JP3866475B2 - Desulfurization method - Google Patents

Description

【００１４】
各領域での脱硫剤としての炭酸カルシウムの反応について説明するに先立ち、炭酸カルシウムを脱硫剤とした場合の反応について整理するとともに、各領域で生じる主な反応について説明する。
＜熱分解・逆反応＞
▲１▼ ＣａＣＯ_３ →ＣａＯ＋ＣＯ_２ 脱炭酸反応
▲２▼ ＣａＯ＋ＣＯ_２ →ＣａＣＯ_３ 再炭酸化反応（１）
＜酸化反応＞
▲３▼ ＣａＣＯ_３ ＋ＳＯ_２ ＋０.５Ｏ_２ →ＣａＳＯ_４ ＋ＣＯ_２ 直接脱硫反応
▲４▼ ＣａＯ＋ＳＯ_２ ＋０.５Ｏ_２ →ＣａＳＯ_４ 酸化脱硫反応
▲５▼ ＣａＯ＋ＣＯ＋０.５Ｏ_２ →ＣａＣＯ_３ 再炭酸化反応 (2)
▲６▼ ＣａＳ＋２Ｏ_２ →ＣａＳＯ_４ 脱硫生成物酸化反応
＜還元反応＞
▲７▼ ＣａＯ＋Ｈ_２Ｓ→ＣａＳ＋Ｈ_２Ｏ 還元脱硫反応
【００１５】
上記Ａ領域では８５０℃以上の高温が維持されており、かつ酸素濃度が高い。これはガス化システムにおいてはチャー燃焼室等、いわゆる酸化炉の炉内条件にほぼ等しく、▲１▼脱炭酸反応、及び▲２▼▲３▼▲４▼▲５▼▲６▼酸化反応が生じる。酸化雰囲気であるので、可燃物が燃焼し、系の圧力が高い場合は炭酸ガス分圧が高まるので、熱分解反応の逆反応である▲２▼再炭酸化反応（１）が生じる場合があり、その場合は▲３▼直接脱硫反応が優勢になる。
【００１６】
Ｂ領域はガス化システムにおけるカーボナイザー、いわゆるガス化炉である。Ｂ領域においては酸素濃度が低く、炭酸ガス濃度が低いので、温度が８００℃以上で熱分解反応である▲１▼脱炭酸反応が生じる。また脱硫反応は▲７▼還元脱硫反応が生じる。
【００１７】
以上のＡ，Ｂの領域での化学的反応の特徴を生かし、脱硫剤ＣａＣＯ_３ の効果的な使用方法について示したのが図１である。尚、以下に示す反応は、常圧から１０ＭＰａ迄の圧力範囲で使用できる。
【００１８】
図１に、本発明における上記２領域の脱硫剤の循環経路を示す。この循環経路において、どのようにしてカルシウム化合物が脱硫機能を維持できるかについて以下に説明する。ガス化原料としてガス化炉１に供給された可燃物中の硫黄分はガス化炉１で硫化水素を発生する。ガス化炉１は、先の説明におけるＢ領域にあたり、条件は先の説明と同等である。一方、脱硫剤として同じくガス化炉１に供給された炭酸カルシウムの一部は炉内で脱炭酸反応によりＣａＯとなり（反応▲１▼）、炉内で硫化水素Ｈ_２Ｓと反応し、ＣａＳを形成する（反応▲７▼）。
【００１９】
ガス化炉１内に滞留している未反応炭酸カルシウムＣａＣＯ_３、及び反応の中間段階であるＣａＯ、及び還元脱硫反応生成物であるＣａＳは、ガス化炉からの連絡路２１を経るなどして移動し、酸化炉２に供給される。酸化炉２は、先の説明におけるＡ領域にあたり、条件は先の説明と同等である。酸化炉２の内部ではＣａＳの一部はＣａＳＯ_４にまで酸化される（反応▲６▼）と共に、未反応のＣａＣＯ_３ の脱炭酸反応によってＣａＯを生成する（反応▲１▼）。酸化炉２においてＣａＯは、酸化炉２に供給される固定炭素（いわゆるチャー）に含まれる硫黄分から発生する硫黄酸化物と反応し、やはりＣａＳＯ_４を生成する（反応▲４▼）。また運転圧力が低い場合、酸化炉２の内部では未反応のＣａＣＯ_３の脱炭酸反応をも生じる（反応▲１▼）。
【００２０】
酸化炉２内に滞留する脱硫剤には、ＣａＳＯ_４、ＣａＳＯ_３、ＣａＯ、ＣａＣＯ_３、場合によってはＣａＳの各々が表面に現れており、これら各々は互いに不均一に脱硫剤の表面に積層し、いわば外観はあばた状になっていると考えられる。そのような脱硫剤表面の最外層がＣａＳＯ_４である部分は、酸化炉内でそれ以上反応が進むことはほとんどないが、ＣａＳＯ_４の層が薄く、且つその層のすぐ下の層にＣａＣＯ_３が存在していれば、脱炭酸反応によってＣａＣＯ_３からＣＯ_２が抜ける際、ＣａＳＯ_４の層を壊して新たな活性反応面を露出させることができる。
【００２１】
しかしながら、本発明とは異なり、一般的な可燃物をガス化してエネルギーを回収しようとするシステムでは、大気圧以上、具体的にはガスタービンを駆動できる１ＭＰａ程度以上の圧力でガス化炉が運転される場合が多く、この場合、酸化炉のＣＯ_２分圧が０.１５ＭＰａ程度以上になることから、ＣａＣＯ_３の脱炭酸反応が抑制され、ＣａＳＯ_４ の層はそのまま不活性面として脱硫剤の表面に存在し続け、その下層のＣａ成分は脱硫剤として機能しないまま取り残されてしまうのである。
【００２２】
本発明では、図１に示すように酸化炉２にはガス化炉１への連絡路２２が設けられており、酸化炉２内の脱硫剤（炭酸カルシウム及びその派生物）をガス化炉１に再度戻すことができる。一般的にガス化炉内では燃焼はほとんど起こさせないので、ＣＯ_２分圧が低く、ＣａＣＯ_３の脱炭酸反応は抑制されない。従って脱硫剤の表面にＣａＳＯ_４、ＣａＳＯ_３、ＣａＯ、ＣａＣＯ_３、場合によってはＣａＳの層があばた状に不均一に積層して形成されても、脱硫剤中のＣａＣＯ_３は
▲１▼ ＣａＣＯ_３→ＣａＯ＋ＣＯ_２ 脱炭酸反応
なる反応によってＣＯ_２ を放出し、その際、前記各成分の層、とりわけＣａＳＯ_４ の層を剥がして新たな反応面を露出させることが可能になるのである。
【００２３】
表面がＣａＳによって被われた部分はＣａＳＯ_４によって被われた部分と比べて生成物の密度が小さいので、気孔の開口率も大きく、その気孔を通じて内部からＣＯ_２を放出することができるので、その被膜が破壊されることはほとんどないが、この脱硫剤粒子が再びガス化炉１から酸化炉２へ循環して戻った際、酸化炉２内でその気孔部が生成したＣａＳＯ_４によって塞がれるので、ガス化炉と酸化炉を何度も循環しているうちに、必ずＣａＳＯ_４の被膜をＣＯ_２の放出によって破壊し、新たな反応面を露出させることができるのである。
【００２４】
ＣａＳはＣａＳＯ_４に比べてモルあたりの容積が小さいので、ＣａＳによって被われた部分はＣａＳＯ_４によって被われた部分と比べて空隙率が大きく、気孔の開口率も大きい。従って、その気孔を通じて内部からＣＯ_２を放出することができるので、ＣａＳの被膜が破壊されることはほとんどないが、この脱硫剤粒子が再びガス化炉１から酸化炉２へ循環して戻った際、酸化炉２内でその気孔部が生成したＣａＳＯ_４によって塞がれるので、ガス化炉と酸化炉を何度も循環しているうちに、必ずＣａＳＯ_４の被膜が脱硫剤表面に形成され、その被膜が内部のＣａＣＯ_３の熱分解によるＣＯ_２の放出によって破壊されれば、新たな反応面を露出させることができるのである。
【００２５】
図２は、脱硫剤粒子の履歴を模式的断面で表したものである。▲１▼はガス化炉に投入された直後のＣａＣＯ_３粒子である。▲２▼はガス化炉に投入され、脱炭酸反応により表面からＣＯ_２を放出しＣａＯの層を作り、更にそのＣａＯ層の表面がＨ_２Ｓと反応しＣａＳを形成している状態である。この状態から酸化炉へ戻して長時間経つと※印で示すように表面に強固なＣａＳＯ_４膜を形成し不活性化してしまう。▲３▼は▲２▼の状態の脱硫剤粒子を酸化炉へ戻し、しばらく経った状態である。表面にはＣａＳＯ_４の層が形成され、その下層にはＣａＯの層が見られる。▲４▼は▲３▼の脱硫剤粒子が再びガス化炉に戻されてしばらく経った状態である。表面のＣａＳＯ_４は脱炭酸反応により剥がれ落ちている。そして以下同様に▲５▼酸化炉→▲６▼ガス化炉→▲７▼酸化炉と繰り返しにより、脱硫剤粒子が表面からどんどん反応していく。
【００２６】
ガス化室１内でＣａＳＯ_４とＣａＣＯ_３との混在層が剥離した脱硫剤は、さらに熱分解で母材であるＣａＣＯ_３が分解され表面にＣａＯが形成される。このＣａＯが新たな活性反応面として機能し、ガス化炉内の硫化水素と反応しＣａＳを形成して再び酸化炉２に戻されるのである。このようにして脱硫剤は表面から徐々に消費されて、有効に利用されるのである。
【００２７】
このようにＣａＯ、ＣａＳ、ＣａＳＯ_４と硫黄分を含む物質（硫化物）の一部または全部を、還元雰囲気Ｂから酸化雰囲気Ａに通したのち、再び、還元雰囲気Ｂを通すことにより炭酸カルシウムを有効に脱硫剤として利用することができるのである。上記説明は炭酸カルシウムを脱硫剤とした場合について説明したが、当然ながら炭酸カルシウムを主成分とするもの、例えば石灰石やドロマイトといった鉱物も炭酸カルシウム粒子と同様に脱硫剤として用いることができることは言うまでもない。
【００２８】
次に、本発明の具体的な実施例を説明する。
図３は本発明者らが発明した前記のガス化炉と前記の酸化炉の機能を統合して、一つにまとめた統合型流動床ガス化炉の概念図である。
【００２９】
図３は、該統合型ガス化炉の基本的な構成を模式的に表現したものであり、熱分解即ちガス化、チャー燃焼、熱回収の３つの機能をそれぞれ担当するガス化室３１、チャー燃焼室３２、熱回収室３３を備え、例えば全体が円筒形又は矩形を成した炉体内に収納されている。ガス化室３１、チャー燃焼室３２、熱回収室３３は仕切壁４１、４２、４３、４４、４５で分割されており、それぞれの底部に流動媒体を含む濃厚層である流動床が形成される。各室の流動床、即ちガス化室流動床、チャー燃焼室流動床、熱回収室流動床の流動媒体を流動させるために、各室３１、３２、３３の底である炉底には、流動媒体中に流動化ガスを吹き込む散気装置が設けられている。散気装置は炉底部に敷かれた例えば多孔板を含んで構成され、該多孔板を広さ方向に分割して複数の部屋に分割されており、各室内の各部の空塔速度を変えるために、散気装置の各部屋から多孔板を通して吹き出す流動化ガスの流速を変化させるように構成している。空塔速度が室の各部で相対的に異なるので各室内の流動媒体も室の各部で流動状態が異なり、そのため内部旋回流が形成される。図中、散気装置に示す白抜き矢印の大きさは、吹き出される流動化ガスの流速を示している。例えば３２ｂで示す箇所の太い矢印は、３２ａで示す箇所の細い矢印よりも流速が大きい。
【００３０】
ガス化室３１とチャー燃焼室３２の間は仕切壁４１で仕切られ、チャー燃焼室３２と熱回収室３３の間は仕切壁４２で仕切られ、ガス化室と熱回収室の間は仕切壁４３で仕切られている。即ち、別々の炉として構成されておらず、一つの炉として一体に構成されている。このガス化炉では、仕切壁４１が本発明の第２の仕切壁を構成する。更に、チャー燃焼室３２のガス化室３１と接する面の近傍には、流動媒体が下降するべく沈降チャー燃焼室３４を設ける。即ち、チャー燃焼室３２は沈降チャー燃焼室３４と沈降チャー燃焼室３４以外のチャー燃焼室本体部とに分かれる。このため、沈降チャー燃焼室３４をチャー燃焼室の他の部分（チャー燃焼室本体部）と仕切るための仕切壁４４が設けられている。また沈降チャー燃焼室３４とガス化室３１は、本発明の第１の仕切壁としての仕切壁４５で仕切られている。
【００３１】
ここで、流動床と界面について説明する。流動床は、その鉛直方向下方部にある、流動化ガスにより流動状態に置かれている流動媒体（例えば珪砂）を濃厚に含む濃厚層と、その濃厚層の鉛直方向上方部にある流動媒体と多量のガスが共存し、流動媒体が勢いよくはねあがっているスプラッシュゾーンとからなる。流動床の上方即ちスプラッシュゾーンの上方には流動媒体をほとんど含まずガスを主体とするフリーボード部がある。本発明でいう界面は、ある厚さをもった前記スプラッシュゾーンをいうが、またスプラッシュゾーンの上面と下面（濃厚層の上面）との中間にある仮想的な面ととらえてもよい。
また「流動床の界面より鉛直方向上方においてはガスの流通がないように仕切壁により仕切られ」というとき、さらに界面より下方の濃厚層の上面より上方においてガスの流通がないようにするのが好ましい。
