Kinetics of Hydrate Formation and Dissociation in Coal at Different Temperatures Based on Impedance Method.

In the process of coal mining, gas outburst is a challenge that must be prevented to guarantee mining safety. Forming gas hydrate in coal can reduce the original gas pressure and delay the concentrative outbursts of gas flow, which is one of the potential technologies to prevent gas outbursts in coal. In this work, we perform the formation and dissociation kinetics experiment of hydrate in the presence of coal and tetrahydrofuran (THF) at the temperature based on different geological conditions in China by means of the experimental device with the impedance measurement function. The results showed that the impedance change can qualitatively describe the kinetic characteristics of hydrate formation and dissociation in coal. The sudden change in pressure and system impedance during gas hydrate formation indicated the nucleation point at which hydrate formation started, by which the induction time can be acquired. Pressure and impedance suddenly changed at the same time, which implied that methane molecules and tetrahydrofuran (THF) molecules entered the hydrate phase at the same time. When the dissociation temperature increased to 303.15 K, the hydrate dissociation rate can be less affected by dissociation temperature if it continued to increase. This work highlights that gas hydrate formation in coal can effectively prevent gas outbursts.