Effects of Sea Salts on the Phase Behavior and Synthesis of Methane Hydrates plus THF: An Experimental and Theoretical Study

To enhance the progress of hydrate-based technologies,obtainingaccurate and comprehensive data on hydrate equilibria is vital. Thepresence of mineral salts in water necessitates an examination oftheir impact on the phase behavior of gas hydrates. This researchaims to explore the influence of NaCl and MgCl2, the primarydissolved salts in natural water, on the tetrahydrofuran (THF)-CH4 hydrate system. Experiments are conducted using the isochoricpressure search method with a step-heating technique, covering a rangeof pressures (1-55 MPa), temperatures (283-300 K), andTHF mass fractions (0.05-0.19). The Chen and Guo theory isutilized to extend a thermodynamic model that predicts the behaviorof the THF-CH4 hydrate system in the absence orpresence of mineral salts. The model demonstrates a satisfactory levelof consistency with the generated hydrate data, with an average absoluterelative deviation of only 6.05%. Methane's properties in thegas phase are derived using the Soave-Redlich-Kwongequation of state (SRK EoS). Additionally, the e-UNIQUAC model isemployed to calculate the activity of water and the activity coefficientof THF in the electrolyte aqueous phase. The experimental resultsindicate that THF effectively addresses the challenges associatedwith methane hydrate formation in saline water, making it a promisingpromoter. Furthermore, the study reveals that the inhibitory effectof salts is more pronounced in concentrated THF solutions, and increasingthe pressure for hydrate formation enhances the inhibitory effectof salts.

Automated summary

To enhance the progress of hydrate-based technologies, comprehensive data on the impact of mineral salts on gas hydrate phase behavior is explored in this research. Using the THF-CH4 hydrate system, the influence of NaCl and MgCl2, the primary dissolved salts in natural water, is examined. Experimental results show that THF effectively addresses the challenges of methane hydrate formation in saline water, making it a promising promoter. Additionally, the inhibitory effect of salts is more pronounced in concentrated THF solutions, and increasing the pressure for hydrate formation enhances the inhibitory effect of salts.