JP4512967B2 - Furnace bottom ash circulation device and fluidized bed boiler operation method - Google Patents

Description

【化２】

【化３】

（４）炉底部から排出されたベッド材をそのまま加圧流動層ボイラ内へ再供給するので、炉底部から抜き出されたベッド材に含まれる粗粉脱硫剤等の粗大粒子も再供給され、このような粗大粒子が流動層内で沈降し流動不良を起こす原因となる可能性があるという課題を有していた。
（５）脱硫反応によって石灰石等の脱硫剤表面にＣａＳＯ₄層（石膏層）が形成されると、反応速度が急激に低下する。ハ号公報では、加圧流動層ボイラから抜き出した流動媒体表面の石膏層を剥離させて脱硫反応速度を高めるために、ＣＯ₂分圧の低い領域に抜き出した流動媒体を供給し脱炭酸反応によって亀裂を生成させる方法が開示されている。しかし、本発明者が鋭意研究した結果、石灰石の亀裂の発生は、最初に加圧流動層ボイラに供給したときに起こるが、加圧流動層ボイラから抜き出した流動媒体を再度加圧流動層ボイラに供給したときにはＣＯ₂分圧の低い領域に供給しても起こり難いことが見出された。従って、流動媒体表面の石膏層の剥離が困難で、脱硫反応に寄与しないという課題を有していた。
（６）粒子径約１ｍｍ以下の流動媒体は脱硫反応がすすみ、石膏層が粒子内部深くまで生成されていることを本発明者は見出した。そのため、粒子表面に形成された石膏層を研磨等を行って削り落とさない限り剥離するのが困難で、脱硫反応に寄与しないという課題を有していた。
（７）ＣＯ₂分圧を低くするために空気比を高くすることが開示されているが、空気比を高めるために大量の空気の供給を要するため、加圧流動層ボイラの空塔速度が上昇する。そのため、流動媒体同士の磨耗が促進されるとともにフリーボードへ飛び出す流動媒体が増え流動層高が低下するので、それを補うために大量の脱硫剤を投入しなければならず脱硫剤の利用率が低下するとともに脱硫剤コストが増大するという課題を有していた。また、大量の空気が供給されると、燃焼排ガスの量や燃焼排ガスに含まれる灰塵の量が増えるので、燃焼排ガスから灰塵を除去するセラミックチューブフィルタ等の精密脱塵装置の負荷が増加し、精密脱塵装置が破損し易くなるという課題を有していた。
（８）イ号，ロ号，ハ号公報に開示の技術において、脱硫剤の有効利用率を高め脱硫効率を向上させるために、脱硫剤の粒子径を１ｍｍ程度以下に微細化させて脱硫剤の比表面積を大きくする方法が用いられることがある。しかし、脱硫剤を微細化するためには、微粉砕工程を要しエネルギーを消費するとともに、脱硫剤の終末速度が空塔速度となる粒子径（空塔速度０．８ｍ／ｓｅｃの場合は約２５０μｍ）より粒子径の小さな脱硫剤が流動層からフリーボードへ飛散し、さらにサイクロンカットサイズ以下の粒子径を有する脱硫剤はサイクロン等の集塵装置に捕集され加圧流動層ボイラ内を循環されないため脱硫率が向上しないという課題を有していた。
（９）また、微細化された脱硫剤で構成された流動層は、層密度が低くスラッギングを起こし易く流動不良を起こし易いという課題を有していた。
【０００７】
本発明は上記従来の課題を解決するもので、炉底部に滞留し流動不良の原因となり易い粗大炉底灰を除去し流動層の安定性を高めるとともに、脱硫剤の再利用をはかることができ有効利用率を向上させることができ、また既存の設備も有効に利用することができ設備負荷が小さく、さらに信頼性が高く長期間の安定運転が可能な炉底灰循環装置を提供することを目的とする。また、本発明は、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めるとともに、省エネルギー性に優れ、さらにスラッギング等の発生を防止し流動不良の発生を防止することができる流動層ボイラの運転方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記従来の課題を解決するために本発明の炉底灰循環装置及び流動層ボイラの運転方法は、以下の構成を有している。
【０００９】
本発明の請求項１に記載の炉底灰循環装置は、流動層ボイラと、前記流動層ボイラの炉底部に接続され前記炉底部に滞留した炉底灰を抜き出す炉底灰抜出管と、を備えた炉底灰循環装置であって、前記炉底灰抜出管から抜き出された前記炉底灰を５００〜５０００μｍの範囲における所定の粒子径で分級し少なくとも所定粒子径以上の粒子径を有する粗炉底灰と所定粒子径より小さい細炉底灰とに分ける分級装置と、固体燃料と脱硫剤と水とが混合されペースト化された燃料スラリーを調整及び貯留する燃料スラリー調整装置と、前記分級装置で分級された前記粗炉底灰を前記燃料スラリー調整装置に供給する粗炉底灰輸送路と、を備えた構成を有している。
この構成により、以下のような作用が得られる。
（１）粗炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が少なく、未反応の炭酸カルシウムの残存量が多いので、流動層ボイラ内に再導入すれば脱硫剤として働き、脱硫剤の有効利用率を高めることができる。
（２）粗炉底灰は酸化カルシウムや硫酸カルシウムの生成量が少ないので、水と接触しても凝結や発熱を起こさないため、石炭等の固体燃料や石灰石等の脱硫剤とともに燃料スラリー中に混合しても凝結や発熱を起こさずスラリー濃度やスラリー粘度の調整を容易に行うことができる。また、燃料スラリーに混合することができるため、粗炉底灰を燃料スラリーとして安定して流動層ボイラ内に供給することができ脱硫剤の有効利用率を高めることができる。
（３）細炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が多く、未反応の炭酸カルシウムの残存量が少ない。そのため、細炉底灰をそのまま流動層ボイラ内に導入しても脱硫剤としての機能は乏しいが、流動層高や層密度を調整する流動媒体として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる。
（４）既存の流動層ボイラの炉底灰抜出管から抜き出された炉底灰を分級する分級装置を配設するだけの小規模な改良によって、脱硫剤の有効利用率を高めることができる。
（５）５００〜５０００μｍの比較的大きな粒子径で炉底灰を分級するので、シフタ等の簡便かつ大量に処理できる分級装置を用いることができ設備負荷が小さいとともに生産性に優れ、さらに分級装置の目詰まり等も発生し難く運転効率に優れる。
（６）分級装置を有しているので、流動媒体が溶融して塊状化したシンター生成物を除去することができ、流動層内の安定性を向上させることができる。
【００１０】
ここで、炉底灰としては、流動層ボイラに供給されたＣａＣＯ₃（又は石灰石），ＭｇＣＯ₃（又はドロマイト）の他、ＣａＯ（生石灰），Ｃａ（ＯＨ）₂（消石灰），Ｋ₂ＣＯ₃，貝殻等のカルシウムを含む水産廃棄物，セメントスラッジ等の脱硫剤や、石炭，亜炭，褐炭，瀝青炭，コークス，石油コークス，オイルコークス，オイルサンド，重質油，石炭液化残渣，ゴム，古タイヤ，廃油，一般ゴミ，一般廃棄物，木質物，炭化物，ＲＤＦやその他の炭化物，木屑，産業廃棄物，食品工場や農業等で排出される有機残渣物，下水汚泥，し尿処理汚泥，工業廃水処理汚泥等やこれらの混合物である固体燃料の燃焼灰が用いられる。
【００１１】
分級装置としては、バイブレーティングスクリーンやシフタ等のふるい分け機械が用いられる。
所定粒子径としては、脱硫剤の種類や流動層ボイラの運転条件等によって異なるが、５００〜５０００μｍ好ましくは１０００〜３０００μｍとされる。所定粒子径が１０００〜３０００μｍの場合は、粗炉底灰（所定粒子径より粒子径の大きな炉底灰）中の未反応の炭酸カルシウム含有量が多く脱硫剤として再利用可能であるため好ましい。所定粒子径が１０００μｍより小さくなるにつれ粗炉底灰中に残存する未反応の炭酸カルシウム量が少なくなる一方で酸化カルシウムや硫酸カルシウムの含有量が増加し、水と接触すると水和反応によって凝結や発熱を起こし易くなる傾向がみられるとともに、分級装置に目詰まり等が発生し運転効率・分級効率が低下する傾向がみられるため好ましくない。さらに、流動層を構成する流動媒体の粒子径が小さくなるため流動が活発になりすぎ、流動媒体による伝熱管等の磨耗が激しくなるため好ましくない。３０００μｍより大きくなるにつれ未反応の炭酸カルシウムが多く含有される粗炉底灰の量が減少する傾向がみられるため好ましくない。特に、所定粒子径が５００μｍより小さくなるか５０００μｍより大きくなると、これらの傾向が著しくなるため、いずれも好ましくない。
【００１２】
粗炉底灰としては、ＣａＣＯ₃をＣａ化合物に対し６０〜１００ｗｔ％好ましくは７０〜１００ｗｔ％含有している炉底灰が用いられる。ＣａＣＯ₃の含有率が７０〜１００ｗｔ％の場合は、脱硫剤としての機能が高いとともに水と接触させても凝結や発熱を起こさず燃料スラリーに混合することができ好ましい。ＣａＣＯ₃の含有率が７０ｗｔ％より低くなるにつれＣａＳＯ₄やＣａＯの含有率が増大し脱硫剤としての機能が低下するとともに水と接触すると凝結や発熱を起こす傾向がみられるため好ましくなく、特に６０ｗｔ％より低くなるとその傾向が著しいため好ましくない。
【００１３】
細炉底灰としては、ＣａＣＯ₃をＣａ化合物に対し０〜４０ｗｔ％好ましくは０〜３５ｗｔ％含有している炉底灰が用いられる。ＣａＣＯ₃の含有率がＣａ化合物に対し３５ｗｔ％より高くなるにつれ粗炉底灰の量が減少する傾向がみられるため好ましくなく、特に４０ｗｔ％より低くなるとその傾向が著しいため好ましくない。なお、表面に形成されたＣａＳＯ₄層（石膏層）を研磨等によって除去すれば、これらの傾向を抑制することができる。
【００１４】
分級装置としては、所定の粒子径で粗炉底灰と細炉底灰とに分級する他、粗炉底灰のうち、流動層ボイラに供給する脱硫剤の最大粒子径よりも大きく塊状化したシンター生成物等の粗大粒子を除去するように分級することもできる。これにより、炉底部から抜き出された炉底灰に含まれるシンター生成物や粗粉脱硫剤等の粗大粒子を除去することができ、このような粗大粒子が流動層内で沈降したり流動媒体を塊状化させたりして流動不良を起こす原因となるのを防止することができ長期間の安定運転が可能になる。
【００１５】
本発明の請求項２に記載の発明は、請求項１に記載の炉底灰循環装置であって、前記粗炉底灰を前記所定粒子径より小さな粒子径を有する粉砕粒子に粉砕する粉砕装置を備えた構成を有している。
この構成により、請求項１で得られる作用に加え、以下のような作用が得られる。
（１）粗炉底灰を粉砕することで粗炉底灰表面の石膏層を剥離させ、また砕いて粒子径を小さくして、未反応のＣａＣＯ₃層を露出させ炉底灰を脱硫剤として再利用することができる。
（２）粗炉底灰のうち、粗大化して流動層ボイラの炉底部に沈降し流動し難い粒子を粉砕して流動層ボイラ内に再供給することにより、流動層の流動状態を活発化させ流動不良の発生を防止することができる。
（３）粉砕装置で粗炉底灰を所定粒子径より小さな粉砕粒子に粉砕して流動層ボイラ内に再供給することにより、次に炉底灰抜出管から抜き出されたときには細炉底灰として分級されるので、燃料スラリーには混合されず燃料スラリー濃度や粘度等の安定性を向上させることができ信頼性を高めることができる。脱硫剤が流動層ボイラ内に何度も供給されて長時間高圧高温下に曝されると、時間の経過とともに炭酸カルシウムの残存量が低下し酸化カルシウムや硫酸カルシウムの生成量が多くなり、水と接触すると水和反応により凝結や発熱を引き起こし燃料スラリー濃度や粘度等を不安定にするからである。
（４）粉砕装置を備えているので、粗炉底灰が所定粒子径より小さな粉砕粒子に粉砕されて流動層ボイラ内へ供給され、供給された粉砕粒子や細炉底灰が流動層ボイラ内で磨耗によって微細化されてフライアッシュとなって系外に排出される。フライアッシュはそれ自体でセメント材料やセメント原料等としてリサイクル可能なので、炉底灰の処理費用や産業廃棄物の発生量等を著しく減少させることができる。
【００１６】
ここで、粉砕装置としては、エッジランナ，ローラミル等のロール転動型粉砕機、遠心分離型ミル等の高速回転式衝撃せん断粉砕機、転動ボールミル，振動ボールミル等のボール媒体ミル、媒体撹拌型粉砕機等の乾式粉砕機が用いられる。特に、連続式で大容量の粉砕が可能なローラミル等のロール転動型粉砕機、遠心分離型ミル等の高速回転式衝撃せん断粉砕機が好ましく用いられる。
【００１７】
なお、粉砕粒子の粒子径としては、５００〜５０００μｍ好ましくは１０００〜３０００μｍの所定粒子径より小さく、飛び出し粒子径（終末速度が流動層ボイラの空塔速度と同じである粒子の粒径）より大きいものとする。粉砕粒子の粒子径が飛び出し粒子径より小さくなると、粉砕粒子が燃焼ガスに随伴して流動層からフリーボードへ飛び出し、流動層を形成しないからである。
【００１８】
本発明の請求項３に記載の発明は、請求項２に記載の炉底灰循環装置であって、前記粗粒子灰、前記細炉底灰、前記粉砕粒子のいずれか１種以上の各粒子表面の石膏層を除去した石膏層除去粒子を生成する石膏層除去装置を備えた構成を有している。
この構成によって、請求項２で得られる作用に加え、以下のような作用が得られる。
（１）石膏層除去装置を有しているので、細炉底灰等の各粒子表面に形成された石膏層を除去して未反応のＣａＣＯ₃層を露出させることができ、再び脱硫反応速度を高め再活性化させ脱硫剤の有効利用率を高めることができる。
（２）水と接触すると水和硬化や発熱を引き起こす石膏層を石膏除去装置で除去することにより、石膏除去粒子を燃料スラリーに混合させることもでき応用性に優れる。また、石膏層を除去した石膏層除去粒子は、空気中の水分と反応し難く保存性に優れる。
【００１９】
ここで、石膏層除去装置としては、ミックスマラー、ウェットパンミル、アイリッヒミル、ローラーミル、コロイドミル等の回転するロール間やロールと円板間等で摩擦・剪断作用を加えて各粒子の表面に形成された石膏層を除去する粉砕機が用いられる。これらの石膏除去装置では、ロール間やロールと円板間等の間隔を５００〜５０００μｍ程度の所定間隔に設定し、この間に細炉底灰等を供給し石膏層を削り取って除去する。発熱を抑えるために、ロールや円板等の回転数は低くするのが好ましい。発熱に伴う膨張歪の発生による石膏層除去粒子の粉化を防止するためである。
なお、粒子表面からの石膏層の除去深さとしては、ロール間等の間隔と細炉底灰等の粒子径との関係にもよるが、１〜１０μｍが好ましい。１μｍより少なくなるにつれ除去する石膏層の厚みが少なく未反応のＣａＣＯ₃層を露出できない傾向がみられ、１０μｍより多くなるにつれ細炉底灰等が粉化し流動層ボイラ内で流動層を形成せずフリーボードに飛散する粒子が増加する傾向がみられるため、いずれも好ましくない。
【００２０】
本発明の請求項４に記載の発明は、請求項３に記載の炉底灰循環装置であって、前記粗炉底灰，前記粉砕粒子，前記石膏層除去粒子のいずれか１種以上を、前記流動層ボイラに供給する脱硫剤に混合して調整する脱硫剤調整装置を備えた構成を有している。
この構成により、請求項３で得られる作用に加え、以下のような作用が得られる。
（１）脱硫剤調整装置を有しているので、粗炉底灰，粉砕粒子，石膏層除去粒子のいずれか１種以上を石灰石等の脱硫剤に混合して調整し流動層ボイラに供給することができ、脱硫剤の有効利用率を高めることができる。
【００２１】
ここで、脱硫剤調整装置としては、石炭等の固体燃料と石灰石やドロマイト等の脱硫剤と粉砕粒子等と水とを湿式混合してペースト化した燃料スラリーを調整する燃料スラリー調整装置、固体燃料と脱硫剤と粉砕粒子等とを乾式混合しロックホッパを介して流動層ボイラ内へ供給する燃料供給ホッパ、固体燃料とは別に脱硫剤と粉砕粒子等とをペースト化する脱硫剤スラリー調整装置、脱硫剤と粉砕粒子等とを乾式混合しロックホッパを介して流動層ボイラへ供給する脱硫剤供給ホッパ等が用いられる。
【００２２】
本発明の請求項５に記載の発明は、請求項３又は４に記載の炉底灰循環装置であって、（ａ）前記細炉底灰、前記粉砕粒子、前記石膏層除去粒子のいずれか１種以上を貯蔵する細炉底灰貯蔵容器と、（ｂ）前記細炉底灰貯蔵容器と前記流動層ボイラとに連通し前記細炉底灰貯蔵容器に貯蔵された前記細炉底灰、前記粉砕粒子、前記石膏層除去粒子のいずれか１種以上を前記流動層ボイラに導入する細炉底灰導入管と、（ｃ）前記流動層ボイラ内の差圧を測定する差圧検出手段と、（ｄ）前記差圧検出手段で検出された差圧に基づいて前記流動層ボイラの層密度を制御する層密度制御手段と、を備えた構成を有している。
この構成により、請求項３又は４で得られる作用に加え、以下のような作用が得られる。
（１）細炉底灰、粉砕粒子、石膏層除去粒子のいずれか１以上を層密度を調整する流動媒体として用いることができるので、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる。
（２）酸化カルシウムや硫酸カルシウムの生成量が多い細炉底灰を燃料スラリーに混合せずに流動層ボイラに供給できるので、燃料スラリーが凝結や発熱せず燃料スラリー濃度や粘度等の安定性を維持することができる。
（３）細炉底灰の表面に形成された石膏層が除去された石膏層除去粒子や粉砕粒子は、未反応のＣａＣＯ₃層が析出し活性化されているので脱硫剤として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる。
（４）差圧検出手段で検出された差圧に基づいて流動層の層密度を制御する層密度検出手段を有しているので、流動層の膨張比（流動化している流動層の高さと固定層高さとの比）を最適にして流動を活発に維持し最適な燃焼状態を保つことができる。
（５）流動を活発に維持できるので供給される脱硫剤の熱破壊や磨耗を起こし易くして流動媒体を細粒化し、さらに流動不良を起こし難くすることができる。
（６）流動層の層密度を最適に制御することができるのでスラッギングを防止することができ、正常な流動層を生成することができる。
（７）スラッギングを防止できるので、スラリー噴射ノズルから噴射された燃料スラリーが伝熱管や流動層ボイラの壁面に付着・固化・塊状化して流動不良が発生し易くなることを防止できる。
（８）流動を活発に維持するとともに流動層の層密度を最適に制御できるので、層内の流動状態を均一化でき、流動層から伝熱管への伝熱を均一にすることができ熱効率に優れる。
（９）流動を活発に維持できるので、スラリーノズル付近での固体燃料の燃焼熱が滞留し難く溶融灰が形成され難いため、溶融灰によって流動媒体が塊状化し流動不良が発生するのを防止することができる。
【００２３】
ここで、差圧検出手段としては、ひずみゲージ方式，静電容量方式，液柱方式，沈鐘方式，ブルドン管式，ベローズ管式等の圧力検出器が用いられ、これらの圧力検出器が、流動層の底部と流動層の所定高さとの間等、流動層の１乃至複数箇所の差圧が検出される位置に配設される。
層密度制御手段としては、細炉底灰貯蔵容器に接続され細炉底灰貯蔵容器内の圧力を流動層ボイラ内の圧力よりも高め又は同じにして細炉底灰貯蔵容器から流動層ボイラへの細炉底灰の供給を促す高圧ガス供給路等の圧力制御装置、炉底灰抜出管からの炉底灰の抜出量を制御するロータリーバルブ等の抜出量制御装置、細炉底灰導入管に接続され細炉底灰導入管から流動層ボイラへの細炉底灰等の供給量を制御するＬバルブ，Ｊバルブ，Ｖバルブ，シールポット等のループシール，ロータリーバルブ，インゼクトフィーダ，テーブルフィーダ，エアスライド，２重ダンパー等の供給量制御装置等やこれらを組み合わせたものが用いられる。
【００２４】
本発明の請求項６に記載の流動層ボイラの運転方法は、流動層ボイラの炉底部に連通する炉底灰抜出管から前記炉底部に滞留した炉底灰を抜き出す炉底灰抜出工程と、前記炉底灰を５００〜５０００μｍの所定粒子径で分級し少なくとも粗炉底灰と細炉底灰とに分ける分級工程と、前記粗炉底灰を燃料スラリーに混合してスラリー濃度やスラリー粘度を調整する工程と、を備えた構成を有している。
この構成により、以下のような作用が得られる。
（１）流動層ボイラの炉底部に滞留した炉底灰を抜き出すので、炉底部に滞留して流動不良の原因となる粗粉脱硫剤等の粗大粒子を抜き出し、流動不良の発生を未然に防ぐことができる。
（２）粗炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が少なく未反応の炭酸カルシウムの残存量が多いので、流動層ボイラ内に再導入すれば脱硫剤として働き、脱硫剤の有効利用率を高めることができる。
（３）粗炉底灰は酸化カルシウムや硫酸カルシウムの生成量が少ないので、水と接触しても凝結や発熱を起こさず、燃料スラリーに混合しても水和反応によって凝結や発熱を起こさずスラリー濃度やスラリー粘度の調整が容易である。
（４）細炉底灰は、脱硫反応や脱炭酸反応で生成される石膏や酸化カルシウムの生成量が多く未反応の炭酸カルシウムの残存量が少ないので、流動層ボイラ内に導入しても脱硫剤としての機能は乏しいが、流動層高を調整する流動媒体として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる。なお、各粒子の表面に形成された石膏層を除去すれば、未反応のＣａＣＯ₃層を露出させることができ、再び脱硫反応速度を高め再活性化させ脱硫剤の有効利用率を高めることができる。
