Preparation And Properties Study Of Wettable Thick TiB₂ Cathode Coating For Drained Aluminum Reduction Cell

The drained aluminum reduction cell (the drained cell) is attracting more and more attentions from aluminum industry for this new-type cell can markedly decrease the energy consumption of aluminum electrolytic process. A key problem in the development of the drained cell is the preparation of new-type cathode. The aim of this paper is to develop large-thickness, long-life TiB₂ cathode coating that possesses excellent performances needed by the drained cell, such as thermal shock resistance, wettability of liquid aluminum, erosion resistance, antiwear property, sodium penetration resistance, etc. As the mechanical performance of TiB₂ cathode coating prepared with the exising TiB₂ cathode coating preparation technology is not fine, therefore, intensifier and particle grade are put forward to improve the mechanical performance of coating, and large-thickness coating was prepared successfully. Main work and achievements are as follows:(1) Intensifier TA was added to the raw materials to improve the matching property between thick TiB₂ cathode coating and carbon matrix, and its electric property was studied. The results showed that the mechanical performance of coating is improved by adding TA, but the electrical resistivity increased with TA content, so when TA content is close to 6%, it could not only improve the mechanical property of the coating but also fit for alunimum electrolysis.(2) The effect of different partical grades of TiB₂ raw materials, petroleum coke and cathodic powder on the mechanical property of coating was studied with the method of orthogonal experiment and under the direction of particle-grading idea. The results showed that the density of TiB₂ cathode coating changed with its partical grade; the surface of the TiB₂ cathode coating with higher density was betterafter high temperature carbonization; there were no obvious cracks, no delamination and no bond failure.(3) The TiB2 cathode coating was tested in existing 190kA prebake cells. After the TiB2 cathode coating was carbonized by the heating in coke-baking process, its distortion status was checked and then its life was calculated by testing the Ti content in the Al liquid; The industrial indexes of reduction cells such as current distribution, current efficiency, ohmic drop of cell bottom, etc. were tested. The results showed that the combination between coating and carbon cathode lining was well; expected long life could be achieved; the uniformity of current distribution was improved; current efficiency was increased and ohmic drop of cell bottom was lessened. The test on the industrial cells provided useful data and experiences for the future application of TiB2 cathode coating in drained aluminum reduction cells.