Entwurf und Betrieb eines Rohrreaktors mit enger Verweilzeitverteilung

In der Verfahrenstechnik ist die Verweilzeit eine wichtige Auslegungsgröße und eine enge Verweilzeitverteilung ist vorteilhaft, um bei komplexen chemischen Reaktionen mögliche Nebenprodukte zu vermeiden Eine gute radiale Vermischung mit geringer axialer Dispersion sorgt für eine enge Verweilzeitverteilung in einem Rohrreaktor. Die axiale Dispersion in laminarer Strömung in einem geraden Rohr ist sehr hoch und erzeugt damit eine breite Verweilzeitverteilung. Jedoch verbessern Sekundärströmungen die radiale Vermischung, die in diesem Beitrag für gekrümmte Rohrreaktoren untersucht werden. Entwurfshinweise zur guten radialen Vermischung und geometrische Ausführungen von Rohreaktoren mit Umlenkungen werden vorgestellt

Der Schnellstart in die digitale Lehre unter Corona‐Randbedingungen

Der Corona‐Lockdown und die Campus‐Schließung der TU Dortmund führten zu einem vollständig digitalen Sommersemester 2020 der Fakultät für Bio‐ und Chemieingenieurwesen. Vollständig digital? Nein! Dieser Beitrag gibt Beispiele für unterschiedliche digitale Lehrveranstaltungen. Aus der Sicht des Studiendekans werden Erfahrungen und persönliche Reflexionen zu diesem ungewöhnlichen Semester bis Juli 2020 dargestellt. Nach einer kurzen Einleitung werden Maßnahmen zur digitalen Lehre mit der schrittweisen Teilöffnung beschrieben. Insbesondere der Erfahrungsaustausch zusammen mit dem Feedback der Studierenden brachte interessante Ergebnisse und Erfahrungen mit digitalen Werkzeugen. Die daraus gezogenen Lehren werden skizziert zusammen mit Empfehlungen für verschiedene digitale Werkzeuge und einem Ausblick auf kommende Semester vorgestellt

3D investigations of microscale mixing in helically coiled capillaries

In capillary reactors, improving radial mixing and narrowing the residence time distribution is of great importance for high selectivity and reaction performance. A well-known approach is inducing secondary flow patterns by coiling the capillary around a cylinder. To increase understanding of transport phenomena in helically coiled capillaries non-invasive 3D imaging approaches are required. In this perspective paper, we introduce X-ray-based micro-computed tomography for the investigation of dispersion of iodide in a helically coiled tube. The methodology presented here allows for the direct evaluation of radial concentration fields. By varying Dean number Dn and modified torsion parameter T∗, the effect of torsion and curvature on the radial concentration profile can be identified. Detailed knowledge of local radial mixing in helically coiled capillaries will help the precise prediction of reaction progress and selectivity

Digital image processing of gas-liquid reactions in coiled capillaries

In the course of the investigation of biocatalytic gas-liquid reactions with color change in straight and coiled capillaries, a non-invasive evaluation method is needed to determine reaction progress and selectivity. Correlations between hydrodynamics, mass transfer phenomena, and reaction kinetics are in the focus of our work. For this purpose, it is necessary to investigate the flow and evaluate the reaction progress without disturbing the flow. Digital image processing (DIP) is presented as a suitable optical evaluation method for reactions with color change in capillary reactor designs. The developed DIP program is independent from the capillary reactor design, applicable to differently colored systems, and can analyze up to three different species simultaneously

Reactor performance estimation in microscale flow calorimeter for rapid characterization of exothermic reactions

Continuous flow calorimeters are a promising tool in process development and safety engineering, especially for flow chemistry applications to characterize the heat release and kinetic parameters of rapid chemical reactions. In this study, the digital accompaniment of an isoperibolic flow calorimeter for characterization of exothermic reactions is presented. To support experimental planning and evaluation, computational fluid dynamic simulations are carried out for single-phase flow in the microreactor. The residence time distribution is obtained and used for estimation of conversion and temperature profiles along the microreactor channel. This leads to an integration of CFD simulations into the calorimeter’s software-guided workflow reducing the experimental effort regarding the determination of thermokinetic data. The approach is tested for a highly exothermic test reaction, which provides further hints for future investigations

X‐ray‐based tomographic imaging for the investigation of laminar mixing in capillaries

Micro-computed tomography is a promising non-invasive imaging technology that offers high spatial resolution without requiring optical access. This opens the opportunity to analyze concentration fields in mixing equipment in 3D. To demonstrate the potential of the methodology, laminar mixing in helically coiled capillaries is investigated by tracking the radial distribution of potassium iodide along the main flow direction. Dean flow can be observed in the helically coiled capillaries, which intensifies with Reynolds number and decreasing effect of gravity

Machine learning based suggestions of separation units for process synthesis in process simulation

As part of Industry 4.0, workflows in the process industry are becoming increasingly digitalized. In this context, artificial intelligence (AI) methods are also finding their way into the process development. In this communication, machine learning (ML) algorithms are used to suggest suitable separation units based on simulated process streams. Simulations that have been performed earlier are used as training data and the information is learned by machine learning models implemented in Python. The trained models show good, reliable results and are connected to a process simulator using a .NET framework. For further optimization, a concept for the implementation of user feedback will be assigned. The results will provide the fundamental basis for future AI-based recommendation systems

Software-guided microfluidic reaction calorimeter based on thermoelectric modules

A software-guided, continuous reaction calorimeter based on thermoelectric modules for direct heat flux measurements is presented. Sensors and actuators of the calorimeter's setup are implemented within a lab automation system, which enables the automated calibration of the heat flux sensors and investigations of chemical reactions through sequential function charts. Functionality of the calibration is shown by heat transfer experiments. Additionally, the calorimeter's performance is demonstrated by good agreement of conducted neutralization experiments with literature data

Software-guided microscale flow calorimeter for efficient acquisition of thermokinetic data

Fast chemical process development is inevitably linked to an optimized determination of thermokinetic data of chemical reactions. A miniaturized flow calorimeter enables increased sensitivity when examining small amounts of reactants in a short time compared to traditional batch equipment. Therefore, a methodology to determine optimal reaction conditions for calorimetric measurement experiments was developed and is presented in this contribution. Within the methodology, short-cut calculations are supplemented by computational fluid dynamics (CFD) simulations for a better representation of the hydrodynamics within the microreactor. This approach leads to the effective design of experiments. Unfavourable experimental conditions for kinetics experiments are determined in advance and therefore, need not to be considered during design of experiments. The methodology is tested for an instantaneous acid-base reaction. Good agreement of simulations was obtained with experimental data. Thus, the prediction of the hydrodynamics is enabled and the first steps towards a digital twin of the calorimeter are performed. The flow rates proposed by the methodology are tested for the determination of reaction enthalpy and showed that reasonable experimental settings resulted

Nucleation in continuous flow cooling sonocrystallization for coiled capillary crystallizers

Nucleation in continuously operated capillary coiled cooling crystallizers is experimentally investigated under the influence of ultrasound. It was found that there is no sharp boundary but rather a transition zone for nucleation under sonication. For this purpose, a tube with an inner diameter of 1.6 mm and a length of 6 m was winded in a coiled flow inverter (CFI) design and immersed into a cooled ultrasonic bath (37 kHz). The CFI design was chosen for improved radial mixing and narrow residence time distribution, which is also investigated. Amino acid l-alanine dissolved in deionized water is employed in a supersaturation range of 1.10 to 1.46 under quiet and sonicated conditions. Nucleation is non-invasive detected using a flow cell equipped with a microscope and camera