JP4540147B2 - Fluidized bed type waste combustion apparatus and combustion method - Google Patents

Fluidized bed type waste combustion apparatus and combustion method Download PDF

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JP4540147B2
JP4540147B2 JP18263299A JP18263299A JP4540147B2 JP 4540147 B2 JP4540147 B2 JP 4540147B2 JP 18263299 A JP18263299 A JP 18263299A JP 18263299 A JP18263299 A JP 18263299A JP 4540147 B2 JP4540147 B2 JP 4540147B2
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combustion
exhaust gas
temperature
waste
fluidized bed
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JP2001012730A (en
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俊之 須田
俊郎 藤森
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IHI Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Description

【０００１】
【発明の属する技術分野】
本発明は、流動床式廃棄物燃焼装置に関するものである。
【０００２】
【従来の技術】
流動床式廃棄物燃焼装置では、廃棄物は流動床内で急激に燃焼するため不完全燃焼が生じてダイオキシンが発生する。
【０００３】
廃棄物の燃焼によるダイオキシンの発生量を低減化させるには、燃焼炉内で高温燃焼することと、燃焼排ガスを急速冷却してダイオキシンの再合成反応が起きるとされる３００〜４００℃での滞留時間を短くすることが重要である。
【０００４】
そこで、流動床式廃棄物燃焼装置では、ダイオキシンの発生量を低減化させるため、燃焼排ガスに同伴されている未燃固形物や不完全燃焼ガスをフリーボード部内で二次燃焼させることによって完全燃焼させたり、燃焼排ガス排出側の下流側に、たとえば、活性炭吸着方式を利用した排ガス処理設備を設けてダイオキシンの除去を行うようにしている。
【０００５】
また、二次燃焼空気を高温化するため、貫流形式の熱交換器（たとえば、シェルアンドチューブ式）や金属の伝熱蓄熱体を有する回転蓄熱式熱交換器を介して高温の燃焼排ガスと低温の二次燃焼空気とを熱交換し、二次燃焼空気を予熱してフリーボード部に吹き込むことが行われている。
【０００６】
一方、ダイオキシンの再合成を防止するため、燃焼排ガスを冷却するのに水噴霧型ガス冷却器を使用しているものもある。
【０００７】
【発明が解決しようとする課題】
このような従来の貫流形式の熱交換器や金属の伝熱蓄熱体を有する回転蓄熱式熱交換器では、高温の燃焼排ガスの入口と出口、低温の二次燃焼空気の出口と入口の温度勾配をあまり大きくとることができないので、フリーボード部に吹き込む二次燃焼空気の高温化と燃焼排ガスの急速冷却には限界がある。また、水噴霧による燃焼排ガスの冷却では、冷却速度が２００℃／ｓ程度で、ダイオキシンの再合成を完全に防止することはできないし、水処理上にも問題がある。そのため、排ガス処理設備に大きな負荷がかかるという問題がある。
【０００８】
本発明は、上記のような問題点を解決するために創案されたもので、高温の燃焼排ガスの排熱を十分回収し、二次燃焼空気を高温化してフリーボード部内の高温燃焼化を図るとともに、燃焼排ガスを急速冷却してダイオキシン再合成量の低減化を図ることができる流動床式廃棄物燃焼装置を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
上記目的を達成するため、本発明によれば、燃焼炉内で加熱されて流動化している流動床に廃棄物を投入して焼却する流動床式廃棄物燃焼装置であって、燃焼炉から排出される燃焼排ガスと燃焼炉内のフリーボード部に供給する二次燃焼空気とをハニカム状セラミックス製の蓄熱体を有する回転蓄熱式熱交換器を介して熱交換し、二次燃焼空気を加熱すとともに、燃焼排ガスを急速冷却する流動床式廃棄物燃焼装置が提供される。
【００１０】
次に本発明の作用を説明する。
