Precipitated calcium carbonate is produced using the most economic process existing
today. Limestone is converted into calcium oxide and carbon dioxide by means of
calcination at temperatures in excess of 900°C. To ensure a high level of purity,
the calcination process is carried out using natural gas. After the calcined lime
has been slaked with water, the resulting milk of lime is purified and carbonated
with the carbon dioxide obtained from the calcination process (See reactions bellow).
Following total carbonation, a suspension of CaCO3 results. A cake comprising 40%
- 60% solid matter (depending on particle diameter) is then obtained by filtration.
This filter cake is then dried and subsequently deagglomerated in grinders. Ultrafine
PCC grades are reacted with fatty acids prior to filtration i.e. when still in the
The fineness of the grain, as well as the crystal form (aragonite, calcite), is
controlled by temperature, concentration of reactants and time.
Depending on the chemical composition of the milk of lime used and on the purifying
stages during production, both technical as well as foodstuff and pharmaceutical
grades can be produced.