A fundamental study of mercury partitioning in coal fired power plant flue gas
Conference
·
OSTI ID:351126
- Physical Sciences, Inc., Andover, MA (United States)
- Univ. of Kentucky, Lexington, KY (United States)
- Massachusetts Inst. of Tech., Cambridge, MA (United States)
Data suggest that coal-fired power plants are a significant source of atmospheric mercury. Predicting the emissions of mercury cannot be done without a fundamental understanding of the chemical reactions of mercury in flue gas. A research program has been designed to address the major mechanisms for speciation and partitioning, leading to a model that enables the utility industry to predict and, therefore, minimize the emission of regulated trace elements, particularly mercury. Results from preliminary experiments and modeling are presented and discussed. Although combustion produces elemental mercury, coals typically contain sufficient chlorine to oxidize a portion of the elemental mercury to HgCl{sub 2} at temperatures in the range of 750--900 K. At temperatures below approximately 600 K, gaseous mercury species interact with flyash and a significant portion of the gaseous mercury is converted to particulate phase mercury. The authors speculate that residual carbon from coal combustion could also act as an oxidation catalyst in the temperature range of 400--600 K. At temperatures below 400 K, adsorption on carbon-containing ash occurs. Comparison of the results of equilibrium calculations with measurements of speciation of gaseous mercury compounds in flue gas indicate that equilibrium is not attained for mercury by the time the flue gas reaches the inlet to the air pollution control device. The data suggest that the equilibrium is frozen at temperatures in the range of 800--900 K. A better understanding of the gas-to-particle conversion is also needed, particularly the relationship between char or carbon properties and oxidation and/or adsorption of mercury. The authors have completed a preliminary analysis of the forms of mercury on three types of carbon-based sorbents using XAFS.
- DOE Contract Number:
- AC22-95PC95101
- OSTI ID:
- 351126
- Report Number(s):
- CONF-970677--
- Country of Publication:
- United States
- Language:
- English
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