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Thesis Advisor郭慕孙
Degree Grantor中国科学院研究生院
Abstract本工作借助激光全息照相术,捕捉了三种固体颗粒(FCC催化剂,硅胶及空心玻璃珠)在垂直气固流动体系中的聚团群(clusters);基于对气固流动体系的观察,提出了聚团的两种形成机理假说;得到了聚团群的统计处理结果及FCC催化剂颗粒单个聚团的形态分析结果的证实。实验结果表明,在低气速下形成的原生聚团(primary cluster)随气速的增加呈减小的趋势。在聚团的两种形成机理之间存在一临界气速Uc,在此气速下,原生聚团体积达到最大。上述三种颗粒的临界气速分别为0.185m/s;0.556m/s;0.231 m/s。对FCC催化剂颗粒在各种操作条件下单个聚团的形态分析表明,湍流聚团的空间填空能力比原生聚团的空间填空能力强。原生聚团的分数维一般在1.2左右,而湍流聚团的分数维则波动较大,与构成它的小聚团的空间排列有关。在假设稀相气固体系仅由不可穿透的聚团相和极限稳态散式颗粒相组成的前提下,并考虑了聚团形态的影响因素后,半理论半经验地关联了聚团大小的计算式:其中,计算式在实验范围内的平均误差为6.1%。
Other AbstractInstantaneous pictures of clusters of three solid materials (FCC catalyst, silica gel, hollow glass beads) in flowing vertical gas/solid systems were captured by laser holography. A hypothesis on two mechanisms of cluster formation was advanced and was verified by the statistical results of cluster measurements for all the three solids and by morphological analysis of FCC catalyst clusters. Experimental results showed that the size of primary clusters formed at low gas velocities increases with gas velocity while that of turbulent clusters formed at high gas velocities through agglomeration tends to decrease with gas velocities. Between these two opposite mechanisms of cluster growth, there exists a critical gas velocity Uc at which the primary clusters attain a maximum size. The critical gas velocities for FCC catalyst, silica gel and hollow glass beads are 0.185 m/s, 0.556 m/s and 0.231 m/s, respectively. Morphological analysis of single FCC catalyst clusters showed that the space filling capacity of turbulent clusters is higher than that of primary clusters. For the latter, the fractal dimension is around 1.2, while for turbulent clusters, it depends on the space arrangement of the component small clusters. By taking into consideration the morphological effects on clusters and supposing that a dilute gas/solid system is composed mainly of a steady dispersed particulate phase and a second phase of impermeable clusters, the following empirical correlation for cluster size was obtained: The mean error of this equation from experimental data is 6.1%.
Document Type学位论文
Recommended Citation
GB/T 7714
韦江华. 垂直气固流动体系中的颗粒聚团[D]. 中国科学院研究生院,1988.
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