https://repositorio.ufu.br/handle/123456789/19021 2026-04-06T03:21:29Z 2026-04-06T03:21:29Z https://repositorio.ufu.br/handle/123456789/48071 2026-01-27T06:19:50Z 2025-07-24T00:00:00Z

Title: Estudo da sedimentação e acomodação de partículas em sistemas submetidos a gradientes de temperaturas Abstract: Sedimentation is a widely used process in industry, encompassing various sectors. Among the factors that influence its efficiency, temperature plays a decisive role in solid-liquid separation. A notable example occurs in oil well drilling, where the drilling fluid is subjected to heating due to geothermal conditions, with a temperature increase as the well depth increases. During interruptions in drilling fluid circulation, suspended particles tend to settle, which can compromise well integrity. In this context, this work investigated the behavior of sedimentation and particle arrangement in systems subjected to different thermal conditions, with emphasis on the formation and structure of the sediment bed. The main objective was to evaluate the behavior of the sediment bed as a function of the sedimentation temperature, considering both isothermal conditions and scenarios with thermal gradients, in systems containing only water as well as more complex fluids, such as drilling fluids. For this purpose, systems containing calcium carbonate suspensions in water and drilling fluids with different solid concentrations were prepared. The analyses included sedimentation tests under isothermal conditions and with horizontal and vertical temperature gradients. The solid concentration profile was determined using the gamma-ray attenuation technique, a non-destructive method that allows the assessment of the solids concentration distribution in the sediment bed. The results indicate that increasing the temperature accelerates the sedimentation process, reduces fluid viscosity, and alters the structure of the sediment bed by promoting sediment expansion. In systems with thermal gradients, particle migration towards heated regions and the formation of asymmetric beds with concentration variations along the horizontal axis were observed. In drilling fluids, temperature directly influenced rheology and resistance to sedimentation, with significant differences observed between the samples analyzed. This research contributes to the understanding of thermal effects on sedimentation, providing insights for the design and operation of industrial systems where temperature variations are relevant, such as in oil well drilling.

2025-07-24T00:00:00Z https://repositorio.ufu.br/handle/123456789/47787 2025-12-03T06:20:44Z 2025-04-29T00:00:00Z

Title: Estudo de catalisadores de cobalto suportados em nióbia mesoporosa aplicados na síntese Fischer-Tropsch Abstract: Fischer-Tropsch synthesis (FTS) is a promising process for converting synthesis gas into high- value fuels and chemicals, typically catalyzed by metals such as iron and cobalt supported on high-surface-area materials. This thesis proposes the use of mesoporous niobia as an alternative support for cobalt catalysts applied in FTS, focusing on the preparation of supports with high surface area and good porosity through the hydrothermal method. The catalytic performance of different cobalt loadings (10, 15, 20, and 30 wt%) supported on Nb2O5-m was evaluated, as well as the effects of the catalyst synthesis method on their activity and selectivity. The results showed that high-surface-area niobia promotes good dispersion of the active phase and high selectivity for liquid hydrocarbons (C5–C19), presenting performance comparable to commercial catalysts, even without the use of noble metal promoters. These findings highlight the feasibility of mesoporous niobia as a catalytic support for hydrocarbon conversion applications, and this research contributes to the advancement of catalytic technologies aligned with global demands for emission reduction and energy transition.

2025-04-29T00:00:00Z https://repositorio.ufu.br/handle/123456789/47015 2025-09-26T06:22:12Z 2025-09-19T00:00:00Z

