Dissertations / Theses on the topic 'Powder flowability'

Made available in DSpace on 2016-06-02T19:56:46Z (GMT). No. of bitstreams: 1 4315.pdf: 4002019 bytes, checksum: a7b7282115bf939f257fd8a5748b615e (MD5) Previous issue date: 2012-03-08<br>Universidade Federal de Sao Carlos<br>There are many industries which use powders somewhere in their production process, such as: food, pharmaceuticals, ceramics, cement and fertilizer industries. The knowledge of properties associated with the flowability of these materials is important, since the characteristics of the powders can go through amendments in processing. Thus, the evaluation of indexes of flowability and the identification of main factors which influence the powders flowability play an important role in the operation and design of industrial devices. The objective of this study was to evaluate the flowability properties of organic and inorganic powders, as well as analyze which factors interfered in these properties. The organic materials were represented by whole and skim milk powders, while alumina and ceramic powder were selected for the assessment of inorganic materials. The physical characterizations carried out were: display materials morphology at SEM (Scanning Electron Microscopy), size distribution, particle density, initial moisture content, aerated bulk density and tapped bulk density. The measured materials flowability properties were: angle of internal friction, effective angle of internal friction, angle of wall (galvanized steel) friction and flow index, all of them determined by Jenike's direct shear cell, Hausner ratio obtained from the values of tapped and aerated bulk densities; angle of repose, determined through the dropping of powder in an acrylic surface. In general, the results obtained, considering all methodologies employed for the determination of materials flowability, demonstrated that alumina, ceramic powder and whole milk powder, if compared to skim milk powder, presented lower indexes of flowability. If these materials were stored in silos made of galvanized steel, alumina and ceramic powder flowability would be more difficult than that of skim and whole milk powders. Thus, the results showed that the material physical properties interfere in powders flowability. The skim milk powder flowed more easily than whole milk powder, because higher fat content and smaller average particle size of whole milk powder decreased the flowability of this material in comparison to the skim milk powder. Likewise, despite they have similar composition, alumina presented lower flowability that ceramic powder, because this powder had larger average particle size and the powder presented fewer agglomerated particles.<br>Existem muitas indústrias que trabalham com pós em alguma parte de seu processo de produção, como: as alimentícias, as farmacêuticas, as cerâmicas, as de cimentos e as de fertilizantes. O conhecimento das propriedades associadas à escoabilidade destes materiais é importante, já que as características dos pós podem sofrer alterações no processamento. Desta forma, a avaliação de índices de escoabilidade e a identificação dos principais fatores que influenciam na escoabilidade de pós são informações que auxiliam as operações industriais e no projeto de equipamentos. Assim, o objetivo deste trabalho foi avaliar a escoabilidade de pós orgânicos e inorgânicos, analisando quais fatores interferiram nesta propriedade. Os materiais escolhidos para representarem os materiais orgânicos foram os leites em pó integral e desnatado, enquanto que a alumina e o pó cerâmico foram selecionados para a avaliação dos materiais inorgânicos. As caracterizações físicas realizadas foram: visualização da morfologia dos materiais no MEV, distribuição granulométrica, massa específica da partícula, teor de umidade inicial, densidade bulk aerada e densidade bulk compactada. A escoabilidade dos materiais foi determinada pelas medidas de: ângulo de atrito interno, ângulo de atrito interno efetivo, ângulo de atrito com a parede de aço galvanizado e índice de escoamento, todos eles determinados pelo cisalhamento direto nas células de Jenike; índice de Hausner obtidos a partir dos valores das densidades bulk compactada e aerada; ângulo de repouso, determinado através do escoamento do pó em uma superfície de acrílico. De maneira geral, os resultados obtidos, considerando-se todas as metodologias empregadas para a determinação da escoabilidade dos materiais, demonstraram que a alumina, o pó cerâmico e o leite em pó integral, se comparados ao leite em pó desnatado, apresentaram menores índices de escoabilidade. Se esses materiais fossem armazenados em silos feitos de aço galvanizado, o escoamento da alumina e do pó cerâmico seria mais difícil do que os leites em pó desnatado e integral. Assim, os resultados mostraram que as propriedades físicas do material interferem na escoabilidade dos pós. O leite em pó desnatado escoou mais facilmente que o leite em pó integral, pois o maior teor de gordura juntamente com o menor tamanho médio das partículas do leite em pó integral diminuíram a escoabilidade deste material em relação ao leite em pó desnatado. Da mesma forma, apesar das composições similares, a alumina apresentou menor escoabilidade que o pó cerâmico, pois este tinha partículas de maior tamanho médio e menos aglomeradas.

Une technologie prometteuse pour répondre à la demande croissante en énergie renouvelable est la gazéification de biomasse lignocellulosique pour la production de biocarburants de deuxième génération. Ce procédé nécessite une alimentation en biomasse sous forme de poudre. Les problèmes de convoyage et de manipulation liés à la faible coulabilité de la biomasse broyée sont un verrou pour l’industrialisation des procédés BtL. La torréfaction comme procédé de prétraitement, en plus d'augmenter densité énergétique de la biomasse, peut influencer également les propriétés des particules obtenues après broyage, et en conséquence, l’écoulement des poudres. L'évaluation de l'écoulement des poudres de biomasse sous différentes conditions de consolidation est essentielle pour concevoir des technologies de manipulation et de convoyage efficaces.L'objectif de ce travail est d'évaluer l'effet des conditions de torréfaction et de broyage sur l’écoulement de poudres de biomasse. Une première partie consiste en une étude expérimentale dans laquelle la coulabilité d'échantillons torréfiés sous différentes intensités a été évaluée à l'aide d'un appareil de cisaillement annulaire. La coulabilité est corrélée à l'intensité de la torréfaction (mesurée par la perte de masse globale) pour deux essences différentes. La forme des particules semble être le paramètre qui influence de manière prédominante la coulabilité des poudres à l'état consolidé. La caractérisation de la coulabilité à l’état non consolidée a été effectuée à l'aide d'un tambour rotatif par l’analyse des avalanches des poudres. Des corrélations entre les caractéristiques des particules et la coulabilité sont ainsi établies. La modélisation de l'écoulement de la biomasse à l'aide de la Méthode des Éléments Discrets (DEM) constitue une deuxième partie de cette recherche. La taille submillimétrique des particules de biomasse, ainsi que leur faible densité, leur forme allongée et leur comportement cohésif sont des défis pour l’implémentation d’un modèle de réaliste d’écoulement particulaire en DEM. Un modèle DEM des particules de biomasse est mis en œuvre à l'aide d'une représentation simplifiée (assemblement de sphères) à gros grains de la forme des particules, ainsi que d'un modèle de force cohésif. Une procédure systématique de calibration des paramètres DEM permet d'obtenir un ensemble de paramètres ajustés. L'évolution expérimentale des contraintes de cisaillement d’une poudre dans un état consolidé peut alors être reproduite de façon réaliste. De même, le comportement d’avalanche des poudres dans un tambour tournant est également bien reproduit par les simulations, de façon qualitative et quantitative. Ces résultats mettent en évidence le potentiel des simulations DEM pour étudier l'effet des caractéristiques des particules, qui sont influencées par la torréfaction et les conditions de broyage, sur le comportement d'écoulement de la biomasse en poudre<br>Gasification of lignocellulosic biomass for production of second-generation biofuels is a promising technology to meet renewable energy needs. However, feeding and handling problems related to the poor flowability of milled biomass considerably hinder the industrial implementation of Biomass-to-Liquid processes. Torrefaction as pretreatment step, in addition to improving energy density of biomass, also affects the properties of the milled particles (namely size and shape) that significantly influence flow behavior. The evaluation of biomass flow characteristics under different flow conditions is essential to design efficient and trouble-free handling solutions.The aim of this work is to assess the effect of the torrefaction and grinding conditions on the biomass flow behavior. A first part consists of an experimental study in which the flow properties of samples torrefied under different intensities were obtained using a ring shear tester. Flowability is correlated to the intensity of torrefaction, as measured by the global mass loss, for two different wood species. Particle shape seems to be the predominant parameter influencing flowability of powders in a consolidated state. Characterization of non-consolidated flowability through avalanching analysis using an in-house rotating drum was also conducted. Correlations between particle characteristics and flow behavior are thus established.The modelling of biomass flow using the Discrete Element Method (DEM) constitutes a second major part of this research. Challenging aspects of biomass particle modeling are their submillimetric size, low density, elongated shape and cohesive behavior. A material DEM model is implemented using a simplified (multisphere) upscaled representation of particle shape, along with a cohesive contact model. A systematic calibration procedure results in an optimal set of DEM parameters. The experimental shear stress evolution and yield locus can then be realistically reproduced. The avalanching behavior of the powders is also well captured by simulations, both qualitatively and quantitatively. These results highlight the potential of DEM simulations to investigate the effect of particle characteristics, which are driven by torrefaction and grinding conditions, on the flow behavior of powdered biomass

