Research subject: One of the common problems in natural gas transmission lines is congestion and pressure drop in gas transmission pipes due to the formation of gas hydrates. Gas hydrates are stable crystalline compounds that are formed from the contact of water molecules with some gas molecules of the right size and under the right thermodynamic conditions (low temperature and high pressure). These compounds are studied from both thermodynamic and kinetic perspectives. Despite many studies in the thermodynamic part of hydrates, the kinetics of hydrates require further study.
Research approach: To this end, in order to determine the equilibrium conditions of natural gas hydrate, 5 different experiments were conducted with a natural gas sample from Gas and Liquefied Gas Refinery 1300 in the temperature range of 285.5, 281.5, 276.21, 275.59, 273.92 Kelvin and pressure of 41.1, 28.2, 18.84, 13.4, 11.5 bar in a reactor using the constant volume method.
Main results: Based on the experimental data, the mass transfer coefficient was 0.243, 0.159, 0.153, 0.094, 0.131 meters per second, respectively, and the molecular diffusion coefficient was 4.516(×10-09), 4.785(×10-09), 1.175(×10-09), 2.847(×10-09), 1.147(×10-09) m2/s. These results show that with increasing reactor temperature (at constant pressure), the mass transfer coefficient decreases and the molecular diffusion coefficient increases. Also, with increasing pressure (at constant temperature), the mass transfer coefficient increases and the molecular diffusion coefficient decreases, which is consistent with empirical equations. Statistical analysis of the results revealed that the reactor pressure parameter has a greater effect on the mass transfer coefficient than temperature. Furthermore, statistical examination showed that temperature is a more influential parameter on the molecular diffusion coefficient (DAB) of natural gas in water.