我国矿产资源丰富，开采量大，煤自燃现象严重，衍生而来的煤炭复燃现象也日益凸显，也就导致了二次氧化现象的出现，煤的二次氧化是指原始煤样发生氧化升温，温度超过临界温度后，降温恢复到常温，再次发生氧化升温的过程。 本文以不同变质程度的煤样作为研究对象，采用实验分析的方法，对煤样的一次氧化和二次氧化过程进行对比分析，研究不同变质程度煤二次氧化自燃的微观特性，发现二次氧化煤更加易于氧化，实验结果对煤二次氧化的机理建立、自然发火的预测预报和防治技术的研究提供了依据，主要工作如下： （1）采用工业分析仪、元素分析仪、真密度分析仪、物理化学吸附仪和X-射线衍射仪，测试了原始煤样和二次氧化煤样中水分、灰分、挥发分和各元素组分的含量，分析了两次氧化过程中煤样比表面积和晶体结构变化情况。掌握了不同变质程度煤样的基础物理特性。实验表明二次氧化煤样水分减小，灰分增大、挥发分减小、C含量减少、真密度增大、比表面积增大、晶体结构略显疏松。 （2）针对一次氧化和二次氧化过程中煤样的特征温度点，利用傅里叶变换红外光谱分析了煤分子结构中官能团的变化规律，分析确定出二次氧化煤分子结构中对氧化反应影响较大的活性官能团是羟基、亚甲基、甲基、羰基和醚键。 （3）通过不同变质程度原始煤样和二次氧化煤样的程序升温实验，分析得出的气体浓度、耗氧速率、气体产生率、放热强度和特征温度等二次氧化煤样的自燃特性。结果表明，煤样在二次氧化过程中产生的CO、CO2气体量在反应初始阶段大于一次氧化，后期小于一次氧化，CH4、C2H6和C2H4气体量始终小于一次氧化过程中产生的气体量，但是产生的种类和顺序不变。耗氧速率、气体产生率、放热强度值在二次氧化反应初期大于一次氧化，而在反应后期小于一次氧化的值。采用指标气体增长率分析法测试得出两次氧化自燃的特征温度点，发现二次氧化的特征温度值向着偏低的位置移动，小于一次氧化。

China has a large quantity of coal, as well as a great production of it. The phenomenon of coal spontaneous combustion is serious and may be disastrous so that coal reignition comes to appear frequently , as so called secondary oxidation. The secondary oxidation means the raw coal comes to spontaneous combustion and the temperature rises to the point after critical temperature, then cooling to original temperature and recurrence of redox reaction process. In this study, different ranks of coal were taken as study object. Experimental analysis was adopted to being a using method to investigate the macroscopic and microscopic characteristic of different ranks of coal and the comparison between initial and the second oxidation. The experimental results showed that the secondary oxidation has much available to oxidate and presented the basis of building the mechanism, prediction and prevention technology of secondary oxidation. The industrial analyzer, elemental analyzer, density analyzer, autosorb-iq-c fully-automatic physical and chemical adsorption analyzer and X - ray diffractometer were adopted to test the elemental constituent, moisture, ash content and volatile of original and the second oxidation. Investigate the change of specific surface area and crystal structure during oxidation. The experiments take above master the basic physical properties of different ranks of coal sample, it is found that moisture decreases, specific surface area increases, crystal structure becomes loose, and much easier to oxidation in second oxidation of coal. Aim to the characteristic temperature during twice oxidation, Fourier infrared spectrometer was used to investigate the change rule of functional group in coal molecular structure. Therefore, -OH, -CH2, –CH3, carbonyl group and ether bond were confirmed being major influence active groups to the oxidation reaction in secondary oxidation. With the analysis of experiment on the secondary oxidation between different ranks of coal, gas concentration, oxygen consumption rate, the gas production rate, heat intensity, and characteristic temperature were obtained. The findings suggest that the volume of CO and CO2, which were produced by the reaction of the secondary oxidation, which are more than the volume of initial oxidation in the earlier stage and lower in the later stage. The volume of CH4, C2H6, and C2H4 which were produced by the reaction of the secondary oxidation, were lower than the volume of initial oxidation. The sequence and all kind of produced gas above did not be changed. Oxygen consumption rate, the gas production rate, and heat intensity values of secondary oxidation were higher in the earlier stage in comparison with later stage. Gas index growth analysis was adopted to obtain the characteristic temperature points of secondary oxidation which were shifted to lower than initial oxidation.