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NANOSTRUCTURED MATERIAL DESIGN FOR HG, AS, AND SE CAPTURE
Impact/Purpose:
A novel material will be designed and fabricated for the selective capture of trace elements (TE), mercury, arsenic, and selenium from the flue gases of coal combustion. The removal process will be incorporated through a novel scrubber design (Phase II; BabcockPower) that will allow for the separation of the TEs from the flue gas stream so that the sorbent byproducts can be recycled separately from the flue gas desulfurization byproducts (FGD). Currently the recycling of FGD byproducts is a million dollar industry with over 7 million tons being recycled to wallboard manufacturing in 2002 alone (Feeley et al., DOE/NETL CUB Characterization Research, 2004). Currently the TE are being recycled along with the FGD byproducts and if funded the proposed research will aid in the invention of a novel sorbent that will prevent TE contamination in these FGD byproducts, allowing for subsequent safe handling and recycling, thus increasing the sustainability of coal combustion. The design of the material will be accomplished through a combination of both modeling and experiments, which the research group has vast experience in. Simulated flue gases generated through methane combustion with added TEs will be passed through a packed-bed reactor that will hold the sorbent material. An electron ionization quadrupole mass spectrometer will be employed for the direct measurement of the TE concentrations in a sampled product stream. Control experiments absent of the TE will allow for the determination of each sorbent’s effectiveness. Further validation will take place through Dr. Wilcox’s collaborators at EPA and DOE, who have agreed to test the sorbents in their entrained-flow and packed-bed reactors, respectively.
Although coal is not a sustainable energy source such as sun, water, or wind, currently there is a demand for its use in both developed and developing countries. With this demand for energy from a source with
A novel material will be designed and fabricated for the selective capture of trace elements (TE), mercury, arsenic, and selenium from the flue gases of coal combustion. The removal process will be incorporated through a novel scrubber design (Phase II; BabcockPower) that will allow for the separation of the TEs from the flue gas stream so that the sorbent byproducts can be recycled separately from the flue gas desulfurization byproducts (FGD). Currently the recycling of FGD byproducts is a million dollar industry with over 7 million tons being recycled to wallboard manufacturing in 2002 alone (Feeley et al., DOE/NETL CUB Characterization Research, 2004). Currently the TE are being recycled along with the FGD byproducts and if funded the proposed research will aid in the invention of a novel sorbent that will prevent TE contamination in these FGD byproducts, allowing for subsequent safe handling and recycling, thus increasing the sustainability of coal combustion. The design of the material will be accomplished through a combination of both modeling and experiments, which the research group has vast experience in. Simulated flue gases generated through methane combustion with added TEs will be passed through a packed-bed reactor that will hold the sorbent material. An electron ionization quadrupole mass spectrometer will be employed for the direct measurement of the TE concentrations in a sampled product stream. Control experiments absent of the TE will allow for the determination of each sorbent’s effectiveness. Further validation will take place through Dr. Wilcox’s collaborators at EPA and DOE, who have agreed to test the sorbents in their entrained-flow and packed-bed reactors, respectively.
Although coal is not a sustainable energy source such as sun, water, or wind, currently there is a demand for its use in both developed and developing countries. With this demand for energy from a source wit
Description:
The goal of this research project is to identify potential materials that can be used as multipollutant sorbents using a hierarchy of computational modeling approaches. Palladium (Pd) and gold (Au) alloys were investigated and the results show that the addition of a small amount of Au is able to enhance the sorbent reactivity, although the binding energy was sensitive to the specific local concentration of Au atoms. While this is an interesting finding it would be difficult to optimize the structure for fabrication due to the invariance of the atomic configuration. Further studies showed that using a monolayer of Pd overlayed on a Au substrate enhances binding compared to the PdAu alloys. The use of monolayers not only removes the dependence on the random atomic arrangement, but it may also lead to a higher capacity because of the surface composition uniformity and subsequent increased number of binding sites. Tests were also run for As and Se and although the trend was not as strong, enhanced adsorption was also found for these elements. To further investigate means of improving the sorbent materials, simulations were run on metal dimers-TE complexes using the software package, Gaussian03, an ab initio, or first principles approach. It was determined that iron (Fe) was the best candidate to capture Hg, As and Se, given that nearly all the interactions with Fe were characterized by strong chemisorption with binding energies of over 50 kcal/mol. In addition, at about $5.50/oz Fe is also economically favorable compared to the other sorbent materials considered, for instance the price of Pd is approximately $445/oz. To investigate the adsorption chemistry, the HOMO/LUMO maps and a molecular orbital analysis were carried out for TE species found to be prevalent in coal combustion and gasification environments.