GB774269A - Processes for separating components of fusible materials - Google Patents

Abstract

<PICT:0774269/III/1> <PICT:0774269/III/2> <PICT:0774269/III/3> A process for treating a solvent-solute system to produce a material having a desired concentration of minor and major ingredients comprises melting in a plurality of receptacles material having at least two ingredients, causing solid material to transfer in one direction by freezing a portion of the material on a carrier in a receptacle, transferring the carrier and the frozen portion to another receptacle and melting the frozen portion therein, causing a reflux of molten material in the direction opposite that of solid transfer, withdrawing from the extreme receptacle in the direction of reflux flow a portion of the material as waste, withdrawing from the extreme receptacle in the direction of solid flow a portion of material as product and adding starting material to an intermediate receptacle. The process may be used to purify a major ingredient, to separate a minor ingredient or for the separation of two or more desired ingredients. In the form of apparatus shown in Fig. 2 for carrying out a purification process, a portion of the material in each tank 9-14 is frozen on to a carrier (not shown) by passage of cooling fluid through the carier. The carriers and the frozen portions are removed simultaneously from the tanks and each placed in the next tank up to the refiner (i.e. to the right) which causes a reflux overflow of material from each tank to the next tank below it. The frozen material introduced into each tank melts and fresh material is frozen on the carrier by further passage of cooling fluid, each carrier being again moved up the refiner. As the step-by-step operation continues, liquid material is fed into an intermediate tank e.g. tank 11, liquid refined material is withdrawn by a pipe 17 from the tank 14 and waste overflows from the tank 9. Although frozen material is introduced in the top tank with the carrier entering it, none is removed when that carrier is withdrawn. The flow of product through the pipe 17 may be controlled by a valve 15 or by regulating the amount of solid material transferred from tank 13 to tank 14. The liquid reflux may also be via tubes instead of overflow, the level of liquid in each tank in this case being the same. In another form of apparatus described, Fig. 3, the tanks 41-46 are arranged in circular fashion and the carriers are transferred from tank to tank by raising and rotating the support 47 by means of a handle 56. The reflux in this form is again by overflow but forms embodying cavities which transfer reflux liquid from tank to tank as the carriers are rotated are also described. As an alternative mode of operation of the type of apparatus shown in Figs. 2 and 3, instead of moving the carriers continuously up the refiner the carriers may be moved with a reciprocating motion, the sequence then being solid material frozen on the carriers, carriers and frozen material withdrawn and advanced to the next tank, the transported material melted, the carrier withdrawn and returned to the original tank, fresh material frozen on the carrier and so on. In this case, one tank more than the number of carriers is required. The coolants used for the carriers may be gaseous or liquid e.g. water, mercury or other molten material and the carriers themselves may be ducted bars or coils. Hot liquid or gas may be passed through the carrier bars to assist melting of the solid material. In two further forms of apparatus described, in which coolant is not passed through the carriers and freezing of the transfer material occurs when the carriers emerge in the cooler atmosphere, (a) the carriers 86 (Fig. 6) up supported from a moving belt 85 and thus enter and leave the tanks 87...91 in turn or (b) the carrier consists of a single metal spiral which rotates and moves axially. The process may be performed under an inert gas, under vacuum or in the case of volatile solvents under a parital pressure of steam. The tanks may be heated in gas or electric furnaces, water or oil baths or by inductive heating. The materials which it is stated may be refined are: metals (see Group II); silicon; table salt; organic and viscous materials. In certain cases, the separation of two materials A and B is facilitated by adding to them a solvent C; the products are then (A + C) and (B + C). Each of these products may be further refined e.g. by the present process or, in the case of comparatively volatile solvents, by evaporation to obtain the required constituent. Specification 769,673 is referred to.