ＮＯｘ濃度制御偏差を適切に解消するためのアンモニア注入量補正装置と、該装置を備えた脱硝装置へのアンモニア注入量制御方法および装置に関する。
【０００２】
【従来の技術】
排ガス用脱硝装置ではＮＯｘ還元剤として一般にＮＨ₃を使用し、これを排ガス中に注入し、装置内に設置した触媒層上で注入したＮＨ₃と排ガス中のＮＯｘを反応させて窒素と水にする。すなわち、
【０００３】
【数１】
ＮＨ₃＋ＮＯ＋１／４Ｏ₂→Ｎ₂＋３／２・Ｈ₂Ｏ
排ガス中のＮＯｘは注入するＮＨ₃と上式で示す反応をして窒素と水になるので、基本的には注入するＮＨ₃量は処理すべきＮＯｘ量に見合った量を注入することになる。
【０００４】
注入したＮＨ₃はＮＯｘとの反応に使用される以外に、触媒表面に吸着し得るだけ吸着する。したがって、それを超えて注入するとリークアンモニアとして脱硝装置から流出し問題となる。
一方、注入するＮＨ₃量が処理すべきＮＯｘ量に対して不足するとＮＯｘを処理しきれなくなり、出口処理ガス中のＮＯｘ濃度を規定値以下にすることができなくなる。
【０００５】
脱硝装置のアンモニア注入量制御方法についての従来技術を図３に示す。被処理ガス中のＮＯｘ量に見合ったＮＨ₃注入量を算出する注入量算出器９は、脱硝装置の入口ＮＯｘ濃度、出口ＮＯｘ濃度設定値、出口ＮＯｘ濃度および被処理ガス量などからＮＨ₃注入量を算出するものである。
【０００６】
すなわち、脱硝装置の入口ＮＯｘ分析計１２で検出された入口ＮＯｘ濃度信号１３と被処理ガス量２８の被処理ガス流量信号２９とを乗算器３１で乗算し、総ＮＯｘ量信号３０を算出する。一方、入口ＮＯｘ濃度信号１３と脱硝装置の出口ＮＯｘ濃度設定器１５で設定された設定ＮＯｘ濃度信号１６との減算を行う減算器１９を有する必要モル比演算器１８で必要モル比（ＮＨ₃モル／ＮＯｘモル）信号２０を算出し、比例積分演算器２５を介して加算器２６に入力する。
【０００７】
一方、出口ＮＯｘ濃度分析計２２で検出された出口ＮＯｘ濃度検出信号２３と設定ＮＯｘ濃度信号１６との偏差を減算器２４により算出し、比例積分演算器２５を介して加算器２６に入力して前記必要モル比信号２０の補正を行う。
補正後の必要モル比信号２７と先に述べた総ＮＯｘ量信号３０とを乗算器３２で乗算し必要ＮＨ₃流量信号３３を算出する。
【０００８】
この必要ＮＨ₃流量信号３３とＮＨ₃流量計３８で検出されたＮＨ₃流量検出信号３９を減算器４０で減算してＮＨ₃流量偏差信号４１を算出し、これを比例積分演算器４２で弁開度信号４３に変換して、電空変換器４４により制御信号４５に変換し、ＮＨ₃配管５の途中に設けられたＮＨ₃流量調節弁１０を開閉して脱硝装置へのＮＨ₃注入量を適正量に制御する。
【０００９】
【発明が解決しようとする課題】
従来技術に係る比例積分演算器２５によるフィードバック制御装置では、出口ＮＯｘ濃度を設定値に漸近させることを目的とするが、制御にやや時間を要するとともに、触媒上のＮＨ₃吸着量を考慮したＮＨ₃注入量制御を行っていないので、
（１）多量の吸着ＮＨ₃が触媒上に残存していて、しかも負荷が降下するときにはＮＯｘの過剰除去による出口ＮＯｘ濃度の設定範囲からの下方への逸脱、（２）過剰なＮＨ₃注入によるリークＮＨ₃量の増大、（３）ＮＨ₃の過剰使用による不経済等の問題が生じていた。
【００１０】
本発明の課題は、上記従来技術の問題点を解決し、触媒に吸着されるＮＨ₃量や装置からのリークＮＨ₃量を正確に把握してＮＨ₃注入量操作にフィードバックさせるとともに、出口ＮＯｘ濃度の設定値と測定値の偏差に基づくＮＨ₃注入量操作へのフィードバックを迅速かつ調節容易とし、負荷に対応した適切なＮＨ₃注入を行い、これにより過剰注入による過脱硝や、リークＮＨ₃の増大を防止し、またはＮＨ₃注入量不足による出口ＮＯｘ濃度の規制値からの逸脱を防止することができる脱硝装置へのアンモニア注入量制御方法および装置ならびにそれらに使用するアンモニア注入量補正装置を提供することにある。
【００１１】
【課題を解決するための手段】
上記課題を解決するため、本願で特許請求する発明は以下のとおりである。
【００１４】
（１）装置入口からＮＯｘを含有する排ガスを導入するとともに該排ガス中にＮＨ₃を注入して装置内に設けた脱硝触媒層により前記ＮＯｘを接触還元したのち装置出口から排出する脱硝装置へ前記ＮＨ₃を注入するＮＨ₃注入量制御装置において、前記装置入口から導入した被処理排ガスのＮＯｘ量を求める手段と、入口ＮＯｘ濃度と出口ＮＯｘ濃度の設定値および測定値に基づきＮＯｘ量に対する必要ＮＨ₃モル比を算出する手段と、前記入口ＮＯｘ量と必要ＮＨ₃モル比から必要アンモニア流量を求める手段と、被処理ガス量と入口および出口ＮＯｘ濃度から脱硝反応に消費したＮＨ₃量を求める手段と、求めた消費ＮＨ₃量と装置からのリークＮＨ₃量とを注入ＮＨ₃量から減算して触媒残存ＮＨ₃吸着量補正バイアス信号を求める手段と、装置出口ＮＯｘ濃度の設定値と測定値の制御偏差量に応じ、かつその偏差がマイナス時はマイナス、プラス時はプラスの値として脱硝出口ＮＯｘ偏差補正バイアス信号を求める手段と、前記２つの補正バイアス信号を加算する手段と、装置出口ＮＯｘ濃度の設定値と測定値の偏差に基づき出口ＮＯｘ偏差補正ゲイン値を算出する手段と、前記加算した補正バイアス信号に上記出口ＮＯｘ偏差補正ゲイン値を乗算してＮＨ₃注入量補正信号を求める手段と、該ＮＨ₃注入量補正信号を前記必要ＮＨ₃流量に加算して補正後必要ＮＨ₃流量を算出する手段と、この補正後必要ＮＨ₃流量と実測ＮＨ₃流量との偏差に基づきＮＨ₃流量調節手段を操作する手段とを設けたことを特徴とする脱硝装置へのアンモニア注入量制御装置。
