calciner

A calciner is an industrial furnace or reactor used to calcine a solid material, i.e., to heat it to high temperature in order to drive off volatile components or induce a chemical decomposition. Calcination is typically performed in controlled atmospheres, often with limited oxygen. Common purposes include converting limestone to lime (calcium oxide) and releasing carbon dioxide, as well as preparing feed material for further processing in a kiln or reactor.

There are several calciner designs, chosen for material type, residence time, and energy efficiency. Rotary calciners use a long heated rotating cylinder in which material gradually moves through the hot zone. Shaft calciners operate with material moving through a vertical or inclined shaft. Flash calciners handle fine powders with rapid gas heating, while fluidized-bed calciners use a suspended bed for fast heat transfer. Construction materials and refractory linings are selected to resist high temperatures, abrasion, and chemical attack. Calcination temperatures commonly range from about 900°C to 1200°C, with limestone calcination typically around 900–1000°C.

Common applications include cement and lime production. In cement plants, calcination is part of the process to decompose raw materials and prepare reactive compounds, often via a precalciner unit that partially calcines material before the main kiln stage. In lime production, limestone is calcined to quicklime. Calcination is also used to dehydrate gypsum to plaster of Paris and to remove volatiles in various chemical processing operations.

Environmental and operational considerations include high energy demand and the management of exhaust gases containing dust and CO2. Modern calciners often employ heat recovery and emission controls, and require materials and systems designed for high-temperature, corrosive, and abrasive conditions. Safety, process control, and maintenance are essential components of efficient operation.