Uploaded May 2014 | Updated September 2026, 1 hour ago
Low-Temperature Thermal Desalination
Today, water scarcity affects one in three people on every continent on the globe. Although Earth is composed of 70% water, only 3% of this is actually drinkable. Further, as the population continues to increase at a rapid pace, water scarcity continues to be a growing problem. Our group sees a large problem developing with respect to world water supply since freshwater is essential to life and its potential depletion threatens all living things on Earth.
The depletion of rivers and lakes has led scientists to explore the idea of using desalination techniques to render water fresh. One of the more popular techniques that has arisen in the last decade is low-temperature thermal desalination, which our group has chosen to research for this project. This technique separates salt from ocean water by evaporating the water, leaving salt behind, then cooling the water vapor back into fresh liquid form.
The key component of this process is the evaporation stage where the salt is physically separated from the water in large evaporation tanks. Most low-temperature desalination plants use stainless steel as the material that makes up evaporation tanks. Stainless steel helps prevent the evaporation tanks from corroding and helps prevent thesodium in the water from creating cracking or stress fractures in the tanks. The use of stainless steel has reduced production costs, eased maintenance, and improved efficiency of the low-temperature desalination plants since the switch from the previously used carbon steel. However, the cost of this process is a concern and stainless steel does not lower costs enough to make widespread use of low-temperature thermal desalination feasible.
The overall desired property of this steel is a "material combining chemical inertness and high mechanical strength" to sufficiently evaporate salt-water pumped to the tank. The desired structure is a steel with relatively large amounts of chromium present which means many stainless steel components must be exposed to mechanical loads in the processing stage. But what comes along with this is a process that creates high strains inside the material and a structure with grain boundaries that are more sensitive to corrosion. This results in stress corrosion cracking in the steel that can impede the entire LTTD process.
Duplex steel -- a stainless steel with higher amounts of chromium is made to resist corrosion, cracking, and fatigue to even a higher degree by avoiding pits with less chromium concentration. The potential use of Duplex could produce thinner shell walls and also higher resistance to corrosion and erosion, which will lead to more efficient evaporation tanks as they will hold the water vapor instead of letting it escape from the cracks created by stress. The combination of thinner walls and more efficient evaporation tanks will all lead to a more cost-efficient process that in turn may lead to the widespread use of this material and make strides toward correcting the world's water crisis.
Douglas, Elliot P. Introduction to Materials Science and Engineering: A Guided Inquiry. N.p.: n.p., n.d. Print.
"Duplex Stainless Steel." - Sandvik Materials Technology. N.p., n.d. Web. 24 Apr. 2014.http://www.smt.sandvik.com/en-us/products/tube-pipe-fittings-and-flanges/high-performance-materials/duplex-stainless-steel/
Global Water Shortage: Water Scarcity & How to Help - Page 2." The Water Project. N.p., n.d. Web. 21 Apr. 2014. thewaterproject.org/how-to-give-clean-water
"Introduction - Microstructures - Low Alloy Steels." Introduction - Microstructures - Low Alloy Steels. N.p., n.d. Web. 24 Apr. 2014. georgesbasement.com/Microstructures/LowAlloySteels/Introduction.htm
Perkins, Sid. "Better Stainless." Science News 161.7 (2002): 99. Print.
"Scarcity, Decade, Water for Life, 2015, UN-Water, United Nations, MDG, Water, Sanitation, Financing, Gender, IWRM, Human Right, Transboundary, Cities, Quality, Food Security." UN News Center. UN, n.d. Web. 21 Apr. 2014. un.org/waterforlifedecade/scarcity.shtml
Sommariva, C., "History and Current Status of Material Selection in Thermal Desalination Processes." Encyclopedia of Life Support Systems.2014. Water and Wastewater Treatment Technologies. Web. 23 April 2014. eolss.net/Sample-Chapters/C07/E6-144-35-00.pdf
"Water Scarcity." WorldWildlife.org. World Wildlife Fund, n.d. Web. 21 Apr. 2014.http://worldwildlife.org/threats/water-scarcity
Stierle, A. "MATERIALS SCIENCE: Tracking Corrosion Cracking." Science 321.5887 (2008): 349-50. Print.
