Influence of Small Amounts of Additives on Gas Hold-Up, Bubble Size, and Interfacial Area
Influence of Small Amounts of Additives on Gas Hold-Up, Bubble Size, and Interfacial Area
复制标题
少量添加剂对含气率、气泡尺寸和界面面积的影响
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
G. Versteeg
中科院分区：
文献类型：
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作者：
A. Cents;D. Jansen;D. Brilman;G. Versteeg
气-液界面面积由气含率和Sauter平均气泡直径决定，它决定了许多工业过程中的生产率。添加剂对该界面面积的影响，特别是在多相系统（气-液-固，气-液-液）中，通常不清楚。第三相的加入会导致气液体系变得完全不透明，这意味着不能使用传统的技术来研究界面面积。为此，在这项工作中使用超声波光谱法来研究这些系统中的界面面积和气泡尺寸分布。在搅拌釜和鼓泡塔中研究了不同添加剂对聚结和非聚结条件下相界面积的影响。有人发现，甲苯的加入到noncoalescing电解质系统减少了界面面积在很大程度上通过把它变成一个聚结系统，由于气泡和液体有机液滴之间的相互作用。此外，周围的甲苯溶解度浓度，气体滞留（使用电导率技术测量）和界面面积增加到类似于在noncoalescing系统中观察到的值。这一显著现象的原因可能在于气泡周围存在小的甲苯层，其可以在超过溶解点时形成。该层在低于溶解度极限的浓度下不存在，并且在这两种情况之间存在大的表面张力梯度，这可能是聚结行为急剧变化的原因。
The gas−liquid interfacial area, which is determined by the gas hold-up and the Sauter mean bubble diameter, determines the production rate in many industrial processes. The effect of additives on this interfacial area is, especially in multiphase systems (gas−liquid−solid, gas−liquid−liquid), often not understood. The addition of a third phase can cause the gas−liquid system to become completely opaque, which means that conventional techniques to study the interfacial area cannot be used. For this reason ultrasonic spectroscopy was used in this work to study the interfacial area and the bubble size distribution in these systems. The influence of different additives on the interfacial area was studied in a stirred vessel and in a bubble column under coalescing and noncoalescing conditions. It was found that the addition of toluene to a noncoalescing electrolyte system decreased the interfacial area to a large extent by turning it into a coalescing system, due to the interaction between gas bubbles and liquid organic droplets. Furthermore, around the toluene solubility concentration, both the gas hold-up (measured using an electric conductivity technique) and the interfacial area increased to values similar to those observed in noncoalescing systems. The cause of this remarkable phenomenon lies probably in the presence of a small toluene layer around the gas bubbles, which can be formed beyond the solubility point. This layer is absent at concentrations below the solubility limit and a large surface tension gradient exists between those two situations, which can be responsible for the sharp change in coalescence behavior.