Mass transfer enhancement as a function of oscillatory baffled reactor design
Mass transfer enhancement as a function of oscillatory baffled reactor design
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DOI：
10.1016/j.cep.2018.06.016
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发表时间：
2018-08-01
影响因子：
4.3
通讯作者：
Harvey, Adam P.
中科院分区：
文献类型：
--
作者：
Ahmed, Safaa M. R.;Phan, Anh N.;Harvey, Adam P.
在半间歇运行模式（连续气相；间歇液相）的振荡条件下，定量和定性地确定了四种振荡折流板反应器（OBR）的空气-水两相流动形式。评估的挡板设计有螺旋挡板、平滑周期收缩挡板、单孔板挡板和多孔板挡板。为了进行比较，还对光滑壁管中的振荡进行了表征。这些设计在振荡雷诺数（Re-o = 0-8000）和通气率（vvm = 0-1）范围内进行了表征。所有反应器具有相同的几何参数，如直径、长径比等。发现了三种不同的流动形式（气泡流、段塞流和搅拌流），它们与传统的气泡柱（bc）相似，但在obr中，在更大的振荡液体速度范围内观察到具有最高传质率的气泡流动形式。这是由于流动模式（通常是漩涡）和由振荡流动和挡板设计的相互作用产生的剪切，导致气泡的合并和破裂。与在光滑管（无挡板柱）中稳定流动（无振荡流动）相比，在多孔设计中，体积传质系数k(L)a显著增加，高达7倍。
Air-water two-phase flow regimes were identified quantitatively and qualitatively for four designs of oscillatory baffled reactor (OBR) over a range of oscillation conditions in semi-batch mode operation (continuous gas phase; batch liquid phase). The baffle designs assessed were helical baffles, smooth periodic constrictions, single orifice plate baffles and multi-orifice plate baffles. Oscillation in a smooth-walled tube was also characterised for comparison purposes. The designs were characterised over a range of oscillatory Reynolds number (Re-o = 0-8000) and aeration rates, vvm = 0-1. All the reactors had the same geometrical parameters such as diameter, ratio of length to diameter etc. Three distinct flow regimes (bubbly flow, slug flow, and churn flow) were identified, which were similar to those found in conventional bubble columns (BCs), but the bubbly flow regime, which exhibits the highest rates of mass transfer, was observed over a wider range of oscillatory liquid velocities in OBRs. This was due to the flow patterns (usually vortices) and shear engendered by the interactions of the oscillatory flows and the baffle designs, which resulted in coalescence and breakage of the bubbles. The volumetric mass transfer coefficients, k(L)a, were significantly increased in the multi-orifice design, up to 7-fold, compared with that for a steady flow (no oscillatory flow) in a smooth tube (unbaffled column).