Low-temperature aluminum electrolysis process and electrolyte

Abstract

The invention relates to a low-temperature aluminum electrolysis process and electrolyte. The electrolyte consists of Na3AlF6, K3AlF6, Al2O3, AlF3 and LiF; and the electrolysis temperature is between 850 and 910 DEG C, the coefficient of an anode effect is smaller than 0.1 time / tank day, and the anode current density is 0.5 to 1.2 A / cm2. The primary crystal temperature of the electrolyte adopting the component formula is low and changes comparatively slowly along with the changes of the components in favor of solving the problems of uneven tank bottom current, unstable tank voltage and the like caused by sharp raising of the primary crystal temperature of a melt and cathode crusting due to directional migration of Na+ and cathode enrichment. Besides, The K3AlF6 in the electrolyte can effectively increase the capability of the melt for dissolving the aluminum oxide, and solve the problem of deposition of the aluminum oxide at the bottom of a tank. Because the electrolysis temperature is lower, the heat loss of an electrolytic tank can be greatly reduced, and the energy-saving current efficiency is high. The low-temperature aluminum electrolysis process is simple and is easy to operate, the electrolyte has reasonable components, and the low-temperature aluminum electrolysis process can effectively reduce the aluminum electrolysis temperature, inhibit the cathode crusting in the process of aluminum electrolysis, improve the current efficiency of the aluminum electrolysis and reduce the energy consumption of the aluminum electrolysis, is suitable for industrial production, and can replace the conventional aluminum electrolysis process.

Description

technical field [0001] The invention discloses a low-temperature aluminum electrolysis process and an electrolytic solution, which belong to the technical field of electrochemistry, and particularly relate to the technical field of molten salt electrochemical electrolysis. Background technique [0002] Although the melting point of metal aluminum is only 660.2°C, since the current aluminum electrolysis industry continues to use the Hall-Héroult molten salt electrolysis method, Na3AlF with a high melting point is used 6 -Al 2 o 3 In the electrolyte system, the electrolysis temperature is usually 930°C to 950°C, which not only leads to high energy consumption and heat loss per ton of aluminum, but also deteriorates the working environment. Therefore, reducing the electrolysis temperature, realizing the smelting and production of primary aluminum at a lower temperature, further reducing the energy consumption of aluminum electrolysis, and improving the working environment hav...

AI Technical Summary

Problems solved by technology

However, studies have shown that in Na 3 AlF 6 -AlF 3 In the melt, Al 2 o 3 The solubility and dissolution rate in the electrolyte decrease with the decrease of molecular ratio and electrolyte temperature, too low dissolution rate will lead to the addition of Al to the electrolytic cell 2 o 3 If it cannot be dissolved and diffused into the electrolyte in time, precipitation will occur at the bottom of the electrolytic cell, which will make the cathode conductive unevenly and affect the normal operation of the electrolytic cell.

[0004] At the same time, during the electrolysis process, due to the Na + The directional migration and enrichment of the cathode can easily cause the primary crystal temperature of the melt in the cathode area to increase. When electrolysis is performed at a lower temperature, it is easy to cause the phenomenon of "cathode crusting", which in turn leads to uneven distribution of cathode current, and the electrolytic cell Increased voltage fluctuations prevent the electrolysis process from proceeding normally

Although the phenomenon of "cathode crusting" can be effectively suppressed by increasing the superheat of the electrolyte melt, that is, increasing the electrolysis temperature, excessive superheat will make it difficult to form the furnace side of the electrolytic cell, which will affect the stable operation and technology of the electrolytic cell. Economic indicators, will also aggravate the volatilization of electrolytes