Dissociation and Combustion of a Layer of Methane Hydrate Powder: Ways to Increase the Efficiency of Combustion and Degassing

Abstract

The interest in natural gas hydrates is due both to huge natural reserves and to the strengthened role of environmentally friendly energy sources conditioned by the deterioration of the global environmental situation. The combustion efficiency increase is associated with the development of understanding of both the processes of dissociation and combustion of gas hydrates. To date, the problems of dissociation and combustion have, as a rule, been considered separately, despite their close interrelation. Usually, during combustion, there is a predetermined methane flow from the powder surface. In the present paper, the combustion of methane hydrate is simulated taking into account the non-stationary dissociation process in the powder layer. Experimental studies on the methane hydrate dissociation at negative temperatures have been carried out. It is shown that due to the increase in the layer temperature and changes in the porosity of the layer over time, i.e., coalescence of particles, the thermal conductivity of the layer can change significantly, which affects the heat flux and the dissociation rate. The flame front velocity was measured at different external air velocities. The air velocity and the vapor concentration in the combustion zone are shown to strongly affect the combustion temperature, flame stability and the flame front velocity. The obtained results may be applied to increase the efficiency of burning of a layer of methane hydrate powder, as well as for technologies of degassing the combustible gases and their application in the energy sector.

Key Areas of Gas Hydrates Study: Review

“…where ∆T is the mean difference between the maximum gas temperature in the boundary layer and the average surface temperature of the layer, V e f is the effective gas rate in the dynamic boundary layer, L is the length of the site with the hydrate, and Pr is the Prandtl number. When describing the gas hydrate dissociation rate, it is important to take into consideration not only the kinetics of dissociation but also the heat and mass transfer inside porous solids [111]. Hassanpouryouzband et al [112] presented the kinetics of gas hydrate formation and dissociation.…”

“…The maximum dissociation rate of gas hydrates is achieved using induction heating [59]. To estimate the effect of gas hydrate geometry on the ignition characteristics, researchers have experimentally studied the combustion behavior of powder [56,58,111], cylindrical [66], and spherical [62,63,69,70] hydrate forms. Their findings revealed that gas hydrates in powder form are ignited more easily and burn out more completely.…”

“…Wang et al [63] experimentally studied the combustion flame behavior of methane hydrate spheres, as well as the effect of the sphere diameter and initial temperature in the center on the characteristics of flame. Four stages of gas hydrate combustion were distinguished: stage (I) is combustion development (the flame height increases gradually), To estimate the effect of gas hydrate geometry on the ignition characteristics, researchers have experimentally studied the combustion behavior of powder [56,58,111], cylindrical [66], and spherical [62,63,69,70] hydrate forms. Their findings revealed that gas hydrates in powder form are ignited more easily and burn out more completely.…”

“…A high heat flux from the combustion region to the layer surface and a high steam concentration in the flame area significantly reduce the flame temperature. The equations considering both the breakup and combustion of gas hydrates were modeled by Misyura et al [111].…”

Simulation Of The Process Of Injection Of Liquid Sulfur Dioxide Into A Porous Reservoir Initially Saturated With Methane And Ice

“…development of gas hydrate deposits, are presented in [13][14][15][16][17]. Modeling of gorenje hydrate methane with account of the non-stationary process of its dissociation in the powder layer is presented, in particular, in [18].…”