JP3548994B2

JP3548994B2 - Control method and apparatus for gasification melting processing plant

Info

Publication number: JP3548994B2
Application number: JP37317099A
Authority: JP
Inventors: 裕一宮本; 英隆宮崎; 博藤山; 健一左近; 章夫東; 正人林; 泰充黒崎
Original assignee: Kawasaki Jukogyo KK
Current assignee: Kawasaki Motors Ltd
Priority date: 1999-12-28
Filing date: 1999-12-28
Publication date: 2004-08-04
Anticipated expiration: 2019-12-28
Also published as: JP2001182925A

Description

【０００１】
【発明の属する技術分野】
本発明は、都市ごみ、産業廃棄物等のごみを還元雰囲気で熱分解を行い、発生した可燃ガスを高温で燃焼させて熱回収を図るとともに、ごみ中の灰分を溶融しスラグ化するガス化溶融処理プラントの制御方法及び装置に関するものである。
【０００２】
【従来の技術】
近年のごみ処理における重要課題として、▲１▼ダイオキシン類等による環境汚染の防止、▲２▼最終処分場延命のための焼却残さの有効利用、▲３▼地球温暖化対策としての廃熱利用、▲４▼焼却コストの軽減、が挙げられている。
ガス化溶融処理技術は、ごみを還元雰囲気で熱分解を行い、発生した可燃ガスを高温で燃焼させて熱回収を図るとともに、ごみ中の灰分を溶融しスラグ化することから、焼却残さの安定化・減容化（減量化）・再資源化が可能となる他、ダイオキシン類等の大気汚染物質の低減や、熱回収効率、発電効率、経済性の向上に寄与するものであり、次世代ごみ処理技術として注目されている。
【０００３】
ガス化溶融処理の従来技術の一例として、特開平１０−１６９９４４号公報には、ごみ供給量やごみ質の変動に対し、空気比を一定範囲に調整し、流動層温度を５５０〜６５０℃になるように制御することにより、アルミニウム等の有価金属を確実に回収するとともに、熱分解ガスの組成を安定させ、溶融炉の燃焼を安定させる方法が記載されている。
【０００４】
【発明が解決しようとする課題】
ごみのガス化溶融では、燃料としてのごみの物理的・化学的性状が不均一であり、ごみの供給量や低位発熱量が変動し、これらの変動がごみのガス化溶融の安定性を阻害する外乱要因となる。具体的には、炉内に供給されたごみの含有水分比など低位発熱量が変動するため、燃焼時の発生熱量、ガス性状が変動する。また、給じん装置速度が一定であっても、ごみの性状、比容積などが不均一であるため、炉内に供給されるごみの重量流量が変動し、発生熱量、ガス量が変動する。このため、安定ガス化、安定溶融が困難となる。
ごみの変動外乱に対し、安定ガス化、安定溶融を確保するには、流動層温度、溶融炉温度の安定化が重要であるが、これらの状態量と主要操作量（ごみ供給量、流動空気量等）の間には相互干渉がみられるため、非干渉化が必要となる。
【０００５】
また、特開平１０−１６９９４４号公報に記載された方法には、以下のような問題点がある。
（１）ごみ供給量やごみ質の変動に対し、安定ガス化、安定溶融を実現するためには、流動層温度及び溶融炉温度の安定化が不可欠である。燃料であるごみの供給量や質の変動は総熱量の変動であり、空気比操作により流動層温度を安定化させるだけでは、溶融炉温度や廃熱ボイラの発生蒸気量等の安定化には限界がある。
（２）安定ガス化、安定溶融に重要な状態量である流動層温度、溶融炉温度と、主要操作量であるごみ供給量、流動空気量とは相互干渉系であり、相互干渉は閉ループを不安定化する可能性があるとともに、調節計の調整を難しくする傾向があり、非干渉化を考慮する必要がある。
【０００６】
本発明は上記の知見に基づき、上記の問題を解決するためになされたもので、本発明の目的は、流動床ガス化炉と溶融炉とを備えたガス化溶融処理プラントにおいて、流動層温度を流動空気量で制御し、溶融炉温度又は蒸気流量をごみ供給量にて制御し、さらに、ごみ供給量操作による流動層温度への干渉を相殺する非干渉器を設けることにより、流動層温度、溶融炉温度（及び発生蒸気量）を安定に保つことができ、安定したガス化溶融を実現することができる制御方法及び装置を提供することにある。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、本発明のガス化溶融処理プラントの制御方法は、ごみを給じん装置により流動床ガス化炉（部分燃焼炉）に供給して流動層内で還元性雰囲気で熱分解し、可燃性ガス及び未燃固形分（チャー、灰分等）を生成させ、流動床ガス化炉で生成した可燃性ガス及び未燃固形分を溶融炉で高温燃焼させて、未燃固形分中の灰分を溶融スラグとして回収すると同時にダイオキシン類を分解するようにしたガス化溶融処理プラントにおいて、流動層温度を流動空気量で制御し、溶融炉温度をごみ供給量で制御し、ごみ供給量操作による流動層温度への干渉を非干渉器での給じん装置速度に比例した流動空気量補正により相殺して、流動層温度及び溶融炉温度を安定化させるように構成されている（図１、図２参照）。
【０００８】
また、本発明のガス化溶融処理プラントの制御方法は、ごみを給じん装置により流動床ガス化炉（部分燃焼炉）に供給して流動層内で還元性雰囲気で熱分解し、可燃性ガス及び未燃固形分（チャー、灰分等）を生成させ、流動床ガス化炉で生成した可燃性ガス及び未燃固形分を溶融炉で高温燃焼させて、後段の廃熱ボイラで熱回収を図り蒸気を発生させるとともに、未燃固形分中の灰分を溶融スラグとして回収すると同時にダイオキシン類を分解するようにしたガス化溶融処理プラントにおいて、流動層温度を流動空気量で制御し、溶融炉温度又は蒸気流量をごみ供給量で制御し、ごみ供給量操作による流動層温度への干渉を非干渉器での給じん装置速度に比例した流動空気量補正により相殺して、流動層温度、溶融炉温度及び発生蒸気量を安定化させることを特徴としている。
