A more affordable, accessible material for seawater desalination

Oct 05, 2012
Composite pipes for seawater desalination. Credit: Fraunhofer IFAM

There are vast quantities of seawater available; drinking water, on the other hand, is in scarce supply. Desalination plants can convert seawater to drinking water. Yet these plants require pipelines made of a special kind of steel or titanium – expensive material that is growing increasingly difficult to procure. Heat-conducting polymer composites may soon replace titanium altogether.

is a scarce commodity – a fact no longer limited to the desert regions of the world. During the hot summer months, drinking water is rare in Mediterranean countries such as Spain and Portugal, too. As a result, industrial plants that can desalinate and convert it to drinking water are on the rise. Here's how the principle of desalination works: seawater is sprayed on pipes heated by pumping hot gas or hot water through them. Pure water evaporates from the seawater, leaving a salty behind. This process subjects the material and its properties to a diverse array of demands: the material from which the pipes are made must conduct heat and be particularly robust in resisting corrosion and the formation of deposits – and these properties must be durable over a long period of time. And for the water to evaporate properly, the piping must also be easily coated with seawater. This is why manufacturers to date have used only titanium and high-alloy forms of steel. Yet these are very costly. The demand for titanium is also constantly on the rise – as a result of the increase in , the is also competing for this material. The results are delivery delays and further increases in price.

Researchers at the Fraunhofer Institute for and IFAM in Bremen are now developing an alternative to the titanium tubes: pipelines made of polymer composites. The special thing about this method: the are a plastic, and yet they conduct heat. Another benefit: they can be produced in continuous lengths and are correspondingly more economical than their metal counterparts. But what did researchers do to make a polymer heat-conducting? "We introduced metal particles into the material - or more precisely, we add up to 50 percent copper microfibers by volume. This does not change the processing properties of the composite, and it can still be processed as any other polymer would," notes Arne Haberkorn, a scientist at IFAM.

The researchers have already developed the material itself; now they want to optimize its thermal conductivity. To accomplish this, they are installing the piping in a pilot seawater-desalination plant: here, they are testing its thermal conductivity, checking to see how much of a microorganism-based coating forms on the pipes, and how heavily the material corrodes in its salty surroundings. They then optimize the composite properties based on the results. The researchers have set the evaporation process to run at a temperature of 70 degrees Celsius – so there is hot gas heated to 70 degrees pumped through the pipelines. This offers several advantages: fewer deposits congregate on the pipes, the material doesn't corrode as quickly, and the pressure differential between the inside and outside of the piping is not as dramatic.

The usages for the material are not confined to seawater desalination, either. "We developed the pipes for desalination plants because they place the highest demands on the material. Designed with these constraints in mind, it will be no problem using it in the food or pharmaceuticals industries," Haberkorn points out.

Explore further: New, more versatile version of Geckskin: Gecko-like adhesives now useful for real world surfaces

More information: Researchers will present this heat-conducting plastic at the Composites trade fair, October 9-11, 2012, in Düsseldorf (Hall 8a, Booth A11).

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User comments : 7

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PPihkala
not rated yet Oct 05, 2012
So the pipes are 50% plastic and 50% copper. And what is the price of copper?
antialias_physorg
not rated yet Oct 05, 2012
And what is the price of copper?

JFGI

Is that too much to ask?
Wolf358
not rated yet Oct 05, 2012
How much better a heat conductor would this material be if silver were used instead of copper? Since it can be extruded, various solar-thermal collectors could take advantage of it. Interesting stuff.
SteveL
not rated yet Oct 05, 2012
Silver is darn expensive when considering production quantities. Copper will continue to be more expensive also as 3rd world countries become more industrialized.
Ober
not rated yet Oct 06, 2012
Yet another reason to mine asteroids. Though manufacturing costs may initially be outrageous!! Gotta do it though, as the Earth only has a certain amount we can dig out of the ground.
antialias_physorg
not rated yet Oct 06, 2012
Yet another reason to mine asteroids.

What makes you think asteroids are 'solid copper' (or 'solid anything' for that matter) which would be necessary to make mining them more economical than mines on Earth?

I can't really find any source about compositions of asteroids that would indicate that the prevalence/purity of minerals there are worth the (immense) added cost of going there.
ValeriaT
not rated yet Oct 06, 2012
Copper is rare element, whereas the titanium is completely abundant and it has ideal properties for most of purposes. The only problem of titanium is, it requires lotta energy for its production. I'm sure, after implementation of cold fusion the role of titanium will become completely reevaluated and it will replace heavy metals from most of their applications.

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