JP4070646B2

JP4070646B2 - Combustion control method and waste treatment apparatus

Info

Publication number: JP4070646B2
Application number: JP2003082333A
Authority: JP
Inventors: 満宮川; 富男杉本
Original assignee: Mitsui Engineering and Shipbuilding Co Ltd; Mitsui E&S Holdings Co Ltd
Current assignee: Mitsui Engineering and Shipbuilding Co Ltd; Mitsui E&S Holdings Co Ltd
Priority date: 2003-03-25
Filing date: 2003-03-25
Publication date: 2008-04-02
Anticipated expiration: 2023-03-25
Also published as: JP2004286413A

Description

【０００１】
【発明の属する技術分野】
本発明は、廃棄物などの焼却対象物を燃焼処理するのに好適な燃焼制御方法及び廃棄物処理装置に係り、特に燃焼空気量の制御に関する。
【０００２】
【従来の技術】
廃棄物の処理法として、廃棄物を熱分解して生成される熱分解ガスを燃焼炉で高温燃焼するとともに、この燃焼炉に熱分解残渣に含まれる固体の可燃物や不燃物の一部を投入して燃焼及び溶融させる燃焼溶融方法が知られている。このような燃焼溶融を行なわせる燃焼溶融炉においては、高温で旋回流を形成しながら供給空気量を２段階で制御する２段燃焼方式が採用されている（特許文献1）。これは、燃焼溶融炉の１段目の燃焼領域に焼却対象物の化学量論比未満の空気量を投入し、化学量論比の残余に一定の過剰率を加えた空気量を燃焼溶融炉の２段目の燃焼領域に供給する方式である。この場合、２段目の燃焼空気量が不足すると排ガス中のＣＯが増加し、過剰すぎるとＮＯｘが発生することから、２段目の空気量を排ガスの酸素濃度が所定値になるように調整して、それらの発生を抑制するようにしている。
【０００３】
ところで、燃焼溶融炉から排出される排ガスは、高温でかつ粉塵などのダストが高い濃度で含まれるため、排ガスの酸素濃度を燃焼溶融炉の出口で直接計測することができない。そこで、従来は、燃焼溶融炉から排出される排ガスの熱を回収する廃熱ボイラ等の下流側の低温域で、かつ排ガス中の粉塵を捕集する集塵装置の下流側において排ガスをサンプリングし、減温されかつ除塵された排ガスを酸素濃度計に導いて排ガス酸素濃度を計測するようにしている。
【０００４】
ところで、燃焼溶融炉から排ガスサンプリング点までの間に設けられた各種の機器（廃熱ボイラ、集塵装置、排ガス浄化装置等）から、系統の運転負圧等によって排ガスに外気等が盛れ込むことから、集塵装置の下流側で計測される排ガス酸素濃度は、燃焼溶融炉出口の排ガス酸素濃度よりも高めになる。
【０００５】
したがって、排ガス酸素濃度の計測値に対応する目標値又は目標範囲（以下、単に目標値と総称する。）を、漏れ込み空気量を考慮して高めに設定しなければならないが、漏れ込み空気量を適正に推定することは必ずしも容易ではない。
【０００６】
そこで、従来は、集塵装置下流側の排ガス酸素濃度を漏れ込み空気量を推定して設定した目標値に保持制御するとともに、排ガスのＮＯｘ濃度を計測し、計測されたＮＯｘ濃度が予め定められた設定範囲から外れたとき、排ガス酸素濃度の目標値を増減補正することが提案されている（特許文献２）。すなわち、排ガスのＮＯｘ濃度と燃焼溶融炉出口の酸素濃度には正の相関があり、排ガスのＮＯｘ濃度は漏れ込み空気量によって変動するものではないから、ＮＯｘ濃度によって燃焼室出口の酸素濃度をおよそ知ることができる。さらに、空気が漏れ込む可能性のある機器の負圧を検出し、その検出値に基づいて漏れ込み空気量を演算し、下流側で計測された酸素濃度を補正することが提案されている（特許文献２）。
【０００７】
【特許文献１】
特開平３−６３４０７号公報
【特許文献２】
特開２００２−２２１３０８号公報
【０００８】
【発明が解決しようとする課題】
しかしながら、漏れ込み空気は単に構成機器の運転負圧に起因して排ガスに漏れ込むだけでなく、機器の種類及び運転態様に起因して空気が排ガスに混入されることから、特許文献２の方法では必ずしも適切な燃焼制御を行なうことができない。例えば、バグフィルタ式集塵装置の逆洗空気が排ガスに混入する漏れ込み空気量のような機器の種類及び運転態様に起因して漏れ込む空気は、単に負圧に応じて定まるものではない。
【０００９】
本発明は、漏れ込み空気量を的確に考慮した排ガス酸素濃度の目標値を適切に設定する燃焼制御方法及び装置を提供することを課題とする。
【００１０】
【課題を解決するための手段】
本発明は、上記課題を解決するため、廃棄物を熱分解して発生する熱分解ガスと熱分解残渣の可燃物とを燃焼させて、前記熱分解残渣に含まれる不燃物の少なくとも一部を溶融する燃焼溶融炉の燃焼を制御するにあたり、前記燃焼溶融炉から排出される排ガスの飛灰を捕集する除塵バグフィルタの下流の排ガス酸素濃度を計測し、該計測値を目標値に保持するように前記燃焼溶融炉の燃焼空気量を制御する燃焼制御方法において、前記除塵バグフィルタの下流の排ガス流量と、前記燃焼溶融炉から前記排ガス流量の計測点に至る排ガス流路系に漏れ込む空気量とを計測し、前記排ガス流量の計測値と、前記漏れ込み空気量の計測値と、前記排ガス酸素濃度の計測値とを用いて、前記燃焼溶融炉出口の排ガス酸素濃度の基準値を前記除塵バグフィルタの下流の排ガス酸素濃度の計測点における排ガス酸素濃度に換算し、該換算値を前記排ガス酸素濃度の前記目標値として設定することを特徴とする。