Low-Temperature Thermal Desalination
Today, water scarcity affects one in three people on every continent on the globe. Although Earth is composed of 70% water, only 3% of this is actually drinkable. Further, as the population continues to increase at a rapid pace, water scarcity continues to be a growing problem. Our group sees a large problem developing with respect to world water supply since freshwater is essential to life and its potential depletion threatens all living things on Earth.
The depletion of rivers and lakes has led scientists to explore the idea of using desalination techniques to render water fresh. One of the more popular techniques that has arisen in the last decade is low-temperature thermal desalination, which our group has chosen to research for this project. This technique separates salt from ocean water by evaporating the water, leaving salt behind, then cooling the water vapor back into fresh liquid form.
The key component of this process is the evaporation stage where the salt is physically separated from the water in large evaporation tanks. Most low-temperature desalination plants use stainless steel as the material that makes up evaporation tanks. Stainless steel helps prevent the evaporation tanks from corroding and helps prevent thesodium in the water from creating cracking or stress fractures in the tanks. The use of stainless steel has reduced production costs, eased maintenance, and improved efficiency of the low-temperature desalination plants since the switch from the previously used carbon steel. However, the cost of this process is a concern and stainless steel does not lower costs enough to make widespread use of low-temperature thermal desalination feasible.
The overall desired property of this steel is a "material combining chemical inertness and high mechanical strength" to sufficiently evaporate salt-water pumped to the tank. The desired structure is a steel with relatively large amounts of chromium present which means many stainless steel components must be exposed to mechanical loads in the processing stage. But what comes along with this is a process that creates high strains inside the material and a structure with grain boundaries that are more sensitive to corrosion. This results in stress corrosion cracking in the steel that can impede the entire LTTD process.
Duplex steel -- a stainless steel with higher amounts of chromium is made to resist corrosion, cracking, and fatigue to even a higher degree by avoiding pits with less chromium concentration. The potential use of Duplex could produce thinner shell walls and also higher resistance to corrosion and erosion, which will lead to more efficient evaporation tanks as they will hold the water vapor instead of letting it escape from the cracks created by stress. The combination of thinner walls and more efficient evaporation tanks will all lead to a more cost-efficient process that in turn may lead to the widespread use of this material and make strides toward correcting the world's water crisis.
Douglas, Elliot P. Introduction to Materials Science and Engineering: A Guided Inquiry. N.p.: n.p., n.d. Print.
"Duplex Stainless Steel." - Sandvik Materials Technology. N.p., n.d. Web. 24 Apr. 2014.http://www.smt.sandvik.com/en-us/products/tube-pipe-fittings-and-flanges/high-performance-materials/duplex-stainless-steel/
Global Water Shortage: Water Scarcity & How to Help - Page 2." The Water Project. N.p., n.d. Web. 21 Apr. 2014. thewaterproject.org/how-to-give-clean-water
"Introduction - Microstructures - Low Alloy Steels." Introduction - Microstructures - Low Alloy Steels. N.p., n.d. Web. 24 Apr. 2014. georgesbasement.com/Microstructures/LowAlloySteels/Introduction.htm
Perkins, Sid. "Better Stainless." Science News 161.7 (2002): 99. Print.
"Scarcity, Decade, Water for Life, 2015, UN-Water, United Nations, MDG, Water, Sanitation, Financing, Gender, IWRM, Human Right, Transboundary, Cities, Quality, Food Security." UN News Center. UN, n.d. Web. 21 Apr. 2014. un.org/waterforlifedecade/scarcity.shtml
Sommariva, C., "History and Current Status of Material Selection in Thermal Desalination Processes." Encyclopedia of Life Support Systems.2014. Water and Wastewater Treatment Technologies. Web. 23 April 2014. eolss.net/Sample-Chapters/C07/E6-144-35-00.pdf
"Water Scarcity." WorldWildlife.org. World Wildlife Fund, n.d. Web. 21 Apr. 2014.http://worldwildlife.org/threats/water-scarcity
Stierle, A. "MATERIALS SCIENCE: Tracking Corrosion Cracking." Science 321.5887 (2008): 349-50. Print.
