Browsing by Subject "Foam destruction"

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Foam management in distillation plants
(2022) Heller, Daniel; Kölling, Ralf
Foam formation occurs for various substrates during distillation processes. A concrete prediction of the foam formation can only be approximated due to the physical, chemical, and biochemical complexity of the influencing factors. Foam formations affect both the design and the operation of distillation plants, due to various undesirable negative effects of foams on the process and the product. In this work, foam formations under boiling conditions in distillation plants of the spirit industry were investigated and different foam control methods for a holistic foam management system were developed. It was intended to make the distillation process more foam-resilient, and less subjected to foam-induced process disruption. To investigate foam formation in distillation processes lab-scale experiments and experiments on a column still were carried out. In the first step for a foam management system, the inhibition of foams by modification of substrate properties was investigated. In experiments various physical and rheological parameters of mashes as well as other foam-relevant parameters were determined. The aim was to derive a possible link with foam formation. It was shown that the viscosity and viscosity-determining compounds of the substrate have a significant influence on the foaming behavior of mashes. Rye mash was used as the demonstration medium in these experiments. In rye mash the compound pentosan was, in particular, influencing the viscosity. The experiments demonstrated, that the degradation of pentosans prior to distillation resulted in a decrease in viscosity and reduced foam accumulation. Next to foam-promoting substrate properties, foam-promoting operating conditions were investigated. The aim was to link passive process parameters to foam formations. On a laboratory scale, the foam formation in rye mashes was investigated as a function of passive process parameters and operating conditions, respectively, during distillation. It was demonstrated, that foam formations only occurred in a narrow temperature range of 89.5 – 98.2 °C. Additionally, foam formations were significantly lower with reduced energy input. The findings of the lab scale experiments were applied to develop foam-resilient heating profiles for distillations in the column still. In addition, it was focused on the separation effectiveness and economic efficiency of the new heating profiles, particularly with regard to process duration and the quality of the distillates obtained. Promising foam-resilient heating profiles were transferred to different substrates and their effectiveness was tested. Based on the findings, recommendations for distilleries for a foam-resilient distillation process could be derived, as well as predictions regarding effects on the product quality and process effectiveness. As the last step, active measures for foam destruction utilizing ultrasound were investigated. Ultrasound was introduced into the column at the level of the foam retention device of the distillation unit. The introduction of ultrasound into the column at the level of the foam retention device resulted in a reduction of foams. The observed decrease in foams was attributed to ultrasound-induced drainage of the liquid phase and subsequent destruction of the foam. However, also limitations of the method were found, e.g. limited area of effect. Further research is needed to validate the results and overcome these limitations. Overall, it was shown that foam management, which is not based on chemical defoamers, is possible in foam formation under boiling conditions in distillation processes. Several proposed measures, including inhibition, reduction, and destruction of foams were proposed. By combining them a holistic foam management is feasible.