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Title: Predicting the devolatilization behavior of any coal from its ultimate analysis

Abstract

FLASHCHAIN has been developed to predict yields and product characteristics from any coal for any operating conditions. This evaluation demonstrates the model`s utility for the usual situation where the ultimate analysis is the only sample-specific information available. It also identifies the key reaction centers in coal as its structural components called labile bridges. Their elemental compositions are grossly different than the analogous whole-coal properties, showing much stronger rank dependences and a much higher degree of sample-to-sample variability. In light of these findings, it is inconceivable that bride conversion rates are rank-independent. Parameters in the rate law for bridge conversion in FLASHCHAIN are now explicitly related to the elemental compositions of bridges. The (O/C){sub B} ratios are the best regression variable for the rate constants because oxygen is the most effective promoter of pyrolytic decompositions. The (O/H){sub B} rates are best for the selectivity coefficient between scission and condensation into char links because oxygen promotes crosslinking but hydrogen addition to broken bridge fragments stabilizes them. These extensions are evaluated in comparisons against a database of 27 coals that span all ranks from lignite to anthracite, for heating rates from 5 to 5,000 K/s, ultimate temperatures to 1,300 K, and pressures frommore » vacuum to 70 MPa. In four out of five cases, predicted total and tar yields are within experimental uncertainties. The model is also used to rigorously define nominal devolatilization rates for diverse coal types and broad ranges of operating conditions. Nominal rates have very low activation energies, proving that heat and mass transport resistances are not responsible for the low values because this theory is completely free of these considerations. Whereas nominal rates are rather insensitive to coal type variations and independent of pressure, they vary in proportion to changes in heating rate.« less

Authors:
 [1]
  1. SRI International, Menlo Park, CA (United States). Molecular Physics Lab.
Publication Date:
OSTI Identifier:
28056
Report Number(s):
CONF-940711-
Journal ID: CBFMAO; ISSN 0010-2180; TRN: IM9516%%182
Resource Type:
Journal Article
Journal Name:
Combustion and Flame
Additional Journal Information:
Journal Volume: 100; Journal Issue: 3; Conference: 25. international symposium on combustion, Irvine, CA (United States), 31 Jul - 5 Aug 1994; Other Information: PBD: Feb 1995
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COAL; CHEMICAL COMPOSITION; DEVOLATILIZATION; CORRELATIONS; F CODES; COAL RANK; CALORIFIC VALUE; COAL TAR; CHEMICAL REACTION YIELD; PYROLYSIS; ACTIVATION ENERGY; MASS TRANSFER; HEAT TRANSFER

Citation Formats

Niksa, S. Predicting the devolatilization behavior of any coal from its ultimate analysis. United States: N. p., 1995. Web. doi:10.1016/0010-2180(94)00060-6.
Niksa, S. Predicting the devolatilization behavior of any coal from its ultimate analysis. United States. https://doi.org/10.1016/0010-2180(94)00060-6
Niksa, S. 1995. "Predicting the devolatilization behavior of any coal from its ultimate analysis". United States. https://doi.org/10.1016/0010-2180(94)00060-6.
@article{osti_28056,
title = {Predicting the devolatilization behavior of any coal from its ultimate analysis},
author = {Niksa, S},
abstractNote = {FLASHCHAIN has been developed to predict yields and product characteristics from any coal for any operating conditions. This evaluation demonstrates the model`s utility for the usual situation where the ultimate analysis is the only sample-specific information available. It also identifies the key reaction centers in coal as its structural components called labile bridges. Their elemental compositions are grossly different than the analogous whole-coal properties, showing much stronger rank dependences and a much higher degree of sample-to-sample variability. In light of these findings, it is inconceivable that bride conversion rates are rank-independent. Parameters in the rate law for bridge conversion in FLASHCHAIN are now explicitly related to the elemental compositions of bridges. The (O/C){sub B} ratios are the best regression variable for the rate constants because oxygen is the most effective promoter of pyrolytic decompositions. The (O/H){sub B} rates are best for the selectivity coefficient between scission and condensation into char links because oxygen promotes crosslinking but hydrogen addition to broken bridge fragments stabilizes them. These extensions are evaluated in comparisons against a database of 27 coals that span all ranks from lignite to anthracite, for heating rates from 5 to 5,000 K/s, ultimate temperatures to 1,300 K, and pressures from vacuum to 70 MPa. In four out of five cases, predicted total and tar yields are within experimental uncertainties. The model is also used to rigorously define nominal devolatilization rates for diverse coal types and broad ranges of operating conditions. Nominal rates have very low activation energies, proving that heat and mass transport resistances are not responsible for the low values because this theory is completely free of these considerations. Whereas nominal rates are rather insensitive to coal type variations and independent of pressure, they vary in proportion to changes in heating rate.},
doi = {10.1016/0010-2180(94)00060-6},
url = {https://www.osti.gov/biblio/28056}, journal = {Combustion and Flame},
number = 3,
volume = 100,
place = {United States},
year = {1995},
month = {2}
}