What is the difference between electrolytic alumina and cryolite (sodium fluoroaluminate)?

Different fluoride salts have different functions in electrolytic aluminum smelting, which is generally used to reduce the initial temperature of the electrolyte and optimize the electrolyte composition.
For example, magnesium fluoride, aluminum fluoride can separate carbon residue and improve the electrolyte conductivity.
When the molecular ratio is high, fluoride is added to adjust.
When the molecular ratio is low, the addition of sodium fluoride or soda can be adjusted.
Aluminum fluoride added methods: aluminum fluoride should be added in the middle of the alumina surface shell parts, after the first to add a layer of alumina after processing, the aluminium fluoride evenly sprinkled on thin shell, and then with insulation material.
Next time processing, can not pick material, fluidized aluminum with face shell to enter the groove.
Add fluoride notes: (1) fluoride can't be added to the electrolyte surface, nor is it near the fire eye and anode.
(2) it is unsuitable to process aluminum fluoride before aluminum.
(3) in order to reduce the loss of aluminium fluoride, aluminum fluoride can be mixed with cryolite, aluminum fluoride in electrolytic cell after the aluminum processing add it is best for the first time, at ordinary times can be added in the electrolytic cell little head processing.
The ice crystal is the first to dissolve the alumina well and the melt can be electrolyzed under the melting point of pure crystal crystal.
And liquidity is better.
Second, under the electrolytic temperature, cryolite, aluminum oxide liquid density is 10% smaller than aluminum liquid density, so the liquid aluminum electrolytic out can be deposited on the cathode electrolyte, which can reduce the oxidation of aluminum loss, and greatly simplifies the structure of the aluminum electrolytic cell;
Thirdly, the crystal has good conductivity.
Fourth, there is no metal impurities that can be corrected by aluminum to ensure the quality of aluminum.
At present, crystal is the most ideal flux in aluminum electrolysis production.

The chemical composition of ice crystals used in general aluminum electrolysis should meet the requirements of national level 2.