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Item type:Publication, Access status: without files , Unresolved CFD-DEM simulation of spherical and ellipsoidal particles in conical and prismatic spouted bedsVarious drag models were implemented in a superquadric CFD-DEM code and validated for the simulation of spherical and ellipsoidal particles in spouted beds. The most suitable drag models were identified by comparing the predicted local particle velocity with those measured by particle tracking velocimetry (PTV). The model by Beetstra et al. is the one that best reproduces the experimental results for the spouting of spherical particles, whereas the one by Sanjeevi et al. is the most suitable for ellipsoidal irregular ones. Their capability for the prediction of key operating parameters was demonstrated in both conical and prismatic spouted beds, as they correctly predict the minimum spouting velocity (u ) and fountain height in different configurations (without draft tube and different draft tubes) for particles of different size and shape. The CFD-DEM model predicts the preferential orientation of ellipsoidal particles at each location in the bed and the influence of internal devices on this parameter, which is of the utmost importance in the design of reliable coating apparatuses in the pharmaceutical industry. msPublicationtype: Journal Article67 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Particle formulation of hydroalcoholic rosemary (Rosmarinus officinalis L.) extracts using a spouted bedIn this study, spouted bed technology was applied to the protection and functionalization of polyphenolic rosemary extracts. First, solid–liquid extraction was performed at 25 °C with ethanol–water. The ethanol–water ratio was chosen to obtain high phenolic acid and diterpene concentrations in the extract. The selected solvent composition gave liquid extracts that could be directly added to a coating mixture for feeding into a spouted bed apparatus. Thus, no preliminary solvent exchange or evaporation of the extraction solvent to dryness was required. Food grade Paselli MD 6 maltodextrin and HiCap 100 modified starch were used as inert core and shell materials in the spouted bed encapsulation process under mild operating conditions. The antioxidant activity of the fresh extract was retained during processing, which indicated that the active constituents were preserved and quantitatively transferred into the encapsulated formulations, which were readily soluble in water. The obtained powders were composed of nearly spherical particles. Their compositions, water solubilities, and particle morphologies make them a strong candidate for food and beverage applications as natural antioxidants, preservatives, or functional ingredients.Publicationtype: Journal Article136 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Novel technique for measurement of coating layer thickness of fine and porous particles using focused ion beam(2019-02-01); ; ; ; A novel technique for the measurement of the coating layer thickness of fine particles was developed in this work based on cross-sectioning of micrometre-sized single coated particles using focused ion beam (FIB) milling. This technique was tested on two batches of aerogel particles coated with thin coatings in a spouted bed. The FIB milling procedure consisted of two steps. First, the desired part of the coated particle was removed using a high ion beam current. The resulting cross-sectioned area was then polished using a lower ion beam current to make the cross-section clearly visible. The FIB milling process was controlled with simultaneous scanning electron microscopy (SEM). Afterwards, the coating layer thickness was evaluated using the SEM images. The coating layer was successfully applied on the porous aerogel microparticles in the spouted bed. The coating uniformity of the highly porous particles increased with increasing sprayed coating solution amount, with up to 91% of the particle pores being covered. The FIB-cross-sectioning technique using an ion beam of 2.50 nA for the first milling and 0.43 nA for polishing of the surface resulted in successful generation of cross-sections of representative particles with a visible particle core and coating layer. A coating layer thickness of approximately 700 nm was achieved on particles with sizes of below 45 μm.Publicationtype: Journal Article262 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Production of composites with high relative permittivity using the spouted bed techniqueThis contribution presents a new application of the spouted bed technique. The developed production process involves coating fine copper particles with a polymer in a spouted bed plant and then hot pressing the produced granules to form a compact consisting of a copper–polymer composite with a high filling degree. The fabricated composites possess high relative permittivity, which is advantageous for the production of effective capacitors. With increasing filling degree of copper, the relative permittivity of the composites increased, with a maximum relative permittivity of 214 obtained for the composite containing 78.1 vol% copper. Such a high filling degree can be achieved with conductive particles without obtaining a conductive composite by using the spouted bed technology in the production process. The high relative permittivity results from the high filling degree of particles isolated by a polymer coating.Publicationtype: Journal Article112 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Using dilute spouting for fabrication of highly filled metal-polymer composite materials(Elsevier, 2017-07-01); ; ; ; This contribution deals with a spouted bed process used for combining of particles and a polymer matrix in order to fabricate highly filled composite materials. The questions how a spouted bed can be used for processing of μm-sized particles and how the apparatus for this aim looks like will be addressed, as well as the flow regime of fine particles will be described. Regarding the mechanical properties of fabricated composite materials the key requirement for the granulation procedure in spouted bed is the continuity of the polymer layers deposited on particles. To evaluate this property electrically conducting copper particles and measurements of electrical resistivity of assembled composite materials were used. The resistivity of produced composite materials rises by up to 15 orders of magnitude in comparison to the compacted pure copper particles. The material remains an insulator up to a very high filling degree of about 74 vol.