（５）５００〜５０００μｍの比較的大きな粒子径で炉底灰を分級するので、シフタ等の簡便かつ大量に処理できる分級装置を用いることができ設備負荷が小さいとともに生産性に優れ、さらに分級装置の目詰まり等も発生し難く運転効率に優れる。
【００２５】
本発明の請求項７に記載の発明は、請求項６に記載の流動層ボイラの運転方法であって、前記分級工程で分級された前記粗炉底灰を前記所定粒子径より小さな粒子径を有する粉砕粒子に粉砕する粉砕工程を備えた構成を有している。
この構成により、請求項６で得られる作用に加え、以下のような作用が得られる。
（１）分級工程で分級された粗炉底灰のみを粉砕するので、粉砕装置は小型のものでよく設備負荷が小さい。
（２）粗炉底灰を粉砕することで粗炉底灰表面の石膏層を剥離させ、また砕いて粒子径を小さくして、未反応のＣａＣＯ₃層を露出させ脱硫剤として再利用することができる。
（３）粗炉底灰のうち、粗大化して流動層ボイラの炉底部に沈降し流動し難い粒子を粉砕して流動層ボイラ内に再供給することにより、流動層の流動状態を活発化させ流動不良の発生を防止することができる。
（４）粗炉底灰を所定粒子径より小さな粉砕粒子に粉砕して流動層ボイラ内に再供給することにより、次に炉底灰抜出管から抜き出されるときには所定粒子径より小さな細炉底灰として分級されるので、燃料スラリーには混合されず燃料スラリー濃度や粘度等の安定性を向上させることができ信頼性を高めることができる。脱硫剤が流動層ボイラ内に何度も供給されて長時間高圧高温下に曝されると、時間の経過とともに炭酸カルシウムの残存量が低下し酸化カルシウムや硫酸カルシウムの生成量が多くなり、水と接触すると水和反応により凝結や発熱を引き起こすからである。
（５）粉砕装置を備えているので、粗炉底灰が所定粒子径より小さな粉砕粒子に粉砕されて流動層ボイラ内へ供給され、供給された粉砕粒子や細炉底灰が流動層ボイラ内で磨耗によって微細化されてフライアッシュとなって系外に排出される。フライアッシュはそれ自体でセメント材料やセメント原料等としてリサイクル可能なので、炉底灰の処理費用や産業廃棄物の発生量を著しく減少させることができる。
【００２６】
本発明の請求項８に記載の発明は、請求項６又は７に記載の流動層ボイラの運転方法であって、前記流動層ボイラに１０〜８０ｗｔ％好ましくは２０〜４０ｗｔ％の１〜５ｍｍの粒子径を有する脱硫剤を供給する構成を有している。
この構成により、請求項６又は７で得られる作用に加え、以下のような作用が得られる。
（１）粒子径が１〜５ｍｍの脱硫剤の大部分は、流動層ボイラに供給されることで熱破壊や磨耗を起こし細粒化されるので、流動層ボイラに供給する以前に脱硫剤を粉砕する必要がなく粉砕に要する工数及び費用を削減することができ省エネルギー性に優れる。
（２）脱硫剤を流動層ボイラに供給する以前に粉砕して微粒化させないので、粒子の終末速度がガス空塔速度となり流動層からフリーボードへ飛散し流動層を構成しない微粒子（この微粒子の粒子径は、ガス空塔速度が０．８±０．４ｍ／ｓのとき約２５０μｍ以下である）の含有率が低く、良好な流動層を構成させることができる。
（３）流動層の底部に粒子径が１〜５ｍｍの脱硫剤を含む流動層を生成することができるので、スラッギングを防止することができ、スラリー噴射ノズルから噴射された燃料スラリーが伝熱管や流動層ボイラの壁面に付着・固化・塊状化して流動不良が発生し易くなることを防止できる。
【００２７】
ここで、脱硫剤としては、請求項１で説明したものと同様のものなので、説明は省略する。
なお、１〜５ｍｍの粒子径を有する脱硫剤の含有率としては、１０〜８０ｗｔ％好ましくは２０〜４０ｗｔ％とされる。含有率が２０〜４０ｗｔ％の場合は、流動層の膨張比が最適で流動が活発にみられるとともに、流動層の安定性に優れスラッギングを発生し難いため好ましい。含有率が２０ｗｔ％より小さくなるにつれ流動層の安定性に乏しくスラッギングを発生し易くなる傾向がみられ、４０ｗｔ％より大きくなるにつれ流動層ボイラ内で熱破壊されずに残存する１〜５ｍｍの脱硫剤の量が多くなり流動層の膨張比が小さくなり流動が不活発になる傾向がみられるため好ましくない。特に、含有率が１０ｗｔ％より小さくなるか８０ｗｔ％より多くなると、これらの傾向が著しくなるためいずれも好ましくない。
【００２８】
【発明の実施の形態】
以下、本発明の一実施の形態を、図面を参照しながら説明する。
（実施の形態１）
図１は本実施の形態１における炉底灰循環装置の要部構成図である。
図中、１はコンプレッサ（図示しない）からの圧縮空気が供給される圧力容器、２は圧力容器１に内設され圧力容器１内に取り入れられた圧縮空気が底部から供給される加圧流動層ボイラ、２ａは加圧流動層ボイラ２の流動層２ｂ内に配設された伝熱管、３は加圧流動層ボイラ２の頂部に配設された燃焼排ガス流路管、４は燃焼排ガス流路管３の出口に配設されたサイクロン等の粗脱塵装置、５は粗脱塵装置４で粗脱塵された粗脱塵ガス流路管、６は粗脱塵ガス流路管５を流れる粗脱塵ガスの脱塵を行うセラミックチューブフィルタ等で構成された精密脱塵装置、７は石炭等の固体燃料と石灰石やドロマイト等の脱硫剤と水とが混合されペースト化された燃料スラリーを調整及び貯留する脱硫剤調整装置としての燃料スラリー調整装置、８は燃料スラリー調整装置７に接続され加圧流動層ボイラ２に燃料スラリーを輸送するスラリーポンプ、９は一端がスラリーポンプ８に接続され他端が燃料スラリーを加圧流動層ボイラ２内に噴射するスラリー噴射ノズル（図示しない）に接続されたスラリー供給路、１０は加圧流動層ボイラ２の炉底部に接続され加圧流動層ボイラ２の炉底部に滞留した石炭灰や石灰石等の炉底灰を加圧流動層ボイラ２及び圧力容器１の外部に抜き出す炉底灰抜出管、１１は炉底灰抜出管１０で抜き出された炉底灰を５００〜５０００μｍの所定粒子径で２種以上の炉底灰に分級するシフタ等の分級装置、１２は分級装置１１で分級された粒子径の大きな炉底灰（以下、粗炉底灰という）を燃料スラリー調整装置７に供給する粗炉底灰輸送路、１３は分級装置１１で分級された粒子径の細かい炉底灰（以下、細炉底灰という）を搬送する細炉底灰輸送路、１３ａは細炉底灰輸送路１３に配設され分級装置１１で分離された細炉底灰を系外に排出する場合に作動させる三方弁からなる分岐弁、１３ｂは細炉底灰輸送路１３に接続され細炉底灰の全部又は一部が搬送される細炉底灰分岐路、１３ｃは細炉底灰分岐路１３ｂに配設され細炉底灰分岐路１３ｂで搬送される細炉底灰の各粒子表面の石膏層を除去し石膏層除去粒子を生成するミックスマラー，ウェットパンミル等の石膏層除去装置、１３ｄは除去された石膏層の排出路、１４は圧力容器１内に配置されて細炉底灰輸送路１３に接続され、細炉底灰輸送路１３を搬送された細炉底灰や石膏層除去粒子を貯蔵する細炉底灰貯蔵容器、１５は細炉底灰貯蔵容器１４に貯蔵された細炉底灰や石膏層除去粒子を加圧流動層ボイラ２の流動層２ｂ内に導入する細炉底灰導入管である。
なお、粗炉底灰輸送路１２，細炉底灰輸送路１３，細炉底灰分岐路１３ｂ等では、気流搬送，バケットエレベータ，ベルトコンベア等の搬送手段によって粗炉底灰や細炉底灰等が搬送される。また、細炉底灰輸送路１３，炉底灰抜出管１０等のように圧力容器１を貫通して常圧系と加圧系が切り替わる箇所には、圧力調整のためのロックホッパシステム（図示しない）が配設されている。
【００２９】
以上のように構成された本実施の形態１の炉底灰循環装置について、以下その運転方法を説明する。
石炭等の固体燃料と石灰石やドロマイト等の脱硫剤と水とを燃料スラリー調整装置７でペースト化し燃料スラリーを調整し、燃料スラリー調整装置７に貯留しておく。圧力容器１内に内設した加圧流動層ボイラ２では燃料スラリーをスラリー供給路９から入れ、圧力容器１内に取り入れた圧縮空気を加圧流動層ボイラ２の底部から供給し、固体燃料と脱硫剤が流動状態になった流動層２ｂを形成させ０．６〜３．１ＭＰａ、８００〜９５０℃の温度で燃焼させている。固体燃料の燃焼で発生した熱は伝熱管２ａで熱交換され蒸気タービン発電機（図示せず）を駆動して発電を行う。燃焼排ガスは燃焼排ガス流路管３から粗脱塵装置４へ流され粗脱塵された後、粗脱塵ガス流路管５から精密脱塵装置６を通過し、ガスタービン発電機（図示せず）を駆動し発電する。
加圧流動層ボイラ２の炉底部に石炭灰や石灰石等の炉底灰が滞留し流動層２ｂの層高が高くなったときは、炉底灰抜出管１０から炉底部に滞留している炉底灰を抜き出す。分級装置１１は、炉底部から抜き出された炉底灰を５００〜５０００μｍの所定粒子径で分級し粗炉底灰と細炉底灰とに分ける。粗炉底灰は、粗炉底灰輸送路１２を通って搬送され所定量秤量され、燃料スラリー調整装置７で燃料等と混合されて燃料スラリーに調整される。一方、細炉底灰は、細炉底灰輸送路１３を通って搬送される。一部は細炉底灰輸送路１３に連通する細炉底灰分岐路１３ｂに運ばれ、石膏層除去装置１３ｃに供給される。石膏層除去装置１３ｃでは、ロール間やロールと円板間等を５００〜５０００μｍ程度の間隔に設定し、この間に細炉底灰を供給し石膏層を表面から約１〜１０μｍの深さで削り取り石膏層除去粒子を生成する。石膏層除去装置１３ｃで生成された石膏層除去粒子と細炉底灰は、細炉底灰貯蔵容器１４に貯蔵される。細炉底灰貯蔵容器１４に貯蔵された細炉底灰及び石膏層除去粒子は、加圧流動層ボイラ２の流動層２ｂの層高が低くなった際には細炉底灰供給管１５から加圧流動層ボイラ２内に導入される。
【００３０】
以上のように、本実施の形態１における炉底灰循環装置は構成されているので、以下のような作用が得られる。
（１）粗炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が少なく未反応の炭酸カルシウムの残存量が多いので、石炭等と混合しスラリー化して加圧流動層ボイラ内に再導入して脱硫剤の有効利用率を高めることができる。
（２）粗炉底灰は酸化カルシウムや硫酸カルシウムの生成量が少ないので、水と接触しても凝結や発熱を起こさないため、石炭等の固体燃料や石灰石等の脱硫剤とともに燃料スラリー中に混合しても凝結や発熱を起こさずスラリー濃度やスラリー粘度の調整を容易に行うことができる。また、燃料スラリーに混合することができるため、粗炉底灰を燃料スラリーとして安定して加圧流動層ボイラ内に供給することができ脱硫剤の有効利用率を高めることができる。
（３）細炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が多く未反応の炭酸カルシウムの残存量が少ない。しかし、石膏層除去装置を有しているので、細炉底灰の各粒子表面に形成された石膏層を除去して未反応のＣａＣＯ₃層を露出させることができ、再び脱硫反応速度を高め再活性化させ脱硫剤の有効利用率を高めることができる。
（４）既存の加圧流動層ボイラの炉底灰抜出管から抜き出された炉底灰を分級する分級装置を配設するだけの小規模な改良によって、脱硫剤の有効利用率を高めその消費量を減らすことができる。
（５）５００〜５０００μｍの比較的大きな粒子径で炉底灰を分級するので、シフタ等の簡便かつ大量に処理できる分級装置を用いることができ設備負荷が小さいとともに生産性に優れる。
（６）分級装置で炉底灰を粗炉底灰と細炉底灰とに分級し、層高等に応じて粗炉底灰と細炉底灰とを別々に流動層内に供給するので、流動層内の粒子径が制御され流動を安定化できる。
【００３１】
なお、本実施の形態１では、分級装置１１は、所定粒子径で粗炉底灰と細炉底灰とに分級するものについて説明したが、これに加えて粗炉底灰のうち特に粒子径の大きなものを除去するように分級することもできる。これにより、炉底部から抜き出された炉底灰に含まれるシンター生成物や粗粉脱硫剤等の粗大粒子を除去することができ、このような粗大粒子が流動層内で沈降し流動不良を起こす原因となるのを防止することができる。
また、細炉底灰の粒子径が小さい場合は、石膏層除去装置１３ｃは設けなくてもよい。細炉底灰の粒子径に対する石膏層の相対的な厚みが厚く、石膏層を除去し難く石膏層除去効率が低いからである。
【００３２】
（実施の形態２）
図２は実施の形態２における炉底灰循環装置の要部構成図である。なお、実施の形態１で説明したものと同様のものは、同じ符号を付して説明は省略する。
図中、１６は粗炉底灰輸送路１２によって輸送された粗炉底灰を５００〜５０００μｍの所定粒子径より小さい粒子径に粉砕するエッジランナ，ローラーミル等の粉砕装置、１７は粉砕装置１６で粗炉底灰が粉砕された粉砕粒子を燃料スラリー調整装置７に供給する粉砕粒子供給路、１８は細炉底灰貯蔵容器１４と粉砕粒子供給路１７とに連通し粉砕装置１６で粉砕された粉砕粒子を細炉底灰貯蔵容器１４に輸送し供給する粉砕粒子輸送路、１８ａは粉砕粒子供給路１７と粉砕粒子輸送路１８との連通部に配設された三方弁等からなる分岐弁である。
なお、粉砕粒子輸送路１８では、気流搬送，バケットエレベータ，ベルトコンベア等の搬送手段によって粉砕粒子が搬送される。また、粉砕粒子輸送路１８において圧力容器１を貫通して常圧系と加圧系が切り替わる箇所には、圧力調整のためのロックホッパシステム（図示しない）が配設されている。
【００３３】
以上のように構成された本実施の形態２の加圧流動層ボイラの流動層循環装置について、以下その運転方法を説明する。
加圧流動層ボイラ２の炉底部に滞留している石炭灰や石灰石等の炉底灰を炉底灰抜出管１０から抜き出し、分級装置１１で、５００〜５０００μｍの所定粒子径で粗炉底灰と細炉底灰とに分ける。分級された粗炉底灰は、次に、粗炉底灰輸送路１２を通って粉砕装置１６へ運ばれる。粉砕装置１６では、ローラー等の間隙を所定粒子径の間隔に保持しておき、粗炉底灰を通過させ５００〜５０００μｍの所定粒子径よりも小さな粉砕粒子に粉砕する。粗炉底灰が粉砕された粉砕粒子は、燃料スラリー調整装置７で燃料等と混合され燃料スラリーに調整される。また、粉砕粒子の一部は分岐弁１８ａで分岐されて粉砕粒子輸送管１８を通って運ばれ、分級装置１１で分級された細炉底灰とともに細炉底灰貯蔵容器１４に貯蔵される。細炉底灰貯蔵容器１４に貯蔵された細炉底灰は、加圧流動層ボイラ２の流動層２ｂの層高が低くなった際に細炉底灰供給管１５から加圧流動層ボイラ２内に導入される。
【００３４】
以上のように、本実施の形態２の炉底灰循環装置は構成されているので、実施の形態１で得られる作用に加え、以下のような作用が得られる。
（１）粗炉底灰を粉砕することで粗炉底灰表面のＣａＳＯ₄層を剥離させ、また砕いて粒子径を小さくして、未反応のＣａＣＯ₃層を露出させ炉底灰を脱硫剤として再利用することができる。
（２）粗炉底灰のうち、粗大化して加圧流動層ボイラの炉底部に沈降し流動し難いシンター生成物等の粒子を粉砕して加圧流動層ボイラ内に再供給することにより、流動層の流動状態を活発化させ流動不良の発生を防止することができる。
（３）粉砕装置で粗炉底灰を所定粒子径より小さな粉砕粒子に粉砕して加圧流動層ボイラ内に再供給することにより、次に炉底灰抜出管から抜き出されるときには所定粒子径より小さな細炉底灰になっているので、燃料スラリーには混合されず燃料スラリー濃度や粘度等の安定性を向上させることができ信頼性を高めることができる。脱硫剤は加圧流動層ボイラ内に何度も供給されて長時間高圧高温下に曝されると、時間の経過とともに炭酸カルシウムの残存量が低下し酸化カルシウムや硫酸カルシウムの生成量が多くなり、水と接触すると水和反応により凝結や発熱を引き起こすからである。
【００３５】
なお、本実施の形態においては、細炉底灰輸送路１３に細炉底灰分岐路１３ｂ及び石膏層除去装置１３ｃが接続されていない場合について説明したが、これらを備えることもできる。これにより、細炉底灰の各粒子の表面に生成された石膏層を除去して再活性化できるので、脱硫作用を高めることができる。
【００３６】
（実施の形態３）
図３は実施の形態３における炉底灰循環装置の要部構成図である。なお、実施の形態１及び２で説明したものと同様のものは、同じ符号を付して説明は省略する。
図中、１１ａはふるい目開きの異なるふるい網面が多段に形成され、炉底灰抜出管１０で抜き出された炉底灰を粗炉底灰、細炉底灰、加圧流動層ボイラ２に供給する脱硫剤の最大粒子径より大きなシンター生成物や粗粉脱硫剤等の粗大粒子の３種に分級するシフター等の分級装置、１１ｂは分級装置１１ａで分級された粗大粒子を系外に排出する粗大粒子排出路、１２ａは分級装置１１ａで分級された粗炉底灰を脱硫剤調整装置としての燃料供給ホッパ１７ａ（後述する）に供給する粗炉底灰輸送路、１２ｂは粗炉底灰輸送路１２ａに接続され粗炉底灰の全部又は一部が搬送される粗炉底灰分岐路、１２ｃは粗炉底灰分岐路１２ｂに配設され粗炉底灰分岐路１２ｂを搬送される粗炉底灰の各粒子表面の石膏層を除去し石膏層除去粒子を生成する石膏層除去装置、１７ａは石炭等の固体燃料と石灰石等の脱硫剤と粗炉底灰輸送路１２ａから供給される粗炉底灰や石膏層除去粒子等とを混合する脱硫剤調整装置としての燃料供給ホッパ、１７ｂは燃料供給ホッパ１７ａの下流に接続され加圧流動層ボイラ２と略同じ圧力である０．６〜３．１ＭＰａ程度の圧力で燃料供給ホッパ１７ａで混合された固体燃料等を貯蔵するロックホッパ、１７ｃはロックホッパ１７ｂの下流と加圧流動層ボイラ２内に配設されたスプレーノズル（図示しない）とに接続されロックホッパ１７ｂ内に貯蔵された固体燃料等を空気流によって搬送して流動層２ｂへ供給する燃料供給路、１７ｄは燃料供給路１７ｃに連通しロックホッパ１７ｂから燃料供給路１７ｃ内に供給された固体燃料等を流動層２ｂに搬送する圧縮空気を供給する搬送空気供給管である。なお、燃料供給ホッパ１７ａからロックホッパ１７ｂに固体燃料等を供給するときには、燃料供給ホッパ１７ａの圧力をロックホッパ１７ｂと略同一の圧力に加圧した後に行われる。
【００３７】
以上のように構成された実施の形態３の炉底灰循環装置が実施の形態１と異なる点は、分級装置１１ａが多段に形成されている点と、燃料スラリー調整装置の代わりに脱硫剤調整装置としての燃料供給ホッパ１７ａとロックホッパ１７ｂとを備えている点と、分級された粗炉底灰の粒子表面の石膏層を除去する石膏層除去装置１２ｃを備えている点である。
【００３８】
以上のように実施の形態３の炉底灰循環装置は構成されているので、実施の形態１又は２に記載の作用に加え、以下のような作用が得られる。
（１）分級装置が多段に形成され、シンター生成物等の粗大粒子、粗炉底灰、細炉底灰を同時に分離できるので分級効率に優れる。
（２）炉底灰に含有されるシンター生成物等の粗大粒子を分級装置で分離して系外に排出できるので、粗大粒子が流動層内で沈降したり流動媒体を塊状化させたりして流動不良を起こす原因となるのを防止することができ長期間の安定運転が可能になる。
（３）脱硫剤等をスラリー化せずに加圧流動層ボイラ内に供給することができ、スラリーに含有される水が蒸発するときの気化熱の損失がなく熱効率に優れる。
（４）粗炉底灰の各粒子表面に生成した石膏層を除去する石膏層除去装置を有しているので、未反応のＣａＣＯ₃層を露出させることができ、脱硫反応速度を高め再活性化させ脱硫剤の有効利用率を高めることができる。
【００３９】
なお、本実施の形態では、粗炉底灰を処理する石膏層除去装置１２ｃ、細炉底灰を処理する石膏層除去装置１３ｃを備えている場合について説明したが、燃料や脱硫剤の粒子径や種類によっては、それらを全く備えない場合もあるし、いずれか片方だけを備えている場合もある。また、実施の形態２で説明した粗炉底灰を粉砕する粉砕装置を備えていない場合について説明したが、それを備えている場合もある。
【００４０】
（実施の形態４）
図４は実施の形態４における炉底灰循環装置の要部構成図である。なお、実施の形態１及び２で説明したものと同様のものは、同じ符号を付して説明は省略する。
図中、１５ａは細炉底灰貯蔵容器１４に貯蔵された細炉底灰等を加圧流動層ボイラ２の流動層２ｂ内に空気流のアシストにより導入する供給量制御装置（層密度制御手段）としてのＬバルブやＪバルブ等が下部に接続された細炉底灰導入管、１９は細炉底灰導入管１５ａの上流に接続され細炉底灰導入管１５ａ内の細炉底灰等を流動層２ｂに搬送する圧縮空気を供給するＬバルブ等の空気供給管、２０は空気供給管１９に配設され空気量の制御を行うＬバルブ等の空気量制御バルブ、２１は炉底灰抜出管１０に配設され炉底灰の抜出量を制御するロータリーバルブ等の抜出量制御装置（層密度制御手段）、２２は両端部が加圧流動層ボイラ２と連通し一端部が流動層２ｂの底部に連通するとともに他端部が流動層２ｂの高さ方向の所定位置に連通し（底部から所定位置までの高さをｚとする）この間の差圧Δｐを検出するひずみゲージ方式，静電容量方式，液柱方式，沈鐘方式，ブルドン管式，ベローズ管式等の圧力検出器からなる差圧検出手段、２３は差圧検出手段２２で検出された差圧をもとに流動層２ｂの層密度を算出しその結果に基づき層密度制御手段としてのＬバルブ等の空気量制御バルブ２０や抜出量制御装置２１の開閉度の制御を行うコントローラである。
【００４１】
以上のように構成された本実施の形態４の流動層循環装置について、以下その運転方法を説明する。
まず、コントローラ２３は、差圧検出手段２２で検出されたΔｐ（Ｐａ）及び既知の間隔ｚ（ｍ）を用いて流動層２ｂの層密度（ｋｇ／ｍ³）を（数１）で算出する。なお、ｇは重力加速度である。
【数１】

