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EFFECTS OF CYCLIC FREEZING AND THAWING ON COALS QUALITY INDICES



The article considers the climatic conditions of coal mining and transportation in the regions of the Arctic and the Far North. It is shown that during the spring and autumn periods, coals can be exposed to multiple freezing and thawing, which determines the possibility of changing the structural and mechanical properties of coal and their quality in general. Experimental studies of the effect of cyclic freeze-thawing (CFT) on the quality indices of coals of different types and their fractured-porous structure have been carried out. CFT conditions were as follows: the minimum exposure temperature is –40 °C, maximum + 5 °C, relative humidity 70%, number of cycles varied from 1 to 4. It is shown that under given conditions of the cyclic impacts, there exists a change in the fractured-porous structure of lignite and hard coals. It is found that, with the increase in the number of CFT cycles, a change occurs in the gross calorific value of coals (on dry ash-free basis of the fuel) as compared to the untreated ones. It has been established that cyclic freezing and thawing of lignite leads to a decrease in its total and, especially, the analytical moisture contents. At the same time, a significant increase in the net calorific value of lignite was noted, which, in the most general case, may be associated with a decrease in its moisture content.

Acknowledgements: This work was financially supported by the Russian Foundation of Fundamental Research (grant No 18-05-70002).

For citation: Epshtein S. A., Nikitina I. M., Agarkov K. V., Nesterova V. G., Minaev V. I. Effects of cyclic freezing and thawing on coals quality indices. MIAB. Mining Inf. Anal. Bull. 2019;(6):5-18. [In Russ]. DOI: 10.25018/0236-1493-2019-06-0-5-18.


: 6
2019
ISBN: 0236-1493
УДК: 552.57+54.03
DOI: 10.25018/0236-1493-2019-06-0-5-18
Authors: Epshtein S. A., Nikitina I. M., Agarkov K. V., etc.

Authors' Information:
S.A. Epshtein, Dr. Sci. (Eng.), Head of Laboratory, e-mail: apshtein@yandex.ru,
I.M. Nikitina, Cand. Sci. (Eng.), Leading Engineer,
K.V. Agarkov, Engineer,
V.G. Nesterova, Cand. Sci. (Eng.), Leading Engineer,
V.I. Minaev, Cand. Sci. (Eng.), Leading Engineer,
National University of Science and Technology «MISiS», Scientific and Training
Laboratory of Physics and Chemistry of Coals, 119049, Moscow, Russia.

Corresponding author: S.A. Epshtein, e-mail: apshtein@yandex.ru.

Key words:
Сoal, cryogenic weathering, freeze-thaw cycle, quality, fracturing.

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