New Group-Contribution Parameters for the Calculation of PC-SAFT Parameters for Use at Pressures to 276 MPa and Temperatures to 533 K

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• 作者：Ward A. Burgess ; Deepak Tapriyal ; Isaac K. Gamwo ; Yue Wu ; Mark A. McHugh ; Robert M. Enick
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：February 12, 2014
• 年：2014
• 卷：53
• 期：6
• 页码：2520-2528
• 全文大小：488K
• ISSN：1520-5045

文摘

Cubic Equations of State (EoSs) typically provide unreliable predictions for phase density and derivative properties at the high-temperature, high-pressure (HTHP) conditions associated with ultradeep petroleum reservoirs (that is, temperatures to 533 K and pressures to 241 MPa). The perturbed-chain statistical associating fluid theory (PC-SAFT) EoS returns improved predictions for density but still can overpredict the experimental value by up to 5% at HTHP conditions. Not surprisingly, when a modified set of the pure-component PC-SAFT parameters m, 蟽, and 蔚/k are fit to HTHP experimental density data, density predictions throughout the HTHP range agree with reference data to better than 卤1%. However, the lack of such HTHP density data for many hydrocarbons presents a hurdle to the more widespread use of this PC-SAFT method. This study presents a group-contribution (G-C) method for calculating PC-SAFT parameters that are designed to yield accurate HTHP density predictions. First- and second-order group contributions are considered. We have extended the group contribution model of Tihic and co-workers, developed for polymers, to accurately determine PC-SAFT parameters for alkanes, aromatics, and cycloalkanes at temperatures to 533 K and pressures to 276 MPa. The parameter values are a function of contributions from the various functional groups present and the nature of the various carbon atoms (aliphatic, aromatic, and naphthenic) comprising the molecule. Furthermore, when using second-order group contributions, it is possible to distinguish the differences in density among isomers. Density values are usually calculated to within 卤1鈥?%. Isothermal compressibility values are calculated to within 卤10%, isobaric heat capacity to within 卤5%, and speed of sound to within 卤4%.