Patent GB-1354704-A (GB)
Title: Method of separating a volatile component from a solution
IPC: C02F1/10
Filed: 1971-05-05
Abstract: 1354704 Evaporation; desalination of water HYDRO CHEMICAL & MINERAL CORP 5 May 1971 [15 May 1970] 13386/71 Heading BIB Solvent is separated from a solution of a non-volatile solute by submitting the solution to evaporation in the presence of an insoluble liquid (heat transfer liquid) of lower vapour pressure and a surfactant which reduces the interfacial tension between the solution and the heat transfer liquid, and is insoluble in the evaporation residues, the evaporation being carried out so that there is strong agitation of the mixture of solution, heat transfer liquid and surfactant. At least in the latter stages of evaporation, the surfactant is in the form of dispersed solid particles. In order to separate fresh water from brine, the heat transfer liquid may be a hydrocarbon oil such as kerosene or naphtha, and the surfactant may be, sodium lauryl sulphate, a fatty alcohol phosphate, sodium dioctyl sulphosuccinate or sodium dodecyl benzene sulphonate. The surfactant is added in concentrations ranging from 0.05 to 1.0% by weight of the residual brine. In order to desalinate sea water, a mixture of heated sea water, hot oil and surfactant is introduced from mixer 12 into the first flash chamber E 1  of a unit 1 comprising serially-arranged flash chambers E 1 ..E n  maintained at progressively lower pressure, each chamber being connected to a condenser in the series C 1 ..C n . Baffle plates 13 promote turbulence and mixing of the water, oil and surfactant in each chamber, and progressive vaporization of water takes place. The vapours are condensed by contact with a stream of initially cool oil flowing through the condensers in the direction C n  to C 1 . The condensate (desalinated water) and oil flow from C 1  to separator 10; and the separated condensate is cooled by contact with oil in heat exchanger 6. The cooled product water is withdrawn from the base of 6. The residue from E n  is passed to separator 8, and precipitated NaCl is discharged from the base, while concentrated brine and oil are withdrawn through outlets 16 and 20 respectively. The oil is washed with cool sea water in stages 7 a .. 7 n  and, after passing through separator 17, some of the oil is passed to condenser C n  and the remainder is passed to heat exchanger 6. A sludge of surfactant, brine, oil and precipitated CaCO 3 , and CaSO 4  flows from outlet 18 of separator 8 to centrifuge 25 where a thick sludge of surfactant and calcium salts is separated from oil, the latter being passed to washer 7. The separated sludge is passed to mixer 26 where it is mixed with sea water from washer 7. The mixture passes to separator 9 where the sea water dissolves the surfactant, and the insoluble calcium salts settle out. The supernatant sea water, containing surfactant, is passed through heat exchanger 4 where it is heated by contact with oil from separator 10 which has passed through heater 11; the sea water then flows to mixer 12 which is also supplied with further hot oil from heater 11 and with sea water which has been heated in heat exchanger 5 by contact with oil from heater 11. The mixture formed in mixer 12 is supplied to the multi-stage flash unit as already described. A modified apparatus, in which two series of flash chambers are associated with a single series of condenser chambers (Fig. 3. not shown) may be used for the separation of magnesium sulphate and chloride, potassium chloride and sodium bromide from sea water.