JP3547296B2

JP3547296B2 - Abnormality detection method of exhaust gas sensor and refuse incinerator

Info

Publication number: JP3547296B2
Application number: JP27754797A
Authority: JP
Inventors: 俊夫中西; 文典今村; 義明高畠
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 1997-10-09
Filing date: 1997-10-09
Publication date: 2004-07-28
Anticipated expiration: 2017-10-09
Also published as: JPH11108326A

Description

【０００１】
【発明の属する技術分野】
本発明は、排ガスセンサの異常検出方法に関し、詳しくは、火炉からの排ガス路に排ガス中の酸素濃度を測定する排ガスセンサを備えて、前記排ガスセンサで検出する排ガス中酸素濃度を燃焼制御指標とするゴミ焼却炉及びその火炉からの排ガス路に配置された前記排ガスセンサの異常検出方法に関する。
【０００２】
【従来の技術】
従来、ゴミ焼却炉においては、図４に示すように、火炉Ｆに、ホッパ１１ａに受け入れたゴミを前記火炉Ｆ内に投入する給塵機構１１と、前記投入されたゴミを搬送しながら焼却するストーカ機構からなる移動式火床１２とを備えており、前記移動式火床１２は、前記給塵機構１１により投入されたゴミを搬送しながら加熱乾燥させる乾燥帯１２Ａと、前記乾燥帯１２Ａからのゴミを搬送しながら燃焼させて燃焼領域を主として形成する燃焼帯１２Ｂと、前記燃焼帯１２Ｂで燃え切ったゴミの燃焼残渣を搬送しながら灰化する後燃焼帯１２Ｃとに領域分割されており、前記燃焼領域からの燃焼ガスを上方に誘導して二次燃焼させる二次燃焼室１３を備え、前記二次燃焼室１３からの排ガスを煙突１８に導く排ガス路１４に、前記排ガスの熱によって蒸気を発生させる廃熱ボイラＢと、前記廃熱ボイラＢ出口からの排ガス中の飛灰等の粉塵を除塵する除塵装置としてのバグフィルタ１５と、前記バグフィルタ１５で除塵した後の排ガスを洗浄する洗煙装置１６と、洗浄後の排ガスを煙突に向けて送り出す誘引送風機１７とをを順次配置して設けてあり、前記バグフィルタ１５と前記洗煙装置１６との間の排ガス路１４に備える排ガスセンサ３により排ガス中の酸素濃度を検出する酸素濃度検出手段２を設けて、前記酸素濃度検出手段２で検出する排ガス中酸素濃度を燃焼制御指標とするように構成されており、特にその酸素濃度検出手段２で検出した排ガス中酸素濃度の異常検出の検査手段は備えていなかった。そして、前記排ガスセンサの検出する検出値に異常がある場合或いは前記排ガスセンサが故障した場合には、前記燃焼制御指標とする排ガス中酸素濃度を、予め定められた設定値（例えば投入されたゴミを標準ゴミであるとして想定される排ガス中酸素濃度が用いられ、或いは故障発生検出直前の排ガス中酸素濃度が用いられる。）に固定して燃焼制御を続行するように構成されていた。
【０００３】
【発明が解決しようとする課題】
つまり、上記従来の排ガスセンサにおいては、例えば検出する酸素濃度の値が設定された酸素濃度範囲から外れたことを知った現場作業者が、そのデータの状態から判断して異常か否かを判定していた。上記排ガスセンサの異常は、吸引管３ａからサンプリングされる排ガスを検査するガス検出素子３ｂを備える一般に多く用いられている構造の排ガスセンサ３（例えば図５参照）の場合には、前記吸引管３ａの腐食その他の原因により、前記ガス検出素子３ｂに導入される排ガスに外部からの漏洩空気が混入して、前記導入される排ガスの酸素含有量が高くなる場合があり、実際には排ガス中の酸素濃度は許容範囲（例えば６〜１４％）内にある（例えば７％）にも拘わらず、漏洩空気の混入によって異常な酸素濃度（例えば１５％）を示す場合、或いは前記ガス検出素子３ｂの劣化により、検出値が上下何れか一方にシフトする場合を例として挙げることができる。上記異常な酸素濃度が上記の例で１８％であれば、正常に火炉の燃焼が維持されている状態では、異常な値として判断できるが、このような状態で検出される酸素濃度が１３〜１４％であれば、実際には７％である場合であっても、炉の制御に携わるオペレータにとっては異常な範囲の酸素濃度ではなく、熟練者が他のプロセスデータを参照して異常と認識する場合を除き看過されてしまう。従って、このように許容範囲内でありながら異常な値を示している場合には、これが異常であると判断できるまでに長時間を要し、例えば、上記のように許容範囲の上限或いは下限に近い値を示している場合には、早くても２〜３時間、長い場合には２〜３日を要し、その間、誤ったデータに基づいて炉の燃焼制御を維持することになり、排ガス中有害成分を許容成分範囲内に維持できなくなるおそれがあった。実際に排ガス中酸素濃度を連続記録した例を図６にグラフとして示したが、火炉内の燃焼状態が安定していても、ゴミの質及び燃焼状態の時間に伴う変化に従って可成りの幅でデータが変動しており、このデータの異常を判別するのは容易ではない。さらに、一旦前記排ガスセンサに異常を発見した後は、排ガス中酸素濃度の検出値の如何に関わらず設定値（例えば８％）に固定されれば、排ガス成分の異常を直接抑制することが困難になると言う問題を有している。
そこで、本発明の排ガスセンサの異常検出方法は、上記の問題点を解決し、火炉における他の燃焼制御指標に基づき排ガスセンサの異常を検出するとともに、排ガス成分を許容範囲内に安定して維持するための手段を提供することを目的とし、さらに、本発明のゴミ焼却炉は、排ガスセンサの異常を検出可能とするとともに、前記排ガスセンサの異常に対しても燃焼制御を正常に維持可能とする点を目的とする。
【０００４】
【課題を解決するための手段】
〔特徴構成〕
【０００５】
上記の目的のための本発明の排ガスセンサの異常検出方法の第１特徴構成は、所定時間内に火炉に投入されたゴミ重量に対する理論空気量を演算導出して、前記演算導出した理論空気量中の酸素量が、前記所定時間内に前記火炉に供給した空気中の酸素量から消費されたものとして排ガス中の推定酸素濃度を演算導出し、排ガスセンサで検出した排ガス中酸素濃度が前記演算導出した排ガス中の推定酸素濃度に基づいて設定される所定の許容範囲から逸脱した場合に、前記排ガスセンサに異常が発生したと判定する点にある。
【０００６】
また、本発明の排ガスセンサの異常検出方法の第２特徴構成は、前記理論空気量を演算導出するに、投入されたゴミが基準ゴミであるとして演算導出する点にある。
【０００７】
さらに、本発明の排ガスセンサの異常検出方法の第３特徴構成は、前記許容範囲を設定するのに、排ガス中の推定酸素濃度を、投入されたゴミが高質ゴミであるとして演算導出した結果を上限値とし、前記排ガス中の推定酸素濃度を、前記投入されたゴミが低質ゴミであるとして演算導出した結果を下限とする点にある。
【０００８】
そして、本発明の排ガスセンサの異常検出方法の第４特徴構成は、排ガスセンサに異常が生じたと判定するのに、前記排ガスセンサで検出した排ガス中酸素濃度と、演算導出した排ガス中の推定酸素濃度に基づいて設定される所定の許容範囲とを、ゴミ焼却炉の制御インターバルに同期して比較する点にある。
【０００９】
さらに、本発明の排ガスセンサの異常検出方法の第５特徴構成は、排ガスセンサの異常発生の判定条件を、検出した排ガス中酸素濃度が、設定時間連続して許容範囲を逸脱した場合とする点にある。
【００１０】
本発明の排ガスセンサの異常検出方法の第６特徴構成は、排ガスセンサの異常発生の判定条件を、検出した排ガス中酸素濃度が、設定時間内に許容範囲を所定回数以上逸脱した場合とする点にある。
【００１１】
本発明の排ガスセンサの異常検出方法の第７特徴構成は、火炉に投入されたゴミ重量に対する理論空気量を演算導出し、前記演算導出した理論空気量中の酸素量と、前記所定時間内に前記火炉に供給した空気中の酸素量とに基づき排ガス路における排ガス中の推定酸素濃度を推定する酸素残量推定手段と、排ガスセンサで検出した排ガス中酸素濃度が前記酸素残量推定手段で推定した排ガス中の推定酸素濃度に基づいて設定される所定の許容範囲から逸脱した場合に、前記排ガスセンサに異常が発生したと判定する検査手段を設けて構成してある点にある。
【００１２】
また、本発明のゴミ焼却炉の第８特徴構成は、前記火炉を制御する燃焼制御手段を設けて、検査手段が異常が発生したと判定した場合の燃焼制御指標を、排ガス中酸素濃度に代えて、酸素残量推定手段で推定した推定酸素濃度とするように構成してある点にある。
【００１３】
〔特徴構成の作用効果〕
【００１４】
