Boliden Aktiebolag

Karl G Bjorling

Goran Lindkvist

The invention relates to a method for continuously separating a hypoeutectic solution into two parts, of which parts, one comprises practically pure solvent and the other a solution which has a higher content of the dissolved substance than the original solution. In accordance with the invention, the starting solution is held in an elongate vessel at a temperature, which, at least at one end of the vessel, lies immediately above the melting point of the solvent, and cooling elements are caused to move in the vessel towards said one end thereof. The temperature of said cooling elements is alternated to levels above and beneath the liquidus temperature of the solution, so that said elements are alternately coated with a layer of frozen solvent having a lower content of the dissolved substance than the ambient solution, and freed from said coating by melting the coating in a warmer region of the solution, wherewith more solvent than dissolved substance is constantly transported to said one end of the vessel, and the residual solution enriched in the dissolved substance is forced in counterflow towards the other end of said vessel. Solvent and enriched solution is tapped from respective ends of the vessel, while charging to said vessel further solution, at a location where the concentration of the solution is the same as that of the starting solution, thereby to maintain a steady state in the system. The ingoing solution may be a metal alloy, in which case it is divided into two metal melts; an aqueous solution in which case it is divided into water and a more concentrated aqueous solution; or an organic solution, in which case it is divided into a solvent and a more concentrated organic solution.

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Djursholm, Sweden

Karl G Bjorling