Experimental study on the contribution of desorbed gas to the propagation and disaster-causing of coal-gas outbursts

Abstract

Coal-gas outburst will take a large amount of coal-gas mixture into the coal mining workspace within a short time, and most of the energy in this process is provided by high-pressure gas. To figure out whether desorption gas participates in the process and how much contribution it makes, we performed comparative simulation experiments with adsorptive/non-adsorptive gas. Contributions of desorption gas in outbursts are revealed from the aspects of its propagation and disaster-causing effects. Then, combining the energy equation of outburst process with the large-scale pipeline transportation equation, a method that can accurately work out the energy contribution of desorption gas in outburst experiments is proposed. The results indicate that the desorption gas will promote the propagation of outburst two-phase flow, delay the attenuation of dynamics and strengthen the disaster-causing effects. With the same outburst pressure, the relative outburst intensity of CO2 as outburst gas is 8.08–12.48% higher than that of N2. When the outburst pressure is 0.5 MPa, in the experiment with 1–2.36 mm coal sample and N2, the overpressure attenuation from sensor 1# to 4# is 83.01%, while it is only 63.16% using < 0.25 mm coal sample and CO2. The action duration of positive pressure (ADPP), specific impulse and damage level of outbursts with CO2 are higher than that with N2, and the smaller the particle size of coal sample, the greater the difference. The total outburst energy of coal samples < 0.25 mm is 1.44 ∼ 1.78 times that of 1–2.36 mm coal samples. For coal samples with larger particle size of 1–2.36 mm, the energy contribution rate of desorption gas increased from 35.05% to 48.23%, while the contribution rate of desorption gas exceeded that of free gas for coal samples with particle size of < 0.25 mm, reaching to 55.35 ∼ 59.46%, verifying the key role of desorption gas in outbursts. Findings of this study highlight the importance of quantifying contributions of rapidly desorbed gas towards effective interpretation of outburst disaster-causing mechanisms.