This thesis describes the development of an empirical model of focus beam reflectance measurements (FBRM) and the application of the model to monitoring batch cooling crystallization and extracting information on crystallization kinetics. Batch crystallization is widely used in the fine chemical and pharmaceutical industries to purify and separate solid products. The crystal size distribution (CSD) of the final product greatly influences the product characteristics, such as purity, stability, and bioavailability. It also has a great effect on downstream processing. To achieve a desired CSD of the final product, batch crystallization processes need to be monitored, understood, and controlled. FBRM is a promising technique for in situ determination of the CSD. It is based on scattering of laser light and provides a chord-length distribution (CLD), which is a complex function of crystal geometry. In this thesis, an empirical correlation between CSDs and CLDs is established and applied in place of existing first-principles FBRM models. Built from experimental data, the empirical mapping of CSD and CLD is advantageous in representing some effects that are difficult to quantify by mathematical and physical expressions. The developed model enables computation of the CSD from measured CLDs, which can be followed during the evolution of the crystal population during batch cooling crystallization processes. Paracetamol, a common drug product also known as acetaminophen, is selected as the model compound in this thesis study. The empirical model was first established and verified in a paracetamol-nonsolvent (toluene) slurry, and later applied to the paracetamol-ethanol crystallization system. Complementary to the FBRM measurements, solute concentrations in the liquid phase were determined by in situ infrared spectra, and they were jointly implemented to monitor the crystallization process. The framework of measuring the CSD and the solute concentration allows the estimation of crystallization kinetics, including those for primary nucleation, secondary nucleation, and crystal growth. These parameters were determined simultaneously by fitting the full population balance model to process measurements obtained from multiple unseeded paracetamol-ethanol crystallization runs. The major contributions of this thesis study are (1) providing a novel methodology for using FBRM measurements to estimate CSD; (2) development of an experimental protocol that provided data sets rich in information on crystal growth and primary and secondary nucleation; (3) interpretation of kinetics so that appropriate model parameters could be extracted from fitting population balances to experimental data; (4) identification of the potential importance of secondary nucleation relative to primary nucleation. The protocol and methods developed in this study can be applied to other systems for evaluating and improving batch crystallization processes.

No description available.

The presence of hydrodynamically generated air bubbles has been observed to enhance fine particle flotation in a high intensity agitation (HIA) flotation cell. In this study, the cavitation in an HIA cell, used in our laboratory, is studied by hydrodynamic computational fluid dynamics. Different types of impellers are studied to obtain flow characteristics such as velocity and pressure distributions and turbulent dissipation rate in a two-baffled HIA cell. A cavitation model in conjunction with a multiphase mixture model is used to predict the vapor generation in the HIA cell. Cavitating flow is simulated as a function of revolution speed (RPM) and dissolved gas concentration to understand the dependency of hydrodynamic cavitation on these operating parameters. For comparison, cavitation in a pressure driven flow through a constriction is also modeled. A population balance model is used to obtain bubble size distributions of the generated cavities in a flow through constriction. / Chemical Engineering

Crystallization is a key unit operation used for obtaining purified products by many process industries. The key properties of the crystalline products, such as size and shape distribution, purity and polymorphic form are controlled by the crystallization process. All these properties impact significantly the downstream operations such as drying or filtration. Therefore, monitoring and controlling this process is fundamental to ensure the quality of the final product. Process analytical technology (PAT) brings numerous new methods and opportunities in the process analytics and real time process monitoring systems, which can be integrated into the control algorithm and provide high level optimal control strategies as well as deeper understanding of the process. Process monitoring helps develop mathematical models which can, in one hand, help in better understanding the processes and consecvently the development and application of advanced control methods in order to achieve better product quality. In this work, image processing