Investigation and Choice of Materials for the Electrical Insulation of the Steel Bloom of an Aluminum Electrolyzer

Resumo

The growth of the modern aluminum industry is characterized by a search for methods of increasing the capacity of electrolyzers, reducing emissions into the environment, and reducing energy consumption. In the production of aluminum, the specific electricity consumption can be reduced and current efficiency increased by decreasing the distance between the anode and cathode and at the same time reducing the horizontal currents in the molten aluminum. The horizontal component of the current density can be reduced by placing electrical insulation between the cathode carbon block and the bloom on the section ‘crust boundary – projection of the anode periphery on the bottom block’. Heatproof materials with the following properties are technologically most effective and economical for use as electrical insulation: good adhesion to steel, chemical resistance to cryolite-alumina melt, and quite low ultimate strength in compression. Low strength and stiffness are needed because during thermal expansion of the materials in the bottom block during the period of heating the tank to the working temperature with high resistance to compression there is a risk of the load increasing on the carbon cathode block and cracks forming in it. Moreover, such properties of the material will make it possible to decrease the risk of fracture of the cathode carbon block if the volume of the electric-insulation insert increases as a result of the electrolyte penetrating into it. The results of the investigations of the mechanical properties of some heatproof materials for use as electrical insulation of blooms in aluminum electrolyzers at high temperatures are presented in order to optimize the composition.