上記第１特徴構成によれば、排ガスセンサの検出した排ガス中酸素濃度の異常を適時検出できるから、誤った排ガス中酸素濃度による燃焼制御を回避でき、排ガス成分が所定成分範囲から逸脱することを防止できる。つまり、推定酸素濃度と排ガスセンサで検出した排ガス中酸素濃度とを比較して、前記推定酸素濃度に基づいて設定される所定許容範囲から逸脱すれば、前記排ガスセンサに異常が発生したと判定できるのである。前記推定酸素濃度は、所定時間内に火炉に投入されたゴミ重量に対する理論空気量を演算導出して、前記演算導出した理論空気量に基づき火炉における消費酸素量を推定して、その酸素量が、前記所定時間内に前記火炉に供給した空気中の酸素量から消費されたものとして排ガス中の推定酸素濃度を演算導出できる。そして、排ガスセンサで検出した排ガス中酸素濃度が前記演算導出した排ガス中の推定酸素濃度に基づいて設定される所定の許容範囲から逸脱した場合に、前記排ガスセンサに異常が発生したと判定できる。上記許容範囲は、常時監視されている排ガス中酸素濃度の変動の範囲を基準に設定することも可能である。
その結果、排ガス成分を許容範囲内に安定して維持することが可能になる。
【００１５】
上記第２特徴構成によれば、前記理論空気量を算出するための特別な手段を必要とせず、さらに設備を簡素化できる。つまり、前記理論空気量を投入されたゴミが基準ゴミであるとして演算導出するので許容範囲を固定できるのである。
【００１６】
上記第３特徴構成によれば、許容範囲を合理的に設定できる。つまり、投入されたゴミが高質ゴミであるとして排ガス中の推定酸素濃度を演算導出した結果を上限値とし、前記投入されたゴミが低質ゴミであるとして前記排ガス中の推定酸素濃度を演算導出した結果を下限とするので、投入されたゴミに対して推定される最大範囲を許容範囲として、焼却ゴミ量と火炉に供給された空気量から設定でき、しかも、この許容範囲から検出値が逸脱すれば、その検出値は明らかに異常である。
従って、排ガスセンサの異常検出における誤判断を防止できる。
【００１７】
上記第４特徴構成によれば、排ガスセンサの異常判定を行わないままに燃焼制御が行われることを防止できる。つまり、ゴミ焼却炉の制御インターバルに同期して、前記排ガスセンサで検出した排ガス中酸素濃度と、演算導出した排ガス中の推定酸素濃度に基づいて設定される所定の許容範囲とを比較して前記排ガスセンサに異常が生じたと判定するのである。しかも、１制御サイクル中に１度の異常判定を行うので、同一サイクル中に異なる判定結果がもたらされることがないから、判断が単純で且つ一意的であると同時に、無駄な演算を回避できる。
【００１８】
上記第５特徴構成によれば、排ガスセンサの異常発生を遅早なく判定できるようになる。つまり、前記排ガスセンサの異常発生の判定条件を、検出した排ガス中酸素濃度が、設定時間（例えば１０分間）連続して許容範囲を逸脱した場合とするのである。この設定時間は、前記排ガスセンサが正常に動作しているにも拘わらず、測定値が分散することがあり、極短時間の前記許容範囲からの逸脱によって異常であると判定すれば、実際は前記排ガスセンサに異常がないにも拘わらず前記排ガスセンサに異常が生じたとする誤判定を招くおそれがあるあらである。上記排ガス中酸素濃度の実際の記録は、図６に示したように分散しているが、例えば図中の一点鎖線を前記許容範囲の上下限とすれば、殆ど前記許容範囲内に収まっており、連続して前記許容範囲外に逸脱している時間は長くはない。尚、上記上下限は、炉内プロセスデータの内のボイラ発生蒸気量についての３時間移動平均値から求めた燃焼発熱量に基づくものであるために変動が均されて前記許容範囲の上下幅が狭くなっているが、この点を是正すると同時にサンプリング周期との関係において適当な時間を定めれば、誤判定を防止できると同時に、早期に排ガスセンサの異常を発見できるようになる。
その結果、排ガスセンサの異常判定の確度を高めることができる。
【００１９】
上記第６特徴構成によれば、排ガスセンサの異常発生を遅早なく判定できるようになる。つまり、検出した排ガス中酸素濃度が、設定時間内に許容範囲を所定回数（例えば３回）以上逸脱した場合を排ガスセンサの異常発生の判定条件とするのである。この排ガスセンサの異常発生には、設定時間内に許容範囲を逸脱する回数が急増するのであるが、前記所定回数としては、予め前記急増する逸脱回数の平均或いは最低値を設定しておけばよいのである。図６に示したように上記排ガス中酸素濃度の実際の記録は分散しているが、例えば図中の一点鎖線を前記許容範囲の上下限とすれば、殆ど前記許容範囲内に収まっており、連続して前記許容範囲外に逸脱している時間は長くはない。尚、上記上下限は、炉内プロセスデータの内のボイラ発生蒸気量についての３時間移動平均値から求めた燃焼発熱量に基づくものであるために変動が均されて前記許容範囲の上下幅が狭くなっているが、この点を是正すると同時にサンプリング周期との関係において適当な回数を所定回数として定めれば、誤判定を防止できると同時に、早期に排ガスセンサの異常を発見できるようになる。
その結果、前記第５特徴構成と同様に排ガスセンサの異常判定の確度を高めることができる。
【００２０】
上記第７特徴構成によれば、ゴミ焼却炉を、排ガスセンサからの異常な排ガス中酸素濃度の出力によって、その燃焼制御を誤ることを防止できるようになる。つまり、火炉に投入されたゴミ重量に対する理論空気量を演算導出し、演算導出した前記理論空気量中の酸素量と、所定時間内に前記火炉に供給した空気中の酸素量とに基づき酸素残量推定手段の推定する排ガス中の推定酸素濃度から、前記推定した排ガス中の推定酸素濃度に基づいて設定される所定の許容範囲から排ガスセンサで検出した排ガス中酸素濃度が逸脱した場合に、前記排ガスセンサに異常が発生したと検査手段で判定するように構成してあるから、例えば図２に示したように、前記排ガス中の推定酸素濃度に基づいて設定される上下限を示す一点鎖線の間を前記許容範囲とすれば、前記許容範囲外に逸脱している時間を、サンプリング周期との関係において適当な長さに特定するか、逸脱した回数を特定すれば、誤判定を防止できると同時に、早期に排ガスセンサの異常を発見できるようになり、前記排ガスセンサの異常に対して早期に対策を講ずることが可能になり、その燃焼制御を誤ることを防止できるようになる。
その結果、ゴミ焼却炉からの排ガス中の有害成分を許容範囲内に安定して維持することが可能になる。
【００２１】
上記第８特徴構成によれば、排ガスセンサの異常発生時の対策が自動的に講ぜられるようになる。つまり、火炉を制御する燃焼制御手段を設けて、検査手段で異常が発生したと判定された場合の燃焼制御指標を、排ガス中酸素濃度に代えて、酸素残量推定手段で推定した推定酸素濃度とするように構成してあるから、排ガスセンサの異常検出と同じ基準によって定められる燃焼制御指標を用いて燃焼制御を行うことになるから、燃焼制御の信頼性を高く維持することが可能になる。
その結果、ゴミ焼却炉からの排ガス中の有害成分を許容範囲内にさらに安定して維持することが可能になる。
【００２２】
【発明の実施の形態】
上記本発明のゴミ焼却炉及びこれに適用可能な排ガスセンサの異常検出方法の実施の形態の一例について、以下に、図面を参照しながら説明する。尚、前記従来の技術において説明した要素と同じ要素並びに同等の機能を有する要素に関しては、先の図４及び図５に付したと同一の符号を付し、詳細の説明の一部は省略する。
【００２３】
ゴミ焼却炉は、燃焼制御手段１を備えており、前記燃焼制御手段１には、単位時間当たりに給塵機構１１から火炉Ｆに投入されるゴミの投入量と、前記火炉Ｆに投入されたゴミのゴミ質（低位発熱量により区分される）等に応じて、移動式火床１２を構成するストーカ機構の搬送速度を調節するゴミ搬送制御手段１ａと、前記ゴミの投入量、前記ストーカ機構によるゴミの搬送速度、燃焼帯１２Ｂにおけるゴミの燃え切り位置、廃熱ボイラＢの蒸気発生量等のプロセスデータに基づき前記火炉Ｆ内に供給される空気の量を調節する火炉供給空気制御手段１ｂと、酸素濃度検出手段２で検出する排ガス中酸素濃度Ｐｏを所定の許容範囲から逸脱しないようにするように二次燃焼室１３に供給する二次空気の量を調節する二次燃焼制御手段１ｃとを設けて、移動式火床１２上での所定量のゴミの燃焼を良好に維持しながら、排ガス中の酸素濃度を所定範囲内に維持して、ダイオキシン、窒素酸化物等の有害成分の放出を低減できるように構成してある。
【００２４】
前記酸素濃度検出手段２は、除塵装置であるバグフィルタ１５と洗煙装置１６との間の排ガス路１４に配置した従来と同様の構造の排ガスセンサ３を備えて、前記排ガスセンサ３からの入力値により排ガス中酸素濃度Ｐｏを検出するように構成してある。そして、前記酸素濃度検出手段２の検出する排ガス中酸素濃度Ｐｏが基準範囲内にあるか否かを検査して前記排ガスセンサ３の異常を検出するための検査手段４と、炉のプロセスデータから前記燃焼帯１２Ｂ上のゴミの低位発熱量を推定する発熱量推定手段５と、前記検査手段４の検査結果で前記排ガスセンサ３が異常であると判定された際の前記酸素濃度検出手段２からの排ガス中酸素濃度Ｐｏに代わる代替燃焼制御指標として排ガス中の残存酸素濃度Ｐｏｅを推定する酸素残量推定手段６とを設けてある。
