Correlation of phase equilibria for gas hydrates in organic inhibitor aqueous solutions within wide concentration range

The calculation result of activity of water (aw) is an important factor affecting the description of phase equilibria for gas hydrate in the inhibited system. In this work, the Chen-Guo model was used to calculate the phase equilibria of simple gas hydrates. In addition, a new aw correlation was proposed to realize the description of gas hydrates in the organic inhibitor solutions containing methanol (MeOH), ethanol (EtOH), monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG) and glycerol (GLY). Mole fraction of these inhibitors ranges from 0.003 to 0.761. Moreover, the calculated results were compared with available experimental data in the literature. Results showed that the existing Margules equation has limited accuracy in the description of methane hydrate within a wide concentration range. Meanwhile, the proposed aw correlation performed much better than the Hu-Lee-Sum (HLS) correlation when incorporated with the Chen-Guo model, which increased the calculation accuracy for methane hydrate by similar to 54%. Furthermore, this work also presented an accurate description for ethane and carbon dioxide hydrates in the organic inhibitor solutions, which was evidenced by a series of experimental data.