Study On Improving The Current Efficiency Of Aluminium Cells

A lot of research on current efficiency has been conducted in China and abroad, but most of the research was experimental data or was conducted on relatively old cells. With the development of the electrolytic technology especially the advanced 190kA reduction cells, its bus configuration, the method of inputing current and the lining constructure have been changed a lot so the effect of temperature, the distance of anode and cathode(ACD) and the alumina concentration are required. The factors which influence the current efficiency(CE) of the reduction cells were studied based on 190kA pre-baked cells of Shanxi Guanlu.CE is a multi-variable parameter, the improvement of CE has a close relation to the control and technological system and the operation techniques. It was not only affected by the cell temperature, the alumina concentration, the ACD, the design of magnetic field and operation, but the mutual cooperation and adaption of each technical and operational condition is more important. In this paper, the effect of several parameters including the hearth of cell, the cell temperature, the ACD, the alumina concentration and the molar ratio on CE was studied firstly. The results showed that the effect of hearth was 2.1-4.3%. The CE increases steadily at the ACD of 4.0-4.8cm and it reduces a little when the ACD is bigger than 4.8cm. Then the effect of the variation of each parameter on other parameters' variation was researched and the effect of operation mode on each parameter was quantitated. The reasonable technical condition was found within a stable and firm hearth: the metal height is 19-21cm, the bath height is 18-20cm, the molar ratio is 2.3-2.4, the average cell voltage is 4.19V and the ACD is 4.0-4.8cm. The effect of anode changing on cell temperature was 6-8℃and it will increase the alumina concentration by 0.7-1%. The temperature compensation was adopted when the anode was changed and the adaption between the metal height and hearth was adjusted using the variation of cell voltage after tapping. Several viewpoints were put forward including the ACD has something to do with the CE curve and the heat stability of the experimental cell.This program fully optimized the electrolytic conditions and improved the stability of the reduction cell which would make every parameters in a reasonable range and be beneficial to the increase of CE. The CE of 190kA series achieved to 94.12% which was 1.22% higher before amelioration and this has been on top in our country.