Rotary kiln - Rotary kiln (English spelling)

A general term for rotary kilns, which are generally used for high-temperature rotary kilns, usually refers to a straight cylindrical kiln with a length sufficiently large compared to its diameter. Rotary kilns with a relatively small length are called trommel kilns and are often treated differently. A typical example is a cement kiln with a diameter of several meters and a length of several hundred meters. Rotary kilns are usually installed at a slight incline to the horizontal, and while rotating slowly, raw materials are fed from above and flames are sent from a combustion device installed below. The high-temperature combustion gases come into contact with the raw materials while facing each other, and are involved in their reaction and preheating. Since multiple raw materials are usually used, rather than a single raw material, the raw ore is crushed and prepared in advance (sometimes water is added and mixed) and then fed from the top of the kiln. The raw materials move downward as the cylinder rotates and come into contact with the high-temperature gas, undergoing preliminary dehydration and reactions, until the temperature required for firing (usually several thousand degrees Celsius) is reached and the kiln is fired. The temperature range varies depending on the object, and the firing of organic polymer materials is carried out at around 200°C.

[Yuji Kawamura]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

回転式の高温焼成装置の総称で回転窯ともいうが、通常、直径に比して長さの十分に大きい直円筒型のものをいう。長さが比較的小さい回転円筒型のものは、トロンメル型などと名づけられ、別の取扱いをされることが多い。直径数メートル、長さ数百メートルに及ぶセメント焼成炉が代表的な例である。ロータリーキルンは、普通、水平に対してわずかに勾配(こうばい)をつけて設置され、緩やかに回転させながら、上方より原料を供給し、下方に設けられた燃焼装置から火炎を送る。高温の燃焼ガスは、原料と対向して接触しながら、その反応や予熱に携わる。通常、単一の原料ではなく、複数の原料が用いられるので、原料鉱石はあらかじめ粉砕・調製（水を加えて練り合わされることもある）後、キルン上方より供給される。この原料は、円筒の回転に伴って下方へ移動しながら高温ガスに接触し、予備的な脱水や反応を行いつつ焼成に必要な温度（通常、千数百℃）に至り、焼成される。温度区分は対象物によって異なり、有機高分子材料の焼成は200℃程度で行われる。

［河村祐治］

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