Including heterogeneous combustion in first-order and distributed activation energies models of coal nitrogen release
✍ Scribed by K.Clark Midkiff; Robert A. Altenkirch
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- English
- Weight
- 605 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0016-2361
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✦ Synopsis
Models of fuel-nitrogen release in pulverized-coal flames are developed to account for (1) the occurrence of parallel heterogeneous and homogeneous coal-N removal and (2) the release of coal-N by numerous different first-order reactions characterized by a normal distribution of activation energies. These models are fitted to previously reported flat-flame, coal-dust burner data. Including heterogeneous combustion effects in a model of coal-N release during the early, largely devolatilization, stage of the flames results in a first-order coal-N devolatilization rate constant with an activation energy that is significantly, but not substantially, higher than the activation energy that is determined neglecting the effects of heterogeneous combustion. Allowance is made for coal devolatilization in excess of that predicted by the ASTM proximate analysis test. A distributed activation energies model is fitted to the combined coal-N release data for particular coals burnt at two different stoichiometries. The mean and standard deviation of the activation temperature for nitrogen devolatilization including the effects of heterogeneous combustion are 82OOf 600 K for the bituminous coal studied and 5100~2300K for a subbitumin&s coal.