GCC is made by just crushing, grinding and powdering the lumps.
Manufacture of PCC involves following chemical changes.
- Calcination:Limestone is heated at about 1000-degree centigrade temperature in a Kiln to produce quick lime.
CaCO3+ Heat → CaO (Lime/quick lime) + CO2
- Hydration/slacking:The quick lime pebbles are mixed with water in a calculated ratio to form hydrated lime slurry, called milk of lime.
2CaO + 2H2O → 2Ca(OH)2
- Carbonation: Milk of lime slurry is then treated with CO2 evolved during calcination process and convert back to CaCO3.
Ca(OH)2 + CO2 → CaCO3 + H2O
- Filtration and Drying: The CaCO3 formed is in slurry form (some application uses as slurry) which is then filtered and dried to powder form.
The size and shape of PCC is controlled and other impurities are removed during the process. Hence PCC has more advanced applications as compared to GCC.