Focusing the graphite
Graphite ore is mined using excavating machines that carry dump trucks with raw ore.
The entire extraction process follows a mining plan, facilitating the selection of the most suitable ore for final products.
The deposition of this ore on the feeding plant is systematised to form feeding piles in layers.
The goal is to reduce the natural variability of the ore.
The ore is subjected to successive grinding and a mechanical process separating impurities from the graphite. The mechanical concentration aims for maximum recovery of the graphite present in the ore, preserving its physical features.
The chemical concentration is used to remove the remaining impurities in the previously graphite mechanically concentrated. Nacional de Grafite uses and treats the residues of the chemical concentration in order not to pollute the environment.
Filtering and drying
After the chemical concentration, the graphite is washed extensively with demineralised water, reaching a neutral pH. The remaining moisture is removed in Press-type filters and rotary dryers.
WORKING WITH PHYSICAL PROPERTIES
Screening techniques are used to classify the particles of the concentrated graphite, reaching the desired particle size distribution.
Jet and hammer mills grind the concentrated graphite until it reaches the desired size. The ground particles are classified, enabling control of the particle size distribution of the product generated. The different methods of grinding and classification allow for shaping of the particle, giving the graphite distinct characteristics of density and a specific surface.
In this process, agglomerated graphite grains are produced for use as carburizer and carbon additives.
Due to its extreme anisotropy, the graphite crystal enables salts to be intercalation in its structure. When heated, these salts evaporate, causing the disruption of inter-planar connections, "expanding" the graphite. Nacional de Grafite developed graphite intercalation and expansion processes compatible with the environment.