% of copper. The results show an outstanding capacity of a spouted bed for deposition of uniform thin coating layers on μm-sized particles. Further increase of filling degrees leads to a strong degradation of both the electrical resistivity and mechanical properties of composite, such as strength and elastic modulus.Publicationtype: Journal Article169 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Improvement of mechanical properties by a polydopamine interface in highly filled hierarchical composites of titanium dioxide particles and poly(vinyl butyral)(Elsevier, 2017-04-15); ; ; ; In this work, the preparation and properties of hierarchical composites of titanium dioxide (TiO2) particles (rutile modification) and poly(vinyl butyral) (PVB) are discussed. The volume fraction of the ceramic particles was approximately 60%. Two types of composites with different fillers were examined, i.e. TiO2 particles with and without a thin coating of polydopamine (PDA). A variety of characterization methods was applied in order to analyze the properties of the particles and the composites. Infrared spectroscopy is used to verify the functionalization of the particles with a thin polydopamine layer. Thermal analysis provides information on the thermal stability and the degree of functionalization of the coated particles and the composites. Scanning electron microscopy investigations reveal that the functionalized TiO2 particles with PDA form larger agglomerates which enable the coating of the TiO2 particles with PVB via the spouted bed technique. Nanoindentation experiments show that the final hierarchical composite material with the use of non-coated TiO2 particles exhibits a hardness of 0.75 ± 0.04 GPa and a Young's modulus of 29.5 ± 1.0 GPa. The composites containing polydopamine coated TiO2 particles show an increase of approximately 40% in hardness and 25% in Young's modulus in comparison to the composites with uncoated TiO2.Publicationtype: Journal Article163 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Characterization and CFD-DEM modelling of a prismatic spouted bed(2015-01-01); ; ; ; In this study a prismatic spouted bed was characterized experimentally and modelled by means of 3D CFD-DEM simulations. The main focus was on the investigation of the influence of the gas flow rate on the bed dynamics and spouting stability. Pressure drop time series obtained at different gas velocities were used for the identification of flow regimes by means of the frequency domain and of chaotic properties such as the correlation dimension and Kolmogorov entropy. The gas and particle dynamics were investigated through simulations of different operational regimes: the spouting onset, as well as stable and instable regimes. A 3-D bed behaviour, typical for slot-rectangular beds, was found. A good agreement between simulations and experiments in the particle flow patterns, bed expansion and dynamics of characteristic gas pressure fluctuations was achieved. The particle dynamics as a function of the gas velocity was investigated for the entire bed. For one of the stable regimes, the bed regions showing different particle dynamics (spout, fountain and annulus) were characterized in detail. A regime map showing the stable operational window in dependence on an inlet-to-bed size ratio and gas velocity is also provided.Publicationtype: Journal Article55 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Intensification of Fluidized-Bed Processes for Drying and Formulation(2014-03-17); ; ; ; Publicationtype: Book Part20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Collision dynamics in fluidised bed granulators : a DEM-CFD study(Elsevier, 2013-02-04); ; ; ; The fluid, particle and collision dynamics inside a fluidised bed granulator are described in detail using coupled DEM-CFD simulations. Three different granulator configurations are compared in terms of their particle-particle interactions, using criteria such as the average particle velocity, angular velocity, average particle-particle and particle-wall collision velocity and the collision frequency. From these measures the agglomeration probability, the breakage and growth rate and the agglomerate strength can be assessed. Depending on the required product properties the results highlight advantages of specific granulator geometries. The top-spray granulator is the simplest device and is often used for large-scale granulation processes in the food and fertilizer industries, but wetting intensity and growth rate are relatively low compared to the other configurations investigated in this work. The spouted bed has the most intensive gas-liquid-solid contact and produces compact and dense agglomerates. Both the agglomeration probability and the breakage rate are very high. The Wurster-coater achieves the fastest growth rate for the applied process conditions and is characterised by homogeneous cyclic particle wetting and a low breakage rate. The simulation results are confirmed by lab scale batch agglomeration experiments using maltodextrin DE21, a model substance for amorphous food powders. It can be concluded that the DEM model offers large potential for process intensification by investigating the effect of geometry modifications on the fluid and particle dynamics and on the homogeneity of particle wetting. This is shown exemplarily for fluidised bed agglomeration.Publicationtype: Journal Article47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Discrete element study of aerogel particle dynamics in a spouted bed apparatusA novel process for fluidization and coating of light spherical aerogel particles in a spouted bed apparatus was numerically studied using discrete particle model. This model describes the interactions between the particles, particles and apparatus walls, as well as between the particles and gas which take place on the microlevel and can be used in the multiscale modeling approach to study the entire production process. The experimentally obtained mechanical properties of aerogel particles, like stiffness, modulus of elasticity, coefficients of friction and restitution were used as material parameters in the performed simulations. The influence of the increasing density and decreasing restitution coefficient of the particles due to the growth of the coating layer on the fluidized bed dynamics regarding the impact forces, collision rates, velocity distributions and rotation of particles was analyzed.Publicationtype: Journal Article33