Separation of zirconium and hafnium
AssigneeAmax Speciality Metal Corporation
InventorDonald R. Spink
Life of this patent
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Abstract
A process is provided for separating zirconium and hafnium tetrachlorides by the direct distillation from their solution in an eutectic mixture of sodium and potassium chlorides. Hafnium tetrachloride and zirconium tetrachloride are provided in adequate purity for direct introduction into reduction units for the production of the respective metals by virtue of controlled ratios of the salt eutectic solvent to the hafnium and zirconium tetrachlorides and by provision of a reflux of hafnium with added increments of the eutectic solvent salt mixture.
Claims13
A continuous process for the separation of the tetrahalides of hafnium and zirconium comprising dissolving a crude feed consisting essentially of hafnium tetrahalide and zirconium tetrahalide in a solvent comprising a near eutectic mixture of zirconium tetrahalide and at least one alkaline metal halide selected from the group consisting of sodium, potassium and lithium to form a first solution, introducing said first solution of an elevated temperature into a distillation tower, withdrawing hafnium tetrahalide vapor from the said solution as the overhead product, adding at least one alkaline metal halide selected from the group consisting of sodium, lithium and potassium to a portion of said hafnium tetrahalide vapor at an elevated temperature to form an eutectic second solution, introducing said second solution into the distillation tower as a reflux, withdrawing an eutectic third solution of zirconium tetrahalide and at least one alkaline metal halide selected from the group consisting of sodium, potassium and lithium as a bottoms fraction from said distillation tower, and separating from said third solution a portion of zirconium tetrahalide.
A continuous process for the separation of the tetrahalides of hafnium and zirconium and for the production of pure zirconium metal comprising mixing crude zirconium tetrachloride containing hafnium tetrachloride with sodium chloride and potassium chloride to form an eutectic salt containing about 65 mole percent zirconium tetrachloride and hafnium tetrachloride, about 29 mole percent potassium chloride and about 8 mole percent sodium chloride, melting the mixture at a temperature less than about 220.degree.C to form a molten salt mixture, feeding the molten salt mixture to a distillation tower and withdrawing pure hafnium tetrachloride vapor as an overhead product, removing a bottoms product from said tower comprising a molten hafnium-free salt containing about 85 percent by weight zirconium tetrachloride, heating said bottoms product to remove a portion of the pure zirconium tetrachloride, reducing said pure zirconium tetrachloride with magnesium to provide pure zirconium metal, recycling the remainder of the bottoms product to said eutectic salt and combining a portion of the hafnium tetrachloride overhead product with a mixture of sodium chloride and potassium chloride to form an eutectic reflux which is introduced to said column.
Dependencies are inferred from the claim text.