The application of chemical additives, known as grinding aids (GA), dates back to 1930 in the cement industry. As opposed to the cement industry, where the use of GAs is on the final processing step, it could be one of the first process steps in ore beneficiation. A few investigations addressed the GA applications in ore dressing; therefore, further studies are required to better understand the GA effects on the product properties and downstream separation processes. This thesis undertakes a comparative study on the dry grinding of magnetite and the resulting product characteristics with and without GAs. The main aim is to reduce energy consumption and to address some of the challenges associated with dry processing.  The effects of GAs on the dry batch ball milling of magnetite were examined to analyze the energy consumption (Ec), particle size distribution, flow properties, bulk properties, surface morphology, particle fineness, and surface chemistry of products. Their effects on the ground product were systematically explored by sieve analysis, powder rheology, BET surface measurements, optical microscopy analysis, and zeta potential measurements. Compared with the absence of GAs, the dry grinding efficiency of magnetite increased after using GAs; however, an optimal dosage exists based on the GA type. Among GAs which considered in this investigation (Zalta™ GR20-587 (Commercial GA) and Zalta™ VM1122 (Commercial viscosity aid) as well as sodium hydroxide), Zalta™ VM1122, a polysaccharide-based additive, was the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t. The PSD became narrower and finer (P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. In general, the results reveal that at sufficient GA dosages, they reduce the average particle size, increase the specific surface area, and narrow the particle size distribution. However, an excessive amount of GAs could be detrimental to the grinding performance.  Further studies on powder rheology indicated that the used GAs resulted in improved material flowability compared to grinding without additives (in the examined dosage range). The rheology measurements by the FT4 Powder Rheometer showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding. There was a strong correlation between the grinding parameters and flow parameters (r &gt; 0.93). These results confirmed the effect of GA on ground particles' flowability. Zalta™ VM1122 showed the best performance with 38.8% reduction of basic flow energy, 20.4 % reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. The present investigation showed that the predominant mechanism of GAs is based on the alteration of rheological properties. Further investigation on the surface properties showed that using GAs could increase the surface roughness, which is beneficial for downstream processes such as froth flotation. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects from the optical microscope images. Furthermore, Zalta™ VM1122 (non-ionic) resulted in similar zeta potentials and pH values for the product compared to experiments without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes.<br>Kolarctic CBC (KO1030 SEESIMA)

The characterisation of cohesive powders for flowability is often required for reliable design and consistent operation of powder processes. This is commonly achieved by the unconfined compression test or shear test, but these techniques require a relatively large amount of powder and are limited to large pre-consolidation loads. There are a number of industrial cases where these tests are not applicable because small amounts of powders have to be handled and processed, such as filling and dosing of small quantities of powder in capsules and dispersion in dry powder inhalers. In other cases, the availability of testing powders could be a limiting issue. It has been shown by Hassanpour and Ghadiri (2007) that under certain circumstances, indentation on a cohesive powder bed by a blunt indenter can give a measure of the resistance to powder flow, which is related to flowability. However, the specification of the operation window in terms of sample size, penetration depth, indenter properties and strain rate has yet to be fully analysed. In the present work, the ball indentation process is analysed by numerical simulations using the Distinct Element Method (DEM). The flow resistance of the assembly, commonly termed hardness, is evaluated for a range of sample quantities and operation variables. It is shown that a minimum bed height of 20 particle diameters is required in order to achieve reliable measurements of hardness. A sensitivity analysis of indenter size reveals that small indenters with diameters less than 16 times the particle diameter exhibit fluctuations in powder flow stress measurements, which do not represent shear deformation. The penetration depth should be sufficiently large to cause notable bed shear deformation. It is found that this minimum penetration depth is approximately equal to 10% of the indenter radius. The hardness measurements are found to be independent of indenter stiffness within the wide range investigated. The friction between the indenter and the particles slightly increases the hardness, although its influence on the internal stresses is negligible. Cubic and cylindrical indenters measure significantly larger hardness value compared to the spherical indenter. Increasing the inter-particle friction and cohesion results in higher hardness values and internal stresses, due to the increase in resistance to shear deformation. Simulations at a range of indenter velocities confirm that the ball indentation technique can be used to analyse powder flowability over a wide range of shear rates.

Il seguente lavoro di tesi ha lo scopo di verificare una procedura di dimensionamento per silo contenenti polveri solide - Jenike's procedure - che è utilizzata al fine di ottenere, durante lo svuotamento degli impianti, il mass flow come regime di flusso. Tale verifica della procedura consiste nel confrontare i valori calcolati dell'angolo di inclinazione rispetto alla verticale della tramoggia del silo e della dimensione principale della sezione d'uscita con i valori direttamente misurati in un silo di piccole dimensioni. L'esecuzione della Jenike's procedure richiede una caratterizzazione della flowability delle polveri indagate: chalk, sawdust, perlite e potato starch. La misurazione delle flow properties delle polveri solide è stata effettuata utilizzando una RST-XS (Ring Shear Tester). Le prove svolte con tale strumento sono lo yield locus test e il wall yield locus test, permettendo di misurare così yield loci, wall yield loci e flow fuctions. In parallelo a questo lavoro sono state effettuate misurazioni dell'AOR (Angle of Repose) al fine di cercare una correlazione diretta con l'angolo di inclinazione della tramoggia dell'impianto pilota. Durante lo svolgimento del progetto è inoltre stato implementato uno stress sensor all'interno del silo con lo scopo di effettuare misurazioni dello stato degli stress agenti in pianta. E' stato ottenuto che la Jenike's procedure sovradimensiona di un certo valore il silo pilota. Ulteriori indagini riguardanti il metodo adottato per effettuare il dimensionamento potrebbero presumibilmente permettere la riduzione del sovradimensionamento. Per quanto riguarda il confronto tra AOR e l'angolo di inclinazione della tramoggia non è stata invece trovata alcuna correlazione. Mentre i valori dello stress misurati con lo stress sensor sono emersi conformi con i valori attesi dalle relazioni teoriche (Janssen's equation e method of Arnold and McLean).

