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Item type:Publication, Access status: without files , Process design of a continuous biotransformation with in situ product removal by cloud point extractionIn this work, a continuous, heterogeneous extractive biocatalysis was realized with penicillin G hydrolysis as a model reaction. Therefore, commercially available structured packing CY from Sulzer were coated with enzyme‐containing gels and their catalytic activity was examined. Thereby, the potential of aqueous micellar two‐phase systems (ATPMS) as an extraction medium was evaluated. Triton X‐114 was used as model surfactant. It was found that the separation efficiency of the packing is not affected by the coating and ATPMS allows for a good separation yield. With these results, different process concepts for the continuous, heterogeneous extractive biocatalysis were compared.Publicationtype: Journal Article106 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Bubble size and bubble velocity distribution in bubble columns under industrial conditions(Wiley, 2017-01-19); ; ; ; Bubble column reactors are widely used in many industrial applications due to their simplicity and safety of operation. Despite these advantages, the design and scale-up of bubble column reactors is still challenging especially for industrial conditions at elevated pressure and temperature. One reason is the uncertainties concerning the specific interfacial area which is directly dependent on the bubble size distribution, bubble velocity, and gas hold-up. All these parameters are difficult to measure under industrial conditions due to the opaqueness of the bubbly flow and the safety risks of using organic solvents at elevated pressures and temperatures. This article introduces endoscopic bubble image velocimetry, a new measuring method that enables the detection of bubble sizes and bubble velocities in organic solvents at elevated pressure and temperature (pmax= 1.85 MPa and Tmax = 70 °C) for maximal gas hold-ups of 16 %. For this system it becomes evident that the bubble size distribution for low superficial gas velocities is almost unaffected by pressure and temperature, whereas the bubble velocity decreases slightly.Publicationtype: Journal Article143 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A discrete element study of wet particle-particle interaction during granulation in a spout fluidized bedIn this article we study the effect of the inter-particle interaction on the bed dynamics, by considering a variable restitution coefficient. The restitution coefficient is varied in time and space depending on the moisture content due to the particle-droplet interaction and evaporation. This study is done computationally, by using an extended discrete element model (DEM). The examined flow regimes comprise the intermediate/spout- fluidization regime (B1), spouting-with-aeration regime (B2) and the jet-in-fluidized-bed regime (B3). For all flow regimes, the averaged bed height increases with decreasing restitution coefficient. Moreover, the averaged bed height for a variable restitution coefficient is larger for all flow regimes compared to a case with a constant restitution coefficient, indicating that the distribution of the restitution coefficient influences the bed dynamics. The effect of evaporation on the distribution of the restitution coefficient is only observed for the jet-in-fluidized-bed regime (B3), where the background velocity is relatively high leading to enhanced evaporation from the particles in the annulus region. This is reflected in the averaged bed height for the evaporation test case, which is larger compared to a test case without evaporation. A larger bed height for cases with variable restitution coefficient is due to the pressure build up in the spout region caused by the longer closing period of the spout channel. This is confirmed by the recorded pressure fluctuation signal and its root mean square which are larger for the cases with the variable restitution coefficient. On étudie dans cet article I'effet de I'interaction entre les particules sur la dynamique de lit, en considerant un coefficient de restitution variable. On a fait varier le coefficient de restitution dans le temps et dans I'espace en fonction de la teneur en humidite due à I'interaction particules-gouttelettes et a I'evaporation. Cette étude a été réalisée par ordinateur, à I'aide d'un modèle d'elements discrets étendu (DEM). Les regimes d'écoulernent examinés comprennent le régime de fluidisation intermediaire/jaillissement (BI), le régime de jaittissement avec aeration (B2) et le régime de jet en lit fluidisé (B3). Pour tous ces régimes d'écoulernent, la hauteur de lit moyennée augmente avec la diminution du coefficient de restitution. En outre, la hauteur de lit moyennée pour un coefficient de restitution variable est plus grande pour tous les régimes d'écoulernent comparativement au cas du coefficient de restitution constant, ce qui indique que la distribution du coefficient de restitution influence la dynamique de lit. L'effet de I'évaporation sur la distribution du coefficient de restitution s'observe seulement pour