Experimental Study On Anode’s Bubbles Behavior In Aluminum Electrolysis

The technical transformations of aluminum reduction cells mainly include new type anodes and cathodes structure in recent years. The new type anodes mainly include slotted anode and perforated anode; the new type cathodes mainly include slotted cathode and cuboids’ cathode. It could further lower the polar distance thereby reducing cell resistance which increases the current efficiency after using the new technology. The reasons of this phenomenon are researched by scholars at home and abroad, but only few results are available yet since the flow of melt is extremely complex and the process is taking place in a high temperature and closed environment. Therefore, it is necessary to study deeply on the causes of this phenomenon in order to undertake technical reformation and continually find out the energy saving potential of cells.The gas is in the form of bubbles growing, merging and departing from the anode in aluminum electrolysis. Due to the bubbles have a great deal of resistance, so the cell resistance is increased when the bubbles attached to anode; the ejection of bubbles would disturb the melt (the molten electrolyte and aluminum) in cells. On the one hand, the aluminum would react with the anode gas which can reduce the quality of aluminum because of the fluctuation of aluminum; what’s more, when the fluctuation of aluminum is very severe, it’s short circuited when the aluminum contact the anode in a lower polar distance, yet the aluminum would be splashed because of the great heat which is produced by the powerful DC, all of these could reduce the current efficiency. On the other hand, the fluctuation of molten electrolyte is benefit to the alumina dissolution and diffusion in cells, so that the concentration gradient of the electric tank of alumina is reduced; it’s also benefit to the convection heat transfer between electrolyte and furnace wall.In conclusion, it is extremely important that understanding and acquiring the behavior of anode’s bubbles in order to undertake technical reformation of cells. Therefore, we designed the model of the aluminum electrolysis experiment which can judge bubbles behavior from the changed current signals. The results show:1) the behavior of bubble’s in electrolytic cell is, influenced by concentration, distance, angle and the anode’s slot, the maximum transverse dimension of the bubble is about20mm, all the bubbles sizes are under5mm when the anode is tilted and slotted.2) Between the size of the bubbles and the escape velocity is inversely proportional.3) With the fluctuations in the frequency of the current signal increases, the bubble detachment rate is increasing, the maximum frequency current signal is about0.05Hz and the minimum frequency is about0.025Hz.We preliminary obtained the connection between bubbles behavior and current signals through the observation of experimental phenomena and current signals wavelet analysis which provides reference for undertaking technical reformation of aluminum reduction cells.