STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION
Significant progress continued to be made during the past reporting quarter on both major technical tasks. During the reporting period at OSU, computational investigations were conducted of addition vs. abstraction reactions of H, O(3 P), and OH with monocyclic aromatic hydrocarbons. The potential energy surface for more than 80 unique reactions of H, O ( 3 P), and OH with aromatic hydrocarbons were determined at the B3LYP/6-31G(d) level of theory. The calculated transition state barriers and reaction free energies indicate that the addition channel is preferred at 298K, but that the abstraction channel becomes dominant at high temperatures. The thermodynamic preference for reactivity with aromatic hydrocarbons increases in the order O(3 P) < H < OH. Abstraction from six-membered aromatic rings is more facile than abstraction from five-membered aromatic rings. However, addition to five-membered rings is thermodynamically more favorable than addition to six-membered rings. The free energies for the abstraction and addition reactions of H, O, and OH with aromatic hydrocarbons and the characteristics of the respective transition states can be used to calculate the reaction rate constants for these important combustion reactions. Experimental work at Brown University on the effect of reaction on the structural evolution of different chars (i.e., phenolic resin char and chars produced from three different coals) have been investigated in a TGA/TPD-MS system. It has been found that samples of different age of these chars appeared to lose their "memory" concerning their initial structures at high burn-offs. During the reporting period, thermal desorption experiments of selected samples were conducted. These spectra show that the population of low temperature oxygen surface complexes, which are primarily responsible for reactivity, are more similar for the high burn-off than for the low burn-off samples of different ages; i.e., the population of active sites are more similar for the �younger� and �older� chars at high burn-offs. Progress continued on experimental work at OSU. Another furnace run was conducted with a Pittsburgh seam coal. Temperature profiles were obtained, as well as char samples from three sampling ports. Nonisothermal TGA reactivities were also obtained for these samples. Work is continuing on final �fine-tuning� of the gas analysis section.
- Research Organization:
- Federal Energy Technology Center (FETC), Morgantown, WV, and Pittsburgh, PA
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC22-96PC96249
- OSTI ID:
- 7485
- Report Number(s):
- DE-FG22-96PC96249-08; ON: DE00007485
- Country of Publication:
- United States
- Language:
- English
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STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION
STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION