Processes for Sea Water Desalination
ENTROPIE can offer sea water desalination systems based on either of the leading technologies depending on fresh water needs
Overview
ENTROPIE is the world leading specialist in sea water desalination through low temperature distillation processes such as :
- Multiple Effect Distillation (MED)
- Multiple Effect Distillation with Thermal Vapour Compression (MED-TVC)
- Multiple Effect Distillation with Mechanical Vapour Compression (MED-MVC)
A Multi Effect Desalination MED unit is an evaporator where sea water is evaporated in one or more ( up to 14 ) evaporation stages at low temperature (< 70°C ) in order to produce clean distillate water.
MED process is designed to produce distilled water with steam or waste heat from power production or chemical processes, and/or to produce potable water.
Standard MED-TVC Process Scheme
- GOR can be enhanced by addition of a thermocompressor (TVC) between one of the cells and the hot one.
- Using LP or MP steam this static compressor will take part of the vapour raised in one cell and recycle it into higher pressure vapour to be used as heating medium for the first one.
- In this example of 3 cells, the GOR is doubled in comparison with standard MED.
Applications
The technology
The GOR of the evaporator in MED can be enhanced by addition of a thermocompressor between one of the cells and the hot one. Using LP or MP steam this static compressor will take part of the vapour raised in one of the cells and recycle it into higher pressure vapour to be used as heating media for the first effect.
The sketch shows the typical arrangement of an MED evaporator with thermocompression (MED-TVC). Whereas the GOR of the evaporator in MED would be in the range of 3 (using LLP steam) the GOR of sketch would rather reach 6 to 10 (using LP or MP steam).
The Advantages
- Very low electrical consumption (less than 1.0 kWh/m3) compared to other thermal processes such as Multi Stage Flash (MSF) or membrane processes (Reverse Osmosis)
- Operate at low temperature (< 70°C) and at low concentration (< 1.5) to avoid corrosion and scaling
- Produce steadily high purity distillate
- Do not need complex pre-treatment of sea water and are tolerant to variations of sea water conditions
- Are highly reliable and simple to operate
- Reduce civil works cost thanks to reduced foot print
- Are simple to install with packaged units mounted on skids and delivered ready for use, after easy installation
- Have a low maintenance cost (no rotating parts except low pressure pumps)
- Operate 24 hours a day with minimum supervision
- Ideal for coupling with power plants, steam can be used at any pressure from 1 to 40 bar abs
- Allow very high thermal efficiencies and savings in fuel costs
- Range up to 15 MIGD (68 000 m3/day) per unit
