Key Laboratory of Environmental Engineering, Shaanxi Province; Key Laboratory of Northwest Water Resources Environment and Ecology, MOE, Xi'an University of Architecture and Technology , Xi'an , People's Republic of China.
Environ Technol. 2019 Nov;40(27):3652-3667. doi: 10.1080/09593330.2018.1484522. Epub 2018 Jun 22.
The flow pattern is considered to play an important role in the formation of aerobic granular sludge in a bubble column reactor; therefore, it is necessary to understand the behavior of the flow in the reactor. A three-dimensional computational fluid dynamics (CFD) simulation for bubble column reactor was established to visualize the flow patterns of two-phase air-liquid flow and three-phase air-liquid-sludge flow under different ratios of height to diameter (H/D ratio) and superficial gas upflow velocities (SGVs). Moreover, a simulation of the three-phase flow pattern at the same SGV and different characteristics of the sludge was performed in this study. The results show that not only SGV but also properties of sludge involve the transformation of flow behaviors and relative velocity between liquid and sludge. For the original activated sludge floc to cultivate aerobic granules, the flow pattern has nothing to do with sludge, but is influenced by SGV, and the vortices is occurred and the relative velocity is increased with an increase in SGV; the two-phase flow can simplify the three-phase flow that predicts the flow pattern development in bubble column reactor (BCR) for aerobic granulation. For the aerobic granules, the liquid flow behavior developed from the symmetrical circular flow to numbers and small-size vortices with an increase in the sludge diameter, the relative velocity is amount up to = 5.0, it is 29.4 times of original floc sludge.
流型被认为在气泡柱反应器中形成好氧颗粒污泥中起着重要作用；因此，有必要了解反应器中的流动行为。建立了一个用于气泡柱反应器的三维计算流体动力学（CFD）模拟，以可视化不同高度与直径比（H/D 比）和表观气上升流速（SGV）下的气-液两相流和气-液-污泥三相流的流动模式。此外，本研究还在相同 SGV 和不同污泥特性下对三相流型进行了模拟。结果表明，不仅 SGV，而且污泥的特性也涉及到流动行为和液相对污泥的相对速度的转变。对于原始的活性污泥絮体来培养好氧颗粒，流型与污泥无关，而是受 SGV 影响，随着 SGV 的增加会发生漩涡，相对速度会增加；两相流可以简化气泡柱反应器（BCR）中预测好氧颗粒化的流动模式发展的三相流。对于好氧颗粒，随着污泥直径的增加，液体流动行为从对称的循环流发展为多个小尺寸的漩涡，相对速度高达 = 5.0，是原始絮体污泥的 29.4 倍。
