β Scribed by Harry M. ten Brink; Simon Eenkhoorn; Gerrit Hamburg
No coin nor oath required. For personal study only.
The mechanism of slag formation by minerals from iron-rich coals was investigated in the reproducible environment of a laboratory burner. Alumina plates were used as substrates on which the particles were deposited. To simulate the highly reducing atmosphere of a cyclone-type flame, the burner was fired with large excess of CO. The mineral fractions of a coal rich in pyrite and a coal rich in iron oxide were used. The pyrite (FeS2)-rich sample produced a low-viscosity slag from which the sulfur rapidly volatilized. The slag from the iron oxide-rich sample was also of low viscosity. The expected reduction of the iron oxide in the slags to elemental iron by the carbon monoxide did not occur. Tests were also performed in an environment simulating a flame of a staged burner with its initial mildly reducing environment followed by an oxidizing atmosphere. Here the whole coals were used. The coal rich in iron oxide did not produce an adherent deposit. This is in agreement with the solid nature of the particles at the temperature of the deposit probe. With the pyrite-rich coal no deposit was formed in the reducing environment, because unburnt coal shielded the deposit plates. However, deposits did form at the position where the atmosphere became oxidizing. The pyrite was deposited here as partly oxidized molten FeS. Before complete oxidation and solidification of the deposit, silicate minerals were deposited into it. This showed for the first time the initiation of a plastic iron silicate slag in progress.
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