Kinetics of methane hydrate formation in an aqueous solution of thermodynamic promoters (THF and TBAB) with and without kinetic promoter (SDS)

Abstract

Kinetic studies concerning the combination of thermodynamic promoters (tetra-n-butyl ammonium bromide, TBAB and tetrahydrofuran, THF) and kinetic promoters (sodium dodecyl sulphate, SDS) have not yet been investigated in detail for methane hydrate system suitable for natural gas storage and transportation. In this work, experiments were conducted at an initial pressure conditions of 7.5 MPa and 276.15 K for pure water, SDS, TBAB, (TBAB + SDS), THF, (THF + SDS) and (THF + TBAB) aqueous systems for various concentrations. Similarly, at 5.5 MPa and 276.15 K, experiments were conducted for pure water, TBAB, (TBAB + SDS), THF and (THF + SDS) aqueous systems for various concentrations. In addition, at 3.0 MPa and 276.15 K, 0.05 and 0.1 mass fraction of TBAB, 0.005 and 0.01 mass fraction of THF and (0.01 + 0.1) mass fraction of (THF + TBAB) aqueous systems have been considered for the experiments. It has been observed that the methane hydrate formed from pure water with SDS shows higher moles of gas consumption per mole of water as compared to other aqueous systems at higher pressure. Also, the use of SDS with THF shows drastic increase in methane consumption as against semiclathrate hydrate/hydrate formed using TBAB aqueous system and pure water. At lower pressure, of about 3 MPa, gas consumption per mole of water in hydrate has found to enhance for a mixed promoter system containing (THF + TBAB) as compared with the other aqueous systems. Theoretical and actual gas storage capacity calculations has also been performed for various concentrations of THF and TBAB aqueous systems. This study essentially helps to understand the behaviour of TBAB and THF aqueous solution with and without SDS and mixed promoter system of (THF + TBAB) for methane hydrate formation desirable for applications like gas storage, transportation and gas recovery using hydrate-based gas separation method.