Matthias Kraume

• Prof. Dr.-Ing.
• Head of Department at Technische Universität Berlin

Zusammenfassung Zur Reduzierung der NO x ‐Emissionen bei der Verbrennung im Gasmotor hat sich die selektive katalytische Reaktion mit Ammoniak durchgesetzt. Insbesondere für kleine Motoren stellt die Katalysatorapplikation und die Einbringung des Reduktionsmittels eine große Herausforderung dar. In dieser Arbeit werden experimentell die Alterungser...

The dynamic behavior of a toluene/NaOH solution system was studied in a batch stirred tank. Characterization by step response experiments showed that the drop size response to stirrer speed steps behaves as a first‐order system, whereas the stirrer speed responds as a second‐order system. The respective time constants differed by at least one order...

The concentration-induced Marangoni effect on single drops is investigated experimentally. The standard chemical system toluene/water/acetone, known for its strong Marangoni instabilities, was chosen for this study. The toluene drops with acetone as solute are immobilised in water by acoustic levitation. The mass transfer from the dispersed to the...

This research study aims at achieving a deeper understanding of the influence of fluid dynamic stress on the fungus’ morphology in lab-scale aerated stirred tank bioreactors, and at identifying low-stress stirring conditions beneficial for the growth of stress-sensitive microorganisms. The effect of stirring on the morphology of various strains of...

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Mixing in biogas fermenters is complex due to the non-Newtonian rheology of biogenic substrates, which exhibit both pseudoplasticity and elasticity....

Acoustic levitation can provide significant benefits for many fundamental research questions. However, it is important to consider that the acoustic field influences the measurement environment. This work focuses on the dissolution of immobilised drops using acoustic levitation in liquid–liquid systems. Previous work demonstrated that the acoustic...

The productivity of Aspergillus niger cultivations is strongly linked to the pellet morphology. In this article, the agitation-and aeration-induced stress on bio agglomerates is studied. To facilitate investigations, non-biological particle systems are extensively used to model the actual biological matter. The literature lacks a direct comparison...

The study aims at utilising the clay floc system and methods of Panckow et al. (2023) to characterise the hydrodynamic stress acting on particles in a lab-scale stirred tank reactor. The effect of flocculation phase on steady-state characteristics, as well as the system's reversibility are examined. Conventional and non-conventional impeller types...

Fluidized particulate systems can be well described by coupling the discrete element method (DEM) with computational fluid dynamics (CFD). However, the simulations are computationally very demanding. The computational demand is drastically reduced by applying the coarse grain (CG) approach, where several particles are summarized into larger grains....

A low-impact acoustic levitation system has been developed to study immobilised single drops in liquid–liquid systems. The ability to observe liquid drops several millimetres in diameter for days enables fundamental research into a wide range of mechanisms. Non-invasive optical measurements with excellent optical accessibility are possible. This ex...

The mixing performance and power consumption for four dual‐impeller configurations in a stirred tank are studied using the mean age theory (MAT) approach, the fully transient techniques (FTT), and experiments. A novel method is developed based on the scaled mean age probability distribution curve, allowing the MAT method to be applied to multi‐impe...

Scaling bioprocesses remains a major challenge. Since it is physically impossible to increase all process parameters equally, a suitable scale-up strategy must be selected for a successful bioprocess. One of the most widely used criteria when scaling up bioprocesses is the specific power input. However, this represents only an average value. This s...

The application of compact NMR instruments to hot flowing samples or exothermically reacting mixtures is limited by the temperature sensitivity of permanent magnets. Typically, such temperature effects directly influence the achievable magnetic field homogeneity and hence measurement quality. The internal-temperature control loop of the magnet and...

Filamentous fungi are widely exploited as cell-factories in industry due to their metabolic diversity, high production capacity and secretion efficiency. In stirred tank bioreactors, the filamentous fungus Aspergillus niger builds agglomerates of complex morphology. The formed morphology has a decisive influence on productivity and is significantly...

CO2-switchable surfactants have selective surface-activity, which can be activated or deactivated either by adding or removing CO2 from the solution. This feature enables us to use them in the fabrication of responsive colloids, a group of dispersed systems that can be controlled by changing the environmental conditions. In chemical processes, incl...

