Elsevier

Fuel

Volume 61, Issue 2, February 1982, Pages 175-181
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Low-temperature air oxidation of caking coals. 2. Effect on swelling and softening properties

https://doi.org/10.1016/0016-2361(82)90231-9Get rights and content

Abstract

Three highly swelling bituminous coals (< 75 um > 63 um size) were pre-oxidized to various levels of weight gain and then their plastic properties monitored during carbonization. Additions of relatively small amounts of oxygen (<1–2% by wt) cause marked changes in swelling and softening properties. In general, oxidation causes: substantial reductions in volume changes, increases in softening and dilation temperatures, and a slight reduction in resolidification temperatures. For coals which exhibit high fluidities, slight oxidation results in an increase in expansion prior to destruction of swelling properties. For a given level of weight gain, reduction in plastic behaviour of a coal becomes more severe as the temperature of pre-oxidation is increased. Weathering studies indicate that exposure of an hvA bituminous coal to moist air at ambient temperature has more effect on subsequent swelling and softening properties than exposure to dry air. Fine coal particles stored for extended periods of time in atmospheres with even slight oxygen concentrations show definite signs of weathering. The plastic properties of an oxidized coal may be partially resotred by grinding to expose new surface.

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