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Title:
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Flame-transformations of coal-pyrite
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Author(s):
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Published by:
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Publication date:
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ECN
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1995
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ECN report number:
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Document type:
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ECN-RX--95-037
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Other
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Number of pages:
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Full text:
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32
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Download PDF
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Abstract:
The flame-kinetics of pyrite (FeS2) particles were studied in alaboratory burner facility. Size and composition of the in-going particles
and the flame-products were analyzed with CCSEM, Computer Controlled Scanning
Electron Microscopy. The particles, of fifty micrometer size, decomposed in
25 milliseconds into pyrrhotite (FeS), which rapidly melted. There were no
further transformations in a reducing flame. In an oxidizing flame,
decomposition and melting occurred prior to oxidation with similar rates. The
pyrrhotite droplets oxidized to solid iron oxide in 100 ms. This time
translates to the characteristic rate for diffusion of oxygen to the
droplets. It shows that the expected slow internal transport of reactants in
the droplets is not the rate-limiting step. The rapid droplet-side transport
is caused by internal flows induced by the surface friction of the
gravitational motion of the droplets relative to the combustion gas. At the
final stage of oxidation, cenospheres were observed. The standard CCSEM
method had classified the cenospheres as small particles which led to a first
erroneous conclusion of particle fragmentation. 5 figs., 2 tabs., 1 appendix,
17 refs.
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