OUR STORY

Research Thrust II

Formation and Control of Gas Hydrate Slurries

  Gas hydrates (or hydrates) are crystalline solids resulting from the water caging of small molecules, e.g. methane, CO2 or cyclopentane. Recent work considers hydrates for CO2 capture, gas storage and transport. For example, hydrate slurries can be used as novel compounds in secondary refrigeration, a topic that we will jointly pursue with our French collaborators (IRSTEA, ENSTA ParisTech). Due to their high energy content and environmentally friendly nature, hydrates can significantly reduce use of hydrofluorocarbons (HFCs). Rheological studies show that hydrate slurries are non-Newtonian and likely thixotropic, with the interfacial behavior playing a key role. Due to the co-existence of three phases in hydrate slurries, heat and mass transfer between different phases induces local thermodynamic non-equilibrium and flow instabilities (e.g., bubble formation, temperature and density gradients, slip at the wall and between phases), which are likely responsible for undesired temperature oscillations in the convective melting of hydrate slurries. Hydrates also appear in petroleum pipelines under high pressure and low temperature and may cause plugging, though understanding and controlling this phenomenon remains challenging. Hydrates form at the water-oil interface, generating a “crust,” whose morphology allows 

formation of a connected network: molecular effects at the interface thus lead to a bridging of scales with major consequences.

 Here, both CO2 and cyclopentane (CP) hydrate formation and slurry flow will be studied, as CP forms hydrates at atmospheric pressure. The goal is to understand control of flow properties of hydrate slurries from the molecular level. Advanced measurement techniques, e.g., focused beam reflectance (FBR) and multi-dimensional NMR, will be used to measure particle size distributions, solid content, contact angles, and molecular structures of hydrate crystals. These properties are keys to understanding the role of adsorbed surfactants on crystal morphology. Both direct rheometry and a custom facility to recover and manage CO2 gas emissions during hydrate melting will generate new rheological data for the CO2 hydrate slurry, including effects of dispersive additives. We will use molecular dynamics (MD) simulations to study interfacial environments, particularly in the three-phase contact line region (hydrate, oil and water). At larger scales, the dynamics of hydrate-laden interfaces will be studied using a new lattice-Boltzmann/phase field method for describing wetted-solid transport.

CCNY: Jeffrey Morris, Vincent Pauchard, Masahiro Kawaji, Sanjoy Banerjee, Robert Messinger, Taehun Lee, Fanny Thomas, Geng Liu

IRSTEA: Laurence Fournaison, Anthony Delahaye

ENSTA ParisTech: Didier Dalmazzone

RUB/Fraunhofer UMSICHT: Goerge Deerberg, Georg Janicki

SINTEF: Martin Fossen