Vapor-compression desalination (VC) refers to a

distillation Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...

process where the evaporation of

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

saline water Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

is obtained by the application of heat delivered by compressed vapor.

Overview

Since compression of the vapor increases both the pressure and temperature of the vapor, it is possible to use the

latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be understo ...

rejected during condensation to generate additional vapor. The effect of compressing water vapor can be done by two methods. The first method utilizes an ejector system motivated by steam at manometric pressure from an external source in order to recycle vapor from the desalination process. The form is designated

ejectocompression Vapor-compression evaporation is the evaporation method by which a blower, compressor or jet ejector is used to compress, and thus, increase the pressure of the vapor produced. Since the pressure increase of the vapor also generates an increase i ...

thermocompression Vapor-compression evaporation is the evaporation method by which a blower, compressor or jet ejector is used to compress, and thus, increase the pressure of the vapor produced. Since the pressure increase of the vapor also generates an increase i ...

. Using the second method, water vapor is compressed by means of a mechanical device, electrically driven in most cases. This form is designated mechanical vapor compression (MVC). The MVC process comprises two different versions: vapor compression (VC) and vacuum vapor compression (VVC). VC designates those systems in which the evaporation effect takes place at manometric pressure, and VVC the systems in which evaporation takes place at sub-atmospheric pressures (under vacuum). The compression is mechanically powered by something such as a compression turbine. As vapor is generated, it is passed over to a heat exchanging condenser which returns the vapor to water. The resulting fresh water is moved to storage while the heat removed during condensation is transmitted to the remaining feedstock. The VVC process is the more efficient distillation process available in the market today in terms of energy consumption and water recovery ratio. As the system is electrically driven, it is considered a "clean" process, it is highly reliable and simple to operate and maintain.

References

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AN ADVANCED VAPOR-COMPRESSION DESALINATION SYSTEMVacuum vapour compression water makers for the oil and gas industry

Vacuum vapour compression water makersAN ADVANCED MECHANICAL VAPOR COMPRESSION DESALINATION with VVC SYSTEM in desalination and purfying water industry
Evaporators Water desalination

Overview

See also

References