Novel gas hydrate reactor design: 3-in-1 assessment of phase equilibria, morphology and kinetics

A novel reactor equipped with a bilateral, temperature-control stage was developed to study gas hydrates. The design allowed for tight control of the crystallization substrate temperature, independent of ambient conditions. Methane hydrate formation was investigated on a surface with a uniform temperature and on a surface with a constant temperature gradient. The uniform temperature experiments showed a previously unreported transition point in methane hydrate morphology and displayed closely reproducible film morphologies. A single temperature-gradient experiment showed transitions in morphology with respect to driving force. These transitions were found to be consistently reproducible, and occurred due to a change from continuous crystal growth to polycrystalline, adhesive type growth. The temperature gradient was also used to control the solid-liquid interface position during gas hydrate dissociation, providing a simple and fast method for hydrate-liquid-vapor (H-L-V) equilibrium measurements. The temperature gradient was used to correlate film velocity and supercooling in order to assess apparent kinetics of hydrate growth. Overall, the ability to observe gas hydrate growth on tightly controlled temperature gradients was found to reduce multi-trial methods to a single experiment that: (1) quantifies morphology/growth mechanism transitions with respect to temperature, (2) measures the H-L-V equilibrium temperature at the experimental pressure, and (3) correlates the apparent kinetics with respect to temperature. Thus, the new design was shown to operate as a 3-in-1 reactor, effectively allowing assessment of phase equilibria, morphology and apparent kinetics of gas hydrates.