本発明の流動床式廃棄物燃焼装置によれば、燃焼炉内から排出される高温の燃焼排ガスと燃焼炉内のフリーボード部に供給する二次燃焼空気とをハニカム状セラミックス製の回転蓄熱式熱交換器を介して熱交換し、高温の二次燃焼空気を燃焼炉内のフリーボード部内に供給するので、燃焼排ガスに同伴されている未燃固形物や不完全燃焼ガスを完全燃焼させることができるとともに、流動床内で発生したダイオキシンをフリーボード部内の高温雰囲気で分解する。また、高温の燃焼排ガスは、高温部と低温部の温度勾配が非常に大きいハニカム状セラミックス製の蓄熱体を有する回転蓄熱式熱交換器によって急速冷却されるので、ダイオキシンの再合成が防止される。燃焼排ガスは、図示しない下流側に設けた燃焼排ガス処理設備を経て放出するが、燃焼排ガスのダイオキシン濃度が低いので、燃焼排ガス処理設備への負荷の低減化を図ることができる。
【００１１】
【発明の実施の形態】
以下、本発明の一実施形態について、図面に基づいて説明する。
図１は本発明の流動床式廃棄物燃焼装置の断面図であり、図２は図１に関連するハニカム状アルミナセラミックス製の蓄熱体を有する回転蓄熱式熱交換器の斜視図である。
【００１２】
図１において、１は廃棄物燃焼装置である。１Ａは廃棄物燃焼装置１の燃焼炉である。１ａは燃焼炉１Ａの底部に設けた風箱であり、１ｂは燃焼炉１Ａのフリーボード部である。２は燃焼炉１Ａの散気板で、多数のガス吹出ノズル２ａを配設している。３は散気板２上に形成する流動床で、流動媒体である多量の珪砂３ａを貯留している。４は燃焼炉１Ａの側方に設けられた廃棄物投入用ホッパで、廃棄物５を燃焼炉１Ａの上方から投入する。６は燃焼空気で、風箱１ａに連結した燃焼空気供給管１０から風箱１ａに供給され、散気板２に設けられた多数のガス吹出ノズル２ａから燃焼炉１Ａ内に吹き出し、燃焼炉１Ａ内に投入された廃棄物５と珪砂３ａを撹拌し、浮遊、流動させながら廃棄物５を燃焼させる。７は廃棄物５の燃焼によって発生した約８００℃の高温の燃焼排ガスで、燃焼炉１Ａの中間で、二次燃焼空気供給管１２ａから供給された二次燃焼空気１６ａにより未燃固形物や不完全燃焼ガスを再燃焼して燃焼炉１Ａのフリーボード部１ｂを上昇し、燃焼炉１Ａの上部に設けた燃焼排ガス排出管１１、１１ａ、１１ｂを通って下流側に排出される。８は燃焼排ガス排出管１１、１１ａ間に介在して設けたサイクロンである。９は燃焼排ガス排出管１１ａ、１１ｂ間および二次燃焼空気供給管１２、１２ａ間に介在して設けた回転蓄熱式熱交換器である。
【００１３】
回転蓄熱式熱交換器９は、図２に示すように、筒体９ａの上面と下面に燃焼排ガス排出管１１ａと１１ｂおよび二次燃焼空気供給管１２ａと１２を連結している。筒体９ａの中間にはハニカム状アルミナセラミックス製の蓄熱体１３が内装されており、筒体９ａの上面に設けたモータ１５により軸１５ａを中心として矢印Ａ方向に回転する。蓄熱体１３の回転速度は、ほぼ１ｒｐｍである。１４は筒体９ａ内の蓄熱体１３の上方に配設した分離板で、筒体９ａ内に送給された燃焼排ガス７ａと二次燃焼空気供給管１２ａへ供給する二次燃焼空気１６ａとを分離する。１４ａは筒体９ａ内の蓄熱体１３の下方に配設した分離板で、筒体９ａ内に送給された二次燃焼空気１６と燃焼排ガス排出管１１ｂへ排出する燃焼排ガス７ｂとを分離する。燃焼排ガス７ａおよび二次燃焼空気１６は、筒体９ａ内に送給され、この回転蓄熱体１３を通過して熱交換される。１７はサイクロン８で燃焼排ガス７から分離された飛灰である。なお、二次燃焼空気供給管１２ａを燃焼炉１Ａの接線方向に連結して二次燃焼空気１６ａを燃焼炉１Ａの接線方向から導入すると二次燃焼空気１６ａを燃焼炉１Ａ内で旋回させるので、二次燃焼空気１６ａの滞留時間を延長することができる。
【００１４】
次に実施形態に基づく作用について述べる。
本発明の流動床式廃棄物燃焼装置１によれば、燃焼炉内１Ａから排出される約８００℃の高温の燃焼排ガス７と燃焼炉１Ａ内のフリーボード部１ｂに供給する二次燃焼空気１６ａをハニカム状セラミックス製の回転蓄熱式熱交換器９を介して熱交換し、回転蓄熱式熱交換器９の蓄熱体１３により７００〜８００℃まで高温化された二次燃焼空気１６ａを燃焼炉１Ａ内のフリーボード部１ｂ内に供給するので、二次燃焼空気１６ａにより燃焼排ガス７に同伴されている未燃固形物や不完全燃焼ガスは完全燃焼されるとともに、流動床３内で発生したダイオキシンを、二次燃焼空気を加熱しない場合よりも大幅に低減することができる。また、高温の燃焼排ガス７は、高温部と低温部の温度勾配が非常に大きいハニカム状セラミックス製の蓄熱体１３を有する回転蓄熱式熱交換器９によって２００℃以下まで急速冷却されるので、ダイオキシンの再合成が防止される。燃焼排ガスは、図示しない下流側に設けた燃焼排ガス処理設備を経て放出するが、燃焼排ガスのダイオキシン濃度が低いので、燃焼排ガス処理設備への負荷の低減化を図ることができる。
【００１５】
【実施例】
次に本発明の効果を実証するための実験結果について説明する。
実験では、流動床式燃焼試験炉を用い、高温予熱空気および燃焼排ガスの急速冷却によるダイオキシン類低減化効果を確認した。実験は、直径０．３ｍ、高さ１５ｍの大きさの流動床式燃焼炉で、流動媒体として平均粒径１．１ｍｍの珪砂を用い、燃料としてごみ固形化燃料（ＲＤＦ）および模擬ごみ（塩ビラミネート紙）を燃焼させ、予熱二次燃焼空気（予熱二次ガス）としては、高空気比で燃焼させた都市ガスバーナの排気を模擬予熱空気として使用した。この予熱二次ガス温度をコントロールし、ダイオキシン類排出挙動に対する高温予熱空気の影響を確認した。また、ハニカム状アルミナセラミックス製の回転蓄熱式熱交換器により燃焼排ガスの急速冷却を行い、通常冷却時と比較することによって、ダイオキシン類排出挙動に対する急速冷却の影響を確認した。
