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Alternative TitleInvestigation of fluid flow and backmixing characteristics in an up-flow reactor
Thesis Advisor雍玉梅  ;  杨超
Degree Grantor中国科学院研究生院
Degree Discipline化学工艺
Keyword上流式反应器   气液固体系   流动和混合   平均停留时间   轴向扩散系数
Abstract上流式反应器作为一种典型的三相反应器已广泛应用于工业生产和实验研究中。上流式反应器在渣油加氢技术领域表现出很大的优势,但在工业应用中仍然存在如催化剂失活快、热点出现及局部结焦等问题。因此对上流式反应器内流动和传递过程进行深入的实验研究很有意义。 本文搭建了二维结构的上流式反应器,以空气和自来水作为气液介质,分别选用了四种粒径的玻璃珠、两种粒径的氧化铝球载体和两种尺寸的拉西环载体作为填充颗粒。基于工业中的催化剂级配原则,对两种玻璃珠进行了组合装填。操作范围为表观气速0.0069 m/s≤ ≤0.0417 m/s,表观液速0.0028 m/s≤ ≤0.0083 m/s。采用了一维轴向扩散模型,利用示踪—响应技术对反应器床层的膨胀率、压降、平均停留时间和轴向扩散系数进行了系统的研究。主要结果如下: (1)小颗粒床层比大颗粒床层易膨胀,床层膨胀存在一个转折点,超过转折点后膨胀率随表观气速的增大呈线性增大的变化关系。 (2)床层压降随表观液速的增大而增大。压降与表观气速的关系较为复杂,颗粒的粒径大小对摩擦压降的增大量和静压降的减小量起到了决定性的作用。 (3)平均停留时间随着表观气速、表观液速的增大而减小,并且表观液速的影响程度要大一些;一定表观液速下,平均停留时间随表观气速减小到一个定值;在一定的气、液表观流速下,平均停留时间随着颗粒粒径的增大而增大,也趋于一个定值。 (4)床层的轴向扩散系数随着表观气速、表观液速及颗粒粒径的增大而增大。 综上所述,液体对压降、平均停留时间和轴向扩散系数的决定性作用比气体重要,但是当表观液速较低时则需要同时考虑气液两相的影响。同时,在一定的操作范围内大颗粒床层的平均停留时间较长。
Other AbstractAs a typical three-phase reactor, the up-flow reactor has been widely used in industrial processes and experiment studies, which exhibits great advantages in residue hydrotreating technology, but there are still some problems such as fast catalyst deactivation, hot spots and local coking etc. So it’s very meaningful for further experimental study on flow and transport processes in up-flow reactors. In this thesis we built a two-dimensional reactor, using air and water as gas and liquid phases, respectively, and choosing four types of glass beads with different diameters, two types of alumina balls with different diameters and two types of Raschig rings with different sizes as filler particles. Besides, the combination of two glass beads has also been loaded based on the industrial catalyst grading principle. The operating range is that the superficial gas velocity 0.0069m/s≤ ≤0.0417m/s and the superficial liquid velocity 0.0028 m/s≤ ≤0.0083 m/s, making use of a one-dimensional axial dispersion model and the tracer-response technology to study expansion, pressure drop, average residence time and axial dispersion coefficient. The main conclusions are as follows: (1) The bed filled with small particles is easier to expand than that filled with big particles, and there is a turning point in the bed expansive process. Above this turning point expansion increases with increasing superficial gas velocity. (2) The bed pressure drop increases with the increase of the superficial liquid velocity, and the relation with superficial liquid velocity is uncertain. Particle size is crucial to the increment of frictional pressure drop and the reduction of static pressure drop. (3) The average residence time decreases with the increase of superficial gas and liquid velocities, and the influence of superficial liquid velocity is larger than that of superficial gas velocity. Average residence time decreases to a constant value with the increase of superficial gas velocity at a certain superficial liquid velocity. The average residence time increases with the increase of particle size, and then gradually tends to a constant value at certain superficial gas and liquid velocities. (4) The axial diffusion coefficient increases with the increase of superficial gas and liquid velocities and particle sizes. In a word, the liquid flow is more important to decide the pressure drop, average residence time and axial diffusion coefficient than the gas flow. But when the liquid superficial velocity is very low, then we need to weight the role of both fluids. At the same time, the larger particles will lead to the longer the average residential time in a limited range.
Document Type学位论文
Recommended Citation
GB/T 7714
娄晓军. 上流式反应器中流体流动及返混特性研究[D]. 中国科学院研究生院,2014.
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