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首页> 外文期刊>Fuel >Selective transport of CO_2, CH_4, and N_2 in coals: insights from modeling of experimental gas adsorption data
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Selective transport of CO_2, CH_4, and N_2 in coals: insights from modeling of experimental gas adsorption data

机译：煤中CO_2，CH_4和N_2的选择性迁移：通过实验气体吸附数据建模获得的见解

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摘要

Selective adsorption and transport of gases in coal are important for natural gas recovery and carbon sequestration in depleted coal seams for environmental remediation. Gases are stored in coal mainly in the adsorbed state. In this study, the interaction energies of adsorbates (CO_2, CH_4, and N_2) and micropores with various widths are investigated using a slit-shape pore model. The experimental adsorption rate data of the three gases conducted on the same coal sample are numerically simulated using a bidisperse model and apparent diffusivities of each adsorbate in the macropore and micropore are determined. The results indicate that the relative adsorbate molecule size and pore structure play an important role in selective gas adsorption and diffusion in micropores. Generally, the microporous coals diffusion is activated and the apparent micropore diffusivities of gases in coal decrease strongly with increase in gas kinetic diameters. Apparent micropore diffusivity of CO_2 is generally one or two order of magnitude higher than those of CH_4 and N_2 because their kinetic diameters have the relation: CO_2 (0.33 nm) < N_2 (0.36 nm) < CH_4 (0.38 nm). In contrast to theoretical values, apparent macropore diffusivity of CO_2 is also larger than those of CH_4 and N_2, suggesting that coal has an interconnected pore network but highly constricted by ultra micropores with width < approx 0.6 nm. It is also found that the apparent diffusivity strongly decreases with an increase in gas pressure, which may be attributed to coal matrix swelling caused by gas adsorption. Therefore, rigorous modeling of gas recovery and production requires consideration of specific interaction of gas and coal matrix.
机译：煤中气体的选择性吸附和运输对于贫化煤层中的天然气回收和碳固存对环境修复至关重要。气体主要以吸附状态存储在煤中。在这项研究中，使用缝隙形孔模型研究了吸附物（CO_2，CH_4和N_2）与不同宽度的微孔之间的相互作用能。使用双分散模型对在同一煤样品上进行的三种气体的实验吸附率数据进行数值模拟，并确定每种吸附物在大孔和微孔中的表观扩散率。结果表明，相对的被吸附物分子大小和孔结构在选择性气体吸附和在微孔中扩散中起重要作用。通常，随着气体动力学直径的增加，煤中的微孔煤扩散被激活，并且煤中气体的表观微孔扩散率大大降低。 CO_2的表观微孔扩散率通常比CH_4和N_2高1-2个数量级，因为它们的动力学直径具有以下关系：CO_2（0.33 nm）

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