Calcination, also known as de-acidification, describes the expulsion of CO2 from the limestone at approx. 850°C upwards. This process step takes place in the calciner and in the calcining zone of the rotary kiln. The calciner is usually to be found in the form of a cyclone pre-heating tower (formerly LEPOL kiln). The raw meal is heated in this counter-current heat-exchanger. The energy for the calcination reaction must also be introduced here, or via a burner in an additional pre-calciner. Modern pre-calciners already use up to 100% replacement fuels.