升温速率对神木煤热解半焦结构性能的影响

利用管式炉和微波材料工作站分别对神木煤煤样进行终温为750 ℃的慢速(3和5 ℃/min)、中速(10和15 ℃/min)及快速(50、100、225、350和750 ℃/min)热解,基于热解半焦X射线衍射谱图解析热解半焦的微晶结构参数,采用傅里叶变换红外光谱表征热解半焦的表面化学,并借助热重分析仪、选用气化活性参数R_T评价热解半焦的气化反应活性。结果表明,随着升温速率的增大,神木煤热解半焦总体上呈现的趋势是:表面含氧官能团含量降低,半焦的微晶层片尺寸L_a和石墨化度明显提高,层间距d₀₀₂和堆积高度L_c略微减小,说明神木煤半焦结构随升温速率的提高变得规整;随着升温速率的增大,半焦的气化活性R_T从0.178 2降低至0.103 6。热解终温为750 ℃的神木煤热解过程中,快速热解有利于获得易石墨化、表面非极性化、气化反应性低的产物。

Influence of heating rate on structure of chars derived from pyrolysis of Shenmu coal

A series of char samples were derived from pyrolysis of Shenmu coal at low (3 and 5 ℃/min), medium (10 and 15 ℃/min) and fast (50, 100, 225, 350 and 750 ℃/min) heating rates, respectively, and at the same pyrolysis temperature of 750 ℃. Then these chars were characterized by means of X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and thermogravimetric analysis (TGA) with the aim to investigate the influence of heating rate in pyrolysis process on the microcrystallite structure, surface chemistry and gasification reactivity of the derived chars. The results show that with the increase of pyrolysis heating rate, the amount of oxygen-containing functional groups on the surface of the chars decreases, the dimension of microcrystallite lamella L_a and the graphitizing degree of the char increase obviously, the distance between lamella d₀₀₂ and mean height of lamella L_c decrease slightly, and the gasification reactivity R_T of chars reduces from 0.178 2 to 0.103 6. It can be concluded that the higher heating rate in the process of pyrolysis at 750 ℃ will result in higher graphitization of char with nonpolar surface and low gasification reactivity for Shenmu coal.