2010 - 2011<br>Changes of cohesive flow properties of powders at high temperature are observed in many industrial process units, such as fluidized bed reactors, granulators and dryers. Many authors investigated the behaviour of powders at high temperature through fluidization experiments (Formisani et al., 1998 and 2002; Lettieri et al., 2000 a d 2001), measurements of the interparticle forces (Pagliai et al., 2004 and 2007) and direct measurements at the bulk level (Kamiya et al., 2002). However, the understanding of the effect of temperature on interparticle interactions and flow properties of bulk solid is not clear yet. A common approach in engineering science consists of the direct characterization of the rheology of powders like bulk solids by means of shear cells. In this work a High Temperature Annular Shear Cell, originally designed at University of Salerno, was set-up and used to measure yield loci up to 500°C and to directly evaluate the effect of temperature on the macroscopic flow properties of sample of fluid cracking catalyst powder, fly ashes, corundum, synthetic porous -alumina and glass beads. Different behaviour was observed for each material. The flowability of the FCC powder, fly ashes and corundum did not show change as the temperature increased differently from glass beads and, at lower extent, porous alumina for which an increment of the cohesive behaviour was observed. In order to give an interpretation of the effect of temperature on the interparticle interactions, a theoretical framework was developed according to the particle-particle approach of Rumpf (1974) and Molerus (1985 and 1993). Furthermore, the availability of a microscopic model able to estimate quantitatively the 2 interparticle interactions might extend the experimental findings to different compaction conditions, in particular lower than within the powder tester. For this purpose, the tensile strength of the powder experimentally evaluated was related to contact forces acting between particles by coupling the Rumpf equation with the equation of the contact force. Only van der Waals’ forces were assumed as present inside the bulk solid, according to DSC analysis performed in this work that revealed no melting points and formation of liquid bridges for all materials in the range of operating temperature. With this regard two alternative assumptions of elastic or plastic deformation at the contact point of particles were considered. Both the assumptions provide correct order of magnitude results in terms of tensile strength, provided that a plausible value of the local curvature at contact points of particles is taken into account by correctly considering the effect of surface roughness and asperities, according to SEM magnification performed for all the materials. A sensitivity analysis on the main parameters of the theoretical framework was performed. Both the increasing cohesive consolidation and the slight increase of the cohesive behaviour with the temperature suggest the occurrence of the plastic deformation of the contact points and, therefore, that the plastic deformation assumption should be adopted to explain the effect of the temperature on the interparticle interactions. However, at room temperature, the effect of consolidation seems to be correctly represented considering also the decrease of the voidage. Finally, a significant increase of the macroscopic cohesive behaviour of powder with the temperature was measured in presence of a liquid phase which promoted the aggregation of the particles, as verified with shear tests and SEM magnifications performed on sample of glass beads mixed with the low-melting temperature high-density polyethylene (HDPE) powder. [edited by author]<br>X n.s.

La fusion laser est un procédé de fabrication additive transformant une poudre de polymère, déposée couche par couche, par fusion grâce à un faisceau laser balayant des zones précises de chaque couche. Les étapes de transformation d’un polymère semi-cristallin par fusion laser sont : l’écoulement de la poudre à haute température, la fusion-coalescence des particules, la résorption des porosités et la solidification par cristallisation lors du refroidissement. Les paramètres prépondérants sont la puissance du laser et le champ de température dans le bac de fabrication. Le matériau subit des températures élevées et des variations thermiques dont les cinétiques sont encore mal connues. La cohésion des couches successives et la microstructure de l’objet fabriqué (porosité, cristallinité) dépendent de ces conditions thermiques complexes. Les relations entre microstructure, propriétés finales et histoire thermique du matériau ne sont pas complètement élucidées. Dans ce travail, deux poudres de polyamides (PA 6 et PA 12) sont étudiées. Tout d’abord, les processus physiques décrits plus haut sont analysés dans des conditions de laboratoire avec une histoire thermique contrôlée. Cela permet de mieux comprendre et de modéliser le rôle des propriétés intrinsèques du polymère dans les phénomènes physicochimiques de sa transformation aux différentes échelles. Cette étude donne accès aux échelles de temps de ces mécanismes, en fonction de la température, et aux microstructures qui en découlent. Ensuite, des pièces sont produites par deux méthodes de fusion de poudre, l’une en laboratoire sur plaque chauffante, l’autre en machine industrielle de fusion laser. La connaissance des temps caractéristiques de la coalescence, de l’évolution des porosités et de la cristallisation permet d’expliquer la microstructure et les propriétés mécaniques des pièces en relation avec leur méthode de production et l’histoire thermique associée. Cette analyse apporte un nouvel éclairage sur le développement des microstructures de polyamides transformés par fusion laser et les propriétés qui en découlent<br>Selective Laser Sintering, also called Powder Bed Fusion, is an additive manufacturing process that transforms a polymer powder layer-by-layer by melting with a laser beam scanning specific areas of each layer. The stages of transformation of a semi-crystalline polymer by laser fusion are: the flow of the powder at high temperature, the melting-coalescence of the particles, the resorption of the porosities and the solidification by crystallization during cooling. The most important parameters are the power of the laser and the temperature field in the manufacturing tank. The material undergoes high temperatures and thermal variations whose kinetics are still poorly known. The cohesion of the successive layers and the microstructure of the manufactured object (porosity, crystallinity) depend on these complex thermal conditions. The relationships between microstructure, final properties and thermal history of the material are not fully understood. In this work, two powders of polyamides (PA 6 and PA 12) are studied. First, the physical processes described above are analyzed under laboratory conditions with a controlled thermal history. This makes it possible to better understand and to model the role of the intrinsic properties of the polymer in the physicochemical phenomena involved in its transformation at different scales. This study gives access to the time scales of these mechanisms, as a function of temperature, and to the resulting microstructures. Then, parts are produced by two methods of powder melting, one in the laboratory on a hot plate, the other in an industrial SLS machine. Knowledge of the characteristic times of coalescence, evolution of porosities and crystallization enables to explain the microstructure and the mechanical properties of the objects in relation to their production method and the associated thermal history. This analysis sheds new light on the development of microstructures of polyamides transformed by laser fusion and the resulting properties

L’enrobage à sec par action mécanique permet de formuler des particules composites dont les fonctionnalités et les propriétés physiques, comme l’écoulement, sont améliorées et cela sans l’ajout de solvant ou de liant. Actuellement la plupart des procédés d’enrobage à sec sont conduits en mode discontinu. L’objectif de ce travail est donc de développer et d’étudier une opération d’enrobage à sec par un procédé continu innovant, une extrudeuse bi-vis corotative sans filière, constituant une rupture technologique dans son domaine. Dans le cadre de ce travail, des sphères de cellulose microcristalline, appelées particules hôtes sont enrobées avec soit des talcs de différentes granulométries soit du stéarate de magnésium, nommées particules invitées. Dans un premier temps, le comportement des particules hôtes est étudié dans le procédé. Les particules sorties du procédé sont analysées par microscopie électronique à balayage, par granulométrie laser et par voluménométrie. Pour la configuration de vis présentant que des éléments de transport, la vitesse de rotation des vis (25 à 200 rpm) et le débit d’alimentation (0,5 à 2 kg/h) choisis influencent le taux de remplissage dans le fourreau, et pour un taux supérieur à environ 14 % : la quantité de particules endommagées est négligeable. Un taux de remplissage faible favorise les frictions particules-particules ou particules-métal au niveau de l’entrefer. L’ajout de zones de mélanges dans la configuration des vis accentue ce phénomène de brisure par l’augmentation des contraintes de cisaillement. Par ailleurs, des masses retenues de la poudre dans le fourreau évoluent linéairement en fonction de la masse de poudre transportée en un tour de vis pour différentes configurations de vis. Ces relations laissent penser à l’existence d’un volume mort. Les mesures de distribution de temps de séjour mettent en évidence par l’application d’un modèle d’association de réacteurs idéaux, la présence d’écoulement piston et d’un volume mort. Dans un second temps, la faisabilité d’une opération d’enrobage à sec par le procédé étudié est analysée. Une couche d’enrobage continu de talc modifiant le comportement hydrophile des particules hôtes, est obtenue pour une vitesse de rotation de vis de 50 rpm et une configuration de vis cisaillante. Le type de particules invitées influence la morphologie de la couche d’enrobage : de type film avec le stéarate de magnésium et de type discret avec le talc micronisé. Néanmoins les propriétés de taille, d’écoulement, de compressibilité des particules composites sont semblables à celle des particules hôtes, seule la propriété de mouillabilité est modifiée. La présence de stéarate de magnésium diminue le temps de séjour des particules dans le procédé grâce à son caractère lubrifiant<br>Dry particle coating with mechanical action allows the production of composite particles whose functionalities and physical properties, such as flowability, are improved thanks to the absence of solvent or binder. Currently, most of dry particle coating processes are carried out in a discontinous mode. The objective of this work is thus to develop and study a dry particle coating operation with a continuous innovative process, twin screw co-rotating extruder without die, constituting a technological rupture in this application field. For this, spherical particles of microcristalline cellulose, as host particles, are coated with either talc particles of two sizes or magnesium stearate particles (MgSt), as guest particles. Firstly, the host particles behaviour is studied in the process. The exiting particles are analyzed by scanning electronic microscopy, laser granulometry and tapping test. Regarding the transport configuration, the chosen screw speed (between 25 an 200 rpm) and the feed rate (between 0.5 and 2 kg/h) have an important influence on the filling level in the barrel. For a filling level superior to approximatly 14 %, the quantity of broken particles is not significant. A low filling level facilitates the particle-particle or particle-metal friction in the barrel gap. When more mixing zones are added to the screw configuration, the shear stresses increase and, therefore, the breakage particle phenomenon becomes more prominent. Futhermore, the retained powder mass increases linearly when the transported mass in one screw turn increases for all the screw configurations. These evolutions suggest the existence of a dead volume. The residence time distribution mesurements highlight, thanks to the application of flowing model, the presence of plug-flow and a dead volume. Secondly, the feasibility of using the process for dry particle coating is analyzed. A continuous coating layer of talc modifiying the hydrophilic behaviour of the host particles is obtained for a low screw rotation speed (50 rpm) and a screw configuration with one mixing zone. The type of guest particles influence the morphology of the coating layer: film layer with the MgSt particles and discontinous layer with the micronized talc. However, size, flow and compressibility of the coated particles are similar to the ones of the initial host particles, only the wettability properties are modified. The presence of MgSt decreases the particle mean residence time in the process thanks to its lubricant action

