Continuous Membrane Emulsification with Pulsed (Oscillatory) Flow
Continuous Membrane Emulsification with Pulsed (Oscillatory) Flow
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DOI：
10.1021/ie3020457
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发表时间：
2013-01-09
影响因子：
4.2
通讯作者：
Piacentini, Emma
中科院分区：
文献类型：
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作者：
Holdich, Richard G.;Dragosavac, Marijana M.;Piacentini, Emma
使用内径为14 mm、长度为60 mm、含有直径为10 μ m和20 μ m的均匀孔的管状微米孔尺寸筛型膜，使用连续相的振荡流产生分散在水中并由吐温20稳定的向日葵油乳液。可以以可控的方式生产直径在30和300 μ m之间的液滴，并且跨度值低至0.4。通过使用脉冲流，可以在膜上的单次通过中提供高达45%v/v的分散相浓度，即，不需要使连续相再循环通过膜管。这是可能的相关的液滴大小产生的剪切条件在膜表面使用波剪切应力方程。振荡雷诺数指示从层流到基本湍流的流动变化，但是流动条件的变化没有显示出对所产生的液滴直径的显著影响，超过了通过应用于波动方程的变化的壁剪切应力所预测的。然而，在某些操作条件下，20 μ m孔径的筛型膜似乎允许压力脉冲通过膜孔，这确实导致产生比预期更细的液滴尺寸。这些通过膜的脉动可以通过操作条件的改变来抑制：更高的分散相注入速率或更粘的连续相，并且它们在与10 μ m孔径筛类型的膜使用的类似操作条件下不发生。使用脉冲连续相流产生这种尺寸的乳液提供了将通过膜乳化在高分散相浓度下产生液滴与下游处理如活塞流反应器中的反应相结合的机会。
Tubular micrometer pore sized sieve type membranes with internal diameter of 14 mm and length of 60 mm containing uniform pores of diameter 10 and 20 mu m were used to generate emulsions of sunflower oil dispersed in water and stabilized by Tween 20 using oscillatory flow of the continuous phase. Drop diameters between 30 and 300 mu m could be produced, in a controllable way and with span values of down to 0.4. By using pulsed flow it was possible to provide dispersed phase concentrations of up to 45% v/v in a single pass over the membrane, that is, without the need to recirculate the continuous phase through the membrane tube. It was possible to correlate the drop size produced with the shear conditions at the membrane surface using the wave shear stress equation. The oscillatory Reynolds number indicated flow varying from laminar to substantially turbulent, but the change in flow conditions did not show a notable influence on the drop diameters produced, over what is predicted by the varying wall shear stress applied to the wave equation. However, the 20 mu m pore sized sieve type membrane appeared to allow the passage of the pressure pulse through the membrane pores, under certain operating conditions, which did lead to finer drop sizes produced than would be predicted. These through-membrane pulsations could be suppressed by changes in operating conditions: a higher dispersed phase injection rate or more viscous continuous phase, and they did not occur under similar operating conditions used with the 10 mu m pore sized sieve type of membrane. Generating emulsions of this size using pulsed continuous phase flow provides opportunities for combining drop generation at high dispersed phase concentration, by membrane emulsification, with downstream processing such as reaction in plug flow reactors.