Combustion fume structure and dynamics. [Quarterly report], July 16, 1992--September 15, 1993
Technical Report
·
OSTI ID:10147679
During pulverized coal combustion, a fume of submicron particles is formed from the mineral matter in the parent coal. Studies of the variation in chemical composition with particle size have revealed that much of the submicron fume is formed from volatilized coal ash. The formation and evolution of the ash fume is governed by homogeneous nucleation, condensation, and coagulation. Vapors of refractory species nucleate relatively early in the combustion process. Coagulation of those fine particles results in a size distribution that is approximately log normal. More volatile species remain in the gas phase until after the nucleation has taken place. Condensation on the surfaces of both the fume and the larger residual ash particles results in the enrichment of the fine particles with volatile, and frequently toxic trace species. The resultant concentration of heavy metals in the size interval between 0.1 and 1 {mu}m may allow disproportionate amounts of these species to escape collection, even by the best of gas cleaning systems. Flagan and Friedlander first modeled the evolution of the ash particle size distribution in pulverized coal combustion beginning with the hypothesis that the fine particles resulted from homogeneous nucleation and grew primarily by coagulation. They predicted much more distinct peaks in the submicron size range than had been observed at that time. Improved instrumentation has verified those predictions, and shown that the situation can be even more complex than their simple model indicated.
- Research Organization:
- California Inst. of Tech., Pasadena, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-90PC90286
- OSTI ID:
- 10147679
- Report Number(s):
- DOE/PC/90286--T7; ON: DE94011134; BR: AA1525050
- Country of Publication:
- United States
- Language:
- English
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