次いで、コントローラ２３は、流動層の層密度と流動媒体の平均粒子径との関係（流動媒体の平均粒子径が小さくなるにつれ膨張比（固定層高さと流動層高さとの比）が上昇し層密度が低下し、流動媒体の平均粒子径が大きくなるにつれ膨張比が低下し層密度が増加するという関係）から最適な層密度を算出し、層密度検出手段としてのＬバルブ等の空気量制御バルブ２０，抜出量制御装置２１の開閉度を制御する。流動層２ｂの層密度が所定値（本実験例では約８００ｋｇ／ｍ³程度）に上昇したときは、コントローラ２３は、抜出量制御装置２１の開度を大きくして加圧流動層ボイラ２の炉底部に滞留している粗大粒を含む炉底灰を炉底灰抜出管１０から抜き出すとともに、Ｌバルブ等の空気量制御バルブ２０の開度を大きくして空気供給管１９を介して細炉底灰導入管１５ａに圧縮空気を供給し細炉底灰導入管１５ａ内の細炉底灰を流動層２ｂの下部に導入し、流動層２ｂの層密度を低下させる。流動層２ｂの層密度が所定値（本実験例では約５００ｋｇ／ｍ³程度）に低下したときは、コントローラ２３は、抜出量制御装置２１を閉止し加圧流動層ボイラ２内の炉底灰を抜き出さないようにするとともに、空気量制御バルブ２０を閉止して細炉底灰導入管１５ａ内の細炉底灰が流動層２ｂに導入されないようにする。これにより、加圧流動層ボイラ２内には燃料スラリー調整装置７で調整された燃料スラリーに含有される石灰石やドロマイト等の脱硫剤が供給されるため、流動層２ｂの層密度が増加する。
なお、加圧流動層ボイラ２内の層密度を制御するために炉底灰抜出管１０から抜き出された炉底灰は、分級装置１１で分級され、粉砕粒子輸送路１８で粉砕粒子として搬送されて、又は、細炉底灰輸送路１３で細炉底灰として搬送されて細炉底灰貯蔵装置１４に貯蔵されて、加圧流動層ボイラ２内へ供給される。又は、粉砕粒子として燃料スラリー調整装置７で燃料スラリーに混合されて、加圧流動層ボイラ２内へ供給される。
【００４２】
以上のように、本実施の形態４の炉底灰循環装置は構成されているので、実施の形態１又は２で得られる作用に加え、以下のような作用が得られる。
（１）細炉底灰、粉砕粒子、石膏層除去粒子のいずれか１以上を層密度を調整する流動媒体として用いることができるので、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる。
（２）酸化カルシウムや硫酸カルシウムの生成量が多い細炉底灰を燃料スラリーに混合せずに流動層ボイラに供給できるので、燃料スラリーが凝結や発熱せず燃料スラリー濃度や粘度等の安定性を維持することができる。
（３）細炉底灰の表面に形成された石膏層が除去された石膏層除去粒子や粉砕粒子は、未反応のＣａＣＯ₃層が析出し活性化されているので脱硫剤として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる。
（４）差圧検出手段で検出された差圧に基づいて流動層の層密度を制御する層密度検出手段を有しているので、流動層の膨張比（流動化している流動層の高さと固定層高さとの比）を最適にして流動を活発に維持し最適な燃焼状態を保つことができる。
（５）流動を活発に維持できるので供給される脱硫剤の熱破壊や磨耗を起こし易くして流動媒体を細粒化し、さらに流動不良を起こし難くすることができる。
（６）流動層の層密度を最適に制御することができるのでスラッギングを防止することができ、正常な流動層を生成することができる。
（７）スラッギングを防止できるので、スラリー噴射ノズルから噴射された燃料スラリーが伝熱管や流動層ボイラの壁面に付着・固化・塊状化して流動不良が発生し易くなることを防止できる。
（８）流動を活発に維持するとともに流動層の層密度を最適に制御できるので、層内の流動状態を均一化でき、流動層から伝熱管への伝熱を均一にすることができ熱効率に優れる。
（９）流動を活発に維持できるので、スラリーノズル付近での固体燃料の燃焼熱が滞留し難く溶融灰が形成され難いため、溶融灰によって流動媒体が塊状化し流動不良が発生するのを防止することができる。
【００４３】
なお、実施の形態１乃至４においては、加圧系で用いられる加圧流動層ボイラの場合について説明したが、本発明の炉底灰循環装置及び流動層ボイラの運転方法は、常圧系で用いられる流動層ボイラの場合でも同様に用いることができる。
【００４４】
【実施例】
次に、本発明を実施例を用いて詳細に説明する。
（実施例１、実施例２）
７１ＭＷ加圧流動層複合発電システムを用い、加圧流動層ボイラ内で（表１）に示す燃料と市販の１〜５ｍｍの粒子径を１０〜８０ｗｔ％含有する脱硫剤としての石灰石を流動状態にして０．６〜３．１ＭＰａ、８００〜９５０℃で燃焼運転させた。実施例１では、（表１）に示すように、ブレアゾール炭７０ｗｔ％と石油コークス３０ｗｔ％とを混合した燃料を用い、津久見産の石灰石を用いた。実施例２では、ブレアゾール炭５０ｗｔ％と石油コークス５０ｗｔ％とを混合した燃料を用い、津久見産石灰石５０ｗｔ％と船尾産石灰石５０ｗｔ％とを混合した石灰石を用いた。なお、石灰石に含有される各化合物の重量％を（表２）に示した。また、脱硫剤の石灰石の粒子径分布を（図５（ａ））に示した。
【表１】

【表２】

次に、加圧流動層ボイラの燃焼運転中に炉底灰抜出管から抜き出した炉底灰の粒子径分布を（図５（ｂ））に示し、各粒子径範囲にある炉底灰のＣａ化合物の重量％を（表３）に示した。また、精密脱塵装置で捕集されたフライアッシュ（平均粒子径２１μｍ）に含有される各化合物の重量％を（表４）に示した。
【表３】

