Evolution of Thermodynamic Properties of Tectonic Coal with Mass Ratios Determined by Isothermal Adsorption Test

Understanding the adsorbability and thermodynamic properties of tectonic coal (TC) is crucial to prevent coal and gas outbursts. Limited research has been conducted on the effects of mass ratios of TC because of its high brittleness and sampling difficulty. By investigating the adsorbability, adsorption heat, entropy, and Gibbs evolution during the adsorption of coal samples, it was revealed that the TC content affected directly the adsorption capacity, which increased at first and then decreased. For virgin coal (VC) and TC of equal quality (50% mass ratio), the adsorption quality, adsorption constant a, specific surface area Gibbs free energy, adsorption heat, and adsorption entropy reached their peaks, except the adsorption constant b, which reached the minimum value. Therefore, when TC accounted for 50%, appropriate measures should be applied to mitigate outbursts. Moreover, a comprehensive control model of several factors under various mass ratios of TC was proposed to describe the adsorption characteristics and corresponding thermodynamic property evolutions of TC and VC before coal–gas outburst. The results of this study provide guidance for preventing coal–gas outburst in high-gas mine working faces.