PURPOSE: To attain energy conservation and miniaturization, by a method wherein pressurized raw water is preheated to perform the vacuum flash evaporation thereof, and this formed steam and steam generated by heating and evaporating brine are together sucked and compressed while brine is heated and evaporated by this compressed combined steam.
CONSTITUTION: Raw water heated under predetermined pressure by a raw water pump is sucked by a compressor 6 to be reduced in pressure so as to reach the pressure in a steam generation chamber 2 and converted to steam on an evaporation tray 14 by flash evaporation while the formed steam is sucked and compressed along with steam generated through the heating and evaporation of brine by the compressor 6 and the compressed combined steam is raised in a temp. to reach a heat transfer pipe 4 where brine is heated and evaporated at the evaporation temp. thereof as well as steam itself is cooled and condensed by this heat exchange to be taken out to the outside as distilled water. By this method, the conservation in the driving power of the compressor or the lowering in the condensing pressure of emitted steam from the compressor is attained.