Multiple Effect Evaporators

Multiple effect evaporator utilizes the heat from the steam and uses it for evaporation. Sequence of vessel is used in a multiple-effect evaporator. The pressure in the vessel is lower than the preceding vessel. As the pressure decreases the boiling point of water also decreases hence the vapor boiled off in one vessel can be used to heat the next. In multi effect evaporator, only the first vessel is heated by an external source of energy. These evaporators can be constructed in any number of stages, but in practice four stages evaporators are generally used.

Multiple effect evaporator or multi effect evaporator is used a multi-effect evaporation (MEE) distillation process. The process was developed in late fifties and since then it has seen many phases of developments. Though scaling is one of the problem that is attached with it but owing to better thermal performance it is still preferred.

In this system, in every stage vapor is condensed thereby giving up its heat to drive more evaporation for the next stage. For improving the performance each stage is operated at a successively lower pressure.

According to the different heat transfer surface the MEE process can have several different configurations. The heat input sources can be used between different stages. The heat can be genearted from sources like mechanical or thermal vapor compression.


Schematic of multiple effect evaporatorApplications
Following are the applications of MEE:

• MEE are used in following applications
• Used in dairy industry for recovering proteins from whey
• MEE is utilized in solvent extraction process
• It can recover easily vulcanizing salts
• Food and beverage industry
• Purifies Wash water
• Desalination of Seawater
• Desalination of brackish water etc.