Process and plant for multi-stage flash desalination of water

摘要

The present invention provides a process and a plant for the desalination of salt water in which at least three desalination zones connected in series are provided. In the process brine at elevated pressure is heated in heat exchanger 201 using heated fluid, e.g. steam in line 202, which is cooled and returned to line 203. The hot brine is released into the first desalination zone 205, where water vapour 206 flashes off as the brine is cooled by the reduction in pressure. The vapour is condensed on condensation conduits 207 cooled by the recirculated brine at a lower temperature flowing towards the heat exchanger 207. The condensed water is collected in product water channel 208. The cooled flashing brine and product water cascade into the next desalination zone. An evaporate 216 from an intermediate desalination zone 214, is withdrawn and is cooled and condensed in a heat pump 217 before being returned to the product water channel 218 of the intermediate desalination zone 214. A portion of the flashing brine stream is drawn from the intermediate desalination zone 214 is extracted by pump 219 and mixed with the brine in the condensation conduit 220 upstream of the intermediate desalination zone. The multiple desalination zones are maintained at successively lower pressures from the upstream end of the series to the downstream end thereof.