Manufacturing process of lime

Lime is manufactured by burning limestone (CaCO₃) in the following steps.

1. Quarrying and selection: pure limestone is quarried and broken into pieces of 50 to 75 mm size.
2. Calcination: the stone is burnt in a clamp or kiln (intermittent or continuous) at 900 to 1000 °C. The fuel is wood, coal or oil.

$$\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$$

3. Cooling and sorting: the quicklime is drawn from the kiln, cooled, and separated from unburnt and over-burnt pieces.
4. Slaking: quicklime is treated with water to get slaked lime, which can be used or stored.

Continuous (vertical) kilns give a better output than clamps. Burning below the correct temperature leaves an unburnt core, and over-burning produces dead-burnt lime.