The ME series of vacuum evaporators have vertical development with the boiling chamber in the lower part and the condensation chamber in the upper part. The vacuum system guarantees minimum energy expenditure. These plants consist of a batteiy of evaporators in series, called `stages`, each of which possesses a heat exchanger. Steam circulates inside the heat exchangers, heating the solution which has to be treated and causing its evaporation. Steam (or hot water) is supplied to the first stage, and the steam produced in this is then harnessed as steam to be used for the following stage. In this way it is possible to considerably reduce the energy required.