【００１６】
実験は、燃料を燃焼炉の流動床の上方より投入し、燃焼排ガスは、燃焼炉のフリーボード部を上昇して通過した後、一次、二次熱交換器、水噴霧式ガスクーラ、下流側に設けたバグフィルタを通過して排出させた。燃焼炉および下流側の各機器には熱電対を取り付け、各地点における燃焼排ガス温度を測定した。予熱二次ガスは、燃焼炉床面の上方２ｍの地点に設けた二次ガス供給管から燃焼炉に導入した。また、予熱二次ガス温度は、４０℃（燃焼させず、直接空気を燃焼炉内に投入）、６６０℃、９２０℃になるよう設定した。なお、予熱二次ガスの高温化と燃焼排ガスの急速冷却の実験は、別々に行った。
【００１７】
図３は二次ガス温度における燃焼炉内温度分布の変化を示す図である。縦軸に温度を、横軸に測定位置を示している。なお、■印は二次ガス温度４０℃を、○印は二次ガス温度６６０℃を、▲印は二次ガス温度９２０℃を示す。
図において、炉底より高さ２．９ｍの地点の温度で比べた場合、通常運転（二次ガス４０℃）の場合に比べ二次ガス温度６６０℃の場合で＋１０５℃、二次ガス温度９２０℃の場合で＋１４５℃となっている。燃焼排ガスの後流では温度差は減少し、一次熱交換器出口ではほとんど差がなくなっている。
【００１８】
図４は二次ガス温度に対する燃焼炉出口で測定したダイオキシン類濃度の測定結果を示す図である。縦軸にダイオキシン類濃度を、横軸に二次ガス温度を示している。
図において、二次ガス温度４０℃でダイオキシン類濃度が０．１５ｎｇ／Ｎｍ3 −ＴＥＱ（Toxicity Equivalent （毒性等価換算値））であるのに対し、二次ガス温度６６０℃および９２０℃でダイオキシン類濃度は０．０２ｎｇ／Ｎｍ3 −ＴＥＱであり、二次ガスの高温化によって燃焼炉出口での温度が上昇し、ダイオキシン類濃度が全体的に減少していることがわかる。
【００１９】
図５は回転蓄熱式熱交換器による燃焼排ガスの急速冷却を行った場合と通常の燃焼排ガス経路で冷却した場合（内部を燃焼排ガスが、外部を冷却水が流れる二重管式の２台の熱交換器で冷却）の燃焼排ガス温度の変化を示す図である。縦軸に二次ガス温度を、横軸に滞留時間を示している。なお、実線は燃焼排ガスの急速冷却時を、破線は通常冷却時における温度変化差を示す。
【００２０】
図において、７００℃から１５０℃までの冷却速度をそれぞれの場合について比較すると、回転蓄熱式熱交換器を使用した場合、燃焼排ガスの冷却速度は７，７００℃／ｓになり、通常時の１８０℃／ｓに比べ約４３倍になっている。
【００２１】
図６は熱交換器によるダイオキシン類全体濃度に対する冷却速度の影響を、実験値および計算値で比較した図である。縦軸にダイオキシン類濃度を、横軸に冷却速度を示している。なお、実線は実験値を、点線はダイオキシン合成反応モデルを用いて計算した計算値を示す。
この結果、計算値ほど減少しないものの、急速冷却によりダイオキシン生成量が減少していることが分かる。
【００２２】
本発明は、上記実施の形態に限定されるものではなく、本発明の要旨を逸脱しない範囲で種々変更し得ることは勿論である。
【００２３】
【発明の効果】
以上述べたように、本発明によれば、燃焼排ガス排出管および二次燃焼空気供給管の中間に設けたハニカム状セラミックス製の回転蓄熱式熱交換器により、二次燃焼空気を高温化して流動床内で発生したダイオキシンをフリーボード部内の高温雰囲気で分解し、また、燃焼排ガスを急速冷却してダイオキシンの再合成を防止することによりダイオキシンの排出を大幅に低減することができるなどの優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明による流動床式廃棄物燃焼装置の断面図である。
【図２】図１に関連ある回転蓄熱式熱交換器の斜視図である。
【図３】本発明の実験により得られた二次燃焼空気（二次ガス）温度における燃焼炉内温度分布の変化を示す図である。
【図４】本発明の実験により得られた二次ガス温度に対する燃焼炉出口で測定したダイオキシン類濃度の測定結果を示す図である。
【図５】本発明の実験により得られた熱交換器による燃焼排ガスの急速冷却を行った場合と通常の燃焼排ガス経路で冷却した場合の燃焼排ガス温度の変化を示す図である。
【図６】本発明の実験により得られた熱交換器によるダイオキシン類全体濃度に対する冷却速度の影響を、実験値および計算値で比較した図である。
【符号の説明】
１ 廃棄物燃焼装置
１Ａ 燃焼炉
１ａ 風箱
１ｂ フリーボード部
２ 散気板
２ａ ガス吹出ノズル
３ 流動床
４ 廃棄物投入用ホッパ
５ 廃棄物
６ 燃焼空気
７，７ａ，７ｂ 燃焼排ガス
９ 回転蓄熱式熱交換器
１０ 燃焼空気供給管
１１，１１ａ，１１ｂ 燃焼排ガス排出管
１２，１２ａ 二次燃焼空気供給管
１３ 蓄熱体
１４ 分離板
１５ モータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluidized bed waste combustion apparatus.
[0002]
[Prior art]
