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.
Highlights
Published: 9 August 2021The huge natural reserves of methane in the form of gas hydrate deposits induce a large number of scientific research and solutions to various technological problems realized in the world’s scientific centers
When describing the dissociation rate of a gas hydrate, it is important to take into account both the dissociation kinetics and the heat and mass transfer inside a porous rock
An increase in the amount of water vapor leads to a decrease in the combustion temperature and, to a drop in the heat flux into the wall
Summary
The huge natural reserves of methane in the form of gas hydrate deposits induce a large number of scientific research and solutions to various technological problems realized in the world’s scientific centers. Modeling of offshore methane hydrate production is considered in [25,26] This simulation should deal with the kinetics of dissociation of natural gas hydrate, and the mechanisms of transfer in a porous space. In the range of temperatures below 273 K, the dissociation of methane hydrate is accompanied by the formation of an ice crust (on the surface of the particle) and gas (methane), which is removed from the particle through a porous space in the ice shell. The kinetic coefficients in the dissociation equation in the Arrhenius form (at negative powder temperatures) are obtained by processing experimental data in [41,42]. Additional experimental data are tothe establish the effect of combustion tion on the non-stationary nature ofnature dissociation.
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