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Investigation of methane diffusion in low-rank coals by a multiporous diffusion model
Li, Zhentao1; Liu, Dameng1; Cai, Yidong1; Shi, Yunlong2
2016-07-01
Source PublicationJOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING
Volume33Pages:97-107
SubtypeArticle
AbstractTo study the methane diffusion behaviors of low-rank coals (R-o,R-m of 0.45% and 0.58%), a combination of CO2 adsorption, N-2 adsorption/desorption, and mercury intrusion porosimetry (MIP) measurements were used to characterize the pore structure of coals, and a new multiporous diffusion model was established to model methane diffusion under dry and moist conditions during the methane adsorption process. The results indicate that the pore structure of low-rank coal samples exhibits a multimodal pore size/volume distribution and has a greater percentage of microporosity and mesoporosity. The multi porous model provides a better fit than the bidisperse model, which deviates significantly from the data, especially during the initial diffusion stage. Based on the multiporous diffusion model, the macropore diffusivity (10(-4)-10(-3) s(-1)) is generally one to three orders of magnitude greater than the mesopore diffusivity (10(-5)-10(-4) s(-1)) and micropore diffusivity (10(-6)-10(-5) s(-1)). Moreover, both the macropore diffusivity and micropore diffusivity show a decreasing trend with increasing pressure, whereas a strong positive correlation exists between the mesopore diffusivities and pressure, indicating that the effect of pressure on methane diffusion in pores with different sizes is different during the adsorption process. This difference may be due to the competition between the different mechanisms of gaseous methane diffusion and the swelling of the coal matrix caused by gas adsorption. Furthermore, the moisture reduced methane diffusivities is mainly due to the moisture in the coal matrix that adsorbs to the pore surface and occupies the pore space, as well as changes the pore structure according to the, effect of mineral swelling from the adsorbing moisture. Therefore, these results may have a significant implication for understanding the transport mechanism of methane in coals and the design of enhanced CBM recovery. (C) 2016 Elsevier B.V. All rights reserved.
KeywordGas Diffusion Multiporous Diffusion Model Pore Structure Pressure Moisture Content
DOI10.1016/j.jngse.2016.05.012
Indexed BySCI
Language英语
WOS IDWOS:000381594000011
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Document Type期刊论文
Version出版稿
Identifierhttp://ir.qdio.ac.cn/handle/337002/135881
Collection海洋环流与波动重点实验室
Affiliation1.China Univ Geosci, Coal Reservoir Lab, Natl Engn Res Ctr, CBM Dev & Utilizat, Beijing 100083, Peoples R China
2.Chinese Acad Sci, Inst Oceanol, Key Lab Ocean Circulat & Waves, Qingdao 266071, Peoples R China
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Li, Zhentao,Liu, Dameng,Cai, Yidong,et al. Investigation of methane diffusion in low-rank coals by a multiporous diffusion model[J]. JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING,2016,33:97-107.
APA Li, Zhentao,Liu, Dameng,Cai, Yidong,&Shi, Yunlong.(2016).Investigation of methane diffusion in low-rank coals by a multiporous diffusion model.JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING,33,97-107.
MLA Li, Zhentao,et al."Investigation of methane diffusion in low-rank coals by a multiporous diffusion model".JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING 33(2016):97-107.
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