Abstract

In the process of pyrolysis and combustion of coal particles, coal structure evolution will be affected by the ash behavior, which will further affect the char reactivity, especially in the ash melting temperature zone. Lu’an bituminous char and ash samples were prepared at the N2 and air atmospheres respectively across ash melting temperature. A scanning electron microscope (SEM) was used to observe the morphology of char and ash. The specific surface area (SSA) analyzer and thermogravimetric analyzer were respectively adopted to obtain the pore structure characteristics of the coal chars and combustion parameters. Besides, an X-ray diffractometer (XRD) was applied to investigate the graphitization degree of coal chars prepared at different pyrolysis temperatures. The SEM results indicated that the number density and physical dimension of ash spheres exuded from the char particles both gradually increased with the increasing temperature, thus the coalescence of ash spheres could be observed obviously above 1100°C. Some flocculent materials appeared on the surface of the char particles at 1300°C, and it could be speculated that β-Si3N4 was generated in the pyrolysis process under N2. The SSA of the chars decreased with the increasing pyrolysis temperature. Inside the char particles, the micropore area and its proportion in the SSA also declined as the pyrolysis temperature increased. Furthermore, the constantly increasing pyrolysis temperature also caused the reactivity of char decrease, which is consistent with the results obtained by XRD. The higher combustion temperature resulted in the lower porosity and more fragments of the ash.

中文翻译：

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温度对热解燃烧中六安烟煤结构演变的影响

摘要

在煤颗粒的热解和燃烧过程中，煤的结构演变将受到灰分行为的影响，这将进一步影响炭的反应性，特别是在灰分熔化温度区。分别在氮气和空气气氛下，通过灰分熔化温度，制备了六安沥青炭和灰分样品。使用扫描电子显微镜（SEM）观察炭和灰的形态。分别采用比表面积（SSA）分析仪和热重分析仪获得煤焦的孔隙结构特征和燃烧参数。此外，采用X射线衍射仪（XRD）研究了在不同热解温度下制备的煤焦的石墨化程度。SEM结果表明，随着温度的升高，焦炭颗粒渗出的烟灰球数密度和物理尺寸均逐渐增加，因此在1100℃以上可以明显观察到烟灰球的聚结。在1300℃的炭颗粒表面出现了絮凝物，推测是在N2下热解过程中产生了β-Si3N4。炭的SSA随热解温度的升高而降低。在炭颗粒内部，随着热解温度的升高，微孔面积及其在SSA中的比例也下降。此外，不断提高的热解温度也导致炭的反应性降低，这与通过XRD获得的结果一致。