热重-FTIR法分析不粘煤氧化特性参数

Oxidation Characteristic Parameters of Non-Caking Coal by TG and FTIR

针对不粘煤粉生产过程的氧化自燃灾害,采用TG分析实验研究煤粉在空气条件下的氧化参数与动力学特征.利用FTIR-850红外光谱仪对煤样做红外光谱图分析,研究不同氧化温度下煤化学结构的官能团变化.结果表明:TG/DTG曲线上存在7个特征温度点,特征温度与升温速率呈正相关.将煤粉氧化过程分为失水失重(T1~T2)、吸氧增重(T2~T4)、热解(T4~T5)与燃烧(T5~T7)4个阶段;红外光谱图不同氧化温度下谱峰的位置类似,但强度有较大差异,这表明不同氧化温度煤样所含官能团的数量有一定的区别.用两种等转化率法(F-WO模型和V-W模型)计算了氧化过程的活化能介于66.2~92.9 kJ/mol之间;采用C-R法计算了煤粉氧化过程中4个阶段的活化能和指前因子,确定了机理函数,得出煤粉在T1~T2阶段、T2~T4阶段、T4~T5阶段、T5~T7阶段分别属于二维扩散反应、三维扩散2级反应、随机成核3级反应、三维扩散2级反应.

Aimed at the spontaneous combustion disaster of non-caking pulverized coal in its production process,the oxidation parameters and dynamic characteristics of pulverized coal under the air condition were studied by thermogravimetric analysis experiments.The FTIR-850 infrared spectrometer was used to analyze the infrared spectrum of coal samples,and the functional groups of coal chemical structure under different oxidation temperatures were studied.The results showed that there are seven characteristic temperature points on the TG/DTG curve.The characteristic temperature was positively correlated with the heating rate.The oxidation process of pulverized coal was divided into four stages:loss of water and weight(T1—T2),oxygen uptake and weight gain(T2—T4),pyrolysis(T4—T5),and combustion(T5—T7).The positions of the peaks were similar,but with different intensities under different oxidation temperatures,showing that the numbers of functional groups in coal samples with different oxidation temperatures were different.The activation energies of oxidation process were calculated by two equal conversion methods(F-W-O model and V-W model),ranging from 66.2 kJ/mol to 92.9 kJ/mol.The activation energies and pre-exponential factors of four stages of pulverized coal oxidation were calculated by the C-R method,and the mechanism functions were determined.It was concluded that the pulverized coal belonged to twodimensional diffusion reaction,three-dimensional diffusion reaction,random nucleation reaction and threedimensional diffusion reaction in T1—T2,T2—T4,T4—T5 and T5—T7 stages,respectively.