Characterising gas behaviour during gas-liquid co-current up-flow in packed beds using magnetic resonance imaging
Characterising gas behaviour during gas-liquid co-current up-flow in packed beds using magnetic resonance imaging
复制标题
DOI：
10.1016/j.ces.2016.04.004
复制
发表时间：
2017-01-10
影响因子：
4.7
通讯作者：
Thomann, Hans
中科院分区：
文献类型：
--
作者：
Collins, James H. P.;Sederman, Andrew J.;Thomann, Hans
利用磁共振成像技术研究了内径为43 mm、填充直径为1.8、3和5 mm的球形无孔元件的柱中共流向上流动过程中的气相动力学。MR测量了气含率、气泡尺寸分布和气泡上升速度作为流量和填料尺寸的函数。分别在20-250 cm(3) s（-1）和0-200 cm(3) min（-1）范围内研究气体和液体流速。床层内气含率随气体流量的增加而增加，随填料尺寸的增加而降低，随液体流量的增加而降低的程度较小。气含率可分为动态气含率和静态气含率，动态气含率仅弱依赖于填料尺寸，并与床上上升的气泡有关；静态气含率指的是床内与暂时不变气含率有关的位置，在512秒的测量时间内，与床内空隙结构中捕获的气体或床内的气体通道有关。这种静态气含率与填料尺寸密切相关，随着填料尺寸的减小而增加。动态气含率由与填料尺寸相当的小气泡组成，这些气泡的上升速度为10-40毫米秒（-1），它们在床层内的填料元件之间移动，同时还有更大的气泡或气泡团，它们的上升速度更高（100-300毫米秒（-1））。这些较大的气泡，可能以较小气泡或变形体气泡的形式存在，就观测到的高上升速度而言，表现为单个大气泡。在所有填料中都观察到气泡在流动方向上的伸长。(C) 2016年Elsevier Ltd.出版
Magnetic resonance (MR) imaging techniques have been used to study gas phase dynamics during co-current up-flow in a column of inner diameter 43 mm, packed with spherical non-porous elements of diameters of 1.8, 3 and 5 mm. MR measurements of gas hold-up, bubble-size distribution, and bubble-rise velocities were made as a function of flow rate and packing size. Gas and liquid flow rates were studied in the range of 20-250 cm(3) s(-1) and 0-200 cm(3) min(-1), respectively. The gas hold-up within the beds was found to increase with gas flow rate, while decreasing with increasing packing size and to a lesser extent with increasing liquid flow rate. The gas hold-up can be separated into a dynamic gas hold-up, only weakly dependent on packing size and associated with bubbles rising up the bed, and a static hold-up which refers to locations within the bed associated with temporally-invariant gas hold-up, over the measurement times of 512 s, associated either with gas trapped within the void structure of the bed or with gas channels within the bed. This static gas hold-up is strongly dependent on packing size, showing an increase with decreasing packing size. The dynamic gas hold-up is comprised of small bubbles of order of the packing size which have rise velocities of 10-40 mm s(-1) and which move between the packing elements within the bed, along with much larger bubbles, or agglomerates of bubbles, which move with higher rise velocities (100-300 mm s(-1)). These larger bubbles, which may exist as streams of smaller bubbles or amoeboid bubbles, behave as a single large bubble in terms of the observed high rise velocity. Elongation of the bubbles in the direction of flow was observed for all packings. (C) 2016 Published by Elsevier Ltd.