Subject: Cement is manufactured in a so-called turn-tube oven. Before the raw material gets into the turn-tube oven it is prepared in the most visible parts of a cement factory, the heat exchanger towers. Here the raw material is pre-heated in cyclones - steel cylinders with a diameter of 4 to 6 m - by hot exhaust gases up to about 1000 °C and partly calcined, i.e. de-acidified. After this preparation the material is transferred directly into the turn-tube oven where the actual burning-process takes place. The oven itself is a about 50 to 70 m long, slightly tilted steel tube with a diameter of 4 to 5 m which turns around its longitudinal axis (max. 20 rpm). Here the oven flour minerals, converted with this chemical process at 1450 °C, will be converted into a sintered clinker mineral – which is basically Calcium-Silicate-Crystals.
