WHICH METHOD TO CHOOSE FOR ALKALINE REDUCTION? EITHER IN THE POT ROOM CRUCIBLE OR IN THE CASTHOUSE

摘要

Lithium, sodium, calcium and magnesium may all be reduced efficiently from molten aluminium to very low levels of ppm in the pot room crucible before transfer to the melter/holder furnace and this, within a few minutes; no chlorine is required, only the use of aluminium fluoride salt. Some removal, particularly of sodium, may also be obtained by simply transferring from one crucible to another whilst transporting or delivering molten aluminium, without the introduction of cither gas or salt. On the other hand, these same elements may also be reduced in the holder furnace in the casthouse, using either salts or gases by various means including: manual additions of fluxes; or chlorine lances; or, more recently, rotary gas/flux injectors. Degassers may also be used as in-line treatment for removing alkalines with the use of argon and chlorine.