【００１１】
本発明の燃焼制御方法によれば、排ガス流量の計測値と、漏れ込み空気量の計測値と、除塵バグフィルタ下流の排ガス酸素濃度の計測値とを用いて、燃焼溶融炉出口の排ガス酸素濃度の基準値を制御点における排ガス酸素濃度に換算しているから、その換算値を排ガス酸素濃度の目標値とすることにより、漏れ込み空気量を適切に考慮した燃焼空気の制御を行なうことができる。
【００１２】
ここで、漏れ込み空気は、燃焼溶融炉から排出される排ガスにより空気を加熱する空気加熱器にパージされる被加熱空気と、排ガス流量の計測点の下流の排ガスを空気加熱器に循環される循環排ガス中の空気と、空気加熱器から排出される排ガスの熱を回収する廃熱ボイラの灰排出機のダンパなどから漏れ込む周囲空気と、廃熱ボイラから排出される排ガスを冷却する減温塔において排ガス中に噴霧される噴霧水に含まれる空気と、除塵バグフィルタの逆洗空気等の少なくとも１つを含めることができる。
【００１３】
この場合において、漏れ込み空気量を実時間で計測しにくい機器の場合（例えば、廃熱ボイラ、減温塔、除塵バグフィルタ、等）は、漏れ込み空気量の計測値に代えて、排ガス流路系を構成する機器ごとに予め計測して設定された計測値を用いることができる。
【００１４】
また、除塵バグフィルタ下流の排ガスのＮＯｘ濃度を計測し、計測されたＮＯｘ濃度が予め定められた設定範囲から外れたとき、排ガス酸素濃度の目標値を増減補正することが好ましい。これによれば、燃焼空気量を一層適切に制御することができる。
【００１５】
また、本発明の排ガス処理装置は、熱分解反応器から発生する熱分解ガスと熱分解残渣の可燃物を燃焼して前記熱分解残渣の不燃物の少なくとも一部を溶融する燃焼溶融炉と、該燃焼溶融炉から排出される排ガスにより空気を加熱する空気加熱器と、該空気加熱器から排出される排ガスの熱を回収する廃熱回収装置と、前記排ガス中に含まれる飛灰を捕集する除塵バグフィルタと、該除塵バグフィルタから排出される排ガスを吸引して大気に排出する誘引送風機と、該誘引送風機から排出される排ガスの一部を前記空気加熱器の入口側流路に戻す排ガス循環路と、前記除塵バグフィルタ出口の排ガス酸素濃度を計測する排ガス酸素濃度計と、該排ガス酸素濃度計により計測された排ガス酸素濃度の計測値を目標値に保持するように前記燃焼溶融炉の燃焼空気量を制御する燃焼制御手段とを備え、前記除塵バグフィルタ下流の排ガス流量を計測する排ガス流量計と、前記排ガス循環路の循環排ガス流量を計測する循環排ガス流量計と、前記空気加熱器にパージされる空気流量を計測するパージ空気流量計とを設け、前記燃焼制御手段は、前記排ガス流量計の計測値と、前記循環排ガス流量計の計測値と、前記パージ空気流量計の計測値と、前記廃熱ボイラと前記減温塔と前記除塵バグフィルタの漏れ込み空気量の設定データと、前記排ガス酸素濃度計の計測値とを用いて、前記燃焼溶融炉出口の排ガス酸素濃度の基準値を前記除塵バグフィルタの下流の排ガス酸素濃度の計測点における排ガス酸素濃度に換算し、該換算値を前記排ガス酸素濃度の前記目標値として設定することを特徴とする。
【００１６】
この場合において、前記除塵バグフィルタから排出される排ガスに脱塩剤を添加して処理する脱塩バグフィルタを備え、前記排ガス流量計は前記脱塩バグフィルタから排出される排ガス流量を計測し、前記排ガス酸素濃度計は前記誘引送風機の下流の排ガス酸素濃度を計測するようにすることができる。
【００１７】
【発明の実施の形態】
（第１実施形態）
本発明の一実施の形態について、図１及び図２を用いて説明する。図１は、本発明の燃焼制御方法が適用された燃焼溶融方式の廃棄物処理装置の一実施形態の全体構成図を示している。燃焼溶融炉１には、図示していない熱分解反応器により熱分解された廃棄物の熱分解ガスと熱分解残渣の可燃物、及び熱分解残渣の不燃物の少なくとも一部が投入されるようになっている。なお、熱分解反応器から排出される熱分解残渣は、冷却、分別、粉砕の各処理を受けた後、燃焼溶融炉１に供給される。燃焼溶融炉１から排出される排ガスは空気加熱器２に導かれ、ここにおいて空気を加熱するようになっている。空気加熱器２で加熱された高温空気は、図示していない熱分解反応器の熱源として用いられる。空気加熱器２から排出される排ガスは廃熱ボイラ４に導かれ、排ガスの熱が水蒸気として回収される。廃熱ボイラ４を通った排ガスは減温塔５に導かれ、ここにおいて水が噴霧され減温される。減温された排ガスは除塵バグフィルタ６に導かれ、排ガス中に含まれる飛灰が捕集される。除塵バグフィルタ６から排出される排ガスに空気輸送される脱塩剤が添加された後、脱塩バグフィルタ７に導かれて排ガス中の塩素分や硫黄分が除去される。脱塩バグフィルタ７の２次側排ガスは誘引送風機８により吸引され、図示していない煙突を介して大気に排出される。誘引送風機８から排出される排ガスの一部は、排ガス循環送風機９を有する排ガス循環流路１０介して、空気加熱器２の入口側流路に供給されるようになっている。
【００１８】
燃焼溶融炉１は、頂部に設けられたバーナ１１と、バーナ１１の下方の炉壁に設けられた複数の第１の空気ノズル１２と、この空気ノズル１２の下方の炉壁に炉高方向に２段に分けて設けられた複数の第２の空気ノズル１３とを備えて構成されている。第２の空気ノズル１３からは、燃焼空気量制御弁１４を介して、２次空気及び３次空気が供給される。なお、バーナ１１から第２の空気ノズル１１３に至る間の空間が第１の燃焼域又は燃焼室と称され、第２の空気ノズル１３の下流側が第２の燃焼域又は燃焼室と称される。また、炉底に設けられた溶融スラグ排出口１５は、図示していない水槽の水面下に位置させて開口され、溶融されたスラグが水中に排出されるようになっている。
【００１９】
空気加熱器２は、排ガスが通流される煙道内に複数の伝熱管を配置して形成され、伝熱管に図示していない送風機から空気２１を通流させて空気を加熱し、加熱された加熱空気２２を前述した熱分解反応器に供給するようになっている。また、空気加熱器２は、伝熱管から一定量の空気を煙道内に放出（パージ）して伝熱管の高温腐食の軽減等が図られている。また、溶融燃焼炉１は、溶融スラグを生成するために高温（例えば、１２００〜１３００℃）高温燃焼するようにしているから、排ガス温度も高温となっている。その高温の排ガスをそのまま空気加熱器２に導くと空気加熱器２を損傷させるおそれがある。そこで、排ガス循環路１０を介して低温の循環排ガスを空気加熱器２の入口に流入させることにより排ガスを減温するようにしている。
【００２０】
廃熱ボイラ４において底部に沈降した飛灰はホッパに集積され、図示していない灰排出機によって排出されるようになっている。また、除塵バグフィルタ６の濾布面に捕集された飛灰は、パルス状の逆洗空気を噴射することによって底部ホッパ内に落下させ、図示していない灰排出機によって排出されるようになっている。同様に、脱塩バグフィルタ７の濾布面に付着した脱塩剤及び反応生成物は、パルス状の逆洗空気を噴射することによって底部ホッパ内に落下させ、図示していない灰排出機によって排出されるようになっている。
【００２１】
次に、本実施形態の特徴に係る燃焼空気量の制御について詳細に説明する。燃焼空気量の制御系は、第１の燃焼室用の１次空気制御系と、第２の燃焼室用の２、３次空気制御系とに分けられる。１次空気制御系は、バーナ１１と第１の空気ノズル１０に供給する空気量を制御する系統であり、１次燃焼空気量は焼却対象物の量に応じて予め定められた化学量論比未満の空気量を投入するとともに、第１の燃焼域の温度を所定の温度範囲に保持するように１次燃焼空気量を補正制御しているが、図１では記載を省略している。第２の燃焼室用の２、３次空気制御系は、第２の空気ノズル１３に空気を供給する系統に設けられた燃焼空気量制御弁１４と、この燃焼空気量制御弁１４を制御する燃焼制御装置３０を備えて構成されている。
【００２２】
燃焼制御装置３０は、除塵バグフィルタ６の出口排ガス酸素濃度の目標値ＳＶｚを設定する演算器３０ａと、設定された目標値ＳＶｚと除塵バグフィルタ６の出口側流路に設けられた排ガス酸素濃度計３１により計測された計測値ＰＶｚとに基づいてＰＩＤ等の制御演算を実行する演算器３０ｂを有して形成されている。演算器３０ａには、脱塩バグフィルタ８の出口側流路に設けられた排ガス流量計３２により計測された排ガス流量Ｑｏと、誘引送風機８の出口側流路に設けられた排ガス酸素濃度計３３により計測された排ガス酸素濃度の計測値Ａとが入力されている。また、空気加熱器２の入口空気流量計３４と出口空気流量計３５によりそれぞれ計測された入口空気流量と出口空気流量との差である漏れ込み空気量（パージ空気量）Ｑｐと、空気加熱器２の入口側流路に設けられた循環排ガス流量計３６，３７により計測された循環排ガス流量Ｑｊ１、Ｑｊ２が入力されている。また、燃焼制御装置３０にはデータベース３０ｃが備えられ、データベース３０には、排ガス酸素濃度の基準値ＳＶｔ、廃熱ボイラ４、減温塔５、除塵バグフィルタ６に漏れ込む空気量を予め計測して得られた漏れ込み空気量の合計設定値Ｑａと、脱塩バグフィルタ７に漏れ込む空気量を予め計測して得られた漏れ込み空気量の設定値Ｑｄ等のデータが格納されている。
【００２３】
ここで、図１の廃棄物処理装置の主要部の排ガス流量と漏れ込み空気量とのマテリアルバランスを図２に示すとともに、各記号の意味及び単位を次に説明する。
【００２４】
Ｑ１［ｍ^３Ｎ／ｈ（乾き）］：燃焼溶融炉の出口の排ガス流量（概念値）
Ｑｏ［ｍ^３Ｎ／ｈ（湿り）］：脱塩バグフィルタ出口の排ガス流量計３２により計測された排ガス流量
Ｑｊ［ｍ^３Ｎ／ｈ（湿り）］：循環排ガス流量計３６，３７により計測された循環排ガス流量Ｑｊ１、Ｑｊ２の合計量
Ｑｐ［ｍ^３Ｎ／ｈ（乾き）］：空気加熱器の漏れ込み空気量（パージ空気量＝入口空気量と出口空気量の計測値の差）
Ｑａ［ｍ^３Ｎ／ｈ（乾き）］：廃熱ボイラ４、減温塔５、除塵バグフィルタ６から排ガス流路系に漏れ込む空気量（廃熱ボイラや除塵バグフィルタの灰排出機ダンパからの漏れ込み空気量、減温塔スプレー噴霧空気量、活性炭噴霧空気量、除塵バグフィルタ逆洗空気量、等々の予め計測して得られた設定値）
Ｑｄ［ｍ^３Ｎ／ｈ（乾き）］：脱塩バグフィルタの漏れ込み空気量（脱塩剤噴霧空気量、逆洗空気量の予め計測して得られた設定値）
ＳＶｔ［％、乾き］：燃焼溶融炉出口の排ガス酸素濃度の基準値
ＳＶｚ［％、湿り］：除塵バグフィルタ出口の排ガス酸素濃度の目標値
ＰＶｚ［％、湿り］：除塵バグフィルタ出口の排ガス酸素濃度計３１の計測値
Ａ［％、乾き］：脱塩バグフィルタ出口の排ガス酸素濃度計３３の計測値
ｗ［無次元］：排ガスの水分割合（予め計測した設定値）
これらのことから、除塵バグフィルタ出口の排ガス酸素濃度の目標値ＳＶｚは、次式の数１により表すことができる。
【００２５】
【数１】