【００３２】
ガス化室３１とチャー燃焼室３２の間の仕切壁４１は、炉の天井４９から炉底（散気装置の多孔板）に向かってほぼ全面的に仕切っているが、下端は炉底に接することはなく、炉底近傍に第２の流通部５１がある。但しこの流通部５１の上端が、ガス化室流動床界面、チャー燃焼室流動床界面のいずれの界面よりも上部にまで達することはない。さらに好ましくは、流通部５１の上端が、ガス化室流動床の濃厚層の上面、チャー燃焼室流動床の濃厚層の上面のいずれよりも上部にまで達することはないようにする。言い換えれば、流通部５１は、常に濃厚層に潜っているように構成するのが好ましい。即ち、ガス化室３１とチャー燃焼室３２とは、少なくともフリーボード部においては、さらに言えば界面より上方においては、さらに好ましくは濃厚層の上面より上方ではガスの流通がないように仕切壁により仕切られていることになる。
【００３３】
またチャー燃焼室３２と熱回収室３３の間の仕切壁４２はその上端が界面近傍、即ち濃厚層の上面よりは上方であるが、スプラッシュゾーンの上面よりは下方に位置しており、仕切壁４２の下端は炉底近傍までであり、仕切壁４１と同様に下端が炉底に接することはなく、炉底近傍に濃厚層の上面より上方に達することのない開口５２がある。
ガス化室３１と熱回収室３３の間の仕切壁４３は炉底から炉の天井にわたって完全に仕切っている。沈降チャー燃焼室３４を設けるべくチャー燃焼室３２内を仕切る仕切壁４４の上端は流動床の界面近傍で、下端は炉底に接している。仕切壁４４の上端と流動床との関係は、仕切壁４２と流動床との関係と同様である。沈降チャー燃焼室３４とガス化室３１を仕切る仕切壁４５は、仕切壁４１と同様であり、炉の天井から炉底に向かってほぼ全面的に仕切っており、下端は炉底に接することはなく、炉底近傍に第１の流通部５５があり、この開口の上端が濃厚層の上面より下にある。即ち、第１の流通部５５と流動床の関係は、第２の流通部５１と流動床の関係と同様である。
【００３４】
ガス化室に投入された石炭等・硫黄分を含む可燃物は流動媒体から熱を受け、熱分解、ガス化される。典型的には、燃料はガス化室では燃焼せず、いわゆる乾留される。残った乾溜チャーは流動媒体と共に仕切壁４１の下部にある流通部５１からチャー燃焼室３２に流入する。このようにしてガス化室３１から導入されたチャーはチャー燃焼室３２で燃焼して流動媒体を加熱する。チャー燃焼室３２でチャーの燃焼熱によって加熱された流動媒体は仕切壁４２の上端を越えて熱回収室３３に流入し、熱回収室内で界面よりも下方にあるように配設された層内伝熱管７１で収熱され、冷却された後、再び第２仕切壁４２の下部開口５２を通ってチャー燃焼室３２に流入する。
ガス化室３１に投入された可燃物の揮発分は瞬時にガス化し、続いて固形炭素分（チャー）のガス化が比較的緩慢に起こる。したがって、ガス化室３１内におけるチャーの滞留時間（ガス化室３１に投入されたチャーがチャー燃焼室３２に抜けるまでの時間）は燃料のガス化割合（炭素転換率）等を決める重要なファクターとなり得る。
【００３５】
硅砂等を流動媒体として用いた場合、チャーの比重が流動媒体の比重と比較して小さいため、主に層の上部に集中してチャーが蓄積される。前記のようにガス化室への流動媒体の流入及びガス化室からチャー燃焼室への流動媒体の流出が仕切り壁下流通部より生じる炉構造とした場合、主に層上部に存在するチャーよりも、主に層下部に存在する流動媒体の方が、ガス化室からチャー燃焼室へと流出し易く、逆にチャーはガス化室からチャー燃焼室へと流出しにくい。したがって、その分だけ、ガス化室が完全混合層となっている場合よりもチャーのガス化室での平均滞留時間を長く維持することが可能になる。
その場合、沈降チャー燃焼室３４よりガス化室へと流入した流動媒体は、ガス化室内で層内に広く混合されることなく、主にガス化室下部のみを通過してチャー燃焼室へと流出することになるが、その場合においても、ガス化室炉床より供給される流動化ガスと流動媒体とが熱交換を行ない、流動化ガスからチャーへと熱を伝えることによって、間接的にチャーのガス化に用いられる熱を流動媒体の顕熱から供給することは可能である。
また、ガス化室内流動化ガス速度を制御し、前記ガス化室内旋回流の様相を制御することにより、ガス化室内での流動媒体とチャーの混合状態を変化させることが可能であり、それにより、チャーのガス化室内平均滞留時間の制御が可能となる。
【００３６】
一方、本炉構造においては、ガス化室とチャー燃焼室との圧力差を制御することにより、ガス化室内流動層高を自由に変化させることが可能であるため、その手法を用いてもガス化室内チャー滞留時間を制御することが可能である。
ここで、熱回収室３３は本発明の燃料のガス化システムに必須ではない。即ち、ガス化室３１で主として揮発成分がガス化した後に残る主としてカーボンからなるチャーの量と、チャー燃焼室３２で流動媒体を加熱するのに必要とされるチャーの量がほぼ等しければ、流動媒体から熱を奪うことになる熱回収室３３は不要である。また前記チャーの量の差が小さければ、例えば、ガス化室３１でのガス化温度が高目になり、ガス化室３１で発生するＣＯガスの量が増えるという形で、バランス状態が保たれる。
【００３７】
しかしながら図３に示すように熱回収室３３を備える場合は、チャーの発生量の大きい石炭から、ほとんどチャーを発生させない都市ゴミまで、幅広く多種類の燃料に対応することができる。即ち、どのような燃料であっても、熱回収室３３における熱回収量を加減することにより、チャー燃焼室３２の燃焼温度を適切に調節し、流動媒体の温度を適切に保つことができる。
一方、チャー燃焼室３２で加熱された流動媒体は第４仕切壁４４の上端を越えて沈降チャー燃焼室３４に流入し、次いで仕切壁４５の下部にある流通部５５からガス化室３１に流入する。
【００３８】
ここで、各室間の流動媒体の流動状態及び移動について説明する。
ガス化室３１の内部で沈降チャー燃焼室３４との間の仕切壁４５に接する面の近傍は、沈降チャー燃焼室３４の流動化と比べて強い流動化状態が維持される強流動化域３１ｂになっている。全体としては投入された燃料と流動媒体の混合拡散が促進される様に、場所によって流動化ガスの空塔速度を変化させるのが良く、一例として図２に示したように強流動化域３１ｂの他に弱流動化域３１ａを設けて流動媒体の旋回流を形成させるようにする。
【００３９】
チャー燃焼室３２は中央部に弱流動化域３２ａ、周辺部に強流動化域３２ｂを有し、流動媒体およびチャーが内部旋回流を形成している。ガス化室３１、チャー燃焼室３２内の強流動化域の流動化速度は５Umf以上、弱流動化域の流動化速度は５Umf以下とするのが好適であるが、弱流動化域と強流動化域に相対的な明確な差を設ければ、この範囲を超えても特に差し支えはない。チャー燃焼室３２内の熱回収室３３、および沈降チャー燃焼室３４に接する部分には強流動化域３２ｂを配するようにするのがよい。また必要に応じて炉底には弱流動化域３２ａ側から強流動化域３２ｂ側に下るような勾配を設けるのが良い。ここで、Umfとは最低流動化速度（流動化が開始される速度）を１Umfとした単位である。即ち、５Umfは最低流動化速度の５倍の速度である。
【００４０】
このように、チャー燃焼室３２と熱回収室３３との仕切壁４２近傍のチャー燃焼室側の流動化状態を熱回収室３３側の流動化状態よりも相対的に強い流動化状態に保つことによって、流動媒体は仕切壁４２の流動床の界面近傍にある上端を越えてチャー燃焼室３２側から熱回収室３３の側に流入し、流入した流動媒体は熱回収室３３内の相対的に弱い流動化状態即ち高密度状態のために下方（炉底方向）に移動し、仕切壁４２の炉底近傍にある下端（の流通部５２）をくぐって熱回収室３３側からチャー燃焼室３２の側に移動する。
【００４１】
同様に、チャー燃焼室３２の本体部と沈降チャー燃焼室３４との仕切壁４４近傍のチャー燃焼室本体部側の流動化状態を沈降チャー燃焼室３４側の流動化状態よりも相対的に強い流動化状態に保つことによって、流動媒体は仕切壁４４の流動床の界面近傍にある上端を越えてチャー燃焼室３２本体部の側から沈降チャー燃焼室３４の側に移動流入する。沈降チャー燃焼室３４の側に流入した流動媒体は、沈降チャー燃焼室３４内の相対的に弱い流動化状態即ち高密度状態のために下方（炉底方向）に移動し、仕切壁４５の炉底近傍にある下端（の開口５５）をくぐって沈降チャー燃焼室３４側からガス化室３１側に移動する。なおここで、ガス化室３１と沈降チャー燃焼室３４との仕切壁４５近傍のガス化室３１側の流動化状態は沈降チャー燃焼室３４側の流動化状態よりも相対的に強い流動化状態に保たれている。このことは流動媒体の沈降チャー燃焼室３４からガス化室３１への移動を誘引作用により助ける。
同様に、ガス化室３１とチャー燃焼室３２との間の仕切壁４１近傍のチャー燃焼室３２側の流動化状態はガス化室３１側の流動化状態よりも相対的に強い流動化状態に保たれている。したがって、流動媒体は仕切壁４１の流動床の界面より下方、好ましくは濃厚層の上面よりも下方にある（濃厚層に潜った）流通部５１を通してチャー燃焼室３２の側に流入する。
【００４２】
一般的には、イ、ロの２つの室間の流動媒体の移動は、イ、ロ室が、上端が界面の高さ近傍にある仕切壁ハによって仕切られているときは、その仕切壁ハ近傍のイ室とロ室の流動化状態を比較して、例えばイ室側の流動化状態がロ室側の流動化状態よりも強く保たれていれば、流動媒体は仕切壁ハの上端を越えてイ室側からロ室側に流入移動する。また、イ、ロ室が、下端が界面より下方、好ましくは濃厚層の上面より下方にある（濃厚層に潜った）仕切壁ニによって仕切られているとき、言い換えれば界面よりも下方に開口を、あるいは濃厚層に潜った開口を有する仕切壁ニによって仕切られているときは、その仕切壁ニ近傍のイ室とロ室の流動化状態を比較して、例えばイ室側の流動化状態がロ室側の流動化状態よりも強く保たれていれば、流動媒体は仕切壁ニの下端の開口をくぐってロ室側からイ室側に流入移動する。これは、イ室側の流動媒体の相対的に強い流動状態の誘引作用によるとも言えるし、ロ室側の相対的に弱い流動状態によるロ室内の流動媒体の密度がイ室側よりも高いことによるとも言える。また以上のような各室間の流動媒体の移動がある一つの箇所で生じたために崩れようとする各室間のマスバランスの平衡状態を保つように、他の箇所で各室間の流動媒体の移動が生じる場合もある。
【００４３】
また、１つの室を画成する仕切壁としての、または１つの室内の仕切壁としての仕切壁ハの上端と、同じく仕切壁ニの下端との相対的関係について言えば、上端を越えて流動媒体を移動させようとする仕切壁ハのその上端は、下端を流動媒体を潜らせて移動させようとする仕切壁のその下端よりも、鉛直方向上方に位置する。このように構成することによって、その室に流動媒体を充填して流動化させたとき、流動媒体の充填量を適切に決めれば、前記上端を流動床の界面近傍に位置させ、かつ前記下端を濃厚層に潜らせるように設定することができ、仕切壁近傍の流動化の強さを前述のように適切に設定することにより、流動媒体を仕切壁ハあるいは仕切壁ニに関して所定の方向に移動させることができる。また、仕切壁ニによって仕切られる２つの室間のガスの流通をなくすことができる。
【００４４】
以上のことを図１の場合に当てはめて説明すれば、チャー燃焼室３２と熱回収室３３とは、上端が界面の高さ近傍にあり下端が濃厚層に潜った仕切壁４２で仕切られており、仕切壁４２近傍のチャー燃焼室３２側の流動化状態が、仕切壁４２近傍の熱回収室３３側の流動化状態よりも強く保たれている。したがって、流動媒体は仕切壁４２の上端を越えてチャー燃焼室３２側から熱回収室３３側に流入移動し、また仕切壁４２の下端をくぐって熱回収室３３側からチャー燃焼室３２側に移動する。
