A team of researchers from Georgia Tech, the New Jersey Institute of Technology and Oak Ridge National Laboratory have formulated a self-cleaning carbon removal method by utilizing barium oxide nano particles, which will enable direct powering of solid oxide fuel cells by coal gas at a low level temperature of 750°C. The new technology, when it becomes fully viable, will substitute the traditional coal powered electricity plants.
The new research will overcome the ‘coking’ problem normally associated with solid oxide fuel cells that use anodes made of nickel and yttria- stabilized zirconia ceramic material. These cells when operated with fuels such as propane or coal gas will swiftly deactivate the Ni-YSZ anodes with carbon deposits at low level temperatures. The technique developed by the researchers has enabled growth of barium oxide nanostructures over the Ni-YSZ anodes. The nanostructures adsorb moisture to introduce a water-based chemical reaction to oxidize the carbon as it is formed thus maintaining the nickel electrode surface clean even during the use of carbon fuels at low temperatures. The nanoparticles in the range of 10 to 100 nanometers create islands on nickel without obstructing the flow of electrons all over the electrode surface.
When water vapor injected in the coal gas stream reaches barium oxide it is immediately adsorbed and breaks into protons and hydroxide (OH) ions. The OH ions travel over the nickel surface and mix with the carbon atoms deposited on the surface and form COH. It is then split into hydrogen and carbon monoxide to power the fuel cell, releasing water and carbon dioxide. In the process around 50% of the carbon dioxide released is put into circulation to vaporize the coal into coal gas.
Forming of barium oxide structures does not need additional steps and can be formed in the traditional anode fabrication process. The anodes produced using the new method can be used with other normal sold oxide fuel cell systems presently being developed for use in automotive applications, home power generation and commercial power generation.
The researchers also tried the use of propane to energize the solid oxide fuels cells that use the new anode structure. Since the hydrogen in the propane produced water during the oxidation process no water vapor was needed during the process and it behaved similar to that of a coal gas fired system. The researchers have tried the process for over hundred hours without the problem of carbon deposits. They are currently facing an uphill task of developing a durable system for fuel cells that are expected to function for a period of five years.
Source: http://www.gatech.edu