Kinetic characteristics of desorption and diffusion in raw coal and tectonic coal and their influence on coal and gas outburst

Abstract

The basic physical parameters and gas desorption characteristics of raw coal and tectonic coal composite seams in northern China were tested, and the gas diffusion kinetic characteristics of raw coal and tectonic coal were investigated. The difference in gas hazard between the raw coal seam and tectonic coal seam was analysed based on this. The results found that: under the same conditions, the adsorption capacity, initial gas discharge rate, accumulated gas desorption volume, initial gas desorption rate and effective diffusion coefficient of tectonic coal are higher than those of raw coal, while Protodyakonov’s coefficient of tectonic coal is much smaller than that of raw coal. This, together with the lower permeability of tectonic coal seam, easily leads to the formation of a gas enrichment zone in tectonic coal seam easily and triggers coal and gas outburst when the external stress environment changes. Under the same conditions, raw coal is more sensitive to changes in initial gas adsorption equilibrium pressure, and the development of cleats and fractures of raw coal is higher than that of tectonic coal, which makes the gas in the area of raw coal easier to extract than that in the area of tectonic coal. When carrying out gas control in the composite coal seam of raw coal and tectonic coal, it is necessary to consider the gas desorption and diffusion characteristics in the raw coal and tectonic coal and to develop precise coal seam gas control measures based on the principles of safety and economy. The results of this study are of great relevance to the prevention and control of coal and gas outburst disasters in raw coal and tectonic coal seams to ensure the safe and efficient mining of coal resources.