(20e) Evaluation of Nanocrystalline Sorbents for Mercury Removal from Coal Gasifier Fuel Gas

Coal-fired utilities are the single largest source of anthropogenic mercury emissions in the U.S. The mercury regulations currently proposed for coal-combustion systems will most likely be extended to the next-generation gasification-based systems. Therefore, a significant amount of research work is currently being carried out to address the concern of mercury release from coal-fired power plants. A majority of this research is focused on development of sorbents for mercury capture from ?warm? fuel gas. Sorbents currently proposed for flue gas application, such as activated carbon, have limited application in fuel gas because of their lower sorption capacity at elevated temperatures. The presence of reducing components provides additional challenge for development of high capacity mercury sorbents for fuel gas applications.

In this paper, development and evaluation of novel nanocrystalline sorbents for mercury removal from warm fuel gas are discussed. Nanocrystalline materials exhibit a wide array of remarkable chemical and physical properties, and can be considered as new materials that bridge molecular and condensed matter. One of their remarkable properties is enhanced surface chemical reactivity (normalized for surface area) toward incoming adsorbates, which is attributed to extremely large surface areas, unique morphology and porous nature of the nanomaterials.

Gas Technology Institute (GTI), in collaboration with NanoScale Materials, Inc., is evaluating highly reactive nanocrystalline metal oxides/sulfides for capture of mercury from high-pressure (300?1000 psi) and high-temperature (300?700°F) fuel gas. The sorbents are evaluated in a lab-scale, fixed bed reactor with the outlet mercury concentration monitored by a semi-continuous mercury analyzer. This paper discusses unique properties of nanoscale sorbents and gives preliminary results of mercury capture by these sorbents. The project is sponsored by DOE's National Energy Technology Laboratory.