Les convoyeurs à vis sont très largement utilisés dans l'industrie chimique. Du fait de leur capacité de mélange et de transport, ils sont mis en œuvre pour différentes applications (convoyage, séchage, pyrolyse, etc.). Cette technologie se voit ainsi utilisée dans le retraitement de matière nucléaire, notamment pour stabiliser des oxalates de plutonium en oxyde. De nombreuses études ont été menées à l'échelle du laboratoire afin d'établir précisément les mécanismes réactionnels par analyse thermogravimétrique (ATG) et les propriétés physico-chimiques des espèces mises en jeu. Il s'agit de réactions de décomposition thermique de chaînes carbonées couplées en phase hétérogène (réactions solide/gaz). Dans un four à vis, les phénomènes de transfert de chaleur, de matière et de quantité de mouvement peuvent significativement modifier la vitesse de réaction apparente et par conséquent l'avancement de la calcination. L'objectif de ce travail est d'améliorer un outil de simulation phénoménologique, permettant de transposer vers les plus grandes échelles les résultats des études menées en ATG sur de petites quantités de poudre supposées uniformes à chaque instant en composition et en température. Ce travail est réalisé en uranium, utilisé comme simulant du plutonium.L'outil de simulation est basé sur un modèle compartimenté, lié à l'hydrodynamique des poudres dans le réacteur. Ainsi, une majeure partie de la thèse se focalise sur l'écoulement à l'échelle globale et locale. Pour le mélange global, le point de débordement, caractérisant le changement de régime hydrodynamique, a été identifié. La Distribution des Temps de Séjour (DTS) a également été mesurée. Des modèles adimensionnels ont été élaborés pour prédire à la fois le point de débordement et la forme de la DTS. Pour le mélange local, deux études expérimentales ont été menées, en utilisant un système optique et des outils de traitement d'images. La première s'est intéressée au renouvellement de la surface du lit de poudre et la seconde au renouvellement des particules dans l'entrefer vis-tube. Ces études hydrodynamiques permettent de mieux comprendre et donc modéliser, respectivement les interactions gaz/solide et solide/paroi. Des modèles adimensionnels ont été développés pour prédire ces paramètres caractéristiques. Enfin, l'écoulement des poudres a pu être étudié en détail grâce à la modélisation de la rhéologie par mécanique des fluides numériques (CFD). En premier lieu, le modèle d'écoulement et ses paramètres ont été calibrés à partir de mesures expérimentales obtenues dans un tambour tournant ; appareil de géométrie plus simple et où la dynamique des poudres est similaire à celle observée dans un convoyeur à vis. Ce modèle a par la suite été confronté avec succès aux mesures expérimentales réalisées sur les maquettes à l'échelle pilote. Au final, le modèle a pu fournir des informations sur des données difficilement accessibles expérimentalement au sein d'un convoyeur à vis, comme l'épaisseur de la surface active ou les vitesses d'écoulement à l'intérieur de la poudre.Des études en ATG couplée à une analyse de calorimétrie différentielle à balayage (ATG/DSC) ont été menées afin d'obtenir des données cinétiques et thermochimiques robustes sur la calcination de l'oxalate d'uranium sous atmosphère oxydante et inerte, ainsi que sur la conversion de l'UO2 en U3O8. Enfin, les signaux ATG obtenus expérimentalement ont pu être modélisés, validant les paramètres cinétiques.L'outil de simulation du four à vis a été amélioré grâce à une meilleure représentation des phénomènes ayant lieu dans ce type de réacteur pendant la calcination de l'oxalate d'uranium. Ces améliorations permettent d'avoir accès aux différents profils de température et de concentration de toutes les espèces dans différentes zones prédéfinies. L'outil de simulation est capable de prédire des données expérimentales mesurées sur le four à vis pilote<br>Screw conveyors are widely used in the chemical industry. Thanks to their mixing and transport capacity, they are used for a variety of applications (conveying, drying, pyrolysis, etc.). This technology is also used in the reprocessing of nuclear materials, in particular to stabilise plutonium oxalates into oxides. Numerous studies have been carried out on a laboratory scale to establish precisely the reaction mechanisms using thermogravimetric analysis (TGA) and the physico-chemical properties of the species involved. The reactions involved are thermal decomposition of coupled carbon chains in a heterogeneous phase (solid/gas reactions). In a screw kiln reactor, heat, mass and momentum transfer phenomena can significantly modify the apparent reaction rate and consequently the progress of the calcination. The aim of this work is to improve a phenomenological simulation tool, enabling the transposition to larger scales the results of studies carried out in TGA on small quantities of powder assumed to be uniform in composition and temperature at all times. This work is carried out in uranium, used as a simulant for plutonium.The simulation tool is based on a compartment model, linked to the hydrodynamics of the powders in the reactor. Thus, a major part of the thesis focuses on the flow at the global and local scales. With regard to global mixing, the overflow point, which characterises the change in hydrodynamic regime, has been identified. The Residence Time Distribution (RTD) was also measured. Dimensionless models were developed to predict both the overflow point and the shape of the RTD. Concerning the local mixing, two experimental studies were carried out, using an optical system and image processing tools. The first one looked at the renewal of the surface of the powder bed, while the second one at the renewal of the particles within the screw-tube clearance. These hydrodynamic studies will allow a better understanding and a modeling of gas/solid and solid/wall interactions respectively. Dimensionless models have been developed to predict these characteristic parameters. Finally, the powder flow was studied in detail by modelling the rheology using Computational Fluid Dynamics (CFD). First, the flow model and its parameters were calibrated using experimental measurements obtained in a rotating drum, a device with a simpler geometry and where the powder dynamics are similar to those observed in a screw conveyor. This model was then successfully compared with the experimental measurements carried out on the pilot-scale models. In the end, the model was able to provide information on data that is difficult to access experimentally within a screw conveyor, such as the thickness of the active layer or the flow velocities within the powder.TGA coupled with differential scanning calorimetry (TGA/DSC) studies were carried out to obtain robust kinetic and thermochemical data on the calcination of uranium oxalate in an oxidising and inert atmosphere, as well as on the conversion of UO2 to U3O8. Finally, the TGA signals obtained experimentally were modeled to validate the kinetic parameters.The screw kiln reactor simulation tool has been improved with a better representation of the phenomena taking place during the calcination of uranium oxalate in such apparatus. These improvements give access to the different temperature and concentration profiles of all the species in different predefined zones. The simulation tool is capable of predicting experimental data measured on the pilot screw kiln reactor