【０００９】
本発明のガス化溶融処理プラントの制御装置は、給じん装置により流動層に投入されたごみを還元性雰囲気で熱分解して可燃性ガス及び未燃固形分（チャー、灰分等）を生成させる流動床ガス化炉（部分燃焼炉）と、流動床ガス化炉で生成した可燃性ガス及び未燃固形分を高温燃焼させて未燃固形分中の灰分を溶融スラグとして回収すると同時にダイオキシン類を分解する溶融炉とを備えたガス化溶融処理プラントにおいて、流動層温度制御が流動空気量の操作で行われる流動層温度制御手段と、溶融炉温度制御が給じん装置速度（ごみ供給量）の操作で行われる溶融炉温度制御手段と、給じん装置速度（ごみ供給量）の操作による流動層温度への干渉を給じん装置速度に比例した流動空気量補正により相殺する非干渉器とを設けたことを特徴としている（図１、図２参照）。
【００１０】
上記の本発明の装置において、溶融炉で発生する高温燃焼ガスから熱回収して蒸気を発生させる廃熱ボイラを備え、溶融炉温度制御手段の代わりに、蒸気流量制御が給じん装置速度（ごみ供給量）の操作で行われる発生蒸気量制御手段を設けた構成とすることができる。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態について説明するが、本発明は下記の実施の形態に何ら限定されるものではなく、適宜変更して実施することができるものである。図１は、本発明の実施の第１形態による制御方法を適用するごみガス化溶融処理プラントの構成を示している。また、図２は、本発明の実施の第１形態によるガス化溶融処理プラントの制御方法を実施する装置の概略構成を示している。
図１に示すように、流動床ガス化炉（部分燃焼炉）１０には、送風機（押込送風機等）１２により流動用空気が散気管１４に供給され、これにより、流動媒体（例えば、砂）が流動化され流動層１６が形成される。１８は、流動用空気の流量を調節するダンパである。なお、風箱に流動用空気を供給して空気分散板から噴出させ流動層を形成させる型式の流動床炉を用いることも勿論可能である。
この流動層１６に給じん装置（例えば、スクリューフィーダ等）２０から被焼却物であるごみ（都市ごみ、産業廃棄物等）が連続的に投入され、流動層１６内で空気比０．２〜０．３程度の還元性雰囲気でガス化され、熱分解ガス（可燃性ガス）、未燃固形分（チャー、灰分等）となる。２２は起動バーナであり、制御弁２４で流量調整された燃料及び空気が供給されて部分燃焼炉を起動させる。
【００１２】
流動床ガス化炉（部分燃焼炉）１０に投入されるごみ量は給じん装置（スクリューフィーダ等）２０の回転数を調節することにより増減できるようになっている。なお、流動層温度は、アルミニウムの融点（６６０℃）以下で鉄、アルミニウム等の金属を未酸化状態で回収するため、また、ガス化反応速度が緩慢になる低温度とし、ごみの変動外乱による入熱変動を均質化するためから、５００〜６００℃で運転する。鉄、アルミニウム等の金属を含む不燃物は、不燃物排出装置２６により流動層下部から抜き出される。２８は、流動媒体から熱回収する伝熱管であり、３０は、流動層に水を噴霧して熱分解ガス温度や流動層温度を調整する水噴射手段である。
【００１３】
流動床ガス化炉（部分燃焼炉）１０で生成した熱分解ガス、未燃固形分は溶融炉３２にて、１３００〜１４００℃の高温で燃焼させ、灰分を溶融スラグとして回収すると同時にダイオキシン類を分解する。
溶融炉３２は旋回溶融炉となっており、予燃焼器３４、旋回溶融炉３６で構成されている。予燃焼器３４には送風機３８により、燃焼用空気を空気予熱器４０により３００〜４００℃程度に予熱し供給する。４２は、溶融炉空気の流量を調節するダンパである。また、４４は起動バーナであり、起動時には制御弁４６で流量調整された助燃燃料が供給されて起動される。旋回溶融炉３６では、予燃焼器３４から接線方向で流入した高温ガスが強旋回され、含まれる溶融スラグが水冷セルフコーティング方式の炉壁に捕捉、除去され、スラグ流下口４８よりスラグ冷却設備５０へ導入され、水冷スラグとして回収される。５２はスラグ搬出コンベアである。
【００１４】
溶融炉３２からの高温排ガスは、冷却塔５４に導入されて冷却される。さらに、冷却塔５４の下流側（上部）には、送風機３８により冷却用空気が供給される。６０は、冷却用空気の流量を調節するダンパである。また、６２は、冷却塔に水を噴霧して排ガスを冷却する水噴射手段である。
冷却塔５４で冷却された排ガスは、ガス冷却室６４に導入され、さらに冷却される。ガス冷却室６４には、水噴射手段６６により冷却用の水が噴霧される。６８は制御弁であり、水の噴射量を調節してガス冷却室出口の排ガス温度を調整する。所定温度に冷却された排ガスは、空気予熱器４０を通って冷却され、後段のバグフィルタ等の集塵器（図示せず）で浄化処理される。
【００１５】
ごみのガス化溶融では、燃料としてのごみの物理的・化学的性状が不均一であることが特徴として挙げられる。このため、つぎのような燃焼変動がみられる。
（１）炉内に供給されたごみの含有水分比など低位発熱量が変動するため、燃焼時の発生熱量、ガス性状が変動する。
（２）給じん装置速度が一定であっても、ごみの性状、比容積などが不均一であるため、炉内に供給されるごみの重量流量が変動し、発生熱量、ガス量が変動する。
これらの変動がごみのガス化溶融の安定性を阻害する外乱要因となる。
【００１６】
つぎに、ごみの低位発熱量やごみ供給量の変動等、外乱が燃焼に及ぼす影響を定量的に把握するため、部分燃焼炉（流動床ガス化炉）、旋回溶融炉の動特性数式モデルを作成し、感度解析を実施した。ごみの含有水分比変化によるごみ低位発熱量変化、ごみ供給量変化、流動空気量変化を与えた感度解析結果を表１に示す。感度解析結果のとおり、低位発熱量変動、ごみ供給量変動、流動空気量変化は、流動層温度、溶融炉温度、排ガスＯ_２濃度など、安定ガス化、安定溶融に重要な状態量への感度に特性差があり、これらの特性差のある外乱の吸収が必須である。
【００１７】
【表１】