【００２５】
前記検査手段４は、前記投入されたゴミが低位発熱量の高い高質ゴミ（低位発熱量２３００ｋｃａｌ／ｋｇに相当）であるとして前記酸素残量推定手段６で推定した推定酸素濃度を上限酸素濃度Ｌ_Ｈとし、前記投入されたゴミが低位発熱量の低い低質ゴミ（低位発熱量１０００ｋｃａｌ／ｋｇに相当）であるとして前記酸素残量推定手段６で推定した推定酸素濃度を下限酸素濃度Ｌ_Ｌとして、前記酸素濃度検出手段２の検出した排ガス中酸素濃度Ｐｏが前記上限酸素濃度Ｌ_Ｈを超え、或いは前記下限酸素濃度Ｌ_Ｌに満たない場合に、前記排ガスセンサ３に異常が発生したものと判定するように構成してある。つまり、低位発熱量の最大のものと最低のもの、即ち、最高低位発熱量と、最低低位発熱量とを想定して、夫々に対して求められる酸素消費量から推定酸素濃度の最高値と最低値を、前記上限酸素濃度Ｌ_Ｈと前記下限酸素濃度Ｌ_Ｌとして求める。例えば図２に示したように、排ガス中酸素濃度Ｐｏが前記上限酸素濃度Ｌ_Ｈと前記下限酸素濃度Ｌ_Ｌとの間にほぼ収まっているので、前記検査手段４では排ガスセンサ３の異常を検出しない。尚、異常を検出する場合についての線図は省略したが、通常想定される異常の場合には、前記排ガス中酸素濃度Ｐｏは上下何れか一方にシフトするので、図２に示したように、前記排ガス中酸素濃度Ｐｏに対してほぼ同じ挙動を示す前記上限酸素濃度Ｌ_Ｈと前記下限酸素濃度Ｌ_Ｌとの間の許容範囲からは連続して、或いは頻繁に何れか一方に逸脱した値を示すようになり、前記排ガスセンサ３の異常を極めて容易に判定できるようになる。このような構成の場合には、サンプリングの都度連続する逸脱により前記排ガスセンサの異常を判定できる。
【００２６】
前記酸素残量推定手段６は、前記火炉Ｆに投入されたゴミ重量に対して、前記発熱量推定手段５からの推定発熱量Ｈｕｅに応じて求められる理論空気量Ｆａｓと、単位時間当たりのゴミ焼却量Ｇと、炉内の発生熱量Ｈｂとから、燃焼用空気としての所要空気量Ｆａｒを推定し、炉内に供給された総空気量Ｆａと比較して推定酸素濃度Ｐｏｅを求めるように構成してある。つまり、各ゴミ質に対して予め求められている代表的成分組成に基づき、ゴミの中の炭素、水素、酸素、硫黄の夫々につき燃焼に要する酸素量を算出して、夫々の酸素量の合計値を基に理論空気量を求めた結果に基づき、予め求めてあるゴミの低位発熱量Ｈｕに対する線形関係式に前記推定発熱量Ｈｕｅを当てはめて理論空気量Ｆａｓを求める。求めた理論空気量Ｆａｓとゴミ焼却量Ｇとから前記所要空気量Ｆａｒが得られる。以上の結果から、前記所要空気量Ｆａｒ中の酸素全量が前記総空気量Ｆａの含有酸素から消費されたとして推定酸素濃度Ｐｏｅを求める。尚、二次燃焼室１３以後の排ガス路１４に空気の流入（例えば冷却用空気の混入、或いは漏洩空気の漏れ込み）量が補正できれば、これらの要因について補正すればよい。
【００２７】
前記発熱量推定手段５では、前記ゴミ焼却量Ｇと前記炉内の発生熱量Ｈｂとから前記推定発熱量Ｈｕｅを求めるが、前記発生熱量Ｈｂは、廃熱ボイラを備える炉においては発生蒸気量Ｇ_Ｓと、出口蒸気のエンタルピＩｓと給水のエンタルピＩｗとから得られる蒸気として炉外に取り出された熱量を、炉毎に求められるボイラ効率ηで除した熱量として求める。尚、他の入出熱量を想定できれば、これを補正して求めればさらに正確になる。
【００２８】
上記のようにして前記酸素残量推定手段６で求めた推定酸素濃度Ｐｏｅを、前記検査手段４においては、ゴミ質を前記最高低位発熱量の高質ゴミ（Ｈｕ＝２３００）として推定した推定酸素濃度Ｐｏｅを前記上限酸素濃度Ｌ_Ｈとし、ゴミ質を前記最低低位発熱量の低質ゴミ（Ｈｕ＝１０００）として推定した推定酸素濃度Ｐｏｅを前記下限酸素濃度Ｌ_Ｌとして、前記排ガスセンサ３の検査基準とし、前記排ガスセンサ３の検出値を異常と判断した場合には、前記発熱量推定手段５で推定した前記推定発熱量Ｈｕｅに基づき前記酸素残量推定手段６で求めた推定酸素濃度Ｐｏｅを、前記排ガスセンサ３からの排ガス中酸素濃度Ｐｏに代わる制御指標として、前記燃焼制御手段１における燃焼制御を継続する。
【００２９】
上述の検査手段４による排ガスセンサ３の異常判定は、１制御サイクルあたり１回実行される。つまり、燃焼制御手段１における制御指令は、上述の検査手段４による各回の判定の後に発せられるのである。従って、前記排ガスセンサ３に異常が生じて、酸素濃度検出手段２から排ガス中酸素濃度の異常な検出値が入力されれば、直ちにその入力値に拘わらず、酸素残量推定手段６からの残存酸素濃度が代替指標として用いられ、この残存酸素濃度に基づいて燃焼制御が行われるようになる。この場合には、排ガスセンサの異常を表示すると同時に制御指標が代替指標に切り替えられていることを表示するように燃焼制御手段を構成しておけば、前記排ガスセンサ３の点検ないしは交換も時機を失することなく容易になる。
【００３０】
次に、本発明の他の実施の形態について説明する。
〈１〉上記実施の形態に於いては、排ガス路１４に廃熱ボイラＢを備えるゴミ焼却炉に本発明を適用した例について説明したが、廃熱ボイラを備えないゴミ焼却炉であってもよく、この場合には、例えば図３に示すように、移動式火床１２の乾燥帯１２Ａの天井壁に、前記乾燥帯１２Ａに臨ませて設けた赤外線検知手段５ａを用いて検出した温度により前記乾燥帯１２Ａのゴミの低位発熱量を推定する発熱量推定手段５を設けてあればよく、前記赤外線検知手段５ａに透過波長３．６〜４μｍのフィルタを取り付けておけば、火炎中の一酸化炭素ガス、二酸化炭素ガス、窒素酸化物、硫黄酸化物、水蒸気等の赤外線エネルギー吸収の影響を抑制できる。尚、この発熱量推定手段５は、前記乾燥帯１２Ａ上のゴミの推定発熱量Ｈｕｅを以下のようにして推定するものである。つまり、前記乾燥帯１２Ａへの送風量が基準流量である場合には、単位時間当たりのゴミ表面温度の平均値が第１基準温度（例えば９００℃）以下であれば低位発熱量Ｈｕの小さい低質ゴミ（例えばＨｕｅ＝１０００）であり、第２基準温度（例えば１０００℃）以上であれば低位発熱量Ｈｕの大きい高質ゴミ（例えばＨｕｅ＝２３００）であり、前記第１基準温度と前記第２基準温度との間にあれば基準ゴミ（例えばＨｕｅ＝１７００）であると推定するのである。このゴミ表面の基準温度の段階を細かく設定すれば、推定発熱量Ｈｕｅを詳細に推定できるようになる。そして、前記検査手段における上限酸素濃度Ｌ_Ｈ及び下限酸素濃度Ｌ_Ｌとしては上記実施の形態において説明したように、高質ゴミ（例えばＨｕ＝２３００）及び低質ゴミ（例えばＨｕ＝１０００）に対して前記酸素残量推定手段６で推定した推定酸素濃度Ｐｏｅを用い、前記検査手段４で前記排ガスセンサ３の検出値が異常であると判定した場合には、上記発熱量推定手段５で推定した推定発熱量Ｈｕｅを基に前記酸素残量推定手段６で推定した推定酸素濃度Ｐｏｅを、燃焼制御手段１における排ガス中酸素濃度Ｐｏに対する代替指標として用いるのである。
〈２〉上記実施の形態に於いては、排ガス路１４に廃熱ボイラＢを備えるゴミ焼却炉に本発明を適用した例について説明したが、廃熱ボイラを備えないゴミ焼却炉であってもよく、この場合には、例えば図３に示すように、ガス冷却機構１９を備える場合には、前記廃熱ボイラ２０の熱収支に代えて、このガス冷却機構１９に供給した空気の量とその含有酸素量を前記推定酸素濃度Ｐｏｅを推定する前記酸素残量推定手段６における演算パラメータに加えればよい。
〈３〉上記実施の形態に於いては、上限酸素濃度Ｌ_Ｈとして最高低位発熱量の高質ゴミ（Ｈｕ＝２３００）として推定した推定酸素濃度Ｐｏｅを用い、下限酸素濃度Ｌ_Ｌとして最低低位発熱量の低質ゴミ（Ｈｕ＝１０００）として推定した推定酸素濃度Ｐｏｅを用いて、検査手段４において排ガスセンサ３の検査を行う例について説明したが、前記発熱量推定手段５で推定した推定発熱量Ｈｕｅに基づき、求めた推定酸素濃度Ｐｏｅを用いて、予め設定された許容範囲を与えて前記上限酸素濃度Ｌ_Ｈと前記下限酸素濃度Ｌ_Ｌとを設定して前記検査手段４における前記排ガスセンサ３の検査に用いるようにしてもよい。このようにすれば、絶対偏差に基づいて検査を行うことになるから、検査条件が時によって異なることを回避できる。
【００３１】
【実施例】
上記実施の形態における各算出計算について例を挙げて説明すれば、前記推定低位発熱量Ｈｕｅは、前記発生熱量Ｈｂと、前記ゴミ焼却量Ｇとから、
Ｈｕｅ＝Ｈｂ／Ｇ
として求めることができる。尚、前記発生熱量Ｈｂは、
ボイラ給水のエンタルピＩｗ：１５１．０（ｋｃａｌ／ｋｇ）
出口蒸気のエンタルピＩｓ：７０７．９（ｋｃａｌ／ｋｇ）
（但し、蒸気温度２７１．０℃、蒸気圧力１８ｋｇ／ｃｍ^２とした。）
ボイラ効率η ：６８．７（％）
他の入熱量Ｈｍ：１０００（ｋｃａｌ／ｋｇ）
として、蒸気発生量Ｇｓから、
Ｈｂ＝Ｇｓ ×（Ｉｓ −Ｉｗ）／η − Ｈｍ
の式を基に求めた。
また、前記理論酸素量Ｏｓを求めるには、例えば表１に示すデータから、
【００３２】
【表１】

