What is Vapor Compression VC

Vapor Compression VC is one type of thermal desalination technologies which also include Muti Stage Flash Distillation MSF and Multi Effect Distillation MED. In Vapor Compression VC, the heat source for vapor compression (VC) systems is compressed vapor produced by a mechanical compressor or a steam jet ejector rather than a direct exchange of heat from steam . In Vapor Compression VC systems the source water is evaporated and the vapor is conveyed to a compressor. The vapor is then compressed to increase its temperature to a point adequate to evaporate the source water sprayed over tube bundles through which the vapor is conveyed. As the compressed vapor exchanges its heat with the new source water being sprayed on the evaporation tubes, it is condensed into pure water. A feed water preheater (plate-type heat exchange) is used to start the process and reach evaporation temperature. Vapor Compression VC and Multi Effect Distillation MED work based on similar principles.

vapor compression tehnology thermal desalination process system

However, in Multi Effect Distillation MED steam produced by source water evaporation is introduced and condensed in a separate condenser. Condenser is located in the downstream effect. In Vapor Compression VC, the steam generated from evaporation of new source water sprayed on the outside surface of the heat exchange tubes is recirculated by the vapor compressor. It is then introduced into the inner side of the of the same heat exchange tubes in which it condenses to form distillate. Vapor Compression VC desalination has found applications mostly in small municipal and resort water supply systems. As well as industrial applications. The total amount of power required for the operation of mechanical Vapor Compression VC systems is typically 8 to 12 kWh/m3 (30 to 45 kWh/1000 gal) of product water.

Reference: “Desalination Engineering” by Nikolay Voutchkov