and image analysis based direct nucleation control (IA-DNC) is developed in order to investigate the evolution of the crystal properties, such as crystal size, and crystal shape distribution. The IA-DNC approach is also compared to alternative DNC techniques, in which particle number were measured by Focused Beam Reflectance Measurement (FBRM) in order to control crystal size. A control approach is introduced that control the nucleation and disappearance of crystals during cooling and heating segments related to the changes of the number of counts (measured by Particle Vision Measurment, so called PVM or combination of FBRM and PVM). The approach was applied to investigate crystallization of compounds with different behavior: potassium dihydrogen phosphate (KDP) water, contaminated KDP -water and Ascorbic acid water systems. The results demonstrate the application of imaging technique for model-free feedback control for tailoring crystal product properties. The second main aim of the thesis is to investigate and control crystallization processes in impure media in the presence of multiple impurities, with an impact on the crystal shape via growth kinetics. The broad impact of the crystal growth modifiers (impurities) on the growth kinetics is observed in real time by using in situ video imaging probe and real-time image analysis. A morphological population balance model is developed, which incorporates a multi-site, competitive adsorption mechanism of the impurities on the crystal faces. The kinetic parameters of primary nucleation, growth and impurity adsorption for a model system of potassium dihydrogen phosphate crystallization in water in the presence of two impurities, were estimated and validated with experimental results. It was demonstrated that the model can be used to describe the dynamic evolution of crystal properties, such as size and aspect ratio during crystallization for different impurity profiles in the system. Manual, feedback and hybrid feedback-feedforward control techniques are developed and investigated numerically for continuous processes, while model-based and model-free control approach for crystal shape are developed for batch processes. The developed morphological population balance model is implemented and applied in the model-based control approaches, which are suitable to describe multicomponent adsorption processes and their influence on the crystal shape. Case studies show the effectiveness of crystal growth modifiers based shape control techniques. Comparison of different control approaches shows the effectiveness of the techniques. The third part of the thesis deals with purification of crystals when adsorption of impurities on crystal surfaces and its incorporation into crystals are considered. A purification method, called competitive purity control (CPC) is proposed and investigated. A morphological population balance model, including nucleation, growth and competitive impurity adsorption kinetics is developed to describe the case when multiple impurities can adsorb competitively on the crystal surface. The model is also combined with liquid phase chemical reaction model, in order to investigate the purity control case when an additive is introduced in the system that reacts with the impurity forming a non-adsorbing reaction product. Both competitive purity control approaches proposed: the adsorption based competitive purity control (A-CPC) and the reaction based competitive purity control (R-CPC); are investigated using detailed numerical simulations then compared with the alternative widely used purification method, called recrystallization. In the last contribution chapter, an integrated process optimization of a continuous chemical reactor and crystallizer is performed and studied numerically. The purpose of this study is to show the way in which the byproduct produced in the chemical reactor may affect the crystallization process and how its negative effect can be reduced by applying integrated process optimization. Sensitivity analysis of the system was performed by considering the flow rate and the concentration of substances in the input stream of the chemical reactor as manipulated process variables. Model based integrated process optimization and the sensitivity analysis in order to obtain improved quality product in terms of crystal size, shape and purity.