【００３３】
Ｏｓ＝８．８９Ｐ_Ｃ＋２６．７（Ｐ_Ｈ− Ｐ_Ｏ／８）＋３．３３Ｐ_Ｓ
として求められる。この理論酸素量Ｏｓから、夫々表２に示す理論空気量Ｆａｓが求められる。
【００３４】
【表２】

【００３５】
以上の結果を基に、前記推定発熱量Ｈｕｅに対応して求めるのに、表２に示した３点の低位発熱量Ｈｕに対して、線形近似式を導出し、
Ｆａｓ＝０．９３ × １０^−３Ｈｕ＋０．４７
として前記理論空気量Ｆａｓを求める。この結果から、前記推定酸素濃度Ｐｏｅは、前記総空気量Ｆａに基づき、
Ｐｏｅ＝（１− Ｆａｓ／Ｆａ） × ０．２１
として求める。尚、図２に示した一点鎖線は、前記酸素残量推定手段６で、上式により求めた高質ゴミに対する推定酸素濃度Ｐｏｅを前記上限酸素濃度Ｌ_Ｈ（一点鎖線で表示）とし、低質ゴミに対する推定酸素濃度Ｐｏｅを前記下限酸素濃度Ｌ_Ｌ（一点鎖線で表示）として、前記酸素濃度検出手段２の検出した１分前の排ガス中酸素濃度Ｐｏ（実線で表示）と共に示したものである。ここに、上記１分は、ここで想定したゴミ焼却炉における廃熱ボイラからの排ガスが排ガスセンサに至るまでの所要時間である。こうして時間的なずれを補正することによって、発熱量に基づく推定酸素濃度と実測酸素濃度の同期を図ることが可能である。
【００３６】
図２に示したように、慣性の大きい熱的計算結果である前記上限酸素濃度Ｌ_Ｈと前記下限酸素濃度Ｌ_Ｌとは、前記酸素濃度検出手段２の検出した排ガス中酸素濃度Ｐｏに比して変化傾向が鈍化してはいるが、可成りよく一致した挙動を示しており、前記酸素濃度検出手段２の排ガスセンサ３を検定するのに好適であることがわかる。
【００３７】
尚、特許請求の範囲の項に図面との対照を便利にするために符号を記すが、該記入により本発明は添付図面の構成に限定されるものではない。
【図面の簡単な説明】
【図１】本発明によるゴミ焼却炉の一例の説明図
【図２】排ガスセンサの異常判定の例を示す線図
【図３】本発明によるゴミ焼却炉の他の例を示す説明図
【図４】従来のゴミ焼却炉の一例の説明図
【図５】排ガスセンサの構造を示す要部断面説明図
【図６】排ガスセンサの異常検出を説明する線図
【符号の説明】
１燃焼制御手段
３排ガスセンサ
４検査手段
５発熱量推定手段
６酸素残量推定手段
１４排ガス路
Ｆ火炉[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for detecting an abnormality in an exhaust gas sensor, and in particular, comprises an exhaust gas sensor for measuring the oxygen concentration in exhaust gas in an exhaust gas path from a furnace, and a combustion control index for the oxygen concentration in the exhaust gas detected by the exhaust gas sensor. The present invention relates to a waste incinerator and a method for detecting an abnormality of the exhaust gas sensor disposed in an exhaust gas path from the furnace.
[0002]
[Prior art]
Conventionally, in a refuse incinerator, as shown in FIG. 4, a dust supply mechanism 11 for introducing trash received in the hopper 11a into the furnace F, and incinerating the fed trash while transporting the trash. A movable grate 12 comprising a stalker mechanism is provided. The movable grate 12 is provided with a drying zone 12A for heating and drying while transporting trash introduced by the dust supply mechanism 11, and a drying zone 12A. Are divided into a combustion zone 12B which mainly forms a combustion area by burning while transporting the refuse, and a post-combustion zone 12C which incinerates while transporting the combustion residue of the refuse burned off in the combustion zone 12B. A secondary combustion chamber 13 for inducing combustion gas from the combustion region upward to perform secondary combustion, and the exhaust gas from the secondary combustion chamber 13 is guided to a chimney 18 in an exhaust gas passage 14, and the heat of the exhaust gas is Waste heat boiler B, which generates steam, and a bag filter 15 as a dust removing device for removing dust such as fly ash in exhaust gas from the outlet of the waste heat boiler B; and exhaust gas after the dust filter 15 removes the dust. And a suction blower 17 for sending out the exhaust gas after washing toward the chimney, and an exhaust gas passage 14 between the bag filter 15 and the smoke washing device 16 is provided. An oxygen concentration detecting means 2 for detecting the oxygen concentration in the exhaust gas by an exhaust gas sensor 3 provided in the apparatus is provided, and the oxygen concentration in the exhaust gas detected by the oxygen concentration detecting means 2 is used as a combustion control index. No inspection means for detecting abnormalities in the oxygen concentration in the exhaust gas detected by the oxygen concentration detection means 2 was provided. When there is an abnormality in the detection value detected by the exhaust gas sensor or when the exhaust gas sensor breaks down, the oxygen concentration in the exhaust gas as the combustion control index is set to a predetermined set value (for example, the input dust). Is used as the standard garbage, or the oxygen concentration in the exhaust gas immediately before the occurrence of the failure is used.), And the combustion control is continued.
[0003]
[Problems to be solved by the invention]
In other words, in the above-mentioned conventional exhaust gas sensor, for example, a site worker who knows that the value of the oxygen concentration to be detected is out of the set oxygen concentration range is judged from the state of the data to determine whether or not there is an abnormality. Was. Abnormality of the exhaust gas sensor is determined by using the suction pipe 3a in the case of an exhaust gas sensor 3 having a gas detection element 3b for inspecting exhaust gas sampled from the suction pipe 3a and having a generally used structure (for example, see FIG. 5). Due to corrosion or other causes, air leaking from outside into the exhaust gas introduced into the gas detection element 3b may increase the oxygen content of the introduced exhaust gas. Despite the fact that the oxygen concentration is within an allowable range (for example, 6 to 14%) (for example, 7%), but shows an abnormal oxygen concentration (for example, 15%) due to the incorporation of leaked air, or when the gas detection element 3b As an example, a case where the detection value shifts up or down due to deterioration can be given. If the abnormal oxygen concentration is 18% in the above example, it can be determined as an abnormal value in the state where the furnace combustion is normally maintained, but the oxygen concentration detected in such a state is 13 to If it is 14%, even if it is actually 7%, it is not an oxygen concentration in an abnormal range for an operator involved in furnace control, but an expert recognizes that it is abnormal by referring to other process data. You will be overlooked unless you do. Therefore, when an abnormal value is shown while being within the allowable range, it takes a long time before it can be determined that the value is abnormal. For example, as described above, the upper limit or the lower limit of the allowable range is set. If the values are close to each other, it takes 2 to 3 hours at the earliest, and 2 to 3 days if the values are long. During that time, the combustion control of the furnace is maintained based on the incorrect data. There was a risk that the harmful components could not be maintained within the allowable component range. FIG. 6 is a graph showing an example in which the oxygen concentration in the exhaust gas is actually continuously recorded. However, even if the combustion state in the furnace is stable, the quality of the garbage and the change with time of the combustion state have a considerable width. Since the data fluctuates, it is not easy to determine the abnormality of the data. Further, once an abnormality is detected in the exhaust gas sensor, it is difficult to directly suppress the abnormality of the exhaust gas component if the abnormality is fixed at a set value (for example, 8%) regardless of the detected value of the oxygen concentration in the exhaust gas. Has the problem of becoming
Therefore, the exhaust gas sensor abnormality detection method of the present invention solves the above problems, detects an exhaust gas sensor abnormality based on another combustion control index in a furnace, and stably maintains exhaust gas components within an allowable range. Further, the refuse incinerator of the present invention can detect an abnormality of the exhaust gas sensor, and can normally maintain the combustion control even with respect to the abnormality of the exhaust gas sensor. The purpose is to do.
[0004]
[Means for Solving the Problems]
(Feature configuration]
[0005]
First characteristic configuration of the exhaust gas sensor abnormality detection method of the present invention for the above purposeCalculates and derives the theoretical amount of air with respect to the weight of the refuse charged into the furnace within a predetermined time, and calculates the amount of oxygen in the calculated and calculated theoretical amount of oxygen in the air supplied to the furnace within the predetermined time. The estimated oxygen concentration in the exhaust gas is calculated and derived as being consumed from the amount, and the oxygen concentration in the exhaust gas detected by the exhaust gas sensor deviates from a predetermined allowable range set based on the calculated and derived estimated oxygen concentration in the exhaust gas. In this case, it is determined that an abnormality has occurred in the exhaust gas sensor.
[0006]
Further, the method for detecting abnormality of the exhaust gas sensor of the present inventionThe second characteristic configuration is the theoretical air amount.Calculates thatReference garbageThe point is that the calculation is derived as follows.
[0007]
Furthermore, the abnormality detection method for an exhaust gas sensor of the present inventionThird feature configurationIsSaidIn order to set the allowable range, the estimated oxygen concentration in the exhaust gas is calculated as the upper limit, and the estimated oxygen concentration in the exhaust gas is calculated as the upper limit. Is the lower limit of the result derived as a result of calculation as low-quality garbage.
[0008]
And the abnormality detection method of the exhaust gas sensor of the present inventionFourth feature configurationIn order to determine that an abnormality has occurred in the exhaust gas sensor, the garbage incineration is performed by setting the oxygen concentration in the exhaust gas detected by the exhaust gas sensor and a predetermined allowable range set based on the calculated and derived estimated oxygen concentration in the exhaust gas. The point is that the comparison is made in synchronization with the furnace control interval.
[0009]
Furthermore, the abnormality detection method for an exhaust gas sensor of the present inventionFifth feature configurationThe point is that the condition for judging the occurrence of an abnormality in the exhaust gas sensor is that the detected oxygen concentration in the exhaust gas deviates from the allowable range continuously for a set time.
[0010]
The abnormality detection method of the exhaust gas sensor of the present inventionSixth feature configurationIs that the condition for judging the occurrence of an abnormality in the exhaust gas sensor is that the detected oxygen concentration in the exhaust gas deviates from the allowable range by a predetermined number of times within a set time.
[0011]
The abnormality detection method of the exhaust gas sensor of the present inventionSeventh feature configurationIsCalculate and derive the theoretical air amount with respect to the refuse weight put into the furnace, based on the calculated and derived oxygen amount in the theoretical air amount and the oxygen amount in the air supplied to the furnace within the predetermined time.Oxygen remaining amount estimating means for estimating the estimated oxygen concentration in the exhaust gas in the exhaust gas path, and the oxygen concentration in the exhaust gas detected by the exhaust gas sensor is set based on the estimated oxygen concentration in the exhaust gas estimated by the oxygen remaining amount estimating means. An inspection means for judging that an abnormality has occurred in the exhaust gas sensor when it deviates from a predetermined allowable range is provided.
[0012]
In addition, the garbage incinerator of the present inventionEighth feature configurationIsSaidA combustion control means for controlling the furnace is provided, and the combustion control index when the inspection means determines that an abnormality has occurred is set to the estimated oxygen concentration estimated by the oxygen remaining amount estimation means instead of the oxygen concentration in the exhaust gas. The point is that it is configured.
[0013]
[Function and effect of feature configuration]
[0014]
