Effect of heating rate on the accuracy of measuring equilibrium conditions for methane and argon hydrates

Abstract This work examined the effect of the heating rate (from 0.2 K/h (5.56·10 −5  K/s) to 10 K/h (277.78·10 −5  K/s)) on the accuracy of measuring the three-phase equilibrium conditions for gas–liquid water–hydrate systems. The H 2 O+CH 4 (CS-I) system was studied over the temperature range of 274.2–285.2 K and the pressure range of 3.0–9.0 MPa. Additionally, the H 2 O+Ar (CS-II) system was studied over the temperature and pressure ranges of 273.7–280.2 K and 9.5–18.5 MPa, respectively. The hydrate formation/dissociation experiments were performed in a Sapphire Rocking Cell RCS6 under isochoric conditions. Gas hydrates were formed using a 0.1% (w/w) solution of sodium dodecyl sulfate. It was found that the dissociation of the methane and argon hydrates (CS-I and CS-II, respectively) proceeds under conditions close to equilibrium at heating rates up to 0.5 K/h (13.89·10 −5  K/s). Significant deviations of the P , T -curve from the equilibrium line are observed at higher heating rates for methane hydrate (>281.2 K) and argon hydrate (>277.2 K). Our data on the equilibrium conditions of argon hydrate complement previous published data over the temperature range of 273.7–280.2 K and the pressure range of 9.5–18.5 MPa.