In a fluidized bed waste combustion apparatus, waste burns rapidly in the fluidized bed, so incomplete combustion occurs and dioxins are generated.
[0003]
In order to reduce the amount of dioxin generated due to the combustion of waste, high temperature combustion in a combustion furnace and rapid chilling of combustion exhaust gas to cause a resynthesis reaction of dioxin occurs at 300 to 400 ° C. It is important to shorten the time.
[0004]
In order to reduce the amount of dioxins generated in the fluidized bed waste combustor, complete combustion is achieved by secondary combustion of unburned solids and incomplete combustion gas accompanying the combustion exhaust gas in the freeboard section. For example, an exhaust gas treatment facility using an activated carbon adsorption system is provided on the downstream side of the combustion exhaust gas discharge side to remove dioxins.
[0005]
In addition, in order to increase the temperature of the secondary combustion air, high-temperature combustion exhaust gas and low-temperature are obtained through a once-through heat exchanger (for example, a shell-and-tube type) or a rotary heat storage heat exchanger having a metal heat transfer heat storage body. The secondary combustion air is heat-exchanged, and the secondary combustion air is preheated and blown into the freeboard portion.
[0006]
On the other hand, some water spray type gas coolers are used to cool the combustion exhaust gas in order to prevent dioxin resynthesis.
[0007]
[Problems to be solved by the invention]
In such a conventional once-through type heat exchanger and a rotary heat storage type heat exchanger having a metal heat transfer heat storage body, the temperature gradient between the inlet and outlet of the high-temperature combustion exhaust gas and the outlet and inlet of the low-temperature secondary combustion air Therefore, there is a limit to the high temperature of the secondary combustion air blown into the free board and the rapid cooling of the combustion exhaust gas. Further, in cooling of combustion exhaust gas by water spray, the cooling rate is about 200 ° C./s, and dioxin resynthesis cannot be completely prevented, and there is a problem in water treatment. Therefore, there is a problem that a large load is applied to the exhaust gas treatment facility.