【００４５】
また、チャー燃焼室３２とガス化室３１とは、下端が濃厚層に潜った第１の仕切壁４５により仕切られており、仕切壁４５のチャー燃焼室側には、上端が界面の高さ近傍にある仕切壁４４と仕切壁４５を含む仕切壁で画成された沈降チャー燃焼室３４が設けられ、仕切壁４４近傍のチャー燃焼室３２本体部側の流動化状態が、仕切壁４４近傍の沈降チャー燃焼室３４側の流動化状態よりも強く保たれている。したがって、流動媒体は仕切壁４４の上端を越えてチャー燃焼室３２の本体部側から沈降チャー燃焼室３４側に流入移動する。このように構成することにより沈降チャー燃焼室３４に流入した流動媒体は少なくともマスバランスを保つように、仕切壁４５の下端をくぐって沈降チャー燃焼室３４からガス化室３１に移動する。このとき、仕切壁４５近傍のガス化室３１側の流動化状態が、仕切壁４５近傍の沈降チャー燃焼室３４側の流動化状態よりも強く保たれていれば、誘引作用により流動媒体の移動が促進される。
【００４６】
さらにガス化室３１とチャー燃焼室３２本体部とは、下端が濃厚層に潜った第２の仕切壁４１で仕切られている。沈降チャー燃焼室３４からガス化室３１に移動してきた流動媒体は、さきのマスバランスを保つように仕切壁４１の下端をくぐってチャー燃焼室３２に移動するが、このとき、仕切壁４１近傍のチャー燃焼室３２側の流動化状態が、仕切壁４１近傍のガス化室３１側の流動化状態よりも強く保たれていれば、さきのマスバランスを保つようにだけではなく、強い流動化状態により流動媒体はチャー燃焼室３２側に誘引され移動する。
【００４７】
図３の実施例では、流動媒体の沈降をチャー燃焼室３２の一部である沈降チャー燃焼室３４で行わせているが、同様な構成をガス化室３１の一部に、具体的には流通部５１の部分に、不図示のいわば沈降ガス化室ともいうべき形で設けてもよい。即ち、沈降ガス化室の流動化状態を隣接のガス化室本体部のそれよりも相対的に弱くして、ガス化室本体部の流動媒体が沈降ガス化室に仕切壁の上端を越えて流入し、沈降した流動媒体が流通部５１を通してチャー燃焼室に移動する。このとき沈降チャー燃焼室３４は、沈降ガス化室と併設してもよいし、設けなくてもよい。沈降ガス化室を設ければ、図２の場合と同様に、流動媒体はチャー燃焼室３２から流通部５５を通してガス化室３１へ、またガス化室３１から流通部５１を通してチャー燃焼室３２へと移動する。
【００４８】
熱回収室３３は全体が均等に流動化され、通常は最大でも熱回収室に接したチャー燃焼室３２の流動化状態より弱い流動化状態となるように維持される。従って、熱回収室３３の流動化ガスの空塔速度は０〜３Umfの間で制御され、流動媒体は緩やかに流動しながら沈降流動層を形成する。なおここで０Umfとは、流動化ガスが止まった状態である。このような状態にすれば、熱回収室３３での熱回収を最小にすることができる。すなわち、熱回収室３３は流動媒体の流動化状態を変化させることによって回収熱量を最大から最小の範囲で任意に調節することができる。また、熱回収室３３では、流動化を室全体で一様に発停あるいは強弱を調節してもよいが、その一部の領域の流動化を停止し他を流動化状態に置くこともできるし、その一部の領域の流動化状態の強弱を調節してもよい。
【００４９】
また、燃料中に含まれる比較的大きな不燃物はガス化室３１の炉底に設けた不燃物排出口６３から排出する。また、各室の炉底面は水平でも良いが、流動媒体の流れの滞留部を作らないようにするために、炉底近傍の流動媒体の流れに従って、炉底を傾斜させても良い。なお、不燃物排出口は、ガス化室３１の炉底だけでなく、チャー燃焼室３２あるいは熱回収室３３の炉底に設けてもよい。
【００５０】
ガス化室３１の流動化ガスとして最も好ましいのは生成ガスを昇圧してリサイクル使用することである。このようにすればガス化室から出るガスは純粋に燃料から発生したガスのみとなり、非常に高品質のガスを得ることができる。それが不可能な場合は水蒸気等、できるだけ酸素を含まないガス（無酸素ガス）を用いるのが良い。ガス化の際の吸熱反応によって流動媒体の層温が低下する場合は、必要に応じて無酸素ガスに加えて、酸素もしくは酸素を含むガス、例えば空気を供給して生成ガスの一部を燃焼させるようにしても良い。チャー燃焼室３２に供給する流動化ガスは、チャー燃焼に必要な酸素を含むガス、例えば空気、酸素と蒸気の混合ガスを供給する。また熱回収室３３に供給する流動化ガスは、空気、水蒸気、燃焼排ガス等を用いる。
【００５１】
ガス化室３１とチャー燃焼室３２の流動床の上面（スプラッシュゾーンの上面）より上方の部分すなわちフリーボード部は完全に仕切壁で仕切られている。さらに言えば、流動床の濃厚層の上面より上方の部分すなわちスプラッシュゾーン及びフリーボード部は完全に仕切壁で仕切られているので、チャー燃焼室３２とガス化室３１のそれぞれの圧力P1，P2のバランスが多少乱れても、双方の流動層の界面の位置の差、あるいは濃厚層の上面の位置の差、即ち層高差が多少変化するだけで乱れを吸収することができる。即ち、ガス化室３１とチャー燃焼室３２とは、仕切壁４５で仕切られているので、それぞれの室の圧力P1，P2が変動しても、この圧力差は層高差で吸収でき、どちらかの層が流通部５５の上端に下降するまで吸収可能である。従って、層高差で吸収できるチャー燃焼室３２とガス化室３１のフリーボードの圧力差（P1-P2又はP2-P1）の上限値は、互いを仕切る仕切壁４５の下部の流通部５５の上端からの、ガス化室流動床のヘッドと、チャー燃焼室流動床のヘッドとのヘッド差にほぼ等しい。
【００５２】
以上説明した統合型ガス化炉では、一つの流動床炉の内部に、ガス化室、チャー燃焼室、熱回収室の３つを、それぞれ隔壁を介して設け、更にチャー燃焼室とガス化室、チャー燃焼室と熱回収室はそれぞれ隣接して設けられている。この統合型ガス化炉は、チャー燃焼室とガス化室間に大量の流動媒体循環を可能にしているので、流動媒体の顕熱だけでガス化のための熱量を充分に供給でき、できるだけ少量の、且つ発熱量の高い生成ガスを得ることが最も容易に実現できる。
さらに、チャー燃焼ガスと生成ガスの間のシールが完全にされるので、ガス化室とチャー燃焼室の圧力バランス制御がうまくなされ、燃焼ガスと生成ガスが混ざることがなく、生成ガスの性状を低下させることもない。
また、熱媒体としての流動媒体とチャーはガス化室３１側からチャー燃焼室３２側に流入するようになっており、さらに同量の流動媒体がチャー燃焼室３２側からガス化室３１側に戻るように構成されているので、自然にマスバランスがとれ、流動媒体をチャー燃焼室３２側からガス化室３１側に戻すために、コンベヤ等を用いて機械的に搬送する必要もなく、高温粒子のハンドリングの困難さ、顕熱ロスが多いといった問題もない。
【００５３】
以上説明したように、図２に示すように、１つの流動床炉内に、燃料の熱分解・ガス化、チャー燃焼、及び層内熱回収の３つの機能を共存させ、チャー燃焼室内の高温流動媒体を熱分解・ガス化の熱源供給の熱媒体としてガス化室に供給する統合型ガス化炉は、前記ガス化室と熱回収室は仕切壁によって炉底から天井にわたって完全に仕切るか、もしくは互いに接しないように配置し、且つガス化室とチャー燃焼室は流動床の界面より上部においては完全に仕切壁で仕切り、該仕切壁近傍のガス化室側の流動化状態の強さとチャー燃焼室側の流動化状態の強さとの相対的な関係を所定の関係に保つことによって、当該仕切壁の炉底近傍に設けた流通部を通じて、チャー燃焼室側からガス化室側へ流動媒体を移動させるように構成されている。また、ガス化室側からチャー燃焼室側へチャーを含んだ流動媒体を移動させるように構成されている。
【００５４】
このため、ガス化室とチャー燃焼室は流動床の界面より上部においては完全に仕切壁で仕切られているので、それぞれの室のガス圧力が変動しても圧力バランスが崩れて燃焼ガスと生成ガスが混ざるという問題を生じない。このため、ガス化室とチャー燃焼室の間に特別な圧力バランス制御を必要としない。そして、該仕切壁近傍のガス化室側の流動化状態とチャー燃焼室側の流動化状態の強弱を所定の状態に保つことによって、当該仕切壁の炉底近傍に設けた流通部を通じて、チャー燃焼室側からガス化室側へ安定に流動媒体を大量に移動させることが出来る。このため、チャー燃焼室側からガス化室側への流動媒体の移動に機械的な高温粒子のハンドリング手段を必要としない。
【００５５】
上記統合型ガス化炉は、前記チャー燃焼室内のガス化室に接した箇所に設けた弱流動化域を沈降チャー燃焼室とし、炉底から流動床界面近傍まで達する仕切壁によって、他のチャー燃焼室と区分けして構成してもよく、また、前記チャー燃焼室、沈降チャー燃焼室、ガス化室内にそれぞれ強流動化域と弱流動化域を設け、各室内に流動媒体の内部旋回流を生じさせるように構成してもよい。
さらに以上の統合型ガス化炉では、前記熱回収室をチャー燃焼室の強流動化域に接するように配置し、該熱回収室とチャー燃焼室は炉底近傍に流通部を備え、且つその上端が流動床界面近傍まで達する仕切壁で仕切り、且つ仕切壁近傍のチャー燃焼室側の流動化状態を熱回収室側の流動化状態よりも相対的に強くして流動媒体の循環力を生じさせるようにしてもよく、また、前記熱回収室を沈降チャー燃焼室の強流動化域に接するように配置し、該熱回収室と沈降チャー燃焼室は炉底近傍に流通部を備え、且つその上端が流動床界面近傍まで達する仕切壁で仕切り、且つ仕切壁近傍の沈降チャー燃焼室側の流動化状態を熱回収室側の流動化状態よりも相対的に強くして流動媒体の循環力を生じさせるようにしてもよい。また、前記ガス化室の流動化ガスとしては無酸素ガスを用いるが、このいわゆる無酸素ガスとしては水蒸気等の全く酸素を含まないガスを用いるようにしてもよい。
また、前記ガス化室、チャー燃焼室、熱回収室の各室の炉底面を、炉底近傍の流動媒体の流線に沿って傾斜させてもよく、前記チャー燃焼室内のガス化炉に接した弱流動化域の流動化状態を制御することによって、該ガス化室の温度を調節するように構成してもよい。
【００５６】
ここで図３に示す統合型ガス化炉ハにおいて、前述のＡ，Ｂの２領域を考察すると、正にチャー燃焼室の流動媒体の流動層部Ａ′が先の説明で示したＡ領域、ガス化室３１の流動媒体部分Ｂ′が同じくＢ領域にあてはまる。ここで各部Ａ′, Ｂ′の条件は、先の説明でＡ領域、Ｂ領域に示したものと同等である。
【００５７】
脱硫剤として流動媒体に同伴する大きさの炭酸カルシウム粒子、石灰石粒子もしくはドロマイト粒子を炉内に供給することによって、本発明の機能が発揮される。図３の統合型ガス化炉は流動媒体に摩耗による損耗の少ない硅砂を用いることができるのが特徴であるが、当然のことながら炭酸カルシウム粒子、石灰石粒子もしくはドロマイト粒子そのものを流動媒体として用いても何ら差し支えない。
また、脱硫剤粒子の供給場所は特に限定されるものではないが、まず脱炭酸反応を起こさせるという意味ではガス化室に供給するのが好ましいといえる。ガス化室には原料供給口が設けられるので、原料と一緒に供給してもよい。特に高温で運転される場合には、供給口はできるだけ少ない方が好ましいので、原料と一緒に供給するのがよい。
【００５８】
統合型ガス化炉Ｘでは、チャー燃焼室とガス化室との間で大量の流動媒体が循環しており、Ａ領域（Ａ′）とＢ領域（Ｂ′）間の脱硫剤の大量循環が容易に実現されている。図３に示す統合型ガス化炉は本発明の理想的な実施例の一つである。
【００５９】
【発明の効果】
