Multi Stage Flash Evaporators

Wärtsilä’s Multi Stage Flash (MSF) principle is the most reliable thermal seawater desalination process in the world. More over: it is the only evaporation principle where heat transfer and evaporation are strictly separated. This approach minimises the risk of scaling and greatly reduces maintenance costs.  

The Wärtsilä's multi-stage flash evaporators are used for producing fresh water from seawater, well or industrial water. A specific advantage of the multi-stage flash technology is that the heat consumption - or thermal efficiency - can continuously be  adjusted to the set requirements of each application.

The distillate produced by a MSF has a very low salt content, which makes it very suitable to be used as technical water (e.g. boiler feed water). The distillate quality and quantity are are not impacted by the seawater temperature. This makes the MSF technology a reliable source for freshwater on board of ships. 

    • Capacity up to 1500 t/d.
    • Steady production of freshwater at seawater temperatures between 0-32°C.
    • Either steam, engine jacket water or a combination of these can be utilized for heating.
    • Full-automatic or semi-automatic operation.
    • Heat transfer and evaporation takes place in different areas, resulting in a minimised risk of scaling (flash).
    • Sturdy construction with low maintenance demands resulting in high availability.
    • Lowest sensitivity to malfunction or maloperation.
    • Components in contact with seawater or distillate are manufactured with corrosion resistant materials (e.g. copper- nickel).
    • Technology with the lowest lifecycle costs.
    • Flexible dimensions allow for the best utilisation of space.
    • Operating frequency converter for pumps saves energy.
    • Salt content of the distillate ≤ 4 ppm NaCI.
    Spare parts and service

    Please send the vessel name, equipment type, serial number (if known), your company details and spares and/or service requirements to and we will respond as soon as possible.

    Principles of operation

    After leaving the first stage condenser, the seawater flows through the brine heater, where the heat input to the plant (steam or engine jacket water) causes a further temperature increase. The seawater leaves the brine heater and enters the first flash chamber, reaching a brine top temperature of approx. 80°C. At this point the pressure of the incoming seawater is suddenly reduced, by means of an orifice, below its equilibrium vapour pressure resulting in explosive boiling or evaporation (flashing). The pure vapour produced is then condensed giving up its latent heat to preheat the incoming seawater. If this process is repeated over a large number of effects, at successively lower pressures and temperatures, large distillate production rates at reasonable performance ratios can be achieved.

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