[0008]
The present invention was devised to solve the above-described problems, and sufficiently recovers exhaust heat of high-temperature combustion exhaust gas and raises the temperature of secondary combustion air to achieve high-temperature combustion in the freeboard section. At the same time, it is an object of the present invention to provide a fluidized bed waste combustion apparatus capable of rapidly cooling combustion exhaust gas and reducing the amount of dioxin resynthesis.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a fluidized bed waste combustion apparatus for injecting and incinerating waste into a fluidized bed heated and fluidized in a combustion furnace, which is discharged from the combustion furnace. The secondary combustion air is heated by exchanging heat between the combustion exhaust gas to be supplied and the secondary combustion air to be supplied to the freeboard part in the combustion furnace through a rotary heat storage heat exchanger having a heat storage body made of honeycomb ceramics. At the same time, a fluidized bed waste combustion apparatus for rapidly cooling combustion exhaust gas is provided.
[0010]
Next, the operation of the present invention will be described.
According to the fluidized bed waste combustion apparatus of the present invention, the high-temperature combustion exhaust gas discharged from the combustion furnace and the secondary combustion air supplied to the free board part in the combustion furnace are rotated and stored by a honeycomb ceramic. Heat is exchanged via a heat exchanger, and high-temperature secondary combustion air is supplied into the free board in the combustion furnace, so that unburned solids and incomplete combustion gases accompanying combustion exhaust gas are completely burned. The dioxins generated in the fluidized bed are decomposed in a high-temperature atmosphere in the freeboard section. Moreover, since the high-temperature combustion exhaust gas is rapidly cooled by the rotary heat storage type heat exchanger having a heat storage body made of honeycomb ceramics in which the temperature gradient between the high temperature portion and the low temperature portion is very large, recombination of dioxins is prevented. . The combustion exhaust gas is discharged through a combustion exhaust gas treatment facility provided on the downstream side (not shown). However, since the dioxin concentration of the combustion exhaust gas is low, the load on the combustion exhaust gas treatment facility can be reduced.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a fluidized bed waste combustion apparatus according to the present invention, and FIG. 2 is a perspective view of a rotary heat storage type heat exchanger having a heat storage body made of honeycomb-like alumina ceramics related to FIG.
[0012]
In FIG. 1, 1 is a waste combustion apparatus. 1 A is a combustion furnace of the waste combustion apparatus 1. 1a is a wind box provided at the bottom of the combustion furnace 1A, and 1b is a free board part of the combustion furnace 1A. Reference numeral 2 denotes a diffuser plate of the combustion furnace 1A, and a large number of gas blowing nozzles 2a are arranged. 3 is a fluidized bed formed on the diffuser plate 2 and stores a large amount of silica sand 3a as a fluidized medium. Reference numeral 4 denotes a waste charging hopper provided on the side of the combustion furnace 1A, and inputs the waste 5 from above the combustion furnace 1A. Reference numeral 6 denotes combustion air, which is supplied from a combustion air supply pipe 10 connected to the wind box 1a to the wind box 1a and blows into the combustion furnace 1A from a number of gas blowing nozzles 2a provided on the diffuser plate 2. The waste 5 and the silica sand 3a thrown into the inside are stirred, and the waste 5 is burned while floating and flowing. 7 is a high-temperature combustion exhaust gas having a temperature of about 800 ° C. generated by the combustion of the waste 5, and in the middle of the combustion furnace 1A, the secondary combustion air 16a supplied from the secondary combustion air supply pipe 12a causes unburned solids and waste. The complete combustion gas is recombusted to ascend the free board portion 1b of the combustion furnace 1A, and is discharged to the downstream side through the combustion exhaust gas discharge pipes 11, 11a, 11b provided in the upper part of the combustion furnace 1A. Reference numeral 8 denotes a cyclone provided between the combustion exhaust gas discharge pipes 11 and 11a. A rotary heat storage heat exchanger 9 is provided between the combustion exhaust gas discharge pipes 11a and 11b and between the secondary combustion air supply pipes 12 and 12a.