【表４】

（表３）から、炉底灰抜出管から抜き出された粒子径１０５〜１１９０μｍの炉底灰は、Ｃａ化合物に対しＣａＯを２０〜４０ｗｔ％、ＣａＳＯ₄を４６〜５５ｗｔ％含有しているのに対し、ＣａＣＯ₃は１２〜３０ｗｔ％しか含有していないことがわかった。一方、粒子径１１９０μｍ以上の炉底灰は、Ｃａ化合物に対しＣａＯを４〜８ｗｔ％、ＣａＳＯ₄を１０〜２０ｗｔ％しか含有してないのに対し、ＣａＣＯ₃を７６〜８２ｗｔ％も含有していることがわかった。
一方、（表４）から、フライアッシュは、ＣａＯを７．５〜１５．３ｗｔ％、ＣａＣＯ₃を３．２〜５．３ｗｔ％、ＣａＳＯ₄を１５．７〜２０．４ｗｔ％含有していることがわかった。
【００４５】
（加水試験）
実施例１及び実施例２で得られた粒子径１０５〜１１９０μｍの炉底灰、粒子径１１９０μｍ以上の炉底灰、フライアッシュを用い、各々に３０ｗｔ％の水を添加・混合しペースト状にしたものの発熱及び凝結現象を観察した。
その結果、粒子径１０５〜１１９０μｍの炉底灰は、水の添加・混合後７日目に凝結現象が確認された。また、フライアッシュは、水の添加・混合後１００分以内に約１０℃程度の温度上昇が確認されるとともに凝結現象が確認された。一方、粒子径１１９０μｍ以上の炉底灰は、発熱及び凝結現象とも確認されなかった。
（加熱試験）
粒子径１１９０μｍ以上の炉底灰を水に３０分間浸漬後、水を切りその炉底灰を８５０℃に加熱した電気炉内に挿入し加熱した後取り出し、炉底灰の破砕状態を観察した。また、比較のために、加圧流動層ボイラに供給される以前の粒子径１１９０μｍ以上の石灰石を同様に水に浸漬後加熱して破砕状態を観察した。
その結果、加圧流動層ボイラに供給される以前の粒子径約２ｍｍ以上の石灰石は、その約７０％が０．２５〜０．５ｍｍの粒子に破砕されたのに対し、加圧流動層ボイラから抜き出された炉底灰は破砕されないことが確認された。なお、炉底灰では、炉底灰の表面に付着していた石膏成分と推察される茶色の皮膜の一部が剥離し、未反応の炭酸カルシウムが露出していることが確認された。
【００４６】
（炉底灰の再利用に関する評価）
実施例１及び実施例２で得られた粒子径１１９０μｍ以上の炉底灰をローラーミル等の粉砕装置で粒子径１１９０μｍ未満の粉砕粒子に粉砕し、得られた粉砕粒子を燃料スラリー調整装置に供給して燃料スラリーに混合した。粉砕粒子を混合しても燃料スラリーの粘度や濃度等の調整は容易であった。一方、粒子径１１９０μｍ未満の炉底灰は細炉底灰貯蔵容器に貯蔵し、流動層の層高や層密度に応じて加圧流動層ボイラ内に供給した。この結果、実施例１の加圧流動層ボイラでは脱硫剤の所要Ｃａ／Ｓモル比３．０が得られ、実施例２の加圧流動層ボイラでは所要Ｃａ／Ｓモル比２．５が得られた。
以上のことから、Ｃａ化合物に対し７０ｗｔ％以上のＣａＣＯ₃を含有している粒子径１１９０μｍ以上の炉底灰は、再び加圧流動層ボイラ内に導入されることにより脱硫剤の有効利用率が高まることが確認された。また、水と接触しても発熱及び凝結現象が起こらないので、燃料スラリーに混合できることが確認された。また、再び加圧流動層ボイラ内に導入されても破砕し難いが、表面に付着した皮膜の一部が剥離し未反応の炭酸カルシウムが露出し脱硫反応に寄与することが確認された。また、加圧流動層ボイラ内で破砕し難いため、加圧流動層ボイラ内に再導入する以前に粉砕装置を用いて粉砕し、比表面積を大きくするとともに脱硫未反応面を露出させることが効果的であることが推察された。また、加圧流動層ボイラに供給される以前の粒子径約２ｍｍ以上の石灰石は、燃料スラリーに混合されて加圧流動層ボイラ内で加熱されることにより、その約７０％が０．２５〜０．５ｍｍの粒子に破砕されることが確認された。これにより、脱硫率を向上させるために加圧流動層ボイラに供給する以前の石灰石を１ｍｍ程度以下に微粉砕する必要がなく、市販の石灰石を使用してもＣａ／Ｓモル比３以下の良好な有効利用率の得られることが確認された。さらに、粒子径１１９０μｍ未満の炉底灰はＣａＯ及びＣａＳＯ₄の含有率が高く、フライアッシュはＣａＳＯ₄、ＳｉＯ₂及びＡｌ₂Ｏ₃の含有率が高いため、セメント材料やセメント原料として使用できることが確認された。
【００４７】
（実施例３、比較例１）
実施の形態２で説明した炉底灰循環装置を７１ＭＷ加圧流動層複合発電システムに備えた場合のカルシウムバランス（石灰石に含有されるカルシウム量に着目し石灰石の移動量を比較したもの）について算出し評価した。計算は、燃料として実施例１で説明した（表１）に示すブレアゾール炭７０ｗｔ％と石油コークス３０ｗｔ％とを混合したものを用い、脱硫剤として津久見産の石灰石を用い、０．６〜３．１ＭＰａの加圧下で８００〜９５０℃で燃焼運転させた場合について行った。同じ条件の加圧流動層複合発電システムにおいて炉底灰循環装置を備えないものを比較例として用いた。
実施例３と比較例１のカルシウムバランスを計算した結果を、図６に示す。図６では、図面を単純化させるため実施の形態２で説明した加圧流動層ボイラ２、分級装置１１、粉砕装置１６、燃料スラリー調整装置７のみを記載した。図６において、Ａ〜Ｇに示す数値が計算結果に基づく単位時間当たりの石灰石の移動量（ｋｇ／ｈｒ）である。なお、上段に示す数値が実施例の石灰石の移動量（ｋｇ／ｈｒ）であり、下段に示す数値が比較例の石灰石の移動量（ｋｇ／ｈｒ）である。加圧流動層ボイラ内には５６１４０ｋｇの石灰石が存在しているとした。
なお、カルシウムバランスの計算においては、比較例のＣａ／Ｓ比が５になるように石灰石の供給量を決定した。また、石灰石や炉底灰等と硫黄酸化物との反応性を考慮し、実施例と比較例の脱硫率が同じになるようにした。さらに、実施例と比較例との比較を容易にするために、比較例で加圧流動層ボイラ２に供給する石灰石の量（Ｂ下段）と、実施例で加圧流動層ボイラ２に供給する石灰石と粉砕粒子（粉砕装置１６によって粉砕された炉底灰）との合計量（Ｂ上段）が、同じ値になるように換算を行った。
【００４８】
図６において、比較例においては、加圧流動層ボイラ２に７６０．６ｋｇ／ｈｒ供給された石灰石（Ｂ下段）が、炉底灰として３８４．２ｋｇ／ｈｒ排出され（Ｃ下段）、燃焼排ガスに随伴して３７６．４ｋｇ／ｈｒ排出される（Ｅ下段）。炉底灰循環装置を有していないため、３８４．２ｋｇ／ｈｒで排出される炉底灰（Ｃ下段）を処理するための処理費用を要する。また、燃料スラリー調整装置７には７６０．６ｋｇ／ｈｒの新たな石灰石の供給が必要とされる（Ａ下段）。
一方、実施例においては、燃料スラリー調整装置７で調整された７６０．６ｋｇ／ｈｒの石灰石及び粉砕粒子（Ｂ上段）及び粉砕装置１１で１３９．０ｋｇ／ｈｒ生成された細炉底灰（Ｇ上段）が加圧流動層ボイラ２に供給され、炉底灰として５０８．５ｋｇ／ｈｒ排出され（Ｃ上段）、燃焼排ガスに随伴して３９１．１ｋｇ／ｈｒ排出される（Ｅ上段）。５０８．５ｋｇ／ｈｒの炉底灰（Ｃ上段）は、分級装置１１で１７０．６ｋｇ／ｈｒの粗炉底灰（粉砕粒子）（Ｆ上段）、１３９．０ｋｇ／ｈｒの細炉底灰（Ｇ上段）、１９８．９ｋｇ／ｈｒの系外に排出する炉底灰（Ｄ上段）に分級される。燃料スラリー調整装置７には１７０．６ｋｇ／ｈｒで粉砕粒子が供給されるので（Ｆ上段）、新たな石灰石の供給量は５９０．０ｋｇ／ｈｒ（Ａ上段）でよいことがわかった。
【００４９】
以上の結果、比較例では７６０．６ｋｇ／ｈｒの新たな石灰石の供給が必要とされたのに対し、本実施例では、新たな石灰石の供給は５９０．０ｋｇ／ｈｒで済むため、（７６０．６−５９０．０）／７６０．６＝２２．４％の石灰石が削減できることが明らかになった。この結果、Ｃａ／Ｓ比は、５から３．９に低減された。また、系外に排出される炉底灰が、比較例では３８４．２ｋｇ／ｈｒであったのに対し、実施例では１９８．９ｋｇ／ｈｒとなったことから、系外に排出される炉底灰の量が約５０％に低減され、それに係る処理費用や産業廃棄物量も従来例の約半分に低減されることが明らかになった。
なお、本実施例では石灰石や燃料等をペースト状にして加圧流動層ボイラに供給する湿式方式について説明したが、石灰石や燃料等を乾式供給する場合についても石灰石の削減量やＣａ／Ｓ比等については同様の効果が得られる。さらに、乾式供給する場合には、ペースト状にして供給された燃料等から水が蒸発するときの気化熱の損失がなく熱効率を向上させることができる。
【００５０】
【発明の効果】
以上のように、本発明の炉底灰循環装置及び流動層ボイラの運転方法によれば、以下のような有利な効果が得られる。
請求項１に記載の発明によれば、
（１）粗炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が少なく、未反応の炭酸カルシウムの残存量が多いので、流動層ボイラ内に再導入すれば脱硫剤として働き、脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
（２）粗炉底灰は酸化カルシウムや硫酸カルシウムの生成量が少ないので、水と接触しても凝結や発熱を起こさないため、石炭等の固体燃料や石灰石等の脱硫剤とともに燃料スラリー中に混合しても凝結や発熱を起こさずスラリー濃度やスラリー粘度の調整を容易にすることができる炉底灰循環装置を提供することができる。また、燃料スラリーに混合することができるため、粗炉底灰を燃料スラリーとして安定して流動層ボイラ内に供給することができ脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
（３）細炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が多く、未反応の炭酸カルシウムの残存量が少ない。そのため、細炉底灰をそのまま流動層ボイラ内に導入しても脱硫剤としての機能は乏しいが、流動層高を調整する流動媒体として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
（４）既存の流動層ボイラの炉底灰抜出管から抜き出された炉底灰を分級する分級装置を配設するだけの小規模な改良によって脱硫剤の有効利用率を高めることができ、設備負荷を抑制することのできる炉底灰循環装置を提供することができる。
（５）５００〜５０００μｍの比較的大きな粒子径で炉底灰を分級するので、シフタ等の簡便かつ大量に処理できる分級装置を用いることができ設備負荷が小さいとともに生産性に優れた炉底灰循環装置を提供することができる。さらに分級装置の目詰まり等も発生し難く運転効率に優れた炉底灰循環装置を提供することができる。
（６）分級装置を有しているので、流動媒体が溶融して塊状化したシンター生成物を除去することができ、流動層内の安定性を向上させることができる炉底灰循環装置を提供することができる。
【００５１】
請求項２に記載の発明によれば、請求項１の効果に加え、
（１）粗炉底灰を粉砕することで粗炉底灰表面の石膏層を剥離させ、また砕いて粒子径を小さくして、未反応のＣａＣＯ₃層を露出させ炉底灰を脱硫剤として再利用することができる炉底灰循環装置を提供することができる。
（２）粗炉底灰のうち、粗大化して流動層ボイラの炉底部に沈降し流動し難い粒子を粉砕して流動層ボイラ内に再供給することにより、流動層の流動状態を活発化させ流動不良の発生を防止することができる炉底灰循環装置を提供することができる。
（３）粉砕装置で粗炉底灰を所定粒子径より小さな粉砕粒子に粉砕して流動層ボイラ内に再供給することにより、次に炉底灰抜出管から抜き出されたときには細炉底灰として分級されるので、燃料スラリーには混合されず燃料スラリー濃度や粘度等の安定性を向上させることができ信頼性を高めることができる炉底灰循環装置を提供することができる。
（４）粉砕装置を備えているので、粗炉底灰が所定粒子径より小さな粉砕粒子に粉砕されて流動層ボイラ内へ供給され、供給された粉砕粒子や細炉底灰が流動層ボイラ内で磨耗によって微細化されてフライアッシュとなって系外に排出される。フライアッシュはそれ自体でセメント材料やセメント原料等としてリサイクル可能なので、炉底灰の処理費用や産業廃棄物の発生量等を著しく減少させることができる炉底灰循環装置を提供することができる。
【００５２】
請求項３に記載の発明によれば、請求項２の効果に加え、
（１）石膏層除去装置を有しているので、細炉底灰の各粒子表面に形成された石膏層を除去して未反応のＣａＣＯ₃層を露出させることができ、再び脱硫反応速度を高め再活性化させ脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
（２）水と接触すると水和硬化や発熱を引き起こす石膏層を石膏除去装置で除去することにより、石膏除去粒子を燃料スラリーに混合させることもでき応用性に優れた炉底灰循環装置を提供することができる。また、石膏層を除去しているので、空気中の水分と反応し難く保存性に優れた石膏層除去粒子の得られる炉底灰循環装置を提供することができる。
【００５３】
請求項４に記載の発明によれば、請求項２又は３の効果に加え、
（１）脱硫剤調整装置を有しているので、粗炉底灰，粉砕粒子，石膏層除去粒子のいずれか１種以上を石灰石等の脱硫剤に混合して調整し流動層ボイラに供給することができ、脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
【００５４】
請求項５に記載の発明によれば、請求項２乃至４の内いずれか１の効果に加え、
（１）細炉底灰、粉砕粒子、石膏層除去粒子のいずれか１以上を層密度を調整する流動媒体として用いることができるので、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
（２）酸化カルシウムや硫酸カルシウムの生成量が多い細炉底灰を燃料スラリーに混合せずに流動層ボイラに供給できるので、燃料スラリーが凝結や発熱せず燃料スラリー濃度や粘度等の安定性を維持することができる炉底灰循環装置を提供することができる。
（３）細炉底灰の表面に形成された石膏層が除去された石膏層除去粒子や粉砕粒子は、未反応のＣａＣＯ₃層が析出し活性化されているので脱硫剤として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる炉底灰循環装置を提供することができる。
（４）差圧検出手段で検出された差圧に基づいて流動層の層密度を制御する層密度検出手段を有しているので、流動層の膨張比（流動化している流動層の高さと固定層高さとの比）を最適にして流動を活発に維持し最適な燃焼状態を保つことができる炉底灰循環装置を提供することができる。
（５）流動を活発に維持できるので供給される脱硫剤の熱破壊や磨耗を起こし易くして流動媒体を細粒化し、さらに流動不良を起こし難くすることができる炉底灰循環装置を提供することができる。
（６）流動層の層密度を最適に制御することができるのでスラッギングを防止することができ、正常な流動層を生成することができる炉底灰循環装置を提供することができる。
（７）スラッギングを防止できるので、スラリー噴射ノズルから噴射された燃料スラリーが伝熱管や流動層ボイラの壁面に付着・固化・塊状化して流動不良が発生し易くなることを防止できる炉底灰循環装置を提供することができる。
（８）流動を活発に維持するとともに流動層の層密度を最適に制御できるので、層内の流動状態を均一化でき、流動層から伝熱管への伝熱を均一にすることができ熱効率に優れた炉底灰循環装置を提供することができる。
（９）流動を活発に維持できるので、スラリーノズル付近での固体燃料の燃焼熱が滞留し難く溶融灰が形成され難いため、溶融灰によって流動媒体が塊状化し流動不良が発生するのを防止することができる炉底灰循環装置を提供することができる。
【００５５】
請求項６に記載の発明によれば、
（１）流動層ボイラの炉底部に滞留した炉底灰を抜き出すので、炉底部に滞留して流動不良の原因となる粗粉脱硫剤等の粗大粒子を抜き出し、流動不良の発生を未然に防ぐことができる流動層ボイラの運転方法を提供することができる。
（２）粗炉底灰は、炭酸カルシウムの脱硫反応や脱炭酸反応で生成される酸化カルシウムや硫酸カルシウムの生成量が少なく未反応の炭酸カルシウムの残存量が多いので、流動層ボイラ内に再導入すれば脱硫剤として働き、脱硫剤の有効利用率を高めることができる流動層ボイラの運転方法を提供することができる。
（３）粗炉底灰は酸化カルシウムや硫酸カルシウムの生成量が少ないので、水と接触しても凝結や発熱を起こさず、燃料スラリーに混合しても水和反応によって凝結や発熱を起こさずスラリー濃度やスラリー粘度の調整が容易である流動層ボイラの運転方法を提供することができる。
（４）細炉底灰は、脱硫反応や脱炭酸反応で生成される石膏や酸化カルシウムの生成量が多く未反応の炭酸カルシウムの残存量が少ないので、流動層ボイラ内に導入しても脱硫剤としての機能は乏しいが、流動層高を調整する流動媒体として用いることができ、脱硫剤の使用量を低減し脱硫剤の有効利用率を高めることができる流動層ボイラの運転方法を提供することができる。
（５）５００〜５０００μｍの比較的大きな粒子径で炉底灰を分級するので、シフタ等の簡便かつ大量に処理できる分級装置を用いることができ設備負荷が小さいとともに生産性に優れた流動層ボイラの運転方法を提供することができる。
【００５６】
請求項７に記載の発明によれば、請求項６の効果に加え、
（１）分級工程で分級された粗炉底灰のみを粉砕するので、粉砕装置は小型のものでよく設備負荷が小さい流動層ボイラの運転方法を提供することができる。
（２）粗炉底灰を粉砕することで粗炉底灰表面の石膏層を剥離させ、また砕いて粒子径を小さくして、未反応のＣａＣＯ₃層を露出させ脱硫剤として再利用することができる流動層ボイラの運転方法を提供することができる。
（３）粗炉底灰のうち、粗大化して流動層ボイラの炉底部に沈降し流動し難い粒子を粉砕して流動層ボイラ内に再供給することにより、流動層の流動状態を活発化させ流動不良の発生を防止することができる流動層ボイラの運転方法を提供することができる。
（４）粉砕工程で粗炉底灰を所定粒子径より小さな粉砕粒子に粉砕して流動層ボイラ内に再供給することにより、次に炉底灰抜出管から抜き出されたときには細炉底灰として分級されるので、燃料スラリーには混合されず燃料スラリー濃度や粘度等の安定性を向上させることができ信頼性を高めることができる流動層ボイラの運転方法を提供することができる。
（５）粉砕工程を備えているので、粗炉底灰が所定粒子径より小さな粉砕粒子に粉砕されて流動層ボイラ内へ供給され、供給された粉砕粒子や細炉底灰が流動層ボイラ内で磨耗によって微細化されてフライアッシュとなって系外に排出される。フライアッシュはそれ自体でセメント材料やセメント原料等としてリサイクル可能なので、炉底灰の処理費用や産業廃棄物の発生量を著しく減少させることができる流動層ボイラの運転方法を提供することができる。
【００５７】
請求項８に記載の発明によれば、請求項６又は７の効果に加え、
（１）粒子径が１〜５ｍｍの脱硫剤の大部分は、流動層ボイラに供給されることで熱破壊や磨耗を起こし細粒化されるので、流動層ボイラに供給する以前に脱硫剤を粉砕する必要がなく粉砕に要する工数及び費用を削減することができ省エネルギー性に優れた流動層ボイラの運転方法を提供することができる。
（２）脱硫剤を流動層ボイラに供給する以前に粉砕して微粒化させないので、粒子の終末速度がガス空塔速度となり流動層からフリーボードへ飛散し流動層を構成しない微粒子（この微粒子の粒子径は、ガス空塔速度が０．８±０．４ｍ／ｓのとき約２５０μｍ以下である）の含有率が低く、良好な流動層を構成させることができる流動層ボイラの運転方法を提供することができる。
（３）流動層の底部に粒子径が１〜５ｍｍの脱硫剤を含む流動層を生成することができるので、スラッギングを防止することができ、スラリー噴射ノズルから噴射された燃料スラリーが伝熱管や流動層ボイラの壁面に付着・固化・塊状化して流動不良が発生し易くなることを防止できる流動層ボイラの運転方法を提供することができる。
【００５８】
【図面の簡単な説明】
【図１】本実施の形態１における炉底灰循環装置の要部構成図
【図２】本実施の形態２における炉底灰循環装置の要部構成図
【図３】本実施の形態３における炉底灰循環装置の要部構成図
【図４】本実施の形態４における炉底灰循環装置の要部構成図
【図５】（ａ）石灰石の粒子径分布
（ｂ）流動層ボイラの燃焼運転中に炉底灰抜出管から抜き出した炉底灰の粒子径分布
【図６】実施例３と比較例１のカルシウムバランスを計算した結果
【符号の説明】
１ 圧力容器
２ 加圧流動層ボイラ
２ａ 伝熱管
２ｂ 流動層
３ 燃焼排ガス流路管
４ 粗脱塵装置
５ 粗脱塵ガス流路管
６ 精密脱塵装置
７ 燃料スラリー調整装置
８ スラリーポンプ
９ スラリー供給路
１０ 炉底灰抜出管
１１，１１ａ 分級装置
１１ｂ 粗大粒子排出路
１２，１２ａ 粗炉底灰輸送路
１２ｂ 粗炉底灰分岐路
１２ｃ，１３ｃ 石膏層除去装置
１３ 細炉底灰輸送路
１３ａ 分岐弁
１３ｂ 細炉底灰分岐路
１３ｄ 排出路
１４ 細炉底灰貯蔵容器
１５，１５ａ 細炉底灰導入管
１６ 粉砕装置
１７ 粉砕粒子供給路
１７ａ 燃料供給ホッパ
１７ｂ ロックホッパ
１７ｃ 燃料供給路
１７ｄ 搬送空気供給管
１８ 粉砕粒子輸送路
１８ａ 分岐弁
１９ 空気供給管
２０ 空気量制御バルブ
２１ 抜出量制御装置
２２ 差圧検出手段
２３ コントローラ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a furnace bottom ash circulation device in a fluidized bed boiler and a method for operating the fluidized bed boiler.
[0002]
[Prior art]
In recent years, fluidized bed boilers that fluidize and efficiently burn fuel such as coal and garbage in power plants and garbage incinerators have been researched and developed. By using the fluidized bed boiler, it is possible to construct a steam turbine power generation system that is driven by the steam generated from the heat transfer tubes disposed in the fluidized bed boiler. In addition to steam turbine power generation, boiler combustion is achieved by using a pressurized fluidized bed boiler that fluidizes and burns fuel under conditions where the oxygen partial pressure in the boiler is increased by pressurizing with air from the compressor. Combined with gas turbine power generation using exhaust gas, a combined power generation system with improved thermal efficiency can be constructed.
In a fluidized bed boiler, a desulfurizing agent such as limestone or dolomite is used as a fluidized medium constituting the fluidized bed. The output of the power generation system can be controlled by controlling the fluidized bed height by controlling the amount and particle size of the fluidized medium in the fluidized bed boiler. It is extracted from the bottom of the furnace and subjected to combustion control, flow control, and the like. The bottom ash extracted from the bottom of the furnace contains unreacted calcium carbonate, unburned coal, etc., so reusing these can improve the effective utilization rate of the desulfurizing agent and improve the desulfurization rate. Can do. For this purpose, a bottom ash circulation device for reusing the bottom ash has been researched and developed.
[0003]
As a conventional furnace bottom ash circulation device, Japanese Utility Model Laid-Open No. 3-128208 (hereinafter referred to as “a”) discloses “solid matter discharge for discharging solid matter such as ash dust, unburnt coal or bed material separated by a cyclone”. There is disclosed a “pressurized fluidized bed boiler” in which an outlet is connected to a fluidized bed forming portion of a fluidized bed boiler and an introduction passage for reintroducing separated ash dust, unburnt coal, and the like is formed.
[0004]
Japanese Utility Model Laid-Open No. 6-65709 (hereinafter referred to as “B”) includes a “bed material discharge pipe for discharging excess bed material, and a replenishment bed material container for storing discharged bed material, There is disclosed a “pressurized fluidized bed boiler in which a bed material is replenished from a replenishment bed material container to a fluidized bed of a boiler body when a bed material for forming a fluidized bed is insufficient.
[0005]
Japanese Patent Application Laid-Open No. 10-238713 (hereinafter referred to as “C”) includes a “system for extracting a fluid medium from a boiler during load adjustment and sending the fluid medium to a fluid medium storage facility, and a system for supplying the fluid medium from the fluid medium storage facility to the boiler; , And a pressurized fluidized bed boiler provided with equipment capable of operating in a direction reverse to that during load adjustment is provided in the system.
[0006]
[Problems to be solved by the invention]
However, the above conventional techniques have the following problems.
(1) The technology disclosed in Gazette No. 1 reintroduces solid matter such as ash dust, unburned coal or bed material separated by a cyclone into the fluidized bed, but the bottom ash extracted from the bottom of the furnace Is discarded. Therefore, in order to obtain a desired desulfurization rate, a large amount of desulfurization agent must be supplied (required Ca / S molar ratio is about 6 with respect to the target of 3 or less), and the effective utilization rate of the desulfurization agent is low. Had.
(2) The technique disclosed in the gazette includes a bed material discharge pipe through which excess bed material is discharged and a replenishment bed material container in which the discharged bed material is stored. The extracted bottom ash can be reintroduced into the fluidized bed. However, since the bed material is replenished from the replenishment bed material container to the fluidized bed of the boiler body only when the bed material for forming the fluidized bed is insufficient, the circulation amount of the furnace bottom ash extracted from the furnace bottom is sufficient. However, the problem was that the effective utilization rate was still low.
(3) In order to improve the circulation amount of the furnace bottom ash, it is desirable to mix with solid fuel such as coal and water to form a slurry and stably supply it into the fluidized bed. However, the bottom ash discharged from the bottom of the furnace is converted into CaO and CaSO by the desulfurization reaction shown in (Chemical Formula 1). _Four When it comes into contact with water, the condensation shown in (Chemical Formula 2) and the heat generation shown in (Chemical Formula 3) occur, making it difficult to adjust the slurry concentration and slurry viscosity, so it cannot be easily mixed into the fuel slurry. It had the problem that.
[Chemical 1]

[Chemical 2]

[Chemical 3]

