不同变质程度煤二次氧化自燃的微观特性试验

Micro-characteristics of spontaneous combustion of second oxidation with different rank coals

为探讨煤二次氧化特性,采用煤质分析、FTIR傅里叶红外光谱分析和程序升温实验分别对榆树井褐煤、黄陵烟煤和汝萁沟无烟煤的原始煤样及其氧化后(二次氧化)煤样进行微观自燃特性对比研究。结果表明:二次氧化煤样中C含量减小,O含量增大,水分减少;而比表面积与孔隙率增大,导致与氧发生反应的面积增大,致使氧化反应前期二次氧化过程中产生的CO浓度大于一次氧化。随着温度的升高,氧化反应后期煤分子中羟基、脂肪烃等活性官能团数量随之变化并大量消耗和再生,裂解产生C_2H_4气体,导致二次氧化过程中产生的CO浓度和C_2H_4浓度小于一次氧化。此外,二次氧化煤样特征温度点均提前于原始煤样,使得发生自燃的时间提前,说明二次氧化煤样氧化性强于原始煤样,更容易自然发火。

To study the spontaneous combustion characteristics of second oxidized coal,the proximate and elementalanalysis,Fourier transform infrared spectroscopy,and temperature-programmed experiment system were used to inves-tigate the micro-spontaneous combustion characteristics of raw coal samples and oxidized coal samples,which werefrom three coal samples of different mines. The findings indicate the content of carbon decreases,oxygen increases,andthe moisture decreases. Moreover,because the specific surface area,pore volume,and porosity of second oxidized coalincrease,the CO concentration of the coal samples with second oxidation become higher than those of the first oxidationin the earlier stage of oxidation. With temperature increase,the number of active functional groups,which are hydroxyland aliphatic hydrocarbons in the coal molecules,change a lot,have a large amount of consumption and regeneration,and cracked in C_2H_4 gas in the later stage of oxidation. Hence,the concentrations of CO and C_2H_4 in the coal sampleswith the second oxidation are lower compared to the first oxidation. In addition,there are advanced characteristic tem-perature points of the second oxidized coal compared to raw samples. That is,the period of spontaneous combustion isgetting earlier. In summary,the oxidation ability of the second oxidized coal is stronger than that at the first time and gets oxidized readily.