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ECN publication
A mechanistic study of the slag formation from iron-rich coals
Published by: Publication date:
ECN 1995
ECN report number: Document type:
ECN-RX--95-041 Other
Number of pages: Full text:
27 Download PDF  

Near-burner slag formation of minerals from two iron rich coals wasinvestigated in the reproducible environment of a laboratory burner. Alumina deposit plates were placed in the flow with the thin edge facing the particle stream. Tests were performed in an environment simulating a low-NOx burner flame and in a sharply reducing atmosphere simulating cyclone-type combustion. In the latter simulation the deposit surface was at approximately 1400 deg C. The burner was fired with large excess CO for this simulation. In this highly reducing atmosphere, the pyrite (FeS2) rich coal produced a low-viscosity slag from which the sulphur rapidly volatilized. In the simulated slag from a coal rich in iron oxide, the slag was also of low viscosity. During cooling the iron crystallized out as dendrites or triangular crystals. These consisted of iron oxide, while reduction of the iron oxide to elemental iron by the carbon monoxide had been expected. In the low-NOx combustion simulation the probe temperature was 1100C. The coal rich in iron oxide did not produce an adherent deposit. Pyrite was found to produce a viscous surface layer of pyrrhotite (FeS) on which other minerals adhered, for the first time showing in fundamental form the slag induction by pyrite in progress. With the probe at a position where the secondary air mixed in, the deposit solidified because of the in-situ oxidation of the pyrrhotite to solid iron oxide. 5 figs., 1 tab., 13 refs.

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