Middle East Desalination

Huntington Beach Proposal

Sources Cited

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Vapor Compression Distillation

Mechanical energy provides a source of thermal energy for condensation processes similar to MED.

Mechanism

Vapor Compression Distillation, or VCD, is often used together with Multi-effect Distillation for large applications or alone when used in smaller settings.  The key difference that makes VCD unique is that the compression of vapor is utilized to change the boiling point of water.  A quick refresher of physics and the ideal gas law PV = nRT reminds us pressure and temperature are proportional.  At a constant volume an increase in pressure leads to an increase in temperature (Loverude et. al. 2001).  VCD plants therefore use compression of vapor as a source of evaporating heat.

Plants are divided into stages and may contain one in smaller plants or more in larger ones.  VCD is simple and reliable compared to other methods of desalination.  It is used most often in industries, resorts, and drilling sites where fresh water is not available.  Depending on the plant, pressure may reach up to 300 pounds per square inch!

image source:http://www.iwra.siu.edu/win/win2000/win03-00/semiat.pdf

Benefits

1) the operating costs are low compared to multi-stage or multi-effect flash distillation systems

2) the equipment is smaller than the multi-stage flash or multi-effect flash distillation systems

Cons

1) maintenance on compressors and heat exchangers is greater than those of other systems

2) energy consumption is high

3) capital costs are high

National Science Foundation: Office of Polar Programs. "Sea water desalination system, McMurdo" 1993.

http://www.nsf.gov/pubs/stis1993/opp93104/opp93104.txt

Sources

Buros, O.K. "The ABC's of Desalting" Second Ed. Topsfield, MA  http://www.idadesal.org/ABCs1.pdf

Loverude, Michael E., Christian H. Kautz, and Paula R. L. Heron. "Student understanding of the first law of
     thermodynamics: Relating work to the adiabatic compression of an ideal gas" University of Washington.
     Seattle, WA. 14 September, 2001. http://chaos.fullerton.edu/~mloverud/AJPthermo.pdf

National Science Foundation: Office of Polar Programs. "Sea water desalination system, McMurdo" 1993.

http://www.nsf.gov/pubs/stis1993/opp93104/opp93104.txt

UNEP - International Environmental Technology Centre. United Nations Environment Programme. "Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean" 1997.