【００１５】
（２）装置入口からＮＯｘを含有する排ガスを導入するとともに該排ガス中にＮＨ₃を注入して装置内に設けた触媒層によって前記ＮＯｘを還元したのち装置出口から排出する脱硝装置へのＮＨ₃注入量を制御するに際し、前記触媒層に吸着されるＮＨ₃量と出口ＮＯｘ濃度の設定値と測定値の偏差に基づき上記ＮＨ₃注入量を補正する装置であって、前記脱硝装置に導入される被処理ガス量と入口および出口ＮＯｘ濃度から脱硝反応に消費したＮＨ₃量を求める手段と、求めた消費ＮＨ₃量と装置からのリークＮＨ₃量を注入ＮＨ₃量から減算して触媒残存ＮＨ₃吸着量補正バイアス信号を求める手段と、装置出口のＮＯｘ濃度の設定値と測定値の偏差量に基づき、かつその偏差がマイナス時はマイナス、プラス時はプラスの値として脱硝出口ＮＯｘ偏差補正バイアス信号を算出する手段と、前記２つの補正バイアス信号を加算する手段と、装置出口ＮＯｘ濃度の設定値と測定値の偏差量に基づき出口ＮＯｘ偏差補正ゲイン値を算出する手段と、前記加算した補正バイアス信号にこの出口ＮＯｘ偏差補正ゲイン値を乗算してＮＨ₃注入量補正信号を求める手段と、該ＮＨ₃注入量補正信号を脱硝装置へのＮＨ₃注入量制御部に入力する手段とを備えてなる脱硝装置へのアンモニア注入量補正装置。
【００１６】
【発明の実施の形態】
本発明の実施の形態を図面を用いて以下、説明する。
図２は、脱硝反応器の概略図である。脱硝反応器１は、例えば被処理ガスＧの発生源であるボイラからの排ガス（被処理ガスＧ）を入口ダクト２から導入し、ＮＨ₃の注入によって脱硝処理してから出口ダクト３に排出し、さらに図示していない煙突により屋外に排出する。この際、被処理ガスＧ中のＮＯｘは入口ダクト２に設けられたＮＨ₃注入器４によって被処理ガスＧ中のＮＯｘ量に見合ったＮＨ₃がアンモニア流量計３８およびアンモニア流量調節弁１０を介して注入され、脱硝反応器１の内部に充填された図示していない脱硝触媒のはたらきによって無害な水蒸気と窒素ガスに分解、除去される。通常、脱硝反応器１の運用は被処理ガスＧの発生源、例えばボイラ等の負荷変化時においても脱硝反応器１の出口ＮＯｘ濃度が規定値以下になるように制御される。ここで被処理ガスＧ中の入口ＮＯｘ濃度は入口ＮＯｘ分析計１２で、出口ＮＯｘ濃度は出口ＮＯｘ分析計２２で計測される。
【００１７】
以下、本発明の実施形態である制御回路の全体構造を図１を用いて説明する。
図１は、上記脱硝反応器１に備えられた脱硝制御装置７の実施の形態を示す制御回路である。この脱硝制御装置７は、アンモニアの注入量を算出する注入量算出器９（従来回路）で使用している一部の信号を流用し、従来回路の代替回路として補正ＮＨ₃流量算出器５０（本発明回路）を設置したものである。
【００１８】
補正アンモニア流量算出器５０では、入口ＮＯｘ濃度信号１３と出口ＮＯｘ濃度信号２３の差分を減算器５７により求め、このＮＯｘ濃度差分信号を乗算器５８にて被処理ガス量２８と乗算する。これは脱硝装置１で還元処理されたＮＯｘ量に相当する。この処理ＮＯｘ量に必要モル比を乗算すればＮＯｘ還元反応に直接使用されたＮＨ₃量が得られる。これを信号５８ａで示す。
【００１９】
アンモニア流量計３８による実測ＮＨ₃流量信号３９と上記信号５８ａの差分を減算器５６で求め５６ａを得る。５６ａは脱硝装置に注入されたアンモニア量のうち、排ガスとの還元反応にはかかわらなかったアンモニア量に相当する。
このアンモニア量５６ａから、リークＮＨ₃流量検出器５９による脱硝装置からの流出アンモニア流量５９ａを減算器６０にて減算すると触媒に吸着されるＮＨ₃量、すなわちＮＨ₃吸着量補正バイアス信号６５を得る。この信号６５はＮＨ₃補正出力信号６６として図１の加算器５１に入力する。
【００２０】
一方、出口ＮＯｘ濃度設定値１５の出力信号１６と出口ＮＯｘ濃度分析計２２の出力信号２３との偏差信号６７を関数発生器５４に入力し、変化率制御器５５を経て出口ＮＯｘ偏差補正バイアス信号６４を得る。この信号６４は加算器６１、乗算器６２を経てＮＨ₃注入補正信号６６として加算器５１に加算される。
【００２１】
なお、出口ＮＯｘ偏差補正バイアス信号６４は、前記偏差信号６７の値がプラスの場合、すなわち信号２３が信号１６より大きい場合はプラスの出力、信号６７がマイナスの場合はマイナスとなる。すなわち出口ＮＯｘ濃度信号２３が設定値１６より大きい場合は信号６４はプラス、信号２３が信号１６より小さい場合は信号６４はマイナスとする。
また、この信号６４と前記したＮＨ₃吸着量補正バイアス信号６５を加算器６１にて加算し、この加算された補正信号６１ａをＮＨ₃注入補正信号６６として加算器５１に入力する。
【００２２】
なお、関数発生器５４は脱硝装置の構造、内蔵された脱硝触媒の構造、成分、性能、排ガス発生源の特性等により規定されるものであり、ボイラ等の試運転時に関数関係が調整される。変化率制御器５５は、前記した信号６４の変化率を制御するものであり、その目的は脱硝装置へのアンモニア注入量に極度の変化を与えることを抑制するものである。
【００２３】
また、出口ＮＯｘ濃度偏差信号６７は関数発生器５２に入力され信号５２ａを出力する。この信号５２ａは１次遅れ要素５３を介して信号６４に対して１次遅れ形式の出口ＮＯｘ偏差補正ゲイン信号６３として出力され、乗算器６２に入力される。
この結果、乗算器６２に入力される前記信号６５、または６５もしくは信号６４と６５を加算した信号に信号６３が乗算され、ゲイン倍された出力信号６６を得る。このゲイン値は０〜Ｘの範囲で調整される。
【００２４】
