Heat and mass transfer at interfaces in decomposition of methane hydrate under combustion

Abstract

The thermodynamic and kinetic mechanism of decomposition of gas hydrate with burning is still in its infancy. The heat and mass transfer are analyzed based on accurate positioning of interfaces in the decomposition of methane hydrate under combustion by ReaxFF molecular dynamics simulation. There is a transition region between the solid–liquid interface of decomposition and the burning boundary. Results show that the water layer in transition region largely hinders the diffusion of methane produced by decomposed hydrate so that hydrate cannot burn steadily. Heat flux at burning boundary is larger than at solid–liquid interface in the early stage of decomposition, so thermal transport in burning boundary drives decomposition of hydrate. The heat flux at solid–liquid interface is larger than at burning boundary in the later stage, and the diffusion and extrusion of liquid water with heat transport through the transition region become the new driving force. The interfacial thermal resistance of solid–liquid interface decrease rapidly to the order of 10−10 m2·K/W at different temperatures. 23.9 % of the heat from burning process at 1600 K can maintain entire decomposition of hydrate within 3000 fs. Although the formation of transition region doesn’t significantly reduce the decomposition rate of hydrate, it is unfavorable for burning. The discharge of water layer in transition region should be focused on in the future.