Comparative study of local gas-liquid hydrodynamics and mass transfer between conventional and modified airlift reactors
Comparative study of local gas-liquid hydrodynamics and mass transfer between conventional and modified airlift reactors
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DOI：
10.1016/j.jece.2019.103206
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发表时间：
2019-08-01
影响因子：
7.7
通讯作者：
Painmanakul, Pisut
中科院分区：
文献类型：
--
作者：
Bun, Saret;Chawaloesphonsiya, Nattawin;Painmanakul, Pisut
在气升式反应器的提升管内设置斜挡板，以提高氧传递系数。与常规反应器相比，MALR可以将K（L）a值提高高达97%。然而，到目前为止，对这种新反应器的流体力学和其他氧传递参数的分析还不够。因此，本文的目的是分析当地的气液动力学和评估的氧传递性能相比，在MALR常规反应器使用清水作为液相。气泡分布采用气泡直径，上升速度，和界面面积。斜挡板保持气泡尺寸在3.88和4.63毫米之间的研究表观气速（Ug），这是小于在气升式反应器（ALR）约0.2毫米。气泡上升速度（U-B）是相对增加与Ug，无论反应器类。新型反应器通过延长斜折流板的气泡流路，延长了气泡在水中的停留时间，使U-B值分别比鼓泡塔反应器（BCR）和ALR降低了39%和52%。因此，这些性能导致界面面积比常规反应器高几乎两倍。MALR的氧传递效率比BCR和ALR分别提高了1.57%和0.63%。这导致与其他检查的反应器相比最高的曝气效率（AE），遵循AE的趋势线表达，其类似于0.046 Ug（-0.）（六）、插入斜挡板产生的死区体积分别比ALR和BCR多5%和12.8%。总之，MALR可以显着提高氧传递性能，由于能够保持气泡尺寸和延长气液传递时间。
Modified airlift reactor (MALR) was developed for improving the oxygen transfer coefficient (K(L)a) by installing the slanted baffles in the riser compartment. MALR can enhance K(L)a value up to 97% compared to a regular reactor. However, insufficient analysis of the hydrodynamics and other oxygen transfer parameters of this new reactor has been performed to date. Therefore, this paper aims to analyse local gas-liquid dynamics and evaluate the oxygen transfer performance in MALR compared to regular reactors using clean water as a liquid phase. Air bubble distribution was employed in terms of bubble diameter, rising velocity, and interfacial area. Slanted baffles maintained the bubble size between 3.88 and 4.63 mm for the studied superficial gas velocity (Ug), which is smaller than that in airlift reactor (ALR) by approximately 0.2 mm. Bubble rising velocity (U-B) is relatively increased with Ug, regardless of reactor classes. New reactor could extend the bubble residence in the water by lengthening the bubble stream path of the slanted baffles leading to decrease U-B values about 39% and 52% compared to bubble column reactor (BCR) and ALR, respectively. These performances consequently resulted in an interfacial area almost two times higher than in regular reactors. Oxygen transfer improved in MALR with an extra amount of oxygen transfer efficiency of 1.57% and 0.63% over BCR and ALR, respectively. This resulted in the highest aeration efficiency (AE) compared to other examined reactors, following a trendline expression of AE similar to 0.046 Ug(-0.)(6). Insertion of slanted baffles produced 5% and 12.8% more dead zone volume than ALR and BCR, respectively. In conclusion, MALR can significantly enhance oxygen transfer performance due to the ability to maintain bubble size and extend the gas-liquid transfer period.