Certains procédés de production d’énergie nécessitent l’utilisation de poudres de biomasse, par exemple la gazéification en réacteur à flux entraîné (RFE). Cependant, les poudres de biomasse ont une mauvaise coulabilité. L’objectif de cette thèse est d’étudier leurs propriétés d’écoulement dans le contexte de la gazéification en RFE, à l’échelle du laboratoire et à l’échelle pilote. A l’échelle du laboratoire, des mesures en tambour rotatif, des tests de cisaillement et des mesures de densité ont été effectués. D’une part, une corrélation est mise en évidence entre la cohésion (issue des tests de cisaillement), la densité et l’angle d’avalanche (tiré des mesures en tambour). Ainsi, un paramètre difficile à obtenir comme la cohésion peut l’être à partir de mesures simples. D’autre part, l’influence de l’humidité sur la coulabilité des poudres de biomasse a été évaluée. L’humidité n’a pas d’effet significatif sous 15 % (en masse, base humide), car l’eau est adsorbée dans la structure de la biomasse ; les particules gonflent et ne sont pas liées par des ponts liquides. Un procédé de granulation humide est proposé. Un liant issu de déchets de biomasse est ajouté à la poudre pour former des granulés d’environ 1 mm. Leur forme sphérique diminue l’entrelacement des particules et leur faible polydispersité diminue le nombre de points de contact. Une amélioration de l’écoulement est observée à l’échelle labo. Une étude énergétique montre que la consommation énergétique du procédé peut descendre jusqu’à 12% du pouvoir calorifique inférieur, ce qui suggère une potentielle rentabilité économique du procédé. Enfin, la caractérisation à l’échelle supérieure est effectuée dans un pilote reproduisant l’injection en RFE. Les résultats montrent le rôle essentiel de la sphéricité et d’une faible polydispersité des particules. L’effet positif de la torréfaction et de la granulation sur la coulabilité est mis en évidence<br>Some power generation processes require the biomass to be finely ground, such as biomass gasification in entrained flow reactors. However, fine biomass powders are cohesive and present flow issues. This thesis aims to study the biomass powder flowability in the context of the entrained flow gasification process. Biomass powders are characterized both at laboratory scale and pilot scale. Characterization at lab scale consisted of rotating drum measurements, shear tests and density measurements. First, a correlation is found between the cohesion (derived from shear tests), the powder density and the avalanche angle (derived from the rotating drum measurements). Thus, parameters difficult to get such as the cohesion can be obtained with easy to perform measurements. Then, the influence of moisture content on wood powder flowability has been assessed. No significant effect of the water content is found below 15 wt% (wet basis). Below 15%, as water is adsorbed in the biomass structure, the particles swell without being linked by liquid bridges. A wet granulation method is proposed. Biomass waste binders are added to the powder to form granules around 1 mm. The spherical shape lowers the interlocking phenomenon. The low size dispersity of the grains decreases the number of contact points between particles. An improvement of the flowability at lab scale is observed. An energetic study of the granulation process is proposed, showing the energy consumption can be as low as 12% of the biomass Lowest Heating Value. Thus, the process is potentially economically profitable. Finally, characterization at pilot scale is performed with a device mimicking the injection in an entrained flow reactor. The results show the essential roles in the injection step of both the spherical shape and the narrow size distribution of the particles. The positive effect of torrefaction and granulation on the flowability is highlighted

L'Hibiscus sabdariffa (hibiscus) est une plante dont les calices comestibles, contiennent des polyphénols et des molécules d'anthocyane qui sont à la fois des composés antioxydants et responsables de leur couleur rouge attrayante pour le consommateur. Ces particularités constituent un fort potentiel santé qui répond aux demandes actuelles du marché et un atout économique pour les industries. Cependant, cette plante tropicale et saisonnière dont les calices riches en eau, sont très périssables, sensibles à l'humidité et à la chaleur, et les molécules d'intérêt (anthocyanes) sont thermosensibles et instables en milieu aqueux. Dans ce contexte, la transformation des calices en poudre permet, en plus d'optimiser le coût du transport et l'espace de stockage, de stabiliser les calices en assurant une longue durée de conservation du produit, de faciliter l'accessibilité aux biomolécules et donc à ses bienfaits pour la santé, ceci, à condition que le procédé soit maîtrisé. L'un des meilleurs moyens de préserver les propriétés nutritionnelles d'origine (teneur en anthocyanes, activité antioxydante) des calices est d'obtenir des produits peu transformés ou « minimally processed products » en combinant le séchage à l'étuve (contrôlé), le broyage et le fractionnement par tamisage. Ce procédé a été étudié dans ce travail et les propriétés physicochimiques (granulométrie, forme, structure, porosité, proportion de fibre, teneur en anthocyanes, activité antioxydante) et fonctionnelles des poudres (écoulement, reconstitution, extractibilité des biomolécules) ont été systématiquement évaluées dans un but de formulation de boisson. L'intérêt d'un tel procédé est la facilité de sa mise en œuvre, applicable à tous végétaux, la facilité d'usage de la poudre, l'amélioration de la disponibilité et l'accessibilité des biomolécules. Ce travail a permis d'identifier l'impact du séchage solaire et du broyage sur les propriétés physicochimiques des poudres, ces dernières impactant directement les propriétés fonctionnelles. La substitution du séchage solaire par le séchage contrôlé à l'étuve et un fractionnement par tamisage supplémentaire après le broyage ont permis d'améliorer les propriétés fonctionnelles des poudres. Ces propriétés singulières des poudres ainsi obtenues, ont permis de distinguer des applications qui leur sont propres<br>Hibiscus sabdariffa (hibiscus) is a plant with edible calyxes containing polyphenol and anthocyanin molecules that are both antioxidant compounds and responsible for their attractive red color for consumers. These particularities constitute a good health potential that meets the current market demands, and an economic potential for industries. However, this tropical and seasonal plant whose water-rich calyxes are highly perishable, sensitive to humidity and heat, and whose the interesting molecules (anthocyanins) are heat-sensitive and unstable in aqueous medium. In this context, the calyx transformation into powder allows, besides optimizing the transport cost and storage space, to stabilize the calyxes by ensuring a long product shelf-life, and to improve the biomolecule accessibility. This allows to benefit to its health assets provided that the process is controlled. One of the best ways to preserve the calyx original nutritional properties (anthocyanin content, antioxidant activity) is to obtain minimally processed products by combining controlled oven-drying, grinding and fractionation by sieving. This process was studied in this work and the powder physicochemical properties (particle size and shape, structure, porosity, fiber proportion, anthocyanin content, antioxidant activity) and functional properties (flowability, reconstitution, biomolecule extractability) were systematically evaluated for drink formulation. The interest of such a process is the ease of its implementation applicable to all plants, the powder ease of use, the improvement of the biomolecule availability and accessibility. This work allows identifying the impact of sun-drying and grinding on the powder physicochemical properties, the latter impacting the functional properties. The substitution of sun-drying by controlled oven-drying and an additional fractionation by sieving preceded by grinding allowed improving the powder functional properties. These powder functional properties were singular and allowed to distinguish specific applications for each powder type (fine or coarse powders)