ここで、（１−ｗ）は乾き排ガス量に換算する係数である。また、「２１」は空気に含まれる酸素の含有率（％）である。数１において、Ｑ１は計測しないとして他の排ガス量等で表すと、数１は次式の数２になる。
【００２６】
【数２】

演算器３０ａは、数２に従って、燃焼溶融炉出口の排ガス酸素濃度の基準値ＳＶｔを、除塵バグフィルタ出口の排ガス酸素濃度に換算し、その換算値を目標値ＳＶｚとして設定する。演算器３０ｂは、排ガス酸素濃度計３１の計測値ＰＶｚと目標値ＳＶｚとの差を求め、その差を低減するように、例えばＰＩＤ演算により２次及び３次の燃焼空気量の指令値Ｆａ＊を求め、燃焼空気量制御弁１４に出力する。これにより、燃焼空気量制御弁１４から空気ノズル１３を介して燃焼溶融炉１の２次燃焼領域に指令値Ｆａ＊の応じた量の燃焼空気が供給される。
【００２７】
したがって、本実施形態によれば、空気加熱器２、廃熱ボイラ４、減温塔５、除塵バグフィルタ６、脱塩バグフィルタ７、排ガス循環路１０から排ガス中に漏れ込む空気量を適正に考慮して、燃焼溶融炉１の出口の排ガス酸素濃度の基準値ＳＶｔに対応した除塵バグフィルタ出口の排ガス酸素濃度の目標値ＳＶｚを設定できる。その結果、燃焼溶融炉の燃焼空気量を適切に制御でき、燃焼溶融炉の排ガス酸素濃度を基準値ＳＶｔに保持することができるから、排ガスのＣＯ濃度及びＮＯｘ濃度を適切に管理することができる。
（第２実施形態）
上記の第１実施形態では、排ガス流量計３２を脱塩バグフィルタ７の出口流路に設けたが、除塵バグフィルタ６の出口流路に設けて、除塵バグフィルタ出口の排ガス流量Ｑ２［ｍ^３Ｎ／ｈ（湿り）］を計測してもよい。この場合の排ガス酸素濃度の目標値ＳＶｚは、次式の数３により表すことができる。
【００２８】
【数３】

（第３実施形態）
図１の実施形態では、循環排ガスの酸素濃度計３３を設けたが、これを省略し、排ガス酸素濃度計３１の計測値ＰＶｚを用いて、次式の数４により循環排ガス酸素濃度の計測値Ａを計算してもよい。
【００２９】
【数４】

