Study On Index Gases Released By Coal's Low Temperature Reacting

The detection of indication gases from coal's self-heating is extensively applied to mine's security. However, sometime the instrument can't directly detect the trace gases released by coal's self-oxidation. In order to improve sensitivity of detection, a quantitative analysis method of ratios of trace C2-C3 hydrocarbon to ethane was set up by a series of experiments. With the adsorption technology described in the article the ratios of C2-C3 to ethane were detected when the temperature of coal rises or lowers. Details are as follows:Concentrated trace C2-C3 hydrocarbons were studied. By the technique of concentration, a quantitative analysis method was set up by a series of experiment. Breakthrough volumes of four adsorbents were determined, and we found that active carbon (AC) and active carbon fiber (ACF) have higher adsorption capacity. As to thermal desorption of pure nitrogen, the recoveries of AC and ACF were measured, and ACF, whose optimal adsorption temperature was determined, was thought as the best adsorbent. We tested linear relation and repeatability, and found them ideal. Due to the fact that the recovery of thermal desorption of pure nitrogen appeared lower, a modified method was put forward. Then with the method much higher recovery was gained. Lastly, a quantitative analysis method for the new desorption was newly set up in the same way.With a series of oxygen contents the research of coal's self-oxidation under low temperatures was done. The paper falls into three parts. Part 1 is the index prediction of coal's spontaneous combustion, which took place with a series of oxygen contents. Part 2 is the index prediction of flameout after coal's spontaneous combustion, which also took place with a series of oxygen contents. Part 3 is index prediction of quench with 7% oxygen after spontaneous combustion, which same took place with a series of oxygen contents. The concerned temperature changed from 50℃ up to 200℃ in the course of temperature rising, and changed from 200℃ down to 60℃ in the course of temperature lowering. Oxygen content entering into coal's reactor is 21%, 15%, 10%, 7%, 0% respectively in the course of coal's temperature rising. We found that ratios of C2-C3 to ethane appear regularly change that is falling before rising under the condition of temperature rising, and the lowest point ofcurve changed from 100℃ to 200℃. And ratio of propane to ethane appears irregular, but ratios of ethylene and propylene to ethane show regularly change that is falling before rising under the condition of temperature lowing. Further more, the change between curves is also regular when oxygen content changes from 21% to 0%. These regularity shows that coal's reaction under condition of low temperature is competition of oxidation and decomposition. All these changes provide important reference to mine's security.