(4) Since the bed material discharged from the furnace bottom is re-supplied into the pressurized fluidized bed boiler as it is, coarse particles such as coarse powder desulfurization agent contained in the bed material extracted from the furnace bottom are also re-supplied, There is a problem that such coarse particles may cause sedimentation in the fluidized bed and cause flow failure.
(5) Desulfurization reaction causes CaSO _Four When a layer (gypsum layer) is formed, the reaction rate decreases rapidly. In the publication No. C, in order to exfoliate the gypsum layer on the surface of the fluidized medium extracted from the pressurized fluidized bed boiler and increase the desulfurization reaction rate, ₂ A method is disclosed in which a fluid medium extracted in a region having a low partial pressure is supplied and cracks are generated by a decarboxylation reaction. However, as a result of intensive research by the present inventors, the occurrence of cracks in limestone occurs when it is first supplied to the pressurized fluidized bed boiler, but the fluidized medium extracted from the pressurized fluidized bed boiler is again used as the pressurized fluidized bed boiler. When supplied to CO ₂ It has been found that even if it is supplied to a region where the partial pressure is low, it hardly occurs. Therefore, it has been difficult to peel off the gypsum layer on the surface of the fluid medium and does not contribute to the desulfurization reaction.
(6) The present inventor has found that a fluid medium having a particle diameter of about 1 mm or less has undergone a desulfurization reaction and a gypsum layer has been generated deep inside the particles. For this reason, it has been difficult to remove the gypsum layer formed on the particle surface unless it is scraped off by polishing or the like, and has a problem that it does not contribute to the desulfurization reaction.
(7) CO ₂ Although it is disclosed that the air ratio is increased in order to lower the partial pressure, since a large amount of air needs to be supplied to increase the air ratio, the superficial velocity of the pressurized fluidized bed boiler increases. For this reason, wear between the fluidized media is promoted, and the fluidized media jumping out to the freeboard increases and the fluidized bed height decreases, so a large amount of desulfurizing agent must be added to compensate for this, and the utilization rate of the desulfurizing agent is reduced. It had the subject that the desulfurization agent cost increased with decreasing. Also, if a large amount of air is supplied, the amount of combustion exhaust gas and the amount of ash dust contained in the combustion exhaust gas increase, so the load of precision dedusting equipment such as a ceramic tube filter that removes ash dust from the combustion exhaust gas increases, There was a problem that the precision dust removing device was easily damaged.
(8) In the technologies disclosed in No. 1, B and C, in order to increase the effective utilization rate of the desulfurizing agent and improve the desulfurization efficiency, the desulfurizing agent is refined by reducing the particle size of the desulfurizing agent to about 1 mm or less. In some cases, a method of increasing the specific surface area is used. However, in order to refine the desulfurizing agent, a fine pulverization step is required and energy is consumed, and the particle size at which the terminal velocity of the desulfurizing agent becomes the superficial velocity (in the case of the superficial velocity of 0.8 m / sec, about 250 μm) desulfurizing agent with a particle size smaller than that is scattered from the fluidized bed to the freeboard, and the desulfurizing agent having a particle size smaller than the cyclone cut size is collected by a dust collector such as a cyclone and circulated in the pressurized fluidized bed boiler. Therefore, there was a problem that the desulfurization rate was not improved.
(9) In addition, the fluidized bed composed of the refined desulfurizing agent has a problem that the layer density is low and slagging is likely to occur and fluidity is likely to occur.
[0007]
The present invention solves the above-described conventional problems, and removes coarse furnace bottom ash that is likely to cause flow failure due to retention in the bottom of the furnace, thereby improving the stability of the fluidized bed and reusing the desulfurizing agent. To provide a bottom ash circulation device that can improve the effective utilization rate, can effectively use existing facilities, has a small facility load, and is highly reliable and capable of stable operation over a long period of time. Objective. In addition, the present invention provides a fluidized bed boiler that reduces the amount of desulfurizing agent used and increases the effective utilization rate of the desulfurizing agent, is excellent in energy saving, and prevents the occurrence of poor flow by preventing the occurrence of slugging and the like. The purpose is to provide a driving method.
[0008]
[Means for Solving the Problems]
In order to solve the above conventional problems, the operation method of the bottom ash circulation device and the fluidized bed boiler of the present invention has the following configuration.
[0009]
A furnace bottom ash circulation device according to claim 1 of the present invention is a fluidized bed boiler, a furnace bottom ash extraction pipe that is connected to the furnace bottom of the fluidized bed boiler and extracts the furnace bottom ash retained in the furnace bottom, A furnace bottom ash circulation device comprising: a furnace having a particle diameter of at least a predetermined particle diameter by classifying the furnace bottom ash extracted from the furnace bottom ash extraction pipe with a predetermined particle diameter in a range of 500 to 5000 μm. For classifying into blast furnace bottom ash having a small particle size and fine furnace bottom ash smaller than a predetermined particle size A fuel slurry adjusting device that adjusts and stores a fuel slurry mixed with solid fuel, a desulfurizing agent, and water, and supplies the crude furnace bottom ash classified by the classifying device to the fuel slurry adjusting device. A roughing furnace bottom ash transportation route, It has the composition provided with.
With this configuration, the following effects can be obtained.
(1) Since the bottom ash of the crude furnace has a small amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate and a large amount of unreacted calcium carbonate, If it is reintroduced, it can act as a desulfurizing agent and increase the effective utilization rate of the desulfurizing agent.
(2) Since the amount of calcium oxide and calcium sulfate produced in the furnace bottom ash is small, it does not cause condensation or heat generation even when it comes into contact with water. Even if mixed, the slurry concentration and the slurry viscosity can be easily adjusted without causing condensation or heat generation. Moreover, since it can mix with a fuel slurry, rough furnace bottom ash can be stably supplied in a fluidized bed boiler as a fuel slurry, and the effective utilization factor of a desulfurization agent can be raised.
(3) The bottom ash of the blast furnace has a large amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate, and a small amount of unreacted calcium carbonate. Therefore, even if blast furnace bottom ash is introduced into the fluidized bed boiler as it is, its function as a desulfurizing agent is poor, but it can be used as a fluidizing medium to adjust the fluidized bed height and density, reducing the amount of desulfurizing agent used. The effective utilization rate of the desulfurization agent can be increased.
(4) The effective utilization rate of the desulfurizing agent can be improved by a small-scale improvement that simply arranges a classification device for classifying the bottom ash extracted from the bottom ash extraction pipe of the existing fluidized bed boiler. it can.
(5) Since the bottom ash is classified with a relatively large particle size of 500 to 5000 μm, a classification device such as a shifter that can be processed easily and in large quantities can be used, and the equipment load is small and the productivity is excellent. Clogging is not likely to occur, and driving efficiency is excellent.
(6) Since the classifier is provided, the sintered product in which the fluid medium is melted and agglomerated can be removed, and the stability in the fluidized bed can be improved.
[0010]
Here, as the furnace bottom ash, CaCO supplied to the fluidized bed boiler _Three (Or limestone), MgCO _Three (Or dolomite), CaO (quick lime), Ca (OH) ₂ (Slaked lime), K ₂ CO _Three , Seafood waste containing calcium such as shells, desulfurization agents such as cement sludge, coal, lignite, lignite, bituminous coal, coke, petroleum coke, oil coke, oil sand, heavy oil, coal liquefaction residue, rubber, old tires , Waste oil, general waste, general waste, wood, carbide, RDF and other carbides, wood waste, industrial waste, organic residue discharged from food factories and agriculture, sewage sludge, human waste sludge, industrial wastewater treatment Solid fuel combustion ash that is sludge or a mixture thereof is used.
[0011]
As the classification device, a sieving machine such as a vibrating screen or a shifter is used.
The predetermined particle size varies depending on the type of the desulfurizing agent, the operating conditions of the fluidized bed boiler, etc., but is 500 to 5000 μm, preferably 1000 to 3000 μm. A predetermined particle diameter of 1000 to 3000 μm is preferable because the unreacted calcium carbonate content in the coarse furnace bottom ash (furnace bottom ash having a particle diameter larger than the predetermined particle diameter) is large and can be reused as a desulfurizing agent. As the predetermined particle size becomes smaller than 1000 μm, the amount of unreacted calcium carbonate remaining in the bottom ash of the coarse furnace decreases, while the content of calcium oxide and calcium sulfate increases. This is not preferable because heat generation tends to occur easily and clogging or the like occurs in the classification device, and the operation efficiency / classification efficiency tends to decrease. Furthermore, since the particle diameter of the fluidized medium constituting the fluidized bed is reduced, the fluidity becomes excessively active, and wear of the heat transfer tube and the like due to the fluidized medium becomes severe, which is not preferable. Since it tends to decrease the amount of rough bottom ash containing a large amount of unreacted calcium carbonate as it becomes larger than 3000 μm, it is not preferable. In particular, when the predetermined particle diameter is smaller than 500 μm or larger than 5000 μm, these tendencies become remarkable, so that neither is preferable.
[0012]
As coarse ash bottom ash, CaCO _Three Furnace bottom ash containing 60 to 100 wt%, preferably 70 to 100 wt% of Ca is used. CaCO _Three A content of 70 to 100 wt% is preferable because it has a high function as a desulfurizing agent and can be mixed with the fuel slurry without causing condensation or heat generation even when brought into contact with water. CaCO _Three As the content of CaO becomes lower than 70 wt%, CaSO _Four In addition, the content of CaO increases and the function as a desulfurizing agent decreases, and when it comes into contact with water, there is a tendency to cause condensation and heat generation, and particularly when it is lower than 60 wt%, the tendency is remarkable, which is not preferable.
[0013]
As blast furnace bottom ash, CaCO _Three Furnace bottom ash containing 0 to 40 wt%, preferably 0 to 35 wt% of Ca is used. CaCO _Three As the content of C is higher than 35 wt% with respect to the Ca compound, the amount of the coarse furnace bottom ash tends to decrease, which is not preferable. Particularly, when the content is lower than 40 wt%, the tendency is remarkable, which is not preferable. CaSO formed on the surface _Four If the layer (gypsum layer) is removed by polishing or the like, these tendencies can be suppressed.
[0014]
As a classifier, in addition to classifying into the bottom ash and blast furnace bottom ash with a predetermined particle size, among the coarse bottom ash, agglomerates larger than the maximum particle size of the desulfurizing agent supplied to the fluidized bed boiler Classification can also be made to remove coarse particles such as sintered products. As a result, coarse particles such as sinter products and coarse powder desulfurization agent contained in the bottom ash extracted from the bottom of the furnace can be removed, and such coarse particles settle in the fluidized bed. It is possible to prevent the occurrence of flow failure by agglomerating the liquid and to enable stable operation for a long period of time.
[0015]
Invention of Claim 2 of this invention is a furnace bottom ash circulation apparatus of Claim 1, Comprising: The grinding | pulverization apparatus which grind | pulverizes the said coarse furnace bottom ash to the grinding | pulverization particle | grains which have a particle diameter smaller than the said predetermined particle diameter. It has the composition provided with.
With this configuration, in addition to the operation obtained in the first aspect, the following operation can be obtained.
(1) The coarse gypsum floor ash is pulverized to peel off the gypsum layer on the surface of the coarse furnace bottom ash, and crushed to reduce the particle size, thereby unreacted CaCO _Three The layer can be exposed and the bottom ash can be reused as a desulfurization agent.
(2) Particles that are coarse in the bottom ash of the furnace and settle down to the bottom of the fluidized bed boiler and are difficult to flow are crushed and re-supplied into the fluidized bed boiler to activate the fluidized state of the fluidized bed. Occurrence of poor flow can be prevented.
(3) By pulverizing the coarse furnace bottom ash into pulverized particles smaller than a predetermined particle size by a pulverizer and re-feeding it into the fluidized bed boiler, the bottom of the fine furnace bottom is extracted from the furnace bottom ash extraction pipe. Since it is classified as ash, it is not mixed with the fuel slurry, and stability such as fuel slurry concentration and viscosity can be improved and reliability can be improved. When the desulfurizing agent is supplied into the fluidized bed boiler many times and exposed to high pressure and high temperature for a long time, the remaining amount of calcium carbonate decreases with the passage of time, and the amount of calcium oxide and calcium sulfate generated increases. This is because the hydration reaction causes condensation and heat generation and makes the fuel slurry concentration and viscosity unstable.
(4) Since the pulverizer is provided, the coarse furnace bottom ash is pulverized into pulverized particles smaller than a predetermined particle diameter and supplied into the fluidized bed boiler, and the supplied pulverized particles and fine furnace bottom ash are contained in the fluidized bed boiler. It is refined by wear and becomes fly ash and is discharged out of the system. Since fly ash can be recycled by itself as cement material, cement raw material, etc., the processing cost of furnace bottom ash, the generation amount of industrial waste, etc. can be reduced significantly.
[0016]
Here, as the pulverizer, roll rolling type pulverizers such as edge runners and roller mills, high-speed rotary impact shear pulverizers such as centrifugal mills, ball medium mills such as rolling ball mills and vibrating ball mills, medium stirring type pulverization A dry pulverizer such as a pulverizer is used. In particular, a roll rolling type pulverizer such as a roller mill capable of pulverizing a large volume continuously and a high-speed rotary impact shearing pulverizer such as a centrifugal mill are preferably used.
[0017]
The particle size of the pulverized particles is smaller than the predetermined particle size of 500 to 5000 μm, preferably 1000 to 3000 μm, and larger than the popping particle size (particle size of which the final velocity is the same as the superficial velocity of the fluidized bed boiler). Shall. This is because if the particle size of the pulverized particles is smaller than the popping particle size, the pulverized particles jump out from the fluidized bed to the free board along with the combustion gas and do not form a fluidized bed.
[0018]
The invention according to claim 3 of the present invention is Claim 2 The bottom ash circulation apparatus according to claim 1, wherein the gypsum layer-removed particles are obtained by removing the gypsum layer on the surface of each of at least one of the coarse particle ash, the fine bottom ash, and the pulverized particles. It has the structure provided with the layer removal apparatus.
With this configuration, Claim 2 In addition to the effects obtained with the above, the following actions are obtained.
(1) Since it has a gypsum layer removal device, it removes the gypsum layer formed on the surface of each particle such as blast furnace bottom ash and unreacted CaCO _Three The layer can be exposed, and the desulfurization rate can be increased again and reactivated to increase the effective utilization rate of the desulfurizing agent.
(2) By removing the gypsum layer that causes hydration hardening and heat generation when contacted with water with a gypsum removal device, the gypsum removal particles can be mixed with the fuel slurry, which is excellent in applicability. Further, the gypsum layer-removed particles from which the gypsum layer has been removed are less likely to react with moisture in the air and have excellent storage stability.
[0019]
Here, as a gypsum layer removing device, friction / shearing action is applied between rotating rolls such as a mix muller, wet pan mill, Eirich mill, roller mill, colloid mill, etc. A pulverizer for removing the formed gypsum layer is used. In these gypsum removal apparatuses, intervals between rolls or between rolls and disks are set to predetermined intervals of about 500 to 5000 μm, and blast furnace bottom ash or the like is supplied during this period to scrape off and remove the gypsum layer. In order to suppress heat generation, it is preferable to reduce the number of rotations of the rolls and disks. This is to prevent the gypsum layer-removed particles from being pulverized due to the generation of expansion strain accompanying heat generation.
The removal depth of the gypsum layer from the particle surface is preferably 1 to 10 μm, although it depends on the relationship between the interval between the rolls and the particle diameter of the bottom furnace ash and the like. Unreacted CaCO with less gypsum layer thickness to be removed as it becomes smaller than 1 μm _Three There is a tendency that the layer cannot be exposed, and as it becomes larger than 10 μm, the blast furnace bottom ash etc. is pulverized, and there is a tendency to increase the particles scattered in the free board without forming the fluidized bed in the fluidized bed boiler. It is not preferable.
[0020]
The invention according to claim 4 of the present invention is Claim 3 The bottom ash circulation device according to claim 1, wherein one or more of the rough bottom ash, the pulverized particles, and the gypsum layer removal particles are mixed with a desulfurization agent supplied to the fluidized bed boiler for adjustment. It has the structure provided with the desulfurization agent adjustment apparatus.
With this configuration, Claim 3 In addition to the effects obtained with the above, the following actions are obtained.
(1) Since it has a desulfurizing agent adjusting device, one or more kinds of coarse furnace bottom ash, pulverized particles and gypsum layer removing particles are mixed and adjusted with a desulfurizing agent such as limestone and supplied to the fluidized bed boiler. It is possible to increase the effective utilization rate of the desulfurizing agent.
[0021]
Here, as a desulfurization agent adjusting device, a fuel slurry adjusting device for adjusting a fuel slurry obtained by wet mixing a solid fuel such as coal, a desulfurizing agent such as limestone or dolomite, pulverized particles, and water, and a solid fuel, a solid fuel , A desulfurizing agent slurry adjusting device that pastes desulfurizing agent and pulverized particles separately from solid fuel, dry-mixing the desulfurizing agent and pulverized particles, etc., and supplying them into a fluidized bed boiler via a lock hopper, A desulfurizing agent supply hopper or the like is used in which a desulfurizing agent and pulverized particles are dry-mixed and supplied to a fluidized bed boiler via a lock hopper.
[0022]
The invention according to claim 5 of the present invention is Claim 3 or 4 A furnace bottom ash circulation device according to claim 1, wherein (a) a furnace bottom ash storage container for storing at least one of the furnace bottom ash, the pulverized particles, and the gypsum layer removal particles, and (b) One or more of the bottom furnace ash, the pulverized particles, and the gypsum layer removal particles stored in the bottom furnace ash storage container in communication with the bottom furnace ash storage container and the fluidized bed boiler Based on the differential pressure detected by the differential pressure detection means, (c) differential pressure detection means for measuring the differential pressure in the fluidized bed boiler, and And a bed density control means for controlling the bed density of the fluidized bed boiler.
With this configuration, Claim 3 or 4 In addition to the effects obtained with the above, the following actions are obtained.
(1) Since any one or more of blast furnace bottom ash, pulverized particles, and gypsum layer removal particles can be used as a fluid medium for adjusting the layer density, the amount of desulfurizing agent used can be reduced and the effective utilization rate of the desulfurizing agent can be reduced. Can be increased.
(2) Because the bottom ash with a large amount of calcium oxide and calcium sulfate produced can be supplied to the fluidized bed boiler without being mixed with the fuel slurry, the fuel slurry does not condense or generate heat, and the stability of the fuel slurry concentration, viscosity, etc. Can be maintained.
(3) The gypsum layer-removed particles and crushed particles from which the gypsum layer formed on the surface of the bottom furnace ash has been removed are unreacted CaCO _Three Since the layer is deposited and activated, it can be used as a desulfurizing agent, and the amount of the desulfurizing agent used can be reduced and the effective utilization rate of the desulfurizing agent can be increased.
(4) Since it has a bed density detection means for controlling the bed density of the fluidized bed based on the differential pressure detected by the pressure difference detection means, the fluidized bed expansion ratio (the height of the fluidized bed and By optimizing the ratio of the fixed bed height), the flow can be maintained actively and the optimum combustion state can be maintained.
(5) Since the flow can be maintained actively, the desulfurization agent to be supplied can be easily destroyed by heat and worn, so that the fluidized medium can be made finer, and further the flow failure can be prevented.
(6) Since the bed density of the fluidized bed can be optimally controlled, slugging can be prevented and a normal fluidized bed can be generated.
(7) Since slugging can be prevented, it is possible to prevent the fuel slurry injected from the slurry injection nozzle from adhering to, solidifying, and agglomerating on the wall surface of the heat transfer tube or the fluidized bed boiler, and thus causing poor flow.
(8) Since the flow can be maintained actively and the bed density of the fluidized bed can be optimally controlled, the flow state in the bed can be made uniform, the heat transfer from the fluidized bed to the heat transfer tube can be made uniform, and the heat efficiency can be improved. Excellent.
(9) Since the flow can be maintained vigorously, the combustion heat of the solid fuel in the vicinity of the slurry nozzle does not stay easily and the molten ash is difficult to be formed. be able to.
[0023]
Here, as the differential pressure detection means, pressure detectors such as a strain gauge method, a capacitance method, a liquid column method, a bellows method, a Bourdon tube type, a bellows tube type, etc. are used. Between the bottom of the bed and a predetermined height of the fluidized bed, it is disposed at a position where the differential pressure at one or more locations of the fluidized bed is detected.
As the bed density control means, the pressure in the bottom ash storage container is connected to the bottom ash storage container and the pressure in the bottom ash storage container is made higher than or equal to the pressure in the fluidized bed boiler, and then from the blast furnace bottom ash storage container to the fluidized bed boiler. Pressure control devices such as high-pressure gas supply channels that encourage the supply of fine blast furnace bottom ash, extraction control devices such as rotary valves that control the extraction amount of bottom ash from the furnace bottom ash extraction pipe, L valve, J valve, V valve, loop pots such as seal pots, rotary valves, and injectors connected to the ash introduction pipe to control the supply of fine furnace bottom ash from the bottom furnace ash introduction pipe to the fluidized bed boiler A feeder, a table feeder, an air slide, a supply control device such as a double damper, or a combination of these is used.
[0024]
The fluidized bed boiler operating method according to claim 6 of the present invention is a furnace bottom ash extraction step of extracting the furnace bottom ash retained in the furnace bottom from a furnace bottom ash extraction pipe communicating with the furnace bottom of the fluidized bed boiler. And classifying the furnace bottom ash with a predetermined particle size of 500 to 5000 μm and dividing it into at least a coarse furnace bottom ash and a fine furnace bottom ash, Mixing the rough furnace bottom ash with fuel slurry to adjust slurry concentration and slurry viscosity; It has the composition provided with.
With this configuration, the following effects can be obtained.
(1) Since the bottom ash staying at the bottom of the fluidized bed boiler is withdrawn, coarse particles such as coarse powder desulfurization agent staying at the bottom of the furnace and causing flow failure are extracted to prevent the occurrence of poor flow. be able to.
(2) Since the bottom ash of the rough furnace is low in the amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate, and the residual amount of unreacted calcium carbonate is large, it is recycled in the fluidized bed boiler. When introduced, it acts as a desulfurizing agent and can increase the effective utilization rate of the desulfurizing agent.
(3) Since the amount of calcium oxide and calcium sulfate produced in the blast furnace bottom ash does not cause condensation or heat generation even when in contact with water, it does not cause condensation or heat generation due to the hydration reaction even when mixed with fuel slurry. Adjustment of slurry concentration and slurry viscosity is easy.
(4) Since the bottom ash of the blast furnace has a large amount of gypsum and calcium oxide produced by the desulfurization reaction and decarboxylation reaction and a small amount of unreacted calcium carbonate, it is desulfurized even if it is introduced into the fluidized bed boiler. Although the function as an agent is poor, it can be used as a fluid medium for adjusting the fluidized bed height, and the amount of the desulfurizing agent used can be reduced and the effective utilization rate of the desulfurizing agent can be increased. If the gypsum layer formed on the surface of each particle is removed, unreacted CaCO _Three The layer can be exposed, and the desulfurization rate can be increased again and reactivated to increase the effective utilization rate of the desulfurizing agent.
(5) Since the bottom ash is classified with a relatively large particle size of 500 to 5000 μm, a classification device such as a shifter that can be processed easily and in large quantities can be used, and the equipment load is small and the productivity is excellent. Clogging is not likely to occur, and driving efficiency is excellent.
[0025]
Invention of Claim 7 of this invention is a driving | operation method of the fluidized-bed boiler of Claim 6, Comprising: The particle diameter smaller than the said predetermined particle diameter is used for the said rough bottom ash classified by the said classification process. It has the structure provided with the grinding | pulverization process grind | pulverized into the grind | pulverized particle which has.
With this configuration, in addition to the operation obtained in the sixth aspect, the following operation can be obtained.
