摘要
为给煤层气中甲烷与氮气的变压吸附分离提供相关的模型和热力学数据,采用静态体积法测试了温度298.15、313.15、328.15 K时,CH4/N2在自制炭分子筛上的吸附量,使用Langmuir等9个吸附模型对吸附量进行了非线性拟合,通过比较各吸附模型的拟合精度,得出最优化体积填充模型DA拟合效果最好,经验方程Freundlich模型拟合效果最差,Langmuir、Sips和Toth等模型拟合效果适中,同种模型对于N_2的拟合程度好于CH_4。同时对各模型的拟合参数进行了分析,BET方程不适合描述CH_4、N_2在该炭分子筛上的吸附,Langmuir、Toth、E-L等模型中饱和吸附量qm均随温度的升高而减小,且温度变化对于N_2的饱和吸附量影响较大;E-L模型、Toth模型和Sips模型中反映吸附剂表面能量不均匀性的参数n随着温度的升高而增大,F-L模型中分形维数D的增大表明温度升高增加了炭分子筛表面不均一性。吸附热力学分析表明,该炭分子筛对于CH_4、N_2的平均等量吸附热分别为11.80、9.06 k J/mol,均属于物理吸附;随着吸附量的增大,N_2的等量吸附热变化范围大于CH_4。
In order to provide the relative adsorption model and thermodynamic data for the separation of CH4/ N2 in coalbed methane by pressure swing absorption,the adsorption capacities of CH4 and N2 on the carbon molecular sieve（ CMS） by self made at 298.15,313.15 and 328.15 K were measured respectively. The Langmuir model and other eight models were used to fit the experimental data. The fitting degree of these models was compared. The optimization volume-filling based model D-A had the best fitting effect while empirical equation Freundlich model was the worst. The fitting effect of langmuir,Sips and Toth models were moderate. The fitting degree of CH4 was better than that of N2 for the same model. Meanwhile,the fitting parameters of different models were compared,the results showed that BET model was unfit to characterize adsorption of CH4 and N2 on this CMS. The saturated adsorption capacity qmwas decreased with the increase of temperature for Langmuir,Toth and E-L models. And that change of temperature had greater influence on N2 saturated adsorption capacity. The parameter n represented surface energy inhomogeneity of adsorbent increased with the temperature increasing for E-L,Toth and Sips models.The increacement of fractal dimension D in F-L model showed higher temperature increased CMS surface inhomogeneity.Through the analysis of the adsorption thermodynamics,the average isosteric heat of CH4 adsorption was 11.80 k J / mol which was comparable to 9.06 k J / mol of N2,the adsorption of CH4 and N2 on this CMS were belong to physical adsorption. With the increase of adsorption,the isosteric heat range of N2 was larger than that of CH4.
出处
《煤炭科学技术》
CAS
北大核心
2016年第9期192-199,共8页
Coal Science and Technology
基金
国家科技重大专项资助项目(2011ZX05037-003)
关键词
煤层气
CH4/N2分离
吸附模型
吸附热力学
coalbed methane
CH_4/ N_2 separation
adsorption model
adsorption thermodynamics
