Systematic studies of foam prevention and inhibition by identification of interfaces-non-existence domains and their realization by means of adaptive design of column random fillers and packs

• Applicant: Professor Dr.-Ing. Antonio Delgado
• Subject Area: Chemical and Thermal Process Engineering ; Fluid Mechanics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 408062554

It intends to contribute to the prevention and inhibition of undesirable foams by means of systematic experimental and simulative studies on local thermos fluid dynamic processes in "functional" column installations of fine chemistry as well as food and beverage technology. The focus lies on dumped-type elements and structure packings which serve the effective transport of material and thermal energy between mostly a gas and a liquid, for example, in extraction, absorption, distillation and rectification counter-current columns. As the gas flows from the column floor to the lid, the liquid flows in the opposite direction as a trickle film, or a rivulet along the surface of the functional elements. This causes regularly a formation of unwanted foam. Chemical foam inhibitors provide no solution because they endanger the purity of chemical products as well as foodstuffs and beverages.The studies planned here consider purely mechanical foam formation on the length scale of dumped-type elements and structure packings. The focus of the planned systematic investigations lies on the prevention and inhibition of undesirable foams by passive physical measures based on the identification of domains, in which gas inclusions and, therefore, foams do not exist. This condition occurs when the net foam balance takes on negative and the (generalized) Deborah number very high values. The proposed identification of the non-existence domain postulates that capillary-mechanical effects play an essential role in the stability of interfaces and, thus, in the inclusion of gases. The investigations start with the static case and consider elements of the zero development stage based on solutions of the Gauss-young-Laplace equation for interfaces that exist only in certain domains. These include capillary-dominated interfaces with high stability that make the formation of bubbles very difficult or impossible. In the context of a proposed theory, currents in the trickle films and rivulets are considered as disturbances of the static equilibrium. By checking the energy level and the stability of the interface, the tendency to create new interfaces as required for the generation of foams can be estimated. This applies to both the laminar and the turbulent state, for which the literature provides corresponding criteria. Based on the findings and methods to be developed regarding passive foam management, it is intended to virtually design and experimentally test new functional column fixtures. Pareto-based genetic algorithms provide the necessary mathematical optimization in iterative development cycles.

• DFG Programme: Research Grants