(1) Since only the coarse furnace bottom ash classified in the classification step is pulverized, the pulverizing apparatus may be small and the equipment load is small.
(2) By crushing the rough ash bottom ash, the gypsum layer on the surface of the rough blast furnace bottom ash is peeled off, and crushed to reduce the particle size, thereby unreacted CaCO _Three The layer can be exposed and reused as a desulfurizing agent.
(3) Of the coarse bottom ash, the particles that have become coarse and settle on the bottom of the fluidized bed boiler and are difficult to flow are pulverized and re-supplied into the fluidized bed boiler to activate the fluidized state of the fluidized bed. Occurrence of poor flow can be prevented.
(4) The coarse furnace bottom ash is pulverized into pulverized particles smaller than a predetermined particle diameter and re-supplied into the fluidized bed boiler, so that the fine furnace smaller than the predetermined particle diameter is next extracted from the furnace bottom ash extraction pipe. Since it is classified as bottom ash, it is not mixed with the fuel slurry, and stability such as fuel slurry concentration and viscosity can be improved and reliability can be improved. When the desulfurizing agent is supplied into the fluidized bed boiler many times and exposed to high pressure and high temperature for a long time, the remaining amount of calcium carbonate decreases with the passage of time, and the amount of calcium oxide and calcium sulfate generated increases. This is because the hydration reaction causes condensation and heat generation when in contact with water.
(5) Since the pulverizer is provided, the coarse furnace bottom ash is pulverized into pulverized particles smaller than a predetermined particle size and supplied into the fluidized bed boiler, and the supplied pulverized particles and fine furnace bottom ash are contained in the fluidized bed boiler. It is refined by wear and becomes fly ash and is discharged out of the system. Since fly ash itself can be recycled as cement material, cement raw material, etc., it is possible to remarkably reduce the cost of treating bottom ash and the amount of industrial waste generated.
[0026]
The invention according to claim 8 of the present invention is the fluidized bed boiler operation method according to claim 6 or 7, wherein the fluidized bed boiler is 10 to 80 wt%, preferably 20 to 40 wt% of 1 to 5 mm. It has the structure which supplies the desulfurization agent which has a particle diameter.
With this configuration, in addition to the action obtained in the sixth or seventh aspect, the following action can be obtained.
(1) Most of the desulfurizing agent with a particle size of 1 to 5 mm is finely granulated by being supplied to the fluidized bed boiler, causing thermal destruction and wear. There is no need to pulverize, the man-hour and cost required for pulverization can be reduced, and energy saving is excellent.
(2) Since the desulfurization agent is not pulverized and atomized before being supplied to the fluidized bed boiler, the final velocity of the particles becomes the gas superficial velocity, and the fine particles that do not form the fluidized bed are scattered from the fluidized bed to the freeboard The particle size is about 250 μm or less when the gas superficial velocity is 0.8 ± 0.4 m / s), and a good fluidized bed can be formed.
(3) Since a fluidized bed containing a desulfurizing agent having a particle diameter of 1 to 5 mm can be generated at the bottom of the fluidized bed, slagging can be prevented, and the fuel slurry injected from the slurry injection nozzle is transferred to a heat transfer tube or It is possible to prevent the occurrence of poor flow due to adhesion, solidification, and agglomeration on the wall surface of the fluidized bed boiler.
[0027]
Here, the desulfurizing agent is the same as that described in claim 1, and thus the description thereof is omitted.
In addition, as content rate of the desulfurization agent which has a particle diameter of 1-5 mm, it is 10-80 wt%, Preferably it is 20-40 wt%. A content of 20 to 40 wt% is preferable because the fluidized bed has an optimum expansion ratio and fluidity is actively observed, and the fluidized bed has excellent stability and hardly generates slagging. As the content ratio becomes smaller than 20 wt%, the fluidized bed tends to be less stable and tends to generate slagging. As the content becomes larger than 40 wt%, 1 to 5 mm of desulfurization remaining without being thermally destroyed in the fluidized bed boiler. Since the amount of the agent increases, the expansion ratio of the fluidized bed decreases, and the flow tends to become inactive. In particular, when the content rate is less than 10 wt% or more than 80 wt%, these tendencies become remarkable, which is not preferable.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a main part configuration diagram of the bottom ash circulation apparatus according to the first embodiment.
In the figure, 1 is a pressure vessel to which compressed air from a compressor (not shown) is supplied, 2 is a pressurized fluidized bed provided in the pressure vessel 1 and supplied with compressed air taken into the pressure vessel 1 from the bottom. A boiler, 2a is a heat transfer tube disposed in the fluidized bed 2b of the pressurized fluidized bed boiler 2, 3 is a combustion exhaust gas channel tube disposed at the top of the pressurized fluidized bed boiler 2, and 4 is a combustion exhaust gas channel. A coarse dust removing device such as a cyclone disposed at the outlet of the pipe 3, 5 is a coarse dust removal gas passage tube coarsely dedusted by the coarse dust removal device 4, and 6 is a coarse dust removal gas passage tube 5. A precision dedusting device composed of a ceramic tube filter that dedusts coarse dedusted gas, 7 is a fuel slurry that is made by mixing solid fuel such as coal, desulfurizing agent such as limestone and dolomite, and water. Fuel slurry adjusting device as a desulfurizing agent adjusting device for adjusting and storing, 8 A slurry pump connected to the fuel slurry adjusting device 7 and transports the fuel slurry to the pressurized fluidized bed boiler 2. A slurry pump 9 has one end connected to the slurry pump 8 and the other end injected the fuel slurry into the pressurized fluidized bed boiler 2. A slurry supply path 10 connected to an injection nozzle (not shown) is connected to the furnace bottom of the pressurized fluidized bed boiler 2 and is used to remove the furnace ash such as coal ash and limestone retained at the furnace bottom of the pressurized fluidized bed boiler 2. Furnace bottom ash extraction pipes 11 that are extracted outside the pressurized fluidized bed boiler 2 and the pressure vessel 1, 11 are two or more types of furnace bottom ash extracted from the furnace bottom ash extraction pipe 10 with a predetermined particle diameter of 500 to 5000 μm. A classifier such as a shifter for classifying into the bottom ash of the furnace, 12 is a bottom of the rough furnace for supplying the bottom ash having a large particle diameter (hereinafter referred to as a rough bottom ash) classified by the classifier 11 to the fuel slurry adjusting device 7 Ash transport path, 13 is a classification device 11 The fine furnace bottom ash transportation path 13a for transporting the fine bottom ash (hereinafter referred to as the fine furnace bottom ash) classified by the blast furnace bottom ash transportation path 13 and separated by the classifier 11 A branch valve made up of a three-way valve that is activated when the blast furnace bottom ash is discharged out of the system, 13b is connected to the blast furnace bottom ash transport path 13 and the whole or part of the blast furnace bottom ash is conveyed. Crossroads 13c is a mix muller, wet pan which is disposed in the bottom ash branch 13b and removes the gypsum layer on the surface of each particle of the bottom ash conveyed by the bottom ash branch 13b to generate gypsum layer-removed particles. A gypsum layer removing device such as a mill, 13d is a discharge path for the removed gypsum layer, 14 is placed in the pressure vessel 1 and connected to the bottom furnace ash transport path 13, and is transported through the bottom furnace ash transport path 13 Blast furnace bottom ash storage container for storing blast furnace bottom ash and gypsum layer removal particles, 15 for blast furnace bottom ash storage Fine furnace bottom ash and gypsum layer removing particles stored in vessel 14 is narrow furnace bottom ash inlet pipe for introducing the pressurized fluid Doso boiler 2 fluidized bed 2b.
In the coarse furnace bottom ash transport path 12, the fine furnace bottom ash transport path 13, the fine furnace bottom ash branch path 13b, and the like, the coarse furnace bottom ash, the fine furnace bottom ash, and the like are conveyed by transport means such as an air flow transport, a bucket elevator, and a belt conveyor. Is transported. Further, a lock hopper system for pressure adjustment (at a place where the normal pressure system and the pressurization system are switched through the pressure vessel 1 such as the fine furnace bottom ash transport path 13 and the furnace bottom ash extraction pipe 10). (Not shown) is provided.
[0029]
The operation method of the bottom ash circulation apparatus of the first embodiment configured as described above will be described below.
A solid fuel such as coal, a desulfurizing agent such as limestone and dolomite, and water are pasted by the fuel slurry adjusting device 7 to adjust the fuel slurry, and stored in the fuel slurry adjusting device 7. In the pressurized fluidized bed boiler 2 installed in the pressure vessel 1, fuel slurry is introduced from the slurry supply passage 9, and compressed air taken into the pressure vessel 1 is supplied from the bottom of the pressurized fluidized bed boiler 2, and solid fuel and The fluidized bed 2b in which the desulfurizing agent is in a fluidized state is formed and burned at a temperature of 0.6 to 3.1 MPa and 800 to 950 ° C. Heat generated by the combustion of the solid fuel is heat-exchanged in the heat transfer tube 2a, and a steam turbine generator (not shown) is driven to generate power. The combustion exhaust gas flows from the combustion exhaust gas flow channel pipe 3 to the coarse dust removal device 4 and is roughly dedusted, and then passes from the coarse dust removal gas flow channel tube 5 to the precision dust removal device 6 to be a gas turbine generator (not shown). Drive) to generate electricity.
When bottom ash such as coal ash or limestone stays in the furnace bottom of the pressurized fluidized bed boiler 2 and the bed height of the fluidized bed 2b becomes high, it stays in the furnace bottom from the furnace bottom ash extraction pipe 10. Remove the bottom ash. The classifier 11 classifies the bottom ash extracted from the bottom of the furnace with a predetermined particle diameter of 500 to 5000 μm, and divides it into a coarse bottom ash and a fine bottom ash. The crude furnace bottom ash is conveyed through the coarse furnace bottom ash transport path 12, weighed by a predetermined amount, mixed with fuel or the like by the fuel slurry adjusting device 7, and adjusted to fuel slurry. On the other hand, the fine furnace bottom ash is conveyed through the fine furnace bottom ash transport path 13. A part is conveyed to a fine furnace bottom ash branching passage 13b communicating with the fine furnace bottom ash transport passage 13 and supplied to the gypsum layer removing device 13c. In the gypsum layer removing device 13c, the interval between the rolls and between the roll and the disk is set at an interval of about 500 to 5000 μm, and the blast furnace bottom ash is supplied during this time, and the gypsum layer is scraped off from the surface at a depth of about 1 to 10 μm Gypsum layer removal particles are produced. The gypsum layer removal particles and the fine furnace bottom ash generated by the gypsum layer removal device 13 c are stored in the fine furnace bottom ash storage container 14. The blast furnace bottom ash and the gypsum layer removal particles stored in the blast furnace bottom ash storage container 14 are removed from the blast furnace bottom ash supply pipe 15 when the bed height of the fluidized bed 2b of the pressurized fluidized bed boiler 2 is lowered. It is introduced into the pressurized fluidized bed boiler 2.
[0030]
As mentioned above, since the bottom ash circulation apparatus in this Embodiment 1 is comprised, the following effects are obtained.
(1) Rough bottom ash is mixed with coal, etc., because the amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate is small and the remaining amount of unreacted calcium carbonate is large. And can be reintroduced into the pressurized fluidized bed boiler to increase the effective utilization rate of the desulfurizing agent.
(2) Since the amount of calcium oxide and calcium sulfate produced in the furnace bottom ash is small, it does not cause condensation or heat generation even when it comes into contact with water. Even if mixed, the slurry concentration and the slurry viscosity can be easily adjusted without causing condensation or heat generation. Moreover, since it can mix with a fuel slurry, rough furnace bottom ash can be stably supplied in a pressurized fluidized bed boiler as a fuel slurry, and the effective utilization factor of a desulfurization agent can be raised.
(3) The bottom ash of the blast furnace has a large amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate, and a small amount of unreacted calcium carbonate. However, since it has a gypsum layer removing device, it removes the gypsum layer formed on the surface of each particle of the blast furnace bottom ash to remove unreacted CaCO _Three The layer can be exposed, and the desulfurization rate can be increased again and reactivated to increase the effective utilization rate of the desulfurizing agent.
(4) The effective utilization rate of the desulfurization agent is increased by a small-scale improvement that simply installs a classifier that classifies the bottom ash extracted from the bottom ash extraction pipe of the existing pressurized fluidized bed boiler. Its consumption can be reduced.
(5) Since the furnace bottom ash is classified with a relatively large particle diameter of 500 to 5000 μm, a classification device such as a shifter that can be processed easily and in large quantities can be used, and the equipment load is small and the productivity is excellent.
(6) Since the furnace bottom ash is classified into the coarse furnace bottom ash and the fine furnace bottom ash by the classifier, the coarse furnace bottom ash and the fine furnace bottom ash are separately supplied into the fluidized bed according to the bed height, etc. The particle size in the fluidized bed can be controlled to stabilize the flow.
[0031]
In the first embodiment, the classification device 11 has been described as being classified into the coarse blast furnace bottom ash and the fine blast furnace bottom ash with a predetermined particle diameter. It is also possible to classify so as to remove large ones. As a result, coarse particles such as sintering products and coarse powder desulfurization agent contained in the bottom ash extracted from the bottom of the furnace can be removed, and such coarse particles settle in the fluidized bed to cause poor flow. It can be prevented from causing.
Moreover, when the particle diameter of the bottom furnace ash is small, the gypsum layer removing device 13c may not be provided. This is because the relative thickness of the gypsum layer with respect to the particle size of the blast furnace bottom ash is large, and it is difficult to remove the gypsum layer and the gypsum layer removal efficiency is low.
[0032]
(Embodiment 2)
FIG. 2 is a main part configuration diagram of the furnace bottom ash circulation device according to the second embodiment. In addition, the thing similar to what was demonstrated in Embodiment 1 attaches | subjects the same code | symbol, and abbreviate | omits description.
In the figure, 16 is a grinding device such as an edge runner or roller mill that grinds the coarse furnace bottom ash transported by the coarse furnace bottom ash transport path 12 to a particle size smaller than a predetermined particle size of 500 to 5000 μm, and 17 is a grinding device 16. A pulverized particle supply path for supplying the pulverized particles obtained by pulverizing the coarse furnace bottom ash to the fuel slurry adjusting device 7, 18 is communicated with the fine furnace bottom ash storage container 14 and the pulverized particle supply path 17 and is pulverized by the pulverizer 16. A pulverized particle transport path for transporting and supplying the pulverized particles to the blast furnace bottom ash storage container 14, 18 a is a branch valve comprising a three-way valve or the like disposed at a communication portion between the pulverized particle supply path 17 and the pulverized particle transport path 18. is there.
In the pulverized particle transport path 18, the pulverized particles are conveyed by conveying means such as air current conveyance, a bucket elevator, and a belt conveyor. Further, a lock hopper system (not shown) for pressure adjustment is disposed at a place where the normal pressure system and the pressurization system are switched through the pressure vessel 1 in the pulverized particle transport path 18.
[0033]
The operation method of the fluidized bed circulation device of the pressurized fluidized bed boiler of the second embodiment configured as described above will be described below.
The bottom ash such as coal ash and limestone staying at the bottom of the pressurized fluidized bed boiler 2 is extracted from the bottom ash extraction pipe 10, and the coarse bottom with a predetermined particle diameter of 500 to 5000 μm by the classifier 11. Separated into ash and blast furnace bottom ash. The classified coarse furnace bottom ash is then conveyed to the pulverizer 16 through the coarse furnace bottom ash transport path 12. In the pulverizing device 16, a gap such as a roller is maintained at a predetermined particle size interval, and the coarse bottom ash is passed and pulverized into pulverized particles smaller than a predetermined particle size of 500 to 5000 μm. The pulverized particles obtained by pulverizing the coarse furnace bottom ash are mixed with fuel or the like by the fuel slurry adjusting device 7 to be adjusted to fuel slurry. Further, some of the pulverized particles are branched by the branch valve 18 a, carried through the pulverized particle transport pipe 18, and stored in the blast furnace bottom ash storage container 14 together with the blast furnace bottom ash classified by the classifier 11. The blast furnace bottom ash stored in the blast furnace bottom ash storage container 14 is supplied from the blast furnace bottom ash supply pipe 15 to the pressurized fluidized bed boiler 2 when the bed height of the fluidized bed 2b of the pressurized fluidized bed boiler 2 is lowered. Introduced in.
[0034]
As described above, since the bottom ash circulation device of the second embodiment is configured, the following operation is obtained in addition to the operation obtained in the first embodiment.
(1) CaSO on the surface of the bottom ash by crushing the bottom ash _Four The layer is exfoliated and crushed to reduce the particle size, and unreacted CaCO _Three The layer can be exposed and the bottom ash can be reused as a desulfurization agent.
(2) By pulverizing particles such as sinter products which are coarsened and settled in the bottom of the pressurized fluidized bed boiler and hardly flow, and re-supplied into the pressurized fluidized bed boiler. The fluidized state of the fluidized bed can be activated to prevent the occurrence of poor flow.
(3) By pulverizing the coarse furnace bottom ash to a pulverized particle smaller than a predetermined particle size by a pulverizer and re-feeding it into the pressurized fluidized bed boiler, the predetermined particle is next extracted from the furnace bottom ash extraction pipe. Since the bottom ash is smaller than the diameter, it is not mixed with the fuel slurry, so that the stability of the fuel slurry concentration and viscosity can be improved and the reliability can be improved. When the desulfurizing agent is supplied many times into the pressurized fluidized bed boiler and exposed to high pressure and high temperature for a long time, the residual amount of calcium carbonate decreases with time and the amount of calcium oxide and calcium sulfate produced increases. This is because contact with water causes condensation and heat generation due to a hydration reaction.
[0035]
In addition, in this Embodiment, although the case where the fine furnace bottom ash branch path 13b and the gypsum layer removal apparatus 13c were not connected to the fine furnace bottom ash transport path 13 was demonstrated, these can also be provided. Thereby, since the gypsum layer produced | generated on the surface of each particle | grain of bottom furnace ash can be removed and reactivated, a desulfurization effect | action can be heightened.
[0036]
(Embodiment 3)
FIG. 3 is a main part configuration diagram of the furnace bottom ash circulation apparatus according to the third embodiment. In addition, the thing similar to what was demonstrated in Embodiment 1 and 2 attaches | subjects the same code | symbol, and abbreviate | omits description.
In the figure, 11a is a multi-stage sieve mesh surface having different sieve openings, and the furnace bottom ash extracted by the furnace bottom ash extraction pipe 10 is used as a coarse furnace bottom ash, a fine furnace bottom ash, and a pressurized fluidized bed boiler. A classifier such as a shifter for classifying into three kinds of coarse particles such as a sinter product larger than the maximum particle size of the desulfurizing agent supplied to 2 and a coarse powder desulfurizing agent, 11b is a coarse particle classified by the classifying device 11a A coarse particle discharge path for discharging to the furnace, 12a is a coarse furnace bottom ash transport path for supplying the coarse furnace bottom ash classified by the classifier 11a to a fuel supply hopper 17a (described later) as a desulfurization agent adjusting apparatus, and 12b is a rough furnace. A rough furnace bottom ash branch path connected to the bottom ash transport path 12a and transporting all or a part of the rough ash bottom ash, 12c is provided in the rough furnace bottom ash branch path 12b, and is sent to the rough ash bottom ash branch path 12b. Removes the gypsum layer on the surface of each particle in the furnace bottom ash to produce gypsum layer removal particles The gypsum layer removing device 17a is a desulfurizing agent adjusting device that mixes solid fuel such as coal, a desulfurizing agent such as limestone, and the rough blast furnace bottom ash and gypsum layer removing particles supplied from the rough blast bottom ash transportation path 12a. The fuel supply hopper 17b is connected to the downstream side of the fuel supply hopper 17a and receives solid fuel mixed in the fuel supply hopper 17a at a pressure of about 0.6 to 3.1 MPa, which is substantially the same pressure as the pressurized fluidized bed boiler 2. The lock hopper 17c to be stored is connected to a downstream of the lock hopper 17b and a spray nozzle (not shown) disposed in the pressurized fluidized bed boiler 2, and the solid fuel etc. stored in the lock hopper 17b is air-flowed. A fuel supply path 17d that conveys and supplies the fluidized bed 2b, and 17d communicates with the fuel supply path 17c and conveys the solid fuel or the like supplied from the lock hopper 17b into the fuel supply path 17c to the fluidized bed 2b. A transport air supply pipe for supplying compressed air that. When supplying solid fuel or the like from the fuel supply hopper 17a to the lock hopper 17b, the pressure of the fuel supply hopper 17a is increased to substantially the same pressure as the lock hopper 17b.
[0037]
The bottom ash circulation device of the third embodiment configured as described above is different from the first embodiment in that the classifying device 11a is formed in multiple stages, and the desulfurization agent adjustment instead of the fuel slurry adjustment device The fuel supply hopper 17a and the lock hopper 17b are provided as devices, and the gypsum layer removing device 12c is provided for removing the gypsum layer on the classified coarse furnace bottom ash particles.
[0038]
As described above, since the bottom ash circulation device of the third embodiment is configured, in addition to the operation described in the first or second embodiment, the following operation can be obtained.
(1) The classification device is formed in multiple stages, and coarse particles such as sintered products, rough furnace bottom ash, and fine furnace bottom ash can be separated at the same time, so the classification efficiency is excellent.
(2) Since coarse particles such as sinter product contained in the bottom ash can be separated and discharged out of the system, the coarse particles settle in the fluidized bed or agglomerate the fluid medium. It is possible to prevent the occurrence of poor flow and stable operation for a long period of time becomes possible.
(3) A desulfurizing agent or the like can be supplied into the pressurized fluidized bed boiler without making a slurry, and there is no loss of heat of vaporization when water contained in the slurry evaporates, resulting in excellent thermal efficiency.
(4) Since it has a gypsum layer removing device that removes the gypsum layer generated on the surface of each particle of the bottom ash of the rough furnace, unreacted CaCO _Three The layer can be exposed, the desulfurization reaction rate can be increased and reactivated to increase the effective utilization of the desulfurizing agent.
[0039]
In the present embodiment, the case where the gypsum layer removing device 12c for treating the rough ash bottom ash and the gypsum layer removing device 13c for treating the fine blast furnace bottom ash are described. Depending on the type, it may not be provided at all, or only one of them may be provided. Moreover, although the case where the crushing apparatus which grind | pulverizes the rough furnace bottom ash demonstrated in Embodiment 2 was not provided was demonstrated, it may be provided.
[0040]
(Embodiment 4)
FIG. 4 is a configuration diagram of a main part of the furnace bottom ash circulation device according to the fourth embodiment. In addition, the thing similar to what was demonstrated in Embodiment 1 and 2 attaches | subjects the same code | symbol, and abbreviate | omits description.
In the figure, reference numeral 15a designates a supply amount control device (layer density control means) for introducing the bottom ash and the like stored in the bottom ash storage container 14 into the fluidized bed 2b of the pressurized fluidized bed boiler 2 with the assistance of air flow. ) And a bottom furnace ash introduction pipe 19 connected to the upstream side of the bottom furnace ash introduction pipe 15a and the bottom ash inside the furnace bottom ash introduction pipe 15a, etc. An air supply pipe such as an L valve that supplies compressed air for conveying compressed air to the fluidized bed 2b, 20 is an air quantity control valve such as an L valve that is disposed in the air supply pipe 19 and controls the air quantity, and 21 is a furnace bottom ash An extraction amount control device (layer density control means) such as a rotary valve disposed on the extraction pipe 10 for controlling the extraction amount of the furnace bottom ash, 22 has one end portion communicating with the pressurized fluidized bed boiler 2 at one end portion. Communicates with the bottom of the fluidized bed 2b and the other end is at a predetermined position in the height direction of the fluidized bed 2b. Through (assuming the height from the bottom to a predetermined position is z) Pressure detection such as strain gauge method, capacitance method, liquid column method, bellows method, Bourdon tube method, bellows tube method, etc. A differential pressure detection means 23 comprising a vessel calculates the bed density of the fluidized bed 2b based on the differential pressure detected by the differential pressure detection means 22, and based on the result, the amount of air such as an L valve as a bed density control means It is a controller that controls the degree of opening and closing of the control valve 20 and the withdrawal amount control device 21.
[0041]
An operation method of the fluidized bed circulation device of the fourth embodiment configured as described above will be described below.
First, the controller 23 uses the Δp (Pa) detected by the differential pressure detection means 22 and the known interval z (m) to set the bed density (kg / m) of the fluidized bed 2b. ^Three ) Is calculated by (Equation 1). In addition, g is a gravitational acceleration.
[Expression 1]

