不同预氧化程度煤二次氧化特性研究

发布时间：2018-02-14 06:01

本文关键词： 预氧化特征温度气体产物热效应微观特性氧化动力学　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：煤炭是我国重要能源,为了节约资源,提高采出率,需要启封已经封闭的火区或者对采空区遗煤进行复采,然而,这些煤层在开采时已经与氧气接触发生了氧化,自燃特性可能发生了改变,称这类煤的再次氧化为二次氧化,即煤在氧化燃烧前已经经过了一定程度的氧化,而后温度又降回到常温。文章选取了三个矿区的煤,分别预氧化至80℃、120℃、160℃和200℃,采用实验分析的方法,对比不同预氧化程度煤的二次氧化与一次氧化过程,研究煤二次氧化自燃特性,为火区启封和遗煤复采煤自燃预测预报技术提供理论依据。主要内容如下:(1)采用工业分析和红外光谱法,对实验煤样的工业参数和原始分子中主要官能团进行测试,发现预氧化至120℃的煤样挥发分含量增加;不同煤样的分子官能团中,含量由多到少依次是含氧官能团芳香烃脂肪烃;不同预氧化煤样官能团含量变化规律较复杂,羟基、羧酸类基团、脂肪烃总含量在预氧化至120℃时达到极大值,醚键和取代苯变化规律性不强。(2)通过TG/DSC-FTIR实验,对煤样一次氧化和二次氧化过程的特征温度、热效应和气体产物变化规律进行分析,结果表明,不同预氧化程度煤二次氧化特征温度主要在受热分解温度之前区别较大。不同预氧化程度的煤特征温度随着预氧化程度的加深,先降低后增加,且一般是预氧化至120℃时煤样的特征温度最低;在热效应方面,煤在氧化燃烧过程中先吸热后放热,但是以放热为主。煤样氧化燃烧放热量随着预氧化程度的增加先增加后减少,但是变质程度不同,放热量最大时对应的预氧化温度不同,大南湖煤预氧化至160℃时放热量最大,顾北煤和阳泉煤预氧化至120℃时放热量最大;在气体产物方面,煤在氧化燃烧过程中CO、CO2及H2O(g)随温度的增加先增加后降低。不同预氧化程度煤样在燃点温度前产生气体随温度的变化较大,过了燃点温度,不同预氧化温度煤样产生气体的曲线基本重合。三种变质程度煤样气体产生量随预氧化程度的增加先增加后降低,其中,预氧化至120℃的煤样产生CO气体的量最多,顾北煤和阳泉煤亦为预氧化至120℃的样品产生H2O(g)的量最多,大南湖煤预氧化至80℃和预氧化至120℃的煤样产生的H2O(g)含量最多。(3)采用傅里叶原位红外实验,对煤样二次氧化过程分子官能团变化规律进行研究,结果表明,不同预氧化程度煤在二次氧化过程中分子官能团变化趋势相同,但变化量不同。不同煤样在氧化过程中分子官能团变化有共性,煤分子中官能团除个别例外的,其余所有煤样在升温氧化过程中游离-OH键、酚、醇、醚、酯C-O键、脂肪烃、芳环C=C结构和芳烃-CH键含量随温度的升高而降低。煤样取代苯和羰基C=O键随着温度的升高含量增加。同一变质程度,不同预氧化温度煤样二次氧化过程分子中主要官能团在氧化前后含量总变化量除个别不同外,其余煤样都是预氧化至80℃-160℃的煤样含量总变化量最大,且在这些煤样中预氧化至120℃的煤样是最大值的比率占一半以上。(4)应用改进的KAS法对煤样在受热分解前动力学进行分析,得出不同煤样在水分蒸发及气体脱附阶段,活化能随转化率的增加而降低。三种变质程度的煤样活化能随预氧化程度的变化规律一致,都是预氧化至120 ℃的煤样活化能最小,原煤及预氧化至200℃的煤样活化能较大。在吸氧增重阶段,活化能随转化率的增加而增大,不同预氧化程度煤样都是预氧化至120℃的煤样活化能最小。
[Abstract]:Coal is an important energy in China, in order to save resources, improve the recovery rate, need to have closed or unsealed fire in goaf of coal mining, however, oxidation occurs a coal seam has been in contact with oxygen in the mining, spontaneous combustion characteristics may change again, said this kind of coal oxidation for two times oxidation, namely coal oxidation in pre combustion has been a degree of oxidation, and then the temperature dropped back to normal. The paper selects three coal mining area, were pre oxidized to 80 degrees Celsius, 120 degrees, 160 degrees and 200 degrees, by the experimental analysis, the ratio of two different oxidation degree of pre oxidation of coal with an oxidation process of coal oxidation and spontaneous combustion characteristics for two times, and the residual coal mining coal firearea unsealing and provide a theoretical basis for the prediction of spontaneous combustion prediction technology. The main contents are as follows: (1) the industrial analysis and infrared spectroscopy of the industrial parameters and experimental coal sample The main functional groups original molecular testing found that volatile coal pre oxidation to 120 DEG C content increased; functional groups in different coal samples, the content from more to less followed by functional groups containing oxygen aromatic aliphatic hydrocarbon; variation of pre oxidation of coal sample groups were more complex, hydroxyl, carboxylic acid groups. Fat total hydrocarbon content reached the maximum value in the pre oxidation to 120 DEG C, substituted benzene ether bond and the variation is not strong. (2) through the TG/DSC-FTIR experiment, the characteristics of temperature of coal oxidation and a two oxidation process, the thermal effect and the variation of gas products were analyzed, the results show that the different pre the oxidation degree of two coal oxidation characteristics of temperature mainly before the thermal decomposition temperature difference is large. The coal characteristic temperature of different pre oxidation degree with pre oxidation degree deepening, firstly decreased and then increased, and generally pre oxidation to 120 DEG C when coal sample. The lowest temperature in heat syndrome; effect on coal oxidation in the combustion process after the first endothermic exothermic, but to heat. Oxidation of coal combustion heat release with the increase of the degree of pre oxidation increased first and then decreased, but the degree of metamorphism, the heat release corresponds to the maximum pre oxidation temperature of different Dananhu coal pre oxidation the heat to 160 degrees C, Gu BEIMEI and Yangquan coal pre oxidation to 120 DEG C when the maximum heat release; in product gas, coal oxidation in the combustion process of CO, CO2 and H2O (g) with the increase of temperature increases first and then decreases. The different degree of pre oxidation of coal samples in producing gas with the ignition temperature the temperature change is bigger, the ignition temperature curve coincide different pre oxidation temperature of coal generating gas. Three kinds of metamorphic degree of coal sample gas production increased with increasing of the degree of pre oxidation decrease after the pre oxidation temperature of 120 coal samples from C The maximum amount of O gas, H2O BEIMEI Gu and Yangquan coal for pre oxidation temperature of 120 samples (g) was highest in Dananhu coal pre oxidation to 80 DEG C and pre oxidation temperature of 120 coal samples from H2O (g) was the most. (3) by Fourier infrared in situ experiment. Study on the coal two molecular oxidation process of functional group changes. The results showed that the two molecules in the oxidation process of functional groups in different trends of pre oxidation degree of coal, but the change is different. Different coal sample molecules in the oxidation process of coal molecular functional groups are common functional groups with few exceptions, all the rest coal free -OH key in heating and oxidation process of phenol, alcohol, ether, ester C-O, aliphatic hydrocarbons, aromatic C=C and aromatic -CH bond content decreases with the increase of temperature. Benzene and carbonyl C=O increased with the increase of temperature in key coal instead. The same degree of metamorphism, different pre The main functional groups of coal oxidation temperature of two oxidation process in a molecular weight content of total variation before and after oxidation in addition to individual differences, the remaining coal is coal content of pre oxidation to 80 DEG -160 DEG the total variation is the largest, and in the coal pre oxidation temperature of 120 coal samples is the ratio of the maximum value. More than half (4). Analysis of coal samples in thermal decomposition kinetics before using the improved KAS method, different coal desorption stage in the evaporation of water and gas, the activation energies decrease with the increase of the conversion decreased. Three coal activation energy consistent with changes of the degree of pre oxidation. Is the pre oxidation temperature of 120 coal samples of coal and the minimum activation energy, pre oxidation temperature of 200 coal samples. The activation energy is higher in oxygen gain stage, the activation energy will increase with increasing conversion rate, different pre oxidation degree of coal samples are pre oxidation temperature of 120 coal samples of the living It can be the smallest.

【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD752.2

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