Experiments and prediction of phase equilibrium conditions for methane hydrate formation in the NaCl, CaCl2, MgCl2 electrolyte solutions

Formation of gas hydrate cause a lot of problems for gas industry in the generation, transmission and processing which caused blockage in the equipment. One of the most common treatments is injection of electrolytes as chemical inhibitors. In this paper, hydrate formation conditions of methane gas in both water and NaCl, CaCl2, MgCl2 electrolyte solutions were measured and a new thermodynamic calculation method based on the original PR model and Chen-Guo model was proposed by introducing a water activity calculation equation. The comparison demonstrates that the inhibiting effect of MgCl2, NaCl, CaCl2 on the hydrate formation decrease respectively. The experimental results showed that the hydrate formation conditions are related to the electrolyte molecular mass and electrolyte concentration to a large extent, the deviation will increase as the temperature or the electrolyte concentration increases, so three parameters t(1), t(2), t(3) (0.034, 0.15, 0.01) which are related to temperature, concentration and molecular weight of electrolyte are introduced in the new calculation method. The absolute average deviation of 41 sets of data is 7.98 and 1.96 respectively before and after the correction parameters were introduced, the accuracy has more than quadrupled. (C) 2018 Elsevier B.V. All rights reserved.