Next, the controller 23 determines the relationship between the bed density of the fluidized bed and the average particle diameter of the fluidized medium (the expansion ratio (ratio of the fixed bed height to the fluidized bed height) increases as the average particle diameter of the fluidized medium decreases). The optimum layer density is calculated from the relationship that the expansion ratio decreases and the layer density increases as the density decreases and the average particle diameter of the fluid medium increases. The degree of opening / closing of the valve 20 and the withdrawal amount control device 21 is controlled. The bed density of the fluidized bed 2b is a predetermined value (in this experimental example, about 800 kg / m ^Three The controller 23 increases the degree of opening of the extraction amount control device 21 and removes the bottom ash containing coarse particles remaining in the bottom of the pressurized fluidized bed boiler 2 to the bottom ash. While extracting from the extraction pipe 10 and increasing the opening degree of the air amount control valve 20 such as an L valve, compressed air is supplied to the fine furnace bottom ash introduction pipe 15a through the air supply pipe 19 to supply the fine furnace bottom ash introduction pipe. The fine furnace bottom ash in 15a is introduced into the lower part of the fluidized bed 2b, and the bed density of the fluidized bed 2b is lowered. The bed density of the fluidized bed 2b is a predetermined value (in this experimental example, about 500 kg / m ^Three The controller 23 closes the extraction amount control device 21 so as not to extract the furnace bottom ash in the pressurized fluidized bed boiler 2 and closes the air amount control valve 20. The fine furnace bottom ash in the fine furnace bottom ash introduction pipe 15a is prevented from being introduced into the fluidized bed 2b. Thereby, since the desulfurizing agent such as limestone and dolomite contained in the fuel slurry adjusted by the fuel slurry adjusting device 7 is supplied into the pressurized fluidized bed boiler 2, the bed density of the fluidized bed 2b increases.
The furnace bottom ash extracted from the furnace bottom ash extraction pipe 10 in order to control the bed density in the pressurized fluidized bed boiler 2 is classified by the classifier 11 and then pulverized particles in the pulverized particle transport path 18. It is conveyed, or is conveyed as fine furnace bottom ash in the fine furnace bottom ash transport path 13, stored in the fine furnace bottom ash storage device 14, and supplied into the pressurized fluidized bed boiler 2. Alternatively, the pulverized particles are mixed with the fuel slurry by the fuel slurry adjusting device 7 and supplied into the pressurized fluidized bed boiler 2.
[0042]
As described above, since the bottom ash circulation apparatus of the fourth embodiment is configured, in addition to the actions obtained in the first or second embodiment, the following actions are obtained.
(1) Since any one or more of blast furnace bottom ash, pulverized particles, and gypsum layer removal particles can be used as a fluid medium for adjusting the layer density, the amount of desulfurizing agent used can be reduced and the effective utilization rate of the desulfurizing agent can be reduced. Can be increased.
(2) Because the bottom ash with a large amount of calcium oxide and calcium sulfate produced can be supplied to the fluidized bed boiler without being mixed with the fuel slurry, the fuel slurry does not condense or generate heat, and the stability of the fuel slurry concentration, viscosity, etc. Can be maintained.
(3) The gypsum layer-removed particles and crushed particles from which the gypsum layer formed on the surface of the bottom furnace ash has been removed are unreacted CaCO _Three Since the layer is deposited and activated, it can be used as a desulfurizing agent, and the amount of the desulfurizing agent used can be reduced and the effective utilization rate of the desulfurizing agent can be increased.
(4) Since it has a bed density detection means for controlling the bed density of the fluidized bed based on the differential pressure detected by the pressure difference detection means, the fluidized bed expansion ratio (the height of the fluidized bed and By optimizing the ratio of the fixed bed height), the flow can be maintained actively and the optimum combustion state can be maintained.
(5) Since the flow can be maintained actively, the desulfurization agent to be supplied can be easily destroyed by heat and worn, so that the fluidized medium can be made finer, and further the flow failure can be prevented.
(6) Since the bed density of the fluidized bed can be optimally controlled, slugging can be prevented and a normal fluidized bed can be generated.
(7) Since slugging can be prevented, it is possible to prevent the fuel slurry injected from the slurry injection nozzle from adhering to, solidifying, and agglomerating on the wall surface of the heat transfer tube or the fluidized bed boiler, and thus causing poor flow.
(8) Since the flow can be maintained actively and the bed density of the fluidized bed can be optimally controlled, the flow state in the bed can be made uniform, the heat transfer from the fluidized bed to the heat transfer tube can be made uniform, and the heat efficiency can be improved. Excellent.
(9) Since the flow can be maintained vigorously, the combustion heat of the solid fuel in the vicinity of the slurry nozzle does not stay easily and the molten ash is difficult to be formed. be able to.
[0043]
In Embodiments 1 to 4, the case of a pressurized fluidized bed boiler used in a pressurized system has been described. However, the operation method of the bottom ash circulating apparatus and the fluidized bed boiler of the present invention is an atmospheric system. The same can be applied to the fluidized bed boiler used.
[0044]
【Example】
Next, the present invention will be described in detail using examples.
(Example 1, Example 2)
Using a 71 MW pressurized fluidized bed combined power generation system, the fuel shown in (Table 1) and the limestone as a desulfurizing agent containing 10 to 80 wt% of a commercially available 1 to 5 mm particle size in a pressurized fluidized bed boiler are put into a fluidized state. The combustion operation was performed at 0.6 to 3.1 MPa and 800 to 950 ° C. In Example 1, as shown in (Table 1), a limestone produced by Tsukumi was used, using a fuel in which 70 wt% of breazole charcoal and 30 wt% of petroleum coke were mixed. In Example 2, the fuel which mixed 50 wt% of breazole charcoal and 50 wt% of petroleum coke was used, and limestone which mixed 50 wt% of Tsukumi limestone and 50 wt% of stern limestone was used. The weight percent of each compound contained in limestone is shown in (Table 2). The particle size distribution of the desulfurizing agent limestone is shown in FIG. 5 (a).
[Table 1]

[Table 2]

Next, the particle size distribution of the bottom ash extracted from the bottom ash extraction pipe during the combustion operation of the pressurized fluidized bed boiler is shown in FIG. 5 (b), and the bottom ash in each particle size range is shown in FIG. The weight percentage of the Ca compound is shown in (Table 3). Moreover, the weight% of each compound contained in the fly ash (average particle diameter of 21 μm) collected by the precision dust remover is shown in (Table 4).
[Table 3]

[Table 4]

From (Table 3), the furnace bottom ash with a particle diameter of 105 to 1190 μm extracted from the furnace bottom ash extraction pipe is composed of 20 to 40 wt% CaO and CaSO with respect to the Ca compound. _Four 46 to 55 wt%, while CaCO _Three Was found to contain only 12-30 wt%. On the other hand, the furnace bottom ash having a particle diameter of 1190 μm or more contains 4 to 8 wt% CaO, CaSO with respect to the Ca compound. _Four Is contained only 10-20 wt%, whereas CaCO _Three It was found that 76 to 82 wt% was contained.
On the other hand, from (Table 4), fly ash is 7.5 to 15.3 wt% CaO, CaCO. _Three 3.2 to 5.3 wt%, CaSO _Four It was found that 15.7 to 20.4 wt% was contained.
[0045]
(Hydrolysis test)
Using the bottom ash having a particle diameter of 105 to 1190 μm, the bottom ash having a particle diameter of 1190 μm or more, and fly ash obtained in Example 1 and Example 2, 30 wt% water was added and mixed to each to make a paste. The exotherm and condensation phenomenon of the thing was observed.
As a result, in the bottom ash having a particle diameter of 105 to 1190 μm, a condensation phenomenon was confirmed on the seventh day after the addition and mixing of water. Further, fly ash was confirmed to have a temperature increase of about 10 ° C. within 100 minutes after the addition and mixing of water, and a condensation phenomenon was confirmed. On the other hand, furnace bottom ash having a particle size of 1190 μm or more was not confirmed to be exothermic or condensed.
(Heating test)
The furnace bottom ash having a particle size of 1190 μm or more was immersed in water for 30 minutes, then the water was cut off, the furnace bottom ash was inserted into an electric furnace heated to 850 ° C., heated, taken out, and the crushed state of the furnace bottom ash was observed. For comparison, the limestone having a particle diameter of 1190 μm or more before being supplied to the pressurized fluidized bed boiler was similarly immersed in water and then heated to observe the crushed state.
As a result, about 70% of the limestone having a particle diameter of about 2 mm or more before being supplied to the pressurized fluidized bed boiler was crushed into particles of 0.25 to 0.5 mm, whereas the pressurized fluidized bed boiler It was confirmed that the bottom ash extracted from the furnace was not crushed. In the furnace bottom ash, it was confirmed that a part of the brown film presumed to be a gypsum component adhering to the surface of the furnace bottom ash peeled off and unreacted calcium carbonate was exposed.
[0046]
(Evaluation on reuse of furnace bottom ash)
The bottom ash having a particle diameter of 1190 μm or more obtained in Example 1 and Example 2 is pulverized into pulverized particles having a particle diameter of less than 1190 μm by a pulverizer such as a roller mill, and the pulverized particles obtained are supplied to a fuel slurry adjusting device. And mixed with the fuel slurry. Even when the pulverized particles were mixed, it was easy to adjust the viscosity and concentration of the fuel slurry. On the other hand, the bottom ash having a particle size of less than 1190 μm was stored in a fine bottom ash storage container and supplied into a pressurized fluidized bed boiler according to the bed height and bed density of the fluidized bed. As a result, in the pressurized fluidized bed boiler of Example 1, a required Ca / S molar ratio of 3.0 of the desulfurizing agent is obtained, and in the pressurized fluidized bed boiler of Example 2, a required Ca / S molar ratio of 2.5 is obtained. It was.
From the above, 70 wt% or more of CaCO with respect to the Ca compound. _Three It has been confirmed that the furnace bottom ash containing 1190 μm or more containing slag increases the effective utilization rate of the desulfurizing agent by being introduced again into the pressurized fluidized bed boiler. In addition, heat generation and condensation did not occur even when contacted with water, so it was confirmed that the fuel slurry could be mixed. It was also confirmed that even if it was introduced again into the pressurized fluidized bed boiler, it was difficult to crush, but part of the coating adhering to the surface peeled off, unreacted calcium carbonate was exposed and contributed to the desulfurization reaction. Also, since it is difficult to crush in a pressurized fluidized bed boiler, it is effective to pulverize using a crusher before reintroducing it into the pressurized fluidized bed boiler to increase the specific surface area and expose the desulfurized unreacted surface. It was inferred that Moreover, about 70% of the limestone having a particle diameter of about 2 mm or more before being supplied to the pressurized fluidized bed boiler is mixed with the fuel slurry and heated in the pressurized fluidized bed boiler. It was confirmed that the particles were crushed into 0.5 mm particles. Thereby, it is not necessary to pulverize the limestone before being supplied to the pressurized fluidized bed boiler to about 1 mm or less in order to improve the desulfurization rate, and even when using commercially available limestone, the Ca / S molar ratio is 3 or less. It was confirmed that an effective utilization rate could be obtained. Furthermore, furnace bottom ash having a particle size of less than 1190 μm is CaO and CaSO. _Four Is high, fly ash is CaSO _Four , SiO ₂ And Al ₂ O _Three It was confirmed that it can be used as a cement material or a cement raw material because of its high content.
[0047]
(Example 3, Comparative Example 1)
Calculating the calcium balance when comparing the bottom ash circulation device described in Embodiment 2 in a 71 MW pressurized fluidized bed combined power generation system (comparing the amount of limestone transferred, focusing on the amount of calcium contained in limestone) And evaluated. The calculation uses a mixture of 70 wt% of breazole charcoal and 30 wt% of petroleum coke shown in Table 1 described in Example 1 as the fuel, and uses limestone produced by Tsukumi as the desulfurizing agent, and 0.6-3. The test was performed when the combustion operation was performed at 800 to 950 ° C. under a pressure of 1 MPa. A pressurized fluidized bed combined power generation system under the same conditions was used as a comparative example without a bottom ash circulation device.
The results of calculating the calcium balance of Example 3 and Comparative Example 1 are shown in FIG. In FIG. 6, only the pressurized fluidized bed boiler 2, the classifying device 11, the pulverizing device 16, and the fuel slurry adjusting device 7 described in the second embodiment are shown to simplify the drawing. In FIG. 6, the numerical values shown in A to G are the movement amount (kg / hr) of limestone per unit time based on the calculation result. In addition, the numerical value shown in the upper part is the movement amount (kg / hr) of the limestone of the example, and the numerical value shown in the lower part is the movement amount (kg / hr) of the limestone of the comparative example. It is assumed that 56140 kg of limestone is present in the pressurized fluidized bed boiler.
In the calculation of the calcium balance, the supply amount of limestone was determined so that the Ca / S ratio of the comparative example was 5. Further, considering the reactivity between limestone, furnace bottom ash, etc. and sulfur oxides, the desulfurization rates of the examples and comparative examples were made the same. Furthermore, in order to make the comparison with an Example and a comparative example easy, it supplies to the pressurized fluidized bed boiler 2 by the quantity (B lower stage) of the limestone supplied to the pressurized fluidized bed boiler 2 by a comparative example, and an Example. Conversion was performed so that the total amount of limestone and pulverized particles (furnace bottom ash pulverized by the pulverizer 16) (upper B) was the same value.
[0048]
In FIG. 6, in the comparative example, limestone (B lower stage) supplied to the pressurized fluidized bed boiler 2 at 760.6 kg / hr is discharged as furnace bottom ash at 384.2 kg / hr (C lower stage) to produce combustion exhaust gas. Concomitantly, 376.4 kg / hr is discharged (lower E). Since it does not have a furnace bottom ash circulation device, a processing cost for processing the furnace bottom ash discharged at 384.2 kg / hr (C lower stage) is required. Further, 760.6 kg / hr of new limestone needs to be supplied to the fuel slurry adjusting device 7 (A lower stage).
On the other hand, in the example, 760.6 kg / hr of limestone and pulverized particles (B upper stage) adjusted by the fuel slurry adjusting apparatus 7 and fine furnace bottom ash (G upper stage) generated by the pulverizer 11 by 139.0 kg / hr. ) Is supplied to the pressurized fluidized bed boiler 2, 508.5 kg / hr is discharged as furnace bottom ash (C upper stage), and 391.1 kg / hr is discharged along with the combustion exhaust gas (E upper stage). 508.5 kg / hr of bottom ash (C upper stage) is 170.6 kg / hr of coarse bottom ash (pulverized particles) (F upper stage) by the classifier 11 and 139.0 kg / hr of fine bottom ash (G (Upper stage) and 198.9 kg / hr of the bottom ash discharged from the system (D upper stage). Since the pulverized particles were supplied to the fuel slurry adjusting device 7 at 170.6 kg / hr (F upper stage), it was found that the supply amount of new limestone may be 590.0 kg / hr (A upper stage).
[0049]
As a result, in the comparative example, a new supply of 760.6 kg / hr of new limestone was required, whereas in the present example, a new supply of limestone was 590.0 kg / hr, so (760. 6-590.0) /760.6=22.4% limestone was found to be reduced. As a result, the Ca / S ratio was reduced from 5 to 3.9. The furnace bottom ash discharged out of the system was 384.2 kg / hr in the comparative example, but 198.9 kg / hr in the example. Therefore, the furnace bottom ash discharged out of the system was It became clear that the amount of ash was reduced to about 50%, and the processing cost and industrial waste amount related to it were reduced to about half of the conventional example.
In addition, although the present Example demonstrated the wet system which supplies limestone, a fuel, etc. to a pressurized fluidized bed boiler in paste form, also when the limestone, a fuel, etc. are supplied dry-type, the reduction amount of limestone and a Ca / S ratio The same effect can be obtained with respect to the above. Furthermore, in the case of dry-type supply, there is no loss of heat of vaporization when water evaporates from the fuel or the like supplied in the form of paste, and the thermal efficiency can be improved.
[0050]
【The invention's effect】
As described above, according to the operation method of the bottom ash circulation device and the fluidized bed boiler of the present invention, the following advantageous effects can be obtained.
According to the invention of claim 1,
(1) Since the bottom ash of the crude furnace has a small amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate and a large amount of unreacted calcium carbonate, When reintroduced, it is possible to provide a bottom ash circulation device that works as a desulfurizing agent and can increase the effective utilization rate of the desulfurizing agent.
(2) Since the amount of calcium oxide and calcium sulfate produced in the furnace bottom ash is small, it does not cause condensation or heat generation even when it comes into contact with water, so it can be contained in the fuel slurry together with a solid fuel such as coal or a desulfurizing agent such as limestone. It is possible to provide a furnace bottom ash circulation device that can easily adjust the slurry concentration and the slurry viscosity without causing condensation or heat generation even when mixed. Moreover, since it can be mixed with the fuel slurry, the bottom ash circulation device that can stably supply the crude bottom ash as the fuel slurry into the fluidized bed boiler and increase the effective utilization rate of the desulfurizing agent. Can be provided.
(3) The bottom ash of the blast furnace has a large amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate, and a small amount of unreacted calcium carbonate. For this reason, even if blast furnace bottom ash is introduced into the fluidized bed boiler as it is, its function as a desulfurizing agent is poor, but it can be used as a fluidizing medium for adjusting the fluidized bed height, reducing the amount of desulfurizing agent used and desulfurizing agent It is possible to provide a bottom ash circulation device that can increase the effective utilization rate of the ash.
(4) The effective utilization rate of the desulfurizing agent can be increased by a small-scale improvement that simply installs a classifier for classifying the bottom ash extracted from the bottom ash extraction pipe of the existing fluidized bed boiler. It is possible to provide a furnace bottom ash circulation device capable of suppressing the equipment load.
(5) Since the bottom ash is classified with a relatively large particle diameter of 500 to 5000 μm, it is possible to use a classifier such as a shifter that can be processed easily and in large quantities, and the equipment bottom is small, and the bottom ash has excellent productivity. A circulation device can be provided. Furthermore, it is possible to provide a bottom ash circulation device that is less likely to cause clogging of the classification device and has excellent operation efficiency.
(6) Since a classifier is provided, a furnace bottom ash circulation device that can remove a sinter product melted and agglomerated in a fluidized medium and can improve stability in a fluidized bed is provided. can do.
[0051]
According to invention of Claim 2, in addition to the effect of Claim 1,
(1) The coarse gypsum floor ash is pulverized to peel off the gypsum layer on the surface of the coarse furnace bottom ash, and crushed to reduce the particle size, thereby unreacted CaCO _Three It is possible to provide a bottom ash circulation device in which the layer is exposed and the bottom ash can be reused as a desulfurization agent.
(2) Particles that are coarse in the bottom ash of the furnace and settle down to the bottom of the fluidized bed boiler and are difficult to flow are crushed and re-supplied into the fluidized bed boiler to activate the fluidized state of the fluidized bed. It is possible to provide a furnace bottom ash circulation device that can prevent the occurrence of poor flow.
(3) By pulverizing the coarse furnace bottom ash into pulverized particles smaller than a predetermined particle size by a pulverizer and re-feeding it into the fluidized bed boiler, the bottom of the fine furnace bottom is extracted from the furnace bottom ash extraction pipe. Since it is classified as ash, it is possible to provide a furnace bottom ash circulation device that is not mixed with the fuel slurry, can improve the stability of the fuel slurry concentration, viscosity, etc., and can improve the reliability.
(4) Since the pulverizer is provided, the coarse furnace bottom ash is pulverized into pulverized particles smaller than a predetermined particle diameter and supplied into the fluidized bed boiler, and the supplied pulverized particles and fine furnace bottom ash are contained in the fluidized bed boiler. It is refined by wear and becomes fly ash and is discharged out of the system. Since fly ash can be recycled by itself as cement material, cement raw material, etc., it is possible to provide a bottom ash circulation device that can remarkably reduce the bottom ash processing cost, the amount of industrial waste generated, and the like.
[0052]
According to invention of Claim 3, Claim 2 In addition to the effect of
(1) Since it has a gypsum layer removing device, the gypsum layer formed on the surface of each particle in the bottom ash of the blast furnace is removed and unreacted CaCO _Three It is possible to provide a furnace bottom ash circulation device that can expose the layer and increase the effective utilization rate of the desulfurization agent by increasing the desulfurization reaction rate again and reactivating it.
(2) By providing a gypsum removal device that removes the gypsum layer that causes hydration and heat generation when contacted with water, the gypsum removal particles can be mixed with the fuel slurry, providing a furnace bottom ash circulation device with excellent applicability. can do. Moreover, since the gypsum layer is removed, it is possible to provide a furnace bottom ash circulation device that can obtain gypsum layer-removed particles that hardly react with moisture in the air and have excellent storage stability.
[0053]
According to invention of Claim 4, Claim 2 or 3 In addition to the effect of
(1) Since it has a desulfurizing agent adjusting device, one or more kinds of coarse furnace bottom ash, pulverized particles and gypsum layer removing particles are mixed and adjusted with a desulfurizing agent such as limestone and supplied to the fluidized bed boiler. It is possible to provide a bottom ash circulation device that can increase the effective utilization rate of the desulfurization agent.
[0054]
According to the invention of claim 5, Claims 2 to 4 In addition to one of the effects,
(1) Since any one or more of blast furnace bottom ash, pulverized particles, and gypsum layer removal particles can be used as a fluid medium for adjusting the layer density, the amount of desulfurizing agent used can be reduced and the effective utilization rate of the desulfurizing agent can be reduced. It is possible to provide a bottom ash circulation device that can be enhanced.
(2) Furnace bottom ash, which produces a large amount of calcium oxide and calcium sulfate, can be supplied to the fluidized bed boiler without being mixed with the fuel slurry, so the fuel slurry does not condense or generate heat, and the stability of the fuel slurry concentration, viscosity, etc. It is possible to provide a bottom ash circulation device capable of maintaining the above.
(3) The gypsum layer-removed particles and crushed particles from which the gypsum layer formed on the surface of the bottom furnace ash has been removed are unreacted CaCO _Three Since the layer is deposited and activated, it can be used as a desulfurizing agent, and it is possible to provide a furnace bottom ash circulation device that can reduce the amount of the desulfurizing agent and increase the effective utilization rate of the desulfurizing agent.
(4) Since it has a bed density detection means for controlling the bed density of the fluidized bed based on the pressure difference detected by the pressure difference detection means, the fluidized bed expansion ratio (the height of the fluidized bed and It is possible to provide a bottom ash circulation device that can maintain the optimum combustion state by actively maintaining the flow by optimizing the ratio to the fixed bed height).
(5) Provided is a bottom ash circulation device capable of actively maintaining the flow so that the supplied desulfurization agent is easily destroyed by heat and is made fine so that the fluidized medium is finely divided and the flow failure is hardly caused. be able to.
(6) Since the bed density of the fluidized bed can be optimally controlled, slagging can be prevented, and a furnace bottom ash circulation device capable of generating a normal fluidized bed can be provided.
(7) Furnace bottom ash circulation that can prevent slagging and prevent the fuel slurry injected from the slurry injection nozzle from adhering, solidifying, and agglomerating on the wall surface of the heat transfer tube and fluidized bed boiler, and causing poor flow. An apparatus can be provided.
(8) Since the flow can be maintained actively and the bed density of the fluidized bed can be optimally controlled, the flow state in the bed can be made uniform, the heat transfer from the fluidized bed to the heat transfer tube can be made uniform, and the heat efficiency can be improved. An excellent furnace bottom ash circulation device can be provided.
(9) Since the flow can be maintained vigorously, the combustion heat of the solid fuel in the vicinity of the slurry nozzle hardly stays and the molten ash is difficult to be formed. It is possible to provide a bottom ash circulation device that can perform the above operation.
[0055]
According to the invention of claim 6,
(1) Since the bottom ash staying at the bottom of the fluidized bed boiler is extracted, coarse particles such as coarse powder desulfurization agent staying at the bottom of the furnace and causing flow failure are extracted to prevent the occurrence of poor flow. It is possible to provide a method for operating a fluidized bed boiler.
(2) Since the bottom ash of the rough furnace is low in the amount of calcium oxide and calcium sulfate produced by the desulfurization reaction and decarboxylation reaction of calcium carbonate, and the residual amount of unreacted calcium carbonate is large, it is recycled in the fluidized bed boiler. When introduced, it can provide a method for operating a fluidized bed boiler that can act as a desulfurizing agent and increase the effective utilization rate of the desulfurizing agent.
(3) Since the amount of calcium oxide and calcium sulfate produced in the blast furnace bottom ash does not cause condensation or heat generation even when in contact with water, it does not cause condensation or heat generation due to the hydration reaction even when mixed with fuel slurry. It is possible to provide a method for operating a fluidized bed boiler in which adjustment of slurry concentration and slurry viscosity is easy.
(4) Since the bottom ash of the blast furnace has a large amount of gypsum and calcium oxide produced by the desulfurization reaction and decarboxylation reaction and a small amount of unreacted calcium carbonate, it is desulfurized even if it is introduced into the fluidized bed boiler. Provided is a fluidized bed boiler operation method that can be used as a fluidized medium that adjusts the fluidized bed height and that can reduce the amount of desulfurizing agent used and can increase the effective utilization rate of the desulfurizing agent, although the function as an agent is poor. be able to.
(5) Since the furnace bottom ash is classified with a relatively large particle diameter of 500 to 5000 μm, a classification device such as a shifter that can be processed easily and in large quantities can be used, and the fluidized bed boiler has low equipment load and excellent productivity. Driving method can be provided.
[0056]
According to invention of Claim 7, in addition to the effect of Claim 6,
(1) Since only the crude furnace bottom ash classified in the classification step is pulverized, the pulverizing apparatus can be small and can provide a method for operating a fluidized bed boiler with a small equipment load.
(2) By crushing the rough ash bottom ash, the gypsum layer on the surface of the rough blast furnace bottom ash is peeled off, and crushed to reduce the particle size, thereby unreacted CaCO _Three It is possible to provide a method for operating a fluidized bed boiler which can expose a bed and be reused as a desulfurizing agent.
(3) Of the coarse bottom ash, the particles that have become coarse and settle on the bottom of the fluidized bed boiler and are difficult to flow are pulverized and re-supplied into the fluidized bed boiler to activate the fluidized state of the fluidized bed. It is possible to provide a fluidized bed boiler operating method capable of preventing the occurrence of poor flow.
(4) By pulverizing coarse furnace bottom ash into pulverized particles smaller than a predetermined particle size in the pulverization step and re-feeding into the fluidized bed boiler, the next time the core ash is extracted from the furnace bottom ash extraction pipe, Since it is classified as ash, it is possible to provide a fluidized bed boiler operating method that is not mixed with the fuel slurry, can improve the stability of the fuel slurry concentration, viscosity, etc., and can improve the reliability.
(5) Since the pulverization step is provided, the coarse furnace bottom ash is pulverized into pulverized particles smaller than a predetermined particle size and supplied into the fluidized bed boiler, and the supplied pulverized particles and fine furnace bottom ash are contained in the fluidized bed boiler. It is refined by wear and becomes fly ash and is discharged out of the system. Since fly ash can be recycled as cement material or cement raw material by itself, it is possible to provide a method for operating a fluidized bed boiler that can significantly reduce the cost of treating bottom ash and the amount of industrial waste generated.
[0057]
According to invention of Claim 8, in addition to the effect of Claim 6 or 7,
(1) Most of the desulfurizing agent with a particle size of 1 to 5 mm is finely granulated by being supplied to the fluidized bed boiler, causing thermal destruction and wear. There is no need to pulverize, the man-hour and cost required for pulverization can be reduced, and an operating method of a fluidized bed boiler excellent in energy saving can be provided.
(2) Since the desulfurization agent is not pulverized and atomized before being supplied to the fluidized bed boiler, the final velocity of the particles becomes the gas superficial velocity, and the fine particles that do not form the fluidized bed are scattered from the fluidized bed to the freeboard The particle size is about 250 μm or less when the gas superficial velocity is 0.8 ± 0.4 m / s) and provides a fluidized bed boiler operation method that can form a good fluidized bed. can do.
(3) Since a fluidized bed containing a desulfurizing agent having a particle diameter of 1 to 5 mm can be generated at the bottom of the fluidized bed, slagging can be prevented, and the fuel slurry injected from the slurry injection nozzle is transferred to a heat transfer tube or It is possible to provide an operation method of a fluidized bed boiler that can prevent the occurrence of fluid failure due to adhesion, solidification, and agglomeration on the wall surface of the fluidized bed boiler.
[0058]
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram of a furnace bottom ash circulation device according to a first embodiment.
FIG. 2 is a configuration diagram of a main part of a furnace bottom ash circulation device according to a second embodiment.
FIG. 3 is a main part configuration diagram of a furnace bottom ash circulation device according to a third embodiment.
FIG. 4 is a main part configuration diagram of a furnace bottom ash circulation device in a fourth embodiment.
Fig. 5 (a) Limestone particle size distribution
(B) Particle size distribution of the bottom ash extracted from the bottom ash extraction pipe during the combustion operation of the fluidized bed boiler
FIG. 6 shows the calculation results of calcium balance in Example 3 and Comparative Example 1.
[Explanation of symbols]
1 Pressure vessel
2 Pressurized fluidized bed boiler
2a Heat transfer tube
2b Fluidized bed
3 Combustion exhaust gas flow pipe
4 coarse dust removal equipment
5 Coarse dedusting gas passage tube
6 Precision dust removal equipment
7 Fuel slurry adjuster
8 Slurry pump
9 Slurry supply path
10 Furnace bottom ash extraction pipe
11, 11a classifier
11b Coarse particle discharge path
12, 12a Rough bottom ash transportation route
12b Rough bottom ash branch
12c, 13c Gypsum layer removal device
13 Furnace bottom ash transport route
13a Branch valve
13b Furnace bottom ash branch
13d discharge channel
14 Furnace bottom ash storage container
15, 15a Furnace bottom ash introduction pipe
16 Crusher
17 Grinding particle supply path
17a Fuel supply hopper
17b Lock hopper
17c Fuel supply path
17d Carrier air supply pipe
18 Grinding particle transportation route
18a Branch valve
19 Air supply pipe
20 Air volume control valve
21 Extraction amount control device
22 Differential pressure detection means
23 Controller

Claims (8)

A furnace bottom ash circulation device comprising a fluidized bed boiler, and a furnace bottom ash extraction pipe connected to the furnace bottom part of the fluidized bed boiler to extract the furnace bottom ash accumulated in the furnace bottom part,
The furnace bottom ash extracted from the furnace bottom ash extraction pipe is classified by a predetermined particle diameter in a range of 500 to 5000 μm, and is smaller than a predetermined particle diameter and a coarse furnace bottom ash having a particle diameter of at least a predetermined particle diameter. Classifying device for dividing into blast furnace bottom ash, fuel slurry adjusting device for adjusting and storing fuel slurry mixed with solid fuel, desulfurizing agent and water, and the rough furnace bottom classified by the classifying device A furnace bottom ash circulation device , comprising: a crude furnace bottom ash transport path for supplying ash to the fuel slurry adjusting device.   The furnace bottom ash circulation apparatus according to claim 1, further comprising a pulverizer that pulverizes the coarse furnace bottom ash into pulverized particles having a particle diameter smaller than the predetermined particle diameter. A gypsum layer removing device that generates gypsum layer-removed particles obtained by removing a gypsum layer on the surface of each of at least one of the coarse particle ash, the fine bottom ash, and the pulverized particles is provided. The furnace bottom ash circulation device according to claim 2 . It comprises a desulfurization agent adjusting device that adjusts by mixing one or more of the coarse furnace bottom ash, the pulverized particles, and the gypsum layer removal particles with a desulfurization agent supplied to the fluidized bed boiler. The furnace bottom ash circulation device according to claim 3 . (A) a blast furnace bottom ash storage container that stores any one or more of the blast furnace bottom ash, the pulverized particles, and the gypsum layer removal particles; and (b) the blast furnace bottom ash storage container and the fluidized bed boiler. A blast furnace bottom ash introduction pipe for introducing at least one of the blast furnace bottom ash, the pulverized particles, and the gypsum layer removal particles stored in the blast furnace bottom ash storage container into the fluidized bed boiler. And (c) a differential pressure detecting means for measuring a differential pressure in the fluidized bed boiler, and (d) a layer for controlling the layer density of the fluidized bed boiler based on the differential pressure detected by the differential pressure detecting means. A furnace bottom ash circulation device according to claim 3 or 4 , further comprising density control means. A furnace bottom ash extraction step for extracting the furnace bottom ash accumulated in the furnace bottom ash from a furnace bottom ash extraction pipe connected to the furnace bottom of the fluidized bed boiler, and classifying the furnace bottom ash with a predetermined particle diameter of 500 to 5000 μm And a step of classifying at least a rough furnace bottom ash and a fine furnace bottom ash, and a step of adjusting the slurry concentration and the slurry viscosity by mixing the rough furnace bottom ash with a fuel slurry. Operation method of fluidized bed boiler.   The operation of a fluidized bed boiler according to claim 6, further comprising a pulverization step of pulverizing the coarse bottom ash classified in the classification step into pulverized particles having a particle size smaller than the predetermined particle size. Method.   The operating method of a fluidized bed boiler according to claim 6 or 7, wherein 10 to 80 wt%, preferably 20 to 40 wt% of the desulfurizing agent supplied to the fluidized bed boiler has a particle diameter of 1 to 5 mm.

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