[0013]
As shown in FIG. 2, the rotary heat storage type heat exchanger 9 has combustion exhaust gas discharge pipes 11a and 11b and secondary combustion air supply pipes 12a and 12 connected to the upper and lower surfaces of a cylindrical body 9a. A heat storage element 13 made of honeycomb-like alumina ceramics is housed in the middle of the cylindrical body 9a, and is rotated in the direction of arrow A about the shaft 15a by a motor 15 provided on the upper surface of the cylindrical body 9a. The rotational speed of the heat storage body 13 is approximately 1 rpm. 14 is a separation plate disposed above the heat accumulator 13 in the cylindrical body 9a, and the combustion exhaust gas 7a fed into the cylindrical body 9a and the secondary combustion air 16a supplied to the secondary combustion air supply pipe 12a. To separate. 14a is a separation plate disposed below the heat accumulator 13 in the cylindrical body 9a, and separates the secondary combustion air 16 fed into the cylindrical body 9a and the combustion exhaust gas 7b discharged to the combustion exhaust gas exhaust pipe 11b. . The combustion exhaust gas 7a and the secondary combustion air 16 are fed into the cylindrical body 9a, and exchanged heat through the rotary heat storage body 13. Reference numeral 17 denotes fly ash separated from the combustion exhaust gas 7 by the cyclone 8. When the secondary combustion air supply pipe 12a is connected in the tangential direction of the combustion furnace 1A and the secondary combustion air 16a is introduced from the tangential direction of the combustion furnace 1A, the secondary combustion air 16a is swirled in the combustion furnace 1A. The residence time of the secondary combustion air 16a can be extended.
[0014]
Next, the operation based on the embodiment will be described.
According to the fluidized bed waste combustion apparatus 1 of the present invention, the secondary combustion air 16a supplied to the high-temperature combustion exhaust gas 7 of about 800 ° C. discharged from the combustion furnace 1A and the free board portion 1b in the combustion furnace 1A. Is exchanged through a rotary heat storage heat exchanger 9 made of honeycomb ceramics, and the secondary combustion air 16a heated to 700 to 800 ° C. by the heat storage body 13 of the rotary heat storage heat exchanger 9 is used as a combustion furnace 1A. Since it is supplied into the free board portion 1b, unburned solids and incomplete combustion gas entrained in the combustion exhaust gas 7 are completely burned by the secondary combustion air 16a, and dioxins generated in the fluidized bed 3 are generated. Can be significantly reduced as compared with the case where the secondary combustion air is not heated. Further, the high-temperature combustion exhaust gas 7 is rapidly cooled to 200 ° C. or less by the rotary heat storage heat exchanger 9 having the honeycomb-shaped heat storage body 13 having a very large temperature gradient between the high temperature portion and the low temperature portion. Resynthesis of is prevented. The combustion exhaust gas is discharged through a combustion exhaust gas treatment facility provided on the downstream side (not shown). However, since the dioxin concentration of the combustion exhaust gas is low, the load on the combustion exhaust gas treatment facility can be reduced.
[0015]
【Example】
Next, experimental results for demonstrating the effects of the present invention will be described.
In the experiment, a fluidized bed combustion test furnace was used to confirm the dioxin reduction effect by rapid cooling of high-temperature preheated air and combustion exhaust gas. The experiment was conducted in a fluidized bed combustion furnace with a diameter of 0.3 m and a height of 15 m, using silica sand with an average particle size of 1.1 mm as the fluid medium, solidified fuel (RDF) and simulated waste (vinyl chloride) as the fuel. As the preheated secondary combustion air (preheated secondary gas), the exhaust of a city gas burner burned at a high air ratio was used as simulated preheated air. The temperature of the preheated secondary gas was controlled, and the effect of high temperature preheated air on the dioxin emission behavior was confirmed. In addition, the flue gas was rapidly cooled by a rotary heat storage heat exchanger made of honeycomb-like alumina ceramics, and the effect of rapid cooling on the dioxin emission behavior was confirmed by comparing with the normal cooling.
[0016]
In the experiment, fuel is injected from above the fluidized bed of the combustion furnace, and the flue gas rises and passes through the free board part of the combustion furnace, then the primary, secondary heat exchanger, water spray type gas cooler, downstream It was discharged through the bag filter provided. Thermocouples were attached to the combustion furnace and downstream equipment, and the combustion exhaust gas temperature at each point was measured. The preheated secondary gas was introduced into the combustion furnace from a secondary gas supply pipe provided at a point 2 m above the combustion furnace floor. In addition, the preheating secondary gas temperature was set to 40 ° C. (not combusted and air was directly introduced into the combustion furnace), 660 ° C., and 920 ° C. Note that the experiments of increasing the temperature of the preheated secondary gas and rapidly cooling the combustion exhaust gas were conducted separately.