L’hydrolyse enzymatique de la biomasse lignocellulosique est une voie prometteuse pour la bioconversion des matières végétales en sucres fermentescibles en vue de la production du bioéthanol de seconde génération. En général, des cocktails enzymatiques contenant différentes familles d’activités, caractérisées par des modes d’action différents, sont utilisés comme biocatalyseurs. L’essentiel des travaux de modélisation de ce procédé abordent la question via des approches cinétiques où les aspects particulaires et dynamique d’évolution des propriétés du substrat/biocatalyseur/système ne sont pas pris en compte. De plus, ce type de modèles, visant à reproduire les cinétiques de production des sucres simples, traite uniquement le cas de la mise en contact simultanée des enzymes et de la matière à hydrolyser (substrat). Dès lors, les questions relatives au design/optimisation du procédé telles que le mode d’alimentation (batch/continu) ou l’ajout séquencé des enzymes et/ou du substrat ne peuvent pas être abordées avec ces modèles. Dans ce travail, une approche de modélisation par le formalisme du bilan de population est proposée. Le modèle est basé sur une hétérogénéité structurale du substrat à savoir la distribution de taille des chaines/particules. Comme première approche numérique, la méthode des classes est utilisée dans le cas de l’hydrolyse de chaines polymères subissant des attaques endoglucanases (rupture aléatoire) et exoglucanases (coupure d’un dimère en bout de chaine). En deuxième lieu, la méthode des moments a été adoptée pour traiter du cas d’un substrat particulaire. Ici la rupture s’opère sous l’effet des contraintes hydrodynamiques tandis que l’hydrolyse enzymatique modifie la cohésion des particules. Par ailleurs, la nécessité de confronter les résultats numériques issus de la méthode des moments avec les distributions expérimentales a motivé un travail sur les méthodes de reconstruction des distributions à partir de leurs moments. Parallèlement à ce travail de modélisation, plusieurs métrologies nécessaires à la caractérisation de ces systèmes ont été mises en oeuvre. Trois techniques granulométriques (Morpho-granulométrie, Focused Beam Reflectance Measurement Technique (FBRM) et Granulométrie laser) ont été utilisées pour accéder à l’évolution de la distribution de taille des particules au cours de l’hydrolyse d’une cellulose microcristalline (Avicel). De plus, les concentrations en sucres réducteurs et en sucres simples (glucose et cellobiose) ont été mesurées. Les modélisations proposées combinent ainsi les aspects de cinétique homogène et de catalyse hétérogène. Intégrées dans une approche de type bilan de population multivariable, elles permettent d’accéder à l’évolution de la distribution de taille des chaines/particules du substrat ainsi qu’aux cinétiques de conversion en sucres simples. / The enzymatic hydrolysis of lignocellulosic biomass is a promising approach for the bioconversion of organic matter into fermentable sugars aiming ultimately to produce second generation biofuel. Globally, enzymatic cocktails, containing different activities which are characterized by their specific mechanisms, are used as biocatalysts. Most of the studies devoted to the modelling of this process address the problem via kinetic approaches in which the particulate aspects and the dynamic evolution of the properties of the substrate/biocatalyst/system are not taken into account. Moreover, such models aim to reproduce the kinetics of release of simple sugars and treat only the case where the enzymes and the substrate are simultaneously mixed at the beginning of the hydrolysis reaction. Therefore, issues related to the design/optimization of the process such as the supplying mode (batch/continuous) and the sequential adding of the enzymes/substrate cannot be addressed with these models. In this work, a population balance formalism is proposed as modelling approach. The model is based on a structural heterogeneity of the substrate namely the chain/particle size distribution. As a first numerical approach, the method of classes is used in the case of polymer chains undergoing endoglucanase (random breakage) and exoglucanase (chain-end scission) attacks. Secondly, the method of moments is adopted to solve the same problem and then adapted to the case of a particulate substrate by introducing the particle cohesion effect which depends on the enzymatic attacks as well as on the hydrodynamic shear stress. Finally, the confrontation of the numerical results from the method of moments to the experimental distributions motivated the development of reconstruction methods in order to restore distributions from a finite sequence of their moments. Alongside this modelling work, the suitable metrology has been developed for the characterization of these systems. Three different granulometric techniques (Morphogranulometry, Focused Beam Reflectance Measurement (FBRM) technique and Laser Diffraction Particle Size Analysis) are used to reach the time-evolution of the particle size distribution of microcrystalline cellulose (Avicel). In this context, numerical tools used for the analysis and the comparison of the different experimental distributions are proposed. In addition, the concentrations of reducing and simple sugars (glucose and cellobiose) are measured all along the hydrolysis reactions. The modeling of enzymatic hydrolysis developed here combines the concepts of homogeneous and heterogeneous catalysis. Integrated into the framework of multivariable population balance model, these allow the chain/particle size distribution evolution during the reaction and the kinetics of simple sugars release to be predicted.

