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Modeling Phase Equilibria of Semiclathrate Hydrates Formed with Tetrabutylammonium Chloride Solutions
Received date: 2014-03-21
Revised date: 2014-06-18
Online published: 2014-06-30
Based on the van der Waals-Platteeuw (vdW-P) theory and the hydrate structure of tetrabutylammonium chloride (TBAC), a thermodynamic approach is proposed to determine the phase equilibrium conditions of TBAC semiclathrate hydrates in this work. Two modifications for evaluations of vapor pressure of water in the empty hydrate lattice and Langmuir constants relating to the salt concentration in aqueous solution and temperature are proposed. To obtain the activity coefficients of species in the aqueous phase and the fugacity of gaseous hydrate former in gas phase, the electrolyte-Non-Random Two-Liquid (e-NRTL) activity model and Peng-Robinson equation of state (PR-EoS) are employed, respectively. Additionally, the model predicted phase equilibrium conditions for hydrates of TBAC + CH4 and TBAC + CO2 over temperature, pressure, and salt concentration ranges from 280.1 K to 293.6 K, from 0.337 MPa to 7.017 MPa, and from 4.34% to 34%, respectively. It is shown that agreement of predicted data with experimental data is satisfactory, with average absolute pressure deviation 3.2637% and 9.2258% for hydrates of TBAC + CH4 and TBAC + CO2, respectively.
SHI Ling-li , LIANG De-qing . Modeling Phase Equilibria of Semiclathrate Hydrates Formed with Tetrabutylammonium Chloride Solutions[J]. Advances in New and Renewable Energy, 2014 , 2(3) : 221 -225 . DOI: 10.3969/j.issn.2095-560X.2014.03.010
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