Kinetics of methane hydrate dissociation at combustion in the air atmosphere at the outer pressure of 1 bar was studied experimentally. Dissociation is divided into several characteristic time stages with different rates of gas hydrate decomposition. There is a very high temperature gradient along the granule radius. At combustion the movement velocities of dissociation front and pores are high. Thermal imaging of the powder surface demonstrates significant temperature maldistribution. Spatially nonuniform escape of methane from a sample leads to local temperature and concentration maldistributions in the flame, which cause thermal instability of the flame front and the loss of hydrodynamic stability. Instability of combustion generates two equivalent mechanisms of convective transfer: the shear laminar flow and large-scale vortices, which intensify fuel and oxidizer mixing. Experimental data have revealed not only the local spatial-time nonuniformities but also significantly nonstationary character of the averaged flow. The measured instantaneous and average velocities of methane on the powder surface allowed an estimate of the stoichiometric ratio. The maximal velocity of methane propagation corresponded to 1 mm/s in experiments without combustion and to 15 mm/s with combustion.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology