May 31, 2012
‘Swiss Cheese’ Molecules Catch Carbon
DM Crumbliss for RedOrbit.com
A study has identified new minerals that could cut the costs of removing carbon dioxide from emissions at power plants. The research was done by scientists at Rice University, the University of California, Berkeley, Lawrence Berkeley National Laboratory (LBNL) and the Electric Power Research Institute (EPRI) was published online this week in the journal Nature Materials.
Fossil fuel power plants are responsible for about half the CO2 emissions added to the atmosphere each year. Commercial power plants do not capture CO2 on a large scale, but the technology has been tested at pilot plants. At test plants, flue gases are funneled through a bath of ammonia-like chemicals called amines. The amines are then boiled to release the captured CO2, and additional energy is required to compress the CO2 so it can be pumped underground.
Utility companies have tried for several years to find a more affordable way to keep and store the CO2. Using current technology the best efforts for carbon sequestration use about a third of the test power plants capacity.
Researchers found that commonly used industrial minerals called zeolites could significantly improve the energy efficiency of carbon capture technology.
“It looks like we can beat the current state-of-the-art technology by about 30 percent, and not just with one or two zeolites,” said study co-author Michael Deem, Rice´s John W. Cox Professor of Bioengineering and professor of physics and astronomy. “Our analysis showed that dozens of zeolites are more efficient than the amine absorbents currently used for CO2 capture.”
Zeolites are common minerals made mostly of silicon and oxygen. About 40 exist in nature, and there are about 160 man-made types. All zeolites are highly porous – like microscopic Swiss cheese – and the pore sizes and shapes vary depending upon how the silicon and oxygen atoms are arranged. The pores act like tiny reaction vessels that capture, sort and spur chemical reactions of various kinds, depending upon the size and shape of the pores. The chemical industry uses zeolites to refine gasoline and to make laundry detergent and many other products.
In 2007, Deem and colleagues used computers to calculate millions of atomic formulations for zeolites, and they have continued to add information to the resulting catalog, which contains about 4 million zeolite structures.
The zeolite database was examined with a new computer model designed to identify candidates for CO2 capture. The new model was created by a team led by co-author Berend Smit, UC Berkeley´s Chancellor´s Professor in the departments of chemical and biomolecular engineering and of chemistry and a faculty senior scientist at LBNL. Smit and his UC Berkeley group worked with study co-author Abhoyjit Bhown, a technical executive at EPRI, to establish the best criteria for a good carbon capture material. Focusing on the energy costs of capture, release and compression, they created a formula to calculate the energy consumption for any materials in the zeolite database.
Smit said, “Our database of carbon capture materials is going to be coupled to a model of a full plant design, so if we have a new material, we can immediately see whether this material makes sense for an actual design.”