脱硝出口ＮＯｘ制御偏差からの必要ＮＨ₃補正ゲイン信号６３は、出口ＮＯｘ制御偏差に見合った値を関数発生器５２により可変出力する。例えば制御偏差（減算器２４出力）がプラス方向の場合は、ＮＨ₃補正流量をプラスゲイン倍とし加算器６１出力を増加させ、脱硝出口ＮＯｘ濃度のピークを抑える方向へと動作する。逆に、出口制御偏差（減算器２４出力）がマイナス側の場合は、関数発生器５２よりマイナスゲイン倍とし、脱硝出口ＮＯｘの沈み込みを防止する方向へ動作する。当然出口ＮＯｘ制御性向上のため関数発生器５２にはデットバンドを設けてあり、制御偏差０付近はＮＨ₃流量補正バイアスを変化させない工夫もしてある。
【００２５】
上記した実施の形態の動作により、脱硝装置出口ＮＯｘのピーク／ボトムを抑えることができるので、その結果、脱硝装置出口ＮＯｘ値を制御管理値範囲内に維持することが可能である。
【００２６】
【発明の効果】
本発明によれば、触媒に吸着されるアンモニア量を考慮し、かつ装置出口のＮＯｘ濃度偏差を早急・適切に解消するためのアンモニア注入量補正手段を設けたので、
（１）脱硝装置出口ＮＯｘ濃度制御偏差の縮小、（２）リークＮＨ₃量の低減、（３）ＮＨ₃消費量の低減といった効果がある。
【図面の簡単な説明】
【図１】本発明の一実施例である脱硝装置へのアンモニア注入量制御方法の装置系統を示す図。
【図２】脱硝装置の概略図。
【図３】従来技術に係る脱硝装置へのアンモニア注入量制御方法の装置系統を示す図。
【符号の説明】
５…ＮＨ₃配管、８…従来脱硝制御装置、９…注入量算出器、１０…ＮＨ₃流量調整弁、１２…入口ＮＯｘ濃度分析計、１３…入口ＮＯｘ濃度信号、１５…出口ＮＯｘ濃度設定器、１６…設定ＮＯｘ濃度信号、１８…必要モル比演算部、１９…減算器、２０…必要モル比信号、２２…出口ＮＯｘ濃度分析計、２３…出口ＮＯｘ濃度信号、２４…減算器、２５…比例積分演算器、２６…加算器、２７…必要モル比信号（補正後）、２８…被処理ガス量、２９…被処理ガス流量信号、３０…総ＮＯｘ量信号、３１…乗算器、３２…乗算器、３３…必要ＮＨ₃流量信号、３８…必要ＮＨ₃流量計、３９…実測ＮＨ₃流量信号、４０…減算器、４１…ＮＨ₃流量偏差信号、４２…比例積分器、４３…弁開度信号、４４…電空変換器、４５…制御信号、５０…補正ＮＨ₃流量算出器、５１…加算器、５２…関数発生器、５３…１次遅れ、５４…関数発生器、５５…変化率制御器、５６…減算器、５７…減算器、５８…乗算器、５９…リークＮＨ₃流量検出器、６０…減算器、６１…加算器、６２…乗算器、６３…出口ＮＯｘ偏差補正ゲイン信号、６４…出口ＮＯｘ偏差補正バイアス信号、６５…ＮＨ₃吸着量補正バイアス信号、６６…ＮＨ₃注入補正信号、６７…脱硝出口ＮＯｘ制御偏差、６８…補正後必要ＮＨ₃流量信号。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for controlling the amount of ammonia injected into a denitration apparatus, and an ammonia injection amount correction apparatus used therefor, and in particular, nitrogen oxide (NOx) in exhaust gas discharged from a combustion apparatus such as a boiler is converted to ammonia (NOx). A method and apparatus for controlling the amount of ammonia injected into a denitration apparatus that reduces and removes by injection of NH ₃ ) and an ammonia injection amount correction apparatus used therefor, taking into account the amount of NH ₃ adsorbed on the catalyst, and at the outlet NOx The present invention relates to an ammonia injection amount correction device for properly eliminating a concentration control deviation, and an ammonia injection amount control method and device for a denitration apparatus equipped with the device.
[0002]
[Prior art]
In exhaust gas denitration equipment, NH ₃ is generally used as a NOx reducing agent, which is injected into the exhaust gas, and NH ₃ injected on the catalyst layer installed in the equipment reacts with NOx in the exhaust gas to form nitrogen and water. To do. That is,
[0003]
[Expression 1]
NH ₃ + NO + 1 / 4O ₂ → N ₂ + 3/2 · H ₂ O