Dans les secteurs industriels tels que l’industrie chimique, pharmaceutique ou agro-alimentaire une faible aptitude à l’écoulement des poudres est souvent à l’origine du mauvais fonctionnement d’un procédé. Une mauvaise coulabilité peut ainsi entrainer le blocage de poudres dans un silo, des problématiques de dosages et de remplissage ou encore une détérioration de la qualité du produit final. Pour assurer un bon fonctionnement du procédé, il est donc nécessaire et essentiel d’évaluer la coulabilité de poudres utilisées. Pour cela, plusieurs techniques expérimentales telles que les dispositifs de mesure d’angle, les cellules de cisaillement, les dispositifs de tassement de poudre peuvent être utilisées. Des indices de coulabilité sont alors définis permettant de classer les poudres selon la qualité de l’écoulement. Des essais expérimentaux ont été menés sur plusieurs types de poudres et les premiers résultats ont montré que le passage d’une technique d’évaluation à une autre peut modifier, voire inverser le classement de la coulabilité des poudres. En effet, selon les techniques étudiées les poudres sont soumises à des sollicitations mécaniques différentes et donc le choix de la technique doit être adapté au cas réel d’étude. Dans ce travail, nous nous sommes intéressé plus particulièrement au cas de l’évaluation de l’écoulement de poudres à partir de dispositifs de compaction. Le travail réalisé a montré que les paramètres dynamiques (amplitude et fréquence de chocs) influencent énormément le classement de la coulabilité des poudres. A partir d’une approche énergétique, il a été montré qu’une évaluation et quantification de la coulabilité à partir du rapport d’Hausner ne peut être donnée par une technique de compaction que si celle-ci permet d’atteindre une valeur d’énergie nécessaire à l’obtention d’une compaction maximale des particules. Enfin, une étude de mise en œuvre des techniques d’évaluation de la coulabilité a été réalisée dans le domaine de la formulation en s’intéressant à l’évaluation quantitative de l’influence d’un agent d’écoulement<br>In industrial sectors, such as chemical, pharmaceutical or food industries, poor flowability of powders is often the causes of process malfunction. Poor flowability can lead to the blocking of powders in a silo, dosing and filling problems, or even bad quality on final product. To ensure proper process operation, it is therefore necessary and essential to evaluate the flowability of powders used. For this purpose, several experimental techniques such as angle of repose devices, shear cells or powder packing devices can be used. Flowability indices can then be defined in order to classify the powders according to the flow quality. Experimental tests have been carried out on several types of powders and the first results have shown that the transition from one technique to another can modify or even reverse the classification of the powder flowability. Indeed, according to the techniques studied, powders are subjected to different mechanical stresses and therefore the choice of the technique must be adapted to the real case of study. In this work, we were particularly interested to the evaluation of powders flowability from compaction devices. The work carried out has shown that the dynamic parameters (amplitude and frequency of taps) greatly influence the classification of powders flowability. From an energy approach, it has been shown that the evaluation of the flowability from Hausner ratio can be given by a compaction technique only if it achieves a value of energy required to obtain a maximal compaction of the particles. Finally, an implementation study of flowability evaluation techniques was carried out in the field of formulation by focusing on the quantitative evaluation of the influence of a glidant

Dans les secteurs industriels tels que l’industrie chimique, pharmaceutique ou agro-alimentaire une faible aptitude à l’écoulement des poudres est souvent à l’origine du mauvais fonctionnement d’un procédé. Une mauvaise coulabilité peut ainsi entrainer le blocage de poudres dans un silo, des problématiques de dosages et de remplissage ou encore une détérioration de la qualité du produit final. Pour assurer un bon fonctionnement du procédé, il est donc nécessaire et essentiel d’évaluer la coulabilité de poudres utilisées. Pour cela, plusieurs techniques expérimentales telles que les dispositifs de mesure d’angle, les cellules de cisaillement, les dispositifs de tassement de poudre peuvent être utilisées. Des indices de coulabilité sont alors définis permettant de classer les poudres selon la qualité de l’écoulement. Des essais expérimentaux ont été menés sur plusieurs types de poudres et les premiers résultats ont montré que le passage d’une technique d’évaluation à une autre peut modifier, voire inverser le classement de la coulabilité des poudres. En effet, selon les techniques étudiées les poudres sont soumises à des sollicitations mécaniques différentes et donc le choix de la technique doit être adapté au cas réel d’étude. Dans ce travail, nous nous sommes intéressé plus particulièrement au cas de l’évaluation de l’écoulement de poudres à partir de dispositifs de compaction. Le travail réalisé a montré que les paramètres dynamiques (amplitude et fréquence de chocs) influencent énormément le classement de la coulabilité des poudres. A partir d’une approche énergétique, il a été montré qu’une évaluation et quantification de la coulabilité à partir du rapport d’Hausner ne peut être donnée par une technique de compaction que si celle-ci permet d’atteindre une valeur d’énergie nécessaire à l’obtention d’une compaction maximale des particules. Enfin, une étude de mise en œuvre des techniques d’évaluation de la coulabilité a été réalisée dans le domaine de la formulation en s’intéressant à l’évaluation quantitative de l’influence d’un agent d’écoulement<br>In industrial sectors, such as chemical, pharmaceutical or food industries, poor flowability of powders is often the causes of process malfunction. Poor flowability can lead to the blocking of powders in a silo, dosing and filling problems, or even bad quality on final product. To ensure proper process operation, it is therefore necessary and essential to evaluate the flowability of powders used. For this purpose, several experimental techniques such as angle of repose devices, shear cells or powder packing devices can be used. Flowability indices can then be defined in order to classify the powders according to the flow quality. Experimental tests have been carried out on several types of powders and the first results have shown that the transition from one technique to another can modify or even reverse the classification of the powder flowability. Indeed, according to the techniques studied, powders are subjected to different mechanical stresses and therefore the choice of the technique must be adapted to the real case of study. In this work, we were particularly interested to the evaluation of powders flowability from compaction devices. The work carried out has shown that the dynamic parameters (amplitude and frequency of taps) greatly influence the classification of powders flowability. From an energy approach, it has been shown that the evaluation of the flowability from Hausner ratio can be given by a compaction technique only if it achieves a value of energy required to obtain a maximal compaction of the particles. Finally, an implementation study of flowability evaluation techniques was carried out in the field of formulation by focusing on the quantitative evaluation of the influence of a glidant

The theoretical part of the thesis focuses on the description of particulate materials and their mechanical behaviors with a focus on flow properties. Great emphasis is placed on measuring the shear properties using a Jenike shear machine, on the correct procedure for standardized measurement and evaluation using Mohr's circles. The theoretical part focuses on the characterization of particulate matter using a variety of methods available, such as visual, separation, sedimentation, surface methods and methods of scanning field and flow. The practical part is focused on the determination of flow characteristics and surface finishing of finely ground limestone Omyacarb VA with various grain sizes. The surface was modified using stearic acid and calcium stearate. Attention was paid to the influence of the concentration of surface-regulating substances on the flowability of the material. The flowability of commercially supplied material was compared with lab modified materials and the determination of the theoretical content of stearic acid or calcium stearate was accomplished. Shear properties were measured using the Jenike shear machine. The material was further tested by laser diffraction and SEM with EDS particle surface analysis and elemental surface mapping.

1 Abstract Charles University in Prague, Faculty of Pharmacy in Hradci Králové Department of: Pharmaceutical Technology Consultant: Doc. PharmDr. Zdeňka Šklubalová, Ph.D. Student: Barbora Jonášová Title of Thesis: Flow equation. Sorbitol and magnesium stearate. This thesis describes influence of the addition of magnesium stearate on bulk properties to size fractions of sorbitol for direct compression in the range 0,100 - 0,346 mm. I studied influence of particle size and the size of the opening hopper to the gravitational speed of flow. The dependence of the flow rate (g/s) on the size of the opening conical hopper was modeled by the squares equation Jones-Pilpel. No significant effect of addition of magnesium stearate 0,5% and 1,0% for the exponent equation was found. This model allows the re-estimation of the flow rate with an accuracy about 11% for the size fraction regardless of the amount of added magnesium stearate; for polydisperse MS200 is the deviation of the experimentally determined values of the flow rate of approximately 19%.

Charles University in Prague, Faculty of Pharmacy in Hradci Králové Department of: Pharmaceutical technology Consultant: doc.PharmDr.Zdeňka Šklubalová, Ph.D Student: Hana Čermáková Title of Thesis: Flow equation. Sorbitol In this diploma thesis, the granulometric, bulk and consolidation properties of sorbitol for direct compression are studied. The effect of particle size on bulk and tapped density, angle sprinkles and the flow rate through the model conical hopper with a different orifice diameter are examined. The relationship of the flow rate (g/s) of particle size fractions on the orifice diameter is modelled by the Jones-Pilpel equation with the accuracy of the flow rate prediction approximately 10 %.

