Wear At Room Temperature And Effects Of KF And LiF On Penetration In Carbon Cathode In Aluminum Electrolysis

Erosion of molten aluminum and penetration of alkali metal are the main reasons of cathode block damage in the process of aluminum electrolysis. Reducing the penetration of the electrolyte can prolong the life of cells. Enormous amount of potassium oxide and lithium oxide in home-made alumina will lead to enrichment of lithium salt and potassium salt in the electrolyte. Potassium salt will particularly corrode the cell. Based on six types of cathode block provided by a foreign company, this thesis studies the resistance to physical wear at normal temperature, resistance to sodium and electrolyte penetration in the system of Na3AlF6-Al2O3-AlF3-KF-LiF, which can provide a basis for the selection of cathode materials and prolongation of cells.The physical and chemical properties of six kinds of cathode carbon blocks from a foreign company are measured, including resistivity, porosity, ash content and graphitization degree. According to the results, A and B are the cathode carbon blocks based on anthracite; C is semi-graphitic cathode carbon; D and E are semi graphitized cathode carbon; F is graphite carbon block. And the degrees of graphitization of this six kind of cathode carbon blocks is 91%、92%、93%,79%,82% and 94%, respectively.The anti-wear performance of six kinds of cathode carbon blocks were studied based on the simulation experiments at room temperature. Results show that wear rate is positive correlative with time and slurry velocity and the anti-wear performance of the cathode carbon blocks based on anthracite, semi-graphitic, semi-graphitization and graphite carbon blocks decreases in order.Penetration-resistant properties of cathode block were tested in Na3AlF6-Al2O3-AlF3-KF-LiF system. It is implied that LiF can restrain alkali metal penetration and KF can have an adverse effect.