According to the first feature configuration,Since the abnormality of the oxygen concentration in the exhaust gas detected by the exhaust gas sensor can be detected in a timely manner, it is possible to avoid the combustion control due to the erroneous oxygen concentration in the exhaust gas and prevent the exhaust gas component from deviating from the predetermined component range. That is, by comparing the estimated oxygen concentration with the oxygen concentration in the exhaust gas detected by the exhaust gas sensor, if it deviates from a predetermined allowable range set based on the estimated oxygen concentration, it can be determined that an abnormality has occurred in the exhaust gas sensor. It is. The estimated oxygen concentration is obtained by calculating and calculating the theoretical amount of air with respect to the weight of refuse charged into the furnace within a predetermined time, and estimating the amount of oxygen consumed in the furnace based on the calculated and calculated theoretical amount of air. The estimated oxygen concentration in the exhaust gas can be calculated and derived as being consumed from the amount of oxygen in the air supplied to the furnace within the predetermined time. When the oxygen concentration in the exhaust gas detected by the exhaust gas sensor deviates from a predetermined allowable range set based on the calculated and derived estimated oxygen concentration in the exhaust gas, it can be determined that an abnormality has occurred in the exhaust gas sensor. The allowable range can be set based on a range of the fluctuation of the oxygen concentration in the exhaust gas which is constantly monitored.
As a result, it becomes possible to stably maintain the exhaust gas component within an allowable range.
[0015]
The second characteristic configurationAccording toThe theoretical air volumeNo special means for calculation is required, and the equipment can be further simplified. That is,The theoretical air volumeGarbageReference garbageTherefore, the allowable range can be fixed.
[0016]
The third characteristic configurationAccording to this, the allowable range can be set reasonably. In other words, the result of calculating and deriving the estimated oxygen concentration in the exhaust gas assuming that the input dust is high quality dust is set as the upper limit value, and the estimated oxygen concentration in the exhaust gas is calculated and derived assuming that the input dust is low quality dust. As a result, the maximum range estimated for the input dust can be set as an allowable range based on the amount of incineration dust and the amount of air supplied to the furnace, and the detected value deviates from this allowable range. If so, the detected value is clearly abnormal.
Therefore, it is possible to prevent erroneous determination in the abnormality detection of the exhaust gas sensor.
[0017]
The fourth feature configurationAccording to this, it is possible to prevent the combustion control from being performed without performing the abnormality determination of the exhaust gas sensor. That is, in synchronization with the control interval of the refuse incinerator, the oxygen concentration in the exhaust gas detected by the exhaust gas sensor is compared with a predetermined allowable range set based on the estimated oxygen concentration in the exhaust gas calculated and derived. It is determined that an abnormality has occurred in the exhaust gas sensor. In addition, since the abnormality determination is performed once during one control cycle, different determination results are not provided during the same cycle, so that the determination is simple and unique, and unnecessary calculation can be avoided.
[0018]
The fifth characteristic configurationAccording to this, it is possible to determine the occurrence of an abnormality in the exhaust gas sensor without delay. In other words, the condition for determining the occurrence of an abnormality in the exhaust gas sensor is that the detected oxygen concentration in the exhaust gas continuously deviates from the allowable range for a set time (for example, 10 minutes). This set time may be scattered even though the exhaust gas sensor is operating normally, and if it is determined that the measurement value is abnormal due to deviation from the allowable range for an extremely short time, the actual This may cause an erroneous determination that an abnormality has occurred in the exhaust gas sensor even though there is no abnormality in the exhaust gas sensor. Although the actual recording of the oxygen concentration in the exhaust gas is dispersed as shown in FIG. 6, for example, if the dashed line in the figure is the upper and lower limits of the allowable range, it is almost within the allowable range. The time continuously deviating from the allowable range is not long. The upper and lower limits are based on the combustion heat value obtained from the three-hour moving average value of the boiler generated steam amount in the in-furnace process data. Although this point is narrowed, if this point is corrected and an appropriate time is determined in relation to the sampling period, erroneous determination can be prevented and an abnormality of the exhaust gas sensor can be found at an early stage.
As a result, the accuracy of the abnormality determination of the exhaust gas sensor can be increased.
[0019]
Sixth feature configurationAccording to this, it is possible to determine the occurrence of an abnormality in the exhaust gas sensor without delay. In other words, the case where the detected oxygen concentration in the exhaust gas deviates from the allowable range by a predetermined number of times (for example, three times) within the set time or more is set as the condition for determining the occurrence of an abnormality in the exhaust gas sensor. In the occurrence of the abnormality of the exhaust gas sensor, the number of times of deviating from the allowable range rapidly increases within a set time, and the predetermined number of times may be set in advance to an average or the minimum value of the number of times of the rapidly increasing deviation. It is. Although the actual record of the oxygen concentration in the exhaust gas is dispersed as shown in FIG. 6, for example, if the dashed line in the figure is the upper and lower limits of the allowable range, it is almost within the allowable range, The time continuously deviating from the allowable range is not long. The upper and lower limits are based on the combustion heat value obtained from the three-hour moving average value of the boiler generated steam amount in the in-furnace process data. Although this point is narrowed, if this point is corrected and an appropriate number of times is determined as a predetermined number in relation to the sampling cycle, erroneous determination can be prevented and an abnormality of the exhaust gas sensor can be found at an early stage.
as a result,The fifth feature configurationSimilarly to the above, the accuracy of the abnormality determination of the exhaust gas sensor can be increased.
[0020]
According to the seventh characteristic configuration,The garbage incinerator can be prevented from being erroneously controlled in combustion by an abnormal output of the oxygen concentration in the exhaust gas from the exhaust gas sensor. That is,Calculate and derive the theoretical amount of air with respect to the weight of the refuse charged into the furnace, and calculate and derive the oxygen amount in the calculated theoretical amount of air and the oxygen amount in the air supplied to the furnace within a predetermined time.From the estimated oxygen concentration in the exhaust gas estimated by the oxygen remaining amount estimating means on the basis of, the oxygen concentration in the exhaust gas detected by the exhaust gas sensor deviates from a predetermined allowable range set based on the estimated oxygen concentration in the exhaust gas. In this case, since the inspection means determines that an abnormality has occurred in the exhaust gas sensor, the upper and lower limits set based on the estimated oxygen concentration in the exhaust gas are set, for example, as shown in FIG. If the range between the dashed lines shown is the allowable range, the time deviating from the allowable range is specified to an appropriate length in relation to the sampling cycle, or if the number of times of deviation is specified, an erroneous determination is made. At the same time, it is possible to detect an abnormality of the exhaust gas sensor at an early stage, and it is possible to take a countermeasure for the abnormality of the exhaust gas sensor at an early stage. It will be able to prevent.
As a result, it is possible to stably maintain harmful components in the exhaust gas from the refuse incinerator within an allowable range.
[0021]
According to the eighth aspect,When an abnormality occurs in the exhaust gas sensor, a measure is automatically taken. In other words, the combustion control means for controlling the furnace is provided, and the combustion control index when the abnormality is determined by the inspection means is replaced by the estimated oxygen concentration estimated by the oxygen remaining amount estimation means instead of the oxygen concentration in the exhaust gas. Therefore, since the combustion control is performed using the combustion control index determined by the same standard as that for detecting the abnormality of the exhaust gas sensor, the reliability of the combustion control can be maintained at a high level. .
As a result, harmful components in the exhaust gas from the refuse incinerator can be more stably maintained within an allowable range.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of an embodiment of the refuse incinerator of the present invention and an abnormality detection method for an exhaust gas sensor applicable to the incinerator will be described below with reference to the drawings. Note that the same elements as those described in the related art and elements having the same functions are denoted by the same reference numerals as in FIGS. 4 and 5, and a part of the detailed description is omitted. .
[0023]
The refuse incinerator is provided with a combustion control means 1. The combustion control means 1 supplies the amount of refuse charged into the furnace F from the dust supply mechanism 11 per unit time and the refuse supplied to the furnace F. Garbage transport control means 1a for adjusting the transport speed of the stoker mechanism constituting the movable grate 12 according to the garbage quality (classified by the lower heating value), etc .; Furnace supply air control means 1b for adjusting the amount of air supplied into the furnace F based on process data such as the transfer speed of the refuse, the position where the refuse is burned off in the combustion zone 12B, and the amount of steam generated in the waste heat boiler B. Secondary combustion control means 1c for adjusting the amount of secondary air supplied to the secondary combustion chamber 13 so that the oxygen concentration Po in the exhaust gas detected by the oxygen concentration detection means 2 does not deviate from a predetermined allowable range. To maintain the oxygen concentration in the exhaust gas within a predetermined range while maintaining good combustion of a predetermined amount of garbage on the mobile grate 12 and release of harmful components such as dioxins and nitrogen oxides. Is configured to be reduced.
[0024]
The oxygen concentration detecting means 2 includes an exhaust gas sensor 3 having the same structure as the conventional one disposed in an exhaust gas passage 14 between a bag filter 15 as a dust removing device and a smoke washing device 16, and an input from the exhaust gas sensor 3. It is configured to detect the oxygen concentration Po in the exhaust gas based on the value. Inspection means 4 for inspecting whether or not the oxygen concentration Po in the exhaust gas detected by the oxygen concentration detection means 2 is within a reference range to detect abnormality of the exhaust gas sensor 3 and process data of the furnace. The calorific value estimating means 5 for estimating the lower calorific value of the refuse on the combustion zone 12B and the oxygen concentration detecting means 2 when the exhaust gas sensor 3 is determined to be abnormal based on the inspection result of the inspecting means 4 And an oxygen remaining amount estimating means 6 for estimating the residual oxygen concentration Poe in the exhaust gas as an alternative combustion control index instead of the oxygen concentration Po in the exhaust gas.
