Methane hydrate dissociation conditions in the presence of triethanolamine aqueous solution: experimental measurement and thermodynamic modeling

Abstract Alkanolamines are chemical compounds that possess both hydroxyl and amino functional groups. Natural gas processing plants utilize these compounds in the gas sweetening unit to remove acid gases from the natural gas stream. Several amines in this class have been shown in previous studies to inhibit hydrate formation. This study aims to evaluate the effect of triethanolamine (TEA) on the dissociation conditions of methane hydrate. TEA has not been investigated as a thermodynamic hydrate inhibitor, although it has a low vapor pressure and low toxicity. Amines like TEA may have several benefits, such as corrosion inhibition or pH buffering, which would provide a flow assurance strategy that is more integrated and cost-effective. The isochoric pressure-search method was employed to measure the dissociation conditions of methane hydrate in the presence of TEA. The temperature and pressure measurements ranged from 275.4 to 282.8 K and 3.32 to 7.02 MPa, respectively. Three concentrations of TEA were utilized. The hydrate suppression temperatures were 0.1, 0.7, and 1.5 K for 3.5, 10.0, and 15.0 mass% of TEA, respectively. This shows that TEA has a weak inhibition effect. Three thermodynamic models, namely (van der Waals-Platteeuw (vdW-P) + Peng-Robinson (PR) + NRTL), (vdW-P + PR + FH), and (vdW-P + PR + UNIQUAC), were employed in the modeling section. For 32 data points, it was concluded that the thermodynamic packages (vdW-P + PR + NRTL), (vdW-P + PR + FH), and (vdW-P + PR + UNIQUAC) had average absolute deviations of 0.2, 0.3, and 0.6 K, respectively. This proves the accuracy of three thermodynamic models.