Application and Parameterization of a 1D Multifluid Population Balance Model for Gas-Liquid Processes
Creators: name: Breit, Ferdinand
name: Weibel, Christian
name: Von Harbou, Erik
Publisher: name: Zenodo
Year: 2023
Subjects: Population balance equation
Bubble column
1D multifluid model
scale-up and optimization
bubble size distribution
OMOP

description: Reactive gas-liquid processes can have very complex behavior. For example, we showed recently that the consumption of gas by a liquid phase reaction can significantly influence the internal circulation flow in jet loop reactors [1]. The reason for that behavior are local differences of the gas fraction. These differences, however, cannot only be caused by consumption of gas but also by local differences of the bubble rise velocity. Consequently, coalescence and breakage of bubbles can also have influence on the internal flow in reactors. In addition to that, the consumption of gas itself depends strongly on the mass transfer between gas and liquid phase and thus on the interfacial area and the bubble diameter respectively. It is clear that many of the processes occurring in gas-liquid reactors e.g. coalescence and breakup depend on the reactor geometry and size. Thus, to enable a reliable scale-up of gas-liquid reactors from lab or mini plant scale to production scale the mutual interdependency of the different processes – interfacial heat and mas transfer, reactions, breakage and coalescence of bubbles – taking place in the reactor and their dependency on reactor dimensions must be known. In principle multiphase CFD approaches can provide that information. So far, however, the computational effort for these CFD simulations models is still very large. For that reason, comprehensive studies of process and design parameter, as are often needed in early stages of process development, will not be possible. In a previous study [2], we showed that a 1D multifluid population balance model (MPB) is well suited to describe the axial profiles of the bubble size distribution (BSD) and gas volume fraction in a (non-reactive) bubble column. The advantage of this approach is, that the partial differential equations, which represent the MPB, can be solved on standard personal computers with low computational costs. However, due to the model simplifications, the model is not fully predictive. Model parameters – for example those describing breakage and coalescence of bubbles – need to be calibration by means of experimental data. For that reason, we established a broad experimental data base. Over 600 experiments were carried out in a laboratory bubble column. Different parameters such as the column height, the superficial gas velocity and the composition of the liquid phase were systematically varied. The BSD was measured at different columns heights with an optical probe developed previously at our laboratory [3]. Based on the experimental data, we developed a calibration procedure. Despite the strong simplification underlying the chosen MPB, only a minimal number of experimental data points were necessary to describe the behavior of the bubbly flow in the column. We will show that a prediction of the BSD and the gas hold-up is possible within a given chemical system in a wide range of compositions, operating points and bubble column heights. These results are an important step for the development of a robust and reliable approach for a simulation-based scale up of gas-liquid reactors. [1] Breit, F., Bey, O., &amp; von Harbou, E. (2022). <em>Processes</em>, <em>10</em>(7), 1297. https://doi.org/10.3390/pr10071297 [2] Breit, F., Mühlbauer, A., von Harbou, E., Hlawitschka, M. W., &amp; Bart, H. J. (2021). <em>Chemical Engineering Research and Design</em>, <em>170</em>, 270–289. https://doi.org/10.1016/j.cherd.2021.03.036 [3] Mickler, M., &amp; Bart, H. J. (2013). <em>Chemie Ingenieur Technik</em>, <em>85</em>(6), 901–906. https://doi.org/10.1002/cite.201200139
description: Ferdinand Breit was the presenter.