（第４実施形態）
本実施形態は、図３に示すように、除塵バグフィルタ６の出口における排ガスのＮＯｘ濃度を計測するＮＯｘ濃度計３４を設け、これにより計測されたＮＯｘ濃度ＮＯｘを燃焼制御装置３０の演算器３０ｄに入力している。演算器３０は、入力されるＮＯｘ濃度が予め定められた設定範囲の上限値Ｈ及び下限値Ｌから外れたとき、排ガス酸素濃度の目標値ＳＶｚを一定量ずつ増減補正する補正信号ΔＳを加算器３０ｅに出力する。加算器３０ｅは、演算器３０ａから出力される排ガス酸素濃度の目標値ＳＶｚに補正信号ΔＳを加算又は減算して目標値ＳＶ’ｚを演算器３０ｂに出力する。
【００３０】
すなわち、排ガスのＮＯｘ濃度と燃焼溶融炉１の出口の酸素濃度には正の相関があり、排ガスのＮＯｘ濃度は漏れ込み空気量によって変動するものではない。そこで、ＮＯｘ濃度によって燃焼室出口の酸素濃度をおよそ知ることができるから、ＮＯｘ濃度の変動によって排ガス酸素濃度の目標値ＳＶｚを補正することにより、燃焼空気量を一層適切に制御することができる。なお、増減補正に係る補正信号ΔＳの一定量は、増加方向と減少方向で異なる値に設定してもよい。
【００３１】
【発明の効果】
以上述べたように、本発明によれば、漏れ込み空気量を的確に考慮した排ガス酸素濃度の目標値を適切に設定することができる。
【図面の簡単な説明】
【図１】本発明の燃焼制御方法が適用された廃棄物処理装置の一実施形態の全体構成図である。
【図２】図１の廃棄物処理装置の主要部の排ガス流量と漏れ込み空気量とのマテリアルバランスを示す図である。
【図３】本発明の燃焼制御方法が適用された廃棄物処理装置の他の実施形態の全体構成図である。
【符号の説明】
１燃焼溶融炉
２空気加熱器
３？？？？
４廃熱ボイラ
５減温塔
６除塵バグフィルタ
７脱塩バグフィルタ
８誘引送風機
１０排ガス循環路
１４燃焼空気量制御弁
３０燃焼制御装置
３０ａ、ｂ演算器
３０ｃデータベース
３１排ガス酸素濃度計
３２排ガス流量計
３３排ガス酸素濃度計
３４入口空気流量計
３５出口空気流量計
３６，３７循環排ガス流量計[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control method and a waste treatment apparatus suitable for combusting incineration objects such as waste, and more particularly to control of the amount of combustion air.
[0002]
[Prior art]
As a waste treatment method, pyrolysis gas generated by pyrolyzing waste is burned at a high temperature in a combustion furnace, and a part of solid combustible and non-combustible substances contained in the pyrolysis residue is burned into this combustion furnace. There is known a combustion melting method in which charging is performed to burn and melt. In the combustion melting furnace for performing such combustion melting, a two-stage combustion system is adopted in which the amount of supplied air is controlled in two stages while forming a swirling flow at a high temperature (Patent Document 1). This is because the amount of air less than the stoichiometric ratio of the incineration object is injected into the first stage combustion zone of the combustion melting furnace, and the amount of air obtained by adding a certain excess ratio to the remainder of the stoichiometric ratio is This is a method of supplying to the second stage combustion region. In this case, if the amount of combustion air in the second stage is insufficient, CO in the exhaust gas increases, and if it is excessive, NOx is generated. Therefore, adjust the amount of air in the second stage so that the oxygen concentration of the exhaust gas becomes a predetermined value. In order to suppress these occurrences.
[0003]
By the way, since the exhaust gas discharged | emitted from a combustion melting furnace is high temperature and dust, such as dust, is contained in high concentration, the oxygen concentration of exhaust gas cannot be measured directly at the exit of a combustion melting furnace. Therefore, conventionally, exhaust gas is sampled in a low temperature region such as a waste heat boiler that recovers the heat of exhaust gas discharged from a combustion melting furnace and downstream of a dust collector that collects dust in the exhaust gas. The exhaust gas that has been subjected to temperature reduction and dust removal is led to an oxygen concentration meter to measure the exhaust gas oxygen concentration.
[0004]
By the way, the exhaust gas from the various equipment (waste heat boiler, dust collector, exhaust gas purification device, etc.) provided between the combustion melting furnace and the exhaust gas sampling point is accumulated in the exhaust gas due to the operating negative pressure of the system. Therefore, the exhaust gas oxygen concentration measured on the downstream side of the dust collector becomes higher than the exhaust gas oxygen concentration at the combustion melting furnace outlet.
[0005]
Therefore, the target value or target range (hereinafter simply referred to as target value) corresponding to the measured value of the exhaust gas oxygen concentration must be set higher in consideration of the leaked air amount. It is not always easy to properly estimate.
[0006]
Therefore, conventionally, the exhaust gas oxygen concentration on the downstream side of the dust collector is held and controlled to the target value set by estimating the amount of air leaked, and the NOx concentration of the exhaust gas is measured, and the measured NOx concentration is determined in advance. It has been proposed to increase or decrease the target value of the exhaust gas oxygen concentration when it deviates from the set range (Patent Document 2). That is, there is a positive correlation between the NOx concentration of the exhaust gas and the oxygen concentration at the combustion melting furnace outlet, and the NOx concentration of the exhaust gas does not vary with the amount of leaked air. I can know. Furthermore, it has been proposed to detect the negative pressure of a device in which air may leak, calculate the amount of leaked air based on the detected value, and correct the oxygen concentration measured downstream ( Patent Document 2).
[0007]
[Patent Document 1]
JP-A-3-63407 [Patent Document 2]
Japanese Patent Laid-Open No. 2002-221308
[Problems to be solved by the invention]
However, since the leaked air is not only leaked into the exhaust gas due to the operating negative pressure of the component equipment, but the air is mixed into the exhaust gas due to the type and operating mode of the equipment. However, appropriate combustion control cannot always be performed. For example, the air that leaks due to the type of equipment and the operation mode, such as the amount of leaked air mixed in the exhaust gas, by the backwash air of the bag filter type dust collector is not simply determined according to the negative pressure.
[0009]
It is an object of the present invention to provide a combustion control method and apparatus that appropriately sets a target value of exhaust gas oxygen concentration that accurately considers the amount of air that leaks.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention burns a pyrolysis gas generated by pyrolyzing waste and a combustible substance of the pyrolysis residue, and at least a part of the non-combustible substance contained in the pyrolysis residue. In controlling the combustion of the melting melting furnace, the exhaust gas oxygen concentration downstream of the dust bag filter that collects the fly ash of the exhaust gas discharged from the combustion melting furnace is measured, and the measured value is held at the target value. In the combustion control method for controlling the amount of combustion air in the combustion melting furnace as described above, the air flowing into the exhaust gas flow path system from the combustion melting furnace to the exhaust gas flow rate measurement point downstream of the dust bag filter and the exhaust gas flow rate measurement point A reference value of the exhaust gas oxygen concentration at the outlet of the combustion melting furnace using the measured value of the exhaust gas flow rate, the measured value of the leaked air amount, and the measured value of the exhaust gas oxygen concentration. Dust removal Baghoff It converted to an exhaust gas oxygen concentration at the measurement point downstream of the exhaust gas oxygen concentration filter, and sets the converted value as the target value of the exhaust gas oxygen concentration.
[0011]
According to the combustion control method of the present invention, the exhaust gas oxygen concentration at the outlet of the combustion melting furnace is measured using the measured value of the exhaust gas flow rate, the measured value of the leaked air amount, and the measured value of the exhaust gas oxygen concentration downstream of the dust bag filter. Since the reference value is converted into the exhaust gas oxygen concentration at the control point, by setting the converted value as the target value of the exhaust gas oxygen concentration, it is possible to control the combustion air appropriately considering the amount of leaked air .
[0012]
Here, the leaked air is circulated through the air heater through the air heater to be heated to be purged by the air heater that heats the air by the exhaust gas discharged from the combustion melting furnace, and the exhaust gas downstream of the exhaust gas flow rate measurement point. Reducing the temperature of the exhaust gas discharged from the waste heat boiler and the ambient air leaking from the damper of the ash discharger of the waste heat boiler that recovers the heat of the exhaust gas discharged from the air heater and the heat of the exhaust gas discharged from the air heater At least one of air included in spray water sprayed into the exhaust gas in the tower and backwash air of the dust bag filter can be included.
[0013]
In this case, in the case of equipment that makes it difficult to measure the amount of leaked air in real time (for example, a waste heat boiler, a temperature-decreasing tower, a dust removal bag filter, etc.), instead of the measured value of the amount of leaked air, Measurement values that are measured and set in advance for each device constituting the road system can be used.
[0014]
Further, it is preferable to measure the NOx concentration of the exhaust gas downstream of the dust bag filter and correct the target value of the exhaust gas oxygen concentration when the measured NOx concentration deviates from a predetermined setting range. According to this, the amount of combustion air can be controlled more appropriately.