硫黄混合物のカルシウム化合物を利用した脱硫方法において、カルシウム化合物を硫黄混合物に混合して、高温の酸化（工程）・還元（工程）の２つの組合せで循環処理を行い、脱硫剤の有効利用効率を高めると共に、多くの活性表面を露出させることで、高い脱硫効率を達成できる。
【図面の簡単な説明】
【図１】本発明の実施形態の脱硫剤の循環経路及び主要な反応を示す図である。
【図２】図１における脱硫剤粒子の履歴を模式的断面で表した図である。
【図３】本発明の実施例の統合型流動床ガス化炉の概念図である。
【符号の説明】
１ 低ＣＯ_２還元雰囲気（Ｂ領域：ガス化炉）
２ 高温酸化雰囲気（Ａ領域：酸化炉）
２１，２２ 連絡通路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a desulfurization method for removing sulfides generated during combustion of coal, municipal waste, etc., and particularly to a desulfurization method using a calcium compound.
[0002]
[Prior art]
When trying to recover energy with high efficiency from combustibles containing sulfur such as coal, there is a need for a technique of gasifying at high temperature and desulfurizing dry so as not to waste sensible heat of the gas. Technologies that use iron oxide and zinc oxide are being developed as promising dry-type desulfurization technologies, but these technologies are used to regenerate reaction products resulting from the desulfurization reaction, that is, iron sulfide and zinc sulfide. The situation is far from being put to practical use in commercial machines due to problems such as not being easy and running costs to increase the desulfurization rate.
[0003]
Conventionally, calcium carbonate is used as a desulfurizing agent. Since calcium carbonate is inexpensive and keeps running costs low, attempts have been made to use calcium carbonate as a dry desulfurization agent for gasification gas. However, desulfurization efficiency is inevitably higher than that using zinc oxide or iron oxide. However, it was difficult to obtain the expected performance.
[0004]
The inactivation of calcium carbonate is considered to be a cause of insufficient performance in this desulfurization method using calcium carbonate. The following two formulas can be considered as a desulfurization mechanism of calcium carbonate under a reducing atmosphere.
1) CaCO ₃ → CaO + CO ₂ Decarboxylation reaction
CaO + H ₂ S → CaS + H ₂ O Desulfurization reaction
2) CaCO ₃ + H ₂ S → CaS + H ₂ O + CO ₂ Direct desulfurization reaction
In both 1) and 2), calcium carbonate becomes CaS and calcium carbonate (CaCO ₃ It is considered that this CaS film inhibits the reaction by inactivating calcium carbonate.
[0005]
In the desulfurization method using calcium carbonate, not only is sufficient desulfurization performance not obtained, but a large amount of unreacted calcium carbonate is generated as waste even though inexpensive calcium carbonate is used. Therefore, there is a problem that the cost of waste disposal increases. In addition, when CaS formed on the surface of calcium carbonate is exposed to the atmosphere, there is a risk that it reacts with water vapor in the atmosphere to generate highly toxic hydrogen sulfide gas, which requires sufficient management during handling. Also occurred.
[0006]
Therefore, when desulfurizing with calcium carbonate, calcium carbonate, which is usually used in the order of several millimeters, is used in a state where the particle size is reduced to about several tens of microns and the specific surface area is increased to increase the reaction area. This method is effective, but the energy required for finely pulverizing calcium carbonate is increased, the handling of fine particles is difficult, and in the case of fine particles, a sufficient time required for the reaction, the gasifier In reality, it is not possible to make full use of the reaction area.
[0007]
Therefore, even if calcium carbonate with a relatively large particle size of about several millimeters is used, sufficient desulfurization performance can be achieved, and generation of unreacted calcium carbonate is suppressed as much as possible, and hydrogen sulfide is generated as a desulfurization reaction product. Not stable CaS but stable CaSO ₄ Such a desulfurization technique was desired.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described circumstances, and as a dry desulfurization method in a combustible material gasification system, calcium carbonate particles are used as a desulfurization agent, and discharge of unreacted calcium carbonate is suppressed, and desulfurization reaction is performed. Stable CaSO as a product ₄ An object of the present invention is to provide a desulfurization method capable of producing slag.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is an integrated fluidized bed gasification furnace comprising a gasification chamber and a char combustion chamber, and circulating a fluid medium between them. From the gasification chamber Injecting a calcium compound into the fluid medium, 800 ° C to 1000 ° C with an oxygen concentration of 0.5% or less and a carbon dioxide partial pressure of 0.1 MPa or less In the gasification chamber Perform decarboxylation reaction and reductive desulfurization reaction of calcium compound, high temperature of 850 ° C to 1000 ° C and oxygen concentration of 3% or more In the char combustion chamber Decarboxylation of calcium compounds and A desulfurization method characterized by performing an oxidation reaction.