Yes<br>Objectives: Cocrystallization of sulfadimidine (SDM) with suitable coformers, such as 4-aminosalicylic acid (4-ASA), combined with changes in the crystal habit can favourably alter its physicochemical properties. The aim of this work was to engineer SDM:4-ASA cocrystals with different habits in order to investigate the effect on dissolution, and the derived powder properties of flow and compaction. Methods: Cocrystals were prepared in a 1:1 molar ratio by solvent evaporation using ethanol (habit I) or acetone (habit II), solvent evaporation followed by grinding (habit III) and spray-drying (habit IV). Key findings: Powder X-ray diffraction showed Bragg peak position was the same in all the solid products. The peak intensity varied, indicating different preferred crystal orientation confirmed by SEM micrographs: large prismatic crystals (habit I), large plate-like crystals (habit II), small cube-like crystals (habit III) and microspheres (habit IV). The habit III exhibited the fasted dissolution rate; however, it underwent a polymorphic transition during dissolution. Habits I and IV exhibited the highest Carr’s compressibility index, indicating poor flowability. However, habits II and III demonstrated improved flow. Spray drying resulted in cocrystals with improved compaction properties. Conclusions: Even for cocrystals with poor pharmaceutical characteristics, a habit can be engineered to alter the dissolution, flowability and compaction behavior.<br>Science Foundation Ireland. Grant Number: SFI/12/RC/2275

碩士<br>國立交通大學<br>機械工程研究所<br>86<br>One of the major differences between powder and solid is the compressibility. In the co-extrusion of ceramic powder/metal solid composite clad rod, the density of powder after extrusion is always one of the most important criterion of the quality of a product. The purpose of the research is to discuss the effect of the initial packing density on the powder density after vibration extrusion. 　　Before extrusion, powder core are divided to several initial packing densities. During extrusion process a vibration turbine vibrator is added on the die set in order to increase the powder density of the extruded product. 　　We found the densities of the product are closedly related to the initial packing density of the core and also affected by the frequence of the vibration.

7 2 Abstract Charles University in Prague, Faculty of Pharmacy in Hradci Králové Department of: Pharmaceutical Technology Consultant: doc. PharmDr. Zdeňka Šklubalová, Ph.D. Student: Alexandra Šofranková Title of Thesis: Fractal aspects of flow and consolidation behaviour of microcrystalline cellulose The object of this diploma thesis was to study the flow and consolidation characteristics of three types of microcrystalline cellulose. The granulometric characteristics, including the linear fractal dimension, were estimated using the optical microscopy. The bulk and tapped density, the angle of repose and the flow rate through an orifice of the hopper were evaluated. True density of the materials and the porosity of a loose powder bed were determined by helium pyknometry. The changes of density by the gravity consolidation were studied; the relationship of Hausner ratio on the number of taps describes best the differences in the consolidation behaviour of the substances. Modelling the consolidation kinetic by the exponential law allowed to determine the parameter N1/2, which shows the number of taps needed to reach one half of the powder volume reduction. The values of N1/2 within a range of 6,9-18 correlated well with the particle size of the used types of microcrystalline cellulose.

Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of: Pharmaceutical Technology Consultant: doc. PharmDr. Zdeňka Šklubalová, Ph.D. Student: Michaela Bérešová Title of Thesis: Study of consolidation behaviour of lactose and its blends Flow behaviour and consolidation properties are important characteristics of the powder substances. The aim of this thesis was to evaluate these properties for four types of lactose with different particle size and for the mixtures of two lactoses with different flow properties. The density and porosity of the powder bed and their changes during the consolidation due to the gravitational tapping were studied. The non-linear regression equation was used to describe the consolidation process for the samples and the parameter N½, which expresses the number of taps needed to achieve a half reduction of a powder bed volume. The value of N½ increased with the decrease in the particle size.

Charles University, Faculty of Pharmacy in Hradec Králové Department of: Department of Pharmaceutical Technology Consultant: doc. PharmDr. Zdeňka Šklubalová, Ph.D Student: Kristýna Kýhosová Title of Thesis: Study of flow and consolidation behaviour of lactose This diploma thesis studies flow and consolidation behaviour of three types of lactose, which differed in the methode of manufacture (crystalization, milling, spray drying). Particle size distribution was characterized by the sieve analysis. The bulk and tapped density, the angle of repose, the flow rate through an orifice of the hopper and true density measured by helium pycnometer were evaluated. The volume changes of powder bed and porosity during consolidation in the relationship on gravitational tapping were studied. To describe the consolidation process, the exponentional mathematical model was used, which made possible to calculate N1/2, that shows the number of taps needed to reach one half of the powder volume reduction. The values noted for lactose were in the range of 3-5.8.

Master of Science<br>Food Science Institute<br>Jayendra K. Amamcharla<br>Milk protein concentrate (MPC) powders are high-protein dairy ingredients obtained from membrane filtration processes and subsequent spray drying. MPC powders have extensive applications due to their nutritional, functional, and sensory properties. However, their flow properties, rehydration behavior, and morphological characteristics are affected by various factors such as processing, storage, particle size, and composition of the powder. Literature has shown that knowledge about the powder flowability characteristics is critical in their handling, processing, and subsequent storage. For this study, FT4 powder rheometer (FT4, Freeman Technologies, UK) was used to characterize the flowability of MPC powders during storage. This study investigated the flowability and morphological characteristics of commercial MPC powders with three different protein contents (70, 80, and 90%, w/w) after storage at 25ºC and 40ºC for 12 weeks. Powder flow properties (basic flowability energy (BFE), flow rate index (FRI), permeability, etc.) and shear properties (cohesion, flow function, etc.) were evaluated. After 12 weeks of storage at 40ºC, the BFE and FRI values significantly increased (P < 0.05) as the protein content increased from 70 to 90% (w/w). Dynamic flow tests indicated that MPC powders with high protein contents displayed higher permeability. Shear tests confirmed that samples stored at 40ºC were relatively less flowable than samples stored at 25ºC. Also, the lower protein content samples showed better shear flow behavior. The results indicated that MPC powders stored at 40ºC had more cohesiveness and poor flow characteristics than MPC powders stored at 25ºC. The circle equivalent diameter, circularity, and elongation of MPC powders increased as protein content and storage temperature increased, while the convexity decreased as protein content and storage temperature increased. Overall, the MPC powders evidently showed different flow properties and morphological characteristics due to their difference in composition and storage temperature. Literature has shown various methods for determining the solubility of dairy powders, but it requires expensive instruments and skilled technicians. The front-face fluorescence spectroscopy (FFFS) coupled with chemometrics could be used as an efficient alternative, which is commonly used as fingerprints of the various food products. To evaluate FFFS as a useful tool for the non-destructive measurement of solubility in the MPC powders, commercially procured MPC powders were stored at two temperatures (25 and 40ºC) for 1, 2, 4, 8, and 12 weeks to produce powders with different rehydration properties, which subsequently influenced their fluorescence spectra. The spectra of tryptophan and Maillard products were recorded and analyzed with principal components analysis. The solubility index and the relative dissolution index (RDI) obtained from focused beam reflectance measurement was used to predict solubility and dissolution changes using fluorescence spectra of tryptophan and Maillard products. The solubility index and RDI showed that the MPC powders had decreased solubility as the storage time and temperature increased. The results suggest that FFFS has the potential to provide rapid, nondestructive, and accurate measurements of rehydration behavior in MPC powders. Overall, the results indicated that solubility and dissolution behavior of MPC powders were related to protein content and storage conditions that could be measured using FFFS.

