Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and Wetting-Drying ()
ABSTRACT
The paper presents the change in grain-size
composition of lignite under cyclic freezing-thawing
(FTC) and wetting-drying (WDC). The article shows that in the
spring and autumn periods the lignites can be subjected to repeated
freezing-thawing and wetting-drying, which determines the possibility of
changing their grain-size composition and structure. Experimental studies in
laboratory conditions on the influence of cyclic freezing-thawing (FTC) and
wetting-drying (WDC) on the quality
indicators of lignites have been carried out, their granulometric (fractional) composition has been studied.
Freezing-thawing cycle conditions are as follows (FTC): minimum exposure
temperature: -20°C; maximum: +5°C; relative humidity: 30%; number of processing cycles: 3. Wetting-drying cycles are as follows (WDC): drying temperatures are
+20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected
to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive
effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher
yield of fine sizes (-6+0; -13+0 mm) than the cycles of freeze-thaw. Furthermore, it
is found that the increase in the yield of fines depends on the heating
temperature: coal disintegration proceeds more intensively at a higher
temperature of drying.
Share and Cite:
Batugina, N. and Fedorov, V. (2024) Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and Wetting-Drying.
Natural Resources,
15, 17-27. doi:
10.4236/nr.2024.151002.
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