Since NOx in the exhaust gas reacts with NH ₃ to be injected to react with nitrogen and water by the above formula, basically, the amount of NH ₃ to be injected is injected in an amount corresponding to the amount of NOx to be processed. .
[0004]
In addition to being used for the reaction with NOx, the injected NH ₃ is adsorbed on the catalyst surface as much as possible. Therefore, if it is injected beyond that, it will flow out from the denitration device as leaked ammonia, causing a problem.
On the other hand, if the amount of NH ₃ to be injected is insufficient with respect to the amount of NOx to be processed, NOx cannot be completely processed, and the concentration of NOx in the outlet processing gas cannot be reduced below a specified value.
[0005]
FIG. 3 shows a conventional technique regarding the ammonia injection amount control method of the denitration apparatus. Injection volume calculator 9 for calculating a NH ₃ injection rate commensurate with the amount of NOx to be treated in the gas, NH ₃ injection inlet NOx concentration of the denitration apparatus, the outlet NOx concentration setting, and the like outlet NOx concentration and the processed gas amount The amount is calculated.
[0006]
That is, the inlet NOx concentration signal 13 detected by the inlet NOx analyzer 12 of the denitration apparatus is multiplied by the gas flow rate signal 29 of the gas to be processed 28 by the multiplier 31 to calculate the total NOx amount signal 30. On the other hand, the required molar ratio (NH ₃ mol) is calculated by a required molar ratio calculator 18 having a subtractor 19 that performs subtraction between the inlet NOx concentration signal 13 and the set NOx concentration signal 16 set by the outlet NOx concentration setter 15 of the denitration apparatus. / NOx mole) signal 20 is calculated and input to adder 26 via proportional-integral calculator 25.
[0007]
On the other hand, the deviation between the outlet NOx concentration detection signal 23 detected by the outlet NOx concentration analyzer 22 and the set NOx concentration signal 16 is calculated by a subtractor 24 and input to an adder 26 via a proportional-integral calculator 25. The required molar ratio signal 20 is corrected.
A necessary NH ₃ flow rate signal 33 is calculated by multiplying the necessary molar ratio signal 27 after correction by the multiplier 32 by the total NOx amount signal 30 described above.
[0008]
The NH ₃ flow rate detection signal 39 detected by the necessary NH ₃ flow rate signal 33 and the NH ₃ flow meter 38 is subtracted by the subtractor 40 calculates the NH ₃ flow rate difference signal 41, the valve in proportional-plus-integral calculator 42 so The opening signal 43 is converted into a control signal 45 by the electropneumatic converter 44, and the NH ₃ flow rate adjusting valve 10 provided in the middle of the NH ₃ pipe 5 is opened and closed to inject NH ₃ into the denitration device. To an appropriate amount.
[0009]
[Problems to be solved by the invention]
The feedback control device using the proportional-plus-integral calculator 25 according to the prior art aims to make the outlet NOx concentration asymptotic to the set value. However, it takes a little time for the control and takes into account the NH ₃ adsorption amount on the catalyst. _{3 Since the} injection volume is not controlled,
(1) A large amount of adsorbed NH ₃ remains on the catalyst, and when the load drops, the NOx excessive removal causes a downward deviation from the set range of the outlet NOx concentration, and (2) due to excessive NH ₃ injection. Problems such as an increase in the amount of leaked NH ₃ and (3) uneconomical due to excessive use of NH ₃ occurred.
[0010]
An object of the present invention is to solve the problems of the prior art, together with a leakage NH ₃ quantity from NH ₃ amount and the device to be adsorbed to the catalyst by accurately grasp is fed back to the NH ₃ injection rate operation, the outlet NOx the feedback to the NH ₃ injection rate operation based on the deviation of the density set value and the measured value is quickly and easily adjusted, performs the appropriate NH ₃ injection corresponding to the load, thereby or excessive denitrification due to excessive injection, leakage NH ₃ A method and apparatus for controlling the amount of ammonia injected into a denitration device and an ammonia injection amount correcting device used therefor, which can prevent the increase in the NO3 concentration or the deviation from the regulation value of the outlet NOx concentration due to the insufficient amount of NH ₃ injection It is to provide.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the invention claimed in the present application is as follows.
[0014]
( 1 ) The NOx containing NOx is introduced from the apparatus inlet, NH ₃ is injected into the exhaust gas, and the NOx is contact-reduced by the denitration catalyst layer provided in the apparatus, and then the NOx is discharged from the apparatus outlet to the denitration apparatus. In the NH ₃ injection amount control apparatus for injecting NH ₃ , means for obtaining the NOx amount of the exhaust gas to be treated introduced from the apparatus inlet, and the required NH for the NOx amount based on the set values and measured values of the inlet NOx concentration and the outlet NOx concentration Means for calculating a ₃ molar ratio, means for determining the required ammonia flow rate from the inlet NOx amount and the required NH ₃ molar ratio, and means for determining the NH ₃ amount consumed in the denitration reaction from the amount of gas to be treated and the inlet and outlet NOx concentrations And means for subtracting the obtained NH ₃ amount and the leaked NH ₃ amount from the apparatus from the injected NH ₃ amount to obtain a catalyst residual NH ₃ adsorption amount correction bias signal; A means for obtaining a denitration outlet NOx deviation correction bias signal in accordance with a control deviation amount between the set value and the measured value of the apparatus outlet NOx concentration, and when the deviation is negative, and when the deviation is positive, a positive value; Means for adding a bias signal; means for calculating an outlet NOx deviation correction gain value based on a deviation between a set value of the apparatus outlet NOx concentration and a measured value; and multiplying the added correction bias signal by the outlet NOx deviation correction gain value. means for determining NH ₃ injection rate correction signal and, means for calculating the NH ₃ injection rate correction signal the need NH ₃ flow rate required NH ₃ flow rate after correction is added to the, and the corrected required NH ₃ flow rate A device for controlling the amount of ammonia injected into the denitration device, comprising means for operating the NH ₃ flow rate adjusting means based on a deviation from the measured NH ₃ flow rate.
