JP4825994B2 - Method for firing powdered calcium carbonate - Google Patents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Description
本発明は粉体状炭酸カルシウム（CaCO３）を含有する製糖廃棄物ライムケーキ（以下原料と略称）を焼成して高活性酸化カルシウム（CaO）を製造しリサイクル利用するための、粉体状炭酸カルシウムの焼成方法に関する技術。 The present invention relates to powdered carbonate for producing and recycling highly active calcium oxide (CaO) by baking a sugar-making waste lime cake (hereinafter abbreviated as raw material ) containing powdered calcium carbonate (CaCO 3 ). Technology related to calcium firing methods.
一般的に、酸化カルシウム（生石灰CaO）の製造は、炭酸カルシウムの原料である石灰石や貝殻などを、1100〜1200℃で焼成することにより行われ，また酸化カルシウムに水を反応させて消化反応により水酸化カルシウム（消石灰Ca(OH)２）を製造する。従来は、特許文献１及び２に開示されているように、竪型シャフト炉において塊状の石灰石や貝殻を焼成する方式が一般的である。竪型シャフト炉は、堅型の炉の上部から原料・燃料などを装入し、下部から燃焼用空気などを吹き込んで炉底から焼成された生石灰を取り出す方式であり、比較的大型炉である。従って、石灰石を原料とする場合、燃焼ガスの通気性より粒径40〜100mm程度の塊状のものを用いている。 In general, calcium oxide (quick lime CaO) is produced by calcining limestone, shells, etc., which are calcium carbonate raw materials, at 1100-1200 ° C, and by reacting calcium oxide with water to digestion reaction. Calcium hydroxide (slaked lime Ca (OH) 2 ) is produced. Conventionally, as disclosed in Patent Documents 1 and 2, a method of firing massive limestone and shells in a vertical shaft furnace is common. A vertical shaft furnace is a relatively large furnace, in which raw materials and fuel are charged from the top of a solid furnace, combustion air is blown from the bottom, and calcined lime is extracted from the bottom of the furnace. . Therefore, when limestone is used as a raw material, a mass having a particle diameter of about 40 to 100 mm is used because of the breathability of combustion gas.
粉体焼成には焼却炉などで使用される流動層炉（特許文献３,特許文献６）は適するが、流動層炉を用いてCaCO３を焼成してCaOを製造することは、あまり一般的ではない。流動層炉を用いる場合、上記の竪型シャフト炉の場合に較べて原料である炭酸カルシウムの粒径は0.1ｍｍ以下の粉体状の炭酸カルシウム（タンカル），さらに微粒子である製糖工場から排出する廃棄物ライムケーキ（粒径0.5μｍ以下）を焼成し得るが，流動層による焼成方式以外の技術は開発されていない。 Fluidized bed furnaces used in incinerators and the like (Patent Documents 3 and 6) are suitable for powder firing, but it is not very common to produce CaO by firing CaCO 3 using a fluidized bed furnace. is not. When using a fluidized bed furnace, the particle size of calcium carbonate as a raw material is 0.1 mm or less compared to the case of the above vertical shaft furnace, and it is discharged from a sugar factory that is fine particles. Although waste lime cake (particle size 0.5 μm or less) can be fired, no technology other than the fluidized bed firing method has been developed.
現在、様々な分野において反応性の良い高活性酸化カルシウム、または高活性水酸化カルシウム（消石灰）を得るために、通常の竪型シャフト炉により石灰石を焼成して製造された酸化カルシウム（生石灰）を、消化過程でアルコールなどを添加して高活性水酸化カルシウム（消石灰）を製造しているが，焼成段階で高活性酸化カルシウムにして，それを消化すると，さらに高活性水酸化カルシウム（消石灰）を製造し得る。 At present, in order to obtain highly active calcium oxide or highly active calcium hydroxide (slaked lime) with good reactivity in various fields, calcium oxide (quick lime) produced by calcining limestone in a normal vertical shaft furnace is used. Alcohol is added during the digestion process to produce highly active calcium hydroxide (slaked lime), but when activated, it is converted to highly active calcium oxide at the firing stage. Can be manufactured.