Title: Estudo da dinâmica e controle de peneiras vibratórias Abstract: This thesis addresses the study of the dynamics and control of shale shakers, crucial equipment in the solids control stage of the oil and gas industry. The main objective was to develop and evaluate methodologies for real-time monitoring and automatic control of these systems, aiming to optimize solid-liquid separation, increase component lifespan, and minimize environmental impacts. To this end, computer vision approaches, including filter-based techniques and neural networks, were investigated to identify the pool area on the screens. A rule-based closed-loop control system was implemented to automatically adjust screen inclination and vibratory motor rotation, maintaining the pool within an optimal operating range. Additionally, a methodology and a computational tool named VibraMap were developed to characterize, in real-time, the three-dimensional movement of the shaker (frequency, g-factor, ellipse shape) using accelerometers. The impact of material load on vibrational dynamics was analyzed. Finally, the influence of operational variables (inclination, g-factor, flow rate) on the fluid content in residual solids was experimentally investigated via factorial design. The results demonstrated the feasibility and effectiveness of computer vision techniques for monitoring, the good performance of the proposed control system in responding to process variations, the VibraMap’s capability to detail shaker dynamics, and the identification of operating conditions that minimize solids moisture. It is concluded that the developed tools and methodologies represent significant advancements for the optimization of shale shakers.; Cette thèse aborde l’étude de la dynamique et du contrôle des tamis vibrants (shale shakers), équipements cruciaux dans l’étape de contrôle des solides de l’industrie pétrolière et gazière. L’objectif principal était de développer et d’évaluer des méthodologies pour la surveillance en temps réel et le contrôle automatique de ces systèmes, visant à optimiser la séparation solide-liquide, à augmenter la durée de vie des composants et à minimiser les impacts environnementaux. À cette fin, des approches de vision par ordinateur, incluant des techniques basées sur des filtres et des réseaux de neurones, ont été investiguées pour identifier la zone de “piscine” (pool area) sur les toiles. Un système de contrôle en boucle fermée, basé sur des règles, a été mis en œuvre pour ajuster automatiquement l’inclinaison des toiles et la rotation des moteurs vibrants, maintenant la piscine dans une plage opérationnelle optimale. De plus, une méthodologie et un outil informatique nommé VibraMap ont été développés pour caractériser, en temps réel, le mouvement tridimensionnel du tamis (fréquence, facteur-g, forme de l’ellipse) à l’aide d’accéléromètres. L’impact de la charge de matériau sur la dynamique vibratoire a été analysé. Enfin, l’influence des variables opérationnelles (inclinaison, facteur-g, débit) sur la teneur en fluide des solides résiduels a été étudiée expérimentalmente via un plan factoriel. Les résultats ont démontré la faisabilité et l’efficacité des techniques de vision par ordinateur pour la surveillance, la bonne performance du système de contrôle proposé face aux variations du processus, la capacité du VibraMap à détailler la dynamique du tamis, et l’identification de conditions opératoires minimisant l’humidité des solides. Il est conclu que les outils et méthodologies développés représentent des avancées significatives pour l’optimisation des tamis vibrants.

2025-09-19T00:00:00Z https://repositorio.ufu.br/handle/123456789/46803 2025-09-13T06:17:22Z 2025-08-14T00:00:00Z

Title: Produção de membranas poliméricas com material de reuso e aplicações Abstract: This study presents an innovative and sustainable approach to developing polymeric membranes from waste materials, aiming to combat the growing generation of solid waste. The research focused on producing membranes from residual cellulose acetate (AC) from unused cigarette filters and polyethylene terephthalate (PET) from plastic bottles. The AC membranes were modified with the addition of anionic and cationic resins, and the PET membranes were modified with the addition of biopolymers: gum arabic (GA) (1%, 3%, 5%, 7.5%, and 10%) and gum karaya (GK) (1%, 3%, 5%, and 7.5%). The produced AC membranes showed a porous morphology similar to non-residual AC membranes, but they had structural failure and ruptured during permeability tests, which made it unfeasible to continue the assays. Due to this limitation, the studies focused on using PET, which proved to be a more suitable material for the proposed soluble medium separation applications due to its higher mechanical resistance and greater availability as waste. The incorporation of the gums into the PET membranes had a significant effect on the material's properties. Scanning electron microscopy (SEM) analyses showed that adding 1% and 3% of GA preserved a well-defined porous structure, while higher concentrations (5%, 7.5%, and 10%) resulted in unfavorable morphological changes, with less interconnected pores and higher density. Micrographs of the membranes with GK revealed a less homogeneous and potentially more fragile structure, with many voids and low density, which was confirmed by the permeability analysis. The permeability of the PET membranes was enhanced with the addition of GA. The membrane with 5% GA (PGA5) reached a maximum of 157.70 L/h m2, but higher concentrations led to a decrease in permeability. The modification with both natural gums also reduced the PET membrane's hydrophobicity, with the contact angle of the pure membrane (94.00°) decreasing to 33.90∘ with the addition of 7.5% GA. Mechanical resistance was improved with the addition of GA, and the PGA3 membrane (3% GA) showed an elongation of 33%, surpassing that of pure PET (20.40%). The GA-modified membranes were more effective for the proposed application than the GK-modified ones. In hydraulic performance tests for water treatment, with a lignin contaminant solution rejection test at 100 mg/L, the PGA3 membrane showed a high flux recovery rate (between 93.55% and 97.30%) and a low irreversible fouling index (from 2.70% to 6.45%). In the rejection tests, the PGA3 membrane was able to retain between 85.34% and 93.10% of the turbidity, which was significantly higher than the pure PET membrane (65.52% to 74.14%). The electrical conductivity analysis confirmed that the separation occurred by ultrafiltration, retaining suspended solids and allowing the passage of low molecular weight species. In conclusion, modifying residual PET membranes with gum arabic is a promising strategy for developing materials with enhanced properties for liquid medium separation processes. The formulation with 3% gum arabic (PGA3) was the most balanced, ideally combining permeability, hydrophilicity, mechanical resistance, and performance in contaminant rejection. This approach contributes to the valorization of plastic waste, promoting the circular economy and offering a sustainable solution for water treatment and other environmental challenges.

2025-08-14T00:00:00Z