[0015]
( 2 ) The exhaust gas containing NOx is introduced from the inlet of the apparatus, NH ₃ is injected into the exhaust gas, the NOx is reduced by the catalyst layer provided in the apparatus, and then discharged from the outlet of the apparatus to NH _3. When controlling the injection amount, the NH ₃ injection amount is corrected based on the deviation between the NH ₃ amount adsorbed on the catalyst layer and the set value and measured value of the outlet NOx concentration, and is introduced into the denitration device. that means for determining the amount of NH ₃ from the treated gas amount and the inlet and outlet NOx concentrations were consumed in denitration reaction is subtracted from the injection amount of NH ₃ leakage NH ₃ quantity from the consumption amount of NH ₃ was determined device catalyst remaining NH ₃ and means for finding an adsorption amount correction bias signal, based on the deviation of the measured value and the set value of the NOx concentration in the apparatus outlet, and the time deviation is negative negative, denitrification outlet plus the time as positive values Means for calculating an Ox deviation correction bias signal; means for adding the two correction bias signals; means for calculating an outlet NOx deviation correction gain value based on a deviation between the set value of the apparatus outlet NOx concentration and the measured value; Means for obtaining the NH ₃ injection amount correction signal by multiplying the added correction bias signal by the exit NOx deviation correction gain value, and inputting the NH ₃ injection amount correction signal to the NH ₃ injection amount controller for the denitration apparatus. A device for correcting the amount of ammonia injected into a denitration apparatus comprising the means.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a schematic view of a denitration reactor. The denitration reactor 1 introduces exhaust gas (treated gas G) from a boiler that is a source of the treated gas G, for example, from the inlet duct 2, denitrates it by injecting NH ₃ , and then discharges it to the outlet duct 3. Further, it is discharged outdoors by a chimney (not shown). At this time, NOx in the gas to be treated G is through the NH ₃ injector NH ₃ ammonia flow rate commensurate with the amount of NOx in the gas to be treated G by 4 meter 38 and the ammonia flow rate regulating valve 10 provided in the inlet duct 2 Then, it is decomposed and removed into harmless water vapor and nitrogen gas by the action of a denitration catalyst (not shown) filled in the denitration reactor 1. Usually, the operation of the denitration reactor 1 is controlled so that the NOx concentration at the outlet of the denitration reactor 1 is not more than a specified value even when the source of the gas G to be processed, for example, a load of a boiler or the like is changed. Here, the inlet NOx concentration in the gas G to be processed is measured by the inlet NOx analyzer 12, and the outlet NOx concentration is measured by the outlet NOx analyzer 22.
[0017]
Hereinafter, the overall structure of a control circuit according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a control circuit showing an embodiment of a denitration control device 7 provided in the denitration reactor 1. This denitration control device 7 diverts a part of the signal used in the injection amount calculator 9 (conventional circuit) for calculating the injection amount of ammonia, and corrects the NH ₃ flow rate calculator 50 (as a substitute circuit for the conventional circuit). The circuit of the present invention is installed.
[0018]
In the corrected ammonia flow rate calculator 50, the difference between the inlet NOx concentration signal 13 and the outlet NOx concentration signal 23 is obtained by the subtractor 57, and this NOx concentration difference signal is multiplied by the gas to be processed 28 by the multiplier 58. This corresponds to the amount of NOx reduced by the denitration apparatus 1. By multiplying the amount of the treated NOx by the required molar ratio, the amount of NH ₃ directly used in the NOx reduction reaction can be obtained. This is indicated by signal 58a.
[0019]
The difference between the actually measured NH ₃ flow rate signal 39 by the ammonia flow meter 38 and the signal 58a is obtained by the subtractor 56 to obtain 56a. 56a corresponds to the amount of ammonia injected into the denitration device that was not involved in the reduction reaction with the exhaust gas.
When the subtractor 60 subtracts the ammonia flow amount 59a flowing out from the denitration apparatus by the leak NH ₃ flow rate detector 59 from the ammonia amount 56a, the NH ₃ amount adsorbed on the catalyst, that is, the NH ₃ adsorption amount correction bias signal 65 is obtained. . This signal 65 is input to the adder 51 of FIG. 1 as an NH ₃ correction output signal 66.
[0020]
On the other hand, a deviation signal 67 between the output signal 16 of the outlet NOx concentration set value 15 and the output signal 23 of the outlet NOx concentration analyzer 22 is input to the function generator 54, and the outlet NOx deviation correction bias signal is passed through the change rate controller 55. Get 64. This signal 64 is added to the adder 51 as an NH ₃ injection correction signal 66 through an adder 61 and a multiplier 62.
[0021]
The outlet NOx deviation correction bias signal 64 is a positive output when the value of the deviation signal 67 is positive, that is, when the signal 23 is larger than the signal 16, and is negative when the signal 67 is negative. That is, when the outlet NOx concentration signal 23 is larger than the set value 16, the signal 64 is positive, and when the signal 23 is smaller than the signal 16, the signal 64 is negative.
The signal 64 and the NH ₃ adsorption amount correction bias signal 65 are added by the adder 61, and the added correction signal 61 a is input to the adder 51 as the NH ₃ injection correction signal 66.
[0022]
The function generator 54 is defined by the structure of the denitration device, the structure of the built-in denitration catalyst, components, performance, characteristics of the exhaust gas generation source, and the like, and the functional relationship is adjusted during a trial operation of a boiler or the like. The change rate controller 55 controls the change rate of the signal 64 described above, and its purpose is to suppress an extreme change in the ammonia injection amount into the denitration apparatus.
[0023]
Further, the outlet NOx concentration deviation signal 67 is input to the function generator 52 and outputs a signal 52a. This signal 52 a is output as an output NOx deviation correction gain signal 63 in a first-order lag format with respect to the signal 64 via the first-order lag element 53, and is input to the multiplier 62.
As a result, the signal 65 or 65 or the signal obtained by adding the signals 64 and 65 input to the multiplier 62 is multiplied by the signal 63 to obtain an output signal 66 multiplied by the gain. This gain value is adjusted in the range of 0 to X.
