Composition and characteristics of electrolyte of aluminium electrolyte

Aluminum electrolyte is the core of aluminum electrolysis. It is the high temperature melt between the anode and cathode. The electrolyte is mainly used as solvent and alumina as solvent.Because of cryolite and aluminum oxide containing a certain amount of impurities, and in the electrolytic production to improve the physical and chemical properties of electrolyte, also add some additive to the electrolyte, so the electrolytes on the industrial production is composed of a variety of ingredients.The industrial aluminum electrolyte usually contains ice crystals (about 80%), aluminum fluoride (9%~13%) and alumina (1.5%~ 3.5%), and additive fluoride, magnesium fluoride and lithium fluoride (5%~ 7%).

The use of cryolite as solvent for melting alumina is because it basically meets the needs of aluminum electrolysis.It has the following characteristics:

(1) molten cryolite can better dissolution of alumina, alumina dissociated into ions and electrochemical reaction can be carried out, and at the beginning of the composition of electrolyte temperature below the melting point of cryolite crystal, thus reducing the alumina electrolysis reduction temperature.

(2) under the electrolytic temperature, molten electrolyte density is about 10% lower than the density of aluminum liquid, it can be a very good floating above the liquid aluminum electrolytic out, this simplifies the cell structure, reducing the loss of the oxidation of aluminium, is advantageous to the electrolytic process.

(3) the molten electrolyte has good liquidity, under normal production conditions, conducive to the separation of aluminum and electrolyte, gas discharge, make the electrolyte temperature and composition in each part of the grooves are evenly.

(4) molten electrolyte has good conductivity and thermal conductivity.

(5) cryolite and solid electrolyte basically do not absorb water and are not volatile, reducing the consumption of electrolytes and ensuring the relative stability of electrolyte components.

The above properties of the crystalline alumina melt are not possessed by other substances.Therefore, it is advisable to use the crystal - alumina fluoride - fluorized system as electrolyte in aluminum electrolysis production.