What is an Evaporator?

An evaporator is used to evaporate a volatile solvent, usually water, from a solution. Its purpose is to concentrate non-volatile solutes such as organic compounds, inorganic salts, acids, or bases. Typical solutes include phosphoric acid, caustic soda, sodium chloride, sodium sulfate, gelatin, syrups, and urea.

Calandria Evaporators

Rising Film Evaporators

Falling Film Evaporators

Multiple Effect Evaporators

Forced Circulation Evaporators

Thermal Vapor Recompression Evaporators

Mechanical Vapor Recompression (MVR) Evaporators

Common Evaporator Applications

In many applications, evaporation results in the precipitation of solutes in the form of crystals, which are usually separated from the solution with cyclones, settlers, wash columns, elutriating legs, filters, or centrifuges. Examples of precipitates are sodium chloride, sodium sulfate, sodium carbonate and calcium sulfate. The desired product can be the concentrated solution, the precipitated solids, or both.


In some applications, the evaporator is used primarily to recover a solvent such as potable water from saline water. In any case, the relatively pure condensed water vapor from many evaporators is recovered for boiler feed makeup, salt washing, salt dissolving, pump seals, instrument purges, equipment and line washing and other uses.

Types of Evaporators

Swenson is an acknowledged leader in the field of evaporation. Swenson’s evaporator designs include forced-circulation, long-tube vertical (both rising and falling film), and calandria-type evaporators. The requirements of a particular process dictate the evaporator style and model best suited for the application.

Forced circulation and calandria evaporators are used for
processes where crystals are formed. These evaporators keep
crystals suspended in solution to prevent scaling of the


Long-tube vertical evaporators, including both falling film and rising film evaporators, concentrate a liquid that does not have solids present.


Multiple effect evaporators are cost effective when inexpensive, high-pressure steam is available to heat the system.


Mechanical vapor recompression (MVR) evaporator use electricity or a gas turbine to drive a compressor that recycles the heat in the evaporator