煤颗粒物性及热转化特性随粒径变化规律研究

Effect of coal particle size on its physical properties and combustion characteristics

与常规煤粉(百微米)相比,超细煤粉(<20mm)的颗粒性质与热转化特性均可得到明显改善。本文以神华烟煤为研究对象,采用元素分析仪、傅里叶变换红外光谱仪和扫描电子显微镜对不同粒径煤粉的元素组成、官能团分布及微观表面形貌进行了分析,采用热重分析仪(TGA)对不同粒径煤样的热解及燃烧特性进行了研究。结果表明:随着煤粉粒径的减小,C元素含量逐渐增加,煤粉表面变得更加粗糙,煤粉表面羟基官能团增多,而芳烃C=C及CH3官能团减少;煤的热解过程可分为干燥、快速热解和热缩聚3个阶段;随着粒径的减小,热解最终失质量逐渐减小;在煤的燃烧过程中,随着煤粉粒径的减小,着火温度Ti、燃尽温度Tf具有减小的趋势,而最大燃烧速率(dω/dt)max与综合燃烧特性指数S具有增大的趋势,煤粉的燃烧特性随着其粒径的减小而得到明显改善。

Compared with the conventional pulverized coal(100 micrometer level), both the physical properties and combustion characteristics of the superfine pulverized coal(<20 mm) can be improved dramatically. By taking Shenhua bituminous coal as the study subject, several instruments, such as the elemental analyzer, Fourier transform infrared spectrometer(FTIR) and scanning electron microscopes(SEM), were adopted to investigate the element composition, functional groups, and microscopic surface morphology of testing samples with five different particle sizes. The thermogravimetric analyzer(TGA) was used to investigate the pyrolysis and combustion characteristics of the coals with different sizes. The results show that, as the particle size decreased, the carbon content increased, the coal particle surface became rougher, the number of hydroxyl group increased while that of aromatic hydrocarbon C=C and CH3 functional groups decreased. The coal pyrolysis was composed of three stages: drying period, fast pyrolysis stage and thermal condensation stage. The final weight loss decreased with the coal particle size. In coal combustion process, with the decreasing of particle size, both the ignition temperature(Ti) and burnout temperature(Tf) reduced, the maximum burning rate(dω/dt)max and the comprehensive combustion characteristic index(S) increased. The combustion characteristics of superfine pulverized coal were greatly improved.