Adsorption Equilibria and Kinetics of Methane + Nitrogen Mixtures on the Activated Carbon Norit RB3

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• 作者：Thomas E. Rufford ; Guillaume C. Y. Watson ; Thomas L. Saleman ; Paul S. Hofman ; Nathan K. Jensen ; Eric F. May
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2013
• 出版时间：October 2, 2013
• 年：2013
• 卷：52
• 期：39
• 页码：14270-14281
• 全文大小：532K
• 年卷期：v.52,no.39(October 2, 2013)
• ISSN：1520-5045

文摘

The separation of methane and nitrogen from binary mixtures using a commercial activated carbon, Norit RB3, was investigated. The adsorption of pure fluids and CH₄ + N₂ mixtures were measured at temperatures of 242, 273, and 303 K, at pressures ranging from 53 to 5000 kPa using a high pressure volumetric apparatus and at pressures from 104 to 902 kPa using a dynamic column breakthrough apparatus (DCB). The pure gas equilibrium adsorption capacities were regressed to Toth, Langmuir, Langmuir鈥揊reundlich, and Sips isotherm models; the Toth model gave the best prediction of measured capacities at pressures from 800 to 5000 kPa. The uptake of components from gas mixtures calculated using the Ideal Adsorbed Solution Theory (IAST), Extended Langmuir and Multi-Sips models were all within the uncertainties of the measured adsorption capacities, suggesting that for this adsorbent there is no significant advantage in using the more computationally intensive IAST method. A linear driving force (LDF)-based model of adsorption in a fixed bed was developed to extract the lumped mass transfer coefficients for CH₄ and N₂ from the pure gas DCB experimental data. This model was used with results from the pure gas experiments to predict the component breakthroughs from equimolar CH₄ + N₂ mixtures in the DCB apparatus. The Norit RB3 exhibited equilibrium selectivities for CH₄ over N₂ in the range 3 to 7 (measured selectivites have an average uncertainty of 37%), while the lumped mass transfer coefficients of CH₄ and N₂ were similar for this activated carbon, ranging from 0.004 to 0.052 s^鈥?. The results presented can serve as a reference data set upon which industrial PSA processes for separating CH₄ + N₂ mixtures using generic activated carbons can be developed and optimized over a wide range of pressures and temperatures.