[0025]
The inspection unit 4 determines that the input dust is high-quality dust having a low calorific value (equivalent to a low calorific value of 2300 kcal / kg) and calculates the estimated oxygen concentration estimated by the oxygen remaining amount estimating unit 6 as an upper limit oxygen concentration. L_HThe estimated oxygen concentration estimated by the oxygen remaining amount estimating means 6 as a low-quality waste having a low lower calorific value (corresponding to a lower calorific value of 1000 kcal / kg) is defined as a lower limit oxygen concentration L._LThe oxygen concentration Po in the exhaust gas detected by the oxygen concentration detecting means 2 is equal to the upper limit oxygen concentration L._HOr the lower limit oxygen concentration L_LIs less than the threshold value, it is determined that an abnormality has occurred in the exhaust gas sensor 3. In other words, assuming the maximum and minimum values of the lower heating value, that is, the highest and lowest heating values, the maximum and minimum values of the estimated oxygen concentration are calculated from the oxygen consumption calculated for each. Value, the upper limit oxygen concentration L_HAnd the lower limit oxygen concentration L_LAsking. For example, as shown in FIG. 2, the oxygen concentration Po in the exhaust gas is equal to the upper limit oxygen concentration L._HAnd the lower limit oxygen concentration L_LAnd the inspection means 4 does not detect any abnormality of the exhaust gas sensor 3. Although a diagram for detecting an abnormality is omitted, in the case of a normally assumed abnormality, the oxygen concentration Po in the exhaust gas shifts up or down, and as shown in FIG. The upper limit oxygen concentration L exhibiting almost the same behavior as the oxygen concentration Po in the exhaust gas._HAnd the lower limit oxygen concentration L_LFrom the permissible range between the two, the value continuously or frequently deviates from one of the values, so that the abnormality of the exhaust gas sensor 3 can be determined very easily. In the case of such a configuration, the abnormality of the exhaust gas sensor can be determined by a continuous deviation each time sampling is performed.
[0026]
The oxygen remaining amount estimating means 6 calculates a theoretical air amount Fas obtained in accordance with the estimated heat value Hue from the heat value estimating device 5 with respect to the weight of the dust charged into the furnace F, and a dust per unit time. The required amount of air Far as combustion air is estimated from the amount of incineration G and the amount of heat generated in the furnace Hb, and the estimated oxygen concentration Poe is obtained by comparing with the total amount of air Fa supplied into the furnace. I have. That is, the amount of oxygen required for combustion for each of carbon, hydrogen, oxygen, and sulfur in the garbage is calculated based on the representative component composition determined in advance for each garbage, and the sum of the respective oxygen amounts is calculated. Based on the result of calculating the theoretical air amount based on the value, the theoretical air amount Fas is obtained by applying the estimated heat generation amount Hue to a linear relational expression for the lower heat generation amount Hu of dust previously obtained. The required air amount Far is obtained from the obtained theoretical air amount Fas and the incineration amount G. From the above results, the estimated oxygen concentration Poe is determined assuming that the total amount of oxygen in the required air amount Far has been consumed from the oxygen content in the total air amount Fa. If the amount of air flowing into the exhaust gas passage 14 after the secondary combustion chamber 13 (for example, mixing of cooling air or leakage of leaked air) can be corrected, these factors may be corrected.
[0027]
The calorific value estimating means 5 obtains the estimated calorific value Hue from the refuse incineration amount G and the calorific value Hb in the furnace. The calorific value Hb is, for a furnace having a waste heat boiler, a vapor amount G._SAnd the amount of heat taken out of the furnace as steam obtained from the enthalpy Is of the outlet steam and the enthalpy Iw of the feed water is calculated as the heat amount obtained by dividing by the boiler efficiency η obtained for each furnace. It should be noted that if other heat input / output amounts can be assumed, it will be more accurate if corrected and found.
[0028]
The estimated oxygen concentration Poe obtained by the oxygen remaining amount estimating means 6 as described above is used by the inspection means 4 to estimate the garbage quality as the high-quality garbage (Hu = 2300) having the highest low heating value. The concentration Poe is set to the upper limit oxygen concentration L._HAnd the estimated oxygen concentration Poe obtained by estimating the dust quality as the low-quality waste having the lowest low heating value (Hu = 1000) is calculated as the lower limit oxygen concentration L._LIf the detection value of the exhaust gas sensor 3 is determined to be abnormal, the oxygen remaining amount estimating unit 6 is determined based on the estimated heat amount Hue estimated by the heat amount estimating unit 5. The combustion control in the combustion control means 1 is continued using the estimated oxygen concentration Poe obtained in the above as a control index in place of the oxygen concentration Po in the exhaust gas from the exhaust gas sensor 3.
[0029]
The abnormality determination of the exhaust gas sensor 3 by the above-described inspection means 4 is executed once per control cycle. That is, the control command in the combustion control unit 1 is issued after each determination by the inspection unit 4 described above. Therefore, if an abnormality occurs in the exhaust gas sensor 3 and an abnormal detection value of the oxygen concentration in the exhaust gas is input from the oxygen concentration detecting means 2, the residual value from the oxygen remaining amount estimating means 6 is immediately regardless of the input value. The oxygen concentration is used as a substitute index, and the combustion control is performed based on the remaining oxygen concentration. In this case, if the combustion control means is configured to display the abnormality of the exhaust gas sensor and to indicate that the control index has been switched to the alternative index at the same time, the inspection or replacement of the exhaust gas sensor 3 can be timely. Easy without losing.
[0030]
Next, another embodiment of the present invention will be described.
<1> In the above embodiment, an example in which the present invention is applied to a refuse incinerator having a waste heat boiler B in the exhaust gas path 14 has been described. In this case, as shown in FIG. 3, for example, the temperature detected by the infrared detection means 5a provided on the ceiling wall of the drying zone 12A of the movable grate 12 so as to face the drying zone 12A. It suffices to provide a calorific value estimating means 5 for estimating the lower calorific value of dust in the drying zone 12A. If a filter having a transmission wavelength of 3.6 to 4 μm is attached to the infrared detecting means 5a, one of the flames The effect of infrared energy absorption of carbon oxide gas, carbon dioxide gas, nitrogen oxides, sulfur oxides, water vapor and the like can be suppressed. The heating value estimating means 5 estimates the estimated heating value Hue of the dust on the drying zone 12A as follows. That is, when the amount of air blown to the drying zone 12A is the reference flow rate, if the average value of the surface temperature of the dust per unit time is equal to or lower than the first reference temperature (for example, 900 ° C.), the low quality heat generation Hu is small. It is dust (for example, Hue = 1000), and if it is equal to or higher than a second reference temperature (for example, 1000 ° C.), it is high-quality dust (for example, Hue = 2300) having a large lower heating value Hu. If it is between the reference temperature and the reference temperature, it is estimated that the reference dust (for example, Hue = 1700). If the level of the reference temperature of the dust surface is set finely, the estimated heat generation Hue can be estimated in detail. And the upper limit oxygen concentration L in the inspection means._HAnd lower limit oxygen concentration L_LAs described in the above embodiment, the estimated oxygen concentration Poe estimated by the oxygen remaining amount estimating means 6 for high quality dust (for example, Hu = 2300) and low quality dust (for example, Hu = 1000) is used, When the inspection means 4 determines that the detection value of the exhaust gas sensor 3 is abnormal, the estimation estimated by the oxygen remaining amount estimation means 6 based on the estimated heat value Hue estimated by the heating value estimation means 5 is performed. The oxygen concentration Poe is used as an alternative index for the oxygen concentration Po in the exhaust gas in the combustion control means 1.
<2> In the above embodiment, an example in which the present invention is applied to a refuse incinerator having a waste heat boiler B in the exhaust gas path 14 has been described. In this case, as shown in FIG. 3, for example, when a gas cooling mechanism 19 is provided, instead of the heat balance of the waste heat boiler 20, the amount of air supplied to the gas cooling What is necessary is just to add the oxygen content to the calculation parameter in the oxygen remaining amount estimating means 6 for estimating the estimated oxygen concentration Poe.
<3> In the above embodiment, the upper limit oxygen concentration L_HAnd the lower limit oxygen concentration L using the estimated oxygen concentration Poe estimated as high-quality waste (Hu = 2300) having the highest low calorific value._LAn example in which the inspection means 4 performs the inspection of the exhaust gas sensor 3 using the estimated oxygen concentration Poe estimated as the low-quality waste (Hu = 1000) having the lowest low calorific value has been described. Using the estimated oxygen concentration Poe obtained based on the estimated calorific value Hue, a predetermined allowable range is given to give the upper limit oxygen concentration L_HAnd the lower limit oxygen concentration L_LMay be set and used for the inspection of the exhaust gas sensor 3 by the inspection means 4. In this way, since the inspection is performed based on the absolute deviation, it is possible to avoid that the inspection conditions are different from time to time.
[0031]
【Example】
To explain each calculation in the above embodiment using an example, the estimated lower heating value Hue is calculated based on the generated heat amount Hb and the refuse incineration amount G.
Hue = Hb / G
Can be sought. The generated heat quantity Hb is:
Bent water supply enthalpy Iw: 151.0 (kcal / kg)
Exit steam enthalpy Is: 707.9 (kcal / kg)
(However, steam temperature 271.0 ° C, steam pressure 18kg / cm²And )
Boiler efficiency η: 68.7 (%)
Other heat input Hm: 1000 (kcal / kg)
From the steam generation amount Gs,
Hb = Gs × (Is−Iw) / η−Hm
Was determined based on the equation.
In order to determine the theoretical oxygen amount Os, for example, from the data shown in Table 1,
[0032]
[Table 1]

