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MED - Multi-effect desalination

Alfa Laval Multi-Effect Distillation (MED) equipment converts seawater to high purity water for use in power plants, the oil & gas industry, solar desalination, on cruise liners and in industries and domestic water production.

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Pioneer within thermal desalination

A multi effect desalination plant is an important component in modern power- and process plants which secures a reliable and cost-effective supply of freshwater by using sea water distillation based on waste heat or low pressure steam.

For modern sea water desalination systems the MED is state of the art in thermal desalination. The distillate from MED plants is high purity water with low dissolved solids content. Further water demineralization downstream of the MED plants is then achieved with significantly reduced chemical consumption and less regeneration of the ion exchange columns.

Custom-designed units

Our product range covers capacities up to 10,000 m3/day per unit. Based on standard components and a modular concept, each unit is custom-designed for each particular installation.

Features

MEP offers high fresh water capacity with small installation footprint and a low weight, a feature particularly valuable in the off shore industry as well as in other marine and land based installations where weight and space can be limiting factors whereas easy installation is of high importance.

 

The MEP design (MED with titanium plate evaporators) offers more features and benefits as for example:

  • Titanium plate type evaporators for long lifetime without corrosion
  • 100% performance recovery after cleaning
  • Lowest total water production costs
  • Highest availability
  • Simple and full automatic operation & easy maintenance
  • High quality distillate for boiler feed, process water and potable water

The application of the Alfa Laval patented plate heat exchanger evaporator has created the second revolution in distillation technology and has opened the door for further advancement in distillation technology for desalination?

How it works

Multi Effect Desalination plants are normally powered by thermal energy, taken as hot water or as low-pressure steam from a boiler or a steam turbine. As the steam has already been used for generating power, the cost of desalination is highly reduced.

The process is based on the evaporation of seawater. This is done by moving the vacuum steam generated by the external energy source over a heating surface to heat the sea water feed on the opposite side of the heat exchanger plates. A part of the seawater flow is evaporated to pure water vapour. The water vapour is then utilized as evaporation energy for the subsequent effect, after which the same process is repeated several times corresponding to the number of effects.

Multe-effect plate distiller

The water vapour generated from the last effect is condensed in the main system condenser cooled by seawater. A dedicated PLC (programmable logic control) system ensures that the desalination unit operates fully automatically with a short start-up period to the required fresh water production.

Special features of MED plants with titanium plates

  • Corrosion resistant due to high-grade titanium evaporators 
  • Compact design with low weight and footprint due to high thermal efficiency of the PHE design 
  • Controlled thin falling film avoiding dry spots, thereby avoiding scaling
  • Short residence time of the media in a PHE unit resulting in faster process response and less scaling
  • Easy maintenance - CIP cleaning as well as fully mechanical cleaning is possible 

 


CIP cleaning can remove alkaline soft scaling, and hard scaling can also be removed 100% in a PHE type desalination unit. 

Today, with more than 50 years experience, over 30,000 sucessful installations and references throughout the world, Alfa laval is one of the technology leaders in the desalination field.

Alfa Laval has installed a total fresh water capacity of more than 1,000,000 m3/day for offshore platforms, cruise ships, merchant vessels of all types and more than 200 land-based installations for power, industrial and municipal applications.

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