Nucleoside analogues are important compounds for the treatment of viral infections or cancers. While (chemo-)enzymatic synthesis is a valuable alternative to traditional chemical methods, the feasibility of such processes is lowered by the high production cost of the biocatalyst. As continuous enzyme membrane reactors (EMR) allow the use of biocata...

In this study, a first approach to model drop size distributions in agitated nanoparticle-stabilized liquid/liquid systems with population balance equations is presented. Established coalescence efficiency models fail to predict the effect of steric hindrance of nanoparticles at the liquid/liquid interface during the film drainage process. A novel...

Detailed measurements of dynamic and steady‐state drop size distributions were performed in liquid‐liquid systems with water and different silicone oils using an in situ endoscope technique in a discontinuously operated stirred tank. The oils used as the dispersed phase vary in dynamic viscosity, while density and interfacial tension are nearly con...

The high water content and low nutrient concentration of digestate complicate its storage, transportation, and utilization. Subsequent digestate processing can effectively remove water and influence nutrient partitioning among digestate fractions and final products. The current study was carried out to evaluate the performance of two typical digest...

OME have diesel fuel like properties with almost soot-free combustion, which can enable a reduction of nitrogen oxides. This makes them promising candidates for internal combustion engines as blends or...

Oxymethylene dimethyl ethers (OME) show promising solubility and combustion properties for applications in various chemical processes and sectors. OME enable clean and quasi soot-free combustion, which can consequently lead to...

Solid Phase Synthesis (SPS) is a powerful tool for synthesizing oligomers, especially peptides, nucleic acids, and glycans. Since Merrifield developed solid-phase peptide synthesis (SPPS) in 1963, organic chemistry and analytics...

This study aims at developing an experimental method to characterise the fluid dynamic stress acting on particles in a lab-scale stirred tank reactor. The method is based on a photo-optical inline particle size measurement technique, which is able to capture the complex morphology of a stress-sensitive clay-floc system. The novel image-based analys...

Unfolding can interrupt the activity of enzymes. Lipase, the enzyme responsible for triglyceride catalysis, can be deactivated by unfolding, which can significantly affect the yield of enzymatic processes in biochemical engineering. Different agents can induce lipase unfolding, among which we study the impact of urea as a strong denaturant. Unfoldi...

The current study shows a new possibility to purify crosslinked hydrogels based on hyaluronic acid (HA) to remove the residual crosslinking agent 1,4 - butanediol diglycidyl ether (BDDE) and its byproduct 1,4-butanediol di-(propan-2,3-diolyl) ether (EPD) using a crossflow filtration (CFF) device. Therefore, a dynamic crossflow-filtration (DCF) devi...

Optimizing bioprocesses requires an in-depth understanding, from a bioengineering perspective, of the cultivation systems used. A bioengineering characterization is typically performed via experimental or numerical methods, which are particularly well-established for stirred bioreactors. For unstirred, non-rigid systems such as wave-mixed bioreacto...

Combining Power‐to‐X (PtX) processes with high temperature heat pumps (HTHP) can significantly increase their energy efficiency. Evaluating the example of oxymethylene ethers (OME) production from H2 via H2O electrolysis and captured CO2 from air shows that by upgrading waste heat streams using HTHP, a process overall energy efficiency of higher th...

Three numerical methods to determine the mixing time in stirred tanks are investigated using Computational Fluid Dynamics (CFD). In a cylindrical tank, the mixing performances of a Rushton turbine (RT) and a pitched blade turbine (PBT) are investigated, using transient methods, i.e., the Unfrozen Flow Field (UFF) and the Frozen Flow Field (FFF) met...

Leider wurde die Latex-Kodierung von „H(t)“ und „Vf(t)“ im Text versehentlich veröffentlicht. Dies wurde nun korrigiert. Bitte die folgende Korrektur übernehmen.

The incorporation of soft hydrophilic particles at the interface of water in non-polar oil emulsion droplets is crucial for several applications. However, the stabilization of water in non-polar oil emulsions with hydrophilic soft material alone is, besides certain exceptions, not possible. In our previous works, we showed that stabilizing the emul...