[0024]
The function generator 52 variably outputs a value corresponding to the outlet NOx control deviation as the necessary NH ₃ correction gain signal 63 from the denitration outlet NOx control deviation. For example, when the control deviation (subtractor 24 output) is in the plus direction, the NH ₃ correction flow rate is multiplied by a plus gain, the adder 61 output is increased, and the operation is performed to suppress the NOx removal NOx concentration peak. Conversely, when the outlet control deviation (output of the subtractor 24) is on the negative side, the function generator 52 sets the negative gain multiple and operates in a direction to prevent the NOx removal outlet NOx from sinking. Naturally, a dead band is provided in the function generator 52 in order to improve the controllability of the outlet NOx, and the NH ₃ flow rate correction bias is not changed in the vicinity of the control deviation 0.
[0025]
The operation of the above-described embodiment can suppress the peak / bottom of the NOx removal outlet NOx, and as a result, the NOx removal outlet NOx value can be maintained within the control management value range.
[0026]
【The invention's effect】
According to the present invention, the ammonia injection amount correction means for considering the amount of ammonia adsorbed on the catalyst and quickly and appropriately eliminating the NOx concentration deviation at the apparatus outlet is provided.
(1) Denitration device outlet NOx concentration control deviation is reduced, (2) Leakage NH ₃ amount is reduced, (3) NH ₃ consumption is reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an apparatus system of an ammonia injection amount control method for a denitration apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic view of a denitration apparatus.
FIG. 3 is a diagram showing an apparatus system of an ammonia injection amount control method for a denitration apparatus according to the prior art.
[Explanation of symbols]
5 ... NH ₃ pipe 8 ... conventional denitration controller, 9 ... injection amount calculator, 10 ... NH ₃ flow control valve, 12 ... inlet NOx concentration analyzer, 13 ... inlet NOx concentration signal, 15 ... outlet NOx concentration setter , 16 ... set NOx concentration signal, 18 ... required molar ratio calculation unit, 19 ... subtractor, 20 ... required molar ratio signal, 22 ... outlet NOx concentration analyzer, 23 ... outlet NOx concentration signal, 24 ... subtractor, 25 ... Proportional integral calculator, 26 ... adder, 27 ... necessary molar ratio signal (after correction), 28 ... gas amount to be processed, 29 ... gas flow signal to be processed, 30 ... total NOx amount signal, 31 ... multiplier, 32 ... Multiplier 33 ... Necessary NH ₃ flow rate signal 38 ... Necessary NH ₃ flow meter 39 ... Measured NH ₃ flow rate signal 40 ... Subtractor 41 ... NH ₃ flow rate deviation signal 42 ... Proportional integrator 43 ... Valve open Degree signal, 44 ... electro-pneumatic converter, 45 ... control signal, 50 Correction NH ₃ flow calculator, 51 ... adder, 52 ... function generator, 53 ... first-order delay, 54 ... function generator, 55 ... change rate controller, 56 ... subtractor, 57 ... subtractor, 58 ... multiplier vessel, 59 ... leakage NH ₃ flow detector, 60 ... subtractor, 61 ... adder, 62 ... multiplier, 63 ... outlet NOx deviation correcting gain signal, 64 ... outlet NOx deviation correction bias signal, 65 ... NH ₃ adsorption correction bias signal, 66 ... NH ₃ injection correction signal, 67 ... denitration outlet NOx control deviation, 68 ... corrected required NH ₃ flow rate signal.

Claims

装置入口からＮＯｘを含有する排ガスを導入するとともに該排ガス中にＮＨ₃を注入して装置内に設けた脱硝触媒層により前記ＮＯｘを接触還元したのち装置出口から排出する脱硝装置へ前記ＮＨ₃を注入するＮＨ₃注入量制御装置において、前記装置入口から導入した被処理排ガスのＮＯｘ量を求める手段と、入口ＮＯｘ濃度と出口ＮＯｘ濃度の設定値および測定値に基づきＮＯｘ量に対する必要ＮＨ₃モル比を算出する手段と、前記入口ＮＯｘ量と必要ＮＨ₃モル比から必要アンモニア流量を求める手段と、被処理ガス量と入口および出口ＮＯｘ濃度から脱硝反応に消費したＮＨ₃量を求める手段と、求めた消費ＮＨ₃量と装置からのリークＮＨ₃量とを注入ＮＨ₃量から減算して触媒残存ＮＨ₃吸着量補正バイアス信号を求める手段と、装置出口ＮＯｘ濃度の設定値と測定値の制御偏差量に応じ、かつその偏差がマイナス時はマイナス、プラス時はプラスの値として脱硝出口ＮＯｘ偏差補正バイアス信号を求める手段と、前記２つの補正バイアス信号を加算する手段と、装置出口ＮＯｘ濃度の設定値と測定値の偏差に基づき出口ＮＯｘ偏差補正ゲイン値を算出する手段と、前記加算した補正バイアス信号に上記出口ＮＯｘ偏差補正ゲイン値を乗算してＮＨ₃注入量補正信号を求める手段と、該ＮＨ₃注入量補正信号を前記必要ＮＨ₃流量に加算して補正後必要ＮＨ₃流量を算出する手段と、この補正後必要ＮＨ₃流量と実測ＮＨ₃流量との偏差に基づきＮＨ₃流量調節手段を操作する手段とを設けたことを特徴とする脱硝装置へのアンモニア注入量制御装置。