Em um tratamento de águas de abastecimento ou residuárias, a coagulação/floculação é um processo de grande importância. A determinação dos agentes coagulante/floculante e a quantidade necessária de cada um deles são problemas rotineiros para os profissionais e podem influenciar na qualidade do tratamento. Determinar o tamanho dos flocos é fundamental para que a operação de floculação ocorra com melhor eficiência. Ainda, variáveis hidrodinâmicas, como a velocidade, volume das partículas e do recipiente, também têm a mesma importância nesta finalidade. No presente trabalho, a modelagem do processo de floculação via balanço populacional foi estudada com o objetivo de prever a formação de agregados/flocos em relação com o tempo até atingir o estado estacionário e em condições de operação distintas. Assim, um modelo de balanço populacional pela técnica de discretização por pivô fixo foi implementado no software EMSO. Um estudo foi realizado através de processamento/análise de imagens capturadas em um experimento de coagulação/floculação. As imagens obtidas do processo de floculação foram analisadas e foi verificado a distribuição do tamanho dos flocos. Com os dados de volume e concentração inicial de partículas foi possível a simulação no modelo matemático. Assim tornou-se possível observar o crescimento, a estabilização, o comportamento dos flocos em comparação com o modelo matemático e a frequência desses flocos em cada tamanho em diferentes condições, como o gradiente de velocidade e a concentração inicial de partículas. Os resultados obtidos em comparação com os dados experimentais e a simulação do modelo matemático foram possíveis verificar comportamento semelhante de distribuição de tamanho de flocos. A partir dessa análise, o modelo matemático mostrou-se satisfatório em prever o comportamento experimental. Em diferentes condições pode-se verificar que o gradiente de velocidade e a concentração inicial de partículas influenciam na formação e estabilização dos flocos. Este estudo teve a utilização de softwares de livre acesso para trazer a proposta de implementação a fim de trazer economia de agentes químicos utilizados e melhoria nos processos de operação da estação tratamento de efluentes. / In a wastewater treatment, coagulation / flocculation is a process of great importance. The determination of coagulant / flocculant agent and the required amount of each problems are routine for professional and can influence the quality of treatment. Determination the flocs size is essential for flocculation operation to occur with greater efficiency. Still, hydrodynamic variables, such as speed, particles volume and the container also have the same importance in this purpose. In the present work, modeling of flocculation process by population balance was studied in order to predict the formation of aggregates / flocs in relation to time to reach steady state and at different operating conditions. Thus, a population balance model by discretization technique for fixed pivot was implemented in EMSO software. A study was conducted through the processing / analysis of images captured on an experiment coagulation / flocculation. Images obtained in the flocculation process were analyzed and it was found the size distribution of flocs. With the volume and initial particle concentration values, simulation was possible in mathematical model. Thus it became possible to observe the growth, establization and behavior of flocs in comparison with the mathematical model, and the frequency of such flocs in each size in different conditions, such as the velocity gradient and the initial particle concentration. The results obtained in comparison to experimental data and simulation of the mathematical model we observed behavior flocs size distribution similar. From this analysis, mathematical model was satisfactory to predict the experimental behavior. Under different conditions can be seen that the velocity gradient and the initial concentration of particles influence the formation and stabilization of flocs. This study was the use of software-free access to bring the implementation of proposal in order to bring savings of chemicals used and improvement in operating processes of wastewater treatment station.

Em um tratamento de águas de abastecimento ou residuárias, a coagulação/floculação é um processo de grande importância. A determinação dos agentes coagulante/floculante e a quantidade necessária de cada um deles são problemas rotineiros para os profissionais e podem influenciar na qualidade do tratamento. Determinar o tamanho dos flocos é fundamental para que a operação de floculação ocorra com melhor eficiência. Ainda, variáveis hidrodinâmicas, como a velocidade, volume das partículas e do recipiente, também têm a mesma importância nesta finalidade. No presente trabalho, a modelagem do processo de floculação via balanço populacional foi estudada com o objetivo de prever a formação de agregados/flocos em relação com o tempo até atingir o estado estacionário e em condições de operação distintas. Assim, um modelo de balanço populacional pela técnica de discretização por pivô fixo foi implementado