A non-conventional mixing strategy utilizing the hysteresis effect of propeller jets in viscoelastic xanthan gum solutions was evaluated through decolorization mixing time experiments. The experiments consisted of capturing and analyzing the images of the flow patterns illustrated by a fast acid-base indicator reaction in a rectangular tank equippe...

This work addresses the influence of partially hydrophobic aluminum particles on the interfacial properties of o/w and w/o dispersions. For this purpose, drop size distributions are determined in an agitated tank followed by batch settling experiments after stirrer stop. In presence of hydrophobized aluminum particles the type of dispersion (o/w or...

The first step in quantifying the performance of organic solvent nanofiltration membranes are usually lab-scale experiments with respect to flux and rejection. The necessary pressurization of the feed is either realized mechanically by a high-pressure pump or by means of a pressurized inert gas. While the latter option is most frequently applied, t...

Protein surfactant (PS) interactions is an essential topic for many fundamental and technological applications such as life science, nanobiotechnology processes, food industry, biodiesel production and drug delivery systems. Several experimental techniques and data analysis approaches have been developed to characterize PS interactions in bulk and...

Hemicellulose and its derivatives have a high potential to replace fossil-based materials in various high-value-added products. Within this study, two purification cascades for the separation and valorization of hemicellulose and its derived monomeric sugars from organosolv beechwood hydrolyzates (BWHs) were experimentally demonstrated and assessed...

Due to the feasibility of running continuous enzymatic reaction and product separation in a single operation, enzymatic membrane reactors (EMRs) are increasingly applied in the areas of biotechnology, (bio)chemistry, agro-food, and energy. By the use of different membrane cut-offs, enhanced separation selectivity can be obtained during the producti...

This work focuses on the measuring and modeling of phase equilibria of interest for the hydroaminomethylation of 1-decene with syngas (CO/H2) and diethylamine to N,N-diethylundecan-1-amine and water in a solvent system of methanol and n-dodecane. H2 solubilities were measured in undecanal and N,N-dimethyldodecan-1-amine at 343 and 363 K between 2 a...

The hysteresis effect of propeller jets in viscoelastic fluids provides a new idea for improving the mixing process related to viscoelastic fluids, such as wastewater digestion. However, the application of this idea to industrial equipment requires a feasible method for flow pattern detection. This work aimed to investigate the hysteresis effect of...

The UAC project as a transdisciplinary research project (see A3) examines the rapidly urbanizing region of Grand Casablanca to understand how agriculture can become an integrated factor of urban development. This involves a redefinition of agriculture as Urban Agriculture at the scale of an urbanizing region. In addition to the possible intermingli...

Hydrodynamic stress on Aspergillus niger agglomerates in stirred tank bioreactors

The description of the mixing characteristics is of fundamental interest for modeling mass transport in fixed‐bed reactors. A method based on Lagrangian parcel tracking is presented to determine the axial dispersion coefficient in the mechanical dispersion regime from particle‐resolved computational fluid dynamics (CFD) results. The impact of fluid...

Stirring experiments were conducted in a pilot scale tank with side-entering axial impellers to study the mixing behavior of biogas fermenters. Propeller flows were analyzed using the PIV technique in dependence of propeller geometry in a viscoelastic fluid, modeling the rheology of organic substrates. Moreover, mixing times via decolorization and...

A general drawback of microgels is that they do not stabilize water-in-oil (w/o) emulsions of non-polar oils. Simultaneous stabilization with solid hydrophobic nanoparticles and soft hydrophilic microgels overcomes this problem. For a fundamental understanding of this synergistic effect the use of well defined particle systems is crucial. Therefore...

A general drawback of microgels is that they do not stabilize water-in-oil (w/o) emulsions of non-polar oils. Simultaneous stabilization with solid hydrophobic nanoparticles and soft hydrophilic microgels overcomes this problem. For a fundamental understanding of this synergistic effect the use of well defined particle systems is crucial. Therefore...

