Stoichiometry and coal-type effects on homogeneous vs. Heterogeneous combustion in pulverized-coal flames
✍ Scribed by K.C. Midkiff; R.A. Altenkirch; R.E. Peck
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 976 KB
- Volume
- 64
- Category
- Article
- ISSN
- 0010-2180
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✦ Synopsis
Results of experiments to determine the extent of heterogeneous combustion in the rapid-devolatihzatton regime of fuel-rich bituminous and subbituminous coal-dust flames are reported. Major gas concentrations, gas and particle temperatures, and solids proximate and elemental compositions were measured as functions of residence time in pulverized-coal/O2/Ar flames stabilized on a flat-flame burner. Proximate fixed carbon and volatile matter measurements are corrected to account for devolatihzation exceeding that predicted by ASTM proximate analysis. The corrected proximate data are used to determine the fraction of volatile matter consumed heterogeneously in situ and the fraction released to the gas phase by pyrolysis. Seven to thirty-five percent of the initial corrected volatile matter is removed heterogeneously. A mass transfer analysis is applied to predict a time dependent critical particle size such that the volatiles flux emerging from larger particles is sufficient to prevent surface oxidation. Critical particle radii as large as 39 #m are calculated. Results of the volatde matter partitioning and critical radius calculations indicate that heterogeneous combustion is more important m the leaner flames and for the subbituminous coal.