[0010]
Thereby, the reaction activity of the calcium compound surface can always be maintained, the discharge of unreacted calcium compound is suppressed, and stable CaSO as a desulfurization reaction product. ₄ Can be produced separately from the calcium compound surface. Therefore, high desulfurization efficiency can be achieved by increasing the effective utilization efficiency of the desulfurizing agent and exposing many active surfaces.
[0011]
Unreacted calcium carbonate CaCO staying in the gasifier ₃ , And CaO, which is an intermediate stage of the reaction, and CaS, which is a reductive desulfurization reaction product, move from the gasification furnace and are supplied to the oxidation furnace. In the oxidation furnace, a part of CaS is CaSO ₄ In addition to being oxidized to unreacted CaCO ₃ CaO is produced by the decarboxylation reaction. In the oxidation furnace, CaO reacts with sulfur oxide generated from sulfur contained in fixed carbon (so-called char) supplied to the oxidation furnace, and again CaSO. ₄ Is generated. The desulfurization agent staying in the oxidation furnace 2 includes CaSO ₄ , CaSO ₃ , CaO, CaCO ₃ In some cases, each of CaS appears on the surface, and each of them is laminated nonuniformly on the surface of the desulfurizing agent, so that it is considered that the appearance is fluttering. The outermost layer on the surface of such a desulfurizing agent is CaSO ₄ The part where is is thin and the layer immediately below is CaCO ₃ In the presence of CaCO ₃ To CO ₂ When it comes off, CaSO ₄ The new active reaction surface can be exposed by breaking the layer.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a reaction of a desulfurizing agent and a circulation path in a high temperature oxidation region and a high temperature reduction region which are embodiments of the present invention. The present invention is characterized in that calcium compound particles are used as the desulfurizing agent particles and the atmosphere in the case of performing a chemical reaction such as oxidation or reduction is circulated through two regions of oxidation and reduction. Thereby, the reaction activity on the surface of calcium carbonate can always be maintained. The regions where calcium carbonate is circulated are the high temperature oxidation region (A region) and the high temperature reduction region (B region) shown in Table 1.
[0013]
[Table 1]

[0014]
Prior to describing the reaction of calcium carbonate as a desulfurizing agent in each region, the reactions when calcium carbonate is used as a desulfurizing agent will be summarized and the main reactions occurring in each region will be described.
<Pyrolysis / reverse reaction>
(1) CaCO ₃ → CaO + CO ₂ Decarboxylation reaction
▲ 2 ▼ CaO + CO ₂ → CaCO ₃ Re-carbonation reaction (1)
<Oxidation reaction>
(3) CaCO ₃ + SO ₂ + 0.5O ₂ → CaSO ₄ + CO ₂ Direct desulfurization reaction
▲ 4 ▼ CaO + SO ₂ + 0.5O ₂ → CaSO ₄ Oxidative desulfurization reaction
▲ 5 ▼ CaO + CO + 0.5O ₂ → CaCO ₃ Re-carbonation reaction (2)
▲ 6 ▼ CaS + 2O ₂ → CaSO ₄ Desulfurization product oxidation reaction
<Reduction reaction>
▲ 7 ▼ CaO + H ₂ S → CaS + H ₂ O Reduction desulfurization reaction
[0015]
In the region A, a high temperature of 850 ° C. or higher is maintained, and the oxygen concentration is high. In a gasification system, this is almost equal to the conditions in a so-called oxidation furnace such as a char combustion chamber, and (1) decarbonation reaction and (2) (3) (4) (5) (6) oxidation reaction occurs. . Since it is an oxidizing atmosphere, combustibles burn, and when the system pressure is high, the carbon dioxide partial pressure increases. Therefore, the re-carbonation reaction (1), which is the reverse reaction of the thermal decomposition reaction, may occur. In that case, (3) the direct desulfurization reaction becomes dominant.
[0016]
Region B is a carbonizer in the gasification system, a so-called gasification furnace. In the region B, since the oxygen concentration is low and the carbon dioxide gas concentration is low, (1) decarboxylation reaction, which is a thermal decomposition reaction, occurs at a temperature of 800 ° C. or higher. Also, desulfurization reaction (7) reductive desulfurization reaction occurs.
[0017]
Taking advantage of the characteristics of the chemical reaction in the above A and B regions, the desulfurization agent CaCO ₃ FIG. 1 shows an effective method of using. The reaction shown below can be used in a pressure range from normal pressure to 10 MPa.
[0018]
FIG. 1 shows a circulation path of the desulfurization agent in the two regions in the present invention. The following describes how the calcium compound can maintain the desulfurization function in this circulation path. The sulfur content in the combustible material supplied to the gasification furnace 1 as a gasification raw material generates hydrogen sulfide in the gasification furnace 1. The gasification furnace 1 corresponds to the B region in the above description, and the conditions are the same as in the previous description. On the other hand, a part of calcium carbonate similarly supplied to the gasification furnace 1 as a desulfurization agent becomes CaO by a decarboxylation reaction in the furnace (reaction (1)), and hydrogen sulfide H in the furnace ₂ Reacts with S to form CaS (reaction (7)).
[0019]
Unreacted calcium carbonate CaCO staying in the gasifier 1 ₃ And CaO which is an intermediate stage of the reaction and CaS which is a reductive desulfurization reaction product move through the communication path 21 from the gasification furnace and are supplied to the oxidation furnace 2. The oxidation furnace 2 corresponds to the A region in the above description, and the conditions are the same as in the above description. In the oxidation furnace 2, a part of CaS is CaSO. ₄ (Reaction (6)) and unreacted CaCO ₃ CaO is produced by the decarboxylation reaction of (Reaction (1)). In the oxidation furnace 2, CaO reacts with sulfur oxides generated from sulfur contained in fixed carbon (so-called char) supplied to the oxidation furnace 2, and again CaSO ₄ (Reaction (4)). Further, when the operating pressure is low, unreacted CaCO within the oxidation furnace 2 ₃ Also occurs (reaction (1)).
[0020]
The desulfurization agent staying in the oxidation furnace 2 includes CaSO ₄ , CaSO ₃ , CaO, CaCO ₃ In some cases, each of CaS appears on the surface, and each of them is laminated nonuniformly on the surface of the desulfurizing agent, so that it is considered that the appearance is fluttering. The outermost layer on the surface of such a desulfurizing agent is CaSO ₄ In the part, the reaction hardly proceeds further in the oxidation furnace, but the CaSO ₄ The layer is thin, and the CaCO ₃ In the presence of CaCO ₃ To CO ₂ When it comes off, CaSO ₄ The new active reaction surface can be exposed by breaking the layer.
[0021]
However, unlike the present invention, in a system for recovering energy by gasifying a general combustible material, the gasification furnace is operated at a pressure higher than atmospheric pressure, specifically about 1 MPa or higher that can drive a gas turbine. In this case, the CO in the oxidation furnace ₂ Since the partial pressure is about 0.15 MPa or more, CaCO ₃ Decarboxylation reaction is suppressed and CaSO ₄ This layer continues to exist on the surface of the desulfurizing agent as an inert surface, and the Ca component in the lower layer is left behind without functioning as the desulfurizing agent.
[0022]
In the present invention, as shown in FIG. 1, the oxidation furnace 2 is provided with a communication path 22 to the gasification furnace 1, and the desulfurization agent (calcium carbonate and its derivatives) in the oxidation furnace 2 is supplied to the gasification furnace 1. You can go back again. In general, almost no combustion occurs in a gasifier, so CO ₂ Low partial pressure, CaCO ₃ The decarboxylation reaction is not suppressed. Therefore, the surface of the desulfurizing agent is CaSO. ₄ , CaSO ₃ , CaO, CaCO ₃ In some cases, the CaS layer in the desulfurizing agent may be formed even if the CaS layer is formed by unevenly laminating. ₃ Is
(1) CaCO ₃ → CaO + CO ₂ Decarboxylation reaction
By the reaction ₂ In this case, the layers of the respective components, in particular CaSO ₄ It is possible to expose the new reaction surface by peeling the layer.
[0023]
The portion of the surface covered with CaS is CaSO ₄ Since the density of the product is small compared with the part covered by ₂ However, when the desulfurizing agent particles are circulated back from the gasification furnace 1 to the oxidation furnace 2 again, the pores in the oxidation furnace 2 are released. Produced CaSO ₄ As it is blocked by the gasification furnace and the oxidation furnace many times, ₄ Coating of CO ₂ It can be destroyed by the release of, exposing a new reaction surface.
[0024]
CaS is CaSO ₄ Since the volume per mole is smaller than that of CaS, the portion covered with CaS is CaSO ₄ The porosity is large compared to the portion covered by, and the aperture ratio of the pores is also large. Therefore, CO from the inside through the pores ₂ However, when the desulfurizing agent particles are circulated back from the gasification furnace 1 to the oxidation furnace 2 again, the pores in the oxidation furnace 2 can be released. Produced CaSO ₄ As it is blocked by the gasification furnace and the oxidation furnace many times, ₄ Is formed on the surface of the desulfurizing agent, and the coating is formed on the inner CaCO. ₃ CO by thermal decomposition of ₂ If it is destroyed by the release of, a new reaction surface can be exposed.
[0025]
FIG. 2 is a schematic cross section showing the history of desulfurizing agent particles. (1) is the CaCO immediately after being put into the gasifier ₃ Particles. (2) is put into the gasifier and CO is removed from the surface by decarboxylation reaction. ₂ To form a CaO layer, and the surface of the CaO layer is H ₂ In this state, it reacts with S to form CaS. After returning from this state to the oxidation furnace for a long time, as shown by the * mark, the surface has strong CaSO ₄ A film is formed and inactivated. (3) is the state after a while after the desulfurization agent particles in the state (2) are returned to the oxidation furnace. CaSO on the surface ₄ A layer of CaO is seen in the lower layer. (4) is a state after a while since the desulfurizing agent particles of (3) are returned to the gasifier again. Surface CaSO ₄ Is peeled off by the decarboxylation reaction. In the same manner, the desulfurizing agent particles react from the surface more and more by repeating the steps (5) oxidation furnace → (6) gasification furnace → (7) oxidation furnace.
[0026]
CaSO in the gasification chamber 1 ₄ And CaCO ₃ The desulfurization agent from which the mixed layer was peeled off is CaCO which is the base material by further thermal decomposition. ₃ Is decomposed to form CaO on the surface. This CaO functions as a new active reaction surface, reacts with hydrogen sulfide in the gasification furnace to form CaS, and is returned to the oxidation furnace 2 again. In this way, the desulfurizing agent is gradually consumed from the surface and used effectively.
[0027]
Thus, CaO, CaS, CaSO ₄ And passing a part or all of the substance (sulfide) containing sulfur content from the reducing atmosphere B to the oxidizing atmosphere A, and again passing the reducing atmosphere B, calcium carbonate can be effectively used as a desulfurizing agent. It can be done. In the above description, the case where calcium carbonate is used as the desulfurizing agent has been described, but it goes without saying that minerals such as limestone and dolomite can be used as the desulfurizing agent as well as the calcium carbonate particles. .
[0028]
Next, specific examples of the present invention will be described.
FIG. 3 is a conceptual diagram of an integrated fluidized bed gasification furnace in which the functions of the gasification furnace invented by the present inventors and the oxidation furnace are integrated into one.
[0029]
FIG. 3 is a schematic representation of the basic structure of the integrated gasification furnace. The gasification chamber 31 and the char are in charge of the three functions of pyrolysis, that is, gasification, char combustion, and heat recovery, respectively. A combustion chamber 32 and a heat recovery chamber 33 are provided, and the whole is housed, for example, in a cylindrical or rectangular furnace. The gasification chamber 31, the char combustion chamber 32, and the heat recovery chamber 33 are divided by partition walls 41, 42, 43, 44, and 45, and a fluidized bed that is a rich layer containing a fluidized medium is formed at the bottom of each. . In order to flow the fluidized media in the fluidized bed of each chamber, that is, the gasification chamber fluidized bed, the char combustion chamber fluidized bed, and the heat recovery chamber fluidized bed, the furnace bottom, which is the bottom of each chamber 31, 32, 33, An air diffuser for blowing fluidized gas into the medium is provided. The air diffuser is configured to include, for example, a perforated plate laid on the bottom of the furnace, and the perforated plate is divided into a plurality of rooms by dividing the perforated plate in the width direction so as to change the superficial velocity of each part in each room. In addition, the flow rate of the fluidizing gas blown out from each room of the air diffuser through the perforated plate is changed. Since the superficial velocity is relatively different in each part of the chamber, the flow medium in each chamber also has a different flow state in each part of the chamber, so that an internal swirl flow is formed. In the figure, the size of the white arrow shown in the air diffuser indicates the flow rate of the fluidized gas blown out. For example, the thick arrow at the location indicated by 32b has a higher flow velocity than the thin arrow at the location indicated by 32a.
[0030]
The gasification chamber 31 and the char combustion chamber 32 are partitioned by a partition wall 41, the char combustion chamber 32 and the heat recovery chamber 33 are partitioned by a partition wall 42, and the gasification chamber and the heat recovery chamber are partitioned by a partition wall. It is partitioned by 43. That is, they are not configured as separate furnaces, but are integrally configured as one furnace. In this gasification furnace, the partition wall 41 constitutes the second partition wall of the present invention. Further, in the vicinity of the surface of the char combustion chamber 32 in contact with the gasification chamber 31, a sedimentation char combustion chamber 34 is provided so that the fluidized medium is lowered. That is, the char combustion chamber 32 is divided into a settling char combustion chamber 34 and a char combustion chamber main body other than the settling char combustion chamber 34. For this reason, a partition wall 44 is provided for partitioning the settled char combustion chamber 34 from the other part of the char combustion chamber (char combustion chamber main body). The sedimentation char combustion chamber 34 and the gasification chamber 31 are partitioned by a partition wall 45 as the first partition wall of the present invention.
[0031]
Here, the fluidized bed and the interface will be described. The fluidized bed has a concentrated layer in a lower part in the vertical direction and containing a fluid medium (eg, silica sand) that is in a fluidized state by a fluidizing gas, and a fluidized medium in the upper part in the vertical direction of the thick layer. It consists of a splash zone where a large amount of gas coexists and the fluid medium is vigorously splashing. Above the fluidized bed, i.e. above the splash zone, there is a free board part mainly containing a gas containing almost no fluid medium. The interface referred to in the present invention refers to the splash zone having a certain thickness, but may also be regarded as a virtual surface intermediate between the upper surface and the lower surface of the splash zone (the upper surface of the dense layer).
In addition, when the phrase “partitioned by a partition wall so that there is no gas flow in the vertical direction above the fluidized bed interface”, it is necessary to prevent gas flow above the upper surface of the dense layer below the interface. preferable.
[0032]
The partition wall 41 between the gasification chamber 31 and the char combustion chamber 32 is partitioned almost entirely from the furnace ceiling 49 toward the furnace bottom (perforated plate of the diffuser), but the lower end is in contact with the furnace bottom. There is nothing, and there is a second circulation part 51 in the vicinity of the furnace bottom. However, the upper end of this circulation part 51 does not reach the upper part of any interface of the gasification chamber fluidized bed interface and the char combustion chamber fluidized bed interface. More preferably, the upper end of the flow part 51 does not reach the upper part of either the upper surface of the rich layer of the gasification chamber fluidized bed or the upper surface of the rich layer of the char combustion chamber fluidized bed. In other words, it is preferable that the distribution part 51 is configured so as to be always hidden in the thick layer. That is, the gasification chamber 31 and the char combustion chamber 32 are separated by a partition wall so that there is no gas flow at least in the freeboard portion, more specifically above the interface, and more preferably above the upper surface of the dense layer. It will be partitioned.
[0033]
The partition wall 42 between the char combustion chamber 32 and the heat recovery chamber 33 has an upper end near the interface, that is, above the upper surface of the thick layer, but below the upper surface of the splash zone. The lower end of 42 extends to the vicinity of the furnace bottom. Like the partition wall 41, the lower end does not contact the furnace bottom, and there is an opening 52 in the vicinity of the furnace bottom that does not reach above the upper surface of the thick layer.
A partition wall 43 between the gasification chamber 31 and the heat recovery chamber 33 is completely partitioned from the furnace bottom to the furnace ceiling. The upper end of the partition wall 44 that partitions the char combustion chamber 32 so as to provide the sedimentation char combustion chamber 34 is in the vicinity of the interface of the fluidized bed, and the lower end is in contact with the furnace bottom. The relationship between the upper end of the partition wall 44 and the fluidized bed is the same as the relationship between the partition wall 42 and the fluidized bed. The partition wall 45 that partitions the settling char combustion chamber 34 and the gasification chamber 31 is the same as the partition wall 41, and is partitioned almost entirely from the ceiling of the furnace toward the furnace bottom, and the lower end is in contact with the furnace bottom. There is no 1st distribution part 55 near the furnace bottom, and the upper end of this opening is below the upper surface of a dense layer. That is, the relationship between the first circulation unit 55 and the fluidized bed is the same as the relationship between the second circulation unit 51 and the fluidized bed.
[0034]
Combustibles containing coal, sulfur, etc. that are put into the gasification chamber receive heat from the fluidized medium, and are pyrolyzed and gasified. Typically, fuel does not burn in the gasification chamber, but is so-called dry distillation. The remaining dry-distilled char flows into the char combustion chamber 32 from the flow part 51 below the partition wall 41 together with the fluid medium. Thus, the char introduced from the gasification chamber 31 is combusted in the char combustion chamber 32 and heats the fluidized medium. The fluid medium heated by the combustion heat of the char in the char combustion chamber 32 flows into the heat recovery chamber 33 beyond the upper end of the partition wall 42, and in the layer arranged to be below the interface in the heat recovery chamber. After being collected and cooled by the heat transfer pipe 71, it again flows into the char combustion chamber 32 through the lower opening 52 of the second partition wall 42.
The volatile matter in the combustible material put into the gasification chamber 31 is instantly gasified, and the gasification of the solid carbon (char) occurs relatively slowly. Accordingly, the residence time of char in the gasification chamber 31 (the time until the char charged in the gasification chamber 31 is discharged into the char combustion chamber 32) is an important factor that determines the gasification ratio (carbon conversion rate) of the fuel and the like. Can be.
[0035]
When dredged sand or the like is used as a fluid medium, the specific gravity of char is smaller than the specific gravity of the fluid medium, so that char accumulates mainly on the upper part of the layer. In the case of a furnace structure in which the inflow of the fluid medium into the gasification chamber and the fluid medium from the gasification chamber to the char combustion chamber are generated from the flow part below the partition wall as described above, mainly from the char existing in the upper part of the layer. However, the fluid medium mainly present in the lower layer is more likely to flow out of the gasification chamber into the char combustion chamber, and conversely, char is less likely to flow out of the gasification chamber into the char combustion chamber. Therefore, the average residence time of char in the gasification chamber can be maintained longer than that in the case where the gasification chamber is a complete mixed layer.
In that case, the fluidized medium that has flowed into the gasification chamber from the settling char combustion chamber 34 is mainly mixed only in the lower part of the gasification chamber and is not mixed into the bed in the gasification chamber. Even in this case, the fluidized gas supplied from the gasification chamber hearth and the fluidized medium exchange heat and indirectly transfer heat from the fluidized gas to the char. It is possible to supply the heat used for char gasification from the sensible heat of the fluidized medium.
Further, by controlling the fluidizing gas velocity in the gasification chamber and controlling the aspect of the swirling flow in the gasification chamber, it is possible to change the mixing state of the fluid medium and char in the gasification chamber, The average residence time of the char gasification chamber can be controlled.
[0036]
On the other hand, in this furnace structure, it is possible to freely change the fluidized bed height in the gasification chamber by controlling the pressure difference between the gasification chamber and the char combustion chamber. It is possible to control the char residence time in the chemical chamber.
Here, the heat recovery chamber 33 is not essential for the fuel gasification system of the present invention. That is, if the amount of char mainly composed of carbon remaining after gasification of the volatile component in the gasification chamber 31 is substantially equal to the amount of char required to heat the fluid medium in the char combustion chamber 32, the flow The heat recovery chamber 33 that takes heat away from the medium is not necessary. If the difference in the amount of char is small, for example, the gasification temperature in the gasification chamber 31 becomes high, and the balance state is maintained in the form that the amount of CO gas generated in the gasification chamber 31 increases. It is.
[0037]
However, when the heat recovery chamber 33 is provided as shown in FIG. 3, a wide variety of fuels can be used, from coal with a large amount of char generation to municipal waste that hardly generates char. That is, for any fuel, by adjusting the amount of heat recovered in the heat recovery chamber 33, the combustion temperature in the char combustion chamber 32 can be adjusted appropriately, and the temperature of the fluidized medium can be maintained appropriately.
On the other hand, the fluid medium heated in the char combustion chamber 32 flows into the sedimentation char combustion chamber 34 over the upper end of the fourth partition wall 44, and then flows into the gasification chamber 31 from the circulation portion 55 below the partition wall 45. To do.
[0038]
Here, the flow state and movement of the fluid medium between the chambers will be described.
In the vicinity of the surface in contact with the partition wall 45 between the gasification chamber 31 and the sedimentation char combustion chamber 34, a strong fluidization region 31 b in which a stronger fluidized state is maintained compared to the fluidization of the sedimentation char combustion chamber 34. It has become. As a whole, the superficial velocity of the fluidized gas is preferably changed depending on the location so that the mixed diffusion of the injected fuel and the fluidized medium is promoted. As an example, as shown in FIG. In addition, a weak fluidization region 31a is provided to form a swirling flow of the fluid medium.
[0039]
The char combustion chamber 32 has a weak fluidization region 32a at the center and a strong fluidization region 32b at the periphery, and the fluid medium and char form an internal swirl flow. The fluidization speed in the strong fluidization zone in the gasification chamber 31 and the char combustion chamber 32 is preferably 5 Umf or more, and the fluidization speed in the weak fluidization zone is preferably 5 Umf or less. If there is a clear difference relative to the chemical range, there is no problem even if it exceeds this range. It is preferable that a strong fluidization zone 32 b is disposed in a portion in contact with the heat recovery chamber 33 and the settling char combustion chamber 34 in the char combustion chamber 32. If necessary, it is preferable to provide a gradient at the bottom of the furnace so as to descend from the weak fluidization zone 32a side to the strong fluidization zone 32b side. Here, Umf is a unit in which the minimum fluidization speed (speed at which fluidization is started) is 1 Umf. That is, 5 Umf is 5 times the minimum fluidization speed.
[0040]
As described above, the fluidization state on the char combustion chamber side in the vicinity of the partition wall 42 between the char combustion chamber 32 and the heat recovery chamber 33 is maintained in a fluidization state relatively stronger than the fluidization state on the heat recovery chamber 33 side. As a result, the fluid medium flows over the upper end of the partition wall 42 in the vicinity of the fluid bed interface and flows into the heat recovery chamber 33 from the char combustion chamber 32 side. Due to the weak fluidized state, that is, the high density state, it moves downward (toward the furnace bottom), passes through the lower end (circulation part 52) of the partition wall 42 in the vicinity of the furnace bottom, and from the heat recovery chamber 33 side to the char combustion chamber 32. Move to the side.
[0041]
Similarly, the fluidization state on the char combustion chamber main body side in the vicinity of the partition wall 44 between the main body portion of the char combustion chamber 32 and the sedimentation char combustion chamber 34 is relatively stronger than the fluidization state on the sedimentation char combustion chamber 34 side. By maintaining the fluidized state, the fluid medium moves and flows from the char combustion chamber 32 main body side to the settled char combustion chamber 34 side beyond the upper end of the partition wall 44 near the fluid bed interface. The fluid medium flowing into the settled char combustion chamber 34 moves downward (toward the furnace bottom) due to a relatively weak fluidized state, that is, a high density state in the settled char combustion chamber 34, and the furnace of the partition wall 45 It passes through the lower end (opening 55) near the bottom and moves from the settling char combustion chamber 34 side to the gasification chamber 31 side. Here, the fluidization state on the gasification chamber 31 side in the vicinity of the partition wall 45 between the gasification chamber 31 and the sedimentation char combustion chamber 34 is relatively stronger than the fluidization state on the sedimentation char combustion chamber 34 side. It is kept in. This assists the movement of the fluid medium from the settling char combustion chamber 34 to the gasification chamber 31 by an attraction action.
Similarly, the fluidization state on the char combustion chamber 32 side in the vicinity of the partition wall 41 between the gasification chamber 31 and the char combustion chamber 32 is relatively stronger than the fluidization state on the gasification chamber 31 side. It is kept. Therefore, the fluidized medium flows into the char combustion chamber 32 through the flow part 51 below the fluidized bed interface of the partition wall 41, preferably below the upper surface of the dense layer (submerged in the dense layer).
[0042]
In general, the movement of the fluid medium between the two chambers (a) and (b) occurs when the chambers (a) and (b) are partitioned by a partition wall c whose upper end is near the height of the interface. Comparing the fluidization state of the neighboring chambers B and B, for example, if the fluidization state on the chamber B side is kept stronger than the fluidization state on the chamber B side, the fluid medium will block the upper end of the partition wall C. Overflow and move from the chamber A side to the chamber B side. Also, when the a and b chambers are partitioned by a partition wall d whose lower end is below the interface, preferably below the upper surface of the thick layer (submerged in the thick layer), in other words, the opening is opened below the interface. Or, when the partition wall D is divided by a partition wall having an opening that is submerged in the dense layer, the fluidization state of the chamber A and the chamber B in the vicinity of the partition wall D is compared. If the fluidized state is maintained stronger than the fluidization state on the chamber side, the fluid medium flows through the opening at the lower end of the partition wall D from the chamber chamber side to the chamber chamber side. This can be said to be due to the attracting action of the relatively strong flow state of the fluid medium on the chamber side, and the density of the fluid medium in the chamber due to the relatively weak fluid state on the chamber side is higher than that on the chamber side. It can also be said. In addition, the fluid medium between the chambers at other locations is maintained so that the balance of the mass balance between the chambers is about to collapse due to the movement of the fluid medium between the chambers at one location as described above. Movement may occur.
[0043]
In addition, in terms of the relative relationship between the upper end of the partition wall C as a partition wall defining one chamber or as a partition wall in one room and the lower end of the partition wall D, the fluid flows beyond the upper end. The upper end of the partition wall C to which the medium is to be moved is positioned vertically higher than the lower end of the partition wall to which the lower end of the partition wall is to be moved. With this configuration, when the chamber is filled with a fluid medium and fluidized, if the filling amount of the fluid medium is appropriately determined, the upper end is positioned near the interface of the fluidized bed, and the lower end is It can be set so as to be hidden in the dense layer, and by appropriately setting the strength of fluidization in the vicinity of the partition wall as described above, the fluid medium is moved in a predetermined direction with respect to the partition wall c or the partition wall d. Can be made. Further, it is possible to eliminate the gas flow between the two chambers partitioned by the partition wall d.
[0044]
If the above is applied to the case of FIG. 1, the char combustion chamber 32 and the heat recovery chamber 33 are partitioned by a partition wall 42 whose upper end is near the height of the interface and whose lower end is submerged in a dense layer. In addition, the fluidization state on the char combustion chamber 32 side in the vicinity of the partition wall 42 is kept stronger than the fluidization state on the heat recovery chamber 33 side in the vicinity of the partition wall 42. Therefore, the fluidized medium flows over the upper end of the partition wall 42 from the char combustion chamber 32 side to the heat recovery chamber 33 side, passes through the lower end of the partition wall 42 and moves from the heat recovery chamber 33 side to the char combustion chamber 32 side. Moving.
[0045]
Further, the char combustion chamber 32 and the gasification chamber 31 are partitioned by a first partition wall 45 whose lower end is submerged in a thick layer, and the upper end of the partition wall 45 is at the height of the interface. A sedimentation char combustion chamber 34 defined by a partition wall 44 and a partition wall 45 including the partition wall 45 is provided, and the fluidization state of the char combustion chamber 32 main body side in the vicinity of the partition wall 44 is in the vicinity of the partition wall 44. It is kept stronger than the fluidized state on the settling char combustion chamber 34 side. Therefore, the fluid medium flows from the main body side of the char combustion chamber 32 to the settling char combustion chamber 34 side over the upper end of the partition wall 44. With this configuration, the fluid medium flowing into the sedimentation char combustion chamber 34 moves from the sedimentation char combustion chamber 34 to the gasification chamber 31 through the lower end of the partition wall 45 so as to maintain at least mass balance. At this time, if the fluidization state on the gasification chamber 31 side in the vicinity of the partition wall 45 is kept stronger than the fluidization state on the sedimentation char combustion chamber 34 side in the vicinity of the partition wall 45, the fluid medium is moved by the attraction action. Is promoted.
[0046]
Further, the gasification chamber 31 and the char combustion chamber 32 main body are partitioned by a second partition wall 41 whose lower end is submerged in a thick layer. The fluid medium that has moved from the settling char combustion chamber 34 to the gasification chamber 31 moves to the char combustion chamber 32 through the lower end of the partition wall 41 so as to maintain the previous mass balance. If the fluidization state on the char combustion chamber 32 side is kept stronger than the fluidization state on the gasification chamber 31 side in the vicinity of the partition wall 41, not only the previous mass balance is maintained, but also strong fluidization is achieved. Depending on the state, the fluid medium is attracted and moved to the char combustion chamber 32 side.
[0047]
In the embodiment of FIG. 3, the sedimentation of the fluid medium is performed in the settling char combustion chamber 34 which is a part of the char combustion chamber 32, but a similar configuration is provided in a part of the gasification chamber 31. You may provide in the part which may be called the sedimentation gasification chamber not shown in the part of the distribution | circulation part 51. That is, the fluidization state of the settling gasification chamber is made relatively weaker than that of the adjacent gasification chamber main body so that the fluidized medium in the gasification chamber main body passes over the upper end of the partition wall into the settling gasification chamber. The fluid medium that flows in and settles moves to the char combustion chamber through the circulation part 51. At this time, the sedimentation char combustion chamber 34 may or may not be provided with the sedimentation gasification chamber. If a sedimentation gasification chamber is provided, the fluidized medium is transferred from the char combustion chamber 32 to the gasification chamber 31 through the circulation portion 55 and from the gasification chamber 31 to the char combustion chamber 32 through the circulation portion 51 as in the case of FIG. And move.
[0048]
The heat recovery chamber 33 is fluidized evenly as a whole, and is usually maintained in a fluidized state that is weaker than the fluidized state of the char combustion chamber 32 in contact with the heat recovery chamber. Accordingly, the superficial velocity of the fluidized gas in the heat recovery chamber 33 is controlled between 0 and 3 Umf, and the fluidized medium forms a sedimented fluidized bed while gently flowing. Here, 0 Umf is a state in which the fluidized gas is stopped. In such a state, heat recovery in the heat recovery chamber 33 can be minimized. That is, the heat recovery chamber 33 can arbitrarily adjust the amount of recovered heat within the range from the maximum to the minimum by changing the fluidization state of the fluid medium. Further, in the heat recovery chamber 33, the fluidization may be uniformly started / stopped or adjusted in the whole chamber, but the fluidization of a part of the region may be stopped and the others may be placed in the fluidized state. However, the strength of the fluidization state in a part of the region may be adjusted.
[0049]
Further, a relatively large incombustible material contained in the fuel is discharged from an incombustible material discharge port 63 provided at the furnace bottom of the gasification chamber 31. In addition, the bottom surface of the furnace in each chamber may be horizontal, but the bottom of the furnace may be inclined according to the flow of the fluid medium in the vicinity of the furnace bottom so as not to form a stagnant portion of the fluid medium flow. Note that the incombustible discharge port may be provided not only at the bottom of the gasification chamber 31 but also at the bottom of the char combustion chamber 32 or the heat recovery chamber 33.
[0050]
The most preferable fluidizing gas in the gasification chamber 31 is to boost the generated gas for recycling. In this way, the gas exiting the gasification chamber is purely gas generated from the fuel, and a very high quality gas can be obtained. If this is not possible, it is preferable to use a gas (oxygen-free gas) that contains as little oxygen as possible, such as water vapor. When the bed temperature of the fluidized medium decreases due to endothermic reaction during gasification, in addition to oxygen-free gas, oxygen or a gas containing oxygen, such as air, is supplied as needed to burn part of the product gas. You may make it let it. The fluidizing gas supplied to the char combustion chamber 32 supplies a gas containing oxygen necessary for char combustion, such as air, a mixed gas of oxygen and steam. The fluidizing gas supplied to the heat recovery chamber 33 uses air, water vapor, combustion exhaust gas, or the like.
[0051]
A portion above the upper surface (upper surface of the splash zone) of the fluidized bed of the gasification chamber 31 and the char combustion chamber 32, that is, the free board portion is completely partitioned by a partition wall. Furthermore, since the part above the upper surface of the dense bed of the fluidized bed, that is, the splash zone and the freeboard part, are completely partitioned by the partition walls, the pressures P1, P2 of the char combustion chamber 32 and the gasification chamber 31, respectively. Even if the balance is slightly disturbed, the disturbance can be absorbed by only a slight change in the difference in the position of the interface between the two fluidized beds or the difference in the position of the upper surface of the dense layer, that is, the difference in the layer height. That is, since the gasification chamber 31 and the char combustion chamber 32 are partitioned by the partition wall 45, even if the pressures P1 and P2 of the respective chambers fluctuate, this pressure difference can be absorbed by the difference in bed height. Such a layer can be absorbed until it descends to the upper end of the circulation part 55. Therefore, the upper limit value of the pressure difference (P1-P2 or P2-P1) between the free board of the char combustion chamber 32 and the gasification chamber 31 that can be absorbed by the difference in the bed height is determined by the flow portion 55 below the partition wall 45 that partitions each other. It is approximately equal to the head difference between the head of the gasification chamber fluidized bed and the char combustion chamber fluidized bed from the top.
[0052]
In the integrated gasification furnace described above, three gasification chambers, a char combustion chamber, and a heat recovery chamber are provided in each fluidized bed furnace via a partition wall, and further, a char combustion chamber and a gasification chamber are provided. The char combustion chamber and the heat recovery chamber are provided adjacent to each other. This integrated gasification furnace enables a large amount of circulating fluid medium to be circulated between the char combustion chamber and the gasifying chamber, so that a sufficient amount of heat can be supplied for gasification using only the sensible heat of the fluidizing medium. The product gas having a high calorific value can be obtained most easily.
Furthermore, since the seal between the char combustion gas and the product gas is perfected, the pressure balance control between the gasification chamber and the char combustion chamber is performed well, so that the combustion gas and the product gas are not mixed, and the properties of the product gas are reduced. There is no reduction.
Further, the fluid medium and char as the heat medium flow from the gasification chamber 31 side to the char combustion chamber 32 side, and the same amount of fluid medium flows from the char combustion chamber 32 side to the gasification chamber 31 side. Since it is configured to return, there is no need to mechanically transport it using a conveyor or the like, in order to return the fluid medium from the char combustion chamber 32 side to the gasification chamber 31 side. There are no problems such as difficulty in handling particles and many sensible heat losses.
[0053]
As described above, as shown in FIG. 2, the three functions of fuel pyrolysis / gasification, char combustion, and in-bed heat recovery coexist in one fluidized bed furnace, so that the high temperature in the char combustion chamber is high. In an integrated gasification furnace that supplies a fluidized medium to a gasification chamber as a heat medium for heat decomposition and gasification, the gasification chamber and the heat recovery chamber are completely partitioned from the furnace bottom to the ceiling by a partition wall, Alternatively, the gasification chamber and the char combustion chamber are completely partitioned by a partition wall above the fluidized bed interface, and the strength of the fluidization state on the gasification chamber side near the partition wall and the char By maintaining a relative relationship with the strength of the fluidization state on the combustion chamber side in a predetermined relationship, the fluid medium from the char combustion chamber side to the gasification chamber side through a circulation portion provided near the furnace bottom of the partition wall. Is configured to move. Further, the fluid medium containing the char is moved from the gasification chamber side to the char combustion chamber side.
[0054]
For this reason, the gasification chamber and the char combustion chamber are completely partitioned by a partition wall above the fluidized bed interface, so that even if the gas pressure in each chamber fluctuates, the pressure balance is lost and combustion gas is generated. The problem of gas mixing does not occur. For this reason, no special pressure balance control is required between the gasification chamber and the char combustion chamber. Then, by maintaining the strength of the fluidization state on the gasification chamber side near the partition wall and the fluidization state on the char combustion chamber side in a predetermined state, the char is passed through the circulation section provided near the furnace bottom of the partition wall. A large amount of fluidized medium can be stably moved from the combustion chamber side to the gasification chamber side. For this reason, mechanical high temperature particle handling means is not required for the movement of the fluid medium from the char combustion chamber side to the gasification chamber side.
[0055]
In the integrated gasification furnace, a weak fluidization zone provided at a location in contact with the gasification chamber in the char combustion chamber is set as a sedimentation char combustion chamber, and other char- acters are separated by a partition wall extending from the furnace bottom to the vicinity of the fluidized bed interface. It may be configured separately from the combustion chamber, and a strong fluidization zone and a weak fluidization zone are provided in the char combustion chamber, the sedimentation char combustion chamber, and the gasification chamber, respectively, and an internal swirling flow of the fluid medium is provided in each chamber. You may comprise so that it may produce.
Further, in the above integrated gasification furnace, the heat recovery chamber is disposed so as to be in contact with the strong fluidization zone of the char combustion chamber, and the heat recovery chamber and the char combustion chamber are provided with a circulation part in the vicinity of the furnace bottom, and Partition with a partition wall whose upper end reaches the vicinity of the fluidized bed interface, and make the fluidization state on the char combustion chamber side near the partition wall relatively stronger than the fluidization state on the heat recovery chamber side to generate circulating force of the fluid medium Further, the heat recovery chamber is disposed so as to be in contact with the strong fluidization region of the settling char combustion chamber, the heat recovery chamber and the settling char combustion chamber have a circulation part near the furnace bottom, and The upper end of the fluidized medium is partitioned by a partition wall that reaches the vicinity of the fluidized bed interface, and the fluidized state on the sedimentation char combustion chamber side near the partition wall is relatively stronger than the fluidized state on the heat recovery chamber side, thereby circulating the fluid medium. May be generated. In addition, an oxygen-free gas is used as the fluidizing gas in the gasification chamber, but a gas containing no oxygen such as water vapor may be used as the so-called oxygen-free gas.
In addition, the bottom surfaces of the gasification chamber, the char combustion chamber, and the heat recovery chamber may be inclined along the flow line of the fluidized medium near the furnace bottom, and contact the gasification furnace in the char combustion chamber. The temperature of the gasification chamber may be adjusted by controlling the fluidization state of the weakly fluidized zone.
[0056]
Here, in the integrated gasifier C shown in FIG. 3, considering the two regions A and B described above, the fluidized bed portion A ′ of the fluidized medium in the char combustion chamber is exactly the region A shown in the above description, The fluid medium portion B ′ of the gasification chamber 31 also applies to the B region. Here, the conditions of the portions A ′ and B ′ are the same as those shown in the A and B regions in the above description.
[0057]
The function of the present invention is exhibited by supplying calcium carbonate particles, limestone particles, or dolomite particles having a size accompanying the fluid medium as a desulfurizing agent into the furnace. The integrated gasification furnace of FIG. 3 is characterized in that it can use dredged sand with little wear due to wear as a fluid medium. Naturally, calcium carbonate particles, limestone particles or dolomite particles themselves are used as a fluid medium. There is no problem.
Further, the supply location of the desulfurizing agent particles is not particularly limited, but it can be said that it is preferable to supply the desulfurization agent particles to the gasification chamber in the sense of causing a decarboxylation reaction. Since the gasification chamber is provided with a raw material supply port, it may be supplied together with the raw material. In particular, when operating at a high temperature, it is preferable that the number of supply ports is as small as possible.
[0058]
In the integrated gasification furnace X, a large amount of fluid medium circulates between the char combustion chamber and the gasification chamber, and a large amount of desulfurization agent is circulated between the A region (A ′) and the B region (B ′). It is easily realized. The integrated gasifier shown in FIG. 3 is one of the ideal embodiments of the present invention.
[0059]
【The invention's effect】
In a desulfurization method using a calcium compound of a sulfur mixture, the calcium compound is mixed with the sulfur mixture and subjected to a circulation treatment in two combinations of high-temperature oxidation (process) and reduction (process) to improve the effective utilization efficiency of the desulfurization agent. High desulfurization efficiency can be achieved by increasing and exposing many active surfaces.
[Brief description of the drawings]
FIG. 1 is a diagram showing a desulfurization agent circulation path and main reactions according to an embodiment of the present invention.
2 is a schematic cross-sectional view showing the history of desulfurizing agent particles in FIG. 1. FIG.
FIG. 3 is a conceptual diagram of an integrated fluidized bed gasifier according to an embodiment of the present invention.
[Explanation of symbols]
1 Low CO ₂ Reducing atmosphere (B area: gasification furnace)
2 High-temperature oxidizing atmosphere (A area: oxidation furnace)
21,22 communication passage

Claims (2)

In an integrated fluidized bed gasification furnace having a gasification chamber and a char combustion chamber and circulating a fluid medium between them,
Calcium compound is charged into the fluid medium from the gasification chamber ,
Performing a decarboxylation reaction and a reductive desulfurization reaction of a calcium compound in the gasification chamber at an oxygen concentration of 0.5% or less and a carbon dioxide partial pressure of 0.1 MPa or less at 800 to 1000 ° C ;
A desulfurization method comprising performing a decarboxylation reaction and an oxidation reaction of a calcium compound in the char combustion chamber having a high temperature of 850 ° C to 1000 ° C and an oxygen concentration of 3% or more . The calcium compound introduced into the fluid medium from the gasification chamber is calcium carbonate particles, and stable CaSO as a desulfurization reaction product. ₄ 2. The desulfurization method according to claim 1, wherein the desulfurization method is produced by separating the calcium compound from the surface of the calcium compound.

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