Study on coal cracking under liquid nitrogen soaking based on nuclear magnetic resonance and stress analysis

doi:10.16265/j.cnki.issn1003-3033.2019.11.025

Abstract

Abstract: In order to study variation law of pore structure of coal under liquid nitrogen soaking, with dry coal as an experimental object, bituminous coal and anthracite were treated under different impacting time respectively. Then, pore variation characteristics of coal before and after liquid nitrogen soaking was analyzed through NMR experiment, and numerical simulation of soaking process was conducted by using COMSOL software before thermal stress was calculated and analyzed on the basis of distribution of coal temperature field. The results indicate that liquid nitrogen soaking has different degrees of damage to pores and fissures of various sizes of coal, and micropore volumes of bituminous coal and anthracite will increase by 86.43% and 20.28%, respectively when they are soaked for 30 minutes. Under liquid nitrogen soaking, low temperature gradually transfers from coal surface of to its inside while thermal stress generated at various points inside coal gradually increases with time until the maximum stress value reaches 9.84 MPa. Generation and change of thermal stress is the main mechanism for permeability increase of dry coal.

Key words: liquid nitrogen soaking, nuclear magnetic resonance (NMR), coal cracking, hole crack, thermal stress

CLC Number:

X936

WANG Chunxia, ZHANG Xuebo, LU Fangchao. Study on coal cracking under liquid nitrogen soaking based on nuclear magnetic resonance and stress analysis[J]. China Safety Science Journal, 2019, 29(11): 156-163.

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