Heat Transfer Inside Particles and Devolatilization for Coal Pyrolysis to Acetylene at Ultrahigh Temperatures

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• 作者：Yue Shuang ; Changning Wu ; Binhang Yan ; Yi Cheng
• 刊名：Energy & Fuels
• 出版年：2010
• 出版时间：May 20, 2010
• 年：2010
• 卷：24
• 期：5
• 页码：2991-2998
• 全文大小：928K
• 年卷期：v.24,no.5(May 20, 2010)
• ISSN：1520-5029

文摘

Coal pyrolysis to acetylene in thermal plasma provides a direct route to make chemicals from coal resources, where the rapid heating and release of volatile matters in coal particles play the dominant role in the overall reactor performance. A mechanism model incorporating the heat conduction in solid materials, diffusion of released volatile gases, and reactions was proposed for a deep understanding of the heat transport inside a coal particle under extreme environmental conditions such as high temperatures greater than 2000 K and milliseconds of reaction time. The two competing rates model, known as the Kobayashi model, was applied to describe the devolatilization kinetics, which was verified by comparing the predicted yield of volatiles with the experimental data in the literature. Thermal balance between coal particles and the hot carrier gas was established, and the four influencing factors including the heating rate, particle size, reactants flow ratio, and heat of devolatilization were paid attention when analyzing the heating profile inside the particles and the yield of volatiles. The results showed that the inherent resistance due to the volatiles released from coal particles seriously impeded the thermal energy transportation from heating gas to the particle. This led to a weakened heating rate, i.e., a long heating up time, and thereafter a low yield of volatiles, especially when the particle size was large (e.g., >40 μm). Meanwhile, the heat conduction inside the coal particle also imposed additional resistance to reduce the heat transportation rate from heating gas to the particle, especially when the particle size was larger than 80 μm. The predicted yield of volatiles considering the mechanism of the two resistances agreed reasonably with the reported experimental data under different operating conditions but was smaller than that which could be obtained when neither resistance is considered. It can be concluded that the proposed heat transport mechanism inside coal particles works well in understanding the coal pyrolysis process at ultrahigh temperatures.