[0015]
Further, the exhaust gas treatment apparatus of the present invention comprises a combustion melting furnace that burns the pyrolysis gas generated from the pyrolysis reactor and the combustible material of the pyrolysis residue to melt at least a part of the incombustible material of the pyrolysis residue, An air heater that heats air with the exhaust gas discharged from the combustion melting furnace, a waste heat recovery device that recovers the heat of the exhaust gas discharged from the air heater, and collecting fly ash contained in the exhaust gas A dust-removing bag filter, an induction fan for sucking exhaust gas discharged from the dust-removing bag filter and discharging it to the atmosphere, and returning a part of the exhaust gas discharged from the induction fan to the inlet-side flow path of the air heater An exhaust gas circulation path, an exhaust gas oxygen concentration meter that measures the exhaust gas oxygen concentration at the outlet of the dust bag filter, and the combustion solution so that the measured value of the exhaust gas oxygen concentration measured by the exhaust gas oxygen concentration meter is maintained at a target value. An exhaust gas flow meter for measuring an exhaust gas flow rate downstream of the dust bag filter, a circulating exhaust gas flow meter for measuring a circulating exhaust gas flow rate in the exhaust gas circulation path, and the air A purge air flow meter for measuring the flow rate of air purged by the heater, and the combustion control means includes a measured value of the exhaust gas flow meter, a measured value of the circulating exhaust gas flow meter, and a purge air flow meter. Exhaust gas oxygen concentration at the outlet of the combustion melting furnace using measured values, setting data of leaked air amount of the waste heat boiler, the temperature reducing tower, and the dust removal bag filter, and measured values of the exhaust gas oximeter Is converted into an exhaust gas oxygen concentration at a measurement point of exhaust gas oxygen concentration downstream of the dust bag filter, and the converted value is set as the target value of the exhaust gas oxygen concentration. To.
[0016]
In this case, a demineralization bag filter for adding and treating a desalting agent to the exhaust gas discharged from the dust removal bag filter, the exhaust gas flow meter measures the exhaust gas flow rate discharged from the desalination bag filter, The exhaust gas oxygen concentration meter can measure an exhaust gas oxygen concentration downstream of the induction blower.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an overall configuration diagram of an embodiment of a combustion melting type waste treatment apparatus to which a combustion control method of the present invention is applied. The combustion melting furnace 1 is charged with at least a part of waste pyrolysis gas, pyrolysis residue combustible, and pyrolysis residue incombustible material pyrolyzed by a pyrolysis reactor (not shown). It has become. The pyrolysis residue discharged from the pyrolysis reactor is supplied to the combustion melting furnace 1 after undergoing cooling, fractionation, and pulverization processes. The exhaust gas discharged from the combustion melting furnace 1 is guided to the air heater 2 where the air is heated. The high temperature air heated by the air heater 2 is used as a heat source of a pyrolysis reactor (not shown). The exhaust gas discharged from the air heater 2 is guided to the waste heat boiler 4, and the heat of the exhaust gas is recovered as water vapor. The exhaust gas that has passed through the waste heat boiler 4 is guided to the temperature reducing tower 5 where water is sprayed to reduce the temperature. The exhaust gas whose temperature has been reduced is guided to the dust bag filter 6 and the fly ash contained in the exhaust gas is collected. After the desalting agent to be pneumatically transported is added to the exhaust gas discharged from the dust bag filter 6, it is guided to the desalting bag filter 7 to remove chlorine and sulfur in the exhaust gas. The secondary side exhaust gas from the desalting bag filter 7 is sucked by the induction blower 8 and discharged to the atmosphere through a chimney (not shown). Part of the exhaust gas discharged from the induction blower 8 is supplied to the inlet-side flow path of the air heater 2 through the exhaust gas circulation flow path 10 having the exhaust gas circulation blower 9.
[0018]
The combustion melting furnace 1 includes a burner 11 provided at the top, a plurality of first air nozzles 12 provided on a furnace wall below the burner 11, and a furnace wall below the air nozzle 12 in a furnace height direction. A plurality of second air nozzles 13 provided in two stages are provided. Secondary air and tertiary air are supplied from the second air nozzle 13 via the combustion air amount control valve 14. The space from the burner 11 to the second air nozzle 113 is referred to as a first combustion zone or combustion chamber, and the downstream side of the second air nozzle 13 is referred to as a second combustion zone or combustion chamber. . Moreover, the molten slag discharge port 15 provided in the bottom of the furnace is opened at a position below the water surface of a water tank (not shown) so that the molten slag is discharged into the water.
[0019]
The air heater 2 is formed by arranging a plurality of heat transfer tubes in a flue through which exhaust gas flows, and heats the air by passing air 21 from a blower (not shown) through the heat transfer tubes. Air 22 is supplied to the above-described pyrolysis reactor. The air heater 2 discharges (purifies) a certain amount of air from the heat transfer tube into the flue to reduce high temperature corrosion of the heat transfer tube. Moreover, since the melting combustion furnace 1 carries out high temperature combustion (for example, 1200-1300 degreeC) in order to produce | generate molten slag, waste gas temperature is also high temperature. If the high-temperature exhaust gas is introduced to the air heater 2 as it is, the air heater 2 may be damaged. Therefore, the temperature of the exhaust gas is reduced by flowing low-temperature circulating exhaust gas into the inlet of the air heater 2 through the exhaust gas circulation path 10.
[0020]
Fly ash that has settled to the bottom of the waste heat boiler 4 is accumulated in a hopper and discharged by an ash discharger (not shown). Further, the fly ash collected on the filter cloth surface of the dust removal bag filter 6 is dropped into the bottom hopper by jetting pulsed backwash air and discharged by an ash discharger (not shown). It has become. Similarly, the desalting agent and the reaction product adhering to the filter cloth surface of the desalting bag filter 7 are dropped into the bottom hopper by jetting pulsed backwash air, and are removed by an ash discharger (not shown). It is supposed to be discharged.
[0021]
Next, the control of the combustion air amount according to the feature of the present embodiment will be described in detail. The combustion air amount control system is divided into a primary air control system for the first combustion chamber and a second and third air control system for the second combustion chamber. The primary air control system is a system that controls the amount of air supplied to the burner 11 and the first air nozzle 10, and the primary combustion air amount is a stoichiometric ratio determined in advance according to the amount of the incineration object. The amount of primary combustion air is corrected and controlled so that less than the amount of air is introduced and the temperature of the first combustion zone is maintained within a predetermined temperature range, but the description is omitted in FIG. The second and third air control systems for the second combustion chamber control the combustion air amount control valve 14 provided in the system for supplying air to the second air nozzle 13 and the combustion air amount control valve 14. A combustion control device 30 is provided.
[0022]
The combustion control device 30 includes a computing unit 30a that sets a target value SVz of the outlet exhaust gas oxygen concentration of the dust removal bag filter 6, and the set target value SVz and the exhaust gas oxygen concentration provided in the outlet side flow path of the dust removal bag filter 6. Based on the measured value PVz measured by the total 31, it has an arithmetic unit 30 b that executes a control calculation such as PID. The calculator 30 a includes an exhaust gas flow rate Qo measured by an exhaust gas flow meter 32 provided in the outlet side flow path of the desalting bag filter 8, and an exhaust gas oximeter 33 provided in the outlet side flow path of the induction blower 8. The measured value A of the exhaust gas oxygen concentration measured by is input. In addition, a leakage air amount (purge air amount) Qp which is a difference between the inlet air flow rate and the outlet air flow rate measured by the inlet air flow meter 34 and the outlet air flow meter 35 of the air heater 2, respectively, and the air heater The circulation exhaust gas flow rates Qj1 and Qj2 measured by the circulation exhaust