【００１８】
ガス化溶融の運転制御では、ごみ変動外乱が低位発熱量変動依存であるか、ごみ供給量変動依存かにより、制御系を構成する必要がある。例えば、ごみ変動外乱がごみの含有水分比の変動による低位発熱量変動の場合、表１の感度解析結果に示すように溶融炉温度の変動が大きく、流動層温度への影響は小さい。一方、ごみ変動外乱がごみ供給量のみの変動による場合、表１に示すように溶融炉温度変動に加えて流動層温度も変動する。また、流動空気量操作を行った場合、流動層温度への影響が大きく、溶融炉温度の影響は小さい。
この感度解析結果より、制御系統は、図２に示すように、流動層温度制御は流動空気量操作にて、また、溶融炉温度制御はごみ供給量（給じん装置速度）操作にて構成するのがよい。しかし、ごみ供給量操作の流動層温度への影響が小さくなく、この干渉を非干渉器にて相殺するようにして、非干渉制御系を構成する必要がある。
【００１９】
図２に示すように、流動層温度の制御を流動空気量の操作で行う流動層温度制御装置７０と、溶融炉温度の制御を給じん装置速度（ごみ供給量）の操作で行う溶融炉温度制御装置７２とを設け、さらに、給じん装置速度（ごみ供給量）の操作による流動層温度への干渉を流動空気量補正により相殺する非干渉器７４を設けた構成とする。なお、図２では、図１で用いている符号と同じ符号を使用している。７６は、給じん装置（スクリューフィーダ等）のモータであり、７８は、流動空気量操作指示を流動空気量補正指示にて相殺を図るのに用いる演算器である。溶融炉温度制御装置７２からの給じん装置速度指令値（モータの回転数）がモータ７６に送られてごみ供給量が操作される。また、流動層温度制御装置７０からの流動空気量操作指示（ダンパの開度）がダンパ１８に送られて流動空気量が操作される。このとき、ごみ供給量操作の流動層温度への干渉を非干渉器７４からの流動空気量補正指示にて相殺を図り、流動層温度制御による流動空気量操作指示の安定性を保つようにする。
【００２０】
例えば、図３に示すように、ごみの変動外乱がごみ供給量のみの変動であれば、ごみ供給量補正を主とした操作で対応すべきであるが、図３の非干渉制御なしの場合は流動層温度制御による流動空気量操作が行われるため、ガス量やＯ_２濃度等の変動が避けられない。一方、非干渉器を給じん装置速度に比例した流動空気量補正とすれば、流動層温度制御による流動空気量操作指示を、ごみ供給量操作に伴う空気比相当分の流動空気量補正指示にて相殺を図れ、非干渉化を実現できる（図３参照）。
非干渉制御なしの場合に同様の効果を得るためには、流動層温度制御をゆるく（ＰＩＤ制御の場合であれば、ゲインを小さく）すれば、同様にごみ供給量補正を主とした操作で対応できるが、図４に示すように、ごみ変動外乱が含有水分比のみの変動であれば、流動層温度の変動が大きくなり安定運転が実現できなくなる（図４参照）。
このように非干渉制御を用いることにより、流動層温度、溶融炉温度を安定化させることができるとともに、それぞれの制御ループの調整のみで安定性が決定されるため、調整を容易にすることができる。
【００２１】
なお、本実施の形態においては、溶融炉の後流側に、溶融炉で発生する高温燃焼ガスから熱回収して蒸気を発生させる廃熱ボイラを設けた構成とすることができる。この場合は、流動層温度制御は流動空気量操作にて、また、蒸気流量制御はごみ供給量（給じん装置速度）操作にて構成するのがよい。
また、部分燃焼炉からの未燃固形分を含む熱分解ガスを、サイクロン等の固気分離器で熱分解ガスと未燃固形分とに分離し、熱分解ガスをボイラに供給し、未燃固形分を溶融炉に供給するという構成のガス化溶融処理プラントの場合も、本発明の制御方法を適用することが可能である。
【００２２】
【発明の効果】
本発明は上記のように構成されているので、つぎのような効果を奏する。
（１）ごみのガス化溶融において、流動層温度、溶融炉温度（及び蒸気流量）を安定に保つことができ、安定ガス化、安定溶融（さらには、安定した熱回収）を実現できる。
（２）ごみのガス化溶融において、流動層温度制御と溶融炉温度制御（又は蒸気流量制御）の相互干渉を抑え、閉ループでの安定性を向上させるとともに、調整を容易にすることができる。
（３）非干渉器での非干渉制御を、給じん装置速度に比例した流動空気量補正とすれば、流動層温度制御による流動空気量操作指示を、ごみ供給量操作に伴う空気比相当分の流動空気量補正指示にて相殺を図れ、非干渉化を実現できる。
【図面の簡単な説明】
【図１】本発明の実施の第１形態による制御方法を適用するガス化溶融処理プラントの一例を示す系統的概略構成説明図である。
【図２】本発明の実施の第１形態によるガス化溶融処理プラントの制御方法を実施する装置を示す概略構成図である。
【図３】ごみ供給量をステップ変化させたときの非干渉制御を行った場合と行わない場合の状態量、操作量の経時変化を示すグラフである。
【図４】ごみ低位発熱量をステップ変化させたときの非干渉制御を行った場合と行わない場合の状態量、操作量の経時変化を示すグラフである。
【符号の説明】
１０流動床ガス化炉（部分燃焼炉）
１２、３８送風機
１４散気管
１６流動層
１８、４２、６０ダンパ
２０給じん装置
２２、４４起動バーナ
２４、４６、６８制御弁
２６不燃物排出装置
２８伝熱管
３０、６２、６６水噴射手段
３２溶融炉
３４予燃焼器
３６旋回溶融炉
４０空気予熱器
４８スラグ流下口
５０スラグ冷却設備
５２スラグ搬出コンベア
５４冷却塔
６４ガス冷却室
７０流動層温度制御装置
７２溶融炉温度制御装置
７４非干渉器
７６モータ
７８演算器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is to gasify wastes such as municipal waste and industrial waste by pyrolysis in a reducing atmosphere, combustible gas generated at high temperature to recover heat, and melt ash in the waste to form slag. The present invention relates to a method and an apparatus for controlling a melt processing plant.
[0002]
[Prior art]
Important issues in waste management in recent years are: (1) prevention of environmental pollution by dioxins, etc., (2) effective use of incineration residues to extend the life of final disposal sites, (3) use of waste heat as a measure against global warming, (4) Reduction of incineration costs.
Gasification and melting treatment technology decomposes refuse in a reducing atmosphere, burns the combustible gas generated at high temperature to recover heat, and melts ash in refuse to form slag, thereby stabilizing incineration residues. In addition to being able to reduce, reduce (reduce) volume, and recycle resources, it contributes to reducing air pollutants such as dioxins and improving heat recovery efficiency, power generation efficiency, and economic efficiency. It is attracting attention as a waste treatment technology.
[0003]
As an example of the conventional technology of the gasification melting treatment, Japanese Patent Application Laid-Open No. 10-169944 discloses that the air ratio is adjusted to a certain range with respect to the change in the amount of waste and the quality of the waste, and the temperature of the fluidized bed is set to 550 to 650 ° C. A method is described in which a valuable metal such as aluminum is reliably recovered by controlling so that the composition of a pyrolysis gas is stabilized, and the combustion of a melting furnace is stabilized.
[0004]
[Problems to be solved by the invention]
