Large-Scale Tests Begin to Convert Flue Gas to Usable Water

Subsidized by the Dutch government, a number of Dutch utilities, the European Membrane Institute at the University of Twente, and Dutch consulting firm KEMA have, for over a decade, been testing membrane technology that promises to directly convert water vapor from power and other industrial plants’ flue gases into drinking water. The technology could provide a new source of large volumes of potable water.

Since October 2010, the European Union and 13 partners from industry and academia across Europe, the Middle East, and Africa have also lent financial backing to the project. KEMA and partners plan to begin large-scale tests at power plants in Spain and Israel and at a geothermal well in Tunisia within the next two years. Armed with €5 million, the new project has been dubbed “CapWa” (short for “Capture of Evaporated Water with Novel Membranes”).

“The power plant in Spain will be a gas-fired power plant (location not confirmed as yet),” Ludwin Daal, a consultant with KEMA told POWER in March. “The Ruthenberg coal-fired power plant in Ashkelon is located near the Gaza strip and provides electricity to both the Palestinian authority and Israel. The end system will be the size of a sea container, capable of capturing 1 [cubic meter] of liquid water. Bypasses will be made at both plants to facilitate this capture.” The consortium ultimately hopes for industrial production and large-scale implementation of the technology by 2014.

As KEMA explains on a dedicated project website (http://www.watercapture.eu), the main membrane technology used is “much different” from other processes, like reverse osmosis or nanofiltration, because it does not directly involve a liquid-to-liquid separation. In the process, water molecules are transported through a membrane fiber via a diffusion mechanism, and the permeated water is collected through a condensation step (Figure 3). KEMA says that copermeation of gases “affects” the vacuum, which stops the process, so the company constructed a dense polymer coated with a selective, water-permeable membrane to make it selective for water molecules over nitrogen gas. The membranes are supposedly thermally and chemically stable at temperatures of 50C to 150C and are resistant to fouling.

3. Catching the flue. Dutch firm KEMA and partners have been researching and developing a novel membrane that promises to convert at least 40% of water in flue gases of power plants into drinkable water. Backed by the European Union and 14 entities from around the world, the project, dubbed “CapWa,” plans to begin large-scale tests at power plants in Spain and in Israel. Courtesy: KEMA

KEMA says pilot tests were begun in 2001 following concerns about water scarcity and rising prices. Since then, the group has significantly improved gas-separation membranes with which water vapor could be captured on a large scale. Tests on industrial plants in the Netherlands and Germany showed that at least 40% of the water in flue gases can be recovered with the new membrane technology. “Beforehand, researchers counted on a recovery of 20%,” the company said in late February. “This means that an average [coal-fired] power plant of 400 megawatts can supply twice as much water as it needs for steam generation.”

—Sonal Patel is POWER’s senior writer.