no software EMSO. Um estudo foi realizado através de processamento/análise de imagens capturadas em um experimento de coagulação/floculação. As imagens obtidas do processo de floculação foram analisadas e foi verificado a distribuição do tamanho dos flocos. Com os dados de volume e concentração inicial de partículas foi possível a simulação no modelo matemático. Assim tornou-se possível observar o crescimento, a estabilização, o comportamento dos flocos em comparação com o modelo matemático e a frequência desses flocos em cada tamanho em diferentes condições, como o gradiente de velocidade e a concentração inicial de partículas. Os resultados obtidos em comparação com os dados experimentais e a simulação do modelo matemático foram possíveis verificar comportamento semelhante de distribuição de tamanho de flocos. A partir dessa análise, o modelo matemático mostrou-se satisfatório em prever o comportamento experimental. Em diferentes condições pode-se verificar que o gradiente de velocidade e a concentração inicial de partículas influenciam na formação e estabilização dos flocos. Este estudo teve a utilização de softwares de livre acesso para trazer a proposta de implementação a fim de trazer economia de agentes químicos utilizados e melhoria nos processos de operação da estação tratamento de efluentes. / In a wastewater treatment, coagulation / flocculation is a process of great importance. The determination of coagulant / flocculant agent and the required amount of each problems are routine for professional and can influence the quality of treatment. Determination the flocs size is essential for flocculation operation to occur with greater efficiency. Still, hydrodynamic variables, such as speed, particles volume and the container also have the same importance in this purpose. In the present work, modeling of flocculation process by population balance was studied in order to predict the formation of aggregates / flocs in relation to time to reach steady state and at different operating conditions. Thus, a population balance model by discretization technique for fixed pivot was implemented in EMSO software. A study was conducted through the processing / analysis of images captured on an experiment coagulation / flocculation. Images obtained in the flocculation process were analyzed and it was found the size distribution of flocs. With the volume and initial particle concentration values, simulation was possible in mathematical model. Thus it became possible to observe the growth, establization and behavior of flocs in comparison with the mathematical model, and the frequency of such flocs in each size in different conditions, such as the velocity gradient and the initial particle concentration. The results obtained in comparison to experimental data and simulation of the mathematical model we observed behavior flocs size distribution similar. From this analysis, mathematical model was satisfactory to predict the experimental behavior. Under different conditions can be seen that the velocity gradient and the initial concentration of particles influence the formation and stabilization of flocs. This study was the use of software-free access to bring the implementation of proposal in order to bring savings of chemicals used and improvement in operating processes of wastewater treatment station.

Orientador: Florencia Cecília Menegalli / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-20T07:44:45Z (GMT). No. of bitstreams: 1 Souza_DiogoOtaviodeCastro_D.pdf: 2512415 bytes, checksum: cc03ff39105bf1fed4d6dae52c95bbce (MD5) Previous issue date: 2012 / Resumo: A granulação é um processo de aumento de tamanho de pós finos, que pode ser utilizado na indústria de alimentos para aumentar a qualidade de alimentos em pó, pelo aumento da sua dispersibilidade e solubilidade em líquidos. O modelo de balanço populacional (MBP) é normalmente utilizado para modelar este processo. Entretanto, nos trabalhos existentes, o MBP não leva em consideração as perdas de partículas no processo por elutriação e incrustação, muito relevantes para granulação de sucos em pó. Além disso, não existe na literatura correlações para estimar estas constantes com base nas condições operacionais do equipamento e nas características das partículas. Diante disso, o objetivo deste trabalho foi o estudo do impacto das condições operacionais no modelo de balanço populacional, durante a granulação de suco de goiaba em pó, em leito fluidizado. Diversos experimentos foram realizados de forma a adquirir os dados que alimentaram os modelos matemáticos desenvolvidos. Estes dados foram obtidos fora das zonas de máximo rendimento a fim de se obter um modelo mais abrangente, que pudesses simular o processo de granulação em todas as condições de processo. Foram desenvolvidas e validadas correlações para estimativa da taxa de elutriação, para estimativa das constantes de aglomeração e de quebra do MBP. Além disso, foi desenvolvido um modelo para estimativa da massa incrustada de partículas. Os modelos se mostraram capazes de estimar o rendimento do processo, os valores de diâmetro médio e da distribuição de tamanho de