Development of a high pressure electrical conductivity probe for experimental studies of gas hydrates in electrolytes

Abstract

We previously reported the development of a high pressure automated lag time apparatus and a high pressure video cell for experimental study of nucleation and growth of gas hydrates. Here we report the development of a high pressure electrical conductivity probe that monitors the electrical conductivity of an electrolyte that is subjected to a linear cooling ramp at elevated hydrate-forming-gas pressures. The electrical conductivity steadily decreases as the linear cooling progresses because of the increasing viscosity of the electrolyte and the consequently decreasing mobility of the ions. The onset of the formation of methane-propane mixed gas hydrate films at the gas-electrolyte interface is marked by an upward spike in the electrical conductivity. The physical mechanisms behind this phenomenon remain to be elucidated. Continued cooling of the electrolyte to, and subsequent holding of, the temperature at 273 K eventually results in decreased electrical conductivity. This conductivity signal can be used for the detection of the onset of the formation of gas hydrates in optically opaque samples that contain electrolytes.