GB900108A - Improvements in or relating to the separation or partial separation of components ofa liquid medium - Google Patents

Abstract

A crystallizable constituent is separated from a liquid in a number of successive crystallization stages, liquid from an intermediate stage passing to the preceding stage while solid from said intermediate stage is melted and passed to the following stage. A portion of the melted solid may pass back to the said intermediate stage as reflux. The process may be continuous or intermittent. As shown in Fig. 1, a liquid is fed from a valved inlet 15 to form a layer 13 in a rotary cylinder 1 which may be partially immersed in a cooling bath 20 and which has one or more helical blades 2 forming a spiral path along the inner periphery of the cylinder. During rotation of the cylinder, liquid passes to the left while the crystallizable constituent passes to the right in spiral flow, rising as a crystalline layer and returning as a liquid, optionally after being melted by an external heating element 21. In a modification (Figs. 4 and 5, not shown), the heating element is situated within the cylinder in the form of a rotary spiral scraper intermeshing with the <PICT:0900108/III/1> <PICT:0900108/III/2> <PICT:0900108/III/3> <PICT:0900108/III/4> blades 2. In a further modification (Figs. 7 and 8, not shown), the crystalline layer may form on a rotary hollow coil associated with a heated scraper within the rotary cylinder. In a further modification (Fig. 8, not shown), the hollow coil may be associated with a horizontally displaceable U- or V-shaped heated scraper having spaced apertures for return of melted solid. As shown in Figs. 10 and 11, the liquid and crystallizable constituent pass in opposite directions in a zig-zag path formed by wedge-shaped partitions 51 in a trough 50, one end of the trough being cooled by bath 20 while the other end is heated by one of heaters 21. Tipping to produce the desired flow and rocking to alternate the heating and cooling is effected by four hydraulically operated reciprocating rods 53, one at each corner of the trough.