[0033]
Os = 8.89P_C+26.7 (P_H− P_O/8)+3.33P_S
Is required. The theoretical air amount Fas shown in Table 2 is obtained from the theoretical oxygen amount Os.
[0034]
[Table 2]

[0035]
Based on the above results, a linear approximation formula was derived for the three lower heating values Hu shown in Table 2 to obtain the estimated heating value Hue.
Fas = 0.93 × 10^-3Hu + 0.47
The theoretical air amount Fas is obtained as follows. From this result, the estimated oxygen concentration Poe is calculated based on the total air amount Fa.
Poe = (1−Fas / Fa) × 0.21
Asking. The dashed line shown in FIG. 2 indicates the estimated oxygen concentration Poe for the high-quality dust obtained by the above equation by the oxygen remaining amount estimating means 6 by the upper limit oxygen concentration L._H(Indicated by a dashed line), and the estimated oxygen concentration Poe for low-quality_L(Indicated by a dashed line) is shown together with the oxygen concentration Po in the exhaust gas one minute before detected by the oxygen concentration detecting means 2 (indicated by a solid line). Here, the above one minute is the time required for the exhaust gas from the waste heat boiler in the waste incinerator assumed here to reach the exhaust gas sensor. By correcting the time lag in this way, it is possible to synchronize the estimated oxygen concentration based on the calorific value and the actually measured oxygen concentration.
[0036]
As shown in FIG. 2, the upper limit oxygen concentration L which is a thermal calculation result with a large inertia_HAnd the lower limit oxygen concentration L_LMeans that although the change tendency is slower than the oxygen concentration Po in the exhaust gas detected by the oxygen concentration detecting means 2, the behavior is fairly well matched, and the exhaust gas of the oxygen concentration detecting means 2 It turns out that it is suitable for testing the sensor 3.
[0037]
Incidentally, reference numerals are written in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings by the entry.
[Brief description of the drawings]
FIG. 1 is an explanatory view of an example of a refuse incinerator according to the present invention.
FIG. 2 is a diagram illustrating an example of abnormality determination of an exhaust gas sensor.
FIG. 3 is an explanatory view showing another example of the refuse incinerator according to the present invention.
FIG. 4 is a diagram illustrating an example of a conventional refuse incinerator.
FIG. 5 is an explanatory sectional view of a main part showing a structure of an exhaust gas sensor.
FIG. 6 is a diagram for explaining abnormality detection of an exhaust gas sensor.
[Explanation of symbols]
1 Combustion control means
3 Exhaust gas sensor
4 Inspection means
5 Calorific value estimation means
6 Oxygen remaining amount estimation means
14 Exhaust gas path
F Furnace

