Graphite and diamond are the two naturally occurring forms of the element carbon © and are mined. Graphite, as natural graphite, was already known in the old ages as a mineral with a typical crystalline structure. Graphite obtained technical importance only a hundred years ago, when E.G. Acheson successfully produced synthetic graphite in large dimensions and shapes. US-patent 542 982 from December 17, 1895 describes the graphitisation of carbon material in an electrically heated resistence furnace, This so-called electro graphite gained increasing use in the, at that time, still young electric industry as current-conducting electrodes due to its excellent electric conductivity.
Graphite can be manufactured from almost any organic material that leaves a high carbon reside when heated in the absence of air. Graphite can come as fine-grained or coarse-grained material. The theoretical density of mono crystalline graphite is 2,26 g/m3. Graphite has a hexagonal layer lattice structure.
Disadvantages of graphite
• Mechanical data lower than anthracite
Mechanical wear
• High thermal conductivity
Longer electrical preheating time
Dissipation of more heat into ramming paste
• Change in current distribution
Increased horizontal currents in the metal pad
• Larger differential expansion
Collector bars can move in the slot after cooling
Baked carbon
Baked carbon is a product manufactured from pitch, carbon black or other raw materials and binders and has a similar hexagonal layer lattice structure to graphite, but this is a less perfect one.
Graphite is a material which has mechanical properties cose to ceramics. Its properties are excellent thermal stability, chemical resistance and high electrical conductivity. It is thus widely used in the field of electro-metallurgy. The particle size of the solids used for production plays an important role as it strongly influences the final properties.
Graphite has been employed in chemical process equipment construction for more than 60 years. In this sector, its applications are determined in the first place by its chemical and physical properties and in the second place by its suitability as a material of construction for equipment.
Advantages of graphite
1) Low electrical resistivity
- Lower cathode voltage drop
- Less energy consumption
2) High thermal conductivity
- Uniform temperature distribution
- Less sludge deposition on cathode surface
3) High thermal shock resistance
- No rodding cracks
4) Low sodium uptake
- No cathode laminations
Result: Higher pot amperage / pot metal productivity
Rapport expansion curves
