OCR Text |
Show temperatures of 800-1100°C, cooled, and examined. The amount of each compound captured is shown in Figure 7. In this figure, sorbent A is magnesia and sorbent B is diatomaceous earth. While these experiments do not address the ability to capture trace metal species in-situ in a utility boiler, they do suggest that sorbents containing compounds commonly found in fly ash may be used to capture trace elements and render them non-leachable. Evaluation of the reaction kinetics is required to assess the applicability of these reactions to capture trace metals under flue gas conditions. SUMMARY Trace elements that may volatilize during combustion or gasification are those whose emissions may be more difficult to control. The results of several studies presented herein suggests the following trends: Volatile: Hg Partially Volatile: As, Se, Sb, Pb Occasionally Volatile: Cr (combustion) , Mn (combustion) Non-volatile: Cd, Co, Ni, Cr (gasification), Mn (gasification) These conclusions are somewhat dependent upon combustion or gasification conditions and are expected to depend upon the form of the individual element in coal. Future research will explore the relationship between elemental form and volatility so that general relationships may be developed. ACKNOWLEDGEMENTS As the work described herein represents an overview of several studies, many agencies are to be thanked for their financial support. The financial contributions of the National Institute for Environmental Health Science, the National Science Foundation, the U.S. D O E / P E T C , the U.S. D O E / M E T C , and the U.S. E P A all made this effort possible. The analysis of the Illinois #6 coal studied under gasification conditions was provided by UND EERC. REFERENCES 1. Finkelman, R.B., in Organic Geochemistry, Engle, M., and Macko, F., eds., Plenum Publishing Co. (1992). 2. Clarke, L.B., and Sloss, L.,"Trace Elements - emissions from coal combustion and gasification," IEA Report IEACR/49, IEA Coal Research, London (1992). 3. Brooks, G., Radian Corporation Final Report submitted to the U S E P A under contract number 68-02-4392, Report No. EPA-450/2-89-001 (1989). 5 11-14 |