Cyclic Formation Stability of 1112-TetrafluoroethaneHydrate in Different SDS Solution Systems and Dissociation CharacteristicsUsing Thermal Stimulation Combined with Depressurization

摘要

Cold storage using hydrates for cooling is a high-efficiency technology. However, this technology suffers from problems such as the stochastic nature of hydrate nucleation, cyclic hydrate formation instability, and a low cold discharge rate. To solve these problems, it is necessary to further clarify the characteristics of hydrate formation and dissociation in different systems. First, a comparative experimental study in pure water and sodium dodecyl sulfate (SDS) solution systems was conducted to explore the influence of SDS on the morphology of the hydrate and the time needed for its formation under visualization conditions. Subsequently, the cyclic hydrate formation stability was investigated at different test temperatures with two types of SDS solution systems—with or without a porous medium. The induction time, full time, and energy consumption time ratio of the first hydrate formation process and the cyclic hydrate reformation process were analyzed. Finally, thermal stimulation combined with depressurization was used to intensify hydrate dissociation compared with single thermal stimulation. The resultsshowed that the growth morphology of hydrate and the time requiredfor its formation in the SDS solution system were obviously differentthan those in pure water. In addition, the calculation and comparisonresults revealed that the induction time and full time of cyclic hydratereformation were shorter and the energy consumption time ratio wassmaller in the porous medium. The results indicated that a porousmedium could improve the cyclic hydrate formation process by makingit more stable and by decreasing time and energy costs. Thermal stimulationcombined with depressurization at different backpressures (0.1, 0.2,0.3, and 0.4 MPa) effectively promoted the decomposition of hydrates,and with the decrease in backpressure, the dissociation time decreasedgradually. At a backpressure of 0.1 MPa, the dissociation time wasreduced by 150 min. The experimental results presented the formationand dissociation characteristics of 1,1,1,2-tetrafluoroethane hydratesin different systems, which could accelerate the application of gashydrates in cold storage.