• methane hydrate;
  • dissociation rate constant;
  • hydrate dissociation model;
  • solubility;
  • depressurization


Rate equations proposed in Part I were extended to dissociation processes induced by different methods such as depressurization, raised temperature, or simultaneous changes in temperature and pressure. For all cases, the dissociation rate of hydrate into the two-phase coexisting region (V-LW) can be expressed by a general form of the product of the rate constant and the logarithm of the solubility ratio of methane in the aqueous solution, xR to xS: xR is the solubility of methane in the aqueous solution that is hypothetically in equilibrium with the hydrate phase under the dissociation pressure and temperature, and xS is the equilibrium solubility of methane in water under the same dissociation condition. The virtual solubility of methane, xR, can be estimated by extrapolating the solubility curve of methane under the conditions in equilibrium with the stable hydrate to the region at which the dissociation occurs by a simple thermodynamic treatment. The dissociation equation was applied to experimental results of dissociation processes induced by depressurization with methane bubble formation. The experimentally observed dissociation rates were well correlated by the rate equation with the dissociation constants determined in Part I. The results suggest that the dissociation equation can be applied generally to dissociation processes that occur by different methods, and the rate constant is a universal parameter within the experimental range examined in this work. © 2007 American Institute of Chemical Engineers AIChE J, 2007.