In the course of their development, the aim of reducing energy costs first led to multiple-effect plants, then to thermal vapour recompression, and finally, to the use of mechanical vapour recompression systems. In a conventional evaporator, the vapour stream produced is condensed, meaning that its energy content is lost to a large extent. In comparison, mechanical vapour recompression permits the continous recycling of this energy stream by recompressing the vapour to a higher pressure and therefore, a higher energy content. Mechanical vapour recompression reduces the consumption of primary energy and, consequently, the environmental load.