Improvement of the service life of cathode blocks in aluminium reduction cells using low-temperature titanium diboride

The present study is aimed at elucidating the possibility of increasing the electrical conductivity of cathode blocks, comprising the reduction cell bottom in aluminium production, as well as examining the process of low-temperature synthesis of titanium diboride for subsequent cathodic application. In order to study the phase transitions of the initial and modified TiO₂ obtained in different atmospheres (argon, vacuum and air), the thermogravimetric analysis method was used in combination with the X-ray diffraction method for determining the composition of the samples under study. Modification of the cathode block was carried out through the stage of preparing a carbon-graphite sample with the addition of low-temperature TiO₂ in amounts up to 15% wt. The electrical conductivity of the experimental cathode block samples was measured by an installation ensuring their static fixing with an Elitech MM 300 multimeter. The carried out thermodynamic calculations of the interaction reactions between the main titanium- and boron-containing components demonstrated the theoretical possibility of obtaining TiO₂. At a temperature of 1050°C and a synthesis duration of 4 h, the yield of TiO₂ powder equal to 97% was established to be achieved. Under calcination at 1000-1500°C for 4 h and subsequent graphitisation (at 2200°C for 24 h), laboratory samples of cathode blocks modified by low-temperature TiO₂ were obtained. When comparing the electrical conductivity of the modified and traditional cathode blocks, the samples with a content of 12.5% wt. of TiO₂ were established to have 35% less electrical conductivity (32 μΩ·m). On the basis of laboratory studies, the maximum extraction of 97.5% under the conditions of low-temperature titanium diboride synthesis was determined to be obtained at a temperature of 1050°C and a duration of 180 min in vacuum (0.101 MPa). On the basis of the thermodynamic calculations and conducted experiments, a principal technological scheme for the low-temperature synthesis of titanium diboride is proposed. The optimal content of TiO₂ in the cathode block aimed at increasing its electrical conductivity varies from 7.5 to 12.5% wt. The introduction of low-temperature TiO₂ into the cathode blocks leads to reduced energy consumption of reduction cells equal to 986 kWh/t or savings of 7.5%.

primary aluminium production, reduction cell, cathode block, titanium diboride synthesis, thermodynamics, electrical resistivity