Calcination characteristics of oyster shells and their comparison with limestone from the perspective of waste recycling

This study investigates the calcination characteristics of Taean and Tongyeong oyster shells and limestone and the factors affecting them from the perspective of waste recycling. Regardless of the differences in the thickness of each layer composing the two oyster shells, with the Taean oyster shell having a relatively thicker prismatic layer, significant differences were observed between the limestone sample and oyster shell samples. Thermal analysis and X-ray diffraction studies showed that the calcination process of calcite in both oyster shells is similar and is completed at a lower temperature than that in limestone. The differences observed can be ascribed to the texture of calcite in the samples. Oyster shells comprise small prisms, foliated laths, and irregularly shaped folia of calcite with a loose texture, whereas the texture of calcite in limestone is crystalline and compact. The calcination process of oyster shells was completed in a shorter time than limestone. With increasing calcination time and temperature (over 800–850 °C), the recrystallization of the particles increased the particle size and decreased the surface area of the samples. Generally, the specific surface area of calcination products from limestone is higher than that of the oyster shells due to the texture of calcite.