In gasification and melting of refuse, the physical and chemical properties of refuse as fuel are not uniform, and the amount of refuse supplied and the lower heating value fluctuate, and these fluctuations hinder the stability of refuse gasification and melting. It becomes a disturbance factor. Specifically, since the lower heating value such as the moisture content ratio of the refuse supplied into the furnace fluctuates, the amount of heat generated during combustion and the gas properties fluctuate. In addition, even if the dust feeder speed is constant, since the properties and specific volume of the refuse are not uniform, the weight flow rate of the refuse supplied to the furnace fluctuates, and the amount of generated heat and the amount of gas fluctuate. For this reason, stable gasification and stable melting become difficult.
Stabilization of fluidized bed temperature and melting furnace temperature is important to ensure stable gasification and stable melting against fluctuation disturbance of garbage, but these state quantities and main operation quantities (garbage supply amount, flowing air , Etc.), mutual interference is observed, so that decoupling is required.
[0005]
The method described in Japanese Patent Application Laid-Open No. 10-169944 has the following problems.
(1) Stabilization of fluidized bed temperature and melting furnace temperature is indispensable in order to realize stable gasification and stable melting in response to fluctuations in waste supply amount and waste quality. Fluctuations in the supply amount and quality of the refuse, which is the fuel, are fluctuations in the total amount of heat, and simply stabilizing the fluidized bed temperature by operating the air ratio is not enough to stabilize the melting furnace temperature and the amount of steam generated by the waste heat boiler. There is a limit.
(2) Fluidized bed temperature and melting furnace temperature, which are important quantities for stable gasification and stable melting, and refuse supply and flowing air, which are the main operation quantities, are mutual interference systems. In addition to the possibility of instability, adjustment of the controller tends to be difficult, and it is necessary to consider decoupling.
[0006]
The present invention has been made to solve the above problems based on the above findings, and an object of the present invention is to provide a fluidized bed gasification furnace having a fluidized bed gasification furnace and a melting furnace, wherein Is controlled by the amount of fluidized air, the melting furnace temperature or the steam flow is controlled by the amount of refuse supplied, and a non-interferor is provided to cancel interference with the fluidized bed temperature due to the refuse supply amount operation. It is another object of the present invention to provide a control method and apparatus capable of stably maintaining a melting furnace temperature (and a generated steam amount) and realizing stable gasification and melting.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a method for controlling a gasification and melting treatment plant according to the present invention is to supply refuse to a fluidized-bed gasification furnace (partial combustion furnace) using a dust supply device and to reduce the refuse in a fluidized bed in a reducing atmosphere. Thermally decomposes to produce flammable gas and unburned solids (char, ash, etc.), and burns flammable gas and unburned solids generated in a fluidized bed gasifier at high temperature in a melting furnace to produce unburned solids. In a gasification and melting treatment plant that collects ash in the waste as molten slag and decomposes dioxins, the temperature of the fluidized bed is controlled by the amount of flowing air, the temperature of the melting furnace is controlled by the amount of waste supplied, and waste is supplied. It is configured to stabilize the fluidized bed temperature and the melting furnace temperature by canceling the interference with the fluidized bed temperature due to the volume operation by correcting the fluidized air amount proportional to the feeder speed in the non-interferor (Fig. 1, see FIG. 2).
[0008]
The method for controlling a gasification and melting treatment plant according to the present invention is characterized in that refuse is supplied to a fluidized-bed gasification furnace (partial combustion furnace) by a dust supply device, thermally decomposed in a reducing atmosphere in a fluidized bed, and combustible gas is supplied. And unburned solids (char, ash, etc.), combustible gas and unburned solids generated in a fluidized bed gasifier are burned at high temperature in a melting furnace, and heat is recovered in a waste heat boiler at the subsequent stage. In a gasification and melting treatment plant that generates steam and recovers ash in unburned solids as molten slag and simultaneously decomposes dioxins, the fluidized bed temperature is controlled by the amount of flowing air, and the melting furnace temperature or The steam flow rate is controlled by the amount of refuse supplied, and the interference with the fluidized bed temperature due to the refuse supply amount operation is offset by the correction of the amount of flowing air in proportion to the speed of the feeding device in the non-interferor, and the fluidized bed temperature and melting furnace temperature And the amount of generated steam It is characterized in that to Joka.
[0009]
The control device of the gasification and melting treatment plant of the present invention generates flammable gas and unburned solids (char, ash, etc.) by thermally decomposing refuse charged into a fluidized bed by a dust supply device in a reducing atmosphere. The fluidized-bed gasifier (partial combustion furnace) and the combustible gas and unburned solids generated in the fluidized-bed gasifier are burned at a high temperature to collect the ash in the unburned solids as molten slag and at the same time to remove dioxins. In a gasification and melting treatment plant equipped with a melting furnace that decomposes, a fluidized bed temperature control means in which the fluidized bed temperature control is performed by controlling the amount of flowing air, Melting furnace temperature control means performed by operation and a non-interferometer that cancels the interference with the fluidized bed temperature due to the operation of the feeder speed (refuse supply amount) by correcting the amount of flowing air proportional to the feeder speed Specially Are (see Figure 1, Figure 2).
[0010]
In the above-described apparatus of the present invention, a waste heat boiler is provided which recovers heat from the high-temperature combustion gas generated in the melting furnace to generate steam, and instead of the melting furnace temperature control means, the steam flow rate is controlled by a feeder speed (dust). (Amount of supply) .
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications. FIG. 1 shows a configuration of a refuse gasification and melting processing plant to which a control method according to a first embodiment of the present invention is applied. FIG. 2 shows a schematic configuration of an apparatus for implementing a method for controlling a gasification and melting processing plant according to the first embodiment of the present invention.
As shown in FIG. 1, in a fluidized bed gasification furnace (partial combustion furnace) 10, fluidizing air is supplied to an air diffuser 14 by a blower (push-in blower or the like) 12, whereby a fluidized medium (eg, sand) Is fluidized to form a fluidized bed 16. Reference numeral 18 denotes a damper for adjusting the flow rate of the flowing air. Of course, it is also possible to use a fluidized-bed furnace of the type in which fluidizing air is supplied to the wind box and ejected from the air distribution plate to form a fluidized bed.
Garbage (municipal garbage, industrial waste, etc.), which is to be incinerated, is continuously charged into the fluidized bed 16 from a dust feeding device (for example, a screw feeder or the like) 20, and an air ratio of 0.2 to 0.2 in the fluidized bed 16. It is gasified in a reducing atmosphere of about 0.3, and becomes pyrolysis gas (combustible gas) and unburned solid (char, ash, etc.). Reference numeral 22 denotes a start-up burner, to which fuel and air whose flow rates have been adjusted by the control valve 24 are supplied to start the partial combustion furnace.
[0012]
The amount of waste introduced into the fluidized-bed gasification furnace (partial combustion furnace) 10 can be increased or decreased by adjusting the number of rotations of a feeding device (such as a screw feeder) 20. The fluidized bed temperature is lower than the melting point of aluminum (660 ° C.) to recover metals such as iron and aluminum in an unoxidized state. The operation is performed at 500 to 600 ° C. in order to homogenize the heat input fluctuation. Incombustibles containing metals such as iron and aluminum are extracted from the lower part of the fluidized bed by the incombustibles discharge device 26. Reference numeral 28 denotes a heat transfer tube that recovers heat from the fluidized medium, and reference numeral 30 denotes a water injection unit that sprays water onto the fluidized bed to adjust the temperature of the pyrolysis gas or the fluidized bed.
[0013]
The pyrolysis gas and unburned solids generated in the fluidized bed gasification furnace (partial combustion furnace) 10 are burned in a melting furnace 32 at a high temperature of 1300 to 1400 ° C., and ash is recovered as molten slag and at the same time dioxins are removed. Decompose.
The melting furnace 32 is a swirling melting furnace, and includes a pre-combustor 34 and a swirling melting furnace 36. The air for combustion is preheated to about 300 to 400 ° C. by the air preheater 40 and supplied to the preburner 34 by the blower 38. Reference numeral 42 denotes a damper for adjusting the flow rate of the melting furnace air. Reference numeral 44 denotes a start-up burner, which is started at the time of start-up by supplying auxiliary fuel whose flow rate has been adjusted by the control valve 46. In the swirling melting furnace 36, the high-temperature gas flowing in the tangential direction from the pre-combustor 34 is vigorously swirled, and the contained molten slag is captured and removed by a water-cooled self-coating furnace wall. And collected as water-cooled slag. 52 is a slag unloading conveyor.
[0014]
The high-temperature exhaust gas from the melting furnace 32 is introduced into the cooling tower 54 and cooled. Further, cooling air is supplied to the downstream side (upper part) of the cooling tower 54 by the blower 38. Reference numeral 60 denotes a damper for adjusting the flow rate of the cooling air. Reference numeral 62 denotes a water injection unit that sprays water onto the cooling tower to cool the exhaust gas.
The exhaust gas cooled by the cooling tower 54 is introduced into the gas cooling chamber 64 and further cooled. Water for cooling is sprayed into the gas cooling chamber 64 by a water injection unit 66. Reference numeral 68 denotes a control valve that adjusts the amount of water injection to adjust the temperature of the exhaust gas at the outlet of the gas cooling chamber. The exhaust gas cooled to a predetermined temperature is cooled through the air preheater 40, and is purified by a dust collector (not shown) such as a bag filter at the subsequent stage.
[0015]
Gasification and melting of refuse is characterized by non-uniform physical and chemical properties of refuse as fuel. Therefore, the following combustion fluctuation is observed.
(1) Since the lower heating value such as the moisture content of the refuse supplied into the furnace fluctuates, the amount of heat generated during combustion and the gas properties fluctuate.
(2) Even if the feeder speed is constant, since the properties and specific volume of the refuse are not uniform, the weight flow rate of the refuse supplied to the furnace fluctuates, and the amount of heat generated and the amount of gas fluctuate. .
These fluctuations are disturbance factors that impair the stability of gasification and melting of the refuse.
[0016]
Next, in order to quantitatively understand the effects of disturbances such as the lower heating value of the refuse and the fluctuation of the refuse supply amount on the combustion, the dynamic characteristics mathematical models of the partial combustion furnace (fluidized bed gasification furnace) and the swirling melting furnace were developed. Created and performed sensitivity analysis. Table 1 shows the results of sensitivity analysis in which a change in the lower heating value of the waste, a change in the supply amount of the waste, and a change in the flowing air amount due to the change in the moisture content ratio of the waste. As sensitivity analysis results, lower calorific value variation, dust supply amount fluctuation, fluidizing air quantity changes, the fluidized bed temperature, the melting furnace temperature, such as the exhaust gas O ₂ concentration, stable gasification, sensitivity to important state quantity in the stable melt There is a characteristic difference, and it is essential to absorb the disturbance having the characteristic difference.
[0017]
[Table 1]

