Modeling on the phase equilibrium of gas hydrate in electrolytes containing system

Abstract

The phase equilibrium of gas hydrate is fundamental for flow assurance, energy exploitation, and hydrate concerning technique. In this study, the electrolyte NRTL equation coupled with the two-step hydrate model of Chen and Guo was successfully applied to predict the phase equilibrium of gas hydrate in the presence of single and binary mixed electrolytes. The predicted results were in good agreement with the available experimental data over a wide range of electrolyte concentrations when taking into account the contributions of long-range and short-range interactions in saline solution. Validated with 943 hydrate experimental data of pure gas and gas mixture formed in single and mixed electrolytes, the average absolute deviations in pressure are 5.42 % and 4.71 %, respectively. More importantly, it is further investigated that the proposed model shows a better performance for the high-concentration saline solution with concentration up to the near-saturation, with an average deviation of 0.59 K for methane hydrate. Therefore, the proposed model in this work is significant for comprehending gas hydrate phase behavior in saline solution, and provides better guidance for hydrate exploitation and industrial applications.