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首页> 外文期刊>Fuel >The effect of pore structure and gas pressure upon the transport properties of coal: a laboratory and modeling study 2. Adsorption rate modeling
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The effect of pore structure and gas pressure upon the transport properties of coal: a laboratory and modeling study 2. Adsorption rate modeling

机译：孔隙结构和气压对煤输运特性的影响：实验室和模型研究2.吸附速率模型

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摘要

The effect of coal composition, pore structure, and gas pressure upon methane and carbon dioxide gas transport in Cretaceous Gates Formation coal is investigated. Coal matrix gas transport models, which assume a homogeneous unimodal pore structure and linear adsorption isotherms, are not appropriate for modeling methane or carbon dioxide adsorption rates in all coal lithotypes. A new numerical model for matrix gas diffusion/adsorption is developed and applied to methane and carbon dioxide volumetric adsorption rate data. The model accounts for nonlinear adsorption in microporosity, a bimodal pore volume distribution, and time-varying gas pressure external to coal particles. Methane and carbon dioxide adsorption rate behaviour of bituminous coals with a multimodal pore volume distribution, such as dull or banded coals, are accurately captured with the current numerical model and an analytical solution which assumes a bimodal pore structure. Single parameter (diffusivity) models may be adequate for some bright coals. Careful consideration of coal pore structure is therefore required for accurate modeling of gas transport through the coal matrix. Carbon dioxide numerical and analytical model diffusivities are larger than methane diffusivities obtained for dry coal. In addition, methane diffusivities obtained using the models for wet coal are smaller than the model diffusivites obtained from dry coal. The numerical model diffusivities, which are corrected for the effects of nonlinear adsorption, are larger than diffusivities obtained for analytical models for pore diffusion. Me thane and carbon dioxide gas analytical and numerical model effective diffusivities are sensitive to the starting pressure in an adsorption step. The pressure-dependence of the analytical solution diffusivities is likely due to the nonlinearity of the adsorption isotherm. The effect of gas pressure upon diffusivities, obtained from the numerical model, indicate that the mechanism of gaseous diffusion is bulk diffusion. Results of the current study have important implications for coalbed methane reservoir characterization, the determination of gas contents for gas resource calculations, gas production simulations, and the prediction of outbursting in coal seams.
机译：研究了煤成分，孔隙结构和气压对白垩纪盖茨组煤中甲烷和二氧化碳气体输送的影响。假设均质的单峰孔隙结构和线性吸附等温线的煤基质气体传输模型不适用于模拟所有煤岩型中甲烷或二氧化碳的吸附速率。建立了用于基质气体扩散/吸附的新数值模型，并将其应用于甲烷和二氧化碳的体积吸附率数据。该模型说明了微孔中的非线性吸附，双峰孔体积分布以及煤颗粒外部随时间变化的气压。使用当前数值模型和假设双峰孔隙结构的解析解可准确捕获具有多峰孔隙体积分布的烟煤（例如无味或带状煤）的甲烷和二氧化碳吸附速率行为。单参数（扩散率）模型可能适合某些亮煤。因此，需要对煤孔结构进行仔细考虑，以对通过煤基质的气体传输进行精确建模。二氧化碳数值和分析模型的扩散率大于干煤获得的甲烷的扩散率。另外，使用湿煤模型获得的甲烷扩散率小于从干煤模型获得的甲烷扩散率。校正了非线性吸附影响的数值模型扩散率大于通过孔扩散分析模型获得的扩散率。甲烷和二氧化碳气体的分析和数值模型有效扩散率对吸附步骤中的起始压力敏感。由于吸附等温线的非线性，分析溶液扩散率的压力相关性很可能。从数值模型获得的气体压力对扩散率的影响表明，气体扩散的机理是整体扩散。目前的研究结果对煤层气储层特征化，天然气资源量的确定，天然气产量的模拟以及煤层突出的预测都具有重要意义。

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