Patent ID: 7112262

Claim:
A device for downward flow evaporation of a liquid substance and subsequent condensation of the vapor formed, comprising: a) a plurality of vertical evaporator tubes housed side-by-side in a common casing; b) a distributor tank which is arranged above the evaporator tubes and from which the substance contained therein can be fed to the evaporator tubes with production of a film of the substance which runs down the tube surface of said evaporator tubes; c) a heat exchanger arrangement arranged in the casing and having a plurality of vertical condensation tubes having a surface upon which the vapor can be condensed; d) receiving means which are housed below the evaporator tubes and below the condensation tubes in the casing and which separately receive unevaporated concentrate of the substance which runs down the tube surface of the evaporator tubes or condensed distillate of the substance which runs down the tube surface of the condensation tubes, wherein the evaporator tubes and the condensation tubes are arranged coaxially one inside the other in pairs, e) an obstacle-free working space defined between the evaporator surface formed by the tube surface of the evaporator tubes and the condensation surface formed by the tube surface of the condensation tubes being coaxially opposite one another and spaced apart from one another by an obstacle-free distance of about between 0.5 cm and 15.0 cm; f) a heating cavity for heating the evaporator tubes, the heating cavity being divided into a plurality of subcavities separately fed with a heating fluid so as to establish different temperatures along the evaporator tubes; and g) pumping means for evacuating the working space to a reduced pressure to a reduced pressure of less than 1 mbar.