Combustion fume structure and dynamics. Semiannual report, February 16, 1994--August 15, 1994
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. This project comprises theoretical and experimental investigations of the dynamics of aggregate aerosols produced as pyrogenous fumes. For the proposes of modeling the dynamics of these complex structures, the particles have been characterized and modeled as having fractal structure. The objective of this study is to develop and validate a model describing the formation and evolution of fine particles from minerals volatilized during coal combustion, with special emphasis on particle structure and its influence on the dynamics of the combustion aerosol. Experimental and theoretical investigations of the individual processes involved in the aerosol evolution, i.e., sintering and aggregation are studied independently using model systems. Theoretical investigations have paralleled the experimental studies to help to interpret the experimental results and as a step toward the develop of quantitative predictive models.
- Research Organization:
- California Institute of Technology (CalTech), Pasadena, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-90PC90286
- OSTI ID:
- 95515
- Report Number(s):
- DOE/PC/90286-T11; ON: DE95017339; TRN: 95:006469
- Resource Relation:
- Other Information: PBD: [1995]
- Country of Publication:
- United States
- Language:
- English
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