Abstract
Inert gases can effectively inhibit coal spontaneous combustion. In this paper, the inhibition effect of inert gases (N2 and CO2) on coal spontaneous combustion was studied. In the low-temperature oxidation stage, the constant-temperature heat release and apparent activation energy of coal sample were measured and calculated by the C80 micro-calorimeter. In the high-temperature combustion stage, the critical temperature, maximum peak temperature, ignition temperature, and burn-out temperature of coal samples were analyzed by the synchronous thermal analyzer. The results demonstrate that with the decrease of O2 concentration, the oxidation heat release of coal samples drops gradually while the apparent activation energy increases gradually. In the N2 and CO2 atmospheres, as the O2 concentration is reduced to 1.5% and 3%, respectively, the value of apparent activation energy changes from negative to positive, and the spontaneous reaction transits to a nonspontaneous reaction. The TG-DTG (thermogravimetric-derivative thermogravimetric) curve of coal sample in the high-temperature combustion stage indicates that the critical temperature exhibits a W-shaped trend with the decrease of O2 concentration, which also leads to gradual increases of maximum peak temperature, ignition temperature, and burn-out temperature. The above results signify that increasing the inert gas concentration can gradually reduce the oxidation and combustion rate and improve the inhibition effect on coal spontaneous combustion. In addition, when the O2 concentration is the same, the inhibition effect of CO2 on coal spontaneous combustion is superior to that of N2.
Highlights
Coal is an important energy source and chemical raw materials [1,2,3,4]
The oxidation heat release properties of coal samples in the N2 and CO2 atmospheres under different O2 concentrations were analyzed by the C80 micro-calorimeter produced by Setaram, France (Figure 1)
The main conclusions are as follows: In the low-temperature oxidation stage, with the decrease of O2 concentration, i.e., the increase of inert gas concentration, the heat release of coal sample gradually drops at an accelerated rate
Summary
Many disasters may occur in the process of coal mining [5,6,7,8,9,10,11]. As one of the main disasters, coal spontaneous combustion (CSC). Burns vast coal resources and releases toxic gases and causes casualties [12,13,14]. In China, 56% of state-owned coal mines have suffered from CSC, accounting for 90–94% of all mine fires [15]. Because coal is a complex organic substance, it will adsorb O2 to undergo a chain reaction and release heat when exposed to an O2 environment. It is of great significance to study the prevention and control technology of coal spontaneous fire to ensure the safety of mine production
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