Claims

In a refuse incinerator provided with an exhaust gas sensor (3) for measuring the oxygen concentration in the exhaust gas in an exhaust gas path (14) from the furnace (F), and using the detected oxygen concentration in the exhaust gas as a combustion control index,
A theoretical amount of air with respect to the weight of the refuse charged into the furnace (F) within a predetermined time is calculated and derived, and the oxygen amount in the calculated and calculated theoretical amount of air is supplied to the furnace (F) within the predetermined time. The estimated oxygen concentration in the exhaust gas is calculated and derived as being consumed from the oxygen amount in the air,
When the oxygen concentration in the exhaust gas detected by the exhaust gas sensor (3) deviates from a predetermined allowable range set based on the calculated and derived estimated oxygen concentration in the exhaust gas, it is determined that an abnormality has occurred in the exhaust gas sensor. Detection method of exhaust gas sensor.

In calculating and deriving the theoretical air amount according to claim 1 ,
An abnormality detection method for an exhaust gas sensor that calculates and derives that the input dust is reference dust .

To set the tolerance,
The estimated oxygen concentration in the exhaust gas, the upper limit is the result of calculation and derivation assuming that the input dust is high quality dust,
3. The abnormality detection method for an exhaust gas sensor according to claim 1 , wherein a result obtained by calculating and estimating the estimated oxygen concentration in the exhaust gas assuming that the input dust is low-quality dust is a lower limit.

In the determination, the oxygen concentration in the exhaust gas detected by the exhaust gas sensor (3) and a predetermined allowable range set based on the calculated and derived estimated oxygen concentration in the exhaust gas are determined by controlling the refuse incinerator. The method for detecting an abnormality of an exhaust gas sensor according to claim 1 , wherein the comparison is performed in synchronization with an interval.

The abnormality detection method for an exhaust gas sensor according to any one of claims 1 to 4 , wherein the determination condition of the occurrence of the abnormality is that the detected oxygen concentration in the exhaust gas deviates from the allowable range continuously for a set time. .

The exhaust gas sensor according to any one of claims 1 to 4 , wherein the determination condition of the occurrence of the abnormality is such that the detected oxygen concentration in the exhaust gas deviates from the allowable range by a predetermined number of times or more within the set time. Anomaly detection method.

An exhaust gas sensor (3) for measuring oxygen concentration in exhaust gas is provided in an exhaust gas path (14) from the furnace (F), and refuse incineration using the oxygen concentration in exhaust gas detected by the exhaust gas sensor (3) as a combustion control index. Furnace,
The theoretical air amount with respect to the weight of the refuse charged into the furnace (F) is calculated and derived, and the oxygen amount in the calculated and calculated theoretical air amount and the oxygen in the air supplied to the furnace (F) within the predetermined time period are calculated. Oxygen remaining amount estimating means (6) for estimating an estimated oxygen concentration in exhaust gas in the exhaust gas path (14) based on the amount and
When the oxygen concentration in the exhaust gas detected by the exhaust gas sensor (3) deviates from a predetermined allowable range set based on the estimated oxygen concentration in the exhaust gas estimated by the oxygen remaining amount estimating means (6), the exhaust gas A refuse incinerator provided with an inspection means (4) for determining that an abnormality has occurred in the sensor (3).

A combustion control means (1) for controlling the furnace (F);
The combustion control index when the inspection means (4) determines that the abnormality has occurred is set to the estimated oxygen concentration estimated by the oxygen remaining amount estimation means (6) instead of the oxygen concentration in the exhaust gas. The refuse incinerator according to claim 7, which is constituted.