[0017]
FIG. 3 is a diagram showing a change in the temperature distribution in the combustion furnace at the secondary gas temperature. The vertical axis represents temperature, and the horizontal axis represents the measurement position. The ■ mark indicates a secondary gas temperature of 40 ° C., the ◯ mark indicates a secondary gas temperature of 660 ° C., and the ▲ mark indicates a secondary gas temperature of 920 ° C.
In the figure, when compared at a temperature at a point 2.9 m above the furnace bottom, when the secondary gas temperature is 660 ° C. compared to the normal operation (secondary gas 40 ° C.), the secondary gas temperature is 920 ° C. In the case of ° C., it is + 145 ° C. The temperature difference decreases at the wake of the flue gas, and almost no difference at the outlet of the primary heat exchanger.
[0018]
FIG. 4 is a diagram showing measurement results of dioxin concentrations measured at the combustion furnace outlet with respect to the secondary gas temperature. The vertical axis represents the dioxin concentration, and the horizontal axis represents the secondary gas temperature.
In the figure, the dioxins concentration is 0.15 ng / Nm 3 -TEQ (Toxicity Equivalent) at a secondary gas temperature of 40 ° C., whereas dioxins are at a secondary gas temperature of 660 ° C. and 920 ° C. The concentration is 0.02 ng / Nm 3 -TEQ, and it can be seen that the temperature at the exit of the combustion furnace rises due to the increase in the temperature of the secondary gas, and the dioxins concentration decreases overall.
[0019]
Fig. 5 shows the case of rapid cooling of flue gas by a rotary heat storage heat exchanger and the case of cooling by a normal flue gas route (two double-tube types in which the flue gas flows inside and the cooling water flows outside) It is a figure which shows the change of the combustion exhaust gas temperature of cooling with a heat exchanger. The vertical axis represents the secondary gas temperature, and the horizontal axis represents the residence time. The solid line indicates the rapid cooling of the combustion exhaust gas, and the broken line indicates the temperature change difference during the normal cooling.
[0020]
In the figure, when the cooling rate from 700 ° C. to 150 ° C. is compared in each case, when the rotary heat storage type heat exchanger is used, the cooling rate of the flue gas becomes 7,700 ° C./s, which is 180 at the normal time. It is about 43 times that of ° C / s.
[0021]
FIG. 6 is a diagram comparing the influence of the cooling rate on the total concentration of dioxins by the heat exchanger with experimental values and calculated values. The vertical axis represents the dioxin concentration, and the horizontal axis represents the cooling rate. The solid line represents experimental values, and the dotted line represents calculated values calculated using a dioxin synthesis reaction model.
As a result, although it does not decrease as much as the calculated value, it can be seen that the amount of dioxin produced decreases due to rapid cooling.
[0022]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.
[0023]
【The invention's effect】
As described above, according to the present invention, the secondary combustion air is heated by the rotary heat storage heat exchanger made of honeycomb ceramics provided between the combustion exhaust gas discharge pipe and the secondary combustion air supply pipe. Dioxins generated in the floor can be decomposed in a high-temperature atmosphere in the freeboard section, and the exhaust gas can be rapidly cooled to prevent dioxin resynthesis, thereby significantly reducing dioxin emissions. There is an effect.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fluidized bed waste combustion apparatus according to the present invention.
FIG. 2 is a perspective view of a rotary heat storage type heat exchanger related to FIG. 1;
FIG. 3 is a diagram showing a change in temperature distribution in the combustion furnace at a secondary combustion air (secondary gas) temperature obtained by an experiment of the present invention.
FIG. 4 is a graph showing measurement results of dioxin concentrations measured at the combustion furnace outlet with respect to the secondary gas temperature obtained by the experiment of the present invention.
FIG. 5 is a diagram showing changes in the combustion exhaust gas temperature when the combustion exhaust gas is rapidly cooled by the heat exchanger obtained by the experiment of the present invention and when it is cooled by a normal combustion exhaust gas path.