高活性水酸化カルシウム（消石灰）の利用分野として，排煙ガスに含まれる有害物質（硫黄酸化物、窒素酸化物，塩化水素）を除去するために，特許文献３に開示されている乾式排煙浄化システムがある。この乾式排煙浄化システムにおける脱硫反応、脱消反応または脱塩反応は固体と気体の反応であるため、カルシウム系排煙浄化剤としては高い反応活性が求められる。高活性のCaOまたはCa(OH)２を得るためには、原料である炭酸カルシウムの焼成温度を、不要に高温とせずにその熱分解温度領域の近傍とし，かつ極力短時間で焼成する必要がある。このような焼成条件を満たすには、微粒子すなわち粉体状の炭酸カルシウムを焼成することが望ましい。 As a field of utilization of highly active calcium hydroxide (slaked lime), dry exhaust smoke disclosed in Patent Document 3 is used to remove harmful substances (sulfur oxide, nitrogen oxide, hydrogen chloride) contained in the exhaust gas. There is a purification system. Since the desulfurization reaction, desulfurization reaction or demineralization reaction in this dry flue gas purification system is a solid-gas reaction, a high reaction activity is required as a calcium-based flue gas purification agent. In order to obtain highly active CaO or Ca (OH) 2 , it is necessary to calcinate the raw material calcium carbonate in the vicinity of its pyrolysis temperature region without making it unnecessarily high, and in as short a time as possible. is there. In order to satisfy such firing conditions, it is desirable to fire fine particles, that is, powdered calcium carbonate.
また別の分野として、甜菜製糖では糖液精製工程において、糖液に酸化カルシウムを添加して水酸化カルシウムとし、この糖液に二酸化炭素を吹き込むことにより炭酸カルシウムを生成させ、この炭酸カルシウム生成過程で糖液中の不純物である懸濁物を吸着させて除去することにより精製糖液を得ている。この結果、炭酸カルシウムを主成分とする廃棄物（ライムケーキ）を多量に生じるが、このライムケーキ含有炭酸カルシウムの粒径は５μm以下である。これを焼成して再び酸化カルシウムとすれば、リサイクルが可能となり、この場合にも粉体状の炭酸カルシウムの焼成技術が必要となる。 As another field, sugar beet sugar is produced by adding calcium oxide to the sugar solution to produce calcium hydroxide in the sugar solution purification process, and by blowing carbon dioxide into the sugar solution to produce calcium carbonate. Thus, a purified sugar solution is obtained by adsorbing and removing a suspension that is an impurity in the sugar solution. As a result, a large amount of waste (lime cake) containing calcium carbonate as a main component is generated. The particle size of the calcium carbonate containing lime cake is 5 μm or less. If this is calcined and recalcified, it can be recycled. In this case as well, a powdered calcium carbonate calcining technique is required.
しかしながら、上述のように、粉体状の炭酸カルシウムの焼成技術では、流動層炉による焼成技術は開発されているが,その他の方式による焼成技術は確立されていない。 However, as described above, in the powdered calcium carbonate baking technique, a baking technique using a fluidized bed furnace has been developed, but baking techniques using other methods have not been established.
粉体状の炭酸カルシウムを焼成する場合、以下の(i)(ii)の問題点がある。
（i）図１及び図２は、従来の流動層炉を用いて粒径1〜3mmの炭酸カルシウムの焼成実験を行った結果を示すグラフである。図１は炭酸カルシウムの焼成温度（流動層炉内のフリーボード部の温度）と活性度の測定結果を示す。この測定では、焼成された酸化カルシウムを１０分間で中和するために要する塩酸（４規定液による）の消費量により、酸化カルシウムの活性を評価している。焼成温度850〜900℃の比較的低温域で、活性の最大値を示している。一方、図２は流動層から飛散した微粉炭酸カルシウムの焼成温度（流動層炉内のフリーボード部の温度）と焼成率の測定結果を示す。焼成温度が低くなるほど、焼成された酸化カルシウムの強熱減量（炭酸カルシウムの未焼成分に相当）が増加する。
When firing powdered calcium carbonate, there are the following problems (i) and (ii).
(I) FIG.1 and FIG.2 is a graph which shows the result of having performed the baking experiment of calcium carbonate with a particle size of 1-3 mm using the conventional fluidized bed furnace. FIG. 1 shows the measurement results of the calcining temperature of calcium carbonate (the temperature of the free board in the fluidized bed furnace) and the activity. In this measurement, the activity of calcium oxide is evaluated by the consumption of hydrochloric acid (by a 4N solution) required to neutralize the calcined calcium oxide in 10 minutes. The maximum value of activity is shown in a relatively low temperature range of calcination temperature 850 to 900 ° C. On the other hand, FIG. 2 shows the measurement results of the firing temperature (temperature of the free board part in the fluidized bed furnace) and the firing rate of the finely divided calcium carbonate scattered from the fluidized bed. The lower the firing temperature, the greater the loss on ignition of the calcined calcium oxide (corresponding to the uncalcined portion of calcium carbonate).
図１及び図２から流動層炉を用いて高活性の酸化カルシウムを得るには、850〜900℃の最大活性が得られる焼成温度で炭酸カルシウムの焼成を行うことが望ましいが、約10〜15％が未焼成となってしまうことが判る。比較的低温域で完全に焼成するには、ある程度の滞留時間は必要であるが、小さい粒子であるほど飛散しやすいため、焼成のための滞留時間が確保し難いという問題点がある。特に、粒径0.１mm以下の粉体状の場合、従来の流動層炉に投入しても、燃焼ガスとともに流出してしまうため、かなりの部分が未焼成のままとなる。従って、最適な焼成温度の流動層炉内において、粉体の十分な滞留時間を確保する技術が求められる。 In order to obtain highly active calcium oxide using a fluidized bed furnace from FIG. 1 and FIG. 2, it is desirable to calcinate calcium carbonate at a calcination temperature at which a maximum activity of 850 to 900 ° C. is obtained. % Is unfired. A certain amount of residence time is required for complete firing in a relatively low temperature range. However, the smaller the particles, the more likely it is to scatter, and there is a problem that it is difficult to ensure the residence time for firing. In particular, in the case of a powder having a particle size of 0.1 mm or less, even if it is put into a conventional fluidized bed furnace, it flows out together with the combustion gas, so that a considerable part remains unfired. Therefore, there is a need for a technique that ensures a sufficient residence time of the powder in a fluidized bed furnace having an optimum firing temperature.
（ii）また、炭酸カルシウムの微粒子が焼成されて酸化カルシウムの微粒子となり、燃焼ガスと共存するとき、燃料の燃焼により生じた二酸化炭素（CO２）と、炭酸カルシウムの熱分解により生じたCO２とにより、燃焼ガスには高濃度のCO２が含まれることになる。このような雰囲気下においては、数１に示す可逆反応から、温度領域により酸化カルシウムの再炭酸化が生じ、燃焼ガスの通路となる機器や配管ダクトの内壁にCaOの再炭酸化した炭酸カルシウムが付着固化し、いわゆるコーティング閉塞現象を生じる。付着固化した炭酸カルシウムを除去するには、操業停止しなければならず、かつ除去作業の負担が大きかった。 (Ii) Further, when the calcium carbonate fine particles are calcined to become calcium oxide fine particles and coexist with the combustion gas, carbon dioxide (CO 2 ) generated by combustion of the fuel and CO 2 generated by thermal decomposition of calcium carbonate. As a result, the combustion gas contains a high concentration of CO 2 . Under such an atmosphere, recalcification of calcium oxide occurs depending on the temperature range from the reversible reaction shown in Equation 1, and the calcium carbonate obtained by recalcifying CaO on the inner walls of the equipment and piping ducts serving as combustion gas passages. It adheres and solidifies, causing a so-called coating blockage phenomenon. In order to remove the adhered and solidified calcium carbonate, the operation had to be stopped, and the burden of the removal work was large.
ここで、特許文献５は、酸化カルシウムの再炭酸化を防止する方法を開示している。特許文献５の段落００１４には、石灰石(炭酸カルシウムCaCO３)または生石灰(酸化カルシウムCaO)をＴ℃で扱う装置を運転するに際し、CaOとCO２の共存する雰囲気においてCaOが再炭酸化してCaCO３になる。雰囲気ガス中のCO２分圧P, 温度Tの関係式を次式に示す。
Ｐ［MPa］＝452exp(−21441／(T＋179)＋17.01)
上式からCaOは雰囲気中のCO２分圧Ｐ未満にすると再炭酸化を防止できる。図３は炭酸カルシウムの熱分解の平衡温度と、CO２分圧との関係を示したグラフである。実線は特許文献５の式に基づいており、破線は非特許文献１に記載の式に基づいている。石灰石の産地、性状により若干の差異を生ずるが、ほぼ同じ傾向を示しており、CO２分圧が高くなるほど、CaCO３の熱分解平衡温度は高くなる。これらの曲線を境界として、高温側が熱分解領域（CaO＋CO２）となり、低温側が結合領域（CaCO３）となる。従って、CaOを含む所定の温度の燃焼ガスにおいて、CaOの再炭酸化を防止するためには、その温度で熱分解領域となるようにCO２分圧を調整する必要がある。つまり、CO２分圧が高すぎる場合は、これを低減する必要がある。
Here, patent document 5 is disclosing the method of preventing recarbonation of calcium oxide. In paragraph 0014 of Patent Document 5 , when operating an apparatus that handles limestone (calcium carbonate CaCO 3 ) or quick lime (calcium oxide CaO) at T ° C., CaO is re-carbonated in an atmosphere where CaO and CO 2 coexist, and CaCO It becomes 3 . The relational expression of CO 2 partial pressure P and temperature T in the atmospheric gas is shown in the following equation.
P [MPa] = 452exp (−21441 / (T + 179) +17.01)
From the above equation CaO can prevent re-carbonation when the CO less than 2 partial pressure P of the atmosphere. FIG. 3 is a graph showing the relationship between the thermal decomposition equilibrium temperature of calcium carbonate and the CO 2 partial pressure. The solid line is based on the formula in Patent Literature 5 , and the broken line is based on the formula in Non-Patent Literature 1. Although there are some differences depending on the production area and properties of limestone, they show almost the same tendency. The higher the CO 2 partial pressure, the higher the thermal decomposition equilibrium temperature of CaCO 3 . With these curves as a boundary, the high temperature side becomes a thermal decomposition region (CaO + CO 2 ), and the low temperature side becomes a bonding region (CaCO 3 ). Therefore, in order to prevent the re-carbonation of CaO in a combustion gas at a predetermined temperature containing CaO, it is necessary to adjust the CO 2 partial pressure so that it becomes a thermal decomposition region at that temperature. That is, if the CO 2 partial pressure is too high, it is necessary to reduce this.
以上の問題点に鑑み、本発明の目的は粉体状（特に粒径0.1mm以下）の炭酸カルシウムを、高い焼成率で効率的に焼成することができる焼成方法を提供することである。 In view of the above problems, an object of the present invention is to provide a firing method capable of efficiently firing powdery calcium carbonate (particularly, a particle size of 0.1 mm or less) at a high firing rate.
上記の問題点を解決するために、本発明は以下の構成を提供する。なお、括弧中の数字は、後述する実施例を示した図面の符号であり、参考のために付する。
（１）本発明では粉体状炭酸カルシウムの焼成炉は、密封された円筒状容器を焼成部とし、披焼成物を円筒焼成部内を円筒軸方向に移動させる機能を有し、円筒焼成部外部より加熱する間接加熱型キルンである。
In order to solve the above problems, the present invention provides the following configurations. The numerals in parentheses are the reference numerals of the drawings showing examples to be described later, and are attached for reference.
(1) In the present invention, the powdered calcium carbonate firing furnace has a function of moving the fired product in the cylindrical firing part in the cylindrical axial direction using a sealed cylindrical container as a firing part. It is an indirect heating kiln that heats more.
（２）前記の間接加熱型キルンを必要に応じて２基直列に使用し、前段を乾燥用キルン(10)，後段を焼成用キルン(20)に使用する。乾燥用キルン(10)に原料を供給し、乾燥キルン加熱部には焼成用キルン(20)で焼成されたＣaCO３の加熱分解により生じたCaOとCO2，及びライムケーキ含有の有機物燃焼ガスを含む、粉体と気体の２相熱流体を流入させて熱回収し原料を加熱乾燥する。 (2) If necessary, two indirect heating kilns are used in series, and the former stage is used as a drying kiln (10) and the latter stage is used as a kiln for firing (20) . The raw material is supplied to the drying kiln (10) , and CaO and CO 2 generated by the thermal decomposition of CaCO 3 baked in the baking kiln (20) and organic combustion gas containing lime cake are supplied to the drying kiln heating section. A two-phase thermal fluid containing powder and gas is introduced to recover heat, and the raw material is heated and dried.
（３）焼成用キルン(20)には加熱された原料が供給され，また原料がライムケーキの場合、含有水分は乾燥用キルン(10)の排出側で水蒸気として分離放出し、ライムケーキ含有有機物の燃焼用空気を焼成用キルン(20)に併給し、ＣaCO３の加熱分解と有機物を焼却する。焼成用キルン(20)の加熱部には燃焼ガス発生炉からの燃焼ガスが供給されてキルン内部のＣaCO３の熱分解に熱供給される。 (3) The heated raw material is supplied to the baking kiln (20) , and when the raw material is lime cake, the water content is separated and released as water vapor on the discharge side of the drying kiln (10) , and the lime cake-containing organic matter The combustion air is supplied to the kiln (20) for burning, and the thermal decomposition of CaCO 3 and the organic matter are incinerated. Combustion gas from the combustion gas generating furnace is supplied to the heating section of the kiln for firing (20) , and heat is supplied to the thermal decomposition of CaCO 3 inside the kiln.
（４）上記（３）において焼成用キルン(20)より流出するCaOとCO2，及びライムケーキ含有の有機物燃焼ガスは２相熱流体として焼成用キルン(20)を流出後，原料の乾燥用キルン(10)の加熱部を流れる途中にて，温度低下により２相熱流体中のCaOはCO2により再炭酸化を生じ，その通過部において固着現象を発生する。その防止のため当該２相熱流体が焼成用キルン(20)を流出直後，または熱回収過程において冷空気か水を供給することにより,当該2相熱流体を600℃以下に急速冷却すると同時にCO2分圧を低減し,または水酸化カルシウムとして再炭酸化炭酸化防止を図る。 (4) The organic combustion gas containing CaO and CO 2 and lime cake that flows out from the firing kiln (20 ) in (3) above flows out of the firing kiln (20) as a two-phase thermal fluid, and then is used for drying raw materials . In the middle of flowing through the heating part of the kiln (10) , CaO in the two-phase thermal fluid is re-carbonated by CO 2 due to the temperature drop, and a sticking phenomenon occurs in the passing part. To prevent this, immediately after the two-phase thermal fluid flows out of the firing kiln (20) , or by supplying cold air or water during the heat recovery process, the two-phase thermal fluid is rapidly cooled to 600 ° C or less and simultaneously with CO. Reduce the partial pressure of 2 or prevent re-carbonation and carbonation as calcium hydroxide.
本発明の図４は間接外熱型キルン2基直列使用による，高含水ライムケーキの焼成システムである。
焼成用キルンより流出した排出ガス中に冷空気または水を混合して600℃以下に急速冷却することにより、焼成後の燃焼ガスに含まれるCO2分圧を低減し、または水酸化カルシウムとして再炭酸化を生ずることなく、コーティング閉塞現象を防止す
ることが粉体状炭酸カルシウム焼成方法のキーポイントである。
FIG. 4 of the present invention is a high water content lime cake baking system using two indirect external heat kilns in series.
Mixing cold air or water into the exhaust gas flowing out of the kiln for firing and rapidly cooling to 600 ° C or lower reduces the partial pressure of CO 2 contained in the combustion gas after firing, or regenerates it as calcium hydroxide. Preventing the coating clogging phenomenon without causing carbonation is a key point of the powdered calcium carbonate baking method.
本発明により、粒径0.1mm以下の微粒子のCaCO３の焼成が可能となり、高活性なCaOを製造することにより、高性能な乾式排煙浄化剤をロ−コストに製造することが可能となる。また，製糖の糖液精製過程で生ずる微粒子のCaCO３を多量に含む廃棄物ライムケ−キを焼成することが可能となり、ライムケーキをリサイクルすることにより、国内資源である石灰石の温存，廃棄物の低減による環境負荷の軽減，または排煙浄化剤としての有効利用が可能になる。 According to the present invention, fine CaCO 3 particles having a particle size of 0.1 mm or less can be baked, and by producing highly active CaO, a high-performance dry smoke cleaner can be produced at low cost. . Also, it becomes possible to bake waste lime cake containing a large amount of fine CaCO 3 produced during the sugar refining process of sugar making. By recycling the lime cake, it is possible to preserve limestone, which is a domestic resource, Reduction of environmental load by reduction or effective use as a flue gas purifier becomes possible.
本発明は、粉体状の炭酸カルシウム(CaCO３）を含有する高含水のライムケーキを焼成して高活性な酸化カルシウム（CaO）を製造する焼成方法に関するものである。以下、本発明実施の形態を図４により説明する。 The present invention relates to a firing method for producing highly active calcium oxide (CaO) by firing a hydrated lime cake containing powdered calcium carbonate (CaCO 3 ). The embodiment of the present invention will be described below with reference to FIG.
図４は本発明の方法を適用した高含水のライムケーキ焼成の実施例の焼成システムのフロー構成図である。本発明の適用対象である製糖の糖液精製工程で排出されるライムケーキに含まれる炭酸カルシウムの粒径は5μｍ以下の微粒子粉体であり、粉体状炭酸カルシウムの焼成にも好適な対象である。 FIG. 4 is a flow configuration diagram of a baking system of an embodiment of baking of a high water content lime cake to which the method of the present invention is applied. The particle size of calcium carbonate contained in the lime cake discharged in the sugar solution refining process of sugar production, which is the application target of the present invention, is a fine particle powder of 5 μm or less, and is also suitable for firing powdered calcium carbonate. is there.
この実施例は、横軸円筒形状炉で内容物を軸方向に移動し得る機能を有する間接外熱型キルンで乾燥用キルン(10)、焼成用キルン(20)を用いて、粉体状炭酸カルシウムの焼成を行う構成である。間接外熱型キルンはキルン本体である内筒に対象物を投入し、キルン加熱部10a，20aに加熱用熱流体を流すことにより対象物を間接的に加熱するように構成されている。 This example is an indirect external heating kiln having a function capable of moving the contents in the axial direction in a horizontal cylindrical furnace, using a drying kiln (10) and a baking kiln (20) to form a powdery carbonic acid. In this configuration, calcium is fired. The indirect external heat kiln is configured to heat an object indirectly by putting the object into an inner cylinder that is a kiln main body and flowing a heating fluid through the kiln heating units 10a and 20a.
本システムでは焼成用キルン(20)の加熱用熱流体としての燃焼ガスを発生するために、燃焼ガス発生炉(6)を設けて燃料(5)には石炭または石油を使用し，燃焼ガスを発生する。燃焼ガスは焼成用のキルン加熱部(20a)の熱流体入口（23）より流入し，焼成用キルン(20)の原料供給口(21)より供給された原料を加熱し、熱流体出口(24)より流出後、ガス・ガス・ヒーター(25)にて燃焼ガス発生炉(6)で使用する燃焼空気を予熱し、バグフイルター(26)で燃焼ガス中の灰(28)が捕集され、誘引通風機(27)を経て煙突(9)より排出する。 In this system, in order to generate combustion gas as a heating fluid for heating the kiln (20) , a combustion gas generation furnace (6) is provided, coal or petroleum is used as fuel (5), and combustion gas is appear. Combustion gas flows from the thermal fluid inlet (23) of the kiln heating section (20a) for firing, heats the raw material supplied from the raw material supply port (21) of the firing kiln (20), ), The combustion air used in the combustion gas generator (6) is preheated by the gas gas heater (25), and the ash (28) in the combustion gas is collected by the bag filter (26). It discharges from the chimney (9) through the induction fan (27).
原料(1)にはライムケーキを使用し，原料加熱用の乾燥用キルン(10)の原料供給部（11）に供給される。乾燥用キルン(10)の加熱には焼成用キルン(20)で原料焼成により熱分解して生成したCaO，CO2の他，ライムケーキ使用の場合には有機物燃焼ガスが混合し、ガスと粉体からなる2相熱流体がキルン排出口（22）から流出し、その2相熱流体は原料加熱用の乾燥用キルン(10)のキルン加熱部(10a)の熱流体入口部(13)より流入して熱流体出口部(14)より流出するが2相熱流体が熱回収される減温過程で再炭酸化を生ずる。 Lime cake is used as the raw material (1) and is supplied to the raw material supply section (11) of the drying kiln (10) for heating the raw material. The kiln for drying (10) is heated with CaO and CO 2 produced by pyrolysis of the raw material in the kiln for firing (20). In addition, when using lime cake, organic combustion gas is mixed, and the gas and powder are mixed. The two-phase thermal fluid consisting of the body flows out from the kiln discharge port (22), and the two-phase thermal fluid flows from the thermal fluid inlet (13) of the kiln heating part (10a) of the drying kiln (10) for heating the raw material. flows to be discharged from the thermal fluid outlet portion (14) is caused to re-carbonation under reduced temperature course of the two-phase thermal fluid is heat recovery.
その再炭酸化は段落００１４に前述したようにCaO ，CO2共存下では800〜600℃の領域で再炭酸化を発生し易いことより，その温度領域を急速に脱出する必要があり，焼成用キルン(20)より流出した2相熱流体はキルン排出口(22)より熱流体が流出直後に冷却混合部(4a)で冷却空気か水を供給する。または乾燥用キルン(10)のキルン加熱部(10a)の熱流体冷却口(15)より冷却空気か水を供給し，2相熱流体を600℃以下に冷却する。また原料がライムケーキの場合は乾燥用キルン(10)の排出側で水蒸気分離部(19)により原料中の水分蒸発による水蒸気を分離放出する。 As described above in paragraph 0014, the re-carbonization is likely to occur in the range of 800-600 ° C in the presence of CaO and CO 2 , so it is necessary to escape rapidly from that temperature range . The two-phase thermal fluid flowing out from the kiln (20) is supplied with cooling air or water in the cooling mixing section (4a) immediately after the thermal fluid flows out from the kiln discharge port (22). Alternatively, cooling air or water is supplied from the hot fluid cooling port (15) of the kiln heating section (10a) of the drying kiln (10) to cool the two-phase thermal fluid to 600 ° C or lower. When the raw material is a lime cake, water vapor due to water evaporation in the raw material is separated and released by the water vapor separation section (19) on the discharge side of the drying kiln (10).
2相熱流体はキルン加熱部(10a)で熱回収され，熱流体の冷却に空気を使用の場合はバグフイルター(16)でCaOを捕集し，また冷却に水を使用の場合はバグフイルター(16)でCa(OH)２を捕集する。分離された熱流体中のガスは煙突(9)より大気放出される。原料にライムケーキを使用し製糖用にリサイクルする場合は熱流体の冷却には水を使用し，CO2濃度を低下させずに製糖精製工程に使用する。 The two-phase thermal fluid is recovered by the kiln heating section (10a). When air is used for cooling the thermal fluid, CaO is collected by the bag filter (16), and when water is used for cooling, the bag filter is used. Collect Ca (OH) 2 in (16). The separated gas in the hot fluid is released into the atmosphere from the chimney (9). When lime cake is used as a raw material and recycled for sugar production, water is used for cooling the hot fluid and used in the sugar refinery process without reducing the CO 2 concentration.
製糖工場から排出したライムケーキを本発明の方法による試験用外部加熱型キルンで焼成試験を実施した。試験条件、および焼成結果は次の通りであった。キルンの焼成温度は900℃が上限である。
試料；ライムケーキ乾燥品 50 kg/ｈ（試験試料は別途乾燥したものを使用）
成 分 CaCO３； 87.5％
有機物； 10.5％
水 分； 1.0％ 以下
その他； 1.0％
間接外熱型キルン（300Φ×4000L) による焼成試験
焼成温度 ７５０℃ ８００℃ ８５０℃ ９００℃
焼成率 ３２〜４０%，８２〜８７％，８８〜９１%，９２〜９
The lime cake discharged from the sugar factory was subjected to a firing test in an external heating kiln for testing according to the method of the present invention. Test conditions and firing results were as follows. The upper limit of the kiln firing temperature is 900 ° C.
Sample: Lime cake dry product 50 kg / h (use test sample separately dried)
Component CaCO 3 ； 87.5%
Organic matter; 10.5%
Water content: 1.0% or less
Other; 1.0%
Firing test with indirect external heat kiln (300Φ × 4000L)
Firing temperature 750 ° C 800 ° C 850 ° C 900 ° C
Firing rate 32-40%, 82-87%, 88-91%, 92-9
１：原料
2，3，4，8：空気
4a：冷却混合部
５：燃料
６：燃焼ガス発生炉
７：燃焼ガス発生炉用送風機
９：煙突
18；酸化カルシウム，または水酸化カルシウム
19；水蒸気分離部
10；乾燥用キルン
20：焼成用キルン
10a,20a;キルン加熱部
11，21：キルン原料供給口
12，22：キルン排出口
13，23；熱流体入口
14，24; 熱流体出口
15; 熱流体冷却口
25；ガス・ガス・ヒーター
16，26; バグフイルター
17，27; 誘引通風機
28；灰
1: Raw material
2, 3, 4, 8: Air
4a: Cooling and mixing section
5: Fuel
6: Combustion gas generation furnace
7: Blower for combustion gas generator
9: Chimney
18; calcium oxide or calcium hydroxide
19; Steam separation part
10; Drying kiln
20: Kiln for firing
10a, 20a; kiln heating part
11, 21: Kiln raw material supply port
12, 22: Kiln outlet
13, 23; Thermal fluid inlet
14, 24; Thermal fluid outlet
15; Thermal fluid cooling port
25; gas, gas heater
16, 26; Bug filter
17, 27; induction fan
28; ash
Claims (1)
Inner and by flowing a hot fluid into the outer cylinder includes an outer tube having a function capable of moving inside the inner cylinder of the contents of the heated inner cylinder in the axial direction, the firing kiln indirect outside thermal kiln In the method in which the combustion gas from the combustion gas generating furnace is used as the heating side thermal fluid of the kiln to heat the kiln inner cylinder to calcine powdered calcium carbonate to produce calcium oxide, the feedstock is lime cake Then, the air for incinerating the organic material contained in the raw material is supplied together to burn the organic material, and if necessary, an indirect external heating type drying kiln is installed in the previous stage of the firing kiln for drying the raw material-containing moisture, and for the drying after steam separation emission flowing from the kiln, the dried raw material is supplied to the firing kiln, after firing kiln outlet and calcium oxide flowing from the firing kiln against associated gas, or supplying cold air or water in the heat recovery system Rapid cooling to simultaneously reduce carbon dioxide partial pressure and the firing method of the powdery calcium carbonate having a means for preventing re-carbonation as calcium hydroxide to 600 ° C. or less Te.
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