Improvements in methods of distillation

Abstract

Abstract In distilling liquids in an apparatus of the kind wherein the liquid to be distilled is spread in a thin layer over a surface of a heat-conducting vapour barrier by means of one or more movable wipers which are repeatedly swept across that surface while heat is applied to the opposite side of the barrier to evaporate the liquid, the speed of movement of the wipers and the resilient force urging them against the vapour barrier are correlated so that almost complete evaporation of the liquid occurs between successive wipings. Preferably the vapours produced are compressed and condensed on the opposite side of the vapour barrier so that no further heat is necessary to effect evaporation and no further cooling is necessary for condensation. The film of distil <PICT:0856489/III/1> <PICT:0856489/III/2> p <PICT:0856489/III/3> <PICT:0856489/III/4> <PICT:0856489/III/5> <PICT:0856489/III/6> land, when spread on a vertical surface, is also preferably so thin that there is substantially no flow under the influence of gravity. In Fig. 1 the distilland, such as sea water, is supplied by pipe 9 to a rotating supply member 14 arranged to supply distilland in advance of the wipers 17 moving over the inside surface of cylinder 5 which forms the vapour barrier. The supply member and the wipers are both driven by rotor 16. Vapours leave by openings 22, are compressed by a compressor 21 and condensed on the outer surface of the cylinder 5. Excess distilland leaves by opening 24 and distillate by opening 25. A number of cylinders may be arranged in a single condensing chamber served by separate compressors or a communal compressor. Drops of condensate forming on the outside of the cylinders may be dislodged by means of circular magnets 54 (Fig. 15) made to revolve by magnets 55 arranged on the rotor 16. The outer magnets are supported by troughs 57 having holes 58. Members 63 may also be provided to prevent condensate flowing over the magnets. In an alternative arrangement, (Fig. 19), the vapour barriers are plane vertical members 124. Distilland is sprayed on to the evaporating surfaces by sprays 104 and both the evaporating and condensing surfaces may be wiped by rotating vanes 122. Several different types of wiper are illustrated including one made in several sections (Fig. 8), which more easily accommodates irregularities in the cylinder, one in which the vapour barrier is flexible and is distorted by the wipers (Fig. 11) and one incorporating its own distilland feed (Fig. 9). The cylinder may be made of flexible material which is distorted by the wipers. Film thicknesses may be up to 0.002 inch when distilling sea water.

Inventors

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