Effects of anthracite calcination and formulation variables on properties of bench scale aluminum smelting cell cathodes

Several anthracites were calcined at temperatures ranging from about 1100 to 2300°C and bench scale cathodes fabricated, baked, and tested for electrical resistivity and expansion during electrolysis. Cathode electrical resistivity did not decrease much with increasing anthracite calcination temperature to about 1800°C but decreased sharply there-after. Cathode expansion during electrolysis was inversely proportional to anthracite calcination temperature to about 2000°C. Electrical resistivity generally decreased during test cell operation. A correlation between anthracite properties and cathode properties for anthracites calcined at 2100°C could not be made. With a commercial electrically calcined anthracite, the finer of two aggregate sizings resulted in cathodes with superior properties, and properties generally optimized at a binder level producing about a zero volume change during baking.