7 results
Now showing1 - 7 of 7
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Unraveling the influence of dissolved gases on permeate flux in organic solvent nanofiltration – Experimental analysis(2022-08-15); ; ; ; 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, the gas may dissolve in the feed mixture and permeate through the membrane, affecting the transport of the other components. This potential effect is commonly neglected, inherently assuming that the gas solubility is negligible. The current study provides a systematic experimental investigation and analysis of the impact of dissolved gases on solvent flux for a hydrophilic DuraMem membrane, with gas solubilities assessed through PC-SAFT. The results prove that a gas with low solubility has a negligible effect on the solvent flux. In contrast, an increasing gas solubility may result in significant gas flux through the membrane with a considerable effect on the solvent flux. Furthermore, the correlation of the solvent flux with the gas solubility in the feed mixture is strongly non-linear. Therefore, gas solubility is recommended to be critically evaluated when conducting OSN experiments, specifically considering the final application. In that context, the permeation of dissolved gas has to be actively accounted for in OSN experiments for gas–liquid systems.Publicationtype: Journal Article52 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigation of Reactive Bubbly Flows in Technical Apparatuses(Springer, 2021-07-30); ; ; ; 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 reaction system dissolved in tetrahydrofuran is transferred to an industrial apparatus that has been already used for a cyclohexane oxidation. First, it is shown with the Taylor bubble experiments that the DBED reaction system can be used as a model system for competitive consecutive reactions with adjustable kinetics. Afterwards, the DBED reaction system is applied to the technical apparatus. It shows that the yield and selectivity of the DBED reaction in the technical apparatus depends on the bubble size distribution and therefore potentially on the local wake structure. Even though numerical simulations with the Euler-Lagrange approach are already able to predict the formation of product and byproduct of a competitive consecutive reaction, the local flow structure within the bubble wake and its potential influence on yield and selectivity can not be covered so far.Publicationtype: Book Part71 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Chemical Reactions at Freely Ascending Single Bubbles(Springer, 2021-07-30); ; ; ; 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 (water and organic solvents) a broad range of reaction kinetics is available. As one measure, the bubble size change over time is investigated. The shrinking of the bubble allows the determination of overall mass transfer rates under diverse conditions. Numerous groups investigated the wake region of the bubble. The influence of the mixing behavior in this region on the mass transfer in general but also, e.g., on competitive consecutive chemical reactions is visualized. For a deeper understanding of the effect of surfactants on mass transfer, simulations are performed providing a high temporal and spatial resolution of the flow and concentration field near the bubbles surface. Furthermore, a compartment model for the description of the mass transfer near a single bubble is developed which allows the calculation of competitive consecutive chemical reactions with reasonable numerical effort.Publicationtype: Book Part131 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigating dry reforming of methane with spatial reactor profiles and particle-resolved CFD simulations(2016-12-01); ; ; ; Dry reforming of methane (DRM) over nickel in a fixed-bed reactor of spheres was studied experimentally and with CFD simulations. Temperature and mole fraction profiles were measured in a dedicated profile reactor as function of axial coordinate. Particle-resolved CFD simulations took into account conjugate heat transfer, surface-to-surface radiation, and surface reactions described by microkinetics. Energy transport of CFD simulations were verified by studying heat transfer without chemical reactions. DRM experiments could not be reproduced with the original microkinetics formulation, even with the axial temperature profile applied. A detailed analysis of the microkinetics showed that thermodynamic inconsistencies are present, which are amplified by high surface coverage of CO*. After modifying the mechanism the experiments could be reproduced. This study shows how complex interactions between local transport phenomena and local kinetics can be quantified without relying on transport correlations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4436–4452, 2016.Publicationtype: Journal Article135 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Stirred Bioreactors: Current State and Developments, With Special Emphasis on Biopharmaceutical Production Processes. Current State and Developments, With Special Emphasis on Biopharmaceutical Production Processes(Elsevier, 2016-09-16); ; ; ; It is undisputed that stirred bioreactors are the most common type of bioreactors for submerged bioprocesses. Stirred bioreactors for biopharmaceuticals, which represent the strongest-growing branch of modern biotechnological products, are the focus of our chapter. They are available in working volumes from milliliters up to 70m3 and are used for a wide range of expression systems that require aseptic conditions. Based on a brief summary of some basic rules for the construction and operation of stirred bioreactors, this chapter will review key engineering issues that affect the design of aseptic stirred bioreactors. We will also provide readers with some general information on transport phenomena in stirred bioreactors before discussing special design aspects and performance parameters for expression systems (mammalian and microbial cells) that prevail in commercial biopharmaceutical production processes. Special attention will be paid to single-use stirred bioreactors, which may have advantages over their reusable counterparts and have become widely accepted over the past years.Publicationtype: Book Part58 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Theoretical and practical issues that are relevant when scaling up hMSC microcarrier production porocesses(Sage-Hindawi, 2016); ; ; ; The potential of human mesenchymal stem cells (hMSCs) for allogeneic cell therapies has created a large amount of interest. However, this presupposes the availability of efficient scale-up procedures. Promising results have been reported for stirred bioreactors that operate with microcarriers. Recent publications focusing on microcarrier-based stirred bioreactors have demonstrated the successful use of Computational Fluid Dynamics (CFD) and suspension criteria (N S1u , N S1) for rapidly scaling up hMSC expansions from mL- to pilot scale. Nevertheless, one obstacle may be the formation of large microcarrier-cell-aggregates, which may result in mass transfer limitations and inhomogeneous distributions of stem cells in the culture broth. The dependence of microcarrier-cell-aggregate formation on impeller speed and shear stress levels was investigated for human adipose derived stromal/stem cells (hASCs) at the spinner scale by recording the Sauter mean diameter (d 32) versus time. Cultivation at the suspension criteria provided d 32 values between 0.2 and 0.7 mm, the highest cell densities (1.25 × 10(6) cells mL(-1) hASCs), and the highest expansion factors (117.0 ± 4.7 on day 7), while maintaining the expression of specific surface markers. Furthermore, suitability of the suspension criterion N S1u was investigated for scaling up microcarrier-based processes in wave-mixed bioreactors for the first time.Publicationtype: Journal ArticleScopus© Citations 44 188 182 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Mass production of mesenchymal stem cells : impact of bioreactor design and flow conditions on proliferation and differentiationThe book serves as a good starting point for anyone interested in the application of tissue engineering. It offers a colorful mix of topics, which explain the obstacles and possible solutions for TE applications. The first part covers the use of adult stem cells and their applications. The following chapters offer an insight into the development of a tailored biomaterial for organ replacement and highlight the importance of cell-biomaterial interaction. In summary, this book offers insights into a wide variety of cells, biomaterials, interfaces and applications of the next generation biotechnology, which is tissue engineering.Publicationtype: Book Part2320 1235