Evolution mechanism of pore structure of water-bearing coal under cyclic microwave radiation

doi:10.16265/j.cnki.issn1003-3033.2024.11.0347

Abstract

Abstract:

In order to better use microwave antireflection technology to safely and efficiently extract coal seam gas, and to explore the influence of coal moisture content change on the antireflection effect under cyclic microwave conditions, firstly, the transverse relaxation time (T₂) spectrum and longitudinal relaxation time (T₁) -T₂ spectrum characterizing the pore structure characteristics of coal samples were obtained by NMR technology. Then, the characteristic parameters of nuclear magnetic resonance were obtained by using T₂ data, and the change of pore structure evolution with water content under cyclic microwave radiation was further clarified. Finally, based on the mechanism of cyclic microwave permeability enhancement, the pore structure evolution mechanism of different water-bearing coal bodies was revealed. The results show that the pore structure of coal with different water saturation is obviously improved under cyclic microwave radiation, and the coal sample with 75% water saturation has a better antireflection effect than other test coal samples. In the process of cyclic microwave radiation promoting the evolution of pores to larger pores, pore blockage occurs due to the thermal fracture of coal, and increasing water saturation can reduce this phenomenon. The cyclic microwave anti-reflection mainly relies on thermal stress and air pressure. With the improvement of coal permeability, the effect of microwave anti-reflection is weakened, and the influence of coal water content is weakened.

Key words: coal seam gas, cyclic microwave radiation, water-contained coal, pore structure, nuclear magnetic resonance(NMR)

CLC Number:

X936

LI He, JIANG Xunqi, LU Yi, SHI Shiliang, LU Jiexin, CAO Jieyan. Evolution mechanism of pore structure of water-bearing coal under cyclic microwave radiation[J]. China Safety Science Journal, 2024, 34(11): 99-107.

Figures/Tables 10

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孔隙类型	含水饱和度/%	T₂谱面积				总增幅程度/%
孔隙类型	含水饱和度/%	原煤	循环1次后	循环2次后	循环3次后	总增幅程度/%
吸附孔	0	2 025.836	1 937.267	1 884.41	1 871.838	-7.60
	25	1 865.448	1 887.79	1 880.006	1 880.845	0.83
	50	2 023.991	1 959.765	1 934.842	1 915.345	-5.37
	75	2 005.109	1 767.157	1 917.584	1 908.728	-4.81
	100	1 941.281	1 902.382	1 873.722	1 854.638	-4.46
渗流孔	0	956.843	1 199.496	1 241.696	1 332.215	39.23
	25	1 341.829	1 396.15	1 456.57	1 501.088	11.87
	50	1 071.94	1 193.319	1 202.64	1 363.123	27.16
	75	983.021	1 287.142	1 432.735	1 454.605	47.97
	100	1 010.553	1 235.637	1 306.645	1 359.339	34.51
总孔隙	0	2 982.679	3 136.763	3 126.106	3 204.053	7.42
	25	3 207.277	3 283.94	3 336.576	3 381.933	5.45
	50	3 095.931	3 153.084	3 137.482	3 278.468	5.90
	75	2 988.13	3 054.299	3 350.319	3 363.333	12.56
	100	2 951.834	3 138.019	3 180.367	3 213.977	8.88