Science & Technology - Posted by Paula Gould-Leeds on Tuesday, July 31, 2012 8:26 - 0 Comments
Low-cost carbon capture gets X-rayed
U. LEEDS (UK) — Researchers are using powerful X-rays to improve a promising, low-cost technique for capturing carbon dioxide.
Calcium oxide (CaO) materials are inexpensive, abundant, and have a large sorption capacity. They capture carbon dioxide (CO2) from flue gases in the temperature range 400 to 800 °C via the formation of calcium carbonate (CaCO3), which can be regenerated with subsequent release of CO2, ready for compression and storage.
However, after multiple capture and regeneration cycles, the materials’ capacity for capture decreases due to the loss of surface area through sintering, a process that fuses powders together to create a single solid object.
Straight from the Source
Although the surface area can be restored through hydration, the material suffers a reduction in mechanical strength. If these problems can be overcome, CaO based materials could provide a low cost answer for carbon capture on a very large scale.
A team of engineers led by Valerie Dupont and Tim Comyn from the University of Leeds carried out a series of experiments at UK’s national synchrotron, Diamond Light Source, using intense X-rays to study the carbon capture and hydration process in CaO-based materials at the nanoscale.
Their observations, reported in the journal Energy & Environmental Science, suggest a mechanism for the interaction between CaO and water during hydration.
“We found that the stresses in the calcium hydroxide phase when bound to CaO were more than 20 times higher than its strength, leading to disintegration and the generation of nanosized crystallites,” says Comyn.
“Although the generation of a high surface area is a good thing, mechanical friability needs to be kept in check in order to achieve long term reliability for these systems.
“Our analysis provides an explanation of the enhanced capture/disintegration observed in CaO in the presence of steam. Now [that] we understand this, the next step is to develop methods for improving the materials used, and apply the same techniques to other systems.”
More news from the University of Leeds: www.leeds.ac.uk/news