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Combustion behavior in air of single particles from three different coal ranks and from sugarcane bagasse

机译:来自三个不同煤种和甘蔗渣的单个颗粒在空气中的燃烧行为

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Comparative combustion studies were performed on particles of pulverized coal samples from three different ranks: a high-volatile bituminous coal, a sub-bituminous coal, and two lignite coals. The study was augmented to include observations on burning pulverized woody biomass residues, in the form of sugarcane bagasse. Fuel particles, in the range of 75-90 urn, were injected in a bench-scale, transparent drop-tube furnace, electrically-heated to 1400 K, where they experienced high-heating rates, ignited and burned. The combustion of individual particles in air was observed with three-color pyrometry and high-speed high-resolution cinematography to obtain temperature-time-size histories. Based on combined observations from these techniques, in conjunction to morphological examinations of particles, a comprehensive understanding of the combustion behaviors of these fuels was developed. Observed differences among the coals have been striking. Upon pyrolysis, the bituminous coal chars experienced the phenomena of softening, melting, swelling and formation of large blowholes through which volatile matter escaped. Combustion of the volatile matter was sooty and very luminous with large co-tails forming in the wake of the particle trajectories. Only after the volatile matter flames extinguished, the char combustion commenced and was also very luminous. In contrast, upon pyrolysis, lignite coals became fragile and experienced extensive fragmentation, immediately followed by ignition of the char fragments (numbering in the order of 10-100, depending on the origin of the lignite coal) spread apart into a relatively large volume. As no separate volatile matter combustion period was evident, it is likely that volatiles burned on the surface of the chars. The combustion of the sub-bituminous coal was also different. Most particles experienced limited fragmentation, upon pyrolysis, to several char fragments, with or without the presence of brief and low-luminosity volatile flames; other particles did not fragment and directly proceeded to char combustion. Finally combustion of bagasse was once again very distinctive. Upon pyrolysis, long-lasting, low-luminosity, nearly-transparent spherical flames formed around slowly-settling devolatilizing particles. They were followed by bright, short-lived combustion of the chars. Both volatiles and chars experienced shrinking core mode of burning. For all fuels, flame and char temperature profiles were deduced from pyrometric data and burnout times were measured. Combustion rates were calculated from luminous carbon disappearance measurements, and were compared with predictions based on published kinetic expressions.
机译:对来自三个不同等级的煤粉样品的颗粒进行了对比燃烧研究:高挥发性烟煤,次烟煤和两种褐煤。扩大了研究范围,包括观察燃烧甘蔗渣形式的粉状木质生物质残留物。将75-90微米范围内的燃料颗粒注入台式透明的滴管式炉中,电加热至1400 K,在那里经历高升温速率,被点燃并燃烧。用三色高温测定法和高速高分辨率摄影术观察空气中单个颗粒的燃烧,以获得温度-时间-尺寸历史。基于对这些技术的综合观察,结合颗粒的形态学检查,对这些燃料的燃烧行为有了全面的了解。观察到的煤间差异一直很大。在热解后,烟煤炭经历了软化,熔化,膨胀和形成大孔的现象,挥发物通过该孔逸出。挥发性物质的燃烧是烟熏的,并且非常发光,在粒子轨迹之后形成了大的尾巴。仅在挥发物火焰熄灭之后,焦炭才开始燃烧并且也非常发光。相反,在热解时,褐煤变得易碎并且经历了广泛的破碎,随后立即燃烧散布成相对较大体积的焦炭碎片(根据褐煤的来源,其数量大约为10-100)。由于没有明显的单独的挥发物燃烧期,因此很可能挥发物在焦炭表面燃烧。亚烟煤的燃烧也不同。在热解下,无论是否存在短暂且低光度的挥发性火焰,大多数颗粒都经历了有限的碎裂,形成了几个焦炭碎片。其他颗粒没有破碎,而是直接进行焦炭燃烧。最终,蔗渣的燃烧再次变得非常独特。热解后,在缓慢沉降的挥发颗粒周围形成长效,低发光度,近乎透明的球形火焰。它们之后是焦炭的明亮短暂燃烧。挥发物和炭都经历了燃烧的收缩核心模式。对于所有燃料,从高温数据得出火焰和炭的温度曲线,并测量燃尽时间。根据发光碳消失量计算燃烧率,并将燃烧率与基于已公开的动力学表达式的预测值进行比较。

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