Abstract
Coal and gas outburst is a dynamic phenomenon with violent eruptions of coal and gas from the working coal seam. It has been proved that the rapid desorption within a short period is necessary for the occurrence of an outburst. Due to limitation of the present test condition, gas desorption characterization for the first 60 s has not been researched sufficiently. In the present study, an experimental apparatus with the ability of high-frequency data collection was developed. Initial desorption characterization of methane and carbon dioxide in coal was experimentally studied. Both the initial desorption characterization of methane and carbon dioxide were experimentally studied with different equilibrium pressures. The desorbed gas pressure was measured at desorption time phase of 0–10 and 45–60 s, besides the initial amount of desorbed gas and initial diffusion velocity of coal gas were calculated to assess their risk of outburst. The results show that the gas pressure for both methane and carbon dioxide increases sharply in the initial time and then levels off, and the total amount of desorbed gas increases with the increasing desorption time. Although the amount of desorption methane is slightly larger than that of carbon dioxide at the beginning, the total amount of desorbed carbon dioxide is significantly larger than that of methane at the desorption process. Therefore, it can be concluded that the coal and carbon dioxide outburst is more dangerous than the coal and methane outburst based on the obtained experimental results.
Highlights
Coal and gas outburst is a dynamic phenomenon with violent eruptions of coal and gas from the working coal seam, which would result in economic loss and casualties
In order to prevent the occurrence of coal and gas outburst in the process of uncovering coal in deep mines, numerous sensitivity indexes attached to the gas desorption properties were established, including the variation of gas emission (KV) (De Vegeron and Belin, 1966a, 1966b; Somnier, 1960; Yan et al, 2017), prediction method attached to the gas adsorption index K1 and Dh2 of drilling cuttings (Zhu et al, 2017), and the index initial velocity diffusion of coal gas (IVDCG) (DP) (Lama and Bodziony, 1998; Skoczylas, 2012)
Due to the small amount of data in this experiment, more studies will be conducted in the future. Both the desorption characterization of methane and carbon dioxide were experimentally studied with different equilibrium pressures
Summary
Coal and gas outburst is a dynamic phenomenon with violent eruptions of coal and gas from the working coal seam, which would result in economic loss and casualties. Several researches show that gas composition has great effect on outburst risk (Lama and Bodziony, 1998), and the index DP increases with the increasing carbon dioxide percentage (Wu et al, 2010). The experimental process is followed by “Determination method for index (DP) of initial velocity of diffusion of coal gas”, which has been defined that the gas desorption process for the first 60 s can be divided into three steps: the releasing of free gas steps (0–10 s), the gas filled in the space between coal sample and pressure tank is the source of released gas; the gas desorption step (10–45 s); and the releasing of desorption gas step (45–60 s). It mainly consists of a pressure container, a constant temperature water bath, a vacuum system, an inflation system, and a self-developed real-time DAS. The application of the real-time DAS is the most remarkable characteristic of the experimental setup
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