FIG. 6 is a diagram comparing the influence of the cooling rate on the total concentration of dioxins by the heat exchanger obtained by the experiment of the present invention with an experimental value and a calculated value.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Waste combustion apparatus 1A Combustion furnace 1a Wind box 1b Free board part 2 Aeration board 2a Gas blowing nozzle 3 Fluidized bed 4 Waste input hopper 5 Waste 6 Combustion air 7, 7a, 7b Combustion exhaust gas 9 Rotational regenerative heat Exchanger 10 Combustion air supply pipe 11, 11a, 11b Combustion exhaust gas discharge pipe 12, 12a Secondary combustion air supply pipe 13 Heat storage body 14 Separating plate 15 Motor

Claims (2)

燃焼炉内で加熱されて流動化している流動床に廃棄物を投入して焼却する流動床式廃棄物燃焼装置であって、燃焼炉から排出される燃焼排ガスと燃焼炉内のフリーボード部に供給する二次燃焼空気とを高温部と低温部の温度勾配を大きくできるハニカム状セラミックス製の蓄熱体を有する回転蓄熱式熱交換器を介して熱交換し、二次燃焼空気を７００〜８００℃まで予熱してフリーボード部内の温度を、フリーボード部内で燃焼排ガスに同伴されている未燃固形物や不完全燃焼ガスを完全燃焼させ、かつ、流動床内で廃棄物が燃焼するときに発生するダイオキシンが分解する温度以上に高めるとともに、燃焼排ガスを２００℃以下まで急冷却してダイオキシンの再合成を防止するようになっており、燃焼炉から排出される燃焼排ガスは上記回転蓄熱式熱交換器に流入する前にサイクロンによって飛灰が分離されることを特徴とする流動床式廃棄物燃焼装置。A fluidized bed type waste combustion apparatus that injects waste into a fluidized bed heated and fluidized in a combustion furnace and incinerates it, in a combustion exhaust gas discharged from the combustion furnace and a free board part in the combustion furnace The supplied secondary combustion air is heat-exchanged through a rotary heat storage type heat exchanger having a heat storage body made of honeycomb ceramics capable of increasing the temperature gradient between the high temperature portion and the low temperature portion, and the secondary combustion air is 700 to 800 ° C. Occurs when the temperature in the freeboard section is preheated until the unburned solids and incomplete combustion gases entrained in the combustion exhaust gas in the freeboard section are completely burned, and the waste is burned in the fluidized bed with dioxin enhances than decompose temperature of, the rapidly cooled flue gas to 200 ° C. or less is adapted to prevent re-synthesis of dioxins, the combustion exhaust gas discharged from the combustion furnace the times Fluidized-bed waste combustion system, characterized in that fly ash is separated by a cyclone before entering the regenerative heat exchanger. 燃焼炉内で加熱されて流動化している流動床に廃棄物を投入して焼却する流動床式廃棄物燃焼方法であって、燃焼炉から排出される燃焼排ガスと燃焼炉内のフリーボード部に供給する二次燃焼空気とを高温部と低温部の温度勾配を大きくできるハニカム状セラミックス製の蓄熱体を有する回転蓄熱式熱交換器を介して熱交換し、二次燃焼空気を７００〜８００℃まで予熱してフリーボード部内の温度を、フリーボード部内で燃焼排ガスに同伴されている未燃固形物や不完全燃焼ガスを完全燃焼させ、かつ、流動床内で廃棄物が燃焼するときに発生するダイオキシンが分解する温度以上に高めるとともに、燃焼排ガスを２００℃以下まで急冷却してダイオキシンの再合成を防止するようになっており、燃焼炉から排出される燃焼排ガスは上記回転蓄熱式熱交換器に流入する前にサイクロンによって飛灰が分離されることを特徴とする流動床式廃棄物燃焼方法。A fluidized bed type waste combustion method in which waste is injected into a fluidized bed heated and fluidized in a combustion furnace and incinerated. The combustion exhaust gas discharged from the combustion furnace and a free board portion in the combustion furnace The supplied secondary combustion air is heat-exchanged through a rotary heat storage type heat exchanger having a heat storage body made of honeycomb ceramics capable of increasing the temperature gradient between the high temperature portion and the low temperature portion, and the secondary combustion air is 700 to 800 ° C. Occurs when the temperature in the freeboard section is preheated until the unburned solids and incomplete combustion gases entrained in the combustion exhaust gas in the freeboard section are completely burned, and the waste is burned in the fluidized bed with dioxin enhances than decompose temperature of, the rapidly cooled flue gas to 200 ° C. or less is adapted to prevent re-synthesis of dioxins, the combustion exhaust gas discharged from the combustion furnace the times Fluidized-bed waste combustion method fly ash by cyclones, characterized in that it is separated before entering the regenerative heat exchanger.
JP18263299A 1999-06-29 1999-06-29 Fluidized bed type waste combustion apparatus and combustion method Expired - Fee Related JP4540147B2 (en)

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