JP2004361018A - Indirect heating furnace - Google Patents

Indirect heating furnace Download PDF

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Publication number
JP2004361018A
JP2004361018A JP2003160798A JP2003160798A JP2004361018A JP 2004361018 A JP2004361018 A JP 2004361018A JP 2003160798 A JP2003160798 A JP 2003160798A JP 2003160798 A JP2003160798 A JP 2003160798A JP 2004361018 A JP2004361018 A JP 2004361018A
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Prior art keywords
heating
temperature
furnace
reaction tube
heated
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JP2003160798A
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Japanese (ja)
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Michio Nakayama
道夫 中山
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Jp Steel Plantech Co
スチールプランテック株式会社
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Priority to JP2003160798A priority Critical patent/JP2004361018A/en
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00Combustion technologies with mitigation potential
    • Y02E20/34Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Abstract

<P>PROBLEM TO BE SOLVED: To provide an indirect heating furnace having greatly increased loading by significantly improving the heat efficiency in a solid heating process where direct contact between a heated object and heating high temperature combustion gas is undesirable. <P>SOLUTION: (1) The indirect heating furnace 1 uses the heating high temperature combustion gas for heating the heated object in a reaction pipe 5 in non-contact with the combustion gas. The reaction pipe is a ceramic fixed reaction pipe. Besides, combustion devices for supplying the heating high temperature combustion gas into the furnace are at least a pair of regenerative burners 7a, 7b. (2) In this case, the temperature of the heating high temperature combustion gas to be supplied into the furnace is 1,000°C or higher. (3) In these cases, a screw conveyor 9 is provided for transferring the heated object in the reaction pipe and a main portion of the screw conveyor is made of ceramic. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】
この発明は、固体無機物質の熱処理、特に前記固体無機物質と加熱用高温燃焼ガスとの直接接触が好ましくない場合の高温熱処理に好適な間接加熱炉に関する。
【0002】
【従来の技術】
被加熱物と加熱用高温燃焼ガスとの直接接触が好ましくない固体加熱プロセスでは、一般に間接加熱炉(外熱炉ともいう。)が用いられる。
【0003】
しかし、従来の間接加熱炉は反応管に金属製のシェルが用いられていたため、最高加熱温度は900℃程度であった。そのため、900℃を超える高温を要する加熱プロセスには間接加熱炉は適用することができなかった。
【0004】
このような問題に対して、反応管をセラミック製とし、反応管内部に固体被加熱物搬送用のスクリューコンベアを備えた間接加熱炉を用いることにより、900℃以上の高温加熱プロセスにも間接加熱炉が適用できることが特表2002−520143号公報(特許文献1)に記載されている。
【0005】
図4に、前記セラミック製の反応管を備えた間接加熱炉を用いて被加熱物の熱処理を行う場合の一般的な装置構成の一例を示す。なお、図4に示す例では、石灰の焼成(石灰石の熱分解)を行う場合について記載している。
【0006】
図4において、原料投入口110から供給室120内に投入された石灰石は、スクリューコンベア130の回転により反応管140内を移送され、出口室150内に運ばれる。石灰石は、前記反応管140内を出口室150に移送される間にその熱処理が行われる。出口室150内の熱処理後の生成物はシュート160を通して炉外に搬出される。
【0007】
また、燃焼バーナ170で発生させた加熱用高温燃焼ガスは、ガス導入口180から炉内に導入され、反応管140内の石灰石を反応管140の管壁を介して間接的に加熱し、排出口190から炉排ガスとして炉外に排出される。前記排出口190から排出された炉排ガスは、空気予熱機200に送られ、前記燃焼バーナ170に供給される燃焼用空気を予熱し、その熱量が有効利用される。
【0008】
【特許文献1】
特表2002−520143号公報
【0009】
【発明が解決しようとする課題】
図4に示すような間接加熱炉の加熱形態は、炉内に供給された加熱用高温燃焼ガスから一度反応管140の管壁へ熱が伝わり、次に反応管140の管壁から被加熱物である石灰石へ伝熱されることにより行われる。このため熱伝達効率が悪く、炉排ガスの温度は約1000℃という高温になる。この高温の炉排ガスで従来の金属製空気予熱機200を用いて燃焼用空気を予熱するには、空気予熱機の焼損を防止するため希釈空気によりガス温度を800℃程度まで下げる必要がある。
【0010】
800℃程度の温度の炉排ガスを用いた場合、得られる予熱空気の温度は最高でも600℃程度である。したがって熱の回収効率は悪く、まだ大量の余剰熱が存在する。この余剰熱を用いて被加熱物である石灰石の予熱に利用する案も考えられるが、もともと加熱用高温燃焼ガスと被加熱物の直接接触は好ましくないプロセスに用いられる装置であることから、被加熱物の予熱も間接方式となり、熱効率の向上は困難である。さらに、希釈空気のために系外に排出される排ガス量が増加し、これがさらなる熱損失量増大の原因ともなる。
【0011】
本発明は以上の問題点を解決するためになされたもので、被加熱物と加熱用高温燃焼ガスとの直接接触が好ましくない固体加熱プロセスにおいて、熱効率を飛躍的に向上させることができ、かつ、処理量を大幅に増大させることが可能な間接加熱炉を提供することを目的とする。
【0012】
【課題を解決するための手段】
上記の課題は次の発明により解決される。
[1]反応管内部の被加熱物を加熱用高温燃焼ガスにより、該燃焼ガスと非接触で加熱する間接加熱炉において、前記反応管がセラミック製の固定式反応管であり、さらに、前記加熱用高温燃焼ガスを炉内に供給するための燃焼装置が少なくとも一対の蓄熱式バーナであることを特徴とする間接加熱炉。
[2]上記[1]において、炉内に供給される加熱用高温燃焼ガスの温度が1000℃以上であることを特徴とする間接加熱炉。
[3]上記[1]又は[2]において、反応管内部の被加熱物を移送するためのスクリューコンベアを備え、且つ、該スクリューコンベア主要部がセラミック製であることを特徴とする間接加熱炉。
【0013】
【発明の実施の形態】
図1は、本発明にかかる間接加熱炉の一実施形態を示す概略構成図である。
【0014】
図1に示す間接加熱炉1は、被加熱物である固体無機物質が投入される固体供給室2と、加熱用の高温燃焼ガスが供給される加熱室3と、加熱処理後の生成物を炉外に搬出する生成物出口室4とを備えている。
【0015】
前記加熱室3内には被加熱物の加熱を行うセラミック製の反応管5が配置される。前記反応管5の一端側は固体供給室2と連通され、他端側は生成物出口室4に連通される。前記反応管5は、加熱室3の炉壁を構成するファイバーブロックやキャスタブル等の耐火物に固定して設置され、被加熱物が入れられる反応管5の内側と加熱室3側とは気密にシールされる。
【0016】
また、前記加熱室3に設けられた加熱用高温燃焼ガスの導入/排出口6a,6bには、一対となる蓄熱式バーナ7a,7bが備えられている。なお、前記蓄熱式バーナは、2基のバーナが一組(一対)として設置されるが、その設置される組の数は炉の規模及び操業状況等により適宜変更され得る。
【0017】
前記セラミック製の反応管5は、固定して設置される。一般に、反応管に金属製のシェルが用いられる金属シェル製横形円筒式キルン(炉)は、反応管が2〜5度程度傾斜して設置され、反応管が回転することにより内容物(被加熱固体)を出口側に送りながら加熱する。しかし、反応管にセラミック製のシェルが用いられるセラミック製横形円筒式キルン(炉)では、強度と変形許容度の問題から反応管を回転させるのは困難であり、その代替案として、反応管は回転させずに固定設置する。内容物(被加熱固体)は反応管の回転ではなく内部に設置したセラミック製スクリューコンベアで搬送される。
【0018】
前記被加熱物である固体無機物質としては、例えば、鉱石(鋭錐石、ボーキサイト、硼砂、方解石、黄銅鉱、クロム鉄鉱、赤鉄鉱等)、金属ハロゲン化物(臭化カルシウム、塩化カルシウム、フッ化カルシウム、ヨウ化カルシウム、同様に、ハロゲン化第二鉄、ハロゲン化第一鉄、ハロゲン化カリウム、ハロゲン化ナトリウム等)、金属炭化物及び金属炭酸塩(炭酸カルシウム等)、金属酸化物(亜クロム酸塩等)、金属リン酸塩(リン酸カルシウム等)、金属硫化物及び金属硫酸塩(硫酸カルシウム等)を挙げることができる。
【0019】
また、前記セラミック製の反応管5としては、例えば、高純度MgO、高純度アルミナ、シリコンカーバイド、ベリリア、シリコンナイトライド、ボロンカーバイド製等の反応管を用いることができる。
【0020】
以下、図1に示す間接加熱炉1を用いて石灰の焼成(石灰石の熱分解)を行う場合について説明する。
【0021】
図1において、原料投入口8から固体供給室2内に投入された石灰石は、スクリューコンベア9の回転により反応管5内を移送され、生成物出口室4内に運ばれる。石灰石は、前記反応管5内を生成物出口室4に移送される間にその熱処理が行われる。生成物出口室4内の熱処理後の生成物はシュート10を通して炉外に搬出される。
【0022】
また、蓄熱バーナ7aで発生させた加熱用高温燃焼ガスは、ガス導入/排出口6aから加熱室3内に導入され、反応管5内の石灰石を反応管5の管壁を介して間接的に加熱し、ガス導入/排出口6bから蓄熱バーナ7bを通って炉排ガスとして炉外に排出される。
【0023】
ここで、前記スクリューコンベア9としては、セラミック製とすることが好ましい。これにより、スクリューコンベアの焼損が防止され、高温の加熱用ガスを用いた場合でも安定した被加熱物の移送を行うことが可能となる。なお、セラミックとしては反応管3と同様のものを用いることができる。
【0024】
以下、一対の蓄熱式バーナ7a及び7bを用いた加熱用高温燃焼ガスの加熱室3内への導入方法について説明する。
【0025】
図示しないブロワ等により吹き込まれた常温の燃焼用空気は切替弁11により蓄熱バーナ7a側に導かれる。蓄熱バーナ7a内に導かれた燃焼用空気は蓄熱バーナ7a内の高温に加熱された蓄熱体を通過し、その際に蓄熱体に蓄えられた熱により高温化される。高温化された燃焼用空気は蓄熱バーナ7aに別途供給される燃料と混合され、その燃焼によって発生した高温ガスが加熱用高温燃焼ガスとしてガス導入/排出口6aから加熱室3内に導入される。なお、燃焼の一部は加熱室3内でも起こる。
【0026】
ここで、前記蓄熱体としては、セラミック製の蓄熱体とすることが好ましい。
【0027】
加熱室3内に導入された加熱用高温燃焼ガスは、反応管5内の石灰石を反応管5の管壁を介して間接的に加熱し、その後、ガス導入/排出口6bから蓄熱バーナ7b、及び、切替弁12を通って炉排ガスとして炉外に排出される。前記ガス導入/排出口6bから排出される炉排ガスは蓄熱バーナ7b内の蓄熱体を通過する構成になっており、その際に蓄熱体に顕熱を与えて蓄熱体を高温化させ、炉排ガス自体は降温する。
【0028】
このような状態で所定時間運転した後、切替弁11及び12を切り替えることによりガスの流れを逆にする。つまり、ブロワ等により吹き込まれた常温の燃焼用空気は、今度は切替弁11により蓄熱バーナ7b側に導かれる。蓄熱バーナ7b内に導かれた燃焼用空気は蓄熱バーナ7b内の高温に加熱された蓄熱体を通過し、その際に蓄熱体に蓄えられた熱により高温化される。高温化された燃焼用空気は蓄熱バーナ7bに別途供給される燃料と混合され、その燃焼によって発生した高温ガスが加熱用高温燃焼ガスとしてガス導入/排出口6bから加熱室3内に導入される。加熱室3内に導入された前記加熱用高温燃焼ガスは、反応管5内の石灰石を反応管5の管壁を介して間接的に加熱し、その後、ガス導入/排出口6aから蓄熱バーナ7a、及び、切替弁12を通って炉排ガスとして炉外に排出される。前記ガス導入/排出口6aから排出される炉排ガスは蓄熱バーナ7a内の蓄熱体を通過する構成になっており、その際に蓄熱体に顕熱を与えて蓄熱体を高温化させ、炉排ガス自体は降温する。
【0029】
このように、一対の蓄熱式バーナの片側を燃焼用、他方を蓄熱用として使用し、例えば20〜30秒間隔で役割を切り替える。これにより、燃焼側のバーナに供給される燃焼用空気は、常に高温の蓄熱体を通過することとなり、燃焼用空気は高温に予熱される。予熱空気の温度は、炉排ガスの温度よりも50〜60℃低い程度の高温に達する。すなわち炉排ガスの温度が1100℃程度の場合には1050℃程度の予熱空気が得られることとなり、熱効率が大幅に向上する。さらに、燃焼用空気が高温化することにより燃料との反応性が格段に向上し、燃焼の安定性にも大きく貢献する。その結果、蓄熱式バーナでの燃焼により発生する窒素酸化物の濃度を極めて低いレベルに抑えることが可能となる。
【0030】
さらに、蓄熱式バーナを用いることにより、加熱室3内のガス流れが所定時間毎に逆転するため、加熱室3内のガスの混合が促進され、燃焼室3内の温度分布を高温で均一化できる。その結果、従来の蓄熱式バーナを使わない加熱方法と比較して、反応管5の単位長さ当たりの被加熱物への伝熱量が大きく増加することとなり、処理量を同一とした場合には炉のサイズをコンパクトにすることが可能となり、また、炉のサイズを同一とした場合には処理量を大幅に増加させることが可能となる。
【0031】
なお、前記蓄熱式バーナの切り替えの間隔は、蓄熱式バーナの設置される組の数、炉の規模及び操業状況等により適宜変更され得る。
【0032】
ここで、前記蓄熱式バーナ7a(又は7b)から加熱室3内に供給される加熱用高温燃焼ガスの温度は1000℃以上とすることが好ましい。加熱室3内に供給される加熱用高温燃焼ガスの温度を1000℃以上とすることにより、放射伝熱効果に基づく被加熱物の加熱を、より効果的に行うことが可能となる。また、炉排ガスによる蓄熱体の加熱温度を高温にすることが可能となり、燃焼用空気の予熱温度を高温化でき、燃焼効率がより向上する。
【0033】
なお、前記加熱用高温燃焼ガスの温度の上限は、セラミックス製の反応管3の耐熱強度によって決定されるが、およそ1500℃程度とすることが好ましい。
【0034】
また、蓄熱式バーナは、2基のバーナを一対とした切り替え式以外に、蓄熱体をバーナ内部で回転させて、1基のバーナで燃焼用空気の加熱と炉排ガスによる蓄熱とを同時に行うようにしたものを用いることもできる。
【0035】
【実施例】
実施例として図1に示した構成の間接加熱炉を用いて粉石灰の焼成を行った場合の加熱室3内の温度分布と、反応管5内部の粉石灰の温度分布を計測した結果を図2に示す。
【0036】
ここで、蓄熱式バーナは2組設置し、それぞれの切り替えは20秒間隔で行った。その結果、加熱室3内の温度は、炉壁を構成する耐火物の蓄熱効果によって約1200℃でほぼ均一に保持された。
【0037】
粉石灰の焼成は、生成物出口室手前で粉石灰の温度が1050℃となるように処理量を調整した。
【0038】
その結果、処理量は1日当たり7.2トンを達成した。また、焼成中の燃焼量は灯油37kg/hであり、この時の製品単位質量当たりの熱原単位は5600kJ/kgであった。
【0039】
比較例として、図4に示した従来技術にかかる間接加熱炉で粉石灰の焼成を行った場合の加熱室3内の温度分布と、反応管5内部の粉石灰の温度分布を計測した結果を図3に示す。
【0040】
加熱室3内の温度分布は、燃焼バーナ170の設置されている出口室150側で約1200℃、供給室120側で約1000℃程度まで降温している。
【0041】
粉石灰の焼成は、実施例同様、出口室150手前で粉石灰の温度が1050℃となるように処理量を調整した。
【0042】
その結果、処理量は1日当たり5.8トン程度であった。また、焼成中の燃焼量は灯油40kg/hであり、この時の製品単位質量当たりの熱原単位は7500kJ/kgであった。
【0043】
以上のように、本発明にかかる間接加熱炉においては、従来の構成と比較して熱効率を飛躍的に向上(熱原単位を7500kJ/kgから5600kJ/kgに向上)できること、さらに、処理量を大幅に増大(5.8t/dから7.2t/dに増大)できることが確認された。
【0044】
【発明の効果】
以上説明したように本発明によれば、被加熱物と加熱用高温燃焼ガスとの直接接触が好ましくない固体加熱プロセスにおいて、熱効率を飛躍的に向上させることができ、かつ、処理量を大幅に増大させることが可能な間接加熱炉が提供される。
【図面の簡単な説明】
【図1】本発明にかかる間接加熱炉の一実施形態を示す概略構成図である。
【図2】実施例として、図1に示した本発明にかかる間接加熱炉で粉石灰の焼成を行った場合の加熱室内の温度分布と、反応管内部の粉石灰の温度分布を計測した結果を示す図である。
【図3】比較例として、図4に示した従来技術にかかる間接加熱炉で粉石灰の焼成を行った場合の加熱室内の温度分布と、反応管内部の粉石灰の温度分布を計測した結果を示す図である。
【図4】従来技術にかかるセラミック製の反応管を備えた間接加熱炉を用いて被加熱物の熱処理を行う場合の一般的な装置構成の一例を示す図である。
【符号の説明】
1 間接加熱炉
2 固体供給室
3 加熱室
4 生成物出口室
5 反応管
6a,6b ガス導入/排出口
7a,7b 蓄熱式バーナ
8 原料投入口
9 スクリューコンベア
10 シュート
11,12 切替弁
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an indirect heating furnace suitable for heat treatment of a solid inorganic substance, particularly high temperature heat treatment when direct contact between the solid inorganic substance and a high-temperature combustion gas for heating is not preferred.
[0002]
[Prior art]
In a solid heating process in which direct contact between an object to be heated and a high-temperature combustion gas for heating is not preferable, an indirect heating furnace (also referred to as an external heating furnace) is generally used.
[0003]
However, since the conventional indirect heating furnace used a metal shell for the reaction tube, the maximum heating temperature was about 900 ° C. Therefore, an indirect heating furnace cannot be applied to a heating process that requires a high temperature exceeding 900 ° C.
[0004]
In response to such problems, the reaction tube is made of ceramic, and an indirect heating furnace equipped with a screw conveyor for conveying the solid object to be heated is used for indirect heating in a high-temperature heating process of 900 ° C. or higher. It is described in JP-T-2002-520143 (Patent Document 1) that a furnace can be applied.
[0005]
FIG. 4 shows an example of a general apparatus configuration in the case where the object to be heated is heat-treated using an indirect heating furnace equipped with the ceramic reaction tube. In addition, in the example shown in FIG. 4, it has described about the case where baking of lime (thermal decomposition of limestone) is performed.
[0006]
In FIG. 4, the limestone charged into the supply chamber 120 from the raw material inlet 110 is transferred through the reaction tube 140 by the rotation of the screw conveyor 130 and is carried into the outlet chamber 150. The limestone is heat-treated while being transferred through the reaction tube 140 to the outlet chamber 150. The heat-treated product in the outlet chamber 150 is carried out of the furnace through the chute 160.
[0007]
In addition, the high-temperature combustion gas for heating generated by the combustion burner 170 is introduced into the furnace through the gas inlet 180, and the limestone in the reaction tube 140 is indirectly heated through the tube wall of the reaction tube 140 to be discharged. From the outlet 190, it is discharged out of the furnace as furnace exhaust gas. The furnace exhaust gas discharged from the discharge port 190 is sent to the air preheater 200 to preheat the combustion air supplied to the combustion burner 170, and the amount of heat is effectively used.
[0008]
[Patent Document 1]
Japanese translation of PCT publication No. 2002-520143
[Problems to be solved by the invention]
In the heating mode of the indirect heating furnace as shown in FIG. 4, heat is once transferred from the high-temperature combustion gas for heating supplied into the furnace to the tube wall of the reaction tube 140, and then the object to be heated from the tube wall of the reaction tube 140. This is done by transferring heat to limestone. For this reason, heat transfer efficiency is poor, and the temperature of the furnace exhaust gas is as high as about 1000 ° C. In order to preheat the combustion air with this high-temperature furnace exhaust gas using the conventional metal air preheater 200, it is necessary to reduce the gas temperature to about 800 ° C. with diluted air in order to prevent the air preheater from burning out.
[0010]
When furnace exhaust gas having a temperature of about 800 ° C. is used, the temperature of the preheated air obtained is about 600 ° C. at the maximum. Therefore, the heat recovery efficiency is poor and a large amount of surplus heat still exists. Although it is conceivable to use this surplus heat for preheating the limestone that is the object to be heated, direct contact between the high-temperature combustion gas for heating and the object to be heated is an apparatus used in an unfavorable process. The preheating of the heated object is also an indirect method, and it is difficult to improve thermal efficiency. Furthermore, the amount of exhaust gas discharged out of the system due to dilution air increases, which causes further increase in heat loss.
[0011]
The present invention was made to solve the above problems, and in a solid heating process in which direct contact between an object to be heated and a high-temperature combustion gas for heating is not preferable, the thermal efficiency can be dramatically improved, and An object of the present invention is to provide an indirect heating furnace capable of greatly increasing the throughput.
[0012]
[Means for Solving the Problems]
The above problems are solved by the following invention.
[1] In an indirect heating furnace in which an object to be heated in a reaction tube is heated by a high-temperature combustion gas for heating in a non-contact manner with the combustion gas, the reaction tube is a ceramic fixed reaction tube, and further, the heating An indirect heating furnace characterized in that a combustion device for supplying high-temperature combustion gas for use in the furnace is at least a pair of regenerative burners.
[2] The indirect heating furnace according to [1], wherein the temperature of the high-temperature combustion gas for heating supplied into the furnace is 1000 ° C. or higher.
[3] The indirect heating furnace according to [1] or [2], wherein the indirect heating furnace includes a screw conveyor for transferring an object to be heated inside the reaction tube, and the main part of the screw conveyor is made of ceramic. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram showing an embodiment of an indirect heating furnace according to the present invention.
[0014]
An indirect heating furnace 1 shown in FIG. 1 includes a solid supply chamber 2 into which a solid inorganic substance as an object to be heated is charged, a heating chamber 3 into which a high-temperature combustion gas for heating is supplied, and a product after heat treatment. And a product outlet chamber 4 to be carried out of the furnace.
[0015]
A ceramic reaction tube 5 for heating an object to be heated is disposed in the heating chamber 3. One end side of the reaction tube 5 communicates with the solid supply chamber 2, and the other end side communicates with the product outlet chamber 4. The reaction tube 5 is fixed to a refractory material such as a fiber block or castable that constitutes the furnace wall of the heating chamber 3, and the inside of the reaction tube 5 into which the object to be heated is placed and the heating chamber 3 side are airtight. Sealed.
[0016]
Further, a pair of regenerative burners 7a and 7b are provided at the heating high temperature combustion gas introduction / discharge ports 6a and 6b provided in the heating chamber 3. In addition, although the said heat storage type burner is installed as one set (a pair) of two burners, the number of the set installed may be changed as appropriate depending on the scale of the furnace and the operation status.
[0017]
The ceramic reaction tube 5 is fixedly installed. In general, a horizontal cylindrical kiln (furnace) made of a metal shell in which a metal shell is used for a reaction tube is installed with the reaction tube inclined at about 2 to 5 degrees, and the contents (heated) are heated by the reaction tube rotating. Solid) is heated to the outlet side. However, in a ceramic horizontal cylindrical kiln (furnace) in which a ceramic shell is used for the reaction tube, it is difficult to rotate the reaction tube due to problems of strength and deformation tolerance. Fixed installation without rotating. The contents (solid to be heated) are conveyed not by the rotation of the reaction tube but by a ceramic screw conveyor installed inside.
[0018]
Examples of the solid inorganic substance that is the object to be heated include ore (pyrestone, bauxite, borax, calcite, chalcopyrite, chromite, hematite, etc.), metal halide (calcium bromide, calcium chloride, fluoride) Calcium, calcium iodide, as well as ferric halide, ferrous halide, potassium halide, sodium halide, etc.), metal carbides and carbonates (calcium carbonate, etc.), metal oxides (chromous acid) Salts), metal phosphates (calcium phosphate etc.), metal sulfides and metal sulfates (calcium sulfate etc.).
[0019]
As the ceramic reaction tube 5, for example, a reaction tube made of high purity MgO, high purity alumina, silicon carbide, beryllia, silicon nitride, boron carbide or the like can be used.
[0020]
Hereinafter, the case where calcination of lime (thermal decomposition of limestone) is performed using the indirect heating furnace 1 shown in FIG. 1 will be described.
[0021]
In FIG. 1, limestone introduced into the solid supply chamber 2 from the raw material introduction port 8 is transferred through the reaction tube 5 by the rotation of the screw conveyor 9 and is carried into the product outlet chamber 4. The limestone is heat-treated while being transferred through the reaction tube 5 to the product outlet chamber 4. The heat-treated product in the product outlet chamber 4 is carried out of the furnace through the chute 10.
[0022]
The high-temperature combustion gas for heating generated by the heat storage burner 7 a is introduced into the heating chamber 3 from the gas introduction / discharge port 6 a, and the limestone in the reaction tube 5 is indirectly passed through the tube wall of the reaction tube 5. It is heated and discharged out of the furnace as furnace exhaust gas from the gas inlet / outlet 6b through the heat storage burner 7b.
[0023]
Here, the screw conveyor 9 is preferably made of ceramic. Thereby, the burnout of the screw conveyor is prevented, and even when a high-temperature heating gas is used, it is possible to stably transfer the object to be heated. In addition, as a ceramic, the thing similar to the reaction tube 3 can be used.
[0024]
Hereinafter, a method of introducing the high-temperature combustion gas for heating into the heating chamber 3 using the pair of regenerative burners 7a and 7b will be described.
[0025]
The room-temperature combustion air blown in by a blower or the like (not shown) is guided to the heat storage burner 7 a side by the switching valve 11. The combustion air introduced into the heat storage burner 7a passes through the heat storage body heated to a high temperature in the heat storage burner 7a, and at that time, is heated to high temperature by the heat stored in the heat storage body. The high-temperature combustion air is mixed with fuel separately supplied to the heat storage burner 7a, and high-temperature gas generated by the combustion is introduced into the heating chamber 3 from the gas introduction / discharge port 6a as high-temperature combustion gas for heating. . Part of the combustion also occurs in the heating chamber 3.
[0026]
Here, the heat storage body is preferably a ceramic heat storage body.
[0027]
The high-temperature combustion gas for heating introduced into the heating chamber 3 indirectly heats the limestone in the reaction tube 5 through the tube wall of the reaction tube 5, and then the heat storage burner 7 b from the gas introduction / discharge port 6 b. And it is discharged out of the furnace as furnace exhaust gas through the switching valve 12. The furnace exhaust gas discharged from the gas inlet / outlet 6b passes through the heat storage body in the heat storage burner 7b. At that time, the sensible heat is applied to the heat storage body to increase the temperature of the heat storage body. The temperature itself falls.
[0028]
After operating for a predetermined time in such a state, the gas flow is reversed by switching the switching valves 11 and 12. That is, the combustion air at normal temperature blown by a blower or the like is led to the heat storage burner 7b side by the switching valve 11 this time. The combustion air introduced into the heat storage burner 7b passes through the heat storage body heated to a high temperature in the heat storage burner 7b, and at that time, is heated to high temperature by the heat stored in the heat storage body. High-temperature combustion air is mixed with fuel separately supplied to the heat storage burner 7b, and high-temperature gas generated by the combustion is introduced into the heating chamber 3 from the gas introduction / discharge port 6b as high-temperature combustion gas for heating. . The high-temperature combustion gas for heating introduced into the heating chamber 3 indirectly heats the limestone in the reaction tube 5 through the tube wall of the reaction tube 5, and then the heat storage burner 7a from the gas introduction / discharge port 6a. And, it is discharged out of the furnace as furnace exhaust gas through the switching valve 12. The furnace exhaust gas discharged from the gas introduction / discharge port 6a passes through the heat storage body in the heat storage burner 7a. At that time, the sensible heat is applied to the heat storage body to increase the temperature of the heat storage body. The temperature itself falls.
[0029]
In this manner, one side of the pair of heat storage burners is used for combustion and the other is used for heat storage, and the roles are switched at intervals of 20 to 30 seconds, for example. Thereby, the combustion air supplied to the burner on the combustion side always passes through the high-temperature heat storage body, and the combustion air is preheated to a high temperature. The temperature of the preheated air reaches a high temperature that is about 50 to 60 ° C. lower than the temperature of the furnace exhaust gas. That is, when the temperature of the furnace exhaust gas is about 1100 ° C., preheated air of about 1050 ° C. is obtained, and the thermal efficiency is greatly improved. Furthermore, the temperature of the combustion air is increased, and the reactivity with the fuel is greatly improved, which greatly contributes to the stability of combustion. As a result, the concentration of nitrogen oxides generated by combustion in the regenerative burner can be suppressed to an extremely low level.
[0030]
Furthermore, by using a regenerative burner, the gas flow in the heating chamber 3 is reversed every predetermined time, so that the mixing of the gas in the heating chamber 3 is promoted and the temperature distribution in the combustion chamber 3 is made uniform at a high temperature. it can. As a result, compared to the conventional heating method that does not use a regenerative burner, the amount of heat transferred to the object to be heated per unit length of the reaction tube 5 is greatly increased. The size of the furnace can be made compact, and when the size of the furnace is the same, the amount of processing can be greatly increased.
[0031]
The switching interval of the regenerative burner can be changed as appropriate according to the number of sets in which the regenerative burner is installed, the scale of the furnace, the operation status, and the like.
[0032]
Here, it is preferable that the temperature of the high-temperature combustion gas for heating supplied into the heating chamber 3 from the regenerative burner 7a (or 7b) is 1000 ° C. or higher. By setting the temperature of the high-temperature combustion gas for heating supplied into the heating chamber 3 to 1000 ° C. or higher, it becomes possible to more effectively heat the object to be heated based on the radiant heat transfer effect. In addition, the heating temperature of the heat accumulator with the furnace exhaust gas can be increased, the preheating temperature of the combustion air can be increased, and the combustion efficiency is further improved.
[0033]
The upper limit of the temperature of the high-temperature combustion gas for heating is determined by the heat resistance strength of the ceramic reaction tube 3, but is preferably about 1500 ° C.
[0034]
In addition to the switching type in which two burners are paired, the heat storage burner rotates the heat storage body inside the burner so that the combustion air is heated and the heat storage by the furnace exhaust gas is performed simultaneously with one burner. What was made can also be used.
[0035]
【Example】
As an example, the results of measuring the temperature distribution in the heating chamber 3 and the temperature distribution of the powdered lime in the reaction tube 5 when the indirect heating furnace having the configuration shown in FIG. It is shown in 2.
[0036]
Here, two sets of heat storage burners were installed, and each switching was performed at intervals of 20 seconds. As a result, the temperature in the heating chamber 3 was kept substantially uniform at about 1200 ° C. due to the heat storage effect of the refractory constituting the furnace wall.
[0037]
In the calcining of powdered lime, the amount of treatment was adjusted so that the temperature of the powdered lime was 1050 ° C. before the product outlet chamber.
[0038]
As a result, the throughput reached 7.2 tons per day. Further, the combustion amount during firing was 37 kg / h of kerosene, and the heat intensity per product unit mass at this time was 5600 kJ / kg.
[0039]
As a comparative example, the results of measuring the temperature distribution in the heating chamber 3 and the temperature distribution of the powdered lime inside the reaction tube 5 when the powdered lime is baked in the indirect heating furnace according to the prior art shown in FIG. As shown in FIG.
[0040]
The temperature distribution in the heating chamber 3 is lowered to about 1200 ° C. on the outlet chamber 150 side where the combustion burner 170 is installed, and to about 1000 ° C. on the supply chamber 120 side.
[0041]
In the calcination of the powdered lime, the amount of treatment was adjusted so that the temperature of the powdered lime was 1050 ° C. before the outlet chamber 150 as in the example.
[0042]
As a result, the processing amount was about 5.8 tons per day. The combustion amount during firing was kerosene 40 kg / h, and the heat unit per product unit mass at this time was 7500 kJ / kg.
[0043]
As described above, in the indirect heating furnace according to the present invention, the thermal efficiency can be drastically improved compared with the conventional configuration (the heat intensity can be improved from 7500 kJ / kg to 5600 kJ / kg), and the processing amount can be reduced. It was confirmed that it can be greatly increased (increased from 5.8 t / d to 7.2 t / d).
[0044]
【The invention's effect】
As described above, according to the present invention, in a solid heating process in which direct contact between an object to be heated and a high-temperature combustion gas for heating is not preferable, it is possible to dramatically improve thermal efficiency and greatly increase the throughput. An indirect furnace that can be increased is provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an indirect heating furnace according to the present invention.
2 shows the results of measuring the temperature distribution in the heating chamber and the temperature distribution of the powdered lime in the reaction tube when the powdered lime is baked in the indirect heating furnace according to the present invention shown in FIG. 1 as an example. FIG.
FIG. 3 shows, as a comparative example, the result of measuring the temperature distribution in the heating chamber and the temperature distribution of the powdered lime in the reaction tube when the powdered lime is baked in the indirect heating furnace according to the prior art shown in FIG. FIG.
FIG. 4 is a diagram showing an example of a general apparatus configuration in the case of performing a heat treatment of an object to be heated using an indirect heating furnace provided with a ceramic reaction tube according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Indirect heating furnace 2 Solid supply chamber 3 Heating chamber 4 Product outlet chamber 5 Reaction tube 6a, 6b Gas introduction / discharge port 7a, 7b Regenerative burner 8 Raw material inlet 9 Screw conveyor 10 Chute 11, 12 Changeover valve

Claims (3)

  1. 反応管内部の被加熱物を加熱用高温燃焼ガスにより、該燃焼ガスと非接触で加熱する間接加熱炉において、
    前記反応管がセラミック製の固定式反応管であり、
    さらに、前記加熱用高温燃焼ガスを炉内に供給するための燃焼装置が少なくとも一対の蓄熱式バーナであることを特徴とする間接加熱炉。
    In an indirect heating furnace that heats an object to be heated inside a reaction tube with a high-temperature combustion gas for heating in a non-contact manner with the combustion gas,
    The reaction tube is a ceramic fixed reaction tube,
    The indirect heating furnace is characterized in that the combustion apparatus for supplying the high-temperature combustion gas for heating into the furnace is at least a pair of regenerative burners.
  2. 炉内に供給される加熱用高温燃焼ガスの温度が1000℃以上であることを特徴とする請求項1に記載の間接加熱炉。The indirect heating furnace according to claim 1, wherein the temperature of the high-temperature combustion gas for heating supplied into the furnace is 1000 ° C or higher.
  3. 反応管内部の被加熱物を移送するためのスクリューコンベアを備え、且つ、該スクリューコンベア主要部がセラミック製であることを特徴とする請求項1又は請求項2に記載の間接加熱炉。The indirect heating furnace according to claim 1 or 2, wherein a screw conveyor for transferring an object to be heated inside the reaction tube is provided, and the main part of the screw conveyor is made of ceramic.
JP2003160798A 2003-06-05 2003-06-05 Indirect heating furnace Pending JP2004361018A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104329948A (en) * 2014-10-20 2015-02-04 辽宁科技大学 Device for using flue gas waste heat of rotary cement kiln to preheat air
CN109114561A (en) * 2018-08-17 2019-01-01 高云桥 A kind of environmental protection and energy saving garbage combustion device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104329948A (en) * 2014-10-20 2015-02-04 辽宁科技大学 Device for using flue gas waste heat of rotary cement kiln to preheat air
CN104329948B (en) * 2014-10-20 2016-04-13 辽宁科技大学 A kind of device utilizing cement rotary kiln preheating air by flue gas afterheat
CN109114561A (en) * 2018-08-17 2019-01-01 高云桥 A kind of environmental protection and energy saving garbage combustion device

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