This experimental study evaluates the inhibition performance of kinetic hydrates inhibitors (KHIs) of three amino acids, namely: glycine, proline, and alanine. It includes the performance comparison with the conventional inhibitor i.e., polyvinyl pyrrolidine (PVP) on methane (CH4) hydrate in oil systems in two different systems, i.e., deionized and brine water systems. The experiments were conducted in a high-pressure hydrate reactor replicating subsea pipeline conditions, i.e., the temperature of 274 K, pressure 8 MPa, and concentration of 1 wt%, by applying the isochoric cooling technique. The formation kinetics results suggest that all the studied amino acids effectively worked as kinetic inhibitors by potentially delaying CH4 hydrate formations due to their steric hindrance abilities. The interesting phenomenon was observed that the different studied amino acids behave differently in the brine-oil and deionized water-oil systems due to their side chain interaction. In a deionized water-oil system, glycine gives the highest inhibition performance by reducing the hydrate formation risk. On the contrary, in the brine-oil system, proline showed a significant inhibition effect. It should be noted that both glycine and proline were giving almost similar inhibition performance compared to the conventional hydrate inhibitor PVP, however glycine and proline significantly reduced CH4 consumption into hydrate due to their high surface active under CH4 conditions, which strengths the surface tension of the liquid/CH4 interface. Furthermore, according to the findings, it shows that increased side alkyl chain lengths of amino acids increase the efficacy of their kinetic hydration inhibition performance due to better surface adsorption abilities. The amino acids' ability to suppress growth is also linked strongly with hydrophobicity and alkyl side chain length. The findings of this study contribute significantly to current efforts to limit gas hydrate formation in offshore pipelines, particularly in oil-dominant pipelines.
Hydrate-based technology has yet to find its way to commercial applications due to several issues, including formation conditions and slow kinetics. Several solid particles were introduced to speed up hydrate formation. However, these solid compounds have given contradictory results. This study investigated the effect of high thermal conductive metallic nanofluids of silver (Ag) and copper (Cu) on CH4 and CO2 hydrates. The solid particles were suspended in a 0.03 wt% SDS aqueous solution, and the results were compared with the 0.03 wt% SDS and deionized water samples. A stirred tank batch reactor was used to conduct the thermodynamic and kinetic experiments. The thermodynamic study revealed that 0.1 wt% of solid particles do not shift the equilibrium curve significantly. The kinetic evaluation, including induction time, the initial rate of gas consumption, half-completion time, t50 and semi-completion time, t95, gas uptake, and storage capacity, have been studied. The results show that the Ag and Cu promote CH4 hydrates while they inhibit or do not significantly influence the CO2 hydrates formation. A predictive correlation was introduced to get the apparent rate constant of hydrate formation in the presence of metal-based fluid at the concentrations range of 0.005-0.1 wt%.