gas flow meters

36 and 37 provided in the two inlet-side flow paths are input. Further, the combustion control device 30 is provided with a database 30c, and the database 30 measures in advance the reference value SVt of the exhaust gas oxygen concentration, the amount of air leaking into the waste heat boiler 4, the temperature reducing tower 5, and the dust removal bag filter 6. Data such as the total set value Qa of the leaked air amount obtained in this manner and the set value Qd of the leaked air amount obtained by measuring in advance the amount of air leaking into the desalting bag filter 7 are stored.
[0023]
Here, the material balance between the exhaust gas flow rate and the leakage air amount of the main part of the waste treatment apparatus of FIG. 1 is shown in FIG. 2, and the meaning and unit of each symbol will be described next.
[0024]
Q1 [m ³ N / h (dry)]: exhaust gas flow rate at the outlet of the combustion melting furnace (conceptual value)
Qo [m ³ N / h (wet)]: Exhaust gas flow rate Qj [m ³ N / h (wet)] measured by the exhaust gas flow meter 32 at the desalting bag filter outlet: Measured by the circulating exhaust

gas flow meters

36 and 37 Total amount Qp [m ³ N / h (dry)] of circulating exhaust gas flow rates Qj1, Qj2: Air heater leakage air amount (purge air amount = difference between measured values of inlet air amount and outlet air amount)
Qa [m ³ N / h (dry)]: The amount of air leaking from the waste heat boiler 4, the temperature reducing tower 5 and the dust bag filter 6 into the exhaust gas flow path system (from the ash discharger damper of the waste heat boiler and dust bag filter) Pre-measured setting values such as air leakage amount, temperature reduction tower spray spray air amount, activated carbon spray air amount, dust removal bag filter backwash air amount, etc.)
Qd [m ³ N / h (dry)]: Leakage air amount of desalting bag filter (desalted agent spray air amount, set value obtained by measuring backwash air amount in advance)
SVt [%, dry]: Reference value SVz [%, wetness] of exhaust gas oxygen concentration at the exit of the combustion melting furnace: Target value PVz [%, wetness] of exhaust gas oxygen concentration at the dust removal bag filter outlet: Exhaust gas oxygen at the dust removal bag filter outlet Measured value A of the densitometer 31 [%, dry]: Measured value w of the exhaust gas oximeter 33 at the outlet of the desalting bag filter w [Dimensionless]: Moisture content of the exhaust gas (preset value measured)
Accordingly, the target value SVz of the exhaust gas oxygen concentration at the dust removal bag filter outlet can be expressed by the following equation (1).
[0025]
[Expression 1]

Here, (1-w) is a coefficient converted to the amount of dry exhaust gas. “21” is the content (%) of oxygen contained in the air. In Equation 1, when Q1 is not measured and expressed in other exhaust gas amounts, Equation 1 becomes Equation 2 below.
[0026]
[Expression 2]

The computing unit 30a converts the exhaust gas oxygen concentration reference value SVt at the outlet of the combustion melting furnace into the exhaust gas oxygen concentration at the dust removal bag filter outlet according to Equation 2, and sets the converted value as the target value SVz. The calculator 30b calculates the difference between the measured value PVz of the exhaust gas oximeter 31 and the target value SVz, and reduces the difference by, for example, the command value Fa * of the secondary and tertiary combustion air amounts by PID calculation. Is output to the combustion air amount control valve 14. As a result, combustion air in an amount corresponding to the command value Fa * is supplied from the combustion air amount control valve 14 to the secondary combustion region of the combustion melting furnace 1 through the air nozzle 13.
[0027]
Therefore, according to the present embodiment, the amount of air leaking into the exhaust gas from the air heater 2, the waste heat boiler 4, the temperature reducing tower 5, the dust removal bag filter 6, the desalination bag filter 7, and the exhaust gas circulation path 10 is appropriately set. In consideration, the target value SVz of the exhaust gas oxygen concentration at the outlet of the dust removal bag filter corresponding to the reference value SVt of the exhaust gas oxygen concentration at the outlet of the combustion melting furnace 1 can be set. As a result, the amount of combustion air in the combustion melting furnace can be appropriately controlled, and the exhaust gas oxygen concentration in the combustion melting furnace can be maintained at the reference value SVt, so that the CO concentration and NOx concentration of the exhaust gas can be managed appropriately. .
(Second Embodiment)
In the first embodiment, the exhaust gas flow meter 32 is provided in the outlet flow path of the desalting bag filter 7. However, the exhaust gas flow meter 32 is provided in the outlet flow path of the dust removal bag filter 6, and the exhaust gas flow rate Q2 [m ^{3] at the} dust removal bag filter outlet. N / h (wetness)] may be measured. The target value SVz of the exhaust gas oxygen concentration in this case can be expressed by the following equation (3).
[0028]
[Equation 3]

(Third embodiment)
In the embodiment of FIG. 1, the oxygen concentration meter 33 for the circulating exhaust gas is provided, but this is omitted, and the measured value PVz of the exhaust gas oxygen concentration meter 31 is used to measure the measured value of the circulating exhaust gas oxygen concentration by the following equation (4). A may be calculated.
[0029]
[Expression 4]