<div>Cocoa is widely used by confectionary industries as a powder raw material for chocolate production. The chemical properties such as high- or low-fat content determine the functionality of the cocoa powder and constitute as a major factor in controlling the behavior of the final product. Additionally, the physicochemical properties such as the cohesive characteristics of cocoa powders create undesirable issues in industrial manufacturing settings. Thus, the evaluation of physical and chemical attributes is relevant to differentiate the powder surface structure and define the material behavior in presence of other materials or distinct environments.</div><div>This work evaluated three kinds of cocoa powders—varying mainly on the lipid content—to assess the powder performance in terms of the role of surface properties on the physical attributes (flowability and wettability) and stability under distinct frameworks. Various analytical tools were used, and several methodologies were developed and implemented to determine the surface area, changes in lipid melting phases at the surface level and particle interactions. The characterization methods included particle true density, flow properties under aerated conditions, bulk permeability, thermal properties, surface energetics, water sorption, and chemical surface compositional analyses.</div><div>The findings of this work revealed that the cocoa surface composition, amount of lipids, did not explain the low-flow performance or the water uptake. On the other hand, physicochemical properties such as lipid polymorphism was introduced as an avenue to further understand the results. From the surface energetics standpoint, a water diffusion mechanism is proposed as a result of the observed effect of water on the performance and stability of the cocoa powder systems. Owing to the hydrophobic nature of cocoa particles, this material can be used as a unique reference to understand cohesive particle models with implications on the performance (flowability and wettability) of lipid-based surface materials. The results indicated that powder behavior on the performance is a confounding effect of all variables.</div><div>The major contribution of this thesis work demonstrates the importance of surface chemistry characterization on the physical attributes of cocoa powder systems and the potential to control surface composition to improve the performance and stability of food complex systems.</div>

Charles University, Faculty of Pharmacy in Hradec Králové Department of: Pharmaceutical technology Supervisor: doc. PharmDr. Zdeňka Šklubalová, Ph.D. Consultant: Ing. Hana Hurychová Student: Eliška Dostálová Title of Thesis: Study of bulk and consolidation properties of size fractions of anhydrous lactose The bulk and consolidation behaviour of pharmaceutical excipients belong to their important properties. Properties of five size fractions of anhydrous lactose having the particle size in the range of 1-400 µm were studied in this thesis. The measurement was carried out by using static and dynamic pharmacopoeial methods. The bulk density and the tapped density, the angle of repose were evaluated as well as the true density of particles by using the gas pycnometry. The mass flow rate through the orifice of a model conical hopper by the force of gravity was estimated for the individual size fractions. The discharge rate through the orifice having the diameter in a range of 0.6-1.5 cm was modelled with the Beverloo et al and Jones & Pilpel power regression equations; the precision of the flow rate prediction was about 3 %. The best bulk properties were detected for the particle size fraction 246 µm. The results of the evaluation of the consolidation dynamic during the tapping of powder bed permitted...

Králové doc. PharmDr. Zdeňka Šklubalová, Ph.D. Ing. Hana Hurychová, Ph.D. Monika Hnatková The objective of this diploma thesis was to evaluate the flow and consolidation behaviour of the size fractions of lactose for direct compression - Tabletose® 80 in a range of 80-400 μm obtained by sieving. The nonlinear influence of the particle size on the flow rate was detected; the fractions of Tablettose® 80 with the mean size of 245 and 346 µm showed the best flowability. The influence of the diameter of the hopper opening on the flow rate was modeled using the Beverloo and/or Jones & Pilpel flow equation; the latter described the results better. The assessment of volume changes by gravitational tapping allowed to observe dynamics of consolidation and to express porosity factor for the powder bed, which enabled an estimation of the angle of internal friction.

1 Abstract Charles University, Faculty of Pharmacy in Hradci Králové Department of: Department of Pharmaceutical Technology Supervisor: Doc. PharmDr. Zdeňka Šklubalová, Ph. D. Consultant PharmDr. Karel Palát, CSc., Mgr. Žofie Trpělková Student: Martina Litošová Title of Thesis: Homogenization of powder blends using a Turbula mixer. In this experimental work, the influencing of the homogeneity of the powder mixture of acetylsalicylic acid (ASA) and microcrystalline cellulose (Avicel PH102) due to the rotational speed of the mixing container in a range of 23−101 rpm, and the mixing time was studied using the Turbula shaker mixer. Within time interval 2-62 minutes, the content of ASA in samples was measured by near-infrared spectrometry. The expression of standard deviation was used to evaluate the homogeneity of samples. The best results were detected at a rotational speed of 34 rpm within time interval of 14−30 min.

Charles University, Faculty of Pharmacy in Hradci Králové Department of: Pharmaceutical technology Supervisor: doc. PharmDr. Zdeňka Šklubalová, Ph.D. Consultant: Mgr. Žofie Trpělková Student: Aneta Mrázková Title of Thesis: The study of influence of the measurement method on static angle of repose of free-flowable excipients. Good flow and consolidation properties of powders represent significant characteristics of pharmaceutical excipients They are important for manufacturing of powders into solid dosage forms. Flow behavior of 6 free flowing excipients was evaluated in this diploma thesis. The main target was a study of the influence of the masurement method and the orifice size of a conical hopper on static angle of repose (AOR). The automatic tester and the prototype for measuring AOR having orifice sizes in a range of 6-15 mm were used for the measurement. A significant difference between the results of these two methods (P <0.01) was observed. The decrease in AOR was detected when increased the orifice diameter, the effect was significant (P <0.01) only in automatic tester for two out of six measured powders. Surprisingly, the significant influence of the orifice size on AOR was registered for a sweetener Palatinose with protype equipment.

Over the last years the pharmaceutical industry has been gradually starting to adhere to the continuous production instead of the traditional batch production. For the production of tablets through continuous direct compression (CDC) it is essential to ensure the control of all the equipment involved in the process, with special attention to the Loss-in-Weight (LIW) Feeders. This is due to the fact that even if there are small oscillations in the initial phase of the process, these will have big repercussions on the quality of the final product, making the drug getting out of the specification. This work explore different materials with the goal of creating a methodology for the selection of the components (the tools) to be assembled on the feeder in order to optimise the process. Furthermore, the minimum and maximum limits of the feeders were tested to determine a stable range of operation for each analysed material. Afterwards, a database with the different properties of the materials was developed with the goal of relating these properties with the components that would be necessary to integrate on the feeder and optimise its performance. To simplify the identification of similarities between the analysed materials, a principal component analysis (PCA) model was developed. Following this, some alternatives to reduce the time and costs of the production process were identified. Thus, the development of partial least squares (PLS) models was essential to predict the feed factor (FF) values. Lastly, the impact that the usage of the feeder had over the materials was analysed in order to find out if this equipment would cause any alterations in the properties of the materials to be used in the formulation.<br>Nos últimos anos a indústria farmacêutica tem vindo gradualmente a aderir à produção em contínuo em detrimento da tradicional produção em batch. Para a produção de comprimidos através de continuous direct compression (CDC) é essencial garantir o controlo de todos os equipamentos do processo, com especial atenção para os Loss-in-Weight (LIW) Feeders. Tal deve-se ao facto de que mesmo que sejam pequenas as oscilações na fase inicial do processo, estas terão grandes repercussões na qualidade do produto final, dando origem a um medicamento fora de especificação. Durante este trabalho procurou-se testar diversos materiais com o objetivo de criar uma metodologia para a seleção dos componentes (peças) a serem integrados no feeder de forma a otimizar o seu funcionamento. Para além disso, foram também testados os limites mínimos e máximos de funcionamento do feeder, de forma a se determinar um intervalo de operação estável para cada material analisado. Posteriormente, foi desenvolvida uma base de dados com as diversas propriedades dos materiais, cujo objetivo seria relacionar essas propriedades aos componentes que viriam a ser necessários integrar no feeder de forma a otimizar o seu funcionamento. Com o objetivo de facilitar a deteção das semelhanças entre os materiais analisados foi desenvolvido um modelo de principal component analysis (PCA). Em seguida, foram identificadas alternativas para reduzir o tempo e o custo dos processos de produção, para o que foi essencial o desenvolvimento de modelos de partial least squares (PLS) para prever os valores dos feed factor (FF). Por último, foi analisado o impacto que a utilização do feeder teve sobre os materiais, no sentido de se averiguar se a utilização deste equipamento provocaria alterações nas propriedades dos materiais a serem utilizados na formulação.