The thermal anhydrite raw material is obtained by calcinating flue gas gypsum (also called FGD gypsum) at a temperature of at least 700 °C.
The process completely expels the water of crystallisation from the FGD gypsum and the surface of the anhydrite (CaSO4) that is formed is reduced by sintering to ensure a more favourable mixing water requirement. As a moist, particulate FGD gypsum, the thermal anhydrite is directed straight into the economic cycle of the building material industry, and its uniform grain size makes it the exemplary manufacturing solution for many products.
Gypsum and anhydrite rock formations originate from the Permian geological epoch and were formed 200 to 250 million years ago. The solubility of carbonate, sulphate and chloride degraded with time due to the crystallization of shallow seas. Gypsum and anhydrite only differ by half a water molecule before being processed, and by the addition of water, the water-free anhydrite is converted to gypsum.
The extraction of natural anhydrite for the production of flowing screed is carried out only from the purest deposits in quarries and underground. Natural anhydrite is used as a binder in building materials as well as in the fertilizer industry and environmental technology.
Knauf Thermal Anhydrite | ICO 25
FGD Gypsum based crystallized water-free calcinated thermal anhydrite for use in the manufacture of calcium sulphate screed as a binder and filler in industrial applications.
Order information: Bulk, Big Bag and 25 kg bag
Oversize material at 90 μm: < 3 %
Oversize material at 63 μm: < 10 %
Purity: > 90 %
Bulk density: 1050-1250 g/l
Knauf Natural Anhydrite | ICO 24
Finely ground, pure natural anhydrite from underground mining for use as a binder and filler in industrial applications.
Order information: Bulk and Big Bag
Grain size: 10 μm
Oversize material at 90 μm: < 1 %
Oversize material at 63 μm: < 2 %
ph value: 5-6
Bulk density: 1000-1200 g/l
Purity: > 80 %