[0018]
In the operation control of gasification melting, it is necessary to configure a control system depending on whether the fluctuation disturbance of the waste depends on the fluctuation of the lower heating value or the fluctuation of the supply amount of the waste. For example, in the case where the fluctuation of the refuse fluctuation is a lower heating value fluctuation due to the fluctuation of the moisture content ratio of the refuse, the fluctuation of the melting furnace temperature is large and the influence on the fluidized bed temperature is small as shown in the sensitivity analysis result of Table 1. On the other hand, when the refuse fluctuation disturbance is caused only by the refuse supply amount, as shown in Table 1, the fluidized bed temperature also fluctuates in addition to the melting furnace temperature fluctuation. In addition, when the fluidized air amount operation is performed, the effect on the fluidized bed temperature is large, and the effect on the melting furnace temperature is small.
From the results of the sensitivity analysis, as shown in FIG. 2, the control system is configured such that the fluidized bed temperature control is performed by a flowing air amount operation, and the melting furnace temperature control is performed by a refuse supply amount (dusting device speed) operation. Is good. However, the influence of the waste supply operation on the fluidized bed temperature is not small, and it is necessary to configure a non-interference control system so that this interference is canceled by a non-interferor.
[0019]
As shown in FIG. 2, a fluidized bed temperature control device 70 for controlling the fluidized bed temperature by controlling the amount of fluidized air and a melting furnace temperature for controlling the melting furnace temperature by controlling the feeder speed (refuse supply amount). A control device 72 is provided, and a non-interferor 74 is provided for canceling the interference with the fluidized bed temperature due to the operation of the dust feeding device speed (refuse supply amount) by correcting the flowing air amount. In FIG. 2, the same reference numerals as those used in FIG. 1 are used. Reference numeral 76 denotes a motor of a dust feeding device (a screw feeder or the like), and reference numeral 78 denotes a computing unit used to cancel a flowing air amount operation instruction by a flowing air amount correction instruction. The dust feeding device speed command value (the number of rotations of the motor) from the melting furnace temperature control device 72 is sent to the motor 76 to operate the dust supply amount. Further, a fluidized air amount operation instruction (opening degree of the damper) from the fluidized bed temperature control device 70 is sent to the damper 18 to operate the fluidized air amount. At this time, interference with the fluidized bed temperature due to the refuse supply amount operation is offset by the fluidized air amount correction instruction from the non-interferor 74 to maintain the stability of the fluidized air amount operation instruction by the fluidized bed temperature control. .
[0020]
For example, as shown in FIG. 3, if the fluctuation disturbance of the refuse is a fluctuation of only the refuse supply amount, it should be dealt with by an operation mainly for refuse supply correction, but in the case without the non-interference control of FIG. In this method, since the amount of flowing air is controlled by controlling the temperature of the fluidized bed, fluctuations in the amount of gas, the concentration of O _{2 and the} like are inevitable. On the other hand, if the non-interferor is assumed to be a flow air amount correction in proportion to the feeding device speed, the flow air amount operation instruction by the fluidized bed temperature control is converted into a flow air amount correction instruction corresponding to the air ratio accompanying the waste supply amount operation. Thus, the interference can be eliminated and the interference can be reduced (see FIG. 3).
In order to obtain the same effect without the non-interference control, if the fluidized bed temperature control is loosened (in the case of the PID control, the gain is reduced), the same operation can be performed mainly for the correction of the refuse supply amount. As shown in FIG. 4, if the dust fluctuation disturbance is only a change in the water content ratio, the fluctuation in the fluidized bed temperature becomes large, and stable operation cannot be realized (see FIG. 4).
By using the non-interference control in this way, the fluidized bed temperature and the melting furnace temperature can be stabilized, and the stability is determined only by adjusting the respective control loops. it can.
[0021]
In the present embodiment, a waste heat boiler for recovering heat from high-temperature combustion gas generated in the melting furnace and generating steam can be provided on the downstream side of the melting furnace. In this case, the fluidized bed temperature control may be constituted by a flowing air amount operation, and the steam flow rate control may be constituted by a dust supply amount (dusting device speed) operation.
The pyrolysis gas containing unburned solids from the partial combustion furnace is separated into pyrolysis gas and unburned solids by a solid-gas separator such as a cyclone, and the pyrolysis gas is supplied to a boiler, The control method of the present invention can also be applied to a gasification and melting processing plant configured to supply a solid content to a melting furnace.
[0022]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
(1) In gasification and melting of refuse, fluidized bed temperature and melting furnace temperature (and steam flow rate) can be kept stable, and stable gasification and stable melting (further, stable heat recovery) can be realized.
(2) In gasification and melting of refuse, mutual interference between fluidized bed temperature control and melting furnace temperature control (or steam flow rate control) can be suppressed, stability in a closed loop can be improved, and adjustment can be facilitated.
(3) If the non-interference control in the non-interferor is a flow air amount correction in proportion to the feeder speed, the flow air amount operation instruction by the fluidized bed temperature control is equivalent to the air ratio corresponding to the dust supply amount operation. Can be canceled by the flowing air amount correction instruction, and non-interference can be realized.
[Brief description of the drawings]
FIG. 1 is a systematic schematic configuration diagram showing an example of a gasification and melting processing plant to which a control method according to a first embodiment of the present invention is applied.
FIG. 2 is a schematic configuration diagram showing an apparatus for performing a control method for a gasification and melting processing plant according to the first embodiment of the present invention.
FIG. 3 is a graph showing a change over time of a state amount and an operation amount when non-interference control is performed and when a non-interference control is performed when a waste supply amount is changed stepwise.
FIG. 4 is a graph showing a change over time of a state amount and an operation amount when non-interference control is performed and when the low-level heat generation amount is changed stepwise.
[Explanation of symbols]
10 Fluidized bed gasifier (partial combustion furnace)
12, 38 Blower 14 Air diffuser 16

