The growth of methane hydrate with impingement influenced by thermodynamic inhibitor

Abstract Thermodynamic inhibitors have been widely used to prevent hydrate formation in natural gas hydrate exploitation and oil/gas transportation. In this article, molecular dynamics simulations of hydrate growth with impingement influenced by thermodynamic inhibitors including NaCl, KCl and ethylene glycol are performed. Consistent with the experimental results, we found that NaCl, KCl and ethylene glycol indeed delay the moment of hydrate come into accelerated growth stages, decreasing the growth rate of the hydrate and reducing the concentration of methane in the water solution. The Cl− ions are observed more frequently to insert into the cages than Na+ ions during the growth stage. The ethylene glycol molecules tend to occupy 51262 cages and occur in pairs or in clusters. The crystal clusters of NaCl are more complete and the ions of KCl are more widely distributed. The salt ions cause some unusual water-occupied defect structures to appear frequently near the ions. The microscopic mechanism of hydrate impingement by salts and ethylene glycol effects has been revealed for the first time and the dual role of the thermodynamic inhibitors: inhibition effect in the growth stage and destroy effect in the impingement stage, has been demonstrated. Our simulation result is not only beneficial for understanding the inhibition mechanisms of traditional inhibitors, but also guiding for the exploitation of novel inhibitors.