partículas. Foram feitas simulações alterando a velocidade do ar de fluidização, a vazão de ligante, o diâmetro médio inicial da distribuição, o formato da distribuição e a massa total de partículas. A análise das simulações realizadas sugere que as condições ótimas precisam ser avaliadas para cada distribuição de tamanho e para cada quantidade de partículas no equipamento, não somente para cada tipo de produto. De modo geral, os modelos desenvolvidos se mostraram adequados para aumentar a compreensão do processo de granulação e para obtenção de ótimos de processamento. Cabe ressaltar a necessidade de futuras investigações para verificar a aplicação destes modelos com outros tipos de material particulado e em outras faixas de operação / Abstract: Granulation is a size-enlargement process, in which small particles are agglomerated together. It is used in the food industry to increase the quality of food powder, by increasing its solubility. The population balance model (PBM) is a widely used model for this process. However, it is usually applied without account losses in the process by elutriation and wall deposition, which are very important for granulation of powdered juices. In addition, there is no correlation in the literature able to estimate the constants of the model from the operational conditions and from the particles¿ characteristics. The objective of this work was to study the impact of operational conditions into the population balance model for the granulation of guava juice powder, in a fluidized bed. Several experiments were performed in order to acquire data that fed the mathematical models developed in this work. These data weren¿t obtained from the zones of maximum process yield in order to achieve a more comprehensive model, which could simulate the granulation process in all process¿ conditions. It was developed and validated a correlation for the estimation of the rate of elutriation, a model for the estimation of the particles¿ wall deposition, a correlation for estimation the constants of agglomeration and for estimation of the breakage constant of the PBM. The models predicted, with good accuracy, the process yield, the mean diameter and particle size distribution. Simulations were made by changing the fluidizing air temperature, the liquid binder flow rate, the fluidizing air velocity, the initial mean diameter, the shape of the particles size distribution and the total mass of particles. The analysis of the simulations suggests that the optimal conditions must be evaluated for each kind of particle size distribution and for each mass of particles into the equipment, not only for each type of product. The models developed showed to be suitable to increase the understanding of the granulation process and to obtain process¿ optimal conditions. It is worth emphasizing the need of further research to verify the application of these models for others types of particles and others operational ranges / Doutorado / Engenharia de Alimentos / Doutor em Engenharia de Alimentos

This thesis presents new methods to study the aerosol synthesis of nano-particles and a new model to simulate the formation of silicon nanoparticles. Population balance modelling is used to model nanoparticle synthesis and a stochastic numerical method is used to solve the governing equations. The population balance models are coupled to chemical kinetic models and offer insight into the fundamental physiochemical processes leading to particle formation. The first method developed in this work is a new mathematical expression for calculating the rate of Brownian coagulation with stochastic weighted algorithms (SWAs). The new expression permits the solution of the population balance equations with SWAs using a computationally-efficient technique of majorant rates and fictitious jumps. Convergence properties and efficiency of the expression are evaluated using a detailed silica particle model. A sequential-modular algorithm is subsequently presented which solves networks of perfectly stirred reactors with a population balance model using the stochastic method. The algorithm is tested in some simple network configurations, which are used to identify methods through which error in the stochastic solution may be reduced. It is observed that SWAs are useful in preventing accumulation of error in reactor networks. A new model for silicon nanoparticle synthesis is developed. The model includes gas-phase reactions describing silane decomposition, and a detailed multivariate particle model which tracks particle structure and composition. Systematic parameter estimation is used to fit the model to experimental cases. Results indicated that the key challenge in modelling silicon systems is obtaining a correct description of the particle nucleation process. Finally, the silicon model is used in conjunction with the reactor network algorithm to simulate the start-up of a plug-flow reactor. The power of stochastic methods in resolving characteristics of a particle ensemble is highlighted by investigating the number, size, degree of sintering and polydispersity along the length of the reactor.