Fluidized bed

18, 42, 60 Damper 20 Dust supply device 22, 44 Start-

up burner

24, 46, 68 Control valve 26 Incombustibles discharge device 28

Heat transfer tube

30, 62, 66 Water injection means 32 Melting Furnace 34 Precombustor 36 Swirling melting furnace 40 Air preheater 48 Slag flow down port 50 Slag cooling facility 52 Slag unloading conveyor 54 Cooling tower 64 Gas cooling chamber 70 Fluidized bed temperature control device 72 Melting furnace temperature control device 74 Non-interferometer 76 Motor 78 arithmetic unit

Claims

The refuse is supplied to the fluidized-bed gasifier by the dust supply device, pyrolyzed in a reducing atmosphere in the fluidized bed to generate combustible gas and unburned solids, and the combustible gas generated by the fluidized-bed gasifier In a gasification and melting treatment plant in which unburned solids are burned at a high temperature in a melting furnace to recover ash in the unburned solids as molten slag and simultaneously decompose dioxins, the temperature of the fluidized bed is adjusted to the amount of fluidized air. The temperature of the melting furnace is controlled by the amount of refuse supplied, and the interference with the temperature of the fluidized bed caused by the operation of the amount of refuse is offset by the correction of the amount of flowing air in proportion to the speed of the dusting device in the non-interferor. A method for controlling a gasification and melting processing plant, comprising stabilizing a temperature and a melting furnace temperature.

The refuse is supplied to the fluidized-bed gasifier by the dust supply device, pyrolyzed in a reducing atmosphere in the fluidized bed to generate combustible gas and unburned solids, and the combustible gas generated by the fluidized-bed gasifier In addition, the unburned solids are burned at a high temperature in a melting furnace, and heat is recovered by a waste heat boiler at the later stage to generate steam, while the ash in the unburned solids is recovered as molten slag and the dioxins are decomposed at the same time. In a gasification and melting processing plant, the fluidized bed temperature is controlled by the amount of flowing air, the melting furnace temperature or the steam flow rate is controlled by the refuse supply amount, and interference with the refuse supply amount operation on the fluidized bed temperature is controlled by a non-interferometer. A fluidized bed temperature, a melting furnace temperature, and a generated steam amount, which are compensated for by a correction of a flowing air amount proportional to a speed of a dust supply device, and a method of controlling a gasification and melting treatment plant .

A fluidized bed gasifier that pyrolyzes refuse introduced into the fluidized bed in a reducing atmosphere to generate combustible gas and unburned solids by a dust supply device, and a combustible gas generated by the fluidized bed gasifier and In a gasification and fusion treatment plant equipped with a melting furnace that burns unburned solids at a high temperature and collects ash in the unburned solids as molten slag, and simultaneously decomposes dioxins, the fluidized bed temperature control controls the amount of fluidized air. Fluidized bed temperature control means performed by operation, melting furnace temperature control means performed by operation of the feeding device speed, and interference with fluidized bed temperature by operation of the feeding device speed. A control apparatus for a gasification and melting processing plant, comprising: a non-interferometer that cancels out by a correction of a flowing air amount proportional to the flow rate.

Equipped with a waste heat boiler that recovers heat from the high-temperature combustion gas generated in the melting furnace and generates steam, and instead of the melting furnace temperature control means, the steam flow rate control means in which the steam flow rate is controlled by operating the feeder speed a control apparatus for gasification and melting treatment plant according to claim 3, wherein provided.