1,027,064. Concentrating solutions by freezing. DESALINATION PLANTS (DEVELOPERS OF ZARCHIN PROCESS) Ltd. Oct. 24, 1962 [May 16, 1962], No. 40286/62. Heading F4H. [Also in Division B1] In a flash evaporative solution purification process additional ice is formed, by direct or indirect contact with a refrigerant, either in the solution before it is flash evaporated or in the concentrated solution leaving the flash evaporator to make more ice available for condensing vapour produced in the evaporation step. As shown, sea water from an inlet pipe 10 is passed through a deaerator 12 and a heat exchanger 16 to a cooling unit 63 in which part of the solvent is frozen, the brine-ice slurry being then supplied through a pipe 18 to an evaporating chamber 20 where more ice is formed. The unit 63 comprises a cylinder having refrigerant passages formed in its walls, which are corrugated, and a rotary scraper for removing ice from said walls (Figs. 3 and 4, not shown). Water vapour is withdrawn from the evaporating chamber 20 by a centrifugal compressor 54 while the resulting ice-brine slurry is passed through a line 25 to a washer 26. The ice forms a rising column in the washer and is washed with product water supplied to the top of the column through a spray 38, waste brine being expelled through a filter 28 into a collecting chamber 32 from which it is pumped through a line 78 to the heat exchanger 16. Part of the brine in line 78 is supplied through a line 86 to the evaporating chamber 20. A scraper 34 at the top of the washer 26 supplies the ice to a vacuum chamber 36 where product water from a line 42 is added, the ice-water mixture being then supplied by a pump 44 through line 46 to an annular condensing chamber 50 which is defined between the evaporating chamber 20 and an insulated jacket 52. The ice in the chamber 50 is contacted with the vapour from the outlet 58 of the compressor 54 thus melting the ice and condensing the water vapour to form product water which is withdrawn by a pump 60. Part of this water is supplied through line 40 to the spray 38, part through line 42 to the chamber 36 and the remainder to the heat exchanger 16 through line 62. The water leaving the heat exchanger is supplied through a line 80 to a storage tank 82 from which it may be withdrawn by a pump 118 and supplied through a line 119 to cool and lubricate the motor 120 of the compressor 54. Water is returned from the motor to the tank 82 through line 121. In one modification (Fig. 5, not shown) the auxiliary ice-making unit 63 is located in a bypass line which receives part of the brine from the line 18 and supplies ice and brine from the unit 63 to the bottom of chamber 20. Alternatively, the unit 63 may be included in the icebrine discharge line 25 from the chamber 20 (Fig. 6, not shown).