Abstract : The industrial partner of this project uses a slurry bubble reactor for the production of biogenic methanol. In the latter syngas is dispersed into the slurry continuous phase containing both liquid and solid phases. The rising bubbles containing a wide spectrum of the bubbles sizes, interact with the continuous phase due to the interface momentum transfer. The latter includes the drag, lift, wall lubrication and turbulent dispersion terms that require average bubble size, which needs to be calculated. One way to predict this average bubble size is by using population balance model (PBM), which can be coupled with the Eulerian framework. PBM also needs closure kernels for the bubble coalescence and bubble breakup. In this study, the influence of bubble coalescence and bubble breakup kernels have been studied in two- and three-phase system using eulerian approach, which solves momentum equation for each phase. The influence of the mesh sizes, number of bubble classes, numerical schemes, wall lubrication force and turbulent dispersion force are also included. In the two-phase system, results show that the Luo coalescence model needs to be tuned when used in combination with the Luo breakup kernel. The combination of the Luo coalescence and the Lehr breakup kernels (Luo-Lehr) show promising time-averaged radial profiles of gas holdup and axial liquid velocity as compared to empirical values. In the three-phase system, the combination of the Luo coalescence and the Lehr breakup kernels (Luo-Lehr) and the Luo coalescence and the Luo breakup kernels (Luo-Luo) predict convincing time-averaged radial profile of axial solid velocity as compared to experiments. However, at an elevated superficial gas velocity, a non-realistic behavior was predicted when compared to empirical observations. The sensitivity analysis results show that the 3 mm mesh size depicts a trend similar to the empirical values of the radial profiles of the gas holdup, axial liquid velocity, and solid axial velocity. The number of bubble classes influence the predicted bubble size distribution in the three-phase system while the numerical discretizing schemes have no influence on the results. The bench simulation results show that the inclusion of the turbulent dispersion term using a single porous tubular sparger influences the hydrodynamic behavior of the bubble column. / Le partenaire industriel de ce projet utilise un réacteur à suspension à trois phases pour la production de méthanol biogénique. Dans celui-ci, le gaz de synthèse est diffusé par barbotement dans la phase à suspension qui contient à la fois les phases liquide et solide. Les bulles en ascension présentent un large spectre de tailles et interagissent avec la phase à suspension en échangeant de la quantité de mouvement via leurs surfaces. Cet échange comprend les forces de trainé, de portance, de lubrification en proche parois et de dispersion par turbulence; lesquelles requièrent notamment le calcul de la taille moyenne des bulles. Une façon de prédire numériquement cette taille moyenne est de recourir à un modèle de bilan de population (PBM, de l’anglais Population Balance Model), qui peut être couplé avec un model multiphasique eulérien. Un tel PBM a requière des modèles de fermetures pour la coalescence et la rupture des bulles. Dans la présente étude, l'influence des modèles noyaux de coalescence et de rupture des bulles a été étudiée pour des systèmes à deux et à trois phases en utilisant l’approche eulérienne. L'influence de la taille du maillage, du nombre de classes de bulles, du schéma numérique, de la force de lubrification en proche parois et de la force de dispersion par turbulence sont également incluses. Dans un système bi-phasique, les résultats montrent que le modèle de coalescence Luo doit être ajusté lorsqu'il est utilisé en combinaison avec le noyau de rupture Luo. La combinaison des noyaux de coalescence Luo et de rupture Lehr (Luo-Lehr) montrent des profils radiaux moyennés dans le temps qui sont valides pour la concentration de gaz et la vitesse axiale du liquide par rapport aux mesures expérimentales. Dans le système triphasé, la combinaison des modèles noyaux de coalescence de Luo et de rupture de Lehr (Luo-Lehr) et de la coalescence de Luo et de rupture de Luo (Luo-Luo) prédisent des profils radiaux moyennés dans le temps qui sont valides pour la vitesse axiale moyenné dans le temps par rapport aux expériences. Cependant, à une vitesse de gaz superficielle élevée, ces profils prédisent un comportement non réaliste par rapport aux observations empiriques. Les résultats de l'analyse de sensibilité du maillage montrent qu’avec des cellules de 3 mm, le model prédit une tendance similaire aux valeurs empiriques pour les profils radiaux de concentration du gaz, de vitesse axiale du liquide et de vitesse axiale solide. Le nombre de classes de bulles influe sur les distributions prédites de taille de bulle dans le système triphasé alors que les schémas de discrétisation numériques n'ont aucune influence sur les résultats. Les résultats des simulations d’un banc d’essai avec diffuseur à bulles poreux montrent que tenir compte du terme de dispersion influence le comportement hydrodynamique de la colonne à bulles.