TITLE:
Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and Wetting-Drying
AUTHORS:
Natalia S. Batugina, Vladislav I. Fedorov
KEYWORDS:
Lignite, Freezing-Thawing Cycle, Wetting-Drying Cycle, Grain Size Composition, Dust Coal, Storage, Loss, Quality
JOURNAL NAME:
Natural Resources,
Vol.15 No.1,
January
26,
2024
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.