Dissociation kinetics of methane hydrate and CO2 hydrate for different granular composition

Abstract

The dissociation of gas hydrate particles (methane hydrate and CO2 hydrate) in a layer with no coalescence of particles (with “true size” of particles), as well as that of pressed pellets have been studied experimentally. The activation energy of gas hydrate at negative temperatures was determined using the statistical method. Values of the kinetic constant and activation energy Ea = 78.3–81 kJ/mol, obtained in the works of Kim, Bishnoi, Clarke et al. at methane hydrate dissociation, are valid only at positive temperatures (temperatures above the melting point of ice). At negative temperatures, only the hydrate cell dissociation and the formation of ice without its melting are realized. In this case, the activation energy is reduced several times Ea = 33.5 kJ/mol. A sharp decrease in Ea at intense heat exchange will lead to faster kinetics of gas hydrate dissociation. The pre-exponential factor for the pressed layer (or pellets) can vary by an order of magnitude and reflects the filtration rate. If the dissociation rate (for a thick layer of coalesced particles or for pressed large pellets) is known from the experiment, then at given Ea = 33.5 kJ/mol, the “true diameter” of the particles can be calculated. This technique is important for the development of modern technologies of storage and transportation of natural gas hydrates, as well as for the study of natural gas hydrates in the permafrost zone.