MOLTEN SALT EXTRACTIVE DISTILLATION PROCESS FOR ZIRCONIUM-HAFNIUM SEPARATION

摘要

Improvements are described to a process in which the extractive distillation separation of zirconium or hafnium may be accomplished using mixtures of fused alkali metal or alkali metal and alkaline earth chlorides as the solvent. The solvent composition is adjusted to provide a low-melting eutectic, permitting recirculation of the stripped solvent in the liquid phase, as well as reducing the temperature required for thermal stripping (reducing the corrosivity of the fluid). Stripping of the bottoms is accomplished at least partially by direct electrolysis of the bottoms stream, producing the zirconium-free salt recycle stream to be transferred to the top of the column, and at least partially eliminating the need for chemical reduction of the tetrachlorides to metal (a costly process generating undersirable waste streams). Regeneration of the reflux is accomplished in a presurized condenser system, of one or more stages, with all material transport to be done in either the liquid or vapor states.