In this work, the ability of different equation of states and mixing rules for prediction of hydrate formation pressure, are compared. For this urpose, by using Van der Waals–Plauteeuw model for solid hydrate phase and six equation of states for calculation of fugacity of components in as and liquid phases, the pressure of hydrate formation in different mixtures have been calculated by three different mixing rules Van der Waals, anesh and GNQ, then by comparison of calculated results with experimental data, determined the accuracy of mixing rules and EOSs. Studied ystems contain binary mixtures CH4, C2H6, C3H8, i-C4H10, N2, CO2, and H2S with water in hydrate forming conditions. The interaction parameters in each mixture have been optimized by using two phase equilibrium data and then the optimized parameters have been used for three phase equilibrium calculations. Comparison of the calculated pressure of hydrate forming with experimental pressure shows that for most of binary mixtures in studied temperature and pressure ranges, GNQ mixing rule with average percent of error 7% has more accuracy than three other mixing rules Van der Waals and Danesh, and among of EOSs, SRK equation of state is better than others and using from YU-LU equation of state be not suggested.
Gas hydrates are crystalline solids that form when gas or volatile liquid molecules suiTable for hydrate formation are enclosed in a cage consisting of water molecules. Natural gas is a one of the most important source of energy in the world and one of the related problems to natural gas is gas hydrate forming. Naturally occurring hydrates, containing mostly methane, exist in vast quantities and are being looked upon as a potential alternative energy source. Carbon dioxide hydrates are also important hydrates . Barrer and Stuart innately suggested a statistical thermodynamic approach to estimate gas hydrate properties . In a similar approach, van der Waals and Platteeuw proposed the foundation of the method currently used . This model is similar to the Langmuir model for the gas adsorption. Later, Parrish and Prausnitz tried to improve this ethod . Efforts to improve the original assumptions by van der Waals and Platteeuw are discussed in detail by Holder et al . This method predicts the equilibrium conditions for both pure and mixture of hydrate formers, precisely.
Publisher : 2nd National Iranian Conference on Gas Hydrate (NICGH)
By : M. Karamoddin , F. Varaminian
File Information: English Language/ 12 Page / size: 557 KB
سال : 1392
ناشر : دومین کنفرانس ملی هیدرات گاز (NICGH)
کاری از : اقای کرامدین -ورامینیان
اطلاعات فایل : زبان انگلیسی / 12 صفحه / حجم : KB 557