基于低温氮吸附法的焦煤孔隙表面分形特征
Surface Fractal Characteristics of Coking Coal Pore Based on Low Temperature Nitrogen Adsorption
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摘要: 以焦煤的孔隙表面及其分形特征为研究对象，基于低温氮吸附法实验，测定煤样BET和Langmiur比表面积。根据低温氮吸附和脱附曲线特征，定性分析不同焦煤煤样BET法比表面积测值与实际值的偏差。分析比表面积与BJH脱附微孔孔容的关系，认为焦煤比表面积主要受控于脱附微孔孔容。分别计算Freundlich表面分形维数、Langmiur表面分形维数、FHH表面分形维数，认为造成较低覆盖度下FHH表面分形维数大于较高覆盖度下FHH表面分形维数的原因：一是焦煤表面具备多重分形特征；二是多层吸附（毛细凝聚）导致焦煤表面粗糙度下降。较低覆盖度下FHH表面分形维数与焦煤比表面积具有弱正相关性。Abstract: Taking the pore surface and its fractal feature of coking coal as the research object, we applied low temperature nitrogen adsorption to measure BET and Langmiur specific surface area. The features of isothermal adsorption and desorption curves were analyzed to compare the two methods of estimating specific surface area. The specific surface area of coking coal is relative to BJH desorption micropore volume. Three fractal methods were applied to analyze the surface fractal property of coking coal including Fractal Freundlich, Fractal Langmiur and Fractal FHH. The FHH surface fractal dimension at low coverage is larger than that at high coverage. There are two reasons for that, multi fractal and capillary condensation. Under the low coverage, FHH surface fractal dimension and coking coal specific surface area has a weak positive correlation.
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Keywords:
- nitrogen adsorption /
- specific surface area /
- porosity character /
- surface fractal
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