Foams occur in many industries, such as chemical and food industry, and also in everyday life. Foam is understood as a disperse system of gas and liquid with a dominating gas-vapor fraction. In the following, only fluid foams will be discussed. On the one hand, foam is desired and deliberately generated, as in the separation process of flotation or even the production of insulation materials, on the other hand, it is a very undesirable event when it occurs in separation apparatus, such as distillation or absorption columns, or in reactors.

Foam formation is still not fully understood. Especially when it is undesirable, appears suddenly, and is the reason for operational disturbances, it is hardly predictable and difficult to diagnose with certainty, e.g., in columns. If foams occur unintentionally in chemical engineering equipment, they often cause major production problems, up to and including the shutdown of entire plants, which results in high economic losses. In columns, foam, among other things, is cited as a frequent cause of operational malfunctions. Here, fast and reliable diagnoses as well as robust and cost-effective countermeasures are then desired. In most cases, the loads and thus the throughputs are reduced, and the use of antifoaming agents is tested, but this is not always possible, as these may remain in the product, albeit in very small quantities, and represent a permanent cost factor.

In addition to chemical methods of foam reduction and control, there are also physical and mechanical methods, whereby mechanical methods often produce a very reduced-volume but stable so-called secondary foam. Physical methods for foam reduction are known in the literature but are not really widely used in chemical engineering. Furthermore, it would be desirable to take possible foam events into account or to counteract them already in the design phase of a plant or apparatus. This is countered by the complexity of the problem, which is caused by surface-active substances that are usually present only in low concentrations, represent impurities, are small amounts of by-products of a reaction or degradation, or act in fluid systems that tend to be demixed (Ross-type foaming), which is difficult to predict.

In the collection of papers presented here, a physically based management of foams was the main guideline of the scientific investigations. The results shown represent a part of a funded larger AIF (German Federation of Industrial Research Associations)/DFG (German Research Foundation) cluster that contributed to physical foam management, focusing on prevention, inhibition, and destruction of foam. The works cover a wide range, from the description and new approaches to the characterization of the foam, through prediction using a multiscale approach, to design studies of new packing geometries and design ideas. Furthermore, foam destruction methods such as ultrasound and acoustic sound, among others, were examined more closely for possible applications in packing columns. The studies and results presented here represent further and new approaches that are worth further investigation to better understand the phenomenon of “unwanted foam”, to take it into account in the design and, if necessary, to combat it efficiently and cost-effectively in the future. The work is certainly not conclusive, but it contributes to the understanding of the phenomena of foam and provides promising starting points for future research and development of foam management methods.

Prof. Dr.-Ing. Jens-Uwe Repke

TU Berlin, Process Dynamics and Operations Group

泡沫出现在许多行业，例如化学和食品工业，以及日常生活中。泡沫被理解为气体和液体的分散系统，具有主要的气体-蒸汽部分。在下文中，将仅讨论流体泡沫。一方面，在浮选的分离过程甚至绝缘材料的生产中，泡沫是需要和故意产生的，另一方面，当它发生在分离设备中，如蒸馏或吸收时，这是一个非常不受欢迎的事件列，或在反应器中。

泡沫的形成仍不完全清楚。尤其是当它是不可取的、突然出现并且是操作干扰的原因时，它几乎是不可预测的并且难以确定地诊断，例如在列中。如果在化学工程设备中无意中出现泡沫，它们通常会导致重大的生产问题，甚至包括整个工厂的停工，从而导致高额经济损失。在色谱柱中，泡沫等被认为是导致操作故障的常见原因。在这里，需要快速可靠的诊断以及稳健且具有成本效益的对策。在大多数情况下，负载和产量都会降低，并且会测试消泡剂的使用，但这并不总是可能的，因为这些可能会残留在产品中，尽管数量非常少，

除了减少和控制泡沫的化学方法外，还有物理和机械方法，其中机械方法通常会产生体积非常小但稳定的所谓二次泡沫。用于减少泡沫的物理方法在文献中是已知的，但在化学工程中并未真正广泛使用。此外，希望在设备或设备的设计阶段就已经考虑到可能的泡沫事件或抵消它们。这被问题的复杂性所抵消，这是由通常仅以低浓度存在的表面活性物质引起的，代表杂质，是反应或降解的少量副产物，或者在倾向于趋向的流体系统中起作用被分层（罗斯型发泡），这很难预测。

在这里展示的论文集中，基于物理的泡沫管理是科学研究的主要指导方针。显示的结果代表了资助的大型 AIF（德国工业研究协会联合会）/DFG（德国研究基金会）集群的一部分，该集群有助于物理泡沫管理，重点是预防、抑制和破坏泡沫。这些作品涵盖了广泛的范围，从泡沫的描述和新方法到表征，通过使用多尺度方法进行预测，再到新包装几何形状和设计理念的设计研究。此外，更仔细地研究了诸如超声波和声学等泡沫破坏方法在填料塔中的可能应用。这里介绍的研究和结果代表了值得进一步研究的进一步和新方法，以更好地了解“不需要的泡沫”现象，在设计中考虑到它，并在必要时在未来。这项工作当然不是结论性的，但它有助于理解泡沫现象，并为未来研究和开发泡沫管理方法提供了有希望的起点。

Prof. Dr.-Ing。Jens-Uwe Repke

柏林工业大学，过程动力学和运营集团