Identification of macroscopic and microscopic behaviors for controlling nucleation and growth of clathrate hydrate: application to particle-based hydrate inhibitor

Abstract

Clathrate hydrate is a crystalline compound that encage guest molecules such as small hydrocarbons or organic molecules inside the cages of hydrogen-bonded water molecules. To control the nucleation and growth of clathrate hydrates, this thesis intensively investigated the macroscopic and microscopic behaviors at the nanoparticle stabilized water-oil interface. By providing fundamental basis for performance improvement and application into industry as well as the inhibition effects and their mechanisms, the utilization of nanoparticles at flow assurance problem was suggested. The contents of each chapters are as follows.In Chapter 2, the hydrophobic silica nanoparticles stabilized at the water-oil interface inhibited the growth of hydrate particles through the anti-adhesive effect, which operates with different mechanisms from common anti-agglomerants. In the water-in-oil type Pickering emulsion system stabilized by magnetic nanoparticles, the agglomeration between hydrate particles was prevented by the anti-adhesive effect, and the induction time for hydrate nucleation was delayed. Thus, in Chapter 3, it was confirmed that the particle-based inhibitors have dual inhibition effects of kinetic hydrate inhibitors and anti-agglomerants. By identifying the conditions for hydrate promotion according to the emulsion properties and enhancing the recovery of inhibitors through boot drum and co-solvents, the application into the offshore platforms was suggested. In Chapter 4, the molecular dynamic simulations showed that the nanoparticle layer at the water-oil interface forms an amorphous solid-like layer that may act as a nucleation seed, while inhibiting the dissolution of the gaseous guest molecules into the aqueous phase. Particle-based inhibitors block the water molecules from heterogeneous nucleation sites as well as guest molecules, but it was investigated that they can also contribute to hydrate promotion by themselves, suggesting optimization objects for improving inhibition performances.