High temperature distillation process with sea water feed decalcification pretreatment

The performance ratio of a desalination plant can be increased to reach 16–18 by coupling it with a decalcification pretreatment by ion exchange of the sea-water make-up, so making MSF comparable with RO from energetic point of view. A new strong cationic resin DECAL has been tailored; its main features are high selectivity towards the calcium ion and low concentration of the regenerating brine. These characteristics make it compatible with the normal operating range of multiflash plants and very suitable for the above service, when compared with other resins.The optimum coupling conditions of the whole plant, as has been pointed out, lie between 140°C and 150 °C for the top brine temperature and 2 to 2.5 for the brine concentration factor. In these conditions it is possible to operate with sea water-resin bed ratio higher than 20.