Gas Hydrate Decomposition

Dissolution and dissociation of gas hydrate both involve the breakdown of the water lattice and release of the gas. In the field of gas hydrate research decomposition is spoken of in two ways. If the breakdown of the hydrate structure occurs outside the hydrate pressure-temperature stability field, the general term dissociation is used. If the breakdown occurs under temperature-pressure conditions at which the hydrate is expected to be stable due to the undersaturation of the surrounding solution, the term dissolution is used.

Temperature and pressure, which are commonly used to define the phase boundary, or conditions at which the hydrate is stable, are not independent of each other in a constantly changing system. In addition, they give no information to the relative amount of each component of the system. In reality, there is a constant feedback loop between the dissociating or forming hydrate and the surroundings. For example, if the temperature increases, the hydrate may begin to dissociate. As dissociation occurs, the concentration of the components, the salinity of the surrounding environment, and possibly the pressure (if the dissociation is occurring in an isolated environment) will change. The change in salinity and concentration of HFG, in an aqueous environment, or water vapor, in a gaseous environment, will have effects on the pressure-temperature phase boundary.