(Fourth embodiment)
In the present embodiment, as shown in FIG. 3, a NOx concentration meter 34 that measures the NOx concentration of the exhaust gas at the outlet of the dust removal bag filter 6 is provided, and the NOx concentration NOx measured thereby is calculated by a calculator 30 d of the combustion control device 30. Is entered. When the input NOx concentration deviates from the upper limit value H and the lower limit value L of the predetermined setting range, the arithmetic unit 30 adds a correction signal ΔS that corrects the target value SVz of the exhaust gas oxygen concentration by a certain amount. To 30e. The adder 30e adds or subtracts the correction signal ΔS to the target value SVz of the exhaust gas oxygen concentration output from the calculator 30a, and outputs the target value SV′z to the calculator 30b.
[0030]
That is, there is a positive correlation between the NOx concentration of the exhaust gas and the oxygen concentration at the outlet of the combustion melting furnace 1, and the NOx concentration of the exhaust gas does not vary with the amount of leaked air. Therefore, since the oxygen concentration at the outlet of the combustion chamber can be roughly known from the NOx concentration, the amount of combustion air can be controlled more appropriately by correcting the target value SVz of the exhaust gas oxygen concentration based on fluctuations in the NOx concentration. Note that the fixed amount of the correction signal ΔS related to the increase / decrease correction may be set to a different value in the increasing direction and the decreasing direction.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to appropriately set the target value of the exhaust gas oxygen concentration in consideration of the amount of leaked air.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of a waste treatment apparatus to which a combustion control method of the present invention is applied.
FIG. 2 is a diagram showing a material balance between the exhaust gas flow rate and the amount of leaked air in the main part of the waste treatment apparatus of FIG. 1;
FIG. 3 is an overall configuration diagram of another embodiment of a waste treatment apparatus to which the combustion control method of the present invention is applied.
[Explanation of symbols]
1 Combustion melting furnace 2 Air heater 3? ? ? ?
4 Waste Heat Boiler 5 Temperature Reduction Tower 6 Dust Removal Bug Filter 7 Desalination Bag Filter 8 Induction Blower 10 Exhaust Gas Circulation Path 14 Combustion Air Volume Control Valve 30 Combustion Control Device 30a, b Calculator 30c Database 31 Exhaust Gas Oxygen Meter 32 Exhaust Gas Flow Meter 33 Exhaust gas oxygen concentration meter 34 Inlet air flow meter 35 Outlet

air flow meter

36, 37 Circulating exhaust gas flow meter

Claims

In controlling combustion of a combustion melting furnace that burns pyrolysis gas generated by pyrolyzing waste and combustible residue of pyrolysis residue and melts at least a part of incombustible substance contained in the pyrolysis residue. Measure the exhaust gas oxygen concentration downstream of the dust bag filter that collects the fly ash of the exhaust gas discharged from the combustion melting furnace, and set the combustion air amount of the combustion melting furnace to keep the measured value at the target value. In the combustion control method to control,
The exhaust gas flow rate downstream of the dust bag filter and the amount of air leaking into the exhaust gas flow path system from the combustion melting furnace to the measurement point of the exhaust gas flow rate are measured, and the measured value of the exhaust gas flow rate and the leaked air Using the measured value of the amount and the measured value of the exhaust gas oxygen concentration, the reference value of the exhaust gas oxygen concentration at the outlet of the combustion melting furnace is converted into the exhaust gas oxygen concentration at the measurement point of the exhaust gas oxygen concentration downstream of the dust bag filter Then, the conversion value is set as the target value of the exhaust gas oxygen concentration.

2. The combustion control method according to claim 1, wherein the measured value of the amount of leaked air includes a measured value set in advance for each device constituting the exhaust gas flow path system.

The leaked air is circulated to the air heater through heated air purged by an air heater that heats the air using exhaust gas discharged from the combustion melting furnace, and exhaust gas downstream of the exhaust gas flow rate measurement point. The air in the circulating exhaust gas, the ambient air that leaks into the waste heat boiler that recovers the heat of the exhaust gas discharged from the air heater, and the spray water of the temperature-decreasing tower that cools the exhaust gas discharged from the waste heat boiler The combustion control method according to claim 1, further comprising at least one of air contained in the air and backwash air of the dust bag filter.

The NOx concentration of the exhaust gas is measured, and when the measured NOx concentration deviates from a predetermined setting range, the target value of the exhaust gas oxygen concentration is corrected to increase or decrease. The combustion control method described in 1.

A combustion melting furnace for combusting a pyrolysis gas generated from a pyrolysis reactor and a combustible material of the pyrolysis residue to melt at least a part of the incombustible material of the pyrolysis residue, and an exhaust gas discharged from the combustion melting furnace An air heater that heats air, a waste heat recovery device that recovers heat of exhaust gas discharged from the air heater, a dust removal bag filter that collects fly ash contained in the exhaust gas, and the dust removal bug filter An induction blower that sucks exhaust gas discharged from the atmosphere and discharges it to the atmosphere, an exhaust gas circulation path for returning a part of the exhaust gas discharged from the induction blower to the inlet-side flow path of the air heater, and the dust removal bag filter outlet An exhaust gas oxygen concentration meter that measures the exhaust gas oxygen concentration, and a combustion control system that controls the amount of combustion air in the combustion melting furnace so that the measured value of the exhaust gas oxygen concentration measured by the exhaust gas oxygen concentration meter is maintained at a target value. In waste disposal and means,
An exhaust gas flow meter for measuring an exhaust gas flow rate downstream of the dust bag filter, a circulating exhaust gas flow meter for measuring a circulating exhaust gas flow rate of the exhaust gas circulation path, and a purge air flow meter for measuring an air flow rate purged by the air heater And
The combustion control means includes a measured value of the exhaust gas flow meter, a measured value of the circulating exhaust gas flow meter, a measured value of the purge air flow meter, the waste heat boiler, the temperature reducing tower, and the dust bag filter. The reference value of the exhaust gas oxygen concentration at the outlet of the combustion melting furnace is used as the exhaust gas at the measurement point of the exhaust gas oxygen concentration downstream of the dust bag filter using the setting data of the leaked air amount and the measured value of the exhaust gas oximeter A waste treatment apparatus that converts to an oxygen concentration and sets the converted value as the target value of the exhaust gas oxygen concentration.

A demineralization bag filter for adding a desalting agent to the exhaust gas discharged from the dust removal bag filter and processing the exhaust gas flow meter, measuring the exhaust gas flow rate discharged from the demineralization bag filter; and the exhaust gas oxygen concentration The waste treatment apparatus according to claim 5, wherein the meter measures an exhaust gas oxygen concentration downstream of the induction blower.

A NOx concentration meter that measures the NOx concentration of the exhaust gas discharged from the dust bag filter is provided, and when the measured value of the NOx concentration measured by the NOx concentration meter deviates from a predetermined setting range, the exhaust gas oxygen concentration The waste processing apparatus according to claim 5, wherein the target value is corrected to increase or decrease.