calcinated

Calcinated, or calcined, describes a material that has undergone calcination, a high-temperature treatment used to drive off volatile components, dehydrate, or induce a thermal decomposition to form a different mineral phase. Calcination is typically performed in air or limited oxygen at temperatures chosen to achieve the desired chemical change without melting the material.

The process involves heating to a material-specific temperature for a period of time. In hydrated minerals, water is removed; in carbonates, carbon dioxide is released, leaving oxides such as CaO from CaCO3. The result is mass loss, altered mineralogy, changed reactivity, and often increased porosity.

Common applications include lime production (calcined limestone to quicklime), cement manufacturing (high-temperature calcination in kilns to form clinker), and processing of calcined clays (metakaolin) for ceramics and cements. Calcination is also used to activate carbon, prepare catalysts, and modify the properties of ceramic and refractory materials. It is distinct from roasting, which typically involves heating ores in air primarily to promote oxidation of metals rather than dehydration or decomposition.

Equipment and measurement: calcination is carried out in furnaces such as rotary kilns, shaft kilns, or fluidized-bed reactors. End points are monitored by temperature, residence time, or mass loss; thermogravimetric techniques can quantify decomposition. Off-gases commonly include water vapor and carbon dioxide, making ventilation and emission controls important.

Safety and environmental considerations focus on high operating temperatures, dust generation, and the release of gases. Proper containment, ventilation, and energy management are important in industrial calcination.