Desalination

The Ruwais Desalination Plant in the United Arab Emirates is part of an industrial complex roughly 200 miles west of the capital city, Abu Dhabi. Ruwais generates 700 megawatts of electric power when operating at capacity.

Abu Dhabi National Oil Company is the primary owner of the facility and plans to increase the plant's refining and petrochemicals capacity as well as its desalination abilities. The desalination plant processes about eight million gallons of water daily, which is then used by the refinery.

Ruwais is representative of a rising number of local refining and processing plants in the Middle East that has attracted European and North American equipment suppliers.

The plant features four GT 13E2 gas turbines with accompanying generators. Each turbine has roughly 160MW capacity coupled with clean combustion natural gas burners. When turbines are used with oil, water injection can lower NOx emissions.

by James E. Miller, Materials Chemistry Department, Sandia National Laboratories: P.O. Box 5800, Albuquerque, NM 87185-1349 - SAND 2003-0800, Unlimited Release, Printed March 2003

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Water shortages affect 88 developing countries that are home to half of the world’s population. In these places, 80-90% of all diseases and 30% of all deaths result from poor water quality. Furthermore, over the next 25 years, the number of people affected by severe water shortages is expected to increase fourfold. Low cost methods to desalinate brackish water and sea water can help reverse this destabilizing trend.
Desalination has now been practiced on a large scale for more than 50 years. During this time continual improvements have been made, and the major technologies are now remarkably efficient, reliable, and inexpensive. For many years, thermal technologies were the only viable option, and multi-stage flash (MSF) was established as the baseline technology. Multi-effect evaporation (MEE) is now the state-of-the-art thermal technology, but has not been widely implemented. With the growth of membrane science, reverse osmosis (RO) overtook MSF as the leading desalination technology, and should be considered the baseline technology. Presently, RO of seawater can be accomplished with an energy expenditure in the range of 11-60 kJ/kg at a cost of $2 to $4 per 1000 gallons. The theoretical minimum energy expenditure is 3-7 kJ/kg.

Since RO is a fairly mature technology, further improvements are likely to be incremental in nature, unless design improvements allow major savings in capital costs. Therefore, the best hope to dramatically decrease desalination costs is to develop “out of the box” technologies. These “out of the box” approaches must offer a significant advantage over RO (or MEE, if waste heat is available) if they are to be viable. When making these comparisons, it is crucial that the specifics of the calculation are understood so that the comparison is made on a fair and equivalent basis.

Proceedings of the FAO Expert Consultation on Water Desalination for Agricultural Applications, 26-27 April 2004, Rome - FAO Land and Water Discussion Paper 5.

Water desalination is the main source of potable water in some countries and in many islands around the world and it is also being used in certain countries to irrigate high-value crops. However, it has proven much less economic for agricultural application than the reuse of treated wastewater, even where the capital costs of the desalination plants are subsidized.

This discussion paper contains an introductory paper on water desalination, some keynote papers of the experts participating in the consultation, the summary report of the expert consultation and a technical
summary with the conclusions and recommendations of the main topics discussed at the meeting.