Investigation of Micro-Mechanism and Crystallization Behavior of Salts in Brine Discharge Tubing of Deep Salt Cavern Gas Storage

To address brine discharge pipe blockage caused by salt crystallization in natural gas storage facilities within salt caverns, this study employed GROMACS molecular dynamics simulations to develop a three-dimensional regulatory model integrating interfacial polarity, roughness, and diffusion fields. By constructing and comparing four representative interface models, rough iron, smooth iron, epoxy resin, and polytetrafluoroethylene interfaces in sodium chloride solution, the study systematically revealed the coupled microscopic mechanisms of ion adsorption, diffusion, and ordering. The rough iron interface exhibits a nanotrapping effect, increasing the sodium ion concentration to 3.8 times that of the bulk solution. In contrast, the epoxy resin interface forms a hydrated buffer layer, thereby reducing adsorption energy. Conversely, the PTFE interface exhibits superior anti-crystallization performance, extending the induction period by 3.2 times through synergistic effects of ultra-low adsorption energy, high diffusion coefficient, and weak interfacial tension. By integrating these key parameters, an innovative interfacial anti-crystallization index was established, exhibiting a significant negative correlation with crystallization mass in experiments. Furthermore, a nanostructure modification strategy featuring nano-pore arrays was proposed. This approach reduces effective adsorption sites while enhancing ion diffusion rates, thereby decreasing crystallization rates. Such atomically precise control offers novel pathways for designing advanced anti-crystallization coatings.