Distribution of unfrozen water and heat transfer mechanism during thawing of liquid nitrogen immersed coal

Lei Qin, Siheng Lin, Haifei Lin, Zitong Xue, Weikai Wang, Xian Zhang and Shugang Li

Energy, 2023, vol. 263, issue PC

Abstract: The content and distribution of pore unfrozen water directly reflect the coal thawing process. It is the key to break through the evolution of coal pore structure under low temperature to study the pore ice melting speed. Taking bituminous coal in Yuan Zhuang, China as the research object, this paper studied pore thawing characteristics of coal samples with different liquid nitrogen freezing time through nuclear magnetic resonance technology. The experimental results clearly demonstrate that appropriate liquid nitrogen freezing time could greatly expand the macropore of bituminous coal, while the expansion effect of micropore and mesopore was less affected by the freezing time. As the freezing time increased, the pores and pore throats of saturated bituminous coal underwent two phases of ice-water transition expansion and liquid nitrogen low-temperature shrinkage. There were differences in the local thermal conductivity of coal samples with different liquid nitrogen freezing time, resulting in different thawing speeds of pore water at the same thawing temperature. When the freezing time increased, the thermal conductivity of coal samples increased due to the pore freezing shrinkage, which can greatly improve the thawing speed of coal samples.

Keywords: Liquid nitrogen freezing time; NMR; Thawing speed; Unfrozen water; Pore throat; Porosity (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:263:y:2023:i:pc:s0360544222027918

DOI: 10.1016/j.energy.2022.125905

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