le régime de jet en lit fluidisé (B3), ou la vitesse de fond est relativement élevée, augmentant ainsi I'evaporation des particules dans la région de I'espace annulaire. Ceci se reflete dans la hauteur de lit moyennée pour le cas testé avec évaporation, qui est plus grande que dans le cas testé sans evaporation. Une hauteur de lit plus grande pour les cas avec coefficient de restitution variable est due à la montée de la pression dans la région du jaillissement qui est causée par la période de fermeture plus longue de la conduite de jaillissement. Ceci se continue par le signal de fluctuation de pression enregistré et son écart quadratique moyen qui sont plus grands pour les cas avec coefficient de restitution variable.Publicationtype: Journal Article30 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , CFD modeling of a prismatic spouted bed with two adjustable gas inletsSince the invention of the spouted bed technology by Mathur and Gishler (1955), different kinds of apparatus design were developed and a huge number of applications in nearly all branches of industry have emerged. Modeling of spouted beds by means of modern simulation tools, like discrete particle models or continuum models, has become a precious opportunity to understand the complexity of multiphase flows in these apparatus. In this work, two-dimensional continuum simulations of a novel kind of spouted bed apparatus with adjustable gas inlets are presented. Different gas-particle drag models are used to obtain a realistic flow structure. Simulated solid phase concentrations are compared with images taken during experiments. Furthermore, simulated and measured gas phase pressure fluctuations over the entire bed are contrasted allowing more accurate comparisons between the simulated and the real hydrodynamic behaviour of the spouted bed. Depuis I'invention de la technologie du lit jaillissant par Mathur et Gishler (1955), unegrande variété de systèmes a été mise au point et un nombre considérable d'applications dans presque toutes les branches de I'industrie ont vu le jour. La modelisation de I its jaillissants au moyen d'outils de simulation modemes, tels que les modeles de particules disc rets ou les modeles en continu, est une excellente occasion pour comprendre la complexité des écoulements multiphasiques dans ces appareils. Dans ce travail, des simulations en continu bidimensionnelles d'une nouveau type de lit jaillissant avec des entrees de gaz ajustables sont présentées. On a testé différents modèles de trainée gaz-particules pour obtenir une structure d'écoulement réafiste. Les concentrations de phases solides simulées sont comparées a des images prises lors des expériences. Par ailleurs, les fluctuations de pression de phase gazeuse simulées et mesurées dans la totalité du lit sont contrastées, ce qui permet des comparaisons plus precises entre le comportement hydrodynamique simule et reel du lit jaillissant. © 2009 Canadian Society for Chemical Engineering.Publicationtype: Journal Article18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fluidized bed air drying: Experimental study and model development(2003-04); ; ; The presented study describes the processes and mechanisms of batch fluidized bed drying. The influencing factors of hot air drying are theoretically and experimentally examined, in order to present the relations between temperature and humidity profiles and all other drying parameters. A physical model is presented to facilitate the calculation of the drying processes under defined conditions. Three succeeding drying stages are therefore modeled. Mass and energy balances including all components taking part in the process are formulated. The model clarities the drying process under the assumption of pure heat transfer mechanisms. It does not contain adaptive parameters and takes into account an inactive bypass fraction of the fluidization and drying medium. The evaluation of the model was successful for two fluidized bed plants with nominal widths of 100 mm and 400 mm. The experiments showed sufficient accuracy and transferability of the model to equipment of application-oriented dimensions.Publicationtype: Journal Article12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , An optimization model of the operating costs of a fluidized bed steam-drying plantA model is developed to determine an optimum apparatus geometry and, for given apparatus dimensions, a financially optimal fluidized bed height. The parameters that effect the operating costs are the bed mass, the apparatus diameter and the gas mass flow rate. To implement such cost optimization, a physics-based mathematical model for describing the thermodynamic processes in fluidized bed steam-drying is briefly explained and presented. The most important conclusion is not to operate the fluidized bed for a drying process below a certain minimum cost, calculated with the help of the modelling. The problem, when describing the drying process and consequently the mass transfer, is that in the superheated steam drying case studied here, water is evaporated as moisture and withdrawn into an atmosphere of vapor water.Publicationtype: Journal Article11