A joint approach of chemists, mathematicians and engineers in the field of chemical reaction enhanced gas-liquid mass transfer on single bubbles is presented. New chemical systems are developed for homogenous chemical reactions in the liquid. By applying different metal-complex based reaction systems with diverse ligands in different reaction media...

Within this project, the mass transfer of single bubbles in an unconfined environment was investigated. Most published works with longer rising paths lack the three-dimensional resolution of the bubble interface while smaller systems lack the long-term effects appearing during the ascent. Here, two cameras were moved in real-time with the bubble al...

In the previous chapters it has been shown that the fluid dynamic conditions in bubbly flows might affect a competitive consecutive chemical reaction concerning yield and selectivity. The question arises if this results are transferable to technical apparatuses with industrial conditions. To clarify this question, the competitive consecutive DBED r...

Micellar multiphase systems are versatile examples for smart solvent systems, which can be applied to intensify important process aspects like reaction rate and product separation. Choosing different temperatures and compositions, the phase behaviour of micellar multiphase systems can be changed, and the reaction conditions altered. Due to the chan...

Recently, the feasibility of Pickering emulsion membrane filtration has been shown to be a promising procedure for efficient catalyst recovery in continuous liquid/liquid multiphase catalysis. In this work, the impact of temperature on the permeation of the pure solvent 1-dodecene as well as on the filtration of water-in-oil Pickering emulsions sta...

Process intensification of catalytic fixed-bed reactors is of vital interest and can be conducted on different length scales, ranging from the molecular scale to the pellet scale to the plant scale. Particle-resolved computational fluid dynamics (CFD) is used to characterize different reactor designs regarding optimized heat transport characteristi...

de Computational‐Fluid‐Dynamics (CFD)‐Simulationen in Kombination mit Tropfenpopulationsbilanzen führen zu einem praxisgerechten Standard, um auf Basis verfügbarer Prozessdaten den Strömungsverlauf – und damit die Verweilzeitverteilung – in liegenden Abscheidern beliebiger Größe zu berechnen. Durch Implementierung des Tropfenverhaltens wird auch di...

de Fluiddynamik und Stofftransportprozessen kommt bei der Dimensionierung von Flüssig/flüssig-Kontaktapparaten eine entscheidende Bedeutung zu. Die Vorhersage von Betriebsparametern wird durch Schwarm- und Grenzflächeneffekte maßgeblich erschwert. Anhand von Einzeltropfenuntersuchungen kann eine grundlegende Vorhersage für fluiddynamisches Verhalte...

Fixed bed reactors are widely used in the chemical, nuclear and process industry. Due to the solid particle arrangement and its resulting non-homogeneous radial void fraction distribution, the heat transfer of this reactor type is inhibited, especially for fixed bed reactors with a small tube to particle diameter ratio. This work shows that, based...

Biogas production is a relevant component in renewable energy systems. The paper addresses modeling approaches from an energy system, as well as from a process optimization, point of view. Model approaches of biogas production show different levels of detail. They can be classified as white, gray, and black box, or bottom-up and top-down approaches...

Hydrodynamische Beanspruchung von filamentös wachsenden Mikroorganismen in gerührten Bioreaktoren

de Für die Dimensionierung von Flüssig/flüssig‐Kontaktapparaten sind Fluiddynamik und Stofftransport in der Dispersion von entscheidender Bedeutung. Schwarm‐ und Grenzflächeneffekte führen zu komplexen Interaktionen und erschweren die Vorhersage von Betriebsparametern. Anhand von Einzeltropfenuntersuchungen kann eine grundlegende Vorhersage für flu...

This work aimed to investigate the flow pattern transformation process resolved in time and to propose a physical explanation for the hysteresis effect of a propeller jet in a viscoelastic fluid. The propeller jet flow in xanthan gum solution was measured using PIV (Particle Image Velocimetry) and UVP (Ultrasound Velocity Profiler). Based on the di...

The design of liquid/liquid gravity separators requires extensive research and optimization. In this context, the current contribution provides experimental insights into the droplet size distributions and the separation behavior of paraffin oil-in-water dispersions. The investigated dispersions result from the two-phase flow through perforated pla...