Insights into the self-preservation effect of methane hydrate at atmospheric pressure using high pressure DSC

Abstract

The self-preservation effect of CH4 hydrate can facilitate the solidified storage and transport of natural gas at mild temperature and pressure conditions. However, the factors affecting the self-preservation of CH4 hydrate are complex and the impacts are not well known. In this work, a high pressure micro-differential scanning calorimeter (HP μ-DSC) was employed to elucidate the impact of preservation time, preservation temperature, and heating rate on the self-preservation of CH4 hydrate at atmospheric pressure (0.1 MPa) from the perspective of thermal analysis. It was found that CH4 hydrate can be stably preserved at 0.1 MPa in the temperature range from 253.15 to 268.15 K, and the self-preservation effect of CH4 hydrate was independent of the preservation time while no heat was injected into the preservation system. This will avail long-distance storage and transport of natural gas under low energy consumption conditions. In addition, two dissociation regimes of CH4 hydrate were identified when varying the heating rate from 0.1 K/min to 1 K/min. At the small heating rate of 0.1 K/min, the ice layer melted prior to the dissociation of CH4 hydrate. When the heating rate was increased to 0.5 and 1 K/min, the ice layer and CH4 hydrate melted simultaneously. Therefore, a large heating rate can be used to recover CH4 quickly from the dissociation of CH4 hydrate and thus the operating time will be saved.