The exhaust gas containing NOx is introduced from the inlet of the apparatus, NH ₃ is injected into the exhaust gas, the NOx is contact-reduced by the NOx removal catalyst layer provided in the apparatus, and then the NH ₃ is discharged to the NOx removal apparatus discharged from the outlet of the apparatus. In the NH ₃ injection amount control device to be injected, means for obtaining the NOx amount of the exhaust gas to be treated introduced from the device inlet, and the required NH ₃ molar ratio to the NOx amount based on the set values and measured values of the inlet NOx concentration and the outlet NOx concentration A means for calculating the required ammonia flow rate from the inlet NOx amount and the required NH ₃ molar ratio; a means for determining the NH ₃ amount consumed in the denitration reaction from the amount of gas to be treated and the inlet and outlet NOx concentrations; It means for determining the catalyst remaining adsorbed NH ₃ amount correction bias signal consumption NH ₃ amount and the leakage NH ₃ quantity from the device by subtracting from the injection NH ₃ amount, device Means for obtaining a denitration outlet NOx deviation correction bias signal as a negative value when the deviation is negative and a positive value when the deviation is negative, according to the control deviation amount of the mouth NOx concentration and the measured value, and the two correction bias signals , Means for calculating the outlet NOx deviation correction gain value based on the deviation between the set value of the apparatus outlet NOx concentration and the measured value, and the added correction bias signal multiplied by the outlet NOx deviation correction gain value. NH ₃ and means for obtaining an injection quantity correction signal, the NH ₃ and means for calculating an injection amount correction signal the need NH ₃ flow rate required NH ₃ flow rate after correction is added to the actual measurement and the corrected required flow rate _of NH ₃ NH _A device for controlling the amount of ammonia injected into the denitration device, comprising means for operating the NH ₃ flow rate adjusting means based on the deviation from the ₃ flow rate.

装置入口からＮＯｘを含有する排ガスを導入するとともに該排ガス中にＮＨ₃を注入して装置内に設けた触媒層によって前記ＮＯｘを還元したのち装置出口から排出する脱硝装置へのＮＨ₃注入量を制御するに際し、前記触媒層に吸着されるＮＨ₃量と出口ＮＯｘ濃度の設定値と測定値の偏差に基づき上記ＮＨ₃注入量を補正する装置であって、前記脱硝装置に導入される被処理ガス量と入口および出口ＮＯｘ濃度から脱硝反応に消費したＮＨ₃量を求める手段と、求めた消費ＮＨ₃量と装置からのリークＮＨ₃量を注入ＮＨ₃量から減算して触媒残存ＮＨ₃吸着量補正バイアス信号を求める手段と、装置出口のＮＯｘ濃度の設定値と測定値の偏差量に基づき、かつその偏差がマイナス時はマイナス、プラス時はプラスの値として脱硝出口ＮＯｘ偏差補正バイアス信号を算出する手段と、前記２つの補正バイアス信号を加算する手段と、装置出口ＮＯｘ濃度の設定値と測定値の偏差量に基づき出口ＮＯｘ偏差補正ゲイン値を算出する手段と、前記加算した補正バイアス信号にこの出口ＮＯｘ偏差補正ゲイン値を乗算してＮＨ₃注入量補正信号を求める手段と、該ＮＨ₃注入量補正信号を脱硝装置へのＮＨ₃注入量制御部に入力する手段とを備えてなる脱硝装置へのアンモニア注入量補正装置。The amount of NH ₃ injected into the denitration device is introduced after exhaust gas containing NOx is introduced from the device inlet and NH ₃ is injected into the exhaust gas and the NOx is reduced by the catalyst layer provided in the device and then discharged from the device outlet. A device for correcting the NH ₃ injection amount based on a deviation between a set value and measured value of the NH ₃ amount adsorbed on the catalyst layer and the outlet NOx concentration when controlled, and to be treated introduced into the denitration device Means for obtaining the amount of NH ₃ consumed in the denitration reaction from the gas amount and the inlet and outlet NOx concentrations, and subtracting the obtained amount of consumed NH _{3 and the} amount of leaked NH ₃ from the apparatus from the amount of injected NH ₃ to adsorb the remaining catalyst NH ₃ Based on the means for obtaining the amount correction bias signal, and the deviation amount between the set value of the NOx concentration at the outlet of the apparatus and the measured value, and when the deviation is negative, it is negative, and when it is positive, it is positive. Means for calculating a correction bias signal; means for adding the two correction bias signals; means for calculating an outlet NOx deviation correction gain value based on a deviation amount between a set value of the apparatus outlet NOx concentration and a measured value; means for determining NH ₃ injection rate correction signal by multiplying the exit NOx deviation correction gain in the correction bias signal, means for inputting the NH ₃ injection rate correction signal to NH ₃ injection rate control unit of the denitration unit A device for correcting the amount of ammonia injected into a denitration apparatus comprising: