塩焼き工程における石灰石中不純物の挙動 Behavior of Impurities in Limestones during Calcination with Sodium Chloride
A behavior of metal impurities in various limestones during the calcination with sodium chloride has been investigated to clarify the chemical effect of sodium chloride additive in the production of calcium oxide. The calcination of the limestones has been carried out at temperature range from 900 to 1200°C under air (oxidation) or carbon monoxide (reduction) atmosphere. Though a small amount of iron (III) oxide was changed to iron chloride under the oxidizing atmosphere, the removal of iron (II) oxide based on vaporization was not observed. However, under the reducing atmosphere, a large amount of iron (III) oxide was removed as FeCl<SUB>2</SUB>.<BR>When the mixture of the limestone (Fe<SUB>2</SUB>O<SUB>3</SUB> : 0.12%) and sodium chloride with the molar ratio of Fe<SUB>2</SUB>0<SUB>3</SUB> : NaCl=1 : 10 was calcined at 1100°C for 1 h, 41.0% of iron was removed. During the calcination process, sodium chloride was found to change partially Na<SUB>2</SUB>CO<SUB>3</SUB> which being fusible as an eutectic mixture with excess sodium chloride. The other metal impurities in the limestone such as zinc, lead, copper, manganese, chromium were removed as chloride or metal state under the reducing atmosphere depending on each intrinsic m. p., b. p. and vapor pressure. On the other hand, alminium and silicon impurities were not removed and remained in the resulting calcium oxide as aluminosilicates. It was concluded that there are many factors affecting diversely the removal of impurities such as crystal grain size, crack, clay mineral content of the limestone as well as the reaction conditions such as calcination temperature and time, amount of sodium chloride additive and calcination atmosphere.
- 無機マテリアル : セッコウ・石灰・セメント・地球環境の科学 = Inorganic materials
無機マテリアル : セッコウ・石灰・セメント・地球環境の科学 = Inorganic materials 4(266), 13-19, 1997-01
The Society of Inorganic Materials, Japan