New Silica Filter for Power Plant Cooling Waters

Sandia researchers studied how hydrotalcite can filter silica out of cooling tower water. Photo by Randy Montoya, Sandia.

Researchers at Sandia National Laboratories (Albuquerque, New Mexico, USA) developed a new silica filter for power plant cooling waters that decreases the amount of water consumed by increasing how often cooling tower water can be reused and recycled.

Power plants draw more freshwater than any other U.S. consumer, accounting for more than 50% of the nation’s use at ~500 billion gal (1,892.5 billion L) daily. While these plants already recycle freshwater, the number of times water can be reused is limited by the silica that builds up with each cycle. Silica is a naturally occurring substance with limited solubility, and is prone to forming scales on turbines, boilers, heat exchangers, transfer pipes, and other equipment. This buildup can disrupt equipment function and is costly to prevent.

“When you have silica buildup, heat transfer is a problem, clogging is a problem, and corrosion is a problem,” says Sandia chemist Tina Nenoff. “So, our project focused on finding an energy- and cost-efficient material and process to remove silica from industrial water.”

To address the problem, Sandia researchers used special filters made of hydrotalcite, a layered material comprised of aluminum hydroxide [Al(OH)3]. The research team designed the hydrotalcite material to filter cooling tower water.

“Envision pellets of hydrotalcite or a powder like the kind found in a drinking water filter,” Nenoff says. “The water flows through or over the material during the filtration process, and the silica from the water crystalizes and remains in the filter while cleaner water flows out.”

The researchers also performed a techno-economic analysis. “As a result of this project, we’ll be able to give [potential users] an estimated cost and energy savings, and even a projected lifetime savings that hydrotalcite could provide over their current method,” Nenoff says.

Source: Sandia National Laboratories,