Kinetics of methane + hydrogen sulfide clathrate hydrate formation in the presence/absence of poly N-vinyl pyrrolidone (PVP) and L-tyrosine: Experimental study and modeling of the induction time

Abstract

Gas hydrates, or clathrate hydrates, formation can dramatically damage the transmission lines and operational equipment of the natural gas dominated system, which in turn to ruptured pipeline or destruction equipment. To prevent these problems, hydrate inhibitor injection is one of the most practical approaches. Subsequently, in several experimental studies, the induction time appraisement is employed as an expression for the inhibition accomplishment of kinetic hydrate inhibitor (KHI). Therefore, predicting/estimating the gas hydrate induction time is a crucial and essential subject in this field. To tackle this substantial issue, in the current investigation, the kinetics of methane + hydrogen sulfide hydrate formation (induction time) was investigated. The effects of using two types of KHI including Poly N-vinyl pyrrolidone (PVP) and L-Tyrosine with different concentrations (less than 2 wt%) on the induction time of the aforesaid system were revealed. The experiments were performed in a 100 cm3 stirred autoclave at temperatures ranging from 274.15 to 280.15 K over the primary pressure of 10 MPa. The experimental results indicate that KHIs at low concentrations (less than 2 wt%) approximately have no observational effects on thermodynamic equilibrium conditions but have a significant impact on increasing the induction time and abating the gas consumption during crystalline solid formation. This study also aimed at utilizing the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) based model of induction time for hydrate phase appearance of the binary gaseous comprising of 0.995 mole fraction (MF) CH4 + 0.005 mole fraction (MF) H2S at different subcooling in the presence and absence of PVP and L-Tyrosine applying the Freundlich adsorption isotherm. Model results show a satisfactory agreement with experimental data. The model can be used for reliable calculation of hydrate formation induction time for the methane + hydrogen sulfide + water system in the presence/absence of the aforementioned KHIs.